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Volume 71, Issue 11
Displaying 1-24 of 24 articles from this issue
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Special Issue on Superconducting Materials-Frontiers of Research and Development
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Kyoji Tachikawa, Hiroaki Kumakura, Yutaka Yamada2007 Volume 71 Issue 11 Pages 927
Published: 2007
Released on J-STAGE: November 02, 2007
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Akiyoshi Matsumoto, Hiroaki Kumakura2007 Volume 71 Issue 11 Pages 928-933
Published: 2007
Released on J-STAGE: November 02, 2007
JOURNAL FREE ACCESSMgB2 wires are now fabricated by two (in situ and ex situ) powder-in-tube (PIT) methods. The superconducting properties of PIT-processed MgB2 wires are sensitive to the quality of the starting powder in both methods, the heat-treatment temperature, the porosity of the MgB2 core, and impurity additions. In the case of the in situ method, a sub-micrometer Mg starting powder is quite effective for enhancing Jc. Some kinds of carbon compound additions to the starting powder introduce a carbon substitution for boron in MgB2 crystal and enhance both Bc2 and Jc in high magnetic fields. In general, ex situ-processed MgB2 wires show lower Jc than in situ-processed wires. The key factor to obtain a high Jc for an ex situ tape is also the high quality of the MgB2 starting powder. Recently, we succeeded in the fabrication of high Jc ex situ MgB2/Fe wires using MgB2 cores removed from in situ MgB2 wires. Al-sheathed ex situ-processed wires are interesting due to their light weight and the high thermal stability of conductor. At the present stage, however, Jc values of MgB2 wires are still below a practical level. Further improvement of the processing of MgB2 wires is essential in order to obtain a practical level of Jc values.
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Shinya Uji2007 Volume 71 Issue 11 Pages 934-939
Published: 2007
Released on J-STAGE: November 02, 2007
JOURNAL FREE ACCESSIn two dimensional organic conductors based on BETS molecule, where BETS is bis(ethylenedithio)tetraselenafulvalene, superconductivity is induced under very high magnetic field parallel to the conducting layers. We review the overall features of the global magnetic phase diagrams and discuss the mechanism of the field induced superconductivity in terms of the Jaccarino-Peter effect, where the exchange interaction between the conduction electron spins on the BETS molecule layers and the localized magnetic moments in the insulating layers plays a crucial role.
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Takashi Hase, Kyoji Zaitsu, Mamoru Hamada, Yukinobu Murakami2007 Volume 71 Issue 11 Pages 940-945
Published: 2007
Released on J-STAGE: November 02, 2007
JOURNAL FREE ACCESSCu-16 mass%Sn-0.5 mass%Ti with a Sn content over a solution limit among Cu has been fabricated as a matrix material of bronze-processed (Nb, Ti)3Sn conductor. This material is well deformed because of no precipitations of Cu-Sn compound in it. The (Nb, Ti)3Sn conductors with the Cu-16 mass%Sn-0.5 mass%Ti matrix have been heat-treated by conventional one-stage and two-stage processes. The resulting conductor has shown high-field superconducting performance which corresponds to the one shifted to 1 T of magnitude higher than that of (Nb, Ti)3Sn conductor with Cu-15 mass%Sn-0.3 mass%Ti matrix.
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Studies on Jelly Roll Processed Nb3Sn Superconducting Wires Using Sn-Ta and Sn-Ti Based Alloy SheetsKyoji Tachikawa, Tatsuro Tsuyuki, Yuuki Hayashi, Koei Nakata, Takao Ta ...2007 Volume 71 Issue 11 Pages 946-951
Published: 2007
Released on J-STAGE: November 02, 2007
JOURNAL FREE ACCESSSn-Ta based alloy buttons of different compositions were prepared by the melt diffusion process among constituent metal powders at ∼780°C. The buttons were then pressed into plates. Sn-Ti based alloy plates were sliced from the melt and cast ingot. Resulting Sn-based alloy plates were rolled into thin sheets. The Sn-based alloy sheet was laminated with a commercial Nb sheet, and wound into a Jelly Roll (JR) composite. The composite was encased in a Nb-3.3 at% Ta sheath, and fabricated into a thin wire followed by the heat treatment at 700-775°C. The application of hydrostatic extrusion was useful for the fabrication of JR processed wires. The JR wires using Sn-Ta and Sn-Ti based alloy sheets show a non-Cu Jc of ∼250 A/mm2 at 20 T and 4.2 K, which is considerably higher than that of 16 wt% Sn bronze processed Nb3Sn wires. In the Sn-Ta based alloy sheet the dispersion of Ta powders improves mechanical strength of the sheet. Furthermore, it has been found that the Nb impregnates into the Sn-Ta based alloy layers, and Nb3Sn layers are synthesized by the mutual diffusion between the Nb and Sn-Ta based alloy sheets. Meanwhile, Sn-Ti based alloy sheet is attractive due to its easiness of mass production. Structure and performance of JR processed Nb3Sn wires prepared from Sn-based alloy sheets with different composition are compared.
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Yasuo Iijima, Akihiro Kikuchi, Nobuya Banno, Takao Takeuchi2007 Volume 71 Issue 11 Pages 952-958
Published: 2007
Released on J-STAGE: November 02, 2007
JOURNAL FREE ACCESSThe RHQT (rapid-heating, quenching and transformation) processed Nb3Al superconducting wire has a larger critical current density Jc in high magnetic fields and better strain tolerance than Nb3Sn does. Thus, the Nb3Al wire is one of the most promising candidate superconductors for the large-scale and high-field applications. Although the RHQ optimization is a key to a high Jc through controlling the microchemstry and grain structure of bcc and hence A15 phases, investigated have been only the RHQ parameters of heating current IRHQ and wire speed vwire for a given electrode spacing (100 mm). From a view point of apparatus design a smaller IRHQ is favorable, but a heating time which it takes for a wire to move between electrodes is instead needed to become longer for heating the wire up to 2273 K. Thus vwire must become slower. However, such a slow vwire also causes a slower cooling rate of wire that would partly form undesirable A15 phase at the RHQ treatment. In the present study, an attempt has been made to extend the electrode spacing from 100 mm to 300 mm. This enables a relatively large vwire (high cooling rate) but a small IRHQ, which ensures a heating time enough to react the precursor. The Nb/Al precursor used has been prepared by the double-stacked rod-in-tube process, where the starting material is a 7-core Nb/Al composite of which Al was alloyed with 5 at% Mg. The final size of Al alloy core calculated is 0.56 μm, several times larger than the thickness of Al layer of jelly-roll Nb/Al precursor. The extension of electrode spacing from 100 mm to 300 mm did not degrade Tc of the Nb3Al transformed from bcc supersaturated-solid solution, which was 17.6 K, and allowed the IRHQ to be reduced to ∼1/√3 in comparison to the conventional IRHQ condition with the same vwire. The newly optimized RHQ condition of 0.33 m/s, 48 A for the electrode spacing of 300 mm eventually doubled the Jc (15 T, 4.2 K), at least, for the rod-in-tube processed Nb3Al that has not been mechanically deformed between RHQ and transformation annealing.
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Yoshimitsu Hishinuma, Akihiro Kikuchi, Yasuo Iijima, Takao Takeuchi, A ...2007 Volume 71 Issue 11 Pages 959-965
Published: 2007
Released on J-STAGE: November 02, 2007
JOURNAL FREE ACCESSA superconducting magnet system is also one of the important components in an advanced magnetic confinement fusion reactor. Then it is required to have a higher magnetic field property to confine and maintain the steady-state burning deuterium (D)-tritium (T) fusion plasma in the large interspace during the long term operation. Burning plasma is sure to generate 14 MeV fusion neutrons during deuterium-tritium reaction, and fusion neutrons will be streamed and penetrated to superconducting magnet through large ports with damping neutron energy. Therefore, it is necessary to consider carefully not only superconducting property but also neutron irradiation property in superconducting materials for use in a future fusion reactor, and a “low activation and high field superconducting magnet” will be required to realize the fusion power plant beyond International Thermonuclear Experimental Reactor (ITER). V-based superconducting material has a much shorter decay time of induced radioactivity compared with the Nb-based materials. We thought that the V3Ga compound was one of the most promising materials for the “low activation and higher field superconductors” for an advanced fusion reactor. However, the present critical current density (Jc) property of V3Ga compound wire is insufficient for apply to fusion magnet applications. We investigated a new route PIT process using a high Ga content Cu-Ga compound in order to improve the superconducting property of the V3Ga compound wire.
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Sakae Saito, Takao Yamazaki, Yutaka Ando, Yuji Kubo, Yukio Konno, Taka ...2007 Volume 71 Issue 11 Pages 966-971
Published: 2007
Released on J-STAGE: November 02, 2007
JOURNAL FREE ACCESSThis paper describes a new fabrication process of V-Ti and Nb-Ti superconducting alloy wires by the clad-chip extrusion (CCE) method. It is one of unique fabrication method of alloy wire without melting and casting process. The CCE method is characterized by the extrusion of thin chips of metal-clad sheet. Its chemical composition is controlled by the thickness ratio of the layers of constituent metals at clad-rolling. The CCE method produces the segregation-free composite because each chip is regarded as the deformation element with the intended chemical composition. The CCE-processed precursor wires with fine-layered structure of constituent metals are then converted to the alloys with the intended chemical composition by the heat treatment of solid state diffusion. The finally obtained wires are measured the critical transition temperature Tc and the critical current density Jc at 4.2 K under the applied magnetic field up to 9 T.
The present experiments showed that V-Ti and Nb-Ti superconducting wires were successfully fabricated by the CCE method and the following diffusive heat treatment. Their superconducting properties were measured as follows; (1) 7.82 K of Tc and 80 A/mm2 of Jc at 6 T for the V-Ti wire. (2) 10.0 K of Tc and 100 A/mm2 of Jc at 8 T for the Nb-Ti wire.
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Yutaka Yamada, Takuya Shimohiro, Takeshi Ohtani, Kyoji Tachikawa, Hito ...2007 Volume 71 Issue 11 Pages 972-976
Published: 2007
Released on J-STAGE: November 02, 2007
JOURNAL FREE ACCESSBi2212 HTS conical tubular conductors have been prepared by diffusion process for current lead. The Bi2212 HTS layers are synthesized through the diffusion reaction between a Sr-Ca-Cu oxide substrate and a Bi-Cu oxide coating with Ag addition. The HTS diffusion layers about 150 μm in thickness are formed around both outside and inside of the conical tubes 34/29 mm in outside/inside diameter at the larger end, 24/19 mm in outside/inside diameter at the smaller end, and 100 mm in length. The Ag added to the coating enhances the diffusion reaction, and precipitates on the surface of the specimen decreasing its contact resistance. The transport current properties were evaluated by measuring system using two cryocoolers at Railway Technical Research Institute. The critical temperature of transport current of 1000 A at 0.5 T for the specimen is 57.4 K, which corresponds to the current density of 33 A/mm2 for the Bi2212 layer. The transport current decreases with increasing temperature at the warm end of the conical specimen, and is about 800 A at 60.2 K and 600 A at 62.5 K. The joint voltage of 20 μV at cold end was generated at 50 K and 0.5 T with transport current of 1000 A, which corresponds to the small heat load of 20 mW resulted from the Joule heating. Present Bi2212 conical tubes seem to be promising as current leads with small heat loads for superconducting magnets.
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Shojiro Ochiai, Jaekyoung Shin, Hiroshi Okuda, Sang Soo Oh, Dong-Woo H ...2007 Volume 71 Issue 11 Pages 977-984
Published: 2007
Released on J-STAGE: November 02, 2007
JOURNAL FREE ACCESSThe bending strain-dependence of critical current of Bi2223/Ag/Ag-Mg alloy superconducting composite tape was studied experimentally and analytically. The measured change of critical current with bending strain was described well by the superconducting core shape-incorporated model. The distribution of damage-inducing parameter (difference between the tensile fracture strain and thermally induced residual one) in the samples was described well by the Weibull distribution. By application of this result, the distributions of irreversible bending strain and critical current at various bending strain were discussed.
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Shojiro Ochiai, Masahiro Fujimoto, Hiroshi Okuda, Michinaka Sugano, Ma ...2007 Volume 71 Issue 11 Pages 985-992
Published: 2007
Released on J-STAGE: November 02, 2007
JOURNAL FREE ACCESSThe damage extent and therefore the critical current are different from position to position in a long sample especially when the sample is deformed severely. In the present work, a 48 cm long Bi2223 composite tape bent by 0.7%, being composed of 48 elements with a length of 1 cm and of 8 parts with a length of 6 cm, was used as the test sample. The V-I curve, critical current and n-value were measured for the 48 elements, 8 parts and overall sample, and the relation of the distribution of the critical current of the elements to the critical current of the parts and overall sample and the sample length dependence of critical current were discussed. It was found that the critical current and n-value of parts and overall sample are described well by the voltage summation model which regards the parts and overall sample to be composed of a series circuit of elements. The critical current distribution of the elements was described by the bi-modal Weibull distribution function. Applying the simulation method, in which the estimated Weibull distribution function for the critical current of elements, the empirical relation between the critical current and n-value, the series circuit model for voltage generation and the Monte Carlo method were combined, the relation of average critical current to sample length could be described well. From these results and the features of the V-I curve of the damaged part, it was shown that the critical current and n-value decrease with increasing sample length and the extent of the decrease in critical current with sample length is dependent on the criterion for the definition of critical current.
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Yuh Shiohara, Masateru Yoshizumi, Teruo Izumi, Yutaka Yamada2007 Volume 71 Issue 11 Pages 993-998
Published: 2007
Released on J-STAGE: November 02, 2007
JOURNAL FREE ACCESSCurrent status and future prospects of developments of coated conductor and its applications in Japan were reviewed. Development of coated conductor and its applications has been investigated under the national project conducted by METI in Japan. Main objectives of this national project are the improvement of the superconductive properties and the reduction of the production costs. YBCO layers deposited by PLD, MOD and MOCVD on IBAD or Ni-W buffered alloy substrates have been investigated to obtain high Ic×L tapes with low cost and the specifications of the tapes approach to the application level. Ic×L values achieved in this project are the world record of MOD derived tapes and the former world record which was realized by PLD process. Lowering the production cost of the wires is still a big issue, however, the applications of coated conductors are close to be practical. AC loss reduction of coils has been firstly realized in the world only by the group in this project. Trial products of power cable and motor have been made by using the wires to study their potentials and issues to be addressed. Further investigation will be performed to lower the production cost and improve coated conductors based on the requirements of applications.
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Masashi Miura, Yutaka Yoshida, Toshinori Ozaki, Yusuke Ichino, Yoshiak ...2007 Volume 71 Issue 11 Pages 999-1005
Published: 2007
Released on J-STAGE: November 02, 2007
JOURNAL FREE ACCESSREBa2Cu3Oy (REBCO) film is required for high-critical current (Ic) at 77 K, when using in power applications such as superconducting magnetic energy storage (SMES) and nuclear fusion. Generally, critical current density (Jc) of REBCO thick film decreases with increasing thickness of superconductor, because the amount of dead layer such as a-axis oriented phase increases with increasing the thickness. We speculated that the formation of a-axis oriented phase in REBCO thick films is owing to reduction of surface temperature. In this study, we fabricated low temperature growth (LTG)-multi Sm1.04Ba1.96Cu3Oy (SmBCO) thick films using a (Sm1.04Ba1.96Cu3Oy/Sm-rich layer)×N (N=1, 2…) multilayer system, to suppress the formation of a-axis oriented phases. The LTG-multi thick films retained a large terrace, as a result, supressing the reduction of surface temperature, even if the thickness of the films becomes thick. Therefore, LTG-multi thick films suppressed the formation of a-axis oriented phases and the films showed Ic=630 A/cm-width with a thickness of 1.35 μm at 77 K. From these results, we suggest that LTG-multilayer system is an effective technique for improving the critical current of coated conductor.
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Toshiya Doi, Kazuhiro Kawahara, Yoshinori Hakuraku, Kunihiro Shima, Na ...2007 Volume 71 Issue 11 Pages 1006-1010
Published: 2007
Released on J-STAGE: November 02, 2007
JOURNAL FREE ACCESSWe investigated the effect of the Ar+ ion beam irradiation on removing NiO and/or S on the {100}<001> textured Ni tape surface, and the validity of the tin doped In2O3 (ITO) as a buffer layer which could be epitaxially grown at lower temperature. Excellent biaxial crystal orientations of the CeO2, YSZ and YBCO were achieved in the YBCO/YSZ/CeO2 prepared on the {100}<001> textured Ni tape, by irradiating the surface of the Ni tape before starting the deposition. The Jc of the YBCO/YSZ/CeO2/Ni tape exceeded 2 MA/cm2 at 77 K. We also prepared the biaxially oriented YBCO on the In2O3 buffered Ni tape. We confirmed that ITO did not react with YBCO, and that ITO aligned biaxially on the {100}<001> textured Ni tape.
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Yutaka Yamada, Akira Ibi, Seiki Miyata, Hiroyuki Fukushima, Hirokazu K ...2007 Volume 71 Issue 11 Pages 1011-1016
Published: 2007
Released on J-STAGE: November 02, 2007
JOURNAL FREE ACCESSA 215.6 m long GdBa2Cu3O7-x (GdBCO) conductor has been successfully fabricated by the multi-plume and multi-turn pulsed laser deposition (MPMT-PLD) method and exhibited high critical current of 220 A at 77 K and 0 T. Furthermore, the GdBCO long conductor showed three times higher critical current of 25 A at 3 T and 77 K than that of YBCO. To demonstrate the high performance of GdBCO conductor, we fabricated a GdBCO coil. The GdBCO coil was successfully energized up to the currents of 74.2 A and the magnetic field of 0.5 T at 77 K and 184.8 A and 1.2 T at 64 K. In a liquid He excitation test (4.2 K), the GdBCO coil transported a large current of 895 A and generated 5.7 T. These large values of magnetic field and transport current are promising for the application. To increase further critical current in a magnetic field, an artificial pinning center was introduced into the coated conductor. Especially, a BaZrO3 doped GdBCO conductor exhibited high critical current more than 40 A at 3 T and 77 K for all magnetic field angles and was considered to be promising for the conductor used in a high magnetic field.
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Teruo Izumi, Masateru Yoshizumi, Junko Matsuda, Koichi Nakaoka, Yasuno ...2007 Volume 71 Issue 11 Pages 1017-1023
Published: 2007
Released on J-STAGE: November 02, 2007
JOURNAL FREE ACCESSThe recent progress in the development of TFA-MOD for a long coated conductor is reviewed. The TFA-MOD process is expected as a low cost process to realize the power application using coated conductors. On the effort for high Ic values, the drastic improvement of Jc value was realized by the control of the composition in starting material. Although the same composition as a stoichiometric one of YBa2Cu3Oy had been used in the previous development, it was found that the shift to Ba-poor composition could make Jc values higher. The composition of Y:Ba:Cu=1:1.5:3 has a peak Jc value in the relation of Jc and Ba-ratio. Consequently, an extremely high Ic value of 735 A/cm-width (@77 K, self field) was achieved. In the development by the batch system, it had been difficult to obtain high characteristics in the long tape. The problem was addressed by the numerical analysis considering gas flow and reaction in the film. Then, a 200 m tape with End-to-End Ic value of 201 A/cm-width was realized. Based on the above mentioned results, a large facility for 500 m was installed.
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Regular Articles
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Ryota Nakanishi, Koji Sueoka, Seiji Shiba, Seishiro Fukutani, Makoto H ...2007 Volume 71 Issue 11 Pages 1024-1031
Published: 2007
Released on J-STAGE: November 02, 2007
JOURNAL FREE ACCESSThe maintenance of the adhesion of material interfaces is important in many technological fields. In this paper, we performed first principles calculation to understand the stable structure and adhesive strength of metallic material interfaces, Ni layer or Cu layer on Fe(100) surface formed by metal plating.
In order to confirm the accuracy of our calculation, we have calculated the total energy and the [100] Young's modulus of Fe, Ni or Cu single crystal, by taking the spin-polarization into account. It was found that the calculated result of the crystal structure and lattice constant of these metals agreed satisfactorily with the values determined by experiments. The calculated [100] Young's modulus of Fe, Ni and Cu was 136.7 GPa, 173.7 GPa and 122.2 GPa, respectively.
Furthermore, we have calculated the stable configuration of Ni atoms at Fe(100) surface. Ni atoms take the corresponding position to the bcc structure of Fe (100) substrate. Similar result was obtained for Cu atoms at Fe(100) surface.
The stable structure of the interfaces of 5 Ni layer/5 Fe(100) layer was determined, which was supported by TEM analysis of plated Ni layer on Fe(100) surface. The calculation also showed that the strength of adhesion of the Ni/Fe(100) interface stronger than that of the Cu/Fe(100) interface.
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Yasunori Miyata, Hikaru Takahashi, Masaharu Herai2007 Volume 71 Issue 11 Pages 1032-1040
Published: 2007
Released on J-STAGE: November 02, 2007
JOURNAL FREE ACCESSSolidification morphology in high rate is studied in the constrained solidification of organic material. Tip radius of curvature of needle crystal has decreased with growth rate by power -1/2, irrespective of interfacial shape, dendrite or cellular. Primary arm spacing of needles has decreased with growth rate, and it has diverged at some critical high growth rate. It has resulted very far from dendrites to each other. It is observed that, near the critical rate, some dendrites predominantly grow and their higher order arms develop in the interdendritic region. These arms will grow to cellular morphology above the critical growth rate.
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Tomohito Kimura, Takanobu Suzuki, Yutaka Koizumi, Tadaharu Yokokawa, H ...2007 Volume 71 Issue 11 Pages 1041-1045
Published: 2007
Released on J-STAGE: November 02, 2007
JOURNAL FREE ACCESSA post service examination of a turbine blade from a civil aeroengine has been carried out to ascertain the degree of microstructural coarsening and the distribution of crack damage induced during service. This was with the purpose to elucidate their correlation with the actual operating conditions. Samples were sectioned from different parts of the turbine blade for detailed examination by optical microscope and scanning electron microscope. The average length of cracks was used as one of the parameters to quantitatively illustrate the distribution of cracks on the turbine blade. Experimental results suggested that cracks were mainly concentrated on certain area of the pressure side. Leading edge of the suction side of the turbine blade consisted of mostly coarsened microstructure due to higher temperature exposure. In conclusions, there was no clear correlation between the crack damage distribution and the degree of microstructure evolution.
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Mikito Ueda, Haku Ryu, Toshiaki Ohstuka, Hidenori Takahashi2007 Volume 71 Issue 11 Pages 1046-1049
Published: 2007
Released on J-STAGE: November 02, 2007
JOURNAL FREE ACCESSA composite oxide produced from used dry battery was used to decrease Mg content in Al-Mg alloy at high temperature. The oxide was found to consist of ZnMn2O4, ZnMnO3, and ZnO by XRD analysis. After a reaction between a pellet made from the oxide powder and the alloy in liquid at 973 K for 2 h, Mg content in the alloy decreased from 4.0 to 3.6 mass%. During the reaction, metallic Mg probably diffused into the pellet to form MgMn2O4 and then exchanged with Zn(II) in ZnMn2O4.
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Sohei Sukenaga, Daiji Nakata, Tomoyasu Ichiki, Noritaka Saito, Kunihik ...2007 Volume 71 Issue 11 Pages 1050-1056
Published: 2007
Released on J-STAGE: November 02, 2007
JOURNAL FREE ACCESSViscosities of the molten RE-Mg-Si-O-N(RE=Y, Gd, Nd and La) glasses have been measured using a newly-developed rotational viscometer with gas tight furnace. Effects of nitrogen and rare-earth additives on the viscosities of RE-Mg-Si-O-N melts have been investigated systematically at elevated temperature (∼1873 K).
The viscosities of molten RE-Mg-Si-O-N glasses exponentially increased with nitrogen content, which indicates that the substitution of nitrogen for oxygen in the melts may lead to a high average coordination of nonmetal atoms, and that the increase of cross-linking produces a more rigid network structure. The viscosities of RE-Mg-Si-O-N melts were found to decrease in the order of cationic radius of rare-earth elements, which suggests that larger rare-earth elements behave as a stronger network modifier of complex silicate or silicon-oxynitride anions in elevated temperature melts. Additionally, the viscosity of the smaller rare earth containing oxynitride melt indicated more sensitive increase with nitrogen content.
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Koji Fujita, Yoshihiro Takahara2007 Volume 71 Issue 11 Pages 1057-1060
Published: 2007
Released on J-STAGE: November 02, 2007
JOURNAL FREE ACCESSWe have studied the effect of the chlorine addition on the ultraviolet transmission property of soda-lime glasses to develop the ultraviolet penetration glass with soda-lime compositions. At first, a molecular-dynamics calculation is carried out to investigate how the addition of chlorine has influence on the non-bridged oxygen which causes the absorption of ultraviolet in the soda-lime glass. It is shown from the calculation that the chlorine addition reduces the amount of the non-bridged oxygen. Based on the result, we fabricate the soda-lime glasses containing chlorine by using a platinum crucible, and then measure the transmittance of ultraviolet at 260 nm wavelength. Apparent improvement of ultraviolet transmittance of the soda-lime glasses is confirmed from the measurements. As a result, improvement of ultraviolet transmittance is below 10%, so enough improvement of ultraviolet transmittance is not available by addition of chlorine.
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Kaita Ito, Manabu Enoki2007 Volume 71 Issue 11 Pages 1061-1065
Published: 2007
Released on J-STAGE: November 02, 2007
JOURNAL FREE ACCESSA laser AE method is non-contact measurement of AE by using laser interferometer sensor. However, the sensitivity of laser interferometer is lower than conventional piezoelectric sensor. In this study, a method to improve signal-to-noise ratio of the output waveform of interferometer is investigated. A new system was developed to record and analyze the waveform continuously. Continuous waveform was transformed into time-frequency-magnitude data by short time Fourier transform (STFT) or wavelet transform. After noise component in this time-frequency-magnitude data is cut, inverse STFT or WT is applied to obtain clear AE signals in time domain. Simulated AE signal generated by thermal stress of YAG laser pulse was analyzed and detection capability of AE event was improved compared to the conventional signal processing method.
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Letters to the Editor
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Kiyoshi Mizuuchi, Kanryu Inoue, Yasuyuki Agari, Shinji Yamada, Masami ...2007 Volume 71 Issue 11 Pages 1066-1069
Published: 2007
Released on J-STAGE: November 02, 2007
JOURNAL FREE ACCESSDiamond particle dispersed copper (Cu) matrix composites were fabricated from Cu-coated diamond particles by Spark Plasma Sintering (SPS) process, and their microstructures and thermal conductivities were examined. Cu-coated diamond particles were readily consolidated into composites at temperatures between 973 K and 1173 K. No reaction at the interface between the diamond particle and the Cu matrix was observed at the sintering temperature range applied in the present study. The relative packing density of the composite fabricated increased with increasing the sintering temperature and the holding time, and reached as high as 99.2% when sintered at 1173 K for 2.1 ks. Thermal conductivity of the composite including 43.2 vol.% diamond particles attained 654 W/mK, when the relative packing density of the composite was 99.2%. This value was about 83% of the thermal conductivity estimated by Maxwell-Eucken's equation.
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