RESEARCH PROGRAMS & HIGHLIGHTS

Again this year we include in the Annual Report, a complete listing of all projects. Responses from you, out target audience, were overwhelmingly supportive of such a detailed listing. In this Programs and Highlights section we have selected various projects and reported the outputs and trends we believe are significant. Our science supports the now familiar technological areas or domains of;

The technologies encompassed within these three headings change as Australian industry responds to various opportunities on the international scene. At present our Australian mineral industry has chosen to move away from chemical processing of beach sand minerals to produce ceramic grade zirconia powders. Such a move does not mean that we give up directing our resources to science themes underlying ceramic, refractory oxide or pigment particle processing; the experience we have gained with such powders as model systems has been of great value as we look right across the mineral and other process engineering fields.

Interestingly, our work has been of sufficiently high quality in the advanced ceramics area to continue to attract interest from that business area overseas. As often happens, an international reputation in an area of science can act as a valuable international link for Australian business.

The highlights that follow and the detailed project listing again emphasizes our core science involvement.

PARTICLE FLUIDS is the essence of our work using "solid" particles of zirconia, alumina, clays, polymer latex, titania, copper sulfides and the like where high volume fraction dispersions become classic non-Newtonian fluids. The lessons we are learning from these studies fall under the two important headings of; The first of these effects has been the subject of many of our projects and in this and earlier reports we demonstrate our success in measuring many components of surface forces. The second, relating to how particles pack in high volume fraction particulate fluids in flow and at rest, is an area of much current concern. A major contributor to our work is Professor P.C. Kapur from the Indian Institute of Technology (I.I.T.), Kanpur.


Professor TW Healy and Professor PC Kapur

He has made many notable contributions to areas of particle physics and chemistry in relation to agglomeration, comminution, flotation and solid-liquid separation. The problem of packing in particulate fluid networks is a singularly difficult field of research. The logic goes as follows: if one knows the interparticle force law, and the volume fraction dependence of packing and nearest neighbour geometry, then one could generate a normalized flow curve. Alternatively one could take flow curves at a series of volume fractions and if one knew the volume fraction dependence of packing and nearest neighbour geometry, then one could generate the two body force law. Some of us are now wondering about turning this kind of logic around using the flow curves and force law to generate the elusive volume fraction dependence of the packing! Professor Kapur will be back with us in early 1996 to face yet another list of difficult questions.

NANOTECHNOLOGY has not been a part of the lexicon of AMPC; It has become none-the-less a word that seems to be here to stay. We have always spoken of nanoparticles as ultrasmall colloids or Q-State particles or cluster colloids - all words that means that the particles are at a size where their physical properties begin to differ from a bulk macroscopic sample of the same material. For example ultrasmall CdS colloids of diameter 4 nm begin to absorb at a wavelength of 450 nm while bulk CdS is dark yellow and adsorbs below 525 nm.


Dr. Michael Giersig

In July 1995 Dr Franz Grieser presented some of his ultrasmall colloid work as an invited lecture at the NATO Advanced Research Workshop entitled "Fine Particle Science and Technology - From Micro to Nanoparticles". The papers at this important international workshop illustrate that the word "nano-particle" is used to describe particles in the 1 - 100 nm diameter range. It is only below the 10 nm range where most semiconductor particles begin to show quantum size effects as detected by blue shifts in their optical properties and where non-linear optical effects are enhanced significantly. Their redox properties change similarly.


Dr. Luiz Liz-Marzan

The great challenge facing the world of nanoparticles is that to keep them from coagulating or ripening they need to be protected by substantial steric or electrosteric barriers of organic polymers, polyphosphates, polysilicates and the like. Thus a move to production of such particles on a large scale - implied by many who use the word nanotechnology, is some way off. We plan to contribute to advancing the world of nanotechnology.

The international team that Paul Mulvaney has assembled consists, in 1995, of himself with Dr Michael Giersig from the Hahn-Meitner Institute in Berlin, Dr Luis Liz-Marzan from Vigo University, Spain, and Mr Thearith Ung, a Ph.D. student. As part of their ÒnanoparticleÓ work they have taken a lateral step of growing quite thick, coherent coatings of hydrous Stober silica onto ultrasmall (15 nm diameter) gold particles. In the past, 5 nm coatings of silica on TiO2 pigment particles were first achieve by Ralph Her in the U.S. and a little bit later by Neil Furlong (then in the U.K.). However, the coatings produced by the Mulvaney group have some very special properties that make the total system quite exciting. As made, the thick silica coating is permeable to oxygen-cyanide and the gold can be dissolved. However, if the coated particles are heat treated hydrothermally or by electron beam irradiation, oxygen-cyanide does not dissolve the gold.

SOLVENT EXTRACTION research has been focused on the development of fundamental issues that relate to reliable methods of scale up of solvent extraction equipment and the optimisation of equipment performance.

Currently we are examining the distribution of organic and aqueous phases in large diameter extraction columns, where the potential for bypassing or maldistribution exists, causing serious reduction in performance. This work has identified a number of important mechanisms by which this can occur and we have been able to develop strategies for overcoming these. In addition we have been using novel tracer techniques to measure the velocity of individual droplets in droplet swarms, and to measure axial and forward mixing in extraction columns. This had led to a series of models for the prediction of the effect of process conditions on the performance of extraction equipment.

During 1995 these techniques have been used to assess and scale up data from the nickel-cobalt pilot plant run by Dominion Mining in Western Australia, the vanadium extraction plant run by Clough Engineering Limited, and uranium and copper extraction in a column test by Western Mining Corporation at Olympic Dam.

In addition, we are working with Gunpowder Mining Operations, ICI and Zeneca in developing a new copper recovery process which will reduce raw materials usage. This environmentally safe process is based on the recovery and recycling of sulphuric acid using extraction column and is about to move into pilot testing stage, making use of our extraction column design techniques.

INTERNATIONAL visitors during 1995 provided AMPC with considerable stimulus. Two very senior visitors were Professors Abraham Lenhoff and John Anderson from the Departments of Chemical Engineering at the University of Delaware and Carnegie-Mellon Universities respectively.


Professors Abraham Lenhoff (left) and John Anderson

Their sabbatical leave with us made sense because of our well tested linkages between Chemical Engineering, Physical Chemistry and Applied Mathematics at the University of Melbourne. John Anderson initiated ongoing work in Maths with Derek Chan, Steve Carnie and Jonathan Ennis-King. Dr Alex Shugai (an ARC Posdoctoral Fellow) is continuing their work. They are considering how colloidal particles move in electrokinetic experiments if a particle double layer is in overlap with that of another particle, or, that of a wall material. Solution of such problems is vital to an understanding of transport in concentrated dispersions.


Dr. Alex Shugai, at work on the rotation of colloidal doublets in electrophoresis

Professor Lenhoff also began work when he was with us on trying to understand the adsorption and packing of colloidal particles on flat surfaces. In collaborative work, again with our Maths group of Derek Chan and Steve Carnie, a "Random Sequential Adsorption" model of adsorption has been developed which accurately predicts the uptake of positive latex particles on anionic mica basal plane surfaces.

The paper on this work will involve the two Delaware students Matt Oberholzer and Chris Johnson who came to AMPC while Professor Lenhoff was here, as well as our student, Jim Stankovich along with Derek Chan and Steve Carnie. We are delighted with the ongoing international links we have built with these two groups in the U.S.A. and of the joint publications that confirm the success of any such interaction.

ENVIRONMENTAL science and engineering is a direct or indirect concern of many of our programs. AMPC is delighted to record the fact that the Finnish Academies of Technology have awarded the 1995 Walter Ahlstrom environmental Prize to Professor David Boger of the University of Melbourne. Professor Boger has developed a technology for dealing with non-Newtonian fluids which has lead to an application in which the residues in connection with aluminium production can be materially reduced. This technology, which is designed for dealing with exceptionally well behaved liquids contributes to knowledge in rheology and potentially applicable in a number of other areas of technology as well. The Walter Ahlstrom Prize is awarded annually for significant technological achievements in the areas of industrially applicable advances in the use of energy and raw materials, and for the minimising of environmental impact. The Walter Ahlstrom Prize is administered by the Finnish Academies of Technology and is funded by the Walter Ahlstrom Foundation. The prize winner is nominated by an international prize committee. Walter Ahlstrom was President of the Ahlstrom Corporation (est. 1851) in the period 1907-1931. He established the foundation bearing his name to encourage and support promising young engineers in their professional work. The Ahlstrom Corporation today is a globally operating paper and engineering group with sales of 2.8 billion USD and around 12,000 employees worldwide.

Australia is the world's largest producer of Alumina and production by the Bayer-process generates enormous quantities of bauxite residue, so called red mud. Boger's research at solving the waste problem was based on non-Newtonian fluid mechanics and funded in part by Alcoa of Australia. The resulting six-year research program was very successful and the technology developed is now used by three major Alcoa plants in Western Australia and is being picked up by other aluminium plants worldwide. The fact that a typical Australian aluminium plant produces as much as 10,000 tonnes of dry residue a day displays the impact of the solution.


Professor DV Boger with the 1995 Walter Ahlstrom Prize

Walter Ahlstrom Environmental Prize, given annually since 1990, was awarded at the Awards Meeting of the Finnish Academies of Technology on November 30, 1995 in Helsinki.