Bai Chenguang

Preparation and Compressive Properties of Magnesium Foam

Abstract As a new structural and functional material, metal foam has been proven to obtain excellent properties when compared with dense ones. In the present paper, the powder metallurgy with a space holder technique was used to prepare magnesium foam. The porosity of the foam ranges from 38.90% to 57.50%, when the elastic modulus decreases from 8.50 GPa to 3.30 GPa, and the initial yield stress decreases from 24.90 MPa to 9.40 MPa. The magnesium foam has lower yield stress and longer stress platform, so it can be used as good cushioning energy absorbing materials.

Structures and Properties of TiMn2-5x(V4Fe)x(x=0.30, 0.35) Hydrogen Storage Alloys

Abstract Structures and electrochemical properties of TiMn2-5x(V4Fe)x(x=0.30,0.35) alloys were investigated. The results of XRD analysis show that the alloys are mainly composed of body centered cubic (bcc) phase, whose lattice parameters are enhanced with the increase of V and Fe content. The SEM images of the alloys show that there are some colonies in the matrix phase. The proportion of colony to the matrix decreases with increasing of V and Fe content. The electrochemical measurements show that TiMn0.25(V4Fe)0.35 alloy has unfavorable activation performance until temperature reaches 327 K, while TiMn0.50(V4Fe)0.30 alloy shows better activation performance, but passivation phenomenon was found in the process of charging at low temperature, which can be eliminated by heating to high temperature. The PCT curves of alloys show that the TiMn0.50(V4Fe)0..30 alloy has a good comprehensive performance, with a favorable plateau pressure at room temperature and wide plateau. The enthalpy and entropy in hydrogen desorption of TiMn0.50(V4Fe)0..30 alloy were also calculated and they are −36.1 kJ/mol, −126.9 J/(mol·K), respectively.

Effect of the Basicity on the Crystallization Behavior of Titanium Bearing Blast Furnace Slag

Abstract Basicity of titanium bearing blast furnace (BF) slag is critical for its crystallization behavior. Thermodynamics calculation indicates that rutile is the main phase after crystallization (or at room temperature). It precipitates during the cooling when the basicity of the slag is lower than 0.7. With increasing basicity, perovskite appears and becomes the main phase instead which contains titanium. Crystallization temperature of perovskite is higher than that of rutile and the other phases. Namely, perovskite crystallizes firstly from the molten slag during decreasing temperature. XRD analysis shows that CaTi21O38 is the main phase with a basicity of 0.6. CaMg0.39Al0.87Ti0.48Si1.26O6, CaTiSiO5 and CaMgSi2O6 are the main crystallization phases with a basicity of 0.8. The difference between experimental and thermodynamics calculation is due to the complicate crystallization behavior of the multiple slag under super cooling rate. When the slag basicity increases to 1.1, the main precipitatied phase is perovskite, which agrees well with theory calculation. In addition, the crystal structure of the synthesized titanium bearing slag is basically similar regardless of the basicity.

Preparation of Titanium Foams with Uniform and Fine Pore Characteristics Through Powder Metallurgy Route Using Urea Particles as Space Holder

Titanium powder particles were used as the matrix and powdery urea particles as the space holder to fabricate porous titanium by powder metallurgy technology. And titanium foams with porosity of 42.7–56.2% were prepared successfully. The uniform distribution of the tiny urea particles in the matrix made the titanium foams have homogeneous and connected pore structure. Pore morphology and compressive behavior of the resulting foam have been studied. The pore structure is composed of large pores and small pores distributed on the hole wall, and these small pores are mostly interconnected. Porous regions contained some micro-pores increasing the connectivity of pores. The mechanical behavior was investigated by compressive test, the foams delineated a relatively stable plateau region and the yield strength and Young’s modulus vary in the range of 93.85–276.52 Mpa and 1.53–3.21 GPa respectively. The results manifested that the processed foams is an ideal medical implant, impact energy absorbing and filterability material.

Surface Tension of Liquid Ti-Al Alloys

Abstract The surface tension of liquid Ti-Al alloys at 1758 K was determined by an improved sessile drop method. The surface tension of liquid Ti-Al alloys was calculated using the Butlers model and several modified ideal solution models. Results show that the surface tension of liquid Ti-Al alloy decreases with increased Al concentration. Experimental results agree well with both the Butlers model and the modified ideal solution model. The segregation of Al atoms to the surface occurs at all bulk concentrations of Ti-Al alloys. Al with lower surface tension prefers to segregate on the surface of liquid Ti-Al alloy, whereas Ti with higher surface tension prefers to segregate inside the molten alloy. The effect of surface active solute on the surface tension of liquid Ti-Al alloy was also discussed. Sulfur is found to have a larger effect on the surface tension of alloy. The surface tension of liquid Ti-Al alloy decreases with increased sulfur concentration. Sulfur concentration on the surface is higher than that in the bulk. Thus, the adsorption of sulfur for Ti-Al alloys is a positive adsorption.

Effect of Electrical Conductivity and Porosity of Cathode on Electro-Deoxidation Process of Ilmenite Concentrate

Abstract The performance of the cathode is always closely related to the electro-deoxidation process and its current efficiency. In this work, the effect of sintering temperature on the electrical resistivity of an ilmenite concentrate cathode was measured. The results show that the sintering temperature has a significant effect on the electrical conductivity of the cathode. The electrical resistivity of the ilmenite concentrate cathode decreases with increasing of the sintering temperature and increasing of the contact area. Besides, the influence of the cathode porosity on electrochemical process during preparation of Ti-Fe alloy in molten salt was studied. The results also reveal that the porosity of ilmenite concentrate cathode directly affects the electro-deoxidation process. The increasing of porosity is beneficial to the formation of intermediate product (CaTiO3) and improvement of the current efficiency.

Crystallization Behavior of Molten Blast Furnace Slag Using Confocal Scanning Laser Microscope

Extracting perovskite from high titanium-bearing blast furnace (BF) slag is a green and potential method to recover the second titanium resource. The non-isothermal crystallization process of perovskite in synthesized high titanium-bearing slag was studied in situ by confocal scanning laser microscope (CSLM) with cooling rate of 20 K/min. The results showed that perovskite was the primary phase formed during cooling process in the titanium-bearing synthesized slag (TiO2=23%). Perovskite started to precipitate at 1719 K and finally presented an orthogonal straight lines morphology.

Reaction Sintering of Mg2Si Thermoelectric Materials by Microwave Irradiation

In order to reduce the oxidizing and volatilizing caused by Mg element in the traditional methods for synthesizing Mg2Si compounds, solid state phase reaction at low temperature was introduced by microwave field. XRD was used to characterize the powders. At the same time, the influences of parameters during the synthesis processing were discussed. The results suggest that the heating profile is also dependent on the initial green density and higher green density provides lower heating rate while power setting are fixed and the oxidation of Mg can be rest rained by changing microwave heating programs. It was found that high purity Mg2Si intermetallic compound can be obtained with excessive content of 8at% Mg from the stoichiometric Mg2Si, 853K and 30min.