Excellent reception for the days of CarbonInspired 2.0 project in the SUDOE space

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One of the main objectives of CarbonInspired 2.0 project is the transfer of knowledge to companies in the SUDOE Space. A culture of innovation undoubtedly promotes the generation of high value-added products.
Within the project 5 seminars for the transference of knowledge in the SUDOE space were performed in the last 18 months. These conferences have been followed by an original format to stimulate discussion and exchange of ideas: a space for meeting colleagues and discuss new projects.
Over 20 companies, manufacturers of nanoparticles such as Avanzare, Arkema or Tolsa or companies with an outstanding track record in research on the advantages of using nanoparticles as Acciona, Gerdau, Grupo Antolin or nanopinturas presented case studies and shared their experiences with attendees.

The days have been very well received with nearly 200 professionals who could see firsthand the importance which involves the integration of nanotechnology in the final product to be a reality in today’s market.

You still have a chance to join them in our seminar in Portugal, which will take place in February 2015.

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Exfoliation of graphene oxide using ionic liquids: experimental and molecular modelling approach

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Graphene, a one-atom-thick planar sheet of sp2 hybridized carbon, has received much attention due to its outstanding properties such as large specific surface area, high electrical and thermal conductivity, excellent chemical stability and mechanical stiffness. Graphite, which is cheap and readily available, consists of stacked graphene sheets. Therefore, one of the most convenient methods for the mass production of graphene sheets is the exfoliation of graphite in the liquid phase. Recently, many attempts to produce graphene sheets in large quantities via chemical reduction of exfoliated graphite oxide (GO) have been reported. During the oxidation process of graphite, the unique electronic properties of graphene dramatically degrade. The electrical conductivity of the graphene oxide sheets can be partially restored by the reduction step; however, this results in their irreversible agglomeration. Therefore, different strategies to disperse graphene sheets before or during reduction step have been used, including stabilization by various polymeric dispersants or surfactants and covalent/non-covalent functionalization [1].
In this context, ionic liquid (ILs) can be used for functionalization of graphene. They can adsorb on the graphene surface through the noncovalent interactions of anion and/or cation with graphene. ILs present several advantages such as enhanced ionic conductivity, thermal stability and excellent mechanical properties. The graphene modified with ILs are endowed with improved conductivity, excellent hydrophilicity and positive charged [2]. The repulsion between the resultant cation-charged GO sheets, the charge transfer between the ions and graphene and the high solubility of the grafted IL contribute to the exfoliation of graphite into graphene sheets and to prepare long-term stable graphene dispersions using ILs [3].
IK4-TEKNIKER is working actively on these activities in the nanoIKER project, financed by the Basque Country Government). In the next figure, Molecular dynamics simulations was used to check that the average interlayer spacing between the exfoliated graphene layers in graphite oxide increases.

Figure. Molecular model of graphite oxide with adsorbed ionic liquid

[1] M Tunckol, J Durand, P Serp, Carbon, 50 (2012) 4303-4334.
[2] R Marcilla, M Sánchez-Paniagua, B López-Ruiz, E López-Cabarcos, E Ochoteco, H Grande, D Mecerreyes, Journal of Polymer Science Part A: Polymer Chemistry, 44 (2006) 3958-3965.
[3] MH Ghatee, F Moosavi, Journal of Physical Chemistry C, 115 (2011) 5626-5636.

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Carbon nanotubes oxidized by solar energy

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Carbon nanotubes (CNT) have attracted considerable attention in some potential applications due to their remarkable properties, such as mechanical and electrical properties. Therefore, they have been expected to be excellent fillers for polymer composites. In order to obtain nanocomposites with enhanced properties, it is necessary to oxidize or functionalize their surface in order to improve CNT-matrix interaction and CNT dispersion in the matrix. Chemical treatments, above all acid treatments, are being widely employed to oxidize CNT [1]. However, the high consume of solvents and energy required for these oxidation processes and the fact that morphology of carbon nanotubes can be highly damaged during the process point out the necessity of more environmentally friendly processes.
IK4-TEKNIKER is working on the oxidation of CNT by the photoFenton process assisted by solar energy. This process is proved that overcomes main problems associated to conventional processes. The Fenton process consists on the generation of hydroxyl radicals, which have a high oxidation potential, using H2O2 as source of OH• radicals and Fe2+ salt as catalyser in an aqueous medium (pH=2.7) [2]. When the process rate is enhanced by UV radiation, it is call photoFenton process. The process conditions such as reactive concentration, reactant ratio and time of reaction have been optimized using a parabolic collector to concentrate solar radiation. The process promotes the generation of carboxylic (-COOH), carbonylic (C=O) and/or hydroxylic (-OH) groups onto CNT surfaces without affecting their structural integrity. The photoFenton process achieves an increase in the oxidation degree in comparison with a usual oxidation method, the oxidation in HNO3 concentrated acid.
In summary, CNT oxidation by the photoFenton process assisted by solar energy is proved a suitable alternative environmentally friendlier and less costly to conventional chemical oxidation processes. Composites obtained by the incorporation of CNT oxidized with the photoFenton process into polyamide 6 show a similar behaviour than the obtained by the incorporation of CNT oxidized with common chemical methods.

[1] V. Datsyuk, M. Kalyva, K. Papagelis, J. Parthenios, D. Tasis, A. Siokou, I. Kallitsis, C. Galiotis, Carbon 46 (2008) 833–840
[2] L. Zhang, J. Li, Z. Chen, Y. Tang, Y. Yu, Applied Catalysis A: General 299 (2006) 292–297

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Development of antisticking nanocoatings by sol-gel technology

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The problem of surface contamination is widespread, especially when considering high energy surfaces such as glass or metal, which have a strong tendency to adsorb other molecules. Common strategies are based on the reduction of the surface free energy without losing the material properties. Generally the water and oil repellency is increased when the contact angle of water is above 100ºC [1]. Anti-sticking and anti-coking surfaces can be obtained by the deposition of nanocoatings synthesized by sol-gel technology, which can simultaneously construct a solid surface with appropriate surface roughness and low surface energy.
The sol-gel process is a chemical synthesis technique for preparing coatings, gels, glasses, and ceramic powders. Compared to the other surface modification techniques, the sol-gel is a simple, economic and effective method to produce high quality coatings. Also, sol-gel has several advantages including low cost, high adherence to the surface, chemical stability, film uniformity and low sintering temperature. Moreover, sol-gel technology shows important advantages concerned the preparation of glassy and glasslike matrices at low temperature with functional properties [2], because the coating of silica and the substrate have the same glassy nature.
This technology involves hydrolysis and condensation reactions of metal alkoxides or organosilanes and optional organic precursors to give gels [3, 4]. They are applied by standard methods such as spray-coating, dip-coating or spin-coating and are widely used due to their excellent adhesion to other materials such as metals being the coating not distinguishable from the original glass, and their high chemical wear resistance [5]. The typical film thicknesses obtained varies between a few nm to a few μm, which makes them extremely interesting for a huge industrial applications, including anti-stick and anti-coking nanocoatings process deposited onto any type of surface composition and geometry.
A SiO2 coating is the most commonly used precursor for the sol-gel process, due to its ability to act as hydrophobic or hydrophilic moiety dependent of synthesis conditions chosen. TEOS (Tetraethyl orthosilicate) is the best known silicon precursor and mainly used for this route of synthesis. Also, an hydrophobic agent can be added to the sol-gel synthesis as the silicon co-precursor, such as isobutyl-trimetoxysilane (iso-BTMS), hexadecyl-trimethoxysilane (HDTMS), trimethyl-ethoxysilane (TMES) or methyl-trimethoxysilane (MTMS). The goal is to minimize the presence of OH groups and replace H atoms of the OH groups by hydrolytically stable Si-R groups. This strategy prevent the water adsorption and increase the hydrophobicity of the surface, always respecting the environmentally friendly conditions.

 

[1] Nanotechnology in Consumer Products, October Nanoforum reports, 2006.
[2] N. Carmona, K. Wittstadt, H. Römich, Journal of Cultural Heritage 10, 403–409, 2009.
[3] M. Pagliaro, R. Ciriminn, G. PalmisanoJ. Mater. Chem. 19,3116-3126, 2009.
[4] J. Ayres, Characterization of titanium alkoxide-based sol-gel systems and their Behavior in icephobic coatings, 2004.
[5] M. Monti, B. Dal Bianco, R. Bertoncello, S. Voltolina, Journal of Cultural Heritage 9, 143-145, 2008.

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NANOCAPSULES. A NEW REVOLUTION FOR MATERIAL DEVOLOPMENT

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A micro-or nanocapsule is shortly defined as a small portion of an active substance that is surrounded by an encapsulating agent with dimensions in the micro- or nanometer regime, thus isolating this substance from the external medium. This protection can be permanent or temporal, in which case the core is generally released by diffusion or in response to a trigger, such as shear, pH, or enzyme action, thus enabling their controlled and timed delivery to a targeted site.
Nanocapsules may range from 1 to 1000 nm in size and they have a multitude of different shapes, depending on the materials and methods used to prepare them. The structure of encapsulated ingredients, which largely depends on the selected shell material and nanoencapsulation method, can be classified into two main categories: capsules with (a) a core that is surrounded by a shell of the matrix material or (b) a core that is entrapped within a continuous network of the matrix material.
Variations of these morphologies include capsules with multiple cores or multilayered capsules. However, the most significant feature of nanocapsules is their nanoscopic size that provides a large surface area. The total surface area is inversely proportional to the capsule diameter. This large surface area is appropriate for incorporating recognition species (functionalization with peptides, antibodies, organic polymers, etc.), sites of adsorption and desorption, chemical reactions, and light scattering, among others.

Morphologies of nanocapsules (from left to right): (a) single-core capsule, (b) dispersed core in polymer gel, (c) multilayer capsule, (d) dual-core capsule, and (e) single-core-multi-shell capsule.

Many different materials can be used as encapsulating matrices, which must be selected depending on the critical properties needed for each intended application. The majority of these carriers are proteins (gelatin and albumin), polysaccharides (dextrin, starch, gums), fats, liposomes, biopolymers, co-polymers (poly(lactic-co-glycolic acid)), micelles, organogels, dendrimers, solid nanoparticles (SLN), polymeric nanoparticles, emulsion-based systems, and metal-organic particles.
The use of encapsulation technologies offer an impressive number of advantages and new properties: (i) unstable materials (e.g. pure chemical substances, viruses, etc.) can be protected from the environment and stabilized or separated from other incompatible components; (ii) the properties of encapsulated materials can also be modified (e.g. taste masking, odor masking, etc.); (iii) the industrial processes can be improved or facilitated (e.g. transformation of liquids into solids for easier handling, reduction of toxicity during manipulation, etc.); and (iv) the release of encapsulated active materials can be modified, providing sustained release (maintaining the right concentration), long lasting (and therefore improving effects), target release (improving adhesion, penetration, or recognition of tissues and cells), or triggered release (mainly by environmental changes in pH, temperature, etc.). Encapsulation and release modification also reduces doses, and therefore, potential toxicity of the encapsulated substances, such as drugs.

 

 

K. G. H. Desai, H. J. Park. Recent developments in microencapsulation of food ingredients. Dry Technol 23 (2005) 1361–1394.
M. A. Augustin, Y. Hemar. Nano- and micro-structured assemblies for encapsulation of food ingredients. Chem. Soc. Rev. 38, 902–912 (2009).
N. V. N. Jyothi, P. M. Prasanna, S. N. Sakarkar, K. S. Prabha, P. S. Ramaiah, G. Y. Srawa. Microencapsulation techniques,factors influencing encapsulation efficiency. J. Microencapsul. 27, 187–197 (2010).

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Nanocarbonaceous additives for lubricants

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There is great diversity of carbonaceous materials such as graphite, fullerenes, carbon nanotubes and graphene, which cause interest in the research society to be applied in many fields due to the properties that such materials have.

The previously mentioned compounds correspond to all diverse ways that carbon can be found, which are called allotropic forms of carbon, and have in common the nanometer scale in which they are given. Despite being constituted of the same element, the properties of nanomaterials are very different from such material on macro scale due to the electron density and the electron mobility for the surface
This kind of materials lend very diverse properties depending on the final matrix where are used, the main advantage they present is that the amount of nanomaterial necessary to generate the change of property is very small. Matrixes can be polymeric, achieving improvements in mechanical characteristics, such as breaking strength, storage modulus and flexion strength. Getting also lighten the weight of the final structure where it is incorporated.
Industrial fluids such as lubricants are another matrix where nanocarbonosos materials are being extensively studied by self-lubricating properties they presented. The proposal is therefore made use of nanoparticles as solid lubricants deposited directly onto the material to be lubricated, as well as the lubricants formulation using carbonaceous materials as additives, achieving lower friction coefficients, extreme pressure and anti-wear (tribological properties)
The following figure shows the carbonaceous structures, -grafeno, layers of graphene, carbon nanotube, and fullereno-

The use of such structures as additives in lubricants to improve the tribological properties, usually accompanied by a prior step of dispersion in the liquid matrix, for which the use of surfactants to stabilize and to ensure homogeneity in the distribution of additives is necessary, or surface functionalization to favor a link between the structure and matrix. Although both options are viable, dispersion with surfactants is presented as the most viable strategy for cost and simplicity.
In recent years graphene is being investigated as additives in lubricants now that compared to the other allotropic carbonaceous structures has shown much better thermal conductivity, friction reduction capability, anti wear properties and viscosity stability.

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Nanopolymers

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Nowadays, the polymers are applied in drugs, packaging, carriers with the goal to substitute others materials used by Man. Nanotechnology is already making a major impact on new product introductions throughout the world, in many industry sectors. Many of these new products are based on the material property changes that may be achieved by incorporation of ingredients, at the nanoscale, into polymeric system. When nanoparticle becomes a great topic in enhancing polymer’s mechanical property, it is a natural combination into microcellular foam.
Most of nanopolymers are at an early stage of market development described applications are often still at research and development stage.

Trends for nanopolymers
Nanoparticles could be an ideal nucleating agent and even dispersion can generate interfacial volume as nucleus for microcellular morphology. This nano-microcellular polymer could be a great product with an impressive performance/weight ratio; excellent physical, mechanical and thermal properties. The nanopolymers are one of the most important nanomaterial for the future. Nanopolymers have applications in medicine, energy and materials science.
The nanofibres, hollow nanofibres, core–shell nanofibres, and nanorods or nanotubes produced have a great potential for a broad range of applications including homogeneous and heterogeneous catalysis, sensors, filter applications, and optoelectronics. The next Table shows an overview of polymer nanofiber applications.

 

 

 

 

Polymer nanoparticles are nanoscale polymeric units, being used in drug delivery systems or as filler material in matrix composites. Core shell fibers of nano particles with fluid cores and solid shells can be used to entrap biological objects such as proteins, viruses or bacteria in conditions which do not affect their functions. Dendrimers are highly branched molecules similar to polymers whose size and shape can be precisely controlled, exhibiting excellent properties such as low polydispersity index, high molecular mass, hydrophobic core and hydrophilic periphery. Dendrimers have been explored as drug delivery vehicles by various routes of drug administration and for other biomedical applications.

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Coating based on nanoparticles for maritime components

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Engineered structures such as ships and marine platforms, as well as offshore rigs and jetties, are under constant attack from the marine environment, needing protection from the influences of the marine environment elements, such as saltwater, biological species and temperature fluctuations.
An epoxy coating based on nanoparticles for maritime components has been developed by AIMPLAS to overcome biofouling and corrosion created by a wide range of exposure conditions in marine structure.
The coating development started with the selection of a commercial epoxy suitable for maritime conditions. Then, several commercial available nanoparticles such as ZnO, SiO2 were selected and submitted to chemical modifications, to improve the compatibility with the epoxy matrix and to promote biofouling effects. After the latter, the hardener was added to the resin and the final mixture was applied to metallic test parts. Samples were introduced in an oven to carry out a suitable curing step. To reproduce the real conditions of the maritime environment, a volume of seawater was used and an inoculum of microalgae was introduced to generate an unfavorable medium. Seawater, microorganisms, light intensity, air contributing and room temperature were the conditions controlled. The samples were submerged in test medium and the exposure was conducted during 45 days. Visual evaluations and microscopy analysis were performed pointing out the growth of microalgae and others organisms. During testing, most of the coated samples demonstrate their antifouling properties, not showing evidence of the presence of algae or other organism deposits in the surface. On the other hand, reference sample without coating, showed corrosion pits and additional defects.
Epoxy coating based on nanoparticles could be a solution to increase the performance of maritime components, due to synergistic effect created by different nanoparticles and the antifouling system resulting in a combination of properties such as hydrophobicity, large surface area of nanomaterials, roughness and anticorrosion. It is important to refer that the antifouling system can be considered a non-toxic approach, without including biocide components according to current regulations.

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Auto heating seat device based on nanoparticles

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One of the prototypes with higher impact in our CarbonInspired seminars, is the one corresponding to a textile based on nanoparticles. This textile can be employed for developing an autoheaing seat device.
Textiles are ideal substrates for the integration of novel properties and functions to enhance the user comfort and the environment, since they are universal interfaces. They provide a versatile structure for the incorporation of novel functionalities with value added. Nanotechnology can be used to enhance textiles attributes, such as fabric softness, durability, breathability, water repellency, fire retardant, anti-microbial properties, and the like in fibers, yarns, and fabrics.
An auto heating seat device has been developed by CTAG, creating a homogenous heating along the seat surface, has showed in the figure.

In a first step, the physical mixing of acrylic resin, commercial solution of MWCNTs, additives and metallic fillers was performed. The acrylic resin was used to ensure the durability of the electro-heating textile, while the additives were used to prevent the re-aggregation of the nanoparticles, improving the conductivity level and optimizing the nanoparticles concentration. The metallic fillers were used to improve the thyrotrophic properties of the final mixture. Then, for a correct impregnation of the mixture, it was deposited on a PES/cotton substrate, and dry in a lab drier at a controlled temperature. After this, thermal measurements were done and a comparative study between the produced prototype and a conventional electric resistances seat, concluding that the application of nanomaterials directly in the textile allow a homogeneous distribution of heat flow. The prototype reaches a thermal leap up to 30ºC, working within the security range to be used in humid environments or outside, with no hazardousness for the user. Moreover, the obtained heat is uniform among the whole seat surface, increasing the comfort and achieving the desired thermal sensation. It is also important to refer that there isn’t loss of physical properties due to rigidity increments.

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Automatization of thegraphene production

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Graphene could be the material on which international industry has pinned its greatest hopes owing to its tremendous application possibilities and its numerous physical properties. It is pure carbon arranged in a sheet that is only one atom thick, a characteristic that gives it the following extraordinary properties: it is flexible, 200 times stronger than steel and 5 times lighter.
However, producing sheets of graphene does pose some difficulties, in view of the material’s nanometric characteristics. That is why Graphenea, an enterprise whose base is in CIC nanoGUNE (The Nanoscience Cooperative Research Centre) and one of the few firms worldwide devoted to producing this material, approached IK4-TEKNIKER to work on the design of a production process that would be more automated, standardizable, scalable and reliable.
Graphene sheets are routinely produced using a technology known as CVD, in other words, chemical vapour deposition. The graphene is deposited onto a copper plate when the vapour in which it is being transported dissipates. One of the problems that the company was having was that the production processes needed extensive manual intervention.
To overcome these difficulties, IK4-TEKNIKER’s Design, Manufacturing and Assembly Unit and Graphenea together designed a system for transferring the graphene from a copper wafer to a silicon wafer, a key material in the electronics industry, by means of various chemical baths that dissolve the copper and allow the product to be deposited onto the silicon.
IK4-TEKNIKER has designed one of the basic tools of the new process of Graphenea: an ergonomic system made of Teflon that allows the graphene to be handled in a more straightforward way while it receives the various chemical baths enabling it to be transferred to the silicon.
According to Rafa Enparantza, head of IK4-TEKNIKER’s Design, Manufacturing and Assembly Unit, “it is a project that is having great repercussions on the company’s internal processes. At our centre we often work on major European projects, but in cases like this, when we are working directly with a client that is funding the R&D of a product or process directly, the results can be applied right away and this is very gratifying indeed,” he said.
The project is at a very advanced stage and the members of Enparantza’s team are already working on the third prototype of the system. The first versions were produced using 3D printers in the materials being worked. But now the third prototype is being manufactured in Teflon in order to provide real conditions for the application tests.

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