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1
Liu, Jingjing. "Generation and characterisation of cold atmospheric liquid-containing plasmas." Thesis, Loughborough University, 2011. https://dspace.lboro.ac.uk/2134/7761.
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This thesis presents an experimental study of non-thermal atmospheric pressure gas plasmas in presence of liquid as an efficient source of transient and reactive species to initiate chemical reactions necessary for many important applications. Two types of liquid-containing plasmas are considered: discharges formed between a needle electrode and a liquid electrode, and plasma jets formed in a water vapour flow mixed in helium or argon gas. Two plasma modes (the pulsed and the continuous mode) are observed in the needle-to-liquid plasma. A comparative study of the needle-to-liquid plasma in the continuous mode with DC and AC excitations reveals that the plasmas are glow discharges, and AC excited plasmas have the highest energy efficiency. A study of helium/water vapour plasma jet shows that “plasma bullets” are formed even with water vapour in the gas mixture, but become quenched when the moist helium flow rate is above 300sccm (~1800ppm water concentration). Moderate amount of water vapour (~250ppm water concentration) is beneficial for active species production mainly due to the high electron density. Hydrogen peroxide production in saline solution with three different plasma sources is investigated due to the importance of H2O2 in several important applications. Long lifetime of H2O2 in the liquid after plasma treatment indicates an exciting possibility of plasma pharmacy.
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Baker, Mark Andrew 1974. "Purification and characterisation of the plasma membrane NADH:oxidoreductase." Monash University, Dept. of Biochemistry and Molecular Biology, 2002. http://arrow.monash.edu.au/hdl/1959.1/8440.
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Haruman, Esa. "Characterisation of compound layers produced by plasma nitrocarburising." Thesis, University of Birmingham, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.558074.
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Ferritic plasma nitrocarburising of iron and steels has been carried out using a pilot scale industrial plasma processing unit. Atmospheres containing nitrogen, hydrogen, carbon dioxide, and in some cases methane were employed during the investigation. The nitrocarburised compound layers formed as a result of this glow discharge thermochemical treatment have been examined using a variety of metallographic and surface analysis techniques (including NRA, EPMA, AES, GDOES). Following the characterisation of the resultant compound layers, falex wear tests were performed on selected specimens to evaluate the wear resistance of the various nitrocarburised surfaces.
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Wade, Graham Andrew. "Characterisation of adhesively bonded, plasma treated, thermoplastic composites." Thesis, University of Liverpool, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.399089.
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Warren, Jamie MacNeill. "The advanced characterisation of gas plasma treated polymers." Thesis, Heriot-Watt University, 2007. http://hdl.handle.net/10399/2150.
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The objective ofthis research was to investigate how gas plasma treatments can alter the surface morphology of polypropylene (PP) fibres and tape with the main focus of the work on the tape. The morphological changes caused by exposure to controlled argon, nitrogen and oxygen gas plasmas were characterised using both Scanning Probe Microscopy (SPM) and Scanning Electron Microscopy (SEM). The research has demonstrated that the extent of surface deformation was dependent on the treatment gas used and on the process parameters. Surface deformation gradually increases with increasing process time and power. Oxygen plasma was found to be the most aggressive plasma followed by nitrogen, with argon the weakest. Different process parameters used during extrusion have an important effect on the nature of the PP morphology. This thesis also demonstrates how the surface morphology can be altered by different cooling techniques and by drawing the tape once extruded. SPM analysis shows a transformation in the spherulitic morphology from hill to valley shaped spherulites when gravity spun PP tape was cooled in water as opposed to air. Deformation of the spherulitic structure to a fibril struct~re was also observed, which became more apparent from gravity via as-spun to fully drawn tapes.
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Shanks, Richard P. "Comprehensive characterisation of laser plasma wakefield accelerated electrons." Thesis, University of Strathclyde, 2012. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=18119.
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Potts, Hugh E. "Characterisation of an atmospheric pressure : microwave induced plasma." Thesis, University of Manchester, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.680177.
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Olabanji, Olumuyiwa. "The study and characterisation of plasma microfluidic devices." Thesis, University of Liverpool, 2012. http://livrepository.liverpool.ac.uk/6533/.
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Controlling the behaviour of atmospheric pressure plasmas and their interaction with polymeric materials is of major interest for surface modification applications across multidisciplinary fields intersecting biomedical engineering, bio-nanoengineering, clinical/medical science, material science and microelectronics. The aim of the present work is to investigate the behaviour of atmospheric pressure dielectric barrier discharges in closed systems (microfluidic devices) and open systems (glass capillary devices) and their polymer-surface interactions. Atmospheric pressure microplasma jets operating in helium gas have been used to modify locally the surface energy of polystyrene (PS) and to interact directly with the surface of analytes using a novel plasma assisted desorption ionisation (PADI) method causing desorption and ionization to occur. Although atmospheric pressure micro-jets are now widely studied for the treatment of materials there is still a lack of understanding of the fundamental plasma-surface processes. A number of recent studies using plasma micro-jets for the surface modification of polymerics have used systems in which the emerging plume impinges directly the substrate head-on. Here, by placing the micro-jet side-on to the substrate we can observe how different flow regions of the jet affect the sample, allowing individual effects to be seen. In addition, this configuration may prove an efficient way of treating samples with reduced or no surface damage. These conclusions are considered to be an important contribution to the study of complex mechanisms underpinning the behaviour of radicals and reactive species in surface modification processes of polymeric materials. The study of the behavioural mechanism involved in the plasma was done using various diagnostic techniques such as electrical measurements, optical emission spectroscopy (OES), Time-averaged and time-resolved ICCD Optical Imaging and Schlieren Photography. The filamentary discharge mode was observed in bonded microchannels using metallic and liquid-patterned electrodes. The treated surfaces were characterised using various techniques such as X-ray photoelectron spectroscopy (XPS), Atomic Force Microscopy (AFM), Optical profiling measurements and Water Contact Angle (WCA) measurements. Schlieren photography has been used to indentify regions of laminar (pre-onset of visual instability) and turbulent flows (post-onset of visual instability) in the exiting gas stream and the nature of their interaction with the substrate surface. The length of both regions varies depending on operating parameters such as frequency, applied voltage and flow rate. WCA results from treated polystyrene (PS) samples exposed directly facing the microjet reveals a change from hydrophobic (high contact angle) to a hydrophilic (low contact angle) surface with substantial reductions in WCA (~ 50 to 60 °) occurring in downstream regions where the turbulent gas mixed with air impinges the substrate surface. In contrast, only small changes in WCA (~ 10 to 20 °) occur in regions where the gas flow is laminar. AFM imaging of treated PS samples reveal holes and ripple like effect with a much larger area than that of the capillary seen on treated samples positioned “head-on” and directly facing the sample but this was not seen using the side-on configuration. The results indicate that excited air species (either mixed or entrained in the He gas flow) which exist only in regions of turbulence are the main agents causing surface covalent bond breaking leading to surface modification. This thesis reports on atmospheric pressure microdischarges and their applications, a brief summary of work done so far including major results, using new and existing technologies including those under development in terms of design, properties and working conditions.
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Richardson, Victoria Rebecca. "Identification and characterisation of novel plasma clot components." Thesis, University of Leeds, 2012. http://etheses.whiterose.ac.uk/4153/.
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Plasma clot structure/function is a major determinant in cardiovascular disease risk and severity. Plasma proteins are incorporated into plasma clots via binding and factor XIII-dependent cross-linking, with complement C3 and factor H previously identified as plasma clot components using proteomics. The aim of this current project was to validate the role of C3 and factor H in fibrin structure and function and to establish a proteomics method for the identification of novel factor XIII substrates. C3 did not affect fibrin structure; however C3 induced a concentration-dependent prolongation of fibrinolysis. C3 was cross-linked to fibrin within purified and plasma clots and bound to plasma clot components. C3 was a substrate for plasmin, with cleavage occurring in the presence and absence of fibrin. C3 also influenced angiostatin production and t-PA and plasminogen interactions within fibrin clots to prevent plasminogen cleavage and plasmin generation. All of these interactions were found to influence fibrinolysis. Whereas factor H was confirmed to be a plasma clot component, was associated with inflammation and fibrin structure and function but was not associated with complement activation in individuals at risk of cardiovascular disease. Further in vitro analyses found that factor H did not affect fibrin structure or fibrinolysis. Factor H was not cross-linked to fibrin in purified and plasma clots, but did form homodimers in the presence and absence of fibrin and factor H was a substrate for thrombin and plasmin, with cleavage occurring within fibrin clots. The proteomic techniques were established for the identification of factor XIII substrates however no novel proteins were identified using these methods, suggesting the sensitivity of the technique may be insufficient to detect novel proteins. This study has added to the growing body of evidence which suggests complement and coagulation pathways interact for the purposes of preventing blood loss and pathogen invasion.
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Hubbard, Paul, and paul hubbard@rmit edu au. "Characterisation of a Commercial Active Screen Plasma Nitriding System." RMIT University. Applied Physics, 2008. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20090212.161932.
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Nitriding is a plasma based processing technique that is used to improve the surface properties of components and products in many areas including the aerospace, automotive and biomedical industries to name a few. Active Screen Plasma Nitriding (ASPN) is a relatively new nitriding technique which has potential advantages over the more traditional nitriding techniques such as Direct Current (DC) plasma nitriding where high substrate biases can be problematic. However, there is considerable debate as to the mechanism for nitriding in ASPN. This thesis focuses on investigating the mechanism for nitriding in a commercial ASPN system. Commercial ASPN treatments of nitrideable alloy steels were found to be unsatisfactory unless a sufficient bias was applied. The level of bias required to produce a satisfactory nitriding response, in terms of the cross sectional hardness, was found to depend on the concentration of strong alloy nitride forming elements present in the steel. Although active screen material was found to be transferred to the workload, no evidence was found that this process played a significant role in enhancing the nitriding response. The primary mechanism for nitrogen mass transfer in ASPN was found to be dependent on the active screen/workload separation distance. When this separation is small (less than approximately 10cm for the conditions used in this study) then nitrogen mass transfer in the form of energetic ions or neutrals can occur between the active screen and the workload. This allows samples to be treated without a substrate bias. On the other hand, when the active screen/workload separation distance is large (greater than approximately 10cm) as is normally the case in a commercial environment, this mechanism for nitrogen mass transfer breaks down and a substrate bias is essential. In this latter case, nitrogen ions attracted to the workload using a bias is the primary nitrogen mass transfer mechanism and the role of the active screen is primar ily to uniformly heat the workload.
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Hough, Tertius Anton. "Characterisation and genetics of mouse plasma alkaline phosphotase mutants." Thesis, Imperial College London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.414376.
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McGarvey, Caron. "Characterisation of plasma closing switches filled with different gases." Thesis, University of Strathclyde, 2017. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=28658.
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Sulphur Hexafluoride (SF6) is one of the most commonly used gases within switching applications for pulsed power applications due to a large number of desirable properties, however, it is a greenhouse gas and global concerns over the emission of this gas into the atmosphere have led to an increase in research into potential environmentally friendly alternatives. This study focused on an experimental investigation into the breakdown characteristics of two commonly used plasma closing switch topologies when filled with different gasses and gas mixtures not previously considered in as much depth for switching purposes (air, N2, 60%/40% N2/O2, 90%/10% Ar/O2, and CO2) as compared to the characteristics of the switches when filled with SF6. A self-breakdown switch and a field-distortion triggered switch topology with varying inter-electrode gap lengths up to 9mm, filled with gasses at pressures in the range 0.1MPa-0.5MPa were studied and some key operational characteristics and switching parameters such as the self-breakdown voltage of the gases, the spread in self-breakdown voltage, time to breakdown and jitter of the switches were investigated and compared. Temperature of the plasma that forms during breakdown and the conductivity of plasma was extracted for each gas and in addition to this, analysis of post-breakdown waveforms allowed for obtaining values of inductance and resistance of the switches. Experimental results have been used in the development of two computational models of Marx Generators which are used in the voltage erection stage of pulsed power systems. The models developed describe the switches as either having constant resistance or taking into account the transient plasma resistance which allows for a more accurate representation of the voltage and current behavior across the output load over the first quarter of the current oscillation after switch closure occurs.
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Buhagiar, Joseph. "Plasma surface engineering and characterisation of biomedical stainless steels." Thesis, University of Birmingham, 2008. http://etheses.bham.ac.uk//id/eprint/3744/.
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Low temperature plasma surface alloying with nitrogen (nitriding), carbon (carburising) and both (carbonitriding) has been successfully employed in hardening medical grade ASTM F138, ASTM F1586 and ASTM F2581 as well as engineering grade AISI 316 by the formation of a modified layer better known as S-phase or expanded austenite. In this study, systematic plasma treatments and characterisation were performed on medical grade stainless steel in order to establish the optimised treatment conditions, especially temperature, which can maximise the hardened case depth without any detriment in corrosion resistance. The surface of a biomaterial must not adversely affect its biological environment and return the material surface must not be adversely affected by the surrounding host tissue and fluids. Experimental results have shown that this duality of concern can be addressed by creating S-phase. It has been shown that low-temperature nitriding (430°C), carburising (500°C) and carbonitriding (430°C) improved the localised corrosion, corrosion-wear and fretting-wear resistance of these medical grade stainless. Also biocompatibility studies have proved that these hardened surfaces were biocompatible under the realms of the tests conducted in this study therefore the use of hardened medical grade austenitic stainless steel might be suitable in implant applications.
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Pratontep, Sirapat. "Production and characterisation of size-selected nanoclusters on surfaces." Thesis, University of Birmingham, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.289304.
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Rafiq, Mineza. "Expression and characterisation of recombinant human ceruloplasmin." Thesis, King's College London (University of London), 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.369290.
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Foster, Peta Suzanne. "Characterisation of plasma mirror activation and laser-driven ion studies." Thesis, Queen's University Belfast, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.676468.
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In this thesis, a body of work is presented which contributes towards the improved understanding of plasma mirror operation and in 'particular, the switch-on dynamics and picosecond timescale reflectivity. Degradation in the performance of the baseline anti-reflective properties of the plasma mirrors is observed 1.5 picoseconds prior to the main pulse peak. This is believed to be the first observation of this effect. The rise time of these plasma optics is measured in a simple numerical model constructed to elucidate the underlying physics. The ultimate aim is to reveal the underlying dynamics so as to be able to ascertain how to best operate these optics to achieve ultra-high contrast. This would benefit high-intensity interactions, potentially enhancing laser-driven ion acceleration and high harmonic production. This thesis also explores the use of these enhanced-contrast pulses in laser-driven ion acceleration studies, at the cutting edge of both on-target intensity and ultra-thin foil thickness. Continuous wave laser heating of skin depth foils is investigated for the purpose of contaminant removal and target thinning. In addition, ultra-high intensity interactions were explored, where it was hoped the dynamics might indicate a transition to a new and more efficient acceleration regime, namely radiation pressure acceleration. Both of these ion studies have a key signature of higher peak ion energies, and although the energy range of ions was not increased as far as had been hoped, the thesis endeavors to shed light on the current observations and highlight limitations encountered, such as to inform the ongoing research moving forward.
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O'Hare, Lesley-Ann. "Surface characterisation of atmospheric pressure plasma-modified and coated polymers." Thesis, Open University, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.424274.
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Jäckel, Oliver. "Characterisation of ion acceleration with relativistic laser-plasmas." Tönning Lübeck Marburg Der Andere Verl, 2009. http://d-nb.info/995862729/04.
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Evans, Steven. "The molecular characterisation of pregnancy-associated plasma protein-A (PAPP-A)." Thesis, Sheffield Hallam University, 1996. http://shura.shu.ac.uk/19631/.
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PAPP-A is a large glycoprotein with alpha2-electrophoretic mobility that is produced by the placenta during pregnancy. In this thesis a biochemical and molecular characterisation of PAPP-A was performed. The polyclonal antiserum (DAKO) directed against PAPP-A has been shown to also interact with proteins other than PAPP-A. These non-specific interactions were abolished by performing Western blotting immunodetection at a high salt concentration (0.6M NaCl). At this salt concentration a single band of 195 kDa was immunodetected and this corresponded to the monomeric PAPP-A molecule. It was also discovered that a subset of paratopes in this antiserum reacted, under the described high salt concentration conditions, with the glycan component of PAPP-A. A placental cDNA library was screened using this antibody for the PAPP-A cDNA but this did not yield a clone for PAPP-A. A possible explanation is that the interaction with this antibody requires carbohydrate components to be present on the PAPP-A molecule. It is known that proteins expressed in bacterial systems are not post-translationally modified. Therefore another approach to the isolation of the PAPP-A cDNA clone was adopted, but this required some primary amino acid sequence of this protein that was unavailable at the time. To generate this information, PAPP-A was purified using its previously unpublished affinity for L-arginine in combination with the already described procedures of ammonium sulphate precipitation, ion exchange and gel filtration. Final purification of PAPP-A was achieved by SDS-PAGE electrophoresis. The isolated monomeric PAPP-A gave a unique single N-terminal amino acid sequence: N-EARGATEEPS. The N terminal sequence combined with the sequence obtained from limited proteolytic digestion of PAPP-A were used to design oligonucleotide primers specific for PAPP-A. These primers were used in a PCR reaction that produced 500 and >1200 bp fragments using the cDNA library as DNA template; thus demonstrating that PAPP-A is synthesised in the placenta. PAPP-A was shown to have O and N-linked carbohydrate chains. Enzymatic deglycosylation demonstrated that the N-linked chains were 8% (w/w) of the molecule. The O-linked groups were extensively modified with the presence of oligomers of N-acetyl-glucosamine. It was also shown that it was these groups the PAPP-A antibodies bind to at high salt concentration. A physical interaction of PAPP-A with endoproteinase Arg-C (EGF-BP) was observed. It was seen that they form a 1:1 (PAPP-A: endoproteinase) sub-unit complex that was stable in SDS. A further investigation revealed that PAPP-A interacted with the endoproteinase Arg-C and this resulted in a 30% inhibition of the esterolytic activity of this enzyme.
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Schmidt, Benita. "Detection and Characterisation of Nanoparticles using Inductively Coupled Plasma Mass Spectrometry." Doctoral thesis, Humboldt-Universität zu Berlin, 2019. http://dx.doi.org/10.18452/20162.
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In dieser Doktorarbeit wurde eine analytische Methode zur Charakterisierung metallischer Nanopartikel (NPs) entwickelt und die Methode bei der Untersuchung natürlicher Proben angewendet. Mit einem analytisches System bestehend aus einem Mikrotropfengenerator (microdroplet generator, MDG) zusammen mit einem pneumatischen Zerstäuber und einem induktiv gekoppeltem Plasma-Massenspektrometer (ICP-MS) konnte eine quantitative und qualitative Charakterisierung von NPs durchgeführt werden.
Der MDG wurde verwendet um die Kalibrierungsfunktion für die massenspektrometrische Quantifizierung der Metalle in den Nanopartikelproben, die über den pneumatischen Zerstäuber eingeführt wurden, einzurichten. Der Hauptvorteil dieser Anordnung besteht darin, dass mit dem MDG für jedes Metall Tropfen einer gewünschten Größe hergestellt werden können und eine 100 %-ige Transporteffizienz gegeben ist. Die eingeführte Masse korrelierte mit der Signalintensität von Nanopartikeln, so dass die mit dem MDG generierten Tropfen für die Kalibrierung verwendet werden konnten ohne dass Referenzmaterial erforderlich war. Die aufwändige und fehleranfällige Bestimmung der Effizienz eines Zerstäubers, die für die Bestimmung des Metallgehaltes von NPs mittels eines Einzelpartikel-ICP-MS (spICP-MS) erforderlich ist, konnte dadurch vermieden werden.
Unter Anwendung dieser dualen Einführungsmethode wurden Größen und Konzentrationen einer Reihe von Standard Silber (Ag) NPs und Referenz Gold (Au) NPs mit hoher Genauigkeit bestimmt.
Zusätzlich wurde mit einem neuen kommerziell verfügbaren ICP-Flugzeitmassenspektrometer (ICP-TOF-MS) Ag und Au NPs in unterschiedlichen Matrices charakterisiert: in verschiedenen Salzsäure (HCl)- und Salpetersäure (HNO3)- Konzentrationen und in Gegenwart verschiedener Elemente. Bei den unterschiedlichen Matrices war die Größenbestimmung innerhalb der gegebenen Standardabweichungen korrekt.In this doctoral thesis an analytical method for characterising metal nanoparticles (NPs) was developed and its application for investigating natural samples verified. An analytical system consisting of a microdroplet generator (MDG) used in combination with a pneumatic nebuliser (PN) and an inductively coupled plasma mass spectrometer (ICP-MS) proved capable of quantitatively and qualitatively identifying NPs. The MDG was used to establish the calibration function for mass quantification of the metal present in the sample NPs introduced via the PN. The major advantage of this configuration is that the MDG generated droplets of tailored size for any given metal while offering a 100 % transport efficiency. The introduced mass correlated with signal intensities of NPs and thus the microdroplet generated droplets could be used for calibration purposes without the need for any reference material. Thus, the tedious and error-prone nebuliser efficiency determination step that is required when determining the NP metal content using the single particle mode ICP-MS (spICP-MS) approach, could be avoided. With this dual sample introduction method, the sizes and concentrations of a range of standard silver (Ag) NPs and gold (Au) reference NPs were determined with high accuracy. Additionally, together with a new commercially available ICP-time of flight-MS (ICP-TOF-MS) the characterisation of Ag- and Au-NPs was carried out in various matrices: In hydrochloric (HCl) and nitric acid (HNO3) at a range of concentration and in different elemental environments. In the presence of matrices, it was found that the size characterisation of the NPs is correct within the standard deviation.
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Bahnev, Blagovest. "Electrical and optical characterisation of an atmosphere pressure plasma jet and its interaction with plasmid DNA." Thesis, Open University, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.543860.
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Hillborg, Henrik. "Loss and recovery of hydrophobicity of polydimethylsiloxane after exposure to electrical discharges." Doctoral thesis, KTH, Polymer Technology, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3082.
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Silicone rubber based on polydimethylsiloxane is used ashigh voltage outdoor insulation, due to its ability to preservethe hydrophobic surface properties during service and evenregain hydrophobicity after exposure to electrical discharges.The underlying processes for the hydrophobic recovery arediffusion of low molar mass siloxanes from the bulk to thesurface and reorientation by conformational changes ofmolecules in the surface region. Only little is known of whichfactors are responsible for the long-term stability of thishydrophobic recovery. It is therefore important to increase theknowledge about the fundamental mechanisms for the loss andrecovery of hydrophobicity of silicone rubbers, exposed toelectrical discharges. Addition-cured polydimethylsiloxanenetworks, with known crosslink densities, were exposed tocorona discharges and air/oxygen-plasma and the loss andrecovery of hydrophobicity was characterised by contact anglemeasurements. The degree of surface oxidation increased withincreasing exposure time with a limiting depth of 100- 150 nm,as assessed by neutron reflectivity measurements. The oxidationrate increased with increasing crosslink density of the polymernetwork, according to X-ray photoelectron spectroscopy. Withinthe oxidised layer, a brittle, silica-like layer was graduallydeveloped with increasing exposure time. The hydrophobicrecovery following the corona or air/oxygen- plasma exposuresoccurred at a slow pace by diffusion of cyclic oligomericdimethylsiloxanes through the micro-porous but uncrackedsilica-like surface layer or at a much higher pace by transportof the oligomers through cracks in the silica-like layer. Theoligomers were present in the bulk, but additional amounts wereformed during exposure to corona discharges. High-temperaturevulcanised silicone rubber specimens were aged in a coastalenvironment under high electrical stress levels (100 V/mm). Thechanges in surface structure and properties were compared tothe data obtained from specimens exposed to coronadischarges/plasma. The dominating degradation mechanism wasthermal depolymerisation, initiated by hot discharges. Thisresulted in the formation of mobile siloxanes, of which the lowmolar mass fraction consisted of cyclic oligomericdimethylsiloxanes. Oxidative crosslinking resulting insilica-like surface layers was not observed during theseconditions.
Keywords:silicone rubber, polydimethylsiloxane,hydrophobicity, corona, air-plasma, oxygen-plasma, surfacecharacterisation, degradation products, crosslink density.
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Lau, Desmond, and desmond lau@rmit edu au. "Characterisation of Novel Carbonaceous Materials Synthesised Using Plasmas." RMIT University. Applied Sciences, 2009. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20091119.102551.
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Novel carbon materials such as carbon onions, nanotubes and amorphous carbon (a-C) are technologically important due to their useful properties. Normally synthesised using plasmas, their growth mechanisms are not yet fully understood. For example, the growth mechanism of the high density phase of a-C, tetrahedral amorphous carbon (ta-C), has been a subject of debate ever since its discovery. The growth mechanism of carbon nanostructures such as carbon onions and nanotubes is also not well known. The aim of this thesis is two-fold. Firstly, to provide insight into the growth of carbon films, in particular, the driving force behind the formation of diamond-like bonding in a-C which leads to ta-C. Secondly, to investigate the growth of carbon onions and other sp2 bonded carbon nanostructures such as nanotubes. To achieve the first aim, carbon thin films were deposited using cathodic arc deposition at a range of ion energies, substrate temperatures and Ar background gas pressures. These films were characterised using electron microscopy techniques to examine their microstructure, density and sp3 content. It was found that the formation of the ta-C is due to a stress-induced transition whereby a critical stress of 6.5±1.5 GPa is needed to change the phase of the film from highly sp2 to highly sp3. Within this region, a preferentially oriented phase with graphitic sheets aligned perpendicular to the substrate surface was found. By investigating the role of elevated temperatures, the ion energy-temperature
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Mahony, Charles Michael Oliver. "The development of advanced measurement techniques for the characterisation of low pressure technological processing plasmas." Thesis, University of Ulster, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.272339.
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Qayyum, Asif. "Preparation and characterisation of plasma CVD a-Si:C:H alloys for solar cells." Thesis, Heriot-Watt University, 1989. http://hdl.handle.net/10399/951.
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Aguiló, Aguayo Noemí. "Production and characterisation of carbon-encapsulated iron nanoparticles by arc-discharge plasma." Doctoral thesis, Universitat de Barcelona, 2012. http://hdl.handle.net/10803/96477.
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Carbon-encapsulated iron nanoparticles have being researched heavily, since they present advantageous properties over other protective coatings such as polymer or silica. The carbon coating protects the iron core from oxidation, chemical and thermal degradation and hence, magnetic cores present stable magnetic properties when nanoparticles are exhibited in air or other environments. Several studies about carbon-encapsulated magnetic nanoparticles were already reported. However, nanoparticles are obtained rather polydisperse and not very uniform in composition, making very difficult their use for several applications. The aim of this thesis is the production and characterisation of carbon-encapsulated iron nanoparticles showing very narrow size distributions with well-characterised magnetic properties for several applications, in particular, those related to the biomedical field (hyperthermia, drug delivery or as agents contrast in MRI). However, the systematic study of these applications was not the framework of this thesis.
The content of this dissertation comprises the design of two arc-discharge plasma (ADP) reactors (a conventional and a modified one); the experimental study of the different reactor parameters involved; the morphological, structural and magnetic characterisation of the obtained nanoparticles; the comprehension of the mechanisms involve in the formation of this kind of nanoparticles in comparison with nanoparticles obtained by other methods; and finally, a first approach to the functionalisation of the nanoparticles for the biomedical applications.
This thesis is structured in four parts: Backgrounds (Chapter 1), Nanotools (Chapter 2 and Chapter 3), Results (from Chapter 4 to Chapter 8) and finally, the Conclusions.
Chapter 1 - Basis of carbon-encapsulated iron nanoparticles:
A general introduction of the nanoparticle properties derived from their nanometric dimensions is presented in this chapter. The state of the art about the formation mechanisms and techniques used for the generation of carbon-encapsulated iron nanoparticles is described. Several applications of this kind of nanoparticles in fields such as biomedicine, electronics or food and environmental, are also presented.
Chapter 2 - Characterisation methods:
The most common characterisation techniques used to investigate the morphological, composition, structural and magnetic properties are described within this chapter. Details about the equipments and conditions used during this thesis for the characterisation of the nanoparticles are also reported.
Chapter 3 - Experimental set-up:
In this chapter, the description of two different arc-discharge reactors used during this thesis is presented. A first reactor (the conventional ADP) was developed by following similar experimental setups described in the literature. Second reactor (a modified ADP) was designed to overcome the disadvantages from the first reactor and to obtain high quality nanoparticles (narrower size distribution, uniform composition).
Chapter 4 - Preliminary studies from conventional ADP reactor:
This chapter presents a design of experiments (DOE) based on the Plackett-Burman design in order to evaluate the reactor parameters that influence the most the final characteristics of the nanoparticles. The study was performed using the conventional ADP reactor and the preliminary results were very useful for the development of next generation of experiments using the second reactor, the modified ADP.
Chapter 5 - Generation of nanoparticles by a modified ADP reactor:
Morphological and structural properties of the nanoparticles obtained by the modified ADP reactor are presented. The discussion of the effect of the most relevant parameters on the formation of the nanoparticles was reported. Iron core diameters with corresponding size distribution as well as the carbon shell formation obtained under different parameter conditions were investigated.
Chapter 6 - Magnetic properties of the nanoparticles:
A systematic study of the magnetic properties of the nanoparticles obtained in Chapter 5 is performed. Size-dependent variables such as magnetic moments, coercivity values, blocking temperature and anisotropy energies were presented. Magnetic properties were in agreement with the morphological characteristics of the nanoparticles.
Chapter 7 – Thermally induced structural evolution of the nanoparticles:
The comparison of annealed nanoparticles obtained by mADP and chemical vapour deposition (CVD) method is presented in this chapter. Differences on the morphological, structural and magnetic properties were studied. Structural evolution of nanoparticles during annealing under in-situ TEM observations was investigated.
Chapter 8 - First approach to biomedical applications:
As a first approach to biomedical applications, the stabilisation of the nanoparticles in aqueous solution by using polyvinyl-alcohol was investigated. Results of the internalisation of the nanoparticles into HeLa cells are presented.Les nanopartícules magnètiques de ferro recobertes de carboni s’estan investigant en gran mesura, ja que presenten avantatjoses propietats sobre d’altres recobriments protectors del nucli magnètic com els polímers o la sílice. El recobriment de carboni protegeix el nucli de ferro de l’oxidació, la degració química i tèrmica, d’aquesta manera els nuclis presenten propietats magnètiques estables quan les nanopartícules s’exhibeixen en aire o en un altre medi. S’han realitzat diversos estudis sobre aquest tipus de nanopartícules, però aquest tipus de nanopartícules s’obtenen amb gran dispersió de grandàries i poca uniformitat en les seves característiques. És encara un repte en aquest camp la producció de nanopartícules de ferro recobertes de carbon amb propietats morfològiques i estructurals, així com l’estudi sistemàtic de les seves propietats magnètiques. Per aquest motiu, l’objectiu d’aquesta tesi es centra en la producció i caracterització de nanopartícules superparamagnètiques de ferro recobertes de carboni amb estreta distribució de mides i amb propietats magnètiques ben caracteritzades per diverses aplicacions, en particular, les relacionades amb el camp de la biomedicina. No obstant això, l’estudi sistemàtic d’aquestes aplicacions es troba fora del marc d’aquesta tesi. El contingut s’estructura en quatre parts: • La primera part d’introducció conté els aspectos bàsics sobre aquest tipus de nanopartícules, així com les propietats derivades de la seva mida nanomètrica, les tecnologies que s’utilitzen per generar aquest tipus de nanopartícules, una explicació sobre els possibles mecanismes responsables de la seva formació i les principals aplicacions d’aquestes nanopartícules. • La segona part descriu les tècniques utilitzades per la seva caracterització que engloben tècniques de microscopia, de difracció de raigs-X, d’espectroscòpia Raman, per la caracterització col•loidal de les nanopartícules fins la seva caracterització magnètica. També inclou la descripció detallada dels equips basats en la descàrrega d’arc utilitzats per la seva producció. El primer equip es va dissenyar seguint les característiques d’un reactor convencional (conventional ADP reactor). El segon equip basat en la mateixa tecnologia de descàrrega d’arc, però modificat (mADP reactor) i dissenyat especialment amb l’objectiu de millorar les característiques del producte final. • La tercera part exposa els resultats obtinguts durant aquesta tesi. L’estudi previ del reactor convencional basat en un disseny d’experiments de Plackett-Burman per avaluar l’efecte dels diferents paràmetres del reactor en la grandària dels nuclis de ferro. A partir d’aquest estudi, es va realitzar un estudi més específic en el nou reactor modificat on es van estudiar l’efecte del corrent d’arc utilizat, la velocitat del flux d’heli i el contigut de ferrocè com a matèria prima del ferro. Després es va realitzar l’estudi sistemàtic de les seves propietats magnètiques observant la dependència d’aquestes propietats amb la grandària dels nuclis de ferro. A continuació, es va presentar la comparació d’aquestes nanopartícules amb d’altres obtingudes mitjantçant el mètode de dipòsit químic en fase vapor (CVD). A partir d’aquesta comparació es va estudiar l’evolució estructural d’aquestes nanopartícules sotmetes a un tractament tèrmic en observació in-situ d’un microscopi de transmissió electrònica. Finalment, es va presentar un primer estudi de les propietats col•loidals en suspensió d’aquestes nanopartícules recobertes amb un polímer d’alcohol de polivinil (PVA). Es presenta un primer estudi de l’internalització d’aquestes nanopartícules en cèl•lules tumorals HeLa. • Per acabar es presenten les conclusions i l’apèndix que conté informació sobre les mostres produïdes i un llistat de publicacions, congressos, patents resultants d’aquest treball.
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Gillespie, Geraldine M. A. "Characterisation and functional analysis of T cell populations in plasma cell disorders." Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.298769.
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Morrison, Dominique Johanne. "The fabrication and characterisation of 4H-SiC Schottky barrier diodes." Thesis, University of Newcastle Upon Tyne, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324784.
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Brown, Wayne. "Characterisation of low energy ions observed near and during the substorm expansion phase onset." Thesis, University of Warwick, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302621.
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Weckmann, Armin. "Material migration in tokamaks: Studies of deposition processes and characterisation of dust particles." Licentiate thesis, KTH, Fusionsplasmafysik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-178026.
Full textAbstract:
Thermonuclear fusion may become an attractive future power source. The most promising of all fusion machine concepts is the tokamak. Despite decades of active research, still huge tasks remain before a fusion power plant can go online. One of these important tasks deals with the interaction between the fusion plasma and the reactor wall. This work focuses on how eroded wall materials of different origin and mass are transported in a tokamak device. Element transport can be examined by injection of certain species of unique and predetermined origin, so called tracers. Tracer experiments were conducted at the TEXTOR tokamak before its final shutdown. This offered an unique opportunity for studies of the wall and other internal components: For the first time it was possible to completely dismantle such a machine and analyse every single part of reactor wall, obtaining a detailed pattern of material migration. Main focus of this work is on the high-Z metals tungsten and molybdenum, which were introduced by WF6 and MoF6 injection into the TEXTOR tokamak in several material migration experiments. It is shown that Mo and W migrate in a similar way around the tokamak and that Mo can be used as tracer for W transport. It is further shown how other materials - medium-Z (Ni), low-Z (N-15 and F), fuel species (D) - migrate and get deposited. Finally, the outcome of dust sampling studies is discussed. It is shown that dust appearance and composition depends on origin, formation conditions and that it can originate even from remote systems like the NBI system. Furthermore, metal splashes and droplets have been found, some of them clearly indicating boiling processes.QC 20151203
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Müller, Meike [Verfasser], and Gregor [Akademischer Betreuer] Morfill. "Characterisation of cold atmospheric plasma afterglow for decontamination / Meike Müller ; Betreuer: Gregor Morfill." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2019. http://d-nb.info/1198112034/34.
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Quaw, M'dimoir. "On the generation and characterisation of non-thermal plasma for physical process conditioning." Thesis, University of Liverpool, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.479089.
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Mariotti, Davide. "Characterisation of a micro-plasma device sensor using electrical measurements and emission spectroscopy." Thesis, Ulster University, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.395336.
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Serrano, Aroca Ángel. "Synthesis and characterisation of macroporous poly(methyl methacrylate) with plasma-polymerised hydrophilic coating." Doctoral thesis, Universitat Politècnica de València, 2008. http://hdl.handle.net/10251/1857.
Full textAbstract:
En estas últimas décadas, la ingeniería tisular ha llegado a ser uno de los campos de aplicación más prometedores de los polímeros macroporosos para soportes o matrices porosas tridimensionales donde las células se pueden cultivar.
Una de las formas de obtener un polímero poroso es mediante la polimerización en disolución. De esta forma, los poros se forman debido a la segregación de disolvente de la red polimérica durante el proceso de polimerización. En esta tesis, se han sintetizado redes poliméricas de polimetacrilato de metilo (PMMA) por polimerización en presencia de etanol con diferentes porosidades y contenidos de entrecruzador. También se ha sintetizado PMMA polimerizado en masa (no poroso) como material de referencia.
El PMMA macroporoso se coloca en una atmósfera saturada de vapor de monómero de acrilato de hidroxietilo. La ausencia de iniciador térmico o fotosensible hace difícil el inicio del proceso de polimerización del monómero adsorbido. Sin embargo, este problema se puede resolver mediante la polimerización por plasma.
Se estudia las propiedades mecánicas de estos nuevos materiales mediante espectroscopía dinámico-mecánica (DMS). El espectro dinámico-mecánico muestra que los materiales sintetizados en esta tesis son un nuevo tipo de hidrogel macroporoso con un alto módulo mecánico a temperatura ambiente y capaz de adsorber agua manteniendo sus propiedades mecánicas.
Mediante medidas de porosidad se determina la fracción en volumen de poros en las muestras antes y después del tratamiento de plasma. La estructura y morfología de estos sistemas macroporosos se ha observado mediante microscopía electrónica de barrido (SEM).
La estabilidad de este recubrimiento hidrófilo se ha analizado mediante calorimetría diferencial de barrido (DSC), ATR FTIR, TGA e inmersión en agua. Estos resultados demuestran que el plPHEA es muy estable y solo en condiciones muy drásticas como en agua hirviendo puede sufrir degradación hidrolítica.Serrano Aroca, Á. (2005). Synthesis and characterisation of macroporous poly(methyl methacrylate) with plasma-polymerised hydrophilic coating [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/1857
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Katsifis, Georgio Andrew. "Analysis and Characterisation of Plasma Treated PEEK Scaffolds and their Implementation in Radiotherapy." Thesis, The University of Sydney, 2022. https://hdl.handle.net/2123/29503.
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Bone sarcomas are a present as tumours which occur in bones and soft tissues. Bone must
often be removed during the treatment of these cancers and a replacement bone scaffold
must be implanted to heal and bridge the removed tissue. Titanium stands as the most
popular implant as a general orthopaedic implant due to its impressive mechanical properties
and bio-compatibility. However, the high stiffness also poses problems due to the material
mismatch with bone and can cause aseptic loosening at the interface, potentially leading to
implant failure. In radiotherapy, titanium perturbs radiation beams and compromises both
radiotherapy and imaging beams as well as damaging the osseointegrating cells. Our solution is to 3D print scaffolds out of Poly-ether-ether-ketone (PEEK), a biocompatible polymer already used in orthopaedics.
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Rossall, Andrew. "Characterisation and measurement of laser produced plasma emission and applications in opacity experiments." Thesis, University of York, 2011. http://etheses.whiterose.ac.uk/1655/.
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The work presented in this thesis investigates the characterization of laser produced plasmas and develops applications in opacity experiments using plasma emission as a back-lighting source. A diagnostic is developed to analyse bremsstrahlung emission from hot electrons produced in the laser plasma interaction. Combining a compensating filter technique with an x-ray diode array allows for the hot electron temperature to be deduced with good accuracy (±0.5keV). A layered target comprising 0.8um Al and 1.0um Fe is used to investigate the opacity of iron plasma. A laser of modest irradiance (~ 10^15 W cm^-2) is fired onto the aluminium surface, producing Al K-alpha emission (1.5 keV) which is used to measure the opacity of the conductively heated iron layer. The aluminium plasma is characterized using source broadened spectroscopy and continuum emission analysis. The experimental transmission data is in good agreement with 2D modelling using opacities from the Ionised Materials Package. A line focus back-lighter, produced using a high power laser system, is characterized through imaging the time and spectrally integrated emission profile of the plasma using a crossed-slit camera. The emission profile is used to infer a spatially dependant electron temperature profile. Finally, a Ti K-alpha back-lighter is used to investigate the temporal evolution of the Rayleigh-Taylor instability in a laser produced plasma. A target, seeded with an initial perturbation between layers of copper and plastic exhibited Rayleigh-Taylor growth within the first 100ps of the interaction with a growth rate of 10 ± 2 ns^-1.
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Bomphrey, J. J. "Growth and characterisation of dilute nitride antimonide layers by plasma-assisted molecular beam epitaxy." Thesis, University of Warwick, 2011. http://wrap.warwick.ac.uk/47155/.
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The work presented in this thesis is concerned with the growth and characterisation of III-NSb films by plasma-assisted molecular beam epitaxy (PA-MBE). The research was motivated by their application in technologically important regions of the IR spectrum. Homoepitaxial growth of GaSb films was conducted and characterised as a function of V:III ratio and growth temperature, permitting observation of morphology changes with growth conditions, also providing insight into surfaces of the ternary dilute nitride. Heteroepitaxial GaSb/GaAs growth has highlighted defect formation and propagation arising from lattice mismatched deposition. Films of GaNxSb1-x, a material of interest for device applications in the 2-5 μm spectral range, have been grown on GaSb(001) substrates. The results demonstrate the degree to which substitutional N content may be controlled through variation of the temperature and rate of deposition. Models based upon kinetic and thermodynamic principles and previously applied to GaNxAs1-x have been evaluated for N content of GaNxSb1-x films as a function of the rate and temperature used for growth. The growth of InNxSb1-x, an alloy of significance in the technologically important wavelength region of 8-12 μm, upon InSb(001) substrates is described. There is qualitative agreement with the temperature dependence of N content. Analysis of the substitutional N content as a function of growth rate, however, suggests a difference between GaNxSb1-x and GaNxAs1-x. An explanation is presented for the trend in the level of substitutional N uptake across III-V-N materials. Further experiments are proposed to extend the parameter space sampled in the investigation of GaNxSb1-x and InNxSb1-x films, with regard to the Sb:III ratio employed during growth. Initial results are reported from measurements undertaken with a pyrometer operating at 1.6 μm, suggesting that growth can be conducted at lower temperatures. Additional preliminary results are presented for the growth of GaxIn1-xNySb1-y films, demonstrating a tuneable band gap quaternary material, lattice matched to GaSb is possible.
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Pollock, Neal. "The synthesis, immobilisation and characterisation of poly(amidoamine) dendrons on plasma polymer thin films." Thesis, University of Sheffield, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.500151.
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Rennick, Christopher John. "Characterisation of the chemical composition of a DC arcjet reactor plasma by laser spectroscopy." Thesis, University of Bristol, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.425141.
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Wantock, Thomas. "Thrust balance performance characterisation and internal Langmuir probe plasma diagnostics for a Halo thruster." Thesis, University of Surrey, 2018. http://epubs.surrey.ac.uk/845862/.
Full textAbstract:
Electric Propulsion (EP) systems can enable novel spacecraft missions requiring high total change in velocity, owing to their high specific impulse compared to chemical propulsion systems. Mature devices, such as Hall Effect Thrusters (HETs), have accumulated significant flight heritage. How- ever, established technologies do not satisfy the requirements of the rapidly growing small satellite sector, because of adverse scaling to low powers. The Halo thruster concept falls within the cat- egory of Cusped Field Thrusters (CFTs), aimed at addressing this issue. The concept concerns the use of ‘magnetic null regions’, formed through the deliberate cancellation of magnetic fields. Two such regions are produced in the thruster, a ‘null point’ at the thruster exit and an annular ‘halo’ near the anode. The work presented in this thesis has provided foundational knowledge of the performance and internal physics of the Halo thruster, using a 5 cm channel diameter, electromagnet laboratory model. Measurements of thrust, specific impulse and thrust efficiency were obtained over a wide range of operating conditions using a pendulum thrust balance in representative high vacuum, and the sensitivity of the measured performance to facility effects was assessed. Trends in plasma potential, electron temperature and plasma density internal to the discharge channel were obtained using a translating Langmuir probe, allowing the basic physics of operation of the device to be inferred. The thruster was found to exhibit comparable performance to other CFTs, with measurements shown to be robust to facility effects. Internal plasma measurements revealed behaviour similar to that of the Cylindrical Hall Thruster, with some differences due to the presence of the halo magnetic null region near the anode which might be exploited to improve performance. As a result of the research presented, design changes are suggested for future iterations. In its current embodiment, the thruster already offers advantages over heritage small satellite EP systems, and is a viable candidate for near-term industrialisation.
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Tang, Qian. "Production and characterisation of vacuum plasma sprayed (VPS) hydroxyapatite and silicon-substituted hydroxyapatite coatings." Thesis, University of Cambridge, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.609136.
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Tegg, Michelle. "Plasma insulin-degrading enzyme: Characterisation and evaluation as a potential biomarker for Alzheimer's disease." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2014. https://ro.ecu.edu.au/theses/1198.
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Alzheimer’s disease (AD) is increasing in prevalence due to increasing lifespan and altered lifestyle. It is the fourth major cause of death in Western countries, resulting in significant economic and social impact (Von Strauss, et al., 1999; Goate, 1997). There are no blood biomarkers currently accepted for the diagnosis of AD, and the identification of suitable biomarkers would eventually reduce the necessity for invasive, expensive and slow diagnostic procedures, as well as facilitate prognostic studies. An AD blood test would decrease the need for delaying diagnosis due to ambivalent presentation, and allow therapeutic intervention to commence at an earlier and more functional stage for the sufferer, thereby maximising the benefits of treatment. It is also feasible that a blood biomarker would be of use in the development of therapeutic treatments, which are currently inadequate.
Numerous studies have suggested that hyperinsulinemia and type II diabetes (DM2) significantly increase the risk of developing Alzheimer’s disease (AD). Therefore, much research interest has been aimed recently toward determining the putative common mechanisms of these conditions. One enzyme which has been implicated in both AD and DM2 is insulin degrading enzyme (IDE). This project focuses largely on the characterisation of plasma IDE expression and catalytic activity, to help determine potential role/s of IDE in the development of AD, and the suitability of IDE as an AD biomarker. Evidence is also provided to support the concept that IDE impairments may be the common factor that links AD, hyperinsulinemia and DM2.
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Yoshitomi, Satoshi. "Application of surface analytical techniques to the characterisation of 60Pb/40Sn solder alloy on PCBs." Thesis, University of Bristol, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294393.
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Olenici-Craciunescu, Stefan-Bogdan [Verfasser]. "Micro capillary dielectric barrier plasma jet discharge : Characterisation by optical spectroscopy / Stefan-Bogdan Olenici-Craciunescu." Dortmund : Universitätsbibliothek Technische Universität Dortmund, 2011. http://d-nb.info/1018125493/34.
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Russell, Benjamin C. "Expanding the radioanalysts toolbox : using the latest generation plasma mass spectrometers for nuclear waste characterisation." Thesis, University of Southampton, 2014. https://eprints.soton.ac.uk/374832/.
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This project investigates the application of sector field inductively coupled mass spectrometry (ICP-SFMS) in low-level radionuclide detection in environmental samples and low-level nuclear waste. The aim was to develop robust and sensitive procedures for measuring medium-long lived emitters of interest to various Nuclear Decommissioning Authority (NDA) sites. ICP-SFMS has been investigated for the measurement of the significant fission product radionuclides of caesium (135Cs and 137Cs) and strontium (90Sr). In the case of some shorter-lived radionuclides such as 90Sr, ICP-SFMS can achieve sensitivities that rival existing radiometric techniques, whilst offering a significant improvement in the speed of analysis. Additionally, long-lived low abundance radionuclides such as 135Cs are not detectable using radiometric techniques, but can be quantified by ICP-SFMS, which is important given their major contribution to the long-term radiological risk associated with deep geological disposal. Measurement of 135Cs also enables measurement of the 135Cs/137Cs ratio, which varies with the source of nuclear contamination, and therefore can provide a powerful forensic tool compared to radiometric 137Cs detection alone. ICP-SFMS has been proven to achieve high sensitivities that will enable low-level radionuclide detection. In order to reach these sensitivities, it is critical to ensure removal of interfering elements that otherwise significantly impact the accuracy of measured values. This led to the development of novel and efficient chemical separation procedures that achieve both a high analyte recovery, and effective decontamination of interferences, which have been proven to be effective for a range of sample matrices including seawater and sediments. The combination of imaginative sample preparation procedures and use of new generation ICP-SFMS offer a streamlining of the process that will contribute to faster more sensitive assessment and clean-up of nuclear sites. This will lead to a reduction in analytical timescales and reduce the demand on existing analytical facilities, benefitting site operators and the NDA.
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Sakildien, Muneer. "Plasma characterisation of an electron cyclotron resonance ion source by means of x-ray spectroscopy." Thesis, University of the Western Cape, 2012. http://hdl.handle.net/11394/5212.
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>Magister Scientiae - MScThe ultimate aim of any multiply-charged ion source, like the Electron Cyclotron Resonance Ion Source, ECRIS, is the production of multiply-charged ions, in sufficiently large quantities. These multiplycharged ions, in the case of the ECRIS, are created by a step-by-step ionisation process, whereby neutral atoms are ionised by energetic electrons. The goal of this thesis was to gain an understanding of the relative importance of various ECRIS parameters on the production of these energetic electrons. This was done by measuring the bremsstrahlung continuum emitted by the mirror confined plasma of an ECR ion source. The focus of our study was to investigate the influence of neutral pressure, incident microwave power and magnetic field configuration on spectral temperature and electron density of the warm electron population of the ECRIS plasma. The thesis begins by familiarising the reader with various aspects of plasma physics as it relates to the measurements. The measurements were done with a high-purity germanium detector and processed with the DGF Pixie-4 module. Analyses of the measured spectra were done with subroutines written in Root. From the measured result, it was concluded that by increasing the incident microwave power from 50 W to 300 W, the spectral temperature increases by 14.01% for helium plasma and 7.88% for argon plasma. Evidence of saturation of spectral temperature and electron density with increasing microwave power was also noticed, as reported by other groups investigating plasma bremsstrahlung. The increase of spectral temperature with neutral pressure was found to be considerable, increasing by 20.23% as the neutral pressure in the plasma chamber of the ECRIS was decreased. This increase in spectral temperature was accompanied by a 40.33% decrease in electron density, which led us to conclude that the increase in spectral temperature was most likely due to an increase in the mean free path of the electrons. The influence of the magnetic field configuration on both spectral temperature and electron density was also investigated. During this investigation, one of the solenoid coil currents was increased, whilst keeping the other constant. This amounts to moving the plasma volume around axially in the plasma chamber of the ECRIS. This was found to significantly enhance the spectral temperature and this effect was attributed to more efficient heating of the electrons near the resonance zone. The electron density on the other hand was found to remain relatively constant, if one excludes the electron density as a result of one particularly setting of the solenoid coils. The decrease of electron density as a result of this particular setting of the solenoid coils enhanced the electron losses through the magnetic bottle. This is evidenced by the increase in photon counts as measured by our detector. The influence of neutral pressure, incident microwave power and magnetic field configuration on the extracted ion beam intensities was also investigated. This investigation led us to conclude that the mean charge state extracted increases with spectral temperature. This result was in agreement with those measured by other groups.
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Dünnbier, Mario [Verfasser]. "Plasma jets for life science applications: characterisation and tuning of the reactive species composition / Mario Dünnbier." Greifswald : Universitätsbibliothek Greifswald, 2015. http://d-nb.info/1080060197/34.
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Devermann, Thomas. "Design, modelling, and characterisation of an integrated welding head for the plasma-augmented laser-welding process." Thesis, Coventry University, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.404731.
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Markkula, Tommi. "Surface characterisation of gas plasma modified PET and PTFE : effect of surface chemistry on cell attachment." Thesis, University of Liverpool, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.275047.
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Welzel, Thomas. "Time-resolved characterisation of pulsed magnetron discharges for the deposition of thin films with plasma diagnostic methods." Doctoral thesis, Universitätsbibliothek Chemnitz, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-81968.
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Research on the characterisation and understanding of pulsed magnetron discharges used for the deposition of thin, especially dielectric, films has been carried out between 2003 and 2008 at Chemnitz University of Technology. This thesis is a collection and summary of the original research during this period. In the main part of the thesis, work published in peer-reviewed scientific papers is summarised and yet unpublished results are given in more detail. Different aspects highlighted in the publications are described in a general context of the characterisation of the pulsed discharges for the principal understanding. The cross-linking of the published results is addressed and where necessary extensions to the publications are given. The main part is organised in three sections. In the first one, basics of pulsed magnetron discharges, their application, and important questions are summarised. The second section describes general results and physics of the discharges that have been obtained during the research work. It also emphasises the successful development or modifications of experimental techniques for the time-resolved characterisation. The third section addresses the possibilities to modify and control the process by external parameters that are typically accessible during the application or required by it. An appendix to the thesis comprises selected published research work which is made available as reprints of the original publications. Other publications which are not included as reprints are referenced to in the main partUntersuchungen zur Charakterisierung und zum Verständnis gepulster Magnetronentladungen, die zur Abscheidung von dünnen Schichten, besonders von dielektrischen Schichten, verwendet werden, wurden in den Jahren 2003 bis 2008 an der Technischen Universität Chemnitz durchgeführt. Diese Arbeit ist eine Sammlung und Zusammenfassung von neuen Forschungsergebnissen, die in diesem Zeitraum gewonnen wurden. Im Hauptteil der Habilitationsschrift werden die Arbeiten, die in referierten wissenschaftlichen Zeitschriften erschienen sind, zusammengefasst und noch unveröffentlichte Ergebnisse ausführlicher beschrieben. Verschiedene Aspekte, die in den Veröffentlichungen herausgestrichen wurden, werden in einem allgemeinen Zusammenhang der Charakterisierung gepulster Entladungen für ein prinzipielles Verständnis dargestellt. Querverbindungen zwischen den veröffentlichten Ergebnissen werden herausgearbeitet und wo nötig werden Erweiterungen der Originalveröffentlichungen vorgenommen. Der Hauptteil der Habilitationsschrift ist in drei Abschnitte unterteilt. Im ersten Teil werden Grundzüge gepulster Entladungen, ihre Anwendung und wesentliche Fragestellungen zusammengefasst. Der zweite Abschnitt beschreibt allgemeine Ergebnisse und die Physik der Entladungen, die während der Forschungsarbeit herausgearbeitet wurden. Er stellt auch die erfolgreiche Neuentwicklung oder Modifikation von Messtechniken zur zeitaufgelösten Charakterisierung heraus. Der dritte Abschnitt befasst sich mit den Möglichkeiten, den Beschichtungsprozess durch externe Parameter, die typischerweise während der Prozessanwendung zugänglich oder auch erforderlich sind, zu modifizieren und zu steuern. Der Anhang der Schrift beinhaltet ausgewählte Originalveröffentlichungen, die in Form von Reprints zugänglich gemacht werden. Andere Veröffentlichungen, die nicht im Anhang enthalten sind, werden im Hauptteil zitiert