添加聚丙烯腈预氧丝粉对泡沫炭结构和性能的影响

Effect of PAN-based preoxidized fiber powders addition on structure and properties of carbon foam

以添加2％～8％（质量分数）的聚丙烯腈（PAN）基预氧丝粉的中间相沥青为原料，通过高温自发泡法制备泡沫炭生料，经炭化、石墨化处理获得炭化泡沫和石墨泡沫。分别采用SEM和XRD观察分析泡沫炭的微观形貌和晶体结构，并测定泡沫炭的压缩强度和热导率。结果表明：预氧丝粉含量为2％的石墨泡沫的密度和抗压强度达到最大值，分别为0．78g／cm3和7．7MPa；随预氧丝粉含量的增加，泡沫炭孔径变大，分布不均匀，裂纹数量增加，韧带片层结构有序度先增加后减小：当预氧丝粉含量达到8％时，石墨泡沫的热导率达到最大值，为64．78W·m-1 K-1，抗压强度为6．7MPa，与未添加预氧丝粉的石墨泡沫相比，分别增加65．3％和63．4％。预氧丝粉对泡沫炭增强作用的主要机理是纤维在界面的拔出效应。

Carbon foams were prepared by graphitization from the nascent foams after carbonization, which were prepared by Mitsubishi naphthalene based mesophase pitch containing 2%-8% （mass fraction） PAN-based preoxidized fiber powders with high temperature self-foaming technology. The microstruetures and crystal parameters of the carbon foams were characterized by SEM and XRD. The compressive strength and thermal conductivity were also measured. The results show that the maximum density and compressive strengths of graphitized carbon foams are obtained at 2% content of PAN-based preoxidized fiber powders, which are 0.78 g/cm3 and 7.7 MPa, respectively. With increasing the preoxidized fiber powder mass fraction, the pore size of graphitized foam increases, and the bubble holes distribution is less uniform, and the number of microcracks increases, and the order degree of the ligament increases firstly, then decreases. The maximum value of thermal conductivity is 64.78 W.m-I.K-1, and the compressive strength is 6.7 MPa with an addition of 8% preoxidized fiber powders, which increase by 65.3% and 63.4%, respectively, compared with undoped graphited foam. The predominant strengthening mechanism is attributed to the pulling-out effect based on the fiber-matrix interface.