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Microanalysis Newsletter - November 2014
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Out with the old, in with the new –
why automated sizing techniques are better than sieving.
It is tradition in mining, oil and gas, agriculture and environmental fields to determine particle size distributions by sieving alone. This is a legacy from long before the advent of modern techniques such as laser diffraction and x-ray attenuation (Sedigraph) techniques, and the automated control system jiggery-pokery we see the benefit of today.
Many industries still adhere to older sieving standards that they have been using for so long, without realizing that there’s a cheaper, quicker and more accurate way. New standards, such as ISO13320, are in place to validate automated sizing techniques as an alternative to older methods.
As well as the obvious benefits listed above, there are a few other differences between the results obtained by sieving as opposed to laser diffraction or Sedigraph. Sieving analysis gives a mass percent size distribution, which is influenced by particles with hetrogeneous densities. Sieving also measures the second largest diameter, rather than the average, hydrodynamic or aerodynamic diameters. Sieving is insensitive to morphological properties - which may be considered more fully with other techniques.
That doesn’t mean sieving is entirely redundant! Many automated techniques are only suitable for particular size ranges, and sieving is required outside those size ranges to create a complete picture.

All That Is Fibrous Is Not Asbestos

Upon visual inspection it would be easy to assume that the sample pictured below was a large piece of asbestos, due to its asbestiform habit of long, thin fibrous crystals and easy friability.

However, by performing analysis with the Energy Dispersive Spectrometer (EDS) on our Scanning Electron Microscope (SEM), the fibres are revealed not to be an asbestos silicate mineral but instead are primarily composed of aluminium, iron, sulphur and oxygen. The elemental ratios indicate that the fibres are likely Halotrichite, a highly hydrated sulphate of aluminium and iron with the chemical formula FeAl2(SO4)4·22H2O.
SEM images of Halotrichite
 
Halotrichite is usually formed by weathering of sedimentary rocks and is commonly found around or in volcanic vents. Unlike asbestos, Halotrichite is water soluble and is not classified as a hazardous respirable fibre, making a big difference to its handling, storage and disposal procedures.
 
If you have a fibrous sample that you are unsure about and would like to send it in for testing and identification, please feel free to contact our lab on (08) 9472 4880 or check out our website (www.microanalysis.com.au) for more information!

Bringing Science to Gamers

Photo: Dr Phill English
Last weekend, I flew over to Melbourne for the 2nd annual PAXAus: the Penny Arcade Expo, Australian edition. It’s essentially a massive gaming convention run over three days in the Melbourne Convention and Exhibition Centre, showcasing the latest and greatest in videogames and tabletop games. It was really fun to run around and see the different  offerings on show, but I was mainly there to present a panel with two of my friends, Tim and Megan, entitled ‘Videogames…FOR SCIENCE!’.
The point of the panel was to explore the relationships between science and video games. My part involved comparing the logical leaps that gamers go through while playing games as being very similar to those experienced by scientists when performing experiments. Tim explored how science is portrayed in video games and media, and Megan showed the audience how she had been using video games to teach science to schoolchildren.
We ended up with a really enthusiastic crowd that packed out the 500-person theatre and interacted fantastically. After the presentation we each had a bunch of excited gamers come up to us and tell us about their jobs as scientists or studies at university science degrees, which was really great. All up, it was an excellent experience and one that we’re hoping to repeat next year with more exploration into the scientific nature of the gaming medium!
SEM Image of the Month

This month we are not going to tell you what our SEM image of the month is - we want you to guess!
What do you think this image is of?
Send your answer to admin@microanalysis.com.au There will be a prize for the first person to contact us with the correct answer.
Image: Sandy Lam
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