Al₂TiO₅–MgTi₂O₅ solid solutions were synthesized by reactive sintering of α-Al₂O₃, TiO₂ anatase and MgCO₃ (basic) powders at 1400°C (and at 1300°C for some composition) for 2 h, with changing the MgTi₂O₅ ratio to form the composition of Al_2(1−x)Ti_1+xMg_xO₅ (x = 0.0–1.0) and evaluated their properties. With increasing MgTi₂O₅ molar ratio, the matrix Al₂TiO₅–MgTi₂O₅ grains became more anisotropic, and the coefficient of thermal expansion increased due to the decrease of microcracks. Al_0.2Ti_1.9Mg_0.9O₅ (x = 0.9) showed the maximum strength of 47.9 MPa. On the other hand, MgTi₂O₅ (x = 1.0) showed low bending strength of 13.2 MPa due to the grain growth during the sintering at 1400°C. Al_0.6Ti_1.7Mg_0.7O₅ (x = 0.7) sintered at 1300°C indicated the highest conductivity. The conductivity of pseudobrookite-type ceramics strongly depends on microcracks.

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Perovskite-type oxide, LaFeO₃, was prepared from coordination polymer precursor, La[Fe(CN)₆]·5H₂O by calcination with the different two systems. In a muffle furnace system, the perovskite-type oxide was given by calcination at >500°C. The specific surface area of LaFeO₃ powder calcined at 500°C for 24 h was 18 m²·g⁻¹, which was the largest among single phase perovskite-type oxides calcined in a muffle furnace. In a gas-flow system, the perovskite-type oxide was given by calcination at significantly low temperature (>250°C). The specific surface area of LaFeO₃ powder calcined at 300°C for 1 h in a gas-flow system was dependent on O₂ partial pressure.

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The low-temperature carbothermal nitridaton of boron oxide (B₂O₃) was induced by the networked carbon structure prepared from a condensed boric acid (H₃BO₃)-poly(vinyl alcohol) (PVA) product. The precursor powder consisting of B₂O₃ and carbon components was formed from the condensed product by thermal decomposition in air, and heated at 1200°C in a N₂ flow. The formation of boron nitride (BN) was accelerated for the product obtained from the precursor powder with the networked carbon structure. The formation of boron carbide (B₄C) by carbothermal reduction was also observed, and the formed B₄C was converted into BN with further increasing heat treatment time.

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Supercritical fluid deposition (SCFD) of SiO₂-based films was proposed using TEOS precursor with oxidizing agents, for the purpose of low-temperature film deposition. The film deposition was performed in a batch-type closed chamber filled with supercritical carbon dioxide (CO₂) fluid. The SiO₂-based films were deposited on aluminum electrodes coated on silicon wafers (Al/Si) at the substrate temperature above 150°C. Oxidizing agents such as O₂ gas and aqueous H₂O₂ solution promoted the removal of C₂H₅OH byproduct and the formation of strong Si–O network, whereas it also promoted the homogeneous nucleation of granular precipitation and the H₂O adsorption in/on the resulting films. The processing temperature of the SCFD was significantly lower than those by thermal CVD and comparable or higher than those by plasma-enhanced CVD, although the resulting films obtained exhibited relatively large dielectric loss which depends on the presence of C₂H₅OH and H₂O byproducts.

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The synthesis conditions of a nano-sized magnetite powder using a reverse coprecipitation method were studied in order to control the particle size and the heat generation ability in an AC magnetic field for thermal coagulation therapy. A low temperature reaction and high concentration of the mixed irons as the starting materials in solution increased the particle size of the magnetite powder. The particle size decreased with an increase in the concentration of the coexisting Na⁺ and Cl⁻ ions. The particle size was enhanced with an increase in the R = Fe²⁺/(Fe²⁺ + Fe³⁺) molar ratio of the divalent iron, and the maximum heat generation ability was obtained at the R = 0.33 molar ratio. The maximum heat generation ability of 0.25–0.28 W·g⁻¹ in the AC magnetic field (370 kHz, 1.77 kA·m⁻¹) was obtained for the magnetite having an ca. 13–14 nm particle size.

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We synthesize a nanosized lanthanum silicate, La_9.33Si₆O₂₆, by means of a hydrothermal method, and then investigate the crystal structure by the Rietveld analysis and the maximum-entropy method using a neutron Bragg profile. In addition, we study electrical conduction properties of the sintered pellet with conductivity measurements under O₂ oxidizing and Ar reducing conditions. From these results, it is indicated that the oxyapatite-type lanthanum silicate with oxide-ion conduction can be prepared at 180°C hydrothermally. By using the nanopowder, we prepare a film of the lanthanum silicate via the electrophoretic deposition. As a result, it is demonstrated that a deposited film can be made successfully in an I₂-added acetone bath and the thickness obtained in an optimized condition is around 10 µm.

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Zn₃V₂O₈ phosphors were synthesized by heat treatment of precursor powders obtained by evaporation of aqueous solutions of peroxo-isopolyvanadic acid and zinc acetate. A precursor solution with a Zn/V molar ratio of 3:1 and a heat-treatment temperature of 600°C gave a powder containing a mixture of Zn₃V₂O₈ and ZnO. The ZnO was removed by treatment with HCl, resulting in a single-phase Zn₃V₂O₈ powder; it showed yellow phosphorescence with a peak at 560 nm at an excitation wavelength of 350 nm.

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A method was developed to fabricate luminescent films at around room temperature based on successive ionic layer adsorption and reaction (SILAR). Nanocrystalline CePO₄:Tb³⁺ films were deposited on bare or surface-modified silica glass substrates through immersion in cation (Ce³⁺ and Tb³⁺) and anion (PO₄³⁻) solutions successively. Experimental conditions for the successful deposition of the films were explored to obtain better luminescent properties related to redox sensibility. The intensity of photoluminescence from CePO₄:Tb³⁺ was increased linearly with increasing the number of SILAR cycles. Sensibility of the nanocrystalline CePO₄:Tb³⁺ films against the oxidation by KMnO₄ and the reduction by L(+)-ascorbic acid in aqueous solutions was proved to be superior to that of a dense and flat CePO₄:Tb³⁺ film fabricated by a common sol–gel dip-coating method.

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Nanocrystalline gadolinium niobate, GdNbO₄ with fergusonite structure was directly formed from the precursor solution mixtures of GdCl₃ and NbCl₅ under weakly basic conditions at temperatures higher than 210°C for 5 h in the presence of aqueous ammonia via hydrothermal route. The as-prepared GdNbO₄ nanocrystals and those after heating at 1000–1300°C showed UV-blue and broad-band emission centered at 435 nm under excitation at 266 nm due to the blue recombination luminescence, associated with charge transfer transitions involving the tetrahedral NbO₄ group. The fergusonite-type complete solid solution nanocrystals having good luminescence in the red spectral region in the GdNbO₄–EuNbO₄ system were directly formed under hydrothermal conditions at 240°C. The photoluminescence spectra of the as-prepared nanocrystalline solid solutions containing europium under excitation at 240 nm are responsible for the characteristic weak orange luminescence (592 nm) and strong red luminescence (611 nm), associated with ⁵D₀ → ⁷F₁ and ⁵D₀ → ⁷F₂ transitions, respectively. In the composition Gd_0.80Eu_0.20NbO₄, the maximum intensity of red emission was observed and the emission was even more enhanced via heating at 1300°C.

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Rapid formation of hydroxyapatite [Ca₁₀(PO₄)₆(OH)₂; HAp] layer on the polyetheretherketone (PEEK) substrate was examined by the combined techniques of vacuum ultraviolet (VUV) irradiation and microwave heating. The surface properties of PEEK substrate were modified by the formation of carboxyl group due to the VUV irradiation at room temperature in air, whereas the formation of HAp layer was encouraged by the microwave heating of surface-modified PEEK substrate in the HAp-dissolved solution. The optimization of the fabrication conditions was conducted by checking (i) the distance of VUV lamp to PEEK substrate (1–12 mm) and VUV irradiation time (0–120 min) for the surface modification of PEEK substrate, and (ii) the microwave heating temperatures (100 and 140°C) for the rapid formation of HAp layer on the PEEK substrate. When the PEEK substrate was surface-modified by the VUV irradiation for 120 min with the distance of VUV lamp to PEEK substrate kept being 1 mm, and then was microwave-heated in the HAp-dissolved solution at 140°C for 10 min, the thickness of the HAp layer on the PEEK substrate attained approximately 10 µm.

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Preparation of CaO core-SiO₂ shell nanoparticles as a chemical thermal storage through hydration/de-hydration of CaO/Ca(OH)₂ was proposed. Firstly, SiO₂ was coated on CaCO₃ template surface using sol–gel route and then the core–shell particles were heated at 700°C to form CaO@SiO₂ nanoparticle by de-carbonization. A thermal storage performance of the CaO@SiO₂ was confirmed by a thermogravimetry (TG) analysis and the result was compared with that of as-received CaCO₃. The heating program was performed as following steps as (i) at 700°C for 30 min for de-carbonization under nitrogen (N₂) atmosphere, (ii) at room temperature for 60 min for hydration under water vapor, and (iii) at 500°C for de-hydration under N₂. By repeating of (ii) hydration/(iii) de-hydration cycle, effect of the number of cycles on thermal storage ability was investigated. An efficiency of thermal storage was defined as difference in weight change between hydration/de-hydration reactions. For the as-received CaCO₃ nanoparticles, with increase in the number of cycles, the thermal storage performance gradually decreased. The microscopic results showed that the heating cycles induces coalescence of CaCO₃ nanoparticles and that decreases specific surface area. On the other hands, efficiency of thermal storage of CaO@SiO₂ didn’t reach theoretical value because CaCO₃ didn’t completely transform into CaO owing to SiO₂’s thermal insulation ability. By decreasing SiO₂ coating thickness, the thermal storage performance of CaO@SiO₂ was improved. The microscopic results showed that the SiO₂ coating prevented from coalescence of CaCO₃ nanoparticles.

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A layered titanate sol was prepared at room temperature (298 K) using dialysis of a mixed solution of ethylene glycol solution of TiCl₃, ammonium carbonate aqueous solution, and hydrogen peroxide. A sol with dispersion of plate-shaped layered titanate nanoparticles was obtained. A stable sol with dispersion of spindle-shaped anatase TiO₂ nanoparticles was obtained by heating the sol with dispersion of layered titanate at 368 K for 24 h in a closed vessel. The optical transmittance spectrum of the TiO₂ thin film obtained by coating the sol with dispersion of anatase nanoparticles and firing at 773 K for 1 h showed no interference of an incident light beam into the TiO₂ thin film. Optical characteristics on interference originated from pores among TiO₂ primary nanoparticles in the thin film, which caused incoherent scattering of incident light into the thin film. When the sols containing both of the plate-shaped layered titanate nanoparticles and the spindle-shaped anatase nanoparticles were used as the coating solution, the interparticle pore volume was controlled by the volume ratio of the anatase sol in the coating solution. The effects of interference on the optical transmittance spectra of the thin films depended on the interparticle pore volume.

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In this study, we successfully synthesized CaAlSiN₃:Ce³⁺ at 1073 K using the ammonothermal method. The synthesis temperature was 900 K lower than that in the conventional solid-state reaction. The product exhibited a broad emission band that was centered at approximately 550 nm by irradiation of 440 nm blue light. Furthermore, we investigated the effects of the reaction temperature and mineralizers on the products synthesized using the ammonothermal method. The results of X-ray diffraction analysis indicated that the optimal temperature for CaAlSiN₃:Ce³⁺ synthesis was 773 K because the sample treated at this temperature exhibited the highest diffraction intensity and the smallest half-value width. The product prepared using NaNH₂ as a mineralizer exhibited the highest emission intensity. Moreover, the products prepared using the ammonothermal method had a plate-like crystal morphology.

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A luminescent material free of rare earth elements was prepared from a partially Ag⁺ exchanged zeolite X. One gram of a commercially available zeolite X (Na⁺ form) was mixed with 100 mL of AgNO₃ aqueous solutions of 2.0 to 50 mmol/L. The mixtures were shaken for 24 h, then the solid products were separated and dried at 50°C. Some of the products were heated at 100 to 800°C in atmospheric air. Luminescence was observed from the products with Ag loadings of 0.5 mmol/g or higher. These products showed yellow luminescence under UV light excitations of 254 and 312 nm. The luminescent products showed two excitation bands with peak maxima at 271 and 311 nm, and a single emission band at 550 nm. The luminescence intensity was low for the 0.5 mmol/g Ag loaded sample, but it significantly increased with the increasing amounts of Ag⁺ up to a 1.0 mmol/g loading, then a quenching occurred with a further increased Ag⁺ loading. Heating of the Ag-loaded zeolite X decreased the luminescence intensity. Heating the Ag loaded zeolite X at 800°C resulted in a low blue luminescence intensity due to collapsing the zeolite X structure into an amorphous phase. This study suggested that a luminescent material free of rare earth elements can be fabricated from Ag-exchanged zeolite X without any heat treatment. The highest luminescence intensity was attained at the Ag loading of 1.0 mmol/g, along with a measured internal quantum efficiency of 20.8% (λ ex. = 311 nm).

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Sodium titanate (NTO) nanosheets were directly synthesized in supercritical water using a flow hydrothermal reaction system (FHRS) from Ti-sols and NaOH solutions. The syntheses were carried out at temperatures from 350 to 410°C, at pressure of 30 MPa, for reaction times from 0.25 to 0.67 s, and initial Na/Ti molar ratio of 2.5 to 10. X-ray diffraction (XRD), Raman spectroscopy, Transmission electron microscopy (TEM), BET surface area, TG–DTA analyses, and Dynamic light scattering (DLS) techniques were used to characterize the samples. Single phase of NTO was achieved under supercritical conditions (>400°C) at initial Na/Ti molar ratio >5. The NTO nanosheets have lateral dimension in the range of approximately several sub-microns and thickness in the order of nanometers which are stacked nanosheets with 40–70 m²/g of specific surface area. Hydrogen ion-exchange and tetrapropylammonium intercalation properties of NTO synthesized by FHRS were compared with those of solid-state reacted NTO. Intercalation of tetrapropylammonium ions into FHRS NTO can readily occur due to enlargement of interlayer spacing after hydrogen-ion exchange whereas it did not take place on the solid-state reacted NTO owing to the shrinkage of interlayer spacing after hydrogen-ion exchange.

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Carbonaceous spheres (CSs) were prepared by hydrothermal treatment of corn, potato and rice starches. Each starch powder (corn: 1.0–4.0 g, potato: 1.0 g, or rice: 1.0 g) was dispersed in 40 mL H₂O in a Teflon-lined stainless autoclave, and the autoclave was heated at 160°C for 4–16 h. The solid products after hydrothermal treatment were washed and dried to obtain CSs. CSs from the potato starch showed the narrowest particle-size distribution, which can be attributed to its B-type starch structure. Although the particle-size distribution of CSs was affected by starting starches, chemical characteristics were almost identical for all starches.

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Partially Ag-exchanged Na-P1 type zeolites were prepared using an Na-P1 type zeolite and a silver nitrate solution. Emission spectra of the samples prepared at various concentrations of the silver nitrate solution and at various subsequent heat-treatment temperatures were compared. The structure of the Na-P1 type zeolites was changed to an amorphous phase by the heat-treatment at 400°C or higher. When the amorphous materials were irradiated with 254 nm ultraviolet light, these samples showed a high intensity violet luminescence with an emission peak around 390 nm.

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Lithium nickel manganese oxide cathode material, LiNi_0.5Mn_1.5O₄, was prepared by an improved microwave heating method. Prepared cathode materials were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), and charge–discharge measurements. XRD results indicated that single-phase LiNi_0.5Mn_1.5O₄ powders were obtained under the optimized preparation conditions. SEM investigation demonstrated that the powders had an octahedron shape and a particles size of about 200–300 nm. The obtained LiNi_0.5Mn_1.5O₄ exhibited good electrochemical performance and delivered an initial discharge capacity of 145 mAh g⁻¹ at a current density of 20 mAg⁻¹.

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Corundum-mullite-spinel composite refractories with excellent mechanical properties were prepared from low-grade ores and γ-Al₂O₃ sintered at 1400–1550°C. The influences of low-grade magnesite minerals and sintering temperature on the phase composition evolution, bending strength, and microstructure were studied. Their phase compositions and microstructures of the samples were determined with X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). According to characterization results, the bending strength of the samples significantly increased with the increase of magnesite addition, whereas the bending strength firstly increased and then decreased with the sintering temperature rise. Compared with the samples prepared under other conditions, the samples prepared with 12 mass % magnesite addition at 1500°C showed the better properties: the bulk density of 2.92 g/cm³, flexural strength of 117.56 MPa. The crystalline phases of samples were corundum, mullite, and MgAl₂O₄ spinel. SEM and EDS revealed that mullite grains existed in long columnar forms with interlocking network structure and MgAl₂O₄ spinel grains existed in octahedral forms. Some impurities were incorporated into crystals to form a transitory liquid phase sintering. The above SEM results contributed to the improved densification behavior and the enhanced bending strength.

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Nb⁵⁺ or W⁶⁺ donor-doped powders were synthesized by applying a mechanochemical synthesis route, in an attempt to improve the multiferroic properties of BiFeO₃ based materials. The as-synthesized samples evidence a highly efficient incorporation of Nb⁵⁺ or W⁶⁺ into the BiFeO₃ perovskite lattice, together with a low presence of secondary phases. The relatively high purity of the mechanosynthetized products is even more appealing when it is compared with the multiphase scenario obtained by a mixed oxides route for these compositions. This confirms this technique as a good alternative to conventional solid state processing; however the thermal evolution of the as-prepared powders also reveals a metastable nature of the synthesized phases which upon an external energy input leads to an unwelcome multiphase system.

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The microwave dielectric properties of Nd₂WO₆ ceramics were investigated with a view to their application in mobile communication. Nd₂WO₆ ceramics were prepared by the conventional solid–state method with various sintering temperatures and sintering times. A maximum density of 7.45 g/cm³ and an open porosity of 2.1% were obtained for Nd₂WO₆ ceramic, sintered at 1500°C for 4 h. A dielectric constants (ε_r) of 15.6, a quality factor (Q×f) of 50,600 GHz, and a temperature coefficient of resonant frequency (τ_f) of −65 ppm/°C were obtained when Nd₂WO₆ ceramics that were sintered at 1500°C for 4 h.

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A high numerical aperture (NA) step-index fiber with As₂Se₃ core and As₂S₅ cladding was fabricated for deep mid-infrared (MIR) transmission over 10 µm. MIR supercontinuum generation covering the wavelength from 3 to 10 µm was successfully demonstrated in this fiber using a MIR pulsed laser source with µJ-level energy output around 7 µm. A 4-cm-long fiber sample is sufficient to enable a spectral broadening spreading from 3 to 10 µm in a 20 dB dynamic range.

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ZrO₂–TiO₂ porous ceramics recently has been great interest in the dielectric resonator materials, as well as in the fields of preparation of optical devices, and bio materials. This study reveals an approach for the production of micro porous ceramics consisting of TiO₂ and ZrO₂ fabricated by colloidal wet processing. ZrO₂ particles in the colloidal suspension was partially hydrophobized using propyl gallate as an amphiphile, with a suitable pH range. The different mole ratios of the TiO₂ suspension was added to the surface modified ZrO₂ suspension. The contact angle was found to be around 75° with the adsorption free energy of 1.8 × 10⁻¹¹–2.15 × 10⁻¹¹ J. The Laplace pressure of about 1.48–1.24 mPa was determined corresponding to the wet foam stability of about 76–80%. The microstructure analysis is done after sintering the dried samples for obtaining the porous ceramics.

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LiAl₅O₈ films were prepared by laser chemical vapor deposition, and the effect of the deposition temperature (T_dep) on the orientation, microstructure, and deposition rate was investigated. In the T_dep range of 980–1040 K, highly (110)-oriented LiAl₅O₈ film comprising flake-like grains elongated to [110] with flatter face of (111) formed at the maximum deposition rate of 70 µm h⁻¹. Above T_dep = 1050 K, dense LiAl₅O₈ films slightly oriented to (100) were deposited with faceted columnar grains of pyramidal and terrace shapes. The electrical properties of the LiAl₅O₈ films were examined using AC impedance spectroscopy. The complex plane plots of the dense LiAl₅O₈ film consisted of a semicircle associated with the bulk response and an inclined spike, suggesting the ionic conduction in the LiAl₅O₈ film.

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The electronic structures of Ag₆M₂O₇ (M = Si, Ge) are investigated by the scalar-relativistic full potential linearized augmented plane wave plus local orbital (FLAPW+lo) method using the modified Becke-Johnson (MBJ) potential combined with the local density approximation (LDA) correlation. For Ag₆M₂O₇ (M = Si, Ge), the valence band maximums (VBM) are approximately located at the X (Si) or A (Ge) and the conduction band minimums (CBM) at the Γ both, indicating that Ag₆M₂O₇ are an indirect energy gap material. The fundamental band gaps of Ag₆Si₂O₇ and Ag₆Ge₂O₇ are calculated to be 1.69 and 1.42 eV, respectively, in the MBJ-LDA calculation. The results are a remarkably contrast to the underestimation based on the generalized gradient approximation (GGA) calculation. On the other hand, there is no distinct difference in the effective masses of photogenerated holes and electrons near the VBM and CBM between MBJ-LDA and GGA approaches. The optical properties of Ag₆M₂O₇ (M = Si, Ge) are contemplated from spectral dependence of the complex dielectric function, ε (ω) = ε₁ (ω) + iε₂ (ω).

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Aluminum oxycarbide (Al₂OC) is known as a promising material for refractory and abrasive uses. However, Al₂OC is synthesized at high temperatures with a long reaction time by an electric furnace. Microwaves are known as a low energy heating method due to its heating mechanism; rapid heating and cooling, selective and internal heating, etc. Therefore, Al₂OC was synthesized from amorphous carbon and alumina using a microwave furnace. The reaction ratio and particle shape were measured by XRD, SEM and TGA. The results showed that the reaction ratio increased by the microwave heating versus conventional heating, because the carbon and alumina interface was efficiently heated by the microwaves.

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In this paper, we investigated fiber orientations and flexural properties of composites, which were prepared from epoxy resin, curing agent and short carbon fiber (CF) below critical fiber length. The prepreg with CF, curing agent and epoxy resin was prepared by an extrusion method. We found that the fiber orientation was caused when the CF/epoxy composite exhibited a plastic behavior. The ratio of this fiber orientation was 0.71 within the angle from 0 to 10°. The flexural modulus and the flexural strength of this composite, which was prepared from fiber orientation prepreg, was 16 GPa and 211 MPa, respectively. The flexural properties were ca. twice large as compared to a composite with random direction of fibers, indicating that the flexural properties were significantly affected by the orientation of fibers even if the fiber was below critical length. Moreover, it was discussed that the effective coefficient of the short fiber orientation distribution was one of important factors to predict the flexural modulus of a composite.

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Ta(V)-based oxynitrides have been prepared by heat-treatment for mixed powders of Ta(V)-based oxide precursors, aluminum nitride and potassium fluoride in nitrogen atmosphere without flowing ammonia. This method is an eco-friendly and cost-effective way suitable for an industrial scale production of the pigments containing Ta(V)-based oxynitrides with the brilliant color of reddish yellow–yellow, as compared to the conventional method such as ammonolysis with flowing large amounts of ammonia. They have a potential to be employed as non-toxic ceramic pigments, and to substitute pigments containing harmful elements. Effect of planetary ball milling time for oxide precursors on chromaticity of the tantalum(V)-based oxynitrides was evaluated. Results showed that the planetary ball millings of oxide precursors for longer time decreased the particle size of Ta(V)-based oxynitride and improved the chroma (C*) of the oxynitride.

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