Fire signatures of spacecraft materials: Gases and particulates

The primary goal of this research is to create a database of fire signatures for practical spacecraft materials in a new combustion facility and to provide recommendations for the development of improved fire sensors for future space exploration. During a fire, foams and plastics can generate three types of residues: condensables, light gases, and particulates (soots). The residues were characterized by gas chromatography (GC), Fourier transform infrared spectroscopy (FTIR), and transmission electron microscopy (TEM). These analyses were performed as a function of oxygen occurrence, temperature, and convective flow direction relative to the normal gravitational vector. Among the four polymers studied in this work, forced convective flow direction has a great impact upon particulate yield. Variation of light gases with temperature and different atmospheres turn out to be more convoluted. Particulates can be used as fire signature for most of the materials; nevertheless no single species serves as a reliable indicator for any given material.     

Microwave-assisted hydrothermal synthesis of zinc oxide particles starting from chloride precursor

Zinc oxide (ZnO) was synthesized using a microwave assisted hydrothermal (MAH) process based on chloride/urea/water solution and under 800 W irradiation for 5 min. In the bath, Zn²⁺ ions reacted with the complex carbonate and hydroxide ions to form zinc carbonate hydroxide hydrate (Zn₄CO₃(OH)₆·H₂O), and the conversion from Zn₄CO₃(OH)₆·H₂O to ZnO was synchronously achieved by a MAH process. The as-prepared ZnO has a sponge-like morphology. However, the initial sponge-like morphology of ZnO could change to a net-like structure after thermal treatment, and compact nano-scale ZnO particles were finally obtained when the period of thermal treatment increased to 30 min. Pure ZnO nanoparticles was obtained from calcination of loose sponge-like ZnO particles at 500 °C. The analysis of optical properties of these ZnO nanoparticles showed that the intensity of 393 nm emission increased with the calcination temperature because the defects were reduced and the crystallinity was improved.     

橡胶呼吸器面罩罩体注射模设计

通过采用ANSYS Workbench有限元分析软件对橡胶呼吸器面罩罩体注射模结构强度进行了有限元分析,为罩体注射模的结构设计和材料选择提供了理论依据,降低了模具设计风险。呼吸器面罩罩体注射模投入生产3年多,模具工作状况良好,极大地提高了生产效率和产品外观质量,降低了劳动强度和生产成本。     

Mesoporous activated carbon fiber as electrode material for high-performance electrochemical double layer capacitors with ionic liquid electrolyte

Activated carbon fibers (ACFs) with super high surface area and well-developed small mesopores have been prepared by pyrolyzing polyacrylonitrile fibers and NaOH activation. Their capacitive performances at room and elevated temperatures are evaluated in electrochemical double layer capacitors (EDLCs) using ionic liquid (IL) electrolyte composed of lithium bis(trifluoromethane sulfone)imide (LiN(SO₂CF₃)₂) and 2-oxazolidinone (C₃H₅NO₂). The surface area of the ACF is as high as 3291 m² g⁻¹. The pore volume of the carbon reaches 2.162 cm³ g⁻¹, of which 66.7% is the contribution of the small mesopores of 2-5 nm. The unique microstructures enable the ACFs to have good compatibility with the IL electrolyte. The specific capacitance reaches 187 F g⁻¹ at room temperature with good cycling and self-discharge performances. As the temperature increases to 60 °C, the capacitance increases to 196 F g⁻¹, and the rate capability is dramatically improved. Therefore, the ACF can be a promising electrode material for high-performance EDLCs.     

过电离层核爆电磁脉冲信号模拟源的实现

设计一种数字式核爆电磁脉冲信号源模拟装置。大气层核爆电磁脉冲纵向传输经过电离层后的信号属于瞬态脉冲信号,频率范围为30 MHz～300 MHz,因为电离层对电磁脉冲信号的色散特性,脉冲信号高频部分出现的时刻早于低频部分出现的时刻。基于DSP+DDS数字电路实现了30 MHz～300 MHz频率色散瞬态脉冲信号的输出,其输出频率的最小控制周期为4 ns,幅值可调、波形规则、可靠性高、调试方便,实验证明模拟信号反映了大气层核爆电磁脉冲信号过电离层后的主要特征。     

时间-计数转换方法对提高核辐射测量效率的改进

以半导体探测器用电荷灵敏放大电路为例进行了时间-计数转换方法的应用研究及计算,目的是从硬件上提高测量线性度,提高最高计数率,改善电路的有效测量量程。     

α/β放射性气溶胶的小流量采样快速测量技术研究

针对放射性气溶胶监测仪的便携要求,设计了一套小流量采样快速测量系统和测量方法。采用累积采样累积测量的方式,联合利用能量甄别修正法与α/β比值法去除Rn子体的干扰,实现小流量采样条件下的α/β放射性气溶胶的同时监测。通过对探测下限的分析,表明该方法可满足应急监测的需求,为便携式α/β放射性气溶胶监测仪设计提供了参考。     

常温低压微功耗电荷灵敏放大电路的设计和测试

就辐射测量的一种常温低压微功耗的半导体探测器用电荷灵敏前放电路进行了设计、计算、仿真和测试,对其实用性进行了分析,并提出了使用改进建议。     

高性能超级电容器用高比表面积、层次孔结构炭材料的简便制备(英文)

采用NaOH一步炭化-活化聚偏二氯乙烯(PVDC)简便制备出高比表面积、层次孔结构炭材料。该炭材料具有发达的微孔-中孔-大孔的层次孔结构,其比表面达到2 815 m·2g-1。独特的微结构使其在无机和有机电解液中都表现出高的比电容和优异的大电流性能。其在6 mol·L-1KOH电解液中以0.05 A·g-1电流充放电测得的比电容高达376F·g-1,电流密度增大到50A·g-1比电容还保持215 F·g-1。在有机电解液1 mol·L-1Et4NBF4/AN中的比电容也达到170 F·g-1(电流密度0.05 A.g-1),电流密度增大到20A·g-1比容量还保持124F·g-1。     

环氧树脂/丙烯酸树脂自分层影响因素研究

对丙烯酸树脂和环氧树脂间的自分层行为进行了研究。研究了不同种类固化剂、湿膜厚度、底材对自分层的影响。试验结果表明:聚酰胺类固化剂利于体系自分层;表面能高的马口铁和玻璃板底材出现自分层,表面能低的聚四氟乙烯底材没有出现自分层;湿膜厚度对自分层影响不大。