温梯法生长掺碳强韧化蓝宝石单晶的研究

研究了温梯法生长不同浓度石墨碳掺杂蓝宝石单晶的室温力学性能。实验发现在蓝宝石单晶中, 掺入适量石墨碳可以显著提高晶体常温断裂强度和断裂韧性, 而不损害晶体的可见和近红外透过性能。当其掺入的石墨浓度为5×10^-3时, 蓝宝石单晶的断裂强度和断裂韧性平均分别提高到752 MPa和2.81 MPa·m1/2, 而其可见和近红外透过率依然达80%。掺杂的石墨碳在蓝宝石晶体中部分作为晶格间隙离子, 对蓝宝石单晶的开裂具有钉扎作用, 达到提高蓝宝石单晶常温力学性能的效果。但是过量石墨碳的掺杂会引起掺质的组分偏析, 晶体中出现碳包裹物, 从而导致晶体力学性能和光学性能的下降。     

蓝宝石光纤与光纤高温传感器

蓝宝石光纤作为一种高品质的单晶光纤,具有极好的高温稳定性和光学、机械特性,因此在光纤高温传感和中红外激光传能方面具有相当重要的应用价值。 浙江大学物理系光纤电子材料研究室单晶光纤及应用研究课题组。于1987年在国内首次拉制成功蓝宝石单晶光纤和YAG单晶光纤,并经过多年努力,在蓝宝石光纤高温传感头及光纤测温仪的实用化研究中,取得了较好的研究结果。目前已建立起稳定的晶体光纤激光加热基座法(LHPG)生长设备;能小批量生长优质的蓝宝石单晶光纤材料,光纤光传输损耗优于     

蓝宝石单晶的质量评价及检验方法

针对目前蓝宝石单晶在半导体衬底、激光窗口等方面的广泛应用,本文主要介绍了光学级蓝宝石单晶（包括晶棒、晶片或晶块）的内部质量要求及作为LED衬底应用所需进行的质量检验。     

气凝胶材料力学性能增强方法研究进展

气凝胶复合材料是一种新型的高效隔热材料,在热学、声学、光学以及电学等领域有广阔的应用,但纯气凝胶力学性能较低,这一缺点极大地限制了其在隔热领域的应用。综述了通过提高气凝胶本体和增强体增加材料强韧性的研究进展,并对气凝胶材料力学性能增强方法的研究做了展望。     

蓝宝石光纤高温测量技术进展

温度是表征物体状态的参数之一,在科学研究和工程应用中具有重要的理论意义和价值。在氧化、高温、腐蚀、电磁干扰等恶劣环境下,温度的准确测量一直是难题。传感器材料是进行温度测量的基础。蓝宝石单晶光纤具有物理化学性能稳定、熔点高、机械性能强等优点,是进行高温测试的一种首选材料。本文介绍了利用蓝宝石单晶光纤进行温度测量的几种方法,即蓝宝石光纤辐射高温测试技术、蓝宝石光纤光栅高温测试技术、蓝宝石光纤珐珀高温测试技术、蓝宝石超声波导高温测试技术的原理、现状、优缺点及发展趋势,并进行了比较,为蓝宝石光纤温度测量应用奠定基础。     

激光加热基座法生长高质量Yb3+掺杂Y3Al5O12单晶光纤

单晶光纤即具有光纤形态的单晶材料, 是功能晶体材料一维化发展的重要体现。单晶光纤兼具单晶材料优异的光学性能和激光光纤散热效率高、光束质量高等特点, 有望解决传统玻璃材质激光光纤非线性效应强、热导率低等瓶颈问题, 实现激光峰值功率、脉冲能量等性能的突破。本工作采用自主研制的激光加热基座(Laser-heated Pedestal Growth, LHPG)单晶光纤炉制备了两组Ф0.2 mm×710 mm的Yb³⁺掺杂Y₃Al₅O₁₂(Yb:YAG)单晶光纤, 并对其进行了表征。制备的单晶光纤长径比大于3500, 直径波动小于5%, 且表现出一定的柔韧性; X射线摇摆曲线测试结果显示Yb:YAG单晶光纤的结晶质量与所用源棒相比有所提升; EDS线扫描结果证明单晶光纤中的Yb³⁺沿轴向呈现均匀分布。实验结果表明: 准一维化的单晶光纤具有良好的结晶质量与光学均匀性, 有望成为一种性能优异的高功率激光增益材料。     

激光加热基座法生长高质量Yb~(3+)掺杂Y_3A_(l5)O_(12)单晶光纤（英文）

单晶光纤即具有光纤形态的单晶材料,是功能晶体材料一维化发展的重要体现。单晶光纤兼具单晶材料优异的光学性能和激光光纤散热效率高、光束质量高等特点,有望解决传统玻璃材质激光光纤非线性效应强、热导率低等瓶颈问题,实现激光峰值功率、脉冲能量等性能的突破。本工作采用自主研制的激光加热基座(Laser-heated Pedestal Growth,LHPG)单晶光纤炉制备了两组Ф0.2 mm×710 mm的Yb~(3+)掺杂Y_3Al_5O_(12)(Yb:YAG)单晶光纤,并对其进行了表征。制备的单晶光纤长径比大于3500,直径波动小于5%,且表现出一定的柔韧性;X射线摇摆曲线测试结果显示Yb:YAG单晶光纤的结晶质量与所用源棒相比有所提升;EDS线扫描结果证明单晶光纤中的Yb~(3+)沿轴向呈现均匀分布。实验结果表明:准一维化的单晶光纤具有良好的结晶质量与光学均匀性,有望成为一种性能优异的高功率激光增益材料。     

金属元素掺杂二维过渡族金属硫化物研究进展

传统二维材料具有丰富的电学、光学特性?在电子器件领域中占据着重要位置?金属元素掺杂二维过渡族金属硫化物不仅可以保持原过渡族金属硫化物所特有的优越性能?还可赋予二维材料特定的铁磁、铁电性能?使其在光学器件、自旋电子学器件以及信息和数据存储等领域得到更广泛的应用?重点介绍了金属元素掺杂过渡族金属硫化物的理论和制备方法?对其结构特性、电子特性以及磁学特性进行了详细讨论?并且着重论述了金属元素掺杂在过渡族金属硫化物中的实验合成方法?其中?化学气相沉积法、化学气相传输法被广泛使用?其他实验方法如固相法、磁控溅射法也可结合运用?最后展望了金属元素掺杂过渡族金属硫化物研究面临的挑战以及未来磁性二维材料的发展方向?     

拓扑绝缘体Bi2Se3单晶体的研究进展

拓扑绝缘体是当前凝聚态物理和材料科学研究的热门课题,其独特的电子态结构使其在自旋电子器件和量子计算机等领域拥有巨大的应用潜力。阐述了拓扑绝缘体Bi2Se3单晶的制备方法﹑输运性质以及表面调控效应等方面的最近进展;总结了各种化学掺杂方法对Bi2Se3费米能级的影响,同时展望了今后Bi2Se3的研究发展方向。     

高镍三元正极材料镍钴铝酸锂的改性方法

高镍三元正极材料镍钴铝酸锂(NCA)因具有较高的能量密度和较低的成本,而拥有广阔的应用前景,但也存在阳离子混排严重、易发生结构相变和安全性能不佳等问题.为了解决这些问题,近年来对NCA材料进行了大量的改性研究.综述了NCA材料表面包覆、体相掺杂、梯度化和单晶化等最新改性方法,并对其研究方向进行了展望.     

热交换器的分类及优缺点分析

热交换器是将不同温度介质之间的热量通过热传导的形式,由高温介质传递给低温介质,使介质达到生产所需温度的工艺设备,也可作为一种节能设备使用.通过对不同热交换器的结构分析,总结不同热交换器的优缺点、适用环境,为生产工艺设计人员及设备制造单位在选择可降低能耗、提高效率的设备上提供参考.     

聚苯胺及其复合物的制备和结构及形貌分析

通过化学氧化法分别制备盐酸,盐酸和十二烷基苯磺酸,碳纳米管(MWNTs-COOH)掺杂的聚苯胺,利用红外光谱,紫外光谱,扫描电子显微镜和透射电子显微镜对所制备聚苯胺的结构和形貌进行分析。分析不同掺杂物对聚苯胺的结构和形貌的影响;同时研究了超声波作用对聚苯胺形貌以及聚苯胺包裹MWNTs-COOH情况的影响。     

Thermodynamic similarity and prediction of the properties and characteristics of substances and processes

Principles of the theory of thermodynamic similarity are considered in application to all aggregate states of a substance, including phase transitions, and to the change in dissipative structures in open systems.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 53, No. 5, pp. 709–716, November, 1987.     

Modelling and computation of curing and damage of thermosets

The curing of thermosets is a complex process involving the transition from a fluid into a (visco-) elastic solid. This phase transition comes along with an increase in stiffness and a volume shrinkage of the polymer. The latter may lead to severe residual strains and stresses, which in turn can cause damage in the final, usually quasi-brittle material. In this contribution a constitutive model is developed which takes into account the curing of a thermosetting material together with the process-induced damage as resulting from curing shrinkage. The curing of the material is governed by a phenomenological hypoelastic constitutive equation which includes temporal evolutions for stiffness and volume shrinkage. Thermal and viscous effects are neglected in the present study. An isotropic gradient-enhanced damage model is adapted to describe the damage evolution. The curing-damage model is implemented into a finite element code and numerical examples for thermosetting materials demonstrate that the proposed model is capable to predict cure-induced damage in thermosets.     

碳化硼陶瓷增韧补强和致密化研究现状及其展望

碳化硼陶瓷具有极高的硬度,然而其低韧性、低抗弯强度、难以致密化限制了它的广泛应用.已有一些研究集中于碳化硼陶瓷增韧补强和致密化,对这一方面国内外研究进展进行了归纳与评述,阐明各种增韧补强和致密化方法的优缺点,提出碳化硼陶瓷增韧补强和致密化研究值得发展的一些方向.     

Measurement and analysis of elastic and anelastic properties of alumina and silicon carbide

Measurements of dynamic Young's modulus, E, and damping as a function of temperature, T, were made for alumina and silicon carbide. The Young's modulus data were compared with some from the literature, and analysed in terms of a theoretical framework relating the Debye temperature, θD, with the elastic constants. For both materials this analysis yielded a ratio T₀/θ_D which was near 0.4, where T₀ is an empirical fitting constant for the plot of (E(0)−E)/T versus 1/T (E(0) is the value of E at 0 K). The analysis of the damping data in terms of an Arrhenius type dependence led to effective activation energies near kT, where k is Boltzmann's constant. This revised version was published online in November 2006 with corrections to the Cover Date.     

Mechanisms of Corosion and Oxidation of Metals and Alloys

Selected topics in field of the study of the mechanisms of corrosion and of oxidation of metals or alloys are presented. The first part reports a new model for the mechanism of the breakaway oxidation of ferritic stainless steels in water vapour. The second part is devoted to the physico‐chemical aspects of oxidation and presents experimental methods useful in the kinetic modelling applied to two alloys, the zircalloy‐4 and an AlMg5 % in the liquid state. In the third part the physical and numerical modelling of the stress corrosion cracking behaviour in face‐centered cubic (fcc) alloys is detailed, which enables the study of the influence of macroscopic parameters (such as the temperature or hydrogen activity) on the fracture process.     

Surface-charge density and potential of coal-liquid mixtures and control of their stability and fluidity

The preparation conditions of concentrated (>70%) aqueous suspensions of coal were optimized, as were the surface charge density and the surface potential of the coal-water suspensions. The theoretical study showed that (1–3) or (2–3) electrolytes such as Na₂SO₄ or Na₅P₃O₁₀, greatly increase the surface charge density and the surface potential of the coal particles in water. This study has led to the interesting result that thinners and stabilizing agents of concentrated clay suspensions, such as lignosulphonates, tripolyphosphates, polynaphtalene sulphonates, etc., must also be good thinners and stabilizing agents for ground coal-water suspensions. Two parameters were controlled: the stability and the fluidity of the suspensions. A penetrometry technique revealed the importance of the resistance coefficient,C _r that can be used as a criterion for the evaluation of coal-water mixture stability and fluidity. Concentrated coal suspensions (about 75% of solid by weight) were prepared in water by using different additives, for instance sodium tripolyphosphate (NaTPP) and surfactants like lignosulphonates (by coupling of the dispersion and stabilizing effects) with the optimum concentration ratio of these two products equal to 1.9. The stability of the suspensions was then greater than 2 months and the viscosity was 1900 cP.     

SARS传染病数学建模及预测预防控制机理研究

首先，利用疾病传播的一般规律及人口守恒统计法则建立了四类人的SARS传染病数学模型，然后运用数学方法对四类人的SARS传染病数学模型进行分析，得出了其生理意义和预防、控制机理。其次，利用人工神经网络理论建立了SARS的预测模型，以北京市的SARS数据为例进行了预测和分析，预测结果显示该模型简单易行，预测精度高。