提高航空电机用电刷寿命的试验研究——灰分对电机电刷磨损的影响

本文研究了一种在地面使用寿命长,高空磨损值小,适用于低电压高电流密度,高低温高速度,负荷变换大的航空用软质电刷。通过采用润滑性高,结晶度高的高温石墨化处理的精炼石墨粉及导电性导热性好的软金属银粉及真空中、高空中润滑性好的MoS_2固体润滑剂而制备的高空和地面润滑性最好的软质石墨化电刷。为了使软质的电刷具有耐磨性,在电刷中加了灰分—碳以外的物质或叫杂质如SiC、SiO_2、Fe_2O_3等作为磨料(研磨剂)来提高电刷的耐磨性。试验结果显示:在石墨粉一阶段料中加入占石墨粉重量比的0.3%~0.8%的细粒SiC可最佳的降低电刷的磨损值,提高电刷的使用寿命,增强了电刷使用的可靠性。在石墨粉一阶段料中加入4种颗较粗的按不同比列组合的占石墨粉重量的1.2%、1.0%、0.8%、SiO_2、SiOxx、Fe_2O_3等破坏了润滑膜的动平衡,地面磨损值增大,高空试验磨损增大,甚至"粉尘化"磨损。     

复合电沉积铜-石墨工艺的研究

在石墨粉经硝酸粗化、蒸馏水洗涤、烘干等处理,并均匀分散的电镀液中,进行复合电沉积,再经热处理、冷却制备铜一石墨复合材料.通过SEM、布氏硬度、电导率、拉伸及摩擦磨损性能的测试分析表明:在该工艺条件下制备的电沉积铜-石墨复合材料具有良好的导电性、自润滑性反摩擦磨损性能.     

沥青黏结剂含量对电化石墨电刷的影响

考察不同含量的沥青黏结剂对电化石墨粉制备的电化石墨电刷的影响。实验数据表明:沥青黏结剂的含量越大,电化石墨电刷的磨损越大,其寿命越低。一方面是由于电化电刷是采用石墨化结晶度较高的电化石墨粉制备,其形成的氧化膜又厚又黑,电机运行过程中滑环与电刷间的工作面不断接触,该氧化膜不断的破坏和生成。另一方面是因为随着沥青黏结剂含量的增加,导致在焙烧过程中形成的沥青焦含量增大,由于沥青焦硬且脆,沥青焦含量增大破坏了氧化膜生成,导致氧化膜变薄润滑性变差而造成磨损变大。     

电机用电刷浸渍的试验研究

根据电刷工作性质的要求,电机用电刷不仅要有良好的导电性,而且要求具有良好的换向性和润滑性。为满足电刷的上述特性,采用电刷适量浸渍的方法,是一有效途径。我们以炭黑基D374牌号电刷为基体进行了有机材料的浸渍试验研究。研究结果表明     

石墨烯复合导电涂料的制备

以石墨粉为原料,通过氧化还原的方法制备石墨烯。对制备出的石墨烯进行了X射线衍射、拉曼光谱检测,同时探讨了石墨烯分散程度对导电性的影响。结果表明:石墨烯分散液分散均匀时,导电性随着石墨烯液的量增加而增强;分散不均匀时,石墨烯液使涂料导电性能减弱。     

神府煤制备超细石墨粉

寻求来源广、价格低、纯度高的炭质原料是目前高性能石墨材料制备研究的一个重要方向。以陕北神府煤为原料,探讨了在高温及惰性气氛下,煤粉粒度、催化剂种类及添加量等因素对煤炭石墨化过程的影响,并通过X射线衍射、扫描电镜及拉曼光谱等技术对煤炭高温热处理产物进行了分析和表征。结果表明:当以低变质程度的神府煤为原料时,在2500℃、惰性气氛及一定催化剂存在的条件下,神府煤可以制备得到超细石墨粉;神府煤煤粉粒径越小,超细石墨粉的石墨化程度越高;氯化铁、硼酸等均可以作为神府煤高温石墨化的催化剂,并且当以硼酸作为催化剂,煤粉粒径D₉₀< 20 mm时,由神府原煤可制得石墨化度为80.35%的超细石墨粉。     

偶联剂处理对树脂结合炭刷性能的影响

探索用偶联剂来处理石墨、焦炭粉末表面，以期改善石墨、焦炭粉末与树脂的结合效果，在树脂结合炭刷的工艺中，将石墨粉或焦炭粉先用偶联荆预处理后再加入配料中。研究了偶联荆种类（KH-550，KH-570，NDZ--311，NDZ-131）及用量，热处理温度等对树脂石墨电刷的电阻率、显气孔率、体积密度、抗压强度的影响，对试样微观组织进行了观察。结果表明：加入的偶联剂，能使电刷的抗压强度增加，硅烷偶联荆用于水溶性酚醛树脂／沥青焦配料，能够得到高抗压强度的电刷制品，试样其抗压强度达到了98MPa，增幅为59％，优选出了偶联剂KH570，其最佳加入值为石墨粉含量的0．5％～1．0％。     

树脂黏结剂含量对电化石墨粉制备的电化石墨电刷的影响

本文考察不同含量的树脂黏结剂对电化石墨粉制备的电化石墨电刷的影响。实验数据表明:树脂黏结剂的含量越大,电化石墨电刷的磨损越大,其寿命越低。这可能是由于随着树脂黏结剂含量的增加,导致在焙烧过程中形成的树脂焦含量增大,由于树脂焦硬且脆,树脂焦含量增大破坏了氧化膜生成,导致氧化膜变薄润滑性变差而造成磨损变大。     

D374B电刷浸渍聚四氟乙烯的研究

一、前言 为了提高电刷的质量,人们不断地致力于各种研究,以降低磨损,改善整流性能和不发生划伤整流子或滑环。对电机用电刷不仅要有良好的导电性,而且具有良好的换向性和润滑性,为了满足电刷的上述特性,采用电刷适量浸渍的方法是其中有效途径之一。本文仅对采用聚四氟乙烯浸渍D374B电刷进行了研究与探讨,并通过实验结果证明,对提高电刷使用寿命、减少磨损,改善电机换向性能及改善碳刷在整流子上的摩擦稳定性有显著效果。     

电刷填塞材料的改进试验

本试验旨在改善传统连接方法。由于机械振动和过电流冲击负荷工作情况下电刷接触电阻增大而产生的局部过热,进而引起连接失效的缺陷。采用含少量粘结剂的石墨粉或废弃的人造石墨粉作为刷体与导线的填塞材料,然后以有机树脂封口的电刷,经过振动,过电流冲击和内燃机车运行的考核,充分显示出其阻值不变的优点。石墨填塞料的来源方便,制造简单,为电刷连接开辟了一条新途径,也为高温电刷的连接提供了一种新颖的填充材料。然而这种方法尚处于试验阶段,需要不断完善,以求进入工业实用。     

Sulfur/graphitic hollow carbon sphere nano-composite as a cathode material for high-power lithium-sulfur battery

The intrinsic low conductivity of sulfur which leads to a low performance at a high current rate is one of the most limiting factors for the commercialization of lithium-sulfur battery. Here, we present an easy and convenient method to synthesize a mono-dispersed hollow carbon sphere with a thin graphitic wall which can be utilized as a support with a good electrical conductivity for the preparation of sulfur/carbon nano-composite cathode. The hollow carbon sphere was prepared from the pyrolysis of the homogenous mixture of the mono-dispersed spherical silica and Fe-phthalocyanine powder in elevated temperature. The composite cathode was manufactured by infiltrating sulfur melt into the inner side of the graphitic wall. The electrochemical cycling shows a capacity of 425 mAh g⁻¹ at 3 C current rate which is more than five times larger than that for the sulfur/carbon black nano-composite prepared by simple ball milling.     

Processing of strong and highly conductive carbon foams as electrode

Porous carbons were processed by the foaming of two-part polymer precursors with pre-loaded carbon powder (graphitic or amorphous), and then resin impregnation and carbonization to control both porosity and mechanical strength of the resulting foam. Electrical conductivity of the foams was improved by nickel-catalyzed graphitization. Different levels of graphitization were obtained for varied concentrations of nickel to the amorphous carbon foams. The presence of graphitic carbon improves the electrical conductivity by a factor of 50, compared to the amorphous counterparts. Electrochemical studies showed that graphitization of the amorphous structures increased the specific electrochemical surface area and electron transfer rate of the carbon electrodes.     

高炉炭砖的导热系数及其影响因素

对微孔、半石墨质和普通等级炭砖试样的导热系数与温度的关系做了回归分析,得到了导热系数和温度的关系表达式,由此,可以从室温导热系数预测高温导热系数。另外,还计算了导热系数与体积密度、显气孔率、透气度和原料等级之间的相关系数。结果表明,导热系数与透气度和原料等级有一定的相关关系,而与体积密度和显气孔率无关。     

Development and electrical conductivity behavior of copper‐powder‐filled‐epoxy graded composites

This article reports the development and direct‐current (dc) conductivity behavior of copper‐powder‐filled‐epoxy graded composite. Copper‐powder‐filled‐epoxy composites with 10 wt % copper powder and epoxy resin were developed. dc conductivity measurements were performed on the graded composites with an electrometer in the temperature range of 28–146°C. The dc conductivity decreased with an increase in the distance in the direction of the centrifugal force, and this showed the formation of a graded structure. The dc conductivity increased as the copper powder content increased. Two‐phase conduction occurred in all the copper‐filled‐epoxy graded samples. The activation energy calculated with an Arrhenius equation for one sample was 0.88 eV, and this was mainly due to conduction electronic. Another sample had an activation energy of 1.33 eV. Three samples exhibited ionic conduction. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Thermal properties of copper-coated carbon foams

Carbon foams, with 97% porosity, were electroplated with copper for different periods of time to achieve desired copper thicknesses and foam porosity. A light flash diffusivity instrument was used to measure the thermal conductivity of the coated samples. An analytical model was developed to calculate the effective thermal conductivity of the coated foams. It was observed that the copper-coated carbon foam with 50% porosity can attain a thermal conductivity of 180 W/m K. The results from the analytical model were compared to the experimental results and they were in a very good agreement. The above analyses demonstrated the significance of copper coating in tailoring carbon foam thermal properties. The developed analytical model was adopted to predict the thermal conductivity of the copper-coated carbon foams.     

炭黑/铝银粉填充导电硅橡胶的性能研究

以炭黑和铝银粉为导电填料,通过溶液共混法制备出导电硅橡胶试样。研究了炭黑/铝银粉对导电硅橡胶导电性能和压阻特性的影响。结果表明,当炭黑含量一定时,随着铝银粉含量的不断增加,导电硅橡胶的电阻先减小后增大;当填料含量一定时,随着压力的不断增加,导电硅橡胶的压阻特性曲线先逐渐下降后趋于稳定;当炭黑含量为30 %（质量分数,下同）、铝银粉含量为3 %时,导电硅橡胶的导电性最好,压阻特性范围也变大。     

Structural studies of electrochemically activated glassy carbon electrode: Effects of chloride anion on the redox responses of copper deposition

The redox behaviors of copper species at electrochemically activated glassy carbon electrodes have been investigated in aqueous solutions containing chloride anions. Experimental results showed that the voltammetric responses of copper species were influenced by the electrochemical activation means employed. Abnormal copper stripping was observed at electrodes obtained by cyclic polarization. Cyclic polarization would cause changes in the interwoven graphitic crystalline surface of glassy carbon, producing electrode interface with low distribution density of electron transfer sites for the early nucleation of metallic copper in the presence of chloride anion. Potentiostatic activation would generate oxygen-containing functionalities and maintain the basic surface structure of graphitic crystalline with high distribution density of electron transfer sites.     

Microwave plasma chemical vapor deposition of graphitic carbon thin films

Thin layers of graphitic carbon were produced from solid organic precursors by a one-step microwave plasma chemical vapor deposition method. Low-pressure Ar-plasma and strong electromagnetic radiation led to the rapid evaporation and pyrolysis of organic precursors at relatively low temperatures, yielding uniform films of nanometer-sized graphitized carbon particles. The structure and morphology of the carbon films were examined using scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy. A direct correlation between electrical conductivity of graphitic thin films and their structure was established.     

Catalytic graphitization of carbons by various metals

A study was made of the catalytic graphitization of carbons by 22 kinds of metals. Heat treatments were carried out at 2600°C for 1 hr and 3000°C for 10 min under argon atmosphere. In graphitizing 3,5-dimethylphenol-formaldehyde resin carbon powder with which 20w/o metal powder (Al, Cr, Mn, Fe, Co, Ni, Ca, Ti, V, Mo and W) was mixed, graphitic carbon was catalytically formed. The first six metals, which belong to the carbon dissolution-precipitation mechanism, gave large graphitic crystal flakes at an early stage of the reaction; the other metals resulted in fine crystals through the carbide formation-decomposition mechanism. For the non-graphitizing phenol formaldehyde resin carbon in which 10w/o metal powder was dispersed, Mg, Si, Ca, Cu and Ge catalyzed formation of only graphitic carbon; and Al, Ti, V, Cr, Mn, Fe, Co, Ni, Mo and W formed both graphitic and turbostratic carbons. Except for Al and Cu, the former effect was exerted by non-transition metals and the latter effect by transition metals. Boron alone markedly accelerated homogeneous graphitization of both kinds of carbon; and Zn, Sn, Sb, Pb and Bi had no catalytic effect. On the basis of these results, the relationships between some properties of the metals, their catalytic abilities and the kind of catalytic effects are discussed.     

Evolution of Carbon during Burnout and Sintering of Tape-Cast Aluminum Nitride

The surface nature and the composition of AlN powder, as-received and exposed to binder burnout, were studied using XPS and TEM. The surface of as-received AlN powder was covered by a thin layer of aluminum oxynitride and oxide mixture. A small portion of residual carbon from binder burnout was bound to oxygen atoms on the AlN powder surface, and the majority of the carbon was amorphous graphitoid carbon which covered the AlN powder surface uniformly. AlN samples were made using tape casting and pressureless sintering. Surface-carbon-to-oxygen ratio of AlN powder after binder burnout was evaluated using XPS. The surface C/O atomic ratios were observed to correlate with the sintering behavior, the composition of the second phase, the second phases distribution, and grain-boundary composition, as well as thermal conductivity of AlN samples.