DESARROLLO DE MATERIALES CERÁMICOS AVANZADOS CON ALTAS PRESTACIONES MEDIANTE TÉCNICAS NO CONVENCIONALES DE SINTERIZACIÓN: MICROONDAS

[EN] Microwave material sintering provides many advantages over conventional methods. This is a non-conventional technique, where materials absorb and convert electromagnetic energy into heat. The heating process is very different from other methods where heat is transferred through mechanisms of conduction, radiation and convection. The main advantages of microwave sintering can be summarized into three main points: reducing processing time and production costs, environmental benefits and processing flexibility. Therefore, microwaves are an attractive alternative to other sintering methods. The main aim of this thesis is to obtain dense lithium aluminosilicate (LAS) ceramics with adequate mechanical performance and exceptional features by the non-conventional sintering technique of microwave heating for specific applications. The high thermal stability of these materials makes them useful for microelectronics, precision optics and aerospace technologies. Mechanical and thermal properties can be improved by microwave sintering technique. To achieve this goal, the microwave sintering equipment will be optimized in order to obtain solid-state LAS materials and their final properties will be evaluated. As a complimentary phase, the feasibility of improving such properties by the addition of selected second phases, such as alumina and graphene, will be investigated.[ES] La sinterización de materiales por medio de las microondas aporta muchas ventajas frente a los métodos convencionales. Se trata de una técnica no-convencional donde los materiales absorben las ondas electromagnéticas y las transforman en calor. Este proceso es muy diferente de otros métodos, donde el calor es transferido a través de los mecanismos de conducción, radiación y convección. Las principales ventajas de la sinterización por microondas se puede resumir en tres: reducción de tiempos y costes económicos de producción, beneficios medioambientales y flexibilidad del procesado. Por lo tanto, las microondas son una clara alternativa a otros métodos de sinterización. El objetivo final de esta Tesis Doctoral es la obtención, mediante la técnica de sinterización no convencional de microondas, de materiales cerámicos basados en aluminosilicato de litio (LAS) densos, que reúnan unas prestaciones mecánicas adecuadas y unas funcionalidades excepcionales, para su utilización en aplicaciones específicas. La alta estabilidad térmica de estos materiales los hace idóneos para aplicaciones en el campo de la microelectrónica, la óptica de precisión y la tecnología aeroespacial. Mediante la utilización de las microondas, se pretende mejorar sus propiedades finales, tanto mecánicas como térmicas. Para lograr este objetivo, se adaptarán los equipos de microondas a la sinterización de los materiales de LAS en estado cristalino y se evaluarán sus propiedades finales. En una última fase, se estudiará la viabilidad de mejorar las propiedades de los materiales obtenidos en la etapa anterior, mediante la adición de segundas fases seleccionadas: alúmina y grafeno.[CA] La sinterització de materials per mitjà de les microones aporta molts avantatges enfront dels mètodes convencionals. Es tracta d'una tècnica no-convencional on els materials absorbeixen les ones electromagnètiques i les transformen en calor. Aquest procés és molt diferent d'altres mètodes, on la calor és transferida per mig dels mecanismes de conducció, radiació i convecció. Els principals avantatges de la sinterització per microones es poden resumir en tres: reducció de temps i costos econòmics de producció, beneficis mediambientals i flexibilitat del processament. Per tant, les microones són una clara alternativa a altres mètodes de sinterització. L'objectiu final d'aquesta Tesi Doctoral és l'obtenció, mitjançant la tècnica de sinterització no-convencional de microones, de materials ceràmics basats en aluminosilicats de liti (LAS) densos, que reunisquen unes prestacions mecàniques adequades i unes funcionalitats excepcionals, per a la seua utilització en aplicacions específiques. L'alta estabilitat tèrmica d'aquests materials els fa idonis per a aplicacions en el camp de la microelectrònica, l'òptica de precisió i la tecnologia aeroespacial. Mitjançant la utilització de les microones, es pretén millorar les seues propietats finals, tant mecàniques com tèrmiques. Per a aconseguir aquest objectiu, s'adaptaran els equips de microones a la sinterització dels materials de LAS en estat cristal·lí i s'avaluaran les seues propietats finals. En una última fase, s'estudiarà la viabilitat de millorar les propietats dels materials obtinguts en l'etapa anterior, mitjançant l'addició de segones fases seleccionades: l'alúmina i el grafé.Benavente Martínez, R. (2015). DESARROLLO DE MATERIALES CERÁMICOS AVANZADOS CON ALTAS PRESTACIONES MEDIANTE TÉCNICAS NO CONVENCIONALES DE SINTERIZACIÓN: MICROONDAS [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/49358TESISPremios Extraordinarios de tesis doctorale

Dense nanostructured zirconia compacts obtained by colloidal filtration of binary mixtures

As starting materials two commercial nanosized zirconias doped with 3 mol% of Y 2O 3 were used: a powder of about 100 nm (TZ3YE, Tosoh, Japan) and a colloidal suspension of about 15 nm (Mel Chemicals, UK). Colloidal stability in water was studied for both zirconias in terms of zeta potential as a function of deflocculant concentration and pH. Concentrated suspensions were prepared by dispersing the powder in the colloidal suspension to solids loadings ranging from 5 to 30 vol.% using a sonication probe to achieve dispersion. The rheological behavior was optimized in terms of solids content, deflocculant content and sonication time. Optimized suspensions with up to 25 vol.% solids showed a nearly Newtonian behavior and extremely low viscosities and maintain stable for long times (days) which is an important drawback of conventional nanoparticle suspensions. Samples obtained by slip casting in plaster moulds were used for dynamic sintering studies and dense, nanostructured specimens were obtained at temperatures of 1300-1400°C.This work has been supported by Spanish Ministry of Science and Innovation (Projects MAT2009-14144-C03-02 and MAT2009-14369-C02-01). R. Moreno thanks to Universidad Politecnica de Valencia for the concession of a grant in the frame of its Programme of Support to R + D (PAID-02-11, R-1752).Benavente Martínez, R.; Salvador Moya, MD.; Alcázar, M.; Moreno, R. (2012). Dense nanostructured zirconia compacts obtained by colloidal filtration of binary mixtures. Ceramics International. 38(3):2111-2117. https://doi.org/10.1016/j.ceramint.2011.10.051S2111211738

Effect of a Powder Mould in the Post-Process Thermal Treatment of ABS Parts Manufactured with FDM Technology

[EN] The post-process thermal treatment of thermoplastics improves their mechanical properties, but causes deformations in parts, making them unusable. This work proposes a powder mould to prevent dimensional part deformation and studies the influence of line building direction in part deformations in a post-process thermal treatment of 3D printed polymers. Two sets of ABS (acrylonitrile butadiene styrene) test samples manufactured by fused deposition modelling (FDM) in six different raster directions have been treated and evaluated. One set has been packed with a ceramic powder mould during thermal treatment to evaluate deformations and mould effectiveness. Thermogravimetric tests have been carried out on ABS samples, concluding that the thermal treatment of the samples does not cause degradations in the polymeric material. An analysis of variance (ANOVA) was performed to study internal building geometry and mould influence on part deformation after the thermal treatment. It can be concluded that powder mould considerably reduces dimensional deformations during the thermal treatment process, with length being the most affected dimension for deformation. Attending to the length, mould effectiveness is greater than 80% in comparison to non-usage of moulding, reaching 90% when the building lines are in the same direction as the main part.This research received partial funding from the Government of Spain under the project PID2019-108807RB-I00.Lluch-Cerezo, J.; Benavente Martínez, R.; Meseguer, M.; García Manrique, JA. (2021). Effect of a Powder Mould in the Post-Process Thermal Treatment of ABS Parts Manufactured with FDM Technology. Polymers. 13(15):1-16. https://doi.org/10.3390/polym13152422S116131

Formación Integral en competencias para Impresión 3D

[EN] Competences, skills and habilities adquired by students in the learning process must be determined by the learning outcomes, previously defined. In the 3D-PRISM European Project, the learning outcomes for 3D-printing students have been stablished. The process for determining the learning outcomes did take in consideration the opinion of University and Professionals of the manufacturing industry. The proposed methodology comprises 4 phases: creation of the profiles for the professionals in the 3D-printing industry, creation of the questionnaire based in previous documental research, on-line questionnaire and data collection and processing[ES] Los conocimientos, competencias y/o habilidades adquiridas por el alumnado en el proceso de formación, han de estar determinadas por los resultados de aprendizaje previamente establecidos. En el Proyecto Europeo 3D-PRISM se han establecido los resultados de aprendizaje en materia de Impresión 3D. El proceso ha sido llevado a cabo mediante el dialogo establecido entre la Universidad y la sociedad representada por expertos profesionales y docentes en la materia. La metodología propuesta en este trabajo se basa en cuatro fases: elaboración de los perfiles de los expertos en materia de impresión 3D, elaboración de un cuestionario basado en una investigación documental previa, distribución on-line de los cuestionarios y la recopilación de los datos obtenidos y tratamiento de los datos.Los autores desean agradecer el apoyo financiero recibido a través del proyecto ERASMUS +: 3D PRINTING SKILLS FOR MANUFACTURIN G 2015-1-UK01-KA202-013432.Benavente, R.; Patrao, I.; Small, G.; Tsianos, N. (2017). Formación Integral en competencias para Impresión 3D. En In-Red 2017. III Congreso Nacional de innovación educativa y de docencia en red. Editorial Universitat Politècnica de València. 756-768. https://doi.org/10.4995/INRED2017.2017.6766OCS75676

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

Mechanical properties and microstructural evolution of alumina-zirconia nanocomposites by microwave sintering

Microwave sintering has emerged in recent years as a novel method for sintering a variety of materials that have shown significant advantages against conventional sintering procedures. This work involved an investigation of microwave hybrid fast firing of alumina–zirconia nanocomposites using commercial alumina powder and monoclinic nanometric zirconia. The suspensions were prepared separately in order to obtain 5, 10 and 15 vol% of ZrO2 in the alumina matrix. The samples were sintered in a monomode microwave furnace at 2.45 GHz in air at different temperatures in the range 1200–1400 1C with 10 min of dwelling time and 200 1C/min of heating rate. The effect of sintering temperature in densification, mechanical properties and microstructure behavior of the composites was investigated. Higher density, hardness and Young's modulus, excellent fracture toughness properties and homogeneous microstructure were achieved by microwave sintering in comparison to conventional heating. Microstructure analysis showed that the alumina grains had not grown significantly, indicating that the zirconia particles provided a hindering effect on the grain growth of alumina. Crown Copyright & 2014 Published by Elsevier Ltd and Techna Group S.r.l. All rights reservedThe authors would like to thank the Polytechnic University of Valencia (UPV) for financial support received for projects SP20120621, SP20120398 and SP20120677 and Spanish Government (TEC2012-37532-C02-01) and co-funded by ERDF (European Regional Development Funds). A. Borrell acknowledges the Spanish Ministry of Science and Innovation for her Juan de la Cierva contract (JCI-2011-10498) and Generalitat Valenciana by Geronimo Forteza funding (FPA/2012/022).Benavente Martínez, R.; Salvador Moya, MD.; Penaranda-Foix, FL.; Pallone, E.; Borrell Tomás, MA. (2014). Mechanical properties and microstructural evolution of alumina-zirconia nanocomposites by microwave sintering. Ceramics International. 40(7, Part B):11291-11297. https://doi.org/10.1016/j.ceramint.2014.03.153S1129111297407, Part

Effect of sintering technology in beta-eucryptite ceramics: Influence on fatigue life and effect of microcracks

β-eucryptite ceramics with low negative or near-zero coefficient of thermal expansion (CTE) with excellent mechanical properties, such as Young’s modulus 100 GPa, have attracted attention for many important industrial applications. The extremely anisotropic thermal expansion behaviour of this material leads to thermal residual stresses, and causes spontaneous microcracking. These microcracks cause large negative CTE with mechanical weaknesses. The appearance of microcracks is due to different factors. The most important are prolonged sintering time and heating source used. The present work shows experimentally the evolution of grain microcracks and residual stresses of the sintered -eucryptite material going through many thermal fatigue cycles (3600). The effect of stresses applied on β-eucryptite crystals due to the thermal cycling could be considered for explaining the small change observed of β-eucryptite to β-spodumene phase, which is higher in the samples obtained by microwave sintering. Therefore, the study of residual stresses has suggested that the heating source employed, such as conventional or microwave, has a great influence on thermal fatigue life and the final mechanical and thermal properties. The microwave heating has a significant impact on β-eucryptite materials lifetime.A. Borrell, acknowledges the Spanish Ministry of Science and Innovation for a Juan de la Cierva contract (JCI-2011-10498) and the Polytechnic University of Valencia (UPV) for financial support received under project SP20120677. The authors would like to thank the SCSIE team of the University of Valencia.Benavente Martínez, R.; Salvador Moya, MD.; Martínez-Amesti, A.; Fernández, A.; Borrell Tomás, MA. (2016). Effect of sintering technology in beta-eucryptite ceramics: Influence on fatigue life and effect of microcracks. Materials Science and Engineering: A. 651:668-674. https://doi.org/10.1016/j.msea.2015.11.013S66867465

Mechanical properties and coefficient of thermal expansion of β-eucryptite sintered by microwave technique

[ES]: La técnica de sinterización no convencional de microondas permite obtener materiales de ß-eucriptita en estado sólido cristalino con densidades cercanas a la teórica (~99 %). Se ha observado una diferencia considerable en estos materiales respecto a la técnica convencional en términos de densificación, microestructura, coeficiente de expansión térmica y propiedades mecánicas. Los valores de dureza y módulo de Young obtenidos mediante sinterización por microondas a 1200 ºC-5 min han sido relativamente altos, 6.8 GPa y 101 GPa, respectivamente, en comparación con el material obtenido mediante horno convencional (3.9 GPa y 58 GPa, respectivamente). Los datos dilatométricos obtenidos, incluyendo el intervalo de temperatura criogénica (-150 ºC a +150 ºC), muestran un coeficiente de expansión térmica controlado y negativo en todo el rango de temperaturas. La combinación de un calentamiento rápido junto con la reducción drástica en el tiempo de ciclo y el ahorro energético, hace que la técnica de microondas sean una clara alternativa a otro tipo de calentamientos.[EN]: Microwave non-conventional sintering technique allows obtaining fully dense glass-free β-eucryptite bulk material (∼99 %). A considerable difference in the densification, microstructure, coefficient of thermal expansion behaviour and mechanical properties, between conventional and non-conventional sintered specimens was observed. The hardness and Young’s modulus values obtained by microwaves at 1200 °C-5min have been relatively high, 6.8 GPa and 101 GPa, respectively, compared to conventional sintering (3.9 GPa and 58 GPa, respectively). Very low thermal expansion materials have been obtained in a wide temperature range including cryogenic temperatures (from -150 ºC to 150 ºC). The high heating rate along with the lower energy consumption makes microwave technique a clear alternative to other types of sintering methods.Los autores desean agradecer el apoyo financiero recibido de la UPV dentro de los proyectos SP20120621 y SP20120677 y, al gobierno español a través del proyecto (TEC2012-37532-C02-01). A. Borrell, agradece al Ministerio de Ciencia e Innovación su contrato de Juan la Cierva (JCI-2011-10498).Peer Reviewe

High thermal stability of microwave sintered low-er beta-eucryptite materials

Low-temperature sinterable microwave LiAlSiO4-based solid-state material was investigated with regard to microwave dielectric properties as functions of the sintering temperature. beta-eucryptite materials and alumina-reinforced beta-eucryptite composites were sintered by microwave technology at 1100 degrees C and 1200 degrees C. The combination of fast heating and the dramatic reduction in cycle time, along with the non-conventional heating source, opens the way to produce materials with desired multifunctional properties. The microstructure and crystalline composition of the materials were characterised, and the mechanical, thermal and microwave dielectric behaviours were analysed. X-ray diffraction showed good chemical stability in materials without between-phase reactions during the microwave sintering process. The excellent mechanical (similar to 8 GPa of hardness and similar to 100 GPa of Young's modulus), thermal (-0.23. 10(-6) K-1) and microwave dielectric properties (epsilon(r)= 4.10; Q=1494) were obtained from the LAS/Al2O3 composites sintered at a very low temperature (1100 degrees C). The results achieved show the possibility of designing ceramic nanocomposites at low sintering temperatures using microwave technology with near-zero thermal expansion coefficients, high mechanical and chemical stability and low dielectric properties.This work has been developed by different funded projects. The authors would like to thank their financial support: Project SP20120677 funded by the Polytechnic University of Valencia (UPV), Project TEC2012-37532-C02-01 (DINAWAVE) funded from Ministerio de Economia y Competitividad (MINECO) - Spanish government- and co-funded by ERDF (European Regional Development Funds) of European Union. Author A. Borrell, acknowledges the Spanish Ministry of Science and Innovation for her Juan de la Cierva contract (JCI-2011-10498).Benavente Martínez, R.; Salvador Moya, MD.; Penaranda-Foix, FL.; García-Moreno, O.; Borrell Tomás, MA. (2015). High thermal stability of microwave sintered low-er beta-eucryptite materials. Ceramics International. 41(10):13817-13822. https://doi.org/10.1016/j.ceramint.2015.08.066S1381713822411