Pressureless sintered silicon carbide matrix with a new quaternary additive for fully ceramic microencapsulated fuels

This study suggests a new additive composition based on AlN–Y₂O₃–Sc₂O₃–MgO to achieve successful densification of SiC without applied pressure at a temperature as low as 1850 °C. The typical sintered density, flexural strength, fracture toughness, and hardness of the SiC ceramics sintered at 1850 °C without applied pressure were determined as 98.3%, 510 MPa, 6.9 MPa·m^1/2, and 24.7 GPa, respectively.Fully ceramic microencapsulated (FCM) fuels containing 37 vol% tristructural isotropic (TRISO) particles could be successfully sintered at 1850 °C using the above matrix without applied pressure. The residual porosity of the SiC matrix in the FCM fuels was only 1.6%. TRISO particles were not damaged during processing, which included cold isostatic pressing under 204 MPa and sintering at 1850 °C for 2 h in an argon atmosphere. The thermal conductivity of the pressureless sintered FCM pellet with 37 vol% TRISO particles was 44.4 Wm^?1 K^?1 at room temperature.     

绍鸭胰岛的分型与分布

绍鸭胰脏分背叶、腹叶和脾叶。本实验用常规染色及ABC免疫组织化学方法,研究胰脏三叶内高血糖素、胰岛素和生长抑素免疫反应细胞(分别称为A、B和D细胞)的形态、相互关系和胰岛的分型分布。结果表明;绍鸭胰岛分三型,即A胰岛、B胰岛和混合型胰岛。三型胰岛分布于胰脏各叶。A胰岛由大量A细胞及散布具内的D细胞组成;B胰岛由团索状排列的B细胞或在其周缘含少量D细胞组成;混合型胰岛由中央的B细胞及周缘少量的A和D细胞组成。A和D细胞还散布在外分泌部和胰导管上皮及周围结缔组织中,并常伸出旁分泌样胞质突起。     

Effects of starting powder on microstructure and thermal conductivity of pressureless-sintered fully ceramic microencapsulated fuels

The effects of the starting SiC powder (α or β) with the addition of 5.67 wt% AlN–Y₂O₃–CeO₂–MgO additives on the residual porosity and thermal conductivity of fully ceramic microencapsulated (FCM) fuels were investigated. FCM fuels containing ～41 vol% and ～37 vol% tristructural isotropic (TRISO) particles could be sintered at 1870 °C using α-SiC and β-SiC powders, respectively, via a pressureless sintering route. The residual porosities of the SiC matrices in the FCM fuels prepared using the α-SiC and β-SiC powders were 1.1% and 2.3%, respectively. The thermal conductivities of FCM pellets with ～41 vol% and ～37 vol% TRISO particles (prepared using the α-SiC and β-SiC powders, respectively) were 59 and 41 Wm^?1K^?1, respectively. The lower porosity and higher thermal conductivity of FCM fuels prepared using the α-SiC powder were attributed to the higher sinterability of the α-SiC powder than that of the β-SiC powder.     

近岸岛屿联合作战船艇装备保障力量需求分析

船艇装备保障力量需求分析研究是近岸岛屿联合作战船艇装备保障力量运用的重要前提。结合船艇装备保障的特点和任务对保障力量进行了定性需求研究,分析了海上船艇装备损坏的主要影响因素,重点围绕第1波次输送的不同阶段从战斗损伤和非战斗损伤2个方面对维修任务量、保障人员数量和保障程度的预测进行定量需求研究,并构建计算模型,为船艇装备保障力量的运用研究打下基础。