电刷摩擦系数测量

本文介绍电刷摩擦系数的测量装置－电刷试验转台。由正压力给定系统测量电刷的正压力,力矩反馈系统测量摩擦力对旋转中心产生的转矩,游标尺测量电刷至旋转中心距离,从而得出摩擦力。摩擦力除以正压力即摩擦系数。文中给出二个测量系统之测试结果。     

炭／炭复合材料可石墨化性能的研究

采用XRD法测量和表征石墨化度，以数种结构组成各异的二维或准二维现役航空刹车用炭／炭复合材料为对象，研究了石墨化度随石墨化处理温度的变化规律，推算出了材料的最终石墨化处理温度，并从材料的结构组成方面对其可石墨化性能特征进行了分析、比较。结果表明：在石墨化度－石墨化处理温度关系曲线上，按温度划分，存在着两个明显不同的区段；近似于直线的快速升高段（AB段）和高温时近似于水平线的缓慢升高段（CD段）。当基体中含有沥青或树脂浸渍炭时，材料的最终石墨化处理温度大多处于AB段，温度为2000－2200℃之间；当基本全部为CVD炭时，材料的最终石墨化处理温度大多处于CD段，温度可能超过2800℃。本所研究的复合材料中的CVD炭的结构皆为RL结构。     

高温热处理对C/C-SiC复合材料制备与力学性能的影响

以针刺整体炭毡为坯体,采用树脂浸渍和化学气相沉积混合法制备C/C多孔体,然后熔硅浸渗制得C/C-S iC复合材料;研究了C/C多孔体的高温热处理对C/C-S iC复合材料密度、孔隙度、力学性能及断裂方式的影响。结果表明:炭涂层进行高温热处理可改变复合材料的弯曲断裂方式,使其具有一定的“假塑性”,弯曲强度下降约16%,压缩强度提高约20%,硬度增加;C/C多孔体的最终高温热处理可打开孔隙,有利于液S i的渗入,制备出密度较高(>2.0 g.cm-3)、开孔率较小(<4%)的复合材料,但导致其力学性能下降,基本上不影响其断裂方式。     

热处理温度对钼酚醛树脂连接炭/炭复合材料接头性能的影响

以钼酚醛树脂为原料基体，添加适量的钼粉，对炭／炭复合材料进行连接试验，测试了不同温度处理后接头的室温剪切强度。结果表明，经1500％处理后接头仍保持较高的连接强度，可达13．3MPa。利用XRD和SEM研究了接头的组成和形貌，发现添加适量钼粉后，不但可以降低酚醛树脂在炭化过程中的体积收缩，还能在1100％时原位生成Mo2C来提高接头的连接强度。     

Conducting polymer coated carbon surfaces and biosensor applications

This review article focuses on several approaches in the characterization and modification of carbon surfaces with electrocoated thin films which has been realized by recent progress in experimental methods. Electropolymerization and electrocopolymerization of π-conjugated polymers (pyrrole, carbazole, N-vinylcarbazole and aniline) onto carbon surfaces are reviewed with 348 references. Particular emphasis is placed on the recent nanoscale surface characterization techniques applied to the resulting electrocoated polymers onto carbon fibers (i.e., scanning electron microscopy (SEM), cyclic voltammetry (CV), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), focused ion beam-secondary ion mass spectroscopy (FIB-SIMS), Fourier transformed infrared spectroscopy (reflectance-FTIR), and Raman spectroscopic measurements).     

高温热处理对C/C复合材料刹车盘尺寸的影响

研究了用CVI工艺制备的二维C／C复合材料刹车盘在进行高温热处理时的尺寸变化。第一次热处理时刹车盘直径增大，厚度减小；第二次、第三次热处理时刹车盘直径和厚度均增加。随着热处理次数的增加，刹车盘尺寸变化越来越小，趋于稳定。刹车盘尺寸的变化与C／C复合材料中碳原子的有序化重新分布和不同炭相产生应力裂纹等因素有关。     

Research progress on polymer-inorganic thermoelectric nanocomposite materials

A thermoelectric (TE) material is a material where a potential difference is generated as a result of a temperature difference or the corollary of this where a temperature difference is generated when a voltage is applied. These phenomena can be used to generate electricity and/or control temperature. Traditionally, thermoelectric materials are inorganic semiconductors which have been limited in their application by low efficiency and high cost. Since the 1990s, both theoretical and experimental studies have shown that low-dimensional TE materials, such as superlattices and nanowires, can enhance the value of the TE figure of merit (ZT) which is an indicator of TE thermodynamic efficiency. To date it has not been feasible to apply these materials in large-scale energy-conversion processes because of limitations in both their heat transfer efficiency and cost. When compared to inorganic materials, organic conducting polymers possess some unique features, such as low density, low cost, low thermal conductivity, easy synthesis and versatile processability and their use in preparing polymer-inorganic TE nanocomposites appears to have great potential for producing relatively low cost and high-performance TE materials. Recently, an increasing number of studies have reported on polymeric and polymer-inorganic TE nanocomposite materials. The purpose of this paper is to review the research progress on the conducting polymers and their corresponding TE nanocomposites. Its main focus is the TE nanocomposites based on conducting polymers such as polyaniline (PANI), polythiophene (PTH), poly (3, 4-ethylenedioxythiophene): poly (styrenesulfonate) (PEDOT:PSS), as well as other polymers such as polyacetylene (PA), polypyrrole (PPY), polycarbazoles (PC) and polyphenylenevinylene (PPV). Typically, polymer-inorganic TE nanocomposites are produced by physical mixing, solution mixing and in situ polymerization. The key factors that limit the use of these polymers and their polymer-inorganic TE nanocomposites as TE materials are their low ZT values. More recent developments designed to overcome the limitation including, for example, the use of carbon nanotubes and graphenes and the use of computational modelling to accelerate the selection of suitable pairs of conductive polymer and inorganic TE materials to achieve best possible nanocomposites are reviewed.     

EW75镁合金高温扩散动力学研究

采用光学显微镜(OM)、扫描电子显微镜(SEM)和能谱分析(XRD),观察EW75合金大型铸锭原始态及高温热处理之后的组织及成分分布,以进行稀土元素在EW75合金中高温扩散动力学的研究。结果表明:EW75铸态合金中存在较为严重的局部偏析,大量非平衡凝固共晶组织在晶界处富集,Gd,Y,Nd在合金中的分布很不均匀,铸态组织呈大块的骨骼状,由α-Mg基体、Mg24Y5、Mg5Gd和Mg41Nd5非平衡凝固相组成,铸态合金晶粒尺寸约为100μm;在505及520℃保温24 h之后依然有较多未溶相残留在晶界上,由于温度稍微偏低,共晶组织未能完全溶解并分散到基体中;经过535℃,20 h高温热处理之后,共晶组织基本分解完全,稀土元素较为均匀地分布在基体中,晶粒长大非常明显;采用(EDS)分析测得各合金元素在EW75中的浓度分布,发现合金元素在EW75中成一定的规律分布,通过动力学方程计算得出了Y,Gd,Nd元素在不同温度下的lnδ-t关系曲线并进行线性拟合,最终得出Gd,Y,Nd在不同温度下的扩散系数。     

密封用炭/炭复合材料的摩擦磨损性能

针对液体火箭发动机涡轮泵密封件磨损量较大问题,在MVF-1A多功能立式摩擦磨损试验机上,以GCr15钢环为对偶件,研究低载荷高线速度(12N,2.25m/s)以及高载荷低线速度(50N,1.25m/s)工况条件下热处理温度不同时(2 250、2 400和2 500℃)对炭/炭(C/C)密封材料摩擦磨损性能的影响,采用扫描电镜观察摩擦表面形貌,利用能谱仪确定摩擦表面元素组成。结果表明:低温(2 250℃)热处理材料石墨化度程度低,弯曲强度高,摩擦因数小,线性磨损量大;随着热处理温度的升高,材料石墨化程度升高、界面结合强度弱化,弯曲强度降低;当热处理温度升高到2 500℃后,材料表面易形成完整致密的磨屑膜,磨损机制由磨粒磨损转变为粘着磨损,摩擦因数大,线性磨损量低。此外,在高载荷条件下,适当增大线速度(1.50、1.88m/s),有利于降低摩擦因数及线性磨损量。由此可知,采用高温(2 500℃)热处理的C/C复合材料具有良好抗磨性能,可较好地满足密封件使用要求。     

Description of the First Registered Case of Lopes–Maciel–Rodan Syndrome in Russia

Lopes–Maciel–Rodan syndrome (LOMARS) is an extremely rare disorder, with only a few cases reported worldwide. LOMARS is caused by a compound heterozygous mutation in the HTT gene. Little is known about LOMARS pathogenesis and clinical manifestations. Whole exome sequencing (WES) was performed to achieve a definitive molecular diagnosis of the disorder. All NGS-identified variants underwent the Sanger confirmation. In addition, a literature review on genetic variations in the HTT gene was conducted. The paper reports a case of LOMARS in a pediatric patient in Russia. A preterm girl of non-consanguineous parents demonstrated severe psychomotor developmental delays in her first 12 months. By the age of 6 years, she failed to develop speech but was able to understand everyday phrases and perform simple commands. Autism-like behaviors, stereotypies, and bruxism were noted during the examination. WES revealed two undescribed variants of unknown clinical significance in the HTT gene, presumably associated with the patient’s phenotype (c.2350C>T and c.8440C>A). Medical re-examination of parents revealed that the patient inherited these variants from her father and mother. Lopes–Maciel–Rodan syndrome was diagnosed based on overlapping clinical findings and the follow-up genetic examination of parents. Our finding expands the number of reported LOMARS cases and provides new insights into the genetic basis of the disease.