<p> Levitation melting was used to measure the equilibrium between H2-H2o or CO-C02 gas mixtures and pure Fe or Fe-Cr alloys over the temperature range 1550 - 1750°C. The effects of thermal diffusion on the two types of gases were investigated. First and second order interaction parameters were employed to describe the interaction between oxygen and chromium {up to 25 wt. pct. of Cr.). </p> / Thesis / Master of Science (MSc)

Today, fastening articles such as screws and nails are treated with different surface coatings to withstand corrosion. The Swedish distributor ESSVE® Produkter AB uses a nano coating called CorrSeal™ for high corrosion protection of their screws. Thermal diffusion galvanization (TDG) is a more environmentally friendly method that the company seeks to use as replacement for the current treatment. This process of zinc diffusion is carried out at around 400 °C for several hours. The aim of the project is to investigate the possibility to surface treat a wood screw using TDG. The elevated temperature is suspected to decrease the hardness of the hardened screw. Therefore, a hardened and tempered screw without surface treatment is sent to a TDG facility. Industrial furnaces are used for similar heat treatments of screws with different hardenings. Both processes are analyzed by evaluating the results of hardness, bending, and microscopy. No immediate correlation between the TDG process and heat treatment in the industrial furnaces is found. Results show that the tested screws softened to a higher degree in the TDG process compared to treatment in the industrial furnaces. The mechanical properties of the tested screws, after the TDG process, are not acceptable. The zinc layer thickness on the screws is uneven yet believed to meet the required demands on corrosion resistance. Results also show that incorporating the TDG process in the tempering step is essential to meet the demands on hardness. Additionally, changing the composition of the material can lead to higher resistance against softening at the elevated temperatures. Further research is however needed to present a screw with sufficient corrosion resistance from the TDG process that will meet the demandson hardness and bending.

Thesis (MSc)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Polystyrene-block-poly(ethylene oxide) (PS-b-PEO) copolymers contain a hydrophilic PEO block and a hydrophobic PS block. PS and PEO have different affinities for most organic solvents and as a result, the PS-b-PEO copolymers are difficult to characterize in solution. In order to achieve a complete characterization of their molecular heterogeneity different techniques have been used. Recently FFF has become a cutting edge technology for polymer analysis because it possesses a number of advantages over conventional SEC and other liquid chromatographic techniques. The mild operating conditions allow the analysis of delicate and sensitive complex analytes such as complex polymer assemblies. The ability to analyze polymers with ultrahigh molar masses has also contributed to its significance in the characterization of polymers. In this study, the FFF behaviour of PS-b-PEO copolymers as well as PS and PEO homopolymers was investigated using Thermal FFF in different organic solvents and AF4. The aim of the study was the correlation of the thermodynamic quality of the solvents and the elution behaviour of the polymers. Unfortunately, PEO homopolymers have been found to interact with the membrane in AF4. Therefore, they were best characterized in organic solvents using Thermal FFF. In contrast to AF4 no specific interactions occurred due to the absence of a membrane. Results for Thermal FFF showed that in all utilized solvents, PS and PEO homopolymers were separated in the direction of increasing molar mass. For PS-b-PEO copolymers the retention in selective (good) solvents for PS was dependent on the molar mass of the PS block in the block copolymer. This was explained by the fact that in poor solvents PEO adopts a collapsed coil conformation while PS is present in extended random coil conformation. Results also showed that polymer retention was dependent on the temperature programme utilized. The fractionations by Thermal FFF indicated that some of the PS-b-PEO copolymer samples contained PS and PEO homopolymers as by-products. After semi-preparative fractionation these homopolymers were qualitatively identified using FTIR spectroscopy. / AFRIKAANSE OPSOMMING: Polistireen-blok-poli(etileenoksied) (PS-b-PEO) ko-polimere bevat 'n hidrofiliese politetileen oksied (PEO) blok en 'n hidrofobiese polistireen (PS) blok. PS en PEO het verskillende affiniteite vir die meeste organiese oplosmiddels, dit bemoeilik die karakterisering van PS-b-PEO ko-polimere in oplossing. Ten einde 'n volledige karakterisering van hul molekulêre heterogeniteit te bepaal moet ‘n verskeidenheid van tegnieke gebruik word. Onlangs het veldvloeifraksionering (FFF) baie grond gewen tov polimeer analise, aangesien dit verskeie voordele het bo tradisionele chromatografiese tegnieke soos grootte-uitsluitingschromatografie (SEC). Die ligte operasionele omstandighede laat die ontleding van ‘n verskeidenheid van polimere toe, enige iets van delikate polimeer komplekse tot ultra hoë molekulêre massa. In hierdie studie is die FFF gedrag van PS-b-PEO ko-polimere asook PS en PEO homopolimere ondersoek met behulp van Termiese FFF(ThFFF) in verskillende organiese oplosmiddels en onsimmetriese vloei-veldvloeifraksionering(AF4). Die doel van die studie was om die verband tussen die termodinamiese gehalte van die oplosmiddels en die eluering gedrag van die polimere te bepaal. Analise van PEO homopolimere was onsuksesvol aangesien daar interaksie was met die membraan. PEO is dus net geanaliseer in organise oplosmiddels met behulp van ThFFF, aangesien daar geen membraan is nie. Analise met ThFFF het gewys dat skeiding plaasvind volgens ‘n toename in molekulêre massa in organise oplosmiddels. Vir PS-b-PEO ko-polimere die retensie in selektiewe (goeie) oplosmiddels vir PS was afhanklik van die molekulêre massa van die PS blok in die ko-polimeer. ‘n Moontlike teorie is dat die PEO blok ‘n ineengestorte spoel struktuur vorm terwyl die PS blok ‘n uitgestrekte lukraake vorm aan neem. Resultate het ook getoon dat die polimeer retensie afhanklik was van die temperatuur program wat gebruik is. Die fraksionering deur ThFFF het aangedui dat sommige van die PS-b-PEO kopolimeer monsters bestaan het uit PS en PEO homopolimere as by-produkte. Hierdie is kwalitatief bewys deur analise van die fraksies na fraksionering van die ko-polimere met behulp van FTIR spektroskopie.

No description available.

Cette thèse porte sur le mouvement de particules colloïdales induit par l’effet thermoélectrique (ou effet Seebeck). Dans un électrolyte soumis à un gradient de température, les ions ont tendance à migrer à des vitesse qui différent d'une espèce à l'autre. On observe alors une accumulation de charge aux bords de l’échantillon. Ce déséquilibre induit un champ électrique qui agit sur les colloïdes chargés présents dans la solution. Cette contribution électrophorétique dans le champ de Seebeck s'additionne à la contribution directe de thermodiffusion. Comme résultat principal,nous obtenons la vitesse phorétique en fonction de la fraction volumique des particules et, dans le cas de polyélectrolytes, du poids moléculaire. Dans la seconde partie, nous étudions l’effet thermoélectrique pour une particule chauffée par absorption d’un faisceau laser. Le gradient de température est alors radial et l’effet Seebeck induit une charge nette dans le voisinage de la particule. Enfin, nous discutons les applications possibles de ce phénomène de thermocharge / In this work we study the motion induced in a colloidal dispersion by thethermoelectric or Seebeck effect. As its basic principle, the ions of the electrolytesolution start moving in a temperature gradient. In general, the velocity of one iondiffers from another. As a result, one observes a charge separation and a macroscopicelectric field. This thermoelectric field, in turn, acts upon the charged colloidalparticle present in the solution. Thus thermophoresis of the particle comprises of anelectrophoretic motion in the thermoelectric or Seebeck field. As an important result,we derive how the corresponding velocity of a colloidal particle depends upon thecolloidal volume fraction or on molecular weight for polymers. In a second part, westudy the thermoelectric effect due to a hot colloidal particle where a radialtemperature gradient is produced by the particle itself. In this temperature gradientthe same Seebeck effect takes place in the electrolyte solution. We find that the hotparticle carries a significant amount of charge around it. Whereas the amount ofsurface charges present at the boundaries of the sample container in the onedimensionalcase is rather insignificant. Possible applications of this thermochargingphenomenon are also discussed.

Submitted by Dilene Paulo (dilene.fatima@ufcg.edu.br) on 2018-02-07T14:27:21Z No. of bitstreams: 1 WALDEMIR SOARES DA COSTA – TESE PPGEP 2015.pdf: 7105919 bytes, checksum: 23f299de189a3af192ed30f53d82a776 (MD5) / Made available in DSpace on 2018-02-07T14:27:21Z (GMT). No. of bitstreams: 1 WALDEMIR SOARES DA COSTA – TESE PPGEP 2015.pdf: 7105919 bytes, checksum: 23f299de189a3af192ed30f53d82a776 (MD5) Previous issue date: 2015-07-17 / Este trabalho tem como objetivo estudar o comportamento da transferência de calor em polpa de jaca acondicionada em recipiente cilíndrico. O estudo apresenta a solução para a equação de difusão com condição de contorno de primeiro tipo variável. Foi desenvolvida uma modelagem físico-matemática para solução de um problema direto de difusão de calor bidimensional, no interior de um recipiente cilíndrico contendo polpa de jaca. O método dos volumes finitos com formulação totalmente implícita foi usado para resolver o problema direto e, por conseguinte, determinar a distribuição de temperatura. O meio pastoso, homogêneo e isotrópico, foi considerado estacionário e, assim, eventuais trocas convectivas e radioativas no interior do meio foram negligenciadas. Dois softwares em Fortran foram desenvolvidos visando, primeiro, à solução do problema de estimativa da difusividade térmica utilizando-se, como função objetivo, o qui-quadrado e o outro para a solução do problema direto. Conjuntamente, foi usado um aparato experimental para a análise inversa (problema inverso). O sistema físico experimental consistiu de dois recipientes cilíndricos de alumínio de dimensões diferentes, que foram preenchidos com polpa de jaca para a qual se estimou a difusividade térmica. Dois termopares conectados a um termômetro digital de dois canais mediram as temperaturas no centro e na interface entre a polpa e o recipiente. As medidas foram enviadas a um computador via RS-232 e salvas em arquivo, através do software Data logger. No que concerne ao problema direto, um modelo de condução de calor bidimensional, com simetria radial e axial, foi usado para obter a resposta transiente das temperaturas medidas no centro e no contorno do cilindro. Quando comparados aos valores da literatura, os resultados obtidos se mostraram coerentes, ou seja, o software desenvolvido neste trabalho pode ser considerado válido, sendo que este pode ser utilizado para outras simulações. Mostraram, também, que a solução proposta representa satisfatoriamente o processo de tratamento térmico de polpa de jaca acondicionada em embalagens cilíndricas proporcionando segurança alimentar com um menor custo de energia. Conhecida a difusividade térmica em função da temperatura local, é possível precisar o tempo adequado de tratamento térmico, tornando desnecessária a realização de experimentos a cada vez que um novo recipiente cilíndrico for utilizado para armazenar o produto. / This work aims to study the heat transfer behavior in jackfruit pulp packed in cylindrical container. The study presents the solution to the diffusion equation type boundary condition for first variable. A physical-mathematical model for solving the problem of a direct two-dimensional diffusion of heat in the interior of a cylindrical container containing jackfruit pulp has been developed. The finite volume method with fully implicit formulation was used to solve the direct problem and therefore, determine the temperature distribution. The medium viscous, homogeneous and isotropic, was considered stationary and thus any radioactive and convective exchanges within the medium they were neglected. Two software in Fortran were developed first to find the solution of the estimated thermal diffusivity problem using as objective function, the chi-square and also for solving the direct problem it self. Together, an experimental apparatus was used to analyze the reverse (inverse problem). The experimental physical system consisted of using two cylindrical aluminum containers of different dimensions, which were filled with jackfruit pulp for which the thermal diffusivity is estimated. Two thermocouples connected to a digital two channel thermometer measured temperatures at the center and at the interface between the pulp and the container. The measures were sent to a computer via RS-232 and saved in a file, through the Data Logger software. Concerning to the direct problem a two-dimensional heat conduction model with radial and axial symmetry it has been used for the transient response of the measured temperatures at the center and the cylinder contour. Compared to literature values, the results obtained were consistent, so, the software developed in this work can be considered valid and this can be used for other simulations the results. Also showed that the proposed solution represents satisfactorily the heat treatment process of wrapped jackfruit pulp in cylindrical packaging providing food security with a lower energy cost. As we know the thermal diffusivity an depending on the local temperature is possible to determine the timing of heat treatment, making it unnecessary to perform experiments each time a new cylindrical container is used to store the product.

Made available in DSpace on 2014-10-09T12:35:17Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:10:06Z (GMT). No. of bitstreams: 0 / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Made available in DSpace on 2014-10-09T12:35:17Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:10:06Z (GMT). No. of bitstreams: 0 / Radioisótopos de gálio são estudados e avaliados para aplicações médicas desde 1949. Nos últimos 50 anos 67Ga tem sido amplamente utilizado no diagnóstico de diversas patologias, incluindo lesões inflamatórias crônicas e agudas, bacterianas ou estéreis e diversos tipos de tumores. No Brasil 30% das clinicas que prestam serviços de Medicina Nuclear utilizam o Citrato de 67Ga com uma demanda de distribuição no IPEN-CNEN/SP de 37 GBq (1 Ci) por semana. O 67Ga apresenta meia-vida física de 3,26 dias (78 horas) e decai 100% por captura eletrônica para o 67Zn estável. Seu decaimento inclui a emissão de raios &gamma; com energias de 93,3 keV (37%), 184,6 keV (20,4%), 300,2 keV (16,6%) e 888 keV (26%). No IPEN o 67Ga era produzido a partir da reação 68Zn(p, 2n)67Ga. Após a irradiação, o alvo era totalmente dissolvido em HCl concentrado e a solução percolada em resina catiônica DOWEX 50W-X8, 200-400 mesh, condicionada em HCl 10 mol L-1. Zinco, níquel e cobre eram eluídos em HCl 10 mol L-1 e o 67Ga em HCl 3,5 mol L-1. O produto final era obtido na forma de citrato de 67Ga. Este trabalho apresenta um método inédito, rápido, direto e eficiente de separação química e obtenção de 67GaCl3 a partir da difusão térmica (aquecimento do alvo) aliada à extração em ácido acético concentrado. A purificação foi realizada por cromatografia de troca iônica. Realizou-se a eletrodeposição do zinco natural em placas de cobre niquelado como substrato e os depósitos de zinco obtidos foram aderentes ao substrato, levemente brilhantes e uniformes. Os alvos foram irradiados com prótons de 26 MeV e corrente integrada de 10 &mu;A.h. Após a irradiação, os alvos foram aquecidos a 300 °C por 2 horas e colocados em contato com ácido acético concentrado por 1 hora. O rendimento médio de extração de 67Ga obtido foi de (72±10)%. Esta solução foi evaporada e o resíduo foi retomado em NH4OH 0,5 mol L-1. O 67Ga foi purificado em resina catiônica Dowex 50WX8 em meio de NH4OH. A recuperação obtida foi de (98 ± 2) %, de 67Ga. O eluido foi evaporado e retomado em HCl 0,1 mol L-1. A pureza química foi verificada por ICP-OES encontrando-se (2 ± 1) &mu;g mL -1 de zinco. As concentrações de ferro, cobre e níquel foram inferiores ao limite de detecção do método e aos limites de utilização de 67Ga. A pureza radionuclídica foi verificada por espectroscopia-&gamma; utilizando um detector de germânio Hiper-Puro encontrando-se valor superior a (99,9%). Este método inédito permite a obtenção de 67Ga com alta pureza química, radioquímica e radionuclídica em condições de processamento menos agressivas e corrosivas que o método comumente utilizado. / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

No description available.

Radioisótopos de gálio são estudados e avaliados para aplicações médicas desde 1949. Nos últimos 50 anos 67Ga tem sido amplamente utilizado no diagnóstico de diversas patologias, incluindo lesões inflamatórias crônicas e agudas, bacterianas ou estéreis e diversos tipos de tumores. No Brasil 30% das clinicas que prestam serviços de Medicina Nuclear utilizam o Citrato de 67Ga com uma demanda de distribuição no IPEN-CNEN/SP de 37 GBq (1 Ci) por semana. O 67Ga apresenta meia-vida física de 3,26 dias (78 horas) e decai 100% por captura eletrônica para o 67Zn estável. Seu decaimento inclui a emissão de raios &gamma; com energias de 93,3 keV (37%), 184,6 keV (20,4%), 300,2 keV (16,6%) e 888 keV (26%). No IPEN o 67Ga era produzido a partir da reação 68Zn(p, 2n)67Ga. Após a irradiação, o alvo era totalmente dissolvido em HCl concentrado e a solução percolada em resina catiônica DOWEX 50W-X8, 200-400 mesh, condicionada em HCl 10 mol L-1. Zinco, níquel e cobre eram eluídos em HCl 10 mol L-1 e o 67Ga em HCl 3,5 mol L-1. O produto final era obtido na forma de citrato de 67Ga. Este trabalho apresenta um método inédito, rápido, direto e eficiente de separação química e obtenção de 67GaCl3 a partir da difusão térmica (aquecimento do alvo) aliada à extração em ácido acético concentrado. A purificação foi realizada por cromatografia de troca iônica. Realizou-se a eletrodeposição do zinco natural em placas de cobre niquelado como substrato e os depósitos de zinco obtidos foram aderentes ao substrato, levemente brilhantes e uniformes. Os alvos foram irradiados com prótons de 26 MeV e corrente integrada de 10 &mu;A.h. Após a irradiação, os alvos foram aquecidos a 300 °C por 2 horas e colocados em contato com ácido acético concentrado por 1 hora. O rendimento médio de extração de 67Ga obtido foi de (72±10)%. Esta solução foi evaporada e o resíduo foi retomado em NH4OH 0,5 mol L-1. O 67Ga foi purificado em resina catiônica Dowex 50WX8 em meio de NH4OH. A recuperação obtida foi de (98 ± 2) %, de 67Ga. O eluido foi evaporado e retomado em HCl 0,1 mol L-1. A pureza química foi verificada por ICP-OES encontrando-se (2 ± 1) &mu;g mL -1 de zinco. As concentrações de ferro, cobre e níquel foram inferiores ao limite de detecção do método e aos limites de utilização de 67Ga. A pureza radionuclídica foi verificada por espectroscopia-&gamma; utilizando um detector de germânio Hiper-Puro encontrando-se valor superior a (99,9%). Este método inédito permite a obtenção de 67Ga com alta pureza química, radioquímica e radionuclídica em condições de processamento menos agressivas e corrosivas que o método comumente utilizado. / Radioisotopes of gallium have been studied and evaluated for medical applications since 1949. Over the past 50 years 67Ga has been widely used in the diagnosis of various diseases, including acute and chronic inflammatory lesions, bacterial or sterile and several types of tumors. In Brazil 30% of clinics that provide services for Nuclear Medicine use 67Ga citrate and the demand for 67Ga at IPEN-CNEN/SP is 37 GBq (1 Ci)/week. The 67Ga presents physical half-life of 3.26 days (78 hours) and decays 100% by electron capture to stable 67Zn. Its decay includes the emission of &gamma; rays with energies of 93.3 keV (37%), 184.6 keV (20.4%), 300.2 keV (16.6%) and 888 keV (26%). In the past 67Ga was produced by the reaction 68Zn (p, 2n) 67Ga at IPEN-CNEN/SP. After irradiation, the target was dissolved in concentrated HCl and the solution percolated through a cationic resin DOWEX 50W-X8, 200-400 mesh, conditioned with 10 mol L -1 HCl. Zinc, nickel and copper were eluted in 10 mol L-1 HCl and 67Ga 3.5 mol L-1 HCl. The final product was obtained as 67Ga citrate. This work presents a new, fast, direct and efficient method for the chemical separation of 67Ga by thermal diffusion (heating of the target) combined with concentrated acetic acid extraction. Purification was performed by ion exchange chromatography. Natural zinc electrodeposition was performed on nickel/copper plates as substrate and the zinc deposits were adherent to the substrate, slightly shiny and uniform. The targets were irradiated with 26 MeV protons and integrated current of 10 &mu;A.h. After irradiation, the targets were heated at 300 °C for 2 hours and placed in contact with concentrated acetic acid for 1 hour. The average yield of extraction of 67Ga was (72 ± 10)%. This solution was evaporated and the residue was taken up in 0.5 mol L-1 NH4OH. The 67Ga was purified on cationic resin Dowex 50WX8 in NH4OH medium. The 67Ga recovery was (98 ± 2)%. This solution was evaporated and taken up in 0.1 mol L-1 HCl. The chemical purity was evaluated by ICP-OES that resulted in (2 ± 1) &mu;g mL-1 of zinc. The concentration of iron, copper and nickel was lower than the detection limits and also than the utilization limits for 67Ga. The radionuclidic purity was greater than (99.9%). This method showed to be suitable to obtain high purity 67Ga in less aggressive chemical conditions than before.