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991.
Yuping Wu Pinghua Lin Guozhi Xie Junhua Hu Ming Cao 《Materials Science and Engineering: A》2006,430(1-2):34-39
High velocity oxy-fuel (HVOF) thermal spray was used to deposit a Fe–Cr–Si–B alloy coating onto stainless steel (1Cr18Ni9Ti) substrate. Microstructures of the powder and the coating were investigated by X-ray diffraction (XRD), scanning election microscopy (SEM), transmission election microscopy (TEM) and differential scanning calorimeter (DSC). The coating had layered morphologies due to the deposition and solidification of successive molten or half-molten splats. The microstructures of the coating consisted of a Fe–Cr-rich matrix and several kinds of borides. The Fe–Cr-rich matrix contained both amorphous phase and nanocrystalline grains with a size of 10–50 nm. The crystallization temperature of the amorphous phase was about 605 °C. The formation of the amorphous phase was attributed to the high cooling rates of molten droplets and the proper powder compositions by effective addition of Cr, Mn, Si and B. The nanocrystalline grains could result from crystallization in amorphous region or interface of the amorphous phase and borides by homogeneous and heterogeneous nucleation. 相似文献
992.
Jianjun Xie Jingying Liao Zhengsong Geng Chongzhi Ye Hui Yuan Wei Xiong Dunhua Cao Zhonggui Zhan Liang Chen Bingfu Shen Zhiwen Yin 《Materials Science and Engineering: B》2006,130(1-3):31-35
The effects of Y3+ doping at different concentration on the luminescnece properties of PbWO4 crystals have been investigated by means of Fourier transform infrared (FT-IR) spectrum, optical transmission, thermoluminescence (TL), X-ray excited luminescence (XEL), photoluminescence (PL) under excitation of UV light and light yield measurements. The series PbWO4:Y crystal samples were grown by modified Bridgman method and the concentration of Y3+ in the melt was in the range of 0–1.0 mol%. The slight blue-shift and evident red-shift of the absorption edge in PbWO4 crystal were observed at low and heavy doping concentration, respectively. TL peaks in the range of from room temperature to 250 °C disappeared after the doping with Y3+. With the increase of doping concentration, the luminescence intensity in the XEL and PL spectra was found to decrease accordingly, especially in the case of heavy doping. The measuring results demonstrate that Y3+ doping concentration below 100 ppm in the crystal seems to be the best for optimizing the optical and scintillation properties of the material. The mechanism of Y3+ doping concentration influence on luminescence was also discussed in this paper. 相似文献
993.
Deliang Zhu Peijiang Cao Wenjun Liu Xiaocui Ma Xiaojun Bai A. Maignan B. Raveau 《Materials Chemistry and Physics》2006,100(2-3):472-476
The magnetic and transport properties of Pr0.5Ca0.5−xAxMnO3 (A = Sr, Ba) have been investigated in this paper. The substitution of Ca with bigger cations such as Sr and Ba can favour the field-induced ferromagnetism and induce sharp steps in the magnetization versus field and resistivity versus field curves. These properties strongly depend on the thermal history of the samples. All the results have been interpreted by a martensitic-like mechanism based on phase separation induced by A-site size mismatch. The above model can also explain the result that the less efficient ability of Sr substitution than Ba substitution to induce ferromagnetism and sharp steps. Another interesting feature in the system is the existence of an optimum substitution range to induce magnetization steps and reach high field-induced magnetization values for both Sr (x = 0.07–0.10) and Ba (x = 0.01–0.08) substitution. We suggest that the disappearance of the steps beyond the optimum substitution range possibly results from the different nature of phase separation in the optimum substitution range and beyond this range. 相似文献
994.
Ming Chen Lijia Pan Jieming Cao Hongmei Ji Guangbin Ji Xianjia Ma Youdou Zheng 《Materials Letters》2006,60(29-30):3842-3845
Triangular and hexagonal CdS nanoplates, with average size about 100 nm and average thickness range from 10 to 30 nm, have been synthesized in the presence of poly (acrylic acid) (PAA) assisted hydrothermal process at 180 °C. The structural characteristics, morphology, and optical properties of the as-prepared CdS products were investigated. UV–vis spectroscopy measurement reveals that the products show a strong quantum size effect. Based on the experiment results, the possible formation mechanism of CdS nanoplates has been proposed. 相似文献
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没有礼物的圣诞节将会是什么样子的呢?别急.从意大利当今最著名的设计师那里我们获得了20个充满创造性的方案。假日里最奇妙的时刻就是举杯共饮的那一瞬间.我们为大家提供的方案正是以干杯为主题的。那么.是什么使这些美好的时刻成为可能的呢?那就是酒杯。设计师们想出了各种各样的点子.这些点子充满了想象力.富于创造性.追求完美.令人兴奋。他们认为酒杯的材料固然重要。 相似文献
998.
曹海英 《北方工业大学学报》2006,18(2):41-47
人与自然和谐发展的价值观的提出源于对现时代环境危机和传统价值观的反思。本文首先阐述了这一价值观的现实基础,即人与自然本质上的整体性;其次论述了这一价值观的基本观点,即把内在价值的概念由人扩展到各种物种以及整个自然共同体,同时也强调了人类的实践能动作用和道德代理人作用,并由此推出人类对自然不可推卸的责任和义务;最后归纳了这一价值观的基本原则,即整体优化原则、尊重自然原则和责任原则。 相似文献
999.
结合数据采集系统在电能质量监测中的应用,介绍了一种基于FPGA的多路高速数据采集系统,给出了硬件原理框图;并对系统进行了模块化的分析,讨论了影响同步采样性能的因素.实际应用证明,采用该方法设计的系统能有效地完成多路同步高速数据采集任务. 相似文献
1000.
曹丹 《安徽电子信息职业技术学院学报》2006,5(2):50-51
本文在查阅、梳理这些论文的基础上,分析国内学界“民生新闻”的研究现状、研究涉及的主要内容及存在的不足,找出研究者尚未探寻的空间。 相似文献