Yan Ruo Hong

A Potentiometric SO2 Gas Sensor with Solid Reference Electrode

A SO2 sensor based on Na-b-Al2O3 interfaced with an auxiliary electrode of Na2SO4 formed in situ and a solid mixture of Fe3O4, Fe2O3, 3Na2O.5Fe2O3 as the reference electrode was developed. The sensor displayed a Nernstian response to changes in the partial pressure of SO2.

Preparation and Characterization of Al2O3 Coated Graphite Powders

Heterogeneous-nucleation formation of Al2O3 coatings on graphite powders via a controlled hydrolysis process of aluminum chloride was investigated, and surface morphology and properties of the coated graphite were examined. The formed Al2O3 coatings were uniform and essentially amorphous. They were bonded well with graphite via chemical interaction between their O atoms and C atoms on graphite surface. Graphite particle size increased from 7.61 µm (as-received graphite) to 9.53 µm (the coated graphite), revealing that average thickness of the coating was ~1µm. Compared with those of as-received graphite, specific surface area and fractal dimension of the coated graphite also increased, which was caused by the porosity present in the coating. The isolectric point (IEP) of the coated graphite (~9) was close to that of pure Al2O3, indicating that the electro-kinetic behavior of the coated graphite was similar to that of Al2O3.

Oxidation Behaviors of MgAlON/Si3N4 Composite at High Temperature

The isothermal oxidation behaviors of MgAlON/Si3N4 composite which was synthesized by pressureless nitridation reaction sintering have been investigated in flowing air at 1100°C, 1200°C and 1300°C respectively. The results show that the composite represents excellent self-healing property of oxidation at 1300°C, which might be attributed to the formation of protective silicate film with reasonable viscosity, good spreading power and very low oxygen diffusion coefficient, and to the formation of compact surface resulted from the expansion effect of forming mullite from SiO2 and Al2O3. However, the self-healing property of it is relatively poor at 1100°C and 1200°C as compared to 1300°C.

Novel Mg Sensors for Application in Molten Al

Mg ion conductors, MgAl2O4 and MgZr4(PO4)6, were prepared by solid state reaction. Their electrical properties were measured and their application in electrochemical sensors for on-line determination of Mg in molten Al in the refining process and alloying process was examined. The activation energies for Mg ion conduction in MgAl2O4 and MgZr4(PO4)6 are 2.08 eV and 1.7 eV, respectively. The sensors have been found to respond rapidly to the change of Mg content in molten aluminium around 1000 K.

Corrosion Behavior of BF Slag to SiAlON Bonded Corundum Refractories

The corrosion behavior of BF slag to sialon bonded corundum refractories using reaction nitriding technology at 1500°C was investigated by crucible test method. The results show that the reaction products of slag corrosion are anorthite, magnalium-spinel and glass phases. The corundum grains can react with MgO in the slag to produce magnalium-spinel, accompanying by expansion and liquating stepwise by slag. Erosion mechanism is oxidation-erosion-dissolving. This study is very necessary and useful to improve the property of BF slag resistance and to yield better overall properties of sialon bonded corundum refractories.

Effect of CaO Content and Microstructure on Hydration Resistance of MgO-CaO Clinkers

Hydration resistance of three commercially available high-purity MgO-CaO clinkers were investigated and compared in the present paper. The results show that, as well as CaO content, microstructural morphology of MgO–CaO clinker affects its hydration resistance. The microstructure in which CaO is present at the grain boundaries of MgO leads to poorer hydration resistance, whereas the one in which CaO and MgO are distributed alternately confers much improved hydration resistance on the clinker, especially when MgO level is high enough to cover most of the CaO crystals.