Papers by Keyword: Zro2

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Authors: Ming Zhi Yang, Ching Liang Dai
Abstract: The project presents an ammonia sensor with heater on-a-chip manufactured using the commercial 0.18 μm CMOS (complementary metal oxide semiconductor) process. The ammonia sensor is composed of a sensitive film, interdigital electrodes and a polysilicon heater. The sensor is a capacitive type and the sensitive film is ZrO2 that is prepared by sol-gel method. The sensor requires a post-process to remove the sacrificial oxide layer and coat the ZrO2 film on the interdigital electrodes. When the sensitive film absorbs ammonia vapor, the capacitance of the sensor generates a change. Experimental results show that the sensitivity of the ammonia sensor is 2.47 pF/ppm at 270 °C.
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: Le Shan Chan, Yu Hao Chang, Kung Yen Lee
Abstract: ZrO2 films were deposited on C-face 4H-SiC substrates by using an RF sputter at a temperature of 200°C. Then, ZrO2 films were treated with RTA (rapid thermal annealing) process in Argon (Ar) ambient at 600°C, 700°C and 800°C for 4 minutes, respectively. The samples with RTA process show the lower leakage currents. As the measure temperature increases from room temperature (RT) to 150°C, the dielectric breakdown voltage reduces from 3 V to 1 V. The difference between quasi C-V characteristics and high frequency C-V characteristics at 1 MHz becomes larger with increasing RTA temperature. The C-V curves also shift to the left side as the measure temperature increases from RT to 150°C. It also shows the ledge on the C-V curves of samples with RTA at elevated measure temperature.
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: M. Kolafová, A. Nežiková, J. Kamprle, J. Strnad, Z. Strnad
Abstract: The apatite-forming ability of zirconia ceramics subjected to various surface treatments was investigated. Zirconia samples (Y-TZP) in the form of disks and rods were sandblasted and chemically etched in strong acids (HF, H3PO4, H2SO4) and/or in NaOH solution at an elevated temperature. The surface properties were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), wettability and roughness measurement. The ability to form bone-like apatite on the surface was evaluated by immersion of the sample in simulated body fluid, which has ion concentrations nearly equal to the inorganic part of human blood plasma. The effect of applied surface treatment on mechanical properties was investigated. Sandblasting resulted in significant increase of roughness. Chemical etching in H3PO4 and H2SO4 caused reduction of contact angle but this effect was lost when subsequent alkali treatment was applied. Etching in NaOH, H2SO4 and two-step treatment combining H2SO4 or H3PO4 with NaOH resulted in the formation of bone-like apatite after immersion in simulated body fluid. These results indicate that sandblasted and chemically etched zirconia may be capable of direct bonding with living bone through an apatite layer created on its surface in a human environment. To avoid possible mechanical failure sandblasting conditions need further optimization.
Authors: R. Yuvakkumar, Sun Ig Hong
Abstract: We report successful synthesis of baddeleyite type monoclinic zirconium oxide nanocrystals formation. The product mixture of zirconium incubated at room temperature for 7 days were thoroughly investigated employing X-ray diffraction, Raman spectroscopy and transmission electron microscopy studies. XRD and Raman studies revealed the formation of baddeleyite type monoclinic zirconium oxide nanocrystals. TEM studies revealed the nanocrystal formation with size ranging from 100 nm to 200 nm.
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.
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