Haruo Kumagai

Surface modification and characterization of carbon black with oxygen plasma

Abstract The surface of carbon black was modified with an oxygen plasma treatment. The initial increase and following reduction of carbon black weight due to the treatment were observed as the treatment time increased. The chemical structure of carbon black surfaces formed by the oxidation process has been characterized by X-ray photoelectron spectroscopy (XPS). The XPS O C atomic ratio of the surfaces showed a plateau after an initial increase and saturated at about 0.42 after 120 minutes regardless of the plasma input power. The introduction rate of oxygen-containing functional groups onto the carbon black surfaces increased by increasing the plasma input power. The oxygen plasma was found to cause changes in surface CO or OCO and OCO functionalities, and their concentrations were proved to increase with the treatment time up to about 120 minutes irrespective of the input power.

Air-blowing reactions of pitch: I. Oxidation of aromatic hydrocarbons

Abstract In order to deepen our understanding of the air-blowing reaction of pitch as a precursor of carbon fiber, aromatic hydrocarbons having 2 to 3 rings were selected as pitch models, and structural analyses of their air-blown products were conducted using FD-MS, GC-MS, NMR, and FT-IR spectroscopies. Alkyl-substituted aromatic compounds polymerized with methylene, biphenyl-type, and ether bonding, leading the methylene to partially change into carbonyl during the air-blowing reaction. Therefore, the pitches containing alkyl-substituted compounds are the most effective source materials for raising the softening point, increasing molecular weight, and suppressing anisotropic texture. The properties of the air-blown products were characterized by, and dependent mainly upon, the crosslinked carbon and the condensed aromatic carbon formed by the air-blowing reaction.

Formation of mesophase spheres from a coal tar pitch upon heating and subsequent cooling observed by an in situ 1H-NMR

Coal tar pitch was heated at a rate of 10 K/min up to 723 K in an atmospheric flow of nitrogen gas, soaked at the temperature for time, tH, ranging from 0 to 480 min. A microscopic observation revealed that soaking for tH shorter than 120 min produced dispersed mesophase spheres, while longer soaking resulted in a flow-textured mesophase due to a progress of coalescence of the spheres. Diameter and yield of the dispersed spheres depended on the rate of cooling, suggesting that the spheres formed upon cooling. In situ proton nuclear magnetic resonance (1H-NMR) detected three components, G1, G2 and W having different transverse magnetization decays, in the pitch upon soaking. Magnetization decays of G1 and W agreed well with those of meso-carbon microbeads (MCMB) and fully fused isotropic pitch, respectively. When tH was shorter than 60 min, no G1 was detected while spheres were observed in the pitch after cooling, confirming mesophase formation upon cooling after soaking. It was also found that the formation of spheres upon cooling accompanies the complete conversion of G2 into G1 and that the G1 formed hardly fuses while reheated to 723 K.

Acid-catalyzed transalkylation of coal with simple aromatic compounds☆

Abstract The treatment of coal with tetralin as an alkyl acceptor has been carried out in the presence of a super acid catalyst (trifluoromethane sulfonic acid) to yield highly extractable and readily liquefiable products. The solubility in pyridine of the coal recovered from this reaction was increased significantly (to over 90%). Better correlation between the solubility of treated coal and the amount of tetralin introduced by transalkylation has been obtained. Model compound reactions have also been carried out to clarify the mechanisms of coal reaction. The results indicate that cleavage of methylene bridge cross-linked aromatic rings occurs more readily than those of ethylene and biaryl bonds. In this reaction system, some side-reactions which hindered the process of coal solubilization took place in competition with transalkylation reactions.

Carbonization of pitches in air blowing batch reactor

Abstract Carbonization of petroleum and coal tar pitches to toluene insoluble fraction (TI) was investigated under air and nitrogen gas blowing systems. The TI yield was evaluated on the basis of the weight of pitch loaded. Changes of the yield with the reaction time were analyzed by a kinetic model of carbonization. The model assumes that pitch as a reactant contains a reactive component, P1, which converts to active thermal fragment, P ∗ , and gas and tar, G, more quickly than the residual component, P2, exhibiting a nonlinear decrease of pitch in semilogarithmic plot against the reaction time in an early stage of the reaction. The activation energies for P1, and P2 conversions depended on pitch and gas atmosphere. In particular, activation energies for P1 conversion in the air blowing system was found to be appreciably smaller than those in the nitrogen blowing system. This less temperature-sensitive carbonization in the former system may be attributed to pitch reactivity improved by oxygen in air.

Surface chemistry of carbon black through curing process of epoxy resin

The effects of oxidized carbon black surfaces on the epoxy resin curing process were examined by differential scanning calorimetry (DSC). The addition of oxidized carbon black accelerated the initial cure reaction of the epoxy-amine system. Peak temperature in DSC exotherm of the resin system falls in proportion to the ratio of surface ester groups on carbon black added. Results obtained from model compounds confirmed that COOH groups on the carbon black surface play an important role in promoting the initial cure reaction of the system. The degree of enthalpy change associated with the cure reaction was found to be almost independent of the chemical structure of the carbon black surface.

E.s.r. study of electron acceptor doped coals

Non-covalent bond interactions play important roles in coal structure. They serve as virtual crosslinks which help to hold the network together. This paper concentrates, particularly, on the structure of coal with respect to charge transfer interaction between coal and electron acceptors. Iodine and tetracyanoquinodimethane (TCNQ) as electron acceptors interact with coal molecules producing charge transfer complexes. A good correlation is obtained between the spin concentration, Ns, of coal-iodine complexes and the Bloch decay value (carbon aromaticity, ƒa) of parent coal. The Ns value increases with the increase of aromaticity in coal. On the other hand, TCNQ is a molecule with strong electron accepting ability, as is iodine. The Ns value for TCNQ doped coal increases with decreasing coal rank. Interpretation of the above fact is that the TCNQ molecule moves to sites associated with oxygen containing functional groups, which are able to form hydrogen bonds.

An additional carbon layer over the surface of C/C composite substrate with the aid of polyvinyl chloride

Abstract The novel bonding of an additional carbon layer over a C/C composite substrate surface was studied. Furan resin was selected for the additional carbon layer precursor. Molding was performed using a hot press apparatus. Polyvinyl chloride resin (PVC) was used as the bonding agent. The bonding mechanisms were studied with thermal gravity analysis, thermal gravity-mass spectroscopy, and high-temperature electron paramagnetic resonance spectroscopy. No peel-off was observed at the boundary between the carbon layer derived from furan resin/graphite powder and the C/C composite after loading by an external stress. The spins in thin carbon derived from PVC are recombined and are erased by the particular sites of graphite surface as one of roles of enhancement of adhesion.

Changes of spin system in coal with addition of iodine

The characteristics of spin system in coal have been compared with and without addition of iodine by means of electron spin resonance spectroscopy. With the addition of iodine, the spectra obtained from low rank coals remain almost unchanged, while those from high rank coals consist of two distinct lines, one narrow and the other broad. The peak intensities of broad component are proportional to the addition of iodine, whereas those of narrow component do not change over the range of iodine doping. Microwave power saturation characteristics of broad component are altered from homogeneous case to inhomogeneous one by iodine doping.

Fluidity of coal with respect to charge-transfer ability

The fluidity of coal is one of the important parameters governing the optical texture of resultant coke. In this paper, we have proposed an iodine doping technique to evaluate the fluidity of coal. The difference between the value of radical concentration for parent coal, Ns 0 , and iodine-doped coal, Ns, was plotted against maximum fluidity of coal. There is no definite relation between the Ns-Ns 0 value and maximum fluidity of parent coal. On the other hand, a clear relation was introduced between the value of Ns-Ns 0 for primary tar derived from the parent coal and the maximum fluidity of coal