Preparation, Structure And Performance Of Microscale Carbon / Inorganic Composite Materials And Nitrides

The point of this dissertation is to explore new synthetic methods for micro-scale carbon/inorganic composites and carbon materials and study their reaction mechanism. We have successfully synthesized various micro-scale carbon/metal sulfide composites, sulfur-doped carbon materials and carbon nanofilaments by supercritical fluid technology, and studied their electrochemical properties; a low-temperature solvothermal route was proposed to prepare amorphous carbon nanotubes (CNTs) and three-dimensional (3D) CNT networks; CNTs encapsuled with cobalt nanoparticles and bamboo-shaped CNTs with high-quality were synthesized in large scale by a catalytic pyrolysis method. In addition, several group VIB nitrides were obtained by rapid solvent-free route at low temperature. The details are summarized as follows:1. Metal sulfide filled CNTs composites were obtained in supercritical CS₂ for the first time. a) Large-scale long continuous FeS₂ nanowire filled CNTs were one-step synthesized in the presence of NaN₃ in supercritical CS₂ at 500℃using ferrocene as the iron source. On the basis of the experiments, a possible mechanism has been proposed, and the thermal, optical, electrochemical properties were studied, b) Based on the synthesis of FeS₂ nanowire filled CNTs, we prepared carbon hollow spheres encapsuled with CoS₂ nanospheres and CoS₂ nanorods filled CNTs. This novel approach may be potentially extended to fill other technologically important sulfides into CNTs in supercritical CS₂. c) Flower-like and rod-like sulfur-doped carbon materials were also obtained in supercritical CS₂. The electrochemical properties of flower-like sulfur-doped carbon materials demonstrate that it delivers a large discharge capacity, showing its promise for application in new electrode materials.2. A simple low-temperature solvothermal route was proposed to prepare amorphous CNTs with novel structures. a) Several amorphous CNTs were obtained by the reactions between ferrocene and CCl₄, C₂Cl₄ or C₄Cl₆ at temperature range from 180-200℃, and the experimental results indicated that Fe derived from the decomposition of ferrocene plays a template for the formation of CNTs. b) By introducing porous nickel into above reactions, novel three-dimensional (3D) CNT networks with the included angle of 90°were also obtained. These interesting structures have relatively large specific surface areas, showing their promise for application in catalyst carriers, hydrogen storage, nanodevices. 3D CNT networks coated with Ag nanoparticles were also obtained for the study of its gas sensitive characteristics in NH₃ at room temperature. c) Carbon nanoantennae have been synthesized through the reaction of cobaltocene and CCl₄ in the presence of porous nickel at 240℃.3. Developed the ethanol thermal route. CNTs encapsuled with cobalt nanoparticles and bamboo-shaped CNTs with high-quality were synthesized in large scale at 500℃, in which methanol or ethanol acted as carbon resource and solvent, cobaltocene acted as catalyst. It is useful to understand the formation mechanism of CNTs.4. A rapid solvent-free route has been successfully developed for the synthesis of group VIB nitrides by the reaction of anhydrous metal chlorides and sodium amide, and it is found that the reaction temperature, initiated forms, the material of reaction container and the amount of reagents play important roles in the composition, phase, and morphology of the nitrides. This approach may be potentially extended to obtain other transition metal nitrides at low temperature.