Dr Richard Holliday from the World Gold Council explains how industries are benefitting from new applications of the planet’s most coveted material.
Gold. Coveted by the pirates of the high seas, worshipped by the ancients, and hoarded by banks for its enduring value; its tale is inextricably linked with the story of mankind’s quest for wealth.
While much of this is down to the metal’s rare beauty, there’s a lot more to gold than its appealing lustre. Indeed, the sheen and malleability that so appealed to ancient jewellery makers also make it an engineering material without compare. Today, around 450 of the 3,000 tonnes mined annually finds its way into engineering applications everywhere from the process industry to the healthcare sector.
Despite its high price and the fast-paced advances elsewhere in the world of materials, gold’s use is on the rise. Indeed, according to Dr Richard Holliday, head of industrial applications for the World Gold Council (WGC), largely thanks to the opportunities created by nanotechnology, we could be on the brink of a new golden age.
Funded by the big gold mining companies — Barrick Gold Corporation, Anglogold Ashanti, Goldfields and Newmont — the role of the WGC is to explore and develop new markets for the shiny stuff, and Holliday, whose brief is to scour the industrial world for applications crying out for gold, claims that this range of applications is spiralling. ‘The perception is still that it’s a jewellery and investment product…but we believe the industrial side is a growth area and is really starting to develop,’ he said.
Joining WGC from Land Rover, where he worked on lightweight vehicle structures, and before that working as a materials engineer at Corus, Holliday has a keen eye for the engineering application of materials. Nevertheless, developing new markets across such a range of disciplines is a stiff challenge. His brief to keep an eye on gold-related research wherever it may occur has, he said, made him a ‘jack of all trades and master of none’.
The main growth area for gold is its oldest industrial customer, the electronics sector, which takes about 300 tonnes a year (around $8bn (£5bn) worth at today’s prices). Much of this is sold to the printed circuit board and chip industry, which uses the gold for plating on contacts and connectors and in the gold bonding wires used in semiconductor chips.
Although there are cheaper alternatives, Holliday claimed that gold’s all-round performance gives it the edge over less exotic materials such as copper. ‘It’s got good conductivity — not as good as silver and copper, but it’s got much better corrosion resistance. Also in terms of the wire used in semiconductors, gold is a very soft and malleable material so it can be drawn into these very fine wires down at 20 micron level — it’s got that combination of properties that demands its use.’
New technologies are likely to make it more appealing, he said. For instance, Canadian firm Microbonds recently unveiled X-Wire, an insulated wire bonding technology that means chip designers no longer have to worry about wires touching or crossing.
Developed with the aid of the gold industry, the technology could be a key weapon in the ongoing struggle to reduce chip size.
Away from the electronics sector, Holliday is increasingly excited about the use of gold as a catalyst. Although the metal has been used in this capacity in the paint industry for a number of years, the recent emergence of processing techniques that enable the production of gold nanoparticles endow the material with a whole new set of properties.
Its potential in this area, he said, flies in the face of everything we are taught about the metal when we are young. ‘If you do chemistry at school you are told it is inert and you can’t do anything with it, but the ability to control things on [the nanoscale] almost creates a new material.’
For instance, one area that is of growing interest is the use of gold catalysts in coal-fired power plants to reduce mercury emissions.
‘There’s a lot of work in the power industry looking at capturing the mercury and they’ve found that precious-metal catalysis is an effective way of oxidising the mercury, and the best catalyst for the job is gold.’ This technology is being trialled at a power station in San Antonio, Texas, and Holliday’s group is supporting a research project at Rice University in Houston that is attempting to understand the process in greater detail.
Away from the world of industrial processes, gold is also poised to make big strides in the auto industry, where it shows promise in the next generation of catalytic converters. Of particular interest is the activity of Silicon Valley start-up firm, Nanostellar, which in 2007 announced the first diesel-engine catalyst containing gold alongside the more commonly used platinum group metals.
Current technology uses platinum and palladium to control emissions, and as platinum is one of the few metals more expensive than gold, the industry could actually find itself in the unusual position of being able to offer a cheaper alternative. ‘The rationale for the auto industry is that gold is a cost-saving opportunity. It’s not very often you can say that, but you can basically use less platinum, which is more expensive than gold,’ said Holliday. The WGC has invested heavily in Nanostellar and, according to Holliday, advanced discussions with a number of European manufacturers could soon lead the commercialisation of the technology.
Elsewhere in the car industry, gold also has potential in the development of hydrogen fuel cells, where it can be mixed with palladium and used to remove carbon monoxide (CO). ‘You need to remove CO because it poisons the fuel cell and a way to do that is to use palladium membrane,’ said Holliday. ‘Research has shown that if you add gold to the palladium the membrane is a lot more durable.’ The council is supporting further development of this technology at the Colorado School of Mines in the US.
The emergence of nanotechnology is also leading to the use of gold in an ever-expanding range of medical applications, particularly within diagnostic devices. ‘When you put gold in the form of nanoparticles it has completely different properties: for a start it’s not gold-coloured but blue or purple or red and can be used, for example, as a visual indicator in medical devices.’ An example is its use in pregnancy testing kits; where the appearance of the indicator line is due to the agglomeration of gold nanoparticles when the hormone indicating pregnancy is detected.
Even more intriguingly, gold could be set to play a major role in the emerging area of nanomedicine.
Of particular promise is technology developed by US healthcare firm Cytimmune Sciences. The company’s Aurimune drug, which is undergoing human clinical trials, consists of a gold nanoparticle coated with a potent anticancer agent called tumour necrosis factor. Injected directly into the body, these drugs kill too much of the healthy tissue. Cytimmune’s treatment targets the tumour directly by attaching the drug to gold nanoparticles, which are too small to pass through healthy blood vessels but are able to pass through the leaky vessels that feed the tumour.
Holliday admitted that with such a range of applications emerging all the time, it’s difficult to predict where gold might end up next, but his team at the WGC appears to have all bases covered. ‘We’re funding research in India, China, the US, Europe and the UK, we generally know what’s going on and over the next five years you’re going to see a whole new range of applications of gold in advanced technologies.’