Sedimentation behavior of high-temperature concentrated colloidal suspension based on potassium cryolite

The paper describes the sedimentation behavior of concentrated high-temperature oxide-fluoride slurries with alumina particles volume fraction range 0.24?≤?φ?≤?0.32 at ～700 °C. The behavior is of interest due to perspectives of the non-Newtonian fluids usage in the future aluminium reduction technology. To characterize sedimentation behavior several techniques were used: density analysis, X-Ray diffraction, microphotography and electron scanning microscopy. Sample with ?63?µm dispersed phase as well as smelter-grade alumina which contains particles in a range of 10–150?µm has been examined. It has been found that particle settling occurs with the initial velocity 0.97·10^?5 m·s^?1 at φ?=?0.24 and gradually reduces reaching zero at φ close to 0.32 which was considered as a maximum packing fraction. MS^?1 sedimentation mode has been identified, the type of sedimentation was found to be changed from type 1 to type 3 in the sample with φ?=?0.24. The alumina partial density distribution in suspension as a function of time was determined. Alumina average motion velocity during sedimentation was calculated to be 154·10^?3?kg·m^?2·s^?1 at φ?=?0.24 in the top layer of the sample within the first 150?s of sedimentation. It had been reducing drastically before it reached zero after 300?s. An alumina flow was higher in the top layers. Some of the rheological properties (such as relaxation time, which increased from 7.2·10^?3 to 17.7·10^?3?s after the increase of φ from 0.24 to 0.28) has been determined.     

高温用镶嵌型固体润滑材料的研制及其摩擦磨损性能的考察

研制了几种可以在大气中直至300℃下使用的镶嵌型固体润滑材料,考察了胶粘剂、添加剂、湿度和温度等对固体润滑剂热膨胀性能及镶嵌材料摩擦磨损性能的影响。作者采用的“栓(球)-盘”试验方法,可以定性地比较固体润滑剂对金属的转移性能,加快了镶嵌用固体润滑剂配方的筛选进程。试验结果表明,3号配方的镶嵌试样在250和300℃时的比磨损分别为7.8×10~(-13)mm/Pa·m和16.2×10~(-13)mm/Pa·m,最大摩擦系数为0.42。通过X-射线衍射分析认为,这种材料在高温下的高摩擦现象应归因于摩擦表面氧化产生的Cu_2O。     

The thermostressed state of electrically conductive bodies subjected to an external electromagnetic field

A technique is proposed for mathematical and numerical modeling of thermomechanical processes in electrically conductive bodies subjected to an external electromagnetic field. The initial relations for the determination of the electromagnetic field are the Maxwell equations. The stress and strain states of the body are described using the equations of nonisothermal elastoplasticity. The model takes into account the coupling of the electromagnetic and thermal fields. All physical and mechanical parameters of the material depend on temperature. The process of high-temperature induction treatment of a ferromagnetic cylinder is considered as an example __________ Translated from Prikladnaya Mekhanika, Vol. 41, No. 12, pp. 13–25, December 2005.     

高温云纹实验炉及控温系统

本文介绍了高温云纹实验的背景，详细叙述了高温实验专用炉设计原理和控温系统，解决了紊流的影响，在高温下可获得清晰稳定的图像。控温系统以８０３１单片机为基础，采用了三次回归方程计算测量温度，运用ＰＩＤ调节控制，提高了高温实验炉的可靠性。     

Comparison of Various Solvents for Poly(Phenylene Sulfide) Microporous Membrane Preparation via Thermally Induced Phase Separation

Six different solvents, i.e., diphenyl sulfone (DPS), diphenyl isophthalate (DPIP), benzoin (BZ), epsilon-caprolactam (CPL), hydrogenated terphenyl (HTP), and cyclohexyl pyrrolidinone (CHPN), were selected as diluents for poly(phenylene sulfide) (PPS) microporous membranes development via the thermally induced phase separation (TIPS) method. Phase separation behaviors for the various solvents were first identified through thermal analysis of their PPS solutions. Liquid-liquid separation behavior was identified for a group of solvents including DPS, DPIP, and BZ, whereas systems with the solvents CPL, HTP, and CHPN underwent solid-liquid separation during the cooling process. A newly designed casting device, which well simulated the industrial film casting process, was then used to produce films; it consisted of a side-by-side high-temperature plate and room-temperature plate. The different cooling conditions able to be produced by this casting device were found to greatly affect the TIPS process and the properties of the final membranes. The properties of PPS membranes prepared on this device from 30 wt.% binary solutions with the six solvents were investigated. The morphology of PPS membranes was also observed on the samples prepared under different cooling processes for the six solvents.     

Synthesis and Characterization of a Novel High-Temperature Structural Adhesive Based on MDA-BAPP-BTDA Co-Polyimide

A series of polyimide(PI) adhesives were synthesized from 2,2'-Bis [4-(4-aminophenoxy)phenyl] propane(BAPP), 4,4'-Diaminodiphenylmethane (MDA) and 3,3',4,4'-Benzophenonetetracarboxylic acid dianhydride (BTDA) via a two-step process. PI adhesives with different BAPP content were characterized in regard to their structure, thermal stability, mechanical properties and adhesive performance. Results showed that these PIs had excellent thermal stability, whose glass transition temperature (Tg) were around 300°C. While, superior dynamic mechanical behavior was observed, and the maximum loss factor declined with the increase of BAPP content. Single-lap shear strength of over 15.58 MPa at room temperature was obtained, and it remained high even at the temperature of 350°C. Factors that could affect bonding strength of these PI adhesives such as molar ratio of the diamine monomers, surface roughness of adherends and curing processes were investigated.     

水热法制备LiMnPO4包覆的LiMn2O4正极材料及其改善的电化学特性

通过水热合成的方法制备了不同质量百分比的LiMnPO4包覆LiMn2O4的复合材料,并且利用XRD、拉曼光谱、SEM、TEM以及充放电测试等手段,对其结构和电化学性能进行了表征。研究表明,适当量的LiMnPO4包覆,不仅可以增加材料的可逆比容量,还可以有效提高材料在55℃下的循环特性。1wt%LiMnPO4包覆的LiMn2O4在55℃下的可逆容量为109 mAh.g-1,是其初始容量的96%。此外,1wt%LiMnPO4包覆的LiMn2O4与未包覆的LiMn2O4相比,在倍率特性上也有明显的改善。     

高温空气煤粉直燃技术的数值模拟

本文通过数值计算的方法,对高温空气煤粉直燃燃烧器的多种运行工况进行了数值试验研究,分析了煤粉气流入口速度、煤粉浓度和高温空气速度等主要因素对煤粉气流着火的影响,模拟结果还可以反映出高温空气无油点火燃烧器内的流动、燃烧和传热情况。与试验数据的对比分析表明,数值模拟结果与试验数据趋势一致。研究结果对此燃烧器的结构及运行参数的优化提供了指导。     

高温核磁共振探头

本文设计研制了一种用于动态核磁共振研究的高温探头,它适用于磁铁极间距离为30mm的核磁共振波谱仪,探头中样品处的温度从室温至1300K连续可变,探头既可用于质子(¹H)也可用于其它核(如¹¹B,³¹P,²³Na等),并给出了高温探头的结构、指标及实际应用于测量的例子。