Journal of the Society of Materials Science, Japan

Preparation and Characterization of TiO₂ and Apatite Coated Photocatalyst

Shinji KATO, Misao IWATA, Toru NONAMI

2002 Volume 51 Issue 6 Pages 599-603
Published: June 15, 2002
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.51.599

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A novel photocatalyst was fabricated by coating TiO₂ and successively apatite on a fibrous ceramic body through the following procedure. At the first step, TiO₂ from Ti[(CH₃)₂CHO]₄ was deposited on the fibrous body by means of the sol-gel method (TiO₂ coated photocatalyst). Then, the resulting TiO₂ coated photocatalyst was soaked for 24h at 37°C in a simulated body fluid with the phosphate ion concentration much higher than that in the human body plasma. By this soaking treatment, apatite crystals were formed on this TiO₂ coated photocatalyst (TiO₂ and apatite coated photocatalyst). It was observed that the composited coating of apatite improved the adsorption ability of TiO₂ coated photocatalyst for colon bacillus, acetaldehyde and methylene blue, and eventually, the TiO₂ and apatite coated photocatalyst could effectively decompose them.

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Lattice Defect in Polished Sapphire and Precise Measurement of Local Strain

Tomohiro SAITO, Hiroshi KAWAMOTO, Takahisa YAMAMOTO, Yuichi IKUHARA

2002 Volume 51 Issue 6 Pages 604-609
Published: June 15, 2002
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.51.604

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Mechanical properties of ceramics strongly depend on the machining condition. In the present study, surface defects and local strain, which was introduced by systematically machining the basal plane of sapphire, were characterized by cross-sectional transmission electron microscopy (XTEM) and convergent beam electron diffraction (CBED) technique. It was found that dislocations and strain were introduced from the surfaces for all specimens examined in this study. Depths of the introduced dislocation were measured by weak beam dark field (WBDF) method, and residual strain in the vicinity of the surfaces were precisely measured by CBED method using the probe size less than 10nm. The experimental CBED patterns were compared with the calculated patterns to quantitatively evaluate the lattice strain around the surfaces. Maximum penetration depths of the dislocations in the specimens ground with #500 diamond wheel, polished with 4-8μm and under 1μm diamond slurry were 1.7μm, 700nm and 250nm, respectively. In addition, twin defect was introduced in the specimen ground by #500 diamond to accommodated the large lattice strain during the machining. Residual local strain was found to remain at the depths of 1.0μm, 1.2μm and 300nm for the specimens ground with #500 diamond, polished with 4-8μm and under 1μm diamond slurry, respectively.

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Effect of Mechano-Chemical Treatment on Consolidation of CaSiO₃ by Carbonation

Haruhisa SHIOMI, Yuko TAKADA, Takeshi SHIONO, Makoto KITAMURA, Takashi ...

2002 Volume 51 Issue 6 Pages 610-616
Published: June 15, 2002
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.51.610

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The effect of a mechano-chemical treatment was investigated on the consolidation of calcium-silicate by carbonation. Amorphous CaSiO₃ powder was used as a starting powder and vibration ball-milled for 24h in air. In order to obtain CaSiO₃ powders with different degree of milling a powder filling in a pot for vibro-milling was varied from 10 to 50g. The wet body of each milled powder was carbonated in 0.33MPa CO₂ atmosphere at 80°C for 6h.
The obtained results are the following:
(1) The starting CaSiO₃ powder had the chain structure of SiO₄ tetrahedron similar to wollastonite and the deviations from structural regularity increased with decreasing powder filling in the pot for milling. The CaSiO₃ powder with larger structural disturbance showed higher solubility in water.
(2) When the fully ground CaSiO₃ was used, a dense consolidated body with high compressive strength was obtained. The compressive strength (σ) of the consolidated body largely depended on porosity, and was showed by the following equation at the porosity of ε.
σ=344exp(-0.56ε)
(3) After carbonation, pores in the consolidated bodies were filled with needle-like crystals. The precipitated crystalline phase was composed of a large amount of aragonite and a slight amount of calcite. The needle-like crystals were aragonite and seemed to play an important role to improve the mechanical strength of the consolidated bodies.
(4) During carbonation, the poly-condensation of SiO₄ tetrahedron occurred as well as the precipitation of CaCO₃ to form three-dimensional networks, and thus the consolidation proceeded.

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High Temperature Deformation and Dislocation Structure of α-Al₂O₃ Single Crystals

Atsutomo NAKAMURA, Takahisa YAMAMOTO, Yuichi IKUHARA

2002 Volume 51 Issue 6 Pages 617-621
Published: June 15, 2002
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.51.617

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The structure and glide behavior of basal dislocations in α-Al₂O₃ single crystals have been studied by high temperature deformation tests and transmission electron microscopy (TEM). Basal slips were dominant in the deformation at 1400°C and edge-type basal dislocations belonging to primary slip system were mainly introduced in the sample. On the other hand, rhombohedral twinning formation frequently took place at 1200°C. It was confirmed by high-resolution electron microscopy (HREM) that the basal dislocation dissociates into two half partial dislocations along the [0001] direction. The two partials were separated with a distance of 4.7nm along the [0001] direction and were located at the nearest neighbor positions along the ‹1120› slip direction. This indicates that the basal dislocation dissociates by self-climb perpendicularly to the basal slip plane, and the stacking fault is formed on the {1120} plane between the two partials. However, the two partials are considered to dissociate on the same basal slip plane during deformation because the basal dislocation with climb dissociation can not glide on the basal slip plane.

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Thermal Cyclic Fatigue of Porous Ceramics for Hot Gas Filters

Yasushi MATSUSHIMA, Satoshi KITAOKA, Hideo AWAJI, Chun-Hong CHEN, Jian ...

2002 Volume 51 Issue 6 Pages 622-627
Published: June 15, 2002
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.51.622

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A thermal cyclic fatigue testing method is proposed for hot gas tube filters made of SiC porous ceramics. The method simulates reverse pulse cleaning of the outer surfaces of the filters during dust removal. O-ring specimens cut from the ceramics were thermally shocked by cyclically blowing air outward through the specimens exposed to a high temperature flue gas. The inner subsurface layer of the specimens fractured preferentially as a result of the thermal tensile stress produced by the temperature difference between the inner and outer surfaces of the specimen. The thermal cyclic fatigue diagram was shown from the maximum thermal tensile stresses calculated on the basis of nonequilibrium thermal conduction, and the O-ring compression fracture behavior of the specimens after the thermal cyclic fatigue tests. The critical conditions that result in the fatigue fracture are given.

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Residual Thermal Stresses in Multilayered Functionally Graded Material Plates

Gang JIN, Hideo AWAJI

2002 Volume 51 Issue 6 Pages 628-632
Published: June 15, 2002
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.51.628

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The one-dimensional calculation of thermally induced residual stresses, generated by fabrication of functionally graded materials (FGMs), is presented. In this study, a laminated plate theory is used to analyze the residual and thermal stresses in the FGM plates fabricated by a multilayered technique. The analytical results indicate that the residual stress distributions can be controlled by adjusting the compositional gradient across the thickness of the FGM plates and that the characteristics of thermal residual stress are more strongly dependent on the thermal expansion coefficients mismatch between ceramic and metal and the volume fraction of metal, in comparison with the mismatch of Young's moduli.

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State of Silver in Ag₂O-B₂O₃-Al₂O₃ Glass and Its Change by Heat Treatment

Takashi WAKASUGI, Atsushi KOTANI, Teppei KATSUMATA, Katsuhisa TANAKA, ...

2002 Volume 51 Issue 6 Pages 633-636
Published: June 15, 2002
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.51.633

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Ag₂O-B₂O₃-Al₂O₃ glasses were prepared by melting and quenching method and the state of silver in the glasses was examined by optical absorption spectra. These glasses have two absorption peaks at less than 300nm and 320nm, which correspond to Ag⁺ ion and atomic Ag, respectively. The content of atomic silver increased with the increase of temperature. Metallic Ag (Ag colloid) precipitated at the glass surface by the heat-treatment at 400°C which causes the absorption peak at 440nm. The origin of the precipitated colloid was considered to be atomic Ag dissolved in the glass because the intensity of the absorption peak at 320nm decreased by the heat treatment. However, the precipitation mechanism is not clear. Since the peak of atomic silver was not observed for the slowly cooled glass, it is considered that the free volume at the glass surface which have high fictive temperature plays an important role for the precipitation of silver.

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Preparation and Structural Control of Porous Hydroxyapatite

Teisuke SATO, Tatsuo BESSHI, Toshinari KORI, Atsuo HATANO, Junji TAMAT ...

2002 Volume 51 Issue 6 Pages 637-641
Published: June 15, 2002
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.51.637

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The porous hydroxyapatite ceramics with various porosity values were prepared using molten wax colloidal process. Graphite powders were used as combustible pore-forming agents. The total porosity of porous hydroxyapatite increased with the graphite content added. The total porosity, mean pore sizes were controlled by changing the content of graphite, the mean graphite particle diameter and sintering temperature. Most of the pores in the resulting ceramics were regarded as the open pores. The flexural strength of porous ceramics markedly decreased with the total porosity.

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Titania Aggregates Formed by Hydrolysis of Ti(OH)₄-HCl-H₂O Concentrated Solutions

Keiji DAIMON, Kouki HORIBA, GUANG Yang, Yasuo HIKICHI, Toshitaka OTA

2002 Volume 51 Issue 6 Pages 642-646
Published: June 15, 2002
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.51.642

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Concentrated Ti(OH)₄-HCl-H₂O solutions were prepared from TiCl₄, and adjusted to the composition of Cl^-/Ti⁴⁺=3 in molar ratio. The crystalline phases and particle morphologies were investigated concerning with the hydrolysis conditions. The titania (TiO₂) powders with fine particles were formed from the solution with the concentration ranging from 0.5mol/l to 4.0mol/l. The anatase crystallizes, at first, and then anatase → rutile phase transition takes place. The rate of the phase transition increases with increasing the concentration of the solution. These products were composed of very fine primary particles having large specific surface areas of about 250m²/g for anatase and 87m²/g for rutile, respectively. Aggregates with the size ranging from 0.1 to 0.8μm were formed from the 3.0mol/l solution at 96°C for 24h. The aggregates become larger as decreasing the concentration of the solution. Spherical aggregates of about 3μm in size was formed from 1mol/l solution.

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A Trial to Prevent the Inpreferable Effect of Local Cellular Formation in Microstructurally-Controlled Ni-Base Superalloys Subjected to Previous Damage on High Temperature Fatigue Strength

For Refurbishment and Recoating Technology

Masakazu OKAZAKI, Reki TAKAKU, Toshio SUZUKI, Kouichi NAMBA, Yoshio HA ...

2002 Volume 51 Issue 6 Pages 647-652
Published: June 15, 2002
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.51.647

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In order to explore a refurbishment technology for advanced gas turbine components, the cellular formation in microstructurally-controlled Ni-based superalloys, CMSX-4 and CM247LC, have been studied. The cellular formation can be seen accompanied with a γ/γ' microstructure coarsened in lamellar or equiaxed arrays, when the superalloys are previously subjected to a damage associated with local plastic deformation, followed by re-heat treatment. During this study special attention was paid to the effect of the cellular formation on the high cycle fatigue strength at high temperature. The experiments indicated that once the cellular formation was reached, the fatigue strength was remarkably reduced, compared with the healthy, or virgin material. The methods to reduce and prevent the above unfavorable effect have been explored. It was strongly suggested by the fatigue tests that the addition of grain boundary strengthening elements would be a promising technique. The application of the surface modification technique, or protective coating, might be also a useful technique. Moreover, nondestructive detection of the cellular formation was also studied, employing ultrasonic technique.

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A Stochastic Analysis of Temperature and Thermal Stress in Functionally Graded Plates with Randomly Varying Initial Temperature

Yoshihiro SUGANO, Ryoichi CHIBA

2002 Volume 51 Issue 6 Pages 653-658
Published: June 15, 2002
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.51.653

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The statistics of the temperature and thermal stress are derived analytically in functionally graded material plates (FGM plates) with randomly varying initial temperature and arbitrary nonhomogeneous thermal and mechanical properties through the thickness of plate. The transient temperature field is analyzed based on a kind of integral transform developed by Vodicka, which is obtained by approximating the FGM plates as multilayered plates with distinct thermal constants in each layer. The associated transient thermal stress is obtained by using the closed-form solution derived by one of the authors for a nonhomogeneous plate with arbitrary variations in mechanical properties. The analytical expressions of autocorrelation function and power spectral density for the temperature and thermal stress are derived. Numerical calculations are carried out, assuming that the random initial temperature of the FGM plates is a white noise disturbance or a homogeneous Markov random field. The effects of the gradual change in material composition on the statistics of temperature and thermal stress for the two homogeneous random fields are discussed.

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The Extension Behavior of Parallel Cracks Based on the Energy Release Rate Criterion

Takahiro ABE, Chikayoshi YATOMI, Ken-ichi HASHIMOTO, Syouji YAMAMOTO

2002 Volume 51 Issue 6 Pages 659-665
Published: June 15, 2002
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.51.659

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In this paper, we examine the crack extension behavior for a linear elastic body with two parallel cracks. Assuming the isotropy of fracture toughness of the body and judging from the criterion based on the energy release rate, we study the influences of the difference of crack length, the relative position of cracks and the load angle on crack extension behavior. The energy release rate is computed for all the extending crack tips at the onset of crack kinking by using the E-integral which is path independent even for a path containing a kinking crack tip and stationary crack tips.

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Crack Extension Behavior in the Brittle Material under Compression Mixed Mode Loadings

Takahiro ABE, Chikayoshi YATOMI, Yoichi SUZUKI, Kazuhiko TSUJINO

2002 Volume 51 Issue 6 Pages 666-672
Published: June 15, 2002
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.51.666

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The purpose of this paper is to examine the crack extension behavior in the brittle material under the compression mixed mode loadings. We here employ a cement paste as the brittle materials. An initial crack was inserted in the center of the disc-type test-piece. The compressive loads were obliquely applied to the initial crack. The extension phenomena of the crack were photographed by a high-speed video camera, and the image analysis was carried out. Using the result of the image analysis, we observed the crack extension behavior in the experiment in detail. It was confirmed that the cracks first occurred from the tips of the initial crack and the secondary cracks were observed after the first cracks. The experimental results were examined using the energy release rate criterion. As a result, the relations between the fracture load in the experiment and the loading angle were found to agree well with the relations between the energy release rate by the E-integral and the loading angle.

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The Effects of Air Atmosphere/High Vacuum/Inner Environment of Materials on Fatigue Fracture Surfaces of High Strength Steel

Takahiro SHIINA, Takashi NAKAMURA, Toru NOGUCHI, Fuyuki HOSOKAWA

2002 Volume 51 Issue 6 Pages 673-680
Published: June 15, 2002
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.51.673

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Uniaxial tension fatigue tests of high strength steel, SNCM439, were carried out in air and high vacuum environments. In order to clarify how different environments affect the fatigue fracture surfaces and interior fatigue crack propagations, fracture surfaces were compared through fractographic analysis under air, high vacuum, and inner environment of materials. The following results were obtained; (1) Compared with surface fractures in air, the fatigue life of surface fractures in high vacuum tended to be longer. (2) High vacuum environment strongly influenced the fatigue fracture surface in initial stage of crack propagation. (3) When the transition of crack propagation from Optically Dark Area (ODA) to Stage II a occurred, there was the possibility that some mechanical factors were involved in the transition. The formation of ODA was closely related to the mean stress. (4) Inner environment of materials gave more similar effects on crack propagation with high vacuum rather than air. (5) When fracture origins were non-metallic inclusions, interior fatigue cracks of materials in Fish eye were propagated in the following order; ODA → Stage II a → Stage II b → Stage II c.

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Identification of Material Constants in Constitutive Equation by Indentation Test with Different Indenters

Takashi WAKUI, Masatoshi FUTAKAWA, Yuji TANABE, Ikuo IOKA

2002 Volume 51 Issue 6 Pages 681-687
Published: June 15, 2002
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.51.681

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This paper describes the novel technique for determining constants in constitutive equation of elastic-plastic materials by the indentation test with indenters having different tip angles. FEM analyses were carried out to evaluate the effect of yield stress (σ_y), work hardening coefficient (A) and exponent (n) and indenter tip angle (θ) on the load-depth curve. The constitutive equation was determined from the characterized curves associated with the effects on the slope. Simulation analyses were performed for some material models to examine accuracy of the presented technique. The maximum discrepancy evaluated so far was 4% at most. It is confirmed that this technique is useful to determine the constitutive equation of a sub-surface of materials or coatings.

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Deposition of Amorphous ITO Thin Film at Low-Temperature by Inclined Opposite Target Type DC Magnetron Sputtering Method

JINGBO Wu, Ri-ichi MURAKAMI, Masaharu KONDO, Yun-Hae KIM

2002 Volume 51 Issue 6 Pages 688-693
Published: June 15, 2002
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.51.688

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The In₂O₃-SnO₂, ITO, thin film is a transparent conductive film. Then, the ITO film is one of the materials for widely practical use. Because the ITO film has high transparency in the area of the visible ray and low resistivity, it should show excellent electromagnetic wave shielding effectiveness. In the present study, the ITO film was produced onto glass substrate at room temperature by the inclined opposite target type DC magnetron sputtering equipment, in which pure In and Sn metal targets were used. The effects of oxygen partial pressure and work voltage on the specific resistivity and transparency of the ITO film were discussed. For low resistivity of the ITO film, the electromagnetic wave shielding effectiveness was studied. The results obtained were summarized as follows: (1) The ITO film produced at room temperature had amorphous structure with very smooth surface. (2) The resistivity of ITO film deposited at room temperature showed minimum value at the oxygen partial pressure of 2.73×10^-2Pa. (3) The resistivity of ITO film deposited at room temperature depended on the work voltage and showed the minimum value in the work voltage of -30V. (4) When the optimum coating conditions were selected, the resistivity of 3.5×10^-4Ω.cm was obtained. (5) When the work voltage was -30V, the ITO film deposited at room temperature showed the most effective electromagnetic wave shielding performance. Also, the electromagnetic wave shielding performance was increased by laminating the film.

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Effect of Bias Voltage and Discharge Current on Mechanical Properties of TiN Film Deposited by D.C. Magnetron Sputtering

Hirotaka TANABE, Yoshio MIYOSHI, Tohru TAKAMATSU, Hideyuki SUGIURA

2002 Volume 51 Issue 6 Pages 694-700
Published: June 15, 2002
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.51.694

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A study on the effects of bias voltage and discharge current on the mechanical properties of TiN films deposited on carbon steel S45C by reactive D.C. magnetron sputtering was carried out. The residual stress, hardness, toughness and adhesive strength was examined by X-ray method, nano-indentation hardness test, IF method and scratch test, respectively. Quite large compressive residual stress was evaluated and it increased as the bias voltage or discharge current increased. With increasing bias voltage or discharge current, the hardness increased, but the adhesive strength decreased. The toughness increased with increasing bias voltage. The each change of these properties had a good correlation with the change of the residual stress, and was arranged as a data-band regardless of the difference of coating conditions. It was considered that these properties were mainly depended on the residual stress. The half value breadth of X-ray diffraction peak also increased with increasing bias voltage or discharge current, and the change of residual stress showed a good correlation with the change of the half width breadth. It was confirmed the residual stress was produced by the bombardments of high-energy ions toward TiN film in coating process. It was concluded that the increase of bias voltage and the increase of discharge current had a same effect to promote the ion bombardment, and the ion bombardment dominantly influenced the mechanical properties of TiN films.

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Materials Science Toward “Super-” and “Ultra-” High Temperature Technologies

II: Materials and Ultra Long Term Elevated Temperature Strength for Ultra Super Critical Energy Components

Yoshiatsu SAWARAGI, Fujio ABE

2002 Volume 51 Issue 6 Pages 701-706
Published: June 15, 2002
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.51.701

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