双组元掺杂钛硅再结晶石墨传导性能的研究

Conductive Property of Recrystallized Graphite Doped with Titanium and Silicon

用煅烧石油焦作填料,煤沥青作粘结剂,钛粉和硅粉作添加剂,采用热压工艺制备了一系列双组元掺杂再结晶石墨.考察了不同质量配比的添加剂对再结晶石墨的热导率、电阻率和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15wt％钛粉再结晶石墨的传导以及力学性能有较大幅度的提高.在掺杂钛粉15wt％、硅粉<2wt％时,双组元再结晶石墨的常温热导率随着硅粉的掺杂量的增加有所提高.当掺杂钛粉及硅粉分别为15wt％和2wt％时,再结晶石墨RG-TiSi-152的常温热导率可达494W/m·K.但是当掺杂钛粉15wt％、硅粉>2wt％时,随着硅粉的继续增加,再结晶石墨的常温热导率反而降低.而双组元掺杂钛硅再结晶石墨的导电以及力学性能却随着硅粉的掺杂量的增加而降低.XRD分析表明,对于双组元掺杂钛硅再结晶石墨而言,钛元素最终在材料中以碳化钛形式存在,而硅元素则大都以气态形式被逸出,XRD物相图谱中未发现硅及其碳化物的存在.材料RG-TiSi-152的微晶尺寸La以及晶面层间距d002分别为864和0.3355nm.

The bi-element doped recrystallized graphite was prepared from calcined coke, coal-tar pitch, titanium and silicon by a hot-pressing process in order to investigate the effects of the amount of dopants on the thermal conductivity, electrical resistivity, bending strength and microstructure. Experimental results show that the basic physical properties of recrystallized graphite with 15wt% of dopant titanium are improved greatly, compared with pure graphite prepared by the same process. The thermal conductivity of recrystallized graphite with 15wt% of titanium and less than 2wt% silicon increases with increasing the amount of silicon at ambient temperature. The thermal conductivity of RG-TiSi-152 with 15wt% titanium and 2wt% silicon is 494W/m.K. The thermal conductivity of bi-element doped recrystallized graphite with 15wt% titanium and more than 2wt% silicon decreases with increasing the amount of silicon at ambient temperature. The electrical conductivity and bending strength of silicon and titanium doped recrystallized graphite decrease with increasing the amount of silicon. XRD analysis indicates that titanium added to carbon substrates exists in the form of TiC precipitates and much of silicon added to carbon substrates will escape from the material at last. The layers spacing d(002) and coherence length La of RG-TiSi-152 are 0.3355 nm and 864nm, respectively.