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Boron neutron capture therapy (BNCT) has been extant for decades and continues to be practiced in many centers around the globe. Most of the active clinical trials utilize boronophenylalanine as the drug containing boron atoms. The important aspect that has been added to the BNCT practice is the use of an F-18 radiolabeled analog for ascertaining targeting and monitoring follow-up studies. The recent widespread application of therapeutic radiopharmaceuticals, especially peptides (somatostatin analogs), prostate-specific antigen-binding ligands, or immunomolecules, offers the ambit for invention of new tumor-specific BNCT agents, especially for BNCT-susceptible tumors, that is, locoregional cancers such as head and neck cancer. Such BNCT agents, when radiolabeled, can enable simultaneous imaging and/or therapeutic applications (depending on the radionuclide used) through multimodal approaches. Development of boron-rich moieties such as sodium borocaptate and neutral carboranes combined with tumor-targeting moieties can lead to a new horizon in BNCT. The review covers various aspects of drug design, tumor targeting, and possible future radiopharmaceutical development for multimodal theranostic application in humans.

The presence of defects at the interface between the perovskite film and the carrier transport layer poses significant challenges to the performance and stability of perovskite solar cells (PSCs). Addressing this issue, we introduce a dual host-guest (DHG) complexation strategy to modulate both the bulk and interfacial properties of FAPbI3-rich PSCs. Through NMR spectroscopy, a synergistic effect of the dual treatment is observed. Additionally, electro-optical characterizations demonstrate that the DHG strategy not only passivates defects but also enhances carrier extraction and transport. Remarkably, employing the DHG strategy yields PSCs with power conversion efficiencies (PCE) of 25.89% (certified at 25.53%). Furthermore, these DHG-modified PSCs exhibit enhanced operational stability, retaining over 96.6% of their initial PCE of 25.55% after 1050 hours of continuous operation under one-sun illumination, which was the highest initial value in the recently reported articles. This work establishes a promising pathway for stabilizing high-efficiency perovskite photovoltaics through supramolecular engineering, marking a significant advancement in the field. The defects at the perovskite/carrier transport layer interface pose significant challenges to the performance of perovskite solar cells. Here, the authors introduce a dual host-guest complexation strategy with Cs-crown-ether and ammonium salt, achieving a high PCE of 25.9% with superior stability. [ABSTRACT FROM AUTHOR]

Halide perovskites show great optoelectronic performance, but their favorable properties are paired with unusually strong anharmonicity. It was proposed that this combination derives from the ns2 electron configuration of octahedral cations and associated pseudo-Jahn–Teller effect. We show that such cations are not a prerequisite for the strong anharmonicity and low-energy lattice dynamics encountered in these materials. We combine X-ray diffraction, infrared and Raman spectroscopies, and molecular dynamics to contrast the lattice dynamics of CsSrBr3 with those of CsPbBr3, two compounds that are structurally similar but with the former lacking ns2 cations with the propensity to form electron lone pairs. We exploit low-frequency diffusive Raman scattering, nominally symmetry-forbidden in the cubic phase, as a fingerprint of anharmonicity and reveal that low-frequency tilting occurs irrespective of octahedral cation electron configuration. This highlights the role of structure in perovskite lattice dynamics, providing design rules for the emerging class of soft perovskite semiconductors. By comparing CsSrBr3 and CsPbBr3 with close structural similarity but the latter lacking lone-pair electrons on the octahedral metal, the authors reveal the similar vibrational anharmonicities in the two perovskites, which disentangles the electronic properties and vibrational anharmonicities. [ABSTRACT FROM AUTHOR]

The atomic scale solid–liquid interfacial process dominates the macro‐dissolution of silica, yet its direct experimental observation is challenging. Here we employed the reactive molecular dynamics to model this process in alkaline condition. An elevated temperature strategy under canonical ensemble (NVT) was applied to accelerate the process for sufficient sampling at temporal domain. A stepwise transformation from fully linked SiO4 network (Q3 and Q4) to reduced linkage and eventually aqueous species (Q0) was revealed. The simulated dissolution rate agrees well with the value predicted by empirical model. By tracing hydrogen atoms, we found that the dehydroxylated silica surfaces in alkaline electrolyte solutions underwent a transition from Si–O–Si bond cleavage‐dominated (mainly reacted with OH−) to hydroxylation‐dominated surface reactions. The free‐energy reconstruction of well‐tempered metadynamics reveals that 1500 K accelerates dissolution without altering the reaction pathways. These findings offer novel insights into the evolution of atomic‐scale surface configurations during the dissolution kinetics of silica. [ABSTRACT FROM AUTHOR]

Sm0.2Ce0.8O1.9‐ 30% Na2CO3 (Sm doped ceria (SDC)‐30N) nano‐composite electrolytes were densified in a single step via cold sintering process (CSP). At 200°C and 450 MPa of uniaxial pressure, samples up to 97% of their theoretical density could be obtained. The effect of processing parameters, such as temperature, uniaxial pressure, processing duration, and moisture content, on the densification of the nano‐composite electrolytes was investigated. The thermal, microstructural, and electrical properties of nano‐composites were investigated by differential scanning calorimetry, X‐ray diffractometer, scanning electron microscope, and EIS analysis. SDC crystallite sizes were found to be around 25 nm, barely coarsened after CSP by which the true nano nature of the nano‐composite could be preserved. Because, by conventional processing high density values could not be attained and high processing temperatures in excess of 600°C had to be used, promoting particle coarsening. The highest total electrical conductivity was found to be 2.2 × 10−2 S cm−1 at 600°C, with an activation energy of 0.83 eV for SDC‐30N nano‐composites. The present investigation revealed that the implementation of cold sintering technique resulted in significant enhancements in the densification of nano‐composite electrolytes, thereby rendering them suitable for efficient utilization in SOFC applications, as compared to the conventional production methods. [ABSTRACT FROM AUTHOR]

Boron neutron capture therapy (BNCT) is one of the most promising treatments among neutron capture therapies due to its long‐term clinical application and unequivocally obtained success during clinical trials. Boron drug and neutron play an equivalent crucial role in BNCT. Nevertheless, current clinically used l‐boronophenylalanine (BPA) and sodium borocaptate (BSH) suffer from large uptake dose and low blood to tumor selectivity, and that initiated overwhelm screening of next generation of BNCT agents. Various boron agents, such as small molecules and macro/nano‐vehicles, have been explored with better success. In this featured article, different types of agents are rationally analyzed and compared, and the feasible targets are shared to present a perspective view for the future of BNCT in cancer treatment. This review aims at summarizing the current knowledge of a variety of boron compounds, reported recently, for the application of BCNT. [ABSTRACT FROM AUTHOR]

The Pliensbachian–Toarcian transition was characterised by a drastic turnover from a cool climate to a period of rapid global warming. While the warming associated with the Early Toarcian Oceanic Anoxic Event is rather well-studied, the cause, intensity and extent of the preceding cooling in the late Pliensbachian are still discussed. Occurrences of glendonite play an important role in this debate, since glendonite is a pseudomorph after the cryophilic carbonate mineral ikaite. This study describes the first glendonite-bearing carbonate concretions from South Germany (Buttenheim clay pit, northern Franconian Alb), which represent the southernmost glendonite occurrence in the late Pliensbachian documented so far. Based on petrographical and sedimentological investigations as well as stable isotope analyses it is concluded that a low temperature was the main factor for ikaite formation in the studied section, suggesting that the late Pliensbachian cooling had a more far-reaching impact on the temperature of the European epicontinental sea than previously assumed. To explain the low temperatures required for ikaite precipitation, a model for the sea-ice driven formation of cold bottom-water masses on the continental shelf is proposed. The occurrence of several layers containing reworked hiatus concretions in the studied outcrop is interpreted as the result of recurrent sea-level falls caused by multiple glacial pulses characterising the overall cool climate in the late Pliensbachian. [ABSTRACT FROM AUTHOR]

Recent research has demonstrated that the CuFeTe2 compound has interesting physical properties. However, less research effort has been afforded to the study of the stable non-stoichiometric Cu1.1Fe1.2Te2 structure and electronic properties. In this paper, we report the synthesis and electronic properties of the non-stoichiometric (Cu, Fe) co-doped CuFeTe2 (Cu1.1Fe1.2Te2) with a stable single phase. The temperature-dependent resistance and magnetic susceptibility measurements showed an obvious phase transition from a semiconductor to metal when the temperature reached 360 K, revealing a spin-density-wave (SDW)-like state existing in the as-grown Cu1.1Fe1.2Te2, which has a higher SDW transition temperature than that of CuFeTe2. Interestingly, a spectral weight evolution of the angle-resolved photoemission spectroscopy in the study of the electronic structure of Cu1.1Fe1.2Te2 is observed at the same temperature of 360 K. Our work provides a scheme for exploration of novel physical phenomena related to SDW in two-dimensional materials. [ABSTRACT FROM AUTHOR]

Globally, rejuvenation of soil health is a major concern due to the continuous loss of soil fertility and productivity. Soil degradation decreases crop yields and threatens global food security. Improper use of chemical fertilizers coupled with intensive cultivation further reduces both soil health and crop yields. Plants require several nutrients in varying ratios that are essential for the plant to complete a healthy growth and development cycle. Soil, water, and air are the sources of these essential macro- and micro-nutrients needed to complete plant vegetative and reproductive cycles. Among the essential macro-nutrients, nitrogen (N) plays a significant in non-legume species and without sufficient plant access to N lower yields result. While silicon (Si) is the 2nd most abundant element in the Earth's crust and is the backbone of soil silicate minerals, it is an essential micro-nutrient for some plants. Silicon is just beginning to be recognized as an important micronutrient to some plant species and, while it is quite abundant, Si is often not readily available for plant uptake. The manufacturing cost of synthetic silica-based fertilizers is high, while absorption of silica is quite slow in soil for many plants. Rhizosphere biological weathering processes includes microbial solubilization processes that increase the dissolution of minerals and increases Si availability for plant uptake. Therefore, an important strategy to improve plant silicon uptake could be field application of Si-solubilizing bacteria. In this review, we evaluate the role of Si in seed germination, growth, and morphological development and crop yield under various biotic and abiotic stresses, different pools and fluxes of silicon (Si) in soil, and the bacterial genera of the silicon solubilizing microorganisms. We also elaborate on the detailed mechanisms of Si-solubilizing/mobilizing bacteria involved in silicate dissolution and uptake by a plant in soil. Last, we discuss the potential of silicon and silicon solubilizing/mobilizing to achieve environmentally friendly and sustainable crop production. [ABSTRACT FROM AUTHOR]

The exceptional optoelectronic properties of metal halide perovskites (MHPs) are presumed to arise, at least in part, from the peculiar interplay between the inorganic metal-halide sublattice and the atomic or molecular cations enclosed in the cage voids. The latter can exhibit a roto-translative dynamics, which is shown here to be at the origin of the structural behavior of MHPs as a function of temperature, pressure and composition. The application of high hydrostatic pressure allows for unraveling the nature of the interaction between both sublattices, characterized by the simultaneous action of hydrogen bonding and steric hindrance. In particular, we find that under the conditions of unleashed cation dynamics, the key factor that determines the structural stability of MHPs is the repulsive steric interaction rather than hydrogen bonding. Taking as example the results from pressure and temperature-dependent photoluminescence and Raman experiments on MAPbBr 3 but also considering the pertinent MHP literature, we provide a general picture about the relationship between the crystal structure and the presence or absence of cationic dynamic disorder. The reason for the structural sequences observed in MHPs with increasing temperature, pressure, A-site cation size or decreasing halide ionic radius is found principally in the strengthening of the dynamic steric interaction with the increase of the dynamic disorder. In this way, we have deepened our fundamental understanding of MHPs; knowledge that could be coined to improve performance in future optoelectronic devices based on this promising class of semiconductors. [ABSTRACT FROM AUTHOR]

The synthesis of monoclinic (γ) tungsten oxide (WO3) nanorods via facile Microwave-assisted hydrothermal route is reported in the present work. The structural characterization of the as-synthesized material by using X-ray diffraction and Fourier-transform infrared spectroscopy confirms the formation of crystalline WO3 phase. The morphology and microstructural study along with elemental composition of the material as obtained by scanning electron microscopy and transmission electron microscopy, respectively, reveals the generation of one-dimensional WO3 nanorods. The nanorods show substantial absorbance in the ultraviolet (UV) region with the bandgap and refractive index of 2.7 eV and 2.48, respectively. Here, the low value of bandgap without adding any catalyst or co-catalyst is attributed to the microwave treatment. The electrochemical properties of WO3 are studied using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The nanorods show high current density at different potentials and diffusion-controlled behavior as exhibited by Warburg impedance. The anodic as well as cathodic peak current values are seen to be increased after the deposition of the thin film of FTO substrate indicating the better diffusion of ions in the electrolyte. The capacitive and diffusive contribution of the thin film is investigated at various scan rates using Dunn's model which shows that the diffusive contribution of the thin film is 120 times more than the capacitive contribution confirming the diffusive behavior of the thin film. The exchange current density of the deposited film is calculated which is found to have higher value than that of bare FTO. I–V characteristics of WO3 are compared with that of bare FTO which reveals the smaller resistance offered by WO3 film. The equivalent circuit as obtained from Nyquist plot is used to estimate the resistance of electrolyte, film and charge transfer resistance along with the double-layer capacitance and Warburg impedance. Further, bode plot is analyzed to study the phase shift and thus the diffusive behavior of the material. [ABSTRACT FROM AUTHOR]

The structural role of an oxide as a former and modifier can have significant effects on the chemical durability and mechanical properties of the glass. Some oxides with high‐field strength cations, for example, MgO and ZrO2, are often labeled as a third group—intermediate, due to their either undetermined or dual structural roles dependent on the glass compositions. Based on our recent modification of the Makishima–Mackenzie (MM) model using the rigid‐unit Packing Fraction (RUPF), we analyzed a series of novel zirconia‐containing bioactive glasses. The RUPF‐based MM‐model provides better prediction of the elastic moduli of these new glasses in comparison to experimental measurements. At the same time, the structural role of zirconia can be determined by comparison with calculations by assuming various structural roles and those from experiments. We reveal that ZrO2 acts as the network former in phosphosilicate glasses, which leading to significant increase in packing fraction and consequent increase in Young's modulus. The recent experimental and atomistic simulation results support the glass former role of zirconia in silicate glasses. This method is general and applicable to other oxides in glasses. [ABSTRACT FROM AUTHOR]

The structure of liquid lithium pyroborate, Li4B2O5 (J = Li/B = 2), has been measured over a wide temperature range by high‐energy X‐ray diffraction, and compared to that of its glass and borate liquids of other compositions. The results indicate a gradual increase in tetrahedral boron fraction from 3(1)% to 6(1)% during cooling from T = 1271(15) to 721(8) K, consistent with the larger N4 = 10(1)% found for the glass, and literature 11B nuclear magnetic resonance measurements. van't Hoff analysis based on a simple boron isomerization reaction BØ3O2– ⇌ BØO22– yields ΔH = 13(1) kJ mol–1 and ΔS = 40(1) J mol–1 K–1 for the boron coordination change from 4 to 3, which are, respectively, smaller and larger than found for singly charged isomers for J ≤ 1. With these, we extend our model for N4(J, T), nonbridging oxygen fraction fnbr(J, T), configurational heat capacity CPconf(J,T)$C_{\rm{P}}^{{\rm{conf}}}(J,T)$, and entropy Sconf(J, T) contributions up to J = 3. A maximum is revealed in CPconf(J,T=Tg)$C_{\rm{P}}^{{\rm{conf}}}(J,T = {T_{\rm{g}}})$ at J = 1, and shown semi‐quantitatively to lead to a corresponding maximum in fragility contribution, akin to that observed in the total fragilities by temperature‐modulated differential scanning calorimetry. Lithium is bound to 4.6(2) oxygen in the pyroborate liquid, with 2.7(1) bonds centered around 1.946(8) Å and 1.9(1) around 2.42(1) Å. In the glass, nLiO = 5.4(4), the increase being due to an increase in the number of short Li–O bonds. [ABSTRACT FROM AUTHOR]

A series of white light-emitting Ca6-xNa2Y2(SiO4)6Cl2:Gd3+ chlorapatite compounds were synthesized by liquid solid solution-based hydrothermal method. The structural, electronic and optical properties of synthesized chlorapatite were studied in detail. The X-ray diffraction (XRD) analysis confirms the formation of monoclinic structure with space group P21/c. Fourier transform infrared spectroscopy shows different modes of SiO4 tetrahedron, with no impurity peaks due to (OH) and (CO2) group. Theoretical calculations were done by B3LYP hybrid GGA approximation using density functional theory. The computational band gap value of 3.8 eV was calculated using 3 × 3 × 3 Monkhorst mesh, which satisfies the experimental value of 4.3 eV calculated by diffuse transmittance spectroscopy. The band gap value calculated by molecular orbital theory was found to be 4.01 eV, which satisfied the above results. Mulliken population analysis shows that Y bonds are more covalent in nature as compared to Ca and Na bonds. The photoluminescence emission peaks obtained at 468 nm, 482 nm, 492 nm, 549 nm and 661 nm are perceived due to 6G7/2 – 6DJ, 6G7/2 – 6IJ and 6PJ – 8S7/2 transitions in white region under 220 nm UV excitation. [ABSTRACT FROM AUTHOR]

Methylammonium (MA) lead trihalide perovskites, CH3NH3PbX3 (X = I, Br, Cl), have emerged as a new class of light-absorbing materials for photovoltaic applications, reaching efficiencies of 23% when implemented in solar cell heterojunctions. In particular, MAPbBr3 is a promising member with a large bandgap that gives rise to a high open circuit voltage. Here we present a structural study from neutron diffraction (ND) data of an undeuterated MAPbBr3 specimen, carried out to follow its crystallographic behaviour in the 2–298 K temperature range. Besides the known crystallographic phases, i.e. the high-temperature Pm 3 ¯ m cubic structure, the intermediate I4/mcm tetragonal symmetry and the low-temperature Pnma orthorhombic phase, we additionally identified, from a detailed sequential ND analysis, a novel intermediate phase within the 148.5–154.0 K temperature range as an orthorhombic Imma structure, early associated with a coexistence of phases. Moreover, our ND data allowed us to unveil the configuration of the organic MA units and their complete localization within the mentioned temperature range, thus improving the crystallographic description of this compound. The evolution with temperature of the H-bonds between the organic molecule and the inorganic cage is also followed. A deep knowledge of the crystal structure and, in particular, the MA conformation inside the perovskite cage seems essential to establish structure–property correlations that may drive further improvements. [ABSTRACT FROM AUTHOR]

A class of radial, polynomial cutoff functions f c n (r) for short-ranged pair potentials or related expressions is proposed. Their derivatives up to order n and n + 1 vanish at the outer cutoff r c and an inner radius r i , respectively. Moreover, f c n (r ≤ r i ) = 1 and f c n (r ≥ r c ) = 0. It is shown that the used order n can qualitatively affect results: stress and bulk moduli of ideal crystals are unavoidably discontinuous with density for n = 0 and n = 1, respectively. Systematic errors on energies and computing times decrease by 20–50% for Lennard-Jones with n = 2 or n = 3 compared to standard cutting procedures. Another cutoff function turns out beneficial to compute Coulomb interactions using the Wolf summation, which is shown to not properly converge when local charge neutrality is obeyed only in a stochastic sense. However, for all investigated homogeneous systems with thermal noise (ionic crystals and liquids), the modified Wolf summation, despite being infinitely differentiable at r c , converges similarly quickly as the original summation. Finally, it is discussed how to reduce the computational burden of numerically exact Monte Carlo simulations using the Wolf summation even when it does not properly converge. [ABSTRACT FROM AUTHOR]

Concrete structures in extremely cryogenic environments may be subject to dynamic loadings as a result of occasional accidents or terrorist attacks during the service life. Considering the cryogenic temperature effect and strain rate effect of each phase for concrete, a meso-scale numerical model of the concrete subjected to cryogenic temperature and dynamic loadings was presented in this study, which serves as a preliminary foundation for calculating and evaluating the performances of concrete structures at cryogenic temperature. Taking concrete cube as an example, the dynamic compressive behavior and strain rate effect of concrete specimens at cryogenic temperature from 20 °C to –160 °C were modelled and investigated. The numerical results indicate that the failure appearances and compressive strength are highly related to the cryogenic temperature and dynamic loadings. The compressive strength at cryogenic temperature is greater than that at ambient temperature, and the sensitivity of dynamic compressive strength to strain rate is enhanced at cryogenic temperature. Moreover, the absorbed energy and dynamic elastic modulus tend to increase with the decrease of temperature and increase of strain rate. According to the numerical results, an empirical formula on dynamic increase factor of compressive strength at cryogenic temperatures (CDIF T) was established. [ABSTRACT FROM AUTHOR]

The computational discovery and design of zeolites is a crucial part of the chemical industry. Finding highly accurate while computational feasible protocol for identification of hypothetical siliceous frameworks that could be targeted experimentally is a great challenge. To tackle this challenge, we trained neural network potentials (NNP) with the SchNet architecture on a structurally diverse database of density functional theory (DFT) data. This database was iteratively extended by active learning to cover not only low-energy equilibrium configurations but also high-energy transition states. We demonstrate that the resulting reactive NNPs retain DFT accuracy for thermodynamic stabilities, vibrational properties, as well as reactive and non-reactive phase transformations. As a showcase, we screened an existing zeolite database and revealed >20k additional hypothetical frameworks in the thermodynamically accessible range of zeolite synthesis. Hence, our NNPs are expected to be essential for future high-throughput studies on the structure and reactivity of siliceous zeolites. [ABSTRACT FROM AUTHOR]

The Landé or g-factors of charge carriers are decisive for the spin-dependent phenomena in solids and provide also information about the underlying electronic band structure. We present a comprehensive set of experimental data for values and anisotropies of the electron and hole Landé factors in hybrid organic-inorganic (MAPbI3, MAPb(Br0.5Cl0.5)3, MAPb(Br0.05Cl0.95)3, FAPbBr3, FA0.9Cs0.1PbI2.8Br0.2, MA=methylammonium and FA=formamidinium) and all-inorganic (CsPbBr3) lead halide perovskites, determined by pump-probe Kerr rotation and spin-flip Raman scattering in magnetic fields up to 10 T at cryogenic temperatures. Further, we use first-principles density functional theory (DFT) calculations in combination with tight-binding and k ⋅ p approaches to calculate microscopically the Landé factors. The results demonstrate their universal dependence on the band gap energy across the different perovskite material classes, which can be summarized in a universal semi-phenomenological expression, in good agreement with experiment. The Landé factors govern all the spin-related basic phenomena and are the key parameters which guide spintronics applications. Here, Kirstein et al. demonstrate a universal dependence of the Landé factors on the bandgap energy of several perovskite materials. [ABSTRACT FROM AUTHOR]

The current study diligently analyzes the physical characteristics of halide perovskites AGeF3 (A = K, Rb) under hydrostatic pressure using density functional theory. The goal of this research is to reduce the electronic band gap of AGeF3 (A = K, Rb) under pressure in order to improve the optical characteristics and assess the compounds' suitability for optoelectronic applications. The structural parameters exhibit a high degree of precision, which correlates well with previously published work. In addition, the bond length and lattice parameters decrease significantly leading to a stronger interaction between atoms. The bonding between K(Rb)–F and Ge–F reveal ionic and covalent nature, respectively, and the bonds become stronger under pressure. The application of hydrostatic pressure demonstrates remarkable changes in the optical absorption and conductivity. The band gap becomes lower with the increment of pressure, resulting in better conductivity. The optical functions also predict that the studied materials might be used in a variety of optoelectronic devices operating in the visible and ultraviolet spectrum. Interestingly, the compounds become more suitable to be used in optoelectronic applications under pressure. Moreover, the external pressure has profound dominance on the mechanical behavior of the titled perovskites, which make them more ductile and anisotropic. [ABSTRACT FROM AUTHOR]

The previously unattained fabrication of single phase Ln2ZrO5 (Ln = Sm, Eu, Gd, and Tb) compounds via relatively low sintering temperature (1400°C) is achieved in this study using a coprecipitation method. The crystal structures have been investigated by neutron, synchrotron X‐ray powder diffraction, and electron diffraction techniques. While the general long‐range structure may be well described by the defect‐fluorite type structure with Fm3¯$\bar{3}$m symmetry, electron diffraction has highlighted a complex underlying modulated structure that varies between each compound. These compounds have been tested for ion‐irradiation response using in situ 1 MeV krypton ions and transmission electron microscopy characterization. None of the compounds undergo a crystalline to amorphous transition, even holding at 50 K. Both the underlying fluorite and modulated superstructures are little affected by the irradiation. However, some atomic rearrangements are observed in the postirradiated electron diffraction patterns for the Sm2ZrO5 specimen. [ABSTRACT FROM AUTHOR]

The use of Al for replacing high-cost alloying metals, like Ag, Bi, and Cu, as the second major element in Sn-based alloys, arises as a promising alternative for the development of low-cost Pb-free solder alloys. To date, however, the interfacial characteristics of Sn–Al solder joints in electronic substrates remain barely explored. Thus, the present study focuses on an understanding of the mechanisms affecting the heat transfer efficiency between a Sn–Al eutectic alloy and two types of substrates, establishing correlations with the microstructure evolution. Results of solidification experiments coupled with mathematical modeling demonstrate an interfacial thermal conductance between the Ni substrate and the Sn-0.5mass%Al alloy higher than that observed for the Sn–Al/Cu couple. Furthermore, Al-rich intermetallics are shown to occur at the interfacial reaction layers for both tested conditions. While dendritic and dendritic/cellular morphologies predominate in the solidification of the Sn–Al eutectic alloy in a Cu substrate, the better heat extraction through the Ni substrate induces the growth of refined high-cooling rate cells. Then, growth laws relating the length scale of the Sn-matrix, represented by cellular or primary dendritic spacings, to solidification thermal parameters such as cooling rate and growth rate are proposed. [ABSTRACT FROM AUTHOR]

Environmental barrier coatings (EBCs) will be needed to protect SiC‐based ceramic matrix composite components for the next generation of high‐efficiency industrial gas turbines (IGTs). The IGT application will require ≥25 kh lifetimes, and little data are available on EBC failure mechanisms, particularly at ≥1300°C. Initial 1‐h furnace cycle testing at 1350°C in 90 vol% H2O/10 vol% air was conducted ≥1000 cycles on thermally sprayed ytterbium disilicate (YbDS) coatings with and without an Si bond coating. By ≥1000 h, both EBCs formed thick, highly cracked, and fully crystalline cristobalite scales. Comparison of thermally grown oxide (TGO) microstructure and kinetics to isothermal rates of Si and SiC steam oxidation indicated a departure from slow‐growing parabolic growth to more rapid rates of silica formation. Possible mechanisms and implications for this acceleration are discussed. [ABSTRACT FROM AUTHOR]

We report a molecular modeling paradigm to describe silica polymerization reactions in aqueous solutions at conditions that are representative of realistic experimental processes like biosilicification or porous silica synthesis – i.e. at close to ambient temperatures and over a wide range of pH. The key point is to describe the Si-O-Si chemical bond formation and breakage processes through a continuous potential with a balance between attractive and repulsive interactions between suitably placed virtual sites and sticky particles. The simplicity of the model, its applicability in standard parallelized molecular dynamics codes, and its compatibility with the widely used MARTINI coarse-grained force-field allows for the study of systems containing millions of atoms over microsecond time scales. The model is calibrated to match experimental results for the temporal evolution of silica polymerization in aqueous solution close to the isoelectric point, and can describe silica polymerization and self-assembly processes during encapsulation of a surfactant micelle. [ABSTRACT FROM AUTHOR]

Objectives: A mechanical metamaterial is introduced herein by drawing inspiration from an Aztec geometric pattern. This metamaterial deformation mechanism for Poisson's ratio and Young's modulus is based on non-rotating rhombi with rotating triangles, while the shear modulus analysis herein is based on rotating rhombi with non-rotating triangles, hence 'partially rotating rigid units'. Methods: The coefficient of thermal expansion was obtained by equating the potential energy expressions from the simple harmonic motion and from the principle of energy equipartition, while the effective-moduli were acquired by equating the strain energy from rotational stiffness with that from the strain energy of deformation based on an assumed homogenized continuum. Due to the zero and extreme Poisson's ratio based on infinitesimal deformation, the finite approach was employed. Results: Results indicate that the proposed metamaterial exhibits anisotropic negative thermal expansion with sign-switching Poisson's ratio when applied stress along one axis is reversed. The Poisson's ratio for loading in another axis is undefined under tension but can be programmed to exhibit either sign when compressed. The Young's and shear moduli are directly governed by the rotational stiffness and strongly influenced by the extent of rotation, followed by the aspect ratio of the rotating units. Conclusion: Due to its uniqueness, the currently considered mechanical metamaterial can be used under specific requirements which are difficult to be attained by other materials with negative properties. [ABSTRACT FROM AUTHOR]

Al-Ni alloys (for Ni < 45 at.%) show a unique property in that, over at least part of the accessible undercooling range, the recalescence velocity measured in electromagnetically levitated samples is observed to decrease as the undercooling increases. This result has been subject to careful validation, including microgravity experiments utilising the TEMPUS levitation facility on-board the International Space Station (ISS). In these experiments, anomalous growth is observed to coincide with a recalescence morphology comprising multiple circular growth fronts [Herlach et al. Phys. Rev. Mat. 3, 073,402 (2019)], termed “scales”. In this paper we present an analysis of high speed video data from the ISS experiments in which we show that such scale-like growth is consistent with a recalescence front that is initially confined to a thin layer on the surface of the sample. This then nucleates a slower, radial inward growth, which is consistent with microstructures observed in Al-Ni droplets. We show that such surface recalescence would be favoured for samples which were surface enriched in Ni, wherein the recalescence velocity (at fixed nucleation temperature) increases rapidly with Ni-concentration. Moreover, it is shown that the anomalous velocity behaviour can be matched in all compositions studied if the surface enhancement in Ni is a linear function of the nucleation temperature with a gradient of 0.03 at.% K−1. Analysis of historical results from the literature indicates that such surface Ni-enhancement may have been present, but overlooked, in other experiments on Al-rich Al-Ni droplets. [ABSTRACT FROM AUTHOR]