Phase and microstructure evolution of Sc2O3–CeO2 –ZrO2ceramics in Na2SO4 + V2O5 molten salts

In this study, the destabilization resistance of Sc₂O₃ and CeO₂ co-stabilized ZrO₂ (SCZ) ceramics was tested in Na₂SO₄ + V₂O₅ molten salts at 750°C–1100 °C. The phase structure and microstructure evolution of the samples during the hot corrosion testing were analyzed with X-ray diffraction (XRD), Raman spectra, scanning electron microscopy (SEM), energy dispersive X-ray spectrum (EDS), and X-ray photoelectron spectroscopy (XPS). Results showed that the destabilization of SCZ ceramics at 750 °C was the result of the chemical reaction with V₂O₅ to produce m-ZrO₂ and CeVO₄, and little ScVO₄ was detected in the Sc₂O₃-rich SCZ ceramics. The primary corrosion products at 900 °C and 1100 °C were CeO₂ and m-ZrO₂ due to the mineralization effect. The Sc₂O₃-rich SCZ ceramics exhibited excellent degradation resistance and phase stability owing to the enhanced bond strength and the decreased size misfit between Zr⁴⁺ and Sc³⁺. The destabilization mechanism of SCZ ceramic under hot corrosion was also discussed.     

Fabrication and laser performances of Yb:Sc2O3 transparent ceramics from different combination of vacuum sintering and hot isostatic pressing conditions

In this paper we report on the preparation and laser performance of transparent 3at.% Yb:Sc₂O₃ ceramics by reactive sintering of commercially available powders under vacuum followed by hot isostatic pressing (HIP). Combinations of different vacuum sintering temperatures (1650 °C and 1750 °C) and different HIP treatments (1700 °C and 1800 °C at 200 MPa) were tested in order to understand how these steps influence the microstructure and thus the optical and lasing properties of the ceramic samples. All the samples showed a good optical quality. The microstructure analysis and the laser tests showed that the vacuum pre-sintering temperature is the key factor determining the quality of the samples and the laser performances. The best values of slope efficiency i.e. η_L = 50 % and output power i.e. P_out = 6.62 W were obtained for the sample pre-sintered under vacuum at 1650 °C and hot isostatically pressed at 1800 °C.     

Microstructure and mechanical properties of hot-pressed SiC nanofiber reinforced SiC composites

This study reports on the preparation and mechanical properties of a novel SiC_nf/SiC composite. The single crystal SiC nanofiber(SiC_nf) reinforced SiC ceramic matrix composites (CMC) were successfully fabricated by hot pressing the mixture of β-SiC powders, SiC_nf and Al–B–C powder. The effects of SiC_nf mass fraction as well as the hot-pressing temperature on the microstructure and mechanical properties of SiC_nf/SiC CMC were systematically investigated. The results demonstrated that the 15 wt% SiC_nf/SiC CMC obtained by hot pressing (HP) at 1850 °C with 30 MPa for 60 min possessed the maximum flexural strength and fracture toughness of 678.2 MPa and 8.33 MPa m^1/2, respectively. The nanofibers pull out, nanofibers bridging and cracks deflection were found by scanning electron microscopy, which are believed can strengthen and toughen the SiC_nf/SiC CMC via consuming plenty of the fracture energy. Besides, although the relative density of the prepared SiC_nf/SiC CMC further increased with the sintering temperature rose to 1900 °C, the further coarsend composites grains results in the deterioration of the mechanical properties for the obtained composites compared to 1850 °C.     

Microstructures and mechanical properties of B4C-TiB2-SiC composites fabricated by ball milling and hot pressing

B₄C-TiB₂-SiC composites were fabricated via hot pressing using ball milled B₄C, TiB₂, and SiC powder mixtures as the starting materials. The impact of ball milling on the densification behaviors, mechanical properties, and microstructures of the ceramic composites were investigated. The results showed that the refinement of the powder mixtures and the removal of the oxide impurities played an important role in the improvement of densification and properties. Moreover, the formation of the liquid phases during the sintering was deemed beneficial for densification. The typical values of relative density, hardness, bending strength, and fracture toughness of the composites reached 99.20%, 32.84?GPa, 858?MPa and 8.21?MPa?m^1/2, respectively. Crack deflection, crack bridging, crack branching, and microcracking were considered to be the potential toughening mechanisms in the composites. Furthermore, numerous nano-sized intergranular/intragranular phases and twin structures were observed in the B₄C-TiB₂-SiC composite.     

The hot compaction behaviour of woven oriented polypropylene fibres and tapes. I. Mechanical properties

The aim of this work was to establish the important parameters that control the hot compaction behaviour of woven oriented polypropylene. Five commercial woven cloths, based on four different polypropylene polymers, were selected so that the perceived important variables could be studied. These include the mechanical properties of the original oriented tapes or fibres, the geometry of the oriented reinforcement (fibres or tapes), the mechanical properties of the base polymer (which are crucially dependant on the molecular weight and morphology), and the weave style. The five cloths were chosen so as to explore the boundaries of these various parameters, i.e. low and high molecular weight: circular or rectangular reinforcement (fibres or tapes): low or high tape initial orientation: coarse or fine weave.A vital aspect of this study was the realisation that hot compacted polypropylene could be envisaged as a composite, comprising an oriented ‘reinforcement’ bound together by a matrix phase, formed by melting and recrystallisation of the original oriented material. We have established the crucial importance of the properties of the melted and recrystallised matrix phase, especially the level of ductility, in controlling the properties of the hot compacted composite.     

深亚微米MOSFET衬底电流的模拟与分析

利用器件模拟手段对深亚微米ＭＯＳＦＥＴ的衬底电流进行了研究和分析，给出了有效的道长度，栅氧厚度，源漏结深，衬底掺杂浓度以及电源电压对深亚微米ＭＯＳＦＥＴ衬底电流的影响，发现电源电压对深亚微米ＭＯＳＦＥＴ的衬底电流有着强烈的影响，热载流子效应随电源电压的降低而迅速减小，当电源电压降低到一定程度时，热载流子效应不再成为影响深亚微米ＭＯＳ电路可靠性的主要问题。     

攀钢1450热轧带钢厂精轧机组电动压下机构带钢压下时的动特性计算和探讨

从理论上和实践上对武钢１７００、鞍钢１７００改造前后、本钢１７００改造前后和攀钢１４５０精轧机组的电动压下机构在带钢压下时的动特性进行计算和探讨，得出有说服力的结论。主题词：     

Effects of hot-carrier stress on high performance polycrystalline silicon thin film transistor with a single perpendicular grain boundary

This paper is a report on the effect of a single perpendicular grain boundary on the hot-carrier and high current stability in high performance polycrystalline silicon (poly-Si) thin film transistors (TFTs). Under a hot carrier stress condition (Vg = Vth + 1 V, Vd = 12 V), the poly-Si TFT with a single grain boundary is superior to the poly-Si without any grain boundary because of the smaller free carriers available for electric conduction. The shift of transconductance in poly-Si TFT with a single grain boundary is less than 5% after hot carrier stress during a period of 1000 s. The shift of transconductance is about 25% in the case of the poly-Si TFTs without a grain boundary in the channel. On high current stress, the poly-Si TFT without the grain boundary is less degraded than the poly-Si TFT with the grain boundary because the concentrated electric field near the drain junction is lower.     

Gleeble 3800热模拟试验机在宝钢的典型应用与功能开发

热模拟试验可研究成分与各工艺参数对组织和性能的影响，用于指导产品设计和实际生产工艺的制定，还有助于建立数学模型。文章介绍了Gleeble 3800热／力模拟试验机在宝钢实际应用中的几个典型试验，包括高温热塑性试验、多道次变形试验、冷轧薄板相转变点试验和HAZ焊接热影响区热模拟试验等。这些试验可用来解决连铸、轧钢和冷轧产品热处理生产中存在的一些问题。     

变形温度和变形程度对Ti－31合金性能和组织的影响

通过高温和室温拉伸试验，研究了变形温度和变形程度对Ｔｉ－３１合金板材性能和组织的影响。结果表明，合金在７５０～８５０℃的温度下变形５％～２０％空冷后，其室温机械性能均能达到材料的技术指标要求。并发现了材料在９００℃的临界变形区。