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In the present work, tungsten powders coated with copper by electroless plating method, and preparation of WCu20 composites by microwave sintering with copper-coated tungsten powder as raw material. The result shows that at the situation of a temperature of 60 °C, pH value of 12–13, with formaldehyde solution (53 ml/L) as reducing agent, iron potassium cyanide solution (0.3 g/L) as stabilizer, tartaric acid potassium sodium (15 g/L) and EDTA-2Na (19 g/L) mixture solution as compound complexing agent, the thickness of surface coating was relatively uniform, which is around 0.6–1.1 μm. The WCu20 composites were fabricated by microwave sintering with copper-coated tungsten powder as raw material shows uniform microstructure distribution, relatively high density. The hardness of the WCu20 composites increased with the temperature. While the temperature of sintering at 1100 °C for 1 h, the density could be up to 15.22 g/cm3, relative density was 97.13%, which shows better properties.

In this work, a chlorination roasting method for the extraction of precious metals (gold and silver) from the cyanide tailings (CT) was investigated. The decomposition mechanism of the CaCl2 used as chloride agent was presented during the chlorination roasting. The Au and Ag recovery as high as 91.6% and 54.7% under the optimum experiment conditions would be achieved. The optimal process conditions were identified to be a CaCl2 content 4%, chlorination temperature 1323 K and chlorination duration of 2 h. The microstructures of CT before and after roasting were examined by using scanning electron microscopy (SEM), and the volatilization process of the chloride of Au and Ag was assessed. The chlorination behaviors of all the phases in the CT in air atmosphere was analyzed using the thermogravimetric analysis (TGA), and the phase transformation of the main phase during roasting were analyzed by using X-ray diffraction (XRD). The chlorination roasting process shows unique advantage for treating the secondary sources of CT, additionally being environmentally benign.

High-purity yttrium oxide (Y2O3) powder is successfully prepared by microwave-assisted calcination of yttrium oxalate. The decomposition process of yttrium oxalate was analyzed by TG-DSC indicate formation of Y2O3 undergoes three stages. The X-ray diffraction (XRD) analysis indicates that there is no peak of yttrium oxalate hydrate (Y2(C2O4)3‧10H2O) after microwave-assisted calcination at 600 °C for 2 h, with the formation of cubic crystalline Y2O3 structure. Fourier transformed infrared spectroscopy (FT-IR) analysis show similar results with emergence of Y2O3 after calcination at 600 °C for 2 h. The precursor had a median particle size diameter 30.719 μm, while that of all the calcined powders at different temperatures significantly decreased to about 4 μm. Scanning electron microscopy (SEM) observations demonstrate the morphologies of the precursor and product, and the calcined Y2O3 preserved the amorphous character of the precursor, with rod-like shape. All the TG-DSC, XRD, FT-IR and SEM were utilized to understand the molecular changes in the process of microwave-assisted calcination of Y2(C2O4)3 to Y2O3.

Microwave heating has been widely used because of its advantages of higher heating rate, energy efficiency and clean utilization. This paper describes the study carried out on the characteristics of microwave melting of metallic copper powders, and a quantitative description of the heating curve of the copper powders in microwave field is given. The changes in microscopic structure and densification during the process of heating to melting of copper powder with microwave is assessed. The result demonstrated that copper powders could be quickly heated to melting. Heating rate for powdered copper of particle size 25 μm is 25.6 °C/min. Microwave heating efficiency and the heating rate were found to be higher with the decrease in the particle size and increase in microwave power. And also the heating rate had a linear relationship with the reciprocal of the particle size. Microstructure and density indicates that the densification process accelerates when the temperature is above 900 °C, and all the copper particles are heated to melting and shrinkage. At lower temperature the migration of the matter for copper particles is mainly internal diffusion. While the temperature above 1083 °C, among copper particles will be form metallurgical bonding, and the melting process complete quickly.

The present work attempts to investigate the influence of microwave heating on thermal decomposition and dissociation behavior of manganese ore. The manganese ore could be rapidly heated volumetrically to 1000 °C in 17 min by microwave heating, with an increase in manganese content of the ore from 30% to 40%. XRD patterns and thermodynamic analysis shows that the process of microwave heating could be divided into three parts, namely the decomposition reaction of MnCO 3 , Mn 2 O 3 and CaCO 3 , respectively. Mn 3 O 4 were obtained at microwave calcination temperatures higher than 577 °C. Based on the results, microwave heating can be applied effectively and efficiently for pretreatment of manganese ore.

The nanocomposite of Cu-CuO is successfully prepared via controlled oxidation of Cu nanoparticles synthesized by liquid-phase reduction in a microreactor. The particle's morphology, size, and elemental compositions have been investigated. Experimental results demonstrate that copper nanoparticles are spherical in shape, with good dispersion and narrow particle size distribution. The surface of Cu nanoparticles was oxidized to CuO, and the size of Cu-CuO composites crystallites was around 10 nm, consistent with the size of copper nanoparticles. The prepared Cu-CuO nanocomposite along with the presence of H 2 O 2 exhibits excellent photocatalytic activity for degradation of methylene blue (MB) under UV irradiation. An overall degradation of 98.5% could be achieved with 10 mg of Cu-CuO nanocomposite along with 1 mL of H 2 O 2 , within duration of 50 min irradiation. The MB degradation kinetics was observed to follow first order.

The tungsten–copper alloys were prepared and characterized utilizing pressureless microwave sintering and hot pressure microwave sintering. The performance of tungsten–copper alloy was assessed based on the relative density and hardness. The influence of different pressure and copper content on the microstructure of tungsten copper alloy has been investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Experimental results indicate tungsten–copper alloy with excellent performance under microwave hot press sintering. The relative density of the alloy was estimated to be 98.14% at a sintering temperature of 1100 °C, applied pressure of 30 MPa for duration of 1 h. The relative density was found to increase with increase in the applied pressure. The microstructure of tungsten–copper alloy sintered by microwave hot press method was more uniform having a compact matrix.

The CuW80 alloy was prepared by the method of microwave vacuum sintering. The effects of temperatures on the performance of CuW80 alloy was assessed based on the relative density and hardness. The micro structure of alloy was characterized using scanning electron microscopy, while XRD was utilized to identify the structure changes. Experimental results indicate CuW80 alloy with excellent performance under vacuum conditions prepared by microwave sintering. Density was found to increase with increase in sintering temperature linearly until 1200 C, while the rate of increase was found to reduce at higher temperatures, reaching an asymptote. The maximum relative density of the alloy was estimated to be 97.95% at 1300 C. At a sintering temperature of 1200 C, CuW80 alloy was more uniform with the main phase of alloy being Cu0.4W0.6 (PDF: 50-1451) and maximum hardness being 222 HBS.

The work addresses phase transformation of titania slag using microwave irradiation. Properties of samples before and after microwave irradiation including thermal stability, crystal structures, microstructure, surface chemical functional groups and molecular structures, have been investigated by TG/DTA, XRD, SEM, FT-IR and Raman, respectively. The results of TG/DTA showed that titania slag have two phase transformation, one at 578.0 °C and another at 850.0 °C. It was confirmed that at roasting temperature in excess of 600 °C, anatase starts to transform as rutile. The property changes can be attributed to microwave irradiation, which causes the crystal transformation.

In this present study, the reducing products of carbonthermal reduction of ilmenite ores were evaluated. The crystal structures, microstructure and surface chemical functional groups of the ilmenite ores and the reducing product of carbonthermal reduction were also analyzed using XRD, SEM, Raman and FT-IR, respectively. Sulphate titanium slag and high titanium slag were the major reducing products of carbonthermal reduction of ilmenite ores. It was found that the low-valent titanium of high titanium slag was increased after carbonthermal reduction of ilmenite ores with higher temperature and longer processing time. Based on the results, this method could be applied effectively and efficiently way for both utilization of ilmenite ores and preparation of sulphate titanium slag and high titanium slag.

In this present study, the effects of mechanical activation on the characterization of titania slag were systematically investigated. The crystal structures, surface chemical functional groups, and microstructure of the samples were characterized before and after mechanical activation using XRD, FT-IR, and Raman spectroscopy techniques, respectively. It was found that untreated titania slag under mechanical activation was mainly composed of Fe3Ti3O10 and rutile TiO2, but that of being treated by mechanical activation was mainly composed of Fe3Ti3O10, Ti2O3 and rutile TiO2. Ti2O3 is transformed partially from Fe3Ti3O10 under moderate mechanical activation conditions for 12 h. The demonstration of mechanical activation techniques can be applied effectively and efficiently to the treatment processing of titania slag.

A new highly efficient method has been developed for the synthesis of the synthesis of rutile TiO2 from titania slag. High quality of rutile TiO2 were obtained by carrying out the synthesis in conventional heating method. The thermal stability, crystal structures and molecular structures of rutile TiO2 and titania slag before and after treatment were characterized using TG/DTA, XRD and Raman, respectively. The results of TG/DTG showed roasting temperature range of 850–1000 °C was used in the further research work in order to transform from anatase TiO2 to rutile TiO2. The XRD results demonstrate that a rutile TiO2 with high crystallinity was prepared. With increasing roasting temperature, the intensity of Raman vibrations bands of anatase TiO2 decrease, and the intensity of Raman vibrations bands of rutile TiO2 increase. Based on the mention results, this method can be applied effectively and efficiently way for both titania slag utilization and rutile TiO2 preparation.