The exceptional physical, chemical, electric, and mechanical properties of ceramics, glass and diamond film make them receive much attention in high-tech industry. Although the electrochemical discharge machining (ECDM) can be used to process those materials, most ECDM are used for machining micro-holes and wire cutting. However, the application on the polishing aspect is still scarce in the literature. In this study, a high-precision dynamic electrical pitting tester with the electrolyte of KOH is employed to investigate the behavior of static electrochemical discharge in terms of supply voltage and gap distance between the steel ball and the diamond film. Furthermore, its machining characteristics are also analyzed. According to the current waveform, the I-V curve is plotted. Results show that the current value of glass is higher than that of diamond film and acrylic. This indicates that the glass is easily to be ionized. According to the observation on the surface of machined diamond film by using SEM, the machined status can be divided into four regimes. In the first regime, the supply voltage is less than 100V where the machined mark on the diamond film cannot be found. Hence, it is called non-machined regime. In the second regime, the supply voltage is in the range between 100 and 107V, where only very slight damage can be observed on the diamond film. Hence, it is called the fine machined regime. In the third regime, the supply voltage is in the range between 107 and 110V, where the machined status on the diamond film is unstable. Hence, it is called the transition regime. In the fourth regime, the supply voltage is larger than 110V, where the machined damage is very heavy. Hence, it is called the rough machined regime. At the supply voltage 105V with the gap less than 80£gm, the annular shape of the machined damage on the surface of the diamond film can be observed. However, when the gap is in the range between 80£gm and 95£gm, the annular shape of the machined damage disappears, but there is still slight damage at the asperity of the diamond film. When the gap is larger than 95£gm, the machined damage is invisible. Hence, the critical gap is defined as 95£gm for the supply voltage of 105V. At the supply voltage of 105V, the gap of 90£gm, and the machining time of 10 min, only the asperity of diamond film shows machined mark, but the surface is flatter. Therefore, it is possible to conduct the fine machining process by using ECDM on diamond film.

Orientador: Teófilo Miguel de Souza / Banca: Celso Eduardo Tuna / Banca: Osiris Canciglieri Junior / Resumo: Visando o conforto e a economia, a ciência, hoje, desenvolve tecnologias capazes de preservar o meio ambiente, diminuindo a perda de energia no processo e na utilização dessas novas técnicas, de forma a garantir um manuseio ecologicamente correto, sem deixar de atender as necessidades do homem. Uma técnica alternativa é o aproveitamento da energia proveniente do sol, que ainda é pouco explorada, podendo ser mais utilizada em coletores solares através do uso de novos materiais. Para isso, o objetivo deste trabalho é comparar o rendimento térmico e o coeficiente global de transferência de calor de materiais como cobre, alumínio e do filme de diamante CVD sobre o silício, pois essas grandezas são essenciais para a caracterização de um bom trocador de calor. Mediante pesquisa experimental foi possível observar que o filme de diamante CVD sobre o silício, mesmo com uma camada muito fina de deposição de filme, mostrou-se mais eficiente no processo de transmissão de calor quando comparado com o cobre e o alumínio / Abstract: To ensure the comfort and economy, science now develops technologies to preserve the environment by reducing energy loss process and the use of these new techniques, to ensure an environmentally friendly handling, while meeting the needs of man. An alternative technique is the use of energy from the sun, which is not explored and may be used in most solar collectors through the use of new materials. For this, the objective is to compare the thermal efficiency and overall coefficient of heat transfer materials such as copper, aluminum and CVD diamond film on silicon, since these quantities are essential for the proper characterization of a heat exchanger. Through experimental research we observed that the CVD diamond film on silicon, even with a very thin film deposition, was more efficient for heat transfer when compared with copper and aluminum / Mestre

Made available in DSpace on 2014-06-11T19:30:10Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-08-01Bitstream added on 2014-06-13T19:39:26Z : No. of bitstreams: 1 dornelas_ln_me_guara.pdf: 431530 bytes, checksum: 5d8aa30beba39823f5403bbf59a82048 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Visando o conforto e a economia, a ciência, hoje, desenvolve tecnologias capazes de preservar o meio ambiente, diminuindo a perda de energia no processo e na utilização dessas novas técnicas, de forma a garantir um manuseio ecologicamente correto, sem deixar de atender as necessidades do homem. Uma técnica alternativa é o aproveitamento da energia proveniente do sol, que ainda é pouco explorada, podendo ser mais utilizada em coletores solares através do uso de novos materiais. Para isso, o objetivo deste trabalho é comparar o rendimento térmico e o coeficiente global de transferência de calor de materiais como cobre, alumínio e do filme de diamante CVD sobre o silício, pois essas grandezas são essenciais para a caracterização de um bom trocador de calor. Mediante pesquisa experimental foi possível observar que o filme de diamante CVD sobre o silício, mesmo com uma camada muito fina de deposição de filme, mostrou-se mais eficiente no processo de transmissão de calor quando comparado com o cobre e o alumínio / To ensure the comfort and economy, science now develops technologies to preserve the environment by reducing energy loss process and the use of these new techniques, to ensure an environmentally friendly handling, while meeting the needs of man. An alternative technique is the use of energy from the sun, which is not explored and may be used in most solar collectors through the use of new materials. For this, the objective is to compare the thermal efficiency and overall coefficient of heat transfer materials such as copper, aluminum and CVD diamond film on silicon, since these quantities are essential for the proper characterization of a heat exchanger. Through experimental research we observed that the CVD diamond film on silicon, even with a very thin film deposition, was more efficient for heat transfer when compared with copper and aluminum

L’objectif principal de ce travail de thèse a été l’optimisation des conditions de croissance du diamant dans un réacteur MPACVD afin d’une part, obtenir des films de diamant monocristallin à faible densité de dislocations, condition sine qua none pour une utilisation dans le domaine de l’électronique de puissance et, d’autre part, synthétiser des films épais (>100 μm) de diamant monocristallin intrinsèque et fortement dopés au bore sur substrats orientés (111), orientation cristalline connue pour favoriser la formation de macles. Dans une première partie, nous avons développé un procédé d’infléchissement et de confinement desdislocations en utilisant des substrats en forme de pyramide orientés (100) et en déterminant des conditions de croissance bien particulières. Cette étude innovante et originale a permis de lever plusieurs verrous scientifiques et technologiques qui ouvrent la voie à la réalisation de films de diamant monocristallin à faible densité de défauts. Dans une deuxième partie, l’effetdes différents paramètres de croissance a été étudié, afin d’optimiser notre procédé de croissance sur orientation (111). Il a ainsi été mis en évidence l’existence d’une fenêtre de couple pression/puissance micro-onde, température et concentration en méthane qui permettent d’assurer un bon compromis entre qualité cristalline et vitesse de croissance, permettant la synthèse de films épais de diamant fortement dopé au bore sur cette orientation ouvrant ainsi la possibilité de combiner l’efficacité de dopage de type n et la réalisation de composants bipolaires verticaux pour des applications en électronique haute tension-hautetempérature. / The main objective of this PhD thesis is the optimization of diamond growth conditions in a MPACVD reactor in order to one hand, synthesize single crystal diamond films with low dislocation density, prerequisite to their use in the field of power electronics and on the other hand, synthesize thick intrinsic and boron doped monocrystalline diamond films (>100 microns) on (111)-oriented substrates, crystallographic orientation which is well known to promote twinning. In a first part, a process of inflection and confinement of the dislocations has been developed using (100) pyramidal shape substrates coupled with specific growth conditions. This innovative and original study open the way for the fabrication of single crystal diamond films with low defect density. In a second part, the effect of different growth parameters has been studied to optimize our growth process for (111) orientation. It was thus demonstrated the existence of a narrow window of growth parameters pressure, microwavepower, temperature and methane concentration which ensures a good trade-off between crystalline quality and growth rate, allowing the synthesis of heavily boron-doped diamond thick films on this specific orientation, thus opening the possibility of combining the n-type doping efficiency and achieving vertical bipolar components for applications in hightemperaturehigh-voltage electronics.

Submitted by MARIA CLAUDIA COSTA DE OLIVEIRA BOTAN null (maclau_oliveira@hotmail.com) on 2017-09-01T16:19:06Z No. of bitstreams: 1 tese_final_Maria_Claudia_Botan.pdf: 4509077 bytes, checksum: 9a0c384b0ba382775d7f33ea6d5ec76e (MD5) / Approved for entry into archive by Luiz Galeffi (luizgaleffi@gmail.com) on 2017-09-01T16:48:26Z (GMT) No. of bitstreams: 1 botan_mcco_dr_guara.pdf: 4509077 bytes, checksum: 9a0c384b0ba382775d7f33ea6d5ec76e (MD5) / Made available in DSpace on 2017-09-01T16:48:26Z (GMT). No. of bitstreams: 1 botan_mcco_dr_guara.pdf: 4509077 bytes, checksum: 9a0c384b0ba382775d7f33ea6d5ec76e (MD5) Previous issue date: 2017-08-04 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A escassez de água potável vem impulsionando diversas pesquisas ao redor do mundo, por este ser um elemento vital e por sua obtenção envolver um grande paradigma, afinal não há efetivamente produção de água, o que existe é uma mudança de estado físico por meio do ciclo hidrológico. É preciso trazer segurança ao abastecimento sem abrir mão do caráter sustentável, utilizando materiais de baixo impacto ambiental associando-os a fontes renováveis de energia para seu funcionamento. Neste sentido, o presente estudo consiste na busca de melhorias de um condensador de vapor atmosférico, utilizando para tal, filmes finos de diamante como trocador de calor. Como este material apresenta condutividade térmica maior que a do cobre e do alumínio, visa-se agregar eficiência energética ao sistema. Dentre os procedimentos tomados identificou-se que o substrato de Silício do tipo P-Boro (111) foi o mais adequado para o crescimento dos filmes, obteve-se diferentes espessuras para comparação de desempenho no condensador e verificou-se a viabilidade técnica da proposta, pois foi possível realizar condensação utilizando o filme de diamante. De maneira geral, não há produção de condensado em umidades relativas inferiores a 50%. A partir de umidades superiores a 80 %, a amostra mais eficiente, no quesito produção de condensado, é a amostra de 4 h de deposição, que atinge o índice de 6 L.h-1.m². O custo ainda se mostra maior se comparado ao cobre e ao alumínio, de qualquer maneira o processo de condensação do vapor apresenta-se como uma alternativa de fonte de abastecimento em locais onde este bem encontra-se de forma escassa, como por exemplo, em plataformas de petróleo e na região árida do Nordeste brasileiro. / The shortage of drinking water has been driving several researches around the world, because its obtaining involves a great paradigm, after all there is no effective production of water, but there is a change of physical state through the hydrological cycle. It is necessary to bring security to the supply without abandoning the sustainable character, using materials of low environmental impact associating them with renewable sources of energy for its operation. In this sense, the present study consists in the search for improvements of an atmospheric vapor condenser, using thin films of diamond as heat exchanger. As this material has higher thermal conductivity than copper and aluminum, it is aimed to add energy efficiency to the system. Among the procedures taken it was found that P-Boron type silicon substrate (111) was the most suitable for the growth of the films, different thicknesses were obtained for the comparison of performance in the condenser and the technical feasibility of the proposal was verified, because it was possible to perform condensation using the diamond film. In general, there is no condensate production at relative humidity of less than 50%. From the humidities more than 80%, the most efficient sample, in the case of condensate production, is the sample of 4 h deposition, which reaches the index of 6 L.h-1 .m². The cost is still unfeasible compared to copper and aluminum, however, the vapor condensation process is an alternative source of supply in places where it is scarce, such as in oil platforms in the arid region of the Brazilian Northeast.

This thesis deals with the determination of carvacrol, thymol, and eugenol by HPLC with electrochemical detection. Carbon paste electrode and boron doped diamond film electrode were used as the working electrodes. For the comparison, UV spectrophotometric detection at 275 nm was used besides the electrochemical detection. The separation was performed on LiChroCART 125-4, RP-18e (5 µm) column. Optimum separation conditions were found: mobile phase consisting of acetonitrile and acetate buffer in ratio 50:50, the optimum buffer pH was pH 5. The optimum potential of working electrode during electrochemical detection was +0,8 V and +1,2 V for carbon paste electrode and boron doped diamond film electrode, respectively. For both electrodes, repeatability of the measurement was examined; the surface of both electrodes had to be renewed between the measurements. Under the obtained optimum conditions, calibration dependences were measured. The studied substances were determined in real samples, in Thymus vulgaris L. and Achillea millefolium L. and in thyme-containing tea and syrup.

This master's thesis is focused on the determination of 6-thioguanine (6-T) by DC voltammetry (DCV), differential pulse voltammetry (DPV) and flow injection analysis with electrochemical detection (FIA-ED) on a boron doped diamond electrode (BDDFE). The optimum conditions for determination of 6-T were found and under these conditions, concentration dependences were measured and the limits of quantification (LOQ) were calculated for each method. Medium of 60% methanol and phosphate buffer (PB) pH 2,0 was chosen as optimum for DCV and DPV determination of 6-T at BDDFE. For both DCV and DPV, the linear concentration dependences were obtained in concentration ranges of 6-T from 2 µmol·l-1 to 10 µmol·l-1 with LOQ 0,9 µmol·l-1 for DCV and 1,5 µmol·l-1 for DPV. Lower LOQ was achieved in PB pH 2,0, where LOQ was 0,6 µmol·l-1 for both DCV and DPV, but the problem was lower repeatability. In PB pH 2 6-T was determined by DCV in drinking and river water with LOQ 1,3 µmol·l-1 in both drinking and river water. The possibility of solid phase extraction was investigated as a method for preliminary separation of 6-T from urine. For FIA under optimized conditions (polarization potential 1300 mV, flow rate 5 ml·min1 and sample volume 50 µl) the linear concentrations dependences were obtained in concentration ranges...

Presented Diploma Thesis deals with the study of electrochemical behavior of 5-nitroimidazole (5-NI), with the search for optimal conditions for its determination using techniques of DC voltammetry (DCV) and differential pulse voltammetry (DPV) at a mercury meniscus modified silver solid amalgam electrode (m-AgSAE) and at a boron-doped diamond film electrode (BDDFE), and with the comparison of reached limits of quantification (LQs). The optimal conditions found for measuring calibration dependences of 5-NI at the m-AgSAE in deionized water were as follows: Britton-Robinson buffer of pH 7.0 and 10.0 for DCV and DPV, respectively. At both thechniques, it is advisable to use an electrochemical regeneration of the electrode surface by the application of a couple of regeneration potentials Ereg,1 = 0 mV and Ereg,2 = −800 mV. The calibration dependences were measured in the concentration range from 1·10−6 to 1·10−4 mol·l−1 , with the LQs of 1.0·10−6 mol·l−1 for DCV at the m-AgSAE and 1.5·10−6 mol·l−1 for DPV at the m-AgSAE. The concentration dependences of 5-NI at the BDDFE were measured using the DCV technique in the BR buffer of pH 3.0. For the DPV technique, the optimal medium seemed to be the BR buffer of pH 2.0, however, because of the presence of an interfering peak in the supporting electrolyte,...