Using rod-like ZrB₂ powders as starting materials, monolithic ZrB₂ ceramics and ZrB₂–20 vol % SiC composites were prepared by tape casting and then hot pressing. The obtained ceramic materials demonstrate partial textured microstructure; however, the morphologies of the ZrB₂ grains are not in rod-like but equiaxial in the final products. It is the ZrB₂ grain growth along the a, b-axis during the hot pressing process that attributes to equiaxial grains instead of rod-like morphology. On the other hand, the textured microstructures might have resulted in strong grain boundaries, which leads to a high flexural strength for monolithic ZrB₂ ceramics.

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Single crystals of Ni₂P and Fe₂P were prepared at an argon pressure of 0.4 MPa by the RF-heated floating-zone method. The grown crystals, about 1 cm in diameter and 4–6 cm in length, had a near-stoichiometric composition.

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A zirconia film synthesized by aerosol gas deposition (AGD) contains a high-temperature phase of zirconia even if synthesized at room temperature. We attempted to clarify the change of the high-temperature phase upon subsequent heat treatment using zirconia powder with a mean particle diameter of 7.7 µm obtained by the dry method. X-ray diffraction (XRD) analysis was used to examine the crystal structure evolution of the AGD zirconia film during heat treatment, and a high-temperature XRD system was also used to measure crystal size at various heating temperatures. The as-deposited zirconia AGD film was found to be composed of monoclinic crystallites about 10 nm in diameter and tetragonal crystallites about 6 nm in diameter. The tetragonal crystallites were stable up to 1373 K, increasing their diameters to 14 nm upon heating. Then, the internal stress of the AGD zirconia film as well as the effects of heating temperature and holding time on internal stress were evaluated. The internal stress induced in the zirconia AGD film was 1.7 GPa, which decreased only up to 1.4 GPa after heat treatment at 1473 K.

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Co-sintering was carried out in air at 1350°C for 1 hr to make two types of symmetrical 3-layered laminates. One is PDP (Porous alumina/Dense alumina/Porous alumina) laminate and another is DPD laminate. For the porous alumina layer, the porosity was set to be 20%; however, pore size was changed by adding three sizes of spherical mono-dispersed polymethyl methacrylate particles (5, 15, 30 µm) in raw alumina powder. Young’s modulus measurements revealed that cracking occurred in both PDP and DPD laminates. The stress in the layer was estimated from an elastic calculation by using the mechanical and thermal expansion properties of each monolayer. In consideration of sintering shrinkage and thermal expansion of the layer, it was suggested that cracking occurred in the dense alumina layer during heating from 1000 to 1200°C, and in porous alumina layer during heating from 1200 to 1350°C. The cracking was mainly attributed to the mismatch of sintering shrinkage between the layers. From the discussion, the elastic model gave an explanation to crack formation during co-sintering.

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Hydroxyapatite (HA) has been introduced as a bone grafting material due to its similar composition to that of natural bone, along with its lack of toxicity and high chemical stability, which prevent inflammatory or antigenic reactions. However, the high porosity of HA leads to increased osteoconductive capacity to the implant, while reducing its mechanical resistance and hence limiting its clinical use. Research on the mechanical properties of HA such as superplasticity has been necessary to solve these disadvantages. In this study, boron nitride (BN; 0, 2, 4 wt %) was added as the second phase reinforcement to increase the bone strength and improve the mechanical combination. The BN was added using the appropriate sintering method in order to control the grain size and reduce the chances of HA being dissociated into tricalcium phosphate (TCP) due to the shorter exposure at high temperature. The microstructures of the samples with various percentages of BN-reinforced HA demonstrated some variation. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses were conducted to determine the elemental composition of the materials and observe the microstructural transformation. As a result, the various percentages of BN-reinforced HA combined with hot press (HP) and spark plasma sintering (SPS) methods demonstrated the improved consolidation of the HA composites with BN, which is a promising result for the development of bioactive load bearing ceramic bone substitution with improved mechanical properties.

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The pH localization phenomenon during electrophoretic deposition (EPD) of the MAX phase-Titanium silicon carbide (Ti₃SiC₂), from suspension in aqueous and mixed (water-ethanol) solvent was experimentally verified in presence of a cationic dispersant, polyethyleneimine (PEI). The local pHs at the electrodes were dependent on solid loadings of the suspensions; pH localization was pronounced at lower solid loading. Higher solid loading resulted in thicker deposits, shielding the electrode surface and hindering direct interaction of the electrode with the particles, thereby suppressing the change in local pH. Comparison of local pH at cathode during EPD from aqueous and mixed solvent revealed a delay in the attainment of isoelectric point (IEP) at the vicinity of electrode and slower deposition rate for mixed solvent. A necessity of concurrence between the IEP of the material and the local pH at the deposition electrode for a given system was established for the formation of good deposits.

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Relationship between the absorption edge energy and glass structure around bismuth ions has been studied in ternary bismuth phosphate and borate glasses by using Raman spectroscopy. Absorption edge energy shifted toward lower energy with increasing theoretical basicity in both phosphate and borate glasses. Raman peaks related to bismuth ions were observed at 150, 270, 390, 570 and 640 cm⁻¹ in borate glasses, and at 160, 240, 320, 380, 480, 550 and 590 cm⁻¹ in phosphate glasses. All peaks related to bismuth ions, except for the peak at around 150 cm⁻¹ in the borate glass (160 cm⁻¹ in the phosphate glass), shifted toward higher wavenumber with increasing theoretical basicity of glass, which suggests a decrease in Bi–O bond length, that is, an increase in bond strength by increasing electron donation. Absorption edge energy had a negative linear relationship with those peaks positions, which was consistent with the increase of electron donation. In contrast, the peaks at both 150 cm⁻¹ in the borate glasses and 160 cm⁻¹ in phosphate glasses shifted toward lower wavenumber with basicity, and the position had a positive linear relationship with the absorption edge energy. The band assigned to a translational mode might indicate the existence of peculiar structure such as a cluster of bismuth oxygen polyhedra, which could be isolated from the glass network resulting in a different correlation to basicity.

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We prepared titanosilicate glasses by the sol–gel method and studied its ability to disperse Ca-α-SiAlON:Eu²⁺ phosphor, which is a typical yellow phosphor and applicable for white light-emitting diodes (LEDs). xTiO₂–(100 − x)SiO₂ glasses dispersed with SiAlON powders were obtained by sintering at 900°C with x ranging from 10 to 30; the glasses changed to black after sintering at 1000°C. Diffuse reflectance spectra suggested that the colorization was caused by the formation of Ti³⁺ ions in the samples. The local structures of Ti and Eu were measured by X-ray absorption fine structure spectroscopy. Ti K-edge spectra showed that the local structure of Ti was 5-coordinated in the glass where x = 10 and 6-coordinated in the glass where x = 30. Eu L_III-edge spectra indicated that both Eu²⁺ and Eu³⁺ were present and the ratio of Eu²⁺ to Eu³⁺ depended on the heating temperature. The reduction atmosphere might affect the colorization of the glasses sintered at 1000°C. The quantum efficiencies (QE) of the glasses sintered at 900°C were estimated and that of the glass with x = 10 was the highest among of the samples, higher than that of the SiAlON powders. It is suggested from the measurement of refractive index and XRD patterns that the improvement in QE is caused by the decrease in the light scattering at the interface between the phosphor and the glasses due to differences in refractive indices and the formation of crystals.

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Textured, dense, polycrystalline Ti₃AlC₂ ceramics was fabricated by spark plasma sintering (SPS) of plate-like Ti₃AlC₂ powder synthesized by a reactive SPS-heat treatment of elemental Ti, Al and carbon black powders. The relative density was found to exceed 99% for samples sintered at 1573 K. The Lotgering orientation factor was determined to be f(00l) = 0.69. The crack propagation behavior near the indentation marks formed by a force of 49 N was observed. On the surface parallel to the SPS-loading direction, the toughening mechanism of crack deflection was observed.

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Magneto-scientific technique combined with colloidal processing was applied to obtain crystalline-oriented zeolite L seed layers. Well-dispersed non-aqueous suspensions of the zeolite L were prepared for the fabrication of thin seed layers on porous substrates by electrophoretic deposition (EPD) in a superconducting magnet. The c-axis oriented seed layers of the zeolite L was successfully obtained on porous YSZ substrates by EPD under the magnetic field.

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We study nitrogen-doping effects on the energetics and electronic properties of titanium dioxide (TiO₂) at high doping concentrations using the first-principles electronic-structure study. From the defect formation energies obtained, it is confirmed that nitrogen atoms should tend to be clustered in the heavily-doped system. This clustering should occur because dopants share the surrounding distorted region and then the lattice-distortion energy per dopant become smaller if dopants are located at shorter distances. We also find that the impurity-induced states seem to be sufficiently hybridized with the original valence band in all the cases studied. The system would show the photoabsorption spectrum expanding to the longer-wavelength region down to around 620 nm in rutile and 730 nm in anatase if nitrogen atoms are sufficiently doped.

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Ceramic and polymer composite biomaterials releasing silicate and calcium ions were developed for the use in bone regeneration. Silicate and calcium ions stimulatory enhance osteogenic cell functions, such as proliferation, differentiation and mineralization. Siloxane-doped vaterite (SiV) particles were prepared using aminopropyltriethoxysilane (APTES) as a siloxane source to achieve an effective release of silicate and calcium ions in a physiological condition. Composite materials consisting of SiV and poly(lactic acid) (PLLA), which is one of the biodegradable polymers, were prepared. In this system, the amino groups and calcium ions on the SiV surface had chemical reactions with the carboxy groups in the PLLA. The composite materials showed a chronic release of trace amounts of silicate and calcium ions in a cell culture medium. Proliferation and differentiation of mouse osteoblast-like cells (MC3T3-E1 cells) were enhanced on the composite material in comparison with the material releasing no silicate ions. The composite fibremats were also developed by an electrospinning method. The fibremats had about 10 µm in fibre-diameter and showed good flexibility. The fibre surfaces were able to be coated with hydroxyapatite by soaking in a simulated body fluid (1.5SBF) for 1 day. The fibremats showed excellent cell and tissue compatibilities in the results of in vitro and vivo tests. Thus, the inorganic ions released from bioceramics should be one of the important factors for achieving high-performance biomaterials for bone regeneration.

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Despite of brittleness, Ceramic-on-Ceramic (CoC) hip joints are appealing to arthritic patients because of its low friction rate, high wear resistance and low risk of osteolysis. The objectives of the study were to review and summarize the performance of Alumina, Zirconia and their functional graded material (FGM) for artificial hip joints in vivo and vitro outcomes. The Method of the study was scoping review which focused on the peer reviewed journals containing with alumina, zirconia and alumina zirconia FGM to CoC hip prosthesis. Advanced version of Alumina CoC was found to have excellent hardness but low fracture toughness. Alumina CoC hip joints was found to have a revision rate as high as 5% after 20 clinical outcomes. Zirconia ceramic had high fracture toughness but relatively low hardness when compared to Alumina ceramic. Alumina-Zirconia FGM consists both high hardness (outer surface) and improved fracture toughness (inner core) which led to better mechanical and tribological properties. However, to date, there is still no literature was found to have long period of clinical outcomes. No article was screened carrying out durability study of Alumina/Zirconia FGM for CoC hip joints with appropriate tribological experiment. Alumina/Zirconia FGM could be very effective for long term durability of CoC hip joints. Nevertheless, this FGM needs to be investigated under appropriate tribological tests considering dynamic loadings, dimension and shape of the joints, lubricant similar to synovial fluid and large number of cycles. The long term clinical outcomes also need to be published to increase its acceptability to young active patients.

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Cubic BaTiO₃ particles of ca. 100 nm in diameter were produced at 25 to 60°C in a highly basic aqueous solution system. The crystalline phase was purely formed by reaction of barium hydroxide and anatase TiO₂ nanoparticles under the highly basic condition. The formation of the pure phase at a lower temperature requires a higher concentration of NaOH and a longer reaction period. At room temperature (25°C), the crystalline BaTiO₃ was obtained through the reaction with 5.2 mol/kg of NaOH for 168 h. A specific mesocrystal architecture of BaTiO₃ consisting of oriented small units was formed as an intermediate at the initial stage of crystal growth.

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Release properties of bovine serum albumin (BSA) and egg white lysozyme (LSZ) on hydroxyapatite containing carbonate ion (CHAp) of various contents were examined with our new flow experimental system. The desorption ratio: the r_de, defined as the ratio of desorbed amount to initially-adsorbed one, was employed as an index of binding strength of these proteins to the surface. Dependency of the content of the carbonate ion on the r_de showed reverse tendency for BSA and LSZ; the r_de of BSA increased as an increase of content of the carbonate ion, while that of LSZ decreased as the increase of the content. This result clarified a difference of primary adsorption sites between BSA and LSZ. As incorporation of the carbonate ion into apatite retarded the growth of the crystal along the c axis, the exposed area of the c face, i.e. the primary adsorption site of LSZ, the p site increased and that of the a (b) face, i.e. the primary site of BSA, the c site decreased.

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Ta(V)-based nitride and oxynitrides have been prepared by solution-precipitation process in a liquid phase formed on the surface of aluminum nitride particles during heat-treatment in nitrogen atmosphere. This eco-friendly and cost-effective process is suitable for an industrial scale production of the pigments containing Ta(V)-based nitride or oxynitrides, compared to the conventional method such as ammonolysis of tantalum oxide with flowing large amounts of ammonia. The pigment synthesized by this method was mixed with a borosilicate frit to prepare an over glaze color. The color applied on glazed ceramic plates showed the brilliant color of yellowish red–yellow with high chroma values. They have a potential to be employed as non-toxic ceramic pigments, and to substitute pigments containing harmful elements.

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