Search results for "ZrO2"
showing 10 items of 13 documents
ZrO2 Based materials as photocatalysts for 2-propanol oxidation by using UV and solar light irradiation and tests for CO2 reduction
2018
Abstract Bare ZrO2, Ce doped ZrO2 and Er doped ZrO2 samples have been prepared by a hydrothermal process and have been used as photocatalysts for 2-propanol oxidation reaction in gas solid regime. Moreover, some preliminary tests have been carried out for CO2 reduction. The samples were physico-chemically characterized and both bare and doped ZrO2 based materials resulted active for oxidation and reduction reactions by using UV and solar irradiation. The reactivity results have been correlated with the compositional, structural and morphological features of the photocatalysts.
Phase formation in mixed TiO2-ZrO2 oxides prepared by sol-gel method
2011
Pure titania, zirconia, and mixed oxides (3—37 mol.% of ZrO2) are prepared using the sol-gel method and calcined at different temperatures. The calcined samples are characterized by Raman spectroscopy, X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption porosimetry. Measurements reveal a thermal stability of the titania anatase phase that slightly increases in the presence of 3—13 mol.% of zirconia. Practically, the titania anatase-rutile phase transformation is hindered during the temperature increase above 700 C. The mixed oxide with 37 mol.% of ZrO2 treated at 550 C shows a new single amorphous phase with a surface area of the…
ZrO2 Acting as a Redox Catalyst
2016
Surface defects are discussed and reviewed with regards to the use of ZrO2 in applications involving interactions with CO, H2, CH4, CO2, water and hydrocarbons. Studies of catalytic partial oxidation of methane reveal that part of the surface lattice oxygen in terraces can be removed by methane at high temperatures (e.g. 900 °C). The reaction proceeds via a surface confined redox mechanism. The studies presented here also highlight that defects play a decisive role in the water–gas-shift reaction, since the reaction is likely carried out via OH groups present at defect sites, which are regenerated by dissociating water. Hydroxyl chemistry on ZrO2 is briefly reviewed related to the studies p…
MoSi2 laser cladding—A new experimental procedure: double-sided injection of MoSi2 and ZrO2
2003
International audience; In the last decade, development of low density advanced material systems for service at temperatures up to 1300 °C was one of the goals of many researches. This kind of material should mainly have moderate fracture toughness and should exhibit oxidation resistant behaviour at low and intermediate temperature. One of the most studied materials continues to be the intermetallic compound MoSi2. The molybdenum disilicide has been considered as an attractive candidate due to its melting point (2030 °C) and excellent oxidation resistance at high temperatures. The main problem associated with the MoSi2 layer synthesized using laser beam is the layer fragility. To avoid this…
Large scale synthesis of nanostructured zirconia-based compounds from freeze-dried precursors
2013
Nanocrystalline zirconia powders have been obtained at the multigram scale by thermal decomposition of precursors resulting from the freeze-drying of aqueous acetic solutions. This technique has equally made possible to synthesize a variety of nanostructured yttria or scandia doped zirconia compositions. SEM images, as well as the analysis of the XRD patterns, show the nanoparticulated character of those solids obtained at low temperature, with typical particle size in the 10–15 nm range when prepared at 673 K. The presence of the monoclinic, the tetragonal or both phases depends on the temperature of the thermal treatment, the doping concentration and the nature of the dopant. In addition,…
Ceramic/metal nanocomposites by lyophilization: Spark plasma sintering and hardness
2014
The present study is focused on the procedure of spray-drying and lyophilization techniques for the preparation of ceramic/metal nanocomposites. The results of the study at all stages are compared with those corresponding to powders conventionally dried by heating in furnace. Starting from aqueous solutions of metal salts and ceramic powders, the procedure follows with spray-drying, lyophilization, calcination of the resulting powders and subsequent Spark Plasma Sintering (SPS). X-ray diffraction analysis of the powders at different stages of the processing routes was used for phase indexing; further characterization was performed by Transmission Electron Microscopy and Energy Dispersive X-…
Properties of atomic layer deposited nanolaminates of zirconium and cobalt oxides
2018
Producción Científica
Síntesis y caracterización de nanopartículas de TiO2 y ZrO2 dopadas con cationes de metales de transición. Aplicaciones como nanopigmentos y en fotoc…
2017
En la presente tesis doctoral se pretende por una parte sintetizar en la escala nanométrica pigmentos cerámicos clásicos de uso industrial, como son el pigmento de color amarillo V-ZrO2, y el pigmento de color naranja-amarillo Cr,Sb-TiO2, mediante métodos de síntesis no convencionales. Para llevar a cabo dichas síntesis se van a utilizar dos métodos de síntesis relativamente sencillos y fácilmente reproducibles a escala industrial, como son el método del poliol y el método hidrotermal, los resultados que se obtengan mediante los dos métodos serán comparados y se hará hincapié en sus ventajas e inconvenientes. Las composiciones nominales estudiadas serán en el caso del VxZr1-xO2 valores 0 ≤ …
Integrated experimental and theoretical study on the phase transition and photoluminescent properties of ZrO2:xTb3+ (x=1, 2, 4 and 8 mol %)
2021
Abstract Zirconia (ZrO2) has been intensively studied as an important ceramic material, and numerous technological applications have been found. The present work deals with synthesizing and characterizing the phase transition (cubic vs tetragonal) and photoluminescence emissions of ZrO2:xTb3+ (x = 1,2,4 and 8 mol%). The samples formed by the complex polymerization were thoroughly characterized for physicochemical properties such powder by X-ray diffraction (XRD), and Raman and diffuse reflectance spectroscopies. First-principle calculations at the density functional theory level were performed to complement and rationalize the experimental results. An energy transfer mechanism which promote…
Osmozes parādība sulfonēta poliēterēterketona un cirkonija dioksīda kompozīta membrānās KHCO3 šķīdumā
2020
Darba ietvaros ir veikta PĒĒK sulfonēšana, SPĒĒK un SPĒĒK – ZrO2 kompozītmembrānu ieguve. Tika izpētīts osmozes ātrums KHCO3 šķīdumā caur Nafion un iegūtajam membrānām, kā arī SPĒĒK – ZrO2 kompozītmembrānu ZrO2 satura ietekme uz osmozes ātrumu.