Synchrotron X-ray Diffraction Research Articles

Microstructure and Phase Transformation Behavior of NiTiCu Shape Memory Alloys Produced Using Twin-Wire Arc Additive Manufacturing

NiTiCu thin walls were produced by twin-wire arc additive manufacturing (T-WAAM) using commercial NiTi and Cu wires as the feedstock materials. This approach aims to solve the problems typically associated with large phase transformation hysteresis in NiTi shape memory alloys. The microstructure, mechanical properties, and phase transformation behavior of the as-deposited NiTiCu alloy were comprehensively examined. The results revealed that the as-deposited NiTiCu alloy was well-formed, with its microstructure showed columnar, equiaxed, and needle-like grains, depending on the location within the deposited walls. The microhardness gradually increased from the first to the third layer. The Cu content was 20.80 at%, and Cu-based precipitates were formed in the as-deposited NiTiCu. The volume fractions and lattice parameters of the matrix and precipitates in the as-deposited NiTiCu material were analyzed using high-energy synchrotron X-ray diffraction. The martensitic phase was identified as a B19 crystal structure, and the as-deposited NiTiCu underwent a one-step B2-B19 phase transformation. The tensile strength and fracture strain were approximately 232 MPa and 3.72%, respectively. In particular, the addition of Cu narrowed the phase transformation hysteresis of the as-deposited NiTiCu alloy from 24.4 to 7.1 ℃ compared with conventional binary NiTi alloys. This study expands the potential of T-WAAM in modifying the phase transformation behavior of NiTi-based ternary alloys.

In situ synchrotron X-ray diffraction study of synthesis reactions in mechanically activated Ti + Al powder mixture under linear heating conditions

In the present work, we studied the features of phase formation in mechanically activated Ti + Al powder mixture at various heating rates for the first time. The study was carried out using high-resolution diffractometry method which made it possible to study the processes of phase formation in situ at any stage of heating. It was established that ignition of the activated mixture can be initiated in the solid phase with an extremely low content of reaction products formed at the preheating stage. An increase in the heating rate leads to a decrease in the average burning rate and an increase in the ignition temperature. At high heating rates, the ignition is initiated in the presence of a liquid phase when the ignition temperatures are close to the melting temperature of aluminum. In this case, the content of reaction products formed during preheating stage is relatively high. It was found that the all main compounds presented in the equilibrium diagram of Ti-Al system are synthesized in parallel. The content of phases in the reaction products depends on the heating rate.

Comprehensive Study of Zr-Doped Ni-Rich Cathode Materials Upon Lithiation and Co-Precipitation Synthesis Steps.

Ni-rich layered oxides LiNi1-x-yMnxCoyO2 (NMC811, x = 0.1 and y = 0.1) are considered promising cathode materials in lithium-ion batteries (LiBs) due to their high energy density. However, those suffer a severe capacity loss upon cycling at high delithiated states. The loss of performance over time can be retarded by Zr doping. Herein, a small amount of Zr is added to NMC811 material via two alternative pathways: during the formation of the transition metal (TM) hydroxide precursor at the co-precipitation step (0.1%-Zr-cp) and during the lithiation at the solid-state synthesis step (0.1%-Zr-ss). In this work, the crystallographic Zr uptake in both 0.1%-Zr-ss and 0.1%-Zr-cp is determined and quantified through synchrotron X-ray diffraction and X-ray absorption spectroscopy. We prove that the inclusion of Zr in the TM site for 0.1%-Zr-cp leads to an improvement of both specific capacity (156 vs 149 mAh/g) and capacity retention (85 vs 82%) upon 100 cycles compared to 0.1%-Zr-ss where the Zr does not diffuse into the active material and forms only an extra phase separated from the NMC811 particles.

Seeing the Unseen: The Structural Influence of the Lone Pair Electrons in PbWO4.

Pair distribution function (PDF) analysis of the scheelite-type material PbWO4 reveals previously unidentified short-range structural distortions in the PbO8 polyhedra and WO4 tetrahedra not observed in the similarly structured CaWO4. These local distortions are a result of the structural influence of the Pb2+ 6s2 lone pair electrons. These are not evident from the Rietveld analysis of synchrotron X-ray or neutron powder diffraction data, nor do they strongly influence the X-ray PDF (XPDF). This illustrates the importance of neutron PDF (NPDF) in the study of such materials. First-principles density function theory (DFT) calculations show that the Pb2+ 6s2 electrons are hybridized with the O2- 2p electrons near the Fermi level. The presence of local-scale distortions has previously been neglected in studies of structure-functionality relationships in PbWO4 and other scheelite-structured photocatalytic materials, including BiVO4, and this observation opens new avenues for their optimization.

Effect of calcination temperature on structure evolution of hematite nanoparticles

The objective of this study is to investigate the transition structure of iron oxide, specifically the change from magnetite to hematite, as well as the influence of calcination temperature on the structural growth of hematite nanoparticles. The magnetite was extracted from the native iron sand in Indonesia using the coprecipitation procedure. To generate hematite, magnetite was calcined at various temperatures (350, 500, 650, and 800 °C). The structural changes resulting from the effect of calcination temperature were investigated by combining a number of characterisation methods. The crystal structure was examined using synchrotron x-ray diffraction (SRD) and the local structure was examined using x-ray absorption spectroscopy (XAS). Crystallite size was calculated using the Debye-Schrerrer equation at the most dominant SRD peak. Surface morphology was investigated using scanning electron microscopy (SEM). SRD data revealed that the sample calcined at 350 °C displayed both the Fe3O4 and α-Fe2O3 phases, while higher temperatures revealed the single-phase α-Fe2O3. Furthermore, an increase in calcination temperature was shown to be associated with an increase in crystallinity and crystallite size. For the samples H350 and H800, the crystallinity increased from 95.56 to 98.17%. In the magnetite, H350, H500, H650, and H800 samples, the crystallite size increased from 9.57 to 29.55, 16.40, 28,48, 29.26, and 29.55 nm. Higher calcination temperatures, on the other hand, increase the interatomic distance while decreasing the Debye–Waller factor, according to XAS fitting data. It can be inferred that around 500 °C, the transition from Fe3O4 to single-phase α-Fe2O3 was observed. While a greater calcination temperature of at least 800 °C would alter the structural parameters, it would not affect the phase.

Tetrahedra Rotational and Displacive Disorder in the Scheelite-Type Oxide CsReO4.

Scheelite-type metal oxides are a notable class of functional materials, with applications including ionic conductivity, photocatalysis, and the safe storage of radioactive waste. To further engineer these materials for specific applications, a detailed understanding of how their properties can change under different conditions is required─not just in the long-range average structure but also in the short-range local structure. This paper outlines a detailed investigation of the metal oxide CsReO4, which exhibits an uncommon orthorhombic Pnma pseudo-scheelite-type structure at room temperature. Using synchrotron X-ray diffraction, the average structure of CsReO4 is found to undergo a transformation from the orthorhombic Pnma pseudo-scheelite-type structure to the tetragonal I41/a scheelite-type structure at ∼440 K. In the X-ray pair distribution function analysis, lattice strain and rotations of the ReO4 tetrahedra are apparent above 440 K despite the increase in long-range average symmetry, revealing a disconnect between the structural models at different length scales. This study demonstrates how the bonding requirements and ionic radii of the A-site cation can induce disorder that is detectable at different length scales, affecting the physical properties of the material.

Coprecipitation Strategy for Halide-Based Solid-State Electrolytes and Atmospheric-Dependent In Situ Analysis.

In the continuous pursuit of an energy-efficient alternative to the energy-intensive mechanochemical process, we developed a coprecipitation strategy for synthesizing halide-based solid-state electrolytes that warrant both structural control and commercial scalability. In this study, we propose a new coprecipitation approach to synthesized Li3InCl6, exhibiting both structural and electrochemical performance stability, with a high ionic conductivity of 1.42 × 10-3 S cm-1, comparable to that of traditionally prepared counterparts. Through the in situ synchrotron X-ray diffraction technique, we unveil the stability mechanisms and rapid chemical reactions of Li3InCl6 under dry Ar, dry O2, and high-humidity atmosphere, which were not previously reported. Furthermore, the fast reversibility capability of moisture-exposed Li3InCl6 was tracked under vacuum, revealing the optimal recovery conditions at low temperatures (150-200 °C). This work addresses the critical challenges in structural engineering and sustainable mass production and provides insights into chemical reactions under real-world conditions.

Unveiling the pressure-induced scheelite to M′-fergusonite phase transition in NaCe(MoO4)2

Sodium-cerium molybdate, NaCe(MoO4)2, belongs to the family of double alkaline rare-earth molybdate, and it holds significant importance across various technological domains, such as environmental remediation and energy conversion. Despite its importance, the behavior of NaCe(MoO4)2 under high-pressure conditions remains unexplored. This study uses synchrotron x-ray diffraction and Raman spectroscopy to investigate NaCe(MoO4)2in situ under high-pressure conditions. We observed a pressure-induced phase transition from the scheelite to the M′-fergusonite structure type on a double molybdate at approximately 10 GPa. These findings contribute to a deeper understanding of the structural stability of NaCe(MoO4)2 and shed light on the broader field of high-pressure studies of double molybdates.

Cyclic Sesquiterpene-Flavanone [4+2] Hybrids, Syzygioblanes A-C, Found in an Indonesian Traditional Medicine, "Jampu Salo" (Syzygium oblanceolatum).

A plant used in an Indonesian traditional herbal medicine as a diabetes treatment and known locally as "Jampu Salo" was collected on Sulawesi Island, Indonesia. It was identified as Syzygium oblanceolatum (C. B. Rob.) Merr. (Myrtaceae) and found for the first time in Sulawesi; it was previously reported only in the eastern Philippines and Borneo. A phytochemical study of S. oblanceolatum led to the isolation of three unprecedented meroterpenoids, syzygioblanes A-C (1-3, respectively). These compounds might be biosynthesized through [4+2] cycloaddition of various germacrane-based cyclic sesquiterpenoids with the flavone desmethoxymatteucinol to form a spiro skeleton. The unique and complex structures were elucidated by microcrystal electron diffraction analysis in addition to general analytical techniques such as high-resolution mass spectrometry, various nuclear magnetic resonance methods, and infrared spectroscopy. Synchrotron X-ray diffraction and calculations of electronic circular dichroism spectra helped to determine the absolute configurations. The newly isolated compounds exhibited collateral sensitivity to more strongly inhibit the growth of a multidrug resistant tumor cell line compared to a chemosensitive tumor cell line.

High-pressure Phase Transition of Olivine-type Mg2GeO4 to a Metastable Forsterite-III type Structure and their Equation of States

Abstract Germanates are often used as structural analogs of planetary silicates. We have explored the high-pressure phase relations in Mg2GeO4 using diamond anvil cell experiments combined with synchrotron X-ray diffraction and computations based on density functional theory. Upon room temperature compression, forsterite-type Mg2GeO4 remains stable up to 30 GPa. At higher pressures, a phase transition to a forsterite-III type (Cmc21) structure was observed, which remained stable to the peak pressure of 105 GPa. Using a 3rd order Birch Murnaghan fit to the experimental data, we obtained V0 = 305.1 (3) Å3, K0 = 124.6 (14) GPa and K0′ = 3.86 (fixed) for forsterite- and V0 = 263.5 (15) Å3, K0 = 175 (7) GPa and K0′ = 4.2 (fixed) for the forsterite-III type phase. The forsterite-III type structure was found to be metastable when compared to the stable assemblage of perovskite/post-perovskite + MgO, as observed during laser-heating experiments. Understanding the phase relations and physical properties of metastable phases is crucial for studying the mineralogy of impact sites, understanding metastable wedges in subducting slabs and interpreting the results of shock compression experiments.

MnO2 superstructure cathode with boosted zinc ion intercalation for aqueous zinc ion batteries

The simultaneous intercalation of protons and Zn2+ ions in aqueous electrolytes presents a significant obstacle to the widespread adoption of aqueous zinc ion batteries (AZIBs) for large-scale use, a challenge that has yet to be overcome. To address this, we have developed a MnO2/tetramethylammonium (TMA) superstructure with an enlarged interlayer spacing, designed specifically to control H+/Zn2+ co-intercalation in AZIBs. Within this superstructure, the pre-intercalated TMA+ ions work as spacers to stabilize the layered structure of MnO2 cathodes and expand the interlayer spacing substantially by 28 % to 0.92 nm. Evidence from in operando pH measurements, in operando synchrotron X-ray diffraction, and X-ray absorption spectroscopy shows that the enlarged interlayer spacing facilitates the diffusion and intercalation of Zn2+ ions (which have a large ionic radius) into the MnO2 cathodes. This spacing also helps suppress the competing H+ intercalation and the formation of detrimental Zn4(OH)6SO4·5H2O, thereby enhancing the structural stability of MnO2. As a result, enhanced Zn2+ storage properties, including excellent capacity and long cycle stability, are achieved.

Shear straining promoted structural transition in bulk metallic glasses

Metallic glasses (MGs) have unusual structural characteristics and resulting unique properties, but effectively modulating their structure is difficult. The recently achieved two-way structural tuning (ordering-disordering) between distinct states in MGs offers an opportunity to overcome this challenge. However, pressures up to tens of GPa were required for the process, which limits sample sizes at the micrometer scale and challenges further comprehensive research. Here, by introducing concurrent shear straining with compressive force using high-pressure torsion, the pressure to trigger the disordering transition is significantly reduced to a few GPa. This enables the acquisition of millimeter-sized samples for comprehensive study, including synchrotron x-ray diffraction and small angle x-ray scatting, nanoindentation, electrical resistivity, and differential scanning calorimetry. It is evidenced that the two-way tuning of MG can be achieved both structurally and thermodynamically, which could help deepen our understanding of the mechanism behind the two-way tuning and promote exploration of distinct MGs.

High Capacity and Fast Kinetics Enabled by Metal-Doping in Prussian Blue Analogue Cathodes for Sodium-Ion Batteries.

Prussian blue analogues (PBAs) have gained tremendous attention as promising low-cost electrochemically-tunable electrode materials, which can accommodate large Na+ ions with attractive specific capacity and charge-discharge kinetics. However, poor cycling stability caused by lattice strain and volume change remains to be improved. Herein, metal-doping strategy has been demonstrated in FeNiHCF, Na1.40Fe0.90Ni0.10[Fe(CN)6]0.85·1.3H2O, delivering a capacity as high as 148 mAh g‒1 at 10 mA g‒1. At an exceptionally high rate of 25.6 A g‒1, a reversible capacity of ~55 mAh g‒1 still can be obtained with a very small capacity decay rate of 0.02% per cycle for 1000 cycles, considered one of the best among all metal-doped PBAs. This exhibits the stabilizing effect of Ni doping which enhances structural stability and long-term cyclability. In situ synchrotron X-ray diffraction reveals an extremely small (~1%) change in unit cell parameters. The Ni substitution is found to increase the electronic conductivity and redox activity, especially at the low-spin (LS) Fe center due to inductive effect. This larger capacity contribution from LS Fe2+C6/Fe3+C6 redox couple is responsible for stable high-rate capability of FeNiHCF. The insight gained in this work may pave the way for the design of other high-performance electrode materials for sustainable sodium-ion batteries.

Behavior of Microstrain in Nd3+-Sensitized Near-Infrared Upconverting Core-Shell Nanocrystals for Defect-Induced Tailoring of Luminescence Intensity.

In an attempt to optimize the upconversion luminescence (UCL) output of a Nd3+-sensitized near-infrared (808 nm) upconverting core-shell (CS) nanocrystal through deliberate incorporation of lattice defects, a comprehensive analysis of microstrain both at the CS interface and within the core layer was performed using integral breadth calculation of high-energy synchrotron X-ray (λ = 0.568551 Å) diffraction. An atomic level interpretation of such microstrain was performed using pair distribution function analysis of the high-energy total scattering. The core NC developed compressive microstrain, which gradually transformed into tensile microstrain with the growth of the epitaxial shell. Such a reversal was rationalized in terms of a consistent negative lattice mismatch. Upon introduction of lattice defects into the CS systems upon incorporation of Li+, the corresponding UCL intensity was maximized at some specific Li+ incorporation, where the tensile microstrain of CS, compressive microstrain of the core, and atomic level disorders exhibited their respective extreme values irrespective of the activator ions.

In situ electric field-dependent structural changes in (Ba,Ca)(Zr,Ti)O3 with varying grain size

The functional properties of piezoelectric ceramic materials, such as barium titanate, are highly dependent on grain size. Lead-free polycrystalline Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT) samples were prepared with a combination of the hydrothermal method and spark plasma sintering to achieve grain sizes from 100 nm to 10 μm by varying the maximum sintering temperature. In this range, a transition from a nearly linear dielectric to a ferroelectric response can be seen in macroscopic electromechanical measurements, demonstrating the importance of grain size on functional properties in BCZT. Furthermore, in situ electric field-dependent synchrotron x-ray diffraction measurements were performed to quantify the intrinsic and extrinsic strain contributions and their variations with grain size. At lower grain sizes, the data revealed a significant loss of extrinsic contributions in the piezoelectric behavior, limiting the response to intrinsic contribution associated with lattice strain. For BCZT, a critical grain size between approximately 0.08 and 0.18 μm is proposed, below which no piezoelectric response was observed.

Role of TiB2 inoculation particles during welding of a AlCoCrFeNi high entropy alloy

High entropy alloys (HEAs) are a novel class of materials that represent an evolution of common engineering alloys to a wider array of compositional and properties possibilities. As such, the exploration of methodologies to achieve improved microstructure and mechanical characteristics of these materials for potential applications in industry is a requirement that is experiencing extended research efforts. One example of a processing method able to expand the potential applications of these alloys is Gas Tungsten Arc Welding (GTAW), which allows to evaluate the metallurgical evolution and corresponding mechanical performance, associated to the impact of a localized heat input on the material. However, GTAW and related fusion-based welding processes are known to generate large grain sized-structures in the fusion zone, which often is detrimental to the joint performance. Thus, the integration of high temperature inoculant particles on the fusion zone during welding is a potential way to improve this region’s microstructure and, therefore, its mechanical performance. In this work, we discuss the effect that the addition of TiB2 micron-sized particles have on the microstructure of a GTAW AlCoCrFeNi-based HEA. For this, the microstructure of the welds was evaluated by means of optical and electron microscopy, synchrotron X-ray diffraction and CalPhaD-based simulations. Mechanical testing was performed using microhardness mapping and tensile testing coupled with digital image correlation. The results evidenced that successful inoculation with TiB2 proved capable of altering the microstructure of the fusion zone (FZ), refining it. Nevertheless, preferential deformation in the relatively softer heat affected zone during tensile testing resulted on premature failure of the inoculated joints, due to the concomitant higher hardness of the FZ.

Vibration-Dependent Dual-Phosphorescent Cu4 Nanocluster with Remarkable Piezochromic Behavior.

The dual emission (DE) characteristics of atomically precise copper nanoclusters (Cu NCs) are of significant theoretical and practical interest. Despite this, the underlying mechanism driving DE in Cu NCs remains elusive, primarily due to the complexities of excited state processes. Herein, a novel [Cu4(PPh3)4(C≡C-p-NH2C6H4)3]PF6 (Cu4) NC, shielded by alkynyl and exhibiting DE, was synthesized. Hydrostatic pressure was applied to Cu4, for the first time, to investigate the mechanism of DE. With increasing pressure, the higher-energy emission peak of Cu4 gradually disappeared, leaving the lower-energy emission peak as the dominant emission. Additionally, the Cu4 crystal exhibited notable piezochromism transitioning from cyan to orange. Angle-dispersive synchrotron X-ray diffraction results revealed that the reduced inter-cluster distances under pressure brought the peripheral ligands closer, leading to the formation of new C-H···N and N-H···N hydrogen bonds in Cu4. It is proposed that these strengthened hydrogen bond interactions limit the ligands´ vibration, resulting in the vanishing of the higher-energy peak. In situ high-pressure Raman and vibrationally resolved emission spectra demonstrated that the benzene ring C=C stretching vibration is the structural source of the DE in Cu4.

Al-Co-Cr-Fe-Ni high-entropy coatings produced by non-vacuum electron beam cladding: Understanding the effect of Al by in-situ synchrotron X-ray diffraction

This study investigates the structure and properties of Al-Co-Cr-Fe-Ni high-entropy alloy (HEA) based coatings on steel substrates produced by non-vacuum electron beam cladding. Powder mixtures with Al molar ratios of 0.5, 1, and 1.5 were used for cladding, resulting in coatings with fcc, bcc + fcc, and bcc structures, respectively. The Fe content, which entered the coating from the substrate during cladding, increased from 9.9 up to 48.1 at. %. with the decrease of the Al molar fraction from 1.5 to 0.5. In-situ synchrotron X-ray diffraction analysis showed that this effect can be attributed to the higher solidus temperatures of the compositions with higher Al content. Electron backscatter diffraction showed that differences in grain morphology and crystallographic texture were related to the crystallization temperatures in different zones of the coatings. The bcc coating with an Al molar ratio of 1.5 demonstrated superior hardness and wear resistance. Fcc coating, which received more Fe from the substrate, had lower hardness and was prone to plastic flow. However, the specific wear rate of the fcc coating was close to that of the bcc + fcc one due to the hardening of the fcc phase during sliding wear.

High pressures studies on bis(L-alaninate)copper(II) by Raman spectroscopy and synchrotron X-ray diffraction

The crystal of bis(L-alaninate)copper(II) [Cu(C3H6NO2)2] was studied by Raman spectroscopy and synchrotron X-ray diffraction as a function of hydrostatic pressure, and its vibrational and structural behavior were investigated to analyze its stability at high pressures. The Raman spectra of bis(L-alaninate)copper(II) show changes in vibrational modes that are associated with deformations and stretching of units involving the copper atom. These results indicate that molecular fragments involving the copper atom undergo rotations and discontinuities in bond lengths. The lattice parameters of bis(L-alaninate)copper(II) obtained from Le Bail fits also exhibit changes in the same pressure ranges as the Raman spectra. The discontinuities in the angular parameter beta are compatible with the rotations of the molecular fragments. Bis(L-alaninate)copper(II) undergoes changes, but maintains monoclinic symmetry in the range of 0–20.1 GPa.

A new perspective on Lüders band formation in medium-Mn steels based on Lüders-strain-rate and dislocation evolution

Propagating Lüders bands with pronounced strain localization are often observed in medium-Mn transformation-induced plasticity (TRIP) steels, which adversely limits the application of such alloys in engineering structures. The present work aims to understand this phenomenon from a dislocation-based perspective, with a focus on the specific role of dislocation multiplication. The material studied is a typical dual-phase medium-Mn steel with a ferrite matrix and a second phase of retained austenite. A warm-rolling process was used as a pre-straining approach to adjust the microstructure of the material, such that materials with two different microstructural states can be obtained: as-received material and pre-strained material. They show distinct differences in initial dislocation density. Stress-controlled rather than conventional strain-controlled tensile testing was adopted, which allowed the Lüders band to develop in an unconstrained manner. In this way, the intrinsic Lüders-strain-rate can be obtained. The results show that the Lüders band-related mechanical parameters, including Lüders strain, Lüders-strain-rate and yield stress drop, all depend on the initial microstructure state and the dislocation evolution process during Lüders band formation. In particular, Lüders-strain-rate is a critical microstructure-sensitive factor. It is closely related to the dislocation multiplication in the formation of Lüders band, which can be characterized and quantified using scanning transmission electron microscope and synchrotron X-ray diffraction. Finally, a quantitative relationship between Lüders-strain-rate and dislocation multiplication rate is established, which allows providing a better understanding of the exceptional Lüders band phenomenon in medium-Mn steels.