• Author / Uploaded
• Lidia Matias

Citation preview

Metallographic Etching Metallographic and Ceramographic Methods f or Revealing Microstructure

Günter Petzow Max Planck InstituteJor Metals R esearch, Institute Jor Materials Science, Stuttgart, West Germany

Translators from the German version:

Rosemarie Koch and James A. Nelson

L11~

AMERICAN SOCIETY FOR METALS

~ Metals Park, 0hio 44073

A I" ON., .... //' . -, - Lt"IISI'rIf'uf\lJl ,~'-__. ,f;:._ .L ~.;. ' 1-

¡-l] "

tq

\JI I lli ,

....c.:......~..... _o..

OriginaUy published in 1976 as Metallographische Atzen '~'\\ UI)N ~I¿¡ -~/ HU L, Ivl lli I __ ___,'".1./ ." ...• Copyright 1976 by Gebrüder Borntraeger, Berlin- Stuttgart

'JU \

0 . . ..

;:.

'J,

f

.

\' ')

Enlarged English translation copyright © ' 1978 - ,.--- ..: . ", .. -- . ~ by the AMERICAN SOCIETY FOR MET ALS AU rights reserved

No part of this book may be reproduced , stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the publisher. Nothing contained in this book is to be construed as a grant of any right of manufacture, sale, or use in connection with any method , process, apparatus , product, or composition, whether or not covered by letters patent or registe red trademark, nor as a defense against liability for the infringement of letters patent or ./} \ registered trademark. {i ~ r

fI

To Robert 1. Gray and E. Daniel A lbrecht, two distinguished contributors to th e development of modern metallography, for their encouragement in preparing th e English version of this book.

~f ./

D· · y

:i

l' I

Library of Congress Cataloging in Publication Data

Petzow, G . Metallographic etching. HAn improved version of the 5th edition of . . . Metallo· graphische Átzen." Contains bibliographic references . Ineludes index o l . Metallographic specimens, 2. Metals- Etching. 1. Title. TN690.7P4713 1978 669' .95'028 78-8023 tIj J'. ISBN 0-87170-002-6 (, ~

PRINTED IN TH E UNITED STATES OF AMERICA

"f , 1 ..h.t

1}

A I" ON., .... //' . -, - Lt"IISI'rIf'uf\lJl ,~'-__. ,f;:._ .L ~.;. ' 1-

¡-l] "

tq

\JI I lli ,

....c.:......~..... _o..

OriginaUy published in 1976 as Metallographische Atzen '~'\\ UI)N ~I¿¡ -~/ HU L, Ivl lli I __ ___,'".1./ ." ...• Copyright 1976 by Gebrüder Borntraeger, Berlin- Stuttgart

'JU \

0 . . ..

;:.

'J,

f

.

\' ')

Enlarged English translation copyright © ' 1978 - ,.--- ..: . ", .. -- . ~ by the AMERICAN SOCIETY FOR MET ALS AU rights reserved

No part of this book may be reproduced , stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the publisher. Nothing contained in this book is to be construed as a grant of any right of manufacture, sale, or use in connection with any method , process, apparatus , product, or composition, whether or not covered by letters patent or registe red trademark, nor as a defense against liability for the infringement of letters patent or ./} \ registered trademark. {i ~ r

fI

To Robert 1. Gray and E. Daniel A lbrecht, two distinguished contributors to th e development of modern metallography, for their encouragement in preparing th e English version of this book.

~f ./

D· · y

:i

l' I

Library of Congress Cataloging in Publication Data

Petzow, G . Metallographic etching. HAn improved version of the 5th edition of . . . Metallo· graphische Átzen." Contains bibliographic references . Ineludes index o l . Metallographic specimens, 2. Metals- Etching. 1. Title. TN690.7P4713 1978 669' .95'028 78-8023 tIj J'. ISBN 0-87170-002-6 (, ~

PRINTED IN TH E UNITED STATES OF AMERICA

"f , 1 ..h.t

1}

Preface

:~,

"Jito.

In the last few years, metallographic prepara.tion techniques have been improved considerably. During this progress, the transition from manual and empirical methods to reproducible and automatic techniques - although not yet complete-has become l;\ reality. Taking this into account, the modern preparation techniques and their functional interrelationships are first treated in the present book, then well-proven metallographic recipes for individual materials are listed. In addition to the classical materials, those special metals and alloys are treated which find their application in aerospace and nuclear engineering. Sirnilarly, techniques and recipes for metal-ceramics and special ceramics are presented, because these materials also are investigated more and more by "metallographic" -or, better, "ceramographic" -methods. Instructions for specimen preparation not only are numerous but also frequently contradict each other. Therefore, mainly the author's experience - rather ' than data in the literature ~ was .used in compiling the preparation recipes in this book. Special attention was given to those pro ce dures that appear particularly suitable for small or medium-size metallographic laboratories, which normally are not equipped with expensive and sophisticated instruments. The selected recipes are simple and well-proven in practice; complicated, seldom used procedures of poor reproducibility have been omitted. . The present English-language book, "Metallographic Etching," is an improved version of the 5th edition of the booklet "Metallographisches Átzen" (in German), published in 1976. The pro ven grouping of the various recipes into certain classes of materials has be en maintained, because it enables the ready exchange, variation, and combination of various procedures between and within certain groups of materials. I wish to thank all those who assisted me in the preparation of this edition in English, particularly Rosemarie Koch and James A. Nelson for their translation services. For their critical reading of the manuscript I am indebted to Winfried J. Huppmann, lan Yapp, and Alan Prince. And, finally, I would like to acknowledge the tedious task of typing the manuscript by Antonie Rohrbach, Gertrud Thede, and Inge Hormann. Stuttgart, 8 July 1977

·,-

GÜNTER PETZOW

v

Preface to the German Edition Vorwort

t ',.

Seit der letzten Auflage des Átzheftes im Jahre 1957 hat sich die Situation auf dem Werkstoffgebiet weitgehend verandert. Das Aufkommen neuer und die Optimierung bekannter Technologiel\ haben viele Werkstoffe hervorgebracht, deren Aufbau und Eigenschaften nicht zuletzt in den metallographischen Laboratorien in Forschung und Praxis aufgeldart und überprüft werden müssen. Dem wurde auch die metallographische Praparationstechnik angepasst: Der Übergang von der handwerklichen Empirie zur reproduzierbaren, automatisierten Metho'de wurde, wenn auch nicht vollstiindig, so doch in erheblichem Ausmass vollzogen. Das alles musste sich natürlich auf Inhalt und Umfang dieser Auflage auswirken. So ist letzten Endes ein neues Buch unter neuem Titel entstanden, das nur noch teilweise mit der vorhergehenden Auflage zu vergleichen ist. Neben einer alle modemen Methoden einschliessenden Beschreibung der Praparationstechniken wurde eine ganze Reihe von Werkstoffgruppen neu aufgenommen; angefangen von metallischen Hochleistungswerkstoffen im Flugzeug-, Reaktor- und Raketenbau bis hin zu den metallkeramischen und keramis,ehen Sondt 99%).

°

10 Diamond

Remarks

1000

Aluminum, zinc, magnesium, copper, silver, gold 4.5

8 ropaz

9 Corundum

Rosiwal grinding hardness

Lead, tin

3 Calcite

13

Table 2. Abrasives and Polishing Compounds (con(inued)

Graphite I Talcum

/

could be used over the en tire range of specimen preparation _ a real possibility with diamond and alumina. Other abrasives are not as versatile, due to economics, availability, and efficiency of application. The subdivision into several grinding and polishing steps shown in Fig. 10 is arbitrary and not intended to be strictly observed; it is presented as a useful guide in practice. Uniform particle size ofknown values is essential for good me tallographic abrasives. Different size designations are in use. Figure 11 shows the relationship between mesh or grit size, emery grade, and true particle size in microns. Mesh is a number used to denote the size of individual

tll

il

14

/

Technical Tips for Preparation of Specimens

Fine Grinding

Technical Típs for Preparatíon of Specimens LKough

I

15

• Control of heat at the specimen-abrasive interface. • Control of harmful dust.

ishi,.!!

• Longer life for fixed abrasives because removed products are continuously flushed away. Pressure, Time, Velocity. Increasing the value of pressure, time, and velocity generalIy works toward a higher material-removal rate. The effect on deformation varies such that:

.

Gl

ao. lO

Mesh 11 1 1

1

11111 1 1 fme¡y

10080 60

40

20

Gr~~~----

jllW a ~

6

Porticle Size in I-'m

Fig. 11. Relationship between mesh size, grit size, emery grade, and particle size in microns.

abrasive grains. ,\his corresponds to the screen openings per linear inch in the standard sieve. For example, an abrasive of 320 mesh contains partieles that will just pass through a screen having 240 openings to the linear inch"but will be retained by the next-finer, 320-mesh screen. In addition to ~esh size, grit size and emery grade are also commonly used as stand~lfds to elassify abras iv e materials. Sharp edges" high hardness, high coating density, and good bonding .. to the suppor(tP,aterial substantially increase the cutting rate and reduce the depth of deformation. Diamond is superior to the other abrasives because of the.degree to which it meets the aboye requirements. Grinding and Polishing Fluids. A1though sorne specimen-preparation work is done in 'áir or inert gas without liquid vehieles, this is the exception. Normally, all metallographic preparation steps require a liquid vehiele as a coolant and/or dispersant, causing loose abrasives to be distributed more uniformly onto eloth surfaces. Wet polishing hasnumerous advantages, which inelude:

• Excessive pressure may cause heating and flowed material, which can cause changes in microstructure. Pressure should not be too high, especially during polishing. • Short grinding times and long polishing times are preferable (Fig. 9). However, cloth polishing with abrasives other than diamond should be as brief as possible, because severe relief effects may result from the differing removal rates for individual microstructural components. • The harder the specimen material, gene rally the lower the applied grinding and polishing speed. However this "rule" is only of limited validity. For sorne extremely hard materials (ceramics, intermetallic compóunds, cemented carbides), higher polishing speeds are preferred in most cases. • Because increased grinding and polishing speeds produce higher surface temperatures, heat-sensitive materials must be polished at lower speeds. Specimen Motion in Grinding and POlishing. The motion of the specitnen during grinding and polishing operations affects edge retention. For the best results, the specimen must be held flat against the abrasive surface at a11 times. To avoid the formation of oriented grinding and polishing grooves, these operations are best performed by rotating the specimen 90° between each step. When using a wheel for grinding and polishing, rotating the specimen opposite to the wheel rotation eliminates directional effects. Grinding and Polishing Substrates. A wide variety of substrate materials are used in metallographic specimen preparation. Paper, eloth, metal, wood, glass, hard rubber, and pitch have a11 been used as supports in abrasive preparation. Coarse grinding is most commonly performed on coated paper discs or eloth belts. Fine grinding is usua11y executed on coated paper abrasives; rough and final polishing is almost always done on fabrics such as wool, silk, cotton, feIt, and various synthetic materials. The choice of eloth type is very important; certain eloths work well in certain applications but not in others. Low-nap eloths are

14

/

Technical Tips for Preparation of Specimens

Fine Grinding

Technical Típs for Preparatíon of Specimens LKough

I

15

• Control of heat at the specimen-abrasive interface. • Control of harmful dust.

ishi,.!!

• Longer life for fixed abrasives because removed products are continuously flushed away. Pressure, Time, Velocity. Increasing the value of pressure, time, and velocity generalIy works toward a higher material-removal rate. The effect on deformation varies such that:

.

Gl

ao. lO

Mesh 11 1 1

1

11111 1 1 fme¡y

10080 60

40

20

Gr~~~----

jllW a ~

6

Porticle Size in I-'m

Fig. 11. Relationship between mesh size, grit size, emery grade, and particle size in microns.

abrasive grains. ,\his corresponds to the screen openings per linear inch in the standard sieve. For example, an abrasive of 320 mesh contains partieles that will just pass through a screen having 240 openings to the linear inch"but will be retained by the next-finer, 320-mesh screen. In addition to ~esh size, grit size and emery grade are also commonly used as stand~lfds to elassify abras iv e materials. Sharp edges" high hardness, high coating density, and good bonding .. to the suppor(tP,aterial substantially increase the cutting rate and reduce the depth of deformation. Diamond is superior to the other abrasives because of the.degree to which it meets the aboye requirements. Grinding and Polishing Fluids. A1though sorne specimen-preparation work is done in 'áir or inert gas without liquid vehieles, this is the exception. Normally, all metallographic preparation steps require a liquid vehiele as a coolant and/or dispersant, causing loose abrasives to be distributed more uniformly onto eloth surfaces. Wet polishing hasnumerous advantages, which inelude:

• Excessive pressure may cause heating and flowed material, which can cause changes in microstructure. Pressure should not be too high, especially during polishing. • Short grinding times and long polishing times are preferable (Fig. 9). However, cloth polishing with abrasives other than diamond should be as brief as possible, because severe relief effects may result from the differing removal rates for individual microstructural components. • The harder the specimen material, gene rally the lower the applied grinding and polishing speed. However this "rule" is only of limited validity. For sorne extremely hard materials (ceramics, intermetallic compóunds, cemented carbides), higher polishing speeds are preferred in most cases. • Because increased grinding and polishing speeds produce higher surface temperatures, heat-sensitive materials must be polished at lower speeds. Specimen Motion in Grinding and POlishing. The motion of the specitnen during grinding and polishing operations affects edge retention. For the best results, the specimen must be held flat against the abrasive surface at a11 times. To avoid the formation of oriented grinding and polishing grooves, these operations are best performed by rotating the specimen 90° between each step. When using a wheel for grinding and polishing, rotating the specimen opposite to the wheel rotation eliminates directional effects. Grinding and Polishing Substrates. A wide variety of substrate materials are used in metallographic specimen preparation. Paper, eloth, metal, wood, glass, hard rubber, and pitch have a11 been used as supports in abrasive preparation. Coarse grinding is most commonly performed on coated paper discs or eloth belts. Fine grinding is usua11y executed on coated paper abrasives; rough and final polishing is almost always done on fabrics such as wool, silk, cotton, feIt, and various synthetic materials. The choice of eloth type is very important; certain eloths work well in certain applications but not in others. Low-nap eloths are

Technical Tips for Preparation of Specimens 16

I

I

17

Technical Tips for Preparation of Specimens

generally preferred for rough polishing and medium-nap c10ths for final polishing. Abrasives are usually applied to c10ths in the form of paste suspensions or slurries.

Thermo

• Hard or firm support materials tend to promote deeper deformation . • More elastic support materials favor less deformation but increase the tendency to relief and edge rounding.

Microtome Cutting Microtome cutting employs a cemented carbide or diamond knife which mechanically slices a layer from the bulk material. Although the action of a microtome is similar to planing or milling, the principies of mechanical grinding and polishing still apply. High-quality cuts, free from deformation and flow , are possible with the micro tome only if the cutting angle is properly adjusted . This technique is particularly useful in cutting aggregate materials such as lamellar structures, having varying degrees of hardness. Microtome cutting is, however, restricted to materials of about 150 HV or less. Similar to microtome cutting is micromilling. Whereas the knife of a microtome removes a surface layer by cutting and acts like aplane, the micromill has a rotating milling head which removes layers 5 to 15 J..I-m in thickness with high precision . As with the cutting knife of the microtome, the milling tool of the milling device is made of either diamond or cemented carbide. Micromilling combines all grinding and polishing operations into one step and produces aplane surface of high quality with respect to scratches and surface damage. Electrolytic Grinding and Polishing Although electrolytic grinding and electroerosive grinding (Fig. 7) are seldom used, electrolytic polishing is commonly employed. Electrolytic polishing, also called anodic polishing, occurs through anodic dissolution of the specimen surface in an electrolytic cell . Figure 12 is a diagram showing a simple electrolytic cell that is easily set up in the laboratory. The orientation of the anode (sample) to the cathode may be adapted to suit the particular application . Commercially designed and produced instruments are available which are versatile enough to meet most laboratory requirements . Electrolytes suitable for metallographic purposes are usually mixtures of acids su eh as phosphoric, sulfuric, and perchloric in ionizing solutions such as water, acetic acid, or alcohol. Glycerol, butyl glycol, urea, etc . are added to in crease the viscosity . Metals which form highly soluble

.---l-----ct---~

Reslst or

-J Fig. 12. Electrolytic polishing cell in series mode .

/ Contolner wlth Electrolyte

~ Cooling Woter

hydroxides are prepared with alkaline solutions, while those forming highly soluble cyanides are treated in cyanides. Most of the electrolytes mentioned in Chapters 2 and 3 are harmless when handled according to known common-sense precautions . Mixtures of perchloric acid, however, are particularly prone to decompose violently and should, therefore, be treated with extreme careo (See Appendix A.) The tendency of perchloric acid mixtures to explode is related to tbe concentration . This is illustrated in Fig. 13 , the ternary diagram for perchloric acid, water, and acetic acid. Mixtures outside the irnmediate danger zone can undergo local changes in concentration by means of evaporation , temperature increase, contact with organic material, or contact with bismuth or sparks . If this occurs, the solution may move into the danger zone without the operator's awareness. To minimize such dangers, the electrolyte should be sti rred and cooled . In any case, and at all times, caution is advised when using perchloric acid. Significant parameters which affect the results of electropolishing are : • • • • • •

2

Current density (A/cm ) V oltage (V) Electrolyte composition, temperature , and flow rate Polishing time Initial condition of the specimen surface Cathode size, shape, and composition .

Most formulas in Chapters 2 and 3 specify these details; they are mitted when they are not critical or can easily be established by the operator.

Technical Tips for Preparation of Specimens 16

I

I

17

Technical Tips for Preparation of Specimens

generally preferred for rough polishing and medium-nap c10ths for final polishing. Abrasives are usually applied to c10ths in the form of paste suspensions or slurries.

Thermo

• Hard or firm support materials tend to promote deeper deformation . • More elastic support materials favor less deformation but increase the tendency to relief and edge rounding.

Microtome Cutting Microtome cutting employs a cemented carbide or diamond knife which mechanically slices a layer from the bulk material. Although the action of a microtome is similar to planing or milling, the principies of mechanical grinding and polishing still apply. High-quality cuts, free from deformation and flow , are possible with the micro tome only if the cutting angle is properly adjusted . This technique is particularly useful in cutting aggregate materials such as lamellar structures, having varying degrees of hardness. Microtome cutting is, however, restricted to materials of about 150 HV or less. Similar to microtome cutting is micromilling. Whereas the knife of a microtome removes a surface layer by cutting and acts like aplane, the micromill has a rotating milling head which removes layers 5 to 15 J..I-m in thickness with high precision . As with the cutting knife of the microtome, the milling tool of the milling device is made of either diamond or cemented carbide. Micromilling combines all grinding and polishing operations into one step and produces aplane surface of high quality with respect to scratches and surface damage. Electrolytic Grinding and Polishing Although electrolytic grinding and electroerosive grinding (Fig. 7) are seldom used, electrolytic polishing is commonly employed. Electrolytic polishing, also called anodic polishing, occurs through anodic dissolution of the specimen surface in an electrolytic cell . Figure 12 is a diagram showing a simple electrolytic cell that is easily set up in the laboratory. The orientation of the anode (sample) to the cathode may be adapted to suit the particular application . Commercially designed and produced instruments are available which are versatile enough to meet most laboratory requirements . Electrolytes suitable for metallographic purposes are usually mixtures of acids su eh as phosphoric, sulfuric, and perchloric in ionizing solutions such as water, acetic acid, or alcohol. Glycerol, butyl glycol, urea, etc . are added to in crease the viscosity . Metals which form highly soluble

.---l-----ct---~

Reslst or

-J Fig. 12. Electrolytic polishing cell in series mode .

/ Contolner wlth Electrolyte

~ Cooling Woter

hydroxides are prepared with alkaline solutions, while those forming highly soluble cyanides are treated in cyanides. Most of the electrolytes mentioned in Chapters 2 and 3 are harmless when handled according to known common-sense precautions . Mixtures of perchloric acid, however, are particularly prone to decompose violently and should, therefore, be treated with extreme careo (See Appendix A.) The tendency of perchloric acid mixtures to explode is related to tbe concentration . This is illustrated in Fig. 13 , the ternary diagram for perchloric acid, water, and acetic acid. Mixtures outside the irnmediate danger zone can undergo local changes in concentration by means of evaporation , temperature increase, contact with organic material, or contact with bismuth or sparks . If this occurs, the solution may move into the danger zone without the operator's awareness. To minimize such dangers, the electrolyte should be sti rred and cooled . In any case, and at all times, caution is advised when using perchloric acid. Significant parameters which affect the results of electropolishing are : • • • • • •

2

Current density (A/cm ) V oltage (V) Electrolyte composition, temperature , and flow rate Polishing time Initial condition of the specimen surface Cathode size, shape, and composition .

Most formulas in Chapters 2 and 3 specify these details; they are mitted when they are not critical or can easily be established by the operator.

18

/

Technical Tips for Preparation of Specimens

Tecllnical Tips for Preparation of Specimens

HCI04

• Commonly Used Eleetrolytes

-:s:-

c:'-

;\0

9

,,:

?

-\0

L

{ I ~- ,Me?:Me+++2e j Me

(5

D I 40H='02+ 2H20 +4e

:

Suilable : t+-Po/ishing Range.......- Oxygen_ I Formallon I

r

I

-Elé

~

iC-- Layer of Reaetion Produels

Polishing-----

..¡..

-

19

A typical idealized current density versus applied voltage relationship for many common eIectrolytes is shown in Fig. 14, with four characteristic regions noted:

----j.,80

"

/

Vo/tage in V

Fig. 14. Idealized current density versus applied voltage. See text for discussion.

A fo B. The anode material goes directly into solution. A liquid layer forms at the surface with a higher metal-ion concentration than is present in the rest of the solution. Electrolytic etching occurs in this area. 2 B fo C. It is assumed that formation of a thin layer of reaction products causes passivity. 3 e fo D. Polishing proceeds due to diffusion and electrochemical processes. 4 D fo E. Oxygen evolutioil occurs at a low rate, initially. Gas bubbles adhere to the surface of the anode and remain there for a relatively long time, with pitting as a resulto With increasing voltage, the rate of oxygen evolution increases and the bubbles remain for shorter periods of time, until they do not adhere at all.

A1though anodic polishing begins at point B of the curve, only between points C and O is there freedom from other negative effects (passivation, oxygen formation). Metallographic specimen preparatíon, therefore, is concerned with area C-O of the current density versus voltage curve. Region O-E is rarely used and then only in industrial applications. The different regions illustrated in Fig. 14 are not always clearly observed. Electrolytes of high specific resistance produce rather flat curves. The initial condition of the specimen surface has a definite influence on the polishing time. In general, the better the surface at the start and the higher the current density, the shorter the polishing time. Electrolytic polishing requires electrical conductivity of the sample material; this is the case for aH metals and aHoys, as well as for sorne nonmetals, such as carbides and graphite. In principIe, all homogeneous metals and alloys are suitable for electrolytic preparation; heterogeneous materials such as gray iron are not ideally suited for electropolishing due to electrochemical potentíal differences between the various phases . However, examples of electropolishing of heterogeneous alloys are becoming increasingly common. Sorne advantages of electropolishing are: • Freedom from deformation and flowed material • Rapidity and reproducibility. However, this is only valid if suitable conditions are established • No (or minimal) surface heating • Capability of sequential electroetching with the same instrument

20

/

Technical Tips for Preparation of Specimens

Technical Tips for Preparation of Specimens

• Possible removal of mechanical damage caused by mechanical grinding and polishing.

In spite of many advantages, chemical polishing is seldom used for metallographic preparation. This may be due to a lack of awareness by practicing metallographers, and by the limited number of published formulas .

• Edges are selectively attacked, producing a radius and resulting in poor edge preservátion. • Macroscopic out-of-flatness cannot be remedied. • Residues may be deposited on the surface during polishing. • Oxidarion of sorne specimens may interrupt the process. • If the mounting material is nonconductive, special mounting procedures are necessary to produce electroconductivity. • Coarse-grain materials are less suited for electropolishing. • Depressions may occur around inclusions because of the higher solution rates of the metallic material in that zone.

Combination Polishing Methods • When a single method of specimen preparation fails to produce the desired results, a combination of methods may work very well. Sorne examples are described below. Etch-Polishing Sequence. Flowed metal layers may be effectively removed by lightly etching and mechanical repolishing one or more times at the conclusion of final mechanical polishing. Attack-PoJishing. This consists of the simultaneous application of a chemical etchant during the final polishing sequence; it is especially use fuI in avoiding flow layers on soft metal s and alloys as well as refractory metals. Multiple'PoJishing. When electrolytic polishing is used with heterogeneous aIloys, sorne undesirable surface effects like relief formation or , surface layers may be produced. A brief intermediate mechanical polishing step may remo ve this condition and produce a satisfactory finish. Electrolytic Lapping. This is the simultaneous electrolytic and mechanical removal of material. In this technique, the specimen (anode) is held against a cloth saturated with electrolyte and mounted on a support or wheel which serves as the cathode . This method, illustrated in Fig. 15, is considered semiautomatic. Although direct current is most frequently used in electrolytic lapping, low-frequency alternating current produces superior results with sorne metals, such as molybdenum,

Chemical Polishing ¡:;,

• Simplicit" and economy • Liúle pre-preparation required; 320-grit finish is adequate; specimens cut with 'an abrasive cutoff wheel may be polished without further preparatión • Simple treatment after polishing; in most cases, rinsing in water 'is adequate • No deformation or flow lines produced • Specimen and/or mount need not be electrical conductors.

Polish ing Disc (Colhode)

Disadvantages of chemical polishing are: • Higher rate of attack at edges

21

• Orange-peel effect with coarse-grain materials • Only small-scale roughness may be smoothed out • Formation of a surface film composed of reaction products.

Restrictions on the use of electropolishing are imposed by the lack of etchants for many heterogeneous alloys as well as by the following disadvantages:

Chemical polishing is a process by which simple immersion of a specimen in a suitable polishing solution (electrolyte) produces a polished surface without the use of externally applied current. When the specimen is agitated in the polishing bath (seconds to minutes), surface roughness is removed and a deformation-free polished surface is produced. The polishing solutions almost always contain oxidizing agents such as nitrie, sulfuric, and chromic acids or hydrogen peroxide. Viscous agents are also added to control diffusion and convection rates, producing a more uniform process. Phosphoric acid, for example, forms a liquid film of high viscosity when reacting with metal ions. Most chemical polishing solu~ions are quite insensitive to concentration changes. The advan\ages of ehemical polishing are:

/

Fig. 15. Electrolytic lapping.

.. ,i'rj

I

¡;¡",~b l

+

20

/

Technical Tips for Preparation of Specimens

Technical Tips for Preparation of Specimens

• Possible removal of mechanical damage caused by mechanical grinding and polishing.

In spite of many advantages, chemical polishing is seldom used for metallographic preparation. This may be due to a lack of awareness by practicing metallographers, and by the limited number of published formulas .

• Edges are selectively attacked, producing a radius and resulting in poor edge preservátion. • Macroscopic out-of-flatness cannot be remedied. • Residues may be deposited on the surface during polishing. • Oxidarion of sorne specimens may interrupt the process. • If the mounting material is nonconductive, special mounting procedures are necessary to produce electroconductivity. • Coarse-grain materials are less suited for electropolishing. • Depressions may occur around inclusions because of the higher solution rates of the metallic material in that zone.

Combination Polishing Methods • When a single method of specimen preparation fails to produce the desired results, a combination of methods may work very well. Sorne examples are described below. Etch-Polishing Sequence. Flowed metal layers may be effectively removed by lightly etching and mechanical repolishing one or more times at the conclusion of final mechanical polishing. Attack-PoJishing. This consists of the simultaneous application of a chemical etchant during the final polishing sequence; it is especially use fuI in avoiding flow layers on soft metal s and alloys as well as refractory metals. Multiple'PoJishing. When electrolytic polishing is used with heterogeneous aIloys, sorne undesirable surface effects like relief formation or , surface layers may be produced. A brief intermediate mechanical polishing step may remo ve this condition and produce a satisfactory finish. Electrolytic Lapping. This is the simultaneous electrolytic and mechanical removal of material. In this technique, the specimen (anode) is held against a cloth saturated with electrolyte and mounted on a support or wheel which serves as the cathode . This method, illustrated in Fig. 15, is considered semiautomatic. Although direct current is most frequently used in electrolytic lapping, low-frequency alternating current produces superior results with sorne metals, such as molybdenum,

Chemical Polishing ¡:;,

• Simplicit" and economy • Liúle pre-preparation required; 320-grit finish is adequate; specimens cut with 'an abrasive cutoff wheel may be polished without further preparatión • Simple treatment after polishing; in most cases, rinsing in water 'is adequate • No deformation or flow lines produced • Specimen and/or mount need not be electrical conductors.

Polish ing Disc (Colhode)

Disadvantages of chemical polishing are: • Higher rate of attack at edges

21

• Orange-peel effect with coarse-grain materials • Only small-scale roughness may be smoothed out • Formation of a surface film composed of reaction products.

Restrictions on the use of electropolishing are imposed by the lack of etchants for many heterogeneous alloys as well as by the following disadvantages:

Chemical polishing is a process by which simple immersion of a specimen in a suitable polishing solution (electrolyte) produces a polished surface without the use of externally applied current. When the specimen is agitated in the polishing bath (seconds to minutes), surface roughness is removed and a deformation-free polished surface is produced. The polishing solutions almost always contain oxidizing agents such as nitrie, sulfuric, and chromic acids or hydrogen peroxide. Viscous agents are also added to control diffusion and convection rates, producing a more uniform process. Phosphoric acid, for example, forms a liquid film of high viscosity when reacting with metal ions. Most chemical polishing solu~ions are quite insensitive to concentration changes. The advan\ages of ehemical polishing are:

/

Fig. 15. Electrolytic lapping.

.. ,i'rj

I

¡;¡",~b l

+

22

/

Technical Tips for Preparation of Specimens Technical Tips for Preparation of Specimens

tungsten, and rhenium. Dilute solutions of sodium thiosulfate, nitnc acid, oxalic acid, piéric acid, and hydrogen peroxide are suitable for both electrolytic lapping and etching. The addition of abrasives such as alumina has no effect in most applications. Electrolytic lapping combines the advantages and disadvantages of electrochemical and mechanical polishing. It can be used for heterogeneous as well as homogeneous metals and alloys, and has pro ven successful as an addition to other methods; in sorne cases, it succeeds when electrolytic or mechanical polishing alone fails.

Automatic Grinding and Polishing Manual specimen preparation tends to be routine, monotonous, and even tedious. This is espeeially .true of mechanical polishing. When operators beeome tired and disinterested, the work they produce may decrease in quality and volume. Preparation errors are more likely to oecur, whieh can ultimately result in erroneous interpretations. Thus, it is understandable that again and again attempts have been made to automate the mechanieal fine grinding and polishing steps. Prior to 1950, manual preparation was the only means eonsidered . satisfactory for the sensitive grinding and polishing steps. Since then, there has be en a considerable upswing in the development of preeision instruments for automation of metallographie preparation. For the most part, these have been confined to individual steps; and, to this date, no satisfactory fully automatie system has been deve1oped. Speeimens must still be handled between steps, but the ideal system would be to insert samples at one end and remove completely polished specimens at the other end. This would be particularly helpful in preparing matefÍals requiring numerous lengthy steps. Nevertheless, the automation of the single steps inereases quality, volume, and uniformity by removing most of the physieal ef(ort from specimen preparation.

Evaluation of Po/~hing Methods Reflectivity of the finish-polished surfaee is one senslÍlve eriterion for judging quality. Deviations from the reflectivity of ideal surfaces with an atomie Toughness give an indication of the effeet of different polishing methods; for example, cleavage surfaces of crystals or surfaces of single crystals ' grown under an ultrahigh vaeuum are good referenee standards. Therefore, reflectivity is suitable in evaluating the effectiveness of in.dividual polishing methods. Figure 16 shows the mean deviation, in percentage of refleetivity, of polished surfaces from ideal surfaces of various materials. The base line represents refleetivity values for freshly cleaved surfaces-the ideal

~

Ir +, Cu++, Ag+, Hg++, Au+++, Pt+++ .

The elements are listed in order of decreasing electroaffinity. AH elements preceding hydrogen ar~ attacked by acids with the evolution of hydrogen (Hz). AH elements following hydrogen cannot be attacked without the addition of an oxidizing agent. Thus, microstructural elements of different electrochemical potentíal are attacked at different rates. This produces differentíal etching, resulting in microstructural contrast. Electrochemical etching maybe considered as "forced corrosion." The differences in potential of the microstructural elements cause a 'subdivision into a network of very small anodic or cathodic regions (local elements). These miniature ceHs cannot oríginate from differences in phase composition only, but also have to come from irregularities in the crystal structure as they are present-for example, at grain boundaries and from other inhomogeneities such as: • Inhomogeneities resulting fromdeformation (deformed zones), which are less resistant to attack than undeformed material. • Unevenness in the formation of oxidation layers (glossy areas are les s resistant). • Concentration fluctuation in the electrolyte (low concentration is less resistant). • Differences in eléctrolyte velocity (higher circulation rates reduce resistance to atta:ck). • Differenc~s in tlie oxygen content of the electrolyte (aerated solutions are more resistint). '

t

',.

* Reduction

...

l

= absorption of electrons (cathodic reaction) Oxidation = emission of eleétrons (anodic reaction) Oxidizing agent + electron ~ reducing agent Fe 3 + + 'e " ~ Fe 2 + Electrolytic grinding and polishing, chemical polishing, and some of the combined methods are based on redox processes. This is not always obvious from convention&1 terminology. ' tHydrogen electrode: a sheet of platínum surrounded by hydrogen at 1 atm pressure and imrnersed into an aqueous solulion ofhydrogen-ion activity aH = l. f

Technical Típs for Preparatíon of Specimens

I

27

• Differences in the illuminatíon intensity, which can initiate differences in potential. Because of differences in potential between microstructural features, dissolutibn of the surface proceeds at differentrates, producing contrast. Contrast can also originate from layers formed simultaneously with material dissolution. This is true in precipitation etching and ,heat tinting where surface reactions are involved. In precipitation (deposit) etching, the material is first dissolved at the surface; it then reacts with certain components of the etchant to form insoluble compounds. These compounds precipitate selectively on the surface, causing interference colors or heavy layers of a specific color. During heat tinting, coloration of the surface takes place at different rates according to the reaction characteristics of different microstructural elements under the given conditions of atmosphere and temperature. A wide variety of etchants is available, including acids, bases, neutral solutions, mixtures of solutions, molten salts and gases; many examples of these are given in Chapters 2 and 3. Most of these formulas were derived empirically. Their composition and mode of application can be easily varied and modified, and so also be usefulfor materials other than those mentioned in the formulas. The rate of attack is mainly determined by the degree of dissociation of the etchant and its electrical conductívity. Both are often influenced in a certain way by small additions of other chemicals. This may explain why many formulas contain small amounts of substances whose significance is not immediately apparent. The stability of many etching solutions is limited; redox potentials change with time. Changes may also occur while the etchant is in use, such that it must be discarded after a limited time. Btching times range from several seconds to some hours. When no instructions are given, progress is judged by the appearance of the surface during etching. Usually, the surface will become less refIective (duHer) as etching proceeds. Etching time and temperature are closely related; by increasing the temperature, the time can usually be decreased. However, this may not be advisable because the contrast could become uneven when the rate of attack is too rapid. Most etching is performed at room temperature. Sources of error are numerous, especially in electrochemical etching. Etching errors may lead to microstructural misinterpretation. For exampie, precipitates from etching or washing solutions could be interpreted as additional phases. Conventional chemical etching is the oldest and most commonly applied technique for producing microstructural contrast. In this technique, the

JI' ..

I

!Iij

't

28

lO

/

Technical Tips for Preparation of Specimens

etchant reacts witb the specimen surface without tbe use of an external cur¡-ent supply. Etching proceeds by selective dissolution according to the electrocbemical cbaracteristic of the component areas. ' In e/ectrolytic or anodic etching, an electrical potential is applied to the specimen by means of an external circuit. Figure 12 illusttates a typical setup consisting of tbe specimen (anode) and its counterelectrode (cathode) immersed in an electrolyte (etchant). During anodic etching, positive metal ions leave the specimen surface and diffuse into the electrolyte with an equivalent number of electrons remaining in the material. This results in a direct etching ,process shown as segment A-B of the current density versus voltage curve in Fig. 14. Sample dissolution of material without the formation of a layer occurs in this instance. If, however, the metal ions leaving the material react with nonmetal ions from the electrolyte with formation of an insoluble compound, precipitated layers ofvarying thickness will form on the specimen surface. The thickness of these layers is a function of the composition and orientation of the microstructural features exposed to the solution. These layers may reveal interference color hues due to variation ,in thickness, determined by the underlying microstructure. When this variation of electrolyticetcbingoccurs, it isreferred to as anodizing. Comparable nonelectrolytic processes are heat tinting and deposit etching. Potentiostatic etching is an advanced form of electrolytic etching, which produces the ultimate etching contrast through highly controlled conditions. The potential of the specimen, which would usually change with changes of electrolyte concentration, is maintained at a fixed level through the use of a potentiostat and suitable reference standards. Clearly pronounced contrast can be obtained with this method where tbis is otherwise not p0ssible. In some cases, tbe cell current can be maintained with a coulombmeter to determine the extent of etching (controlled etching). On completion of any chemical or electrochemical etching process, the specimen ihould be rinsed in clean water to remove the chemicals and Stol" any reactions from proceeding further. Sometimes, for example, in etching for, segregations usüíg the Oberhoffer metbod, it is advisable to rinse in alóohol first. Otherwise, copper could precipitate on the specimen surface because of the change in the degree of dissociation. After specimens are water rinsed, they should be rinsed in alcohol and dried in a stre,a m of warm air. The use of alcohol speeds up the drying, action and prevents the formation of water spots. If etching produces water-soluble layers, water must be avoided in the rinsing step. Mounted specimens musí be cleaned thorougbly to avoid the destructive effects of etchants and solvents seeping from pores, cracks, or clamp interfaces.

Technical Tips for PreparaÍion of Specimens

/

29

It may be helpful to use an ultrasonic cleaner to avoid these problems. If specimens are of a high porosity or if highly concentrated acids are used for etching (as for example, for deep etching), it is advisable to neutralize the chemicals befo re rinsing and drying the specimen.

Physical Etching

Basic physical phenomena are also oH en used to develop structural contrast, mainly when conventional chemical or electrolytic techniques fail. They have the advantage of °leaving surfaces free from chemical residues and also offer advantages where electrochemical etching is difficult-for example, when there is an extremely large difference in electrochemical potential between microstructural elements, or when chemical etchants produce ruinous stains or residues. Some probable applications of these methods are plated layers, welds joining highly dissimilar materials, porous materials, and ceramics. Cathodic vacuum etching, also referred to as ion etching, produces structural contrast by selective removal of atoms from the sample surface. This is accomplished by using high-energy ions (such as argon) accelerated by voltages of 1 to 10 kV. Individual atoms are removed at various rates, depending on the microstructural details such as crystal orientation ' of the individual grains, grain boundaries, etc. Thermal etching, used in high-temperature (hot-stage) microscopy, is also partly based on atoms leaving the material surface, as a result of additional energy. The predominant force in thermal etching, however, is the formation of slightly curved equilibrium surfaces having individual grains with minimum surface tension. Structural contrast produced by evaporated interference /ayers is often considered to be an optical method. Since no modification in the optical path of the microscope is made, it is considered here as a physical technique. Tbis is rational since the polished specimen is treated in a way which distinguishes it from optical etching. The surface of tbe speciInen is coated under vacuum with an evaporated layer of material, producing interference effects. High refractive index materials, such as ZnSe, Ti0 2 , etc., are commonly used. The effect of the evaporated interference layer is caused by multiple light reflection produced at the interface between object and evaporated layer (Fig. 19). Gas-reaction chambers are a recent development which permit precise control of evaporation during simultaneous microscopic observation. Specimen Storage

When polished and etched specimens are to be stored for long periods of tiIlle, they must be protected from atmospheric corrosion. Desiccators

28

lO

/

Technical Tips for Preparation of Specimens

etchant reacts witb the specimen surface without tbe use of an external cur¡-ent supply. Etching proceeds by selective dissolution according to the electrocbemical cbaracteristic of the component areas. ' In e/ectrolytic or anodic etching, an electrical potential is applied to the specimen by means of an external circuit. Figure 12 illusttates a typical setup consisting of tbe specimen (anode) and its counterelectrode (cathode) immersed in an electrolyte (etchant). During anodic etching, positive metal ions leave the specimen surface and diffuse into the electrolyte with an equivalent number of electrons remaining in the material. This results in a direct etching ,process shown as segment A-B of the current density versus voltage curve in Fig. 14. Sample dissolution of material without the formation of a layer occurs in this instance. If, however, the metal ions leaving the material react with nonmetal ions from the electrolyte with formation of an insoluble compound, precipitated layers ofvarying thickness will form on the specimen surface. The thickness of these layers is a function of the composition and orientation of the microstructural features exposed to the solution. These layers may reveal interference color hues due to variation ,in thickness, determined by the underlying microstructure. When this variation of electrolyticetcbingoccurs, it isreferred to as anodizing. Comparable nonelectrolytic processes are heat tinting and deposit etching. Potentiostatic etching is an advanced form of electrolytic etching, which produces the ultimate etching contrast through highly controlled conditions. The potential of the specimen, which would usually change with changes of electrolyte concentration, is maintained at a fixed level through the use of a potentiostat and suitable reference standards. Clearly pronounced contrast can be obtained with this method where tbis is otherwise not p0ssible. In some cases, tbe cell current can be maintained with a coulombmeter to determine the extent of etching (controlled etching). On completion of any chemical or electrochemical etching process, the specimen ihould be rinsed in clean water to remove the chemicals and Stol" any reactions from proceeding further. Sometimes, for example, in etching for, segregations usüíg the Oberhoffer metbod, it is advisable to rinse in alóohol first. Otherwise, copper could precipitate on the specimen surface because of the change in the degree of dissociation. After specimens are water rinsed, they should be rinsed in alcohol and dried in a stre,a m of warm air. The use of alcohol speeds up the drying, action and prevents the formation of water spots. If etching produces water-soluble layers, water must be avoided in the rinsing step. Mounted specimens musí be cleaned thorougbly to avoid the destructive effects of etchants and solvents seeping from pores, cracks, or clamp interfaces.

Technical Tips for PreparaÍion of Specimens

/

29

It may be helpful to use an ultrasonic cleaner to avoid these problems. If specimens are of a high porosity or if highly concentrated acids are used for etching (as for example, for deep etching), it is advisable to neutralize the chemicals befo re rinsing and drying the specimen.

Physical Etching

Basic physical phenomena are also oH en used to develop structural contrast, mainly when conventional chemical or electrolytic techniques fail. They have the advantage of °leaving surfaces free from chemical residues and also offer advantages where electrochemical etching is difficult-for example, when there is an extremely large difference in electrochemical potential between microstructural elements, or when chemical etchants produce ruinous stains or residues. Some probable applications of these methods are plated layers, welds joining highly dissimilar materials, porous materials, and ceramics. Cathodic vacuum etching, also referred to as ion etching, produces structural contrast by selective removal of atoms from the sample surface. This is accomplished by using high-energy ions (such as argon) accelerated by voltages of 1 to 10 kV. Individual atoms are removed at various rates, depending on the microstructural details such as crystal orientation ' of the individual grains, grain boundaries, etc. Thermal etching, used in high-temperature (hot-stage) microscopy, is also partly based on atoms leaving the material surface, as a result of additional energy. The predominant force in thermal etching, however, is the formation of slightly curved equilibrium surfaces having individual grains with minimum surface tension. Structural contrast produced by evaporated interference /ayers is often considered to be an optical method. Since no modification in the optical path of the microscope is made, it is considered here as a physical technique. Tbis is rational since the polished specimen is treated in a way which distinguishes it from optical etching. The surface of tbe speciInen is coated under vacuum with an evaporated layer of material, producing interference effects. High refractive index materials, such as ZnSe, Ti0 2 , etc., are commonly used. The effect of the evaporated interference layer is caused by multiple light reflection produced at the interface between object and evaporated layer (Fig. 19). Gas-reaction chambers are a recent development which permit precise control of evaporation during simultaneous microscopic observation. Specimen Storage

When polished and etched specimens are to be stored for long periods of tiIlle, they must be protected from atmospheric corrosion. Desiccators

30

/

Technical Tips for Preparation of Specimens

Technical Tips for Preparation of Specimens

and desiccator cab~ets are the most common means of specimen storage, although plastic coatings and cellophane tape are sometimes used.

Reproducibility in, Etching For the most part, metallographic etching continues to be an empirical method with overtones of black magic. This condition is the result of the' abundance of etching methods, nonuniform nomenclature and, frequentIy, the lack of knowledge concerning etchant mechanisms. For these reasons, it is difficult to present a cIear review of etching processes. Conventional etching, in particular, is difficult to reproduce, regardless of its simplicity. During the electrochernical processes, numerous side effects must be taken into account. For example, changes in the electrolyte and inhibiting reactions at the specimen surface must be considered, which cause polarization phenomena, overpotential, etc. With the goal of achieving more reproducible and dependable structural contrast, various new methods have been developed in recent years. Electrolytic potentiostatic etching, ion etching, and evaporation of interference layers are advanced methods gradually becoming accepted. The principIes by which these techniques operate are illustrated in Fig. 19. In the fírst two methods, the microstructure becomes visible through selective removal of the surface. In the last method, the contrast is produced by multiple refIection of the light beam in the evaporated layer of a material with high refractive indexo The development of more reproducible and contrasting etching methods is of particular importance for quantitative image analysis. These instruments are used to automatically determine the area fraction of various phases and are not sensitive to subtle differences. Therefore, sharply reproducible etching. contrast is necessary to obtain accurate information. + C ..d, = urií~:;:¡~~u¡.... . !::

;

'" '"

'C ;>

~

l.'"

-== '"'" :a='"=

",1++ 1 1 1+

'" + 1 1 1 + ;;; + + 1 1 1 +

='=-0,> :;~] o ·[~~.~ ",!:!os~ ..cqi~g¡ cQ)o~~~Q./ü 0 ..... S8_" K ·.::;:O ..... '-''''C''tjf.nG) u¡::':=-¡gc::os S ~9V1o==~a o '...... =.~ rJl Q) ... ~ t) gb.g td "'C E3 ~ E c;g~-

00 111 11+++ 1 1+++1+1+++ ~ 11+++++++++++++++++ ~+ 11111+++1++++++1+ 1 1 ~++1 1 1 111+++1++++++1+++ ~1 1 1 I 1111++++1++++++1+++ -:> _::::::_:>:>+1 ~1 1 1 111111++++1++++++++++ ~I 1 1 1111111++++1++++++++++ =11+11111111++++1++++++++++ S++++++++++I+++++++++I 1 1 1++1 '" 1 +++++++++++ 1 +++++ 1 +++++++ 1 + 00+++++++++++++++++++++++++++++ r- 1 ++++++++++ 11 +++++++++++++++++ -0+++++++++++++++++++++++++++++++ ~I+++++++++++++++++++++++++++++++ ~++++++I 1 1 1++1+++11++++11+++++1+++ ~I+++++++++++++I 1 1+++++++++++++++++ ",+++++++++++++++1+1+1++++11++11+++++ _1++++++++++++++++11++1++++++++++1+++

.~

~

~

•

l ·!:! Q

~

~

:c'"

~

QI)

bO = .f _ j : au bD t) bI)"" .SbD,-.. ~Su

bO :au c::bO

bO ,S ~ bO = ~ .9tIO bO ~ fj:a _ u . ~.. ..c: c:: U "'..c::: wu (.) bI) ' -

d " : : : ' oooI

bO .§ ~ bO I .o .S _ ~ c:: c::bO ..s= o :.aC:lti .- " '_~13 .= bO .... . B'Q) bO.5' o~ ~_vB ·5bOvd-5 Q) .... .... b.O bO..... b.Q ... ..::: = d ..d o =..c:: bO t..:I CIl el.) u..d = '- ... c::bObO""bObOc::C::"=bO :;~] o ·[~~.~ ",!:!os~ ..cqi~g¡ cQ)o~~~Q./ü 0 ..... S8_" K ·.::;:O ..... '-''''C''tjf.nG) u¡::':=-¡gc::os S ~9V1o==~a o '...... =.~ rJl Q) ... ~ t) gb.g td "'C E3 ~ E c;g~-

00 111 11+++ 1 1+++1+1+++ ~ 11+++++++++++++++++ ~+ 11111+++1++++++1+ 1 1 ~++1 1 1 111+++1++++++1+++ ~1 1 1 I 1111++++1++++++1+++ -:> _::::::_:>:>+1 ~1 1 1 111111++++1++++++++++ ~I 1 1 1111111++++1++++++++++ =11+11111111++++1++++++++++ S++++++++++I+++++++++I 1 1 1++1 '" 1 +++++++++++ 1 +++++ 1 +++++++ 1 + 00+++++++++++++++++++++++++++++ r- 1 ++++++++++ 11 +++++++++++++++++ -0+++++++++++++++++++++++++++++++ ~I+++++++++++++++++++++++++++++++ ~++++++I 1 1 1++1+++11++++11+++++1+++ ~I+++++++++++++I 1 1+++++++++++++++++ ",+++++++++++++++1+1+1++++11++11+++++ _1++++++++++++++++11++1++++++++++1+++

.~

~

~

•

l ·!:! Q

~

~

:c'"

~

QI)

bO = .f _ j : au bD t) bI)"" .SbD,-.. ~Su

bO :au c::bO

bO ,S ~ bO = ~ .9tIO bO ~ fj:a _ u . ~.. ..c: c:: U "'..c::: wu (.) bI) ' -

d " : : : ' oooI

bO .§ ~ bO I .o .S _ ~ c:: c::bO ..s= o :.aC:lti .- " '_~13 .= bO .... . B'Q) bO.5' o~ ~_vB ·5bOvd-5 Q) .... .... b.O bO..... b.Q ... ..::: = d ..d o =..c:: bO t..:I CIl el.) u..d = '- ... c::bObO""bObOc::C::"=bO,

~:.''"

/

93

1"

"

wheel covered by moistened velvet or felt. Finish with high pressure. Clean sample under running water inimediately after polishing. f. With electrically conductive ceramics (for example, carbides), electrolytic polishing is possible. The etchants listed below are often suitable for electrolytic polishing. Polishing times are six to ten times the 'etching time.

No.

.'

Preparation of Oxides

Oist. water O m18 Glacial acetic acid (1.84) Hydrofluoric acid O ml9 (40%) Nitric acid (1.40) (Concentration variab1e)

15 mi 5 min to 2 h. Boiling. 85 mI 10(100) mI 3·s to 5 min, room 10(15)ml tempe'rature to 60 oC (140 °F). 1 min to 2 h. 1-2 min, 60 OC (140°F). 50(1O)m! 1-5 min, boiling. 50(1)ml 1-5 min, 30 oC (85 °P). lO sec, 30 oC (85 °P). 100 mI Secs to mins.

MgO. Th02 (!!!). Al,NiO., Pu0 2 (gamma, sintered) (!!!). yp,-ZrO, and Srn,O,-ZrO, mixtures. AI20,. Relief formation. MgO, V0 2 (!!!).

AlzO" VO, (!!!). ThO,(!!!), AI,O,-MgO mixtures ZrO z· V,08 (!!!). Conceritration in parentheses for Nd,O,. ZnO.

5m! S- lO min, 60-80 oC 10(l) ml (140-180°F). 50(30) mi !!! See Appendix A. 10 min, boiling. 30 s to 1 min, boiling.

20 (100) mI 5-15 min. Oist. water O 20(90)m! !!! See Appendix A. m20 Nitric acid (1.40) Rydrofluoric acid 1O(10)rn1 (40%) 7 min to 2 h. Rydrochloric acid O 10 m! !!! See Appendix A. m21 (1.19) Rydrofluoric acid 3 mI (40%) 1-11 min Rydrogen peroxide O 1 (10) mI m22 .(30%) 10(1) m! Sulfuric acid (1 .84) (Concentration variable) 9 mi Secs to mins. Oist. water O 1 mI m23 Nitric acid (1.40) Rydrogen peroxide 2m! (30%) 15-70 sec aqueous sol. of Sato O m24 sodium sulfide

VO, (!!!). Th,VP2 (!!!).

PuO" cast (!!!). PuO, (gamma, sintered) (!!!) CeO" SrTiO, . AI,O, . ZrO-ZrC mixtures.

BaTiO, . BaTi,07'

VO,. VO,-PuF,. VO,-V.O. and V0 2CeO, mixtures (!!!).

V.o. (!!!).

CaO.

94

/

100 mI 3- 5 min, 60 oC (140 °F). 25-50 g Prewarm sample in water.

Dist. water O m25 Ammonium hydrogen fluoride Lactic acid (90%) O m26 Nitric acid (1.40) Hydrofluorie aeid (40%)

90 mi 10 min to 1 h, 15 mi 65 oC (150 °F) . !!! See Appendix A. 5 ml

Dist. water O m27 Nitrie aeid (1.40) Hydrofluorie aeid (40%) Cerium (IV) nitrate

80 mi Secs to mins , 20 mi !!! See Appendix A.

100 mI 1 mino !!! See Appendix A. 3 mI

15 mI 10 mi 20 mi Ig

O Elllctrolytic: m30 Dist. water Cone. aqueous oxalie acid Cone. aqueous eitrie aeid Laetie aeid (90%) Ethanol (96%) Phosphoric aeid (1.71)

Hydrofluorie acid (40%) Glacial aeetie ~eid

"".. No.

10-15 V de, I Ajcm2, stainless steel eathode . 60-90 s (eteh). 30-50 s (polish). !!! See Appendix A.

35 mi 3 s to 6 min, 17- 20 V de, stainless 'steel 30 mi eathode. !!! See Appendix A. 30 mi 10 mi 60 mi

U02 -PU02 mixtures (!!!).

MgO-AI, 0 3-SiO, Zr02 mixtures.

U0 2 (!!!).

Hydrogen sulfide

C m4

Thermal etching

C m5

Sodium or potassium bícarbonate melt

!!! See Appendix A.

C m6

Sodium tetraborate melt

Few mins. !!! See Appendix A.

C m7

Nitrie acid (1.40)

Sees to mins.

C m8

Dist. water Nitrie acid (1.40)

C m9

Nitrie aeid (1.40) Hydrofluorie aeid (40%)

10(30) mI Sees to mins. !!! See Appendix A. 10 (10) mi

Dist. water C mIO Nitrie acid (1.40) Hydrofluorie acid (40%)

10 mi Secs to mins. 10 mI GlyeeroI instead of disto water. 10 mi !!! See Appendix A.

cre, HCC .

Hydrofluoric acid C mll (40%) Nitrie aeid (1.40) Lactie acid (90%)

Secs to mins. 10 mi !!! See Appendix A . · 10 mi 20 mi

Ta(C,N,O).

60-70 mi 30-45 s, 2-4 mA/em2 , I '. 6-12 V de, stainless 25 mi steel eathode ~ 25 mi !!! See Appendix A.

• " l.

Etehant

Conditions

. ....

Air

e

Dry, high-purity argon

~-

_ t

Carbides Remarks

10 min to 24 h, 20- 25 oC (70-80 0F).

ThC (!!!).

20min to 24 h, 20-25 oC (70-80 0 F).

Th02 (!!!).

I :

¡ .

~

'~ '.

\\;

95

KC.

3 :$ 10- torr, 1200 oC (2200 °F).

SiC.

10 min, molten salt.

SiC. SiC. UC-Cr23 C6 mixtures

(!!!).

lO mi Secs to mins . 10 mi 1-45 min o

10 mi Sees to mins. 10 mi 10 mi Swab. Few drops oC oxalic aeid or hydrofluorie aeid (40%). !!! See Appendix: A .

NiO.

/

!!! See Appendix A.

Dist. water C ml2 Nitrie acid (1.40) Glacial acetic acid

Nb oxides . NbO (blue), Nb0 2 (eyan), Nb2 0 S (reddish-brown).

12-30 s.

C m3

5 mi

C mi m2

BeO (! !!).

0.5 mi

Electrolytic: O m29 Dist. water Sulfurie acid (1.84) Glacial aeetie acid Chromium (VI) oxide

Electrolytic: O m31 Dist. water

BeO (!!!).

3 drops 1g

MethanoI (95 %) O rD28 Hydroehlorie acid (1.l9) Hydrofluorie acid (40%)

{I

Preparation of Carbides

Preparation of Oxides

(Th,U)C (!!!) with U jTh ratio < 3. ThC2 (!!!). (Fe,Si)C. Coneentration in parentheses for TaC.

VC, (Al, Ti)C.

UC, U(C,O), UCUC UC,-U2C3 " mixtures. (U,Pu)C high in C. U(C,N), UC-ZrC mixtures (!!!).

Dist. water C. m 13 Nitrie acid (1.40) Hydroehlorie aeid (1.l9)

25 mi Sees to mins. 25 mi

Nitrie acid (1.40) C ml4 Hydroehlorie acid (1.19) Sulfurie aeid (1.84)

10 mi Sees to mins. Hydrofluorie aeid 10 mi (40%) can be used in10 mi stead of hydroehlorie acid. !!! See Appendix: A .

TaC.

Secs to mins .

Wc.

C Hydrochlorie aeid mI5 (1.19) Hydrogen peroxide (30%) Dist. water C ml6 Formie aeid (1.22)

ThC (!!!).

Iml

10 mi 10 mi 10 mi 4 10 mi

S.

UC-Pu mixtures (!!!).

94

/

100 mI 3- 5 min, 60 oC (140 °F). 25-50 g Prewarm sample in water.

Dist. water O m25 Ammonium hydrogen fluoride Lactic acid (90%) O m26 Nitric acid (1.40) Hydrofluorie aeid (40%)

90 mi 10 min to 1 h, 15 mi 65 oC (150 °F) . !!! See Appendix A. 5 ml

Dist. water O m27 Nitrie aeid (1.40) Hydrofluorie aeid (40%) Cerium (IV) nitrate

80 mi Secs to mins , 20 mi !!! See Appendix A.

100 mI 1 mino !!! See Appendix A. 3 mI

15 mI 10 mi 20 mi Ig

O Elllctrolytic: m30 Dist. water Cone. aqueous oxalie acid Cone. aqueous eitrie aeid Laetie aeid (90%) Ethanol (96%) Phosphoric aeid (1.71)

Hydrofluorie acid (40%) Glacial aeetie ~eid

"".. No.

10-15 V de, I Ajcm2, stainless steel eathode . 60-90 s (eteh). 30-50 s (polish). !!! See Appendix A.

35 mi 3 s to 6 min, 17- 20 V de, stainless 'steel 30 mi eathode. !!! See Appendix A. 30 mi 10 mi 60 mi

U02 -PU02 mixtures (!!!).

MgO-AI, 0 3-SiO, Zr02 mixtures.

U0 2 (!!!).

Hydrogen sulfide

C m4

Thermal etching

C m5

Sodium or potassium bícarbonate melt

!!! See Appendix A.

C m6

Sodium tetraborate melt

Few mins. !!! See Appendix A.

C m7

Nitrie acid (1.40)

Sees to mins.

C m8

Dist. water Nitrie acid (1.40)

C m9

Nitrie aeid (1.40) Hydrofluorie aeid (40%)

10(30) mI Sees to mins. !!! See Appendix A. 10 (10) mi

Dist. water C mIO Nitrie acid (1.40) Hydrofluorie acid (40%)

10 mi Secs to mins. 10 mI GlyeeroI instead of disto water. 10 mi !!! See Appendix A.

cre, HCC .

Hydrofluoric acid C mll (40%) Nitrie aeid (1.40) Lactie acid (90%)

Secs to mins. 10 mi !!! See Appendix A . · 10 mi 20 mi

Ta(C,N,O).

60-70 mi 30-45 s, 2-4 mA/em2 , I '. 6-12 V de, stainless 25 mi steel eathode ~ 25 mi !!! See Appendix A.

• " l.

Etehant

Conditions

. ....

Air

e

Dry, high-purity argon

~-

_ t

Carbides Remarks

10 min to 24 h, 20- 25 oC (70-80 0F).

ThC (!!!).

20min to 24 h, 20-25 oC (70-80 0 F).

Th02 (!!!).

I :

¡ .

~

'~ '.

\\;

95

KC.

3 :$ 10- torr, 1200 oC (2200 °F).

SiC.

10 min, molten salt.

SiC. SiC. UC-Cr23 C6 mixtures

(!!!).

lO mi Secs to mins . 10 mi 1-45 min o

10 mi Sees to mins. 10 mi 10 mi Swab. Few drops oC oxalic aeid or hydrofluorie aeid (40%). !!! See Appendix: A .

NiO.

/

!!! See Appendix A.

Dist. water C ml2 Nitrie acid (1.40) Glacial acetic acid

Nb oxides . NbO (blue), Nb0 2 (eyan), Nb2 0 S (reddish-brown).

12-30 s.

C m3

5 mi

C mi m2

BeO (! !!).

0.5 mi

Electrolytic: O m29 Dist. water Sulfurie acid (1.84) Glacial aeetie acid Chromium (VI) oxide

Electrolytic: O m31 Dist. water

BeO (!!!).

3 drops 1g

MethanoI (95 %) O rD28 Hydroehlorie acid (1.l9) Hydrofluorie acid (40%)

{I

Preparation of Carbides

Preparation of Oxides

(Th,U)C (!!!) with U jTh ratio < 3. ThC2 (!!!). (Fe,Si)C. Coneentration in parentheses for TaC.

VC, (Al, Ti)C.

UC, U(C,O), UCUC UC,-U2C3 " mixtures. (U,Pu)C high in C. U(C,N), UC-ZrC mixtures (!!!).

Dist. water C. m 13 Nitrie acid (1.40) Hydroehlorie aeid (1.l9)

25 mi Sees to mins. 25 mi

Nitrie acid (1.40) C ml4 Hydroehlorie acid (1.19) Sulfurie aeid (1.84)

10 mi Sees to mins. Hydrofluorie aeid 10 mi (40%) can be used in10 mi stead of hydroehlorie acid. !!! See Appendix: A .

TaC.

Secs to mins .

Wc.

C Hydrochlorie aeid mI5 (1.19) Hydrogen peroxide (30%) Dist. water C ml6 Formie aeid (1.22)

ThC (!!!).

Iml

10 mi 10 mi 10 mi 4 10 mi

S.

UC-Pu mixtures (!!!).

96

/

P'.patal;o. o. Ca,b;d.,

C m 17 C ml8

Glacial acetic acid . Phosphoric acid (1.71) Ethylene glycol (1.11) Ethanol (96%) Phosphoric acid (1.17) C Dis!. water ml9 SodiUIn hydroxide Potassium ferricyanide C E/ectro/ytic: m20 Aqueous sol. (8%) of sodium hydroxide Phosphoric acid (1.71) Sulfuric acid (1 84) Copper (11) sulfate 'C E/ectrolytic: m21 Same as C ml2

C E/ectrolytic: m22 Same as C m17

.l

10 mi 10 mi 8 mi 5 mi 5 mi 100 mi 10 mi 10 g

8-10 min

(Th,U)C 2 (!!!).

5.,.60 s. Swab. n! See Appendix A. 2- 20 min, 50 oC (120 0 P). !!! See Appendix A.

(U,Pu)C (!!!).

. Up to 50 s, 80 mAlcm2 , stainless steel cathode.

3-5 s, 5-7 V, dc, stainless steel cathode.

C E/ectro/ytic: m24 Lactic acid (90%) o Nitric acid(1.40) Hydrofluoric acid (40%)

50 m1 S . ecsto mms. 30 mi 20-25 "C (70-80 0F), 17-20 V dc, stain8 mi less steel cathode. !!! See Appendix A.

C Electro/y tic: m25 Dist. water Potassium hydroxide

, :'

. .t .

i

C '€~ectrolytlc: • " \. m26 DIst.. water.. GlacIal. acetlc aCld. . ChromlUm (VI) OXIde' C Electroly lic: '" :' m27 Dist. water Butyl glycol Phosphoric acid (1.71)

~~I

p.uC (dend") ntIc (",) ... .

tio. of NII,ld..

/

NItndes

l.

No. Etchant Conditions Remarks N Hot etching in dry 5 h, 1600 oc (2900 °P). Si3N•. mi high-purity Variable. ___ nt_·tr_o.:::g:.-en_ _ _ _~_ _ _ _ _ _ _ _ _ _ _ _ _ _ __ N Hot etching in dry 3 h, 1650 oC (3000 °P). UN (!!!). m2 high-purity !!! See ~ppendix A. _ _-,hy:...d_r~o:::.ge_n_ · _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ N

m3 N

m4 N m5 N

m6 ThC2 (!!!).

.......

m7

N m8 (U,Pu)C highin U. UC-PuN mixtures (!!!).

NbC , NbC'2' N m9

Thermal etching

-18 h, 1650 oC (3000 °P) :S 10-5 torr . " PotasslUm carbonate 95.4 g 1-4 mm, molten salto Sodium fluoride 12 g !!! See Appendix A. Phosphoric acid (1.71) 5-1.5. min. BoIlmg. Hydrofluoric acid 10-15 mino (40%) !!! See Appendix A. Dist. water 10 mi Secs to mins. Glacial acetic acid 10 mi Nitric acid (1.40) 10 mi Lactic acid (90%) 10 mi 30 s to I mino Nitric acid (1.40) 10 mi After etching Cor 30 s, add 7 drops oC hydrofluoric acid (40%). !!! See Appendix A. 3 ~in, 40 oC (100 o~ wlthout hydrofluoflc ac'd I . Dist. water 60 mi 30 s, lO oC (50 °P). Glacial acetic acid 600 mi !!! See Appendix A. Chromium (VI) oxide 50 g

E/eclrolytic: mIO Sulfuric acid (1.84) Phosphoric acid (1.71) Glycerol N Electrolytic: mil Glacial acetic acid Chromium (VI) oxide

UN (!!!). SI3N•. Si3N•. UN (!!!). Si3 N•. (AI,Ti)N.

UN, UN-U 2N) tures (!!!).

ffiÍX-

U~-U(N2?{-U2N3 mIXtures ( ... ) UN (!!!).

N

PotasslUm hY~,roXlde .

.'\

• 2

..

N I min, 30-35 V, dc,

C E/ectro/ytic: m23 Sato aqueous sol. of arnmonium acetate

.

2

30 s, 25 oC (80 °P), 3.5 TiC. 80 mi V dc, 0.9 Alcm1 , 80 mi Cu cathode. 10 l 10 :

stainless steel cathode.

. .

MoC , CrC

¡-

10 mi 2-30 s, 2 V dc, 302 g 60 mAlcm2 ¡ Pt cathode. Move specimen. 20 ~, 6 V dc, I Al cm . 2 0.1 g 40 ':1 dc, 3 Al cm , stainless steel cathode. 7 mi I min, 20 V dc, stain133 mi less steel cathode. 25 g !!! See Appendix A.

TiC, TaC.

. SIC. B,C. PuC (!!!).

I mi 20-40 s, 5-10 V de, (U,Pu)C high in Pu 6 mi 10-15 mAlcm2 , (!!!). 3 mi stainless steel cathode.

Electrolytic: ml2 Dist. water Ethanol (96%) Sat. aqueous sol. of oxalic acid Sat. aqueous sol. oC citric acid Lactic acid (90%) Phosphoric acid (1.71)

10 mi 3-10 s, 4 V dc, stain30 mi less steel cathode. 30 nIi !!! See Appendix A.

UN (!!!).

18 mi 4 s, 40 V dc, stainI g less steel cathode. !!! See Appendix A.

UN-U2 N) mixtures

35 mi Secs to mins. 60 mi 17-20 V dc, stainless steel cathode. 3 mi !!! See Appendix A.

NbN (yeUow). Nb2N (light red).

(!!!).

N

3 mi lO mi 5 mi

'TI

96

/

P'.patal;o. o. Ca,b;d.,

C m 17 C ml8

Glacial acetic acid . Phosphoric acid (1.71) Ethylene glycol (1.11) Ethanol (96%) Phosphoric acid (1.17) C Dis!. water ml9 SodiUIn hydroxide Potassium ferricyanide C E/ectro/ytic: m20 Aqueous sol. (8%) of sodium hydroxide Phosphoric acid (1.71) Sulfuric acid (1 84) Copper (11) sulfate 'C E/ectrolytic: m21 Same as C ml2

C E/ectrolytic: m22 Same as C m17

.l

10 mi 10 mi 8 mi 5 mi 5 mi 100 mi 10 mi 10 g

8-10 min

(Th,U)C 2 (!!!).

5.,.60 s. Swab. n! See Appendix A. 2- 20 min, 50 oC (120 0 P). !!! See Appendix A.

(U,Pu)C (!!!).

. Up to 50 s, 80 mAlcm2 , stainless steel cathode.

3-5 s, 5-7 V, dc, stainless steel cathode.

C E/ectro/ytic: m24 Lactic acid (90%) o Nitric acid(1.40) Hydrofluoric acid (40%)

50 m1 S . ecsto mms. 30 mi 20-25 "C (70-80 0F), 17-20 V dc, stain8 mi less steel cathode. !!! See Appendix A.

C Electro/y tic: m25 Dist. water Potassium hydroxide

, :'

. .t .

i

C '€~ectrolytlc: • " \. m26 DIst.. water.. GlacIal. acetlc aCld. . ChromlUm (VI) OXIde' C Electroly lic: '" :' m27 Dist. water Butyl glycol Phosphoric acid (1.71)

~~I

p.uC (dend") ntIc (",) ... .

tio. of NII,ld..

/

NItndes

l.

No. Etchant Conditions Remarks N Hot etching in dry 5 h, 1600 oc (2900 °P). Si3N•. mi high-purity Variable. ___ nt_·tr_o.:::g:.-en_ _ _ _~_ _ _ _ _ _ _ _ _ _ _ _ _ _ __ N Hot etching in dry 3 h, 1650 oC (3000 °P). UN (!!!). m2 high-purity !!! See ~ppendix A. _ _-,hy:...d_r~o:::.ge_n_ · _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ N

m3 N

m4 N m5 N

m6 ThC2 (!!!).

.......

m7

N m8 (U,Pu)C highin U. UC-PuN mixtures (!!!).

NbC , NbC'2' N m9

Thermal etching

-18 h, 1650 oC (3000 °P) :S 10-5 torr . " PotasslUm carbonate 95.4 g 1-4 mm, molten salto Sodium fluoride 12 g !!! See Appendix A. Phosphoric acid (1.71) 5-1.5. min. BoIlmg. Hydrofluoric acid 10-15 mino (40%) !!! See Appendix A. Dist. water 10 mi Secs to mins. Glacial acetic acid 10 mi Nitric acid (1.40) 10 mi Lactic acid (90%) 10 mi 30 s to I mino Nitric acid (1.40) 10 mi After etching Cor 30 s, add 7 drops oC hydrofluoric acid (40%). !!! See Appendix A. 3 ~in, 40 oC (100 o~ wlthout hydrofluoflc ac'd I . Dist. water 60 mi 30 s, lO oC (50 °P). Glacial acetic acid 600 mi !!! See Appendix A. Chromium (VI) oxide 50 g

E/eclrolytic: mIO Sulfuric acid (1.84) Phosphoric acid (1.71) Glycerol N Electrolytic: mil Glacial acetic acid Chromium (VI) oxide

UN (!!!). SI3N•. Si3N•. UN (!!!). Si3 N•. (AI,Ti)N.

UN, UN-U 2N) tures (!!!).

ffiÍX-

U~-U(N2?{-U2N3 mIXtures ( ... ) UN (!!!).

N

PotasslUm hY~,roXlde .

.'\

• 2

..

N I min, 30-35 V, dc,

C E/ectro/ytic: m23 Sato aqueous sol. of arnmonium acetate

.

2

30 s, 25 oC (80 °P), 3.5 TiC. 80 mi V dc, 0.9 Alcm1 , 80 mi Cu cathode. 10 l 10 :

stainless steel cathode.

. .

MoC , CrC

¡-

10 mi 2-30 s, 2 V dc, 302 g 60 mAlcm2 ¡ Pt cathode. Move specimen. 20 ~, 6 V dc, I Al cm . 2 0.1 g 40 ':1 dc, 3 Al cm , stainless steel cathode. 7 mi I min, 20 V dc, stain133 mi less steel cathode. 25 g !!! See Appendix A.

TiC, TaC.

. SIC. B,C. PuC (!!!).

I mi 20-40 s, 5-10 V de, (U,Pu)C high in Pu 6 mi 10-15 mAlcm2 , (!!!). 3 mi stainless steel cathode.

Electrolytic: ml2 Dist. water Ethanol (96%) Sat. aqueous sol. of oxalic acid Sat. aqueous sol. oC citric acid Lactic acid (90%) Phosphoric acid (1.71)

10 mi 3-10 s, 4 V dc, stain30 mi less steel cathode. 30 nIi !!! See Appendix A.

UN (!!!).

18 mi 4 s, 40 V dc, stainI g less steel cathode. !!! See Appendix A.

UN-U2 N) mixtures

35 mi Secs to mins. 60 mi 17-20 V dc, stainless steel cathode. 3 mi !!! See Appendix A.

NbN (yeUow). Nb2N (light red).

(!!!).

N

3 mi lO mi 5 mi

'TI

98

l'

/ Preparation of Borides, Phosphides and Sulfides

~

"

Borides No .

Etehant

Conditions

Remarks

B mi

Laetie aeid Nitrie aeíd (1.40) Hydrofluorie aeid (40%) -

30 mi Sees to mins. 10 mI Instead .of laetic aeid, lO mi glycerol can be 10 mi used.

ZrB2 • TiB 2 •

B m2

Hydroéhlorie aeid (1.19) Nitrie aeíd (1.40)

1-5 min 10 mi 40 oC (lOO °F), vapor 10 mi etehing.

CrB2 • MoB 2 •

B m3

Hydroehlorie aeíd (1.19) Nitrie aeid (1.40)

B m4

Hydroehlorie aeid (1.19) Nitrie aeíd (1.40) Hydrofluoríe aeid (40%)

B m5

Oist. water Hydrofluorie aeid (40%) Nitrie aeíd (1.40)

10 mi Sees to mins. !!! See Appendix A. 10 mi 10 mi

ZrB

B m6

Oist. water Sulfurie aeid (1.84)

IOml 15 Iml

TiB 2 •

B m7

Electrolytic: Oist. water Sodium hydroxide

15 s

9 s, 3{).4() oC (85-100 6 mi ~F) . 2 mi !!! See Appendix A.

10 mI Sees to mins, 10-15 1-2 g V de, stainless steel cathode.

HfB 2 -NbB 2 mixtures.

2•

TaB 2 • LaB •.

P mi p m2

•, t

Laetie aeid (90%)

(40~)

Nitrie aeid (1.40) Sulfurie aeid (1.84) p m3

Hydroehloric aeíd (1.19)

P

Hydrogen peroxide (30%) Sulfurie aeid (1.84)

m4

,;1

'¡ '

• "l,

'.,

lO mi Sees to mins. !!! See Appendix A . 10 mi 20 mi . 20 mi

Secs to mins. 10 mI I mi

Etehant

Conditions

Remarks

2.5 h, 1500 oC (2730 °F). !!! See Appendix A.

U02 -Mo (!!!).

el m2

Hydrogen sulfide

15-30 s, room temperature. !!! See Appendix A.

U0 2-Cr (!!!).

et m3

a. Oist. water Potassium ferrieyanide b. Oist. water Potassium or sodíum hydroxide (Coneentration varí- ' able)

et m4

Nitrie aeid (1.40)

et m5

Oist. water Nitrie aeíd (1.40) Hydrofluorie aeíd (40%)

100 mi Mix (a) and (b) in ratio 1: 1 before use. IOg 1-4 mino 100 mi !!! See Appendix A. IOg

Sees to mins.

Zr0 2-W. Th0 2-W (!!!). W2C-W. UC-Cr (!!!). UC-Fe (!!!). UC-Ni (!!!). UC-UFe2 (l!!).

Cr23 C.-UFe2 (!!!). US-U (!!!). UC2-UNí,

US (!!!).

L

50 (10) mi Sees to mins. 30(10)ml !!! See Appendix A. 10 (10) mi

TiN-Co, TiN-Fe. TiN-Mo, TiN-W. eoneentrations in parentheses for HfCHf.

et m6

Oist. water Nitrie aeid (1.40) Glacial aeetie aeid

US-Co, UC2 -Fe, lO mI Sees to mins. lO mI Possibly several (UZr)C-Nb, (UZr)C10 mi drops oC hydrofluorie Ta, (UZr)C-W (!!!) . aeid (40%) !!! See Appendix A.

et m7

Nitrie aeid (1.40) Sulfurie aeid (1.84) Hydrofluorie aeid (40%)

lO mi Sees to mins. 20 mI !!! See Appendix A.

et m8

Ois!. water Nitrie aeíd (1.40) Hydroehlorie aeid (1 .19)

50 mI Sees to mins. 47 mi

et m9

Hydrofluorie aeid (40%) Nitrie acid (1.40) Laetie aeíd (90%)

1-5 mino 50 mi !!! See Appendix A. 50 mi 3 mI

UO (!!!).

6-12 S . CdS. Boiling, vapor etehing.

't_. , ''''

PbS.

Hot etehing in dry, high-purity hydrogen

Remarks PuP (!!!), PuS (!!!).

\

Oist. water Hydrofluorie aeid

99

(!!!).

eonditions Sees to mins.

30 mi 1- 10 min, 60 oC (140 °F) 10 mi Ig

Ct mi

1

I

Etehant

/

Cermets No.

Phosphides and SuJfides No.

Oist. water Hydroehlorie aeíd (1.19) Oimethylene thiourea

_,o

Iml

S.

p m5

~;;'

TiB 2 •

100 mi 10 mi

Preparation of Cermets

, .. :;

NbCz-NbFe-Nb.

10 mI TiC-Ni.

3 mI U02 -Nb (!!!).

98

l'

/ Preparation of Borides, Phosphides and Sulfides

~

"

Borides No .

Etehant

Conditions

Remarks

B mi

Laetie aeid Nitrie aeíd (1.40) Hydrofluorie aeid (40%) -

30 mi Sees to mins. 10 mI Instead .of laetic aeid, lO mi glycerol can be 10 mi used.

ZrB2 • TiB 2 •

B m2

Hydroéhlorie aeid (1.19) Nitrie aeíd (1.40)

1-5 min 10 mi 40 oC (lOO °F), vapor 10 mi etehing.

CrB2 • MoB 2 •

B m3

Hydroehlorie aeíd (1.19) Nitrie aeid (1.40)

B m4

Hydroehlorie aeid (1.19) Nitrie aeíd (1.40) Hydrofluoríe aeid (40%)

B m5

Oist. water Hydrofluorie aeid (40%) Nitrie aeíd (1.40)

10 mi Sees to mins. !!! See Appendix A. 10 mi 10 mi

ZrB

B m6

Oist. water Sulfurie aeid (1.84)

IOml 15 Iml

TiB 2 •

B m7

Electrolytic: Oist. water Sodium hydroxide

15 s

9 s, 3{).4() oC (85-100 6 mi ~F) . 2 mi !!! See Appendix A.

10 mI Sees to mins, 10-15 1-2 g V de, stainless steel cathode.

HfB 2 -NbB 2 mixtures.

2•

TaB 2 • LaB •.

P mi p m2

•, t

Laetie aeid (90%)

(40~)

Nitrie aeid (1.40) Sulfurie aeid (1.84) p m3

Hydroehloric aeíd (1.19)

P

Hydrogen peroxide (30%) Sulfurie aeid (1.84)

m4

,;1

'¡ '

• "l,

'.,

lO mi Sees to mins. !!! See Appendix A . 10 mi 20 mi . 20 mi

Secs to mins. 10 mI I mi

Etehant

Conditions

Remarks

2.5 h, 1500 oC (2730 °F). !!! See Appendix A.

U02 -Mo (!!!).

el m2

Hydrogen sulfide

15-30 s, room temperature. !!! See Appendix A.

U0 2-Cr (!!!).

et m3

a. Oist. water Potassium ferrieyanide b. Oist. water Potassium or sodíum hydroxide (Coneentration varí- ' able)

et m4

Nitrie aeid (1.40)

et m5

Oist. water Nitrie aeíd (1.40) Hydrofluorie aeíd (40%)

100 mi Mix (a) and (b) in ratio 1: 1 before use. IOg 1-4 mino 100 mi !!! See Appendix A. IOg

Sees to mins.

Zr0 2-W. Th0 2-W (!!!). W2C-W. UC-Cr (!!!). UC-Fe (!!!). UC-Ni (!!!). UC-UFe2 (l!!).

Cr23 C.-UFe2 (!!!). US-U (!!!). UC2-UNí,

US (!!!).

L

50 (10) mi Sees to mins. 30(10)ml !!! See Appendix A. 10 (10) mi

TiN-Co, TiN-Fe. TiN-Mo, TiN-W. eoneentrations in parentheses for HfCHf.

et m6

Oist. water Nitrie aeid (1.40) Glacial aeetie aeid

US-Co, UC2 -Fe, lO mI Sees to mins. lO mI Possibly several (UZr)C-Nb, (UZr)C10 mi drops oC hydrofluorie Ta, (UZr)C-W (!!!) . aeid (40%) !!! See Appendix A.

et m7

Nitrie aeid (1.40) Sulfurie aeid (1.84) Hydrofluorie aeid (40%)

lO mi Sees to mins. 20 mI !!! See Appendix A.

et m8

Ois!. water Nitrie aeíd (1.40) Hydroehlorie aeid (1 .19)

50 mI Sees to mins. 47 mi

et m9

Hydrofluorie aeid (40%) Nitrie acid (1.40) Laetie aeíd (90%)

1-5 mino 50 mi !!! See Appendix A. 50 mi 3 mI

UO (!!!).

6-12 S . CdS. Boiling, vapor etehing.

't_. , ''''

PbS.

Hot etehing in dry, high-purity hydrogen

Remarks PuP (!!!), PuS (!!!).

\

Oist. water Hydrofluorie aeid

99

(!!!).

eonditions Sees to mins.

30 mi 1- 10 min, 60 oC (140 °F) 10 mi Ig

Ct mi

1

I

Etehant

/

Cermets No.

Phosphides and SuJfides No.

Oist. water Hydroehlorie aeíd (1.19) Oimethylene thiourea

_,o

Iml

S.

p m5

~;;'

TiB 2 •

100 mi 10 mi

Preparation of Cermets

, .. :;

NbCz-NbFe-Nb.

10 mI TiC-Ni.

3 mI U02 -Nb (!!!).

100

/

Preparation of lron Oxide Layers on Iron Preparation of Iron Oxide Layers on Iron

Ct mIO

Sulfunc acid (1.84) Lactic acid (90%) Glacial acetic acid

Ct a. Dist. water mil Hydrochloric acid (1.19) Nitric acid (1.40) Hydrofluoric acid (40%) b. Dist. water Nitric acid (1.40) Ct mI2

Lactic acid (90%)

Ct m13

Hydrogen peroxide (30%) Ammonia water

10 mI Secs to mins. 10 mI 10 mI 100 mIlOs, 50 oC (120°F). !!! See Appendix A. 6 mI 2ml

PuC-Pu (!!!).

U02 -AI (!!!).

5ml 10 mI 3 min, 25 oC (80°F). 10 mI Use (a) tirst, then (b). Secs to mins.

(Y3AI)C-Y3 C-Y.

Secs to mins.

UN-U, UN-W (!!!).

10m!. 10 mI

Iron Oxide Layers on Iron No. OFe mI

Etchant Dist. water Aqueous sol.of nitric . acid (1%) Aqueous sol of citric acid (5%) Aqueous sol. of thioglycolic acid (5%)

OFe m2

Aqueous sol. of citric acid (10%) Aqueous sol. of sodium thiocyanate (10%) OFe a. Dist. water m3 Formic acid (1.22) b. Dist. water Fluoboric acid

OFe m4

Conditions 10 mI 15-60 S. Swab. 5ml 5ml 5 mI 45-90 S. 5 mI Swab. 5 mI 15 mI 5 S. 5 mI Swab, followed by 15 mI (b)' 2 S. 5ml

i

Thioglycolic aeid (5%) Aqueous sol. of po- I tassium diphthalate • " \. (5%) Aqueous sol. of ammonium citrate (5%>""' Aqueous sol. of citric., acid (5%)

Remarks Fe2 0 3 • Fe3 0. and Fe are not attacked.

30--60 S. 10 mI Swab. 5mI 2ml 3 mI

Fe2 0 3 • Fe3 0. is not attacked. Fe3 O•. If Fe2 0 3 is to be etched simultaneously, use OFe m2 rust and follow up with OFe m3. FeO.

OFe m5

/

101

Electrolyl¡c:

Thioglycolic acid (5%) Aqueous sol. of potassium diphthalate (5%) Aqueous sol. of ammonium citrate (5%) Aqueous sol of sodium chromate (0.5%)

15 s, 2-4 mA/cm2 , 9 10 mI V dc, stainless steeI cathode. Add sodium chro5 mI mate solution only shortly before use. 2 mi 50 mI

Fe3 0 •. Fe and Fe2 0 3 are not attacked.

100

/

Preparation of lron Oxide Layers on Iron Preparation of Iron Oxide Layers on Iron

Ct mIO

Sulfunc acid (1.84) Lactic acid (90%) Glacial acetic acid

Ct a. Dist. water mil Hydrochloric acid (1.19) Nitric acid (1.40) Hydrofluoric acid (40%) b. Dist. water Nitric acid (1.40) Ct mI2

Lactic acid (90%)

Ct m13

Hydrogen peroxide (30%) Ammonia water

10 mI Secs to mins. 10 mI 10 mI 100 mIlOs, 50 oC (120°F). !!! See Appendix A. 6 mI 2ml

PuC-Pu (!!!).

U02 -AI (!!!).

5ml 10 mI 3 min, 25 oC (80°F). 10 mI Use (a) tirst, then (b). Secs to mins.

(Y3AI)C-Y3 C-Y.

Secs to mins.

UN-U, UN-W (!!!).

10m!. 10 mI

Iron Oxide Layers on Iron No. OFe mI

Etchant Dist. water Aqueous sol.of nitric . acid (1%) Aqueous sol of citric acid (5%) Aqueous sol. of thioglycolic acid (5%)

OFe m2

Aqueous sol. of citric acid (10%) Aqueous sol. of sodium thiocyanate (10%) OFe a. Dist. water m3 Formic acid (1.22) b. Dist. water Fluoboric acid

OFe m4

Conditions 10 mI 15-60 S. Swab. 5ml 5ml 5 mI 45-90 S. 5 mI Swab. 5 mI 15 mI 5 S. 5 mI Swab, followed by 15 mI (b)' 2 S. 5ml

i

Thioglycolic aeid (5%) Aqueous sol. of po- I tassium diphthalate • " \. (5%) Aqueous sol. of ammonium citrate (5%>""' Aqueous sol. of citric., acid (5%)

Remarks Fe2 0 3 • Fe3 0. and Fe are not attacked.

30--60 S. 10 mI Swab. 5mI 2ml 3 mI

Fe2 0 3 • Fe3 0. is not attacked. Fe3 O•. If Fe2 0 3 is to be etched simultaneously, use OFe m2 rust and follow up with OFe m3. FeO.

OFe m5

/

101

Electrolyl¡c:

Thioglycolic acid (5%) Aqueous sol. of potassium diphthalate (5%) Aqueous sol. of ammonium citrate (5%) Aqueous sol of sodium chromate (0.5%)

15 s, 2-4 mA/cm2 , 9 10 mI V dc, stainless steeI cathode. Add sodium chro5 mI mate solution only shortly before use. 2 mi 50 mI

Fe3 0 •. Fe and Fe2 0 3 are not attacked.

Appendix A:

Suggestions for Handling Hazardous Materials AH chemicals, including many metals and oxides, pose sorne degree of danger to the human organismo This may come about by ingestion through the respiratory or digestive tracts or by external contact with the skin or eyes. Basically, the same precautions apply to the metallographic laboratory as to all chemical laboratories, except that certain specific areas are particularly critical. Sorne significant precautions are:

,¡

t '/

.,..

• ,.1,.

• CIearly IabeI all storage containers. • Dilute eoneentrated ehemieaIs before disposal and observe alllocal waste-disposal regulations. • CritieaI substanees (flammable, explosive, toxic, or corrosive) should be stored in approved containers in cool, fireproof, isolated areas. • Caustie materiaIs, such as acids, bases, peroxides, and sorne salts, should be handled only when wearing protective de vices such as safety glasses, rubber gloves, and laboratory coats or aprons. Vapors of such materials are often harmful, too. Actual work should be carried out in an effective fume hood with an additional gas mask if evolution of toxic gases and vapors is suspected. • When preparing etchants containing aggressive ehemieals such as sulfuric acid, the chemical should always be added to the solvent (water, alcohol, glycerol, etc.) slowly with gentle stirring. External cooling may also be required if heat evolution is particularly strong. • VoIatile, flainmabIe, and explosive materials, such as benzene, acetone, ether, perchlorate, nitrate, etc. , should not be heated or kept near open flames. • When preparing microsections of toxíe materíals such as beryIlium, and radioaetíve substances or alloys containing uranium, thorium, and plutonium, a glove box or hot cell must be used.

'"

...., ".

Particularly hazardous chemicals listed in the etchant compositions (Chapters 2 and 3) and in Appendix B are indicated by (!!!). These de serve additional comments .. • Perchlorie acid in concentrations exceeding 60% is highly flammable and explosive. This danger is greatly iucreased by the presence

~

!,: 1

103

104

/

Handling Hazardous Materials

of organic materials or metals such as bismuth, which oxidizes readily. Avoid the higher concentration and heating of these solutions, particularly in electrolytic polishing and etching; never store highconcentration perchloric solutions in plastic containers. When mixing perchloric acid and alcohol, highly explosive alkyl perchlorates may form : Perchloric acid should be added slowly under constant stirring. Keepthe temperature of the solution below 35 oC (95 °P) and, if necessary, use a coolant bath. Wearing safety glasses is helpful, but working behind a safety shield is preferable. • Mixtures of alcohol and hydrochloricacid can react in various ways . to produce aldehydes, fatty acids, explosive nitrogen compounds, etc. The tendency toward explosion increases with increasing molecule size. Hydrochloric acid content should not exceed 5% in ethanol or 35% in methanol. These mixtures shduld not be stored. • Mixtures of alcohol and phosphoric acidcan result in the formation of esters, some of which are potent nerve poisons. If absorbed through the skin or inhaled, severe personal damage may result. • Mixtures of methanol and sulfuric acid may form dimethylene sulfate, an odorless, tasteless compound that may be fatal if absorbed in . sufficient quantities into the skin' or respiratory tract. Even gas masks do not offer adequate protection. Sulfates of the higher alcohols, however, are not potentially dangerous poisons. • Mixtures of chromium (VI) oxide and organic materials are explosive. Mix with care and do not store. • Lead and lead salts are highly toxic, and the damage produced is cumulative. Care is also recommended when handling cadmium, thallium, nickel, mercury, and other heavy metals. • Al! cyanide compounds (eN) are highly dangerous because hydrocyanic acid (HCN) may easily formo They are fast-acting poisons that can cause death, even in relatively low concentrations. • Hydrofluoric acid i~ a very strong skin and respiratory poison that is hard to control. " should be handled with extreme care, beca use sores resulting f;oIp. its attack on skin do not heal readily. Hydrofluoric acid also a:ttacks glass, and fumes .from specimensetched ~ HP solution c"uld easily damage front elements of microscope lenses. Specimens 'should be rinsed thoroughly and in sorne cases placed in a vacuum desiccator for one to two hours before examination. . • Picric acid anhydri'a~ is an explosive. The references on saféty and toxicology in Appendix C contain information on potential poisons, symptoms of poisoning, treatment, and prevenÚon. ~

1)1

Appendix B:

Chemicals Used to Prepare Etchants in Chapters 2 and 3 F = flammable, !!! D = density.

toxic, E

Name Acetic acid Acetylacetone (2,3-pentanedione, diacetylmethane) Aluminum chloride Ammonia Ammonia water Ammonium acetate Ammonium chloride Ammonium dicitrate (diammonium hydrogen citrate) Ammonium ditartrate Ammonium hydrogen fluoride Ammonium paramo!ybdate (mo!ybdic acid) Ammonium peroxydisu!fate Ammonium polysulfide Ammonium thiosulfate Argon Bromine !-Butano! Cadmium chloride Cerium (IV) nitrate Chromium (IlI) oxide Chromium (VI) oxide (chromic acid) Citric acid Copper (11) ammonium chloride Copper ammonium persulfate Copper (11) chloride Copper (I1) nitrate Copper (11) sulfate .(

explosivé, L

liquid, G

Formula CH,COOH C 5 H~02

°

(NH.). M0 7 2. , 4H 2 (NH.)2 S 2O~ (NH')2 Sx (NH.)2 S20) Ar Br 2 CH j (CH 2» OH CdCI 2 ' H,O Ce(NO»4 Cr,O) CrO, C.H ~ 07H,O

(NH4)2 [CuCl41·2H,O [Cu(NH,).] S2 O. CuCl,'H, O Cu(No,),'6H,O CuS04 '5H 2O

105

crystalline,

Remarks !!! (caustic) F, L, D 0.972

(CH, COCH 2eOCH» AICl) NH) NH) + H 20 CH)COONH. NH.Cl C.H,.N20 7 [(NH.)2 HC.H,071 (NH')2 C. H. O. (NH.)HF 2

°

gas, C

C !!!, G, D 0.596 !!!, L, 00.91 C C C C C C C !!!, L C C !!! (vapor), L, D 3.11 F, L !!l, C C C !!! (caustic), e C l!!, C C !!!,e l!!, C !l!, C

104

/

Handling Hazardous Materials

of organic materials or metals such as bismuth, which oxidizes readily. Avoid the higher concentration and heating of these solutions, particularly in electrolytic polishing and etching; never store highconcentration perchloric solutions in plastic containers. When mixing perchloric acid and alcohol, highly explosive alkyl perchlorates may form : Perchloric acid should be added slowly under constant stirring. Keepthe temperature of the solution below 35 oC (95 °P) and, if necessary, use a coolant bath. Wearing safety glasses is helpful, but working behind a safety shield is preferable. • Mixtures of alcohol and hydrochloricacid can react in various ways . to produce aldehydes, fatty acids, explosive nitrogen compounds, etc. The tendency toward explosion increases with increasing molecule size. Hydrochloric acid content should not exceed 5% in ethanol or 35% in methanol. These mixtures shduld not be stored. • Mixtures of alcohol and phosphoric acidcan result in the formation of esters, some of which are potent nerve poisons. If absorbed through the skin or inhaled, severe personal damage may result. • Mixtures of methanol and sulfuric acid may form dimethylene sulfate, an odorless, tasteless compound that may be fatal if absorbed in . sufficient quantities into the skin' or respiratory tract. Even gas masks do not offer adequate protection. Sulfates of the higher alcohols, however, are not potentially dangerous poisons. • Mixtures of chromium (VI) oxide and organic materials are explosive. Mix with care and do not store. • Lead and lead salts are highly toxic, and the damage produced is cumulative. Care is also recommended when handling cadmium, thallium, nickel, mercury, and other heavy metals. • Al! cyanide compounds (eN) are highly dangerous because hydrocyanic acid (HCN) may easily formo They are fast-acting poisons that can cause death, even in relatively low concentrations. • Hydrofluoric acid i~ a very strong skin and respiratory poison that is hard to control. " should be handled with extreme care, beca use sores resulting f;oIp. its attack on skin do not heal readily. Hydrofluoric acid also a:ttacks glass, and fumes .from specimensetched ~ HP solution c"uld easily damage front elements of microscope lenses. Specimens 'should be rinsed thoroughly and in sorne cases placed in a vacuum desiccator for one to two hours before examination. . • Picric acid anhydri'a~ is an explosive. The references on saféty and toxicology in Appendix C contain information on potential poisons, symptoms of poisoning, treatment, and prevenÚon. ~

1)1

Appendix B:

Chemicals Used to Prepare Etchants in Chapters 2 and 3 F = flammable, !!! D = density.

toxic, E

Name Acetic acid Acetylacetone (2,3-pentanedione, diacetylmethane) Aluminum chloride Ammonia Ammonia water Ammonium acetate Ammonium chloride Ammonium dicitrate (diammonium hydrogen citrate) Ammonium ditartrate Ammonium hydrogen fluoride Ammonium paramo!ybdate (mo!ybdic acid) Ammonium peroxydisu!fate Ammonium polysulfide Ammonium thiosulfate Argon Bromine !-Butano! Cadmium chloride Cerium (IV) nitrate Chromium (IlI) oxide Chromium (VI) oxide (chromic acid) Citric acid Copper (11) ammonium chloride Copper ammonium persulfate Copper (11) chloride Copper (I1) nitrate Copper (11) sulfate .(

explosivé, L

liquid, G

Formula CH,COOH C 5 H~02

°

(NH.). M0 7 2. , 4H 2 (NH.)2 S 2O~ (NH')2 Sx (NH.)2 S20) Ar Br 2 CH j (CH 2» OH CdCI 2 ' H,O Ce(NO»4 Cr,O) CrO, C.H ~ 07H,O

(NH4)2 [CuCl41·2H,O [Cu(NH,).] S2 O. CuCl,'H, O Cu(No,),'6H,O CuS04 '5H 2O

105

crystalline,

Remarks !!! (caustic) F, L, D 0.972

(CH, COCH 2eOCH» AICl) NH) NH) + H 20 CH)COONH. NH.Cl C.H,.N20 7 [(NH.)2 HC.H,071 (NH')2 C. H. O. (NH.)HF 2

°

gas, C

C !!!, G, D 0.596 !!!, L, 00.91 C C C C C C C !!!, L C C !!! (vapor), L, D 3.11 F, L !!l, C C C !!! (caustic), e C l!!, C C !!!,e l!!, C !l!, C

106

I

Chemicals for Etchants in Chapters 2 and 3

Chemicals for Etchants in Chapters 2 and 3

1,2-ethanediol (dihydroxy ethane, ethylene glycol, glycol) .

C, H. O, (HOCH 2 CH 2OH)

L, D 1.11

Ethanethiol Ethanol

C6 H,.02 C2 H, OH

L, D 0.90 F,L,D 0.81-0.79

Ethylene glycol Fluoboric acid

(See 1,2-ethanediol) HBF.

Formic acid Glycerol (glycerine) Gold (111) chloride Hydrochloric acid

HCOOH C,H.03 (HOCH 2CHOHCH 2 OH) AuCI 3·H 20 HCI

!!! (caustic), L, D 1.23 L, D 1.22 L, D 1.26 C

!!! (caustic), L, D 1.19

Hydrofluoric acid

HF

+ H2 0

!!! (caustic), L, 40%

Hydrogen Hydrogen peroxide Hydrogen sulfide Iron (I1I) chloride lron (III) nitrate Iron (H) sulfate Lactic acid Lead acetate Magnesium oxide (magnesia) Mercury (11) nitrate . Methanol Nitric acid

H, H 2 0, H2 S FeCI 3·6H 2 0

Fe(N0 3)3 ·9H 2° FeSO.·7H 20 C 3 H. O, Pb(CH 3COO), MgO Hg(N°3)2· 8H 20 CH 30H HN03

N2

Nitrogen Oxalic acid Perchloric acid

¡ >,

C 2 H 20.·2H 2° HCIO.

¡

~.

Phosphoric acid

H 3 PO.

\

Picric acid

Potass~m bicarbonate Potassium carbonate Potassium chloride P~tassium cyanide Potassium dichromate Potassium ferricyanide Potassium ferrocyanide ~

:P

¡'

., ','

'!. ... . ....

C. H3 N 30, KHCO, K 2 C03 KCI KCN K 2Cr,O, K) [Fe(CN).l K. [Fe(CN).l

E, F,G L, D 1.11 !!!,G C C C L, D. 1.21 !!!, C C !!!, C !!! L, D 0.76 !!!(caustic), L, D 1.19 G JI!, C !!! (caustic), L, E, D 1.67 !!! (caustic), L, D 1.71 !!! (caustic), E,C C

Potassium hydrate solution Potassium hydrogen fluoride Potassium hydrogen sulfate Potassium hydroxide Potassium iodide Potassium metabisulfite Potassium nitrate Potassium phthalate (di-) Potassium thiocyanate Silver cyanide Silver nitrate Sodium bicarbonate Sodium carbonate Sodium chloride Sodium chromate Sodium cyanide Sodium dichromate Sodium f1uoride Sodium hydrogen phosphate Sodium hydroxide Sodium sulfate Sodium sulfate, anhydrous Sodium sulfide Sodium tetraborate Sodiumthiocyanate Sodium thiosulfate (fixer) Spirits of ammonia Sulfuric acid Tártaric acid Thioglycolic acid Thiourea 1,3-dimethyl 2-thiourea Tin (11) chIoride Vogel's special reagent (stainless steel etchant)

C

C !!!,C !!! (caustic), C C C

Wetting agents Zinc chloride

107

!!!(caustic), L C C !l! (caustic), C

KOH+H 20 KHF, KHSO. KOH KI K,S,O, KN03

t

C. H. K,O" KSS::;N AgCN AgN0 3 NaCHO) Na 2 CO, · 10H,O NaCl Na 2 CrO. NaCN Na 2 Cr 2 07 · 2H , NaF

°

Na, HPO. · 12H 2° NaOH Na, SO.' IOH, Na 2 SO. Na 2 S

I

°

Na 2 B.O, NaSCN Na, S2 0, . 5H,O NH,+H 2 0 H 2 SO. C.H.O. HSCH 2COOH CS(NH 2)2 C,H.N 2S (CH) NHCSNHCH,) SnCI 2 ·2H,O Mixture of tar and sulfurous acid, boiled and filtered; protected trade product Additives for lowering surface tension ZnCI 2

C C C !l!, C !l!, C

C C C C C !!!, C !!! (caustic),C C C

!l! (caustic), C C C ':C

C C C

!!!, L, D 0.91

!!! (caustic), L, DI.84 L L C C

!!! (caustic), C L

!!! (caustic), C

106

I

Chemicals for Etchants in Chapters 2 and 3

Chemicals for Etchants in Chapters 2 and 3

1,2-ethanediol (dihydroxy ethane, ethylene glycol, glycol) .

C, H. O, (HOCH 2 CH 2OH)

L, D 1.11

Ethanethiol Ethanol

C6 H,.02 C2 H, OH

L, D 0.90 F,L,D 0.81-0.79

Ethylene glycol Fluoboric acid

(See 1,2-ethanediol) HBF.

Formic acid Glycerol (glycerine) Gold (111) chloride Hydrochloric acid

HCOOH C,H.03 (HOCH 2CHOHCH 2 OH) AuCI 3·H 20 HCI

!!! (caustic), L, D 1.23 L, D 1.22 L, D 1.26 C

!!! (caustic), L, D 1.19

Hydrofluoric acid

HF

+ H2 0

!!! (caustic), L, 40%

Hydrogen Hydrogen peroxide Hydrogen sulfide Iron (I1I) chloride lron (III) nitrate Iron (H) sulfate Lactic acid Lead acetate Magnesium oxide (magnesia) Mercury (11) nitrate . Methanol Nitric acid

H, H 2 0, H2 S FeCI 3·6H 2 0

Fe(N0 3)3 ·9H 2° FeSO.·7H 20 C 3 H. O, Pb(CH 3COO), MgO Hg(N°3)2· 8H 20 CH 30H HN03

N2

Nitrogen Oxalic acid Perchloric acid

¡ >,

C 2 H 20.·2H 2° HCIO.

¡

~.

Phosphoric acid

H 3 PO.

\

Picric acid

Potass~m bicarbonate Potassium carbonate Potassium chloride P~tassium cyanide Potassium dichromate Potassium ferricyanide Potassium ferrocyanide ~

:P

¡'

., ','

'!. ... . ....

C. H3 N 30, KHCO, K 2 C03 KCI KCN K 2Cr,O, K) [Fe(CN).l K. [Fe(CN).l

E, F,G L, D 1.11 !!!,G C C C L, D. 1.21 !!!, C C !!!, C !!! L, D 0.76 !!!(caustic), L, D 1.19 G JI!, C !!! (caustic), L, E, D 1.67 !!! (caustic), L, D 1.71 !!! (caustic), E,C C

Potassium hydrate solution Potassium hydrogen fluoride Potassium hydrogen sulfate Potassium hydroxide Potassium iodide Potassium metabisulfite Potassium nitrate Potassium phthalate (di-) Potassium thiocyanate Silver cyanide Silver nitrate Sodium bicarbonate Sodium carbonate Sodium chloride Sodium chromate Sodium cyanide Sodium dichromate Sodium f1uoride Sodium hydrogen phosphate Sodium hydroxide Sodium sulfate Sodium sulfate, anhydrous Sodium sulfide Sodium tetraborate Sodiumthiocyanate Sodium thiosulfate (fixer) Spirits of ammonia Sulfuric acid Tártaric acid Thioglycolic acid Thiourea 1,3-dimethyl 2-thiourea Tin (11) chIoride Vogel's special reagent (stainless steel etchant)

C

C !!!,C !!! (caustic), C C C

Wetting agents Zinc chloride

107

!!!(caustic), L C C !l! (caustic), C

KOH+H 20 KHF, KHSO. KOH KI K,S,O, KN03

t

C. H. K,O" KSS::;N AgCN AgN0 3 NaCHO) Na 2 CO, · 10H,O NaCl Na 2 CrO. NaCN Na 2 Cr 2 07 · 2H , NaF

°

Na, HPO. · 12H 2° NaOH Na, SO.' IOH, Na 2 SO. Na 2 S

I

°

Na 2 B.O, NaSCN Na, S2 0, . 5H,O NH,+H 2 0 H 2 SO. C.H.O. HSCH 2COOH CS(NH 2)2 C,H.N 2S (CH) NHCSNHCH,) SnCI 2 ·2H,O Mixture of tar and sulfurous acid, boiled and filtered; protected trade product Additives for lowering surface tension ZnCI 2

C C C !l!, C !l!, C

C C C C C !!!, C !!! (caustic),C C C

!l! (caustic), C C C ':C

C C C

!!!, L, D 0.91

!!! (caustic), L, DI.84 L L C C

!!! (caustic), C L

!!! (caustic), C

References

109

la, Ausg. Dez. 1965 jMarz 1969, Hauptverband dergewerblichen Berufsgenossen_ schaften, C. Heymanns Ver!. KG, Kiiln.

Appendix C:

15. Registry of Toxic Effects of Chemical Substances, U. S. Department of Hea1th, Education, and Welfare. Public Hea1th Service - Center for Disease Control- National Institute for Occupational Safety and Health (NIOSH), Rockville, Md., June 1976. (Published every year.)

References The references listed in this appendix are suggested for obtaining a better understanding. Only selected texts are represented; not all sources used to prepare the manual are listed. Safetyand Toxicology 1. W. Braun, A. Donhardt, Poisoning Register (in German) Vergiftungsregister, Georg Thieme Verl., Stuttgart, 1970. 2. L. V. Cralley, L. J. Cralley, G. D. Clayton, J. A. Jurgiel, Ed., Industrial Environmental Health, The Worker and the Community, Academic Press, New York and London, 1972.

3. A. Hamilton, H. L. Hardy, Industrial Toxicology, Publishing Sciences Group, Inc., Acton, Mass., 1974. 4. A. Loomis, Essentials of Toxicology, Lea & Febinger, Philadelphia, 1974.

5. F. A. Patty, Ed., Industrial Hygiene and Toxicology, Interscience Publishers; New York, 1963. 6. N. 1. Sax, Dangerous Properties of Industrial Materials, Van Nostrand Reinhold Co., New YorkjCincinnatijTorontojLondonjMelbourne, 1975. 7. G. Sorbe, Toxins and Explosives (in German) Gifte und explosive Substanzen, Berufskundliche Reihe zur Fachzeitschrift Chemie für Labor und Betrieb, Bd. 7. Umschau Verl., Frankfurt am Main, 1968. 8. P. G. Stecher, The Merck Index of Chemicals and Drugs, Merck & Co., Inc., Rahway, N. J. (Get newest edition. Useful for identification of unknown materials). 9. H. E. Stockinger, Ed., Beryllium: Its Industrial Hygiene, Aspects, Academic Press, N ew York j London, 1966. I

lO. C. Xinteras, B. C. J04nson, 1. de Groot, Ed., Behavioral Toxicology, Early Detection of Occupational Hazards, U. S. Department of Health, Education,and Welfare. Public Hea1th Service-Cenker for Disease Control-National Institute for Occupational Safety and Hea1th '(N,IOSH), Rockville, Md., 1974. , 11. F'ederal Controls on