Research Interests:
Chitosan (CS) is a natural biopolymer that shows promise as a biomaterial for bone-tissue regeneration. However, because of their limited ability to induce cell differentiation and high degradation rate, among other drawbacks associated... more
Chitosan (CS) is a natural biopolymer that shows promise as a biomaterial for bone-tissue regeneration. However, because of their limited ability to induce cell differentiation and high degradation rate, among other drawbacks associated with its use, the creation of CS-based biomaterials remains a problem in bone tissue engineering research. Here we aimed to reduce these disadvantages while retaining the benefits of potential CS biomaterial by combining it with silica to provide sufficient additional structural support for bone regeneration. In this work, CS-silica xerogel and aerogel hybrids with 8 wt.% CS content, designated SCS8X and SCS8A, respectively, were prepared by sol-gel method, either by direct solvent evaporation at the atmospheric pressure or by supercritical drying in CO2, respectively. As reported in previous studies, it was confirmed that both types of mesoporous materials exhibited large surface areas (821 m2g−1–858 m2g−1) and outstanding bioactivity, as well as os...
Research Interests:
Research Interests:
Research Interests:
Nowadays the sol–gel process is used by an increasing number of researchers for the pre-paration of various products, including bulk materials, films, membranes or fibers. The application of ultrasound (sonocatalysis) to the precursors... more
Nowadays the sol–gel process is used by an increasing number of researchers for the pre-paration of various products, including bulk materials, films, membranes or fibers. The application of ultrasound (sonocatalysis) to the precursors gives rise to materials with new properties, known as sonogels. The absence of additional solvent and, mainly, the effects of ultrasonic cavitation create a unique environ-ment for sol–gel reactions leading to particular features in the resulting gels: high density, fine texture, homogeneous structure etc. These prop-erties determine the evolution of sonogels on further processing and the final material struc-ture. In this sense, the full exploitation of sonocatalysis requires a thorough understanding of the processes involved and their sensitivity to reaction parameters. For this purpose, we have used diverse techniques to investigate the micro-structural evolution during different steps in the sonogel process. The results of these studies are report...
Research Interests:
Research Interests:
Abstract This paper presents the rheological properties of three types of lime putty, specifying the influence of their origin. The study aims to compare a special lime putty prepared from phosphogypsum with a commercial lime powder and... more
Abstract This paper presents the rheological properties of three types of lime putty, specifying the influence of their origin. The study aims to compare a special lime putty prepared from phosphogypsum with a commercial lime powder and an aged lime putty. The results obtained in terms of chemical composition, crystalline structure, grain size and rheological characterization, (linear viscoelasticity, shear rate and time-dependent flow behaviour) are presented in the study. Putties studied present a similar rheological response, which mainly depends on the particle size and water content. Lower values of the linear viscoelastic functions and viscosity were found for the phosphogypsum lime putty, in agreement with the higher particle size. Transient flow tests reveal a predominant elastic response with no significant shear-induced structural perturbations. However, either a thickening phenomenon over time, i.e. rheopexy, favoured at low shear rates, or a viscosity decrease, i.e. thixotropy, favoured at high shear rates, was observed.
Research Interests:
SiO2 organically modified silicate (ormosil) gels doped with different concentration of PbS quantum dots ranging from 0.5 to 4 wt%, were synthesised via sol-gel. The synthesis implied a process including the hydrolysis assisted with high... more
SiO2 organically modified silicate (ormosil) gels doped with different concentration of PbS quantum dots ranging from 0.5 to 4 wt%, were synthesised via sol-gel. The synthesis implied a process including the hydrolysis assisted with high power ultrasounds of tetramethylorthosilicate (TMOS) mixed with polydimethylsiloxane (PDMS). Colloidal dispersions of PbS embedded in sono-ormosil matrices were obtained by using two different control size
Research Interests:
Research Interests:
Research Interests: Chemical Engineering, Condensed Matter Physics, Materials Science, Inorganic Chemistry, Microstructure, and 12 moreElectron Microscopy, Small Angle X Ray Scattering, Nanoparticles, Transmission Electron Microscopy, Porosity, High Resolution Transmission Electron Microscopy, Functionalization, Silica, Surface Area, Microstructures, Functional Group, and Surface Analysis
An analysis of the atomic radial distribution function of Al 0.20 As 0.30 Te 0.30 , Al 0.10 As 0.40 Te 0.50 and Al 0.10 As 0.20 Te 0.70 amorphous alloys obtained from quenching of the molten mixture of the elements was performed. A... more
An analysis of the atomic radial distribution function of Al 0.20 As 0.30 Te 0.30 , Al 0.10 As 0.40 Te 0.50 and Al 0.10 As 0.20 Te 0.70 amorphous alloys obtained from quenching of the molten mixture of the elements was performed. A structure in which all the Al atoms are ...
Research Interests:
Research Interests: Materials Engineering, Materials Science, Microstructure, Monte Carlo Simulation, Monte Carlo Simulations, and 11 moreMonte Carlo Methods, Porous Materials, Porosity, Computer Simulation, Non crystalline solids, Specific surface area, Microstructures, Porous Material, Structural model, Cluster model, and Monte Carlo Integration
Organic-inorganic hybrid materials were synthesized by controlled hydrolysis of tetraethoxysilane (TEOS), methyltrimethoxysilane (MTES), synthetic wollastonite powders and polydimethylsiloxane (PDMS) in an ethanol solution. Aerogels were... more
Organic-inorganic hybrid materials were synthesized by controlled hydrolysis of tetraethoxysilane (TEOS), methyltrimethoxysilane (MTES), synthetic wollastonite powders and polydimethylsiloxane (PDMS) in an ethanol solution. Aerogels were prepared from acid hydrolysis of TEOS and MTES with different volume ratio in ethanol, followed by addition of wollastonite powder and PDMS in order to obtain aerogels with 20 wt% of PDMS and 5 wt% of CaO of the total silica. Finally, when the wet gels were obtained, they were supercritically dried at 260 degrees C and 90 bar, in ethanol. In order to obtain its bioactivity, one method for surface activation is based on a wet chemical alkaline treatment. The particular interest of this study is that we introduce hybrid aerogels, in a 1 M solution of NaOH, for 30 s at room temperature. We evaluate the bioactivity of TEOS-MTES aerogel when immersed in a static volume of simulated body fluid (SBF). An apatite layer of spherical-shaped particles of uniform size smaller than 5 microns is observed to form on the surface of the aerogels after 25 days soaking in SBF.
Research Interests: Materials Engineering, Materials Science, Biomedical Engineering, Materials, Polymers, and 15 moreMedicine, Humans, Silica, Pressure, Room Temperature, Polydimethylsiloxane, Materials Testing, Calcium Compounds, Silicates, Biocompatible Materials, Simulated Body Fluid, Silicones, Body Fluids, Acid hydrolysis, and silanes
Research Interests:
Research Interests:
En el presente trabajo se pretende evidenciar la utilidad de los ultrasonidos en el procesado de polvos cerámicos como elemento acelerador del proceso de cristalización y herramienta eficaz de redispersión. Palabras clave: YSZ,... more
En el presente trabajo se pretende evidenciar la utilidad de los ultrasonidos en el procesado de polvos cerámicos como elemento acelerador del proceso de cristalización y herramienta eficaz de redispersión. Palabras clave: YSZ, ultrasonidos, dispersión. Using ultrasounds to optimize YSZ ceramic powders processing This work tries to show out the utility of ultrasounds in ceramic powders processing as a speeding element for crystallization process and as useful tool for redispersion.
Research Interests:
Research Interests:
En el presente trabajo se pretende evidenciar la utilidad de los ultrasonidos en el proeceesado de povlos ceramicos como elemento acelerador del proceso de cristalizacion y herramienta eficaz de redispersion.
Research Interests:
SiO2 gels obtained by sonocatalytic method combined with DCCA were used as host-matrices for extremely fine dispersions of CdS semiconductor particles. Small crystallites were produced "in situ" by H2S gas diffusion method. The... more
SiO2 gels obtained by sonocatalytic method combined with DCCA were used as host-matrices for extremely fine dispersions of CdS semiconductor particles. Small crystallites were produced "in situ" by H2S gas diffusion method. The particles were characterized by TEM and HRTEM, EXAFS, UV-Vis and Raman spectroscopies. The size of crystallites ranged from 5 to 10 nm. The optical transmission spectra showed the characteristic blue shift as a function of the particles size, as predicted by the theory. The optical and mechanical qualities of the samples were substantially improved by an infiltration method using a sono-sol which sealed the superficial pores thus ensuring greater longevity and the possibility of obtaining transparent gels by polishing.
Research Interests:
Research Interests:
Research Interests:
This work addresses the reuse of waste products as a raw material for lime putties, which are one of the components of mortar. 1:3 Lime/sand mortars very similar to conventional construction mortars were prepared using a lime putty... more
This work addresses the reuse of waste products as a raw material for lime putties, which are one of the components of mortar. 1:3 Lime/sand mortars very similar to conventional construction mortars were prepared using a lime putty obtained from the treatment of phosphogypsum with sodium hydroxide. The physical, rheological and mechanical properties of this phosphogypsum-derived mortar have been studied, as well as the mineralogical composition, microstructure by scanning electron microscope (SEM) and curing process by monitoring carbonation and ultrasonic propagation velocity. Considering the negative influence of sulphates on the hardened material, the behaviour of the material after sulphates precipitation by adding barium sulphate was additionally tested. Carbonation progressed from the outside to the inside of the specimen through the porous system by Liesegang rings patterns for mortars with soluble sulphates, while the carbonation with precipitated sulphates was controlled by...
An analysis of the atomic radial distribution function of A10.2oAs0.5oTeo.3o, Alo.loASo.aoTeo.5o and Al0.aoAso.2oTeo.vo amorphous alloys obtained from quenching of the molten mixture of the elements was performed. A structure in which all... more
An analysis of the atomic radial distribution function of A10.2oAs0.5oTeo.3o, Alo.loASo.aoTeo.5o and Al0.aoAso.2oTeo.vo amorphous alloys obtained from quenching of the molten mixture of the elements was performed. A structure in which all the AI atoms are tetrahedrally bonded to the other types of atoms in the material, would satisfy the requirements of the experimental curve. Tetrahedral groups might be linked to each other by As and Te atoms, or directly through a Te or As atom belonging to more than one tetrahedra.
Industrial wet phosphoric acid production in Huelva (SW Spain) has led to the controversial stockpiling of waste phosphogypsum (PG) byproducts, resulting in the release of significant quantities of toxic impurities in salt marshes in... more
Industrial wet phosphoric acid production in Huelva (SW Spain) has led to the controversial stockpiling of waste phosphogypsum (PG) byproducts, resulting in the release of significant quantities of toxic impurities in salt marshes in the Tinto river estuary. A twofold objective is proposed: removing hazardous and unpleasant wastes and mitigating the emission of greenhouse gases into the atmosphere. Thus, the first aim of this research is to synthesize materials with the ability for CO2 sequestration from wastes as preliminary work for designing industrial processes, which involve a reduction of CO2 emissions. In this regard, PG from the fertilizer industry, soda solutions, and liquid alkaline wastes from aluminum industries have been considered as precursors. Our results demonstrate the high efficiency of portlandite precipitation by PG dissolution using alkaline solutions. Carbonation experiments performed at ambient pressure and temperature resulted in total conversion of the port...
Research Interests:
Research Interests:
ABSTRACT Thin and very uniform silica–alumina films were deposited by dip-coating onto AISI-304 stainless steel and submitted to different heat treatments. They were prepared by simultaneous ultrasound-assisted hydrolysis and... more
ABSTRACT Thin and very uniform silica–alumina films were deposited by dip-coating onto AISI-304 stainless steel and submitted to different heat treatments. They were prepared by simultaneous ultrasound-assisted hydrolysis and polycondensation of tetraethylorthosilicate and aluminium-sec-butylate or aluminium nitrate in an atmosphere rich in water vapour. The resulting materials were characterised by ellipsometry in order to optimise the process of avoiding porosity which was submitted to molecular probing. This method informs us of the micropore size distribution, using adsorptive different-sized molecules.The thickness ranges from 60 to 350 nm, depending on the sol processing and heat treatment. In some samples most of the micropores are only sensitive to molecular probe below 0.7 nm diameter. These and other characteristics will be discussed.
Research Interests:
La presente invención se refiere a la síntesis de materiales secuestradores de CO2, tipo silicatos de calcio, a partir de residuos, subproductos o co-productos con contenido en calcio y silicio tales como el hidróxido cálcico de la... more
La presente invención se refiere a la síntesis de materiales secuestradores de CO2, tipo silicatos de calcio, a partir de residuos, subproductos o co-productos con contenido en calcio y silicio tales como el hidróxido cálcico de la industria de producción del acetileno (vía carburo), cáscara de arroz, co-producto de la industria arrocera, sílice en polvo y cloruro de calcio. Así mismo, la presente invención se refiere a la aplicación del material en la captura selectiva de CO2 en corrientes gaseosas, mediante proceso de carbonatación en condiciones húmedas y presión y temperatura ambiental.
Research Interests: Monte Carlo Simulation, Information Extraction, Computer Simulation, Physical sciences, Wide Angle X-Ray Scattering, and 9 moreCHEMICAL SCIENCES, Fourier transform, Information Gain, Coordination number, Spatial structure, Short Range Order, extended x-ray absorption fine structure (EXAFS), Spatial Model, and Distribution Function
ABSTRACTThe copolymerization between TEOS (tetraethoxysilane) and silane derivatives was promoted by the application of high power ultrasound to the precursor liquid mixtures in the same way as in the classical sol-gel method. The... more
ABSTRACTThe copolymerization between TEOS (tetraethoxysilane) and silane derivatives was promoted by the application of high power ultrasound to the precursor liquid mixtures in the same way as in the classical sol-gel method. The specific organic precursor was selected from the silanol-terminated polymer family with different molecular functionality and the inorganic precursor was from the silicon alkoxide family. Ultrasound, through the acoustic cavitation process, influences the formation of a very fine distribution of silica particles and avoids cyclidation of the polymer, thus favoring copolymerization with the inorganic particles and leading to the formation of a highly porous and rubber-like solid aerogel. Creep compliance curves, corresponding to the time-dependent depth response to a step load, are imprint site dependent, with pore, soft and stiff sites discerned. In all cases, an instantaneous elastic deformation is apparent. For longer test times, depending on the imprint...
Research Interests:
ABSTRACT
Research Interests:
Research Interests:
The invention relates to a CO2 y SO2 capture method comprising the following steps consisting in: a) introducing an aqueous stream of a hydroxide of an alkali or alkaline-earth metal and another gas stream of CO2 into a bubble column... more
The invention relates to a CO2 y SO2 capture method comprising the following steps consisting in: a) introducing an aqueous stream of a hydroxide of an alkali or alkaline-earth metal and another gas stream of CO2 into a bubble column purifier/reactor, in order to form a carbonate of the alkali or alkaline-earth metal; b) introducing the carbonate of the alkali or alkaline-earth metal into a bubble column purifier/reactor, into which a stream of a gas mixture of CO2 and SO2 is introduced in order to form sulphite of an alkali or alkaline-earth metal and carbon dioxide; c) transforming the sulphite from step (b) into sulphate of said metal by means of oxidation with air; and d) re-circulating the unreacted CO2 produced during step (b) by reacting the slurry with the SO2, in the reactor from step (a).
ABSTRACT Ultrasonic treatment of mixtures of TEOS + water enables gels to be obtained without the necessity of using alcohol as a common solvent. The effects of composition, length of sonication and temperature of treatment on the... more
ABSTRACT Ultrasonic treatment of mixtures of TEOS + water enables gels to be obtained without the necessity of using alcohol as a common solvent. The effects of composition, length of sonication and temperature of treatment on the properties of the sonogels and their conversion into glasses were studied
Research Interests:
The properties (texture, mechanical behaviour, etc.) of hybrid organic–inorganic silica aerogels change dramatically when the concentration of the organic additive is varied from a given value. It has been known for several years that... more
The properties (texture, mechanical behaviour, etc.) of hybrid organic–inorganic silica aerogels change dramatically when the concentration of the organic additive is varied from a given value. It has been known for several years that this critical concentration is around 40% of the total weight of silica present in the sample. We have made use of a new structural model to
Research Interests:
Research Interests:
Abstract Synthetic wollastonite has been used as the active phase embedded into two different silica aerogel composites. These composites are different in respect of the route used for the synthesis of the wollastonite powder. Texture and... more
Abstract Synthetic wollastonite has been used as the active phase embedded into two different silica aerogel composites. These composites are different in respect of the route used for the synthesis of the wollastonite powder. Texture and composition of both types of ...
Research Interests:
Research Interests:
ABSTRACT The object of this paper is to evaluate behaviour during drying of two stone consolidants: Wacker OH and Tegovakon V, containing tetraethoxysilane. During drying, the gel network contracts due to capillary pressure generated by... more
ABSTRACT The object of this paper is to evaluate behaviour during drying of two stone consolidants: Wacker OH and Tegovakon V, containing tetraethoxysilane. During drying, the gel network contracts due to capillary pressure generated by solvent evaporation. When the consolidant dries inside the stone porous structure, the shrinkage is constrained in all three dimensions. In these conditions, the dried gel suffers a high stress that could cause it to crack. When there is a free surface, as for a consolidant layer on the surface of a pore, the stress can relax in the direction normal to the surface. In this case, the stress is controlled by network rigidity.