Hironobu Chiyoda

Laser-assisted exfoliation of potassium-ammonia-graphite intercalation compounds

Potassium-ammonia-graphite intercalation compounds (K-NH3-GIC) synthesized from small natural graphite particles from China were rapidly heated by a cw-Nd:YAG laser beam (1.056 μm) in an Ar purge environment to yield exfoliated small graphite particles as sources for electrical conductive films. The laser heating method was demonstrated to be effective for exfoliation of K-NH3-GIC prepared from natural graphites in sizes of under 37 μm, 37 ~ 63 μm and 63 ~ 88 μm, whereas no exfoliation of these graphites occurred by either gas burner heating or electric furnace heating. The results also show that K-NH3-GIC prepared from natural graphite 350 ~ 500 μm in size was exfoliated to 32-fold of the volume of feed natural graphite. This exfoliation ratio is 2.6 times larger than the ratio obtained by the gas burner heating method.

Effect of exfoliation ratio on the flakiness of fine graphite particles obtained by grinding of exfoliated graphite.

In this study, we ground exfoliated graphite and investigated the flakiness of the ground products using the previously reported particle size measurement techniques

Grinding characteristics of bromine-exfoliated graphite and natural graphite

The grinding characteristics of natural graphite are discussed and a new graphite grinding method is proposed for obtaining fine particles. Natural graphite was well ground in dry air after vacuum drying at 10−3 Torr and 80°C and its 50% diameter of cumulative underside of products ground for 12 h was approximately 1.4 μm. The new grinding method was performed in dry air after treatments designed to increase the distance between layers and weaken the bonding strength by use of an intercalation reaction. Bromine gas was used as an intercalate and bromine graphite intercalation compounds were exfoliated by vacuum heating. The product size distribution for the exfoliated bromine graphite ground in dry air after vacuum drying was slightly different from that of ground natural graphite.

Production of fine flaky ground particles of potassium graphite intercalation compounds and potassium exfoliated graphite

Abstract A new grinding method for obtaining fine flaky graphite particles was investigated by using an intercalation reaction. The grinding characteristics of potassium graphite intercalation compounds and exfoliated graphite in a vacuum were studied and compared with those of natural graphite. The grinding of potassium graphite intercalation compounds in a vacuum for 12 h provided fine flaky particles with a mean size of 0.4–0.5 μm. The particle shape of the ground product of the potassium intercalation compound in a vacuum was flaky compared with those of natural graphite. The ground product of exfoliated potassium graphite was also found to be flaky.

Gas desorption and adsorption properties of carbon based material used for cathode ray tube

Abstract For numerous carbon based materials used as coatings of cathode ray tube, the gas desorption properties were examined by using a technique of thermal desorption spectroscopy. The major outgassing species were CO 2 and H 2 O. The peak temperature of the desorption was 373–473 K. The desorption amount was very small for the material with TiO 2 powder and water glass, and large for the material with graphite powder. The baking temperature required for reduction of the gas desorption amount is 673–773 K. Gas adsorption experiments were also conducted. The adsorption amounts of H 2 O or CO 2 increased with the composition ratio of graphite powder. In particular, the gas adsorption capability was largely increased by addition of TiO 2 powder. This enhancement was caused by the fact that the porosity of surface structure and the effective surface area were increased by the addition of TiO 2 powder.

Gas desorption and adsorption properties of graphite and water glass mixtures used as inner coatings of a cathode ray tube

Abstract The gas desorption properties of mixed graphite and water glass (K 2 SiO 3 + H 2 O) were investigated by thermal desorption spectroscopy. It was observed that mainly H 2 O and CO 2 were desorbed from the materials after a baking treatment in the atmosphere. The surface morphology became rough or smooth as the graphite content or the water glass increased, respectively. The amounts of the desorbed gases decreased with the graphite content or increased with the content of the water glass. Namely, the gas desorption amount became small as the enhancement of the surface roughness. The gas adsorption property for H 2 O or CO 2 was also examined for the materials baked in a vacuum. The adsorption amount of H 2 O or CO 2 was proportional to the graphite content, and this result corresponded with the effective surface area of the mixed graphite and water glass.