Activator-assisted electroless deposition of copper nanostructured films

This paper showed simple and effective synthesis of copper nanoparticles within controlled diameter using direct electroless deposition on glass substrates, following the sensitization and activation steps. Electroless-deposited metals, such as Cu, Co, Ni, and Ag, and their alloys had many advantages in micro- and nanotechnologies. The structural, morphological, and optical properties of copper deposits were characterized using X-ray diffraction (XRD), atomic force microscopy (AFM), and UV-Vis spectroscopy. The structural data was further analyzed using the Rietveld refinement program. Structural studies reveal that the deposited copper prefers a (111) orientation. AFM studies suggest the deposited materials form compact, uniform, and nanocrystalline phases with a high tendency to self-organize. The data show that the particle size can be controlled by controlling the activator concentration. The absorption spectra of the as-deposited copper nanoparticles reveal that the plasmonic peak broadens and exhibits a blue shift with decreasing particle size.     

Improved photocatalytic activity of nano CuO-incorporated TiO2 granules prepared by spray drying

4 wt% CuO–96 wt% TiO2 granules were prepared by a spray drying process. The microstructure and optical property of CuO–TiO2 granules were studied. The results indicate that copper existed in the form of CuO. The spray dried granules possess spherical geometry and smooth surface with grain size in the range of 40–80 μm. CuO–TiO2 has a relatively smaller E g value(2.85 eV) than Ti O2(3.17 eV). The photocatalytic property of CuO–TiO2 granules was investigated by degradation of a model pollutant(the azo dye methyl orange) under the irradiation of the xenon lamp equipped with a band pass fi lter of 365 nm. The CuO–TiO2spray-dried granules degrade about 10% more MO than TiO2spray-dried granules under UV irradiation within the same time. The XPS spectra suggested that Cu2 tand reduced copper species were coexistent in reacted CuO–TiO2 photocatalyst. The improvement of photocatalytic activity for CuO–TiO2 was mainly attributed to effective separation of photogenerated electron–hole pairs in the presence of CuO.     

Synthesis of Mesoporous Silica Nanoparticles with Tunable Shape and Size

The structural and morphological properties of mesoporous silica nanoparticles( MSNs) have dramatical influence on their in vivo biological behaviors,and thereby synthesis of MSNs with well-defined shape and size has recently attracted much more attention in the biomedical field. The synthesis of MSNs with controllable size and shape was presented by controlling the reaction temperature and the concentration of templating agent(cetyltrimethylammonium bromide,CTAB). The results indicated that MSNs were larger in particle size and more round in shape with increasing of the reaction temperature,but their particle size and dispersivity became smaller and poorer as CTAB concentration increased. Therefore,the particle size and shape of MSNs can be tuned by using the optimal synthesis conditions for specific biomedical applications.     

Aerosol flotation of low-grade refractory molybdenum ores

The characteristics of aerosol flotation, which include the effect of the concentration and particle size of kerosene aerosol on the molybdenum (Mo) flotation index and the effect of kerosene aerosol dosing method on the kerosene dosage and flotation time, were studied in the flotation of low-grade refractory molybdenum ores using kerosene aerosol. The results revealed that the particle size and concentration of kerosene aerosol had little effect on the Mo grade but had significant effect on the Mo recovery. A smaller particle size and a lower concentration of kerosene aerosol were beneficial to the Mo aerosol flotation. For the received Mo ore samples, the optimized particle size of kerosene aerosol was 0.3-2 μm and the optimized aerosol concentration was 14 mg/L. The compressed air atomizer had a more uniform distribution of aerosol particles than the ultrasonic atomizer, and the aerosol concentration was controlled easily, so the compressed air atomizer was more suitable for the research of aerosol flotation. Compared with conventional flotation in which kerosene was directly added into the ore pulp, the flotation time was reduced by ~30%, and the dosage was decreased by ~20% in aerosol flotation, while the Mo flotation index was similar.     

Preparation of fine copper powders and their application in BME-MLCC

The preparation of fine copper powders by chemical reduction method was investigated. The reaction of [Cu(NH₃)₄]2+ complex with hydrazine hydrate gives spherical monodispersed fine copper powders. The spherical copper powder with a uniform size of 3.5 ± 0.5 μm was processed to obtain flake copper powder having a uniform size of 8-10 μm, excellent dispersibility and uniform shape. The spherical copper powder of 2.5 ± 0.3 μm in size, flake copper, glass frit and vehicle were mixed to prepare copper paste, which was fired in 910-920°C to obtain BME-MLCC (base metal multilayer ceramic capacitor) with a dense surface of end termination, high adhesion and qualified electrical behavior. Polarized light photo and SEM were employed to observe the copper end termination of BME-MLCC. The rough interface from the interfacial reaction between glass and chip gives high adhesion.     

Influence of pH,immersion time,and benzotriazole concentration on copper corrosion in citric acid based slurries

Copper corrosion in citric acid based slurries with or without benzotriazole (BTA) was investigated as a function of the slurry pH,immersion time and BTA concentration by static etching and electrochemical experiments.The chemical composition of the corroded surface was determined using X-ray photoelectron spectroscopy (XPS).The static etching rate of copper in a H2O2 +citric acid+BTA slurry was lower than that in a H2O2 +citric acid slurry at pH 4.4-8.When the pH of the slurry was >8 or <4.4,the results were reversed and the static etching rate of copper increased when BTA was added to the H2O2 +citric acid slurry.The inhibitory effect of BTA in the H2O2 +citric acid slurry at pH 6 increased with the increasing immersion time of the copper.The corrosion current density of copper gradually decreased with increasing BTA concentration in slurry.     

Extracting copper from copper oxide ore by a zwitterionic reagent and dissolution kinetics

Sulfamic acid (SA), which possesses a zwitterionic structure, was applied as a leaching reagent for the first time for extracting copper from copper oxide ore. The effects of reaction time, temperature, particle size, reagent concentration, and stirring speed on this leaching were studied. The dissolution kinetics of malachite was illustrated with a three-dimensional diffusion model. A novel leaching effect of SA on malachite was eventually demonstrated. The leaching rate increased with decreasing particle size and increasing concentration, reaction temperature and stirring speed. The activation energy for SA leaching malachite was 33.23 kJ/mol. Furthermore, the effectiveness of SA as a new reagent for extracting copper from copper oxide ore was confirmed by experiment. This approach may provide a solution suitable for subsequent electrowinning. In addition, results reported herein may provide basic data that enable the leaching of other carbonate minerals of copper, zinc, cobalt and so on in an SA system.     

Atomic force microscope study of WC-10Co cemented carbide sintered from nanocrystalline composite powders

In order to compare the spark plasma sintering (SPS) process plus hot isostatic press (HIP) with vacuum sintering plus HIP, an investigation was carried out on the topography, microstructure and gain size distribution of nanocrystalline WC-l0Co composite powder and the sintered specimens prepared by SPS plus HIP and by vacuum sintering plus HIP by means of atomic force microscopy (AFM). The mechanical properties of the sintered specimens were also investigated. It is very easy to find cobalt lakes in the specimen prepared by vacuum sintering plus HIP process. But the microstructure of the specimen prepared by SPS plus HIP is more homogeneous, and the grain size is smaller than that prepared by vacuum sintering plus HIP. The WC-10Co ultrafine cemented carbide consolidated by SPS plus HIP can reach a relative density of 99.4%, and the transverse rupture strength (TRS) is higher than 3540 MPa, the Rockwell A hardness (HRA) is higher than 92.8, the average grain size is smaller than 300 nm, and the WC-10Co ultrafine cemented carbide with excellent properties is achieved. The specimen prepared by SPS with HIP has better properties and microstructure than that prepared by vacuum sintering with HIP.     

Separation of hydrophobic gold nanoparticles less than 10 nm by electrophoresis

An electrophoresis device was used to separate hydrophobic gold nanoparticles with particle size less than 10 nm dispersed in organic solvent. Image of transmission electron microscope （TEM） and UV-Vis spectra showed that the particles in the vicinity of cathode have a smaller mean diameter than those near the anode. This result indicates that the nanogolds in chloroform bring a positive charge in opposition to what is predicted by Coehn rule, and provides an electrophrosis method for separating hydrophobic nanogold particles of different sizes.     

Characterization of γ-Fe2O3 nanoparticles prepared by transfor- mation of α-FeOOH

γ-Fe2O3 nanoparticles were successfully synthesized by a chemically induced transformation of α-FeOOH.In this method,the precursor(α-FeOOH)was prepared by chemical precipitation,and then treated with a mixed FeCl2/NaOH solution to produce the nanoparticles.X-ray diffraction indicated that when the precursor was treated with FeCl2(0.22 mol/L)and NaOH(0.19 mol/L),pure γ-Fe2O3 nanoparticles were obtained.However,when the concentration of FeCl2 was<0.22 mol/L or the concentration of NaOH was<0.19 mol/L,α-FeOOH and γ-Fe2O3 phases co-existed in the nanoparticles.Transmission electron microscopy observations showed that in the samples with co-existing phases,the nanoparticles did not have identical morphologies.The pure γ-Fe2O3 nanoparticles were polygonal rather than spherical.The volume ratio of α-FeOOH and γ-Fe2O3 was estimated for the two-phase samples from magnetization data obtained from a vibrating sample magnetometer.This chemically induced transformation is novel,and could provide an effective route for the synthesis of other metal oxide nanocrystallites.