Pulsed Arc System Research Articles

An Ultrasonic-Frequency Pulsed Arc Approach to Improve the Life of Plasma Cutting Electrode

The present work proposes an ultrasonic-frequency pulsed arc approach to improve effectively the service life of oxidative plasma cutting electrode, and introduces the implementation and principle of the pulsed arc system. A number of electrode arcing experiments were then carried out to demonstrate effectiveness of this novel way. Experimental results show that this ultrasonic frequency pulsed process can contract the cathode zone of the arc while speeding up the movement of the cathode spots, and thus reduced the scope and depth of erosion pit on the hafnium electrode. The life of the electrode was finally increased by 47.8% at the pulse frequency of 40 kHz.

Synthesis and characterization of silver–carbon nanoparticles produced by high-current pulsed arc

In this paper, we report the formation of silver–carbon encapsulated metal nanoparticles (EMN's) using a high-current pulsed arc system in an argon atmosphere. The deposits were studied by Optical Extinction Spectroscopy (OES), X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM); the chemical analysis of the deposits was performed using Energy Dispersion X-ray spectroscopy (EDX). Using the total nanoparticle diameter, the bulk crystalline density of silver and an estimate amorphous carbon (a-C) density we have calculated the size of the silver nucleus and the thickness of the a-C coating as a function of the argon gas pressure. The OES spectra of the EMN's exhibited two peaks characteristic of the Surface Plasmon Resonance (SPR) of elongated/very close silver nanoparticles; a subsequent thermal annealing strongly increased the SPR peaks. The double peak SPR spectra were modeled using calculations based on the existence of silver nanoparticles in the form of prolate spheroids. The main advantage of our preparation method is that the metal nanoparticles are encapsulated in a-C from the beginning and this layer acts as an efficient chemical barrier.

Electrical properties of AuN thin films

Gold nitride (AuN) is a recently synthesized component and is being studied for properties like optical, electrical and mechanical. Plasma-assisted physical vapor deposition (PAPVD) in pulsed arc system is used for deposition of AuN thin film. The system is formed of a reactor in which there are two faced electrodes, and a power-controlled system that performs the discharge systematically. Chemical analyses were realized by x-ray photoelectron spectroscopy (XPS) technique, and narrow N 1s and Au 4f spectra are shown using film stoichiometry, and I–V curves were obtained in two ways (substrate–film and film–substrate), to observe the electrical properties.

Organic layer-coated metal nanoparticles prepared by a combined arc evaporation/condensation and plasma polymerization process

A process for the synthesis of organic layer-coated metal nanoparticles is presented. Metal nanoparticles are synthesized by the low-pressure pulsed arc evaporation of a metal cathode surface, followed by the in-flight deposition of a thin organic layer by capacitively coupled radio-frequency plasma polymerization from a gaseous hydrocarbon monomer. The stability of the pulsed arc system and the cathode erosion rate are discussed. The effects of operating conditions such as power, reactor pressure and inert gas flow rate on the average size of produced bare copper nanoparticles and the properties of the organic coating are studied. A ‘characteristic map’ for the in-flight plasma polymerization from the C2H6 monomer of the organic layer onto the Cu nanoparticles is developed. The produced copper nanoparticles are characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and x-ray photoelectron spectroscopy (XPS). The FE-SEM and TEM images reveal coated copper nanoparticles with the diameter of the metal core ranging from a few to 50 nm and the thickness of the organic layer ranging from 3 to 10 nm. The XPS results show that the plasma polymer film is chemically adsorbed onto the surface of the copper nanoparticle.

Diamond and DLC Layers for a Wide Range of Aplications

Diamond and diamond-like carbon (DLC) layers are nowadays of increasing importance for electrical and mechanical applications. In our laboratory we grow diamond on different substrates (Si, WC-Co) using Hot Filament Chemical Vapor Deposition (HF CVD)method improved by double biasing and DLC layers using pulsed arc system again on different substrates (Si, Ni, glass, Ti-6Al-4V, steel, WCCo). Growth parameters facilitate to control crystallinity of diamond layers from microcrystalline to nanocrystalline type. Mechanical, electrical and optical parameters are possible to change using doping with hydrogen, nitrogen, or oxygen. The goal of this article is to summarize recent results achieved in our laboratory related to applications of diamond and DLC layers for their use in sensors of hard metal in water and medical implantable joints.

Synthesis of organic layer-coated copper nanoparticles in a dual-plasma process

Copper nanoparticles were synthesized in an inert (Ar) low-pressure pulsed arc system using a simple copper rod as the cathode and the source of metal vapors and subsequently coated in-flight with a thin organic layer in a capacitively coupled RF C2H6 plasma. The produced copper nanoparticles were characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and Fourier-transform infrared spectroscopy (FT-IR). Typical nanoparticle size ranges from a few to 50 nm, while the thickness of the organic layer deposited onto the nanoparticles ranges from 3 to 10 nm. The copper nanoparticles are crystalline while the coatings show a polymer-like structure.