碳化硅浇注料在1000℃空气和水蒸气中的高温氧化行为

利用扫描电镜、X射线衍射仪等对碳化硅浇注料在1000℃静态空气和纯水蒸气(参照ASTM C863—2000)中分别保温50、100、150 h的高温氧化行为进行了研究.结果表明:1)纯水蒸气氧化条件下,碳化硅浇注料的质量变化率和体积变化率均明显大于静态空气条件下的.2)和空气相比,水蒸气氧化对碳化硅浇注料的结构破坏更严...     

YT30硬质合金刀片的热电特性与其耐磨性的相关性研究

热电特性是导电材料很容易测量的宏观物理量,如果通过测量热电特性来分析材料的磨损很有意义。本文以最常用的刀具材料YT30硬质合金为研究对象,通过实验探索了刀片磨损量与其热电特性的相关性。本实验证明YT30硬质合金刀片的热电特性与其磨损量有很高的相关度。这为进一步深入研究采用测量硬质合金刀片材料的热电特性来预测其使用寿命建立了良好的基础。     

可换头式硬质合金钻头弹性夹紧结构设计与有限元分析

可换头式钻头是一种新型、高效、内冷却钻头,仅钻尖采用少量的整体硬质合金材料,并以特殊的定位和夹紧方式与钻杆配合实现装卸、可换。本文对两种可换头式钻头结构进行了定位原理和结构特点的分析,提出了一种新型弹性夹紧式结构。对新型可换头结构进行了设计与力学建模,使用ANSYS有限元软件对其弹性变形部分的位移与应力进行分析,为钻杆与钻尖的结构设计与改进提供依据。     

硬质合金喷涂技术应用分析

介绍了利用氧-乙炔线材火焰喷涂设备、喷涂硬质合金棒材,并对制备硬质合金涂层工艺参数的选择制备方法,以及应用前景作了详细阐述。     

4H-SiC MESFET大信号非线性特性分析

采用Voherra级数法对4H-SiC射频MESFET的大信号非线性特性进行了分析,并研究了器件尺寸与线性度的关系.模型考虑了陷阱效应对非线性特性的影响,模拟结果能够较好地反映实验结果.进一步分析表明,在1GHz和1.01GHz频率下,当栅长从0.8μm增大到1.6μm,器件的输入(输出)三阶截取点从33.55dBm(36.26dBm)减小到18.1dBm(13.4dBm),1dB压缩点从24dBm下降到7.43dBm.为实际器件的线性化设计提供理论依据.     

碳化硅单晶切割技术研究

碳化硅单晶材料是第三代宽禁带半导体材料的代表,对电子产业的发展起到强有力的支撑。晶片加工技术是器件生产的重要基础和基本保证,任何具有优异特性的材料只有在成功有效的加工技术下才能发挥实际效能。本文介绍了切割工艺,通过工艺实验及对实验结果的分析,确定了切割工艺参数。     

The compressive strength experimental study of cemented soil under H2SO4 corrosive in earlier period

In order to simulate and study the erosion effect process such as the changes of corrosive depth and unconfined compression strength of cemented soil sample in earlier period from 0 day to 60 days, a series of tests including unconfined compressive tests, measuring the blocks＇ sizes, and taking photos, are conducted on the cemented soil blocks which were cured in different concentrations of H2SO4 solutions. The results of tests show that the corrosive depth is increasing and the unconfined compression strength is decreasing with the increase of H2SO4 solution concentration at the same erosion time, and the corrosive degree is increasing with the corrosive time. In the earlier state, the corrosive effect is serious, but the effect becomes slow in the later state in the same concentrated H2SO4 solution. After take statistics the date, a coefficient a is put forward to predict the reduction of the compressive strength of cemented soil in various concentration of H2SO4 solution, which could be used in practical design.     

Defect Analysis of Barrier Height Inhomogeneity in Titanium 4H-SiC Schottky Barrier Diodes

Over 350 4H-SiC Schottky barrier diodes (SBDs) of varying size are characterized using current–voltage (I–V) measurements, with some also measured as a function of temperature. Devices display either a characteristic single-barrier height or atypical dual-barrier heights. Device yields are shown to decrease as device area increases. Molten KOH etching is used to highlight defects for analysis by optical microscopy and atomic force microscopy. The I–V characteristics are compared against the defect density. A positive correlation between effective barrier height and effective electrically active area of the SBDs is found. No correlation is found between threading dislocations and ideality factor or barrier height.     

Evolution of Deep Defect Centers in Semi-Insulating 4H-SiC Substrates under High-Temperature Annealing

The influence of postgrowth high-temperature anneals between 1400°C and 2400°C on the behavior of the D₁ center in semi-insulating 4H-SiC was studied by photoluminescence. The optical signature of D₁ was observed up to 2400°C with intensity maxima at 1700°C and 2200°C. It was also found that changes in the postannealing cooling rate drastically influence the behavior of the D₁ center and the concentrations of the V_C, V_Si, V_C–V_Si, and V_C–C_Si lattice defects observed from electron paramagnetic resonance experiments. The change in intensity of the D₁ defect has some correlation with the intensity change of the V_C–V_Si pair defect at temperatures above 1900°C. In addition, infrared photoluminescence spectroscopy studies showed that changes in the intensity of the D₁ defect at 2100°C to 2400°C annealing temperatures and variable cool-down rates have close correlation with intensity changes of the UD2 defect.     

SF6/O2气氛中SiC ICP刻蚀的微沟槽效应

本文采用SF6 + O2作为刻蚀气体,对单晶6H-SiC 材料的感应耦合等离子体( ICP) 刻蚀工艺进行了研究。着重分析了ICP 功率、偏置电压、气体混合比等工艺参数对微沟槽效应的影响。结果表明,O2的加入对于微沟槽的形成起到了极其重要的作用,微沟槽是加入氧气后形成的SiFxOy中间层的充电造成的。ICP功率与偏置电压的增大会增强微沟槽效应,进一步促进微沟槽的形成,另外入射离子的角度分布也会影响微沟槽的形成.