It is demonstrated that a Contactless Flash Technique (CFT) can be employed to fabricate large SiC platelets. The rapid crystal growth of the platelets is attributed to the high temperatures (estimated ≈2300°C) reached by the sample during the 33 s process. The SiC platelets consisted of elongated hexagonal crystals (thickness between 2–4 µm, length up 50–100 µm) with their c-axis corresponding to the slow growth direction. The mechanisms involved in the development of the platelet morphology are discussed in relation to well-established literature on the conventional growth of SiC platelets.

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Nanocrystals have great potential to achieve extremely high electrical properties induced by their shapes, size, and facet surfaces. BaTiO₃ nanocube (BT NC) 3D-assemblies with numerous interfaces and closely packed nanostructure are attracting as materials for next-generation dielectric devices due to their advantages for enhancing dielectric properties such as high packing density, high orientation, and interaction of the interfaces between the nanocubes. In this paper, we review our studies on the solution-based processing of BT NC 3D-assemblies and their high dielectric properties. BT NCs 15 nm in size have already been synthesized by the hydrothermal method with aqueous compounds and surfactants. As NCs were well-dispersed in non-polar organic solvent, BT NC 3D-assemblies were fabricated by a dip-coating process while controlling the up-stroke rate of the substrate and evaporation rate of the solvent. The capillary force generated through the dip-coating assisted in ordering the NCs. We also successfully fabricated micro-patterning of BT NC assemblies using polymeric micro-molds and removing them by a chemical wet process. This soft process has the great advantages of avoiding both etching damage occurring in the dry process and the clamping effect of substrate. The ordering and cubic shape of the BT NC 3D-assemblies were maintained under heat-treatment up to 900°C. The local strain at the BT NC interfaces was induced by epitaxial attachment with small angle tilting between neighboring NCs. The dielectric constant of the BT NC assembly heat-treated at 850°C achieved above 4000 with relatively low loss tangent below 7%. The local strain at the interfaces seemed to enhance the dielectric properties without the nanosize effect and thickness effect of dielectric materials.

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Multifunctional nanoparticles have contributed to several advances in the biomedical field. For example, many have been shown to provide higher level analysis in fundamental studies on cancer and regenerative medicine. Application of multifunctional nanoparticles as contrast agents or probes for diagnostic imaging enables integration of various imaging modalities which provides greater detail and more accurate information for diagnosis. In addition, these multifunctional materials may help researchers and clinicians combine diagnostics and treatment, called theranostics or image-guided therapy, for minimally invasive treatment of metastatic and minute cancers. Based on the viewpoint of the toxicity and the easily-controlled surface characteristics, shape, and internal function of silica-based hybrid nanoparticles, this review describes that the hybrid nanoparticles break ground for various analytical methods for fundamental studies, diagnostic techniques, and therapies. In particular, the present review focuses on seamless imaging, dual-modal imaging, and image-guided therapy using silica-based multifunctional hybrid nanoparticles with visible and near-infrared fluorescence, as well as X-ray-absorbing, photoresponsive, drug-releasing, and photoinduced heat- and reactive oxygen species-generating capabilities.

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Aqueous solution processes are environmentally friendly and produce materials with excellent properties. We focus on the synthesis of crystals with controlled nano- and microstructures and the development of new materials using aqueous solution-based methods. Using water-soluble titanium complexes, various additives can be used to control morphology. As a result, titania polymorphs including not only anatase and rutile, but also brookite and TiO₂(B) with various morphologies were synthesized. In addition, this approach produced magnetite, exposing high index facets. These crystals with controlled structures showed excellent properties. Moreover, the development of new complexes below 373 K was achieved using aqueous solution methods. Water plays a key role in the controlled synthesis of crystalline structures and morphologies and the development of new materials.

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We have explored a solvothermal method for synthesizing various metal oxides in alcohol or glycol media at temperatures around 300°C. This review summarizes our recent results on the solvothermal synthesis of metal-oxide nanoparticles and their catalytic and photoluminescence performances. We have described the principles of solvothermal processing by classifying solvothermal methods according to the type of solvent used as follows: alcohol, vicinal glycol and 1,4-butanediol. (1) Solvothermal reaction of metallic cerium in alcohol yields a colloidal solution containing CeO₂ nanoparticles, and the pore structure of the CeO₂ coagulate can be controlled by the choice of bases added to the colloidal solution. Furthermore, the solvothermally synthesized CeO₂ nanoparticles show good redox properties and an improved performance as a catalyst support in the selective oxidation of benzyl alcohol to benzaldehyde. (2) Solvothermal method in vicinal glycol produces an inorganic–organic composite, which is an effective precursor for the synthesis of metal-oxide nanoparticles. Nb₂O₅ nanoparticles synthesized via a solvothermal reaction in ethylene glycol show high activities as photocatalysts for the selective oxidation of alcohol. (3) Solvothermal reactions in 1,4-butanediol can yield various mixed oxides directly. Mn-modified hexagonal YbFeO₃ synthesized by the solvothermal method has a higher catalytic activity for hydrocarbon combustion when compared to noble metal catalysts.

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We prepared the 16H-SiAlON crystal with the general formula of Si_3−xAl_5+xO_xN_9−x (Z = 2), and characterized it by X-ray powder diffraction, transmission electron microscopy, scanning electron microscopy, and energy dispersive X-ray spectroscopy. The x-value was determined to be 2.61(2) from the [Si:Al] molar ratios of [0.049(2):0.951(2)]. The space group was found to be P6₃/mmc (centrosymmetric) for the Si_0.39(2)Al_7.61(2)O_2.61(2)N_6.39(2) compound. The hexagonal unit-cell dimensions were a = 0.305831(7) nm, c = 4.29942(12) nm, and V = 0.348260(15) nm³. These values were in good accordance with the high correlation between the unit-cell dimensions and concentrations of octahedral layer in the unit cell, which was determined for AlN, 20H-AlON, 21R-AlON, and 27R-AlON in a previous study. The initial structural model was derived by the charge flipping method, and it was further refined by the multi-phase Rietveld method. The final structural model showed the positional disordering of two of the five types of (Si,Al) sites. The disordered crystal structure was successfully described as a statistical average of four types of domains with ordered atom configurations.

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The purpose of this work is to clarify the thermal expansion properties of hexacelsian solid solutions (Sr_xBa_1−xAl₂Si₂O₈, x = 0–1.0) using high-temperature powder X-ray diffraction and dilatometry of sintered polycrystals. Hexacelsian solid solutions were prepared from BaCO₃, SrCO₃ and finely purified kaolin powder (Al₂O₃·2SiO₂·2H₂O) by heat-treatment above 1000°C. Hexacelsian polycrystals showed more sluggish α-β phase transitions, and the transition temperature increased from 300 to 700°C with the increase in Sr content. The average thermal expansion coefficient of hexacelsian polycrystals strongly depended on the temperature range and on the Sr content because of their nonlinearity of expansion curves. The thermal expansion gap of the unit cell associated with the α-β hexacelsian phase transition was found to increase from 0.13 to 0.50% with the increase in Sr content by high-temperature powder X-ray diffraction. The average linear thermal expansion coefficients of the α-hexacelsian and β-hexacelsian unit cells showed nearly constant values of 6 × 10⁻⁶/K, though the expansion anisotropy of the crystal axes in unit cell altered depending on the chemical composition.

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This work describes the degradation of ZrO₂–4 mol%Y₂O₃ (YSZ) coatings obtained by EB-PVD. YSZ coatings were exposed at 1200°C for 10 min–50 hr by isothermal heat treatment in the presence of an erosive impurity of volcanic ash. At the interface between the YSZ coatings and volcanic ash, the coatings were partially dissolved in the volcanic ash, resulting in the degradation of coatings by the formation of the reacted region. A ZrSiO₄ or glassy phase is formed by the chemical reaction between YSZ coatings and volcanic ash at 1200°C. The chemically reacted region from the top surface of the YSZ coatings showed a tendency for increased degradation depth with an increase in isothermal heat-treatment time.

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ZrB₂–SiC–ZrC (ZSZ) ternary composites of four differing compositions were fabricated by spark plasma sintering (SPS). The effect of the ZrB₂/ZrC ratio on the oxidation behavior was examined by thermogravimetric (TG) analysis and microstructural observations. In addition, in-situ observation above 1500°C was performed using a high-temperature observation system (HTOS). ZSZ composites with high ZrC contents were fully oxidized at temperatures below 1500°C. However, ZSZ composites with low ZrC contents formed protective oxide layers during heat exposure. These layers protected the unreacted regions from further oxidation. Island nucleation was successfully observed on the surface oxide layer at 1500°C using the HTOS. The nucleation of islands strongly depended on the ZSZ composition. The difference in oxidation behavior originated from the concentration and interparticle distance of the ZrC in the as-sintered compacts.

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Carbon nanotubes (CNTs)-dispersed ceramics were usually obtained by simple mixing, or firstly dispersing the metal catalysts inside ceramic powders, and then growing CNTs from the thermal decomposition of hydrocarbon gas. In the present study, a novel route for the fabrication of Al₂O₃–Ni–CNTs nanocomposites was proposed by co-precipitation of CNTs and Ni nanoparticle on Al₂O₃ powder using nickelocene as a precursor in a rotary CVD reactor. Fine Ni nanoparticles (10–50 nm in diameter) and CNTs (20–50 nm in diameter and as long as 1 µm in length) were uniformly dispersed on agitated Al₂O₃ powders. After spark plasma sintering at 1923 K for 0.6 ks, the Al₂O₃–Ni–CNTs nanocomposites showed uniform microstructure and enhanced mechanical properties. Carbon incorporated in nickel changed from amorphous to crystalline phase state after the high temperature treatment. No other impurities were identified, and the incorporation of CNTs and Ni was also found to enhance the relative density and mechanical properties of Al₂O₃. Thus the present method is promising for fabrication of high performance CNTs-ceramic composites.

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According the solid state reaction routine, Ca_0.61Nd_0.26Ti_1−xAl_4x/3O₃ (x = 0, 0.05, 0.1, 0.15, 0.2) ceramics were synthesized and their microwave dielectric properties were determined. The X-ray diffraction results showed a single perovskite phase (JCPDS Card No. 01-082-0229) for 0 ≤ x ≤ 0.1. Dielectric constant (ε_r) decreased from 102.8 to 72.24, the Q×f value almost doubled, from 8560 to 15437 GHz, and the temperature coefficient of resonant frequency (τ_f) dropped from +247 to +155 ppm/°C. Then the X-ray diffraction patterns showed the appearance of secondary phase that degraded microwave dielectric properties of the system rapidly. At last, a ceramic possessing microwave dielectric properties of ε_r = 72.24, Q×f = 15437 GHz and τ_f = +155 ppm/°C could be obtained when sintered at 1400°C for 2 h in air, x = 0.1.

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Local DC electrical measurements were carried out to clarify the electrical properties of the grain boundaries of La_2/3−xLi_3xTiO₃ ceramics. The I-Time curves exhibited a steep current decay with respect to time. The curves showed that the grain boundaries exhibited two types of behaviours. Partial grain boundaries were found to exhibit a higher current flow than the other curves. An equivalent circuit analysis was conducted with a circuit consisting of both resistance and capacitance components. The analysis results indicated that the partial grain boundary exhibited a larger capacitance, which was regarded as being the origin of the higher current flow. The increased capacitance was explained by the piling up of ions near the grain boundary, as a result of the boundary layer capacitance effect. These findings indicate that the conductivity of La_2/3−xLi_3xTiO₃ ceramics could possibly be improved by controlling the electrical properties of the grain boundaries themselves, rather than by simply reducing the density.

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Bismuth sodium titanate (Bi_0.5Na_0.5TiO₃, BNT) and its solid-solution with BaTiO₃ (BNT–BT) are promising lead-free piezoelectric ceramics. Around the morphotropic phase boundary (MPB), the 0.94BNT–0.06BT composition shows high piezoelectric performance. In this paper, we have investigated the effect of ZnO-doping on the reactive sintering and piezoelectric properties of 0.94BNT–0.06BT ceramics. Bi₂O₃, anhydrous Na₂CO₃, TiO₂ (anatase), BaCO₃ and ZnO powders were wet ball-milled in ethanol, cold isostatically pressed at 200 MPa for 10 min, and reactively sintered at 1150°C for 2 h in air. The relative density drastically increased from 83.3% (without ZnO) to 93.7% (with 0.5 mol% ZnO). The sample with 0.5 mol% ZnO showed the highest piezoelectric constant d₃₃ of 124 pC/N. Even by the one-step reactive sintering, the d₃₃ value was comparable with that of the two-step conventional sintering.

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Oxide Li₃BO₃–Li₂CO₃ glasses were synthesized by a mechanochemical technique. The glasses were heat treated to obtain the glass-ceramics. Raman spectra indicated that these glasses were composed of ortho-borate, carbonate and lithium ions. After milling, a solid solution based on Li₂CO₃ was obtained at the 20Li₃BO₃·80Li₂CO₃ composition. By heating the milled sample at 500°C, the crystallinity and conductivity increased. This heated sample showed the conductivity of 1.2 × 10⁻⁶ S cm⁻¹ at room temperature, which is eight orders of magnitude higher than that of Li₂CO₃ crystal.

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The effect of the CeO₂ doped in 60P₂O₅–9B₂O₃–21ZnO glasses on the crystallization kinetics and hydrophobic properties was investigated. The kinetic parameters, activation energy for crystallization (E_c), and Avrami constant (n) were evaluated under non-isothermal conditions using differential thermal analysis (DTA) performed for a range of heating rates. Each DTA curve exhibited one exothermic peak associated with the crystallization of the glass. X-ray diffractometry (XRD) analysis identified the crystalline phase as BPO₄ and CePO₄. The calculated values of the activation energies for the glass samples were obtained using the Kissinger and the Marotta methods. The hydrophobic properties as a function of the CeO₂ content were identified by water contact angle goniometer. The results indicated that the water contact angle increased as the doped of CeO₂. However, as crystallization progressed within the glass samples, the water contact angles decreased.

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Bi₂O₃–Nb₂O₅ solid solutions were synthesized by conventional ceramic method and their color properties were investigated as environmental-friendly inorganic yellow pigments. Powder samples showed from light yellow color to brilliant reddish yellow color depending on their composition. The most brilliant reddish yellow color was obtained for 0.94Bi₂O₃–0.06Nb₂O₅ composition heated at 800°C for 30 min, which had color parameters (L*a*b*) of L* = 66.8, a* = 21.4, and b* = 63.6. The a*, b* values are comparable to that of commercial Cr₂O₃–Sb₂O₅–TiO₂ based reddish yellow pigments. Since the present compounds are composed of nontoxic elements, it should be an attractive alternative to the conventional reddish yellow pigments.

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The surface activity of three raw silica powders with different structures, one crystalline (C1) and two amorphous (A1 and A2 with different purities) as well as the powders obtained by milling at different conditions measured as the amounts of dissolved Si⁴⁺ ion into ammonia solution was reported previously by the authors. In the present work the surface of the same powders is evaluated by the quantity of OH surface groups. The intensity of the OH bands quantified by DRIFT correlates with the amount of dissolved Si⁴⁺ measured by ICP for all powders. The amount of silanol surface groups (SiOH) increased at any milling condition and reach maximum value. The amorphous powders show higher surface activities than the crystalline powder. The A2 powder shows the highest amount of surface groups and quantity of dissolved Si⁴⁺ in ammonia solution and the crystalline powder shows the least. The effect of particles size distribution, particle size and morphology on powders surface activity is discussed.

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Tantalum oxide-doped, nano-sized tin oxide powder was consolidated by spark plasma sintering by systematically varying the sintering temperature, heating rate, holding time at the sintering temperature, and doping amount. The relative densities of the TaO_2.5-doped SnO₂ sintered specimens increased with the increasing sintering temperature from 800 to 1000°C, but were almost independent of the heating rate and holding time in the ranges from 30–90°C/min and 5–120 min, respectively. The DC electrical conductivity, in contrast, reached a maximum value at the sintering temperature of 900°C, but decreased at 1000°C due to decomposition of the SnO₂. In addition, a faster heating rate and shorter holding time resulted in a higher electrical conductivity of the TaO_2.5-doped SnO₂ specimens due to the solution of Ta⁵⁺ in the SnO₂ and formation of a metastable compound.

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In the present study, novel scheelite-type (tetragonal) LiCe(WO₄)₂ was synthesized through a solid-state reaction between Li₂CO₃, CeO₂, and WO₃. Rietveld refinement of the product indicated the presence of an almost single-phase material with crystal structure of the space group I4₁/a, having parameters of a = 529.4(8), c = 1149.(8), and S = 1.35. The lattice parameters show agreement with lanthanoid contraction of ionic radii. Upon excitation at 235 and 360 nm, LiCe(WO₄)₂ exhibits several different emissions due to the effects of Ce³⁺ and WO₄²⁻. The results obtained in this study indicate the possibility of a new fluorescent substance having a new crystal system.

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Calcium phosphate cement (CPC) is an injectable, self-setting artificial bone material that has recently been used as a drug delivery system for bone infection therapy because of its high capacity for antibiotic elution. Despite this advantageous property, the mechanical strength of CPC dramatically decreases upon impregnation with certain types of antibiotics. A novel CPC material (CPC-A) with four-fold higher initial compression strength than that of conventional CPC (CPC-B) was developed by decreasing the median particle size of alpha-tricalcium phosphate powder in CPC from 6.34 to 2.30 µm. However, the elution profile and mechanical strength of the material following antibiotic impregnation remain unclear. In the present study, we compared the elution profiles and physical properties of CPC-A and CPC-B impregnated with vancomycin hydrochloride (VCM) and gentamicin sulfate (GM). CPC-A showed 3.6-fold higher initial (1 h after hardening) compression strength than CPC-B, even when impregnated with VCM. Scanning electron microscopy and porosimetry analyses revealed that the high compression strength of CPC-A was attributable to the densely arranged micro-porous structure. The small pores, which had a median size of 11.3 nm and served as passages for antibiotic elution, reduced the VCM elution rate and promoted long-term (18-week) antibiotic release compared to CPC-B, which contained larger pores (19.6 nm) and did not release VCM beyond 16 weeks. In contrast to VCM, GM impregnation did not markedly affect the compression strength of either material, and the GM elution profiles from CPC-A and CPC-B were nearly identical throughout the measurement period. Taken together, these findings demonstrate that the novel CPC material CPC-A has higher initial compression strength than conventional CPC and the potential for prolonged antibiotic release, suggesting that CPC-A would be an effective bone substitute material, particularly for bone infection therapy.

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A new program for electrochemical impedance analysis has been developed based on the expanded measurement model. The main feature of this program is that it allows the user to easily estimate the equivalent circuit, as well as an initial guess of the fitting parameters, through a graphic user interface (GUI). The function to illustrate the partial impedance spectra is implemented in the graphs of log f–Z_real and log f–Z_imag. In this context, f represents the alternating current frequency applied to the sample; Z_real and Z_imag represent the real and imaginary components of the impedance, respectively. By employing the GUI supporting function, the impedance spectrum can be analyzed without the use of a pseudo-element such as a constant phase element and with an empirical parameter in the Warburg and Gerischer impedance. Based on the results, it is possible to calculate a discrete distribution of the relaxation times from the optimized parameters.

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Blue fluorescence phosphor ZrO₂:Ti, P/Al₂O₃ composite bodies were fabricated by sintering {ZrO₂ + 1000 ppm Ti + 4000 ppm P} powder, which had been heat-treated at 1500°C, and α-Al₂O₃ powder at 1500°C. No cracks were observed on the fabricated blue fluorescent ZrO₂:Ti, P/10, 30, 50, and 70 wt%–Al₂O₃ composite sintered bodies. The fluorescence intensities of the ZrO₂:Ti, P/10, 30, 50, and 70 wt%–Al₂O₃ composite sintered bodies were 77, 82, 85 and 82% that of the ZrO₂:Ti, P blue phosphor powder, respectively. The internal quantum efficiency of the blue fluorescent ZrO₂:Ti, P/50 wt%–Al₂O₃ composite bodies was 57% when excited at 280 nm.

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Ta(V) oxynitride (TaON) powders for new pigments were prepared by heat-treatment for mixed powders of Ta(V) oxide, nitrides and alkaline fluorides in nitrogen atmosphere without flowing ammonia. This synthetic method is an eco-friendly and cost-effective way suitable for an industrial scale production of the powder containing TaON with the color of 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 pigments, and to substitute pigments containing harmful elements. In this study, influence of nitrides as the agent for nitridation of tantalum oxide on the formation of TaON in the synthetic method was examined. It has become apparent that the formation of TaON was promoted by using silicon nitride (Si₃N₄) for nitridation of tantalum oxide.

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Li₂FeSiO₄ nanoparticles/carbon composite powders were synthesized using spray pyrolysis (SP), followed by heat treatment and grinding. Glucose, added to the precursor solution for SP, was used as the carbon source. Both Li₂FeSiO₄ nanoparticles and carbon were formed simultaneously during SP. The primary particle size of the Li₂FeSiO₄ powder obtained from this process was smaller than 20 nm. Graphitic carbon formation was inferred based on results obtained from FT-IR and Raman spectra. The Li₂FeSiO₄ crystallite size decreased concomitantly with increasing carbon concentration. The composite powder exhibited excellent discharge capacity of 250 mAh·g⁻¹ and excellent cycle performance. Results show that the carbon produced by glucose improves electric conductivity and discharge capacity by suppressing Li₂FeSiO₄ grain growth.

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