A new technique for preparing metal/oxide TEM cross sections

Abstract

H i g h q u a l i t y , e l e c t r o n t r a n s p a r e n t specimens o f m e t a l / o x i d e cross s e c t i o n s a r e necessary t o p e r f o r m some of t h e more s o p h i s t i c a t e d s t u d i e s i n v o l v i n g TEM and STEM a p p l i c a t i o n s . d u r a b l e specimens i n a simple and c o n s i s t e n t f a s h i o n . T h i s communication d e s c r i b e s a t e c h n i q u e t h a t can be used t o p r e p a r e specimens o f m e t a l i o x i d e c r o s s s e c t i o n s i n a 3 mm diameter mount.The a l l o y of i n t e r e s t i s c u t i n t o b a r s a p p r o x i m a t e l y 1.5 mm by 0.75 mm by 10 mm. Only one of t h e l a r g e f a c e s need be prepared f o r o x i d a t i o n t r e a t m e n t s . The b a r s a r e o x i d i z e d under t h e a p p r o p r i a t e e x p e r i m e n t a l c o n d i t i o n s . Next, a t h i n c o a t of s i l v e r p a i n t i s a p p l i e d t o t h e d e s i r e d o x i d i z e d s u r f a c e o f each b a r ( F i g . 1 ) . The p a i n t e d surfaces a r e p l a c e d and h e l d t o g e t h e r u n t i l t h e p a i n t d r i e s . The r e s u l t i n g j o i n t has s u f f i c i e n t s t r e n g t h f o r s u i t a b l e h a n d l i n g o f t h e specimen b a r sandwich. The sandwich i s then p l a c e d i n a s p e c i a l l y designed s t a i n l e s s s t e e l mold and c e n t e r e d w i t h set-screw p i n s ( F i g . 2 ) . The purpose o f t h e mold d e s i g n i s t o h o l d t h e sandwich i n p l a c e i n s i d e a 3 mm diameter bore i n t o which a m o l t e n a l l o y i s i n j e c t e d . F o l l o w i n g a l i g n i n g o f t h e sandwich i n t h e mold, a p i e c e ofa Zn-4 a t % A l -1 a t % Cu a l l o y i s p l a c e d i n t h e r i s e r p o r t i o n o f t h e mold. T h i s a l l o y was chosen because o f i t s low m e l t i n g temperature (415 " C ) , s u f f i c i e n t s t r e n g t h and h i g h thermal expansion c o e f f i c i e n t which r e s u l t s i n a compressive s t r e s s on t h e specimen sandwich h e l p i n g t o h o l d t h e two h a l v e s t o g e t h e r . The e n t i r e mold i s heated q u i c k l y w i t h an o x y -a c e t y l i n e t o r c h u n t i l t h e a l l o y i s m o l t e n . A g l a s s tube connected t o a r u b b e r b u l b i s p l a c e , 1983; Newcomb and Stobbs, 1985; S a w h i l l and Hobbs, 1984; Bennett, D e s p o r t and Labun, 1987). The use o f epoxy r e s i n s ( K i n g , Peterson and Reddy, 1984) i s e l i m i n a t e d so t h a t o r g a n i c s o l v e n t s can be used t o c l e a n t h e specimens. Two d i f f e r e n t e x p e r i m e n t a l c o n d i t i o n s can be i n c o r p o r a t e d i n t o one specimen. d over t h e r i s e r and i n c o n t a c t w i t h t h e mold. A b l a s t o f a i r causes t h e m o l t e n a l l o y t o flow around and encapsulate t h e specimen b a r sandwich. The i n j e c t i o n process i s necessary t o c o u n t e r s u r f a c e t e n s i o n e f f e c t s o f t h e m o l t e n a l l o y d r o p l e t . 4 f t e r...

Preparation of cross‐sectional specimens of ceramic thermal barrier coatings for transmission electron microscopy

“…Since the failure mechanism in these systems often involves spallation of the ceramic coating from the metallic substrate, it is important to prepare cross-sectional thin films of the ceramic-metal interface for transmission electron microscopy (TEM) in order to relate service performance of the coatings with phase distribution and microstructure in this region. The preparation of cross-sectional specimens for TEM has been described previously on several occasions (Abraham and Buicchi, 1974;Bravman and Sinclair, 1984;Doychak, 1989;Flutie, 1986;Shen and Marcus, 1980;Wetzel, 19891, particularly for systems involving semiconductor substrates. The basic procedure involves joining several interfaces by means of a suitable epoxy and slicing this resulting composite with a saw to obtain a cross-sectional thin film.…”