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Mechanochemistry and Reactivity of Materials

Broad objectives:
Application of non-conventional methodologies (mechanochemistry, sonication, microwaves, and SCTA) in the development of new leading materials, Study of the chemical reactivity of materials under operating conditions, Materials diagnostics in Cultural Heritage
Specific objectives:
Design and implementation of instrumentation for non-conventional processing
Specific advantages
Exhaustive control of the chemical processing to produce tailored materials, New scientific equipments for processing and characterisation of materials at high temperature. Solid background and international recognition on Thermal Analysis, Mechanochemistry, Development of non destructive techniques for Cultural Heritage studies

Development of cermets with high entropy alloys as binder phase for machining applications



Research head: Francisco José Gotor Martínez
Period: 01-01-2015 / 31-12-2018
Financial source: Ministerio de Economía y Competitividad
Code: MAT2014-52407-R
Research group: José Manuel Córdoba Gallego, María Dolores Alcalá González, Pedro José Sánchez Soto, Concepción Real Pérez, María Jesús Sayagués de Vega

Abstract[+]

Machining is an essential part of the manufacturing processes in many industries and has significant economic implications, as it represents an important proportion of the total manufacturing cost. The success of machining depends on many factors, among which the correct choice of the cutting tool. High-speed machining and difficult-to-cut materials, such as superalloys employed in the fabrication of aircraft engines, impose extreme working conditions to cutting-tools, which are characterized by high temperatures, pressures and tensions that can lead to the premature failure in service. Furthermore, the deterioration of the cutting-tool due to an excessive wear and deformation makes it difficult to maintain the tolerances and the surface integrity of the workpiece, severely compromising the fatigue properties and, therefore, its applicability and lifetime. The European industry has as a main objective to improve the productivity, accuracy and quality of these highly-demanding machining processes, stimulating the search for new cutting-tool materials that are better suited to these new requirements.
Cermets have properties, such as high wear resistance, high chemical stability and good mechanical strength at high temperature, well-adapted to the requirements of these machining processes. But for a realistic application, it is necessary to significantly increase the fracture toughness and damage tolerance to values close to those of cemented carbides. In the last few years, there has been an ongoing process of cermets optimization, mainly by modifying the microstructure and chemical composition of the ceramic phase. In a previous project (MAT2011-22981), we have shown that the so-called complete solid solution cermets, characterized by single phase ceramic particles consisting of a complex carbonitride, allow achieving a good combination of hardness and fracture toughness.
In this new project, which can be considered as complementary to MAT2011-22981, we propose to further improve the properties of cermets, also acting on the binder phase as it is ultimately responsible for the cohesion and toughness of the material. High entropy alloys (HEAs), which are composed of at least five major metal elements in equal or near equal atomic percent (as opposed to traditional alloy systems that are typically based on only one or two major elements), can be postulated as suitable to replace current binder phase in cermets. These alloys often exhibit superior properties than conventional alloys, including high strength and ductility at high temperature and good wear and corrosion resistances. The main goal of this project focuses on the development of complete solid solution cermets with HEAs as the binder phase. The cermets to be developed will have a simple microstructure; similar to cemented carbides, but high compositional complexity, since the two constituent phases (ceramic and binder) will be complex solid solutions with a high number of components (at least five). With these new cermets, we try to maintain their current optimal properties, while improving those limiting their potential use in the most demanding machining processes.


Hybrid thermochemical storage of concentrated solar energy SOLARTEQH



Research head: Luis Allan Pérez Maqueda
Period: 01-01-2015 / 31-12-2017
Financial source: Ministerio de Economía y Competitividad
Code: CTQ2014-52763-C2-1-R
Research group: María Jesús Diánez Millán, José Manuel Criado Luque

Abstract[+]

There are current projects within the Sunshot (USA) initiative and UE FP7 program in which the feasibility of fluidized beds for permanent chemical storage of concentrated solar energy is analyzed. One of the materials considered is the cheap and abundantly available natural limestone (CaCO3). Using a CO2/air mixture in suitable relative proportions according to the operating temperatures (600-900ºC), CaCO3 would be decarbonated by endothermic reaction in periods of high irradiation or the CaO would be carbonated releasing heat when the temperature falls below a certain value. By varying the %CO2 in the fluidization gas, either decarbonation or carbonation would be provoked as desired to reduce or increase the bed temperature based on the intensity of solar radiation and electricity demand. This control would help to alleviate the effect of the variability of sunlight intensity. Besides of the permanent storage of energy, the energy density of CaCO3 (about 1 MWhr/m3) is greater than that of molten salts currently used in commercial plants (0.25-0.40 MWhr /m3). Furthermore, natural limestone is non-corrosive material, not degradable and would allow operation at higher temperatures thus increasing the thermoelectric conversion efficiency. However, the fluidization of limestone is typically very heterogeneous, being characterized by the formation of gas channels and large unfluidizable aggregates in the bed which greatly reduce the effectiveness of solid/gas contact and thus the heat transfer efficiency of the reaction. On the other hand, other projects have leaded to the development of successful small-scale pilot plants based on the thermal storage in fluidized beds of inert solids with high heat capacity such as fine silica sand or silicon carbide with good fluidization properties and thus characterized by a high heat transfer. However, these systems present unavoidable heat losses and large volumes are needed to ensure a supply of heat to the power cycle in periods of low solar irradiation. Our project is based on synergistically combine the heat storage in fluidized beds of fluidizable inert solids (such as sand) with the permanent chemical storage of CaO precursors (such as natural limestone) by the use of fluidized beds of mixtures of both granular materials. Experimental measurements will allow characterizing the behavior of the sand/natural limestone mixtures for the transfer and storage of concentrated solar energy. The working plan shall limit the optimum concentration of CO2 in the fluidizing gas and proportion of sand/limestone as a function of temperature for optimizing the energy storage efficiency. The physic-chemical properties of mixtures of sand/limestone that favor heat transfer and storage according to the intensity of solar radiation will be delimited. Also thermal and chemical stabilization methods will be explored in order to increase the reversibility of the carbonation/calcination reaction under practical conditions. In parallel, a thermodynamic modeling work will be carried out that includes processes that affect the energy efficiency and serve as a starting point to establish optimum operating parameters with the ultimate goal of transferring the knowledge to the technology sector. For this final purpose the project has the support of Abengoa Solar.


Ferroelectric polymer-based piezoelectric nanogenerators for energy harvesting and sensor applications



Research head: Pedro E. Sánchez Jiménez
Period: 01-10-2014 / 30-09-2016
Financial source: Junta de Andalucia
Code: TAPOST-134. Programa Talent HUB
Research group:

Abstract[+]

Harvesting energy from ambient sources in our environment has generated tremendous interest as it offers a fundamental energy solution for small-power applications including, but not limited to, ubiquitous wireless sensor nodes, portable, flexible and wearable electronics, biomedical implants and structural/environmental monitoring devices. As an example, consider that the number of smart devices linking everyday objects via the internet is estimated to grow to 50 billion by the year 2020. Most of these “Internet of Things” devices will be extraordinarily small and in many cases embedded, and will wirelessly provide useful data that will make our lives easier, better and more energy-efficient. The only sustainable way to power them is using ambient energy harvesting that lasts through the lifetime of the product, and hence the need for commercially viable small‑scale energy harvesters that can operate in any environment. In this context, energy harvesting from ambient vibrations is particularly attractive, as these are ubiquitously available and easily accessible, originating from ever-present sources such as the moving parts of devices and machines, fluid flow and even body movements. Nanoscale piezoelectric energy harvesters, also known as nanogenerators2, are capable of converting small-scale vibrations into electrical energy, thus offering a means of superseding batteries that require constant replacing/recharging, and that do not scale easily with size. Nanogenerators can thus pave the way for the realization of the next generation of self-powered electronic devices, with profound implications in disciplines as far-reaching as biomedicine, robotics, smart environmental monitoring and resource management, to name a few. Nano-piezoelectric energy harvesting is an emerging technology and this proposal is designed to tackle the challenge of developing novel materials with enhanced piezoelectric properties that are cheap, environment-friendly, bio-compatible and easily integrated as nanogenerators into electronic devices.


Synthesis and characterization of non oxide ceramic obtained by the thermal decomposition of polymeric precursors



Research head: Pedro E. Sánchez Jiménez
Period: 16-05-2014 / 15-05-2016
Financial source: Junta de Andalucia
Code: TEP-1900
Research group: Antonio Perejón Pazo, Cristina García Garrido

Abstract[+]

There has been a substantial interest during the last years in polymer derived ceramics due to the wide array of interesting properties they exhibit. This type of ceramic, best known by the acronym PDCs, are obtained by the thermal decomposition of a polymeric precursor and are mainly non oxidic, such as SiC, Si3N4, BN, etc. PDCs exhibit a wide array of thermomechanical and electrical properties of great interest, as well as a high thermal and oxidation resistance which make them promising candidates for working under extreme environmental conditions. Thus, several potential applications ranging from nanotechnology to aeronautics have been proposed. A big advantage of these materials is that their properties depend on both the chemical properties of the original polymeric precursor and the processing conditions. Therefore, by carefully selecting the precursor and the experimental degradation conditions it would be possible to tailor the properties of the final ceramic. Moreover, the temperatures needed to prepare these ceramics are much milder than those required by means of conventional ceramic processing or powder consolidation techniques. However, there is an important disadvantage that has severely limited their usability in that cracks are formed during the transformation into a ceramic so that the final pieces might be rendered unusable. Despite the important of processing, there are few systematic studies assessing the influence of ceramification conditions on the final properties. In this proposal, we plan to use smart temperature controlled methods to study the synthesis of different types of PDC. This methodology allows for great precision in the control of experimental conditions such as temperature and gas pressure and has been previously proved useful to help control the microstructure of materials synthesized by thermal transformations from precursors. Thus, we plan to use this methodology to synthesise defect-free PDCs and to study the influence of experimental conditions on the nanostructure and properties of the final ceramic material. At the same time, the information provided by the systematic study will help to better comprehend the underlying physics of the as yet poorly understood polymer-ceramic transformation. The prepared powders will be characterised in terms of nanostructure and properties such of piezoresistivity, porosity, lithium insertion capability and oxidation resistance. 


Preparation of technically interesting nanocomposites by mechanochemistry



Research head: Luis A. Pérez Maqueda
Period: 16-05-2013 / 15-05-2017
Financial source: Junta de Andalucía
Code: P11-TEP-7858 (Proyecto de Excelencia)
Research group: José Manuel Criado Luque, María Jesús Diánes Millán, José Luís Pérez Rodríguez, Juan Poyato Ferrera, Pedro Enrique Sánchez Jiménez, Antonio Perejón Pazo

Abstract[+]

Nanocomposites are of the most academic and technical interest. Those materials consist of two or more different phases being the dimension of one of the phases smaller than 100 nm. Thus, those materials have outstanding properties as compared with conventional ones. In this project, mechanochemistry is proposed for the preparation of different nanocomposites. This preparation procedure is sustainable from the environmental point of view and easy to scale-up. In the frame of the project, a unique high energy planetary ball mill will be developed in collaboration with the MC2 enterprise. Moreover, a study of the forces as a function of the milling conditions will be performed in order to get a better understanding of the processes involved in the mechanochemical reactions. Two types of nanocomposites will be prepared: a) copper reinforced nanocomposites and b) partially and totally stabilized zirconia. In the latter case, powders will be sintered using a kind of field assisted sintering procedure. It is expected a reduction in the sintering temperature of the zirconia. The kinetics of the sintering process with and without electric field will be performed within the project using an new dilameter that will be constructed for this purpose.


Mechanochemical desing of structural materials for high-temperature technological applications



Research head: Francisco José Gotor Martínez
Period: 01-01-2012 / 31-12-2014
Financial source: Ministerio de Ciencia e Innovación
Code: MAT2011-22981
Research group: M. Jesús Sayagués de Vega, Concepción Real Pérez, M. Dolores Alcalá González, Pedro José Sánchez Soto, José Manuel Córdoba Gallego, Ernesto Chicardi Augusto

Abstract[+]

Carbides, nitrides and borides of transition metals are essential components of a large number of composite materials used for structural and protective applications at high temperature because they show an excellent combination of physical and chemical properties, which confers good mechanical strength, and wear, oxidation and corrosion resistances. The materials based on these refractory compounds are designed by employing multiphasic systems, due to the high multi-functionality that are required and the inability to achieve the intended properties from a single phase material.

During the processing of these materials is common to observe important compositional gradients and interactions between the different constituent phases that hinder achieving the desired properties. In this project, we intend to undertake a new design for this type of material of incorporating most of its key components such as complex solid solutions. This will reduce the final number of phases in the material and obtain greater assurance of success with the preset properties for technological applications. To this end, we propose a new synthesis route based on the mechanochemical process called as mechanically-induced self-sustaining reaction (MSR). Our research group has shown that this method allows obtaining solid solutions belonging to M-B-C-N systems with a high control of the stoichiometry. The main objective of this project is to incorporate the method MSR to the methodology used for the development of materials consisting of solid solutions that can be used in high temperature applications. It is intended to adequately characterize the properties of the developed materials and to compare them with those made using the methods so far employed.


Processing of advanced ceramics from polymeric precursors by smart temperature methods



Research head: Luis Pérez Maqueda
Period: 01-01-2012 / 31-12-2014
Financial source: Ministerio de Ciencia e Innovación
Code: CTQ2011-27626
Research group: Maria Jesús Diánez Millán, José Manuel Criado Luque, Pedro E. Sánchez Jiménez, Antonio Perejón Pazo

Abstract[+]

Ceramic materials prepared from polymer precursors, known as polymer-derived ceramics (PDC) are a subject of the most interest. These materials are prepared from a polymer that is first cured and then ceramified, usually by thermal treatment at relatively low temperature if compared with those needed in conventional ceramic processing from ceramic powders. Thus, the final product is directly obtained in a near-net shape process. These materials have very interesting electrical, thermomecanical and oxidation resistance properties. Thus, a number of applications from nanotechnology to aeronautics have been proposed. Nevertheless, a significant limitation of the use of these materials is is related with the ceramification process of the preceramic piece. During this thermal conversion, some defects, such as cracks, appear in the pieces. In this project, we propose the use of smart temperature controlled methods for the processing of the preceramic polymeric precursors. In previous studies, we have shown the advantages of this methodology for controlling the structure and microstructure of the products prepared by thermal transformation of precursors. In addition, this methodology is also useful for kinetic studies of solid state reactions. In the present project, we expect to obtain defect free PDC materials and to study the influence of the preparation conditions on the nanostructure of the products and get new insights in polymer to ceramic conversion process, paying special attention to the study of the kinetics of the involved processes. The so-obtained products will be characterized in terms of their nanostructure and properties, in particular piezoresistivity, lithium insertion capacity and oxidation resistance.


Mechanosynthesis of technological materials



Research head: Francisco José Gotor Martínez
Period: 01-01-2011 / 31-12-2011
Financial source: Ministerio de Ciencia e Innovación
Code: MAT2010-17046
Research group: M. Jesús Sayagués de Vega, Concepción Real Pérez, M. Dolores Alcalá González, José Manuel Córdoba Gallego, Ernesto Chicardi Augusto

Abstract[+]

High-energy ball milling devices, such as planetary, vibratory and attritor mills, intro-duce into the starting powders increasing amounts of energy. Collisions and friction between the balls and between the balls and the wall of the vial result not only in a steadily reduction of particle size, but also induce solid state chemical reactions. During high-energy milling, inti-mate mixing of reactants takes place and fresh surfaces are continually created, which make possible that solid-state reactions progress gradually at room temperature. The new phase has frequently a nanometric character and a great amount of defects, which favours a subsequent sintering process. The mechanochemistry method represents an attractive and alternative route in the synthesis of nanocrystalline materials. Mechanochemical techniques are simple, flexible, and able to prepare a large variety of materials in a bulk-manner at room temperature. Mechanochemistry has been revealed as a practical way to obtain cost-effective materials and more convenient than other synthesis methods because of avoiding the use of heat and solvents can reduce environmental contamination. Due to an almost infinite compositional flexibility, mechanochemistry is suitable for the production of complex solid solutions and composites because of excellent powder homogeneity can be achieved at the same time as the nanostructure. In this project, the ability of mechanochemistry to produce easily and in a re-producible manner different materials that sometimes cannot be synthesized via conventional routes is explored. The following systems have been selected: (i) carbides, nitrides, and borides of transition metals, and (ii) oxides with a perovskite structure and general formula (A1-xA’x)(B1-yB’y)O3-z (A/A’=La, Sr; B/B’=Mn, Cr, Mg, Ga). In the first case, the aim is to develop composite materials based on complex solid solutions of the after-mentioned refractory compounds for structural applications. In the second case, the final goal is to design solid oxide fuel cells where all the components possess the same perovskite structure and similar chemical composition. In addition, the study and modelling of high-energy ball milling processes will be intended in order to permit more easily the scaling-up of the process.


Study of the degradation processes on the materials used in the manufacture of historical organs



Research head: Angel Justo Erbez
Period: 2010 / 2013
Financial source: Ministerio de Ciencia e Innovación
Code: MAT2010-20660
Research group: Adolfo Iñigo Iñigo, Juan Poyato Ferrera, José Luis Pérez Rodríguez, Liz Karen Herrera Quintero, Angel Justo Estebaranz, Adrián Durán Benito, M. Carmen Jiménez de Haro, Belinda Sigüenza Carballo

Abstract[+]

The main objective of the project is to know the composition, microstructure and mechanical properties of tin-lead alloys from Spanish historical pipe organs. Also, we will study the degradation and corrosion processes on the pipe organs and the products of corrosion produced by these processes. Analyses will be performed in Spanish research and technological institutes (ICMSE, AIMEN, IRNASA) and European facilities (ESRF, C2RMF). This objective pursues to know the vectors that produce the corrosion, like the volatile compounds from the wood and other organic materials used in the construction of pipe organs, water vapour and/or carbon dioxide. The work will be carried out in materials with different grades of corrosion taken in the organs, including alloys and woods. Also, alloys with different tin-lead ratios, and with traces of other elements (As, Bi) will be prepared and will be undergone to corrosion tests. Results from the composition and results of tensile and creep tests will be correlated with the corrosion rate. The results obtained in the laboratory will be compared with the samples coming from the organs, and conclusions will be reached about the possible alteration causes, the suitable compositions for the restorations, and the most resistant alloys to the corrosion, to apply them to the construction of new organs.


Preparation of multiferroic materials by mechanical alloying and termal methods with smart temperatura control



Research head: Luis A. Pérez Maqueda
Period: 01-01-2009 / 31-12-2011
Financial source: Ministerio de Ciencia y Tecnología
Code: MAT2008-06619
Research group: Maria Jesús Diánez Millán, José Manuel Criado Luque

Abstract[+]

Multiferroic materials are those with two or more ferroic properties. There is a signifi-cant interest in those materials due to the large number of possible applications due to their properties. It has been claim in literature that the lack of reliable preparation methods for stoichiometric defect-free compounds hinders the development of applications of these compounds in devices. In this project, we propose the use of two alternative procedures for the preparation of multiferroic compounds: mechanical alloying and thermal decomposition of precursors under smart temperature conditions. The first procedure implies the use of a high-energy mill designed in cooperation with MC2 firm. The mill is connected to the gas system during operation. Thus, it is possible to control pressures up to 20 atm of any reactive or inert gas. The alternative proposed procedure implies the preparation of several precursors and their decomposition under smart temperature conditions. In the smart temperature control methods, the process itself determines the temperature evolution according to a function of the process evolution with time. These methods differ from the conventional ones in the control procedure, thus, in the conventional ones the function temperature-time is fixed while in the smart temperature control methods the process itself determines the evolution of temperature. In previous publications, we have observed that by using the smart temperature procedure, microestructure of samples could be tailored, while by using conventional heating procedures such control could not be achieved. Prepared samples will be characterized in terms of the oxidation state of the different cations, structure, microstructure and properties.


Mechanosynthesis of metallic hydrides and multiferroic perowskites in a high energy mil under high pressure



Research head: Luis Allan Pérez Maqueda
Period: 01-02-2008 / 31-03-2011
Financial source: Junta de Andalucía
Code: TEP-03002
Research group: Gotor, F.J., Diánez, M.J., Criado, J.M., Alcalá, M.D., Poyato, J., Pérez Rodríguez, J.L., Sánchez Jiménez, P.E.

Abstract[+]

The main objective of the Project is the use of a high energy mil, developed in cooperation with the firm MC2, ingeniería y sistemas, S.L., that allows controlling the atmosphere during the treatment at pressure of up to 20 bar of any inert or reactive gas, for the preparation of two kinds of materials: modified magnesium hydrides for hydrogen storage and multiferroic ceramics. In this project we propose for the first time the preparation of multiferroic ceramics by mechanical alloying at room temperature. This is a challenging topic because the preparation of such materials requires pressure of up to several GPa. The prepared materials will be characterized in terms of their properties. Metallic hydrides will be prepared by mechanical alloying under high pressure of hydrogen. The prepared materials will be characterized in terms of their structure, microstructure and hydrogen storage behavior, including the kinetics of hydrogenation and dehydrogenation.


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