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- All Subjects: Sustainability
- All Subjects: Hydrogen
Different heat treatments were applied to commercial Pd77Ag23 membranes to promote surface segregation. X-ray photoelectron spectroscopy (XPS) analysis indicates that the membrane surface composition changed after heat treatment. The surface area of all membranes increased after heat treatment. The higher the surface Pd/(Pd+Ag) ratio, the higher the hydrogen permeability. Surface carbon removal and surface area increase cannot explain the observed permeability differences.
Previous computational modeling predicted that Cu54Zr46 would have high hydrogen permeability. Amorphous metallic Cu-Zr (Zr=37, 54, 60 at. %) membranes were synthesized and investigated. The surface oxides may result in the lower experimental hydrogen permeability lower than that predicted by the simulations. The permeability decrease indicates that the Cu-Zr alloys crystallized in less than two hours during the test (performed at 300 °C) at temperatures below the glass transition temperature. This original experimental results show that thermal stability of amorphous metallic membranes is critical for hydrogen separation applications.
The hydrogen permeability of Ni60Nb35M5 (M=Sn, Ti and Zr) amorphous metallic membranes was investigated. Nanoindentation shows that the Young’s modulus and hardness increased after hydrogen permeability test. The structure is maintained amorphous after 24 hours of hydrogen permeability testing at 400°C. The maximum hydrogen permeability of three alloys is 10-10 mol m-1 s-1 Pa-0.5. Though these alloys exhibited a slight hydrogen permeability decreased during the test, the amorphous metallic membranes were thermally stable and did not crystalize.
In 2019, the World Health Organization stated that climate change and air pollution is the greatest growing threat to humanity. With a world population of close to 8 billion people, the rate of population growth continues to increase nearly 1.05% each year. As the world population grows, carbon dioxide emissions and climate change continue to accelerate. By observing increasing concentrations of greenhouse gas emissions in the atmosphere, scientists have correlated that the Earth’s temperature is increasing at an average rate of 0.13 degrees Fahrenheit each decade. In an effort to mitigate and slow climate change engineers across the globe have been eagerly seeking solutions to fight this problem. A new form of carbon dioxide mitigation technology that has begun to gain traction in the last decade is known as direct air capture (DAC). Direct air capture works by removing excess atmospheric carbon dioxide from the air and repurposing it. The major challenge faced with DAC is not capturing the carbon dioxide but finding a useful way to reuse the post-capture carbon dioxide. As part of my undergraduate requirements, I was tasked to address this issue and create my own unique design for a DAC system. The design was to have three major goals: be 100% self-sufficient, have net zero carbon emissions, and successfully repurpose excess carbon dioxide into a sustainable and viable product. Arizona was chosen for the location of the system due to the large availability of sunlight. Additionally, the design was to utilize a protein rich hydrogen oxidizing bacteria (HOB) known as Cupriavidus Necator. By attaching a bioreactor to the DAC system, excess carbon dioxide will be directly converted into a dense protein biomass that will be used as food supplements. In addition, my system was designed to produce 1 ton (roughly 907.185 kg) of protein in a year. Lastly, by utilizing solar energy and an atmospheric water generator, the system will produce its own water and achieve the goal of being 100% self-sufficient.