The ternary metal borocarbide Al3BC3 forms plate-shaped particles having a crystallographic orientation along the c-axis and is expected to have low resistance to shear strain, similar to layered ternary carbides. This work demonstrates the first-ever synthesis of a textured polycrystalline Al3BC3 sample with anisotropic mechanical properties. The sintering characteristics of monophasic Al3BC3 were evaluated and a dense specimen with some degree of c-axis orientation was produced via spark plasma sintering. Nanoscale hardness and modulus maps of an Al3BC3 grain were generated using a nanoindenter and the hardness along the c-axis was shown to be approximately twice that in the basal plane direction. The elastic modulus along the c-axis was also approximately 1.25 times that along the basal plane, in good agreement with predicted anisotropic Young's moduli. Microstructural observations showed that fracture surfaces had laminated structures similar to those of layered ternary carbides, indicating potential applications as damage-tolerant materials.

Abstract We present a novel synthesis method for single-phase LaHfO2N via the ammonolysis of amorphous oxide-based precursors in the presence of active metal powders such as Mg and MgH2. Hf-containing oxynitrides and nitrides are difficult to synthesize by conventional ammonolysis because oxygen removal from the thermodynamically stable Hf–O framework and subsequent nitridation require strongly reducing conditions. The present active-metal-assisted ammonolysis process provides an effective synthetic strategy for such Hf-containing compounds, as demonstrated by the successful formation of phase-pure LaHfO2N. The addition of Mg or MgH2 significantly enhanced the nitridation process; increasing the Mg or MgH2 content led to a higher proportion of the perovskite LaHfO2N phase and a corresponding decrease in the residual oxide-based precursor phase, La2Hf2O7. In contrast, excessive addition of active metals induced over-reduction, resulting in colored impurity phases and enhanced optical absorption in the visible and near-infrared regions. Therefore, careful control of the active-metal content was essential for obtaining high-purity LaHfO2N powders. Optimal phase purity was achieved at precursor-to-Mg or MgH2 mixing ratios of approximately 1.0:2.0. The optical absorption of the resulting LaHfO2N powders decreased when oxide-based precursors preheated at lower temperatures were used, indicating that amorphous oxide-based precursors are effective for suppressing undesired coloration. After treatment with a dilute HNO3 solution, the perovskite phase remained intact, with no detectable impurities such as HfNx and no significant Mg substitution at the Hf sites. The photocatalytic activity of the LaHfO2N samples was evaluated under ultraviolet irradiation. The powders exhibited water-splitting capability, predominantly producing oxygen with only trace amounts of hydrogen.

This paper describes the detailed high-temperature properties of monophasic Al3BC3, including the thermal expansion characteristics of its crystal structure and thermal shock resistance. We examined the differences in physical properties between Al(3)BC(3)and Al8B4C7, which was previously thought to be Al3BC3. Compared with the thermal conductivity and CTE of Al(3)BC(3)measured in the present study, those reported for Al(8)B(4)C(7)in a previous study were higher, which is attributable to residues of Al and B. The densification of Al8B4C7 is supported by gas-phase diffusion via Al- and B-based gases or liquid, whereas the sintering of Al(3)BC(3)is dominated by solid-phase diffusion. The bending strength of Al(3)BC(3)was 226 MPa at RT and was maintained even at high temperatures. Al(3)BC(3)was found to exhibit a good thermal shock fracture resistance parameter R' of 3.3, equivalent to that of Al2O3 and substantially better than that of commonly used engineering ceramics Al(4)SiC(4 )and Al6Si2O13, mainly because of the higher thermal conductivity and lower elastic modulus of Al3BC3. The dense Al(3)BC(3)sample exhibited excellent thermal stability under N-2 and inert gas atmospheres but was easily oxidized to monophasic Al2O3 at 1300 degrees C under ambient air.

This paper describes a new, simple, and convenient method to prepare porous Al2O3 through oxidation of Al3BC3 via a direct pore-forming approach using only Al3BC3 powder as a starting material. Oxidation of Al3BC3 to Al18B4O33 started at 1050 degrees C, and a porous microstructure was formed because of the volatilization (sublimation) of B2O3 and CO2. When heated at high temperature for a long period, Al18B4O33 decomposed, accompanied by further volatilization of B2O3, resulting in monophasic Al2O3 with high porosity. The highest porosity was 71.6 %, and small pores of 1-4 mu m and large pores of 20 mu m were observed in the present study. The pore size could be controlled by varying the heat-treatment temperature. The bending strength was 34.7-36.3 MPa, which is superior to those of other porous ceramics despite the high porosity of the Al2O3. This high bending strength is likely due to the high homogeneity of the Al2O3 and the formation of a porous Al2O3 network structure in which the particles are firmly bonded together at high temperatures. The proposed method easily provides a homogeneous porous Al2O3 sample without awkward processes such as mixing or dispersing a pore-forming agent into the matrix material.

Iron(III) oxyhydroxides such as goethite (α-FeOOH) and lepidocrocite (γ-FeOOH) can be prepared via the oxidation of iron salts such as iron(II) chloride (FeCl2), iron(II) sulfate (FeSO4) and iron(III) nitrate [Fe(NO3)3] in solution based on adjusting the pH using sodium hydroxide (NaOH). Lepidocrocite can act as a precursor for the generation of maghemite (γ-Fe2O3), which exhibits unique magnetic, electrical and pharmacological properties and thus has attracted significant attention. The present study prepared lepidocrocite, goethite and the spinel structure iron oxides maghemite and magnetite (Fe3O4) without controlling the pH of the reaction solution. Specifically, both lepidocrocite and goethite were precipitated by oxidizing iron(II) chloride in solutions containing calcite (CaCO3) under air. The extent to which goethite was produced increased with increases in the calcite concentration. Spinel structure iron oxide particles with 50 nm in size were also obtained by oxidation of the same solutions under N2.

Reddish, purplish red, brownish, and lustrous gold colors can appear on the surfaces of Bizen stoneware after firing in a firewood kiln. The reddish color results from the formation of an Fe-substituted spinel [(Mg,Al,Fe)3O4] and from composite particles consisting of corundum (alpha-Al2O3) and hematite (alpha-Fe2O3). The brownish and lustrous gold colors were found to be caused by the generation of dendritic luogufengite (epsilon-Fe2O3) and 100-nm-thick hematite particles, respectively. These oxides are formed by reactions between the Bizen clay and K supplied by the firewood used as fuel. The present study reproduced these colors by heating Bizen clay pellets with K2CO3 instead of firewood in an electric furnace. Specifically, a reddish sample was obtained by heating at 1230 degrees C for 5 h in air. A brownish color appeared after annealing pellets at 1200 degrees C for 2 h in air after heating at 1230 degrees C with K2CO3 under an Ar:CO (90:10, v:v) mixture for 5 h. A lustrous gold color was produced by annealing at 900 degrees C for 2 h in air after heating in the same Ar:CO mixture. The color and chemical composition of the stoneware surfaces were found to be largely determined by the temperature at which the specimen was heated in air.

Traditionally, Japanese Bizen stoneware is produced by firing shaped green clay in a firewood kiln at approximately 1200 °C using red pine as fuel. In some cases, an ocher coloration known as goma appears on the finished product due to reactions between the clay and firewood ash. This work shows that goma results from the formation of augite [(Ca,Mg,Fe)2Si2O6], plagioclase [(Ca,Na) (Si,Al)4O8] and glassy phases. Bizen ceramicware exhibiting goma was fabricated by heating a mixture of Bizen clay with an artificial ash based on the analysis of red pine ash and produced using chemical reagents. An ocher coloration appeared on the sample surface after heating a 70:30 (on a mass basis) mixture of clay with this artificial ash at 1220 °C for 5 h followed by annealing at 1100 °C for 2 h in an electric furnace.

Bluish glass was successfully prepared by mixing oxides and carbon as a reductant into the starting materials, whereas the addition of only α-Fe2O3 into the glass raw materials provided greenish glass. The chemical state of the iron ions in the glass was likely modified from Fe3+ to Fe2+ by the reducing atmosphere caused by carbon during the heating process. Mössbauer spectra and spectrophotometric measurements indicated that the bluish glass contained a high proportion of Fe2+ (67.4%) and mainly absorbed visible light with wavelengths longer than 500 nm.

Spinel-type InGaMgO4 with a = 8.56615(3) Å was prepared by treating layered YbFe2O4-type InGaMgO4 at 6 GPa and 1473 K. DFT calculation and Rietveld analysis of synchrotron X-ray powder diffraction data revealed the inverse spinel structure with In3+:Ga3+/Mg2+ = 0.726:0.274 in the tetrahedral site and 0.137:0.863 in the octahedral site. InGaMgO4 spinel is an insulator with an experimental band gap of 2.80 eV, and the attempt at hole doping by post-annealing in a reducing atmosphere to introduce an oxygen defect was unsuccessful. This is the first report of the bulk synthesis of AB2O4 compounds with both YbFe2O4 and spinel polymorphs.

(Z)-Enediynes were successfully synthesized from a trio of terminal ethynes through consecutive three-step reactions: iodosulfonylation of ethyne with I2/PhSO2Na, followed by ethynylations of iodo and sulfonyl moieties of the resulting iodosulfonylethene via Sonogashira-Hagihara coupling and nucleophilic addition-elimination, respectively. The molecular structure of the obtained (Z)-enediyne was fully characterized by X-ray crystal structure analysis, revealing that the nucleophilic substitution of (E)-sulfonylethene with arylethynide underwent a selective stereoinversion. The (Z)-enediynes exhibited photoluminescence in both the solution and solid states (crystals and powders). Ph2N-substituted derivatives showed remarkable solvatofluorochromism, and upon replacing the solvent from toluene to acetonitrile, the emission color changed from blue to yellow.

Copper-doped ZnO nanoparticles with a dopant concentration varying from 1-7 mol% were synthesized and their structural, magnetic, and photocatalytic properties were studied using XRD, TEM, SQUID magnetometry, EPR, UV-vis spectroscopy, and first-principles methods within the framework of density functional theory (DFT). Structural analysis indicated highly crystalline Cu-doped ZnO nanoparticles with a hexagonal wurtzite structure, irrespective of the dopant concentration. EDX and EPR studies indicated the incorporation of doped Cu2+ ions in the host ZnO lattice. The photocatalytic activities of the Cu-doped ZnO nanoparticles investigated through the degradation of methylene blue demonstrated an enhancement in photocatalytic activity as the degradation rate changed from 9.89 × 10-4 M min-1 to 4.98 × 10-2 M min-1. By the first-principles method, our results indicated that the Cu(3d) orbital was strongly hybridized with the O(2p) state below the valence band maximum (VBM) due to covalent bonding, and the ground states of the Cu-doped ZnO is favorable for the ferromagnetic state by the asymmetry of majority and minority states due to the presence of unpaired electron.

Bizen stoneware is produced by firing shaped green clay in a firewood kiln at around 1200 degrees C. A purplish red color referred to as shiso happens to appear on the stoneware, but does not appear on the same stoneware heated in an electric furnace. Shiso was found to be caused by the formation of an approximately 0.5 mu m thick hematite (alpha-Fe2O3) oe layer by reaction between the Bizen clay and K supplied from the firewood. Purplish red-colored samples similar to shiso Bizen were successfully prepared by annealing at 1100 degrees C for 2 h in air after heating the Bizen clay pellets with K2CO3 at 1230 degrees C in a gas mixture of 10 vol % CO and 90 vol % Ar. (C) 2022 The Ceramic Society of Japan. All rights reserved.

This paper describes the effect of oxygen vacancies, which are induced by a carbothermal reduction process and spark plasma sintering (SPS) treatment, on the thermoelectric properties of spinel-structured zinc ferrites ZnxFe3−xO4 (0.2 ≤ x ≤ 1.0). Characterization of the oxygen-deficient ZnxFe3−xO4−δ materials revealed that Zn2+ preferentially occupy the octahedral B-sites and that valence modification of Fe3+ to Fe2+ occurred, resulting in an excess of n-type carriers at B-sites and an increased power factor. In addition, Co substitution enhanced the power factor for the materials over the entire investigated temperature range. Compared with the carbothermal reduction process, SPS treatment effectively introduced oxygen vacancies within a short time and resulted in a material with a substantially improved electrical conductivity.

Bizen stoneware is produced by firing shaped green clay in a firewood kiln at around 1200°C. The brownish and blackish colors that appear on the stoneware surface in a firewood kiln do not appear on stoneware heated in an electric furnace. The brownish color was found to be caused by the formation of single crystalline, branched, dendritic, Al-substituted ε-Fe2O3 particles. Composite particles consisting of Al-substituted ε-Fe2O3 and Fe-substituted spinel solid solution also formed on the stoneware surface. In this study, we successfully prepared brownish samples that were similar in color to Bizen stoneware by annealing at 1200°C for 2 h in air after heating Bizen clay pellets with K2CO3 at 1230°C under a 10 vol% CO and 90 vol% Ar gas mixture in an electric furnace instead of firing in a firewood kiln. Dendritic hematite particles also formed on the reproduced samples. The blackish color on Bizen stoneware fired in a firewood kiln was caused by the formation of augite [(Ca,Mg,Fe)2Si2O6], which was produced by a reaction between the Bizen clay and firewood ash.

This paper describes the formation mechanism of monophasic Al3BC3 powder with hexagonal plate-like morphology using Al, B4C, and C powders in a stoichiometric ratio. For the synthesis of pure Al3BC3 by the conventional solid-state reaction method, it is important to avoid contamination from the starting powders. Thermogravimetry-differential thermal analysis curves and quantitative analysis by inductively coupled plasma-atomic emission spectroscopy revealed that there was no vaporization of the powder mixture during heating up to 1470 °C in a high-purity argon atmosphere. We found that the phases and Al3BC3 particle morphology after heating at 1800 °C strongly depended on the mixing conditions. In the case of a two-step process (remixing and reheating the sample), particles with random morphology were observed. On the other hand, well-faceted Al3BC3 particles were predominantly formed in a one-step process that involved heating after ball-milling for 24 h.

A supersaturated spinel solid solution having a nominal compositional ratio of Mg/Al/Fe = 0.5:1.0:1.5 was prepared using a conventional solid-state reaction at 1573 K in air followed by quenching in ice water. The formula of the resulting spinel structure compound (the spinel) was determined to be (Mg0.50AlFe0.262+Fe1.243+)0.97O4 based on a Rietveld refinement and thermogravimetry, indicating a cation-deficient spinel structure having mixed valences of Fe. This spinel was found to decompose to γ-Fe2O3 and a modified, Fe-poor spinel structure compound via a spinodal decomposition below 855 K. The spinodal temperature was estimated using the sidebands appearing in X-ray diffraction patterns in addition to the temperature dependence of magnetization values. This spinodal decomposition was accompanied by the oxidation of Fe2+ to Fe3+ and produced a unique grid-like microstructure (with a grid width of approximately 25 nm) along with enhancement of the saturated magnetization of the material. A sample cooled to room temperature in a furnace after heating at 1573 K in air had a lamella structure having a width of approximately 0.1 μm and comprised particles with a mixture of γ-Fe2O3 and the Fe-poor spinel compound on their surfaces. Subsequent heating of this same material to 1373 K in air formed ε-Fe2O3 in the particles. The crystallographic relationship between ε-Fe2O3 and the modified spinel structure compound was aε // [112̅]s, bε // [1̅10]s, and cε // [111]s (where ε and s indicate the ε-Fe2O3 and spinel, respectively).

Anthrylene-and ferrocenoyl-assisted composite fabrication was achieved between visible -light absorbing anthrylene-and ferrocenoyl-substituted acetylenic dyes and single-wall carbon nanotubes (SWCNTs). The composite formation was con-firmed via UV-Vis, Raman, mass, and XPS spectra analyses. In the UV-Vis absorption spectrum, the resulting dye-SWCNT composites showed bathochromic shifts ascribable to the pi-pi interaction. One-pot fabrication of the composite was also accomplished via Cu-catalyzed dimerization of anthrylene-and ferrocenoyl-substituted terminal ethyne and the subsequent adsorption of the resulting butadiyne dye to SWCNT. We con-firmed that the dye-SWCNT composite dispersed in water by using amphiphilic poly(amidoamine)dendrimer could transfer an electron from 1-benzyl-1,4-dihydronicotinamide (BNAH) to methyl viologen dichloride (MV2+) upon irradiation with visi-ble light (>422 nm).

Control of spin alignment in magnetic materials is crucial for developing switching devices. In molecular magnets, magnetic anisotropy can be rationally controlled by varying their ligands that allow tuning of ligand field splitting energy. However, the inherent weak magnetic interaction between spins or spin-cluster results in spin reorientation (SR) occurring only at low temperatures. Here, we show that layered perovskite oxyfluoride Pb 3 Fe 2 O 5 F 2 exhibits a SR transition at 380 K, with the magnetic moments changing from perpendicular to parallel to the c -axis. It is found that the SR is caused by a ferroelectric-like phase transition, where the magnetic HOMO-LUMO interaction changes upon the structural transition due to the concerted effect of the heteroleptic FeO 5 F coordination and the steric effect of Pb. This finding indicates that the design of spin orientation by local coordination environment, which is common in molecular magnets, can be extended to extended oxides by introducing different anions.

Traditional Japanese Bizen stoneware is produced by firing a specific type of green clay in a wood-fired kiln at approximately 1200 °C. During this process, single crystalline branched dendrite-like particles of Al-substituted ε-Fe2O3 (ε-Fe1.7Al0.3O3) with widths and lengths of approximately 15 and 30 μm, respectively, are formed on the surface of the ceramic. Composite particles consisting of ε-Fe2O3 epitaxially connected to spinel structure compounds [comprising the Fe-substituted spinel (Mg,Fe)(Al,Fe)2O4 and γ-Fe2O3)] with lengths of approximately 3 μm are also generated. The present work clarified the crystallographic relationship between ε-Fe2O3 and the spinel structure compounds. In addition, brown-colored samples similar to Bizen pottery and with surface Al-substituted ε-Fe2O3 particles were prepared by heating clay with K2CO3 under a 10 vol % CO gas and 90 vol % Ar gas mixture using an electric furnace instead of a firewood kiln. Hence, a traditional method was adapted to achieve the industrial production of ε-Fe2O3 crystals.