Plasma-enhanced thermal growth of copper oxide nanostructures on anode of glow discharge setup (original) (raw)
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Enhanced field emission from O2 and CF4 plasma-treated CuO nanowires
Chemical Physics Letters, 2006
The effects of tetrafluoro methane (CF 4) and oxygen (O 2) plasmas on the morphology and field emission of copper oxide (CuO) nanowires are investigated. The tip diameter of nanowires is found to be reduced and the tips sharpened by both plasmas. Furthermore, O 2 plasma removes the amorphous layer on the surface of as-grown nanowires, while CF 4 plasma treatment deposits a thick amorphous coating which results in a decrease in the surface work function. All these factors contribute to the large enhancement of the field emission performance after the plasma treatment.
Plasma-chemical synthesis of copper oxide nanoparticles in a low-pressure arc discharge
The influence of a pressure of gas mixture (10 vol% O 2 þ 90% N 2) on an average size of copper oxide nanoparticles, produced in the plasma of low pressure arc discharge, has been studied as a basic process variable. A correlation between the dependence of average particle size on gas mixture pressure and the dependence of discharge gap voltage on product of interelectrode distance by a gas mixture pressure, has been found. The estimation was carried out by means of X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). A mathematical model of the cathode region, which shows the applicability of the similarity theory to the low pressure arc discharge, has been represented.
Growth of Flower-like Copper Oxide Nanostructures by Glow Discharge in Water
In this work, synthesis of flower-like copper oxide nanostructures via a plasma-assisted technique based on glow discharge in liquids has been reported for the first time. The preparation process was carried out in a reactor containing a glass discharge chamber with two copper electrodes immersed in distilled water. The effect of distance between electrodes on the rate of nanopowder production and the structural and morphological properties was investigated by XRD and FESEM. From the XRD patterns of as-grown samples, besides the CuO monoclinic structure, reflection peaks corresponding to Cu2O phase were also observed. It was found that Cu2O phase could be easily eliminated by annealing at 400 °C. FESEM images showed that the flower-like copper oxide nanostructures were composed of nanorods in size of a few hundreds of nanometers in length and 50-80 nm in diameter. In addition, the possible formation mechanism of flower-like copper oxide nanostructures was discussed.
Room temperature growth and field emission characteristics of CuO nanostructures
Vacuum, 2017
A variety of CuO nanostructures have been synthesized directly on copper foils by room temperature oxidation of copper through wet chemical method. Alkaline condition necessary for the growth process was maintained by the application of NaOH and NH 3 precursors. pH of the solution and reaction time were selected as the process variables. Formation of CuO was confirmed by X-ray diffraction pattern analysis. Evolution of morphologies of the phases formed was characterized by field emission scanning electron microscopy, leading to elucidation of the growth mechanism. Different types of CuO nanostructures were observed to be formed at different process parameters, selected for the present study. Field emission characteristics of CuO nanorods and CuO nanoflakes were also investigated. Emission current density of CuO nanorods and CuO nanoflakes were determined to be 0.90 mA/cm 2 and 0.48 mA/ cm 2 , respectively. Huge difference in the emission current density indicates that field emission properties of CuO nanostructures are strongly affected by their morphology.
Synthesis and coating of copper oxide nanoparticles using atmospheric pressure plasmas
Surface and Coatings Technology, 2007
Metals and metal oxides are well-known catalysts in many applications. TNO investigates metal and metal oxide nanoparticles as catalysts in rocket and gun propellants. Using nanosize particles allows to tune the curing, mechanical or ballistic properties of the propellant, but to avoid undesired chemical side-reactions a coating of these nanoparticles is sometimes desirable. As a model compound copper oxide was selected. Two atmospheric plasma techniques are presented for synthesis of nanoparticles with suitable coating layers. The first technique is based on injection of existing copper particles (30 nm) in a dielectric barrier discharge. The second technique is based on the combination of a thermal wire arc technique and a non-thermal dielectric barrier discharge. Copper nanoparticles are synthesised via evaporation of copper wire followed by nucleation. Coating takes place in the dielectric barrier discharge zone. The thermal plasma synthesised nanoparticles have been characterised by a narrow size distribution and a main size around 50 nm. For both techniques evaporation of liquid acetone and methyl methacrylate have been used to provide gas phase coating precursors. The coated particles are collected on polycarbonate membranes and TEM grids to be characterised by SEM and TEM. The results show nanoparticles coated with a 5 to 10 nm thick carbon layer.
Nano Select, 2021
This work reports an environment friendly alternative to epitaxially grow copper oxide nanowires (NWs) on copper substrates using single step atmospheric pressure plasma jet assisted oxidation. NWs of average length 300 nm are grown rapidly in 5 minutes along with transforming the surface to superhydrophilic. This method introduces defects in the nanowire structure which is otherwise difficult to achieve due to the highly isotropic nature of nanowire growth. High resolution transmission electron microscopy reveals vacancies and structural defects such as lattice twinning and kinks. Theoretical investigations using density functional theory calculations indicated that oxygen vacancies reduces the adsorption energy of methanol molecules onto the CuO (111) surface and shifts the Fermi level towards conduction band. During electrocatalysis, these defect-rich nanowires exhibit twice the catalytic activity toward oxygen evolution reaction (OER) and methanol oxidation reaction (MOR) in comparison to the traditionally thermally grown nanowires. Moreover, retreating the electrodes after each stability test drops the contact resistance similar to the prisitine sample. Additionally, these NW photocathodes demonstrate an exceptional photocurrent of 2.2 mAcm-2 and have an excellent degradation activity towards organic pollutants namely phenol and paracetamol. This facile growth method can be used to engineer nanowires of other transition metals with enhanced activities.
Materials Letters, 2012
We report on the direct formation of phase pure nanocrystalline cuprous oxide (Cu 2 O) film with band gap ~ 2 eV by microwave plasma oxidation of pulsed dc magnetron sputtered Cu films and the highly controlled oxidation of Cu in to Cu 2 O and CuO phases by controlling the plasma exposure time. The structural, morphological and optoelectronic properties of the films were investigated. p-type Cu 2 O film with a grain size ~20-30 nm, resistivity of ~66 Ω cm and a hole concentration of ~2×10 17 cm-3 is obtained for a plasma exposure time of 10 min without using any foreign dopants. The optical absorption coefficient (~10 5 cm-1) of the Cu 2 O film is also reported.
Synthesis and Characterization of CuO Nanowires
2006
Synthesis of copper oxide nanowires was done heating up copper wires in wet ambient air at 400 and 500degC. The existence of nanowires was confirmed by SEM images and EDX spectroscopy. Nanowires were not formed in nitrogen ambient. The diameters of synthesized nanowires are between 30 to 160 nm and lengths up to 39 mum. SEM image shows that CuO nanowires were formed on top of the oxide grains. Vapor-solid growth mechanism is also suggested for the growth of this nanowire.
Large-scale synthesis and field emission properties of vertically oriented CuO nanowire films
Nanotechnology, 2005
Using a simple method of direct heating of bulk copper plates in air, oriented CuO nanowire films were synthesized on a large scale. The length and density of nanowires could be controlled by growth temperature and growth time. Field emission (FE) measurements of CuO nanowire films show that they have a low turn-on field of 3.5-4.5 V µm −1 and a large current density of 0.45 mA cm −2 under an applied field of about 7 V µm −1. By comparing the FE properties of two types of samples with different average lengths and densities (30 µm, 10 8 cm −2 and 4 µm, 4 × 10 7 cm −2 , respectively), we found that the large length-radius ratio of CuO nanowires effectively improved the local field, which was beneficial to field emission. Verified with finite element calculation, the work function of oriented CuO nanowire films was estimated to be 2.5-2.8 eV.