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基于点缺陷扩散理论与离散位错动力学耦合的位错攀移模型研究
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作者 高原 柳占立 +3 位作者 赵雪川 张朝晖 庄茁 由小川 《物理学报》 SCIE EI CAS CSCD 北大核心 2011年第9期493-499,共7页
位错的攀移运动对高温下晶体材料的塑性行为有重要影响,为了能够有效揭示攀移的物理本质及其对塑性行为的作用,本文基于点缺陷扩散理论,通过将体扩散和管扩散机理的共同作用与三维离散位错动力学耦合,建立了适用条件更广的位错攀移模型... 位错的攀移运动对高温下晶体材料的塑性行为有重要影响,为了能够有效揭示攀移的物理本质及其对塑性行为的作用,本文基于点缺陷扩散理论,通过将体扩散和管扩散机理的共同作用与三维离散位错动力学耦合,建立了适用条件更广的位错攀移模型.利用此模型我们模拟了单个及多个棱柱型位错环的收缩变形过程,发现影响位错攀移速率的决定因素不是传统理论认为的机械攀移力,而是位错周围(体扩散)及位错段上(管扩散)的空位浓度梯度.该模型也能够完全重现棱柱型位错环群的粗化过程中不同位错环半径及晶体内平均空位浓度随时间变化的三个阶段. 展开更多
关键词 位错攀移 缺陷扩散理论 位错动力学 棱柱位错环
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钛合金扩散焊微小缺陷弱磁检测试验研究 被引量:7
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作者 张斌 于润桥 +1 位作者 刘怡 胡博 《中国测试》 CAS 北大核心 2020年第3期6-11,共6页
针对60 mm厚钛合金扩散焊中未焊合和紧贴型微小缺陷,提出一种新的钛合金扩散焊弱磁检测方法。利用基于弱磁原理的固相焊缝检测系统采集试件表面弱磁信号,分析扩散焊不同缺陷的磁信号特征。结果表明:弱磁方法可检测出埋深60 mm,厚度0.02... 针对60 mm厚钛合金扩散焊中未焊合和紧贴型微小缺陷,提出一种新的钛合金扩散焊弱磁检测方法。利用基于弱磁原理的固相焊缝检测系统采集试件表面弱磁信号,分析扩散焊不同缺陷的磁信号特征。结果表明:弱磁方法可检测出埋深60 mm,厚度0.02 mm未焊合缺陷和直径0.01 mm紧贴型缺陷,可根据表面磁感应强度和磁感应强度梯度信号判断缺陷位置。磁异常幅值、磁异常宽度和基于拉依达准则的磁梯度阈值可作为识别缺陷类型的磁信号特征量,可有效判别出钛合金扩散焊中的未焊合和紧贴型微小缺陷。弱磁检测技术在大厚度钛合金扩散焊微小缺陷的无损评估中具有可行性。 展开更多
关键词 弱磁检测 扩散缺陷 拉依达准测 磁感应强度
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锆自辐射损伤的分子动力学模拟与缺陷判定研究
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作者 钟睿 付宝勤 +1 位作者 崔节超 侯氢 《四川大学学报(自然科学版)》 CAS CSCD 北大核心 2020年第1期123-129,共7页
采用分子动力学方法,模拟了300 K温度时由能量10 keV到50 keV的初级反冲原子(primary knock-on atom, PKA)在密排六方(hexagonal close packed, HCP)结构锆晶体内自辐射造成的级联碰撞. 采用离位原子判定法、自间隙原子(self-interstiti... 采用分子动力学方法,模拟了300 K温度时由能量10 keV到50 keV的初级反冲原子(primary knock-on atom, PKA)在密排六方(hexagonal close packed, HCP)结构锆晶体内自辐射造成的级联碰撞. 采用离位原子判定法、自间隙原子(self-interstitial atom, SIA)判定法以及Wigner-Seitz(WS)原胞分割法等三种方法对级联碰撞过程中产生的点缺陷进行了判定. 通过对比不同方法获得的点缺陷变化趋势、统计涨落、鲁棒性等特征,发现采用WS分割方法获得的点缺陷数更适合用于描述锆晶体中级联碰撞的辐射损伤. 此外还研究了自间隙原子的基本扩散特征,结果发现其更倾向于一种二维(2D)扩散. 展开更多
关键词 分子动力学 级联碰撞 缺陷判定 缺陷扩散
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高密度纳米孪晶镍镀层的电化学腐蚀行为 被引量:4
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作者 张义 孟国哲 +2 位作者 邵亚薇 张涛 王福会 《中国腐蚀与防护学报》 CAS CSCD 北大核心 2009年第2期99-103,共5页
利用脉冲电镀技术在Q235钢基体上制备了纳米孪晶镍镀层,分别测试了纳米孪晶镍镀层和铸态镍在pH8.4的硼酸缓冲溶液(0.1 mol/L H_3BO_3+0.025 mol/L Na_2B_4O_7)中的动电位极化曲线。结果表明,两者在硼酸缓冲溶液中均能自钝化,并且前者具... 利用脉冲电镀技术在Q235钢基体上制备了纳米孪晶镍镀层,分别测试了纳米孪晶镍镀层和铸态镍在pH8.4的硼酸缓冲溶液(0.1 mol/L H_3BO_3+0.025 mol/L Na_2B_4O_7)中的动电位极化曲线。结果表明,两者在硼酸缓冲溶液中均能自钝化,并且前者具有较好的耐腐蚀和钝化性能。利用Mott-Schottky关系和点缺陷模型(PDM),分别从热力学和动力学两方面研究了纳米孪晶结构对钝化膜性能的影响,发现纳米孪晶结构对钝化膜中的缺陷密度影响较小,对缺陷在钝化膜中的扩散系数(D_m)却有着显著的影响,这是导致其上生长的钝化膜薄且致密、耐蚀性能好的主要原因。 展开更多
关键词 纳米孪晶 钝化膜 Mott-Schottky 关系 缺陷扩散系数
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First-principles study of intrinsic defects,dopants and dopant-defect complexes in LiBH_4 被引量:2
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作者 张国英 刘贵立 张辉 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2012年第7期1717-1722,共6页
A first-principles study was reported based on density functional theory of hydrogen vacancy,metal dopants,metal dopant-vacancy complex in LiBH4,a promising material for hydrogen storage.The formation of H vacancy and... A first-principles study was reported based on density functional theory of hydrogen vacancy,metal dopants,metal dopant-vacancy complex in LiBH4,a promising material for hydrogen storage.The formation of H vacancy and metal doping in LiBH4 is difficult,and their concentrations are low.The presence of one kind of defect is helpful to the formation of other kind of defect.Based on the analysis of electronic structure,the improvement of the dehydrogenating kinetics of LiBH4 by metal catalysts is due to the weaker bonding of B—H and the new metal-like system,which makes H atom diffuse easily;H vacancy accounts for a trace amount of BH3 release during the decomposing process of LiBH4;metal dopant weakens the strength of B—H bonds,which reduces the dehydriding temperature of LiBH4.The roles of metal and vacancy in the metal dopant-vacancy complex can be added in LiBH4 system. 展开更多
关键词 LiBH4 hydrogen storage material first-principles calculation DEFECT H diffusion dehydrogenating properties
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Characterization of Phosphorus Diffused ZnO Bulk Single Crystals
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作者 张瑞 张璠 +2 位作者 赵有文 董志远 杨俊 《Journal of Semiconductors》 EI CAS CSCD 北大核心 2008年第9期1674-1678,共5页
Phosphorus was diffused into CVT grown undoped ZnO bulk single crystals at 550 and 800℃ in a closed quartz tube. The P-diffused ZnO single crystals were characterized by the Hall effect, X-ray photoelectron spectrosc... Phosphorus was diffused into CVT grown undoped ZnO bulk single crystals at 550 and 800℃ in a closed quartz tube. The P-diffused ZnO single crystals were characterized by the Hall effect, X-ray photoelectron spectroscopy (XPS), photoluminescence spectroscopy (PL), and Raman scattering. The P-diffused ZnO single crystals are n-type and have higher free electron concentration than undoped ZnO, especially for the sample diffused at 800℃. The PL measurement reveals defect related visible broad emissions in the range of 420-550nm in the P-diffused ZnO samples. The XPS result suggests that most of the P atoms substitute in the Zn site after they diffuse into the ZnO single crystal at 550℃ ,while the P atom seems to occupy the O site in the ZnO samples diffused at 800℃. A high concentration of shallow donor defect forms in the P-diffused ZnO,resulting in an apparent increase of free electron concentration. 展开更多
关键词 DIFFUSION DEFECT ZNO PHOSPHORUS
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Micro-structure of PECVD Diamond Films by Slow Positron Beam
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作者 Yan Xu Hui-min Weng +6 位作者 Bang-jiao Ye Hai-yun Wang Cheng-xiao Peng Chuan-ying Xi Bin Cheng Xian-yi Zhou Rong-dian Han 《Chinese Journal of Chemical Physics》 SCIE CAS CSCD 北大核心 2006年第4期291-293,共3页
The microstructure of diamond films was studied by slow positron beam and Raman spectroscopy. For the Raman spectroscopy experiment on diamond films, a high fraction of the sp3 hybridized bond was detected in samples.... The microstructure of diamond films was studied by slow positron beam and Raman spectroscopy. For the Raman spectroscopy experiment on diamond films, a high fraction of the sp3 hybridized bond was detected in samples. Positron annihilation spectra analysis further illuminated that the concentration and types of defects were different in each sample. S-E curves of all samples showed that diamond crystal structures had obvious variation in each sample. These results indicated that positron annihilation spectroscopy was an effective means to measure microstructure of diamond films. 展开更多
关键词 Diamond film DEFECT Slow positron DIFFUSION
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Formation Mechanism of PPS as Antireflection Coating
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作者 WANGHai-yan SUNXiao-feng ZHANGYu-xiang LIWei-qiang LUJing-xiao 《Semiconductor Photonics and Technology》 CAS 2005年第1期32-36,39,共6页
The whole chemical etching process on a P-type polycrystalline silicon substrate with resistivity 1-2Ω·cm is described. The formation mechanism of porous polycrystalline silicon(PPS) microstructure was investi... The whole chemical etching process on a P-type polycrystalline silicon substrate with resistivity 1-2Ω·cm is described. The formation mechanism of porous polycrystalline silicon(PPS) microstructure was investigated. Those how the initial pits were formed and an uniform morphology of PPS was obtained are explained. Two types of etching mechanism were characterized as defect control reaction and diffusion control reaction. The morphology formed after the isotropic acidic solution etching with different etching time and HF/HNO3 concentration was compared with the effect of the same etching process after anisotropic alkaline etching. The study showed that the thickness of porous polycrystalline silicon layer with chemical acidic etching entirely depended on the existence of various types of defects. 展开更多
关键词 Diffusion control Defect control Point defect Line defect
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Noise Reduction of Welding Defect Image Based on NSCT and Anisotropic Diffusion 被引量:4
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作者 吴一全 万红 +1 位作者 叶志龙 刚铁 《Transactions of Tianjin University》 EI CAS 2014年第1期60-65,共6页
In order to reduce noise effectively in the welding defect image and preserve the minutiae information, a noise reduction method of welding defect image based on nonsubsampled contourlet transform(NSCT) and anisotropi... In order to reduce noise effectively in the welding defect image and preserve the minutiae information, a noise reduction method of welding defect image based on nonsubsampled contourlet transform(NSCT) and anisotropic diffusion is proposed. Firstly, an X-ray welding defect image is decomposed by NSCT. Then total variation(TV) model and Catte_PM model are used for the obtained low-pass component and band-pass components, respectively. Finally, the denoised image is synthesized by inverse NSCT. Experimental results show that, compared with the hybrid method of wavelet threshold shrinkage with TV diffusion, the method combining NSCT with P_Laplace diffusion, and the method combining contourlet with TV model and adaptive contrast diffusion, the proposed method has a great improvement in the aspects of subjective visual effect, peak signal-to-noise ratio(PSNR) and mean-square error(MSE). Noise is suppressed more effectively and the minutiae information is preserved better in the image. 展开更多
关键词 welding defect detection noise reduction nonsubsampled contourlet transform total variation model Catte_PM model
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NaHCO3溶液中X100和X80管线钢钝化膜性能比较 被引量:14
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作者 赵阳 梁平 +3 位作者 史艳华 王秉新 刘峰 武占文 《中国腐蚀与防护学报》 CAS CSCD 北大核心 2013年第6期455-462,共8页
采用动电位极化曲线分析了X100和X80钢在0.5 mol/L NaHCO3溶液中的极化行为,通过电流密度-时间曲线以及Mott-Schottky曲线研究了两种钝化膜的生长机制和钝化膜的半导体性质,借助电容测量和点缺陷模型计算了两种钝化膜内的缺陷密度和缺... 采用动电位极化曲线分析了X100和X80钢在0.5 mol/L NaHCO3溶液中的极化行为,通过电流密度-时间曲线以及Mott-Schottky曲线研究了两种钝化膜的生长机制和钝化膜的半导体性质,借助电容测量和点缺陷模型计算了两种钝化膜内的缺陷密度和缺陷扩散系数。结果表明:两种管线钢在该介质中都存在一个很宽的钝化区间,钝化膜的生长均受电迁移和溶解-沉积混合机制控制,钝化膜均为n型半导体。但与X80钢相比,X100钢具有更低的自腐蚀电流密度和维钝电流密度,及更高的击穿电位。X100钢表面钝化膜也更为致密、均匀、稳定,钝化膜的施主密度更低,缺陷扩散系数约是X80钢的1/3。因此,X100钢比X80钢生成的钝化膜表现出更好的抗均匀腐蚀性能和抗点蚀性能。 展开更多
关键词 X100管线钢 钝化膜 耐蚀性 Mott-Schottky分析 半导体性能 缺陷扩散系数
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