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31.
Ternary Ti-Al-Nb elemental powder blends with minor addition of SiC were synthesized in a high energy ball mill in order to understand the structural evolution during mechanical alloying (MA) and subsequent thermal treatment. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) techniques were employed to study the structural development during MA. Ti-48%Al-4%Nb-3%SiC and Ti-48%Al-8%Nb-3%SiC blends milled to 20 h were subjected to thermal treatment at 750 °C for 1 h in vacuum. Repeated cold welding and fracturing events of MA resulted in nanocrystalline structure with supersaturated solid solution and amorphous phase. The powder particles were also refined to submicron size due to high energy collision. The nanocrystalline supersaturated solid solution evolved by MA was sustained for prolonged milling time. There was no evidence of intermetallics formation even after early solid solubility extension and formation of nanocrystalline structure. However, nanostructured TiAl and Ti3Al intermetallic compounds were observed after giving thermal treatment to MA powder blend. Since their surface area and energy were enhanced to a great extent, the dispersed ceramic particles reacted with titanium and formed nanosilicide particles. 相似文献
32.
The structural properties and hydrogen bonding of undoped and phosphorous doped polycrystalline silicon produced by step-by-step laser dehydrogenation and crystallization technique were investigated using Raman spectroscopy and hydrogen effusion measurements. At low laser fluences, EL, a two-layer system is created. This is accompanied by the change in hydrogen bonding. The intensity of the Si–H vibration mode at 2000 decreases faster than the one at 2100 cm−1. This is even more pronounced in phosphorous-doped specimens. The laser crystallization results in an increase of the hydrogen binding energy by approximately 0.2–0.3 eV compared to the amorphous starting materials. 相似文献
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用化学气相沉积法制备了液晶光阀中光电导层———非晶硅薄膜,从实验中得出最佳制备工艺的参数取值。给出了用包络线法测量非晶硅薄膜光吸收系数的原理,测量了样品的光吸收系数随波长的变化规律。得到样品在最佳工艺条件下的光吸收系数高于1×103cm-1。 相似文献
36.
Mgidi Donald Dlamini 《Solar Energy Materials & Solar Cells》1996,43(4):353
In this paper results on surface photovoltage (SPV) and electron beam induced conductivity (EBIC) studies of edge-defined film-fed growth (EFG) and floating zone (FZ) silicon solar cell materials (both p-type) are presented. A systematic comparison based on minority carrier diffusion length and carrier recombination is made between: (i) samples contaminated with Ti and/or Fe, (ii) samples gettered by phosphorous diffusion, and (iii) as-received samples. Deep level transient spectroscopy (DLTS) measurements, together with the iron-boron (FeB) pairing kinetics [1] have successfully been used to detect the presence of Fe in the samples. Even though this process is effective in revealing Fe impurities in p-type FZ silicon it is evidently not suitable for Fe identification in p-type EFG silicon. Ti, like Fe, is found to be a prominent lifetime-limiting metallic impurity in both EFG and FZ silicon. Phosphorous diffusion is proven to be an effective external gettering technique for fast-diffusing impurities such as Fe, but not for Ti. 相似文献
37.
以YAG为添加剂的气压烧结氮化硅 总被引:2,自引:1,他引:1
本文以添加YAG的反应烧结氮化硅(RBSN)为前驱体,采用气氛加压烧结的工艺,在0.5~9.0MPa氮气压力范围,研究了不同氮压对烧结体的密度、相组成、强度和显微结构的影响及其相互间的关系。研究表明,通过改变氮气压力能有效地调控材料的显微结构,材料的性能又受控于显微结构的变化。 相似文献
38.
利用挤压铸造制备氧化铝/锌合金复合材料,在扫描电镜(SEM)上观察复合材料的界面。结果表明,在复合材料中纤维与基体间存在致密界面层,合金元素通过适当的化学反应可改善纤维与基体间的结合;在凝固过程中,纤维/基体界面上的硅在共晶体的共生生长过程中起了领先相作用,导致复合材料的共晶转变是由铝硅共晶转变和锌铝共晶转变两者组成。 相似文献
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采用X射线衍射分析技术,研究了脉冲化学镀非晶态Ni-P合金的原子分布和函数,得出其短程有序原子集团的尺度为0.754nm,约为熔体激冷法获得的非晶态Ni-P合金短程有序畴的1/2。并利用脉冲化学沉积非晶态合金的微机制择这一结果进行了解释。 相似文献