Loading...
Search for: zirconia
0.007 seconds
Total 98 records

    Interface formation and bond strength in 3Y-TZP/Cr composite bilayers produced by sinter–joining [electronic resource]

    , Article Materials Science and Engineering: A ; Volume 527, Issue 3, 15 January 2010, Pages 449–453 Dourandish, M ; Simchi, A. (Abdolreza) ; Hokamoto, K ; Tanaka, S ; Sharif University of Technology
    Abstract
    The mechanism of interface formation during sinter–joining of nanostructured yttria stabilized zirconia (27 nm) compacts with chromium powder was investigated. The effect of sintering atmosphere, i.e. argon or vacuum, was studied. Microstructural evaluation and phase formation was examined by scanning electron microscopy (SEM), electron probe micro-analysis (EPMA), and micro-focused X-ray diffraction (MFXRD) methods. It is shown that spreading and evaporation–condensation mechanisms are responsible for the interface formation. An improved joint shear-strength was obtained after sintering in vacuum (74 MPa) compared with argon (41 MPa). The result of MFXRD indicated formation of Cr-island at... 

    Preparation and Investigation of Properties of Zirconia Coatings on Zirconium Substrate by MAO Method

    , M.Sc. Thesis Sharif University of Technology Zareian, Shayan (Author) ; Faghihi Sani, Mohammad Ali (Supervisor) ; Kokabi, Amir Hossain (Supervisor)
    Abstract
    Zirconium is one of the most applicable metals in the production of chemical materials’ industry due to its great corrosion resistance. Coating method of microarc oxidation is a novel method to manufacture oxide coatings on metal substrates. Lots of studies have been done on the creation of these coatings on light metals such as Aluminum, Magnesium and Titanium hitherto; however, there is a scarcity regarding manufacture of zirconium oxide on zirconium metal via MAO method. In the current study, aiming to create proper zirconia coatings on zirconium substrate, firstly, by the change of process parameters like current waveform, electrolyte concentration, current density, time and frequency,... 

    A Study on Properties of Composite Coating with Al2O3 Base Prepared by Hard Anodizing with ZrO2 Nanoparticles

    , M.Sc. Thesis Sharif University of Technology Motamen, Ali (Author) ; Afshar, Abdollah (Supervisor)
    Abstract
    In this study anodized none composite and composite film containing ZrO2 nanoparticles were prepared on 1050 Al Alloy using hard anodizing method in sulfuric and oxalic acid mixed solution by pulse Currents. The microstructure and properties of the film were studied by field emission scanning electron microscopy with EDS analyzer and XRD diffraction and friction wear test were performed to evaluate the mechanical properties of coating . Results indicate that the composite film with ZrO2 nanoparticles have reduced friction coefficient with high micro hardness friction coefficient of composite film can be small as 0.16 which is much smaller than that 0.39 of none composite film. Micro hardness... 

    Phase formation during sintering of nanocrystalline zirconia/stainless steel functionally graded composite layers [electronic resource]

    , Article Journal of Materials Letters ; 15 February 2011, Volume 65, Issue 3, Pages 523–526 Dourandish, M ; Simchi, A. (Abdolreza) ; Hokamoto, K ; Tanaka, S ; Sharif University of Technology
    Abstract
    Microstructural development and phase formation at the interface of yttria stabilized zirconia (3Y-TZP)/430L stainless steel composite layers produced by co-sintering method were studied by SEM, HRTEM, micro-focus XRD, and EPMA. Formation of a rich chromium boundary layer at the interface was noticed, which revealed Cr aggregation at the interface at the elevated temperatures. Misfit dislocations were also observed at the joint interface to tackle the mismatch crystallographic orientations between the ceramic and metal layer. The results of the micro-focus XRD showed formation of no new phases at the boundary zone. Microstructural studies also revealed a retarded grain growth in the... 

    The effects of composition and sintering conditions on Zirconia Toughened Alumina (ZTA) nanocomposites

    , Article Advanced Materials Research, 7 December 2009 through 9 December 2009 ; Volume 93-94 , December , 2010 , Pages 695-698 ; 10226680 (ISSN) ; 9780878492855 (ISBN) Esfahani, H ; Nemati, A ; Salahi, E ; Sharif University of Technology
    2010
    Abstract
    Zirconia Toughened Alumina (ZTA) Nanocomposites were prepared using Nano sized Zirconia (ZrO2) powders doped with 3% mol of yttria (Y 2O3) nanopowders. Diffusion of α-alumina (Al 2O3) nanoparticles as well as yttria into the Zirconia lattice network drives monoclinic - tetragonal martensitic transformation. Zirconia toughened alumina (ZTA) composites containing different amount of partially stabilized Zirconia (PSZ) 5, 10, 15 and 20% mol, were prepared via wet mixing and axial pressing. After sintering at different temperatures,1450, 1550 and 1650 °C, phase change in the samples were monitored. X-ray diffraction patterns showed that at constant composition, tetragonal zirconia was increased... 

    Energy aspects and workpiece surface characteristics in ultrasonic-assisted cylindrical grinding of alumina-zirconia ceramics

    , Article International Journal of Machine Tools and Manufacture ; Volume 90 , 2015 , Pages 16-28 ; 08906955 (ISSN) Zahedi, A ; Tawakoli, T ; Akbari, J ; Sharif University of Technology
    Abstract
    Ultrasonic assisted grinding is a novel method for improving the grinding process of difficult-to-cut materials. In the present research a novel setup has been designed and manufactured for utilizing ultrasonic vibrations in external cylindrical grinding. The designed ultrasonic head vibrates a rotating workpiece in axial direction. An alumina-zirconia ceramic (AZ90) has been selected as the workpiece material. Energy aspects and workpiece surface characteristics of ultrasonic assisted cylindrical grinding (UACG) and conventional cylindrical grinding (CG) processes have been analytically modeled and corresponding grinding experiments have been performed. The combined kinematics of the... 

    Characterization of yittria stabilized zirconia/titania core-shell powders synthesized via air plasma spray method

    , Article Materials Chemistry and Physics ; Volume 200 , 2017 , Pages 280-286 ; 02540584 (ISSN) Dadfar, M. R ; Rahimipour, M. R ; Vaezi, M. R ; Gholamzadeh, A ; Sharif University of Technology
    Abstract
    In this study, Yittria Stabilized Zirconia/Titania powders synthesized via air plasma spray (APS) method such as morphology changes and phase transformations of core-shell structure characterized. Phase analysis of powders was performed by XRD. The crystallite size and lattice strain of YSZ/TiO2 core-shell structure was calculated by Williamson-Hall method. Morphology was observed with scanning electron microscope. EDS and map analysis were used for core-shell characterization. Results revealed that all TiO2 nano particles were melted around YSZ powders with the thickness between 1 up to 5 μm. After spraying the YSZ/TiO2 mixture in water, strain values increased but crystallite size... 

    Reverse martensitic transformation in alumina-15 vol% zirconia nanostructured powder synthesized by high energy ball milling

    , Article Journal of Alloys and Compounds ; Volume 459, Issue 1-2 , 2008 , Pages 531-536 ; 09258388 (ISSN) Maneshian, M. H ; Banerjee, M. K ; Sharif University of Technology
    2008
    Abstract
    In the present work, three alumina-15 vol% zirconia composites with Y2O3, MgO as dopants and without oxide as dopant have been investigated. High energy ball milling (HEBM) provides the positive thermodynamic driving force for monoclinic to tetragonal transformation and it reduces starting temperature for the reverse martensitic transformation, meanwhile mobility of zirconium cations and oxygen anions are enhanced in zirconia by HEBM. The general, albeit heuristic, reasoning is corroborated by nanocrystallity, particle size and also the retained monoclinic seem to play an important role. After 10 h HEBM, approximately 28% zirconia tetragonal phase is achieved. Non-stoichiometric tetragonal... 

    Investigation on Mechanical Properties of Alumina Spinel Zirconia Nanocomposites Fabricated Through Gelcasting Process

    , M.Sc. Thesis Sharif University of Technology Khoshkalam, Mohamad (Author) ; Faghihi Sani, Mohammad Ali (Supervisor)
    Abstract
    Zirconia Toughened Alumina (ZTA) is a well-known ceramic matrix composite due to its high fracture toughness and good mechanical properties. Addition of spinel (MgAl2O4) to ZTA inhibits alumina grain growth and produces phase boundaries with low strength. This phenomenon leads to formation of a ceramic matrix composite with special mechanical properties such as high temperature super plastic deformation. However, the room temperature mechanical properties of alumina-spinel-zirconia (AMZ) composite such as fracture toughness were rarely investigated by researchers. In this research the AMZ nanocomposite powders were synthesized via solution combustion method. The dense AMZ composite samples... 

    Preparation and Investigation of ZrO2 Coating on AZ31 Alloy Processed by Plasma Electrolytic Oxidation Method

    , Ph.D. Dissertation Sharif University of Technology Eienkhah, Feryar (Author) ; Faghihi Sani, Mohammad Ali (Supervisor)
    Abstract
    Magnesium alloys are used in various industries, due to their excellent combination of low density, high strength to weight ratio and biocompatibility. However, a main drawback of Mg alloys is their poor corrosion and tribological behavior which could be improved by different surface treatments such as plasma electrolytic oxidation (PEO). Recently, PEO method as a simple and economic process is used to provide thick ceramic coating on Mg alloys. Based on some problems in zirconia coating on Mg substrates, two step PEO coating was introduced. The aim of the present study is to prepare and investigate the properties of zirconia-containing coating by two-step PEO process on the AZ31 Mg alloy... 

    Effect of SiO2 content on Y-TZP/Al2O3 ceramic-nanocomposite properties as potential dental applications

    , Article Ceramics International ; Volume 46, Issue 8 , 2020 , Pages 10910-10916 Rahimi, S ; SharifianJazi, F ; Esmaeilkhanian, A ; Moradi, M ; Safi Samghabadi, A. H ; Sharif University of Technology
    Elsevier Ltd  2020
    Abstract
    Yttria-stabilized tetragonal zirconia polycrystals (Y-TZP) have been widely applied in fixed partial prostheses as well as dental uses i.e. a substructure for crowns. However, Y-TZP has limited applications, which is due to the presence of defects in its microstructure introduced during the manufacturing process. Accordingly, due to Y-TZP limitations, the novel (X)Y-TZP- 20Al2O3-(80-X) SiO2 (X = 65, 70 and 75) ceramic nanocomposites were successfully fabricated via the powder metallurgy method. X-ray diffraction (XRD) patterns of commercial powders showed the stabilization of monoclinic zirconia (ZM) by increasing the silica content. In order to determine the fracture load and micro-bending... 

    Pressureless sintering of 3Y-TZP/stainless-steel composite layers

    , Article Journal of the American Ceramic Society ; Volume 91, Issue 11 , 2008 , Pages 3493-3503 ; 00027820 (ISSN) Dourandish, M ; Simchi, A ; Tamjid Shabestary, E ; Hartwig, T ; Sharif University of Technology
    2008
    Abstract
    A pressureless sintering method was utilized to fabricate metal/ceramic joints out of yttria-stabilized zirconia (3Y-TZP) and stainless steels (SS). Ultrafine (150 nm) and nanoscale (75 nm) 3Y-TZP particles and micrometric 17-4PH, 316L, and 420 SS (<31 μm) powders were tested. Isothermal and nonisothermal sintering behaviors of the powders and composite layers in hydrogen, argon, and vacuum atmospheres were examined. It was found that the mismatch strain between the zirconia ceramic and SS during cosintering is significant, which leads to bond cracking and joint failure. Nevertheless, interlayer diffusion of Zr, Fe, and Cr and the formation of a reaction zone, particularly during vacuum... 

    Densification and grain growth of nanocrystalline 3Y-TZP during two-step sintering

    , Article Journal of the European Ceramic Society ; Volume 28, Issue 15 , 2008 , Pages 2933-2939 ; 09552219 (ISSN) Mazaheri, M ; Simchi, A ; Golestani Fard, F ; Sharif University of Technology
    2008
    Abstract
    Two-step sintering (TSS) was applied on nanocrystalline yttria tetragonal stabilized zirconia (3Y-TZP) to control the grain growth during the final stage of sintering. The process involves firing at a high temperature (T1) followed by rapid cooling to a lower temperature (T2) and soaking for a prolonged time (t). It is shown that for nanocrystalline 3Y-TZP (27 nm) the optimum processing condition is T1 = 1300 °C, T2 = 1150 °C and t = 30 h. Firing at T1 for 1 min yields 0.83 fractional density and renders pores unstable, leading to further densification at the lower temperature (T2) without remarkable grain growth. Consequently, full density zirconia ceramic with an average grain size of 110... 

    Partially stabilization of Zirconia and its effects on the Magnesia - Spinel refractory properties

    , Article UNITECR '05 - Unified International Technical Conference on Refractories: 9th Biennial Worldwide Congress on Refractories, Orlando, FL, 8 November 2005 through 11 November 2005 ; 2006 , Pages 715-721 ; 1574982656 (ISBN) Kazemi, A ; Nemati, Z. A ; Faghihi Sani, M. A ; Zahed, F ; Sharif University of Technology
    2006
    Abstract
    In this research, Magnesia Spinel refractories were formulated by using sintered magnesia, Tabular and Calcined Alumina and sintered Spinel. The grain size distribution of raw materials was modified, using the Andreessen equation. In order to improve the physical and mechanical properties and corrosion resistance of specimens, none stabilized Zirconia was added to the system. The pressed samples were sintered at 1700°C and the properties were evaluated at room and high temperatures. The formed phases and resultant microstructure were also, analyzed by XRD and SEM. The corrosion test was conducted in two parts. First, the depth of corrosion was measured in two zone, within 0-1mm and 1-2 mm... 

    Spark plasma sintered YSZ gas electrode produced from powders synthesized by a large-scale method

    , Article Materials Chemistry and Physics ; Volume 289 , 2022 ; 02540584 (ISSN) Ghayoor, R ; Yousefi, M. H ; Sharif University of Technology
    Elsevier Ltd  2022
    Abstract
    Monitoring the oxygen in the fume and controlling its amount at high temperatures is an efficient way to regulate combustion efficiency. Zirconia can be an attractive candidate for use in oxygen sensors due to its good physical and chemical properties. The crystal structure of pure zirconia nanopowder due to the lack of cubic phase cannot be used for the fabrication of gas sensor electrodes. Moreover, the change of temperature during ceramic processing and application can promote structural and phase stresses. In this work, to achieve a pure cubic phase, yttria was successfully added to zirconia by a large-scale and effective method called Pechini. The yttria-stabilized zirconia nanopowders... 

    Investigation of the Kinetics of Zirconium Oxide Synthesis Reactions by Co-Precipitation Method and Design of an Appropriate Reactor in Pilot Scale

    , M.Sc. Thesis Sharif University of Technology Abdollahi, Mohsen (Author) ; Ghotbi, Cyrus (Supervisor) ; Fotovat, Farzam (Supervisor)
    Abstract
    To study the kinetics of the yttria-stabilized zirconia produced by co-precipitation method from the chemical engineering point of view, this process was studied in two parts of hydrolysis and precipitation. the hydrolysis reaction was studied by titration method, and the rate constant and fraction of formation of hydrous zirconia was determined by applying Avrami equation. The results showed that the percentage of zirconia formation until the boiling time of 12 hours was zero and after 48 hours boiling was 2.81%. moment definitions were used In order to study the kinetics of precipitation. changes in precipitated powder concentration with pH of the solution was obtained based on the... 

    Effect of Zirconia Content and Powder Processing on Mechanical Properties of Gelcasted ZTA Composite

    , Article Transactions of the Indian Ceramic Society ; Volume 72, Issue 3 , May , 2013 , Pages 175-181 ; 0371750X (ISSN) Khoshkalam, M ; Faghihi Sani, M. A ; Nojoomi, A ; Sharif University of Technology
    2013
    Abstract
    Addition of fine zirconia particles in the alumina matrix in order to produce ZTA composite is a well-known method for improving the mechanical properties of alumina ceramics such as flexural strength and fracture toughness. Increasing homogeneity and reducing alumina grain size are two key factors for achieving proper mechanical properties in this ceramic matrix composite. In this work two batches of ZTA powder precursor were prepared through mixing of alumina and zirconia by ball milling and in situ synthesis of ZTA composite via solution combustion method. The bending strength testing samples were fabricated through gel-casting process. The effects of different powder processing methods... 

    Ultrasonic-assisted cylindrical grinding of Alumina-zirconia ceramics

    , Article ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE) ; Volume 2 A , Volume 2 A , 2013 ; 9780791856185 (ISBN) Tawakoli, T ; Akbari, J ; Zahedi, A. M ; ASME ; Sharif University of Technology
    American Society of Mechanical Engineers (ASME)  2013
    Abstract
    Due to its vast applications and stochastic nature, grinding has been the subject of investigations and modifications for decades. Applying ultrasonic vibration in grinding has been a successful innovation introducing benefits such as reduced forces and temperature, improved surface quality, and making higher removal rates possible. In this work a set-up is developed for utilizing ultrasonic vibrations in cylindrical grinding. This is done by rotating and simultaneously vibrating the workpiece material. The set-up is used for cylindrical grinding of Alumina-zirconia ceramic as a difficult-to-grind and widely used industrial ceramic. Optimized parameters for efficient grinding and surface... 

    Preparation of robust antistatic waterborne polyurethane coating

    , Article Progress in Organic Coatings ; Volume 139 , February , 2020 Yousefi, E ; Dolati, A ; Najafkhani, H ; Sharif University of Technology
    Elsevier B.V  2020
    Abstract
    In this study, a novle robust antistatic waterborne polyurethane (WBPU)-ZrO2 nanoparticle (NP) coating is specially designed using sol-gel process. For this purpose the effective parameters on resin performance and surface resistivity of the synthesized coating investigated and optimized. The WBPU composite containing 6 wt% ZrO2 NPs, dissipates electrostaic charges with surface resistivity of 9.1 × 109 Ω sq−1 and also improves adhesion strength about 30 % compared with neat resin. Moreover, the homogenous distribution of modified ZrO2 NPs provides a surface roughness of 27.0 nm which can avoid the absorption of dust on the surface. Facile fabrication of robust WBPU–ZrO2 coating with... 

    Mechanical Properties of Al2O3-ZrO2 Nanocomposites Fabricated by Gelcasting

    , M.Sc. Thesis Sharif University of Technology Arvandi, Shahab (Author) ; Faghihi Sani, Mohammad Ali (Supervisor)
    Abstract
    Gelcasting is a new ceramic forming technique getting worldwide attention. The process is based on casting of slurry; containing powder, water and water-soluble organic monomers. The premix solution was prepared using Acrylamide as a monomer and Methylene bisacrylamide as a crosslinker with AM:MBAM ratio of 25:1, and Poly Acrylic Acid Sodium as a dispersant (1 wt% based on ceramic powders weight). A series of Al2O3/ZrO2 ceramic nanocomposites with 15, 17.5 and 20 wt% content of ZrO2 and 40, 43, 45, 47, 50, 53 and 55 vol.% of solid loading were fabricated by gelcasting. After casting the mixture, the monomer was polymerized to form gel parts. Drying, burning out and sintering completed the...