Papers by Keyword: Y-TZP

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Authors: R.H.L. Garcia, Valter Ussui, Nelson Batista de Lima, Dolores Ribeiro Ricci Lazar
Abstract: The addition of alumina in a zirconia stabilized in a tetragonal phase matrix enhances ceramic hardness and inhibits the tetragonal → monoclinic phase transformation of zirconia when exposed to an aqueous environment. These characteristics are important for applications such as bioceramics and structural materials. For these purposes, the strict control of powder synthesis and the processing conditions are vital to tailor the ceramic characteristics. This work evaluates the influence of 20 wt% alumina in a Y-TZP matrix on powder characteristics, obtained by coprecipitation route, and calcined from 600 to 1200°C for 1 and 3 hours. The powders obtained were characterized by X-ray diffraction, scanning electronic microscopy, laser diffraction and gaseous adsorption (BET). The results reveal that presence of Al3+ inhibits the crystallization of composite at lower temperatures.
Authors: Yoshinobu Motohashi, Makoto Kikuchi, Takaaki Sakuma, Eitaro Yukutake, Isao Kuboki
Abstract: During superplastic deformation (SPD) of tetragonal zirconia polycrystals containing 3 mol% yttria (3Y-TZP) at high strain-rates, a number of crack-like flat cavities having very narrow gaps lying along grain boundaries mostly normal to the tensile axis are produced in addition to conventional cavities. The formation and growth of these flat cavities are responsible for the strain softening that appears on the true stress versus true strain curves. The growth and coalescence of the flat cavities were a main cause of the degradation of elongation to fracture. We have found that a simple treatment, in which the superplastic deformation is temporally stopped, i.e., the cross-head movement is reversed and accordingly the applied load is removed, and then the specimen is kept at the test temperature for several minutes, is surprisingly effective to reduce the flat cavities. Carrying out this simple treatment repeatedly, after 30% nominal stain during the SPD, led to an increace in total elongation by about three times larger than that of a specimen not subjected to such a treatment. This treatment can also recover the strength and accordingly mechanical properties of the superplastically deformed 3Y-TZP to that of the undeformed state. This finding is believed to be quite significant for practical applications of superplasticity in 3Y-TZP, because the flat cavities can be closed very simply by keeping a product at the forming temperature after or during the superplastic forming process.
Authors: A.J.A. Winnubst, S. Ran, K.W. Wiratha, D.H.A. Blank, H.R. Pasaribu, J.-W. Sloetjes, D.J. Schipper
Authors: Anelyse Arata, Tiago Moreira Bastos Campos, João Paulo Barros Machado, Walter Kenji Yoshito, Valter Ussui, Nelson Batista de Lima, Rubens Nisie Tango, Dolores Ribeiro Ricci Lazar
Abstract: Yttria-stabilized tetragonal zirconia polycrystals (Y-TZP) is used for dental prosthodontics, however, it can present accelerated tetragonal to monoclinic phase transformation in oral environment. The aim of this study was to compare the behavior of a Y-TZP synthesized in laboratory by the coprecipitation method to a commercial Y-TZP, after hydrothermal aging in pressurized reactor (150°C/ 35 hours). The discs were sintered at 1520°C for two hours. The kinetics curve of phase transformation was determined through the data collect by XRD diffractograms treated by the Rietveld method. The experimental and commercial control groups did not present monoclinic phase. After 35 hours of aging, the experimental group presented 69% of monoclinic phase compared to 67% for the commercial group. Scanning electron microscopy and atomic force microscopy images suggested that the commercial group presented heterogeneity of grain size and that the experimental group was more homogeneous. All groups presented superficial degradation process.
Authors: Chang Tian Huan, Jin Feng Xia, Dan Yu Jiang, Qiang Li
Abstract: This paper compares the low-temperature aging performance of 5Y-TZP and 8Y-TZP by coprecipitation and solid-phase synthesis methods in the steam. Analysis the weight changes of samples using analytical balance, and the sample surface microstructure and phase changes with SEM, XRD. The results show that the content of Y2O3 and synthesis method all affect the aging properties of zirconia ceramics; solid-phase synthesis of 8Y-TZP has the best anti-aging performance.
Authors: Sabrina Conoci, Cesare Melandri, Goffredo de Portu
Authors: Zhen Tao Shang, Ping Li, Gui Zhi Xie
Abstract: Engineering ceramics have been extensively used as structural materials in modern manufacturing industries due to their excellent properties. High Efficiency Deep Grinding (HEDG) with Electrolytic In-process Dressing (ELID) process can realize the stabilized and controlled grinding process of engineering ceramics, but there lies many questions to be done. In the light of Y-TZP materials, the grinding process of HEDG with ELID was optimized, and comparisons were made between HEDG with ELID and HEDG without ELID process for Y-TZP ceramics, and mechanisms of HEDG with ELID were revealed.
Authors: Dolores Ribeiro Ricci Lazar, Christiane A.B. Menezes, Valter Ussui, E. Fancio, Nelson Batista de Lima, Ana Helena A. Bressiani, José Octavio A. Pascoal
Authors: A. Feder, Daniel Casellas, Luis Llanes, Marc Anglada
Authors: B. Basu, R.G. Vitchev, Jef Vleugels, J.P. Celis, Omer Van der Biest
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