Understanding on the hydrogen detection of plasma sprayed tin oxide/tungsten oxide (SnO2/WO3) sensor

The plasma spray technique was well proven in producing metal oxide based gas sensors in the last two decades using different powder feedstocks. However, limited research was made to fabricate hydrogen gas sensor from tin oxide layer coated over tungsten oxide layer. This paper attempts to interpret the hydrogen gas sensing performances of plasma sprayed coating derived by depositing tin oxide layer over tungsten oxide (SnO₂/WO₃) layer. Plasma sprayed SnO₂/WO₃ sensor showed maximum response of 90% at 150 °C in contrast to stand-alone WO₃ (89% at 350 °C) and stand-alone SnO₂ (89% at 250 °C). The lower operating temperature of SnO₂/WO₃ sensor without compromising gas response was attributed to the WO₃–SnO₂ hetero-junction. SnO₂/WO₃ sensor showed selective sensing towards hydrogen with respect to carbon monoxide and methane gases. This sensor also possessed repeatable characteristics after 39 days from the initial measurement. In a nut-shell, plasma spayed SnO₂/WO₃ sensor showed stability of base resistance, repeatability after successive response and recovery cycles, selective sensing towards 500 ppm H₂ with significant magnitude of gas response of 90%, response time of 35 s and recovery time of 269 s at a temperature of 150 °C.     

Influence of thermal runaway in styrene–acrylonitrile bulk copolymerization revealed by computational fluid dynamics modeling

The computational fluid dynamics (CFD) and kinetic-based moment methods coupled approach is adopted to simulate the bulk copolymerization of styrene–acrylonitrile (SAN) in a stirred tank reactor. Numerical simulations are carried out to investigate the impacts of impeller speed, monomer ratio, initiator ratio, and initial reaction temperature on the copolymerization process and product properties. Particularly, the Chaos theory is selected as a criterion for evaluating the occurrence of the thermal runaway. The Flory's and Stockmayer's distributions are employed to calculate chain length distribution and copolymer composition distribution of copolymer. The simulation results highlight that the appearance of thermal runaway can be postponed by properly increasing the rotation speed, decreasing the initiator loadings, initial acrylonitrile contents and initial reactor temperature. Furthermore, significant differences exist in the product properties that predicted by the ideal and non-ideal models, which demonstrates that the temperature heterogeneity plays a crucial role in SAN copolymerization. This study could offer references for the safe operation and design of polymerization processes.     

钨中空位及其团簇的能量学和动力学性质参数

在总结前人钨中空位及其团簇的能量学和动力学行为的研究成果基础上，采用第一性原理方法系统计算了钨中空位及其团簇的结合能和扩散能垒。研究发现，交换关联泛函PW91和PBE较PBEsol、AM05和LDA更适合用于计算钨空位的能量学性质。基于第一性原理计算结果对文献中单空位形成能、双空位作用性质等争议性问题进行了讨论，并对钨经验势进行了评估。研究结果表明，钨中孤立单空位间总是相互排斥，而空位团簇（V_n>3）对单空位具有很强的吸引作用，其结合能随着所含空位个数增多呈现波动性增大的趋势。空位团簇稳定结构可通过最小化Wigner-Seitz表面积来确定，其结合能与V_n与V_n-1之间的Wigner-Seitz面积之差呈正比。     

朝凯煤矿露天台阶爆破装药结构优化应用研究

本文以神达朝凯煤矿正在开采的台阶为工程背景,针对该矿在台阶爆破过程中存在着大块率高、根底多的现象,通过改变装药结构的方式对爆破参数进行优化。实践证明,优化后大块率和根底问题的治理效果明显。     

2219铝合金搅拌摩擦焊和钨极保护焊焊接件残余应力的中子衍射研究

利用中子衍射法对2219铝合金搅拌摩擦焊（FSW）和钨极保护焊（TIG）焊接件开展了三维残余应力测量，并对残余应力分布规律进行了分析。结果表明：焊接件的纵向残余应力数值较大；FSW焊接件残余应力整体较TIG焊接件的小；FSW和TIG焊接件的残余拉应力最大值分别为101 MPa和174 MPa，FSW焊接件残余拉应力最大值较TIG焊接件的小；FSW残余拉应力最大值处于轴肩边缘，且前进侧峰值大于后退侧峰值；TIG焊接件残余拉应力最大值处于焊缝边缘。通过中子衍射实验获得的焊接件残余应力分布，将可用于焊接工艺的优化与焊接件的寿命预测。     

基于地质雷达与孔内摄像的爆破防漏施工方法

为了解决在裂隙溶洞岩体条件下,散装炸药由于良好的流动性,容易发生炸药泄漏,形成安全隐患并影响爆破效果的问题。结合具有典型喀斯特地貌特征的贵阳龙洞堡机场三期扩建工程中露天爆破施工的实际情况,以检测数据为基础,提出了一种适用于不良地质条件的散装炸药施工新方法。设计前,对爆区采用地质雷达进行地质检测,探测地下溶洞等不良构造,基于探测数据有针对性的进行爆破设计;使用孔内摄像技术对炮孔内部条件进行检测,从而确定可能发生炸药泄漏的位置。在施工过程中,采用分段装药、包装炸药隔离、高强度聚乙烯膜柔性隔离等技术控制炸药泄漏。在龙洞堡机场扩建工程的露天爆破中应用结果表明,合理运用该技术,可以有效避免混装炸药因泄漏而流失,从而改善裂隙岩体条件的爆破效果。     

中国散裂中子源靶体研制

中国散裂中子源(CSNS)靶体选用钨为靶材、钽为包覆层，采用包套法结合热等静压扩散焊工艺制备了钽包覆钨靶片。经检测，钨钽界面结合良好，钽层与钨基体平均结合强度大于64.07 MPa。靶体将钨靶片分成厚度不等的11片，散热采用一进一出的并行流结构，利用CFD软件进行了模拟计算，钨靶片间冷却流道间隙为1.2 mm，100 kW满功率运行情况下靶体最高温度为182.3 ℃，冷却水温升为7.1 ℃。经过半年多的试运行，CSNS靶体各参数满足CSNS的要求。