Scientific Papers in SCI
2023
2023
Nanotecnología en Superficies y Plasma
Strontium/zinc phytate-based self-assembled monolayers on titanium surfaces enhance osteogenesis and antibacterial performance in vitro
Asensio, G; Hernández-Arriaga, AM; Martin-del-Campo, M; Prieto, MA; González-Elipe, AR; Rojo, L; Vázquez-Lasa, BApplied Surface Science, 620 (2023) 156818
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The accumulation of bacteria over implant surfaces is still the first cause of failure, and the development of antimicrobial surfaces constitutes a first line in implant research. Besides, the durability and mechanical performance of implants, in special in the dental area, are mainly determined by their osseointegration capacity into the maxillofacial bone and the appearance of infections. Consequently, implant osseointegration and infection prophylaxis remain as big challenges to attain so a huge investigation is being developed on the production of bioactive surfaces to achieve improvements in these aspects. In this work we propose the functionalization of titanium surfaces (Ti Cp) with self-assembled monolayers (SAMs) of bioactive organophosphate compounds: phytic acid (Ti-PA) and its metallic phytate de- rivatives bearing Sr2+ and/or Zn2+ (Ti-SrPhy, Ti-ZnPhy and Ti-SrPhy/ZnPhy) which exhibited tunable in vitro osteogenic, antimicrobial and antioxidant properties in a previous work. Thus, phytate compounds are chemically anchored onto Ti discs through a simple procedure consisting of a condensation reaction promoted by heat treatment. EDS and XPS spectroscopies confirm the obtaining of the modified surfaces and the topographic properties and wettability analysed by SEM, AFM, profilometry and contact angle measurements, respectively, are explored. Additionally, phytate-SAMs do not release any cytotoxic compound after 14 days and stimulate in vitro adhesion and proliferation of human osteoblast cells after 14 days of culture. The osteogenic ability of the modified surfaces evaluated by the quantification of ALP activity and matrix mineralization degree shows a significant improvement with respect to unmodified surfaces. Furthermore, the antimicrobial activity of phytate-SAMs against Streptococcus mutans cultures is evaluated. The count of viable cells and the quantification of produced biofilm are significantly reduced by all phytate-SAMs groups (p < 0.001). Cell membrane integrity studies by LIVE/DEAD staining and SEM imaging confirm a decreased viability of adhered bacteria when phytate-based surfaces are tested, due to a disruption in the function and permeability of the cell membrane. Therefore, phytate-SAMs exhibit suitable in vitro features suggesting their promising potential as bioactive coatings of dental implants.
May, 2023 | DOI: 10.1016/j.apsusc.2023.156818
Reactividad de Sólidos
Direct comparison of surface crystal growth kinetics in chalcogenide glass measured by microscopy and DSC
Shanelova, J; Honcova, P; Malek, J; Perejon, A; Perez-Maqueda, LAJournal of the American Ceramic Society, 106 (2023) 6051-6061
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Surface crystallization in fine powder Se70Te30 chalcogenide glass was studied by differential scanning calorimetry (DSC) and optical microscopy. A complex kinetic analysis of these experimental data reveals that the contracting sphere mechanism (R3 model) is the rate determining step of crystal growth, and the conventional Johnson-Mehl-Avrami-Kolmogorov model cannot be used in this case. Moreover, it is clearly shown that the particle size distribution should be considered in crystallization studies. Actually, when the particle size effect is taken into account, the simulated DSC curves for the R3 model agree very well with the experimental data over the entire temperature range. The crystallization kinetics determined from the nonisothermal DSC data are consistent with previously reported isothermal crystallization data for the same powder fraction. The crystal growth rate calculated from isothermal and nonisothermal DSC data agrees very well with the microscopically measured surface and bulk crystal growth rate.
May, 2023 | DOI: 10.1111/jace.19204
Reactividad de Sólidos
Limits of powder metallurgy to fabricate porous Ti35Nb7Zr5Ta samples for cortical bone replacements
Rodriguez-Albelo, LM; Navarro, P; Gotor, FJ; de la Rosa, JE; Mena, D; Garcia-Garcia, FJ; Beltran, AM; Alcudia, A; Torres, YJournal of Materials Research and Technology-JMR&T, 24 (2023) 6212-6226
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The use of 13-Titanium alloys to fabricate metal implants with Young's modulus that re-sembles bone tissues is presented as an alternative to commercially pure titanium or a- Titanium alloys, although it is still necessary to introduce proper implant porosity to reach the Young's modulus of cortical bones. In this work, porous samples were fabricated by loose sintering (0 MPa) and compared to samples manufactured at 1000 MPa, both sintered under the same conditions. Raw powders and sintered samples of the 13-Titanium alloy, Ti35Nb7Zr5Ta, were characterized in detail in terms of both physicochemical and micro-structural properties. Moreover, the tribo-mechanical behavior of sintered samples was evaluated by performing ultrasound technique, instrumented micro-indentation (P-h curves), and scratch tests. The bio-functional behavior was studied by impedance spec-troscopy and contact angle measurements. The results allowed the evaluation of the limits of conventional powder metallurgy (percentage of porosity, size, and morphology of pores), as well as the influence of the porosity and chemical composition to achieve a better biomechanical and bio-functional behavior that would guarantee bone requirements. The Ti35Nb7Zr5Ta alloy showed relatively high electrical impedance values compared to commercially pure titanium, indicating an improved bio-corrosion behavior. Furthermore, wettability measurements indicated that porous disks fabricated by loose sintering exhibit higher hydrophilicity, often associated with a better antibacterial response
May, 2023 | DOI: 10.1016/j.jmrt.2023.04.212
Materiales y Procesos Catalíticos de Interés Ambiental y Energético
Catalytic performance of cobalt supported onto APTES functionalized TiO2 for Fischer-Tropsch reaction
Platero, F; Caballero, A; Colon, GFuel, 340 (2023) 127528
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Cobalt supported TiO2 catalysts have been prepared by wet-impregnation and by immobilization over APTES (3-aminopropyl triethoxysilane) grafted TiO2. Impregnated system showed better catalytic performance after reduction at 260 degrees C but significant deactivation is observed. On the contrary, functionalized catalyst showed better catalytic performance after reduction at 400 degrees C with notable stability. We have stated from CO-DRIFT operando analysis that impregnated system is strongly affected by negative SMSI (strong metal-support inter-action) upon reduction at higher temperature. While immobilization on APTES hinders the loss of metal active sites. The study of spent catalysts denotes that Co is redispersed in the impregnated catalyst while functionalized trends to form agglomerates.
May, 2023 | DOI: 10.1016/j.fuel.2023.127528
Materiales Avanzados
Characterization, thermal and ceramic properties of clays from Alhabia (Almeria, Spain)
Rat, E; Martinez-Martinez, S; Sanchez-Garrido, JA; Perez-Vilargejo, L; Garzon, E; Sanchez-Soto, PJCeramics International, 49 (2023) 14814-14825
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Clays from Alhabia (Almeria, Spain) have been investigated in this work using several analytical techniques: X-Ray Diffraction (XRD), X-Ray Fluorescence (XRF), thermal analysis (Thermogravimetry, TG, and its first deriv-ative, DTG), Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray Spectroscopy (EDS). Texture characteristics (granulometry) and plasticity have been examined. The main ceramic properties (firing shrinkage, water absorption, bulk density, open porosity, flexural strength and thermal conductivity) have been determined using pressed and fired clay samples. Thus, the mineralogical, chemical, textural and ceramic features of these clays have been evidenced for the first time. The mineralogical analysis by XRD indicated that the clay samples are constituted by a mixture of chlorite and illite, as main clay minerals, being quartz and other minerals in lower relative proportion (calcite, gypsum and hematite). This finding is important because the investigations on chlorite-illite-calcitic clays are very scarce. The chemical analysis by XRF showed that silica and alumina are predominant, as expected by the mineralogy, with medium contents of calcium oxide, from calcite, and alkalis, from illite, being-8 and-5%, respectively, besides iron and titanium oxides (-8%). The particle size analysis showed 71.76% of "clay fraction" (<2 mu m) and 21.66% of silt fraction (2-50 mu m). The plasticity index (Atterberg) was 14.3%, with acceptable moulding and extrusion properties. Thermal analysis by TG/DTG indicated a weight loss associated to dehydroxylation of structural water of the clay minerals and decarbonation of calcite by progressive heating. After the characterization of raw clays, the next step was the determination of ceramic properties of mixed and ground clays after firing using pressed bodies. For this purpose, two firing temperatures were selected (900 and 1100 degrees C) for 1 h. The examination of the resultant fired bodies indicated that porous ceramic materials (-36% open porosity and-22% of water absorption capacity) can be obtained by firing at 900 degrees C, with small variations in dimensions (<0.8% at 1100 degrees C). The porosity changed at relatively lower values by firing at 1100 degrees C (-34-35%), being associated to the presence of decomposed calcite. Bulk density was found almost constant from 900 to 1100 degrees C, with a maximum value of-1.67 g/cm3 at 1100 degrees C. Flexural strength reached a maximum value of 34.47 MPa at 1100 degrees C for the ground sample. Finally, thermal conductivity after firing the clay bodies was found almost constant at 900 and 1100 degrees C (0.457 and 0.479 W/mK, respectively). Taking into account these results, the main applications of the Alhabia clays have been evaluated. These clays can be used for the fabrication of porous ceramic supports and tiles by firing at 900 degrees C. Firing the clays at higher temperature (1100 degrees C) is of great interest for the fabrication of ceramic tiles and ceramic bricks of higher flexural strength with variable porosity and practically constant in dimensions. It is economically important although at higher processing costs. Finally, it can be emphasized that this work is a contribution of a better scientific knowledge of chlorite-illite-calcitic clays as ceramic raw materials.
May, 2023 | DOI: 10.1016/j.ceramint.2022.05.328
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