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Volume 40, Issue 12
Displaying 1-5 of 5 articles from this issue
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Hiroaki Masuda, Daisuke Yasuda, Akihiko Ema, Hideaki Mizutani, Ken-ich ...2003 Volume 40 Issue 12 Pages 860-867
Published: December 10, 2003
Released on J-STAGE: April 30, 2010
JOURNAL FREE ACCESSTribo-electrification due to collisions of glass beads onto an aluminum plate was studied by measuring the current generated by the electrification of glass beads. When the tangential velocity component upon impact was relatively low, the current was always positive. However, at a higher tangential velocity, the current changed from positive to negative as the collisions continued. When the tangential velocity component was changed abruptly, the current changed its polarity according to the tangential velocity component, suggesting that the polarity of current was determined only by the tangential velocity. It was further shown that the property of metal surface affects the polarity of current. When we used a target which was left under atmospheric conditions for a day, the positive current generated by the collisions gradually decreased with time and eventually becomes negative. Two independent experiments supported that the polarity change found in this study was not related to surface oxidization.
The effect of water molecules adsorbed on the target surface was investigated by thermally desorbing the water from the target. Desorption at a higher temperature resulted in a sharper decrease in the current, which suggests that the water molecules adsorbed on the target surface was one of the main factors which led to the polarity change in current generated by the tribo-electrification.View full abstractDownload PDF (865K) -
Katuo Saitou2003 Volume 40 Issue 12 Pages 868-875
Published: December 10, 2003
Released on J-STAGE: April 30, 2010
JOURNAL FREE ACCESSControl of diameter of ultrafine particles (UFPs) is an important problem from both scientific and technololgical points of view when they are produced by means of a plasma method. The purpose of this work was to investigate the effects of production conditions on the specific surface area and the morphology of UFPs produced by DC plasma jet using an insulated constrictor plasma torch.
Nickel UFPs were produced by feeding Ni powder of 10μm diameter into Ar or Ar-H2 plasma jet. Specific surface area of UFPs increased with hydrogen contents up to 5%, whereas further increase in hydrogen content did not affect the specific surface area. Increase in hydrogen content changed the morphology of UFPs from isolated particles to coagulated shapes.
Specific surface area of UFPs produced with hydrogen content of 15% increased with increasing plasma gas flow rate to a certain extent; further increase of the flow rate caused a decrease in specific surface area. The morphology of UFPs changed from coagulated shapes to isolated particles as plasma gas flow rate increased.
The relation between specific surface area, Sw, and powder feeding rate, Jp, is described by Sw=fJpn, where f and n are the constants determined experimentally. The value of n determined from the experiments was close to the theoretical value of 0.4. This suggests that the formation mechanism is Brownian coagulation. Control of specific surface area of UFPs is possible by optimizing the powder feeding rate under conditions of low hydrogen content and high flow rate of plasma gas.View full abstractDownload PDF (6967K) -
Tadafumi Adschiri2003 Volume 40 Issue 12 Pages 876-884
Published: December 10, 2003
Released on J-STAGE: April 30, 2010
JOURNAL FREE ACCESSDownload PDF (7230K) -
Minoru Kuniyoshi2003 Volume 40 Issue 12 Pages 895-896
Published: December 10, 2003
Released on J-STAGE: April 30, 2010
JOURNAL FREE ACCESSDownload PDF (2014K) -
[in Japanese]2003 Volume 40 Issue 12 Pages 898
Published: December 10, 2003
Released on J-STAGE: April 30, 2010
JOURNAL FREE ACCESSDownload PDF (135K)
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