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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Rates and mechanisms of chemical processes affecting the treatment of ferruginous mine water

Geroni, Jennifer January 2011 (has links)
This thesis presents the results of research undertaken into the rates of Fe(II) oxidation and CO2 stripping from ferruginous mine drainage. It also provides new insight into the applicability of Vertical Flow Reactors (VFRs) to the treatment circumneutral waters. Batch-wise experiments were used to determine Fe(II) oxidation rates in the field. The data collected were used to show that values for the rate constant k1 were up to 3 orders of magnitude greater at the field sites than would be predicted from previously published laboratory studies. A methodology was also developed for determining k2 (the heterogenous oxidation rate constant) in the field. The results of field based monitoring of aeration cascades as well as batchwise CO2 stripping experiments conducted using waters of varying chemistry were combined with geochemical modelling to demonstrate the evolution of the chemistry in these systems over time. The aeration cascades were shown to remove approximately 50% of the dissolved CO2 initially present but this was not shown to have an appreciable effect on mine water treatability. Continued removal of the residual CO2 fraction by mechanical aeration resulted in the elevation of pH by up to 2 units. Trials of pilot scale Vertical Flow Reactors (VFR) at two sites in South Wales showed that rapid decreases in bed permeability over time make these systems unsuitable for deployment in the treatment highly net alkaline waters. As a result of adverse weather conditions and other technical difficulties there was insufficient data collected to determine the performance of these systems under net acid conditions. Qualitative observations suggest however that Fe removal was taking place at a significantly higher rate than would be seen in settling lagoons under the same conditions.
42

Development of a micro crystallisation system for the production of sub-micron particulates with narrow-size-distribution

Alghaffari, Nabeel Kadhim Abbood January 2015 (has links)
Recent advancements in applied, medical materials engineering sciences and micro/nano technology have stimulated increasing demand for novel, high quality and precisely-shaped particles. As most of the materials that are used by these scientific fields are in crystalline forms, it is evident that crystallization, in particular micro-scale crystallisation is a very useful tool to satisfy this demand. This research charts the investigation and optimisation of micro-scale continuous crystallisation of a fine and commonly used compound, i.e. paracetamol, with attempts to overcome the limitations of such process, for instance to produce particles with narrow particle size distribution and maintain a smooth and continuous operation without microchannel blockage. In this thesis, efforts have been directed to design and test a micro scale continuous crystalliser using two different crystallisation techniques; namely: cooling down of saturated solution and adding antisolvent agent. The former technique was not so successful due to the difficult thermal control of such microfluidic system with available resources, as well as due to the inherent nature of such crystallisation mode, which required long induction time to start crystallisation. The latter technique, on the other hand, was successful due to the short induction time required to drive crystallisation and it does not require any thermal management, as it is performed at ambient temperature. Using the antisolvent technique require very short mixing time to mix the mother liquor with an antisolvent agent to produce supersaturated solution. This was achieved by proposing a novel microfluidic design consisting of baffled microchannel devices operated by superimposing a fully reverse oscillatory flow to facilitate fast non-axial mixing regardless of the very low axial flow rate that is typical to microfluidic devises. Computational fluid dynamics simulations in addition to microfluidic flow visualisation experiments were carried out to examine the non-axial mixing performance for the proposeddesign. Subsequently, the proposed design was tested as a con- tinuous crystalliser and showed very good performances by producing sub-micrometre particles with a very narrow particle size distribution. Finally, the performance of the micro scale continuous crystalliser was optimised to produce particle with minimum particle size using custom design of experiment technique. Results of this optimisation process were successful and produced paracetamol particles having average Z-Ave = 99.89 nm with standard deviation equivalent to 7.315 nm. Finally, this thesis shows a successful demonstration of a simple yet versatile microcrystallisation system capable of producing particles of consistent size by utilising fully reverse oscillatory flow into baffled microchannel.
43

Hydrogen production through sorption-enhanced steam reforming of ethanol using CaO-based sorbent mixed with iron oxide catalyst

Elfaki, Hind Omer Elsheikh January 2016 (has links)
Novel synthetic CaO-based sorbents for carbon dioxide (CO2) capture in sorption-enhanced steam reforming (SESR) were prepared by the co-precipitation method. Magnesium oxide (MgO) and cerium oxide (CeO2) were mixed with calcium oxide (CaO) in different molar percentages in order to obtain the optimum percentage, which provide high CO2 uptake capacity and cyclic stability. The TGA results for CO2 uptake, revealed that for the molar ratio of CaO, MgO and CeO2 of (6:2:1) and (4:2:1), the sorbents had CO2 capture capacity of 29 and 25 wt.%, respectively. The fresh sorbents were characterized using X-ray diffraction, mercury porosimetry, N2 physisorption and scanning electron microscopy. It was found that the sorbents with higher CO2 uptake capacities had relatively high porous surface structure with porosity percentage (>66%). Modelling of CO2 uptake kinetics showed that JMA (Johnson-Mehl-Avrami) fits best the first and second stages except for the molar ratio of CaO, MgO and CeO2 of (4:2:1) sample where, surface chemisorption (SC) fits the initial stage and JMA fits the second stage. While the contracting volume model (CV2/3) fits the final stages of all the studied sorbents. The stability of sorbents at high temperatures was examined over multiple cycles of carbonation/de-carbonation reactions. After 45 cycles, the sample with a molar ratio of CaO, MgO and CeO2 of (6:2:1) remained as high as 25 wt.% (0.43g CO2 /1g CaO) with only 25% decrease from its CO2 uptake capacity as a fresh sample. Therefore, the latter sample was selected to be mixed with iron oxide catalyst and used for the SESR. The study of ethanol steam reforming employing an iron oxide as a catalyst, with and without in-situ CO2 removal, has been investigated. The results confirmed that iron oxide exhibited catalytic activity for hydrogen (H2) production from ethanol steam reforming/decomposition reactions. Furthermore, the CaO-based sorbent had sucessfully decrease the amount of CO2 produced during ethanol reforming reaction up to 70 min of reaction time. Ethanol reformation with in-situ CO2 removal was investigated at 550-700 °C. The maximum H2 yield achieved was 3.5 mol (H2) /mol (EtOH) at 600°C. GC results revealed that there was no evidence of CO and C across the studied temperature range. The results showed an enhancement in reaction reactivity by increasing the gas hourly space velocities (GHSVs). The amount of H2 produced remained stable within 10 cycles, which is equivalent to 30 hours of reaction time.
44

Degradation of biomass fuels during long term storage in indoor and outdoor environments

Graham, Shalini L. January 2015 (has links)
This project has investigated the degradation of freshly harvested Willow chips, thermally treated wood pellets and white wood pellets in both indoor and outdoor storage. Novel research has been carried out, by combining a range of fuels, storage scenarios, stockpile sizes and weather/seasonal patterns. A wide spectrum of tests was regularly performed on the stored fuel samples, to determine the extent of chemical, mechanical and biological degradation. The storage trials have been divided into Phase 1 and Phase 2, with Phase 1 starting in April 2011 and Phase 2 in November 2011. The results showed that the extent of chemical degradation was not significant for the different fuels. The main concern for the Willow storage was the high concentration of different fungi on the chips and two pathogenic fungi were identified. In order to fully appreciate the deposition, inhalation and ingestion potential of fungal spores, the release mechanism of the spores from the wood fuels into the air would be recommended as future work. The indoor white wood pellet pile stored in an open barn suffered severe mechanical degradation and it would be therefore advisable to store white wood pellets in a fully enclosed environment with no exposure to ambient temperature and humidity. For the thermally treated pellets, the extent of degradation in the outdoor piles was far more significant than in the indoor one, with rainfall and humidity having an impact on the extent of degradation. Therefore, while the long term storage of thermally treated wood pellets in an open barn with covered storage would be a viable option; pellets stored in outdoor stockpiles would still be vulnerable to mechanical degradation. So outside storage of thermally treated pellets might be an option for short term strategic stocks, but in the majority of cases, covered storage would still be necessary.
45

Solubility studies on poly(ethylene oxide) and cellulose

Michael, Michael January 1997 (has links)
This study has consisted of two related areas of research. The first area concerned the measurement of the proportions of gauche rotamer about C-C and C-O bonds ofpoly(ethylene oxide) (PEO) from NMR coupling constants. 3J HCCH and 3J HCOC couplings in 1,2-dimethoxyethane and bis-(2-methoxyethyl)ether, both model compounds for PEO, plus 3JHCCH in poly(ethylene oxide), have been obtained in five solvents by iterative fitting. The deduced proportions of gauche rotamers are higher than previous estimates, and higher still after allowance is made for the pentane effect. They fit well with gas phase electron diffraction data, with current gas phase theoretical calculations and with standard RIS parameters for the polymer. The influence of solvent arises more from its H-bond donor properties than in its dielectric. This study was undertaken partly in order to elucidate likely conformations of the glycosidic bond in the ensuing work on cellulose dissolution. The second area of research was concerned with the dissolution of cellulose in amine oxides. Courtaulds PLC have successfully used N-methylmorpholine-N-oxide (NMMO) to produce cellulosic spinning solutions. However, the interaction between cellulose and NMMO is not clearly understood. We have therefore sought to amplifY the understanding of this polymer-solvent interaction, first with optical microscopy experiments, and then with solution-state and solid-state NMR techniques. Optical microscopy experiments showed several different behaviours of ramie fibres (natural, highly crystalline cellulose I) as they dissolved in NMMO with added ~O. In 81.2 % NMMO solution, the fibres were observed to swell without dissolution, or burst into tiny fragments or else bend at certain regions creating a "zigzagging" pattern before dissolution. The rates of dissolution were also variable. Some amine oxides that are non-solvents for cellulose were also found to swell ramie, though in this case without subsequent dissolution. The changes in the proton NMR chemical shifts of NMMO and N-ethylmorpholine-N-oxide (NEMO), dissolved in dry DMSO-d6, on addition of water or methyl-P.o-glucopyranoside (a soluble model compound for cellulose) were used to obtain binding constants. The binding between methyl-P.oglucopyranoside and NMMO (a solvent for cellulose) is about twice as strong as the binding between the non-solvent NEMO and the same saccharide, under these conditions. In contrast, the binding between NEMO and water is stronger than that measured between NMMO and water. The stronger interaction of NMMO (relative to the interaction of NEMO) with the saccharide helps to explain its potency as a solvent for cellulose, but the reason for its occurrence, and the weakened interaction with water, is not fully understood. The carbon NMR shift differences of methyl-P.o-cellobioside on addition of various amine oxides (both solvents and non-solvents for cellulose) were found to be similar. We propose that the 1:1 interactions of all amine oxides with cellulose may be similar but that the competing interaction between amine oxide molecules decides if they become a solvent or non-solvent for cellulose. The variation of spin-lattice relaxation measurements on the cellobiose carbons upon addition of NMMO was also studied It indicates an increase of mobility of the C5-C6 bond in the presence ofNMMO. This implies the breaking ofH-bonds in this region. Solid-state NMR spectra (both CPMAS and HPDEC/MAS) were run on aliquots of cellulose samples in NMMO, taken out at various stages of the dissolution process. A faster disappearance of the C4 peak from the crystalline phase relative to the C4 peak from the amorphous phase suggests that the crystalline phase must first be penetrated by the solvent before dissolution. In contrast ramie treated with the non-solvent NEMO was found to have been converted from cellulose I to cellulose illr Theamorphous phase of ramie fibres treated with the non-solvent trimethylamine-N-oxide was found to increase at the expense of the crystalline phase, although in this case no cellulose ~ was detected. Evidently, some amine oxides that are non-solvents for cellulose can nevertheless penetrate between layers of cellulose that are held together by Vander Waals forces, even though they cannot pull apart adjacent chains of cellulose (necessary for dissolution to occur) that are held together by strong H-bonds.
46

Thermodynamic and heat transfer analysis of a carbon-ammonia adsorption heat pump

Rivero Pacho, Ángeles María January 2014 (has links)
The modelling, design, construction and experimental testing of a carbon-ammonia adsorption heat pump is presented. The main objective of the research was to computer simulate and test a 4-beds thermal wave adsorption cycle and to improve the heat transfer rate in an existing shell and tube generator. The existing generators were shell and tube type and were made of nickel brazed stainless steel but their heat transfer performance was poor. New heat exchangers with same design but larger in size were manufactured. The sorbent material, active carbon, was tested in order to characterise its thermal properties and a new generator filling technique was developed and presented. Computational modelling was carried out to evaluate the performance of the 4-beds thermal wave adsorption cycle. The proposed system was an air source heat pump that could deliver an output heating power of 7 kW and a seasonal heating COP of 1.47. The adsorption generators were tested in a 4-bed thermal wave air-source heat pump system and achieved heating output powers between 4.5 to 5.20 kW if taking into account the system heat losses (4.30 to 4.90 kW without heat losses) and heating COP’s of between 1.26 and 1.31 if taking into account the system heat losses (1.13 to 1.18 kW without heat losses). These values were significantly lower than the predicted performance of the simulation. The main cause of this discrepancy was the water distributors located at the end of the generators that distorted during the testing stage and blocked the tubes of the generators.
47

Respiratory gas carriers in plant culture systems

Anthony, Paul January 1999 (has links)
A crucial pre-requisite in genetically manipulating higher plants involves systems for culturing plant protoplasts and cells under static conditions with an adequate oxygen supply. This is especially the case for cells from cryopreservation, where respiratory perturbations are known to occur during early post-thaw recovery. Therefore, studies were undertaken to assess the potential, and actual, beneficial effects involving culture of cells at an interface between inert, oxygen-gassed perfluorocarbon (PFC) liquid overlaid with liquid or semi-solidified media supplemented with or without the non-ionic surfactant, Pluronic F-68. Assessments were also made to compare the efficacy of PFC supplementation with other physical (medium implanted with glass rods to increase the surface area available for gaseous exchange) and chemical (haemoglobin; Hb) options, both alone and in combination, for gaseous manipulation of plant protoplast cultures. Investigations involving novel PFC-mediated oxygen delivery to cultured protoplasts were carried out on a broad range of plant species, which included Petunia hybrida (a herbaceous species) and Passiflora giberti (a woody species), as model systems, together with cassava (Manihot esculenta) a relatively recalcitrant species in tissue culture. Studies revealed enhanced protoplast initial plating efficiencies (IPEs) as measured by increased mitotic division, thereby demonstrating no short-term detrimental effects of exposure to PFC. Similarly, supplementation of culture media with Hb, at 1:50 (v/v), increased the mean IPEs of both Petunia and Passiflora protoplasts over that of untreated controls. Additionally, supplementation of aqueous medium with 0.01% (w/v) Pluronic® F-68 not only lowered interfacial tension, but further enhanced mitotic activity over that stimulated by both oxygenated PFC and Hb. In the context of cryopreservation, media supplementation with Pluronic F-68, at 0.01-1.0% (w/v), significantly improved the post-thaw viability and growth of embryogenic suspension cells of the rice (Oryza sativa L.) cultivars Taipei 309 and Tarom, together with non-embryogenic cells of Lolium multiflorum and Moricandia arvensis. Moreover, a more pronounced synergistic effect in terms of viability and growth was observed for Taipei 309 cells when 0.01% (w/v) Pluronic® F-68 was evaluated in conjunction with oxygenated PFC. Plants regenerated from such cryopreserved cells were morphologically normal with expected chromosome complements (2n = 2x = 24), thus confirming the long-term biocompatibility of PFCs, with no adverse effect up on cellular totipotency. These results indicate, for the first time, that both oxygenated PFC and Hb provide options for enhancing cellular oxygen supply to cultured eukaryotic cells in vitro. However, the recoverability and, hence, recyclability of PFCs make them a commercially more attractive option, despite the high initial investment cost. Overall, PFC-facilitated improvements in cell culture technology will have increasingly important biotechnological implications in the context of plant micropropagation, somatic hybridisation, transgenic plant production and commercial exploitation of these technologies. NB. This ethesis has been created by scanning the typescript original and may contain inaccuracies. In case of difficulty, please refer to the original text.
48

Digital decoration of polymers : innovations in the dye sublimation process

Makenji, Kylash January 2011 (has links)
There are numerous techniques that can be used for the decoration of polymeric substrates, dye sublimation, self-colouring, paint spraying, granular injection paint technology, pad printing, in-mould decoration and hot foil stamping. Dye sublimation was selected for this research as it was found to be both the most relevant technology area for IDT Systems Limited and the least understood. It is a customisable digital process which uses specialist Cyan, Magenta, Yellow and Black (CMYK) inkjet-able dyes that are transferred into a substrate via a carrier. During the process heat is applied which transforms the dyes from a solid into a gas phase. Analysis of literature identified a number of knowledge gaps, which are addressed during this research and detailed in this report. Initial experimentation concluded that the sublimation dyes can penetrate a range of commercially available amorphous polymers, comparably to semi-crystalline types. These findings dispute previously published work, but these also lacked rigorously recorded methodologies to confirm comparable data. All of the materials, equipment and methodologies used throughout this research were therefore developed in this report. Further detailed experimentation was completed, using amorphous polycarbonate, (PC) and semi-crystalline polybutylene terephthalate, (PBT) focusing on the process time and temperature to understand their influence on the level of dye penetration. The results revealed that increasing the process temperature and time improves the level of dye penetration and that comparable penetration levels were noted at 140-180 oC. Further research identified the importance of free volume in the polymer, this increases in size and connectivity as temperature increases above the glass transition points. Additional experimentation confirms that the free volume enables the dyes to penetrate into the polymer. Characterisation of the CMYK sublimation dyes was completed using Differential Scanning Calorimetry enabling the thermal transitions to be identified. Visual experimentation confirmed that the dyes start and finish sublimation between 145-210 oC. As no software tool existed to visualise the dye penetration, one was developed using MatLab. The tool imports and then interpolates the data and graphically outputs it for the user. This allows a quicker set up time of the process and reduces the number of samples to be destroyed. As a direct result of the innovations described in this report, the industrial sponsor has benefited with an increase in commercial exploitation. Aspects of this research have been published, presented and a patent has been published, details are provided within.
49

Silver-based nanocomposite materials for marine antifouling applications

Yee, Swee Li Maxine January 2018 (has links)
Biofouling of marine surfaces is an age-old problem that affects natural and man-made surfaces exposed to the aquatic environment. The tenacious attachment of seaweed and invertebrates to man-made surfaces, notably on ship hulls, has incurred undesirable economic losses. The initial stage of the biofouling process has been attributed to the attachment of marine bacteria and their subsequent formation of biofilm which attract the settlement of larger sessile organisms including barnacles and seaweed. Silver nanostructured materials have a well-documented history as antimicrobial agents against pathogenic bacteria due to their ability to penetrate cell walls and interfere with crucial cellular processes. However, there is a surprising lack of information on their activity against marine biofilm bacteria that have critical roles in the initiation of marine fouling processes. This PhD project explores the antifouling properties of novel silver nanocomposite materials as potent antifouling agents against targeted organisms present in marine environments. The study consists of the syntheses of novel silver nanocomposite materials using various templates/matrices such as ion-exchange polymeric microspheres, zeolites, TiO2 nanotubes and graphene nanosheets. These materials were characterized through various instrumentation techniques including scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDX), X-ray powder diffraction (XRD), UV-visible (UV-vis) spectrophotometry, transmission electron microscopy (TEM), accelerated surface area porosimetry (ASAP), thermal gravimetric analysis (TGA), and Raman spectroscopy to elucidate their physical properties. Their antifouling effects were evaluated on Halomonas pacifica, a model marine microfouling bacterium, through an established static biofilm assay. In addition, the biological effects of these silver nanocomposites were also studied on marine microalgae Dunaliella tertiolecta and Isochrysis sp. Silver-polymer nanocomposite (Ag-PNC) microspheres were formed through a rapid chemical synthesis procedure at room temperature via the reduction of silver nitrate by sodium borohydride. The introduction of Ag nanoparticles (AgNPs) enhanced the thermal stability of the Dowex microspheres by shifting the glass transition temperature to above 300°C and the material decomposition occurred above 460°C. XRD analysis confirmed the presence of metallic Ag, while UV-vis absorption studies showed the characteristic surface plasmon resonance (SPR) for AgNPs ranging from 406 – 422 nm maximum absorption wavelengths. SEM imaging revealed the uniform distribution of AgNPs with diameters between 20 – 60 nm on the surface of the microbeads. The Ag-PNC materials, diluted to a concentration of 1 mg/mL in marine broth, showed a potent inhibitory effect on H. pacifica biofilm formation, with up to 76% decrease of biofilm when contrasted with the polymeric microspheres without Ag. Ag-PNCs also caused significant growth inhibition of D. tertiolecta and Isochrysis sp. Silver-zeolite nanocomposite clusters (AgZ) were formed through a low temperature chemical reduction method using the environmentally friendly trisodium citrate. The stable and porous inner structure of ZSM-5 zeolites performed a dual role as a stable size-control template and a reservoir of antimicrobial nanosilver. SEM revealed the globular and cluster-like morphology of the AgZ composites, with a homogenous distribution of silver particles on the surface of the clusters. EDX results displayed an increasing Ag loading with higher concentrations of Ag precursor, up to 10 wt% Ag. The UV-visible absorption displayed the characteristic SPR absorption maximum ranging from 408 – 500 nm. The AgZ clusters with metallic silver loading of up to 10 wt% Ag, diluted to a concentration of 1 mg/mL, reduced H. pacifica biofilm attachment of up to 81% compared to pure zeolite alone. XRD analysis clearly indicated the presence of metallic Ag while the ZSM-5 zeolite crystalline framework remained largely intact after the Ag crystal growth process. Brunauer-Emmett-Teller (BET) analysis showed a reduction in surface area of up to 44% with the incorporation of AgNPs into the zeolite, indicating the formation and growth of Ag within the internal pores and channels of the zeolite. Although the introduction and crystal growth of silver nanoparticles within the porous structure of the zeolite caused a change from a mesoporous to a largely macroporous structure, the integrity of the zeolite template was preserved. Silver-titania nanotube (Ag/TNT) composite material was prepared through a novel 2-step hydrothermal synthesis method. Titania nanotubes were chosen as a support material for the AgNPs as its greater specific surface area on the inner and outer surfaces of its tubular structure lead to enhanced properties. The morphology, particle size, chemical content, crystal structure, optical properties and surface area were systematically characterized. Determination of biofilm inhibitory properties revealed that Ag/TNT (concentration of 0.1 mg/mL) with the lowest silver content (0.95 wt% Ag) decorated with AgNPs of approximately 3 nm reduced biofilm formation of H. pacifica by 98% compared to pure titania nanotubes and bulk silver alone. Growth inhibition of D. tertiolecta and Isochrysis sp. were also observed. Interestingly, the antifouling properties were improved with a size decrease of AgNPs. The work shows that titania nanotubes are a stable and effective support for the anchoring and growth of AgNPs. The addition of very low amounts of Ag enhanced the antifouling property of pure TiO2 to produce an extremely potent antifouling effect on the targeted organisms. Graphene-Ag (GAg) nanocomposites were prepared from a novel and mild hydrothermal synthesis method which bypasses the formation of graphene oxide. The GAg nanocomposite combines the antimicrobial property of silver nanoparticles and the unique structure of graphene as a support material, with potent marine antifouling properties. The results show that GAg nanocomposites displayed significant biofilm inhibition property on H. pacifica and antiproliferative effects on D. tertiolecta and Isochrysis sp. As low as 1.3 wt% of Ag loading on a GAg sample, diluted to a concentration of 0.1 mg/mL, inhibited biofilm formation from H. pacifica. The GAg sample with 4.9 wt% Ag loading was associated with a biofilm inhibition of 99.6%. The marine antifouling properties of GAg nanocomposites were a synergy of the biocidal AgNPs anchored on the flexible graphene sheets, thereby providing maximum active contact surface areas to the target organisms. The GAg material was characterized with SEM, EDX, TEM, XRD and Raman spectroscopy. In addition, the GAg material exhibited the surface-enhanced Raman scattering (SERS) effect. The AgNPs were estimated to be between 72-86 nm, observed supported on micron-scaled graphene flakes. These results strongly suggest that the 4 types of silver-based nanocomposite materials are promising marine antifouling agents. The addition of very low amounts of Ag enhanced the antifouling property of the support structure, and the nanocomposites were shown to be more effective on the targeted organisms compared to the matrix material or bulk silver alone. In addition, the precursor materials used in the syntheses are affordable and easily available, whilst the synthetic methods and conditions are facile, environmentally friendly, and capable of producing high yields.
50

Supercritical carbon dioxide for green polymer chemistry

Curia, Silvio January 2016 (has links)
This thesis details novel research on the design of new approaches that might lead to a more sustainable polymer industry by combining the use of supercritical carbon dioxide, a commercially available immobilised enzyme and renewable monomers. First, the key themes explored in this thesis are outlined. Green polymer chemistry, biodegradable and renewable polymers, biocatalysts for polymerisations (i.e. enzymes) and supercritical carbon dioxide as a reaction medium for polymer synthesis and processing are introduced (Chapter 1). Then, the high-pressure equipment and characterisation techniques are detailed. The reaction vessel used extensively in this research work is meticulously described. The high-pressure fixed-volume view cell and the high-pressure rheometer are also detailed (Chapter 2). This chapter includes also the standard operating procedure (SOP) for each piece of equipment. In the first research chapter, the carbon dioxide-induced melting point depression of poly(e-caprolactone) is investigated; thorough rheometric studies are used to provide a rheological viewpoint to this phenomenon (Chapter 3). Shear-viscosity studies were performed in order to assess the advantages that high-pressure carbon dioxide could deliver for semi-crystalline polymer processing. Visual observations of the polymer plasticisation and comparisons with high-temperature studies are also shown. In the subsequent chapter, the development of a novel enzymatic low-temperature approach for the preparation of functional low molecular weight polyesters is detailed (Chapter 4). By exploiting the unique properties of supercritical carbon dioxide and an enzyme catalyst, polymerisations ordinarily conducted using metal catalysts in excess of 200 °C were successfully conducted at milder conditions. Functional molecules could be used to end-cap the chains, thus producing green telechelics. Then, this innovative synthetic approach was extended to the preparation of bio- based amphiphilic polymers, which could be useful for drugs encapsulation and as surfactants in detergent formulations (Chapter 5). Specifically, the self-assembly of these novel polymers and the stability of the aggregated structures in water were investigated in detail. Additionally, encapsulation of a highly lipophilic molecule (Coumarin-6) and surface tension studies provided a clear demonstration of the usefulness of these polymers for a wide range of applications. The final part of the thesis sums up the overall conclusions obtained from this research work and outlines possible opportunities for future research in this area (Chapter 6).

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