An amorphous silica with distinct bimodal pore structure containing both macropores and mesopores was prepared from an acidified solution of water glass in the presence of poly (acrylic acid) by inducing phase separation together with gelation. Both of pore sizes of the macropores and the mesopores can be controlled in the ranges from 1 to 10μm and from 4 to 30nm, respectively.

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The surface cells of cellular ceramic foams are analyzed using an optical microscope. The cell density is so abundant that the cell structure can feature a high cell volume fraction, a high degree of interconnection to neighboring cells, variable cell sizes and a high roughness of cell boundaries. To segment these cell or other strut images, a novel image analysis procedure was designed. This includes an application of an algorithm of detecting local maximum regions of light intensity between cells in images and regarding them as strut regions, while the conventional segment operations can only recognize the global maximum or minimum light intensity regions with a threshold intensity value. Then, an effectiveness of the proposed method was compared with earlier typical methods by quantifying the various properties of the cells in each image. As the results, the proposed method shows a good availability in that this gives more efficient presentation of the tiny cells and their strut regions as well as a programmability and reproducibility. However, the improved boundary construction methods are required to enable the proposed method to become more effective.

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Added arc glow discharge method is to deposit Cu metal electrode on ferrite ceramic chips in a vacuum atmosphere. A lot of phenomena, different from usual printing silver electrode method occurred during the deposition, as observed by scanning electron microscopy (SEM) the microstructure of electrode joints and energy-dispersive X-ray (EDX) analysis. Interfacial migration and diffusion occur within the metal layer and the ceramic matrix, respectively. The effect of different deposition procedures on the electrical and magnetic properties of the ceramic samples (chip and toroidal) was also investigated. The results show that, through an optimized procedure, the joint quality of deposited Cu electrodes and the properties of the relative components can significantly improved.

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The size of the frontal process-zone at the crack tip of ceramics is an important factor to assess the toughening mechanisms operative in the material. An indirect technique is proposed here to estimate the critical size of the frontal process zone in ceramics using a single-edge V-notched beam (SEVNB) method. A three-point flexure test was carried out on alumina specimens containing a sharp V-shaped notch whose depth was varied. Then, a critical local stress was calculated at a critical distance from the notch tip. The frontal process-zone size at the beginning of crack propagation, namely, the critical frontal process-zone size, was determined as the distance between the notch tip and the point where the critical local stress has the same value as the flexural strength of the specimen. This concept is based on a local fracture criterion. The calculated critical frontal process-zone size of alumina ceramics was 11.4μm based on the linear elasticity, and 22.8μm based on the Dugdale model.

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Alumina-zirconia-graphite (AZG) refractories were obtained through a baking technique using fused Al₂O₃, partially stabilized ZrO₂ and flake graphite as the starting materials with Al, Si, and SiC powder additives. A particle size distribution was designed by the Furnas model for coarse Al₂O₃ (500-1000μm/medium Al₂O₃ (61-125μm/fine Al₂O₃ (<44μm, in which the contents of coarse, medium and fine Al₂O₃ powders were varied with a constant amount of fine particles in the matrix. The bulk density increased from 3.05 to 3.29g·cm^-3 for the sample with a mass ratio of (coarse Al₂O₃)/(medium Al₂O₃)=2.14 the forming pressure being from 100 to 150MPa. However, when the forming pressure increased from 150 to 170MPa, the bulk density gradually decreased from 3.29 to 3.26g·m^-3. The lowest porosity (5.1%) was achieved by compacting the powders with a mass ratio of 2.14 at 150MPa. The average pore size readily decreased from 5.3-5.8 to 3.1-3.9μm as the forming pressure increased from 100 to 150MPa. Besides, the average pore size gradually decreased from 3.1-3.9 to 3.0-3.7μm when the forming pressure increased from 150 to 170MPa. The bulk density increased with increasing baking temperature and attained an inflection value at 200°C above which it gradually increased up to 240°C.

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Fracture toughness, fracture surface energy and crack initiation load of single crystal and polycrystalline SiC sintered with different additives were evaluated by Vickers indentation technique. Resistance to crack initiation and propagation in sintered SiC with Al₂O₃ additive was>sintered SiC with B and C additives>single crystals. The properties of single crystals depended on crystal orientation, while little difference of properties was observed between 4H and 6H structures. High fracture toughness and fracture surface energy of Al₂O₃ containing SiC resulted from crack deflection and branching at grain boundaries. Slightly higher fracture toughness and fracture surface energy of SiC sintered with B and C additives, in comparison with single crystals, was caused by crack deflection which was observed even when transgranular propagation occurred due to the different crystal orientation of cleavage planes in each grain. A microstructure favorable for high toughness involves a more severe local damage beneath the indentation.

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Al₂O₃/YAG fiber composite was prepared and its high temperature mechanical properties investigated. The mechanical properties did not show any remarkable degradation up to temperatures≤1673K in comparison with room-temperature values. The strength and fracture toughness at high temperature could be remarkably improved above those of monolithic alumina by adding YAG fibers. As factor leading to such an improvement, it was observed that the fracture mode of the YAG fibers becomes intergranular with rising temperature. The degradation of Young's modulus caused upon temperature rise in alumina ceramics was compensated by the increase of fracture energy due to the change of fracture mode for the YAG fibers.

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Titanium containing organic compounds were synthesized through reactions of titanium isopropoxide with o-, m- and p-hydroxybenzonic acid (hence-forth, abbreviated as o, m and p, respectively). The effects of isomers (o, m and p) on the properties of titanium containing organic compounds were investigated. Titanium containing organic compounds were self-assembled and, in o, the particles were of a uniform size and spherical, approximately 2-4μm in diameter. m and p consisted of massive particles of diameter approximately 1-3mm. A porous material was prepared by thermal decomposition of titanium containing organic compounds. For o, it was prepared at 400°C, while for m and p, it was prepared at higher temperatures (500-600°C). A material with a large pore volume was prepared from o, the average pore size being approximately 2nm in radius. Rutile easily formed from both o and m.

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SiC/SiC composites have been considered one of the most attractive materials for high temperature structural applications. The fabrication processes for SiC/SiC composites are typically divided into four types; chemical vapor infiltration (CVI), precursor impregnation and pyrolysis (PIP), hot pressing (HP) and reaction sintering (RS) method. In this work, the microstructures of SiC/SiC composites were evaluated using mercury intrusion method and scanning electron microscopy (SEM) observation. Effect of fabrication process on the microstructures was investigated, and the relationships between microstructural features and some properties, such as bending strength, Young's modulus, thermal conductivity and thermal shock resistance, were discussed.

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Transparent and crack-free Bi₁₂GeO₂₀ single crystals have been grown by the pulling-down method with a continuous powder feed system. Bi-rich feed powder having a composition of 14.1mol% GeO₂ is favorable to obtain stoichiometric crystals. Striation-free crystals with an increased transmittance are grown under a small temperature gradient. The shape of the solid-liquid interface during the crystal growth is nearly flat, which is advantageous to avoid core formation. Average dislocation density is estimated to be 2×10⁴/cm², which is comparable to that of Bi₁₂GeO₂₀ crystals grown by the conventional Czochralski method.

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Dense amorphous PLZT films with composition (Pb_0.925La_0.075) (Zr_0.4Ti_0.6)O₃ were deposited on Pt/MgO (100) substrates by rf-magnetron sputtering without heating the substrates and were subsequently crystallized by postdeposition annealing. The optimum conditions in the two-step annealing process to crystallize the amorphous PLZT films were investigated. The post-deposition-annealed films showed excellent crystallinity and c-axis orientation when the amorphous PLZT films were annealed in an oxygen flow at a soaking temperature for the initial nucleation process of T₁=300°C, a temperature for crystal growth process of T₂=750°C, and the T₂-soaking time of t₂=60min. Conventional Pt/PLZT/Pt capacitors were fabricated by forming Pt top electrodes on crystallized 300-nm-thick PLZT films. The remanent polarization and the coercive field of the present capacitors, which indicated almost symmetric P-E hysteresis loops, were 2P_r≅30μC/cm² and 2E_c≅90kV/cm, respectively. The high-endurance PLZT capacitors with excellent ferroelectric properties produced by the present optimized crystallization have great potential for application to nonvolatile memory devices.

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β-quartz solid solution consisting of zinc aluminocilicate was prepared from a Zn-exchanged zeolite A (Zn-A) as a precursor. In the thermal-transformation process of Zn-A, two kinds of β-quartz solid solutions were obtained. Zn-A became an amorphous material upon heating at 873K. The β-quartz solid solution (β-Qss (Z)), which has a composition close to that of Zn-A (ZnAl₂Si₂O₈), formed with the presence of small amounts of gahnite and mullite from the amorphous material at temperatures above 1163K. The β-Qss (Z) decomposed at temperatures above 1223K and then another β-quartz solid solution (β-Qss (S)) formed. The composition of β-Qss (S) was richer in SiO₂ than that of β-Qss (Z). The d value in the (101) plane of β-Qss (S) decreased with increasing heating temperature, which suggested that the amounts of Al and Zn in the specimen decreased and that β-Qss (S), formed above 1573K, has the composition of nearly pure SiO₂.

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Transparent YAG (Y₃Al₅O₁₂) ceramics containing 4.3mol% Pr were fabricated by a solid-state reaction method using high purity powders. This ceramics had excellent optical properties. The 4.3mol% Pr: YAG ceramics obtained were confirmed optically to have prefect isotropy and transmittance, and a garnet structure only. The characteristic absorption and fluorescence spectra of Pr³⁺ ions for the garnet host (YAG) were observed in this work.

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Tensile property/strain characteristics were determined for a composite based on the SiC/SiC system at room temperature and elevated temperature up to 1300°C in vacuum and air. Instantaneous modulus/strain relationships were characterised by three distinct regions when tested up to 1200°C in vacuum. Stress/strain relationships characteristic of brittle failure were generally observed at elevated temperature in air. The results were explained in terms of component and fiber/matrix interface properties.

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This review covers international research on the fabrication, microstructure, properties and applications of glass and glass-ceramic matrix composites reinforced with continuous fibres. The most important research work reported in the scientific literature since the discovery of these composites in the late 60s is reviewed. It will be shown that several fabrication procedures have reached an advanced development stage and that nowadays reliable, high-quality glass matrix composite materials are available. However, the literature analysis demonstrates that several challenges remain for future developments in this area. These include the need for a further understanding of the thermomechanical behaviour of the composites and the assessment of environmental and chemical interactions under in-service realistic conditions, i.e., mostly at high temperatures and in oxidative or corrosive atmospheres. It is also emphasised that relatively limited R & D work has been carried out so far in the area of manufacturing of engineering components and structures having complex geometry and large dimensions. Specifically there is a lack of development of adequate machining and joining techniques. The ultimate goal of this review is to generate a broader interest in glass and glassceramic matrix composites in both the scientific and industrial communities, so that the high technological potential of these materials can be exploited more widely.

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This paper reviews grain boundary and interface structures in ceramics. Firstly, geometrical treatments are briefly described for both grain boundary and hetero-interface. For the grain boundary, grain boundary character, small angle grain boundary, coincidence site lattice (CSL) theory, structure unit, segregation and amorphous grain boundary are reviewed to show a couple of examples observed in ceramics. For the hetero-interface, O-lattice theory, lattheory, latry, latace, O-lattice theory, latry, lattttice coherency and interfacial dislocation are discussed and the results obtained for metal/ceramics interfaces are introduced. Transmission electron microscopy (TEM) enables us to characterize the very narrow regions less than 1nm, and therefore is powerful technique for investigating grain boundary and interface structures. In this paper, recent experimental TEM studies are presented to demonstrate grain boundary and interface characterization at high spatial resolution.

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