National Centre for Nano-structured Materials
The CSIR-hosted National Centre for Nanostructured Materials (NCNSM) focuses on the modelling, synthesis, characterisation and fabrication of new and novel nano-structured materials with specific properties.
Research and development at this centre supports the manufacturing of bulk materials with improved properties, such as plastics that can tolerate very high and low temperatures and plastics that possess fire retardant properties or that have high resistance to tearing. It also includes the development of detection devices that use nanomaterials capable of detecting with greater sensitivity and accuracy, gases at parts-per-million levels. This can save lives in mining or industrial environments, and be used to detect certain disease indicators in patients.
The facility houses a wide range of imaging instruments (high-resolution transmission and scanning electron, scanning probe, visible light, Raman and Fourier Transform Infra-Red microscopes). Imaging is used to characterise the structure of materials at atomic and molecular levels, so that scientists can understand how changes in structure translates into improved properties.
The facility also has state-of-the-art equipment to obtain ultra-thin sections required for transmission electron microscopy from hard materials (focused ion beam milling) or soft polymers (cryo-ultramicrotomy). A significant part of this equipment was funded by the DST.
The centre is a hub of world-class analytical and imaging instrumentation that is unique, in that it has unrivalled expertise and a rare spread of analytical and imaging instrumentation, all under one roof. The characterisation facility is rapidly becoming a leading centre in the imaging of polymers, which are notoriously difficult materials to study at the nano-scale level because they demand delicate sample preparation routines. At this level, they also rapidly degrade under the beam inside electron microscopes.
Wide empowerment of materials researchers
The nano facility is also available for use by researchers from universities and industry to further their research. Researchers at the CSIR oversee post-graduate and post-doctoral fellows from South African universities. Access to all equipment is charged on a running cost-recovery basis. The ethos of the facility is to teach students and staff to operate instruments at the highest level and in doing so, empower them to progress in their research careers.
The scaling-up of the manufacture of polymer nano-composites entails progressing from a modest laboratory bench-scale project that produces a few grams of the improved material, to an industrial one with the potential of producing 100 kg or more that can be tested in industrial applications. This amounts to a ‘proof of concept’ or ‘acid test’ regarding the usefulness of the new product. Improvements to the bulk properties of materials will impact various industries such as automotive, paint, cosmetics and pharmaceuticals.
Adding expertise and capabilities
The centre has appointed additional staff to cope with the growing demands for analysis. The addition of a scanning attachment system to the high resolution transmission electron microscope increases its ability to visualise the interaction between nano-clays and the surrounding polymer matrix, as well as establish the 3D dispersion of the nano-additives that underlies the success or failure of these new materials. The use of clays in nano-composites increases desirable properties, such as tensile strength, modulus and fire-retardancy. Optimum results are achieved when the clay particles become exfoliated and highly dispersed in the polymer matrix during processing.
Establishing the degree of dispersion without distorting the structure of the nano composite is challenging, but three approaches used at the centre make this possible. The focussed ion beam scanning electron microscope enables accurate milling (etching) of nanometre-thin layers of material at a time. Successive capture and stacking of images acquired after each milling step allows 3D visualisation of the distribution of clays in the material. Alternatively, the relatively soft nano-composites can be hardened by cooling to -120 °C and 70-100 nm thin sections cut at that temperature using a cryo-microtome for subsequent observation using the transmission electron microscope. Soon, the centre will also be able to perform tomography of these thin sections using high-resolution transmission electron microscopy, which will provide even higher 3D information on the interface between clays and polymers than previously achieved.