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Volume 44, Issue 8
Displaying 1-14 of 14 articles from this issue
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Eiji Kamijo1997 Volume 44 Issue 8 Pages 721-728
Published: August 15, 1997
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThis paper review recent research on synthesis of ceramics thin films with ion beam assisted deposition, electron cyclotron resonance plasma sputtering deposition and vacuum arc ion plating deposition method. These deposition method are generally applied to that technique in which deposition and simultaneous ion bombardment of a growing film surface are performed with a low-energy activated particles. The effects of the bombardment during deposition may result in either physical, structural change in the chemical reaction. Examples include improved adhesion, preferred crystal orientation, improved stoichiometry and synthesis of diamond and cubic BN at room temperature. There remain however, important items of study that have not yet received sufficient attention. One may be study in atomic level of these modifications caused by the ion bombardment during the nucleation stage of film growth.View full abstractDownload PDF (1713K) -
Tsutomu Inuzuka, Satoshi Tomioka, Shinji Harada1997 Volume 44 Issue 8 Pages 729-733
Published: August 15, 1997
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSTo fabricate a sintered Al2O3 with high dimensional accuracy by near-net-shape firing, oxidation and sintering behavior of compacts of a mixture of Al2O3 and Al powders was studied. The compacts were prepared by compressing green-sheets obtained by doctor-brade method at 196MPa and fired at 1600°C or less in air. The oxidation of Al in the compact occured between about 450°C and 1300°C, and prevents the compact from shrinking in firing process at 1300°C or less. A part of melting Al in the compact spilled out of the compact in firing process, because Al melts below 800°C, its oxidation temperature. MgO, CaCO3 and TiO2 powders were added to prevent the Al spillage and Si powder was added to prevent the shrinkage by sintering at 1400°C or more. As a result, the sinterd Al2O3 having a density of 3.72g/cm3 and 0.7% shrinkage by sintering was fabricated by sintering with oxidation of Al and formation of mullite.View full abstractDownload PDF (4075K) -
Kenta Takagi, Takuro Waki, Akira Kawasaki, Ryuzo Watanabe1997 Volume 44 Issue 8 Pages 734-739
Published: August 15, 1997
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe main problem in thermal barrier coatings (TBCs) applied to gas turbine components is the spallation of ceramic coating under thermal cyclic environments. To clarify the spalling behavior of ceramic coating under cyclic thermal loading, plasma-sprayed TBCs are evaluated by the burner heating test which simulates the actual thermal environment. In the test the top surface is heated by combution flame and the bottom is cooled by water flow. The monitoring of acoustic emission (AE) allows us to in-situ detection of cracking in the ceramic over coat during testing. The TBCs consist of NiCrAlY bond coat and ZrO2-8wt. %Y2O3 top coat, where both coating layers were deposited by air plasma spraying on stainless steel substrates.
The spalling mechanism has been discussed on the basis of the crack observation, frequency of AE events and the variation of effective thermal conductivity. We have concluded the sequence of spalling behavior to be; vertical crack formation on the top surface during cooling, parallel crack formation at the top coat/bond coat interface during heating, and the growth of parallel cracks and their coalescence which leads eventually the ceramic coat to spall.View full abstractDownload PDF (3740K) -
Keijiro Terashita, Susumu Natsuyama, Kei Miyanami1997 Volume 44 Issue 8 Pages 740-745
Published: August 15, 1997
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSA fundamental study was conducted for the design of high-performance antibacterial kneaded resin containing ABS as basic resin, and a antibacterial agent of the silica gel-silver type. The following findings were revealed:
(1) The effectiveness (performance) of antibacterial resin correlates with the dispersion effectiveness number, defined as the product of the dispersion and area ratio of antibacterial agent particles.
(2) Optimum kneading conditions were established which enable the higher-effectiveness of the antibacterial resin (killing almost 100% of bacteria). It is suggested that the three-dimensional contour line graph should be used to represent the kneading conditions and the antibacterial resin effectiveness, in order to establish the optimum kneading conditions to ensure effective antibacterial resin. Such a graph could reduce the number of preliminary experiments.View full abstractDownload PDF (1568K) -
Yukio Fujihara, Watanabe Watanabe, Takino Takino1997 Volume 44 Issue 8 Pages 746-750
Published: August 15, 1997
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSA dry method of the powder preparation for tantalum solid electrolytic capacitor was studied using particle omposition equipment. The effects of paticle size and concentration of PMMA binder on the powder characteristics and the frequency response of impedance of the coducted powder was investigated in detail.
It was confirmed that the existence state of binder in a dry method differs with that of a wet method by SEM photographs. The impedance behavior of powder bed can be described by the model of the existence state of binder.View full abstractDownload PDF (1464K) -
Diffusion Bonding of Compacts Composed of SUS304 Based MaterialsKazuo Asaka, Tsuyoshi Kagaya1997 Volume 44 Issue 8 Pages 751-756
Published: August 15, 1997
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe diffusion bonding of green compacts composed of austenitic stainless steel during sintering were investigated. In this case, carbon can not be added to promote the diffusion bonding, because it decrease the corrosion resistance of stainless steels. So that, cupper and nickel were chosen to increase the diffusion bonding.
The specimens composed of a SUS304L-Cu inner and a SUS304L outer shows higher bonding strength than those of a SUS304L inner and a SUS304L-Ni outer. However, as too much addi-tion of cupper make the density of sintered compacts lower, it is considered that the most suitable combination is a SUS304L-2.0Cu inner and a SUS304L outer. The joining surfaces are well diffused and many twins can be observed accrossing the joining surfaces.View full abstractDownload PDF (2745K) -
Shigeru Unami, Koji Hayashi1997 Volume 44 Issue 8 Pages 757-764
Published: August 15, 1997
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSFe4N is expected to be used as a superior soft or hard magnetic material mainly because of its high saturation magnetization (186emu/g). The production of its dense compact by using pressureless sintering is said to be difficult, because the diffusivity of Fe atoms is poor even at temperatures just below its decomposition temperature of 940K. Therefore, we investigated whether the dense compact can be obtained by pressureless liquid phase sintering of Fe4N and Zn mixed powder; the melting point of Zn (693K) is lower by 247K than the above decomposition temperature.
It was found that a usual simple method, i.e., sintering of Fe4N and Zn mixed powder compact resulted in the expansion of the compact. We, however, succeeded in enhancing the densification of the sintered compact from 54% of theoretical density to 84% by applying the following unique process: Fe4N and 10mass%Zn mixed powder was heat-treated in flowing H2 gas at 703K for 10.8ks to form Fe-Zn compound layer on the surface of Fe4N powder particles, and then the product was mixed with 20mass%Zn powder, compacted and sintered in H2-NH3(2:1) flowing gas at 823K for 3.6ks. The enhanced densification was attributed to good wetting characteristics between Zn liquid phase and the Fe-Zn compound layer.View full abstractDownload PDF (4239K) -
Shigeru Unami, Koji Hayashi1997 Volume 44 Issue 8 Pages 765-769
Published: August 15, 1997
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSWe think that the dimensional accuracy of sintered machine part can be controlled mainly by regulating the relative density of green compact (Dg) and sintering shrinkage and by adding post-treatment such as repressing (cold forging), grinding or cutting in some cases, even if the compact is designed to considerably be densified by sintering. This opinion is based on the fact that such idea have been adopted since about 15-20 years ago in the fabrication of cemented carbides cutting tools and also in MIM or PIM process, where Dg in both cases is as low as 60% and the relative density of sintered compact (Ds) is 100%; the sintering shrinkage is as large as about 14%. Then, we thought that the promotion of the densification is valuable to increase the mechanical properties of sintered machine parts and thus investigated the conditions in the first step for obtaining high Ds as much as possible for coarse powder (45-150μm) of Fe which is the base metal of the parts.
The results obtained were as follows. (1)As for Fe coarse powder compact, Ds was nearly equal to Dg when the compact was sintered in vacuum or H2 gas for 3.6-14.4ks at 1573K. Sintering for 14.4ks at 1743K was necessary for obtaining Ds of 97% even in case of Dg=90%. (2)The addition of a small amount (2-4mass%) of Mo could enhance the densification; the compact with Ds of 96-98% was obtained by solid phase sintering at 1573K for 3.6-14.4ks, under which condition pure Fe compacts hardly densified. This enhancement was attributed to the considerable increase of diffusivity of Fe atoms due to the change in the crystal structure of Fe from fcc to bcc which is caused by the addition.View full abstractDownload PDF (1633K) -
Kazushige Kamihira, Kinichi Honda, Tadayuki Fujii1997 Volume 44 Issue 8 Pages 770-774
Published: August 15, 1997
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSA new technique for preparation of molybdenum single crystal with a desired orientation has been proposed. The technique was performed as follows; first, a specimen with a comb shape was mechanically fabricated from hot-rolled sheet with various rolling procedures and reductions. Then the edge of specimen with a comb shape was locally heated by the optical-beam image furnace in order to make some secondary recrystallized grains with various orientations. After the secondary recrystallized grains were mechanically eliminated except for a secondary grain having a desired orientation, the specimen was zone-annealed at 2000-2200°C at the zone-speed of 5 mm/ hr to grow the secondary grain. Consequently, molybdenum single crystal with a desired crystallographic orientation can easily be produced.View full abstractDownload PDF (2602K) -
Yoshihisa Kishimoto, Osamu Yamashita1997 Volume 44 Issue 8 Pages 775-780
Published: August 15, 1997
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSNd-Fe-B alloy powder was granulated by spray drying method using organic binder consisted of polyvinylalcohol (PVA) or carboxymethylcellulose (CMC) with different tensile strength, in order to improve the powder flowability during feeding and compacting. The relationships between binder composition, polymer/plasticizer ratio and content of binder, and granulated powder characteristics or magnetic characteristics were investigated. By using a polymer with high tensile strength, the bonding strength between alloy powders increased, so that the powder flowability of granulated powders was improved. After compacting these powders in a magnetic field, compacted bodies were heated at 673K in H2. About 96% of carbon in binder was removed, although the oxygen in binder remained. In the case of high tensile strength polymer, remanences (Br) of sintered magnets decreased by about 20%, as compared with those of low tensile strength one. However, by increasing the plasticizer content in organic binder both of Br and maximum energy product (BH)max were improved remarkably.View full abstractDownload PDF (1871K) -
Hideki Matsuzawa, Etsuo Otsuki1997 Volume 44 Issue 8 Pages 781-786
Published: August 15, 1997
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSSince practically attainable coercivity for ferrites is relatively small in comparison with anisotropy field, many attempts have been made to enhance the coercivity by chemical and powder metallurgical methods. SrO⋅nFe3O3(n=1-6) powders were attempted to be prepare with glycine nitrate process, which is a self-combustion process using metal-nitrate/glycine complex aqueous solution. The crystal structure and magnetic properties of the powders were investigated. The powders prepared in a beaker were mixtures of a-Fe2O3 and Sr(NO3)2, which transform to M-phase with the coercivity of 7kOe after an appropriate heat-treatment. The change in coercivity by heat-treatment can be attributed to grain size of the M-phase. Spray roasting process can afford to produce Mphase directly, which shows σ(18)=56emu/g, HCJ=5.3kOe.View full abstractDownload PDF (4335K) -
Shinjiro Tochihara, Ken-ichiro Harashima, Hiroshi Yasuoka, Hiromasa Ma ...1997 Volume 44 Issue 8 Pages 787-791
Published: August 15, 1997
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSTo test the utility of the modified Kim-Anderson model for study of the magnetic response of ceramic superconductors, we measured ac complex susceptibilities xn=x'n-ix"n(n=1, 2, 3, 5, 7) of a single-crystal thin film Bi2Sr2CaCu2Oy, and attempted to simulate the results in the framework of this model. Analyses of xn, have shown that generation of the higher-harmonics can be reproduced pretty well, where the material parameters k and B0, the surface barrier ΔH and the lower critical field HCI involved were used as the fitting parameters. From the even-n harmonic susceptibility x2 which reflects the asymmetric nature of the magnetization curve, we foundthat the critical-current density Jc of the Bi2Sr2CaCu2Oy film depends sensitively on the local flux density Bi. This result is a provoking contrast to the Bi, dependence of Jc. for an YBa2Cu3Oy film.View full abstractDownload PDF (288K) -
Hirofumi Joko, Masashi Fujiwara, Makoto Nakanishi, Tatsuo Fujii, Jun T ...1997 Volume 44 Issue 8 Pages 792-796
Published: August 15, 1997
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSEffects of electrochemical Li-doping to the Pb-substituted Bi-2212 phase on its structural and superconducting properties were studied. Bi1.8Pb0.2Sr1.5Ca1.5Cu2Oz was lithiated through an electrochemical method at constant applied potential at room temperature. In the electrochemically Li-doping samples, the original crystal symmetry, tetragonal structure, was maintained and any secondary phase was not formed. The amount of doped Li for Bi1.8Pb0.2Sr1.5Ca1.5Cu2Oz was much lager than that for Bi2Sr1.5Sr1.5Ca1.5Cu2Oz at the same reaction periods. Analysed maximum Li content y for LiyBi1.8Pb0.2Sr1.5Ca1.5Cu2Oz was found to be 0.53, which was remarkably high in comparison with y=0.37 for LiyBi2Sr1.5Ca1.5Cu2Oz The lattice parameters (a, c) of LiyBi1.8Pb0.2Sr1.5Ca1.5Cu2Oz increased continuously in a similar trend to that of LiyBi2Sr1.5Ca1.5Cu2Oz Tc remains almost constant around 85K as the Li content y increased.View full abstractDownload PDF (310K) -
Gohki Murakami, Yoshio Masuda, Jisun Jin, Shinobu Fujihara, Toshio Kim ...1997 Volume 44 Issue 8 Pages 797-802
Published: August 15, 1997
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSA sol-gel method was applied to preparation of the NdBa2Cu3O7-δ superconducting ceramics.
Influence of synthesizing processes and heating conditions of gels on magnetic and electrical properties of NdBa2Cu3O7-δ was investigated. It has been found that samples consisting of a single phase of NdBa2Cu3O7-δ are obtained by reheating baked gels at 700°C under vacuum, which temperature is lower than those used till now for producing the NdBa2Cu3O7-δ ceramics. It has also been confirmed that undergoing the incongruent melting is effective to improve the superconducting properties. Tc(onset) was reached 93K, and Jc of 1.47×106 A/cm2 was obtained.View full abstractDownload PDF (2246K)
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