Basically, the unique competences at national level regard:
- the design of materials having controlled chemico-physical properties as well as innovative performances, obtained through a careful engineering of structures and a strict control of processes. This can be reached starting from the basic study and characterization of raw materials and mixtures, passing through the process optimization of powders' synthesis, forming and sintering of both dense and porous materials, with a simple or more complex shape, presenting controlled textures and properties.
- the knowledge of the processing porcedures and the ability to control the evolution of the microstructure and structure, consequently of the porperties and performance, of the final materials and devices. Joining of dissimilar materials and surface coating technologies have been dveloped as well
- the expertise in designing materials tailored to specific performances, in evaluating relationships among microstryure and mechanical/functional properties and in the engineering of the processing route to produce materials and components suitable for the application requirements in terms of properties/performance and shape/size of the devices.
These features are applied to a variety of ceramics and composites for a variety of applications. In the following a brief sumamry of the main fields where the competences of ISTEC are succesfully exploited.
CERAMIC MATERIALS FOR BUILDING AND CONSTRUCTION
- Innovation in materials
The recent innovations on house building and construction ceramic materials are focused on the design and development of light components with reduced thickness and desired aesthetic features. ISTEC offers innovative solutions regarding both materials (ceramic tiles, ceramic slabs, bricks, lightweight aggregate, refractories, sanitaryware, tableware, etc.) and technological processes. Studies are focused on the production process in order to evaluate the dependence of the main functional characteristics of the product on process parameters; relationships between characteristics of raw materials and properties of semifinished and finished products.
- RAW Materials
ISTEC is involved not only in prospecting, characterizing and developing new deposits and uses of raw materials for ceramics, but also in modelling their properties and technological behaviour. Special attention is paid to the recycling of industrial waste and byproducts in the manufacturing cycle of the ceramic products for house-building. ISTEC has 30 years of experience that includes: laboratory tests, assistance in the industrial trials, consultancy for product and processing problems, data-base on the use of civil and industrial residues in ceramics.
- Ceramic Pigments and Decoration Techniques
Decoration has a growing importance, as a means to add value to ceramic products, and is living a period of fast innovation rate for application techniques and materials used by the industry. CNR-ISTEC is contributing to set up new decoration technologies (e.g. ink jet printing, dry "screen printing") by developing inks, powders and their functionalization and synthesis procedures, in order to improve yield, stability and durability in the ceramic process.
Ceramic pigments are coloured crystals that are dispersed into a vitreous matrix, in which are insoluble, to impart colour by heterogeneous mixture. Ceramic pigments are widely used to colour tiles, tableware, sanitaryware, glazes and glasses. CNR-ISTEC is developing novel pigments, in collaboration with universities and companies in Italy and abroad, in order to improve optical properties, stability in the ceramic process, industrial manufacturing and cost, health and safety.
ISTEC designs and develops raw compositions (metakaolin, and secondary phases such as fibres and ceramic particles) and produces low cost, environmantally friendly materials and composites. Industrial wastes and by-products can be recycled as raw materials or inert fillers.
ISTEC produces geopolymer-based materials for structural and thermo-mechanical applications: panels for thermal insulation, soundproofing and fire-proofing, foams with a functional porosity for filters, catalysis, biomaterials , etc.
Geopolymers have a high heat tolerance because they do not burn or ignite, they do not release gases or smokes and they do not "explode" because they do not incorporate water of hydration within the structure as hydraulic cements do.
CERAMICS ENERGY AND ENVIRONMENT
- Dye Sensitized Solar Cells (DSSC)
Photovoltaic solar cells are used to convert solar light into electricity. In 1991 O'Regan and Graetzel realized a prototypes solar cell with good efficiency with materials at low-cost in respect to silicon solar cell.
DSSC (Dye Sensitized Solar Cell) are made of multilayer materials with selected band gap that allow photon adsorption and electron injection in the conduction band of the anodic material to produce electric energy. Heart of the system is a semiconductor layer (generally TiO2) that can either receive the high energy electrons coming from the dye and support the dye itself. For both functions the porous structure is highly important and must be carefully optimized.
ISTEC is mainly involved in the design and optimization of the semiconductor ceramic layers and of the glass ceramic sealing
- High Temperature Ceramic Batteries
ZEBRA batteries (Zero Emission Battery Research Activities), due to their high energy and power density, are one of the best solutions to the actual energy demand for stationary applications and to the sustainable mobility with electric and hybrid cars. These systems are based on nickel-sodium chloride cells operating at high temperatures (about 270°C-350 °C), enclosed in a thermal container and uses a ceramic ²"-alumina tube as solid electrolyte. The ceramic process needed to produce the electrolytic compartment has a key role to enhance and adapt the batteries performances to the specific requirements for stationary regime applications. Each minimal composition or process deviation strongly influences the final properties of the device. For this porpoise ISTEC mainly deals with the ad-hoc study of the productive process, from the powders synthesis to their forming and sintering needed to obtain ²"-alumina membranes with suitable morphological-structural characteristics. The research is deeply focused onto the analysis of the materials sintering behavior, on the study of reactive sintering processes and how the thermal treatments could influence the chemical-structural properties of the material. The optimization of the entire ceramic process aims to the production of a full density material with chemical-microstructural properties suitable for high efficiency batteries.
- Solid Oxide Fuel Cells (SOFC)
Solid Oxide Fuel Cells (SOFC), generally used for stationary applications, are flexible systems in terms of either fuels (hydrogen, methane, bio-masses) and generated power making them attractive for both industrial and residential applications. Despite these advantages, the SOFC systems are still at laboratory scale or at a pre-competitive stage due to their high costs related to either the cells production and the whole apparatus management.
ISTEC activities mainly deal with the study and optimization of those ceramic processes cheap and easily scalable able to produce the abovementioned ceramic devices in an easy and environmental friendly way. ISTEC exploits the most common techniques used in the traditional ceramic industry: tape casting, screen printing, die pressing
to optimize the production of the three generations of planar SOFC: electrolyte- supported cells, electrode- supported cells, metal-supported cells.
- Transparent ceramics for high power lasers
Many industrial and scientific laser applications require high energy, high peak power and nanosecond duration laser pulses that are exclusive domain of devices based on bulk crystalline and ceramic materials.
In this frame, laser ceramics can play a significant role due to several reasons:
the fabrication of large samples is easier than with the usual crystal growth technologies;
Laser ceramics can provide a definite advantage in the fabrication of complex structures such as dopant gradients or layered structures and so forth, which can be exploited to improve the management of the thermal load and of the thermally induced stresses in the lasing material, which are among the limiting factors for the achievement of high average power levels.
At ISTEC research in the field of ceramic for Diode Pumped Solid State Lasers (DPSSL) with different dopants have been developed. The research has been focused on the YAG-based system. Now the processing technique has been optimized for various compositions and doping levels: Nd:YAG, Yb:YAG, Er:YAG
- Solid oxide electrolysers (SOEC)
A solid oxide electrolyser planar cell (SOEC) is a device that allows hydrogen production in a faster and cheaper way than the correspondent polymer or alkaline cells due to the high operating temperature. This system could be consider as a ceramic multilayer where the dense electrolyte is sandwiched between two porous electrodes.
This ceramic architecture can be effectively produced as long as each step of the production process: powders synthesis, forming, thermal treatments.
- Piezoelectric materials for electro-mechanic applications.
The Research unit holds a remarkable experience in the development of materials and components both for fundamental as well as applied research. Materials are produced in the systems:
PZT - Lead Zirconate-Titanate solid solution) with several dopants.
PLZT - Lead Lanthanum Zirconate-Titanate solid solution,
BNT - Bismuth Sodium Titanate,
BNBT - solid solution of BNT with barium titanate
BST - Barium Strontium Titanate
Activity is currently focused on multiferroic composites (ferroelectric and magnetic) processes for the development of new materials and especially the production of composites by combining a magnetic material with a dielectric or ferroelectric material. Therefore the process parameters for the production of individual materials are optimized, particularly magnetic materials are produced such as Co, Ni, Ba, -ferrite, etc., which are then coupled to the ferroelectric dielctric material with different architectures (bulk materials or thick film).
- Ceramic solar absorbers for concentrating solar power systems
Solar thermal technology is a safe, sustainable and cost-effective energy supply. The maximum operating temperatures of a solar power plant are usually less than 600°C because of the rapid degradation of its components.
The scope of the present activity is fundamental research on materials to be employed in thermal solar energy plants as solar receivers for temperatures higher than 1000°C. Ideal candidate materials should possess a combination of properties such as: intrinsically selective absorption of the sun spectrum, reduced emissivity at high temperature, high electrical conductivity, high temperature chemical stability.
Ceramics with different bulk and surface characteristics are fabricated and analyzed to investigate their fundamental optical properties (in collaboration with other institutions, national and foreign) and thermo-mechanical properties at room and high temperature.
Research is presently focused on ceramics based on: SiC, AlN e Si3N4, HfC, ZrC, HfB2, ZrB2 (UHTCs).
- Porous structures with complex architecture
Realization of structures with functional, controlled and specifically organized porosity.
They are designed for specific applications and thus can be characterized or differentiated in terms of:
* morphology of pores, in general distinguishable in globular-isotropic or channel like-anisotropic pores;
* pore size distribution from submicronic to ultra-macrometric dimension
* pore inteconnection
* 3D spatial distribution of pores with or without porosity gradient in the 3D body
* anisotropy, preferential development of pores toward specific directions
* composition of the constituting material (typology and stoichiometry of the ceramic phase, ceramic-ceramic composite or hybrid composite)
* treatments of consolidation and sintering
- Ultra high temperature ceramics for space and industrial applications
Transition metals (Ti, Zr, Hf, Ta) form borides and carbides that belong to a class of advanced materials defined as Ultra High Temperature Ceramics (UHTCs) for their high melting points between 3000K and 4200K. Scientific activities at ISTEC concern:
. Innovative processing for fabrication of dense or porous bulks, composites with fibers, whiskers, platelets, CNT;
. Advanced characterization: high temperature thermo-mechanical, aero-thermal behaviour study (in collaboration), high resolution-TEM characterization, optical properties at room and high temperature (in collaboration);
. Design and fabrication of lab-scale prototypes.
- Multifunctional Ceramic composites
Besides the long-term studies on oxide and non-oxide based ceramics, recently new functional/structural ceramics have been considered to widen the application perspectives in demanding high-tech sectors. The development of ceramic composites that are electrical conductors and display good high-temperature structural properties is of great interest for a wide range of mechanical and electrical applications. Composites made of insulating ceramics (such as alumina, silicon nitride, aluminum nitride, silicon carbide ) and variable amounts of electroconductive phases (metallic, intermetallic or ceramic) can fulfill these requirements.
The following composites are produced and studied at ISTEC:
* Si3N4-TiN, Si3N4-MoSi2
* AlN-SiC-MoSi2, AlN-SiC-ZrB2, AlN-SiC-ZrC
* Al2O3-TiC, Al2O3-TiB2, Al2O3-TiN, Al2O3-Mo, Al2O3-NiAl.
On these non-oxide materials, high temperature properties and oxidation or corrosion resistance in severe environments and high temeprature have been extensively studied.
- Joining of dissimilar materials
Joints between ceramic and other materials as metals or glasses is strategic for those application where the coupling of dissimilar materials (ceramic and metals for example) is requested or when complicated shapes are needed. Ceramics can hardly be shaped in complicated shapes and this feature limits their potential applications. The bonding techniques offer the possibility to overcome this problem. Experimental procedures have been set up for several joining methodologies: brazing, direct bonding, solid-state bonding, bonding through glassy interlayers.
- Luminescent ceramics for LED applications
The LED lighting market is growing of about 30 % per year because of various concurrent factors. Traditional incandescent lighting will soon be prohibited in Europe and USA whereas it is already in Australia and numerous requests come from the governments for low energy consumption components. LED systems are currently proposed for: External lighting, Commercial lighting, Retrofit and solar energy systems.
Activity at ISTEC has been focused on the control of raw powders, dopants amount, composition and processing conditions to tailor microstructure, properties and performance of this class of luminescent materials.
NANO-CERAMICS AND NANO-TECHNOLOGIES
- Nanomaterial synthesis and design options
The present activity is addressed to the synthesis, characterization and application of nano dispersed colloidal systems. Three main topics are addressed:
* synthesis and functionalization of nano sols and/or nanopowders;
* nanosols formulation (pH, amount of inorganic phase and additives);
* processes of solid surfaces functionalization through the deposition of ceramic nano sols.
The experience gained in the field nano-phase engineering and of colloidal science has been fruitfully transferred to the control of nano particles (NPs) confinement and surface chemistry, opening new challenges towards the control of potentially adverse health impact of nanomaterials.
- Ceramization of textiles
The functionalization of textile substrates by ceramic nanostructured coating via sol-gel dip-coating has been achieved through the following steps:
* optimization of nano sols to be deposited;
* optimization of deposition process parameters: pre and post treatment of substrate, dipping time, post thermal treatments for coating curing;
* physical-chemical and functional characterization of coated samples.
Protective coatings with self-cleaning, flame retardant, anti-wear, hydrophilic/hydrophobic properties can be exploited in the production of highly durable Technical Textile.
- Ceramic systems with functional surfaces
The funzionalization of surfaces has recently received significant attention in different industrial sectors. The focus on the surfaces' performances within ISTEC CNR is a hot topic so that different research lines are active on:
Self-cleaning surfaces, superhydrophilic (contact angle with water <5 °) and superhydrophobic (water contact angle > 150°)- Oleophobic surfaces that can repel liquids with low surface tension (limit value of ³ = 25 mN/m);- Photocatalytic surfaces, active in the decomposition of organic dyes, VOCs and NOx.- Surfaces with implemented aesthetic features (obtained by deposition of nanometric inks, nanosuspensions of oxide metals and core-shell structured alloys).
Surface treatments can be applied to metals, alloys, steel, glsses and ceramics. The control of surface wettability is generating considerable interest in different industrial sectors from the ceramic one to that of metals and composites for aerospace and naval applications. The design of materials with improved repellence against water (mimicking the natural superhydrophobicity of Lotus leaves) can provide their surface of relevant de-icing properties, extremely important in adverse environmental conditions during, for example, the takeoff and landing of aircrafts.
Metals or alloys with a very low surface energy are the best candidates to the construction of hulls or marine propulsion systems with the ability to greatly reduce the marine fouling, which greatly affects the speed of vehicles and the effectiveness of cleaning and removal of marine pollutants operations. A further advantage is represented by the ability of superhydrophobic surfaces in contact with different fluids to reduce friction in correspondence of the boundary layer. This has recently led ISTEC CNR to design components for axial pumps with high affinity towards lubricants molecules, achieving a significant reductions of friction coefficients.
The regeneration of critical-size bone defects requires the implantation of porous scaffolds exchanging suitable chemical, morphological and mechanical signals with cells so as to activate new bone formation and colonization of the whole scaffold.
Pore size and morphology must be designed to achieve cell penetration and the establishment of a suitable vascular network to sustain the bone metabolism.
The mechanical strength of the scaffolds should be sufficient for early physical stabilization soon after implantation. Several forming techniques, such as replica, foaming, spin casting, slip casting, freeze casting, are applied to establish stable suspensions of bioactive powders (e.g.: hydroxyapatite, tricalcium phosphate, titania and their composites) to be consolidated into 3D macroporous devices.
In particular, by foaming process scaffolds with very high porosity extent and good mechanical strength can be obtained; freeze casting processes allow to obtain implants with oriented porosity and anisotropic mechanical properties, similarly to what occurs in long bones. The oriented porosity also supports the development of a vascular network that in turn favours the bone formation and maturation in the whole scaffold. Bioactive composites associating calcium phosphates and reinforcing phases such as titania are developed and optimized to produce bone scaffolds with high osteogenic character and increased mechanical strength that can be used for regeneration of load-bearing bone parts. Sintering processes are settled and optimized to achieve the highest extent of consolidation and to maximize the mechanical strength.
Competences developed on bio-hybrid materials:
- Synthesis of biomimetic nano-powders and Magnetic nano-apatites for drug delivery systems and tissue engineering,
- Functionalizations and nanocrystalline apatites for the preparation of smart nano-systems
- Hybrid nano-composites for the regeneration of multi-functional anatomical regions
- Biomorphic, Template-oriented and Biologically inspired syntheses
- Bio-mineralization processes
- Synthesis of new biocompatible and bioactive magnetic phases
- Synthesis processes in hydrothermal and supercritical conditions
- Redox processes to control electronic vacancies in ceramic/ceramic composites
- Surface functionalization to control cell phenotype
- Bio-hybrid nanostructured graded composites to regenerate multi-functional regions
- Nanostructured polymeric blends based on natural and bio-erodible polymers to regenerate cardiac tissues
- Biomimetic bio-resorbable porous implants with anisotropic and hierarchically organized structure
- Bioactive and bio-resorbable pastes and bone cements
- Fibrous ligament-like scaffolds to regenerate tendons and ligaments
- Magnetic bio-hybrid and ceramic composites for tissue regeneration
- New bio-resorbable magnetic phases for the healing of tumours in hyperthermia
- New ceramic materials for articular prostheses and dental applications
- Bioglasses: bulk implants and coatings
- Design and development of Drug Delivery Systems
Bioinert ceramics for structural prostheses ISTEC has been studied for: minimal wear articular surfaces and load bearing implants; crowns, abutments and endoosteal implants; electroconductive ceramic composites that can be machined in complex shapes by EDM.
- Products and technologies for conservation and restoration: geopolymers and hydraulic mortars
The products for the preservation and restoration of ceramics and stone in the Cultural Heritage must be compatible with the materials on which you operate and durable and stable over time.
Geopolymers, mortars based on hydraulic lime or nano- limes + meta kaolin meet these requirements.
- Ceramics, mosaic and mortars in the Cultural Heritage: Archaeometry and diagnostics
Archaeometric studies through chemical, mineralogical, petrographic, micro-structural and physical characterizations allow to know the material of a cultural object in order to define the raw materials and their provenance and also precise information on the production technologies.