Compressive Strength Of Carbon Foams Research Articles

Preparation and characterization of coal-based carbon foams by microwave heating process under ambient pressure

Abstracts To reduce significantly the preparation time and cost in energy of coal-based carbon foams and to develop facile synthesis condition, a microwave heading process (MHP) for fabricating coal-based carbon foams was suggested. The preparation time, the structure and the compressive strength of carbon foams fabricated respectively by MHP and carbonization in nitrogen atmosphere at high pressure (CNHP) were contrastively studied. The results show that MHP exhibited three distinct characteristics in contrast to CNHP. First, the preparation time of green foam is shortened by 55.2% based on the microwave heating principle. Secondly, the preparation conditions are more moderate, only under ordinary pressure instead of high pressure. Thirdly, the resultant carbon foams display small pore diameter with narrow pore size distribution and high compressive strength. More importantly, the strategy of coal-based carbon foam by microwave heating process can be applied to other thermoplastic precursor foaming to obtain macro-porous materials.

카본블랙이 내첨된 핏치로부터 폴리우레탄 조공제를 이용한 탄소 폼의 제조 및 특성

To improve mechanical strength of carbon foams, the carbon black (CB) added carbon foams were fabricated by impregnating different contents of carbon black (CB) and mesophase pitch using polyvinyl alcohol (PVA) solution into polyurethane foam and being followed by heat treatment. The cell wall-thicknesses of carbon foams were controlled by adding amounts of CB, and it was confirmed that the compressive strength of carbon foams was increased as increasing cell wall-thickness. The compressive strength had the highest value of with the highest bulk density of when adding 5 wt% CB in carbon foam. However, the thermal conductivity was decreased by adding CB in carbon foam. The results indicated that the thermal conductivities of carbon foams were reduced by increased interlayer spacing () with the addition of CB in carbon foams.

Preparation, microstructure, and compressive strength of carbon foams derived from sucrose and kaolinite

Abstract

Effect of different secondary quinoline insoluble content on the cellular structure of carbon foam derived from coal tar pitch

Carbon foam was produced using mesophase pitches obtained under different temperatures as precursors, via foaming and carbonization process. The physicochemical properties of mesophase pitch, as well as the microstructure and physical properties of carbon foam were investigated by optical microscope, infrared spectrometer, thermograviment analyzer (TGA), X-ray diffractometer (XRD), scanning electron microscope (SEM) and universal testing machine, respectively. The results show that the amount of secondary quinoline insoluble in mesophase pitches increase with heat-treatment temperature increase, meanwhile, the cell size of carbon foams increased firstly and then reduced. Moreover, the compressive strength of carbon foams also exhibited the same variation trend. The cellular structure of carbon foam can be severely affected by the secondary quinoline insoluble content of mesophase pitch; thus it is critical to tailor the secondary quinoline insoluble content of mesophase pitch for obtaining carbon foam with high performance.

Preparation of AlN/C composite foam through annealing recrystallization and its mechanical performance study

Order to get a new type carbon foam material, AlN/C composite foam was successfully synthesized by using AlN as an additive and hollow microspheres/reticulated carbon foam as a basement thought the annealing high-temperature heated process. The prepared samples were characterized by Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM). The results of test indicated that AlN whiskers with diameter of 50nm, length large than 10 um and larger length-diameter ratio were prepared by amorphous AlN recrystallization at the surface of carbon microspheres. Diffraction peaks of XRD demonstrated that the sample was characterized as graphitization and AlN whiskers were hexagonal structure. XPS test showed that there was an obvious peak of CN bond on 287.5 eV, which revealed that AlN and carbon foam through CN bond combined on their interfaces. Meanwhile, it was showed that AlN/C foam material's compression strength was 40.27 MPa through the analysis of the stress-strain of mechanical performance, which increased nearly one order of magnitude compared with the carbon foam material. The results of test showed that compressive strength of carbon foam was obvious reinforced by AlN whisker. And this new composite foam has infinite applications value in various kinds of resist compression and absorbing aeronautical materials.

Effects of Microstructure of Mesophase Pitch Precursor on the Compression Behaviour of Carbon Foam

The compression behaviour of carbon foams derived from synthetic naphthalene based and coal tar based mesophase pitch is studied. After carbonization and graphitization, the structure of carbon foam is modified obviously and compression behaviour decreased dramatically due to the transition of foam from two-dimensional turbostratic structures to graphite structures. The SEM, X-Ray diffraction and compression behaviour are used in the study of modification of mechanical properties. The results show that the compressive strength of carbon foam obtained from synthetic mesophase pitch is only 30% of the foam obtained from coal tar based mesophase pitch. The SEM shows that the length of micro-cracking of foam derived from synthetic mesophase pitch is as high as 5 μm and that of foam derived from coal tar based mesophase pitch is less than 2 μm. The causes of the differences in properties focused on rod structure of naphthalene based pitch transformed easier to three-dimensional sandwich structure.

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.