助剂对Pd/AC催化剂催化三氟氯乙烯加氢脱氯的影响

采用等体积浸渍法制备了Cu-Pd/AC和K-Pd/AC催化剂,分别考察了Cu和K助剂添加量对三氟氯乙烯加氢脱氯生成三氟乙烯的反应性能的影响,并采用N_2-物理吸附、X射线粉末衍射(XRD)测试、透射电镜(TEM)和H_2-程序升温还原(TPR)等对催化剂进行表征。结果表明:加入助剂Cu,其与Pd形成Pd-Cu合金,抑制催化剂的加氢性能,从而降低催化剂反应活性;加入助剂K,其改变了Pd的电子结构,增强了Pd的电子云密度,使Pd活化H的能力增强,从而提高催化剂的活性。助剂K质量分数为3%的催化剂,在250℃下,具有较好的催化活性,三氟氯乙烯的转化率可达90%左右,三氟乙烯的选择性可达85%左右。     

Composition and characteristics of primary combustion products of boron-based propellants

Primary combustion products of boron-based propellants are incomplete combustion products that are emitted from the gas generator of a solid ducted rocket. Studying the composition of primary combustion products provides valuable information about the primary combustion process and also helps to better understand the secondary combustion process. The particle size of the primary combustion products is analyzed by a laser particle size analyzer. The qualitative analysis of the sample composition is performed by using x-ray diffraction, x-ray photoelectron spectroscopy, and thermogravimetry–differential scanning calorimetry experiments. Based on these results, an integrated quantitative analysis of the sample composition is conducted. The quantitative analysis methods include tube furnace heating, ion chromatography, infrared spectroscopy, and inductively coupled plasma chromatography. In addition, scanning electron microscopy and energy dispersive spectrometry are also used to analyze the micro-morphology and distribution of different components in the sample. The primary combustion products mainly contain B, C, B _m C _n , H₃BO₃, B₂O₃, BN, Mg, MgCl₂, and NH₄Cl. B _m C _n (22–24%), H₃BO₃ (20%), and B (16.8%) are the three major components, while B _m C _n , B, and C (9.8–11.8%) are the three combustible components present in the highest amounts. The oxidant NH₄ClO₄ is completely consumed during the primary combustion, while the metal additive Mg does not show much reactivity. The micro-morphology and distribution of B _m C _n , H₃BO₃ (or B₂O₃), B, Mg, and C in the sample are investigated. Some components in the primary combustion products are found to be agglomerated, while some components are dispersed. Large particles in the sample mainly include B and Mg, while B _m C _n , H₃BO₃ (or B₂O₃), and C particles are small. In general, the combustion completeness of the primary combustion products is rather low. Therefore, better understanding and controlling of the secondary combustion process is very important to improve the performance of B-based propellants.     

Numerical Simulation of Particle Dispersion in the Wake of a Circular Cylinder

In this article, numerical simulation of the Navier-Stokes equations was performed for the large-scale structures of a two-dimensional temporally developing cylinder flow and the associated dispersion patterns of particles were simulated. The time-dependent Navier-Stokes equations were integrated in time using a mixed explicit-implicit operator splitting rules. The spatial discretization was processed using spectral-element method. Non-reflecting conditions were employed at the outflow boundary. Particles with different Stokes numbers were traced by the Lagrangian approach based on one-way coupling between the continuous and the dispersed phases.

The simulation results of the flow field agree well with experimental data. Due to the effects of the coherent structures, the particles demonstrate a more organized dispersion process in the space and a periodic dispersion characteristic in the time. Particle dispersion increases with the flow Reynolds number and so does for particle concentration, which is independent of particle size. However, for particles at different Stokes numbers, the dispersion patterns are different. The particles at smaller Stokes number congregate mainly in the vortex core regions and the particles at larger Stokes number disperse much less along the lateral direction with the even distribution. The higher density distribution at the outer boundary of large-scale vortex structure characterizes the dispersion pattern of particles at the Stokes numbers of order of unity. Furthermore, these particles disperse largely along the lateral direction and show the nonuniform distribution of concentration.     

钢制薄壁内压短圆筒承载能力的试验研究

通过试验对16 MnR钢制薄壁内压短圆筒的承载能力进行了研究;建立了薄壁短圆筒屈服强度和爆破强度的经验公式;得到了区分内压长短圆筒的临界长度计算公式;分析了封头结构对16 MnR钢制薄壁短圆筒屈服强度和爆破强度的加强程度和加强范围的影响。结果表明:标准椭圆封头对短圆筒爆破强度的加强范围比屈服强度的广;碟形封头对短圆筒爆破强度和屈服强度的加强范围基本无差异;标准椭圆封头对16MnR钢制薄壁内压短圆筒屈服强度和爆破强度的加强作用比采用碟形封头的大,其加强范围也比采用碟形封头的广。     

抗肝炎类瑶族药的研究现状

对瑶族民间抗肝炎植物药进行了较系统的研究和调查,有属于33科47种的植物药有抗肝炎作用。并对其中的野葛花、枸骨叶、白马骨和小紫金牛护肝作用进行了初步的研究。     

中国南海总状蕨藻中脂肪酸和甾醇GC-MS分析

采用GC—MS分析中国南海总状蕨藻中的脂肪酸及甾醇化合物,鉴定出二十三种脂肪酸及四种甾醇。其中脂肪酸主要为十六碳酸(34．42％)、9,12,15-十八碳三烯酸(10．39％)、9,12-十八碳二烯酸(7．63％)、7,10．13-十六三烯酸(5．60％);甾醇主要为穿贝海绵甾醇。     

聚丙烯/玻璃纤维的界面改性研究(Ⅱ)聚丙烯-马来酸酐接枝共聚物的界面改性研究

研制高性能的玻璃纤维增强聚丙烯复合材料的关键是提高非极性的聚丙烯和极性的玻璃纤维的界面粘结强度。本文首次明确提出接枝率、熔融指数、结晶温度是影响聚丙烯 -马来酸酐接枝共聚物作为界面剂使用的关键因素 ,当接枝共聚物的接枝率高、熔融指数大、结晶温度与聚丙烯基体接近时 ,接枝共聚物有较好的界面改性效果 ,可以使用较少量的接枝共聚物使复合材料的力学性能得到最大程度的改善。     

过程参数对微型机械模内组装成型流固耦合变形影响

聚合物模内组装成型,是解决聚合物微型机械成型加工技术难题的先进成型技术,其成型的微型零件的制造精度和零件组装配合精度,主要受控于二次成型熔体充填流动与固体微型零件之间的流固耦合作用。该文通过有限元数值模拟技术,研究聚合物微型机械模内组装二次成型过程参数,对一次成型固体微型零件的流固耦合作用效应和流固耦合变形的影响规律。研究结果表明,增加二次成型熔体注射速度,可使二次成型熔体的充填流动与一次成型固体微型轴表面间的流固耦合作用效应增强,并使一次成型微型零件整体温度场趋于均匀,从而导致一次成型固体微型零件流固耦合弯曲应力和弯曲变形增加,热应力和热变形减小;降低二次成型熔体注射速度,可提高聚合物微型机械模内组装成型的成型加工精度及组装配合的精度。