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Owen & Ian report back from AXAA 2017 and Nimue's XRD Tutorial
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AXAA Conference 2017

 
February got off to a flying start with Ian and I heading to Melbourne for the Australian X-ray Analytical Association Workshops, Conference and Exhibitions. Nathan Webster of CSIRO and his team at AXAA did a fantastic job of compiling an interesting mix of speakers covering innovations and developments in x-ray diffraction and x-ray fluorescence techniques and instrumentation.
 
Ian Madsen of CSIRO (ret.) and Matthew Rowles of Curtin University kicked off the XRD proceedings with workshops spanning everything from the basics of x-ray diffraction principles to advanced quantitative analysis techniques. There were also informative presentations from Mark Raven of CSIRO on the challenges of quantitative XRD analysis on clay samples as well as a few cool projects working with carbon sequestration by Jessica Hamilton of Monash University and selective gas adsorption with metal organic materials by Josie Auckett of ANSTO to name but a few.
 
Dr. Helen Maynard-Casely’s (of ANSTO) public lecture gave an interesting insight into how planetary scientists can recreate the high pressure conditions deep within the core of planets and Michael Varcoe-Cocks of the National Gallery of Victoria presented the very dramatic transformations that artwork can undergo when XRF techniques are used to aid in the restoration process. You can watch them both here.
 

Ian Davies "networking" at the morning tea
We enjoyed an entertaining dinner with great food and wine where Greg Moore and Mark Raven were honoured with the Keith Norrish AXAA Award for Excellence in X-ray Fluorescence Analysis and Bob Cheary AXAA Award for Excellence in X-ray Diffraction Analysis respectively. To finish off the week we were treated to a tour of the Australian Synchrotron. The whole conference was a great experience where we were exposed to new tips, tricks and techniques for quantitative XRD analysis many of which we are looking to incorporate into the analyses we offer to further improve the quality of the results we provide. Here’s hoping we get invited back to the next AXAA conference!

Owen Carpenter
 

Crystallography - a quick tutorial in X-ray Diffraction

The majority of things around you (and inside you!) are made of atoms. Atoms are arranged in some sort of order – they can be found in meandering long chain molecules in fats and proteins and the like, in cute little pairs or triplets floating around as gases, or arranged in military order in iron and diamond.
Those materials where the atoms are arranged in repeating patterns, like wallpaper or synchronised swimmers, are referred to as ‘crystalline’ materials. Any material that is not crystalline (or semi-crystalline but that’s a whole other kettle of eels) is considered amorphous.
Crystalline vs Amorphous
When X-rays interact with these crystalline materials, they diffract the radiation a different amount depending on the distance between the atom and its neighbours. When many X-rays interact, these many diffractions build up a pattern that allows us to see how the atoms are arranged in the solid. Since different sized atoms result in different sized gaps between the atoms in the structure, which changes this diffraction pattern.
The arrangement, or ‘packing’ of the atoms results in the main pattern of the resulting diffraction. If you think about how you could stack ping pong balls in a plasic tube, or stack apples on a table, that gives you an idea of different crystal structures that might be possible. The basic crystal structures are shown below.
The way these atoms are arranged, the crystal structure, determines how a crystal is formed and grows over time – you may have noticed the little hematite cubes you can see at the markets, or the way some gemstones form a hexagonal shape. This arrangement of atoms determined how the crystal will look on a macro scale. Sometimes individual atoms in a crystal structure will be substituted with another atom type (for example manganese for iron), which usually won’t change the overall structure, but might change the colour of the crystal or the way the light bounces through it.
X-ray diffraction analysis uses this unique interaction between X-ray radiation and crystalline materials to build a diffraction pattern which is then compared to a huge database of reference patterns in order to determine which crystal structures are present in the material. This allows up to tell the difference between Halite and Sylvite, and between Goethite and Hematite without any trouble.
Want to identify your crystals? Ask for X-ray Diffraction!

Nimue Pendragon

Image Of The Month
This month’s image is of a seed pod.

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