The Preparation And Characterization Of Nano-Carbon Powders

Nanopowders are the powders with the size of no more than 100 nm. Owing to the extremely small dimensions, nano-materials are structurally characterized by a large volume fraction of grain boundaries or interphase boundaries, which exhibit some unique structural characteristics and properties compared to the conventional materials. With the development of science and technology, nano-materials play an important role in the society and are widely applied in many fields, such as information, manufacturing, biotechnology and agriculture etc. Nano-carbon powders are the new turbostratic carbon materials and have broad prospects in catalysis and its supports, functional ceramics, binder, stationary phases for chromatography, electrode materials and producer. Therefore, it is much concerned to prepare nano-carbon powders with interesting and useful properties.In this paper, The nano-carbon powders were prepared by sol-gel method, in which the coal tar pitch was first oxidized into aqua-mesophase pitch (AMP) by mixtures of concentrated sulfuric acid and nitric acid, and then the AMP was dissolved in aqueous solution of ammonia hydroxide to form the carbonaceous hydrogel, which was directly exchanged with ethanol to remove water and dried by different drying methods temperature. After carbonization at 950 ℃, the nano-carbon powders were obtained. Preparation and performance analysis of AMP was investigated by oxidation with mixtures of concentrated sulfuric acid and nitric acid. The effects of oxidation conditions, such as raw materials, temperature, reaction time and stirring velocity, on the yields and properties of AMP were studied in detail. The effect of drying media and methods of wet gel on the nano-carbon powders yield and properties was also investigated. The AMP, the primary nano-carbon powders and their heat-treated products were characterized by FT-IR, TG, XRD and TEM methods. Mechanisms of oxidation are discussed briefly.The results show that oxidation conditions greatly affect the yields and properties of AMP. The reactions such as nitration, oxidation and sulfonation mainly happen during the reactions of coal tar pitch with mixing acids. The pyrolysis of the primary nano-carbon powders can be divided into four stages, including removal of drying media and water, pre-thermol decomposition, thermol decomposition and rearrangement of carbon structure. The different drying methods and medias of wet gel are found to affect the chemical and carbon structure of the primary nano-carbon powders and nano-carbon powders. The ball-like nano-carbon powders with the average size about 10nm and turbostratic carbon structure can...