Hydration of lubricant-derived ash in the wall-flow particle filter
Carl Kamp, MIT
Recent investigations of field-returned particle filters (DPF, GPF) have found that lubricant-derived ash can exist in both hydrous and anhydrous analogs due to the local environmental and thermal histories. Observed hydrated ash species undergo significant and often irreversible structural changes which affect the operational functionality of the wall-flow particle filter. This study has utilized a range of analytical tools to investigate the ash hydration mechanisms including focused ion beam milling (FIB), in-situ X-ray diffraction (XRD), Scanning electron microscopy (SEM) and Thermogravimetric analysis (TGA). Details of hydrated ash from field-returned samples are presented in this study whereby the interactions between ash and the catalyst/substrate become more critical from a perspective of the filter durability. It was also found that the typical ash species (sulfates and phosphates of Ca, Mg, Zn) vary in the amount of hydration and stability based on their chemistry. The findings in this work have far reaching implications especially in applications with higher exhaust or ambient humidity levels.