In situ Formation of Platinum-Carbon Catalysts in Propane Dehydrogenation

The catalytic production of propylene via propane dehydrogenation (PDH) is a key reaction in the chemical industry. By combining operando transmission electron microscopy with density functional theory analysis, we show that the intercalation and ordering of carbon on Pt interstitials to form Pt-C solid solutions is relevant for increasing propylene production. More specifically, we found that at the point of enhanced propylene formation, the structure of platinum nanoparticles is transformed into a transient caesium chloride-type Pt-C polymorph. At more elevated temperatures, the zincblende and rock salt polymorphs seemingly coexist. When propylene production was highest, multiple crystal structures consisting of Pt and carbon were occasionally found to coexist in one individual nanoparticle, distorting the Pt lattice. Catalyst coking was detected at all stages of the reaction, but did initially not affect all particles. These findings could lead to the development of novel synthesis strategies towards tailoring highly efficient PDH catalysts.

Interfacial Engineering for Oriented Crystal Growth toward Dendrite-Free Zn Anode for Aqueous Zinc Metal Battery

Zn deposition with a surface-preferred (002) crystal plane has attracted extensive attention due to its inhibited dendrite growth and side reactions. However, the nucleation and growth of the Zn(002) crystal plane are closely related to the interfacial properties. Herein, oriented growth of Zn(002) crystal plane is realized on Ag-modified surface that is directly visualized by in situ atomic force microscopy. A solid solution HCP-Zn (~1.10 at. % solubility of Ag, 30 °C) is formed on the Ag coated Zn foil (Zn@Ag) and possesses the same crystal structure as Zn to reduce its nucleation barrier caused by their lattice mismatch. It merits oriented Zn deposition and corrosion-resistant surface, and presents long cycling stability in symmetric cells and full cells coupled with V2O5 cathode. This work provides insights into interfacial regulation of Zn anodes for high-performance aqueous zinc metal batteries.

Effects of Ni Content and Heat Treatment on the Properties, Microstructures, and Precipitates of Cu-0.2 wt% Be-x wt% Ni Alloys

Cu-Be alloys exhibit excellent comprehensive performance in electrics, thermotics, and mechanics, and hence, they attract much attention. Among them, low-Be copper alloys are more environmentally friendly and promising. This study explores the effects of different Ni contents and heat treatment parameters on the properties, microstructures, and precipitates of Cu-0.2 wt% Be-x wt% Ni (0 < x < 2.0) alloys. The experimental results demonstrate that the fast cooling rate of cast alloys during solidification contributes to retention of the solute atoms in the copper matrix, which is beneficial for subsequent solid solution treatment. Furthermore, solid solution treatment slightly reduces the electrical conductivities, microhardness values, and compressive yield strengths of Cu-0.2 wt% Be-1.0/1.6 wt% Ni alloys. The optimal solution temperature and time are about 925 ℃ and 60 min, respectively. Aging treatment significantly increases the electrical conductivities, microhardness values, and compressive yield strengths of Cu-0.2 wt% Be-1.0/1.6 wt% Ni alloys. The best aging temperature is around 450 ℃. However, the properties of Cu-0.2 wt%Be-0.4 wt%Ni alloys remain unaffected by solution and aging treatments. Around x = 1.0, Cu-0.2 wt% Be-x wt% Ni alloys possess the best comprehensive properties, which are about 72%IACS of electrical conductivity, 241 HV of microhardness, and 281MPa of compressive yield strength, respectively. TEM and EDS analyses reveal that the precipitate evolution of Cu-0.2 wt% Be-1.0 wt% Ni alloys with aging time is GP zones → γ″ → γ'. Notably, a distinct double-peak age strengthening phenomenon emerges with Cu-0.2 wt% Be-1.0/1.6 wt% Ni alloys. The precipitation of plenty of GP zones at the early stage of aging should account for the first strengthening peak, and the strengthening mechanism transformation of the γ″ or γ' phase from shear to Orowan should induce the second strengthening peak. This work may help to design new low-Be copper alloys and their preparation processes.

Gap-Free Tuning of Second and Third Harmonic Generation in Mechanochemically Synthesized Nanocrystalline LiNb1-xTaxO3 (0 ≤ x ≤ 1) Studied with Nonlinear Diffuse Femtosecond-Pulse Reflectometry

The tuning of second (SHG) and third (THG) harmonic emission is studied in the model system LiNb 1-xTa xO 3 (0≤x≤1, LNT) between the established edge compositions lithium niobate (LiNbO 3, x=0, LN) and lithium tantalate (LiTaO 3, x=1, LT). Thus, the existence of optical nonlinearities of the second and third order is demonstrated in the ferroelectric solid solution system, and the question about the suitability of LNT in the field of nonlinear and quantum optics, in particular as a promising nonlinear optical material for frequency conversion with tunable composition, is addressed. For this purpose, harmonic generation is studied in nanosized crystallites of mechanochemically synthesized LNT using nonlinear diffuse reflectometry with wavelength-tunable fundamental femtosecond laser pulses from 1200 nm to 2000 nm. As a result, a gap-free harmonic emission is validated that accords with the theoretically expected energy relations, dependencies on intensity and wavelength, as well as spectral bandwidths for harmonic generation. The SHG/THG harmonic ratio ≫1 is characteristic of the ferroelectric bulk nature of the LNT nanocrystallites. We can conclude that LNT is particularly attractive for applications in nonlinear optics that benefit from the possibility of the composition-dependent control of mechanical, electrical, and/or optical properties.

Fabrication of (Ge0.42Sn0.58)S Thin Films via Co-Evaporation and Their Solar Cell Applications

In this study, as a novel approach to thin-film solar cells based on tin sulfide, an environmentally friendly material, we attempted to fabricate (Ge, Sn)S thin films for application in multi-junction solar cells. A (Ge0.42 Sn0.58)S thin film was prepared via co-evaporation. The (Ge0.42 Sn0.58)S thin film formed a (Ge, Sn)S solid solution, as confirmed by X-ray diffraction (XRD) and Raman spectroscopy analyses. The open circuit voltage (Voc), short circuit current density (Jsc), fill factor (FF), and power conversion efficiency (PCE) of (Ge0.42 Sn0.58)S thin-film solar cells were 0.29 V, 6.92 mA/cm2, 0.34, and 0.67%, respectively; moreover, the device showed a band gap of 1.42-1.52 eV. We showed that solar cells can be realized even in a composition range with a relatively higher Ge concentration than the (Ge, Sn)S solar cells reported to date. This result enhances the feasibility of multi-junction SnS-system thin-film solar cells.

Photo-Activated Growth and Metastable Phase Transition in Metallic Solid Solutions

Laser processing in metals is versatile yet limited by its reliance on phase transformation through heating rather than electronic excitation due to their low absorptivity, attributing from highly ordered structures. Metastable states (i.e., surfaces, glasses, undercooled liquids), however, present a unique platform, both energetically and structurally to enable energy landscape tuning through selective stimuli. Herein, this ansatz is demonstrated by exploiting thin passivating oxides to stabilize an undercooled state, followed by photo-perturbation of the near surface order to induce convective Marangoni flows, edge-coalescence and phase transition into a larger metastable solid bearing asymmetric composition between the near surface and core of the formed structure. The self-terminating nature of the process creates a perfectly contained system which can maintain a high relaxation energy barrier hence deep metastable states for extended periods of time.

Fe-Doped SDC Solid Solution as an Electrolyte for Low-to-Intermediate-Temperature Solid Oxide Fuel Cells

Ceria-based oxides, such as samaria-doped ceria (SDC), are potential electrolytes for low-to-intermediate-temperature solid oxide fuel cells (SOFCs). The sinterability of these materials can be improved by adding iron as the sintering aid. This work reveals that Fe is soluble in SDC, forming an Fe-doped SDC solid solution. It is found that the solubility is affected by the sintering temperature. Fe doping has obvious effects on electrolyte properties, including sintering characteristics, thermal expansion behaviors, and electrical conductivities in both air and hydrogen atmospheres. The conductivity obviously increases while the activation energy decreases by doping Fe. Compared with that of the bare SDC electrolyte, the performance of the single cell with the Fe-doped SDC is enhanced; for example, the peak power density is increased by 52.8% to 0.726 W cm-2 at 600 °C when humidified hydrogen is used as the fuel and ambient air is used as the oxidant. The single cell showed stable operation at 600 °C under a constant current density of 0.3 A cm-2 for 150 h. Therefore, the Fe-doped SDC solid solution shows promise as a potential electrolyte for low-to-intermediate-temperature SOFCs.

Beyond Constant Current: Origin of Pulse-Induced Activation in Phase-Transforming Battery Electrodes

Mechanistic understanding of phase transformation dynamics during battery charging and discharging is crucial toward rationally improving intercalation electrodes. Most studies focus on constant-current conditions. However, in real battery operation, such as in electric vehicles during discharge, the current is rarely constant. In this work we study current pulsing in LiXFePO4 (LFP), a model and technologically important phase-transforming electrode. A current-pulse activation effect has been observed in LFP, which decreases the overpotential by up to ∼70% after a short, high-rate pulse. This effect persists for hours or even days. Using scanning transmission X-ray microscopy and operando X-ray diffraction, we link this long-lived activation effect to a pulse-induced electrode homogenization on both the intra- and interparticle length scales, i.e., within and between particles. Many-particle phase-field simulations explain how such pulse-induced homogeneity contributes to the decreased electrode overpotential. Specifically, we correlate the extent and duration of this activation to lithium surface diffusivity and the magnitude of the current pulse. This work directly links the transient electrode-level electrochemistry to the underlying phase transformation and explains the critical effect of current pulses on phase separation, with significant implication on both battery round-trip efficiency and cycle life. More broadly, the mechanisms revealed here likely extend to other phase-separating electrodes, such as graphite.

Mechanical Alloying as a Way to Produce Metastable Single-Phase High-Entropy Alloys beyond the Stability Criteria

Various stability criteria developed for high-entropy alloys are applied to compositions produced by mechanical alloying. While they agree with the annealed samples, these criteria fail to describe the as-milled metastable systems, highlighting the ability of mechanical alloying to overcome the limitations imposed by these criteria. The criteria are based on atomic size (Ω ≥ 1.1 and δr ≤ 6.6%) and/or electronegativity misfit, as well as on mixing enthalpy (Λ>0.95 J mol-1K-1 and -5 kJ mol-1<∆Hmix<0), or purely thermodynamic (ϕYe>20; ϕKing>1; Teff<500 K). These criteria are applied to several compositions found in the literature and to two metastable fcc solid solutions produced by mechanical alloying with compositions Al0.75CoXFeNi with X = Cr and Mn. Single-phase microstructures are stable up to above 600 K, leading to more stable multiphase systems after annealing above this temperature. Mössbauer spectrometry shows that, whereas the alloy with Cr is paramagnetic in the as-milled and annealed state, the alloy with Mn changes from paramagnetic to ferromagnetic behavior (Curie temperature ~700 K) after annealing. Thermomagnetic experiments on annealed samples show for both compositions some hysteretic events at high temperatures (850 to 1000 K), probably ascribed to reversible ordering phenomena.

Enhancing the Resistive Memory Window through Band Gap Tuning in Solid Solution (Cr1-xVx)2O3

Memories based on the insulator-to-metal transition in correlated insulators are promising to overcome the limitations of alternative nonvolatile memory technologies. However, associated performances have been demonstrated so far only on narrow-gap compounds, such as (V0.95Cr0.05)2O3, exhibiting a tight memory window. In the present study, V-substituted Cr2O3 compounds (Cr1-xVx)2O3 have been synthesized and widely investigated in thin films, single crystals, and polycrystalline powders, for the whole range of chemical composition (0 < x < 1). Physicochemical, structural, and optical properties of the annealed magnetron-sputtered thin films are in very good agreement with those of polycrystalline powders. Indeed, all compounds exhibit the same crystalline structure with a cell parameter evolution consistent with a solid solution over the whole range of x values, as demonstrated by X-ray diffraction and Raman scattering. Moreover, the optical band gap of V-substituted Cr2O3 compounds decreases from 3 eV for Cr2O3 to 0 eV for V2O3. In the same way, resistivity is decreased by almost 5 orders of magnitude as the V content x is varying from 0 to 1, similarly in thin films and single crystals. Finally, a reversible resistive switching has been observed for thin films of three selected V contents (x = 0.30, 0.70, and 0.95). Resistive switching performed on MIM devices based on a 50 nm thick (Cr0.30V0.70)2O3 thin film shows a high endurance of 1000 resistive switching cycles and a memory window ROFF/RON higher by 3 orders of magnitude, as compared to (Cr0.05V0.95)2O3. This comprehensive study demonstrates that a large range of memory windows can be reached by tuning the band gap while varying the V content in the (Cr1-xVx)2O3 solid solution. It thus confirms the potential of correlated insulators for memory applications.

The Addition of Co into CuO-ZnO Oxides Triggers High Antibacterial Activity and Low Cytotoxicity

In the present work, a simple two-step method is proposed for mixed oxide synthesis aimed at the achievement of antibacterial nanomaterials. In particular, Cu, Zn and Co have been selected to achieve single-, double- and triple-cation oxides. The synthesized samples are characterized by XRD, IR, SEM and EDX, indicating the formation of either crystalline or amorphous hydrocarbonate precursors. The oxides present one or two crystalline phases, depending on their composition; the triple-cation oxides form a solid solution of tenorite. Also, the morphology of the samples varies with the composition, yielding nanoparticles, filaments and hydrangea-like microaggregates. The antibacterial assays are conducted against E. coli and indicate an enhanced efficacy, especially displayed by the oxide containing 3% Co and 9% Zn incorporated into the CuO lattice. The oxides with the highest antibacterial properties are tested for their cytotoxicity, indicating a low toxicity impact, in line with literature data.

Mevacor/Poly(vinyl acetate/2-hydroxyethyl methacrylate) as Solid Solution: Preparation, Solubility Enhancement and Drug Delivery

Mevacor/Poly(vinyl acetate-co-2-hydroxyethyl methacrylate) drug carrier systems (MVR/VAC-HEMA) containing different Mevacor (MVR) contents were prepared in one pot by free radical copolymerization of vinyl acetate with 2-hydroxyethyl methacrylate using an LED lamp light in the presence of camphorquinone as a photoinitiator and Mevacor as a drug filler. The prepared material was characterized by FTIR, 1H NMR, DSC, SEM and XRD methods. Different parameters influencing the efficiency in the Mecvacor-water solubility and the drug delivery of this system, such as the swelling capacity of the carrier, the amount of Mevacor loaded and the pH medium have been widely investigated. The results obtained revealed that the Mevacor particles were uniformly dispersed in their molecular state in the copolymer matrix forming a solid solution; the cell toxicity of the virgin poly(vinyl acetate-co-2-hydroxy ethyl methacrylate) (VAC-HEMA) and MVR/VAC-HEMA drug carrier system exhibited no significant effect on their viability when between 0.25 and 2.00 wt% was loaded in these materials; the average swelling capacity of VAC-HEMA material in water was found to be 45.16 wt%, which was practically unaffected by the pH medium and the solubility of MVR deduced from the release process reached more than 22 and 37 times that of the powder dissolved directly in pH 1 and 7 media, respectively. The in vitro MVR release kinetic study revealed that the MVR/VAC-HEMA system containing 0.5 wt% MVR exhibited the best performance in the short gastrointestinal transit (GITT), while that containing 2.0 wt% is for the long transit as they were able to considerably reduce the minimum release of this drug in the stomach (pH1).

Advantages of a Solid Solution over Biphasic Intercalation for Vanadium-Based Polyanion Cathodes in Na-Ion Batteries

The efficient operation of metal-ion batteries in harsh environments, such as at temperatures below -20 °C or at high charge/discharge rates required for EV applications, calls for a careful selection of electrode materials. In this study, we report advantages associated with the solid solution (de)intercalation over the two-phase (de)intercalation pathway and identify the main sources of performance limitations originating from the two mechanisms. To isolate the (de)intercalation pathway as the main variable, we focused on two cathode materials for Na-ion batteries: a recently developed KTiOPO4-type NaVPO4F and a well-studied Na3V2(PO4)2F3. These materials have the same elemental composition, operate within the same potential range, and demonstrate very close ionic diffusivities, yet follow different (de)intercalation routes. To avoid any interpretation uncertainties, we obtained these materials in the form of particles with merely identical morphology and size. A detailed electrochemical study revealed a much lower capacity and energy density retention for phase-transforming Na3V2(PO4)2F3 compared to NaVPO4F, which exhibits a single-phase behavior over a wide range of Na concentrations. The reasons for the inferior rate capability and temperature tolerance for the phase-separating Na3V2(PO4)2F3 material should be affiliated with slow phase boundary propagation. We hope that the comprehensive information on limiting factors provided for both mechanisms is useful for the further optimization of electrode materials toward a new generation of high-power and low-temperature metal-ion batteries.

Influence of Solid Solutions on the Al2024 High-Temperature Deformation Behavior

The mechanical properties of 2024 aluminum alloy were studied after two different tempers. The T351 temper (solution heat treatment, stress relief, and natural aging) leads to high hardness and toughness. A thermal treatment consisting of heat-treating at 280 °C for 48 h and slow cooling in a furnace, named TT temper, was performed to increase the precipitate size and their separation while minimizing the amount of solutes in solid solution, which produced the minimum hardness for an overaged Al2024 alloy and a lower tensile flow stress than for the T351 temper. The flow stress strongly decreases and the elongation to failure strongly increases for both materials above 300 °C. Differences in strain rate at a given stress in the power law regime at all temperatures for both tempers and compared with pure aluminum are attributed to the influence of solutes in solid solutions, affecting both the glide and climb of dislocations. However, the stacking fault energy, SFE, alone does not account for the hot deformation behavior. Thus, it is the synergistic effect of various solutes that affects the entire deformation process, causing a decrease of three or four orders of magnitude in strain rate for a given stress with respect to the pure aluminum matrix values.

Reducibility of Al3+-Modified Co3O4: Influence of Aluminum Distribution

The reduction of Co-based oxides doped with Al3+ ions has been studied using in situ XRD and TPR techniques. Al3+-modified Co3O4 oxides with the Al mole fraction Al/(Co + Al) = 1/6; 1/7.5 were prepared via coprecipitation, with further calcination at 500 and 850 °C. Using XRD and HAADF-STEM combined with EDS element mapping, the Al3+ cations were dissolved in the Co3O4 lattice; however, the cation distribution differed and depended on the calcination temperature. Heating at 500 °C led to the formation of an inhomogeneous (Co,Al)3O4 solid solution; further treatment at 850 °C provoked the partial decomposition of mixed Co-Al oxides and the formation of particles with an Al-depleted interior and Al-enriched surface. It has been shown that the reduction of cobalt oxide by hydrogen occurs via the following transformations: (Co,Al)3O4 → (Co,Al)O → Co. Depending on the Al distribution, the course of reduction changes. In the case of the inhomogeneous (Co,Al)3O4 solid solution, Al stabilizes intermediate Co(II)-Al(III) oxides during reduction. When Al3+ ions are predominantly on the surface of the Co3O4 particles, the intermediate compound consists of Al-depleted and Al-enriched Co(II)-Al(III) oxides, which are reduced independently. Different distributions of elemental Co and Al in mixed oxides simulate different types of the interaction phase in Co3O4/γ-Al2O3-supported catalysts. These changes in the reduction properties can significantly affect the state of an active component of the Co-based catalysts.

Photo- and Thermocatalytic CO2 Methanation: A Comparison of Ni/Al2O3 and Ni-Ce Hydrotalcite-Derived Materials under UV and Visible Light

Catalysts derived from Ni/Al/Mg/Ce hydrotalcite were prepared via a co-precipitation method, varying the Ce/Al atomic ratio. All of the catalytic systems thus prepared were tested for CO2 methanation under dark and photocatalytic conditions (visible and ultraviolet) under continuous flow with the light intensity set to 2.4 W cm-2. The substitution of Al by Ce formed a solid solution, generating oxygen vacancies and Ce3+/Ce4+ ions that helped shift the dissociation of CO2 towards the production of CH4, thus enhancing the activity of methanation, especially at lower temperatures (<523 K) and with visible light at temperatures where other catalysts were inactive. Additionally, for comparison purposes, Ni/Al2O3-based catalysts prepared via wetness impregnation were synthesized with different Ni loadings. Analytical techniques were used for the characterization of the systems. The best results in terms of activity were as follows: Hydrotalcite with Ce promoter > Hydrotalcite without Ce promoter > 25Ni/Al2O3 > 13Ni/Al2O3. Hydrotalcite, with a Ce/Al atomic ratio of 0.22 and a Ni content of 23 wt%, produced 7.74 mmol CH4 min-1·gcat at 473 K under visible light. Moreover, this catalyst exhibited stable photocatalytic activity during a 24 h reaction time with a CO2 conversion rate of 65% and CH4 selectivity of >98% at 523 K. This photocatalytic Sabatier enhancement achieved activity at lower temperatures than those reported in previous publications.

Facile Preparation of SrZr1-xTixO3 and SrTi1-xZrxO3 Fine Particles Assisted by Dehydration of Zr4+ and Ti4+ Gels under Hydrothermal Conditions

In recent decades, perovskite-type compounds (ABB'O3) have been exhaustively studied due to their unique ferroelectric properties. In this work, a systematic study aiming to prepare fine particles in the binary system SrZrO3-SrTiO3 was conducted under hydrothermal conditions in a KOH (5 M) solution at 200 °C for 4 h under a constant stirring speed of 130 rpm. The precursors employed were SrSO4 powder (<38 μm size) and coprecipitated hydrous gels of Zr(OH)4•9.64 H2O (Zr-gel) and Ti(OH)4•4.5H2O (Ti-gel), which were mixed according to the stoichiometry of the SrZr1-xTixO3 in the compositional range of 0.0 > x > 100.0 mol% Ti4+. The XRD results revealed the formation of two crystalline phases rich in Zr4+, an orthorhombic structured SrZr0.93Ti0.07O3 and a cubic structured SrZr0.75Ti0.25O3 within the compositional range of 0.1-0.5 mol of Ti4+. A cubic perovskite structured solid solution, SrTi1-xZrxO3, was preferentially formed within the compositional range of 0.5 > x > 0.1 mol% Ti4+. The SrZrO3 and SrZr0.93Ti0.07O3-rich phases had particle sizes averaging 3 μm with a cubic morphology. However, a remarkable reduction in the particle size occurred on solid solutions prepared with hydrous Ti-gel over contents of 15 mol% Ti4+ in the reaction media, resulting in the formation of nanosized particle agglomerates with a cuboidal shape self-assembled via a 3D hierarchical architecture, and the sizes of these particles varied in the range between 141.0 and 175.5 nm. The limited coarsening of the particles is discussed based on the Zr-gel and Ti-gel dehydration capability differences that occurred under hydrothermal processing.

Stable and low-threshold photon upconversion in nondegassed water by organic crystals

Photon upconversion (UC) is a technology that converts lower-energy photons (longer wavelength light) into higher-energy photons (shorter wavelength light), the opposite of fluorescence. Thus, UC is expected to open a vast domain of photonic applications that are not otherwise possible. Recently, UC by triplet-triplet annihilation (TTA) between organic molecules has been studied because of its applicability to low-intensity light, although the majority of such studies have focused on liquid samples in the form of organic solvent solutions. To broaden the range of applications, solid-state UC materials have been an active area of research. We recently developed air-stable, high-performance molecular UC crystals that utilize a stable solid-solution phase of bicomponent organic crystals. This article begins with a brief overview of previous challenges in developing and improving solid-state TTA-UC materials. Then, we briefly review and explain the concept as well as advantages of our molecular solid-solution UC crystals. We applied these organic crystals for the first time to a water environment. We observed blue UC emission upon photoexcitation at 542 nm (green-yellow light) and then measured the excitation intensity dependence as well as the temporal stability of the UC emission in air-saturated water. In nondegassed water, these organic crystals were stable, functioned with a low excitation threshold intensity of a few milliwatts per square centimeter, and exhibited high photo-irradiation durability at least over 40 h; indicating that the developed organic crystals are also viable for aqueous conditions. Therefore, the organic crystals presented in this report are expected to extend the domain of UC-based photonic applications in practical water systems including in vivo diagnostic, clinical, and therapeutic applications.

Structure and Phase Composition of WNb Alloy Formed by the Impact of Compression Plasma Flows

The results of a tungsten-niobium alloy synthesis by the impact of pulsed compression plasma flows are presented. Tungsten plates with a 2 μm thin niobium coating were treated with dense compression plasma flows generated by a quasi-stationary plasma accelerator. The plasma flow with an absorbed energy density of 35-70 J/cm² and pulse duration of 100 μs melted the niobium coating and a part of the tungsten substrate, which caused liquid-phase mixing and WNb alloy synthesis. Simulation of the temperature distribution in the top layer of the tungsten after the plasma treatment proved the formation of the melted state. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to determine the structure and phase composition. The thickness of the WNb alloy was 10-20 μm and a W(Nb) bcc solid solution was found.

Copper-doped ZnO-ZrO2 solid solution catalysts for promoting methanol synthesis from CO2 hydrogenation

Copper-doped ZnO-ZrO₂ solid solution catalysts were synthesized via co-precipitation for promoting CH₃OH synthesis via hydrogenation of CO₂. Various testing methods were applied to investigate the effect of various copper contents on the catalysts. The catalytic performance was evaluated by a fixed bed reactor. XRD, HRTEM and Raman spectra collectively indicated that a ZnO-ZrO₂ solid solution catalyst with 3% Cu had a higher Cu dispersion, while the H₂-TPR results confirmed that a catalyst with 3% Cu had more Cu active sites under low temperature H₂ pretreatment. When the copper content increased to 5% and 10%, the catalyst showed a better Cu crystallinity and a worse Cu dispersion, which could have a negative effect. Therefore, the CO₂ conversion and methanol yield with a 3% CuZnO-ZrO₂ catalyst at 5 MPa, 250°C and 12 000 ml/(g h) increased by 8.6% and 7.6%, respectively. Moreover, the CH₃OH selectivity and catalytic stability of the solid solution catalyst were better than those of the traditional CZA catalyst.

Easily Scalable Shell-Structured Copper Catalyst with High Activity and Durability for Carbon Dioxide Hydrogenation

Inducing strong metal-support interaction (SMSI) has been a useful way to control the structure of surface active sites. The SMSI often causes the encapsulation of metal particles with an oxide layer. Herein, an amorphous ceria shell was formed on Cu nanoparticles under a mild gas condition with high activity and durability for surface reaction. Cu-Ce solid solution promoted the transfer of surface oxygen species, which induced the ceria shell formation on Cu nanoparticles. This catalyst was used for CO2 hydrogenation, selectively producing CO with high low-temperature activity and good durability for operation at high temperature. CO2 activation and H2 spillover could occur at low temperatures, enhancing the activity. The shell prevented the sintering, assuring durability. This catalyst was applied to a bench-scale reactor without loss in performance, resulting in high CO productivity in all temperature ranges.

Microstructure and Mechanical Properties of HfC-SiC Ceramics Influenced by WC Addition

The development of HfC-SiC has been challenging due to difficulties in achieving sintering and satisfactory mechanical properties. However, this study aims to overcome these limitations by incorporating WC as an additive. SPS was employed to process HfC-SiC and HfC-SiC doped with 5 vol.% WC. The resulting samples were then evaluated for their oxygen content, relative density, Vickers hardness, bending strength, indentation fracture toughness, and microstructure. The Vickers hardness (20.50 ± 0.20 GPa), flexural strength (600.19 ± 84.00 MPa), and indentation fracture toughness (5.76 ± 0.54 MPa·m^1/2) of HfC-30 vol.% SiC-5 vol.% WC ceramics are higher than HfC-30 vol.% SiC ceramics. Doping 5 vol.% WC in HfC-30 vol.% SiC not only reduces the oxygen content of samples but also produces the (Hf,W)C solid solution and refines the microstructures, which are the main reasons for the higher mechanical properties of HfC-30 vol.% SiC-5 vol.% WC ceramics. In summary, this study successfully addresses the challenges associated with HfC-SiC by incorporating WC as an additive, leading to improved mechanical properties and microstructures.

High-Temperature Behaviour of Zn-Based Galvannealed Coatings on Steel

The potential of using a Zn-based, hot-dip coating to limit steel scale formation was investigated. The phase evolution within a pure Zn and a Zn0.1Al coating on a medium-carbon (0.5 wt.% C, 0.25 wt.% Si) steel sheet during a series of heat treatment steps was investigated. Such Zn-based coatings react with the steel substrate depending on the actual heat treatment condition. A series of expected intermetallic phases was observed via SEM/EDX and XRD techniques, such as ζ, δ and Γ phases along the η(Zn) phase. The η(Zn) phase was transformed to mainly δ and Γ phases during galvannealing (500 °C). The rapid quenching from 850 °C enabled the formation of the supersaturated α-(Fe) solid solution with increased Zn content. A continuous, intact, ~20 µm thick coating was observed after the final step of the heat treatment procedure, while signs of liquid metal embrittlement (LME) were not observed near the coating/steel interface. This will ensure reliable protection against heavy scale formation on heat-treated steel parts.

Facile Tailoring of Surface Terminations of MXenes by Doping Nb Element: Toward Extraordinary Pseudocapacitance Performance

MXenes show promising potential in supercapacitors due to their unique two-dimensional (2D) structure and abundant surface functional groups. However, most studies about MXenes have focused on tailoring surface structures by alternating synthesis methods or post-etch treatments, and little is known about the inherent relationship between surface groups and M elements. Herein, we propose a simple and novel strategy to adjust the surface structure of few-layered MXene flakes by adding a small amount of Nb element. Because of the strong affinity between Nb and O elements, the as-received V_1.8Nb_0.2CT_x and Ti_2.7Nb_0.3C₂T_x MXenes have much fewer -F functional groups and a higher O content than V₂CT_x and Ti₃C₂T_x MXenes, respectively. Thus, both V_1.8Nb_0.2CT_x and Ti_2.7Nb_0.3C₂T_x MXenes show enhanced pseudocapacitance performance. Especially, V_1.8Nb_0.2CT_x delivers an ultrahigh volumetric capacitance of 1698 F/cm³ at a scan rate of 2 mV/s. Moreover, benefiting from the high activity of MAX precursors obtained through a fast self-propagating high-temperature synthesis, the etching time to produce V-based MXenes is much shorter than that in previous reports. Therefore, the results presented here are applicable to the surface engineering and rational design of 2D MXene materials and develop them into promising, cost-effective electrode materials for supercapacitors or other energy-storage equipment.

Enhanced Solid-State Fluorescence of Flavin Derivatives by Incorporation in the Metal-Organic Frameworks MIL-53(Al) and MOF-5

The flavin derivatives 10-methyl-isoalloxazine (MIA) and 6-fluoro-10-methyl-isoalloxazine (6F-MIA) were incorporated in two alternative metal-organic frameworks, (MOFs) MIL-53(Al) and MOF-5. We used a post-synthetic, diffusion-based incorporation into microcrystalline MIL-53 powders with one-dimensional (1D) pores and an in-situ approach during the synthesis of MOF-5 with its 3D channel network. The maximum amount of flavin dye incorporation is 3.9 wt% for MIA@MIL-53(Al) and 1.5 wt% for 6F-MIA@MIL-53(Al), 0.85 wt% for MIA@MOF-5 and 5.2 wt% for 6F-MIA@MOF-5. For the high incorporation yields the probability to have more than one dye molecule in a pore volume is significant. As compared to the flavins in solution, the fluorescence spectrum of these flavin@MOF composites is broadened at the bathocromic side especially for MIA. Time-resolved spectroscopy showed that multi-exponential fluorescence lifetimes were needed to describe the decays. The fluorescence-weighted lifetime of flavin@MOF of 4 ± 1 ns also corresponds to those in solution but is significantly prolonged compared to the solid flavin dyes with less than 1 ns, thereby confirming the concept of "solid solutions" for dye@MOF composites. The fluorescence quantum yield (Φ_F) of the flavin@MOF composites is about half of the solution but is significantly higher compared to the solid flavin dyes. Both the fluorescence lifetime and quantum yield of flavin@MOF decrease with the flavin loading in MIL-53 due to the formation of various J-aggregates. Theoretical calculations using plane-wave and QM/MM methods are in good correspondence with the experimental results and explain the electronic structures as well as the photophysical properties of crystalline MIA and the flavin@MOF composites. In the solid flavins, π-stacking interactions of the molecules lead to a charge transfer state with low oscillator strength resulting in aggregation-caused quenching (ACQ) with low lifetimes and quantum yields. In the MOF pores, single flavin molecules represent a major population and the computed MIA@MOF structures do not find π-stacking interactions with the pore walls but only weak van-der-Waals contacts which reasons the enhanced fluorescence lifetime and quantum yield of the flavins in the composites compared to their neat solid state. To analyze the orientation of flavins in MOFs, we measured fluorescence anisotropy images of single flavin@MOF-5 crystals and a static ensemble flavin@MIL53 microcrystals, respectively. Based on image information, anisotropy distributions and overall curve of the time-resolved anisotropy curves combined with theoretical calculations, we can prove that all fluorescent flavins species have a defined and rather homogeneous orientation in the MOF framework. In MIL-53, the transition dipole moments of flavins are orientated along the 1D channel axis, whereas in MOF-5 we resolved an average orientation that is tilted with respect to the cubic crystal lattice. Notably, the more hydrophobic 6F-MIA exhibits a higher degree order than MIA. The flexible MOF MIL-53(Al) was optimized essentially to the experimental large-pore form in the guest-free state with QuantumEspresso (QE) and with MIA molecules in the pores the structure contracted to close to the experimental narrow-pore form which was also confirmed by PXRD. In summary, the incorporation of flavins in MOFs yields solid-state materials with enhanced rigidity, stabilized conformation, defined orientation and reduced aggregations of the flavins, leading to increased fluorescence lifetime and quantum yield as controllable photo-luminescent and photo-physical properties.

Microstructures and Enhanced Mechanical Properties of (Zr, Ti)(C, N)-Based Nanocomposites Fabricated by Reactive Hot-Pressing at Low Temperature

Dense and enhanced mechanical properties (Zr, Ti)(C, N)-based composites were fabricated using ZrC, TiC_0.5N_0.5, and Si powders as the raw powders by reactive hot-pressing at 1500-1700 °C. At the low sintering temperature, both (Zr, Ti)(C, N) and (Ti, Zr)(C, N) solid solutions were formed in the composites by adjusting the ratio of ZrC to TiC_0.5N_0.5. During the sintering process, the Si added at a rate of 5 mol% reacted with ZrC and TiC_0.5N_0.5 to generate SiC. With the increase in Si addition, it was found that the residual β-ZrSi was formed, which greatly reduced the flexural strength of composites but improved their toughness. The reaction and solid-solution-driven inter-diffusion processes enhanced mass transfer and promote densification. The solid solution strengthening and grain refinement improved the mechanical properties. The ZrC-47.5 mol% TiC_0.5N_0.5-5 mol% Si (raw powder) composite possessed excellent comprehensive performance. Its flexural strength, Vickers hardness, and fracture toughness were 508 ± 33 MPa, 24.5 ± 0.7 GPa, and 3.8 ± 0.1 MPa·m^1/2, respectively. These reached or exceeded the performance of most (Zr, Ti)(C, N) ceramics reported in previous studies. The lattice distortion, abundant grain boundaries, and fine-grained microstructure may make it possible for the material to be resistant to radiation.

A mixed phosphine sulfide/selenide structure as an instructional example for how to evaluate the quality of a model

This paper compares variations on a structure model derived from an X-ray diffraction data set from a solid solution of chalcogenide derivatives of cis-1,2-bis-(di-phenyl-phosphan-yl)ethyl-ene, namely, 1,2-(ethene-1,2-di-yl)bis-(di-phenyl-phoshpine sulfide/selenide), C₂₆H₂₂P₂S_1.13Se_0.87. A sequence of processes are presented to ascertain the composition of the crystal, along with strategies for which aspects of the model to inspect to ensure a chemically and crystallographically realistic structure. Criteria include mis-matches between F _obs ² and F _calc ², plots of |F _obs| vs |F _calc|, residual electron density, checkCIF alerts, pitfalls of the OMIT command used to suppress ill-fitting data, comparative size of displacement ellipsoids, and critical inspection of inter-atomic distances. Since the structure is quite small, solves easily, and presents a number of readily expressible refinement concepts, we feel that it would make a straightforward and concise instructional piece for students learning how to determine if their model provides the best fit for the data and show students how to critically assess their structures.

Effect of Si on the Oxidation Behaviors of Ti3 Al1-x Six C2 at 1000 °C

In this work, Ti₃ Al_1-x Si_x C₂ (x=0, 0.2, 0.4, and 0.6) with Al/Si solid solution structure are synthesized, and the effects of Si on their oxidation behaviors at 1000 °C are evaluated. The addition of Si not only contributes to the formation of Ti₅ Si₃ impurity but also affects the composition of the oxide scale. Particularly, the incorporation of Si in the TiO₂ lattice is demonstrated, which alters the formation energy of the (110) plane in TiO₂ , thus leading to the preferential growth of Si-doped TiO₂ to dendritic congeries. Moreover, the Si addition is believed to affect mass transportation during the oxidation process, which accelerates the formation of a continuous Al₂ O₃ layer in the oxide scale. With an optimized Si content, the oxidation of Ti₃ Al_1-x Si_x C₂ is restrained. However, with excess Si content, the continuity of the resulting Al₂ O₃ layer is destroyed, thus the oxidation rate rises again.

Macro- and Microstructure of In Situ Composites Prepared by Friction Stir Processing of AA5056 Admixed with Copper Powders

This paper is devoted to using multi-pass friction stir processing (FSP) for admixing 1.5 to 30 vol.% copper powders into an AA5056 matrix for the in situ fabrication of a composite alloy reinforced by Al-Cu intermetallic compounds (IMC). Macrostructurally inhomogeneous stir zones have been obtained after the first FSP passes, the homogeneity of which was improved with the following FSP passes. As a result of stirring the plasticized AA5056, the initial copper particle agglomerates were compacted into large copper particles, which were then simultaneously saturated by aluminum. Microstructural investigations showed that various phases such as α-Al(Cu), α-Cu(Al) solid solutions, Cu₃Al and CuAl IMCs, as well as both S and S'-Al₂CuMg precipitates have been detected in the AA5056/Cu stir zone, depending upon the concentration of copper and the number of FSP passes. The number of IMCs increased with the number of FSP passes, enhancing microhardness by 50-55%. The effect of multipass FSP on tensile strength, yield stress and strain-to-fracture was analyzed.

The Local and Electronic Structure Study of LuxGd1-xVO4 (0 ≤ x ≤ 1) Solid Solution Nanocrystals

Rare-earth-doped mixed crystals have demonstrated tunable optical properties, and it is of great importance to study the structural characteristics of the mixed-crystal hosts. Herein, Lu_xGd_1-xVO₄ (0 ≤ x ≤ 1) solid solution nanocrystals were synthesized by a modified sol-gel method, with a pure crystalline phase and element composition. The X-ray diffraction (XRD) and Rietveld refinement results showed that Lu_xGd_1-xVO₄ nanocrystals are continuous solid solutions with a tetragonal zircon phase (space group I4₁/amd) and the lattice parameters strictly follow Vegard's law. The detailed local structures were studied by extended X-ray absorption fine structure (EXAFS) spectra, which revealed that the average bond length of Gd-O fluctuates and decreases, while the average bond length of Lu-O gradually decreases with the increase in Lu content. Furthermore, the binding energy differences of core levels indicate that the covalent V-O bond is relatively stable, while the ionicity of the Lu-O bond decreases with the increasing x value, and the ionicity of the Gd-O bond fluctuates with small amplitude. The valence band structures were further confirmed by the first-principles calculations, indicating that the valence band is contributed to by the O 2p nonbonding state, localized Gd 4f and Lu 4f states, and the hybridized states between the bonding O 2p and V 3d. The binding energies of the Lu core and the valence levels tend to decrease gradually with the increase in Lu content. This work provides insight into the structural features of mixed-crystal hosts, which have been developed in recent years to improve laser performance by providing different positions for active ions to obtain inhomogeneous broadening spectra.

Homogeneous Nanoparticles of Multimetallic Phosphides via Precursor Tuning: Ternary and Quaternary M2P Phases (M = Fe, Co, Ni)

Transition metal phosphides (TMPs) are a highly investigated class of nanomaterials due to their unique magnetic and catalytic properties. Although robust and reproducible synthetic routes to narrow polydispersity monometallic phosphide nanoparticles (M₂P; M = Fe, Co, Ni) have been established, the preparation of multimetallic nanoparticle phases (M_2-x M' _x P; M, M' = Fe, Co, Ni) remains a significant challenge. Colloidal syntheses employ zero-valent metal carbonyl or multivalent acetylacetonate salt precursors in combination with trioctylphosphine as the source of phosphorus, oleylamine as the reducing agent, and additional solvents such as octadecene or octyl ether as "noncoordinating" cosolvents. Understanding how these different metal precursors behave in identical reaction environments is critical to assessing the role the relative reactivity of the metal precursor plays in synthesizing complex, homogeneous multimetallic TMP phases. In this study, phosphorus incorporation as a function of temperature and time was evaluated to probe how the relative rate of phosphidation of organometallic carbonyl and acetylacetonate salt precursors influences the homogeneous formation of bimetallic phosphide phases (M_2-x M' _x P; M, M' = Fe, Co, Ni). From the relative rate of phosphidation studies, we found that where reactivity with TOP for the various metal precursors differs significantly, prealloying steps are necessary to isolate the desired bimetallic phosphide phase. These insights were then translated to establish streamlined synthetic protocols for the formation of new trimetallic Fe_2-x-y Ni _x Co _y P phases.

Mesoporous crystalline Ti1-xSnxO2 (0 < x < 1) solid solution for a high-performance photocatalyst under visible light irradiation

We report a facile and effective inorganic polycondensation combined with aerosol-spray strategy towards high-performance photocatalyst by fabricating mesoporous Ti_1-xSn_xO₂ (0 < x < 1) solid solution. Such Ti_1-xSn_xO₂ nanocrystals with high Sn-doped contents are self-assembled into mesoporous spheres can effectively promote visible-light harvest and high quantum yield, leading a longer lifetime of the photoelectron-hole pairs and less recombination. Such the photocatalysts enhanced photocatalytic activity for the degradation of Rhodamine B (RhB). The representative Ti_0.9Sn_0.1O₂ and Ti_0.8Sn_0.2O₂ compounds reach an optimum degradation of ≈50% and 70%, respectively, after 120 min irradiation under visible irradiation. The mesoporous Ti_1-xSn_xO₂ solid solution could inhibit the recombination of electron-hole pairs, which promote reaction thermodynamics and kinetics for RhB degradation.

Origin of Ferroelectricity in BiFeO3-Based Solid Solutions

We investigate the origin of ferroelectricity in the BiFeO₃-LaFeO₃ system in rhombohedral R3c and tetragonal P4mm symmetries by ab initio density functional theory calculations and compare their electronic features with paraelectric orthorhombic Pnma symmetry. We show that a coherent accommodation of stereo-active lone pair electrons of Bi is the detrimental factor of ferroelectricity. A Bloch function arising from an indirect Bi_6p-Fe_3d hybridization mediated through O_2p is the primary origin of spontaneous polarization (P_s) in the rhombohedral system. In the orthorhombic system, a similar Bloch function was found, whereas a staggered accommodation of stereo-active lone pair electrons of Bi exclusively results in paraelectricity. A giant P_s reported in the tetragonal system originates from an orbital hybridization of Bi_6p and O_2p, where Fe-3d plays a minor role. The P_s in the rhombohedral system decreases with increasing La content, while that in the tetragonal system displays a discontinuous drop at a certain La content. We discuss the electronic factors affecting the P_s evolutions with La content.

Efficient Photocatalytic Hydrogen Production over NiS-Modified Cadmium and Manganese Sulfide Solid Solutions

In this work, new photocatalysts based on Cd_1-xMn_xS sulfide solid solutions were synthesized by varying the fraction of MnS (x = 0.4, 0.6, and 0.8) and the hydrothermal treatment temperature (T = 100, 120, 140, and 160 °C). The active samples were modified with Pt and NiS co-catalysts. Characterization was performed using various methods, including XRD, XPS, HR TEM, and UV-vis spectroscopy. The photocatalytic activity was tested in hydrogen evolution from aqueous solutions of Na₂S/Na₂SO₃ and glucose under visible light (425 nm). When studying the process of hydrogen evolution using an equimolar mixture of Na₂S/Na₂SO₃ as a sacrificial agent, the photocatalysts Cd_0.5Mn_0.5S/Mn(OH)₂ (T = 120 °C) and Cd_0.4Mn_0.6S (T = 160 °C) demonstrated the highest activity among the non-modified solid solutions. The deposition of NiS co-catalyst led to a significant increase in activity. The best activity in the case of the modified samples was shown by 0.5 wt.% NiS/Cd_0.5Mn_0.5S (T = 120 °C) at the extraordinary level of 34.2 mmol g^-1 h^-1 (AQE 14.4%) for the Na₂S/Na₂SO₃ solution and 4.6 mmol g^-1 h^-1 (AQE 2.9%) for the glucose solution. The nickel-containing samples possessed a high stability in solutions of both sodium sulfide/sulfite and glucose. Thus, nickel sulfide is considered an alternative to depositing precious metals, which is attractive from an economic point of view. It worth noting that the process of photocatalytic hydrogen evolution from sugar solutions by adding samples based on Cd_1-xMn_xS has not been studied before.

Phytosterols and γ-Oryzanol as Cholesterol Solid Phase Modifiers during Digestion

Literature reports that ingestion of phytosterols and γ-oryzanol contributes to cholesterol lowering. Despite in vivo observations, thermodynamic phase equilibria could explain phenomena occurring during digestion leading to such effects. To advance the observations made by previous literature, this study was aimed at describing the complete solid-liquid phase equilibrium diagrams of cholesterol + phytosterol and γ-oryzanol systems by DSC, evaluating them by powder X-ray, microscopy, and thermodynamic modeling. Additionally, this study evaluated the phenomena observed by an in vitro digestibility method. Results confirmed the formation of solid solution in the cholesterol + phytosterols system at any concentration and that cholesterol + γ-oryzanol mixtures formed stable liquid crystalline phases with a significant melting temperature depression. The in vitro protocol supported the idea that the same phenomena can occur during digestion in which mechanochemical forces were probably the mechanisms promoting cholesterol solid phase changes in the presence of such phytocompounds. In this case, these changes could alter cholesterol solubility and possibly its absorption in the gastrointestinal lumen.

Enhanced Mechanical Properties of Yellow ZrN Ceramic with Addition of Solid Solution of TiN

As a superhard ceramic with a yellow color and excellent electrical conductivity, ZrN has potential applications in the field of decoration, but it is limited by its poor mechanical properties. In this work, the mechanical properties of ZrN ceramic were improved by forming a (Zr, Ti)N solid solution via spark plasma sintering of a ZrN and TiN powder mixture. The influences of the amount of TiN additive on the sinterability, microstructure, color, and mechanical properties of ZrN ceramic were investigated. X-ray diffraction analysis, energy-dispersive spectroscopy, and microstructural images indicated that Ti atoms dissolved into a ZrN lattice, and a (Zr, Ti)N solid solution was formed during the sintering process. When the content of TiN was 10 vol%, the obtained (Zr, Ti)N composite exhibited the best comprehensive mechanical properties; the Vickers hardness, flexural strength, and fracture toughness were 15.17 GPa, 520 MPa, and 6.03 MPa·m^1/2, respectively. The color coordinates and color temperature diagram revealed the addition of TiN hardly impacted the color performance of the ZrN ceramic.

Synthesis of Metal Chalcogenide Semiconductors by Thermal Decomposition of Organosulfur and Organoselenium Compounds

Metal chalcogenides - because of their excellent optical and electrical properties - are important semiconductor materials for optical devices, such as solar cells, sensors, and photocatalysts. The challenges associated with metal chalcogenides are the complexity of the conventional synthesis methods and the stringent synthesis conditions. In this study, the synthesis conditions were simplified in a solvent-free synthesis method using cadmium precursor, thiourea and selenium to synthesize metal chalcogenides, such as CdS and CdSe, which have particularly suitable band gaps for the optical devices. CdS_x Se_1-x solid solution was successfully synthesized under molten thiourea as the reactive reaction medium at relatively low temperatures, even at 180 °C, with residual melamine derivatives in the solid phase. The luminescence properties of CdS_x Se_1-x and the products in the gas and solid phases were investigated. Optimization of the synthesis conditions for solid solutions of CdS_x Se_1-x and the role of organic compounds in the formation of metal chalcogenides are discussed.

Structural Characterization of Phosphorous Slag Regarding Occurrence State of Phosphorus in Dicalcium Silicate

Phosphorous slag is a solid waste generated in the process of yellow phosphorus production. In order to deeply understand the structural and cementitious characteristics of phosphorous slag, comprehensive characterizations, including X-ray fluorescence spectrometry, X-ray diffraction, thermogravimetry, Fourier transform infrared spectrometry, Raman, scanning electron microscope, and inductively coupled plasma mass spectrometry were adopted to investigate the composition, thermal stability, microstructure, and cementitious activity of phosphorous slag. In addition, scanning electron microscope with energy dispersive X-ray spectroscopy, electron microprobe analysis, and solid-state nuclear magnetic resonance techniques were used to analyze the occurrence state of P in phosphorous slag. The results show that phosphorous slag is mostly vitreous with good thermal stability. Its chemical composition mainly comprises 43.85 wt % CaO, 35.87 wt % SiO_2, and 5.57 wt % Al₂O₃, which is similar to that of blast furnace slag, but it presents lower cementitious activity than blast furnace slag. P is uniformly distributed in the phosphorous slag with P₂O₅ content of 3.75 wt %. The distribution pattern of P is extremely similar to that of Si. P is mainly existing in orthophosphate of 3CaO·P₂O₅, which forms solid solution with dicalcium silicate (2CaO·SiO₂). This work specifically clarifies the occurrence state of P in dicalcium silicate within the phosphorous slag. It is theoretically helpful to solve the retarding problem of phosphorous slag in cement and concrete.

Bright UV-C Phosphors with Excellent Thermal Stability-Y1-xScxPO4 Solid Solutions

The structural and luminescence properties of undoped Y_1-xSc_xPO₄ solid solutions have been studied. An intense thermally stable emission with fast decay (τ_1/e ~ 10^-7 s) and a band position varying from 5.21 to 5.94 eV depending on the Sc/Y ratio is detected and ascribed to the 2p O-3d Sc self-trapped excitons. The quantum yield of the UV-C emission, also depending on the Sc/Y ratio, reaches 34% for the solid solution with x = 0.5 at 300 K. It is shown by a combined analysis of theoretical and experimental data that the formation of Sc clusters occurs in the solid solutions studied. The clusters facilitate the creation of energy wells at the conduction band bottom, which enables deep localization of electronic excitations and the creation of luminescence centers characterized by high quantum yield and thermal stability of the UV-C emission.

Cu2+-Ion-Substitution-Driven Microstructure and Microwave Dielectric Properties of Mg1-xCuxAl2O4 Ceramics

In this work, Cu-substituted MgAl₂O₄ ceramics were prepared via solid-state reaction. The crystal structure, cation distribution, and microwave dielectric properties of Mg_1-xCu_xAl₂O₄ ceramics were investigated. Cu²⁺ entered the MgAl₂O₄ lattice and formed a spinel structure. The substitution of Cu²⁺ ions for Mg²⁺ ions contributed to Al³⁺ ions preferential occupation of the octahedron and changed the degree of inversion. The quality factor (Qf) value, which is correlated with the degree of inversion, increased to a maximum value at x = 0.04 and then decreased. Ionic polarizability and relative density affected the dielectric constant (ε_r) value. The temperature coefficient of the resonant frequency (τ_f) value, which was dominated by the total bond energy, generally shifted to the positive direction. Satisfactory microwave dielectric properties were achieved in x = 0.04 and sintered at 1550 °C: ε_r = 8.28, Qf = 72,800 GHz, and τ_f = -59 ppm/°C. The Mg_1-xCu_xAl₂O₄ solid solution, possessing good performance, has potential for application in the field of modern telecommunication technology.

The Reaction Behavior of 2CaO·SiO2 with CaO-SiO2-FeO-P2O5 Slag

It is important to clarify the reaction behavior of 2CaO·SiO₂ (C₂S) during hot metal dephosphorization. In this study, C₂S was prepared and added to steel slag to investigate the reaction of C₂S particles with CaO-SiO₂-FeO-P₂O₅ slag at 1723 K. The diffusion coefficient of phosphorus in C₂S was calculated. In addition, the influence of the addition of BaO to C₂S was discussed. The results show that the diffusion coefficient of phosphorus in C₂S is 9.23 × 10^-14 m²·s^-1. The Ca in C₂S can be replaced by Ba. Small particles in the solid solution were easily generated from the C₂S body by the addition of BaO, which is beneficial for improving the phosphorus partition between the C₂S solid phase and the liquid phase of the slag.

Activated Sintering of Cr2O3-Based Composites by Hot Pressing

The paper presents and discusses questions on structure formation during the sintering process of Cr₂O₃-based composites using the hot pressing method, when a chemical reaction between the components takes place. The task was difficult because Cr₂O₃ decomposes when sintered at temperatures above 1300 °C. The proposed novel method allowed for interaction between aluminum and chromia, thus avoiding the decomposition of the latter. Here, ultrafine aluminum powder played the role of the active agent forming a liquid phase and reacting with Cr₂O₃. The appearance of the solid solutions of (Cr,Al)₂O₃ with different stoichiometry of Cr and Al depended on the aluminum content in the initial mixture. The solid solution significantly strengthened boundaries between composite phases, resulting in the composite material of high fracture toughness between 5 and 7 MPa m^½ and bending strength of ca. 500 MPa. The best mechanical properties exhibited the cermet with 22 wt.% of the restored chromium.

Effects of Nb Additions and Heat Treatments on the Microstructure, Hardness and Wear Resistance of CuNiCrSiCoTiNbx High-Entropy Alloys

In this research, a set of CuNiCrSiCoTi (H-0Nb), CuNiCrSiCoTiNb_0.5 (H-0.5Nb) and CuNiCrSiCoTiNb₁ (H-1Nb) high-entropy alloys (HEAs) were melted in a vacuum induction furnace. The effects of Nb additions on the microstructure, hardness, and wear behavior of these HEAs (compared with a CuBe commercial alloy) in the as-cast (AC) condition, and after solution (SHT) and aging (AT) heat treatments, were investigated using X-ray diffraction, optical microscopy, and electron microscopy. A ball-on-disc configuration tribometer was used to study wear behavior. XRD and SEM results showed that an increase in Nb additions and modification by heat treatment (HT) favored the formation of BCC and FCC crystal structures (CS), dendritic regions, and the precipitation of phases that promoted microstructure refinement during solidification. Increases in hardness of HEA systems were recorded after heat treatment and Nb additions. Maximum hardness values were recorded for the H-1Nb alloy with measured increases from 107.53 HRB (AC) to 112.98 HRB, and from 1104 HV to 1230 HV (aged for 60 min). However, the increase in hardness caused by Nb additions did not contribute to wear resistance response. This can be attributed to a high distribution of precipitated phases rich in high-hardness NiSiTi and CrSi. Finally, the H-0Nb alloy exhibited the best wear resistance behavior in the aged condition of 30 min, with a material loss of 0.92 mm³.

Internal Sulphate Attack in Masonry Mortars with Thaumasite Formation

The present paper focuses on the study of mortar samples where expansions with thaumasite formation occur as a consequence of sulphate attack. The samples correspond to a masonry mortar used in a rural construction located in the Spanish province of Toledo made of cement with limestone filler addition CEM II/AL. Composition and microstructure of the mortars have been analysed by means of scanning electron microscopy (SEM) using secondary and backscattered electrons (BSE) and X-ray diffraction (XRD). The results show that aggregates are contaminated with gypsum, which is the source of the sulphates for the internal attack. It seems that thaumasite is formed through an ettringite transformation where aluminium atoms are replaced with silicon atoms by means of a solid solution. The study highlights that thaumasite can be formed in warm weather through an internal sulphate attack due to gypsum contamination of aggregates.

Tuning the Band Gap in the Halide Perovskite CsPbBr3 through Sr Substitution

The ability to continuously tune the band gap of a semiconductor allows its optical properties to be precisely tailored for specific applications. We demonstrate that the band gap of the halide perovskite CsPbBr₃ can be continuously widened through homovalent substitution of Sr²⁺ for Pb²⁺ using solid-state synthesis, creating a material with the formula CsPb_1-xSr_xBr₃ (0 ≤ x ≤ 1). Sr²⁺ and Pb²⁺ form a solid solution in CsPb_1-xSr_xBr₃. Pure CsPbBr₃ has a band gap of 2.29(2) eV, which increases to 2.64(3) eV for CsPb_0.25Sr_0.75Br₃. The increase in band gap is clearly visible in the color change of the materials and is also confirmed by a shift in the photoluminescence. Density-functional theory calculations support the hypothesis that Sr incorporation widens the band gap without introducing mid-gap defect states. These results demonstrate that homovalent B-site alloying can be a viable method to tune the band gap of simple halide perovskites for absorptive and emissive applications such as color-tunable light-emitting diodes, tandem solar cells, and photodetectors.

The Influence of SiO2 + SiC + Al (H2PO4)3 Coating on Mechanical and Dielectric Properties for SiCf/MWCNTS/AlPO4 Composites

SiC fiber-reinforcedAlPO₄ matrix (SiC_f/MWCNTs/AlPO₄) composites were fabricated using a hot laminating process with multi-walled carbon nanotubes (MWCNTs) as the absorber. A coating prepared from SiO₂ + SiC + Al (H₂PO₄)₃ was applied to the surface of the SiC_f/MWCNTs/AlPO₄ composites prior to an anti-oxidation test at 1273 K in air for 40 h. The anti-oxidation effect was verified by a three-point bending test, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and a dielectric property test. Anti-oxidation mechanism investigations revealed that the coating effectiveness could be attributed to three substances, i.e., SiO₂, SiP₂O_7, and SiO₂ +AlPO₄ solid solution from the reactions of SiC + O₂→SiO₂ + CO, SiO₂ + P₂O₅→SiP₂O₇ and SiO₂ +AlPO₄→solid solution, respectively.

Synthesis of a New Ferroelectric Relaxor Based on a Combination of Antiferroelectric and Paraelectric Systems

Relaxor ferroelectric-based energy storage systems are promising candidates for advanced applications as a result of their fast speed and high energy storage density. In the research field of ferroelectrics and relaxor ferroelectrics, the concept of solid solution is widely adopted to modify the overall properties and acquire superior performance. However, the combination between antiferroelectric and paraelectric materials was less studied and discussed. In this study, paraelectric barium hafnate (BaHfO₃) and antiferroelectric lead hafnate (PbHfO₃) are selected to demonstrate such a combination. A paraelectric to relaxor ferroelectric, to ferroelectric, and to antiferroelectric transition is observed by varying the composition x in the (Ba_1-xPb_x)HfO₃ solid solution from 0 to 100%. It is noteworthy that ferroelectric phases can be realized without primal ferroelectric material. This study creates an original solid solution system with a rich spectrum of competing phases and demonstrates an approach to design relaxor ferroelectrics for energy storage applications and beyond.

Fluorine-Assisted Low-Temperature Synthesis of GaN:ZnO-Related Solid Solutions with Visible-Light Photoresponse

Wurtzite-structured Ga_1-xZn_x(N,O,F) was successfully synthesized by nitridation of mixtures of a Ga-containing oxide and ZnF₂. The addition of ZnF₂ lowered the nitridation temperature for the synthesis of Ga_1-xZn_x(N,O,F) to 823 K, even when bulk ZnGa₂O₄ was used as a paired precursor. This lowering of the synthesis temperature was ascribed to the enhancement of nitridation through the addition of fluorine. The low-temperature nitridation achieved by the addition of fluorine suppressed the volatilization of Zn compared with that during the synthesis of a GaN:ZnO solid solution by a conventional high-temperature ammonolysis reaction. The higher concentration of Zn, as well as the higher N concentration in Ga_1-xZn_x(N,O,F) achieved through the fluorine-assisted nitridation, led to a redshift of the absorption edge of Ga_1-xZn_x(N,O,F) to 560 nm compared with that of GaN:ZnO synthesized by the conventional ammonolysis reaction. The visible-light absorption of Ga_1-xZn_x(N,O,F) can be used to drive the photoelectrochemical oxidation of water.

Degenerated Hole Doping and Ultra-Low Lattice Thermal Conductivity in Polycrystalline SnSe by Nonequilibrium Isovalent Te Substitution

Tin mono-selenide (SnSe) exhibits the world record of thermoelectric conversion efficiency ZT in the single crystal form, but the performance of polycrystalline SnSe is restricted by low electronic conductivity (σ) and high thermal conductivity (κ), compared to those of the single crystal. Here an effective strategy to achieve high σ and low κ simultaneously is reported on p-type polycrystalline SnSe with isovalent Te ion substitution. The nonequilibrium Sn(Se1- x Tex ) solid solution bulks with x up to 0.4 are synthesized by the two-step process composed of high-temperature solid-state reaction and rapid thermal quenching. The Te ion substitution in SnSe realizes high σ due to the 103 -times increase in hole carrier concentration and effectively reduced lattice κ less than one-third at room temperature. The large-size Te ion in Sn(Se1- x Tex ) forms weak SnTe bonds, leading to the high-density formation of hole-donating Sn vacancies and the reduced phonon frequency and enhanced phonon scattering. This result-doping of large-size ions beyond the equilibrium limit-proposes a new idea for carrier doping and controlling thermal properties to enhance the ZT of polycrystalline SnSe.

High-Mobility Metastable Rock-Salt Type (Sn,Ca)Se Thin Film Stabilized by Direct Epitaxial Growth on a YSZ (111) Single-Crystal Substrate

Metastable cubic (Sn_1-xPb_x)Se with x ≥ 0.5 is expected to be a high mobility semiconductor due to its Dirac-like electronic state, but it has an excessively high carrier concentration of ∼10¹⁹ cm^-3 and is not suitable for semiconductor device applications such as thin film transistors and solar cells. Further, thin films of (Sn_1-xPb_x)Se require a complicated synthesis process because of the high vapor pressure of Pb. We herein report the direct growth of metastable cubic (Sn_1-xCa_x)Se films alloyed with CaSe, which has a wider bandgap and lower vapor pressure than PbSe. The cubic (Sn_1-xCa_x)Se epitaxial films with x = 0.4-0.8 are stabilized on YSZ (111) single crystalline substrates by pulsed laser deposition. (Sn_1-xCa_x)Se has a direct-transition-type bandgap, and the bandgap energy can be varied from 1.4 eV (x = 0.4) to 2.0 eV (x = 0.8) by changing x. These films with x = 0.4-0.6 show p-type conduction with low hole carrier concentrations of ∼10¹⁷ cm^-3. Hall mobility analysis suggests that the hole transport would be dominated by 180° rotational domain structures, which is specific to (111) oriented epitaxial films. However, it, in turn, clarifies that the in-grain carrier mobility in the (Sn_0.6Ca_0.4)Se film is as high as 322 cm²/(Vs), which is much higher than those in thermodynamically stable layered SnSe and other Sn-based layered semiconductor films at room temperature. Therefore, the present results prove the potential of high mobility (Sn_1-xCa_x)Se films for semiconductor device applications via a simple thin-film deposition process.