掺杂钛催化机理及其再结晶石墨导热性能的研究

用煅烧石油焦作填料、煤沥青作粘结剂、钛粉作添加剂,采用热压工艺制备了一系列不同质量配比的掺杂钛再结晶石墨.考察了不同质量配比的添加钛对再结晶石墨的热导率、抗弯强度的影响以及微观结构的变化.实验结果表明,与相同工艺条件下制备的纯石墨材料相比较,掺杂钛再结晶石墨的热导率、抗弯强度均有较大的提高.室温下,RG-15再结晶石墨的层面方向热导率可达424W/(m·k),抗弯强度可达50.2MPa.微观结构分析表明,少量的掺杂钛,即可使材料达到很高的石墨化度;过多的钛掺杂量不利于材料的热导率以及抗弯强度;原料中掺钛量为15wt％时,再结晶石墨的微晶发育以及排列程度最好,此材料的石墨化度为96.4％,微晶参数La为306nm.XRD物相分析表明,钛元素在再结晶石墨中以碳化钛的形式存在.钛对再结晶石墨制备过程的催化作用可以用液相转化机理来解释.

Thermal Conductivity and Catalytic Mechanism of Recrystallized Graphite by Titanium

The recrystallized graphite was prepared from calcined coke, coal-tar pitch and titanium by hot-pressing progress in order to investigate the effects of the amount of titanium on the thermal conductivity, bending strength and microstructure of recrystallized graphite. Experimental results show that the recrystallized graphite exhibits higher thermal conductivity and higher bending strength than the pure graphite prepared by the same process. For the orientation of graphite layers of the present RG-15 materials, the thermal conductivity and the bending strength are 424W/(m·k) and 50.2MPa at room temperature, respectively. Microstructure analysis reveals that a little amount of titanium can increase the degree of graphitization of recrystallized graphite, but overlarge amount of titanium dopant makes basic physical properties worse. For the recrystallized graphite with titanium concentration of 15wt%, the degree of development and arrangement of graphite crystallite is the best. The degree of graphitization of the present RG-15 material is 96.4% and the value of L_a is 306nm. XRD analysis indicates that titanium added to carbon substrate is in the form of TiC precipitates. The catalytic role of titanium to preparing recrystallized graphite can be explained by the liquid phase transition mechanism.