CO2 reforming of methane over Ni/ZnAl2O4 catalysts: Influence of Ce addition on activity and stability

The catalytic performance of Ni supported on Ce-promoted ZnAl₂O₄ was evaluated in methane dry reforming. The effect of different nominal loadings of cerium (3, 5 and 7 wt%) in the activity, product yield and stability was studied. Ce presented a promote effect in catalytic activity, product yield and especially in stability. However the catalytic performance was considerably influenced by the amount of cerium. SEM images presented smaller particles and TPR profiles revealed stronger active phase/support interaction by Ce addition which led to increasing methane conversion and decreasing coke deposition. Although high amount of Ce was not in favor of its promoting effect due to aggregation of CeO₂ on the catalyst surface. Among the catalysts investigated, the optimal catalytic activity and stability was achieved over the sample with 5 wt% of cerium.     

The influence of contact geometry on friction and wear characteristics

This paper describes some results of evaluating the influence of contact geometry on tribological characteristics. Friction characteristics obtained for a distributed contact (pin‐on‐disc and block‐on‐ring), a linear concentrated contact (pin and vee‐block and block‐on‐ring) and a point concentrated contact (ball‐on‐disc and three cylinder‐cone) are presented. The wear scars were analysed using scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). The results show different values of friction and wear coefficients for the different types of contact geometry. The paper also assesses the effect of non‐test characteristics, e. g., vibration.     

U型井开发干热岩井筒温度场研究

干热岩开发主要采用水力压裂的方式,而以U型井方法取代固有开发模式,具有减少水损、提高能量衰减周期,避免诱发地震等显著优势。因此,建立了U型井井筒和干热岩储层非稳态流动传热耦合模型,采用有限体积法结合Crank-Nicolson全隐式格式进行离散求解,并通过地热井数据验证了模型的可靠性。研究了干热岩开采过程中井筒及地层的温度变化特征,定量分析不同的敏感性因素对出口温度的影响,利用正交试验法明确影响取热量大小的因素排列。结果表明：各个因素的大小对出口温度影响明显,而影响取热量的因素由主到次为注入流量、水损率、岩石导热系数、水平段长度、入口温度、井筒直径。研究成果进一步完善了干热岩高效热提取理论,可为我国干热岩地热能的开发利用提供借鉴作用。     

Modern solid lubrication: Recent developments and applications of MoS2

An important and growing field of lubrication lies in the use of solid films, although they are in general more expensive than oils or greases, and require specialist attention both in mechanical design and in coating application techniques. In this paper, the general classification of solid lubricant types is reviewed, along with the reasons for choosing, and methods of depositing, solid lubricants, in particular MoS₂. The best‐performing and most flexible technique for making MoS₂ films is by physical vapour deposition (PVD), and the variants of that technology are considered. The intrinsically lubricating, lamellar structure of pure MoS₂ is described, along with a brief summary of its wear and failure modes. Present applications for lubrication by MoS₂ in spacecraft and dry machining are outlined, as are anti‐adhesive uses in extruding and moulding. The current state of the art of modification of MoS₂ films consists in the addition of dopants (co‐sputtering), in multilayering as a series of films, each fulfilling a specific task, or in stacking repeating nano‐metre‐scale films. Composite films of MoS₂ islands in a hard film matrix are also being developed.     

独立新风系统(DOAS)研究(3):常规风机盘管独立新风系统

分析了以风机盘管机组为空调末端装置,以普通冷水机组为冷源的独立新风空调系统的特点。结合设计实例,介绍了该空调系统的设计方法。详细说明了如何实现风机盘管的干工况运行。     

Gelation of poly(vinyl alcohol)/water/dimethylformamide solutions and properties of dried films

The properties of solutions for syndiotacticity-rich poly(vinyl alcohol) (s-PVA)/dimethylformamide (DMF)/water systems, the gelation of the s-PVA solutions, and the properties of the dried s-PVA gel films were examined. From the results of the dissolution temperature of the polymer, the gelation temperature of the solutions, the melting temperature of the gels, and the compressive modulus of the gels, the solubility of the polymer was the highest at DMF contents of 10–20 vol %. The maximum dynamic tensile modulus of the drawn (×18) films obtained from the dried gel films with a DMF content of 10 vol % was 54.9 GPa at 20°C. The orientation of the polymer chains in the amorphous regions was higher than that in the crystalline regions. The orientation of the polymer chains in the amorphous regions for the drawn films with a DMF content of 10 vol % was higher than that for the drawn films with a DMF content of 60 vol %. The orientation of the polymer chains in the amorphous regions was considered to play an important role in the properties of high strength and high modulus. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 1661–1667, 1998     

干水法制备核壳聚合物微球及其性能评价

以疏水SiO2、单体、引发剂和交联剂为原料,水为溶剂,采用干水法制备核壳聚合物微球PMS@SiO2,分别考察了SiO2疏水性、硅水质量比、搅拌速度和搅拌时间对形成稳定干水微反应器的影响。以过硫酸铵和亚硫酸氢钠为引发剂,N,N''-亚甲基双丙烯酰胺为交联剂,通过正交实验对内核水相发生聚合反应的条件进行了优化。采用傅里叶变换红外光谱仪、热重分析仪、激光粒度仪、扫描电子显微镜和透射电子显微镜对微球的化学结构、热稳定性及微观形貌进行了表征,评价了微球的吸水膨胀性能和调驱性能。结果表明,核壳聚合物微球PMS@SiO2的最佳制备条件为：SiO2-R812S与水相质量比1∶10,搅拌速度12000 r/min,搅拌时间120 s,交联剂用量0.1%（以单体总质量为基准,下同）,引发剂用量0.15%,反应温度50 ℃,反应时间4 h。与常规聚合物微球PMS相比,该微球在90 ℃环境中水化20 d,膨胀倍数约为5.0,具有缓膨特性。物模调驱实验结果表明,PMS@SiO2的封堵率达90.39%,残余阻力系数为10.409,采收率增幅可达34.02%。与PMS相比,其采收率提高了11.89%,具备良好的调驱性能。     

Preparation and characterisation of oil-containing POM/PU blends

Polyoxymethylene (POM), one of the major engineering thermoplastics, has high strength and stiffness, excellent chemical resistance and superior antifriction and wear resistance. It suffers, however, from poor impact resistance due to its higher crystallinity. In this study we have investigated how to improve the toughness of POM by blending polyurethane (PU) with POM using dual-roller compaction. The influences of PU, silicone oil, a surfactant, and fillers such as ultra-high molecular weight polyethylene (UHMWPE), polytetrafluoroethylene (PTFE), graphite and carbon black, on the mechanical properties of oil-containing POM/PU blends and its self-lubrication performance in dry sliding against AISI1045 steel are examined. The results show that blends of POM with 10 wt.% PU reached the maximum notched Izod-impact strength. The best processing method for oil-containing POM/PU blends, and the optimal compositions of modified POM/PU blends were also determined.     

干法合成淀粉阳离子絮凝剂

研究了干法合成阳离子淀粉絮凝剂的方法。结果表明,制备阳离子淀粉絮凝剂的最佳工艺条件为:在反应体系中水的质量分数为35%,阳离子醚化剂与NaOH混合液温度低于10℃,阳离子醚化剂与淀粉质量比为0.35,NaOH与阳离子醚化剂质量比为1.40,反应温度90℃,反应时间4h。在此条件下合成的阳离子淀粉絮凝剂相对黏度为2.0mPa·s。     

赤泥微波干法固定碱及其机理分析

赤泥是通过拜耳法精炼铝土矿产生的一种强碱性工业固体废物。以遵义某拜耳法氧化铝厂排出的赤泥为样品,开发出微波干法快速固碱技术,并就其干法固碱原理进行研究。研究表明,赤泥经过微波干法固碱,功率为392 W,微波频率2 450 MHz,波长122 mm,仅需要40 min,其pH可以从10.88降低至8.11,固碱过程不产生二次污染物。通过XRD和SEM分析发现,赤泥成分、外貌颜色、表观形态及粒径都存在变化。