Yoshiteru Nakagawa

Removal of ionic substances from dilute solution using activated carbon electrodes

Abstract Removal of various electrolytes from aqueous solution and a recycling operation were carried out using a flow-through capacitor. The amount of ions removed corresponds to the surface area and especially the micropore volume of the activated carbon electrode. Introduction of acidic functional groups on the surface of the carbon promoted ion removal (i.e. increase in rate and capacity), but there is a limit to the amount of functional groups that can be introduced with good effect. The adsorption–desorption properties of various alkali, alkaline earth and heavy metal sulfates were investigated. It was found that removal characteristics were different for the different types of ions. Depletion of the electrode also differed depending on the electrolyte that was removed. When copper and zinc ions were removed, the surface area of the cathode was reduced by a small amount.

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.

Molecular Alignment and Domain Assembles in the Uni-chromic Mesophase Spherules Prepared from Synthetic Naphthalene Isotropic Pitch

TitleMolecular Alignment and Domain Assembles in the Uni-chromicMesophase Spherules Prepared from Synthetic Naphthalene Isotropic PitchAuthor(s)Chang, Young-Chul; Sohn, Hun-Joon; Wang, Yong-Gang; Korai, Yozo;Nakagawa, Yoshiteru; Mochida, IsaoCitation九州大学大学院総合理工学研究科報告 ¦¦ 21(2) ¦¦ p161-165; Engineeringsciences reports, Kyushu University ¦¦ 21(2) ¦¦ p161-165Issue Date 1999-09URL http://hdl.handle.net/2324/16557Right