SiCw/6061 Al复合材料中界面相的研究

利用电子显微镜分析研究了ＳｉＣ２／６０６１Ａｌ复合材料的界面相。电子衍射分析表明，ＳｉＣｗ／６０６１Ａｌ面相 体心立方结构，点阵常数为１．２８ｎｍ用Ｘ－射线能谱仪测定了界面相的化学成分。     

Dehydration of sodium carbonate monohydrate with indirect microwave heating

In this study, dehydration of sodium carbonate monohydrate (Na₂CO₃·H₂O) (SCM) in microwave (MW) field with silicon carbide (SiC) as an indirect heating medium was investigated. SCM samples containing up to 3% free moisture were placed in the microwave oven. The heating experiments showed that SCM is a poor microwave energy absorber for up to 6 min of irradiation at an 800 W of microwave power. The heat for SCM calcination is provided by SiC which absorbs microwave. The monohydrate is then converted to anhydrous sodium carbonate on the SiC plate by calcining, i.e. by removing the crystal water through heating of the monohydrate temperatures of over 120 °C. The calcination results in a solid phase recrystallization of the monohydrate into anhydrate. In the microwave irradiation process, dehydration of SCM in terms of indirect heating can be accelerated by increasing the microwave field power.     

SiC纤维的化学气相生长与表征

以一甲基三氯硅烷为气源化合物, 二茂铁为催化剂, 噻吩为催化助剂, 用化学气相生长法直接制备SiC纤维. 研究了裂解温度、催化剂及助剂浓度及H2与MTS的配比等因素对裂解产物形态的影响. 分别采用SEM, EDX和XRD对产物的组成和形貌进行了表征. 结果表明, 产物由单一的β-SiC组成. 通过改变反应条件, 无需高、低压气氛及激光辅助, 即可以获得直径为20 nm~1.5 μm、长度从10 μm至数毫米的高长径比SiC纤维.     

碳化硅耐火材料浸渍AlPO_4溶液对材料晶相结构与性能影响

浸渍AlPO4饱和溶液有利于SiC耐火材料晶相结构的转化,有利于材料性能的优化。AlPO4是SiC的低温稳定-型向高温稳定-型转化的适宜矿化剂,浸渍2次可将-型全部转化成-型。材料性能随浸渍次数的增加而优化,浸渍4次的抗折强度、热震抗折强度保持率和体积密度为最高,而吸水率和显气孔率较低。     

液相烧结碳化硅晶界内氮化反应的研究

碳化硅 ( Si C)由于其高度的共价键结合特性而具有高硬度、耐磨性和高化学稳定性等优异性能而成为热机、高温环境和化学化工等领域的研究应用对象 .碳化硅材料的无压烧结最早是由 Prochazka[1] 实现的 .2 0世纪 80年代初期 ,Omori[2 ] 通过采用氧化物 ( Al2 O3,Y2 O3和稀土氧化物等 )添加剂的手段大大降低了无压烧结的温度 .这些氧化物具有较低的共熔点 ,在高温下易形成液相 ,从而促进了碳化硅的晶粒重排和晶体生长 .2 0世纪 90年代以来 ,氮化物和氧化物的混合添加剂 (如 Al N- Y2 O3) [3]被广泛应用于碳化硅的液相烧结 .这是因为氮在…     

Natural rubber nanocomposites with SiC nanoparticles and carbon nanotubes

Single-walled carbon nanotubes (SWNTs) and SiC nanoparticles were dispersed in natural rubber (NR) polymer solution and subsequently evaporated the solvent to prepare NR nanocomposites. Using this technique, nanoparticles can be better dispersed in the NR matrix. The influence of nano-fillers on the mechanical properties of the resulting nanocomposites was quantified.Mechanical test results show an increase in the initial modulus with nanoscale reinforcements for up to 50% strain compared to pure NR. The modulus and strength of natural rubber with 1.5% SiC nanoparticles appear to be superior to those of SWNTs with the same filler content. In addition to mechanical testing, these nanocomposites were studied using the SEM and Raman spectroscopy techniques in order to understand the morphology of the resulting system and the load transfer mechanism, respectively. The Raman spectrum of the SWNT/NR system is characterized by a strong band at 1595 cm⁻¹ (G mode—C-C stretching) and other two bands at 1300 cm⁻¹ (D mode-disorder induced) and 2590 cm⁻¹ (D* band). A shift of the 2590 cm⁻¹ Raman band to the lower wavenumber was observed after subjecting SWNT/NR sample to cyclic stress testing. Ageing SWNT/NR specimen in distilled water for 30 days also provided a similar result. The Raman shift in aged samples indicates internal stress transfer from the natural rubber matrix to the SWNTs implying the existence of bonding at the interface.     

Ozone oxidation of 4H-SiC and flat-band voltage stability of SiC MOS capacitors

We investigate the effect of ozone (O₃) oxidation of silicon carbide (SiC) on the flat-band voltage (V_fb) stability of SiC metal-oxide-semiconductor (MOS) capacitors. The SiC MOS capacitors are produced by O₃ oxidation, and their V_fb stability under frequency variation, temperature variation, and bias temperature stress are evaluated. Secondary ion mass spectroscopy (SIMS), atomic force microscopy (AFM), and x-ray photoelectron spectroscopy (XPS) indicate that O₃ oxidation can adjust the element distribution near SiC/SiO₂ interface, improve SiC/SiO₂ interface morphology, and inhibit the formation of near-interface defects, respectively. In addition, we elaborate the underlying mechanism through which O₃ oxidation improves the V_fb stability of SiC MOS capacitors by using the measurement results and O₃ oxidation kinetics.     

Characterization of laser‐treated Rene 41 surface due to B4C and SiC particles at surface prior to laser treatment

Laser surface treatment of Rene 41 high‐performance alloy is carried out with the presence of hard particles at the surface. B₄C and SiC particles are uniformly distributed within 40 µm carbon film at the workpiece surface prior to laser treatment process. The effect of hard particles on residual stress and microhardness variations is investigated at the treated surface. Morphological and metallurgical changes in the treated layer are examined by using electron microscopy, energy dispersive spectroscopy, and X‐ray diffraction. Residual stress formed at the surface is determined from the X‐ray data. It is found that the treated surface is free from asperities such as large size voids and cracks. A dense layer is formed in the surface region, which causes volume shrinkage while contributing to microhardness and residual stress enhancement at the surface. B₄C hard particles result in the highest residual stress and microhardness at the surface, which is attributed to its high thermal expansion coefficient. Copyright © 2013 John Wiley & Sons, Ltd.     

Photoluminescence in SiCGe thin films grown on 6H-SiC

Intense visible luminescence is observed at room temperature from SiCGe films on 6H-SiC (0 0 0 1) substrate. The PL intensity increases rapidly under the UV laser excitation during the first 2 h. This phenomenon may be explained by an effect similar to the Steabler-Wronski effect in hydrogenated amorphous Silicon. High density of defects such as double phase boundaries and stacking faults are observed by TEM characterization, which produce the quasidefects and accelerate the effect.     

纳米SiC基光催化剂研究进展

工业化无疑促进了经济的发展,提高了生活水平,但也导致了一些问题,包括能源危机、环境污染、全球变暖等, 其中这些所产生问题主要是由燃烧煤炭、石油和天然气等化石燃料引起的。光催化技术具有利用太阳能将二氧化碳转化为碳氢化合物燃料、从水中制氢、降解污染物等优点,从而在解决能源危机的同时避免环境污染,因此被认为是解决这些问题的最有潜力的技术之一。在各种光催化剂中,碳化硅(SiC)由于其优良的电学性能和光电化学性质,在光催化、光电催化、电催化等领域具有广阔的应用前景。本文首先系统地阐述了各种SiC的合成方法,具体包括模板生长法、溶胶凝胶法、有机前驱物热解法、溶剂热合成法、电弧放电法,碳热还原法和静电纺丝等方法。然后详细地总结了提升SiC光催化活性的各种改性策略,如元素掺杂、构建Z型(S型)体系、负载助催化剂、可见光敏化、构建半导体异质结、负载炭材料、构建纳米结构等。最后重点论述了半导体的光催化机理以及SiC复合物在光催化产氢、污染物降解和CO₂还原等领域的应用研究进展,并提出了前景展望。