Persona: Martín Fernández, Santiago
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Martín Fernández
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Publicación Micro-Raman spectroscopy of rock paintings from the Galb Budarga and Tuama Budarga rock shelters, Western Sahara(Elsevier, 2018-03) Iriarte, Mercedes; Hernanz, Antonio; Sáenz de Buruaga, Andoni; Gavira Vallejo, José María; Martín Fernández, SantiagoRock paintings of two recent discovered rock shelters, Galb Budarga and Tuama Budarga, from the southeastern area of the Western Sahara, Sahrawi Arab Democratic Republic, have been studied by micro-Raman spectroscopy and scanning electron microscopy coupled with energy dispersive X-ray spectrometry in order to characterize the composition of the materials present in the painting panels. An unusual white pigment has been used in the zoomorphic pictographs of the Galb Budarga shelter which main components are the anhydrite (CaSO4) polymorphs I and II. Red and orange zoomorphic figures and ancient Berber scripts have been painted in the Tuama Budarga rock shelter. Haematite (α-Fe2O3) is the main component of the paints used; amorphous carbon and different manganese oxides have also been detected. Accretions of gypsum (CaSO4·2H2O) and anhydrite have been observed on the shelter wall used to paint. α-Quartz (α-SiO2), albite (NaAlSi3O8), dolomite, CaMg(CO3)2, calcite (CaCO3) and traces of hydroxylapatite (Ca10(PO4)6(OH)2) have been identified in the rocks supporting the paintings of both sites. Layers of calcium oxalates, whewellite (CaC2O4·H2O) and weddellite (CaC2O4·(2 + x)H2O, x ≤ 0.5) cover the pictorial panels of these rock shelters. A microestratrigraphic study of the paint used in the Tuama Budarga shelter revealed that the pigment layer is bracketed between oxalate layers.Publicación Feasibility of ultra-low Pt loading electrodes for high temperature proton exchange membrane fuel cells based in phosphoric acid-doped membrane(ELSEVIER, 2019) Martín Fernández, Santiago; Jensen, Jens Oluf; Li, Qingfeng; García Ybarra, Pedro Luis; Castillo Gimeno, José Luis; https://orcid.org/0000-0002-2427-7763; https://orcid.org/0000-0002-5460-055XFactors as the Pt/C ratio of the catalyst, the binder content of the electrode and the catalyst deposition method were studied within the scope of ultra-low Pt loading electrodes for high temperature proton exchange membrane fuel cells (HT-PEMFCs). The Pt/C ratio of the catalyst allowed to tune the thickness of the catalytic layer and so to minimize the detrimental effect of the phosphoric acid flooding. A membrane electrode assembly (MEA) with 0.05 mgPtcm−2 at anode and 0.1 mgPtcm−2 at cathode (0.150 mgPtcm−2 in total) attained a peak power density of 346 mW cm−2. It was proven that including a binder in the catalytic layer of ultra-low Pt loading electrodes lowers its performance. Electrospraying-based MEAs with ultra-low Pt loaded electrodes (0.1 mgPtcm−2) rendered the best (peak power density of 400 mW cm−2) compared to conventional methods (spraying or ultrasonic spraying) but with the penalty of a low catalyst deposition rate.Publicación Enseñanza de las Ciencias: Cómo funciona un microscopio electrónico de barrido(Universidad Nacional de Educación a Distancia (España). Facultad de Ciencias, 2006-01-01) Martín Fernández, Santiago