本研究以奈米 α-Al2O3 粉體作為載體,並選用 Ni-P 合金做為披覆層,製備奈米核-殼結構複合粉體。採用無電鍍法 (Electroless Plating Method) 進行表面披覆。實驗結果顯示,選用 Na2C4H4O4•6H2O 作為錯化劑,需在較高溫度之環境下進行沈積,導致 Ni-P 合金顆粒析出速率較快而形成尺寸約 100 nm 且分散性不佳的沈積顆粒披覆在 α-Al2O3 顆粒表面;選用 Na3C6H5O7•2H2O 作為錯化劑並給予超音波震盪的環境能夠有效降低起始反應溫度,鍍浴未調整 pH 值的情況下 (pH=4.7),在溫度為 45oC 的環境即可進行析鍍,Ni 析出速率較慢且反應時間長達5個小時以上,並獲得披覆顆粒尺寸約 30 nm 且分散性較佳的 Ni-P 合金顆粒;鍍浴中添加成長抑制劑,能夠再進一步縮小析出顆粒尺寸至約 10 nm,仍可維持高分散性與良好的披覆情況;延續製程參數調整鍍浴的酸鹼度,顯示鍍浴反應速率隨著 pH 值的上升而上升,且反應結束時間縮短並提高 Ni 的生成量,鍍浴 pH 值為 7、8 及 9 時反應析出的顆粒具有兩種,表面粗糙且尺寸約為 50 nm 的團塊及酸性鍍浴的析出顆粒。本實驗製備出的奈米核-殼結構複合粉體,Ni-P 合金以顆粒狀披覆在 α-Al2O3 粉末表面且尺寸約 10 nm,形成不完全型核-殼結構。
Synthesis of nanosized α-Al2O3/Ni-P core-shell composite powders by electroless plating method was investigated in this study. The synthetic core-shell composite powders could be applied in catalysis field. The experimental results showed that the Na2C4H4O4•6H2O as a complexing agent in the electroless bath, the electroless plating occurred at high temperature (70oC), and the deposition particles formed aggregate and the size larger than 100 nm which was due to the higher reaction rate. The reaction temperature could be lower to about 45oC if Na3C6H5O7•2H2O was used as the complexing agent, the pH value of electroless bath was 4.7 and the bath was disturbed by ultrasonic wave vibration during electroless plating. The deposition particles with a size of 30 nm disperse homogeneously on α-Al2O3 particles. When inhibitive growth agent was added into electroless plating bath, the size of deposition particles was decreased to 10 nm and deposited homogeneously on the surface of α-Al2O3. The deposition of Ni-P particles on the α-Al2O3 powders affected by the pH value, temperature, components of the electroless bath. However, nanosized of α-Al2O3/Ni-P core-shell composite powders have been prepared successfully in this study.