J.A. Amézquita Martínez, O.A. Vargas Ceballos, D.Y. Peña Ballesteros
Universidad Industrial de Santander,
Colombia
Keywords: metal hydride, hydrogen storage, titanium-vanadium-chromium alloys, grain size
Summary:
The usage of clean energies based on renewable sources, trying to generate zero polluting wastes such as carbon dioxide has transcended to be a crucial topic to the whole world. On one side, hydrogen has been studied to replace these fossil fuels for several purposes, since it is a green energy vector and an element associated to abundant sources. In this project we present a metallic hydride synthesis, based on Titanium-Vanadium-Chromium at different conditions, such as milling time, stoichiometry, initial hydrogen pressure, and the temperature used for the insertion performing some variations to those characteristics stating with which of them the most quantity of the fluid is absorbed with. To know how much gas is getting into the sample, the theoretical volume is established every second of the process, using the Peng-Robinson equation of state by implementing the Newton-Raphson method, by comparing the pressure curves obtained where there’s a considerable change between them, the new mass is calculated. These graphics are achieved by executing the experiment under the exact same conditions, and comparing with a "blank test". The extracted material is acquired, attempting always to keep a base of one gram of mass, through mechanical milling over three, six, nine, fifteen, and twenty-one hours, initially with an equal stoichiometry relationship, pretending to form a ternary alloy. Then changes in the gas absorption are determined by decreasing the proportion of Chromium to a half and to zero from the original. Subsequently, the original quantity of the fluid is changed to 15 and 30 bars and the temperature to 300°C and 350°C. Besides, a scanning electron microscope (SEM) and X-ray diffraction (DRX) take place for some of the samples, determining the significant changes relating to particle size, phases, and percentage composition. Although the grinding time wasn’t long enough to form the expected structure, to the higher time a new phase is produced by two of the main elements, even so, with a lower range better results, in terms of hydrogen adsorption are found. The lower the Cr content in the base material, the lower the hydrogen insertion, and the same happens by raising the temperature. Finally, the pressure increase represents a greater capacity of hydrogen storage, nevertheless there isn’t a direct relationship between them.