High‐rate deposition of electrochromic organotungsten oxide (WOxCy) films onto flexible PET (polyethylene terephthalate)/ITO (indium tin oxide) substrates by a tmospheric p ressure‐ p lasma e nhanced c hemical v apor d eposition (AP‐PECVD) with a tmospheric p ressure p lasma j et (APPJ) under various substrate distances is investigated. A precursor (tungsten carbonyl, W(CO)6, TC) vapor, carried by argon gas, is injected into air plasma torch for the synthesis of WOxCy films. Uniform light modulation up to 1 cm wide on PET/ITO/WOxCy is produced, while the moving PET/ITO substrate is exposed to a 0.3 cm diameter plasma torch at room temperature (≈23 °C) and atmospheric pressure. The porous APPJ‐synthesized WOxCy films result in fast responses using potential steps for coloration of 11.5 s at −1V and bleaching of 7.2 s at +1V, respectively. APPJ‐synthesized WOxCy films offer noteworthy electrochromic performance in light modulation with up to 73.0% of transmittance variation, optical density change of 0.72 and coloration efficiency of 67.7 cm2 · C−1 at a wavelength of 800 nm.
The flux and the incident kinetic energy are the most important deposition variables in thin film growth processes. By changing these variables, one can, in principle, alter the reaction pathways and the rate at which they occur and produce a different material than under thermody-namic equilibrium conditions. The significance of supersonic molecular jets stems from the fact that both, the flux and the incident kinetic energy of neutral growth species, can be varied independently. The number of studies that are exploring these advantages in a wide range of materials systems is growing rapidly. In this article the application of supersonic molecular jets in semiconductor thin film growth is reviewed. The effects of both the superthermal incident kinetic energy and the flux on the growth and properties of elemental and compound semiconductors are examined. 相似文献
SiO2 thin films were deposited by a cold arc plasma jet at atmospheric pressure. The cold arc plasma jet was operated with O2 gas of 30 L · min−1, while a He/TEOS mixture of 1 000 sccm was added to the plume of the plasma jet as a precursor. The plasma jet was continuously moved in the xy direction for uniform film thickness. The deposition rate at various conditions was studied by controlling the substrate distance, precursor inlet position, and substrate temperature; the physical and chemical properties of the films were characterized by SEM and XPS. A high deposition rate was attained using the cold arc plasma jet deposition system in open air; it is suggested that this originates from the abundant oxygen atoms produced in the cold arc plasma jet.
Atmospheric pressure microplasma jet sources driven by radio‐frequency wave of 13.56 MHz and by low frequency continuous wave of several kHz ac were fabricated and characterized. The source consists of an ac‐driven copper wire (needle) surrounded by dielectric layer that are placed in a glass tube, and a ground plane electrode (pin‐to‐plane electrode configuration). The basic physical and chemical properties of the plasma jet sources, such as optical emission spectrum, gas temperature, and power deposition were investigated. With various geometrical and operational parameters changed, plasma jets showed different discharge characteristics. The geometrical parameters include the length of the pin wire exposed to the plasma, the distance between the pin to the outlet of the glass tube, and the distance between the pin and the plane electrode. The operational parameters include the applied voltage (amplitude and frequency) and the gas flow rate. As an example of biomedical application of the microplasma jets, the bacterial inactivation experiment was performed. Plasma power (or applied voltage), treatment time, and needle‐to‐sample distance were varied and the bacterial inactivation effects of these parameters were observed.
Further studies on high-speed liquid diesel fuel jets injected into ambient air conditions have been carried out. Projectile impact has been used as the driving mechanism. A vertical two-stage light gas gun was used as a launcher to provide the high-speed impact. This paper describes the experimental technique and visualization methods that provided a rapid series of jet images in the one shot. A high-speed video camera (106 fps) and shadowgraph optical system were used to obtain visualization. Very interesting and unique phenomena have been discovered and confirmed in this study. These are that multiple high frequency jet pulses are generated within the duration of a single shot impact. The associated multiple jet shock waves have been clearly captured. This characteristic consistently occurs with the smaller conical angle, straight cone nozzles but not with those with a very wide cone angle or curved nozzle profile. An instantaneous jet tip velocity of 2680 m/s (Mach number of 7.86) was the maximum obtained with the 40
nozzle. However, this jet tip velocity can only be sustained for a few microseconds as attenuation is very rapid.Received: 13 December 2003, Accepted: 11 April 2004, Published online: 11 February 2005[/PUBLISHED]K. Pianthong: Correspondence to: 相似文献
In this paper, a mixing of gases through square Jets issuing normally Into a CrossFlow (JICF) is investigated by means of
both numerical simulation and experiment. The jets are emitted by two injectors mounted at the top and bottom of an Injector
Frame (IF) which is installed at the center of an Eiffel type wind-tunnel. This jet configuration makes it possible to approximate
an industrial gas mixer placed at the center of a pipe. Large Eddy Simulation based on the Smagorinsky model is used, enabling
characterization of the mean and fluctuating velocities as well as the oscillating flow frequencies. Different diagnostic
techniques, such as Laser Doppler Anemometry and Particle Image Velocimetry are employed for validating the numerical models,
and a good agreement between prediction and experiment is obtained. In the numerical simulation, introduction of a passive
scalar through the jet makes it possible to show three dilution phenomena. They are generated respectively by the wake of
the IF, the jet/wake assemblage and the jets alone in function of the momentum flux ratio between jet and crossflow. Influence
of the various parameters on the mixing process between the jets and the crossflow is identified. The numerical results show
that if the IF wake is suppressed with the presence of a trailing edge behind the IF, classical formation of Counter-rotating
Vortex Pair is found. 相似文献
This review focuses on one of the fundamental phenomena that occur upon application of sufficiently strong electric fields to gases, namely the formation and propagation of ionization waves–streamers. The dynamics of streamers is controlled by strongly nonlinear coupling, in localized streamer tip regions, between enhanced (due to charge separation) electric field and ionization and transport of charged species in the enhanced field. Streamers appear in nature (as initial stages of sparks and lightning, as huge structures—sprites above thunderclouds), and are also found in numerous technological applications of electrical discharges. Here we discuss the fundamental physics of the guided streamer-like structures—plasma bullets which are produced in cold atmospheric-pressure plasma jets. Plasma bullets are guided ionization waves moving in a thin column of a jet of plasma forming gases (e.g., He or Ar) expanding into ambient air. In contrast to streamers in a free (unbounded) space that propagate in a stochastic manner and often branch, guided ionization waves are repetitive and highly-reproducible and propagate along the same path—the jet axis. This property of guided streamers, in comparison with streamers in a free space, enables many advanced time-resolved experimental studies of ionization waves with nanosecond precision. In particular, experimental studies on manipulation of streamers by external electric fields and streamer interactions are critically examined. This review also introduces the basic theories and recent advances on the experimental and computational studies of guided streamers, in particular related to the propagation dynamics of ionization waves and the various parameters of relevance to plasma streamers. This knowledge is very useful to optimize the efficacy of applications of plasma streamer discharges in various fields ranging from health care and medicine to materials science and nanotechnology. 相似文献
