Inhomogeneous Structure Research Articles

Changes in the structure of the amorphous phase under heat treatment and deformation

The influence of heat treatment and deformation on the change in the structure of amorphous alloys Co67Fe7Si12B9Nb5, Al87Ni8Y5, Al88Ni6Y6, Al87Ni8Gd5, Al87Ni8La5, Zr50Cu15Ti16Ni19 obtained by melt quen-ching has been studied. It has been established that both heat treatment and deformation lead to the for-mation of a heterogeneous structure, while structure inhomogeneities can be due to formation the regions both with different concentrations of components (during heat treatment) or/and with different density (free volume concentration). At the early stages of crystallization, the phase composition of the emerging struc-ture depends on the type of impact on the amorphous structure and processing parameters (temperature, type and degree of deformation). The sizes of nanocrystals and the fraction of the nanocrystalline component depend on the prehistory of the sample.

Lattice dynamics and elastic waves scattering by surrogate atoms in quasi-one dimensional atomic assemblies

An analytical and numerical formalism is developed to study the influence of the various positions of substitution atoms B on the scattering and transmission vibration modes in quasi-1D monatomic structures A. The matching technique is employed to calculate the dynamical properties and transmittance spectra of two substituted atomic sites. The theoretical formalism gives a complete description of the lattice dynamics and the vibration-waves propagation in the presence of the impurity sites. Numerical calculations are performed for three different positions of the two substituted atoms B in the low-dimensional structure consisting of double monatomic parallel chains. First, we examine the position where the two B atoms are adjacent in the y-direction, afterwards, we place the two sites side by side in the x-direction. Lastly, the two sites are placed in oblique configuration. The obtained results show that phonons associated to the inhomogeneous structures are strongly dependent on the scattering frequency, elastic force parameters and the position of the atomic substituted sites. In the three considered positions, the presence of the B atoms gives rise to localized vibration effects. The fluctuations observed in the vibration spectra are related to resonances due to the coherent coupling between travelling phonons and the localized vibration modes in the neighborhood of the impurity sites.

Effect of inhomogeneous structure on the water desalination performance of graphitic carbon nitride nanochannels: A molecular dynamics study

The transport behaviors of aqueous solution in two-dimensional (2D) nanomaterial-based separation membranes are correlated with the structure of the nanoconfined geometry. However, little is known about the impact of asymmetric structures on the transport behavior of aqueous solutions in membranes. In this work, we use molecular dynamics (MD) simulations to investigate the transport behaviors of aqueous solution in non-parallel stacked graphitic carbon nitride (g-C3N4) nanochannels. Interestingly, the non-parallel stacking of g-C3N4 could lead to the local aggregation of water, resulting in an inhomogeneous density distribution within the nanochannel. The high-density region in g-C3N4 nanochannel significantly disrupted the continuum fluid of water. Moreover, the inhomogeneous density distribution of water could impede ion transport in the non-parallel g-C3N4 nanochannel. It was found that ions cannot maintain compact hydration structures in the high-density region. This work reveals the unique properties of slightly tilted membrane structures, providing novel perspective for the design of next-generation nanofluidic devices.

Single-crystalline oligomer-based conductors modeling the doped poly(3,4-ethylenedioxythiophene) family.

Conductive polymers with highly conjugated systems, such as the doped poly(3,4-ethylenedioxythiophene) (PEDOT) family, are commonly used in organic electronics. However, their structural inhomogeneity with various chain lengths makes it difficult to control their conductivities and structural details. On the other hand, low-molecular-weight materials have well-defined structures but relatively narrow conjugate areas with a limited range of Coulomb repulsion between carriers (Ueff), which hamper the flexible control of conductivities. To bridge this gap, we developed oligomer-based conductors, which are intermediate materials between polymers and low-molecular-weight materials. Using a library of single-crystal charge-transfer salts of oligo(3,4-ethylenedioxythiophene) (oligoEDOT) analogs that model the doped PEDOT family, we have investigated the structure-determining factors affecting their conductivities, such as counter anion variations, lengths of oligomer donor, and band fillings. Through the screening study, we developed oligoEDOT analogs with tunable room temperature conductivities by several orders of magnitude, including a metallic state above room temperature. In this study, we consistently evaluated the electronic structural insights by first-principles calculations and revealed that Ueff is the dominant factor that determines the relationship between the structures and conductivities. The unique features of oligoEDOT conductor systems with widely variable Ueff can differentiate these systems from strongly electron-correlated systems.

Effect of Decompression Hole Structure Design on Stress Inhomogeneity of Stainless Steel Base Force Transducers

In order to reduce the stress inhomogeneity of the stainless steel base force transducer, the force transducer structure with decompression holes of different depths and different hole morphologies is designed in this paper and compared with the traditional force transducer structure without decompression hole design. According to the finite element analysis theory, the stress inhomogeneity level under different pressures and different structures is tested using a simulation platform. When a flat-bottomed hole is used and the depth of the decompression hole is 7 mm, the stress inhomogeneity of the inner ring of the force measurement structure is 32.77% of the original scheme, and the stress inhomogeneity of the outer ring is 90.12% of the original scheme. The simulation results show that the use of a suitable decompression hole structure can help to reduce the stress inhomogeneity of the force measurement structure. This work provides a new idea in the field of sensor optimization.

Influence of the coagulation bath on the nanostructure of cellulose films regenerated from an ionic liquid solution.

Cellulose membranes were prepared from an EMIMAc ionic liquid solution by nonsolvent-induced phase separation (NIPS) in coagulation baths of water-acetone mixtures, ethanol-water mixtures and water at different temperatures. High water volume fractions in the coagulation bath result in a highly reproducible gel-like structure with inhomogeneities observed by small-angle neutron scattering (SANS). A structural transition of cellulose takes place in water-acetone baths at very low water volume fractions, while a higher water bath temperature increases the size of inhomogeneities in the gel-like structure. These findings demonstrate the value of SANS for characterising and understanding the structure of regenerated cellulose films in their wet state. Such insights can improve the engineering and structural tuning of cellulose membranes, either for direct use or as precursors for carbon molecular sieve membranes.

3D Polarisation of a Structured Laser Beam and Prospects for its Application to Charged Particle Acceleration

A Structured Laser Beam (SLB) is a type of optical beam with spatially inhomogeneous 3D polarisation structures. Generating SLBs from vector beams allows the creation of Hollow Structured Laser Beams (HSLB) with a dark central core. In this way, atypical electric and magnetic field vectors, which are purely longitudinally polarized in the dark zones of the beam, are obtained. The SLB spatial distribution can also include regions with both the electric and magnetic fields longitudinally polarized and oriented in the same or opposite directions. The SLB has a transverse distribution similar to that of a Bessel beam but can theoretically propagate to infinity, therefore giving the potential to generate strong, longitudinally oriented electric fields over long distances, which could possibly allow the acceleration of charged particles. The results of the study of this phenomenon, including simulations of the spatial distribution of the electromagnetic field components, are presented in this paper.

Композиционные мембраны для обессоливания воды

Methods of coatings forming on the surface of a poly(ethylene terephthalate) track-etched membrane by magnetron and electron-beam sputter deposition of polytetrafluoroethylene in vacuum are considered. It is established that the involve of these modification methods leads to the formation of composite membranes consisting of two layers, one of which is the original track-etched membrane, characterized by an average level of hydrophilicity. The second layer has a hydrophobic nature. The contact angle of wettability by water of this layer varies depending on its thickness and the modification method used. It is shown that deposition of coatings by magnetron sputtering of polytetrafluoroethylene leads to smoothing of structural inhomogeneities of the surface of the initial membrane. Deposition of coatings by electron-beam dispersion of polymer, on the contrary, causes an increase in surface roughness. The observed differences in the morphology of the composite membranes surface layer are related to the size of the deposited polymer nanostructures. Nanostructures formed on the surface of track-etched membranes, when polytetrafluoroethylene is dispersed under the action of electron beam, have greatly large sizes. A significant increase in roughness due to the increase in the size of nanostructures makes it possible to obtain coatings with high- and superhydrophobic properties. It is shown that composite membranes consisting of a hydrophilic base with a hydrophobic coating deposited on the surface provide higher separation selectivity during desalination of an aqueous solution of sodium chloride by membrane distillation compared with the initial poly(ethylene terephthalate) track-etched membrane. In addition, the performance of two-layer composite membranes in the process of membrane distillation due to low resistance to mass transfer is higher in comparison with a track-etched membrane made of polypropylene.

Determination of interaction parameters in a bottom-up approach employed in reactive dissipative particle dynamics simulations for thermosetting polymers.

The limitations in previous dissipative particle dynamics (DPD) studies confined simulations to a narrow resin range. This study refines DPD parameter calculation methodology, extending its application to diverse polymer materials. Using a bottom-up approach with molecular dynamics (MD) simulations, we evaluated solubility parameters and bead number density governing nonbonded interactions via the Flory-Huggins parameter and covalent-bonded interactions. Two solubility parameter methods, Hildebrand and Krevelen-Hoftyzer, were compared for DPD simulations. The Hildebrand method, utilizing MD simulations, demonstrates higher consistency and broader applicability in determining solubility parameters for all DPD particles. The DPD/MD curing reaction process was examined in three epoxy systems: DGEBA/4,4'-DDS, DGEBA/MPDA and DGEBA/DETA. Calculations for the curing profile, gelation point, radial distribution function and branch ratio were performed. Compared to MD data for DGEBA/4,4'-DDS, the maximum deviation in secondary reactions between epoxy and amine groups according to DPD simulations with Krevelen-Hoftyzer was 14.8%, while with the Hildebrand method, it was 1.7%. The accuracy of the DPD curing reaction in reproducing the structural properties verifies its expanded application to general polymeric material simulations. The proposed curing DPD simulations, with a short run time and minimal computational resources, contributes to high-throughput screening for optimal resins and investigates mesoscopic inhomogeneous structures in large resin systems.

On modeling radiation-induced charge effects in objects of complex geometry

Algorithms for supercomputer modeling of the radiation-induced charge effects in materials of a complex multimodal structure are constructed. A geometric model of an object is created using Stilinger-Lubachevsky algorithms for objects of complex geometry. The model includes a system of detectors for statistical evaluation of functionals on the space of solutions of the photon-electron cascade transport equations. Visualization of simulation results is carried out using the three-dimensional approximation based on the neural network technology. The thechnique of mathematical simulating the generation and development of a photon-electronic cascade in a medium is used. The examples of results of calculations of the charge effects in a fragment of a bimodal material are presented. The results of the calculations show that the spatial distribution of the radiation-induced charges has a sharply inhomogeneous structure caused by the presence of boundaries of materials with different radiation properties.

Application of Green’s Functions of Stratified Media to Calculate the Radiation Field of Antennas Near a Reflecting Surface

We are examining a method of calculating the electromagnetic field emitted by an aperture antenna near a reflecting boundary using the Huygens element model. We utilize the Green’s tensor functions to calculate the electromagnetic field, considering the inhomogeneous structure of the medium under the boundary and taking into account electric and magnetic currents as a source. Unlike standard electromagnetic modeling, programmes that require determination of the field components in the entire area, our approach allows calculating the distribution of amplitude and phase of all field components only in the desired area. We also consider the parameters of the layered medium under the reflecting boundary in recording the characteristic parts of the Green’s functions, leading to multiple gains in computing resources. Our method and the ANSYS HFSS programme are used to calculate the electromagnetic field patterns. We found that using a volumetric sampling grid in the ANSYS HFSS programme leads to phantom defects in the field structure and its asymmetry, even with a symmetrical position of the sources. We present field patterns for both the Huygens element and the open end of a rectangular waveguide for different types of reflecting boundary. We assert the validity and physical plausibility of the obtained solutions. We also consider the change in the reflection coefficient from the boundary, taking into account the curvature of the phase in front of the radiator in the near zone. This proposed model can be used to develop domestic software for electromagnetic modeling.

Multilayered Inhomogeneous Beams under Torsion and Bending: An Analytical Study of Energy Dissipation

The present theoretical paper is devoted to the problem of energy dissipation in multilayered inhomogeneous beam structures of visoelastic behaviour. In particular, our attention is concentrated on studying the energy dissipation for the case of a beam that is loaded simultaneously in torsion and bending. Both torsion and bending moments which are applied on the beam change with time so that the angles of twist and rotation of the beam end vary continuously with time. The viscoelastic mechanical behaviour of the beam under torsion is treated by a viscoelastic model that has two linear springs and a linear dashpot. The model is under time-dependent shear stress. The viscoelastic behaviour of the beam under bending is modelled in a similar way. An analytical approach of deriving the energy dissipation is applied. The approach treats a multilayered beam that has an arbitrary number of layers of different thicknesses and material properties. The layers are longitudinally inhomogeneous. An investigation of the energy dissipation is carried-out to clarify the effect of the parameters of the time-dependent bending and torsion moments, the material inhomogeneity and the beam size on the energy dissipation.

Simulation of Structure Inhomogeneity and Stress Behavior Generation in Titanium Alloys During Pulsed Electromechanical Treatment

Simulation of Structure Inhomogeneity and Stress Behavior Generation in Titanium Alloys During Pulsed Electromechanical Treatment

Optical Approach for Mapping the Intercalation Capacity of Porous Electrodes.

The intercalation capacity of a porous electrode in real batteries is not uniform spatially due to the inevitable structural and compositional inhomogeneity and site-dependent ion and electron transport features. Reliable methods to quantify the capacity distribution are highly desirable but absent so far in battery research. In this paper, a novel optical technique, oblique incident reflection difference (OIRD), was employed to monitor in situ the electrochemical ion (de)intercalation behavior of Prussian blue analogue (PBA) porous films. The OIRD signal responded synchronously to the ion (de)intercalation, and the change in the OIRD signal (ΔI) was positively correlated with the local electrochemical capacity, thereby enabling mapping of the spatially resolved ion storage capacity of the films. Optical analysis further showed that the OIRD response originated from the ion (de)intercalation-induced dielectric constant change of PBA films. This work therefore offers an intriguing in situ and spatially resolved tool for the study of rechargeable batteries.

Understanding the Influences of Laser Perforation on Thick Electrodes for Lithium Ion Batteries Via 3D Microstructure Simulations

Laser perforation is a precise technique to decrease ionic diffusion limitations by selectively removing material with spatial precisions of tenth of micrometres. It is mainly applied in thick electrodes to improve foremost rate capability, as well as cycle stability, Li plating detention and wetting efficiency.[1] [2]Mostly, holes are created in the batteries through-direction leading to a material removal of about 5%-10% of the initial load. This removal creates inhomogeneous diffusion channels especially into layers close to the current collector, as opposed to a homogeneous increase in porosity.It is of interest to find an optimal trade-off between the competing factors of capacity loss and increase in ion conductivity due to material ablation. Optimization of structuring parameters requires intimate knowledge of electrode and material properties. However, there is a lack of an adequate description of the inhomogeneous structure and its influence on the electrochemical performance. [1]In our presentation we show a detailed 3D microstructure resolved simulation study, examining the influencing parameters for laser perforation. The data suggests, that perforating holes with small diameter at a short distance, which results in an ablation of ca. 8% gives generally desirable improvements for the rate capability. Laser perforation is distinctively favourable in contrast to a raise in homogenous porosity.Moreover, the microstructure resolved simulation also allows for a detailed analysis of different hole shapes and hole misalignment in electrodes after stacking. We evaluate the impact of different configurations on the electro chemical performance. [3]

Compression behavior of the wood-inspired cellular structure of acrylonitrile butadiene styrene

Abstract In wood science and technology, researchers increasingly focus on the additive manufacturing in different aspects through assembly, mechanical, and physical characterization of the printed parts. One of the main parameters influence the wood features is the inhomogeneity of cellular structure. The effect of dislocation on the compression behavior was evaluated over the wood-inspired cellular structure. The 4.4 × 4.4 mm cross-cut–sized cell (0.8 mm cell wall thickness and 2.8 mm lumen diameter) with 10 mm thickness was arrayed by 6 columns and 3 rows to design the control model. The middle row was 0.8, 1.6, and 2.4 mm dislocated to obtain irregular models. Objects were fabricated through the deposition of acrylonitrile butadiene styrene filament using DaVinci 1.0 all in one three-dimensional printer. The effect of printing orientation (vertical and horizontal) on compression behavior was also figured out. The compression test was performed to obtain the load–deformation behavior of samples. According to the results, the horizontally printed samples presented better performance. Furthermore, horizontal alignment, rectilinear infill type, 90 % infill density, and 0.2 mm layer height combination presented the highest (5719 N) load-carrying capacity. The statistical analysis (P < 0.05) figured out that cell dislocation has significant influences on mechanical properties.

On the Existence of an Infinite Spectrum of Damped Leaky TE-Polarized Waves in an Open Inhomogeneous Cylindrical Metal–Dielectric Waveguide Coated with a Graphene Layer

We consider the problem of leaky waves in an inhomogeneous waveguide structure covered with a layer of graphene, which is reduced to a boundary value problem for the longitudinal components of the electromagnetic field in Sobolev spaces. A variational statement of the problem is used to determine the solution. The variational problem is reduced to the study of an operator function. The properties of the operator function necessary for the analysis of its spectral properties are investigated. Theorems on the discreteness of the spectrum and on the distribution of the characteristic numbers of the operator function on the complex plane are proved.

Polydopamine-modified cellulose-based composite separator for inhibiting dendritic growth of lithium metal batteries

The inhomogeneous pore structure and lack of polar groups in lithium metal battery separators lead to uneven transport of Li+ through the separator, the uneven flux of Li+, and eventually the formation of lithium dendrites. Therefore, to provide uniform Li+ transport and inhibit the growth of lithium dendrites, a polydopamine-modified cellulose membrane (PDA-CM) was created by oxidative self-polymerizing dopamine and binding it to the surface and interface of the cellulose membrane through hydrogen bonds. The successful preparation of the PDA-CM separator by PDA-modified cellulose membrane by hydrogen bonds was proved by the FT-IR test. TGA, thermal shrinkage test, tensile strength test, FESEM, and porosity test results indicated that neither the PDA-CM nor the CM separators shrank at 160 °C, the PDA-CM separator also had better tensile strength (Stress = 31.1 MPa), and uniform pores (Porosity = 54.95 %) with homogeneous Li+ flux. The polar functional groups (-NH- and -OH) in PDA improved the electrolyte uptake rate (Electrolyte uptake rate = 469.77 %), the electrolyte retention (Electrolyte retention = 409.04 %), and electrolyte wettability (Contact angle = 18.35°) of the separator and promoted the uniform distribution of Li+ through the PDA-CM separator. In addition, the PDA-CM separator had better ionic conductivity (1.54 × 10−3 S·cm−1) and lower impedance (849 Ω). The catechol on the PDA molecule created strong adhesion between the separator and the lithium metal, reduced the local tension on the surface of the lithium metal and inhibited dendrite growth. The lithium metal anode remained smooth after cycling. The lithium metal battery prepared by the PDA-CM separator showed decent cycle performance and remained a high capacity retention rate (90.48 %) after 100 cycles. This study provides a new solution for the modification of cellulose-based lithium metal battery separators, which can achieve uniform transmission of Li+, inhibit the growth of lithium dendrites, and improve battery performance.

Optimization of nanostructured Zr doped bismuth oxide (Bi2O4) thin films for physical and biological properties

Sol-gel dip-coating deposition was used to create Zr-doped Bi2O4 thin films with Zr in the range of 1-5 wt%. The monoclinic Bi2O4 phase was confirmed by an X-ray diffraction (XRD) analysis. After Zr doping in Bi2O4, there was a minor change in crystallite size and a reduction in the lattice parameters. UV-VIS-NIR spectrophotometry showed a decrease in the band gap of Bi2O4. These films were useful as absorbing layers for solar cells due to their decreased band gap, which allowed them to absorb a wide range of visible portions of the electromagnetic spectrum. SEM micrographs for each film showed an almost spherical-like appearance. The agglomeration of Bi2O4 into bigger particles with a lower surface area may be the cause of the decrease of the dielectric constant with an increase in Zr concentration. The AC conductivity of thin films increased with an increase in Zr concentration. Electrochemical charge-discharge test findings revealed the specific capacitance, power density, and energy of Zr-doped Bi2O4. Magnetic measurements of Zr-doped Bi2O4 nanostructures revealed ferromagnetic ordering at the surrounding temperature. The rise in saturation magnetization that occurred with an increase in Zr doping emerged from the formation of defects in the Bi2O4 lattice caused by oxygen vacancies and structural inhomogeneity, which promoted the growth of bound magnetic polarons. Additionally, Zr doping improved the photocatalytic qualities of Bi2O4. The enhanced photocatalytic activity of Zr-doped Bi2O4 nanoparticles was attributed to the higher UV-VIS light absorption and the reduced recombination rate of the photoinduced electron-hole pair making it a promising substance for water filtration. When Bi2O4 was combined with Zr, it inhibited the growth of Staphylococcus aureus (S. aureus), which was gram-positive while, Klebsiella pneumoniae (K. pneumoniae), Pseudomonas aeruginosa (P. aeruginosa) and Escherichia coli (E. coli) were gram-negative bacterial stains. Zr doping in Bi2O4 improved its antibacterial action.

An order of magnitude enhancement in ductility of a metallic glass of peak rejuvenation

Exceptional ductility has been a long-sought-after property of metallic glasses, and cryogenic thermal cycling rejuvenation has been actively explored to enhance the plasticity of metallic glasses. By tuning the holding time and number of cycles of cryogenic thermal cycling processing, we here report a (Zr0.8125Cu0.1875)79Ni10Al10Nb1 metallic glass of peak rejuvenation with the plasticity of an order of magnitude higher than that of the as-cast glass, without sacrificing its strength. Characterizations indicate that the loose atomic packing of the metallic glass of peak rejuvenation facilitates the generation and proliferation of shear bands in the early stage of plastic deformation, and the resultant dense shear bands tend to be deflected due to their interaction with each other and/or structural inhomogeneity in the matrix, hindering their rapid propagation and in turn increasing the plasticity. The combination of high relaxation enthalpy and high plasticity obtained here is outstanding from the previous rejuvenated metallic glasses which have either high relaxation enthalpy or high plasticity, while never both. This work identifies an alloy system with very high efficiency in plasticity improvement through cryogenic thermal cycling rejuvenation and represents a promising guide for improving the plasticity of metallic glasses.