Advanced Metallographic Techniques Applied to Diesel Particulate Filters

Diesel Particulate Filters (DPFs) are designed to capture exhaust particulates from engines. The filter material collects the particulates deep in the substrate (deep-bed filtration) before transitioning to other filtration methods on the surface. The deep-bed filtration has been characterized by modeling studies but little experimental information about the particulate, or soot, penetration in the filter material is available. Traditional evaluation methods do not provide sufficient contrast between the soot and mounting resins.Due to the difficulty of locating carbon soot in the pores in these filters, ultra-thin section techniques (under 10-micron-thick sections) were used for the characterization of these samples. Under transmitted light, the carbon soot is black because it blocks the light, and the carbon in the resin material is relatively clear.

Ultrastructure and cleavage of chlamydospore chains of Thielaviopsis basicola

Electron microscopy revealed that numerous spherical or ellipsoidal globules of reserve nutrient material fill the chlamydospore cells, with cytoplasm as a thin film between these globules. The basal cell of the chain is not a chlamydospore; it is filled with cytoplasm and does not contain these globules. Its plasma membrane, nucleus, mitochondria, lomasomes, and endoplasmic reticulum are evident in ultra-thin section. The walls of chlamydospore cells are thick and without distinct layers, except for an electron-dense outer region and a more electron-transparent inner region. Chlamydospore cells in the chain are separated by a very thin electron-transparent binding layer. A thin two-layered envelope surrounds the entire chain. When chlamydospore chains are treated with chitinase, this envelope remains attached around single separated cells, rather than dissolving away. Cytoplasm of cells in the chain is continuous through septal pores. The end walls of the cells become the opercula after the cells are freed from the chain. The germ tube always emerges at the side where the operculum opens, never through the septal pore.