Papers by Keyword: Zro2

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Authors: Qiang Li, Dan Yu Jiang, Ya Jun Fan, Cheng Zhang
Abstract: This paper reports a novel non-aqueous solvent chemical process to prepare nano ZrO2 powders. ZrOCl2•6H2O and urea were directly dissolved into an organic solvent of glycol. After this solution was put into an oven and reacted at 950C for 2 h, a transparent gel was obtained. As-received gel was heated at 2100C for 5 hrs to remove glycol, and dry powders were obtained. Then the powders were calcined at 7500C, and monoclinic phase of ZrO2 was obtained. With different concentration of ZrOCl2, a range of nano ZrO2 powders were obtained. Furthermore, a surfactant of polyglycol was added into the solution to improve the dispersion of nano-particles in the gel. XRD analysis confirmed the monoclinic phase of ZrO2. SEM imaging showed the characteristics of nanoparticles. BET analysis was employed to test the aggregation of as-received nano ZrO2 particles. Considering the effects of both the concentration of ZrOCl2 and the surfactant, the optimized synthesis process of nano ZrO2 particles was formed.
Authors: Hyun Hwi Lee, Seung Ho Kim, Bhupendra Joshi, Soo Wohn Lee
Abstract: Oxide ceramics such as alumina and zirconia are industrially utilized as cutting tools, a variety of bearings, biomaterials, and thermal and corrosion-resistant coatings due to their high hardness, chemical inertness, high melting point, and ability to retain mechanical strength at elevated temperatures. In this research, the effect of other ceramic additives (TiO2) and h-BN within alumina(α-Al2O3) and yttria-stabilized tetragonal (Y-TZP) composite was studied with respect to the mechanical and tribological properties. The lowest coefficient of frction of 0.45 was observed for the ZTA ceramic composite with hBN-TiO2. The highest hardness, fracture toughness and flexural strength were obtained as 15.7GPa, 5.2MPam-1/2, 712MPa, respectively.
Authors: B. Kasanická, Thomas Wroblewski, Volker Schulze, Detlef Löhe
Abstract: Analysis of the residual stress state, the microstructure and surface topography of ceramic microcomponents made of Y2O3-stabilized ZrO2 produced by micro powder injection moulding were performed. During the production of the microspecimens sintering conditions were varied. The measurement of residual stresses has been carried out using the MAXIM (MAterials XRay IMaging) diffractometer at HASYLAB beamline G3 at DESY in Hamburg (Germany). The microstructure and surface topography of differently moulded specimens were examined using a scanning electron microscope (SEM) and a confocal white light microscope type NANOFOCUS. The findings are used to establish correlations between process parameters and characteristics of the microcomponents. These will allow to improve the production process with respect to the mechanical properties of the microcomponents.
Authors: Melis Arin, Hilal Yazici, Gultekin Goller
Abstract: In order to study bicompability properties of fully dense ZrO2 ceramics containing 2-3 mol% Y2O3 stabilizer, and ZrO2-TiN composites containing 1-1.75 mol Y2O3 and 1 mol% Nd2O3 stabilizers, and electrical conductive TiN particles (40-60 vol%), cell viability was evaluated based on the reduction of tetrazolium salt to formazan crystals by living cells, the alkaline phosphatase production was investigated, and nitrite quantification was done for indirect evaluation of osteoblast NO production. The samples were defined biocompatible since there is not any significant change observed in the physiological functions of the cells when incubated together.
Authors: Huai Xiu Lu, Bin Deng, Long Quan Shao, Yuan Fu Yi, Jie Liu, Wei Wei Zhang, Ning Wen
Abstract: Objective: To evaluate the biological safety of a colored zirconia ceramic in terms of cellular toxicity and a skin sensitivity test. Methods: the cytotoxicity of the ceramic was evaluated by a molecular filtration method and skin irritation activity of the composite was assessed via intradermal injection of a guinea pig test solution, by inducing, enhancing, and stimulating an allergic response after local tissue exposure. Results: cell-coated filter paper in contact with test material showed the appearance of intracellular blue dye at the same staining density as in control samples, leading to a 0 toxicity rating. Guinea pigs showed no obvious erythema or edema from the irritation test, such that the assessment of colored zirconia ceramic skin allergy response in guinea pig was 0%. Conclusion: this colored zirconia ceramic showed low cytotoxicity and elicited no allergic skin inflammation response, indicating good overall biological safety under these conditions.
Authors: Huai Xiu Lu, Bin Deng, Long Quan Shao, Yuan Fu Yi, Jie Liu, Wei Wei Zhang, Ning Wen
Abstract: Objective: To evaluate the biological safety of a colored zirconia ceramic regarding its hemolytic activity and short-term systemic toxicity. Methods: Fresh anti-coagulating rabbit blood was mixed with test materials and the hemolytic activities detected spectrophotometrically. Suspensions of the ceramic were fed to rats for one week while monitoring food consumption and relative growth rate and with subsequent pathology examinations of vital organs and tissues. Results: The hemolytic activity of the ceramics was <5%, and rats in all groups showed weekly relative growth rates of food utilization and body weight with no statistically significant differences. There were also no pathological changes observed among the various examined organs between the experimental and control groups. Conclusions: This colored ceramic showed good biocompatibility in terms of hemolytic activity and short-term systemic toxicity.
Authors: S.H. Kim, I.S. Byun, I.R. Hwang, J.S. Choi, B.H. Park, S. Seo, Man Jong Lee, D.H. Seo, E.J. Jeoung, D.-S. Suh, Y.S. Joung, I.K. Yoo
Abstract: Polycrystalline ZrO2 and yttria-stablilized ZrO2 thin films have been deposited on Pt/Ti/SiO2/Si substrates by pulsed laser deposition methods. Pt/ZrO2/Pt and Pt/YSZ/Pt capacitor structures show giant conductivity switching behaviors which can be utilized for nonvolatile memory devices. Maximum on/off ratio of 106 and good endurance even after 105 times conductivity switching are observed in a typical Pt/ZrO2/Pt whose ZrO2 film has been deposited at 100 °C and an oxygen pressure of 50 mTorr. The Pt/ZrO2/Pt structure exhibits two ohmic behaviors in the low voltage region (V < 1.4 V) depending on the value of previously applied high voltage and Schottky-type conduction in the high voltage region (1.4 V < V < 8.9 V). It seems that conductivity switching behaviors in our Pt/ZrO2/Pt structure result from the changes in both the Schottky barrier and the bulk conductivity controlled by applied voltages. A Pt/YSZ/Pt capacitor structure has more stable reset voltage and current state than a Pt/ZrO2/Pt capacitor structure. Moreover, a Pt/YSZ/Pt capacitor structure shows higher Conductivity than a Pt/ZrO2/Pt capacitor structure, which may result from substitution of Y3+ ions for Zr4+ ions.
Authors: Chao Zhao, Gert Roebben, Marc M. Heyns, Omer Van der Biest
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