Effect of initial precursor concentration on TiO_2 thin film nanostructures prepared by PCVD system

TiO2 thin film was prepared on Si substrate by plasma chemical vapor deposition （PCVD） system and the morphologies of ZiO2 thin film were controlled by adjusting the initial precursor concentration. As the initial titanium tetra-isopropoxide （TTIP） concentration increases in PCVD reactor, the shapes of TiO2 particles generated in PCVD reactor change from the spherical small-sized particles around 20 nm and spherical large-sized particles around 60 nm to aggregate particles around 100 nm. The TiO2 particles with different shapes deposit on the substrate and become the main building blocks of resulting TiO2 thin film. We observed the TiO2 thin film with smooth morphology at low initial TTIP concentration, granular morphology at medium initial TTIP concentration, and columnar morphology at high initial TTIP concentration. It is proposed that we can prepare the TiO2 thin film with controlled morphologies in one-step process just by adjusting the initial precursor concentration in PCVD .

Simple reactor for the synthesis of silver nanoparticles with the assistance of ethanol by gas-liquid discharge plasma

Atmospheric pressure plasma technology is gaining increasing importance because it is a simple and tunable synthesis process for the production of metallic nanoparticles.In addition to the development of the power supply,improving the reactor is also one of the main strategies to enhanee the utility.In this study,a simple reactor for the gas-liquid discharge plasma induced by argon gas was applied to synthesize silver nanopailicles from silver nitrate(AgNO3)in solution.An AC power supply with a peak voltage of 3.5 kV was used.The frequency and on-time were set to 50 kHz and 2.5“s,respectively.The oscilloscope showed that the rising time was approximately 2“s.The ethanol was used as the source for the reactive reducing agent.No more additional comp on ents existed in the solution during the discharge and neither of the electrodes was in contact with the treated solution.The temperature in creased by 10°C within 1 min without a cooling system.Carbon was the main impurity and was expected to be produced from the decomposition of the organics under the plasma.The elevated temperature decreased the organic by-products by evaporation and could also decrease the production of carbon.Transmission electron microscopy showed that the spherical silver nanoparticles with a size of approximately 10 nm were synthesized with a crystal structure and that a low concentration of ethanol prefers the production of the mono-dispersed colloid.

Decomposition of Nitrogen Trifluoride Using Low Power Arc Plasma

The low power arc plasma is characterized by extremely high enthalpy and temper- ature and it is easy to generate and control, and thus thermal decomposition process based on the plasma torch is receiving a great attention for decomposing non-degradable greenhouse gases. In order to elevate the economic feasibility, the effects of input power, waste gas flow rate and additive gases on the destruction and removal efficiency （DRE） of NF3 are examined. Specific energy density （SED） deceases as the flow rate increases, and accordingly, the DRE is reduced. The DRE is basically determined by the specific energy density. The highest DRE of NF3 was 97% for the waste gas flow rate of 100 L/min at a low input power level of 2 kW with the help of hydrogen additional gas. The inlet and outlet concentration of NF3 was analyzed using Fourier transform infrared spectroscopy （FT-IR） for DRE of NF3 evaluation. As a result, large amount of NF3 can be efficiently decomposed by low power arc plasma systems.

Submerged arc plasma system combined with ozone oxidation for the treatment of wastewater containing non-degradable organic compounds

Submerged arc plasma technology was assessed for the removal of phenols from wastewater.The OH radicals generated from the boundary between the plasma and waste solution were considered as a significant factor on the degradation reaction.In this study,the effects of highly energetic electrons released from the submerged arc plasma were mainly studied.The highly energetic electrons directly broke the strong chemical bond and locally increased the reaction temperatures in solution.The effects of the submerged-arc plasma on the decomposition of phenol are discussed in terms of the input energy and initial concentration.The single use of submerged arc plasma easily decomposed the phenol but did not increase the mineralization efficiency.Therefore,the submerged arc plasma,coupled with the ozone injection,was investigated.The submerged arc plasma combined with ozone injection had a synergic effect,which led to significant improvements in mineralization with only a small increase in input energy.The decomposition mechanism of phenol by the submerged arc plasma with the ozone was analyzed.