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News: October 2006Environment & Sustainability
Industry & Innovation
Materials & Minerals Processing
ENVIRONMENT & SUSTAINABILITY
No more heavy metal
The technique makes use of a zirconium oxide vehicle bath rather than the conventional heavy metal zinc phosphate bath. The traditional process comprises 13 steps. The phosphate stage involves a three-cation heavy metal material (zinc, nickel and manganese) conversion coating. The bath is 140,000 gallons and is kept at a constant temperature of 120ºF (48.8ºC).
Tim Weingartz Manager of Paint Materials and Strategy, based in Dearborn, USA, explains, ‘The chemical reaction creates a sludge in the bath that needs to be filtered out and then hauled away. The vehicle bodies then pass through two stages of city water rinse [and] four stages of de-ionised water to ensure that [they] have been completely rinsed of all residual cleaner and phosphate chemicals before they enter the electrocoat dip system.’
The zirconium oxide-based system cuts this entire process down to eight steps, and is said to be comparable to zinc phosphate in its corrosion resistance properties.
Weingartz says, ‘The current system consists of multilayers of protection. The main components are two-sided zinc coated steel, dip phosphate and lead-free electrocoat. Zirconium oxide in this application is not a crystalline structure like zinc phosphate, but an amorphous and thinner coating on the steel surface.
‘The new process is more environmentally friendly because it does not use bio-accumulating heavy metals, it does not generate sludge, does not need to be heated [saving energy] and reduces the amount of water used.’ The technology can be run at ambient temperatures. Field tests will continue up to early 2008, when Ford will determine its rollout plans to paint shops in North America.
‘Even though zinc phosphates are robust and provide excellent corrosion protection, there is potential that heavy metals will be regulated in the future,’ adds Weingartz.
For further information, visit www.ford.com. Also see Materials World, September 2007, p6-7, for a novel approach of ‘exploding’ paint in an automotive paint shop to reduce the consumption of energy.
On your bike
Fuel tanks that help motorcycle manufacturers meet stringent emission standards in the USA are on their way thanks to research conducted at the Polymer Processing Research Centre (PPRC) at Queen’s University Belfast, UK.
International polymer suppliers Total Petrochemicals and Arkema Inc, both headquartered in the USA, approached researchers at the PPRC to investigate rotational moulding of new types of polymer materials for use in fuel tanks.
High fuel barrier materials are required to meet regulations passed by the US Environmental Protection Agency (EPA) in 2002, in accordance with the federal Clean Air Act. From 2008, all new motorcycles and recreational vehicles, such as snowmobiles and dirt bikes, must have fuel permeation rates of less than 1.5g/m2/day. Conventional blow-moulded high-density polyethylene tanks have rates greater than 8g/m2/day.
The new Petro-Seal technology creates multilayer tanks with an inner barrier layer of Rilsan polyamide 11 resin and an outer shell of metallocene polyethylene. Both resins were developed to enhance adhesion between the layers.
Mark Kearns, Moulding Research Manager at the PPRC, says, ‘We optimise the processing of the tank materials – what you can and cannot do. There are subtleties in the required temperatures for each material, the addition of the second layer [using a drop box] and the overall part cooling.’
The result is a tough, low-cost machineable tank that, Arkema claims, meets the new emission standards.
Kearns explains that although many manufacturers in Europe still use metal tanks, in North America, the trend is towards polymer tanks, and manufacturers are not keen to return to the ‘heavier’ metal varieties. ‘There is a push away from metal tanks because if there is a crash, there may be sparking. Polymers also improve impact and corrosion resistance, and are more cost effective,’ says Kearns.
He adds, ‘I would not be surprised if these new tanks were used in Europe in three to five years.’ Motorcycle emission regulations are not as stringent in the UK. Yet, according to the EPA in the US, ‘motorcycles produce more harmful emissions per mile than a car’.
For further information, visit www.qub.ac.uk/researchcentres/PolymerProcessingResearchCentre.
In the face of climate change and decreasing fossil fuel sources, companies and research institutions are heavily investing in bioenergy.
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INDUSTRY & INNOVATION
Manufacturing in the emerging markets
China remains the number one destination for manufacturers.
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Using photonics for e-paper
Normally, electronic paper displays involve electrical manipulation of black or white polyethylene or titanium dioxide particles within tiny microcapsules. Colour images are created by limiting each pixel to a single primary colour. Varying the intensity of each pixel generates different colours, but obtaining an intense colour on the entire display is difficult as only one-third of the pixels could create that colour. Opalux, a company based in Toronto, Canada, has created P-Ink, a technology that employs photonic crystals and the light reflected between them.
Each pixel in the display contains hundreds of silica spheres that are around 200nm in diameter and embedded in a polymer containing iron atoms. These are sandwiched between a pair of electrodes along with an electrolyte fluid. When voltage is applied to the electrodes, the electrolyte is drawn into the iron polymer, causing it to expand and the silica beads to be pushed apart. This changes their refractive index, allowing different colours to be achieved. Once a pixel has been tuned to a colour, it can hold that image for days without requiring a power source.
‘We are using microAmps/cm2 while applying a low voltage (under two volts),’ says Dr Andre Arsenault, Chief Technology Officer of Opalux. ‘The base materials we are using are cheap, and the processes we are developing should be low cost. We believe that our price points will be competitive.’
The company has demonstrated 0.3mm pixels – same size as many LCD displays – to independently generate a range of colours. ‘Our switching speeds are a little bit below one second at the moment,’ says Arsenault. ‘Clearly this is too slow for video, but the applications we are targeting [including large area digital advertising screens] do not require video speed.’
Dr Sergei Romanov, Senior Researcher in the Photonic Nanostructure Group at University College Cork, Ireland, says ‘The idea of applying 3D colloidal crystals with variable lattice parameters to e-paper displays is a fantastic example of clever material engineering to materialise very simple physical phenomenon of light diffraction.
‘The principal drawback of the proposed display is the narrow viewing angle for each single colour. In particular, each colour is stable within approximately plus/minus five degrees from certain directions.’
Romanov explains that scanning from higher degrees could distort the colour. The long switching times of the pixels, and the potential for the iron polymer to degrade, leading to reduced switching cycles, are also areas that need to be addressed.
Nevertheless, ‘a number of suggested innovations [by P-Ink], like the use of diffraction instead of filtering and enabling the same pixel to display different colours, makes this work very important for the field,’ he adds. For further information, visit www.opalux.com.
Hydrogels for tissue regeneration
A novel peptide-based hydrogel may one day be injected to repair human tissue.
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Researchers from the Risoe National Laboratory – Technical University of Denmark, in Roskilde, have successfully achieved an 8.7ºC drop in magnetic cooling, bringing environmentally friendly refrigeration closer to development.
Magnetic cooling technology exploits materials such as gadolinium that heat up when exposed to a magnetic field and cool down when that field is removed. ‘Other groups have reported larger drops [using magnetic cooling]. However, our result was achieved with a small and versatile machine,’ says Nini Pryds, Senior Research Scientist at Risoe.
‘Our system is contrary to others in that the configuration of the regenerator is in the form of plates and not phorous/spherical particles. Using plates [gives us the] advantage [of] controlling the flow characteristics inside the regenerator as well as obtaining a low pressure drop along [it], which reduces the consumption of energy.’
The research group ultimately aims to build a prototype refrigerator by 2010, using ceramic plates made of lanthanum, strontium, calcium and manganese, to replace gadolinium. ‘Ceramic materials are much cheaper than gadolinium. Also, they do not corrode in water, and tuning [their] Curie temperature (the temperature with the maximum magnetocaloric effect) is possible,’ says Pryds.
In the prototype, the magnetised plates will transfer their heat to water which will be pumped to a hot heat exchanger located outside the machine. When the magnetic field is removed, the plates will become cooler, drawing heat from the water, which will transfer its low temperatures to the cold heat exchanger located in the fridge. ‘This is the same principle as the cold and hot loops of a compressor-based refrigerator,’ explains Pryds. But while traditional fridges can use up to 150W to induce temperature changes, the magnetic refrigerator will only require energy to circulate the water. And no damaging hydrofluorocarbons will be used.
The initial drop of 8.7ºC was obtained using a large electromagnet which requires high power consumption, making it unsuitable for practical use. ‘We are currently implementing a permanent magnet field source of the Halbach type (a cylinder assembly of neodymium iron boron magnet blocks with a diameter of around 20cm)’, adds Pryds.
There is still some fine-tuning that needs to be done before the system can achieve the 40ºC temperature range required for refrigeration. Pryds expects the technology will initially be used in industry, but would like to see it one day used in household refrigeration.
See Materials World, August 2007, p4, for more on ‘Magnetocaloric materials’.
MATERIALS & MINERALS PROCESSING
Scientists from the North West Laser Engineering Consortium at the Universities of Liverpool and Manchester, UK, say they have developed a more efficient way of producing nanoparticles using a continuous wave (CW) fibre laser.
By applying the CW laser ablation in liquid, the team was able to produce titanium-oxide nanoparticles with a mean diameter of 30-40nm at a rate of around two grammes/hour. Traditional pulsed laser sources operate at rates of 4.4 milligrammes/hour.
‘It is the first time to our knowledge that a CW laser has been used [to generate] nanoparticles via laser ablation of a metallic target in liquids,’ says Dr Amin Abdolvand of The University of Manchester. ‘Fibre lasers were proposed for their high average power and brightness, a feature that is difficult to achieve in bulk lasers.’ The output beam quality is determined by the guiding properties of the doped core, so the beam is focused onto a spot of less than 20µm. It has a relatively large depth of focus, providing high and uniform irradience. ‘Thus the material processing/ablation can be tailored as desired,’ adds Abdolvand.
In an experiment, the group submerged a one-millimetre high-purity titanium plate in eight millilitres of an aqueous surfactant solution. Using a ytterbium-doped high-power, high-brightness CW fibre laser, the team focused 250W on a spot 40nm in diameter, with a power density of 20MWcm-2. ‘Even a short exposure time of one second was enough to remove up to 0.4mg of the material,’ says Abdolvand. The team has also applied this technique to nickel.
While the CW laser consumes more energy than pulsed laser ablation, ‘the efficiency of CW fibre lasers [is] higher,’ says Dr Martin Sharp of the University of Liverpool. ‘It is a clean, one-step process. It may be possible to build a “nanoparticle-on-demand” machine, capable of delivering nanoparticles of a wide range of materials.’
‘We hope to achieve faster production rates,’ adds Abdolvand. ‘More importantly, we would like to have a more controllable process to gain control over the size distribution of the particles’. Preliminary results indicate that the size, distribution and composition of the nanoparticles is dependant on laser parameters, such as spot size and the type of environment.
Closing the loop in engineering education
Incorporating sustainable development into engineering education.
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New science degree covers all bases
Following successful pilot trials, the Institute of Physics (IOP), UK, will launch its Integrated Science degree in four universities from September 2008.
The interdisciplinary degree aims to appeal to students who are interested in a broad spectrum of sciences. It will offer the opportunity to learn several different disciplines, including physics, chemistry, engineering and biology. Each degree has been tailored according to the expertise of its host institutions – the Universities of Surrey, Leicester, East Anglia and the London South Bank University.
‘The purpose [of the degree] was to encourage more people to study a physics-based degree course at university,’ explains Professor Peter Main, Director of Education and Science at the IOP. ‘This can be achieved by appealing to students who do not want to specialise but would like a broadly-based science course.’
Graduates of the degree could then complete a four-year master’s degree specialising in a specific science.
The IOP has worked with the participating universities to develop their core physics curriculum. The University of Surrey’s BSc degree will cover the physical and life sciences, including atoms molecules and quanta, medical imaging and soft solids. The University of Leicester focuses on chemistry, biology and the earth sciences. London South Bank University’s degree will look at medical applications, communications, modern materials, energy and sustainability. Meanwhile, the University of East Anglia will cover spectroscopy, polymer and materials chemistry and astrophysics.
‘More than one commentator has stressed the importance of a multidisciplinary approach to science research in the 21st century, so there is a strong argument for degrees of this type,’ adds Main.
Professor Chris Grovenor, Head of the Materials Department at Oxford University, UK, says the new degree sounds similar to other integrated degrees offered in the UK, such as materials science, which can be interdisciplinary. However, he expressed concerns about the degree’s aim to appeal to students who would not normally go into science. ‘Attracting people just to increase enrolment numbers is not very rational. Nobody wins,’ says Grovenor. ‘You want to make sure you’re keeping the best students in your subject.’
©Copyright 2006 The Institute of Materials, Minerals and Mining