Haowei Wang

A new coral structure TiO2/Ti film electrode applied to photoelectrocatalytic degradation of Reactive Brilliant Red

A novel structure TiO2/Ti film was prepared on a titanium matrix using anodic oxidation technique and applied to degrade Reactive Brilliant Red (RBR) dye in simulative textile effluents. The film was characterized by Field-Emission Scanning Electron Microscope (FE-SEM), Laser Micro-Raman Spectrometer (LMRS), UV-vis spectrophotometer (UVS) and Photoelectrocatalytic (PEC) experiment. The results show that the surface morphology of the film is coral structure, and the crystal structure of the film is anatase. The absorbency of the coral structure TiO2/Ti film is 87-93% in the UV light region, and 77-87% in the visible light region. PEC experiment indicates that the photocurrent density of the coral structure TiO2/Ti film electrode achieves 160 microA/cm(2). The color and Chemical Oxygen Demand (COD) removal efficiencies of RBR achieve 73% and 60% in 1h, respectively. These are 16% and 58% higher than those of nanotube TiO2/Ti film electrode. These were attributed to that these electrodes with different surface morphologies exhibit distinct surface areas and light absorption rate.

Compressive behavior of high particle content B4C/Al composite at elevated temperature

Abstract The compressive properties of the aluminum matrix composite reinforced with 55% B 4 C (volume fraction) particles were characterized using Gleeble 3500 thermal-mechanical testing machine. The compressive stress—strain curves were obtained at the temperature ranging from 298 to 773 K and strain rate ranging from 1×10 −3 to 5 s −1 . The results showed that the dynamic compressive strength decreased more slowly than the quasi-static compressive strength at elevated temperatures, which was attributed to the different failure modes of the composite under dynamic and quasi-static load. The strain rate sensitivity increased from 0.02 to 0.13 when the temperature increased from room temperature to 773 K, suggesting that the strain rate sensitivity of this type of composite is a function of temperature.

First-principles investigation of thermodynamic, elastic and electronic properties of Al3V and Al3Nb intermetallics under pressures

The thermodynamic, elastic, and electronic properties of D022-type Al3V and Al3Nb intermetallics were studied using the first-principle method. The results showed the pressure has profound effects on the structural, mechanical and electronic properties in both Al3V and Al3Nb. Thermodynamically, the formation enthalpies for Al3V and Al3Nb were derived, which agreed well with available experimental and theoretical values. Comparably, Al3Nb was a more stable phase with the more negative Hf than Al3V. Mechanically, the calculated elastic constants showed linearly increasing tendencies, and satisfied the Borns criteria from 0–20 GPa, indicating the mechanically stability of Al3V and Al3Nb under this pressure range. Further, the mechanical parameters (i.e., bulk modulus (B), shear modulus (G), and Youngs modulus (E)) were derived using the Voigt-Reuss-Hill (VRH) method, and in good agreement with available experimental results at the ground state. All these parameters presented the linearly increasing depende...

Effect of alloy elements on the morphology transformation of TiB2 particles in Al matrix.

To reveal the effect of alloy element on the morphology of in situ TiB2 particles, a series of TiB2 particles with various morphology were obtained via controlling synthesis process. Si and Cu can affect the morphology transformation of TiB2 particles significantly. Si preferentially adsorbed on (101¯1), (112¯0) and (12¯13¯) planes resulting in the polyhedron morphology of TiB2. Cu adsorbed on (101¯0) preferentially leading to the minimum aspect (the ratio of the diameter and thickness).

Study on the load partition behaviors of high particle content B4C/Al composites in compression

High particle content B4C/Al composites reinforced with different particle sizes were fabricated. Based on the tensile and compressive stress–strain behaviors of these composites, the effective medium approach was employed to investigate the load partition behaviors between the matrix and reinforcement. The results showed that the load borne by the particles increased in compression, which lead to larger compressive strength than the tensile strength. Meanwhile, the load borne by particles increased with decreasing particle size during compression. These observations were rationalized based on the combined theories of geometrically necessary dislocations and metal-based cemented granular material behaviors.

Improvement of Grain Refinement Efficiency in Pure Aluminum by Embryos Proliferation

The present research was undertaken to investigate the improvement of embryos proliferation process on refining efficiency of Al–5Ti–1B master alloy on the commercial purity aluminum. In order to achieve the proliferation of embryos, a special casting launder was designed and used. The polarized light microstructure showed that the fine equiaxed and better homogeneous grains were obtained through embryos proliferation. With the same addition level of 0.2% Al–5Ti–1B master alloy, the average grain sizes were 149 µm for direct casting and 102 µm for special casting launder, respectively. The analyses showed that the free nucleation energy barrier was smaller and the nucleation rate was greater when casting through embryos proliferation processing than direct casting. The experimental results indicated that the refinement efficiency of commercial purity aluminum could be improved significantly through embryos proliferation processing.

Investigation on fracture toughness of aluminum matrix composites reinforced with in situ titanium diboride particles

Compared to the massive damage caused by SiC/Al2O3 particles to fracture toughness of conventional metal matrix composites in previous reports, an effective improvement in fracture toughness of Al matrix composites with 3, 5.6, and 7.8 vol.% in situ nano/submicron TiB2 has been obtained by improving the particle size and distribution. It is found that the fracture toughness of TiB2/Al composites are only slightly lower than that of the unreinforced alloy, having a mere reduction of 3% to 8%. This is because the in situ TiB2 particles can weaken the damage caused by reinforcing phases to fracture toughness due to their fine sizes, near-spherical shapes, and relatively uniform distributions. Fractography shows the dominant fracture mechanisms of TiB2/Al composites are matrix rupture, eutectic silicon particles fracture as well as TiB2 particles separation.

Stability of nanopore formation in aluminum anodization in oxalic acid

Abstract The effect of applied voltage on nanopore formation stability of porous anodized alumina (PAA) in oxalic acid electrolyte was investigated. The Al anodization at a constant applied voltage is a popular electrochemical method to synthesize PAA templates. The experimental observations of Al anodization are used to compare the predictions of the THAMIDA model for interpore distance and the stability criterion of the SINGH model. It is found that, in the electrolyte of pH = 0.96, the interpore distance—applied voltage has a linear dependence coefficient of 2.24 nm/V, which agrees well with the THAMIDA model. It has also been confirmed that pore formation is instable at above 60 V which can be predicted by SINGH model. A second unstable growth regime below 30 V is also observed, which is not predicted by any of the models.

Simultaneously increasing strength and ductility of nanoparticles reinforced Al composites via accumulative orthogonal extrusion process

ABSTRACT Ceramic particles have been introduced into metal matrices to improve the strength and stiffness of metals, albeit at the cost of the ductility unfortunately. Simultaneously increasing the strength and ductility of metal matrix composites (MMCs) is still a challenge. Accumulative orthogonal extrusion process (AOEP), which disperses nanoparticles and refines grain structures of particles reinforced MMCs via severe plastic deformation, is proposed in this paper. The high strength (687 MPa) and superior ductility (14.8%) are simultaneously achieved in the resultant TiB2 particles reinforced Al–Zn–Mg–Cu matrix composites, and the underlying mechanisms are discussed in terms of particles’ influences. GRAPHICAL ABSTRACT IMPACT STATEMENT An easily realized SPD technology is proposed to effectively optimize the structures of nanoparticles reinforced composites in industrial scale. High strength and good ductility are simultaneously achieved in the resultant composites.

Improvement of yttrium on the hot tearing susceptibility of 6TiB2/Al-5Cu composite

Abstract To improve the severe hot tearing susceptibility of TiB 2 reinforced Al-5Cu matrix composites, the present research investigated the influence of Y on the hot tearing susceptibility of 6TiB 2 /Al-5Cu composite. For the composite added with Y, the solidification temperature range was shortened, which was caused by the novel τ 1 -Al 8 Cu 4 Y phase. The grain size of 6TiB 2 /Al-5Cu composite was 39.8 µm. The addition of Y promoted the grain refinement, and the grain sizes were 36.33, 33.42 and 26.77 µm for 6TiB 2 /Al-5Cu with 0.2 wt.%, 0.5 wt.% and 1 wt.% Y, respectively. The decrease of solidification temperature range and grain size was beneficial to the hot tearing susceptibility improvement. Furthermore, the hot tearing initiation force increased from 44 to 288 N, when 1 wt.% Y was added in 6TiB 2 /Al-5Cu. For the above significant influence, the hot tearing susceptibility values were reduced by 12.2 wt.%, 57.7 wt.% and 66.8 wt.% for 6TiB 2 /Al-5Cu with 0.2 wt.%, 0.5 wt.% and 1 wt.% Y, accordingly.