ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1983.tb04179.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1983.tb04180.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

SummaryCurrent assumptions in wave aberration theory and specimen scattering theory are reviewed. More quantitative image simulations would be valuable as well as use of a wider range of imaging techniques, particularly STEM. The severe difficulties of high resolution three‐dimensional reconstruction are described and illustrate

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1983.tb04181.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

SummaryThe characteristics of scanning transmission electron microsopy, which make it a particularly powerful tool for the study of surfaces and small crystals, include the serial nature of the image signal which makes it amenable to recording and image processing procedures, the possibility of correlating the image data with microdiffraction patterns and microanalysis of chosen small regions and the possibilities for combining several different image signals obtained simultaneously. Images obtained from surfaces using reflected diffraction beams may be very sensitive to variations of surface structure but the resolution, depth of focus and contrast of the images are strongly dependent on the nature of the surface and the aperture sizes used in the microsope. Microdiffraction patterns may be obtained from small surface features. Electron energy loss analyses of the diffracted beams provides sensitive indications on surface electron excitations. Microdiffraction patterns obtained in transmission from regions of 1–5 nm diameter provide valuable information on the structure and defects of small crystals, such as those of platinum and gold which are of interest in relation to the study of catalyst

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1983.tb04182.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

SummaryComputer image simulations predict that the detailed atomic arrangements along extended CS defects in slightly‐reduced rutile may be identified in 500 kV high‐resolution electron micrographs. Experimental images from a chromia‐doped rutile have generally confirmed these predictions although also indicating that considerable disorder remains. The need for very careful control of sample preparation, including heat treatments, is empha

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1983.tb04183.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

SummaryThe relative advantages and disadvantages of a variety of experimental electron microscopical techniques for the measurement of rigid body displacements are considered. The principles of the application of a moiré method of great simplicity and high potential accuracy are then further discussed as are the experimental difficulties associated with the superposition of suitable reference latices on a substrate. The method is then applied to obtain an upper limit for the rigid body displacement at {111} Σ3 twin boundaries in stainless stee

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1983.tb04184.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

SummaryA high‐resolution 500 kV study of the long‐period (n= 8) perovskite Bi9Ti3Fe5O27has revealed a variety of order/disorder effects, in marked contrast to low‐nmaterials, as well as the occurrence of a new two‐dimensional superlattice structure corresponding to a 3 ×d110ordering along the bismuthate layers. Intergrowths of the 2‐D SL phase with the ‘usual’ perovskite/bismuthate phase, as well as sharp interfaces between these two phases, were observed and the common occurrence of steps along these interfaces suggested ledge migration as one possible transformation mechanism. Coherent intergrowths of structural elements rather similar to tetragonal‐tungsten‐bronze (TTB)‐type were also found and these sometimes appeared to be relics of the super‐lattice phase. The chemical implications of the sevarious observations

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1983.tb04185.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

SummaryThe characteristic defects in the martensitic phase of the memory alloy Cu–Zn–Al have been investigated using the Cambridge University 600 kV High Resolution Electron Microscope. Conditions are found under which the images can be quantitatively simulated when this involves the transfer of structural information at resolutions beyond the first zero of the contrast transfer function. Defects of sequence‐type were positively identified by the comparison of high‐resolution micrographs with full dynamical image simu

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1983.tb04186.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

SummaryA comparison is described of the structures of an M9R Cu–Zn–Al alloy as quenched directly into the martensitic state, and as stabilized, with the structure of the material after up‐quenching into the β1state after which treatment the martensitic memory transformation occurs thermoelastically. Preliminary results on the increased tendency for the stabilized alloy to form f.c.c. stacking sequence regions are given and dis

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1983.tb04187.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

SummaryHigh resolution and conventional studies have been made on the inclined twin boundaries occurring near the tip of wedge microtwins in the case of repeated wedge microtwins occurring at twin intersections. These inclined boundaries appear to be continuous and all the atomic planes are also continuous so that we suggest the use of the term ‘inclined coherent boundaries’ instead of ‘incoherent’ which one generally employs, in analogy to the case of precipitates in a matrix. This is different from what occurs in the case of isolated wedge microtwins for the same material and for the same kind of twins where the inclined twin boundary is really not coherent, being made of non‐inclined coherent regions separated by steps containing a dislocation.The coherent inclined boundaries of repeated wedge microtwins appear to be rotated about two perpendicular axes of the habit plane (tilt and twist) giving rise to a distribution of microdislocations whose role has been studied. The values of the tilt and twist angles are related to a minimization of the total energy by a mechanism that is likely to appear only in the case of thin foils. A comparative study of the different roles related to the different structures of inclined twin boundaries for isolated and repeated wedge microtwins has been made, and also a comparative study of the mechanisms of stress relaxation in each case. The studies have been made on (313) twins of a monoclinic samarium se

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1983.tb04188.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY