High-temperature ceramic materials gain a continuous growing interest due to the various properties they can offer. Among all their specific features, their outstanding thermal and mechanical stability attract much attention to save energy. In the category of ceramics, silicon-based non-oxide compositions display a great potential for many applications involving high temperatures, high stresses or harsh environments. Since the major binary silicon carbide and silicon nitride, which are currently used as high-performance ceramics, were discovered, the role of chemistry in the design of materials has become major. Its potential lies in the exploitation of new chemical systems and the development of new preparative routes. As a consequence, new ceramic properties can be envisioned. The polymer derived ceramic (PDC) route is a “ceramic through chemistry” concept which allows synthesizing new materials in terms of compositions and shapes difficult to tailor using more conventional approaches. This review highlights the works made in the last decades concerning the preparation of PDC fibers with a particular focus on amorphous SiCN and SiBCN networks using melt-spinning and electrospinning processes of preceramic polymers. One main emphasis of this review is set on addressing the intimate relationship between molecular structure/architecture of preceramic polymers, their spinning/curing/pyrolysis behavior and the properties of the final fibers.

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Within the present work, reduced-graphene oxide (rGO)/silicon nitride (Si₃N₄) nanocomposites were prepared upon pyrolysis of a graphene oxide (GO)-filled polysilazane. The novel preparative approach consists in the synthesis of the polysilazane in the presence of different concentrations of GO, yielding a homogeneous GO/polysilazane composite which was subsequently thermally converted in Ar atmosphere into rGO/Si₃N₄ nanocomposites. Hot-pressing of the obtained nanocomposite powders delivered monolithic rGO/Si₃N₄. All prepared samples exhibited the presence of homogeneously dispersed rGO phase within an amorphous or crystalline silicon nitride matrix, as for the as-prepared and hot-pressed samples, respectively. An increasing amount of rGO in the nanocomposites was found to gradually suppress the crystallization of the silicon nitride matrix into α-Si₃N₄. Moreover, depending on the volume fraction of the graphene phase in the ceramic nanocomposites, different dielectric properties were observed, indicating a facile preparative method to produce materials with tunable electromagnetic waves (EMW) behavior.

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Amorphous silica-based alkylamine-functionalized hybrid membrane materials were synthesized through polymer-derived ceramics (PDCs) route, in order to selectively transport CO₂. Commercially available perhydropolysilazane (PHPS) was chemically modified with primary and secondary amino silane derivatives, and subsequently oxidized in air at room temperature to afford alkylamine-functionalized amorphous silica materials. CO₂ uptake by the powdered samples was investigated by the thermogravimetric analysis under CO₂ atmosphere, in-situ diffuse reflectance infrared fourier transform spectroscopic analysis and measurement of CO₂ sorption isotherm. In the case of alkylamine-functionalized silica samples, CO₂ uptake mechanism involved chemisorption at very low partial pressures and physisorption at higher partial pressures, demonstrated by the temperature dependence of CO₂ isotherms. The reaction paths and sorption mechanisms related to the nature of the functionalized amino groups were discussed from a viewpoint to develop CO₂-selective facilitated transport ceramic-based membranes.

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Two sets of sol–gel derived glass materials have been prepared and subjected to different thermal treatments. Pyrolysis in inert atmosphere lead to the formation of amorphous Si(B)CO ceramics whereas if the inert atmosphere is changed to NH₃ once the carbon substituents of the preceramic hybrid material transform to a glassy network, the nitrogen is incorporated efficiently while the carbon is retained into the structure, as revealed by ²⁹Si NMR analysis. Raman spectra show a less graphitized structure in the case of B-rich materials because of the reduced mobility of the C atoms due to the formation of mixed (B)CN bonds.

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The present study deals with the synthesis of Mg₂SiO₄ (Forsterite) applying the route of polymer derived ceramics (PDCs). The liquid, inorganic perhydropolysilazane (PHPS) was used because it is very reactive during pyrolysis in air and forms amorphous SiNO ceramic containing a tremendous amount of SiO₂. Both facts are crucial for the reaction with MgO in order to synthesize Mg-silicates. The results of this study demonstrate, that the Mg-orthosilicate phase is formed at the MgO/SiNO interface via solid state reaction at comparably low temperatures of 1100°C during pyrolysis in air for 2 h. Furthermore the high reactivity of the polysilazane leads to an almost full conversion of the MgO to Mg₂SiO₄ under the used conditions.

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In this work, a lutetium-modified silicon oxycarbide (SiOC) glass ceramic was prepared from a single-source precursor via pyrolysis and subsequent hot pressing. It is shown that the main crystalline phase in the hot-pressed SiLuOC is Lu₂Si₂O₇. The high-temperature (HT) creep behavior of SiLuOC was assessed by compression creep experiments performed between 1100 and 1300°C at constant true stresses between 25 and 75 MPa. The calculated viscosity values of SiLuOC were found to be significantly higher as compared to those of SiRE(Al,Mg)ON glasses (RE = rare earth elements). Thus, the presented SiLuOC-based glasses might be used as alternative sintering aids for the liquid-phase sintering of HT creep resistant Si₃N₄ monolithic samples.

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Graphite-like carbon nitride inorganic compounds were synthesized from molecular 1,2,4-triazole C₂N₃H₃ in high pressure and temperature conditions using a DIA-type multianvil large press. It was found that the N/C content ratio of the carbon nitrides can be systematically controlled by changing the heating temperature at 5 GPa. The substitution of nitrogen for carbon in graphene layers results in the low crystallinity of the synthesized C–N compounds. It should be noted that the c-axis which is equivalent of the distance between two graphene layers, decreases monotonously with increasing N/C content ratio. This is attributed to both of the smaller atomic size of nitrogen than that of carbon and Van der Waals attraction between C–N graphene layers because of the different electronegativity between nitrogen and carbon.

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In this study precursor derived SiOC/MoSi₂ composites were evaluated with respect to their potential for the application as glow plug material. In a first step, fully dense composite materials with different fractions of electrical conductive MoSi₂ were fabricated by field-assisted sintering technique (FAST). The percolation threshold, where the electrical properties change from insulating to a suitable level of conduction depends on the microstructure, which can be controlled by the initial particle size of the used SiOC particles. It becomes principally possible to fabricate both, the insulating part and the heater material with the same MoSi₂ content and therefore without thermal mismatch. Room temperature properties, high temperature strength, oxidation and creep behaviour depend strongly on the MoSi₂ volume fraction. MoSi₂ contents beyond the percolation threshold lead to significantly enhanced creep rates. At high temperatures, reactions between SiOC and MoSi₂ can be observed, which differ at the air exposed surface and in the interior of the samples. From these findings, an upper limit for the application temperature can be derived.

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A simple process for synthesizing SiOC foams with low density (45–115 kg/m³) and high porosity (95–98%) is reported here. The process involves the impregnation of a flexible polyurethane foam with a preceramic polymer solution and pyrolysis in the inert atmosphere. SEM analysis showed that the resultant SiOC foam had a fully open interconnected porous structure with dense struts. N₂ adsorption test performed on the as-pyrolyzed SiOC foams showed very low surface area, which can be increased by leaching out the SiO₂-rich network by HF, leaving behind a mesoporous C-rich SiOC foam. The remarkably high surface area up to 147 m²/g (7350 m²/liter) has been reached after 24 h etching. HF etching leads to a decrease of the compressive strength. However, a good combination of compressive strength (∼80 kPa), porosity (95%) and surface area (7315 m²/liter) of the foam has been obtained and it makes the SiOC foam a potential candidate for specific applications.

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A processing technique for the preparation of porous, silicon carbonitride-based ceramics in tubular geometry derived from a liquid polysilazane precursor is presented. After casting of polysilazane/polymer-microbead dispersions, cross-linking, and subsequent pyrolytic conversion and selective removal of polymer templates, specimens with an inner and outer diameter of 6 and 10 mm, respectively, and a length of up to 65 mm were obtained. Porosity was controlled by sacrificial template content and reached values up to 48% after pyrolytic conversion, at average pore opening radii of 1 µm. The tubular specimens exhibited diametral compression strengths (C-ring test) between 24 ± 6 and 36 ± 4 MPa. Darcian permeability constants of up to 1.7·10⁻¹⁴ m² were found by gas permeability testing. The results demonstrate that this methodology facilitates the straightforward generation of complex-shaped porous specimens, further allowing for a control of strength and permeability in a specific range. Potential applications for the tubular, porous structures developed can be anticipated in the fields of separation or catalysis.

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A damage tolerant weak matrix SiC fiber reinforced composite was developed by utilising a polyvinylsilazane in the polymer infiltration and pyrolysis (PIP) process. The polysilazane was infiltrated via resin transfer moulding in a layup of SA3 fabrics, thermally cured and pyrolyzed. This process was repeated until a residual open porosity of below 5% was reached. During pyrolysis the polyvinylsilazane converts to an amorphous SiCN matrix. In combination with the high modulus Tyranno SA3 SiC fibers a weak matrix composite is created. To protect the composite in oxidative environment at high temperatures, an exterior SiC coating by means of chemical vapour deposition was applied. The polyvinylsilazane was investigated in terms of differential scanning calorimetry and measurement of viscosity to find the ideal temperatures for the polymer infiltration step. Specimens of the precursor were cured and pyrolyzed. The densification during pyrolysis was investigated in terms of He gas pycnometry and X-ray diffraction. The composite was characterized by SEM, µCT and mercury intrusion porosimetry. To determine the suitability of the SiC/SiCN composite for high temperature applications, samples were oxidized and tested by means of 3-point bending.

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Polymer-derived silicon oxycarbides exhibiting ≤1 and 10 vol.% of segregated carbon finely dispersed within a glassy Si_xO_yC_z matrix have been investigated by UV Raman spectroscopy using a laser excitation of 4.8 eV (λ = 256.7 nm). Carbon exists as amorphous sp²–sp³ bonded component in SiOC/C (≤1 vol.%) pyrolyzed at 1100°C in H₂, including C–C single bonds, polymeric chains and small polycyclic aromatic hydrocarbons (PAHs). The formation of nanocrystalline carbon at T > 1400°C is seen in the Raman spectra of SiOC/C (≤1 vol.%) and SiOC/C (10 vol.%) by the appearance of the G band of graphite. Tempering at 1600°C increases the degree of order within the carbon phase. However, the slight narrowing of the G peak with processing temperature (by about 5%) indicates still not well-crystallized carbon: the Raman results can be best explained by turbostratic carbon (with a lateral size L_a of ≈2 nm) and do not support the model description in literature as a network of single layer graphene.

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Modified graphitic C₃N₄ was synthesized by the ionothermal copolymerization method and composited with BiOBr by water-bath heating. The microstructure, specific surface area, photocatalytic activity and optical property of the resulting hybrid photocatalysts were characterized. The results showed that layered BiOBr was formed on the surface of modified graphitic C₃N₄ nanoparticles. The modified graphitic C₃N₄/BiOBr hybrid photocatalysts had a higher specific surface area than that of BiOBr and show a broad response range under visible light. The synergetic effect between the two semiconductors was more favorable for the separation of electron–hole pairs. Rhodamine B solution can be effectively degraded using the hybrid photocatalysts. When the weight ratio of modified graphitic C₃N₄ in the hybrid photocatalyst was up to 50%, the photocatalyst showed the best activity. Photocurrent testing indicated that the recombination of photo-generated electron–hole pairs was inhibited. The photocatalyst showed a good stability by a cycling experiment.

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The visible-light-induced photocatalytic water oxidation activity without cocatalyst has been demonstrated for the first time on tantalum (oxy)nitride nanocrystals synthesized by a Ca-assisted nitrogen-rich molecular approach. Monodisperse TaON and Ta₃N₅ nanocrystals were synthesized by using suitable urea/Ta ratios in the presence of Ca²⁺ ions. The as-synthesized (oxy)nitrides are in the form of spherically-shaped and well-defined nanocrystals with an average diameter of ca. 7 nm. Both nanocrystals showed absorption edges in the visible region. The band gap energies of TaON and Ta₃N₅ nanocrystals were determined from the Tauc’s plots of the UV–Vis diffuse reflectance spectra to be 2.27 and 2.08 eV for indirect allowed transitions, respectively. The O₂ evolution rate was increased and reached the maximum in the following order: 2.01, 3.32, and 4.66 µmol·h⁻¹ for the samples synthesized with Ca²⁺/urea molar ratio of 0.10, 0.50, and 0.25, respectively, due to the decrease in the optical band gap.

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Metal oxynitrides with perovskite AMO_3−xN_x structure have been shown to exhibit promising optical, dielectric, magnetoresistive or photocatalytic properties. They are formally obtained from perovskite oxides via substitution of oxygen by nitrogen. However, due to the stability of the M–O bond, only a limited number of nitrogen-doped perovskites AMO_3−xN_x and stoichiometric oxynitrides (AMO₂N and AMON₂) has been synthesized and studied so far. Different case studies revealed that the oxidation states of the cations, the O/N ratio, as well as the anion ordering can significantly affect their properties. With the aid of density functional theory calculations, the effect of O/N anion ordering was investigated for a series of different metallic perovskite phases AMO₂N (A = Rb, Sr, Y and M = Cr, Mo, W). Results indicate that well-defined cis-MO₄N₂ octahedra in the structures are energetically preferred over trans-MO₄N₂ octahedra, leading to zigzag M–N chains in the materials.

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The hypothetical spinel carbon nitride (γ-C₃N₄) has received a large amount of attention due to its predicted hardness being comparable to that of diamond. The group 14 spinel binary nitrides that have been synthesized are limited so far to: γ-Si₃N₄, γ-Ge₃N₄ and γ-Sn₃N₄. However, there still remains significant interest in γ-C₃N₄ in the hope that it will eventually be synthesized, but there are no successful reports, thus making the study of γ-C₃N4 strictly theoretical. Through an empirical relationship that correlates hardness, crystal structure and the electronic band gap, we examine a series of group 14 spinel nitrides: γ-C₃N4 γ-Si₃N₄, γ-Ge₃N₄ and γ-Sn₃N₄, as well as their ternary compounds. The hardness and electronic band gap of these materials are calculated using ab initio density functional theory. These results show that in the case of the solid solutions, γ-(Si,Ge)₃N₄ and γ-(Ge,Sn)₃N₄, the tetrahedral site is filled first by the larger cation, Ge and Sn, respectively. Furthermore, the deviation of carbon containing group 14 spinel nitrides from the expected hardness and bandgap trend suggests that γ-Si₃N₄ may remain the hardest known group 14 spinel nitride. Additionally, an improved method to calculate the hardness using the nitrogen bonding tetrahedron provides more unambiguous results and the trend of the hardness agrees with experimental measurements.

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Highly porous lamellar and cellular cathodes for Li-ion batteries were fabricated from additive-stabilized aqueous suspensions of lithium iron phosphate and carbon black by the unidirectional freeze-casting method and characterized by optical microscopy, scanning electron microscopy, mercury porosimetry, helium pycnometry and X-ray microtomography. The size and orientation of the pores in the specimens were controlled through the variation of the freezing parameters. The diameters of the pores, which are in the range from 0.7 to 30 µm, as well as the wall thickness, decrease as the cooling rate increases. Pore volume and total porosity increase while the solid content of the suspension decreases. The specimen’s structure was changed from lamellar to cellular by increasing the gelatin concentration and solid content in the suspensions. The lamellar specimens demonstrate higher porosity (82–84%) than the cellular samples. Cathodes with lamellar structure possess higher specific capacity and less loss of energy density in comparison to those having cellular structure.

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The enthalpy of formation of Li₂MnO₃ was measured by high temperature oxide solution calorimetry in a sodium molybdate solvent and the heat capacity of the compound was determined using differential scanning calorimetry. The enthalpy of formation of Li₂MnO₃ from the elements is slightly less exothermic than that of the orthorhombic and monoclinic modifications of LiMnO₂ but more exothermic than that of LiNiO₂, LiCoO₂, the LiNi_1−xCo_xO₂ solid solutions and the Li_1+xMn_2−xO₄ spinels. The heat capacity of Li₂MnO₃ is also slightly lower than the estimated heat capacity based on stoichiometric amounts of Li₂O and MnO₂ according to the Neumann-Kopp approximation. The slight differences in heat capacities are attributed to the differences in the bonding environments of Li⁺ ions in Li₂MnO₃ and the constituent binary oxide Li₂O. The thermochemical data presented here are essential for the advanced thermodynamic modeling of multicomponent electrode materials based on the promising xLi₂MnO₃·(1 − x)LiMO₂ nano-composite cathode system.

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Tetragonal zirconia polycrystals (TZP) are ceramics combining high strength and fracture resistance which are applied in biomedical and engineering applications. In this study, a nanoscale monoclinic zirconia nanopowder was coated with 3 mol-% ytterbia via a wet chemical route. The powders obtained after calcination and milling were consolidated into dense samples by hot pressing at 1275–1500°C for 1 h at 50 MPa axial pressure. Microstructure phase composition and mechanical properties were determined. The materials were initially very fine grained and showed grain growth starting at sintering temperatures exceeding 1350°C. At low sintering temperatures bending strength values of 1000–1100 MPa were recorded along with high fracture resistance of >10 MPa√m. In the sintering temperature range between 1350–1375°C, a steep decline of toughness to a level of 6 MPa√m was observed. This decline in fracture resistance is accompanied by a drop in transformability of the tetragonal phase and grain growth. While TZP from coprecipitated powders tend to become tougher with sintering temperature and increasing grain size, materials from stabilizer coated powders showed an adverse tendency. The tough to brittle transition in the 3Yb-TZP studied was attributed to the elimination of the initial stabilizer concentration gradient in the tetragonal grains.

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A sol–gel-derived carboxyl-functionalized lamellar-type silsesquioxane was prepared to investigate its potential for use as a host material for intercalation reactions with n-alkylamines and alkylene diamines. Upon intercalation of n-alkylamines and alkylene diamines, the interlayer distances increased as shown by X-ray powder diffraction patterns, and IR spectra showed the presence of absorption bands attributable to ν(COO⁻) and δ(NH₃⁺) modes. The amounts of intercalated n-alkylamines were determined from n-C_nH_2n+1NH₂/–COOH molar ratios which, based on CHN analysis, exhibited values from 0.76 to 0.88; whereas the values determined for the alkylene diamines were 0.83 (NH₂C₄H₈NH₂), 0.45 (NH₂C₈H₁₆NH₂) and 0.33 (NH₂C₁₂H₂₄NH₂). These results show that intercalation of n-alkylamines and alkylene diamines into lamellar-type silsesquioxane bearing carboxyl groups proceeded successfully via acid-base mechanisms.

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Si–O–C(–H) ceramics were synthesized from polycarbosilane (PCS) by a combinatorial procedure of thermal oxidation curing and H₂ decarbonization. In the case of PCS precursor with particle form (diameters of 100–500 nm), thermal oxidation curing at 340°C was most effective to achieve white appearance with photoluminescence even after H₂ decarbonization at 800 or 1100°C. In the case of fiber form (diameter of 10 µm), the curing temperature of 290°C was effective to obtain white PL fiber after the decarbonization at 800°C. Heat treatment at 1100°C, however, changed the color of the fiber to black. Spectroscopic analysis of the decarbonized products revealed that structure of the white materials with strong PL mainly consisted of SiO₄–SiO₃C mixed units, whereas incorporation of SiC₄ units decreased PL intensity. In addition, the materials with apparent PL usually exhibited a sharp absorption band at 880 cm⁻¹ in FT-IR spectra, which was possibly assigned to a kind of Si–C bonds modified by hydrogen incorporated in the amorphous network.

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The mass-transfer mechanisms of polycrystalline alumina with and without oxygen reactive elements (REs) such as Ln (Y and Lu) and Hf were investigated by evaluation of the oxygen permeability through alumina wafers, which served as a model for alumina scale, at accelerated temperatures up to 1923 K. Oxygen permeation proceeded via grain boundary (GB) diffusion of oxygen from the higher oxygen partial pressure [P_O2(hi)] surface side to the lower P_O2 [P_O2(lo)] surface side, along with the simultaneous GB diffusion of aluminum in the opposite direction, maintaining the Gibbs–Duhem relationship. The chemical potentials, GB diffusion coefficients, and fluxes of oxygen and aluminum in alumina wafers with applied oxygen potential gradients (dμ_O) were calculated from the oxygen permeability constants. The fluxes of oxygen and aluminum at the outflow side of the wafer were significantly larger than those at the inflow side. Ln and Hf segregation at the GBs selectively reduced the diffusivity of oxygen and aluminum, respectively. Thus, the mesoscopic dopant arrangements, which were selected by taking into consideration the behavior of the diffusion species and the role of dopants, enabled the alumina layers to have enhanced oxygen shielding capability at high temperatures. Furthermore, the GB diffusion data derived from the oxygen permeation experiments were compared to those for alumina scale formed by the so-called two-stage oxidation of alumina-forming alloys.

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Interfaces are important in the functionality of materials with composite structures. Focusing mainly on our studies, this article provides an overview of the functionality that can be achieved by the careful design of interfaces in inorganic composites. Molecular selective photocatalysts have been realized by developing nanostructures, in which photocatalytically active metal oxide particles are surrounded by mesoporous silica. Such composites structure achieved combined function of molecular selective adsorption and photocatalytic decomposition. Solid acid catalysts that are active in water have been realized by exploiting the nanostructure of mesoporous silica. Catalytically active inorganic molecules such as heteropolyacids have been anchored on the walls within the pores of hydrophobic organic layers. The resulting nanocomposite exhibited high acid catalytic activity in water. Sponge crystals are a more recently discovered class of porous crystals. We discuss their structure, and propose revised classifications of microporous crystals, mesocrystals and sponge crystals. Thin films of metal nitrides such as Sr₂N and metal oxides have been prepared by molecular beam epitaxy and pulsed laser deposition. The effects of the interface between the film and substrate are discussed.

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This study investigates the influence of sintering pressure on the microstructure and properties of Ti(C,N)–TiB₂–Co cermets prepared by reactive hot processing from a Co–Ti–C–BN system. With increasing sintering pressure, the apparent relative density, fracture toughness and hardness first increase, and then decrease. Cermets with low densities are produced at low applied pressures because liquid cannot infiltrate into the pores, whereas the decomposition of Ti(C,N) and extrusion of cobalt at high pressure produce nano-sized pores that reduce the relative density and mechanical properties. Sintering at 34 MPa produces the optimum combination of high apparent relative density (99.8%) with a fine grain size and few crystal defects, which result in a fracture toughness, hardness, and wear groove depth of 6.71 MPa·m^1/2, 19.01 GPa, and 2.2 µm, respectively.

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In this study, Fe–W₂B-based composite coating on the inner surface of a steel pipe was produced by centrifugal- Self-propagating high-temperature synthesis (SHS) process. There were FeWO₄, B₂O₃, and Al powders as the major reactants. The effects of coupled additives X(Fe₂O₃–Al) of X = 1, 3, and 5 molar ratio on morphology, composition and micro-hardness of the obtained composite coatings were investigated. The results showed that the system of X = 1 mole was the optimum condition due to its reasonable smoothness (6.5 µm) and hardest (727.90 and 1170.71 HV on alloy and ceramic layers, respectively).

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(001)-epitaxial (Pb_0.91La_0.09)(Zr_0.65Ti_0.35)O₃ (PLZT) ferroelectric thin films were fabricated on SrTiO₃ and MgO substrates, with an SrRuO₃ bottom electrode layer, using pulsed laser deposition. When films were deposited in a single step at a high temperature conventionally used for epitaxial growth, island growth was observed. To suppress the island growth, we used a two-step growth technique. First, a thin initial layer was deposited at a low temperature to promote rapid strain relaxation from the lattice mismatch. Consequently, the island growth was suppressed and when a second layer was deposited at high temperature, a remarkably flatter surface was achieved as compared with that of conventional one-step-grown films. The two-step-grown PLZT films are promising for use in ferroelectric thin film-based plasmonic electro-optic devices.

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A poled lead titanate zirconate rectangular parallelepiped is subjected to compressive stress-induced switching at room and high temperatures. From measured electric displacement and strains, piezoelectric and elastic compliance coefficients are estimated and plotted versus remnant state variables. Then a set of modeling equations is proposed to predict the high temperature behavior of the material reported in one of the authors' previous work. The equations are applied to the present work to calculate the evolutions of reference remnant state variables during mechanical depolarization. Finally, the high temperature behavior of the material during mechanical depolarization is compared with the behavior during electric field-induced polarization reversal in terms of reference remnant state variables.

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Fully dense transparent alumina is obtained after spark plasma sintering at 1000°C by using the electrically conductive SiC molding set. Compared to the conventional graphite set, the new mold material lowered the sintering temperature by 150°C for full densification. The SiC set has a lower electrical conductivity than that of the graphite set, which resulted in higher electric field during heating. The enhanced densification is attributed to the high electric field. In this study, the effects of the electric field and the heating rate on the densification of alumina are examined with the SiC molding set, and compared to the results with the graphite set.

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In this work, the sonocatalytic property of CaTiO₃ nanoparticles synthesized via a polyacrylamide gel route was investigated by degrading rhodamine B (RhB), methyl orange (MO) and methylene blue (MB) under ultrasonic irradiation. It is revealed that CaTiO₃ particles exhibit an excellent sonocatalytic activity toward the dye degradation. The influence of various experimental parameters [reaction solution temperature, catalyst dosage, initial dye concentration, pH value, and inorganic anions (including NO₃⁻, SO₄²⁻, H₂PO₄⁻, and HCO₃⁻)] on the sonocatalytic efficiency was systematically investigated. Hydroxyl (•OH) radicals were detected by fluorimetry using terephthalic acid as a probe molecule and are found to be produced over the ultrasonic-irradiated CaTiO₃ particles. The addition of ethanol, which acts as a •OH scavenger, leads to a quenching of •OH radicals and a simultaneous decrease in the dye degradation. This suggests that •OH radicals are the dominant active species in the present sonocatalytic reaction. In addition, the recycling sonocatalytic experiment reveals that CaTiO₃ particles exhibit a good stability in their sonocatalytic activity and crystal structure.

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The magnetically recyclable MnFe₂O₄/Polyaniline (PANI) composite was successfully synthesized by a combination of a salt-assisted solution combustion method and an in situ oxidative polymerization method. X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV–vis diffuse reflectance spectroscopy (DRS) were employed to characterize the physical and chemical properties of the samples. The results showed that MnFe₂O₄/PANI composite exhibited higher photocatalytic activity and stability than pure PANI and MnFe₂O₄ nanoparticles toward the degradation of rhodamine B (RhB) under visible light irradiation, suggesting the existence of a synergic effect between PANI and MnFe₂O₄. The excited state electrons in the lowest unoccupied molecular orbital (LUMO) of PANI can readily migrate into conduction band (CB) of MnFe₂O₄, while the holes in the valence band (VB) of MnFe₂O₄ migrate to the π-orbital of PANI because of the enjoined electric fields of the two materials, which can further improve the separation of the photoinduced electron–hole pairs.

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Ag₃VO₄/Bi₂MoO₆ nanocomposites were successfully synthesized by sonochemical method. The as-synthesized products were characterized by X-ray powder diffraction (XRD), field emission scanning electron microscopy (FE-SEM), selected area electron diffraction (SAED), transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM). The results revealed the formation of heterostructure Ag₃VO₄/Bi₂MoO₆ nanocomposites. Photocatalytic activity of the nanocomposites was evaluated through the degradation of rhodamine B (RhB) dye under visible white light irradiation. Among them, heterostructure 10.0 wt% Ag₃VO₄/Bi₂MoO₆ nanocomposites exhibited the highest photocatalytic activity up to 56.26% for the degradation of RhB dye under visible white light within 240 min.

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Needle-like single crystals of aluminum nitride (AlN) were synthesized by the direct nitridation of an Al–Si binary melt. The growth behavior and shape of the needles were changed by varying the Al:Si ratio. With lower Al content, needles with high aspect ratio (>20) preferentially grew on the Al–Si melt and crucible wall. With increasing Al content, needles with lower aspect ratios having various shapes such as ribbon-like and bended shapes tended to grow. The longer directions of the needles could mainly correspond to the c-axis of a wurtzite-type AlN.

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We performed depth analysis of a compression layer in Corning Gorilla Glass 3, one of commercialized chemically-strengthened glasses, using depth-resolved micro-Raman spectroscopy. We obtained a depth variation of Raman spectra and an ion-exchange rate of Na for K was determined by energy dispersive X-ray spectroscopy. We found that a peak position around 1100 cm⁻¹ in the Raman spectra is shifted to higher wavenumber and the ion-exchange rate of Na for K increases with a decreasing depth when shallower than ∼30 µm. This correlation can be qualitatively explained as follows: compression of a TO₂ tetrahedra network (T = Si or Al) induced by the ion exchange gives rise to an increase in frequency of vibrational modes of the TO₄ tetrahedra.

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Zirconia particles were prepared by interfacial reaction crystallization in a coaxial tubular reactor. Zirconia particles were prepared by neutralization reaction in interfacial reaction crystallization, not by alkoxide method from viewpoint of inexpensive and simplified approach. A microfluidic channel was utilized for fabricating monodispersed zirconia particles in a continuous flow process. Particle size distribution and morphology of zirconia prepared by a coaxial tubular reactor were evaluated. Monodispersed solid zirconia particles were obtained by a coaxial tubular reactor in one step process. Furthermore, monodispersed porous zirconia particles were obtained by a coaxial tubular reactor in two step process. We succeeded in preparing monodispersed zirconia particles controlled morphology by inexpensive and simplified approach using two different kinds of tube reactor.

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