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Ebara Engineering Review No.191

Ultrasonic Attenuation Peak during Fatigue of Polycrystalline Copper

by Toshihiro OHTANI, Hirotsugu OGI, & Masahiko HIRAO

Micro-structural evolution in 4N polycrystalline copper, subjected to zero-to-tension fatigue, was studied by in situ monitoring of ultrasonic attenuation and velocity, using EMAR (Electromagnetic Acoustic Resonance). A contact-less transducer, based on the Lorentz force mechanism, was used as it establishes a continuous monitoring for micro-structural changes in bulk metal with high sensitivity. Within a short interval, 20% - 40% of the total life in the order 104 - 105 cycles, a large peak in attenuation was observed and a depression was indicated by ultrasonic velocity, independent of cyclic stress amplitude. This novel phenomenon was interpreted in terms of drastic change in dislocation mobility and rearrangement, supported by the replication for slip bands and TEM observation of the dislocation structure. Concurrently with this phenomenon, it was observed that the dense dislocation structure began to transform into cells, temporarily accompanying long, free dislocations which absorb much ultrasonic energy in producing the attenuation peak. The following outlines the EMAR method, and discusses assessment on metal fatigue and the possibility of predicting the remaining life of a metal by this method.

Keywords
Electromagnetic acoustic resonance, Copper, Fatigue, Dislocation, Non-destructive evaluation

Cleaning of a 300 mm Wafer Carrier Box - A UV/Photoelectron·photocatalyst Cleaning Unit for Preventing Si Wafer Contamination -

by Toshiaki FUJII, Mitsuo KAWAGUCHI, Tukuru SUZUKI, Sin YOKOYAMA, Takenobu YOSHINO, & Kazuhiko SAKAMOTO

A test was carried out to verify the performance of a UV/photoelectron·photocatalyst cleaning unit which was attached to a 300 mm Si wafer plastic carrier box. The cleaning unit was found to sufficiently remove high molecular weight, cyclic organic compounds, selectively adhering on the surface of the 300 mm wafers stored in the carrier box, as well as gaseous and particle contaminants in the same. Test results suggested that this cleaning unit was fit for next-generation LSI manufacturing.

Keywords
Cleanroom, Wafer, Wafer carrier box, Contaminant, Organic compound, Photocatalyst, UV/Photoelectron, Cleaning unit

Simulation of Molecular Dynamics for Predicting the Adsorption Characteristics of Activated Carbon

by Xinming WANG, Mingyang JIA, Hirokuni HIYAMA, & Yoko SUZUKI

The adsorption process of alkanes in a micro-pore of activated carbon was studied through a simulation of molecular dynamics in order to evaluate the adsorption characteristics of carbonaceous adsorbents. A crystal aggregate model of a carbon wall was made based on a non-graphitizing shape of a micro-pore. The methyl and methylene in dodecane, selected as the adsorbent, were regarded as unit particles having all internal degrees of freedom. The Lennard-Jones potential was used for non-bonded interaction. Inter-molecular potentials, due to bond stretches, angle bends, and periodical torsion, were included to describe the interaction among adjacent particles. The effectiveness of the proposed model was verified by comparing calculated results with experimental data. The adsorption characteristics of different counts of dodecane in the carbon pores were clarified. The adsorption energy was calculated to clarify the effects of activated carbon pore size and the dodecane count on the adsorption performance.

Keywords
Molecular dynamics method, Adsorption, Activated carbon, Micropore, Alkane, Gaseous contamination, Filter, Clean room

A New Ion Exchange Resin with Minimized Production of Leachables in Nuclear Power Plants

by Takeshi IZUMI, Shigeo MIYA, Akira MATSUMOTO, Takao INO, Toshi TAKAI, & Masahiro HAGIWARA

A new ion exchange resin, featuring high crosslinkage and uniform particle size distribution, has been developed and tested for use in nuclear power plants. Simulation test results proved that this resin significantly minimizes the generation of sulfate ion deriving from leachables in condensate demineralizers, i.e. as compared with conventional such resins. It was also found that leachables from this resin had a significantly low molecular weight distribution, thus having minimized affect on anion resin kinetics. Although high cross-linkage resins are regarded as inferior in terms of kinetics and regeneration efficiency, it was found that there was no particular problem in using the newly developed resin in nuclear power plants. This resin is expected to become the solution for minimizing the generation of sulfate ions and keeping the feed water clean in nuclear power plants.

Keywords
Ion exchange resin, High crosslinkage, Condensate demineralizers, Leachables, Cation exchange resin, Molecular weight distribution, Kinetics, Regenerating characteristics, Water retention capacity, Leaching rate of TOC

A Study on Garbage Composition Effects and Kinetic Analysis on Mesophilic and Thermophilic Fermentation of Garbage

by Naoaki KATAOKA, Chun-feng CHU, Akiko MIYA, & Takayuki SUZUKI

The influence of C/N ratio in garbage, organic loading rate, and ammonia concentration on methane fermentation was investigated by batch-culture experiments using synthetic garbage under mesophilic (35°C) and thermophilic (55°C) conditions. The methane production from garbage of high C/N ratio at more than 20 under thermophilic conditions was 1.36 to 1.51 times that under mesophilic conditions. On the other hand, results suggested that methane production from garbage having a low C/N ratio of 12, owing to high protein content, was inhibited at NH4+-N concentrations of 2 500 to 2 800 mg/l. A kinetic analysis using a modified Haldane equation indicated that the maximum organic loading rate and the maximum specific methane production rate under thermophilic conditions were about 1.8 and 2 times of that under mesophilic conditions, respectively. The maximum organic loading rates under mesophilic and thermophilic conditions were 0.18 gVS/gVSS and 0.33 gVS/gVSS, respectively. The potential maximum specific methane production rates under mesophilic and thermophilic conditions were 141 ml-CH4/gVSS·d and 303 ml-CH4/gVSS·d, respectively. MIC50, expressing the ammonia concentration at which the methanogenic activity dropped 50%, was 6 020 mg/l and 4 940 mg/l under mesophilic and thermophilic conditions, respectively, indicating that thermophilic conditions are liable to cause inhibitory action by ammonia.

Keywords
Methane Fermentation, Mesophilic, Thermophilic, Garbage, Kinetic Analysis, Organic loading rate, Specific methane production rate, Ammonia, C/N ratio, Organic waste

Thermal Elutriation System for Recycling of Composite Material Waste

by Hiroshi KOZUKA, Tatsuo TOKUDOME, Toshio NAKAMURA, Kiyoshi SAKURAI, & Hideki KONDO

A new recycling method for composite material waste (metals and plastics), such as discarded electric appliances, has been developed. The main feature of this method is that the waste needs not to be crushed but thermally treated in the original form. Plastics are melted-gasified and as metals are dismantled easily, highly pure metals can be recovered at a high rate. As the plastics themselves are used as a heat source for the treatment, the consumption of power for the treatment from an outside source is minimized. Furthermore, no special CFC recovery equipment is necessary for refrigerators and such, as the CFC becomes decomposed during thermal treatment. This method was developed in line with the TES project, within the framework of the IMS International Collaborative Program.

Keywords
Composite material waste, Electrical household appliance, Recycling, Energy, High purity, Gasification, Melt, No crushing, Disposal of CFC, Dismantle

Development of Dendritic Web Silicon Solar Cells

Akio SHIBATA, Kenji TERAO, Kentaro FUJITA, Daniel L. MEIER, & John R. EASOZ

Dendritic web silicon technology was used to develop a single-crystalline silicon substrate for solar cells. Consequently, a 100-micron thick substrate was produced directly from molten silicon. This established a resource-efficient, crystalline silicon wafer manufacturing process, in that no slicing process was necessary and therefore making it possible to use raw material effectively. Special effort was put in improving the furnace design and process throughput, both of which constituted problems in conventional technology for dendritic web silicon manufacturing. In addition, some unique solar cell configurations were developed making use of the dendritic web silicon substrate.

Keywords
Solar cell, Dendriticweb, Single crystalline silicon, Crystal growth furnace, Puller, Back contact, Bi-facial solar cells, P-n junction, Diffusion length, Flexible