A particulate filter (diesel particulate filter, DPF, or gasoline particulate filter, GPF; filter à particules, FAP) is a component of the exhaust system that is installed after the catalytic converter and works closely with it. It has been compulsory for diesel cars since 2006 (in response to the introduction of EURO IV standards). For petrol cars, the GPF was made compulsory in 2014, when the next stricter emission rules came into force (EURO VI).
The image shows the structure of the dpf filter insert: plugged inlet channels, engine exhaust gas inlet, filter base, porous baffles, plugged outlet channels, exhaust gas outlet.
It is composed of a stainless steel box, inside of which there is a ceramic cartridge, composed of inlet and outlet ducts (alternately plugged) forming a dense net. The walls of the channels are made of silicon carbide, oxides of aluminium, cerium and platinum, their surface is porous, thanks to which particles produced by the engine are deposited on it. Increasingly, filters in which the channels have been made of metal sinter are being used.
In the picture above we can see under the microscope: