Crystal Phase Transformation Research Articles

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.

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

In this paper, we present an in-depth examination of the absorption dynamics of a silver plasmonic grating incorporating Kerr-type nonlinear graphene-oxide (GO) nanoslits and a Ge2Sb2Se4Te1 (GSST) phase-change material, both in linear and nonlinear regimes. Linear absorption approaches unity at the resonant wavelength when GSST is amorphous. Upon exposure to a nanosecond Gaussian pulse laser irradiation with appropriate fluences, the amorphous GSST partially crystallizes through a thermoplasmonic-induced process, resulting in a significant reduction of the linear on-resonance absorption in the form of a step-like curve. Additionally, the weak off-resonance linear absorption of the system can be enhanced owing to the non-uniform phase-transition within the GSST. Transitioning to a nonlinear regime, considering the third-order nonlinearity of GO nanoslits, reveals distinct absorption behaviors. Temporal analysis reveals that at the on-resonance wavelength, the unit absorption decreases with increasing laser intensity, reaching a minimum at the pulse peak due to the Kerr nonlinearity in the GO. Intriguingly, the absorption exhibits a U-shaped curve at lower fluences, while at higher fluences, it stabilizes at a lower value post-pulse peak where the amorphous GSST undergoes a thermally driven partially crystallization phase transformation. In the off-resonance mode, the weak absorption enhances dramatically by increasing the fluence, tracing an imperfect parabolic trajectory that reaches nearly unit at the trailing edge of the pulse, attributed to the Kerr nonlinearity within the GO nanoslits. By further increasing the laser fluence, the photothermal response of the GSST emerges as the dominant factor, diminishing the unity absorption observed at the trailing edge of the pulse. These findings underscore the dynamic responsiveness of the proposed grating to pulsed laser illumination, driven by the nonlinear Kerr effect and GSST reconfigurability, offering promising opportunities for developing active optical switching devices.

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

Poly(vinylidene fluoride) (PVDF) with a high content of β phase shows great potential for applications in the pulse energy storage field because of its high dielectric constant and breakdown strength. The stretching process can significantly induce the crystal phase transformation and change the structure of the aggregated state. To deeply investigate the influence mechanism of the fabrication process, solution casting (SC), melt stretching (MS), static biaxial orientation (SBO), and continuous biaxial orientation (CBO) were used to fabricate PVDF films. The essential difference between the four technological routes lies in the different forms of tensile orientation imposed. Stretching perpendicular to the machine direction promotes the transition of the original α phase crystals to the β phase. Stretching orientation can regulate the crystalline phase structure of the film and its applicability. The relative fraction of β phase crystals in the PVDF-CBO film reaches 84.1 %, resulting in a much higher dielectric constant (12.22 @1 kHz) than that of the PVDF-SC film (7.16). The continuous biaxially oriented PVDF exhibited excellent insulation properties with a breakdown strength of 759.21 kV/mm. Meanwhile, the CBO film obtained an energy storage density of 16.76 J/cm3 with a charge-discharge efficiency of 80.13 % at 675 kV/mm. This work is of great scientific significance for the in-depth study of the influence of different film-forming processes on the internal structure of films, ranging from laboratory fabrication to industrialized production.

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

Celsian (BaAl2Si2O8) is an important component of aluminosilicate-based ceramics, which is widely used in high temperature/high pressure process. However, limited data available on its high pressure (HP)/high temperature (HT) behavior and HT studies were based on multi-component samples only. Here we present data on crystal structure stability and phase transformation processes of celsian studied under extreme conditions (up to ∼22 GPa/∼1110 °C) using in situ X-ray diffraction. Under HP conditions celsian undergoes three phase transitions: at the pressures below 10 GPa the main changes in the crystal structure of celsian associated with the changes in the coordination Ba-centered polyhedron (celsian-II and celsian-III), whereas at higher pressures AlO4 tetrahedra transforms into AlO6 octahedra (celsian-IV). Though the HP behavior of some isostructural compound has been studied before, the HP transformation of celsian is not similar to any previously studied mineral or synthetic compound. Celsian demonstrate stability and low thermal expansion coefficients (αV = 12 × 10−6 °C−1) in the studied temperature range.

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

Vanadium dioxide (VO2) has great potentials to be used in energy-related fields due to its unique reversible thermochromic metal-insulating properties. In this paper, we used in-situ XRD technique to study the phase transition kinetics of VO2 thin films, which can change phase from monoclinic VO2 (M) to tetragonal rutile VO2 (R). The VO2 thin films were prepared by a simple solution-based sol-gel method followed by spin coating to achieve the nanoscale thickness on a quartz substrate. During heating, the critical phase transition of VO2 (M) occurred at 70 °C, which dropped to 45 °C during cooling. A martensite-like crystal phase transformation kinetic model was established based on the Koistinen and Marburger (KM) technique. The relative content of the two phases was quantitatively analyzed using the Rietveld method, and the transformation rate coefficient α was obtained as 0.20345 and 0.12585, for the heating process from VO2 (M) to VO2 (R) and the cooling process from VO2 (R) to VO2 (M), respectively. This research offers an effective tool for understanding the structural characteristics of thin film VO2, paving the way for its future design and applications towards energy-related fields such as in smart windows.

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

The photoelectrochemical (PEC) water splitting performance is conventionally limited by the process of photogenerated carrier separation and transport. This work provides an innovative strategy by combination of the spin-polarized electric field and homogeneous junction to address this critical issue. In this work, it finds that a spin-polarized electric field can be fabricated in the CdS photoanode with cubic phase by S vacancy intervention. Furthermore, after controlling the annealing temperature to reach 500 °C, cubic phase CdS photoanode translates to hexagonal phase by localized, forming a homogeneous junction CdS photoanode. By the synergy, the optimized CdS photoanode achieves a photocurrent density exceeding ∼5.0 mA/cm2 for hydrogen evolution under 100 mW/cm2 white light illumination, a 2.4-fold improvement over the performance of the unoptimized photoanodes. Thus, this work provides a novel method to regulation of the photogenerated carrier separation and transport processes for sulfur-based semiconductor photoelectrodes.

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

Accelerated carbonation curing contributes to the carbon sequestration effect of cementitious materials and enhances surface density. However, in large-scale applications, traditional high CO2 concentration conditions (>5 % CO2) are constrained by economic costs. This study traces the early-stage accelerated carbonation process of cement mortar under low CO2 concentration (3 % CO2) condition from the perspectives of the evolution of CaCO3 crystal types, phase transformations, and microstructural changes, and compares the results with those under the 20 % CO2 condition. The results show that the carbonation depth of mortar specimens cured under the 3 % CO2 condition is shallower, but the cumulative concentration of CaCO3 within the surface 3 mm is not significantly lower than that under the 20 % CO2 condition; The carbonation zone generates more low-crystalline forms of CaCO3; The accelerated carbonation process does not affect the formation of CH and ettringite. Microscopic results indicate that under the 3 % CO2 condition, the synergistic effects of hydration and carbonation are better, and appropriately extending the curing time helps to refine the pore structure of the carbonation zone and improve the density of the substrate surface.

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 120 μM with a low detection limit of 167 nM 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

The synthesis of zeolites and porous heteropolyhedral silicates is usually accompanied by crystal phase transformations. Typically, this process is irreversible and characterized by a conversion from a metastable phase to a stable one. Here we demonstrate a reversible transformation between porous (K3LnSi3O9·nH2O) and layered (K3LnSi3O8(OH)2) structures exemplified by a dual synthesis (hydrothermal and solid-state transformation). We discuss structural and photoluminescent properties of the obtained microporous lanthanide silicates MS-4 (Minho-Sofia, solid number 4; K3LnSi3O9·nH2O, Ln = Y, Dy; orthorhombic, Pmc21). These materials are metastable, transforming from 3D porous to a 2D layered structure after prolonged crystallization time at hydrothermal conditions and returning to the same but distorted (≈ 2 % smaller lattice volume) porous 3D framework by calcination of 2D structure. The mechanism of 3D-2D structure transformation is driven by interzeolite-like transformation, while the rearrangement of common structural fragments controls 2D-to-3D conversion. We also show how the avoidance of Dy and preference for Y ions during MS-4 hydrothermal synthesis may be overcome by a 2D-3D conversion, allowing the production of white light emitters with controllable photoluminescence.

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

The phase transformation and superelastic behavior of nanocrystalline Ni48Ti50Mo2 alloy wires were investigated. Nanocrystalline (NC) alloys were obtained via severe plastic deformation of cold-drawing followed by annealing at low temperatures. The results indicate that the NC Ni48Ti50Mo2 undergoes a single-step B2→R phase transformation and a two-step B2→R→B19′ phase transformation in coarse crystals (CG). The NC alloy wire exhibits 8 % recoverable strain under a tensile stress of 1.1 Ga and superelasticity exists in a wide temperature range from −60 °C to 100 °C. After 50 cycles of tension fatigue testing, the superelastic upper plateau stress reduction rate is 7 % with almost no residual strain accumulation, which has excellent superelastic stability compared with fine crystals and coarse crystals. Transmission electron microscope (TEM) reveals an average grain size of 20 nm. The stable superelasticity is attributed to the nanocrystalline reinforced matrix, which hinders dislocation generation and slip.

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.

Programming of Supercrystals Using Replicable DNA-Functionalized Colloids.

The development of self-replicating systems is of great importance in research on the origin of life. As the most iconic molecules, nucleic acids have provided prominent examples of the fabrication of self-replicating artificial nanostructures. However, it is still challenging to construct sophisticated synthetic systems that can create large-scale or three-dimensionally ordered nanomaterials using self-replicating nanostructures. By integrating a template system containing DNA-functionalized colloidal seeds with a simplified DNA strand-displacement circuit programmed subsystem to produce DNA-functionalized colloidal copies, we developed a facile enthalpy-mediated strategy to control the replication and catalytic assembly of DNA-functionalized colloids in a time-dependent manner. The replication efficiency and crystal quality of the resulting superlattice structures can be effectively increased by regulating the molar ratio of the template to the copy colloids. By constructing binary systems from two types of gold nanoparticles (or proteins), superlattice structures with different crystal symmetries can be obtained through the replication and catalytic assembly processes. This programmable enthalpy-mediated approach was easily leveraged to achieve the phase transformation and catalytic amplification of colloidal crystals starting from different initial template crystals. This work offers a potential way to construct self-replicating artificial systems that exhibit complicated phase behaviors and can produce large-scale superlattice nanomaterials.

Programming of Supercrystals Using Replicable DNA‐Functionalized Colloids

AbstractThe development of self‐replicating systems is of great importance in research on the origin of life. As the most iconic molecules, nucleic acids have provided prominent examples of the fabrication of self‐replicating artificial nanostructures. However, it is still challenging to construct sophisticated synthetic systems that can create large‐scale or three‐dimensionally ordered nanomaterials using self‐replicating nanostructures. By integrating a template system containing DNA‐functionalized colloidal seeds with a simplified DNA strand‐displacement circuit programmed subsystem to produce DNA‐functionalized colloidal copies, we developed a facile enthalpy‐mediated strategy to control the replication and catalytic assembly of DNA‐functionalized colloids in a time‐dependent manner. The replication efficiency and crystal quality of the resulting superlattice structures can be effectively increased by regulating the molar ratio of the template to the copy colloids. By constructing binary systems from two types of gold nanoparticles (or proteins), superlattice structures with different crystal symmetries can be obtained through the replication and catalytic assembly processes. This programmable enthalpy‐mediated approach was easily leveraged to achieve the phase transformation and catalytic amplification of colloidal crystals starting from different initial template crystals. This work offers a potential way to construct self‐replicating artificial systems that exhibit complicated phase behaviors and can produce large‐scale superlattice nanomaterials.

Thermal stability and strength degradation of lithium slag geopolymer containing fly ash and silica fume

This paper investigates the thermal stability of lithium slag geopolymer (LSG) containing fly ash (FA) and silica fume (SF) exposed up to 900˚C. The effects of elevated temperatures on the microstructural evolution were investigated by thermogravimetric analysis (TGA), X-ray Diffraction (XRD), mineral analysis, surface porosity, and compressive strength of LSG modified by optimum incorporation of fly ash and silica fume. The results indicated that elevated temperature exposure significantly affects compressive strength, surface porosity, void size, weight loss, and phase transformation of fly ash incorporated lithium slag geopolymer (LSGFA) and silica fume incorporated geopolymer (LSGSF). The maximum loss in compressive strength of 44.07% was observed in LSGFA compared to 31.50% loss in LSGSF after exposure at 900˚C. The weight loss of LSGSF was higher than that of LSGFA between 500 and 800˚C and 800–1000˚C indicating a higher degree of dehydroxylation, crystal phase transformation, and viscous sintering observed in the former mix. A larger shrinkage cracking was observed in LSGSF by self-desiccation of the aluminosilicate paste matrix by dehydroxylation of mordenite molecules. Therefore, the degradation of compressive strength is governed by the combination of the crystallization of aluminosilicate gel and the formation of voids.

Realization of magnetic-field-induced martensitic transformation in melt-spun Fe-Mn-Ga alloys

This study investigates the crystal structural, magnetic properties, and phase transformation of melt-spun Fe-Mn-Ga alloys. We found that melt-spun Fe50Mn25Ga25 alloy crystallizes into a γ phase, which exhibits ferromagnetism at room temperature, and undergoes a magnetic transition at 257 K. On the other hand, melt-spun Fe49Mn24Ga27, Fe43Mn28Ga29 and Fe44Mn28Ga28 alloys exhibit a single body-centered cubic phase, with the latter two alloys undergo martensitic transformation during cooling. Additionally, a magnetic-field-induced martensitic transformation was observed within the temperature range of 180 to 160 K. Notably, the martensitic transformation temperatures of these two melt-spun Fe-Mn-Ga alloys are significantly lower compared to other fabrication methods, potentially attributed to the atomic disorder, microstructure and internal stresses that arise during the melt-spun fabrication process. These findings expand the available preparation methods for Fe-Mn-Ga alloys and offer new possibilities for future applications.