Poly(propylene glycol) (PPG) samples of different molecular mass were characterized using differential scanning calorimetry, modulated differential scanning calorimetry, thermogravimetry and thermally stimulated current (TSC) spectroscopy. It was shown, by TSC, that the glass transition temperature and the degree of molecular mobility increased with increasing molecular mass of PPG. Additional experiments showed that PPGs of molecular mass 425, 1000 and 2000 Da undergo one global relaxation process; however, PPG 2700 (Da) undergoes an additional relaxation process after the glass transition which has been attributed either to the release of the excess charge delocalised in the polymer structure or a liquid-liquid transition. Thermally induced phase separation in aqueous solutions of PPG has been examined using a variety of techniques including high sensitivity scanning calorimetry (HSDSC), hot stage microscopy, small angle neutron scattering, and turbidity measurements. The data suggest that phase separation is a consequence of PPG aggregation (droplets); the aggregates grow in size, as the temperature is raised further. It is postulated that phase separation occurs via nucleation and growth, which is corroborated by model fitting the calorimetric data using a mass action aggregation model. It is concluded that phase separation of PPG occurs as a result of the disruption of a hydrogen bonded network between water and PPG. The effect of five sugars (mannitol, maltose, raffinose, sucrose and trehalose) on the Tm (transition temperature) of aqueous PPG 1000 solutions was studied by HSDSC and turbidity measurements. All the sugars decreased the phase separation temperature of the PPG solutions, with trehalose and maltose showing the greatest effect. A series of experiments, using HPLC, showed that phase separated PPG (1000 Da) increased the apparent aqueous solubility of naphthalene.

1D and 2D graphitic materials (carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs)) are of great interest due to their extraordinary electrical, thermal, mechanical and optical properties rarely found in bulk materials. The transfer of such properties to polymers has been limited and the development of scalable, cost-effective, multi-functional composite materials not fully realised. Polymers filled with 1D and 2D graphitic nanomaterials have uses in a wide range of applications and industries ranging from aerospace and automotive to personal care and high-tech products. Growing global economic development has sharply increased the world’s energy needs and in particular, our energy storage needs. In addition, they have potential applications in electronics, sensors and energy conversion. Another application in the area of personal care has shown that CNT-polymer composites can be used to speed up the process of bone-regeneration by being used as tissue scaffold materials. An application of interest is to use graphitic nanomaterials to produce composites with high mechanical performance (stiffness and strength) with low filler quantity providing innovative light-weighting solutions. Further potential applications of 1D and 2D graphitic nanomaterials include; touch screens, capacitors, spintronic devices, fuel cells, conductive films, high frequency circuits and flexible electronics. The development of such innovative materials requires the nanofiller to be homogenously dispersed within the polymer matrix, e.g. poly(propylene)(PP). The formation of an interconnected filler network structure at a low percolation threshold will result in the enhancement of electrical and thermal conductivity. In addition, efficient interfacial adhesion and stress transfer between filler and polymer results in improved mechanical strength and stiffness. However, poor compatibility between filler and the PP matrix prevents efficient homogenous dispersion and network formation. To address this major technical challenge, the use of a polymer compatibiliser which non-covalently functionalised graphitic nanomaterials was explored. By way of example, poly(lauryl acrylate) P[LA] was selected based upon its known compatibility with PP and it was proposed that it would also non-covalently functionalise such fillers via CH-π wrapping. P[LA] was synthesised using controlled living radical polymerisation methods and was shown to both be thermally stable for extrusion and physisorbed onto the surface of MWCNTs. For composites of PP, P[LA] and either MWCNTs or GNPs evidence was obtained confirming that P[LA] improved filler dispersion however, the most notable observation was a significant reduction in Tg of PP which was associated with P[LA] plasticising PP. Further polymer compatibilisers based on copolymers (statistical and block) of P[LA] and poly(2-phenyl ethyl acrylate) P[2PEA] where also synthesised and their potential to non-covalently functionalise CNTs and GNPs via both CH-π wrapping and π-π stacking examined. A range of characterisation techniques were employed to thoroughly understand the behaviour of these compatibilisers when added to composites of MWCNTs/GNPs and PP. Evidence for π-π stacking of P[2PEA] onto the surface of both graphitic fillers was observed from extensive electron microscopy observations. The potential of P[LA-co-2PEA] block copolymers as compatibilisers for 1D and 2D graphitic materials and PP was proven. The use of poly(acrylate)s as compatibilisers to assist the dispersion of 1D and 2D graphitic nanofillers in a PP has proven to be a concept with limited potential to alter the mechanical, electrical and thermal properties of polymers. The excellent thermal stability demonstrated by poly(acrylate)s for the purpose of melt blending with PP provides scope for further work through alternative functionalisation strategies e.g. covalent functionalisation. Throughout the project, the discussion has centred around the use of P[LA] and P[2PEA] due their potential to adsorb onto surface of 1D and 2D graphitic fillers and promote their dispersion in a PP matrix however, further work should investigate a range of poly(acrylate)s with various structures, chemistries, molecular weights and dispersities. For example, the use poly(acrylate)s with longer side chains such as poly(octadecyl acrylate) or poly(acrylate)s containing aromatic side chains with a greater number of benzene rings such as pyrene, for example pyrene acrylate. It is evident that the viscosity of the compatibilising polymer influences the extent of dispersion of the compatibiliser in the PP and matrix and therefore, it would be interesting to investigate if there is a correlation between the viscosity of the polymer compatibiliser and the extent of its dispersion in the PP matrix. GNPs with a greater aspect ratio are predicted to achieve percolation at lower loadings, increase electrical and thermal conductivity as well as improve the mechanical properties. Additionally, it would be interesting to explore what GNP quantity is required to achieve electrical and rheological percolation with the same type of GNPs and correlate those findings with graphenes with different aspect ratios to understand the role of flake dimensions. It is clear, P[LA] is not particularly successful in compatibilising the GNPs used in this study. In addition, it would useful to conduct dynamic cross-polarized optical microscopy and WAXS/SAXS scattering experiments during heating and cooling to investigate transcrystallinity phenomena at the interface between GNPs and the PP matrix.

Due to the increasing concern towards depleting petroleum resource and pollutions done by conventional plastics, polyhydroxyalkanoates (PHAs) which have diverse structure variability and rapid biodegradation have gained increasing attentions as potential replacement for plastics. However, PHAs have a much higher production cost compared to that of conventional plastics due to expensive carbon source and downstream processing. Aqueous two-phase extraction (ATPE) outshines other PHAs purification techniques by having the advantages of providing a mild environment for bioseparation, being green and non-toxic, and easily scaled-up. Henceforth, this research aimed to study on the purification and recovery of PHAs using thermoseparation-based ATPE. Firstly, cloud point extraction technique which based on thermoseparating polymers (TSP)/water two phase system was employed. The recovery yield of 94.8 % and purification factor (PF) of 1.41 fold was achieved under the conditions of 20 wt/wt % ethylene oxide-propylene oxide (EOPO) with 3900 g/mol MW and 10 mM of NaCl addition at thermoseparating temperature of 60 °C. TSPs have also been coupled with ammonium sulfate to form a two-phase system. Under the condition of 14 wt/wt % of both EOPO 3900 and (NH4)2SO4 at pH 6, yield and purity up to 72 % and 60 % can be achieved. Without the need of additional TSPs top-up, recycling and reutilization of phase-forming polymers can be done at least twice with satisfying yield and PF. Using two-level full factorial design, the statistical analysis demonstrated that the phosphate and thermoseparating polymer concentration are the most significant parameters due to their individual influence and synergistic interaction between them on all response variables. Utilizing the two significant parameters, the purification and recovery of PHAs were further optimized using central composite design and achieved recovery yield as high as 99.9 %. The optimum PF of 1.431 fold was obtained at 17.12 wt/wt % of phosphate salts and 18.52 wt/wt % of EOPO 3900. Using the addition of fresh phase-forming components, a total of 4 successive purification cycles with satisfying yield and PF were demonstrated. Utilizing the carbon source screened by the preliminary integrated economic and environmental assessment developed, the feasibility of extractive bioconversion of PHAs under the influence of different parameters was studied. The strategy successfully achieved a yield and PF of 97.6 % and 1.36 fold respectively under the condition of 5 wt/wt % EOPO 3900 concentration, 30 °C fermentation temperature and pH 6. The scaling-up to 2 L bioreactor proved that the scale-up of ATPE can be predicted reliably from laboratory-scale experimental data. In the final section, the evaluation of economic and environmental performance of two processes (which are with and without thermoseparating ATPE as primary purification step) were performed. With the basis of 9,000 tons PHAs production per year and 7,920 operating hours, the process with thermoseparating ATPE as primary purification step standout in terms of both economic and environmental performance. PHA production cost of 5.77 US$/kg with a payback period of fewer than 4 years and ROI of 25.2 % was achieved. The research proved that thermoseparating ATPE is a powerful and potential technique for PHAs purification and recovery as the technique showed a much higher PHAs recovery yield (approximately 2 times) in comparison with the literature (Divyashree and Shamala, 2010). In conclusion, this opens promising standpoints for utilizing thermoseparating ATPE as the primary step in the isolation and purification of PHAs from fermented broth.

Energy security, affordability and availability, as well as ensuring environmental sustainability are crucial considerations necessary for determining the future energy mix. The forecasted continuous use of coal in power generation and chemical industries makes it an important, yet polluting energy source. This has motivated researchers into investigating various clean coal processes such as the increased interest in co-blending of coal with alternative fuels like biomass due to its carbon lean nature. However, the utilisation of coal and biomass blends in conventional thermal reactors has high potential of operational challenges associated with the differences in the physical and chemical characteristics of coal in comparison to biomass. Moreover, the differences in these fuels’ properties have been studied and concluded to lead to synergy in fuel blends reactions. Synergy in fuel blends are interactions between the biomass and coal samples that results in non-additive improvement in the experimental outcome of the thermal reaction in comparison to the additive expectation from both contributing fuels. In order to improve the uptake of such fuel blends in power plants, a clear knowledge and understanding of the fuel blends thermal behaviour is essential. There is, therefore, a need to develop suitable and efficient characterisation technique for coal and biomass blends so that their combustion performance such as optimal operating temperatures and burnout temperatures can be predicted more effectively especially relating to the cause and degree of synergy observed in such fuel blends. In this work, a series of experiments were conducted for the thermal characterisation of two coal samples (Guizhou and Yunnan coal) and three biomass samples (oat straw, rice husk and spruce wood) and their fuel blends during combustion reaction. The thermal analysis was carried out using a thermogravimetric analyser. The influence of biomass organic and inorganic constituents on coal samples during the co-blending reaction, especially the synergy influence on the char oxidation reaction has been investigated. This was to study the catalytic and non-catalytic mode of synergy. This was done by blending of coal samples with biomass ash, demineralised biomass, simulated biomass and potassium impregnated biomass samples. In addition, the quantification of the degree of synergy interaction observed was done by formulating a synergy index. Finally, the effect of such interactions in coal and biomass blends gasification was also investigated. The observations in the results included substantial decrease in the peak temperature, burnout temperature and activation energy of the char oxidation stage of most of the fuel blends. This is representative of the non-additive interaction between the coal and biomass samples and was detected in both catalytic and non-catalytic mode of synergy in varying extent. The catalytic mode of synergy are all improvements associated with the inorganic content of biomass, mostly the alkali and alkaline earth metals while the non-catalytic synergy is resulting from the organic content of biomass. During the non-catalytic mode of synergy, the deviation in the char reaction zone and its characteristic temperatures remained similar for all blend ratios, and does not vary significantly with increase in biomass blending ratio. However, the influence of hydrogen donation from the biomass volatiles increases the reactivity significantly especially relating to reaction time and burnout. In contrast, the disparity in the peak and burnout temperature associated with catalytic synergy increased rapidly with biomass blend ratio, indicating a multiplying influence of the catalysing alkali and alkali earth metals (AAEMs). Additionally, the extent of synergistic deviation was also dependent on coal’s constituents such that Guizhou coal revealed the least degree of both synergy modes. This is associated with its with high hydrogen – to –carbon ratio which minimise the interactive influence from biomass hydrogen donation and its high ash content which has potential for deactivating catalytic inorganic elements. The results of this research show that at 50wt% biomass blend ratio, Yunnan coal and oat straw shows the highest synergy while Yunnan coal and rice husk remained additive in behaviour. In addition to this, a degree of synergy inhibition and promotion was observed between the two modes of synergy such that Yunnan coal blends which high catalytic and high non-catalytic synergistic interaction had revealed only 6.1 – 73.8% combined synergy efficiency. The synergy efficiency measures the degree of competition or promotion between the catalytic and non-catalytic synergy modes during the thermal reaction. Whereas Guizhou coal which had insignificant and moderate indication of synergy with organic and inorganic elements of biomass respectively showed up to 1.4 and 5 times multiple of the expected combined synergy. This was resulting from the somewhat overlapping functions of both synergy modes. Lastly, the difference in the efficacy of different biomass inorganic elements during high temperature gasification was observed in the coal and biomass fuel blends. The result obtained indicated that blends with calcium – rich spruce wood revealed negligible improvement compared to potassium rich oat straw due to their restricted mobility on the char surface and their deactivation at higher temperatures >900°C by forming thermally stable calcium oxide. The increase in micro-porosity of the blended fuel’s char was also observed. These fundamental results have provided insights into coal and biomass co-blending behaviour during co-firing and gasification that can be used in aiding the design considerations and optimising the biomass blending ratio to ensure appropriate operation of co-fired fuel reactors. The result revealed that in this study, synergy was highest in the Yunnan coal and oat straw blends at 50:50wt% ratio. This was resulting from the potassium - rich nature of oat straw and low hydrogen content of Yunnan coal, making it a viable proton acceptor in both catalytic and non-catalytic synergy reactions.

Natural rubber (NR) or cis-1, 4-polyisoprene is obtained from the latex that is tapped from a tree known as Hevea Brasiliensis. It can be in the form of preserved latex concentrates or further processed into sheets, crepes, block rubber that associated with its unique characteristics such as great elongation strength, excellent building tack, low rolling resistance, low heat build-up and good low-temperature performance. These are essential characteristics in dynamic working environment and application especially for vehicle tyre and rubber thread. To produce good quality of technically specified rubber or block rubber from raw natural rubber, drying process plays a vital role in the raw rubber processing. To date, the level of technology involves rubber drying is still inefficient and primitive. Non-uniform drying and the occurrence of wet rubber in the final product are the major drawbacks when using the conventional type of trolley dryer. Also, fuel and electricity usage for a single drying operation is noticeably intense and costly. Indeed, the main limitation of conventional drying method is the drying time that is mainly dependent on temperature gradient inside the product and cannot be sustainably reduced because the product is heat sensitive; whereas drying at high temperature for prolong hours could result in quality deterioration too. The prime objective of this research was to investigate combined drying as a mean of crumb rubber processing to reduce the drying time, energy consumption and to produce the desirable dried product. In the present study, crumb rubbers were dried by alternative drying strategies whereby additional drying technologies such as hot air, vacuum, and microwave was integrated into the drying system. Both engineering properties (drying kinetics, effective moisture diffusivity and specific energy consumption) and physicochemical properties (colour, thermal oxidative level, rheological, textural and surface topography) of all dried products were measured and evaluated. The comparisons were made against samples from hot air drying. The finding shows the drying time of microwave-convective drying (MWHA) was found 89% and 50% shorter than convective hot air drying (HA) and microwave (MW) drying, respectively. In terms of drying rate performance, the maximum drying rate of MWHA was found 455% and 62.5% higher than HA and MW drying, respectively. On the other hand, effective diffusion coefficient (Deff) values of both MW drying and MWHA were ranging from 1.48 x 10-8 m2/s to 5.59 x 10-8 m2/s that is six times higher than HA which has lowest Deff recorded at 0.22 x 10-8 m2/s. It is noteworthy to mention that the energy consumption of MWHA is much lower than other drying strategies due to its excellent time saving and energy efficient features in the drying process. The average specific energy consumption (SEC) values of MWHA’s drying strategies were scored below 0.22 MJ/ gH2O whereby HA drying yields SEC values of 0.36-0.44 MJ/gH2O and highest was recorded in vacuum assisted drying which scored at 0.75 MJ/ gH2O. MWHA dried rubber has exhibits lightest colours, minimum total colour change and consistent colour appearance over the range of drying methods. The lesser colour change can be an indication of reduced oxidative reaction and hence better ageing properties of dried rubber. This is corresponding to the high value of activation energy obtained by MWHA’s dried rubber in the thermal degradation study by using the Coats-Redfern methods. Similarly, the rheological properties of MWHA dried rubber including PRI and Po were found in par and the volatile matter was 28.6% lower in comparison with SMR 20 block rubber. In terms of springiness indices, MWHA dried rubbers gave the highest at 72.23% showing marked performance in mechanical properties. In a nutshell, the potential of combined drying techniques in crumb rubber has been proven through this research and able to improve both engineering and physicochemical properties while the drying time is significantly reduced. Furthermore, these findings will supplement the knowledge on crumb rubber drying process which is beneficial to raw rubber processing industries in having economically feasible drying option to be applied to the existing plants.

Extensive development of biotechnology over the past several decades has induced a great impact in the production of biological products in various industries. To date, major challenges in the biotechnology industry includes the production process of biomolecules with high purity and low cost, whilst retaining functionality. The conventional downstream processing of valuable bioproducts which are widely employed usually involves multi-processing steps, high energy and chemical consumption and often has a large influence on the cost of the finishing product. Therefore, the demand for cost-efficient and simple downstream processes has directed towards an intensive research for exploiting novel separation tool that can achieve high level of product purity with minimum number of processing stages and greener approach. The aim of this thesis is to develop a new separation method that has minimum number of steps, environmentally friendly and with the ability to achieve maximum level of product purity. Liquid biphasic flotation system is a novel technique which incorporates the principles of aqueous two-phase systems and mass transfer mode of solvent sublation. This system has been proposed as an ideal purification technique for separation, purification and concentration of biomolecules. Liquid biphasic flotation have been utilised previously to purify several biomolecules whilst maintaining their functionality. This thesis emphasised on extending the applications, improvising and to diversify liquid biphasic flotation technique as an efficient tool for downstream processing. This thesis has four objectives, in which all the objectives highlight on the usage of liquid biphasic flotation system for maximum biomolecules extraction. The initial part of liquid biphasic flotation application study is to investigate the effect of full and continuous recycling of alcohol and salt phase components in large scale liquid biphasic flotation system for lipase extraction. In this section, main focus was to optimize operating conditions for the recycling of both phase component and to investigate the competence of recycling phase components using liquid biphasic flotation system on a large scale. The liquid biphasic flotation system investigated is composed of 1-propanol and ammonium sulphate whereby both phase components went through complete recycling process. From the results obtained, it is exhibited that by reusing the bottom phase, separation efficiency of lipase was sustained beyond 77.33 % and yield with 80%. This study showed that the recovered phase components could be recycled effectively up to four cycles and able to produce a significantly high yield of lipase. Next study was on a novel approach of liquid biphasic flotation system for lipase recovery utilizing recycling phase components comprising surfactant and sorbitol. This novel method utilized Triton X-100 and xylitol for lipase extraction from Burkholderia cepacia. The scope of this study focuses on eliminating pollution and environmentally friendly process for enzyme extraction via liquid biphasic flotation. This scope is achieved by utilising phase forming components that have recovery and recycling abilities to minimize the use of chemicals for enzyme extraction. A set of optimum conditions were identified which provides a high yield of lipase with 87.49 % and separation efficiency of 86.46%. From the recycling study, it is revealed 97.20% and 98.67% of Triton X-100 and xylitol respectively were recovered after five times of recycling and 75.87% lipase separation efficiency was obtained. Third objective is on the study of the integration process of fermentation and separation of lipase from Burkholderia cepacia using liquid biphasic flotation. Integration process exhibited high lipase separation efficiency reaching 92.29% and a yield of 95.73%. This study has proven the diversification of liquid biphasic flotation system in integration of upstream and downstream processes. Since liquid biphasic flotation system can be utilised for various type of biomolecules, the final study was done to examine the integration process of sonication and protein extraction from microalgae using sugaring-out effect. Various operating conditions were assessed for high separation efficiency and yield of protein. Maximum protein separation efficiency of 86.38% and yield with 93.33% were attained from this integration process. This study demonstrated that liquid biphasic flotation system could be integrated with ultrasound for protein separation. This thesis demonstrates the importance and diverse applications of liquid biphasic flotation for biomolecules extraction. This study has led to several novel discoveries of liquid biphasic flotation applications with economic downstream processes on an industrial scale.

Rapid development of micropropulsion systems arose from growing interest on micro- and nanosatellites. Utilization of liquid energetic materials such as hydrazine and hydrogen peroxide as propellant in propulsion yielded promising results. However, safety issue remains a great concern as hydrazine is highly toxic. This drives the development of propellants towards lower toxicity and more environmental friendly, namely green propellants. Hydroxylammonium nitrate (HAN) was selected among three green propellants due to its high energy density in addition to ease in storage and handling properties. In order to understand the effect of addition of fuel into HAN binary solution, electrolytic decomposition of zero oxygen balance HAN ternary mixture in thermal isolated beaker was performed at macroscale. Addition of a fuel to binary HAN solution generally has more stages of decomposition, as opposed to single stage in binary HAN solution. Rate of temperature increase in the first stage of decomposition (Ṫ1) was found to be directly proportional to electrical resistivity of the HAN ternary mixture, while maximum electrolytic decomposition temperature (Tmax) of HAN ternary mixture obtained was dependent on fuel added. Visualization of HAN decomposition was demonstrated using transparent PDMS microreactors. A novel DPST integration in triggering the power supply and high speed camera was proposed. Such integration greatly reduced the cost of using a DAQ system, and was shown to capture the decomposition successfully at 5000 fps. Parametric optimization was also carried out in PDMS microreactors. Usage of 3 pairs of electrodes has increased overall reaction rate as high as 225 %, as compared to 1 pair counterpart. The overall reaction rate is proportional to flowrate and applied voltage. 3 pairs of electrodes can initiate decomposition in low voltage region. Applied voltage is the most significant parameter affecting the overall reaction rate. HAN-dextrose has lower decomposition performance compared to binary HAN solution in PDMS microreactor, using the optimized parameters carried out on binary HAN solution. This work has demonstrated both effect of fuel addition in binary HAN solution and parametric optimization in binary HAN solution towards their decomposition phenomena at macroscale and microscale,respectively. Several recommendations were made in future work section, including using screen-printing technology on the microreactor and adding a catalytic reactor after HAN was electrolyzed, to further improve decomposition efficiency.

Structural ceramics such as zirconia and alumina are widely used in the materials industry owing to their high hardness, chemical inertness and electrical insulation properties. However, they bear the disadvantage of low fracture toughness that has limited their further applications. As such, ceramics with improved fracture toughness are desired in many engineering fields. As for silicones, they are extensively used in current micro-electromechanical system (MEMS) components such as fuel cells and combustion engines. However, in hot and aggressive environments, silicon reduces functionality and efficiency of the components. Besides, low hardness and toughness of silicone material is undesirable in MEMS components. The ideal MEMS components require that the material has excellent structural strength at high temperature, exceptional thermal shock resistance and resistant to chemical corrosion. In view of these limitations, ceramics are currently being used to fabricate MEMS components. This PhD project sets out to tackle the disadvantages of ceramics such as brittleness and low electrical conductivity by developing ceramic nanocomposites using nanostructured fillers. Graphene nanoplatelets (GNPs) - a newly emerging carbon nanomaterial and alumina were chosen as the reinforcing fillers. Two types of composites namely alumina toughened zirconia (ATZ) and yttria stabilized zirconia- graphene (YSZ-Gr) composites were fabricated and their properties were investigated. These composites were produced by gel-casting route on PDMS soft molds. There were two main problems in fabrication of YSZ-Gr composites: (i) achieving homogenous dispersion of graphene in ceramic matrix and (ii) production of good quality graphene. The first problem was solved by dispersing commercially available graphene platelets in a surfactant;cetyltrimethylammonium bromide (CTAB). Scanning electron microscopy (SEM) ascertains homogenously dispersion of graphene in the ceramic matrix. In order to solve the second problem, processing parameters such as stirring speed and duration were optimised before fabricating the composites. Nearly dense ATZ and YSZ-Gr ceramic composites were obtained after sintering and infiltration with PDC resin (RD-212a). The prepared ceramic composites were characterized and their properties were studied. Analysis shows that hardness and fracture toughness of composites increased with the addition of fillers. For ATZ composites, there was an improvement of ≈25.26 % in fracture toughness and ≈16.29 % in hardness with 20 wt. % alumina. For YSZ-Gr composites, there was an improvement of ≈20.31 % in fracture toughness and ≈25.78 % in hardness with 1 wt. % GNP. Electrical conductivity of YSZ-Gr composites was increased by ≈9 orders of magnitude with 2 wt. % GNP compared to pure YSZ. The idea of this research is to use the two materials (ATZ and YSZ-Gr) to fabricate a MEMS scale chemical microthruster for space applications. Graphene provides conductive paths to decompose propellant (hydroxylammonium nitrate, HAN) and hence produces thrust. The characterization and testing of microthruster revealed that the proposed design is a success where; optimum thrust of 180.5 mN was achieved at a propellant flow rate of 60 µl/min. Future work should focus on optimization of chamber geometry, nozzle geometry and fuel choices to enable thruster to produce larger forces while decreasing the power consumption. Modelling and simulation of MEMS microthrusters can be used to verify the experimental results obtained.

Biomass is used for fuel by humanity from prehistoric times. With the passage of time and to meet the energy needs, non-conventional ways of utilizing the conventional sources became an interest with use of technologies. Biomass gasification is a proven technology that can economically use alternative energy resource of “Carbon Neutral”. Biomass product gas from biomass gasification is composed of CO, CO2, CH4, H2, other hydrocarbons, traces of other components and tar from biomass gasification. Fluidized bed gasification is one of the promising technologies to achieve high thermal conversion efficiency as it takes great advantages of fluidization in terms of uniform temperature profiles and excellent gas-solid interactions. The present research is aimed to evaluate the performance of a bubbling fluidized bed biomass gasifier for product gas production composition using air as gasification agent and SRC willow chips as biomass. Particle capture efficiency of the mop fan and an effect of different operating conditions such as bed temperature, equivalent ratio on the product gas composition and heating value are also investigated at Institute of Sustainable Energy Technology, University of Nottingham. The concentrations of particulate matter in the product gas before and after the mop fan cleaning unit are measured to assess the performance of the cleaning unit. Different fan rotating speeds and different flow rates of spray water are used to optimise the particle removal efficiency of this unit. It has been found that the mop fan cleaning unit has achieved an efficiency of 90% in removing particle matters and an efficiency of more than 80% in removing N-species presented in the product gas. Tars appear as a major issue in the product gas and should be removed from the product gas before they get condensed in the equipments which utilise product gas. Tar arrest techniques were successfully tested in this investigation such as woodchips bed, water spray and mop fan. The synergic effect of tar removal of water spray and mop fan found to be more effective in removing tars as if used individually. Different spray water amounts were used with a constant fan speed for keen observation of tars’ solubility in the water and found reasonable removal of tars from product gas.

Roll compaction is commonly used as a dry granulation technique in the pharmaceutical industry to produce tablets for formulations sensitive to heat and moisture. This thesis reports systematic studies on the behavior of pharmaceutical excipients in associated unit operations (i.e. roll compaction, milling, tabletting), as well as their correlations. Roll compaction experiments were carried out using an instrumented roll compactor with a gravity feeding system. The influence of the process parameters, material properties and powder conditioning were investigated Ribbons produced in roll compaction were granulated using an oscillating mill to investigate the milling process. A first order kinetics equation was introduced to describe the mass throughput of the granules. Using positron emission particle tracking technique, which provided a measurement of instantaneous velocity and the location of the ribbons, two milling regions (i.e. impact and abrasion) involving distinct fracture mechanisms were identified. Tabletting of the granules was performed using a universal test machine. A reduction in the compressibility and compactibility of the granules compared to the feed powders, due to work hardening, was also observed. A method was introduced to determine the optimized process conditions for roll compaction and milling through a close examination of the correlation between the unit operations.