环路热管碳纤维毛细芯表面改性性能对比

Comparative Study of Surface Modified Carbon Fiber Capillary Wicks in Loop Heat Pipe

目的改善碳纤维表面亲水性能以应用于平板型环路热管毛细芯,并对比两种方法的优劣。方法采用两种方法对碳纤维表面进行改性—化学镀铜法(在碳纤维表面形成均匀铜镀层)、火焰喷涂金属粉末法(在碳纤维表面形成金属涂层),采用高速摄像机(High-speedCamera)、电子扫描显微镜(SEM)和红外成像仪(IR Camera)等表征设备,比对了处理后的表面形貌、亲水性能以及毛细抽吸力。通过IR图片测量吸液高度,建立数学模型,定量计算出两种方法改性后碳纤维的毛细抽吸性能。结果通过两种方法改性后的碳纤维,内部多孔结构均未被破坏且亲水能力都得到明显的提高,液滴接触碳纤维表面后迅速吸入纤维内部。化学镀层非常紧密平整,火焰喷涂涂层没有开裂,极少剥落。化学镀碳纤维的抽吸压为3.2kPa,渗透率为3′10-11 m^2,火焰喷涂金属涂层碳纤维的抽吸压为2.94 kPa,渗透率为8.16′10-11 m^2,说明通过两种方法改性得到的碳纤维均达到了平板型环路热管毛细芯的要求。结论通过化学镀和火焰喷涂对碳纤维进行表面处理均可以使碳纤维的浸润性得到明显改善,从而使其内部固有的多孔结构发挥出对水的毛细抽吸力,鉴于碳纤维作为一种厚度灵活的柔性材料,不受蒸发器尺寸的限制,可以成为传统烧结和金属丝网毛细芯的替代方法。

The work aims to improve the wet ability of carbon fiber applied in copper-water flat loop heat pipes and compare the advantages of different modified methods.The electroplate copper and flame spraying process metal powder were respectively used to form uniform copper plate and metal coating on the carbon fiber to modify the surface of carbon fiber.The treated surface morphology,improved wet ability and pumping of capillary wicks were characterized by high-speed camera,SEM and IR camera.The suction range was measured by IR image and mathematical model was established to quantitatively calculate the capillary pumping properties of carbon fiber after modification by two methods.As for the modified carbon fiber wicks by two methods,the internal porous structure was not damaged and the wet ability was improved significantly.The liquid drop could be absorbed into the fiber quickly after falling on the carbon fiber.The electroless plating was dense and flat and the flame spraying coating was free from crack and peeling off.The capillary pressures and permeability of the electroless plated carbon fiber capillary wicks were 3.2 kPa and 3?10?11 m2,while those for flame spraying metal coated carbon fiber were 2.94 kPa and 8.16?10?11 m2 respectively.These two methods both made the carbon fiber meet the requirements of flat loop heat pipe capillary wicks by modification.The treatment to the surface of carbon fiber by electro plating and flame spraying can improve the wettability of carbon fiber and then make the internal porous structure exhibit the capillary pumping ability for water.Carbon fiber can be used to replace the traditional sintering and metal mesh capillary wicks due to the flexible thickness not being limited by the evaporator size.