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Advanced complex inorganic materials by a novel bottom-up (nano)chemistry approach: processing and shaping

Research project P6/17 (Research action P6)


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Description :

Inorganic materials, which exhibit very specific properties and cannot be replaced easily by other materials, play a significant role in the performance of a lot of the devices and equipments. In order to tailor a device property to its function, a good knowledge of the correlation between property and microstructure is required. Because the microstructure depends on the processing route, processing methods are decisive factors in developing new materials. While applications are most of the time well identified, material scientists continue to develop new processing methods that can produce components of a complex shape and high reliability with a minimum of machining and cost.

The objective of the project and its great novelty resides in the fact that completely innovative, nanochemical routes will be developed to engineer advanced inorganic materials. Therefore, this research project will focus on new routes for near-net shape forming of such advanced materials for fabricating components with high reliability at acceptable costs. The objective of the project is also the processing of advanced inorganic materials with minimal energy expenditure. The work to be performed thus encompasses both fundamental research on the understanding and control of the synthesis of precursor entities, the so-called building blocks, to the more applied research of their processing into complex shape materials. Synthesis must involve the spontaneous and sometimes reversible organization of small building blocks for the purpose of synthesizing a larger conglomerate structure. The materials will be designed first on the nanometer scale by the use of well identified multi-metallic molecular precursors following a bottom-up approach starting at the molecular level, in presence or not of ordered nanoscale opened systems offering many opportunities for the design of complex functional systems via self-assembling or templating. Much still needs to be done to advance the scientific underpinnings of these processes as well as the controlled assembly of particles, patterning, rapid sintering, prototyping, and densification of systems of complex shape and multimaterial combinations. Organization of the building blocks across several length scales is a key challenge in the design of advanced materials. From molecular level to macrostructure, synthetic pathways went up different routes from solution to powder processing and shaping. In meeting this challenge we propose also to learn much from bio-inspired processes in current use in nature.

Chemical synthesis procedures will be developed to prepare the required (sub)nanometer-scale particles, and particle assembly and/or densification will be controlled to achieve the desired performances. The research will be subdivised into seven different Work Packages:

• WP1: The "gel-state", fundamental and applications.
• WP2: Solution and precursor thin film processes
• WP3: Powder synthesis at nano- and microscale.
• WP4: Wet and dry shaping methods including prototyping techniques
• WP5: Densification (nanoscale, multimaterial, complex shapes, novel approaches)
• WP6: Templates, self assembly and bio-inspired architecture concept
• WP7: Novel characterization and imaging tools

Target products (especially oxides, carbides and nitrides) for this new technology area are the following :
- (nano)deposition methods for coating and machining (multi)functional parts (fuel cells, batteries, membranes, catalysts, optical, magnetic and chemical sensors, gas storage materials,…)
- complex shaped « to be integrated » materials (hot structures, abrasives, « bio »inspired architectures,…)

Work Packages 1 and 2 will concentrate on the use of gel precursors to promote the formation of tailor-made materials through controlled hydrolysis and condensation of a network-forming reagent with specific functionalities. Whatever the final product, a powder or a thin film, to extent gelification from classical Si- or Ti-based precursors towards multimetal combinations, input/expertise/research are required for a better understanding on a thermodynamic, theoretical and structural points of view, through determination of stability constants of metal complexes in the gel state, modelling of metal complexes in a porous 3D network, establishment of relationships between chemical composition of the gel, structure, texture and phase composition of the decomposed gel, tomography and texture analyses by X-ray spectroscopies and transmission electron microscopy. Especially when a thin film is required for application, the physicochemical process underlying film formation needs to be fundamentally investigated through chemically oriented tasks (modification of surface properties of the substrate, wettability properties of the liquids, use of external stimuli to improve film formation and/or to ensure local organization,…) and film growth mechanism and material properties.

Work Packages 3, 4 and 5 rely on the powder processing and shaping either directly through compaction and densification, or through wet colloidal processing where small particles in a suspension are conglomerated in orderly, homogeneous arrays. A smart densification method will be developed through modelling the compaction for different shape and size distribution of particles in the powder, selecting in such a way the best suited granulomorphometric parameters for the starting powder. New sintering technologies will be implemented and studied (like microwave sintering, pulsed electric current sintering, plasma spray sintering) in order to improve the final properties of the material. A similar approach will be followed for shaping particles in a suspension through electrophoretic deposition process. A special emphasis will be put on the use of controlled-size particles as precursors in engineering new structures. Interparticle interactions can be monitored through a combination of surface treatment, solvent choice, or the addition of other materials such as nonadsorbing molecules, or the use of external forces (magnetic field, deposition on patterned surfaces,…) to modulate the behavior of the particles in order to gain control over the nature of the structures produced. This is the so-called « directed » assembly approach. Strategies will be also implemented to prepare powder with well defined stoichiometries, and adequate chemical, structural and textural properties in view of their potentialities and uses. For examples, new routes based on the use of homo/heterometallic coordination compounds as precursors or the nanoreactor concept for the production of multifunctional nanoparticles will be investigated.

Work Package 6 is concerned with the development of strategies, most of them inspired from nature, towards advanced complex inorganic-based architectures and processes. New tools will be implemented: (i) the « transcription » using pre-organized or self-assembled molecular structures as templates for elaborating a material, (ii) the « synergetic assembly » corresponding to a co-assembly of molecular precursor with a material and template in situ, (iii) the « morphosynthesis » using chemical transformations in confined geometries (micelles, micro-emulsions,…), (iv) the « integrative synthesis » which combines all the previous methods to produce complex material with hierarchical structures, and finally (v) the «self generation » by the control of environmental conditions like in nature, leading to a highly sophisticated hierarchy with defined chemical composition spontaneously generated. Thus elucidating the basic components of inorganic chemistry and building principles selected by nature to propose more reliable, efficient and environment-respecting materials is one of the key issues of WP6.

Whenever it is possible, all the methodologies implemented in the WP’s will be strengthened by a continuous monitoring of the successive phenomena occurring during synthesis and shape forming. Work Package 7 relies thus on the development and use of unconventional « imaging » techniques to probe the assembly of entities (molecules, complex ions, particles, agglomerates,…), their interactions, and the resulting occurring structure. Time and temperature-resolved pictures of the phenomena underlying transformation from precursors to final product will be accesssible through structural, morphological and chemical spectroscopies specifically dedicated to a sort of material different from each partner. Priority extension of these « imaging » tools from one partner to the consortium utility and use will be considered.

Our objective is thus focused on the discovery of the fundamental and applied knowledge required to generate new advanced inorganic materials with minimal energy expenditure by interconnecting steps for which all the partners have partial answers. It brings together specialists from several fields of material science research with long standing expertise and international recognition. Furthermore, by firmly putting chemistry at the core of this research effort, research will be developed and stimulated in those areas which were traditionally the weakest part in condensed matter joint projects. Thus, a thermodynamically favorable pathway which benefits from inspiration from biological materials, from theoretical modelling, from novel and dedicated methods for analysis and sintering and in fact from the development of the whole physicochemistry of the soft solution processings will be found.


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