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Articles 31 - 60 of 181

Full-Text Articles in Mineral Physics

Quantification Of Organic Carbon Sequestered By Biogenic Iron Sulfide Minerals In Long-Term Anoxic Laboratory Incubations, Nader Nabeh, Cheyenne Brokaw, Aude Picard Apr 2022

Quantification Of Organic Carbon Sequestered By Biogenic Iron Sulfide Minerals In Long-Term Anoxic Laboratory Incubations, Nader Nabeh, Cheyenne Brokaw, Aude Picard

Life Sciences Faculty Research

Organic carbon sequestration in sedimentary environments controls oxygen and carbon dioxide concentrations in the atmosphere. While minerals play an important role in the preservation of organic carbon, there is a lack of understanding about the formation and stability of organo-mineral interactions in anoxic environments, especially those involving authigenic iron sulfide minerals. In this study, we quantified organic carbon and nitrogen sequestered in biogenic iron sulfide minerals co-precipitated with sulfate-reducing bacteria (SRB) in freshwater and marine conditions in long-term laboratory experiments. The amounts of C and N associated with biogenic iron sulfide minerals increased with increasing cell biomass concentrations available in …

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Augmenting Field Nuclear Forensics Capabilities With Handheld Atomic Spectroscopy Devices For Nuclear Debris Analysis, Ashwin P. Rao, Christopher M. Sutphin, Christina L. Dugan Apr 2022

Augmenting Field Nuclear Forensics Capabilities With Handheld Atomic Spectroscopy Devices For Nuclear Debris Analysis, Ashwin P. Rao, Christopher M. Sutphin, Christina L. Dugan

Faculty Publications

The realm of technical nuclear forensics remains a critical part of joint counterproliferation capabilities. Since the passage of the Nuclear Forensics and Attribution Act (H.R.730) in 2010, the nuclear science community has undertaken steps to bolster national nuclear forensics capabilities under the National Technical Nuclear Forensics Center. Within the technical nuclear forensics umbrella, one particular area of interest involves developing capabilities for in-field analysis of nuclear material. This includes engaging in field training exercises across relevant branches of the military and investigating new technologies to conduct field nuclear forensic analyses. The integration of novel analytical technologies into real-world nuclear detection …

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Pascoite Minerals And Potential Application Of Nmr Spectroscopy, Craig C. Mclauchlan, Beth Trent-Ringer, Debbie C. Crans Jan 2022

Pascoite Minerals And Potential Application Of Nmr Spectroscopy, Craig C. Mclauchlan, Beth Trent-Ringer, Debbie C. Crans

Faculty Publications – Chemistry

The 20 minerals encompassing the pascoite family of decavanadate isopolyanion-containing [V10O28]6− minerals include a few minerals, such as rakovanite, that have been described as containing a protonated decavanadate anion. Rakovanite was originally assigned the formula Na3[H3V10O28]•15H2O and now is redefined with an ideal formula (NH4)3Na3[V10O28]•12H2O. Nuclear magnetic resonance (NMR) and particularly 51V NMR spectroscopy is an informative method used to describe the protonation state and speciation in both solid and solution states …

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Viscous Anisotropy Of Wet Olivine Aggregates, Megan Ryan Jan 2022

Viscous Anisotropy Of Wet Olivine Aggregates, Megan Ryan

Williams Honors College, Honors Research Projects

I will deform natural olivine aggregates (Anita Bay dunite) cores in various orientations relative to a natural mineral alignment in the rock under both dry and wet conditions. Different orientations in regards to this mineral alignment will produce deformation on different slip systems. Stress measurements will be taken during the deformation of the samples in order to characterize any changes in viscous anisotropy observed due to the changes in slip system. Anita Bay dunite is a proxy for the main mineral found in the mantle wedge of subduction zones. Therefore, understanding the transformation of viscosity and slip systems in this …

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Numerical Modeling Of Mineralizing Processes During The Formation Of The Yangzhuang Kiruna-Type Iron Deposit, Middle And Lower Yangtze River Metallogenic Belt, China: Implications For The Genesis And Longevity Of Kiruna-Type Iron Oxide-Apatite Systems, Xunyu Hu, Simon Jowitt, Feng Yuan, Guangxian Liu, Jinhui Luo, Yuhua Chen, Hui Yang, Keyue Ren, Yongguo Yang Dec 2021

Numerical Modeling Of Mineralizing Processes During The Formation Of The Yangzhuang Kiruna-Type Iron Deposit, Middle And Lower Yangtze River Metallogenic Belt, China: Implications For The Genesis And Longevity Of Kiruna-Type Iron Oxide-Apatite Systems, Xunyu Hu, Simon Jowitt, Feng Yuan, Guangxian Liu, Jinhui Luo, Yuhua Chen, Hui Yang, Keyue Ren, Yongguo Yang

Geoscience Faculty Research

The Yangzhuang iron deposit is a Kiruna-type iron oxide-apatite (IOA) deposit within the Ningwu mining district of the Middle and Lower Yangtze River Metallogenic Belt (MLYRMB), China. This study applies a numerical modeling approach to identify the key processes associated with the formation of the deposit that cannot be easily identified using traditional analytical approaches, including the duration of the mineralizing process and the genesis of iron orebodies within intrusions associated with the deposit. This approach highlights the practical value of numerical modeling in quantitatively analyzing mineralizing processes during the formation of mineral deposits and assesses how these methods can …

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Comprehensive Report On Extraterrestrial Resource Extraction, Robinson Raphael Dec 2021

Comprehensive Report On Extraterrestrial Resource Extraction, Robinson Raphael

Student Works

The prospect of asteroid mining provides a plethora of riches that include metals and water. As the number of discovered asteroids continues to grow, opportunities arise to commercialize these resources within Near-Earth Asteroids (NEAs). With urgent applications on Earth and in space, NEAs allow for a surge in sales. Planning forward, Astroider Aerospace Systems follows a mission split into four phases. Phase 1 develops a series of spacecraft using existing technologies, titled as Near-Earth Asteroid Miners and Near-Earth Asteroid Surveyors. Phase 2 first launches the surveyors to candidate NEAs, prospecting them for ores. To identify potential celestial bodies for this …

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Single-Crystal Elasticity Of Tremolite At High-Pressure Conditions And Its Implication For The Mid-Lithospheric Discontinuity, Soisiri Charin Jul 2021

Single-Crystal Elasticity Of Tremolite At High-Pressure Conditions And Its Implication For The Mid-Lithospheric Discontinuity, Soisiri Charin

Earth and Planetary Sciences ETDs

Tremolite is the calcium magnesium amphibole that widely occurs in igneous and metamorphic rocks of the crustal and upper mantle lithosphere, especially in the greenschist facies to amphibolite facies of ultramafic assemblages. The stability field of amphibole reaches 3-4 GPa and 1100-1200°C depending on water content and cation substitutions giving rise to amphibole to occur in highly variable compositions. This P-T condition, corresponding to the depth about 80-120 km, coincides with the depth range that a negative velocity gradient usually found within most stable cratonic lithospheres. This depth range is seismically called Mid-lithosphere discontinuity (MLD). The geologic processes that might …

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Ultralow Velocities Of Caco3 And The Origin Of Seismic Anomalies In The Earth's Upper Mantle, Mingqiang Hou, Ming Hao, Jin Liu, Xiaowan Su, Wen-Yi Zhou, Rostislav Hrubiak, Jin S. Zhang May 2021

Ultralow Velocities Of Caco3 And The Origin Of Seismic Anomalies In The Earth's Upper Mantle, Mingqiang Hou, Ming Hao, Jin Liu, Xiaowan Su, Wen-Yi Zhou, Rostislav Hrubiak, Jin S. Zhang

Earth and Planetary Sciences Faculty and Staff Publications

Calcium carbonate (CaCO3) is a major host for CO2 in the deep Earth. The physical and chemical properties of CaCO3 at extreme pressure-temperature (P-T) conditions are indispensable to decipher the circulation of carbon between the Earth's interior and surface via volcanism and subduction. Using the pulse-echo-overlap method combined with Paris-Edinburgh press, we measured velocities of CaCO3 and observed an anomalous drop associated with the amorphization of aragonite under upper mantle conditions. The compressional (VP) and shear (VS) wave velocities of the partially amorphized CaCO3 are reduced …

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Equation Of State For Natural Almandine, Spessartine, Pyrope Garnet: Implications For Quartz-In-Garnet Elastic Geobarometry, Suzanne R. Mulligan, Elissaios Stavrou, Stella Chariton, Oliver Tschauner, Ashkan Salamat, Michael Wells, Alexander G. Smith, Thomas D. Hoisch, Vitali Prakapenka Apr 2021

Equation Of State For Natural Almandine, Spessartine, Pyrope Garnet: Implications For Quartz-In-Garnet Elastic Geobarometry, Suzanne R. Mulligan, Elissaios Stavrou, Stella Chariton, Oliver Tschauner, Ashkan Salamat, Michael Wells, Alexander G. Smith, Thomas D. Hoisch, Vitali Prakapenka

Geoscience Faculty Research

The equation of state (EoS) of a natural almandine74spessartine13pyrope10grossular3 garnet of a typical composition found in metamorphic rocks in Earth’s crust was obtained using single crystal synchrotron X-ray diffraction under isothermal room temperature compression. A third-order Birch-Murnaghan EoS was fitted to P-V data and the results are compared with published EoS for iron, manganese, magnesium, and calcium garnet compositional end-members. This comparison reveals that ideal solid solution mixing can reproduce the EoS for this intermediate composition of garnet. Additionally, this new EoS was used to calculate geobarometry on a garnet sample from the same rock, which was collected from the …

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Bat Guano Minerals And Mineralization Processes In Chameau Cave, Eastern Morocco, Philippe Audra, Vasile Heresanu, Lionel Barriquand, Mohamed El Kadiri Boutchich, Stephane Jaillet, Edwige Pons-Branchu, Pavel Bosak, Hai Cheng, R Lawrence Edwards, Michel Renda Apr 2021

Bat Guano Minerals And Mineralization Processes In Chameau Cave, Eastern Morocco, Philippe Audra, Vasile Heresanu, Lionel Barriquand, Mohamed El Kadiri Boutchich, Stephane Jaillet, Edwige Pons-Branchu, Pavel Bosak, Hai Cheng, R Lawrence Edwards, Michel Renda

International Journal of Speleology

The decay of bat guano deposits in caves produces mineral accumulations, mainly phosphates and secondary sulfates. Chameau Cave, Eastern Morocco, is located in the semi-arid Bni Snassen Mountains. It is composed of semi-active and dry passages, and is featured by strong condensation-corrosion on the walls, presence of fluvial sediments, and old corroded flowstones. Due to forced and convective airflow, the cave is generally very dry, with some damp sites related to condensation. Samples collected on the surface of different passages and along two sediment profiles yielded minerals related to bat guano decay. On recent or fresh guano, precursor minerals correspond …

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Chemical Mapping To Evaluate Post-Depositional Diagenesis Among The Earliest Ceramics In The Teotihuacan Valley, Mexico, Wesley D. Stoner, Barry J. Shaulis Apr 2021

Chemical Mapping To Evaluate Post-Depositional Diagenesis Among The Earliest Ceramics In The Teotihuacan Valley, Mexico, Wesley D. Stoner, Barry J. Shaulis

Anthropology Faculty Publications and Presentations

Chemical and mineral sourcing techniques are commonly employed in archaeology to reconstruct patterns of ceramic exchange and raw material procurement practices for the past, but the effects of post-depositional diagenesis are still often ignored despite a number of key studies warning that the composition of ceramics from archaeological deposits often diverges greatly from their original composition at the time of production. This current study on diagenesis derives from a large chemical and petrographic analysis of some of the earliest ceramics (1500-100 cal Before Common Era [BCE]) in the Basin of Mexico at a time when the development of ceramic trade …

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Microstructural Characteristics Of Deformed Quartz Under Non-Steady-State Conditions, Hamidreza Soleymani Feb 2021

Microstructural Characteristics Of Deformed Quartz Under Non-Steady-State Conditions, Hamidreza Soleymani

Dissertations, Theses, and Capstone Projects

Because of the long timescale of many geological processes (millions of years), it has been traditionally assumed that the existing forces acting on the rocks at deep crustal levels are in equilibrium (i.e., steady-state). An alternative assumption, however, suggests that rocks in the lower crust and upper mantle are continuously evolving and exchanging energy at various time scales. Under the latter assumption (i.e., non-steady-state), certain geologic systems may never attain equilibrium regardless of the length and the time scale of operating geologic events. These two “endpoint” assumptions suggest there is a wide range of geologically reasonable conditions under which rocks …

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Frozen In Time: A Numerical Modeling Approach To The Study Of Ice Bearing Planetesimals Through Carbonaceous Chondrites, Jasmine M. Bayron Feb 2021

Frozen In Time: A Numerical Modeling Approach To The Study Of Ice Bearing Planetesimals Through Carbonaceous Chondrites, Jasmine M. Bayron

Dissertations, Theses, and Capstone Projects

Icy planetesimals are significant objects of study for meteoritics, planetary science, and astrobiology due to their connections to the origins of life and liquid water on Earth. An existing closed system aqueous alteration model was adapted to simulate several scenarios involving early Solar System geologic processes occurring in an icy planetesimal interior. The model described in this work has been developed not only to test the validity of constraints currently thought to apply to CM1 parent bodies, but to directly compare the implications of these constraints for the isotopic composition and the modal mineralogy of carbonaceous chondrites. Isotopic ratios of …

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Microstructural And Microchemical Studies Of Fluid–Chondrule Interactions In A Pristine Cr Carbonaceous Chondrite And Apatite In Martian Nakhlites, Marina Martínez Jan 2021

Microstructural And Microchemical Studies Of Fluid–Chondrule Interactions In A Pristine Cr Carbonaceous Chondrite And Apatite In Martian Nakhlites, Marina Martínez

Earth and Planetary Sciences ETDs

PROJECT 1: Chondrites are the most primitive objects in the solar system, aggregates of the material that formed in the solar protoplanetary disk during the first 1-5 million years of its formation. However, petrographic observations indicate that most chondrites have been modified by secondary processes, including aqueous alteration, thermal metamorphism, and shock. Fortunately, a few chondrites largely escaped these processes and are considered pristine, such as the CR carbonaceous chondrite Queen Alexandra Range (QUE) 99177. QUE 99177 is an excellent sample for deciphering information about the reactions that took place between unaltered anhydrous solar nebular components and water under highly …

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Ultralow Velocities Of Caco3 And The Origin Of Seismic Anomalies In The Earth's Upper Mantle, Mingqiang Hou, Ming Hao, Jin Liu, Xiaowan Su, Wen-Yi Zhou, Jin S. Zhang, Rostislav Hrubiak Jan 2021

Ultralow Velocities Of Caco3 And The Origin Of Seismic Anomalies In The Earth's Upper Mantle, Mingqiang Hou, Ming Hao, Jin Liu, Xiaowan Su, Wen-Yi Zhou, Jin S. Zhang, Rostislav Hrubiak

Earth and Planetary Sciences Faculty and Staff Publications

Calcium carbonate (CaCO3) is a major mineral host for CO2 in deep Earth. The physical and chemical properties of CaCO3 at extreme pressure-temperature (P-T) conditions are important for understanding the CO2 circulation between the Earth's surface and interior primarily via volcanism and subduction. Using the pulse-echo-overlap method combined with Paris-Edinburgh (PE) press, we measured velocities of CaCO3 under upper mantle conditions and observed an anomalous velocity drop associated with the amorphization of aragonite. The compressional (VP) and shear (VS) wave velocities of the partially amorphized CaCO …

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The Effects Of Heterogeneities And Syn-Deformational Partial Melting On Rock Strength Evolution And Melt Migration, Nicole Wagner Jan 2021

The Effects Of Heterogeneities And Syn-Deformational Partial Melting On Rock Strength Evolution And Melt Migration, Nicole Wagner

Williams Honors College, Honors Research Projects

In nature, the segregation of granitic melts at the source may be controlled by fabric and compositional heterogeneities in the source rock, such as foliation and lineation. To investigate the influence of foliation/lineation orientation and composition on rock strength and melt interconnectivity, I performed a series of experiments on cores of a fine-grained gneiss (Gneiss Minuti) and a fine-grained muscovite-bearing quartzite (Moine Thrust quartzite). These rocks were cored at six primary orientations parallel, 45 degrees, and perpendicular to the foliation and lineation and were deformed at a constant temperature of 900°C, pressure of ~2 GPa, and strain rate of ~10-6/s …

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Analysis Of Water Concentration Formed Within Deformed Synthetic Quartz Crystals, Andrew Steward Jan 2021

Analysis Of Water Concentration Formed Within Deformed Synthetic Quartz Crystals, Andrew Steward

Williams Honors College, Honors Research Projects

Analyzing the strength of synthetic quartz is essential to understanding the strength of natural milky quartz, which likely controls the strength of Earth’s continental crust. Synthetic quartz is sometimes used for deformation experiments because it has a homogenous water distribution unlike natural milky quartz. The purpose of this study is to determine if annealing synthetic quartz at T = 600°C will convert the water in synthetic quartz to free water, like milky quartz, but with little water loss. Following two annealing experiments at Texas A&M University, I performed four annealing experiments to measure the water content of five synthetic quartz …

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Alteration Reactions In A Hornblende-Biotite-Anthophyllite-Fluid System: Implications For Cu-Au Ore Deposits, James Mitchell Lightner Jan 2021

Alteration Reactions In A Hornblende-Biotite-Anthophyllite-Fluid System: Implications For Cu-Au Ore Deposits, James Mitchell Lightner

Graduate Research Theses & Dissertations

High-grade porphyry Cu-Au ore deposits are typically contained in the potassic alteration zone, which forms through the alteration of preexisting country rock by a magmatic volatile phase (MVP) exsolved from an igneous intrusion. The MVP is a H2O dominant phase that contains high concentrations of NaCl, KCl, FeCl2, HCl, sulfur (as H2S or SO2) and minor concentrations of metals. The minerals in the potassic alteration zone are predominantly K-feldspar and biotite with a shreddy texture. Shreddy biotite forms from the replacement of prismatic-tabular shaped hornblende crystals, resulting in a characteristic shreddy texture. The alteration of hornblende to biotite can neutralize …

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Optimizing Raman Spectral Collection For Quartz And Zircon Crystals For Elastic Geothermobarometry, Mayara F. Cizina Dec 2020

Optimizing Raman Spectral Collection For Quartz And Zircon Crystals For Elastic Geothermobarometry, Mayara F. Cizina

Boise State University Theses and Dissertations

Raman microspectroscopy is widely used to identify and characterize organic and inorganic compounds. In the geosciences, Raman microspectroscopy has been used to identify mineral and fluid inclusions in host crystals, as well as to calculate pressure-temperature (P-T) conditions using mineral inclusions in host crystals, such as quartz-in-garnet barometry (QuiG). For thermobarometric applications, the reproducibility of Raman peak position measurements is crucial to obtain accurate P-T estimates. In this study, we explored how to optimize Raman spectral collection of quartz and zircon inclusions and reference crystals by monitoring machine stability and by varying spectral parameters. We also monitored a reference Hg …

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Structure Analysis Of Natural Wangdaodeite—Linbo3-Type Fetio3, Oliver Tschauner, Chi Ma, Matthew G. Newville, Antonio Lanzirotti Dec 2020

Structure Analysis Of Natural Wangdaodeite—Linbo3-Type Fetio3, Oliver Tschauner, Chi Ma, Matthew G. Newville, Antonio Lanzirotti

Geoscience Faculty Research

© 2020 by the authors. Licensee MDPI, Basel, Switzerland. This paper reports the first structure refinement of natural wangdaodeite, LiNbO3-type FeTiO3 from the Ries impact structure. Wangdaodeite occurs together with recrystallized ilmenite clasts in shock melt veins which have experienced peak shock pressures of between 17 and 22 GPa. Comparison of natural and synthetic wangdaodeite points toward a correlation between the distortion of ferrate-and titanate-polyhedra and the c/a ratio of the unit cell. The Raman spectrum of wangdaodeite is calculated based on the refined structure. Comparison to the reported spectrum of the type-material shows that the Raman peak at 738–740 …

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Framework Grain Composition And Texture Of The Wedington Sandstone Member, Fayetteville Shale, As A Provenance And Sediment Dispersal Indicator For Clastic Depositional Systems Across The Northern Arkansas Structural Platform During The Late Mississippian, Tanner Wayne Corbin Dec 2020

Framework Grain Composition And Texture Of The Wedington Sandstone Member, Fayetteville Shale, As A Provenance And Sediment Dispersal Indicator For Clastic Depositional Systems Across The Northern Arkansas Structural Platform During The Late Mississippian, Tanner Wayne Corbin

Graduate Theses and Dissertations

The Wedington Sandstone Member of the Fayetteville Shale is a constructive delta complex in the Chesterian section of the Late Mississippian record in Northwest Arkansas. A comparative analysis of framework grain composition between the Wedington and two other stratigraphically proximal Carboniferous sandstones: the Batesville Sandstone (older) and the Basal Atoka-Spiro Sandstone (younger) has addressed three questions: 1) Is there similarity in sediment provenance for the three sandstones? 2) Do these three sandstone units have a similar sediment dispersal vector? 3) What are likely sediment source terrains for the Wedington Sandstone? Wedington samples overwhelmingly plot as quartzarenites with fewer samples plotting …

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Foliar Application Of Low Concentrations Of Titanium Dioxide And Zinc Oxide Nanoparticles To The Common Sunflower Under Field Conditions, Marek Kolenčík, Dávid Ernst, Martin Urík, Ľuba Ďurišová, Marek Bujdoš, Martin Šebesta, Edmund Dobročka, Samuel Kšiňan, Ramakanth Illa, Qian Yu, Huan Feng, Ivan Černý, Veronika Holišová, Gabriela Kratošová Aug 2020

Foliar Application Of Low Concentrations Of Titanium Dioxide And Zinc Oxide Nanoparticles To The Common Sunflower Under Field Conditions, Marek Kolenčík, Dávid Ernst, Martin Urík, Ľuba Ďurišová, Marek Bujdoš, Martin Šebesta, Edmund Dobročka, Samuel Kšiňan, Ramakanth Illa, Qian Yu, Huan Feng, Ivan Černý, Veronika Holišová, Gabriela Kratošová

Department of Earth and Environmental Studies Faculty Scholarship and Creative Works

Nano-fertilisers have only recently been introduced to intensify plant production, and there still remains inadequate scientific knowledge on their plant-related effects. This paper therefore compares the effects of two nano-fertilisers on common sunflower production under field conditions. The benefits arising from the foliar application of micronutrient-based zinc oxide fertiliser were compared with those from the titanium dioxide plant-growth enhancer. Both the zinc oxide (ZnO) and titanium dioxide (TiO2) were delivered by foliar application in nano-size at a concentration of 2.6 mg·L−1. The foliar-applied nanoparticles (NPs) had good crystallinity and a mean size distribution under 30 nm. …

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Storm Surges In The Bohai Sea: The Role Of Waves And Tides, Yuanyi Li, Huan Feng, Guillaume Vigouroux, Dekui Yuan, Guangyu Zhang, Xiaodi Ma, Kun Lei May 2020

Storm Surges In The Bohai Sea: The Role Of Waves And Tides, Yuanyi Li, Huan Feng, Guillaume Vigouroux, Dekui Yuan, Guangyu Zhang, Xiaodi Ma, Kun Lei

Department of Earth and Environmental Studies Faculty Scholarship and Creative Works

A storm surge is a complex phenomenon in which waves, tide and current interact. Even though wind is the predominant force driving the surge, waves and tidal phase are also important factors that influence the mass and momentum transport during the surge. Devastating storm surges often occur in the Bohai Sea, a semi-enclosed shallow sea in North China, due to extreme storms. However, the effects of waves on storm surges in the Bohai Sea have not been quantified and the mechanisms responsible for the higher surges that affect part of the Bohai Sea have not been thoroughly studied. In this …

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Comparative Geochemical Analysis Of Ordovician And Mississippian Cherts In Relation To The Northern Arkansas And The Tri-State Mississippi Valley-Type Ore Districts, Jonathan T. Chick May 2020

Comparative Geochemical Analysis Of Ordovician And Mississippian Cherts In Relation To The Northern Arkansas And The Tri-State Mississippi Valley-Type Ore Districts, Jonathan T. Chick

Graduate Theses and Dissertations

It has been hypothesized that Ordovician, Mississippian, and younger carbonate and clastic formations found within the Ouachita Basin of west-central Arkansas and northward onto the Ozark Dome have experienced interaction with hydrothermal fluids due to tectonic forces produced by the Ouachita Orogeny. Lead (Pb) isotope analyses and resulting values produced through previous and concurrent geochemical studies of several formations indicate that the Mississippi Valley-type (MVT) ores were produced from a mixing and cooling of these sedimentary basinal brines by meteoric or connate waters. Reduction of sulfate to sulfide is one of the possible mechanisms by which MVT ore precipitation may …

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Structure-Strength Relations Of Distinct Mon Phases From First-Principles Calculations, Cheng Lu, Changfeng Chen Apr 2020

Structure-Strength Relations Of Distinct Mon Phases From First-Principles Calculations, Cheng Lu, Changfeng Chen

Physics & Astronomy Faculty Research

Molybdenum mononitrides (MoN) exhibit superior strength and hardness among the large class of transition-metal light-element compounds, but the underlying atomistic mechanisms for their outstanding mechanical properties and the variations of those properties among various MoN phases adopting different crystal structures remain largely unexplored and require further investigation. Here we report first-principles calculations that examine the stress-strain relations of these materials, and systematically compare results under pure and indentation shear deformations. In particular, we examine the distinct bonding structures and the associated mechanical properties in four different crystal phases of MoN that have been experimentally synthesized and stabilized under various physical …

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Indentation-Strain Stiffening In Tungsten Nitrides: Mechanisms And Implications, Cheng Lu, Changfeng Chen Apr 2020

Indentation-Strain Stiffening In Tungsten Nitrides: Mechanisms And Implications, Cheng Lu, Changfeng Chen

Physics & Astronomy Faculty Research

We report on a systematic computational study of ideal strengths, i.e., the lowest stresses needed to destabilize a perfect crystal under a variety of loading conditions for six stable and metastable tungsten nitrides identified by advanced crystal structure search algorithms. We employ first-principles calculations to determine stress-strain relations and examine the corresponding atomistic bonding changes for a microscopic understanding of the structural deformation modes. The obtained results show that, in stark contrast to many previously studied transition-metal borides, carbides, and also most nitrides, the tungsten nitrides exhibit surprisingly broad and common patterns of strain-stiffening effects under indentation strains. These extraordinary …

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Riesite, A New High Pressure Polymorph Of Tio2 From The Ries Impact Structure, Tschauner, Chi Ma, Antonio Lanzirotti, Matthew G. Newville Jan 2020

Riesite, A New High Pressure Polymorph Of Tio2 From The Ries Impact Structure, Tschauner, Chi Ma, Antonio Lanzirotti, Matthew G. Newville

Geoscience Faculty Research

This paper describes riesite, a new high-pressure polymorph of TiO2 from the Ries impact structure, Germany. Riesite occurs in shock-induced melt veins within xenoliths of bedrock in suevite. It is structurally closely related to srilankite from which it differs by having two distinct cation sites rather than one and through its monoclinic symmetry. It is indicative that riesite forms only upon release from the shock state upon back transformation from akaogiite.

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Statistical Analysis Of Nutrient Loads From The Mississippi-Atchafalaya River Basin (Marb) To The Gulf Of Mexico, Phyllis Okwan, Yi Zhen, Huan Feng, Shinjae Yoo, Murty S. Kambhampati, Abreione Walker, Shayne Boykin, Joe Omojola, Noel Blackburn Jan 2020

Statistical Analysis Of Nutrient Loads From The Mississippi-Atchafalaya River Basin (Marb) To The Gulf Of Mexico, Phyllis Okwan, Yi Zhen, Huan Feng, Shinjae Yoo, Murty S. Kambhampati, Abreione Walker, Shayne Boykin, Joe Omojola, Noel Blackburn

Department of Earth and Environmental Studies Faculty Scholarship and Creative Works

This study investigated the annual and seasonal variations in nutrient loads (NO2− + NO3− and orthophosphate) delivered to the Gulf of Mexico from the Mississippi-Atchafalaya River Basin (MARB) and examined the water quality variations. The results indicate that (1) annually, the mean NO2− + NO3− and orthophosphate loads showed a steady increase during 1996–1999, a persistent level during 2000–2007, and a moderate increase during 2008–2016; (2) seasonally, NO2− + NO3− and orthophosphate in MARB in spring and summer were higher than those in autumn and winter. Analysis of …

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Seismic Visibility Of Eclogite In The Earth’S Upper Mantle – Implications From High Pressure-Temperature Single-Crystal Elastic Properties Of Omphacite, Ming Hao, Jin S. Zhang, Wen-Yi Zhou, Qin Wang Jan 2020

Seismic Visibility Of Eclogite In The Earth’S Upper Mantle – Implications From High Pressure-Temperature Single-Crystal Elastic Properties Of Omphacite, Ming Hao, Jin S. Zhang, Wen-Yi Zhou, Qin Wang

Earth and Planetary Sciences Faculty and Staff Publications

Eclogite, constituting the subducted crust, is one of the most important geochemical and geophysical heterogeneities in the Earth’s mantle. As the dominant anisotropic phase in eclogite, precise high pressure-temperature single-crystal elastic properties of omphacite provides the basis for detecting eclogite in the Earth’s upper mantle. In this study, we measured the single-crystal elastic moduli of omphacite up to 18 GPa and 700 K using Brillouin spectroscopy. A least-squares fit to a third-order finite strain equation of state yields KS0’=4.5(1), G0’=1.53(5), ∂KS0/∂T=-0.029(5) GPa/K, ∂G0/∂T=-0.013(5) GPa/K, with ρ0=3.34(1) g/cm3, K …

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Analysis Of Deformation Mechanisms That Formed The Shear Zones Found In The Scituate Granite, Rhode Island, Usa, Jacob Waller Jan 2020

Analysis Of Deformation Mechanisms That Formed The Shear Zones Found In The Scituate Granite, Rhode Island, Usa, Jacob Waller

Williams Honors College, Honors Research Projects

The rheology of the ductile middle and lower crust affects the rate and intensity of aftershocks following major seismic events. This ductile deformation in the middle crust is commonly localized in narrow shear zones, which requires a process that causes strain weakening to operate in order to form these shear zones. In order to determine the mechanisms that cause strain localization in a common crustal rock, microstructures were analyzed in and around a shear zone found in a granite, Scituate, RI, deformed during the Alleghenian orogeny. Evolution of shear zone growth was observed through optical and scanning electron microscope (SEM) …

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