Theoretical study on a kind of cyclization mechanism of boron trichloride and hexamethyldisilazane to form the borazine ring for SiBCN ceramics precursor

Borazine rings act as a pivotal part in siliconboroncarbonitride ceramics (SiBCN) for high-temperature stability and great resistance to crystallization. A detailed investigation of the ring formation mechanism will guide the design and synthesis of SiBCN to meet application requirements under extreme conditions. Boron trichloride (BCl₃) and hexamethyldisilazane (HN(SiMe₃)₂) are common raw materials for the synthesis of precursors for SiBCN. In this paper, quantum chemical calculation was used to study the cyclization reaction mechanism between BCl₃ and HN(SiMe₃)₂ to form trichloroborazine (TCBZ) at the MP2/6-31G (d,p) level of theory. We discussed the structure properties, reaction pathways, energy barriers, reaction rates, and other aspects in detail. The results show that BCl₃ and HN(SiMe₃)₂ alternately participate in the reaction process, accompanied by the release of trimethylchlorosilane (TMCS), and that the entire reaction shows an absolute advantage in terms of energy. In the Step by step reaction, lower reaction barriers are formed due to the introduction of BCl₃ with more heat released compared to that for the introduction of HN(SiMe₃)₂. The final single-molecule cyclization and TMCS elimination steps are found to be faster compared to all previous bimolecular reactions.     

汽车密封件双料一体旋转模具设计

针对PP+TPE汽车密封件设计了大型双料一体旋转注射模,介绍了二次合模的精确定位、可控注射系统、顶出平衡设计。该模具技术能够使两种性能完全不同的材料按照指定区域分布,并且达到塑件尺寸的精度需求,实现同时与钣金、玻璃、塑件等不同材质的零件进行复合配套。本项目实施后,在模具精度、寿命等方面接近或部分达到国外同类产品先进水平,而价格仅为国外产品的40%,性价比优势明显。     

一种X射线环焊缝图像质量评价方法

为了缩小增强后环焊缝图像质量主客观评价的差距,提出了一种基于人眼视觉的无参考质量评价指标。通过分析人眼的视觉特性,建立图像模糊评价模型,设定主观评价方法;主客观评价值进行曲线拟合,经验证,评价结果与主观评价结果具有线性拟合关系,评价结果接近人眼最佳视觉,验证了评价指标的可行性。     

加氢反应器头盖密封质量控制探讨

加氢反应器是加氢装置的重要组成部分,反应器头盖因工况复杂,导致密封难度较大,密封不严,会导致整个装置不能正常运转。为此,就其头盖拆装及密封问题进行探讨,提出有效的质量控制措施。     

Simulation studies on a rotating ring disk electrode: Effects of ionic migration with kinetic complication-disk results

In continuation to my previous work (Guha S. AIChE J. 2013;59(4):1390-1399), in this work, effects of ionic migration are evaluated for disk region of a rotating ring disk electrode system by numerically solving complex differential equations, developed for mass transfer along with kinetic complication in presence of ionic migration under limiting current condition. The system for simulation is 0.01 M Fe₂(SO₄)₃ solution with H₂SO₄ as supporting electrolyte. Simulation cases are presence and absence of ionic migration with kinetic complication (oxidation of Fe²⁺ to Fe³⁺ under O₂ pressure). Results show that concentration boundary layer thickness of reactant Fe³⁺ reduces appreciably and steady-state disk current reduces substantially in presence of migration. Simulated steady-state disk current in absence of migration case agrees well with published data. Results indicate higher Fe²⁺ concentration in presence of migration and thereby higher rate of oxidation of Fe²⁺ to Fe³⁺ at all rate constant values.     

木片筛余物高得率半化学法清洁制浆技术研究

以太阳纸业备料车间木片筛选碎料（筛余物）为原料，对其烧碱法半化学制浆的实验室工艺和生产试验进行了研究。结果表明，筛余物采用半化学法制浆可获得较高得率和环压强度的纸浆，且用碱量对纸浆性能有显著影响。相对8%NaOH （相对于绝干原料）化学预处理，采用14%NaOH化学预处理结合两段浆浓22%的高浓磨浆工艺，所制半化学浆抄造浆张的裂断长和环压指数分别达2.89 km和9.76 N·m/g，是前者的1.9倍和1.2倍，而且优于现用国内OCC废纸浆抄造浆张；生产试验得到的浆张性能指标与实验室相吻合，其中紧度和环压强度分别达到GB/T 13023—2008瓦楞芯（原）纸AA级和A级优等品要求。     

磁流体端面动压润滑特性的试验研究

以非接触式机械密封为原型,建立磁流体端面动压润滑试验装置,研究转速、被密封介质压力、磁场强度对液膜润滑特性的规律;同时基于Muijderman窄槽理论,建立磁流体动压润滑特性的解析计算方法,并将解析计算结果与试验结果进行对比分析。结果表明:随转速和被密封介质压力增大,摩擦扭矩、泵送量均增大,而膜厚均减小;随着磁场强度增大,摩擦扭矩增大,泵送量和膜厚减小;相比于转速和密封介质压力,磁场强度对磁流体的动压润滑性能的影响尤为显著,因而当工况变化时可以通过调节磁场强度使密封性能始终保持在最佳工作范围。解析计算方法得到的结果与试验结果基本趋势一致,即验证了试验方法的可靠性,也表明提出的解析计算方法可用于流体动压润滑性能的预测。     

热效应影响下浮环轴承润滑静特性研究

建立计入热效应的浮环轴承流体动压润滑模型,利用数值差分法联立求解雷诺方程,进而求解浮环轴承端泄流量;通过与实验数据的对比,验证所建模型的正确性;考虑浮环受热膨胀变形的影响,研究供油温度对摩擦功耗、温升、浮动环转速、端泄流量等浮环轴承润滑静特性参数的影响。结果表明:提高润滑油供油温度会明显提升浮动环旋转速度,增大轴承内间隙的供油量,减小内外油膜摩擦功耗和端泄温升;端泄温升随轴颈转速的升高而增大,温升随轴颈转速变化的幅度在采用较低温度的润滑油时表现得更为剧烈。