Objective
A.BACKGROUND
Nanophase materials and nanocomposites, characterized by an ultrafine grain size (< 50 nm) have created a high interest in recent years by virtue of their unusual mechanical, electrical, optical and magnetic properties. For example:
Nanophase ceramics are of particular interest because they are more ductile at elevated temperatures as compared to the coarse-grained ceramics.
Nanostructured semiconductors are known to show various non-linear optical properties. Semiconductor Q-particles also show quantum confinement effects which may lead to special properties, like the luminescence in silicon powders and silicon germanium quantum dots as infrared optoelectronic devices. Nanostructured semiconductors are used as window layers in solar cells.
Nanosized metallic powders have been used for the production of gas tight materials, dense parts and porous coatings. Cold welding properties combined with the ductility make them suitable for metal-metal bonding especially in the electronic industry.
Single nanosized magnetic particles are mono-domains and one expects that also in magnetic nanophase materials the grains correspond with domains, while boundaries on the contrary to disordered walls. Very small particles have special atomic structures with discrete electronic states, which give rise to special properties in addition to the super-paramagnetism behaviour. Magnetic nanocomposites have been used for mechanical force transfer ferrofluids), for high density information storage and magnetic refrigeration.
Nanostructured metal clusters and colloids of mono- or pluri-metallic composition have a special impact in catalytic applications. They may serve as precursors for new types of heterogeneous catalysts (Cortex-catalysts) and have been shown to offer substantial advantages concerning activity, selectivity and lifetime in chemical transformations and electrocatalysis (fuel cells). Enantioselective catalysis were also achieved using chiral modifiers on the surface of nanoscale metal particles.
Nanostructured metal-oxide thin films are receiving a growing attention for the realization of gas sensors (NOx, CO, CO2, CH4 and aromatic hydrocarbons) with enhanced sensitivity and selectivity. Nanostructured metal-oxide (MnO2) find application for rechargeable batteries for cars or consumer goods. Nanocrystalline silicon films for highly transparent contacts in thin film solar cell and nanostructured titanium oxide porous films for it high transmission and significant surface area enhancement leading to strong absorption in dye sensitized solar cells.
Polymer based composites with a high content of inorganic particles leading to a high dielectric constant are interesting materials for photonic band gap structure produced by the LIGA.
Nanophase engineering expands in a rapidly growing number of electronic materials, both inorganic and organic, allowing the manipulation of optical and electronic functions. The production of nanophase or cluster-assembled materials is usually based upon the creation of separated small clusters, which are then fused into a bulk-like material or on their embedding into compact liquid or solid matrix materials. For example, nanophase silicon, which differs from normal silicon in physical and electronic properties, could be applied to macroscopic semiconductor processes to create new devices. For instance, when ordinary glass is doped with quantized semiconductor "colloids", it becomes a high-performance optical medium with potential applications in optical computing.
A.1.Influence on properties by "nanostructure induced effects"
For the synthesis of nanosized particles and for the fabrication of nanostructured materials, laser or plasma driven gas phase reactions, evaporation-condensation mechanism, sol-gel-methods or other wet chemical routes such as inverse micelle preparation of inorganic clusters have been used. Most of these methods result in very fine particles, which are more or less agglomerated. The powders are amorphous, crystalline or show a metastable or an unexpected phase, the reason for which is far from being clear. Due to the small sizes, any surface coating of the nanoparticles strongly influences the properties of the particles as a whole. Studies have shown that the crystallization behaviour of nanoscaled silicon particles is quite different from micron-sized powders or thin films. It was observed that tiny polycrystallites are formed in every nanoparticle, even at moderately high temperatures.
Roughly two kinds of "nanostructure induced effects" can be distinguished: first, the size effect, in particular, the quantum size effects, where the normal bulk electronic structure is replaced by a series of discrete electronic levels and, secondly, the surface or interface induced effect, which is important because of the enormously increased specific surface in particle systems. While the size effect is mainly considered to describe physical properties, the surface or interface induced effect plays an eminent role for chemical processing, in particular in connection with heterogeneous catalysis. Experimental evidence of the quantum size effect in small particles has been provided by different methods, while the surface induced effect could be evidenced by measurement of thermodynamic properties like vapour pressure, specific heat, thermal conductivity and melting point of small metallic particles. Both types of size effects have also been clearly separated in the optical properties of metal cluster composites. Very small semiconductor (<10 nm), or metal particles in glass composites, and semiconductor/polymer composites show interesting quantum effects and non-linear electrical and optical properties.
The numerous examples, which are far from complete, indicate that these materials will most probably gain rapidly increasing importance in the near future. In general, properties, production and characterization methods and their inter-relations are, however, not yet satisfactorily understood. Hence, efforts need to be made to enable the directed tailoring of nanophase, nanoscopic and nanocomposite materials needed for future technical and industrial applications.
A.2.Research and development on nanostructured materials in the world
Research on nanoscale science and technology is carried out in all major industrialized countries. Although financing, organization, work distribution between industry and universities and programmes vary from country to country, some examples are given below:
In the USA, the scientific activities are more widespread and better financed than in Europe. For example, NIST is coordinating the activities in the area of giant magnetoresistance in the USA (Consortium Richmond, Virginia, USA).
The major research activities in Japan are focused on the refinement of advanced manufacturing processes and instrumentation in diverse fields such as microelectronics, optics, ultra-precision machining, as well as the progress in fundamental nanometer-scale materials sciences research. MITI has identified nanotechnology as a very important discipline for which it has announced a budget of US $210 million for the next ten years for foreign and Japanese academic, government and corporate R&D.
Europe has no uniform programme on nanomaterials. On the contrary, almost each major industrialized country has its own nanomaterials programme. The progress on a common European Programme is therefore relatively small, despite important programmes in each of the following countries:
In Germany, the DFG is at present funding a package project involving seven academic institutions on nanocrystalline materials. Wider DFG research on the same topic is under consideration at the moment. Nanotechnology is being supported by ongoing BMBF projects as well as by DFG and Volkswagen Foundation.
In Great Briatin, the Advanced Magnetic Programme of EPSRC also covers nanomagnetism. Additionally, research programmes regarding nanostructured materials are at present being evaluated.
In Sweden, a national consortium for nanostructured materials exists, whereas in Finland, the national research programme "Ultrafine Particles (UFP)" has been started on nanomaterials at VTT Chemical Technology (1995-1998) with funds: ECU 1 million per year.
In Switzerland, parts of the three research programmes in the area of nanotechnology and nanomaterials (MINAST and Swiss Science Foundation NFP36) support some activities.
In France, CNRS (Centre national de la recherche scientifique) coordinates specific governmental research actions (GdR-CNRS) concerning:
-Wave propagation in random linear and/or non-linear media (resp. A. Migus).
-Aggregates (resp. C. Brchignac).
-Magnetic nanostructures (resp. A. Fert).
-Physico-chemical study of Si-based nanophase ceramic powders (resp. C. Snmaud).
-Nanocomposites and cermets by chemical process (resp. Y. Laurent).
-C60 and its derivatives (P. Bernier).
Periodic workshops (Nano95, Nano96) were organized in Odeillo (three days, around seventy participants from governmental research and industry) on "Preparation, characterization, properties and application of nanomaterials".
As well as in other domains of material science, the projects and research programmes are characterized by a certain interdisciplinarity. Nevertheless, Europe shows a lack of a coherent inter-state strategy to support and subsidize this important interdisciplinary cooperation in nanomaterials.
For these reasons, the proposed COST Action will be the ideal frame to implement European cooperation in the domain of nanomaterials. The Action proposed supports coordination with the existing COST Action D5 "Nanochemistry at surfaces and interfaces", especially with the part "Nanomaterials", as well as with the planned COST Actions of the ad hoc working group "Technology-driven physics", namely "Nanophysics, nanostructured materials and nanotechnology" and "Modelling of physical phenomena in technological application". A more detailed description of this coordination will be given in Part D "Organization and timetable".
B.OBJECTIVES AND BENEFITS
The main objective of the COST Action is to develop nanostructured materials with new and unique structural and functional properties. This should be carried out in European industries but it has to be combined with fundamental research in order to solve technological problems. The last are at the origin of the present limited commercial diffusion of these materials.
The fundamental issues in nanostructured materials are:
(1)ability to control the scale (size) of the system;
(2)ability to obtain the required composition - not just the average composition - but details such as defects, concentration gradients, etc.;
(3)ability to control the modulation dimensionality;
(4)during the assembly of the nanosized building blocks, one should be able to control the extent of the interaction between the building blocks as well as the architecture of the material itself.
Therefore, the more specific objectives are the following:
development of synthesis and/or fabrication methods for raw materials (powders) as well as for the nanostructured materials;
better understanding of the influence of the size of building blocks in nanostructured materials as well as the influence of microstructure on the physical, chemical and mechanical properties of this material;
better understanding of the influence of interfaces on the properties of nanostructured material;
development of concepts for nanostructured materials and, in particular, their elaboration;
investigation of catalytic applications of mono- and pluri-metallic nanomaterials;
transfer of developed technologies into industrial applications including the development of the industrial scale of synthesis methods of nanomaterials and nanostructured systems.
C.SCIENTIFIC PROGRAMME
The scientific programme can be structured in the following tasks:
Materials synthesis.
Nanostructured materials for structural applications.
Nanostructured materials for functional applications
-chemical (catalysis),
-electrical,
-optical,
-magnetic.
It is evident that this classification of the scientific programme into these "classical tasks" of materials research programmes is an artificial one. The first task group especially will have strong interactions with all other task groups, because this work fundamentally influences the following materials applications. Both groups of nanostructured materials have to be investigated on their mechanical and physical needs, but in different evaluations as carried out under the following paragraphs.
Material synthesis and processing
Synthesis techniques for nanostructured materials can be basically divided into the following four categories:
-Atomic or molecular precursors form a basis from which larger building blocks can be constructed. The commonly used techniques in this class are gas condensation, chemical precipitation, aerosol reactions, low temperature biological templating, etc.
-Another useful but "less elegant" approach is to start from conventional coarse-grained precursors and break them down to ultrafine grains by high energy mechanical attrition.
-Crystallization of an amorphous precursor at low temperatures to obtain nanocrystalline material.
-or production of nanosized precipitates from a coarse-grained structure by conventional phase separation methods.
-Early meteorites, interstellar dust, and biological systems, which are hierarchical systems based on nanostructures and which are present in nature.
In experiments designed for basic understanding, particles of controlled size, shape, crystallinity and surface-pureness need to be studied. New techniques of particle production and coating, as well as methods of determining and selecting particle properties before compacting, must be applied or developed for this purpose. The major problem is the availability of high performance, low-cost starting materials (e.g. nanosized agglomerate-free powders) and appropriate processing methods, which allow components, parts, coatings or micro-patterned parts to be produced by industrially applicable processing techniques. Meanwhile, chemical routes to solve these problems become interesting, but especially with respect to the materials' production, the potential of chemistry is exploited only to an insufficient extent. A similar observation can be made for the processing step. On the other hand, as already shown in a variety of examples, processes like chemical vapour reaction (CVR), aerosol reactions, chemical precipitation using control of growth processes or microemulsion techniques are able to produce large quantities of high-grade powders at comparably low costs.
It is proposed to investigate and to develop chemistry-based production and processing methods since it has already been shown that these processes allow nanoparticles to be handled with techniques suitable for industry. It is quite necessary to exploit these fields to develop broadly applicable industrial processes. These developments focus on optical materials, for components of integrated optics as well as for new shaping techniques for nanosized ceramic parts or direct use of nanoparticles for drug targeting or magnetic imaging.
Besides the size of building blocks of the nanostructured material, the microstructure of the materials has an extremely important influence on the properties. Therefore, the aim of this task will be to develop "integral synthesis" of nanostructured materials. Depending on the application and the properties of the material, different synthesis methods will be developed in cooperation with the other task groups. It is also important to note that, especially for this task, robust cooperation with related COST Action D5 is planned.
C.2.Structural application (mechanical properties)
Fundamentally, the mechanical behaviour of a material is determined by the type of bonding and defect structure. Metals - with non-directional bonds - are highly ductile. Ionic solids are more difficult to deform because charge neutrality conditions have to be satisfied. Covalent solids have strong directional bonds. Thus, ceramics and inter-metallics are subject to brittle fracture, while metals are soft and easily deformable due to dislocations. In the nanophase, both types of "bulk-like" behaviour are altered.
Nanophase metals show increasing hardness with decreasing grain size. For example, there is a five-fold increase in hardness in nanophase Cu (grain size = 6 nm) as compared to coarse-grained Cu (grain size = 50?m). In nanophase Pd (grain size = 7 nm), the yield stress goes up by a factor of 5 from the bulk metal (grain size = 100?m).
In the case of inter-metallics - at large grain sizes, the hardness increases with decreasing grain sizes, but often decreases or saturates below a limiting size - thus showing a transitional behaviour. The stress-strain curve for the very brittle alloy (Fe28Al2Cr) shows macroscopic failure at a relatively low strain. However, in the corresponding nanophase material (grain size = 80 nm), compression produces a continuous plastic deformation and fracture does not occur.
Ceramics are normally the most brittle of the three classes. The brittleness of ceramics can be quantified in terms of the strain rate sensitivity, m, which is the exponent in the equation: ? = k(d?/dt)m, and can vary from 0 (perfectly brittle) to 1 (perfectly ductile). For conventional ceramics such as ZrO2 and TiO2, m < 0,01. For nanophase ZrO2 and TiO2 (grain size = 100 nm), m 0,02 at 300 K and m increases almost exponentially below 50 nm for both of the oxides. Fully dense nanophase TiO2 becomes highly ductile at 800?C.
Much effort will have to be dedicated to explaining in detail the mechanical properties in an atomistic scale. We believe that only an approach which includes all three classes of material (metals, inter-metallics, ceramics) can provide a complete overview on how the size of building blocks of nanostructured materials can influence the mechanical properties.
C.3.Functional application (electrical, optical, chemical and magnetic properties)
Electrical properties
The investigation of electrical properties of nanostructured and composite materials has a long tradition, and products of interesting resistance properties have been attained. However, this field is shown as still having a large potential for further development, in particular by more directed topology manipulation, by inclusion of "zero dimensional" units (quantum dots), ballistic transport, electroluminescence of clusters, electrolytic cluster cells, etc.
Examples are:
1.Varistors with non-linear dependence of electrical conductivity on electric field (the applications mentioned are not very clear).
2.Cermets (ceramic-metal composites) with extreme temperature dependencies and non-linear behaviour due to (single electron) tunnelling currents over Coulomb barriers between adjacent clusters.
3.PTC thermestors which use the temperature dependence of the conductivity as thermometers, current sensors and for current control.
4.Current-sensitive conductors which have applications as current limiters and sensors.
5.Non-linear insulators with non-linear dependence of the dielectric constant on electric field and temperature. They are applied for high voltage shielding.
6.Piezoresistors with pressure-dependent electrical resistivity which are used as pressure sensors and switches.
The scientific goal of this working group will be the understanding of the influence of the microstructure (or topology) of nanostructured materials, mainly of nanostructured composites on the properties. Besides the characterization of such new materials, this fundamental understanding as well as the methods for these syntheses need to be developed.
Optical properties
Noble metal colloids have been used for staining or colouring glasses for hundreds of years, e.g. for ruby-red glass. Au-colloids are used, while for yellow glass use is made of Ag-colloids, both typically about 10 nm in size. The unusual linear optical properties of these materials are ascribed to surface plasmon resonance of the conducting electrons induced by light which dramatically increase the local fields.
These resonances occurring at particular frequencies of light lead to selective absorption bands. Surface resonances of metal clusters are sensitive to the particle material, the particle geometry (shape, size, etc.), the interface between particle and surrounding and the topology of the clusters in many-particle-systems. Hence, by directed manipulation of these features, the optical properties can be modified over broad regions of frequencies. High-efficiency optical colours, absorbers, and filters of widely varying properties can thus be produced, e.g. they can be outstandingly stable for a large range of temperatures.
The non-linear optical properties of clusters, as well, are of general interest. If local field resonances, as described above, occur in metal clusters or many-cluster-samples, this induces dramatically enhanced non-linearity compared to the bulk, e.g the third-order susceptibility increases, compared to the bulk value proportional to the fifth order of the resonance factor. Effects are described for both non-linear clusters and non-linear embedding media. They were observed, for example, in noble metal colloids embedded in glass. It is also possible to obtain strong non-linear behaviour by embedding in matrices like barium titanate. Thus, the aim of this task is the development of new nanostructured composite materials with unusual linear or non-linear optical properties. Because the sizes, as well as the shapes, of the particles play an important role, close cooperation with the working group "Synthesis" is planned.
Chemical properties
Nanostructured metal clusters and colloids of mono- or pluri-metallic composition have a special impact in catalytic applications. They may serve as precursors for a new type of heterogeneous catalysts (Cortex-catalysts) and were shown to offer substantial advantages concerning activity, selectivity and lifetime in chemical transformations and electrocatalysis (fuel cells). Enantioselective catalysis was also achieved using chiral modifiers on the surface of nanoscale metal particles.
Industries (chemical and oil companies) are greatly interested in better controlled ways for the preparation of heterogeneous catalysis. Nanoscale metals and metaloxides offer new ways to improve activity, selectivity and stability. By sequential reduction or co-reduction of metal-salts in the presence of protecting groups, mono- and bi-metallic nanoparticles can be prepared, and the resulting colloid particles may be supported by carbon, oxides, polymers or ceramics yielding highly effective catalysis of a new type. Hydrogenation catalysts based on nanoscale noble metal precursors showed significant advantages when compared with conventionally prepared industrial catalysts.
The aim of this task is therefore the development of nanoscale catalyst precursors which could be exploited for the design of highly efficient, selective and long-time-stable catalysts for chemical and electrochemical processes. The amount of catalyst applied is tiny compared to the huge amounts of products used, and hence the manufacturing cost of these advanced systems is not an obstacle for practical uses.
Magnetic properties
Giant Magneto-Resistance (GMR) is observed in 10 nm thick multilayers of Fe separated by a suitable thickness of non-magnetic layers of Cr. Depending on the layer-repeat distance, the magnetic layers may be coupled either ferromagnetically (parallel) or anti-ferromagnetically (anti-parallel). When the resistance R of an anti-ferromagnetically coupled multilayer system is measured as dependent on a magnetic field H normal to the current direction, the change of the magneto resistance (Rh - Ro)/Rh, which in normal metals amounts to some 2%, can be 40% or even higher.
GMR materials are promising as highly sensitive sensors and next generation read/write devices in information technology. A large value of GMR (?R/?H) at low fields is already in test use in anti-locking automobile devices. It is also expected that these elements would allow the data storage density to be raised to much higher values (? 1 Gb).
GMR is very sensitive not only to the nature of the magnetic coupling but also that of the interface and intermediate layers. It is thus possible to replace the multilayer system by a system of fine particles dispersed in a non-magnetic matrix. The aim of this work is therefore the fundamental understanding of the effect of the structure of the material and the interfaces on the GMR-effect. Based on this knowledge, the development of new particulate materials with unusual magnetic properties will possibly be a main target of this group.
D.ORGANIZATION AND TIMETABLE
The Action shall be in operation for six years. The Management Committee (MC) of the Action will be organized and operated according to the COST 400/94 "Rules and Procedures". In a specific organization, this COST Action will ensure the contact to the members of the Management Committee (MC) of
(a)the planned COST Action "Nanophysics, nanostructured materials and nanotechnologies";
(b)"Modelling of physical phenomena in technological applications";
(c)the ad hoc working group "Technology-driven physics", as well as
(d)the existing COST Action D5.
The Action organizational structure will be based on working groups (WG), which have well-defined tasks. A liaison team will be formed for continuous monitoring of relations with other national and international projects in the field and short term missions (STM) will be identified to allow interested Action participants to visit and work in other laboratories for a few weeks. These STMs will be used especially to reinforce the contact as well as the technology transfer between academic and industrial R&D groups. Moreover, interdisciplinary seminars placed in regular time intervals (12 months), as well as special workshops, will be organized.
The organization diagram shows two special aspects:
1.The synthesis and processing (Working Group 1) will be included into the other working groups. This means that the research groups working more deeply in the area of synthesis for one specific application will also act as members of this special Working Group 1. With this type of organization, we can guarantee an intensive transfer of knowledge and technologies between the different areas or applications and therefore more effective research work.
2.After three years, a special seminar is planned. In this seminar, an evaluation of the project as well as of the direction of the COST Action is envisaged. Together with the Technical Committee "Materials" as well as with representatives of other related COST Actions, a selection of topics for a more advanced programme for the second phase will be carried out.
E.ECONOMIC DIMENSION
This COST Action is proposed by the "European Consortium for Nano Materials" which includes at present nearly 60 research groups from about 17 countries (including 13 European countries). Several other research groups from varying disciplines, but with interest in the research field of nanomaterials, have indicated their interest.
The following COST countries have actively participated in the preparation of the Action or otherwise indicated their interest: B, CH, D, E, F, GR, I, NL, S, SF, UK.
On the basis of national estimates provided by the representatives of these countries, and taking into account the coordination costs to be covered over the COST budget of the European Commission, the overall cost of the activities to be carried out under the Action has been estimated, at 1997 prices, at ECU 21 million.
This estimate is valid on the assumption that all the countries mentioned above, but no other countries, will participate in the Action. Any departure from this will change the total cost accordingly.
Keywords
Programme(s)
Call for proposal
Data not availableFunding Scheme
Data not availableCoordinator
Switzerland