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Dr Colin Nexhip was interviewed in 2001 for the Interviews with Australian scientists series. By viewing the interviews in this series, or reading the transcripts and extracts, your students can begin to appreciate Australia's contribution to the growth of scientific knowledge.
The following summary of Nexhip's career sets the context for the extract chosen for these teachers notes. The extract covers some of his most recent research projects. Use the focus questions that accompany the extract to promote discussion among your students.
Colin Nexhip was born in 1969 in Kyabram, Victoria. He received a BEd in 1991, a BSc (Hons) in 1992 and in 1998 a PhD in chemical engineering, all from the University of Melbourne.
His PhD research was on the physical chemistry of foaming in molten slag systems, a phenomenon seen in iron- and steel-making. For these studies he was enrolled at the Chemical Engineering Department at the University of Melbourne, but his research was done at the CSIRO Division of Minerals, where he was an ‘industrial trainee'. In 1997, while still a student, Nexhip was invited to present his doctoral research to the Royal Society of London. That same year he was awarded the CSIRO Innovation Award for the design of a high temperature laser spectrometer, used for measuring the thickness of molten oxide bubble films.
After completing his PhD, Nexhip was appointed as a research scientist at CSIRO Minerals. In 2000 he was promoted to senior research scientist/engineer there. He works on a variety of pyrometallurgy projects, including molten oxide chemistry, high temperature physical chemistry and how to improve phase mixing and separation of molten liquids.
In 1999 Nexhip was awarded a Victoria Fellowship that he used to undertake an overseas study mission relating to high temperature surface chemistry.
In 2001 he received an International Scientific Technology Networks Grant from the Australian Academy of Science to be a visiting scientist at the German Aerospace Research Centre. There he was part of a program called 'Metals in Orbit' and conducted ground-based preparatory experiments to measure the high temperature properties of metals in different gravity settings. He hopes that one day these experiments will be done on the International Space Station.
Inspired projects in mixing and separating metal phases
What did you do after completing your PhD?
I stayed on at the CSIRO Division of Minerals. I had some offers to do a postdoctoral fellowship in the US and the UK, but partly for reasons of job security I decided to stay. I have managed to maintain the links with those institutions and visit anyway, basically getting the sort of interaction I would have got as a postdoc. At CSIRO I managed to get a position as research scientist, in effect circumventing the postdoctoral level and going straight into the project level.
I am currently working on many, many projects, as project leader and also now senior research scientist/engineer. I do a multitude of contract projects, which we would call externally funded work – from both international and local companies – for probably 30 or 40 per cent of my time. The other 60 to 70 per cent would be the government funded, 'blue-sky' research, which is generally long-term, looking at trying to solve problems maybe 10 years hence, whereas the industry funding tends to be to solve day-by-day issues.
What sorts of projects have you got going?
I've got a couple that I can't talk about, but generally the theme of those sorts of projects is waste immobilisation – for example, using molten oxides to trap nasties like arsenic and lead, making them basically silicate oxides (called 'slag' in the metallurgical industry). They are essentially what you dig up out of the ground, so they become like geopolymers. You can immobilise toxins in slags and then put them in the ground, and we do leaching tests to see how environmentally stable they are. That's a booming area of work, as you would imagine.
Other areas I'm looking at include phase mixing. Just as you might make salad dressing at home, usually as a bottle of vinegar with oil, and often the two liquids will not mix until you shake them, so we want to bring the two phases – for example, oxide and metal – to mix together in a metallurgical vessel so as to get a good fast reaction. But then we want to look at ways to make those phases separate as fast as possible, so we can tap off the metal product with minimum impurities. That has both economic and also environmental implications, because the more efficient you can make that reaction, the fewer raw materials you need for a given output. The mixing of liquids and foams has been probably my main focus, and it has led to some other interesting new research areas also.
Defying gravity: container-less melting for impurity-free measurements
Would 'container-less levitation' be one of those other areas of research?
Yes. In this relatively new method we use very high frequency radio waves, about 400 kilohertz, to melt and actually levitate pieces of metal. You can use these radio waves to generate a very high current in a copper coil, a bit like a transformer coil. If you put a piece of metal – maybe one or two grams, not all that large – inside this coil, quite amazingly it will just suspend itself in air.
We call this melting or levitation 'container-less' because the metal sample now is not sitting in any crucible from which it could pick up impurities. The advantage is that we can do very accurate measurements on the surfaces of liquid metals without any influence from impurities. For example, we can measure the surface tension of the levitated metal and see how it changes with the oxygen partial pressure. That is, we can simulate how the oxygen in a metallurgical vessel gets less and less as you go deeper towards the metal – we can see how the surface tension changes, to help us predict how phases will mix in current processes or new ones.
Did your recent overseas visit relate to this work?
It did. As part of the Scientific Visits to Europe program of the Australian Academy of Science I received a grant to go to Germany, and at the invitation of some people that I had networked with at the German aerospace research centre in Cologne, near Bonn, I went there as a visiting scientist for one month. (I have just got back.) That group has sent experiments up on the microgravity research laboratories with NASA – into space on the Shuttle, and up on things like sounding rockets and the parabolic flights, the so-called 'Vomit Comets'.
It was very exciting. I was able to work there with them, learn about their new techniques, and look for ways to build German-Australian bilateral links and, hopefully, get involved in microgravity processing of materials. That is really another way of levitating metals. I have been levitating them on Earth by using radio waves, but if you use the microgravity on the international space station you need only heat the samples and do experiments. The idea is to look at advanced materials – how to make new metal alloys much cleaner, things like this – to get ideas for processing them back on Earth, so that when you do make ultra-strong alloys you don't have the impurities or the fatigue problems that you might get with aerospace alloys.
Focus questions
Select activities that are most appropriate for your lesson plan or add your own. You can also encourage students to identify key issues in the preceding extract and devise their own questions or topics for discussion.
levitation
metallurgy
microgravity
phase mixing
slag
waste immobilisation
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