Curvaturas diferidas en piezas de gres procelánico

Las “curvaturas diferidas” es un fenómeno que consiste en el cambio de curvatura de las baldosas después de su salida del horno durante un periodo de tiempo variable y origina problemas durante la fase de clasificación y sobre la calidad del producto final. En el caso del gres porcelánico, la curvatura de las baldosas suele mostrar una evolución en un sentido inmediatamente después de la cocción para, después de cierto tiempo, invertir esta tendencia. Se establecieron las causas de las curvaturas en diferido en piezas de gres porcelánico. Para ello, se caracterizó el comportamiento de 14 modelos industriales y se estudió la influencia de las variables del proceso. Asimismo, se propuso y validó un modelo matemático que explica el fenómeno. Esta tesis doctoral aporta una solución industrial al permitir establecer condiciones de proceso que evitan o reducen las curvaturas diferidas y adoptar medidas de control efectivas en un entorno industrial.Ceramic tiles can suffer changes in their curvature after firing during variable periods of time. This process is known as “delayed curvature”. In the case of porcelain tiles, the curvature initially evolves in a direction and, after a certain time, this tendency is inverted. At industrial level, the existence of delayed curvature leads to lower product quality. Thus, it is fundamental to understand its origin and minimize its impact. This study establishes the causes of the delayed curvature in porcelain tiles. The behavior of 14 industrial models of porcelain stoneware regarding delayed curvature is characterized. The influence of the process variables is studied. A mathematical model is proposed and validated to explain the delayed curvature in porcelain tiles. An industrial solution to the problem is defined as the results allow to establish process conditions which avoid or reduce the delayed curvature, and to adopt effective control actions in industrial environment

Atmospheric plasma spraying coatings from alumina titania feedstockcomprising bimodal particle size distributions

In this work, Al2O3 13 wt% TiO2 submicron-nanostructured powders were deposited using atmospheric plasma spraying. The feedstocks were obtained by spray drying two starting suspensions of different solids content, prepared by adding nanosized TiO2 and submicron-sized Al2O3 powders to water. The spray-dried granules were heat-treated to reduce their porosity and the powders were fully characterised in both untreated and thermally treated state. Comparison with two commercial feedstocks was carried out. Characterisation allowed a temperature for the thermal treatment to be chosen on the basis of the sprayability of the feedstock and the preservation as much as possible of the submicron-sized structure of the unfired agglomerates. Optimisation of the deposition conditions enabled the reconstituted powdrs to be successfully deposited, yielding coatings that were well bonded to the substrate. The coating microstructure, characterised by SEM, was mostly formed by a matrix of fully molten particles where the presence of semi-molten feedstock agglomerates was also observed. Moreover, microhardness, toughness, adhesion and tribological behaviours were determined, and the impact of the granule characteristics on these properties was studied. It was found that changing the feedstock characteristics allows controlling the coating quality and properties. In general, good mechanical properties were obtained using a feedstock comprising a binary mixture of submicrometric Al2O3 and nanometric TiO2 particles in the spray-dried powderThis work has been supported by Spanish Ministry of Economy and Competitiveness (MAT2009-14144-C03 and MAT2012-38364-C03).Vicent, M.; Bannier, E.; Moreno, R.; Salvador Moya, MD.; Sanchez, E. (2013). Atmospheric plasma spraying coatings from alumina titania feedstockcomprising bimodal particle size distributions. Journal of the European Ceramic Society. 33:3313-3324. doi:10.1016/j.jeurceramsoc.2013.05.009S331333243

Multilayer and particle size-graded YSZ coatings obtained by plasma spraying of micro- and nanostructured feedstocks

This work was supported by the Spanish Ministry of Science and Innovation (Project MAT2012-38364-C03) and the Research Promotion Plan of Universitat Jaume I, action 3.1 (Ref. PREDOC/2009/10), and it has been co-funded by the European Regional Development Fund (ERDF). The authors also thank the SCIC of Universitat Jaume I for the FEG-SEM observationsCarpio, P.; Bannier, E.; Salvador Moya, MD.; Benavente Martínez, R.; Sanchez Vilches, E. (2014). Multilayer and particle size-graded YSZ coatings obtained by plasma spraying of micro- and nanostructured feedstocks. Journal of Thermal Spray Technology. 23(8):1362-1372. https://doi.org/10.1007/s11666-014-0143-9S13621372238D.R. Clarke and S.R. Phillpot, Thermal Barrier Coatings Materials, Mater. Today, 2005, 8, p 22-29N.P. Patdure, M. Gell, and E.H. Jordan, Thermal Barrier Coatings for Gas-Turbine Engine Applications, Science, 2002, 296, p 280-284L. Pawlowski, Finely Grained Nanometric and Submicrometric Coatings by Thermal Spraying: A Review, Surf. Coat. Technol., 2008, 205(43), p 18-28R.S. Lima and B.R. Marple, Thermal Spray Coatings Engineered from Nanostructured Ceramic Agglomerated Powders for Structural, Thermal Barrier and Biomedical Applications: A Review, J. Therm. Spray Technol., 2007, 16(1), p 40-63P. Fauchais, G. Montavon, R.S. Lima, and B.R. Marple, Engineering a New Class of Thermal Spray Nano-Based Microstructures from Agglomerated Nanostructured Particles, Suspensions and Solutions: An Invited Review, J. Phys. D, 2011, 44(9), 93001, p 1-131M. Gell, E.H. Jordan, Y.H. Sohn, D. Goberman, L. Shaw, and T.D. Xiao, Development and Implementation of Plasma Sprayed Nanostructured Ceramic Coatings, Surf. Coat. Technol., 2001, 146-147, p 48-54R.S. Lima and B.R. Marple, Nanostructured YSZ Thermal Barrier Coatings Engineered to Counteract Sintering Effects, Mater. Sci. Eng. A, 2008, 485, p 182-193H. Chen, X. Zhou, and C. Ding, Investigation of the Thermomechanical Properties of a Plasma-Sprayed Nanostructured Zirconia Coating, J. Eur. Ceram. Soc., 2003, 23, p 1449-1455K.A. Khor and Y.W. Gu, Thermal Properties of Plasma-Sprayed Graded Thermal Barrier Coatings, Thin Solid Films, 2000, 372, p 104-113A.M. Limarga, T.S. Widjajab, and T.H. Yip, Mechanical Properties and Oxidation Resistance of Plasma-Sprayed Multilayered Al2O3/ZrO2 Thermal Barrier Coatings, Surf. Coat. Technol., 2005, 197, p 93-102X. Chen, Y. Zhao, X. Fan, Y. Liu, B. Zou, Y. Wang, H. Ma, and X. Cao, Thermal Cycling Failure of New LaMgAl11O19/YSZ Double Ceramic Top Coat Thermal Barrier Coating Systems, Surf. Coat. Technol., 2011, 205, p 3293-3300G. Mauer, M.O. Jarligo, D.E. Mack, and R. Vassen, Plasma-Sprayed Thermal Barrier Coatings: New Materials, Processing Issues and Solutions, J. Therm. Spray Technol., 2013, 22(5), p 647-658A. Portinha, V. Teixeira, J. Carneiro, J. Martins, M.F. Costa, R. Vassen, and D. Stoever, Characterization of Thermal Barrier Coatings with a Gradient in Porosity, Surf. Coat. Technol., 2005, 195, p 245-251M. Vicent, E. Sánchez, G. Mallol, and R. Moreno, Study of Colloidal Behaviour and Rheology of Al2O3-TiO2 Nanosuspensions to Obtain Free-Flowing Spray-Dried Granules for Atmospheric Plasma Spraying, Ceram. Int., 2013, 39(7), p 8103-8111F. Müller, W. Peukert, R. Polke, and R. Stenger, Dispersing Nanoparticles in Liquids, Int. J. Miner. Process., 2000, 74, p S31-S34M. Vicent, E. Bannier, R. Moreno, M.D. Salvador, and E. Sánchez, Atmospheric Plasma Spraying Coatings from Alumina-Titania Feedstock Comprising Bimodal Particle Size Distributions, J. Eur. Ceram. Soc., 2013, 33, p 3313-3324C.W. Kang and H.W. Ng, Splat Morphology and Spreading Behaviour due to Oblique Impact of Droplets onto Substrates in Plasma Spray Coating Process, Surf. Coat. Technol., 2006, 200, p 5462-5477Y. Zeng, S.W. Lee, L. Gao, and C.X. Ding, Atmospheric Plasma Sprayed Coatings of Nanostructured Zirconia, J. Eur. Ceram. Soc., 2002, 22, p 347-351R.S. Lima, A. Kucuk, and C.C. Berndt, Integrity of Nanostructured Partially Stabilized Zirconia After Plasma Spray Processing, Mater. Sci. Eng. A, 2001, 13, p 75-82L. Wang, Y. Wang, X.G. Sun, J.Q. He, Z.Y. Pan, and C.H. Wang, Microstructure and Indentation Mechanical Properties of Plasma Sprayed Nano-bimodal and Conventional ZrO2-8 wt%Y2O3 Thermal Barrier Coatings, Vacuum, 2012, 86(8), p 1174-1185L.L. Shaw, D. Goberman, R. Ren, M. Gell, S. Jiang, Y. Wang, T.D. Xiao, and P.R. Strutt, The Dependency of Microstructure and Properties of Nanostructured Coatings on Plasma Spray Conditions, Surf. Coat. Technol., 2000, 130(1), p 1-8R.S. Lima, A. Kucuk, and C.C. Berndt, Bimodal Distribution of Mechanical Properties on Plasma Sprayed Nanostructured Partially Stabilized Zirconia, J. Mater. Sci. Eng. A, 2002, 327, p 224-232T. Wakui, J. Malzbender, and R.W. Steinbrech, Strain Dependent Stiffness of Plasma Sprayed Thermal Barrier Coatings, Surf. Coat. Technol., 2006, 200(16-17), p 4995-5002J. Malzbender and R.W. Steinbrech, Determination of the Stress-Dependent Stiffness of Plasma-Sprayed Thermal Barrier Coatings Using Depth-Sensitive Indentation, J. Mater. Res., 2003, 18(8), p 1975-198

Effect of TiO2 addition on the microstructure and nanomechanical properties of Al2O3 Suspension Plasma Sprayed coatings

Alumina–titania coatings are widely used in industry for wear, abrasion or corrosion protection components. Such layers are commonly deposited by atmospheric plasma spraying (APS) using powder as feedstock. In this study, both Al2O3 and Al2O3–13 wt% TiO2 coatings were deposited on austenitic stainless steel coupons by suspension plasma spraying (SPS). Two commercial suspensions of nanosized Al2O3 and TiO2 particles were used as starting materials. The coatings microstructure and phase composition were fully characterised using FEG-SEM and XRD techniques. Nanoindentation technique was used to determine the coatings hardness and elastic modulus properties. Results have shown that the addition of titania to alumina SPS coatings causes different crystalline phases and a higher powder melting rate is reached. The higher melted material achieved, when titania is added leads to higher hardness and elastic modulus when the same spraying parameters are use

Effect of particle size on processing of bioactive glass powder for atmospheric plasma spraying

The work addresses the effect of the particle size of a bioactive glass feedstock on the processing and microstructure of the resulting coatings obtained by atmospheric plasma spraying (APS). It was observed that the reduction of particle size negatively affects the flowability of the powder. In addition the thermal behaviour (weight losses, glass transitions, crystallisations, etc.) also depended on the particle size of the glass powder. No coating was obtained with the coarser fractions (higher than 200 μm) due to their low melting degree in the plasma. For the intermediate fractions (200–63 μm) coatings were obtained but insufficient particle melting was produced. On the contrary, the finest fraction (<63 μm) needed a fluidiser which enabled the samples to be sprayed.Authors wish to acknowledge the University Jaume I of Castellon for the support in the RECUBIO project (P1–1B2013–69) and Fritta S.L. for the support in feedstock synthesis

Análise e medida de fatores que afetam as curvaturas retardadas em porcelanato

Os revestimentos cerâmicos de porcelanato, tanto os esmaltados como os não esmaltados, apresentam um fenômeno conhecido como “curvaturas retardadas”, que consiste na mudança de curvatura das peças depois da saída do forno. Este fenômeno é mais problemático a medida de aumentam as dimensões das peças. Neste trabalho se quantificou a variação da curvatura ao longo do tempo em peças industriais de porcelanato esmaltado, observando-se que a curvatura parece apresentar uma evolução em um sentido (habitualmente em direção ao sentido côncavo, ou em forma de barco) para, após transcorrido certo tempo, inverter esta tendência. A cinética deste processo foi parametrizada considerando que existem dois mecanismos, simultâneos e antagônicos, com cinéticas diferentes.As análises teóricas apontam que somente existem dois fatores que podem produzir curvaturas retardadas: as tensões residuais e a expansão dos suportes. Em ambos os casos é necessário condições adicionais para que as curvaturas efetivamente se manifestem: Deste modo, por exemplo, a presença de tensões residuais não é sinônimo de curvaturas retardadas, mais sim um mecanismo adicional que permita a liberação progressiva destas tensões; este mecanismo é chamado de fluência. Além disso é necessário que o perfil de tensões residuais não seja simétrico em relação ao plano central da peça. No que diz respeito a expansão dos suportes, também são necessárias condições especiais para que estas possam provocar curvaturas retardadas; em particular, é necessário que estas sejam diferentes nas duas faces da peça (face lisa e tardoz). Uma expansão uniforme provocaria uma leve mudança dimensional, mas não uma curvatura retardada, nem mesmo para peças esmaltadas. A medida dos fatores que influenciam sobre as curvaturas retardadas é complexa pois requer o emprego de técnicas diferentes das habitualmente empregadas para a caracterização de revestimentos cerâmicos. Foram criados, especialmente para este trabalho, procedimentos para a medida dos diferentes fatores que produzem as curvaturas retardadas e se estudou a influencia de algumas variáveis sobre estes fatoresGlazed and unglazed porcelain tiles exhibit a phenomenon known as delayed curvatures, which consists of the change in tile curvature after the tiles leave the kiln. This phenomenon becomes more problematic as tile size increases. In this study, the variation of curvature in time has been quantified in industrial glazed porcelain tiles. It was observed that the curvature usually displays an evolution in one direction (customarily in a concave direction or vessel shape) which, after a certain time has elapsed, reverses this trend. The kinetics of this process has been parameterised, assuming there are two simultaneous, opposing mechanisms, with different kinetics. Theoretical analyses indicate that only two factors can produce delayed curvatures: residual stresses and expansion of the tile body. In both cases, additional circumstances need to occur for delayed curvatures to appear; thus, for example, the presence of residual stresses is not synonymous with delayed curvatures, but an additional mechanism is needed that allows progressive release of these stresses, a mechanism known as creep. In addition, the condition that the stress profile is not symmetrical with respect to the centre plane of the tile also needs to be obeyed. In regard to the expansion of the bodies, special conditions must also occur for these to cause delayed curvatures. In particular, it is necessary for the expansion at the tile fair face and at the rib face to be different. Uniform expansion would cause a slight dimensional change, but not a delayed curvature, not even in the presence of glaze. The measurement of the factors that influence delayed curvatures is complex because different techniques from those typically used in characterising ceramic tiles are required. Procedures have been fine-tuned to measure the different factors that give rise to delayed curvatures, and the influence of certain variables on these factors has been studiedVersió editoria

Effect of the initial particle size distribution on the properties of suspension plasma sprayed Al2O3-TiO2 coatings

Al2O3–TiO2 coatings have been deposited by atmospheric plasma spraying from agglomerated, nanostructured powders showing better properties than those of their conventional (microstructured) counterparts. These nanostructured coatings can be also obtained by suspension plasma spraying however the research on suspension plasma sprayed Al2O3–TiO2 is still scarce. Consequently, it is crucial to study the effect of the suspension characteristics on the coating properties and to optimize the deposition process. In this work, Al2O3–13 wt.% TiO2 tribological coatings were successfully deposited by suspension plasma spraying from three different feedstocks: a nanometric suspension and two bimodal suspensions with different solid contents made up of titania nanoparticles and alumina submicron-sized particles. The coating microstructure and phase composition were characterized using scanning electron microscopy and X-ray diffraction analysis. Moreover, nanoindentation technique was used to determine the nanomechanical properties of coatings. The influence of the feed suspension characteristics on the final coating quality was analyzed. Findings showed that similar microstructures and phases were developed after depositing the different feedstocks. In addition suspension feedstock made up of nanoparticles resulted in a coating with better mechanical properties. However the use of submicron-sized particles in the suspension feedstocks gives rise to some technical and economic advantages in the process which should be taken into account when a suspension plasma spraying process is to be set up

Deposition of Al2O3-TiO2 Nanostructured Powders by Atmospheric Plasma Spraying

Al2O3-13%TiO2 coatings were deposited on stainless steel substrates from conventional and nanostructured powders using atmospheric plasma spraying (APS). A complete characterization of the feedstock confirmed its nanostructured nature. Coating microstructures and phase compositions were characterized using SEM, TEM, and XRD techniques. The microstructure comprised two clearly differentiated regions. One region, completely fused, consisted mainly of nanometer-sized grains of c-Al2O3 with dissolved Ti+4. The other region, partly fused, retained the microstructure of the starting powder and was principally made up of submicrometer-sized grains of a-Al2O3, as confirmed by TEM. Coating microhardness as well as tribological behavior were determined. Vickers microhardness values of conventional coatings were in average slightly lower than the values for nanostructured coating. The wear resistance of conventional coatings was shown to be lower than that of nanostructured coatings as a consequence of Ti segregation. A correlation between the final properties, the coating microstructure, and the feedstock characteristics is give

Influence of atmospheric plasma spray parameters on YSZ coatings obtained from micro and nanostructured feedstocks

[ES] En el presente trabajo se ha estudiado la influencia de cada uno de los parámetros de la proyección térmica por plasma atmosférico (atmospheric plasma spraying, APS) en la deposición de dos polvos comerciales de YSZ, uno convencional y otro nanoestructurado. En primer lugar se ha estudiado cómo afecta la variabilidad de los diferentes parámetros en el comportamiento de las partículas durante la proyección. Para tal fin, se ha utilizado un sensor que permite determinar la temperatura y la velocidad de las partículas en el interior del plasma. Una vez conocido cómo influyen los parámetros de proyección se han depositado ambos polvos sobre sustratos de acero inoxidable mediante APS modificando aquellos parámetros con un mayor impacto en el comportamiento de las partículas. Estos recubrimientos han sido caracterizados y se ha analizado la influencia del comportamiento de las partículas durante la proyección en la microestructura y propiedades del recubrimiento final. En este trabajo se concluye que la variación de los parámetros de proyección afecta en la velocidad y temperatura de las partículas en el interior del plasma y este comportamiento influye a su vez, y de forma diferente al emplear los distintos polvos (micro- y nanoesctructurado) en las características de los recubrimientos finales.[EN] In the present work, the influence of atmospheric plasma spray (APS) parameters on the deposition of two commercial YSZ feedstocks, one conventional and one nanostrcutured, has been studied. First the study focused on how the variability of the different parameters affects the particle behaviour during spraying. For this purpose, a sensor which enables to measure the particle temperature and velocity inside the plasma was used. Once the spraying parameters influence was known, both powders were deposited by APS onto stainless steel substrates modifying the higher influencing parameters. These coatings have been characterised and the influence of the particle behaviour on the coating microstructure and properties has been analysed. This work concludes the spraying parameters variation affects on the particle velocity and temperature inside the plasma plume and this behaviour influences, in turn but in a different way, on the final coating characteristics when using different powders (micro- and nanostructured).Este trabajo ha sido financiado por el Ministerio Español de Economía y Competitividad (MAT2012-38364-C03) y el Plan de Promoción a la Investigación de la Universidad Jaume I, acción 2.4 (ref. E-2012-04) y acción 3.1 (ref. PREDOC/2009/10). Los autores están agradecidos con el Servicio Central de Soporte a la Investigación Experimental (SCSIE) de la Universitat de Valencia por el uso del MEB. A. Borrell agradece al Ministerio Español de Ciencia e Innovación su contrato Juan de la Cierva (JCI-2011-10498).Carpio, P.; Bannier, E.; Borrell Tomás, MA.; Salvador Moya, MD.; Sánchez, E. (2014). Influencia de los parámetros de proyección por plasma atmosférico en recubrimientos de YSZ obtenidos a partir de polvos micro y nanoestructurados. Boletín de la Sociedad Española de Cerámica y Vidrio. 53(4):162-170. https://doi.org/10.3989/cyv.202014S16217053

Effect of particle size distribution of suspension feedstock on the microstructure and mechanical properties of suspension plasma spraying YSZ coatings

In this work, aqueous suspension feedstocks with different particle size distribution from submicron- and nanosized YSZ powders were prepared. A previous colloidal characterisation allowed concentrated suspensions (~40 wt%) to be prepared. These suspensions were then successfully deposited by suspension plasma spraying (SPS) onto stainless steel substrates at different spraying distances. Coatings were characterised in terms of microstructure and mechanical properties (hardness and elastic modulus) by nanoindentation. All coatings displayed a two-zone microstructure formed by partially melted areas containing nanometre or submicrometre-sized particles surrounded by fully melted areas. These partially melted areas strongly increased as standoff distance lengthened. Mechanical properties worsened with spraying distance increase. The finer the feedstock particle size the more the spraying distance effect was. A clear correlation between mechanical properties and amount of partially melted areas has been proved. Thus the use of a mixture of nano/submicron-sized particles as a SPS feedstock can represent a good balance between suspension processability and final coating performance.This work has been supported by the Spanish Ministry of Science and Innovation and by ERDF (European Regional Development Funds) (Project MAT2012-38364-C03). The authors also acknowledge the SCSIE of the University of Valencia for the FEG-SEM observations. Finally, the Research Promotion Plan of the Universitat Jaume I, action 3.1 (ref. PREDOC/2009/10) and the Spanish Ministry of Science and Innovation for Juan de la Cierva contract (JCI-2011-10498) is also grateful.Carpio, E.; Bannier, E.; Salvador Moya, MD.; Borrell Tomás, MA.; Moreno, R.; Sánchez, E. (2015). Effect of particle size distribution of suspension feedstock on the microstructure and mechanical properties of suspension plasma spraying YSZ coatings. Surface and Coatings Technology. 268:293-297. https://doi.org/10.1016/j.surfcoat.2014.08.063S29329726