Interview with Lindsay Chapman (audio)

Hi all,

Something a bit different today. As part of a new section on thermal analysis on the Materials Today website, I interviewed  NPL Senior Research Scientist Lindsay Chapman. We talked about some of the measurement challenges in thermal analysis, and on the role of the National Physical Lab (yes, my “alma mater”) in establishing good practise in this area. Lindsay is a true expert in her field, so its really worth a listen.

http://www.materialstoday.com/characterization/podcasts/thermal-analysis/

Enjoy :)

Posted in Its Just Science! | Leave a comment

Aerogels for insulation: it’s all about particle size

This news story originally appears here: http://www.materialstoday.com/energy/news/aerogels-for-insulation-particle-size/

A team of Norwegian researchers have shown that the thermal and optical properties of aerogels depend on their particle size – useful in the design of insulating windows.

We’ve all seen images of the ghostly-looking material aerogel. Famously, in 2006, panels of it were used on NASA’s Stardust mission to capture tiny samples of interstellar dust. But here on Earth, its low density and thermal conductivity have attracted the interest of a much more ‘urban’ research effort – in the development of insulating windows.

Photograph of Aerogel-AB (a). Scale bar: 10 mm.

Photograph of Aerogel-AB (a). Scale bar: 10 mm.

Windows have a huge impact on a building’s energy efficiency, with some figures suggesting that ~50% of the total energy loss from a standard office building happens through its windows. As global efforts to produce ‘green’ buildings become ever more ambitious, we’re seeing a growth in research programmes on windows. So far, there have been several window innovations which have shown potential to meet the requirement of energy efficient buildings – multi-layered, vacuum, and silica aerogel windows.

Arild Gustavsen and his team at the Norwegian University of Science and Technology are focused on the use of silica aerogel granules as the “filler” in double-glazed windows [Applied Energy 128 (2014) 27-34 DOI: 10.1016/j.apenergy.2014.04.037]. Because aerogel is mechanically very weak, much of the current research on aerogel glazing units (AGUs) focuses on the synthesis of the aerogel. But Gustavsen and his team specifically looked at the effect that aerogel granule size and layer thickness have on the thermal and optical properties of standard double-glazings.

Both AGUs show improved thermal insulation performance when compared to double glazings – AGUs containing ‘large’ aerogel granules (diameter 3–5 mm) showed a 58% reduction in heat loss. Smaller particles (<0.5 mm) had an even larger effect on the thermal conductivity of the window unit – there, the team saw a 63% reduction in heat losses. However, the introduction of these granules did have an effect on the optical transmittance of the windows – Gustavsen showed that the smaller the particle, the more diffuse the transmitted light. The team believe that this property may be useful in situations where glare and/or privacy need to be considered.

Highly insulating glazing units are defined as those with U-values of about 0.5–0.7 W/(m2K) – so far, results on these AGUs fall short. But this work has opened the debate on how to optimise not only the aerogel, but the design of the final glazing units for a range of building applications.

To download the article related to this news story, please click here.

Posted in Its Just Science! | Leave a comment

Roll-to-roll synthesis of CNT supercapacitor electrodes

Another news story for Materials Today – originally appeared here on 7th July

US researchers have developed a scalable process to produce continuous ribbons of aligned carbon nanotubes (CNTs), for the next generation of double-layer capacitors.

In the last decade, there has been a considerable growth in the wide-spread use of carbon nanomaterials across a range of industries. But the most common bottleneck to any further development is the scalability of their production. Although CNTs can be synthesised in large quantities, present processes for the growth of vertically-aligned CNTS – particularly of interest to the electronics market – are limited to a small range of substrate materials.

380eca81-9e2f-4f15-b3ca-3281edb7731e

But a group of researchers from Clemson University in the US have developed a relatively low-cost roll-to-roll method – their system can grow vertically-aligned CNTs (VACNTs) directly onto aluminium foil ribbons that are continuously draw through a reactor. Their process produces high density, high capacity (~50 F/g) forests of aligned CNTs that outperform commercial CNTs. The team also used these ribbons of aligned CNTs as the electrodes in a range of high-performance supercapacitor cells.

Today’s supercapacitors tend to use carbon materials in their electrodes, with their performance related to the electrode’s surface area. So, considerable research effort has focussed on using CNTs as supercapacitor electrodes. But issues of substrate preparation and high operating temperatures have rendered the system complex and inefficient.  What the Clemson team have done is develop a system that negates these issues – by adapting a standard Chemical Vapour Deposition (CVD) system, they have managed to decrease the growth temperature to 600 °C, which is below the melting temperature of aluminium. This means that it can be used to directly synthesise VACNTs onto a current collector substrate – in this case, aluminium foil ribbons.

The work, recently published in Nano Energy (2014) 9-16 [DOI: 10.1016/j.nanoen.2014.05.004], also reports on the direct assembly of these VACNT ribbons into supercapacitors. When compared with capacitors made with buckypaper and CNT forests from a stationary CVD set-up, the roll-to-roll electrodes performed well, with a charge capacity of 24.8 mAh/g. But their discharge time (630 ms), energy density (11.5 Wh/kg) and power density (1270 W/kg) all vastly outperformed the other electrodes. The roll-to-roll devices also showed excellent cycle stability, with no loss of performance over more than a thousand cycles.

These results demonstrate the real potential for this technique, and the team believe that it offers a viable process for the production of supercapacitor electrodes.

To download the article related to this news story, please click here.

Posted in Its Just Science! | Leave a comment

Nanocrystalline titania for smart windows

Science time! Turns out that two of my news stories for Materials Today this month made spots #1 and #3 on the most-read list :) You can read the one that made #1 elsewhere on my blog (go here)

#3 can be read on the MT site here: http://www.materialstoday.com/crystalline-materials/news/nanocrystalline-titania-for-smart-windows/ and as always, have copied the text below. Enjoy!

Anatase titanium dioxide is a promising material for the next generation of “smart windows”, according to new results from researchers in India.

Titanium dioxide (or titania, TiO2) is used in a wide range of applications – in everything from paint pigment to ceramics. It can be found in five main mineral forms, the most common three being rutile, brookite and anatase. The unique catalytic properties of the anatase form have been studied for decades, and in the last few years, has seen a renewed interest, alongside an ongoing debate. Anatase is generally more photocatalytically-active than the other two forms of the material, but as yet, little consensus has been reached to explain the difference.

A team from VIT University in India now reports that in the midst of this debate, they have found a real-world application for nanocrystalline thin films of TiO2. They have reported, in an issue of Materials Science in Semiconductor Processing 26 (2014) 251–258 [DOI: 10.1016/j.mssp.2014.05.006] , that TiO2may be used to produce a new generation of “smart windows”. Smart windows can apply to any glass products that do more than just ‘keep the elements out’. Due to their surface chemistry, they can break up dirt (photocatalytic) and be self-cleaning, or with the application of a small voltage, switch from transparent to opaque (electrochromatic).

The secret to producing a window that can do both is to find a material that combines beneficial photocatalytic and electrochromatic properties.

It has been known for some years that titania’s photocatalytic effect is further pronounced in nanocrystalline films of anatase – an observation generally attributed to the increase surface-to-volume ratio. But Meher and Balakrishnan have demonstrated that alongside this, specially-designed films of anatase also have reasonable electrochromatic properties. Using low-cost sol-gel processes, the team deposited anatase thin films (200 – 300nm thick) onto glass, silicon and ITO substrates, and annealed them at a range of temperatures. They found that the films annealed at 400 °C showed both high-efficiency photocatalytic degradation of the test dye and could switch from transparent (at 550nm) to opaque in 10 s.

These initial results certainly show some potential for the use of nanocrystalline anatase in smart windows. But unanswered questions remain, including a full analysis of the wetting properties of the films. If they are found to be hydrophilic, anatase may yet find its way onto the windows of our future homes.

To download the article related to this news story, please click here.

Posted in Its Just Science! | Leave a comment

To London

Hi guys, 

Apologies in advance if you were hoping for a sciencey post. Regular readers will know that, on occasion, my posts veer toward the more personal. This is one of them. Feel free to ignore it – it’s more a cathartic exercise than anything :)

Today, Thursday 3rd July, marks a mini-landmark in my life. This time nine years ago, I arrived into Heathrow to start my life in London. It didn’t feel like that at the time of course – like many adopted Londoners, I thought “yep, I’ll be here for two or three years and then move on to somewhere else”.… And yet, here I am. You can probably imagine that I’m experiencing some mixed feelings today – in some ways, it feels like just yesterday that I hopped off my one-way flight, laden down with bags, with a vague plan for my future. But then I think about how I was before I lived in this great city, and it’s all a bit blurry and indistinct – like I hadn’t quite figured myself out yet. Which is certainly true.

It’s been up and downy, but I can’t deny that so far, it’s been an adventure. I arrived just a few days before the most iconic 24hours in London’s history – I was here when it was announced that we’d host the Olympics, and on the very next day, when the tube was bombed. I’ve lived at six addresses, all in South / West London, I’ve met some wonderful friends and flatmates, adopted two families and have had my heart broken, then healed, then smashed to smithereens. I’ve done a masters, researched everything from water-repellent surfaces to energy harvesting, and discovered the wonderful world of science outreach / communication. I’ll soon start my third ‘real’ job, and I am writing my very first book. I’ve explored many of London’s wonderful secret places, and been a tour guide to visiting friends and family. I’ve travelled the world and found new hobbies, and have been to more live events (including Wimbledon and the Olympics) than most people do in their lifetimes.

But my greatest achievement over this past nine years has been to finally see myself clearly. I might not like everything I see when I look in the mirror, but I can honestly say that I know who I am and what I am capable of. And how many people can truly say that?! I’ve found that fear is my greatest friend – I am often told that I “…have no fear”, but frankly, that is total bullsh*t. I am afraid all the time. Thankfully I am just afraid enough to stay driven and motivated, but not enough to become paralysed. This is not to say that I’m always ‘on’ – sometimes I need to collapse into a heap – but it’s the fear that this will be my future that helps to drag my ass off the floor. Fear can also be an enemy – I’ve seen wonderful people debilitated by fear, who are now living a half-lived life, far beneath what they deserve – and it breaks my heart. I can only hope that one day soon, they will see how happy they could be if only they embraced the fear and took a huge, terrifying leap, even just once.

Anyway, what I wanted to say before I went off on that tangent, is that London has helped me to become who I am. I am definitely a product of my environment and I’m exceptionally lucky that in this vast, sprawling (and occasionally lonely) city, I’ve found “Laurie’s army” – a group of people who love and support me no matter what. I could never have imagined, when I arrived on that scorching hot July day in 2005, that this could happen. On my darkest days, a walk across Waterloo Bridge, or down Grosvenor Road, followed by a coffee with one of my army’s generals helps me to find a tiny chink of light :)

So, happy anniversary to myself and London. To my wonderful city, I say thank you for welcoming me and for helping me to find a home amongst your busy streets. Thank you for looking after me and allowing me to (at the risk of sounding like a d*ckhead) “find myself”. Lately, the road has been very bumpy, so I don’t know if our love affair will last forever, but right now, there is no place I’d rather be.

L x

 

Posted in Life etc. | 1 Comment

Large area metal foams for energy applications

This article appeared on the Materials Today site this morning…. you can, of course, read it there too :)

A group of Korean researchers have developed a new technique for producing metal foams with highly ordered, sub-micrometre-scale pores.

Nanoporous foams have been a buzz word in materials research over the last decade, but much of the work has focused on organic or inorganic materials. Until recently, producing metallic foams with reliable pore size remained elusive. With their high surface area, such foams have been proposed for use in a range of applications, from sensors to high-efficiency heat-exchangers.

AFM images of (a) the top morphology of the nanoporous Cu foam taken at a low magnification and (b) the smooth surface of a zoomed-in Cu strut with an average surface roughness (Ra) ~13 nm.
AFM images of (a) the top morphology of the nanoporous Cu foam taken at a low magnification and (b) the smooth surface of a zoomed-in Cu strut with an average surface roughness (Ra) ~13 nm.

In a recent issue of Materials Letters, a Korean research group presented a new technique for producing copper and nickel foams that display sub-micrometre-scale, highly-ordered pores. They believe that these foams could be promising electrode materials for energy storage systems, such as the next generation of batteries.

To produce these foams, the team developed a modified electroless plating technique, based on a proximity-field nanopatterned (PnP) polymer template. The polymer template was produced in-house, and activated so that it became catalytic. The template was then plated with either nickel of copper (to a thickness of 45 – 51 nm), resulting in foams with uniform pore size or up to 330 nm in diameter.

The researchers, who published the work in Materials Letters [doi:10.1016/j.matlet.2014.05.043], believe that their technique offers a number of advantages over conventional techniques – by using the polymer template, it can produce highly ordered submicron pores in both Ni and Cu foams, and the resulting foams can be several tens of microns in thickness. The use of electroless plating also has the added benefit of preventing corrosion of the metal in the foam.

Mechanical strength is also a key consideration for all battery materials, and so the strut structure of the Cu and Ni foams was also analysed, and was found to outperform other types of metallic foams fabricated by the conventional de-alloying process.

The structural and mechanical properties of the metal foams render them suitable for practical applications, such as for use as electrodes in batteries, dye-sensitised solar cells, or fuel cells.

Materials Letters (2014) doi:10.1016/j.matlet.2014.05.043

To download the article related to this news story, please click here.

UPDATE: This was the most popular news story on Materials Today in June :)

MAToday

Posted in Its Just Science! | 1 Comment

Inkjet printing for drug delivery

[This article originally appeared here - thanks to Materials Today for their continued support :)]

Inkjet printing for drug delivery

Most people are familiar with inkjet printers. But did you know that they can be used to print much more than just colored ink? Across the globe, researchers have used this technology to print light emitting polymers for flat panel displays, to create data storage devices using magnetic nanoparticles, or even to produce highly-sensitive biosensors, using arrays of proteins.

In the past two decades, there has been a push toward using inkjet technology to “print” pharmacologic agents onto small needles – producing a low-cost, painless drug delivery system. And in the latest issue of Materials Today, a team of US scientists have demonstrated the latest breakthrough in this field. Using inkjet printing, they coated arrays of microneedles with Miconazole, a drug used to treat fungal skin infections. The team also showed that the drug remained completely active throughout the printing process, by testing it on a common fungus (Candida albicans).

Scanning electron micrographs of miconazole-loaded Gantrez® AN 169 BF microneedles. (a) Front view of a miconazole-loaded Gantrez® AN 169 BF microneedle array, which shows the entire array of five microneedles above the rectangular prism-shaped substrate. (b) Front view of a single miconazole-loaded Gantrez® AN 169 BF microneedle.
Scanning electron micrographs of miconazole-loaded Gantrez® AN 169 BF microneedles. (a) Front view of a miconazole-loaded Gantrez® AN 169 BF microneedle array, which shows the entire array of five microneedles above the rectangular prism-shaped substrate. (b) Front view of a single miconazole-loaded Gantrez® AN 169 BF microneedle.

Inkjet printing uses piezoelectric micro-nozzles to accurately and reproducibly deposit very small liquid droplets (1 -100 pl) onto a surface. Roger Narayan and his team have applied inkjet printing to microneedles – arrays of tiny lancet-shaped polymer needles that are already being used to painlessly deliver vaccines. The accuracy of the technique means that the pharmacologic agents can be directly applied to the microneedles, without the need for further processing steps.

One of the advantages of inkjet printing is that it only a small amount of liquid is needed – in Narayan’s work, each array of microneedles (substrate area = 7.25 mm2) used just 38 µg of miconazole  – but this was enough to inhibit growth of fungus in an area over seven times larger than the array size.

Narayan has said that there are wider applications to their work – “(The approach) can be used for many classes of pharmacologic agents that exhibit poor solubilities”. There are challenges remaining, such as a further reduction in the cost of suitable inkjet printing equipment, but this approach has real potential to become commercially significant. Narayan’s team continue to work in the field – and are currently looking at using a single microneedle array to simultaneously treat several medical conditions in a patient.

This news article is based on research from “Inkjet printing for pharmaceutical applications” by Ryan D. Boehm, Philip R. Miller, Justin Daniels, Shane Stafslien, and Roger J. Narayan. It appears in Materials Today, DOI: http://dx.doi.org/10.1016/j.mattod.2014.04.027. The article is available here.

Posted in Its Just Science! | Leave a comment