Swelling and related mechanical and physical properties of carbon nanofiber filled mesophase pitch for use as a bipolar plate material

Current status of research on composite bipolar plates for proton exchange membrane fuel cells (PEMFCs): nanofillers and structure optimization

“…With 15% CNFs and CNTs, the composite bipolar plates achieved a flexural strength of 45.3 MPa and a planar conductivity of 8.2 S cm −1 . Chris Calebrese 100 investigated the potential of CNFs-modified intermediate-phase bitumen as a composite bipolar plate material, which was able to slow down swelling due to the intertwined structure of CNFs that facilitates the reduction of the swelling effect of intermediate-phase bitumen due to the outgassing caused by the heating and carbonization process. The results show that the composites exhibit good electrical conductivity (40–80 S cm −1 ) and flexural strength (40–0 MPa), which are potential alternative materials for composite bipolar plates.…”

Highly Thermal Conductive Silicon Carbide Ceramics Matrix Composites for Thermal Management: a Review

“…近年来，国产高导热石墨纤维制备技术日臻成 熟，性能逐渐完善 [40] ，赋予高导热碳化硅陶瓷基复 合材料更优的热物理性能以及更广阔的应用前景。 作为一种热塑性材料，沥青是一种结构和化学 组成非常复杂的物质，通常由带有烷基侧链的稠环 芳烃和杂环化合物混合而成 [41] 。原料沥青，如石油 沥青、煤沥青和萘系沥青等，经调制改性处理可得 到各向同性沥青或各向异性沥青，再经熔融纺丝、 均质预氧化、碳化、高温石墨化后得到沥青基碳纤 维。按照原料，沥青基碳纤维可分为各向同性沥青 基碳纤维和中间相沥青基碳纤维(高性能沥青基碳 纤维) [43] 。其中，中间相沥青基碳纤维(Mesophase Pitchbased Carbon Fiber, MPCF) 中含有大量向列型液晶 表 2 沥青基碳纤维性能及产品 [42][43] Table 2 Properties and products of pitch based carbon fibers [42][43] [42][43] ，如表 2 所示。 纺丝过程中的纤维预氧化制度以及喷丝板结构 造成中间相沥青基碳纤维横截面不同 [44] 。Edie 等 [45] 认为中间相沥青基碳纤维横截面主要有辐射状、洋 葱皮状、乱层状、叠层状、放射褶皱结构、线型结 构以及混合结构。其中，辐射状结构具有良好的导 热性能，但皮部收缩程度比芯部剧烈，容易产生裂 纹，力学性能降低；洋葱皮状以及乱层状结构在热 处理过程中收缩较均匀，缺陷较少，具有较高的拉 伸强度；放射褶皱状结构在具有较好力学性能的同 时还兼具优良的导热性能；而对于线型结构，沥青 熔体在更为充分的剪切力作用下， 具有更好的取向， 可避免热处理过程中的热应力集中和开裂现象，使 得纤维拉伸强度提高 [46] 。 因此，可根据实际需要， 调控中间相沥青基碳纤维的横截面结构。 如图 3 所示，Huang 等 [25] [25] Fig. 3 Diagram of the fabrication and microstructure of the 3D HTC C/C-SiC composite [25] Fang 等 [47] 研究了氧乙炔焰考核高导热碳化硅 陶瓷基复合材料的烧蚀机制。如图 4 所示，升华是 中心区域的主要消融行为，氧化是中心区域的主要 烧蚀行为；硅的氧化以及氧化硅气体的沉积是外部 区域形成二氧化硅颗粒的主要原因， 如图 4(c)所示； 图 4(a)中的中心区域烧蚀后，由于增强纤维(M30, Japan) 的高导热性和相邻端升华速度的差异，纤维 形成了针状微结构。因此，高导热碳化硅陶瓷基复 合材料氧乙炔焰烧蚀机理是热物理作用和热化学冲 蚀的综合作用。 图 4 烧蚀后的碳纤维增强碳化硅陶瓷基复合材料表面形貌 [47] Fig.…”

The Control of Volume Expansion and Porosity in Carbon Block by Carbon Black (CB) Addition for Increasing Thermal Conductivity

“…The CB addition increased the thermal conductivity of the carbon block, but the thermal conductivity did not show a significant change even when the amount of CB added increased. In general, as the volume expansion and porosity of the carbon block decreased, the thermal conductivity increased [36][37][38][39]. Therefore, the thermal conductivity of C_CB_10 (the lowest volume expansion and porosity) should be the highest, but the thermal conductivity of C_CB_10 was not significantly different from C_CB_1 and C_CB_5.…”