The development of nano-composite materials puts higher demand on morphological analysis techniques. The bio-nano-composite material systems is among the most challenging nano-composite materials for morphology characterization due to its sensitivity to damage, complex molecular conformations and nano-structures. The aim of this project is to provide a nanometer resolution and convenient chemical mapping tool based on scanning electron microscope (SEM) and electron spectroscopy for complex bio-composite systems. This would combine the backscattered electron and secondary electron techniques based on the angle-selection and energy-filtering methods. Theoretical electron behavior in the SEM is calculated using Monte Carlo simulations for reference. This SEM technique is validated and applied on representative artificial and natural bio-composite systems. Poly(N-isopropylacrylamide) (PNIPAM) composite material is a family of widely applied temperature-responsive bio-materials. The phase separation and morphology in PNIPAM nano-composites can affect the bio-compatibility of material system. Silk fiber is a well known natural bio-material with exceptional properties as well as a model hierarchical material system. The organization of nano-repeating unit in silk is expected to be a key factor in the mechanical property formation. Direct chemical mapping of this organization was not available up to now in convenient methods. Our SEM techniques (secondary electron hyperspectral imaging, SEHI) were validated and applied for mapping of these bio-materials and provided high-resolution chemical characterization of their nano-structures. The application of SEM techniques were further extended to different silk fibers and artificial silk materials. Such experiment validated the complex fine structure of secondary electron spectra measured on silk materials. The comparison of the electron spectra in different silk materials suggested a possible reflection of protein conformation in secondary electron spectra and this may be exploited for characterization of such complex materials in future applications. In summary, SEM analysis technique using electron selective detection methods capable of nano-resolution chemical characterization were validated and applied on nano-bio-composite materials. These techniques show great potential for morphological analysis in complex and sensitive composite materials in the future.

In this thesis, a range of new techniques are developed in the scanning electron microscope (SEM) for investigating and imaging the nanoscale morphology of polymer:fullerene blends with organic photovoltaic (OPV) applications. The primary focus of these techniques is energy-selective detection of secondary electrons (SE) emitted in the SEM, applied both to measure the energy spectrum of a sample’s SE emissions, and for high-resolution energy-filtered SEM (EFSEM) imaging with improved material contrast. The SE energy-filtering performance of a FEI Sirion SEM is evaluated, and the SE spectrum of P3HT, a popular polymer for OPV, is measured and found to demonstrate a range of spectral features. These features are believed to reflect molecular ordering in the polymer. It is also found that degradation of the P3HT film under air and light alters the SE spectrum of the sample. Based upon SE spectroscopy methods, energy-filtered SE images are then applied to image the phase-separated morphology of a P3HT:PC60BM film with increased material contrast. EFSEM images of the blend film surface are found capable of mapping the blend morphology with a lateral resolution of (0.8 ± 0.1) nm, and demonstrate approximately double the material contrast in conventional SEM images. This improved contrast allows for the direct identification of mixed phase material in the image data, a first for this particular blend system. In P3HT:PC60BM films processed for optimal performance, (25 ± 5) % of the imaged phase area is classified as mixed phase by the technique. A further imaging technique is developed using low-energy backscattered electrons (BSE) in the SEM to probe the 3-dimensional morphology of the polymer:fullerene film as well as the surface. The technique is used to compare reference P3HT:PC60BM blends with a modern, high-performance PffBT4T-2OD:PC70BM blend film. At the surface, correlation between the phase size of fullerene domains in both blend systems is found, with both films showing a most probable domain radius of 6 nm. Further, by carefully tuning the primary beam energy, BSE images are used to probe for ‘columnlike’ phases that penetrate a large fraction of the film’s thickness; a characteristic feature of optimised OPV blend morphologies. The subsurface characterisation of the two blend systems reveals the highly optimised morphology of the modern, high-performance system.

Swarm robots are not yet ready to work in real world environments in spaces shared with humans. The real world is unpredictable, complex and dynamic, and swarm systems still are unable to adapt to unexpected situations. However, if humans were able to share their experience and knowledge with these systems, swarm robots could be one step closer to work outside the research labs. To achieve this, research must be done challenging human interaction with more realistic real world environment constraints. This thesis presents a series of studies that explore how human operators with limited situational and/or task awareness interact with swarms of robots. It seeks to inform the development of interaction methodologies and interfaces so that they are better adapted to real world environments. The first study explores how an operator with bird's-eye perspective can guide a swarm of robots when transporting a large object through an environment with obstacles. As an attempt to better emulate some restricted real world environments, in the second study, the operator is restricted from access to the bird's-eye perspective. This restriction limits the operator's situational awareness while they are collaborating with the swarm. Finally, limited task awareness was included as a additional restriction. In this third study, the operator not only has to deal with limited situational awareness but also with limited information regarding the objective. Results show that awareness limitations can have significant negative effects over the operator's performance, yet these effects can be overcome with proper training methods. Through all studies a series of experiments are conducted where operators interact with swarms of either real or simulated robots. In both cases, the development of the interaction interfaces suggest that careful design can support the operator in the process of overcoming awareness problems.

The erosion of components subjected to water droplet impact has been documented in various applications e.g. aircraft and wet-steam turbine blades. In wet-steam turbine systems, erosion of the of leading edge turbine blades causes significant loss of efficiency. Despite the efforts that have been put into this field over the past 50 years, no one has solved the problem of water droplet erosion. This may be attributed to the different damage phenomena; extremely high contact pressure; stress wave propagation; jetting and excessive heating etc. that occur in high- speed water droplet erosion. The main purpose of this thesis work was to attempt to link existing (but fragmented) knowledge of different aspects of water droplet erosion and the requirements to construct a protective coating to resist it. Discoveries from critical literature reviews were that the impact energy may be viewed as mechanical dissipation of stresses/strains or acoustic attenuation of stress waves. Therefore, architectural designs of protective WDE coating structures must try to satisfy both of these considerations. To provide some validation of both the mechanical (stresses/strains) and acoustical (stress waves) considerations, titanium-based monolithic and multilayer PVD coatings will be investigated and characterization techniques (i.e. nano-indentation, x-ray diffractometer (XRD, Optical Microscopy (OM) Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Stylus profilometry) will be performed. Selected (both monolithic and multilayer) coatings will be subjected to both particulate (ball-on-plate) impact testing and water droplet erosion (WDE) testing. This thesis illustrates the versatility of the triode ion-plating PVD technique and its feasibility to produce thick (Ti, Ti(N) and TiN) monolithic coatings and (TiN/Ti, TiN/Ti(N)) multilayer coatings with reliable controllability in terms of chemical composition and designate d i 2 layer thickness. According to the results of this work, there is a definite distinction between the coating requirements for solid particle impact tests and liquid particle water droplet erosion, due to the differences in the way that the impact energy is delivered (i.e. strain rate, duration of the impact impulse, etc.) However, the results are inconclusive as to whether multilayer or monolithic coatings perform better in water droplet erosion. Finally, the information gathered experimentally was analyzed (with existing proposed models and theories) and interpreted to propose a coating architecture which will be superior in water droplet erosion performance.

As advances in the remote sensing of fluid flows forge ahead at an impressive rate, we face an increasingly compelling question of how best to exploit this progress. Light detection and ranging (LIDAR) measurement equipment still presents the problems of having only radial (line-of-sight) wind speed measurements (Cyclops' dilemma). Substantial expanses of unmeasured flow still remain and range weighting errors have a considerable influence on LIDAR measurements. Clearly, more information needs to be extracted from LIDAR data and an estimation problem naturally arises. A key challenge is that most established estimation techniques, such as Kalman filters, cater for systems that are finite-dimensional and described by ordinary differential equations (ODEs). By contrast, many fluid flows are governed by the Navier-Stokes equations, which are nonlinear partial differential-algebraic equations (PDAEs). With this motivation in mind, this thesis proposes a novel statistical signal processing framework for the model-based estimation of a class of spatio-temporal nonlinear partial differential-algebraic equations (PDAEs). The method employs finite-dimensional reduction that converts this formulation to a nonlinear DAE form for which new unscented transform-based filtering and smoothing algorithms are proposed. Gaussian approximations are derived for differential state variables and more importantly, extended to algebraic state variables. A mean-square error lower bound for the nonlinear descriptor filtering problem is obtained based on the posterior Cramér-Rao inequality. The potential of adopting a descriptor systems approach to spatio-temporal estimation is shown for a wind field estimation problem. A basis function decomposition method is used in conjunction with a pressure Poisson equation (PPE) formulation to yield a spatially-continuous, strangeness-free, reduced-order descriptor flow model which is used to estimate unmeasured wind velocities and pressure over the entire spatial region of interest using sparse measurements from wind turbine-mounted LIDAR instruments. The methodology is validated for both synthetic data generated from large eddy simulations of the atmospheric boundary layer and real-world LIDAR measurement data. Results show that a reconstruction of the flow field is achievable, thus presenting a validated estimation framework for potential applications including wind gust prediction systems, the preview control of wind turbines and other spatio-temporal descriptor systems spanning several disciplines.

Multicomponent materials containing a comparatively large number of different elemental components, yet exhibiting simple crystal structures have opened up a new era of materials design with the possibility of tuning properties of materials with greater degrees of freedom. This poses a formidable challenge in terms of design as the number of parameters involved in simulating such systems increase significantly with the increasing number of components. This work reports a sampling methodology based on hybrid genetic algorithm-molecular dynamics for sampling positional-disordered materials such as high-entropy systems. This investigation also demonstrates the influence of individual cationic species on the evolution of distortion in single-phase solid solution with the rock-salt structure, when oxides such as CoO, CuO, MgO, NiO and ZnO are mixed together. Additionally, the relationship between the number of atomic species and its effect on the lattice distortion has been presented. The influence of alloying elements on the evolution of lattice friction in substitutional alloys has been studied using Monte Carlo simulations with a continuum elasticity relation for dislocations. The spread in energy-range due to elastic properties and size-misfit of elements provides physical justification for friction stress being low in CoNi alloy, high in CoCrNi (medium entropy alloy), along with intermediate values in CoCrFeNi (High Entropy Alloy). A similar approach justifies strengthening due to dilute addition of Al into CoCrFeMnNi and CoCrFeNi. This approach is a computationally cheap method of screening a range of possible alloys with respect to their lattice friction stress. Spin-polarised density functional theory (DFT) calculations presented here were carried out to study the charge transfer among elements and evolution of distortion in substitutional alloys. To study the characteristics of the individual element, impurity-in- matrix type calculations were carried out. The charge transfer between impurity and matrix element is presented to determine issues with the electronegativity parameter of Miedema’s model for enthalpy calculations. The distortion in substitutional alloys, particularly due to Cr has been found to be related to interaction of electrons with complementary spins in their d-orbitals.

Lean maraging steels were designed for several application sectors by providing very high strength and ductility, with the addition of relatively cheaper elements like manganese. In this work, the microstructural and mechanical properties of four niobium-containing (0.035 wt. %) and vanadium-containing (0.02 wt. %) Fe-7Mn-2Ni-1Ti-1Mo-0.03C (in wt. %) with different content of aluminium (1~2 wt. %) aged at different temperatures between 420 °C and 570 °C were investigated. As-quenched Fe-7Mn alloys exhibited a good combination of high strength (~700 MPa of 0.2 proof strength, ~ 850 MPa of UTS) and ductility (~ 10 % tensile elongation). The as-quenched microstructure consisted of lath martensite and a small amount (~ 0.3 vol. %) of micronsized (Ti, Mo, Nb/V)C carbides. The aging process significantly strengthened/hardened the Fe-7Mn alloys which is due to the formation of nano-sized Nix(Ti, Mn, Al) precipitates. Nix(Ti, Mn, Al) precipitates exhibit a very high number density (52.9×1014/m2 in the peak-aged state of Alloy 2, aged at 500 °C for 24 h) and fine size (average diameter was 17.4 ± 4.2 nm after aged at 500 °C for 168 h). The Vickers hardness increased with aging time in the under-aged stage which was due to the precipitate growth and the alloy was strengthened by Orowan bypassing mechanism. The hardness decreased with aging time after the peak hardness as the precipitate coarsened. There were two types of the crystal structure observed for Nix(Ti, Mn, Al) precipitates: The L21-Ni2(Ti, Mn, Al) phase (lattice parameter, a = 0.5863 ~ 0.5895 nm, which is co-planar with martensite matrix, with only 1.72 % of lattice misfit. And the L12-Ni3(Ti, Mn, Al) structure ( a = 0.3598 ~ 0.3613 nm). A short time-aging resulted in a yield strength above 1 GPa but led to embrittlement of Fe-7Mn alloys, which was believed to be due to the segregation of Mn to the grain boundaries. Both carbides and nano-precipitates formed along grain boundaries were likely to reduce the cohesion across the boundary plane, as well as resulted in stress-strain incompatibilities. However, the prolonged aging resulted in the formation of reverted austenite (RA) in the over-aged stage, which led to the recovery of ductility when aged at 570 °C as the austenite reversion removed the Mn solute from the grain boundaries. Reverted austenite exhibited lath-like shape with the length between 50 and 2000 nm. Both the size and volume fraction of RA increased with the increasing aging time and aging temperature. RA was formed with the diffusion-controlled mechanism, and it was observed exhibiting a Kurdjumov-Sachs (K-S) orientation relationship with the neighbouring aged martensite grains with an enrichment of Mn and Ni. Higher content of Al addition resulted in ~ 25 vol. % of δ-ferrite in the as-quenched microstructure, which was stable during aging. 2 wt. % of Al also resulted in higher volume fraction of nano-precipitates and increased the dissolution temperature of precipitates, however, it delayed the peak-aging time and austenite reversion. Nb-containing alloys exhibited relatively finer size of prior austenite grains and (Ti, Mo, V)C carbides, larger size and higher number density of Ni(Ti, Mn, Al) precipitates, but slightly lower austenite fraction, compared to V-containing alloys. Based on the results, it is suggested that Alloy 3 aged at 570 °C for 2~6 h gives the optimized mechanical properties.

Structural integrity and reliability of sealing materials for planar type solid oxide fuel cells (pSOFCs) is key to attaining the required functionality and subsequent commercialisation of such fuel cells. In this thesis a number of different series of alumino-borosilicate glasses containing alkaline earth modifiers, as well as ZnO and La2O3 are studied as potential sealant materials. The glass ceramics derived from these glasses were also studied. Vickers hardness indentation was used to assess the hardness and indentation fracture toughness of these glasses and acoustic measurements were used to determine their moduli. The results reveal a decrease in mechanical properties with modifier additions in all the series except for increasing La2O3 in xSi(20-x)La(Sr) with little variation of mechanical properties in the case of xB(15-x)Zn (10BaO-(15-x)ZnO-15La2O3-5Al2O3-(10+x)B2O3-45SiO2 (X= 2.5, 5, 7.5, 10)) and xSi(20-x)Zn (10BaO-(20-x)ZnO-15La2O3-5Al2O3-10B2O3-(40+x)SiO2 (X=2.5,5,7.5) mol%) hardness. Electrical conductivity of sealing glasses must be lower than 10-4 S cm-1 and or > 104Ω cm. Hence the electrical properties the electrical properties of these glasses were measured using impedance spectroscopy and the results indicated that all of the glass and glass ceramic samples studied are electrically resistive and show promise for use as sealing materials. Another important parameter is the thermal properties where the TEC of the sealing glass must be compatible with the other components because differences in TEC of sealing glasses and adjoining SOFC parts result in mismatch and induce thermal stresses during thermal cycling and this may generate cracks through which gas leakages occur. The TEC of xBa(10-x)Al series (10+x)BaO-5ZnO-20SrO-(10-x)Al2O3-20B2O3-35SiO2 (X= 0, 2, 3, 4, 5) and some of xBa(40-x)Si samples (15+x)BaO-5ZnO-15La2O3-5Al2O3-20B2O3-(40+x)SiO2 (X=2.5,5,7.5, 10) have fall within the requirement for sealing glasses. Apart from the TEC the Tg is also a determining factor as to the suitability or otherwise of a sealing glass to be a promising candidate due to the following reasons: (i) thermal stresses develop below the Tg where the glass is brittle therefore the Tg should be as low as possible; (ii) due to high temperature material degradation research efforts are on to reduce the operating temperatures of SOFCs to enhance materials service life and the opportunity for variety of materials selection to construct the SOFCs components. Heat treating series xB(15-x)Zn, xSi(20-x)Zn and xBa(40-x)Si lead to the formation of lanthanum borosilicate single phase. The evolution of these phase lead to not only increased in conductivity as mentioned above but also in the hardness as they are higher in the glass ceramics. However the TEC of the glass ceramics compared with the parent glasses were slightly lower and its reported in this study that this is a good sign of thermal stability as the TEC did not exhibit the possibility of continues increase.

An investigation into the phase transformation of metastable alloys such as high entropy alloys (HEAs) and high entropy bulk metallic glasses (HE-BMGs) was performed. Bulk metallic glasses (BMGs) and HEAs were known to have a metastable phase at high temperature, while HEAs was reported to have a sluggish diffusion at high temperature. Besides, the drawback of many single phase HEAs is that they are mechanically unstable due to the presence of single phase either body centred cubic (BCC) or face centred cubic (FCC) structures. Here, a systematic study on the crystal structure, physical and mechanical properties of TiZrHfNiCu HE-BMG and FeCoNi(BxAl1-x)0.1Si0.1 (0 ≤ x ≤ 1) lamellar structured HEA were explored. It was revealed that, a phase transformation occurred in HE-BMG in isothermal and non-isothermal conditions, yet the nucleation and growth behaviour was relatively slow at high temperature compared to most Zr-based amorphous alloys. This phenomenon was proven by the attained data of activation energy and crystallisation mechanism which reflect the crystallisation resistance of the alloy. The addition of boron as a substitution of aluminium in FeCoNi(BxAl1-x)0.1Si0.1 alloy changed the phase formation, phase stability, morphology characteristics and mechanical properties of the alloy. The unique lamellar herringbone-like structure was formed with increasing boron content and led to improvement of mechanical properties of the alloy such as the hardness from B0.4 to B1.0. Lamellar structured-HEA was designed to obtain a balance in strength and ductility for FeCoNi(Bx Al1-x)0.1Si0.1 HEA where it can be tailored by modifying the boron content. The optimum balance of strength (1550 MPa) and ductility (19%) was attained at 0.5 at% boron content.

Large-scale Systems are gaining more importance in the modern world requiring flexible techniques capable of handling interactions. This thesis is concerned with the development of suitable algorithms based on Model Predictive Control (MPC) that guarantee stability, recursive feasibility and constraint satisfaction. In the first part of this thesis, the main properties and control challenges for controlling an Large-Scale System are brought together, and the main distributed approaches for solving these problems are surveyed. Also, two novel Distributed MPC algorithms are presented. A non-centralised approach to the output-feedback variant of tube-based model predictive control of dynamically coupled linear time-invariant systems with shared constraints. A tube-based algorithm capable of handling the interactions–not rejecting them– that replaces the conventional linear disturbance rejection controller with a second MPC controller, as is done in tube-based nonlinear MPC. Following this, a smart-grids application of the developed algorithm is presented to solve the load frequency control for a power network. The approach achieves guaranteed constraint satisfaction, the recursive feasibility of the MPC problems and stability while maintaining on-line complexity similar to conventional MPC. The second part of the thesis covers reconfigurable distributed MPC. Two novel approaches are considered: a nominal MPC methodology that incorporates information of external disturbances, and a coalitional approach for robust distributed MPC. The first approach uses available disturbance predictions within a nominal model predictive control formulation is studied. The main challenge that arises is the loss of recursive feasibility and stability guarantees when a disturbance, which may change from time step to time step, is resent in the model and on the system. We show how standard stabilising terminal conditions may be modified to account for the use of disturbances in the prediction model. Robust stability and feasibility are established under the assumption that the disturbance change across sampling instances is limited. The proposed coalitional approach to robust Distributed MPC aims to tackle the existing trade-off between communication and performance in Large-Scale System by exploiting the different network topologies of system dynamics. The algorithm employs a method to switch between topologies using a multi-rate control approach. The optimal topology selection problem is solved using a consensus approach appropriately constrained to reduce the effects of any combinatorial explosion. The robust control algorithm is capable of recomputing the necessary parameters online to readjust to new partitions. Robust constraint satisfaction, recursive and stability are guaranteed by the proposed algorithm.