Domain Size Research Articles

Advancing piezoelectric properties of barium titanate ceramic through AC + DC field poling over Curie temperature

The significance of increased domain nucleation sites from smaller grain size (GS) of barium titanate (BT) ceramics on piezoelectric properties was analyzed for different types of poling, including conventional DC poling, modified DC poling, and AC plus DC poling, conducted at different poling temperatures. The AC plus DC poling conducted at 1.5 °C above the Curie temperature (T C) showed the highest piezoelectric constant (d 33) of 528 pC/N, with an average domain size of 100 nm observed after poling. The d 33 improvement was attributed to smaller domain size formation from field-induced phase transitions and homogenous distribution of point defects achieved by the AC field. Comparative analysis with larger grain BT ceramics under AC plus DC poling suggests that defects and volume fraction of grain boundaries in BT ceramics could have an effect on domain sizes.

Underestimates of Orographic Precipitation in Idealized Simulations. Part II: Underlying Causes

Abstract Warm-sector orographic precipitation in a midlatitude cyclone encountering a ridge is simulated in a “Cyc+Mtn” experiment. A second “Shear” simulation is conducted with horizontally uniform unidirectional flow over the same mountain having thermodynamic and cross-mountain wind profiles identical to those on the centerline in the “Cyc+Mtn” simulation. The relationship between integrated vapor transport (IVT) and orographic precipitation in the Mtn+Cyc case is consistent with observations, yet the same IVT in the Shear simulation produces far less precipitation. The difference between the precipitation rates in the Cyc+Mtn and Shear cases is traced to differences in the cross-mountain moisture-flux convergence and is further isolated to differences in the cross-mountain-velocity convergence over the windward slope. The winds at the ridge crest are stronger in the Shear case, leading to more velocity divergence and decreased moisture-flux convergence. The stronger ridge-crest winds in the Shear case are produced by a stronger mountain wave, which persists after being generated during the artificial startup of the Shear simulation. Initializing with a gradually ramped-up unidirectional flow and integrating to a quasi-steady state fails to adequately capture the processes regulating the leeside circulations. Even worse results are obtained if the shear flow is instantaneously accelerated from rest. An alternative microphysical explanation for the precipitation difference between the Cyc+Mtn and Shear simulations is examined using additional numerical experiments that enhance the seeder–feeder process. Although such enhancements increase precipitation, the increase is too small to account for the differences between the Cyc+Mtn and Shear simulations. Significance Statement Our results highlight the difficulty in conducting studies of mesoscale atmospheric circulations in isolation from their surrounding environment. This approach often allows for more computationally efficient and detailed analysis of the target phenomena by reducing the size of the computational domain. But, at least in the case of orographic precipitation, such isolation can significantly limit the realism of the simulated process.

Simultaneous control of ferromagnetism and ferroelasticity by oxygen octahedral backbone stretching

Abstract Coexistence of ferromagnetism and ferroelasticity in a single material is an intriguing phenomenon, but has been rarely found. Here we studied both the ferromagnetism and ferroelasticity in a group of LaCoO3 films with systematically tuned atomic structures. We found that all films exhibit ferroelastic domains with four-fold symmetry and the larger domain size (higher elasticity) is always accompanied by stronger ferromagnetism. We performed synchrotron x-ray diffraction studies to investigate the backbone structure of the CoO6 octahedra, and found that both the ferromagnetism and the elasticity are simultaneously enhanced when the in-plane Co–O–Co bond angles are straightened. Therefore the study demonstrates the inextricable correlation between the ferromagnetism and ferroelasticity mediated through the octahedral backbone structure, which may open up new possibilities to develop multifunctional materials.

Reduced energies for thin ferromagnetic films with perpendicular anisotropy

We derive four reduced two-dimensional models that describe, at different spatial scales, the micromagnetics of ultrathin ferromagnetic materials of finite spatial extent featuring perpendicular magnetic anisotropy and interfacial Dzyaloshinskii–Moriya interaction. Starting with a microscopic model that regularizes the stray field near the material’s lateral edges, we carry out an asymptotic analysis of the energy by means of [Formula: see text]-convergence. Depending on the scaling assumptions on the size of the material domain versus the strength of dipolar interaction, we obtain a hierarchy of the limit energies that exhibit progressively stronger stray field effects of the material edges. These limit energies feature, respectively, a renormalization of the out-of-plane anisotropy, an additional local boundary penalty term forcing out-of-plane alignment of the magnetization at the edge, a pinned magnetization at the edge, and, finally, a pinned magnetization and an additional field-like term that blows up at the edge, as the sample’s lateral size is increased. The pinning of the magnetization at the edge restores the topological protection and enables the existence of magnetic skyrmions in bounded samples.

Fabrication of co-continuous morphology of polysulfone/nylon 6, 6 nanocomposites by varying the concentration of organically modified clay content

A unique morphology was fabricated using melt mixing of polysulfone (PSU) and nylon 6, 6, as well as organically modified clay to produce two blended nanocomposite compositions (80/20 and 60/40 w/w) of polysulfone and nylon 6, 6. The morphology of PSU/Nylon 6, 6 blend nanocomposites with various amounts of clay has been examined using scanning electron microscope (SEM), transmission electron microscope (TEM), and wide-angle X-ray diffraction (WAXD). In the case of 80/20 (w/w) PSU/Nylon 6, 6 without clay, the Nylon 6, 6 is dispersed in the PSU matrix with an average particle size of about 6.81 micrometers (μm). After adding clay (2%, 4%, and 8%), the domain size of nylon 6, 6 decreases, although the decrease rate is much slower than initially observed. However, we discovered that when the organoclay level exceeds 2%, the matrix-domain structure transforms into a co-continuous morphology for the 60/40 (w/w) blends. The TEM studies clearly demonstrate that the organoclay preferentially positions itself in the nylon 6, 6 phase, exhibiting a high degree of exfoliation, while the PSU phase of the nanocomposites remains devoid of clay, irrespective of the amount present. This study indicates that the size of clay platelets dispersed in the PSU/Nylon 6, 6 blend plays an important role in determining the morphology and stability of these blends. Moreover, the co-continuous structures were stable against further annealing at high temperatures, thus inhibiting the coalescence of the dispersed phase in addition to reducing interfacial tension.

Stress related magnetic imaging of iron-based metallic glass produced with laser beam powder bed fusion

Additive manufacturing makes the production of bulk metallic glasses possible in thicknesses exceeding the critical casting thickness. However, a crucial challenge is the build-up of thermally induced stress, often resulting in printed parts suffering from cracking. In this study, the process parameters are optimised for printing soft-magnetic metallic glass samples of an Fe-based alloy (Fe73.8P10.6Mo4.2B2.3Si2.3C6.7), using laser beam powder bed fusion. In addition, the structural and magnetic properties of as-received and heat-treated powder are investigated and compared to those of the printed samples. Kerr microscopy is used for imaging the magnetic domains on single track cross-sections produced on top of a polished printed sample. This reveals the shape of the melt pool of a single laser track, as well as the magnetic domains around it and in other regions of the printed sample. The shape and size of the magnetic domains reflect the residual stress in the sample through the effect of magneto-elastic coupling. This magnetic contrast could be used to get further insights into how to control the development of stress during the printing process.

Two-scale concurrent simulations for crack propagation using FEM–DEM bridging coupling

The Discrete element method (DEM) is a robust numerical tool for simulating crack propagation and wear in granular materials. However, the computational cost associated with DEM hinders its applicability to large domains. To address this limitation, we employ DEM to model regions experiencing crack propagation and wear, and utilize the finite element method (FEM) to model regions experiencing small deformation, thus reducing the computational burden. The two domains are linked using a FEM–DEM coupling, which considers an overlapping region where the deformation of the two domains is reconciled. We employ a “strong coupling” formulation, in which each DEM particle in the overlapping region is constrained to an equivalent position obtained by nodal interpolation in the finite element. While the coupling method has been proved capable of handling propagation of small-amplitude waves between domains, we examine in this paper its accuracy to efficiently model for material failure events. We investigate two cases of material failure in the DEM region: the first one involves mode I crack propagation, and the second one focuses on rough surfaces’ shearing leading to debris creation. For each, we consider several DEM domain sizes, representing different distances between the coupling region and the DEM undergoing inelasticity and fracture. The accuracy of the coupling approach is evaluated by comparing it with a pure DEM simulation, and the results demonstrate its effectiveness in accurately capturing the behavior of the pure DEM, regardless of the placement of the coupling region.

Enhancing LES efficacy in wind load evaluation of low-rise buildings using synthesized inflow turbulence

In Large-Eddy Simulation (LES), the turbulence inflow can be generated synthetically, where the input value of the maximum turbulence frequency can impact the accuracy. LES efficacy can be influenced by the designated computational domain (CD) size and grid specifications. This study proposes multiple parametric studies that aim to correlate the effective parameters controlling the accuracy of numerical wind load evaluation on a low-rise building without compromising the computational cost. The study includes the efficient selection of turbulence maximum frequency (fmax) that can accurately capture the pressure fluctuation induced on the building facade. Both CD size, which involves the distances from the building to the boundary condition, and CD discretization in terms of grid size scheme and shape, are examined. The error assessment is conducted by comparing wind flow aerodynamics and evaluating the RMSE for the pressure parameters with respect to the wind tunnel test. The findings of this study suggest using fmax which can be resolved by the minimum grid size as an input in the inflow turbulence generated to accurately transport the majority of eddies when a satisfactory wavelength of 4 Δx is utilized. This study shows that computational domain size and discretization can be significant sources of error that can reach 21 %, compromising the reliability of computational wind load predictions. The current code in selecting computational minimum width and length is found to be insufficient. In addition, it is found that there are currently no recommendations for selecting the width computational dimension specifications when examining low-rise buildings oriented in an oblique wind direction. The domain grid specification induced a considerable error of 14 % in the mean pressure across the roof when tetrahedral grid shapes were used. Overall, this study's proposed recommendations can significantly impact the efficacy of computational wind load evaluation for low-rise building geometry.

Investigation of physico-mechanical, thermal, morphological, and antibacterial effects of bio-based epoxidized soybean oil plasticizer on PLA-ZnO nanocomposites as flexible food packaging

Polylactic acid (PLA) has attracted considerable attention because of its excellent properties compared to petroleum-based materials. However, improving its toughness, crystallization, and functionalities is challenging. Using a laboratory internal batch mixer, we produced unique blended nanocomposites comprising polylactic acid (PLA) as the host matrix, epoxidized soybean oil (ESO) as the plasticizer, and zinc oxide nanoparticles (ZnO NPs) as the reinforcements. The SEM-EDS test showed that neat PLA had a smooth surface, but the PLA-ZnO nanocomposite had rough micrographs and a uniform dispersion state of the nanoparticles. It was also found that adding ESO to the blend nanocomposites created a matrix droplet structure, and the size of the oil domains decreased as the ZnO content increased. All results derived from FTIR, XRD, and DSC tests were consistent with the morphological features in which ZnO NPs acted as the blend’s compatibilizer and heterogeneous nucleating agent. Our team observed that adding ESO decreased the PLA-ZnO nanocomposites’ glass transition temperature (Tg) by an average of 2 °C and increased the crystallization rate. It was also confirmed that the presence of ESO improved the flexibility and reduced the strength of the PLA. The tensile strength was further enhanced by incorporating ZnO into the blend. Adding 5 wt% of ZnO NPs increased the tensile strength of the PLA containing 10 wt% ESO by approximately 3.5 MPa. Furthermore, the tensile modulus was predicted using theoretical models; for example, the Paul model fitted with experimental findings. The addition of ESO increased the overall surface free energy of the nanocomposites. On the other hand, increasing ZnO content resulted in high contact angles and antibacterial properties of the blended nanocomposites. The favorable characteristics of the resulting films emphasized the potential use of these nanocomposite films as a promising choice for food packaging materials.

Inter-layer coupling strength in lipid bilayer can control the size of lipid domains

Inter-layer coupling strength in lipid bilayer can control the size of lipid domains

A systematic evaluation of high-cloud controlling factors

Abstract. Clouds strongly modulate the top-of-the-atmosphere energy budget and are a major source of uncertainty in climate projections. “Cloud controlling factor” (CCF) analysis derives relationships between large-scale meteorological drivers and cloud radiative anomalies, which can be used to constrain cloud feedback. However, the choice of meteorological CCFs is crucial for a meaningful constraint. While there is rich literature investigating ideal CCF setups for low-level clouds, there is a lack of analogous research explicitly targeting high clouds. Here, we use ridge regression to systematically evaluate the addition of five candidate CCFs to previously established core CCFs within large spatial domains to predict longwave high-cloud radiative anomalies: upper-tropospheric static stability (SUT), sub-cloud moist static energy, convective available potential energy, convective inhibition, and upper-tropospheric wind shear (ΔU300). We identify an optimal configuration for predicting high-cloud radiative anomalies that includes SUT and ΔU300 and show that spatial domain size is more important than the selection of CCFs for predictive skill. We also find an important discrepancy between the optimal domain sizes required for predicting locally and globally aggregated radiative anomalies. Finally, we scientifically interpret the ridge regression coefficients, where we show that SUT captures physical drivers of known high-cloud feedbacks and deduce that the inclusion of SUT into observational constraint frameworks may reduce uncertainty associated with changes in anvil cloud amount as a function of climate change. Therefore, we highlight SUT as an important CCF for high clouds and longwave cloud feedback.

Spatially-resolved in-situ/operando structural study of screen-printed BaTiO3/P(VDF-TrFE) flexible piezoelectric device

The incorporation of lead-free BaTiO3 particles into P(VDF-TrFE) provides a versatile way for tuning dielectric and piezoelectric properties. Screen-printing enables the easy production of flexible capacitors. To prevent particle aggregation, the BaTiO3 particles are functionalized with a surfactant. Initially, 60 % vol. BaTiO3 particles are deposited in the second layer out of three layers. After annealing and cooling, the particle distribution is successfully homogeneous in the whole film. After poling at 80 °C, the relative permittivity and the piezoelectric coefficient d33 significantly increase up to 159 and 8 pC/N respectively. In situ/operando spatially-resolved X-ray techniques allow exploring the structural evolution of the composite device during annealing and during an applied electric field. The application of an electric field leads to the quasi-disappearance of the P(VDF-TrFE) ferroelectric state. As a matter of fact, the interactions between the P(VDF-TrFE) and the surfactant may limit the rotation of P(VDF-TrFE) chains near the particles. Hence, paraelectric polymers could be chosen on a mechanical or economic basis for the matrix in piezoelectric composite devices. Regarding BaTiO3, the lattice strain evolves from an extrinsic strain at RT to an intrinsic strain after annealing and cooling. At the cooled state, the tetragonality c/a is higher than 1.01, leading to improved piezoelectric properties. The increase of the average domain size leads to the increase of the composite permittivity. Finally this knowledge facilitates the development of tailored flexible piezoelectric composite devices.

A compact open boundary treatment for a pure thermal plume by direct numerical simulation

This study introduces a novel open boundary treatment method for simulating thermal plumes in natural convection, utilizing a combination of the Perfectly Matched Layer (PML) and local one-dimensional inviscid (LODI) methods within a compressible flow solver for Direct Numerical Simulation (DNS). This innovative approach significantly reduces the size of the computational domain yet effectively captures the complex transition from laminar to turbulent flow. Validation of the proposed methodology includes comparisons with existing empirical formulations, experimental data, and well-resolved DNS results, incorporating both time-averaged and spectral analyses. Additionally, the buoyancy-induced laminar-turbulent transition is investigated to enhance understanding of the dynamics and behaviors of thermal plumes. The findings offer insights into optimizing computational efficiency without compromising the accuracy needed to analyze intricate fluid dynamics in thermal engineering applications.

Excellent low-E energy storage and fluorescence temperature sensing features in Bi0.5Na0.5TiO3-based transparent ceramics

Transparent dielectric ceramics with ultrafast discharge rates and gigantic power densities are ideal candidates for transparent pulse capacitors (TPCs). However, the requirement of a high external electric field and inferior temperature stability hinder practical applications. (Bi0.5Na0.5)TiO3-based ceramics exhibit large polarization and two characteristic dielectric peaks, easy to obtain high energy-storage density under low electric fields (low-E) and maintain stable energy-storage performance (ESP) within a wide temperature range. However, their low optical transmittance (T%) limits their development into TPCs. In this work, to concurrently obtain high T% and excellent ESP and stability under low-E conditions, we propose a collaborative optimization strategy for determining the regulations of grain size, bandgap energy and domain structure. The results show that the pellucidity and energy-storage characteristics improve with decreasing grain and domain sizes. A relatively high T% of 45.6 % (at 710 nm) and recoverable energy-storage density (Wrec ∼ 3.46 J cm−3 at 197 kV cm−1) are obtained for the (1-x)[0.85(Bi0.5-3yNa0.5-yYb3yHoyTiO3)-0.15SrZrO3]-xBaHfO3 ceramics. Additionally, the dielectric temperature stability also results in splendid storage temperature stability (ΔWrec/Wrec < 3.1 % in the range of 0–200 °C). Importantly, codoping Ho/Yb in the ceramics induces excellent fluorescence temperature sensing feature. The multifunctional TPCs have application potential in the field of search and rescue signal transmission, providing ideas for developing novel optoelectronic devices.

MuSK-BMP signaling in adult muscle stem cells maintains quiescence and regulates myofiber size.

MuSK, in its role as a BMP co-receptor, regulates adult muscle stem cell quiescenceThe MuSK-BMP pathway acts cell autonomouslyIncreased muscle size and function with preservation of myonuclear density and stemness in mice with attenuated MuSK-BMP signaling.

Analysis of the APR1400 Benchmark Using High-Fidelity Pin-Wise Core Calculation Codes

The KEPCO Nuclear Fuel Company (KNF) has undertaken considerable efforts to improve the KARMA/ASTRA nuclear design code system to meet the increasing demand for high-fidelity core analyses. Through years of effort, the KARMA lattice transport code based on the method of characteristics (MOC) has evolved into KARMA2, a direct whole core calculation code using a 3D calculation method based on planar (2D) MOC principles. Simultaneously, ASTRA2, designed as the successor to the ASTRA nodal diffusion code, has been developed. ASTRA2 exhibits enhanced capabilities in multigroup pin-by-pin core calculations, achieved by decoupling the 3D whole core problem into a series of planar and axial problems. The domain size of each axial problem can be adjusted, ranging from pin-cell to assembly scale, thereby optimizing efficiency. The verification and validation process of the KARMA2/ASTRA2 code system involves various benchmark problems and measured data from operational PWRs. In this study, the APR1400 benchmark analysis was performed to verify the neutronics calculation capabilities of both codes. The results underscore the reliability and accuracy of the KARMA2 solutions across various core conditions, exhibiting close agreement with the McCARD reference solutions. Similarly, the ASTRA2 results agree with the corresponding KARMA2 results. These successful results demonstrate the high-fidelity core calculation capabilities of KNF’s next-generation code system.

Ionic liquid mediated one-step perpendicular assembly in block copolymer thin films for ultrafiltration membrane applications

The rapid rise of oil and gas, petrochemical, food processing, and pharmaceutical industries has added a complex mixture of contaminants like oil, particulates, metals, and other organic compounds to wastewater. Multipurpose membranes with precise pore structure can offer a solution to this problem and block copolymers (BCP) can be used to achieve such structures. Achieving vertical assembly of BCP domains provides a perfect template for developing uniform through film channels for separation and transport of material, besides being useful for the rectification of defects in photolithography patterns. Producing such morphologies may require extensive film/substrate processing and is not always feasible for scale-up. With this article, we demonstrate a facile solution casting method to induce vertical domain assembly in as-cast diblock copolymer thin films in the presence of an ionic liquid (IL) additive that preferentially segregates to one block and neutralizes interfacial interactions. We also show the tunability of domain sizes by controlling the additive concentration. These vertically aligned morphologies are important for the development of next-generation lithographic techniques and form excellent templates for ultrafiltration membranes with uniform pore sizes. This article demonstrates how IL additives can be used to obtain stable non-equilibrium morphologies in as-cast BCP films and the effect of BCP molecular mass, block volume fractions, and IL content on self-assembly.

Amplifying High‐Performance Organic Solar Cells Through Differencing Interactions of Solid Additive with Donor/Acceptor Materials Processed from Non‐Halogenated Solvent

AbstractDeveloping non‐halogenated solvent‐processed organic solar cells (OSCs) demands precise control over the bulk‐heterojunction (BHJ) morphology of the photoactive layer. However, the limited solubility of halogen‐free solvents to photoactive materials hinders microstructure morphology fine‐tuning for boosting photovoltaic performance. This study not only examines the debated intermolecular interactions between the DBrDIB solid additive and photoactive materials but also analyzes the substantial influence of volatile solid additive on the BHJ morphological properties. The DBrDIB effectively restricts the excessive aggregation of Y6‐BO and regulates the phase separation, which is attributed to strong intermolecular interactions with Y6‐BO and rapid quenching during morphology formation. It then achieves a well‐mixed D/A phase with favorable domain size, resulting in a balanced aggregation and dispersion of D/A, ultimately leading to markedly enhanced charge transfer and transport as well as suppressed charge recombination. The transformative use of the o‐xylene/DBrDIB solvent system propels PM6:Y6‐BO and PM6:Y6‐HU OSCs to impressive efficiencies of 17.9% and 19.1%, respectively, outperforming those of the control devices. These findings provide crucial insights into theoretical and experimental areas, offering actionable guidelines for designing high‐performance OSCs processed from halogen‐free solvent.

Integrated Framework to Model Microstructure Evolution and Decipher the Microstructure-Property Relationship in Polymeric Porous Materials.

Unraveling the microstructure-property relationship is crucial for improving material performance and advancing the design of next-generation structural and functional materials. However, this is inherently challenging because it requires both the comprehensive quantification of microstructural features and the accurate assessment of corresponding properties. To meet these requirements, we developed an efficient and comprehensive integrated modeling framework, using polymeric porous materials as a representative model system. Our framework generates microstructures using a physics-based phase-field model, characterizes them using various average and localized microstructural features, and evaluates microstructure-aware properties, such as effective diffusivity, using an efficient Fourier-based perturbation numerical scheme. Additionally, the framework incorporates machine learning methods to decipher the intricate microstructure-property relationships. Our findings indicate that the connectivity of phase channels is the most critical microstructural descriptor for determining effective diffusivity, followed by the domain shape represented by curvature distribution, while the domain size has a minor impact. This comprehensive approach offers a novel framework for assessing microstructure-property relationships in polymer-based porous materials, paving the way for the development of advanced materials for diverse applications.

Direct observation of twisted stacking domains in the van der Waals magnet CrI3

Van der Waals (vdW) stacking is a powerful technique to achieve desired properties in condensed matter systems through layer-by-layer crystal engineering. A remarkable example is the control over the twist angle between artificially-stacked vdW crystals, enabling the realization of unconventional phenomena in moiré structures ranging from superconductivity to strongly correlated magnetism. Here, we report the appearance of unusual 120° twisted faults in vdW magnet CrI3 crystals. In exfoliated samples, we observe vertical twisted domains with a thickness below 10 nm. The size and distribution of twisted domains strongly depend on the sample preparation methods, with as-synthesized unexfoliated samples showing tenfold thicker domains than exfoliated samples. Cooling induces changes in the relative populations among different twisting domains, rather than the previously assumed structural phase transition to the rhombohedral stacking. The stacking disorder induced by sample fabrication processes may explain the unresolved thickness-dependent magnetic coupling observed in CrI3.