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Synthesis of Room Temperature Ionic Liquid Based Polyimides for Gas SeparationsLi, Pei 14 June 2010 (has links)
No description available.
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[pt] DESENVOLVIMENTO E VALIDAÇÃO DE MÉTODO FOSFORIMÉTRICO EM SUBSTRATO DE CELULOSE PARA DETERMINAÇÃO DE PIRENO E CRISENO / [en] DEVELOPMENT AND VALIDATION OF THE PHOSPHORIMETRIC METHOD IN CELLULOSE SUBSTRATE TO DETERMINATION OF PYRENE AND CHRYSENEALESSANDRA LICURSI MAIA CERQUEIRA DA CUNHA 27 September 2007 (has links)
[pt] Neste trabalho, a fosforimetria em temperatura ambiente em
substrato
sólido (SSRTP) foi utilizada para o desenvolvimento de
método para
determinação ultra-traço e seletiva de criseno e de pireno
em amostras
complexas contendo diversos outros hidrocarbonetos
policíclicos
aromáticos (HPA). O criseno e o pireno foram selecionados
por serem
classificados pela Agência Americana de Proteção ao Meio
Ambiente
(U.S. Environmental Protection Agency - EPA) como dois dos
dezesseis
HPA poluentes prioritários e por serem conhecidos como uma
ameaça à
saúde pública e à integridade dos ecossistemas marinhos. A
capacidade
seletiva da SSRTP foi explorada por meio do efeito externo
seletivo do
átomo pesado e do ajuste de pH da solução carreadora de
solução de
analito para o substrato de celulose. O efeito da
modificação da celulose
com o surfactante SDS também foi investigado, assim como o
uso da
varredura de modo sincronizado para melhoria da resolução
espectral. O
nitrato de prata em substratos contendo SDS foi
identificado como indutor
seletivo de fosforescência do criseno em relação ao pireno
e demais HPA
em estudo (antraceno, benzo[a]pireno, 1-hidroxipireno,
fluoranteno,
fenantreno, benzo[ghj]perileno e 1,2 benzoantraceno). Já o
pireno foi
determinado seletivamente com varredura convencional e
sincronizada de
fosforescência em substratos contendo nitrato de chumbo
como indutor
seletivo e soluções carreadoras de analito em meio básico
(pH 12). Essa
seletividade foi em relação aos HPA citados, e ao 1-
hidroxipireno, mesmo
este tendo uma estrutura molecular muito semelhante a do
pireno. O planejamento fatorial foi usado, principalmente
visando verificar as
interações mútuas entre os efeitos das diferentes
variáveis do método
desenvolvido, e, conseqüentemente, a escolha da melhor
condição
experimental. Neste estudo, foram enfatizados: (i) a
análise experimental
estatística (testou-se a significância dos efeitos dos
fatores usando a
análise de variância, teste F e teste t), (ii) o uso do
método gráfico (gráfico
de Pareto) para a interpretação das interações (entre as
variáveis) e dos
resultados obtidos, assim como o refinamento do modelo, se
necessário,
excluindo variáveis irrelevantes. As características de
desempenho foram
obtidas, a fim de se validar o método proposto, obtendo
assim a
credibilidade técnica das medições. Testes estatísticos
(testes de
hipótese) com o uso de material de referência certificado
(SRM NIST
1647d) e método de referência alternativo (HPLC com
detecção por
fluorescência) também foram incluídos no processo de
validação e os
resultados encontrados estão dentro do nível de 95% de
confiança. Os
limites de detecção do criseno e do pireno em termos de
massa efetiva do
analito depositada no substrato (limite de detecção
absoluto - LDA)
encontram-se na ordem do ng. A quantificação das fontes de
variação
associadas à medição, a incerteza da medição, foi estimada
pelo ISO
GUM e método de simulação de Monte-Carlo. Testes de
seletividade com
criseno e pireno na presença de outros HPA também foram
realizados e
os resultados obtidos permitiram que a técnica fosse
utilizada para
determinações seletivas. A aplicação do método em
diferentes tipos de
matrizes (bílis de peixe e aguardente de cana) também foi
realizada e os
percentuais de recuperação encontrados foram 109 (+ -) 18%
(criseno) e 108
(+ -) 20% (pireno). Esses resultados são comparáveis com os
obtidos por
HPLC-fluorescência: 104 (+ -) 13% (criseno) e 102 (+ -) 15%
(pireno). Estudos
de caracterização, homogeneidade e estabilidade do criseno
em matriz
biológica, bílis de peixe da espécie Mugil liza, e a
estimativa da incerteza
da medição do material analisado também foram realizados.
A incerteza
da medição encontra-se na ordem do ng (referente à massa
efetiva depositada no substrato de celulose). / [en] In this work, solid surface room-temperature
phosphorimetry (SSRTP)
was used to develop ultra-trace and selective methods for
determination of
chrysene and pyrene in complex samples containing several
other
polycyclic aromatic hydrocarbons (PAHs). Both chrysene and
pyrene were
selected because they are classificated by the U.S.
Environmental
Protection Agency (EPA) as two out of the sixteen major
pollutants,
affecting public health and marine ecosystems. The
selective capability of
SSRTP was explored through the selective external heavy
atom effect and
the adjustment of pH of the analyte solution used to carry
out the analyte
to the cellulose substrate. Cellulose modification with
the use of the
surfactant sodium dodecyl sulphat (SDS) has also been
evaluated as well
as the use of synchronous scanning to improve its spectral
resolution.
Silver nitrate together with SDS was identified as
selective
phosphorescence inducer for chrysene in the presence of
pyrene and
other PAHs which are being studied (anthracene, benzo[a]
pyrene, 1-
hidroxipyrene, fluoranthene, phenanthrene, benzo[ghi]
perylene and 1,2
benzoanthracene). On the other hand, pyrene was
selectively determined
with synchronous and conventional phosphorescence scanning
in
substrates treated with lead nitrate as a selective
inducer and using
analyte carrier solution with pH 12. This selectivity
towards pyrene was
achieved in the presence of all the other tested PAHs,
including the 1-
hidroxipyrene, even though they have quite similar
molecular structures. A
factorial design was applied in order to verify mutual
interactions among factors of the different variables and
to find the best experimental
conditions. It has been emphasized in this study: (i)
statistical experimental
analysis (testing the significance of the factors using
the analysis of
variation, F-test and t-test), (ii) graphic method
(Pareto´s chart) to the
interpretation and evaluation of the interactions among
all the variables
and obtained results, the model was refined whenever
necessary so
exclude irrelevant variables. After choosing the best
experimental
condition, the performance characteristics were obtained
validating the
proposed method. Statistical tests were applied in order
to compare
results obtained using a standard reference material
analysis (NIST SRM
1647d). The proposed method was also compared with a
reference
analytical technique (HPLC with fluorescence detection)
and the results
obtained are within 95% confidence level. Chrysene and
pyrene absolute
detection limits were found in the ng order. The
quantification of the
variation sources associated to the measurement (the
measurement´s
uncertainty) was estimated based on ISO GUM and Monte-Carlo
simulation method. Selectivity tests for chrysene and
pyrene, in presence
of the other PAHs were also performed. The methods were
applied to
different types of samples (fish bilis and spirit drink
from sugar cane) and
the recoveries were 109 (+ -) 18% (chrysene) and 108 (+ -) 20%
(pyrene) by
SSRTP. These results are comparable to ones obtained by
HPLCFluorescence:
104 (+ -) 13% (chrysene) and 102 (+ -) 15% (pyrene).
Characterization, homogeny and stability studies in a
biological matrix (fish
bilis of the type Mugil liza) and the estimation of
uncertainty of the
analysed material were also done. The measurement
uncertainty was
found in ng order (in terms of the effective mass deposit
in the cellulose
substrate).
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[pt] DESENVOLVIMENTO E APLICAÇÃO DE MÉTODOS ANALÍTICOS PARA DETERMINAÇÃO DE PICOXISTROBINA E PIRACLOSTROBINA POR CROMATOGRAFIA ELETROCINÉTICA CAPILAR MICELAR E DE ENROFLOXACINA POR FOSFORIMETRIA EM TEMPERATURA AMBIENTE / [en] DEVELOPMENT AND APPLICATION OF ANALYTICAL METHODOS FOR THE DETERMINATION PICOXYSTROBIN AND PYRACLOSTROBIN BY MICELLAR ELECTROKINECTIC CAPILLARY CHROMATOGRAPHY AND ENROFLOXACIN BY ROOM-TEMPERATURE PHOSPHORIMETRYCABRINI FERRAZ DE SOUZA 02 March 2009 (has links)
[pt] No presente trabalho, a cromatografia eletrocinética capilar micelar (MECC) e a fosforimetria em temperatura ambiente em substrato sólido (SSRTP) foram utilizadas como técnicas analíticas para a determinação de duas estrobilurinas (picoxistrobina e piraclostrobina) e de uma fluoroquinolona (enrofloxacina), respectivamente. As condições ótimas de analise por MECC foram determinadas a partir de um estudo univariado dos seguintes parâmetros experimentais e instrumentais: pH do eletrólito de corrida, concentração do tampão, concentração de surfactante (dodecil-sulfato de sódio - SDS), tipo e quantidade de modificador orgânico, temperatura de trabalho e diferença de potencial aplicada. Depois de definidas as condições ótimas (tampão borato 40 mmol L-1, pH igual a 8,5; SDS 30 mmol L-1; acetonitrila 15 por cento em volume, 25 gruas Celsius e 25 kV) foi realizado um estudo para diminuir o limite de detecção (LD) e o limite de quantificação (LQ) do método. Para tal, foi usado o modo de pré-concentração no capilar denominado modo de empilhamento normal (NSM). Nessa abordagem, as soluções de padrões e amostras foram dissolvidas em uma solução de maior impedância (água: borato 40 mmol L-1 pH igual a 8,5 50:50 por cento v/v). Uma cela de caminho óptico alongado também foi utilizada para a tentativa de aumentar a sensibilidade do método. As curvas analíticas foram construídas com o uso de padrão interno (azoxistrobina) e apresentaram comportamento linear e homocedástico com valores de R2 próximos a 0,999. Com o modo NSM, os valores de LD (xb mais 3sb) e de LQ (xb mais 10sb) para a picoxistrobina e para a piraclostrobina ficaram na ordem de 10-7 mol L-1. A precisão do método (repetitividade e reprodutibilidade interna) apresentaram valores entre 5 e 8 por cento para tempo de migração e área dos picos. O método foi aplicado na análise de urina e água de riacho, ambas fortificadas com as estrobilurinas. As amostras de urina foram previamente passadas em coluna de extração em fase sólida (C-18).
As recuperações obtidas para a piraclostrobina foram 75 mais ou menos 4 por cento para as amostras de urina e 94 ou menos 10 por cento para as amostras de água de riacho. Para a picoxistrobina os valores de recuperação foram de 109 mais ou menos 9 por cento e 102 mais ou menos 9 por cento para as amostras de urina e água do riacho respectivamente. As características fosforescentes da enrofloxacina foram estudadas de modo univariado em função de vários parâmetros experimentais tais como o tipo e quantidade de sal de átomo pesado indutor de fosforescência, presença de surfactante modificador de superfície de celulose, influência de concentração hidrogeniônica na solução do analito e estudo do tempo de exposição ao UV para a formação de fotoproduto de sinal mais estável. As melhores condições para o método fosforescente para enrofloxacina foram obtidas em solução básica (solução acetona: NaOH 0,05
mol L-1 50:50 por cento v/v) irradiada com UV por 30 min e substrato contendo 80 Vg de TlNO3. O método foi aplicado em formulações farmacêuticas contendo enrofloxacina e que são utilizadas na medicina veterinária (solução e comprimidos). Um método com a técnica de cromatografia líquida de alta eficiência (HPLC) adaptado da literatura foi utilizado para análise das amostras de enrofloxacina, sendo os resultados comparáveis àqueles obtidos por SSRTP. A curva analítica apresentou resposta linear e homoscedástica na faixa de trabalho escolhida com R2 maior que 0,99. Os valores de LD (xb mais 3sb) e de LQ (xb mais 10sb) foram respectivamente 2,1 and 4,8 ng respectivamente. A precisão (repetitividade e reprodutibilidade interna com troca de analista) do método apresentaram valores entre 2 e 19 por cento. A incerteza de medição do sinal fosforescente foi calculada usando o método sistemático indicado no ISO GUM e valores entre 18 e 26 por cento foram alcançados, com valores de repetitividade com troca de substrato a fonte mais importante de incerteza. No procedimento de validação, os valores de concentração de enrofloxacina encontrados nas amostras de medicamento analisadas por SSRTP e por HPLC foram estatisticamente semelhantes (valor de texperimental iguais a 0,48 e 1,04 sendo menor que o valor de tcrítico igual a 2,23). / [en] In the present work, micellar electrokinectic capillary
chromatography
(MECC) and solid surface room-temperature phosphorimetry
(SSRTP) were used
as analytical techniques for the determination of two
strobilurins (picoxystrobin
and pyraclostrobin) and of one fluoroquinolones
(enrofloxacin), respectively. The
experimental conditions for MECC have been optimized using
an univariate
approach for the following experimental and instrumental
parameters: pH of the
working electrolyte, concentration of the buffer,
concentration of surfactant
(sodium dodecyl-sulphate - SDS), type and amount of organic
modifier, working
temperature and applied potential. After defined the best
conditions (borate buffer
40 mmol L(-1) pH=8.5; 30 SDS mmol L(-1); acetonitrile 15%
in volume, 25 ºC and 25
kV), a study was carried through to improve the limit of
detention (LD) and the
limit of quantification (LQ) of the method. In order to do
that, an on-line analyte
pre-concentration called normal stacking mode (NSM) was
used. In such
approach, the standards and samples have been dissolved in
a solution of higher
impedance (water: borate 40 mmol L(-1) pH=8.5 50:50% v/v).
A high sensitivity
detection cell also was used to attempt the increasing of
the sensitivity of the
method. The analytical curves have been constructed with
the use of an internal
standard (azoxystrobin) and a linear response and
homocedastic behavior were
observed with R2 values of at least 0.999. The NSM mode
allowed the values of
LD (x(b) + 3(sb)) and of LQ (x(b) + 10(sb)) in the order of
10(-7) mol L(-1) for picoxystrobina
and pyraclostrobina. The precision of the method
(repeatability and intermediate
precision) was characterized by values between 5 and 8%.
The method was
applied in the analysis urine and stream water, both type
of samples fortified with
the strobilurins. The urine sample was previously passed
through a solid phase
extraction column (C-18). The recoveries achieved for
pyraclostrobina were 75 Â +-
4% for urine and 94 Â +- 10% for stream water samples. For
picoxystrobin, the
recovery values were 109 Â +- 9% and 102 Â +- 9% respectively for
urine and stream
water samples. The phosphorimetric characteristics of
enrofloxacin have been
studied in an unvaried way for experimental parameters such
as the type and
quantity of phosphorescence inducer (heavy atom salt),
surfactant used as cellulose surface modifier, influence of
the hidrogenionic concentration in the
analyte solution and study of the UV exposition time for
the formation of a more
signal stable photoproduct. The best conditions for the
phosphorimetric method
for enrofloxacin were the use of basic solution (solution
acetone: NaOH 0.05 mol
L-1 50:50% v/v) irradiated with UV for 30 min and cellulose
substrates containing
80 Vg of TlNO3. The method was applied in pharmaceutical
formulations
containing enrofloxacin employed in veterinary medicine
(solution and pills). A
method based on high efficiency liquid chromatography
(HPLC), adapted from
literature, was used as a reference method and the the
results obtained for
enrofloxacin was comparable to the ones achieved by SSRTP.
The analytical
curve presented linear and homocedastic behavior with R2
values higher than
0.99. The LD (x(b) + 3(sb)) and the LQ (x(b) + 10(sb))
values were 2.1 and 4.8 ng
respectively. The precision (repeatability and intermediate
precision with change
of analyst) of the method presented values between 2 and
19%. The uncertainty
of the phosphorescence measurement was calculated using the
systematic
method indicated in the ISO GUM. Values between 18 and 26%
had been
achieved, with the repeatability with substrate change the
most important source
uncertainty. In the validation procedure, enrofloxacin
concentration values found
in the medicine samples analyzed by SSRTP and HPLC were
statistically similar
( t(experimental) value of 0.48 and 1.04 smaller than the
t(critic) value of 2.23).
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Process Parameter Optimization of a Polymer Derived CeramicCoatings for Producing Ultra-High Gas BarrierChanna, I.A., Shah, A.A., Rizwan, M., Makhdoom, M.A., Chandio, A.D., Shar, Muhammad A., Mahmood, A. 27 October 2021 (has links)
Yes / Silica is one of the most efficient gas barrier materials, and hence is widely used as anencapsulating material for electronic devices. In general, the processing of silica is carried out at hightemperatures, i.e., around 1000◦C. Recently, processing of silica has been carried out from a polymercalled Perhydropolysilazane (PHPS). The PHPS reacts with environmental moisture or oxygen andyields pure silica. This material has attracted many researchers and has been widely used in manyapplications such as encapsulation of organic light-emitting diodes (OLED) displays, semiconductorindustries, and organic solar cells. In this paper, we have demonstrated the process optimization ofthe conversion of the PHPS into silica in terms of curing methods as well as curing the environment.Various curing methods including exposure to dry heat, damp heat, deep UV, and their combinationunder different environments were used to cure PHPS. FTIR analysis suggested that the quickestconversion method is the irradiation of PHPS with deep UV and simultaneous heating at 100◦C.Curing with this method yields a water permeation rate of 10−3g/(m2·day) and oxygen permeationrate of less than 10−1cm3/(m2·day·bar). Rapid curing at low-temperature processing along withbarrier properties makes PHPS an ideal encapsulating material for organic solar cell devices and avariety of similar applications. / King Saud University
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Na-Sb-Sn-based negative electrode materials for room temperature sodium cells for stationary applicationsMartine, Milena 27 June 2017 (has links) (PDF)
The implementation of energy storage systems in the current electrical grid will increase the grid's reliability and e ciency. Room temperature sodium batteries are seen as potential technology, especially to assist renewable energy generation sources. Currently, suggested negative electrode materials, however, are still not satisfactory for practical use in terms of fabrication costs, gravimetric /volumetric energy densities, cyclability, and irreversible capacity losses occur at the rst cycle. The literature describes various strategies that enhance the specific capacity and/or the cyclability of negative electrode materials but all involve increasing the fabrication costs due to the chosen synthesis or the complexity of the electrode's design. Furthermore, strategies, that reduce the irreversible capacity loss at first cycle, are not discussed. In this present experimental research work, presodiating bulk metallic negative electrode materials prior to cycling, prepared via a simple, cheap and easy-to-scaleup synthesis route, is introduced as a new strategy to improve the cyclability and to effectively reduce the first cycle irreversible capacity loss.
Electrochemical and structural experiments were carried out to investigate sodiumtin-antimony powders. Presodiating mechanically bulk Sn-Sb negative electrode materials e ectively reduces the irreversible capacity loss at first cycle and enhances the specific capacity when compared to the non-presodiated powder, while the proper choice of electrode composite and electrolyte formulation improves the cycle life of the electrodes. The enhancement of the electrochemical properties of the presodiated NaSnSb powder, composed of the ternary phase Na5Sb3Sn and an unknown ternary phase crystallising in a hexagonal setting P6, is associated with the stabilisation of the SnSb as desodiation product.
Presodiating bulk SnSb negative electrode material is a viable strategy to reduce the first cycle irreversible capacity loss, alleviating the volume changes. With an optimised system, this approach may be extended to other negative electrode materials, reducing the fabrication costs of high capacity negative electrode materials for room temperature sodium batteries. Presodiated NaSnSb negative electrode material may be combined with non-sodiated positive electrode material, such as sulphur to develop competitive room temperature sodium-sulphur batteries. / Die Implementierung von Energiespeichersystemen im bereits bestehenden Stromnetz ist eine der Lösungen, um die Zuverlässigkeit und die Effizienz des Netzes zu nutzen. Raumtemperatur Natrium-Batterien gelten als erfolgsversprechende Technologie insbesondere zur Unterstützung erneuerbarer Energieerzeugungsquellen. Jedoch sind die naheliegenden negativen Elektrodenmaterialien für eine praktische Anwendung hinsichtlich Herstellungskosten, gravimetrischer oder volumetrischer Energiedichte, Zyklenfestigkeit und irreversiblen Kapazitätsverlusten im ersten Zyklus noch nicht zufriedenstellend.
Die Literatur beschreibt verschiedene Strategien, die die spezifische Kapazität und / oder die Zyklenfestigkeit von negativen Elektrodenmaterialien verbessern. Diese führen jedoch alle zu einer Erhöhung der Herstellungskosten aufgrund der gewählten Synthese oder des Designs der komplexierten Elektrode. Darüber hinaus werden Strategien zur Reduzierung des irreversiblen Kapazitätsverlusts im ersten Zyklus nicht erörtert. Diese experimentelle Forschungsarbeit präsentiert mit Natrium angereicherte metallische negative Elektrodenmaterialien vor der Wechselbeanspruchung/dem periodischen Durchlaufen, die durch einen schlichten, billigen und einfach zu skalierenden Syntheseweg hergestellt wurden, als eine neue Strategie zur Verbesserung der Zyklenfestigkeit und zur wirksamen Verringerung des irreversiblen Kapazitätsverlusts im ersten Zyklus.
Elektrochemische und strukturelle Experimente wurden durchgeführt, um mit Natrium angereichertes Zinn-Antimon-Pulver zu untersuchen. Die mechanischen mit Natrium angereichertes Sn-Sb-negativen Elektrodenmaterialien verringert effektiv den irreversiblen Kapazitätsverlust im ersten Zyklus und erhöht die spezische Kapazität im Vergleich zu dem ohne Natrium angereicherte Pulver, während die richtige Wahl der Elektrodenzusammensetzung und der Elektrolytformulierung die Lebenszyklus der Elektroden verbessert. Die Verbesserung der elektrochemischen Eigenschaften des mit Natrium angereicherten NaSnSb-Pulvers, bestehend aus der ternären Phase Na5Sb3Sn und einer unbekannten ternären Phase, die in einer hexagonalen Aufbau P6 kristallisiert, ist mit der Stabilisierung des Enddesodiationsproduktes beim periodischen Zyklus verbunden, wobei das intermetallische SnSb nach Rekristallisation vorliegt. Mit Natrium angereicherte SnSb negativen Elektrodenmaterialien sind eine tragfähige Strategie zur Verringerung des irreversiblen Kapazitätsverlustes im ersten Zyklus, die Volumenänderungen abschwächen. Mit einem optimierten System kann dieser Ansatz auf andere negative Elektrodenmaterialien erweitert werden um die Herstellungskosten von negativen Elektrodenmaterialien mit hoher Kapazität für Raumtemperatur-Natrium-Batterien zu verringern. Mit Natrium angereichertes NaSnSb-negatives Elektrodenmaterial kann mit nicht mit Natrium versetztem positivem Elektrodenmaterial wie Schwefel kombiniert werden, um realisierbare Raumtemperatur Natrium-Schwefel-Batterien zu entwickeln.
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Na-Sb-Sn-based negative electrode materials for room temperature sodium cells for stationary applicationsMartine, Milena 14 June 2017 (has links)
The implementation of energy storage systems in the current electrical grid will increase the grid's reliability and e ciency. Room temperature sodium batteries are seen as potential technology, especially to assist renewable energy generation sources. Currently, suggested negative electrode materials, however, are still not satisfactory for practical use in terms of fabrication costs, gravimetric /volumetric energy densities, cyclability, and irreversible capacity losses occur at the rst cycle. The literature describes various strategies that enhance the specific capacity and/or the cyclability of negative electrode materials but all involve increasing the fabrication costs due to the chosen synthesis or the complexity of the electrode's design. Furthermore, strategies, that reduce the irreversible capacity loss at first cycle, are not discussed. In this present experimental research work, presodiating bulk metallic negative electrode materials prior to cycling, prepared via a simple, cheap and easy-to-scaleup synthesis route, is introduced as a new strategy to improve the cyclability and to effectively reduce the first cycle irreversible capacity loss.
Electrochemical and structural experiments were carried out to investigate sodiumtin-antimony powders. Presodiating mechanically bulk Sn-Sb negative electrode materials e ectively reduces the irreversible capacity loss at first cycle and enhances the specific capacity when compared to the non-presodiated powder, while the proper choice of electrode composite and electrolyte formulation improves the cycle life of the electrodes. The enhancement of the electrochemical properties of the presodiated NaSnSb powder, composed of the ternary phase Na5Sb3Sn and an unknown ternary phase crystallising in a hexagonal setting P6, is associated with the stabilisation of the SnSb as desodiation product.
Presodiating bulk SnSb negative electrode material is a viable strategy to reduce the first cycle irreversible capacity loss, alleviating the volume changes. With an optimised system, this approach may be extended to other negative electrode materials, reducing the fabrication costs of high capacity negative electrode materials for room temperature sodium batteries. Presodiated NaSnSb negative electrode material may be combined with non-sodiated positive electrode material, such as sulphur to develop competitive room temperature sodium-sulphur batteries. / Die Implementierung von Energiespeichersystemen im bereits bestehenden Stromnetz ist eine der Lösungen, um die Zuverlässigkeit und die Effizienz des Netzes zu nutzen. Raumtemperatur Natrium-Batterien gelten als erfolgsversprechende Technologie insbesondere zur Unterstützung erneuerbarer Energieerzeugungsquellen. Jedoch sind die naheliegenden negativen Elektrodenmaterialien für eine praktische Anwendung hinsichtlich Herstellungskosten, gravimetrischer oder volumetrischer Energiedichte, Zyklenfestigkeit und irreversiblen Kapazitätsverlusten im ersten Zyklus noch nicht zufriedenstellend.
Die Literatur beschreibt verschiedene Strategien, die die spezifische Kapazität und / oder die Zyklenfestigkeit von negativen Elektrodenmaterialien verbessern. Diese führen jedoch alle zu einer Erhöhung der Herstellungskosten aufgrund der gewählten Synthese oder des Designs der komplexierten Elektrode. Darüber hinaus werden Strategien zur Reduzierung des irreversiblen Kapazitätsverlusts im ersten Zyklus nicht erörtert. Diese experimentelle Forschungsarbeit präsentiert mit Natrium angereicherte metallische negative Elektrodenmaterialien vor der Wechselbeanspruchung/dem periodischen Durchlaufen, die durch einen schlichten, billigen und einfach zu skalierenden Syntheseweg hergestellt wurden, als eine neue Strategie zur Verbesserung der Zyklenfestigkeit und zur wirksamen Verringerung des irreversiblen Kapazitätsverlusts im ersten Zyklus.
Elektrochemische und strukturelle Experimente wurden durchgeführt, um mit Natrium angereichertes Zinn-Antimon-Pulver zu untersuchen. Die mechanischen mit Natrium angereichertes Sn-Sb-negativen Elektrodenmaterialien verringert effektiv den irreversiblen Kapazitätsverlust im ersten Zyklus und erhöht die spezische Kapazität im Vergleich zu dem ohne Natrium angereicherte Pulver, während die richtige Wahl der Elektrodenzusammensetzung und der Elektrolytformulierung die Lebenszyklus der Elektroden verbessert. Die Verbesserung der elektrochemischen Eigenschaften des mit Natrium angereicherten NaSnSb-Pulvers, bestehend aus der ternären Phase Na5Sb3Sn und einer unbekannten ternären Phase, die in einer hexagonalen Aufbau P6 kristallisiert, ist mit der Stabilisierung des Enddesodiationsproduktes beim periodischen Zyklus verbunden, wobei das intermetallische SnSb nach Rekristallisation vorliegt. Mit Natrium angereicherte SnSb negativen Elektrodenmaterialien sind eine tragfähige Strategie zur Verringerung des irreversiblen Kapazitätsverlustes im ersten Zyklus, die Volumenänderungen abschwächen. Mit einem optimierten System kann dieser Ansatz auf andere negative Elektrodenmaterialien erweitert werden um die Herstellungskosten von negativen Elektrodenmaterialien mit hoher Kapazität für Raumtemperatur-Natrium-Batterien zu verringern. Mit Natrium angereichertes NaSnSb-negatives Elektrodenmaterial kann mit nicht mit Natrium versetztem positivem Elektrodenmaterial wie Schwefel kombiniert werden, um realisierbare Raumtemperatur Natrium-Schwefel-Batterien zu entwickeln.
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Liquides ioniques : structure et dynamique. / Room temperature ionic liquides : structure and dynamicsAoun, Bachir 14 December 2010 (has links)
Les Liquides Ioniques [LI] à température ambiante forment une nouvelle classe de matériaux, prometteurs dans des applications diverses. Les avantages que les LI soulèvent par rapport aux autres liquides moléculaires ou sels fondus résident dans la facilité à changer leurs propriétés intrinsèques en jouant sur la nature chimique de la combinaison [cation-anion]. Cependant, on n’est pas encore près à prédire les propriétés d’un LI en connaissant uniquement sa composition chimique. Par conséquent, nous avons fait des expériences de diffraction de rayons-x et de neutrons, complétées par une série de simulations de dynamiques moléculaires sur une famille de LI à bases de cations d’alkyl-methylimidazolium et d’anion Bromure. Ainsi, en changeant la longueur de la chaine alkyl, nous avons comparé la structure et la dynamique de trois LI de chaines ethyl, butyl et hexyl. La comparaison des résultats structuraux obtenus par la simulation avec ceux des rayons-x donnèrent complète satisfaction. Des résultats intéressants ont été obtenus, spécialement ceux issus de la comparaison de la structure et la dynamique du LI 1-ethyl-3-methylimidazolium Bromide en phase cristalline et liquide. Par ailleurs, l’hétérogénéité en phase volumique a pu être quantifiée ce qui a permis de déterminer que la ségrégation augmente avec la longueur de la chaine alkyl cationique. / Room temperature ionic liquids constitute a class of materials with many promising applications in very diverse fields. Their potentiality stems from the fact that their properties are very different from those of typical molecular solvents and furthermore they can be tailored by modifying the combination of ions forming the liquid. However it is not yet possible to predict which species will produce a particular set of properties. Therefore we have done a systematic computer simulation study on a series of three room temperature ionic liquids based on the alkyl-methylimidazolium cation combined with the bromium anion. The length of the alkyl chain of the cation and the anions has been increased progressively, going from ethyl to butyl and hexyl, in order to explore the structural and dynamical changes brought about by such change. Simulation results are also compared satisfactorily to high-energy x-ray diffraction and quasi elastic neutron scattering data obtained by us. Our results show that the structure of liquid 1-ethyl-3methylimidazolium Bromide presents large similarities with the crystal one. This resemblance appears also when the local dynamics of the ethyl chain is investigated using neutron spectroscopy. Moreover we have quantified the heterogeneity found in the bulk state, finding that segregation is favored by the length of the cation’s alkyl chain.
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[en] SELECTIVE DETERMINATION OF FLUORQUINOLONES FOR CELLULOSE SURFACE ROOMTEMPERATURE PHOSPHORIMETRY WHITH THORIUM NITRATE / [pt] DETERMINAÇÃO SELETIVA DE FLUOROQUINOLONAS POR FOSFORIMETRIA NA TEMPERATURA AMBIENTE SUPORTADA EM SUBSTRATO DE CELULOSE COM NITRATO DE TÓRIOILFRAN DA SILVA NAVA JUNIOR 16 October 2007 (has links)
[pt] Neste trabalhou desenvolveu-se métodos analíticos baseados
na
fosforimetria em temperatura ambiente em substrato sólido
(FTASS) para
determinação seletiva de fluorquinolonas. Mais
especificamente, avaliou-se a
viabilidade do uso do nitrato de tório como sal de átomo
pesado indutor de
fosforescência visando a determinação seqüencial de
norfloxacino (NOR) e
levofloxacino (LEV), determinação seletiva de NOR em
presença de
ciprofloxacino (CIP), assim como a determinação seletiva
de CIP em presença
de gatifloxacino (GAT) ou moxifloxacino (MOX). Realizou-se
uma cuidadosa
comparação entre o sinal fosforescente obtido com o uso do
nitrato de tório e os
obtidos pelos sais indutores tradicionalmente utilizados
na FTASS. Estudou-se
univariadamente o efeito da quantidade de sal indutor de
átomo pesado
depositado no substrato sólido, a quantidade de um
surfactante modificador de
superfície e a concentração hidrogeniônica da solução
carreadora de analito na
magnitude do sinal fosforescente. Também foram avaliadas
possíveis interações
entre esses fatores experimentais por meio de um
planejamento fatorial 23. Com
a estratégia de análise bem definida, desenvolveram-se
metodologias para a
determinação de NOR, LEV e CIP em formulações
farmacêuticas comerciais e
simuladas e em urina enriquecida sem que se fosse aplicado
procedimentos de
separação do analito de interesse das outras substâncias
concomitantes. Para
tal, a estratégia de varredura sincronizada foi
fundamental. Os parâmetros
analíticos de mérito obtidos com o uso do nitrato de tório
foram comparados com
os obtidos com o do acetato de cádmio (átomo pesado
indutor de fosforescência
de fluorquinolonas já descrito na literatura). Em todos os
casos estudados, a
resposta analítica apresentou comportamento linear em
função da massa
depositada de NOR, LEV e CIP no substrato (R2>0,99), com
boa repetitividade e
sensibilidade (avaliada pelos limites de detecção e
quantificação absolutos na
ordem de ng). Tanto nas formulações farmacêuticas quanto
em urina
enriquecida, os resultados obtidos com o método
desenvolvido com o uso do sal de tório na determinação
seqüencial de NOR/LEV e na determinação seletiva de
NOR/CIP foram mais vantajosos que os obtidos com o uso do
sal de cádmio. Em
ambos os casos, o método desenvolvido com o uso do Th(NO3)
4 mostrou-se
válido desde que a proporção molar das misturas NOR/LEV e
NOR/CIP não
ultrapassem a condição de 1 (analito) para 5
(interferente). Para o método
desenvolvido na determinação seletiva de CIP em misturas
contendo GAT, o
Th(NO3)4 também mostrou-se mais adequado que o acetato de
cádmio,
Cd(OAc)2, sendo obtidos resultados satisfatórios, desde
que a proporção molar
CIP/GAT não ultrapassasse 1 para 2. No entanto,
interferências do tipo nãoespectral
foram observadas na presença de quantidades maiores de GAT
(até
10 vezes mais), as quais podem ser facilmente corrigidas
utilizando o método de
adição do analito. Já nas misturas contendo CIP/MOX, o
método desenvolvido
para a determinação seletiva de CIP com o uso do sal de
tório foi muito favorável
em proporções equimolares e em quantidades contendo duas
vezes mais MOX.
Em misturas contendo maiores quantidades de MOX, observou-
se interferências
do tipo espectral que não puderam ser contornadas por
sincronização, devido
seus (Lambda)sinc.muito próximos. Porém, utilizando Cd(OAc)
2 nas
misturas contendo
CIP/MOX em razões molares maiores que 1:2 se observou
interferências apenas
do tipo não-espectral, que podem ser corrigidas por
procedimento adequado de
calibração. Esse caso foi o único cujo sal de cádmio
mostrou-se superior ao
método desenvolvido com o uso do sal de tório. / [en] In this work, analytical methods based on solid surface
room-temperature
phosphorimetry were developed aiming the selective
determination of
fluorquinolones. More spectilly, thorium nitrate was
evaluated as
phosphorescence inducer aiming the sequential
determination of norfloxacin
(NOR) and levofloxacin (LEV), selective determination of
NOR in presence of
ciprofloxacin (CIP), as well as the selective
determination of CIP in the presence
gatifloxacin (GAT) or moxifloxacin (MOX). In order to
that, the phosphorescence
induced by thorium nitrate was compared with the ones
achieved using other
traditionally employed heavy atom enhancers in solid
surface room-temperature
phosphorimetry (SSRTP). Univariated studies were made in
order to evaluate the
effect of the amounts of heavy atom salt and surface
modifier present in the
substrate as well as the influence of the pH of the
analyte carrier solution. The
interaction among these factors were also studied through
experimental factorial
desings (23). After the definition of the analytical
strategy to be employed,
analytical methods were developed for the determination of
NOR, LEV and CIP in
simulated mistures and analyte spiked urine without
employing any procedure to
physically separate the analyte from the others components
of the sample. In
order to do that, the use of syncronized scanning was
fundamental. The
analytical figures of merit achieved using thorium nitrate
and cadmium acetate
(heave atom inducer already reported in the literature for
fluorquinolones) were
campared. In both cases, linear analytical responses in
function of the amount of
analyted present in the substrate were achieved (R2>0,99).
Good repetitivity of
results and sensibility (evaluated through the estimation
of the limits of detection
and quantification) were in the ng order. When testing
pharmaceutical
formulations and spiked urine, the use of Th(NO3)4 showed
clear advantage over
Cd(OAc)2, allowing the sequential determination of NOR/LEV
and the selective
determination of NOR in the presence of CIP. The selective
determination of
NOR using Th(NO3)4 could be made for mixtures containing
up to five times more LEV or CIP in molar proportion. For
the developed method aiming the
determination of CIP in mistures containing GAT, Th(NO3)4
was found to be more
adequate heavy atom enhancer than Cd(OAc)2. The method was
free from
interferences for samples containing two times more GAT
than CIP (in molar
proportion). However, interferences observed for mixtures
containing higher
amounts of GAT could be easily corrected by the using of
the standard addition
method for quantification. In mixtures containing CIP and
MOX, the developed
method using Th(NO3)4 was suitable for mixtures containing
equimolar
proportions of these two fluorquinolones. Spectral
interferences were observed
for higher amounts of MOX. Such interference could not be
resolved due to close
(lambda) values characteristic for the two FQs. However,
for the
method using
Cd(OAc)2 in mixtures containing CIP/MOX in molar
proportion more them 1:2
only non spectral interferences were observed, but this
interferences can be
corrected by the use of proper calibration strategy. This
was the only situation
where Cd(OAc)2 demonstrate better results than Th(NO3)4.
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Intégration de transistor mono-électronique et transistor à atome unique sur CMOS / Scaling Beyond Moore : Single Electron Transistor (SET) and Single Atom Transistor Integration on CMOSDeshpande, Veeresh 27 September 2012 (has links)
La réduction (« scaling ») continue des dimensions des transistors MOSFET nous a conduits à l'ère de la nanoélectronique. Le transistor à effet de champ multi-grilles (MultiGate FET, MuGFET) avec l'architecture «nanofil canal» est considéré comme un candidat possible pour le scaling des MOSFET jusqu'à la fin de la roadmap. Parallèlement au scaling des CMOS classiques ou scaling suivant la loi de Moore, de nombreuses propositions de nouveaux dispositifs, exploitant des phénomènes nanométriques, ont été faites. Ainsi, le transistor monoélectronique (SET), utilisant le phénomène de «blocage de Coulomb», et le transistor à atome unique (SAT), en tant que transistors de dimensions ultimes, sont les premiers dispositifs nanoélectroniques visant de nouvelles applications comme la logique à valeurs multiples ou l'informatique quantique. Bien que le SET a été initialement proposé comme un substitut au CMOS («Au-delà du dispositif CMOS»), il est maintenant largement considéré comme un complément à la technologie CMOS permettant de nouveaux circuits fonctionnels. Toutefois, la faible température de fonctionnement et la fabrication incompatible avec le procédé CMOS ont été des contraintes majeures pour l'intégration SET avec la technologie FET industrielle. Cette thèse répond à ce problème en combinant les technologies CMOS de dimensions réduites, SET et SAT par le biais d'un schéma d'intégration unique afin de fabriquer des transistors « Trigate » nanofil. Dans ce travail, pour la première fois, un SET fonctionnant à température ambiante et fabriqués à partir de technologies CMOS SOI à l'état de l'art (incluant high-k/grille métallique) est démontré. Le fonctionnement à température ambiante du SET nécessite une île (ou canal) de dimensions inférieures à 5 nm. Ce résultat est obtenu grâce à la réduction du canal nanofil ‘‘trigate'' à environ 5 nm de largeur. Une étude plus approfondie des mécanismes de transport mis en jeu dans le dispositif est réalisée au moyen de mesures cryogéniques de conductance. Des simulations NEGF tridimensionnelles sont également utilisées pour optimiser la conception du SET. De plus, la cointégration sur la même puce de MOSFET FDSOI et SET est réalisée. Des circuits hybrides SET-FET fonctionnant à température ambiante et permettant l'amplification du courant SET jusque dans la gamme des milliampères (appelé «dispositif SETMOS» dans la littérature) sont démontrés de même que de la résistance différentielle négative (NDR) et de la logique à valeurs multiples. Parallèlement, sur la même technologie, un transistor à atome unique fonctionnant à température cryogénique est également démontré. Ceci est obtenu par la réduction de la longueur de canal MOSFET à environ 10 nm, si bien qu'il ne comporte plus qu'un seul atome de dopant dans le canal (diffusée à partir de la source ou de drain). A basse température, le transport d'électrons à travers l'état d'énergie de ce dopant unique est étudié. Ces dispositifs fonctionnent également comme MOSFET à température ambiante. Par conséquent, une nouvelle méthode d'analyse est développée en corrélation avec des caractéristiques à 300K et des mesures cryogéniques pour comprendre l'impact du dopant unique sur l'échelle MOSFET à température ambiante. / Continuous scaling of MOSFET dimensions has led us to the era of nanoelectronics. Multigate FET (MuGFET) architecture with ‘nanowire channel' is being considered as one feasible enabler of MOSFET scaling to end-of-roadmap. Alongside classical CMOS or Moore's law scaling, many novel device proposals exploiting nanoscale phenomena have been made either. Single Electron Transistor (SET), with its unique ‘Coulomb Blockade' phenomena, and Single Atom Transistor (SAT), as an ultimately scaled transistor, are prime nanoelectronic devices for novel applications like multivalued logic, quantum computing etc. Though SET was initially proposed as a substitute for CMOS (‘Beyond CMOS device'), it is now widely considered as a compliment to CMOS technology to enable novel functional circuits. However, the low operation temperature and non-CMOS fabrication process have been major limitations for SET integration with FET. This thesis makes an effort at combining scaled CMOS, SET and SAT through a single integration scheme enabling trigate nanowire-FET, SET or SAT. In this work, for the first time, fabrication of room temperature operating SET on state-of-the-art SOI CMOS technology (featuring high-k/metal gate) is demonstrated. Room temperature operation of SET requires an island (or channel) with dimensions of 5 nm or less. This is achieved through reduction of trigated nanowire channel to around 5 nm in width. Further study of carrier transport mechanisms in the device is carried out through cryogenic conductance measurements. Three dimensional NEGF simulations are also employed to optimize SET design. As a step further, cointegration of FDSOI MOSFET and SET on the same die is carried out. Room temperature hybrid SET-FET circuits enabling amplification of SET current to micro-ampere range (proposed as ‘SETMOS device' in literature), negative differential resistance (NDR) and multivalued logic are shown. Alongside this, on the same technology, a Single Atom Transistor working at cryogenic temperature is also demonstrated. This is achieved through scaling of MOSFET channel length to around 10 nm that enables having a single dopant atom in channel (diffused from source or drain). At low temperature, electron transport through the energy state of this single dopant is studied. These devices also work as scaled MOSFETs at room temperature. Therefore, a novel analysis method is developed correlating 300 K characteristics with cryogenic measurements to understand the impact of single dopant on scaled MOSFET at room temperature.
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Étude de l'influence d'éléments d'addition sur les propriétés de stockage de l'hydrogène dans le système Ti-V-Fe / Study of the influence of alloying elements on hydrogen storage properties in the Ti-V-Fe systemDenis, Jean-Benoît 22 September 2016 (has links)
Cette thèse s'inscrit dans la thématique du stockage de l'hydrogène sous forme d'hydrure métallique. Pour pallier aux coûts importants des éléments utilisés pour l'élaboration des matériaux hydrurables, il est possible d'utiliser des alliages de pureté moindre comme précurseurs. Cela implique la présence d'éléments supplémentaires dans matériaux. Le matériau étudié appartient à la famille des composés intermétalliques Ti-V-Fe de structure cubique centrée. Cette structure est connue pour donner de fortes capacités réversibles d'absorption d'hydrogène durant une utilisation dans des conditions proches de l’ambiant. Grâce à une modélisation des principaux paramètres des hydrures formés à partir de ces alliages, il est apparu que le composé Ti15V71Fe14 présente des pressions d’équilibre intéressantes à température ambiante. Toutes les propriétés de ce matériau de référence ont été mesurées par diffraction des rayons X, microsonde de Castaing, microscopie à balayage électronique et banc d’hydruration. Une petite quantité des éléments d’addition est ajoutée individuellement puis ensemble dans la composition du matériau référent. Les échantillons sont analysés et les résultats sont comparés à ceux obtenus avec le référent. Il apparait que l’aluminium forme une solution solide de structure cubique centrée simple et améliore la capacité d’absorption du matériau référent. Il en est de même pour le silicium malgré un comportement plus complexe avec l’apparition de plusieurs phases supplémentaires. En contrepartie la vitesse d’absorption de l’hydrogène dans le matériau est diminuée / This Ph.D takes place on the hydrogen storage theme in metal hydride. In order to reduce the cost of the elements used for the preparation of hydridable materials, it is possible to use lower purity alloys as precursors. The compound selected belongs to the body centered cubic family consisting of Ti, V and Fe. This structure is known to store reversibly good quantities of hydrogen in conditions close to ambient. Thanks to modeling of the main parameters, it appears that the compound Ti15V71Fe14 presents interesting equilibrium pressure at room temperature. All properties of this reference material are measured by X-ray diffraction, EPMA, scanning electron microscopy and hydriding apparatus. A small amount of alloying elements has then been added individually then together in the composition of the reference material. Samples are analyzed and the results are compared to the referent. It appears that aluminum forms a solid solution of body centered cubic structure and improves the absorption capacity of the reference material. It is the same for silicon despite more complex behavior with the formation of several additional phases. In return the absorption kinetic of the material is reduced
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