Prof Julian Evans
Materials and Inorganic Chemistry
Prof Julian Evans
Address: Department of Chemistry, UCL
Phone No: +44 (0)20 7679 4689
Fax No: +44 (0)20 7679 7463
Research areas of interest include:
- Ceramic and powder processing
- Solid freeforming and rapid prototyping
- Ceramic ink-jet printing
- Extrusion freeforming (hard tissue scaffolds and metamaterials)
- Solid freeforming of 3D functional gradients
- Combinatorial and high throughput methods for materials discovery
- Polymer-clay nanocomposites
- Ordered polymer clay nanocomposites: the quest to simulate the nacre microstructure
- Polymers derived from biomass, particularly food waste
- Foams and their deployment for enhancement of oceanic albedo
Our work includes Polymer-clay Nanocomposites in which low levels of mineral addition increase mechanical and transport properties of polymers, Ordered, Biomimetic Mineral-polymer Composites in which layered minerals at high volume fraction emulate the structure of mollusc shells, Extrusion freeforming of EBG structures and hard tissue scaffolds and High Throughput experiments on ceramics. The image shows a robotic ink-jet printer for making thick film ceramic samples.
- X.Lu, Y.Lee, S.Yang, Y.Hao, J.R.G.Evans, C.G.Parini, Solvent-based paste extrusion solid freeforming, J.Euro. Ceram. Soc. 30, 1-10, 2010
- F.Akthar, J.R.G.Evans, High porosity (>90%) cementitious foams, Cement Conc. Res. 40, 352-358, 2010.
- L.F.Chen, J.R.G.Evans, Spontaneous manufacturing: ceramic 128-well plates made by droplet drying, Adv. Appl. Ceram. 109, 51-55, 2010.
- H.Y.Yang, X.P.Chi, S.Yang, J.R.G.Evans, Mechanical strength of extrusion freeformed calcium phosphate filaments, J. Mat. Sci. Mater. in Medicine 21 , 1503 2010
- R.C.Pullar, Y.Zhang, L.Chen, S.Yang, J.R.G.Evans, A.N. Salak, D.A.Kiselev, A.L.Kholkin, V.M.Ferreira, N.McN.Alford, Dielectric measurements on a novel Ba1-xCaxTiO3 (BCT) bulk ceramic combinatorial library, J. Electroceram. 22, 245-251, 2009.
Professor J.R.G.Evans BSc, PhD, CEng, CSci, FIMMM, MRSC has a wide background in the materials sciences, starting out with a degree in industrial metallurgy followed by a Ph.D in polymer-metal adhesion and surface science, two years as a post-doc in adhesive bonding, a short period in the specialist printing industry and four years in the Ceramics Department at Leeds University. He worked for 14 years at Brunel University helping to set up a very successful group in ceramic processing using injection moulding, adapting other polymer processes for ceramics, then pioneering the direct ink-jet printing of ceramics and related techniques. He moved to Queen Mary, University of London in 1998 focusing on solid freeforming for applications in hard tissue scaffolds and metamaterials and starting work on polymer-clay nanocomposites. He joined UCL in 2007 where he engages with the widely distributed Materials Science community throughout the College.
He has eclectic interests and is especially keen on the philosophy and history of science, believing fervently that their study, wisely mediated, benefits the imaginative and creative features of the scientific mind, helping to release, from the enclosures of the pedagogic process, a discovery mentality. He also believes that humour is an important ingredient of the creative process as expressed in an article in UCL’s magazine, Sophia. His other interests are baroque music, to the consternation of his colleagues in adjacent offices and art blacksmithing to the consternation of his neighbours in adjacent houses and the rebuilding of antique clocks which, unlike the other activities, only offers nuisance value on the hour.
What role does Materials Science have in a Chemistry Department?
Chemistry is a subject so vast that it could fill the undergraduate curriculum many times over. Does this mean that there is room for nothing but core chemistry? Maybe. There is a view that the dangers of over-teaching and consequent over-assessment, which can contribute to motivational loss among students can only be addressed by pruning the curriculum down to principles. Perhaps we need a version of Plato’s ‘pure forms’ in the Chemistry curriculum as distinct from Plato’s ‘actuals’.
The problem is that only a small proportion of today’s students have a high tolerance for pure abstraction just as did only a small proportion of scientists through history. Paul Dirac is perhaps an exception that tests the rule but Faraday and Newton, for example, were involved in all sorts observation of macroscopic forms which, I suspect, informed them and from which abstraction , ergo theory, emerged.
Consult the personal statements of applicants to chemistry, formulaic as they may be, and you find clues to motivation. “My sister died from cancer and I want to participate in finding cures for horrific diseases”. The experienced admissions tutor might smile benignly at these enthusiasms but the maintenance of motivation throughout a challenging four year undergraduate course is an integral part of the responsibility of an educator.
Part of the constraint on the Chemistry curriculum is the limit to scale. The Chemist deals with dimensions that are a small multiple of the chemical bond and nothing much beyond. Beyond lie the territories of ‘others’. The Materials Scientist’s province, on the other hand, is located anywhere between Chemistry and Engineering. The properties of a material are causally related to structure. But this means structure at all levels: electronic structure, molecular structure, crystal structure, microstructure and even macrostructure. The strength of a macroscopic body constructed from a brittle material is a function of its absolute volume. This arises from the probability of finding a large critical defect. So one of the first things Materials Science contributes to the student Chemist is that the properties of materials are not wholly related to the chemical bond by causation. In that case, how far up the scale should they be allowed to roam?
The approach that I have been taking is that they can roam
where they like provided that they are at home with the pair potential curve
and its derivative which should always be seen as a safe place to which they
can return and is firmly embedded in Chemistry. I have found that the potential
energy curve is rarely differentiated in the Chemistry curriculum. But as soon
as it is, we have a bridge from Chemistry into Engineering (see diagram below),
for once differentiated we see how force depends on separation distance. The
force is related to stress and the separation distance to strain. The slope of
the curve at F=0 gives us the elastic moduli. The turning point gives us the theoretical
strength. Many properties can be traced back to these diagrams. The asymmetry
of the well gives us thermal expansion coefficient. The dislocation pipe
presents higher energy because the atoms are locally out of position and that
in turn explains why the dislocation has a line tension. Stacking fault energy
is explained, grain boundary, surface and phase boundary energies appear
inevitable. The pair potential and its
derivative therefore allow the student to roam through the orders of magnitude
and yet be anchored to an intellectual home that is firmly in the Chemistry