This study presents the energy storage potential of nitrate salts for specific applications in energy systems that use renewable resources. For this, the thermal, chemical, and morphological characterization of 11 samples of nitrate salts as phase change materials (PCM) was conducted. Specifically, sodium nitrate (NaNO₃), sodium nitrite (NaNO₂), and potassium nitrate (KNO₃) were considered as base materials; and various binary and ternary mixtures were evaluated. For the evaluation of the materials, differential Fourier transform infrared spectroscopy (FTIR), scanning calorimetry (DSC), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) to identify the temperature and enthalpy of phase change, thermal stability, microstructure, and the identification of functional groups were applied. Among the relevant results, sodium nitrite presented the highest phase change enthalpy of 220.7 J/g, and the mixture of 50% NaNO₃ and 50% NaNO₂ presented an enthalpy of 185.6 J/g with a phase change start and end temperature of 228.4 and 238.6 °C, respectively. This result indicates that sodium nitrite mixtures allow the thermal storage capacity of PCMs to increase. In conclusion, these materials are suitable for medium and high-temperature thermal energy storage systems due to their thermal and chemical stability, and high thermal storage capacity.

This work reports on the assessment of a non-hydrolytic electrochemical sensor for glucose sensing that is developed using functionalized carbon nanotubes (fCNTs)/Co(OH)₂. The morphology of the nanocomposite was investigated by scanning electron microscopy, which revealed that the CNTs interacted with Co(OH)₂. This content formed a nanocomposite that improved the electrochemical characterizations of the electrode, including the electrochemical active surface area and capacitance, thus improving sensitivity to glucose. In the electrochemical characterization by cyclic voltammetry and chronoamperometry, the increase in catalytic activity by Co(OH)₂ improved the stability and reproducibility of the glucose sensor without the use of enzymes, and its concentration range was between 50 and 700 μmol L⁻¹. The sensor exhibited good linearity towards glucose with LOD value of 43.200 µmol L⁻¹, which proved that the Co(OH)₂-fCNTs composite is judicious for constructing cost effective and feasible sensor for glucose detection.

This work presents the thermochemical analysis of a packed-bed reactor via multi-dimensional CFD modeling using FlexPDE and COMSOL Multiphysics. The temperature, concentration, and reaction rate profiles for methane production following the Fischer–Tropsch (F-T) synthesis were studied. To this end, stationary and dynamic differential equations for mass and heat transfer were solved via the finite element technique. The transport equations for 1-D and 2-D models using FlexPDE consider dispersion models, where the fluid and the catalyst can be treated as either homogeneous or heterogenous systems depending on the gradient extents. On the other hand, the 3-D model obtained in COMSOL deems the transport equations incorporated in the Porous Media module. The aim was to compare the FlexPDE and COMSOL models, and to validate them with experimental data from literature. As a result, all models were in good agreement with experimental data, especially for the 2-D and 3-D dynamic models. In terms of kinetics, the predicted reaction rate profiles from the COMSOL model and the 2-D dynamic model followed the temperature trend, thus reflecting the temperature dependence of the reaction. Based on these findings, it was demonstrated that applying different approaches for the CFD modeling of F-T processes conducts reliable results.

La presente investigación se enfocó en el análisis de los materiales de cambio de fase. Para realizar el estudio, se seleccionaron tres sales de nitrato. Nitrato de sodio, nitrato de potasio y finalmente nitrito de sodio. Las técnicas de caracterización utilizadas fueron la calorimetría diferencial de barrido, análisis mediante termogravimetría, análisis de espectrometría infrarroja mediante la transformada de Fourier y finalmente se realizó un estudio de la microestructura de los compuestos con el microscopio electrónico de barrido. Como resultado del estudio, se llegó a determinar el potencial de almacenamiento energético de los nitratos para aplicaciones específicas en sistemas energéticos que utilizan recursos renovables. Además, se analizó el comportamiento de los materiales analizados trabajando en conjunto como compuestos binarios y ternarios. Por todo ello, esta investigación pretende aportar a la temática de almacenamiento de energía con materiales de cambio de fase, con resultados relevantes. Para ello, se han utilizado metodologías probadas por investigadores a nivel mundial y equipamiento adecuado de caracterización térmica Los resultados obtenidos de entalpía de fusión, permiten concluir que estos materiales son adecuados para sistemas de almacenamiento energético.