Materials Analysis
Identification and Characterisation
We have a wide range of microscopic techniques available which provide imaging,
elemental analysis and spatial resolution of molecular information. These include:
optical, SEM with EDX and
TEM and microscopic Raman.
Spectroscopic analysis
We can identify the chemical nature of a material using FT-IR
or Raman spectroscopy in the laboratory. We can also apply our own portable instruments
on site if required. These techniques measure the molecular vibrations of the samples
either in the laboratory or through fibre optics in-situ. The analysis can be used
to calculate concentration, not only for the sample but of individual molecular
components. We can also monitor reactions and determine parameters such as degree
of cure and reaction kinetics.
The image shows the Raman spectra generated during an in-situ measurement of the
polymerisation of styrene. The C=C band at 3010cm-1 due to the vinyl
group in the styrene decreases as the band at 2900cm-1 due to the CH
stretch in polystyrene increases. From this analysis we were able to determine the
degree of polymerisation as a function of temperature and time.
Microscopic analysis
We can examine the morphology of materials using optical or electron microscopy
(using electrons rather than light to produce a high resolution image. SEM
works by detecting backscattered and secondary electrons emitted from the sample
after contact with the electron beam. X-rays are also emitted so by using an EDX detector, composition information is produced.
We use SEM for surface analysis. For Bulk analysis we use TEM , this works on a similar principal to the SEM but uses
different detectors and has a higher magnification capability.
The image is a TEM image of a carbon replica of permanganically etched XLPE
. The individual lamellae are clearly visible. TEM analysis was used to identify
voids in XLPE power cable. This was combined with spectroscopic analysis of the
cable which showed rate of migration of additives from the semiconducting cable
layer into the XLPE and the degradation of peroxide additives in the XLPE itself.
This allowed us to predict the lifetime of the cable in service.
The SEM Image is of worn flame retarded fabric and the accompanying EDX image is
of a particle found in the fabric. The SEM shows the fibre structure while the EDX
shows elements such as bromine and antimony in the particle. Analysis of flame retarded
fabrics allowed us to assess the health risks of using flame retardants in home
furnishings.
Properties and Performance
Thermal methods such as DSC
, TGA ,
DMA
and Dielectric Spectroscopy are used to determine properties such as glass transition
temperature (Tg), melting, curing and degradation behaviour; this is combined with
mechanical, electrical and dielectric property measurements, as a function of temperature
and frequency, to determine physical properties. We also have special experiment
rigs for thermal conductivity, wear rate and dynamic friction measurements.