02-09-2013, 03:42 PM
A Report On SYNTHESIS OF NANOPARTICLES BY SPARK DISCHARGE GENERATION AND THEIR APPLICATIONS
Introduction:-
Spark discharge generation (SDG) was introduced by Schwyn et al.1988 as a method for nanoparticle production. The production of nanoparticles by microsecond spark discharge evaporation in inert gas is studied systematically applying transmission electron microscopy, mobility analysis and BET surface area measurement. The method of spark discharge is of special interest, because it is continuous, clean, and extremely flexible with respect to material and scale-up is possible. The particle size distributions are narrow and the mean primary particle size can be controlled via the energy per spark. Separated, unagglomerated particles, 3–12 nm in size, or agglomerates can be obtained depending on the flow rate. The Nano particulate mass produced is typically 5 g/kWh. Spark generation is therefore of special interest for producing monodisperse aerosols or particles of uniform size via electrical mobility analysis.
Procedure:-
A spark discharge generator (Fig. 3) was used in combination with different silicon electrodes. Intrinsic silicon rods (99.95% wt. purity, 8 mm in diameter and 6 cm in length) were purchased from Alfa Aesar and p-type Si rods (6 mm in diameter and 6 cm in length, with a resistivity of 0.17 X cm) were obtained from Si Mat Company. For comparison with a typical metal, a set of magnesium rods were used as well (99.9% pure, 6.35 mm diameter and 8 cm length, Mateck GmbH). A Technix CCR-5-P-150, 0–5 kV, positive output, maximum 60 mA DC high voltage power supply is applied as a constant current source
Argon 5.0 was used as a carrier gas at flow rates between 1 and 1.6 standard liters /min. The voltage across the capacitor (VC) and the current through the plasma of the spark generator (ISG) were measured using a Tektronix P6015 high-frequency, high-voltage probe (3.0 pF capacitance) and a Pearson 110 current probe connected to a LeCroy 9354 500 MHz oscilloscope. This oscilloscope was connected to a computer in order to record the observed waveforms. The spark generator was run between 100 and 300 Hz (sparks per second).
Extensive measures were taken to prevent contact of the particles with oxygen and water. To prevent oxygen and/or water from diffusing through the walls or through rubber O-rings the entire setup was constructed from stainless steel components, using metal-on-metal seals and leak-tested using a helium leak detector. The argon 5.0 carrier gas is first passed through a molecular sieve bed (4Å) to remove any traces of water, behind which a copper-based catalyst (BASF R3-11 BTS catalyst) removes oxygen.