超临界石墨烯脉冲复合电沉积工艺研究

发布时间：2018-02-23 03:17

本文关键词： 超临界CO_2流体石墨烯复合电沉积脉冲电沉积显微硬度耐磨性　出处：《江苏理工学院》2017年硕士论文　论文类型：学位论文

【摘要】：石墨烯因其独特的二维晶体结构,使其具有众多的优异性能。金属基石墨烯复合材料具有较高的显微硬度和耐磨性,在材料领域具有重大的研究意义。目前金属基石墨烯复合材料主要是通过压制的方法在高温条件下将石墨烯纳米薄片与基体材料复合制备而成,存在石墨烯结构因受到压制机械力而易破坏现象,影响复合材料组织结构和力学性能。以石墨烯纳米薄片作为复合电沉积层的第二相,采用电沉积方法制备金属基石墨烯复合材料,可以避免破坏石墨烯结构。传统复合电沉积过程中,第二相易团聚,电沉积层表面粗糙,析氢严重。针对此现象,本文将超临界CO_2流体(SCF-CO_2)的高度传质性和扩散性特性与脉冲复合电沉积技术有机结合,开展超临界石墨烯脉冲复合电沉积技术研究,细化复合电沉积层晶粒,提高石墨烯嵌入量和分布均匀性,制备高性能复合电沉积层。重点研究平均电流密度、占空比和频率对复合电沉积层微观组织结构和力学性能的影响规律,并与普通常温、常压条件下制备的复合电沉积层进行对比,研究探讨超临界条件对复合电沉积的影响机理,提出了一套优异的制备镍基石墨烯复合电沉积层的技术工艺。主要研究内容如下:1.研究了超临界状态下,脉冲电沉积镍基石墨烯复合电沉积层的工艺方法。通过正交试验获得各电参数对复合电沉积层显微硬度的影响顺序:平均电流密度频率占空比;最佳工艺组合为平均电流密度6A·dm-2,频率1500Hz,占空比0.2。2.通过单因素试验,研究分析各电参数对石墨烯复合电沉积层性能的影响规律。(1)平均电流密度。随着平均电流密度的增大,复合电沉积层微观组织致密度、显微硬度和耐磨性均呈现先上升后下降的趋势,在平均电流密度为6A·dm-2时,电沉积层微观组织致密、石墨烯含量多、分布均匀,显微硬度和耐磨性达到最大;(2)占空比。占空比为0.25时,复合电沉积层晶粒细小、致密,石墨烯嵌入量多、分布均匀,力学性能最好。占空比小于0.25时,组织疏松不致密,表面有析氢孔洞。占空比大于0.25时,晶粒粗大,石墨烯团聚,分布不均;(3)频率。频率为1500Hz时,复合电沉积层组织致密,显微硬度和耐磨性最大。频率低于1500Hz时,组织疏松,晶粒粗大且部分脱落。频率高于1500Hz时,析氢副反应加剧,析氢孔洞增多,石墨烯团聚严重。3.研究获得超临界条件下脉冲电沉积镍基石墨烯复合电沉积层的最优工艺方案。在平均电流密度为6A·dm-2、占空比为0.25、频率为1500Hz和电沉积时间90min条件下,制备的复合电沉积层力学性能最佳。4.相比于普通常压条件,SCF-CO_2条件下制备的镍基石墨烯复合电沉积层中石墨烯嵌入量提高了1.7倍,分布更加均匀,镍粒尺寸达到纳米级,电沉积层平整、致密,显微硬度提高了0.67倍,磨痕截面积缩小了4.68倍,耐磨性大幅提高。超临界环境可以增加镍基石墨烯复合电沉积层中(200)晶面的择优度,降低(111)和(220)晶面的择优度。
[Abstract]:Graphene due to its unique two-dimensional crystal structure, which has many excellent properties. The metal / graphene composite material has high hardness and wear resistance, which is of great significance in the field of materials. The metal / graphene composites is mainly through the pressing method under high temperature conditions of graphene nanosheets with the matrix composites prepared by pressing existing graphene structure mechanical force and easy to damage phenomenon, affect the structure and mechanics of composite materials. The microstructure and properties of graphene nanosheets as composite electrodeposition layer in the second phase, the preparation of metal / graphene composites prepared by electrodeposition method, can avoid the destruction of graphene the traditional structure. The composite electrodeposition process in the second phase, easy to agglomerate, electrodeposit surface roughness, hydrogen evolution is serious. In view of this phenomenon, the supercritical fluid CO_2 (SCF-CO_2) high pass The quality and the diffusion characteristics and the organic combination of pulse composite electrodeposition technique research of composite electro deposition technology of supercritical graphene pulse composite electrodeposition layer, refine grain, improve the embedding capacity of graphene and distribution uniformity, the preparation of high performance composite electrodeposition layer. Focus on the average current density, duty cycle and frequency the composite effect of electro mechanical properties and microstructure of the deposited layer and the ambient temperature, atmospheric conditions for the preparation of the composite electrodeposition layer were compared, study the mechanism of supercritical conditions of composite electrodeposition, put forward a set of excellent preparation of nickel based graphene composite electrodeposition layer technology. The main contents are as follows: 1. the study of the supercritical condition, process of electrodeposited nickel based graphene composite electrodeposition pulse. By orthogonal test to obtain the electrical parameters on the microstructure of composite electrodeposition layer Effect of hardness: the average current density frequency duty ratio; the best combination for the average current density of 6A - DM-2, frequency 1500Hz, duty ratio of 0.2.2. by single factor test, analysis of the electrical parameters on the graphene composite electrodeposition layer properties. (1) the average current density increases with the average current. The density of the composite microstructure of deposited layer density, hardness and wear resistance decreases, the average current density of 6A - DM-2, electric microstructure of deposited layer is dense, the content of graphene, uniform distribution, microhardness and wear resistance reaches the maximum; (2) accounted for duty ratio. The duty cycle is 0.25, the composite electrodeposition layer of fine grain size, dense, graphene embedding quantity, uniform distribution, the best mechanical properties. The duty ratio is less than 0.25, loose tissue is not dense, the surface of hydrogen pores. The duty ratio is greater than 0.25, coarse grain Large, graphene reunion, uneven distribution; (3) frequency. The frequency of 1500Hz, composite electrodeposition layer microstructure, microhardness and wear resistance. Loose tissue frequencies below 1500Hz, and coarse grains and partially exfoliated. Frequency is higher than 1500Hz, increasing the hydrogen evolution reaction, hydrogen evolution holes increased graphene serious agglomeration.3. study the pulse electrodeposition of nickel based graphene composite electrodeposition layer of the optimum solution under supercritical conditions. The average current density is 6A / DM-2, 0.25 duty cycle, the frequency is 1500Hz and deposition time under the condition of 90min, the preparation of composite electrodeposition layer the best mechanical properties.4. compared to normal atmospheric conditions, SCF-CO_2 conditions for the preparation of nickel based graphene composite electro deposition layer embedded in graphene graphite volume increased by 1.7 times, more uniform distribution of particle size of nickel nano electrodeposition layer is smooth, dense, microhardness increased 0.67 times, grinding The cross-sectional area is reduced by 4.68 times and the wear resistance is greatly improved. Supercritical environment can increase the preferred degree of (200) crystal plane in the nickel base composite electrodeposition layer, reduce (111) and (220) the preferred degree of the crystal face.

【学位授予单位】：江苏理工学院
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG174.4;TQ153

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