Christian Trassy

The role of radiation in modelling of argon inductively coupled plasmas at atmospheric pressure

Modelling of inductively coupled plasmas at atmospheric pressure has been developed for years, integrating fluid dynamics, electromagnetism and heat transfer. In this work, special attention has been devoted to radiation transfer. Two radiation models have been implemented: the net emission coefficient and the P1 model. These models have been run with different torch geometries and input powers. The parametric study shows that they are very sensitive to parameters such as the thermal and electrical conductivity of the gas and input power. The temperature distributions have been compared with the measurements available in the literature. The spectral P1 model is more accurate at the expense of the computing time. The radiative heat losses are below 5% in small torches such as those used in spectrochemical analysis, but can exceed 40% in large torches (40 mm diameter or more), becoming the main cooling mechanism.

On-line heavy metal analysis in the fumes from a laboratory fluid-bed incinerator

An inductively coupled plasma spectrometer was used with a laboratory fluidized-bed reactor and adapted to continuously measure the heavy metal concentrations in exhaust gases. The system is devoted to the thermal treatment of metal-spiked model wastes; on-line analyses were performed to study heavy metal release. This method was used to study the kinetics of heavy metal vaporization from pure mineral and pure organic matrices to determine the roles of temperature, residence time, gas and matrix composition, and initial metal speciation. Then, a more complex metal-spiked matrix, derived from real waste, was burned to simulate metal release during municipal solid-waste incineration. Three metals were considered: Cd, Pb, and Zn. In all cases, the experimental setup was successfully used to monitor the metal evaporation process during fluidized-bed incineration.

N type multicrystalline silicon wafers from an upgraded metallurgical route

N-type silicon wafers present some definite advantages for photovoltaics, mainly due to the low capture cross sections of minority carriers for most metallic impurities. This peculiarity is beneficial for multicrystalline silicon (mc-Si) wafers. Most importantly, this peculiarity could be of a great interest when mc-Si ingots are produced directly from upgraded and purified metallurgical silicon feedstock. It is of a paramount importance to verify if the advantages of conventional n-type silicon also characterises n-type wafers provided by the direct metallurgical route. It is found, in raw wafers, that minority carrier diffusion lengths are 3 times higher in n-type than in p-type wafers, when the wafers are cut from the same ingot, which the bottom is p- type and the top is n-type. The results confirm the interest for n type silicon.