Functional Materials Group

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 have now been studying the structure, dynamics and phases of nano-structured to micro-structured liquids and their solids for more than 20 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.

Some of this basic research has been carried out at the University of Kent, some of the more recent work in conjunction with Heriot Watt University. Lab-Tools are continuing these investigations in conjunction with both universities, both in the Lab-Tools NMR laboratory and at central neutron scattering facilities. This research is of great interest in its own right, but also as needed to support the metrology development. Dr. Beau Webber has also been awarded a total of 88 days of neutron scattering time to aid these studies (23 days as main proposer), at the central facilities at the Institute Laue Langevin in Grenoble (ILL); Laboratoire Leon Brillouin (LLB), Saclay, Paris; at the Jülich Centre for Neutron Science (JCNS), Germany, and ISIS at the Rutherford Lab., to investigate this nano-science and nano-metrology.

Our main experimental techniques are based on: NMR relaxation, NMR Cryoporometry (NMRC), (figure 2, 3), NMR diffusion in a magnetic gradient (Static or Pulsed), Neutron Diffraction (NS), Neutron Diffraction Cryoporometry (NDC), (figure 4), Small Angle Neutron Scattering (SANS), Quaasi-Elastic Neutron Scattering (QENS), X-Ray Diffraction (XRD), 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)

NMR Cryoporometry is a technique for measuring pore size distributions that we originated at Kent and that I have extensively developed. 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.

Figure 2: An example melting point curve, for water ice melting in nominal 100 Angstrom pore diameter Sol-Gel Silica.

Figure 3: 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. We have now extended the range of the technique from about 1nm to nearly 10µm.

Figure 4: Neutron Diffraction Cryoporometry (NDC) - a technique which I originated for studying phases as a function of temperature.

Ice Flow in Glaciers and Ice Packs

Gas Hydrates confined in Marine Sediments

Nano-scale to micro-scale metrology :

We have completed many academic research projects and also industrial and commercial analysis projects for high-profile companies 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.

More information on Lab-Tools Ltd. contract nano- to micro-metrology may be found on our nano-metrology page : www.nano-metrology.co.uk/ 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.

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 to nearly 10µm. Please contact us ( Dr. Beau Webber ) to discuss pore size measurements on your samples. Prices are competitive, but depend on the number of decades of pore-size range to be covered, and precision needed, as these determine the duration of the measurement meeded, which can range from 2 hours to 36 hours. 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. Dr. Beau Webber has been awarded measurement time at the Institute Laue Langevin (ILL), on the D4 and D22 instruments, and this has enabled him to develop and verify his models. Dr. Beau Webber was recently awarded measurement time (as first user) on the excellent new wide-scattering range ISIS Target Station 2 instrument NIMROD, and 17 porous samples were measured on this most successful run, with very pleasing preliminary results. Simulation models are being run to match the results, and the models, results and conclusions will be presented in a paper.

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).

Cryoporometry pages

Porous Media pages

Publications

• Combined publications list
• Prof. John Dore
• Prof. John Strange
• Dr. Beau Webber