Fast neutron emitted from the fission or fusion nuclear reactions induces various kinds of crystalline defects into ceramics. These defects can cause degradation of material properties. Dislocation loops are frequently formed in crystalline materials after high fluence fast neutron irradiation. These structures have been analyzed based on high-resolution electron microscopy and image simulations based on defects models. Local atomic configurations of interstitial loops formed in SiC, AlN and Si₃N₄ are reviewed. These loops are commonly formed on the closest packing plane in each crystal, and more than one layer is arranged to form specific atomic configurations in spite of an extra thickness corresponding only one tetrahedral layer. Physical property changes of these materials are discussed based on the presence of these defects.

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Structure and surface functional rare earth materials were synthesized and their physicochemical properties were characterized to design high-performance materials, viz. (1) Efficient phosphors, (2) persistent spectral hole burning devices, (3) permanent magnets and (4) nitrogen storage materials: (1) Strontium borates consisting of BO₄ units, SrB₄O₇ and δ-SrB₂O₄ (high-pressure phase), were good host lattices to provide intense blue emissions owing to the lowered phonon effect of three-dimensional BO₄ network. (2) Persistent spectrum hole burning spectra were observed on the sol-gel-derived silica-based glasses dispersed with europium(III) crown ether complex, of which the mechanism was based on the reduction of Eu³⁺ ions. (3) Rare earth intermetallic compounds such as Sm₂Fe₁₇N_x (x = ∼3) and Nd₂Fe₁₄B provided high-performance bonded magnets by effective surface coating for the raw fine powders, Zn metal vapor sorption and/or silylation with alkyl silane. (4) Nitrogen storage systems were established by nitrogenation and denitrogenation cycle between the rare earth-iron intermetallic compounds and metal nitrides, by which ammonia was formed even at ambient pressure.

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The solubility of Dy³⁺ ions in binary Ge-S glasses is studied. A mixture of Dy₂S₃, Ge and S raw materials in a silica ampoule was sealed under vacuum with 1-2 × 10⁴ Pa, melted at 1000°C for 20 h with a slow rotation rate of <1 rpm and then quenched to room temperature to form a glass. The solubility is evaluated by naked eye, optical microscopy and absorption measurements in glass samples. A linear relation between absorption coefficient and Dy₂S₃ concentration is obtained for the ⁶H_15/2→⁶H_9/2, ⁶F_11/2 transition in the dissolved glasses. The dissolved concentration of Dy₂S₃ increases with decreasing S concentration in the Ge-excess compositions under 66.7 mol% S. A solubility model is proposed based on GeS₂-like clusters existing in Ge-S glass melts. The dissolved concentration of Dy₂S₃ is at least 5 mass% (∼4 × 10²⁶ Dy/m³) at 60-62 mol% S (38-40 mol% Ge). This relatively-high solubility is related to the existence of Ge²⁺ modifier ions as discussed in our previous study.

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The synthesis of organic-inorganic hybrid precursors for low-melting glass has been proposed. In this process, a non-aqueous acid-base reaction of P-OH+Si-Cl→P-O-Si+HCl↑ was employed using orthophosphoric acid (H₃PO₄) and trimethylchlorosilane (Me₃SiCl) as starting materials. The formation of P-O-SiMe₃ linkage and the disappearance of P-OH group were confirmed by ²⁹Si and ³¹P NMR spectra. The viscosity decrease of the precursors observed at high Si concentrations was caused by the decrease in the number of P-OH, which was correlated to the decrease of the hydrogen bond. By the use of P-O-SiMe₃ linkage, low-melting glasses in the system of Me₃SiO_0.5-Me₂SiO-SnO-P₂O₅ have also been prepared through the non-aqueous acid-base reaction. The hybrid glasses thus obtained exhibited low glass transition temperatures, which changed from 29 to −47°C as the -SiMe₃ content increased. Termination of the oxide framework by the organic functional groups lowered the network dimension, giving rise to the lower glass transition temperature.

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Nanometer-sized particles of zinc gallate (ZnGa₂O₄) spinel solid solutions over wide compositional range (Zn/Ga molar ratio = 0.341-0.499) were directly synthesized from aqueous solutions of gallium and zinc sulfates (Zn/Ga = 0.5-2.0) in the presence of urea under hydrothermal conditions at 120 to 240°C. Under almost neutral conditions in the presence of urea (pH = 7.65), zinc gallate spinel was hydrothermally formed over 200°C, although ZnCO₃ and GaO(OH) were formed at 120°C. The synthesized temperature of zinc gallate spinel was able to decrease from 240 to 120°C, with the increase of the concentration of urea from 0.8 to 2.4 mol·dm^-3. Zinc gallate spinel with almost stoichiometric composition (Zn/Ga = 0.499) was synthesized from the solution with Zn/Ga = 2 at 240°C. The obtained zinc gallate spinel powder was fully densified by sintering over 1200°C for 1 h.

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CaO ceramics was sintered from reagent-grade CaCO₃ powder at 1500°C by the addition of 0-20% (molar ratio). The densification of the compact was promoted due to the effect of MgO on inhibiting the growth of CaO grain. With increasing addition of MgO, the microstructure of the clinker underwent a restructuration process. Homogeneous microstructure, with well growing MgO grains occupying most of the boundary triple points of CaO grain, formed by the addition of 20% MgO. The slaking resistance of the clinker was significantly improved due to the formation of CaO solid solution, promotion of densification and modification of microstructure by the addition of MgO.

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The objective of the present paper is to give a mathematical model simulating the heat transfer problem of the bottom refractory lining of a top-closed submerged electric arc furnace and to use this model to predict the deterioration of the lining. The problem is considered in one dimension and the furnace is simulated by a finite number of superposed infinite plates of uniform thicknesses and different temperature-dependent thermal conductivities. The working layer is exposed to the melt metal temperature and the external layer is subject to a cooling ventilation under a given ambient temperature. The influence of the variation of the operating parameters is studied and analyzed. The calculated results were compared with the measured results of a case study, obtained from the observations of the bottom lining deterioration of the submerged Electric Arc Furnace (EAF) used for the production of ferromanganese alloys at Sinai Manganese Company in Egypt during the period from 1993 to 2000. A satisfactory agreement has been obtained between our theoretical results and the measured ones.

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Silicon nitride calcined body with open pores was infiltrated with an iron-alcoxide solution, and sintered in nitrogen gas at high temperature to obtain a dense silicon nitride based material. Transmission Electron Microscope (TEM), Energy Dispersive X-ray Spectroscopy (EDS), and X-ray diffraction (XRD) analyses revealed that comparatively roundish Fe₅Si₃ particles with less than 2μm in size formed within the silicon nitride matrix. Under boundary and mixed lubricating conditions, the frictional coefficient of the obtained material was remarkably lower than that of normal silicon nitride, and equivalent to silicon nitride with dispersed Fe₅Si₃ particles fabricated by a conventional process. Moreover, the obtained ceramics showed a high flexure strength of 1187 MPa due to the very small size of the Fe₅Si₃ particles despite the existence of Fe-Si compounds in the surface layer.

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Sr- and Mg-doped lanthanum gallate which exhibits high ionic conductivity was synthesized by a citrate method using industrial raw materials. X-ray diffraction analysis revealed that the powder by a citrate method was single-phase. Electron probe micro analysis (EPMA) showed that the sintered body which was formed by synthesized powder by a citrate method and fired at 1723 K for 6 h had inhomogeneous texture caused by segregation of Sr and Ga elements. Scanning electron microscope (SEM) images and densimetry revealed that the sintered body synthesized by a citrate method had high density, the sintered bodies synthesized by a citrate method had much higher oxide ion conductivity than those by a solid state reaction method.

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A Monte Carlo simulation method using a three dimensional lattice was developed to analyze the connectivity of pores in sintered materials. The changes in porosity (f_V), mean grain diameter (D_S), intercept length of pores (D_V), contiguity of the solid phase (C) and fraction of connected pores (f_{V, C}) with the number of Monte Carlo steps (MCS) were analyzed as a function of initial porosity (f_{V, 0}) and initial grain diameter (D_{S, 0}). In many cases, f_{V, C} decreased with MCS down to 0%, particularly at small and intermediate values of f_{V, 0} and D_{S, 0}. However, in some cases of large f_{V, 0} and D_{S, 0}, an f_{V, C} of 100% was maintained irrespective of MCS, which means that all pores may remain connected in the material. Systematic plots of D_V, D_S and C vs f_{V, 0}×f_{V, C}, which indicate the amount (%) of connected pores, are found to be useful for designing sintering and grain growth processes of porous materials.

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Multilayer ceramic capacitors (MLCCs) were fabricated by laminating layers with different Curie temperatures to improve the temperature coefficient of capacitance in the Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃-Pb(Ni_1/2W_1/2)O₃ ternary system. A green sheet was prepared by tape casting using a mixture of Pb(Mg_1/3Nb_2/3)O₃, PbTiO₃ and PbO, NiO, WO₃. 80Ag-20Pd was attached on the green sheet as an internal electrode. The green sheets with the electrode were then laminated under 2.9×10⁷ Pa at 70°C and sintered at 1000°C for 2h. MLCCs with 11 layers of 0.85PMN-0.05PT-0.1PNW, 2 layers of 0.7PMN-0.2PT-0.1PNW and 4 layers of 0.6PMN-0.3PT-0.1PNW showed an improved temperature coefficient of capacitance (ΔC/C; −13.26−3.85%) in the temperature range from −50 to 80°C.

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The current-voltage characteristic and the temperature distribution of the BaTiO₃ ceramic rod were investigated. When a certain voltage was applied to the rod, the current through the rod abruptly decreased, and the temperature distribution markedly changed resulting in the appearance of a hot spot where the temperature was higher than that of the rest of the rod. With increasing voltage after the appearance of the hot spot, the current remained constant and the temperature and size of the hot spot increased. The results have shown that the hot spot regulates the current through the rod by changing its temperature, which may lead to new applications of BaTiO₃.

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