Industrial Applications of Pulsed Particle Beams and Pulsed Power Technologies, страница 2

The UNP of silicon has been successfully prepared by the ion-beam irradiation on a Si target in He gas at 1 Torr and at –10^° C [15]. Photoluminescence from the Si nanosized powder is shown in Figure 2. From Figure 2, blue-light emission of the UNP can be observed. Furthermore, it is noted here that the photoluminescence has been observed even being left for four months in an air after the synthesis. It is very often found that the blue-light emission from porous Si is immediately oxidized by the exposure in air for several seconds and that subsequently the peak wavelength is increased, so called red-shift of the emission wavelength. In this experiment, on the other hand, neither red-shift nor blue-shift have been observed, although the reason is not certain yet.

NOVEL CRITICAL TEMPERATURE RESISTOR OF SINTERED Ni-Fe-O NANOSIZED POWDERS

The basic principle of synthesis of Ni-Fe-O nanosized powders by PWD is schematically illustrated in Figure 3. The pulsed current passes through Ni and Fe wires that are located between the electrodes in O₂ ambient gas (Figure 3a). The pulsed current deposits the energy into the wires due to their finite resistance. The deposited energy melts, evaporates and ionizes the wires. As a result, the plasma with high density is produced efficiently, and expands into the O₂ ambient gas (Figure 3b). Moreover, since the plasma is rapidly cooled by the interaction with the ambient molecule of O₂, such plasma is solidified as the UNP of Ni-Fe-O [14].

Figure 4 shows resistivity (ρ) of the UNP of Ni-Fe-O as a function of temperature (T) sintered at 600^o C for one hour in air. Furthermore, the UNP of Ni-Fe-O were synthesized in the O₂ ambient gas at the pressure range from 200 to 600 Torr. In Figure 4, the resistivity of the UNO of Ni-Fe-O is decreased rapidly with increasing T above 200^° C. Until now, V-O samples, which have been known to indicate similar resistivity dependence on temperature, were widely used as critical temperature resistors. However, the changes in such a resistivity change have never been reported in Ni-Fe-O system. Reasons to explain the above resistivity changes may be due to order-disorder transition, semiconductor-metal transition and/or surface spin pinning.

FIGURE 3. Basic principle of synthesis of Ni-Fe-O nanosized powders by PWD

FIGURE 4. Resistivity as a function of temperature of Ni-Fe-O nanosized powders sintered at 600 ^°C for one hour in air

NO_x TREATMENT BY INTENSE, PULSED, RELATIVISTIC ELECTRON BEAM

A large amount of NO_x is produced by electron power plants, ironworks, and diesel engines, which are the source for the significant environmental problems, such as acid rain and photochemical smog. The removal of NO_x has been studied by using intense, pulsed, relativistic electron beam (IREB) generated using pulsed-power generator, «ETIGO-III» [16, 17]. This method is a promising to the new application of IREB to the environmental field of interests. The IREB is irradiated on NO_x contained in flue gas, and then the NO_x is dissociated by the collision with the radical species produced by the IREB.

Figure 5 shows the schematic of the experimental setup for NO_x removal by the IREB. It consists of an electron-beam diode, drift tube, distant IREB-gas-interaction chamber, external magnetic field, and gas mixer. The IREB generated by induction linear accelerator «ETIGO-III» is injected into the distant interaction chamber through not only the two bulkheads but also the 1.6-m-long drift tube filled up with an air. The interaction chamber is filled up with a dry-N₂/O₂-balanced NO gas mixture with the total pressure of 270 kPa.

Figure 6 shows the NO_x concentration as a function of number of IREB shots at the initial NO concentration of 88 ppm. It is found that the NO is removed by the irradiation with the IREB. Until the second shot of IREB, on the other hand, NO₂ is generated by the irradiation of IREB because of high NO concentration. The NO₂ concentration decreases with increasing the number of IREB shots after the fourth shot of the IREB. We found that 70 % of NO_x is removed by firing 10 shots of the IREB. The removal efficiency of NO_x is estimated to be 20–100 g/kWh.

NOx TREATMENT BY INDUCTIVE-ENERGY-STORAGEPULSED POWER GENERATOR

Sulfur oxides (SO_x), nitrogen oxides (NO_x) and suspended particulate matter (SPM) are being produced by various diesel combustion engines, which are released into earth’s atmosphere. These polluting substances have caused serious environmental problems. The reduction of the amount of these substances in the exhaust gas has become the major interest of scientific research and engineering development.