Transcalent Silicon Power Rectifier

The transcalent rectifier can dissipate power losses while rectifying 250 amperes; it rectified 60-Hz alternating current at conduction angles of 180°, 120°, and 60°, and at frequencies varying from 200 to 2600 Hz at a conduction angle of 180°. It was surge-current tested to a peak of 6500 amperes, life tested for 4108 hours, and cycle-life tested for 10 867 cycles while rectifying 250 amperes of current. The transcalent rectifier dissipates heat more effectively and at lower junction temperature than conventional rectifiers as heat is transferred isothermally by vaporization of liquid in the heat pipe. Operational characteristics are: a thermal impedance of 0.030 C/W between junction and fins; a thermal impedance of 0.21 C/W between fins and ambient; a junction operating at 1300C; size less than 14 cubic inches; and weight less than 10 ounces.     

SiC晶须增韧SiC mini复合材料的制备与性能分析

采用CVI工艺制备了SiC晶须增韧SiC(SiCW/SiC)mini复合材料,研究了其微观结构和力学性能.实验结果表明:SiC晶须的体积分数达到45%～50%,SiCW/SiC mini复合材料的维氏显微硬度平均值为19.04GPa,断裂韧度平均值达到6.51MPa·m1/2.微观结构观察证实SiC晶须的引入在mini复合材料中产生了晶须桥联、晶须拔出、晶须断裂和裂纹偏转等增韧机制,为后续SiCW/SiC复合材料的制备奠定了基础.     

SiC_(f)/SiC复合材料铣削加工表面质量北大核心CSCD

使用PCD立式铣刀对聚合物浸渍裂解法(PIP)制备的SiC_(f)/SiC复合材料开展单因素铣削试验,通过对加工中产生的切削力和加工后的表面粗糙度进行测量,分析了铣削工艺参数对其的影响;对加工表面、纤维断口进行SEM分析,讨论了SiC_(f)/SiC复合材料加工表面的形成。研究结果表明,表面粗糙度与切削力的变化趋势相同,高主轴转速和小切削宽度有利于得到表面粗糙度较小的加工表面;近孔洞区域与远离孔洞区域的材料去除方式不同;材料中纤维发生面内偏移和层间屈曲,纤维存在多种去除方式。     

Characteristics of Disorder and Defect in Hydrogenated Amorphous Silicon Nitride Thin Films Containing Silicon Nanograins

The hydrogenated amorphous silicon nitride (SiNx) thin films embedded with nano-structural silicon were prepared and the micro-structures at the interface of silicon nano-grains/SiNx were identified by the optical absorption and Raman scattering measurements. Characterized by the exponential tail of optical absorption and the band-width of the Raman scattering TO mode, the disorder in the interface region increases with the gas flow ratio increasing. Besides, as reflected by the sub-gap absorption coefficients, the density of interface defect states decreases, which can be attributed to the structural mismatch in the interface region and also the changes of hy-drogen content in the deposited films. Additional annealing treatment results in a significant increase of defects and degree of disorder, for which the hydrogen out-diffusion in the annealing process would be responsible.     

新型反射镜材料——碳化硅

对几种常用反射镜材料的物理性能和工艺性能进行了比较，研究了碳化硅轻质反射镜的制作工艺，结果认为：反应烧结是实现这种材料作为反射镜材料的巨大潜力的最有效的工艺，可以实现形状复杂产品的近净尺寸成型，样品在烧结过程中无收缩；样品处理时间短；无需特殊设备，在烧结过程中无需加压，样品尺寸原则上仅受烧结炉大小的限制,帛品近乎安全致密。这项研究的突破，主要依赖于反射镜成型方法及反射镜面光学加工的研究进展。最后简述了美国和俄罗斯在这方面的研究进展。     

多晶硅沉淀的灰色分析

本文给出了灰色信噪比的定义，并将其用于多晶硅沉淀的数据分析，使表面缺陷和沉淀厚度在最佳条件下试验结果与灰色预估值更符合。     

氮化硅的氧化机制研究

研究了氮化硅的氧化机制以及被动氧化至主动氧化的转捩温度,并结合试验结果做了分析。结果表明氮化硅在高温下极易炸裂,在被动氧化机制下生成氮气和SiO2薄膜,转捩温度和碳化硅材料基本一致。     

Silicon Solar Cells at Low Temperature

Electrical characteristics of n-p silicon solar cells have been obtained experimentally over the temperature range of +28 to ?175° and for illumination intensities from 140 to 1.5 mW/cm2. Critical parameters and their distribution are presented for several hundred solar cells from various manufacturers. The effect of cell selection either to a minimum power output at 28° at 5 mW/cm2 or to a minimum open-circuit voltage at ?128° at 5.16 mW/cm2 upon the magnitude and distribution of the critical parameters is investigated. Considerable differences are noted, not just between cells, but also between lots from various manufacturers. Correlation analysis reveals no parameter which when measured at room temperature will predict the power output at low temperatures. This is due to a number of anomalies of the output characteristics at low temperature. These are a lack of the open voltage to continue to increase with decreasing temperature and a double break in the current-voltage characteristics. In addition, some cells show low shunt resistance which makes them have a poor performance at low intensities.     

一种新型的硅片转子调谐陀螺仪

本文介绍一种硅薄片转子调谐式陀螺仪。该陀螺仪继承了动力调谐陀螺仪的结构形式和工作原理,利用微电机驱动陀螺转子,利用两对扭杆和平衡环实现动力调谐,其扭杆、平衡环、陀螺转子和信号器、力矩器均由微机械工艺加工,转子偏角采用差动电容检测,力平衡反馈通过静电力实现。论文详细介绍了该陀螺仪的结构,分析了调谐条件和信号器、力矩器标度因数,讨论了信号检测与力反馈回路的组成与原理。硅薄片转子调谐陀螺仪的体积和质量略大于硅微机械陀螺仪,精度与动力调谐陀螺仪相近（理论可达0.01°/h或更高）,且环境适应性较好,成本低,适于要求较高精度和小体积的应用场合。     

硅基复合材料烧蚀特性试验研究

在电弧加热试验条件下,通过一定范围内压力和焓值的匹配,进行不同热流密度下的硅基复合材料驻点烧蚀试验,获得该防热材料的质量烧蚀率和有效烧蚀焓,并利用回归分析得出该防热材料质量烧蚀率与冷壁热流和驻点压力的试验关系式:mt=0.07232qs,cw O.08784ps0.1206;有效烧蚀焓与气流总焓、驻点压力和热壁焓的两个试验关系式,即Heff=2.0042H00.7753ps-0.08和Heff=1.0024(H0-Hhw)+6.1229.     

氮化硅陶瓷切削仿真与实验

针对金刚石砂轮磨粒尺寸、形状的不规则性和空间位置不确定性的特点,采用球坐标中随机点产生的空间平面切分实体和截角多面体相结合的方法,并考虑氮化硅陶瓷工件的磨削亚表面形貌和裂纹损伤,建立了截角多面体磨粒和含有典型裂纹的工件模型。进行单颗磨粒切削氮化硅陶瓷的有限元仿真和实验,结果表明:磨削加工和数值仿真的磨削力值变化趋势相同,差值小于8%,切削力随砂轮转速增大而减小、随工件速度和切削深度增大而增大,而切削深度对切削力的影响程度最大。     

有机硅材料用于冲压发动机绝热层的研究

介绍了以硅树脂作为冲压发动机绝热层的基体材料,以YJ 短纤维或纤维织物作为增强材料的两 种绝热层配方的烧蚀性能。考察了YJ 短纤维的含量、硅树脂/ 纤维织物的质量配比对绝热层烧蚀率和工艺性 能的影响。结果表明:YJ 短纤维为4 份时,硅树脂/ YJ 短纤维/ 氧化锆配方的烧蚀与工艺的综合性能最佳,而 硅树脂与纤维织物的质量配比为1. 1 ∶1 时,硅树脂/ 纤维织物配方的氧乙炔烧蚀率最小,仅为15. 2 μm/ s。20 s 缩比发动机地面试验结果表明,两种配方绝热层均对冲压发动机实施了有效热防护。     

新型碳化硅先驱体的制备及其性能研究

采用溶胶凝胶法，以正硅酸乙酯和酚醛树脂为原料，在草酸和六次甲基四胺的催化作用下，制备出了不含硫和氯等有害杂质的均相碳化硅先驱体，并在特定条件下，对所得先驱体进行烧结，使之转化为陶瓷。结果表明，溶胶凝胶法制得的先驱体呈黄色透明的玻璃态，其微观组成为几十纳米的微粒，树脂与SiO2可能通过氢键相互作用，有利于树脂在先驱体中均匀分布而形成均相先驱体，其陶瓷产率为78％；另外硝酸镍的加入对先驱体烧结过程中β-SiC的生成起到明显的促进作用。     

Silicon Solar Cell Performance at High Intensities

The theoretical and experimental work performed since 1960 in the area of high-intensity and high-temperature operation of silicon and gallium arsenide photovoltaic devices is reviewed. Test results for conventional 5-grid silicon cells, for specially designed 13-grid silicon cells, and for a GaAs cell are presented parametrically for the illumination intensity range from 0.07 to 2.8 W/cm2 and the temperature range from 30 to 1 50°C. The data cover the 3 points on the currentvoltage characteristic required to reconstruct the full characteristic in the power-generating quadrant. The 13-grid silicon cells showed much better performance than the GaAs cell.     

Amorphous Silicon Electronic Devices and their Applications

Hydrogenated amorphous Si (a-Si:H) devices first made a significant impact in photovoltaic application, 70% of the photovoltaic solar cells produced in Japan in 1984 were a-Si:H. More recently, thin film transistor (TFT) and sensor devices have been developed for consumer and business products. The ability to produce large area uniform films of a-Si:H makes the application of TFTs and sensors well suited for input and output imaging devices such as image scanners, display and printers. This paper reviews the operation, material issues and physics of a-Si:H TFTs and sensors. The circuit and technology issues in large area systems incorporating these devices are described.     

含硅芳炔树脂的化学流变特性

含硅芳炔树脂的流变特性对于其RTM成型工艺有重要参考价值,采用DSC热分析及黏度测量表征了含硅芳炔树脂的固化特性和黏度与温度的关系,发现含硅芳炔树脂为典型的牛顿流体,且在100～130℃范围内具有较低黏度,维持时间长.根据其黏度-温度-时间关系建立了双阿伦尼乌斯黏度模型,模型分析与实验结果取得较好的一致性,可为RTM成型工艺窗口的预测提供支撑.     

碳化硅反射镜材料性能预测

预测了反应烧结SiC（RBSiC）的物理及部分力学性能与游离Si含量的变化关系，并对预测值与测量值进行比较以验证其符合程度。经预测，随Si含量的增加，RBSiC的密度呈线性下降，尤其是气孔对材料密度的影响非常明显;线膨胀系数和热导率均应呈加速上升趋势，比热容稍有下降；各模量均有下降趋势。随着气孔的增加，RBSiC的膨胀量变化不明显，比热容和热导率均呈减速下降趋势。RBSiC测量值与预测值产生偏差是因为材料中Si含量的增加导致缺陷增多以及计算性能用数据有偏差所致，但预测仍能较符合RBSiC性能随Si含量变化趋势，因此认为预测值较为合理可作为性能参考值使用。     

单晶硅电火花线切割表面损伤层形成机理

 为了研究单晶硅电火花线切割(WEDM)表面损伤层的损伤形式和形成机理,以电火花线切割加工后的单晶硅表面为研究对象,采用表面形貌观察分析及择优腐蚀方法研究了单晶硅经过电火花线切割后的加工表面.研究结果表明单晶硅经电火花放电加工后表面损伤形式分为4种:热损伤、应力损伤、热与应力综合作用损伤及电解/电化学腐蚀损伤.热损伤使得硅表面形成多晶或非晶硅;应力损伤使硅表面产生裂纹;热与应力综合作用会产生小孔效应,且随着放电功率密度的增加,小孔会明显增多;电解/电化学作用会加快损伤区域及杂质元素富集区域的腐蚀.     

用有机硅树脂YR3370连接RBSiC陶瓷

 以一种聚硅氧烷类有机硅树脂YR3370(GE Toshiba Silicones)为连接剂，连接了反应烧结SiC(RBSiC)陶瓷。连接件在1 100~1 300℃的99.99%N₂气流中进行热处理。用三点弯曲强度实验测定连接件的强度，用场发射扫描电镜、X射线衍射和热重测试分析显微结构和化学反应。在连接温度为1 200 ℃时，连接件的三点弯曲强度达到最大值197 MPa。连接层是由有机硅树脂YR3370裂解生成的无定形Si_xO_yC_z陶瓷，其结构连续均匀致密，厚度在2~5 μm之间。连接机理是通过无定形Si_xO_yC_z陶瓷的无机粘接作用在RBSiC陶瓷基体和连接层之间形成连续的化学键。     

速率检测中新型定角脉冲产生电路

介绍了一种用于转台速率检测的新型定角脉冲产生电路,详细说明了其工作原理和性能,并给出了实测结果。