Super small, super strong
By : Michael Gibb
Really, really small, but very, very strong: this sums up the very specific advanced material that scientists at CityU have created.
What they have produced is the first-ever supra-nano magnesium alloy, according to the principle investigator, Professor Lu Jian, Vice- President (Research and Technology) and Chair Professor of Mechanical Engineering at CityU.
The innovation has just been published in top academic journal Nature, and has been featured as the cover page for the May 4 issue, 2017. It is the 21st century’s first-ever Nature cover page for China in the research area of physical science (structural material or mechanical science).
“This is really a major breakthrough,” explained Professor Lu. “The alloy is 10 times stronger than what we refer to as a more conventional crystalline magnesium alloy, and it has superdeformation capacity two times higher than that of magnesium-based metallic glass.” This means that the material is very strong but also capable of dealing with deformations in materials.
What are the benefits? One of the stresses on the human body is too many major rounds of general surgery if you get sick. Senior citizens are not always well enough for too many prolonged sessions under general anesthetic. However, the new alloy can be developed into biodegradable material that can be implanted in the human body.
“The new alloy can be developed into biodegradable material that can be implanted in the human body.”So a patient would not have to undergo an operation to retrieve a medical device placed in the body during a previous operation: the implant would biodegrade after it had performed its task, vastly reducing time in hospital, cutting costs, making illness more bearable, and perhaps even saving lives.
“The material could be used as a coating for artificial joints for knees and hips, too. It has excellent wear and corrosion resistance, and may also reduce the risk of allergic reactions to metallic joints,” Professor Lu said.
The electronics industry might well be interested, too. Making devices such as smart phones, tablets and laptops lighter is very attractive. We know that devices have to weigh something, but the lighter the better seems to be the popular mantra.
Professor Lu JianUnder Professor Lu’s guidance, Dr Wu Ge, Postdoctoral Fellow; Dr Chan Ka-cheung, Assistant Scientific Officer; Dr Zhu Linli, Research Fellow and Associate Professor at Zhejiang University; and Dr Sun Ligang, Senior Research Associate, are dedicated to fabricating the supra-nano-dual-phase glass-crystal alloy and studying its deformation mechanism.
The supra-nano-dual-phase glass-crystal alloy film structure is one of the outcomes of this research programme. Supra-nano means that the size of each phase is less than 10 nanometres (nm), and glass is in the general amorphous phase. In fact, the basic element of this newly developed material is composed by the nanocrystalline grain (6 nm) enclosed in an amorphous glassy shell (2 nm). It represents a new family of alloy structure: suprananostructure – a world first.
The new alloy was produced using a special magnetron-sputtering technology, Professor Lu added, and its strength was enhanced by modifying the volume proportion of the crystalline phase and amorphous phase in the material. The breakthrough paves the way for developing other supra-nano-structured materials with special physical and chemical properties.
“We hope that our new material will promote really positive developments in technology for society,” said Professor Lu.