Petoca, Ltd.

Kabushiki Kaisha Toshiba

Yoshiyuki Nishimura

Toshio Tamaki

Hiroshi Ejiri

Hideyuki Nakajima

Yoshikazu Nagata

Akio Takamatsu

Norio Takami

Mikio Watanabe

Takahisa Ohsaki

Tetsuji Takemura

Yoshinori Yamazaki

Kazuo Jonouchi

Milled carbon fibers are provided which have a fiber cut surface and a fiber axis intersecting with each other at cross angles, the smaller one thereof being at least 65&deg; on the average. The milled carbon fibers may have a specific surface area as measured by the BET method of 0.2 to 10 m,/g. The milled carbon fibers may be obtained by a process comprising melt spinning of mesophase pitch, infusibilization, milling of the infusibilized pitch fibers as obtained or after a primary heat treatment at low temperatures in an inert gas and a high-temperature heat treatment in an inert gas. Even when the graphite layer plane has achieved high-level growth, the above milled carbon fibers have low reactivity with a metal of high temperature or the like during the molding or use thereof because the proportion of reactive exposed surface of the inner portion of the fiber is small, so that the use of the milled carbon fibers can improve the mechanical strength and high-temperature heat resistance of the composite material.

Milled carbon fiber and process for producing the same

A mesophase pitch-based carbon fiber for use as a material for a negative electrode of a secondary battery, and a process for producing the same. The mesophase pitch-based carbon fiber comprises a columnar core part having a texture composed of a plurality of graphite layers extending along an axial direction and extending with minute flexures in a plane perpendicular to the axis and an outer-shell part surrounding the core part. The outer-shell part has a texture composed of a laminate of a plurality of graphite layers extending along an axial direction. The graphite layers are oriented in a plane perpendicular to the axis in a fashion such that the graphite layers extend along a circumferential direction with minute flexures while gradually receding from a center of the core part. In the carbon fiber, the graphite layers composing the outer-shell part have a laminate face forming a surface of the outer-shell part, channels permitting entry and exit of lithium ions being formed between graphite layers at the laminate face.

Mesophase pitch-based carbon fiber for use in negative electrode of

A negative electrode material for use in lithium-ion secondary batteries, comprising milled pitch-based graphite fibers (A) obtained by graphitization at 2400.degree. C. or higher and milled pitch-based carbon fibers (B) obtained by carbonization at 550.degree. to 1300.degree. C. In this negative electrode material, it is preferred that both the milled pitch-based graphite fibers (A) and the milled pitch-based carbon fibers (B) have an average particle size of 10 to 30 .mu.m, that the ratio of milled pitch-based carbon and graphite fibers having a particle size of 5 .mu.m or less to all the milled pitch-based carbon and graphite fibers is not greater than 10% by weight and that the milled pitch-based graphite fibers (A) and the milled pitch-based carbon fibers (B) are blended at a weight ratio (A/B) of 95/5 to 40/60. A negative electrode which has a large capacity at the time of having been stabilized, exhibits a high charge and discharge efficiency at the initial stage and is excellent in charge and discharge cycle characteristics can be provided by the blending of milled pitch-based carbon fibers with milled pitch-based graphite fibers.

Negative electrode material for use in lithium-ion secondary battery and

A carbon material for use in a lithium secondary battery, which is obtained by graphitization conducted in the presence of a boric compound so as to contain boron in an amount ranging from 1,000 ppm to 30,000 ppm and which, when subjected to X-ray diffractometry, exhibits an interplanar spacing of 002 surface (d.sub.002) of not greater than 0.338 nm, a crystallite size along c-axis (Lc) of at least 35 nm, a crystallite size along a-axis (La) of at least 50 nm and a ratio of diffraction peak (101) to diffraction peak (100), designated as P.sub.101 /P.sub.100, of at least 1.0; a negative electrode and a lithium secondary battery each produced by using the above carbon material; and a process for producing the carbon material. This carbon material exhibits large charge and discharge capacities, so that it can provide a negative electrode for use in a lithium secondary battery which is excellent in charge and discharge cycle characteristics.

Carbon material for lithium secondary battery and process for producing

A negative electrode for use in a secondary battery is disclosed, comprising milled carbon fibers derived from mesophase pitch wherein the milled carbon fibers each has a fiber cut surface and a fiber axis intersecting with each other at cross angles, the smaller one thereof being at least 65.degree. on the average. This negative electrode does not suffer from property deterioration, irrespective of multiple repetitions of charge and discharge, from which a nonaqueous-electrolyte-loaded lithic secondary battery having excellent cycle characteristics can be fabricated.

Negative electrode for use in a secondary battery

The mesophase pitch based and melt blown discontinuous carbon fibers of a peculiar structure are provided. These fibers are characterized in that a large number of small domains, each domain has an average equivalent diameter of from 0.03 .mu.m to 1 .mu.m and has a nearly unidirectional orientation of folded carbon layers, assemble to form a mosaic structure on the cross-section of the said carbon fibers and that the folded carbon layers of each domain are oriented at an angle to the direction of the folded carbon layers of the neighboring domains on the boundary.

Carbon fibers and non-woven fabrics

A process for providing activated carbon fibers consisting of optically anisotropic components and optically isotropic components by spinning a pitch into fibers, and infusibilizing the resulting fibers, followed by an activation treatment. The pitch for spinning is prepared by melt mixing together (A) 100 parts by weight of an optically isotropic pitch having a softening point of 230.degree.-300.degree. C. obtained by heat treatment of a pitch while blowing an oxygen containing gas into the pitch, and (B) 10-50 parts by weight of an optically isotropic pitch having a softening point of 200.degree.-270.degree. C. obtained by polymerization of naphthalene in the presence of a Lewis acid catalyst. The optically isotropic pitch (B) is further characterized as having the property of being converted into an optically anisotropic pitch by the stress occurring at the time of spinning. The carbon fibers produced by spinning the spinning pitch into fibers have a double layer structure, the surface layer exhibiting optical isotropy and the center portion exhibiting optical anisotropy. The spun fibers are infusibilized, followed by carbonization and/or graphitization.

Process for producing pitch based activated carbon fibers and carbon

The disclosed carbon fiber felting material has a bulk density of 0.01 to 0.5 g/cm.sup.3 and a thermal conductivity of at most 1.0 kcal/m.multidot.hr.multidot..degree.C. in the thickness-wise direction thereof at 2,200.degree. C. The carbon fiber felting material is formed through physical and/or chemical interfiber entanglement. The carbon fiber felting material is very stable in an inert atmosphere, and excellent in heat insulating properties in a high-temperature range and against radiant heat transfer in particular.

Carbon fiber felting material and process for producing the same

There is disclosed a process for continuously producing a pitch-based carbon fiber felt which comprises the steps of spinning a pitch by melt blow spinning system; accumulating the spun fibers as a pitch fiber web composed of the aggregate of short fibers; continuously cross lapping the web; subsequently stabilizing the cross lapped web; carbonizing and/or activating the stabilized web; and then felting the resultant web. The above-mentioned process is capable of efficiently producing a pitch-based carbon fiber felt having uniform unit weight and excellent physical properties and well suited for use in high-performance thermal insulator, cushioning thermal insulator, filter media and adsorbent for water purification and solvent recovery, etc.

Process for producing carbon fiber felt

An infusiblized, or infusiblized and slightly carbonized fiber of optically anisotropic pitch type is combined with a phenolic resin fiber to produce a high bulk density carbon fiber structure in the form of a laminate of mutually entangled carbon fiber sheets with improved handleability of fiber sheets and improved stability of a laminate structure formed through entanglement. A high flexural strength carbon-carbon composite material with a high volume fiber content is produced by impregnation with a precursor of carbon and subsequent carbonization of the carbon fiber structure of the kind as described above or a fiber laminate of mutually entangled sheets of the infusiblized, or infusiblized and slightly carbonized fiber of optically anisotropic pitch type blended with the phenolic resin fiber.

Carbon fiber structure and process for producing the same

Flexible materials for reflecting electromagnetic waves can be provided by using adhesive type non-woven fabrics formed by self adhesion of the principal component of pitch based carbon fibers.

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Kamisu-machi, Japan

Yoshiyuki Nishimura