Hao WANG
,
T.S.YEN
,
Hanrui ZHUANG and Weiying SUN (State Key Lab. on High Performance Ceramics and Superfine Microstructure
,
Shanghai Institute of Ceramics
,
Chinese Academy of Sciences
,
Shanghai
,
200050
,
China)
材料科学技术（英文）
The sintering processes of Re-(α' + β')-sialon composites (Re=Sm, Dy, Yb) have been investigated by using a specially designed high temperature dilatometer. The initial densification of various samples starts at about 1200℃, and the maximum shrinkage rate of these sialon composites occurs at about 1500℃. The light rare earth sialon has a noticeably tower densification temperature and a higher final shrinkage. The sirtering kinetics of Re-(α' +β')-sialonare much more complex. The Kingery's liquid phase sintering model appears to be applicable,but the mechanism of mass transport in stage two appears to be changeable. The controlling factor shiffs from solution-precipitation to diffusion when densification process proceeds from the earlier part to the later part of this stage.
关键词:
Wenbo FEI
材料科学技术（英文）
This paper shows that it is easier to form intelligent ceramics than other materials. Self-adaptive factors and relevant function mechanisms, which determine the formation of intelligent ceramics, are studied and data from the design of the PLZT with complex functions are presented.
关键词:
Zhijun LIN
,
Meishuan LI
,
Yanchun ZHOU
,
null
,
null
材料科学技术（英文）
Layered ternary ceramics represent a new class of solids that combine the merits of both metals and ceramics. These unique properties are strongly related to their layered crystal structures and microstructures. The combination of atomic-resolution Z-contrast scanning transmission electron microscopy (STEM) and transmission electron microscopy (TEM), selected area electron diffraction (SAED), convergent beam electron diffraction (CBED) represents a powerful method to link microstructures of materials to macroscopic properties, allowing layered ternary ceramics to be investigated in an unprecedented detail. Microstructural information obtained using TEM is useful in understanding the formation mechanism, layered stacking characteristics, and defect structures for layered ternary ceramics down to atomic-scale level; and thus provides insight into understanding the ``Processing-Structure-Property" relationship of layered ternary ceramics. Transmission electron microscopic characterizations of layered ternary ceramics in Ti-Si-C, Ti-Al-C, Cr-Al-C, Zr-Al-C, Ta-Al-C and Ti-Al-N systems are reviewed.
关键词:
Layered ternary ceramics
,
ternary
,
ceramics
,
MAX
,
phase
,
TEM
,
S
Applied Physics Letters
The effect of high-energy ball milling on the structure of nanometer sized amorphous ceramics, a-Si3N4 and a-Si-N-C, respectively, has been investigated. At high milling intensity, a-Si3N4 may rapidly crystallize into a mixture of alpha-Si3N4 and beta-Si3N4 after the initial 4 s of milling whereas no structural changes were observed at low milling intensity. For a-Si-N-C, mechanical milling does not cause structural changes at both low and high intensity. It was found that extension of mechanical milling of these hard ceramics can introduce large volume fractions of contamination fragments from the milling media. We conclude that the observed structural changes occurring in a-Si3N4 may be due to mechanical effect, rather than local heating and/or impurity effect. (C) 1996 American Institute of Physics.
关键词:
ni-zr;alloys;powders;metals
Materials Science and Technology
In order to meet increasing requirement for the evaluation and design of damage tolerance of brittle materials, a simple expression was proposed to estimate the damage tolerance quantitatively using basic material parameters, based on the features of damage tolerance and fracture mechanics. The calculated results from this equation indicated that the damage tolerance of nanolayer grained ceramics was over 10 times higher than that of some brittle ceramics, while glass has the lowest damage tolerance. Therefore, the damage tolerance of various ceramics can be estimated directly using their basic properties data without the necessity of additional tests. SEM examination and finite element simulation showed that the high damage tolerance of the layer grained ceramics was attributed to delamination in grains, interlocking microstructures and crack deflection.
关键词:
damage tolerance;brittle material;nanolayer grained ceramics;reliability;liquid reaction synthesis;ti3sic2;ti3alc2;microstructure;indentations;glass
Transactions of Nonferrous Metals Society of China
The influence of some additives on bulk density, phase composition, mechanical strength and thermal shock resistance of aluminium titanate (AT) ceramics was investigated. AT ceramics with different additives of MgO, SiO(2) and Fe(2)O(3) were prepared by reaction sintering. Properties of AT ceramics were tested by using Archimedes, three-point bending and thermal cycling tests. It was found that additives of MgO, SiO(2) and Fe(2)O(3) or their compound additives are favorable to reduce the porosities of AT, enhance mechanical strength and thermal shock resistance. The role of additives can be rationalized in terms of promotion of sintering process, formation of new phases and influence on lattice constant c of AT ceramics.
关键词:
aluminium titanate ceramics;additive;bulk density;mechanical;properties;thermal-stability;mullite;composites;sol
