Publications (6)21.29 Total impact
- [Show abstract] [Hide abstract] ABSTRACT: Knowing the affinity of boron aqueous species for cis-diol organic groups, five different hybrid materials have been prepared by anchoring glucose groups onto the surface of silica matrices with a different surface topology: UVM-7 bimodal mesoporous silica, UVM-11 unimodal non-templated mesoporous silica, commercial silica fume and two silica xerogels with pores within the mesoporous range (13–50 nm). After optimizing the experimental conditions, a comparison was made of the boron adsorption capacities in water. The relationship of the structural and functionalization parameters is discussed and the importance of the surface topology in the final adsorption behaviour is revealed. Hence, despite the UVM-7 based material being the best boron adsorbent, the solid based on one of the xerogels is seen to be a good candidate for preparing low-cost boron adsorbents.
- [Show abstract] [Hide abstract] ABSTRACT: Both bulk and mesoporous silica nanoparticles can be obtained in the form of granular aggregates using chitosan flakes as additive under very soft biomimetic reaction conditions.
- [Show abstract] [Hide abstract] ABSTRACT: The mechanical properties of epoxy-silica nanocomposites have been studied; the silica nanosphere fillers used were un-functionalised, functionalised with amine, with epoxy, or a mixture of both kinds. Dynamic mechanical analysis measurements revealed an increase in the shear storage modulus, for all samples with a filler content of 3-5%. Improvements were observed in the glassy and rubbery states, without affecting the glass transition temperature of the materials. Above these strengthening percentages, the mechanical properties began to deteriorate, but in all cases they remained superior to those of the pristine epoxy resin. For low strengthening percentages, samples reinforced with both nanospheres functionalised with amine and with epoxy showed better mechanical behaviour. As the strengthening percentage increased, materials reinforced with silica nanoballs functionalised with epoxy groups alone showed higher mechanical strength than the rest. To improve the mechanical properties of these systems, it was important to optimise both the percentage of added filler and the type of reinforcement. The parameter determining the flow stress was the cohesion of the solid state, which was represented by the storage modulus in shear.
- [Show abstract] [Hide abstract] ABSTRACT: The mechanical strengths of epoxy composites reinforced with silica nanospheres, unfunctionalised or functionalised with either amine or epoxy groups, increase up to a proportion of 5 wt.% of filler, as reflected in a study of the shear storage modulus carried out in dynamic mechanical analysis. This improvement is observed in both glassy and rubbery states, moderately affecting the glass transition temperature of the material. From this percentage of strengthening substance the mechanical properties begin to deteriorate, but keeping (up to 10 wt % of strengthening material), a greater storage modulus in shear than that of the pristine epoxy resin. A trend can be discerned as the percentage of filler increases in the nanocomposite, where the materials strengthened with silica nanospheres functionalised with epoxy groups show better mechanical behaviour than the rest. To improve the mechanical properties in the systems, it is important to use an intermediate percentage of strengthening material (not much higher than 5-7 wt.%), the exact proportion depending on the type of strengthening substance.
- [Show abstract] [Hide abstract] ABSTRACT: Ordered macroporous–mesoporous carbonaceous materials were produced as a direct replica of the Thalassiosira pseudonana diatom by infiltration of the skeleton with furfuryl alcohol. The final carbon-rich material preserves the macropores of the diatom acting as bio-template and new hierarchical macro–mesopores appears as the silica is eliminated through chemical etching. The final solid can be described as an organized array of carbon macrotubes. In order to understand the progressive silica etching and the subsequent effect on the final carbon material, different etching reagents have been used. Moreover, the similar pore topology of T. pseudonana and the well known MCM-41 mesoporous silica (hexagonal ordered arrays of non-interconnected pores), allowed us to consider this system as a micrometric model to understand in 3-D the carbon replication of MCM-41 silicas.
- [Show abstract] [Hide abstract] ABSTRACT: Composites of silica nanospheres coated with crosslinked epoxy-amine were synthesised and examined by 29Si-magic-angle-spinning nuclear magnetic resonance spectroscopy, thermogravimetric analysis, Fourier transform infrared spectroscopy and scanning electron microscopy. The most representative fact is that epoxy-modified nanospheres lost less weight at high temperatures. At temperatures greater than 300°C the loss of weight for epoxy-modified nanospheres was rather lower than for unmodified nanospheres. This helped them to retain their structures, as the loss of weight can have adverse effects on network defects, due to the loss of crosslinks by unit of volume.
University of Valencia
Valenza, Valencia, Spain
- Institute of Materials Science