碳化硅压腔和高压下的中子衍射

使用宝石级碳化硅晶体作为压砧材料,成功研制出了碳化硅压腔（MAC）,并应用全景式MAC进行了高压下物质的中子衍射实验研究.结果表明,MAC是一种既能产生高的压力又具有大的高压样品室的装置,特别适合于高压下的中子衍射研究.     

碳化硅压腔和高压下的中子衍射

使用宝石级碳化硅晶体作为压砧材料，成功研制出了碳化硅压腔（MAC），并应用全景式MAC进行了高压下物质的中子衍射实验研究。结果表明，MAC是一种既能产生高的压力又具有大的高压样品室的装置，特别适合于高压下的中子衍射研究。     

大口径轻质SiC反射镜的研究与应用

介绍了大口径轻质碳化硅反射镜镜坯的基本结构、性能测试指标、国内应用及发展前景;阐述了碳化硅凝胶注模成型（Gel-casting）、反应烧结SiC（RB-SiC）与压力成型、常压烧结SiC（SSiC）两种国内主要制备大口径轻质碳化硅反射镜的方法;并对两种方法制备得到的ø1.45 m碳化硅镜坯的性能、测试数据及光学加工后的光学特性进行分析和比对,提出存在的问题,以供商榷,进而促进国内大口径轻质碳化硅反射镜的研究和发展。     

表面改性碳化硅基底反射镜加工技术现状

针对表面改性SiC基底反射镜在空间光学系统中的应用,总结了该类反射镜在国内外的研究现状。概括了碳化硅基底反射镜的发展趋势。介绍了常用的碳化硅材料,分析了它们的性质。给出了几种常用的碳化硅镜坯制备工艺,包括成型、改性和不同的抛光技术。通过对国内现有加工工艺和改性技术的分析,总结出了适应我国的表面改性碳化硅反射镜加工的发展方向。     

大口径碳化硅轻质反射镜镜坯制造技术的研究进展

比较了目前空间遥感相机中常用的四种反射镜镜体材料——ULE,Zerodur,铍(Be)和碳化硅(Sic)的各项性能。结果表明:SiC陶瓷具备比较明显的综合优势,是制备空间用反射镜的最佳候选材料。阐述了碳化硅反射镜镜坯的四种制备工艺。介绍了当前国内外碳化硅质轻型反射镜镜坯的发展情况。     

锯齿型与扶手椅型碳化硅纳米管光电性质第一性原理研究

本文基于密度泛函理论计算分析了手性参数为(17,0)、(20,0)、(26,0) (10,10)、(12,12)、(15,15)的碳化硅纳米管的能带图,态密度及主要光学性质。结果表明：锯齿型与扶手椅型碳化硅纳米管均具有明显的半导体性质;在相近直径下,扶手椅型碳化硅纳米管带隙宽度要大于锯齿型碳化硅纳米管的带隙宽度;碳化硅纳米管的光吸收峰在100nm~200nm之间,可用于制作紫外线探测器件。     

界面态电荷对6H碳化硅N沟MOSFET阈值电压和跨导的影响

针对界面态密度在禁带中的不均匀分布,并且考虑到碳化硅材料中杂质的不完全离化,分析了界面态电荷对N沟6H碳化硅MOSFET阈值电压和跨导的影响.结果显示界面态密度的不均匀分布不仅使阈值电压增大,而且还会导致器件跨导变低,它是影响SiCMOSFET特性的一个重要因素 关键词： 碳化硅 界面态 阈值电压 跨导     

新型NO2化学传感器:碳化硅纳米管

气体吸附对碳化硅纳米管的电子结构的影响是理解碳化硅纳米管气敏传感器工作机理的基础.基于密度泛函理论,利用CASTEP软件包计算NO₂气体吸附前后的碳化硅纳米管的结构及其电子结构.结果表明,NO₂气体与碳化硅纳米管间形成了稳定的吸附,并明显的增强了碳化硅纳米管的导电特性.碳化硅纳米管是制备气体传感器的理想材料之一,为开发应用于NO₂气体检测的碳化硅纳米管提供必要的理论支持.     

极端条件下碳化硅的变形、损伤与破坏研究进展

碳化硅作为重要的陶瓷和半导体材料,在国防军工、航空航天等应用领域和高压物质科学等方面具有重要的应用研究和科学价值。本文对动加载下碳化硅的变形、损伤和破坏等物理力学行为和特性研究进行了梳理,分别从实验研究和计算模拟角度概述了碳化硅在不同加载条件和微结构下的变形与破坏行为研究进展,总结归纳了碳化硅材料动态响应相关研究的若干现存问题,并展望了该领域内几个重要的发展方向,以期为相关群体的研究工作提供有益参考。     

非球面碳化硅反射镜的加工与检测

为了获得高精度非球面碳化硅(SiC)反射镜,对非球面碳化硅反射镜基底以及改性后碳化硅反射镜表面的加工与检测技术进行了研究。介绍了非球面计算机控制光学表面成型（CCOS）技术及FSGJ-2非球面数控加工设备。采用轮廓检测法和零位补偿干涉检测法分别对碳化硅反射镜研磨和抛光阶段的面形精度进行了检测,并采用零位补偿干涉检测法及表面粗糙度测量仪对最终加工完毕的碳化硅反射镜的面形精度和表面粗糙度进行检测。测量结果表明：各项技术指标均满足设计要求,其中非球面碳化硅(SiC)反射镜实际使用口径内的面形精度（RMS值）为0.016λ(λ=0.6328μm）,表面粗糙度（RMS值）为0.85nm。     

碳硅石压腔在高温高压拉曼光谱研究中的应用

描述了碳硅石压腔的结构和特点。碳硅石压腔主要包括碳硅石压砧、支撑加压系统、加热系统和金属垫片等部分。合成碳硅石的硬度高、热导性好、膨胀系数小、热稳定性好,并且它的晶体颗粒大,透明度好,价格也很便宜,因此是一种很好的压砧材料。还介绍了应用碳硅石压腔对Na₂CO₃溶液、Na₂SO₄溶液、水的拉曼光谱进行高温高压原位测量的实例。     

An opposed-anvil-type apparatus with an optical window and a wide-angle aperture for neutron diffraction

We designed new anvil assemblies for acquiring high-quality neutron diffraction data and ruby fluorescence spectra inside a sample chamber. The conical aperture of Ni-binded WC anvils was expanded by a factor of two. A hybrid gasket made of TiZr- and Al-alloy was developed to prevent outward extrusion. A small and optically transparent window of moissanite was introduced to allow for the determination of pressure and hydrostaticity by measurement of ruby fluorescence spectra. High pressure-generation tests that make use of Bi electrical conductivity and ruby pressure markers revealed that pressure could be determined over 10 GPa. In situ synchrotron X-ray diffraction experiments were also carried out using NaCl as the pressure calibrants. The maximum pressure achieved was approximately 13 GPa. The neutron diffraction intensity from the newly generated anvil assemblies was 2.5–3.0 times greater than that using the standard toroidal anvil assemblies used previously.     

Powder neutron diffraction of wüstite (Fe0.93O) to 12 GPa using large moissanite anvils

High-pressure powder neutron diffraction of wüstite-Fe_0.93O has been achieved to 12 GPa using a large gem-moissanite (SiC) anvil cell. The moissanite anvils are weakly absorbing and provide greater neutron fluxes to the sample than is possible with tungsten carbide anvils. There is minimal diffraction overlap from the single-crystal moissanite anvils compared to tungsten carbide or synthetic diamond anvils, providing cleaner background profiles. The required sample volume for high-pressure neutron diffraction is dramatically reduced to several cubic millimeters. High-quality powder diffraction patterns of wüstite were recorded at 90 min exposure times on the HIPPO diffractometer at LANSCE when the sample volume was in the range of ～10 mm³. This is about two orders of magnitude smaller than the necessary sample volume (～1.0 cm³) for the same kind of experiment with other high-pressure cells and nominal neutron fluxes.     

Raman Spectroscopic Studies of Pressure-Induced Phase Transitions on 1-Dodecene

Raman spectroscopic features of 1-dodecene are studied in a moissanite anvil cell up to 3.0 GPa at 21℃. Our data indicate that 1-dodecene is chemically stable under the experimental condition because no new Raman peaks can be observed. However, two significant discontinuities in the plots of Raman shift versus pressure indicate two phase transitions of 1-dodecene. One is liquid~olid transition at pressure of about 500 MPa, the other is solid-solid phase transition at pressure from 1300 to 1550 MPa. The latter is considered to be related to the orientational change of the plane structure of ethylene. A rudimentary phase diagrams for 1-dodecene, n-pentane, n-hexane are proposed based on the results and previous data.     

Raman Scattering Spectroscopy of Phase Transition in n-Pentadecane under High Temperature and High Pressure

The Raman spectroscopy of n-pentadecane is investigated in a moissanite anvil cell at normal temperatures and a diamond anvil cell under pressure to about 3000MPa and at temperature from 298 to 573K. Result indicates that at room temperature the vibration modes, assigned to the symmetric and asymmetric stretching of CH3 and CH2 stretching, shift to higher frequency and display a pressure dependent quasi-linear curve. A liquid-solid phase transition appears at a pressure of 150 MPa. The high temperature solidus line of n-pentadecane follows a quadratic function of P = 0.02369T^2 - 9.117T ＋ 725.58, in agreement with previous conclusion derived from studies of other hydrocarbons. Upon phase transition, fitting the experimental data obtained in a temperature range of 283 553 K to the Clausius-Clapeyron equation allows one to define the thermodynamic parameters of n-pentadecane of dP/dT = 0.04738T - 9.117.     

3D Raman mapping of uniaxially loaded 6H‐SiC crystals

Raman spectroscopy is used to investigate the three‐dimensional stress distribution in 6H‐silicon carbide (SiC) specimens subjected to stresses up to 3.7 GPa along the c‐axis. Specifically, the relative Raman shift of the longitudinal optic phonon of 6H‐SiC is used to evaluate the local stress across the bulk crystal. For this purpose, an anvil device with opposed 6H‐SiC and sapphire specimens was used. After subjecting the anvils to uniaxial load, several series of two‐dimensional Raman maps were registered at different depths in the 6H‐SiC anvil. The analysis of the Raman spectra reveals an exponential decay of the stress as a function of the depth. A novel phenomenological Grüneisen‐like model is introduced here to account for such observation. On the contrary, the in‐plane stress analysis shows a radial Gaussian‐like distribution regardless the depth, a distinct behavior that is attributed to the appearance of shear stress components. The suitability of both models and their applicability to other materials are discussed, along with some future directions. Copyright © 2013 John Wiley & Sons, Ltd.     

Raman spectra of aragonite at the pressure of 0.1-2 GPa and ambient temperature

Raman spectra of aragonite were studied at ambient temperature and pressure of 0.1 - 2 GPa in a moissanite anvil cell using Raman spectrum technique. The relations between the Raman shifts of aragonite and the system pressure are given as follows: v153 (cm(-1)) = 0.003 5p (MPa) +154.0, v206 = 0.006 0p + 206.3, v704 = 0.002 1p + 704.2, v1085 = 0.003 5p + 1 085.3. No phase transition occurred in aragonite within the range of experimental pressure. Similar to other carbonate minerals (magnesite, dolomite), the measured relative pressure-shift of the Raman line of the symmetric stretching vibration of aragonite is greater at 0.1-2 GPa than at ultrahigh pressure, which indicates that the C-O bond compressibility of the CO3 groups is related to the pressure, and it is more compressible at 0.1 - 2 GPa than at higher pressure.     

常温及常压至1.2GPa条件下异辛烷的拉曼光谱研究

利用碳化硅压腔在室温(25℃)下,研究了异辛烷(2,2,4-三甲基戊烷)在常压至1.2GPa条件下的拉曼光谱特征。研究结果表明,异辛烷CH2和CH3的碳氢伸缩振动的拉曼位移随着压力的增大均呈线性向高频方向移动,其拉曼位移与压力的函数关系为:ν2 873=0.002 8P+2 873.3;ν2 905=0.004 8P+2 905.4;ν2 935=0.002 7P+2 935.0;ν2 960=0.012P+2 960.9。在1.0GPa附近,异辛烷的拉曼位移出现突变,与显微镜下观察发生的异辛烷液-固相变一致。结合异辛烷在常压下的熔点数据,获得了异辛烷的液-固两相相图,并根据克拉贝龙方程获得了液-固相转变过程中的摩尔体积变化量ΔVm=4.46×10-6 m3.mol-1和熵变ΔS=-30.32J.K-1.mol-1。