Interfacial Energy Difference Research Articles

Eutectoid decompositions in Ce‐containing ABO3 perovskites: Part II, the case of divorced growth in CeCrO3

AbstractA eutectoid phase transformation was exhibited by the perovskite CeCrO3 when heated in air. The kinetics of the reaction, microstructure of the product, and mechanisms of the transformation were studied using thermogravimetric analysis, X‐ray and Raman spectroscopy, X‐ray diffraction, and electron microscopy. Fluorite CeO2 and corundum Cr2O3 were formed from the decomposition of CeCrO3. The CeO2 particles were porous and polycrystalline, a consequence of nucleation, growth, and impingent of CeO2 domains on the CeCrO3 particles. Anisotropic growth is indicated by the morphology of the CeO2 grains, while the Cr2O3 particles were single crystals without any crystallographic orientation relationship to the parent phase. Unlike the CeAlO3 eutectoid, the microstructure comprised of CeO2 and Cr2O3 show no characteristics of a microstructure formed by cooperative growth. The disparity between the eutectoid reactions in CeCrO3 and CeAlO3 is attributed to a difference in interfacial energy between the fluorite and sesquioxide phases (i.e., CeO2/Al2O3 versus CeO2/Cr2O3).

Grain boundary segregation predicted by quantum-accurate segregation spectra but not by classical models

In alloys, solute segregation at grain boundaries is classically attributed to three driving forces: a high solution enthalpy, a high size mismatch, and a high difference in interfacial energy. These effects are generally cast into a single scalar segregation energy and used to predict grain boundary solute enrichment or depletion. This approach neglects the physics of segregation at many competing grain boundary sites, and can also miss electronic effects that are energetically significant to the problem. In this paper, we demonstrate that such driving forces cannot explain, nor thus predict, segregation in some alloys. Using quantum-accurate segregation spectra that have recently become available for some polycrystalline alloys, we predict strong segregation for gold in aluminum, a solvent-solute combination that does not conform to classical driving forces. Our experiments confirm these predictions and reveal gold enrichment at grain boundaries that is two orders of magnitude over the bulk lattice solute concentration.

The Influence of Site of Co and Holes in PCD Substrate on Adhesive Strength of Diamond Coating with PCD Substrate

Polycrystalline diamond (PCD) prepared by the high temperature and pressure method often uses Co as a binder, which had a detrimental effect on the cutting performance of PCD, thus Co needed to be removed. However, the removal of Co would cause residual holes and also make the cutting performance of PCD poorer. To address this issue, hot filament chemical vapor deposition (HFCVD) was used. During deposition, the residual holes cannot be filled fully, and Co would diffuse to the interface between CVD diamond coatings and the PCD substrate, which influenced the adhesive strength of the diamond coating with the PCD substrate. In order to investigate the influencing mechanism, both experiments and the density functional theory (DFT) calculations have been employed. The experimental results demonstrate that Co and the holes in the interface would reduce the interfacial binding strength. Further, we built interfacial structures consisting of diamond (100), (110), (111) surfaces and PCD to calculate the corresponding interfacial binding energy, charge density and charge density difference. After contrast, for Co and the holes located on the (110) surface, the corresponding interfacial binding energy was bigger than the others. This means that the corresponding C-C covalent bond was stronger, and the interfacial binding strength was higher. Based on this, conducting cobalt removal pretreatment, optimizing the PCD synthetic process and designing the site of Co can improve the performance of the PCD substrate CVD diamond coating tools.

Eco-Friendly Dispersant-Free Purification Method of Boron Nitride Nanotubes through Controlling Surface Tension and Steric Repulsion with Solvents.

Boron nitride nanotubes (BNNTs) were purified without the use of a dispersant by controlling the surface tension and steric repulsion of solvent molecules. This method effectively enhanced the difference in solubilities of impurities and BNNTs. The purification process involved optimizing the alkyl-chains of alcohol solvents and adjusting the concentration of alcohol solvent in water to regulate surface tension and steric repulsion. Among the solvents tested, a 70 wt% t-butylalcohol in water mixture exhibited the highest selective isolation of BNNTs from impurities based on differences in solubilities. This favorable outcome was attributed to the surface tension matching with BNNTs, steric repulsion from bulky alkyl chain structures, and differences in interfacial energy between BNNT-liquid and impurity-liquid interfaces. Through this optimized purification process, impurities were removed to an extent of up to 93.3%. Additionally, the purified BNNTs exhibited a distinct liquid crystal phase, which was not observed in the unpurified BNNTs.

A comparative study on the stability of six Ir/Ir3X (X = Ti, V, Zr, Nb, Hf, Ta) interfaces by first-principle and AIMD calculations

Interfacial stability is critical for dual-phase Ir/Ir3X materials used in ultra-high temperature applications. Despite this, this property remains poorly recognized and understood. In the present work, the interfacial energies and the generalized stacking fault energies (GSFE) curves are calculated to investigate the thermodynamic and kinetic stability of the six Ir/Ir3X interfaces by DFT and AIMD methods. It is found that Ir/Ir3Ti possesses the lowest interfacial energy at 0 K and 2000 K, as well as the highest unstable stacking fault energy, indicating it is the most stable interface. The comparison shows that the considered interfaces containing IVB elements (Ti, Hf and Zr) are more stable than those containing VB elements (V, Nb and Ta). Furthermore, the analysis reveals that interfacial energy differences in Ir/Ir3X may contribute to interfacial lattice misfit and charge redistribution at the interface. We aim to provide essential theoretical guidance for the design of novel high-temperature dual-phase Ir-based alloys.

Growth mechanism of metal iron particles with sulfur additives in direct reduction: First-principles calculations and experiments

Sulfur additive can greatly promote iron particles growth in direct reduction. However, promotion mechanism for metallic iron particles growth is unclear. FeS was found as the thermodynamic stable sulfur phase in reduction, intensifying in metal iron particles growth. Therefore, microstructure evolution and phase transition of metallic iron growth with FeS was investigated by reduction experiments. There were three stages in reduction. Firstly, liquid FeS was found, and Fe was produced around pore. Secondly, Fe was wetted and wrapped by liquid phase (Fe-FeS). Thirdly, Fe migrated to even in liquid phase, then irregular fine Fe particles gradually transformed and aggregated to sphere. Furthermore, controlling mechanisms in each stage were identified. The first stage was driven by reduction reaction. For second stage, interfacial interaction was found as the driving force. As wettability is macroscopic manifestation of interfacial interaction, wetting experiments was used. The best wettability was found in Fe/FeS interface followed wetting order: Fe/FeS(1200 °C) > FeS/SiO2(1200 °C) > Fe/SiO2 (1570 °C) with contact angle of 1.86°, 71.5° and 100°, respectively. First-principles calculations further revealed that the strongest interfacial interaction between Fe/FeS drive second stage due to its combining ionic and covalent bonding, and the highest interfacial separation work in Fe(200)/FeS(110) which was 1.998 J/m2. Meanwhile, the well wettability of Fe/FeS also provides a well kinetic basis for third stage, and the huge Fe concentrations difference in FeS and irregular fine particles interfacial energy are combined to drive the stage. Summary, the growth mechanisms of metallic iron particles in direct reduction with sulfur is systematic established.

Effect of particle anisotropy on the thermodynamics and kinetics of ordering transitions in hard faceted particles.

Monte Carlo simulations were used to study the influence of particle aspect ratio on the kinetics and phase behavior of hard gyrobifastigia (GBF). First, the formation of a highly anisotropic nucleus shape in the isotropic-to-crystal transition in regular GBF is explained by the differences in interfacial free energies of various crystal planes and the nucleus geometry predicted by the Wulff construction. GBF-related shapes with various aspect ratios were then studied, mapping their equations of state, determining phase coexistence conditions via interfacial pinning, and computing nucleation free-energy barriers via umbrella sampling using suitable order parameters. Our simulations reveal a reduction of the kinetic barrier for isotropic-crystal transition upon an increase in aspect ratio, and that for highly oblate and prolate aspect ratios, an intermediate nematic phase is stabilized. Our results and observations also support two conjectures for the formation of the crystalline state from the isotropic phase: that low phase free energies at the ordering phase transition correlate with low transition barriers and that the emergence of a mesophase provides a steppingstone that expedites crystallization.

Fluctuation–dissipation analysis of heat and mass flow in energy transport at different CO2 hydrate dissociation interfaces

Understanding the mechanism of kinetic behaviors is necessary for gas hydrate application. In this paper, the system of three-phase and two-interface was established, and the kinetic dissociation characteristics in different CO2 hydrate interfacial areas were compared using molecular dynamic simulations. It is found that the dissociation rate in the right interfacial region with relatively more carbon dioxide molecules is faster than that with relatively more water molecules. The mechanism of different kinetic behaviors at different dissociation interfaces was analyzed from the perspective of mass transfer, heat transfer and energy transport. The results show that the fluctuation–dissipation theory holds well for the number of hydrate-like CO2 molecules in the whole and part of the bulk hydrate at the near-equilibrium state, the interfacial latent heat flow in both interfacial areas, the interfacial average atomic potential energy difference, and the interfacial sensible heat flow in the left interfacial area at the non-equilibrium state. In which, the potential energy transport from the adjacent liquid to hydrate-like water molecules has an inherent correlation with the interfacial latent heat flow, and both have the similar fluctuation period, 900 ps and 1000 ps. The interfacial thermal resistance (ITR) was used to represent the dissipation of the net heat flow fluctuation amplitude, the values for the left and right interfacial regions are 5.57 × 10-10 m2·K/W and 5.46 × 10-10 m2·K/W, which reveals the faster heat transfer (including latent and sensible heat) in the right interfacial regions with relatively more carbon dioxide molecules. In addition, it was inferred that the mass transfer plays a leading role when there is no initial temperature gradient between the hydrate and the water (gas) phase, and in contrary, the heat transfer dominants.

A biodegradable bioinspired oil-coated adhesive film for enhanced wet adhesion

Bioinspired and biodegradable polymer-based adhesive films have attracted attention in the medical field because of their stable adhesion performance and ability to decompose in the body without additional surgical procedures. Among biodegradable materials, poly (glycerol sebacate) (PGS) can be applied to softenss-tuned microarchitecture-based adhesive films, because it has bioresorbable and residue-free characteristics. Herein, we presented a bioinspired oil-coated adhesive film fabricated using PGS, which can maintain adhesion on a wet surface by mimicking the toe pad and mucus of a frog. To implement frog-like adhesive architectures, the particular criteria under which PGS can be patterned were presented using simple models based on the degree of esterification and interfacial energy difference. Wet adhesion of our oil-coated film was achieved by replicating the frog-like hexagonal micro-channel and concave cup structures coated with vicious glycerol oil, resulting in a stable residue-free wet adhesion against diverse non-flat soft organ surfaces.

ZnO/Sn3O4 amorphous-crystalline heterojunctions for Cr(VI) visible photocatalysis: Simple synthesis with excellent performance

This paper is devoted to the construction of amorphous/crystalline heterojunction by a simple one-step hydrothermal method to realize the effective photocatalytic reduction of high concentration chromium. Taking amorphous ZnO/crystalline Sn3O4 (Z/S) as an example, the precursor of Sn(II) preferentially formed crystalline Sn3O4 based on the difference of complex constant (1010.8vs 104.4). The precursor of Zn(II) is then hydrolyzed and bonded to the surface of Sn3O4 by sn-O-Zn. The capping effect produced by citric acid selective adsorption on crystal surface significantly improves the proportion and stability of amorphous ZnO (aZnO). Interestingly, the introduction of aZnO transformed the surface structure of the Sn3O4 from micropore to hierarchical pore structure, which accelerated the adsorption of pollutants. The typical catalytic and characterization result illustrated that rich interfacial chemical bonds, abundant of oxygen vacancies and high interfacial potential energy difference collectively expedite the photoreduction of Cr(VI) on Z/S heterojunction. Up to 95.6 % (60 min for 0.1 g/L) and 59.1 % (100 min for 0.2 g/L) removal efficiency, importantly, proved that sequential-crystallization-based adsorption inducted design has advantages in the simple construction of high-quality amorphous heterostructures.

Film thickness and strain rate dependences of the mechanical properties of polystyrene-b-polyisoprene-b-polystyrene block copolymer ultrathin films forming a spherical domain

While the mechanical properties of ultrathin polymer films have been extensively studied, only few studies have focused on the ultrathin block copolymer films with complex topologies. The structure-property relationship of ultrathin films (thickness = 35–1000 nm) of polystyrene- b -polyisoprene- b -polystyrene (SIS) containing 14 wt% polystyrene (PS) is established in this study. Grazing-incidence small-angle X-ray scattering, dynamic secondary ion mass spectrometry, and atomic force microscopy were used to characterize the film structure. The difference in surface energy and interfacial energy of the domains resulted in the SIS thin films to primarily consist of three layers: a PS-rich subsurface layer (30 wt%), a spherical PS bulk layer (14 wt%), and a PS-rich interface layer (20 wt%). The film-on-water tensile test was used to investigate both the film thickness and strain rate dependences of mechanical properties. We found that the Young's modulus increased dramatically as film thickness decreased, although only few PS-rich layers consisting of disperse cylindrical and spherical PS domains existed at the surface and interface. Furthermore, the strain rate dependence of the modulus and stress relaxation was more significant for thinner films than for thicker films. The increase in modulus and unusual relaxation behavior are hypothesized to be the result of a combination of different factors, including PS domain alignment, confinement effects, and surface and interface interactions. • The structure-property relationship of ultrathin SIS films is analyzed. • Young's modulus increases upon decreasing thickness. • The extent of stress relaxation is larger for thinner films. • The stiffening may result from PS domain alignment.

Spontaneously Induced Hierarchical Structure by Surface Energy in Novel Conjugated Polymer‐Based Ultrafast‐Response Organic Photodetectors (Advanced Optical Materials 9/2022)

In article number 2102607, Jong Ho Won, In Hwan Jung, and co-workers report ultrafast-response organic photodetectors (OPDs) by making bulk heterojunction photoconductive layer composed of a novel conjugated polymer donor and fullerene acceptor. The non-halogenated xylene-processed OPDs exhibit significantly improved static and dynamic properties. These superior OPD properties were achieved by spontaneously induced hierarchical arrangement between donor and acceptor due to differences in interfacial energies.

Spontaneously Induced Hierarchical Structure by Surface Energy in Novel Conjugated Polymer‐Based Ultrafast‐Response Organic Photodetectors

AbstractA novel conjugated polymer, poly(4‐(4,8‐bis(5‐(2‐ethylhexyl)thiophen‐2‐yl)benzo[1,2‐b:4,5‐b']dithiophen‐2‐yl)‐2,6‐dioctylbenzo[1,2‐d:4,5‐d']bis(oxazole)) (PBB), is synthesized for use in ultrafast‐response organic photodetectors (OPDs). The PBB synthesis is considered facile because a monomer could be isolated without column chromatography purification. The excellent solubility of PBB allows easy dissolution in both halogenated and nonhalogenated solvents, facilitating the fabrication of p‐n heterojunction OPDs based‐on PBB and 6,6‐phenyl‐C71‐butyric acid methyl ester (PC71BM) using either chloroform (CF) or o‐xylene (Xy). Notably, Xy‐processed OPDs show superior performance with a responsivity (R) of 0.385 A W−1 and specific detectivity (D*) of 1.33 × 1013 Jones at –1 V, whereas CF‐based devices showed an R of 0.349 A W−1 and D* of 5.86 × 1012 Jones. More importantly, Xy‐processed OPDs exhibited an ultrafast signal response time of 3 µs, which is much faster than that of CF‐processed OPDs (42 µs). These superior static and dynamic properties of PBB:PC71BM devices are achieved by the inverted hierarchical arrangement of PBB and PC71BM via a biased orientation of PC71BM toward the ZnO layer as well as a homogenous nanomorphology. This ideal morphology is spontaneously induced due to the difference in interfacial energy between PBB and PC71BM toward the ZnO surface and a well‐mixed PBB:PC71BM blend in Xy solvent.

Strategy for achieving high-performance PVD nano-multilayered AlTiN/TiN coated milling tool: Fine platelet-grained WC–Co substrate and interface regulation

For a coating and substrate system, the ability to jointly resist external force damage determines the tool-life. To enhance such a mutual synergy, one-dimensional ultrafine platelet-grained WC–10Co–0.4TiC–0.6Cr3C2 alloy (PG alloy) was designed and prepared, based on Ti-induced enlargement of the interfacial energy difference. Submicron-grained WC–10Co–0.6Cr3C2 alloy was used as the reference. On the two kinds of substrates, nano-multilayered Al0.55Ti0.45N/TiN coating was deposited. The results show that compared with the reference, PG alloy with a texture coefficient TCWC(0001) of 3.27 and free of apparent micro-pore defect within the WC grains is characterized by higher hardness (1632 vs. 1567HV30), higher toughness (14.7 vs. 13.4 MPa∙m0.5), high strength (3737 vs. 4434 MPa), and stronger dislocation-forming ability. By using PG alloy as the substrate, high film adhesion strength (>100 N) is achieved, and readily formed coherent and semi-coherent interfaces between TiN (film) and WC are revealed by high-resolution transmission electron microscopy observation. As a result of interface strengthening and excellent combination of the substrate and the coating couple, compared with the reference tool, 1.4–1.5 times higher average tool-life under a wet or dry milling condition of 316L stainless steel is achieved.

Importance of Interfacial Structures in the Catalytic Effect of Transition Metals on Diamond Growth.

Here, using ab initio calculations, we investigated the interaction between transition metals (M) and diamond C(111) surfaces. As a physical parameter describing the catalytic effect of a transition metal on diamond growth, we considered interfacial energy difference, ΔEint, between 1 × 1 and 2 × 1 models of M/C(111). The results showed that the transition-metal elements in the middle of the periodic table (groups 4–10) favor a 1 × 1 M/C(111) structure with diamond bulk-like interfaces, while the elements at the sides of the periodic table (groups 3, 11, and 12) favor a 2 × 1 M/C(111) structure with the 2 × 1 Pandey chain structure of C(111) underneath M. In addition, calculations of MC carbide formation for early transition metals (groups 3–6) showed that they have a tendency to form MC rather than M/C(111), which explains their low efficiency as catalysts for diamond growth. Further analysis suggests that ΔEint could serve as another parameter (catalytic descriptor) for describing catalytic diamond growth in addition to the conventional parameter of the melting temperature of M.

Investigations of the 80/20 (wt/wt) PA6/ABS blends system in presence of SMA co-polymers as Reactive Compatibilizer and Encapsulated Multiwall Carbon Nanotubes (MWNTs)

Introduction: The modification of a polymeric material with tailored properties was carried out either by blending with another polymer or by using suitable filler or by taking the advantages of both. The immiscible polymer blends were generally forming coarse and unstable phase morphology, which hamper mechanical properties of the materials. Therefore, it was essential to control and stabilize a desired type of morphology in order to generate polymeric materials with favourable properties through controlling composition, processing conditions, viscosity of the materials and can be compatibilized by using either reactive compatibilizer or filler or combination of both to reduce the interfacial tension. Methods: Keeping these aspects in mind, a novel strategy was introduced during melt-mixing of 80/20 (wt/wt) polyamide6 (PA6) and acrylonitrile-butadiene-styrene (ABS). Styrene maleic anhydride (SMA) co-polymer having 8, 14 and 50 wt% of maleic anhydride (MA) content was utilized as reactive compatibilizers for 80/20 (wt/wt) PA6/ABS blends system. Multiwall carbon nanotubes (MWNTs) were considered as a filler material to improve the stiffness and strength of the blends composites. To overcome the van der Waals’ forces of the MWNTs and achieve the uniform dispersion of the MWNTs in the blends phosphonium based modifier, namely octadecyl triphenyl phosphonium bromide (OTPB) was studied with Raman spectroscopy and transmission electron microscopic analysis (TEM). To restrict the MWNTs in one of the phase and/or at the interfaces and taking the advantages of the compatibilizer and filler, the MWNTs were encapsulated by the SMA (8, 14, 50) co-polymer. A simple solution method was adopted for the preparation of the SMA (8, 14, 50) encapsulated MWNTs. Results & Discussions: A detail morphological analysis was carried out in context to the migration of the MWNT along with a decrease in dispersed droplet size of ABS phase with varying interfacial energy differences between the matrix and the dispersed phase. The morphological observations were further substantiated by FTIR spectroscopy and DSC non-isothermal crystallization studies. To understand the morphological changes (refinement) in 80/20 (wt/wt) PA6/ABS binary blends in presence of SMA encapsulated MWNTs in context to melt-viscosity factor and thermodynamic aspect during melt-mixing. These observations were supported by the torque rheometry, FTIR analysis and TEM images. Conclusions: Dynamic mechanical thermal analysis (DMTA) concluded that all combinations enhances the storage modulus with decrease in Tg compared to the 80/20 (wt/wt) PA6/ABS blends. However, SMA encapsulated MWNTs enhances highest storage modulus, may be due to the better interfacial adhesion between filler and polymers. Hence, a novel compatibilization strategy was developed and evaluated for 80/20 (wt/wt) PA6/ABS blends using a hybrid compatibilizer involving MWNT. Keywords: PA6/ABS blends, Reactive and hybrid compatibilizers, Multi-wall carbon Nanotubes, Encapsulation Acknowledgment: Professor Arup Ranjan Bhattacharyya, MEMS and SAIF Indian Institute of Technology Bombay (IITB), Mumbai. References B.F. Jogi, M. Sawant, M. Kulkarni and P.K. Brahmankar, Dispersion and Performance Properties of Carbon Nanotubes (CNTs) Based Polymer Composites: A Review. Journal of Encapsulation and Adsorption Science, Scientific Research Publishing, 2012;(2):69–78. doi: 10.4236/jeas.2012.24010. G.S. Lohar, P.B. Tambe, B.F. Jogi, Influence of dual compatibilizer and carbon black on mechanical and thermal properties of PP/ABS blends and their composites. Composite Interfaces, Taylor and Francis, 2020;(12)1101–1136. https://doi.org/10.1080/09276440.2020.1726137. R.M. Dhajekar, B. F. Jogi and S.R. Nirantar, Preparation and Characterization of PAEK based Polymer Nanocomposites in the Presence of MMT Clay as Nanofiller to Study Tensile and Impact Properties. Materials Today: Proceedings, 2018;(5),6848–6854.

Large-scale simulations of biological cell sorting driven by differential adhesion follow diffusion-limited domain coalescence regime.

Cell sorting, whereby a heterogeneous cell mixture segregates and forms distinct homogeneous tissues, is one of the main collective cell behaviors at work during development. Although differences in interfacial energies are recognized to be a possible driving source for cell sorting, no clear consensus has emerged on the kinetic law of cell sorting driven by differential adhesion. Using a modified Cellular Potts Model algorithm that allows for efficient simulations while preserving the connectivity of cells, we numerically explore cell-sorting dynamics over very large scales in space and time. For a binary mixture of cells surrounded by a medium, increase of domain size follows a power-law with exponent n = 1/4 independently of the mixture ratio, revealing that the kinetics is dominated by the diffusion and coalescence of rounded domains. We compare these results with recent numerical studies on cell sorting, and discuss the importance of algorithmic differences as well as boundary conditions on the observed scaling.

Droplet Energy Harvesting Is Reverse Phenomenon of Electrowetting on Dielectric

AbstractElectric energy is generated when water droplets slide down electrodes coated with a hydrophobic dielectric layer. The principle of energy generation needs to be clarified for the optimization and scalable design of the energy‐harvesting system. In this study, it is shown that droplet energy harvesting is the reverse phenomenon of voltage‐driven droplet actuation or electrowetting‐on‐dielectric (EWOD). For this reverse EWOD, the interfacial energy difference generated between the three‐phase contact line of the advancing and receding part of the droplet is the cause of the generation of electric energy. To prove the effect of interfacial energy on energy harvesting, the wetting property of the dielectric layer is controlled by nanopatterning while maintaining the chemical properties. The width and gap of the electrodes and the droplet size determine whether the harvested voltage waveform is monophasic or biphasic. The energy conversion efficiency is determined by the wetting properties of the surface, and the maximum value is as high as 40%.

Enhanced Static and Dynamic Properties of Highly Miscible Fullerene-Free Green-Selective Organic Photodetectors.

We developed p-n junction organic photodetectors (OPDs) composed of a polymer donor and a nonfullerene acceptor (NFA) to increase both the responsivity (R) and detectivity (D*) while maintaining a narrow wavelength selectivity. The selection of the polymer donor and NFA with similar green (G) absorption is important for achieving G-wavelength selectivity in these OPDs, which differentiates them from current fullerene-based OPDs and NFA-based panchromatic absorption OPDs. In addition, mixing the polymer donor and asymmetric NFA was efficient toward increasing the miscibility and decreasing the interfacial energy difference of the blended films, resulting in the formation of a uniform and well-mixed nanomorphology in the photoconductive layer. Two-dimensional (2D) grazing incidence X-ray diffraction and Fourier-transform infrared spectroscopy revealed that the lamellar ordering of the polymer donor was enhanced in the blend film prepared with an asymmetric NFA, whereas the aggregation of a symmetric NFA in the blend films did not increase the lamellar ordering of the polymer donor. Consequently, we achieved an R value of 0.31 A/W and D* value of 2.0 × 1013 Jones with a full width at half-maximum value of 230 nm at -2 V and fast response time of 27 μs without any external bias in the asymmetric NFA-based OPDs. The enhancement in the lamellar ordering and miscibility of the blended films are crucial toward increasing the static and dynamic properties of OPDs.

Selection and mechanical evaluation of γ/γ boundary in γ-TiAl alloy

Simulation of lamellar boundary (γ/γ) selection during the transformation of α2’→α2+γ in γ-TiAl alloy has been investigated using an improved 3D Phase Field (PF) model, and the mechanical properties of γ/γ boundaries are evaluated by Molecular Dynamics (MD) simulation. The effects of elastic strain energy and interfacial energy difference among different types of γ/γ interfaces on the occurrence frequencies of the three types of γ/γ boundaries (i.e., true twin (TT), pseudo-twin (PT) and ordered domain (OD)) have been studied. It is found that the boundary fraction of TT increases with increasing elastic strain energy or increasing interfacial energy difference among γ/γ interfaces. Besides TT, the elastic interaction also favors OD while PT is suppressed. The relative fractions of PT and OD could be effectively controlled by elastic strain energy. Furthermore, the frequency of PT or OD can also be adjusted by their interface energy ratio. The simulation results well explain the phenomenon that boundary frequencies via experimental statistics deviate from those under random distribution without interface selection. It can also be found that one-twin-dominant zones (OTDZ) can be induced by higher elastic strain energy and larger interface energy difference among different γ/γ boundaries through the merging of adjacent small clusters with the same γ/γ boundary type under the premise of correlated and sympathetic nucleation. Through MD simulation, it is found that the strengths of the configurations with true twin boundary (TTB) and ordered domain boundary (ODB) are almost the same, while the strength of that with pseudo-twin boundary (PTB) is relatively low. The order of plasticity of the configurations with three types of γ/γ interfaces is ODB > TTB > PTB.