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The outstanding properties of single-layer graphene sheets for energy storage are hindered as agglomeration or restacking leads to the formation of graphite. The implications of the aforementioned arise on the difficulties associated with the aqueous processing of graphene sheets: from large-scale production to its utilization in solvent-assisted techniques like spin coating or layer-by-layer deposition. To overcome this, aqueous dispersions of graphene were stabilized by cellulose nanocrystals colloids. Aqueous cellulose nanocrystals dispersion highlights as a low-cost and environmentally friendly stabilizer towards graphene large-scale processing. Colloids of cellulose nanocrystals are formed by electrostatic repulsion of fibrils due to de-protonated carboxyl or sulfate half-ester functional groups. Graphene dispersions are obtained by hydrothermal reduction of electrochemically exfoliated graphene oxide in the presence of cellulose nanocrystals. This approach allows the preservation of the intrinsic properties of the nano-sheets by promoting non-covalent interactions between cellulose and graphene. The dispersions could be cast to form free-standing flexible conducting films or freeze-dried to form foams and aerogels for capacitive energy storage.
Danny Illera; Chatura Wickramaratne; Diego Guillen; Chand Jotshi; Humberto Gomez; D. Yogi Goswami. Stabilization of Graphene Dispersions by Cellulose Nanocrystals Colloids. Volume 12: Materials: Genetics to Structures 2018, 1 .
AMA StyleDanny Illera, Chatura Wickramaratne, Diego Guillen, Chand Jotshi, Humberto Gomez, D. Yogi Goswami. Stabilization of Graphene Dispersions by Cellulose Nanocrystals Colloids. Volume 12: Materials: Genetics to Structures. 2018; ():1.
Chicago/Turabian StyleDanny Illera; Chatura Wickramaratne; Diego Guillen; Chand Jotshi; Humberto Gomez; D. Yogi Goswami. 2018. "Stabilization of Graphene Dispersions by Cellulose Nanocrystals Colloids." Volume 12: Materials: Genetics to Structures , no. : 1.
Cellulose-based aerogels hold the potential to become a cost-effective bio-based solution for thermal insulation in buildings. Low thermal conductivities (−1·K−1) are achieved through a decrease in gaseous phase contribution, exploiting the Knudsen effect. However, several challenges need to be overcome: production energy demand and cost, moisture sensitivity, flammability, and thermal stability. Herein, a description and discussion of current trends and challenges in cellulose aerogel research for thermal insulation are presented, gathered from studies reported within the last five years. The text is divided into three main sections: (i) an overview of thermal performance of cellulose aerogels, (ii) an identification of challenges and possible solutions for cellulose aerogel thermal insulation, and (iii) a brief description of cellulose/silica aerogels.
Danny Illera; Jaime Mesa; Humberto Gomez; Heriberto Maury. Cellulose Aerogels for Thermal Insulation in Buildings: Trends and Challenges. Coatings 2018, 8, 345 .
AMA StyleDanny Illera, Jaime Mesa, Humberto Gomez, Heriberto Maury. Cellulose Aerogels for Thermal Insulation in Buildings: Trends and Challenges. Coatings. 2018; 8 (10):345.
Chicago/Turabian StyleDanny Illera; Jaime Mesa; Humberto Gomez; Heriberto Maury. 2018. "Cellulose Aerogels for Thermal Insulation in Buildings: Trends and Challenges." Coatings 8, no. 10: 345.
Heriberto Maury; José Wilches; Danny Illera; Víctor Pugliese; Jaime Mesa; Humberto Gómez. Failure assessment of a weld-cracked mining excavator boom. Engineering Failure Analysis 2018, 90, 47 -63.
AMA StyleHeriberto Maury, José Wilches, Danny Illera, Víctor Pugliese, Jaime Mesa, Humberto Gómez. Failure assessment of a weld-cracked mining excavator boom. Engineering Failure Analysis. 2018; 90 ():47-63.
Chicago/Turabian StyleHeriberto Maury; José Wilches; Danny Illera; Víctor Pugliese; Jaime Mesa; Humberto Gómez. 2018. "Failure assessment of a weld-cracked mining excavator boom." Engineering Failure Analysis 90, no. : 47-63.
New trends in product design require the use of modularity as key feature aimed to improve functional performance and the generation of open architecture products. For mechanical systems, one of the challenges during early design stages of these products involves the proper selection of joining methods among their constructive components. A robust joint selection process must consider product requirements, life cycle analysis and eventual procedures for assembly and disassembly. However, the general approach towards a Design-for-Assembly (DFA)/Design-for-Disassembly (DFD) only considers design, manufacturing and in some cases final disposal stage. Additionally, most of the works found in the literature are merely focused on assembly operations, disregarding economic and environmental benefits from optimising disassembly complexity. Herein, a functional characterisation of mechanical joint methods for the assembly and disassembly activities that take place throughout the product life cycle is proposed, focusing on open architecture products. Additionally, a classification of joining methods, a joint complexity metric valuation and a selection process are proposed for the conceptual design stage. The approach integrates both DFA and DFD principles in a formal methodology. The proposed selection roadmap can be implemented to increase product sustainability positively regarding resources optimisation, operational time and costs in reuse, remanufacturing and recycling tasks.
Jaime A. Mesa; Danny Illera; Iván Esparragoza; Heriberto Maury; Humberto Gómez. Functional characterisation of mechanical joints to facilitate its selection during the design of open architecture products. International Journal of Production Research 2017, 56, 7390 -7404.
AMA StyleJaime A. Mesa, Danny Illera, Iván Esparragoza, Heriberto Maury, Humberto Gómez. Functional characterisation of mechanical joints to facilitate its selection during the design of open architecture products. International Journal of Production Research. 2017; 56 (24):7390-7404.
Chicago/Turabian StyleJaime A. Mesa; Danny Illera; Iván Esparragoza; Heriberto Maury; Humberto Gómez. 2017. "Functional characterisation of mechanical joints to facilitate its selection during the design of open architecture products." International Journal of Production Research 56, no. 24: 7390-7404.
Computational Fluid Dynamics (CFD) models allows the three-dimensional simulation of the complex electrochemical, fluid dynamics, and thermodynamic phenomena related to the temperature and pressure distribution in the channels and the porous media than occurs inside the fuel. This work presents a CFD Multiphysics simulation of a PEM Fuel Cell under different operational conditions in their inlet streams. The simulation was done by using COMSOL Multiphysics® software, and it takes into account the mass transfer of gases in the channels, the porous media and the electrochemistry from reactions in a 5 cm2 active area. From the electrochemical perspective, the relationship between the charge transfer and the overpotentials are taken into account by kinetic expressions. In addition, the ohm’s law is applied in conjunction with the charge transfer to describe the conduction of current in the electrodes and electrolytes. Gas diffusion layers (GDL) along with the catalyst layers are modeled as porous media restricting the electrochemical reaction. As the result of different simulation scenarios representing different operational conditions, the characteristic Polarization Curve of the fuel cell, the dependence between the voltage in the cell, and the demanded current by the load are obtained. A reduction in the electrical potential was evidenced due to the reaction activation potential, the ohmic losses due to the electrical resistance of the materials and the concentration losses as a result of deficiencies in the diffusion of the reactants through the porous medium. Currents distributions and water content are analyzed in order to understand the role of temperature, load, and humidity over the fuel cell performance.
Victor Fontalvo; Danny Illera; Humberto Gomez; Marco Sanjuán. CFD Multiphysics Modeling and Performance Evaluation of PEM Fuel Cells. Volume 4A: Dynamics, Vibration, and Control 2017, 1 .
AMA StyleVictor Fontalvo, Danny Illera, Humberto Gomez, Marco Sanjuán. CFD Multiphysics Modeling and Performance Evaluation of PEM Fuel Cells. Volume 4A: Dynamics, Vibration, and Control. 2017; ():1.
Chicago/Turabian StyleVictor Fontalvo; Danny Illera; Humberto Gomez; Marco Sanjuán. 2017. "CFD Multiphysics Modeling and Performance Evaluation of PEM Fuel Cells." Volume 4A: Dynamics, Vibration, and Control , no. : 1.
Renewable energy sources demands sustainable energy storage technologies through the incorporation of low-cost and environment-friendly materials. In this regard, cellulose nanocrystals (CN), which are needle-shaped nanostructure derived from cellulose-rich resources, are extracted by sulfuric acid hydrolysis of biomass and used as both template and binder for the construction of electrochemical capacitors electrodes. A composite material is synthetized comprising CN and a conjugated electroactive polymer (CEP) to overcome the electrical insulating properties of cellulose as well as to exploit enhanced electrochemical activity by increased electrode surface-area. A one-step in-situ film synthesis protocol is evaluated by performing simultaneous polymerization and film deposition. The effect of proportion of starting components are evaluated through statistical Response Surface Methodology towards optimizing the electrochemical performance. Depending on the mass proportion of the starting components, a conducting network could be created by surface coating of the CEP on the whiskers during polymerization. Electrochemical measurements suggest an increase in specific surface area by at least a factor of two relative to bare CEP as a consequence of the template role of cellulose. Therefore, adjustment of the proposed one-step synthesis parameters allows tuning the material properties to meet specific application requirements regarding electrochemical performance.
Danny Illera; Victor Fontalvo; Humberto Gomez. Cellulose Nanocrystals Assisted Preparation of Electrochemical Energy Storage Electrodes. Volume 4A: Dynamics, Vibration, and Control 2017, 1 .
AMA StyleDanny Illera, Victor Fontalvo, Humberto Gomez. Cellulose Nanocrystals Assisted Preparation of Electrochemical Energy Storage Electrodes. Volume 4A: Dynamics, Vibration, and Control. 2017; ():1.
Chicago/Turabian StyleDanny Illera; Victor Fontalvo; Humberto Gomez. 2017. "Cellulose Nanocrystals Assisted Preparation of Electrochemical Energy Storage Electrodes." Volume 4A: Dynamics, Vibration, and Control , no. : 1.