Z.Y. Lu 1)
,
S.M.An 2)
,
B.H.Cuo 2)
,
W.M.Li 1)
,
Y.Mei
,
Y.L.Xia 2) and J.Xu 2) 1) Department of Mechanical Engineering
,
Yangzhou University
,
Yangzhou 225009
,
China 2) Dalian University of Technology
,
Dalian 116024
,
China
金属学报(英文版)
This study raised a new assisted technique used for chemical vapor deposition (CVD) in which a laser beam irradiated the surface of substrate and simultaneously the plasma surroundings created in the reactive room, but both laser and plasma were at lower energy level in order to perform easily. The chemical vapor deposition reaction could be performed only just using simultaneously above two assisted methods. If not, the reaction could not be performed, too. It is laser plasma assisted chemical vapor deposition (LPCVD). For these reasons, a LPCVD device had been designed and manufactured, and was carried on practical operation. The results indicated that this technique is successful and feasible. Acting on the system of SiH 4 NH 3 N 2 with both CO 2 laser and RF plasma, expectant film of silicon nitride had been obtained on the surface of stainless steel.
关键词:
CVD
,
null
,
null
,
null
Journal of Alloys and Compounds
The bonding characteristics of A(3)B L1(2) intermetallics have been studied by the discrete variational X(alpha) cluster method. Two concepts, i.e. similarity of bonding strength and delocalization of bonding electrons, are introduced to explain the ductility or brittleness of the materials. The analysis of bonding characteristics shows that the strength of the A-A bond is similar to that of the A-B bond in A(3)B L1(2) intermetallics, and the delocalized degree of bonding electrons is different between the ductile and brittle intermetallics. This is a dominant factor in governing the ductile/brittle behavior of the materials. Environmental embrittlement in some intermetallics is related to the reactive centers in grain boundaries, which is due to the directional bonding and a small amount of charge transfer, and the reactive centers weaken the ability against the attack of the environmental species. The effect of stoichiometry on ductility contributes to the degree of delocalized bonding electrons. Mechanical strength of the materials is correlated with the covalent bond strength.
关键词:
intermetallics;mechanical properties;bond strength calculations;intergranular hydrogen embrittlement;grain-boundary strength;ll2;ordered alloys;environmental embrittlement;fracture;ductility;co3ti
Journal of the European Ceramic Society
Y2SiO5 has potential applications as functional-structural ceramic and environmental/thermal barrier coating material. As an important grain-boundary phase in the sintered Si3N4, it also influences the mechanical and dielectric performances of the host material. In this paper, we present the mechanical properties of Y2SiO5 including elastic moduli, hardness, strength and fracture toughness, and try to understand the mechanical features from the viewpoint of crystal structure. Y2SiO5 has low shear modulus, low hardness, as well as high capacity for dispersing mechanical damage energy and for resisting crack penetration. Particularly, it can be machined by cemented carbides tools. The crystal structure characteristics of Y2SiO5 suggest the low-energy weakly bonded atomic planes crossed only by the easily breaking Y-O bonds as well as the rotatable rigid SiO4 tetrahedra are the origins of low shear deformation, good damage tolerance and good machinability of this material. TEM observations also demonstrate that the mechanical damage energy was dispersed in the form of the micro-cleavages, stacking faults and twins along these weakly bonded atomic planes. which allows the "microscale-plasticity" for Y2SiO5.
关键词:
Y2SiO5;mechanical properties;damage;strength;fracture;yttrium silicate;ceramics;system;si3n4-sio2-y2o3;coatings;monazite;strength;phases
Materials Science and Technology
The mechanical properties of 20 vol.-%SiC whisker reinforced ZrO2-Y2O3 composites containing 2 and 6 mol-% Y2O3 were measured at room temperature and the fracture surface was examined. The results indicate that the mechanical behaviour of the composites is strongly influenced by the Y2O3 content. The magnitude of the enhancement ofthe toughness in composites containing 2 mol.-% Y2O3 compared with unreinforced ZrO2-Y2O3 matrix is larger than that for the composites containing 6 mol-% Y2O3. Crack propagation modes were characterised by crack deflection, whisker bridging, and whisker pullout. High resolution electron microscopic observations show that in composites containing 2 mol.-% Y2O3 the whiskers are directly bonded to the matrix. However; in composites containing 6 mol.-%Y2O3 there is always a thick amorphous layer at the interface, indicating that the high Y2O3 content has promoted the formation of interfacial amorphous layers. These interfacial amorphous layers strengthen the interfacial bonding, resulting in a composite with a low fracture toughness.
关键词:
Journal of the American Ceramic Society
In this paper, the mechanical properties of bulk single-phase gamma-Y2Si2O7 ceramic are reported. gamma-Y2Si2O7 exhibits low shear modulus, excellent damage tolerance, and thus has a good machinability ready for metal working tools. To understand the underlying mechanism of machinability, drilling test, Hertzian contact test, and density functional theory (DFT) calculation are employed. Hertzian contact test demonstrates that gamma-Y2Si2O7 is a "quasi-plastic" ceramic and the intrinsically weak interfaces contribute to its machinability. Crystal structure characteristics and DFT calculations Of gamma-Y2Si2O7 suggest that some weakly bonded planes, which involve Y-O bonds that can be easily broken, are the sources of the low shear deformation resistance and good machinability.
关键词:
yttrium disilicate powder;low-temperature synthesis;population;analysis;glass-ceramics;gel method;microstructure;nitride;monazite;composites;evolution
Ceramics International
Mechanical properties and fracture mechanisms of 20 vol% SiC whisker-reinforced ZrO2 (Y2O3) composites were investigated. The phase composition, fractography and the microstructure of the whisker-matrix interface were studied by XRD, SEM, TEM and HREM. The results show that flexural strength and fracture toughness of SiCw/ZrO2 (with 2 mol% Y2O3) composites increase by 453 MPa and 2.6 MPa m(1/2), respectively. However, in the composites with 6 mol% Y2O3, the increment is only 17 MPa and 1.6 MPa m(1/2), respectively. It reveals that the ZrO2 (2 mol% Y2O3) composites have a good toughening effect by incorporating SiC whiskers. HREM observations indicate that the whiskers in ZrO2 (2 mol% Y2O3) composites are directly bonded with the ZrO2 matrix, only few atom disorder zones exist at the interface. In contrast, for ZrO2 (6 mol% Y2O3) composites, there is a thin, uniform layer of amorphous phase at the interface between SiC whisker and ZrO2 matrix, indicating that high Y2O3 content promotes the formation of an interfacial layer. The study of fracture surfaces by SEM indicates that the main toughening mechanisms in SiCw/ZrO2 (with 2 mol% Y2O3) composites are crack deflection, crack bridging, whisker pull-out and dynamic t-->m transformation. Crack deflection is the main toughening mechanism in SiCw/ZrO2, (with 6 mol% Y2O3) composites.
关键词:
LI Ying
,
WANG Xiaotian
,
JIN Zhihao Xi'an Jiaotong University
,
Xi'an
,
China SHl Guoshun Beijing Measuring and Analysing Center.Beijing
,
China
金属学报(英文版)
The effect of subzero treatment on the microstructure and mechanical properites of Y_2O_3- ZrO_2 ceramic have been investigated by TEM,X-ray diffraction and test of mechanical properties.It was shown that the microstructre of 3Y-PSZ after subzero treatment by liquid nitrogen exhibits very long and parallel laths of m-phase and some microcracks around the larger and finer lath of m-phase may be discovered.Suitable subzero treatment can improve the strength and toughness of Y-PSZ efficiently because of decreasing the stability of t-phase and incresing the amount of t-m transformation when exerting a stress.However,when the time of subzero treatment exceeds,the over aging effect may arise.which can decrease the strength and toughness of the material.
关键词:
Y_2O_3-ZrO_2 partially stabilized zirconia(PSZ)
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null
,
null
孙建春
,
盛光敏
,
陈登明
,
周安若
,
朱光俊
功能材料
1J50软磁合金的性能主要是通过H_2热处理获得的,在1130℃和H2气氛保护下对冷轧态1J50软磁合金进行了热处理.运用MATS-2010SA软磁测试仪对处理前后1J50软磁合金的磁性能进行了检测,运用金相显微镜、XRD等手段对处理前后1J50软磁合金的组织结构进行了分析.结果表明,通过H_2热处理,1J50软磁合金的矫顽力显著降低,起始磁导率和最大磁导率提高;组织结构发生明显变化,冷轧态1J50软磁合金组织为孪晶奥氏体,平均晶粒尺寸为200μm,处理过后,晶粒显著长大,平均晶粒尺寸为100μm;由于在600℃时采取了快冷,处理后1J50软磁合金中未出现大量FeNi相和FeNi_3相.
关键词:
H2热处理
,
1J50
,
组织结构
,
性能
Physica B-Condensed Matter
The magnetic properties and magnetocaloric effect of Tb(1-x)Y(x)CoC(2) (x = 0, 0.1, 0.2, 0.3, 0.4) compounds have been investigated systematically. All the compounds undergo second-order transitions from paramagnetic to ferromagnetic states without thermal and magnetic hysteresis. With increasing Y content from 0 to 0.4, the Curie temperatures decrease nearly linearly from 28 to 18 K. The nature of the second-order phase transitions can be confirmed by Arrott plots. For Tb(0.6)Y(0.4)CoC(2) compound, the maximum value of the magnetic entropy change -Delta S(M) at 20 K is 9.35 J kg(-1) K(-1) for an external field change of 5T (5.14 J kg(-1) K(-1) for 2T). The large reversible magnetic entropy change makes Tb(0.6)Y(04)CoC(2) compound an attractive candidate for the application at hydrogen liquefaction temperature. (C) 2010 Elsevier B.V. All rights reserved.
关键词:
Curie temperature;Magnetocaloric effect;Magnetic properties;ac susceptibility
