De Montfort Medal recognises early-career research scientists

Materials World magazine
1 May 2007

Britain’s Top Early-Career Research Scientists, Engineers and Technologists received recognition in March at a poster competition held at the House of Commons in London. Over 200 entries were presented throughout the morning and evening sessions, of which 14 achieved awards.

Yi Zhang, a PhD student from the Materials Science and Metallurgy department at the University of Cambridge, UK, won the top prize, £1,000 and the 2007 De Montfort Medal. Zhang, along with his supervisor, Professor Lindsay Greer, has devised a simple yet effective method for enhancing the plasticity of metallic glasses.

Metallic glass exhibits excellent mechanical properties such as high yield stress and strain, corrosion resistance and fracture toughness, which shows promise for industrial application. However, it can also be brittle. Under ambient conditions, plastic deformation of bulk metallic glasses is localised into thin shear bands with characteristic thickness of over 10nm. This restricts the tensile ductility of the material.

Using a simple shot-peening technique, commonly used in the metallurgical industry to increase fatigue resistance, Zhang and Greer improved plasticity by up to four times. ‘Glass is very brittle, and [manufacturers] have successfully solved this problem by introducing compressive strength. So we thought, why not try it on metallic glass?’ explains Zhang.

‘One of the best ways to come up with an idea is to think outside the box and try [an older technique] in a new way.’

Winning the De Montfort Medal was an exciting achievement for Zhang. ‘The work we have done is original. A lot of [researchers] have attempted to solve this problem before. Comments from professors were that we were original and creative, so I thought we could win, but I had no idea how serious the competition would be. So it was hard to say.’

Zhang, who is originally from China, has been studying at Cambridge since 2004 and will complete his PhD this year. He has applied for a fellowship at Trinity College in Cambridge and hopes to continue working with metallic glasses, improving on the shot-peening process. ‘This is not the end of the research but just the start of it,’ says Zhang.

Another Cambridge materials science and metallurgy PhD student, Carol Johnston, was equally impressed with the calibre of researchers who entered the poster contest. Johnston, who won a commendation prize for her work with gallium nitride (GaN) based light emitting diodes (LEDs), found the event provided a good opportunity to meet and interact with young researchers studying varying scientific areas.

‘I met one guy who was doing research on biomineralisation. Some of the processes in his poster which are used in muscle cells are actually similar to [those] we use to grow gallium nitride crystals. Just to know that these processes aren’t specific to what we do is interesting,’ she says.

Working as part of a group within Cambridge’s Centre for Gallium Nitride, under the supervision of Professor Colin Humphreys, Johnston has been using transmission electron microscopy to study the microstructure of quantum wells grown on polar and semi-polar GaN for LEDs (pictured right). Semi-polar GaN is a promising material for reducing the internal quantum inefficencies of traditional polar GaN LEDs.

‘My PhD is about characterising [GaN] crystals using electron microscopy and X-ray diffraction to see what the crystallography is actually like and how defective [the crystals] are,’ she explains.

Light emitting diodes appeal to Johnston, who also has a MSci in Physical Natural Sciences from Cambridge, because of the environmental benefits. ‘We need to save the planet and be greener, and LEDs are really an easy way to do it,’ she says. They use a fifth of the power of regular 60W incandescent lamps.

‘Things like traffic lights are starting [to use] LEDs, so it’s already happening. But we’re going to make them a lot better.’