锂离子电池碳纳米管负极材料储锂性能研究

将碳纳米管用于锂离子电池负极材料,用循环伏安及充放电实验研究了电极的性能.结果表明,碳纳米管用作锂离子电池负极,具有较高的储锂容量,首次放电容量达560mAh/g,但首次不可逆容量损失也大,高达430mAh/g.经过第1次充放电的容量损失后,随后各次的容量损失很小,碳纳米管的循环性能趋于稳定.     

多孔硅/石墨烯锂离子电池负极材料的制备及其电化学性能研究

以Al-20Si合金为原料制备多孔硅粉体材料和多孔硅/石墨烯复合材料,并将其用作锂离子电池的负极材料。采用盐酸浸蚀合金的方法制备多孔硅粉体材料,通过借助超声向硅基材料中分别添加不同含量的石墨烯(0,5%,10%,15%,20%,25%)制备多孔硅/石墨烯复合材料。实验结果显示,在多孔硅基材料中添加10%石墨烯的电化学性能最好,首次充放电容量为2 552 mAh/g,最后稳定在540 mAh/g。首次充放电效率为78.5%,循环至第5次后,后续充放电过程中效率维持在98%左右。石墨烯添加量超过10%后。随着添加量的增加性能逐渐下降。石墨烯的加入会使充放电比容量有所降低,但会使硅的循环稳定性增加。     

碳芯结构LiFePO_4/C复合材料的表征及电化学性能

采用环氧树脂为碳源制备出碳芯结构LiFePO4/C复合材料.利用X射线衍射、扫描电镜、透射电镜和X光电子能谱等分别对复合材料的晶体结构、表面形貌及表面成分进行表征,采用恒电流充放电和电化学阻抗方法研究试样的电化学性能.实验结果表明:碳芯结构复合材料是由无定形碳线和纳米LiFePO4颗粒组成.碳芯结构LiFePO4/C复合材料在15mA/g的电流密度下,首次放电容量达到166mAh/g,当电流密度增加到750mA/g,放电容量高达131mAh/g,经过50次循环后,容量保持率高达99.2%.     

锂离子电池硫复合正极材料的制备及性能研究

用一种简单、成本低的方法制备出碳纳米管/硫复合材料.通过X射线衍射(XRD)和扫描电镜(SEM)表征产品的结构及形貌;通过充放电测试及循环伏安测试表征其电化学性能,复合材料首次放电比容量为539mAh/g.     

碳纳米管/微膨石墨复合负极材料的制备及电化学性能研究

通过对两种天然鳞片石墨进行微膨胀处理得到微膨石墨,然后以微膨石墨为基体采用化学气相沉积(CVD)法于微膨石墨的孔洞结构中原位生长碳纳米管,制备了碳纳米管/微膨石墨复合负极材料.电化学测试结果表明两种复合材料分别具有443和477 mAh/g的首次可逆容量.两种复合材料在0.2C倍率下循环充放电30次后容量均能保持95%以上;在1C下循环充放电50次后,可逆容量分别稳定在259和195 mAh/g.微膨胀处理形成的微纳米级孔洞以及原位碳纳米管的网络结构,提供了更多的储锂空间,并能够有效地缓冲电极材料在充放电时的体积变化;电解质溶液浸润在纳米孔洞中,有利于缩短锂离子的扩散路径,提高倍率循环性能;同时原位生长的类似常春藤形的碳纳米管可以起到桥梁的作用,避免"孤岛"的形成,增强了复合材料的导电性能.     

碳纳米管/中间相炭微球复合材料锂离子电池负极材料研究

采用热缩聚法(温度为420℃、反应时间为2 h)制备出碳纳米管/中间相炭微球复合材料。研究了碳纳米管添加量对中间相炭微球的形成和形貌的影响,以及对碳纳米管/中间相炭微球复合材料充放电性能的影响。实验结果表明,5%(质量分数)的碳纳米管添加量有利于中间相炭微球的形成,碳纳米管/中间相炭微球复合材料作为负极材料的锂离子电池充放电容量可达到337 mAh/g,20次循环后容量仍保持88%。     

无黏结剂柔性Si/CNT/纤维素复合阳极及其电化学性能

硅/碳复合材料作为最具潜力的下一代阳极材料,受到广泛关注。为减少硅巨大膨胀所产生的应力,避免硅纳米颗粒的粉化,提高硅基锂离子电池的电化学性能,制备了一种多微孔结构的多壁碳纳米管(MWCNTs)纸,嵌入纳米硅制得Si/MWCNTs/纤维素复合柔性锂离子电池阳极。FESEM显示,纳米硅均匀地嵌入在MWCNTs构建的三维导电网络中,纳米硅和导电载体具有良好的接触,使得界面电阻大幅下降,同时纳米硅在电池充放电过程中具有足够的膨胀空间,保证了材料的结构稳定性和化学稳定性。电化学检测显示,其首次放电比容量达到2024 mAh/g,循环30次后比容量维持在850 mAh/g,展示出良好的循环稳定性和较高的比容量。同时,其制作工艺相比传统涂敷类阳极得以简化,可操作性高,易于实现产业化。     

锂离子电池中高容量硅铝/碳复合负极材料的制备与性能研究

锂离子电池用高容量负极材料普遍存在首次不可逆容量高、循环性能差等问题. 本文采用高温固相法制备了硅铝/碳锂离子电池负极材料, 制备出的复合负极材料的比容量远高于目前锂离子电池普遍使用的中间相碳微球, 循环寿命则优于同粒度的硅单体为活性中心的硅碳复合材料. Al引入Si/C复合材料中, 有效抑制了材料的首次嵌锂深度,且减缓了电压滞后现象. 制备的复合负极材料首次可逆容量达到600mAh/g, 首次充放电效率在85\%以上, 25次循环后容量仍保持90%以上.     

纳米Si掺杂SiOx-Si@C@碳纳米管复合负极材料的制备及性能

在对氧化亚硅(SiO)材料进行表面碳包覆和添加导电材料的基础上,掺杂少量纳米Si进一步提高其首次充放电容量和首次库仑效率。采用XRD、SEM、TEM、Raman、FTIR分析材料的物相结构和微观形貌,通过恒流充放电测试仪分析复合材料的电化学性能。结果显示,纳米Si质量为SiO_x质量10%的复合材料(SiO_x-Si@C@碳纳米管(CNTs)-10)的首次充放电容量分别为1 348.1 mA?h/g和1 874.4 mA?h/g,首次库仑效率为71.9%,循环100周后材料的可逆容量为1 116.2 mA?h/g,容量保持率为82.8%;以不同电流密度充放电,其放电容量远远高于没有纳米Si掺杂的材料。SiO_x-Si@C@CNTs复合材料具有较高的首次库伦效率、较好的循环性能和倍率性能。      

铝/石墨复合材料的制备及其电化学性能研究

铝作为负极材料其理论容量较高,但铝在充放电过程中会出现严重的体积膨胀,导致循环性能差。为克服铝体积膨胀严重的缺点,采用简单的球磨法成功制备出铝/石墨复合材料。利用X射线衍射仪、扫描电子显微镜对复合材料的结构和形貌进行分析。电化学性能测试表明,铝/石墨复合材料首次放电比容量高达1004mAh/g,循环15次后容量保持在300mAh/g。铝/石墨复合材料拥有较高的放电比容量和较好的循环性能,在锂离子电池负极材料中具有潜在的应用价值。     

Diamond formation on carbon/carbon composite

A carbon/carbon composite was used as substrate for low-pressure diamond deposition. To enhanced diamond nucleation on carbon/carbon composites, a total of ten surface preparation methods have been investigated. These methods involved the use of atomic hydrogen etching, mechanical polishing, sonication, or coating. Diamond nucleation was found to occur on either the defects of the carbon/carbon composite substrates or diamond particulate left on the substrates. The defects were created primarily by atomic hydrogen etching during the coating process. Seeding with diamond powders was performed by dip coating, sonication, or spray-coating processes. It was found that these seeding processes resulted in excellent nucleation of diamond.     

Characterization of fibre/matrix interfaces in carbon/carbon composites

The present paper proposes an approach to characterizing fibre/matrix (F/M) interface in carbon/carbon (C/C) composites with respect to both modes of loading that may be expected: opening or shearing. Push-out and tensile tests were used. The former tests involve the shearing mode whereas the latter ones involve the opening one. Push-out tests use a diamond indenter to load the fibres. The interface sliding shear stress was obtained from the load-fibre displacement curve. The tensile tests were conducted on specimens having fibres oriented at 90° with respect to loading direction in order to preferentially open the interfaces. Interface opening strength was extracted from the composite tensile stress–strain behaviour. The specimens were examined under load and after ultimate failure by optical microscopy (OM). The mechanical properties of the F/M interfaces were then discussed.     

Vitreous joining of SiC-coated carbon/carbon composites

This paper investigated the feasibility of joining of carbon/carbon (C/C) composites by using a silicate as interlayer. A SiC coating was pre-prepared on C/C substrate by pack-cementation technique to improve the wettability of glass on C/C composites, then the joints were prepared by a one-shot and low cost way. Microstructure and morphologies of the as-received joints were characterized by XRD, SEM and EDS. The results indicated that the SiC coating not only had a strong bonding with C/C composites, but also had a good physical and chemical compatibility with silicate glass. The room-temperature shear strength of the joints gives encouraging results, which can be up to 26 MPa. The fracture mode and the fracture behavior were discussed also.     

Structural response of oxidation-resistant carbon/carbon composites

Computational simulation of time, temperature, and oxidation-dependent response of carbon/carbon composites is illustrated and compared to experimental data. The material system examined is a SiC-coated, balanced eight-layer 8-harness satin weave carbon fibre cloth with boron carbide inhibitors in the matrix. Two representative cells, in-plane and through-the-thickness of the textile architecture, are developed to describe time(oxidation)-dependent material properties and thermo-mechanical response under static and cyclic loads with two-dimensional finite elements. These intelligible models enable a realistic interpretation of the overall response of the laminate subjected to the complex thermal-oxidative-mechanical loading conditions, and closely agree with the experimental data.     

Static friction properties of carbon/carbon composites

Preforms were made from 1K PAN plain carbon cloth and densified using the rapid directional diffusion chemical vapor infiltration (RDD CVI) processes. Four carbon/carbon (C/C) composite specimens treated at 1800 (specimen A), 1800+2000 (B), 2000 (C), and 2300 °C (D), respectively, were prepared, then machined into ring-on-ring specimen configurations. The influence of high-temperature heat treatment and the test temperatures on the static friction properties of the C/C composites has been researched. The results show that the high-temperature heat treatment processes has an important impact on the static friction behaviors of RDD CVI C/C composites. With raising the treatment temperature, the interlayer spacing of the matrix carbon in them becomes small, and the crystallite width as well as height increase. Under the test at room temperature, the static friction coefficients (FC) of the specimen treated at 1800 °C (A) are the lowest, but become very big and the highest under the test temperature of 260 °C due to desorption of the water absorbed on the friction surface. The composites treated at 2000 °C (C) exhibit enough high static friction coefficients under room temperature owing to their absorption of less water and the difficult delamination of the matrix carbon. However, in the test temperature of 260 °C or after the dynamic friction tests, their static FC is low. The specimen treated at 2300 °C (D) has a low FC at 260 °C heat condition, but its FC is higher than that of A and C under room temperature and largest after dynamic friction tests. No matter how high the heated temperatures are, the static FC of C/C composites decreases with an increase of the brake-specific pressure. When the specific pressure is very high and exceeds a certain value, the static FC is almost the same for specimens B, C, and D.     

超高温陶瓷改性碳/碳复合材料

碳/碳(C/C)复合材料因密度低、抗热震性能好以及高温力学性能优异等众多优点被广泛应用于航空航天领域,但抗氧化性较差使其应用受到很大限制.将超高温陶瓷(UHTCs)引入C/C复合材料基体制备超高温陶瓷基体改性碳/碳复合材料(C/C-UHTCs)是目前提高C/C复合材料抗氧化性的主要途径.当前C/C-UHTCs的多种制备工艺都无法兼具低成本、高效率、均匀致密的效果;相比于C/C复合材料,C/C-UHTCs的抗氧化耐烧蚀性能和力学性能都得到了提升.为了满足现代尖锐前缘飞行器的发展需求,C/C-UHTCs的抗氧化耐烧蚀性能还需要进一步提高;同时,还需要降低C/C-UHTCs的脆性,提高材料的可靠性,避免发生脆性断裂.为了给后续研究提供参考,从制备工艺、结构特征、抗氧化耐烧蚀性能以及力学性能四个方面综述了C/C-UHTCs当前的研究进展,并预测C/C-UHTCs的制备工艺将从降低成本、减小对纤维增强体的损伤等角度进一步优化,以赋予制备材料更为均匀致密的结构以及更优的性能.     

碳/碳复合材料的应用研究进展

综述了碳/碳(C/C)复合材料的性能及其在各个领域的应用现状.     

碳/碳复合材料纤维束/基体界面强度的表征

为了获得准确表征纤维束界面强度的方法,对影响纤维束界面强度的因素进行了研究.通过顶出方法对纤维束界面强度进行表征,利用SEM和Micro-CT研究了纤维束界面层微结构对纤维束界面强度的影响,并通过有限元分析方法对纤维束界面的断裂行为进行分析.结果表明：在纤维束界面层含有不同程度的脱粘和裂纹缺陷结构,影响了纤维束的界面强...     

炭/炭复合材料表面C/SiC/Si-Mo-Cr多层复合防氧化涂层研究(英文)

为提高炭/炭(C/C)复合材料的高温抗氧化性能,采用料浆涂刷法首先在C/C复合材料表面制备了预炭层,然后以Si粉及石墨粉(Si粉与石墨粉的质量配比为:60～80:10～25)为原材料采用包埋法经高温热处理获得C/SiC内涂层,最后在涂有C/SiC内涂层的C/C复合材料表面采用包埋法制备Si-Mo-Cr外涂层。借助扫描电镜、X射线衍射、电子能谱等分析测试手段对涂层试样的微观结构进行了分析,研究了涂层C/C复合材料在1 873 K和1 973 K下的氧化行为。结果表明:由于涂层氧化过程中表面生成了SiO2和Cr2O3复合玻璃层,其在1 873 K温度下表现出优异的防氧化性能,可以有效保护C/C复合材料达135 h。当氧化温度提高至1 973 K并氧化30 h后,该复合涂层氧化过程玻璃层完整性被破坏,涂层失效。