高取向聚乙烯的形态与晶体形变

采用ＳＥＭ和ＷＡＸＤ分析了高取向ＨＤＰＥ的形态,晶粒尺寸及结晶度,ＨＤＰＥ经口模拉伸,形态由台材料的微球状结构转变为纤维结构,随着拉伸比的提高,晶粒沿拉伸方向（ｃ轴）的尺寸增大,横向（ａ,ｂ轴）尺寸减小,有序性提高,结晶度增大,口模温度提高,晶粒沿ａ,ｂ,ｃ轴的尺寸均增大,有序性和结晶度提高,表明口模拉伸过程中既存在应力诱导的结晶过程,又存在温度诱导的二次重结晶过程。     

近空间升华法制备PbI_2厚膜及其性质研究

采用近空间升华法在玻璃衬底上制备PbI2厚膜,研究了工艺参数对样品晶体结构、形貌和光致发光性质的影响。实验显示,沉积速率随着源温度的升高和沉积气压的下降而急剧增大。XRD谱表明PbI2膜为沿[001]晶向择优取向的六方多晶体,晶粒尺寸随沉积速率的增大而逐渐减小。同时,沉积速率增大还导致膜压应力变大,晶格常数减小,使（001）晶面衍射峰向大角度方向移动。SEM照片显示样品为（001）晶面堆积而成的片状晶粒结构,晶粒c轴与衬底平行。随着沉积速率的增大,晶粒有序性和膜致密度下降,同时（001）晶面上由于六方中心亚晶粒的出现而导致表面粗糙度大幅增大。样品的PL发光谱显示了本征发射特征,发光锋随沉积速率的增大向长波方向移动,同时峰位展宽,强度减弱。     

水热-溶剂热法制备纳米CdS

硫化镉（CdS）是典型的半导体材料之一，因其在光电、光学和催化方面的应用前景，引起了广泛的重视．文中结合水热法和溶剂热法，在高压釜中形成以水和正已烷为溶剂的两相溶剂，并借助超声分散，以氯化镉（CdCl2）和硫代乙酰胺（TAA）为原料，在不同的加热时间和加热温度条件下成功制得CdS纳米粒子和纳米棒，并用X射线衍射（XRD）、高分辨透射电镜（HRTEM）、扫描电镜（SEM）、能谱及荧光光谱（LS）对其晶型、形貌、尺寸、组成进行了袁征，结果表明，制得的CdS纳米粒子与纳米棒尺寸分布均匀，分散性好；加热时间和加热温度是CdS晶型的主要影响因素，即较低的温度有利于CdS立方晶的形成，较高的温度有利于六方晶的形成；同时，延长加热时间有利于晶型的完善，但颗粒粒径会随之增大．     

Ti（1-x）CoxO2的溶胶-凝胶法制备与结构

采用溶胶-凝胶方法制备了Ti（1-x）CoxO2样品。研究了不同的热处理温度和掺杂浓度对样品晶型和颗粒尺寸的影响。样品400℃热处理呈锐钛矿相，600℃转变为全红石相并且晶粒尺寸明显增大。掺杂对晶型没有影响，但是随掺杂量的增大晶格常数减小。     

NiAl金属间化合物热爆合成动力学的试验研究

通过粉坯密度，加热速率，颗粒尺寸及合金元素等对ＮｉＡｌ热爆的点燃温度及最高反应放热温度的影响，研究了热爆合成的动力学规律，结果表明，热爆合成的点燃温度随颗粒尺寸的增大，加热速率的加快，粉坯密度的地加而升高。其反应最高温度随镍颗粒尺寸的增大，加热速率的加快和粉坯密度的增加而升高。     

工程金属材料的表面纳米化技术（二）

在表面机械处理方式下，材料表面可以通过强烈塑性变形而实现纳米化，获得表面为纳米晶、晶粒尺寸沿厚度方向逐渐增大的梯度结构。表面纳米化（SNC）技术一方面能为研究形变诱发的纳米化过程和宽尺寸范围内（从微米到纳米量级）结构与性能的关系提供思路，制备理想样品；另一方面能通过纳米化显著地提高金属材料的性能，因此可望在工业上取得实际应用。文章从基本原理、制备技术、结构、性能和化学处理等方面介绍表面纳米化研究工作已取得的进展。     

工程金属材料的表面纳米化技术（一）

在表面机械处理方式下，材料表面可以通过强烈塑性变形而实现纳米化，获得表面为纳米晶、晶粒尺寸沿厚度方向逐渐增大的梯度结构。表面纳米4E（SNC）技术一方面能为研究形变诱发的纳米化过程和宽尺寸范围内（从微米到纳米量级）结构与性能的关系提供思路，制备理想样品；另一方面能通过纳米化显著地提高金属材料的性能，因此可望在工业上取得实际应用。文章从基本原理、制备技术、结构、性能和化学处理等方面介绍表面纳米化研究工作已取得的进展。     

U型镍钛合金丝热定型及力学性能分析

采用不同的加热条件对镍钛合金丝进行定型,研究镍钛合金丝的力学性能及内部组织结构,确定了镍钛合金丝的最优热定型工艺参数。使用拉伸所用强力仪对镍钛丝进行拉伸性能测试,使用光学金相显微镜对镍钛丝进行金相组织观察。结果表明,热定型温度越高,加热时间越长,镍钛丝热定型效果越好,镍钛丝尺寸越接近定型模具尺寸;镍钛丝上下平台应力随加热时间的增加变小,其中,加工条件为550℃、20 min的上下平台应力最小,残余应变在加热时间多于10 min时显著增加;随着温度和加热时间的增加,镍钛丝内部奥氏体组织分布越来越均匀,奥氏体晶界越来越明显,其组织晶粒平均尺寸也越来越大。      

形变对Fe－30Mn－6Si基合金形状记忆效应的影响及其机理研究

本文用膨胀法比较了Ｆｅ－３０Ｍｎ－６Ｓｉ合金在拉伸应变下纵向（沿拉伸方向）和横向（垂直拉伸方向）恢复率的不同；研究了预应变对纵向恢复量，恢复率以及Ａ_ｓ，Ａ_ｆ的影响；还用一个大应变量下的样品在Ａ_ｓ和Ａ_ｆ范围内的不同温度区间进行了加热和冷却循环试验，得到了一些很有意义的信息。用正电子湮灭方法研究了Ｆｅ－３０ＭＤ－６Ｓｉ，Ｆｅ－３０Ｍｎ－６Ｓｉ－５Ｃｒ合金时效和非时效样品拉伸预应变量对合金中缺陷量，缺陷密度，γ→ε相变量等的影响。     

热处理对溶胶-凝胶TiO2薄膜的晶相转变和性能影响

以钛酸丁酯（TPOT）为有机醇盐前驱体，采用溶胶－凝胶技术制备了TiO2溶胶。为测量方便起见，分别制备了凝胶粉体和薄膜，并对样品进行了不同温度的热处理。X射线衍射（XRD）、椭偏仪和紫外－可见光谱（UV－vis)的测量表明：随热处理温度的升高，TiO2的结构由非晶到锐钛矿再到金红石相转变，400℃为锐钛矿相，600℃开始出现金红石相，800℃完全转变为金红石相；晶粒尺寸随热处理温度的升高而逐渐增大，锐钛矿结构的晶粒尺寸范围是2.5-5.5nm，金红石结构的晶粒尺寸范围是5.9-6.8nm；TiO2薄膜的折射率随热处理温度的升高而增大，同时薄膜厚度降低；禁带宽度随热处理温度的升高而增大，同时薄膜厚度降低；禁带宽度随热处理温度升高而变窄，锐钛矿结构的禁带宽度为3.45eV，而金红石结构的禁带宽度为3.30eV。     

Comparison of absolute spectral irradiance responsivity measurement techniques using wavelength-tunable lasers

Independent methods for measuring the absolute spectral irradiance responsivity of detectors have been compared between the calibration facilities at two national metrology institutes, the Helsinki University of Technology (TKK), Finland, and the National Institute of Standards and Technology (NIST). The emphasis is on the comparison of two different techniques for generating a uniform irradiance at a reference plane using wavelength-tunable lasers. At TKK's Laser Scanning Facility (LSF) the irradiance is generated by raster scanning a single collimated laser beam, while at the NIST facility for Spectral Irradiance and Radiance Responsivity Calibrations with Uniform Sources (SIRCUS), lasers are introduced into integrating spheres to generate a uniform irradiance at a reference plane. The laser-based irradiance responsivity results are compared to a traditional lamp-monochromator-based irradiance responsivity calibration obtained at the NIST Spectral Comparator Facility (SCF). A narrowband filter radiometer with a 24 nm bandwidth and an effective band-center wavelength of 801 nm was used as the artifact. The results of the comparison between the different facilities, reported for the first time in the near-infrared wavelength range, demonstrate agreement at the uncertainty level of less than 0.1%. This result has significant implications in radiation thermometry and in photometry as well as in radiometry.     

Designing light-emitting diode arrays for uniform near-field irradiance

We analyze the first-order design of light sources consisting of multiple light-emitting diodes (LEDs) to uniformly illuminate a near target plane by considering each single LED as an imperfect Lambertian emitter. Simple approximate equations and formulas are derived for the optimum LED-to-LED spacing, i.e., the optimum packaging density, of several array configurations to achieve uniform near-field irradiance.     

Aperture averaging effects on the probability density of irradiance fluctuations in moderate-to-strong turbulence

The lognormal (LN) and gamma-gamma (GG) distributions are compared to simulated and experimental data of the irradiance fluctuations of a Gaussian beam wave propagating through the atmosphere along a horizontal path, near the ground, in the moderate-to-strong turbulence regime. Irradiance data were collected simultaneously at three receiving apertures of different sizes. Atmospheric parameters were inferred from the measurements and scintillation theory and were used to develop the parameters for the theoretical probability density functions. Numerical simulations were produced with the same C(n)(2) value as the experimental data. Aperture-averaging effects were investigated by comparing the irradiance distributions for the three apertures at two different values of the structure parameter C(n)(2), and, hence, different values of the coherence radius rho(0). For the moderate-to-strong fluctuation regime, the GG distribution provides a good fit to the irradiance fluctuations collected by finite-sized apertures that are significantly smaller than rho(0). For apertures larger than or equal to rho(0), the irradiance fluctuations appear to be LN distributed.     

Tensile strength of fibre-reinforced metal matrix composites with non-uniform fibre spacing

The influence of non-uniform fibre spacing on the strength of unidirectional fibre-reinforced metal matrix composites was studied by means of a Monte-Carlo computer simulation experiment. The influence of yield stress of the matrix and scatter of the fibre strength on the strength of composites were also studied for both uniform and non-uniform fibre spacings. It was demonstrated that (1) the strength of composites with non-uniform fibre spacing is lower than that with uniform spacing due to the high stress concentration arising from the breakage of fibres, and (2) the reduction in strength of composites due to the non-uniformity increases with increasing scatter of fibre strength. For both cases of uniform and non-uniform spacings, the following tendencies were observed : (a) the strength of composites increases but then decreases with increasing yield stress of matrix, (b) it is very sensitive to yield stress of the matrix when the scatter of fibre strength is large but not when it is small, and (c) it decreases but then increases with increasing scatter of fibre strength when the yield stress of the matrix is high, while it decreases monotonically with increasing scatter of fibre strength when the yield stress is low.     

酚醛树脂/木粉复合材料制备木材陶瓷结构变化过程研究

酚醛树脂/椴木木粉复合材料经高温真空碳化制成了木材陶瓷。利用XRD、SEM和FTIR技术对碳化温度和酚醛树脂/木粉质量比对木材陶瓷物相、微观结构和物理化学结构变化的影响进行了表征和研究。结果表明,木材陶瓷具有拓扑均匀的连通孔的三维网络结构,是含有C C、C—O—C和C—H等基团的类石墨结构的碳/碳复合材料;随碳化温度的升高,(002)峰强度增大,晶面间距d₍₀₀₂₎降低,碳化木粉收缩,其间隙增大;酚醛树脂/木粉质量比增大,浸渍树脂的木粉成形能力改善,所得木材陶瓷结构更均匀,但其对木材陶瓷的XRD衍射花样影响不大。      

Reflectors for uniform far-field irradiance: fundamental limits and example of an axisymmetric solution

We establish a fundamental bound on the field of view over which strictly uniform far-field irradiance can be achieved in symmetric two-dimensional (2D, troughlike) and three-dimensional (3D, conelike) illumination systems. Earlier results derived for particular 2D devices are shown to be special cases of the general formula. For a rotationally symmetric 3D luminaire with a Lambertian disk light source and a prescribed uniform core region half-angle theta(c), no more than tan(2)(theta(c)) can be projected within a uniform core region. Hence the efficiency with which such illuminators can produce uniform flux is severely limited for many problems of practical interest. Guided by the tailored edge-ray device formalism for the design of 2D luminaires, we develop a 3D reflector that produces extremely uniform far-field illuminance.     

From primary standard to mobile measurements — Overview of the Spectral Irradiance Calibration Equipment at PTB

The Spectral Irradiance Calibration Equipment (SPICE) at PTB incorporates several radiometric installations. They can be flexibly combined for a large variety of measurement requirements. The instrumentation consists of high-temperature blackbodies as primary radiometric standards, high-quality spectroradiometer systems and a variety of auxiliary measurement equipment. Besides the realization and dissemination of spectral irradiance to various international customers, SPICE enables PTB to investigate new developments in the field of source-based spectroradiometry. Several successfully finished international intercomparisons and cooperations validate the quality and flexibility of SPICE.     

改善多指功率SiGe HBTs热稳定性的版图设计

提出非均匀指间距结构功率SiGe HBTs的版图设计用以改善热稳定性。模拟和实验结果均表明,与传统的均匀指间距结构相比,非均匀指间距结构HBT的峰值结温和温度分布非均匀性均得到显著改善。上述改善归功于非均匀指间距结构HBT中心指间距的增加,从而有效阻止热流由外侧指流向中心指处。此外,与均匀指间距结构器件相比,其热阻改善13.71%,热退化功率水平提高22.8%。因此,模拟和实验均证明采用非均匀指间距结构HBT的版图设计可有效改善功率HBTs热稳定性。     

Monte Carlo simulation of light transport in tissue: unscattered absorption events

A source of error in the Monte Carlo simulation of the fluence rate in turbid media is the inaccurate recording of unscattered absorption events. The form and magnitude of the error have been studied for Gaussian and uniform beam profiles simulated in cylindrical and Cartesian coordinates. In each case the error decreases as the lateral sampling lattice spacing decreases and is less than 2% of the incident peak irradiance when the beam radius is greater than five lattice spacings. To avoid the error, one may calculate analytically the fluence rate caused by unscattered absorption events.