Effects of thickness and hydrophobicity of double microporous layer on the performance in proton exchange membrane fuel cells

In this paper, a multi-layer gas diffusion layer (GDL) is designed. The GDL consists of a single carbon paper backing layer and dual microporous layers (MPLs). Moreover, the effects of thickness and hydrophobicity of double MPL on the performance of proton exchange membrane fuel cells are investigated. From the test results of the water contact angle, conductivity, pore size distribution, and the polarization curve, it is found that the thickness adjustment increases the number of 0.5 to 7 μm and 20 to 100 μm pores in GDL, which is more conducive to water discharge. Therefore, the thickness adjustment is more favorable to the cell performance under high humidity. While the gradient hydrophobic design makes the MPL of the modified intermediate layer have a certain water-retaining capacity to humidify the reaction gas, which has better effect under low humidity. At last, the results show that the optimized GDL meets a limit power density of 1.772 W/cm² under 60% humidification and 1.600 W/cm² under 100% humidification.     

Appropriate conditions for preparing few-layered graphene oxide and reduced graphene oxide

Oxidation time and exfoliated conditions of graphite oxides (GOs) were investigated to prepare few–layer graphene oxide and reduced graphene oxide via a modified Hummers approach. Different oxidative degree of GOs was prepared by changing oxidation time, and the effects of oxidative degree of GOs in different oxidation time were studied by XRD, FT-IR. Afterwards, highly oxidized GOs were used as precursor to prepare graphene oxide and reduced graphene oxide by ultrasonic dispersion method and thermal expansion method. The exfoliated conditions (ultrasonic power and ultrasonic time, thermal exfoliated temperature) were investigated to prepare few-layered graphene oxide and reduced graphene oxide.     

反蛋白石结构光子晶体及其应用的研究

反蛋白石结构光子晶体因具有完全光子带隙、制备材料广泛、特殊的周期结构、大的比表面积和连通的孔洞结构,近年来在自发辐射的调制、提高光催化反应速率和染料敏化太阳能电池反应速率等领域成为研究热点之一,并且在光、电、催化、传感、显示、检测等领域有着巨大的应用价值。介绍了反蛋白石结构光子晶体的基本概念及制备方法,阐述了反蛋白石结构在材料自发辐射的调制、能量传递的调制、促进物理化学反应、外界环境响应材料等方面的作用及其应用。     

逆子结构理论在运输包装中的研究进展

微动态逆子结构方法在解决由产品、包装和运载体(如车辆)组成的产品运输包装系统的相关问题上效果显著。综述了运输包装中逆子结构理论的发展与完善及其在其他方面的应用成果、测量信息不完备下的逆子结构分析以及间接逆子结构分析。逆子结构理论的发展为了解运输过程中产品的动态特性提供了新的方法,也为今后运输包装的进一步发展提供了参考。     

三维编织复合材料紧固件剪切强度预报

建立了三维缎纹编织复合材料代表性体积单元(RVE)和紧固件剪切试件模型,引入周期性边界条件,建立了材料的宏观力学性能预报方法,并采用跨尺度计算方法对不同受载角度下的紧固件剪切破坏过程进行了有限元模拟。进行了三维缎纹编织复合材料紧固件的剪切试验,有限元计算结果与试验结果吻合较好,验证了本方法的可行性。分析了不同受载角度对剪切破坏模式及强度的影响,结果表明,该编织复合材料剪切强度随受载角度增大而降低,且具有不同的损伤起始位置和扩展过程。     

The Densification of Cu／Ti System by Spark Plasma Sintering

In order to unclose the dynamics of SPS densification, a special sintering sample (Cul Ti wires compact) was designed. Characters of the shrinkage rates during sintering process and mierostructures of products fabrieated by the spark plasma sintering( SPS ) and hot-press .sintering were investigated. The experimental results reveal that a higher temperature field is formed at the connected area and conductive net of the compact. These high-temperature parts deformed more easily than other parts, which is believed to be the main cause of SPS fast densification, according to a hard-core and soft-hell material model.     

ZBO(ZnO∶B)靶材烧结机理与特征的研究

用常压烧结方法，在1200℃-1350℃烧结不同含B量的掺硼氧化锌（ZBO）靶材。研究了掺杂量、烧结温度对ZBO靶材微观结构的影响。实验表明，随着烧结温度的增加。ZBO陶瓷的晶粒大小和密度逐渐增大。指出了由于B2O3的挥发，造成ZBO靶材的剩余含B量与掺B量的不符，要获得含定量B的ZBO就必须掺入大约2倍所需量的B2O3。     

华龙一号包络功率形状验证方法研究

堆芯功率分布可用径向功率分布和轴向功率分布分别描述,功率分布对堆芯偏离泡核沸腾（DNB）具有较高的重要性。核电厂在运行过程及事故过程中可能出现的功率分布各不相同,为有效简化热工水力设计及事故分析所需的功率形状,根据事故过程中功率分布的变化程度以及核电厂保护系统特性,将事故分析所需的极限功率形状分类包络。根据华龙一号的保护系统设置,以堆芯功率能力分析方法为基础,介绍了华龙一号工况Ⅰ包络功率形状和参考功率形状的验证方法。计算结果表明,工况Ⅰ包络功率形状和参考功率形状分别为各自适用场景下的包络功率形状。结果不仅有助于工程设计人员快速理解包络功率形状的验证方法,也有利于包络功率形状在后续事故分析中合理使用。     

脉冲电流加热条件下原子的扩散研究

脉冲电流热加工(pulse electric current heat treatment,PECHT)具有低温、快速的特点。研究了脉冲电流烧结过程中温度和脉冲比对Fe烧结体性能的影响,并与相同温度、压力和保温时间下辐射加热热压烧结的Fe烧结体进行了比较。结果表明：脉冲电流烧结在较低温度下样品就能获得更高的致密度。脉冲比(ON／OFF)对烧结有很大影响,说明脉冲电流加热促进了颗粒之间的原子扩散。同时,脉冲电流加热烧结和辐射加热烧结过程中Al2O3和Cu的收缩曲线也为脉冲电流加热条件下扩散加强提供了佐证。2种加热条件下接触线之间原子扩散的研究表明：脉冲电流加热促进了原子的扩散。     

纳米微晶结构氧化锌中激子发光的研究进展

由于ZnO具有大的激子束缚能,有利于在室温下获得高效稳定的紫外辐射.因此,对ZnO激子发光的研究极有希望解决半导体照明、紫外半导体激光器等多种技术面临的瓶颈问题.综述了ZnO中激子的典型光致发光谱、激子的结构及复合发光过程.重点介绍了温度、激发功率、量子限域效应以及激光辐照等因素对ZnO激子发光的影响.