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Avalia??o da dessulfuriza??o de diesel utilizando adsorventes mesoporosos modificados p?s-situ com ?ons met?licosSales, Rafael Viana 21 December 2015 (has links)
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Previous issue date: 2015-12-21 / A emiss?o de compostos sulfurados provenientes da queima de combust?veis derivados do refino do petr?leo, como ?leo diesel e gasolina, ? respons?vel por ocasionar danos ambientais, ? sa?de humana e aumento de custos industriais. Neste trabalho, foram estudados processos adsortivos de compostos sulfurados do diesel proveniente da Refinaria Potiguar Clara Camar?o, RPCC, com elevado teor de enxofre, utilizando s?licas mesoporosas do tipo MCM-41, que foram obtidas por m?todo hidrot?rmico, a partir de duas s?licas amorfas, s?lica MP1, novo material avaliado neste trabalho e uma s?lica comercial, utilizada para compara??o. Para os adsorventes mesoporosos MCM-41, sintetizados, foi avaliada a capacidade de adsor??o de enxofre em colunas de leito fixo e, posteriormente, os mesmos foram modificados, p?s-situ, com c?tions met?licos por impregna??o ?mida e dispers?o f?sica. Diferentes composi??es qu?micas dos compostos met?licos foram testadas, com a utiliza??o de ?xidos e sais, para a obten??o de s?tios ativos e avalia??o da complexa??o, entre o enxofre dos compostos org?nicos e os c?tions met?licos inseridos nos adsorventes, favorecendo a adsor??o. Os adsorventes sintetizados, puros e modificados, foram caracterizados atrav?s das t?cnicas de difratometria de raios X - DRX, espectroscopia de infravermelho com transformada de Fourier - FTIR, an?lises termogravim?tricas - TG/DTG, an?lises texturais pelo m?todo de BET/BJH e microscopia eletr?nica de varredura ? MEV com espectroscopia de energia dispersiva (EDS). Um planejamento fatorial do tipo 23, foi aplicado para o estudo do processo de adsor??o onde blends dos c?tions met?licos foram testados na adsor??o dos compostos sulfurados existentes. O monitoramento do teor de enxofre no diesel, durante o processo de adsor??o, ocorreu por t?cnica de Espectrometria de Fluoresc?ncia na Regi?o do Ultravioleta (FUV). A cin?tica e o equil?brio de adsor??o foram avaliados, onde isotermas de equil?brio foram obtidas para a avalia??o da capacidade m?xima de adsor??o de compostos sulfurados, nos sistemas adsorventes desenvolvidos neste trabalho. Foram obtidas capacidades m?ximas de adsor??o, em mg.g-1, de 16,64 e 14,98, respectivamente, para os adsorventes testados: 2AgS/MCM-41(M) e 1NiS1AgS/MCM-41(M). Os dados experimentais foram ajustados aos modelos de equil?brio de Langmuir e Freundlich. A remo??o de enxofre presente no diesel foi significante, atingindo o m?ximo de adsor??o de 94,9%, em rela??o ? concentra??o inicial deste contaminante. Atrav?s do estudo estat?stico, constatou-se que os blends preparados a partir dos adsorventes modificados por sais apresentaram uma capacidade de adsor??o maior em rela??o aos preparados por impregna??o de ?xidos met?licos, o que pode contribuir para a redu??o de custos industriais, uma vez que o m?todo de impregna??o ?mida dispensa uma segunda calcina??o. / The emission of sulfur compounds from the burning of oil products, such as diesel and gasoline, is responsible for causing environmental damage to human health and increase industrial costs. In this work, adsorptive processes of sulfur compounds from the diesel provided by the refinery Potiguar Clara Camar?o, RPCC, with high sulfur content, were studied using MCM-41 type of mesoporous silica which were obtained by hydrothermal method, from two amorphous silicas, MP1 silica, a new material evaluated in this work and a commercial silica, used for comparison. For MCM-41 mesoporous adsorbents, synthesized, it was evaluated the capability of sulfur adsorption in fixed bed columns, and later they were modified post-situ with metal cations by wet impregnation and physical dispersion. Different chemical compositions of metal compounds were tested with the use of oxides and salts, to obtain active sites and evaluation of complexing, between the sulfur of organic compounds and the metal cations inserted on the adsorbent, favoring adsorption. The synthesized adsorbents, pure and modified, were characterized by the techniques of X-ray diffraction - XRD, Fourier transform infrared spectroscopy - FTIR, thermogravimetric analysis - TG / DTG, textural analysis by the method of BET / BJH and scanning electron microscopy - SEM with energy dispersive spectroscopy (EDS). A 23 factorial plan was applied to study the adsorption process which metal cations blends were tested in the adsorption of existing sulfur compounds. The sulfur content monitoring in diesel fuel during the adsorption process occurred by ultraviolet fluorescence Spectrometry (UVF). The adsorption kinetics and equilibrium were evaluated, where equilibrium isotherms were obtained for the evaluation of the maximum adsorption capacity of sulfur compounds in adsorbent systems developed in this work. Maximum adsorption capacities were obtained ,at mg.g-1, 16,64 and 14,98, respectively, for the tested adsorbent: 2AgS/MCM-41(M) e 1NiS1AgS/MCM-41(M. The experimental data were fit to a Langmuir balance models and Freundlich. The removal of sulfur present in the diesel was significant, ranging from 54.3% to 88.9% compared to the initial concentration of contaminant. By statistical analysis it was found that blends prepared from the adsorbent modified by salts showed a higher adsorption capacity than the ones prepared by impregnation of metal oxides, which may contribute to the reduction of industrial costs, since the wet impregnation method dispenses a second calcination.
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S?ntese e caracteriza??o de rutenato de b?rioVital, Ang?lica Belchior 29 January 2015 (has links)
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Previous issue date: 2015-01-29 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / Compostos contendo rut?nio
possuem vasta aplica??o
em processos
catal?ticos. Muitas vezes esse metal ?
utilizado
em ?xidos porosos
, suporte,
com alta
estabilidade t?rmica. Os ?xidos mistos do tip
o perovskita (ABO
3
) apresentam boa
dispers?o met?lica
, elevada estabilidade t?rmica e qu?mica, sendo empregados em
processos oxidativos
. Em vista disso, este trabalho teve como objetivo principal
sintetizar e caracterizar o
catalisador de
rutenato de b?rio
(BaRuO
3
) com estrutura do
tipo perovskita. Para isso, foram utilizadas duas metodolog
ias de s?ntese
de BaRuO
3
, a
complexa??o combinada EDTA
-
Citrato e a coprecipita??o em meio oxalato. BaRuO
3
produzido passou por tratamentos t?rmicos a 950?C por 5, 10 e 15
horas.
O precursor
foi utilizado
na an?lise termogravim?trica (TG) para avaliar a estabilidade t?rmica, e os
p?s cer?micos
calcinados
foram caracterizados por:
difra??o de raios X (DRX) para
identifica??o
das fases formadas
, an?lise estrutural e avalia??
o do tamanho m?dio de
cristalitos; microscopia eletr?nica de varredura (MEV) para observa??o da morfologia;
espectroscopia de energia dispersiva (EDS) para determina??o da composi??o qu?mica
local. Observou
-
se que pela metodologia EDTA
-
Citrato o BaRuO
3
apr
esentou estrutura
rombo?drica com o grupo espacial R
-
3mH (ICSD:
10253) com morfologia heterog?ne
a
e com larga distribui??o de tamanho de cristais. Por outro lado, o ?xido sintetizado pelo
m?todo
de
coprecipita??o apresentou dois polimorfos, um com estrutura
hexagonal com
o grupo e
spacial P63/mmc (ICSD:84652) e
outro rombo?drico (ICSD:10253), com
morfologia homog?nea e maior controle de distribui??o de cristais. / Ruthenium compounds are widely use
d in catalytic processes. Often this
metal
is supported on porous oxides having high thermal stability.
Perovskite
-
type
o
xides
(ABO
3
) have good metal dispersion
,
high
thermal and chemical s
tability, it are
used in
oxidative processes
.
T
his study aimed
to synthesize and characterize
barium
ruthenate
(BaRuO
3
) with perovskite
-
type structure. For this, two methods
for
BaRuO
3
synthesis
have been used
,
combined complexation EDTA
-
Citrate
and oxalat
e coprecipitation.
BaRuO
3
produced underwent heat treatment at 950 ? C for 5, 10 and 15 hours.
The
precursor was used in thermogravimetric analysis (TG) to evaluate thermal stability
,
ceramic powders obtained were characterized by X
-
ray diffraction (XRD) t
o identify
the phases, structural analysis and assessment of the average size of crystallites;
scanning electron microscopy (SEM) to observe the morphology; energy dispersive
spectroscopy (EDS) to determine local chemical composition. It was observed that
BaRuO
3
for
EDTA
-
citrate methodology presented rhombohedral structure with space
group R
-
3mH (
ICSD
: 10253) heterogeneous morphology with a broad distribution and
crystal size.
thereby
, the oxide synthesized by
oxalate
coprecipitation method presented
two po
lymorphs, with hexagonal
structure with space group P63/
mmc (
ICSD
: 84652)
and a rhombohedral (
ICSD
: 10253) with homogeneous morphology and crystals
distribution control.
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Formas e biodisponibilidade de f?sforo no solo em resposta ? adi??o de ?cido c?trico. / Forms and bioavailability of phosphorus in the soil in response to the addition of citric acid.Santos, Sheila Renata January 2012 (has links)
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Previous issue date: 2012 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (Capes) / Melhorar a efici?ncia da absor??o de P no solo pelas culturas, por meio de manejos diferenciados da aduba??o fosfatada, diz respeito a um melhor aproveitamento do nutriente adicionado via fertiliza??o, que significa ganhos em produtividade. Em solos onde predominam argilas de baixa atividade e ?xidos em sua fra??o mineral, a fixa??o de P por meio dos processos de adsor??o e precipita??o torna a nutri??o fosfatada um fator limitante para produ??o da maioria das esp?cies cultiv?veis. O ?nion citrato, derivado da dissocia??o do ?cido c?trico no solo, possui elevado poder complexante de metais. Al?m disso, sua carga negativa garante afinidade com as cargas positivas dos ?xidos no solo, competindo com o fosfato pelos mesmos s?tios de liga??o. Com objetivo de verificar o potencial do ?cido c?trico em aumentar a biodisponibilidade ao milho e modificar as formas de P inorg?nico no solo, testou-se a combina??o das doses 0; 45; 90 e 180 mg dm-3 de P num Neossolo Quartzar?nico e 0; 100; 200 e 400 mg dm-3 de P num Latossolo Vermelho Amarelo, com doses equivalentes a 0; 1; 2 e 4 kg ha-1 de ?cido c?trico, em experimentos em vasos, em condi??es de casa de vegeta??o. No Neossolo Quartzar?nico, 119 mg dm-3 de P e equivalente a 0,8 kg ha-1 de ?cido c?trico proporcionaram m?ximo crescimento das plantas de milho. J? no Latossolo Vermelho Amarelo, a estimativa das doses foi de 96 mg dm-3 de P e equivalente a 2,0 kg ha-1 de ?cido c?trico. A resposta das plantas ? aplica??o do ?cido c?trico deveu-se ? solubiliza??o de formas menos l?beis aumentando as formas mais l?beis de P inorg?nico no solo. Os teores de P na planta e aqueles extra?dos por Mehlich-1e Resina de Troca Ani?nica n?o se correlacionaram quanto ? adi??o de ?cido c?trico no Latossolo Vermelho Amarelo. / Disserta??o (Mestrado) ? Programa de P?s-Gradua??o em Produ??o Vegetal, Universidade Federal dos Vales do Jequitinhonha e Mucuri, 2012. / ABSTRACT To improve the efficiency of absorption, by crops, of P in soil, through differentiated maneuvers of phosphorus fertilization, relates to a better utilization of nutrients added through fertilization, which means productivity gains. In soils with a predominance of low activity clays and oxides in their mineral fraction, the P fixation through the processes of adsorption and precipitation makes phosphorus nutrition a limiting factor for production of most cultivable species. The anion citrate derived from citric acid dissociation of the soil has high metal complexing power. Furthermore, its negative charge ensures an affinity with the positive charges of the oxides in the soil, competing with phosphate for the same binding sites. In order to verify the potential of citric acid to increase the bioavailability for maize and to modify the forms of inorganic P in the soil, there had been tested the combination doses of 0, 45, 90 and 180 mg dm-3 of P in a Typic Quartzipsamment soil and 0; 100, 200 and 400 mg dm-3 of P in a Typic Hapludox soil, with doses of 0, 1, 2 and 4 kg ha-1 of citric acid in experiments conducted in pots under greenhouse conditions. In Typic Quartzipsamment soil, 119 mg dm-3 of P and an equivalent to 0.8 kg ha-1 of citric acid gave maximum growth of maize crops. In the Typic Hapludox soil, the estimated dose was 96 mg dm-3 of P and equivalent to 2.0 kg ha-1 of citric acid. The plant response to the application of citric acid was due to solubilization of less labile forms increasing the more labile forms of inorganic P in soil. The phosphorus content in the plant and those extracted by Mehlich-1 and Anion Exchange Resin were not correlated to the addition of citric acid in the Typic Hapludox soil.
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Caracteriza??o morfol?gica e microestrutural da perovskita BaCexPr1-xO3 sintetizada a partir do m?todo de complexa??o combinando EDTA/CitratoLobato, Maxwell Ferreira 18 March 2011 (has links)
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Previous issue date: 2011-03-18 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / In this study, binary perovskite (BaCexO3) were doped with praseodymium (Pr) to obtainment
of the ternary material BaCexPr1-xO3. This material was synthesized by the complexation
method combining EDTA/Citrate with the stoichiometric ratio of the element Praseodymium
ranging from x = 0.1 to x = 0.9 in order to determine the influence of this rare earth element
on the morphology and microstructure of the final powder. At first the material was
synthesized based on the route proposed by literature (Santos, 2010), and then characterized
by SEM and XRD, besides being refined by the Rietveld method. In the material that had
lowest residual parameter, S, and lowest average size of crystal, pH variation of synthesis
solution was made in order to identify the influence of this parameter on the morphology and
microscopy of the final powder. The results show that addition of praseodymium did not
directly influence the crystallographic and lattice parameters, keeping even the same
orthorhombic structure of the binary material BaCexO3, according to Yamanaka et al (2003).
Material type BaCe0,2Pr0,8O3 had lowest residual parameter (S=1.4) and lowest average size of
crystallite (26.4 nm), being used as reference in the pH variation of synthesis solution for 9,
7, 5 and 3, respectively. Variation of this parameter showed that when the synthesis solution
pH was decreased to below 11, there was an increase in the average size of crystals, for pH 9,
about 58.3%, for pH 7 (30.3 %), for pH 2 (2.3%) and for pH 3 (42%), indicating that the
value initially used and quoted by Santos (2010) was the most coherent / No presente trabalho, perovskitas bin?rias do tipo (BaCexO3) foram dopadas com
praseod?mio (Pr) para obten??o de materiais tern?rios do tipo BaCexPr1-xO3. Esse material foi
sintetizado pelo m?todo de complexa??o combinando EDTA/Citrato, com a raz?o
estequiom?trica do elemento praseod?mio variando de x=0,1 a x=0,9, com objetivo de
determinar a influ?ncia deste terra rara na morfologia e microestrutura do p? final. Em
principio o material foi sintetizado com base em rota proposta na literatura (Santos, 2010),
sendo em seguida caracterizado via MEV e DRX, al?m de serem refinados pelo m?todo
Rietveld. No material que obteve menor par?metro residual, S, e menor tamanho m?dio de
cristal foi feita a varia??o do pH da solu??o de s?ntese a fim de identificar a influ?ncia deste
par?metro na morfologia e microscopia do p? final. Os resultados mostram que a adi??o do
elemento praseod?mio n?o influenciou diretamente os par?metros cristalogr?ficos e de rede,
mantendo, inclusive, a mesma estrutura ortorr?mbica do material bin?rio do tipo BaCexO3, de
acordo com Yamanaka et al (2003). O material do tipo BaCe0,2Pr0,8O3 obteve menor
par?metro residual (S=1,4) e menor tamanho m?dio de cristalito (26,4 nm), sendo usado como
refer?ncia na varia??o do pH da solu??o de s?ntese para 9, 7, 5 e 3, respectivamente. A
varia??o desse par?metro mostrou que quando foi diminu?do o pH da solu??o de s?ntese para
valores abaixo de 11, houve um aumento no tamanho m?dio dos cristais, para o pH 9, em
torno de 58,3 %, para o pH7 (30,3%), para o pH2 (2,3%) e para o pH3 (42%), indicando que o
pH 11 utilizado inicialmente e citado por Santos (2010) foi o mais coerente
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Efeito da G?lia como aditivo de sinteriza??o em eletr?litos cer?micos ? base de c?ria sintetizados pelo m?todo de complexa??o de c?tionsOhl, Wilson Jos? 21 October 2013 (has links)
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Previous issue date: 2013-10-21 / Fuel cells are considered one of the most promising ways of converting electrical
energy due to its high yield and by using hydrogen (as fuel) which is considered one of
the most important source of clean energy for the future. Rare earths doped ceria has
been widely investigated as an alternative material for the electrolyte of solid oxide fuel
cells (SOFCs) due to its high ionic conductivity at low operating temperatures compared
with the traditional electrolytes based on stabilized zirconia. This work investigates the
effect of gallium oxide (Gallia) as a sintering aid in Eu doped ceria ceramic electrolytes
since this effect has already been investigated for Gd, Sm and Y doped ceria
electrolytes. The desired goal with the use of a sintering aid is to reduce the sintering
temperature aiming to produce dense ceramics. In this study we investigated the effects
on densification, microstructure and ionic conduction caused by different molar fraction
of the dopants europium (10, 15 and 20%) and gallium oxide (0.3, 0.6 and 0.9%) in
samples sintered at 1300, 1350 and 1450
0
C. Samaria (10 and 20%) doped ceria samples
sintered between 1350 and 1450 ?C were used as reference. Samples were synthesized
using the cation complexation method. The ceramics powders were characterized by
XRF, XRD and SEM, while the sintered samples were investigated by its relative
density, SEM and impedance spectroscopy. It was showed that gallia contents up to
0.6% act as excellent sintering aids in Eu doped ceria. Above this aid content, gallia
addition does not promote significant increase in density of the ceramics. In Ga free
samples the larger densification were accomplished with Eu 15% molar, effect
expressed in the microstructure with higher grain growth although reduced and
surrounded by many open pores. Relative densities greater than 95 % were obtained by
sintering between 1300 and 1350 ?C against the usual range 1500 - 1600
0
C. Samples
containing 10% of Sm and 0.9% of Ga reached 96% of theoretical density by sintering
at 1350
0
C for 3h, a gain compared to 97% achieved with 20% of Sm and 1% of Ga co-doped cerias sintered at 1450
0
C for 24 h as described in the literature. It is found that
the addition of gallia in the Eu doped ceria has a positive effect on the grain
conductivity and a negative one in the grain boundary conductivity resulting in a small
decrease in the total conductivity which will not compromise its application as sintering
aids in ceria based electrolytes. Typical total conductivity values at 600 and 700 ?C,
around 10 and 30 mS.cm
-1
respectively were reached in this study. Samples with 15% of
Eu and 0.9 % of Ga sintered at 1300 and 1350 ?C showed relative densities greater than
96% and total conductivity (measured at 700 ?C) between 20 and 33 mS.cm
-1
. The
simultaneous sintering of the electrolyte with the anode is one of the goals of research in
materials for SOFCs. The results obtained in this study suggest that dense Eu and Ga
co-doped ceria electrolytes with good ionic conductivity can be sintered simultaneously
with the anode at temperatures below 1350 ?C, the usual temperature for firing porous
anode materials / As c?lulas a combust?vel s?o tidas como uma das mais promissoras formas de
convers?o de energia el?trica devido ao seu alto rendimento e por utilizar o hidrog?nio
como combust?vel, considerado por muitos a principal fonte limpa de energia para o
futuro. C?ria dopada com terras raras tem sido amplamente investiga como material
alternativo para eletr?lito de c?lulas a combust?vel de ?xido s?lido (SOFC) devido sua
alta condutividade i?nica em baixas temperaturas de opera??o quando comparado com
os tradicionais eletr?litos ? base de zirc?nia estabilizada. Neste seguimento de pesquisa,
este trabalho investiga o efeito do ?xido de g?lio (G?lia) como aditivo de sinteriza??o
em eletr?litos cer?micos a base de c?ria dopada com eur?pio, uma vez que este efeito j?
foi investigado por outros em eletr?litos ? base de c?ria dopada com Gd, Sm e Y. A
meta almejada com a utiliza??o do aditivo de sinteriza??o ? reduzir a temperatura de
sinteriza??o para a produ??o de cer?micas densas. Neste trabalho investigou-se o efeito
na densifica??o, na microestrutura e na condu??o i?nica causado por diferentes fra??es
molares do dopante eur?pio (10, 15 e 20%) e do aditivo de sinteriza??o ?xido de g?lio
(0,3; 0,6 e 0,9%), em amostras sinterizadas a 1300, 1350 e 1450
0
C. A c?ria co-dopada
com 10 e 20% de Sm e com os mesmos teores do aditivo de sinteriza??o g?lia,
sinterizadas a 1350, 1450 e 1500
0
C, tamb?m foi investigada, por sua vez, como
par?metro de refer?ncia experimental, haja visto que, nesta pesquisa, adotou-se s?nteses
pelo m?todo de complexa??o de c?tions enquanto que os trabalhos encontrados na
literatura utilizaram o m?todo convencional. Os p?s cer?micos sintetizados foram
caracterizados por FRX, DRX e MEV e as amostras cer?micas sinterizadas por sua
densidade relativa, MEV e espectroscopia de imped?ncia. Verifica-se que a G?lia com
teores at? 0,6% atua como um excelente aditivo de sinteriza??o na c?ria dopada com Eu.
Acima deste teor e at? 0,9% a adi??o da g?lia n?o promove significativos aumentos na
densidade da cer?mica. Nas amostras livres do Ga, as maiores densifica??es foram
alcan?adas com 15% de Eu, efeito manifestado na micro-estrutura com os maiores
crescimentos de gr?os, embora ainda reduzidos e circundados por muitos poros abertos.
Densidades relativas superiores a 95% da densidade te?rica podem ser obtidas com
sinteriza??es entre 1300 e 1350
0
C, contra as usuais 1500 a 1600
0
C. Com a c?ria co-dopada com 10% de Sm e 0,9% de Ga alcan?ou-se neste trabalho 96% da densidade
te?rica com sinteriza??o a 1350
0
C por 3h, um ganho em rela??o aos 97% alcan?ados
com a c?ria co-dopada com 20% de Sm e 1% de Ga sinterizada a 1450
0
C por 24h
conforme encontrado na literatura. Verifica-se que a adi??o da G?lia em eletr?litos ?
base de c?ria dopada com Eu apresenta efeito positivo na condutividade do gr?o e
negativo na do contorno de gr?o resultando em uma pequena redu??o na condutividade
total, a qual n?o compromete sua promissora aplica??o como aditivo de sinteriza??o.
Valores t?picos da condutividade total a 600 e 700
0
C, em torno de 10 e 30 mS.cm
-1
respectivamente, foram alcan?ados neste trabalho. As amostras de eletr?litos ? base de
c?ria co-dopada com 15% de Eu e 0,9% de Ga, sinterizados a 1300 e 1350
0
C,
alcan?aram densidades relativas superiores a 96% e condutividade a 700
0
C entre 20 e
33 mS.cm
-1
. A sinteriza??o simult?nea do eletr?lito com o anodo ? uma das metas da
pesquisa em materiais para SOFCs. Os resultados alcan?ados neste trabalho sugerem
que eletr?litos densos ? base de c?ria co-dopada com Eu e Ga podem ser sinterizados
simultaneamente com o anodo ? temperatura de sinteriza??o entre 1300 e 1350
0
C, a
faixa de temperatura usual de sinteriza??o do anodo poroso
|
6 |
Obten??o de ferrita de cobalto atrav?s de dois m?todos de s?ntese: m?todo de complexa??o combinando EDTA/Citrato e m?todo hidrot?rmico / Obtaining cobalt ferrite through two synthesis methods: Complexation Method Conbining EDTA/Citrate and Hydrothermal MethodMedeiros, Indira Aritana Fernandes de 17 December 2013 (has links)
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Previous issue date: 2013-12-17 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / In this work it was synthesized and characterized the cobalt ferrite (CoFe2O4) by
two methods: complexation combining EDTA/Citrate and hydrothermal investigating the
influence of the synthesis conditions on phase formation and on the crystallite size. The
powders were mainly characterized by x-ray diffraction. In specific cases, it was also used
scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), x-ray
fluorescence (XRF) and isotherms of adsorption and desorption of nitrogen (BET method).
The study of the crystallite size was based on the interpretation of x-ray diffractograms
obtained and estimated by the method of Halder-Wagner-Scherrer and Langford. An
experimental design was made in order to assist in quantifying the influence of synthesis
conditions on the response variables. The synthesis parameters evaluated in this study were:
pH of the reaction medium (8, 9 and 10), the calcination temperature (combined complexation
method EDTA/Citrate 600?C, 800?C and 1000?C), synthesis temperature (hydrothermal
method 120?C, 140?C and 160?C), calcination time (combined complexation method
EDTA/Citrate - 2, 4 and 6 hours) and time of synthesis (hydrothermal method 6, 15 and 24
hours). By the hydrothermal method was possible to produce mesoporous powders with high
purity, with an average crystallite size up to 7 nm, with a surface area of 113.44 m?/g in the
form of pellets with irregular morphology. By using the method of combined complexation
EDTA/Citrate, mesoporous powders were produced with greater purity, crystallite size up to
22nm and 27.95 m?/g of surface area in the form of pellets with a regular morphology of
plaques. In the experimental design was found that the hydrothermal method to all the studied
parameters (pH, temperature and time) have significant effect on the crystallite size, while to
the combined complexation method EDTA/Citrate, only temperature and time were
significant / Neste trabalho foi sintetizada e caracterizada a ferrita de cobalto (CoFe2O4)
atrav?s dos m?todos complexa??o combinada EDTA/Citrato e hidrot?rmico, investigando a
influ?ncia das condi??es de s?ntese na forma??o da fase e no tamanho m?dio de cristalito. Os
p?s foram caracterizados principalmente por difra??o de raios-x. Em casos espec?ficos,
tamb?m foi utilizado microscopia eletr?nica de varredura (MEV), espectroscopia de energia
dispersiva (EDS), fluoresc?ncia de raios-x (FRX) e isotermas de adsor??o e dessor??o de
nitrog?nio (M?todo BET). O estudo do tamanho de cristalito foi baseado na interpreta??o dos
difratogramas de raios-x obtidos e estimado atrav?s do m?todo de Halder-Wagner-Langford
(HWL) e de Scherrer. Um planejamento experimental foi realizado com a finalidade de
auxiliar na quantifica??o da influ?ncia das condi??es de s?ntese nas vari?veis-resposta. Os
par?metros de s?ntese avaliados neste trabalho foram: pH do meio reacional (8, 9 e 10),
temperatura de calcina??o (m?todo de complexa??o combinando EDTA/Citrato 600?C,
800?C e 1000?C), temperatura de s?ntese (m?todo hidrot?rmico 120?C, 140?C e 160?C),
tempo de calcina??o (m?todo de complexa??o combinando EDTA/Citrato 2, 4 e 6 hrs) e
tempo de s?ntese (m?todo hidrot?rmico 6, 15 e 24 hrs). Pelo m?todo hidrot?rmico foi
poss?vel produzir p?s mesoporosos com elevado grau de pureza, com tamanho m?dio de
cristalito de at? 7nm, com ?rea superficial de 113,44m?/g e na forma de aglomerados com
morfologia irregular. Ao se utilizar o m?todo de complexa??o combinando EDTA/Citrato
foram produzidos p?s mesoporosos com maior pureza, cristalitos com at? 22nm de tamanho,
27,95m?/g de ?rea superficial e na forma de aglomerados com morfologia regular de placas.
No planejamento experimental foi constatado que no caso do m?todo hidrot?rmico todos os
par?metros estudados (pH, Temperatura e tempo) apresentam efeito significativo no tamanho
de cristalito, enquanto que, para o m?todo de complexa??o combinando EDTA/Citrato,
apenas a temperatura e o tempo foram significativos / 2020-01-01
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