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41.
机械合金化过程中Fe70B30粉末晶粒尺寸和微观应变的研究 总被引:2,自引:0,他引:2
用X射线和电镜研究了Fe_(70)B_(30)粉末经不同时间高能球磨后晶粒尺寸和微观应力的变化。在机械合金化过程中,粉末的X射线衍射谱的宽度随球磨时间的增加逐渐加宽,这是晶粒细化和内部微观应力共同作用的结果。X射线衍射结果表明:随着机械合金化的进行,粉末的晶粒尺寸逐渐减小,球磨初期晶粒尺寸下降较快,经15h球磨,晶粒尺寸为25nm,机械合金化进行到一定时间后晶粒尺寸下降缓慢,80h球磨后晶粒尺寸可达5nm。在机械合金化过程中球磨所造成的微观应变不大,球磨初期粉末的内应力随球磨时间增加而增加,当粉末粒子尺寸很小时,随球磨的进行粉末中的微观应变显著下降。 相似文献
42.
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
43.
根据胜利油区的地层渗透率、孔隙度,在27个低渗透油田和46个中、高渗透油田的放射性同位素测井中进行了粒径为100~300μm、300~600μm、600~900μm放射性同位素131Ba微球粒径选择实验,确定了放射性同位素131Ba微球的选择原则。当油藏渗透率K<100×10-3μm2、孔隙度<20%时,放射性同位素粒径为100~300μm;当油藏渗透率K>100×10-3μm2、孔隙度>20%时,放射性同位素粒径为300~600μm或600~900μm。在此基础上得到胜利油区选用同位素粒径明细表,对于指导施工,提高放射性测井资料的可靠性具有重要意义。 相似文献
44.
Alena Orlov 《Materials Science and Engineering: A》1996,220(1-2):117-122
The present work studies the collection of experimental data from which Raj and Pharr (Mater. Sci. Eng., 81 (1986) 217) deduced a universal empirical dependence of the subgrain size on the applied stress. In accord with their result and some theoretical predictions the normalized subgrain size ds/b was ssumed to be proportional to G/σ (G is the shear modulus, b the Burgers vector length, σ the applied stress). The evaluated factor of proportionality K1, having the value within the interval from 0.76 to 180 in the inspected data sets, was discussed from the point of view of various factors which can influence the experimental data. 相似文献
45.
46.
In our previous works, we have shown that most existing ceramic superconductors can be considered to be built of superconductor-semiconductor composite and we have estimated the change in phonon spectrum of the intrinsic superconductor unit if a semiconductor unit is attached to it. Moreover, the proximity effect under the size quantization condition has been examined in the superconductor-semiconductor composite. Each of the stated effects by itself could causeT
c
enhancement in general as more semiconductor blocks are added to the system. We extend our study in this paper to analyze the combined actions of phonon spectral change and proximity effect without size quantization condition onT
c
variation in members of the Tl1 series of high-T
c
superconductors. Our results indicate that an optimumT
c
is obtained if the stated effects are included in the idealized unit cells of the superconductors made up of a superconductor-semiconductor array. 相似文献
47.
提高大直径井眼机械钻速的几项措施 总被引:1,自引:0,他引:1
随着我国西部地区石油勘探开发的进展,5000-7000m的深探井所钻数量不断增多,套管程序增加,特别是大尺寸井眼所钻深度明显加大。由于国产大尺寸钻头结构单一、型号少,破岩机械能量和水力能量不足,在易斜井段目前尚无可靠的防斜保直措施,以及钻井液性能不适宜等原因,大尺寸井眼的钻这远远低于215.9mm井眼的钻速。据此,提出了几项可以提高大尺寸井眼钻速的措施:增加大尺寸钻头的种类,采用阶梯式扩眼钻头,强化钻井参数和水力参数,选用中速动力钻具,改善钻井液性能以及采用冲击旋转钻具等。 相似文献
48.
泥浆制备中工艺改造的研究 总被引:1,自引:0,他引:1
根据室条件下粉磨试验结果,发现球磨过程中筛上料变化存在的突变范围,提出两次加料一次加水可改变泥浆颗粒分布,并找出适宜的加料种类与时间。另外给予测粒度分布提供了宝贵的试验基础数据。 相似文献
49.
50.
B. Bary 《Cement and Concrete Research》2006,36(11):2061-2073
In this paper, the porosity of cementitious materials is described in terms of pore size distribution by means of a 3-dimensional overlapping sphere system with polydispersivity in size. On the basis of results established by Lu and Torquato [B. Lu, S. Torquato, Nearest-surface distribution functions for polydispersed particle systems, Phys. Rev. A 45(8) (1992) 5530-5544] and Torquato [S. Torquato, Random Heterogeneous Media: Microstructure and Macroscopic Properties. Springer-Verlag: New York, 2001] providing relations for nearest-neighbor distribution functions, the volume fraction of pores having a radius larger than a prescribed value is explicitly expressed. By adopting an appropriate size distribution function for the sphere system, it is shown that the pore size distribution of cementitious materials as detected for instance by mercury intrusion porosimetry (MIP), which generally points out several pore classes, can be well approached. On the basis of this porosity representation, the evaluation of the capillary pressure in function of the saturation degree is provided. The model is then applied to the simulation of the saturation degree versus relative humidity adsorption curves. The impact of the pore size distribution, the temperature and the thickness of the adsorbed water layer on these parameters are assessed and analyzed for three model materials having different pore characteristics. 相似文献