Study On The Preparation Of Pitch Modified MCMB And Its Graphite Material Structure And Performance

Isostatic pressure graphite is characterized by high density,high intensity,isotropic and thermal stability and other excellent characteristics,widely used in electrical discharge machining,semiconductor,solar energy and other industries.Intermediate carbon microspheres(MCMB)have good self-sintering ability and low volatile characteristics.By cold isostatic pressing molding can make dense green,in the process of heat treatment,MCMB spheres were uniform shrinkage and bonding,form a high strength,high density,isotropic graphite materials.The pitch is decomposed and carbonized in the carbonization process,and the coking particles are securely attached to each other.So pitch is used as a common binder for the production of graphite materials.Poor based on the sintering property of mesophase carbon microspheres(MCMB)as matrix,pitch binder,tetrahydrofuran as solvent,using the mixed solution method on modification to pitch modified MCMB preparation of isostatic pressing graphite material.Firstly,the effect of pitch modification on MCMB structure and the weight loss of carbonization was studied first.Results show that after the MCMB small sphere surface adhesion of pitch modified with some pitch,with the increase of pitch content,MCMB more and more small sphere surface adhesion of pitch,pitch modification of MCMB in diameter(D50)increased gradually.During the process of heat treating,with the increase of heat treatment temperature,sample volume presents a tendency to expand and then contract,MCMB and different pitch modification of MCMB exist two weightlessness peak.The first pure MCMB weightlessness peak at about 520℃,and after pitch modification of MCMB first weightlessness peak shift to the low temperature area,all roughly at 390℃.The second weightlessness peak appeared at about 780℃.Secondly,the influence of type and content on structure and performance of graphite materials was studied.The results show that the mechanical properties and volume density of graphite materials decrease with the increase of MS content.At the maximum of 18 wt%,the flexural strength is 62.6 MPa,the scleroscope hardness is 55.9 HS,the volume density is 1.96 g/cm3.Along with the increase of the content of MP,the graphite material mechanical properties and bulk density increase gradually,increasing the MP content can further enhance the mechanical properties and bulk density.Finally,the influence of molding pressure on structure and performance of graphite materials was studied.The results show that the hole size of graphite material is significantly reduced and the material structure is more uniform and compacted with the increase of molding pressure.The porosity of graphite material decreases with the increase of molding pressure.The structure of graphite materials prepared under the lower molding pressure(100 MPa and 125 MPa)is porous and has large pore structure and large size.When the pressure reaches or exceeds 175 MPa,the pores in the material are significantly reduced and evenly distributed.The volume density and flexural strength of the graphite material increases with the increase of molding pressure.When the molding pressure of 200 MPa,the volume density of 2.01 g/cm3,flexural strength is 52.6 MPa,the molding pressure influence on shore hardness is not obvious,the size of the range of shore hardness in 53～55 HS.