Effects of pitch fluoride on the thermal conductivity of carbon foam derived from mesophase pitch

Carbon foams with high thermal conductivity were obtained from mixtures of mesophase pitch and pitch fluoride. The addition of pitch fluoride in mesophase pitch could significantly increase the specific thermal conductivity of as-prepared carbon foams. After graphitization at 2873 K, the specific thermal conductivity of carbon foams increased from 82 up to 155.4 (W/mK)/(g/cm³) when the content of pitch fluoride was 3% in the raw material.     

Carbon foams with high compressive strength derived from mixtures of mesocarbon microbeads and mesophase pitch

Carbon foam with relatively high compressive strength and suitable thermal conductivity was prepared from mixtures of mesocarbon microbeads (MCMBs) and mesophase pitch, followed by foaming, carbonization and graphitization. The influence of addition amount of MCMB on the properties of as-prepared carbon foams was investigated in detail. Results showed that addition of MCMBs into mesophase pitch could significantly reduce the amount and length of cracks in carbon foams, which results in increase of compressive strength of carbon foams. Carbon foam with high compressive strength of 23.7 MPa and suitable thermal conductivity of 43.7 W/mK, was obtained by adding 50% MCMBs into mesophase pitch, followed by foaming, carbonization and graphitization.     

High strength carbon fibers from mesophase pitch

The tensile strengths of carbon fibers derived from mesophase pitch were determined as a function of gauge length in the range of 1.4–40 mm. Filaments were examined from a fiber apparently free from flaws, and the results were compared with data from filaments weakened by internal voids. Strengths with averages as high as 3.4 GPa were measured on 8 μm diameter filaments at a length of 1.4 mm. The tensile strength data were analyzed at each gauge length by using a two-parameter form of the Weibull equation. The shapes of the probability of failure versus strength plots, as well as the appearance of the histograms, showed that a secondary flaw population becomes significant at the longer filament lengths. Extrapolations based on the distributions of flaws which control the tensile strengths of the filaments at short test gauge lengths resulted in a predicted strength of 7 GPa at 0.1 mm length for both the void free and the flawed filaments. This average strength equals the best values reported for carbon filaments made from PAN.     

Large diameter carbon fibres from mesophase pitch

Large diameter carbon fibres of 15-60 μm were produced from naphthalene-derived mesophase pitch. In the as-spun state, preferred orientation increases with fibre diameter, confirming a previous study. However, the sheath-core structure that develops during carbonisation of large diameter fibres results in a decrease in preferred orientation. As a consequence, the strength, modulus and electrical resistivity also decrease. The coarse optical texture of the partially relaxed core allows a higher degree of graphitisation. With extended stabilisation, the core can be eliminated and the mechanical properties improve whilst the electrical resistivity increases.     

Anisotropy of mesophase pitch-derived carbon foams

Carbon foams with uniform pore size were produced from mesophase pitch in a high-pressure chamber. The morphologies, crystal structure and mechanical properties of as-grown carbon foams, carbonized and graphitic foams were investigated. The microwave absorbing properties of carbon foam sandwich composites at 2-18 GHz were also examined. It was found that the extension of pores in the xz-plane direction (parallel to the direction of gravitational force) was larger than that in the xy-plane direction (perpendicular to the direction of gravitational force). The compressive strength and modulus of resultant foams in the xz-plane direction were higher than those in the xy-plane direction. Further, the reflection loss of the sandwich composites composed of xy-plane carbon foam slabs was lower than that of xz-plane composites. The results of this work showed that carbon foam was a kind of anisotropic material.     

Structure of carbon fiber obtained from nanotube-reinforced mesophase pitch

Flow-induced orientation of discotic mesophase precursor typically leads to a center-origin, radial microstructure in the resulting carbon fibers. In the present study, we report the microstructure of carbon fibers that were derived from mesophase pitch that was modified using carbon multi-wall nanotubes (MWNTs). For an MWNT content as low as 0.1 wt.%, the microstructure was found to be fairly random (rather than radial).     

The mesophase and high modulus carbon fibers from pitch

The evolution of the basic carbonization studies which led to the development of carbon fibers from mesophase pitch is described. The structure and properties of these fibers and comparisons with carbon fibers from other precursors are also discussed. Several basic areas related to fibers, the mesophase, and the mechanism of carbonization require further investigation.     

中间相沥青基泡沫炭的研究进展

不同的原料和方法所制备的泡沫炭结构和性能也有所不同,本文阐述了以石油系、萘系和煤沥青为原料制备中间相沥青基泡沫炭的制备工艺以及常用的改性方法。指出泡沫炭主要有五边形十二面体和球形气孔状两种结构,具有密度小、强度高、良好的导电和导热等优异性能,并展望了泡沫炭的应用及发展方向。     

Preparation of carbon fiber from isotropic pitch containing mesophase spheres

Naphthalene based synthetic isotropic pitch was found to give spinnable precursors which carried 10–100 μm anisotropic spheres of 45 and 50 vol% in the isotropic matrix, when the pitch was heat-treated at 375 and 380 °C for 20 and 23 hours, respectively. The spun fiber was stabilized and carbonized into a carbon fiber, which showed anisotropic belts running along the fiber axis, suggesting that both anisotropic spheres and isotropic matrix are deformed to align within the nozzle. The structure and mechanical properties of the carbon fibers, thus prepared, were examined under microscopes and by mechanical testing.     

炭素专利

公开号：CN102643114A 公开日：2012—08—22 申请人：华东理工大学 发明人：路贵民,张灿,于建国,等 发明名称：一种新型炭素材料抗氧化处理方法 本发明涉及一种新型提高炭素材料抗氧化性能的处理方法,其具体步骤为,将水溶液加热沸腾后,再将炭素材料放入水溶液中：或者单独将溶质加热沸腾,而不采用溶剂水,再将炭素材料放人;在浸渍液中沸腾浸渍炭素材料;最后将炭素材料取出冷却。本发明的优点：炭素材料的多孔结构和沸腾原理相结合构建了完美浸渍效果,工艺简单、浸渍效率高、能耗低、抗氧化效果好。     

中间相沥青基泡沫炭的研究及应用

中间相沥青基泡沫炭具有低密度、高强度、高导热、抗冲击、耐高温、抗氧化等诸多特点,因而具有广泛的应用前景.目前,中间相沥青基泡沫炭最常用的制备方法是自发泡法.本文详细综述了中间相沥青基泡沫炭制备过程中的影响因素,也概述了近几年来国内外对泡沫炭的改性研究及应用.     

The electronic and structural characteristics of carbon fibers from mesophase pitch

The electronic properties (resistivity, magnetoresistance, and electron spin resonance) of mesophase pitch-based carbon fibers have been studied in relation to the fiber structure and processing conditions. Reproducible correlations between the electronic properties and the structure demonstrate that the electronic properties are a sensitive indicator of the degree of graphite order in the fibers. Fibers having radial transverse structure are more easily graphitized than fibers with random transverse structure. The effect of differences in the thermosetting procedure is relatively unimportant. The ultimate degree of graphitization attainable by these fibers is comparable to that of similarly heat-treated pyrolytic carbons, whereas PAN-based carbon fibers are ultimately capable only of properties comparable to pitch-based fibers treated in the 1700–2300°C range.     

Carbon fibres from mesophase pitch

Union Carbide Corporation has recently developed a process for preparing high-modulus carbon fibres from mesophase pitch. These high-modulus carbon fibres can be prepared from low-cost carbonaceous pitches which have been converted to a liquid crystal state. The liquid crystal or mesophase state results when a proper size distribution of planar aromatic molecules is produced by dehydrogenative condensation reactions. Mesophase pitches can be melt-spun into fibres possessing a high degree of axial preferred orientation which can be preserved and enhanced through carbonizing and graphitizing. Mesophase pitch-derived carbon and graphite fibres can have several transverse structures and are capable of achieving various combinations of high strength and high modulus. Their electronic properties are extremely sensitive to structure and further confirm the graphitizability of carbon fibres derived from mesophase pitch. A number of strength-limiting defects have been identified and their incidence reduced. The number of applications of carbon fibres continues to increase. The unique structure and properties of mesophase pitch-based carbon fibres make them particularly suitable for those applications requiring high stiffness, high electrical conductivity, high thermal conductivity, and low coefficient of thermal expansion.     

Single-walled carbon nanotube buckypaper and mesophase pitch carbon/carbon composites

Carbon/carbon composites consisting of single-walled carbon nanotube (SWCNT) buckypaper (BP) and mesophase pitch resin have been produced through impregnation of BP with pitch using toluene as a solvent. Drying, stabilization and carbonization processes were performed sequentially, and repeated to increase the pitch content. Voids in the carbon/carbon composite samples decreased with increasing impregnation process cycles. Electrical conductivity and density of the composites increased with carbonization by two to three times that of pristine BP. These results indicate that discontinuity and intertube contact barriers of SWCNTs in the BP are partially overcome by the carbonization process of pitch. The temperature dependence of the Raman shift shows that mechanical strain is increased since carbonized pitch matrix surrounds the nanotubes.     

Fabrication of mesophase pitch-derived open-pore carbon foams by replication processing

The replication process, extensively used for the fabrication of metallic sponges, is proposed for the fabrication of mesophase pitch-derived open-pore carbon foams. The mesophase pitch is liquid infiltrated into packed preforms of leachable NaCl particles which are afterwards water dissolved. The resulting material is a pitch-derived foam with an interconnected porous network that replicates the architecture of the salt packed preform. These structures are stabilized by an oxidation treatment and can be subsequently subjected to further treatments of carbonization and graphitization. Replication processing allows precision and uniformity in the pore size and versatility in the volume fraction and shape of pores.