Material Science in surfboards

Summer hiatus for Made2Measure, but we thought that you might like this topical post from Engineering Breakdown! (Comments disabled – please post these at Engineering Materials’ site).

ENGINEERING BREAKDOWN

During my recent visit to the American West Coast, I had the opportunity to have a first contact with surfing. Although I didn’t have a totally satisfactory experience, I must say I found this sport quite interesting and, for that reason, I started asking some questions about the materials which are used to manufacture surfboards to my surfing expert brother. In this post I will introduce very briefly the main materials and a bit of comparison between their performance.


To begin with, the surfboards can be classified in two main categories with regards to the materials used in the outer part. For people who, like me, are not familiar with this sport, the way for identifying which of the two types of surfboards is in front of us is simply to look at the external appearance of the board itself. Trust me, anyone can spot the difference!

The first type corresponds…

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Made2Measure Heaven: Plasma FIB

Who are you? Dr Mark J. Whiting

What is your role? I’m an Academic in the Department of Mechanical Engineering Sciences at the University of Surrey.

What is your work about? My research centres on the role of microstructure and especially interfaces in the manufacture and performance of advanced metallic materials. One way to study interfaces is to use a plasma focused ion beam or PFIB.

I beg your pardon? The engineering performance of many materials depends on the nature of interfaces as well as the physical processes that occur at these boundaries. Many current and next-generation structural materials bring together diverse materials in composites, combing a metal and an inorganic material. These include glass-to-metal seals, previously featured on this site. Another example, also featured here, are SiC monofilament reinforced titanium matrix composites. The interfaces not only determine some aspect of performance, but their exact nature depends on processing and manufacture. Even monolithic materials owe some of their performance to interfaces created during manufacture—additive manufacturing processes for metallic materials have a molten metal/gas interface throughout production. Gas absorption and oxidation etc. can all alter this interface prior to its becoming part of the bulk.

A new method for studying interfaces as well as other microstructural features is plasma focused ion beam, PFIB, technology. My two colleagues, Professor John Watts and Dr David Cox, and I were recently awarded an EPSRC grant to purchase such an instrument for the University of Surrey. This venture is in partnership with the NPL who are interested in the materials metrology capability the instrument.

Mark

Figure 1 – The author discussing plasma technology with a Cyberman (Cyber-leader 768HY98)

What is a PFIB? FIB, or focused ion beam, techniques have become firmly established in the last decade as ways to make both devices and specimens for characterisation. In these traditional FIB methods liquid gallium is ionised and used to remove material. In this way, thin slices of many functional and structural materials can be made for study by techniques such as transmission electron microscopy. The selective removal of material down to the nanometre scale means that very small devices can be fabricated from a multiplicity of materials. The study of interfaces by electron microscopy and allied advanced characterisation techniques requires greater effort to gain nanometre-scale information reproducible over reasonable length scales. The use of gallium to remove material poses some problems. Gallium can react with many metals, in some cases forming low melting point eutectic alloys. More fundamentally, there is a limit to the ion current and therefore speed with which a gallium ion beam can remove or ‘cut’ material. The recently commercialised plasma FIB uses xenon ions. Xenon is not only inert but can also offer significantly increased ion currents and sputter yield. The two current manufacturers both quote at least a sixty-fold increase in throughput. In most cases this enhanced milling speed will offer the opportunity to fabricate bigger devices with nanometre-scale detail or the production of larger more representative samples.

And? Much materials characterisation studies specimens which are so small that there are often significant doubts as to whether the specimen is representative of the bulk material. Rather than study a handful of grains and three grain boundaries, PFIB means that hundreds of grains and thousands of boundaries can be studied. The speed of PFIB also makes possible the 3D characterisation of materials on a sensible timescale.

So what? The University of Surrey’s PFIB will be used for a multiplicity of engineering projects. The work that I will do with it offers science which will enable (i) the manufacture of lighter, stronger and stiffer structural materials, and (ii) the additive manufacture of advanced structural materials which produce less waste than materials made by subtractive manufacture.

Final Thought: Plasma FIB offers the ultimate in Made2Measure Materials. It offers new possibilities for the manufacture of devices, new capabilities for materials metrology as well as being a technique that offers characterisation capability informing the science underpinning modern materials manufacture.

Made to Measure… Printed Solar Cells

Who are you? Harry Cronin

What is your role? I’m an EngD Research Engineer at the University of Surrey and DZP Technologies

What is your work about? I’m working on the scale-up of printable solar cells based on organic-inorganic halide Perovskite materials.

I beg your pardon? Perovskite materials have the general formula ABX3. By changing the atoms or molecules which sit at the A, B and X positions these fascinating materials can be designed to have a wide range of optical and electronic properties. Recently, it has become clear that halide Perovskites are an excellent material for making solar cells. These materials use a small organic molecule on the A site, a metal like lead or tin on the B site and a halide such as iodine on the X site. The efficiency with which the best Perovskite devices convert sunlight into electricity has been pushed from 3.8% in 2009 to over 20% today. But the real advantage of Perovskite solar cells is that they are simple to make – simply deposit a precursor solution, and the Perovskite forms on drying. This property makes them ideal for printing, but owing to a number of unsolved challenges a printed Perovskite cell has yet to be commercially demonstrated.

Solar Harry

Figure 1 – The author, grinning inanely, prepares to coat a conductive silver substrate with a second layer using doctor blading.

Why? Solar cells could potentially play a major role in reducing carbon emissions, but are currently too expensive to compete with fossil fuels in many applications. By using cheap, high-throughput printing technologies, similar to those used to produce newspapers, cell prices could potentially be slashed. This is part of a wider trend in electronics manufacturing, in which people are trying to make all sorts of ultra-low cost devices by means of printing. Previous work at DZP Technologies has produced prototype printed cells, and the aim of my project is to improve the efficiency of these prototypes by the introduction of Perovskites. There are many challenges to be overcome with the scale-up of this technology.

And? Printed solar cells consist of multiple layers, each of which must be simultaneously optimised and controlled both in terms of materials and processing. In my research I have looked at a method for increasing the conductivity of several of these layers using high intensity light pulses. Put simply, more highly conductive interlayers will mean better-performing solar cells. In parallel to this I have investigated the behaviour of the Perovskites under different processing conditions, which will be vital knowledge as we work towards scaling up the technology.

So what? If this technology can be taken from the lab to commercial scale, we could start to see solar cells in many new places. As well as being cheaper, printed solar cells open up a range of new applications due to their light weight and mechanical flexibility. For example, flexible solar parking shades could be used to charge electric vehicles parked underneath them. Or, highly portable rolls of solar cells could be developed for camping or use in disaster zones.

Final Thought: Made to measure printed solar cells have the potential to offer a step change in the affordability of solar power, alongside flexibility, low weight and large area. Coming soon to a rooftop near you (we hope)!