D. P. Subedi

Study of the Wettability of ZnO Nanofilms

RetractionThis article was mistakenly published twice. For this reason this duplicate article has now been retracted. For citation purposes please cite the original:http://www.inljournal.com/?_action=articleInfo&article=21AbstractAl-doped and un-doped ZnO thin films deposited on quartz substrates by the nebulized spray pyrolysis method were studied to investigate the wettability of the surface. The main objective of the present study was to investigate the wettability of ZnO thin film by changing the concentration of Al doping. Microstructure and water contact angles of the films were measured by scanning electron microscopy (SEM) and using a contact angle goniometer. SEM studies revealed that the grain size within the film increases with the doping concentration. The contact angles were studied to see the effect of aluminum doping on the hydrophilicity of the film. ZnO films were found to be hydrophobic in nature. A good correlation was observed between the SEM micrographs and contact angle results. The nature of the film was found to change from being hydrophobic to hydrophilic after the treatment in low-pressure DC glow discharge plasma, which, however, was reversible with the storage time.

Effect of calcination environments and plasma treatment on structural, optical and electrical properties of FTO transparent thin films

The dependence of the structural, optical and electrical properties of the FTO thin films on the film thickness (276 nm - 546 nm), calcination environment, and low temperature plasma treatment were examined. The FTO thin films, prepared by spray pyrolysis, were calcinated under air followed by either further heat treatment under N2 gas or treatment in low temperature atmospheric plasma. The samples before and after calcination under N2, and plasma treatment will be represented by Sair, SN2 and SPl, respectively, hereafter. The thin films were characterized by measuring the XRD spectra, SEM images, optical transmittance and reflectance, and sheet resistance of the films before and after calcination in N2 environment or plasma treatment. The presence of sharp and narrow multiple peaks in XRD spectra hint us that the films were highly crystalline (polycrystalline). The samples Sair with the thickness of 471 nm showed as high as 92 % transmittance in the visible range. Moreover, from the tauc plot, the optica...

Dielectric Barrier Discharge (DBD) Plasmas and Their Applications

Gas discharge plasmas, also known as low-temperature plasmas, have drawn much attention in past few decades because of their importance in many technological developments. In this chapter, recent development in producing cost effective plasmas at atmospheric pressure has been introduced along with a brief description of low pressure gas discharge. An overview of corona discharge, arc discharge, dielectric barrier discharge (DBD), surface discharge (SD), atmospheric pressure glow discharge (APGD) and atmospheric pressure plasmas jet has been presented. In particular, generation of atmospheric pressure DBD of different configuration, their characterization by optical and electrical methods and application of these DBD systems for surface treatment of different polymers have been reviewed. The chapter also includes atmospheric pressure plasma jet in argon and its application in biomedicine.

Improvement of wettability and absorbancy of textile using atmospheric pressure dielectric barrier discharge

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 induc...

Surface treatment of polypropylene (PP) film by 50 Hz dielectric barrier discharge produced in air and argon/air mixture at atmospheric pressure

Thin films of polypropylene (PP) are treated for improving hydrophilicity using non-thermal plasma generated by 50 Hz line frequency dielectric barrier discharge produced in air and argon/air mixture at atmospheric pressure. PP samples before and after the treatments are studied using contact angle measurements, surface free energy calculations and scanning electron microscopy (SEM). Distilled water (H2O), glycerol (C3H8O3) and diiodomethane (CH2I2) are used as test liquids. The contact angle measurements between test liquids and PP samples are used to determine total surface free energy using sessile drop technique. PP films show a remarkable increase in surface free energy after plasma treatment. SEM analysis of the plasma-treated PP films shows that plasma treatment introduces greater roughness on the surface leading to the increased surface free energy. Furthermore, it is found that introducing a small quantity of argon can enhance the surface treatment remarkably.

One-Step Combustion Synthesis of Novel Nanocarbons via Magnesiothermic Reduction of Carbon-Containing Oxidants

The aim of this work was to transform carbon-containing ammonium oxalate, (NH4)2C2O4, and ammonium acetate, NH4CH3CO2, into 3D graphene-like carbon nanomaterials via magnesiothermic reduction. Both raw and purified products were characterized by XRD, SEM, TGA, and Raman spectra. The conversion of the initial amount of carbon (in salts) into solid carbon (in purified product) varied between 8.5% (for oxalate) and 90.0% (for acetate). The XRD results confirmed the absence of starting salts in the raw products (MgO and C). The purified product was found to contain largely the turbostratic carbon forming a petal-like 3D graphene material. The application potential of synthesized materials was demonstrated on the example of the removal of 4-chlorophenol from its aqueous solution.

Cost-Effective Plasma Experiments for Developing Countries

Plasma technology forms the backbone of many modern industries today in the field of electronics, agriculture, medicine as well as environmental remediation sectors. However, plasma systems for industrial applications can be expensive to set up with the need for ultralow pressure operation and sophisticated power sources. With the goal of developing cost-effective plasma devices for industrial purposes, we present the development of plasma devices and their applications undertaken in selected small laboratories among the AAAPT fraternity. These include the 50 Hz AC glow discharge to treat biomedical materials (Chulalongkorn University, Thailand); dielectric barrier discharge for treating polymer surfaces and as a chemical reactor (Kathmandu University, Nepal); nonequilibrium atmospheric pressure plasma jets for bacterial inactivation and killing of malignant cells as well as nanoparticles synthesis (University of Malaya, Malaysia); and pulsed plasma sources (small vacuum spark as EUV and X-ray source, nanoparticles synthesis via wire explosion method) (University of Malaya, Malaysia).

Treatment of Wastewater by Ozone Produced in Dielectric Barrier Discharge

There is rapid diminishing of water resources in many countries due to, for example, population growth and constant reduction in fresh water supply. The sewage wastewater, industrial effluents, and municipal wastewater are directly and indiscriminately discharged into rivers and lakes and thus primarily cause water pollution in Nepal. This has increased the water crisis and also causes environmental deterioration. Therefore, the need for the development of an effective, cheap, and environmentally friendly process for the treatment of wastewater before discharging into aquatic environment has emerged. Treatment by ozone produced from dielectric barrier discharge is one of the emerging technologies for such application. The ozonation process is more effective for disinfection and degradation of organic pollutants from water. The current study describes the treatment of wastewater of selected site within Kathmandu. Results on various physicochemical and microbial parameters of the inlet and outlet samples are discussed. Our results showed slight increase in pH, decrease in chemical oxygen demand, and significant increase in dissolved oxygen after ozonation. Importantly, ozonation caused total reduction of fecal coliform.

Cost effective plasma technology for bio-medical materials treatment

In this paper, we summarise the efforts of our group in the development of cost effective plasma devices for applications in the treatment of materials, in particular bio-medical materials.