Crystal Phase Transformation Research Articles

Electrocatalytic synergy from Ni-enhanced WS2 for alkaline overall water splitting with tuning electronic structure and crystal phase transformation.

Due to the limited active sites and poor conductivity, the application of tungsten disulfide (WS2) in alkaline water electrolysis remains a challenge. Herein, Ni-WS2 nanosheet arrays were in situ grown on the carbon fiber paper (Ni-WS2/CFP) as an electrocatalyst for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline media, and the introduction degree of Ni can be regulated by adjusting the electrodeposition time. When the electrodeposition time is 3min, Ni ions are doped into the lattice of WS2, and by prolonging the electrodeposition time to 10min, the nickel disulfide (NiS2) crystal phase is generated to form NiS2@WS2 heterojunction. The optimized Ni-WS2/CFP-10min catalyst requires the overpotentials of 65mV for HER and 251mV for OER to achieve the current density of 10mAcm-2. A two-electrode water electrolysis device employing the Ni-WS2/CFP-10min electrocatalyst requires a cell voltage of 1.63V at the current density of 10mAcm-2. This work provides a new perspective for enhancing the electrocatalytic performance of WS2-based electrocatalysts by introducing heteroatoms and constructing heterojunction.

Effect of SiO2 monocrystalline substrate orientation on the crystal structure and properties of VO2 film

Effect of SiO2 monocrystalline substrate orientation on the crystal structure and properties of VO2 film

Deformation mechanism and microstructure evolution of newly developed Ti-42.5Al-4Nb-0.5Mo-0.1B-(C, W, Y) alloy

Deformation mechanism and microstructure evolution of newly developed Ti-42.5Al-4Nb-0.5Mo-0.1B-(C, W, Y) alloy

Investigation of the effects of alumina particle phase transition on internal flow field and engine performance in solid rocket motors

This study integrates theoretical modeling with numerical simulation methods to establish a comprehensive phase change dynamics model. The model encompasses critical stages of the phase change process, including undercooling, nucleation, solidification, and crystal phase transformation. We also utilize the latest drag coefficient model and heat transfer model in the two-phase flow field. Through numerical simulation, we delve into the impact of the phase change process of monodisperse particles on the flow field characteristics within a nozzle, extending our investigation to polydisperse particles phase change process. Furthermore, we systematically analyze the specific effects of variations in particle size distribution and particle loading on nozzle performance. In our simulation results, the most significant specific impulse enhancement was achieved under conditions of d43 = 2.63 μm and 20% particle loading, resulting in a specific impulse increase in approximately 0.53% compared to scenarios neglecting phase change. This work provides a solid theoretical foundation for accurately evaluating engine performance through numerical simulation.

Crystal structure stability and phase transition of celsian, BaAl2Si2O8, up to 1100 °C / 22 GPa

Crystal structure stability and phase transition of celsian, BaAl2Si2O8, up to 1100 °C / 22 GPa

In-situ XRD study on phase transition kinetics of vanadium dioxide thin film

In-situ XRD study on phase transition kinetics of vanadium dioxide thin film

Dynamic tunability of NIR absorption in a plasmonic grating through nonlinear kerr-effect of graphene-oxide and photothermal phase transition of GSST

Dynamic tunability of NIR absorption in a plasmonic grating through nonlinear kerr-effect of graphene-oxide and photothermal phase transition of GSST

Effect of stretching orientation on the crystalline structure and energy storage properties of poly(vinylidene fluoride) films

Effect of stretching orientation on the crystalline structure and energy storage properties of poly(vinylidene fluoride) films

Crystallite size and phase purity in Pb1-xSrxTiO3 ferroelectric perovskites for biomedical applications via controlled sintering

ABSTRACT Lead strontium titanate (Pb1-xSrx)TiO3 (PST) is a ferroelectric perovskite material with tunable properties, including Curie temperature, spontaneous polarization, and high dielectric permittivity, making it promising for advanced biomedical applications, such as biosensors, bioimaging, and light-activated therapeutics. This study investigates the effect of varying sintering temperatures on the crystallite size and phase purity of PST, aiming to optimize its performance for biomedical devices. PbCO3, SrCO3, and TiO2 powders were processed via ball milling for 58 hours, followed by sintering at temperatures ranging from 500°C to 1100°C. Laser diffraction particle size analysis and X-ray diffraction (XRD) were used to assess the particle size and crystal phase transformations. The results demonstrate that higher sintering temperatures improve the PST phase composition, reducing impurities and enhancing crystallite growth. The most significant crystal growth was observed at 900°C, while the optimal phase purity and crystallite size (91.5 nm) were achieved at 1100°C, producing 100% single-phase PST. These findings emphasize the critical role of sintering temperature in tailoring PST’s properties, enhancing its suitability for electronic and microelectronic biomedical devices. Controlled sintering in perovskite materials opens new pathways for their application in medical diagnostics and therapeutic technologies.

Modulation the carrier separation mechanism of CdS photoanode: From vacancy to crystal phase transformation

Modulation the carrier separation mechanism of CdS photoanode: From vacancy to crystal phase transformation

Early age accelerated carbonation of cementitious materials surface in low CO2 concentration condition

Early age accelerated carbonation of cementitious materials surface in low CO2 concentration condition

Study on the effect of heat treatment on the structure, mechanical and electrical properties of alumina fiber insulation

In this paper, the heat treatment of alumina fiber was studied. The infiltration agent on the fiber surface was removed after heat treatment at 450 °C for 6 h. TG-DSC, scanning electron microscope, x-ray diffraction, Fourier infrared spectrometer, energy dispersive spectrometer, and patterning were used to analyze the thermal weight loss, fiber surface morphology, crystal structure, and composition of alumina fibers. The results show that the aluminum oxide fiber has excellent temperature resistance and does not undergo crystal phase transformation during thermal weight loss. After heat treatment, the fiber surface infiltration agent ablates and dissolves from the fiber surface, and the internal crystal structure of the fiber remains stable. The tensile testing machine was utilized to test the breaking strength of alumina fiber. The fiber still maintained high strength after heat treatment, and the retention rate of breaking strength was greater than 74%. ZC-90G high insulation resistance measuring instrument and WDY-Ⅱ automatic voltage tester were utilized to analyze the insulation resistivity and breakdown strength of alumina fiber before and after heat treatment. The results show that heat treatment can effectively improve the insulation performance and breakdown strength of alumina fiber.

Fabrication of a two-dimensional bi-lanthanide metal-organic framework as a ratiometric fluorescent sensor based on energy competition

Bimetallic lanthanide metal-organic frameworks (bi-Ln-MOFs) exhibit great appeal for ratiometric luminescent sensors due to their unique advantages. Specially, the low-lying energy of the empty 4f band of Ce4+ ions benefits Ce-MOFs with robust and broad fluorescent emission. Therefore, constructing ratiometric sensors based on Ce-MOFs is of significance but remains a challenge. Here, a two-dimensional (2D) bi-Ln-MOF is fabricated using Eu3+/Ce4+ and 5-boronoisophthalic acid (5-bop) via a crystal phase transformation strategy to construct a ratiometric luminescent Hg2+ sensor. Due to the lower energy gap of Ce4+ compared to Eu3+ and the corresponding stronger energy-absorption ability, the Ce4+ in bi-Ln-MOF shows a stronger and broader fluorescent emission than that of Eu3+. The substitution of the boric acid group in the bi-Ln-MOF by Hg2+ amplifies the difference between the two lanthanide ions. Therefore, the fluorescence intensity of Ce4+ increases whereas that of Eu3+ decreases accordingly, a behavior distinct from individual Eu-MOF or Ce-MOF performance. This novel bi-Ln-MOF sensor not only achieves a wide linear response range from 0.5 to 120μM with a low detection limit of 167nM for Hg2+, but also demonstrates exceptional selectivity and stability. The intriguing sensing mechanism of energy competition and the novel synthesis approach for 2D bi-Ln-MOF are anticipated to broaden the application possibilities of bi-Ln-MOFs for designing ratiometric sensors.

Nano-cutting mechanism of ion implantation-modified SiC: reducing subsurface damage expansion and abrasive wear

This study utilized ion implantation to modify the material properties of silicon carbide (SiC) to mitigate subsurface damage during SiC machining. The paper analyzed the mechanism of hydrogen ion implantation on the machining performance of SiC at the atomic scale. A molecular dynamics model of nanoscale cutting of an ion-implanted SiC workpiece using a non-rigid regular tetrakaidecahedral diamond abrasive grain was established. The study investigated the effects of ion implantation on crystal structure phase transformation, dislocation nucleation, and defect structure evolution. Results showed ion implantation modification decreased the extension depth of amorphous structures in the subsurface layer, thereby enhancing the surface and subsurface integrity of the SiC workpiece. Additionally, dislocation extension length and volume within the lattice structure were lower in the ion-implanted workpiece compared to non-implanted ones. Phase transformation, compressive pressure, and cutting stress of the lattice in the shear region per unit volume were lower in the ion-implanted workpiece than the non-implanted one. Taking the diamond abrasive grain as the research subject, the mechanism of grain wear under ion implantation was explored. Grain expansion, compression, and atomic volumetric strain wear rate were higher in the non-implanted workpiece versus implanted ones. Under shear extrusion of the SiC workpiece, dangling bonds of atoms in the diamond grain were unstable, resulting in graphitization of the diamond structure at elevated temperatures. This study established a solid theoretical and practical foundation for realizing non-destructive machining at the atomic scale, encompassing both theoretical principles and practical applications.

Metastable microporous lanthanide silicates – Light emitters capable of 3D-2D-3D transformations

Metastable microporous lanthanide silicates – Light emitters capable of 3D-2D-3D transformations

Stable and wide temperature range superelasticity in an Mo-doped nanocrystalline Ni–Ti–Mo shape memory alloy

Stable and wide temperature range superelasticity in an Mo-doped nanocrystalline Ni–Ti–Mo shape memory alloy

CO2 Promoting Polymorphic Transformation of Clarithromycin: Polymorph Characterization, Pathway Design, and Mechanism Study

Carbon dioxide (CO2) has a wide range of uses such as food additives and raw materials for synthetic chemicals, while its application in the solid-state transformation of pharmaceutical crystals is rare. In this work, we report a case of using 1 atm CO2 as an accelerator to promote the polymorphic transformation of clarithromycin (CLA). Initially, crystal structures of Form 0′ and three solvates were successfully determined by single crystal X-ray diffraction (SCXRD) analysis for the first time and found to be isomorphous. Powder X-ray diffraction (PXRD) and thermal analysis indicated that the solvate desolvates and transforms into the structurally similar non-solvated Form 0′ at room temperature to ~50 °C. Form 0′ and Form II are monotropically related polymorphs with Form II being the most stable. Subsequently, the effect of CO2 on the transformation of CLA solvates to Form II was studied. The results show that CO2 can significantly facilitate the transformation of Form 0′ to Form II, despite no significant effect on the desolvation process. Finally, the molecular mechanism of CO2 promoting the polymorphic transformation was revealed by the combination of the measurement of adsorption capacity, theoretical calculations as well as crystal structure analysis. Based on the above results, a new pathway of preparing CLA Form II was designed: transform CLA solvates into Form 0′ in 1 atm air at 50 °C followed by the transformation of Form 0′ to Form II in 1 atm CO2 at 50 °C. This work provides a new idea for promoting the phase transformation of pharmaceutical crystals as well as a new scenario for the utilization of CO2.

Crystal-Phase-Engineered High-Entropy Alloy Aerogels for Enhanced Ethylamine Electrosynthesis from Acetonitrile.

Crystal-phase engineering that promotes the rearrangement of active atoms to form new structural frameworks achieves excellent result in the field of electrocatalysis and optimizes the performance of various electrochemical reactions. Herein, for the first time, it is found that the different components in metallic aerogels will affect the crystal-phase transformation, especially in high-entropy alloy aerogels (HEAAs), whose crystal-phase transformation during annealing is more difficult than medium-entropy alloy aerogels (MEAAs), but they still show better electrochemical performance. Specifically, PdPtCuCoNi HEAAs with the parent phase of face-centered cubic (FCC) PdCu possess excellent 89.24% of selectivity, 746.82mmol h-1 g-1 cat. of yield rate, and 90.75% of Faraday efficiency for ethylamine during acetonitrile reduction reaction (ARR); while, maintaining stability under 50h of long-term testing and ten consecutive electrolysis cycles. The structure-activity relationship indicates that crystal-phase regulation from amorphous state to FCC phase promotes the atomic rearrangement in HEAAs, thereby optimizing the electronic structure and enhancing the adsorption strength of reaction intermediates, improving the catalytic performance. This study provides a new paradigm for developing novel ARR electrocatalysts and also expands the potential of crystal-phase engineering in other application areas.

Phase Engineering of Zirconium MOFs Enables Efficient Osmotic Energy Conversion: Structural Evolution Unveiled by Direct Imaging.

Creating structural defects in a controlled manner within metal-organic frameworks (MOFs) poses a significant challenge for synthesis, and concurrently, identifying the types and distributions of these defects is also a formidable task for characterization. In this study, we demonstrate that by employing 2-sulfonylterephthalic acid as the ligand for synthesizing Zr (or Hf)-based MOFs, a crystal phase transformation from the common fcu topology to the rare jmt topology can be easily facilitated using a straightforward mixed-solvent strategy. The jmt phase, characterized by an extensively open framework, can be considered a derivative of the fcu phase, generated through the introduction of missing-cluster defects. We have explicitly identified both MOF phases, their intermediate states, and the novel core-shell structures they form using ultralow-dose high-resolution transmission electron microscopy. In addition to facilitating phase engineering, the incorporation of sulfonic groups in MOFs imparts ionic selectivity, making them applicable for osmotic energy harvesting through mixed matrix membrane fabrication. The membrane containing the jmt-phase MOF exhibits an exceptionally high peak power density of 10.08 W m-2 under a 50-fold salinity gradient (NaCl: 0.5 M|0.01 M), which surpasses the threshold of 5 W m-2 for commercial applications and can be attributed to the combination of large pore size, extensive porosity, and abundant sulfonic groups in this novel MOF material.

Experimental investigation on effect of tool geometry on thermal and crystallization characteristics in drilling of carbon fiber reinforced PEEK composite

AbstractThis paper comprehensively investigated the effect of the tool geometries on heat transfer and special crystallization characteristics in the drilling of carbon fiber‐reinforced polyetheretherketone (CF/PEEK) composite for the first time. Three tools with different geometries (twist, brad, and dagger drill) are carried out on CF/PEEK drilling experiments, and temperature, as well as crystallinity and surface roughness, are introduced to make a comparative evaluation on the effect of the tool geometries. The results show that the drilling temperature is determined by the contact length of the profile between the drill and the material. Correspondingly, better surface quality with lower surface roughness and smoother surface is obtained by using a twist drill due to the heat‐induced PEEK smearing effect. Further, in situ XRD and differential scanning calorimeter (DSC) were used to characterize the crystallization characteristics where crystal phase transformation at different temperatures was measured. The occurring temperature of the strongest crystallization characteristics for CF/PEEK is basically not affected by tool geometries, all at 300°C, and the limiting crystallization temperature is 344.5 ± 0.7°C. The crystallinity is found to be affected by drilling temperature and cooling rate and gradually decreases along the heat transfer direction. This work provides a new sight into the improvement of CF/PEEK drilling.Highlights The effect of tool geometries on thermal and crystallization for CF/PEEK is provided. In situ XRD and DSC are used to characterize crystallization characteristics. The drilling temperature and cooling rate are both determinants of crystallinity. The limiting crystallization temperature of the CF/PEEK composite is 344.5 ± 0.7°C. Heat‐induced PEEK smearing effect improves the surface quality of CF/PEEK drilling.