威尼斯人app

Biomedical Applications of Covalently Modified Carbons

Prof. Nikolai Kalugin

New Mexico Tech

Abstract

The covalent modifications of graphite and graphene have the potential to greatly impact material applications in the
fields of biomedical and pharmaceutical sciences. [1, 2] A large number of pharmaceuticals currently on the market are sold as a mix of racemates and can pose significant complications in vivo as they are biologically two different types of compounds. Due to the inherent chemical stability and low fabrication costs, carbon materials have been investigated for use as Chiral Stationary Phases (CSPs) in drug purification applications. Functionalized 3D Graphene Nanosheets (3D GNS)- based CPSs were synthesized via the
covalent attachment of various chemical moieties to the substrate surface. [1] The successful covalent modification of the substrate surface of graphene-based materials prompted investigations of other applications of modified graphite, particularly in neuron electrophysiology. [1] Graphite was functionalized with the affinity tag biotin, and the epitope tags of histidine (His), and human influenza hemagglutinin (HA)
demonstrating a functional, molecularly-defined carbon electrodes. [2]

[1] Candelaria, L., Frolova, L.V., Kowalski, B.M., Artyushkova, K., Kalugin, N. G. Surface-modified three-dimensional graphene
nanosheets as a stationary phase for chromatographic separation of chiral drugs. Sci Rep 8, 14747 (2018).

[2] Candelaria, L., Kalugin, P.N., Kowalski, B.M., Kalugin, N.G. Covalent Epitope Decoration of Carbon Electrodes using Solid Phase
Peptide Synthesis. Sci Rep 9, 17805 (2019).

The Critical Role Played by Materials Science in enabling Sandia Mission Needs

Rajan Tandon

Analytical and Materials Sciences Department Component Science, Engineering and Production (CSEP) Center

Sandia National Laboratories, Albuquerque, New Mexico

Abstract

We will briefly describe Sandia’s mission areas, and the enabling role materials science and engineering play in achieving success. Next, we will describe the CSEP center mission, and describe some of the capabilities and efforts underway in our department. Two short presentation, one on hydriding of titanium films, and one on brazing technologies employed to join alumina to kovar will be described to highlight some of the materials science issues and capabilities.     

Process Development of Ferritic Steels for High Dose Fast Reactor Applications

Dr. Stuart Malloy

Los Alamos National Laboratory

Abstract

The Nuclear Technology R&D program is investigating options to transmute minor actinides.  To achieve this goal, new fuels and cladding materials must be developed and tested to high burnup levels (e.g. >20%) requiring cladding to withstand very high doses (greater than 200 dpa) while in contact with the coolant and the fuel.  New ferritic/martensitic and ferritic Oxide Dispersion Strengthened (ODS) alloys are being developed with improved radiation tolerance.  The ferritic/martensitic alloys include slight variations in the composition of HT-9 to improve resistance to low temperature embrittlement and void swelling.  This material maintained 5% uniform elongation after irradiation to 6 dpa at 290C while all other alloys exhibited less than 2% uniform elongation. In recent research, ferritic/martensitic steels have been produced using additive manufacturing showing similar properties to wrought materials after normalizing and tempering the microstructure.  Also, in the as-deposited condition, additively manufactured grade 91 steel shows a significant increase in yield strength at 300 °C and 600°C over that measured for wrought normalized and tempered material.  The irradiation tolerance of these alloys is being measured through high dose ion irradiations. In addition, ferritic ODS alloys are being processed into tube form and tested for future nuclear applications.  Tubes over 3 feet in length are being produced by pilger processing. Recent progress in high dose irradiated materials testing and materials development will be presented.

What counts as a flaw? Interactions between Geometry, Material Properties, and Defects in AM Metals

Jay Caroll

 Sandia National Laboratories, Albuquerque, NM USA

Abstract

All additively manufactured (AM) components will contain flaws, but many flaws are allowable within component requirements. This work focuses on a method for identifying different flaw types and defining acceptable thresholds for each type. The criticality of a flaw can vary throughout a part and a joint modeling-inspection-experimental effort should be able to inform designers as to which flaw types and sizes are acceptable and what inspection techniques are needed to identify disqualifying flaws. This work considers structural properties of an exemplar component made of 316 stainless steel vs AlSi10Mg with intentionally-introduced flaws in each. Tension, compression, fracture toughness, and other structural properties are measured on adjacent test coupons. The interaction between intentional flaws with inherent material properties, component geometry, and other flaws is examined. In the end, this work hopes to define a new paradigm for qualification of AM components with known flaws.

 Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.

Chemical and Physical Aging of Epoxies

Jamie M. Kropka,¹ Gabriel K. Arechederra,^1,2 Kelsey M. Wilson,^1,2 John D. McCoy,² Craig M. Tenney¹and Kevin N. Long¹

¹Sandia National Laboratories

²New Mexico Institute of Mining and Technology

Abstract

While “plastics” have a reputation of longevity in places that most of us do not want them-in our landfills and oceans, they are falling apart in places that they are meant to last forever-in our national museums.¹  Many of the items in museums, such as Neil Armstrong’s spacesuit, may not have been designed to last for decades.  Yet the fact that the polymeric materials that make up these items can deteriorate under the relatively benign conditions of a museum display begs questions about what may be occurring in many Sandia National Laboratories (SNL) applications, in which materials are asked to perform their required function(s) over multiple decades.  Unlike the museum materials, the plastics in SNL applications are typically under a stress.

The high cross-link density of epoxy thermosets may lead some to regard the aging of these materials as a low priority, as it would require the severance of many covalent bonds within these materials to make them fall apart.  However, the wide use of epoxy thermosets, often in regions of high consequence should the epoxy fail, makes it important to distinguish whether the aging of these materials affects their performance requirements.  Furthermore, it often does not require the material to “fall apart” in order to “fail”.  The gigapascal modulus of these materials means that even small strains, of order 0.01, can generate stresses that initiate “yield” in the material.  Thus, it is important to be able to measure and predict the aging behavior of epoxies with high fidelity.  In this presentation, we will report recent results assessing the aging of two epoxy thermosets relevant to SNL applications: one that has been widely used for decades but is still poorly understood ^{2. 3} and one that has been introduced as part of recent modernization efforts.^4,5  The aging mechanisms observed in these materials will be presented along with data measuring the effect of these mechanisms on the mechanical response of the material.  Initial assessments of the ability of current nonlinear viscoelastic models to predict the effect of aging on the mechanical response of the material that has been widely used will be also be presented.

Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia LLC, a wholly owned subsidiary of Honeywell International Inc. for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.

1. Lim, XiaoZhi, “These Cultural Treasures Are Made of Plastic. Now They're Falling Apart.” The New York Times, 28 Aug 2018.
2. McCoy, J.D. et al., “Cure mechanisms of diglycidyl ether of bisphenol A (DGEBA) epoxy with diethanolamine”, Polymer, 2016, 105, 243.
3. Arechederra, G., “Evolution of Mechanical Properties During Structural Relaxation of the 828/DEA Epoxy Thermoset”, MS Thesis, New Mexico Institute of Mining and Technology, 2017.
4. Clarkson, C.M., McCoy, J.D. and Kropka, J.M., “Enthalpy recovery and its relation to shear response in an amine cured DGEBA epoxy”, Polymer, 2016, 94, 19.
5. Wilson, K.M., “Physical Aging in a Polyether-amine Cured DGEBA Epoxy”, MS Thesis, New Mexico Institute of Mining and Technology, 2018.

Control of Optical Response of Rare Earth Metal Organic Frameworks

Jessica M. Rimsza

Geochemistry Department, Sandia National Laboratories, Albuquerque, NM USA

Abstract

 Acid gases including NO_x, SO_x, and CO₂ are generated during industrial processes and represent significant environmental and health hazards, requiring them to be removed from gas streams. Due to the complex mixtures and high reactivity of acid gases, many candidate materials do not offer the selectivity or the stability to meet current industrial requirements. Metal-organic-frameworks (MOFs) represent a class of porous organic materials with cage like structures that have demonstrated promise in acid gas separation. Here, rare-earth dihydroxyterephthalic acid (RE-DOBDC) MOFs are explored for their use in acid gas separations and for the impact of guest molecules on the optical properties through density functional theory (DFT) simulations. RE-DOBDC MOFs (RE = Y, Eu, Tb, Yb) were characterized for their sensitivity to computational method, with a clear requirement for the use of full valence potential and Hubbard U corrections for simulation of electronic properties ¹. For adsorption and structural studies, large core potentials could be used without significant variation in results, allowing for more complex ab initio molecular dynamics (AIMD) studies to be performed. The unique luminesce properties of RE-DOBDC MOFs also demonstrated sensitivity to hydrogen bonding orientation, with an increase in the band gap of 0.75 eV from 0% to 100% hydrogen bonded DOBDC linkers ². Such changes in the optical properties of the MOF indicate that guest molecules which bind with the linker can be detected by changes in the optical properties ³. As an example, binding of NO₂ to the linker in Eu-DOBDC quenched the luminesce properties, seen both experimentally and computationally. Ultimately, RE-DOBDC MOFs demonstrate tunability in their electronic and optical properties through linker-guest interactions and hydrogen bonding orientations, indicating a sensitivity to the surrounding environment that has potential applications in sensing technologies. Sandia National Laboratories is managed and operated by NTESS under DOE NNSA contract DE-NA0003525. SAND2020-0620 A.

 References:

1. Vogel, D. J.; Gallis, D. F. S.; Nenoff, T. M.; Rimsza, J. M., Structure and Electronic Properties of Rare Earth Dobdc Metal–Organic-Frameworks. Phys. Chem. Chem. Phys. 2019, 21, 23085-23093.
2. Vogel, D. J.; Rimsza, J.; Nenoff, T., Tuned Hydrogen Bonding in Rare Earth Mofs for Design of Optical and Electronic Properties: An Exemplar Study of Y-DOBDC. 2020, ACS Appl. Mater. Interfaces.
3. Sava, D. G.; Vogel, D.; Vincent, G.; Rimsza, J.; Nenoff, T., NO_x Adsorption and Optical Detection in Rare Earth Metal-Organic Frameworks. ACS Appl. Mater. Interfaces 2019.

Stacking Fault Energies of High Entropy Alloys Calculated Using Density Functional Theory

Prof. Chelsey Hargather

New Mexico Tech

Abstract

High entropy alloys (HEAs) are composed of equal or nearly equal quantities of five or more metals that typically solidify into a single, or sometimes dual, solid solution phase. Some promising qualities of HEAs are: higher resistance to fracture, corrosion and oxidation resistance, and improved ratios between mechanical properties (ductility, strength and toughness) and weight. Stacking fault energy (SFE) is investigated in the present work due to its use in modeling mechanical and deformation behavior, such as nano-twinning.  Body centered cubic refractory high-entropy alloys are selected for their promising high temperature properties and minimal exploration in the current literature. Density functional theory (DFT) and special quasi-random structures (SQS) are used to calculate the SFE of these alloys. The results are then used to analyze the usefulness of these calculation methods in producing high-throughput databases for down-selection and development of these alloys. Additionally, several methods of increasing the speed and fidelity of these property databases are introduced and investigated, including: (i) a lower order averaging method for reducing the number of required calculations, and (ii) an inferential statistics method for predicting error bars on data sets.

Advanced scanning transmission electron microcopy and spectroscopy for nanoscale materials characterization

Dr. Ping Lu

Sandia National Laboratories, Albuquerque, New Mexico

Abstract

Recent technical advances in aberration-corrected scanning transmission electron microscopy (AC-STEM) and spectroscopy provide an unprecedented opportunity for materials characterization.  Chemistry and structures of crystal lattices, interfaces and defects down to atomic-scale can now be directly determined under proper experimental conditions by using a combination of electron detectors and spectrometers. In this talk, I will describe some progresses made recently in STEM imaging and spectroscopy and present several examples of utilizing the advanced STEM techniques for the nanoscale microstructural characterization, including quantifications of unknown structures of alloys and oxides and phase transformation of layered lithium and manganese-based oxides for lithium ion battery applications.

Tissue-level oxygen flux as a biological "materials" problem

Sally Pias

Chemistry, New Mexico Tech

Abstract

Oxygen (O₂) diffusion to cells within human tissues is a critical process in energy metabolism, and oxygen deficiency can promote disease or cell death. The circulatory system uses convection to deliver oxygen close to its site of consumption, while diffusion takes over after that. I will discuss our group's investigations into the pathway and rate of oxygen diffusion -- governed largely by the biological "materials" that make up the tissue. My talk will focus primarily on our efforts to model this complex phenomenon at atomistic and larger scales.

Density Functional Theory Applications to Molecular Materials at Finite Temperatures

John McCoy

Materials Engineering, New Mexico Tech

Abstract

Thermodynamic Density Functional Theory (DFT) has applications both to phase transitions (e.g., crystallization of polymers) and to inhomogeneous materials (e.g., tethered chains). Dr. McCoy (in collaboration with Chandler and Singer) extended the atomic theory of Haymet and Oxtoby to molecular materials during his graduate work.  He subsequently extended the theory to treat complex polymeric systems in collaborations with Haymet, Curro and others. The theory is based on a functional Taylor series of the Helmholtz Free Energy.  The expansion coefficients in the Taylor series are evaluated using statistical mechanics based, molecular, liquid-state theory. This results in a mapping of the dense condensed phase system onto a non-interacting (or ideal gas) system in an effective external field that mimics the effects of the other molecules.  Free energy minimization optimizes the field in a self-consistent manner. The non-interacting molecules in this optimized effective external field approximate the density distribution of the fully interacting system. The resulting effective field and density profile can then be used to evaluate the free energy.  This has similarities to the Kohn-Sham (electronic) DFT theory where the self-consistent-field permits the Schrodinger equation to be solved for a single electron in an effective external field that mimics the many-electron system of interest. Under certain circumstances, multiple local minima are found.  Because the free energy can be evaluated for each, the stable minima can be determined.  For instance, a minimum of a uniform (liquid-like) density is often found in conjunction with a minimum of density peaks in a crystal lattice (e.g., FCC).  The liquid-like density is stable at high temperature while the crystal density is stable at low temperature.  By exploring different densities, the phase diagram can be mapped out.Applications to phase transitions include crystallization of hard spheres, Lennard-Jones atoms, quantum helium, and polyethylene.  Applications to inhomogeneous materials examples will include diblock copolymers, Langmuir monolayers, tethered chains and thermo-responsive films.Discussion of the basic theory will follow that given in the appendices of

McCoy, Honnell, Schweizer, Curro, Crystallization of polyethylene and polytetrafluoroethylene by density functional methods, Journal of Chemical Physics 95, 9348 (1991).

Deep ultraviolet photoemission electron microscopy as a new tool to study nanomaterials’ electronic properties and nano-scale optical phenomena

Dr. Taisuke Ohta

Sandia National Laboratories, Albuquerque, New Mexico

Abstract

Photoemission electron microscopy, or PEEM, is a microscopy approach that can probe light-matter interactions. In this talk, I will present our efforts in using PEEM to determine the electronic band alignment of nano-materials and observe buried structures beneath dielectric films with sub-micron lateral resolution.

Electronic band alignment is an important material specific parameter, which determines the applicability of atomically-thin transition metal dichalcogenides (TMDs) to build semiconductor heterostructures or electronic devices. Because electronic properties of TMDs vary significantly by the layer number, stacking sequence, doping, and dielectric environment, empirical determination of their electronic band alignment is of technological importance. Exploiting the sensitivity of photoemission spectra to the electronic density of states, work function, and ionization energy, we use PEEM to determine the electronic band alignment of MoS₂, WS₂, and MoSe₂. I will present the results with the emphasis on how we extract the band alignment information from the measurements.

In the second part, I will show an unconventional approach using PEEM to visualize TMDs sandwiched between thin-film dielectrics. We show imaging of atomically-thin MoS₂ flakes buried beneath HfO₂ overlayers up to 120 nm in thickness by exploiting the optical standing wave formation (i.e., resonance of the dielectrics cavity). This approach can be extended to non-destructive imaging of buried interfaces and sub-surface features needed for nanomaterial integration into optoelectronics platforms. I will discuss the role of optical effects in photoemission imaging, and the potential of PEEM to study nano-scale optical phenomena.

The works presented here are conducted in collaboration with M. Berg, R. G. Copeland, T. E. Beechem, and C. Chan at Sandia National Laboratories, F. Liu at Los Alamos National Laboratory, and K. Keyshar, X. Zhang, R. Vajtai, P. M. Ajayan, and A. D. Mohite at Rice University. We performed the PEEM work at the Center for Integrated Nanotechnologies (CINT), an Office of Science User Facility operated for the U.S. Department of Energy (DOE) Office of Science (DE-AC04-94AL85000). This work was supported by the CINT user program and Sandia LDRD. Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525. The views expressed in the article do not necessarily represent the views of the U.S. Department of Energy or the United States Government.