Zheng Liu Liangxian Chen Chengming Li Lifu Hei Jianhua Song Guangchao Chen
材料科学技术（英文）
Thermal stress in large area free-standing diamond films was remarkable during the post-deposition cooling of direct current (DC) arc plasma jet chemical vapor deposition (CVD) process. In this research, the stress release caused by delamination of Cr interlayer was of great importance to ensure the integrity of free-standing diamond film. The effects of Cr interlayer on Mo substrate, namely composite substrate, on thermal stress were investigated. Thermo-mechanical coupling analysis of the thermal stress was applied by finite element analysis (FEA) using ANSYS code. It was found that the interlayer could be destroyed first by the large thermal stress, and then the stress could be released and the probability of diamond film crack initiation would be reduced. The stress concentration at the bent edge of diamond film was also discussed. In addition, diamond films deposited on Mo substrates with and without Cr interlayer were prepared by DC arc plasma jet CVD system and experimental measurements were used to characterize these films. It was found that composite substrate could be an effective method of growing free-standing crack-free diamond films by DC arc plasma jet CVD system when there is no special requirement to the film strength.
关键词:
CVD diamond film
,
Cr interlayer
,
Thermal stress
,
Finite element analysis
王唱舟
,
周丽
,
王洋
,
丁昊
材料科学与工程学报
本文运用有限元法模拟了SiC颗粒体积分数和颗粒尺寸对SiCp/Al复合材料弹性模量、屈服强度、延伸率的影响.为了建立与真实显微结构相似的复合材料模型,假定任意尺寸的SiC颗粒随机地分布在SiCp/Al复合材料中.计算结果表明:SiC颗粒体积分数对复合材料的力学性能的影响更加显著.随着体积分数的增加,SiCp/Al复合材料的弹性模量和屈服强度逐渐增加;而其延伸率会相应降低.其应力应变曲线由韧性材料的特性向脆性材料的特性逐渐过渡.相反,当平均颗粒尺寸在一定的范围内变化时,颗粒尺寸对其应力-应变曲线的影响并不显著.
关键词:
SiCp/Al复合材料
,
体积分数
,
颗粒尺寸
,
力学性能
,
有限元
Hui She
材料科学技术（英文）
The vertical and lateral interactions in a multisheet array of InAs/GaAs quantum dots are analyzed by finite element method (FEM). It is shown that due to the effects of vertical interaction, nucleation prefers to happen above buried quantum dots (QDs). Meanwhile, the effects of lateral interaction adjust the spacing of lateral neighboring QDs. The vertical coupling becomes strong with deceasing GaAs spacer height and increasing number of buried layers, while the lateral coupling becomes strong with increasing InAs wetting layer thickness. The phenomenon that, after successive layers, the spacing and size of QDs islands become progressively more uniform is explained according to the minimum potential energy theory.
关键词:
Quantum dots
,
null
,
null
