scholarly journals Nondestructive real-space imaging of energy dissipation distributions in randomly networked conductive nanomaterials

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Takahiro Morimoto ◽  
Seisuke Ata ◽  
Takeo Yamada ◽  
Toshiya Okazaki
Keyword(s):  
Functional Materials ◽  
Real Space ◽  
Network Structures ◽  
Conductive Heat ◽  
Frequency Space ◽  
Dynamical Method ◽  
Intensity Images ◽  
Lock In ◽  
Conductive Nanomaterials ◽  
Micrometer Scale

Abstract For realization the new functional materials and devices by conductive nanomaterials, how to control and realize the optimum network structures are import point for fundamental, applied and industrial science. In this manuscript, the nondestructive real-space imaging technique has been studied with the lock-in thermal scope via Joule heating caused by ac bias conditions. By this dynamical method, a few micrometer scale energy dissipations originating from local current density and resistance distributions are visualized in a few tens of minutes due to the frequency-space separation and the strong temperature damping of conductive heat components. Moreover, in the tensile test, the sample broken points were completely corresponding to the intensity images of lock-in thermography. These results indicated that the lock-in thermography is a powerful tool for inspecting the intrinsic network structures, which are difficult to observe by conventional imaging methods.

Nonlinear Lock-In Infrared Microscopy: A Complementary Investigation Technique for the Analysis of Functional Electroceramic Components

2015 ◽  
Vol 21 (5) ◽  
pp. 1145-1152 ◽  
Author(s):  
Michael Hofstätter ◽  
Nadine Raidl ◽  
Bernhard Sartory ◽  
Peter Supancic
Keyword(s):  
Electrical Properties ◽  
Electron Backscatter Diffraction ◽  
Barrier Properties ◽  
Infrared Microscopy ◽  
Polar Crystal ◽  
Dependent Behavior ◽  
Electroceramic Material ◽  
Lock In ◽  
Backscatter Diffraction ◽  
Micrometer Scale

AbstractUsing lock-in infrared microscopy as a tool for current detection on the micrometer scale in AC-driven specimens in combination with iterative grinding procedure allows preparation of current dominating microstructure regions on well-polished surfaces. This technique is applied successfully on varistor components based on specially doped ZnO-based varistor ceramics. This peculiar electroceramic material exhibits exceptional high nonlinear current–voltage (I-V) characteristics, described by a power law according I~Vα, caused by double Schottky barriers at the grain boundaries. As a novelty the thermographic response is used to evaluate local electrical properties, namely the nonlinearity coefficient α, on basis of higher order harmonics with respect to the basic electrical driving AC-frequency.To correlate the observed electrical properties to the microstructure, the polar crystal orientation of the relevant ZnO grains is determined by combining electron backscatter diffraction and orientation-dependent patterns as a result of a chemical etching procedure. These findings support a modified new model for describing the grain boundary controlled current flow in a varistor microstructure including orientation-dependent barrier properties. Hence, the experimentally observed current direction-dependent behavior can be described consistently.

scholarly journals Surface-Induced Nanostructures and Phase Diagrams of ABC Linear Triblock Copolymers under Spherical Confinement: A Self-Consistent Field Theory Simulation

Polymers ◽  
2018 ◽  
Vol 10 (11) ◽  
pp. 1276 ◽  
Author(s):  
Ji Wu ◽  
Zhihong Huang ◽  
Wenchang Lang ◽  
Xianghong Wang ◽  
Shiben Li
Keyword(s):  
Field Theory ◽  
Phase Diagrams ◽  
Triblock Copolymers ◽  
Functional Materials ◽  
Real Space ◽  
Consistent Field ◽  
Spherical Cavities ◽  
Self Consistent ◽  
Self Consistent Field ◽  
Self Consistent Field Theory

We investigate the nanostructures and phase diagrams of ABC linear triblock copolymers confined in spherical cavities by using real-space self-consistent field theory. Various 3D morphologies, such as spherical concentric lamellae, dumbbell-like cylinder, and rotational structures, are identified in the phase diagrams, which are constructed on the basis of the diameters of spherical cavities and the interaction between the polymers and preferential surfaces. We designate specific monomer-monomer interactions and block compositions, with which the polymers spontaneously form a cylindrical morphology in bulk, and firstly study morphology transformation with a neutral surface when a confining radius progressively increases. We then focus on phase morphologies under the preferential surfaces and consolidate them into phase diagrams. The spherical radius and the degree of preferential interactions can obviously induce the formation of a cylindrical morphology. Theoretical results correspond to an amount of recent experimental observations to a high degree and contribute to synthesising functional materials.

scholarly journals Altermagnetism: spin-momentum locked phase protected by non-relativistic symmetries

2021 ◽  
Author(s):  
Tomas Jungwirth ◽  
Libor Šmejkal ◽  
Jairo Sinova
Keyword(s):  
Functional Materials ◽  
Real Space ◽  
Spin Splitting ◽  
Spin Coherence ◽  
Energy Bands ◽  
Quantum Phases ◽  
Magnetic Symmetry ◽  
Crystal Space ◽  
Inversion Asymmetry ◽  
Spin Momentum

Abstract The search for novel magnetic quantum phases, phenomena and functional materials has been guided by relativistic magnetic-symmetry groups in coupled spin and real space from the dawn of the field in 1950s to the modern era of topological matter. However, the magnetic groups cannot disentangle non-relativistic phases and effects, such as the recently reported unconventional spin physics in collinear antiferromagnets, from the typically weak relativistic spin-orbit coupling phenomena. Here we discover that more general spin symmetries in decoupled spin and crystal space categorize non-relativistic collinear magnetism in three phases: conventional ferromagnets and antiferromangets, and a third distinct phase combining zero net magnetization with an alternating spin-momentum locking in energy bands, which we dub "altermagnetic". For this third basic magnetic phase, which is omitted by the relativistic magnetic groups, we develop a spin-group theory describing six characteristic types of the altermagnetic spin-momentum locking. We demonstrate an extraordinary spin-splitting mechanism in altermagnetic bands originating from a local electric crystal field, which contrasts with the conventional magnetic or relativistic splitting by global magnetization or inversion asymmetry. Based on first-principles calculations, we identify altermagnetic candidates ranging from insulators and metals to a parent crystal of cuprate superconductor. Our results underpin emerging research of quantum phases and spintronics in high-temperature magnets with light elements, vanishing net magnetization, and strong spin-coherence.

scholarly journals Direct visualization of orbital electron occupancy

2021 ◽  
Author(s):  
Tongtong Shang ◽  
Dongdong Xiao ◽  
Fanqi Meng ◽  
Xiaohui Rong ◽  
Xiaozhi Liu ◽  
...  
Keyword(s):  
Functional Materials ◽  
Real Space ◽  
Physical Parameters ◽  
X Ray Diffraction ◽  
The Real ◽  
Large Size ◽  
Structure Factors ◽  
Orbital Electron ◽  
Orbital Occupancy ◽  
Convergent Beam

Abstract Orbital is one of the primary physical parameters that determine materials’ properties. Currently, experimentally revealing the electron occupancies of orbitals under the control of external field remains a big challenge due to the stringent requirements for samples such as the atomically sharp surface or defect-free large-size single crystals. Here, we developed a method with the combination of quantitative convergent-beam electron diffraction and synchrotron powder X-ray diffraction, and demonstrated the visualization of the real-space orbital occupancy by choosing LiCoO2 as a prototype. Through multipole modelling of the accurately measured structure factors, we found the opposite changes of Co t2g and eg orbital occupancies under different electrochemical states which can be well-correlated with the CoO6 octahedra distortion. This robust method provides a feasible route to quantify the real-space orbital occupancy on small-sized particles, and opens up a new avenue for exploring the orbital origin of physical properties for functional materials.

scholarly journals Multivalent, multiflavored droplets by design

2018 ◽  
Vol 115 (37) ◽  
pp. 9086-9091 ◽  
Author(s):  
Yin Zhang ◽  
Xiaojin He ◽  
Rebecca Zhuo ◽  
Ruojie Sha ◽  
Jasna Brujic ◽  
...  
Keyword(s):  
Self Assembly ◽  
Functional Materials ◽  
Building Blocks ◽  
Dna Origami ◽  
Emulsion Droplets ◽  
Slow Kinetics ◽  
Open Structures ◽  
Functional Dna ◽  
Valence Control ◽  
Micrometer Scale

Nature self-assembles functional materials by programming flexible linear arrangements of molecules and then folding them to make 2D and 3D objects. To understand and emulate this process, we have made emulsion droplets with specific recognition and controlled valence. Uniquely monovalent droplets form dimers: divalent lead to polymer-like chains, trivalent allow for branching, and programmed mixtures of different valences enable a variety of designed architectures and the ability to subsequently close and open structures. Our functional building blocks are a hybrid of micrometer-scale emulsion droplets and nanoscale DNA origami technologies. Functional DNA origami rafts are first added to droplets and then herded into a patch using specifically designated “shepherding” rafts. Additional patches with the same or different specificities can be formed on the same droplet, programming multiflavored, multivalence droplets. The mobile patch can bind to a patch on another droplet containing complementary functional rafts, leading to primary structure formation. Further binding of nonneighbor droplets can produce secondary structures, a third step in hierarchical self-assembly. The use of mobile patches rather than uniform DNA coverage has the advantage of valence control at the expense of slow kinetics. Droplets with controlled flavors and valences enable a host of different material and device architectures.

Problem behavior in autism spectrum disorders: A paradigmatic self-organized perspective of network structures

2019 ◽  
Vol 42 ◽  
Author(s):  
Lucio Tonello ◽  
Luca Giacobbi ◽  
Alberto Pettenon ◽  
Alessandro Scuotto ◽  
Massimo Cocchi ◽  
...  
Keyword(s):  
Autism Spectrum Disorder ◽  
Problem Behaviors ◽  
Autism Spectrum ◽  
The Self ◽  
Network Structures ◽  
Self Organized ◽  
Critical Equilibrium ◽  
Self Organized Criticality ◽  
Acute Agitation ◽  
Spectrum Disorders

AbstractAutism spectrum disorder (ASD) subjects can present temporary behaviors of acute agitation and aggressiveness, named problem behaviors. They have been shown to be consistent with the self-organized criticality (SOC), a model wherein occasionally occurring “catastrophic events” are necessary in order to maintain a self-organized “critical equilibrium.” The SOC can represent the psychopathology network structures and additionally suggests that they can be considered as self-organized systems.

High-resolution structure determination by ALCHEMI

1983 ◽  
Vol 41 ◽  
pp. 178-181 ◽  
Author(s):  
Peter G. Self ◽  
Peter R. Buseck
Keyword(s):  
Site Occupancy ◽  
Real Space ◽  
Unit Cell ◽  
Bragg Angle ◽  
Electron Current ◽  
High Resolution Structure ◽  
Beam Incident ◽  
Crystallographic Planes ◽  
Electron Beam Incident ◽  
Resolution Structure

ALCHEMI (Atom Location by CHanneling Enhanced Microanalysis) enables the site occupancy of atoms in single crystals to be determined. In this article the fundamentals of the method for both EDS and EELS will be discussed. Unlike HRTEM, ALCHEMI does not place stringent resolution requirements on the microscope and, because EDS clearly distinguishes between elements of similar atomic number, it can offer some advantages over HRTEM. It does however, place certain constraints on the crystal. These constraints are: a) the sites of interest must lie on alternate crystallographic planes, b) the projected charge density on the alternate planes must be significantly different, and c) there must be at least one atomic species that lies solely on one of the planes.An electron beam incident on a crystal undergoes elastic scattering; in reciprocal space this is seen as a diffraction pattern and in real space this is a modulation of the electron current across the unit cell. When diffraction is strong (i.e., when the crystal is oriented near to the Bragg angle of a low-order reflection) the electron current at one point in the unit cell will differ significantly from that at another point.

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