空间遥感器高体份SiC/Al复合材料反射镜组件设计

为消除反射镜与支撑结构材料线胀系数差异产生的热变形对反射镜面形精度、系统成像质量的影响, 采用高体份SiC/Al复合材料作为新型反射镜组件的材料。首先, 通过合理的结构设计及有限元分析比较, 确定了Ф600 mm口径反射镜结构参数, 然后, 对反射镜组件进行了静力学和动力学分析, 在1 g重力载荷作用下, 反射镜X、Y、Z方向去除刚体位移后的镜面变形RMS值分别为12.6, 12.7, 12.6 nm, 达到了λ/50(λ=632.8 nm)。最后, 为了验证高体份SiC/Al复合材料反射镜组件的结构性能及检验结构在振动条件下的抗干扰能力, 对反射镜组件进行了力学试验, 反射镜组件的一阶谐振频率为556.6 Hz。力学试验前后, 反射镜镜面面形误差RMS分别为0.021λ、0.025λ, 没有明显变化。实验结果表明:高体份SiC/Al复合材料反射镜达到了与SiC材料反射镜相同的设计指标要求, 能够满足空间应用。     

Characterization of a SiC/SiC composite by X-ray diffraction, atomic force microscopy and positron spectroscopies

A SiC/SiC composite is characterized by X-ray diffraction, atomic force microscopy and various positron spectroscopies (slow positron implantation, positron lifetime and re-emission). It is found that besides its main constituent 3C-SiC the composite still must contain some graphite. In order to better interpret the experimental findings of the composite, a pyrolytic graphite sample was also investigated by slow positron implantation and positron lifetime spectroscopies. In addition, theoretical calculations of positron properties of graphite are presented.     

Synthesis of SiC/graphene nanosheet composites by helicon wave plasma

We report an approach to the rapid, one-step, preparation of a variety of wide-bandgap silicon carbide/graphene nanosheet(Si C/GNSs) composites by using a high-density helicon wave plasma(HWP) source. The microstructure and morphology of the Si C/GNSs are characterized by using scanning electron microscopy(SEM), Raman spectroscopy, x-ray diffraction(XRD), x-ray photoelectron spectroscopy(XPS), and fluorescence(PL). The nucleation mechanism and the growth model are discussed. The existence of Si C and graphene structure are confirmed by XRD and Raman spectra.The electron excitation temperature is calculated by the intensity ratio method of optical emission spectroscopy. The main peak in the PL test is observed at 420 nm, with a corresponding bandgap of 2.95 e V that indicates the potential for broad application in blue light emission and ultraviolet light emission, field electron emission, and display devices.     

基于低体分SiC/Al主镜框的空间相机主支撑结构热特性分析与验证

基于微小卫星平台对高分辨相机的重量约束,以高分微纳卫星CX6-02数字超分辨相机研制为例,提出一种基于低体分SiC/Al主镜框的空间相机主支撑的结构形式,并开展主镜框一体拓扑优化设计分析和试验验证.Zernike多项式计算及光机热集成仿真结果验证了低体分SiC/Al主镜框作为空间相机主支撑结构的有效性.热光试验数据及在...     

碱溶ICP—AES法同时测定AISi／SiC复合材料中的高含量硅和低含量？…

本文采用碱溶ＩＣＰ－ＡＥＳ法对ＡＩＳｉ／ＳｉＣ复合材料中的高含量硅和低含量镁、钛、铁的测定进行研究,着重进行基体元素铝及特测定元素硅、镁、钛、铁之间的干扰试验,进行了碱度试验和酸度试验,测定和ＡＩＳｉ／ＳｉＣ复合材料中的硅、镁、钛、铁含量,得到了较好的精密度和准确度。方法简便可靠,可获得满意的分析结果。     

Formation of atomically smooth SiO2/SiC interfaces at ∼120 °C by use of nitric acid oxidation method

Conventional thermal oxidation of SiC requires heating at ∼1100 °C. In the present study, we have developed a method of oxidizing SiC at low temperatures (i.e., ∼120 °C) to form relatively thick silicon dioxide (SiO₂) layers by use of nitric acid. When 4H-SiC(0 0 0 1) wafers are immersed in 40 wt% HNO₃ at the boiling temperature of 108 °C and the boiling is kept for 5 h after reaching the azeotropic point (i.e., 68 wt% HNO₃ at 121 °C), 8.1 nm thick SiO₂ layers are formed on the SiC substrates. High resolution transmission electron microscopy measurements show that the SiO₂/SiC interface is atomically flat and the SiO₂ layer is uniform without bunching. When SiC is immersed in an azeotropic mixture of HNO₃ with water from the first, the SiO₂ thickness is less than 0.3 nm. The metal-oxide-semiconductor (MOS) diodes with the SiO₂ layer formed by the nitric acid oxidation method possess a considerably low leakage current density.     

Properties and characteristics of P(VDF/TrFE) transducers manufactured by a solution casting method for use in the MHz-range ultrasound in air

Highly effective piezoelectric polymer transducers operating in air at high frequencies have been successfully made by casting a solution of ferroelectric poly(vinylidene fluoride-co-trifluoroethylene) P(VDF/TrFE) directly on a backing metal plate, and their performance has been evaluated. By utilizing this method, it has been possible to develop the three kinds of transducers that operate respectively at 4, 6 and 10 MHz in air. For precise evaluation of the performance of the P(VDF/TrFE) transducers, the absorption loss in air was measured up to 10 MHz. It was confirmed that the empirical formula obtained from the measured absorption values in air at high frequencies was in alignment with its theoretical value. In addition, a high lateral resolution acoustic image of a ROM-Chip (amplitude-image) at 6 MHz in air was successfully displayed using an air coupled concave type P(VDF/TrFE) transducer by bonding an epoxy adhesive.