Papers by Keyword: Carbon/Carbon Composite

Abstract: A new multi-chamber detonation accelerator (MCDS) was applied to fabricate ZrB₂–MoSi₂ composite coating containing 20 mol.% of MoSi₂ on carbon/carbon composites. Phase composition and microstructure of the coating were characterized by X-ray diffraction and scanning electron microscopy. The ZrB₂–20MoSi₂ coating displayed compact and lamellar microstructure with porosity lower than 1%, where SiO₂ phase was uniformly distributed in the ZrO₂ matrix. The coating was well-adhered with carbon/carbon composites. Silica, m-ZrO₂, and small amount of Zr(MoO₄)₂ were formed.

Abstract: Carbon fibre reinforced carbon composites (C/C) are characterised by their excellent thermal, chemical and mechanical properties. The intrinsic porosity and fibre reinforcement grant them an excellent damage tolerance. The production of complex structures is time consuming and very expensive. An innovative approach to this topic is the integration of simple geometric ceramic composite materials within complex polymer structures. The motivation of this contribution is to investigate the influence of hexamethylenetetramine as hardener (hardener content: 4, 8, 12 and 16 %) and curing parameters (tempered and non-tempered) on the microstructure and mechanical properties of the porous C/C composites. During the course of this contribution, selected carbon fibre reinforced polymer (CFRP) composites with different porosities were produced while adjusting the resin or hardening agent-ratio, as well as the processing parameters. Subsequent to the curing of the CFRP samples, porous C/C composites were produced by means of a pyrolysis process. The final part of the contribution is comprised of the microstructural analysis by light microscopy and the explanation of the flexural strengths, by utilising a “three-point-bending test”.

Abstract: Straight carbon nanotubes (CNTs) with radially-growing morphologies and long length were grafted on carbon fibers by catalytic chemical vapor deposition and they were used to reinforce carbon/carbon composites (C/Cs). Mechanical tests indicate that CNTs can increase the interlaminar shearing strength of C/Cs by about 200 %. The reinforcement mechanism was concretely discussed with emphasis placed on the change of the cohesion of pyrocarbon matrix.

Abstract: Carbon/Carbon composite is considered to be one of the best biomaterials substitute to human hard tissues due to its excellent biocompatibility and the much closed elastic modulus to human skeleton. It has been widely used and studied to the fields of artificial bones materials, but the osteoinductivity need to be improved. In recent years, the commonly used surface modification to improve their bone induction, such as hydroxyapatite, chitosan and so on, which prompted the adsorption of osseous protein, adhesion and growth of cells. It is believed the surface modification and coating of the carbon/carbon composite should promote its application in artificial bones. This article reviews the modified coat of medical carbon / carbon composites in recent years, and proposed some recommendations for the development of medical carbon / carbon composite in the future.

Abstract: This paper reviewed published research into catalytic fabrication techniques and recent progresses of carbon/carbon (C/C) composites. It’s described the catalytic chemical vapor deposition theory and reviewed the catalytic properties of different metal catalysts. Merits and demerits of the traditional chemical vapor deposition, improved chemical vapor deposition and other new rapid densification techniques were analyzed. The new densification techniques are to shorten the preparation cycle, but most of them are limited in the laboratory with application problems. Finally, the prospect on the application and development tendency of improved catalytic chemical vapor deposition technique is put forward in the rapid low cost fabrication of C/C composites in the future.

Abstract: In order to improve the oxidation resistance property of carbon/carbon composites, the C/C matrix was modified with a borate sol precursor and B₄C micro-powders by a sol-gel integrating with a solvothermal process. The phase compositions, surface and cross-section microstructures of the C/C matrix modified by different B₄C content were particularly investigated. Results show that the surface of the modified composites is covered by a coating composed of B₂O₃ and B₄C, meanwhile, the internal micro-holes of the C/C composites are occupied by B₂O₃ and B₄C. After oxidation in air at 973 K, the B₂O₃ glassy phase, due to the oxidation of B₄C, seals the cracks and holes and effectively prevents C/C composites from oxidation. The weight loss of the modified C/C composites is only 2.21 % after oxidation in air at 973 K for 20 h.

Abstract: In order to improve the oxidation resistance of carbon/carbon (C/C) composites, a ZrSiO₄ coating on SiC pre-coated C/C composites was prepared by a hydrothermal electrophoretic deposition process. The phase composition, surface and cross-section microstructure, anti-oxidation property of the as-prepared ZrSiO₄/SiC coating was investigated. Results show that hydrothermal electrophoretic deposition is an effective route to achieve crack-free ZrSiO4 outer coatings. The ZrSiO₄/SiC coating can protect C/C composites from oxidation at 1773 K for 332 h with a weigh loss rate of only 4.83×10^-5g/cm²·h.

Abstract: The aim of the proposed studies is the development of the carbon/carbon composite with prescribed elastic properties. To achieve this, a microstructure optimisation problem for estimation of the microstructure with prescribed stiffness is formulated. The design variables of the posed problem are the local fibers distribution and porosity. The volume fractions of the fibers and pores in the whole microstructure are fixed. Material properties of the local microstructure of the composite are calculated using virtual models. Semi-analytical homogenization procedures were used for the development of these models. Modeling results are compared with elastic properties obtained experimentally by tension and compression test and ultrasonic studies of the bulk material. Approach to design microstructure for three point bending test is proposed.

Abstract: The effect of alkaline hydrothermal temperature on the transformation of induction heating deposited monetite coatings to hydroxyapatite coatings on the H₂O₂ treated C/C composite was investigated. These monetite coatings were hydrothermally treated for 4h at 353K, 373K and 393K in a 50ml autoclave with 0.1M alkaline solution. After hydrothermal post-treatment, the structure, morphology and the chemical composition of these HA coatings were characterized with XRD, FTIR, SEM and EDS. A scratch test was conducted to measure the strength of the adhesion of the coatings to the HT-C/C substrate. The results showed that only part of hydroxyapatite phases at 393K could be transformed from the monetite coatings on HT-C/C substrate, while pure hydroxyapatite phases were observed to form in the as-converted coatings with critical loads of 45.9N and 51.1N respectively when the alkaline hydrothermal post-treatment treating temperatures were 353K and 373K. The reasons for these results were suggested.

Abstract: PAN-carbon fibers were pretreated using three methods. 2D-C/C composites were fabricated by a rapid chemical liquid-vaporized infiltration (CLVI) processing. Surface morphologies of carbon fiber pretreated and fracture micrographs of 2D-C/C composites were observed by scanning electron microscopy (SEM) and high resolution transmission electron microscope (HRTEM). The interlaminar shear strength(ILSS) of C/C composites was tested. The influences of carbon fiber surface pretreatments on ILSS and fracture behaviors of C/C composites were analyzed. The experimental results indicated that the C/C composite with carbon fiber coated CVI pyrocarbon possesses both higher flexural strength and interlaminar shear strength than composites with other fiber pretreatments. The fractographes revealed the differences in the mechanical behavior depending on the interface strength of fiber/matrix.