Naiheng Ma

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.

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).

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.

Phase stability, elastic and electronic properties of Hf–Rh intermetallic compounds from first-principles calculations

The phase stability, elastic and electronic properties of binary Hf–Rh compounds have been studied using first-principles calculations based on density functional theory. The equilibrium lattice constants, formation enthalpies, elastic constants, and elastic moduli are presented. Among the binary Hf–Rh compounds, Hf3Rh5 is the most stable with the lowest formation enthalpy. For the equiatomic HfRh phase, it tends to crystallize in the ZrIr-type structure, followed by L10, and then B2 at the ground state based on the analysis of formation enthalpies. Therefore, the crystal structure of the lower temperature HfRh phase is suggested to be the ZrIr-type. This conclusion is in agreement with the experimental reports in the literature. Besides, Hf3Rh4 are proposed to be the Pu3Pd4-type for the first time. Furthermore, our calculated elastic constants for Hf2Rh, ZrIr-HfRh, L10-HfRh, B2-HfRh, Hf3Rh4, Hf3Rh5 and HfRh3 can all satisfy the Born criteria, indicating their mechanical stabilities. When ZrIr-HfRh is adopted, the bulk modulus (B) increases linearly with the growing Rh atomic concentration. Meanwhile, Youngs modulus linearly increases with growing shear modulus, and the compound with a higher Poissons ratio owns a higher B/G ratio simultaneously. Overall, the results also indicate that all the considered Hf–Rh compounds should be ductile. Finally, the electronic structure is analyzed to understand the essence of structural stability of the binary compound.

Assessment on the structural, elastic and electronic properties of Nb3Ir and Nb3Pt: A first-principles study

The pressure dependent behaviors on the structural, elastic and electronic properties of the A15 structure Nb3Ir and Nb3Pt were studied using first-principles calculations based on the density functional theory within generalized gradient approximation and local density approximation methods. Initially, the optimized lattice constants of Nb3Ir and Nb3Pt are consistent with the available experimental and theoretical results. Furthermore, Nb3Ir is found to be more thermodynamically stable than Nb3Pt due to its lower formation enthalpy and higher melting temperature. In addition, the elastic constants of Nb3Ir and Nb3Pt show an increasing tendency, and keep mechanically stable structures under pressures to 40 GPa. Besides, the increasing Cauchy pressures and B/G values have indicated that higher pressures can improve their ductility in both Nb3Ir and Nb3Pt. Finally, the pressure-dependent behaviors on the density of states, Mulliken charges and bond lengths are discussed for both compounds.

Hot tearing susceptibility of TiB2-reinforced Al–5Cu matrix composite:

This work investigated the hot tearing susceptibility of TiB2 reinforced Al–5Cu matrix composites. The results indicated that the hot tearing susceptibility of Al–5Cu alloy was significantly decreased when the TiB2 content was less than 3%. The improvement was attributed to the TiB2 particles promoted the grain refinement. The hot tearing susceptibility of TiB2-reinforced Al–5Cu matrix composite decreased first and then increased with the increase of TiB2 content. The 2TiB2/Al–5Cu composite had the smallest hot tearing susceptibility value. It could be ascribed to the refined grain and shortened solidification temperature range, which contributed to the hot tearing susceptibility decrease. Nevertheless, the 4TiB2/Al–5Cu and 6TiB2/Al–5Cu composites had more severe hot tearing susceptibility than others. The reason was that the enlarged solidification temperature range increased the solidification shrinkage strain, which was adverse to the hot tearing susceptibility improvement. Furthermore, the increase of TiB2 led to the formation of large particles agglomeration, which lowered the hot tearing initiation force and the feeding capacity of liquid metal.