Papers by Keyword: Zirconium Dioxide

Abstract: The temperature dependence of the thermal conductivity of plasma‑sprayed ZrO₂-5 wt.% CaO, (ZrO₂-5 wt.% CaO)-10 wt.% Ni, and (ZrO₂-5 wt.% CaO)-30 wt.% Ni coatings was investigated. A combined experimental and numerical approach was employed, comprising specimen heating with a propane–oxygen torch with in situ temperature field measurements and numerical simulation using COMSOL Multiphysics®. Thermal conductivity was calculated via an iterative solution of the inverse heat conduction problem. It was found that thermal conductivity increases with increasing Ni content: for the ZrO₂/CaO ceramic coating, thermal conductivity in the temperature range 20–1100°C ranged from 0.76 to 1.22 W·m⁻¹·K⁻¹, whereas for the metal–ceramic coatings containing 10% and 30% Ni, the values were 1.11–1.87 W·m⁻¹·K⁻¹ and 1.71–4.18 W·m⁻¹·K⁻¹, respectively. These results provide valuable insights for the design and optimization of thermal barrier coatings.

Abstract: In this present work, Pristine and 10 at.% of In-doped ZrO₂thin films were deposited by spray pyrolysis technique at optimized substrate temperature [Ts=450°C]. The greater the proportion of Indium ion dopant, significantly influences the structural, optical, morphological, and electrical properties of deposit thin films. The deposited thin films were characterized with XRD, UV-Vis, PL, HR-TEM with EDAX, and I-V characterization Studies. The crystallinity of Zirconium dioxide thin film was improved and size of crystals were decreased by Indium ion substitution. Optical study revealed that the film's optical transmittance enhanced from 80.3 percent to 86.5% as a result of the dopant. The energy bandgap increased at 4.93eV - 4.57eV, systematically. HR-TEM studies show the homogeneous particle distribution and denser surface texture at 22nm and 19nm of average particle agglomerations. The study of PL emission shows an increase in intensity on the blue emission band with enriched crystalline quality. The conductivity of the ZrO₂ was higher affected by Indium ion may result in increased conductivity, with low resistivity property.

Abstract: Preparation of boride by chemical vapor deposition (CVD) is sensitive to oxygen, subtle changes in oxygen concentration during the deposition of ZrB₂ can induce the formation of Zirconium dioxide (ZrO₂) with a novel nanoplate-stacked structure and nanowire structure. The ZrO₂ nanostructure changed with - oxygen concentration. Nanowires with uniform size of 50-100 nm in diameter and over 100 μm in length were obtained at high oxygen concentration, while highly-ordered nanoplate arrays were obtained at low oxygen concentration. Both of these nanostructures were grown in situ on the surface of ZrB₂-coating. In this paper, the preparation method of novelty ZrO₂ nano-structures grown in situ was provided, the morphologies and compositions of the nano-structural ZrO₂ were characterized and the formation mechanism was proposed, which also provides experimental basis for the industrial morphology control of ZrB₂ deposited by CVD method.

Abstract: The prospects for improving microhardness and strength characteristics of corundum ceramics (Al₂O₃) modified by zirconium dioxide (3YSZ) are investigated. Ceramic samples are molded by semi-dry pressing followed by sintering. It is experimentally established that an increase in 3YSZ content in Al₂O₃/3YSZ composite ceramics fired at temperatures above 1450 ^oC increases strength and decreases microhardness. Ceramics of optimal composition (100–x) Al₂O₃–x 3YSZ, x = 5–10 wt. % 3YSZ has high strength and hardness values, and the average value is 700MPa and 22.3±1.8 GPa.

Abstract: The article presents the results of studies on preparation of amorphous zirconium dioxide from zirconium nitrate by its hydrolysis in the presence of oxalic acid. It is determined that the balance of reagents taken for synthesis (1 ml 0,025 M ZrO(NO₃)₂ is 1.35 ml 4 M HOOC-COOH), and the optimum temperature of the received gel drying, which is 230 ̊С, is established, too. Morphology of the obtained ZrO₂ samples was explored. It has been found that the calcining temperature is independent of the size and shape forming irregular agglomerates, consisting of smaller spherical particles, whose diameter varies between 50 and 300 nm. The X-ray analysis of the sample is represented, which showed a low degree of crystallinity of the substance. IR spectroscopy data showed the presence of zirconium dioxide-characteristic peaks on the IR spectrum. The same spectrum reflects the presence of a large amount of sorbed water in the obtained sample, as well as peaks characteristic of the gas adsorbed by the sample from the environment.

Abstract: When zirconium alloy is corroded, an oxide film is formed on the surface, which hinders the ion transfer during the corrosion process. Therefore, the analysis of the oxide film is an important part of the research on the corrosion resistance of zirconium alloys. In this paper, two kinds of Zr-Sn-Nb alloys were corroded in 400 °C/10.3 MPa pure steam and 500 °C/10.3 MPa pure steam in autoclave to obtain samples with oxide thickness of 14 um and 18 um respectively. Then they were annealed at 800 °C at a pressure of 10^-4 Pa for 18 h. XRD and WDS studies were used to analyze the structure and oxygen content of the oxide film after annealing. The results indicate that the oxide films of alloys change from zirconium dioxide to zirconium after annealing. The oxygen diffuses into the substrate and its content decreases continuously with increasing diffusion distance. Combined with the SEM analysis of cross-section samples, it is found that the annealed samples are composed of several layers. An oxygen-saturated zirconium layer, a transitional layer with micro-cracks, an oxygen-dissolved α-Zr layer and a β-Zr layer are identified. Based on these results, the mechanism of the ion transfer in the oxide film during annealing is analyzed deeply. It is proposed that space charges in the oxide film have a major impact on deoxidation kinetics. This study provides a new research method for the corrosion mechanism of zirconium alloys.

Abstract: The paper discusses application possibilities of nanostructured crystals of partly stabilized zirconium dioxide in greaseless running of plain bearings in order to support normal operation of friction joints at high temperatures and in aggressive conditions. This issue is a burning one in different industries, e.g. circulating pumps in nuclear power engineering, mixing units of crystal synthesizing lines in chemical engineering; motors in space-based targets, rotors of guide blades in axial compressors of airplane engines, supports of high-speed gas centrifuges. Micro-hardness was investigated, and friction surfaces were explored using methods of X-ray, electron-microscopic and element analysis to find a wear mechanism for crystals ZrO₂- Y₂O₃. The paper reports on tribological properties of partly stabilized zirconium dioxide crystals and prospects of their industrial usage.

Abstract: The high-intensity electron-beam treatment of the submillisecond duration is used to treat the surface layer of sintered zirconium dioxide ceramics partially stabilized by yttrium. The electron beam irradiation parameters are obtained allowing the structural modification under a rapid solidification. It is shown that the structural modification of ceramics under melting conditions with the subsequent rapid solidification is accompanied by the formation of a sub-microcrystalline structure that fosters a multiple magnification (≈ 2 times) of the modified layer hardness.

Abstract: To improve the preparation technology and mechanical properties of carbon/carbon composites, a kind of Zirconium dioxide modified Carbon/carbon (C/C–ZrO2) composites were prepared by Sol-Gel Process combined with isothermal chemical vapor infiltration (ICVI) method. This method could shorten preparation cycle greatly to reduce the cost. The microstructures and mechanical properties of the C/C–ZrO2 composites were investigated. The results indicate that the ZrO2 modified phase is uniformly distributed in the carbon matrix, the bending strength and modulus of C/C–ZrO2 composites are much higher than unmodified C/C composites due to its particle toughening and fiber toughening.

Abstract: Formation of ZrO₂-5 wt.% Y₂O₃ nanostructured powders in glycine-nitrate combustion synthesis was investigated and the effect of "glycine-to-NO₃^-" ratio and heating method on the reaction product composition and particle morphology studied. Urea and ammonium nitrate additives were used to optimize the regime of the process. The effect of these reagents on gas generation required for the dispersion of particles, and on the process temperature was investigated.