Dissertations / Theses on the topic 'CuWO4'

Solar energy conversion and storage into hydrogen is a valuable approach to capture the energy that is freely available from sunlight and to turn it into a clean fuel. Photoelectrochemical (PEC) water splitting through the dual-absorber tandem cell technology has emerged as a promising strategy to this aim. The work conducted in the frame of this PhD thesis aimed at playing a part in the development and optimization of efficient oxide-based semiconductor photoanodes for water oxidation, which is the kinetic bottleneck of the overall PEC water splitting process. Photoanodes based on films of absorbing materials were successfully synthesized with a high optical transparency as important requirement for maximizing the solar energy conversion efficiency of the final tandem cell device. Subsequently, their intrinsic properties as single photoabsorber photoanodes were largely improved, on the basis of the results obtained through comprehensive PEC studies in parallel with thorough structural, morphological, and spectroscopic investigations. The attention was focused on three different classes of promising ternary metal oxides, able to absorb a large portion of the solar spectrum, namely i) BiVO4 (bandgap Eg = 2.4 eV), known for its excellent solar light to hydrogen conversion efficiency, ii) the copper tungstate-based materials CuWO4 (Eg = 2.3 eV) and CuW(1-x)Mo(x)O4 (Eg = 2.0 eV), ideal to be employed as visible-light active alternative to WO3, and iii) ZnFe2O4 (Eg = 2.0 eV) belonging to the spinel ferrites class, possessing excellent photothermal and chemical stability. Specifically, BiVO4 was studied either as a visible light sensitizer towards TiO2 or as a single photoanode material to focus on the identification and improvement of its intrinsically poor electron transport and interfacial transfer properties. In the first case, the TiO2/BiVO4 heterojunction system was proved to be effective in producing highly reductive electrons, suitable for overall water splitting, through TiO2 sensitization towards visible light. This, together with the counterintuitive mechanism at the basis of the observed impressive functionality, was effectively disclosed through combined PEC and photocatalytic reduction test studies. The multifaceted role of Mo6+ doping onto both the bulk and surface properties of BiVO4 films was also revealed through an in-depth PEC and impedance spectroscopy study. By improving either the bulk conductivity or the interfacial charge transfer of optimized Mo6+ doped BiVO4 photoanodes a conspicuous enhancement was attained of their photoactivity towards water oxidation with respect to the pure material. The presence of intra-gap states in CuWO4, acting as electron traps and thus being responsible for a severe internal charge recombination, was verified by means of the first ultrafast transient absorption study performed with this material, in combination with both an electrochemical and a photochromic characterization. This issue, which strongly limits the PEC performance of CuWO4 photoanodes, was addressed by adopting a 50% Mo for W substitution resulting in CuW0.5Mo0.5O4 photoanodes, exhibiting not only a greatly extended visible light-induced photoactivity compared to the pure material, as a result of enhanced absorption, but also a considerably improved charge separation. All these factors contributed to the much better PEC performance attained with respect to CuWO4 electrodes. This study was finalized by the identification of a suitable hole scavenger species for copper tungstate-based materials, able to ensure enhanced photocurrent generation compared to pure water oxidation while minimizing dark currents. Finally, in the frame of my seven months stage in Prof. Sivula’s group at the EPFL in Lausanne, a thorough study was performed on the impact that several parameters, such as the annealing temperature, the film thickness and the creation of oxygen vacancies through a reductive treatment in hydrogen atmosphere, have on the PEC performance of ZnFe2O4 photoanodes. The verified synergism between the higher crystallinity of the films subjected to a high-temperature annealing treatment and the hydrogenation efficiency, which proved effective in optimizing charge separation in the thicker photoactive layers, allowed one to maximize the performance of ZnFe2O4 electrodes for water oxidation. This study also shed light onto the strict correlation occurring between structural parameters, i.e. the film crystallinity and the spinel inversion degree, and the resulting PEC performance, which proved to be in turn controlled by the film morphology.

Disertaciniame darbe naudojant IR-spektrometrijos, rentgenofazinės analizės, atominės absorbcinės spektroskopijos, kolorimetrijos analizės metodus buvo ištirta sistemose CuSO4 – K4P2O7 – H2O ir CuSO4 – (NH4)4P2O7 – H2O susidarančių mažai tirpių junginių sudėtis, jų susidarymo dėsningumai ir vykstančios reakcijos, įvairių veiksnių įtaka nuosėdų sudėčiai ir struktūrai. Nustatyta, kad sistemoje CuSO4 – K4P2O7 – H2O, be jau žinomų mažai tirpių junginių (paprastosios druskos Cu2P2O7 5H2O ir dvigubosios druskos Cu3K2(P2O7)2 H2O, susidaro ir naujas mokslinėje literatūroje neaprašytas junginys (Dimorfas B), dvigubajai druskai patiriant polimorfinį perėjimą. Polimorfinio perėjimo trukmė labai priklauso nuo pH ir reaguojančių jonų koncentracijų. FTIR duomenų analizė parodė, kad difosfato jonų energetinė būsena Cu – K ir Cu – NH4 Dimorfuose B panaši. Jų rentgenogramos yra panašios, tikėtina, kad šie junginiai – izostruktūriniai, jų kristalinės gardelės tipas – monoklininis. Naudojant Lazarevo lygtį bei Rulmonto priklausomybę buvo apskaičiuoti Cu – K ir Cu – NH4 Dimorfų A ir B bei paprastosios druskos P – O – P kampai, gauta, kad jie mažai keičiasi siaurame 123,1 – 127,1 º intervale. Nustatyta, kad dviguboji druska susidaro iš paprastosios, vykstant heterogeninei reakcijai: 3Cu2P2O7 5H2O↓ + H2P2O72– + 4K+ → 2Cu3K2(P2O7)2∙3H2O↓ + 2H++ 9H2O. Mokslinėje literatūroje tokia reakcija neaprašyta jokiai polifosfatų sistemai, jos tyrimo duomenys yra nauji. Taip pat nustatyta, kad heterogeninės... [toliau žr. visą tekstą]
At least three poorly soluble compounds can be formed in the CuSO4 – K4P2O7 – H2O system: a single salt Cu2P2O7.5H2O and two dimorph’s both having chemical formula Cu3K2(P2O7)2.3H2O. A previously known form of Cu3K2(P2O7)2.3H2O (we named it Dimorph A) transforms into a novel Dimorph B, which has a different structure. The similarities between the XRD patterns and vibrations spectra of copper–ammonium and copper–potassium Dimorph’s B imply that they are isostructural. The values of the angle for copper–potassium and copper–ammonium salts and Cu2P2O7.5H2O are relatively low and vary within a narrow range (123.1 – 127.1°). The formation of the compounds significantly depends on the conditions of the experiment. A double salt in the CuSO4 – K4P2O7 – H2O system may be formed after some time in the reaction mixture as a result of the following heterogeneous reaction: 3Cu2P2O7∙5H2O↓ + H2P2O72– + 4K+ → 2Cu3K2(P2O7)2∙3H2O↓ + 2H+ + 9H2O This reaction has not been previously described for any polyphosphate system. Therefore, novel results of scientific investigation are presented. The rate, duration and yield of heterogeneous reaction substantially depend on pH of the solution, [Cu2+ + P2O74–] and n ([P2O74–] / [Cu2+]). At a relatively low pH the induction time is high, the reaction rate is low and duration is long. The maximal yields close to 100% can be achieved when [Cu2+ + P2O74–] = 0.1 M. At increased pH values, the induction time, the yield and duration of the reaction diminish... [to full text]

At least three poorly soluble compounds can be formed in the CuSO4 – K4P2O7 – H2O system: a single salt Cu2P2O7.5H2O and two dimorph’s both having chemical formula Cu3K2(P2O7)2.3H2O. A previously known form of Cu3K2(P2O7)2.3H2O (we named it Dimorph A) transforms into a novel Dimorph B, which has a different structure. The similarities between the XRD patterns and vibrations spectra of copper–ammonium and copper–potassium Dimorph’s B imply that they are isostructural. The values of the angle for copper–potassium and copper–ammonium salts and Cu2P2O7.5H2O are relatively low and vary within a narrow range (123.1 – 127.1°). The formation of the compounds significantly depends on the conditions of the experiment. A double salt in the CuSO4 – K4P2O7 – H2O system may be formed after some time in the reaction mixture as a result of the following heterogeneous reaction: 3Cu2P2O7∙5H2O↓ + H2P2O72– + 4K+ → 2Cu3K2(P2O7)2∙3H2O↓ + 2H+ + 9H2O This reaction has not been previously described for any polyphosphate system. Therefore, novel results of scientific investigation are presented. The rate, duration and yield of heterogeneous reaction substantially depend on pH of the solution, [Cu2+ + P2O74–] and n ([P2O74–] / [Cu2+]). At a relatively low pH the induction time is high, the reaction rate is low and duration is long. The maximal yields close to 100% can be achieved when [Cu2+ + P2O74–] = 0.1 M. At increased pH values, the induction time, the yield and duration of the reaction diminish... [to full text]
Naudojant IR-spektrometrijos, rentgenofazinės analizės, atominės absorbcinės spektroskopijos, kolorimetrijos analizės metodus buvo ištirta sistemose CuSO4 – K4P2O7 – H2O ir CuSO4 – (NH4)4P2O7 – H2O susidarančių mažai tirpių junginių sudėtis, jų susidarymo dėsningumai ir vykstančios reakcijos, įvairių veiksnių įtaką nuosėdų sudėčiai ir struktūrai. Nustatyta, kad sistemoje CuSO4 – K4P2O7 – H2O, be jau žinomų mažai tirpių junginių (paprastosios druskos Cu2P2O7 ∙ 5H2O ir dvigubosios druskos Cu3K2(P2O7)2 ∙ 3H2O), susidaro ir naujas mokslinėje literatūroje neaprašytas junginys (Dimorfas B), dvigubajai druskai patiriant polimorfinį perėjimą. Polimorfinio perėjimo trukmė labai priklauso nuo pH ir reaguojančių jonų koncentracijų. FTIR duomenų analizė parodė, kad difosfato jonų energetinė būsena Cu – K ir Cu – NH4 Dimorfuose B panaši. Jų rentgenogramos yra panašios, tikėtina, kad šie junginiai – izostruktūriniai, jų kristalinės gardelės tipas – monoklininis. Naudojant Lazarevo lygtį, bei Rulmonto priklausomybę buvo apskaičiuoti Cu – K ir Cu – NH4 Dimorfų A ir B bei paprastosios druskos P – O – P kampai, gauta, kad jie mažai keičiasi siaurame 123,1 – 127,1 º intervale. Nustatyta, kad dviguboji druska susidaro iš paprastosios, vykstant heterogeninei reakcijai: 3Cu2P2O7 ∙ 5H2O↓ + H2P2O72– + 4K+ → 2Cu3K2(P2O7)2∙ 3H2O↓ + 2H++ 9H2O. Mokslinėje literatūroje tokia reakcija neaprašyta jokiai difosfatų sistemai, jos tyrimo duomenys yra nauji. Taip pat nustatyta, kad heterogeninės reakcijos... [toliau žr. visą tekstą]

Klövsjukdomen digital dermatit hos kor ger upphov till smärta hos djuren samt störningar i produktionen. För att förebygga och behandla klövsjukdomen används olika preparat, däribland CuSO4-lösning. Syftet med studien är att undersöka om och i så fall i vilken omfattning spridande av kopparförorenad gödsel påverkar Cu-halten i jordbruksmark. Studien genomfördes med provtagning av två oberoende jordbruksmarker där ett av områdena gödslas med kopparförorenad gödsel. Resultaten visar att jordbruksmark där förbrukad CuSO4 spridits med stallgödseln ger upphov till en signifikant ökad Cu-halt i markens översta lager, 0-25 cm.
The hoof disease digital dermatitis rise pain with the cows as well as production disruption. To prevent and treat the hoof disease different substances are used, including CuSO4 solutions. The purpose of this study is to examine if, and in that case in which incidence, the spread of copper contaminated manure affects the copper content in agricultural land. The study was performed sampling two independent agricultural areas. One of the areas was fertilized with copper contaminated manure. The results show that agricultural land where CuSO4 has been spread with the manure has a significant higher content of Cu in the upper level of the soil, 0-25 cm.

Os aÃos inoxidÃveis austenÃticos tÃm sido bastante utilizados em equipamentos de utilidades de dessulfurizaÃÃo de petrÃleo devido à sua boa resistÃncia à corrosÃo em temperatura elevada.Contudo, esses materiais estÃo sujeitos a sensitizaÃÃo (deficiÃncia em cromo na regiÃo vizinha ao contorno de grÃo) quando expostos a temperaturas de 425 a 815ÂC, durante a operaÃÃo ou processos de fabricaÃÃo. A sensitizaÃÃo torna o equipamento suscetÃvel à corrosÃo sob tensÃo causada por aÃos politiÃnicos, formados pela interaÃÃo de compostos sulforoso, umidade e ar em temperatura ambiente. A resistÃncia à corrosÃo sob tensÃo de amostras de aÃo inoxidÃvel austenÃtico AISI 321 e 347, removidas de um tubo, foi investigada atravÃs do procedimento ASTM 262 Pr. E â ensaio alternativo e de execuÃÃo mais fÃcil do que a simulaÃÃo dos aÃos politiÃnicos. Os corpos de prova foram submetidos aos tratamentos tÃrmicos de estabilizaÃÃo (900ÂC, durante 75 minutos) e de sensitizaÃÃo (600ÂC, durante 20, 40, 80, 120 e 140 horas), apÃs o que foram expostos ao meio corrosivo de CuSO4 + H2SO4 durante 72 horas e depois dobradas, nÃo apresentando trincamento. A agressividade do meio utilizado no ensaio foi verificada atravÃs da utilizaÃÃo de amostras de aÃo AISI 304L sensitizadas (600ÂC, 24, 28 e 72 horas e 677ÂC durante 4, 45 e 72 horas). Neste caso, somente as amostras com acabamento superficial feito com lixa n 100 sofreram um intensivo processo corrosivo.
Os aÃos inoxidÃveis austenÃticos tÃm sido bastante utilizados em equipamentos de utilidades de dessulfurizaÃÃo de petrÃleo devido à sua boa resistÃncia à corrosÃo em temperatura elevada.Contudo, esses materiais estÃo sujeitos a sensitizaÃÃo (deficiÃncia em cromo na regiÃo vizinha ao contorno de grÃo) quando expostos a temperaturas de 425 a 815ÂC, durante a operaÃÃo ou processos de fabricaÃÃo. A sensitizaÃÃo torna o equipamento suscetÃvel à corrosÃo sob tensÃo causada por aÃos politiÃnicos, formados pela interaÃÃo de compostos sulforoso, umidade e ar em temperatura ambiente. A resistÃncia à corrosÃo sob tensÃo de amostras de aÃo inoxidÃvel austenÃtico AISI 321 e 347, removidas de um tubo, foi investigada atravÃs do procedimento ASTM 262 Pr. E â ensaio alternativo e de execuÃÃo mais fÃcil do que a simulaÃÃo dos aÃos politiÃnicos. Os corpos de prova foram submetidos aos tratamentos tÃrmicos de estabilizaÃÃo (900ÂC, durante 75 minutos) e de sensitizaÃÃo (600ÂC, durante 20, 40, 80, 120 e 140 horas), apÃs o que foram expostos ao meio corrosivo de CuSO4 + H2SO4 durante 72 horas e depois dobradas, nÃo apresentando trincamento. A agressividade do meio utilizado no ensaio foi verificada atravÃs da utilizaÃÃo de amostras de aÃo AISI 304L sensitizadas (600ÂC, 24, 28 e 72 horas e 677ÂC durante 4, 45 e 72 horas). Neste caso, somente as amostras com acabamento superficial feito com lixa n 100 sofreram um intensivo processo corrosivo.
Because of their resistance to high temperature corrosion by hydrogen sulfide, austenitic stanless steels are commonly used for equipment in desulfurization process. However, these materials are subject to sensitization (chromium carbide precipitation) from exposure in the temperature range 425 to 815ÂC during fabrication or operation. Sensitization makes the equipment susceptible to failure from intergranular stress corrosion cracking caused by polythionic acid. Polythionic acid is formed by sulfur compounds, moisture, and air at ambient temperature. The main goal of the present work is to investigate the stress corrosion cracking susceptibility of stainless steels AISI 321 and 347 in polythionic acids using an alternative process that is to submit the samples to cooper-cooper sulfate-16% sulfuric acid test (ASTM A262 Pr.E). After the stabilization heat treatment at 900ÂC for 75 minutes, samples were heat treated at 600ÂC during 20, 40, 80, 120 and 140 hours and then exposed to boiling acidified copper sulfate solution for 72 hours. After exposure, the specimens were bent. The appearance of fissures or cracks was not observed in AISI 321 and 347 samples. The effectiveness of the solution has been made by submitting AISI 304L samples to the same environment . The AISI 304L samples with higher finishing have been cracked. The ones with fine-ground finishing have not been attacked.
Because of their resistance to high temperature corrosion by hydrogen sulfide, austenitic stanless steels are commonly used for equipment in desulfurization process. However, these materials are subject to sensitization (chromium carbide precipitation) from exposure in the temperature range 425 to 815ÂC during fabrication or operation. Sensitization makes the equipment susceptible to failure from intergranular stress corrosion cracking caused by polythionic acid. Polythionic acid is formed by sulfur compounds, moisture, and air at ambient temperature. The main goal of the present work is to investigate the stress corrosion cracking susceptibility of stainless steels AISI 321 and 347 in polythionic acids using an alternative process that is to submit the samples to cooper-cooper sulfate-16% sulfuric acid test (ASTM A262 Pr.E). After the stabilization heat treatment at 900ÂC for 75 minutes, samples were heat treated at 600ÂC during 20, 40, 80, 120 and 140 hours and then exposed to boiling acidified copper sulfate solution for 72 hours. After exposure, the specimens were bent. The appearance of fissures or cracks was not observed in AISI 321 and 347 samples. The effectiveness of the solution has been made by submitting AISI 304L samples to the same environment . The AISI 304L samples with higher finishing have been cracked. The ones with fine-ground finishing have not been attacked.

CAMPOS, C. V. F. Suscetibilidade à corrosão sob tensão dos aços AISI 321 e 347 em meio de H2SO4 + CuSO4. 2003. 68 f. Dissertação (Mestrado em Engenharia e Ciência de Materiais) - Centro de Tecnologia, Universidade Federal do Ceará, Fortaleza, 2003.
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Because of their resistance to high temperature corrosion by hydrogen sulfide, austenitic stanless steels are commonly used for equipment in desulfurization process. However, these materials are subject to sensitization (chromium carbide precipitation) from exposure in the temperature range 425 to 815ºC during fabrication or operation. Sensitization makes the equipment susceptible to failure from intergranular stress corrosion cracking caused by polythionic acid. Polythionic acid is formed by sulfur compounds, moisture, and air at ambient temperature. The main goal of the present work is to investigate the stress corrosion cracking susceptibility of stainless steels AISI 321 and 347 in polythionic acids using an alternative process that is to submit the samples to cooper-cooper sulfate-16% sulfuric acid test (ASTM A262 Pr.E). After the stabilization heat treatment at 900ºC for 75 minutes, samples were heat treated at 600ºC during 20, 40, 80, 120 and 140 hours and then exposed to boiling acidified copper sulfate solution for 72 hours. After exposure, the specimens were bent. The appearance of fissures or cracks was not observed in AISI 321 and 347 samples. The effectiveness of the solution has been made by submitting AISI 304L samples to the same environment . The AISI 304L samples with higher finishing have been cracked. The ones with fine-ground finishing have not been attacked.
Os aços inoxidáveis austeníticos têm sido bastante utilizados em equipamentos de unidades de dessulfurização de petróleo devido à sua boa resistência à corrosão em temperatura elevada. Contudo, este materiais estão sujeitos à sensitização (deficiência em cromo na região vizinha ao contorno de grão) quando expostos a temperaturas de 425 a 815°C, durante a operação ou processos de fabricação. A sensitização torna o equipamento suscetível à corrosão sob tensão na presença de tensões de tração e de ácidos politiônicos, formados pela interação de compostos sulfurosos, umidade e ar em temperatura ambiente. A resistência à corrosão sob tensão de amostras de aço inoxidável austenítico AISI 321 e 347, removidas de um tubo, foi investigada através do procedimento ASTM 262 Pr. E - ensaio alternativo e de execução mais fácil do que a simulação dos ácidos politiônicos. Os corpos de prova foram submetidos aos tratamentos térmicos de estabilização (900°C, durante 75 minutos) e de sensitização (600°C, durante 20, 40, 80, 120 e 140 horas), após o que foram expostos ao meio corrosivo de CuSO4 + H2SO4 durante 72 horas e depois submetidos ao ensaio de dobramento, não apresentando trincamento. A agressividade do meio utilizado no ensaio foi verificada através da utilização de amostras de aço AISI 304L sensitizadas durante 08, 14, 24 e 48 horas a 600°C e 24, 48 e 72 horas a 677°C. Verificou-se que somente as amostras com acabamento superficial feito com lixa n° 100 sofreram um intenso processo corrosivo.

Double perovskites with a single s = ½ magnetic ion and rocksalt order can show geometric frustration, due to arrangement of electron spins such that they cannot satisfy all nearest-neighbour antiferromagnetic interactions simultaneously. This can give rise to exotic magnetic states at low temperature. Compounds with unpaired 4d and 5d electrons have in this respect been studied far less than 3d compounds. Here, results of studies on the compounds Sr2CuWO6, Ba2YWO6 and LaSrMgWO6 are presented. The synthesis of the previously reported compound Ba2Y1WO6 (W5 +, 5d1) was attempted by many methods, but yttrium deficiencies were present in all samples. This led to the series Ba2YxWO6 with ⅔ ≤ x ≤ 0.8, dependent on the synthesis conditions. The x = ⅔ compound is known to exist as a metastable cubic phase and an 18H rhombohedral thermodynamic phase. The one-third vacant B sites on the x = ⅔ cubic material are doped with lithium, resulting in the Ba2Y2/3LixWO6 compound. This thesis focuses on the new x = 0.75 phase, and characterises its structural and magnetic properties. The Jahn-Teller distorted Sr2CuWO6, with the Cu2+ (3d9) magnetic ion, has an elongated c axis leading to separation of ab planes. This compound had been proposed as a pseudo-2D spin liquid model candidate, following a lack of evidence of transition to long-range order in SQUID magnetometry and heat capacity. However, recent μSR measurements did show a transition to long-range ordered state at 24K. This thesis details further bulk and local probe measurements which indicate that the low-temperature state is type-2 antiferromagnetic, and which point to a thermally activated spin-liquid-like state which occurs between 24K and ∼100K. La0.5Sr1.5MgWO6, has also been synthesised. The 1:1 compound LaSrMgWO6 had previously been reported as W5+ and described as “pseudo-cubic”: X-ray and neutron diffraction studies here characterise the low-temperature structure within the P2₁/n monoclinic space group, and suggest that no ordering of the atoms on the A site is observed.

Orientador : Prof. Dr. Marcos R. Mafra
Dissertação (mestrado) - Universidade Federal do Paraná, Setor de Tecnologia, Programa de Pós-Graduação em Engenharia Química. Defesa: Curitiba, 03/02/2017
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Resumo: Os sistemas de duas fases aquosas (SDFA) sao uma alternativa aos sistemas de extracao liquido-liquido convencionais. Estes sao formados atraves da adicao de solucoes aquosas de dois polimeros soluveis em agua, ou um polimero soluvel em agua e um componente de baixa massa molar, tal como sais inorganicos. Para aplicacoes industriais, sistemas formados por polimero, sal e agua sao de maior preferencia, uma vez, que apresentam baixa viscosidade, menor custo e menor tempo de separacao de fase. O conhecimento do comportamento termodinamico destes sistemas e de fundamental importancia para o projeto de unidades de extracao. Este trabalho teve como objetivo levantar dados experimentais e realizar a modelagem termodinamica do equilibrio liquido-liquido (ELL) dos sistemas de duas fases aquosas (SDFA) de PEG 2.000 e 6.000 + CuSO4 + H2O, PEG 2.000, 4.000 e 6.000 + MnSO4 + H2O e PVP 10.000 e 40.000 + MnSO4 + H2O em diferentes temperaturas (298,15, 318,15 e 338,15 K) utilizando o metodo de ponto de nevoa. Os dados de equilibrio obtidos para os SDFA demonstraram que o aumento de temperatura e da massa molar do polimero resultam em um aumento da regiao de duas fases dos sistemas, em um aumento da inclinacao e do comprimento das linhas de amarracao. Na analise do efeito de salting-out os sistemas compostos por sulfato de manganes obtiveram os maiores valores de coeficiente de salting-out devido a maior cosmotropicidade do cation Mn2+. A substituicao do polimero PEG pela polivinilpirrolidona (PVP) nos SDFA tambem foi avaliada. Os ajustes dos modelos termodinamicos NRTL e UNIQUAC foram eficazes para os sistemas formados por PEG, para os sistemas composto por PVP somente o UNIQUAC foi eficiente. Palavras Chaves: Sistemas de duas Fases Aquosas, Salting-out, Sais cosmotropicos, NRTL e UNIQUAC.
Abstract: Aqueous two-phase systems (ATPS) are an alternative to conventional liquidliquid extraction systems. These are formed by the addition of aqueous solutions of two water soluble polymers, or a water soluble polymer and a low molar mass component, such as inorganic salts. For industrial applications, systems formed by polymer + salt + water are more favorite, once, they have low viscosity, lower cost and less time of phase separation. The knowledge of the thermodynamic behavior of these systems is of fundamental importance for the design of extraction units. The objective of this work was to obtain experimental data and thermodynamic modeling the liquid-liquid equilibrium (LLE) of aqueous two-phase systems of PEG 2,000 and 6,000 + CuSO4 + H2O, PEG 2,000, 4,000 and 6,000 + MnSO4 + H2O and PVP 10,000 e 40,000 + MnSO4 + H2O at different temperatures (298.15, 318.15 and 338.15 K) using the cloud point method.The equilibrium data obtained for SDFAs demonstrated that the increase in temperature and molar mass of the polymer results in an increase of the two-phase region of the systems in an increase of the slope and length of the tie-lines. In the analysis of the salting-out effect the systems composed of manganese sulfate obtained the highest values of the salting-out coefficient due, to the higher cosmotropicity of the cation Mn2+.The substitution of PEG polymer by polyvinylpyrrolidone (PVP) in SDFA was also evaluated.The adjustments of the thermodynamic models NRTL and UNIQUAC were effective for the systems formed by PEG, for systems composed of PVP only UNIQUAC was efficient. Keywords: Aqueous Two-Phase Systems, Salting-out, Cosmotropic Salts, NRTL and UNIQUAC.

The well-known lanthanide cuprates exist in two principal forms, T and T´, which behave as p-type and n-type conductors, respectively. In order to understand the structural properties and crystal chemistry from the T to T´ phase, the Nd₁.₈₋ₓLaₓPr₀.₂CuO₄ (NLPCO) system was studied varying the La substitution ratio (0≤x≤1.8) and then characterised using high temperature X-ray powder diffraction. From analysis of the X-ray diffraction patterns obtained at room temperature, there are clearly five distinguishable regions for the NLPCO system. They are, (1) monophasic T´ solid–solution (2) two phase mixture T´ + T´´ (3) monophasic T´´solid–solution (4) two phase mixture T´´ + O and finally (5) monophasic O phase solid–solution. The T´´ form has previously been suggested as an ordered form of T´; however here we show via high temperature X-ray diffraction studies that it is a non-transformable metastable phase formed on quenching of the T phase via an orthorhombically distorted variant. Also neutron diffraction and selected area electron diffraction (SAED) studies confirmed that the T ´´phase is 4- fold Cu coordinated. The structural, magnetic and electrical properties of this NLPCO series have been investigated for the selected compositions using X-ray diffraction, magnetization measurements, thermal analysis and conductivity measurements. The aim of the second half of this work was to discover the basic high temperature electrical characteristics of Nd₂₋ₓPrₓCuO₄ and investigate how this matches with those required for components on the SOFC cathode side to identify which dopant level shows highest conductivity and whether it is stable at different temperatures. The idea was to make a new concept in SOFC cathodes and current collector development, using n-type conductors instead of p- type conductors and to try to produce a high conductivity material which is stable under the chemical and thermal stresses that exist while under load that can be used in cathode or current collector applications. The Nd₂₋ₓPrₓCuO₄ (NPCO) series has been studied over a range of dopant levels (x=0.15 - 0.25) and maximum conductivity of 86.7 Scm⁻¹ has been obtained for the composition where x = 0.25. Also NPCO shows n-type semiconductor behaviour which gives operational advantages when operating at mild oxygen deficiency. AC impedance studies have been carried out on symmetrical cells to investigate the performance of NPCO as a cathode material. These studies mainly focused on polarization resistance and the activation energies of the cells. Low Rp values and low activation energies are obtained for a composite cathode compared to pure cathode material. Two configurations of NPCO as cathode materials were tested, pre-fired and in-siu fired. Pre-fired NPCO exhibited better performance than in-situ fired NPCO. Both in-situ and pre-fired current collecting NPCO still showed lowest activation energies which suggest good catalytic activity. From all of these studies, it is evident that the praseodymium doped neodymium cuprate material shows considerable promise as a potential cathode material for solid oxide fuel cell applications.

博士
國立清華大學
化學工程研究所
82
The objective of this thesis is to study the characteristic of the photoelectrochemical reac- tions in the CuSO4/MeOH/TiO2 suspension systems. Reduction of cupric ions and oxidation of methanol are preceded on TiO2 simultaneously. Reaction curves of the cupric ion conversion with time show a two-stage behavior, which a slow stage is followed by a rapid stage. Besides,the rapid stage shows a little concavity. These characteristics were studied via product, nucleation and para- meters'' studies. The Cu2O being produced at high pH can retard electrons to penetrate the Cu2O/TiO2 interface. The metallic Cu being produced at low pH acts as an electron trap.It can increase the photoelectrochemical reaction too. Successive reduction of cupric ions is preceded at existed Cu nuclei. Results of mechanism study on MeOH oxidation demonstrate that the active sites of Ti2O are the defects and the undamaged surface. Absorption of MeOH on TiO2 is identified as physisorption. Film breakdown and S doping were found during the studies of Ti anodization in Na2SO4 solution. The discussion of nucleation is confirmed by photoelectrochemical study on the anodized TiO2 surface. Establishment of the electric field needs a certain distance for Cu nucleation.

碩士
大同大學
化學工程學系(所)
97
In this research, using twice anodization on aluminum and adding citric acid in an anodizing electrolyte simultaneously is the purpose to obtain a better pore structure than the process of once anodization. And the best operating conditions to obtain a blacker anodic film using electrolytic coloring solution of CuSO4 or AgNO3 had been found out. The experimental results show that, the larger and more orderly pores structure after the second anodization are obtained. Using the second anodization brfore the process of electrolytic coloring has many benefits to the properties of the colored film than using the first anodization, like film thickness, chromatism, reflectivity and anticorrosion. Electrolytic coloring in AgNO3 solution has the advantage of short reaction time and lower operating voltage to obtain blacker film than coloring in CuSO4 solution. The best operating conditions to obtain the blackest film are：the second anodizing current density of 2A/dm2 , the electrolytic coloring voltage of 25V in CuSO4 and coloring time of 30 min, it has a △E* value of 8.39; For the electrolytic coloring solution in AgNO3, the coloring voltage of 25V and coloring time of 20 min are the best operating conditions to obtain the blackest film with △E* value of 7.76.

碩士
國立中興大學
物理學系所
105
In this thesis, cuprous oxide (Cu2O) was prepared on the sapphire substrate (Al2O3) by chemical bath deposition (CBD) method using copper sulfate (CuSO4) and sodium sulfite (Na2SO3) as the precursor solution. Also, the influence of the addition of glucose (catalyst) and the annealing temperature on the morphology and structural properties of Cu2O was investigated by Scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray energy dispersive (EDS) and UV-Vis spectroscopy. The results show that the addition of glucose to the CBD solution prior to heating will curb the agglomeration of the Cu2O particles, and Cu2O appears as isolated nuclei rather than clustered particles. It was found that the grain size of Cu2Obecame coalesced with the increase of annealing temperature, and the crystallization quality of Cu2O was also improved with the increase of annealing temperature. However, after the annealing temperature is higher than 600°C, Cu2O phase was found to transforming into copper oxide (CuO) phase and copper metal (Cu).