Sumihito Ishida

Stabilization and carbonization properties of mesocarbon microbeads (MCMB) prepared from a synthetic naphthalene isotropic pitch

Carbonization properties and stabilization reactivity of MCMB prepared at a high yield from a particular synthetic naphthalene isotropic pitch with and without carbon black (CB) were evaluated in terms of their fusibility, adhesion ability and graphitizability. MCMB prepared without CB carried much higher hydrogen content which is attributed to aliphatic or naphthenic hydrogens, showing high fusibility when MCMB were further carbonized. Addition of carbon black at preparation decreased the fusibility of MCMB in successive carbonization. Oxidative stabilization decreased naphthenic hydrogens from MCMB to introduce oxygen functional groups, such ester and anhydride groups, inhibiting their deformation. Although MCMB exhibited lower oxidative reactivity than that of the parent isotropic pitch, oxidative stabilization for 60 min at 300°C was sufficient to maintain the spherical shape of MCMB without CB, introducing 8.3 wt% oxygen. Oxidative stabilization was also completed after 120 min at 270°C, introducing 4.7 wt% oxygen. Complete stabilization was achieved by 60 and 30 min at 270°C for MCMB prepared with 1 and 3 wt% BP2000, taking up 3 and 2 wt% oxygen, respectively. It is noted that CB reduced the oxygen uptake necessary for the complete stabilization. Both CB and oxidative stabilization reduced the graphitizability of MCMB.

Pitch-based carbon fiber of high compressive strength prepared from synthetic isotropic pitch containing mesophase spheres

Two pitches containing mesophase spheres were prepared from a synthetic isotropic naphthalene pitch at 360°C and 375°C so as to contain spheres of different diameters. Both pitches were smoothly spun into thin fibers, which were converted into carbon fibers through stabilization, carbonization and graphitization. The fiber from the pitch with finer spheres exhibited a higher compressive strength, which reflected smaller microdomains, smaller, and thinner fibrils, being different from both isotropic and anisotropic pitch fibers. The isotropic fraction of the pitch appears to give areas of smaller microdomains. The fiber exhibited intermediate values in graphitic parameters between those of isotropic and anisotropic pitch-based fibers.

Effects of carbon black addition on preparation of meso-carbon microbeads

Abstract The preparation of meso-carbon microbeads (MCMB) has been studied by heat-treating two synthetic isotropic naphthalene pitches at 380–430 °C for 1-12 hours in the presence of several types of carbon blacks. A larger number of beads with small diameter, ranging from 1 to 10 μm, were obtained. The yields of the beads assessed volumetrically by microscope and gravimetrically by pyridine extraction reached to as high as 45 vol% and 30 wt%, respectively. A particular heat-treatment temperature (400 °C) appears optimum to give a narrower size distribution of the spheres than other temperatures (380 and 420 °C) with 1 wt% carbon black. The lower temperature and longer time with 3 wt% Ketjen Black favored the formation of uniform size of beads. The carbon black appears to enhance the nucleation and to inhibit the growth and coalescence of the mesophase sphere. In the presence of carbon blacks the synthetic isotropic pitches tended to produce extracted spheres consisting of basic domain units in coagulated forms.

Efficient preparation of meso-carbon microbeads from synthetic isotropic pitch derived from naphthalene

Abstract An efficient preparation of mesophase spheres was attempted from synthetic isotropic pitches of naphthalene oligomers. A large number of spheres of rather uniform diameter were obtained by the carbonization at 380 °C for 20 h. Volumetric and yields of spheres in the pitch were volumetrically measured under the optical microscope and extracted; a pyridine soluble fraction as high as 42 vol% and 15 wt%, respectively was reached. Such a difference in the yields suggests that the spheres prepared in the present study included a significant amount of the pyridine soluble fraction. The extracted sphere carried a number of pores, leaving rod-like units. Self-assembling units of pyridine insoluble fraction produced in the mesophase are suggested to be precipitated to form a spherical shape.

Preparation of mesocarbon microbeads by dispersing mesophase pitch in isotropic pitches

Abstract Mesocarbon microbeads of 1–10 μm were prepared through dispersing the synthetic mesophase pitches in synthetic isotropic pitches and successive solvent extraction. The suitable ratio of mesophase pitch/isotropic pitch, temperature and rapid agitation at dispersion were found to be key factors to obtain the high yields of tetrahydrofuran and pyridine insoluble microbeads which were 34 and 20 wt%, of the highest yield, respectively. In contrast, the combinations of coal tar derived mesophase pitch/synthetic pitch or synthetic mesophase pitch/petroleum A240 pitch failed to disperse spheres of mesophase pitch in the isotropic matrix, leaving bulk grains of mesophase pitch at the bottom of the matrix. The melt mesophase pitch of adequate viscosity is dispersed by the agitation into viscous droplets in the isotropic matrix, while the droplets stay afloat because of their similar specific gravities. The lighter component in the droplet of the mesophase pitch was extracted into the isotropic matrix while the mesophase pitch is melted, leaving spheres of smooth surface. Extraction by the solvent at a lower temperature than the softening point leaves mesocarbon microbeads isolated, removing the solvent soluble fraction.