Advanced Materials Research Vols. 284-286

Abstract: Using SiO₂ – Al₂O₃ – B₂O₃ – K₂O – Na₂O system glaze as base material, under different temperature, sintering states of glaze were test. The influence of heat treatment on glaze melting characteristics was study. The results show that high heat treatment temperature can debase softening point, raise flow point, extend melting temperature range, long heat treatment time.has little effect on glaze melting characteristics.

Abstract: The high pressure and high temperature sintering of α-Si₃N₄ and γ-Si₃N₄ with Y₂O₃-Al₂O₃-La₂O₃ as additives were studied under pressures of 5.4 GPa and temperatures of 1420-1770 K. The effects of sintering temperatures and pressures on properties of sintered ceramic samples were investigated with X-ray diffraction and scanning electron microscopy. The results show that γ-Si₃N₄ and α-Si₃N₄ is transformed to β-Si₃N₄ completely. The highest relative densities and Vickers hardness (H_V) of sintered samples are 98.71 and 21.76GPa, respectively. The sintered samples were composed of elongated β-Si₃N₄ rod crystals with disordered orientation and had intergranular interlocks and uniform and compact microstructure. Pulled out crystal grains on the fractured cross sections were obviously observed by SEM.

Abstract: A new function-oriented theoretical basis for mechatronic system design is presented in the paper, with a technology-independent functional description of such aspects in a mechatronic system as 1) relations and distinctions among purpose function, transformation function and state transition and 2) structure of information processing. All discussions are summarized in a set of principles, which consequently form the basis for devising design models and methods for mechatronic systems.

Abstract: La₂O₃-doped lead-free 0.82Bi_0.5Na_0.5TiO₃-0.18Bi_0.5K_0.5TiO₃ (abbreviated to 0.82BNT-0.18BKT) piezoelectric ceramics were synthesized by the conventional mixed-oxide method, and the effect of La₂O₃ addition on the dielectric and piezoelectric properties was investigated. X-ray diffraction (XRD) patterns show that La₂O₃ diffuses into the lattice of the 0.82BNT-0.18BKT ceramics to form a solid solution with a pure perovskite structure. SEM images indicate that the grain size of the 0.82BNT-0.18BKT ceramics increased with the addition of La₂O₃ doping. The electrical properties of 0.82BNT-0.18BKT ceramics have been greatly improved by certain amount of La₂O₃ substitutions. At room temperature, the 0.82BNT-0.18BKT ceramics doped with 0.25 wt. % La₂O₃ exhibited the optimum properties with high piezoelectric constant (d₃₃ = 142 pC/N) and high planar coupling factor (k_p = 0.23).

Abstract: Porous silicon carbide ceramics were prepared by coat mix process using silicon powders and phenolic resin as silicon and carbon resource. The formation mechanism of silicon carbide was proposed based on the liquid silicon infiltration mechanism, reaction dynamics and thermodynamics analysis. Results show that the formation of silicon carbide by the coat mix process includes the following phases. 1) Infiltration of liquid silicon into porous carbon gap. 2) Formation of silicon carbide particles through the contact and reaction between liquid silicon and silicon surface. 3) Fracture and falling off of silicon carbide layer from the carbon surface. 4) Formation of new silicon carbide layer and particles. 5) The repetition of phase 3) and phase 4) till the reaction is complete and the porous silicon carbide ceramics are formed.

Abstract: As(III) removal from low-arsenic concentration drinking water treated by coagulation with mixture titanium tetrachloride and titanium sulfate as coagulants were studied in this paper. Without any pre-oxidation process, the residual concentration of As(III) after treated by the coagulant (concentration of 25mg/L) was less than 4μg/L,which can be satisfied the most rigid guideline for arsenic maximum contaminant level (MCL) proposed by WHO or USEPA. Operated with rapid water dynamics will get the better efficiency for As(III) removal. In the pH range of 3-6 the variation of As(III) removal efficiency was minimal, but the As(III) removal declined gradually with the increase of pH while in the alkaline range. Ferrous salts can significantly increase the efficiency of As(III) removal by coagulation treatment with mixed titanium salts as coagulant.

Abstract: Glutin-urea system was used in alumina gelcasting. And alumina suspension with 53vol% solid loading was prepared. Urea was decomposed by using urease therefore it was possible that hydrogen bond could be rebuilt. Alumina green bodies with 8.26MPa bending-strength were prepared when the dose of urease was 20 iu per milimole urea.

Abstract: The surfaces of Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3−δ (BSCFO) membranes were decorated by laser ablation treatment in order to increase the specific surface of these membranes. Arc shape stripes with width about 150µm and depth about 25µm were formed on the surface of these membranes. The oxygen permeation fluxes through these membranes were measured. Comparing with the membrane without laser ablation treatment, the oxygen permeation fluxes through the membranes with cross stripes pattern decorated on both sides after laser ablation treatment can increase by 34.7%.

Abstract: In order to utilization the molybdenum tailings which be deposited in large quantities. Test used it to prepare glass-ceramics as main raw material, TiO₂ as nucleation agents and CaO-Al₂O₃-SiO₂ system and wollastonite as the principal crystalline phase. Heat treatment system of glass-ceramics was based on the differential thermal analysis. The crystalline phase, microstructure and characteristics of glass-ceramics were analysis by XRD, SEM and physical, chemical properties test. The result shows that the performance of glass-ceramics was superior to the other types of building decoration stone.

Abstract: By introducing Ti vacancies for valence compensation, Nd-doped SrTiO₃ ceramics yielding the formula Nd_xSr_1-xTi_1-x/4O₃ (0≤x≤0.200) were successfully prepared by solid state reaction route in air. All the ceramics had single perovskite structure indexed by XRD profiles, while the symmetry changed from cubic to tetragonal with increasing x value. The grain size markedly decreased from ~30 μm for un-doped SrTiO₃ ceramics to ~1 μm for Nd_xSr_1-xTi_1-x/4O₃ ceramics with x=0.024, which was observed by scanning electron microscopy (SEM). The dielectric properties were measured at 1 kHz in ambient temperature. The dielectric constant was found to be leading to a maximum value of 5410 for as-sintered sample with x=0.104. The breakdown strength of all Nd_xSr_1-xTi_1-x/4O₃ samples was examined to be higher than 10 kV/mm. These results indicated that Nd-doped SrTiO₃ ceramics could be used to fabricate high voltage capacitors with enhanced energy storage density.