Bornali Sarma

Surface modifications of natural Kanchipuram silk (pattu) fibers using glow discharge air Plasma

Experimental investigations have been carried out to modify the surface properties of natural Kanchipuram silk (pattu) fibers using a low temperature DC glow discharge air Plasma. Silk is an externally spun fibrous protein secretion formed into fibers. Plasma treatment is an eco-friendly, dry, and clean process over wet chemical method and does not suffer from any environmental and health concerns. Experiments have been performed considering three parameters such as discharge current, treatment time, and working pressure. The structural, thermal, morphological, optical, and mechanical studies of raw and plasma treated silk fibers have been obtained out using attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) spectroscopy, X-ray diffraction (XRD), thermo gravimetric analyzer (TGA), scanning electron microscope (SEM) with energy dispersive spectroscopy (EDS), diffuse absorbance spectroscopy, and tensile test. A comparative study has been done for the untreated and different treated fibers. Various characterization analyses reveal that surface roughness of the plasma treated silk fiber is increased and also crystallite size of treated samples is enhanced, plasma treated silk fibers maintain the whiteness effect and it is observed that UV transmittance region (A & B) is more for the treated fiber which signifies enhanced UV protection.

Onset of normal and inverse homoclinic bifurcation in a double plasma system near a plasma fireball

Plasma fireballs are generated due to a localized discharge and appear as a luminous glow with a sharp boundary, which suggests the presence of a localized electric field such as electrical sheath or double layer structure. The present work reports the observation of normal and inverse homoclinic bifurcation phenomena in plasma oscillations that are excited in the presence of fireball in a double plasma device. The controlling parameters for these observations are the ratio of target to source chamber (nT/nS) densities and applied electrode voltage. Homoclinic bifurcation is noticed in the plasma potential fluctuations as the system evolves from narrow to long time period oscillations and vice versa with the change of control parameter. The dynamical transition in plasma fireball is demonstrated by spectral analysis, recurrence quantification analysis (RQA), and statistical measures, viz., skewness and kurtosis. The increasing trend of normalized variance reflects that enhancing nT/nS induces irregularity...

Investigation of complexity dynamics in a DC glow discharge magnetized plasma using recurrence quantification analysis

Recurrence is an ubiquitous feature which provides deep insights into the dynamics of real dynamical systems. A suitable tool for investigating recurrences is recurrence quantification analysis (RQA). It allows, e.g., the detection of regime transitions with respect to varying control parameters. We investigate the complexity of different coexisting nonlinear dynamical regimes of the plasma floating potential fluctuations at different magnetic fields and discharge voltages by using recurrence quantification variables, in particular, DET, Lmax, and Entropy. The recurrence analysis reveals that the predictability of the system strongly depends on discharge voltage. Furthermore, the persistent behaviour of the plasma time series is characterized by the Detrended fluctuation analysis technique to explore the complexity in terms of long range correlation. The enhancement of the discharge voltage at constant magnetic field increases the nonlinear correlations; hence, the complexity of the system decreases, whic...

Comparative study on nonlinear dynamics of magnetized and un-magnetized dc glow discharge plasma

Various nonlinear dynamical behaviors are experimentally observed to exist in magnetized dc glow discharge plasma. Nonlinear plasma fluctuations are seen evolving when the initial parameters such as discharge voltage, filling pressures, etc are changed in the presence of external magnetic field. A transition pattern of chaotic to quasiperiodicity is experimentally observed when a magnetic field is applied, which is not the case in the un-magnetized one. Hence, a comparative analysis is being conducted for both the cases of magnetized and un-magnetized plasma. The nonlinear behavior of the plasma oscillations are diagnosed by different techniques namely: power spectrum, phase space plotting, correlation dimension, Liapunov exponent, fractal dimension and Hurst exponent. Furthermore, it is noticed that with increasing discharge voltage, the glow emerges from the cathode, slowly moves toward the anode and finally sinks into the anode in a ballooning manner.

Mixed mode oscillations in presence of inverted fireball in an excitable DC glow discharge magnetized plasma

The typical phenomena of mixed mode oscillations and their associated nonlinear behaviors have been investigated in collisionless magnetized plasma oscillations in a DC glow discharge plasma system. Plasma is produced between a cylindrical mesh grid and a constricted anode. A spherical mesh grid of 80% optical transparency is kept inside a cylindrical grid to produce an inverted fireball. Three Langmuir probes are kept in the ambient plasma to measure the floating potential fluctuations at different positions of the chamber. It has been observed that under certain conditions of discharge voltages and magnetic fields, the mixed mode oscillation phenomena (MMOs) appears, and it shows a sequential alteration with the variation of the magnetic fields and probe positions. Low frequency instability has been observed consistently in various experimental conditions. The mechanisms of the low frequency instabilities along with the origin of the MMOs have been qualitatively explained. Extensive linear and nonlinear...

Surface and moisture characteristics of jute using a D.C. glow discharge argon plasma

ABSTRACT A D.C. glow discharge plasma source was employed to characterize changes in water absorbance and surface morphology of natural jute fibers. The low temperature plasma removed moisture from the fibers and significantly modified surface properties. Scanning electron microscopy and energy dispersive X-ray spectroscopy were used for characterization. Open source software was used for the processing of the scanning electron micrographs. The changes in the macromolecular structure and the crystallinity were characterized by X-ray diffraction. Thermogravimetric analysis demonstrated moisture removal from the fibers following plasma treatment.

Continuous wavelet transform analysis for self-similarity properties of turbulence in magnetized DC glow discharge plasma

Abstract. Characterization of self-similarity properties of turbulence in magnetizedplasma is being carried out in DC glow discharge plasma. The time series floatingpotential fluctuation experimental data are acquired from the plasma by Langmuirprobe. Continuous wavelet transform (CWT) analysis considering db4 motherwavelet has been applied to the experimental data and self-similarity propertiesare detected by evaluating the Hurst exponent from the wavelet variance plotting.From the CWT spectrum, effort is made to extract a highly correlated frequencyby locating the brightest spot. Accordingly, those signals are treated for findingout correlation dimension and the Liapunov exponent so that the exact frequencyresponsible for the chaotic behavior could be found out. 1. Introduction Different methods arising from scientific investigationhave been introduced so far to analyze the chaotictime series signals. Fourier analysis is a well-establishedand suitable tool for analyzing stationary time serieswhose statistical properties do not vary with time. TheFourier technique decomposes a signal into harmoniccomponents, where the basic functions are trigonometricfunctions. Another tool for analyzing time series is thewavelet transform (WT; Daubechies 1992; Mallat 1999).The WT has been introduced and developed to study alarge class of phenomena such as image processing, datacompression, chaos, fractals, etc. The basic functions ofthe WT have the key property of localization in time(orspace)andinfrequency,contrarytowhathappenswith trigonometric functions. In fact, the WT works asa mathematical microscope on a specific part of a signalto extract local structures and singularities (Daubechies1992; Mallat 1999). This makes the wavelets ideal forhandling non-stationary and transient signals as wellas fractal-type structures. Since WT is a useful tool,many general aspects of nonlinear time series analysisare reviewed in Chua et al. (1992), Wornell et al. (1992),Carroll (1995), Abarbanel (1996), Staszewski et al.(1999), and Krommes (2002). The identification of thephysical processes underlying low-frequency turbulencein magnetized plasmas is a challenging topic in contem-porary plasma science (Horton 1999). By low frequencyit is meant that the characteristic frequency of the fluc-tuating quantities,

Hydrophobic Surface Modification Of Silk Fabric Using Plasma Polymerized HMDSO

In this work, we study the hydrophobic properties of silk fabrics by deposition of plasma-polymerized (pp) hexamethyldisiloxane (HMDSO) using low-pressure plasma-enhanced chemical vapor deposition. Recently, hydrophobic properties are under active research in textile industry. The effects of coating time and power on the HMDSO-coated silk fabrics are investigated. Water contact angle of pp-HMDSO-coated silk fabric surface is measured as a function of power and coating time. Fabric surface shows an enhancement in hydrophobicity after coating. Attenuated total reflectance-Fourier transform infrared spectroscopy reveals the surface chemistry, and scanning electron microscopy shows the surface morphology of the uncoated and HMDSO-coated fabrics, respectively. In the case of uncoated fabric, water droplet absorbs swiftly, whereas in the case of HMDSO-coated fabric, water droplet remains on the fabric surface with a maximum contact angle of 140∘. The HMDSO-deposited silk surface is found to be durable after detergent washing. Common stains such as ink, tea, milk, turmeric and orange juice are tested on the surface of both fabrics. In HMDSO-coated fabrics, all the stains are bedded like ball droplet. In order to study the self-cleaning property, the fabric is tilted to 45∘ angle; stain droplets easily roll off from the fabric.

Irregular-regular mode oscillations inside plasma bubble and its fractal analysis in glow discharge magnetized plasma

Experimental evidence of different kinds of oscillations in floating potential fluctuations of glow discharge magnetized plasma is being reported. A spherical gridded cage is inserted into the ambient plasma volume for creating plasma bubbles. Plasma is produced between a spherical mesh grid and chamber. The spherical mesh grid of 80% optical transparency is connected to the positive terminal of power supply and considered as anode. Two Langmuir probes are kept in the ambient plasma to measure the floating potential fluctuations in different positions within the system, viz., inside and outside the spherical mesh grid. At certain conditions of discharge voltage (Vd) and magnetic field, irregular to regular mode appears, and it shows chronological changes with respect to magnetic field. Further various nonlinear analyses such as Recurrence Plot, Hurst exponent, and Lyapunov exponent have been carried out to investigate the dynamics of oscillation at a range of discharge voltages and external magnetic field...

Oscillating plasma bubble and its associated nonlinear studies in presence of low magnetic field

Oscillating plasma bubbles have been created around a cylindrical mesh grid of 75% optical transparency in a DC plasma system with a low magnetic field. Plasma bubbles are created by developing ion density gradient around a cylindrical grid of 20 cm in diameter and 25 cm in height, inserted into the plasma. Relaxation and contraction of the plasma bubbles in the presence of external conditions, such as magnetic field and pressure, have been studied. A Langmuir probe has been used to detect the plasma floating potential fluctuations at different imposed experimental conditions. Nonlinear behavior of the system has been characterized by adopting nonlinear techniques such as Fast Fourier Transform, Phase Space Plot, and Recurrence Plot. It shows that the system creates highly nonlinear phenomena associated with the plasma bubble under the imposed experimental conditions. A theoretical and numerical model has also been developed to satisfy the observed experimental analysis. Moreover, observations are extende...