http://www.kent.ac.uk

Functional Materials Group
nano-science.co.uk

Research into the Physics of Liquids and Solids on the Nano- to Meso-Scale

Dr. J.B.W. Webber.



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Nano-science :

We study the structure, dynamics and phases of nano-structured to micro-structured liquids and their solids.

Nano-scale to micro-scale volumetric metrology :

The techniques we are developing for nano-scale metrology are based on both physical thermodynamics (Gibbs equations) and on neutron and X-ray scattering.

Nano-science :

The properties of matter change considerably when the matter is structured on the nano-scale to meso-scale. In confined geometry the Gibbs Free Energy is greatly modified, resulting in changes to parameters such as diffusion, transport and the temperature at which phase changes take place.

We have now been studying the structure, dynamics and phases of nano-structured to micro-structured liquids and their solids for more than 15 years, and are actively unraveling the behaviour of liquids in confined geometry, and at and near surfaces. Even so there is much that we still need to understand about even such basic systems as water in a silica pore.

Much of this basic research has been carried out at the University of Kent, some of the recent work in conjunction with Heriot Watt University, and Lab-Tools are intending to continue these investigations in conjunction with both universities, both as research of great interest in its own right, but also as needed to support the metrology development.

Our main experimental techniques are based on:
  • NMR relaxation,
  • NMR cryoporometry (figure 2),
  • NMR diffusion in a magnetic gradient,
  • Neutron Diffraction (NS),
  • Small Angle Neutron Scattering (SANS) (figure 3),
  • X-ray Scattering,
  • N2 Gas Adsorption,
  • Differential Scanning Calorimetry (DSC) and
  • Thermoporosimetry.
Our analytic and simulation techniques include:
  • Direct analytic/numerical calulation of small angle neutron scattering from model porous systems, and their alignment to measured scattering results.
  • ab-initio Quantum Mechanical - Molecular Dynamic simulation of liquids at and near surfaces, in model porous systems - Figure 1.
3D Model of laminar silicon, with surface films of liquid nitrogen - one timestep from a CASTEP ab-initio QM MD simulation.
Figure 1: 3D model of laminar silicon porous system, with surface films of liquid nitrogen - one timestep from a CASTEP ab-initio QM MD simulation.

Nano-scale to micro-scale metrology :

There are numerous techniques for studing the metrology of surfaces. We are developing the application of physical thermodynamics and neutron and X-ray scattering techniques as tools for studying the metrology throughout the volume of a sample, on the nano-scale through meso-scale to micro-scale dimensions.

We have completed a number of academic research projects and industrial and commercial analysis projects using the techniques that we have developed.

Following the above basic research into the behaviour of liquids and their solids in confined geometry, in well characterised porous materials, we then apply this by imbibing these liquids into as yet uncharacterised porous systems, and use the knowledge that we have gained about the changes in their physical properties, when nano-structured, to deduce information about the host porous structure and metrology.
The basic techniques that use these changes in the thermodynamic properties in nano-structured systems are :
  • Gas adsorption,
  • Thermoporosimetry,
  • NMR Cryoporometry.
Of these techniques, NMR Cryoporometry is now often our preferred technique, although the others may provide invaluable comparative information. We have used NMR Cryoporometry in a number of academic research projects and industrial contracts, to measure pore volumes and pore size distributions in materials such as porous carbons, fired and un-fired clays, marine sediments, oil-bearing rocks, meteorite fragments ....
More detailed information about NMR Cryoporometry is available by following the link below to our NMR Cryoporometry pages.
Figure 2: Normalised pore size distributions for selected porous silicas, as measured by NMR Cryoporometry. The intrinsic resolution of the technique is better than the red curve, for SBA-15, which is fully resolved.

Lab-Tools performs contract analyses of Pore Size Distributions using NMR Cryoporometry :

Lab-Tools has measured pore sizes in a wide range of materials, and the technique can be applied to oil and/or water wet materials, and also to materials that can not be dried out without losing their structure.

The Lab-Tools pore-size distribution measurement range extends from about 1nm up to over 2Ám. Please contact us to discuss pore size measurements on your samples. Prices are competitive, but depend on the pore-size range to be covered, and precision needed.
We frequently find these techniques may be preferable to more established methods such as BET gas adsorption or DSC thermal porisimetry.

X-ray and neutron scattering based metrology calibration program :

With all these thermodynamic techniques, however there is increasingly a supposition that as atomic dimensions are approached, the calibration from the thermodynamics may change.

Thus we have mounted a separate metrology program using neutron and X-ray scattering. These have the advantage that they are inverse techniques, by which is meant that the smaller the structure being observed, the larger is the scattering angle.

Further, there is no existing reason to suppose that these scattering techniques are length-scale dependent. i.e. if one has a good calibration at one length-scale, it should also be good at all other length-scales.

To transform a measured scattering to a metric of the structures in the sample, we create extended models of pore systems, and calculate the scattering using numerical integration. These show very good agreement with measured scattering, figure 3.

Our existing measurements using sol-gel silicas have shown that while the thermodynamic techniques are in close agreement with the scattering measurements for dimensions above 10nm, below this dimension there appears to be an increasing divergence between the scales of the thermodynamic and scattering metrologies.

Figure 3: Fully density corrected radial distribution function measured for 7 sol-gel silicas (red lines), compared with that calculated for extended arrays of pores with Gaussian variance (green dots). FullScreen
cryoporometry.com
Cryoporometry pages
Porous-Media.com
Porous Media pages

Characterisation Capabilities

Lab-Tools Analysis Services are based in the Canterbury Enterprise Hub at the University of Kent, U.K., and in liason with the School of Physical Sciences at the University of Kent can offer a range of characterisation services, using both Chemical and Physical techniques. One of our main strengths is the range of characterisation techniques we can offer using Nuclear Magnetic Resonance, to study liquids, solids and structured matter.

Previous users

We have made physical analysis measurements for a number of international companies, including Shell, Unilever, Coates Lorilleux, and Lafarge Braas.

Publications

Some of our publications in the field of porous-media, nano-scale to micro-scale structured matter, and confined liquids :
For more information : E-mail me : J.B.W.Webber@kent.ac.uk, see : my publications , go to my research home page. Also, see my Thesis, or some of my posters, or our NMR pages.

Content, design & creation Dr. Beau Webber 2005.
2005_03_20, 2005-04-20, 2005-09-14, 2005-09-30