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Our Group has been recognized by the Catalan Government as a Consolidated Research Group (2014-SGR-1015). Our main research topics are:

 
Magnetic, Magnetoelectric and Magneto-ionic studies of thin films and Lithographed Structures
Nanocomposite Materials
Thin Films, Foams and Micro/Nanostructures by Electrochemical Methods
Permanent and Biodegradable Biomaterials
Mesoporous oxide materials for advanced functional applications
             
 

MAGNETIC, MAGNETOELECTRIC AND MAGNETO-IONIC STUDIES OF THIN FILMS AND LITHOGRAPHED STRUCTURES
Led by J. Sort

This line of research encompasses the design, synthesis, characterization and integration of ME materials into a variety of applications that share in common the combined action of electric and magnetic fields, with emphasis on low-power magnetic data storage. Our research aims at probing and understanding the fundamental reversal mechanisms of magnetic lithographed nanostructures and multilayered thin films, by systematically tuning patterning, exchange coupling conditions, dipolar interactions and application of electric field. Research is pursued on how to tailor magnetization reversal in magnetic heterostructures, not simply by varying their shape, size, and separation, but by adding external electric stimuli or additional layers to which the ferromagnet can be exchange coupled. In parallel to the experiments, micromagnetic numerical simulations are also conducted. The simulations help to quantitatively interpret the experimental results. Besides magnetic recording, the investigated materials are also suitable for applications in spintronics and wireless magnetically-actuated micro-/nano-electro-mechanical systems (MEMS/NEMS).

     
   
 

NANOCOMPOSITE MATERIALS
Led by E. Pellicer, J.Fornell and J. Sort

We investigate diverse types of nanocomposite materials: (i) metal-ceramic composites, (ii) nanocomposites formed by two metallic crystalline phases with distinct microstructure and (iii) inorganic-organic hybrid materials.

The overall mechanical behavior of composite materials depends on the mechanical properties of each of the constituent phases. New progress in the improvement of flow properties relies very much on finding combinations of strengthening mechanisms that lead to synergetic effects. Grain size reduction is one of the most appealing routes for improving strength. Enhanced mechanical properties are obtained in nanocomposites consisting of a nanoeutectic matrix with micrometer-sized dendrites embedded.

Nanocomposite materials can be also obtained by thermally-induced partial nanocrystallization of a metallic glass. These nanocrystals act as pinning sites for shear band propagation, thus hindering premature mechanical failure during deformation. Nanoparticles can be also purposely dispersed during the fabrication of metallic glasses or be obtained by other surface treatments, such as shot penning or ion irradiation.

Finally, organic-inorganic hybrid nanocomposites have attracted much interest because they can combine useful chemical, optical, magnetic and mechanical characteristics. In collaboration with the Department of Materials and Environmental Chemistry, Stockholm University in Sweden, we are currently studying the properties of hybrids composed of (i) nanofibrillated cellulose and titania nanoparticles and (ii) nanocrystalline cellulose and amorphous calcium carbonate, prepared in aqueous media. These bionanocomposites are especially appealing as they combine impressive properties with environmentally benign and energy efficient production routes.

 
 
 

THIN FILMS, FOAMS AND MICRO/NANOSTRUCTURES BY ELECTROCHEMICAL METHODS
Led by E. Pellicer and J. Sort

Electrochemical methods are one of the powerful options for the synthesis of a great variety of materials including continuous or porous films of tuneable thickness, nanoparticles, nanorods, nanowires and nanotubes made of either single-phase or multi-phase (i.e., composite) materials. Electrochemical methods have many inherent advantages over physical deposition techniques such as simple set-up, low cost, low power demand and high compatibility with micro and nanofabrication technologies. We are interested in the growth of technologically relevant continuous metallic thin films by electrodeposition (e.g. Cu-Ni, Co-Ni, Co-W, CoNiReP) and in the scaling down of the synthetic procedures for the production of micro- and nanostructures (e.g. micropillars, nanowires and nanopillars). To this end, photo- and e-beam lithographed silicon based substrates and anodic alumina membranes (AAO) templates are used as matrices to accommodate the electrodeposited materials. Also, the synthesis of 3D hierarchically porous films by electrochemical means is tackled. Fully metallic (e.g. Cu-Ni) or composite (e.g. Cu-BiOCl) foams showing diverse properties (e.g. superhydrophobicity, ferromagnetism, photoluminescence or electrocatalytic characteristics) are pursued. Particular emphasis is given to new alloy compositions suitable for environmental / sustainable development applications (based on Fe, Cu or Al, without the presence of large amounts of costly noble metals or rare earths), obtained  using non-hazardous approaches. Finally, the synthesis of oxide nanotube arrays with tunable lengths and diameters by anodization of Ti-based alloys is investigated.

   
                     
               
     
 

PERMANENT AND BIODEGRADABLE BIOMATERIALS
Led by J.Fornell, E. Pellicer and J. Sort

We investigate the mechanical properties, corrosion resistance and cytotoxicity of different types of metallic materials (crystalline or amorphous) suitable for permanent orthopedic implants. Traditionally, 316L austenitic stainless steel and Co-Cr alloys have been employed as metallic orthopedic implants. However, these materials exhibit an exceedingly large Young’s modulus and can be cytotoxic. Ti–6Al–4V is currently the most widely used structural Ti-based material for the replacement of hard tissues in artificial joints. Nevertheless, the release of both V and Al ions from this alloy to the human body might cause long-term health problems, such as peripheral neuropathy, osteomalacia, and Alzheimer diseases. Elements like Nb, Zr, Mo or Ta are the safest that can be alloyed with titanium, leading to the so-called “second generation biomaterials”. Usually these alloys contain a large proportion of bcc-Ti solid solution and are known as beta-phase Ti alloys. Alternatively, Ti-based bulk metallic glasses have also attracted huge interest in recent years since they show higher strength and lower Young’s modulus than their crystalline counterparts. All these materials are produced and characterized in our Group.

In turn, the need for temporary implants such as plates, screws, pins, stents and sutures has recently prompted a lively research activity in the field of biodegradable materials. Polymers and metals have been advocated as potential bioabsorbable candidates. Compared to polymers, metals show superior mechanical properties (e.g. higher strength to bulk ratio) which make them the material of choice in many applications. Our research activity in this field focuses on the study of Mg-based amorphous and crystalline alloys. In collaboration with the Department of Cellular Biology, Physiology and Immunology at UAB, we study mouse preosteoblast cells adhesion onto the surfaces of these alloys. The obtained results in this field aim to provide baseline information to fathom out the mechanisms responsible for in vitro biocorrosion of this type of alloys and give some insights regarding their cytotoxicity in a physiological environment.

   
           
         
   
 

MESOPOROUS OXIDE MATERIALS FOR ADVANCED FUNCTIONAL APPLICATIONS - Led by A.Nicolenco, E. Pellicer and J. Sort

Among the synthesis pathways leading to nanostructured oxide porous materials, the nanocasting route and evaporation induced self-assembly (EISA) constitute facile, versatile, and easily-scalable procedures. We use the multi-step nanocasting concept to synthesize ordered mesoporous nanocomposite powders from diverse silica templates (e.g. SBA-15, SBA-16, and KIT-6). The obtained materials benefit from the long-range ordering and high specific surface area provided by the packing of the mesopores along with the functional and synergetic properties (e.g. magnetic and optical) arising from the phase constituents. We are interested in combining different metal oxides (e.g. Co3O4-NiCo2O4) in a single mesoporous structure with the aim to either produce novel physicochemical features or to enhance the properties of one of the phase constituents. EISA is used to grow mesoporous oxide films. Some of the investigated materials are: Fe2O3, Co ferrite or Co3O4. Mesoporous dilute-oxide magnetic semiconductors (constituted of In2O3 doped with transition metals) are also being studied. Magneto-ionic phenomena (i.e., voltage-driven magnetic changes caused by oxygen ion diffusion effects) are investigated in these materials during electrolyte gating.