硫化锌窗口上CVD法制备金刚石膜的研究进展

金刚石具有优异的红外透过性能,可作为硫化锌红外窗口的保护膜。但由于CVD金刚石的沉积过程会刻蚀硫化锌衬底,导致在窗口表面直接生长金刚石膜比较困难。本文主要综述了近年来通过添加过渡层沉积金刚石薄膜的方法和光学焊接金刚石厚膜的方法来增强硫化锌窗口的性能,并介绍了CVD金刚石膜的光学应用及其目前所存在的问题,最后对未来CVD金刚石膜发展的方向作出了展望。     

CVD金刚石的高温氧化及其保护

化学气相沉积(CVD)金刚石具有优异的机械、光学和热学性能,成为高速长波红外窗口的首选材料,但是当高速飞行时,由于空气动力加热会产生很高的温度而使其迅速遭受氧化,甚至完全失效.简要概述了CVD金刚石高温氧化现象及机理、抗氧化保护的最新研究进展.     

MPCVD法合成单晶金刚石的研究及应用进展

单晶金刚石因其优异的物理化学性质,使其成为高新技术领域最有潜力的材料之一。本文首先对CVD(化学气相沉积)法制备单晶金刚石进行了简介,然后对MPCVD(微波等离子体化学气相沉积)制备单晶金刚石过程中衬底选择、预处理、沉积参数等进行了详细评述,最后对MPCVD单晶金刚石在超精密加工、光学领域、粒子探测器、高温半导体及电子器件等方面的应用进行了介绍,并对未来单晶金刚石的发展作出了展望。     

甲烷浓度对金刚石薄膜质量的影响

纳米金刚石薄膜具有优异的性能,已在多个领域获得广泛应用.但微波等离子体化学气相沉积制备的金刚石薄膜质量却严重受沉积工艺的影响,为了深入了解沉积工艺对制备的金刚石薄膜质量的影响,本文详细研究了甲烷浓度对微波等离子体化学气相沉积( MPCVD)金刚石薄膜质量的影响,利用扫描电镜、X射线衍射、拉曼光谱以及原子力显微镜对其进行...     

超纳米金刚石薄膜及其在MEMS上的应用研究进展

硅基MEMS器件最主要的问题是硅具有低的机械和摩擦性能,限制了其在弯折和运动MEMS器件中的应用.超纳米金刚石薄膜优异的机械、化学惰性、热稳定性、摩擦磨损性能使其成为能长期可靠运行的理想MEMS元件材料.阐述了微波化学气相沉积和Ar、CH4为主的超纳米金刚石薄膜的制备及其机理,综述了超纳米金刚石薄膜与MEMS相关性能及在微摩擦磨损、残余应力方面的研究现状,介绍了超纳米金刚石薄膜覆形沉积、选择性生长和光刻图形化等微加工技术及其在MEMS上的应用研究进展.     

金刚石自支撑膜的高温红外透过性能

由于金刚石具有低吸收和优异的力学与导热性能使其成为长波(8~12μm)红外光学窗口材料的重要选择。对于许多极端条件的应用,化学气相沉积(CVD)金刚石自支撑膜的高温光学性质至关重要。应用直流电弧等离子喷射法制备光学级金刚石自支撑膜进行变化温度的红外光学透过性能研究,采用光学显微镜、X射线衍射、激光拉曼和傅里叶变换红外-拉曼光谱仪检测CVD金刚石膜的表面形貌、结构特征和红外光学性能。结果表明:在27℃时金刚石膜长波红外8~12μm之间的平均透过率达到65.95%,在500℃时8~12μm处的平均透过率为52.5%。透过率下降可分为3个阶段。对应于透过率随温度的下降,金刚石膜的吸收系数随温度的升高而增加。金刚石自支撑膜表面状态的变化,对金刚石膜光学性能的影响显著大于内部结构的影响。     

类金刚石膜的应用及制备

类金刚石膜（DLC）是由无定形碳和金刚石相混合组成的碳材料，由于具有与金刚石膜（DF）相类似的性能－优异的机械特性、电学特性、光学特性、热学和化学特性以及生物相溶性，同时制备方法相对容易实现，因此引起人们极大兴趣，现在已经应用到很多领域。本文将简要介绍类金刚石膜的性能、应用以及制备方法。     

金刚石-硫化锌复合窗口的弹性应变研究

对于金刚石－硫化锌复合红外光学窗口，结构中存在的热应力和挠曲度的大小对其可靠性有很大的影响。利用弹性应变模型研究了在光学焊接中不同粘接温度和金刚石厚度下金刚石－硫化锌复合窗口将发生的最大应力、曲率和衬底到边缘的挠曲率。计算结果表明，当膜厚在极值附近时，复合结构明显弯曲、ZnS表面的应力极大；如何粘接温度较高，复合结构将严重变形，ZnS中所受的应力可能会超过其自身的断裂强度。当对金刚石－硫化锌复合红外窗口设计时，了解结构中存在的热应力和挠曲度的大小是很有用的。     

微波CVD金刚石热沉片的制备研究

采用化学气相沉积法（CVD）制备的金刚石薄膜具有接近于天然金刚石的导热性能,是目前最为理想的热沉材料。利用微波等离子体化学气相沉积法（MPCVD）制备了金刚石热沉片,并在此基础上研究了不同沉积工艺对金刚石热沉片散热性能的影响。采用扫描电子显微镜（SEM）和激光拉曼光谱（Raman）检测了薄膜的表面形貌及纯度,金刚石热沉片的导热性能则通过测量封装LED后薄膜的散热效果来进行表征。结果表明,在其他条件不变的情况下,提高生长过程中的微波输出功率、降低反应气压以及增加基片温度有利于制备出散热性能更佳的金刚石热沉片。     

分体圆柱谐振腔法用于金刚石膜微波介电性能测试的研究

针对金刚石膜微波介电损耗低、厚度薄带来的微波介电性能测试难点, 研制了一台分体圆柱谐振腔式微波介电性能测试装置。利用不同直径的蓝宝石单晶样品, 用上述装置对低损耗薄膜类样品微波介电性能的测试能力及样品直径对测试结果的影响进行了实验研究。在此基础上, 使用分体圆柱谐振腔式微波介电性能测试装置对微波等离子体化学气相沉积法和直流电弧等离子体喷射法制备的高品质金刚石膜在Ka波段的微波介电性能进行了测试比较。测试结果表明, 由Raman光谱、紫外-可见光谱等分析证明品质较优的微波等离子体化学气相沉积法制备的金刚石膜具有更高的微波介电性能, 其相对介电常数和微波介电损耗值均低于直流电弧等离子体喷射法制备的金刚石膜。     

宽频磁性碳基复合吸波材料的制备及性能研究

目的 以可再生的生物质作为碳源，通过添加氯化钠作为活化剂，制备一种具有优良性能的吸波材料。方法 用一步热解法制备磁性碳基复合吸波材料，用X射线衍射仪（XRD）、扫描电镜（SEM）、氮吸附比表面与孔径分布仪（BET）、超导量子干涉仪（SQUID）等对其物相、形貌、磁性能等进行表征，用矢量网络分析仪（VNA）测试其电磁参数。结果 不同组分的复合材料均具有宽频的微波吸收性能，表现出对生物质用量一定范围内的不敏感特性。生物质用量分别为0.8、1.0、1.5和2.0 g时，制备的不同磁性生物质碳复合材料在填充量（质量分数）为30%时，有效吸收带宽分别达到5.7、6.2、5.8和5.9 GHz。结论 吸波性能对生物质用量一定范围内的不敏感特性，可以避免生物质由于产地、季节等的不同对吸波性能造成影响，同时也有利于制备工艺的实际操作，提高了吸波性能实验结果的稳定性。     

Growth, processing and properties of CVD diamond for optical applications

In recent years there has been an increased need for optical materials for use in adverse chemical, thermal, abrasive, and/or radiation environments. Diamond is a natural candidate for many of these applications because of its radiation hardness, superb resistance to chemical attack and abrasive wear, high thermal conductivity, and low absorption coefficient throughout the visible and much of the infrared. The use of synthetic (high pressure-high temperature) and natural diamond in optical components has been limited by the size and shapesof available crystals, and the inability to coat optical elements. The chemical vapor deposition (CVD) of polycrystalline diamond does not suffer the same limitations, and is therefore the focus of an expanding worldwide research effort. CVD diamond is not without its own shortcomings, however, and in this paper a status report is given on the obstacles and current research related to using CVD diamond as an optical material. Natural diamond's relevant physical properties and the optical applications envisioned for CVD diamond are also discussed.     

介电型石墨烯吸波复合材料研究进展EI北大核心CSCD

石墨烯因其独特的介电特性、高比表面积、低密度等性质,被认为是新一代吸波材料的有力候选。然而,单一组分的石墨烯吸波性能不佳,因此近年来石墨烯基吸波复合材料成为研究热点。本文介绍石墨烯及其复合材料的吸波机理与特性,指出介电型石墨烯作为极具发展潜力的吸波复合材料具有轻质、高强、宽频、薄层的特点。从石墨烯基体与掺杂体两方面综述了介电型石墨烯吸波复合材料的研究进展。最后指出,开发损耗能力强的新型介电掺杂体、构筑多组分吸波复合材料体系、建立通用的设计方法以及探索大批量的制备方法是未来的研究方向。     

平面光波导膜的ECR-PECVD制备及特性研究

采用微波电子回旋共振等离子体增强化学气相沉积技术 ,在单晶硅衬底上制备了用于平面光波导的SiO2 薄膜 ,研究了沉积速率与工艺参数之间的关系 ,并对射频偏置对成膜特性的影响作了初步实验研究。通过X射线光电子能谱、傅立叶变换红外光谱、扫描电镜、原子力显微镜、以及扫描隧道显微镜三维形貌和椭偏仪等测量手段 ,分析了样品的薄膜结构和光学特性等。结果表明 ,在较低温度下沉积出均匀致密、性能优良的SiO2 薄膜。此外 ,还成功制备出掺Ge的SiO2 薄膜 ,并可以精确控制掺杂浓度 ,以适应不同光波导芯的要求     

Single-material inhomogeneous optical filters based on microstructural gradients in plasma-deposited silicon nitride

Transparent hydrogenated amorphous silicon nitride (SiNx:H) coatings were prepared by dual-mode microwave-radio-frequency plasma-enhanced chemical vapor deposition. By controlling the effects of plasma density and ion energy on the film growth, it was possible to modify the microstructure of the coatings and hence the refractive index n. Using this method, we were able to vary n from 1.6 to 2.0, at 550 nm, by adjusting the power levels of the radio-frequency and microwave components while keeping the gas composition (SiH4, N2) and pressure constant. An inhomogeneous bandpass filter with a controlled refractive-index depth profile was fabricated, and its optical performance was compared with that of its multilayer counterpart. Besides the attractive optical features of such single-material rugate filters, we found that the mechanical resistance of inhomogeneous films is superior to that of multilayer systems.     

Cellulosic fines: Properties and effects

Any cellulosic pulp consists of particles of different dimensions. When trying to understand and control its properties, it is important to consider not only the bulk amount of long fibres, but also the material known as ‘fines’, which may comprise between 1 and 40% of a pulp. These fines have a great impact on the behaviour of pulp, on its processing, and on the characteristics of the resulting products. We compiled a review of research efforts to characterise the fines fraction by origin, morphology, and chemical composition, and to evaluate the fines’ effects especially in papermaking. The main feature of fines is the large specific surface area associated with their size. Their chemical constitution, particularly their charge, and the magnitude of their surface are the basis for their interactions with other pulp components such as extractives, fillers, and retention aids. The surface of fines affects drainage, as well as sheet density and strength. Several optical paper properties are influenced by the morphology of fines and by their chemical composition, which deviates from that of the long fibre fractions. The targeted utilisation of fines is a potential control variable in papermaking applications in order to obtain desirable paper properties.     

Structural and electrochemical studies of tungsten oxide (WO<Subscript>3</Subscript>) nanostructures prepared by microwave assisted wet-chemical technique for supercapacitor

Tungsten oxide (WO₃) nanostructures were synthesised using the microwave-assisted wet chemical method without any addition of surfactant for three different microwave irradiation times (10, 20 and 30 min). Then as-prepared nanostructures were characterised using various characterization techniques to know their structural, morphology and optical properties. The monoclinic and orthorhombic (WO₃) crystal structure was obtained from the as-prepared nanostructures by using X-ray diffraction analysis and its calculated crystalline size were found to be increased from 14 to 18 nm on increasing microwave irradiation time. The functional groups were investigated by using Fourier transform infrared spectroscopy analysis and the W–O chemical bonding nature was confirmed. The surface morphology was unclear using scanning electron microscope analysis, and a careful observation in high resolution transmission electron microscope studies shows that rod shaped structure. A blue-shifted optical absorption spectrum was observed by ultraviolet–visible spectroscopy analysis analysis and the bandgap energy value of WO₃ was calculated as approximately 3.62 eV. The emission behaviours were investigated by using photoluminescence spectrofluorometer analysis and an enhanced defect reduced emission was obtained. Finally, the electrochemical properties were analyzed by using cyclic voltammogram and galvanostatic charge–discharge analysis analyses. The maximum capacitance was recorded at 264 F/g which was declined to 149 F/g with the growth of WO₃ nanostructures size. Hence, the effect of microwave on structure and morphology, and consequent supercapacitor performances of WO₃ were discussed in details.     

Atmospheric aerosol optical properties: a database of radiative characteristics for different components and classes

A database management system has been realized that, by taking physical and chemical properties (the complex refractive index and the size distribution) of basic components as its starting point, allows the user to obtain optical properties of default as well as user-defined aerosol classes. Default classes are defined in accordance with the most widely known and used aerosol models. We obtain user-defined classes by varying the mixing ratio of components, creating new mixtures of default components, or by defining user components, thereby supplying the size distribution and the refractive index. The effect of relative humidity (RH) on the refractive index and the size distribution is properly accounted for up to RH = 99%. The two known mechanisms of obtaining classes from components are allowed (internal or external mixing).     

Fiber-optic chemical sensor using polyaniline as modified cladding material

An intrinsic fiber-optic chemical sensor is developed by replacing a certain portion of the original cladding with a chemically sensitive material, specifically, polyaniline. Both the light absorption coefficient and the refractive index of the polymer change upon its exposure to different chemical vapors. These changes induce the optical intensity modulation of the transmitted optical signal. Therefore, the developed structure is proposed for optical sensor applications. The performance of the sensor depends on the optical properties of the replaced cladding material, the cladding modification process, and the properties of the transmitted light within the optical fiber.     

Optical vector network analyzer as a reflectometer

An optical vector network analyzer similar to that of the microwave network analyzer has been shown to be feasible for the evaluation of optical components. It is shown that this instrument can also be used as a reflectometer. Heterodyne mixing and small linewidth lasers with a large tunable range make it a flexible tool for optical device evaluation and design. Experimental results are presented.