中间相沥青粒子对PEMFC用碳纤维纸性能的影响

以酚醛树脂和中间相沥青为粘合剂,通过浸渍、模压、碳化过程将一种廉价的国产碳纤维纸原纸改性成为一种质子交换膜燃料电池扩散层使用的碳纤维纸,大大降低了其成本。表征了所得碳纤维纸的主要性能——厚度、密度、孔隙率、透气性、电阻率和拉伸强度。结果表明,中间相沥青粒子不仅能够提高碳纤维纸的导电性和强度,而且不会像石墨粉一样引起孔隙率的极大降低。当中间相沥青粒子含量为15%时,所得碳纤维纸的性能基本满足质子交换膜燃料电池扩散层的使用要求。     

Electrically conductive carbon-coated ceramic fiber media

Porous ceramic fiber composites were coated with pyrolytic carbon by the decomposition of either propane or infiltrated phenolic resin in a nitrogen atmosphere at 800–900^∘C. The amount of carbon coating was varied to tailor the electrical conductivity of the carbon-coated composites. The electrical and thermal conductivity of the composites were measured at room temperature using a two-point method and a hot-wire one, respectively. Up to 30 wt% pyrolytic carbon, the electrical conductivity σ showed linearly increasing tendency and was fitted by the effective conductivity according to the parallel rule of a mixture σ =ΣV _i⋅σ_i with an effective conductivity of pyrolytic carbon σ_c and volume fraction of coated carbon V _c. The electrical conductivity of coated carbons prepared from propane at 900^∘C and phenolic resin at 800^∘C was of the order of 10⁰ and 10⁻¹ S cm⁻¹, respectively.     

大孔强碱阴树脂在电厂水处理中的应用研究

由于活性炭再生困难，废弃后造成生态破坏，通过树脂的静态-动态吸附实验，筛选出D730丙烯酸系大孔强碱阴树脂，并优化其吸附-脱附条件。D730树脂代替颗粒活性炭去除水中有机物的小试结果显示，D730树脂较GAC再生容易，抗污染能力强，经济和社会效益高。D730树脂吸附-脱附的稳定性试验表明，各周期出水水质均很好且稳定，CODcr去除率迭到80％以上，10个周期后，树脂理化性能仍保持很好，可望在电厂水处理中代替颗粒活性炭实现工业化应用。     

La0.67-xBixSr0.33MnO3化合物多孔陶瓷样品的微结构与CMR效应

用固相反应法制备了钙钛矿型氧化物La0．67-xBixSr0．33MnO3(x=0，0．1，0．2)多孔陶瓷样品，研究了这些化合物的电磁性质和CMR效应j实验结果显示，Bi有助于晶粒的长大，并使电阻率峰值向低温方向移动。多孔样品的MR主要取决于显微结构，在0-300K温度范围内MR随温度升高单调下降。在较高的温度下观察到了低场磁电阻(LFMR)效应。与多晶致密样品相比，化合物多孔样品的电阻率峰变宽，峰值下降。     

超级电容器用复合炭极板电极的电化学性能

用高比表面积活性炭作为原料,酚醛树脂为粘结剂,在高温下粘结成型制备系列超级电容器用固体活性炭极板。采用直流恒流循环法和低温N2吸附对超级电容器电极进行充放电和孔结构分布测试,考察其电化学性能和结构的关系。实验发现,在不同组成的成型活性炭电极中,微孔活性炭含量大,则比电容高,炭化时温度高于800 ℃复合活性炭电极比电容下降。成型活性炭炭化后比表面积降低,微孔孔结构分布变宽,孔容在2~3 nm左右的分布明显加宽。     

嵌段共聚物对树脂基多孔炭电化学性能的影响

以间苯二酚(R)、甲醛(F)为原料,盐酸作催化剂,通过添加嵌段共聚物F127作致孔剂,利用溶液协同自组装和炭化处理制备多孔炭材料。采用扫描电镜、透射电镜和N2吸附分析不同F127加入量制得的多孔炭材料的形貌和孔隙结构,并利用直流充放电、交流阻抗技术和循环伏安法测定以上述多孔炭材料为电极的双电层电容器(EDLC)的电化学性能。结果表明:酸催化下的酚醛树脂基体网络结构在炭化过程中较好地保留了F127形成的微相结构,不同F127加入量制得的多孔炭材料比表面积在640～700 m2/g。F127/R为1.3时制得的多孔炭材料比表面积为701.2 m2/g,孔容为0.54cm3/g,其中中孔孔容0.362 cm3/g,中孔率达67.04%;在30%KOH电解质溶液中低电流密度(1 mA/cm2)充放电时的比电容为165 F/g,电流密度增大20倍,容量保持率为95%,经过5 000次循环,容量保持率达94%以上,具有良好的大电流充放电性能和循环性能。     

高压直流输电单极运行对土壤电阻率的影响(英文)

UHVDC transmission system is characterized by transferring large amount of electrical power over long distance , which plays an important role in the west-to-east power transmission project. Since the underground current can reach several kA under UHVDC monopole operation, the safe and stable operations of grounding electrode are highly relative with nearby soil resistivity. This paper introduces porous media model and analyzes the influence of rising temperature around grounding electrode on soil resistivity. Based on researching soil conduction mechanism under DC, calculation formula for soil resistivity and the rule of DC density on soil resistivity are presented. Furthermore, the relationship between DC density and soil resistivity is obtained, which was demonstrated by current characteristics experiment of soil resistivity.     

碳纤维水泥基复合材料研究中存在的若干问题探讨

碳纤维水泥基复合材料的研究方兴未艾。本文结合近年来对碳纤维水泥基复合材料的研究,对电阻(率)测试方法、渗滤阈值、物理性能、电性能的稳定性等方面进行了探讨,得到了一些相关结论,旨在为碳纤维水泥基复合材料的后续研究提供一定参考。     

Electrical resistance of electroconductive plastic composite with carbon fiber filler

To obtain a new electroconductive composite, the vapor-grown carbon fiber (VGCF) has been applied to the thermoplastic resin composite as a conductive filler. The stability of electrical conductivity of the composite is investigated. The resistivity of VGCF composite is 1.7 × 10^?1 Ω·cm at room temperature which is one order smaller than that of commercial grade composites with carbon filler. The stability of electrical conductivity, under temperature change (?35 to +60°C) and for exposure tests (at room temperature and at 60°C), the VGCF composites have high degree of stability. The stability of electrical conductivity of the present composites are superior to those of conventional carbon fibers such as PAN-based, under tensile stresses and bending stresses. It is suggested that the fine conductive networks in the present composites give rise to these desirable performances.     

镍粉/环氧树脂复合材料的压敏性

探讨了镍粉/环氧树脂复合材料电阻率的测试方法,研究了不同镍粉掺量、不同柔韧性环氧树脂掺量的镍粉/环氧树脂复合材料在单轴压缩下的电阻率变化规律,并结合镍粉/环氧树脂复合材料的静态电阻率和压力下的体积变化讨论了其压敏性产生机理.研究结果表明:采用直流两端电极法与直流四端电极法所测得的镍粉/环氧树脂复合材料的电阻值较为一致,...     

Preparation and characterization of negative temperature coefficient (Ni,Mn)<Subscript>3</Subscript>O<Subscript>4</Subscript>–La(Mn,Ni)O<Subscript>3</Subscript> composite

The composites made of spinel-structured (Ni,Mn)₃O₄ and perovskite-structured La(Mn,Ni)O₃ were investigated for potential application as negative temperature coefficient (NTC) thermistor. The composites were prepared using the standard ceramic route. The electrical resistivity of the composite at 25°C was found to decrease by one to two orders of magnitude depending the amount of the low-resistivity perovskite phase, while the thermal constant determining the temperature sensitivity of the NTC thermistor was still reasonably large in the range of 4,000 to 3,000 K, and the resistivity drift after annealing at 150°C for 1,000 h in air was relatively small (∼1.2%). The general effective media model was adopted to fit the electrical resistivity data of the composites, giving a value of 0.37 for the percolation volume fraction of the perovskite phase. This work demonstrates that it is possible to tune the electrical resistivity and thermal constant of the spinel-structured oxide through making composite with low-resistivity perovskite-structured oxide.     

含氮酚醛树脂的合成研究

介绍了含氮酚醛树脂的合成方法,研究了原料配比、催化剂种类及用量和pH值对合成含氮酚醛树脂的影响。结果表明:当酚、醛、有机胺的配比为10∶8∶2,催化剂M2用量为4%,pH值为10时,合成的含氮酚醛树脂产率最高,含氮量最大。用该含氮酚醛与环氧树脂复配制备的环氧酚醛玻璃布层压板具有较好的阻燃性能、力学性能和电气性能。     

Preparation of Functionally Graded PZT Ceramics Using Tape Casting

Functionally graded ferroelectric ceramics (FGM) have been fabricated for pyroelectric applications by an aqueous tape casting technology. The FGM produced in this study consisted of a porous Lead Zirconate Titanate (PZT) tape-cast ceramic, which was made by starch inclusions; sandwiched between two dense PZT layers by stacking and lamination. This paper investigates the effect of porosity on the microstructure and electrical properties of the PZT FGM samples produced. The microstructure of the porous and laminated sintered structures was studied using Scanning Electron Microscopy (SEM). The grain size of the porous layer tended to decrease with increasing corn-starch content. The dielectric constant and pyroelectric coefficient of the FGM both showed decreasing behaviour with increasing porosity.     

酚醛树脂包覆改性对废旧石墨负极材料结构与18650电池性能的影响

采用液相浸渍的方法,以5%~8%酚醛树脂(包覆量为质量分数,下同)为包覆碳源,废旧石墨作为核壳结构的核,经过850℃、4h高温热处理,制得核壳结构的酚醛树脂热解碳/废旧石墨复合材料。通过XRD、SEM、拉曼、BET等检测手段研究碳包覆改性对石墨样品的微观形貌、近表面区域结构以及以该复合材料为负极的18650型电池的高温、常温荷电保持率和电化学性能的影响。结果表明,酚醛树脂包覆碳化之后,石墨颗粒的表面形貌变得光滑,材料的石墨化度降低。电池的高温、常温荷电保持率从未包覆时的85%和82.4%提高到93.8%和91.2%。酚醛树脂包覆量为8%时,循环稳定性最好,1C循环1000次后,容量保持率仍有91.5%。     

碳纤维的纳米压痕行为

通过纳米压痕测试法探讨了碳纤维和基体材料的压入响应,获得了在各自载荷范围下的载荷和位移曲线,得到了在载荷作用下压痕参数即最大压入深度、接触深度和残留压痕深度,以及相应的硬度和接触弹性模量。研究结果表明,最大压入深度、接触深度和残留压痕深度均随载荷的增加而线性增加;而硬度、接触弹性模量随着载荷的增加而基本上保持稳定的值。当载荷继续增加至其所产生的压痕尺寸不足于周围区域的十分之一,所测得碳纤维的接触弹性模量较小,所测得的基体材料接触弹性模量较大,碳纤维的接触弹性模量与基体性能在较大载荷下存在较明显的依赖关系即基体效应。     

The application of porous silicon to optical waveguiding technology

The porosification of silicon can be achieved by the partial electrochemical dissolution (anodization) of the surface of a silicon wafer. The degree of porosity is dependent on the anodization parameters and can generally be controlled within the constraints imposed by substrate dopant type and concentration. Control of porosity leads to control of refractive index, and therein lies the concept of using porous silicon as an optical waveguide. We discuss porous silicon wavegides, for the visible to the infrared, produced by a number of approaches: 1) epitaxial growth onto porous silicon (where the porous layer acts as a substrate for a higher refractive index waveguide epilayer); 2) ion implantation (where either selective areas of high electrical resistivity can be produced, which act as a barrier against porosification, or where the surface of a porosified layer is amorphised to form a waveguide; 3) porous silicon multilayers (where the anodization parameters are periodically varied to produce alternate layers of different porosity and thus refractive index); and 4) oxidation of porous silicon (where a porosified layer is oxidized to form a graded-index, dense or porous, oxide waveguide)     

高速冲击过程中碳纤维／环氧树脂复合材料筒体强度分析

利用复合材料层合板理论对碳纤维/环氧树脂复合材料筒体在高速冲击过程中的受力状况进行了简要分析,并结合高速冲击试验结果,对碳纤维/环氧树脂复合材料筒体的破坏形式进行了简析。     

多孔微晶炭的制备及储锂性能研究

将AR树脂液相炭化、高温炭化后,通过KOH活化及氢气还原制备了多孔微晶炭。采用N2物理吸附、X射线衍射(XRD)和X射线光电子能谱(XPS)等手段表征了炭化、活化及氢气还原样品的孔结构、微晶结构和表面化学性质,并通过恒电流充放电测试和循环伏安测试研究了该材料作为锂离子电池负极材料的电化学性能。研究结果表明:炭化样品首次可逆比容量为565.6 mAh/g,活化样品高达925.3 mAh/g,但循环性能欠佳;经氢气还原后首次可逆比容量仍可达684.0 mAh/g,30次循环后维持在约600 mAh/g,具有很好的循环性能。     

高电压大容量陶瓷电容器组开发与应用

为了防止机车驶过分相绝缘器的过电压损害机车控制系统,保证火车正常运行,常在绝缘器两端加装阻容装置,高电压大容量的电容是该装置的核心元件。本文通过选用一种高介电常数的瓷料,设计并制造了一种小体积、低介质损耗的陶瓷电容器组。该电容器包含16个并联的电容器单元,每个电容器单元由3个陶瓷电容器元件串联组成。通过合理布置电容器组的结构,在保证基本电气性能的基础上预防了环氧树脂浇注的应力集中,同时减少了环氧树脂的用量,提高了产品的环保性能。该产品具有电容量大、介质损耗小、环保无油污染的特点,并已开始工业化生产且投入相关线路的使用。     

Application of SiC-Si functionally gradient material to thermoelectric energy conversion device

Because of its high–temperature chemical stability, SiC ceramic is a promising material for high-temperature device applications such as thermoelectric energy converters. However, the electrical conductivity of SiC ceramic is too low for it to be used as a thermoelectric energy converter at the cold junction. Therefore, we propose a SiC-Si functionally gradient material (FGM) in order to improve the electrical conductivity of the SiC ceramic at the cold junction. An SiC rod was fired in a temperature gradient furnace. One end of the SiC rod was maintained at 2473 K and the other end was maintained at 1973 K for 30 min. After firing, the porous SiC edge fired at 1973 K was dipped into molten Si in order to infiltrate molten Si into the porous SiC. The microstructure of the FGM is classified into three regions: the SiC-Si composite material; the porous SiC ceramic; and the densified SiC ceramic. The electrical conductivity, the Seebeck coefficient and the thermal conductivity for each region of SiC-Si FGM was measured at 300 K; a figure of merit was calculated. The figure of merit of the SiC-Si FGM at the cold junction, at room temperature, was 10⁸ times higher than that of a nongradient SiC ceramic.