Advanced Materials Research Vols. 562-564

Abstract: Medium-sized tungsten particles are obtained through circulatory oxidation-reduction twice. The samples are characterized by laser particle size analyzer and scanning electron microscope (SEM). Blue tungsten oxide (BTO) is prepared with ammonium paratungstate (APT) in the argon gas. Tungsten powders are obtained with BTO through deoxidation in the hydrogen gas (Rate of purity: 99.99%, dew point: -40°C), and tungsten powders are oxidized in the air. Tungsten oxide WO3) is reduced into tungsten powders in hydrogen gas again. The routes are repeated. The volume percent content of medium-sized tungsten powders between 3 μm and 10 μm is 83.86 %.

Abstract: The δ-phase growth process of Fe-0.2%C-0.6%Mn steel during solidification was in-situ observed using Confocal Scanning Laser Microscope (CSLM). The effects of shape of solid/liquid interface on the growth rate were investigated. The results indicate the growth rate of concave-shaped solid/liquid interface is faster than that of convex-shaped solid/liquid interface at the beginning of δ-phase growth. The two kinds of growth rates decreased both and approached to the same gradually as the solidification continues. The intrinsic reasons were discussed in detail.

Abstract: Fourier transform infrared spectroscopy (FTIR) and attenuated total reflection (ATR) technology were successfully applied for the rapid no-reagent determination of chemical oxygen demand (COD) in sugar refinery wastewater. An appropriate waveband with stability was selected by the moving window partial least-squares (MWPLS) regression through a rigorous modeling process. The selected waveband was 3198 cm-1 to 2376 cm-1, the corresponding PLS factor was 5. The modeling effect M-SEPAve, M-RP,Ave, M-SEPStd, and M-RP,Std were 31.5 mg/L, 0.962, 3.9 mg/L, and 0.012, respectively. The validation effect V-SEP and V-RP were 31.9 mg/L and 0.965, respectively. It indicated that the method has good prediction effect and stability, and provided valuable references for designing specialized spectroscopic instruments.

Abstract: 7A60 aluminum alloy was treated under different retrogression time, and the micro-structure, mechanical properties and stress corrosion behaviors were observed and determined by optical microscopy, transmission electron microscopy and slow strain rate tester. The results shown that with the increasing of retrogression time the precipitates within the grains were gradually grown up, and the precipitates along the grain boundaries were changed from small and closely spaced into coarse and widely spaced ones. The elongation and toughness ratio of 7A60 alloy increased obviously with the retrogression time, whereas the tensile strength and hardness of 7A60 alloy decreased. The optimum retrogression time is about 60min, under which 7A60 alloy has a best combination of tensile strength, ductility and stress corrosion resistance.

Abstract: To overcome low formability and springback problems in forming aluminium panel parts, a novel process of hot stamping is introduced in this paper. It is good plasticity and low deformation resistance when aluminum alloys under high temperature, which makes it possible to form complex parts such as B pillars. Finite element method is used to analysis the thinning regions in this part, it can be acquired that the quality of the part in hot stamping is better than in cold stamping.

Abstract: In this paper, two types of Zn-Al-Ti-B-C master alloys were produced by a two-step method and were found to have good refinement effect for Zn-50Al alloy. SEM results show that TiC and TiB2 particles act as the nucleating center of α-Al grains in Zn-50Al alloy. The presence of TiAl3-xZnx phase in the matrix of Zn-Al-Ti-B-C master alloy was found to further enhance the refinement effect. The melt thermal-rate treatment process present good grain refinement effect for Zn-50Al alloy and it was further promoted by the addition of Zn-Al-Ti-B-C master alloy into Zn-Al matrix.

Abstract: The effects of heat treatment on the microstructure, tensile property and fracture behavior of as-extruded AZ91 magnesium alloy were studied by OM and SEM. The results show that the grain of as-cast AZ91 alloy is refined by extruding and dynamic recrystallization, and the mechanical properties increase obviously. The ductility is significantly enhanced after solution treatment of the as-extruded AZ91 alloy, tensile strength is almost the same before and hardness is significantly reduced after solution treatment and artificial aging treatment. The tensile strength reduced and the ductility is significantly enhanced of as-extruded AZ91 magnesium alloy after annealing processes. The fracture surface of as-extruded AZ91 magnesium alloy has the mixture of ductile and brittle characteristic. But after T6 or annealing treatment, its dimple number increases evidently.

Abstract: Ni-TiN; Composite coating; Ultrasonic-magnetic-electrodeposition Abstract: In this paper, Ni-TiN composite coatings were prepared by ultrasonic-magnetic- electrodeposition. The optimum parameters were achieved by experiments and analysis. The structure of Ni-TiN coatings was observed using HRTEM. And the wear resistance was tested by the grinding machine. The results illuminated that the optimum technical parameters prepared Ni-TiN coatings are TiN particle concentration 4g/L, ultrasonic power 200W, magnetic intensity 0.6T, current density 5A/dm2, temperature of the electrolyte 50°C, pH 4.5. The HRTEM showed that the diameter of Ni grains and TiN particle in Ni-TiN coatings were about 60nm and less than 40nm, respectively.

Abstract: ZnO nanorods and nanoparticles were successfully modified by NDZ-311w titanate coupling agent. The result of lipophilic degree showed that both ZnO nanocrystals with different morphologies were well lipophilic. Although both values of lipophilic degree firstly became larger and then smaller with the increase of modifier dosage, the different maximal lipophilic degree of ZnO nanorods and nanoparticles could be 68.8% and 77.9%, respectively. By comparing the two curves of lipophilic degree of surface modified ZnO nanocrystals with different morphologies, it could be demonstrated that the optimal dosage of NDZ-311w titanate coupling agent is inversely proportional to the grain size. TEM and XRD results showed that the grain size of ZnO nanoparticles were much smaller than that of ZnO nanorods, which can be the evidence for the equation. Otherwise, the surface modified ZnO nanoparticles displayed better dispersion than unmodified ones.

Abstract: Iron-doped titania (TiO2) nanocrystalline were prepared by sol-gel method at room temperature. The samples were characterized by using transmission electron microscope, X-ray diffractometer and ultaviolet-visible spectrophotometer. X-ray diffraction shows that iron-doped titania have the titania anatase and brookite structure, and the more iron doped in, the less titania brookite structure. When the doping content of 10at% iron, the titania brookite structure disappear absolutely. Transmission electron microscopy shows that with the increase of iron-doping from 0.00 to 0.25, the average size of the grains decrease from 5.7nm to 4.3nm. And samples have higher crystallinity. Using UV-visible spectrophotometer to measure its photocatalytic properties the results show that it has the highest rate of 60% photocatalytic degradation when it is absorbed in methylorange in two hours. With the increase of iron-doping from 0.00 to 0.25, the more iron doped in, the higher photocatalytic properties.