【摘要】：鎳包石墨復(fù)合粉體兼具金屬鎳優(yōu)良的導(dǎo)磁性、耐磨性和石墨的自潤(rùn)滑性、耐高溫等優(yōu)異性能,可用做導(dǎo)電硅橡膠填料、微波吸收材料以及電磁屏蔽材料。采用粉體電沉積的方法制備鎳包石墨復(fù)合材料,可以避免傳統(tǒng)化學(xué)鍍鍍液不穩(wěn)定,工藝流程復(fù)雜,成本高且污染環(huán)境的問題,制備出鍍層致密均勻有一定厚度的鎳包石墨復(fù)合粉體。本文采用微米級(jí)的天然鱗片石墨為原材料,利用間歇電鍍工藝制備鎳包石墨復(fù)合材料。優(yōu)化了前處理工藝,在電鍍前增加化學(xué)鍍預(yù)鍍步驟以提升電鍍效果。對(duì)電沉積工藝參數(shù)進(jìn)行了研究,并對(duì)電沉積成核機(jī)理進(jìn)行了探究。通過掃描電鏡對(duì)復(fù)合粉體的表面形貌和鍍層厚度進(jìn)行分析,用EDS能譜分析表面元素,獲得了以下研究結(jié)果。(1)利用SEM電鏡觀察化學(xué)鍍預(yù)鍍后再電鍍制備的鎳包石墨復(fù)合粉體的表面形貌,比較不同活化處理方法對(duì)石墨的活化效果。通過石墨沉降實(shí)驗(yàn)研究化學(xué)鍍預(yù)鍍影響電鍍效果的原因。(2)通過電鍍效率、復(fù)合粉體的鎳含量和表面形貌確定電鍍制備鎳包石墨粉體的電流密度、溫度、裝載量、占空比、電鍍時(shí)間等最佳工藝條件。使用沉降—電鍍—攪拌的周期循環(huán)電鍍,有效電鍍時(shí)間為30 min時(shí),獲得的鎳包石墨粉體包覆率高、鍍層均勻。提高電解液中Ni Cl2含量和陽(yáng)極與陰極面積比,能有效避免陽(yáng)極鈍化。(3)利用開路電位和陰極極化測(cè)試研究石墨在電鍍初期對(duì)鍍液的影響。利用恒電位暫態(tài)階躍實(shí)驗(yàn)研究在大電流密度下,鎳在石墨上沉積的成核機(jī)理。(4)鍍液中加入有機(jī)添加劑可以增大陰極過電位和電化學(xué)反應(yīng)阻抗,提高鎳的電結(jié)晶幾率,細(xì)化晶粒,提升鍍層光亮度。
[Abstract]:Nickel-coated graphite composite powder has excellent magnetic conductivity, wear resistance, self-lubricating property of graphite, high temperature resistance and so on. It can be used as conductive silicone rubber filler, microwave absorbing material and electromagnetic shielding material. The preparation of Ni-coated graphite composites by powder electrodeposition can avoid the problems of traditional electroless plating solution instability, complex process flow, high cost and environmental pollution. Nickel-coated graphite composite powder with dense and uniform coating was prepared. In this paper, nickel-coated graphite composites were prepared by batch electroplating using micron-grade natural flake graphite as raw material. The pretreatment process was optimized and the electroless plating pre-plating step was added before plating to improve the plating effect. The technological parameters of electrodeposition and the nucleation mechanism of electrodeposition were studied. The surface morphology and coating thickness of the composite powders were analyzed by scanning electron microscopy (SEM), and the surface elements were analyzed by EDS. The following results were obtained. (1) the surface morphology of Ni-coated graphite composite powder prepared by electroless plating and re-plating was observed by SEM electron microscope, and the activation effects of different activation treatments on graphite were compared. The reason of the influence of electroless plating preplating on plating effect was studied by graphite deposition experiment. (2) the current density, temperature, loading and duty cycle of nickel-coated graphite powder were determined by electroplating efficiency, nickel content of composite powder and surface morphology. Plating time and other optimal technological conditions. When the plating time is 30 min, the coating rate of nickel-coated graphite powder is high and the coating is uniform when sedimentation-plating-stirring cyclic plating is used. The passivation of anode can be effectively avoided by increasing the content of Ni Cl2 and the area ratio of anode to cathode in electrolyte. (3) the effect of graphite on plating bath is studied by open circuit potential and cathodic polarization test. The nucleation mechanism of nickel deposited on graphite under high current density was studied by potentiostatic transient step experiment. (4) the cathodic overpotential and electrochemical impedance could be increased and the electrocrystallization probability of nickel could be increased by adding organic additives into the plating bath. Refine the grain and improve the brightness of the coating.
【學(xué)位授予單位】：湖南大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TQ153.12;TQ127.11

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