Lamellar Structure Research Articles

Formation mechanism of lamellar structure of inner rust layer in weathering steel and its influence on Cl− erosion resistance

Formation mechanism of lamellar structure of inner rust layer in weathering steel and its influence on Cl− erosion resistance

Impact-resistant titanium alloy with fine equiaxed structure fabricated by powder metallurgy

Although fine equiaxed structure benefits both strength and ductility in titanium alloys, it is often considered incompatible with high toughness, for its insufficient ability to deflect propagating cracks compared to coarse lamellar structure. This work reports an excellent combination of standard Charpy impact toughness (∼100 J) and yield strength (∼820 MPa) in a powder metallurgy titanium alloy with fine equiaxed structure (∼1.5 μm), wherein the β matrix exists as equiaxed nodules and fine ligaments for globularization of α grains. The impact curve divided with the “compliance changing rate” (CCR) method indicates that the energy consumed by crack propagation is dominant (∼82%) during the impact process. Fractographic and structural examinations indicate that multiple micro-voids nucleation near boundaries between fine β ligaments and α grains mitigates local stress concentration, and that coordinated deformation between equiaxed β nodules and α grains hinders crack propagation, which together enable the excellent combination of yield strength and impact toughness. Our work provides a new pathway for designing impact-resistant titanium alloys.

Enhancing strength and ductility of CuCrZr high-conductivity alloy via lamellar heterostructures on grain boundaries

Heterogeneous lamellar structure materials have attracted extensive attention due to their exceptional strength and ductility. In this study, Y element was introduced into CuCrZr alloys to adjust the liquid phase formation temperature of the CuZrY phase during the solution annealing process. By employing cold rolling deformation prior to annealing to elongate the grains, the liquid phase was promoted to wet the elongated grain boundaries during the annealing process, ultimately forming lamellar CuZrY heterostructures distributed along the grain boundaries. The heterogeneous lamellar structure, the grain boundary distribution characteristics, and the effect of Y on stacking fault energy enhanced the hetero-deformation induced working hardening, thereby improving both the strength and ductility of the CuCrZrY alloy. Besides, the investigated CuCrZrY alloy achieved an excellent combination of tensile strength, uniform elongation, electrical conductivity and thermal conductivity, with values of 527 MPa, 10.66%, 83% IACS and 335.5 W/(m·K), respectively. Therefore, the method of controlling liquid phase temperature through composition adjustment and liquid phase infiltration path through grain deformation offers new possibilities for the design of heterogeneous lamellar structure materials.

Multi-cation doped CuCrO[formula omitted] crystallite matrix: Exploring bandgap tunability through Ni-Zn and Ni-Zn-Mg doping for optoelectronic application

Bandgap tuning is a key approach to optimizing materials for advanced technologies, enabling the development of more efficient and specialized devices. In this study, we demonstrate the tunability of the bandgap of CuCrO2 from 2.38 to 4.37 eV via single cation-doping with Ni and Zn, and multi-cation doping with Ni-Zn and Ni-Zn-Mg. XRD analysis reveals structural changes due to lattice distortions by cationic substitution, while FESEM shows the impact of doping on particle size, surface morphology, and crystallinity. The lamellar structure observed with multi-cation doping in FESEM investigations indicates increased structural disorder and defects, causing tailing above the valence band and below the conduction band, significantly reducing the bandgap. The effect of Zn-Ni doping on the lattice is reversed with Mg2+ insertion due to p-p orbital interactions between Mg2+-O, replacing the d-p interaction in the Cr3＋-O bond, as confirmed by optical studies. UV–Vis and photoluminescence analyses reveal significant shifts in bandgaps and emission spectra, with Ni doping yielding a bandgap of 3.97 eV, Zn doping 3.16 eV, Zn-Ni doping expanding it to 4.37 eV, and Zn-Ni-Mg doping reducing it to 2.38 eV. The dopants also affect emission characteristics, including band edge and deep-level emissions. This study provides valuable insights into the relationship between cationic doping and material properties, guiding the design of CuCrO2-based materials with tailored functionalities.

Efficient Photocatalytic Degradation of Humic Acid in Water Using N‐Doped Ti3AlC2 MAX

AbstractHumic acid (HA) is the main precursor of carcinogenic compounds such as trichloromethane, which form during the disinfection of drinking water. Therefore, removing HA from water sources is crucial for producing safe drinking water. This study introduces a novel approach using dilute nitric acid as a nitrogen source to dope pristine Ti3AlC2 (TAC) to varying degrees, enhancing the material‘s photocatalytic degradation performance for HA. Characterisations through X‐ray diffraction, Fourier transform infrared, scanning electron microscopy, UV–vis and X‐ray photoelectron spectroscopy revealed that the surface morphology of the modified catalyst changed from an original blocky lamellar structure to a rod‐like cluster structure, which is advantageous for light trapping. In addition, the incorporation of nitrogen reduced the band gap of the material from 1.25 to 1.15 eV, considerably enhancing its overall light responsiveness and thereby improving its photocatalytic performance. The results demonstrated that the photocatalytic degradation efficiency of HA by TAC under optimal conditions reached 93.8 %, which is 4.3 times higher than the 21.8 % efficiency achieved using the undoped TAC material. The enhanced photocatalytic activity is attributed to N doping, which not only reduces the TiO2 band gap at the TAC surface but also improves the electrochemical behaviour of TAC. This results in enhanced light response and more efficient separation of photogenerated electron–hole pairs. The mechanism for CTAC–Nx photocatalytic degradation of HA was investigated using trapping agent experiments, revealing that the primary active substance responsible for the degradation is O2−.

Fabrication and characterization of potato short amylose, zein, and pectin ternary composite particles stabilized pickering emulsions and their application on nuciferine delivery

Nuciferine exhibits properties such as reducing blood sugar and fat, however, it is hindered by its poor water solubility and low bioavailability. Pickering emulsions can efficiently encapsulate, protect and deliver active ingredients. In recent years, the use of biologically derived natural materials as emulsifiers to construct Pickering emulsions has become a research hotspot. This research utilized an enzymatic hydrolysis technique to produce short amylose. Subsequently, a ternary composite of short amylose (DBS), zein, and pectin (PEC) was formulated to stabilize Pickering emulsion, with the incorporation of nuciferine aiming to enhance the performance of lotus leaves in terms of both stability and bioavailability. The study revealed that varying amounts of DBS addition had a significant impact on the micromorphological structure and functional properties of DBS-Zein-PEC ternary composite particles. Specifically, the addition of 0.4 g of DBS led to a notable reduction in particle size to 735.2 nm and Zeta potential to −29.6 mV, creating a three-dimensional network with a closely packed lamellar structure. Optimal process conditions for preparing Pickering emulsion included a 3-minute homogenization time, rotation speed of 15000 rpm, and 5 % ternary composite particle addition. Under these conditions, O/W Pickering emulsion was successfully prepared, achieving a 90.5 % encapsulation rate for nuciferine. The resulting emulsion exhibited a minimum particle size of 4.09 μm, displayed good storage stability, resistance to salt ions and pH variations, viscous fluid characteristics, tolerance to oral and gastric environments, and slow release of nuciferine in the small intestine, thereby enhancing its bioavailability. These findings offer insights into the loading and delivery of nuciferine and serve as a technical guide for developing highly stable emulsion gel systems.

Vertically stacked heterostructure in MoS2/rGO to accelerate ion diffusion kinetics for aqueous zinc ion batteries

The two-dimensional (2D) layered MoS2 is highly desirable as a host cathode material for aqueous zinc ion batteries (AZIBs) due to the typical lamellar structure bonded with weak van der Waals interlayer forces. Nevertheless, sluggish kinetics of Zn2+ diffusion in MoS2 usually leads to inferior Zn2+ storage capability. Herein, a vertically stacked heterostructure of reduced graphene oxide (rGO) and 1 T-2H phase mixed MoS2 (1 T-2H MoS2/rGO) is successfully realized through a bottom-up assembly method. The presence of graphene in the interlayer of MoS2 not only increases the interlayer spacing but also induces the phase transition of MoS2. The flower-like nanocomposite is featured with expanded interlayer spacing of 9.6 Å, abundant 1 T phase, and good hydrophilicity, which facilitate Zn2+ diffusion, charges transfer and electrolyte infiltration. Consequently, the 1 T-2H MoS2/rGO based AZIB achieves exceptional electrochemical performance: admirable specific capacity of 294.6 mAh g−1 at 0.2 A g−1, good rate capability (130.9 mAh g−1 at 4 A g−1), and excellent long-term stability (96.8 % capacity retention after 1600 cycles at 3 A g−1). Experimental and density functional theory (DFT) calculation results reveal that the vertical-stacked structure of MoS2/rGO accelerates Zn2+ diffusion kinetics and charges transfer by reducing the ions migrate energy barrier and band gap. The multiple ex situ characterizations demonstrate that the Zn2+ insertion/extraction process is accompanied by highly reversible phase transition between 2H and 1 T MoS2. This bottom-up assembly strategy can be extended to design more 2D materials with vertically stacked heterostructure as cathodes for high-performance AZIBs.

Quantification of phase separation in high moisture soy protein extrudates by NMR and MRI

High-moisture (HM) extrusion is the dominant industrial process to create structured plant-based protein products that can be used for animal-free meat alternatives. Yet, the underlying mechanisms, such as phase separation, that govern structure formation in plant-protein extrudates, are still poorly understood. Current hypotheses require experimental data in order to be verified, but measurement techniques able to quantify phase-separated anisotropic protein extrudates are lacking, or have yet to be validated. In this study, Low-Field Time Domain (LF TD)-NMR and High-Field (HF) MRI techniques have been employed to unravel phase separation in HM extrudates of soy proteins. Results show that swelling with water enhances the 1H NMR/MRI signal-to-noise ratio in the measurements and unveils the presence of lamellar regions, while freeze-thawing enhances phase separation due to freeze concentration. Phase separation could be quantified by the observation of two distinct populations by LF TD-NMR T2 measurements. MRI images of dead-stop ribbon samples from HM extrusion revealed how the thickness of the aligned lamellar regions increases during passage of the protein melt through the cooling die. We conclude that TD-NMR can quantify phase separation, while spin-echo MRI can spatially resolve the lamellar structure conformation of HM extrudates. Thus, NMR and MRI are powerful techniques for non-invasively characterizing ex situ structure formation during HM extrusion, and for validating hypotheses on shear- and temperature-induced phase separation.

Neodymium oxide-based hybrid phase few-layer MoS2 nanocomposite as high-performance symmetric supercapacitor electrode

The two-dimensional layered materials (for example MoS2) are potential electrodes for supercapacitors with their excellent lamellar structure, high surface area, mechanical flexibility, and potential redox activity. However, due to restacking of chemical structure and low electrical conductivity of the pure MoS2 electrodes are prevented for energy storage applications. Therefore the electrodes are made up of a composite by a mixture of MoS2 and rare-earth metals significantly addressing these issues with improved electrical conductivity, large electrochemical active surface, and shorter ion-diffusion kinetics. In the present study, the MoS2 and MoS2/Nd2O3 composite were synthesized by hydrothermal method. The structural phase identification of prepared samples was accomplished by using an X-ray diffractometer (XRD) and Raman spectra. Furthermore, TEM reveals changes in the shape of nanosheets and interlayer spacing. The GCD of symmetric MoS2/Nd2O3 composite electrodes displayed remarkable charging/discharging performance, with increased stability and rate capability. The MoS2/Nd2O3 composite shows utmost Csp of 2528.18 Fg-1 at 1 Ag-1. In addition, the CV and GCD studies suggest that the electrodes exhibit pseudocapacitive behavior and excellent energy density(E) of 191 Wh kg-1 at 1474.1 W kg-1 power density(P) in 1M H2SO4. The supercapacitor device made up of MoS2/Nd2O3 composite shows greater performance in practical LED glowing applications. Therefore, the composites make advancements in energy storage devices like batteries and supercapbatteries due to their excellent energy storage, high electrochemically active surface area, and stability.

Structure and function of skin barrier lipids: Effects of hydration and natural moisturizers in vitro

Lipid membranes play a crucial role in regulating the body’s water balance by adjusting their properties in response to hydration. The intercellular lipid matrix of the stratum corneum (SC), the outermost skin layer, serves as the body’s primary defense against environmental factors. Osmolytes, including urocanic acid (UCA) and glycerol, are key components of the natural moisturizing factor that help the SC resist osmotic stress from dry environments. This study examines the effects of UCA and glycerol (each at 5 mol %) on isolated human SC lipids. For this, different techniques were employed, offering complementary information of the system’s multiscale characteristics, including humidity-scanning quartz crystal microbalance with dissipation monitoring, infrared spectroscopy, x-ray diffraction, electrical impedance spectroscopy, and studies of water loss and permeability. Our results show that UCA increases water sorption and makes lipid films more liquid-like at high relative humidity, without significantly altering the lipid lamellar structure, chain order, or orthorhombic chain packing. Lipid films containing UCA exhibited higher water loss and significantly higher model drug permeability compared to lipid films without UCA. Further, incorporation of UCA resulted in kinetically faster changes in electrical properties upon contact with aqueous solution compared with control lipids. These observations suggest that UCA reduces lipid cohesion in regions other than the acyl chain-rich leaflets, which may impact SC desquamation. In contrast, glycerol did not influence the hydration or permeability of the SC lipid matrix. However, it increased the proportion of orthorhombic domains at high humidities and slowed the kinetics of the hydration process, as evidenced by slower changes in the dielectric properties of the lipid film. These findings suggest that glycerol enhances lipid cohesion rather than increasing water uptake, which is typically the expected function of humectants. Consequently, UCA and glycerol appear to have distinct roles in maintaining epidermal homeostasis.

Printed flexible supercapacitors utilizing composites of MWCNT/MOF ultrathin nanosheets: Exploring 1D/2D structural adjustment

The self-stacking propensity of metal–organic frameworks (MOFs) during synthesis, combined with their intrinsic limitations in electrical conductivity and mechanical stability, constrains their utility as high-capacity energy sources in wearable electronics. Here, we employ a surfactant-assisted method to mitigate the Z-axis stacking of zinc metalloporphyrin organic frameworks (NMOFs), yielding ultrathin two-dimensional (2D) material sheets. By integrating carboxyl multiwalled carbon nanotubes into these nanosheets (denoted as C-NMOF-x), the lamellar structure of MOF is preserved while promoting the formation of rich multistage micropores and continuous conductive channels. This structural refinement remarkably enhances electrochemical properties, including capacitance, electronic conductivity, and cycling stability. Leveraging synergistic interactions, the resulting C-NMOF-4 composite achieves a specific capacitance of 0.152 mAh/g in a three-electrode system at a current density of 1 A/g. Furthermore, the modulated C-NMOF-4 composites are successfully formulated into homogeneous e-inks suitable for dispensing printing, enabling the mass production of flexible micro-supercapacitors (MSCs). Notably, these MSCs maintain 95 % of their capacitance even after 180° bending under wearable conditions. This surface and interface microstructure modulation strategy holds promise for enhancing the synergistic coupling effects of 2D materials and offers new avenues for the application of innovative 2D materials in wearable electronics.

Phase-field modeling of peritectic coupled growth in the TRIS–NPG model system

Microstructures forming during the directional solidification of the hypo-peritectic TRIS–NPG model alloy were studied by phase-field simulations. Steady state growth forms could be obtained under conditions similar to those in recent space experiments. In two dimensions, the wavelength range of stable lamellar structures has been determined as function of the temperature gradient and the melt composition. Front temperatures extracted from simulations were compared to the predictions of the modified Jackson–Hunt theory. In three dimensions, structures and phenomena known from eutectic systems were reproduced. Transitions between lamellar and rod structures were induced by slowly changing the melt composition. The regularizing effect of tilting the temperature gradient, transforming a random labyrinth pattern to an ordered one, has also been demonstrated. These simulations show the universality of the basic governing mechanism — that is, the competition of solute diffusion with capillary effects — in the pattern formation of these multi-phase systems.

Bimetallic ions pre-intercalated hydrated vanadium oxides for high-performance aqueous zinc-ion batteries

A new generation of rechargeable batteries known as Aqueous Zinc-Ion Batteries (AZIB) offers benefits including affordability, eco-friendliness, dependability, and safety. Hydrated vanadium oxides (V2O5·nH2O) show potential as cathodes for AZIB due to their layered structure and multivalent properties. However, the zinc storage performance is limited by the structural instability and slow zinc ion mobility. In this work, TiK-VOH (the bimetallic ions system of Ti4+ and K+ co-pre-intercalated in V2O5·nH2O) with lamellar fish scale-like structure is synthesized using a simple sol-gel method. The high positive charge density of the tetravalent Ti4+ is more beneficial to attract the electrons in the V-O layer and regulate the layer spacing (12.1 Å), which not only improves the diffusion kinetics of zinc ions, but also acts as a pillar to stabilize the layer structure. K+ mainly plays the role of improving electrical conductivity, and then accelerates the charge transfer in the electrode reaction process. Auxiliary density functional theory simulation further confirms that the diffusion energy barrier and Fermi level are optimized by pre-intercalating bimetallic ions. Based on the synergistic effect of Ti4+ and K+, the TiK-VOH material shows excellent zinc storage performance, the highest specific capacity of TiK-VOH reaches 393.4 mAh g−1 at a current density of 0.2 A g−1, even at 10 A g−1 (increased by 20 times), it still maintains a discharge specific capacity of 202 mAh g−1 with a capacity retention rate of 94 % after 2000 cycles, the overall performance is much better than the Ti-VOH and K-VOH. This work offers an alternative perspective for the modification of vanadium-based cathode of AZIBs.

Experimental study on shear mechanism of a new TU-type connector at HSS-UHPC interface

To maximize the benefits of high-strength steel (HSS) and ultra-high performance concrete (UHPC) composite structures, proper connections at HSS-UHPC interfaces are essential. Due to the significant variations in material strengths and component dimensions, traditional shear connectors could be unsuitable for HSS-UHPC interfaces. This study proposes a new TU-type connector (T-shaped rib with U-shaped holes), which has the advantages of high shear and tensile capacity, good slip capacity, low height limitation, and easy installation. Firstly, eighteen push-out tests of HSS TU-type connectors embedded in UHPC were performed to investigate the effect of connector heights and the contribution of connector flanges. The failure process, including the yielding of hole walls, the fracture of connector webs, and the development of fracture surfaces was discussed. Besides, the microstructures involving smooth areas, lamellar structures, and dimples on the fracture surfaces were presented by scanning electron microscope (SEM), and the effect of flange foam blocks on the out-of-plane displacements of UHPC slabs was investigated by digital image correlation (DIC). Secondly, the shear force–displacement curves and the load–strain relations of steel plates and rebars were discussed. In addition, the effects of considered parameters on shear capacity, peak slips, and shear stiffness were investigated. Finally, a strut-and-tie model was established to reveal the shear mechanism of TU-type connectors. Based on the principle of virtual work, the shear capacity equations of TU-type connectors were proposed.

Relationship between the heterogeneity in mechanical properties, bone density and composition parameters of cortical bone to design and develop bone scaffolds and implants: Analysis of bone microstructure

Bone is heterogeneous and anisotropic because its mechanical characteristics vary by anatomic location and loading direction. Previous research established a correlation between bone density, mineral, organic content, and porosity and mechanical qualities. Medical and bioengineering researchers can learn about bone heterogeneity and anisotropy by analysing bone density and later composition parameters across the bone diaphysis in both longitudinal and transverse orientations. This research examines bone density and composition parameters in bovine femoral cortical bone from higher, middle, and lower diaphysis regions and longitudinal and transverse orientations. At three homogeneous diaphysis sites, these properties did not alter in longitudinal or transverse orientations. At the upper and lower diaphysis locations, mineral and organic content were statistically different in both longitudinal and transverse orientations, contributing to anisotropy. At the middle location, all measured parameters were not statistically different. Transverse bone density and water heterogeneity were greater, while longitudinal values were higher for the other metrics. Upper and lower sites had increased bone variability due to %water, although mineral content was more homogenous. The longitudinal and transverse organic content and apparent density heterogeneity was greater at the middle position. At the later site, bone density and mineral content were more homogenous longitudinally and transversely. Lamellar bone microstructure with canalicular/vascular network, cavities, and holes contributed to bone materials' %water content. Collagen fibres contributed to bone material's organic composition, whereas intrafibrillar and extra fibrillar minerals contributed to its mineral content.

Hierarchical CuO nanosheets encasing nanorods via a singular potential-cycling activation: Innovations in supercapacitor energy density and longevity

Copper oxides (CuO), by virtue of their exceptional electrical conductivity, benign environmental profile, and economic viability, have emerged as indispensable constituents in the design and development of binder-free electrodes for advanced supercapacitor systems. The ongoing quest for the synthesis of CuO nanomaterials through gentle yet economically feasible methodologies held considerable promise for broadening their applicability within the domain of energy storage devices. In this investigation, a novel architectural innovation was achieved through the integration of carbon nanotubes (CNTs) within the framework of an in-situ electrooxidation process, culminating in the formation of a distinctive CuO-CNT nanorod configuration. Subsequent to this fabrication, the electrode material was subjected to an extensive cyclic voltammetry (CV) activation for 2000 cycles, which precipitated a profound morphological evolution. This process resulted in the emergence of 2D hierarchical nanosheet arrays enveloping 1D nanorods, a configuration herein designated as CuO-CNT-2000. This meticulously engineered lamellar structure conferred upon the material an extraordinary specific surface area, quantified at 219.6 m2 g⁻1, and an impressive specific capacitance of 709.1 F g⁻1. Moreover, the asymmetric supercapacitor (ASC) assembled utilizing this advanced material exhibited a remarkable energy density, measured at 38.09 Wh kg⁻1. Notably, even after enduring 60,000 charge-discharge cycles, the device demonstrated a retention of 82.36 % of its initial energy density, coupled with a Coulombic efficiency of 99.43 %, thus attesting to its superior electrochemical stability and longevity. The efficacy of the CV activation technique in facilitating significant morphological refinement, augmenting the specific surface area, and enhancing the electrochemical performance of the material suggests a broad applicability of this method to a diverse array of other electrode materials, potentially revolutionizing the design and fabrication of next-generation energy storage systems.

Atomic-scale insights into the effect of layer thickness ratio on the tensile properties of heterostructured nano-aluminum

Gradient-structured alloys with lamellar microstructures show extraordinary potential in breaking the strength-ductility trade-off dilemma. When partial grain size exceeds the Hall-Petch limit, the deformation mechanism is not fully understood. In this study, the competing relationship between grain boundary (GB) softening and hetero-deformation-induced (HDI) strengthening in laminated nano-grained aluminum was investigated under uniaxial tensile loading. In the soft domains, the high activity of grain boundaries results in pronounced GB softening. However, when the volume fraction of the soft layer exceeds 50 %, the flow stress surpasses the predicted values of the rule of mixtures (ROM), demonstrating a significant HDI strengthening. A detailed analysis of microstructural evolution is conducted, including strain gradients, GB migration, and dislocation distribution. The effects of mechanical incompatibility between soft and hard layers on the distribution of plastic strain and overall material strength are elucidated in gradient structures. The study provides critical theoretical insights into the design and development of high-performance gradient nanocrystalline aluminum alloys, particularly in applications where a balance between strength and ductility is of paramount importance.

Elucidating the effects of metal transfer modes and investigating the material properties in wire-arc additive manufacturing (WAAM)

AbstractStudies have shown the influence of WAAM process parameters on mechanical properties, bead formation, dimensional accuracy, and microstructure. However, metal transfer modes and their interactions with input variables have not been investigated thoroughly. Therefore, short/spray, pulse and double pulse modes were investigated in this study at different current levels. Bead-on-plate trials were conducted by depositing ER70S-6 wire to investigate bead morphology, dilution, microstructure, and hardness. The study was supported by a detailed statistical approach, including analysis of variance (ANOVA) and regression analysis. Similarly, the combined effects of hatch distance and current were studied on bead formation in multi-layer deposits. Moreover, a thin wall and a cubic structure were deposited to realize the WAAM capability for larger depositions. The microstructures of thin wall and cubic structure were analyzed using optical microscopy (OM) and scanning electron microscopy (SEM). The study concludes that metal transfer modes at various currents significantly influence bead geometry, microstructure and hardness. The microstructure of bead-on-plate trials show fine lamellar structure at low current in all modes. Higher current results in coarse grains with a polygonal and columnar morphology. The hardness shows a decreasing trend as the current increases. The combined effects of current and hatch distance alter bead morphology; however, an optimized combination yields smoother surfaces. The microstructure of thin wall showed a slight anisotropy along the building direction. The presence of small pores was witnessed from OM and SEM images. Similarly, the cubic structure showed a more homogeneous microstructure with much lower porosity. The hardness profile of the thin wall exhibited small fluctuations along the building direction, while that of the cubic structure was more uniform.

CALPHAD-aided design for superior mechanical behavior in Ti40Zr20Hf40-xCrx eutectic refractory high-entropy alloys

TiZrHf-based refractory high entropy alloys (RHEAs) are becoming the focus in advanced metal materials owing to the excellent mechanical properties under the condition of medium and high temperatures. Nevertheless, the strength of TiZrHf-based RHEAs at medium temperatures has hindered the further application. This work proposed a novel approach to improve the mechanical properties of TiZrHf-based RHEAs. An innovative series of Ti40Zr20Hf40-xCrx (x = 19, 24 and 29, denoted by HfCr19, HfCr24 and HfCr29, respectively) eutectic refractory high entropy alloys (ERHEAs) were designed and prepared. The designed Ti40Zr20Hf40-xCrx alloys can form lamellar eutectic structure including BCC/HCP phase and Laves precipitating phase in solidification with the decrease of Hf/Cr ratio. The microstructure of HfCr19 and HfCr24 alloys was composed of BCC, HCP and Laves phase, while the HfCr29 alloy consisted of BCC and Laves phase. The formation of HCP phase in the Ti40Zr20Hf40-xCrx alloy were attributed to the lattice of Ti0.5Zr0.5 phase reconstruction during the rapid cooling, which promoted the formation of isomers in the alloy. Hence, the part of BCC phase was transformed into HCP phase in the HfCr19 and HfCr24 alloys, and the lamellar eutectic structure consisted of BCC/HCP phase and Laves phase. In addition, compared with the near-eutectic HfCr19 and HfCr29 alloys, the HfCr24 alloy with a complete lamellar eutectic structure has higher compressive strength at room temperature, which can reach 1648.7 MPa. In addition, the compressive strength (1261.7 MPa) can still be achieved at 600 °C. This work successfully prepared a high-strength TiZrHf-based ERHEA, and the compression mechanical properties at room temperature and middle-high temperature were studied and analyzed.

Mechanistic understanding of changes in physicochemical properties of different rice starches under high hydrostatic pressure treatment based on molecular and supramolecular structures

The molecular and supramolecular structures of japonica and waxy rice starches under high hydrostatic pressure treatment (450 MPa) were studied and the changes in physicochemical properties were analyzed based on these structures. The molecular structures of japonica and waxy rice starch cause differences in the lamellar structure and physicochemical properties. The thickness of amorphous lamella of japonica rice starch increased at 5 min (2.95 nm) followed by a gradual collapse of lamellar structure. Whereas the thickness of crystalline lamellae of waxy rice starch increased at 15 min (5.92 nm) and the lamellae collapsed suddenly at 20 min. The pasting, rheological and textural characteristics of both starches increased significantly within 10 to 15 min. The decreasing onset temperature and enthalpy of high hydrostatic pressure-treated starches indicated easier gelatinization. High hydrostatic pressure-treatment offers potential for developing starch-based products with low swelling capacity, easy gelatinization, high viscosity and hardness.