Amorphous Ring Research Articles

Mechanism analysis and optimization of dynamic functional response of nanoscale thermal cloak

In recent years, with the booming development of nanodevices and technologies, the nanoscale thermal cloak has gradually attracted researchers’ interest due to its unique way of utilizing heat energy. However, most existing studies only restrictively place the nanoscale thermal cloak in a constant external environment but neglect the study of its performance under dynamic conditions, which results in insufficient understanding and limits the application scope of this functional structure. Therefore, in this paper, we design a nanoscale thermal cloak and explore functional response in a triangular waveform-based dynamic temperature, in which temperature peak and change period are set as variables. The results show that the nanoscale thermal cloak performs well in three different dynamic environments and that the larger the amorphous ring width, the smaller the temperature peak, and the larger the variation period, the better the cloaking effect. Furthermore, we propose to use the response temperature to quantify the disturbance of the cloak's presence in the external environment. The smaller the amorphous ring width, the smaller the disturbance to the external temperature. When the ring width is fixed, the temperature peak is smaller, the variation period is longer, and the external temperature disturbance is smaller. Finally, we use phonon localization theory to explain the underlying mechanism. By calculating and analyzing the phonon density of states (PDOS) and mode participation rate (MPR), we find that phonon localization in the functional region is the main reason for the cloaking phenomenon. In addition, we plot the spatial distribution information of phonon localization to visualize the phenomenon of localization. This study expands the application scope of the nanoscale thermal cloak and can provide a reference for the development of other nanoscale devices.

Modeling Dynamic Hysteresis Curves in Amorphous Magnetic Ribbons

A description of magnetic hysteresis is important for the prediction of losses in soft magnetic materials. In this paper, a viscosity-type equation is used to describe dynamic hysteresis loops in an amorphous ring core for symmetric excitation, as prescribed by international standards. The value of the exponent appearing in the viscosity-based equation can be assumed to be constant if the maximum induction is away from the saturation value. The viscosity-type equation is used to describe the shape variation of magnetization curves due to eddy currents in different time and space scales. Modeling is carried out for various excitation frequencies and induction amplitudes. The discrepancies between the experimental and modeled curves (and also losses) are acceptable in the wide range of the frequency and maximum induction. The paper indicates that the viscosity-type effects, mostly due to eddy currents generated in the conductive material, play an important role in energy dissipation at increased excitation frequencies. The modeling results might be interesting to the designers of magnetic circuits.

Direct Observation of Evolution from Amorphous Phase to Strain Glass.

The amorphous phase and strain glass are both disordered states of solids. The amorphous phase is an atomic packing disordered phase, while strain glass is a glassy state with transformation strain disorder in a crystalline matrix, which both bring extraordinary properties to alloys. Previous studies have mostly focused on the properties and structure of single glass; however, the link between them has seldom been considered. In this work, the specimen of the almost amorphous state was obtained from the heavy-defects-doping Fe67.8Pd32.2 strain glass ingot by arc melting and 90% cold rolling, which were characterized by amorphous packages in X-ray diffraction and amorphous rings in transmission electron microscope diffraction. The evolution from the amorphous phase (metallic glass) back to strain glass was directly observed by an in situ high-resolution transmission electron microscope, which revealed that strain nanodomains began to form on the amorphous matrix below the crystallization temperature of the amorphous phase. Here, direct observation of the evolution process provides a theoretical basis for achieving precise control of crystallinity to obtain the desired microstructure, while the study of the unusual crystallization process offers a possible way to tailor the mechanical and functional properties through tuning the amorphous and strain glass coexistence. This work presents the specific pathway and realization possibilities for the design of glass composite materials with enhanced properties.

Self-Assembly of Porous Structures From a Binary Mixture of Lobed Patchy Particles

We report simulation studies on the self-assembly of a binary mixture of snowman and dumbbell shaped lobed particles. Depending on the lobe size and temperature, different types of self-assembled structures (random aggregates, spherical aggregates, liquid droplets, amorphous wire-like structures, amorphous ring structures, crystalline structures) are observed. At lower temperatures, heterogeneous structures are formed for lobed particles of both shapes. At higher temperatures, homogeneous self-assembled structures are formed mainly by the dumbbell shaped particles, while the snowman shaped particles remain in a dissociated state. We also investigated the porosities of self-assembled structures. The pore diameters in self-assemblies increased with an increase in temperature for a given lobe size. The particles having smaller lobes produced structures with larger pores than the particles having larger lobes. We further investigated the effect of σ, a parameter in the surface-shifted Lennard-Jones potential, on the self-assembled morphologies and their porosities. The self-assembled structures formed at a higher σ value are found to produce larger pores than those at a lower σ.

A Roadmap for the Chalcogenide-graphene Composites Formation Under a Glassy Regime

Background: Nano-composite is an innovative material having nano in which fillers dispersed in a matrix. Typ-ically, the structure is a matrix- filler combination, where the fillers like particles, fibers, or fragments are surrounded and bound together as discrete units by the matrix. The term nano-composite encompasses a wide range of materials right from three dimensional metal matrix composites to two dimensional lamellar composites. Therefore, the physical, chemical and biological properties of nano materials differ from the properties of individual atoms and molecules or bulk matter. The chalcogenide – graphene composites in glassy regime is the growing novel research topic in the area of composite material science. It is obvious to interpret such materials different physicochemical mechanism. Objective: The key objective of this research work to explore the internal physicochemical mechanism of the chalcogenide – graphene composites under the glassy regime. Including the prime chalcogen alloying element selenium amorphous atomic structure and their fullerene like bonding nature. By accommodating the essential properties of the stacked layers of bilayer graphene. The diffusion, compression and dispersion of the bilayer graphene in selenium rich ternary (X(1-x-y)-Y(x)- Z(y) + GF (bilayer graphene); X = Se, Y = Semimetal or metalloid, Z = None metal) alloys under the complex regime on and after thermal melting process are addressed. Materials and Methods: To synthesize the composite materials the well-known melt quenched method had adopted. More-over, to interpret the amorphous selenium (Se8) chains and rings molecular structures we had used vista software with an available CIF data file. While to show the armchair and zig-zag bonds with bilayer graphene structure the nanotube modeler simulation software has used. Results: Outcomes of this study reveals the chalcogenide -graphene nano composite formation under a glassy regime changes the individual materials structural and other physical properties that is reflecting in different experimental evi-dences, therefore, the modified theoretical concepts for the different properties of such composite materials are interpreted in this study. Discussion: The dispersion and diffusion of the high stiff graphene bonds in low dimension chalcogen rich alloys has been interpreted based on their quadric thermal expansion behaviour. In addition to this, a possible bond angle modification in the formation of X(1-x-y)-Y(x)- Z(y) + GF composites are also addressed. To interpret the distinct optical property behavior of the formed X(1-x-y)-Y(x)- Z(y) + GF composites and parent chalcogenide glassy alloys a schematic model of the energy levels is also addressed. Conclusion: To make a better understating on the formation mechanism such composites, the diffusion and deformation of high stiff graphene σ and π bonds in a low dimension chalcogenide alloy basic mechanism are discussed on basis of novel “thermonic energy tunneling effect” concept, which could result in quadratic thermal expansion of graphene. Moreover, the structural unit modifications of such composite materials are described in terms of their bond angle modifications and in-fluence of the coordination defects. The energy levels suppression and creation of addition sub energy levels in such com-posite materials are discussed by adopting the viewpoint impact of the foreign alloying elements and surface π-plasmonic resonance between the graphene layers in the honeycomb band structure. Thus, this study has described various basic aspects of the chalcogenide system – bilayer graphene composites formation under a glassy regime.

Ti3SiC2 irradiation damage at electron beam energy levels of 120 keV and 200 keV

Irradiation damage response under electron beam irradiation energies of 120 keV and 200 keV on Ti3SiC2 was investigated in this study. The surface of material became rough under 120 keV caused by the electron beam sputtering. Under 200 keV electron irradiation, the surface damage was more serious. Diffraction spots with low intensity of some crystal planes due to the displacement of Si atoms at 200 keV. Point defects caused by irradiation reduced the a-axis lattice constant by 1.8%. However, even after irradiation for 600 s, no amorphous ring was observed.

Vibration and noise characteristics of high-frequency amorphous transformer under sinusoidal and non-sinusoidal voltage excitation

The vibration test of silicon steel, amorphous and nanocrystalline magnetic rings shows that the magnetostriction of amorphous materials is much larger than that of silicon steel and nanocrystalline. This paper focuses on the measurement and analysis of the vibration and noise of a 5kVA/4.5 kHz amorphous high-frequency transformer (HFT) under sinusoidal and non-sinusoidal excitation. Comparing and analyzing the measured data of vibration and noise, the results show that the vibration of HFT under the non-sinusoidal excitation is much larger than that of the sinusoidal excitation. The vibration excited by sinusoidal excitation basically concentrates on the double frequency of the excitation. Most of the vibration under non-sinusoidal excitation is also on the double frequency, but contains many harmonics. The influences are analyzed of duty cycle of rectangular excitation and the natural frequency of HFT on the vibration and noise.

Processing soft ferromagnetic metallic glasses: on novel cooling strategies in gas atomization, hydrogen enhancement, and consolidation

Processing soft ferromagnetic glass-forming alloys through gas atomization and consolidation is the most effective technique to produce bulk samples. The commercial viability of these materials depends on commercial purity feedstock. However, crystallization in commercial purity feedstock is several orders of magnitude faster than in high purity materials. The production of amorphous powders with commercial purity requires high cooling rates, which can only be achieved by extending the common process window in conventional gas atomization. The development of novel cooling strategies during molten metal gas atomization on two model alloys ({(Fe0.6Co0.4)0.75B0.2Si0.05}96Nb4 and Fe76B10Si9P5) is reported. Hydrogen inducement during liquid quenching significantly improved the glass-forming ability and soft magnetic properties of {(Fe0.6Co0.4)0.75B0.2Si0.05}96Nb4 powders. Spark plasma sintering experiments verified that amorphous rings could be produced regardless of the cooling strategies used. While the saturation magnetization was almost unaffected by consolidation, the coercivity increased slightly and permeability decreased significantly. The magnetic properties of the final bulk samples were independent of feedstock quality. The developed cooling strategies provide a great opportunity for the commercialization of soft ferromagnetic glass-forming alloys with commercial purity.

Iron Loss and Hysteresis Properties of an Amorphous Ring Core at High Temperatures under Inverter Excitation

Iron Loss and Hysteresis Properties of an Amorphous Ring Core at High Temperatures under Inverter Excitation

Mesoscale magnetic rings: Complex magnetization reversal uncovered by FORC

In this work, we investigate mesoscopic amorphous magnetic rings prepared by ion-implantation. The analysis is carried out combining conventional magnetization vs field measurements alongside MOKE microscopy imaging and, for the first time, first-order reversal curves (FORCs). With the information extracted from the FORC diagram, we can identify the presence of typical onion and vortex magnetic configurations, and also determine with high resolution the fields connected to their formation, stability, and annihilation. Furthermore, depending on the field and history, two different onion configurations exist, characterized by the presence of transverse or vortex domain walls. The FORC data reveal the different reversible/irreversible nature of the annihilation of the two onion configurations, and a signal peculiar of the presence of vortex domain walls. All these crucial information are not accessible with conventional M(H) loops, demonstrating that FORCs offer a unique perspective for the investigation of the physical phenomena of magnetic elements with complex geometries.

Effect of ripening on in vitro digestibility and structural characteristics of plantain (Musa ABB) starch

This study focused on the effect of ripening on in vitro digestibility and the multi-scale structural characteristics of plantain starch. It was shown that the RS content of plantain starch gradually decreased during ripening process, while RDS and SDS contents increased. Scanning electron micrographs showed the layer-by-layer degradation of the surfaces of starch granules. The transformation from CB-type to CA-type crystalline structure of starch was revealed by wide angle X-ray diffraction patterns. Relative crystallinity, IR ratio 1045/1022 and the apparent amylose content all decreased with increasing maturity. Meanwhile, branched chain length distributions of amylopectin indicated that the content of short chain increased and that of long chain decreased, leading to the changes of digestion performance. In addition, the serious damage to amorphous region in semi-crystalline lamellae and amorphous growth ring was caused. All above factors contributed to the decrease of plantain starch resistance to digestion with increasing maturity. This work provides a fundamental understanding of the changes that plantain starch undergoes during ripening.

Determination of Silica and Germania Film Network Structures on Ru(0001) at the Atomic Scale

The detailed structure of silica and germania films supported on Ru(0001) metal substrates are compared to each other. Surface science techniques together with density functional theory calculations have been used to gain insights into the atomic arrangement of these prominent glass-forming materials. The monolayer films of these materials both show predominantly crystalline hexagonal lattices with characteristic domain boundary structures. For the germania monolayer films a large variety of ring elements within domain boundaries have been observed. Density functional calculations predict stronger interaction with the metal substrate for bilayer germania as compared to bilayer silica films. Scanning tunneling microscopy images with atomically resolved structural features have given access to silica and germania bilayer film structures. Both bilayer films form characteristic amorphous ring structures. However, the germania bilayer films appear to be more corrugated, pointing to a stronger interaction with the metal support thus giving rise to slightly different connectivity rules.

Investigating Iron Loss Properties in an Amorphous Ring Excited by Inverters based on Silicon and Gallium Nitride

Investigating Iron Loss Properties in an Amorphous Ring Excited by Inverters based on Silicon and Gallium Nitride

Local nanoscale strain mapping of a metallic glass during in situ testing

The local elastic strains during tensile deformation in a CuZrAlAg metallic glass are obtained by fitting an elliptic shape function to the characteristic amorphous ring in electron diffraction patterns. Scanning nanobeam electron diffraction enables strain mapping with a resolution of a few nanometers. Here, a fast direct electron detector is used to acquire the diffraction patterns at a sufficient speed to map the local transient strain during continuous tensile loading in situ in the transmission electron microscope. The elastic strain in tensile direction was found to increase during loading. After catastrophic fracture, a residual elastic strain that relaxes over time was observed.

Possibilities of further improvement of 1 s fluxgate variometers

Abstract. The paper discusses the possibility of improving temperature and noise characteristics of fluxgate variometers. The new fluxgate sensor with a Co-based amorphous ring core is described. This sensor is capable of improving the signal-to-noise ratio at the recording short-period geomagnetic variations. Besides the sensor performance, it is very important to create the high-stability compensation field that cancels the main Earth magnetic field inside the magnetic cores. For this purpose the new digitally controlled current source with low noise level and high temperature stability is developed.

Fabrication of amorphous micro-ring arrays in crystalline silicon using ultrashort laser pulses

We demonstrate a simple way to fabricate amorphous micro-rings in crystalline silicon using direct laser writing. This method is based on the fact that the phase of a thin surface layer can be changed into the amorphous phase by irradiation with a few ultrashort laser pulses (800 nm wavelength and 100 fs duration). Surface-depressed amorphous rings with a central crystalline disk can be fabricated without the need for beam shaping, featuring attractive optical, topographical, and electrical properties. The underlying formation mechanism and phase change pathway have been investigated by means of fs-resolved microscopy, identifying fluence-dependent melting and solidification dynamics of the material as the responsible mechanism. We demonstrate that the lateral dimensions of the rings can be scaled and that the rings can be stitched together, forming extended arrays of structures not limited to annular shapes. This technique and the resulting structures may find applications in a variety of fields such as optics, nanoelectronics, and mechatronics.

Isolated DC and AC Current Amplifier with Magnetic Field Sensor in Loop and Amorphous Ring Core

Isolated DC and AC Current Amplifier with Magnetic Field Sensor in Loop and Amorphous Ring Core

Microscopic Analysis of High Lithium-Ion Conducting Glass-Ceramic Sulfides

We explore the crystalline structure and phase transition of lithium thiophosphate (Li₇P₃S 11 ) solid electrolyte using electron microscopy and X-ray diffraction. The glass-like Li₇P₃S 11 powder is prepared by the high-energy mechanical milling process. According to the energy dispersive X-ray spectroscopy (EDS) and selected area diffraction (SAD) analysis, the glass powder shows chemical homogeneity without noticeable contrast variation at any specific spot in the specimen and amorphous SAD ring patterns. Upon heating up to 260℃ the glass Li₇P₃S 11 powder becomes crystallized, clearly representing crystal plane diffraction contrast in the high-resolution transmission electron microscopy image. We further confirm that each diffraction spot precisely corresponds to the diffraction from a particular Li₇P₃S 11 crystallographic structure, which is also in good agreement with the previous X-ray diffraction results. We expect that the microscopic analysis with EDS and SAD patterns would permit a new approach to study in the atomic scale of other lithium ion conducting sulfides.

Effect of electron irradiation on different crystal planes of titanium aluminum carbide

Ti3AlC2 is irradiated by electron-beams at the energy of 200keV for different times. For the first time, the electron irradiation resistance of Ti3AlC2 of two crystal planes ((0001) and (112¯0)) is studied. It is found that the sputtering of atoms occurs in both morphologies of the two selected planes by performing high-resolution transmission electron microscopy (HRTEM). There’s no amorphous ring observed on their selected area electron diffraction (SAED) patterns. Some weakened diffraction spots on their SAED patterns are observed. Structure transformation from α to β phase is attributed to the weakened diffraction spots on (112¯0) plane by simulated electron diffraction patterns (EDPs), indicating the high irradiation resistance of Ti3AlC2.

3D micro- and nano-machining of hydrogenated amorphous silicon films on SiO2/Si and glass substrates

We report on the hydrogen-assisted deep reactive ion etching of hydrogenated amorphous silicon (a-Si:H) films deposited using radio-frequency plasma enhanced chemical vapor deposition (RF-PECVD). High aspect-ratio vertical and 3D amorphous silicon features, with the desired control over the shaping of the sidewalls, in micro and nano scales, were fabricated in ordered arrays. The suitable adhesion of amorphous Si film to the underlayer allows one to apply deep micro- and nano-machining to these layers. By means of a second deposition of amorphous silicon on highly curved 3D structures and subsequent etching, the fabrication of amorphous silicon rings is feasible. In addition to photolithography, nanosphere colloidal lithography and electron beam lithography were exploited to realize ultra-small features of amorphous silicon. We have also investigated the optical properties of fabricated hexagonally patterned a-Si nanowire arrays on glass substrates and demonstrated their high potential as active layers for solar cells. This etching process presents an inexpensive method for the formation of highly featured arrays of vertical and 3D amorphous silicon rods on both glass and silicon substrates, suitable for large-area applications.