Phase Structure Evolution Research Articles

Microscopic Interactions Between Different Block Ratios of Styrene–Butadiene–Styrene and Asphalt During Their Miscibility

Styrene–butadiene–styrene (SBS)-modified asphalt is widely used in the field of road construction because it helps asphalt pavements achieve good road performance. However, SBS-modified asphalt has problems of poor compatibility, leading to insufficient thermal storage stability. As a block copolymer of styrene and butadiene, the compatibility of SBS with asphalt is also influenced by its styrene-to-butadiene (S/B) ratios. To reveal the compatibility mechanisms of different S/B ratios of SBS and asphalt during system stabilization, the interactions of SBS with asphalt at the molecular level were investigated in this study. Based on the molecular dynamics simulation method, interfacial models of SBS and asphalt were constructed; the miscible process of SBS in asphalt was simulated, with the characteristics of phase structure evolution and molecular distribution being analyzed; and the binding energy of the SBS/asphalt miscible systems was calculated. The results show that a higher butadiene content benefits the miscibility of SBS in asphalt and that the S/B ratios affect the interaction of SBS with asphalt and its components. SBS with a 3:7 ratio of styrene to butadiene exhibits stronger adsorption with the resin component and has the highest binding energy and best compatibility with asphalt. The findings contribute to the understanding of the miscibility and compatibility mechanisms between different S/B ratios of SBS and asphalt.

Synergistic Phase and Structural Engineering for Enhanced Zinc Storage in V2O3@N-Doped Carbon Nanofibers.

Vanadium-based oxide cathodes are promising energy-storage systems for aqueous zinc-ion batteries (AZIBs) because of their high energy density and safety, and low cost. However, their limited ion/electron transfer rates and rapid capacity decay pose challenges to their practical application. To overcome these limitations, V2O3 nanoparticles are developed with surface oxygen vacancies integrated with N-doped carbon nanofibers (V2O3@NCNFs), using an electrospinning method combined with an in situ oxidation/reduction strategy. By precisely controlling the reaction atmosphere, synergistic regulation of the phase transition and structural evolution of vanadium oxide are achieved. The unique combination of oxygen vacancies and N-doped carbon nanofibers enhances the zinc storage capacity, rate capability, and cycle stability of the V2O3@NCNFs electrode, achieving high reversible capacities of 554.6 mAh g-1 at 0.1 A g-1 with a high loading mass of ≈2.0-2.5mg cm-2. Moreover, the V2O3@NCNFs electrode can achieve a high initial capacity of 434.3 and 266.6 mAh g-1 even at high current densities of 1.0 and 5.0 A g-1, respectively, with minimal capacity decay rates of 0.012% per cycle over 500 cycles and 0.003% per cycle over 2000 cycles. More importantly, this innovative approach can be universally applied to the design of novel nanostructured Mn- and V-based oxide cathodes, which is promising for the development of advanced electrodes for high-performance energy storage devices.

Mechanistic Insights and Technical Challenges in Sulfur-Based Batteries: A Comprehensive In Situ/Operando Monitoring Toolbox.

Batteries based on sulfur cathodes offer a promising energy storage solution due to their potential for high performance, cost-effectiveness, and sustainability. However, commercial viability is challenged by issues such as polysulfide migration, volume changes, uneven phase nucleation, limited ion transport, and sluggish sulfur redox kinetics. Addressing these challenges requires insights into the structural, morphological, and chemical evolution of phases, the associated volume changes and internal stresses, and ion and polysulfide diffusion within the battery. Such insights can only be obtained through real-time reaction monitoring within the battery's operational environment, supported by molecular dynamics simulations and advanced artificial intelligence-driven data analysis. This review provides an overview of in situ/operando techniques for real-time tracking of these processes in sulfur-based batteries and explores the integration of simulations with experimental data to provide a holistic understanding of the critical challenges, enabling advancements in their development and commercial adoption.

Regulation strategy of preparation methods for new spherical La-Y-Ni hydrogen storage alloy with ultra-long cycle lives

La-Y-Ni-based alloys are high-performance superlattice rare-earth H2-storage electrode materials. However, their complex phase structural evolution results in poor electrochemical cycle lives. In this study, a gas atomization method develops to obtain spherical La-Y-Ni-based hydrogen storage alloys with high structural stability. The spherical La-Y-Ni powder exhibits a narrow particle size distribution between 30 and 75 μm and capacity retention over 60 % for 600 cycles. A three-dimensional particle insertion strain model and finite element simulations reveal the direct effects of the particle morphology on the stress distribution during hydrogen embedding. The spherical powder exhibits a uniform strain, good mechanical properties, and resistance against pulverization and damage. The new preparation strategy for spherical powders prominently regulates the [A2B4] subunit, decreasing the subunit mismatch and lattice strain, and improving the structural stability during the hydrogen absorption/desorption. In addition, the morphology regulation, phase composition controllability, platform characteristics and electrochemical properties investigate by comparing the use of gas atomization, casting, and rapid quenching. This study provides a new direction for developing high-performance spherical electrode materials.

Effect of thermal annealing on phase structure and hydrogen evolution reaction of molybdenum carbide thin films prepared by co-sputtering

Molybdenum carbide (MoxC) has attracted extensive attention owing to its rich valence states and excellent catalytic activity. Herein, the influences of thermal annealing on phase structure and hydrogen evolution reaction (HER) of MoxC thin films have been systematically studied by X-ray diffractometer, scanning electron spectroscopy, transmittance electron spectroscopy, and X-ray photoelectron spectroscopy. It has been found that annealing temperature shows a high impact on the phase structure of the MoxC thin films. The as-sputtered MoxC film and the films annealed at the temperatures of 500–600 °C are nearly in the mono α-MoC phase; the films annealed at 700 °C are β-Mo2C phase, while the film annealed at 650 °C is in mixed MoC/Mo2C phases. The MoC/Mo2C hybrid films exhibit promoted HER performance with overpotential as low as 119 mV at 10 mA cm−2 and the corresponding Tafel slope of 73 mV dec−1 in acid, where the structural transformation from MoC to MoC/Mo2C hybrid gives rise to the optimized electronic structure and intensively regulates the H adsorption energy. Benefiting from the synergistic effect of the dual-phase MoC/Mo2C characteristics, the MoC/Mo2C@CP hybrids can be directly used as binder-free electrocatalysts. This work provides an archetype for modulating the phase of MoxC thin film by a co-sputtering strategy for an efficient hydrogen evolution reaction.

Insights into Lithium Ion Battery Charging Mechanisms: Ex Situ Studies on NMC Materials

Lithium-ion batteries are crucial in modern energy storage systems, and their performance is heavily influenced by the properties of the positive electrode materials they employ. Nickel-rich layered oxide cathodes, such as NMC811 (LiNi0.8Mn0.1Co0.1O2) and NMC622 (LiNi0.6Mn0.2Co0.2O2), have received significant attention due to their high energy density and potential for enhancing battery performance[1]. Understanding the structural and chemical changes occurring within these cathodes during charging is essential for optimizing LIB performance and longevity. Raman mapping and X-ray diffraction (XRD) can be employed as powerful analytical techniques to probe the structural and chemical changes occurring within the cathode materials. Raman spectroscopy provides insights into the evolution of the cathode's local structure, phase transitions, and chemical composition, while XRD enables the determination of crystallographic changes and phase transitions. Thus far, Raman spectroscopy mapping has been employed to differentiate between charged and discharged regions, but transient states have not been indicated[2,3]. Regarding X-ray diffraction, the research primarily concentrated on in situ investigations, conducting measurements while the cell was in operation[4].In this study, we present ex situ investigations employing Raman mapping and X-ray diffraction (XRD) techniques to clarify the charging mechanisms of NMC811 and NMC622 cathodes. Since lithium ion batteries mainly use a charging method based on a constant current followed by a constant voltage[5], we applied a similar sample preparation technique based on this typical charging procedure (CCCV). The combination of ex situ studies based on Raman spectroscopy and XRD gives insight into the phenomena occurring in NMC materials during cell charging and consequences for its structure stability. By analyzing samples at different SOC, we aim to clarify the impact of cycling on the structural integrity, phase evolution, and chemical composition of NMC811 and NMC622 cathodes. Specifically, we investigate how the cathode materials evolve in response to lithium-ion insertion and extraction processes during charge and discharge cycles. Additionally, we focus on the charging strategies employed, emphasizing the influence of charging protocols on the structural stability and electrochemical performance of the cathode materials. Understanding the relationship between charging protocols and cathode degradation is crucial for optimizing battery cycling protocols to enhance performance and prolong battery lifespan. Our findings provide valuable insights into the structural changes of NMC811 and NMC622 cathodes under selected cycling conditions, guiding the development of strategies to mitigate possible degradation and improve the overall performance and durability of nickel-rich NMC-based lithium-ion batteries. This work was funded by the National Center for Science in Poland through the Sonata BIS 11 programme (No. UMO-2021/42/E/ST5/00390).

Sintering activation energy and low-temperature sinterable process of Boron-lanthanide glass/Li2Zn3Ti4O12 ceramic composite systems for LTCC technology

This work investigates the characteristics of wettability, activation energy for sintering, evolution of phase structure, and behavior during the low-temperature sintering process of B2O3-La2O3-MgO-TiO2 (BLMT) glass/Li2Zn3Ti4O12 ceramic composites for low temperature co-fried ceramics technology (LTCC). As the BLMT glass content increases from 0 to 10 wt%, the average sintering activation energy (Ea) of the composite decreases from 450 ± 8 to 356 ± 37 kJ/mol. There are two phases the primary Li2Zn3Ti4O12 phase and the secondary LaBO3 phase, the latter precipitates from the BLMT glass after sintering at 700 °C. This indicates that BLMT glass promotes the sintering of Li2Zn3Ti4O12 ceramic below 900 °C. In composites containing 20 wt% or more glass, sintering is governed by both liquid-phase sintering and reactive viscous sintering. As the BLMT glass content increases, the impact of viscous flow on the densification process becomes more pronounced. Simultaneously, when the glass content is greater than 20 wt%, the glass precipitates LaBO3, TiO2, and MgLaB5O10 phases between 700 and 750 °C. After 850 °C, the glass melts and reacts with Li2Zn3Ti4O12 phase to produce a new TiO2 phase. Accordingly, the activation energy (Ea) of sintering the composite material increases from 393 ± 17 to 667 ± 1 kJ/mol.

Phase structure evolution and electric properties of PSN-PIN-PT ferroelectric ceramics near MPB

Phase structure evolution and electric properties of PSN-PIN-PT ferroelectric ceramics near MPB

Evolution of the Active Phase of Pt/Sn-Al2O3 Catalysts During Acidic Impregnation and Their Use in Propane Dehydrogenation.

Alumina-supported PtSn is an industrialized catalyst for propane dehydrogenation. During the catalyst impregnation, the acidic impregnation solution with chloroplatinic acid as a precursor inevitably leads to the partial dissolution of the surface of amphoteric alumina support and finally varies catalytic performance. Herein, the structure evolution of the active phase, induced by an impregnated acidic solution, was studied with special care. According to the diffused double layer theory, we proposed a model of microgels during impregnation. The microgels formed in the solution with suitable acidity on the surface of the catalysts evolved into a structure of Al2O3-coated oxidized Pt by reprecipitation during drying and calcination. The covered Pt species could be exposed by Ar+ sputtering or migrate to the surface during reduction to serve as active sites for propane dehydrogenation. Noticeably, the surface Sn0 species was generated when the pH of the impregnated solution was around 0.56, which is solid proof for the unique active phase with the PtSn alloy present on SnOx species existing on the surface of the Sn-Al2O3 support. The synthesized catalyst exhibited high propylene selectivity (99.4%) and superior stability (kd = 0.002 h-1). This study provides new insight for the precise preparation of Pt/Sn-Al2O3 catalysts.

Phase structure evolution and coercivity mechanism of high-Co containing permanent magnets

Abstract The phase structure and magnetic properties of high-Co containing permanent magnets with high thermal stability have been systematically studied in this work. It is abnormal that the coercivity of annealed samples was slightly lower than that of sintered samples, while the coercivity was usually enhanced after annealing in conventional Nd–Fe–B samples. Further analysis showed that in addition to RE2(Fe,Co)14B main phase and RE-rich grain boundary phase, there were also new Co-rich magnetic phases located in the grain boundary. During annealing, the phase structures of high-Co containing magnets were readjusted, especially the increasing Co-rich magnetic phase and emerging RE-rich particles precipitated from the main phase. Eventually, the isolated RE-rich particles would act as the pinning center of the domain wall movement in demagnetization process. It was confirmed that the coercivity of annealed high-Co containing magnets was controlled by both nucleation and pinning. Pinning mechanism can partially compensate for the weakening of magnetic isolation due to increased Co-rich magnetic phase, which explained the moderate decrease in coercivity of annealed high-Co containing magnets. The discovery of new coercivity mechanism contributed to in-depth understanding of high-Co containing magnets.

Phase structure evolution and its effect on magnetic and mechanical properties of B-doped Sm2Co17-type magnets with high Fe content

Abstract The unique cellular microstructure of Fe-rich Sm2Co17-type permanent magnets is closely associated with the structure of the solid solution precursor. We investigate the phase structure, magnetic properties, and mechanical behavior of B-doped Sm2Co17-type magnets with high Fe content. The doped B atoms can diffuse into the interstitial vacancy, resulting in lattice expansion and promote the homogenization of the phase organizational structure during the solid solution treatment in theory. However, the resulting second phase plays a dominant role to result in more microtwin structures and highly ordered 2 : 17R phases in the solid solution stage, which inhibits the ordering transformation of 1 : 7H phase during aging and affects the generation of the cellular structure, and to result in a decrease in magnetic properties, yet the interface formed between it and the matrix phase hinders the movement of dislocations and enhances the mechanical properties. Hence, the precipitation of high flexural strain grain boundary phase induced by B element doping is also a new and effective way to improve the flexural strain of Sm2Co17-type magnets. Our study provides a new understanding of the phase structure evolution and its effect on the magnetic and mechanical properties of Sm2Co17-type magnets with high Fe content.

Large ferroelectric polarization and high dielectric constant in HfO2-based thin films via Hf0.5Zr0.5O2/ZrO2 nanobilayer engineering

HfO2-based ferroelectric films have been extensively explored and utilized in the field of non-volatile memory and electrical programmability. However, the trade-off between ferroelectric polarization and dielectric constant in HfO2 has limited the overall performance improvement of devices in practical applications. Herein, a novel approach is proposed for the Hf0.5Zr0.5O2/ZrO2 (HZO/ZrO2) nanobilayer engineering, which can effectively regulate the phase structure evolution of HfO2 films to construct a suitable morphotropic phase boundary (MPB). The findings highlight that the top ZrO2 layer can regularly promote the formation of either the ferroelectric o-phase or the antiferroelectric t-phase. An ideal MPB is successfully established in HZO/ZrO2 (6/9 nm) nanobilayer film by carefully optimizing the HZO/ZrO2 thickness ratio, which presents a high dielectric constant of 52.7 and a large 2Pr value of up to 72.3 μC/cm2 without any wake-up operation. Moreover, the HZO/ZrO2 nanobilayer thin films demonstrate faster polarization switching speed (1.09 μs) and better fatigue performance (109 cycles) compared to the conventional HZO solid solution films. The relationship between ferroelectric and dielectric properties can be harmoniously balanced through the designation. The results indicate that the HZO/ZrO2 nanobilayer engineering strategy is quite potential to pave the way for the development of next-generation memory technologies with superior performance and reliability.

Study on the micromorphologies and structural evolution in cold-mixed epoxy asphalt

Cold-mixed epoxy asphalt (CMEA) is a high performance paving material that can be constructed and cured at room temperature. It forms thermal and mechanical performances during curing process. In this study, the phase state and structural evolution characteristics of CMEA during curing were evaluated by curing rheological behavior, mechanical properties, and micromorphology. Viscosity tests and dynamic mechanical analyses (DMA) were applied to study the curing rheological behavior, and tensile tests were used to determine the mechanical properties. Moreover, fluorescence microscopy (FM), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) were implemented to investigate the micromorphological and molecular structure evolution. The results showed that the curing reaction behavior of CMEA was closely related to temperature. The viscosity–time curves of CMEA satisfied the Arrhenius equation above 45 ℃ and followed a linear trend at low temperature. During the curing of CMEA, the toughness increased in three stages: the toughness growth stage, toughness stability stage and toughness decay stage. Furthermore, the presence of asphalt and its solvent weakened the curing reaction of epoxy asphalt. However, increasing the reaction temperature could increase the epoxy group conversion rate. When the curing reaction was complete, a considerable amount of asphalt solvent mixed with the asphalt and was uniformly distributed within the three-dimensional network structure of the epoxy resin. This mixture adversely affected the toughness of the cured CMEA.

An Emergent Quadruple Phase Ensemble in Doped Bismuth Ferrite Thin Films Through Site and Strain Engineering

AbstractIn ferroic materials, giant susceptibilities can be realized at artificially constructed phase boundaries through deterministic manipulation of the order parameter. Here, emergent ferroelectric structural phase evolution behavior is demonstrated through a synergistic combination of A‐site doping and strain engineering. Using chemical solution deposition derived (001)‐oriented Sm‐substituted bismuth ferrite (Bi1‐xSmxFeO3) films as a prototypical system, a morphotropic phase boundary comprising a coexistence of four distinct crystallographic phases is uncovered. These ferroelectric, polar, and nonpolar phases form a nanoscale mixture without the presence of crystallographically hard boundaries. The system thus possesses the ability to show both polarization rotation and extension, effectively releasing the polarization from its crystallographic constraint. Consequently, both robust ferroelectric properties and giant electromechanical responses are obtained. For instance, the optimized composition with x = 0.14 has a remnant polarization of 2Pr = 103 µC cm−2 and electromechanical response 175% that of undoped BFO. These findings showcase the tremendous potential of synthetic phase boundaries, particularly in the context of lead‐free functional multiferroics.

Multi-scale study on strength development, hydration behavior and phase evolution of recycled powder multi component cementitious materials

Recycled powder (RP) is considered to be a successful low-carbon alternative to ordinary Portland cement (OPC). However, the microstructure and synergistic mechanism of RP multi-component cementitious materials (RP-MCCM) after physical activation are still unclear. The purpose of this study is to study the strength development, hydration and phase structure evolution of MCCM by constructing RP-MCCM. When the content of RP after grinding activation is 30% (C70RG30), its 28 days compressive strength is increased by 7.6% on the basis of non-activation. Compared with the ternary system of RP and FA mixed with 15% (C70RG15F15), its 28 days compressive strength increased by 8.08%. After RP incorporation, the Al-OH is enhanced, the C-O and CO32- bonds peaks become narrower, and the S is evenly distributed, which is beneficial to the increase of the AFt and the CaCO3 content, but weakens the C-S-H and C-A-H phases. In the C70RG15F15 ternary system, CaCO3, Ca(OH)2, and SiO2 nanostructures are tightly bonded together without obvious faults, which improves the structural compactness and strength. RP grinding activation is mainly manifested in surface improvement, internal C-S-H activation and increase of active sites.

LiNbO3-induced phase structure evolution and improved piezoelectric properties in BiFeO3–BaTiO3 ceramics

Eco-friendly (0.73-x)Bi1.05FeO3-xLiNbO3-0.27BaTiO3 ternary ceramics were designed and prepared via a solid-state sintering route. Based on the X-ray diffraction results and Rietveld refinement, it was found that the structure of the ceramics transformed from rhombohedral to tetragonal symmetry with the addition of LiNbO3, and at x = 0.003, there existed a morphotropic phase boundary separating the two phases. Near the phase boundary, the largest values were achieved for the piezoelectric constant d33 and planar electromechanical coupling coefficient kp, being 180 pC/N and 0.27, respectively. Due to the addition of LiNbO3, the grain size tended to become smaller. Additionally, the ceramics were transitioned from normal to relaxor ferroelectrics with increasing x. Despite the fact that the LiNbO3 addition would result in a gradual decrease of Curie temperature, a relatively high Curie temperature (535 °C) was still maintained at x = 0.003, the phase boundary composition, which also showed good temperature stability of piezoelectric properties. These experimental results can provide a reference for the practical applications of high-temperature lead-free ceramics.

Structural Evolution of GaOx-Shell and Intermetallic Phases in Ga-Pt Supported Catalytically Active Liquid Metal Solutions.

We present a comprehensive scale-bridging characterization approach for supported catalytically active liquid metal solutions (SCALMS) which combines lab-based X-ray microscopy, nano X-ray computed tomography (nano-CT), and correlative analytical transmission electron microscopy. SCALMS catalysts consist of low-melting alloy particles and have demonstrated high catalytic activity, selectivity, and long-term stability in propane dehydrogenation (PDH). We established an identical-location nano-CT workflow which allows us to reveal site-specific changes of Ga-Pt SCALMS before and after PDH. These observations are complemented by analytical transmission electron microscopy investigations providing information on the structure, chemical composition, and phase distribution of individual SCALMS particles. Key findings of this combined microscopic approach include (i) structural evolution of the SCALMS particles' GaOx shell, (ii) Pt segregation toward the oxide shell leading to the formation of Ga-Pt intermetallic phases, and (iii) cracking of the oxide shell accompanied by the release of liquid Ga-Pt toward the porous support.

Effects of hydrogen doping on the phase structure and optoelectronic properties of p-type transparent SnO

Hydrogen (H) is a ubiquitous impurity, which can significantly affect the phase structure and the optoelectronic properties of oxide semiconductors. To date, a well-established understanding of the effects of H doping on the properties of p-type transparent SnO is still lacking. Here, we present a comparative study to reveal the role of H in SnO films by magnetron sputtering. We find that in as-grown undoped SnO films, in addition to the tetragonal SnO phase, secondary phases of SnO2 or Sn3O4 are present under certain growth temperatures. In contrast, a small fraction of metallic Sn phase is included in the as-grown H-doped SnO (SnO:H) films, attributed to the partial reduction of SnO by the H2 in the sputtering gas. Effects of post thermal annealing (PTA) on the properties of SnO films are also explored. Results strongly indicate that H doping or PTA facilitates the formation of Sn phase and Sn vacancies related defects, giving rise to the p-type conductivity observed in the undoped or H-doped SnO films. The present study provides a comprehensive understanding of the evolution of phase structures as well as defect properties of SnO films, which is crucial for their future studies and optoelectronic applications.

Tuning the Electro‐Optic Properties of BaTiO3 Epitaxial Thin Films via Buffer Layer‐Controlled Polarization Rotation Paths

AbstractBaTiO3 thin films emerge as a highly promising material platform for integrated photonics due to their outstanding electro‐optic properties and diverse functionalities. Despite extensive studies, there remains a notable gap in the understanding of the intricate relationship between the phase structure, domain switching kinetics and electro‐optic performance of these materials. By controlling the structural phase evolution, it is possible to gain deep insights into the physical mechanisms underlying the electro‐optic performance. Here, the phase constitution of BaTiO3 epitaxial thin films is successfully tuned by the insertion of a GdScO3 buffer layer. Continuous polarization rotation paths are observed from an out‐of‐plane tetragonal‐like phase, to an intermediate rhombohedral‐like phase, and finally an in‐plane tetragonal‐like phase, achieving an enhanced effective electro‐optic coefficient of 175 pm V−1 compared to unbuffered films. Furthermore, by in situ second harmonic generation microscopy and electro‐optic measurements, the domain switching behaviors in both statistical and spatially resolved manners are examined, resulting in a clear delineation of the key domain nucleation processes. The in‐depth explorations of these structural mechanisms and kinetics inform the rational design of strong electro‐optic thin films and help in the realization of high‐performance integrated photonic devices such as electro‐optic modulators and multilevel phase shifters.

Na1/2Bi1/2TiO3‐based ceramics with increased depolarization temperature and piezoelectric coefficient

AbstractSodium bismuth titanate‐based materials are expected to be an alternative candidate to lead‐based ceramic materials due to their excellent electrical properties. However, the low depolarization temperature (Td) limits their practical application. In this work, the phase structure evolution and microstructure of 0.9(0.4Na1/2Bi1/2TiO3–0.6BiFeO3)–0.1BaTiO3: xZnO (x = 0.01, 0.03, 0.05, and 0.07) (abbreviated as 100xZnO) composite ceramics are investigated, and their piezoelectric properties are improved by combination of constructing 0–3 type composites and quenching treatment technology. The addition of ZnO can increase both Td and d33 because ZnO can enhance the lattice distortion of rhombohedral phase and lead to the increase in ferroelectric order. Specifically, the optimum composition x = 0.03 obtains the d33 value of 106 pC/N (25°C), which retains 84% of the value at room temperature up to 240°C. And the quenching technology further enhances the ferroelectric order and increases Td, which is up to 280°C for x = 0.03.