Use of SEM for studying fabric of undistributed natural sediment

Abstracts of Scandinavian Society for Electron Microscopy

SURFACE STRUCTURE ANALYSES G A L V A N I Z E D STEEL

OF

Else B r e v a l Surface Coatings Technology, Technol o g i c a l I n s t i t u t e , B o x 141, D K - 2 6 3 0 o Tastrup, Denmark

Five d i f f e r e n t types of steel have b e e n h o t - d i p galvanized. The crude surfaces w e r e p r e t r e a t e d and c o a t e d w i t h six d i f f e r e n t p a i n t systems. S u r f a c e s t r u c t u r e a n a l y s e s of the crude zinc surface, the p r e t r e a t e d and c o a t e d zinc s u r f a c e w e r e c a r r i e d out. These e x a m i n a t i o n s W e r e c o r r e l a t e d with the m e c h a n i c a l p r o p e r t i e s , as for ins t a n c e h a r d n e s s and a d h e s i o n of the p a i n t film. The results s h o w e d that s u r f a c e s t r u c t u r e and p a i n t p r o p e r t i e s vary from one area to a n o t h e r even w i t h i n one type of steel. Further, it was found to be of i m p o r t a n c e h o w the p r e t r e a t m e n t s w e r e c a r r i e d out. The s u r f a c e s t r u c t u r e was e x a m i n e d by use of o p t i c a l m i c r o s c o p y (differential i n t e r f e r e n c e contrast), s c a n n i n g e l e c tron m i c r o s c o p y , e n e r g y - d i s p e r s i v e X - r a y analysis, t r a n s m i s s i o n e l e c t r o n m i c r o s c o p y , X - r a y d i f f r a c t i o n as well as m o r e a d v a n c e d s u r f a c e a n a l y s e s such as R u t h e r f o r d B a c k s c a t t e r i n g S p e c t r o s copy, ESCA and i n f r a r e d analysis.

E L E C T R O N E N E R G Y LOSS A N A L Y S I S MATERIALS SCIENCE Christian

IN

Colliex

L a b o r a t o i r e de P h y s i q u e d e s S o l i d e s , B a t i m e n t 510, U n i v e r s i t e P a r i s XI, 91405 Orsay, France

High s p a t i a l r e s o l u t i o n c h a r a c t e r i z a tion of s o l i d thin films is g e n e r a l l y a c h i e v e d w i t h i n the newly d e v e l o p e d ana l y t i c a l e l e c t r o n m i c r o s c o p e s , by a c o m b i n a t i o n of s e v e r a l features: a) high r e s o l u t i o n imaging; b) c o n v e r g e n t m i c r o b e a m d i f f r a c t i o n ; e) X - r a y a n a l y s i s and d) e l e c t r o n energy 10ss s p e c t r o s c o p y (EELS). This talk reviews the recent d e v e l o p m e n t s in EELS w i t h s p e c i a l refe r e n c e to the w o r k p e r f o r m e d w i t h i n the p l u r i d i s c i p l i n a r y STEM p r o g r a m in Orsay. C h e m i c a l a n a l y s i s w i t h EELS is mainly a c h i e v e d by the s t u d y of the coreloss s i g n a l s w h i c h are d e t e c t a b l e for all e l e m e n t s w i t h Z > 2. It is therefore p a r t i c u l a r l y s u i t e d to low-Z ele-

267

m e n t s d e t e c t i o n , as in b o r i d e s , carbides, n i t r i d e s or oxides. M o r e o v e r , the l o c a l i z a t i o n along the b e a m trajectory, of the i n e l a s t i c event r e s p o n s i b l e for the c o r e - l o s s e x c i t a t i o n , is f a v o r a b l e to the i n v e s t i g a t i o n of p r o b l e m s w i t h typical lateral d i m e n s i o n s down to the n a n o m e t e r range, such as p r e c i p i t a t i o n or s e g r e g a t i o n p h e n o m e n a . The f o l l o w i n g topics are d i s c u s s e d : a) P r o g r e s s in i n s t r u m e n t a t i o n ; it concerns the m i c r o s c o p e itself, the spect r o m e t e r and its c o u p l i n g to the column, the d e t e c t i o n chain, the c o m p u t e r ass i s t a n c e and the new d e v e l o p m e n t s in c h e m i c a l m a p p i n g by p r o c e s s i n g s e v e r a l e n e r g y - f i l t e r e d images; b) Q u a l i t a t i v e m i c r o a n a l y s i s , c o v e r i n g the a s s i s t a n c e of useful c o m p l e t e lib r a r i e s of edges and s h o w i n g s e v e r a l t y p i c a l examples; c) Q u a n t i t a t i v e m i c r o a n a l y s i s , i n t r o d u c ing the b a s i c formulae due to E g e r t o n i l l u s t r a t e d by some rather d i f f e r e n t situations. E x a m p l e s such as the analysis of u n i d e n t i f i e d p r e c i p i t a t e s in V3Si p o i n t out the m a j o r steps in q u a n t i t a t i o n (measurement of the signal, c a l c u l a t i o n of the r e l e v a n t crosssection, s p e c i m e n - i n d u c e d e f f e c t s . . .) and define the n e c e s s a r y c o r r e c t i o n procedures. d) L i m i t s in s e n s i t i v i t y in terms of m i n i m u m d e t e c t a b l e n u m b e r of atoms (~i0 in the p r e s e n t state of the art for Very f a v o r a b l e c i r c u m s t a n c e s ) and in terms of m i n i m u m d e t e c t a b l e c o n c e n t r a t i o n (~0.1% to 1% in m o s t problems). A comp a r i s o n w i t h o t h e r a n a l y t i c a l techniques, A u g e r or X - r a y s p e c t r o s c o p y , w i l l be i n i t i a t e d ; e) E n v i r o n m e n t a l i n f o r m a t i o n c o n v e y e d in the e x t e n d e d fine s t r u c t u r e s above the edge (ELXEFS) in in the near edge fine s t r u c t u r e s at the t h r e s h o l d (ELNES). A c o m p l e t e review of the d i f f e r ent aspects c o v e r e d by this talk is to be p u b l i s h e d in the next v o l u m e of the series "Advances in O p t i c a l and Electron Microscopy." This w o r k has b e e n a c h i e v e d ' w i t h the h e l p of a RCP 647 CNRS grant, and thanks are due to all c o l l a b o r a t o r s in this program.

USE OF SEM F O R S T U D Y I N G F A B R I C OF UNDISTURBED NATURAL SEDIMENT Edward Derbyshire Soils

Research

Laboratory,

University

Abstracts o/ScandinavianSociety fi)r Hectron Microscopy

268

of Keele, Staffordshire ST5 United Kingdom

5BG,

SEM s t u d y of u n d i s t u r b e d s a m p l e s of n a t u r a l s e d i m e n t s shows that the m i c r o f a b r i c varies w i t h g e n e t i c type and with post-depositional stress h i s t o r y . D i s c r i m i n a t i o n in g l a c i a l , m a r i n e and a e o l i a n s e d i m e n t s is a i d e d by a n a l y s i s of g r a i n f o r m and q u a n t i t a t i v e e v a l u a tion of v o i d s r a t i o and fabric a n i s o t r o py u s i n g image e n h a n c e m e n t e q u i p m e n t and laser s c a n n i n g t e c h n o l o g y . Post-depositional c h a n g e s such as c o n s o l i d a t i o n including hydroconsolidation a l t e r the m i c r o f a b r i c and the r e s u l t a n t e n g i n e e r ing b e h a v i o r . The d i s t r i b u t i o n of clay g r a d e m a t e r i a l is of p a r t i c u l a r i m p o r t ance in c h a r a c t e r i z i n g the m i c r o f a b r i c , a n d a p p e a r s to be the c r u c i a l f a c t o r in the s e t t l e m e n t of loess, for example. M i c r o f a b r i c m a y c o n t a i n a n u m b e r of artifacts. T y p e of s a m p l i n g , m e t h o d of drying, s a m p l e s u r f a c e d i s p o s i t i o n and p r e p a r a t i o n , a n d s c a l e of v i e w i n g all h a v e a b e a r i n g on i n t e r p r e t a t i o n . Genetic c l a s s i f i c a t i o n of d i a m i c t s such as m o d e r n tills and flow d e b r i s is r e l a t i vely advanced but geologically older m a t e r i a l a l t e r e d by d i a g e n e s i s or der i v e d from c l a y - r i c h p a r e n t m a t e r i a l is m o r e d i f f i c u l t to d i s c r i m i n a t e . The rel a t i o n s h i p b e t w e e n m a t r i x fabric and i n t a c t s t r e n g t h is of i m p o r t a n c e in f o u n d a t i o n studies.

v i e w s of the s p e c i m e n taken at d i f f e r ent tilt angles in the m i c r o s c o p e . E x a m p l e s of b o t h types of s p e c i m e n are b e i n g s t u d i e d in S t o c k h o l m . Examples of t w o - d i m e n s i o n a l c r y s t a l s are e n z y m e c o m p l e x e s from the i n n e r mitoc h o n d r i a l m e m b r a n e i n v o l v e d in o x i d a t ive p h o s p h o r y l a t i o n , for e x a m p l e cytochrome o x i d a s e and c y t o c h r o m e reductase, t o g e t h e r w i t h b a c t e r i a l cell w a l l s . A new m e t h o d for d e t e r m i n i n g the h e i g h t of the m e m b r a n e s h e e t in the m i c r o s c o p e has b e e n d e v e l o p e d , and the h e i g h t has b e e n m e a s u r e d as a f u n c t i o n of r a d i a t i o n dose. R e s u l t s show that v e r t i c a l s h r i n k a g e of n e g a t i v e l y s t a i n e d s p e c i m e n s is m u c h m o r e s e r i o u s than h i t h e r t o b e l i e v e d . S e c t i o n s of t h r e e - d i m e n s i o n a l crystals b e i n g s t u d i e d i n c l u d e c r y s t a l l i n e i n c l u s i o n s in s k e l e t a l m u s c l e m i t o c h o n d r i a of p a t i e n t s s u f f e r i n g f r o m c h r o n i c progressive external ophthalmoplegia, o b t a i n e d from Prof. A. M. S t a d h o u d e r s , N i j m e g e n , and c r y s t a l l i n e i n c l u s i o n s f o u n d in v i v o in s e v e r a l cell types of Salix, o b t a i n e d from Dr. M a r j a Uotila, Helsinki.

STRUCTURE STUDIES DIFFRACTION Jon

USING

Gj~nnes Physics Department, Oslo, Norway

S T R U C T U R E OF B I O L O G I C A L M O L E C U L E S BY I M A G E P R O C E S S I N G OF E L E C T R O N M I C R O G R A P H S George Farrants, Sven Hovmoller

Agneta

Sjogren

and

Department of Structural Chemistrw, Arrhenius Laboratory, University of S t o c k h o l m , S - 1 0 6 91 S t o c k h o l m , S w e d e n

Crystallographic image p r o c e s s i n g of e l e c t r o n m i c r o g r a p h s p r o v i d e s an excellent m e t h o d for s t r u c t u r a l a n a l y s i s of biological molecules. T w o b a s i c types of s p e c i m e n s can be s t u d i e d in s t a i n e d conditions: flat sheets of m o l e c u l e s one unit cell thick a r r a n g e d on a c r y s t a l l o g r a p h i c l a t t i c e ( a t w o - d i m e n s i o n a l crystal), or thin s e c t i o n s of t h r e e - d i m e n s i o n a l crystals. By c a l c u l a t i n g the F o u r i e r t r a n s f o r m of a d i g i t i z e d electron m i c r o g r a p h of such a s p e c i m e n , n o i s e in the m i c r o g r a p h can be f i l t e r e d out, and an a v e r a g e d p i c t u r e of the s t r u c t u r e c a n be obtained. Three-dimensional inf o r m a t i o n can be o b t a i n e d by c o m b i n i n g

ELECTRON

University

of

R a p i d d e v e l o p m e n t of the d i f f r a c t i o n side of e l e c t r o n m i c r o s c o p y may be e x p e c t e d - - a f t e r a p e r i o d w h e n the m o s t r e m a r k a b l e i m p r o v e m e n t s h a v e b e e n in h i g h r e s o l u t i o n i m a g i n g and in s p e c t r o scopic analysis. At least four lines of d e v e l o p m e n t can be p o i n t e d out: In new m i c r o s c o p e s b e t t e r v a c u u m and finer b e a m s can p r o d u c e d i f f r a c t i o n pattern from areas d o w n to less t h a n i0 nm - - w i t h c o n v e r g e n t b e a m d i f f r a c t i o n as a s t a n d a r d technique. C o n s i d e r a b l e p r o g r e s s in the interp r e t a t i o n of the c o n v e r g e n t b e a m diffraction, i.e., d e t e r m i n a t i o n of crystal s y m m e t r y , l a t t i c e c o n s t a n t and s t r u c t u r e f a c t o r s d e m o n s t r a t e s that thi~ is a v e r y s e n s i t i v e t e c h n i q u e in s t r u c ture studies. The i n t r o d u c t i o n of d a t a t e c h n i q u e in c o n n e c t i o n w i t h d i g i t a l i z e d s c a n n i n g s w e l l as v i d e o s i g n a l p r o c e s s i n g w i l l s p e e d up data c o l l e c t i o n and i m p r o v e a c c u r a c i e s in b o t h g e o m e t r i c a l and