Crystals In Temperature Range Research Articles

Crystallization behavior of smelting slag for recovery of platinum group metals from spent automotive catalysts and preparation of foamed glass-ceramics

Spent automotive catalysts (SAC), as a significant secondary resource for platinum group metals (PGMs), can be recovered on a large scale through high-temperature smelting. Besides, as a byproduct, the glass slag lacks high-value applications. This paper proposes a recyclable method to convert slag, graphite powder (GP), and ferric oxide (Fe2O3) into foamed glass-ceramics through low-temperature sintering, significantly reducing environmental impacts and production costs. Non-isothermal differential thermal analysis was used to explore the transition and crystallization temperature range, transition kinetic, crystallization kinetic, and crystallization behavior of the glass slag. Furthermore, the influence of the foaming agent composition and heat treatment temperature on the physical properties, chemical resistance, and mechanical properties of the foamed glass-ceramics was investigated. Foamed glass-ceramics composed of 60wt% slag-30wt% Fe2O3-10wt% GP exhibited the excellent properties of a geometric density of 1.43 g/cm3, a volumetric water absorption of 26.32%, a compressive strength of 8.08 MPa, and a mass loss of 3.56% in strong acid and 0.08% in strong alkali after low temperature heat treatment at 1160°C. This study provides an insight into transforming low-value waste into high-performance foamed glass-ceramics.

Thermotropic liquid crystalline and fluorescence resonance energy transfer under temperature excitation of imidazolium salt/CdTe quantum dots composites

ABSTRACT The optical characteristics and surface area of quantum dots (QDs) render them a compelling platform for the development of composite materials based on fluorescence resonance energy transfer (FRET). A novel luminescent liquid crystal nanocomposite (CBphCM-CdTe) has been successfully prepared through the ionic self-assembly route using imidazolium salt (CBphCM) and CdTe QDs. DSC and POM analyses confirm that CBphCM-CdTe undergoes the smectic A and C phases, but its liquid crystal temperature range is narrower compared to that of pure CBphCM. Concurrently, CBphCM-CdTe exhibits excellent fluorescence characteristics. Increasing temperature serves as a trigger for fluorescence resonance energy transfer between CdTe QDs and CBphCM, wherein the fluorescence of CdTe QDs is quenched, while the fluorescence intensity of CBphCM increases with rising temperature. A strong correlation exists between temperature and fluorescence intensity within the liquid crystal temperature range. Such thermochromic materials are anticipated to facilitate innovative development in dynamic thermo-optical sensing, thereby enabling enhanced control over light manipulation in stimuli-responsive devices.

From birth to death: The role of upper-crustal thermal maturation and volcanism in porphyry ore formation revealed in the Yerington district

The current race towards greener energy and its intertwined increase in Cu demand imposes the need to find mineralized centers that are economic despite greater depths. To this end, a better understanding of the processes controlling the metal tonnage of porphyry Cu deposits, the main source of Cu, is needed and the focus of current research and debate. This study provides a comprehensive view of the duration of upper-crustal magmatism and its significance in the degree of metal endowment in porphyry Cu deposits using the Yerington batholith, Nevada, USA, as a case study. The Yerington district constitutes an exceptional example of an exposed porphyry Cu system where the plutonic environment that fed the porphyritic dikes is accessible. Combining trace element geochemistry and high-precision geochronology of zircon from all exposed units, we propose that the thermal maturation of the upper crust by a continuum in magmatic activity without significant hiatuses is a key factor in enabling the formation of large porphyry Cu style mineralization. The Yerington magmatic system transitioned from a volcanically active environment with coeval plutonism to a growing upper-crustal magmatic reservoir that fed the porphyritic dikes and associated mineralized centers to then resume its volcanic activity terminating the ore-forming episode. A relatively high volcanic/plutonic ratio characterized the first expressions of Jurassic magmatism in the district from ∼170 Ma with the coeval eruption of the Artesia Lake volcanics and the protracted emplacement of the McLeod Hill pluton. Geochemically, this period recorded distinctive negative Eu anomalies and a gentle increase in Yb/Dy ratios in zircon with decreasing Ti contents over a large range of zircon crystallization temperatures. This persistent magmatism over ∼2 Myr thermally matured the upper crust, enabling the growth of magmatic reservoirs that formed the Bear and Luhr Hill plutons without known volcanic activity for ∼1.3 Myr. Zircon trace element compositions indicate that this transition occurred as a continuum in decreasing negative Eu anomalies and increasing Yb/Dy with decreasing Ti contents and age across the plutonic units, reaching the more evolved signatures and lowest crystallization temperatures in the zircon from porphyry dikes. An increase in the volcanic/plutonic ratio with the eruption of the Fulstone Spring sequence likely terminated the ore-forming potential of the district. Although many other studies have provided important views on the timing and duration of porphyry Cu deposit formation, the link to their plutonic roots has been limited due to their inaccessibility. Therefore, this study offers the first complete picture into the temporal and chemical evolution of an upper-crustal magmatic system and the roles that factors like prolonged magmatism and volcanism play before and after ore formation. We argue that without the thermal maturation of the upper crust, the construction of a long-lived magmatic reservoir would not have been possible, precluding the formation of porphyry Cu deposits. Under this premise, not only the duration of ore-related magmatic activity, but the occurrence of long-lived precursor magmatism might exercise crucial control on the final tonnage of the deposit and should be considered during exploration for new porphyry deposits.

Crystallization and melting of Poly(4-hydroxybutyrate) characterized by fast scanning calorimetry

Poly (4-hydroxybutyrate) (P4HB) is a marine biodegradable polyester with promising applications. Unfortunately, the crystallization and melting behavior of P4HB has not been systematically studied, due to the rapid crystallization near room temperature. In particular, the characterization of crystallization and melting of P4HB by fast scanning calorimetry (FSC) has not been reported previously. In this article, the common differential scanning calorimeter (DSC), polarized optical microscopy (POM), atomic force microscopy (AFM) and FSC were performed to investigate the crystallization and melting behavior of P4HB. The results indicated that melt crystallization facilitated the formation of fragmented crystals rather than complete spherulites. Furthermore, the P4HB exhibited a broad crystallization temperature range from −19 °C to 49 °C, and the crystallization and melting of P4HB was notably affected by the temperature, in addition to the heating or cooling rates. The higher crystallization temperature and lower cooling rates facilitated the formation of well-developed crystals. Remarkably, the P4HB is found to be unable to crystallize at heating or cooling rates exceeding 6 K/s. Moreover, double melting peaks could be discerned at moderate isothermal crystallization temperature exhibiting faster crystallization rate. The findings will provide theoretical guidance on how to optimize the processing parameters in modulating the crystallization of P4HB.

Crystallization Kinetics and Melting Behavior of Novel Biobased Poly(butylene 2,5‐thiophenedicarboxylate)

AbstractPoly(butylene 2,5‐thiophenedicarboxylate) (PBTh) is a novel biobased semicrystalline polyester with superior thermal, mechanical, and gas barrier properties; however, the crystallization kinetics and melting behavior of PBTh have not been studied in detail so far. The crystallization kinetics of PBTh was first studied in this research. The Ozawa equation failed to describe the nonisothermal melt crystallization kinetics of PBTh due to the secondary crystallization. The crystallization activation energy value was calculated by the Friedman method, which was negative and exhibited the conversion dependence. The isothermal melt crystallization kinetics of PBTh was well described by the Avrami equation in a wide range of crystallization temperature from 84 to 120 °C. PBTh showed the fastest crystallization rate at 104 °C; moreover, the Avrami exponent value slightly varied between 2.2 and 2.7, suggesting the same crystallization mechanism within the investigated temperature range. PBTh displayed one or two melting endotherms depending on crystallization temperature, which was well explained by the melting, recrystallization, and remelting mechanism. In addition, the equilibrium melting point of PBTh was estimated to be 163.1 °C with the Hoffmann−Weeks equation.

Fabrication of highly b-oriented MFI zeolite film over broad temperature window

Despite that oriented MFI zeolite films exhibit significant prospects for a wide range of applications due to microstructural superiority, their precise orientation control entails rigorous demands on reaction conditions (e.g., reaction temperature). In this work, we achieved facile synthesis of continuous b-oriented MFI zeolite films with few twins over a wide crystallization temperature range of 30–210 °C through adopting NH4F-mediated gel as nutrient during epitaxial growth. Both ammonium ions and fluorine ions were found crucial for enhancing the gel reactivity, endowing epitaxial growth with higher crystallization rates; moreover, the above morphology could be maintained even under fluctuating temperature conditions during film processing, thereby showing great potential for their bath production in a facile and reproducible manner.

Synthesis of trehalose-grafted poly(ester amide) with potential ice recrystallization inhibition activity

The ice recrystallization inhibition (IRI) activity of a macromolecular cryoprotectant is of great significance for applications in cryopreservation of biosamples. Herein, in order to create a possibly biodegradable trehalose-modified polymer, thiol-monosubstituted trehalose was synthesized by a simplified method, and then tethered to allylated-based poly(ester amide) (PEA) via thiol-ene click reaction. The synthesized PEA-g-trehalose (PEA-g-Tre) was able to inhibit ice recrystallization by 55% at 10 mg mL−1 compared to PBS control, superior to poly(ethylene glycol). Differential scanning calorimetry results showed that PEA-g-Tre exhibited a significantly higher glass transition temperature at 92.4 °C than PEA at 33.5 °C, and had a narrowed ice crystallization temperature range due to introduction of trehalose. Raman spectroscopy indicated that the IRI activity of PEA-g-Tre was attributed to the presence of trehalose residues in the side groups, which disrupted the regular arrangement of freezable water molecules. It is suggested that modification by trehalose can give rise to the IRI activity of the polymer through adsorption and diffusion mechanism with water, and thiol-ene reaction provides a feasible way for preparing polymeric cryoprotectants containing trehalose.

Effects of shear-induced crystallization on the complex viscosity of lamellar-structured concentrated surfactant solutions.

Material relationships at low temperatures were determined for concentrated surfactant solutions using a combination of rheological experiments, cross-polarized microscopy, calorimetry, and small angle X-ray scattering. A lamellar structured 70 wt% solution of sodium laureth sulfate in water was used as a model system. At cold temperatures (5 °C and 10 °C), the formation of surfactant crystals resulted in extremely high viscosity. The bulk flow behavior of multi-lamellar vesicles (20 °C) and focal conic defects (90 °C) in the lamellar phase was similar. Shear-induced crystallization at temperatures higher than the equilibrium crystallization temperature range resulted in an unusual complex viscosity peak. The effects of processing-relevant parameters including temperature, cooling time, and applied shear were investigated. Knowledge of key low-temperature structure-property-processing relationships for concentrated feedstocks is essential for the sustainable design and manufacturing of surfactant-based consumer products for applications such as cold-water laundry.

Microstructure and properties of Al−2Mg−0.5Mn alloy with narrow crystallization temperature range realized by adding trace elements

The wide crystallization temperature range of Al−Mg alloys is a key factor for the surface defect formation during continuous casting and rolling process. To reduce the crystallization temperature range of the alloy, the influences of trace Zn, Si, Zr and Ti elements on the microstructure and properties of Al−2Mg−0.5Mn alloy were investigated. The X-ray photoelectron spectroscopy, atomic force microscopy, scanning and transmission electron microscopy were used for microstructural characterization. The Ti and Zr additions could refine the grain size and improve the strength of the Al−Mg−Mn alloy by forming Al3Ti and Al3Zr in the alloy, while the crystallization temperature ranges of these alloys were wider. It was revealed that Zn and Si additions could form new secondary phases with Mg in the alloy, thus reducing the actual Mg content during later eutectic solidification process. Therefore, the crystallization temperature range of Al−2Mg−0.5Mn−0.2Zn−0.2Si alloy was narrower than that of Al−2Mg−0.5Mn alloy. The mechanical properties and corrosion resistance of Al−2Mg−0.5Mn alloy were also improved by the additions of Zn and Si.

ИДЕНТИФИКАЦИЯ ПРОДУКТОВ КРИСТАЛЛИЗАЦИИ СТЕКОЛ ДЛЯ ПРОИЗВОДСТВА СТЕКЛОВОЛОКНА, ПОЛУЧЕННЫХ НА ОСНОВЕ ТЕХНОГЕННЫХ ОТХОДОВ ТЭЦ

Achieving technological sovereignty in the field of production of composite materials today requires a rapid increase in production volumes of special-purpose glass fibers. At the same time, scientific solutions in this area must be effective, both from a technological and economic point of view. The article presents research results that form an idea of the possibility of using technogenic waste from thermal power plants in the industrial production of electrical insulating and high-modulus glass fibers. Since the technological efficiency of fiber formation is largely determined by the tendency of melts to crystallize, most of the research was aimed at studying the crystallization process, determining the temperature range of crystallization and identifying the nature of crystallization products. It has been established that in the temperature range of 1100-1200°C the crystallization products are represented by diopside and anorthite, which, with increasing temperature, undergo amorphization and subsequent dissolution in the glass phase. In glass S, the products of crystallization in the temperature range 1200-1300°C are represented by minerals of the continuous isomorphic series albite-anorthite and an insignificant content of ferruginous minerals - magnetite, hematite or goethite. The data obtained will make it possible to develop rational parameters for the process of forming glass fibers or methods for suppressing such an undesirable phenomenon for technology as crystallization in the molding range.

Study on improving the fluidity of Ti2AlNb alloy

In this paper, the effects of main elements like Al, Nb and trace elements like Fe, Mo, W, Co, B and Si on the fluidity of Ti–22Al–25Nb alloy were investigated. The alloy composition which is beneficial to improve the fluidity was selected by calculating the thermal property parameters affecting the fluidity of the alloy through thermodynamic software, numerical simulation test of the fluidity of the alloy and verification test of the fluidity of the preferred alloy. Finally, the improvement mechanism of the alloy fluidity was discussed. Results showed that the appropriate reduction of Nb element was better than Al element for the improvement of fluidity. The addition of trace Fe, B and Si elements was beneficial to the improvement of fluidity, the improvement effect of B element was the best, while the addition of trace Mo, W, and Co was not conducive to the improvement of fluidity. The cessation mechanism of Ti2AlNb alloy is the cessation mechanism of the alloy with a wide crystallization temperature range. The composition which was the most beneficial to improve the fluidity was Ti–22Al–24Nb-0.1B. The main reasons for the improvement of the fluidity were that on the one hand, reducing 1 at% Nb and adding 0.1 at% B not only increased the superheat and crystallization latent heat but also reduced the melt viscosity and thermal conductivity, thus improving the fluidity. And on the other hand, the TiB phase refined the grains, and the fine grains prevented the dendrites from growing into a well-developed dendritic network, inhibited the adverse effect of the increase in the width of the solidification zone on the fluidity, and further improved the fluidity.

Crystallization behavior of CMAS + sea salt mixture and its effect on the mixture penetration into thermal barrier coatings

When aero-engines are operated in dusty and near-sea environments, thermal barrier coatings (TBCs) are threatened by coupling corrosion of calcium-magnesium-alumina-silicate (CMAS) and sea salt. Investigating the crystallization behavior of CMAS + sea salt that affects the melt penetration into TBCs is the key to seeking protection methods against coupling corrosion. In this study, the crystallization temperature range and crystalline products of CMAS + sea salt were investigated. The results indicated that the crystallinity of CMAS + sea salt is affected by temperature. CMAS, CMAS+5SS (95 wt% CMAS + 5 wt% sea salt), and CMAS+10SS (90 wt% CMAS + 10 wt% sea salt) were crystalized initially at 1000 °C, but the crystallinity was low. At 1100 °C, more crystallization occurred, with diopside (CaMgSi2O6), akermanite (Ca2MgSi2O7), and anorthite (CaAl2Si2O8) being precipitated. With the temperature increasing to 1200 °C, wollastonite (CaSiO3) instead of akermanite was precipitated in both CMAS and CMAS+5SS samples, while the CMAS+10SS sample became almost amorphous glass with little crystallization indicating that higher sea salt content narrows the crystallization temperature range. Moreover, at the appropriate crystallization temperature (1100 °C), the addition of sea salt in CMAS played a depolymerization role and promoted discrete precipitation of dendritic akermanite, which reduced the crystalline layer compactness increasing the threat of mixture penetration into TBCs.

Modeling of the kinetics of polymorphic isothermal crystallization of poly(l-lactide) subjected to uniaxial molecular orientation

Kinetic model of polymorphic crystallization of uniaxially oriented amorphous poly(l-lactide) under isothermal conditions is formulated basing on the Hoffman-Lauritzen theory. Entire ranges of the crystallization temperatures and amorphous orientation factor are considered. The inverse transformation half-times of the amorphous phase to the individual polymorphs, between the unstable α’ and stable α polymorphs, as well as of the overall crystallization are discussed. The kinetic effects are assigned to the decrease in the amorphous phase entropy caused by deformation and orientation of the flexible chain macromolecules.The model predicts that crystallization to the stable α form is controlled by the rate of transformation of the amorphous phase to α’. Concentration of heterogeneous nuclei typical for commercial polymer is assumed and in this case the role of homogeneous nucleation in the transformation kinetics is negligible. The role of homogeneous nucleation at different hypothetical concentrations of heterogeneous nuclei is estimated vs. the Hermans amorphous orientation factor and crystallization temperature. Ranges of domination of heterogeneous and homogeneous nucleation are predicted as dependent on the heterogeneous nuclei concentration.The increase of the overall oriented crystallization rate is predicted for the entire crystallization temperature range as resulting from the increase of the amorphous-to-α′ transformation rate at increasing amorphous orientation. The model provides a view on the mechanisms for possible control of the development of α’/α composition by adjusting the crystallization time vs. orientation and temperature.

Synchronous formation of the ‘forearc’ Bay of Islands ophiolite and its basal high-temperature metamorphic sole constrained by U–Pb zircon ages

The welded metamorphic sole at the base of the Bay of Islands Ophiolite Complex (BOIC) in the Northern Appalachians of Newfoundland shows a typical inverted pressure-temperature (P-T) metamorphic gradient from HT-MP granulite to LT-LP greenschist facies. It incorporates mafic volcanic/plutonic protoliths mixed with pelagic, hemi-pelagic and coarser epiclastic sedimentary protoliths. New LA-ICP-MS U–Pb concordia ages, trace elements, and Ti-in-zircon geothermometry for ∼250 zircon analyses from three metabasites of the upper HT sole amphibolites with N-MORB-like protoliths are reported. Two samples collected within meters of the ophiolite peridotite-sole contact of the Blow Me Down Mountain and North Arm Mountain massifs yielded the oldest comparable concordia ages of 487.7±2.6 Ma and 489.1±3.1 Ma, respectively, that are both within error of the igneous age of 488.3±1.5 Ma of the directly overlying BOIC ophiolite, which formed at a supra-subduction zone (SSZ) forearc spreading center. A third slightly younger age of 484.2±2.4 Ma was obtained for an upper HT amphibolite sample with similar phase assemblages but collected ∼30 m below the peridotite contact of the Table Mountain massif. Zircon crystals analyzed have similar size and morphologies, subparallel rare earth element (REE) variation patterns, and steep heavy REE-enrichments ((Lu/Gd)cn >20), significant positive Ce anomalies (dominantly >5) and slight positive to dominantly negative Eu anomalies (1.2 – 0.4). Zircon shows Th/U mean values of 0.37 – 0.48 with little to no rim to core variation. Minimum Ti-in-zircon mean crystallization temperatures range from ∼764 – 787 °C. These neocrystallized zircon crystals appear to be derived from thin leucosomes within the three amphibolites. Two other samples also from the upper HT sole show evidence of inherited detrital zircon with core dates spanning the Cambrian Notre Dame Arc through older Laurentian-like basement and rift age ranges.Subcretion of the sole took place below a hot forearc asthenospheric wedge, that is, a consequence of the newly-formed BOIC forearc spreading center extending from the back arc to a triple junction along the westward- (or paleo-northward) verging trench of the Notre Dame arc. The early HT sole formation age at ca. 489–488 Ma is long prior to initiation of obduction at ca. 470 Ma and long after initiation of subduction beneath the paleo-northward verging Notre Dame peri-Laurentian arc at ca. 514 Ma. This indicates Newfoundland sole ages of the BOIC and St. Anthony Complex are correlated with the age of SSZ spreading, but not necessarily subduction initiation because previously existing and self-sustaining subduction was ongoing. Sole ages are then not correlated with the younger age of obduction-related orogenic events (e.g., proposed Taconic I and II) in the Newfoundland Appalachians.

On the mechanism of Si-promoted destabilization of TiCx particles in Al alloys

TiCx is an excellent composite strengthening particle and grain refiner for Al alloys. However, the stability of TiCx is poor when solute Si exists in Al alloy melts, which significantly depresses its strengthening and grain refining effects. In this work, the destabilization mechanisms of the TiCx particles in Al-Si alloy melt with a composition of Al-7Si-7.5TiC were explored via experiments, first-principles calculations and thermodynamic calculations. The experimental results show that Si atoms diffuse into TiCx and Ti atoms are released into the Al melt to form a Ti-rich transition zone during the insulation of TiCx in Al-Si melt, and the TiAlySiz and Al4C3 phases are solidified in the Ti-rich zone and at Ti-rich zone/TiCx interface, respectively. The first principles calculations show that the low formation energy of C vacancies facilitates the rapid diffusion of Si atoms in TiCx, while the doping of Si atoms reduces the energy barrier of diffusion of Ti atoms in TiCx and promotes the formation of Ti-rich zones. The thermodynamic calculations show that the wide crystallization temperature range of the destabilized product TiAlySiz phase is the key to continuous decomposition of TiCx particles. In addition, the driving force of the main destabilization reaction of TiCx in the Al-Si alloys is about 44 times higher than that in the Al alloys without Si addition. This indicates that the presence of solute Si remarkably promotes the subsequent decomposition process of TiCx in the Al-Si alloy melts.

Compositional variation and Sn isotope fractionation of cassiterite during magmatic-hydrothermal processes

Cassiterite (SnO2) precipitates over a wide physicochemical range during magmatic-hydrothermal processes. Significant variations in chemical and Sn isotopic compositions of cassiterite have been increasingly reported from hydrothermal deposits worldwide. However, the mechanisms responsible for such notable changes in cassiterite geochemistry remain to be fully addressed. Toward this end, we investigated the chemical and Sn isotopic compositions of distinct generations of cassiterite from a highly-evolved magmatic-hydrothermal-metallogenic system (Xianghualing Sn polymetallic deposit, South China). Cassiterite is widespread in the albite granite, greisen, skarn, and sulfide ore of this deposit, covering most of the known cassiterite-bearing rock/ore types. Based on distinct morphologies and mineral paragenesis, three generations of the Xianghualing cassiterite are identified: (1) Cst 1 occurs in albite granite and greisen; (2) Cst 2 occurs in skarn; and (3) Cst 3 is present in sulfide ore. A lattice strain model indicates that inter-element compositional differences of cassiterite are dual-controlled by cassiterite element partition coefficients and melt/fluid compositions for sufficient and deficient elements, respectively. The variations in Zr, Hf, Nb, and Ta elements in cassiterite are recognized as thermo-indicators of the melt/fluid physicochemical conditions. Their concentrations are influenced by pre- and syn-precipitated Zr-Hf-Nb-Ta-enriched minerals that have a wide crystallization temperature range. Due to differentiations of multiple cationic valences, concentrations and interelement ratios of Sb, Fe, V, and U can be utilized to monitor the relative melt/fluid redox state of different cassiterite generations. Tin stable isotopic compositions are notably fractionated in the Xianghualing cassiterite samples, with δamuSn values relative to standard NIST 3161a ranging from −0.16‰ to 0.19‰. By comparison with compiled Sn isotopes of other hydrothermal deposits, kinetic disequilibrium fractionation is proposed as the main control on cassiterite Sn isotopes fractionation. A Rayleigh fractionation model generates fractionation factors of 1.00010–1.00025, consistent with fractionation factors predicted by first principles calculations (1.00013 to 1.00037). Thus, progressive precipitation of Sn-enriched minerals due to the change of physicochemical conditions during magmatic-hydrothermal processes will cause lighter Sn isotopic compositions in residual melt/fluid. This study highlights that cassiterite chemical and Sn stable isotopes are novel indicators to magmatic-hydrothermal processes.

Microscopic and Small-/Wide-Angle Microbeam X-ray Analyses on Dendritic Crystals in Poly(butylene succinate)

A unique composite dendritic spherulite is detected in a specific crystallization temperature range (Tc = 60–78 °C), whose assembly is probed using microscopy techniques and powerful synchrotron X-ray microbeam analyses. Composite dendritic spherulites composed of feather-like and fern-like branches in poly(butylene succinate) (PBSu) crystallized with poly(ethylene oxide) diluent are analyzed on top surface morphologies correlating with interior-dissected assembly, concurrently through polarized-light optical microscopy, scanning electron microscopy, and synchrotron-radiation X-ray microbeam analysis. The feather-like branch is composed of fully edge-on crystal plates, while the fern-like branch is composed of flat-on crystal plates. These branches originate from a common nucleus with different growth rates. For the first time, the dendritic PBSu spherulite serves as a convenient model for understanding the mechanisms how edge-on and flat-on crystal orientations can alternate not only in a serial mode to form ring bands but also in a parallel mode to form straight dendrites. Morphology evidence and detailed microbeam techniques collectively prove that these discontinuous lamellar plates discretely and gradually tilt and bend to transform from a vertical to a horizontal crystal plate with a corresponding alteration in birefringence.

Crystal structure, electrical and magnetic properties of anion-deficient perovskite-like Ba3SmFe2O7.5

Anion-deficient perovskite-like Ba3SmFe2O7.5 was prepared using a glycerol–nitrate synthesis. Using high-temperature X-ray diffraction in situ a crystal structure transition temperature range 800 and 840 °C was established. These results were further confirmed by high-temperature dilatometric analysis. The average thermal expansion coefficient (TEC) of Ba3SmFe2O7.5 is about 12.8 × 10−6 K−1 between 25 °C and 800 °C. Magnetic experiments proved an excellent phase purity of the oxide and reveal that Fe3+ ions stay in high and intermediate spin states in a ratio of 75% and 25% respectively.

Influence of Cr Doping on Structural, Optical, and Photovoltaic Properties of BiFeO3 Synthesized by Sol-Gel Method

In this work, pure BiFeO3 and samples doped with different concentrations of chromium were synthesized to improve the optical properties and efficiency of solar cells based on BiFeO3. The sol-gel method was used for synthesis due to its ability to produce nanostructured materials with high purity and good homogeneity, as well as the possibility of controlling the size and shape of the resulting particles. The samples were characterized by different analytical techniques. Thermal analysis results indicate that the dopant increases the weight loss of the sample from 61 to 81%, with an increase in the exothermal in the nucleation and crystallization temperature range. The X-ray diffraction patterns and UV-visible spectra show a dependence of the crystallite size and bandgap with respect to the amount of Cr dopant, decreasing from 168 to 73 nm and from 2.14 to 1.92 eV, respectively. Scanning electron microscopy images display a decreasing grain size as a result of an increasing amount of dopant. The I-V analysis results show a 1% Cr-doped BiFeO3 photovoltaic device exhibits enhanced photovoltaic performance with higher photocurrent and 4.17 times greater energy conversion efficiency compared with a pure BiFeO3 photovoltaic device. For their behavior, Cr-doped BiFeO3-based photoelectrodes are very promising materials for photovoltaic devices.

Bio-Based, Self-Healing, Recyclable, Reconfigurable Multifunctional Polymers with Both One-Way and Two-Way Shape Memory Properties

Shape memory polymers (SMPs) have attracted wide attention over the past few decades due to their fantastic applications in modern life. Nevertheless, excellent self-healing properties, recyclability, solid-state plasticity, and reversible shape-switching ability are necessary but can rarely be satisfied in one material. Herein, we report multifunctional SMPs by constructing a dynamic boronic ester bond cross-linking network using sustainable Eucommia ulmoides gum as a raw material. Thanks to the crystallization and wide melting temperature range, these kinds of SMPs have thermal-triggered one-way shape memory performance and show two-way shape memory properties, whether under constant stress or stress-free conditions. Owing to the dynamic nature of the boronic ester bond, it exhibits good self-healing properties (near 100% at 80 °C), shape reconfigurability, and chemical recyclability. In addition, by incorporating multiwalled carbon nanotubes, the formed composite is responsive to 808 nm near-infrared light. Its applications are further exploited, including photoresponsive actuators, vascular stents, and light-driven switches. This paper provides a simple way for fabricating multifunctional SMPs, and the as-prepared materials have potential applications in diverse fields, such as biomedicine, intelligent sensing, and soft robotics.