Stacking faults in semi‐polar 6H‐SiC single crystals

6H‐SiC single crystals have been successfully grown on (1015) plane seed by sublimation method. High density stacking faults (SFs) were observed by transmission synchrotron radiation X‐ray topography. Based on the invisibility criteria of stacking faults, the displacement vectors of most SFs were determined to be the type of 1/6[1120]. Laser scanning confocal microscopy (LSCM) was used to observe the etching morphology of (0115) wafer. The etching steps of SFs were found and their density decreased from 3.6×10³ cm^‐1 to 2.0×10² cm^‐1 along the <0001> projection direction. The inclination angles of the SFs etching step plane to (10‐15) plane were measured by line scanning of LSCM. It was found that the inclination angles decreased from 20° to 10° along the <0001> projection direction. Different etching characteristics of SFs along radial direction of 6H‐SiC (1015) wafer should be attributed to different displacement vectors and different stacking fault energies for these stacking faults. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

碳化硅颗粒增强铝合金复合材料在不同条件下的磨损行为

动载磨损是工程应用的一种常见现象，然而已有的试验研究大都是以平稳加方式进行的，这样得到的磨损规律显然与实际工况下的不符。因此，利用滑动磨损和喷砂冲员两种不同的试验方法，对ＳｉＣ颗粒增强２０２４Ａｌ复合材料的磨损行为进行了试验研究。     

具有碳化硅纳米线编织结构的氧化铝泡沫陶瓷的制备及性能研究

本文利用简单、高效的浆料直接发泡法制备气孔率高达96%的Al₂O₃/Si泡沫陶瓷,并选用简便、易行的焦炭埋烧工艺在Al₂O₃/Si泡沫陶瓷坯体中生长出大量SiC纳米线。通过控制烧结温度来观察分析SiC纳米线的生长形貌变化。采用扫描电子显微镜(SEM)、X射线衍射仪、BET比表面积测试仪、电子万能试验机等对泡沫陶瓷的微观结构、物相组成、比表面积、气孔率、抗压强度、热导率进行分析与表征。结果表明,1 450 ℃烧结时得到的SiC纳米线最多,纳米线在泡沫陶瓷孔壁交织缠绕。同时观察到SiC纳米线的存在改变了氧化铝泡沫陶瓷固有的脆性断裂模式,SiC纳米线可有效促进泡沫陶瓷在压缩过程中的裂纹偏转。本实验制备了一种新型的纳米线缠绕在孔壁上的三维网络结构的泡沫陶瓷,为在泡沫陶瓷内部原位生长SiC纳米线提供了新的方法,更好地拓展了泡沫陶瓷在环境过滤、催化剂载体等领域中的应用。     

碳化物衍生碳涂层/氮化硅摩擦副在水润滑下的摩擦学性能

基于SiC陶瓷在水润滑条件下可能出现因摩擦界面无水或过载引起的失效问题,考察了SiC陶瓷、碳化物衍生碳(CDC)涂层在干摩擦和水润滑条件下的摩擦磨损性能.研究结果表明:CDC涂层在干摩擦和水润滑条件下均具有优异的摩擦学性能,可在摩擦界面无水或过载下正常工作;在水润滑条件下,CDC涂层在宽的载荷和滑动速度下具有优异的摩擦学性能.从微结构角度分析比较了CDC涂层与商品石墨的差异,并由此讨论了其摩擦学性能的差异.讨论了加工SiC陶瓷引起的表面织构对CDC涂层在水润滑条件下摩擦学性能的影响机制.     

Al/Ti/4H-SiC Schottky barrier diodes with inhomogeneous barrier heights

This paper investigates the current-voltage (I-V) characteristics of Al/Ti/4H-SiC Schottky barrier diodes (SBDs) in the temperature range of 77 K-500 K,which shows that Al/Ti/4H-SiC SBDs have good rectifying behaviour.An abnormal behaviour,in which the zero bias barrier height decreases while the ideality factor increases with decreasing temperature (T),has been successfully interpreted by using thermionic emission theory with Gaussian distribution of the barrier heights due to the inhomogeneous barrier height at the Al/Ti/4H-SiC interface.The effective Richardson constant A =154 A/cm 2 · K 2 is determined by means of a modified Richardson plot ln(I 0 /T 2)-(qσ) 2 /2(kT) 2 versus q/kT,which is very close to the theoretical value 146 A/cm 2 · K 2.     

Study of deposition patterns of plating layers in SiC/Cu composites by electro-brush plating

SiC reinforced copper composite coatings were prepared by electro-brush plating with micron-size silicon carbide (SiC) ranging from 1 to 5 μm on pure copper sheet in this paper. The micro-structural characterizations of SiC/Cu composite coatings were performed by optical microscope and Scanning Electron Microscope (SEM) coupled with spectrometer, to study co-deposition mechanism of SiC/Cu. It was found that there were three different patterns of SiC deposition in plating layers during electro-brush plating process, i.e. the particles could deposit inside copper grains, in grain boundaries, or in holes of the surface. To investigate deposition mechanism of each pattern, size of SiC and copper grains was compared. By comparison of size of copper grains and hard particles, SiC were either wrapped in copper grains or deposited in grain boundaries. Moreover, electro-brush plating layers at different brush velocities and current densities were obtained respectively, to analyze the microstructure evolution of the composite coatings. The hardness of plating layers was measured. The results indicated at the current density of 3 A/dm², the SiC/Cu coating was compact with SiC content at a high level and the hardness reached a maximum.     

Effect of Polyvinylpyrrolidone on Rheology of Aqueous SiC Suspensions Stabilized with Polyacrylic Acid

The effect of polyvinylpyrrolidone (PVP) on rheology of aqueous SiC suspensions stabilized with polyacrylic acid (PAA) was investigated. At pH 6.0, as the total amount of dispersants was fixed at 0.3 wt%, the suspensions with co-addition of PAA and PVP obtained much lower viscosity than those added separately, displaying Newtonian behavior. The improvement in rheology of SiC suspensions arose from enhanced steric hindrance, which was caused by the presence of PVP molecules in association with PAA molecules adsorbed on SiC particle surfaces. However, this effect was relatively weak in alkaline condition because of complete dissociation of PAA.     

SiC单层内Co空间选位对自旋组态的调控

基于第一性原理的密度泛函理论,对SiC单层不同位置掺杂Co进行了能带结构、电子态密度、净自旋密度和自旋纹理等计算,结果表明不同位置的掺杂引起不同特征的自旋积累及单层的电子结构特性。由于Co的不同选位掺杂而产生一些新奇现象,如扭曲的Co-C键在掺杂SiC内激发了自旋流而诱导了自旋重新分布,不同选位的Co原子通过调整内磁场改变了小极化子内巡游电子的定域属性,增加了Dirac点附近磁振子的色散强度等。这些研究结果为得到一个人工调控量子自旋电路和选频自旋波器件内自旋谷电子提供了理想平台。