No description available.

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.

O objetivo deste trabalho foi o desenvolvimento de metodologia analítica versátil e rápida para a determinação de Cr, Mn e Ni em aços martensíticos e austeníticos, através do processo de dissolução química parcial em sistema de injeção em fluxo acoplado ao Espectrômetro de Emissão Ótica acoplado indutivamente (ICP-OES). O procedimento, também priorizou menor manipulação de amostra e consumo de reagentes. A solução extratora, HNO3 e HCI 7,0 mol L-1 e 6,0 mol L-1 respectivamente 1:1 v/v foi utilizada para a dissolução química parcial dos aços inoxidáveis. A quantificação dos metais dissolvidos foi feita utilizando-se o método da somatória, que relaciona a concentração de um elemento individual com a somatória dos elementos determinados, segundo a fórmula: i% = Ci /Ct x 100, onde Ci é a concentração do elemento i e Ct é a soma das concentrações de todos elementos determinados. Os resultados não apresentaram diferença significativa em um nível de confiança de 95% com os valores certificados das amostras de referência e com os valores da dissolução total assistida por microondas. O procedimento apresentou freqüência analítica de 20 determinações por hora. / The objective of this work was the development of a versatile and fast analytical methodology for the determination of Cr, Mn, and Ni in martensitic and austenitic steels, through on-line partial chemical dissolution using a flow injection system coupled to an ICP-OES. The procedure also aimed the smallest sample manipulation and reagents consumption. The extractor solution, 7.0 mol L-1 HNO3 and 6.0 mol L-1 HCI 1:1 v/v, was used to the on-line partial chemical dissolution of the stainless steels. The quantification of the dissolved metals was made using a method, that relate the concentration of an individual element with the sum of all elements concentrations, applying the formula: i% = Ci /Ct x 100, where Ci is the concentration of the element i and Ct is the sum of the concentration of all elements determined. No significant difference has been present by the results, at a confidence level of 95%, with the certified values of the reference materials and with the total dissolution values obtained by microwave - assisted sample pretreatment. The procedure presented analytic frequency of 20 determinations per hour.

O objetivo deste estudo foi avaliar parâmetros para o desenvolvimento de métodos visando à determinação elementar em alumina, cimento e quartzo por espectrometria de emissão óptica com plasma indutivamente acoplado (ICP OES) com amostragem de suspensão. Alguns elementos foram investigados como possíveis candidatos a padrões internos (PIs) Be, Dy, Gd, In, La, Sc, Y, Yb eTl. Amostras de material de referência certificado (CRM) de alumina (Alumina Reduction Grade 699), de cimento Portland (1889a Blended with Limestone e 1886a White Portland cement with low iron) do National Institute of Standard and Technology (NIST), e amostras de quartzo, cedidos pelo Departamento de Física da Universidade Federal de São Carlos (UFSCar), denominados T-4FI, T-2FI e T-4GR, foram utilizadas na otimização instrumental, no desenvolvimento e na avaliação da exatidão do método. Nanopartículas de sílica de alta pureza (Wacker HDK&#174; T40), Wacker Chemie AG foram utilizadas no estudo de adsorção dos elementos e padrões internos como proposta de produção de material calibrante para a análise direta de sólidos. Para a escolha dos PIs foram construídos gráficos de correlação usando valores de potenciais de excitação, energias de ionização e temperaturas de fusão dos analitos e dos candidatos a PIs. Análise exploratória por agrupamentos hierárquicos (HCA) e análise dos componentes principais (PCA), também foram realizadas. A avaliação de desempenho do ICP OES foi feita em meio das suspensões das amostras a partir do estabelecimento de figuras de mérito como sensibilidade, robustez, seletividade e repetibilidade. Na otimização do foram considerados os parâmetros potência, vazão de nebulização e vazão de gás auxiliar. A determinação de Ca, Fe, Ga, Na, Si e Zn em alumina foi feita após dissolução em forno de micro-ondas com posterior precipitação do Al(III) com NH3. O uso de padrão interno foi essencial para a exatidão do método, com recuperações do CRM que variaram de 83 a 117%. Para a matriz cimento foram avaliados o efeito da concentração de ácido nítrico na extração dos analitos ( Al, Ca, Cr, Fe, K, Mg, Mn, Na, P, S, Si, Sr, Ti e Zn) e na adsorção dos elementos candidatos a PIs (Be, Sc, In, Dy). As determinações por suspensão e uso de padrão interno (exceto para Cr, S e Zn), com 0,5% v v-1 de HNO3, nebulizador Burgener e condições robustas do ICP geraram resultados com recuperações entre 68 e 119%. As determinações de Al, Ba, Cr, Fe, K, Li, Mg, Na, Sr e Ti em quartzo foram executadas com introdução de suspensão e ausência de padrão interno, usando condições do ICP similares àquelas adotadas na determinação elementar para matriz de cimento. Nesse caso as recuperações variaram de 90 a 107%. A adsorção dos analitos e padrões internos sobre as nanopartículas de sílica pode ser uma alternativa para a preparação de padrões de calibração quando se deseja realizar a introdução direta do material sólido em suspensão. / The aim of this study was to evaluate parameters for the development of methods for elements determination in alumina, cement and quartz by inductively coupled plasma optical emission spectrometry (ICP OES) with slurry sampling. Some elements were investigated as candidates for internal standards (ISs) Be, Dy, Gd, In, La, Sc, Y, Yb and Tl. Samples of certified reference material (CRM) of alumina (Alumina Reduction Grade - 699), Portland cement (blended with the 1889a and 1886a Limestone White Portland cement with low iron) from the National Institute of Standards and Technology (NIST), and quartz samples, suplied by the Department of Physics from Federal University of São Carlos (UFSCar), named T-4FI, T-2FI and T4GR were used to optimize instrumental, method development and accuracy evaluation of the method. Nanoparticles of high purity silica (Wacker HDK T40 &#174;), Wacker Chemie AG were used in the study adsorption of the analytes and internal standards as calibrating material for direct analysis of solids. Correlation graphs using excitation potentials, ionization energies and melting point temperatures were used for chosing the best ISs. Exploratory analysis using hierarchical cluster analysis (HCA) and principal component analysis (PCA) were also performed. Optimization of ICP OES was performed in aqueous and slurry samples to establishment figures of merit, such as sensitivity, robustness, selectivity and repeatability. In the optimization of ICP, power supply, nebulizer flow rate and auxiliary gas flow rate were considered. The determination of Ca, Fe, Ga, In, Si and Zn in alumina was made after decomposition in a microwave oven with subsequent precipitation of Al(III) with NH3 gas. The internal standard was essential to obtain the accuracy of the method, with recoveries of CRM analysis ranging from 83 to 117%. For the cement analysis was evaluated the effect of nitric acid concentration over analytes extraction (Al, Ca, Cr, Fe, K, Mg, Mn, Na, P, S, Si, Sr, Ti and Zn) and ISs candidate adsorption (Be, Sc, In and Dy). Determinations of the elements in cement slurry with the internal standard (except for Cr and Zn), with 0.5% v v-1 HNO3, nebulizer Burgener and robust conditions of ICP produced results with recoveries between 68 and 119%. The determinations of Al, Ba, Cr, Fe, K, Li, Mg, Na, Sr and Ti in quartz were performed with the slurry introduction and without of internal standard, using similar conditions of those adopted for cement matrix. In this case the recoveries ranged from 90 to 107% with addition and recovery test. The adsorption of the analytes and internal standards on silica nanoparticles could be an alternative for the preparation of calibration standards when considering performing the direct introduction of solid material.

O objetivo deste estudo foi avaliar parâmetros para o desenvolvimento de métodos visando à determinação elementar em alumina, cimento e quartzo por espectrometria de emissão óptica com plasma indutivamente acoplado (ICP OES) com amostragem de suspensão. Alguns elementos foram investigados como possíveis candidatos a padrões internos (PIs) Be, Dy, Gd, In, La, Sc, Y, Yb eTl. Amostras de material de referência certificado (CRM) de alumina (Alumina Reduction Grade 699), de cimento Portland (1889a Blended with Limestone e 1886a White Portland cement with low iron) do National Institute of Standard and Technology (NIST), e amostras de quartzo, cedidos pelo Departamento de Física da Universidade Federal de São Carlos (UFSCar), denominados T-4FI, T-2FI e T-4GR, foram utilizadas na otimização instrumental, no desenvolvimento e na avaliação da exatidão do método. Nanopartículas de sílica de alta pureza (Wacker HDK&#174; T40), Wacker Chemie AG foram utilizadas no estudo de adsorção dos elementos e padrões internos como proposta de produção de material calibrante para a análise direta de sólidos. Para a escolha dos PIs foram construídos gráficos de correlação usando valores de potenciais de excitação, energias de ionização e temperaturas de fusão dos analitos e dos candidatos a PIs. Análise exploratória por agrupamentos hierárquicos (HCA) e análise dos componentes principais (PCA), também foram realizadas. A avaliação de desempenho do ICP OES foi feita em meio das suspensões das amostras a partir do estabelecimento de figuras de mérito como sensibilidade, robustez, seletividade e repetibilidade. Na otimização do foram considerados os parâmetros potência, vazão de nebulização e vazão de gás auxiliar. A determinação de Ca, Fe, Ga, Na, Si e Zn em alumina foi feita após dissolução em forno de micro-ondas com posterior precipitação do Al(III) com NH3. O uso de padrão interno foi essencial para a exatidão do método, com recuperações do CRM que variaram de 83 a 117%. Para a matriz cimento foram avaliados o efeito da concentração de ácido nítrico na extração dos analitos ( Al, Ca, Cr, Fe, K, Mg, Mn, Na, P, S, Si, Sr, Ti e Zn) e na adsorção dos elementos candidatos a PIs (Be, Sc, In, Dy). As determinações por suspensão e uso de padrão interno (exceto para Cr, S e Zn), com 0,5% v v-1 de HNO3, nebulizador Burgener e condições robustas do ICP geraram resultados com recuperações entre 68 e 119%. As determinações de Al, Ba, Cr, Fe, K, Li, Mg, Na, Sr e Ti em quartzo foram executadas com introdução de suspensão e ausência de padrão interno, usando condições do ICP similares àquelas adotadas na determinação elementar para matriz de cimento. Nesse caso as recuperações variaram de 90 a 107%. A adsorção dos analitos e padrões internos sobre as nanopartículas de sílica pode ser uma alternativa para a preparação de padrões de calibração quando se deseja realizar a introdução direta do material sólido em suspensão. / The aim of this study was to evaluate parameters for the development of methods for elements determination in alumina, cement and quartz by inductively coupled plasma optical emission spectrometry (ICP OES) with slurry sampling. Some elements were investigated as candidates for internal standards (ISs) Be, Dy, Gd, In, La, Sc, Y, Yb and Tl. Samples of certified reference material (CRM) of alumina (Alumina Reduction Grade - 699), Portland cement (blended with the 1889a and 1886a Limestone White Portland cement with low iron) from the National Institute of Standards and Technology (NIST), and quartz samples, suplied by the Department of Physics from Federal University of São Carlos (UFSCar), named T-4FI, T-2FI and T4GR were used to optimize instrumental, method development and accuracy evaluation of the method. Nanoparticles of high purity silica (Wacker HDK T40 &#174;), Wacker Chemie AG were used in the study adsorption of the analytes and internal standards as calibrating material for direct analysis of solids. Correlation graphs using excitation potentials, ionization energies and melting point temperatures were used for chosing the best ISs. Exploratory analysis using hierarchical cluster analysis (HCA) and principal component analysis (PCA) were also performed. Optimization of ICP OES was performed in aqueous and slurry samples to establishment figures of merit, such as sensitivity, robustness, selectivity and repeatability. In the optimization of ICP, power supply, nebulizer flow rate and auxiliary gas flow rate were considered. The determination of Ca, Fe, Ga, In, Si and Zn in alumina was made after decomposition in a microwave oven with subsequent precipitation of Al(III) with NH3 gas. The internal standard was essential to obtain the accuracy of the method, with recoveries of CRM analysis ranging from 83 to 117%. For the cement analysis was evaluated the effect of nitric acid concentration over analytes extraction (Al, Ca, Cr, Fe, K, Mg, Mn, Na, P, S, Si, Sr, Ti and Zn) and ISs candidate adsorption (Be, Sc, In and Dy). Determinations of the elements in cement slurry with the internal standard (except for Cr and Zn), with 0.5% v v-1 HNO3, nebulizer Burgener and robust conditions of ICP produced results with recoveries between 68 and 119%. The determinations of Al, Ba, Cr, Fe, K, Li, Mg, Na, Sr and Ti in quartz were performed with the slurry introduction and without of internal standard, using similar conditions of those adopted for cement matrix. In this case the recoveries ranged from 90 to 107% with addition and recovery test. The adsorption of the analytes and internal standards on silica nanoparticles could be an alternative for the preparation of calibration standards when considering performing the direct introduction of solid material.

<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>

<p>The spectroscopic, SEM and Raman measurements on carbon nanotubes under the exact conditions of which OES analysis were made showed that at<br /> a pressure of 400 Torr and a flow rate of 200 sccm, the quality and quantity of single-walled carbon nanotubes was the highest.</p>

No description available.

<p>The spectroscopic, SEM and Raman measurements on carbon nanotubes under the exact conditions of which OES analysis were made showed that at<br /> a pressure of 400 Torr and a flow rate of 200 sccm, the quality and quantity of single-walled carbon nanotubes was the highest.</p>

Made available in DSpace on 2014-12-17T14:06:48Z (GMT). No. of bitstreams: 1 JulioCPB.pdf: 2433728 bytes, checksum: 9509a2a35ebc0e4009df0a9bced418db (MD5) Previous issue date: 2007-11-14 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Plasma process like ionic nitriding and cathodic cage plasma nitriding are utilized in order to become hard surface of steels. The ionic nitriding is already accepted in the industry while cathodic cage plasma nitriding process is in industrial implementation stage. Those process depend of plasma parameters like electronic and ionic temperature (Te, Ti), species density (ne, ni) and of distribution function of these species. In the present work, the plasma used to those two processes has been observed through Optical Emission Spectroscopy OES technique in order to identify presents species in the treatment ambient and relatively quantify them. So plasma of typical mixtures like N2 H2 has been monitored through in order to study evolution of those species during the process. Moreover, it has been realized a systematic study about leaks, also thought OES, that accomplish the evolution of contaminant species arising because there is flux of atmosphere to inside nitriding chamber and in what conditions the species are sufficiently reduced. Finally, to describe the physic mechanism that acts on both coating techniques ionic nitriding and cathodic cage plasma nitriding / Processos a plasma como nitreta??o i?nica e nitrteta??o por gaiola cat?dica s?o utilizados para endurecimento de superf?cies de a?os. A nitreta??o i?nica sendo j? consolidada em aplica??es industriais enquanto que o processo por gaiola cat?dica ainda se encontra em est?gio de pesquisa. Esses processos dependem dos par?metros de plasma como temperatura eletr?nica e de ?ons (Te, Ti), densidade de esp?cies (ne, ni,) e da fun??o de distribui??o das mesmas. No presente trabalho, o plasma utilizado para esses dois processos foi diagnosticado utilizando a t?cnica de Espectroscopia de Emiss?o ?ptica EEO para identificar as esp?cies presentes no ambiente de tratamento e quantifica-las relativamente. Assim, plasma de mistura gasosa t?pica como N2 H2 foi monitorado, com o intuito de estudar a evolu??o dessas esp?cies durante o processo. Al?m disso, foi realizado um estudo sistem?tico, tamb?m atrav?s de EEO, que acompanha a evolu??o das esp?cies contaminantes surgidas em vazamentos de modo a buscar condi??es onde as mesmas s?o suficientemente reduzidas. Finalmente busca-se, atrav?s do diagn?stico de plasma por EEO, descrever o mecanismo f?sico de atua??o das duas t?cnicas de tratamento: nitreta??o i?nica e gaiola cat?dica