A direct electroless copper （Cu） coating on tungsten powders method requiring no surface treatment or stabilizing agent and using glyoxylic acid （C2H203） as a reducing agent was reported. The effects of copper sul...A direct electroless copper （Cu） coating on tungsten powders method requiring no surface treatment or stabilizing agent and using glyoxylic acid （C2H203） as a reducing agent was reported. The effects of copper sulfate concentration and the pH of the plating solution on the properties of the prepared W@Cu composite powders were assessed. The content of Cu in the composite powders was controlled by adjusting the concentration of copper sulfate in the electroless plating solution. A uniform, dense, and consistent Cu coating was obtained under the established optimum conditions （flow rate of C2H203 = 5.01 mL/min, solution pH = 12.25 and reaction temperature 45.35℃） by using central composite design method. In addition, the crystalline Cu coating was evenly dispersed within the W@Cu composite powders and Cu element in the coating existed as Cu~. The formation mechanism for the W@Cu composite powders by electroless plating in the absence of surface treatment and stabilizing agent was also proposed.展开更多
We reported a dripping solvothermal method for synthesizing metal-organic framework-5（MOF-5）. It started from separately dissolving Zn（NO3）2 and terephthalic acid（H2BDC） in dimethyl formamide（DMF）, and then dr...We reported a dripping solvothermal method for synthesizing metal-organic framework-5（MOF-5）. It started from separately dissolving Zn（NO3）2 and terephthalic acid（H2BDC） in dimethyl formamide（DMF）, and then dripping one solution into the other. Results of SEM, XRD and laser particle size distribution show that regular cubic-shaped and micro-crystallite powder of MOF-5 can be obtained. The d0.5（volume-median-diameter） values are 4.32 μm for particles prepared by dripping Zn（NO3）2 into H2BDC（ZH） and 9.32 μm for those prepared by dripping H2BDC into Zn（NO3）2（HZ）, much smaller than 22,7 μm that of particles prepared by the traditional adding water solvothermal method（L）. The standard deviations of the particle size distributions fitted by the GaussAmp model are 2.49, 4.38 and 15.4 respectively for ZH, HZ and L, further revealing narrower size distributions of particles prepared by the dripping method. In addition, the Langmuir specific surface areas are 923 m^2/g for ZH and 868 m^2/g for HZ. The TGA results present mass losses of 4.18% and 3.62% at 105 ℃, 17.19% and 14.78% at 245 ℃, 39.04% and 34.85% at 600℃ separately for ZH and HZ, which correspond to the removal of H20, DMF and the decomposition of MOF-5. This indicates that MOF-5 has a strong adsorption ability for small molecules. Besides, the mass loss of 48.39%（ZH） and 41.02%（HZ）between 400 ℃ and 600 ℃ are less than the theoretical value of 57.81% for MOF-5 decomposition to ZnO, suggesting that an impure phase with an extra amount of ZnO may exist in the cavities of MOF-5.展开更多
基金Funded by the National Natural Science Foundation of China(Nos.51202175 and 11072228)the National 111 Project(No.B13035)
文摘A direct electroless copper （Cu） coating on tungsten powders method requiring no surface treatment or stabilizing agent and using glyoxylic acid （C2H203） as a reducing agent was reported. The effects of copper sulfate concentration and the pH of the plating solution on the properties of the prepared W@Cu composite powders were assessed. The content of Cu in the composite powders was controlled by adjusting the concentration of copper sulfate in the electroless plating solution. A uniform, dense, and consistent Cu coating was obtained under the established optimum conditions （flow rate of C2H203 = 5.01 mL/min, solution pH = 12.25 and reaction temperature 45.35℃） by using central composite design method. In addition, the crystalline Cu coating was evenly dispersed within the W@Cu composite powders and Cu element in the coating existed as Cu~. The formation mechanism for the W@Cu composite powders by electroless plating in the absence of surface treatment and stabilizing agent was also proposed.
基金Supported by the National Natural Science Foundation of China（No.51274239）, the Fundamental Research Funds for the Central Universities of Central South University, China（No.2013zztsl91） and the Open-end Fund for the Valuable and Precision Instruments of Central South University, China（No.CSUZC2013028）.
文摘We reported a dripping solvothermal method for synthesizing metal-organic framework-5（MOF-5）. It started from separately dissolving Zn（NO3）2 and terephthalic acid（H2BDC） in dimethyl formamide（DMF）, and then dripping one solution into the other. Results of SEM, XRD and laser particle size distribution show that regular cubic-shaped and micro-crystallite powder of MOF-5 can be obtained. The d0.5（volume-median-diameter） values are 4.32 μm for particles prepared by dripping Zn（NO3）2 into H2BDC（ZH） and 9.32 μm for those prepared by dripping H2BDC into Zn（NO3）2（HZ）, much smaller than 22,7 μm that of particles prepared by the traditional adding water solvothermal method（L）. The standard deviations of the particle size distributions fitted by the GaussAmp model are 2.49, 4.38 and 15.4 respectively for ZH, HZ and L, further revealing narrower size distributions of particles prepared by the dripping method. In addition, the Langmuir specific surface areas are 923 m^2/g for ZH and 868 m^2/g for HZ. The TGA results present mass losses of 4.18% and 3.62% at 105 ℃, 17.19% and 14.78% at 245 ℃, 39.04% and 34.85% at 600℃ separately for ZH and HZ, which correspond to the removal of H20, DMF and the decomposition of MOF-5. This indicates that MOF-5 has a strong adsorption ability for small molecules. Besides, the mass loss of 48.39%（ZH） and 41.02%（HZ）between 400 ℃ and 600 ℃ are less than the theoretical value of 57.81% for MOF-5 decomposition to ZnO, suggesting that an impure phase with an extra amount of ZnO may exist in the cavities of MOF-5.
