SiC增强颗粒分布规律对梯度装甲板抗侵彻过程的影响

利用LS-DYNA软件,对SiC颗粒增强铝合金复合材料的增强相体积百分含量沿厚度连续分布的梯度装甲板进行了抗侵彻过程的数值分析。给出了四种SiC体积含量连续分布的梯度板模型抗侵彻过程的数值计算结果,并与钢板材料进行比较。结果表明：改变梯度装甲板增强颗粒的体积含量沿装甲板厚度方向的分布,能极大地提高梯度装甲板的抗弹击性能,大大地降低防护装甲的自身重量。当SiC颗粒平均体积含量一定时,SiC增强颗粒在表面的体积含量越高,抗侵彻性能越好,也就是f0=0.80,参数b＝4时,具有最佳的抗侵彻能力,比同厚度的钢板要好得多。     

碳化硅单晶生长用高纯碳化硅粉体的研究进展

碳化硅(SiC)以其宽带隙、高临界击穿场强、高热导率、高载流子饱和迁移率等优点,被认为是目前较具发展前景的半导体材料之一.近年来,物理气相传输(PVT)法在制备大尺寸、高质量SiC单晶衬底方面取得了重大突破,进一步推动了SiC在高压、高频、高温电子器件领域的应用.SiC粉体是PVT法生长SiC单晶的原料,其纯度会直接影...     

Identification of substitutional and interstitial Fe in 6H-SiC

Iron impurities on interstitial (Fe_i) and substitutional sites (Fe_S) in SiC have been detected by ⁵⁷Fe emission Mössbauer spectroscopy following implantation of radioactive ⁵⁷Mn⁺ parent ions. At temperatures <900 K two Fe_i species are found, assigned to quasi-tetrahedral interstitial sites surrounded by, respectively, four C (Fe_i,C) or Si atoms (Fe_i,Si). Above 900 K, the Fe_i,Si site is proposed to “transform” into the Fe_i,C site by a single Fe_i jump during the lifetime of the Mössbauer state (T _1/2?=?100 ns). Fe_i,C and substitutional Fe_S sites are stable up to >1,070 K.     

Formation of tubular silicon carbide from a carbon–silica material by using a reactive replica technique: infra-red characterisation

Thermal treatment of carbon fibres covered with silica prepared by a sol–gel technique leads to the formation of a tubular silicon carbide material keeping the morphology of the carbon source. The conversion of silica into silicon carbide, its kinetics and the structure of the final material were mainly determined by infra-red (IR) spectroscopy. The analytical results were crossed examined with those obtained by gravimetric and microscopic methods. In particular, it is shown, here, that IR-spectroscopy is a suitable technique to quantitatively determine the amount of SiC formed during the heat treatment of a C/SiO₂ material.     

SiC Schottky结反向特性的研究

对Ti/6H-SiC Schottky结的反向特性进行了测试和理论分析，提出了一种综合的包括SiC Schottky结主要反向漏电流产生机理的反向隧穿电流模型，该模型考虑了Schottky势垒不均匀性、Ti/SiC界面层电压降和镜像力对SiC Schottky结反向特性的影响，模拟结果和测量值的相符说明了以上所考虑因素是引起SiC Schottky结反向漏电流高于常规计算值的主要原因.分析结果表明在一般工作条件下SiC Schottky结的反向特性主要是由场发射和热电子场发射电流决定的.     

Structural and optical characterization of GaN heteroepitaxial films on SiC substrates

We have estimated the threading dislocation density and type via X-ray diffraction and Williamson-Hall analysis to elicit qualitative information directly related to the electrical and optical quality of GaN epitaxial layers grown by PAMBE on 4H- and 6H-SiC substrates. The substrate surface preparation and buffer choice, specifically: Ga flashing for SiC oxide removal, controlled nitridation of SiC, and use of AlN buffer layers all impact the resultant screw dislocation density, but do not significantly influence the edge dislocation density. We show that modification of the substrate surface strongly affects the screw dislocation density, presumably due to impact on nucleation during the initial stages of heteroepitaxy.     

Exciton-polariton state in nanocrystalline SiC films

We studied the features of optical absorption in the films of nanocrystalline SiC (nc-SiC) obtained on the sapphire substrates by the method of direct ion deposition. The optical absorption spectra of the films with a thickness less than ~500 nm contain a maximum which position and intensity depend on the structure and thickness of the nc-SiC films. The most intense peak at 2.36 eV is observed in the nc-SiC film with predominant 3C-SiC polytype structure and a thickness of 392 nm. Proposed is a resonance absorption model based on excitation of exciton polaritons in a microcavity. In the latter, under the conditions of resonance, there occurs strong interaction between photon modes of light with λ_ph=521 nm and exciton of the 3С polytype with an excitation energy of 2.36 eV that results in the formation of polariton. A mismatch of the frequencies of photon modes of the cavity and exciton explains the dependence of the maximum of the optical absorption on the film thickness.     

Study in the oxygen contamination on the surface of C?SiC films

C? SiC films were prepared with an ion‐mixing technology and then introduced with hydrogen by using hydrogen ion irradiation or high‐pressure permeation. It is found that the surfaces of the C? SiC films are always covered by contamination oxygen. XPS was used to analyze the behavior of the contamination oxygen on the surfaces of the C? SiC films before and after hydrogen introduction. The results show that apart from the adsorbed top layer‐containing contaminations like oxygen, carbon, and oxyhydrogen species, the oxygen can react with elements of films and hydrogen. Different carbon–oxygen–hydrogen configurations and C? Si? O or C? Si? OH on the subsurfaces can be formed with different hydrogen introduction methods. Also, the thicknesses of these species‐related oxygen on the subsurface of C? SiC films are estimated in this article. Copyright © 2009 John Wiley & Sons, Ltd.     

Crystal recovery from Al‐implantation induced damaging in 3C‐SiC films

Damaging in Al‐implanted 3C‐SiC and subsequent crystal recovery due to thermal treatments up to 1350 °C are evaluated by X‐ray diffraction and micro‐Raman spectroscopy. Reciprocal space mapping of (004) 3C‐SiC planes shows a low‐intensity implantation‐induced secondary peak at higher interplanar spacing in the as‐implanted 3C‐SiC sample, with a generated misfit between the implanted and the epitaxial region of about 0.6%. Increasing the annealing temperature from 950 °C to 1350 °C, the secondary peak is gradually re‐absorbed within the epitaxial 3C‐SiC reciprocal lattice point. Finally, the disappearance of the secondary peak after a 1350 °C thermal treatment is observed. Thus, implantation‐induced average strain, resulting in a severe 3C‐SiC deforma‐ tion, has been totally relieved at the highest annealing temperature. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Development of core‐shell structure aided by SiC‐coated MWNT in ABS/LCP blend

Agglomeration is an issue of major concern for unmodified multi‐walled carbon nanotubes (MWNTs)‐aided polymeric composites. To overcome the above‐mentioned problem, multi‐walled carbon nanotubes (MWNTs) are modified by polycarbosilane (PCS)‐derived Silicone carbide (SiC). Acrylonitrile Butadiene Styrene (ABS)/Liquid Crystalline polymer (LCP)/MWCNT nanocomposites are prepared through melt blending in a twin screw extruder. X‐Ray Diffraction (XRD) studies authenticate the creation of ß‐SiC particles. Field Emission Scanning Electron Microscopy (FESEM) and Transmission Electron Microscopy (TEM) studies reveal the formation of core–shell morphology involving MWNT as the core and SiC‐coated MWNT as the shell. The degree of dispersion of MWNT is far better when it has been coated with SiC. As viewed from Thermo‐gravimetric analysis (TGA), the thermal stability is substantially increased in SiC‐aided nanocomposite in comparison to ABS/LCP/unmodified CNT blend. Glass transition temperature as well as mechanical properties are improved significantly (in the presence of SiC‐coated MWNT) as a result of homogeneous dispersion exhibited by MWNT. Copyright © 2009 John Wiley & Sons, Ltd.