Reducing water ingress into the Shaft at Dounreay is essential for the success of future intermediate level waste (ILW) recovery using the dry retrieval method. The reduction is being realised by forming an engineered barrier of ultrafine cementitious grout injected into the fractured rock surrounding the Shaft. Grout penetration of 6m in <50μm fractures is being reliably achieved, with a pattern of repeated injections ultimately reducing rock mass permeability by up to three orders of magnitude.

An extensive field trials period, involving over 200 grout mix designs and the construction of a full scale demonstration barrier, has yielded several new field techniques that improve the quality and reliability of cementitious grout injection for engineered barriers.

In particular, a new method has been developed for tracking in real-time the spread of ultrafine cementitious grout through fractured rock and relating the injection characteristics to barrier design. Fieldwork by the multi-disciplinary international team included developing the injection and real-time monitoring techniques, pre- and post injection hydro-geological testing to quantify the magnitude and extent of changes in rock mass permeability, and correlation of grout spread with injection parameters to inform the main works grouting programme.

The hardnesses of secondary cell wall laminae (SCWL) and compound corner middle lamellae (CCML) in wood were measured at indentation strain rates between approximately 7×10-4 s-1 and 20 s-1, using a new method called broadband nanoindentation creep. The wood was subsequently modified with ethylene glycol (EG) and the properties were re-measured. The SCWL and CCML responded differently to this modification: in the SCWL, hardness decreased uniformly by a factor of 3.7 ± 0.3 across all strain rates, whereas in CCML, the modification had a similar effect at low strain rates. However, at high strain rates, hardness was only lowered by a factor of 1.8. The EG modification also lowered elastic modulus of the SCWL and CCML, swelled the SCWL and CCML, and caused previously placed indents to disappear (CCML) or partly disappear (SCWL).

In the UK, blended high level nuclear waste (HLW) streams from the Magnox and THORP reprocessing plants are currently vitrified using a lithium sodium borosilicate base glass frit. Laboratory and full size non-radioactive simulations (produced on the Vitrification Test Rig at Sellafield [1]) of these compositions have shown that these glasses need to be melted at circa 1050°C to obtain a reasonable viscosity for pouring. Also, at high waste loadings an alkali molybdate phase (termed “yellow phase”) can form in these glasses [e.g. 2, 3]. Vitrification flowsheets are set to avoid yellow phase formation as this phase is highly corrosive to the inconel melter in the molten state and is partially water soluble at ambient temperature and so may challenge product quality.

Ca and Zn additions to the base glass frit have been found to reduce viscosity and allow melt homogeneity and pouring at lower temperatures. It was also theorised that Ca additions could increase the solubility of Mo and thus reduce the likelihood of yellow phase formation. The composition of the phase separated material in as-cast and heat treated specimens of Ca and Zn HLW glasses produced at both laboratory and full scale is examined in this work

Excess plutonium not destined for burning as MOX or in Generation IV reactors is both a long-term waste management problem and a security threat. Immobilisation in mineral and ceramic-based waste forms for interim safe storage and eventual disposal is a widely proposed first step. The safest and most secure form of geological disposal for Pu yet suggested is in very deep boreholes and we propose here that the key to successful combination of these immobilisation and disposal concepts is the encapsulation of the waste form in small cylinders of recrystallized granite. The underlying science is discussed and the results of high pressure and temperature experiments on zircon, depleted UO2 and Ce-doped cubic zirconia enclosed in granitic melts are presented. The outcomes of these experiments demonstrate the viability of the proposed solution and that Pu could be successfully isolated from its environment for many millions of years.

Magnesium hafnium tungstate [MgHf(WO4)3] was synthesized by high-energy ball milling followed by calcination. The material was characterized by variable- temperature neutron and x-ray diffraction. It crystallized in space group P21/a below 400 K and transformed to an orthorhombic structure at higher temperatures. The orthorhombic polymorph adopted space group Pnma, instead of the Pnca structure commonly observed for other A2(MO4)3 materials (A = trivalent metal, M = Mo, W). In contrast, the monoclinic polymorphs appeared to be isostructural. Negative thermal expansion was observed in the orthorhombic phase with αa = −5.2 × 10−6 K−1, αb = 4.4 × 10−6 K−1, αc = −2.9 × 10−6 K−1, αV = −3.7 × 10−6 K−1, and αl = −1.2 × 10−6 K−1. The monoclinic to orthorhombic phase transition was accompanied by a smooth change in unit-cell volume, indicative of a second-order phase transition.

Vertical stacking of transistors is a promising technology which can realize compact and high-speed integrated circuits (ICs) with a short interconnect delay and increased functionality. Two layers of low-temperature fabricated single-grain thin-film transistors (SG TFTs) have been monolithically integrated. NMOS mobilities are 565 and 393 cm2/Vs and pMOS mobilities are 159 and 141 cm2/Vs, for the top and bottom layers respectively. A three-dimensional (3D) inverter has also been fabricated, with one transistor on the bottom layer and the other on the top layer. The inverters showed an output voltage swing of 0 to 5 V with a switching voltage of around 2 V.

We have shown recently that the degradation of AC electroluminescence (EL) in ZnS:Cu,Cl and similar phosphors can be significantly reversed by a short anneal near 200°C. To better understand the degradation/rejuvenation processes, we investigated EL degradation and rejuvenation under different conditions. To probe for changes in the local atomic structure about the Cu sites, we collected Extended X-ray Absorption Fine Structure (EXAFS) data at the Cu K-edge EXAFS data for several as-made, thermally degraded (240°C anneal), and EL degraded powders.

In this work the Si interstitial contribution of F+ implants in crystalline Si is quantified by the analysis of extended defects and B diffusion in samples implanted with 25 keV F+ and/or 40 keV Si+. We estimate that approximately 0.4-0.5 Si interstitials are generated per implanted F+ ion, which is in good agreement with the value resulting from the net separation of Frenkel pairs obtained from MARLOWE simulations. The damage created by F+ implants in crystalline Si may explain the presence of extended defects in F-enriched samples and the evolution of B profiles during annealing. For short anneals, B diffusion is reduced when F+ is co-implanted with Si+ compared to the sample only implanted with Si+, due to the formation of more stable defects that set a lower Si interstitial supersaturation. For longer anneals, when defects have dissolved and TED is complete, B diffusion is higher because the additional damage created by the F+ implant has contributed to enhance B diffusion.

Because of its significant potential in controlling key steps of apatite mineralization, recombinant amelogenin has been applied in different in vitro systems for the synthesis of uniquely ordered composite material similar to enamel. Here we summarize the results of a series of experiments, in which mineral deposition took place on the exposed surface of enamel from extracted human third molars soaked in calcium phosphate solution, in the presence of amelogenin and fluoride. Analysis of crystal size and morphology revealed that in the presence of both amelogenin (50-100 μg/mL) and fluoride (1 ppm), bundles of oriented rod- like fluoridated apatite crystals were formed creating a dense coating on the enamel substrate. Such organized bundles were not formed at low concentrations of rP172 (< 30 μg/mL). Preparation of such ordered nanocomposites provides a promising approach for development of new generation of dental restorative materials with improved esthetic and mechanical properties.

Increase in modulus upon hydration in copolymers of desaminotyrosyl-tyrosine ethyl ester (DTE) and poly(ethylene glycol) (PEG) with iodinated tyrosines, poly(I2DTE-co-PEG carbonate)s, was investigated by varying the fraction and the molecular weight of the hydrophilic PEG component. Water, as expected, acts as plasticizer in polymer with PEG content < 15 wt% and > 30 wt%. But, water has the opposite effect in iodinated polymers with moderate PEG contents, between 15 to 20 wt%: it enhances the Young's modulus. The strength and modulus of hydrated poly(I2DTE-co-15%PEG2K carbonate)s increased by as much as fifteen fold upon hydration. While the decrease in the mechanical properties in most polymeric materials with diluents such water is due to the solvent-induced swelling, the increase in strength and modulus that is observed is most likely due to the reinforcing effect of the increased cross-linking efficiency of the hydrated PEG domains in the iodinated polymer.

The deposition of amorphous InGaZnO4 (a-IGZO) semiconductor film, via a sputtering process, has been demonstrated in the literature. In this paper, we present a solution method as an alternative to obtain this semiconducting film. The dispersible IGZO colloids is formed first by co-precipitation of precursors, followed by hydrothermal treatment at 200°C for 1 hour and using CMC as the dispersion agent. The crystalline colloid would become amorphous when it was heated at above 250°C. The TFT structure was made by growing a dielectric silica layer using the CVD method, a metal layer using the sputtering method, and an active IGZO layer using the solution method. This device exhibits low operating voltage, the mobility is about 2cm2V−1s−1 and the Ion/Ioff ratio is 104. Further improvement in processing is needed.

Si-rich SiOX strip-loaded waveguide with silicon (Si) nanocrystals contributed amplified spontaneous emission at 750-850 nm with associated spectral linewidth of 140 nm is characterized. By using variable stripe length (VSL) method we demonstrate the optical gain and loss coefficients of 65 and 5 cm−1, respectively, for such a waveguide amplifier. The optical gain and loss coefficients are observed by fitting the one dimensional amplifier equation. The small-signal power gain of 18.4 dB at wavelength of 805 nm under He-Cd laser pumping of 40 mW at 325 nm is obtained from the SiO2/SiOX/SiO2 waveguide amplifier with length of 1 cm.

TiO2 is an attractive anode material for Li-ion batteries due to its high capacity, high mechanical stability during Li intercalation/deintercalation process, limited side reactions with the electrolyte, low cost, and environmental friendliness. In this study, titanium hydroxide gel films were prepared in acidic aqueous solutions of TiOSO4, H2O2 and KNO3 by potentiostatic cathodic electrosynthesis on various copper substrates, including planar Cu foil, mechanically polished planar Cu foil, and Cu nanorod arrays grown on Cu foil. Crystalline TiO2 films were obtained by heat treating the electrodeposited titanium hydroxide gel films at 500 oC in argon atmosphere. The morphology and microstructure of the TiO2 films were characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD). SEM results showed that after deposition, each Cu nanorod has been covered by a layer of TiO2 gel, forming a core-shell structure. The effects of Cu nanorod arrays on the morphology and the electrochemical property of the TiO2 deposits were discussed.

Spatially and spectrally resolved electroluminescence (EL) measurements are powerful methods to characterize solar cells, if the EL is properly interpreted. The task of interpreting the results and modeling the spectral and absolute EL emission is strongly simplified by considering the link between EL and quantum efficiency. Using this connection, we show how to quantify the influence of light trapping on the solar cell absorptance using EL.

In parallel with the effort to improve the efficiency of Quantum cascade lasers (QCL) for high power continuous wave (CW) operations, the peak power in pulsed mode operation can be easily scaled up with larger emitting volumes, i.e., processing QCLs into broad area lasers. However, as the emitter width increases, multi-mode operation happens due to poorer lateral mode distinguishability. By putting a two dimensional photonic crystal distributed feedback (PCDFB) layer evanescently coupled to the main optical mode, both longitudinal and lateral beam coherence can be greatly enhanced, which makes single mode operation possible for broad area devices. For PCDFB laser performance, the linewidth enhancement factor (LEF) plays an important role in controlling the optical coherence. Being intersubband devices, QCLs have an intrinsically small LEF, thus serves better candidates over interband lasers for PCDFB applications. We demonstrate electrically pumped, room temperature, single mode operation of photonic crystal distributed feedback quantum cascade lasers emitting at λ ∼ 4.75 μm. Ridge waveguides of 50 μm and 100 μm width were fabricated with both PCDFB and Fabry-Perot feedback mechanisms. The Fabry-Perot device has a broad emitting spectrum and a broad far-field character. The PCDFB devices have primarily a single spectral mode and a diffraction limited far field characteristic with a full angular width at half-maximum of 4.8 degrees and 2.4 degrees for the 50 μm and 100 μm ridge widths, respectively.

Ionic Polymer Metal Composites (IPMCs) are manufactured by electroless deposition of metal on Nafion. This deposition method results in the IPMCs with thickness between 0.17mm to 0.20mm with the electrode thickness of around a few m each. It is now generally accepted that on mechanical deformation IPMC produces charge thus making these materials potentially suitable for energy harvesting applications. Due to thin metal plating and inherited flexibility of the Nafion film the IPMCs suffer in stiffness that may be required for some energy harvesting applications. Also earlier works have shown that 0.20mm thick IPMC produce better battery charging than 0.17mm thick one. Hot pressing, using metal mold, Nafion films was employed to produce thicker and comparatively stiffer IPMCs electroded with Palladium metal. Palladium was used because of shorter manufacturing time. This IPMC shows improved energy harvesting. Due to the increased thickness these IPMCs also function as better capacitors than their conventional counterparts. On application of voltage, these IPMCs show charging and discharging effects of a capacitor. This property of IPMC may be useful for storing charge.

The roll-to-roll reverse gravure (RG) coating technique was used to produce thin homogeneous films (∼100 nm) for organic bulk heterojunction solar cells. The conducting polymer poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) and the active layer regioregular poly(3-hexylthiophene-2,5-diyl):[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM) were successfully subsequently RG coated on an ITO covered plastic substrate in ambient air. Working solar cells were achieved after annealing and thermal evaporation of the top contact. The AM1.5 power conversion efficiency (PCE) of the RG coated organic solar cells was determined to 0.74% (at 100 mW/cm2). This was very similar to the results of a reference device that was spin coated on a glass substrate in a nitrogen glove box.

The microstructure of hot-wire microcrystalline silicon films prepared at a wide range of deposition conditions was characterized by both the microstructure parameter from infrared absorption data (analyzing the Si-H stretching modes) and the effusion spectra of (low dose) implanted He and Ne. Parameter ranges leading to the growth of a dense material are identified. A (relatively) high silane flow at rather high filament temperature is found to result in a dense material at high deposition rate. The microstructure data obtained by the two microstructure characterization methods are found to be largely correlated.

Chemical gardens are biomimetic structures in the form of plants formed by a combination of salts which precipitate by a combination of convection forced by osmosis, free convection and chemical reactions. Chemical gardens may be implicated in other phenomena of industrial interest which involve precipitation across a colloidal gel membrane which separates two different aqueous solutions, for example, in cement technology and metal corrosion process. However, the variation in chemical composition, morphology and mechanical properties of the different surfaces of these formations is not well known yet. Several salts in different concentrations and conditions have been explored under terrestrial gravity and microgravity. The chemical garden structures have been characterised by morphology analysis, scanning electron microscopy, chemical analysis and x-ray diffraction, correlating these data with the biomimetic growth and the physical-chemical nanoprocesses involved in it. This approach can also be useful for the analysis of biomaterials with interesting biomechanical properties.

We have developed a new method to produce hybrid particles with polyhedral shapes in very high yield (liter quantities at up to 70% purity) using a combination of emulsion polymerization and inorganic surface chemistry. The procedure has been generalized to create complex geometries, including hybrid line segments, triangles, tetrahedra, octahedra, and more. The optical properties of these particles are tailored for studying their dynamics and self-assembly. For example, we produce systems that consist of index-matched spheres allowing us to define the position of each elementary particle in three-dimensional space. We present some preliminary studies on the self-assembly of these complex shaped systems based on electron and optical microscopy.