纤维增强复合材料在探测机器人主车体上的应用

天然纤维增强复合材料亚麻纤维具有良好的抗冲压强度和自洁防腐功能,延伸率和密度也较小,选用其替换由45号钢制作的煤矿井下探测机器人的主车体,在保证主车体性能要求的前提下,质量减少190.5 kg,占主车体质量的80.9%。     

基于光纤光栅的GIS导体温度巡检方法与装置

针对GIS设备导体温度监测和回路过热性故障预防,在分析光纤光栅测温原理和成像解调技术的基础上,提出了一种基于光纤光栅温度传感网络的GIS导体温度巡检方案。通过现场温升试验建立了GIS导体温度测量模型并根据相关标准制定了GIS导体温度过热性故障判据。研制了可应用于不同GIS母线温度测量的便携式巡检装置,设计了温度巡检装置的硬件系统和软件系统。现场实验表明该设备工作稳定,测温精度高,对于保障GIS设备的安全稳定运行具有现实意义。     

Non-isothermal crystallization kinetics of polypropylene and hyperbranched polyester blends☆

Polypropylene (PP) with different contents of the second generation hyperbranched polyester (HBP) is prepared by melt blending method. The non-isothermal crystallization kinetics of PP and PP/HBP blend...     

聚丙烯与超支化聚酯共混物的非等温动力学(英文)

Polypropylene (PP) with different contents of the second generation hyperbranched polyester (HBP) is prepared by melt blending method. The non-isothermal crystallization kinetics of PP and PP/HBP blends is investigated under differential scanning calorimetry (DSC). The Mo equation is used to analyze the DSC data. The results show that the Mo theory is suitable for crystal ization kinetics of the blends. Fast cooling rate is not good for crys-tallizing and nucleating. The values of half crystal ization time (t1/2), crystal ization enthalpy (ΔHc) and temper-ature range (ΔT) of PP/HBP blends decrease when HBP is added. The required cooling rate of PP is higher than that of PP/HBP blends in order to reach the same relative crystal inity. Crystallization rate increases with the ad-dition of HBP. The crystallization rate reaches a maximum when the content of HBP is 5%. In addition, the activa-tion energies of PP and PP/HBP blends are calculated by Kissinger equation, revealing that the content of HBP has a little effect on the crystallization activation energy.     

硫酸亚铁铵制备实验的改进

硫酸亚铁铵制备的经典方法是经过蒸发,浓缩,冷却来得到晶体,既耗时长,Fe2+又易氧化,影响硫酸亚铁铵产率及等级。此次改进利用复盐的溶解度比组成它的简单盐溶解度小的特点,而硫酸亚铁铵又不溶于乙醇及水与乙醇可任意比互溶的特征,通过常压过滤于乙醇中,即刻可得浅蓝绿色硫酸亚铁铵单斜结晶,省去经典方法中的蒸发、浓缩,冷却步骤,同时也有利于防止Fe2+被氧化。     

Preparation of Alumina Fiber-Reinforced Aluminum by Squeeze Casting and Their Machinability

Alumina fiber-reinforced aluminum alloy composites were prepared by squeeze casting, and the effect of the reinforcement on the machinability of the alloy was investigated. Two kinds of short alumina fibers, which have the same fiber size but different hardness, were used. Preform in which the fibers were in a random arrangement was formed with SiO₂ binder, and then was infiltrated with the alloy melt to prepare the composite. The fiber–matrix interfacial bond via the binder is sufficient and no reaction product was detected. The cutting force of the alloy was reduced by the fiber-reinforcement. The lower the hardness of the fiber in the composite, the lower the cutting force of the composite. The roughness of the machined surface was drastically decreased by the reinforcement. Observation of the chip formed on the machined surface indicated that the fiber suppressed the formation of the built-up-edge, and this fact would lead to the reduction in the surface roughness by the reinforcement. The chips were shortened by the reinforcement. The difference in hardness of the alumina fiber hardly affected the roughness and the chip morphology. The hardness of the fiber has a strong effect to decrease the tool life.     

短螺距手性液晶热敏旋光特性的研究

利用Berreman 4×4矩阵建立理论模型对短螺距手性液晶的旋光率进行求解,使用MATLAB计算得到了手性液晶旋光角随入射角、螺距、盒厚等外界因素变化规律的仿真结果,且通过实验验证了此方法的准确性。对手性液晶旋光效应作为热敏材料的使用进行了实验探究,使用旋光仪测量螺距为250~310nm的手性液晶旋光角,得到手性液晶的热敏旋光特性。结果显示,螺距不同时,液晶的旋光角随温度具有不同程度的变化,但每种螺距下,手性液晶旋光率随温度的变化明显且规律。验证了旋光率热敏效应的稳定性,结果证明将手性液晶作为一种潜在的热敏材料应用的可行性,为手性液晶在温度传感器中的应用提供了实验依据。     

基于EBSD的金属变形激活滑移系的确定方法

针对多晶金属力学变形过程中的激活滑移系,提出了一种基于电子背散射衍射(Electron Back-Scatter Diffraction,EBSD)技术的滑移系确定方法。借助材料表面晶体取向和滑移带形貌分析,计算并测量滑移带与加载应力轴之间的夹角,通过两者比较确定滑移面;计算该滑移面对应的可能滑移系的Schmid因子,根据Schmid定律确定滑移方向,从而判断实际被激活滑移系。以奥氏体不锈钢为例,试验证实了该方法的可行性。与其他方法相比,该方法可获得表面损伤形貌及其晶体取向分布,更适用于多晶材料力学变形后的滑移系分析。     

Photonic band gap in 1D multilayers made by alternating SiO2 or PMMA with MoS2 or WS2 monolayers

Atomically thin molybdenum disulfide (MoS₂) and tungsten disulfide (WS₂) are very interesting two dimensional materials for optics and electronics. In this work we show the possibility to obtain one-dimensional photonic crystals consisting of low-cost and easy processable materials, as silicon dioxide (SiO₂) or poly methyl methacrylate (PMMA), and of MoS₂ or WS₂ monolayers. We have simulated the transmission spectra of the photonic crystals using the transfer matrix method and employing the wavelength dependent refractive indexes of the materials. This study envisages the experimental fabrication of these new types of photonic crystals for photonic and light emission applications.     

Crystal growth,structure, infrared spectroscopy,and luminescent properties of rare-earth gallium borates RGa3(BO3)4, R = Nd,Sm–Er,Y

Crystals of the rare-earth gallium borates RGa₃(BO₃)₄, where R = Nd, Sm–Er, or Y, were grown by the flux method. The crystal structures of RGa₃(BO₃)₄ (R = Eu, Ho) were studied on the basis of single-crystal X-ray diffraction measurements. The hexagonal unit-cell parameters are a = 9.4657(1) Å, c = 7.4667(1) Å and a = 9.4394(2) Å, c = 7.4322(1) Å for EuGa₃(BO₃)₄ and HoGa₃(BO₃)₄, respectively, space group R32. Structure model was determined by “charge flipping” method and refined to R = 1.93% [EuGa₃(BO₃)₄] and R = 1.89% [HoGa₃(BO₃)₄] in anisotropic approximation. All grown gallium borates were investigated by infrared (IR) spectroscopy technique in a middle and far IR region. IR spectra of rare-earth gallium borates correspond to a pure rhombohedral (R32) polytype structure. Small inclusions of a monoclinic phase were detected only in Eu and Nd compounds. Luminescence of Eu and Ho gallium borates was studied at room temperature. The measured decay times for the most intensive emission lines of EuGa₃(BO₃)₄ (∼614 nm) and HoGa₃(BO₃)₄ (434 nm) are 940 μs and 140 μs, respectively. The scheme of crystal-field energy levels of Eu³⁺ in EuGa₃(BO₃)₄ was built on the basis of the temperature-dependent optical transmission measurements combined with the luminescence data. The measured UV absorption edge for RGa₃(BO₃)₄ is at about 300 nm.