Shift Of Diffraction Peak Research Articles

Synergistic effects of liquid phase sintering and B-site substitution to enhance proton conductivity of BaZr0.1Ce0.7Y0.1Yb0.1O3-δ for protonic ceramic fuel cell

This paper is dedicated to improving the sintering and conductivity of BaZr0.1Ce0.7Y0.1Yb0.1O3-δ (BZCYYb) by adding ZnO-CuO dual-sintering aids. The synergistic effects of liquid-sintering of Zn and B-site substitution of Cu on the sinterability and proton conductivity of BZCYYb are systematically investigated. X-ray diffraction (XRD) analysis of BZCYYb after addition of ZnO-CuO (BZCYYb-Zn-Cu) confirms the complete perovskite phase formation without any secondary phase. The substitution of Ce4+ (0.87 Å) with Zn2+ (0.74 Å) or Cu2+ (0.73 Å) induces a shift in XRD diffraction peak to higher angle due to a decrease in lattice constant. Energy dispersive X-ray spectroscopy analysis indicate a distinct distribution of Zn primarily at the grain boundaries, while Cu is predominantly located within the grains of BZCYYb-Zn-Cu. The addition of ZnO-CuO into BZCYYb results in a denser microstructure with larger average grain size. Furthermore, the substitution of Ce4+ by Cu2+ increases the concentration of oxygen vacancies and reduces activation energy. For BZCYYb-Zn-Cu, the proton conductivity reaches 4.52×10-2 S/cm at 750 °C, approximately 3 times higher than that of BZCYYb. This enhancement can be attributed to the synergistic effects of larger average grain size resulting from liquid phase sintering of Zn, low active energy, and high concentration of oxygen vacancies arising from Cu B-site substitution. BZCYYb-Zn-Cu is used as the electrolyte for anode support SOFC, and the single cell exhibits remarkable electrochemical performance and excellent stability in H2 fuel. This research establishes a crucial theoretical foundation for the preparation and performance evaluation for large-size protonic ceramic cell.

Microstructure and Crystal Modulus of Polyamide 4 α-form in the Direction Parallel to the Chain Axis

Polyamide 4 (PA4) is a lactam-based aliphatic synthetic polymer with promising properties and admirable biodegradability. In this study, oriented PA4 fibers were fabricated by dry spinning followed by thermal drawing. Elastic modulus (El) of the crystalline regions (crystal modulus) of PA4 fibers in the direction parallel to the chain axis was evaluated from the X-ray diffraction peak shift owing to the tensile stress. The apparent El value of PA4 is 67 GPa for meridional 004 reflection and 119 GPa for 0010 reflection, respectively. The reason for the different El is that the decrease of crystallite size of PA4 by the applied stress brought extra shifts of 004 reflection peak to lower angle based on the Laue factor. In contrast, 0010 reflection peak received less effects from this effect, and the El value of 119 GPa obtained from 0010 reflection was considered to be a reliable value. The observed El value of PA4 is much lower than the calculated values assuming fully extended planar zigzag skeleton for PA4. Thus the low El value is attributed to the highly contraction (-1.9%) from the fully extended conformation as observed for another polyamides.

Probing structural and electrochemical properties of a 2D CoMoO4@hBN nanocomposite as pseudocapacitive electrode for high-performance supercapacitors

The effectiveness of energy storage is largely determined by the electrode material's performance in critical areas. Enhancements in ion transport, cyclic stability, rate capability, and specific capacitance directly boost the supercapacitors' overall performance and broaden their application potential. This study aims to enhance these properties by incorporating hexagonal boron nitride (hBN) into cobalt molybdate (CoMoO4) material in a 1:1 stoichiometric ratio. The CoMoO₄@hBN nanocomposite was synthesized using a hydrothermal method followed by ball milling. The X-ray diffraction (XRD) analysis confirmed the formation of a single-phase CoMoO4@hBN composite, with a significant increase in crystallite size from 18.21 nm in pure CoMoO₄ to 25.6 nm, along with a slight shift in diffraction peaks, indicating enhanced crystallinity and structural defects due to the substitution of oxygen with boron atoms. Raman spectroscopy revealed that the composite retains the characteristic peaks of both CoMoO₄ and hBN, with stable sharp peaks at 936 cm−1 (Mo=O bond) and 1367 cm−1 (E2g peak of hBN) even after 20 depth measurements, confirming successful conjugation and consistent vibrational properties. The X-ray photoelectron spectroscopy (XPS) showed a slight shift in Co 2p and Mo 3d binding energies to higher values, suggesting improved electronic interactions between CoMoO4 and hBN, which could enhance the composite's conductivity. The electrochemical analysis demonstrated that incorporating h-BN significantly boosts the electrode's performance compared to pristine CoMoO4, with about 37 % increase in specific capacitance at 1 A g−1, reduced charge transfer resistance (0.11 Ω), and superior cyclic stability with 96 % capacitance retention after 5000 cycles. These findings indicate that hBN enhances both the electrical conductivity and structural integrity of CoMoO4, positioning the CoMoO4@hBN composite as a promising material for high-performance supercapacitors.

Preparation and Adsorption Photocatalytic Properties of PVA/TiO2 Colloidal Photonic Crystal Films.

Polyvinyl alcohol (PVA)/TiO2/colloidal photonic crystal (CPC) films with photocatalytic properties are presented, where TiO2 nanoparticles were introduced into the PVA gel network. Such PVA/TiO2/CPC films possess three-dimensional periodic structures that are supported with a PVA/TiO2 composite gel. The unique structural color of CPCs can indicate the process of material preparation, adsorption, and desorption. The shift of diffraction peaks of CPCs can be more accurately determined using fiber-optic spectroscopy. The effect of the PVA/TiO2/CPC catalyst films showed better properties as the degradation of methylene blue (MB) by the PVA/TiO2/CPC film catalyst in 4 h was 77~90%, while the degradation of MB by the PVA/TiO2 film was 33% in 4 h, indicating that the photonic crystal structure was 2.3~2.7 times more effective than that of the bulk structure.

Molecularly imprinted photonic polymer for rapid visual detection of sulfamethoxazole in environmental water samples

AbstractSulfamethoxazole (SMX) has numerous adverse effects and is present in various water systems; thus, the development of a rapid and accurate analytical method to detect SMX in water systems is crucial for protecting the environment and human health. A sulfamethoxazole molecularly imprinted photonic polymer (MIPP‐SMX) capable of facile naked‐eye recognition of target molecules was synthesized using the dual‐functional monomers acrylamide and methacrylic acid. The color of the MIPP‐SMX changed from green to blue in water samples containing sulfamethoxazole (SMX) in the concentration range of 0.5–5.0 mM. Furthermore, a linear correlation existed between the detected Bragg diffraction peak shift Δλ and SMX concentrations in water ranging from 0.5 to 2.0 mM. The detection limit for SMX was 0.3 mM. A recovery rate of 91.9%–108.5% was achieved when the polymer sensor was used to detect SMX in river water samples, with a relative standard deviation of 4.9%–6.0%. The designed MIPP‐SMX enabled rapid visual detection of SMX in water samples. The proposed method represents a significant advancement in the visual detection of SMX in environmental water samples.

Influence of calcination temperature on the morphology, structure, and spectral performance of chromium oxide

Cr(OH)3 was synthesized by a hydrothermal method using Na2Cr2O7 as precursor and starch as reducing agent. The resulting Cr(OH)3 was then calcined at different temperatures to produce Cr2O3 pigments. X-ray diffraction (XRD), X-ray photoelectron Spectrometer (XPS), UV–Vis-NIR spectroscopy, scanning electron microscopy (SEM) and automated whiteness measurement (AWM) were used to characterize the crystalline phase, reflectivity, morphology and color of Cr2O3. At temperatures below 1000 °C, Cr2O3 was identified as the dominant phase during calcination. The results showed that when the calcination temperature was <1000 °C, the phase was identified as Cr2O3. When the calcination temperature was ≥1000 °C, some oxygen atoms (O) escaped from the Cr2O3 crystal structure to from Cr2O2.4, and a shift of the Cr2O3 diffraction peak to a higher angle was observed. XPS analysis revealed that the valence state of O in the samples subjected to calcination at both 700 °C and 1200 °C remained unchanged. However, the sample treated at 1200 °C displayed a distinct CrOx (X < 1.5) peak at 575.25 eV, indicating a lower oxidation state of Cr. Morphologically, a conversion from particle-shaped Cr2O3 to larger plate-like Cr2O2.4 structures was observed, with Cr2O3 being concentrated on the Cr2O2.4. The uneven distribution of crystal particles in chromium oxide samples led to an increase in reflectance and a decrease in brightness as a result of the presence of Cr2O3 and Cr2O2.4 with distinct structural forms.

Modification sub-nano Zn-Co Metal-Organic framework for electrochemical detection of neurotransmitter

We developed a novel platform that was constructed using an in-situ technique to simultaneously synthesize sub-nano Zn-Co on the metal–organic framework (MOF) with a dodecahedron size of 150 nm. The hybridization structure of sub-nano Zn-Co MOF has been demonstrated through shifts of diffraction peaks (XRD patterns) and shake-up satellite peaks, shifting negativity of metallic Co (XPS spectra). The electrochemical dopamine (DA) sensing mechanism was thoroughly analyzed. The sub-nano Zn-Co MOF hybrid material has shown excellent electrochemical results in detecting DA detection at extremely low concentrations. Results from DPV showed that the Zn-Co MOF/GCE has a linear range of 0.01–300 µM of DA and a limit of detection of 6.72 nM. The interference experiments of neurotransmitters (UA, GABA, AA, Gly, Ser) demonstrated not much effect on amperometry changes of DA. Especially, sub-nano Zn-Co MOF/GCE electrode indicated good results in the serum samples, high reproducibility, and can practical application. With advantages including a simple, environmentally friendly, non-enzymatic production process, high selectivity, and reproducible outcomes, DA-detecting sub-nano Zn-Co MOF that has been developed can be used for the initial diagnosis of neurological disorders, the functional evaluation of dopaminergic neurons, chemicals or drugs on human neuronal cells.

Stoichiometry ratio-induced structural and electronic properties changes of TaN thin films prepared by reactive magnetron sputtering

Tantalum nitride (TaN) is a representative compound with a variety of compositions and mesoscopic phases, which ultimately leads to a diversity of properties. In order to explore relationship between the stoichiometry and properties, in this work, TaN thin films were prepared by reactive sputtering and modulated by controlling the percentage of nitrogen (PN2). All the prepared films were dense and uniform, which exhibited a δ-TaN phase structure. The decrease of nitrogen vacancies directly caused the slightly shift of XRD diffraction peaks and the increase in grain size, both of which showed a lattice distortion of the films. It is also found that the presence of nitrogen vacancies affectes the distribution of the Ta cation as well as the nitrogen-tantalum stoichiometry ratios, so that the deficient material exhibits different electrical properties. The TCR of TaN in this work achieved as low as 32.9 ppm/°C (nitrogen-tantalum ratio of 0.843), which is attributed to the nitrogen vacancies in TaN lattice effectively regulating the electron scattering in the vicinity of Ta atoms. Meanwhile, the change in resistivity is only 1 %, indicating a good long-term stability of TaN. This study provides a point of reference for the preparation of film resistors from the perspective of material modulation.

Synthesis and Characterization of PES/PEG/PVA/SiO2 Nanocomposite Ultrafiltration Membrane

This study aims to synthesis and characterize PES/PEG/PVA/SiO2 composite membranes. The composite membranes were synthesized by phase inversion method with composition (% w/w) Polyethersulfone/ PES (17.25), Polyvinylalcohol/ PVA (3.58; 0.85; 1.43; 2.57; 3.57, Polyethylene glycol/ PEG (3.72), Silica/SiO2 (0.35; 0.85; 1.43; 2.57; 3.57), and Dimethyl acetamide/DMAc solvent. Composite membranes were characterized using FTIR spectroscopy, X-ray diffraction, Scanning Electron Microscopy (SEM), and water contact angle. The results showed that the interaction between PES, PVA, and SiO2 was indicated by a shift in the typical absorption spectrum of the FTIR. SEM cross-sectional photos showed that the addition of PVA and SiO2 caused significant changes in the morphology and pore structure of the PES membrane. The results of the X-ray diffractogram (X-Ray) showed a shift in the typical diffraction peaks of PES, PEG, PVA and the presence of new diffraction peaks of SiO2. The crystallinity of the membrane increased from 34.99% to 57.25% which indicated that the composite membrane was successfully synthesized. The addition of PEG/PVA/SiO2 also increased the hydrophilicity of the composite membrane. Based on these findings, it can be concluded that the PES/PEG/PVA/SiO2 composite membrane has been synthesized through the phase inversion method with the optimum composition of PES: PEG: PVA: SiO2 was 17.25%: 3.72%: 0.85%: 0.35%, respectively. The addition of PEG/PVA/SiO2 increased the hydrophilicity and modified the morphological structure of the PES membrane.

Ternary sulfide nanoparticles anchored in carbon bubble structure for oxygen evolution reaction

The synergistic effect and unique interfacial structure of ternary transition metal (Co, Ni, Fe) sulfides are significant in improving the catalytic performance of oxygen evolution reaction (OER). Herein, the ultrathin Co0.3Ni0.3Fe0.2S ternary sulfide nanoparticles (Co0.3Ni0.3Fe0.2S NPs) anchored in carbon bubble structure with rich pore structures (Co0.3Ni0.3Fe0.2S NPs/C) were firstly constructed via a cost-effective and general solid-phase synthesis strategy. Co0.3Ni0.3Fe0.2S NPs/C has a crystalline structure of Co1−xS, accompanying the shift of diffraction peaks, which indicate the doping of nickel and iron atoms into Co1−xS lattice. Co0.3Ni0.3Fe0.2S NPs/C catalyst has good OER activity with a low overpotential of 322 mV at 100 mA cm−2 in 1.0 M KOH electrolyte, superior to single metal sulfide synthesized at the same conditions. More importantly, the Co0.3Ni0.3Fe0.2S NPs/C catalyst possesses excellent stability with a low current density decrease in the continuous 336 h I-t test. The good catalytic intrinsic activity may originate from the synergistic effect among the highly exposed Fe, Co, and Ni sulfide grown on the porous carbon bubbles and the unique reconstruction structure formed during the OER process. This work provides some reference significance for the systematic study of the synergistic effects between multicomponents and the relationship between interfacial modulation and OER.

Carbon dot embedded photonic crystal molecularly imprinted as dual-mode fluorometric/colorimetric sensor for the determination of sulfadimethoxine in fish

A novel fluorescent membrane based on carbon dot embedded photonic crystal molecularly imprinted polymer ([email protected]) was developed for fluorometric and colorimetric dual-mode determination of sulfadimethoxine with excellent selectivity, quick response, and reusability. In the presence of sulfadimethoxine, fluorescence quenching and red shift of diffraction peak from [email protected] were observed because of the photo-induced electron transfer and structural change of [email protected], accompanied by a visual color change from blue to green. The fluorescence quenching efficiency and the red-shift of the diffraction peaks were positively correlated with the logarithms of the sulfadimethoxine concentration at 10-12–10-5 and 10-10–10-5 mol L-1, respectively. The sensor achieved a limit of detection of 0.08 pmol L-1 (fluorescence method) and 2.75 pmol L-1 (colorimetric method, 3σ, n=9). The developed [email protected] membrane was applied for the detection of sulfadimethoxine in fish samples with favorable recovery of 84.8%–102.9%.

Preparation of ultrafine (W,Mo)B, (W,Mo)B2.5 and (Mo,W)AlB solid solution composite powders

In this study, ultrafine borides powders including (W,Mo)B, (W,Mo)B2.5 and (Mo,W)AlB were successfully fabricated via boronizing ultrafine W-Mo solid solution composite powder with B4C as the boron source under the assistance of Ca melt or Al melt. Ultrafine W-Mo solid solution powder was obtained by using a two-stage reduction route to reduce the precursor powder synthesized by spray drying. Meanwhile, the effects of Mo/W ratio on the phase composition, morphological characteristics and particle size distribution of boride solid solution composite powder were thoroughly investigated. The shift of diffraction peak in the XRD spectrum, the linear change of lattice constant and the homogeneous distributions of W, Mo, B and Al in the EDS energy spectrum comprehensively confirmed that the boride solid solution with different Mo/W ratios could be prepared. Due to the essentially insolubilities of W and Mo in Ca melt, the (W, Mo)B grains grew following a template growth mechanism, and inherited the nearly spherical morphology feature of ultrafine W-Mo solid solution composite powder with a particle size of approximately 200 nm. Nonetheless, as a result of the high solubilities of W, Mo, and B in Al melt, the process of dissolution-precipitation led to the formations of flaky (W, Mo)B2.5 and short rod-shaped (Mo, W)AlB.

Important factors of the A-site deficient Mn perovskites design affecting the CO oxidation activity

A-site deficient La0.4Sr0.4MnxTi1−xO3 (LSMT, x = 0, 0.4, 0.6, 0.8) perovskites were investigated for their structural change and effect on CO oxidation activity. The XRD, XPS, TPR and O2-TPD analysis represent the change in Mn concentration, known as an active species in oxidation, affecting the crystal structure, oxidation state of the B-site cation (Mn), number of oxygen vacancies, and the reducibility of the catalysts. The shift in the main perovskite diffraction peak in XRD spectra of the perovskites with a change in Mn content represents the formation of cationic vacancies. At the lower temperature (<200 oC), CO oxidation efficiency of LSMT perovskite catalysts was found to be almost identical. This can be attributed to their similar perovskite structure and surface area. Compared to the higher temperature (>200 oC) CO oxidation activity, the LSMT catalyst with lower Mn content of 0.4 shows relatively better performance than the higher Mn content samples, which signifies the active role of the Mn oxidation state and lattice oxygen species of the perovskite catalysts. Moreover, the LSMT4446 catalyst shows stable activity for more than 12 h with an average CO conversion of 80 %. From these results, we found that the factors of the Mn oxidation state and the type of oxygen species are crucial when designing an Mn-based perovskite catalyst for catalytic applications.

Synergistic Effect of Y Doping and Reduction of TiO2 on the Improvement of Photocatalytic Performance.

Pure TiO2 and 3% Y-doped TiO2 (3% Y-TiO2) were prepared by a one-step hydrothermal method. Reduced TiO2 (TiO2-H2) and 3% Y-TiO2 (3% Y-TiO2-H2) were obtained through the thermal conversion treatment of Ar-H2 atmosphere at 500 °C for 3 h. By systematically comparing the crystalline phase, structure, morphological features, and photocatalytic properties of 3% Y-TiO2-H2 with pure TiO2, 3% Y-TiO2, and TiO2-H2, the synergistic effect of Y doping and reduction of TiO2 was obtained. All samples show the single anatase phase, and no diffraction peak shift is observed. Compared with single-doped TiO2 and single-reduced TiO2, 3% Y-TiO2-H2 exhibits the best photocatalytic performance for the degradation of RhB, which can be totally degraded in 20 min. The improvement of photocatalytic performance was attributed to the synergistic effect of Y doping and reduction treatment. Y doping broadened the range of light absorption and reduced the charge recombination rates, and the reduction treatment caused TiO2 to be enveloped by disordered shells. The remarkable feature of reduced TiO2 by H2 is its disordered shell filled with a limited amount of oxygen vacancies (OVs) or Ti3+, which significantly reduces the Eg of TiO2 and remarkably increases the absorption of visible light. The synergistic effect of Y doping, Ti3+ species, and OVs play an important role in the improvement of photocatalytic performances. The discovery of this work provides a new perspective for the improvement of other photocatalysts by combining doping and reduction to modify traditional photocatalytic materials and further improve their performance.

Sm doped ZnO-SnO2 nanocomposites with improved photo-degradation strength and antibacterial properties

In this work, we devoted our effort to synthesize rare-earth (Sm3+) doped ZnO-SnO2 nanocomposites by sol-gel method to address issues like wastewater treatment and minimization of bacterial infection. Successful formation of multi-phase nanocomposites of hexagonal ZnO and tetragonal SnO2 has been confirmed by x-ray diffraction (XRD) analysis. The effect of Sm doping is understood from the enhancement in ZnO grain growth and shift in diffraction peaks. The morphology study by FESEM reveals the variation in sample morphology with Sm doping with energy-dispersive analysis of x-ray (EDAX) study providing the confirmation on the existence of Sm ions in the crystal lattice of ZnO-SnO2 heterostructure. Transmission electron microscopic (TEM) study manifests the formation of two distinct types of particles (hexagonal & spherical) corresponding to ZnO and SnO2 which has been further clarified from the measurement of lattice spacing from the high-resolution TEM images and indexing of selected area electron diffraction (SAED) pattern. The near band edge emission (NBE) of ZnO is blue shifted along with the evolution of oxygen vacancy defects which induced new bands at 488 nm and 613 nm upon Sm doping. Further, intra-4f transitions of Sm3+ ions have also been observed at 560 nm, 590 nm and 638 nm linked to 4G5/2– 6HJ (J = 5/2, 7/2, 9/2) transitions. The Zn, Sn, O, and Sm elements are confirmed to exist in the nanocomposite according to the X-ray photoelectron spectroscopy (XPS) investigation which provided information on the chemical composition and electronic states of the material. Photocatalytic degradation study of toxic environmental dyes like methylene blue (MB), Congo red (CR) and methyl orange (MO) shows that Sm3+ ions in ZnO/SnO2 helps to enhance the degradation efficiency by the formation of Z-scheme heterojunctions between ZnO and SnO2. This allows the delay in recombination rate of the photoinduced electron/hole pairs. The antibacterial behavior of the prepared nanocomposites against E. Coli and S. Aureus has also been studied in detail which demonstrates improved antibacterial efficiency of the samples.

Optimization of parameters for adsorption of acid yellow 36 dye onto nitrate‐intercalated MgAl LDH nanoparticle using Box–Behnken design

AbstractBACKGROUNDLayered double hydroxide nanoparticles have been extensively investigated and exploited for the removal of harmful anions from contaminated water. For adsorption of acid yellow dye (AY) from contaminated water, nitrate‐intercalated MgAl layered double hydroxide (LDH) nanoparticles were synthesized using the co‐precipitation method with the refluxing condition in a nitrogen atmosphere.RESULTSThe X‐ray diffraction pattern of LDH nanoparticles showed that LDH nanopowder with nitrate in the interlayer position was successfully synthesized. The shift in (003) basal plane diffraction peak to a lower angle (2θ) of 7.75° in the LDH‐AY from 10.40° in the pristine LDH confirmed the intercalation of AY in the interlayer space of LDH. Variable factors for the adsorption of the AY on the LDH nanoparticles were examined in the batch process using ultraviolet–visible spectroscopy and those included the adsorbent dose (5–30 mg), the incubation time (3–60 min), the temperature (25–50 °C), the pH of the AY aqueous suspension (5–9) and the AY concentration (0.03–0.1 mg mL−1). Box–Behnken design was used to optimize the three independent variables of temperature, incubation time and pH of AY solution for the adsorption of the dye. The optimized values of the incubation time, temperature and pH were found to be 25.89 min, 35.99 °C and 5.16, respectively. A maximum adsorption rate of 0.00515 g mg−1 min−1 of AY onto LDH nanoparticles was found at a solution pH of 5 and a temperature of 50 °C. The adsorption kinetics of the AY at different suspension pH values and temperature followed a pseudo‐second‐order kinetic model. Furthermore, an adsorption isotherm study for the adsorption of AY at a temperature of 40 °C and pH 5 followed a Langmuir isotherm model, and the maximum adsorption capacity of the AY was calculated to be 412.55 mg g−1 with excellent regeneration capacity.CONCLUSIONThe study revealed that the synthesized nitrate intercalated Mg Al LDH nanoparticles using the reflux conditions offered promising potential to adsorb acid yellow 36 dye form its aqueous solution. © 2023 Society of Chemical Industry (SCI).

Regulating the phase transition temperature of VO2 films via the combination of doping and strain methods

Phase change materials have the potential for reversible modulation of the physical and chemical properties of other materials, making them suitable for a wide range of applications. Among these phase change materials, VO2 is particularly attractive for electronic applications due to its ultrafast reversible phase transition at near room temperature (68 °C). Regulating the phase transition temperature of VO2, however, remains a challenge. In this study, two factors, i.e., film thickness and buffer layer, that can effectively regulate the phase transition temperature of VO2 films were introduced, and the effect of doping on the phase transition temperature was also investigated. The interfacial strain between the VO2 film and substrate was modulated by adjusting the film thickness and doping concentration in the buffer layer. This was to explore the effect of strain on the phase transition temperature of the film. Changes in VO2 lattice parameters were reflected by the shifts of XRD diffraction peaks. Test and measurement results show that the phase transition temperature of VO2 gradually increased as the interfacial strain increased. For instance, the phase transition temperature (Th) of the GeVO/AlGeO-3 sample reached 91.2 °C. Moreover, some samples exhibited increased abrupt parameters, such as phase transition amplitude and thermal hysteresis width. These findings have important implications for the use of VO2 materials in applications, including switches, sensors, and amnesic resistors.

Medium-range order endows a bulk metallic glass with enhanced tensile ductility

Developing ductile bulk metallic glasses (BMGs) can benefit from an in-depth understanding of the structure-property relation during plastic deformation. However, endowing BMGs with tensile ductility in BMGs needs to reveal the response of critical structure units during deformation. Here, we report the experimental results of an in-situ synchrotron high-energy X-ray study of a Zr-based BMG under uniaxial tension after preprocessing by canning compression of the three-dimensional compressive stress state. It is revealed that the canning-compressed BMG (CC-BMG) sample has better tensile ductility and higher ultimate strength than the as-cast sample, which possesses heterogeneous and loosely packed local structures on medium-range scales. The experimental results revealed two stages of plastic deformation in the CC-BMGs compared with one stage of plastic deformation in the as-cast BMG. Moreover, the shift in the first sharp diffraction peak along the tension direction for the canning-compressed sample is substantially more pronounced than that of the as-cast sample. Furthermore, the real-space analysis illustrates a competition mechanism between the 2-atom and 3-atom connection modes on medium-range order during the plastic deformation of the CC-BMG. Additionally, the ordering on the medium-range scale decreases in the first plastic deformation stage but increases in the second plastic deformation stage. Therefore, a structural crossover phenomenon occurs in the CC-BMG during plastic deformation. Our results demonstrate a structure-property correlation for the CC-BMGs of heterogeneous medium-range ordered structures, which may be beneficial for endowing BMGs with ductility based on medium-range order engineering techniques.

Design of Titanium Alloys Insensitive to Thermal History for Additive Manufacturing

Powder bed fusion is the most common technology used for 3D printing, where thermal energy is used to selectively melt/sinter granular materials into solid shapes. The build platform is then lowered, more powder is added, and the process is repeated for the next layer to fully print the design. As a result, the built-up part is repeatedly heated. Therefore, materials that are not sensitive to thermal history are preferred for this process. The Ti–Zr system forms a continuous solid solution for both β- and α-phases. The presence of Fe in Ti alloys is inevitable; however, it provides some beneficial effects. The purpose of this work was to prepare Ti–Zr–Fe alloys and investigate their heat treatment behaviour. Ti-xmass%Zr-1mass%Fe alloys (x = 0, 5, 10) were prepared with arc melting. The formation of a solid solution of Zr in Ti was confirmed on the basis of X-ray diffraction peak shifts and hardening effects. A small amount of β-phase precipitation was suggested by the change in electrical resistivity after isothermal ageing at 673 and 773 K. However, no obvious phase or microstructural changes were observed. The laser scanning increased the volume of the precipitates and also coarsened them, but the effect was limited.

Band-gap-engineered mixed-halide perovskite films through vacuum-based deposition approach

Mixed-halide perovskites offer the important characteristic of band-gap tunability, which is essential for tandem solar cells. Herein, the single-source vapor deposition method is reported for MAPbBr2Cl1 (MA (methyl ammonium) = CH3NH3), MAPbBr1.5Cl1.5 and MAPbBr1Cl2 perovskite films utilizing the corresponding mixed-halide perovskite nanoparticles as a source for thermal evaporation. Further, band-gap tuning in vacuum-deposited MAPbBr3 thin films is performed through MACl treatment with successful band-gap tuning from 2.37 to 2.48 eV. The limitation of chlorine (Cl) incorporation into the perovskite structure at room temperature is tackled by MACl treatment of vapor-deposited MAPbBr2Cl1, MAPbBr1.5Cl1.5 and MAPbBr1Cl2 films. The structural properties of MAPbBr3−x Cl x films show a continuous shift in the X-ray diffraction peak toward a higher 2θ value, confirming chlorine incorporation into the perovskite structure. Band-gap tuning in MAPbBr3−x Cl x films, from 2.37 to 2.86 eV, is confirmed by absorption spectroscopy. The mixed-halide perovskite films show an improved microstructure with MACl treatment, as observed from the increased grain size of the films. Further, emission studies show good stability of MAPbBr3−x Cl x films against phase segregation under continuous exposure to 325 nm wavelength illumination of 100 mW/cm2 for more than 60 min. The diminished phase segregation might help in advancing the application of mixed-halide perovskites for reliable optoelectronic devices.