β-环氧树脂电子模塑料的导热性能研究

选用β—Si3N4粉体代替传统的SiO2填料与环氧树脂复合，制备新型高导热电子模塑料．初步研究了单独添加β—Si3N4及与SiO2复合添加对复合材料导热性能的影响．结果表明：β—Si3N4粉体可以显著提高复合材料的导热性能，当填充率达到50vol％时，β—Si3Na填充复合材料热导为SiO2填充复合材料的约3．8倍．并在实验基础上，探讨了复合材料的热导率计算模型，给出了单一填充和复合填充复合材料的Agari热导率计算模型表达式及相关参数．     

中间相碳微球/氰酸酯树脂复合材料的导电导热性能

选取M22、M15和M23三种不同粒径中间相碳微球（MCMBs）作为填料,分别以10vol%、25vol%、40vol%和50vol%体积分数填充氰酸酯树脂（CE）制备了MCMBs/CE复合材料,通过SEM、XRD、拉曼光谱仪、导热仪、体积电阻仪分析了不同粒径的MCMBs/CE复合材料的性能。结果表明:三种球形粉体都具有石墨化结构,其中M22粉体球形度最好、石墨化程度最高（I_D/I_G=0.23）、体积电阻率最小。三种MCMBs粉体制备的MCMBs/CE复合材料的吸水性、导热性和导电性均随填充量的增加而增大,冲击强度则先增大后减小。其中以M22在40vol%填充率下所得MCMBs/CE复合材料的综合性能最优,吸水率为0.45%,冲击强度为23.6 kJ/m2,热导率达1.28 W/（m·K）,体积电阻率达1.5 Ω·cm。      

Al_2O_3粒径与形貌对尼龙复合材料导热性能影响研究

以尼龙(PA)为基体、三氧化二铝(Al2O3)为导热填料经熔融共混、模压成型后制得尼龙导热复合材料。通过扫描电子显微镜、导热分析仪对复合材料微观形貌、导热性能进行表征。结果表明,Al2O3在尼龙基体中具有良好的分散性;Al2O3填料含量、粒径和形貌都对复合材料导热率有影响,当粒径为5μm的片状Al2O3的填充量达到50%(质量分数)时,其导热率可达0.838 W/(m·K);不同形貌的Al2O3填料复配使用可以有效构建导热通路、提高复合材料热扩散系数,但会降低材料热容、使复合材料导热系数减小。     

氮化物对增强线性酚醛树脂导热性能的对比研究

目的对比探讨氮化物陶瓷颗粒AlN和BN对热塑性酚醛树脂复合材料导热率的影响,制备高导热复合材料,并将其应用于电子塑封领域。方法首先,采用硅烷偶联剂对AlN和BN进行表面改性,以增强其在有机聚合物中的分散性。然后通过在线性酚醛树脂中添加不同粒径的陶瓷颗粒,对比粒径及填料含量对线性酚醛树脂复合材料导热率的影响,从声子角度分析,获取适合作为提高复合材料导热性能的填料。结果经过硅烷偶联剂表面改性后,陶瓷颗粒AlN、BN与水的接触角变大,与树脂的接触角变小,能够更好地分散在线性酚醛树脂中。在线性酚醛树脂中添加不同粒径、不同含量的AlN和BN,发现在不同含量范围内,填料粒径对复合材料导热率的影响不同。根据声子传递热量理论分析,BN较AlN在与C形成的界面上更容易传输热量,从而实现了较高的导热率。结论氮化物陶瓷颗粒能够很好地增强复合材料的导热率,尤其是BN,其态密度和C的态密度重叠率极高,更适合在BN与C的界面快速传递热量。     

聚合物基复合材料的导热性能研究

讨论了聚合物基高导热高绝缘纳米复合材料的导热机理与常用的导热理论模型。考虑到填充率、温度等的影响，用不同的理论模型计算了氧化铝纳米颗粒填充环氧树脂的热导率，并结合相关研究实验对不同的导热理论模型进行分析比较。     

聚合物基复合材料导热性的研究

讨论了聚合物基高导热高绝缘纳米复合材料的导热机理与常用的导热理论模型。考虑到填充率、温度等的影响，采用不同理论模型计算了用氧化铝纳米颗粒填充环氧树脂时材料的热导率，并结合相关研究实验对不同导热理论模型进行了分析比较。     

无机粉体活化及填充改性PP/PE复合材料的研究

概述了无机粉体表面改性剂的选用以及粉体的活化工艺,无机粉体种类、粒径和形貌等因素对改性填充PP/PE复合材料性能的影响以及无机粉体填充PP/PE基体结晶行为的变化。     

基于Lattice-Boltzmann方法的填充型复合导热材料的导热性能数值分析

陶瓷被广泛用作催化燃烧的催化剂载体。为及时将反应热导出,避免催化剂烧结、失活,需提高陶瓷导热能力。针对通过填充高导热性的金属或无机填料的方法制成的陶瓷复合导热材料,引入二维九速度不可压格子多相Lattice-Boltzmann模型,对构造的5种规则填充形状(圆形、正八边形、正六边形、正四边形和正三角形)的陶瓷基复合材料进行了完整的二维导热过程的数值分析。结果表明,在相同的填料和填充体积分数下,三角形填充的复合材料有效导热系数最大,填充形状愈趋近圆形则有效导热系数越小。同时模拟了各填充形状下,填充材料与基体材料的导热系数之比kp/km对复合材料有效导热系数的影响。研究结果表明,孤立的导热填料对于复合材料导热系数的提高作用是有限的,当kp/km增大到一定程度,有效导热系数不再明显增加。     

氧化铝/环氧树脂复合材料的制备及散热性能研究

针对目前LED散热材料导热系数不高的问题,采用粉末冶金法制备氧化铝/环氧树脂复合散热材料,研究了氧化铝粒径、添加量以及加入金属对复合材料导热系数的影响;分析了不同粒径、固化温度对其抗弯强度的影响,对于获得高性能LED散热材料具有很高的参考价值。结果表明:当氧化铝颗粒的粒径为50μm、填充量为75%(体积分数,下同)时,加入10%Cu所制备的复合材料其导热系数达到最大值3.02W/(m·K),同时其耐击穿电压高于行业标准。     

纳米碳管改善氧化铝填充硅橡胶复合材料的导热与机械性能(英文)

纳米碳管由于其优异的特性可以用于改善复合材料的导热和机械性能。本文通过传统的机械混合工艺,采用氧化铝粉体和少量纳米碳管填充甲基乙烯基硅橡胶,研究了氧化铝粉体的质量分数、表面改性和纳米碳管的添加对复合材料热导率、杨氏模量和硬度的影响。结果表明:氧化铝粉体的质量分数越高,复合材料的热导率越高;当氧化铝粉体的质量分数固定时,对其表面改性和添加纳米碳管能够明显提高复合材料的热导率、杨氏模量和硬度,发现改性氧化铝和纳米碳管并用可以协同增强填料与橡胶间的界面作用,促进橡胶基底中更好的导热通道和网络结构的形成,从而改善复合材料的导热和机械性能。     

Estimation of Parameters of Universal Distribution of Moments of Failure of Products

A method is proposed for estimating the parameters of a mixture of exponential and Weibull distributions for which the accuracy of preliminary estimates obtained by graphical analysis is refined in accordance with the criterion of maximum likelihood. The efficiency of the proposed method is supported by the results of statistical modeling.     

Evaluation of optical properties of highly scattering media by moments of distributions of times of flight of photons

A novel method for the determination of the optical properties of tissue from time-domain measurements is presented. The data analysis is based on the evaluation of the first moment and the second centralized moment, i.e., the mean time of flight and the variance of the measured distribution of times of flight (DTOF) of photons injected by short (picosecond) laser pulses. Analytical expressions are derived for calculation of absorption and of reduced scattering coefficients from these moments by application of diffusion theory for infinite and semi-infinite homogeneous media. The proposed method was tested on experimental data obtained with phantoms, and results for absorption and reduced scattering coefficients obtained by the proposed method are compared with those obtained by fitting of the same data with analytical solutions of the diffusion equation. Furthermore, the accuracy of the moment analysis was investigated for a range of integration limits of the DTOF. The moment analysis may serve as a comparatively fast method for evaluating optical properties with sufficient accuracy and can be used, e.g., for on-line monitoring of optical properties of biological tissue.     

Analysis of the rate of propagation of the wave of change of boiling modes

An approximate analytical expression is derived for the velocity of the front of the wave of change of boiling modes on a rod and on a plate. The impact of the Thomson effect and of the heater orientation in the gravity field is included. Adequate agreement is demonstrated between the derived relations and experimental data.     

Estimation of potentialities of methods of summation of direct measurement errors

Conventional methods for summation of direct measurement errors are considered. Conditions under which these methods provide consistent results are stated. It is proposed to utilize for characteristic of the total error, its interval estimator or the half-sum of the value obtained by adding up its arithmetic and geometric random errors.Translated from Izmeritel'naya Tekhnika, No. 4, pp. 10–12, April, 1995.     

空压机轴承箱蜗壳温度探头油封改造

由于空压机进气侧轴承箱蜗壳温度探头密封效果不好,使空压机及其后续管道受到油污染。后将温度探头的O形圈密封改为骨架油封,杜绝了轴承箱漏油问题。文章简介空压机的结构和技术参数,详细介绍了骨架油封的制作和优点。     

Characteristics of mechanical properties of materials in studies of conditions of attainment of marginal states

It is shown that conditions of attainment of marginal states in the material of structural components are formulated on the basis of analysis of force and deformation criteria of formation and development of destruction. The parameters of these criteria are data on types of structural materials, standard and special characteristics of their mechanical properties, structural forms of considered elements of the equipment, and their operating stress loading. In this case, the construction of a system of state equations for describing interrelation of current damage, external actions, and responses to them is based on the concept of calculating variations in properties of materials at all stages of the design life cycle.     

Determination of parameters of microstructural inhomogeneity of deformation of metals by the method of modeling

The article suggests a method of evaluating the microstructural inhomogeneity of deformation of metals by modeling. The method includes the measurement of deformations of metal according to meshes of a dividing grid with small base and the calculation of the distribution parameters of microdeformations in model representation. It is shown that the modeling method makes it possible objectively to evaluate the microinhomogeneity of deformation of metals independently of the chosen mesh size of the dividing grid. New structural characteristics are introduced: the base and wave of variation expressing the degree of crumbling or amalgamation of metal grains by inhomogeneity of deformation.Translated from Problemy Prochnosti, No. 7, pp. 40–44, July, 1991.     

水三相点复现的不确定度评定

水三相点是开尔文热力学温度的唯一基准点，也是ITS-90国际温标重要的定义固定点。因此，水三相点不确定度分析对整个温标的建立、温度量值传递起着至关重要的作用。近3年来，中国计量科学研究院研制出一系列高质量的水三相点容器，加强了水三相点的研究，为不确定度的分析提供了更为可靠的实验依据。同时，不确定度的分析也是客观评价新研制容器性能的一个重要指标。因此，根据实验结果对新研制容器所复现的水三相点进行了不确定度评定。评定结果表明，其扩展不确定度为0．16mK(k=2．69，P=0．99)。