Showing papers in "Journal of the Ceramic Society of Japan in 1995"
TL;DR: In this paper, the spark plasma sintering (SPS) method was used to bring dense silicon carbide ceramics at a sintered temperature of 1800°C, which was about 200°C lower than that of the hot-pressing process.
Abstract: Silicon carbide ceramics which 5 mass% Al2O3 and 2 mass% Y2O3 were added to were prepared by the spark plasma sintering (SPS) method under the conditions of 30 MPa and 5 min. Mechanical properties at room temperature were eximined. The SPS brought dense silicon carbide ceramics at a sintering temperature of 1800°C, which was about 200°C lower than that of the hot-pressing process. The silicon carbide obtained by SPS had higher strength and fracture toughness than those obtained by hot-pressing. The results suggest that the inside temperature of the sintered bodies during spark plasma sintering was higher than the measured temperature.
175 citations
TL;DR: In the interior of glass-ceramic A-W, both the apatite and β-wollastonite were homogeneously dispersed in a glassy matrix, taking a form of rice grain 50 nm in width and 100 nm in length as discussed by the authors.
Abstract: In the interior of glass-ceramic A-W, both the apatite and β-wollastonite were homogeneously dispersed in a glassy matrix, taking a form of rice grain 50 nm in width and 100 nm in length. The apatite layer formed on the glass-ceramic in the simulated body fluid consisted of fine needle-like apatite crystals about 10 nm in thickness and 100 nm in length, which are elongated along c-axis and randomly oriented. The apatite crystals in the surface layer were in direct contact with those within the glassceramic without intervention of such silica gel layer as observed for Bioglass®-type glasses. No crystallographic relation was observed between them. The apatite crystals in the surface layer were calciumdeficient, and contained small amounts of Mg and Si.
64 citations
TL;DR: In this paper, the nuclei of barium titanate particles were formed via the reaction of titanium tetrahydroxide gel with barium hydroxide and then grow.
Abstract: Barium titanate fine particles with average particle sizes from 20 to 90 nm were prepared by a hydrothermal method using titanium tetrahydroxide gel and barium hydroxide. The particle size was inversely proportional to the Ba/Ti atomic ratio in the starting material, while it was independent of temperature in the narrow range from 70 to 150°C. For the explanation of these findings, we proposed the following mechanism for the formation of barium titanate fine particles, i.e., the nuclei of barium titanate form via the reaction of titanium tetrahydroxide gel with barium hydroxide and then grow. In these particles, there were many lattice defects in the form of hydroxyl groups and barium vacancies, and their concentration increased with decreasing particle size. We explained this result using the model that a particle can be divided into two parts: a defective surface layer with many defects and the bulk with fewer defects. The crystal structure of barium titanate particles was cubic with an expanded lattice (a-0.402nm) independent of particle size. This result indicated the possibility that the lattice defects influenced the crystal structure.
64 citations
TL;DR: The Reaction Bonding of Aluminum Oxide (RBAO) as discussed by the authors is a new technology to fabricate low-to-zero shrinkage Al2O3-based composites, which can be modified by incorporating other metals or ceramic phases to change the final composition, to enhance the mechanical properites and to further compensate for the sintering shrinkage.
Abstract: A new technology to fabricate low-to-zero shrinkage Al2O3-based composites, Reaction Bonding of Aluminum Oxide (RBAO), is presented: Al and Al2O3 precursor powder mixtures are intensively milled, compacted, and heat-treated in air, such that Al fully oxidizes to Al2O3. The volume expansion associated with the oxidation partially compensates for the sintering shrinkage. The process can be modified by incorporating other metals or ceramic phases to change the final composition, to enhance the mechanical properites, and to further compensate for the sintering shrinkage. Interesting characteristics of this technology are easy green machining without binders, superior mechanical properties of reaction-bonded bodies without final machining (also when green machined), superplastic formability, near-net-shape capability, and broad microstructural and compositional versatility.
46 citations
TL;DR: In this article, the synthesis process and the formation mechanism of Al 4 SiC 4 were investigated using Al, Si, and C as starting materials and properties such as hydration resistance of the synthesized Al 4 siC 4 are examined.
Abstract: The synthesis process and the formation mechanism of Al 4 SiC 4 were investigated using Al, Si, and C as starting materials. Properties such as hydration resistance of the synthesized Al 4 SiC 4 were examined. SiC and Al 4 C 3 begin to form from about 800°C and 900°C, respectively. When the temperature is above 1300°C, both products further react with each other to form Al 4 SiC 4 . With increasing temperature and time, the formation ratio of Al 4 SiC 4 increases. The addition of Al 2 O 3 can facilitate the formation of Al 4 SiC 4 . The hydration resistance of Al 4 SiC 4 is excellent and sufficient for the practical use.
41 citations
TL;DR: In this article, a new crystal engineering of oxide thin films grown epitaxially was claimed for a future ferroelectric nonvolatile memory (FeRAM) from a point of view of scaling and size effect, and its epitaxial growth technology was reviewed.
Abstract: A new crystal engineering of oxide thin films grown epitaxially was claimed for a future ferroelectric nonvolatile memory (FeRAM) from a point of view of scaling and size effect, and its epitaxial growth technology was reviewed. A few ideal models for epitaxial oxide thin films on Si were proposed as a future oxide-FeRAM. The results are summarized as follows. (1) Bi layer-structured ferroelectric thin film with c-axis inplane orientation: This structure is not easy to made, but is an ideal model to pick up the merit of ferroelectric anisotoropy. (2) Bi layer-structured ferroelectric thin film with a planar-type, which means that electric field is applied parallel to a film surface: This idea is based on attaching a greater importance to epitaxial growth of a ferroelectric layered oxide. (3) Ferroelectric oxide artificial superlattice thin film: This is basically interesting structure from a point of view of material searching, and has a possibility to create a new function such as ferroelectric properties standing aloof from the conventional size effect. (4) Ferroelectric oxide artificial superlattice thin film with the planar-type: This film includes at least a paraelectric oxide layer, and this may create a new 2-dimensional anisotropy of ferroelectric property as a result.
41 citations
TL;DR: In this article, the effect of methanol on the morphology of hydroxyapatite (HAp) crystals has been studied under hydrothermal conditions, and the results indicated that the variation of the HAp morphology can be attributed to the adsorption of the surface of the hap nuclei inhibiting the crystal growth along a particular axis.
Abstract: The effect of methanol on the morphology of hydroxyapatite (HAp) crystals has been studied under hydrothermal conditions. A precursor HAp slurry prepared from CaCO3 and CaHPO4⋅2H2O was synthesized hydrothermally in the presence of methanol. The products obtained from slurries containing varying amounts of methanol were found to be carbonate-containing HAp by X-ray diffraction and IR spectrometry. TEM showed that the morphology of the products was influenced by the amount of methanol added to the slurry. The products obtained from slurries without methanol were rod-like or granular crystals, about 20 to 100nm in size. Addition of methanol to the slurries caused an increase in the ratio of plate-like crystals to rod-like crystals or granular crystals. When the weight of methanol added was equal to the weight of the slurry, only plate-like crystals 20 to 200nm in size were obtained. X-ray diffraction patterns of oriented products indicated that the plane grown selectively was the a-plane of the plate-like crystals. The results by DTA suggested that the variation of the morphology can be attributed to the adsorption of methanol on the surface of the HAp nuclei inhibiting the crystal growth along a particular axis.
38 citations
TL;DR: Kim et al. as mentioned in this paper showed that SiC is more compatible with oxide liquid than β-SiC at temperatures above 1950°C, while β−SiC showed homogeneous microstructure although significant β→α transformation has occurred during sintering.
Abstract: Sintering behavior of SiC with oxide additives is controlled by SiO2 content and particle size of starting powders at temperatures below 1900°C and chemical reactions, which evolve gaseous products (possibly SiO, Al2O, CO), between SiC, free carbon, SiO2 on SiC and oxide additives at temperatures above 1900°C.The higher SiO2 content leads to a higher sinterability at temperatures below 1900°C. The higher carbon content leads to a lower sintered density at temperatures above 1900°C. The β→α phase trasformation might be affected by the amount of 2H phase in raw materials. The materials sintered at 1950°C show homogeneous microstructure although significant β→α transformation has occurred during sintering. The α-SiC is more compatible with oxide liquid than β-SiC at temperatures above 1950°C.Acknowledgment Stay of Young-Wook Kim in National Institute for Research in Inorganic Materials was supported by Japan-Korea Industrial Technology Co-operation Foundation (JKF).
37 citations
TL;DR: In this article, a transparent transparent YAG ceramics, which contain Nd additives from 1.2 to 7.2 at%, were fabricated by the solid-state reaction method using high purity powders (>99.99 mass%) of Al 2O3, Y2O3 and Nd2O 3, and the precipitated phase (Y1-δNdδAlO3) in accordance with increase in Nd content was clearly observed in YAGs undoped with ethyl silicate.
Abstract: Excellent transparent YAG ceramics, which contain Nd additives from 1.2 to 7.2 at%, were fabricated by the solid-state reaction method using high purity powders (>99.99 mass%) of Al2O3, Y2O3 and Nd2O3. The precipitated phase (Y1-δNdδAlO3) in accordance with increase in Nd content was clearly observed in Nd: YAG ceramics undoped with ethyl silicate. In the case of Nd: YAG ceramics doped with ethyl silicate, the precipitated phases in Nd: YAG ceramics disappeared with adequate addition of ethyl silicate. The Nd: YAG ceramics doped with ethyl silicate were confirmed optical perfect isotropy in dark field image under cross nicols and fully transparent. Beam scattering was hardly observed when the He-Ne laser beam was irradiated into the polished 4.8 at% Nd: YAG ceramics.
37 citations
TL;DR: In this article, the dispersion behavior of the SiC in solutions with PEI dispersant was characterized by their surface potential and isoelectric point (IEP), and interpreted according to the chemistry and adsorption of the PEI.
Abstract: Colloidal dispersion and pressure-casting to prepare SiC green pieces of two types and pressureless sintering of SiC were sequentially conducted to obtain homogeneous, dense SiC bodies. Polyethyleneimine (PEI) was selected as a dispersant, and Al2O3/Y2O3 additives served as a sintering aid for the ceramic systems. The dispersion behavior of the SiC in solutions with PEI dispersant was characterized by their surface potential and isoelectric point (IEP), and interpreted according to the chemistry and adsorption of the PEI dispersant. The resulting crystalline phases and grain morphologies of sintered SiC were investigated by quantitative X-ray diffractometry (QXRD), scanning and transmission electron microscopies (SEM & TEM) and high resolution transmission electron microscopy (HRTEM). α-SiC was sintered at ambient pressure to a higher density than β-SiC with Al2O3 and Y2O3. The densification and resulting microstructure depended greatly on the polytypes of the starting SiC powders, types of packing powder to buy samples, and types and amount of sintering additives. The effects of seeding with 6H-SiC powder on phase evolution, the transformation temperature and densification of the β-SiC matrix are discussed.
36 citations
TL;DR: The thermal decomposition behavior of 1:1 cyano complexes and the composition of decomposition products have been examined in this paper, where a mixture of single oxides (Co3O4 and Ln2O3) and perovskite-type oxide was formed.
Abstract: The thermal decomposition behavior of Ln-Co (1:1) cyano complexes and the composition of decomposition products have been examined. Decomposition of their CN-bridged structures proceeded on heating at about 300°C in air, generating amorphous phases containing carbonate complexes. For the complexes comprising La-Nd, submicron sized particles of perovskite-type oxide were formed (without single phase oxides Co3O4 and Ln2O3) from an amorphous phase by heating at about 620°C. For the complexes comprising Eu, Gd and Dy, a mixture of single oxides (Co3O4 and Ln2O3) and perovskite-type oxide was formed. The content of the perovskite-type oxide increased with the increase in decomposition temperature. For the complexes containing Ho and Yb the corresponding perovskite-type oxide could not be obtained even when the complex was decomposed at 1100°C.
TL;DR: In this article, an electrophoretic sol-gel deposition method in the presence of sodium dodecyl sulfate (SDS) was used for the preparation of thin silica films.
Abstract: Thick silica films were prepared on a stainless steel sheet by the electrophoretic sol-gel deposition method in the presence of sodium dodecyl sulfate (SDS). Electrophoretic deposition was carried out for the silica sols prepared from tetraethoxysilane under the basic conditions. SDS was added as a dispersant in sol preparation. While deposited films were peeled off during drying process in the absence of SDS, thick films were prepared in the presence of SDS; the maximum thickness of the films was about 20μm at an applied voltage of 30V and an SDS content of 0.05 mass%.
TL;DR: In this article, the sinterability and thermal conductivity of Y203 doped AlN powders with diverse specific surface areas (42-2.9m 2 g -1 ) and oxygen contents (0.2-2 mass%) were evaluated.
Abstract: The sinterability and thermal conductivity of Y203 doped AlN powders with diverse specific surface areas (42-2.9m 2 g -1 ) and oxygen contents (0.2-2 mass%) were evaluated. It was found that sintering of fine powders induces the densification at lower processing temperatures, and for raw AlN powders with specific surface area larger than 20m 2 g -1 and oxygen content higher than 1.1 mass%, densified specimens were obtained by sintering at 1650°C for 4h. However, the resultant thermal conductivity of AlN specimens fabricated from fine powders was extremely lower than the theoretical thermal conductivity of AlN, at a level of 80 Wm -1 K -1 . The deterioration of the thermal conductivity has been attributed to the agglomeration of primary particles, and to subsequent formation of oxygen-related defect in grown AlN grains occurring at an early stage of sintering.
TL;DR: In this article, graphite powder was coated with a chelate compound of aluminum and heated at 500°C in air to prepare Al2O3-coated graphite powders.
Abstract: Graphite powder was coated with a chelate compound of aluminum and heated at 500°C in air to prepare Al2O3-coated graphite powder. The sedimentation volume and the heat of immersion in water indicated that the wettability of the graphite powder by water was improved by the Al2O3 coating. The oxidation resistance of Al2O3-coated powder was higher than that of the uncoated one. The first and second adsorption isotherms of water vapor indicated that H2O vapor was adsorbed not only physically but also chemically on the Al2O3-coated layer. The specific surface area by N2 and the second adsorption isotherms of water vapor suggest that the layer has micro pores<0.4nm in diameter.
TL;DR: In this article, a novel continuous reactor was developed for industrial production of monodispersed powders via alkoxide route, where Couette-Taylor vortex flow was used for solution mixing.
Abstract: A novel continuous reactor was developed for industrial production of monodispersed powders via alkoxide route. Couette-Taylor vortex flow was used for solution mixing. Each of Taylor vortices can be worked as a batch reaction vessel. Monodispersed silica powders were prepared by the hydrolysis of ethyl silicate with water and ammonia in ethanol using this reactor. The results were comparable to those obtained using batch process. The effect of Taylor number and residence time on the particle size, particle size distribution, yield, and particle number density of monodispersed silica powders was investigated. Monodispersed silica powders could be continuously produced for 5h using this reactor.
TL;DR: In this article, a 3Dimensional Tyranno fiber reinforced SiC composites were fabricated by infiltration of molten polycarbosilane into a 3-dimensional textile preform (volume fraction: 39%) in an autoclave followed by pyrolysis in an argon atmosphere up to 1200°C.
Abstract: 3-Dimensional Tyranno fiber reinforced SiC composites were fabricated by infiltration of molten polycarbosilane into a 3-dimensional textile preform (volume fraction: 39%) in an autoclave followed by pyrolysis in an argon atmosphere up to 1200°C. An attempt was made to improve the density of the composite by repeating the infiltration and pyrolysis process. Ten times repetition increased the density of the composite to 2.4×103kg·m-3 (relative density: 83%, open porosity: 5%). The bending strength and fracture toughness of the composite were 420 MPa and 11.5 MPa·m1/2, respectively. The composite showed semistable fracture behavior because of bridging of fibers parallel to the tensile direction.
TL;DR: In this paper, the authors measured the conductivities of Fe2O3-Sb2O-3-TeO2 glasses by the pressquenching method and their do conductivities were measured.
Abstract: Fe2O3-Sb2O3-TeO2 glasses were prepared by the pressquenching method and their do conductivities were measured. The glass formation region was found to be 0≤Fe2O3≤15mot%, 0≤Sb2O3≤18mol%, and 78≤TeO2<100mol%. Seebeck coefficient measurements showed that these glasses were n-type semiconductors. The glasses gave conductivities σ ranging from 1.62×10-6 to 1.86×10-7 S·cm-1 at 473K. The dc conductivity increased with an increase in Fe2O3 content. Evaluated carrier mobility and concentration ranged from 7.5×10-10 to 5.3×10-3cm2·V-1·s-1 and from 1.5×1021 to 1.9×1015cm-3 at 473K, respectively. The conduction of these glasses was due to non-adiabatic small polaron hopping.
TL;DR: The behavior and effect of Al4SiC4, an excellent hydration-resistant compound, as an antioxidant for carbon-containing refractories have been investigated, and the corresponding mechanisms have been discussed.
Abstract: The behavior and the effect of Al4SiC4, an excellent hydration-resistant compound, as an antioxidant for carbon-containing refractories have been investigated, and the corresponding mechanisms have been discussed. Al4SiC4 added to the refractories initially reacts with CO to form Al2O3, SiC and C. After the reaction, if the temperatures are below -1560°C, the formed SiC and Al2O3 will further react with CO to form mullite (Al6Si2O13) and C. The above reaction processes can form protective layers on the surfaces of the refractories, which inhibit the oxidation of the refractories. From the results obtained, Al4SiC4 was found to markedly inhibit the oxidation of the carboncontaining refractories.
TL;DR: In this paper, a theoretical approach for explaining the mechanical behavior of brittle metals, polymers or other monolithic ceramics is presented, which cannot substantiate any tangible synergistic effect by nanosized ceramic dispersoids.
Abstract: Toughening and strengthening effects, addressed as intrinsic material properties, are discussed in the case of ceramic-ceramic and ceramic-metal nanocomposites according to fracture mechanics argument. The theoretical approach followed is conceptually the same as that usually adopted for explaining the mechanical behavior of brittle metals, polymers or other monolithic ceramics. The theory cannot substantiate any tangible synergistic effect by nanosized ceramic dispersoids, it is worked out either in terms of toughness or in terms of strength. It is suggested that the improved mechanical properties, as reported in some ceramic-ceramic nanocomposites, may be related to residual microstresses stored into the material after the sintering process or even be affected by extrinsic factors related to the specimen preparation and/or to the testing procedure. Addition of metallic nanodispersoids seems to be a potentially suitable way to obtain a 30-40% increase in the inherent material strength, although a much larger dispersoid size may be required for gaining better toughness. The present theoretical treatment, although simplified in order to obtain solutions in close form, may provide some general and physically sound directives for the development of ceramicmatrix composites. This study intends to provide a theoretical counterpart to recent empirical practices in the field which are lacking in scientific logic.
TL;DR: In this article, the authors showed that the NO2-gas sensitivities of thick Zn2SnO4 films decrease with increasing temperature, however, high sensitivities are obtained in the temperature range of 573 to 673K.
Abstract: Thick Zn2SnO4 films have the highest sensitivities to NO2 among the examined complex oxides with spinel structure. Although the NO2-gas sensitivities of thick Zn2SnO4 films decrease with increasing temperature, high sensitivities are obtained in the temperature range of 573 to 673K. The sensitivities of the present Zn2SnO4 films are comparable to those of NO2-sensitive oxides such as WO3 and ZnO.
TL;DR: In this article, the paraelectric phase of layer-structured BaBi4Ti4O15 single crystals in the parallel and perpendicular directions to the (Bi2O2)2+ layer were identified by complex impedance and modulus analysis at 600 to 767°C.
Abstract: Electrically equivalent circuits for the paraelectric phase of layer-structured BaBi4Ti4O15 single crystals in the parallel and perpendicular directions to the (Bi2O2)2+ layer were identified by complex impedance and modulus analysis at 600 to 767°C. The same form of single semicircle in complex impedance plots for both directions could be differentiated by using complex modulus plots. The equivalent circuits for the parallel and perpendicular directions to the (Bi2O2)2+ layer were identified as a single parallel RC circuit and two parallel RC circuits in a series array, respectively.
TL;DR: In this article, the feasibility of microwave sintering of lead zirconate titanate (PZT) ceramics was examined and the results showed that high strength and high electric properties were obtained compared with the conventional process.
Abstract: The feasibility of microwave sintering of lead zirconate titanate (PZT) ceramics was examined. Microwave sintering was performed at low temperature and short soaking time, using a heating control system with single mode cavity (2.45GHz). Higher density and electric properties were obtained compared with the conventional process, because the sintering reaction was accelerated by microwave radiation. Moreover, higher strength was obtained due to smaller grain size. The microwave sintering was expected to give both high strength and high electric properties.
TL;DR: In this paper, a fine-grained α-Si3N4 and β′-sialon sintered body was fabricated by the gas-pressing sintering method and showed a very high strength of about 2.0 GPa at room temperature, shock resistance of about 20kJ·m-2 (Charpy impact value) and 3-point bending fatigue limit of about 1.3 GPa.
Abstract: Silicon nitride sintered bodies composed of finegrained α-Si3N4 and β′-sialon were fabricated by the gas-pressing sintering method. The silicon nitride sintered body showed a very high strength of about 2.0 GPa at room temperature, shock resistance of about 20kJ·m-2 (Charpy impact value) and 3-point bending fatigue limit of about 1.3 GPa.
TL;DR: In this article, contact angles of β-tricalcium phosphate composite ceramics were measured by the sessile drop and adhesion tension methods, and reproducible values were obtained by the adhesive tension method if the sample was ground to less than 0.6mm in thickness.
Abstract: To evaluate the wettability of phosphate ceramics by water, contact angles of hydroxyapatite-tricalcium phosphate composite ceramics were measured by the sessile drop and adhesion tension methods. It was difficult to obtain an equilibrium contact angle by the sessile drop method. On the other hand, reproducible values were obtained by the adhesion tension method if the sample was ground to less than 0.6mm in thickness. The contact angles of hydroxyapatite and β-tricalcium phosphate ceramics were 30.7° and 23.5°, respectively. The contact angle of the composite ceramics obtained by mixing of hydroxyapatite with tricalcium phosphate increased suggesting that the hydrophilicity of the surface decreased. The wettability of the composite ceramics increased with increasing surface hydroxyl group density measured by X-ray photoelectron spectroscopy.
TL;DR: In this paper, the microstructure of sintered monolithic SiC varied depending on the polytypes of the starting SiC powders, α and β, as well as on the sintering conditions.
Abstract: Monolithic SiC and SiC-AlN composites were prepared by liquid-phase sintering. Polytypes of SiC, transformation of its polytypes and microstructure of the sintered materials were investigated. The SiC-AlN composites were composed of the 2H phase with dispersed SiC grains. The microstructure of sintered monolithic SiC varied depending on the polytypes of the starting SiC powders, α and β, as well as on the sintering conditions. The SiC-AlN composites showed the same microstructure irrespective of the initial phase of SiC. The 2H phase was a SiC-AlN solid solution and had a spherical grain shape, and the 4H-SiC had a platelike shape.
TL;DR: In this paper, the double-torsion method was employed to study the effect of environments on crack-growth law of hydroxyapatite, and three regions (regions 1, 2 and 3) were distinctly observed for measurement in air.
Abstract: The double-torsion method was employed to study the effect of environments on crack-growth law of hydroxyapatite. Three regions (regions 1, 2 and 3) were distinctly observed for measurement in air. In water only region 1 was observed. As the temperature increased, the crack-propagation curves in water shifted to lower applied K I values. The change of crack velocity with increasing K I in region 2 was small compared with those detected in regions 1 and 3. It was argued that crack propagation in region 2 is controlled by the rate of water diffusion towards the crack tip. Region 3 was observed in air and toluene. Intergranular fracture was dominant in the specimen fractured in water, while both transgranular and intergranular fracture were observed in air. On the other hand, the specimens showed only transgranular fracture in toluene. Since a low Ca/P ratio phase was observed at grain boundaries of hydroxyapatite, it was deduced that this phase is selectively dissolved into water.
TL;DR: In this article, the films of hydroxyapatite-calcium phosphate were coated on alumina ceramic substrates by electrophoretic deposition technique and homogeneous films were obtained by using a mixed solution of ethanol and 2, 4-pen-tanedione (acetylacetone).
Abstract: The films of hydroxyapatite-calcium phosphate were coated on alumina ceramic substrates by electrophoretic deposition technique. Homogeneous films were obtained by using a mixed solution of ethanol and 2, 4-pen-tanedione (acetylacetone). The calcium phosphate compound with low melting point played a role of binder between HAp and alumina substrate. The apatite phase of coated layers was decomposed to α- and β-tricalcium phosphate, on sintering at 1300°C.
TDK1
TL;DR: In this article, the preparation of hydroxyapatite (HAp) with elongated diopside grains was studied and it was proved that diop side has no general toxicity in cell culture and the bending strength of HAp-diopside composite was 265 MPa and fracture toughness was 3.2 MPa·m1/2.
Abstract: Preparation of hydroxyapatite (HAp) with elongated diopside grains was studied. Diopside powder with a composition of CaO 23.3 mass%, MgO 14.2 mass%, SiO262.5 mass% was added to HAp powder (BET value was 65m2/g) and sintered at 1280°C for 2h. These powders were selected to control the reaction of HAp and diopside and to obtain composites with elongated diopside grains. The bending strength of HApdiopside composite containing 60 vol% diopside was 265 MPa and the fracture toughness was 3.2 MPa·m1/2. These values were about 2 or 3 times higher than those of HAp. The increase in bending strength of the composite was attributed to an increase in fracture toughness. It was proved that diopside has no general toxicity in cell culture. It is expected that HAp-diopside composite ceramics are useful for artificial bone and dental root.
TL;DR: In this paper, the starting material is zeolite A, which has the tetrahedral framework structure with homogeneous arrangement of Si, Al, and O atoms, and the experimental results supported the previous hypothesis proposed for the formation process of mullite.
Abstract: Zeolite A (NH4-A) exchanged with NH4+ was used as a precursor of mullite. NH4-A was dehydrated and deammoniated by heating up to 300°C and it entered an amorphous state. Mullite crystallized directly from the amorphous phase at above 950°C without forming a spinel phase as an intermediate phase. Since the starting material is zeolite A, which has the tetrahedral framework structure with homogeneous arrangement of Si, Al, and O atoms, these experimental results supported the previous hypothesis proposed for the formation process of mullite.
TL;DR: In this paper, high-oriented AlN thin films were prepared on polycrystalline MoSi2 substrates by rf magnetron sputtering and the films responded to mechanical impact and produced voltage.
Abstract: Highly oriented AlN thin films were prepared on polycrystalline MoSi2 substrates by rf magnetron sputtering. The films responded to mechanical impact and produced voltage. The maximum produced voltage increased almost linearly with the impact intensity. Furthermore, the capacitance of the films increased almost linearly with applied pressure, indicating that the films can measure the pressure. The films responded to thermal shock. These results suggested that the films possessed various functions like human skin.