Preparation And Modification Research Of Mesophase Pitch Carbon Foams At Low Pressures

In this thesis, mesophase pitch carbon foam was produced from AR mesophase pitch by self-foaming method. The microstructure and crystal parameters of carbon foams were characterized by scanning electron microscopy (SEM), optical microscopy (OM) and X-ray diffraction (XRD). The properties such as bulk density, compressive strength and thermal conductivity and so on were also measured. The influence of the initial foaming pressures, Titanium/PAN-based preoxidized fiber powders(SGPs) bi-component doped and superfine graphite powders doped on the structure and properties of mesophase pitch based carbon foams were studied. The main results were as follows:(1) carbon foam poessed big pore diameter, high open porosity, narrow and long Ligament and large number of cracks under low initial foaming pressure. As the initial foaming pressure increased, the ligament width of carbon foam was increased, and the number of cracks was decreased. The maximum compressive strength and thermal conductivity of graphitized carbon foam were obtained when the initial foaming pressure was4MPa, which were3.5MPa and79.00(W·m-1·K-1)/(g·cm-3).(2) Titanium powders/PAN-based preoxidized fiber powders bi-component doped could obviously improve compressive strength and thermal conductivity of carbon foam. With the increase of titanium powders content, compressive strength and thermal conductivity of graphite carbon foam decreased slightly after initially increased. Graphite carbon foam with2wt%preoxidized fiber powders and12wt%titanium powders had the maximum compressive strength and thermal conductivity, which were3.47MPa and120.30(W·m-1·K-1)/(g·cm-3). The titanium dopant could react with carbon to form titanium carbide eventually. But the compressive strength and thermal conductivity of graphite foam might decreased with more titanium addition.(3) Superfine graphite powders (SGPs) could obviously improve the compress strength of carbon foam due to the inhibition of crack propagation. With the increase of SGPs content, the compressive strength of graphite carbon foam increased gradually, and the thermal conductivity first increased and then decreased. The maximum thermal conductivity and specific thermal conductivity was obtained when SGPs content was15wt%, respectively were43.24W·m-1·K-1and96.09(W·m-1·K-1)/(g·cm-3).