We have employed the self-consistent kinetic theory to study the linear dispersion relation of ion acoustic waves in a four-component plasma consisting of nonextensive hot electrons, Maxwellian cold ...electrons, positive ions, and dust particles. The dust charging process with the modified ion acoustic wave damping, as well as its unstable mode, has been graphically illustrated. It is found that the dust charging mechanism depends on the density of hot electrons, the degree of nonextensive electron distribution, and the temperature ratio of hot to cold electrons. It is shown that the damping and instability rates of ion acoustic waves due to dust charge fluctuations explicitly depend on the choice of electron distribution and the magnitude of dusty plasma parameters. In addition, we have studied the ion acoustic Landau damping in the absence of dust particles. It is found that the weak damping region broadens, while the strong damping region shrinks and is shifted toward the short wavelength region for the increase in the temperature ratio of hot to cold electrons.
We have investigated the Bohm sheath criterion and evolution of dust charge at the sheath edge for the collisional active magnetized plasma in the presence of q-nonextensive electron distribution. ...The set of governing equations has been numerically solved for given initial conditions, whereas the dust charging equation has been solved using the –Raphson method. The Bohm sheath condition for active plasma has been extended using the Sagdeev potential approach, and it has been found that gas pressure, obliqueness of the magnetic field, source and sink terms, and choice of electron distribution affect the Bohm velocity, sheath thickness, floating potential, and evolution of dust charge. As the magnetic field, gas pressure, and nonextensive parameter q increase, the Bohm velocity is found to be decreasing (from supersonic to subsonic), and its explicit effect can be seen on the dust charging process. The magnitude of the E × B drift velocity of ions at the sheath edge determines the Bohm velocity, floating potential, and dust screening length as well. Furthermore, we have presented the comparison of the obtained results for two different cases: (i) unmagnetized and magnetized cases and (ii) active and quiescent plasmas.
Presheath and sheath structures of collisional two ion species (helium and argon) plasma in the presence of bi-Maxwellian electrons have been investigated by using a fluid model. As the thermal ...energy of hot electrons is higher than cold electrons, the electron impact ionization process is governed by the concentration of hot electrons. The velocity of positive ions at the sheath boundary, i.e., the Bohm criterion, gets modified in the presence of ion–neutral drag force, source term, and bi-Maxwellian electrons. It is found that the ion–neutral drag force, ionization rates, and volumetric composition of electrons affect the characteristics of the presheath and sheath. The scale length of the sheath region widens from about 1.09 mm to 5.80 mm with the increase in the concentration of hot electrons. The acoustic speed of helium ions at the sheath boundary is higher than its common speed, whereas the acoustic speed of argon ions is lower than its common speed. The common speed of positive ions at the sheath boundary is slower by 13% in magnitude than in the collisionless case. Furthermore, the effect of ion–neutral drag force on streaming instability for two ion species plasma has been systematically presented.
The proper understanding of magnetized plasma wall-interaction is important in various plasma applications such as surface modifications, sputtering and etching. A multi-component plasma interacting ...with carbon surface in presence of an oblique magnetic field has been investigated using three-fluids model. In the present case, the plasma is assumed to consist of two species of positive ions (H+ and He+) and electrons. The governing equations are solved numerically for given initial and boundary conditions. The results show that the magnitude of sheath potential increases with the increase in electron temperature and it affects velocity of both ion species, which is crucial in the understanding of plasma wall-transition mechanism. The reflection coefficients of lighter and heavier ions for the carbon surface decrease with the increase in ion velocity and in reduced energy; however the lighter ions are reflected more than the heavier ions. Hence, the absorption coefficients of both the ions increase for the increase in ion velocity and reduced energy as well. Furthermore, the reflection coefficient of hydrogen ions is about 20% more in magnitude than that of helium ions for the carbon surface.
In this study, cotton textile samples, commonly used in making quilt covers were subjected to atmospheric pressure dielectric barrier discharge treatment to study their surface wettability and ...absorbancy. Samples were treated in the discharge using a rotatory mechanism and the effects of plasma treatment were examined by contact angle measurement and weight measurement. Air plasma treatment was successful in incorporating hydrophilic functional groups on the textile surface due to which wettability as well as absorbancy immediately after the treatment were highly improved. Effects of plasma treatment started to appear only after 20 cycles (9 mins) and got saturated after 24 cycles (10.8 mins) of treatment. The contact angle reduced from
137
°
(untreated sample) to a value less than
30
°
while absorbancy increased by more than two times as compared to untreated sample. Also, the aging behavior of the plasma treated samples were studied for about a week after plasma treatment. It was observed that the induced oxygen containing groups re-oriented into the bulk of the material during their storage in the environment due to which initial properties of the samples recovered gradually. Our results indicate that low temperature plasma can be successfully applied to modify the properties of textiles and textile industries could utilize this by standardization.
Contact angle measurements are a widely used method for evaluating surface wettability, but their accessibility is limited by the high cost of commercial goniometers. To address this issue, we ...developed a low-cost prototype goniometer using locally available materials and a smartphone-based image analysis system to measure contact angles. We validated our approach by comparing its results with those of a standard goniometer for both organic and inorganic materials. For organic samples, the accuracy is greater than 86%, and for inorganic samples, it is greater than 94%. The good agreement between the two methods demonstrates the feasibility of our proposed method for accurate contact angle measurements at a lower cost.
We study the effect of collision and ion Mach number in a magnetized plasma sheath having two species of positive ions using fluid model. It is assumed that both the ions are singly ionized and in ...thermal equilibrium, and the electrons obey Boltzmann distribution. Our work signifies that the collision greatly affects the ion densities, which explicitly affect space charge density, net current density and the transverse drift of ions. On increasing the collisional frequency, ions accumulation point and current saturation point shift towards the sheath entrance (away from the wall). The ion Mach number affects potential profile and velocity profiles of both ion species. The magnitude of wall potential increases from 34 V to 45 V with the increase in ion Mach number from 0.3 to 0.9. Furthermore, it is shown that the effect of collisional force and Lorentz force is reduced at the sheath entrance by increasing the ion Mach number, which helps to control the flux of particles, momentum flow and energy flow towards the wall.
The use of plasma treatment in agriculture has shown promising results in improving seed germination and crop production. In this work, we have investigated the effects of atmospheric pressure plasma ...treatment on wheat seed germination and production qualities. Dielectric barrier discharge and plasma-activated water (PAW) made by gliding discharge plasma have been used for the treatment. Our results show that plasma-treated wheat seeds have better germination rates and higher production qualities. Among the various treatment times tested, 3 min of direct plasma treatment yields the highest germination rates, and 15 min of PAW produces the best results. Furthermore, the wettability and contact angle of the seeds decreases significantly with increasing treatment time. Our findings suggest that the atmospheric pressure plasma treatment can enhance the germination rate of wheat seeds and their production, which has potential applications in agriculture.
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