Advanced Materials Research Vols. 105-106

Abstract: Owing to the defects of the fixed TiO2 photocatalysts, the research employed the approach of anodic oxidation to produce high efficiend N-TiO2/Ti ceramic film oxidized on the surface of titanium, in order to make the absorbable spectrum of light catalyst spread to the visible region and constrain the high recombination rate of electron-hole pairs during photoreaction. The surface appearance and the distribution of elements have been checked with scanning electron microscopy and EPMA. The microcrystal structure of the films has been checked with XRD. The results showed that the main components of nitrogen-doped catalyzer were rutile and anatase, meanwhile, the nitrogen element distributing on the film was fairly uniform. Films of N-TiO2 photocatalysis reduction K2CrO4 revealed that with the amount of N-contained increased, the rate of reduction K2CrO4 decreased under ultraviolet light while that increased under visible light. It was found that the highest reduction rate of K2CrO4 was achieved through an optimal (NH4)2S2O8 dosage of 0.4g/L in ceramic film prepared processes.

Abstract: The crystallization behavior and microstructure of Li+-doped TiO2 thin films prepared by sol-gel dip coating were investigated by means of differential themal analysis (DTA), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The crystallization apparent activation energy (E) both in the absence and in the presence of Li+ ion was also measured with Kissinger method. As a result the E values of Li+-doped TiO2 thin film were decreased, thus the crystallization of non-crystalline to anatase and antase to rutile was promoted.

Abstract: Silicon carbide (SiC) powders have been prepared at 1200–1500°C by carbothermal reduction of two kind precursors of carbonl/silica mixtures: coked rice husk with high-carbon content, and gasified rice husk with low-carbon content mixed with carbon powders as an external carbon sources. The differences in nature of carbon matter in the external source and coked rice husk, and their effect on SiC synthesis have been studied by TG-DSC, TEM, XRD and laser diffraction technique. Experimental results show that the difference in nature of carbon source may affect the formation of SiC powders. The characteristics of the synthesized SiC particles strongly depend on the characteristics of the carbon sources.

Abstract: Composition of stainless steel slag was compared with that of ceramic paste first. DTA curves of ceramic samples were obtained to determine the firing temperature schedule. It is concluded that the stainless steel slag mixed with certain chemically pure materials can serve as raw material for the production of high added value ceramics. Pilot plant scale tests show that the principal crystal phase is diopside, contributing to the making of high strength and high density ceramics. Heating rate, cooling rate and holding time should be controlled appropriately during sintering process for the sake of forming and growth of crystals. The total performance detection of ceramic samples accords with national standards in China when stainless steel slag is used to sinter calcium-magnesium-silicon type ceramic in roller kiln. The proportion of stainless steel slag is 45% during pilot tracey. Dissolution rate of chromium during stainless steel slag used as mainly diopside type of building ceramic is only 25.17 mg/kg ceramic, which resolves the harmless of chromium. This work provides a feasible and effective way for resource of stainless steel slag.

Abstract: The xerogel of mullite precursor with high specific surface area (422m2•g-1) was successfully prepared from the sol of aluminium isopropanol (AIP) and tetraethyl orthosilicate (TEOS) tuned by supercritical CO2 and subsequent supercritical fluid extraction. Nanometer mullite was prepared by calcining the xerogel of the precursor, and the obtained mullite together with the xerogel precursor was characterized by SEM, XRD, N2-adsorption and IR. The results showed that the xerogel precursor exhibit a shape of amorphous structure, with size of no more than 100 nm, and no huge blocks was found, indicating that the supercritical CO2 plays an important role in controlling the process of hydrolyzation, sol-gel transition, in which supercritical CO2 may promote the mixture of Si and Al on atomic scale. SEM indicated that the obtained mullite were mainly 2-3 μm in length and lath in shape with aspect ratios of 6-10, and the laths were interlaced with each other to construct a relative dense mullite aggregation. The mineralogical phases tracing experiment showed that the mullitization process underwent from 1200 °C to 1400 °C as followed by the phase transition from -Al2O3 to -Al2O3, and to -Al2O3, and the temperature of complete phase transformation into mullite was 1400 °C.

Abstract: Insulation effect and mechanical performance of foam glass depend, to a large extent, on foam structure. Hence understanding foam formation is not only a problem of significant fundamental interest but also of tremendous practical impact. In this paper, foam growth was modeled comparing to grain growth theory in sintering. TG-DTG analysis of carbon black indicated that pre-oxidation took place prior to foaming temperature. Furthermore effects of heating rate and particle size of carbon black on foam structure have been taken into account. Several borosilicate foam glasses were fabricated by powder sintering process at different heating rates using carbon black of different particle sizes as foaming agent, respectively. It was found that increasing the heating rate tended to decrease the pre-oxidation of carbon black resulting in inhomogeneous foam distribution. Foam structure of sample heated at a rate of 8°C/min using carbon black with particle size of 0.15mm was optimal.

Abstract: Fused magnesite, α–Al2O3 micropowder and aluminum powder were used as starting materials to form MgAlON and MgAlON-bonded MgO materials in nitrogen atmosphere. Influence of technical conditions, such as composition, on formation of MgAlON was studied. Influence of vapouring of MgO in low PO2 atmosphere at high temperature on sintering of MgAlON-bonded MgO material was also discussed, showing that vapouring of MgO makes the material porous and damages its sintering.

Abstract: A laboratory preparation process of glass ceramics from nickel slag was introduced. The controlled heat treatment processes were carried out on the basis of differential scanning calorimetric (DSC) measurements. Mineral phase and microstructure of crystallized glass were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The modified Kissinger equation was employed to investigate the crystallization kinetic parameters, activation energy E and the k(Tp). The Avrami exponent, n, was calculated by Augis-Bennett equation. Analysis indicated that the glass with 10%TiO2 added was peril to crystallize, of a large value of k(Tp), its k(Tp) is 0.244, E is 522.76kJ/mol and n is 3.42. The crystal phase is diopside.

Abstract: Crystalline glaze is a kind of art glaze with excellent decorative performance, the existing crystalline glaze mainly willemite crystalline glaze, systems on a single track. In this paper, the use of crystalline glaze raw materials for glass, ZnO and coke gemstones, CuO as coloring agents, using ortho- gonal to determine the formula, this paper researched that added TiO2 to the willemite crystalline glaze crystal phase composition as well as the amount of TiO2 and processing conditions on the preparation of crystalline glaze crystal flower morphology impact. The results show that under the conditions of 1250°C melting 1130°C crystallization process crystal spontaneous growth in crystalline glaze can be able to cover the entire glazed, shape of crystals was feathered, cross growth, the number of crystal increased with crystallization temperature, glaze was smooth and shiny sense. XRD and optical microscopy analysis showed that the precipitation of crystals was the long column of rutile, crystal distributed equality, under a polarizing microscope in purple, green and black, with strong aesthetic values.

Abstract: Arc-shaped integrated alumina ceramic armor for body bulletproof with the size of 300 × 250 × 6 mm, R400mm were prepared by semi-aqueous gel-casting. The excellent characters and advantages of the semi-aqueous gel-casting were analyzed; ballistic experiments were carried out to test the protection coefficient of 92%, 96%and 99 alumina ceramics. The experimental results showed that the 92% alumina ceramic and the 99% alumina ceramic had favorable performance while the 96% alumina ceramic had the worst one. But the 92% alumina ceramic had the highest protection coefficient which is 9.96.