The Characterisation of Diesel Internal Injector Deposits by Focused Ion-Beam Scanning Electron Microscopy (FIB-SEM), Transmission Electron Microscopy (TEM), Atomic Force Microscopy and Raman Spectroscopy. 2015-01-1826

The effect of legislation in driving towards lower emissions has seen significant changes in injector design, (common- rail) and fuel composition (ULSD). This has led to numerous reports of deposits throughout the vehicle diesel system, filters, tanks, pumps and injectors. In recent examples, deposits internal to the fuel injector on the needle have become prevalent and characterisation of the deposits on the injector needle has become an industry priority. A number of studies have made progress on this but the deposits have proven difficult to fully characterise and often have an ineradicable nature, which makes analysis other than in situ difficult. This paper will describe for the first time the application of a number of surface techniques, in combination which not only provide characterisation data but also the ability to provide cross-sectional lifts out of the sample, which may then be the subject of further analysis. The techniques used were:

Focused Ion-Beam Scanning Electron Microscopy, (FIB-SEM): has allowed direct structural assessment on the microscale, precise manipulation by use of the ion beam to reveal deep structure, nanomachining and section parts of the deposit for further analysis.

Transmission Electron Microscopy (TEM): has allowed the deposit to structure to be assessed at the 10nm level to show ordering.

Atomic Force Microscopy (AFM): has allowed the micro and nano scale topography, morphology and material properties to be investigated.

Raman Spectroscopy: has allowed the mapping of carbonaceous order in the deposit.

The insights achieved in understanding of internal carbonaceous diesel injector deposits from the combined application of these techniques is described. Further, the potential such analyses may bring to improving our understanding of the buildup history, origin and relation to other diesel system deposits is also discussed.