Fabrication and Thermal Dissipation Properties of Carbon Nanofibers Derived from Electrospun Poly(Amic Acid) Carboxylate Salt Nanofibers

Polyimides (PIs) possess excellent mechanical properties, thermal stability, and chemical resistance and can be converted to carbon materials by thermal carbonization. The preparation of carbon nanomaterials by carbonizing PI‐based nanomaterials, however, has been less studied. In this work, the fabrication of PI nanofibers is investigated using electrospinning and their transformation to carbon nanofibers. Poly(amic acid) carboxylate salts (PAASs) solutions are first electrospun to form PAAS nanofibers. After the imidization and carbonization processes, PI and carbon nanofibers can then be obtained, respectively. The Raman spectra reveal that the carbon nanofibers are partially graphitized by the carbonization process. The diameters of the PI nanofibers are observed to be smaller than those of the PAAS nanofibers because of the formation of the more densely packed structures after the imidization processes; the diameters of the carbon nanofibers remain similar to those of the PI nanofibers after the carbonization process. The thermal dissipation behaviors of the PI and carbon nanofibers are also examined. The infrared images indicate that the transfer rates of thermal energy for the carbon nanofibers are higher than those for the PI nanofibers, due to the better thermal conductivity of carbon caused by the covalent sp² bonding between carbon atoms.     

Making reusable reaction-bonded silicon nitride crucibles for silicon casting from kerf-loss silicon waste

Silicon kerf loss during wafer slicing and the broken quartz crucibles after silicon casting are two major solid wastes from photovoltaic (PV) industry. Especially, the recycle of kerf-loss silicon has become an urgent issue because near 100 000 t of solid wastes are generated every year. One of the most meaningful recycle routes of the kerf-loss silicon is to make silicon nitride crucibles to replace the quartz crucibles. In this study, we demonstrated how this is feasible through acid leaching refining, slip casting, and nitridation. The reaction-bonded silicon nitride (RBSN) crucibles after oxidation were found pure enough for silicon ingot growth. More importantly, they could be reused after ingot growth. With the present examples, the potential of using the kerf-loss silicon for fine ceramics is prominent.     

广东省水利厅办公业务资源系统体系结构与功能技术特点

通过介绍广东省水利厅办公业务资源系统的建设思路、体系结构和功能技术特点,推介一些改进和发展办公业务系统的思路和方法,提出信息系统可持续发展的观点,探索面向政府部门的综合政务网上协同办公平台的构建方法。     

南京绿博园主展馆钢结构设计

介绍了南京绿博园主展馆钢结构的设计概况、整体静动力分析、斜柱和起伏翻折屋面的处理,对关键梁柱节点的构造进行了探讨,提出了柱外环加劲板的计算方法并推导出简便计算公式,供同类设计参考。     

Co64Fe11Nb5Si12B8合金磁导率与温度的关系

采用铁芯测试仪测得合金样品的初始磁导率随温度的变化曲线, 用磁化强度小角旋转法测量非晶及晶化合金条带的饱和磁致伸缩系数λs;研究了不同温度退火后Co64Fe11Nb5Si12B8合金的磁导率随温度的变化、磁性以及磁致伸缩系数;结果表明:合金在580、590℃热处理磁性变好的反常现象是由于磁致伸缩系数变小所致.     

辽河断陷西部凹陷欢喜岭——曙光斜坡储层特征

对辽河断陷西部凹陷欢喜岭-曙光斜坡（西斜坡）古近系砂岩储层的岩石组合、孔隙类型、孔隙特征等进行研究,同时进行了储集性能及储集性能影响因素评价。结果表明：研究区砂岩储集层的储集物性差别很大,不但不同层位,即使同一层位砂岩的储集性能差别也很大。砂体产状特征对物性有一定的影响,单层砂体较厚的储层往往比薄层砂储层的物性要好;影响研究区砂岩储层储集性能的主要因素有：沉积作用、成岩作用、物源区母岩岩性、断裂活动及古地形等。多数情况下,储层的储集性能受成岩作用的影响更大一些,甚至是决定性的。     

“都灵V”内腔膜厚的提高

电泳漆膜厚度是衡量电泳漆质量的一项关键性指标,直接影响到涂层的耐腐蚀性与丰满度。针对IVECO“都灵V”车身内腔电泳漆膜厚偏低的问题,进行了工艺分析,采取调整电泳施工工艺参数、设计辅助阳极等措施,使得车身内电泳漆膜厚度达到工艺要求,并同步改善了车身电泳膜厚的均一性。     

烷基糖苷平均聚合度和α-,β-吡喃葡糖苷比例影响因素的研究

以一水葡萄糖、月桂醇为原料 ,对甲苯磺酸为催化剂 ,经直接苷化法合成了月桂基葡糖苷 ,对产品结构进行了表征 ,计算了烷基多苷的平均聚合度、α 吡喃糖苷和 β 吡喃糖苷的比例。考察了反应条件对平均聚合度、α 和 β 吡喃糖苷比例及吡喃糖苷与呋喃糖苷比例的影响。结果表明 :通过改变醇糖摩尔比、反应温度、催化剂用量、反应时间等条件可有效控制平均聚合度、α 和 β 吡喃糖苷比例及呋喃糖苷的生成     

双组分催化剂作用下的碳酸二甲酯直接合成

在双组分催化剂的作用下 ,由CO2 、甲醇和环氧烷烃直接合成碳酸二甲酯 (DMC)。研究了反应条件对反应的影响 ,得到最佳反应条件为 :反应时间 2h ,温度 1 60℃ ,加入无机碱 7.5g和Lewis酸 5 .0g ,在此条件下DMC的收率达 1 1 .75 %。通过改变催化剂组成研究了反应机理     

5-甲基-2-(对-N,N-二苯氨基苯基)-4-乙酰基噁唑的合成

将亚硝酸钠溶液加入到溶于冰醋酸中的乙酰丙酮中 ,温度保持在 0～ 5℃得到了羟亚氨基乙酰丙酮 (Ⅰ ) ,产率 4 4 %。对 N ,N 二苯氨基苯甲醛 (Ⅱ )由三苯胺、N ,N 二甲基甲酰胺、三氯氧磷经Vilsmeier反应合成 ,产率 89%。羟亚氨基乙酰丙酮和对 N ,N 二苯氨基苯甲醛溶于冰醋酸中 ,在干燥的氯化氢作用下 ,温度保持在 0～ 5℃ ,首先生成盐酸盐中间体 (Ⅲ ) ,然后控制温度为 4 0～ 5 0℃ ,盐酸盐在冰醋酸中经锌粉还原为 5 甲基 2 (对 N ,N 二苯氨基苯基 ) 4 乙酰基口恶唑 (Ⅳ ) ,反应时间 3h ,产率 2 2 %