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With stricter emissions standards, low back pressure requirements, and 100,000 mile durability specifications, ceramic catalysts have undergone significant developments over the past few years. The thrust in the ceramics area has centered on thin-wall structures to minimize back pressure and on high cell density for rapid light-off in close-coupled applications. The thin-wall structures are extruded from low expansion cordierite ceramic with adequate strength and thermal shock resistance equivalent to those of standard cordierite substrate. Examples of thin-wall substrate include 350XT which is extruded from a very low expansion dense cordierite ceramic, and 400/4 and 600/4 cell structures extruded from a low expansion modified cordierite ceramic. This paper will focus on the high fatigue resistance, excellent conversion efficiency, and low back pressure of 350 XT substrates with advanced washcoat system.

This paper employs a systematic approach to packaging design and testing of a system and its components in order to determine the long term durability of light duty diesel filters. This effort has utilized a relatively new aluminum titanate filter technology as well as an advanced support mat technology engineered to provide superior holding force at lower temperatures while maintaining its high temperature performance. Together, these two new technologies form a system that addresses the unique operating conditions of diesel engines. Key physical properties of both the filter and the mat are demonstrated through laboratory testing. The system behavior is characterized by various laboratory techniques and validation procedures.

The preconverter is an essential element of exhaust gas treatment to help meet the tighter emission standards of TLEV and LEV levels. Its design must be chosen so as to meet the simultaneous requirements of compactness, faster light-off, low back pressure, high temperature durability and low cost. This paper presents design options for a ceramic substrate and durable package which lead to an optimum and cost-effective preconverter system. Preliminary data for high temperature physical durability of selected converter systems are presented. Performance parameters for light-off activity and back pressure are also computed and compared with those of standard substrates used in underbody application. Laboratory tests comprising of axial push-out test, high temperature vibration test, exhaust gas simulation test and the engine dynamometer test demonstrate the viability of ceramic preconverters for automotive application.

New test methods were developed to characterize the high temperature durability of intumescent mats that are used to mount ceramic catalyst supports in stainless steel cans. The key attribute of these tests is the use of an electric resistance heating method to maintain a temperature gradient through the thickness of the mat when a cyclic or constant shear stress is applied to the mat interface. These tests are simple to perform and do not require expensive equipment or highly skilled operators. Using these new test methods, the durability of ceramic preconverters mounted with 4070 gm/m2 intumescent mat was studied. The results of these tests indicate that a preconverter package with 4070 gm/m2 intumescent mat can perform satisfactorily in the close-coupled application where temperatures exceed 900°C. The mat performance can be quantified in terms of applied stress and test temperature by utilizing the experimental methods described in the present study.

The use of a Calrod type electrical faceheater, powered by two 12V heavy duty batteries in series, as a regeneration initiator for a 12 in (30.5 cm) diameter × 12 in (30.5 cm) long segmented honeycomb ceramic filter is described. Recent test data, obtained on Deutz mining engines during the regeneration process, is presented. The effects of various regeneration parameters on the reliability and long-term durability of the filter is discussed together with the effect of fuel additives. The test data include both the measured temperature profiles and calculated thermal stresses in the filter with and without fuel additives.

The oven shock test is an accelerated test which is often used to quantify the thermal durability of both coated and uncoated ceramic substrates. The test calls for heating the substrate for 30 minutes in an oven, which is preheated to specified temperature, and then cooling it in ambient environment for 30 minutes. Such a cycle induces axial and tangential stresses, during cooling, in the skin region whose magnitude depends on physical properties, oven temperature, radial temperature gradient and the aspect ratio of substrate. In addition, these stresses vary with time; their maximum values occur as soon as the substrate is taken out of the oven. This paper evaluates the severity of thermal stresses as function of above factors and estimates the probability and mode of failure during cooling using thermocouple data. Methods to reduce these stresses are discussed.