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The effect of oxygen on the reaction between copper and saphire O’Brien, Thomas Edward 1973

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THE EFFECT OF OXYGEN ON THE REACTION BETWEEN COPPER AND SAPPHIRE  BY  THOMAS EDWARD O'BRIEN B . A . S c , U n i v e r s i t y o f B r i t i s h Columbia, 1970  A THESIS SUBMITTED I N PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE i n t h e Department of METALLURGY  We a c c e p t t h i s t h e s i s as c o n f o r m i n g t o t h e r e q u i r e d standard.  THE UNIVERSITY OF BRITISH COLUMBIA A p r i l , 1973  In  presenting  an  advanced  the I  Library  further  for  degree shall  agree  scholarly  by  his  of  this  written  this  thesis  in  at  University  the  make  that  it  purposes  for  may  be  It  financial  for  O c t o b e r 8,  1974  of  Columbia,  British  by  gain  Columbia  for  the  understood  Metallurgy  The U n i v e r s i t y o f B r i t i s h V a n c o u v e r 8, Canada  of  extensive  granted  is  fulfilment  available  permission.  Department of  Date  freely  permission  representatives. thesis  partial  shall  Head  be  requirements  reference copying  that  not  the  of  agree  and  of my  I  this  or  allowed  without  that  study. thesis  Department  copying  for  or  publication my  ABSTRACT  The e f f e c t o f oxygen p o t e n t i a l on t h e w e t t i n g b e h a v i o r and i n t e r f a c i a l energy between copper and s a p p h i r e was s t u d i e d u s i n g t h e s e s s i l e drop t e c h n i q u e i n a CO-CC^ atmosphere.  A linear relationship  —6 was found between Y 10  atmosphere Y  q t  c t  and l o g p0„ from 10  —5 t o 10  approached a c o n s t a n t v a l u e  b a r r i e r s u r f a c e l a y e r was proposed  atmosphere.  Beyond  asymptotically. A  t o e x p l a i n t h i s change.  The Gibbs' a d s o r p t i o n e q u a t i o n was used t o e v a l u a t e t h e c h a r a c t e r i s t i c of the i n t e r f a c e s .  F o r m a t i o n o f a C^O  f i l m a t the l i q u i d -  vapour i n t e r f a c e and a CuAlC^ f i l m a t t h e s o l i d - l i q u i d i n t e r f a c e was suggested. The work o f a d h e s i o n was found t o r e a c h a maximum a t -2 a p p r o x i m a t e l y 10  atomic p r e c e n t oxygen.  Measurements o f t h e b a s a l r a d i u s as a f u n c t i o n o f oxygen c o n t e n t were used t o e v a l u a t e t h e r o l e o f oxygen i n promoting  spreading.  I t was found t h a t s p r e a d i n g on s a p p h i r e was d i r e c t l y p r o p o r t i o n a l t o t h e l o g a r i t h m o f oxygen p r e s e n t i n t h e molten copper  drops.  E v a l u a t i o n o f t h e p e n e t r a t i o n o f copper i n t o s a p p h i r e was e v a l u a t e d u s i n g t h e e l e c t r o n probe m i c r o a n a l y s e r .  Data o b t a i n e d i n d i c a t e d  t h a t i n absence o f oxygen copper does n o t p e n e t r a t e a p p r e c i a b l y .  Between  0.13 and 1.39 wt.% [0] copper p e n e t r a t i o n was n o t dependent on oxygen c o n t e n t and time.  I t was found t h a t copper p e n e t r a t e s v e r y r a p i d l y  i n i t i a l l y and then appears t o s t o p . An attempt has been made t o o b t a i n an e q u a t i o n based on t h e Young-Dupre e q u a t i o n , when t h e d i f f e r e n t en"-:»y v a l u e s a r e a f f e c t e d by t h e oxygen p o t e n t i a l o f the system.  iii  TABLE OF CONTENTS  gage TITLE PAGE  ,  .  .  ABSTRACT  .  i i i  TABLE OF CONTENTS  i i i  LIST OF FIGURES  v i  ACKNOWLEDGEMENTS  viii  CHAPTER I .  INTRODUCTION  A.  General Discussion  B.  Cu-Al 0  C.  Copper-Oxygen System  ; D. E.  2  B.  1  System  2  4  Other R e l a t e d Work  -.  Aim o f P r e s e n t I n v e s t i g a t i o n  CHAPTER I I . A.  3  1  EXPERIMENTAL  6  7 9  Materials  9  1.  Sapphire  9  2.  Copper  10  3.  C u p r i c Oxide  10  4.  A l u m i n a and Cuprous Oxide  10  A p p a r a t u s f o r S e s s i l e Drop E x p e r i m e n t s  1?  1.  Furnace  12  2.  Atmosphere C o n t r o l l e r  3.  O p t i c a l System.  .  . . . . .  12 ^  iv  Page  C.  Apparatus f o r D i f f u s i o n E x p e r i m e n t s  14  D.  Specimen P r e p a r a t i o n  14  1.  Sapphire  14  2.  Copper B u t t o n s  17  Experimental Procedure  17  1.  S e s s i l e Drop E x p e r i m e n t s  17  2.  D i f f u s i o n Experiments  18  3.  E l e c t r o n Probe M i c r o a n a l y s i s  19  4.  M i c r o s t r u c t u r e Examination  20  5.  Scanning E l e c t r o n M i c r o s c o p y  20  E.  CHAPTER I I I . RESULTS AND DISCUSSION A.  B.  21  S e s s i l e Drop E x p e r i m e n t s  21  1.  C o n t a c t A n g l e Measurements  .  2.  I n t e r f a c i a l Energy  23  3.  Adsorption  25  4.  Work o f A d h e s i o n  5.  I n t e r f a c i a l Area.  6.  E x a m i n a t i o n o f S o l i d i f i e d Drops  Isotherms  21  29 .,  29 .  31  D i f f u s i o n Experiments  35  1.  I n t e r f a c i a l Region  36  2.  Copper P e n e t r a t i o n i n A l u m i n a  38  3.  Copper P e n e t r a t i o n Without Oxygen P r e s e n t  . . . .  43  V  Page  C.  4.  Copper A l u m i n a t e D i f f u s i o n  44  5.  Interface Microstructures  45  6.  Copper M i c r o s t r u c t u r e s  48  A F i t of Data f o r Y  49  C T  CHAPTER I V .  CONCLUSION  .  CHAPTER V.  RECOMMENDATIONS FOR FUTURE STUDY  APPENDIX I . SESSILE DROP TECHNIQUE AND GIBBS  1  52 54  EQUATION . . .  55  A.  S e s s i l e Drop Technique  55  B.  Gibbs' Equation  57  APPENDIX I I . ZIRCONIA (CALCIA STABILIZED) FOR CONTROL OF OXYGEN ATMOSPHERE  .  58  APPENDIX I I I . SESSILE DROP DATA  60  APPENDIX I V . SIEVERT'S LAW  61  APPENDIX V. ELECTRON PROBE MICROANALYSIS  62  APPENDIX V I . Y  63  C T  VALUES  APPENDIX V I I . X-RAY ANALYSIS. BIBLIOGRAPHY  .  64 $  6  vi  LIST OF FIGURES  Figure  Page  1.  3  2.  5  3.  E f f e c t of Oxygen on t h e S u r f a c e T e n s i o n o f Copper (1200°C)  6  4.  11  5.  13  6.  15  7.  16  8.  18  9.  19  10.  22  11.  23  12.  24  13.  26  14.  27  15.  28  16.  30  17.  31  18.  32  19.  33  20.  34  21.  35  22.  36  vii  Figure  Page  23.  X - r a y Images  37  24.  Copper P e n e t r a t i o n i n t o A l u m i n a  39  25. 26.  "  "  "  "  11  "  "  .  .  .  .  .  .  .  .  .  39  "  40  27.  "  "  "  "  40  28.  "  "  "  "  4.1  29.  "  "  "  "  41  30.  Specimen w i t h no Oxygen A d d i t i o n  43  31.  Copper P e n e t r a t i o n w i t h no Oxygen P r e s e n t  44  32.  Cu-CuA10 -Al 0  45  33.  Fracture Surface  46  34.  I n t e r f a c i a l Void  47  35.  Structure at Void  36.  Scanning E l e c t r o n M i c r o s c o p i c View o f I n t e r f a c e . . . .  48  37.  E u t e c t i c a t 0.13 [0] wt.%  50  38.  E u t e c t i c a t 0.27 [0] wt.%  50  39.  E u t e c t i c a t 0.57 [0] wt.%  51  40.  E u t e c t i c a t 1.39 [0] wt.%  51  41.  Contact A n g l e R e l a t i o n s h i p s  56  42.  ASTM Standard X - r a y Card  43.  D i f f r a c t i o n P a t t e r n f o r S y n t h e t i c CuAlO-  2  2  3  Couple  .  .  47  64 65  ACKNOWLEDGEMENTS  The research  a u t h o r would l i k e t o e x p r e s s h i s g r a t i t u d e t o h i s  a d v i s o r , Dr. A . C D . C h a k l a d e r , f o r h i s v a l u a b l e  advice.  Thanks a r e a l s o due t o o t h e r f a c u l t y , t e c h n i c a l s t a f f and f e l l o w g r a d u a t e s t u d e n t s f o r t e c h n i c a l a s s i s t a n c e and u s e f u l The Fellowship  f i n a n c i a l assistance provided  i s g r a t e f u l l y acknowledged.  discussions.  by t h e H.R. M a c M i l l a n  The b e s t l a i d p l a n s o f mice and men  .•.  R. Burns  1  I.  A.  INTRODUCTION  General D i s c u s s i o n The c o m b i n a t i o n o f d i f f e r e n t t y p e s o f m a t e r i a l s i s o f e v e r  i n c r e a s i n g t e c h n i c a l importance.  I t may be p o s s i b l e w i t h such c o m b i n a t i o n s  to make use o f t h e b e s t p r o p e r t i e s o f a l l m a t e r i a l s concerned.  Of utmost  importance i s t h e a b i l i t y t o o b t a i n a good bond and matching between t h e s e materials. A c c o r d i n g t o Helgess^on^ t h e t e c h n i c a l l y i m p o r t a n t c o m b i n a t i o n s of m e t a l s and c e r a m i c s can be i t e m i z e d as f o l l o w s :  and  1.  d i s p e r s i o n strengthened metals.  2.  metal f i b r e r e i n f o r c e d ceramics.  3.  ceramic f i b r e r e i n f o r c e d metals.  4.  cermets.  5.  c e r a m i c c o a t i n g s on m e t a l s  6.  metal coatings of ceramics.  The bonding formed between t h e m e t a l and t h e c e r a m i c i n such systems i s o f t e n s u b j e c t e d t o severe c o n d i t i o n s d u r i n g u s e .  Therefore i n v e s t i g a t i o n s of the  s t a b i l i t y o f t h i s bond a r e i m p o r t a n t from a t e c h n i c a l p o i n t o f view.  The  s t a b i l i t y o f t h e whole composite may depend on t h e s t a b i l i t y o f t h e i n t e r f a c i a l bond i t s e l f .  I n t h e case o f a t h i n - f i l m d e p o s i t on a ceramic  2 substrate, its  the i n t e r f a c i a l r e a c t i o n and s t a b i l i t y  functional properties,  subsequent  such as r e s i s t i v i t y ,  of the t h i n f i l m and a l s o  may s o l e l y depend on the  o x i d a t i o n and d i f f u s i o n r e a c t i o n of the f i l m w i t h the  substrate.  Much of the e a r l y work i n metal to ceramic bonding d e a l t metal to g l a s s s e a l s . electronic  The i n v e n t i o n of the e l e c t r i c  vacuum tubes prompted much r e s e a r c h  2  with  l i g h t b u l b and l a t e r  i n t o the p r o d u c t i o n o f  E a r l y w o r k . i n t o c r y s t a l l i n e c e r a m i c - m e t a l s e a l s employed a g l a s s y  seals.  layer  12 between the ceramic and m e t a l p h a s e s . various metals, a bond.  L a t e r developments  '  employed ;  o x i d e s and s i l i c a t e s e i t h e r alone or i n m i x t u r e s to form  Due to the c o m p l e x i t y of the i n t e r f a c i a l r e g i o n ,  of many bonds, has not been c a r r i e d o u t .  Many p o s s i b l e  characterization  interfacial  ,  3-10 reactions  f o r v a r i o u s systems have been proposed  , which can a f f e c t  bonding.  There can be s o l i d s o l u t i o n by d i f f u s i o n ,  p r o d u c t i o n of an i n t e r -  mediate compound or g l a s s and so o n . i n t e r f a c i a l tension  Reactions  such as these lower  and hence the s u r f a c e f r e e energy of the s o l i d ,  the  the by.the  f o r m a t i o n of an i n t e r f a c i a l compound. Widman^ found t h a t • i n systems where a bond between an oxide and a metal was to be made, atmosphere c o n t r o l was v e r y i m p o r t a n t . of the systems i n v e s t i g a t e d ,  he found b e t t e r  c o n t r o l l e d amount of oxygen was added to the B.  adhesion was p o s s i b l e  In.all if  a  atmosphere.  CU-AIQO-J System  The use of p r i n t e d c i r c u i t s has r a p i d l y i n c r e a s e d the i n copper-alumina bonding.  Oxygen and i t s  interest  r o l e i n the bond f o r m a t i o n  between copper and alumina has thus become v e r y i m p o r t a n t . Cu^O was found  12 13 '  to f a c i l i t a t e  the f o r m a t i o n of a second  14 phase which s t a b i l i z e d  the g r a i n growth of Al 0„. o  Others  have found  that,  i n t h e presence o f oxygen d u r i n g t h e t r e a t m e n t o f m i x t u r e s o f Cu and Al^O^,  a complex phase was formed.  E x a m i n a t i o n o f t h e phase diagram f o r  CuO-Ci^O-A^O^ i n d i c a t e s t h e p o s s i b i l i t y formed.  These a r e CuAlC^ and CuAl^O^  1800  (Figure 1 ) .  _  Liquid  —  %  -{  m /  /  *  •  • *•  Liquid +  o  1200  2  •  •  —  3  •  •  1  • • •  •  -»/••/•  •  •  »  • ••  ~I260°  2  _J e m •  •  t  jU 0 L i q u i d + Cu A I 0 > • • • • II65°C •  IK  •  1  y  u  -  •  •  •  + AI 0 2  -  • 3  •  •  Al 0  2  2  •  Cu(AI0|) +AI 0  •  CuO+  700L . . 6001«i  2  •  2  c*  —*  1  2  800  •  CuAI0  • CuO + C u ( A I 0 )  • •  * Cu A l 0  -1  2  ••  •  2  Cu-0+CuAIO,*  t< 1000 CC Cu 0 liJ 0. 9 0 0 iu » LU  Al 0  •  Liquid-*- a _ C u 0 /  #  o  compounds b e i n g  /  1600  1400  o f two d i s t i n c t  2  Al 0 2  2  3  3  •  3  i 20  0  CuO  F i g u r e 1.  40 Wt.%  60 Al 0 2  Phase Diagram f o r  3  80  100 Al 0 2  CuO-Cu^-Al^  3  15  16 Chaklader e t a l .  have found t h a t w i t h t h e a d d i t i o n o f l a r g e amounts o f  c u p r i c o x i d e t o l i q u i d copper drops r e s t i n g on a l u m i n a s u b s t r a t e s i s formed a t t h e i n t e r f a c e .  CuA10  2  A l l t h e works mentioned p r e v i o u s l y d e a l t  w i t h l a r g e oxygen a d d i t i o n s , u s u a l l y w e l l over t h e s o l u b i l i t y l i m i t .  Such  a d d i t i o n s would e f f e c t t h e e l e c t r i c a l p r o p e r t i e s o f t h e c o p p e r , t h e r e f o r e i t i s important to consider  s m a l l e r a d d i t i o n s o f oxygen and what e f f e c t i t  4 may have on the f i n a l p r o p e r t i e s and as w e l l as on the s t a b i l i t y of the interface. I t i s e s p e c i a l l y i m p o r t a n t t o n o t e whether t h e f o r m a t i o n of CuAlO^ a t the c o p p e r - a l u m i n a i n t e r f a c e can a c t a s a b a r r i e r l a y e r t o p r e v e n t subsequent d i f f u s i o n of copper i n t o t h e s u b s t r a t e . d i f f u s i o n may  As f u r t h e r  r e s u l t i n t h e l o s s o f the e l e c t r i c a l p r o p e r t i e s of  such as p r i n t e d  devices,  circuits.  I t has a l s o been c l a i m e d " ^ t h a t CuAlO^ was o b s e r v e d t o form w i t h the s m a l l e s t most of the  concentration  of oxygen a d d i t i o n (<v 1 w t . % ) .  However,  d a t a r e l a t e t o t h e mechanism o f c o p p e r - a l u m i n a bonding  higher concentrations  of oxygen, much above the s o l u b i l i t y  with  l i m i t o f oxygen  i n copper.  C.  Copper-Oxygen System The phase diagrams f o r the copper-oxygen  Figures  2(a)  & (b).  system a r e shown i n  I t i s apparent from the most r e c e n t d a t a o f  Osterwald"^k t h a t , under e q u i l i b r i u m c o n d i t i o n s , the s o l u b i l i t y oxygen i n copper i s 1.8 w e i g h t p e r c e n t a t 1200°C. a v a i l a b l e from t h e phase diagram t h e a c t i v i t y dilute liquid  limit for  I n a d d i t i o n t o the d a t a  c o e f f i c i e n t of oxygen i n  Cu-0 a l l o y s has been found to be 0.205.  18 19 20 '  '  19  Wilder  a l s o d e t e r m i n e d t h a t the f r e e energy f o r t h e d i s s o l u t i o n o f oxygen i n l i q u i d copper i s  -18.10 k c a l f o r t h e e q u a t i o n : k0  2  — • [0] (atm p e t ) 21  From t h i s v a l u e the S i e v e r t s law that i s :  c o n s t a n t i s c a l c u l a t e d t o be 485,  ;  Atomic  °c 10  1400  Percentage  20 h  30  + L2  1083'  50 6  G+  !&k  1200°  1200  Oxygen  40  + ' 1-2.2200  10.2  1065°  1075°  1000  1800 y-  p-  800  y  p+.y  +  600  1400  y  ~G—I  1000  375°—20A  400  "! \  600  : 7  200.  Cu  8  12  Weight  16  20  Percentage  100  Oxygen  oxygen in atom %,  »  2  o x y g e n i n wt %  F i g u r e 2 ( a ) & ( b ) . Copper-Oxygen System.  17a & b.  6 485  [0]  P  0  2 2  (atm)  (atm p e t )  (see Appendix IV)  The e f f e c t of oxygen on the s u r f a c e t e n s i o n of copper has a l s o been evaluated  (see F i g u r e 3)  LV (ergs,  -6^)1 12 11 XIO  2  10  8 01  0-2  0-3  0-4  0-5  0-6 [0] a t m % 22  F i g u r e 3.  D.  E f f e c t o f Oxygen on t h e S u r f a c e T e n s i o n o f Copper  (1200°C).  Other R e l a t e d Work Eremenko  23 2A 23 26 ' ' e t a l . and Knox and Baker have s t u d i e d the  i n t e r f a c i a l energy of l i q u i d c o p p e r , n i c k e l and s i l v e r , i n c o n t a c t w i t h a l u m i n a , a t v a r i o u s oxygen  potentials.  I n the i n v e s t i g a t i o n of the s i l v e r - o x y g e n - a l u m i n a  system  Eremenko and N a i d i c h  23  suggested t h a t t h e i n c r e a s e i n w e t t i n g o f t h e a l u m i n a  by s i l v e r , w i t h i n c r e a s i n g oxygen c o n c e n t r a t i o n , c o u l d be a t t r i b u t e d t o a s u r f a c e f i l m o f o x i d e on t h e s i l v e r .  T h i s monolayer was r e p o r t e d t o form  b o t h a t t h e m e t a l - c e r a m i c i n t e r f a c e and a t t h e m e t a l - v a p o r i n t e r f a c e . a l s o suggested t h a t once t h e s u r f a c e f i l m was formed no f u r t h e r  They  spreading  26 occurred.  Knox and Baker  showed t h a t f u r t h e r s p r e a d i n g o c c u r r e d  with  i n c r e a s e i n oxygen p o t e n t i a l beyond t h e r e g i o n s t u d i e d by Eremenko and Naidich.  Knox and Baker e x p l a i n e d t h i s b e h a v i o r by s u g g e s t i n g  f o r m a t i o n of a compound, AgAlC^ o r t h e a c c u m u l a t i o n  e i t h e r the  o f Ag^O a t t h e i n t e r f a c e .  S i m i l a r l y i n t h e i r study o f the nickel-oxygen-alumina  system,  24 Eremenko and N a i d i c h  found a r e d u c t i o n i n t h e i n t e r f a c i a l energy o f n i c k e l  w i t h t h e a d d i t i o n o f oxygen.  They a l s o a t t r i b u t e d t h i s t o a s u r f a c e  film  of o x i d e . 25 Analogous r e s u l t s were r e p o r t e d system.  f o r t h e copper-oxygen-alumina 2  I n t e r f a c i a l energy was found t o drop from 1370 ergs/cm  down t o  2 530 ergs/cm as t h e oxygen i n c r e a s e d from 0 t o 0.88 p e r c e n t a g e by w e i g h t . E v a u l a t i o n o f t h i s d a t a u s i n g t h e Gibb's e q u a t i o n s u g g e s t s a s u r f a c e l a y e r f o r m a t i o n a t t h e g a s - l i q u i d i n t e r f a c e t o a maximum v a l u e o f 34 x 10 ^ ^molqs/ 2 cm . E.  Aim o f P r e s e n t I n v e s t i g a t i o n 15 16 25 26 Previous studies  '  '  '  have suggested t h a t t h e a d d i t i o n  o f oxygen t o l i q u i d copper tends t o reduce t h e i n t e r f a c i a l energy and promote s p r e a d i n g .  I n these s t u d i e s t h e oxygen a d d i t i o n s were g e n e r a l l y  i n l a r g e c o n c e n t r a t i o n s and l i t t l e attempt was made t o c o n t r o l oxygen p a r t i a l p r e s s u r e above t h e d r o p l e t s .  Some o f t h e i n v e s t i g a t o r s d i d n o t  attempt t o d e t e r m i n e how much o f t h e o r i g i n a l oxygen was l e f t a f t e r t h e  experiments.  A l s o some of the work was c a r r i e d out u s i n g p o l y c r y s t a l l i n e  a l u m i n a p l a t e s , a t the s u b s t r a t e . To overcome t h e s e problems i t was proposed i n t h i s s t u d y t o s t a r t w i t h pure copper and m e l t t h i s on s i n g l e c r y s t a l s a p p h i r e ( A ^ O ^ ) discs.  I n o r d e r t o i n t r o d u c e a c e r t a i n amount of oxygen i n t o the copper  and c o n t r o l the oxygen p o t e n t i a l , the atmosphere i n the c l o s e d chamber s u r r o u n d i n g the specimen was r e g u l a t e d u s i n g a CO-CO^ gas m i x t u r e . the use of thermodynamic  With  r e l a t i o n s h i p s i t would be p o s s i b l e t o d e t e r m i n e  the oxygen p o t e n t i a l i n the system and t h e amount of d i s s o l v e d oxygen i n t h e copper.  I t was proposed a l s o t o use t h e s e s s i l e drop t e c h n i q u e t o  determine the fundamental r o l e p l a y e d by oxygen i n t h i s system. A f u r t h e r purpose of t h i s s t u d y was t o i n v e s t i g a t e the pene t r a t i o n of copper i n t o s a p p h i r e .  The dependence of copper p e n e t r a t i o n  on pxygen p o t e n t i a l and time was t o be e v a l u a t e d .  From t h i s s t u d y i t  was hoped t o d e t e r m i n e whether t h e copper w i l l c o n t i n u e t o p e n e t r a t e , f o l l o w i n g the i n i t i a l m e l t i n g , and d e s t r o y t h e i n s u l a t i n g p r o p e r t i e s of the a l u m i n a and e l e c t r i c a l p r o p e r t i e s ( c o n d u c t i v i t y ) of t h e copper l a y e r .  9  I I . EXPERIMENTAL  A.  Materials  1.  Sapphire The s i n g l e c r y s t a l d i s c s of s a p p h i r e (aluminum o x i d e ) used  throughout the i n v e s t i g a t i o n were s u p p l i e d by A d o l f M e l l e r Company. Specimens were c u t from 0.6  cm d i a m e t e r s i n g l e c r y s t a l r o d s , so as t o g i v e  two p a r a l l e l s u r f a c e , the top s u r f a c e b e i n g p o l i s h e d t o an o p t i c a l  finish.  The p o l i s h e d w o r k i n g s u r f a c e was a p p r o x i m a t e l y p a r a l l e l t o the (1012) p l a n e . I  The s a p p h i r e rods were produced  a maximum i m p u r i t y o f 200 ppm.  from gamma-alumina powder h a v i n g  During f a b r i c a t i o n the i m p u r i t y l e v e l  was  d e c r e a s e d , as s p e c t r o g r a p h s a n a l y s i s , c a r r i e d out i n the Geology Department of the U n i v e r s i t y r e v e a l e d the f o l l o w i n g i m p u r i t y l e v e l i n a t y p i c a l d i s c : Ca <  5 ppm,  Cr ^ 4 ppm,  Cu ^  3  ppm  Ga <  1 ppm,  Mg  Mn ^  8  ppm  S i 'V 15  ppm  Na < 10 ppm, i  5 ppm,  Pb ^ 1 ppm, .'  } •  T h i s a n a l y s i s i n d i c a t e s i m p u r i t y of a p p r o x i m a t e l y 51 ppm maximum, a c o n s i d e r a b l e improvement over t h e o r i g i n a l i m p u r i t y l e v e l of 200 ppm the a l u m i n a powder.  in  10 2.  Copper Copper was s u p p l i e d by t h e American S m e l t i n g and R e f i n i n g  Company i n t h e form o f 99.999+% copper r o d s .  Spectrographs analysis  s u p p l i e d w i t h t h e r o d l i s t e d i m p u r i t y l e v e l s as f o l l o w s : Fe  <  0.7 ppm, Sb < 1  Ni < 1  ppm, Pb < 1  ppm, B i < 0.1 ppm, Ag < 0.3 ppm, As < 2 ppm  Cr < 0.5 ppm, S i < 0.1 ppm, Te < 2 S  < 1  ppm, Sn < 1 ppm  ppm, Se < 1 ppm,  ppm.  Swaging and m a c h i n i n g were c a r r i e d o u t on t h e r o d s t o produce shaped specimens.  cylindrically  These were 0.2 cm d i a m e t e r f o r t h e w e t t i n g e x p e r i m e n t s  and 0.6 cm d i a m e t e r f o r t h e d i f f u s i o n s t u d i e s . 3.  C u p r i c Oxide C u p r i c o x i d e employed i n t h e d i f f u s i o n s t u d i e s was 99.999+%  purity. the  I t was s u p p l i e d by Johnson Matthey Chemicals L t d . , who r e p o r t e d  a n a l y s i s o f i m p u r i t i e s as f o l l o w s :  Cd = 5 ppm, Ba = 2 ppm, Bo < 1 ppm, Ca < 1 ppm, Mg < 1 ppm, Na < 1  4.  pm.  Alumina and Cuprous Oxide To produce t h e s y n t h e t i c copper a l u m i n a t e  cuprous o x i d e (Ck^O) were used.  (CUAIO2), a l u m i n a  The a l u m i n a (99.99+% p u r i t y ) was s u p p l i e d  by Koch and L i g h t Company and had i m p u r i t i e s l i s t e d a s :  Fe < 10 ppm, Na < 10 ppm, S i < 10 ppm, a l l o t h e r s < 1 ppm The cuprous o x i d e was s u p p l i e d by Rocky Mountain R e s e a r c h In,c. and was s p e c i f i e d as 99.999+% p u r i t y .  and  F i g u r e 4.  Furnace f o r S e s s i l e Drop Experiments.  These components were combined i n a s t o i c h i o m e t r i c m i x t u r e , b l e n d e d and heated a t 1000°C f o r t w e n t y - f o u r hours t o produce CuAlO^ Appendix V I ) .  H o t - p r e s s i n g was used t o g i v e a dense b u t t o n from w h i c h  s m a l l e r c y l i n d r i c a l specimens were c u t u s i n g an u l t r a s o n i c c u t t e r . f i n a l specimen d i a m e t e r was 0.6  B.  (See  The  cm.  Apparatus f o r S e s s i l e Drop E x p e r i m e n t s The a p p a r a t u s f o r c a r r y i n g out the s e s s i l e drop e x p e r i m e n t s  c o n s i s t e d of t h r e e major components - f u r n a c e , atmosphere c o n t r o l l e r and o p t i c a l system. 1.  Furnace S e s s i l e drop specimens were m e l t e d i n the f u r n a c e of the  d i l a t o m e t e r a p p a r a t u s (Theta I n d u s t r i e s , D i l a t r o n i c V, see F i g u r e 4 ) .  The  a l u m i n a d i s c s were p l a c e d on a h i g h p u r i t y (99.9%) Al^O-j p l a t e r e s t i n g on a l u m i n a powder i n t h e tube of the f u r n a c e .  Once t h e f u r n a c e was t u r n e d on  i t t o o k about 30 minutes t o r e a c h 1200°C. 2.  Atmosphere  Controller  I n o r d e r t o c o n t r o l the oxygen p a r t i a l p r e s s u r e i n the f u r n a c e , carbon monoxide and carbon d i o x i d e gases were mixed. r e g u l a t e d u s i n g f l o w meters.  The m i x t u r e was  T h i s m i x t u r e was t h e n f e d i n t o the f u r n a c e  c o n t a i n i n g the specimen and back t h r o u g h a second f u r n a c e t p w h i c h was attached a c a l c i a s t a b i l i z e d  z i r c o n i a oxygen probe (See Appendix I I ) .  By  measuring the p o t e n t i a l a c r o s s the z i r c o n i a probe, between the f u r n a c e atmosphere and a i r , i t was p o s s i b l e t o d e t e r m i n e the oxygen p a r t i a l p r e s s u r e i n t h e system.  F i g u r e 5 shows the atmosphere  controller.  13  F i g u r e 5.  Atmosphere C o n t r o l l e r .  3.  O p t i c a l System In o r d e r t o a s c e r t a i n the e x a c t shape of the m o l t e n copper drop  on the s a p p h i r e s u b s t r a t e an o p t i c a l system f o r d i r e c t o b s e r v a t i p n constructed.  T h i s system c o n s i s t e d of a 300 mm  the end of a 54 cm l o n g s t e e l tube ( F i g u r e 6 ) . a f f i x e d half-way the o t h e r end.  t e l e p h o t o l e n s e mounted on An 8X o b j e c t i v e l e n s e  was  a l o n g the tube and a 35 mm.single l e n s e r e f l e x camera a t Use of the s i n g l e l e n s e r e f l e x camera a l l o w e d f o r d i r e c t  o b s e r v a t i o n s as w e l l as t o photograph the s e s s i l e drop. Kodak p l u s - X f i l m (ASA 125) was  C.  was  For t h i s purpope  used w i t h exposure times o f 1 t o 2 seconds.  Apparatus f o r D i f f u s i o n Experiments For the d i f f u s i o n e x p e r i m e n t s the CENTORR f u r n a c e was  T h i s f u r n a c e was  used. ,  a t u n g s t e n f i l a m e n t surrounded by molybdenum heat s h i e l d s  i n a w a t e r c o o l e d copper chamber ( F i g u r e 7 ) .  A h e l i u m atmosphere was  i n the f u r n a c e ; under s l i g h t l y more than one atmosphere p r e s s u r e . c a l c i a s t a b i l i z e d z i r c o n i a oxygen probe was  uped  A  used t o d e t e r m i n e the p a r t i a l .  p r e s s u r e of oxygen i n the atmosphere above the specimens.  D. 1.  Specimen P r e p a r a t i o n Sapphire As the s a p p h i r e c y l i n d e r s a r r i v e d , w i t h two p a r a l l e l f a c e s ,  o p t i c a l l y p o l i s h e d , v e r y l i t t l e p r i o r p r e p a r a t i o n was  required.  one  The  s a p p h i r e c y l i n d e r s were washed w i t h e t h a n o l , d r i e d i n a bla^st of a i r , and weighed p r i o r t o use.  F i g u r e 6.  O p t i c a l System.  F i g u r e 7.  CENTORR Furnace.  17 2.  Copper B u t t o n s Once machined t h e copper b u t t o n s were washed i n t r i c h l o r e t h e n e  t o remove machine o i l and s t o r e d i n a d e s i c c a t o r f i l l e d w i t h n i t r o g e n . J u s t p r i o r t o use they were r i n s e d i n 50% HNO^ t o remove s u r f a c e c o n t a m i n a t i o n , washed w i t h water and e t h a n o l and d r i e d i m m e d i a t e l y w i t h a b l a s t of a i r . A f t e r w e i g h i n g t h e b u t t o n s used i n t h e s e s s i l e drop work were p l a c e d i n the furnace.  The b u t t o n s used i n t h e d i f f u s i o n e x p e r i m e n t s were weighed  and t h e n had c u p r i c o x i d e p l a c e d i n t o t h e c a v i t y machined i n t o t h e specimen. These were s u b s e q u e n t l y weighed a g a i n t o determine  t h e amount o f o x i d e  added, and p l a c e d i n t h e f u r n a c e .  E.  Experimental  Procedure  1.  S e s s i l e Drop  Experiments  An a l u m i n a support p l a t e was p l a c e d a t t h e bottom o f t h e tube f u r n a c e i n o r d e r t o g i v e a h o r i z o n t a l base on w h i c h t o r e s t t h e specimens. The s a p p h i r e c y l i n d e r s were then p l a c e d on t h e p l a t e and l e v e l was u s i n g a s t e e l sphere.  Once l e v e l was a c h i e v e d t h e s m a l l e r copper  were p l a c e d on top o f t h e s a p p h i r e , ( F i g u r e 8 ) t h e f u r n a c e r o l l e d p o s i t i o n and t h e s e a l s t i g h t e n e d .  checked buttons  into  Gas v a l v e s were t u r n e d on t o g i v e a f l o w  of a d e s i r e d m i x t u r e of C0-C0 and t h e over a l l f l o w was r e g u l a t e d w i t h an 2  o i l bubbler. test.  An approximate  e q u a l volume o f gas f l o w was used f o r each  The f l o w was a l l o w e d t o purge t h e system f o r one hour, checks were  mac^e t o f i n d t h e oxygen p a r t i a l ;pressure i n t h e system and s l i g h t a d j u s t ments were made t o a c h i e v e t h e d e s i r e d atmosphere i f n e c e s s a r y .  Once  s t a b i l i t y was reached t h e f u r n a c e was s w i t c h e d on and a l l o w e d t o r e a c h 1200°C (h hour r e q u i r e d ) .  O b s e r v a t i o n s and photographs were t a k e n o f t h e  18 drop a l o n g w i t h checks of the oxygen p a r t i a l p r e s s u r e . s w i t c h e d o f f and a l l o w e d t o c o o l down. o f f , and the specimen was  F i g u r e 8.  2.  The  furnace  was  A f t e r t h i s the gas f l o w was  turned  removed and weighed.  S e s s i l e Drop Specimen P r i o r t o M e l t i n g .  D i f f u s i o n Experiments A f t e r CuO  i t was  a d d i t i o n s t o the c a v i t y of the copper b u t t o n  p l a c e d on the s a p p h i r e and an alumina  This sleeve prevented copper-sapphire  s l e e v e was  ( F i g u r e 9)  p l a c e d over them.  the m o l t e n copper from f a l l i n g o f f the s a p p h i r e .  c o u p l e s were p l a c e d i n a s m a l l alumina  i n t o the h e a t i n g zone of the f u r n a c e .  The  c r u c i b l e and  l i d of the f u r n a c e was  lowered  b o l t e d on _3  and vacuum was  a p p l i e d t o out gas the system.  Once the vacuum o f  The  10  19  F i g u r e 9.  D i f f u s i o n Specimen P r i o r t o M e l t i n g .  atmospheres was o b t a i n e d t h e system was purged w i t h h e l i u m .  This  procedure  was r e p e a t e d t h r e e times and then t h e chamber was f i l l e d w i t h h e l i u m one atmosphere was r e a c h e d . out t h e experiment  A s l i g h t f l o w o f h e l i u m was m a i n t a i n e d  u s i n g an o i l b u b b l e r t o a s s u r e a p r e s s u r e  h i g h e r t h a n one atmosphere.  until through-  slightly  Once one atmosphere o f h e l i u m was reached t h e  f u r n a c e was s w i t c h e d on and a l l o w e d t o r e a c h 1200°C ( a p p r o x i m a t e l y 15 m i n u t e s ) . The  specimen was h e l d a t 1200°C f o r v a r i o u s p e r i o d s o f t i m e .  The f u r n a c e was  s w i t c h e d o f f and t h e specimen was a l l o w e d t o c o o l down ( a p p r o x i m a t e l y h h o u r ) . A f t e r t h i s t h e h e l i u m f l o w was t u r n e d o f f and t h e specimen was removed and weighed.  3.  E l e c t r o n Probe M i c r o a n a l y s i s A f t e r w e i g h i n g , t h e a l u m i n a s l e e v e s were removed and t h e s a p p h i r e  p o r t i o n o f t h e c o u p l e was c u t l e n g t h w i s e by a diamond saw. p o r t i o n o f t h e c o u p l e was then c u t u s i n g a j e w e l l e r s saw.  The copper A f t e r mounting  20 and p o l i s h i n g ( t o l u diamond p a s t e ) a carbon f i l m was d e p o s i t e d on t h e s u r f a c e t o a v o i d charge b u i l d - u p d u r i n g e x a m i n a t i o n i n t h e e l e c t r o n probe microanalyser.  A n a l y s i s was t h e n c a r r i e d out on the JOELGO E.P.M.  A number o f runs were made p a r a l l e l t o t h e i n t e r f a c e and s i n c e no a p p r e c i a b l e change was n o t e d i n p e n e t r a t i o n a c r o s s t h e specimen, random l o c a t i o n s were chosen a c r o s s t h e i n t e r f a c e .  five  From t h e s e l o c a t i o n s ,  a n a l y s i s was c a r r i e d out f o r copper i n t h e a l u m i n a i n s t e p s p e r p e n d i c u l a r t o the i n t e r f a c e .  Both copper and aluminum were m o n i t o r e d and counts over t e n  second i n t e r v a l s were r e c o r d e d .  I n o r d e r t o d e t e r m i n e t h e amount o f copper  p r e s e n t i n t h e s a p p h i r e , comparisons were made w i t h s t a n d a r d s o f copper, and alumina.  C o n s i d e r i n g oxygen as t h e o n l y o t h e r element p r e s e n t , c o r r e c t i o n s  were a p p l i e d t o c o n v e r t counts i n t o w e i g h t p e r c e n t copper u s i n g t h e MAGIC ( M i c r o p r o b e A n a l y s i s G e n e r a l I n t e n s i t y C o r r e c t i o n ) computer program. S i m i l a r a n a l y s e s were a l s o c a r r i e d out on some o f t h e s a p p h i r e - c o p p e r specimens produced d u r i n g t h e s e s s i l e drop e x p e r i m e n t s . 4.  M i c r o s t r u c t u r e Examination The specimens p r e p a r e d f o r a n a l y s i s on t h e e l e c t r o n probe  m i c r o a n a l y s e r were a l s o examined u s i n g an o p t i c a l m i c r o s c o p e , r e g i o n s as w e l l as i n t e r n a l s t r u c t u r e s were observed and i n a l l  Interface cases  r e p r e s e n t a t i v e photographs were t a k e n . 5.  Scanning E l e c t r o n M i c r o s c o p y A number o f t h e beads produced d u r i n g the s e s s i l e drop e x p e r -  iment were examined i n t h e ETEC s c a n n i n g e l e c t r o n m i c r o s c o p e .  A l s o some o f  the i n t e r f a c e r e g i o n s o f t h e d i f f u s i o n c o u p l e s were examined.  Representative  photographs were t a k e n .  21  III.  RESULTS ANJJ DISCUSSION. ,  A.  S e s s i l e Drop Experiments  1.  C o n t a c t Angle Measurements From the photographs  d i s c s ( F i g u r e 10)  , ,  of t h e m o l t e n copper drop on the s a p p h i r e  t h e c o n t a c t a n g l e was measured, a t a s p e c i f i c oxygen  p a r t i a l p r e s s u r e (Appendix I I ) .  The d e c r e a s e I n c o n t a c t a n g l e w i t h  i n c r e a s i n g oxygen p a r t i a l p r e s s u r e Is  o b v i o u s from t h e s e photographs.  The  a n g l e goes from an obtuse a n g l e a t a p a r t i a l p r e s s u r e o f oxygen a t 3.98 10  —16  (10.a) t o about a r i g h t a n g l e a t a p a r t i a l p r e s s u r e of 3.22  (lO.f).  Complete r e s u l t s a r e t a b u l a t e d i n Appendix  IV.  I t appears from F i g u r e 11  r e l a t i o n s h i p i s l i n e a r over the range s t u d i e d . found was 125°.  a t a p a r t i a l p r e s s u r e o f oxygen of 3.98  10  —5  On the b a s i s o f  these t a b u l a t e d r e s u l t s a p l o t of c o n t a c t a n g l e v e r s u s pO^ was on a s e m i - l o g s c a l e ( F i g u r e 11).  x  x  produced,  that; the  The maximum c o n t a c t a n g l e x 1Q  and was  123°-  T h i s v a l u e i s c o n s i d e r a b l y l o w e r t h a n the r e p o r t e d e q u i l i b r i u m  27 v a l u e of 163°  f o r supposedly pure copper, on s a p p h i r e , i n vacuum.  P r o b a b l y thijS d i f f e r e n c e i s due t o the a d s o r p t i o n of CO t o the s u r f a c e of t h e m o l t e n copper. I n f a c t the v a l u e s f o r s u r f a c e t e n s i o n of l i q u i d copper 15b 22 2 2 i n vacuum and CO have been r e p o r t e d as 1172 ergs/cm and 1250 ergs/cm respectively.  22  e  -  P„  2  -  F i g u r e 10.  1.48  x  1(T  6  f -  Po  2  - 3.22  S e s s i l e Drops at V a r i o u s Oxygen P o t e n t i a l s .  x  W'  (17x)  2.  I n t e r f a c i a l Energy T a k i n g the v a l u e s of 9 a t v a r i o u s p a r t i a l p r e s s u r e s o f oxygen  ( F i g u r e 11)  t h e i n t e r f a c i a l energy can be c a l c u l a t e d u s i n g the Young-Dupr  relationship  Y  where  y  = C T  y  copper-Al„0„ = A1_0_  SL  =  Y  SV " LV Y  C O S  6  i n t e r f a c i a l energy  - vapour i n t e r f a c i a l energy  Y „ = copper-vapour i n t e r f a c i a l energy. T  23(a)  To s o l v e t h i s e q u a t i o n , t h e v a l u e f o r t h e s o l i d - v a p o r i n t e r f a c i a l 2 energy was t a k e n a s 748 ergs/cm.  28 , a t 1200°C.  The v a l u e s f o r  l i q u i d - v a p o r i n t e r f a c i a l e n e r g i e s were found u s i n g t h e B a s h f o r t h and 40 Adams a n a l y s i s  . The v a l u e s found employing  t h i s t e c h n i q u e had a  r a t h e r l a r g e s c a t t e r and t h e r e f o r e were compared t o t h o s e v a l u e s found by Monma and Suto (from f i g u r e 3 ) . F i g u r e 11-a shows t h a t t h e v a l u e s found i n t h e p r e s e n t s t u d y agreed r e a s o n a b l y w e l l w i t h t h o s e r e p o r t e d by Monma and Suto.  F i g u r e 11-a  Y T T  7  versus l o g [0~]  24  From t h e s e d a t a a p l o t of i n t e r f a c i a l energy as a f u n c t i o n of l o g a r i t h m the oxygen p a r t i a l p r e s s u r e has been produced ( F i g u r e  of  12).  14 XIO  2  12  10-  8  10-16  |Q-<4  |0"  I0"  1 2  10  I0"  I0"  8  I0"  6  pOg  F i g u r e 12.  y  g L  V e r s u s pG^  (log  I0"  4  2  (atm)  scale)  From a p a r t i a l p r e s s u r e of oxygen of 3.98  x 10  -16  t o 5.07  x  2 the i n t e r f a c i a l energy v a r i e s from 1429-1465 ergs/cm T h i s v a r i a t i o n would e x p l a i n the change i n c o n t a c t of v e r y l i t t l e w e t t i n g  10  —3  2 t o 667-798 ergs/cm .  a n g l e from a c o n d i t i o n  to p r o g r e s s i v e l y b e t t e r wetting  as t h e oxygen p a r t i a l  pressure increases. The r e l a t i o n s h i p appears t o be l i n e a r ( i n a s e m i l o g a r i t h m i c p l o t ) up t o a p a r t i a l p r e s s u r e of oxygen of a p p r o x i m a t e l y 10  ,  beyond w h i c h the Y g T h i s c o u l d be due d i s t i n c t compound  3.  Adsorption  v a l u e s tend t o approach a c o n s t a n t a s y m p t o t i c a l l y .  L  t o the f o r m a t i o n of an i n t e r f a c i a l b a r r i e r J e i t h e r a 16  25 o r an oxygen l a y e r .  Isotherms 22  Monma and  Suto  have found t h a t the s u r f a c e t e n s i o n o f  copper v a r i e s w i t h oxygen c o n t e n t  (Figure 3).  i  a d s o r p t i o n on t h e l i q u i d - v a p o u r i n t e r f a c e was equation  From t;heir c u r v e , oxygen calculated using  Gibbs'  29  (see Appendix I ) i n the form:  RT  where:  liquid  Y T JjV T  8C  2 s u r f a c e t e n s i o n (ergs/cm )  =  7  C = [0] at % R = gas  constant  T = temperature  (°K)  2 T = coverage (mol/cm ) The use of t h i s form of the e q u a t i o n i s v a l i d f o r low c o n c e n t r a t i o n  of  s u r f a c e a c t i v e e l e m e n t s , w h i c h i s the case when oxygen i s d i s s o l v e d i n a l i q u i d metal.  V a l u e s of  .  were found by d i f f e r e n t i a t i n g the curve  surface tension versus composition i s o t h e r m was ,  evaluated  adsorption  (Figure 13).  The a d s o r p t i o n i s o t h e r m goes through a maximum of about -10  14.3  and from these v a l u e s the  of  x 10  2 mol/cm  I f t h i s v a l u e was  a t an oxygen c o n c e n t r a t i o n o f about 0.14  at.% [0].  taken as b e i n g e q u a l t o the s u r f a c e c o n c e n t r a t i o n , then interface  the s u r f a c e o c c u p i e d by one oxygen i o n on the l i q u i d - v a p o r / c a n be from the  expression  calculated  where N = Avogadro's number. —  T h i s v a l u e was  16  found t o be 11.6 x 10  2 cm .  r 1  (mol  IV  [0] F i g u r e 13.  A d s o r p t i o n Isotherm  otm%  (liquid-vapor).  An oxygen i o n i n the s t r u c t u r e of a densely-packed =2  O  s u r f a c e has an i o n i c r a d i u s o f 1.32A. —16 10  f i l m on a  Hence one 0  i o n o c c u p i e s 6.04  x  2 cm  .  T a k i n g i n t o account the d i s c r e p a n c y between t h i s v a l u e and  t h a t d e r i v e d from the e x p e r i m e n t a l r e s u l t s , and the f a c t t h a t r e p u l s i v e f o r c e s e x i s t between oxygen i o n s i t i s not l i k e l y the f i l m was packed oxygen i o n s . w i t h two C u i o n s +  densely  I f i t i s assumed t h a t each oxygen i o n was a s s o c i a t e d  of r a d i u s 0.96A t h e n the o x i d e f i l m would have o c c u p i e d  a l a r g e r a r e a per oxygen i o n .  The a r e a o c c u p i e d i n a d e n s e l y packed  film  i s 3.19  x 10  16  cm  2  t o t a l a r e a f o r 2 Cu  o r 6.38 +  16  x 10  i o n s and one  cm  0  =  2  f o r 2 Cu  i o n i s 12.4 —16  w i t h the e x p e r i m e n t a l  v a l u e of 11.6  H~  x 10  ions.  Therefore  —16  x 10  cm  at and beyond an oxygen c o n t e n t The  solid-liquid  , w h i c h agrees  2 .  I t appears t h a t on  b a s i s of t h i s c a l c u l a t i o n the l i q u i d - v a p o r i n t e r f a c e was f i l m of Cu^O,  2  cm  of 0.14  covered w i t h a  at.%  t o e v a l u a t e the amount of  d i s s o l v e d oxygen ( F i g u r e 14).  .  r  -  phe  i n t e r f a c i a l energy can be p l o t t e d as a f u n c t i o n  of d i s s o l v e d oxygen by i n v o k i n g S i e v e r t ' s Law  (ergs  the  SL  cm ) 14 2  XIO  2  12  10  8  10"?  ICf  IO"  4  3  I0"  2  10"'  10° [0]  F i g u r e 14.  Y  g L  V e r s u s [0] atm.%  (log  10'  atm% scale)  A g a i n a p p l y i n g the G i b b s ' e q u a t i o n  i t i s p o s s i b l e t o c o n s t r u c t the adsorp-  t i o n i s o t h e r m f o r the s o l i d - l i q u i d  i n t e r f a c e ( F i g u r e 15).  two a d s o r p t i o n isotherms  i t appears t h a t the oxygen was  Comparing the  f j.rst adsorbed a t  the l i q u i d - v a p o r i n t e r f a c e and then a t the s o l i d - l i q u i d i n t e r f a c e .  A  maximum of the s o l i d - l i q u i d a d s o r p t i o n i s o t h e r m was  18.78  -10 atomic p e r c e n t oxygen as 5.37 o c c u p i e d by each adsorbed  I  5  I0"  mol/cm .  l  I0"  4  2  s p e c i e s (S = —•)  |  I  I  IO"  x 10  3  IO"  2  D e t e r m i n i n g the a r e a  gave an apparent a r e a p e r i o n  I  I  I  10"'  10°  I0 [0]  F i g u r e 15.  A d s o r p t i o n Isotherm  t a k e n t o be a t  I. 1  atm  ( s o l i d - l i q u i d ) [ 0 ] atm.%  %  - log  scale).  Comparing t h i s v a l u e t o t h e a r e a o c c u p i e d by each adsorbed  species  a t t h e g a s - l i q u i d i n t e r f a c e , i t i s apparent t h a t t h e i n t e r f a c e i s n o t as d e n s e l y packed i f o n l y a monolayer of oxygen o r C u 0 i s c o n s i d e r e d . 2  i f i t i s assumed t h a t C u 0 i s adsorbed 2  of A^O^  and t h a t f o r each m o l e c u l e C^O  However, one  i s a s s o c i a t e d w i t h i t t h e n the a r e a a s s o c i a t e d w i t h the a d s o r p t i o n  o f eaeh oxygen i o n from t h e atmosphere can be c a l c u l a t e d . m o l e c u l e of C u 0 i s 12.4 x 10 o  —16  The a r e a f o r each  and s i n c e the i o n i c r a d i u s o f AI  III  29 o -16 2 i s 0.51A i t s a r e a w i l l be 0.9 x 10 cm . —16 oxygen i o n s w i l l then occupy 19.9 x 10  Two aluminum i o n s and t h r e e  2 cm .  The t o t a l a r e a a s s o c i a t e d —16 2 w i t h each a d s o r b i n g oxygen i o n i s t h e n 32.3 x 10 cm . T h i s v a l u e i s i n —16 2 good agreement w i t h t h e e x p e r i m e n t a l v a l u e o f 32.1 x 10 cm . The  agreement between e x p e r i m e n t a l  and c a l c u l a t e d v a l u e s f o r  the two i n t e r f a c e s i n d i c a t e s t h a t a Cu^O f i l m e x i s t s a t t h e l i q u i d - v a p o r i n t e r f a c e and a CuAlGv, f i l m e x i s t s a t t h e s o l i d - l i q u i d i n t e r f a c e , (Note: Cu„0 + A l 0 —>• 2CuA10 ). 2 3 2 o  1  4.  Work o f A d h e s i o n By l o w e r i n g t h e s u r f a c e t e n s i o n a t b o t h l i q u i d i n t e r f a c e s ( l i q u i d -  vapor and s o l i d - l i q u i d ) t h e bond s t r e n g t h between t h e m e t a l and c e r a m i c would i n c r e a s e , as i n d i c a t e d by t h e i n c r e a s e i n w e t t i n g .  The work r e q u i r e d t o  r u p t u r e t h i s bond, w h i l e t h e m e t a l i s i n t h e l i q u i d s t a t e , i s c a l l e d t h e work o f a d h e s i o n .  By d e f i n i t i o n i t i s g i v e n a s :  W  A  =  Y  LV  +  Y  SV ~ S L Y  ^  S 6 e  A  PP  e n d i x  I  )  T h i s d e f i n i t i o n was a p p l i e d t o d a t a p r e v i o u s l y r e p o r t e d and t h e r e l a t i o n s h i p o f t h e work o f a d h e s i o n t o oxygen c o n t e n t was found ( F i g u r e 16). appears t h a t t h e maximum a d h e s i o n o f t h e copper t o t h e s a p p h i r e o c c u r s a t about 0.01 atomic p e r c e n t  5.  It  substrate  oxygen.  I n t e r f a c i a l Radius C o n s i d e r i n g t h e s p r e a d i n g o f t h e drop w i t h oxygen a d d i t i o n s  can a l s o i n d i c a t e what r o l e t h e oxygen t a k e s i n p r o m o t i n g w e t t i n g . ' i n t e r f a c i a l a r e a can be expressed The  increase i n t h i s area  The  2 i n terms o f t h e b a s a l r a d i u s as Trr .  2 2 [ i . e . tr(r - r ) ] s h o u l d be a f u n c t i o n o f t h e o  500.  !—j  10  ;  —u,—:  ——: 10  [0  1 - ,  IO  Z  [0] atm F i g u r e 16.  ,  1  %  Work o f A d h e s i o n Versus, [0] atm.% ( [ 0 ] atm.% - l o g scal§).  a c t i v i t y o f oxygen.  S i n c e t h e a c t i v i t y can be approximated, a t low c o n -  c e n t r a t i o n s by t h e c o n c e n t r a t i o n , then a l i n e a r r e l a t i o n s h i p should  exist  between t h e d i f f e r e n c e i n a r e a and l o g [ 0 ] . The  r a d i u s , and hence t h e degree o f s p r e a d i n g , was measured as 2  a function of log^IO]. as i s F i g u r e 17.  These d a t a a r e p l o t t e d as r  2 r  versus  log [0] e  T h i s p l o t i n d i c a t e s t h a t as expected t h e s p r e a d i n g was  d i r e c t l y p r o p o r t i o n a l t o t h e l o g a r i t h m o f oxygen c o n c e n t r a t i o n , and hence the l o g a r i t h m o f a c t i v i t y a t l o w c o n c e n t r a t i o n s o f oxygen.  Which means  t h a t t h e i n t r o d u c t i o n o f oxygen i n t h e system a l t e r s t h e c h e m i c a l which enhances s p r e a d i n g by i n c r e a s i n g t h e i n t e r f a c i a l a r e a . possible, i f the y  i s higher than y J_iV  potential,  This i s  ( i n t h i s case s p r e a d i n g  will  t>J-i  d e c r e a s e t h e t o t a l f r e e energy o f t h e system) o r i f oxygen being a s u r f a c e a c t i v e agent l o w e r s t h e s u r f a c e t e n s i o n o f t h e l i q u i d copper (which was confirmed  by Monma and Sato) and as c a l c u l a t i o n showed t h a t t h e i n t e r f a c i a l  area i s covered by a s u r f a c e l a y e r w h i c h can i n t e r a c t w i t h A^O-j t o lower 27 the Y  S L  J  as A F f o r t h e r e a c t i o n between C u 0 and A 1 0 ^ i s h i g h l y n e g a t i v e . ?  9  31  E  00100  00050  -16 F i g u r e 17.  6.  -12  •8  log,  [cj ( [of in atm- °/ ) 9  S p r e a d i n g Versus l o g [ 0 ]  Examination of S o l i d i f i e d  e  Drops  A number of the s o l i d i f i e d drops were examined i n an o p t i c a l m i c r o s c o p e , i n t h e s c a n n i n g e l e c t r o n m i c r o s c o p e and i n t h e e l e c t r o n probe microanalyser.  On e x a m i n a t i o n i n an o p t i c a l m i c r o s c o p e i t was  upon s o l i d i f i c a t i o n some of the oxygen was an e u t e c t i c .  found t h a t  t r a p p e d i n t h e copper and  formed  The amount of e u t e c t i c formed was o b v i o u s l y dependent on the  p a r t i a l p r e s s u r e o f oxygen i n t h e system and hence on the d i s s o l v e d oxygen (Figure 18). E x a m i n a t i o n o f t h e t o p s o f t h e specimens  a l s o showed a marked  d i f f e r e n c e i n the e x t e r n a l s t r u c t u r e o f t h e drops as w e l l ( F i g u r e  19).  Upon s o l i d i f i c a t i o n t h e specimens w i t h h i g h e r oxygen c o n t e n t had a v e r y i r r e g u l a r s u r f a c e , due t o the f o r m a t i o n o f l a r g e copper g r a i n s w i t h c o p p e r oxygen e u t e c t i c a t t h e g r a i n b o u n d a r i e s .  In fact i r r e g u l a r i t i e s  i n the  32  Figure 18.  Eutectic Structure Sessile Drops. (350x).  a.  pC>2 = 3.98 x 10 ^  b.  pC^ = 2.16 x 10  F i g u r e 19.  -6  atmospheres.  atmospheres  Top S u r f a c e of S o l i d i f i e d Drops.  (lOOx)  s u r f a c e s were observed i n specimens s u b j e c t e d t o an atmosphere o f oxygen g r e a t e r t h a n 10 ^  atmospheres.  Cut and p o l i s h e d specimens examined on t h e e l e c t r o n probe microanalysers was  i n d i c a t e d t h a t copper p e n e t r a t e d  d e t e c t e d up t o a p p r o x i m a t e l y  100  microns.  i n t o the alumina. An a p p r o x i m a t i o n  p e n e t r a t i o n under t h e drops appeared as i n F i g u r e  L_J  centre  i_  0 05  ,  i  i  015  distance  F i g u r e 20.  of the  20.  ,  010  Copper  (cm)  Copper P e n e t r a t i o n Under S e s s i l e Drop.  F i g u r e 20 i n d i c a t e s t h a t t h e copper p e n e t r a t e s d i r e c t l y under t h e d r o p , and not t o t h e s i d e o f i t .  More p e n e t r a t i o n o c c u r s toward t h e c e n t r e o f t h e  drop as compared t o t h e edges.  35 B.  Diffusion  Experiments  In o r d e r t o determine i f the copper p e n e t r a t e s by a d i f f u s i o n a l p r o c e s s , t o determine the dependence of t h e p e n e t r a t i o n on time and oxygen c o n t e n t and t o examine f u r t h e r  the copper m i c r o s t r u c t u r e s upon s o l i d i f i c a t i o n ,  l a r g e r d i f f u s i o n c o u p l e s were p r e p a r e d .  Experiments were c a r r i e d out at  5, 20, 60 and 240 m i n u t e s , w i t h oxygen a d d i t i o n s of 0.13, 0.27,  0.57  and  1.39 wt.% f o r each time. A n a l y s i s of the h e l i u m atmosphere above the specimens, u s i n g a z i r c o n i u m oxygen sensor s i m i l a r t o t h a t used f o r s e s s i l e drop work, indicated  a v e r y low oxygen p a r t i a l p r e s s u r e .  The oxygen p a r t i a l p r e s s u r e  -13 was of the o r d e r of 10  atmospheres  i n a l l runs r e g a r d l e s s of the amount  of o x i d e added t o the copper specimens.  A t y p i c a l specimen upon removal  from t h e f u r n a c e appeared as i n F i g u r e 21.  F i g u r e 21.  A Diffusion  Specimen  36 1.  Interfacial  Region  The c u t and p o l i s h e d specimens were examined under the e l e c t r o n probe m i c r o a n a l y s e r .  I n s p e c t i o n o f t h e absorbed e l e c t r o n image  ( F i g u r e 22) i n d i c a t e d t h a t a d i s t i n c t  I t appears t h a t two d i s t i n c t  i n t e r f a c i a l zone was  formed.  r e g i o n s e x i s t i n the i n t e r f a c i a l zone.  r e g i o n i m m e d i a t e l y a d j a c e n t t o t h e a l u m i n a s u r f a c e appears t o be narrow and i s p o s s i b l y an adsorbed f i l m .  In addition to t h i s  One  fairly  region  a n o t h e r l a r g e r r e g i o n i n the copper a d j a c e n t t o the f i r s t r e g i o n appears to have a r e l a t i v e l y the  l a r g e amount of copper-oxygen e u t e c t i c .  X - r a y s f o r copper and aluminum  Monitoring  ( F i g u r e 23) i n d i c a t e s t h a t a t the  i n t e r f a c e t h e copper p o r t i o n i s s l i g h t l y d e f i c i e n t i n copper, h a v i n g a l a r g e r amount of e u t e c t i c .  T h i s d e f i c i e n c y s u g g e s t s the f o r m a t i o n of a  f i l m a t the i n t e r f a c e , of e i t h e r o x i d e o r copper a l u m i n a t e .  a.  F i g u r e 23.  Aluminum  X-Ray Images (2075x).  The p r o d u c t i o n o f a s u r f a c e l a y e r f i l m was  a t lower  c o n c e n t r a t i o n s than p r e d i c t e d by the s e s s i l e drop work. due  oxygen  T h i s was  probably  t o the d e c r e a s e i n r a t i o o f l i q u i d - v a p o u r i n t e r f a c e i n comparison t o  the l i q u i d - s o l i d i n t e r f a c e due  t o the d i f f e r e n c e i n shape o f the specimens  and due t o the use of an a l u m i n a s l e e v e . 2.  Copper P e n e t r a t i o n i n A l u m i n a P r e l i m i n a r y r u n s c a r r i e d out p a r a l l e l t o the i n t e r f a c e i n d i c a t e d  t h a t p e n e t r a t i o n of copper i n t o a l u m i n a was specimen t o the o t h e r . specimen.  constant  from one  s i d e of  F i v e random l o c a t i o n s were chosen a c r o s s each  C h a r a c t e r i s t i c X - r a d i a t i o n f o r copper and aluminum was  and r e c o r d e d  the  monitored  f o r t e n second counts a t s t e p s p e r p e n d i c u l a r t o the i n t e r f a c e .  These v a l u e s were a n a l y s e d u s i n g the "MAGIC" program (See Appendix V)  and  c a l c u l a t i n g the c o n c e n t r a t i o n o f oxygen by d i f f e r e n c e . Figures  24-29 i n c l u s i v e a r e p l o t s of the copper c o n c e n t r a t i o n s  p r o f i l e s beyond 20u i n t h e a l u m i n a . was  The  r e g i o n from the i n t e r f a c e t o 20u  not i n c l u d e d as the s c a t t e r of d a t a and the f a i l u r e o f c o r r e c t i o n  p r o c e d u r e s i n these r e g i o n s a l l o w e d o n l y q u a l i t a t i v e a n a l y s i s . due  i n p a r t t o the i r r e g u l a r n a t u r e of t h i s r e g i o n .  Scatter  From F i g u r e s  was  24-29 i t  appears t h a t the p e n e t r a t i o n of copper i n t o a l u m i n a i s c o n s t a n t w i t h time and oxygen c o n c e n t r a t i o n .  F u r t h e r i t appears t h a t copper i s d e t e c t a b l e up  to about 300u. The  l a c k o f dependence of the c o n c e n t r a t i o n p r o f i l e s on t i m e  i n d i c a t e s t h a t the p e n e t r a t i o n of copper i n t o a l u m i n a was d i f f u s i o n a l process.  I t appears t h a t the copper p e n e t r a t e d  w i t h i n the f i r s t f i v e minutes ( t h e y wpre i n c o n t a c t ) , and Further penetration probably p o s s i b l y be due  not a t r u l y  to d i f f u s i o n .  i n t o the  alumina,  then stopped.  o c c u r s , but t h i s w i l l be v e r y slow as i t would The p e n e t r a t i o n o f cppper as noted i n  40  F i g u r e 27.  Copper P e n e t r a t i o n i n t o AI 0  ( [ 0 ] =r 1.39  wt.%;  time = 60  min).  08  [0]  (wt%)=OI3  time =240 min  06  04  02h  4  0  80  120  160  200 distance  F i g u r e 28. Copper P e n e t r a t i o n i n t o A 1 0  -L 240  280  (microns)  ( [ 0 ] = 0.13 wt.%; time = 240 min)  2  10  08  ?  I  [o]  06|  (wt%)=l39  time = 240  min-  04  02  oL 4  0  80  120  160  ^200 distance  F i g u r e 29. Copper P e n e t r a t i o n i n t o A 1 0 2  240~  280  (microns)  ( [ 0 ] = 1.39 wt.%; time = 240 min)  42 F i g u r e s 26-29 i s p r o b a b l y c o n t r o l l e d by some r e a c t i o n w h i c h o c c u r s r a p i d l y as soon a s t h e copper m e l t s . The  e x i s t e n c e o f a r a p i d r e a c t i o n a t f i r s t m e l t i n g i s supported  by t h e o b s e r v a t i o n o f t h e s e s s i l e d r o p s .  These specimens were n o t e d on  m e l t i n g t o form a rounded drop w h i c h changed shape w i t h i n t h e f i r s t few seconds and then assumed a shape w h i c h d i d n o t a l t e r w i t h The  time.  l a c k o f dependence o f p e n e t r a t i o n on oxygen c o n t e n t , i n t h e  r e g i o n o f 0.13-1.39 [0] wt.%, i n d i c a t e s t h a t v e r y l i t t l e oxygen i s r e q u i r e d i n order t o a l l o w p e n e t r a t i o n t o occur. compositions  A l s o w i t h i n t h e g i v e n range o f  f u r t h e r copper p e n e t r a t i o n does n o t occur w i t h i n c r e a s e d  oxygen c o n c e n t r a t i o n s .  T h i s f a c t a l l o w s f o r t h e s e l e c t i o n o f t h e most  advantageous oxygen c o n c e n t r a t i o n (up t o 1.8 wt.%) t o be based s o l e l y on c o n s i d e r a t i o n s o f bond s t r e n g t h and copper m i c r o s t r u c t u r e s .  ;  43  Copper P e n e t r a t i o n Without Oxygen P r e s e n t I n o r d e r t o d e t e r m i n e i f any p e n e t r a t i o n o c c u r s w i t h o u t any oxygen, two experiments were c a r r i e d out w i t h no oxygen added.  W i t h no  oxygen p r e s e n t t h e copper d i d not wet the a l u m i n a , as i n d i c a t e d by t h e c u r v a t u r e o f t h e copper c l o s e t o t h e a l u m i n a i n t e r f a c e ( F i g u r e 3 0 ) .  F i g u r e 30.  Specimen w i t h no Oxygen A d d i t i o n (4 hours h o l d i n g t i m e ) .  44 Once removed from t h e a l u m i n a s l e e v e t h e copper drop c o u l d be e a s i l y s e p a r a t e d from t h e a l u m i n a drop w i t h v e r y l i t t l e e f f o r t .  Once c u t and  p o l i s h e d t h e a l u m i n a i n d i c a t e d v i r t u a l l y no p e n e t r a t i o n o f copper ( F i g u r e 31)  08  04  02  40  80  120  160  200 distance  -l  240  280  (microns)  F i g u r e 31. Copper P e n e t r a t i o n w i t h no Oxygen P r e s e n t ,  The s l i g h t c o n c e n t r a t i o n o f copper noted r i g h t a t t h e i n t e r f a c e i s p r o b a b l y due t o some s t i c k i n g a t t h e a l u m i n a s u r f a c e due p o s s i b l y - t o oxygen i m p u r i t i e s o r roughness a t t h e i n t e r f a c e .  5.  Copper A l u m i n a t e D i f f u s i o n In o r d e r t o determine t h e e f f e c t o f a CuAlO^ phase a t  i  j:he i n t e r f a c e , s y n t h e t i c C u A K ^ was produced w i t h copper-CuA102-alumina  (see Appendix V I ) .  A couple  was produced and h e l d a t 1200°C f o r f o u r hours.  Very l i t t l e p e n e t r a t i o n o c c u r r e d as i n d i c a t e d by t h e ease o f p u l l i n g t h e  45 v a r i o u s phases a p a r t  ( F i g u r e 32).  F i g u r e 32.  the copper a l u m i n a t e alumina i n d i c a t e s  The  l a c k of p e n e t r a t i o n of copper i n t o  Cu-CuAlO -AI 0  Couple.  and the subsequent l a c k of p e n e t r a t i o n o f copper i n the  that i f  CuA10 was 2  p e n e t r a t i o n of copper would o c c u r .  produced a t the i n t e r f a c e then no  Any p e n e t r a t i o n t h a t does occur must  have been p r i o r t o the f o r m a t i o n of t h i s phase a t the i n t e r f a c e .  This  statement i s i n agreement w i t h the p r e v i o u s l y noted r e s u l t s , t h a t copper penetrates  r a p i d l y and then s t o p s .  The p e n e t r a t i o n was  probably  the s p r e a d i n g of the oxygen a c r o s s the i n t e r f a c e p r i o r to the  during  formation  of an i n t e r m e d i a t e phase.  6.  Interface Microstructures E x a m i n a t i o n s were c a r r i e d out on the s c a n n i n g e l e c t r o n and  o p t i c a l microscopes. A number of specimens were f r a c t u r e d w h i l e b e i n g removed from the a l u m i n a s l e e v e s .  The copper appeared t o have a good bond w i t h  a l u m i n a as p i e c e s o f a l u m i n a were s t i l l a t t a c h e d t o the copper.  It  the  46 appeared  t h a t the i n t e r f a c e was a t l e a s t as s t r o n g as the a l u m i n a .  i n a r e a s where a c r a c k was propogated  In f a c t  a l o n g the i n t e r f a c e , i t would stop and  c o n t i n u e through t h e a l u m i n a c r y s t a l ( F i g u r e 3 3 ) .  The zone on the l e f t  s i d e of F i g u r e 33 r e p r e s e n t s f r a c t u r e through the i n t e r f a c e and the zone to the r i g h t through the a l u m i n a .  F i g u r e 33  t  Fracture Surface.  F r a c t u r e through the i n t e r f a c e was p r o b a b l y promoted by v o i d s which were developed on some specimens ( F i g u r e 34).  A c l o s e r examination  of these h o l e s ' ( F i g u r e 35) i n d i c a t e d a v e r y s i m i l a r s t r u c t u r e as found  on  -6 the top o f s e s s i l e drops above 10  atmospheres oxygen ( F i g u r e 1 9 ( b ) ) .  T h i s would i n d i c a t e t h a t a l o c a l pocket of oxygen was p r o b a b l y trapped i n t h i s a r e a c a u s i n g f o r m a t i o n o f t h e v o i d and the subsequent during  solidification.  structure  47  F i g u r e 35.  Structure at Void.  (800x)  48 Further examination,  i n the s c a n n i n g e l e c t r o n m i c r o s c o p e , of  the i n t e r f a c e of a specimen cut by a diamond saw adjacent  t o the i n t e r f a c e the s t r u c t u r e i s d i f f e r e n t than i n the b u l k of  the copper.  T h i s wide r e g i o n i s v e r y s i m i l a r to the one observed on  e l e c t r o n probe absorbed e l e c t r o n image. immediately  adjacent  F i g u r e 36.  7.  i n d i c a t e d t h a t i n a zone  the  U n f o r t u n a t e l y the r e g i o n  to the i n t e r f a c e i s not o b s e r v a b l e  i n t h i s photograph.  Scanning E l e c t r o n M i c r o s c o p e View of I n t e r f a c e . (3000x - 1.39 [0] wt.%)  Copper M i c r o s t r u c t u r e s Observations  of the changes i n s t r u c t u r e of the copper w i t h  oxygen a d d i t i o n s were c a r r i e d out on the o p t i c a l microscope. o f e u t e c t i c formed was  The amount,  i n c r e a s e d w i t h i n c r e a s i n g a d d i t i o n of oxygen.  F i g u r e s 37 to 40 show the e f f e c t of added oxygen on the m i c r o s t r u c t u r e of the copper.  From these photographs i t i s obvious t h a t w i t h p r o g r e s s i v e  a d d i t i o n s of oxygen the c o n d u c t i n g  p r o p e r t i e s of the copper w i l l  probably  d e c r e a s e due t o i n c r e a s e i n t h e amount of copper-oxygen e u t e c t i c . On t h e b a s i s o f t h e o b s e r v a t i o n s o f t h e copper m i c r o s t r u c t u r e s i t i s o b v i o u s t h a t t o have a r e l a t i v e l y c l e a n copper p o r t i o n o f t h e c o u p l e as l i t t l e oxygen as p o s s i b l e i s t h e most d e s i r a b l e .  Considering t h i s  fact  w i t h t h e work of a d h e s i o n ( F i g u r e 16) i t would appear t h a t an oxygen -2  c o n t e n t of about 10  a t o m i c p e r c e n t i s p r o b a b l y optimum.  T h i s c o u l d be  a c h i e v e d by m e l t i n g t h e copper on t h e a l u m i n a s u b s t r a t e i n an atmosphere -8  w i t h a p a r t i a l p r e s s u r e of oxygen o f about 10  C.  atmosphere.  A F i t of D a t a f o r y L>J_|  A f i t of t h e d a t a f o r Y T C  t e r m  s of c o n s t a n t s and  oxygen  was found t o be: Y  and Y  S L  SL  -  for l o g = Y " Y S V  for l o g  Y  SV- LV Y  Q  cos (95.5 - 2.20 l o g  e  10=])  L V  I 0 ] < —3.75 -{126(3,65 + l o g ^ O " ] ) }{cos (95.5 - 2.20  e  [0 ] > —3.75  e  =  logjp"])}  =  These e q u a t i o n s a r e b a s e d on the Young - Dupre  1  e q u a t i o n , and show t h e  e f f e c t of oxygen on t h e s o l i d - l i q u i d i n t e r f a c i a l e n e r g y . p o s s i b l e t o a p p l y t h i s e q u a t i o n t o o t h e r s i m i l a r systems.  I t may  be  50  F i g u r e 38.  E u t e c t i c a t 0.27 [ 0 ] wt.%.  F i g u r e 40.  E u t e c t i c at 1.39 [0] wt.%.  IV.  An i n v e s t i g a t i o n  CONCLUSION  on the i n t e r f a c i a l r e a c t i o n , d i f f u s i o n and  w e t t i n g b e h a v i o r between molten copper and s a p p h i r e has been c a r r i e d —16  —3  under c o n t r o l l e d oxygen p a r t i a l p r e s s u r e i n the range 10  out  to  10  atmosphere. I t was found t h a t the c o n t a c t angle p o r t i o n a l to l o g  p0  2  w i t h i n the range of p 0  2  (0) was d i r e c t l y p r o -  used.  S i m i l a r l y the  solid-  l i q u i d i n t e r f a c i a l energy was e v a l u a t e d and found to be d i r e c t l y p r o p o r t i o n a l to l o g Beyond 10  p0  2  up to a v a l u e of a p p r o x i m a t e l y 10 ^ atmosphere.  atmosphere,the  s o l i d - l i q u i d i n t e r f a c i a l energy approaches a  constant v a l u e a s y m p t o t i c a l l y i n d i c a t i n g the f o r m a t i o n of a b a r r i e r The G i b b s '  a d s o r p t i o n e q u a t i o n was used to e v a l u a t e  a d s o r p t i o n of oxygen to the l i q u i d - v a p o r and s o l i d - l i q u i d Calculations,  based on the G i b b s '  layer.  the  interfaces.  adsorption equation,  indicated  t h a t the l i q u i d - v a p o r i n t e r f a c e was covered w i t h a C u 0 l a y e r and the 2  s o l i d - l i q u i d interface with a CuAl0 iis,ing t h e o r e t i c a l i o n i c r a d i i U s i n g the v a l u e s  2  layer.  These r e s u l t s were confirmed  to determine coverage per i o n . of energies a s s o c i a t e d  w i t h the two  interfaces  the work of adhesion was c a l c u l a t e d as a f u n c t i o n of c o n c e n t r a t i o n of  oxygen.  -2 T h i s showed t h a t the work o f adhesion reached a maximum a t abput 10 oxygen.  atm.%  53 The  e f f e c t of oxygen on the b a s a l r a d i u s was  e v a l u a t e the e f f e c t on s p r e a d i n g . c o n t a c t a r e a was content.  I t was  a l s o used t o  found t h a t the change i n the  d i r e c t l y p r o p o r t i o n a l t o the l o g a r i t h m of oxygen  Hence s p r e a d i n g was  p r o p o r t i o n a l t o the l o g a r i t h m of oxygen  a c t i v i t y i n the system. F u r t h e r i t was  found t h a t a d i s t i n c t i n t e r f a c i a l r e g i o n  e s t a b l i s h e d between copper and a l u m i n a , the alumina.  The p e n e t r a t i o n was  and  t h a t copper p e n e t r a t e d  into  not dependent on time or oxygen c o n t e n t .  Copper appeared t o p e n e t r a t e w i t h i n the f i r s t few m i n u t e s and -9 10  was  the  diffusion  2  c o e f f i c i e n t was  approximately  cm / s e c .  p e n e t r a t i o n was  almost n o n - e x i s t e n t .  The bond a t the i n t e r f a c e was  W i t h no oxygen p r e s e n t ,  s t r o n g except i n r e g i o n s where  v o i d s were formed. F i n a l l y the m i c r o ^ t r u c t u r e of the copper was oxygen c o n t e n t .  From the Cu-0  found t o v a r y w i t h  phase diagram, i t i s e x p e c t e d t h a t the amount  of e u t e c t i c formed s h o u l d i n c r e a s e w i t h i n c r e a s i n g oxygen a d d i t i o n and was  experimentally  this  confirmed.  An attempt has been made to o b t a i n an e q u a t i o n based on  the  Young-Dupre e q u a t i o n , when the d i f f e r e n t energy v a l u e s are a f f e c t e d by oxygen p o t e n t i a l of the system.  the  V.  RECOMMENDATIONS FOR FUTURE STUDY  S i n c e i t has been shown t h a t oxygen a d d i t i o n s a i d t h e w e t t i n g of copper t o a l u m i n a , i t would be u s e f u l t o i n v e s t i g a t e t h e m e c h a n i c a l s t r e n g t h o f t h e bond formed on s o l i d i f i c a t i o n o f t h e d r o p s .  Further i t  would be u s e f u l t o s t u d y t h e m e c h a n i c a l p r o p e r t i e s o f c o p p e r - a l u m i n a cermets as a f u n c t i o n o f copper o x i d e a d d i t i o n s .  I t s h o u l d be p o s s i b l e  to i n c r e a s e t h e s t r e n g t h o f t h e s e b o d i e s w i t h o n l y s l i g h t  additions of  oxygen. Use of oxygen as a bonding agent f o r m i c r o c i r c u i t s c o u l d a l s o be i n v e s t i g a t e d .  Of importance would be t h e e f f e c t o f oxygen on t h e  c o n d u c t i v i t y o f t h i n copper  film.  S i m i l a r work as c a r r i e d o u t i n t h e p r e s e n t s t u d y would be u s e f u l i n t h e n i c k e l - a l u m i n a system.  also  N i c k e l - a l u m i n a composite would  be more u s e f u l i n a p p l i c a t i o n where m e c h a n i c a l s t r e n g t h s a t e l e v a t e d temperatures a r e o f i m p o r t a n c e .  55  APPENDIX I  SESSILE DROP TECHNIQUE AND GIBBS' EQUATION  A.  S e s s i l e Drop  Technique  The t h e o r y o f w e t t i n g o f c e r a m i c s by l i q u i d m e t a l s has been 31 o u t l i n e d i n d e t a i l by T a y l o r .  Considering  t h e shape o f a m o l t e n drop on  a s o l i d s u r f a c e , an e q u i l i b r i u m w i l l d e v e l o p so t h a t t h e i n t e r f a c i a l t e n s i o n s w i l l tend t o form a minimum o v e r a l l energy c o n f i g u r a t i o n .  For  s m a l l drops t h e t r u e e q u i l i b r i u m a t a s o l i d - l i q u i d m e t a l - v a p o r i n t e r f a c e can be shown d i a g r a m a t i c a l l y as i n F i g u r e 41(a) where: ff „ c  OVJ  a  = YCTT bV  = y  cr  Lo  = y  i n t e r f a c i a l t e n s i o n between t h e s o l i d and v a p o r .  =  = i n t e r f a c i a l t e n s i o n between t h e l i q u i d and t h e vapor. interfacial 1.1 solid.  = Tc  LD  t e n s i o n between t h e l i q u i d and t h e  6 = c o n t a c t a n g l e - a n g l e t h r o u g h l i q u i d , between l i q u i d and p l a n e o f s o l i d . ty = a n g l e t h r o u g h l i q u i d , between l i q u i d and s o l i d liquid interface.  Thus t h e b a l a n c e o f f o r c e s when r e s o l v e d h o r i z o n t a l l y i s :  Y  SV  =  Y  LV  C  O  S  9  +  Y  LS  C  P  i  n  *  S  and when v e r t i c a l l y i s :  Y  LS  S  i  n  *  =  Y  LV  S  6  56  q  fi  Gas (G)  (a)  Q Liquid  -Jjf-lU ?^"~~*Osi  °st  F i g u r e 41. (a) (b)  Solid (S)  Solid (S)  Contact A n g l e R e l a t i o n s h i p s .  31  w i t h b a l a n c e o f v e r t i c a l components. w i t h o u t b a l a n c e of v e r t i c a l components.  Under p r a c t i c a l c o n d i t i o n s t h e s o l i d can accomodate s t r e s s and the v e r t i c a l f o r c e s seldom o c c u r , and hence i n the m a j o r i t y o f cases w e t t i n g d e s c r i b e d by the p s e u d o e q u i l i b r i u m c o n f i g u r a t i o n shown i n F i g u r e 4 1 ( b ) .  Thus the pseudo-  e q u i l i b r i u m c o n d i t i o n can be s t a t e d as f o l l o w s : 32,33. Y  SV  =  Y  LS ' LV Y  C  °  S  From the above r e l a t i o n s h i p t h e work o f a d h e s i o n follows: ^ LV Y  = Y  L V  +  Y  SV^  Y  SL  ( 1 + cos 6)  i s d e f i n e d as  Hence the work o f a d h e s i o n can a l s o be d e r i v e d from the contact angle  B.  Gibbs'  pseudoequilibrium  0.  Equation  The  e f f e c t of a d d i t i o n s t o the l i q u i d melt i s d i c t a t e d by  change i n f r e e s u r f a c e energy caused by the a d d i t i o n .  Preferential  surface  a d s o r p t i o n o f the a d d i t i o n r e s u l t s i r i a minimum f r e e s u r f a c e energy. 29  Q u a n t i t a t i v e l y t h i s a d s o r p t i o n i s expressed  by the Gibbs'  equation r.  -  =  i and at low  a) ±  concentrations:  a#  r  1  and s i n c e :  3i  RT3(ln  _  3  Y  RT3(ln  3(In C J ) = -  c ) ±  9c. —— c  the  adsorption  58  APPENDIX I I  ZIRCONIA (CALCIA STABILIZED) PROBE FOR CONTROL OF OXYGEN ATMOSPHERE  The  d e s i g n and o p e r a t i o n o f t h e oxygen probe have been o u t l i n e d 34  in detail previously.  B r i e f l y , t h e probe c o n s i s t e d o f a c l o s e d  calcia  s t a b i l i z e d z i r c o n i a tube w i t h p l a t i n u m c o n t a c t s on t h e i n t e r i o r and e x t e r i o r o f t h e c l o s e d end.  When t h e c l o s e d end was p l a c e d i n c o n t a c t w i t h t h e gas  t o be measured and a r e f e r e n c e gas o f known oxygen c o n t e n t p o t e n t i a l was e s t a b l i s h e d a c r o s s t h e z i r c o n i a tube.  ( a i r 0 . 2 1 atm) a  From t h i s p o t e n t i a l  the oxygen p a r t i a l p r e s s u r e i n t h e system c o u l d then be c a l c u l a t e d u s i n g the f o l l o w i n g thermodynamic r e l a t i o n s h i p : E  ^^2^s  where:  (p0 ) 2  r  =  o x  yS  = — • In o nF  e n  (  P V s  ( o ) P  2  [1] r  p a r t i a l pressure  i n t h e system (atmospheres)  = r e f e r e n c e oxygen p a r t i a l p r e s s u r e  R = gas c o n s t a n t  (atmospheres)  (calories/mole)  T = t e m p e r a t u r e (°K) F = Faraday c o n s t a n t  (cal/equiv.)  n = no. o f molar e q u i v a l e n t  The  C0  2  (4 f o r 0^)  - CO gas e q u i l i b r i u m can be c o n s i d e r e d u s i n g t h e f o l l o w i n g e q u a t i o n :  co ^=±: 2  CO + ho  2  59 from  which: p(CO) • p ( 0 )  2  2  K  o  [2]  plcOJ  s o l v i n g f o r p(C> ) g i v e s : 2  K  p(o )  H2  q  p(C0 ) 2  [3]  p(CO)  2  35 reported value  forK  i s given as:  q  l o g  10 o K  _M^57  +  4  >  5  2  [4]  8  =  s u b s t i t u t i n g t h i s i n t o t h e above e q u a t i o n and t a k i n g l o g a r i t h m e y i e l d s :  p(co ) 2  l°g  1 0  P0  2  = 2 log  + 2(-  1  P(CO)  4  ,  7  5  7  + 4.528)  [5]  S u b s t i t u t i n g [5] i n t o e q u a t i o n [1] g i v e s t h e r e l a t i o n s h i p :  E  o  =  2.30 RT nF  p(co X 2  log  1 0  ( 0 ) P  2  r  - 2 log  1 ( )  ^  I t i s now p o s s i b l e t o c a l c u l a t e t h e v a l u e of S u b s t i t u t i n g t h i s v a l u e i n t o e q u a t i o n [3] p a r t i a l p r e s s u r e i n t h e system.  2(-  1  4  ,  7  5  7  + 4.528)  [6]  P(C0 ) . * from e q u a t i o n [ 6 ] , p (.00)  and s o l v i n g g i v e s t h e oxygen  APPENDIX I I I  SESSILE DROP DATA  Run No.  Measured  O2 probe  o  wt.AI2O3  wt. Cu  8 (deg)  (g)  (g)  (g)  Voltage  Temp.°C  X 201  111 -115°  0.6344  0.1145  0.792  0.707  941  1.90  X 202  84°- 91°  0.6350  0.1122  0.7476  0.360  896  3.18 x 1 0  X 203  108°-111°  0.6344  0.1156  0.7507  0.953  904  0.234  2.74 X I O "  1 3  X 205  112°-117°  0.6344  0.1054  0.7400  0.894  858  1.16  6.79 X I O "  1 2  X 206  109°-114°  0.6373  0.1131  0.7422  0.805  866  6.57  2.16 X I O "  1 0  X 207  H5°-120°  0.6338  0.1093  0.7438  1.005  871  0.108  5.85 X I O "  1 4  X 208  123°-125°  0.6359  0.1060  0.7436  1.131  861  8.91 x IO"  3.98 X I O "  1 6  X 209  107°-110°'  0.6372  0.1113  0.7487  0.775  862  1.27  8.08 X I O "  1 2  0.6349  0.1147  0.7479 -  0.736  863  2.78  3.87 X I O "  1 1  91.65  4.21 X IO"  8  6  X 210  0  107.5°-109°  F i n a l wt.  Probe  p(C0 )  P  2  P(C0)  2  1.81 X I O " 5.07 X 1 0 "  4  3  X 211  100°-105.5°  0.6348  0.1142  0.7492  0.687  849  X 212  90°- 94°  0.6369  0.1174  0.7548  0.591  862  5.43 x 1 0  2  1.48 X IO"  X 215  94°- 96°  0.6374  0.1100  0.7477  0.509  870  2.53 x 1 0  3  3.22 X I O  1 1  3  - 5  APPENDIX IV  SIEVERT'S LAW  19 U s i n g t h e v a l u e f o r AF as g i v e n by W i l d e r  y i e l d s the f o l l o w i n g :  AF = 18,100  %0  y [0] a t . p e t . i n  AF = RT InK -AF  K = exp  K = 485  -^r  R = 1.987 c a l / m o l e °K T = 1200 + 273 °K  @ 1200°C  21 Hence S i e v e r t ' s Law  c a n be w r i t t e n as f o l l o w s : [0] = 485 [at.%]  P  0 z  62  APPENDIX V  ELECTRON PROBE MICROANALYSIS  The use o f the e l e c t r o n probe m i c r o a n a l y s e r t o  determine 36  c o n c e n t r a t i o n s o f v a r i o u s s p e c i e s has been reviewed by Brown.  I n the  p r e s e n t s t u d y counts taken f o r t e n second i n t e r v a l s were a n a l y s e d u s i n g the "MAGIC" program, of Colby  37  as adapted by O'Brien  T h i s program c o r r e c t s raw microprobe  ^8  (Feb. 1970).  X-ray i n t e n s i t y d a t a f o r dead-time  l o s s e s , background a d s o r p t i o n ( H e i n r i c h , Duncumb-Shields, P h i l i b e r t ) c h a r a c t e r i s t i c f l u o r e s c e n c e (Reed), b a c k s c a t t e r l o s s e s (Duncumb) and i o n i z a t i o n - p e n e t r a t i o n l o s s e s ( P h i l i b e r t - T i x i e r ) , but uses the S e l t z e r v a l u e s f o r the mean i o n i z a t i o n p o t e n t i a l . i s r e p o r t e d by Colby t o g i v e r e s u l t s t o w i t h i n ± 4%  Berger-  Use o f t h i s program ( r e l a t i v e ) of  chemical  analysis. I n the r e g i o n l e s s than ^ 20um from t h e s u r f a c e , the a t i o n of t h e c o n c e n t r a t i o n of Cu was v e r y u n r e l i a b l e due t o two One  determinreasons.  - due t o d i f f e r e n c e s i n the t h i c k n e s s o f t h e i n t e r f a c e l a y e r l a r g e  amounts of s c a t t e r o c c u r r e d i n t h e d a t a .  Second - c o r r e c t i o n f a c t o r s i n  t h i s r e g i o n were v e r y h i g h (over 30% and c l o s e t o the copper w e l l 100%)  and as a r e s u l t f i n a l c o m p o s i t i o n would not be r e l i a b l e .  over  Beyond  ^ 20 microns however, s c a t t e r and c o r r e c t i o n f a c t o r s were a c c e p t a b l e .  APPENDIX V I  Y  Run Number  6 (deg)  O T  VALUES  Y  * L V  2 (ergs/cm )  Y ( e r g 3/cm ) S L  £  X 203  108  X 205  112  -  117  1250  1216  X 206  109  - 114  1235  1155  X 207  115  -  120  1250  1276  X 208  123  - 125  1250  1429  -  X 209  107  - 110  1250  1113  - 1176  X 210  107. 5- 109  1250  1124  X 211  100  1080  935  X 212  90  X 215  94  X 201 X 202  * see F i g u r e 3.  111 84  1276  1250  1196  91  776  667  111  1250  1134  - 1196 - 1315  - 105.5  -  -  115  798  1256 1373 1465  -  1035  1155  94  852  748 -  950  96  775  802  -  829  APPENDIX V I I  X-RAY ANALYSIS  The ASTM s t a n d a r d X-ray c a r d f o r CuAlC^ i s g i v e n below. Comparison o f t h e peaks on t h e d i f f r a c t i o n p a t t e r n t a k e n (as on t h e f o l l o w i n g page) i n d i c a t e s t h a t t h e m a t e r i a l produced was CuA10 . o  9-185 d  2.38 100  I/I.  FUd. CuKa Cutoff Ref.  HAHN  2.44  5.61  CUAL0  80  80  30  COPPER  1.542 I/I,  A AND  2.82  LORENT,  Filter Nl  2  ALUMINATE  dA  Dia. ?  Z.  ANIORG.  ALLGEM.  CHEM.  279  241  (i95f; Sys.  a,, 5.896 o 28.1° Ref.  S.G.  RHOMB O H E D R A L  bo  Co  S  y  D'  3D  - R3M  A Z 1  C Ox  IBID.  n IU &  iQ  2V Ref. "HEXAGONA  D 4.897  L:  Sign  Color  rnp  A =2.849, C =16.98, C=5.95, Z = l ; D  ISOSTRUC TURAL  0  0  *ITH  CUFE0 ; 2  NAHF  2  TYPE.  X  5.104,  nil  dA  I/I,  hkl  HEXAGONAL  0.974 .939 .93B  20 5 10  .912  10  1.0.16 0.0.18 (211,212 (1.0.17 214  I/I.  VISUAL  1NDICES  5.61 2.82 2.437 2.376 2.133  30 80 80 100 50  1.877 1.732 1.612 1.426 1.401  20 10 50 40 30  1.274 1.225 1.188 1.14B 1.089  40 116 20 202 10 204 20 119,0.0.1! 10 1.0.14 30 208 30 j 1.1.12 2.0.10  1.069 1.00B  003 006 101 102 104 009 107 108 110 1.0.10  1  F i g u r e 42. ASTM S t a n d a r d X-ray Card.  u r e 43.  D i f f r a c t i o n P a t t e r n f o r S y n t h e t i c CuAlO  66  BIBLIOGRAPHY  1.  H e l g e s s o n , C l a e s I . , " C e r a m i c - t o - M e t a l Bonding", Boston Tech. Pub. Cambridge, Mass. (1968).  Inc.,  2.  van Houten, C R . , "A Survey of C e r a m i c - t o - M e t a l Bonding", Am. B u l l . 38, (6) 301 (1959).  Soc.  3.  A l l e n , B.C.  4.  S h e v l i n , T.S.,  5.  C a r t e r , R.E.,  6.  Adams, R.B.  7.  Campbell, J.B., M a t e r i a l s and Methods 31 (5) 59  8.  K i n g s t o n W.E., N.Y., (1951).  9.  Pask, J.A. and F u l r a t h , R.M.,  and K i n g e r y , W.E., J . Am.  Trans. A.I.M.E. 215, 30  Cer. Soc. 37_, 140  i b i d . 44, 116  and Pask, J.A.,  (1961). i b i d . 44, 430  (1961). (1950).  "The P h y s i c s of Powder M e t a l l u r g y " , 1 s t ed., M c G r a w - H i l l , Cer. Soc. 45, 592  11.  Widman, H.,  Glas-Email-Keramo-Technik  12.  Bron, V.A.,  Ogeneupory 16 (7) 312  13.  Comstock, G.E.,  14.  Komatsu, N. and G r a n t , N.J., Trans A.I.M.E. 224, 705  16.  i b i d . 57, 359  J . Am.  P i n c u s , A.G.,  b. i b i d . ,  (1959).  (1954).  10.  15a. M i s r a , S.K.,  Cer.  (1962).  (1953). 14 (6) 205  (1963).  (1951).  (Norton Co.), U.S.P. 2, 618, 567  M.A.Sc. t h e s i s , U n i v e r s i t y of B.C.,  (1952). (1962).  p.34  (1964).  p.22.  C h a k l a d e r , A.CD., Armstrong, A.M. 51 (11) 630 (1968).  and M i s r a , S.K.,  J . Am.  Cer.  Soc.  17a. M e t a l s Handbook, 7 t h ed. p.1199. b. O s t e r w a l d , J . , Z. M e t a l l . , 59, 573 and R i c h a r d s o n , F.D.,  (1968).  18.  Diaz, CM.  Trans. I.M.M. ( S e c t . C ) , 7_6, 196  19.  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Young, T., P h i l . T r a n s . 1805, p.74; Young, T., m i s c e l l a n e o u s work, London, J . Murray, 1855, V . I . (ed. P e a c o c k ) , p.432.  33.  Duprd, A., " T h d o r i e mdchanique de l a chaleur'J P a r i s , 1869, p.369.  34.  B a r t o n , R.G., M e t a l l u r g y 455 R e p o r t , Department o f M e t a l l u r g y , U n i v e r s i t y of B r i t i s h Columbia, 1972.  35.  Hagemrk, K. and B r o l i , M.,  36.  Brown, L.C. and Thresh H., T o o l s and Techniques i n P h y s i c a l M e t a l l u r g y ed. Weinberg, F., M a r c e l Dekker, I n c . , N.Y. V.2, p.600 (1970).  37.  C o l b y , J.W., "MAGIC I I I - A Computer Program f o r Q u a n t i t a t i v e E l e c t r o n M i c r o p r o b e A n a l y s i s " , B e l l T e l . Lab., A l l e n t o w n , Penn. (1969).  38.  O ' B r i e n , T.E., "MAGIC Program" Dept. of M e t a l l u r g y , U n i v e r s i t y of B r i t i s h Columbia (1970).  39.  P a l a d i n o , A.E.  40.  B a s h f o r t h , F. and Adams, J.C., "An Attempt t o T e s t t h e T h e o r i e s o f C a p i l l a r y A c t i o n " , Cambridge, U n i v e r s i t y P r e s s , 1883.  and N a i d i c h , Y.V.,  and Baker, E.H.,  J . Am.  Trans. A.I.M.E., 345, 1721  J . of Mat.  Cer. Soc. 55 (6) 300  Scientific  Sc. 7_, 476  (1961). Inst. Metall.  i  (1957).  Russ. J . of Phys. (1972). (1964).  (1972).  P a p e r s , Dover, N.Y.  V^JL (1961).  J . Chem. Phys. 33_ ( 2 ) , 480  (1960).  Gauthier-Villars,  J . I n o r g . N u c l . Chem., V.28,  and K i n g e r y , W.D.  (1969).  1966,  , J . Chem. Phys. 37_ (5) 957  p.2840.  (1962).  

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