Degradationresistance of silicon carbide diesel particulate filters to diesel fuel ash deposits
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M.J. Pomeroy Materials and Surface Science Institute, University of Limerick, Limerick, Ireland
S. Hampshire Materials Ireland Research Centre, University of Limerick, Limerick, Ireland, and Materials and Surface Science Institute, University of Limerick, Limerick, Ireland
M.J. Murtagh Corning Incorporated, Corning, New York 14831 (Received 7 January 2004; accepted 2 June 2004)
A series of experiments were conducted to investigate chemical interactions between silicon carbide (SiC) and synthetic ash compositions expected to be deposited on the surfaces and within the pore structure of a diesel particulate filter. The chosen ash compositions simulated those arising from lubricants and three fuel types: standard diesel, diesel containing ferrocene as a catalytic additive, and diesel containing a cerium-based catalyst. Results demonstrated that SiC suffered little chemical or oxidative degradation in the presence of the ashes at 900 °C. For the ash not containing Fe or Ce, ash sintering effects were a possible mechanism causing filter blockage at temperatures above 970 °C. For ashes containing Fe or Ce, appreciable sintering effects were not observed below 1100 °C. Based upon the work conducted the suitability of SiC as a construction material for diesel particulate filters is not compromised by chemical degradation in the presence of lubricant/additive derived ash at temperatures less than 1100 °C.
I. INTRODUCTION
Ceramic-based diesel particulate filters, used in mobile diesel engine exhaust abatement, have been commercially available for nearly two decades.1,2 The principal function of the filter is to capture solid carbon particles with high efficiency (up to 99%). The solid carbon is intimately mixed with combustion hydrocarbons and other soluble organic fractions as well as contaminants such as calcium, zinc and phosphorous from the engine lubricating oil. Iron is also introduced from engine abrasion. Such composite carbon soot particles are known as particulate matter. Wall-flow diesel particulate filters are ceramic honeycomb structures that have a checker board pattern of open and closed cells at the entry face and at the exit face. Open cells at the entry face are blocked at the exit face and the blocking of alternate cells forces the exhaust gas to flow through the porous walls trapping the particulate matter in the pores and on the surfaces of the open channels. Essential properties of candidate materials for DOI: 10.1557/JMR.2004.0373 J. Mater. Res., Vol. 19, No. 10, Oct 2004
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use in diesel particulate filters are low coefficient of thermal expansion, high thermal shock resistance, and thermal stability. With time, the diesel particulate filter will become overloaded with particulate matter on and in the wall of the filter. To avoid an unacceptable back pressure in the engine, particulate matter is regenerated via in-situ incineration. Although the incineration temperature is nominally 550–650 °C, particulate matter burn-off can be reduced by as mu
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