混合稀土对共晶Al-2%Fe合金组织形态的影响

研究了富La混合稀土对共晶Al-2?合金组织形态的影响. 当混合稀土加入量较少时, 合金中的α-Al相为明显的胞状枝晶;随着混合稀土加入量的增加, α-Al枝晶优先形核生长得到抑制, 共晶Al3Fe相得到细化;当稀土加入量增至0.6% (质量分数)共晶Al3Fe相尺寸逐渐增大. 并对混合稀土对共晶Al-2?合金组织形态的影响机制进行了探讨.     

混合稀土对共晶Al-2％Fe合金组织形态的影响

研究了富La混合稀土对共晶Al-2％Fe合金组织形态的影响。当混合稀土加入量较少时，合金中的α—Al相为明显的胞状枝晶；随着混合稀土加入量的增加，α-Al枝晶优先形核生长得到抑制，共晶Al3Fe相得到细化；当稀土加入量增至0．6％(质量分数)共晶Al3Fe相尺寸逐渐增大。并对混合稀土对共晶Al-2％Fe合金组织形态的影响机制进行了探讨。     

Growth of aligned single-walled carbon nanotubes under ac electric fields through floating catalyst chemical vapour deposition

Through floating catalyst chemical vapour deposition(CVD) method,well-aligned isolated single-walled carbon nanotubes (SWCNTs) and their bundles were deposited on the metal electrodes patterned on the SiO₂/Si surface under ac electric fields at relatively low temperature(280℃). It was indicated that SWCNTs were effectively aligned under ac electric fields after they had just grown in the furnace.The time for a SWCNT to be aligned in the electric field and the effect of gas flow were estimated. Polarized Raman scattering was performed to characterize the aligned structure of SWCNTs. This method would be very useful for the controlled fabrication and preparation of SWCNTs in practical applications.     

衬底对化学气相沉积法制备氧化硅纳米线的影响

通过化学气相沉积法在不同衬底上制备了大量的氧化硅纳米线.选用衬底为Si片、带有约100nm厚SiO2氧化层Si片和石英片.利用场发射扫描电子显微镜(SEM)和透射电镜(TEM，配备有能谱仪)对样品的表面形貌、结构和成分进行研究.结果表明：这些纳米线都为非晶态，但在不同衬底上生长的纳米线形貌、尺寸和化学成分不同.讨论了各种衬底对不同特征氧化硅纳米线生长的影响. 关键词： 化学气相沉积 纳米线 纳米颗粒     

Generalized probabilistic perturbation method for static analysis

ＧＥＮＥＲＡＬＩＺＥＤＰＲＯＢＡＢＩＬＩＳＴＩＣＰＥＲＴＵＲＢＡＴＩＯＮＭＥＴＨＯＤＦＯＲＳＴＡＴＩＣＡＮＡＬＹＳＩＳＺｈａｎｇＹｉｍｉｎ（张义民）ＣｈｅｎＳｕｈｕａｎ（陈塑寰）ＺｈｏｕＺｈｅｎｐｉｎｇ（周振平）（Ｄｅｐａｒｔｍｅｎｔｏｆｍｅｃｈａｎ...     

Li-Mn-O 体系电极材料的微波合成

研究了微波场中以Li2CO3和EMD（电解氧化锰）为原料,不同x=Li/Mn原料配比的Li Mn O体系电极材料的化学合成,其主要产物为LixMn2O4尖晶石,可作为锂离子电池的电极材料.与常规固相合成相比,微波场中的化学合成可在短的时间内完成. Li/Mn的配比对LixMn2O4尖晶石相的形成具有重要影响. x >1.0有利于得到产物成份纯、结晶好、电化学性能良好的LixMn2O4尖晶石相,其中x=1.05的试样最佳.采用XRD、SEM、XPS等方法研究微波场中化学合成产物的微观结构及其影响因素,分析了微观结构对性能的影响.     

Morphologies and microstructures of carbon nanotubes prepared by self—sustained arc discharging

We have investigated the morphology and microstructure of carbon nanotubes and nanoparticles in cathode deposits prepared by self-sustained arc discharge. Scanning electron microscopy images indicate that there are two regions exhibiting different morphologies on the top surface of the cathode deposits. In the central region, there is a triangular pattern of spots with a diameter up to 100μm, which consists of carbon nanotubes and nanoparticles. In the fringe region, carbon nanotubes and nanoparticles are distributed randomly. In addition, carbon nanotubes in the central region have a larger inner diameter, compared with those in the fringe region. The outer diameter distribution of tubes in the central region is narrower than that of tubes in the fringe region, while the former has a smaller peak value than the latter. For the nanoparticles, they exhibit a different behaviour from the tubes existing in the same region. The difference between the microstructure of tubes or particles in the two regions is attributed to the different temperatures and temperature gradients during their formation.     

复合材料层合板的谱随机无网格伽辽金法

针对基于摄动理论的计算方法不适用于分析随机结构参数大变异问题,提出谱随机无网格伽辽金法,该方法基于随机场正交分解理论,将随机场采用Karhunen-Loève级数展开为一系列不相关随机变量,再引入结构位移随机响应的混沌多项式分解,结合无网格伽辽金法,从而导出含随机变量的复合材料层合板的谱随机无网格伽辽金法,给出结构响应的统计特征值的计算公式,该方法既适用于随机参数大变异情况,又具有无网格法的优势;数值算例结果表明该方法是正确有效的。     

疲劳裂纹扩展寿命的可靠性及灵敏度分析

将影响结构疲劳裂纹扩展寿命的不确定因素视为随机变量,用随机有限元和可靠性分析理论,从概率论和数理统计的角度出发对含裂纹平面结构的断裂过程进行了可靠性分析。通过疲劳裂纹扩展寿命可靠度对随机变量的灵敏度分析,可以看出不同因素对疲劳裂纹扩展寿命可靠度影响的差别很大。     

Nanoscale carbon tubules deposited in anodic aluminium oxide template： a study of soft x-ray transmission

Well-aligned, catalyst-free nanoscale carbon tubules array was prepared by organic compound vapour deposition method using anodic aluminium oxide (AAO) as a template. The experiment of soft x-ray channelling in such carbon tubules array deposited in AAO template was performed at Beijing Synchrotron Radiation Facility. The transmission of x-rays in carbon tubules array with AAO template support was found even higher than that in bare AAO template at high-energy part of energy spectrum though the porous area of the former was smaller than that of the latter. A qualitative explanation is presented to interpret our results.