Evaluating the microstructure of a material is fundamental to material science
As more information is inferred from images it is increasingly important that the magnification and scaling used is accurate and traceable, and that the features observed are from the material, and not an artefact or response to the way it has been prepared.
3D electron microscopy
We are improving the 3D characterisation of microstructure through serial sectioning using both focused ion beam milling in Scanning Electron Microscopes and broad Argon ion beam milling by:
- Comparing the two techniques and developing good practice for sample preparation and instrument operating guidance
- Reduction of distortion in the tomographic reconstruction of the microstructure due to drift and quantifying the errors in slice thickness using ruler artefacts
- Quantifying the damage to the structure though ion implantation from the milling process
- Improved procedures and understanding in uncertainties in reconstruction of data sets, by conducting a critical intercomparison of commercial software for image manipulation and analysis (also applicable to x-ray computed tomography methods)
Direct electron detection
Improving the sensors within the SEM will have many benefits, such as lower noise, faster analysis times and lower energy signal analysis. Collaborative research on direct electron detectors aims to simplify methods and improve accuracy for 3D EBSD.
Material characterisation and micromechanical testing
We are developing methods to meet the challenges presented by the complex microstructures occurring as part of the Additive Manufacturing process for metallic parts. These include powder analysis to quantify powder size, chemistry and structure as a function of recycling and product properties; defect identification and linking structure to final product performance. This work includes the development of test systems that fit within the microscope so that deformation or damage to the microstructure can be observed during the test.
Environmental SEM and biomedical imaging
An Environmental SEM (ESEM) broadens the types of materials we study. The ESEM is run for a major healthcare company on a regular basis, but for the majority of the time it is being used to study hydrated biological materials and medicines, for example tablet structure and drug polymorphs. Micro mechanical testing of drug powder particles aims to improve the manufacture of drug delivery systems.
Find out more about NPL's Microstructural characterisation services