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Contrast development in thin cryosections by electron beam exposure at low dose
426
Abstracts of Tlle Netherlands Society of Electron Microscopy
passed through the cabinet and led away into a laboratory fume cupboard.
CONTP~.ST DEVELOPMENT IN THIN C R Y O S E C T I O N S BY ELECTRON BEAM EXPOSURE AT LOW DOSE P. H. H. Bomans and P. M. F r e d ~ r i k P a t h o l o g y , U n i v e r s i t y o f LY nburg, P. 0. B o x 616, 6200 MC M a a s t r i c h t , The N e t h e r l a n d s
C r y o - e l e c t r o n microscopy of hydrated biological materials requires thin and vitrified specimens. For specimens that cannot be captured in thin films this implies that vitrified samples have to be sectioned on a cryo-ultramicrotome. Vitrification of pancreas samples was accomplished by infiltrating aldehyde-fixed samples in vitrifying concentrations of methanol (80%), propylene glycol (80%) or glycezol (67%). According to the theories of contrast formation there should be an increasing electron o p a c i t y from methanol through glycerol of these aqueous embeddings. In our low-dose pictures of cryo-sections from vitrified pancreas samples no contrast has been observed in the "virgin" exposures; c o n t r a s t developed gradually in consecutive exposures. This was confirmed for the three aqueous embeddings tested. In addition the development of contrast was m o n i t o r e d with a TV cameza with an image intensifier. The video images show an appearance o£ contrast at an electron dose o ~ ca. i000 e/nm 2 . The apparent anomaly in contrast of thin cryo-sections compared to thin vitrified films can only be explained by a larger contribution of m u l t i p l e - s c a t tered electrons to the image of cr,yosections. Our findings d e m o n s t r a t e a contrast-inducing effect of the electron beam, even at low dose conditions, on cryosections from infiltrated and vitrified pancreas samples.
HREM OF S T A C K I N G IRREGULARITIES CHLORITE CRYSTALS
IN
A. J. Bons and D. Schryvers* I n s t i t u u t voor A a r d w e t e n s c h a p p e n , Rijksuniversiteit Utrecht, Budapestlaan 4, U t r e c h t , The N e t h e r l a n d s ; *Rijksuniversitair Centrum Antwerpen, G r o e n e n b o r g e r l a a n 171, A n t w e r p , B e l g i u m
Chl>rite crystals from slate rocks have been studied by high resolution
electron m i c r o s c o p y . Chlorite is one of the most common phyllosilicates in natural rocks. The crystal structure is formed by a l t e r n a t i n g talc-like sheets, (Fe, Mg,AI)3(Si,AI)4OIo(OH) 2, and brucire-like sheets (Fe,Mg,AI) 3(OH) 6. (001)-lattice fringe images of chlorite (d=14~) are characterised by a strong variation in i n t e n s i t y of the individual fringes. D e v i a t i n g fringe s p a c i n g s (7~ and 9~) are also common. The n a t u r e of these irregularities has been i n v e s t i g a ted by HREM p e r f o r m e d on a t o p - e n t r y JEOL 200CX e l e c t r o n microscope at the University of A n t w e r p (RUCA). The v a r i a t i o n in intensity of the lattice fringes can be explained by irregular shifts of the crystal lattice of magnitude b/3 in d i r e c t i o n s parallel to (001). The H R E M images, combined with computer simulations, show that these shifts can take place at two levels in the unit cell: (i) at the centre of the talc sheet and (2) at the b r u c i t e sheet. The 9~ fringes arise from layers w h e r e the brucite sheet is missing. The 7~ fringes are caused by i n t e r c a l a t i o n s w i t h a kaolinite structure.
THE ANALYTICAL $EM AND STEM, AN INDISPENSABLE TOOL IN CERAMICS RESEARCH B. A. Boukamp, A. J. A. Winnubst, K. Keizer, K. J. de Vries and A. J. Burggraaf u n x v e r s i t y o f T w e n t e , P.O. B o x 219, 7500 A E E n s c h e d e , The N e t h e r l a n d s
The analytical scanning and (scanning) transmission e l e c t r o n microscopes are indispensable tools in the research field of advanced ceramics. The EMs are used for c h a r a c t e r i z a t i o n and analysi3 at the various stages in the sample p r e p a r a t i o n procedure and b e y o n d the final stage, in subsequent a n n e a l i n g and aging e x p e r i ments. In this presentation the involvement of EM a n a l y s i s in the ceramic materJals research p r o g r a m of our laboratory is discussed. In the d e v e l o p m e n t of tough ceramics based on tetragonal ZY, the EM is used for monitoring the (precursor) powder particle sizes (about i0 nm), the measurement of grain growth (<0.5 mu) during the sintering process and change in morphology due to aging experiments. (Un)w a n t e d second phase is c h a r a c t e £ i z e d with EDS. Microporous ceramic membranes consisting of one to three layers, with decreasing pore sizes, on top of a porous
Abstracts of Tlle Netherlands Society of Electron Microscopy
passed through the cabinet and led away into a laboratory fume cupboard.
CONTP~.ST DEVELOPMENT IN THIN C R Y O S E C T I O N S BY ELECTRON BEAM EXPOSURE AT LOW DOSE P. H. H. Bomans and P. M. F r e d ~ r i k P a t h o l o g y , U n i v e r s i t y o f LY nburg, P. 0. B o x 616, 6200 MC M a a s t r i c h t , The N e t h e r l a n d s
C r y o - e l e c t r o n microscopy of hydrated biological materials requires thin and vitrified specimens. For specimens that cannot be captured in thin films this implies that vitrified samples have to be sectioned on a cryo-ultramicrotome. Vitrification of pancreas samples was accomplished by infiltrating aldehyde-fixed samples in vitrifying concentrations of methanol (80%), propylene glycol (80%) or glycezol (67%). According to the theories of contrast formation there should be an increasing electron o p a c i t y from methanol through glycerol of these aqueous embeddings. In our low-dose pictures of cryo-sections from vitrified pancreas samples no contrast has been observed in the "virgin" exposures; c o n t r a s t developed gradually in consecutive exposures. This was confirmed for the three aqueous embeddings tested. In addition the development of contrast was m o n i t o r e d with a TV cameza with an image intensifier. The video images show an appearance o£ contrast at an electron dose o ~ ca. i000 e/nm 2 . The apparent anomaly in contrast of thin cryo-sections compared to thin vitrified films can only be explained by a larger contribution of m u l t i p l e - s c a t tered electrons to the image of cr,yosections. Our findings d e m o n s t r a t e a contrast-inducing effect of the electron beam, even at low dose conditions, on cryosections from infiltrated and vitrified pancreas samples.
HREM OF S T A C K I N G IRREGULARITIES CHLORITE CRYSTALS
IN
A. J. Bons and D. Schryvers* I n s t i t u u t voor A a r d w e t e n s c h a p p e n , Rijksuniversiteit Utrecht, Budapestlaan 4, U t r e c h t , The N e t h e r l a n d s ; *Rijksuniversitair Centrum Antwerpen, G r o e n e n b o r g e r l a a n 171, A n t w e r p , B e l g i u m
Chl>rite crystals from slate rocks have been studied by high resolution
electron m i c r o s c o p y . Chlorite is one of the most common phyllosilicates in natural rocks. The crystal structure is formed by a l t e r n a t i n g talc-like sheets, (Fe, Mg,AI)3(Si,AI)4OIo(OH) 2, and brucire-like sheets (Fe,Mg,AI) 3(OH) 6. (001)-lattice fringe images of chlorite (d=14~) are characterised by a strong variation in i n t e n s i t y of the individual fringes. D e v i a t i n g fringe s p a c i n g s (7~ and 9~) are also common. The n a t u r e of these irregularities has been i n v e s t i g a ted by HREM p e r f o r m e d on a t o p - e n t r y JEOL 200CX e l e c t r o n microscope at the University of A n t w e r p (RUCA). The v a r i a t i o n in intensity of the lattice fringes can be explained by irregular shifts of the crystal lattice of magnitude b/3 in d i r e c t i o n s parallel to (001). The H R E M images, combined with computer simulations, show that these shifts can take place at two levels in the unit cell: (i) at the centre of the talc sheet and (2) at the b r u c i t e sheet. The 9~ fringes arise from layers w h e r e the brucite sheet is missing. The 7~ fringes are caused by i n t e r c a l a t i o n s w i t h a kaolinite structure.
THE ANALYTICAL $EM AND STEM, AN INDISPENSABLE TOOL IN CERAMICS RESEARCH B. A. Boukamp, A. J. A. Winnubst, K. Keizer, K. J. de Vries and A. J. Burggraaf u n x v e r s i t y o f T w e n t e , P.O. B o x 219, 7500 A E E n s c h e d e , The N e t h e r l a n d s
The analytical scanning and (scanning) transmission e l e c t r o n microscopes are indispensable tools in the research field of advanced ceramics. The EMs are used for c h a r a c t e r i z a t i o n and analysi3 at the various stages in the sample p r e p a r a t i o n procedure and b e y o n d the final stage, in subsequent a n n e a l i n g and aging e x p e r i ments. In this presentation the involvement of EM a n a l y s i s in the ceramic materJals research p r o g r a m of our laboratory is discussed. In the d e v e l o p m e n t of tough ceramics based on tetragonal ZY, the EM is used for monitoring the (precursor) powder particle sizes (about i0 nm), the measurement of grain growth (<0.5 mu) during the sintering process and change in morphology due to aging experiments. (Un)w a n t e d second phase is c h a r a c t e £ i z e d with EDS. Microporous ceramic membranes consisting of one to three layers, with decreasing pore sizes, on top of a porous