Professor Allan Matthews, Professor of Surface Engineering and Tribology at The University of Manchester and the Director of the BP International Centre for Advanced Materials, delivered the fourth ICAM webinar of 2017 on the topic of developing and selecting tribological coatings.
For many years, it was widely believed that the best way to reduce the wear of a surface was to make it harder. Here, Professor Allan Matthews outlines the reasons why it is in fact the ratio of the hardness to elastic modulus which gives us the best indicator of wear resistance, especially for coatings. The implications for the development of improved wear-resistant surfaces are outlined and examples of coatings which achieve this ratio were also discussed, including nanocomposite and nanolayered coatings. Mention was also given to so-called ‘duplex’ coating systems, which combine surface treatments with coatings to gain maximum tribological benefits.
“This talk will cover new approaches to sensing and analysis using optical approaches namely Raman analyse, optical coherence tomography and light sheet imaging. Examples will include whisky analysis, label free drug detection, blood analysis and applications for biomedical science.”
“Nanostructured thin films of titanium dioxide, tungsten trioxide and vanadium dioxide have been deposited using a novel electric field assisted chemical vapor deposition methodology onto glass and gas sensor substrates. Electric fields were generated during the deposition reaction by applying a potential difference across the inter-digitated electrodes of the gas sensor substrate or by applying an electric field between two transparent conducting oxide coated glass substrates. The deposited films were analyzed and characterized using scanning electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy and X-ray diffraction. It was found that applying an electric field led to large changes in film microstructure, preferential orientation and an increase in the film growth rate.
This led to improved materials properties such as increased photo-catalytic activity, enhanced wetting behavior, reduction in thermochromic transition temperature and improved supercapacitor electrode behaviour. The gas sensor properties of the films were also tested and it was found that by tuning the microstructure of the films a two to three fold enhancement in sensor response could be obtained compared to sensors deposited in the absence of an electric field. Electric field assisted chemical vapor deposition shows great promise as a method for nano-structuring and tailoring the properties of metal oxide thin films.”
“There are aspects of hydrogen in steels that are crystal clear. For example, that hydrogen in solid solution embrittles, does not require further work. The mechanism by which it embrittles is far from clear, and there is no generic theory capable of rationalising the vast quantities of data available in the published literature. When combined with the fact that practical alloys have complex mixtures of phases and defects, the confusion can be said to be complete.
However, all is not lost because measures can in principle be taken to limit the potency of hydrogen. I will begin with an introductory review of the subject, mention specific examples where significant performance enhancements have been observed, and deal with the theory and new experimental data on the passage of hydrogen through complicated mixtures of phases.”