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Scientific Papers in SCI



2021


Química de Superficies y Catálisis

Mesoporous Carbon Production by Nanocasting Technique Using Boehmite as a Template

Ortega-Franqueza, M; Ivanova, S; Dominguez, MI; Centeno, MA
Catalysts, 11 (2021) 1132

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A series of mesoporous carbonaceous materials were synthesized by the nanocasting technique using boehmite as a template and glucose as a carbon precursor. After pyrolysis and template removal, the resulting material is a mesoporous carbon that can be additionally doped with N, B and K during prepyrolysis impregnation. In addition, the influence of doping on the morphology, crystallinity and stability of the synthesized carbons was studied using X-ray diffraction, nitrogen physisorption, thermogravimetry, Raman and IR spectroscopy and transmission electron microscopy. While the nanocasting process is effective for the formation of mesopores, KOH and urea do not modify the textural properties of carbon. The use of H3PO4 as a dopant, however, led to the formation of an AlPO4 compound and resulted in a solid with a lower specific surface area and higher microporosity. All doped solids present higher thermal stability as a positive effect of the introduction of heteroatoms to the carbon skeleton. The phosphorus-doped sample has better oxidation resistance, with a combustion temperature 120-150 degrees C higher than those observed for the other materials.


September, 2021 | DOI: 10.3390/catal11091132

Tribología y Protección de Superficies

Effect of Al content on the hardness and thermal stability study of AlTiN and AlTiBN coatings deposited by HiPIMS

Mendez, A; Monclus, MA; Santiago, JA; Fernandez-Martinez, I; Rojas, TC; Garcia-Molleja, J; Avella, M; Dams, N; Panizo-Laiz, M; Molina-Aldareguia, JM
Surface & Coatings Technology, 422 (2021) 127513

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The microstructure, mechanical properties and thermal stability of AT(x)Ti(1-x)N and Al1Ti1-xBN coatings grown by reactive high-power impulse magnetron sputtering (HiPIMS) have been analyzed as a function of Al/(Al + Ti) ratio (x) between 0.5 and 0.8. The coatings were predominantly formed by a face-centered cubic Ti(Al)N crystalline phase, both with and without B, even for x ratios as high as 0.6, which is higher than the ratio typically encountered for AlxTi1-xN coatings deposited by reactive magnetron sputtering. B doping, in combination with the highly energetic deposition conditions offered by HiPIMS, results in the suppression of the columnar grain morphology typically encountered in AlxTi1-xN coatings. On the contrary, the AlxTi1-xN coatings grown by HiPIMS present a dense nanocomposite type microstructure, formed by nanocrystalline Ti(Al) N domains and amorphous regions composed of Ti(Al)B 2 and BN. As a result, high-Al content (x approximate to 0.6) AlxTi1-xN coatings grown by HiPIMS offer higher hardness, elasticity and fracture toughness than AlxTi1-xN coatings. Moreover, the thermal stability and the hot hardness are substantially enhanced, delaying the onset of formation of the detrimental hexagonal AlN phase from 850 degrees C in the case of Al0.6Ti0.4N, to 1000 degrees C in the case of Al0.6Ti0.4N.


September, 2021 | DOI: 10.1016/j.surfcoat.2021.127513

Fotocatálisis Heterogénea: Aplicaciones

Photocatalytic production of hydrogen and methane from glycerol reforming over Pt/TiO2–Nb2O5

Iervolino, G; Vaiano, V; Murcia, JJ; Lara, AE; Hernández, JS; Rojas, H; Navío, JA; Hidalgo, MC
International Journal of Hydrogen Energy

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In this study, platinized mixed oxides (TiO2–Nb2O5) were tested on photocatalytic hydrogen production from a glycerol solution under UV light. Different samples with different Ti:Nb ratios were prepared by using a simple method that simultaneously combined a physical mixture and a platinum photochemical reduction. This method led to improved physicochemical properties such as low band gap, better Pt nanoparticle distribution on the surface, and the formation of different Pt species. Niobia content was also found to be an important factor in determining the overall efficiency of the Pt–TiO2–Nb2O5 photocatalyst in the glycerol reforming reaction. The photocatalytic results showed that Pt on TiO2–Nb2O5 enhanced hydrogen production from the aqueous glycerol solution at a 5 wt% initial glycerol concentration. The influence of different operating conditions such as the catalyst dosage and initial glycerol concentration was also evaluated. The results indicated that the best hydrogen and methane production was equal to 6657 μmol/L and 194 μmol/L, respectively after 4 h of UV radiation using Pt/Ti:Nb (1:2) sample and with 3 g/L of catalyst dosage. Moreover, the role of water in photocatalytic hydrogen production was studied through photocatalytic activity tests in the presence of D2O. The obtained results confirmed the role of water molecules on the photocatalytic production of hydrogen in an aqueous glycerol solution.


September, 2021 | DOI: 10.1016/j.ijhydene.2021.09.111

Tribología y Protección de Superficies

Nb-C thin films prepared by DC-MS and HiPIMS: Synthesis, structure, and tribomechanical properties

Sala, N; Abad, MD; Sánchez-López, JC; Caro, J; Colominas, C
Surface & Coatings Technology, 422 (2021) 127569

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Nanostructured Nb-C thin films were prepared by direct current magnetron sputtering (DC-MS) and high-power impulse magnetron sputtering (HiPIMS). The films were characterized in depth by X-ray diffraction (XRD), grazing incidence X-ray diffraction, scanning electron microscopy, atomic force microscopy, electron probe microanalysis, and Raman spectroscopy. The mechanical properties were measured by nanoindentation, and the tribological properties were measured by pin-on-disk tests in ambient air. The wear tracks and ball scars were analyzed by Raman spectroscopy to elucidate the tribochemical reactions that occurred at the contact area and to determine the wear mechanism for each specimen type. The thermal stability of the coatings was studied up to 1000 degrees C using Raman spectroscopy and XRD. The samples prepared by DC-MS were very dense, and the phase composition changed from purely nanocrystalline (Nb2C and NbC) to a mixture of NbC crystals embedded in an amorphous carbon-based matrix (NbC/a-C(:H)). However, the samples prepared by HiPIMS developed a marked columnar morphology with a NbC/a-C(:H) nanocomposite structure. The hardness values ranged from 11 to 20 GPa depending on the deposition technique and the amount of the soft a-C(:H) phase present in the sample. The tribological properties of all the coatings were remarkably good when the carbon content was approximately 50 at.%. The formation of a lubricating sp(2)-rich C tribofilm between the ball and coating during the pin-on-disk tests was observed by Raman spectroscopy. The tribofilm formed preferentially on the samples prepared by HiPIMS, which had higher C contents. At 750 degrees C, the degradation of the NbC phases resulted in the formation of an additional a-C phase and niobium oxides.


September, 2021 | DOI: 10.1016/j.surfcoat.2021.127569

Fotocatálisis Heterogénea: Aplicaciones

ZnO/Ag3PO4 and ZnO–Malachite as Effective Photocatalysts for the Removal of Enteropathogenic Bacteria, Dyestuffs, and Heavy Metals from Municipal and Industrial Wastewater

Murcia, JJ; Hernández Miño, JS; Rojas, H; Brijaldo, MH; Martin-Gómez, AN; Sánchez-Cid, P; Navío, JA; Hidalgo, MC; Jaramillo-Pérez, C
Water, 13 (2021) 2264

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Different composites based on ZnO/Ag3PO4 and ZnO–malachite (Cu2(OH)2CO3) were synthesized in order to determine their effectiveness in the treatment of municipal and industrial wastewaters (mainly polluted by enteropathogenic bacteria, dyes, and heavy metals). The addition of Ag3PO4 and malachite did not significantly modify the physicochemical properties of ZnO; however, the optical properties of this oxide were modified as a result of its coupling with the modifiers. The modification of ZnO led to an improvement in its effectiveness in the treatment of municipal and industrial wastewater. In general, the amount of malachite or silver phosphate and the effluent to be treated were the determining factors in the effectiveness of the wastewater treatment. The highest degree of elimination of bacteria from municipal wastewater and discoloration of textile staining wastewater were achieved by using ZnO/Ag3PO4 (5%), but an increase in the phosphate content had a detrimental effect on the treatment. Likewise, the highest Fe and Cu photoreduction from coal mining wastewater was observed by using ZnO–malachite (2.5%) and ZnO/Ag3PO4 (10%), respectively. Some of the results of this work were presented at the fourth Congreso Colombiano de Procesos Avanzados de Oxidación (4CCPAOx).


August, 2021 | DOI: 10.3390/w13162264

 

 

 

 

 

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