Search

To optimize the comprehensive performance of rare earth (RE) aluminates as thermal/environmental barrier coatings (T/EBCs), we engineered six kinds of novel high-entropy RE aluminate multiphase ceramics with the coexisting garnet and perovskite phases by regulating equivalent ionic radius of RE3+, and the relationship between the microstructure and thermal properties, as well as resistance to CMAS corrosion was investigated in-detail. The findings revealed that the garnet (5RE 0.2) 3 Al 5 O 12 content gradually decreased in multiphase ceramics with the increasing equivalent ionic radius of RE3+. The interaction between garnet and perovskite grains can decrease grain size, which in turn enhanced phonon scattering, thereby leading to the decrease in thermal conductivity. Moreover, the synergistic effect in the different dissolution rates of garnet and perovskite phases can form a dense garnet/apatite barrier layer at corrosion front, thereby contributing to CMAS corrosion resistance. These results provide a robust theoretical foundation for the advancement of next-generation T/EBCs. [ABSTRACT FROM AUTHOR]

A series of orange-red-emitting phosphors, Ba2Y1−xSmxAlO5 (x = 1 mol.%, 2 mol.%, 5 mol.%, 10 mol.%, 15 mol.%, 20 mol.%, 25 mol.%, and 30 mol.%), were successfully synthesized using a high-temperature solid-state method at 1400°C, with Sm3+ serving as the activator. The crystallinity of the samples was confirmed in the space group P21/c (14). Efficient excitation was observed in the Ba2YAlO5:xSm3+ phosphors when exposed to 405 nm irradiation. Upon excitation at 405 nm, the synthesized Ba2YAlO5:xSm3+ phosphors displayed three distinctive peaks, which corresponded to the transitions of Sm3+ at 4G5/2–6HJ (J = 5/2, 7/2, and 9/2). Optimal luminescence properties were achieved at a Sm3+ concentration of 2 mol.%. The phenomenon of concentration quenching was elucidated through the application of dipole–dipole interaction theory. The quenching temperature of Ba2YAlO5:0.10Sm3+ exceeded 480 K. The CIE chromaticity coordinates of Ba2YAlO5:xSm3+ closely align with the recognized standard red defined by the National Television System Committee (NTSC). This conformity underscores the potential of Ba2YAlO5:xSm3+ phosphors for applications demanding precise color reproduction, as required in advanced display technologies and lighting systems. [ABSTRACT FROM AUTHOR]

The addition of boron oxide is well‐known to dramatically extend the afterglow persistence (PersiL) from minutes to hours in Sr4Al14O25 (S4A7) co‐doped with 1 at% Eu and 1 at% Dy (S4A7EDxB), while the longest duration occurs when 30–40 mol% B2O3 is used. To elucidate the influence of B2O3 on the S4A7EDxB structure supporting PersiL, the thermodynamics and kinetics of phase transformation from amorphous preceramics of S4A7EDxB are investigated in the present work. Powders of S4A7EDxB containing x = 0, 10, 20, 30, and 40 mol% B2O3 were prepared by Pechini processing, and their phase evolution was analyzed at characteristic exothermic reaction temperatures. Differential thermal analysis and thermogravimetry at different heating rates, X‐ray diffraction, micro‐Raman, and scanning electron microscopy methods are used to reveal that S4A7 forms along different reaction pathways involving SrAl2O4, γ‐Al2O3, and SrAl4O7, with the pathway determined primarily by the amount of boron oxide present. Evidence is presented correlating the energy barrier of different phase transformations to the relative stability of Al3+ coordination polyhedral networks that form the scaffolding in each crystal phase. To lift the kinetic limitations for direct crystallization of S4A7, at least 30 mol% B2O3 is required for sufficient liquid borate to enable both the Sr2+ diffusion and the reorganization in topological connectivity in the Al3+ polyhedral scaffolding. [ABSTRACT FROM AUTHOR]

Tm3+/Ho3+ co-doped tellurite aluminate glasses were prepared using the melt-quenching technique. Under 808 nm laser diode (LD) excitation, these glasses exhibit intense 2 μm band luminescence, with a full width at half-maximum (FWHM) of 144 nm. The energy transfer mechanism between Tm3+ and Ho3+ was explored to investigate the luminescence behavior further. Furthermore, the forward energy transfer coefficient (Tm3+→Ho3+) is greater than the backward energy transfer coefficient (Ho3+→Tm3+), indicating that Tm3+ can effectively sensitize Ho3+. As mentioned above, Tm3+/Ho3+ co-doped tellurite aluminate glass is a competitive material in the laser field. [ABSTRACT FROM AUTHOR]

Facility agriculture has been widely used around the world due to its effective strategy of increasing the added value of agricultural products. The study of Mn4+ doped oxidized red phosphors has become a prominent area of research aimed at addressing the shortage of red light in agriculture and horticulture. In this work, SrZnAl 10 O 17 far-red phosphors doped with Mn4+ were deliberately designed through a high-temperature solid-state reaction. The crystal structure was determined through Rietveld refinement, and a comprehensive analysis of the photoluminescence properties was conducted. When illuminated with light at either 396 or 552 nm, the SrZnAl 10 O 17 :Mn4+ phosphors displayed a distinct narrow emission band, covering the wavelength range of 600–800 nm, with a peak occurring at 692 nm. Notably, the photoluminescence intensity of these phosphors did not show significant variations under 396 and 552 nm light excitation—a relatively uncommon occurrence in Mn4+-doped red oxide phosphors. Furthermore, the photoluminescence spectra of SrZnAl 10 O 17 :Mn4+ phosphors closely matched the absorption spectra of PFR, suggesting the potential application of these phosphors in agricultural cultivation. [ABSTRACT FROM AUTHOR]

Highlights SrAl2O4 co‐doped with Eu2+ and Dy3+ ions (SAOED) have great potential in lighting field due to the unique light energy absorption‐storage‐released properties. In this work, a series of SAOED/poly(methyl methacrylate) (PMMA) luminescent composites were prepared and investigated. The maximum afterglow intensity of SAOED/PMMA composites was reached when the SAOED particle size was 26 μm, the mass ratio of SAOED to PMMA was 0.6 and the thickness of composites was 4.3 mm. Meanwhile, the tensile strength and modulus of the SAOED/PMMA composites were 22.06 MPa and 3.92 GPa, respectively. After being reexcited by a 3.5 W white diode used as normal functional lighting, SAOED/PMMA composites were able to achieve the requirement on landscape lighting (>2 lx), which showed promising engineering prospects in alternative lighting. The particle size, mass ratio and thickness effected the afterglow intensity. The optimal composites presented promising long persistent luminescence. Resulting SrAl2O4 co‐doped with Eu2+ and Dy3+ ions (SAOED)/poly(methyl methacrylate) (PMMA) composites possessed high tensile performance. The SAOED/PMMA composites showed great potential in alternative lighting. [ABSTRACT FROM AUTHOR]

In this work, we design an efficient and cost-effective porous membrane composed by polymeric blend that supports different photocatalytic materials. The thin (300 μm) porous photocatalytic membrane has a tubular shape and was flexible for easy handle in the reactor. The membrane is composed of a polymeric blend based on cellulose acetate, crystalline nanocellulose and polyvinyl alcohol, obtained by the phase inversion method, using cold water as non-solvent. Bismuthates (KBiO 3 , NaBiO 3) and aluminates (ZnAl 2 O 4 and Cu 0·9 Zn 0·1 Al 2 O 4) powders were synthesized by diverse methodologies and were embedded into polymeric matrix. The hydrogen evolution performance of photocatalyst powders and photocatalytic composite membranes, under UV light irradiation during 180 min, were compared. The best result of hydrogen evolution was obtained by Cu 0·9 Zn 0·1 Al 2 O 4 powders reaching 117.74 μmolg−1h−1 and the M−CuZn membrane reaching 90.07 μmolg−1h−1. The obtained results show the high potential of these polymeric membranes as a green alternative support for photocatalysts for hydrogen evolution. [Display omitted] • Cost-effective membrane composed by polymeric matrix (CA/CNC/PVA) such as Support for different photocatalysts. • Tubular shape, porous, flexibility and hydrophilicity character and easy of handle are shown in all membranes. • M − CuZn membrane reached 90.07 μmolg-1h-1 of hydrogen evolution performance. • The reuse of M − CuZn proved stability after three cycles of use with a decrease only 28% of initial performance. • Not sacrificial reagents were used in this work. [ABSTRACT FROM AUTHOR]

Smart waterborne coatings have shown various functions, such as afterglow photoluminescence, antimicrobial activity, water resistance, ultraviolet blocking, and anti-counterfeiting properties. However, photoluminescent organic agents have shown poor photostability and high cost. Additionally, waterborne acrylic coatings have shown poor mechanical properties. Herein, nanoparticles of rare-earth strontium aluminate (NRESA) and electrospun glass nanofibers (EGN) were used to strengthen the bulk of acrylic (ACR) coatings to develop smart products with mechanical reliability, hydrophobicity, ultraviolet blocking, and persistent photoluminescence. By physically integrating nano-scaled particles of RESA, colorless smart coatings of EGN@ACR were produced. Photoluminescence spectra showed that the transparent EGN@ACR changed its appearance to greenish when exposed to ultraviolet rays. Hybrids of EGN@ACR with trace amounts of NRESA showed fluorescence emission with instant reversibility. As the phosphor concentration in the EGN@ACR hybrids increased, afterglow photoluminescence with delayed reversibility was detected. When excited at 370 nm, the hybrid coatings displayed an emission band at 519 nm. The morphological analysis of NRESA by transmission electron microscopy (TEM) displayed diameters of 9–21 nm. After being prepared using electrospinning technology, glass nanofibers were introduced into acrylic emulsion coatings as a reinforcement agent. Scanning electron microscopic (SEM) analysis of EGN showed diameters of 70–120 nm. The smart coatings had better resistance to scratches as compared to the control sample of NRESA-free acrylic paint. A higher concentration of NRESA resulted in enhanced hydrophobicity and ultraviolet blocking. [ABSTRACT FROM AUTHOR]

In the SrO‐Al2O3‐B2O3‐SiO2 glass system, a SrAl2O4:Eu2+, Dy3+ long‐persistent luminescence glass‐ceramic (SAGC) with Li2O was successfully synthesized for the first time using the recrystallization‐melting method. The composition, micromorphology, long‐persistent luminescence (LPL) properties, photoluminescence (PL) properties, and water resistance were measured by X‐ray diffractometer, scanning electron microscope, brightness meter, fluorescence spectrophotometer, and pH meter, respectively. The method involves the formation of grains below the glass transition temperature, followed by the formation of the glass phase at a higher temperature, and finally the formation of products through cooling. The samples exhibited green PL and LPL emissions and demonstrated excellent color purity, homogeneity, and LPL luminescence. After doping Li2O, the purity and crystallinity of the SrAl2O4 were improved, and scalene hexagonal or monoclinic prismatic SrAl2O4 crystals with high regularity were synthesized in the glass matrix. This research indicates that excellent LPL benefits from the complete crystal structure, abundant crystals, and large crystal size. When the Li2O content reached 5 mol%, the crystal size was ∼30 µm, the PL and LPL properties performed best, and greater water resistance was exhibited. The SAGC in this new glass system has potential in optical storage. [ABSTRACT FROM AUTHOR]

Potassium alunite is a potential mineral resource of potassium and aluminum that can serve as a valuable resource. An effective potassium and aluminum recovery method is developed using gradient leaching with a KOH sub‐molten salt. The key part of this process is seeded precipitation of the potassium aluminate leach solution. Therefore, this study aims to optimize the seeded precipitation process by investigating the effects of alkali concentration, molecular ratio, stirring rate, temperature, and seed coefficient on the precipitation ratio and particle size of Al(OH)3. The results show that alkali concentration, molecular ratio, temperature, and seed coefficient are key factors influencing seeded precipitation. Furthermore, the process is optimized by using these four identified factors as variables. A 9L(34) orthogonal experiment determines optimal conditions for maximizing the precipitation ratio and achieves the desired average particle size. Under the optimal condition of 200 g L−1 alkali concentration, 1.5 molecular ratio, 1.0 seed coefficient, and 343.15 K temperature, the precipitation ratio reaches 54% and the average Al(OH)3 particle size is 114 µm. Further work is required to scale up this optimized seeded precipitation process and evaluate applications of the Al(OH)3 product. [ABSTRACT FROM AUTHOR]

Reticulated ceramic filters play an important role in the reduction of non-metallic inclusions in molten steel, which can improve the quality of steel products. In this work, periclase-magnesium aluminate spinel ceramic filters with Al 2 O 3 and TiO 2 functional coatings were fabricated by using microporous MgO powder, respectively. The effects of the functional coatings on their microstructure, properties and purification capacity on molten steel were studied. The filter with Al 2 O 3 functional coating exhibited the best mechanical properties owing to the good rheological properties of the coating slurry, as well as the formation of in-situ spinel layer connection between the Al 2 O 3 functional coating and the microporous MgO layer of the filter substrate. Compared with the filters without functional coating or with TiO 2 functional coating, the filter with Al 2 O 3 functional coating made more Al 2 O 3 inclusions deposit on the filter surface by physical adsorption due to the same chemical composition between the functional coating and inclusions, which significantly improved the adsorption capacity of filter for Al 2 O 3 inclusions in molten steel. Overall, the filter with Al 2 O 3 functional coating had the highest cold compressive strength of 1.4 MPa, a residual retention of cold compressive strength after thermal shock of 65.71 % and an efficiency of 36.56 % in reducing the total oxygen content of the steel. [ABSTRACT FROM AUTHOR]

Lithium‐containing components in batteries, electronics, and renewable energy pose material and waste challenges. Ongoing research focuses on eco‐friendly recycling, emphasizing electrostatic separation as a method to recover, for instance, lithium, especially in battery recycling. This study investigates forced dry triboelectric charging and electrostatic separation of powdered materials, with a focus on the charging behavior of lithium aluminate and talcum. The electrostatic separation efficiency for a blend of powders is also evaluated. Collected samples are analyzed via inductively coupled plasma‐mass spectrometry testing to assess component enrichment. Results show successful lithium enrichment from a talcum‐lithium aluminate mixture, highlighting significant separation success. [ABSTRACT FROM AUTHOR]

The oxidative coupling of methane (OCM) provides a direct route to transform methane into higher value products. The alkali metal tungstate catalysts have demonstrated high selectivity towards C2 products, ethane (C2H6) and ethylene (C2H4). However, the severe sintering of the SiO2 support limits the reaction rate requiring active site densification to compete with unselective gas phase combustion reaction especially at high pressure operations. This work studies alkaline earth metal oxides as supports for K2WO4 catalysts to maintain comparatively high surface area under OCM conditions. Among Mg, Ca, and Sr aluminates, the K2WO4/MgAl2O4 catalyst exhibited the highest C2 yields. To achieve high C2 product selectivity, a relatively large loading of K2WO4 (20 wt %) was required likely to cover the unselective surface sites of MgAl2O4 support. The catalyst further showed high levels of stability when utilized at high pressures (0.9 MPa) for over 60 h, without any change in product selectivity. The Mn/K2WO4/MgAl2O4 showed multifold higher CH4 conversion rate, compared with the SiO2 counterpart. The findings showcase the potential of the MgAl2O4 support as a viable candidate for alkali metal tungstate catalysts for OCM, which introduces high density of active components in given volume in the reactor, which induces high contribution of the catalyst relative to the pure gas phase oxidation. [ABSTRACT FROM AUTHOR]

Spinel nickel aluminate samples are doped with various percentages of FexOy nanoparticles (1, 5, and 10%) wherein FexOy i.e. Fe2O3 and Fe3O4, are tested as a catalyst for the partial oxidation of methane. The as-synthesized nanocomposite materials were characterized by XRD, FTIR, and N2 adsorption–desorption techniques and the surface morphology was examined by HRTEM. The reduction behavior and the basicity were measured using H2-TPR and CO2-TPD techniques. The synthesized nanocomposites exhibit superior catalytic activity towards the partial oxidation of methane. The nanocomposite with 5% FexOy doping exhibited the highest catalytic activity (68%) at 600 °C along with the highest H2 selectivity (32%) among the 3 nanocomposites. Conversion of methane was increasing gradually and the time-on-stream of 4 h displayed higher activity and a stable profile when the reaction temperature was set to 600 °C. [ABSTRACT FROM AUTHOR]

Mechanically reliable photoluminescent bricks were prepared from polyurethane (PUR) by reinforcement with electrospun glass nanofibers (EGNF). To enhance the mechanical qualities of the PUR sheets, EGNF were electrospun and applied to the PUR sheets as a reinforcement agent. We physically incorporated nanoparticles of rare-earth doped strontium aluminate (NRSA) into EGNF@PUR bricks to create photoluminescent and photochromic properties. In order to confirm the transparency of EGNF@PUR with the ability to change color to greenish beneath ultraviolet irradiation, both photoluminescence spectra and CIE (Commission Internationale de l'Eclairage) Lab coordinates were examined. When irradiated at 365 nm, an emission peak was monitored at 519 nm. With low concentrations of NRSA, the emission characteristic of the EGNF@PUR hybrid bricks was immediately reversible, revealing fluorescence emission. Persistent emission with delayed reversibility was observed in EGNF@PUR when using high concentrations of NRSA. Examining the morphological properties of NRSA and EGNF using transmission electron microscopy (TEM) revealed diameters of 4-9 nm and 75-125 nm, respectively. Both EGNF and EGNF@PUR bricks were subjected to morphological analysis using different analytical methodologies. As the concentration of NRSA rose, the material became more hydrophobic and more ultraviolet-protective. When compared to NRSA-free EGNF@PUR bricks, those containing NRSA had superior scratch resistance. [ABSTRACT FROM AUTHOR]

In the present study, commercially available different sources of magnesia and alumina were used to produce reaction sintered magnesium aluminate spinel (MgAl2O4). Initially, spinel with stoichiometric composition was prepared from three different sources of Al2O3 and two sources of MgO and then the effect of dysprosia (Dy2O3) in a concentration range of 1–4 wt.% on the sintered properties of spinels was studied in the temperature range of 1550–1650°C. The densities of the doped compositions were higher compared with the undoped ones, and the maximum density was found for the 1 wt.% Dy2O3‐doped samples. Phase analysis and microstructural studies revealed that formation of dysprosium aluminum garnet (Dy3Al5O12) phase along the intergranular positions, which served as grain‐growth inhibitors and improved densification. Further, 1 wt.% Dy2O3‐doped compositions also revealed better flexural strength and retained strength post thermal shock values than undoped spinel. [ABSTRACT FROM AUTHOR]

Thermometry of thermal barrier coatings (TBCs) is essential for designing effective thermal management systems and prolonging the service life of components in aeroengines and gas turbines. However, conducting on-line thermometry in these systems is challenging because it requires physical or optical access to components during operation. A promising alternative is off-line thermometry, in which phosphorescent thermal-history sensors are used to record exposure temperatures after operation. In this study, we synthesized europium (III)-ion-doped barium aluminate (BaAl 2 O 4 :Eu3+) via a solid-state reaction and confirmed its ability to function as a thermal history sensor. Subsequently, we developed a new thermal-sensing strategy based on the self-reduction of Eu3+ to Eu2+ in a BaAl 2 O 4 :Eu3+ phosphor exposed to high temperatures (900–1300 °C) in ambient air. The Eu3+ concentration decreased as the heat exposure temperature increased due to self-reduction of Eu3+ to Eu2+, which irreversibly changed the phosphorescence of BaAl 2 O 4 :Eu3+, i.e., its spectra, the ratio of the phosphorescence intensities of Eu3+ and Eu2+, and the lifetime of Eu3+. As the heat exposure temperature increased, the ratio of the phosphorescence intensities of Eu3+ and Eu2+ monotonically decreased due to self-reduction, whereas the phosphorescence lifetime of Eu3+ initially gradually increased until the heat exposure temperature reached 1000 °C because of the degeneration of concentration quenching, and then decreased as the temperature exceeded 1000 °C because of the degeneration of lattice distortions. This demonstrates that heat exposure temperatures exceeding 1000 °C can be quantitatively evaluated through off-line analysis of Eu3+ and Eu2+ phosphorescence intensity ratios and Eu3+ lifetime at room temperature. Thus, BaAl 2 O 4 :Eu3+, a self-reducing phosphor, is a potential sensor for off-line thermometry of TBCs. [ABSTRACT FROM AUTHOR]

Stably luminescent strontium aluminates (SAO) co-doped with Eu2+ and Dy3+ were synthesized by a solid-state reaction for digital optical data storage applications. The SAOs were composed of monoclinic SrAl2O4 and hexagonal SrAl12O19 in nearly identical composition ratios. The substitution of Dy3+ for Sr2+ decreased the high binding energy components of Sr 3d and Al 2p while decreasing the phosphor luminescence. However, co-doping with Dy3+ improved the persistent luminescence of Eu2+. When the phosphor was heated to 110°C, the luminescence intensity decreased by only 10.6%. Further, no change in the emission color was noted when the phosphor was placed in water and heated at 50°C for 20 min. The luminescence intensity of the phosphor changed with the switching of the optical stimulation; the higher the switching frequency, the better the optical storage performance. This indicates the promise of the polymorph SAO:Eu2+, Dy3+ for digital optical data storage applications utilizing near-infrared excitation. [ABSTRACT FROM AUTHOR]

The results of a study of the GdAlO3–SrO section, which is one of the internal sections of the Gd2O3–SrO–Al2O3 ternary system, are presented. In the GdAlO3–SrO section three triple compounds, Gd2SrAl2O7, GdSrAlO4, and GdSr2AlO5, crystallizing in the tetragonal system, are synthesized. The data on the mechanism of their solid-phase formation are systematized. The results of the thermal stability of perovskite-like phases in the GdAlO3–SrO system are presented in a wide temperature range of 1100–1800°C in air. The congruent character of the melting of Gd2SrAl2O7, GdSrAlO4, and GdSr2AlO5 complex oxides is established and their melting temperatures are determined. [ABSTRACT FROM AUTHOR]

Group-II aluminates have a spinel structure widely used for energy storage purposes due to high thermal, chemical, and dielectric properties. These applications can be enhanced by the substitution of a small content of magnetic transition metals. In this study, MxSr1-xAl2O4 (where M = Mn, Fe, and Co and x = 0.1) compositions were successfully synthesized via a well-known hydrothermal technique. The uniform nano-sized sheets with the monoclinic structure without any impurity phase were confirmed by X-ray diffraction and field emission electron microscopy analysis. The qualitative and quantitative analysis studies reveal the presence of expected elements with their respective wt.% ratio observed through energy dispersive spectroscopy analysis. A clear non-magnetic and paramagnetic behavior with high saturation and remnant magnetization was observed from the M-H loop at room temperature for pure and transition metal (Mn, Fe, and Co) substituted Sr-aluminate samples. The highest values Ms, Mr, and Hc, i.e., 0.020 emu·g−1, 0.005 emu·g−1, and 0.026Oe are recorded for Co-doped SrAl2O4 composition. The dielectric studies reveal an increase in the value of the dielectric constant and a decrease in energy loss factor from 0.27 to 0.18 confirming the stability of the structure, and enhancement in ferroelectric parameters making these suitable candidates for energy storage applications. [ABSTRACT FROM AUTHOR]

This work involves the introduction of niobium oxide into lanthanum aluminate (LaAlO3) via a conventional solid-state reaction technique to yield LaAlO3:Nb (LaNbxAl1−xO3+δ) samples with Nb5+ doping levels ranging from 0.00 to 0.25 mol%. This study presents a comprehensive investigation of the effects of niobium doping on the phase evolution, defect control, and reflectance of LaNbxAl1−xO3+δ powder. Powder X-ray diffraction (XRD) analysis confirms the perovskite structure in all powders, and XRD and transmission electron microscopy (TEM) reveal successful doping of Nb5+ into LaNbxAl1−xO3+δ. The surface morphology was analyzed by scanning electron microscopy (SEM), and the results show that increasing the doping concentration of niobium leads to fewer microstructural defects. Oxygen vacancy defects in different compositions are analyzed at 300 K, and as the doping level increases, a clear trend of defect reduction is observed. Notably, LaNbxAl1−xO3+δ with 0.15 mol% Nb5+ exhibits excellent reflectance properties, with a maximum infrared reflectance of 99.7%. This study shows that LaNbxAl1−xO3+δ powder materials have wide application potential in the field of high reflectivity coating materials due to their extremely low microstructural defects and oxygen vacancy defects. [ABSTRACT FROM AUTHOR]

Mechanoluminescent (ML) materials, which have the ability to convert mechanical energy to optical energy, have found huge promising applications such as in stress imaging and anti-counterfeiting. However, the main reported ML phosphors are based on trap-related ones, thus hindering the practical applications due to the requirement of complex light pre-irradiation process. Here, a self-recoverable near infrared (NIR) ML material of LaAl1-xO3: xCr3+ (x = 0.2 %, 0.4 %, 0.6 %, 0.8 %, 1.0 %, and 1.2 %) has been developed. Based on the preheating method and corresponding ML performance analysis, the influences of residual carriers are eliminated and the detailed dynamic luminescence process analysis is realized. Systematic experiments are conducted to reveal the origin of the ML emissions, demonstrating that ML is dictated more by the non-centrosymmetric piezoelectric crystal characteristic. In general, this work has provided significant references for exploring more efficient NIR ML materials, which may provide potential applications in anti-counterfeiting and bio-stress sensing. [ABSTRACT FROM AUTHOR]

The increasing attention on the unique properties of oxyhydride materials motivates the exploration of their potential applications in optical fields, and the theoretical studies of their luminescence properties are still under progress. Here, we report the experimental and theoretical high-pressure photoluminescence (PL) studies on Eu-activated Sr3–xAxAlO4H (A = Ca and Ba; x = 0 and 1) oxyhydride materials. Under hydrostatic pressures from ambient pressure up to 6.41 GPa, the luminescence band in all the samples exhibits redshift with increasing pressure and the highest energy-shift rate of −101.85 cm−1/GPa was observed in Sr3AlO4H:Eu2+. The asymmetric bands were deconvoluted into two peaks corresponding to the two Eu sites with different coordination environments. Although the shift rates of Eu2+ centers in Sr3AlO4H are not remarkable as expected for the large compressibility of hydride ion ligands, their pressure-dependences in opposite directions were successfully reproduced by constrained density functional theory calculations using the advanced on-site Coulomb interaction parameter (U) determination method. The lower shift rate as seen in conventional oxide phosphors indicates that Eu-4f and 5d level positions are determined by the interaction with less compressive oxide ion ligands. Therefore, the high shift rate required for pressure sensing applications is expected in more hydrogen-rich oxyhydrides and related hydride compounds. [ABSTRACT FROM AUTHOR]

Deciphering the structure-property relations of densified oxide glasses is a problem of longstanding interest. For example, it is important for understanding the fracture mechanism under sharp contact loading as well as fabricating glasses with tunable physical characteristics. Recent advances in both experimental and simulation techniques have prompted research breakthroughs in understanding the response of glasses to high pressure. In this Perspective, we first briefly discuss the facilities for the high-pressure treatment of glasses, including in situ and ex situ investigations. The recent work on pressure-induced structural changes of archetypical oxide glass families (silicates, germanates, borates, aluminates, phosphates) is discussed and compared to the changes in macroscopic properties induced by densification, as densification treatment can be used to produce oxide glasses with improved hardness, stiffness, and toughness. We also discuss the new insights from atomistic simulations combined with topological analysis tools to unravel the densification mechanism of oxide glasses on the medium-range order length scale. Drawing on these recent studies, we clarify how densification treatment has proved to be an important tool to both understand the disordered nature of glasses and tune their physical properties, although many open questions and challenges remain that require further investigations. [ABSTRACT FROM AUTHOR]

Multicomponent oxides have received significant recent attention due to their potential for improved property tunability. In simple structures, compositionally complex oxides can be stabilized by increased configurational entropy and are sometimes called "high entropy" ceramics. In phases with multiple cation sublattices or complex stoichiometries, it is more difficult to achieve high configurational entropy. However, there is limited knowledge about the factors influencing stability and solubility limits in many systems. This study investigated the limits on the stability of rare earth (RE) aluminates containing mixtures of RE cations including Gd, La, Nd, Yb, and Y in cases where (i) a fixed RE:Al ratio attempts to constrain the material into a single‐phase aluminate or (ii) a two‐phase aluminate, and in equilibrium with RE zirconates that readily dissolve multiple RE3+. The results show that it is difficult to form single‐phase, equimolar mixed‐RE aluminates encompassing a range of RE3+ sizes. Instead, the RE3+ selectively partition into specific phases based on RE‐size trends in the constituent binary systems. The results are discussed in terms of the phase stability and cation partition trends and potential applications. [ABSTRACT FROM AUTHOR]

SrO has attracted attention for its use as a heterogeneous catalyst in producing biodiesel from transesterification owing to its high alkaline character and low solubility in methanol. In studies conducted in this decade, reaction conditions such as the methanol–oil molar ratio, reaction time, catalyst loading and temperature have been optimized in these systems. Furthermore, several works have been carried out to improve the physicochemical properties and increase the leaching resistance of this material. Thus, the new trends in using SrO in transesterification reactions are that this oxide should be supported or combined with Al2O3, TiO2, ZrO2, or Fe2O3, CaO, metal–organic frameworks, zeolites or La2O3. It has been observed that strontium can form mixed crystalline phases with these oxides by increasing the (M2+O2−) pairs and Lewis basicity of the oxygens, resulting in increased basicity and catalytic activity. Moreover, the transition metal oxides may provide Lewis acidity. Hence, these strontium‐containing catalytic systems have demonstrated a bifunctionality that can perform esterification and transesterification reactions at the same time. In addition, the combination of these oxides decreases the leaching of the catalyst. Other materials such as metal–organic frameworks, zeolites, and La2O3 have been studied as SrO supports, showing that they can be used in oil transesterification reactions. [ABSTRACT FROM AUTHOR]

Anionic donor-functionalized NHC (N-heterocyclic carbene) complexes of Al are rare. We report one such case here, an NHC-aryloxido AlMe2 complex [Al(L)Me2] (2), following a stepwise synthesis from the proligand [HO-4,6-tBu2-C6H2-2-CH2{CH(NCH＝CHNAr)}]Br [LH2Br; Ar = 2,6-iPr2-C6H3 (Dipp)] and AlMe3via the zwitterionic intermediate [Al(LH)Me2Br] (1). The ligand's flexibility in 2 is evident from the conformational fluxionality revealed by VT-1H NMR spectroscopic analysis. The ∠O–Al–C (ca. 100.5°) bite angle is also wider than the ∠O–Ti–C (ca. 80.6°) as seen in our recently reported Ti complex [Ti(L)(NMe2)2Br]. DFT analysis showed that the CNHC–Al bond is significantly ionic, as is the CNHC–Ti bond. Both 1 and 2 are active in the ring-opening polymerization (ROP) of ε-caprolactone (CL). 2, similar to [Ti(L)(NMe2)2Br], exhibits bifunctional MLC-type monomer activation, but only at an elevated temperature. However, the 2/BnOH combination is catalytically active at room temperature, likely through a zwitterionic [Al(LH)Me2(OBn)]. The 1/BnOH combination follows a similar mechanism but surprisingly at a faster rate. [ABSTRACT FROM AUTHOR]

Deep red phosphors have attracted much attention for their applications in lighting, medical diagnosis, health monitoring, agriculture, etc. A new phosphor host material based on fluorine-doped lithium aluminate (ALFO) was proposed and deep red emission from Cr3+ in this host material was demonstrated. Cr3+ in ALFO was excited by blue (~410 nm) and green (~570 nm) rays and covered the deep red to near-infrared region from 650 nm to 900 nm with peaks around 700 nm. ALFO was a fluorine-doped form of the spinel-type compound LiAl5O8 with slightly Li-richer compositions. The composition depended on the preparation conditions, and the contents of Li and F tended to decrease with preparation temperature, such as Al4.69Li1.31F0.28O7.55 at 1100 °C, Al4.73Li1.27F0.17O7.65 at 1200 °C, and Al4.83Li1.17F0.10O7.78 at 1300 °C. The Rietveld analysis revealed that ALFO and LiAl5O8 were isostructural with respect to the spinel-type lattice and in a disorder–order relationship in the arrangement of Li+ and Al3+. The emission peak of Cr3+ in LiAl5O8 resided at 716 nm, while Cr3+ in ALFO showed a rather broad doublet peak with the tops at 708 nm and 716 nm when prepared at 1200 °C. The broad emission peak indicated that the local environment around Cr3+ in ALFO was distorted, which was also supported by electron spin resonance spectra, suggesting that the local environment around Cr3+ in ALFO was more inhomogeneous than expected from the diffraction-based structural analysis. It was demonstrated that even a small amount of dopant (in this case fluorine) could affect the local environment around luminescent centers, and thus the luminescence properties. [ABSTRACT FROM AUTHOR]

Weakly coordinating anions (WCAs) are used throughout chemistry to minimise cation‐anion interactions in the solid and solution states. The ability to suppress ion‐pairing has important bearings ‐ or impacts on the properties of materials, on single‐site catalysis and on ionic conductivity. Fluorinated alkoxy aluminates (containing [Al(ORF)4]− anions) are an attractive class of WCA owing to their high thermodynamic stability, stemming from strong aluminium‐oxygen bonds, and the ability to tailor their steric and electronic properties by changing the organic substituents (R). This work explores the structural and electrochemical properties of sodium tetrakis(hexafluoroisopropyloxy)aluminate, Na[Al(hfip)4] ⋅ xDME (hfip=hexafluoroisopropyloxy, OiPrF, DME=1,2‐dimethoxyethane, x=3 or 1). When solvated with one DME molecule, Na[Al(hfip)4] ⋅ DME is a room‐temperature solvated ionic liquid, with an activation energy of conduction of 0.4 eV. Both Na[Al(hfip)4] ⋅ 3DME and Na[Al(hfip)4] ⋅ DME have been studied as electrolyte salts for sodium‐ion batteries, where sodium‐ion cycling proceeds but with low capacity retention. [ABSTRACT FROM AUTHOR]

Broadband near-infrared (NIR) phosphors, as key materials in NIR phosphor-converted light-emitting diodes (pc-LEDs) for emerging applications, have recently attracted considerable attention. Herein, by selecting a comprehensive engineering strategy of co-substituting [Al3+-Al3+] with [Mg2+-Ge4+] units and increasing Cr3+ concentration, a novel Cr3+-doped ZnAl 1.16 Mg 0.4 Ge 0.4 O 4 (ZA(MG) 0.4 :2 at.%Cr3+) phosphor with continual broadband NIR emission was synthesized. The site occupation of Mg2+/Ge4+ in ZnAl 2 O 4 is unraveled by Rietveld structure refinement and density functional theory (DFT) calculations. According to the photoluminescence behaviors, the formed defect clusters of Zn Al '-Cr3+-Ge Al · and Mg Al '-Cr3+-Ge Al · can not only introduce shallow defects to serve as new traps to obtain long-persistent luminescence but can also enhance the emission intensity at ∼689 nm and ∼694 nm. The quantity and scale of Cr3+-Cr3+ pairs and Cr3+ in distorted sites, which can improve the thermal quenching resistance and emission intensity in the range of 700–800 nm, can be accurately regulated by varying the concentration of Cr3+. Under 387 nm excitation, the designed material exhibits intensive NIR emission from 685 to 750 nm with a wide full-width at half maximum (FWHM) of 95 nm. The electroluminescence spectrum and potential applications of the NIR pc-LED prepared using ZA(MG) 0.4 :2 at.%Cr3+ phosphor are also reported. The results promise a feasible strategy to develop NIR phosphors as NIR pc-LEDs lighting sources for applications in non-destructive detection and anti-counterfeiting. [ABSTRACT FROM AUTHOR]

The spinel type of cobalt aluminate was achieved by an ultrasonic-assisted coprecipitation method. The morphologies of the cobalt aluminate nanoparticles were enhanced by the capping agent effect. The samples were characterised with the techniques of colour analyses, X-ray diffraction (XRD), UV-Vis spectroscopy, Brunauer-Emmett-Teller (BET), and scanning electron microscope (SEM). The characteristic blue colour of the powders was characterised by the b* values ranging from −42 to −51. The prepared compounds were identified as cubic forms of spinel (CoAl2O4). The BET analysis results indicated the highest surface area of 14.35 m2/g for the PVP-capped CoAl2O4. In comparison with the traditional methods, smaller particles were synthesised following the SEM analyses. The samples at different particle sizes and distributions were utilised in the removal of Congo red (CR) dye from wastewater by using a batch adsorption route. The sample prepared by the PVP capping agent was the most effective in CR adsorption. Among the applied isothermal and kinetic analyses, the adsorption mechanism could be explained by the Langmuir isothermal method (R2 = 0.9996 and RL = 0.7280) and the intraparticle diffusion kinetic model (R2 = 0.9650–0.9870). [ABSTRACT FROM AUTHOR]

[Display omitted] Aluminate ionic liquid [Et 3 NH]+[Al 2 Cl 7 ]− was found to be an effective catalyst for the reactions of haloadamantanes with trimethylsilyl azide to produce the corresponding azido- adamantanes in 92–98% yields. Using 'click chemistry', the thus obtained azidoadamantanes were reacted with terminal alkynes under thermal or microwave conditions to cleanly afford the expected 1,4-disubstituted 1,2,3-triazoles some of which were new. [ABSTRACT FROM AUTHOR]

Copper (Cu2+)-and-magnesium (Mg2+)-doped Zinc aluminate ZnAl2O4 is a promising material with diverse applications in electronic and energy storage devices. In this study, the synthesis of Zn0.9MxAl2O4 (M = Cu2+ and Mg2+; x = 0.00 and 0.10) was conducted via the sol–gel combined combustion technique. The structural, spectral, optical and dielectric parameters of the synthesized spinel aluminates were analysed to explore the substitution effect of Cu2+ and Mg2+ content. The formation and crystallinity analyses of the single-phase cubic spinel structure in the synthesized spinel aluminates were confirmed using XRD patterns. The lattice parameter and grain size were ascertained from the XRD data. The crystallite size of Cu2+ and Mg2+ substituted into ZnAl2O4 using Scherrer's formula was found to be around 22 nm. The spinel structure formations in the prepared spinel aluminates were ascertained through an FT-IR study. The UV-Vis spectra exhibited a broad absorption band in the UV-Vis region, indicating the presence of electronic transitions. The band gap energy of the prepared aluminates was estimated from the absorption edge, with values varying between 2.90 eV and 3.03 eV, revealing its suitability for optoelectronic applications. Measurement of the dielectric parameters was performed in the frequency range of 100 Hz to 20 MHz at temperatures ranging from 30 °C to 250 °C. The dielectric constant (ε′) and dielectric loss (ε") were determined as a function of frequency at different temperatures. The results showed that the dielectric constant decreased with increasing frequency for all the observed temperatures, while the dielectric loss exhibited a peak at a specific temperature. The conductivity results indicate that the conduction mechanism occurred due to polaron hopping. The Arrhenius relation was adopted to calculate the activation energies Ea for all the samples, and the values were between 0.70 eV and 0.38 eV. The obtained results were discussed and interpreted. These findings contribute to our understanding of the electrical behaviour of doped zinc aluminate materials and their useful applications in different electronic and energy systems. [ABSTRACT FROM AUTHOR]

The effect of cathodic polarization on plasma electrolytic oxidation (PEO) of the refractory metal of tantalum is investigated in 10 g/l NaAlO 2 +2 g/l KOH under 1000 and 100 Hz. Ceramic coatings are formed under various cathodic-to-anodic current densities ratios (R = jc/ja) of 0, 0.6, 1.3 and 2.3. For PEO under 1000 Hz, the plasma discharges intensify with the increase of R from 0 to 1.3, with optical emission from Ta being detected at later stage of PEO under cathodic polarization. However, excessive R ratio of 2.3 has caused early extinguishment of the plasma discharges. Correspondingly, thicker coatings are formed as the R ratio increases from 0 to 1.3, and the coating under R = 1.3 exhibits a most porous outer layer. A thin and compact coating is formed under R = 2.3. It is also found that the application of cathodic polarization increases the Na content in the resultant coatings, with a new crystalline phase NaTaO 3 being formed under R = 2.3. Cathodic polarization also decreases the corrosion resistance of the coatings. Surface wettability tests show that the coatings formed under R = 1.3 are the most hydrophilic. PEO under 100 Hz shows some differences in discharge and coating formation. Larger sized discharges are also observed at the later stage under R = 0.6, but Ta species are detected at a delayed time. For the R values of 1.3 and 2.3, patches of soft sparking occur on the sample surface, leading to non-uniform coatings. This study shows that both cathodic polarization and frequency significantly affect the PEO process. Moreover, compared with the PEO of Al, tantalum responds quite differently to cathodic polarization. Mechanisms of coating formation have been illustrated: Protons and other cations are attracted by cathodic electric field into the coatings, where they undergo a series of reactions to significantly affect the PEO behaviors. [ABSTRACT FROM AUTHOR]

Zinc aluminate nanomaterial provide a potential candidate for photocatalytic and sensor applications. Using biofuel (banana peel powder), zinc aluminate was synthesized by SCM (solution combustion method) in the current study. The properties of the phase structures, chemical composition, morphologies, and photocatalytic sensors were characterized by utilizing powder X-ray diffraction, scanning electron microscope, CH analyzer, UV-Visible spectroscopy, and photocatalytic reactor. Indigo Carmine (IC) dye degradation under UV light was used to assess the photocatalytic activity. The results showed that zinc aluminate makes a superior photocatalyst for degrading organic dyes like indigo carmine. In a potassium hydroxide electrolyte medium, zinc aluminate was also an effective substance for paracetamol and lead metal sensing. The results confirm that the novel material could be used for various industrial applications. [ABSTRACT FROM AUTHOR]

For the first time, high‐entropy rare‐earth monoclinic aluminate crystals were grown via directional solidification using the micro‐pulling‐down method. Five high‐entropy compositions were formulated with a general formula RE4Al2O9, where RE is an equiatomic mixture of five rare‐earth elements. The rare‐earth elements included were Lu, Yb, Er, Y, Ho, Dy, Tb, Gd, Eu, Sm, Nd, and La. High‐temperature powder X‐ray diffraction and Rietveld structure refinement indicated that all crystals were a single monoclinic phase and that rare‐earth average ionic radius did not affect phase purity. At room temperature, the refined lattice parameters increased consistently with increasing average ionic radii of the five compositions. One of the crystals had a typical high‐temperature phase transition of single‐RE RE4Al2O9 in the range of 1100–1150°C, which consisted of a lattice contraction upon heating. Differential scanning calorimetry indicated a thermal event corresponding to that phase transition. Electron probe microanalysis revealed Al‐rich inclusions on the surface of the crystals. Crystals containing Tb had dark surface features that became lighter after annealing in a reducing atmosphere, which indicated that Tb4+ may be responsible for the dark features. [ABSTRACT FROM AUTHOR]

Barium aluminate ceramics with iron (III) oxide and lithium hydroxide additives was obtained by solid-phase synthesis. It has been established that high-temperature treatment in an oxidizing environment contributes to the production of vacuum-tight samples that meet the "absolutely impermeable" tightness criterion, while having a density of 3.75 g/cm3, compressive strength of 597.1 MPa, and electrical conductivity ranging from 1.50·10 – 7 to 1.05 × 10–4 S/cm (at 90 – 300°C). [ABSTRACT FROM AUTHOR]

Non-oxidative propane dehydrogenation (PDH) is becoming an increasingly important approach to propylene production, while cobalt-containing catalysts have recently demonstrated great potential for use in this reaction, providing efficiencies comparable to those of industrially employed Pt- and Cr-based catalytic systems. It is therefore essential to clarify the nature of their active sites, especially since contradictory opinions on this issue are expressed in the literature. In this study, efforts were made to determine the state of Co in cobalt aluminates (CoAl2O4-Al2O3) responsible for PDH under typical operating conditions (600 °C, 1 atm). It is shown that the catalyst with a low cobalt content (Co/Al = 0.1) ensured the highest selectivity to propylene, ca. 95%, while maintaining significant propylene conversion. The structural motifs such as cobalt oxide and metallic cobalt nanoparticles, in addition to tetrahedral Co2+ species in the CoAl2O4 spinel system, were evaluated as potential active-site ensembles based on the obtained catalytic performance data in combination with the XRD, H2-TPR, TEM and XPS characteristics of as-synthesized, spent and spent–regenerated catalysts. It is revealed that the most likely catalytic sites linked to PDH are the Co-oxide forms tightly covering alumina or embedded in the spinel structure. However, additional in situ tuning is certainly needed, probably through the formation of surface oxygen vacancies rather than through a deeper reduction in Co0 as previously thought. [ABSTRACT FROM AUTHOR]

In this review we will present several research papers pertaining to white colour (or other) emission from Dy3+ doped and undoped phosphor materials. The search for a single component phosphor material that could deliver high quality white light under UV or near UV excitation is an area of active research for commercial purposes. Amongst all rare earth elements Dy3+ is the only ion that could deliver simultaneously blue and yellow light under UV excitation. In optimizing the Yellow/Blue emission intensity ratios, white light emission can be realized. Dy3+ (4f9) displays approximately 4 emission peaks at around 480 nm, 575 nm, 670 and 758 nm corresponding to transitions from the metastable 4F9/2 state to various lower states, such as 6H15/2 (blue), 6H13/2 (yellow), 6H11/2 (red) and 6H9/2 (brownish red), respectively. In general, the hypersensitive transition at 6H13/2 (yellow) is electric dipole in nature and becomes prominent only when Dy3+ ions are positioned at low symmetric sites with no inversion symmetry in the host matrix. On the other hand, the blue magnetic dipole transition at 6H15/2 becomes prominent only when Dy3+ ions are positioned at highly symmetric sites in the host material with inversion symmetry. Despite the white colour emission from the Dy3+ ions, these transitions are mainly associated with parity forbidden 4f -4f transitions, the white light produced maybe diminished at times, hence the need to include a sensitizer to bolster the forbidden transitions experienced by Dy3+ ions. In this review we will focus on the variability of the Yellow/Blue emission intensities in different host materials (phosphates, silicates, and aluminates) from Dy3+ ions (doped or undoped) by studying their photoluminescent properties (PL), their CIE chromaticity coordinates and correlated colour temperature (CCT) values for white colour emissions that is adaptable to different environmental conditions. [ABSTRACT FROM AUTHOR]

The purpose of this research is to examine the effect of strontium aluminate (SrAl2O4) in copper samples on phosphorescence and tarnish resistance properties. The samples were fabricated by powder metallurgy using the compression moulding technique and then sintered in argon atmosphere. Phosphorescence, hardness, microstructure and tarnish resistance were studied. In the process of the compression moulding, the samples contain 100, 90, 80 and 70 percent of copper powder, by weight, with the addition of 0, 10, 20 and 30 percent of strontium aluminate, by weight, respectively. Polyvinyl alcohol (PVA) was used as a binder and mixed with copper and strontium aluminate powder to produce the green specimens using a hydraulic machine. Then, the green samples were sintered at 900 °C for one hour. After sintering, PVA was eliminated and the samples became denser. It was found that the hardness of the sample without strontium aluminate (30.5 HV) is higher than that of the sample with 10% of strontium aluminate addition (12.84 HV). Furthermore, copper samples containing strontium aluminate were fluorescent under ultraviolet at 517 nm. The sample with the largest amount of strontium aluminate (70Cu-30SrAl2O4) has higher phosphorescence than 90Cu-10SrAl2O4. In sulphur atmosphere, the tarnish resistance was found to be improved when strontium aluminate was added into copper. The colour difference (DE*) of 100Cu, which has no strontium aluminate, was 6.42 and higher than that of 90Cu-10SrAl2O4 (DE*= 3.5), 80Cu-20SrAl2O4 (DE*= 1.37), and 70Cu-30SrAl2O4 (DE*= 0.49), when testing in sulphur atmosphere for 30 min. 70Cu-30SrAl2O4, containing the highest amount of strontium aluminate, has the least colour changing on its surface resulting in the resistance in tarnishing. [ABSTRACT FROM AUTHOR]

The influence of process parameters in the three-stage purification of aluminate solution from the Bayer process and aluminum hydroxide was considered in this paper. One of the ways of purification is treating the aluminate solution in order to reduce the concentrations in the starting raw material (solution) and then treating the aluminum hydroxide at a certain temperature and time in order to obtain an alumina precursor of adequate quality. The purification process itself is divided into three phases. The first phase involves the treatment of sodium aluminate with lime in order to primarily remove Ca2+ and (SiO3)2− impurities. Phase II aims to remove impurities of Zn2+, Fe2+, and Cu2+ by treatment with controlled precipitation using specially prepared crystallization centers. In Phase III, Na+ is removed by the process of hydrothermal washing of Al2O3 ∙ 3H2O. In this work, parameters such as temperature (T), reaction time (t), and concentration of lime (c) were studied in order to remove the mentioned impurities and obtain the purest possible product that would be an adequate precursor for special types of alumina. [ABSTRACT FROM AUTHOR]

The high hot strength of MgO–Cr2O3 refractory is often ascribed to its intimate aggregate/matrix bonding. For a fundamental comparison with it, ∼2 mm aggregates of MgO and Al2O3 were separately embedded in ZnAl2O4 and MgAl2O4 matrices, sintered at 1600°C, and examined. It was found that similarity of thermal expansion coefficient (TEC) between the aggregate and the matrix is critical to achieve good bonding and this is more important than the extent of interdiffusion. The TEC mismatch of ≥5.7 × 10−6 K−1 caused significant undesirable debonding in MgO aggregate/MgAl2O4 matrix sample and MgO/ZnAl2O4 despite >736 μm Zn2+ diffusion depth in the latter. Direct bonding, as inferred from a thicker interfacial reaction layer and a greater shift of the aggregate/matrix interface before and after firing, was better in MgAl2O4/ZnAl2O4 combination, followed by tabular Al2O3/ZnAl2O4 and Al2O3/MgAl2O4. Powder X‐ray diffraction indicated that the volatilization of ZnAl2O4 at 1600°C in air was negligible compared to MgO–Cr2O3. [ABSTRACT FROM AUTHOR]

Nanoscale carbon/Ca aluminate nanoplates (NC–CAS) with different NC content, orthorhombic Ca5Al6O14 and hexagonal C phases were obtained by a facile route. X-ray diffraction and electron microscopy observation show that the thickness of the nanoplates is about 50 nm. NC–CAS possesses a polycrystalline structure. The band gap of the NC–CAS decreases to 1.78 eV with increasing NC content to 5 wt.%. NC–CAS exhibit strong visible-light absorption performance owing to the NC introduction into the CAS. Results showed that 20 mL gentian violet (GV, concentration of 10 mg L−1) can be degraded over a period of 30 min using 20 mg NC–CAS with NC content of 5 wt.% under visible light. The visible-light catalytic activity of the NC–CAS for GV degradation is greatly enhanced due to the reduction of band gap and recombination efficiency of carriers. Hydroxyl radicals and holes are the main reaction active substances. NC–CAS photocatalysts are stable and highly efficient for GV degradation under visible light. [ABSTRACT FROM AUTHOR]

In this study, we report a group of alkali metal aluminates bearing bis(organoamido)phosphane ligand. The starting complex {[PhP(NtBu)2]AlMe2}Li·OEt2 (1) was prepared by stepwise deprotonation of the parent PhP(NHtBu)2 by nBuLi and AlMe3. Further derivatization of aluminate 1 was performed by the virtual substitution of lithium -{[PhP(NtBu)2]AlMe2}K (2), methyl substituents – {[PhP(NtBu)2]AlH2}Li·THF (3), modification of steric bulk and induction effects on the phosphorus atom – {[tBuP(N-2,6-iPr2C6H3)2]AlMe2}Li·(OEt2)2 (4), and phosphorus atom oxidation state {[Ph(Y)P(NtBu)2]AlMe2}Li (Y = O (5), S (6), Se (7), Te (8)). The structure causing non-covalent interactions in 1–4 were evaluated with the help of theoretical calculations and topological analysis ranging from π-electron system-metal to agostic interactions of various types. The further reactions of 1 with various nucleophiles were found to be a versatile tool for the preparation of iminophosphonamides via the formation of P–E bond (E = Si, Ge, Sn, Pb, P, and C) and followed by P(III) → P(V) tautomeric shift. [ABSTRACT FROM AUTHOR]

A series including single and mixed Ni-Co aluminates was obtained using the precursor method, with malic acid as a ligand. The malate precursors (polynuclear coordination compounds) were isolated and characterized by Fourier Transform Infrared (FTIR), Ultraviolet/Visible/Near Infrared (UV–Vis–NIR) spectroscopy, and thermal analysis. The UV–Vis–NIR spectra of the synthesized complex compounds highlighted the presence of Co2+ and Ni2+ in an octahedral environment. The thermal decomposition of these precursors led to Co1−xNixAl2O4 (x = 0, 0.1, 0.25, 0.5, 0.75, 0.9, and 1) spinels. The effect of Ni2+ substitution on the structure, morphology, and optical properties of the obtained oxides was studied with the help of different characterization tools. XRD, FTIR, and Raman spectra evidenced the formation of the spinel phase. The size of the crystallites and the agglomeration degree of the particles decrease when the nickel content increases. The band gap (BG) value is not significantly influenced by the Ni substitution. The fluorescence spectra recorded for all samples show a similar pattern, but different intensities of the emission bands. [ABSTRACT FROM AUTHOR]