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To try and increase the applicability of carbon fibre composites, the present work considers the use of thermal coatings on its surface. After a study on relevant literature pertaining to conventional and alternate thermal barrier coatings, it was believed that YSZ-based and/or aerogel-based systems had the most potential. But successful application of these coatings required additional research, particularly on processing routes and long-term performance. Therefore to try and achieve a more efficient thermal coating on composite substrates, aerogel-based materials were investigated since they showed the most promise. These aerogel/polymer composites were further characterized using different morphological, optical and thermal techniques. The experimental results showed particularly promising trends for aerogel/epoxy materials whose best sample had an aerogel damage coefficient value of 18.3%. Hence, this system was applied as a coating on a carbon fibre reinforced polymer substrate and the whole system showed better thermal performance compared to a pure epoxy coating. The coating and the substrate were subsequently modelled and solved using finite element analysis to determine the most effective system under a cyclic thermal load. Although, the selection of the coating type (double, top or bottom) is dependent on the exact application; the top coating displayed the best performance balance. Nevertheless, both, experimental measurements and simulation results in the current work point to a potential application of the coating in industries such as aerospace, automotive and/or construction.

For the first time, a new type of reactor which can combine thermoelectric energy harvesting and electrochemical promotion of catalysis was developed. A novel use of thermoelectric material as a catalyst support and promoter was investigated. A facile, cost-effective and scalable synthesis of thermoelectric material BiCuSeO has been developed. It was discovered that the catalytic activity of Pt supported on the thermoelectric material BiCuSeO, through the ethylene oxidation, can be increased by several tens to several hundreds of times by a thermoelectric voltage. We call this Thermoelectric Promotion of Catalysis (TEPOC). The catalytic activity under fuel-lean and fuel-rich conditions was also investigated for ethylene oxidation. It is believed that oxygen was more strongly and C₂H₄ was weakly adsorbed on the catalyst Pt surface under lean-fuel conditions (O₂/C₂H₄ > 1). However, under rich-fuel conditions (C₂H₄/O₂> 1.4), C₂H₄ became strongly adsorbed (probably chemisorbed) to the surface especially at a high Seebeck voltage, this blocked the catalyst surface, reduced the catalytic active site, hence the rate became smaller. To further investigate the TEPOC effect, the CO₂ hydrogenation over the same catalysts supported on the thermoelectric BiCuSeO was also studied and the results confirmed similar significant promotional effect. It also was found that a negative thermoelectric voltage shifted chemical equilibrium towards the reverse water gas shift (RWGS) reaction and CO selectivity. As a results, the CO₂ hydrogenation conversion reached 48.4% (CO₂:H₂ = 1:4) with 100% CO selectivity for Pt(80)/BCSO at 656 K, which was above the thermodynamic equilibrium conversion (TEC) under no Seebeck voltage without methanation. It was established a linear relationship between Ln(r) and -eV/kьT, where -eV/kьT is the ratio between the extra electrochemical energy induced by thermoelectric effect and the thermal energy of an electron. From this it was derived that the promotional effect was attributed to the change of work function of the catalyst surface, accompanied by charge transfer from the bulk to the surface due to the thermoelectric effect. ii The discovery of TEPOC prompts that many catalytic chemical reactions can be tuned in-situ and independently from the change of conditions within the reaction chamber, to achieve much higher reaction rate, or at lower temperature, or have better desired selectivity through changing the backside temperature of the thermoelectric catalyst support.

The production of x-rays has been a useful technique in many areas of science, medicine and various industries for over 100 years. Over this time various new methods of generating x-rays have been produced, allowing improved performance in existing applications as well as the application of x-rays in new areas. In this project a novel method of electron beam production, with the potential for development into a novel method of x-ray production is presented, using both pyroelectric and ferroelectric materials. The pyroelectric e ect, i.e. the generation of a charge due to a change in temperature is an e ect exhibited by certain dielectric materials. This e ect has previously been used in x-ray generation, and has been su ently successful that a commercial device has been produced: the Amptek Cool-X. While the Cool-X has only a limited electron / x-ray energy, high energy applications of this technology are present in the literature. This shows that these materials are capable of high voltages. However, the technique is not suitable for high beam intensity applications, limiting the potential use of pyroelectric x-ray devices. Ferroelectric electron emission is a technique used to generate elec- tron beams by applying a high voltage pulse to a specially prepared cathode. This technique has shown great potential for very high intensity pulsed electron beam generation. The major drawback of this technique is that while the cathodes are relitivly cheap and easy to produce, the other required equipment (such as high vacuum systems and high voltage pulse generators) is typically large and expensive. This project combines these two technologies to create an electron beam generation system that exhibits many of the ad- vantages of each technology, while minimizing the drawbacks. The result is a device using pyroelectric materials as voltage generatingelements for electron acceleration and high voltage pulse production, while a ferroelectric cathode is employed as the electron generating element. This system has been shown to, depending on con guation, be capable of accelerating voltages above 5 kV, and generating total collected charges of more than -40 nC per pulse.

Pyroelectric materials have the ability to generate electrical response when they experience a thermal stimulus. This has lead to their deployment in applications such as Infra-Red detectors/sensors, energy harvesting, and ferroelectric electron emission cathodes, among others. All the “Figures of merit” presented in the literature for assessing pyroelectric materials are proportional to the pyroelectric coefficient. Hence, enhancing this coefficient should improve the performance of the pyroelectric element in any application. This research has been conducted to find ways of enhancing the pyroelectric coefficient of a given material through product property in the secondary pyroelectric effect arising from thermal expansion coefficient mismatch. Analytical model for describing such enhancement in 2-2 connectivity laminate composites has been developed and simulated on Mathematics package Maple, while Finite Element Analysis package ANSYSR⃝ was used to perform thermo-structural analysis investigating the effect of bonding/interfacial layer on the strain transfer between the laminate layers. Indicators for judging the credentials of various pyroelectric materials in pyroelectric coefficient enhancement have been identified and evaluated for six different pyroelectric materials. These six pyroelectric materials were paired with six different non-pyroelectric materials to form thirty-six 2-2 connectivity laminate composites for the purpose of comparing pyroelectric coefficient enhancements, whereby various factors affecting the enhancement have been determined. Potential applications of this enhancement and what it may mean in terms of improvement in the outputs of these applications has been reviewed. In particular, two electrical boundary conditions, namely short and open circuit conditions, have been explored while the effects of thermal mass variation due to the introduction of non-pyroelectric layer have also been inspected. Experimental verification of pyroelectric coefficient enhancement under short circuit condition in Lead zirconate titanate/Stainless steel 2-2 connectivity laminate composites has been conducted with observed pyroelectric coefficient enhancements of more than 100 % while theoretical enhancements of up to 800 % is predicted in certain laminate composites of Lead zirconate titanate/Chlorinated polyvinyl chloride thermoplastic. Consideration of the open circuit condition pyroelectric coefficients and their enhancements revealed significant dissimilarities from their short circuit condition counterparts, prompting the need for more distinction to be made between the two than it has previously been thought. For instance, appraising employment credentials of pyroelectric elements in applications such as pyroelectric X-ray generation, electron accelerator, and nuclear fusion should involve the use of open circuit pyroelectric coefficient rather than the short circuit one. The effects of thermal mass has also been considered using quantities termed “Figures of merit for efficiency”, comparing the laminate composite’s thermal-to-electrical conversion efficiency to that of stand alone pyroelectric material. Up to twenty fold increase in thermal-to-electrical conversion efficiency under short circuit condition has been predicted in laminate composites of Lead zirconate titanate/Chlorinated polyvinyl chloride thermoplastic, insinuating a potential for increased employment of Lead zirconate titanate in areas such as pyroelectric sensors and pyroelectric energy harvesting. Pyroelectric energy harvesting application has been examined in detail as a potential beneficiary of this enhancement, with various analysis tools for assessing pyroelectric energy harvesting performance of a given pyroelectric element presented and evaluated. A pyroelectric energy harvesting system was designed as a hypothetical application of pyroelectricity and pyroelectric coefficient enhanced 2-2 connectivity laminate composites. Theoretical analysis confirms that large improvement in pyroelectric energy harvesting performance can be expected in Lead zirconate titanate materials by converting them into 2-2 connectivity laminate composites. The use of newly defined “New electrothermal coupling factor for composites” (k2 N ew) for assessing credentials of particular pyroelectric element in pyroelectric energy harvesting application has been proposed and vindicated while the experimental samples from the pyroelectric coefficient enhancement study were demonstrated to show significant improvement in their pyroelectric energy harvesting performance via pyroelectric coefficient enhancement. The analysis techniques used in this dissertation provide a methodology for assessing the potentials of particular pyroelectric material and its 2-2 connectivity laminate composites for applications under both short and open circuit conditions.