热解有机前驱体制备超长的含硅一维纳米材料

介绍了一种超长含硅一维纳米材料的新的制备方法。使用的设备为一石英管式炉,制备温度在1100℃左右,氩气保护。当采用的前驱体分别为聚二甲基硅油、六甲基二硅烷或六甲基二硅胺烷时分别可得到长度为毫米级的SiC/SiO_2纳米电缆、SiC纳米线和SiCN纳米线。采用上述原料但采用不同催化剂、不同气氛及不同基板时可得到不同成分、不同形貌的含硅一维纳米材料,产物除了上述一维纳米材料外,还可制备非晶SiO_2纳米线、SiCN/SiON纳米电缆、SiC—SiO_2并行复合纳米线、以及非晶SiCN纳米线等。     

SiC一维、准一维纳米材料的制备工艺研究

综述了近年来SiC一维、准一维纳米材料制备工艺的最新研究进展,重点介绍了模板生长法、化学气相沉积法、熔体生长法、碳热还原法和溶胶-凝胶法的工艺特点,并对不同工艺方法制备的SiC一维、准一维纳米材料的微观形貌、优异性能进行了简要概述,总结了现阶段SiC一维、准一维纳米材料制备工艺研究所面临的问题及发展前景.     

一维纳米稀土氧化物的研究进展

概述了国内外在一维纳米稀土氧化物(纳米管、纳米棒、纳米线)方面的研究现状,介绍了硬模板法、软模板法、水热法、超声法和微乳液法制备一维纳米稀土氧化物的工艺方法和机理,并对这些方法的优缺点进行了比较,指出了当前一维纳米稀土氧化物合成中存在的不足,并对一维稀土纳米氧化物的应用作了展望.     

一维纳米结构导电聚苯胺的研究进展

概述了一维纳米结构导电聚苯胺的研究进展,详细介绍了最新的合成方法,包括模板法、乳液聚合法、电化学合成法、静电纺丝法以及界面聚合法,并简要介绍了一维纳米结构导电聚苯胺的特性和潜在应用前景。     

一维氧化锌纳米棒制备技术的最新研究进展

综述了一维氧化锌纳米棒制备技术的研究进展,着重介绍了氧化锌纳米棒的气相和液相合成方法.介绍了不同方法的反应特征、产物形貌及其性能,并对水热法、模板法、热分解前驱物法、离子液体分解法和化学气相沉积法的生长机理进行了描述,展望了一维氧化锌纳米棒的后续研究.     

SiC纳米复合涂层的制备及特性

SiC纳米复合涂层是一种新型的陶瓷材料.介绍了湿胶化学法和激光熔覆法两种最容易的制备方法,同时还讨论了SiC纳米复合涂层不同于其它常规涂层的特性,如涂层与基体之间的强粘结性、涂层致密性和高热辐射性等,最后分析了SiC纳米涂层的应用前景和未来的发展空间.     

静电纺丝法制备SiC纳米纤维的研究进展

SiC纳米纤维具有许多优良的性能,如低的热膨胀系数、高的比表面积、高强度以及高的热稳定性和热导率。静电纺丝法制备SiC纳米纤维被认为是最简单最通用的方法之一,并成功应用到了力学、电学、光学、热学等多个领域。对静电纺丝原理和装置,静电纺丝法SiC纤维的制备和影响因素进行了全面详细的介绍和归纳,并对纤维的二级结构做了简短的介绍,最后对SiC纤维未来的研究方向和应用提出了个人观点。     

SiC/CNTs纳米复合材料吸波性能的研究

采用聚碳硅烷前驱体转化法制备了SiC/CNTs纳米复合材料, 采用扫描电子显微镜、透射电子显微镜、高分辨电子显微镜对样品进行了微观结构分析, 并测试了材料在2～18GHz频率范围内的电磁参数. 结果表明, 当初始聚碳硅烷/二甲苯溶液浓度为10%～15%时, 聚碳硅烷前驱体转化法在CNTs表面可以制备SiC包覆层均匀致密的复合一维纳米材料. SiC包覆CNTs一维纳米材料的电磁参数测试表明, 其损耗机制以介电损耗为主, 当聚碳硅烷含量为15%时, SiC/CNTs纳米复合材料具有最高的介电常数和损耗角, 较好的电磁波吸收特性, 并表现出复合效应.     

气-液-固法在半导体纳米线生长中的应用

气-液-固法(VLS)是目前生长各种准一维纳米结构的主要工艺技术.本文首先介绍了VLS的生长原理,然后以生长机制为主线,着重评论了近3-5年内它在ZnO、GaN、Si以及SiC等纳米线及其阵列合成中应用的某些新进展.最后提出了改进VLS方法的几项措施,并展望了它的今后发展趋势.     

气-固反应法合成准一维纳米结构材料的研究

综述了利用气-固反应法合成准一维纳米结构材料的研究进展,简要介绍了气-固反应法与气相法的不同点,重点讨论了用气-固反应法直接热氧化或硫化铜、铁、锌等金属以合成准一维纳米结构氧化物、硫化物的过程以及气-固反应法的生长机理,并介绍了准一维纳米结构材料的潜在应用.     

碳化硅颗粒填充的碳纳米管/环氧树脂复合材料的吸波性能

以碳纳米管、碳化硅颗粒为原料制备环氧树脂复合吸波材料,并对其吸波性能进行测试,研究了碳纳米管、碳化硅颗粒含量与复合材料吸波性能的关系.结果表明碳纳米管、碳化硅颗粒的含量对复合材料的吸波性能有较大影响.随碳纳米管含量的增加,碳纳米管/环氧树脂复合材料的吸波性能先提高后降低,碳纳米管含量存在最佳值(12%,质量分数).将碳...     

The concept of cutting lines in carbon nanotube science

A review is presented of one-dimensional cutting lines that are utilized to obtain the physical properties of carbon nanotubes from the corresponding properties of graphite by the zone-folding scheme. Quantization effects in general low-dimensional systems are briefly discussed, followed by a more detailed consideration of one-dimensional single-wall carbon nanotubes. The geometrical structure of the nanotube is described, from which quantum confined states are constructed. These allowed states in the momentum space of graphite are known as cutting lines. Different representations of the cutting lines in momentum space are introduced. Electronic and phonon dispersion relations for nanotubes are derived by using cutting lines and the zone-folding scheme. The relation between cutting lines and singularities in the electronic density of states is considered. The selection rules for carbon nanotubes are shown to be directly connected with the cutting lines. Different experimental techniques are considered that confirm the validity of cutting lines and the zone-folding approach.     

不同物相电沉积CNTs对C/SiC复合材料力学性能的影响

采用电沉积法与化学气相渗透(CVI)法将碳纳米管(CNTs)分别引入到碳纤维表面和SiC基体中,制得了不同物相电沉积CNTs的C/SiC复合材料(CNTs-C)/SiC和C/(CNTs-SiC)。研究了CNTs沉积物相对C/SiC复合材料力学性能的影响,分析了不同CNTs沉积物相的C/SiC复合材料的拉伸强度及断裂机制。结果表明:相较于未加CNTs的C/SiC复合材料,CNTs沉积到碳纤维表面的(CNTs-C)/SiC复合材料的拉伸强度提高了67.3%,断裂功提高了107.2%;而将CNTs引入到SiC基体中的C/(CNTs-SiC)复合材料的断裂功有所降低,拉伸强度也仅提高了6.9%,CNTs没有表现出明显的增强增韧效果;C/(CNTs-SiC)复合材料与传统的C/SiC复合材料有相似的断裂形貌特征,断裂拔出机制类似,主要为纤维增强增韧,CNTs的作用不明显。     

Processing and properties of carbon nanotubes–nano-SiC ceramic

Carbon nanotubes–nano-SiC ceramic has been fabricated by the hot-press method. The preparation steps involved the use of dispersing nano-SiC powders and carbon nanotubes in butylalcohol using an ultrasonic shaker. The reasonable relative density of about 95% has been achieved by hot-pressing at 2273 K (at 25 MPa in Ar for 1 h). The three-point bending strength and fracture toughness of the composite has about 10% increment over monolithic SiC ceramic which was fabricated under the same process. The reasons for the increment are the strengthening and toughening role of carbon nanotubes occuring in the matrix.     

Templated,carbothermal reduction synthesis of mesoporous silicon carbide from carbon nanotube–mesoporous silica core–shell composite

Mesoporous materials are the subject of extensive interest due to their large surface area and multiscale structural order. These properties are especially relevant for applications such as catalyst supports in both chemical and electrochemical systems. The first part of this study details the synthesis of carbon nanotube–mesoporous silica core–shell composites starting with single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs) through micellar self-assembly. The formation of such a composite structure was verified using scanning electron microscopy and further analysis was carried out through X-ray diffraction (XRD). The subsequent refinement of the diffraction pattern revealed the silica shell to be of the continuous cubic (Ia3d) MCM48 structure. The mesoporous silica–carbon nanotube core–shell composite was later subjected to high-temperature carbothermal reduction. Subsequent XRD analysis showed that the reduction product was mesoporous silicon carbide (SiC). Thus, this study details a novel synthesis method for mesoporous SiC, which is an attractive material for possible diverse applications such as catalyst supports, intercalation electrodes and other emerging high technology areas.     

Formation of multi-walled carbon nanotubes with a metal-free chemical vapor deposition and their stepwise evolution

Multi-walled carbon nanotubes and one-dimensional wire-like nanostructures have been synthesized using acetylene as carbon sources with a metal-free mild chemical vapor deposition process. It shows that anisotropic carbon nanostructures can interact to form nanotubes by self-function. Furthermore, the detailed microscopic observation of the obtained nanostructures indicates that the development of fully hollow carbon nanotubes should undergo a quite complex physical and chemical transformation process, and their formation abides by the “particle-wire-tube” stepwise evolution mechanism. In this process, the one-dimensional wire-like nanostructures can be viewed as the intermediate stages of carbon nanotube formation, which record traces about nanotube evolution.     

碳化硅纳米晶须生长和显微结构

采用两步生长生在碳化硅纳米晶须，首先是二氧化硅与硅反应生成一氧化硅，再与碳纳米管先驱体反应生成β－ＳｉＣ纳米晶须，其直径为３～３５ｎｍ，长度为２～２０μｍ，用高分辨透射电镜研究晶须形貌，显微结构，讨论了碳化硅纳米晶须生长机制。     

Design,Fabrication, Characterization and Simulation of PIP-SiC/SiC Composites

Continuous SiC fiber reinforced SiC matrix composites (SiC/SiC) have been studied and developed for high temperature and fusion applications. Polymer impregnation and pyrolysis (PIP) is a conventional technique for fabricating SiC/SiC composites. In this research, KD-1 SiC fibers were employed as reinforcements, a series of coatings such as pyrocarbon (PyC), SiC and carbon nanotubes (CNTs) were synthesized as interphases, PCS and LPVCS were used as precursors and SiC/SiC composites were prepared via the PIP method. The mechanical properties of the SiC/SiC composites were characterized. Relationship between the interphase shear strength and the fracture toughness of the composites was established. X-ray tomographic scans of the SiC/SiC composites were performed and the closed porosities of the composites were calculated. The compatibility of the SiC/SiC composites with liquid LiPb at 800 °C and 1000 °C was investigated. High-resolution synchrotron X-ray tomography was applied to the SiC/SiC composite and digital volume correlation was employed for Hertzian indentation testing of the SiC/SiC composite. A Cellular Automata integrated with Finite Elements (CAFE) method was developed to account for the effect of microstructure on the fracture behavior of the SiC/SiC composite.     

Stability of single-wall silicon carbide nanotubes – molecular dynamics simulations

One-dimensional silicon carbide (SiC) nanotubes and nanowires are both realizable and may co-exist. The stability of SiC nanotubes relative to nanowires and against heating is still unknown. Using classical molecular dynamics simulations, the authors investigate the stabilities of SiC nanotubes; as a first step, the study focuses on single-wall nanotubes (SWNTs). The results show that SiC nanotubes are more stable than nanowires below a critical diameter of about 1.6 nm, while SiC nanowires are more stable than nanotubes beyond that. As temperature increases, melting takes place at about 1620 K in SiC nanotubes by heterogeneous nucleation from the non-hexagonal defects due to reconstruction at a free end, and at about 1820 K in nanotubes without free ends by homogeneous nucleation within the wall from thermally activated 5-7-7-5 defects. In both cases formation of Si–Si and C–C bonds proceeds melting.