Crystal Phase Research Articles

Doping Engineering in Manganese Oxides for Aqueous Zinc-Ion Batteries.

Manganese oxides (MnxOy) are considered a promising cathode material for aqueous zinc-ion batteries (AZIBs) due to their high theoretical specific capacity, various oxidation states and crystal phases, and environmental friendliness. Nevertheless, their practical application is limited by their intrinsic poor conductivity, structural deterioration, and manganese dissolution resulting from Jahn-Teller distortion. To address these problems, doping engineering is thought to be a favorable modification strategy to optimize the structure, chemistry, and composition of the material and boost the electrochemical performance. In this review, the latest progress on doped MnxOy-based cathodes for AZIBs has been systematically summarized. The contents of this review are as follows: (1) the classification of MnxOy-based cathodes; (2) the energy storage mechanisms of MnxOy-based cathodes; (3) the synthesis route and role of doping engineering in MnxOy-based cathodes; and (4) the doped MnxOy-based cathodes for AZIBs. Finally, the development trends of MnxOy-based cathodes and AZIBs are described.

Frustration of H-Bonding and Frustrated Packings in a Hexamorphic Crystal System with Reversible Crystal-Crystal Transitions.

The study of transitions between polymorphic phases is a less investigated chapter of the widely studied book of polymorphism. In this paper, we discuss the phase behavior of a new compound that has been rationally designed to show frustration of H-bonds for the strong amide N-H donor, which cannot be involved in H-bonding nor in van der Waals interactions. The compound (ImB) is a showcase of almost all possible cases of transitions between polymorphs [monotropic/enantiotropic, fast/slow, diffusive/displacive, and single-crystal-to-single-crystal (SCSC)] and of relation between polymorphs with different Z'. Six crystal phases (I, II, III, IV, V, and VI) were identified for it with five crystal-crystal transitions. Two transitions are reversible/SCSC/fast. Of the three monotropic transitions, all non-SCSC, one is slow, and the others are fast. Of the two enantiotropic SCSC transitions, one does not exhibit undercooling, while the other shows strong undercooling. Phase III, with Z' = 6, is stable at room temperature between phase II (Z' = 1), stable at high temperature, and phase IV (Z' = 2), stable at low temperature. All six polymorphs are based on the same O-H···O═C H-bonding synthon, which produces infinite chains in five polymorphs and ring tetramers in one. The sequence of reversible SCSC transitions IV ⇆ III ⇆ II involves a remarkable ping pong of the symmetry rules by which H-bonded chains are built. Based on all of this, a possible roadmap for prediction of SCSC transitions in crystals is shortly outlined.

Model of Suppression of Dynamic Conductivity in Solid-State Phases of an Organic Ionic Plastic Crystal

Model of Suppression of Dynamic Conductivity in Solid-State Phases of an Organic Ionic Plastic Crystal

Mechanistic Study on the Influence of Wax on Hydrate Formation Process.

To manage the interactions between wax and hydrate formation, a comprehensive understanding of the system's thermodynamics and flow characteristics is essential. Wax and hydrates coexist under low-temperature and high-pressure conditions, mutually influencing each other both thermodynamically and kinetically. This study focused on two main aspects: how wax affects the rate of hydrate formation in the oil-water system and how hydrate formation influences the thermodynamics of wax crystal precipitation. The presence of wax decreased the rate of hydrate formation, especially at higher wax contents. In systems with high wax content, over 70% of wax precipitated before hydrate formation, leading to less precipitation within the hydrate formation temperature range. With low water content, there were more nucleation sites for wax crystals in the oil phase, resulting in a greater difference in precipitation rates among different wax contents. For water content greater than 10%, the differences in precipitation rates were less significant, indicating a diminished effect of water content on wax crystal precipitation rates. Hydrates' hydrophilic nature had a limited impact on wax crystal nucleation and growth. Generally, wax crystals precipitate before hydrate formation, necessitating control measures for wax deposition during production processes.

Phase behavior and rheology of the sucrose laurate/sorbitan mono-laurate (Span 20)/water pseudo-ternary system

In order to develop a lamellar liquid crystal system consisting of temperature-insensitive and mild non-ionic surfactants, we construct the phase diagram of sucrose laurate (L1695)/sorbitan monolaurate (Span 20)/water pseudo-ternary systems at 25 ℃ based on the direct visual inspection and polarized microscopy. In contrast to the phase diagrams of polyoxyethylene alkyl ethers and co-surfactant mixtures reported in relevant studies, the single-phase region of the liquid crystalline phase in sucrose laurate (L1695)/sorbitan monolaurate (Span 20)/water pseudo-ternary systems is shown to be narrower. Moreover, the liquid crystal phase behaviors of the sucrose laurate/sorbitan mono-laurate (Span 20)/water pseudo-ternary systems are examined in depth applying cryo-SEM, X-ray scattering measurements, rheological test and low field NMR experiments. In the abovementioned aqueous systems with a L1695 to Span 20 mass ratio (between 53.9: 46.1 and 43.3:56.7), sucrose mono-laurate combines with a certain number of sorbitan monolaurate molecules to form a single lamellar liquid crystalline phase. Furthermore, the present experimental results as well as their analysis could give the quantitative playground for the interaction between sugar-based surfactants in aqueous system, which has rarely been investigated compared with the phase behavior of polyoxyethylene alkyl ethers in aqueous solution.

Atomic scale insights on mechanical behavior and crack propagation in Mg-Al based nanolaminates

In this paper, the mechanical properties and plastic deformation mechanisms of Mg25Al75 metallic glass (MG) and three Mg-Al based nanoscale crystal/glass nanolaminates (NCGNLs) during crack propagation under tension loading are investigated using Molecular Dynamics (MD) simulations. The results observed in NCGNLs are compared with those related to pure MG to determine the effect of the NCGNLs on material strength and fracture toughness. The results show that the NCGNLs have a higher Young's modulus (E) and ultimate tensile strength (UTS) compared to pure MG. Which mean that the heterogeneous interphase between the crystalline layers and the amorphous pure glass behaves as the barriers behind the plastic deformation. Nano-patterning involving Aluminum (Al) and Magnesium (Mg) positively affects the fracture toughness of the material, while Mg25Al75/glass NCGNLs was found to be the most brittle and most prone to failure under tensile strain. The Al/glass NCGNLs is found to be the most ductile and able to withstand higher levels of strain before cracking. The simulations also reveal the deformation mechanisms at the atomic level, showing the nucleation/emission of dislocations types, twin boundary (TB), and stacking faults (SF) from the amorphous layer and their propagation to the Mg and Al crystal phases, respectively. These findings provide valuable insights into the mechanical properties of Mg-Al based nanolaminates and can inform the design of stronger and more durable materials.

Correlating Thickness and Phase of Single Co(OH)2 Micro-Platelets to the Intrinsic Activity of Oxygen Evolution Electrocatalysis.

Morphology, crystal phase, and its transformation are important structures that frequently determine electrocatalytic activity, but the correlations of intrinsic activity with them are not completely understood. Herein, using Co(OH)2 micro-platelets with well-defined structures (phase, thickness, area, and volume) as model electrocatalysts of oxygen evolution reaction, multiple in situ microscopy is combined to correlate the electrocatalytic activity with morphology, phase, and its transformation. Single-entity morphology and electrochemistry characterized by atomic force microscopy and scanning electrochemical cell microscopy reveal a thickness-dependent turnover frequency (TOF) of α-Co(OH)2. The TOF (≈9.5 s-1) of α-Co(OH)2 with ≈14nm thickness is ≈95-fold higher than that (≈0.1 s-1) with ≈80nm. Moreover, this thickness-dependent activity has a critical thickness of ≈30nm, above which no thickness-dependence is observed. Contrarily, β-Co(OH)2 reveals a lower TOF (≈0.1 s-1) having no significant correlation with thickness. Combining single-entity electrochemistry with in situ Raman microspectroscopy, this thickness-dependent activity is explained by more reversible Co3+/Co2+ kinetics and larger ratio of active Co sites of thinner α-Co(OH)2, accompanied with faster phase transformation and more extensive surface restructuration. The findings highlight the interactions among thickness, ratio of active sites, kinetics of active sites, and phase transformation, and offer new insights into structure-activity relationships at single-entity level.

Red mud treated with KOH: synthesis of sustainable materials from waste for water treatment.

Solid waste resulting from bauxite ore (red mud) was converted into useful products consisting in hydrogarnet together with zeolite. Red mud (RM) transformation from disposal material into new source was carried out using potassium hydroxide as an activator and hydrothermal process (HY) or vapor phase crystallization (VPC) approach. HY process was performed at 60, 90, and 130°C whereas during the VPC method, red mud was contacted only with vapor from the distilled water heated at 60 and 90°C. The results indicate the formation of katoite and zeolite L (LTL topology) with both approaches. All the synthetic products display magnetic properties. In addition, a preliminary investigation on arsenic removal from drinking water (from 59 to 86%), makes the synthetic materials appealing for environmental applications. Finally, the synthesis of a large amount of very useful newly-formed phases using vapor molecules confirms the efficiency of the innovative and green VPC process in waste material transformation.

Small-Angle X-ray Scattering as a Powerful Tool for Phase and Crystallinity Assessment of Monoclonal Antibody Crystallites in Support of Batch Crystallization.

Crystalline suspensions of monoclonal antibodies (mAbs) have great potential to improve drug substance isolation and purification on a large scale and to be used for drug delivery via high-concentration formulations. Crystalline mAb suspensions are expected to have enhanced chemical and physical properties relative to mAb solutions delivered intravenously, making them attractive candidates for subcutaneous delivery. In contrast to small molecules, the development of protein crystalline suspensions is not a widely used approach in the pharmaceutical industry. This is mainly due to the challenges in finding crystalline hits and the suboptimal physical properties of the resulting crystallites when hits are found. Modern advances in instrumentation and increased knowledge of mAb crystallization have, however, resulted in higher probabilities of discovering crystal forms and improving their particle properties and characterization. In this regard, physical, analytical characterization plays a central role in the initial steps of understanding and later optimizing the crystallization of mAbs and requires careful selection of the appropriate tools. This contribution describes a novel crystal structure of the antibody pembrolizumab and demonstrates the usefulness of small-angle X-ray scattering (SAXS) for characterizing its crystalline suspensions. It illustrates the advantages of SAXS when used to (i) confirm crystallinity and crystal phase of crystallites produced in batch mode; (ii) confirm crystallinity under various conditions and detect variations in crystal phases, enabling fine-tuning of the crystallizations for phase control across multiple batches; (iii) monitor the physical response and stability of the crystallites in suspension with regard to filtration and washing; and (iv) monitor the physical stability of the crystallites upon drying. Overall, this work highlights how SAXS is an essential tool for mAb crystallization characterization.

Imaging tunable Luttinger liquid systems in van der Waals heterostructures.

One-dimensional (1D) interacting electrons are often described as a Luttinger liquid1-4 having properties that are intrinsically different from those of Fermi liquids in higher dimensions5,6. In materials systems, 1D electrons exhibit exotic quantum phenomena that can be tuned by both intra- and inter-1D-chain electronic interactions, but their experimental characterization can be challenging. Here we demonstrate that layer-stacking domain walls (DWs) in van der Waals heterostructures form a broadly tunable Luttinger liquid system, including both isolated and coupled arrays. We have imaged the evolution of DW Luttinger liquids under different interaction regimes tuned by electron density using scanning tunnelling microscopy. Single DWs at low carrier density are highly susceptible to Wigner crystallization consistent with a spin-incoherent Luttinger liquid, whereas at intermediate densities dimerized Wigner crystals form because of an enhanced magneto-elastic coupling. Periodic arrays of DWs exhibit an interplay between intra- and inter-chain interactions that gives rise to new quantum phases. At low electron densities, inter-chain interactions are dominant and induce a 2D electron crystal composed of phased-locked 1D Wigner crystal in a staggered configuration. Increased electron density causes intra-chain fluctuation potentials to dominate, leading to an electronic smectic liquid crystal phase in which electrons are ordered with algebraical correlation decay along the chain direction but disordered between chains. Our work shows that layer-stacking DWs in 2D heterostructures provides opportunities to explore Luttinger liquid physics.

Synthesis of 4A Zeolite Molecular Sieves by Modifying Fly Ash with Water Treatment Residue to Remove Ammonia Nitrogen from Water

The widespread presence of ammonia nitrogen (NH4+–N) pollutants poses a serious threat to water environment health. In this study, a novel zeolite (WTR–CFA zeolite) with excellent adsorption performance is synthesized using CFA as the raw material and water treatment residue (WTR) as the aluminum source through an ultrasonic–assisted alkali melt hydrothermal method. Compared with traditional CFA–zeolite, WTR–CFA zeolite only generates 4A zeolite with a single crystal phase, and the peak shape is sharp, which results in better crystallization. WTR–CFA zeolite perfectly solves the technical problems of the low utilization rate and poor controllability of the crystal form in traditional artificially synthesized zeolites. The maximum NH4+–N adsorption capacity of WTR–CFA zeolite is 29.80 mg/g, which is higher than that of most adsorbents reported in previous studies. After five cycles of adsorption regeneration, the regeneration efficiency of WTR–CFA zeolite only decreased from 98.84% to 97.12%, which demonstrates excellent environmental value. The adsorption isotherms and kinetics of NH4+–N conform to the Langmuir model and quasi–second order kinetic model, respectively, which indicates that ion–exchange–dominant chemical adsorption plays a major role in the adsorption mechanism. In summary, this study combines the use of CFA and WTR resources with the treatment of aquatic pollution to reduce material synthesis costs, control the crystal structure of WTR–CFA zeolite, and increase adsorption capacity. This approach achieves the goals of “waste treatment and turning waste into treasure”.

Optical pulse-induced ultrafast antiferrodistortive transition in SrTiO3

The ultrafast dynamics of the antiferrodistortive phase transition in perovskite SrTiO3 is monitored via time-domain Brillouin scattering. Using femtosecond optical pulses, we initiate a thermally driven tetragonal-to-cubic structural transformation and detect the crystal phase through changes in the frequency of Brillouin oscillations (BO) induced by propagating acoustic phonons. Coupling the measured BO frequency with a spatiotemporal heat diffusion model, we demonstrate that, for a sample kept in the tetragonal phase, deposition of sufficient thermal energy induces a rapid transformation of the heat-affected region to the cubic phase. The initial phase change is followed by a slower reverse cubic-to-tetragonal phase transformation occurring on a timescale of hundreds of picoseconds. We attribute this ultrafast phase transformation in the perovskite to a structural resemblance between atomic displacements of the R-point soft optic mode of the cubic phase and the tetragonal phase, both characterized by anti-phase rotation of oxygen octahedra. The structural relaxation time exhibits a strong temperature dependence consistent with the prediction of the equation of motion describing collective oxygen octahedra rotation based on the energy landscape of the phenomenological Landau theory of phase transitions. Evidence of such a fast structural transition in perovskites can open up new avenues in information processing and energy storage sectors.

Preparation of graphene from polyethylene terephthalate (PET) bottle wastes and its use for the removal of Methylene blue from aqueous solution

We present a method to produce graphene flakes (GFs) from polyethylene terephthalate (PET) bottle wastes by the pyrolysis method using modified bentonite as a catalyst. The as-synthesized GFs are analyzed in terms of crystal phase, morphology, and surface chemistry. The synthesized GFs have a porous, thin, and leaf-like morphology with a length ranging from a few hundred nanometers to a few tens of micrometers. The XRD and FT-IR results confirm the graphitization of PET and the presence of oxygen-containing functional groups on the surface of synthesized GFs. The obtained GFs are used as adsorbents for the removal of methylene blue (MB) from aqueous solution. The effects of various factors including, contact time, pH, and initial MB concentration, on the MB removal efficiency are examined. In addition, the adsorption isotherm models of Langmuir and Freundlich are studied. The best-fitting model is observed with the Freundlich isotherm model.

Thermal Stability of Chalcogenide Perovskites.

Chalcogenide perovskites (CPs) have recently attracted interest as a class of materials with practical potential in optoelectronics and have been suggested as a more thermally stable alternative to intensely studied halide perovskites (HPs). Here we report a comparative study of the thermal stability of representative HPs, MAPbI3 (MA = CH3NH3+, methylammonium) and CsPbI3, and a series of CPs with compositions BaZrS3, β-SrZrS3, BaHfS3, SrHfS3. Changes in the crystal structure, chemical composition, and optical properties upon heating in air up to 800 °C were studied using thermogravimetric analysis, temperature-dependent X-ray diffraction, energy-dispersive X-ray spectroscopy, and diffuse reflectance spectroscopy. While HPs undergo phase transitions and thermally decompose at temperatures below 300 °C, the CPs show no changes in crystal phase or composition when heated up to at least 450 °C. At 500 °C CPs oxidize on time scales of several hours, forming oxides and sulfates. The structural origins of the higher thermal and phase stability of the CPs are discussed.

High-alumina and low-lithium glass-ceramics modulated by heat treatment and its structural evolution mechanism

In this work, one high-alumina and low-lithium glass-ceramic was successfully developed. The crystal phase, structure and properties of glass-ceramics were precisely modulated by heat treatment. DSC, XRD, TEM and SEM were used to investigate crystallization behavior and the results show that a high alumina content can refine crystal particles. Additionally, FTIR, SAXS NMR and XPS were used to investigate the effect of heat treatment on structure and its modulation mechanism was systematically analyzed. The findings indicate that crystallinity is positively correlated with the glass network polymerization degree. Moreover, the properties of product were evaluated using Vickers hardness and transmittance tests, revealing that the mechanical properties of glass-ceramics could be improved while maintaining transmittance with appropriate heat treatment. Ultimately, this method of heat treatment to modulate glass-ceramics properties provides valuable guidance for high-performance glass-ceramics development.

Influence of rapid heat treatment on the photocatalytic activity and stability of calcium titanates against a broad range of pollutants

Calcium titanate (CTO) photocatalysts were synthesized using a sol–gel method by adopting a cost-efficient, rapid calcination technique. The CTOs were characterized by X-ray diffractometry, X-ray photoelectron spectroscopy, infrared spectroscopy, nitrogen adsorption, porosimetry measurements, scanning/transmission electron microscopy, and diffuse reflectance spectroscopy. Their photocatalytic activity was assessed through the photocatalytic degradation of phenol, oxalic acid, and chlorophenol under UV light exposure, using a commercial CTO as a reference. The stability of the samples was evaluated using compounds with –OH, –COOH, and –Cl functional groups. Characterization results showed that CTO composites containing anatase, rutile, and brookite titania were obtained. Increasing the calcination temperature led to various crystalline compositions, higher crystallinity, larger primary crystallite sizes, and smaller specific surface areas. The photocatalytic activity of all CTO/TiO2 composites was superior compared to the commercial CTO we used as a reference. The high photocatalytic activity of the best-performing composites was attributed to their higher specific surface areas and the synergistic effect between the crystal phases. A cost comparison was also made between our unique calcination technique and conventional calcination, and it was found that our method is approximately 35% more cost-effective, while retaining the photocatalytic activity.

Influence of high field strength ions on the crystallization characteristics and properties of slag glass-ceramics

Blast furnace slag glass–ceramics were prepared by melting using rare-earth-containing blast furnace slag (REBFS) as the main raw material and Fe2O3 and Cr2O3 as composite nucleating agents. By adding different TiO2 contents, the study comprehensively revealed the effects of high field strength ions on the glass network structure, crystalline properties, elemental distribution and physicochemical properties. Raman spectroscopy and differential scanning calorimetry revealed that TiO2 acted primarily as a network modifier in the glass network. The appropriate TiO2 content disrupted the glass network, decreasing the crystallization activation energy (EC) of the glass–ceramic. However, excess TiO2 repaired the network structure, thereby increasing the EC. The combined effect of the Cr and Ti substantially improved the crystallization characteristics of the glass-ceramics. Cr2O3 induced the formation of spinel, which promoted the crystallization of the main crystalline augite phase. The self-aggregation of the high field strength Ti4+ ion induced the formation of a titanium- and cerium-containing titanite phase, which also contributed to grain refinement. This titanite phase effectively increased the Vickers hardness and acid and alkali resistances of the glass-ceramics to 9.16 GPa and over 98.5 %, respectively. The excellent physicochemical properties render REBFS glass–ceramics as being promising materials for various construction applications. This research provides theoretical support for comprehensively utilizing blast furnace slag and provides theoretical guidance for preparing slag glass–ceramics possessing desirable physicochemical properties.

Phase thermal stability and low thermal stress in MgO–BaO–CaO–Al2O3–B2O3–SiO2 glass-ceramic for long-term solid oxide fuel cells

The crystallization thermal stability plays an essential role in affecting thermal stress of glass-ceramic sealant for long-term planar-type solid oxide fuel cells (SOFC) to prevent fuel leakage during operation. Due to the lack of systematic research on regulating the stable performance of glass-based sealant with the working time at operation temperature, herein, the effect of MgO on crystallization kinetics, phase stability, and thermal and mechanical properties of MgO–BaO–CaO–Al2O3–B2O3–SiO2 (MBCABS) glass-ceramic has been firstly analyzed at heat-treatment of 750 °C with working time of 1∼1000h in this work. Subsequently, the relationship evolution of crystallization thermal stability-coefficient of thermal expansion (CTE) match-thermal stress was established by Finite Element Method (FEM). The main reasons for the decrease of CTE of MBCABS glass-ceramics with low-content MgO are the precipitation of hexagonal BaAl2Si2O8 phase and the transformation of hexagonal BaAl2Si2O8 to low-CTE monoclinic BaAl2Si2O8 phase, bring about that the Von Mises thermal stress of sealant itself and interface having tripled at 1000h (more than 200 MPa) according to FEM simulation results. The thermal stable and high-CTE BaMgSiO4, Ba8Mg16Si16O56, and BaCa2Mg(SiO4)2 phases crystallized in MBCABS glass-ceramics with high-content MgO, therefore the maximum stress at all time parameters was below 100 MPa for 1∼1000h. This study was useful for identifying the optimal phase option and CTE matching of glass-based sealant for efficient and stable long-term operation of solid oxide fuel cells.

Harnessing Cu incorporation for achieving stable superior microwave dielectric properties in low permittivity MgSiO3-based ceramics through effective phase transition suppression

MgSiO3 ceramics with a low dielectric constant are highly promising for application in 5G communication due to their excellent performance and cost-effectiveness. However, the application remains constrained by phase transitions. This study aims to unlock their full potential by introducing Cu ions to mitigate phase transitions, thereby achieving stable and superior performance. Mg1-xCuxSiO3 (0 ≤ x ≤ 0.25) ceramics were synthesized by solid-state method, and the effects of Cu introduction on the crystal structure, phase constitution, microstructure and microwave dielectric properties were systematically investigated. Through XRD patterns and Rietveld refinement, it was found that when x = 0, both protoenstatite (PEN) and low-temperature clinoenstatite (CEN) phases coexist due to a phase transition from PEN to CEN. As x increases, the PEN phase dominance rises while the CEN phase diminishes, indicating that the addition of Cu ions inhibits the occurrence of phase transition. At x ≥ 0.2, only the orthoenstatite (OEN) phase was observed. SEM and EDS analyses revealed the beneficial impact of Cu introduction on sintering, yet excessive amounts can lead to abnormal grain growth, local segregation, and uneven distribution of Cu elements, thereby deteriorating microwave dielectric properties. The optimal microwave dielectric performance was achieved at x = 0.05: εr = 6.2, Qf = 93,600 GHz, τf = −33.7 ppm/°C. A one-year long-term comparative study revealed the stabilizing effect of Cu incorporation for obtaining stable excellent performance. These findings underscore the potential of introducing an appropriate amount of Cu to achieve stable and superior microwave dielectric properties in MgSiO3 ceramics, paving the way for practical applications in 5G communication.

Effects of MgO/CaO ratio on the crystal phase composition and performance of MgO-CaO-B2O3-SiO2 glass–ceramics for LTCC applications

Effects of MgO/CaO ratio on the crystal phase composition and performance of MgO-CaO-B2O3-SiO2 glass–ceramics for LTCC applications