Professor Peter McDonald

Nuclear magnetic resonance (NMR) spin-lattice (T?1 1 ) and spin-spin (T?1 2 ) relaxation rate mea- surements can act as e ective non-destructive probes of the nano-scale dynamics of 1H spins in porous media. In particular, fast- eld-cycling T?1 1 dispersion measurements contain information on the dynamics of di using spins over time scales spanning many orders of magnitude. Previously- published experimental T?1 1 dispersions from a plaster paste, synthetic saponite, mortar and oil- bearing shale are re-analysed using a model and associated theory which describe the relaxation rate contributions due to the interaction between spins ensembles in quasi-two-dimensional (Q2D) pores. Application of the model yields physically-meaningful di usion correlation times for all systems. In particular, the surface di usion correlation time and the surface desorption time take similar values for each system suggesting that surface mobility and desorption are linked processes. The bulk uid di usion correlation time is found to be 2-5 times the value for the pure liquid at room temperature for each system. Re-analysis of the oil-bearing shale yields di usion time constants for both the oil and water constituents. The shale is found to be oil-wetting and the water T?1 1 dispersion is found to be associated with aqueous Mn2+ paramagnetic impurites in the bulk water. These results escalate the NMR T?1 1 dispersion measurement technique as the primary probe of molecular-scale dynamics in porous media yielding di usion parameters and a wealth of information on pore morphology.

H nuclear magnetic resonance (NMR), supported by a measurement of the degree of hydration using X-ray diffraction, has been used to fully characterise the nano-scale porosity and composition of calcium-silicate-hydrate (C-S-H), the active component of cement. The resultant "solid" density and composition are Á = 2.68 g/cm; (Ca). (Si,Al)O. (HO) for an underwater cured, never-dried cement paste with an initial mix water-to-cement ratio of 0.4 after 28 days of hydration. In addition, the first pore-type resolved desorption isotherm of cement that shows the location of water as a function of relative humidity has been measured. Critical to our results is verification of the assignment of the different NMR spin-spin relaxation time components. These have been corroborated with conventional analyses. The new methodology is key to enabling design of cement pastes with lower environmental impact.

This thesis describes a series of 1H nuclear magnetic resonance (NMR) experiments to investigate connectivity of the the nanopores of the calcium-silicate-hydrates (C?S?H) in cement based materials. This is achieved by coupling 1H NMR relaxometry in one and two relaxation times dimensions and 1H NMR cryoporometry down to about -80C. In particular the thesis contains the first use in any system of coupled two dimensional relaxometry and low temperature cryoporometry.
The cryoporometry has been validated on model porous silica glass (SiO2) materials with known pore sizes and then applied to C2S and C3S, in cement chemistry notation, otherwise known as alite and belite. The 1H NMR cryoporometry data was used to estimate the pore sizes in C2S. It was found that the T2 relaxation time depends on temperature in C2S and C3S, but not in porous glasses SIO2 and MCM-41. There are two possible explanations. It could be due to the interaction of water with the -OH groups on the pore surface. It is known, that water, or a monolayer of water becomes physisorbed on silanol groups. Silanol groups are present both at the silica glasses surfaces as well at the cement pores surfaces. However, there are no many studies available on the interaction of water-silanol groups and temperature dependency below 0C. The other explanation concerns hydrated calcium ions in cementitious materials not present in silica glasses. However, little is known about C?S?H surfaces.
A two dimensional 1H NMR T2 ? T2 exchange experiment was used to investigate the exchange of water between interlayer spaces, gel pores and capillary pores at temperatures of room temperature, -5C and -30C on cooling and again on warming in C3S. A 3- site exchange numerical model was written to solve the associated coupled differential magnetisation exchange equations. By comparing the model output and experimental data it was shown that water exchanges between interlayer spaces and gel pores and between interlayer spaces and capillary pores. However, there is no exchange from gel pores to capillary pores.
A further set of room temperature experiments were carried out to investigate the change in the pore size distribution of C-S-H in white cement following desorption and resorption of water as a function of drying severity. Rearrangements of the nano porosity were seen dependant on the severity of the drying. There were both reversible and irreversible changes. However, the total pore volume remained constant within measurement error. Most interestingly for more severe drying relaxation of the pore size distribution was seen for several days following resorption of water.
All the experimental work was carried out at the LafargeHolcim research laboratories in Lyon, France. The thesis also contains details of the adaptation necessary to carry out experiments described on a standard Maran Ultra 23.5 MHz NMR spectrometer.

A model linking the molecular-scale dynamics of fluids confined to nano-pores to nuclear magnetic resonance (NMR) relaxation rates is proposed. The model is used to re-analyse fast field-cycling spin-lattice relaxation rate measurements for the separate water and oil dispersions from an oil-bearing shale [Korb et al., J. Phys. Chem. C, 118, 199 (2014)]. The model assumes that pore fluid can be characterized by three time constants: the surface and bulk diffusion correlation times and a surface desorption time constant. Results are shown to yield meaningful and consistent intra-pore dynamical time constants, insight into diffusion mechanisms and pore morphology. The shale is found to be oil-wetting and the water dispersion is found to be due to the interaction of aqueous Mn2+ ions with bulk water spins. Clay, mortar and plaster paste dispersions measurements have also been successfully re-analysed and a summary of the results is presented. The results demonstrate the wide applicability of the model which advances NMR dispersion experimentation as a powerful tool for measuring nano-porous fluid properties.

Changes of water state within the pore structure of cement paste due to temperature changes are followed by means of 1H-proton nuclear magnetic resonance (NMR) relaxation analysis. The study shows that with increasing temperature, the signal due to water contained in the smallest C-S-H interlayer spaces decreases while that from the larger gel pores, and to a lesser extent from the capillary pores, increases. On cooling, the opposite behavior is observed with complete reversibility. The observed changes in water populations appear to be instantaneous compared to the rate of temperature change in the samples. These changes are postulated to be responsible for macroscopically observed changes of relative humidity in pores during heating/cooling and are therefore key in understanding thermal deformations of cement based materials. It is evident that the previous hypothesis of microstructural delayed water transport being responsible for macrostructural delayed thermal deformations can be rejected. Different microstructural mechanisms are discussed that could explain the redistribution in water signals, namely water migration and pore rearrangement mechanisms.

Improvement in the signal-to-noise ratio of Nuclear Magnetic Resonance (NMR) systems may be achieved either by increasing the signal amplitude or by decreasing the noise. The noise has multiple origins ? not all of which are strictly ?noise?: incoherent thermal noise originating in the probe and pre-amplifiers, probe ring down or acoustic noise and coherent externally broadcast radio frequency transmissions. The last cannot always be shielded in open access experiments. In this paper, we show that pulsed, low radio-frequency data communications are a significant source of broadcast interference. We explore two signal processing methods of de-noising short

This paper describes results that combine Shan-Chen two-phase (liquid-vapour) and
partial-bounce back (semi-permeable membrane) methods of Lattice Boltzmann
numerical modelling of fluid dynamics in order to understand how bordered pits
influence the drying and rewetting of wood. In addition, preliminary results that
introduce pressure induced distortion are included.

This paper demonstrates a model of softwood geometry that can be used for multiscale
modelling of the longitudinal movement of water through spruce wood. Previous results
obtained from a high resolution X-ray CT scan and subsequent image analysis of a large
number of Norway spruce tracheids were here used to produce a model that can
represent the variability in wood anatomy found within a timber joist or log. A
demonstration of that model is given.

The role of a PhD programme is to train
students for a career in research ? be it at
university or in industry. In our experience,
almost all physics students who begin a PhD
hope for an academic career, yet the overwhelming
majority eventually move into
industry where they contribute hugely to
the research and development of firms.
Although this picture seems to be accepted
by those now embarking on a PhD, many
students still have little idea how they could
exploit their physics PhD beyond the narrow
confines of their research project.
In 2008 ? a difficult time for UK physics,
which suffered funding cuts and department
closures ? nine university departments
in the south east of England came
together to form the South East Physics network
(SEPnet). This collaboration helped
revive physics in the region by focusing on
outreach as well as student employability
via a summer industry placement scheme.
In 2013 SEPnet launched GRADnet to
give PhD physics students greater awareness
of opportunities outside academia and
a broader set of the skills that are needed
to exploit them.

Fast-field-cycling nuclear-magnetic-resonance (FFC NMR) experimentation measures the spin-lattice relaxation rate T1?1=R1 as a function of NMR frequency f. It is a proven technique for probing the nanoscale dynamics of H1 spins over multiple timescales. In many porous systems, fluid is confined to quasi-zero-dimensional (closed), quasi-one-dimensional (channel), or quasi-two-dimensional (planar) pores. Expressions are presented for R1(f) providing simulated dispersion curves for closed, channel, and planar pores where relaxation is associated with fluid movement relative to fixed relaxation centers in the solid. It is shown that fluid confined to nanosized (1?5 nm) spaces can be identified by submillisecond relaxation times for any geometry. The shape and magnitude of R1(f) is shown to be sensitive to pore geometry at low frequency only if relaxation is dominated by the motion of pore bulk fluid. Relaxation in most porous material is dominated by slow-moving surface fluid. Here, the pore geometry can only be distinguished if the relaxation center density is known a priori and then only at very low frequency. Systems containing mixtures of closed, channel, and planar pores of similar characteristic dimension h would present as three peaks at low frequency with closed pores providing the largest R1 and planar pores the smallest. Pore size and shape variability in real systems is shown to diminish the ability to distinguish the three peaks. We show that the ratio T1/T2, where T2 is the spin-spin relaxation time, is a complex function of h, the surface diffusion time constant Ä?, and NMR frequency for f>1 MHz. It is shown that measurements of T1/T2 at 20 MHz in cement paste and hydrocarbon rock capture information on both Ä? and h.

¹H nuclear magnetic resonance (NMR) relaxometry, supported by X-Ray diffraction and thermogravimetric analysis, has been used to characterise microstructure of white cement pastes underwater cured at temperatures in the range 10°C to 60°C. As the temperature increases, so the C-S-H, capillary pore water and interhydrate pore water content all increase; the ettringite and gel pore water content decrease; and the Portlandite content stays constant. A non-linear increase in the C-S-H ?solid? and ?bulk? densities, that exclude and include gel pore water respectively, has been observed with the increase of temperature. This is accompanied by a decrease in C-S-H water content but no change in the Ca/(Si/+/Al) ratio. The increase in the C-S-H ?solid? density has been attributed to a decrease in the number of locally stacked C-S-H layers. The increase in the C-S-H ?bulk? density is additionally attributed to the decrease in the gel porosity.

The mobility of water within the microstructure of hardened cement paste has been at the center of a long-lasting debate, motivated by the need to understand the fundamental mechanisms that play a role in drying, shrinkage, creep and thermal expansion. Our ¹H NMR results show for the first time that externally-applied pressure can lead to migration of water within the microstructure (microdiffusion). Upon compression, the gel water signal decreases. For the most part, this is accommodated by a corresponding increase in the signal of water in larger, interhydrate and capillary spaces. However, there is also an increase in the signal corresponding to the water in most confined spaces. Normally such tiny spaces are classified as hydrate interlayers. However, we do not conclude that there is a significant increase in interlayer water. Rather we attribute this part of the increase to a rearrangement of the microstructure upon compression with some water confined in increasingly small gel pore spaces. These findings show that the deformability of the microstructure (C-S-H gel) at the expense of gel porosity may explain part of the macroscopic deformations due to short-term creep.

This study aimed to define the variability in the microstructure of Norway spruce within an annual ring by examining differences between earlywood and latewood. In particular we were interested in obtaining new information on bordered pit occurrence and locations relative to tracheid ends, plus the lumina dimensions and longitudinal overlap of tracheids that collectively define the longitudinal hydraulic pathways. A stacked series of X-ray micro-CT scans of an annual ring of Norway spruce were made and stitched together longitudinally to form a three-dimensional volume. The imaging resolution was carefully chosen to capture both longitudinal and transverse anatomical details. Measurements of tracheid length; overlap; radial lumen diameter and bordered pit location were made semi-automatically using image analysis. The distribution of radial lumen diameter was used to define earlywood and latewood. Then bordered pit linear density and spatial distribution, tracheid length and overlap were analysed, presented and contrasted for earlywood and latewood. Further differences between earlywood and latewood were found only in bordered pit linear density.

Clear trends in radial lumen diameter and pit linear density were observed with radial position within the growth ring. These results provide new information on the variability of the Norway spruce microstructure within an annual ring.

The link between anomalous water sorption and dynamic porosity in cement pastes is explored using spatially resolved GARField 1H nuclear magnetic
resonance (NMR) relaxation analysis. A model is developed in which the effective capillary di?usion coe?cient is dependent on the instantaneous pore
size distribution. This and earlier data show changes in pore size distribution resultant from changes in saturation that do not occur instantaneously
with changes in degree of saturation. Therefore, it is assumed that the pore size distribution is always relaxing exponentially towards a (saturation de
pendent) equilibrium. It follows that the di?usivity is sample history (i.e.time) dependent as well as saturation dependent. This is su?cient to ex
plain anomalies in rapid capillary water sorption. The same concepts are applied to slow drying. In this case, porosity changes occur on a timescale
much shorter than drying so the system is always in dynamic equilibrium and anomalies are therefore not seen.