• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 10
  • 9
  • 4
  • 3
  • Tagged with
  • 60
  • 21
  • 21
  • 19
  • 16
  • 15
  • 15
  • 14
  • 14
  • 14
  • 14
  • 14
  • 14
  • 12
  • 12
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Determinação de Na+, Zn2+, Fe2+ e Cu2+ em etanol combustível por voltametria de redissolução anódica

Pereira, Gerry Marcio Rosa 29 October 2015 (has links)
Submitted by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2016-07-25T19:10:12Z No. of bitstreams: 1 Dissertação - Gerry Marcio Rosa Pereira.pdf: 2455484 bytes, checksum: 4bb0220f3f659f4cfbfdb9bc33806e80 (MD5) / Approved for entry into archive by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2016-07-28T13:58:20Z (GMT) No. of bitstreams: 1 Dissertação - Gerry Marcio Rosa Pereira.pdf: 2455484 bytes, checksum: 4bb0220f3f659f4cfbfdb9bc33806e80 (MD5) / Approved for entry into archive by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2016-07-28T13:59:02Z (GMT) No. of bitstreams: 1 Dissertação - Gerry Marcio Rosa Pereira.pdf: 2455484 bytes, checksum: 4bb0220f3f659f4cfbfdb9bc33806e80 (MD5) / Made available in DSpace on 2016-07-28T13:59:02Z (GMT). No. of bitstreams: 1 Dissertação - Gerry Marcio Rosa Pereira.pdf: 2455484 bytes, checksum: 4bb0220f3f659f4cfbfdb9bc33806e80 (MD5) Previous issue date: 2015-10-29 / CNPq - Conselho Nacional de Desenvolvimento Científico e Tecnológico / For being less polluting, use of fuel ethanol as an alternative energy source has contributed to reducing CO2 emission levels in Brazil and in the world. But despite this advantageous feature, this matrix may suffer contamination from metals throughout its manufacturing process causing damage to the engines and consequently contamination of the environment. Typically quantification of metal ions is based on atomic absorption techniques. Alternatively electrochemical techniques perform well in the quantification of metal ions more specifically methods anodic stripping voltammetry and Square Wave (SWCSV) using a Boron Doped Diamond electrode (BDD). The support electrolyte chosen in the detection of metals were H2SO4 0,5 mol. L-1 for Na+, Zn2+, Cu2+ mol.L and Briton Robinson buffer 0,5 mol.L-1. ~ pH 1.8 for Fe2+. The hydroalcoholic solution with better response was 90:10 v/v ratio. The optimizing (SWCSV) parameters were: deposition potential: Na+= 0,1 V, Zn2+= 0,2 V, Fe2+= -0,1 V and Cu2+= -0,3 V; DepositionTime: 250 s for all metals; amplitude: 80 mV for Na+ and Zn2+, e 70 mV for Fe2+ and Cu2+; Frequency: 80 Hz for Na+ and Zn2+, 70 Hz for Fe2+ and Cu2+.The determination limits was found to be: 0,1 ppm for Na+, 0,2 ppm for Zn2+; 0,03 ppm for Fe2+ and 0,017 ppm for Cu2+. / Por ser menos poluente, a utilização do etanol combustível como fonte alternativa de energia tem contribuído para reduzir os níveis de emissão de CO2 no Brasil e também no mundo. Mas, apesar dessa característica vantajosa, essa matriz pode sofrer contaminação de metais ao longo de seu processo de fabricação causando danos aos motores e consequentemente a contaminação do meio ambiente. Normalmente a quantificação de íons metálicos é baseada em técnicas de absorção atômica. Alternativamente as técnicas eletroquímicas apresentam bom desempenho na quantificação de íons metálicos mais especificamente os métodos de Voltametria de Redissolução Anódica e Voltametria de Onda Quadrada VRA/VOQ. Este trabalho apresenta a otimização de parâmetros eletroanalíticos para determinação de íons Na+, Zn2+, Fe2+ e Cu2+ em etanol combustível através da VRA/VOQ utilizando um eletrodo de Diamante Dopado com Boro (DDB). Os eletrólitos suporte escolhidos para detecção dos metais foram: H2SO4 0,5 mol. L-1 para Na+, Zn2+, Cu2+ e tampão Briton Robinson 0,5 mol. L-1 pH ~1,8 para Fe2+. A composição da solução hidroalcoolica que melhor respondeu aos parâmetros eletroanaliticos foi a 90:10 v/v. Os melhores parâmetros VRA/VOQ encontrados foram: Potencial de deposição (Ed): Na+= 0,1 V, Zn2+= 0,2 V, Fe2+= -0,1 V e Cu2+= -0,3 V; Tempo de deposição (td): 250 s para os quatros metais; Amplitude (a): 80 mV para Na+ e Zn2+, e 70 mV para Fe2+ e Cu2+; Frequência (f): 80 Hz para Na+ e Zn2+, e 70 Hz para Fe2+ e Cu2+. Os limites de detecção foram de 0,1 ppm para Na+, 0,2 ppm para Zn2+,0,03 ppm para Fe2+ e 0,017 ppm para o Cu2+.
12

Aplicacao de diferentes metodologias na preparacao de matrizes organicas para a determinacao voltametrica de elementos traco

SISTI, CRISTINA 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:45:12Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:01:26Z (GMT). No. of bitstreams: 1 07287.pdf: 2056507 bytes, checksum: 770280526de75f4fc2cf87a5aa34f1e9 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
13

Determinacao da razao estequiometrica em amostras de dioxido de uranio

MOURA, SERGIO C. 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:25:35Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:03:43Z (GMT). No. of bitstreams: 1 06787.pdf: 4759327 bytes, checksum: 684951b3a2da400d6d50eb781069690c (MD5) / Dissertacao [Mestrado] / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
14

Estudo tecnologico do reprocessamento eletroquimico de combustiveis de uranio em meio de cloretos fundidos

FERNANDES, DAMARIS 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:47:02Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:08:38Z (GMT). No. of bitstreams: 1 08285.pdf: 5294618 bytes, checksum: 54177af21437f509ff2b3826c6ca78b8 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
15

Aplicacao de diferentes metodologias na preparacao de matrizes organicas para a determinacao voltametrica de elementos traco

SISTI, CRISTINA 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:45:12Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:01:26Z (GMT). No. of bitstreams: 1 07287.pdf: 2056507 bytes, checksum: 770280526de75f4fc2cf87a5aa34f1e9 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
16

Determinacao da razao estequiometrica em amostras de dioxido de uranio

MOURA, SERGIO C. 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:25:35Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:03:43Z (GMT). No. of bitstreams: 1 06787.pdf: 4759327 bytes, checksum: 684951b3a2da400d6d50eb781069690c (MD5) / Dissertacao [Mestrado] / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
17

Estudo tecnologico do reprocessamento eletroquimico de combustiveis de uranio em meio de cloretos fundidos

FERNANDES, DAMARIS 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:47:02Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:08:38Z (GMT). No. of bitstreams: 1 08285.pdf: 5294618 bytes, checksum: 54177af21437f509ff2b3826c6ca78b8 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
18

Určení vlivu iontů ve struktuře hydroxidu nikelnatého / The influence of metal ions on nickel hydroxide structure

Navrátil, Jan January 2010 (has links)
Diploma thesis is involved in basic properties of nickel materials for alkaline accumulators. Practical part deals with measuring of nickel hydroxides by cyclic voltametry. Next practical part is above measuring and optimalization various proportion of nickel and cobalt in layer made by electrodeposition on nickel electrodes.
19

Elektrochemické senzory s 3-D strukturou elektrod / The electrochemical sensors with 3-D structure of electrodes

Štekovič, Michal January 2012 (has links)
Miniature electrochemical sensors can be produced by thick-film technology. The optimal properties of thick-film electrode system, the production technology optimization of thick-film sensors and the adjustment of optimal technological properties are main problems of sensor design. An area of working electrode and an electrode topology design is the important parts in design of electrode system optimization. The rules for optimization of electrode systems in classical electrochemistry exist. The design of standard thick-film electrode construction is limited (2-D construction, substrate dimensions, resolution, paste parameters …). Therefore rules for classical electrode systems cannot be used fully in this case and larger electrode area can be making by 3D structure only. One of resolutions is unconventional method. The increase of working electrode surface by unconventional method – ball and wire bonding is discussed in this work.
20

Optické stanovení stavu nabití průtokových vanadových článků / Optical determination of the state of charge of vanadium flow battery cells

Šacl, Vojtěch January 2015 (has links)
The investigated subject for this diploma thesis is getting know properties of the vanadium redox battery (VRB), especially electrolyte. Specialization is applied to the state of charge of this cell and its measurements using the optical methods. Upon different state of charge is changed oxidation number of vanadium and resultant color of the electrolyte. Using spectrofotometry method that characteristic property is undergone measurement. The basic thing was learning to handle a measurement system. The first practical measurement was executed on example foils. Upon measurement of vanadium cell there was obtained the values of absorbation, which they were used for determination of state of charge.

Page generated in 0.029 seconds