Academic literature on the topic 'Solvothermal method'

Dióxido de titânio com alta área superficial específica na fase anatase é considerado um material promissor para aplicações ambientais. Neste trabalho, TiO2 com boa aplicabilidade em processos fotocatalíticos e na produção de hidrogênio foi obtido pelo método com baixo consumo de energia baseado na rota dos peróxidos oxidantes combinado com tratamento solvotermal assistido por microondas. Para preparar o material, propóxido de titânio, peróxido de hidrogênio e álcool isopropílico foram utilizados. A influência do tempo, do pH e da temperatura durante a etapa solvotermal nas propriedades como morfologia, cristalinidade, composição de fase, área superficial específica e comportamento fotocatalítico foram investigados. As amostras foram caracterizadas por difração de raios X (DRX), microscopia eletrônica de varredura (MEV), microscopia eletrônica de transmissão (MET), análise termogravimétrica (ATG), teoria Brunauer-Emmett-Teller (BET), reflectância difusa e espectroscopia por emissão fluorescente. A fotoatividade foi determinada usando o método de decomposição do corante alaranjado de metila em luz UV-A e a produção de hidrogênio foi realizada em água usando etanol como agente de sacrifício. Com o aumento da temperatura durante a etapa solvotermal, as propriedades fotocatalíticas foram melhoradas. As nanoestruturas de TiO2 sintetizadas a 200°C e 30 min a partir deste método mostraram atividade fotocatalítica comparável ao do TiO2 P25 comercial Aeroxide©. Isso pode ser atribuído ao fato de que a energia associada a esta temperatura tenha sido suficiente para converter a maioria dos precursores em produtos cristalinos e pouca fase amorfa está presente. Foi possível produzir, com sucesso, nanoestruturas de TiO2, via método dos peróxidos oxidantes e tratamento solvotermal assistido por microondas em diferentes pHs. O material tratado em pH 1 exibiu melhor comportamento fotocatalítico na degradação da solução contendo alaranjado de metila. Aparentemente, o pH do meio não afetou significativamente a microestrutura das amostras. Foi observado uma diminuição na intensidade fotoluminescente da amostra preparada em pH ácido. Isso ocorre provavelmente porque as modificações ácidas em TiO2 favorecem eficientemente a separação das cargas, que está também relacionada com o comportamento dessa amostra durante o processo de degradação. Em relação à produção de hidrogênio, foi possível observar que a razão aumentou com o aumento do pH da solução. Isso pode ser atribuído ao aumento da concentração de OH- fisisorvidos, os quais podem participar dos processos de trapeamento das lacunas e nas reações de transferência de cargas. Por último, esses resultados foram notáveis porque foi utilizado um método de preparação com baixo consumo de energia onde apenas precursores orgânicos e baixas temperaturas foram empregados. Além disso, calcinação ou dopagem não foram necessários para alcançar tal desempenho, uma vez que, os catalisadores assim preparados exibiram boa atividade fotocatalítica na remoção de poluentes da água como o alaranjado de metila e na produção de hidrogênio.<br>Titanium dioxide with high specific surface area in the crystalline anatase phase is a promising material for environmental applications. In this work, TiO2 with good applicability for photocatalytic processes and hydrogen production has been obtained using the low energy consumption synthesis based on oxidant peroxide method combined with microwave-assisted low temperature solvothermal treatment. To prepare the material, titanium propoxide, hydrogen peroxide, and isopropyl alcohol were used. The influence of time, pH and temperature during the solvothermal step on properties like, morphology, crystallinity, phase composition, specific surface area, and photocatalytic behavior were investigated. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), scanning electron transmission (TEM), thermal gravimetric analysis (TGA), Brunauer- Emmett-Teller theory (BET), UV–Vis diffuse reflectance and fluorescence emission spectroscopy. Photoactivity was determined using the methyl orange decomposition method in UV-A light and hydrogen production was performed in water using ethanol as sacrificial agent. Increasing temperature during solvothermal step, photocatalytic properties could be improved. The nanostructured TiO2 particles synthesized at 200ºC and 30 min with this method showed photocatalytic activity comparable to commercial Aeroxide® TiO2 P25. This can be attributed to the fact that the energy associated with this temperature has been sufficient to convert most of precursors into crystalline products and small amount of amorphous phase is present. We successfully produced nanostructured TiO2 via the oxidant peroxide method and microwave-assisted solvothermal treatment at different pHs. The material that we treated at pH 1 exhibited better photocatalytic performance on the degradation of methyl orange solutions. It appears that the pH of the medium does not significantly affect the microstructure of the samples. It was observed a decrease in the photoluminescence intensity of the sample prepared at acidic pH. This finding likely occurred because the acidic modification of TiO2 favors efficiently separating the charge carriers, which is also related to the behavior of this sample during the degradation process. Related to hydrogen production, it was possible to observe that the rate increases with increasing solution pH. This has been attributed to the increased concentrations of physisorbed OH− groups at basic solutions, which participate in hole trapping processes and charge transfer reactions. Lastly, these results are remarkable because of the low energy consumption preparation method: only organic-metalic compounds and low temperatures were employed. Furthermore, calcination or doping was not necessary to achieve such performance, since the asprepared catalysts exhibited good photocatalytic activity on removal of pollutants from water as the methyl orange and on hydrogen production.

博士<br>國立高雄應用科技大學<br>能源科技與化工材料研究所博士班<br>101<br>Titanium dioxide (TiO2) is promising and popular material in photocatalysts, because TiO2 has the special physical and chemical properties such as high surface area (in the form of nanotube), excellent photocatalytic activity under direct light irradiation, high stability, and low cost, especially its safety to humans and environment friendly. They are also easily produced by a simple and effective hydrothermal/solvothermal method. In this study, TiO2 photocatalysts are synthesized by a solvothermal process at a low temperature in a highly alkaline solution with a mixed solvent that is composed of organic solvents and water and calcined at different temperatures. The used organic solvents are alcohol and ketone solvents with low boiling points (< 100 oC), including methanol, ethanol, n-propanol, isopropanol, acetone and methyl ethyl ketone. The first step has studied that the titanate samples synthesized in the methanol-water volume ratios of 10:90, 20:80 and 30:70 were still highly effective adsorption of methylene blue dye; and the titania nanotubes formed at a calcination temperature of 300 °C using the methanol-water volume ratio of 30:70 showed the highest photocatalytic performance. The subsequent experiments used the volume ratio between water and organic solvents was 70:30 % of 70 ml of aqueous solution; The general solvothermal synthesis parameters such as temperature (130 oC), time (24 h), the concentration of NaOH solution (10M), post-treatment using distilled water to wash product to pH ~ 7, then the products were dried at 80 °C for 6 h and finally were calcined from 100 oC to 500 oC. The characteristics of samples are identified by powder X-ray diffraction (XRD), Raman spectra, transmission electron microscopy (TEM), specific surface area (BET), Fourier transform infrared spectroscopy (FTIR) and UV-Vis absorption spectroscopy. The as-prepared samples are tested by the photodegradation reaction of methylene blue (MB) dye under visible-light irradiation. The volumetric ratios of solvents and water, as well as the calcination temperature, affect the morphology, nanostructure, and photocatalytic performance. Especially, this study found that the importance of the protonation process in enhancing the formation of crystalline anatase phase for the case of methanol-thermal synthesis. The organic solvents play an important role in the formation of crystalline phases, which affects the photocatalytic activities of the final products. The results indicate that the TiO2 nanotubes synthesized with different solvents such as methanol, ethanol and methyl ethyl ketone still exhibit a high MB adsorbance and good performance in the photocatalytic reactions, much higher than that using the water solvent and TiO2-P25 powder.

碩士<br>國立東華大學<br>物理學系<br>102<br>Two-dimensional (2D) crystalline Bi2Te3 nanoplates were fabricated by a solvothermal method. Organic surfactants of polyvinylpyrrolidone (PVP). Bismuth (III) oxide (Bi2O3) and tellurium dioxide (TeO2) were used for sources of Bi and Te, respectively. The solvothermal method was processed in an autoclave at 200 ºC, and ethylene glycol (EG) and sodium borohydride (NaBH4) were exploited as solvent and reducing agent, respectively. During the solvothermal reaction, the 2D crystalline Bi2Te3 nanoplates were monodispersively synthesized. The structures and morphologies of the Bi2Te3 nanoplates were characterized via field-emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), energy dispersive spectrometry (EDS), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, X-ray diffractometry (XRD) and transmission electron microscopy (TEM). The FESEM images showed that the as-prepared Bi2Te3 nanoplates are hexagonal with edge lengths of ~100-150 nm. Chemical quantitative analysis from XPS verified that the Bi2Te3 nanoplates consist of only Te and Bi, and the elemental ratio of Bi:Te is 2:3. Room-temperature XRD results demonstrate the Bi2Te3 nanoplates to be a hexagonal phase in space group R-3m with lattice constants of a = b = 4.38 Å, c = 30.48 Å, α = β =90º, and γ = 120º. The selected area electron diffraction (SAED) patterns of the Bi2Te3 nanoplates are in good agreement with the XRD results. The variable XRD results demonstrates that the volumes of the 2D Bi2Te3 nanoplates expand and contract at low and high temperatures, indicating that thermal contraction occurs in the 2D Bi2Te3 nanoplates.

碩士<br>逢甲大學<br>材料科學與工程學系<br>105<br>During the past few decades, environmental pollution has become an ever-growing global issue. Bi2O3 is an excellent visible light activated photocatalyst with a direct band gap of 2.8 eV. The electron-hole pair separation under UV and visible light irradiation in photocatalyst has been reported to be enhanced by adding lanthanide, resulting in the increase in photocatalytic activity. In the present study, Bi2O3 powders with various Er concentrations (0, 0.5, 1.0, 3.0, 5.0 and 10.0 mol%) were prepared by solvothermal method, the effects of microstructural properties on photocatalytic activity of bismuth oxide (Bi2O3) were investigated as a function of lanthanide (Erbium) doping. The photocatalytic activity was evaluated by the degradation of methyl orange (MO) under visible light irradiation. The results revealed that the Er-doped Bi2O3 photocatalysts possessed a flowerlike structure with a higher specific surface area, and the visible light absorption ability of the Er-doped Bi2O3 photocatalysts was also enhanced as compared to that of the undoped Bi2O3. The 1 mole% Er3+-doped Bi2O3 exhibited a higher photocatalytic activity for the degradation of methyl orange under visible light irradiation. The doping structure was not only responsible for the high visible light absorption but also played a vital role in improving the separation of photo-induced electrons and holes.

碩士<br>義守大學<br>材料科學與工程學系<br>101<br>The preparation of oxide phosphors generally requires a high temperature heat treatment (> 1200oC), then, a high energy consumption is unavoidable and the seriously agglomerated powders are obtained. Recently, scientists attempt to overcome these problems by using different preparation methods, including coprecipitation, sol-gel method, and hydrothermal/solvothermal method. This study prepared three kinds of oxide phosphors by hydrothermal/solvothermal method, the microstructure and photoluminescence behavior were further explored in details. At first, the preparation of cerium doped yttrium aluminum garnet (YAG:Ce3+) are carried by different solvents and the addition of surfactants, the growth mechanism, luminescent properties, and thermal decay of YAG:Ce3+ were studied. The Y2O3:Eu3+ are prepared by co-precipitation method and solvothermal treatment in different solvents. The influence of precursors and solvents on the crystalline phase, powder morphology and luminescence properties are discussed. Finally, preparation of Zn2GeO4:Mn2+ is performed by hydrothermal method, the effect of the process, hydrothermal temperature/time, manganese content, surfactant and co-precipitation method on the crystalline phase, powder morphology and PL properties are investigated systematically. The YAG:Ce3+ phosphors were prepared by different solvents (Ethanol, ethylene glycol and ethylenediamine), only ethylenediamine can yield YAG phase. The increase of temperature and retention time improves the crystallinity of YAG phase. When the temperature is 270 oC and the retention time is 24 hrs, the YAG particles are nearly spherical and exhibit excellent dispersion state. Based on the results of this study, YAG crystal growth mechanism in ethylenediamine could be in-situ growth mechanism. The different surfactants can change significantly the powder morphology and PL behaviors. For Y2O3:Eu3+ system, it can be found that the different precipitations and solvents produce a variety of precursor particles with miscellaneous shapes and different crystal phases. However, the hydrothermal treatment does not be able to produce a cubic Y2O3:Eu3+ phase, but in the case of ethylenediamine, the PL intensity of resulted precursor powders is superior. Furthermore, after calcination at 900°C for 4hrs, the morphologies of these powder are not the same as ones before calcination, but it is found that the larger particles exhibit the better crystallinity, resulting in the higher PL intensity. For Zn2GeO4:Mn2+ system, the intermediate phase (ZnGeO3) does not exist at temperatures more than 120oC and sufficient retention time (>2hrs). As the temperature or time increases, the crystallinity of Zn2GeO4 increases. However, a good crystallinity does not enhance the photoluminescence properties of Zn2GeO4, this is due to the fact that the Zn2GeO4 phase is by defect emission. The addition of manganese make the emission of Zn2GeO4 move to the different wavelengths (530 nm). Besides, it is observed that the XRD peak intensity in (113)/ (410) planes and powder morphology has a significant relationship. If the Zn2GeO4:Mn2+ is prepared by deionized water, PL spectrum displays a wider wavelength range, so to improve their luminescent properties, we prepared Zn2GeO4:Mn2+ by different methods. The first method is the excess addition of manganese content. The second method is the addition of ethylenediamine. The third method is the combination of manganese and zinc ions by coprecipitation method. The second and third methods can successfully prepare Zn2GeO4:Mn2+ phosphors with the emission wavelength of 454nm, uniform size, excellent dispersion, oval shape, narrow wavelength range and high color purity.

碩士<br>國立高雄應用科技大學<br>化學工程與材料工程系<br>98<br>In this study, we have synthesized the bismuth telluride powder by hydrothermal and solvothermal method and investigated the thermoelectric properties. By using Te powder and BiCl3 as starting materials, EDTA as the chelating agent and NaBH4 as reducing agent for synthesis Bi2Te3 powder at different reaction temperature and time and investigation the physical properties of materials by XRD, SEM, TEM, etc. Preparation of bulk bismuth telluride by sintering and measure the Seebeck coefficient, thermal conductivity and resistivity. By the XRD analysis results, showed that Bi4Te3 transform into Bi2Te3 crystalline phase at hydrothermal reaction temperature of 140℃. Studies on the morphology and microstructure of the products from hydrothermal and solvothermal methods respectively, which displayed bar and irregular polygon by SEM and TEM. After uniaxial compressed and calcined at temperature of 300℃, the samples results of thermoelectric properties showed that hydrothermal reaction temperature at 180℃ for 24h and solvothermal reaction temperature at 180℃ for 16h, the 300K Seebeck coefficient is -143 μV / K, -230μV / K and thermal conductivity is 0.49W/mK, 0.41W/mK, respectively. Finally, obtain the doped carbon nanotubes commercial that improve the thermoelectric properties.

碩士<br>國立臺南大學<br>電機工程學系碩博士班<br>106<br>In this paper, we are mainly studying the synthesis of semiconductor material thin film CuIn0.7Ga0.3Se2. The quaternary phase CuIn0.7Ga0.3Se2 nano-ink was prepared by Solvothermal Refluxing Method with a simple, convenient and low-cost non-vacuum technology. Use elemental powder of copper (Cu), indium (In) , gallium (Ga) and selenium (Se) powder as material with stoichiometric ratio of 1 : 0.7 : 0.3 : 2 to add into the novel organic solvent D400 (polyetheramine) And then heats at 200-250℃ for 3-20 hours to discuss. First of all, we observe the phase change at different time, and then we know the reaction mechanism of Cu, In, Ga, Se and D400 (polyetheramine) by measurement further to deduce the reaction pathway of CuIn0.7Ga0.3Se2 and the effect of Ga at this experiment. We find Ga is the key to synthsis CuIn0.7Ga0.3Se2 and successfully synthesize pure phase CuIn0.7Ga0.3Se2. We think Ga is more difficult than In to join the reaction of synthesizing CuIn0.7Ga0.3Se2 because the activity difference and both of them are III at Periodic Table of Elements. It means they have similar chemical properties lead to competition. So we try to form CuGaSe2 to make Ga join the reaction first. But it is hard to synthsis a pure CuGaSe2 with Solvothermal process and low reaction temperature. We do our best to synthsis a pure CuGaSe2 and discuss his reaction¬ way. And then we mixture the pure CuGaSe2 and CuInSe2 with a 3: 7 ratio to selenized at 600~675OC to synthsis CuIn0.7Ga0.3Se2, improve its crystallinity and observe the characteristics.

碩士<br>國立高雄大學<br>應用化學系碩士班<br>102<br>The treatment of waste-water has been attracted much research attention in the past few years. Adsorption is one more economical and efficient method for water purification. Recently, tungsten oxide (WO3) has attracted attention of its unique adsorptive property. In this research, WO3-WO3‧0.33H2O with different shapes have been synthesized with a nonionic surfactant by solvothermal method. The products have been characterized by using XRD, SEM, FT-IR and Raman. By controlling the surfactant in the precursor solution or changing the reaction time, the product was changed from urchin-like WO3 to plate-like WO3-WO3‧0.33H2O. The surfactant played an important role in the growth of WO3-WO3‧0.33H2O. The adsorption ability of WO3-WO3‧0.33H2O has also been investigated. The results showed the WO3-WO3‧0.33H2O nanowires with high surface area (158.69 m2/g) and great adsorption ability (137.27 mg/g) were obtained. Tungsten oxide can be as a viable and excellent water treatment material to purify wastewater.