Investigation on gradient material fabrication with electron beam melting based on scanning track control

A new electron beam control system was developed in a general vacuum electron beam machine by assembling with industrial control computer, programmable logic control （PLC）, deflection coil, data acquisition card, power amplifier, etc. In this control system, scanning track and energy distribution of electron beam could be edited off-line, real-time adjusted and controlled on-line. Ti-Mo gradient material （GM） with high temperature resistant was fabricated using the technology of electron beam melting. The melting processes include three steps, such as preheating, melting, and homogenizing. The results show that the GM prepared by melting technology has fine appearance, and it has good integrated interface with the Ti alloy. Mo and Ti elements are gradually distributed in the inter.face of the gradient material. The microstructure close to the Ti alloy base metal is α ＋ β basket-waver grain, and the microstructure close to the GM is a single phase of β solid solution.     

TPR处理剂的研究

利用活性单体苯乙烯与氯丁橡胶、高苯乙烯热塑弹性体接枝聚合，所得产物稀释后用于ＴＰＲ（ＴｈｅｒｍａｌＰｌａｓｔｉｃＲｕｂｂｅｒ）粘接前的预处理，可明显提高剥离强度。     

The deposition of coke from methane on a Ni/MgAl2O4 catalyst

Temperature-programmed reaction techniques and Raman spectroscopy were used to characterize coke species deposited on a 5% Ni/MgAl₂O₄ catalyst for dry reforming of methane. The CH₄ temperature-programmed decomposition profiles showed that the ignited decomposition temperatures of CH₄ increased from 273 to 378 °C when MgAl₂O₄ replaced the catalyst support γ-Al₂O₃. The temperature-programmed oxidation, temperature-programmed hydrogenation and temperature-programmed CO₂ reaction profiles showed that there were three carbon species (i.e. C_α, C_β and C_γ) on the catalyst surface. Raman spectroscopy showed that C_γ was graphite-like carbon species, which was responsible for catalyst deactivation. The C_γ species was the most inactive species toward H₂ and O₂, while it was unexpectedly more active toward CO₂. The unique reactivity of CO₂ with different coke specie could be ascribed to the carbonate, bidentate and formate species formation on MgAl₂O₄ surface. These surface species enhanced the oxidation of C_γ species and thus contributed to the high stability of Ni/MgAl₂O₄ catalyst.     

Braking Behavior of C/SiC Composites Prepared by Chemical Vapor Infiltration

Carbon fiber-reinforced silicon carbide matrix composites have the potential to overcome the shortcoming of the currently used carbon/carbon friction materials in aircraft brakes. In this article, the carbon/silicon carbide (C/SiC) composites were prepared by chemical vapor infiltration method, and the brake disks with different densities and component content were finally obtained. The friction coefficient and friction stability can be significantly improved by increasing both material density and carbon content. When the density of C/SiC composite is 2.3 g/cm³, the coefficient of friction measured is 0.23, the coefficient of friction stability remains about 0.43, the liner wear rate is less than 9.3 μm/cycle, and the weight wear rate is less than 9.1 μm/cycle. The rapid increase of friction coefficient approaching the end of braking is mainly related to the increasing of surface temperature in a short time and the enhanced adhesion and abrasion of contact conjunctions and asperities. The C/SiC composites exhibited a good stability of braking against fading versus the braking number and surface temperature. The surfaces of C/SiC brake disks were covered with wear debris including the fragment of carbon fibers after the braking tests. The wear on the surfaces is significantly determined by cyclic mechanical and thermal stresses, which result in the micro-cracks in the SiC matrix, the thin flakes of the surface materials as well as the grooves.     

锐钛型TiO2对尿素热解过程的影响

通过实验的方法收集了不同温度下纯尿素和尿素/TiO₂混合物热解后的固体残留物，使用红外光谱（IR）及气相色谱质谱联机（GC-MS）方法对这些热解残留物进行成分分析；使用热重-红外联机（TG-FTIR）技术研究尿素及三聚氰酸在有无催化剂TiO₂的情况下的热解特性及气体产物的生成规律；根据Coats-Renfern方法对尿素热解第一阶段的非等温热失重率曲线的数据进行动力学研究，建立动力学方程。结果表明，100~250℃的尿素热解残留物中主要为尿素和缩二脲，300~400℃的尿素热解残留物中主要为三聚氰酸等含氮杂环有机化合物；锐钛型TiO₂能促进尿素和三聚氰酸的热解反应，缩短其反应进程，HNCO与水蒸气在TiO₂表面易发生反应；尿素第一阶段热解的反应级数为2，单独热解时活化能为113.25kJ/mol，指前因子A为2.01×10¹¹min^-1，在催化剂TiO₂的作用下，活化能E为77.42kJ/mol，指前因子A为4.82×10⁷min^-1。     

Grafting of alkoxyamine end-capped (co)polymers onto multi-walled carbon nanotubes

Multi-walled carbon nanotubes (MWNTs) have been successfully modified by polystyrene, poly(?-caprolactone), and their block copolymers by addition reaction of the alkoxyamine-terminated precursors. Polymer-modified MWNTs are easily dispersed in good solvents for the grafted polymer, such as toluene and THF. This observation has been confirmed by TEM analysis. The grafting ratio of polystyrene chains at the surface of MWNTs depends on the polymer molecular weight.     

臭氧氧化法除地表水有机物试验研究

本文阐述臭氧化法除地表水有机物的重要意义，实验结果表明：臭氧氧化有机物的总氧化速率受活化控制，影响氧化率的最高显著因素是温度，其次是ｐＨ，接触时间等，臭氧很容易氧化腐植酸，在３０℃，ｐＨ９．０～１０．０，７ｍｉｎ内，ＣＯＤ去除率可达６０％以上，对邯郸热电厂生产处理也取得良好效果，３５℃，ｐＨ７．４～７．６，１０ｍｉｎ内，ＣＯＤ去除率可达６７％，可望将臭氧化水处理工艺应用于电厂水处理。     

High-performance dispersant of coal–water slurry synthesized from wheat straw alkali lignin

Environmental concerns have stimulated interest in utilizing plant-derived materials in various industrial fields. The main objective of the present study was to synthesize a new type of high-performance lignin series dispersant of coal–water slurry (CWS) from wheat straw alkali lignin (WAL), and determine the affecting factors in the reaction and the application performance for CWS preparation. The experimental results showed that the inherent viscosity and the sulfonic group content of the modified wheat straw alkali lignin (MSL) are the key factors affecting its dispersing effect for CWS. In the reaction, the reactant mass concentration and the sulfonating agent amount were changed to obtain the MSL with different inherent viscosities and sulfonic group contents, and the MSL with intermediate inherent viscosity (6.0 ml/g) and higher sulfonic group content (1.80 mmol g^− 1) was found to have excellent dispersing effect for CWS. The MSL obtained from optimized process was used as dispersant for CWS preparation, the studies of the properties of CWS showed that MSL has similar dispersing effect with naphtalenesulfonate–formaldehyde condensate, and far better dispersing effect than lignosulphonate. Recently this kind of new dispersant has been applied in several power plants in China.     

氯化聚乙烯接枝氯乙烯聚合速率及传热

本文用气相色谱技术研究氯化聚乙烯(CPE)-接枝(g)-氯乙烯(VC)聚合动力学,对不同引发剂体系分析热负荷分布,并对7 m~3聚合釜传热面进行校核。     

一种适用于物联网节点的高效轻量级嵌入式系统设计

物联网技术成为当前一个比较热门的研究主题,但适用于物联网传感器的嵌入式操作系统在国内未被广泛提及。本文针对嵌入式多任务程序设计所面对的问题,结合物联网传感器资源受限、低功耗等特点,探讨该类程序的一般设计方法,提出了一种基于事件驱动抢占式系统的基本实现方法,并使之顺利应用于基于MSP430物联网传感器采集节点的系统中。