Hugo Uvegi

Bio: Hugo Uvegi is an academic researcher from Massachusetts Institute of Technology. The author has contributed to research in topics: Dissolution & Solubility. The author has an hindex of 6, co-authored 9 publications receiving 91 citations. Previous affiliations of Hugo Uvegi include Johns Hopkins University.

Characterization of Nanoporous Metal-Ionic Liquid Composites for the Electrochemical Oxygen Reduction Reaction

Abstract: The activity for an electrocatalyst for the oxygen reduction reaction (ORR) is most often assessed using bare metal electrodes in direct contact with an aqueous electrolyte. This architecture allows all reactants and products to have equivalent geometric access to the catalyst surface, but this does not always lead to an optimal reaction environment. By adding an intermediate phase as a layer between the catalyst and the electrolyte, diffusive driving forces can be engineered into the system to force reactants to the catalyst and products away from it, increasing the overall system activity. For instance, previous research explored nanoporous Ni/Pt electrodes encapsulated with the ionic liquid [MTBD][beti]. The high oxygen solubility in this ionic liquid was thought to explain the nearly doubled increase in the composite electrocatalyst activity, but it is possible that other ionic liquid properties (water solubility, oxygen diffusivity, ionic conductivity, viscosity) might also be affecting ORR activity. In this work, we surveyed a number of ionic liquids in nanoporous NiPt/ionic liquid composite catalysts with an eye toward clarifying to what extent the physical properties of the IL have on the activity of the composite ORR catalyst. Overall, we find the oxygen solubility and water solubility most strongly affect the decrease in ORR overpotential.

Mineralogical and microstructural characterization of biomass ash binder

Abstract: While the incineration of biomass residues is gaining traction as a globally available source of renewable energy, the resulting ash is often landfilled, resulting in the disposal of what could otherwise be used in value-added products. This research focuses on the beneficial use of predominantly rice husk and sugarcane bagasse-based mixed biomass ashes, obtained from two paper mills in northern India. A cementitious binder was formulated from biomass ash, clay, and hydrated lime (70:20:10 by mass, respectively) using 2M NaOH solution at a liquid-to-solid mass ratio of 0.40. Compressive strength of the biomass ash binder increased linearly with compaction pressure, indicating the role of packing density. Between the two mixed biomass ashes used in this study, the one with higher amorphous content resulted in a binder with higher strength and denser reaction product. Multi-faceted characterization of the biomass ash binder indicated the presence of aluminum-substituted calcium silicate hydrate, mainly derived from the pozzolanic reaction.

Dealloying and Dealloyed Materials

Abstract: A successful working model for nanoporosity evolution during dealloying was introduced 15 years ago. Since that time, the field has rapidly expanded, with research groups from across the world studying dealloying and dealloyed materials. Dealloying has grown into a rich field, with some groups focusing on fundamentals and mechanisms of dealloying, other groups creating new porous metals and alloys, and even more groups studying their properties. Dealloying was originally considered only in the context of corrosion, but now it is considered a facile self-organization technique to fabricate high-surface-area, bicontinuous nanoporous materials. Owing to their high interfacial area and the versatility of metallic materials, nanoporous metals have found application in catalysis, sensing, actuation, electrolytic and ultracapacitor materials, high-temperature templates/scaffolds, battery anodes, and radiation damage–tolerant materials. In this review, we discuss the fundamental materials principles underlying th...

Coupled dissolution and precipitation at mineral-fluid interfaces

Abstract: Reactions occurring at mineral–fluid interfaces are important in all geochemical processes and essential for the cycling of elements within the Earth. Understanding the mechanism of the transformation of one solid phase to another and the role of fluids is fundamental to many natural and industrial processes. Problems such as the interaction of minerals with CO2-saturated water, the durability of nuclear waste materials, the remediation of polluted water, and mineral reactions that can destroy our stone-based cultural heritage, are related by the common feature that a mineral assemblage in contact with a fluid may be replaced by a more stable assemblage.

A Combined Overview of Combustion, Pyrolysis, and Gasification of Biomass

Abstract: From the conventional use of biomass in the form of heating to the modern day use of biomass in the form of electricity generation and biofuel production, biomass has always been part of the evolution of mankind Modern day use of biomass is gradually becoming more complex, and engineering played an important role in defining different directions This review provides an overall view of biomass utilization through thermal treatment including combustion, pyrolysis, and gasification Efficient use of biomass with the desired output and minimizing the drawbacks are the core of the research, and marginal focus is being held on developing new techniques The variety of composition and uptake of different elements throughout the lifespan of biomass produces a mixture of results In general, it can be seen that the optimization was observed either in the form of chemical looping combustion to prevent greenhouse gas emission or in upgrading of bio-oil to produce biofuels The significant factor is the reaction co

Role of Polymerization in the Dissolution of Nepheline, Jadeite, and Albite Glasses: Toward Better Models for Aluminosilicate Dissolution

Abstract: Introduction: Dissolution and precipitation of feldspar is an important reaction in many environmental systems, as plagioclase feldspar is the most common mineral in the crust. However, the mechanism of dissolution of feldspar has remained in dispute despite twenty or more years of analysis of feldspar dissolution. We are pursuing an approach toward better understanding of feldspar dissolution by investigating reactivity of aluminosilicate glasses of variable composition. In particular, to investigate the effects of Al/Si ratio on plagioclase dissolution without complications of varying Na/Ca content or exsolution, three glasses with varying Al/Si ratio (albite, jadeite, nepheline) were synthesized. Glass powders were then prepared and dissolved at various values of pH in batch reactors under ambient conditions. Solution chemistry was analyzed by inductively coupled plasma -optical emission spectroscopy or -mass spectrometry. In addition, alteration of the glass surface was investigated using Xray photoelectron spectroscopy, secondary ion mass spectrometry, and Fourier transform infrared spectroscopy. Dissolution results: Many similarities in dissolution behavior between plagioclase crystals and this suite of glasses were observed: 1) dissolution was slowest at near-neutral pH and increased under acid and basic conditions, 2) dissolution rate at all pH values increased with increasing Al/Si ratio, 3) the pH dependence of dissolution was higher for the phase with Al/Si = 1 than the phase with Al/Si = 0.3, 4) after acid leaching, the extent of Al-depletion of the altered surface increased with increasing bulk Al/Si ratio from Al/Si = 0.3 (albite) to 0.5 (jadeite), but then decreased in nepheline (Al/Si = 1.0), which dissolved stoichiometrically with respect to Al, and 5) little to no Al depletion of the surface of any glass occurred at pH > 7. However, in contrast with some observations for plagioclase dissolution, log(rate) increased almost linearly with Al content, and n, the slope of the log(rate)pH curve at low pH, varied smoothly from albite to jadeite to nepheline (n = 0.3, 0.6, 1.0 respectively). At high pH, the slope of this curve, m, did not differ between glasses (m = -0.4 + 0.1). Mechanistic interpretation: These results are consistent with an identical mechanism controlling dissolution of nepheline, albite, and jadeite glass, although no Si-rich layer can develop on nepheline because of the lack of Si-O-Si linkages. Such a conclusion is consistent with a transition state for these aluminosilicates at high pH consisting of a deprotonated Q3 hydroxyl group (where Qv refers to an x atom in a tetrahedral site with v bridging oxygens) or a five-coordinate Si site after nucleophilic attack by OH, and, at low pH, a protonated Q4OQ4. At low pH, we infer that Q4OQ4 Al linkages are ratelimiting because they are presumed to hydrolyze more slowly than Qv OQw Si (v,w < 3). According to this model, dissolution rate increases from albite to jadeite to nepheline because hydrolysis of Al-O-Si linkages becomes more energetically favorable as the number of Al atoms per Si tetrahedral increases, a phenomenon documented by geometry optimizations using ab initio methods (for example, Figure 1). However, a model wherein Q4OQ4 Si linkages are faster to hydrolyze than lower connectivity linkages between Si atoms (Qv OQw , v,w < 3) may also explain aspects of this data.