Neutron Imaging: A Non-Destructive Testing Method to Investigate Canned Exhaust After-Treatment System Components for the Three Dimensional Soot, Ash, Urea and Coating Distributions

摘要

Neutron imaging (NI) is an alternative non-destructive inspection technique compared to the well-known X-ray method. Although neutron imaging data look at a first glance similar to X-ray images it must be underlined that the interaction mechanism of the sample material with neutrons differs fundamentally. X-ray interaction with matter occurs with the electrons in the atomic shells whereas neutrons interact only with the atomic nuclei. Hence, both methods have a different and to great extent complementary contrast origin. Neutron imaging allows for a higher penetration through heavier elements (e.g. metals) whereas a high contrast is given for light elements (e.g. hydrogen). By the use of neutrons instead of X-rays exhaust after-treatment systems can be successfully examined non-destructively for their soot, ash, urea and coating distributions. The big advantage of neutron imaging is that detailed, high-contrast images can be obtained even in canned substrates (silicon carbide or cordierite). Neutron imaging can be applied to substrates of passenger cars, trucks and even heavy duty vehicles. We can offer a maximum field of view up to 400mm × 400mm and a spatial resolution down to 13,5 μm/pixel. The paper briefly outlines the method of neutron imaging and its advantage and complementary character compared to the conventional X-ray method. We present neutron tomography results of diesel particulate filter (DPF) and gasoline particulate filters (GPF) concerning: (i) Soot, ash, metallic particle and coating distributions in a canned passenger car DPF. (ii) Urea distributions in passenger car DPF. (iii) Ash distribution in a canned passenger car GPF. (iv) Ash residuals of a truck DPF after cleaning with different techniques.