Advanced Materials Research Vols. 284-286

Abstract: Using Li₂O-B₂O₃-SiO2 (LBS) glass and LiF as a liquid phase sintering additive, the effects of it on the microstructure and properties of 16CaO-9Li₂O-12Sm₂O₃-63TiO₂（CLST）ceramics were investigated. The results indicated that the compound sintering aids of LBS glass and LiF reduced the sintering temperature of CLST from 1300 °C to 950°C. Compared with the sample doped single LBS glass, the optimum dielectric properties, Kr=81, Tanδ=0.0073 could be obtained when the CLST ceramic samples doped 3 wt% LBS glass and 0.25 wt% LiF were sintered at 950°C for 3 h.

Abstract: TiN/O′-Sialon ceramics were prepared by pressureless sintering using high titania slag, silicon fume and bauxite chalmette as the starting materials. Phase compositions and microstructure were analyzed by XRD and SEM. The effect of TiO₂ content in the staring materials on densification behavior and mechanical properties was studied. The results showed that the sintered samples consisted of O′-Sialon and TiN. O′-Sialon exhibited equiaxied morphology and the particle sizes were about 1-3μm. TiN showed fine granular morphology and most of the particle have lower size than 0.5μm. For the samples sintered at 1500°C using raw materials containing 30wt%TiO₂, bulk density, hardness and flexure strength are 3.1g/cm³, 9.2GPa and 169MPa, respectively.

Abstract: Porous catalyst support was prepared using gangue of bauxite tailing which was a solid waste material. It was found that the mass ratio of gangue of bauxite and knar clay was 4: 1. The masses of cellulose and water were individually 1 wt% and 25 wt% of the total mass of gangue of bauxite tailing and knar clay. The pore forming agent M was optimum among the selected pore forming agents. The pore forming agent M didn’t residue in support after sintering so that the support wasn’t polluted. The appropriate addition of the pore forming agent M was 4%, and the catalyst support with the porosity of 41.3% was preparated. The appropriate sintering temperature and holding time were 1250 °C and 2.0 h, respectively. Mullite and quartz were the main mineral phase of the porous catalyst support and the catalyst support have good chemical stability and heat-resisting property.

Abstract: Conical parts forming is one of the complex and difficult fields in sheet metal forming processes; because of the low contact area of the sheet with the punch in the initial stages of forming, too much tension is applied to the sheet causing bursting occurrence. Furthermore, since the major part of the sheet surface between the blank holder and punch tip is free, wrinkles appear on the wall of the drawn parts. Therefore, these parts are normally formed in the industry by spinning, explosive forming or multi-stage deep drawing processes. In this paper, the effect of punch tip radius and conical- cylindrical radius on formability and thickness distribution of the conical parts for three different punch angles were studied.

Abstract: Fused quartz granule (d₅₀=0.019 mm) was used as raw material, nano-Y₂O₃ (size<0.08 μm) was used as additive with dosages of 1% (in mass, similarly hereinafter), 2% and 3%. Fused quartz ceramic materials were fabricated in reduction atmosphere at 1300 °C, 1350 °C and 1400 °C for 1 h. Properties of samples were researched by measurements of apparent porosity, bending strength and thermal expansion rate, and analyzed by XRD and SEM. The results showed that additive nano-Y₂O₃ had good inhibiting effect on crystallization of fused quartz sintered at various temperatures, sample added 2% nano-Y₂O₃ had least thermal expansion rate, diffraction peak intensity and apparent porosity, and it had higher bending strength and more compact microstructure, especially sample sintered at 1350 °C. It can be deduced that 2% nano-Y₂O₃ plays the excellent role as the crystallization inhibitor and sintering assistant to fused quartz materials sintered at various temperatures.

Abstract: On the preparation of porous ceramics with composite sintering auxiliaries Y₂O₃-Al₂O₃ , the main ingredient of SIC , and CMC as the porous agent . Having studied the C content of composite structure and mechanical properties , And analysised the composite fracture morphology with SEM . The results show that, when using different particle size of carbon powders mixed the porous silicon carbide ceramic sample size powdered carbon than a single sample of micro skeleton intact, the shapes of holes, and more rules are uniformly distributed, comprehensive mechanics performance is better.

Abstract: In the poling process of PZT ceramics, the poling temperature is a critical condition. When the poling temperature is too low, no matter how high is the poling field and how long is the poling time, the planar electromechanical coupling factor k_p is lower. When the poling temperature is higher enough, the k_p can reach to a saturated value with a lower poling field and short poling time. The variation of dielectric constant with the poling conditions is the same as that of planar electromechanical coupling factor. When poling with a low temperature, the dielectric constant after poling is lower than 1400. When poling with higher temperature, no matter how high is the poling field and how long is the poling time, the dielectric constant after poling is higher than 1500.

Abstract: Preparation of porous silica from thermally activated kaolinite was investigated by using acid dissociation process, and the relationship between structural transformation and acid dissociation properties of aluminium were elucidated. Al^VI transfers into Al^V and Al^IV when kaolinite changes into metakaolinite during thermal activation. Al^V is dissoluble in acid, while Al^VI, Al^IV are difficult to be dissolved into acid, therefore, the coordinations of aluminium affect acid dissociation of alumina markedly. Mesoporous silica is made by acid dissociation alumina of metakaolinite, and the specific surface area of porous silica is determined by acid dissociation ratio of alumina. The dissociation ratio of aluminum is up to 97% when kaolinite is activated at 900°C for 15 min. Specific surface area of the porous silica material is 357 m²/g, the pore volume is 0.43 cc/g, and BJH pore diameter is 2.18 nm. The pore is found to be in the worm-like shape by high resolution TEM analysis.

Abstract: Forming conical parts is one of the complex and difficult fields in sheet metal forming processes. Because of low contact area of the sheet with the punch in the initial stages of forming, too much tension is applied to the sheet causing burst occurrence. Furthermore, since the major part of the sheet surface between the blank holder and punch tip is free, wrinkles appear on the wall of the drawn parts. Therefore, these parts are normally formed in industry by spinning, explosive forming or multi-stage deep drawing processes. In this paper, the effect of punch conical angle in hydroforming of conical-cylindrical parts has been studied. It is shown that by increasing the angle the thickness reduction will be reduced.

Abstract: The effect of Ce substitution at the A-site on the properties of Na_0.5Bi_4.5Ti₄O15 (NBT)–based ceramics was systematically investigated. The substitution at A-site caused distortion of lattice and improved piezoelectric activity correspondingly. The piezoelectric coefficient d₃₃ of the Na_0.5Bi_4.5-xCe_xTi₄O₁₅ (x=0.03) ceramic was found to be as high as 26 pC/N, together with high mechanical quality factor Q ( 2769 ), and stable piezoelectric properties, demonstrating that the Ce-modified NBT-based materials are promising candidates for high-temperature applications.