Increasing concern about the rapid escalation of environmental pollution has led to strong legislation to ensure, for example, that the emission of pollutants from vehicles and industries is controlled to an acceptable level. As a consequence, there has been a rapid expansion of research into developing more efficient and low-cost gas monitoring systems. Currently, commercial solid-state atmospheric gas detection systems are based on one sensor for each gas, while research systems are an array of sensors for the detection of multiple gases. In this research, techniques are developed whereby more than one gas is detected using a single resistive gas sensor. A novel modulated temperature technique was used to enhance the selectivity of the resistive SnO2 gas sensor. Fast Fourier transforms was used to extract the Fourier coefficients. These in turn were used as input to neural networks for training and subsequently for prediction purposes. The result has shown that a single doped SnO2 resistive microsensor can be used to classify binary gas mixture in air. The research objectives have been fulfilled in that a novel way in detecting the components and the concentration level of a binary gas mixture was developed. Additionally, a low-cost low-power intelligent gas monitoring system was designed. This included the design of a novel temperature/thermometer circuit.

The theme of this research was the development of an integrated approach to establish how the stiffness of a thermoplastic material could be measured and modelled for use in impact simulations. By undertaking this an understanding was obtained of how thermoplastic materials behave and the structures that are made from them perform when subjected to mechanical impact loads. A series of tensile tests was undertaken using three control methods to establish a tensile test control method suitable for a wide range of strain rates. The effect of applied strain rate on the mechanical performance of High Density Polyethylene (HDPE), as illustrated by the tensile stress-strain curve, was investigated. Tests were performed at various elongation rates and temperatures to simulate different practical operating conditions. Extensive use of the finite element method was made in simulating the mechanical impact performance of various beam, disc and automotive fuel tank structures with the predictions of these analyses being correlated with experimental test data. The research is novel and of direct practical relevance as indicated by the prediction and correlation with experimental data, of the impact performance of a HDPE fuel tank, which to the author's knowledge has not been previously done. The demonstrated methodology thus provides a significant advance in the prediction of the impact performance of components made from polymers, whose mechanical performance is strain rate sensitive.

The co-injection moulding process was studied. The experimental work from several tools, such a square plaque plate moulding has led to an understanding of the mechanism of dual injection mould filling. Emphasis has been focussed the relationships between the rheological property of the polymers and the relevant moulding parameters. The skin-core formations, which cot-relate to these relationships, were also studied. Many factors were introduced for understanding the effect on the skin-core adhesion where the two polymers are incompatible. In this case a compatibiliser was found to be one of the most important factors. In the presence of compatibiliser, the chemical reaction between active functional groups of skill and compatibiliser in the core occurred. Suitable conditions were necessary to produce good bonding between skin and core. The greater thickness of skin layer and greater . simultaneous injection times led to more probability for the skin and core active functional groups to react with each other before the skin became no-flow layer. Methods available to achieve these thicknesses and simultaneous injection times were possible by controlling the moulding parameters, such as melt temperature, tool temperature, injection speeds, and lengths of simultaneous phase-, these parameters could affect the skin-core thickness formations and their adhesion to different degrees.

This project aimed to study the feasibility of making a thermoset sandwich injection moulding from a novel thermoset co-injection moulding system. Two thermoset polyesters, BMC and a powder coating, were used for all experiments. Flow and cure of those materials in a newly designed manifold system were studied and some thermoset sandwich injection mouldings have been produced. Despite producing novel co-injection mouldings using two thermoset materials together, the results showed that the existing system was not applicable for large-scale production of sandwich parts and needed some improvements. The experiments on the moulding materials and single injection of each material gave temperature windows and settings for the co-injection moulding. The results from all experiments indicated that temperature and the time of applying heat to a thermoset material were very important to its flow ability and formation. Especially when producing a sandwich moulding, adequate heat and time was necessary for the skin material to form a sufficient layer to cover the core material. Investigation of the sandwich moulding cross-sections showed that applying more core injection delay time could help to increase the skin thickness. Surface assessmenitn dicated that the surface quality was also improved when the skin layer was thicker. However, core break-through at the position opposite to the mould gate was found in all sandwich mouldings showing that the type of mould gate was also important. A central sprue gated mould used in these experiments was found to be not suitable for producing a sandwich component using this machine configuration. A new manifold design was proposed and was compared to the existing manifold designed by using a simulation software package from Moldflow. Thermoset single injection moulding simulation was used to help to understand the flow and cure of a thermoset material in both manifold designs. It was shown that the new manifold system design was an improvement on the existing one.

The fire retardant properties of inorganic silicate based materials were characterised by Thermal, Infrared (IR), Karl Fischer (KF), Mass Spectrometry (MS) and Cone Calorimetry (CC) techniques. Scanning Electron Microscopy (SEM) was also employed to study the sample morphologies. In this study, spectral data were analysed by multivariate Target Factor Analysis (TFA) to determine the relative evolution profiles of selected fire gases. A combination of the gas evolution profiles and further numerical treatment of the thermal characterisation data provided a novel set of protocols to assess the high temperature behaviour of the fire protective silicate materials. In the context of this work, the study discusses the structure-property relationships of the silicates, identifies the degradation stages and elucidates the processes involved during thermal treatment by comparison with mechanistic findings in published literature. The following conclusions were drawn. Five transitions were detected by thermal analyses, which correspond to; i) the evolution of water and flammable species ii) the rearrangement of interstitial ions and water molecules iii) the evaporation of water of condensation from silanol groups iv) the decomposition of samples and i) structural rearrangement. Cone calorimetry studies revealed that samples with low polyol (P) and high SiO2:Na2O weight ratio (WR) exhibited very low heat release rates (HRR) and vice versa. It was observed that in general, low polyol content and high SiO2:Na2O WR enhanced fire resistivity. This provided a better understanding of the thermo-degradation patterns of samples and the underlying chemistry influencing the performances of the inorganic silicate based materials.

Stirred tanks are widely used in the chemical reactions and the mixing operations for process industries to enable high product quality and process efficiency. Despite there being a large body of studies on the hydrodynamics of water in the stirred tanks, the understandings of the hydrodynamics of the ionic liquids in the stirred tanks are still very limited. In this study, Computational Fluid Dynamics (CFD) modelling is used to investigate the detailed flow characteristics of the single and multiphase ionic liquid flows in the stirred tanks which are experimentally validated using Particle Image Velocimetry (PIV). The ANSYS FLUENT was employed in this investigation to carry out the CFD simulation. Initially, the hydrodynamics of single phase flows were numerically studied where the single phase turbulent water flow and single phase transitional ionic liquid flow were modelled using a RANS and LES approach respectively in the three stirred tanks equipped with different bottom shapes and length of baffles. The simulation results indicated that the bottom shape and baffles’ length have significant effect on the flow field in a stirred tank when the water was operated in the turbulent state, where a large dead zone region was identified below the impeller. However, the magnitude of the dead zone region reduced a lot when the ionic liquid was operated in the transitional state. Before carrying out the gas-ionic liquid multiphase flow simulation in a stirred tank, the bubble size needs to be identified as it is crucial information for the accurate gas-ionic liquid multiphase flow modelling. In order to obtain the bubble size data, a high speed camera and a microscope were employed to experimentally measure the bubble size in the ionic liquid solutions. The correlations between the bubble size in the ionic liquid solutions and the impeller agitation speed were established. It showed that both the bubble breakage and coalescence has significant effect on determining bubble size in the ionic liquid. In addition, it was suggested that the surface tension of the ionic liquid is more important than the liquid viscosity on affecting the bubble size in the stirred tank. Afterward, the gas-ionic liquid multiphase flow modelling was carried out in the stirred tank at various impeller speeds and gassing rates. The simulation results indicated that the presence of gas phase did not have significant effect on changing the flow of liquid phase under the selected operation conditions due to the small bubble size, low gas flow rate and high viscosity of ionic liquid. The gas phase followed well with the liquid phase and circulated in the majority region of the stirred tank, which implied better gas holdup and mass transfer of the multiphase flow system. A correlation was proposed to predict the impeller power consumption of the gas-ionic liquid transitional flow in a stirred tank agitated by a Rushton turbine impeller. Finally, in order to validate the above single phase and multiphase flow CFD models adopted in this study, an experimental rig was established and the advanced visualization technique Particle Image Velocimetry (PIV) was used to measure the single phase water and ionic liquid flows and gas-ionic liquid multiphase flow in a stirred tank. The PIV data showed agreement with the CFD results in terms of the flow pattern and velocity components, which indicates good accuracy of the computational models and approaches presented in this investigation.

When considering targeted regulation of transient response to changes in relative humidity within closed environments, selection of a material’s suitability requires fundamental understanding of its hygrothermal functional properties as well as the morphology of mesoporous materials. The overall aim of this research was to develop a top-down design technique using hygrothermal modelling simulations that enabled the design of mesoporous desiccants materials. This technique was used to inform the specification of optimized hygrothermal properties with the intention to enhance regulation of any relative humidity buffering application within closed environments. In order to accomplish this, a series numerical simulations using as a template pre-existing mesoporous desiccants properties data were performed. It was found that the linear portion of the hypothetically-created water vapour isotherms correlated with the rate of decline in adsorption/ desorption. This was found to be highly sensitive to the moisture content gradient, Δw between the upper and the lower relative humidity limits of the water vapour adsorption isotherm. The stages of the kinetics of water vapour adsorption found consistent agreement with the moisture content gradient and the exchange rates for moisture loads. This assisted the design process for newly created mesoporous solids (MCM-41 and SBA-15) when informing the optimized hygrothermal properties with respect to targeted relative humidity buffering applications. The latter enabled the quantification of the relative effect on energy efficiency (latent heat) when assisting an HVAC system as a dehumidifier. The major implication of this research was the novel theoretical insight that enabled a top-down predictive design using hygrothermal numerical modelling. This allowed functional properties optimization for mesoporous solids with respect to specific targeted closed environments, by informing material’s preparation via enhanced modulation of ‘ideal’ pore geometry.

In the light of growing concern over greenhouse gas emissions and limited fossil fuels, the use of renewable energy sources such as biomass is becoming more vital. Jatropha curcas seed cake, which is a waste product of biodiesel production, has been identified as a potential candidate to be co-fired with coal in existing boilers. There is a dearth of information on the effective utilisation of Jatropha curcas seed cake in this manner, and this research work contributes to bridging this knowledge gap. The seed cake received was divided into two distinct classes based on appearance and texture, identified as type A (harder and lower oil content) and type B (the more abundant class). As an initial step, the fundamental fuel properties of the seed cake were determined; these include the proximate and ultimate analyses, higher heating value (HHV) and inorganic content. The HHV of type A and type B was 20.76 MJ/kg and 24.06 MJ/kg, respectively; their dry ash content was 5.9% and 4.4%, respectively. K was the most abundant inorganic element present. The main hindrances to co-firing of a typical biomass with coal arise due to the difference in properties of biomass and coal. Torrefaction and leaching were carried out with the aim of bringing the thermochemical (primarily the HHV) and chemical (inorganic content) properties, respectively, of the seed cake closer to those of coal. An envelope of torrefaction conditions was recommended –~250°C for 45-60 min for the type A, and < 5 min at > 280°C to > 45 min at 220°C-250°C for the type B. These conditions ensured that the HHV of the type A and type B were enhanced to > 24.5 MJ/kg and > 27 MJ/kg, respectively, while not compromising excessively on the energy yield. Leaching at 20°C for < 24 h was considered adequate in the case of the untorrefied seed cake, and this result ed in a reduction of the potassium content (the most abundant and critical inorganic element in the seed cake) by 85%. Leachability of the torrefied biomass was markedly reduced, and leaching at least at 50°C was deemed necessary. Combustion modelling using Ansys Fluent 14.0 was carried out to assess the combustion and co-firing characteristics of untorrefied and torrefied Jatropha curcas seed cake. The effect of torrefaction on the devolatilisation characteristics, flame properties and consequently NOx pollutant formation was established. Compared to the torrefied biomass, the untorrefied seed cake devolatilised earlier, had a more dispersed flame and higher NO formation. The higher reactivity of the biomass was shown to have a positive effect on the devolatilisation rate of the less reactive coal under co-firing simulations.

Electrochemical capacitors, also known as supercapacitors, have attracted considerable attention over the past decades owing to their higher power density, long cycle life and moderate energy density compared. A high-performance supercapacitor integrates innovative electrode materials with desirable properties coupled with low cost and sustainability. In this thesis, a series of low cost transition metal oxide-activated carbon composite materials, lithium iron phosphate-activated carbon composite materials as well as metal oxide-graphene composite materials were prepared, characterized and evaluated as supercapacitor electrodes. Iron oxide (Fe3O4) – activated carbon (AC), zinc oxide (ZnO) – AC and titanium oxide (TiO2) – AC nanocomposites were prepared by using simple mechanical mixing method. The charge storage capabilities of these metal oxide-based composites with different loading ratios were evaluated in both mild aqueous 1 M Na2SO3 and 1 M Na2SO4 electrolytes. The incorporation of small amount of metal oxides onto AC could effectively enhance the capacitive performance of pure AC electrodes. It is believed that the presence of metal oxide nanoparticles can provide favourable surface adsorption sites for sulphite anions (SO32-). Nevertheless, bulk increasing of the metal oxide content is found to distort the capacitive performance and deteriorate the specific surface area of the electrode, mainly due to the aggregation of the metal oxide particles within the composite. On the other hand, composite materials consisting of lithium iron phosphate (LiFePO4) and AC exhibit high specific capacitance of 112.41 F/g in 1 M Na2SO3 with the incorporation of 40 wt % of LiFePO4. The synergistic effect between the faradaic battery type materials and the EDLC-based materials is greatly demonstrated. The intercalation and extraction of Li+ ions in LiFePO4 lattices are responsible for the reversible Faradaic reaction on top of the adsorption and de-adsorption of SO32- anions from Na2SO3 electrolyte. In the preparation of SnO2-graphene and MoO3-graphene nanocomposites, low-temperature solvothermal method using mild reducing agents was adopted. The preparation steps do not require high pressure or extreme synthetic condition and do not involve the usage of hazardous reactants. The electrochemical results of SnO2-graphene composite electrodes demonstrate that the composite electrodes possess a high specific energy (14 Wh/kg) with 93 % capacitive retention after 1500 cycles while MoO3-graphene composite electrodes yield an enhanced specific energy (16.3 Wh/kg) which is 28 % higher than that of pure MoO3 (11.8 Wh/kg). A maximum specific capacitance of 99 F/g was obtained from the optimized SnO2-graphene composite electrodes while a high average specific capacitance of 148 F/g was achieved for MoO3-graphene composites at a scan rate of 5mV/s in neural 1 M Na2SO3 electrolyte. The incorporation of graphene onto both SnO2 and MoO3 respectively, can promote the electrochemical utilization of metal oxides as well as the electrical conductivity of the electrodes. The graphene sheet serves as a good support in promoting effective charge transfer for redox reactions of MoO3. Additionally, deposition of metal oxides on graphene sheets prevents the graphene sheets from agglomeration, resulting in facile ion transportation pathway for electrolyte to access the surface of active material.

Biomass is one of the renewable energy resources that has carbon in its building blocks that can be processed into liquid fuel. Napier grass biomass is a herbaceous lignocellulosic material with potentials of high biomass yield. Utilization of Napier grass for bio-oil production via pyrolysis is very limited. Bio-oil generally has poor physicochemical properties such as low pH value, high water content, poor chemical and thermal stabilities which makes it unsuitable for direct use as fuel and therefore requires further processing. Upgrading of bio-oil to liquid fuel is still at early stage of research. Several studies are being carried out to upgrade bio-oil to transportation fuel. However, issues regarding reaction mechanisms and catalyst deactivation amongst others remain a challenge. This thesis gives insights and understanding of conversion of Napier grass biomass to liquid biofuel. The material was assessed as received and characterized using standard techniques. Pyrolysis was conducted in a fixed bed reactor and effect of pyrolysis temperature, nitrogen flow rate and heating rate on product distribution and characteristics were investigated collectively and pyrolysis products characterized. Effects of different aqueous pre-treatments on the pyrolysis product distribution and characteristics was evaluated. Subsequently, in-situ catalytic and non-catalytic, and ex-situ catalytic upgrading of bio-oil derived from Napier grass using Zeolite based catalysts (microporous and mesoporous) were investigated. Upgraded bio-oil was further fractionated in a micro-laboratory distillation apparatus. The experimental results showed that high bio-oil yield up to 51 wt% can be obtained from intermediate pyrolysis of Napier grass at 600 oC, 50 oC/min and 5 L/min nitrogen flow in a fixed bed reactor. The bio-oil collected was a two-phase liquid, organic (16 wt%) and aqueous (35 wt%) phase. The organic phase consists mainly of various benzene derivatives and hydrocarbons while the aqueous phase was predominantly water, acids, ketones, aldehydes and some phenolics and other water-soluble organics. Non-condensable gas (29 wt%) was made-up of methane, hydrogen, carbon monoxide and carbon dioxide with high hydrogen/carbon monoxide ratio. Bio-char (20 wt%) was a porous carbonaceous material, rich in mineral elements. Aqueous pre-treatment of Napier grass with deionized water at severity factor of 0.9 reduced ash content by 64 wt% and produced bio-oil with 71 % reduction in acid and ketones. Performance of mesoporous zeolites during both in-situ and ex-situ upgrading outweighed that of microporous zeolite, producing less solid and highly deoxygenated organic bio-oil rich in alkanes and monoaromatic hydrocarbons. The Upgraded bio-oil produced 38 wt% light fraction, 48 wt% middle distillate and 7.0wt% bottom product. This study demonstrated that bio-oil derived from Napier grass can be transformed to that high-grade bio-oil via catalytic upgrading over hierarchical mesoporous zeolite.