生物质多孔碳基复合相变材料制备及性能

目前,通过多孔高导热载体与相变材料复合的方式提升有机复合相变材料综合性能的方法得到广泛应用。多孔碳作为负载能力强,导热性能良好的载体材料成为研究的热点,但如何绿色、廉价、简易地制备出该类载体仍是研究的难点。本文以天然生物质材料松木和竹木为碳源,在梯度温度和氮气气氛下热处理,使生物质材料碳化并进一步发生石墨化转变,制备出生物质天然孔道结构的多孔高导热碳基载体材料。采用真空熔融浸渍法将有机相变材料石蜡和多孔碳基载体材料进行高效复合,制备得到生物质多孔碳/石蜡复合相变材料。通过扫描电子显微镜（SEM）、红外光谱仪（FTIR）、同步热分析仪（TGA）、X射线衍射仪（XRD）、拉曼光谱仪（Raman）、压汞分析仪（MIP）、差示扫描量热仪（DSC）、激光导热仪对载体材料及复合相变材料进行结构表征和性能测试。测试结果表明:生物质多孔碳载体材料孔道结构保存完好,石墨化转变明显,保证了有机相变芯材的高效稳定负载。传热效率上,相比于纯石蜡芯材,以松木和竹木为碳源制得的多孔碳/石蜡复合相变材料热导率分别提高了100%和216%,达到了0.48 W·m?1·K?1和0.76 W·m?1·K?1。在此基础上,通过对比松木和竹木为原料制得的复合相变材料的芯材负载量,相变焓值,热导率的变化,进一步探讨了生物质结构对复合相变材料性能的影响机制。      

茄子衍生多孔碳负载聚乙二醇相变复合材料

以茄子为原材料,通过水热处理–后续热解法及直接热解法分别制备出两种不同的茄子衍生多孔碳材料（HBPC和BPC）。以茄子衍生多孔碳材料为载体,采用真空浸渍法负载相变芯材聚乙二醇（PEG2000）,制备出聚乙二醇/茄子衍生多孔碳材料复合相变材料。通过扫描电镜、拉曼光谱、压汞法、傅里叶变换红外光谱分析、X射线衍射仪、热重分析仪和差示扫描量热仪对其进行结构表征及性能测试。结果表明,通过直接热解法制得的茄子衍生多孔碳材料为载体的聚乙二醇/茄子衍生多孔碳材料复合相变材料具有更好的相变储热效果,负载聚乙二醇的质量分数高达90.60%,熔融潜热为133.98 J·g?1,达到了较好的定形相变效果及良好的循环稳定性。      

Principles of the design of highly porous layered composites working in the bending mode

A comparative analysis is made of the spesific mechanical characteristics of a sandwich-type laminated porous composite under bending. The external layers of the composite are compact while the internal layer consists of a highly porous material made by using a pore-forming agent. The specific stiffness, strength, and yield load as a function of the volume fraction of pores Θ and the porous/compact-layer thickness ratio λ are considered. The stiffness, strength, and yield load are shown to be affected by variations of Θ and λ when the weight of the composite is constant. Translated from Poroshkovaya Metallurgiya, Nos. 3/4(412), pp. 70–78, March–April, 2000.     

Comparison of the Wear Properties of Polymer Composites Having CNT With and Without Glass Fiber Reinforcement

The adoption of light weight and high performance polymer matrix composites are needed for industries related to aerospace, automotive, consumer goods, etc. Polymer fiber reinforced composite material have very good desirable mechanical and thermal properties like low density, higher specific stiffness with high specific strength and a controlled co-efficient of thermal expansion with dimensional stability. The addition of carbon nanoparticle in these composites improved mechanical as well as wear properties of the material, which leads to more applications of these composites in various fields. In the present investigation carbon nanotube addition along with the glass fiber reinforced composite material was used as work material. The sliding wear tests were carried out on pin on disc wear tester. The tribological performance was studied by varying the applied load. The wear surfaces were analyzed by using scanning electron microscope, X-ray diffraction and energy-dispersive X-ray spectroscopy which are presented in detail.     

Formation of the properties of antimony matrix alloys for frame-type composite materials

A frame-type composite material (CM) produced upon impregnation represents a system consisting of a rigid porous frame and a matrix material filling its voids. When metals are used as a matrix material, they bring up specific problems related to melting of a metal, such as the thermal effect of the metal on the frame and the chemical interaction of the matrix and frame with the formation of brittle compounds. A CM that combines the best characteristics of its components can be produced. Since impregnation is, as a rule, performed under vacuum, melting of a matrix metal is accompanied by an increase in the evaporation rate. The evaporation of a matrix metal can be decreased by controlling its chemical composition, decreasing the melting temperature of the melt, and controlling the cooling rate. In this work, antimony alloys are used as a matrix material and their properties are studied.     

Work and kinetics of densification in the free forging of a reinforced composite consisting of a porous matrix and uniaxially aligned fibers

Conclusions An analysis is carried out of the energy expenditure in the densification of a uniaxially reinforced material with a porous matrix by free forging. It is shown that the specific work of densification of such a composite depends on the porosity and resistance to plastic deformation of the matrix and on the geometry of the composite. A kinetic equation is derived for the densification of a uniaxially reinforced material by free forging. It is demonstrated that the amount of energy expended in the densification of a composite to the monolithic state is greater in free forging than in pressing in a die.Translated from Poroshkovaya Metallurglya, No. 10(190), pp. 19–25, October, 1978.     

Influence of additives of carbon nanotubes on the structure and properties of metal binders for a diamond tool

The possibility of alloying the powder alloy of the Fe-Cu-Co-Sn system with multilayered carbon nanotubes (MCNTs) in order to form a dispersion-hardened composite material with improved mechanical and tribological properties, which can be used as a binder for a diamond cutting tool, is considered. The mixing mode of carbon nanotubes with the starting powder binder is selected. The dependence of physicochemical properties of the composite material on the MCNT content is investigated in a range of 0.01–3%. The composite binders with the optimal MCNT content at a level of 0.01% are fabricated. The alloy is characterized by improved mechanical properties; namely, hardness increases by 9–11 HRB units and the bending strength for three-point bending increases by 100 MPa.     

“碳纤维增强复合材料”在汽车刹车片上的应用

汽车刹车片主要是由基体粘结剂、增强纤维以及摩擦性能调节剂组成。对于每一种具体的摩擦材料一般都是由几种到十几种组份组成,每种组份在其中都会起到一定的作用,而且各组份的性能、比例、物理化学状态都会影响摩擦材料的综合性能[1]。本文将从汽车刹车片摩擦材料所用碳纤维增强复合材料的特点、优势、使用效果方面进行分析。     

半焦制备活性炭的新工艺

摘要：基于煤基直接还原过程,以半焦为原料,利用铁矿预热氧化球团还原产生的气体为活化剂,开发一步法炭化、活化制备高性能活性炭新工艺,并通过优化制备温度、制备时间及还原剂用量等工艺参数,可同时得到优质还原球团。结果表明：在制备温度850℃、时间1h,半焦/球团的质量比为1∶1～4∶1的条件下,活性炭产率大于67%,耐磨强度达90%以上,比表面积和碘吸附值分别高于330m2/g、500mg/g,远优于商品活性炭,同时可得到金属化率为85%以上的预还原球团。     

锂离子电池负极材料PSi@GO的制备及其电化学性能

具有高能量密度的硅材料是锂离子电池负极的优选材料之一。但是,低电导率和在充放电过程中伴随的巨大体积变化而导致循环过程中容量迅速衰减,阻碍了硅材料商业化。本文以商业化的铝硅合金为硅源,通过冷冻干燥方法将氧化石墨烯（GO）包覆在其表面,制备了微米级的多孔硅（PSi）与GO的复合材料PSi@GO。该复合材料核层多孔硅内部丰富的孔隙提供充足的空间以适应硅的体积变化,外层的氧化石墨烯可以加速离子和电子传输,并再次缓冲硅的体积变化,从而可以有效地改善硅负极的循环稳定性和倍率性能。研究结果表明,电流密度为500mA/g时,PSi@GO-2（PSi与GO质量比为10∶5）复合电极材料循环100次后,比容量仍可达到1 275 mAh/g;在电流密度为4 A/g时,该复合材料也可达到980 mAh/g的高比容量。该PSi@GO-2复合材料显示了优异的倍率性能,具有良好的应用前景。      

Structure and mechanical properties of a multilayer carbide-hardened niobium composite material fabricated by diffusion welding

The structure, the bending strength, and the fracture mechanism of an artificial niobium-based composite material, which is fabricated by high-pressure diffusion welding of multilayer stacks assembled from niobium foils with a two-sided carbon coating, are studied. The microstructure of the composite material is found to consist of alternating relatively plastic layers of the solid solution of carbon in niobium and hardening niobium carbide layers. The room-temperature proportional limit of the developed composite material is threefold that of the composite material fabricated from coating-free niobium foils using the proposed technology. The proportional limit of the developed composite material and the stress corresponding to the maximum load at 1100°C are 500 and 560 MPa, respectively. The developed material is considered as an alternative to Ni–Al superalloys.     

聚苯胺/碳复合材料的导电性

采用原位聚合法制得聚苯胺/碳复合材料,通过扫描电子显微镜(SEM)、X射线衍射仪(XRD)、傅立叶红外光谱仪(FT-IR)、四探针测试仪和电化学工作站对试样进行表征测试。结果表明,掺杂不同碳材料对聚苯胺(PANI)复合材料的导电性影响较大、微观形貌变化明显,其中掺杂石墨烯制得的复合材料电导率是纯PANI电导率的2.5倍,掺杂r-GO/Fe_3O_4制得的复合材料的电导率最高且阻抗最小,电导率达6.49 s/cm。掺杂后制得的PANI复合材料中,PANI的衍射峰及特征吸收峰依然存在,碳材料的掺杂改性未破坏PANI的性质,且可增强复合材料的导电性。     

超细氧化钨的制备及其光催化性能研究

以钨酸钠和盐酸为原料,碳纳米管为载体,采用一步法将钨酸颗粒直接沉积在碳纳米管管壁上,形成钨酸-碳纳米管(H2WO4-CNTs)复合物.或采用二步法将钨酸沉淀与碳纳米管复合,形成H2WO4-CNTs复合物.之后,在氧气气氛下进行煅烧,生成了氧化钨粉末.经物理性能测试,2种方法制备的H2WO4-CNTs复合物中钨酸颗粒的平均粒径分别为10 nm和100 nm.氧化钨粉末的平均粒径分别为250 nm和2μm,比表面积分别为36.53 m2/g和13.99 m2/g.采用紫外可见分光光度计测定了氧化钨的光催化性能,在11 W的日光灯照射下,当光照时间为30 min时,脱色率分别达到93.8%和79.1%.结果表明,一步法制备的氧化钨因具有更小的平均粒径和更大的比表面积,表现出更好的物理吸附性能和光催化性能.     

改性多孔钢渣/橡胶复合材料的制备及其性能

用磷酸、硅烷KH550和钢渣制备改性多孔钢渣, 以改性多孔钢渣取代部分炭黑.利用改性多孔钢渣、炭黑、橡胶、促进剂、硫磺、硬脂酸和氧化锌进行复合, 制备一系列改性多孔钢渣/橡胶复合材料, 研究了磷酸/钢渣质量比、硅烷KH550/多孔钢渣质量比、促进剂/硫磺质量比、硬脂酸/氧化锌质量比和改性多孔钢渣/炭黑质量比对改性多孔钢渣/橡胶复合材料力学性能的影响, 并且分析其影响机理.结果表明, 当磷酸用量为1.2 g、钢渣用量为30 g、硅烷KH550用量为0.3 g、炭黑用量为20 g、促进剂用量为0.8 g、硫磺用量为1.2 g、硬脂酸用量为0.8 g、氧化锌用量为2.2 g和橡胶用量为100 g时, 改性多孔钢渣/橡胶复合材料的力学性能较好, 即拉伸强度为18.4 MPa、邵尔A硬度为68.8、撕裂强度为44.6 kN·m-1.磷酸与硅烷KH550可以改善钢渣的孔结构与表面结构; 适量的促进剂/硫磺质量比与硬脂酸/氧化锌质量比可以消除硫磺形成的内硫环, 促使橡胶交联键稳定.改性多孔钢渣与橡胶以物理方式进行复合形成良好的包裹结构.      

二次电池电极基板用复合多孔金属材料的研究

介绍了一种复合金属多孔体的制备及其方法，首先以泡沫塑料为芯膜，经过导电化处理使其具有导电性，其次进行电沉积金属铁，再进行电沉积金属镍，经过热处理后可制备出复合金属多孔体。该复合金属多孔体用铁取代金属镍，其抗拉性能优于单质泡沫镍，同时可以降低制造成本，主要用于载体如电池电极。     

碳纳米管对W-Cu复合材料致密度和硬度的影响

采用机械合金化技术并结合真空烧结制备W-20％Cu／C复合材料,利用碳纳米管具有良好的综合性能作为W-20％Cu复合材料的强化相．采用粒度测试仪分析碳纳米管添加量不同时的W-20％Cu复合粉末粒径并测试W-20％Cu／C烧结体的密度和硬度,分析碳纳米管添加对W-20％Cu复合粉末粒度及W-20％Cu复合材料密度和硬度的影响．研究结果表明：添加碳纳米管可不断细化W-20％Cu复合粉末晶粒,W-20％Cu复合材料的密度和硬度随着碳纳米管质量分数的增加而逐渐提高,说明采用机械合金化技术能够使碳纳米管弥散分布在W-20％Cu复合材料中,充分发挥细晶强化作用．     

Forming porous fibrous materials by the pendant drop melt extraction

A method for forming porous material based on metallic fibers, which are obtained by pendant drop melt extraction (PDME) method, is proposed. An installation for forming porous fibrous materials by the PDME method is developed and fabricated. Samples of porous materials made of fibers of heat-resistant and corrosion-resistant steels, nickel alloys, zirconium, etc., are obtained. Mechanisms for forming the bonds between the fibers are investigated and an interaction model between the fibers in a formed material is proposed. The possibility of forming bonds between the fibers in a porous material based on copper and steel fibers at various extraction velocities is evaluated according to the proposed model.     

类松果状NiMoO4/MnO2复合材料的合成及超级电容性能

以Na₂MoO₄·2H₂O、NiSO₄·6H₂O和MnO₂为原料, 采用水热法成功制备了类松果状NiMoO₄/MnO₂复合材料.通过X射线衍射、扫描电子显微镜、恒电流充放电、循环伏安和交流阻抗对材料进行表征.结果表明, MnO₂的最佳质量分数为10%, 所得NiMoO₄/MnO₂复合材料具有类松果状形貌, 其颗粒直径为200~600 nm, 且表面粗糙、多孔; 在1 A·g-1的电流密度下, MnO₂质量分数为0、5%、10%、15%、20%时, 所得复合材料NM0、NM5、NM10、NM15和NM20的放电比电容分别为260、248、650、420和305 F·g-1.在电流密度为10 A·g-1下, 最佳样品NM10复合材料的首次放电比容量为102 F·g-1, 经过100次循环后, 其放电比电容稳定在147 F·g-1.该性能的提高, 主要是由于MnO₂的引入弥补了NiMoO₄单一材料存在的不足, 从而达到协同增效的作用.      

碳纳米管对W-Cu 复合材料致密度和硬度的影响

采用机械合金化技术并结合真空烧结制备W-20 %Cu/C 复合材料,利用碳纳米管具有良好的综合性能作为W-20 %Cu 复合材料的强化相. 采用粒度测试仪分析碳纳米管添加量不同时的W-20 %Cu 复合粉末粒径并测试W-20 %Cu/C 烧结体的密度和硬度, 分析碳纳米管添加对W-20 %Cu复合粉末粒度及W-20 %Cu 复合材料密度和硬度的影响.研究结果表明:添加碳纳米管可不断细化W-20 %Cu 复合粉末晶粒,W-20 %Cu 复合材料的密度和硬度随着碳纳米管质量分数的增加而逐渐提高,说明采用机械合金化技术能够使碳纳米管弥散分布在W-20 %Cu 复合材料中,充分发挥细晶强化作用.