The effects of SiC_p addition on the z-value, microstructure and mechanical properties of β-Si_6−zAl_zO_zN_8−z–SiC_p were investigated. The results showed that z-value of β-Sialon decreased from 2.66 to 1.20 with the increase of SiC_p addition, while the apparent porosity of β-Sialon–SiC_p composites increased. The bending strength and compressive strength decreased due to the increase of the apparent porosity and the weak cohesion resulted from the thermal expansion coefficient mismatch between SiC_p and β-Sialon matrix. Moreover, a linear regression model used to identify the relationship between the content of SiC and z value of β-Sialon is fitted.

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The influence of the joining time and temperature on the flexural strength of B₄C ceramics joined using an Al sheet was investigated. The B₄C ceramics were joined over a temperature range 600–1400°C for 2–72 h in vacuum (10⁻²–10⁻⁴ Pa) and in an Ar atmosphere. A joining interlayer with a dense structure was found in the B₄C joint formed at 1000°C after 2 h in vacuum, and mainly Al was present in this joining interlayer. On the other hand, some voids existed in the joining interlayer in the B₄C joint formed after 72 h. In addition, Al was not present in this interlayer owing to its reaction with B₄C as well as the evaporation of Al. Four-point bending tests of the B₄C joints formed at 1000°C in vacuum for periods ranging from 2 to 72 h were performed at room temperature. The average four-point bending strengths of the B₄C joints formed after 2 h at 700–1100°C were close to that of the B₄C base material, and the B₄C ceramics were considered to have successfully bonded. However, the joint strength decreased with an increase in the joining time, and the B₄C ceramics did not bond at temperatures over 1200°C in vacuum. On the other hand, the B₄C ceramics did bond at 1200–1400°C in Ar.

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Enthalpy-enhancing gas is used to optimize the ionic conductivity of atmospheric plasma-sprayed 3.9 mol % yttria-stabilized zirconia (3.9YSZ) electrolyte. In the experiment, three hydrogen gas flow rates are used to control the plasma energy. The 3.9YSZ feedstock powder is sieved to obtain particles with sizes in the range of 75–106 µm. The electrolyte has the highest hardness and lowest roughness when sprayed at hydrogen gas flow rates of 12 and 7 Lmin⁻¹, respectively. The electrolyte bulk density increases and the apparent porosity decreases with increasing hydrogen gas flow rate. A 3.9YSZ electrolyte with an ionic conductivity of 1789 µ(Ω cm)⁻¹ is obtained at 800°C with a hydrogen gas flow rate of 12 Lmin⁻¹. It is controlled by the grain-boundary conductivity. The increase in grain-boundary conductivity is closely related to a low apparent porosity, low migration energy, and a decrease in grain size. Hydrogen gas enhances the growth of columnar grains and suppresses the formation of the monoclinic phase, which is attributed to increased intragrain conductivity.

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This paper describes a novel experiment involving the joining of alumina using a polymer blend method and Al foil. Alumina pieces were dipped into a polymer blend containing polycarbosilane and polymethylphenylsiloxane, which is a kind of polysiloxane. After curing and ceramization of the polymer on the alumina pieces, the pieces sandwiching Al foil were heated under vacuum at 1073 K. The samples near the center of the joining area (SC samples) were mainly composed of metal Si without any cracks, and their average tensile strength was very high, approximately 252 MPa. On the other hand, the samples on the periphery of the joining area (SP samples) were mainly composed of a carbon-rich substance such as aluminum carbide with deep cavities, and their average tensile strength was poor in comparison to the SC samples, approximately 56.9 MPa.

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In this paper, porous aluminum titanate (Al₂TiO₅) ceramic was fabricated by reaction sintering method using Al₂O₃ and TiO₂ as raw materials and corn starch as pore-forming agent. In order to decrease the decomposition and improve strength of porous Al₂TiO₅ ceramic, 5 wt % of Fe₂O₃ and 4 wt % of SiO₂ were added as modifying agents. The influences of sintering temperature and content of pore-forming agent on phase constitution, apparent porosity, compressive strength and elemental distributions of the sintered products were investigated. The results show that porous Al₂TiO₅ ceramics with apparent porosity about 45–48% can be produced by reaction sintering method at temperature of 1500°C for 2 h. The synthesis yield of pure Al₂TiO₅ can achieve more than 95% using 5 wt % Fe₂O₃ and 4 wt % of SiO₂ as modifying agents when sintering temperature was 1500°C. The distributions of Fe, Ti, Al and O are homogeneous in the grain, however majority of Si distributed in the grain boundaries of Al₂TiO₅ which is proved by the EMPA (elemental mapping image analysis).

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The fundamental theory of void fractions with an arbitrary size distribution was applied to a system with a lognormal distribution. The theoretical void fraction was in good agreement with the experimental values for a glass-sphere system. We also considered the particle-shape effect under extreme conditions for spherical particles and crushed particles in a system having a lognormal distribution.

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The effects of doping of Fe ions in lithium aluminosilicate glass-ceramic under varied thermal treatment conditions were studied by synchrotron X-ray powder diffraction, X-ray absorption near edge structure (XANES) and infrared microscopy. When doping concentration is high (>0.6 wt %), Fe ions tend to migrate into the main crystalline phases; while these ions remain in a disorder environment at low doping level. In high doping samples heated at higher than 800°C, multiple scattering peaks in XANES spectra can be observed in samples, which imply that Fe ions substitute into the Li sites of the main solid solution phase. The diffraction results show that a small amount of Fe oxide (<0.2 wt %) in a LAS glass-ceramic material decreases the crystallization temperature of β-quartz solid solution by ~50°C. Samples doped with ~0.6–3 wt % of Fe ions results in a raised formation temperature of β-quartz solid solution and a retarded phase transformation of β-quartz solid solution to β-spodumene solid solution.

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The V₂O₅ nano-particles were synthesized by using the Liquid Phase Precursor (LPP) method in air atmosphere. LPP method is a new synthesis technology conducted by using the nano-structured cellulose (pulp) and vanadyl sulfate hydrate (VO[SO₄]₇H₂O) solution, that is called the precursor. A vanadium solution was impregnated into the pulp for trapping vanadium ions. Impregnated pulp was fired at 400 to 600°C to evaporate the cellulose and then V₂O₅ particles were obtained.
Burning temperatures and decomposition behavior of impregnated pulp as a function of precursor concentration were measured by TG–DTA. Their crystal structure and morphology of obtained particles were evaluated by XRD, FE-SEM and TEM. Nano-sized V₂O₅ particles of around 70 nm were obtained without grinding by firing at 400°C for 1 h. Burn-out mechanism of impregnated pulp was studied.

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Two types of silica powder with different structures, one crystalline (C1) and one amorphous (A1) were mechanically treated using a planetary type mill. Three different rotation speeds (100, 200, 300 rpm), milling times (15, 30, 60 min) and ball sizes (1, 5, 10 mm) were used. The structure and morphology of the powders did not change by milling. The effect of milling conditions on particle size distribution was investigated. By the milling treatment the original particle size of both powders could be effectively reduced. For the amorphous powder rotation speeds of 200 and 300 rpm and prolonged milling causes the formation of a broad range of particles of larger sizes. This behavior is not observed for the crystalline powder. The surface activity of raw and treated powders was measured as the amounts of dissolved Si⁴⁺ ion into ammonia solution. For the crystalline powder the smallest ball size, 1 mm, was the most changing in the amount of dissolved Si⁴⁺ for all milling speeds and milling times and its changing increased by increasing both rotation speed and milling time. In the case of the amorphous powder the 5 mm ball size was the most effective for 100 and 200 rpm rotation speeds almost independently of the milling time. A possible activation reaction mechanism occurring during the milling process is also discussed. The findings indicate that from a technical and economical point of view as the low total energy consumption for milling with 15 min milling time at 200 rpm with a 5 mm ball will be sufficient to considerably reduce the particle size and increase the specific surface activity of the amorphous powder making it suitable for different applications in non-firing ceramics processing.

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Trivalent cation oxides were added to zinc phosphate glasses by conventional melt-quenching technique to dope excess electrons in order to create donor electrons easily excited by the incident light, in specific Ga₂O₃ and Sb₂O₃. By exciting 200 and 250 nm light, the glasses containing Sb₂O₃ emitted visible light, while no emission from those containing Ga₂O₃ could be observable.
The intensity of emission light depended upon Sb₂O₃ concentration, and 0.3–1.0 mol % Sb₂O₃ addition was most effective for the emission, and concentration quenching was seen in over 5 mol % Sb₂O₃ addition. With respect to necessity of the presence of ZnO was explored by replacing ZnO by CaO and BaO. Even by changing of ZnO by CaO and BaO, the emission intensity was not influenced. Further, we used borate glasses instead of phosphate glasses. Since only weak emission was obtained from borate glasses, P₂O₅ can be considered to be indispensable for photoluminescence (PL) phenomena.

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Functional ceramics were synthesized using ceramic powders activated by mechanochemical processing. The activated powders were dispersed in an alkali-containing solvent to dissolve the metallic ions at the powder surface and effect re-precipitation between the grains. The “non-firing ceramic process” afforded high-strength ceramic solids without the need for calcination. The key step in this technique is surface activation of the ceramic powders through mechanochemical processing. We investigated the bonding and activity of the atoms near the surface by spectroscopic analysis of desorption of the adsorbed water molecules, a convenient and quantitative method. The powder surface contained an increased number of uncoordinated defects after mechanochemical processing, and powders with high compact strength showed high activity and had high surface Al^V content. Diffuse reflectance infrared Fourier transform measurements of the desorption of water molecules allowed for easy and rapid determination of differences in the surface activity, which was not possible when using alternative analysis methods.

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The influence of ultraviolet (UV) irradiation on vinylsilsesquioxane (ViSiO_3/2) films was investigated using a nanoindentation technique, and the structural changes were analyzed. Solid-state ¹³C cross-polarization magic-angle-spinning nuclear magnetic resonance and infrared spectra of the films confirmed the polymerization of C=C bonds and formation of a C–C bridge structure upon UV irradiation. Since the vinyl group is a photosensitive organic component with a short organic chain, it is expected to show a large improvement in mechanical properties as a result of the formation of an organic network under the influence of UV irradiation. It is shown that varying the intensity of the UV irradiation leads to changes in the hardness and elasticity. The irradiation energy was found to determine the mechanical properties of the ViSiO_3/2 films, regardless of the effects of different UV intensities on the hybrid films.

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