Fuxing YIN
,
Nanju GU (Hebei Institute of Technology
,
Tianin 300132
,
China)T.Shigematsu
,
N.Nakanishi(Faculty of Science
,
Konan University Kobe 658
,
Japan)Y.Osawa
,
A.Sato(National Research Institute of Metals
,
Tsukuba 305
,
Japan)
材料科学技术（英文）
Amorphization of Mn carbides by rapid quenching method has been proved to be unsuccessful.By mechanical milling in the present work, amorphous phases have been formed in the perovskitetype Mn3AlC compound. The transformation process from crystalline to amorphous phase was found to be milling time controlled, and 10 h is a critical period for the macroscopically single amorphous phase to form. It has been clarified that the redistribution of C atoms is an instinctive factor for amorphous phase to nucleate, and the atomic configuration in the amorphous phase is changed much in longer milling that different crystallizing behaviours have been caused. With X-ray diffraction and differential scanning calorimetry (DSC) results, an atomic configuration transition model is considered for the structures of the amorphous phases changed during milling.
关键词:
LIU Guoquan Department of Materials Science and Engineering
,
University of Science and Technology Beijing
,
100083
,
China.
材料科学技术（英文）
Quantitative analysis of populations having a geometric structure,which has developed into a special scientific subject called microstructology or stereology,is of great importance to the characterization and evaluation of microstructures and their evolution in various processes.This paper, besides a brief discussion on those topics such as the recent developments of computer assisted image analysis,mathematical morphology,and fractal analysis,will mainly focus on the scope,fundamen- tals,present status,and perspectives of classical stereology.Several case examples of its application to materials science will also be given.
关键词:
stereology
,
null
,
null
,
null
N.V.Ch
,
ra Shekar
,
P.Ch.Sahu
,
K.Govinda Rajan
材料科学技术（英文）
Laser-heated diamond-anvil cell (LHDAC) is emerging as the most suitable, economical and versatile tool for the measurement of a large spectrum of physical properties of materials under extreme pressure and temperature conditions. In this review, the recent developments in the instrumentation, pressure and temperature measurement techniques, results of experimental investigations from the literature were discussed. Also, the future scope of the technique in various avenues of science was explored.
关键词:
Laser heating
,
null
,
null
,
null
Douxing LI and Hengqiang YE (Laboratory of Atomic imaging of Solids
,
Institute of Metal Research
,
Chinese Academy of Sciences
,
Shenyang
,
110015
,
China)
材料科学技术（英文）
The present paper summarizes the current status of high resolution electron microscopy (HREM)and the applications of HREM to materials science and condensed matter physics. This review recounts the latest development of high resolution electron microscope, progress of HREM and the applications of HREM, including the crystal structure determination of microcrystalline materials and characterization of the local structure of the defects and nanostructured materials as well as qualitative and quantitative analysis of the grain boundaries, interfaces and interfacial reactions in the advanced materials by means of HREM in combination with electron diffraction,subnanometer level analysis, image simulation and image processing.
关键词:
Ceramics International
The dispersion behavior of Si3N4 nanopowders prepared by laser-induced gas-phase reaction in a non-aqueous solvent, N-N-dimethylformamide (DNIF) was studied, and triethanolamine (TEA) was selected as a dispersant. One hundred and sixty-six-day sedimentation tests were used to study the stability of the suspensions. Photon correlation spectroscopy was employed to measure the sizes of aggregates and coagulation rates. TEA was proved an effective dispersant for nano-Si3N4 in DMF, presoaking treatment could enhance the effect of the dispersant. TEA 1.0 wt.% referred to Si3N4 and a 1-month-presoaking gave the best dispersion, the dispersion stability was improved from several minutes to several months, and the average size of the aggregates was reduced to about a twenty-fifth. The dispersion ability of TEA was believed being related to its strong affinities both to the powder surface and to the solvent. (C) 2002 Elsevier Science Ltd and Techna S.r.l. All rights reserved.
关键词:
Si3N4;dispersion;nanopowders;N-N-dimethylformamide;triethanolamine;composite;powders
Thin Solid Films
The microstructure of Fe-N films with different thicknesses prepared by reactive radio-frequency magnetron sputtering has been investigated by transmission electron microscopy (TEM) and high-resolution transmission electron micrscopy (HREM) in cross-section and plan view. The film showed a small surface roughening at a nanometer scale. Grain clusters were clearly visible in the film. The electron diffraction analysis indicated that the sputtered Fe-N film was polycrystalline with a mixture of alpha-Fe and alpha"-Fe16N2 phases. A small amount of Fe2O3 was also observed. The thickness of the film and crystal size may be important factors causing distinct differences in magnetic properties of sputtered Fe-N films. (C) 2002 Elsevier Science B.V. All rights reserved.
关键词:
Fe-N film;microstructure;HREM;single-crystal films;fe16n2 films;magnetization;density;moment
Corrosion Science
An electrochemical investigation was carried out to study the corrosion of pure magnesium in 1 N NaCl at different pH values involving electrochemical polarisation, scanning tunnel microscopy (STM), measurement of hydrogen gas evolution and measurement of the elements dissolved from the magnesium specimen which were determined by inductively coupled plasma atomic emission spectrophotometry (ICPAES). A partially protective surface film was a principal factor controlling corrosion. Film coverage decreased with increasing applied electrode potential. Application of a suitable external cathodic current density was shown to inhibit magnesium dissolution whilst at the same time the hydrogen evolution rate was relatively small. This showed that cathodic protection could be used to significantly reduce magnesium corrosion. A new definition is proposed for the negative difference effect (NDE). (C) 1997 Elsevier Science Ltd.
关键词:
magnesium;electrochemical corrosion;cathodic protection;STM;kinetics;behavior;mg
