Akio Shindo

Structural variation during pyrolysis of furfuryl alcohol and furfural-furfuryl alcohol resins

Abstract Films of furfuryl alcohol resin and a furan resin prepared from a mixture of furfural and furfuryl alcohol were heated to several stages of different temperatures up to 600°C in Ar gas and in HCl gas. Weight loss and shrinkage, elemental composition and IR spectra were measured on the resin films, and heated films obtained. Absorbance, per the same area and thickness of the resin films, of several characteristic bands in the spectra was estimated for those films. The absorbance showed that furan rings in the films continued to break up to a temperature between 300°C and 450°C with increasing heating temperature and aromatic rings began to form between 300°C and 400°C. The HCl heating atmosphere increased the amounts of carbon element remaining in the 400–600°C films and the carbon yields of 900°C films. The variation of the absorbance with increasing heating temperature suggested the occurrence of some reactions during the pyrolysis of the resins.

Influence of carbide formation on the strength of carbon fibres on which silicon and titanium have been deposited

Silicon or titanium was deposited on the filaments of carbon fibres by chemical vapour depositions and the reactions between the deposited silicon or titanium and the carbon fibres were investigated below 1300° C. Between the silicon and the carbon fibres, β-SiC layers formed at rates of 1.5 to 3 nm in 3 h at 1300° C. These rates were 10−4 times that of the TiC formation by the reaction of titanium with carbon fibre. Furthermore, the effect of the reaction on fibre strength was investigated. By reaction with silicon, the carbon fibre at a carbonized stage decreased in strength at the beginning of the reaction, but afterwards it recovered to the original level. The carbon fibre at a graphitized stage maintained its original strength after heat treatment for several hours at 1300° C. With the TiC-coated carbon fibres, the carbon fibres decreased in strength following the relation σm ∝ d−1/2, where d is the thickness of the TiC layer.

Torsional properties of carbon fibers

Abstract The torsional behavior, together with the tensile behavior, of PAN-based and mesophase pitchbased carbon fibers was studied by means of single-filament test methods, followed by scanning electron microscope examination. The torsional modulus decreased with increasing Youngs modulus for both fibers. And the mesophase pitch-based carbon fibers exhibited lower torsional moduli than those of PAN based carbon fibers, in particular markedly lower moduli at higher Youngs modulus. The torsional modulus depended to a large extent on the orientation structure of the graphite crystallites in the cross-section, but also upon the linking force between neighboring graphitic-layer planes. The torsional strength of both the carbon fibers increased with increasing tensile strength and that of the PAN-based carbon fibers increased as the torsional modulus increased. The spiral face of torsional fracture surfaces of the PAN based carbon fibers and the very long longitudinal faces which the torsional-fracture surfaces of the mesophase pitch-based carbon fibers have, were also considered to be associated with the orientation structures.

Clamping Methods for Tensile Test of Carbon Fiber Strand

Clamping methods for evaluating tensile properties of carbon fibers in a form of strand were studied. When clamped with the three-plates aluminum tab and loaded through pins, the strand specimens in which the carbon fiber was impregnated with resin so as to penetrate fully among filaments exhibited the highest tensile forces. In this case, the strand specimens often broke into several pieces. With the clamping method using abrasive cloth, the strand specimens exhibited 95% of them, but their preparations were less time- consuming.

Orientation structure in transverse sections of carbon fibers from dehydrated polyvinyl alcohol

Abstract Transverse sections of carbon fibers prepared from two different lots of dehydrated polyvinyl alcohol fibers, with and without graphitizing treatment, were observed by both polarized light and scanning electron microscopy. Several different types of transverse layer plane preferred orientation were found in the graphitized fibers: layers aligned parallel with the section major axis in the central zone of elliptical cross sections; parallel with the fiber surface in concave regions of an irregular cross section shape; and parallel with the fiber surface in a highly crystallized fiber with an irregular cross section shape. These graphitic layer plane configurations are considered in connection with the lamellar structure in crystalline regions of the dehydrated polyvinyl alcohol fibers.

Crystallinity of SiC coated on carbon fiber

モノメチルトリクロロシラン, 水素, メタン, アルゴンの混合ガスから1200℃に加熱した炭素繊維上にSiCを被覆し, 被覆SiCの構造, 結晶性, 配向性をX線回折法によって調べた. その結果, SiCは最密充てん面の [111] 方向に沿う積層順序がかなり乱れた3C構造と同定された. 更に, ガス中の水素濃度の減少, あるいはメタン濃度の増加によってこの面が繊維フィラメント表面に平行に配向するようになること, またそれに伴って結晶子が粗大になることを認めた. このような結晶子の配向性とサイズの変化は, メタンの過飽和度の増大に起因すると考えられた.

CHARACTERIZATION OF CARBON FIBER SURFACE RELATING TO INTERFACIAL ADHESION IN COMPOSITES

ABSTRACT Methods for evaluating the surface activity and surface roughness were investigated on PAN-based carbon fibers. The specific surface areas were determined by krypton adsorption measurements at -195°C on the carbon fibers degassed at 100°C and 950°C. After the krypton adsorption measurement, the carbon fiber was degassed again at 950°C, and then oxygen chemisorption was measured at 300°C and an adsorbing time of 24 hours. The active surface area was determined from the amount of chemisorbed oxygen, and the ratio of active surface area to the surface area from the krypton adsorption at a degassing temperature of 950°C was calculated as an active surface area rate. Concentration of oxygen atoms on the fiber surface and relative amount of the boundary carbon atoms in the fiber skin were measured by XPS and Raman spectroscopy, respectively. They varied depending on the active surface area rate. Surface roughness was evaluated using the geometrical surface area obtained from optical diffraction diameters of the fiber and the specific surface area at a degassing temperature of 100°C. The interfacial shear strength in the composite increased with increasing active surface area rate.