This diploma thesis is focused to the plasma chemical reduction of model corrosion layers prepared on bronze samples. Bronze was the main material for production of the subjects in Bronze Age. First, it was very rare, and therefore was used only for making jewellery and other decorative subjects. Later, the objects of daily use and weapons were produced of bronze. These objects are found and it is necessary to restore him and preserve the cultural heritage for future generations. The research and the optimalization of plasmochemical reduction of model corrosion layers on bronze samples contributes to this. A metallographic grinder was used to create a defined surface, first with the sandpaper P 280 and then after sample 90 degree rotation with the sandpaper P 600. This ensured uniform surface at all bronze samples that is necessary to provide the same corrosion conditions. The grinded samples were washed by ethanol and dried by hot air stream. To prevent contact with the surrounding atmosphere and successive initiation of corrosion, the samples were stored in lockable polyethylene bags. This step was followed by the preparation of model corrosion layers. Hydrochloric and sulfuric acids were chosen as corrosive environments. Petri dish containing 20 ml of the selected acid was placed at the bottom of the desiccator. Samples were placed to the ceramic grate, over the dish, and they were corroded (in vapours of hydrochloric acid for 34 days and in vapours of sulfuric acid for 27 days). The corroded samples were treated using low-pressure hydrogen plasma excited by RF generator. Treatment of samples was carried out in quartz cylindrical reactor (length of 90 cm, inner diameter 9.5 cm) with copper electrodes placed outside. The pressure in the reactor was ranged around 160 Pa at hydrogen flow rate of 50 sccm during the experiments. The continuous and pulse modes (duty cycle of 25%, 50% or 75%) at peak power of 50–300 watts were used for the treatment of 90 minutes duration. The plasma treatment was monitored by optical emission spectroscopy of OH radical using compact Ocean Optics HR4000 spectrometer. Its integral intensity is proportional to the corrosion layer removal. The rotational temperatures of plasma were calculated using selected OH rotational lines, too. The sample temperature during the treatment was measured by thermocouple installed inside the additional non-corroded samples. The reduction of corrosion layer is successful when the maximum of relative intensity of OH radicals is produced and follow gradual decline. The samples which corroded in vapours of sulphuric acid and were treated in pulse modes with duty cycle of 25 % or with delivered power of 50 W has produced no maximum. To the remain samples the maximum although were observed, but reduced corrosion products on the surface were very cohesive. The maximum of relative intensity of OH radicals was observed at all samples corroded in vapours of hydrochloric acid. But there is problem with temperature of sample during experiment. The samples which layer of corrosion product was after experiment incoherent produced the layer of deposit tin. This effect formation at a higher temperature of sample during experiment and therefore with greater deliver energy.

The presented Thesis deals on the nitrogen-hydrogen DC post-discharge observations by optical emission spectroscopy. The plasma was generated in Pyrex tube in flowing regime at pressure of 1 kPa at discharge current of 100 mA. The optical emission spectra were recovered at discharge times up to 50 ms in nitrogen containing 0 – 92 % of hydrogen; the gas mixture volume, i.e. the gas speed in the system was conserved for all mixtures. The experiments were carried out at two reactor wall temperatures at the spectra collecting point – at ambient temperature and at the wall temperature of liquid nitrogen (temperature in plasma was about 150 K). The nitrogen first and second positive and first negative spectral systems were identified in the spectra, the hydrogen atomic Balmer series lines were recorded, too. No molecular hydrogen emission was determined during the post-discharge. Some non-identified bands (but with high probability bands of nitrogen Herman infrared system) at 690 and 780 nm were detected, too, mainly at low temperature. The intensities of all determined radiating species decreased exponentially or more than exponentially with the decay time. The experimental data showed strong quenching of all nitrogen radiative states even at very a few percent hydrogen additions. The shape of the selected intensity dependencies on both hydrogen concentration, and the decay time are nearly the same for N2(C) and N2+(B) states, dependencies for N2(B) levels differs of them. The hydrogen line emission was nearly independent on the hydrogen content in the gas mixture up to about 50%, at highest hydrogen concentrations it slightly increased. The results obtained at the decreased wall temperature were very similar, only intensities of all nitrogen spectra increased by the factor about 3, the intensities of levels populated by the recombination of nitrogen atoms increased by factor about five. The atomic hydrogen alpha line (at 656 nm) was the most sensitive on temperature decrease; its intensity increased over one order in whole observed time interval. The obtained results will be confronted with numeric model of kinetic processes in the near future. After that, the specific conditions applicable for the technological applications of nitrogen-hydrogen gas mixtures under post-discharge conditions will be proposed.

Thin films have been used to modify surface properties of various materials for many years. Plasma Enhanced Chemical Vapor Deposition (PECVD) is one of the possible methods for their preparation and this technique is applied in this work as well. An organosilicone – hexamethyldisiloxane – is used as precursor. Thin films are created on the surface of the substrate using mixture of precursor and oxygen in radiofrequently excited capacitively coupled plasma. The aim of the thesis is to find the optimal deposition conditions for production of transparent thin layers with good barrier capabilities, low oxygen transmission rate especially. Thin film depositions were realized for different compositions of the deposition mixture in continuous and pulsed mode of plasma with varying supplied power and duty cycle values. The deposition process itself was monitored in situ by optical emission spectroscopy. Thin film coatings were analyzed to determine their physical chemical properties (infrared spectroscopy, surface energy) and barrier properties. Using optical emission spectroscopy, important particles were identified in the deposition plasma. Vibrational, rotational and electron temperatures were determined from relative intensities of chosen fragments. Composition of thin films was studied by infrared spectroscopy. The best results of oxygen transmission rate were achieved with layers prepared from deposition mixture with high oxygen content. It was possible to improve barrier properties by performing deposition in pulsed plasma mode with 20–30% duty cycle. In this diploma thesis, optimal deposition conditions of thin films from hexamethyldisiloxane with low oxygen transmission rate were determined. It is possible to use these results in practical applications, such as corrosion inhibitors for archaeological objects. Optionally, they can be used in various industry branches where it is desirable and feasible to prevent oxygen access to the material by deposition of barrier coatings.

This master thesis deals with determination of temperature field in a real circuit breaker. This issue is solved by analysis of measured emission spectra at selected points of the circuit breaker. Spectral line ratios and Boltzmann plot are used for calculation of temperature. These methods are based on elemental analysis of plasma. The main result is finding significant changing of chemical composition of plasma beyond determination of temperature field.

Les matériaux (nano)composites font partie intégrante de l’industrie de l’aéronautique et de l’espace depuis plus de 50 ans. De nos jours, le concept de matériaux multifonctionnels combinant diverses propriétés pour réaliser des objectifs de performance multiples en un seul et unique système est devenu une exigence pour le développement de surfaces innovantes, et ce, pour une vaste gamme d’applications technologiques. Cependant, pour plusieurs applications, un des principaux verrous est l’obtention de revêtements formés de nanoparticules isolées (non-agrégées) et de petite taille (<10 nm) dispersées de manière contrôlée dans une matrice. Dans ce contexte, une nouvelle méthode de synthèse souple, verte, sécuritaire et industrialisable a récemment été proposée. Celle-ci repose sur un réacteur-injecteur de nanoparticules et permet de synthétiser des nanoparticules à partir de précurseurs organométalliques liquides juste avant de les injecter dans un réacteur de dépôt par plasma en limitant les phénomènes d’agglomération associés à la vaporisation de gouttelettes et en évitant les problèmes de toxicité éventuelle en lien avec la manipulation de nanoparticules avant le dépôt. Cependant, contrairement aux procédés de dépôt par plasma habituels qui s’effectuent la plupart du temps à pression constante, la conception du réacteur-injecteur de nanoparticules implique inévitablement une dynamique temporelle complexe associée à des variations assez brutales de la pression dans le réacteur à plasma. À l’évidence, ces variations temporelles de pressions vont se répercuter sur l’évolution temporelle des propriétés fondamentales du plasma telles que la densité et la température des électrons. Dans ce travail de maîtrise, nous avons eu recours à la spectroscopie optique d’émission couplée aux prédictions de modèles collisionnels-radiatifs pour déterminer des conditions opératoires du réacteur-injecteur dans un plasma rf d’argon minimisant ces variations d’une part, et permettant de mieux comprendre leurs implications sur la température des électrons, d’autre part. Ces travaux serviront ainsi d’effet levier à des études plus complexes en présence de précurseurs et de nanoparticules. / (Nano) Composite materials have been an integral part of the aeronautics and space industry for more than 50 years. Nowadays, the concept of multifunctional materials combining various properties to achieve multiple performance objectives in a single system has become a prerogative in the development of innovative surfaces for a wide range of technological applications. However, for several applications, one of the main challenges is the production of coatings formed of isolated (non-aggregated) and small (<10 nm) nanoparticles dispersed in a controlled manner in a matrix. In this context, a new flexible, green, safe and scalable method of synthesis has recently been proposed. It is based on a reactor-injector of nanoparticles and can synthesize nanoparticles from liquid organometallic precursors just before injecting them into a plasma deposition reactor by limiting the agglomeration phenomena associated with the vaporization of droplets and by avoiding problems of possible toxicity related to the manipulation of nanoparticles before the deposit. However, unlike conventional plasma deposition processes, which are usually carried out at constant pressure, the design of the reactor-injector of nanoparticles inevitably involves a complex temporal dynamic associated with rather sudden changes in the pressure in the plasma reactor. Obviously, these temporal variations of pressures will affect the temporal evolution of the fundamental properties of the plasma such as the density and the temperature of the electrons. In this master work, we used optical emission spectroscopy coupled with the predictions of collisional-radiative models to determine operating conditions of the reactor-injector in an argon rf plasma minimizing these variations on the one hand, and to better understand their implications on the electron temperature, on the other hand. This work can thus be expected to serve as building blocks for more complex studies in the presence of precursors and nanoparticles.

The aim of this thesis is a study of processes during organosilicone thin film deposition via plasma polymerization. Recently, thin films are the most expanding way of surface modification of materials. They are used as protective coatings, functional layers, they can increase or decrease adhesion to different compounds (e.g. water), or just improve mechanical properties of bulk materials. Plasma polymers, which are not known so long, are a modern trend in evolution of thin film deposition. They have perfect adhesion to the substrate and they are highly resistant against most of chemical compounds. Their structure is quite different from the structure of classical polymers. Recently, organosilicon compounds are used as precursors for plasma polymers because silicon built in the structure of plasma polymer allows thin film deposition on glass substrate and the organic part of monomer gives us infinite possibilities of modification. In our case dimethylphenylsilane (DMPS) was used as a monomer. Various RF low pressure discharges were used during this study. Plasma diagnostic was performed by optical emission spectroscopy of inductive coupled plasma. This method allows us to determine plasma composition during the deposition process. Thus we can predict the composition of deposited thin film according to input parameters. From relative populations of fragments we are able to find out optimal conditions for deposition process. We can also calculate temperature of particles in plasma which gives us some information about particle energies. The first part of the study deals with the identification of particles (fragments) created by fragmentation of monomer in plasma environment. We successfully identified hydrogen atomic lines of Balmer’s series in the spectra. Many rotational lines of hydrogen molecule were also detected. Atomic carbon occurred only in small amount. Much more carbon was detected in the form of CH radical. We also found some weak lines connected to atomic silicon. When we used a mixture of DMPS and oxygen, OH radical and O2+ were present in spectra. Next, optimal settings of deposition were determined for particular fragments from relative intensities of these fragments in optical emission spectra. Using this information we are able to set up the process to deposit thin films of desired composition and properties. We calculated electron temperature from intensities of hydrogen lines in Balmer’s series. Rotational temperature was obtained from CH radical intensity. Unfortunately, there was no convenient radical from which intensity we would be able to calculate vibrational temperature. All results and information obtained during the research can be used in industrial plasma polymerization processes and development of new coatings and functional thin films. Other studies on DMPS or similar monomer may also be realized to get more knowledge about processes in plasma and this thesis could serve as a basis for further research. Moreover, this study is a part of an international project. The aim of this project is to study processes during plasma polymerization both theoretically and practically. Once finished, the project and its results will be presented in scientific literature and at international conferences.

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Thesis (PhD)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: In this work a robust reversed phase ion-pairing high performance liquid chromatographic (RP-HPLC) method has been developed for the separation, characterization and quantification of all possible [PtCl6-nBrn]2- (n = 0 – 6) and [PtCl4-nBrn]2- (n = 0 – 4) complex anions using UV-Vis detection. High resolution 195Pt NMR of more concentrated PtII/IV solutions served to validate the relevant species assignments, particularly those of the stereoisomer species, cis- and trans- [PtCl4Br2]2-, [PtCl2Br4]2- and mer- and fac-[PtCl3Br3]2-. Quantification of the PtII/IV species was achieved by means of IP-RP-HPLC coupled to either ICP-MS or ICP-OES, and together with the UV-Vis absorption spectra obtained by photodiode array (PDA) recording of all eluted species, allowed for the determination of the photometric characteristics (λmax and ε) of all the PtII/IV species. This data enables practical speciation studies of such PtII/IV complex anions using standard analytical equipment. The hyphenation of ion-pairing RP-HPLC to ICP-OES allows for the successful determination of the Pt to halide mole ratios of individually separated species in order to characterize these species in a novel manner. The Pt to chloride and/or Pt to bromide mole ratio of the [PtCl4]2- and the series of [PtCl6-nBrn]2- (n = 0 – 6) complexes were determined using HPLC-ICP-OES based on the 177.708 nm Pt, 134.724 nm Cl and 148.845 nm Br emission lines and served as a technique for the unambiguous chemical speciation of such complexes. An increase in sensitivity of the developed method was achieved by the use of an ion-pairing reversed phase ultra high performance liquid chromatography electrospray ionization quadrupole time-of-flight mass spectrometry (UHPLC-ESI-Q-TOF-MS) method. This method proved capable of separating and characterizing the homoleptic and heteroleptic [PtIVCl6-nBrn]2- (n = 0 – 6) and mono-aquated [PtIVCl5-nBrn(H2O)]- (n = 0 – 5) complex anions in well defined acidic aqueous solutions. Ion-pairing ultra high performance liquid chromatography separation based on the volatile ion-pairing reagent, tributylamine, provided adequate chromatographic resolution as well as sufficiently low background noise for high resolution ESI-Q-TOF-MS detection. The wealth of structural information contained in the mass spectra obtained for each PtIV species simplified the identification of individual species. Moreover, the general fragmentation trends encompassing a constant incremental change of 44 Da (79/81Br - 35/37Cl) resulting from the successive substitution of Cl- by Br-, in combination with the observed elution order, facilitated the relevant species assignments. The developed method enabled the relative rapid (<13 min) characterization of all 22 [PtCl6-nBrn]2- (n = 0 – 6) and mono-aquated [PtCl5-nBrn(H2O)]- (n = 0 – 5) species. Quantification of each individual [PtCl6-nBrn]2- (n = 0 – 6) species by means of ion-paring HPLC-UV-Vis allowed for the determination of all 17 stability constants for the PtIV chloridobromido halide exchange reaction network. Determination of the associated Gibbs free energies for each ligand exchange reaction step, o rxnK ΔG n (n = 1 - 17), together with energy conservation relationships, served to validate the accuracy of the experimentally calculated stability constants. The experimentally determined overall formation constant, or ΔGo rxn, and those calculated using the standard reaction half cell reduction potentials of [PtCl6]2- and [PtBr6]2- were in good agreement, further confirming the experimentally obtained thermodynamic parameters. The thermodynamic driving force for the PtIV chloride-bromido exchange reactions is attributed to the hydration of the halide ligands, which drives the reaction towards the bromido PtIV species in aqueous solutions, even though the chlorido PtIV complexes are energetically favoured in this reaction network. Evaluation of other metal cation halido exchange reactions shows that all metal halido complexes exhibit the F- >> Cl- > Br- > I- order of thermodynamic stability and is only inverted due to the solvation of the relevant halide ligands. Furthermore, density functional theory (DFT) was used to predict the thermodynamic stabilities with respect to the isodesmic reactions involving chlorido-bromido PtIV stereoisomer pairs and chlorido-bromido PtIV ligand exchange reactions of the [PtCl6-nBrn]2- (n = 0 – 6) species and confirm the F- >> Cl- > Br- > I- order of thermodynamic stability as well as determining the ΔΔGo rxn within the range of 8 - 20 kJ.mol-1 to the experimentally determined ΔΔGo rxn. / AFRIKAANSE OPSOMMING: Tydens hierdie studie is „n robuuste “reverse-phase” ioonparing hoë-verrigting vloeistof chromatografie, RP-IP-HPLC, metode ontwikkel vir die skeiding, karakterisering en kwantifisering van alle moontlike [PtCl6-nBrn]2- (n = 0 – 6) en [PtCl4-nBrn]2- (n = 0 – 4) kompleks anione waar UV-Vis as detektor gebruik word. Die relavante spesies toedelings wat gemaak is, veral ten opsigte van die cis- en trans-[PtCl4Br2]2-, [PtCl2Br4]2- en mer- en fac-[PtCl3Br3]2- stereo-isomeerpare, is deur middel van hoë-resolusie 195Pt KMR van meer gekonsentreerde PtII/IV oplossings bevestig. Die PtII/IV spesies was gekwantifiseer deur die IP-RP-HPLC aan of „n ICPMS of „n ICP-OES te koppel. Daarenbowe was dit moontlik om die fotometriese eienskappe (λmax en ε) van elke individuele PtII/IV komplex anion te bepaal deur die UV-Vis absorpsie spektrum van elke elueerende spesies met PDA op te neem. Die nuwe metode wat tydens hierdie studie ontwikkel is het dit dus moontlik gemaak om sulke PtII/IV komplek sanione met standaard analitiese toerusting prakties te skei. Verder is gevind dat deur IP-RP-HPLC aan ICP-OES te koppel dit moontlik is om die Pt tot halied mol verhoudings van elke individueel geskeide spesies te bepaal en dus hierdie spesies op „n oorspronklike, nuwe manier te karakteriseer. Die Pt tot chloried en/of Pt tot bromied mol verhoudings van die [PtCl4]2- en die reeks van [PtCl6-nBrn]2- (n = 0 – 6) kompleks anione, soos bepaal deur gebruik te maak van HPLC-ICP-OES, is gebasseer op die 177.708 nm Pt, 134.724 nm Cl en 148.845 nm Br emissie lyne. Hierdie metode kan gebruik word vir die eenduidige chemiese skeiding van hierdie komplekse. Die sensitiwiteit van hierdie metode was egter verder verbeter deur gebruik te maak van ioonparing “reverse-phase” ultra hoë-verrigting vloeistof chromatografie gekoppel met elektrosprei ionisasie quadropool “time-of-flight” massa spektrometrie (UHPLC-ESI-Q-TOFMS). Deur dit te doen is dit nou selfs moontlik om die homoleptiese en heteroleptiese [PtIVCl6-nBrn]2- (n = 0 – 6) spesies, asook die “mono-aqauted” [PtIVCl5-nBrnH2O]- (n = 0 – 5) spesies in „n goed gedefinieërde aangesuurde waterige oplossings te skei en te karakteriseer. Die vlugtige ioon-paringsreagent, tributielamien, is vir die skeidingsproses op die IP-UHPLC gebruik om te verseker dat voldoende chromatografiese resolusie, so wel as lae genoeg agtergrondgeraas, verkry word vir hoë-resolusie ESI-Q-TOF-MS deteksie. Die rykdom informasie vervat in die massaspektrum van elke PtIV spesies het die indentifikasie van elke spesies vergemaklik. Daarenbowe het die fragmentasie tendens, aanduidend van „n konstante inkrementele verandering van 44 amu (71/81Br – 35/37Cl) weens die opeenvolgende substitusie van Cl- met Br-, tesame met die elusie volgorde, die spesies-toedelings gefasiliteer. Met hierdie nuut ontwikkelde metode is dit nou moontlik om al 22 [PtCl6-nBrn]2- (n = 0 – 6) en “mono-aquated” [PtCl5-nBrnH2O]- (n = 0 – 5) spesies in „n relatiewe kort tydperk (< 13 min) te karakteriseer. Deurdat elke [PtCl6-nBrn]2- (n = 0 – 6) spesies nou individueel met IP-HPLC-UV-Vis gekwantifiseer kan word, is dit moontlik om al 17 stabiliteitskonstantes vir die PtIV chloridobromido halied uitruilingsreaksienetwerk te bepaal. Die geassosieerde Gibbs vrye energie, ΔG°rxnKn (n = 0 – 17), wat vir elke stap in die uitruilingsreaksienetwerk bepaal is, tesame met die energiebewaring verhoudings, was gebruik om die akkuraatheid van die eksperimenteel bepaalde stabiliteitskonstantes te bekragtig. Verdermeer was die waarde van die algehele formasie konstante wat eksperimenteel bepaal is, ΔG°rxn, in goeie ooreenstemming met dit wat bereken is deur die standaard reaksie halfsel reduksie potensiale van [PtCl6]2- en [PtBr6]2-. Dus is die eksperimenteel verkrygde termodinamiese parameters bevestig. Die termodinamiese dryfkrag vir die PtIV chloried-bromied uitruilingsreaksies is toegereken aan die hidrasie van die halied ligande, wat in waterige oplossings die reaksie na die bromied PtIV spesies dryf, al is die chloried PtIV spesies energeties bevoordeel in hierdie reaksienetwerk. Evaluering van ander metaalkatioon- halied-uitruilreaksies wys dat alle metaal-halied komplekse die F- >> Cl- > Br- > I- orde van termodinamiese stabiliteit volg en dat hierdie volgorde slegs omgekeer sal word weens solvasie van hierdie halied ligande. Darenbowe digtheids funksionele teorie (DFT) gebruik om die termodinamiese stabiliteit met betrekking tot isodesmiese reaksies wat chloried-bromied PtIV stereoisomeer pare behels te voorspel, sowel as van chloried-bromied PtIV liganduitruilingsreaksies van die [PtCl6-nBrn]2- (n = 0 – 6) spesies, en bevestig die F- >> Cl- > Br- > I- volgorde van termodinamiese stabiliteit. Verder was dit ook moontlik om met DFT die ΔΔG°rxn tot so naby as 8 – 20 kJ.mol-1 te bereken.

<p>Izmereni su Stark-ovi pomeraji maksimuma 8 spektralnih linija neutralnog helijuma u gustoj niskotemperaturnoj plazmi impulsnog luka. Osobine izvora plazme, sem postizanja visoke elektronske koncentracije, obezbeđuju relativno jednostavan način određivanja Stark-ovog pomeraja. Izvr&scaron;ena je dijagnostika plazme, pri čemu je određena elektronska koncentracija u intervalu od (6.2 &minus; 70) &middot; 10²² m^&minus;3 i elektronska temperatura u intervalu (16400 &minus; 21400) K. Eksperimenatlne vrednosti Stark-ovih pomeraja upoređene su sa do sada objavljenim eksperimentalnim rezultatima kao i sa rezultatima teorijskih pristupa. Proveren je uticaj Debye-evog ekraniranja na pomeraj ovih linija. Dobijeni rezultati ukazuju na popravku Stark-ovog pomeraja uračunavanjem<br />uticaja Debye-evog ekraniranja, kao i potrebu korigovanja semiklasičnih teorijskih vrednosti elektronske sudarne polu-polu&scaron;irine i pomeraja.</p> / <p>The results of an experimental study of the Stark shifts AB of 8 neutral helium lines are presented. The plasma sour-ce was a linear pulsed arc with plasma electron&nbsp; density in the range (6.2 &minus; 70) &middot; 10 ²² m^&minus;3 and plasma temperature in the range (16400 &minus; 21400) K. Details of the experimental setup that enables a relatively quick&nbsp; Stark shift determination technique is presented. The results of these measurements are presented together with the corresponding plasma parameters and compared to other experimental and theoretical data. The influence of Debye shielding is carefully examined from the semiclassical point of view. The comparison of experimental&nbsp; results obtained in this work with the semiclassical results suggests that Debye shielding has an important role on higher electron densities. Also, based on all the available experimental data, appropriate correction factors are suggested for the semiclassical Stark shift calculations for the examined lines.</p>