Kai Jin Huang

Preparation and Exothermic Characterization of Hydroxyl-Terminated Polybutadiene(HTPB)-Coated Aluminum Nanopowders

The HTPB-coated aluminum nanopowders were prepared by using horizontally-mounted kneading machine. The HTPB-coated aluminum nanopowders were characterized by TEM, XRD and FTIR. The exothermic characterization of the HTPB-coated aluminum nanopowders was analysized by simultaneous TG-DSC. The results show that the HTPB-coated aluminum nanopowders have a core-shell structure and the release heat enthalpy in pure oxygen is 4.954KJ/g at 542.7°C. The stability of HTPB-coated aluminum nanopowders excelled Al2O3-passivated aluminum nanopowders due to the hydrophobic nature of HTPB and the hydrophilic nature of Al2O3.

Effect of Surfactants on the Morphologies of ZnO Nanostructures Synthesized by Hydrothermal Method and its Gas Sensitivity to Formaldehyde

Based on the principle of the higher surface-to-volume ratios, the higher formaldehyde gas sensitivity, different morphologies’s ZnO nanostructures have been synthesized by hydrother- mal method using different surfactants including polyvinyl alcohol (PVA), cetyltrimethyl ammon- ium bromide (CTAB), sodium tripolyp hosphate (STPP) and citric acid(CA). The crystal structur- es and morphologies were characterized by XRD and FESEM. The results show that different morphologies’s ZnO nanostructures were induced on the surface of alumina substrate, and the surfactants had an important effect on the morphologies of ZnO nanostructures and then affected the formaldehyde gas sensitivity. The ZnO nanorods with diameters of 100-500 nm and lengths of 200-900nm were obtained using PVA surfactant. The ZnO nanosheets with thickness of about 10nm were obtained using CTAB surfactant. The ZnO nanodisks with two layers and thickness of 5-10nm were obtained using STPP surfactant. The ZnO microspheres composed of thin flakes with thickness of about 10 nm were obtained using CA surfactant. The growth mechanisms of different morphologies’s ZnO nanostructures using different surfactants were given in detail. In addition, the formaldehyde gas sensitivities of different morphologies’s ZnO nanostructures were measured and showed the higher formaldehyde gas sensitivity compared with nano-ZnO without surfactant.

Synthesis, Characterization and Visible Light Photocatalytic Properties of BiOCl0.2Br0.1I0.7

The ternary solid solution BiOCl0.2Br0.1I0.7 was successfully synthesized using a wet chemical method. The visible light photocatalytic properties of BiOCl0.2Br0.1I0.7 were investigated for the first time. Powder samples were characterized by XRD, SEM, UV-vis spectrophotometry and nitrogen sorption. BiOCl0.2Br0.1I0.7 absorbs intensely in the visible light region and the optical bandgap is 1.82eV. The chlorine and the bromine elements have an obvious effect in changing the bandgap energy and the particle size of the catalysts. The deep valance band edge position, the internal electric fields and the morphology give the BiOCl0.2Br0.1I0.7 best visible light photocatalytic properties.

Preparation, Characterization and Visible-Light Photocatalytic Properties of BiOCl/BiOI Nanocomposites

BiOCl/BiOI nanocomposites were synthesized using a thermal impregnation method for the first time. The intense visible-light absorption and large specific surface area gave 4wt.％BiOCl/BiOI nanocomposites the best visible-light photocatalytic properties among all the catalysts for the photodegradation of methyl orange,about 78％ after 2 h. But decreased activities were obtained with the increase of BiOCl content in the nanocomposites. Considering the light absorption,specific surface area and the quantum efficiency, the high recombination of the photoinduced electron-hole pairs of the catalysts that lowed the quantum efficiency was believed to be the critical factor for their decreased photocatalytic activities.

Laser Cladding of Zr55Al10Ni5Cu30/SiC Amorphous Composite Coatings on AZ91D Magnesium Alloy for Improvement of Corrosion Resistance

To improve the corrosion property of magnesium alloys, Mg-based amorphous composite coatings have been fabricated on AZ91D magnesium alloy by laser cladding using mixed powders Mg65Cu25Y10/SiC. The microstructure of the coating was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The corrosion resistance of the coatings was tested in 3.5wt.% NaCl solution. The results show that the coatings mainly consist of amorphous and different crystalline phases. The coatings compared to AZ91D magnesium alloy exhibit good corrosion resistance because of the presence of the amorphous phase in the coatings.

Microstructure and Wear Resistance of AlFeCuCoNiCrTi1.5 High Entropy Alloy Coating on AZ91D Magnesium Alloys by Laser Cladding

To improve the wear properties of AZ91D magnesium alloys, a AlFeCuCoNiCrTi1.5 high entropy alloy (HEA) coating was fabricated on AZ91D magnesium alloys by laser cladding using mixed powders of Al, Fe, Cu, Co, Ni, Cr, and Ti. The microstructure of the HEA coating was characterized by OM, SEM, and XRD. The wear resistance of the HEA coating was evaluated under dry sliding wear test condition at room temperature. The results show that the HEA coating mainly consists of a simple BCC solid solution phase. The HEA coating exhibits excellent wear resistance. The main wear mechanisms of the HEA coating and the AZ91D substrate were different, the former dominated by oxidative abrasive wear and the latter suffered from both adhesive and abrasive wear.

Laser Cladding of TiN-Based Coating on 00Cr13Ni4Mo Hydro Turbine Blade Stainless Steel for Improvement of Wear Resistance

To improve the wear propery of 00Cr13Ni4Mo hydro turbine blade stainless steel, TiN-based coating was fabricated on 00Cr13Ni4Mo stainless steel by laser cladding using mixed powders of Ni60 and TiN. The microstructure of the coating was characterized by XRD and SEM techniques. The wear behaviour of the coating was also investigated. The wear resistance of the coating was evaluated under dry sliding wear condition at room temperature. The results show that the coating mainly consists of Ni-based solid solution and TiN phases. The coating exhibits excellent wear resistance due to its high hardness of TiN phase. The main wear mechanisms of the coating and the 00Cr13Ni4Mo sample are different, the former is abrasive wear and the latter is adhesive wear.

Visible Light Photocatalytic Degradation of Reactive Deep Blue K-R by BiOI and BiOCl0.2Br0.1I0.7

The visible-light photocatalytic degradation of an azo dye Reactive Deep Blue K-R by BiOI and BiOCl0.2Br0.1I0.7 photocatalysts was investigated. When the reaction proceeded for 1 h under the conditions of 15mg/l Reactive Deep Blue K-R solution and PH=3, the visible-light degradation degrees of Reactive Deep Blue K-R were 93% and 52% for BiOCl0.2Br0.1I0.7 and BiOI, respectively.Moreover, the photodegradation of Reactive Deep Blue K-R by BiOI and BiOCl0.2Br0.1I0.7 followed a first-order reaction kinetic and the values of k for BiOI and BiOCl0.2Br0.1I0.7 are 0.911h-1 and 1.981h-1, respectively. BiOCl0.2Br0.1I0.7 exhibits better visible-light-responsive photocatalytic performance for photodegradation of Reactive Deep Blue K-R than BiOI due to the smaller particle size, the larger specific surface area and the stronger redox potential of BiOCl0.2Br0.1I0.7.

High Ethanol Gas Sensitivity of Nano γ-Fe2O3/ZnO Double-Layer Films Prepared by the Screen Printing Technology and the Hydrothermal Method

The gas sensor with high ethanol gas sensitivity made of nano γ-Fe2O3/ZnO double-layer films was fabricated by the screen printing technology and the hydrothermal process with addition of citric acid (CA) surfactant based on Zn(NO3)2·6H2O and HMTA. XRD and SEM techniques were used to characterize the phases and morphologies of the films. The gas sensing properties of the gas sensor to ethanol were investigated. The result shows that the gas sensitivity of the nano γ-Fe2O3/ZnO double-layer films is higher than that of the nano γ-Fe2O3 single-layer film fabricated by the screen printing technology and the nano ZnO single-layer film fabricated by the hydrothermal process with addition of citric acid (CA) surfactant based on Zn(NO3)2·6H2O and HMTA, respectively. The high ethanol gas sensitivity of the nano γ-Fe2O3/ZnO double-layer films was caused by the nano effect and the special energy band structure

Laser Cladding of Ni60/WC/TiN Composite Coatings on 00Cr13Ni4Mo Hydro Turbine Blade Stainless Steel for Improvement of Wear Resistance

To improve the wear property of 00Cr13Ni4Mo hydro turbine blade stainless steel, Ni-based composite coatings were fabricated on 00Cr13Ni4Mo stainless steel by laser cladding using mixed powders of Ni60, WC and TiN. The microstructure of the coatings was characterized by XRD and SEM techniques. The wear resistance of the coatings was evaluated under dry sliding wear condition at room temperature. The results show that the coatings mainly consist of Ni-based solid solution, WC and TiN phases. The coatings exhibit excellent wear resistance due to its high hardness of WC and TiN phases. The main wear mechanisms of the coatings and the 00Cr13Ni4Mo sample are different, the former is abrasive wear and the latter is adhesive wear.