Ya Wei Li

Preparation of Light-Weight Forsterite Insulation Materials Through Extrusion Processing

Light-weight insulation materials were prepared by extrusion processing using forsterite raw tailings, light-burned magnesia and fused magnesia as main raw materials with addition of rice hull powder as a pore-forming agent. The results show that the plasticity of green compact and the cold compressive strength of bricks are improved with the addition of 2-3 wt% dextrin as plasticizer. Light weight insulation materials, which meet different application requirements, were prepared by controlling the addition amount of rice hull powder by firing at 1550 °C with volume weight of obtained materials varies from 1.4-1.8 g/cm3, thermal conductivity at 600 °C is less than 0.48 W/(m•K), cold compressive strength varies from 8-24MPa and reheating linear change rate is less than 1% (1400°C × 6h).

Effect of Reactive-Al2O3 Addition on the Pore Size Distribution and Thermal Conductivity of Carbon Blocks for Blast Furnace

The effect of reactive-Al2O3 addition on the pore size distribution and thermal conductivity of carbon blocks for blast furnace was investigated by using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray, mercury porosimetry, and a laser thermal conductivity meter. The results showed that the pore size distribution and the thermal conductivity of carbon block were mainly influenced by SiC whiskers and reactive-Al2O3. With increasing addition of reactive-Al2O3, the mean pore diameter reduced and < 1μm pore volume increased of open pores owing to the more efficient filling of pores by SiC and reactive-Al2O3, and the thermal conductivities of samples increased due to the facts that the higher thermal conductivity of reactive-Al2O3 than that of brown corundum and the more formation amount of high thermal conductivity of SiC.

Preparation of Light-Weight Alumina-Spinel Refractory by Foaming Process

In order to reduce energy costs, light-weight alumina-spinel refractories with tri-modal pores were prepared by foaming process. The influence of foaming agent and magnesia on the properties of light-weight alumina-spinel refractory was investigated. The rheology of the original slurry and the density, mechanical properties and microstructure of samples were evaluated. The results showed that light-weight alumina-spinel refractory contained a highly interconnected network of spherical cells, consisting of the large-sized cells (larger than 40 um), moderate-sized pores( averaging about 20 um) and small-sized voids, which mainly attributed to the foaming agent and in-situ formation of spinel. The cold compressive strength of the samples varied within the range of 2-12MPa, corresponding to densities of 0.8~1.2g/cm3,and the thermal conductivity changed from 0.273W/(m•K) to 0.315 W/(m•K) at the 500 °C. It was found that the density of the sintered samples was dependent both on the content of foaming agent and magnesia. With the help of magnesia, light-weight alumina-spinel refractories with good volume stability were prepared by foam method.

Relationship Between Porosity Characteristics and Thermal Conductivity of Different Graphite Size Containing Carbon Refractories

High-property carbon refractories for blast furnaces should have high thermal conductivity and excellent porosity characteristics. The relationship between porosity characteristics and thermal conductivity of different graphite size (100mesh, 200mesh, 325mesh, 600mesh and 100mesh respectively) containing carbon refractories was investigated by using mercury porosimeter and laser thermal conductivity instrument. The results indicate that the thermal conductivity was reduced with the increase of porosity and <0.1μm pore volume as well as the decrease of mean pore diameter under the same condition, which was related to the short of thermal conductive route.

Microstructure and Phase Composition of AlN/Al Composite Fabricated by Directed Melt Nitridation

AlN/Al ceramic composite was fabricated by directed melt nitridation of pure Al block covered with 10wt% Mg powder at 1300°C in a high purity flowing N2. Microstructure and phase composition of the composite were investigated by scanning electron microscopy with energy dispersive spectroscopy and X-ray diffraction. Results showed that AlN is the main phase in the composite and its lattice parameters of a and c are 3.1110Å and 4.9806Å, respectively. The phase composition of the composite changes along the growth direction and a gradient sandwich structure forms. The surface of the composite is made up of a dense and thin nodular AlN layer, underneath which an AlN/Al layer appears, followed by an AlN/Al/MgAl2O4 layer. Thermodynamic calculations predicted the formation of possible phases with the addition of Mg. It suggested that the content of Mg at the reaction frontier of nitridation is considerably lower to 0.15wt% where MgAl2O4 was stable, because of escape and reaction exhaustion of Mg. Once Mg is lower than 0.05wt%, only a dense AlN layer can exist, which prevents the further nitridation of Al melt.

Effect of Artificial Graphite and Nickel Nitrate on the Microstructure and Properties of Carbon Blocks for Blast Furnace

Improving thermal conductivity of carbon blocks is one of the most important developing trends for carbon blocks. In this work, artificial graphite and nickel nitrate catalyst were introduced into carbon blocks with an attempt to improve thermal conductivity of carbon blocks and their effect on microstructure and properties of carbon blocks were systematically studied by means of X ray diffraction (XRD), scanning electron microscopy (SEM) and laser thermal conductivity meter. The results revealed that artificial graphite possessed lower oxidation activation energy than electrically calcined anthracite, and thus, higher reactivity, which could accelerate the formation of SiC whiskers in carbon blocks and have a positive effect on thermal conductivity of carbon blocks. Moreover, it was interestingly noted that one dimensional nano-carbon was catalytically formed at 1000 °C and lots of Sialon phases were formed at 1400 °C when nickel nitrate catalyst was further added in carbon blocks containing artificial graphite. These in-situ ceramic phases formed in carbon blocks constructed high thermal conductive network and reduced the interface thermal resistance, thus improving the thermal conductivity of carbon blocks significantly.

New Characterization Method of Hot Metal Penetration Resistance for Blast Furnace Carbon Blocks

The main causes for deterioration of carbon blocks are due to the penetration and dissolution of hot metal against pores and surfaces. The active national standard GB/T 24201-2009 can only judge the hot metal dissolution, but the penetration of hot metal during test has been neglected. On the basis of national standard, a new measurement and characterization method is proposed. The study shows that with the help of back-scattered electron detect technology combined with statistical analysis, the penetration depth of hot metal could be quantitative evaluated, which could provide a reference for optimize the production of blast furnace refractories.

Control of the Spring Back in Rice Husk by Al2O3 Sol

The effects of Al2O3 sol on the mechanical, morphological, and water sorption properties of rice husk were studied by means of compression-strain tester, and scanning electron microscopy (SEM) associated with the energy spectrum analysis. The results showed that the spring back of materials is found to decrease with increasing coating concentration. With the increase in Al2O3 sol concentration, the gaining of mass fraction of the materials increased proportionally, while the water absorption, which measured at ambient temperature, was gradually decreased with increasing Al2O3 sol concentrations. The gaining of mass fraction, lowest water absorption and lowest of compressive recovery ratio of 10.15%, 34.5% and 16.58%, respectively, were obtained when Al2O3 sol solid content was 8%, and resulted mainly from an increase in the rigidity increase. The Al2O3 sol had a positive effect on the morphology stabilization of rice husk.

Effect of Zircon Content on the Microstructure and Physical Properties of Chamotte Refractories

In this work, chamotte with dispersions of up to 30wt% zircon is sintered at 1500 °C to investigate the effect of zircon content on the microstructure and physical properties of chamotte refractories. The microstructure and physical properties of samples are investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDS), three-point bending and dilatometer. The result shows that the main phases of chamotte with and without sintering at 1500 °C are mullite and cristobalite, the addition of zircon has no impact on the main phase compositions of chamotte matrix. For the sintered samples, zircon grains are wrapped with glass and no obvious bonding are detected between the interface of zircon and mullite grains. Increasing zircon content leads to the increase in bulk density and has a negative effect on the flexural strength, besides, linear thermal expansion ratio decreases as the zircon content increases.

Preparation and Properties of High-Purity Porous Calcium Hexaluminate Material

In this paper, high-purity porous calcium hexaluminate materials were prepared with α-alumina, nano-meter calcium carbonate and ρ-alumina as raw materials. The properties of the prepared porous materials, such as bulk density, true density, thermal conductivity, and cold crushing strength, were investigated. The increase in sintering temperature led to the increase of true density. Bulk density and cold crushing strength of the specimen fired at 1500°C had the lowest values. As ρ-alumina content increased, bulk density, true density, and cold crushing strength had no obvious changes, but the thermal conductivity decreased at first and then increased. The calcium hexaluminate formation was intense from 1450°C to 1500°C and finished at 1500°C. Above 1500°C, the main phase of specimens was calcium hexaluminate (CA6). And CA6 grains were regular hexagonal plates morphology and widely spread after firing at 1550°C.