Multifunctional Composite Material with Efficient Microwave Absorption and Ultra-High Thermal Conductivity

The increasing demands for electronic devices to achieve high miniaturization, functional integration, and wide bandwidth will exacerbate the heat generation and electromagnetic interference, which hinders the further development of electronic devices. Therefore, both the issues of microwave absorption and heat dissipation of materials need to be addressed simultaneously. Herein, a multifunctional composite material is proposed by periodic arrangement of copper pillars in a matrix, based on the ...     

Thermophysical and Dielectric Properties of Polymer Composites Filled with Hexagonal Boron Nitride

Russian Physics Journal - Thermophysical and dielectric properties of polymer composites based on linear low density polyethylene (LLDPE) and polylactide (PLA) filled with hexagonal boron nitride...     

氮化铝陶瓷低温热导率的实验研究

根据轴向稳态热流法原理 ,实验研究了 Al N陶瓷的低温热导率 ,为高温超导制冷机直接冷却提供了必要的实验数据。 Al N的热导率在 30～ 170 K之间 ,随温度的升高而增大 ,在 10 0 K时达到 5 8.36 W/ (m· K)。根据平均自由程理论 ,对影响氮化铝陶瓷热导率的微观因素进行了分析 ,影响本次测试氮化铝样品低温热导率的主要因素为声子与缺陷之间的散射。     

气凝胶及其复合绝热材料的导热系数测量

采用瞬态热带法在不同压力和不同温度下对气凝胶、硬硅钙石-气凝胶及陶瓷纤维-气凝胶复合绝热材料的导热系数进行了测量.结果表明,随着测试压力的降低,三种材料的导热系数都显著降低,在大约104 Pa时基本趋于常数;随着温度的升高,三种绝热材料的导热系数几乎与温度的立方成正比;当气凝胶的密度为145 kg/m3时,其导热系数具...     

基于非平衡电桥原理的热导池

热导池的核心结构是非平衡电桥,介绍了热导池的工作原理,并进行了程序升温还原和程序升温脱附实验.     

Thermal Conductivity of Periodic Composite Media with Spherical Inclusions

The thermal conductivity of periodic composite media with spherical inclusions embedded in a homogeneous matrix is discussed. Using Green's function, we show that the Rayleigh identity can be generalized to deal with the thermal properties of these systems. A technique for calculating effective thermal conductivities is proposed. Systems with cubic symmetries (including simple cubic, body centered cubic and face centered cubic symmetry) are investigpted in detail, and useful formulae for evaluating effective thermal conductivities are derived.     

Investigation of the Kinetics of Curing Reaction for the Resin Matrix Polymer Composite Based on Near-Infrared Spectroscopy

Abstract

Near-infrared (NIR) spectroscopy is a rapid and nondestructive method for the simultaneous measurement of different constituents in resin matrix polymer composites. This strategy has been applied in the synthesis of resin matrix polymer composites. In this article, we mainly review the control of curing reaction kinetics of the phenolic, epoxy resin, polyester resin, polyurethane, and other polymer resin based on NIR spectra, which is important to control the quality of the resin matrix polymer composites during synthesis.     

All-Optical Switching Based on Azo Polymer Material

Conventional all-optical switches based on azo polymer films and the all-optical switches based on the attenuated total reflection （ATR） geometry are investigated. A conventional switch system, including a pump beam of 532 nm and a probe beam of 650 nm, is based on the photoinduced birefringence effect of azo polymer. An ATR switch in a prism-multilayer configuration is achieved by changing the reflectance of the probe beam with an external pump beam. The ATR method provides the substantial improvement of the speed and the efficiency of the modulation over the conventional method. Although the azo polymer response still remains relatively slow, an enhanced nonlinear refractive index of the azo polymer film can effectively increase the modulation.     

高分子聚合物热输运调控的研究进展

高分子聚合物基热界面材料对高密度集成电路的散热起到至关重要的作用。本文主要阐述 高分子聚合物热导率的理论及实验研究进展,重点介绍近年来关于调控高分子聚合物热导率的相 关工作。此外,本文还对高分子聚合物热输运调控的发展趋势进行了展望,讨论目前研究中尚未 解决的问题及瓶颈。     

含六方氮化硼的一维光子晶体的光学特性

从麦克斯韦方程组出发,结合电磁场边界条件推导出在倾斜光轴条件下的传输矩阵。利用该传输矩阵研究了光轴方向对基于六方氮化硼的光子晶体光学特性的影响。研究表明,当Ф=0~°时,此结构会在六方氮化硼Ⅱ型双曲区域出现全方位禁带。随着Ф的不断增大,TE波和TM波在Ⅱ型双曲区域内的光子禁带逐渐错开,对于TM波,Ⅰ型双曲区域开始产生禁带,且朝着低频方向移动;Ⅱ型双曲区域内的禁带不断变窄,并往高频方向移动。利用这些特性,可实现偏振光分离和禁带加宽。     

二维多孔热密封材料的有效导热系数模拟

本文对于二维多孔热密封材料的有效导热系数模拟提出一种简单有效的方法,它可以模拟介于固相连续和固相不连续之间的任何形式的孔隙分布结构,通过类比多孔渗流模型得出一种相关系数,再根据热阻串并联的关系计算四种可计算模型的有效导热系数,通过相关系数得到具体模型的有效导热系数。本文的模拟方法可以控制孔隙率、孔径、孔隙分布、温度等影响有效导热系数的重要参数,考虑了辐射的影响,而且模拟简单,计算快速,模拟结果与文献中实验的结果相比较能很好的吻合,验证了本文方法的正确性。     

Strain Effects on Electronic Properties of Boron Nitride Nanoribbons

We investigate the strain effects on the electronic properties of boron nitride nanoribbons （BNNFts） by using firstprinciples calculations. The results show that the energy gap of BNNRs with both armchair edges （A-BNNRs） and zigzag edges （Z-BNNFts） decreases as the strain increases. As strain increases, the energy gaps of Z-BNNRs decrease rapidly as the width increases and reduce significantly to small values, which makes Z-BNNRs change from wide-gap to narrow-gap semiconductors.     

六方氮化硼薄膜对石墨烯-碳化硅结构近场热辐射的增强

六方氮化硼(hBN)具有跟石墨烯类似的层状结构和晶格参数,研究发现hBN薄膜具有良好的热传导、电绝缘、光学和力学等性能.本文从理论上研究了 hBN薄膜对石墨烯-碳化硅(G/S)结构的近场热辐射的影响.研究发现在红外频段,hBN薄膜在低频率区和高频率区会增强G/S结构的近场热辐射,经计算在G/S结构中加入厚度为10 nm...     

纤锌矿氮化硼及其应用的研究（Ⅱ）——纤锌矿型氮化硼的等温状态方程

 使用两种不同的高压在位X光衍射法，研究了用爆炸法合成的纤锌矿型氮化硼（wBN）在室温下的等温状态方程。一种方法是用转靶X光角色散粉末衍射法，研究了它在0~40 GPa压力范围内的等温压缩行为。结果表明，wBN在0~40 GPa的压力范围内是稳定的，没有发生结构相变。通过p-V数据对Murnaghan方程拟合，得到wBN在p=0时的等温体模量B₀=(335±34) GPa及其对压力的一阶导数B₀'=4.21；另一种是用同步辐射X光能量色散衍射法，研究了它在0~25 GPa压力范围内的等温状态方程。实验中，使用了改进的自动加压的DAC高压装置，此装置保证了实验中衍射角θ₀固定不变。将获得的p-V数据仍用Murnaghan方程拟合，得到wBN在p=0时等温体模量B₀=(280±56) GPa，及其B₀'=4.39。     

Modification of Optical Characteristics of a Polymer Composite Material under Irradiation

Polymer composites based on polystyrene and modified SiO₂ are synthesized. Effect of the SiO₂ concentration on the surface (thermostatic) properties of the composites is analyzed. Surfaces of composites with different SiO₂ concentrations are microscopically studied. Minor amounts of spherical agglomerates are obtained at relatively high SiO₂ concentrations, and the size of the agglomerates may amount to 80 μm at a SiO₂ concentration of 30 wt %. Variations in the integral absorbance of solar radiation are studied for the polymer composites irradiated with vacuum-UV radiation at a temperature of 125°C.     

Luminescence of a Polymer Composite Doped with Boron Chelates. Mechanism of Luminescence Sensitization

It has been revealed that a sensitized luminescence of AntAcBF₂ is observed in the boron difluoride dibenzoylmethanate (DBMBF₂)–boron difluoride anthracenoylacetonate (AntAcBF₂) system in the polystyrene matrix. The emission mechanism of energy transfer from DBMBF₂ to AntAcBF₂ has been established. The luminescence properties of bilayer films with one layer containing DBMBF₂ and another one containing AntAcBF₂ have been investigated. At luminophore contents in equimolar quantities, one observes a white luminescence of the bilayer polymer composite.     

Growth Feature of Cubic Boron Nitride on c-BN Crystal Substrates

Cubic boron nitride （c-BN） films were deposited on highly-oriented （111） bulk c-BN crystal by using the rf magnetron sputtering method. The growth films are characterized by micro-Raman spectroscopy （μ-RS） and scanning electron microscopy （SEM）, The results show that the high crystallization electron transparent c-BN films in thickness of about 10μm are obtained, Island and step growth models are clearly shown.     

基于不确定度处理的导热系数实验挖掘

在计算机普及和大物实验智能化的时代背景下,许多理工院校特别是普通工科院校中对实验数据的处理要求逐渐简化,甚至已不再有不确定的数据处理要求。部分学有遗力或感兴趣的学生希望有更深入的数据处理与分析,但缺乏比较有可操作性的实例参考,目前导热系数的数据处理相关文献尚无不确定度处理的报道。特别是不确定处理,成了学生难以触及触摸的禁区。针对这样的现状,我们提供了方程回归法、作图法和逐差法这三种有效的数据处理方法,并首次详细给出了不确定度处理过程。基于不确定处理结果,我们进行了有效的误差分析并针对性地提出了实验的操作建议,具有一定的参考价值。