Yunfeng Shi, Rensselaer Polytechnic Institute
Katharine Flores, Washington University
Tanguy Rouxel, University de Rennes
John Mauro, The Pennsylvania State University
CM02.01: Distinctions and Commonalities of Glasses
Monday AM, November 26, 2018
Hynes, Level 2, Room 200
8:00 AM - *CM02.01.01
The Continuous Random Network—A Review
Harvard University1Show Abstract
The continuous random network (CRN), introduced by Zachariasen for oxide glasses, became the paradigm for the structure of covalent, directionally bonded amorphous materials. Elemental amorphous Si and Ge, which form one of the simplest CRNs, have been studied for more than fifty years. We will review their structure, thermodynamic properties, phase transformations, flow and structural relaxation. We will revisit some striking features, such as their density being higher than that of the diamond cubic crystal, their negative activation volumes for crystallization, and the bimolecular kinetics of their structural relaxation.
8:30 AM - *CM02.01.02
Understanding Indentation Behavior of Oxide Glass from Molecular Dynamics Simulation
Rensselaer Polytechnic Institute1Show Abstract
To evaluate the damage resistance of glasses, instrumented indentation using sharp indenters is the method of choice, as it can mimic real-life damage incidents under controlled conditions. Furthermore, indentation provides a useful system to study crack initiation, as unstable crack propagation is prevented by the highly localized stress state. However, unravelling the nature of structural change under indentation is a formidable task in experiment because of the complexity that originates from the atomic-scale disorder of glass, and the experimental difficulties associated with the in-situ investigation at a local scale (tens of microns) under very high stresses. To this send, computer simulations can provide an important complement to experimental approaches. In this work, we carried out large scale molecular dynamics (MD) simulations to investigate the effect of quench pressuring during hot compression and chemical composition variation on the response of glass to nanoindentation. A rigid hollow Vickers indenter made of carbon atoms is used to indent the glass sample with a fixed loading rate, during which atoms in the indenter interact with the glass via a repulsive force field. To minimize the boundary condition effects in simulated nanoindentation tests, large samples of several hundred nm in lateral dimensions are used. The indenter angle is varied to study the effect of the indenter sharpness on the deformation of glasses, as what has been done in experiments. Short- and medium-range order of the plastically deformed glass are compared with those in the undeformed region. These simulated nanoindentation tests reveal how the stress field and glass structure evolve with the deformation underneath the indenter, which in turn shed light on the degree of densification and pile-up in different glasses.
9:00 AM - *CM02.01.03
Connecting Mechanical Properties of Amorphous Polymers to Chain Alignment and Entanglements
Mark Robbins1,Marco Galvani Cunha1
Johns Hopkins Univ1Show Abstract
Polymer glasses are frequently used in a form of additive manufacturing called fused filament fabrication (FFF). Melts are extruded onto previous layers and form a weld before the temperature drops below the glass transition temperature. Extrusion is typically fast enough to produce significant chain alignment that affects the welds formed by diffusion between layers and leads to a strongly anisotropic amorphous structure. Improved understanding of the structure property relations in printed parts is essential to optimizing FFF for structure-critical parts and FFF offers unique opportunities to create non-crystalline materials with continuously tunable local alignment and entanglement densities.
We have used molecular dynamics simulations of a generic polymer model to examine the relaxation of aligned melts, including the evolution of alignment and the entanglement density in bulk regions and at the interfacial weld. The mechanical properties of the resulting structures are then studied under tensile and shear loading. Local structure determines the initial yield stress while entanglements lead to strain hardening and crazing that strongly affects the total fracture energy. Alignment of chains along the deposition direction means that there are more weak van der Waals bonds in the perpendicular directions. This reduces the yield strength for shear and tensile failure perpendicular to the deposition axis. Alignment and changes in entanglement density also produce profound changes in the strain to failure and ultimate fracture energy. Welded regions are most affected by diffusion during cooling and may be stronger than adjacent bulk material which has higher entanglement density than the weld but is also strongly aligned.
9:30 AM - *CM02.01.04
Modeling Slip Statistics and Dynamics in Bulk Metallic Glasses, Granular Materials and Other Systems
Karin Dahmen1,Wendelin Wright2,Dmitry Denisov3,Todd Hufnagel4,Peter Liaw5,Peter Schall3,Jonathan Uhl6
University of Illinois at Urbana-Champaign1,Bucknell University2,University of Amsterdam3,Johns Hopkins University4,The University of Tennessee, Knoxville5,Los Angeles6Show Abstract
Slowly strained solids deform via intermittent slips that exhibit a material-independent statistics and dynamics. We compare predictions of a simple model for the plastic deformation, the slip statistics and dynamics, and time series properties to experiments on slowly deformed bulk metallic glasses and granular materials. We highlight measures that can be used to differentiate between different systems and explain connections to other systems with avalanches. Predictions for future experiments will be discussed. The results are important for transferring results across scales and material structures.
10:30 AM - *CM02.01.05
Tailoring Glass Structure to Break the Speed Record of Phase-Change Memory
Johns Hopkins University1Show Abstract
This talk describes our recent success (F. Rao et al., Science 2017) in controlling the amorphous structure of chalcogenide Sc-Sb-Te glass to accelerate its crystallization, reaching an unprecedented operation speed for memory and switch applications. Specifically, we have designed a new phase-change memory alloy with drastically reduced crystal nucleation stochasticity from the parent amorphous phase. The ultrafast transition between the two metastable states accomplishes sub-nanosecond switching for cache-type phase-change random-access memory (PCRAM) technology. This is a milestone in memory materials, because operation speed is currently a key challenge in PCRAM technology, especially for achieving sub-nanosecond high-speed cache-memory (such as SRAM). The limiting factor in the commercialized PCRAM products is the writing speed (~currently several tens of nanoseconds), which originates from the stochastic crystal nucleation during the crystallization of the amorphous Ge2Sb2Te5 glass. Here we use alloying into the parent glass to speed up the crystallization kinetics by orders of magnitude. The newly designed chalcogenide Sc-Sb-Te alloy enables a record-setting writing speed (as short as ~700 picoseconds) in a conventional PCRAM device, with no requirement for pre-programming or additional device design. This ultrafast crystallization stems from the reduced stochasticity of nucleation via geometrically matched and robust chemical bonds that stabilize crystal precursors in the amorphous state, which are found via ab initio simulations to exhibit long life-times, shortening the incubation time for crystallization. This discovery is an example of physical metallurgy principles in action, using atomic-scale insight into glass structures (bonding configurations and sub-critical nuclei) to control properties. For details, see F. Rao et al., Science 358 (6369), 1423 (2017).
11:00 AM - *CM02.01.06
The Interaction Between Stress, Light and Chemistry in Glass
Dalhousie Univ1Show Abstract
Application of mechanical stress to glass causes interesting changes in how it transmits light. This interplay is summarized by the elasto-optic tensor, the key metric for technological applications including zero stress-optic glass, and reduced stimulated Brillouin scattering glass. Fundamentally, these effects are controlled by the glass chemistry, and in particular the nature of the chemical bonds that make up the glass. We will summarize our approach to this problem, which is focused on both an empirical and ab initio approach to the structure-property relations governing the elasto-optic tensor. We will describe the control of the stress-optic response through judicious choice of glass chemistry, and also describe our current progress in understanding and developing glass with reduced stimulated Brillouin scattering. We will include discussion of both average properties and energy-dispersive effects. We will show how these effects may be computed ab initio, with a reasonable trade-off between accuracy and speed, and illustrate a bond-based model we are developing that attempts to put in simple terms the empirical relations we have discovered.
11:30 AM - *CM02.01.07
Ductility and Residual Liquidity in Metallic Glasses
Takeshi Egami1,2,Wojciech Dmowski1
Univ of Tennessee1,Oak Ridge National Laboratory2Show Abstract
Lack of ductility is one of the major shortcomings of bulk metallic glasses which hamper their wide application as structural material. Ductility is a complex mechanical property which is difficult to characterize precisely. In a sense metallic glass is always microscopically ductile, because applied shear stress can locally liquefy glass. But it has no work-hardening, thus often local yielding results in catastrophic shear failure. In order to achieve macroscopic ductility glass must be able to relax local stress concentration before it starts macroscopic shear band or crack. In our view the key is the residual liquidity in glass. The structure of supercooled liquid is heterogeneous, and the frozen-in structure at the glass transition contains weak liquid-like and strong solid-like regions. It is difficult to assess such heterogeneity directly from the structure itself, but it is possible to characterize it through the structural response to applied stress. We determined the anisotropic pair-density function (PDF) of various metallic glass samples under uniaxial stress by high-energy x-ray diffraction using the spherical harmonics expansion of the structure function S(Q) and the PDF. The measured anisotropic PDF at large distances agrees with the one expected for affine (uniform) deformation which determines the long-range strain e∞. However, at short distances it deviates from the affine deformation, and at the first neighbour the local strain, e1, is smaller than e∞. The deviation from the affine deformation occurs because of local liquid-like regions, so that the ratio G = e0/e∞ , or ΔG = 1 - G, characterizes the strength of residual liquidity in glass. We found that the ratio e0/e∞ is closely related to ductility. In particular, Gc = 0.77 is the threshold which separates brittle and ductile behaviors. If G > Gc the samples are brittle, whereas if G < Gc the samples are ductile. Thus we suggest that the percolation of the liquid-like regions results in ductile behaviour. This new parameter is compared to other criteria for ductility.
CM02.02: Structures of Glasses
Monday PM, November 26, 2018
Hynes, Level 2, Room 200
1:30 PM - *CM02.02.01
Network Structures and Dissolution Behavior of Specialty Oxide Glasses
Missouri University of Science and Technology1Show Abstract
Borate, phosphate, and borophosphate glasses have been developed for a variety of technological applications, including fast ion conductors, optical substrates, and biomedical devices. For the latter, compositions are often tailored to control the rate at which physiologically significant ions are released to induce the desired biomedical response. These reaction rates depend on the hydrolysis of bonds that link neighboring glass forming polyhedra as well as the hydration of bonds associated with other metal cations that modify the glass forming network, and so detailed understanding of the glass structure connects composition to design performance. For borate and borophosphate glasses, the network hydrolysis rates decrease with increasing fractions of tetrahedral borate. For phosphate glasses, hydrolysis is not significant in neutral pH physiological conditions, but the hydration rates of metal cations are faster when they are linked to chain-forming P-tetrahedra than when they are linked to a chain-terminating tetrahedron. Quantitative and qualitative structural information about Na-Ca-borate, phosphate, and borophosphate glasses, obtained by techniques like nuclear magnetic resonance spectroscopy, Raman spectroscopy, and ion chromatography, will be described and used to explain their bio-functionality.
2:00 PM - CM02.02.02
Progress in Scattering with the Neutron Electrostatic Levitator (NESL) at the Spallation Neutron Source
Oak Ridge National Laboratory1Show Abstract
There is great interest in a developing understanding of the relationships between structures and
dynamics in liquid and glassy systems. Metallic liquids, which exhibit a degree of short and medium range ordering, are well suited to scattering probes, but there are many difficulties associated with selecting the proper furnaces for such studies. The Neutron Electrostatic Levitator (NESL)  at the Spallation Neutron Source is a containerless environment developed for challenging systems, including high temperature alloys and undercooled liquids. It provides a high vacuum, high purity, non-contact environment for fundamental studies of materials at wide temperature ranges. Combined with x-ray scattering data and isotopic substitution, the system is well suited to structural characterization of liquids via pair distribution function analysis, as has been successfully demonstrated at the Nanoscale Ordered Materials Diffractometer (NOMAD) [2,3].
A series of upgrades has improved the stability of the levitator and enabled new avenues of exploration. Recently, the system has been operated at the Wide Angular Range Chopper Spectrometer (ARCS)  and is currently being commissioned at the Cold Neutron Chopper Spectrometer (CNCS)  for high resolution inelastic and quasi-elastic scattering, enabling non-contact probes of excitations in glass forming liquids as well as high temperature self-diffusion measurements. The current capabilities and characteristics of the levitation furnace, progress in inelastic scattering measurements, and early results from the commissioning at CNCS will be discussed.
 Mauro, N. A., A. J. Vogt, K. S. Derendorf, M. L. Johnson, G. E. Rustan, D. G. Quirinale, A. Kreyssig et al. "Electrostatic levitation facility optimized for neutron diffraction studies of high temperature liquids at a spallation neutron source." Review of Scientific Instruments 87, no. 1 (2016): 013904.
 Neuefeind, Jörg, Mikhail Feygenson, John Carruth, Ron Hoffmann, and Kenneth K. Chipley. "The nanoscale ordered materials diffractometer NOMAD at the spallation neutron source SNS." Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 287 (2012): 68-75.
 Johnson, M. L., M. E. Blodgett, K. A. Lokshin, N. A. Mauro, J. Neuefeind, C. Pueblo, D. G. Quirinale et al. "Measurements of structural and chemical order in Z r 80 P t 20 and Z r 77 R h 23 liquids." Physical Review B 93, no. 5 (2016): 054203.
 Abernathy, Douglas L., Matthew B. Stone, M. J. Loguillo, M. S. Lucas, O. Delaire, Xiaoli Tang, J. Y. Y. Lin, and B. Fultz. "Design and operation of the wide angular-range chopper spectrometer ARCS at the Spallation Neutron Source." Review of Scientific Instruments 83, no. 1 (2012): 015114.
 Ehlers, Georg, Andrey A. Podlesnyak, Jennifer L. Niedziela, Erik B. Iverson, and Paul E. Sokol. "The new cold neutron chopper spectrometer at the Spallation Neutron Source: design and performance." Review of Scientific Instruments 82, no. 8 (2011): 085108.
2:15 PM - CM02.02.03
High-Resolution 3D Imaging for Drug Micro-Structure Characterization and Release Prediction
Merck & Co., Inc1Show Abstract
Modern drug delivery increasingly relies on micro- and nano-structures to achieve specific release rate and therapeutic target. The delivery systems modulate drug release via engineering control of the API domain and pore size. Other approaches involve the use of functional coating or performance-enabling excipients. The small-scale nature of pores, drug domains, and delivery vehicles demands higher resolution technique to characterize. High-resolution image-based characterization has been broadly utilized in drug product development for fundamental understanding on the process-property-performance interplay and optimizing formulation process and design. It finds applications in various novel drug release systems such as tailoring rate-limiting film coat thickness where the pore formation is critical to control drug release and interrogating the underlying mechanism of in-situ drug nanoparticle formation from amorphous solid dispersions in dissolution media for solubility enhancement. 3D micro-imaging can qualitatively visualize micro-structures, quantify their spatial and chemical distribution, and predict release behavior. In recent years, the emerging image-based numerical simulation has received significant traction and plays an important role on predicting drug release performance. Information-rich 3D images can be converted to characteristic drug transport parameters through intelligent analysis and applied to numerical simulation models to predict release performance. This image-based simulation approach represents a potential paradigm shift in drug design and evaluation, with significantly reduced evaluation time, improved release performance, and lowered in-vitro and in-vivo experiment cost.
2:30 PM - CM02.02.04
Nanoscale Imaging of Bulk Bottlebrush Polymers Using Helium-Ion Microscope
Nikolay Borodinov1,Alex Belianinov1,Dongsook Chang1,Jan-Michael Carrillo1,Matthew Burch1,Yuewen Xu2,Anton Ievlev1,Bobby Sumpter1,Olga Ovchinnikova1
Oak Ridge National Laboratory1,Kimberly-Clark Corporation2Show Abstract
Recently, bottlebrush polymers have attracted significant interest due to their potential applications in drug delivery and electronics. The tunability of their properties, stemming from the diversity of sidechains and their spatial arrangement, have emphasized their industrial potential as compared to the linear macromolecules. In this context, the structural information and organization of these systems play a major role in the rational design of functional bottlebrush polymers. Specifically, direct observation of the molecular organization can reveal inter-chain interaction phenomena and explain the fundamental physical properties of these systems. Here, we report a new method to analyze bulk macromolecular chain arrangement of bottlebrush polymers based on Helium Ion Microscopy (HIM). By using the HIM we were able to quantify structural nematic-type ordering in an amorphous polymer bottlebrush system. High-resolution imaging coupled with data analytics has proven to highlight the location and distribution of the polymer backbones, after oxygen plasma-generated height contrast; as well as map changes in the backbone spatial arrangement as a function of thermal annealing. Our experimental findings are corroborated by the coarse-grained molecular dynamics simulations. Overall, this approach can generate clear insights on the internal structure of amorphous materials and provides a complimentary information channel to scattering techniques and theoretical modelling.
This work was performed at the Center for Nanophase Materials Sciences, a US Department of Energy Office of Science User Facility. This research used resources of the Oak Ridge Leadership Computing Facility, which is a DOE Office of Science User Facility supported under Contract DE-AC05-00OR22725. The authors acknowledge Scott Retterer at the Center for Nanophase Materials Science at Oak Ridge National Laboratory for helpful input and discussion
2:45 PM - CM02.02.05
Correlating Nanoscale Structural Heterogeneity to Glass Forming Ability and Mechanical Properties of Metallic Glasses
Soohyun Im1,Jared Johnson1,Gabriel Calderon Ortiz1,Menglin Zhu1,Pengyang Zhao1,Geun Hee Yoo2,Eun Soo Park2,Yunzhi Wang1,Jinwoo Hwang1
The Ohio State University1,Seoul National University2Show Abstract
We determine the nano-to-mesoscale structural heterogeneity in metallic glasses (MGs) using 4- dimensional (4D) nanodiffraction in scanning transmission electron microscopy (STEM). Structural heterogeneity in MGs has been suggested by both experiments and simulations previously. The heterogeneity must involve local structural ordering at the nanoscale, commonly known as medium range order (MRO), some of which has been studied using small electron probes in the past. However, the statistically reliable information on how such MRO constitutes the heterogeneity has remained difficult to determine. Our new approach to determine the MRO and structural heterogeneity involves 4D-STEM, which uses a new-generation pixelated fast STEM detector that allows for the continuous collection of the diffraction patterns from a large area of the MG sample. Using angular correlation and intensity variance analyses, the diffraction patterns can then be converted to real space maps of the local ordering, which we use to precisely determine the type, size, distribution, and volume fraction of MRO. We will present two cases of how the heterogeneity affects the important properties of MGs, one is the glass stability in Ti-based MGs, and the other is the ductility of Zr-based MGs. To connect the structural heterogeneity to ductility, we use a new mesoscale simulation that incorporates the experimentally determined heterogeneity, which can simulate realistic shear band formation and overall deformation that match the spatial and temporal scales of the deformation of real MGs.
3:30 PM - *CM02.02.06
Structure is the Organization Plan of Glasses—But Dynamics Might Bring Deeper Insight
Bernhard Frick1,Henriette Hansen1,2,3,Kristine Niss2
Institut Laue–Langevin1,Roskilde University2,Chalmers3Show Abstract
It is well known that for a large number of glass forming liquids the static structure factor, S(Q), shows no or only subtle changes when passing from the liquid into the glass. In contrast the dynamic structure factor S(q,ω) of simple or more complex glass forming liquids evidences in the GHz - THz frequency range and close to the glass transition clear and common signatures which have been addressed by several theories over the last decades. In spite of large experimental and theoretical activity in this field the glass transition is still not fully understood. Quasielastic neutron scattering plays a vital role for the experimental investigation of dynamic properties of disordered materials, glasses and undercooled liquids. We will give a brief overview over typical experimental findings near the glass transition and over recent instrumental progress on neutron spectrometers before presenting some examples. We then focus on our recent investigations on simple organic, hydrogen bonded and ionic liquids for which we have probed the dynamics near the glass transition by simultaneous dielectric and neutron spectroscopy. For these simultaneous experiments we have controlled both temperature and pressure which did allow us to map lines in the (P,T)-diagram along which the dynamics is unchanged and therefore is isochronous over a wide time range.
4:00 PM - CM02.02.07
Spatially Heterogeneous Dynamics in Metallic Glass Nanowires Imaged by Electron Correlation Microscopy
Debaditya Chatterjee1,Pei Zhang1,Jittisa Ketkaew2,Jan Schroers2,Paul Voyles1
University of Wisconsin–Madison1,Yale University2Show Abstract
We have used electron correlation microscopy (ECM) to image the nanometer scale heterogeneities in the relaxation dynamics of the supercooled liquid of a metallic glass forming alloy . The length and time scales of the heterogeneous dynamics are central to the glass transition and influence nucleation and growth of crystals from the liquid. Electron correlation microscopy (ECM) experiments use time-resolved tilted dark field transmission electron microscopy with sub-nanometer resolution for direct measurement of those length and time scales. ECM data on Pt-based metallic glass nanowires above the glass transition temperature (Tg) reveal a relaxation time scale that varies from a few seconds to hundreds of seconds and a length scale that varies from 0.8 to 1.4 nm. They also demonstrate the existence of a ~1 nm thick near-surface layer with an order of magnitude shorter relaxation time than inside the bulk which may influence crystallization of the wires. Additional measurements of the surface layer relaxation time below the bulk Tg, and its connection to enhanced surface diffusion in metallic glasses and surface crystallization will be discussed.
 P. Zhang, J. J. Maldonis, Z. Liu, J. Schroers, P. M. Voyles, Nat. Commun. 9, 1129 (2018)
4:15 PM - CM02.02.08
Kinetic Metallic Glass Evolution Model
Thomas Hardin1,Christopher Schuh1
Massachusetts Institute of Technology1Show Abstract
Metallic glass is a heterogeneous composite on the scale of a few nanometers; the structure of the glass on this scale governs its macroscopic thermo-mechanical response. This structure evolves in response to thermal and mechanical loading; this evolution is mediated by discrete kinetic events in which clusters of atoms locally rearrange themselves. We present a model of this structural evolution and mechanical response which consists of a thermodynamic state space, density of states, and models for relaxation and shear transformation events which move the glass through that state space. We implement this model in a homogenized statistical sense and compare to homogeneous relaxation and flow data previously in literature; we also implement it in a discrete mesoscale framework. We conclude with a discussion of gaps in the current understanding of the fundamental structure of metallic glass.
4:45 PM - CM02.02.10
Hierarchical Machine Learning to Decode Structural Origin of Heterogeneous Deformation in Disordered Materials
Qi Wang1,Anubhav Jain1
Lawrence Berkeley National Lab1Show Abstract
When subjected to external stimuli such as mechanical loading, atoms in disordered solids respond heterogeneously. Due to lack of representations to resolve the subtle packing difference around atom sites and approaches to deal with the long-range correlation involved, it is hard to quantitatively predict this heterogeneous, site-specific response solely from the structure. Here, by designing a robust hierarchical machine learning framework, we show that it is possible to predict the mechanical heterogeneity in disordered solids a priori, directly from the quenched structural state itself. We encyclopedically create a large pool of 810+ site descriptors, from 40+ sets of structural measures, spanning topological and chemical short- and medium-range order, and develop a novel hierarchical scheme to further extend the studied scale to an unprecedentedly long-range while still retaining good interpretability and generality. Impressive predictability is achieved in a fairly large strain regime, suggesting a long-lived inheritance of the quenched state until later obstructed by shear banding. The framework is robust over a range of compositions and processing conditions and can well detect the site environments tuned by these conditions. We also identify a bag of promising structural signatures unrevealed previously, with their predictability exhaustively benchmarked and discussed. This hierarchical learning framework is general and could potentially be applied to decode structural origin of any site-specific properties in the family of disordered materials.
CM02.03: Poster Session I: Structure-Property Relations in Non-Crystalline Solids
Monday PM, November 26, 2018
Hynes, Level 1, Hall B
8:00 PM - CM02.03.01
Microstructure Design for Ductile Glass Composite
Yanming Zhang1,Binghui Deng1,Liping Huang1,Yunfeng Shi1
Rensselaer Polytechnic Institute1Show Abstract
In this work we use molecular dynamics (MD) simulations to investigate glass composites constituted by two brittle model glasses with different stiffness. We show that tuning the stiffness ratio (SR), shape, volume fraction and distribution of the two brittle glass constituent scan trigger a brittle to ductile (BTD) transition. Such composite glasses can exhibit high strength, remarkable toughness and some work hardening. The highest failure strain of 80% can be reached in composite glasses as compared to 7% in monolithic model glasses. We also found that mechanical properties of such glass composites will not be deteriorated by introduction of pre-notch. Excellent load redistribution capability introduced by structural heterogeneity is responsible for high ductility in our composite glasses. Through a systematic analysis, we unveil the design principles that lead to the aforementioned BTD transition. We believe the current approach could enhance ductility and broaden the application of glasses as enabling structural materials.
8:00 PM - CM02.03.02
Molecular Modeling of Stress Corrosion Behavior
Swastik Basu1,Liping Huang1,Yunfeng Shi1
Rensselaer Polytechnic Institute1Show Abstract
Glass is well known to be susceptible to stress corrosion cracking caused by chemicals in the environment, a phenomenon that can cause delayed failure of glasses due to growth of pre-existing surface defects in the presence of humidity. The complex macroscopic effects of stress corrosion, like fracture, occur due to microscopic interactions, which demand a study to replicate the microstructural interactions within a model, which should reproduce the macroscopic behaviors. The purpose of this research is to study the stress corrosion behavior of a model metallic glass system with a view towards representing the underlying atomic level mechanisms using a molecular dynamics approach.
8:00 PM - CM02.03.03
Liquid Metal Nanoscale Structures as Novel Platform for Characterization of Structural Relaxation of Metallic Glasses
Ziyang He1,Chen Liang2,Chenhao Qian3
Columbia University1,University of Liverpool2,Jiangnan University3Show Abstract
This poster firstly introduces a new microfluidic method for preparing nanostructures of gallium-indium liquid alloy systems. Due to its smaller nanometer size (50-100nm diameter), good self-healing behavior, strong oxide layer formed by spontaneous oxidation, rich changeable nanomorphology driven by voltage variation and large undercooling range, the alloy system has become a good platform for studying amorphous structure transformation and internal structure of liquids using in-situ characterization technology under current conditions. We have successfully discovered the presence of secondary structures in this liquid metal system through in situ TEM lithiation experiments and subsequent nanomechanical and electrical experiments. By comparing the structural relaxation of the same kinetic fragility liquid with or without the oxide layer structure, we found that the oxide layer structure could guide the dynamic non-uniformity of the nano-amorphous system to some extent. At the same time, we are also actively exploring the future application of this alloy system in liquid metal self-healing electrodes, nano-heat pipes, nanoscale self-propelled robots and other industrial fields.
8:00 PM - CM02.03.04
Self-Diffusion Mechanism of Atoms in Forsterite Glass
Junya Nishizawa1,Tomoko Ikeda-Fukazawa1
Meiji University1Show Abstract
Forsterite glass exists as dust grains in interstellar molecular clouds and young stellar objects . In interstellar molecular clouds, elements such as hydrogen, oxygen, carbon, and nitrogen deposit on dust grains, and form various molecules (e.g., H2O, CO, CO2, NH3, CH4, H2CO, CH3OH, and so on) . These molecules undergo chemical evolutions to organic molecules through various processes on the surface of dust grains . Dust grains are important materials governing the chemical and thermal evolutions in space. However, the transport coefficients of forsterite glass are less conclusive, because forsterite glass is easily to crystallize. To investigate the mechanism of self-diffusion of atoms in forsterite glass, molecular dynamics (MD) calculations were performed.
The MD calculations were performed using an atom-atom potential model with MXDORTO program . The potential parameters were empirically determined by constraining the model to reproduce the experimental results of density, thermal expansion coefficient, and bulk modulus . The transition point from glassy state of supercooled liquid state (Tg) for our potential model is 1567 K. A fundamental orthorhombic cell consisting of 160 Mg2SiO4 with three-dimensional periodic boundary conditions was used. The glass structure was prepared by quenching the liquid phase from 3000 K to 10 K with 0.4 K/ps in rate. The quenched glass was warmed to 3000 K with the same rate. The MD code was run with NTP ensemble. The pressure was kept at 0.1 MPa.
The self-diffusion coefficients of Mg, Si and O were calculated using mean-square displacement (MSD). To investigate the mechanisms of self-diffusion, the temporal variations of pair correlations functions for Mg were analyzed. The result shows that the jumping probability of Mg, which is located at a position with high Si and low Mg densities is high. Because of the strong Si–O bonds in the tetrahedral SiO4 units, the jump of Mg atom (or MgOx unit) was induced by structural distortion of the surrounded SiO4 units. From analyses of spatial distribution of MSD, it was found that the MSD values of Mg are inhomogeneous at temperatures just below Tg. Because the self-diffusion coefficient of Si is significantly low at < Tg, the distribution of Si in forsterite glass is inhomogeneous. Therefore, the diffusivity of Mg depends on surrounded Si distribution.
 J. P. Bradley, L. P. Keller, T. P. Snow, M. S. Hanner, G. J. Flynn, J. C. Gezo, S. J. Clemett, D. E. Brownlee, J. E. Bowey, Science, 285, 1716 (1999).
 N. Watanabe, A. Kouchi, Prog. Sur. Sci., 83, 439 (2008).
 K. Kawamura, MXDORTO, Japan Chemistry Program Exchange, #029 (1990).
 T. Ikeda-Fukazawa, J. Soc. Inorg. Mater. Jpn., 23, 130 (2016).
8:00 PM - CM02.03.06
Methods for Estimating Appearance of Metal-Like Plastic
Sun Chul Jin1,Hyungjin Roh1,Kiyong Kim1,Sunghawn Cho1
A plastic has a lower specific gravity than glass or metal and has many advantages such as lightweight and good mechanical properties.
These thermoplastics are rapidly replacing conventional glass and metal areas in fields such as electronic and automobile parts. Recently, as increasing need for environmentally friendly material, there is an increasing demand for plastic that can feel a metallic appearance similar to a metal without a spray process.
For the development of metal-feeling thermoplastics, it is well-known way to use metallic pigment. But because of difference in flowability between metal pigment and plastic, There is an appearance problem such as flow mark and weld-line. This is why metal-feeling plastic can’t be expanded. In order to solve these problems, much research have been studied to control the shape and aspect ratio of metallic pigment and to improve the surface coating of it. However, it is limited to improve the appearance problems such as aggregation and orientation.
In addition, there is no effective method for objectively estimating the appearance of the metallic feeling except for flop index. But the flop index can evaluate only the metallic brightness and the degree of defects such as flow mark and weld-line caused by the metallic pigment could not be evaluated. As a result, there is no method of evaluating the appearance that can represent the overall phenomenon caused by the metallic pigment as an objective numerical value. In this research, development of method for estimating appearance of metal-feeling plastic is studied. Through correction of flop index, new index named as ‘T/N_Flop_X’ was developed. Using this index, it is available to objective evaluation and comparison of metal-feeling. And using the CCD camera, it was studied that correlation of sparkle effect, metallic pigment’s orientation and weld-line.
Based on these studies, we found out sparkle index that could be explained about orientation and metal-feeling. Additionally we studied about control of metallic pigment for reduce an appearance problem. Orientation is important factor to determine weld-line degree and in a constant direction makes decrease it.
We found out factors that could control orientation especially additive having an affinity of polar and non-polar.
8:00 PM - CM02.03.07
Amphiphilic Modification of PDMS Surface with PVA/PSBMA Zwitterionic Semi-Interpenetrating Hydrogel for Marine Antifouling Application
Xingyang Xu1,Rongrong Chen1,Jun Wang1
College of Material Science and Chemical Engineering, Harbin Engineering University1Show Abstract
Marine biofouling is a highly complex process and a worldwide problem which involve a wide variety of species. The common techniques proposed inculde heavy metals (Cu2O), or organic biocide, are bring potential harm to marine environment and ecosystem. Therefore, the nontoxic approaches, particularly silicone-included low-surface-energy Fouling Release Coatings (FRCs) may be the alternatives to chemically active coatings and more environmentally friendly AF strategies. In this study, a facile and versatile approach to the formation of amphiphilic marine antifouling is reported. The approach used boric acid (BA) to mediate the the plasma treated PDMS elastomer and subsequent immobilization of polyvinyl alcohol/poly (sulfobetaine methacrylate) (PVA/PSBMA) zwitterionic semi-interpenetrating hydrogel on solid substrates. PVA/PSBMA was immobilized on the PDMS surface via hydrogen bond and chemical bond. The resulting substrates were tested for the algae attachment test and protein adsorption assay, in which diatom and protein adhesion was significantly inhibited compared to PDMS. Advantageously, this approach allowed marine antifouling coatings to be prepared by a simple immersion process under environmentally friendly conditions.
This paper is funded by the International Exchange Program of Harbin Engineering University for Innovation-oriented Talents Cultivation.
8:00 PM - CM02.03.08
The Effect of Arm Segment Length on Thermally Induced Self-Healing Behavior of Supramolecular Star Poly(ε-caprolactone)s Network
Woojin Lee1,Dae-Yeon Won1,Hyo-bin Wi1,Jae Woo Chung2,Seung-Yeop Kwak1
Seoul National University1,Soongsil University2Show Abstract
Supramolecular polymer is comprised of oligomers or polymers that are held together by reversible non-covalent supramolecular interactions. It is capable of responding to damage or crack and restoring the polymer`s performance without affecting the initial materials properties. The healing property of supramolecular polymer network depends on two factors, that is, the first being the supramolecular interactions, and the second being the chain dynamics of the individual polymer chains. In this study, we synthesize the simple supramolecular network consisted of ureidopyrimidinone (UPy) ends functionalized 6-arm star poly(ε-caprolactone)s and investigate the effect of arm length on thermally induced self-healing behavior of the supramolecular star poly(ε-caprolactone) network. The resulting materials can be healed several times at 90C during 10 minutes, and even can be healed at 60C after 40 minutes. We find the compromise between number of tie points by supramolecular force and chain dynamics related to sufficient mobility of network. Both supramolecular end clustery crystal and main chain crystal might affect the mobility of network. For the efficient healing behavior, the crystalline domain of supramolecular polymer network should be collapsed. Thus, the sufficient thermally induced healing behavior can be achieved through the enhanced mobility of network.
8:00 PM - CM02.03.09
Ab Initio Study of the Amorphous Cu-Bi System
Isaías Rodríguez2,David Hinojosa-Romero1,Alexander Valladares2,Renela Valladares2,Ariel Valladares1
IIM-UNAM1,Facultad de Ciencias-UNAM2Show Abstract
As a pure element, bismuth is a semimetal which possesses several interesting physical properties, not all of them well understood. The recent discovery of superconductivity , as predicted by our group , and the increasing superconducting transition temperature as the pressure applied increases, are some examples of its particularities. Also, the fact that the amorphous phase is superconductive with a transition temperature several orders of magnitude larger than the crystalline at ambient pressure is unusual . These phenomena have also motivated our predictions for the transition temperatures of Bi-bilayers  and the Bi-IV phase . When mixed with other elements, bismuth seems to contribute to the superconducting character of the resulting material. Here we study the binary copper-bismuth amorphous system which is known to superconduct in diverse compositions . Using ab initio molecular dynamics and the undermelt-quench method, we generate an amorphous structure for a 144-atom supercell corresponding to the Cu88Bi56 system. We shall report the calculated electronic and vibrational densities of states for this system and relate them to the superconducting properties of this alloy.
 O. Prakash, A. Kumar, A. Thamizhavel, S. Ramakrishnan. Evidence for bulk superconductivity in pure bismuth single crystals at ambient pressure. Science 355 (2017), pp. 52-55. DOI: 10.1126/science.aaf8227.
 Z. Mata-Pinzón, A. A. Valladares, R. M. Valladares, A. Valladares. Superconductivity in Bismuth. A New Look at an Old Problem. PLoS ONE 11 (2016), e0147645. DOI:10.1371/journal.pone.0147645.
 D. Hinojosa-Romero, I. Rodriguez, A. Valladares, R. M. Valladares, A. A. Valladares. Possible superconductivity in Bismuth (111) bilayers. Their electronic and vibrational properties from first principles. MRS Advances 3 (2018), pp. 313-319. DOI: 10.1557/adv.2018.119.
 A. A. Valladares, I. Rodríguez, D. Hinojosa-Romero, A. Valladares, R. M. Valladares. Possible superconductivity in the Bismuth IV solid phase under pressure. Scientific Reports 8 (2018) 5946 DOI:10.1038/s41598-018-24150-3.
 N. E. Alekseevskii, V. V. Bondar and Yu. M. Polukarov, Zh. Eksperim. i Teor. Fiz. 38 (1960), p. 294 [translation: Soviet Phys. - JETP 38 (1960), p. 213].
8:00 PM - CM02.03.10
Structural Commonalities in Different Classes of Non-Crystalline Solids—A Pair Distribution Function Analysis
Isaías Rodríguez1,David Hinojosa-Romero2,Renela Valladares1,Alexander Valladares1,Ariel Valladares2
Faculty of Science, UNAM1,IIM-UNAM2Show Abstract
In the past decades the research community has explored diverse structures and new fabrication methods of non-crystalline solids. Glassy materials that belong to the semiconductor realm and to the metallic type are the most studied both experimentally and simulationally. The present work investigates common structural trends whenever they exist and different trends among different classes. Amorphous semiconductors display Pair Distribution Functions (PDF) that are very similar among themselves and this indicates that these network forming materials have properties that are alike . Analogously metallic systems have comparable PDFs but different from the network forming materials, as it should be, since the properties between these two classes are very different .
Here we pay attention to the Short-Range Order (SRO) and Intermediate Range Order (IRO) of these two classes. In particular, the first peaks of the structures studied are contrasted, while the second peaks are shown to differ considerably. Whereas the semiconductor structures display a simple first and second peak with a near-zero value between them, the metallic systems have a very well defined non-zero value between the first and second peaks and they also display what we have come to identify as an “elephant” second peak . To manifest the uncommonalities with amorphous semimetals we recall calculations carried out by our group for bismuth where the elephant peak does not appear but the non-zero behavior between the first and the second peak is present . The Plane Angle Distribution (PAD) functions are also reported.
 A. A. Valladares, J. A. Díaz-Celaya, J. Galván-Colín, L. M. Mejía-Mendoza, J. A. Reyes-Retana, R. M. Valladares, A. Valladares, F. Alvarez-Ramirez, D. Qu and J. Shen, New Approaches to the Computer Simulation of Amorphous Alloys: A Review. Materials, 4, 716-781 (2011).
 C.U. Santiago-Cortés, Simulación de sistemas metálicos amorfos y porosos de elementos nobles, Thesis (PhD), Universidad Nacional Autónoma de México, México (2011).
 I. Rodríguez, R. M. Valladares, A. Valladares, A. A. Valladares, to be published (2018).
 A. de Saint-Exupéry, Le Petit Prince, Reynal & Hitchcock, pp 1-2 (1943).
 Z. Mata-Pinzón, A. A. Valladares, R. M. Valladares, A. Valladares, Superconductivity in Bismuth. A New Look at an Old Problem. PLOS ONE, 11(1): e0147645 (2016).
8:00 PM - CM02.03.11
Dependence of Modulus on the Annealing Conditions of Pt57.5Cu14.7Ni5.3P22.5 Bulk Metallic Glass
Zheng Chen1,Amit Datye1,Jittisa Ketkaew1,Sungwoo Sohn1,Jan Schroers1,Udo Schwarz1
Yale University1Show Abstract
The mechanical properties of bulk metallic glasses are often tuned by annealing, which influences these properties by adjusting the relaxation or crystallization status of the glasses. Here, we studied the modulus of Pt57.5Cu14.7Ni5.3P22.5 bulk metallic glass (Pt-BMG) annealed at different temperatures in the metastable regime by nanoindentation, where the annealing gives the BMG different fictive temperature and fractions of crystallization. We find the modulus of the investigated BMG samples exhibits a “V trend”: As the annealing temperature increases, we first observe a decrease that is followed by an increase until saturation is reached. This phenomenon can be explained as a result of the combination of the glasses relaxation and the glasses crystallization: Relaxation caused by higher fictive temperatures lead first to higher free volumes, which leads to lower moduli, while past a specific temperature, crystallization generates new, denser phases with higher moduli. The latter finding is confirmed by nanoindentation measurements at which fully amorphous Pt-BMG samples with different fictive temperatures are compared with partially crystalline samples featuring the same fictive temperature.
8:00 PM - CM02.03.12
Theoretical Support to Hydrogen Elimination Monitoring by Ultraviolet Photodissociation Mass Spectrometry Using Density Functional Theory
Wenrui Chai1,Lindsay Morrison1,Jake Rosenberg1,Graeme Henkelman1,Jennifer Brodbelt1
The University of Texas at Austin1Show Abstract
Mass spectrometry (MS) has became an increasingly popular and useful in analyzing structures of proteins. Initially only information of low resolution and of the whole protein in general can be obtained. Many techniques that utilize property differences between parts of the protein to produce signature fragmentation patterns and products have been developed to gain more information on local geometry, such as collision induced dissociation (CID), electron transfer dissociation (ETD), electron capture dissociation (ECD) and ultraviolet photodissociation (UVPD). A new method called hydrogen elimination monitoring (HEM) was invented by Brodbelt et. al, to overcome disadvantage of other methods. For example, CID disrupts protein structure prior to fragmentation therefore higher order structural information is lost and ECD cannot differentiate highly ordered surface regions with internal buried regions. HEM aims finding out higher order structure anywhere in the protein by using hydrogen elimination information after fragmentation to determine the level of hydrogen binding prior to fragmentation, therefore determining local geometry. Experiments have demonstrated that hydrogen elimination correlates strongly to absence of backbone hydrogen bonding yet the underlying process and reason to this correlation is unknown. DFT studies of model peptides at ground state can help in illustrating the process and in providing theoretical support to HEM method.
In the computational study complementary to experimental findings, we used 3 structures of Ala8 peptide models with increasing amount of hydrogen binding: an unstructured linear peptide, a hairpin turn and a helix, to study the thermodynamics as well as the kinetics of the fragmentation process, by finding out the enthalpy change of the fragmentation reaction and the minimum energy pathways (MEPs) for the processes. The thermodynamics show that fragmentation products without hydrogen elimination are much higher in energy compared to products with hydrogen elimination, and therefore extremely unfavorable. The MEPs revealed reasons why the thermodynamic favorable product may not always form. In the unstructured peptide, hydrogen elimination always take place at the same time as the C-C back bone is cleaved. In the hairpin turn and helix structure, however, the MEP show that C-C cleavage takes place first and produces spatial separation that could prevent hydrogen elimination. This finding shows the underlying principle of the correlation between hydrogen elimination and amount of hydrogen binding prior to fragmentation, and therefore supports HEM as an effective method for analyzing protein structure.
8:00 PM - CM02.03.13
The Molecular Influence on High Strain Rate Microscale Impact Response of Synthetic Polymeric Materials
Yuchen Sun1,David Veysset1,Alex Hsieh2,Steven Kooi1,You-Chi Wu1,John Mikhail1,A. Maznev1,Jan Andzelm2,Gregory Rutledge1,Timothy Swager1,Keith Nelson1
Massachusetts Institute of Technology1,U.S. Army Research Laboratory, RDRL-WMM-G2Show Abstract
The deformation of materials in extreme dynamical environments such as high-velocity microparticle impact is a challenge to understand though important for many areas of science and technology from space exploration to sand erosion. While impact dynamics of macroscale projectiles have been studied in real time using high-speed imaging, investigations of microscale impact have been essentially limited to post-mortem analysis of impacted specimens. Here, we present real-time observations of supersonic microparticle impacts using multi-frame imaging. In a laser-induced projectile impact test, a microparticle is accelerated by laser ablation from a sacrificial gold layer on a glass substrate. These particles can be accelerated into free space with controllable speeds up to 1.0 km/s depending on laser pulse energy and particle characteristics. The particles are monitored in flight and during impact with an ultra-high-speed camera that can record up to 16 images with a minimum interframe time of 3 ns. We investigated the high-velocity impact deformation response of elastomers to further the fundamental understanding of the molecular influences on high strain rate elastomeric response. The types of materials that were synthesized and tested are glassy polymers, graft copolymers, and other materials. We show the dynamic stiffening response of various elastomers including poly(urea urethane) upon impact at strain rates of ~108 s-1 and demonstrate the significance of molecular constitution in the response. These results provide an impetus for modeling the molecular influence on high strain rate microscale impact responses in these polymeric materials.
8:00 PM - CM02.03.14
Enhancing the Mechanical Properties of Biodegradable PLA Using Ternary Polymer Blends
Xianghao Zuo1,Yuan Xue1,Elena Urquiola2,Ruilin Yin3,Jinghan Tang4,Miriam Rafailovich1
Stony Brook University1,Hunter College High School2,St. Anthony's High School3,Mater Dei High School4Show Abstract
Acrylonitrile butadiene styrene (ABS) has a similar matrix structure to the styrene acrylonitrile copolymer but has additional distribution of polybutadiene which strengthens it and allows ABS to surpass the properties of traditional commercial polymers. PLA is a 100% biodegradable polymer which can be regarded as a replacement to many current commercial plastics. However, it’s brittleness limited its application in the industrial processing. Commonly, binary blends including PLA and another polymer additives are created to enhance the mechanical properties of PLA, but this has been found to be ineffective due to the poor interfacial reaction between the polymers. Previous studies have determined that a 70:30 PLA: ABS ratio effectively balances the bio-based properties of PLA with the exceptional mechanical properties of ABS. Many have observed that the binary PLA/ABS blend actually has worse mechanical properties than just the PLA alone. Therefore, an efficient compatibilizer with good affinity with both PLA and ABS is a key factor to solve this problem. In our previous work, we have certified that PMMA is miscible with PLA and considering the structure of ABS, we hypothesis PMMA should be an excellent compatibilizer to the blend.
To create the ternary blends, the polymers were added to a C.W. Brabender and then molded into the tensile and impact test shapes using a Carver Hot Press. The blends were also run through an extruder to create filaments for 3D printing. A 286% increase for the molded sample in the impact test was observed when 4% by weight PMMA was used with the 70PLA/30ABS blend. Mechanical tests also showed that this ternary polymer material can maintain high mechanical properties even when 3D printing, as the mechanical properties of the 3D printed surpassed the pure PLA sample and PLA/ABS binary blend by 24.3% and 55.5% respectively. SEM and TEM imaging were used to verify the location of PMMA phase. And contact angle tests show that ABS has a higher affinity with PMMA than PLA.
The ternary blends reached their peak mechanical properties with less than 5% by weight of compatibilizer added, suggesting the economic efficiency of this blend for industrial use. For future study, interfacial properties in the ternary blends could be investigated using secondary ion mass spectrometry (SIMS) analysis to reveal interactions that contribute to mechanical strength.
8:00 PM - CM02.03.15
Enhancing Impact Resistance of Polymer Blends via Self-Assembled Nanoscale Interfacial Structures
Xianghao Zuo1,Yuan Xue1,Yichen Guo1,Miriam Rafailovich1
Stony Brook University1Show Abstract
We have designed and engineered ternary polymer blends with the mechanical properties comparable to high impact resistant conventional polymers under the guidance of the lattice self-consistent field model. Tow formulas were used to study the mechanical properties. In one system, poly (methyl methacrylate) (PMMA) was used as the compatibilizer for the widely studied biodegradable polymer blend, poly (lactic acid) (PLA)/Poly (butylene adipate-co-butylene terephthalate) (PBAT) blend. We characterized the compatibility of those components and found PMMA was miscible with PLA and partially compatible with PBAT, which allowed it to self-assemble to a nanoscale interfacial layer on the PLA/PBAT interface. This PMMA layer can significantly decrease the interfacial energy and strongly entangle with either PLA or PBAT, resulting in the strengthening of the interface and dramatically enhancement of the impact resistance of the ternary blend. The optimal mechanical performance was achieved when the total PMMA concentration was less than 10 wt %. Higher PMMA content embrittled the blend since the additional PMMA did not contribute to the minimization of the interfacial energy but remained in the PLA phase, increasing the glass transition temperature of the matrix. In the other system, as in our previous study, PMMA is miscible with PLA and PS is totally miscible with styrenic polymers such as HIPS and ABS, therefore, PLA/Styrene Acrylic Copolymers (SMMA) with different styrenic polymers were blended during the study. SMMA will self-assemble to become an interfacial layer on the PLA/PS (or HIPS or ABS) interface at very low concentration (SMMA concentration less than 2%), and enhance the impact resistance of the ternary blend up to 50% compared to the binary blend of PLA/styrenic polymers. Increasing the SMMA concentration will form a third phase domain in the polymer matrix which will embrittle the whole system.
8:00 PM - CM02.03.16
Electronic Transport in Aperiodic Labyrinth Lattices
Vicenta Sanchez1,Fernando Sanchez1,Chumin Wang1
Universidad Nacional Autonoma de Mexico1Show Abstract
The search for a simple and direct relationship between atomic scale arrangement and macroscopic properties of a material constitutes a principal task of the materials science. For example, the Bloch theorem establishes extended electronic wavefunctions and then a ballistic conduction if the atoms of a crystalline material are periodically ordered. At the other extreme, one- and two-dimensional amorphous solids with randomly arranged atoms possess only exponentially localized eigenstates . Nowadays, the study of electronic transport in artificial structures is of great importance in condensed matter physics, because such structures introduce many new physical properties essential for technological applications of atomic-scale devices. In this work, we report a new convolution theorem developed for the Kubo-Greenwood formula in Labyrinth tiling by transforming the original two-dimensional lattice into a set of independent chains with rescaled Hamiltonians . Such transformation leads to an analytical solution of the direct-current conductance spectra, where quantized steps with height of 2g0 are found in Labyrinth tiling with periodic order along the applied electric field direction, in contrast to the step height of g0 observed in the corresponding square lattices, being g0 the conductance quantum. When this convolution theorem is combined with the real-space renormalization method , we can address in a non-perturbative way the electronic transport in macroscopic aperiodic Labyrinth tiling based on generalized Fibonacci chains . Furthermore, we analytically demonstrate the existence of ballistic transport states in such aperiodic Labyrinth tiling. This finding suggests that the periodicity should not be a necessary condition for the single-electron ballistic transport even in multidimensional fully non-periodic lattices.
This work has been partially supported by UNAM-IN114916, UNAM-IN106317 and CONACyT-252943. Computations were performed at Miztli of DGTIC, UNAM.
 E. Abrahams, et al., Phys. Rev. Lett. 42, 673 (1979).
 F. Sánchez, V. Sánchez, C. Wang, Eur. Phys. J. B (2018) doi: 10.1140/epjb/e2018-90070-4.
 V. Sánchez and C. Wang, Phys. Rev. B 70, 144207 (2004).
 F. Sánchez, V. Sánchez, C. Wang, J. Non-Cryst. Solids 450, 194 (2016).
8:00 PM - CM02.03.17
Fracture Tensile Test for Brittle Diamond-Like-Carbon at the Nanoscale
Dahye Shin1,Dongchan Jang1
Korea Advanced Institute of Science and Technology1Show Abstract
Ceramics are well used in various fields as functional materials and their property range is a way more expanded these days by adding new nanoscale properties. Even though a number of studies have been achieved for investigating electronic, magnetic, optic properties etc. at nanoscale, the fracture behavior is not reached to the same level of evaluation. It is in need of investigating the fundaments of fracture mechanics for nano-sized ceramic materials to guarantee the reliability of the systems adding to enjoy the newly enhanced nano-properties at the same time. Brittle failure of ceramics is usually mediated by a rapid crack propagation due to the lack of intrinsic crack tolerant mechanism which requires extremely high critical stress for its activation, usually never been reached before the total failure in bulk scale. However, in some theoretical studies, fracture of nanomaterials becomes insensitive to flaws when they shrink below a certain critical size and enables to reach almost theoretical strength of the material . Getting ideas from this, here we present an unwonted roll of cracks at the nanoscale as an activator of a fracture resisting mechanism not as an enemy of brittle ceramics through nanoscale tensile experiments and finite element methods analysis. In situ SEM tensile fracture tests with different crack geometries were carried out. Diamond-like-carbon (DLC) was chosen to be conductive for SEM image quality, isotropic, and brittle material to eliminate any complicate material issues and to make the best focus on the mechanical analysis. Single-edge-notched-tension (SENT) and double-edge-notched-tension (DENT) samples with pre-notch size of 60 nm and thickness of 200 nm were fabricated in mushroom like shape with head size of ~2 μm using Focused Ion Beam (FIB) on DLC film of ~1.5 μm coated on Si wafer. The head part was grabbed and pulled by a self-produced claw-like tip. In short, we observed that the DENT samples were deviated from the expectations based on classical linear elastic fracture mechanics showing 150% higher fracture strength even with 60% of total crack length out of thickness. It is explained by the interaction between the two stress fields of each crack that activates additional fracture resisting mechanism in the neck region of the specimen preventing the whole sample from the failure.
 Gao, Huajian, et al. "Materials become insensitive to flaws at nanoscale: lessons from nature." Proceedings of the national Academy of Sciences 100.10 (2003): 5597-5600.
8:00 PM - CM02.03.18
Studies of Photo-Thermal Dual Curing Behaviors of Acrylate Monomers with FTIR and Photo-DSC
Hyuck Sik Wang1,Seung Hyuk Lee1,Seok Hyung Bu1,Kigook Song1
Kyung Hee University1Show Abstract
The photo-curing behaviors of acrylate monomers capable of urethane thermal reaction were investigated using time-resolved FTIR spectroscopy and photo-DSC (Differential Scanning Calorimetry). Faster photo-reaction and lower conversion of acrylate reactions were observed in the thermal-photo dual curing process compared to the photo-curing only process. In the case of the acrylate system with long chain oligomers, faster photo-reaction was also observed in the dual curing process although no difference was found in the degree of conversion of acrylates between two photo-curing processes. The photo-curing process of three acrylate monomers was investigated using ATR-FTIR spectroscopy with a deuterated acrylate compound. In the free-radical terpolymerization, the conversion of three acrylate monomers into terpolymer as a function of time was monitored by observing the characteristic FTIR peaks of each component. In order to identify the acrylate components involved in the free-radical terpolymerization, careful peak assignments were made for the acrylate terpolymer such that characteristic FTIR bands from different monomers chosen for quantitative analysis should not overlap with one another. The use of deuterium substituted acrylate monomer as an aid in the interpretation of the FTIR spectra of three component systems has been demonstrated in this study.
8:00 PM - CM02.03.19
Fluorescent Carbon Particles Formed from Concentrated Glucose Solutions
Tomilola Obadiya1,Harsh Uppala1,David Sidebottom1
Creighton University1Show Abstract
Carbon dots (C-dots) are a class of low-dimensional carbon-based particles which exhibit a signature photoluminescence (PL) consisting of a red-shifted emission when irradiated with uv-visible light. This Photoluminescence (PL) has been explained as either the effects of quantum confinement, or of energy traps on the particle surface. Recently, several groups have reported the synthesis of C-dots directly from the thermal treatment of aqueous solutions of simple sugars (e.g., glucose, sucrose) either in a conventional autoclave or in a microwave oven. These studies have looked exclusively a preparation from low concentration (less than 10 wt% sugar) solutions reacted at rather high temperatures (between 160 to 200 C). We report the synthesis of fluorescent carbon particles produced from viscous glucose solutions of a much higher concentration heated at much lower temperatures. Analysis by photon correlation spectroscopy (PCS) reveals the particles form immediately with a size (approximately 300 nm) that is nearly 100 times larger than the precursor clusters of sugar but which decrease slightly in size with additional heating. Despite their larger size, PL shows emission similar to that of smaller C-dots but with clear indications of fine structure suggesting a set of discrete surface energy levels likely associated with different functional groups attached to the particle's surface.
8:00 PM - CM02.03.20
Modeling of the Resistance Drift Phenomenon in Chalcogenide-Based PCMs
Military University of Technology1Show Abstract
Chalkogenide phase change materials (PCM), such as those based on Ge-Sb-Te alloys, have been shown to have unique properties that have been used for a long time in optical memories (DVD), and, more recently, in non-volatile resistive memories [1, 2].
Nonetheless, several challenges must be overcome if PCM memory technology is to enter the market. The most critical of these challenges is that the resistance of the PCM amorphous phase increases with time (so-called "resistance drift phenomenon") due to the ageing of the material, and this drift has a negative effect on the storage of information.
The basic physical mechanisms underlying drift phenomena are still unclear and are currently the subject of intense discussion. Different and sometimes contradictory mechanisms have been proposed, such as : increasing  or reducing [5, 4] disorder during drift; increase  or decrease  density of defect states during drift; impact  or no effect  of stress on drift.
Despite all the recent research efforts, we do not yet have a clear picture of the structural mechanism of relaxation occurring during the ageing of the amorphous PCM phase, and further research is needed.
Discussion and analysis of different mechanisms proposed for increasing of the resistivity of the chalcogenide based PCM amorphous phase with time is presented – taking into account recent reported results of measurements and concepts, eg: clustering of Ge atoms in the amorphous phase of GeTe during ageing ; thermal excitations of electrons trapped in defect states within the electronic gap ; correlation between drift coefficient and activation energy ; increasing of the band gap during ageing ; increase in the proportion of homopolar Ge-Ge bonds with ageing ; densification of the films during ageing ; localization of the gap states during ageing [13, 14]; formation of Ge-Ge bonds upon ageing in thin films .
Structural and quantum chemical analysis was carried out using modified procedures described eg in .
Noé P et al 2018, Semicond. Sci. Technol. 33, 013002];  Kolobov AV et al 2017, Semicond. Sci. Technol. 32, 123003;  Fantini P et al 2012, Appl.Phys. Lett. 100 213506;  Ielmini D et al 2009, Microel. Eng. 86 1942; [5 ] Gopalakrishnan K et al 2010 Symp. on VLSI Tech. Dig. pp 205; [6 ] Pirovano A et al 2004, IEEE Trans. El. Dev. 51 714; [7 ] Ielmini D et al 2008, Appl.Phys. Lett. 92 193511; [8 ] Mitra M et al 2010, Appl.Phys. Lett. 96 222111; [9 ] Rizzi M et al 2011, Appl. Phys. Lett. 99 223513;  Noé P et al 2016, J. Phys. D: Appl.Phys. 49 035305;  Mitrofanov K V et al 2014, J. Appl. Phys. 115 173501;  Kalb J et al 2003, J. Appl. Phys. 94 4908;  Gabardi S et al. 2015, Phys. Rev. B 92 054201;  Sosso G et al 2012, Phys. Stat. Sol. B 249 1880;  Luckas J et al 2013, J. Appl. Phys. 113 023704;  Plucinski K J et al 2015, Mat. Sci. in Sem. Proc, 38, 184-187.
8:00 PM - CM02.03.21
The Relationship Between Photoluminescence and Short-Range Order Structure in SrTi1-xAlxO3 Amorphous Compounds
Valmor Mastelaro1,Yajaira D.R. Jerez1,Lauro Maia2,Alain Ibanez3
University of Sao Paulo1,Federal University of Goias2,Institut NÉEL - CNRS3Show Abstract
Although compounds exhibiting the perovskite structure, and particularly SrTiO3, have been very well studied concerning their photoluminescence (PL) properties, to our knowledge, the effect of water purity used and the addition of aluminum substituting partially titanium atoms on the PL properties have not yet been studied. To complete the previous studies, samples of SrTi1-xAlxO3 composition with x ranging from 0.005, 0.01, 0.03 and 0.05 were prepared by the modified polymer precursor method under different water purity. SrTi1-xAlO3 (STAO) composition samples with the amounts of aluminum equal to x = 0.005, 0.01, 0.03 and 0, 05 were synthesized by the modified polymer precursor method. The obtained resins were subsequently thermally treated at 250 °C at a heating rate of 10 °C/min for 4h under air atmosphere and subsequently ground to obtain fine black amorphous powders. Different temperatures of heat treatments between 450 ~ 500 ° C were selected as well as different calcination times between 2h and 8h. XANES spectra were collected at Ti K-edge using the transmission mode at the XAFS2 beam line of Brazilian storage ring. The pre-edge region of the XANES spectra on the Ti K-edge presents four transitions. They were attributed to a quadrupolar excitation of the 1s electron level to the octahedron t2g orbitals; a transition of the 1s electron to unoccupied 3d level; transitions attributed to the dipole excitation of the 1s electron level to the t2g and eg orbitals of the neighboring octahedron. Significant differences in the intensity of the pre-edge transition for samples containing 3% and 5% of aluminum were observed indicating that in these samples the local symmetry around titanium presents a greater distortion or a greater degree of disorder. This distortion or disorder may originate from the existence of sites with titanium pentacoordinate (Ti) or hexacoordinated (Ti). The comparison of the intensity of the transition present in the pre-border region of the XANES spectra of the samples versus the value of the PL intensity area, in agreement with literature data, shows a clear evolution of PL emission with the relative proportions / amounts of pentacoordinate and hexacoordinated symmetries and also the PL decreasing with the beginning of the crystallization process.
8:00 PM - CM02.03.22
Modifier Cations in Silicate Glasses—Possible Changes of the Local Structures During the Very Early Stages of Crystallization
Valmor Mastelaro1,Edgar Zanotto2
University of Sao Paulo1,Federal University of São Carlos2Show Abstract
Crystallization is a key issue in understanding glass and plays a fundamental role in the development of advanced glass-ceramics. In the absence of catalyzing agents, most supercooled liquids crystallize heterogeneously from the external surfaces; only a few systems crystallize homogeneously in the interior. , it is essential to follow the formation of the first nuclei. Is the whole local structure around the cations modified well before crystallization is completed? The precise role of nucleating agents in glass-ceramic formation will likely only be understood by investigating the very first stages of crystallization with a strictly local structural probe having atomic selectivity. The X-ray Absorption Fine Structure (XAFS) technique is quite appropriate to characterize the local structure of specific cations present in glassy samples from the earliest stage of crystal nucleation. In this work, partially crystallized and fully crystallized samples were obtained after treatment at temperatures and times defined in previous studies. The XANES and EXAFS spectra of selected cations ions in the BaO-SiO2, Ba2TiSi2O7, CaMgSi2O6 – 9 mol% Fe2O3, MgO-SiO2, 1NaO-2CaO-3SiO2 and 2NaO-1CaO-3SiO2 glassy systems were collected at room temperature by using the transmission and total electron yield modes. A preliminary analysis of the data indeed showed modifications in the local order around some cations as the time of crystallization increased. The results will be fully discussed.
8:00 PM - CM02.03.23
Shear Band Nucleation and Propagation in Metallic Glass Matrix Composites
Jonathan Gentile1,Douglas Stauffer2,Jason Trelewicz1
Stony Brook University1,Bruker Nano2Show Abstract
Metallic glass matrix (MGM) composites combine high-strength amorphous metals with ductile crystalline inclusions to overcome the inherent brittleness of metallic glasses. While the crystalline heterogeneities have been shown to influence the process of shear localization, the underlying mechanisms are not well understood especially since they seemingly operate at disparate length scales. To explore the role of crystalline inclusions in the process of strain delocalization, we employ instrumented nanoindentation, which is particularly suited to study the deformation physics of these composite materials due to its ability to detect individual shear band propagation events and its precise control over plastic zone size. Using nanoindentation, we focus on elucidating three specific phenomena including the onset of plasticity through the formation of shear bands, the propensity for shear localization and its dependence on indentation strain rate, and the nature of shear band propagation. In this presentation, we describe instrumented Hertzian contact experiments that provide quantitative evidence for enhanced shear band nucleation as the shear band trajectory evolves with indentation depth to encompass the crystalline phase. Additionally, by measuring the fraction of discrete plastic events deriving from shear band plasticity during loading, we outline a transition from discrete to continuous deformation with increasing indentation strain rate, which is consistent with the behavior of monolithic metallic glasses. Through comparison of the propensity for shear localization with microstructural length scales of the MGM composites, we show that the presence of amorphous-crystalline interfaces simultaneously limit shear band propagation and promote a more homogeneous response through the partitioning of shear strain to the crystalline phase.
8:00 PM - CM02.03.26
Atomistic Simulation of Nearly Defect-Free Models of Amorphous Silicon—An Information-Based Hybrid Approach
Dil Limbu1,Raymond Atta-Fynn2,Parthapratim Biswas1
The University of Southern Mississippi1,The University of Texas at Arlington2Show Abstract
We present an information-based total-energy optimization method to produce nearly defect-free structural models of amorphous silicon. Using geometrical, structural and topological information from tetrahedral networks, we have shown that it is possible to generate structural configurations of amorphous silicon, which are superior than the models obtained from conventional reverse Monte Carlo methods involving structural constraints and total-energy optimization. The new static (i.e. relaxation-based) approach presented here is capable of producing atomistic models with structural properties which are on a par with those obtained from the modified Wooten-Winer-Weaire (WWW) models of amorphous silicon. Structural, electronic, and vibrational properties of the hybrid models are compared with the best dynamical models obtained from using machine-intelligence-based algorithms and efficient molecular-dynamics simulations, reported in the recent literature. We have shown that, together with the WWW models, our hybrid models represent one of the best static models so far produced by total-energy-based Monte Carlo methods in conjunction with experimental diffraction data of amorphous silicon.
8:00 PM - CM02.03.27
Metastable Hydrogenated Amorphous Silicon (a-Si:H) as Reversible Programmable Photonic Material
Mahir Mohammed1,Ripalta Stabile1,Jimmy Melskens1,Wilhelmus (Erwin) Kessels1,Oded Raz1
Eindhoven University of Technology1Show Abstract
Hydrogenated amorphous silicon (a-Si:H) is known to exhibit light-induced metastable properties that are reversible upon annealing. Although these metastable properties suggest the existence of reversible optical properties of a-Si:H as well, very little is known about this effect. If indeed properly identified and characterized, such reversible optical properties may find application in the reversible programmable photonic integrated circuits (PICs) that can enable multiple functionalities on the same chip, similar to field-programmable gate arrays (FPGAs). However, the required reversible effective refractive index change due to light soaking and annealing has not been reported yet nor has it been thoroughly investigated. Therefore, the effects of prolonged high intensity light soaking and annealing on a-Si:H on the near infrared (NIR) optical properties are studied in this work. A thin-film interferometric technique was developed to detect minute changes probed using a NIR laser source (1465-1575 nm). Using this approach, an increase in refractive index resulted in a red shift of the sharp reflection minimum and a blue shift for the decrease in refractive index. To detect the changes in optical properties more precisely, double-layered thin films were used: a-Si:H was deposited by inductively coupled plasma-enhanced chemical vapour deposition (ICP-PECVD) on SiO2, which was in turn deposited by PECVD on a crystalline silicon substrate. The a-Si:H deposition temperature was set to 80 °C and 300 °C, such that significantly different structural properties, e.g. hydrogen content and density, could be achieved. An irreversible blue shift was observed during the first cycle of annealing and light soaking after the deposition. However, from the second cycle onwards, a red shift of the spectrum due to light soaking, i.e. reversal of the annealed state was observed. It appeared that the initial irreversible changes are inevitable and only after these changes reversibility is observable. The reversibility was sustained after further cycles of annealing and light soaking. The reversibility appears for both a-Si:H deposited at 80 °C and 300 °C. However, the magnitude of the reversibility for a-Si:H deposited at 80 °C is significantly larger when compared to a-Si:H deposited at 300 °C. This suggests a correlation of the metastable properties of a-Si:H on the hydrogen content and density of the material, i.e. porous films (deposited at 80 °C) are more susceptible to light-induced change than dense films (deposited at 300 °C). The magnitude of the reversibility in refractive index for a-Si:H deposited at 80 °C is estimated to be around 0.03%. Although small, this metastable change should be sufficient for an application in reversible programmable optical switch. These results therefore indicate that a-Si:H has potential in enabling reversible programmable PICs and work to implement this material in a photonic device is currently ongoing.
8:00 PM - CM02.03.28
Ag+ Ion Emission from Sharp-Edged Ag+ Ion Conducting Glasses and Two Emission Mechanisms
Yusuke Daiko1,Hiroki Mori1,Sawao Honda1,Yuji Iwamoto1
Nagoya Institute of Technology1Show Abstract
Ion implantation is an effective method for surface modification of materials, and that has been used in various fields such as the semiconductor and metal industries, and bio-technology.In general, a discharged plasma (gas) or liquid (e.g., liquid Ga for a focused ion beam) is used as the ion source so far. However, in these cases, side reactions (generation of radicals or various ions with different mass, e.g. in the case of H+ emission, H2+ and H3+ etc. are also generated) are unavoidable. Also, ion accelerators are huge and expensive.
On the other hand, ion emissions from high ion conducting solid electrolytes have also been investigated because in a good solid electrolyte the mobile ions can move almost as freely as those in a liquid. The emission of O−ions from O2−-ion-conducting yttria-stabilized zirconia (YSZ) was first reported in 1997. Similarly, continuous Ag+ion emissions for a few days were reported using Ag-ion-conducting (AgI)0.5(AgPO3)0.5or RbAg4I5[8,9]. For 12CaO-7Al2O3(C12A7) clathrate crystals, it was found that not only electrons but also ions such as O−, H−, and F−ions can incorporate inside cages, and emissions of these anions from C12A7 pellets were also observed. In this ion emission method, a plasma is not required for ionization and the ion emission apparatus becomes simple.
We have studied ion emissions from various types of ion-conducting glasses [1-3]. One advantage of utilizing glass is its formability for tip sharpening because the electric field strength is proportional to the inverse of the curvature radius of the tip. Here we report Ag+ ion emission from a sharpened Ag+ ion conducting glasses. An aluminum phosphosilicate glasses Ag2O-Al2O3-P2O5-SiO2 show Ag+ ion conductivity of 3×10−3 S/cm at 300 °C, and an ionic current of Ag+ ion emission was successfully observed at 300 °C and 1×10−5 Pa. A good linear correlation is obtained between the log(current) and the square root of the acceleration voltage, suggesting the emission of Ag+ ion from the tip of glass fiber is expressed by Schottky model similar to a thermionic electron emission. On the other hand, in the case of AgI-B2O3-Ag2O glasses known as a super-ion-conducting glass, an Ag+ ion conductivity was higher than 5×10−3 S cm