Scholarly Works, Materials Science and Engineering (MSE)

Permanent URI for this collection

https://hdl.handle.net/10919/24370
Research articles, presentations, and other scholarship

Browse

Browsing Scholarly Works, Materials Science and Engineering (MSE) by Department "Geosciences"

Now showing 1 - 4 of 4
  • Thumbnail Image
    Abundance and Speciation of Surface Oxygen on Nanosized Platinum Catalysts and Effect on Catalytic Activity
    Serra-Maia, Rui; Winkler, Christopher; Murayama, Mitsuhiro; Tranhuu, Kevin; Michel, F. Marc (2018-06-18)
    Oxygen at the surface of nanosized platinum has a direct effect on catalytic activity of oxidation−reduction chemical reactions. However, the abundance and speciation of oxygen remain uncertain for platinum with different particle size and shape characteristics, which has hindered the development of fundamental property−activity relationships. We have characterized two commercially available platinum nanocatalysts known as Pt black and Pt nanopowder to evaluate the effects of synthesis and heating conditions on the physical and surface chemical properties, as well as on catalytic activity. Characterization using complementary electron microscopy, X-ray scattering, and spectroscopic methods showed that the larger average crystallite size of Pt nanopowder (23 nm) compared to Pt black (11 nm) corresponds with a 70% greater surface oxygen concentration. Heating the samples in air resulted in an increase in surface oxygen concentration for both nanocatalysts. Surface oxygen associated with platinum is in the form of chemisorbed oxygen, and no significant amounts of chemically bonded platinum oxide were found for any of the samples. The increase in surface oxygen abundance during heating depends on the initial size and surface oxygen content. Hydrogen peroxide decomposition rate measurements showed that larger particle size and higher surface chemisorbed oxygen correlate with enhanced catalytic activity. These results are particularly important for future studies that aim to relate the properties of platinum, or other metal nanocatalysts, with surface reactivity.
  • Thumbnail Image
    First-principles study of several hypothetical silica framework structures
    Teter, D. M.; Gibbs, Gerald V.; Boisen, Monte B. Jr.; Allan, D. C.; Teter, M. P. (American Physical Society, 1995-09-15)
    Several hypothetical silica structures have been generated using a simulated-annealing strategy with an ab initio based covalent-bonding potential. First-principles total-energy pseudopotential methods have been used to examine several. promising hypothetical structures and to compare their structural parameters, cohesive energies, and bulk moduli with those of low quartz;, low cristobalite, silica sodalite, and stishovite. The cohesive energies of these hypothetical structure types are found to be equivalent to those of low quartz, low cristobalite, and silica sodalite, and significantly lower than that of stishovite.
  • Thumbnail Image
    Natural, incidental, and engineered nanomaterials and their impacts on the Earth system
    Hochella, Michael F. Jr.; Mogk, David W.; Ranville, James; Allen, Irving C.; Luther, George W.; Marr, Linsey C.; McGrail, B. Peter; Murayama, Mitsuhiro; Qafoku, Nikolla P.; Rosso, Kevin M.; Sahai, Nita; Schroeder, Paul A.; Vikesland, Peter J.; Westerhoff, Paul; Yang, Yi (2019-03-29)
    Nanomaterials are critical components in the Earth system's past, present, and future characteristics and behavior. They have been present since Earth's origin in great abundance. Life, from the earliest cells to modern humans, has evolved in intimate association with naturally occurring nanomaterials. This synergy began to shift considerably with human industrialization. Particularly since the Industrial Revolution some two-and-a-half centuries ago, incidental nanomaterials (produced unintentionally by human activity) have been continuously produced and distributed worldwide. In some areas, they now rival the amount of naturally occurring nanomaterials. In the past half-century, engineered nanomaterials have been produced in very small amounts relative to the other two types of nanomaterials, but still in large enough quantities to make them a consequential component of the planet. All nanomaterials, regardless of their origin, have distinct chemical and physical properties throughout their size range, clearly setting them apart from their macroscopic equivalents and necessitating careful study. Following major advances in experimental, computational, analytical, and field approaches, it is becoming possible to better assess and understand all types and origins of nanomaterials in the Earth system. It is also now possible to frame their immediate and long-term impact on environmental and human health at local, regional, and global scales.
  • Thumbnail Image
    Pulmonary Exposure to Magnéli Phase Titanium Suboxides Results in Significant Macrophage Abnormalities and Decreased Lung Function
    McDaniel, Dylan K.; Ringel-Scaia, Veronica M.; Morrison, Holly A.; Coutermarsh-Ott, Sheryl; Council-Troche, McAlister; Angle, Jonathan W.; Perry, Justin B.; Davis, Grace; Leng, Weinan; Minarchick, Valerie; Yang, Yi; Chen, Bo; Reece, Sky W.; Brown, David A.; Cecere, Thomas E.; Brown, Jared M.; Gowdy, Kymberly M.; Hochella, Michael F. Jr.; Allen, Irving C. (Frontiers, 2019-11-28)
    Coal is one of the most abundant and economic sources for global energy production. However, the burning of coal is widely recognized as a significant contributor to atmospheric particulate matter linked to deleterious respiratory impacts. Recently, we have discovered that burning coal generates large quantities of otherwise rare Magnéli phase titanium suboxides from TiO2 minerals naturally present in coal. These nanoscale Magnéli phases are biologically active without photostimulation and toxic to airway epithelial cells in vitro and to zebrafish in vivo. Here, we sought to determine the clinical and physiological impact of pulmonary exposure to Magnéli phases using mice as mammalian model organisms. Mice were exposed to the most frequently found Magnéli phases, Ti6O11, at 100 parts per million (ppm) via intratracheal administration. Local and systemic titanium concentrations, lung pathology, and changes in airway mechanics were assessed. Additional mechanistic studies were conducted with primary bone marrow derived macrophages. Our results indicate that macrophages are the cell type most impacted by exposure to these nanoscale particles. Following phagocytosis, macrophages fail to properly eliminate Magnéli phases, resulting in increased oxidative stress, mitochondrial dysfunction, and ultimately apoptosis. In the lungs, these nanoparticles become concentrated in macrophages, resulting in a feedback loop of reactive oxygen species production, cell death, and the initiation of gene expression profiles consistent with lung injury within 6 weeks of exposure. Chronic exposure and accumulation of Magnéli phases ultimately results in significantly reduced lung function impacting airway resistance, compliance, and elastance. Together, these studies demonstrate that Magnéli phases are toxic in the mammalian airway and are likely a significant nanoscale environmental pollutant, especially in geographic regions where coal combustion is a major contributor to atmospheric particulate matter.