Jing an Yu

Analysis of Fused Magnesia Production Process with 3000kVA Electric Arc Furnace

The present study is related to a process development for producing high purity fused magnesia. A newly designed 3000 kVA electric arc furnace is used in the field experiment. The electric resistance characteristic of fused magnesia is analyzed and the effect of electrode diameters and electrode depth buried in molten magnesia on melting electric resistance and electric arc heat conversion are discussed in detail. It shows that, for the new 3000 kVA electric arc furnace, 350~450 mm diameter electrode and ~300mm depth in molten magnesia are suitable.

Synthesis of Nano Amorphous In2O3 by Microwave Method and its Photocatalysis

Precursor In(OH)3 was synthesized by ultrasonic method with carbamide and indium salt, and was performed microwave radiation, then nano amorphous In2O3 was obtained. The structural and morphology of precursor and In2O3 were characterized by TG-DTA, XRD, TEM, etc. The results show that the In2O3 is nano amorphous with average grain size 12nm by microwave method. This paper discovered that nano amorphous In2O3 has good photocatalysis when we used it to degrade acidic black dye.

Energy Saving by Applying 3000kVA Electric Arc Furnace in Fused Magnesia Production

Fused magnesia is an essential basic material for metal making and construction industries. Fused magnesia is usually produced with mineral arc furnace. In China, 1600 kVA arc furnaces are widely used as fused magnesia production facility. The unit power consumption for magnesia production is about 3000 kWh/t, higher than that in developed countries. In this research, a 3000 kVA new arc furnace was used to produce fused magnesia, and the unit consumption decreased to 2560kWh/t. The experimental results showed that the new furnace has good energy saving effect and market prospects.

Study on Preparation of Gradient Porous Ti by Powder Metallurgy Method

Gradient porous Ti was prepared by powder metallurgy method using NH4HCO3 as pore former. The effect of content and distribution of NH4HCO3 and sintering temperature on pore characteristic, sintering shrinkage, flexural property was studied. Stress-strain curves of gradient and uniform porous Ti material were compared. The results show the porosity, sintering shrinkage rate and flexural strength vary from 51.8% to 41.3%, from 23.5% to 28.7%, and from 145.7 MPa to 221.6 MPa when the distribution of NH4HCO3 varying form uniformity to gradient. Additionally, with the increase of sintering temperature, the porosity of gradient samples first increases and then decreases. When sintered at 1573K for 2h, the porosity of gradient porous Ti has the maximum of 45.6%. Moreover, there is pseudo yield phenomenon according to the test curve of three points bending of the gradient porous Ti with three layers structure.

Preparation of Gradient ZTA Ceramic by Centrifugal Slip Casting Method

Gradient Zirconia toughened alumina (ZTA) ceramics with high fracture strength and toughness were prepared using centrifugal slip casting method. Aqueous Al2O3-20vol% ZrO2 slurries with different solid contents were prepared and the rheological characteristic of the slurries were investigated. The effect of solid loading of slurries on green density difference of ZTA ceramic compacts was observed. Mass segregation of Al2O3 and ZrO2 particles were studied. Microstructure and bending property of the sintered ZTA ceramics were investigated. The results show that the segregation phenomenon of Al2O3-ZrO2 slurries comes form the difference of settling velocity of Al2O3 and ZrO2 particles. With the increase of solid content of slurries, the gradient distribution of green density becomes unconspicuous. After sintered at 1550○C for 2 h, the gradient ZTA ceramics centrifuged with 20vol% slurries have high sintered density (99.2% TD) and continuous gradient distribution of Al2O3 and ZrO2 particles. The fracture strength and toughness of gradient ZTA ceramic are 732MPa and 5.4MPam1/2, respectively.

Study on Effect of Sintering Temperature on Microstructure and Compressive Property of Porous NiTi Alloys

Porous NiTi alloys were prepared by powder metallurgy method using NH4HCO3 as space-holder. The effect of sintering temperature on pore characteristic, phase composition and compressive property of porous NiTi alloys was studied by XRD, SEM, EDS and a universal testing machine. The results show with the increase of sintering temperature the porosity of porous NiTi alloys first increases and then decreases, but the content of NiTi phase, compressive strength and modulous of sintered products continuously increase. When sintered at 980°C for 2h, the porous NiTi alloys have higher porosity of 53.6%, better compressive strength of 173.7MPa and elastic modulous of 4.2GPa. The phases of sinter products are mainly composed by TiNi, Ti2Ni, and TiNi3 phases.

Magnesium Incorporation in Sol-Gel Derived Apatite Coating on Ti6Al4V Substrate

A series of the magnesium apatite coatings according to (Ca10-xMgx)(PO4)6(OH)2, where x = 0 to 2, was synthesized through a sol-gel dip-coating method. The roughness of the magnesium coatings increased as more magnesium incorporated into the coatings. The mechanical properties of the coatings were analyzed with Nanoindentor. The incorporation of magnesium decreased the hardness and the Young’s modulus of the coating. The X-ray Photoelectron Spectroscopy (XPS) analysis revealed that only part of magnesium was incorporated into the apatite structure while the rest existed in the form of MgO in the coating.

Study on Characteristic and Compressive Property of Porous NiTi Alloys Fabricated by Thermal Explosion Method

Porous NiTi shape memory alloys were fabricated by thermal explosion method using different Ti and Ni powder as initial materials. The effect of process parameters including heating rate, and particle size of Ti on pore characteristic and phase composition was analyzed. Microstructure, phase composition, and mechanical properties were studied by SEM, XRD, and compression test, respectively. The mechanism of thermal explosion reaction was studied. The results show higher heating rate and smaller Ti particle size result in higher porosity and bigger pores. The thermal explosion reaction starts with the melting of a eutectic between β-Ti(Ni) and Ti2Ni and the main phases of as-reacted products are TiNi phase which are the desired phases. NiTi2 and TiNi3 phases are also present in small amounts. The content of TiNi phase increases with increasing heating rate or decreasing Ti particle size. The compressive strength and Young’s modulus of compacts decrease with the increase of the porosity.

Preparation of Open-Cell Alumina Ceramic Foam with Uniform Cell Structure Using Plant Seed Template

Open-cell Al O ceramic foams with uniform cell structures and dense cell struts were fabricated by centrifugal slip casting using the plant seeds as the templates. The rheological characteristic of Al O slurries with up to 50 vol.% solid content was investigated. The shrinkage matching between the Al O green compact and the plant seeds during drying was studied. The effect of solid contents of slurries on change of green density of cell struts along the height of compacts was analyzed. The drying and sintering schedule of Al O green cakes were studied. The results indicated mass segregation of Al O particles with different sizes during centrifugal process was negligible for slurries with high solid loadings with 50 vol. %. The cell struts of green bodies had high density of 63.8% TD. After sintered at 1500 °C for 2 h, the final products had dense cell struts with high sintered density of 98.9%TD and homogeneous microstructure. The porosity and compressive strength of sintered products was 66.5% and 5.26 MPa, respectively.

Study on Synthesis and Thermal Decomposition Kinetics of Mg(OH)2 Modified with SDBS by Liquid Phase Method

The Thermal Decomposition Kinetics of Mg(OH)2 Modified with Sodium Dodecyl Benzene Sulfonate (SDBS) by the Liquid Phase Method Was Investigated Using Differential Thermal Analysis and Thermo Gravimetric (DTA-TG) at Different Heating Rates. the Results Show that the Mg(OH)2 Modified with SDBS Is Mg(OH)2 with Hexagonal Phase Structure. the Average Apparent Activation Energy of the Decomposition Stages of Mg(OH)2 Modified with SDBS Was Calculated Using the Doyle-Ozawa and Kissinger Methods as 169.13 Kj•mol-1. the Reaction Order and Frequency Factor Can Be Also Determined by Kissinger Method. the Kinetics Equations of Reaction Were Deduced as Dα/dt = (5.71×1012/β) e-20340/T (1-α)1.52.