Research On Preparation And Formation Mechanism Of MCMB

Since Brooks and Taylor discovered meso-phase in 1960s, meso-phase has been paid much attention by researchers and companies worldwide due to its ascendant properties. As a sort of advanced carbon material derived from meso-phase , meso-carbon micro-beads (MCMB) have been widely used in aviation,mechanical airtight,electricity spark process,metallurgy mould,and nucleus graphite and have been developed quickly in recent years.Carbon materials have large varieties in terms of morphology, texture, micro-texture and crystal style depending on their preparation processes and raw marerials. There are two different viewpoints about formation mechanism at present. Both of them have limitations. The structure and performance of MCMB will change with outfield strength. It will possess science sense and practical value to study the formation mechanism of MCMB in terms of these changes.Our research focused on the preparation, the influence of magnetic field and the formation mechanism of MCMB. MCMB was prepared with mid-temperature coal pith at normal pressure and not isolation with oxygen. The influence was researched with adding a certain magnetic field to the preparation course. The preparation process and the microstructure of MCMB were characterized by scanning electron microscopy (SEM),X-ray diffraction (XRD),Infra-red spectra (IR) and the formation mechanism was clarified. The results showed that:The main property indexes of MCMB prepared at normal pressure include that the appearance of MCMB is sphere-like and diameter distributing is between 1 to 30μm;the main elements are carbon , hydrogen, oxygen ; The degree of graphite ,density and the yield are lower .The main influence factor of preparation process include that the react time is 10 to 12 hours and the catalyzer and solvent to separate MCMB from meso-pitch are nickel bichloride and quinoline.The surface of MCMB will be apple-like when being affected by a magnetic field with magnetic intensity 150～200T and upright direction. The structure analysis by XRD showed that MCMB prepared at normal pressure have a bigger interface space. the split of the most strong peak characterized the microstructure of MCMB.The sphere which diameter is 1μm observed by SEM is the core of MCMB. MCMB were growing up based on this core.Snowball formation mechanism was put forward .This theory include that: 1 )the formation of planar molecules. Some pitch molecules with a few rings formed the planar molecules by thermal poly-condensation and some with more rings by thermal discomposed. 2) the formation of stacking units . the planar aromatic molecules parallel stacked up effect by the force among molecules and stacked up along the direction perpendicular the magnetic field. 3) the formation of sphere-like core. The stacking units are growing up gradually. When they achieved a certain volume, the difference of surface tensile force came into being with anisotropic pitch molecules. These units formed a spherical core which is sphere-like .4) the growth of the sphere. The spherical core operated with the stacking units quickly. The stacking units packed the core up and formed MCMB. The shape of sphere was adjusted by the surface tensile force. When grown up to a certain size, the ability of MCMB absorb impurity enhanced, otherwise, the stacking units will slip and the fault will appear. The unitary anisotropy become weaken and the formation speed will slow down.