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Kozerski S.,Wroclaw University of Technology | Latka L.,Wroclaw University of Technology | Latka L.,University of Limoges | Pawlowski L.,University of Limoges | And 5 more authors.
Journal of the European Ceramic Society | Year: 2011

ZrO2+8wt.% Y2O3 powder of a mean diameter dVS=38μm was milled to obtain fine particles having mean size of dVS=1μm. The fine powder was used to formulate a suspension with water, ethanol and their mixtures. The zeta potential of obtained suspensions was measured and found out to be in the range from -22 to -2mV depending on suspension formulation. The suspension was injected through a nozzle into plasma jet and sprayed onto stainless steel substrates. The plasma spray experimental parameters included two variables: (i) spray distance varying from 40 to 60mm and (ii) torch linear speed varying from 300 to 500mm/s. The microstructure of obtained coatings was characterized with scanning electron microscope (SEM) and X-ray diffraction (XRD). The coatings had porosity in the range from 10% to 17% and the main crystal phase was tetragonal zirconium oxide. The scratch test enabled to find the critical load in the range of 9-11N. Finally, thermal diffusivity of the samples at room temperature, determined by thermographic method, was in the range from 2.95×10-7 to 3.79×10-7m2/s what corresponds to thermal conductivities of 0.69W/(mK) and 0.97W/(mK) respectively. © 2011 Elsevier Ltd.

Basile N.,University of Mons | Gonon M.,University of Mons | Petit F.,Belgium Ceramic Research Center | Cambier F.,Belgium Ceramic Research Center
Journal of the European Ceramic Society | Year: 2012

The research work reported in this paper is an investigation of the behavior of barium titanate powders under selective laser irradiation. Our goal is to determine suitable conditions to sinter the powders and form dense layers usable in some electronic components. On that purpose, compacts of micro/nano BaTiO 3 powder mixes are used for a parametric investigation of the laser scans parameters (power, speed, etc.) with a Nd-YVO 4 laser (23W). The microstructures obtained after laser treatments are evaluated by XRD, SEM and EDS and compared to a reference specimen manufactured in a conventional way. From this work it can be concluded that a high laser beam power is required to obtain a consolidation of the powder grains and the use of a high scan speed avoids the melting. The scanning speed also influences the final crystallographic state of BaTiO 3. Optimal parameters were founded in order to form a dense and homogeneous tetragonal BaTiO 3 surface. © 2012 Elsevier Ltd.

Basile N.,University of Mons | Gonon M.,University of Mons | Petit F.,Belgium Ceramic Research Center | Cambier F.,Belgium Ceramic Research Center
Ceramics International | Year: 2016

The context of the present work is a large research project aiming at manufacturing functionalised surfaces by selected laser treatment with a focused beam [1]. More specifically, this paper aims at showing the possibility of obtaining a dense glass ceramic layer, with controlled microstructure, from a glass powder coating. In the present state of the research, laser scans are performed on glass powder compacts in order to investigate the operating conditions (power, speed and vectorisation) required to achieve the objective. The selected glass belongs to the Sr-Ti-Si-Al-K-O system, its crystalisation leads to a glass-ceramics containing piezoelectric Sr-fresnoïte crystals (Sr2TiSi2O8) Maury et al. (2011). The selective laser treatment is carried out by mean of a focused Nd-YVO4 laser beam. Characterisation of the thermal state of the surface during the treatment is performed thank to an IR camera. The surface microstructure is evaluated by X-ray diffraction and scanning electron microscopy. The results presented shows that Sr-fresnoïte glass ceramics layers can be processed by applying a two stage process: first the melting of a glass powder to form a dense amorphous layer; then the crystallisation of this layer. However, the microstructures resulting of a crystallisation step performed by mean of a one-scan laser treatment are heterogeneous. IR camera analysis highlights that this heterogeneity is due to thermal profile strongly depending on the position on the scanned surface. Moreover, the high energy scanning conditions required to promote crystallisation make that this later takes place on cooling after surface has been re-melted. Processing by a multi-scan mode (numerous successive rapid scans) seem more suitable. In that case, IR camera analysis shows a homogeneous thermal state of the surface. Additional investigations have to be performed in order to be able to master the relation between the thermal profile and the laser scan parameters. © 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

Kim B.,Pusan National University | Jeon S.,Pusan National University | Erauw J.P.,Belgium Ceramic Research Center | Lee H.,Pusan National University
Advances in Applied Ceramics | Year: 2016

The scavenging effect of magnesium oxide (MgO) addition on electrical property of 9 mol-% MgO partially stabilised zirconia (Mg-PSZ) was investigated in terms of phase transformation and intergranular phase formation. The addition of MgO up to 5 mol-% caused a stabilisation of Mg- PSZ, which led to an increase in the cubic phase and a decrease in the monoclinic and tetragonal phases in Mg-PSZ. The Mg-PSZ with the addition of 5 mol-% of MgO also exhibited the maximum ionic conductivity (0.3915 S cm-1 at 1500°C) and forsterite (Mg2SiO4) was observed on the grain boundaries of Mg-PSZ. The intergranular phases, formed by reactions between the silicon in Mg-PSZ and MgO addition, reduced the grain boundary resistance, because the siliceous phase which is a hindrance for oxygen ion conduction was scavenged by the formation of Mg2SiO4. © 2016 Institute of Materials, Minerals and Mining.

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