Various modified CVD processes, such as modified hot filament method, vapor phase diffusion process, in-situ CVD process, catalytic CVD process, for the preparation of ceramics single crystals and fibers were developed. The preparation conditions, morphologies, microstructure and properties of transition metal carbides, nitrides, borides, silicides, sulfides, etc were examined. We have first found that various ceramic fibers with 3D-helical/spiral structure, such as Si₃N₄, carbon, TiC, TiO₂, etc. were obtained using metal-catalyzed CVD and/or vapor phase diffusion processes under critically controlled reaction conditions. Carbon microcoils (CMC) with double-helical structure were obtained with high reproducibility by metal catalyzed pyrolysis of acetylene. The CMCs have many interesting and eminent characteristics, such as 3D-helical/spiral microstructure with μm orders in coil diameters, diverse microstructures from amorphous to graphite structure, changing in electrical parameters under the application of various stimuli, high microwave absorption and microwave heating abilities, breeding or anti-breeding effect on cells, fibrils of organisms, etc.

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This paper describes a convenient and rapid colloidal measuring process of electrokinetic (ζ-potential, ESA signal) properties of the relatively concentrated aqueous suspensions of a submicron α-Al₂O₃ powder with the anionic polyelectrolyte (Dolapix CE64) dispersant by applying of an advanced electrokinetic sonic amplitude "ESA" technique without dilution. In addition to ESA measurement, the following measurements were also applied: the viscosity, sedimentation, Bingham yield value and prticle size distribution. Very good agreement is observed from the relationship between the electrokinetic (ζ, ESA) values, the viscosity and its pH dependence for each concentrated α-Al₂O₃ suspension with different amounts of dispersant. The results indicate that the amount of 0.4 mass% Dolapix CE64 is the optimum amount of dispersant that can cause electrosteric effect and decreases mean (d₅₀) particle size of different concentrated (2 vol% and 45.68 vol%) α-Al₂O₃ suspensions near to the original size. Finally, the study illustrates that Dolapix CE64 is an effective dispersant at all solid loading conditions.

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Low-temperature co-fired ceramics (LTCC) is a glass-ceramic composite, in which the glass crystallization occurs during firing. The amount and type of the crystalline and amorphous phases determine the final properties. A commercial glass-ceramic powder was selected in this study. The phase development was studied by XRD, the thermal properties were studied by DTA and dilatometry. The dielectric properties were measured by the Hakki and Coleman method. The results show that Al₂O₃, TiO₂, and Zn₂SiO₄ existed in the as-received powder and their quantities decreased as the firing temperature increased. BaAl₂Si₂O₈ appeared at 850°C and its quantity increased with temperature. At 900°C, Sr₂Al₂SiO₇, and (K_0.94Na_0.06) (Al_0.99Si_3.01)O₈ were formed. The degree of crystallinity of the as-received powder was around 53 mass% and gradually increased, reaching a maximum of ~96 mass% at 900°C. As the firing temperature increased, the dielectric constant of the fired specimens decreased, but the quality factor increased. The decrease in dielectric constant can be attributed to the porous microstructure and the increase of the quality factor can be attributed to the increasing degree of crystallinity at high temperatures. However, the porous microstructure deteriorates the mechanical strength of the fired specimens. So a trade-off between the dielectric properties and the mechanical strength should be made.

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The ceramic tile industry faces up to a saturated market and needs to offer innovative products constantly, competitive in quality and optimal from the economic and environmental point of view. Ceramic tiles lightened by the execution of a deep back relief could be manufactured with less raw material than the traditional one, which has an effect in the saving of weight and energy. Additionally, a lighter final product improves working conditions on the shopfloor and at the building site. Nevertheless, lightened tiles are structurally different, and so is their mechanical and thermic behaviour. Because it is a constructive element it is necessary to know its response under typical loads and assure fulfilment of the valid standards. This paper aims at the objective of evaluating lightened ceramic floorings employing solid three-dimensional modelling and finite elements method (FEM), establishing an optimal definition of the back relief. In order to achieve this objective, 1 reference model and 56 different relief versions were defined, which underwent 4 structural tests. After deciding that both mass and principal stresses (Rankine criterion), were the magnitudes to consider in the study, the maximal stresses of each version for each test were calculated, as much as their distribution. Next, 4 comparison coefficients were defined and a suitability order was established. Finally, thanks to the collaboration with a ceramic company it was verified that the employed methodology was appropriate. Altogether, it has been concluded that lightened tiles could improve both raw material consumption and structural response simultaneously. A set of fundamental behaviour guidelines has been extracted and could be taken as a basis for the back relief design of any enterprise. Regardless these guidelines, this paper proposes a methodology for the geometric evaluation of floorings that could be extended to other kinds of products and design variables.

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The magnetite/hydroxyapatite (HA) composite that facilitates direct bonding to bones through HA and generation of heat from magnetite exposed to AC magnetic field is considered suitable for hyperthermia therapies of cancer in bones. Porous magnetite/hydroxyapatite (HA) composite was prepared by a hydrothermal treatment of α-tricalcium phosphate (α-TCP) and nano-sized magnetite powder mixture having magnetite concentrations varying between 10 and 50 mass% at 120°C under saturated vapor pressure for 24 h. This composite had micro-sized pores of about 400 μm and submicron-sized pores of about 0.2 μm in size and magnetite particle aggregates were strongly trapped in the cages of rod-shaped HA particles only when the magnetite contents were 30 mass% or less. At magnetite concentrations higher than 30 mass%, the composite cannot hold the particles completely and considered unsuitable for biomedical applications. When magnetite/hydroxyapatite (HA) composites with various magnetite concentrations were exposed to high frequency magnetic field for 10 min, the temperature rise in the composite was a function of magnetite concentration and the temperature rise in 30 mass% was 55°C, which is well above the temperature required for treatment. However generation of higher temperatures, which could be achieved by controlling the magnetic field strength, frequency, and exposure time, may be required because the heat loss due to blood flow, etc., is considered during hyperthermia therapies of cancer in bones.

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The effects of amide types drying control chemical additives on the morphologies, BET surface areas, pore sizes, crystal structures, and photoluminescence intensities of the Y₂O₃:Eu phosphor powders prepared by spray pyrolysis were investigated. The phosphor powders obtained from the spray solutions with N,N-dimethylacetamide (DMA) and N,N-dimethylformamide (DMF) had filled inner structures, low surface areas and high photoluminescence intensities under vacuum ultraviolet illumination. The photoluminescence intensity of the phosphor powders obtained from the spray solution with DMA was 120% of that of the phosphor powders obtained from the spray solution without drying control chemical additive.

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Double oxidation of SiC single crystal was carried out in oxidizing gas (O₂ or H₂O) at 1673 K first and then in isotopic water (H₂¹⁸O or D₂O) at 1473 K or 1573 K to trace diffusing species during oxidation at high temperatures. SIMS analysis revealed that deuterium was enriched near SiO₂/SiC interface when SiC was oxidized in Ar/D₂O gas mixture at the second oxidation step, indicating that water molecules or hydroxyls diffused in SiO₂ layer to the SiO₂/SiC interface. Large amount of carbon in SiO₂ scale near the SiO₂/SiC interface after oxidation in dry Ar/O₂ gas mixture suggests a possibility that outward diffusion of carbonaceous species can be rate-controlling step during oxidation in dry Ar/O₂ atmosphere. Decrease in the amount of the carbon with oxidation time in Ar/H₂¹⁸O gas mixture at the second oxidation step implies that the outward diffusion of carbonaceous species in SiO₂ scale was promoted during oxidation in atmosphere containing water vapor.

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Purified HiPco SWNTs were dispersed in lactose aqueous solutions containing sodium deoxycholate (SDC) as the dispersant, with the assistance of ultrasonication. After removing the large bundles of SWNT by high speed centrifugation, the resulted SWNTs aqueous dispersion was spray-dried, and then the SWNTs-lactose solid dispersions (or composite particles) were obtained. They were mostly of spherically shell-structured shape with several microns in diameter. Vis-NIR spectroscopy and TEM observation revealed that SWNTs presented as small bundles and individual tubes inside the lactose solid matrix. These results indicate that lactose precipitated out from the aqueous droplets in the spray-drying, and transformed to solid matrix rapidly, which prevented the dispersed SWNTs from re-aggregation, thus immobilize the isolated SWNTs inside the matrix. The present solid dispersions can readily be re-dispersed in water and form SWNTs aqueous dispersion.

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Nano-sized Ce_1-xGd_xO₂ (0 ≤ x ≤ 0.2) particles were prepared by spray pyrolysis process from the spray solution with ethylene glycol. The mean sizes of Ce_1-xGd_xO₂ (x = 0, 0.05, 0.1, 0.2) particles were each 46, 33, 29, and 28 nm. The mean crystallite size of pure CeO₂ was 33 nm. However, the Gd-doped CeO₂ had the mean crystallite size of 28 nm irrespective of the molar ratio of Gd to Ce components. The mean grain size of the sintered CeO₂ pellet was about two or four times larger than those of the Gd-doped CeO₂ pellets. The mean grain sizes of Ce_0.9Gd_0.1O₂ and Ce_0.8Gd_0.2O₂ pellets are about 0.5-0.4 μm. The pure CeO₂ pellet had low relative density of 80%. However, Ce_0.9Gd_0.1O₂ and Ce_0.8Gd_0.2O₂ pellets had the high relative densities above 95%. The Ce_0.9Gd_0.1O₂ and Ce_0.8Gd_0.2O₂ pellets had similar conductivities at all measuring temperatures. The Ce_0.9Gd_0.1O₂ pellet had conductivities of 4.73 × 10^-2 and 1.16 × 10^-1 Scm^-1 at measuring temperatures of 800 and 900°C respectively.

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Rod-like aluminum nitride (AlN) nanoparticles were prepared by the nitriding combustion synthesis method. A charge composed of Al and AlN diluent powders (40/60 mol%) with 5 mass% MgO as additive was combusted under 1 MPa nitrogen atmosphere. The combustion temperature of the reaction was 2030°C and the speed was 1.58 mm/s. The FE-SEM observation showed that the rod-like AlN nanoparticles have diameters in the range of 90-300 nm and maximum length about 2 μm. It also showed evidences of the core-shell model of nitridation where the nanorods grew near the flow-out of eggshell-type AlN hollows. The EDX analyses showed the formation of Mg-Al-O-N droplets on the tips of AlN nanorods which strongly suggested that the vapor-liquid-solid (VLS) mechanism was the predominant growth mode. However, when the liquid droplets necessary for VLS were exhausted with continuous covering on the surface of the growing nanorods, the growth mode changed probably to vapor-solid (VS) mechanism. Furthermore, a growth model of the formation of rod-like AlN nanoparticles was proposed and discussed in accordance with experimental results.

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β-SiAlON was synthesized from a zeolite by NH₃ gas nitridation and its formation mechanism was investigated using X-ray diffraction and ²⁹Si and ²⁷Al NMR spectroscopy. It was revealed that most of the Si and Al atoms react to form β-SiAlON via amorphous forms of Si-Al-O-N and O-SiAlON. Nitridation using NH₃ gas is an effective means of preventing mullite formation and promoting the introduction of nitrogen into aluminosilicate materials at lower temperatures than temperatures required by the carbothermal reduction nitridation process. Further, the NMR spectra showed that the siliceous part of the system changed into low z-value of Si_6-zAl_zO_zN_8-z (β-SiAlON) and the incorporation of Al components into the β-SiAlON was promoted in the later stages of the reaction.

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Boehmite (Al(OH)O) was employed for the removal of aqueous phosphate in the presence of harmful anions such as carbonate, sulphate, nitrate, nitrite, chloride and fluoride at 298 K. Although boehmite was shown to remove a certain simultaneous removal of phosphate together with fluoride, no influence of the presence of carbonate, sulphate, nitrate, nitrite and chloride on the removal of phosphate by boehmite was observed. In the present study, two kinds of boehmite, a commercially available form and boehmite prepared using a sol-gel technique, were employed for the simultaneous removal of phosphate and fluoride, and it was found that the latter form was superior for such removal. Solid-state ³¹P MAS NMR analyses revealed that, in the presence of fluoride, phosphate was removed onto boehmite as different types of phosphate species, depending on the solution pH and the source of boehmite.

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We recently found dark-brown SnO₂ films were formed in a chemical vapor deposition process under a limited oxygen supplying condition and the nature was investigated in this work. Those films were deposited from SnCl₂ at 350-600°C in a tubular furnace. The films had the rutile-type structure with the significant preferred-orientation along <1 0 0> normal to the substrate surface. Thermogravimetric and elemental analyses revealed that the oxygen deficiency (V_O) and Cl contamination occurred in the films. An as-deposited film at 350°C contained V_O of 1.5 × 10²¹ cm^-3, which corresponded to that about 2.5% was vacant in the O site. On the other hand, Cl was contained at 7.4 × 10²⁰ cm^-3 in the 350°C-prepared film. The Cl concentration decreased with deposition temperature and became 1.8 × 10²⁰ cm^-3 at 600°C. The films showed moderate electric-conductivity and the film deposited at 500°C had the lowest resistivity of 2.5 × 10^-2 Ωcm, where the carrier density and the Hall mobility were 1.3 × 10²⁰ cm^-3 and 2.0 cm² V^-1s^-1, respectively.

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We present the O₂-blowing method for the growth of high-quality single crystals of Bi-based perovskite ferroelectrics, in which O₂ gas is directly introduced inside crucibles during crystal growth. The O₂-blowing method is demonstrated to be effective for enhancing polarization and piezoelectric properties as well as reducing leakage current for (Bi,Na)TiO₃-BaTiO₃ crystals. The superior properties are suggested to originate from the reduced reorientation of non-180° domains. Ab initio calculations suggest that the interaction between spontaneous polarization and defect dipole composed of Bi vacancy and O vacancy is the origin of the reorientation of non-180° domains.

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Mechanical properties of hydroxyapatite (HAp) ceramics and HAp/β-tricalcium phosphate (β-TCP) composites were measured at room temperature and at 1100°C to investigate influence of the β-TCP dispersion. HAp powder was synthesized by precipitation method, and the ceramics and its composites were obtained by sintering the powder. The HAp/30% β-TCP exhibited the best contribution to mechanical properties in this study. The compression test at 1100°C showed that the β-TCP dispersion reduced yield stress and work hardening of the HAp ceramics. Moreover, it was found that the composites were largely deformed without the change in grain shape and grain size. The result suggests superior superplasticity in the HAp/β-TCP composites to the HAp ceramics.

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