Low-temperature catalytic oxidation of chlorobenzene over MnOX/TiO2–CNTs nano-composites prepared by wet synthesis methods

Catalytic oxidation of chlorobenzene (CB) was studied over MnO_X/TiO₂–CNTs (carbon nanotube) nano-composites prepared by the solvothermal and sol–gel methods. Microstructures and redox properties of these composites were characterized by X-ray diffraction, electron microscopy, and temperature-programmed reduction. The catalytic activity for CB oxidation was promoted with the introduction of CNTs into MnO_X/TiO₂, and CB oxidation efficiencies of 90% and almost 100% could be obtained at 150 °C and 300 °C, respectively, under a gas hour space velocity of 36,000 h^− 1.The high catalytic performance could be attributed to the good dispersion of active component and the selective adsorption of CB by CNTs.     

Kinetic study of Diels–Alder reaction involving in maleimide–furan compounds and linear polyurethane

Linear polyurethane was synthesized by Diels–Alder (DA) reaction between a polyurethane prepolymer end-capped with furan rings (MPF) and bismaleimide (BMI). The polymerization kinetics were studied following a preliminary kinetic study of the DA reaction between furfuryl alcohol (FA) and BMI compounds by attenuated total reflection infrared, ultraviolet–visible and in situ ¹H NMR spectroscopies, where in situ ¹H NMR spectroscopy was selected as the analytical method of choice to study the DA reaction between MPF and BMI. The results showed that the reaction followed second-order kinetics, and the most beneficial experimental conditions to maximize conversion were identified.     

Effects of hydrolysis of precursor on the structures and properties of polymer-derived SiBN ceramic fibers

In this paper, polyborosilazane precursor was synthesied from HMDZ, HSiCl₃, BCl₃ and CH₃NH₂ using a multistep method. By controlling the storage conditions, parts of the polyborosilazane fibers were hydrolyzed. FT-IR, NMR, XRD, TEM and monofilament tensile strength test were employed to study the effects of hydrolysis of precursor on the structures and properties of polymer-derived SiBN ceramic fibers. FT-IR and NMR results indicate that Si-N group in PBSZ reacts with H₂O to form Si-O-Si group. After pyrolysis reaction at 1400℃, Si-O-Si group will finally transformed into highly ordered cristobalite and β-quartz, resulting in formation of the wrinkled surface of the obtained SiBN ceramic fiber. The strip-like defects on fiber surface, according to monofilament tensile strength test, had a significant effect on mechanical property of the obtained SiBN ceramic fiber and caused no increase in fiber tensile strength of hydrolytic polyborosilazane fiber before and after pyrolytic process.     

Material property requirements for analysis and design of UHTC components in hypersonic applications

Analytical modeling of thermal and mechanical response is a fundamental step in the design process for ultra-high-temperature ceramic components, such as nose tips and wing leading edges for hypersonic applications. The purpose of the analyses is to understand the response of test articles to high-enthalpy flows in ground tests and to predict component performance in particular flight environments. Performing these analyses and evaluating the results require comprehensive and accurate physical, thermal, and mechanical properties. In this paper, we explain the nature of the analyses, highlight the essential material properties that are required and why they are important, and describe the impact of property accuracy and uncertainty on the design process.     

复合溶胶–凝胶一锅法制备锂离子电池氧化亚硅/碳复合负极材料

采用复合溶胶–凝胶法结合后续热处理,制备了具有包埋结构的氧化亚硅/碳(SiO_x/C)复合负极材料。扫描电子显微镜分析结果表明:氧化亚硅纳米颗粒嵌入在无定形碳中。电化学性能测试表明:SiO_x/C复合材料具有较高的比容量、优异的循环稳定性和倍率性能。材料在0.1 A/g的电流密度下100次循环后的可逆比容量为710 m A·h/g,容量几乎无衰减;在1.6 A/g的电流密度下,可逆比容量为380 m A·h/g。优异的电化学性能是由于材料的包埋结构能有效地缓冲SiO_x充放电过程中的体积膨胀,保证材料的结构完整性和电化学循环稳定性。     

高硅铝合金T/R盒体激光封焊应力分析及优化设计

采用有限元软件MSC. Marc对高硅铝合金盒体焊接残余应力和真空服役状态下的内压应力进行分析,提出了封装盒体的优化设计方法. 考察了盒体形状、尺寸和盖板厚度对内压应力的影响规律,结果证明,内压应力随着短边边长的增大而增大,随着盖板厚度的提高而减少,基本不受长边边长变化的影响,指出窄长型盒体是提高盒体面积和降低内压应力进而提高可靠性的发展方向. 分析了试验用盒体的内压应力和残余应力叠加后的服役应力特点并进行了可靠性分析,指出内压应力和焊接应力的最大应力不在同一方向上,叠加后的等效应力小于两者加和. 讨论了盒体的极限尺寸,验证了试验用盒体服役状态下是可靠的.     

面向STEP-NC的零件可制造性评价方法研究与实现

在零件加工前,对其可制造性进行评价是实现零件智能化加工的一个关键环节。针对STEP-NC新型接口标准引入数控加工后的可制造性评价问题,提出了一种面向STEP-NC数控加工的零件可制造性评价方法。在对STEP-NC数控加工程序中工艺信息描述进行分析的基础上,建立了面向STEP-NC的机床信息模型,阐述了零件的可制造性评价目标,提出了实现零件可制造性评价的具体算法。基于Solidworks三维CAD平台,开发了面向STEP-NC的零件可制造性评价模块,并通过实例对所提方法的可行性与有效性进行了验证。     

国内CFB锅炉风帽存在问题及对策

介绍了国内CFB锅炉常用的几种主流风帽，分析了各种风帽的特点，并指出了其在应用中存在的问题，结合实际情况提出了相应的对策。     

A kinetic study of gaseous alkali capture by kaolin in the fixed bed reactor equipped with an alkali detector

In this study, the interaction between gas phase potassium species and kaolin was investigated in a fixed bed reactor equipped with a surface ionization detector, which is capable of detecting alkali metals in gas phase at ppb level. The effects of mass transport, space time, sorbent temperature and concentration of KCl on the rate of potassium adsorption on kaolin were studied in air. Kaolin, mainly composed of kaolinite—Al₂Si₂O₅(OH)₄, was found to be very efficient in removing gaseous alkali species from hot flue gases at fluidized bed combustion temperatures. The removal efficiency increased as temperature was decreased or KCl concentration was increased. The capture of potassium by kaolin was irreversible with formation of both water-soluble and water-insoluble products. Kaolin captured KOH almost as effectively as KCl, but K₂SO₄ was captured much less effectively than KCl.     

现代制造初探

现代制造是服务经济时代的制造形态。阐述了现代制造形态、现代制造模式、现代制造组织形态等问题，提出了上海工业企业适应现代制造的要求，实现企业转型的问题。