(1. 中南大學(xué) 材料科學(xué)與工程學(xué)院，長沙 410083；
2. 中南大學(xué) 教育部有色金屬材料科學(xué)與工程重點(diǎn)實(shí)驗(yàn)室，長沙 410083)
摘 要: 采用化學(xué)鍍工藝，以聯(lián)氨為還原劑制備純Ni包覆的TiC復(fù)合粉體，并優(yōu)化化學(xué)鍍過程的工藝參數(shù)；采用DSC、XRD、SEM、EDS等測試方法對優(yōu)化的工藝參數(shù)下制備的Ni包覆TiC粉體的表面形貌、形核長大機(jī)制和相組成進(jìn)行分析。結(jié)果表明：當(dāng)TiC裝載量為10 g/L，施鍍溫度為70 ℃、pH=10、聯(lián)氨濃度為100 mL/L時(shí)，可得到覆鍍速度和鍍層質(zhì)量都比較高的鍍層。在優(yōu)化的工藝參數(shù)下，單位質(zhì)量TiC上平均反應(yīng)速率為0.013 g/min、平均覆鍍量為0.8 g、反應(yīng)時(shí)間約為60 min。TiC表面預(yù)處理后形成的臺階狀區(qū)域成為Ni非均勻形核的活化區(qū)域。胞狀Ni顆粒長大并彼此接壤后，形成均勻致密的Ni層。溫度的變化強(qiáng)烈地影響著鍍層的形貌，當(dāng)施鍍溫度從70 ℃升高至95 ℃時(shí)，鍍層從致密的胞狀結(jié)構(gòu)轉(zhuǎn)變?yōu)槭杷啥嗫椎暮＞d狀結(jié)構(gòu)。化學(xué)鍍后得到的Ni層為晶態(tài)和非晶態(tài)的混合體，經(jīng)500 ℃保溫1 h后，結(jié)晶完全。
關(guān)鍵字: 化學(xué)鍍；Ni包覆TiC復(fù)合粉末；顯微組織；形核長大機(jī)制
（1. School of Materials Science and Engineering, Central South University, Changsha 410083, China;
2. Key Laboratory of Nonferrous Metal Materials, Ministry of Education, Central South University,）
Abstract:The Ni-coated TiC composite powder was prepared by electroless plating using hydrazine as the reductant, and the process parameters were optimized. The surface morphology, nucleation growth mechanism and phase component of the optimized TiC powders coated by pure nickel were studied using DSC, XRD, SEM and EDS. The results show that a better and faster formed coating can be obtained when the TiC powder load is 10 g/L, the plating temperature is 70 ℃, pH=10 and the hydrazine concentration is 100 mL/L. The mean reaction speed and plating per unit mass TiC are 0.013 g/min and 0.8 g, respectively, and the reaction time is about 60 min. The heterogeneous nucleation of nickel occurs in the bench-shape area which forms in the surface pretreatment. The cellular Ni particles grow up and form uniform and compact nickel coating finally. The temperature variation strongly affects the morphology of the coating. The coating turns to loose porous spongiform structure from compact cellular when the plating temperature varies from 70 ℃ to 95 ℃. The obtained nickel coating turns out to be the association of crystalline and amorphous, and is crystallized completely after heat preservation at 500 ℃ for 1 h.
Key words: electroless plating; Ni-coated TiC composite powder; microstructures; nucleation growth mechanism
