| Diamond, as one of the limit function materials, is widely used in the fields of machining ofmetals, semiconductor chip encapsulation, microwave devices, optical window and so on.However, natural diamond is scare, which couldn’t meet the requirement of social developmentfor a long time and prompts the demands of synthetic diamond, so its production is increasing byyears. Currently, the production of synthetic diamond is mainly from the method of hightemperature and high pressure, and one of difficulties in it is how to decompose the diamondblocks in a rapid, economic and green way because that cotians important economic value. Inaddition, the depth development of diamond composite materials continues to make progresssince diamond has many properties such as high thermal conductivity, high hardness and others.For example, diamond/Cu composites is regarded as the most promising next-generationelectronic packaging material, however, diamond’s special crystal structure and physicochemicalproperties make the intensity of interface between diamond and Cu very low, which badlyweaken the exertion of diamond high thermal conductivity. So, how to improve the wettabilityand interface bonding ability between the diamond and matrix metals like Cu becomes a key andscientific issue in the field of diamond compound machining. This paper studies the traditionalelectrolytic technology on purifying diamond from blocks, and proposes a new set of efficientand economical post-processed technology. Meanwhile, put forward some measures made thediamond surface active against it hardly wets out with others, namely formaldehyde-freeelectroless copper plating on and high temperature-copper catalyzed coating boron nanowires todiamond surface, which are also suitable for large-scale application, and can prepare highquality raw diamond materials for deep process. What this paper describes is as follows:Designs and develops a new electrolyte used to purify diamonds from synthetic blocks,which is composed by NH4Cl, H3BO3, citric acid, NaCl and C6H4SO2NNaCO. And studies onthe effects of every component on purifying diamonds in electrolytic process, analyzes thechanging rule of every component and electric current density as well as pH value on cathodeweight increment, acquires an efficient and economic electrolyte and technique aboutelectro-refining diamonds: NH4Cl15g/l，H3BO330g/l，citric acid25g/l，NaCl15g/l， C6H4SO2NNaCO10g/l, and electric current density8A/dm2, pH=5. Observing the diamondsafter purified, they are integrated, clean, no impurities, and the recovery rate of by-products likeFe, Ni is up to92％, the efficiency of purification is very high.For electroless plating copper on diamond surface, the plating solution is composed by NaBH4, CuSO45H2O, C4O6H4KNa, EDTA-2Na and K4[Fe(CN)6]. Replacing expensive PdCl2withAgNO3and poisonous formaldehyde with NaBH4are also novelties in the use of activating agentand reducing agent. Studies on the effects of every component of the solution and temperature,pH value of the technology on depositing rate, coating grains, stability of solution and so on, getsan optimal formula: NaBH41.5g/L，CuSO45H2O20g/L，C4O6H4KNa15g/L，EDTA-2Na20g/L，K4[Fe(CN)6]65mg/L，double pyridine15mg/L；pH=13，temperature60℃. Observingthe plated diamonds with stereoscopic microscope, their coating are evenly and compactly,grains are small and uniform. Analyzing the structure and components of the coating using XRDand EDS, the results show the cladding material is high purity copper. In the technology, thesolution is stable, the reaction is mild, plating rate is controllable, and it is suitable for large scaleprocessing in producing diamond powder materials.Boron nanowires grow on diamond surface with hightemperature-coppercatalyzed method.The method is that mixes diamond, Cu powders, boron powders and then processes heattreatment under the hydrogen atmosphere, then gets boron nanowires with length0.5～1.5μmand diameter20～100nm. The changing temperature will bring a great influence on boronnanostructure morphology, at1090℃,boron nanowires grow on diamond surface; at1110℃,boron nano-blocks grow, and when the temperature is up to1130℃, boron nanostructureis no obviously regular. Besides the temperature, holding time is another influence factor. Whenthe temperature is1090℃and the holding time is less than90min, there is no boron nanowire,when the holding time is120min, the boron nanowires grow uniform, and if the holding time islonger, the nanowires would be more curved. In addition, the ratio of diamonds, copper powdersand boron powders will influence the growth. When the ration of diamond is lower than60%,can’t get boron nanowire, When more than60%, and the mass ratio of copper powders as well asboron powders is between2and4, can get uniform boron nanowires. The mechanism of boronnanowires growth is connected to the structure of diamond, catalysis of copper droplets, boriclow solid solubility in the diamond and free transmission in copper droplets. Boron can dissolve into diamond and the solid solubility is very low, so it is easy to get saturated in the diamondsurface, then forms nucleation points at the interface between diamond and copper droplets underthe effect of catalysis from copper droplets. Boron atom gets the points through copper droplets,then boron nanowires grow completed finally. Diamond coated the boron nanowires has higheractivity, copper can successfully be plated on diamonds with the process of chemical platingwithout sensitization and activation, and the cladding is fine and close. |
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