Phase Domain Research Articles

Designing gradient nanograined dual-phase structure in duplex stainless steel for superior strength-ductility synergy

Similar to other metallic materials, duplex stainless steel dramatically loses its advantage of high ductility as they are strengthened. Here, we produce a gradient nanograined dual-phase structure in the 2101 duplex stainless steel, thus facilitating a superior strength-ductility synergy: a yield strength of 1009.5 MPa being two times higher than that of the as-received sample, a total elongation of 23.4% and a uniform elongation of 5.9%. This novel structure is produced through a processing route of ultrasonic severe surface rolling and annealing, which realizes a superposition of gradient nanostructure and lamellar dual-phase structure with austenite and ferrite. During the tension deformation of gradient nanograined dual-phase structured duplex stainless steel, a significant accumulation of geometrically necessary dislocations occurs. These dislocations are formed to accommodate the deformation incompatibility caused by the layer-by-layer difference in strength and hardness of individual phase domains, as well as the inherent difference in properties between the austenite and ferrite domains. This results in a stronger hetero-deformation induced strengthening and hardening significantly contributing to superior mechanical properties. Our study provides a new avenue to develop advanced steels with high strength and ductility.

High dynamic reflection surface 3D reconstruction with sharing phase demodulation mechanism and multi-indicators guided phase domain fusion.

Accurate and complete 3D measurement of complex high dynamic range (HDR) surfaces has been challenging for structured light projection technique. The behavior of spraying a layer of diffuse reflection material, which will inevitably incur additional thickness. Existing methods based on additional facilities will increase the cost of hardware system. The algorithms-based methods are cost-effective and nondestructive, but they generally require redundant patterns for image fusion and model training, which fail to be suitable for practicing automated 3D measurement for complex HDR surfaces. In this paper, a HDR surface 3D reconstruction method based on sharing demodulation phase unwrapping mechanism and multi-indicators guided phase fusion strategy is proposed. The division of the exposure interval is optimized via the image entropy to generate an optimal exposure sequence. The combination of temporal-spatial binary (TSB) encoding fringe patterns with time-integration strategy and the variable exposure mode of digital mirror device (DMD)-based projector with a minimum projection exposure time of 233μs enables the proposed approach to broadly adapt complex HDR surfaces. We propose an efficient phase analysis solution called sharing mechanism that wrapped phase sequences from captured different intensity fringe images are unwrapped through sharing the same group of misaligned Gray code (MGC) decoding result. Finally, a phase sequences fusion model guided by multi-indicators, including exposure quality, phase gradient smoothness and pixel effectiveness, is established to obtain an optimum phase map for final 3D reconstruction. Comparative experiments indicate that the proposed method can completely restore the 3D topography of HDR surfaces with the images reduction of at least 65% and the measurement integrity is maintained at over 98% while preserving the measurement accuracy and excluding the outliers.

Passivity enforcement of wideband model through a new and full perturbation formulation

Passive component models are necessary to ensure numerical stability in the simulation of electromagnetic transients in power systems. However, it is challenging to represent transmission lines and cables with frequency-dependent wideband models that are accurate, efficient, and passive. This paper proposes a new method for the passivity enforcement of wideband line and cable models. The wideband models rely on pole-residue identification of characteristic admittance and propagation function in rational forms. In case the resulting models are not passive, the proposed method simultaneously applies perturbation to the residue matrices of characteristic admittance and propagation function. The set of equations related to passivity enforcement through the residues of propagation function in phase domain is complex and presented for the first time in this paper. The proposed approach minimizes the overall perturbation for maintaining passivity as opposed to the existing simplified approaches that rely on the perturbation of the residues of either characteristic admittance or diagonal elements of propagation function. The performance of the method is validated with application cases, and it is shown that it outperforms the existing methods that seek simplification in problem formulation.

On pathological orthorhombic models

AbstractThe singularity directions are very important for wave propagation in anisotropic media since they result in complications of the wavefront, amplitudes and polarization fields. Usually, the singularities are associated with shear waves. However, there is a class of anisotropic models with orthorhombic symmetry, which results in both S1S2 and PS1 types of singularities with abnormal polarization. In this case, we can have the singularity points and singularity lines of different types. Thus, we classify and analyse these models in the phase domain. The group velocity images of both singularity points and lines are also defined.

The strategy of solid-liquid phase separation diffusion with DyH3 to approach a trade-off between properties and cost for sintered Nd-Fe-B magnets

Approach a trade-off between properties and cost for sintered Nd-Fe-B magnets in grain boundary diffusion (GBD) helps widen their application. In this study, we fabricated GBD Nd-Fe-B magnets via solid-liquid phase separation diffusion (SepD) with DyH3 nanopowder as the diffusion source. Investigations and comparisons with the traditional solid-liquid phase simultaneous diffusion (SimD) magnets were made regarding the liquid phase diffusion (LPD) temperature, magnetic characteristics, microstructures, diffusion coefficient, and domain morphology of SepD magnets. In addition, the cost was calculated and compared with TbH3 SepD magnets. It is determined that the optimal LPD temperature of DyH3 was 625 °C. Compared to the SimD magnet, Dy had a faster LPD rate in the SepD magnet, which leads to a deeper diffusion depth of 1200 µm. Consequently, the SepD magnet develops more core-shell structures. Additionally, SepD could prevent the development of anti-core-shell formations in the magnet's surface region. As a result, the SepD magnet had higher comprehensive magnetic properties and coercivity temperature stability. Impressively, compared to TbH3 SepD magnets, the cost of per kOe coercivity enhancement for per kilogram magnets of DyH3 SepD magnets can be reduced by more than 50 %.

Microphase Separation with Sub-3 nm Microdomains in Comb-Like Poly(n-alkyl acrylate) Homopolymers Facilitated by Charged Junction Groups between the Main Chains and Side Chains.

The phase structure with a small domain size in polymers is expected to provide a template for lithography to fabricate electronic devices, while the uniformity and thermal stability of the phase structure are vital in lithography. In this work, we report an accurately microphase-separated system of comb-like poly(ionic liquid) (PIL)-based homopolymers containing imidazolium cation junctions between the main chain parts and the long alkyl side chains, poly(1-((2-acryloyloxy)ethyl)-3-alkylimidazolium bromide) (P(AOEAmI-Br)). The ordered hexagonally packed cylinder (HEX) and lamellar (LAM) structures with small domain sizes (sub-3 nm) were successfully achieved. Since the microphase separation was induced by the incompatibility between the main chain parts and the hydrophobic alkyl chains, the microdomain spacing of the ordered structure was independent of the molecular weight and molecular weight distribution of P(AOEAmI-Br) homopolymers and could be precisely regulated by changing the length of the alkyl side chains. Importantly, the microphase separation was promoted by the charged junction groups; thus, the phase structure and domain size of P(AOEAmI-Br) exhibited excellent thermal stability.

PHASE MORPHOLOGY OF NR, BR, AND EPDM BLENDS PRODUCED BY AN OPTIMIZED SEQUENTIAL MIXING PROCEDURE

ABSTRACT The use of EPDM in NR/BR blends for imparting ozone resistance is well known, as are the challenges of retaining desired mechanical properties in the cured rubber due to uneven distributions of carbon black and cure system across the blended polymer phases, favoring the NR/BR phase. This work explores how different sequential mixing options and mixing intensity can affect polymer phase dispersion and filler distribution, showing that excellent cured physical properties can be obtained using a commercially viable sequential mixing process where a proportion of the filler, cure system, and other compounding ingredients is first mixed into an EPDM masterbatch compound, which is subsequently used in a second mixing stage when it is combined with NR/BR at a suitable level to achieve good ozone resistance. Because only a proportion of the EPDM masterbatch is added to the second mixing stage, further filler, cure system, and other compounding ingredients are also added to reach the desired levels of the final compound. Variations of the sequential mixing process are reported, including the addition of a small amount of BR to the EPDM masterbatch and the use of an extended milling process. This study confirms that sequential mixing allows the retention of carbon black within the dispersed EPDM phase and shows how the EPDM masterbatch composition and the intensity of mixing can influence the phase morphology of EPDM/NR/BR blends. For comparison, an NR/BR control compound, typical of that used in tire sidewalls, is included in the evaluation. By applying transmission electron microscopy and atomic force microscopy imaging, phase domain sizes are evaluated quantitatively, and the Young’s moduli of the rubber phases are determined. The phase morphology is rationalized by the Hansen solubility parameters and the volume fractions of the rubber phases.

Thermochromic-based bimodal sensor for strain-insensitive temperature sensing and synchronous strain sensing

High-sensitivity flexible sensors have broad applications, but their cross-sensitivity to temperature variations and deformations often results in unwanted signal interference, significantly hindering their real-world implementation. Herein, we present a unique bimodal sensor that, for the first time, achieves thermochromic-based strain-insensitive temperature sensing while also displaying synchronous strain sensing without signal interference. This bimodal sensor is based on a dual-network hydrogel, combining a poly(ionic liquid) (PIL) with UCST behavior and a neutral polymer with LCST behavior. By adjusting the LCST/UCST network ratio, polymer concentration, and hydrophilicity of the LCST network, these sensors demonstrate a broad range of operating temperatures (∼65 ℃), ultra-high temperature detection sensitivity (10.13 %/℃), and a favorable gauge factor within the low strain region. Meanwhile, we investigated the microscopic mechanism of the bimodal sensor using SAXS and 2Dcos IR analysis, which revealed the strain-insensitive change in transmittance is due to the transition between the ellipsoidal and core–shell phase domains in the double-network (DN) hydrogel, related to subtle changes in the interactions between different polymer chain segments and H2O. This work not only expands design ideas to eliminate signal interference between temperature variations and deformations but also provides a highly sensitive sensing unit for advanced smart wearable electronics.

The NANOGrav 15 yr Data Set: Search for Signals from New Physics

The 15 yr pulsar timing data set collected by the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) shows positive evidence for the presence of a low-frequency gravitational-wave (GW) background. In this paper, we investigate potential cosmological interpretations of this signal, specifically cosmic inflation, scalar-induced GWs, first-order phase transitions, cosmic strings, and domain walls. We find that, with the exception of stable cosmic strings of field theory origin, all these models can reproduce the observed signal. When compared to the standard interpretation in terms of inspiraling supermassive black hole binaries (SMBHBs), many cosmological models seem to provide a better fit resulting in Bayes factors in the range from 10 to 100. However, these results strongly depend on modeling assumptions about the cosmic SMBHB population and, at this stage, should not be regarded as evidence for new physics. Furthermore, we identify excluded parameter regions where the predicted GW signal from cosmological sources significantly exceeds the NANOGrav signal. These parameter constraints are independent of the origin of the NANOGrav signal and illustrate how pulsar timing data provide a new way to constrain the parameter space of these models. Finally, we search for deterministic signals produced by models of ultralight dark matter (ULDM) and dark matter substructures in the Milky Way. We find no evidence for either of these signals and thus report updated constraints on these models. In the case of ULDM, these constraints outperform torsion balance and atomic clock constraints for ULDM coupled to electrons, muons, or gluons.

Detecting nonlinear information about drought propagation time and rate with nonlinear dynamic system and chaos theory

Current approaches for calculating propagation time and rate from meteorological to hydrological drought mainly focus on the time series of SPI and SRI, and most of these methods are conducted in time domain (e.g., correlation analysis) and frequency domain (e.g., wavelet analysis), which are regarded as linear statistic methods. Inaccuracy could emerge when the complexity and nonlinearity of drought propagation is addressed by such linear methods. In light of this problem, this research adopts Nonlinear Dynamic System (NDS) conducted in phase domain, which provides a nonlinear and systematic perspective on drought propagation. NDS may conditionally generate chaos (commonly known as “butterfly” phenomenon), which was not covered by previous studies on drought propagation. Assuming an underlying NDS for drought events, we demonstrate the NDS of drought propagation could generate chaos, and the nonlinear information about the propagation from meteorological to hydrological droughts can be detected within such chaotic NDS. The propagation time of 1–5 months and the propagation rate of 0.686 were found in the Pearl River Basin. In addition, the propagation time of 3, 7 and 11 months was also found in the Wei River Basin, to prove the broad applicability of our method. The results for these two basins are verified by previous studies.

Effect of A-site cation ordering on oxygen diffusion in NdBa2Fe3O8 through molecular dynamics

RE1+xBa2-xFe3O8+δ (RE = Pr, Nd, Sm, …) compounds have been presented recently as potential electrode materials for Solid Oxide Fuel Cells. Depending on the composition, these materials may present a disordered cubic perovskite phase, an ordered quintuple perovskite or a mixing of both. Such an evolution in the structure would potentially affect the oxygen ion diffusion at the core of the air electrode property. Aiming to identify the influence of such an ordering on oxygen diffusion mechanism, we perform, in the present study, molecular dynamics simulations, through which we determine both macroscopic diffusion coefficients and also extract some information about atomic scale mechanisms for different structures. Similarly to previous results on double cobaltites, we explore if the disordering of A-site cations favours or not oxygen diffusion in these ferrites. We thus studied a fully disordered cubic perovskite structure, a quintuple perovskite structure with ordering on A-site, and a nano-ordered structure which present small domains of the quintuple perovskite phase. We show that this nano-ordering, as observed experimentally, leads to a slight improvement of the oxygen ions diffusion process compared to the fully ordered structure, having still its oxygen diffusion coefficient much smaller than the one of the disordered structure.

Relationship Between The Co-Continuous Morphology of Immiscible Polymer Blends and the Structure of An In Situ Formed Graft Copolymer.

Suitable compatibilizers are essential to prepare immiscible polymer blends with stable co-continuous morphologies. From the thermodynamic point of view, such compatibilizer should not only reduce the interfacial tension, but also promote the formation of flat interface between different phases. Meanwhile, it must not hinder the coalescence of dispersed phase. Therefore, asymmetric structures are required for those block or graft copolymer compatibilizers. However, from the kinetic point of view, copolymers with asymmetric structures are prone to be dragged out from the interface and form micelles in one phase under the processing conditions, which will lose their compatibilization effects. The balance between such thermodynamic and kinetic factors remains unclear. In this paper, the relationship between the morphology of the compatibilized polystyrene/nylon 6/styrene-maleic anhydride copolymers (PS/PA6/SMA) immiscible polymer blends and the structures of the in-situ formed SMA-g-PA6 graft copolymers as well as the processing conditions are studied. Two kinds of SMA are used as compatibilizers: SMA28 (Mw = 110,000g/mol, MAH content 28wt.%) and SMA11 (Mw = 110,000g/mol, MAH content 11wt.%). After melt blending with PA6 into an internal mixer, the in-situ formed copolymer SMA28-g-PA6 has an average four PA6 side chains grafted on one SMA backbone, while that of SMA11-g-PA6 has only one PA6 side chain. Dissipative particle dynamics (DPD) simulation results indicate that both SMA28-g-PA6 copolymer and PS/PA6/SMA28 blends tend to form co-continuous structure, while SMA11-g-PA6 copolymer and PS/PA6/SMA11 blends form sea-island morphologies. However, these results are confirmed experimentally only at relatively low rotor speed of the internal mixer (60rpm). When the rotor speed of the mixer is higher (105rpm), sea-island morphologies are obtained in PS/PA6/SMA28 blends and co-continuous ones are found in PS/PA6/SMA11 systems. These results indicate that higher shear stress will favor to elongate the minor phase domains and form flat interfaces, which is benefit for the formation of co-continuous morphologies; meanwhile, high shear stress may pull the graft copolymers with asymmetric structures (SMA28-g-PA6) out from the interface of PS and PA6 and induce the formation of sea island morphologies. This article is protected by copyright. All rights reserved.

Translational Boundaries as Incipient Ferrielectric Domains in Antiferroelectric PbZrO_{3}.

In the archetypal antiferroelectric PbZrO_{3}, antiparallel electric dipoles cancel each other, resulting in zero spontaneous polarization at the macroscopic level. Yet in actual hysteresis loops, the cancellation is rarely perfect and some remnant polarization is often observed, suggesting the metastability of polar phases in this material. In this work, using aberration-corrected scanning transmission electron microscopy methods on a PbZrO_{3} single crystal, we uncover the coexistence of the common antiferroelectric phase and a ferrielectric phase featuring an electric dipole pattern of ↓↑↓. This dipole arrangement, predicted by Aramberri etal. to be the ground state of PbZrO_{3} at 0K, appears at room temperature in the form of translational boundaries. The dual nature of the ferrielectric phase, both a distinct phase and a translational boundary structure, places important symmetry constraints on its growth. These are overcome by sideways motion of the boundaries, which aggregate to form arbitrarily wide stripe domains of the polar phase embedded within the antiferroelectric matrix.

Machine Learning-Enabled Superior Energy Storage in Ferroelectric Films with a Slush-Like Polar State.

Heterogeneities in structure and polarization have been employed to enhance the energy storage properties of ferroelectric films. The presence of nonpolar phases, however, weakens the net polarization. Here, we achieve a slush-like polar state with fine domains of different ferroelectric polar phases by narrowing the large combinatorial space of likely candidates using machine learning methods. The formation of the slush-like polar state at the nanoscale in cation-doped BaTiO3 films is simulated by phase field simulation and confirmed by aberration-corrected scanning transmission electron microscopy. The large polarization and the delayed polarization saturation lead to greatly enhanced energy density of 80 J/cm3 and transfer efficiency of 85% over a wide temperature range. Such a data-driven design recipe for a slush-like polar state is generally applicable to quickly optimize functionalities of ferroelectric materials.

Robust binary fringe pattern optimization for optical three-dimensional shape measurement

Current studies show that binary fringe patterns can be optimized in the phase or intensity domain. The problem with the former is the poor sensitivity to defocusing levels and the problem with the latter is that phase errors can not be restricted efficiently. In this paper, a binary fringe pattern optimization technology, combining intensity similarity and phase similarity, is proposed to improve fringe pattern structure similarity and defocusing robustness. Moreover, a binary patch optimization framework is also proposed to solve the time-consuming problem. Simulation and experiment results show that the proposed optimization can produce binary fringe patterns with high phase quality and defocusing robustness.

An investigation into the nonlinear rheological behavior of modified asphalt binders using large amplitude oscillatory shear rheology

ABSTRACT Asphalt binders have been studied extensively with respect to their linear viscoelastic properties. From these properties, performance metrics have been derived and used for specification purposes. However, these materials are used in asphalt concrete pavements where they may experience time-dependent loads in the nonlinear regime. In the past, the vast majority of asphalt binders exhibited strong correlations between their linear and nonlinear properties and so despite this mismatch in characterization and the actual use phase domains, a system based on linear properties could be reliably deployed. More recently though, novel binders and additives have been introduced with differing relationships between linear and nonlinear behaviors. As such there is a need to characterize the asphalt binder response under large strains and use specifications that more explicitly account for the binder nonlinearity. Here, an attempt has been made to characterize the nonlinear rheological properties of asphalt binder using large amplitude oscillatory shear. The response of a single terminal blend, crumb rubber modified binder under large strains is analyzed using Lissajous-Bowditch plots while the contribution of higher harmonics is evaluated using Fourier-transform rheology. Finally, the elastic and viscous contributions are obtained using stress decomposition to an orthogonal set of Chebyshev polynomials. It is found that the relative nonlinearity increases with increasing strain and frequency under the tested conditions. The asphalt binder evaluated in this study predominantly exhibits shear thinning and either strain stiffening or softening behavior depending upon the test conditions. The applicability of time-temperature superposition in the nonlinear regime for asphalt binders is also evaluated.

Amorphous BaTiO3 Electron Transport Layer for Thermal Equilibrium‐Governed γ‐CsPbI3 Perovskite Solar Cell with High Power Conversion Efficiency of 19.96%

Compared to organic–inorganic hybrid perovskites, the cesium‐based all‐inorganic lead halide perovskite (CsPbI3) is a promising light absorber for perovskite solar cells owing to its higher resistance to thermal stress. Nonetheless, additional research is required to reduce the nonradiative recombination to realize the full potential of CsPbI3. Here, the diffusion of Cs ions participating in ion exchange is proposed to be an important factor responsible for the bulk defects in γ‐CsPbI3 perovskite. Calculations based on first‐principles density functional theory reveal that the [PbI6]4− octahedral tilt modifies the perovskite crystallographic properties in γ‐CsPbI3, leading to alterations in its bandgap and crystal strain. In addition, by substituting amorphous barium titanium oxide (a‐BaTiO3) for TiO2 as the electron transport layer, interfacial defects caused by imperfect energy levels between the electron transport layer and perovskite are reduced. High‐resolution transmission electron microscopy and electron energy loss spectroscopy demonstrate that a‐BaTiO3 forms entirely as a single phase, as opposed to Ba‐doped TiO2 hybrid nanoclusters or separate domains of TiO2 and BaTiO3 phases. Accordingly, inorganic perovskite solar cells based on the a‐BaTiO3 electron transport layer achieved a power conversion efficiency of 19.96%.

Magnetic-field-controlled growth of magnetoelastic phase domains in FeRh

Magnetic phase transition materials are relevant building blocks for developing green technologies such as magnetocaloric devices for solid-state refrigeration. Their integration into applications requires a good understanding and controllability of their properties at the micro- and nanoscale. Here, we present an optical microscopy study of the phase domains in FeRh across its antiferromagnetic–ferromagnetic phase transition. By tracking the phase-dependent optical reflectivity, we establish that phase domains have typical sizes of a few microns for relatively thick epitaxial films (200 nm), thus enabling visualization of domain nucleation, growth, and percolation processes in great detail. Phase domain growth preferentially occurs along the principal crystallographic axes of FeRh, which is a consequence of the elastic adaptation to both the substrate-induced stress and laterally heterogeneous strain distributions arising from the different unit cell volumes of the two coexisting phases. Furthermore, we demonstrate a magnetic-field-controlled directional growth of phase domains during both heating and cooling, which is predominantly linked to the local effect of magnetic dipolar fields created by the alignment of magnetic moments in the emerging (disappearing) FM phase fraction during heating (cooling). These findings highlight the importance of the magnetoelastic character of phase domains for enabling the local control of micro- and nanoscale phase separation patterns using magnetic fields or elastic stresses.

Synergetic Effect of the Iridium Complex for Morphology Optimization in Efficient and Thermally Stable Polymer Solar Cells

Active layer morphology is one of the crucial factors for achieving excellent device performance in polymer solar cells. Recently, solid additives have drawn great attention due to their great potential in morphology control, but a detailed explanation about the working mechanism of solid additive systems is still lacking. In this work, we provided an iridium complex-based solid additive (Ir-OH) to control the morphology and crystallinity of the photoactive layer by utilizing the synergetic effect of dual additives 1-chloronaphthalene and Ir-OH. The morphology of the devices with dual additives exhibited appropriate phase separation and domain size, which provided more continuous pathways for charge transport and also exhibited condensed π–π stacking and fine molecular ordering of photoactive materials, resulting in enhanced charge collection probability. Consequently, the treatment of dual additives exhibited enhanced power conversion efficiency (PCE) with enhanced exciton dissociation, charge collection, and reduced bimolecular recombination. In addition, we found that the device with dual additives exhibited strong thermal stability under a constant heat treatment at 130 °C, and the device performance retained 65% during 24 h, showing an improved PCE of 13.89%. We expected that the favorable morphology of active materials in metal complexes can suppress thermal degradation and lead to improved device performance.

The high nano-domain improves the piezoelectric properties of KNN lead-free piezo-ceramics

Due to their high Curie temperature and large dielectric constant, potassium sodium niobate-based lead-free piezo-ceramics (KNN) are regarded as one of the most hopeful piezo-ceramics candidate materials. Herein, (1-x) (K0.5Na0.5)(Nb0.96Sb0.04)O3 - x (Ba0.5Sr0.25)ZrO3 [abbreviated as (1-x) KNNS - x BSZ, x = 0, 0.01, 0.02, 0.03, 0.04 and 0.05] lead-free piezo-ceramics are prepared through chemical doping using the traditional solid phase method. The phase structure, domain structure, and microstructure of KNN ceramics have been thoroughly examined. Doping of BZS causes the formation of R-O-T phase boundaries and increases the proportion of polar nano-domains within the crystals, thus increasing the rate of motion of the domain walls and making the domains more easily deflected. The piezoelectric and dielectric properties of the material are improved simultaneously. When x = 0.04, the piezoelectric properties of ceramics reach the optimal value (d33 = 351 pC/N, TC = 305 °C, Kp = 43% and εr = 41267). This work offers a fresh concept for enhancing the overall performance of lead-free piezo-ceramics and aids in understanding the nature of doping modification of lead-free piezo-ceramics.