UL team get to the heart of glass and ceramics

Team leader was first Irishman to receive prestigious award from the European Ceramics Society, writes Anna Nolan

Team leader was first Irishman to receive prestigious award from the European Ceramics Society, writes Anna Nolan

Glass is anything but transparent when it comes to research conducted by Stuart Hampshire and his team at the University of Limerick. He creates new materials with novel characteristics using most exotic forms of glass.

It's all down to using nitrogen atoms in place of some oxygen atoms in glass, which leads to improved mechanical properties, he explains.

"My current research is largely based on oxynitride glasses, which are special types of silicate or alumino-silicate glasses in which nitrogen replaces some of the oxygen atoms in the glass structure," says Prof Hampshire, who holds the chair of Materials Science in the Department of Materials Science and Technology. He is also a founding member of the Materials and Surface Science Institute (MSSI) at UL.

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"The effect of this is to increase cross-linking within the glass structure, which gives higher mechanical properties such as stiffness, hardness and toughness and also increases the fluid flow resistance of the glass melts."

These improvements in the mechanical properties of oxynitrides, as compared with oxide glasses, are attributed to an increase in the number of cross-links between certain atoms in the structure. This is because the change induced in the basic structure allows three silicon ions to make links to the nitrogen instead of just two links in the oxide glasses.

"The improvements in properties with nitrogen are quite substantial," he told Science Today.

"Hardness and stiffness increase by 20-25 per cent with the replacement of one in five oxygen atoms by nitrogen atoms. Modern technologies are currently searching for stiffer, lighter materials for various applications," he explained. "For example, stiffer lighter materials would allow hard disk drives to operate at faster speeds, and transparent, stiffer lighter materials would allow their use as thinner windows in transport but with the same mechanical characteristics, thus resulting in potential weight and energy savings."

He and his team have recently begun working on related systems involving the addition of fluorine as well as nitrogen to silicate glasses. "We are assessing their potential as biomedical materials or in fibre-optic applications," Hampshire says.

The group has also been studying crystallisation of oxynitride glasses at certain temperatures to form glass-ceramics containing nano-crystals.

Although oxynitrides are his core research area, he is also interested in ceramic nanocomposites for biomedical applications.

"Hydroxyapatite (HA) is employed for repairing skeletal defects, because it resembles bone and is bioactive," he says. "However, its poor strength has limited its load-bearing applications and so we are using new ceramic nanocomposite processing techniques to improve the properties of HA."

He has received several awards for his work, and has now become the first Irish researcher to receive the prestigious Stuijts Award of the European Ceramic Society. He gave the Stuijts lecture on his work at the society's recent 2007 conference and exhibition in Berlin.

This award is made every second year to a European scientist who has made a major contribution to the science and technology of ceramics and glasses. It is named in honour of Prof A Leo Stuijts (1922-1982), who contributed considerably to the development of the science and technology of magneto-ceramic and electro-ceramic materials.