Materials Science

Materials Science

 

 

Poster Number: MSE-01

Authors: David Hernández Escobar, Hakan Yilmazer, Carl J. Boehlert

Title:  High-pressure Torsion as a Novel Technique for Processing Zn-based Cardiovascular Stents

 

Abstract: High-pressure torsion (HPT) is a severe plastic deformation (SPD) technique in which a disc sample is subjected to torsional shear strain under a high hydrostatic pressure simultaneously. HPT, firstly documented in 1935, has recently gained popularity in the biomaterials field as it provides the potential for achieving nanograined microstructures that can significantly improve mechanical material properties such as microhardness and tensile strength. A satisfactory combination of bioabsorption, biodegradability and mechanical properties are some of the challenging requirements for cardiovascular stents that have not been recorded yet for current Fe and Mg alloys used in these applications. Therefore, alternative materials have to be considered in order to fully satisfy all design constraints. There are numerous reasons for considering metallic Zn a great candidate for bioabsorbable metal stents. It is an essential element for basic biological functions and shows strong antiatherogenic properties that enhance endothelium stabilization. However, in order to overcome its poor tensile strength, pure Zn needs to be alloyed without compromising its good elongation-to-failure and corrosion resistance. In this work, a set of Zn-3Mg samples processed by HPT at 1, 5, 15 and 30 turns under 6 GPa at a rotational speed of 1 rpm have been chosen. Scanning electron microscopy (SEM) was used to analyze the grain features along the radius of the disk-like samples as well as to compare the distribution of Zn and Mg phases at different number of turns. Energy dispersive spectroscopy (EDS) combined with SEM was also used for chemical composition analysis of the present phases.

 

This work was supported in part by National Science Foundation

 

 

 

Poster Number: MSE-02

Authors: Kwang Jin Kim, James Wortman, Sung-Yup Kim, Yue Qi

Title:  Atomistic Structural Evolution and Li Trapping Due to Delithiation Rates in Si Electrodes

 

Abstract: To minimize the irreversible capacity loss and enhance the long-term capacity retention of Si anode, it is important to gain fundamental understanding of the intrinsic response of Si upon delithiation with different rates. In this study, we developed a new continuous delithiation algorithm based on ReaxFF-MD simulations by utilizing a lithiated Al2O3 coating layer on fully lithiated Si to generate a driving force for Li to naturally diffuse out of the a-LixSi. Specifically, we investigate the mechanism of irreversible structural changes and its consequences on subsequent lithiation process. The delithiation rate is considered to be “slow”, with respect to the size of Si and the diffusion rate, when Li can completely diffuse out of Si (the residual Li in Si is less than Li0.2Si) and the Si exhibits negligible amount of isolated inner-pore. However, upon fast delithiation (10 times faster), a Li concentration gradient with higher Li concentration in the center of Si and lower Li concentration near the surface is formed which ensembles a cage-like structure with locally dense Si network near the surface. As we have demonstrated before that Li diffusion in Si increases with Li concentration, this concentration gradient leads to significant amount of Li trapped inside Si. As a result, at the end of fast delithiation process, a- Li1.2Si with non-uniform Li concentration distribution shows 141 % volume inflation. Meanwhile, during fast delithiaon, isolated inner-pores continuously collapse and reform, and eventually, agglomerates into a large pore with severe coating delamination. However, irreversible structure change was discovered even during the slow delithiaton process, where the delithiated a-Li0.2Si remains 44 % inflated with uniform Li concentration at the end of slow delithiation. This is due to the loss of directly bonded Si-Si pairs, which makes the delithiated a-Li0.2Si exhibit faster lithiation rate in the next cycle.

 

This work was supported in part by NEES (Nanostructures for Electrical Energy Storage)

 

 

 

Poster Number: MSE-03

Authors: Matthew Klenk, Niina H. Jalarvo, Sydney Boeberitz, Wei Lai

Title:  Lithium Diffusion Dynamics through Quasi-elastic Neutron Scattering and Molecular Dynamics

 

Abstract: Critical to the prospect of a clean energy future, battery technology will need to develop to a point where large scale grid storage, electric vehicles, and low cost personal battery systems become ubiquitous in society. To avert the inherent safety issues with today’s liquid electrolytes, proposals for safer all solid-state batteries are gaining traction in the literature. The solid electrolyte Li7-xLa3TaxZr2-xO12 (LLZT) has been shown to be a promising substitute for conventional electrolyte systems exhibiting room temperature conductivity approaching 1E-3 S/cm and stability to a range of anode and cathode materials.

In the present study LLZT is investigated using quasi-elastic neutron scattering (QENS), classical molecular dynamics (MD), and density functional theory (DFT) to better understand the phase transformation behavior, lithium diffusion mechanism, and effects of dopant concentration on lithium distribution in the crystal.

We see that lithium diffusion is mostly carried out through collective hopping with its neighbors maximized at compositions between 0.3 < x < 0.5. Within this range lithium is optimally distributed increasing the number of repulsive Li-Li interactions driving diffusion. We show that it is possible to use lithium site occupancy and lithium sub-lattice excess entropy as descriptors for the observed maximum in the conductivity. To verify our simulations QENS was performed to calculate the self-diffusivity, residence time, and jump length distribution for the end member composition LLT (x=2). The dynamic structure facture S(Q,E) is calculated and compared to the intermediate scattering factor I(Q,t) calculated through velocity autocorrelation of the MD simulations.

 

This work was supported in part by Ceramics Program of National Science Foundation (DMR-1206356)

 

 

 

Poster Number: MSE-04

Authors: Junchao Li, Wei Lai, Donald T. Morelli

Title:  First-principle Study of Atomic Dynamics in Tetrahedrite Thermoelectrics

 

Abstract: Tetrahedrite are high-performance thermoelectrics which contain earth-abundant and environmentally friendly elements. At present, the mechanistic understanding of their low lattice thermal conductivity remains limits. This work applies first-principle molecular dynamics simulations, along with extended X-ray absorption fined structure (EXAFS) experiments, to study the incoherent and coherent atomic dynamics in tetrahedrites materials, in order to deepen our insight into mechanisms of anamalous dynamic behavior and the origin of low lattice thermal conductivity.

 

This work was supported in part by Thermal Transport Processes Program of National Science Foundation

 

 

 

Poster Number: MSE-05

Authors: Yuanchao Liu, David P. Hickey, Jing-Yao Guo, Erica Earl, Sofiene Abdellaoui, Ross D. Milton, Matthew S. Sigman, Shelley D. Minteer, Scott Calabrese Barton

Title:  Multi-scale Simulation on Substrate Channeling

 

Abstract: Nature has a very efficient metabolic pathway to produce energy within the cell, through a series of chemical reactions. In this one-pot multi-step catalysis, carbohydrates are oxidized on sequential enzymatic active sites. Although the cell has a very complicated chemical environment, these superamolecular complexes are able to maintain a high reaction efficiency and prevent unproductive side reactions. To mimic these cascade reactions, a key factor is found to be substrate channeling [1], where the reaction intermediates are directly transported to a downstream active site without first equilibrating with bulk media. We simulate substrate channeling at multiple scales to study the effect of electrostatic pathways on the channeling of charged intermediates [2]. Specifically, molecular dynamics (MD) elucidates the surface interaction between negative intermediate molecules and cationic peptide surfaces, revealing a surface diffusion mode. Based on MD and experimental results, a coarse-grained Kinetic Monte Carlo (KMC) method is used to quantify the overall cascade kinetics, bridging the gap between molecular-level interaction and experiment. KMC reveals rate limiting steps that can be further studied to improve cascade design. 1. I. Wheeldon, S. D. Minteer, S. Banta, S. C. Barton, P. Atanassov and M. Sigman, "Substrate channelling as an approach to cascade reactions", Nature Chemistry, 8, 299–309 (2016). doi:10.1038/nchem.2459. 2. Y. Liu, D. P. Hickey, J.-Y. Guo, E. Earl, S. Abdellaoui, R. D. Milton, M. S. Sigman, S. D. Minteer and S. C. Barton, "Substrate Channeling in a Cross-Linked Enzyme Complex: A Molecu-lar Dynamics Blueprint for an Experimental Peptide Bridge", ACS Catalysis, Revision, (2017).

 

This work was supported in part by Army Research Office MURI (#W911NF1410263) via The University of Utah

 

 

 

 

 

 

Poster Number: MSE-06

Authors: Yuxi Ma, Jason D. Nicholas

Title:  Development and Application of a Wafer Curvature Platform for In-situ Measurements of the Physical Properties of Thin Film Materials

 

Abstract: A Multi-Beam Optical Stress Sensor (MOSS) provides a contact free, in-situ technique to measure stress based on the curvature of the sample. Originally, this technique was used to measure the film stress during deposition. However, when combined with special sample design and experimental setup, it can be used to measure the physical properties of thin film materials. In this work, the oxygen surface exchange coefficients (kchem) of thin film material were measured when combining MOSS with curvature relaxation technique; thermal expansion coefficient (CTE), chemical expansion coefficient (CCE) and biaxial modulus (M) were measured when combining the MOSS with dual substrates technique. Praseodymium doped ceria was chosen as the film material in order to validate the feasibility of curvature relaxation and dual substrate techniques for measuring kchem, CTE, CCE and M values. The results showed that: (1) Curvature relaxation is able to measure kchem accurately and reproducibly (2) the Dual substrate technique is capable of measuring CTE, CCE and M of a mixed ionic electronic conductor (3) kchem, CTE, CCE and M can all be measured within the same curvature measurement platform.

 

This work was supported in part by Department of Energy under Award Number DE-FE0023315

 

 

 

Poster Number: MSE-07

Authors: Natalia Pajares Chamorro, Neal Hammer, Kurt Hankenson, Xanthippi Chatzistavrou

Title:  Antibacterial-bioactive Glass-ceramic Particles

 

Abstract: Biomaterials possess a key role in tissue regeneration for 50 years. Sol-gel (solution-gelation) derived glass ceramics have demonstrated enhanced bioactive properties. However, the presence of infections or the formation of a biofilm is still a significant problem since they are mainly formed by antibiotic resistant bacteria. In order to overcome this antibiotic resistance, a growing interest towards the use of heavy metals as an inhibit agent has recently arisen. In this work, silicate glass-ceramic particles have been fabricated with dual bioactive and antibacterial action. Different microstructures and morphologies will be addressed through the sol-gel process and then, they will be correlated with their action on alive entities. Bioglass has proven its good bioactive performance in previous works inducing cell proliferation and differentiation. Silver-doped bioactive (Ag-BG) microparticles are expected to deliver also bactericidal properties when silver ions are released into the system. The biological properties of Ag-BG particles with size <20 µm have been studied in culture with bone marrow mesenchymal stem cells (MSCs). The cytotoxicity and cell proliferation were observed. Their bactericidal action has also been addressed against Staphylococcus aureus - the main bacteria in the development of osteomyelitis. Further work will be done in this area to narrow the size and load antibiotics in the particles. It is anticipated that a system with dual delivery of bactericidal agents (release of both heavy metal ions and drug) in a nanometric size would be a useful tool in clinical practices. However, never before such a system has been reported.

 

 

 

Poster Number: MSE-08

Authors: Mariana D. R. Batista, Lawrence T. Drzal

Title:  Carbon Fiber Polymer Matrix Composite Interphases Modified with Cellulose Nanocrystals

 

Abstract: Lightweight, high-strength and high-stiffness are often identified as desirable properties for aerospace and automotive applications. To achieve these engineering needs and meet the growing requirement for fuel economy, carbon fiber reinforced polymer (CFRP) composites have gained attention because of their high strength-to-weight ratio. The global carbon fiber reinforced plastic market is projected to reach USD 35.75 billion by 2020. However, one drawback of CFRP, specifically epoxy-based CFRP, is its brittle fracture mechanism, which reveals low level of adhesion between the carbon fiber (CF) and the polymeric matrix. Therefore, to achieve good mechanical properties and resist crack propagation, a well-bonded interphase is required. Cellulose nanocrystals (CNCs) have attracted attention due to their high mechanical properties, low cost, low density and sustainable nature. In this work, we developed a process to coat CF with CNCs to investigate how they could simultaneously strengthen and toughen CF-epoxy composites. CNCs were surface treated with (3-aminopropyl)triethoxysilane (APTES) and applied as part of a sizing agent to improve the stress transfer at the fiber-matrix interphase. Dispersion of APTES-CNCs on the CF surface was characterized by scanning electron microscopy (SEM), and interfacial adhesion was assessed by the interfacial shear strength (IFSS) of the APTES-CNC sized CFs in epoxy matrix. An optimum concentration was investigated and a considerable IFSS increase up to 81% was observed for APTES-CNC sized CFs compared to non-sized CFs. This research is an effective approach to increase interfacial properties in CF-epoxy composites, and potentially also be utilized for interfacial optimization in biobased natural fiber composites.

 

This work was supported in part by Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) through the Science Without Borders program (BEX: 13655-13-2)

 

 

 

Poster Number: MSE-09

Authors: David Smiadak, Alex Zevalkink

Title:  Scintillator Candidate Compounds Grown by the Micro-pulling Down Method

 

Abstract: Crystals with composition MgTa2O6 and Ce:LuAG were synthesized using the micro-pulling-down method. The crystals were prepared from powdered oxides and the results were characterized with x-ray powder diffraction, x-ray luminescence, scanning electron microscopy, and energy-dispersive x-ray spectroscopy. Analysis confirmed single crystal growths of Ce:LuAG while two phases were identified in the MgTa2O6 growths. Production parameters for these crystal growths are detailed. Further development is required in the case of MgTa2O6 as growth results did not produce detectable emission spectra required of scintillators. The growth of single crystal Ce:LuAG was confirmed and the spectral analysis matched those of published values. Ce:LuAG was confirmed to be an appropriate scintillator material that can be grown with in-house equipment at Lawrence Berkeley National Laboratory. Scanning electron microscopy and energy-dispersive x-ray spectroscopy testing were performed at Michigan State University.

 

This work was supported in part by Michigan State University; Lawrence Berkeley National Laboratory; Department of Energy; Department of Homeland Security’s Domestic Nuclear Detection Office

 

 

 

Poster Number: MSE-10

Authors: Erik Stitt, Markus Downey, Mahmood Haq, Lawrence Drzal

 

Title:  Enhancing Multi-material Bond-strengths via Plasma Surface treatment of Thermoplastic Adhesives

 

Abstract: Multi-material adhesive joining is gaining attention in automotive applications as a means to enhance light-weighting, fuel-efficiency and reduce greenhouse emissions. Specifically, reversible adhesives comprising of thermoplastics embedded with conductive graphene nanoplatelets (GnP) enable ‘selective heating’ of the adhesive while exposed to electromagnetic radiation; thereby allowing for rapid assembly, re-assembly and repair. The efficiency of an adhesive joint is dependent on sufficient and excellent transfer of stresses from the substrates to the adhesive. This requires adequate compatibility to create a good bond between surfaces of the adhesive and substrate.

In this work, efficiency of multi-material joints made of carbon fiber reinforced polymer (CFRP) and Aluminum (Al) substrates bonded with high-impact polystyrene (HIPS) thermoplastic adhesive was experimentally evaluated. The HIPS films were surface treated with O2-Plasma exposure and its efficacy was compared with similar joints without surface treatments. Additionally, the GnP concentration was varied and its effect on joint behavior was evaluated. Preliminary results indicate enhancement is both ultimate loads and displacements with O2-plasma treated joints. Structure-property relationships, improvements in wettability of HIPs due to O2 surface treatment and the path forward will be presented.

 

This work was supported in part by Department of Energy

 

 

 

Poster Number: MSE-11

Authors: Spencer L. Waldrop, Donald T. Morelli

Title:  Effect of Non-stoichiometry on the Thermal and Electrical Properties of Polycrystalline PtSb2 at Low Temperature

 

Abstract: In narrow bandgap materials non-stoichiometry can dramatically change the measured electrical and thermal properties below room temperature. The work here attempts to examine the effects of non-stoichiometry on the low temperature properties of polycrystalline PtSb2. It was found that at antimony deficiencies of only 1% a change in the sign of the Seebeck coefficient was observed from 80 to 120 K. Further reduction of the antimony content resulted in a negative Seebeck for all temperatures measured. Antimony excess was found to retain positive values in the Seebeck coefficient, but with a reduction in the magnitude. The electrical resistivity was found to vary largely at low temperature, however converged to similar values at room temperature. These results show the importance of stoichiometry in narrow bandgap materials at low temperature.

 

This work was supported in part by Air Force Office of Scientific Research under the Multi-University Research initiative (MURI), “Cryogenic Peltier Cooling,” Contract No. FA9550-10-1-0533

 

 

 

Poster Number: MSE-12

Authors: M. Wang, D. Kang, P. J. Lee, A. A. Polyanskii, C.C. Compton, T.R. Bieler

Title:  Investigation of the Effect of Strategically Selected Grain Boundaries on Superconducting Properties of SRF Cavity Niobium

 

Abstract: High purity Nb is the most used material for the fabrication of SRF cavities due to its high critical temperature and ease of formability. However, microstructural defects such as dislocations and grain boundaries in niobium can serve as favorable sites of pinning centers for magnetic flux that may degrade SRF cavity performance. In this study, bi-crystal Nb samples with strategically selected grain boundaries were designed, and their effect on magnetic flux behavior was investigated. Grain boundaries with different orientations were chosen to favor specific slip systems, which can be activated during tensile deformation and generate dislocations with special angles with respect to the grain boundaries. Laue X-ray and EBSD-OIM crystallographic analyses were used to characterize grain orientations and orientation gradient, while Electron Channeling Contrast Imaging (ECCI) was performed to investigate the dislocation structures. Cryogenic Magneto-Optical Imaging (MOI) was used to directly observe the penetration of magnetic flux into Nb at about 5-8 K, and relationships between flux penetration and grain boundary structures were identified.

 

This work was supported in part by DOE/OHEP (contract number DE-FG02-09ER41638 at MSU and DE-SC0009960 at FSU); State of Florida

 

 

 

Poster Number: MSE-13

Authors: Daniel Weller, Donald Morelli

Title:  Thermoelectric Performance of Tetrahedrite Synthesized by a Modified Polyol Process

 

Abstract: Tetrahedrite, a promising thermoelectric material composed of earth-abundant elements, has been fabricated utilizing the rapid and low energy modified polyol process. Synthesis has been demonstrated for Cu12Sb4S13 and Cu11ZnSb4S13 on the gram scale requiring only 1 hour at 220 °C. This method is capable of incorporating dopants and producing particles in the 50-200 nm size regime. For determination of bulk thermoelectric properties, powders produced by this solution-phase method were densified into pellets by spark plasma sintering. Thermopower, electrical resistivity, and thermal conductivity were obtained for temperatures ranging from 323 to 723 K. Maximum ZT values at 723 K were found to be 0.66 and 1.09 for the undoped and zinc-doped tetrahedrite samples, respectively. These values are comparable to or greater than those obtained using time and energy intensive conventional solid-state methods. Consolidated pellets fabricated using nanomaterial produced by this solution-phase method were found to have decreased thermal conductivity, increased electrical resistivity, and increased thermopower. Exceptionally low total thermal conductivity values were found (below 0.7 Wm-1K-1 for undoped tetrahedrite and 0.5 Wm-1K-1 for zinc-doped tetrahedrite), with both having lattice thermal conductivities below 0.4 Wm-1K-1. This study explores how nanostructuring and doping of tetrahedrite via a solution-phase polyol process impacts thermoelectric performance.

 

This work was supported in part by NSF-CBET-1507789; U.S. Dept. of Education GAANN program

 

 

Poster Number: MSE-14

Authors: Jared B. Williams, Spencer Mather, Alexander Page, Ctirad Uher, Donald T. Morelli

Title:  Increasing the Power Factor of Ge17Sb2Te20 by Adjusting the Ge to Sb Ratio

 

Abstract: The ever increasing energy demands of humans show no signs of stopping. Unfortunately the majority of this energy is produced by means which are nonrenewable and detrimental to the environment. In response to this issue researchers from a myriad of fields have looked for new reliable energy sources such as solar, wind, geothermal, or even nuclear. However, perhaps a more important issue to tackle is the fact the efficiency by which we use the energy we generate is approximately 40%. The majority of this unused energy is expelled as thermal energy. Thermoelectric materials possess the unique ability to convert thermal energy to electrical energy, and could therefore improve how effectively we use energy. The efficiency of thermoelectric power generation is, however, is dependent on the Carnot efficiency and the unitless parameter, ZT. The ZT of a material is dependent on the electrical and thermal properties of the material. However, to achieve a high ZT, and therefore high efficiency, novel materials science must be used to overcome the contraindicated property relations of ZT, namely: high Seebeck coefficient and electrical conductivity, and low thermal conductivity. In this work, the carrier concentration of Ge17Sb2Te20, a thermoelectric compound from the phase change material family, was tuned in order to optimize the thermoelectric power factor. This was achieved by altering the stoichiometry of Ge and Sb, and therefore does not require additional foreign elements during synthesis. The result was a more than 30% increase in the power factor of the material.

 

This work was supported in part by Department of Energy; Michigan State University Distinguished Fellowship

 

 

Poster Number: MSE-15

Authors: Yubo Zhang, Jason D. Nicholas

Title:  Barium Oxide (BaO) Infiltrated Lanthanum Strontium Manganese Oxide (LSM)-Gadolinium Doped Ceria (GDC) Solid Oxide Electrochemical Reduction Cells for Reduced Diesel NOx Emissions

 

Abstract: Diesel engines are widely used in automobiles for their high fuel efficiency, low carbon monoxide emissions, and low hydrocarbon emissions. Unfortunately, due to their lean-burn operating environment, diesel engines emit higher amounts of NOx than gasoline engines. Although NOx Storage and Reduction (NSR) and Selective Catalytic Reduction (SCR) technologies have been commercialized and offer high deNOx (i.e. NOx decomposition) efficiency, they suffer from a loss of fuel efficiency during catalyst regeneration and a need for large-volume, on-board ammonia storage and replenishment, respectively. Further, expensive precious metal catalysts are needed to enable deNOx chemical reactions in these conventional technologies. In contrast, Solid Oxide Electrochemical Reduction Cells (SOERCs) utilizing an external bias to electrochemically drive NOx decomposition promise precious-metal-free operation without the need for catalyst regeneration or large-volume, on-board storage. Here, the deNOx performance of barium oxide (BaO) infiltrated lanthanum strontium manganese oxide (LSM)-gadolinium doped ceria (GDC) SOERCs were measured as a function of operating temperature, AC amplitude, and AC frequency. The BaO-LSM-GDC SOERCs tested here displayed better low-temperature NOx conversion efficiencies than those previously reported in the literature; achieving 22% at 350C compared to the 3% reported in literature. The application of an AC electric bias was found to produce higher BaO-LSM-GDC NOx conversion efficiencies than a DC bias of the same magnitude and BaO-LSM-GDC SOERCs exhibited current and thermodynamic efficiencies of a few percent, and a few tenths of a percent, respectively.