• Carbon letters
• /
• v.5 no.1
• /
• pp.23-26
• /
• 2004

A study of partial carbonisation of green pitch fibres to temperatures in the range of 500-$1000^{\circ}C$ was carried out on three precursors - a neat pitch and two polymer modified pitches, with a view to find out a suitable temperature at which the fibres acquire considerably improved toughness or handleability (compared to that in the green stage) for their subsequent processing into carbon fibres. A partial carbonisation temperature of 500-$600^{\circ}C$ has been identified to result in a remarkable improvement in the toughness/handleability of the fibres in all the three cases. However, from techno-economical considerations, the neat pitch appears to provide the best precursor system for the production of pitch based carbon fibres.

• Carbon letters
• /
• v.6 no.1
• /
• pp.15-24
• /
• 2005

Sixteen clinically healthy New Zealand white rabbits of either sex were divided into two equal groups I and II of 8 animals each. Under thiopental sodium (2.5%) anaesthesia a linear full thickness abdominal wall defect of 3 cm in length was created and repaired with continuous suture pattern using 3000 filaments of carbon fibres and 1~0 black braided nylon suture, ingroup I and II respectively. Increased vascularity was observed in carbon fibres (group I) and on day 30 the carbon fibres were covered by white fibrous tissue. Significantly higher (P < 0.05) values of glucose was seen on day 14 in group I, whereas, decrease in glucose value was observed in group II. Histopathologically, the carbon fiber implant induced extensive fibrous tissue (collagen fiber) reaction. Negligible inflammatory cells in the stroma indicate the host tissue tolerance to carbon fibers. Histochemically, gradually increased alkaline phosphatase activity up to day 14 in group I, suggested the proliferation of fibroblasts in early stages.

• Carbon letters
• /
• v.4 no.3
• /
• pp.117-120
• /
• 2003

Asbestos is being replaced throughout the world among friction materials because of its carcinogenic nature. This has raised an important issue of heat dissipation in the non-asbestos brake pad materials being developed for automobiles etc. It has been found that two of the components i.e. carbon fibres as reinforcement and graphite powder as friction modifier, in the brake pad material, can playa vital role in this direction. The study reports the influence of these modifications on the thermal properties like coefficient of thermal expansion (CTE) and thermal conductivity along with the mechanical properties of nonasbestos brake pad composite samples developed in the laboratory.

• Carbon letters
• /
• v.7 no.3
• /
• pp.166-170
• /
• 2006

Silicon carbide whiskers ($SiC_w$) having the diameter in the range of 20-80 nm were synthesised from coconut fibres through sol-gel process. The coconut fibres were impregnated with tetraethoxysilane and methyltriethoxysilane derived sol and pyrolyzed at $1400^{\circ}C$ in argon. X-ray of the pyrolyzed samples showed the formation of ${\beta}$-SiC.

• Carbon letters
• /
• v.7 no.2
• /
• pp.81-86
• /
• 2006

During a 3-year period (2001-2004) 18 animals were surgically treated because of abdominal wall defects (hernia). Out of 18 animals 8 were bovines, 5 caprines and 5 canines. In each case the defect was bridged with carbon fibres. Carbon fibres were placed either in simple interrupted pattern or as mattress overlapping pattern. All the cases were successfully treated and no complication was observed up to six months postoperatively.

• Geomechanics and Engineering
• /
• v.5 no.2
• /
• pp.87-97
• /
• 2013

In this paper, a novel fibrous material known as axially reinforced braided composite rods (BCRs) have been developed for reinforcement of soils. These innovative materials consist of an axial reinforcement system, comprised of longitudinally oriented core fibres, which is responsible for mechanical performance and, a braided cover, which gives a ribbed surface texture for better interfacial interactions with soils. BCRs were produced using both thermosetting (unsaturated polyester) and thermoplastic (polypropylene) matrices and synthetic (carbon, glass, HT polyethylene), as well as natural (sisal) core fibres. BCRs were characterized for tensile properties and the influence of core fibres was studied. Moreover, BCRs containing carbon fibre in the core composition were characterized for piezoresistivity and strain sensing properties under flexural deformation. According to the experimental results, the developed braided composites showed tailorable and wide range of mechanical properties, depending on the core fibres and exhibited very good strain sensing behavior.

• Carbon letters
• /
• v.5 no.2
• /
• pp.62-67
• /
• 2004

Performance of carbon-carbon composites is known to be influenced by the fibre matrix interactions. The present investigation was undertaken to ascertain the development of microstructure in such composites when carbon fibres possessing different surface energies (T-300, HM-35, P120 and Dialed 1370) and pitch matrices with different characteristics (Coal tar pitch $SP110^{\circ}C$ and mesophase pitch $SP285^{\circ}C$) are used as precursor materials. These composites were subjected to two different heat treatment temperatures of $1000^{\circ}C$ and $2600^{\circ}C$. Quite interesting changes in the crystalline parameters as well as the matrix microstructure are observed and attempt has been made to correlate these observations with the fibre matrix interactions.

• Carbon letters
• /
• v.4 no.3
• /
• pp.111-116
• /
• 2003

Carbon/carbon composites were developed using PAN based carbon fibres and phenolic resin as matrix in different volume fractions and heat treated to temperatures between $1000^{\circ}C$ to $2500^{\circ}C$. Although both the starting precursors are nongraphitizing hard carbons individually, their composites lead to very interesting properties e.g. x-ray diffractograms show the development of graphitic phase for composites having fibre volume fractions of 30~40%. Consequently the electrical resistivity of such composites reaches a value of $0.8\;m{\Omega}cm$, very close to highly graphitic material. However, it was found that by increasing the fibre volume fraction to 50~60%, the trend is reversed. Optical microscopy of the composites also reveals the development of strong columnar type microstructure at the fibre (matrix interface due to stress graphitization of the matrix. The study forcasts a unique possibility of producing high thermal conductivity carbon/carbon composites starting with carbon fibres in the chopped form only.

• Journal of Industrial and Engineering Chemistry
• /
• v.67
• /
• pp.358-364
• /
• 2018

An isotropic pitch precursor for fabricating carbon fibres was prepared by co-carbonization of ethylene bottom oil(EBO) and polyvinyl chloride (PVC). Various pre-treatments of EBO and PVC, and a high heating rate of $3^{\circ}C/min$ with no holding time, were evaluated for their effects on the oxidative stabilization process and the mechanical stability of the resulting fibres. Our stabilization process enhanced the volatilization, oxidative reaction and decomposition properties of the precursor pitch, while the addition of PVC both decreased the onset time and accelerated the oxidative reaction. Aliphatic carbon groups played a critical role in stabilization. Microstructural characterization indicated that these were first oxidised to carbon-oxygen single bonds and then converted to carbon-oxygen double bonds. Due to the higher heating rate and lack of a holding step during processing,the resulting thermoplastic fibers did not completely convert to thermoset materials, allowing partially melted, adjacent fibres to fuse. Fiber surfaces were smooth and homogeneous. Of the various methods evaluated herein, carbon fibers derived from pressure-treated EBO and PVC exhibited the highest tensile strength. This work shows that enhancing the naphthenic component of a pitch precursor through the co-carbonization of pre-treated EBO with PVC improves the oxidative properties of the resulting carbon fibers.

• Maxillofacial Plastic and Reconstructive Surgery
• /
• v.37
• /
• pp.34.1-34.14
• /
• 2015

Background: Over the past 30-40 years, various carbon implant materials have become more interesting, because they are well accepted by the biological environment. The traditional carbon-based polymers give rise to many complications. The polymer complication may be eliminated through carbon fibres bound by pyrocarbon (carbon/carbon). The aim of this study is to present the long-term clinical results of carbon/carbon implants, and the results of the scanning electron microscope and energy dispersive spectrometer investigation of an implant retrieved from the human body after 8 years. Methods: Mandibular reconstruction (8-10 years ago) was performed with pure (99.99 %) carbon implants in 16 patients (10 malignant tumours, 4 large cystic lesions and 2 augmentative processes). The long-term effect of the human body on the carbon/carbon implant was investigated by comparing the structure, the surface morphology and the composition of an implant retrieved after 8 years to a sterilized, but not implanted one. Results: Of the 16 patients, the implants had to be removed earlier in 5 patients because of the defect that arose on the oral mucosa above the carbon plates. During the long-term follow-up, plate fracture, loosening of the screws, infection or inflammations around the carbon/carbon implants were not observed. The thickness of the carbon fibres constituting the implants did not change during the 8-year period, the surface of the implant retrieved was covered with a thin surface layer not present on the unimplanted implant. The composition of this layer is identical to the composition of the underlying carbon fibres. Residual soft tissue penetrating the bulk material between the carbon fibre bunches was found on the retrieved implant indicating the importance of the surface morphology in tissue growth and adhering implants. Conclusions: The surface morphology and the structure were not changed after 8 years. The two main components of the implant retrieved from the human body are still carbon and oxygen, but the amount of oxygen is 3-4 times higher than on the surface of the reference implant, which can be attributed to the oxidative effect of the human body, consequently in the integration and biocompatibility of the implant. The clinical conclusion is that if the soft part cover is appropriate, the carbon implants are cosmetically and functionally more suitable than titanium plates.