Our optical microscopy Laboratory, includes a low power stereo microscope model, suitable for initial investigations and for rough or non-flat samples. Higher magnifications and improved resolution can be obtained from our compound microscopes (up to 1000 x magnification). Digital cameras are fitted as standard and image analysis and measurement software is available in the unit. Although requiring greater sample preparation than SEM, optical micrography has the extra dimension of colour to add further diagnostic capabilites. This traditional but powerful technique is an excellent complement to SEM and has particular uses in determining e.g. coating thicknesses, corrosion profiles and grain structure.
The scanning electron microscope (SEM) allows us to image samples at much higher magnifications (from 20 x to 50,000 x), with better resolution and greater depths of field compared with optical instruments. SEM combines high magnifications exceptional depth of field to allow detailed microstructural examination of most materials. Sample preparation is quick and simple and the images obtained can have immense diagnostic value. Fracture surface topography, 3-D particulate morphology and surface finish can be qualitatively assessed by visual inspection.
Allied to the conventional SEM, the associated technique of energy dispersive X-ray spectroscopy (EDS) enables the qualitative elemental composition of material to be determined. EDS spectra can be collected from a large area of the sample, or the electron beam can be focussed on to a particular feature and a spectrum obtained from cubic microns of material. This is particularly useful for determining the elemental composition of inclusions and foreign bodies, and for identifying contaminants. By scanning many such points, elemental ‘maps’ of a surface can be produced to identify where individual elements are concentrated within the sample. With careful use, the composition of the constituent microstructural parts of a sample, e.g. grains, domains or particles, can be determined.
The analytical facilities and staff expertise within the group are available for routine and non-routine characterisation and analysis of many different types of material. We have experience of providing analytical services for scientific and materials engineering research and product development, and for troubleshooting/quality problems for a wide range of industries and business sectors. Often a combination of analytical techniques is required during investigations.
- Surface finish – a component that looks and feels smooth will appear somewhat different at a few hundred/thousand times magnification, and the surface finish can dramatically alter a components performance. This may enable optimisation of the surface finish procedure, or help to understand the performance variation between two apparently identical components. It can also help when studying the affect of changes in tooling/supplier, or investigating the properties of a competitor’s product.
- Paints/Coating failures – modern systems are made of multilayers which may only be a few microns thick. When problems arise, for instance delamination, it is necessary to determine which layer(s) are involved and whether the problem is adhesive or cohesive, i.e. failure between layers or failure within a single layer. Analysing the cross-section by SEM with EDS can often quickly identify where the problem occurs.
- Foreign object/debris identification – analysis of the elemental fingerprint of unidentified swarf/debris/foreign particle can help with the identification of the origin of such material. Paint defects can be cross-sectioned, filter debris analysed, foreign particles in packaged material or a production line identified.
- Particle shape and size – from explosives to clays, the morphology and size of particles can be critical to the materials designed performance. The greater depth of field of the SEM will be of great help in this case with most, if not all the particle in focus.
- Failure analysis – analysis of the fracture surface of a component can help determine whether the failure occurred due to fatigue, or a one-off overload event, or even if a corrosive agent was present.