The variation in particle size distribution of SnO₂ nano-particles by the pulsed wire discharge (PWD) process has been clarified. Special attention has been paid for the influence of both synthesis conditions of ambient pressure and charging voltage on the distribution. The geometric standard deviation (σ_g) and the count mean diameter (d) were clearly influenced by these conditions. This can be summarized by means of a parameter being proportional to the plasma expansion volume. It was found that σ_g and d monotonically decreased with increasing this parameter. This tendency can be explained by the reported results of numerical simulations in which both coagulation and chemical reaction in the free molecule regime are taken into account, indicating that a relatively slow reaction rate compared to the coagulation rate broadens the particle size distribution during PWD process.

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Calcium alginate fibres with an average diameter of 5 μm were prepared by extruding an aqueous sodium alginate solution through nozzles with holes of 0.1 mm diameter into an aqueous calcium chloride solution, and then through a calcium chloride methanol solution. The ratio of D-mannuronate (M) to L-gluronate (G) subunits in the calcium alginate ranged from 0.7 to 2.0. The fibres were soaked in an aqueous saturated calcium hydroxide solution for 5 d, and then soaked in a simulated body fluid (SBF) with ion concentrations nearly equal to those of human blood plasma. Fibres with an M/G ratio of 2.0 had apatite deposited on their surfaces within 7 d in SBF, but fibres with M/G ratios of 0.7 and 1.5 did not. The higher apatite-forming ability of the former fibres was attributed to their release of more calcium ions from the fibres, that is, the formation of a larger number of free carboxyl groups, effective for apatite nucleation and more efficient acceleration of the apatite nucleation by increasing the ionic activity product of the apatite in SBF.

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Powders of LiNbO₃ were synthesized by novel peroxide route based on reaction of niobium peroxide and lithium hydroxide. A pH of 11 was found to provide optimum condition for the formation of peroxo niobium precursor complex [Nb(O₂)₄]^3-. The replacement of peroxide ligand was favored by increasing the reaction temperature above ambient. This method demonstrated its efficacy in obtaining pure and homogeneous crystalline LiNbO₃ powders at reduced temperature (400°C) without involvement of organic substance. The crystalline phase was characterized via powder X-ray diffraction and Infrared, Raman spectroscopy. SEM micrographs enabled in detecting the formation of inverse opal of LiNbO₃. For comparison LiNbO₃ was also prepared by amorphous complex method independently and characterized. The peroxide approach presented here gives an alternative for the preparation of multi component oxides free from organics and chlorides.

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Ferrimagnetic glass-ceramics are useful as thermoseeds for hyperthermal treatment of malignant tumors, especially those located in deep parts of the body, since hysteresis loss heating occurs locally at the cancer site when they are implanted around the tumor and subjected to an alternating magnetic field. In the present study, glass-ceramic powders containing a large amount of fine particles of zinc-iron ferrite (Zn_xFe_3-xO₄) in a CaO-SiO₂-based glassy matrix were prepared by the heat treatment of ZnO-Fe₂O₃-CaO-SiO₂ glasses at various temperatures for 1 h in a 95CO₂+5H₂ atmosphere. The Zn_xFe_3-xO₄ precipitated above 700°C, and its crystallite size and fraction increased with increasing heat-treatment temperature, reaching 130 nm and 37 mass% at 1150°C, respectively. The saturation magnetization of the specimen increased to 38.4 emu•g^-1 with increasing heat-treatment temperature up to 1150°C. The coercive force of the specimen increased to 167.6 Oe at 1000°C, and then decreased with increasing heat-treatment temperature. When the heat-treatment period at 1150°C in a 95CO₂+5H₂ atmosphere was increased from 1 to 5 h, the content of Zn_xFe_3-xO₄ was not changed, whereas the crystallite size of Zn_xFe_3-xO₄ increased from 130 to 170 nm. The saturation magnetization and coercive force of the powders heat treated at 1150°C for 5 h in a 95CO₂+5H₂ atmosphere were 26.5 emu•g^-1 and 150.5 Oe, respectively. The prepared glass-ceramic powders showed a large amount of heat generation of 12.4 W•g^-1, under conditions of 300 Oe and 100 kHz.

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Alkaline earth cation doped PrGaO₃ dense ceramics, Pr_1-xM_xGa_1-yMg_yO_3-δ (M=Ca, Sr, and Ba), were synthesized by using a solid-state reaction method, and their total conductivity was measured under different kinds of atmospheres. The optimum dopant for the enhancement of conductivity was Sr for the Pr site, and Pr_0.9Sr_0.1Ga_0.85Mg_0.15O_3-δ (PSGM) showed higher electrical conductivity than other systems. From the total electrical conductivity values measured in Ar and O₂, it is strongly suggested that p-type electronic conduction is dominant in all of the doped PrGaO₃ system. The difference between the conductivity in O₂ and that in Ar was the largest in Pr_0.9Ca_0.1Ga_0.85Mg_0.15O_3-δ (PCGM) and the smallest in PSGM. To examine whether proton conduction occurs in Pr_1-xCa_xGa_1-yMg_yO_3-δ system, the total electrical conductivity in Pr_0.93Ca_0.07Ga_0.85Mg_0.15O_3-δ was measured by changing the partial pressure of O₂ and H₂O (or D₂O) in the atmosphere. The results indicate that Pr_0.93Ca_0.07Ga_0.85Mg_0.15O_3-δ predominantly shows hole conduction below 873 K, and proton conductivity is negligibly small.

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Monodispersed α-Fe₂O₃ nanoparticles were prepared at 100°, 120°, and 140°C using 0.02, 0.05, and 0.1 M-Fe(NO₃)₃•9H₂O solutions by microwave-hydrothermal (M-H) and conventional-hydrothermal(C-H) reactions. Compared to the formation of monodispersed α-Fe₂O₃ particles using the C-H reaction, the M-H reaction led to increased rate of formation by 3 times at 120°C and 5 times at 140°C from 0.1 M-Fe(NO₃)₃ solutions. α-Fe₂O₃ nanoparticles of 23-25 nm in diameter were obtained from 0.02 M solution at 100°C after treatment for 4 h by applying microwaves, which led to the formation of smaller sized particles with a narrow particle size distribution. The coagulation of nano-sized single crystals of 5 to 6 nm in diameter was enhanced by increasing the concentration of Fe(NO₃)₃ solutions.

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Silicon nitride (Si₃N₄) coated with lutetium disilicate (Lu₂Si₂O₇) layer through the intermediate silica (SiO₂)-rich phase was fabricated by reaction sintering after dip-coating. The Lu₂Si₂O₇ layer with a thickness of 3-29 μm was formed on Si₃N₄ substrate. It was relatively dense with several pores, and strongly jointed to the substrate through the intermediate phase. Oxidation resistance and strength retention of the coated Si₃N₄ were investigated and compared with those of the uncoated Si₃N₄. Apparent activation energy for oxidation at 1300-1500°C in air increased up to 523.1 kJ/mol with increasing thickness of the coating layer, which was about 1.7 times higher than that of the uncoated Si₃N₄ (310.3 kJ/mol). After long-term cycling oxidation at 1500°C for up to 1000 h in air, the total weight gain decreased by up to 51%, indicating that oxidation resistance improved by about 100%. The improvement was attributed to the protection of the substrate from an oxidative environment by the Lu₂Si₂O₇ layer and underlying SiO₂-rich phase. Flexural strength of the coated Si₃N₄ was not deteriorated before and after the cycling oxidation at 1500°C for up to 1000 h in comparison with that of the uncoated Si₃N₄. However, the high-temperature strength at 1400-1500°C in air was a little less than that of the uncoated Si₃N₄. The deterioration was attributed to the softening of amorphous SiO₂ phase, which existed in the intermediate phase (between the Lu₂Si₂O₇ layer and substrate) and inside the substrate.

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Two kinds of hydrate phases, Hydrate I and II, were obtained in water by soaking the magnesium potassium titanate (K_0.8Mg_0.4Ti_1.6O₄, KMT) that was synthesized from hydrous potassium tetratitanate. As interlayer potassium ions were replaced by water molecules and oxonium ions, the distance between the host crystal layers increased. The interlayer distances of Hydrate I and II were 0.884 nm and 1.130 nm, respectively. The empirical formulae of Hydrate I and II were K_0.30H_0.50Mg_0.4Ti_1.6O₄•0.94H₂O and H_0.80Mg_0.4Ti_1.6O₄•2.46H₂O, respectively.

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The aim of the present work is to develop a self-diagnosis material with excellent sensing abilities via measurement of change in electrical resistance. A new self-diagnosis material, in which conductive RuO₂ particles are dispersed in a glass matrix, was successfully fabricated by sintering at 850°C. The sensing properties of this self-diagnosis material were investigated in real time during tensile tests by measuring the electrical resistance change. The electrical resistance increased remarkably with increasing applied tensile load and materials showed excellent sensing performance at low strains <0.4% strain. The high sensitivity of the electrical resistance change is due to partial separation of the percolated structure between RuO₂ particles, when microcracks form in the glass matrix. Sample were found to exhibit a residual electrical resistance after unloading during cyclic loading tests and the resistance value increased with increasing number of cycles.

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Spherical Au-Pd particles in the submicron range were prepared using an ultrasonic spray-pyrolysis method. HAuCl₄/H₂PdCl₆ in hydrochloric acid and Au(OH)₃/Pd(NO₃)₂ in nitric acid were used as starting solutions. At high Au/Pd ratios, particles derived from the HAuCl₄/H₂PdCl₆ solution had a spherical morphology. At low Au/Pd ratios, the particle morphology gradually deformed due to the influence of the thermal decomposition of H₂PdCl₆. The Au(OH)₃/Pd(NO₃)₂ solution could not be atomized continuously because of its instability. To overcome this problem, the Pd(NO₃)₂ solution was preoxidized with H₂O₂ before mixing with the Au(OH)₃ solution. As a result, the Au/Pd mix solution was stabilized and spherical particles were obtained at various Au/Pd ratios. Particles produced from the Au(OH)₃/Pd(NO₃)₂ solution were more uniformly alloyed than those from the HAuCl₄/H₂PdCl₆ solution. This is also indicated in the thermo-gravimeter (TG) analysis, which shows Pd oxidation inside the particles, which inhibits the overall increase in mass.

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This paper describes a new method to precipitate the precursor of porous alumina particles by using a porous organic matrix as the template and an enzyme as the precipitant supplier. In this work, the precursor of alumina was precipitated in urease-containing alginate gel spheres dispersed in aqueous solutions containing urea and Al³⁺ ion. Urease was used to hydrolyze urea so that the precursor of alumina, basic aluminum sulfate, may be precipitated selectively within the gel spheres. By burning off the gel matrices after the precipitation of the precursor, porous alumina particles were obtained. The resultant alumina particles about 1 to 2 mm in diameter had sharp pore size distribution profiles around 0.1 to 0.01 μm. The inside of the alumina particles was able to be made either hollow or filled, depending on the aging time after the precipitation of the precursor.

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