Papers by Keyword: Zro₂

Abstract: This research aims to synthesize ZrO₂ by combustion reaction in batches of 15 g of the product and to evaluate the calcination influence on the structural and morphological characteristic about synthesized sample. For the synthesis of ZrO₂, the stoichiometry of phase was established in accordance with the propellants and explosives chemical concept, whereas the stoichiometric coefficient φ =1. After the synthesis, the sample as synthesized was calcined at 600 and 700°C and subsequently characterized by XRD, SEM, textural analysis (BET) and FTIR. The results have shown to the sample as synthesized and then calcined at 600°C the majority phase formation of orthorhombic zirconia with monoclinic phase dashes. The temperature increase to 700°C, has been transformed a part of the orthorhombic ZrO₂ to a monoclinic phase, contributing to a surface area reduction of the samples, showing irregular agglomerates in morphology, with adsorption/desorption isotherms type IV and mesoporosity characteristic.

Abstract: A high-temperature resistant coating that can be used at 1300 °C was prepared in combination with silicone resin and fillers. The effect of ZrO₂ on high-temperature resistant and mechanical properties of the coating was studied by thermo gravimetric analysis (TG) and X ray diffraction (XRD) .The results shows that the performance of the coating is the best when the amount of ZrO₂ is 20wt%.the coating can resist 1300 °C, pencil hardness reaches 3H; Meanwhile, It can improve the adhesion and flexibility of the coating.

Abstract: Fused zirconia alumina has been broadly applied in abrasive industry due to its excellent strength and toughness. The aim of the present work is to investigate the effect of t-ZrO₂ content on grinding performance of fused zirconia alumina. Commercial fused alumina zirconia (ZA25) powder was used to fabricate the particle size of 380-830 μm abrasive samples for grinding experiment by pressure granulation and sintering at different temperatures. Phase identification of abrasives sintered at different temperatures was made by X-ray diffractometry and the correlations between t-ZrO₂ content and grinding performance of abrasive were also tested. The results showed that t-ZrO₂ content of abrasive decreased with sintering temperature increasing within a range of sintering temperatures from 1375 °C to 1450 °C. Grinding performance of abrasive was enhanced as increasing t-ZrO₂ phase in abrasive. The better the toughness of abrasive powders, the less shape and size change of abrasive powders during grinding, this is the reason why the high t-ZrO₂ phase contained fused zirconia alumina abrasive exhibit high grinding performance.

Abstract: Anodic oxidation of titanium (Ti), zirconium (Zr) and niobium (Nb) foils in fluoride ethylene glycol (EG) added to it 1 H₂O₂ as oxidant was done to produce oxide film with nanostructures at 40 V. Whilst arrays of aligned nanotubes were successfully formed on the surface of Ti and Zr respectively, anodic Nb₂O₅ was found to consist of nanoporous structure with pore size of ~ 20 nm. Despite long nanotubes were formed on both Ti (2 μm) and Zr (3 μm), the surface of the nanotubes suffered from severe dissolution, thinning the wall and collapsing them. Well defined, ordered surface structure of the nanotubes is required as they will be used as template for subsequent deposition of nanoparticles. This was achieved when Ti anodised in 5 ml H₂O₂ fluoride EG. With excess H₂O₂ etching at the surface occur more uniformly forming homogenous surface structure. α-Fe₂O₃ were then electrodeposited on this surface at-3 V from chloride solution and the mode of formation is believed to be due to electrogeneration of base at the surface of the TiO₂.

Abstract: Effect of ZrO₂ on sintering properties of MgO prepared from natural brine from Qarhan Salt Lake, crystalline bischofite and MgCl₂·6H₂O(AR) was studied. The results showed that ZrO₂ of addition exceeded 1 wt% had promotive effect on sintering of magnesia prepared from MgCl₂·6H₂O(AR). While 1.5 wt% ZrO₂ was added, the bulk density of sample was 3.37 g/cm³, and relative density was 94.1%. With 1 wt% ZrO₂, the bulk densities of magnesia prepared from crystalline bischofite and brine were 3.10 and 3.27 g/cm³, and the relative densities increased by 10.0% and 19.6%, respectively. The main reasons for promoting MgO sintering with ZrO₂ were that monoclinic phase ZrO₂ converted to cubic phase Zr₂O and excess ZrO₂ reacted with MgO to generate Mg_0.13Zr_0.87O_1.87, which activated lattice and promoted the diffusion of ions during sintering process. In addition, liquid phase sintering was also one of the main reasons for promoting the sintering of brine magnesia.

Abstract: The single and synergism effect of SiC and ZrO₂ nanoparticles on low temperature oxidation resistance of MoSi₂ were investigated by thermo-gravimetric analysis (TGA), phase and micrograph analysis of surface film. The results show that at the oxidation temperature of 600°C, the addition of 10%ZrO₂ results in obvious oxidation mass gain of MoSi_2, and discontinuous protective film forming on the surfaces, which makes “pesting” phenomenon still occur. The addition of 10%SiC accelerates the oxidation of MoSi₂, but compact SiO₂ protective film formed on the surface after some time of oxidation, avoiding the occurrence of large scope of “pesting” phenomenon. The synergism of 10%ZrO₂ and 10%SiC promotes the formation of compact, even silicate glass film on the surface of MoSi₂, as a result, significantly improves the low temperature oxidation resistance of MoSi₂.

Abstract: nanocomposite used widely with the development of nanotechnology, and the dispersion of different composition is important. ZrO₂ often used as the second phase to improve the toughness of Al2O3 ceramics^[1,. nanoAl2O3 and ZrO2 are added to water to prepare suspension, and PVP was used as dispersant to improve the dispersion of suspension. The suspension of Al₂O₃ and ZrO₂ adjusted from 2 to 11 with the addition of dispersant is 0.5%. The flocculation of suspension was observed after 3h, 6h, 12h and 24h. Result shows that two kinds suspension dispersant better in acid liquid than in alkaline and natural liquid. The pH values that are choose as the best dispersion and flocculation are 5 and 7. Morphology and element distribution of composite powder are tested in the SEM. Results show that the composite powder is finely disseminated.

Abstract: This article describes the alumina ceramic mixed with two kinds of additives in order to improve the performance of ceramic, such as mixed with submicron ZrO₂ and MnO₂ Monoclinic zirconia (m-ZrO₂) and tetragonal zirconia (t-ZrO₂) of reversible phase transition of volume change is used to improve the toughness and wear resistance of composite alumina ceramic. Through doing various tests about fired products, including hardness testing, SEM test and bulk density measurement, we can understand the microstructure and mechanical properties of samples.

Abstract: The synthesis used urea and Zr (NO₃)₄·5H₂O as material to prepare tetragonal-ZrO₂ nanocrystals through microwave-induced combustion process. The tetragonal-ZrO₂ nanocrystals were characterized by X-ray diffraction (XRD). The effect of Zr⁴⁺/urea molar ratio on the synthesis of tetragonal-ZrO₂ were studied. It was found that tetragonal-ZrO₂ crystal would be better when the Zr⁴⁺/urea molar ratio was larger than 1:3.The SEM images of the samples showed the hollow structures formed at different levels of molar ratio of Zr⁴⁺/urea. This method is a simple but effective route to prepare tetragonal-ZrO₂ nanocrystals.

Abstract: Zinc Crystal Glaze has its limits in practical use of commercial glaze due to the sensitive firing schedule. In order to overcome these limits, and to improve the practical usage, this study is aimed to develop a stable zinc crystalline glaze. This study altered the quantity of nuclear formation of zinc crystal glaze in order to control the willemite (Zn₂SiO₄) formation in the glaze. The addition of ZrO₂ to zinc crystal glaze influences the quantity of nuclear formation and its preservation; thus ZrO₂ was used to control the optimal firing temperature and the size of the crystal formation in the glaze to find a zinc crystal glaze capable of withstanding various ranges of temperatures.