Kagehiro Itoyama

Contact Erosion Pattern of DC Break Arcs

Contour figures of crater structures and changes of erosion pattern were examined as a function of operations for break arcs on Au, Ag, Cu, and Ni contacts in a resistive circuit. Erosion pattern and crater structures estimated from the cathode spot behavior were confirmed, and the distinctive crater structures for each contact material were estimated by observing and analyzing closely the cathode spot behavior after a large number of operations. The size of eroded area for each contact corresponded to the values of the maximum moving width (l mw ) of the cathode spot behavior for each contact material. A knowledge of the formation of the uniform erosion pattern was discussed from the present results.

Velocity Distribution of the Moving Cathode Spot in Breaking Contact Arcs

The motion of cathode spot in Au, Ag, Cu, and Ni contacts, which affects the formation of the pip and crater structures, has been precisely observed by utilizing a high-speed camera in moderate current, atmospheric pressure dc break arcs. Dependencies of contact material, current and voltage on the motion of cathode spot were examined experimentally. Behaviors of the cathode spot were evaluated by three factors: 1) the maximum length moved (l mx ) which was defined as a maximum shift distance of the spot in an arcing; 2) the maximum moving width (l mw ) which was the difference between the maximum and minimum distances on the motion of cathode spot; and 3) distributions of velocity of moving cathode spot. For these contact materials, the cathode spot moved rapidly in the sequence of Au > Ag > Cu > Ni. Moreover, the crater structures of each contact have been reasonably explained through the above behavior of the cathode spot.

Formation Process of the Crater Structures of Ni and Cu Contacts at Breaking Arcs

For the investigation of the formation process of the crater structure, evaporated Ni and Cu thin films being formed on bulk Ni and Cu electrodes were eroded by a Single break arc in a de resistive circuit. It was concluded through observations of the eroded area by a scanning electron microscope (SEM) that the diameter of a cathode spot of Ni electrodes is proportional to a square root of current. The diameter of a cathode spot could be estimated to be 30-40 #m for Ni contacts at 60-V dc and 1 A and 22-27µm for Cu contacts at 60-V dc and 0.5 A. The cathode spot of Ni and Cu contacts did not move continuously; they moved the length of the radius of a cathode spot. The cathode spot behavior could be discussed based on the temperature distribution on the cathode spot and the decomposition of the oxide layer on the cathode surface. The model of the formation of a crater structure was proposed by combining the model of microcrater formation and the behavioral model of a cathode spot.

The effect of carbonaceous deposit for NO/sub x/ dissociation by barrier discharge

Summary form only given. A carbonaceous deposit was formed on the dielectric and the surface of electrodes, when the barrier discharge is generated in the mixed gas of CH/sub 4/ and N/sub 2/+NO. The authors have done this pre-treatment, changing the ratio of CH/sub 4/ and N/sub 2/+NO gases from 60 to 80%, under the condition of 500 to 700 Torr in pressure. After this pre-treatment was carried out, we introduced N/sub 2/+NO gas into the chamber. NO/sub x/ dissociation was done with 700 Torr of pressure in the chamber and 300 ml/min of flow rate. The authors investigated the effect of carbonaceous deposit and barrier discharge for NO/sub x/ dissociation. We measured mass spectra on NO/sub x/ by Q-mass. The dielectric is hard glass of 0.15 mm in thickness. The length of gap is 0.8 mm. An applied potential between electrodes was about 4,000 volts AC (peak value) and its frequency was 4.7 kHz.

NOx Dissociation Phenomena In Using Catalyst And Plasma Treatment Device

Poster Session 1PO1-10: Space Plasmas Previous discharges of this type used an alternating current of 50 104 HZ, resulting in spontaneous formation of plasma filaments in both time and space. We study the influence of using a pulsed voltage of duration 20-100 nsec in order to localize the formation of the plasma filaments in time, and increase the density of the filaments in space. Various circuit parameters (pulse amplitude, repetition rate, peak current) are varied. We report a comparison for NOx decomposition with initial concentration of 1000 ppm and the outlet concentration <lo ppm. The removal rate characteristics and the decomposition efficiency will be discussed. lP0l

NO/sub x/ dissociation phenomena using catalyst and plasma treatment device

New approaches for dissociating NO/sub x/ directly are tested from various aspects which are classified basically as catalyst effect, plasma effect and their mixing effects(not the same stage) at atmospheric pressure. However, there may be some problems about the conversion rate, the selectivity of catalyst, the power efficiency of plasma, the thermal stability and the endurance life when considering applying these technologies to production. We propose a new device which is named catalyst and plasma treatment (CAPT). This is in order to solve the above problems in the case of NOx, COx, SOx and so on. The CAPT device may have the possibility of direct dissociation in the above toxic gaseous species which may react under both catalyst and plasma effects at the same stage by applying fundamentally the reed switch configuration.

On the Relation between Semantic Network and Association Map for the Assessment of Class Work

Authors had reported a paper [1] that two association methods were useful for the assessment of class work. Especially, association map was very useful to know the changes of schema of learners before and after class work. However, the association map does not express the flow that learners get the concepts in the class work.

On decomposition of CH/sub 4/ and CO/sub 2/ by barrier discharge

In this work, keeping in mind that we recycle in CO/sub 2/, replacing H/sub 2/ of the energy circulation system with CH/sub 4/, and we tried to clarify the properties of decomposition of CH/sub 4/, CO/sub 2/ by barrier discharge. In case that the decomposition of CH/sub 4/ was carried out, CH/sub 2/, CH/sub 3/ and CH/sub 4/ decreased. And H/sub 2/, C/sub 2/H/sub 2/, C/sub 2/H/sub 4/ and C/sub 2/H/sub 6/ increased as a function of time. The increase of H/sub 2/, C/sub 2/,H/sub 2/, C/sub 2/H/sub 4/ and C/sub 2/H/sub 6/ showed the linear relation with increasing the potential of power supply. The rate of increase became larger with shortening electrode gap range from 2700V to 3500V in the potential of power supply. In the case that the decomposition of CO/sub 2/ was carried out, CO and O/sub 2/ increased after barrier discharge. The rate of increase for O/sub 2/ shows convex curve that had the maximum value at about 3800V.

The characteristics of the starting potential of barrier discharge

Authors intended to clarify the most suitable condition of the reactor by using barrier discharge as plasma process for removing TO/sub x/ gas. The starting potential of barrier discharge was measured with changing electrode gap, thickness of dielectric substrate. And we investigated the condition of impedance matching for the reactor circuit. As results, the power consumed by barrier discharge increased as a function of the electrode gap, load resistance and discharge current. The rate of NO decomposition depended on the thickness of dielectric substrate. This corresponded to the tendency of the power consumed by barrier discharge.

Development of glow discharge plasma-catalytic reactors operated under atmospheric condition

Summary form only given. Two kinds of glow discharge plasma-catalytic reactors, the zone discharge tube plasma reactor and the rotating electrode ring plasma reactor, have been developed and evaluated in various chemical reactions under atmospheric conditions. In the former, a glow discharge occurs between two electrodes through a dielectric materials (Pyrex or quartz tube) and in the latter, between a rotating (rotor) and a fixed electrode (stator) to make large volumes of the plasma zone under atmospheric pressure. Each electrode is, furthermore, coated with catalytically active metals, such as Pt, Pd, Rh, Cu or Ni. Various kinds of decomposition reactions of chemically stable compounds have been examined in order to evaluate the performance of these reactors, such as decompositions of CO/sub 2/, H/sub 2/O, NO, CH/sub 4/ and Freon into simple molecules. Different characteristic capabilities were observed between these reactors. The conversions of various reactants depend on the input power (voltage, current and frequency), the catalytic metal employed, carrier gas with different metastable level and the flow rate of reactant. In most of the reactions investigated, generally speaking, both of reactors showed excellent results in comparison with conventional catalytic reactors.