Magnesium hydroxide sulfate hydrate (MHSH) whiskers were synthesized via a hydrothermal reaction by using MgO as the reactant as well as the acid solution. The effects of the H2SO4 amount and reaction time at the same temperature were studied. In general, MHSH whiskers were prepared using MgSO4 in aqueous ammonia. In this work, to reduce the formation of impurities and increase the purity of MHSH, we employed a synthesis technique that did not require the addition of a basic solution. Furthermore, the pH value, which was controlled by the H2SO4 amount, acted as an important factor for the formation of high-purity MHSH. MgO was used as the raw material because it easily reacts in water and forms Mg+ and MgOH+ ions that bind with SO4 2- ions to produce MHSH. Their morphologies and structures were determined using X-ray diffraction (XRD) and scanning electron microscopy (SEM).

MoO3 metal oxide nanostructure was formed by hydrothermal synthesis, and a perovskite solar cell with an MoO3 hole transfer layer was fabricated and evaluated. The characteristics of the MoO3 thin film were analyzed according to the change of hydrothermal synthesis temperature in the range of 100 ℃ to 200 ℃ and mass ratio of AMT : nitric acid of 1 : 3 ~ 15 wt%. The influence on the photoelectric conversion efficiency of the solar cell was evaluated. Nanorod-shaped MoO3 thin films were formed in the temperature range of 150 ℃ to 200 ℃, and the chemical bonding and crystal structure of the thin films were analyzed. As the amount of nitric acid added increased, the thickness of the thin film decreased. As the thickness of the hole transfer layer decreased, the photoelectric conversion efficiency of the perovskite solar cell improved. The maximum photoelectric conversion efficiency of the perovskite solar cell having an MoO3 thin film was 4.69 % when the conditions of hydrothermal synthesis were 150 ℃ and mass ratio of AMT : nitric acid of 1 : 12 wt%.

In the present work, we synthesize nano-sized ZnO, SnO2, and TiO2 powders by hydrothermal reaction using metal chlorides. We also examine the energy-storage characteristics of the resulting materials to evaluate the potential application of these powders to dye-sensitized solar cells. The control of processing parameters such as pressure, temperature, and the concentration of aqueous solution results in the formation of a variety of powder morphologies with different sizes. Nano-rod, nano-flower, and spherical powders are easily formed with the present method. Heat treatment after the hydrothermal reaction usually increases the size of the powder. At temperatures above 1000oC, a complete collapse of the shape occurs. With regard to the capacity of DSSC materials, the hydrothermally synthesized TiO2 results in the highest current density of 9.1 mA/cm² among the examined oxides. This is attributed to the fine particle size and morphology with large specific surface area.

Transition-metal oxide semiconductors have various band gaps. Therefore, many studies have been conducted in various application fields. Among these, methods for the adsorption of organic dyes and utilization of photocatalytic properties have been developed using various metal oxides. In this study, the adsorption and photocatalytic effects of WO3 nanomaterials prepared by hydrothermal synthesis are investigated, with citric acid added in the hydrothermal process as a structure-directing agent. The nanostructures of WO3 are studied using transmission electron microscopy and scanning electron microscopy images. The crystal structure is investigated using X-ray diffraction patterns, and the changes in the dye concentrations adsorbed on WO3 nanorods are measured with a UV-visible absorption spectrophotometer based on Beer-Lambert’s law. The methylene blue (MB) dye solution is subjected to acid or base conditions to monitor the change in the maximum adsorption amount in relation to the pH. The maximum adsorption capacity is observed at pH 3. In addition to the dye adsorption, UV irradiation is carried out to investigate the decomposition of the MB dye as a result of photocatalytic effects. Significant photocatalytic properties are observed and compared with the adsorption effects for dye removal.

YSZ (Yttria-stabilized zirconia) is a ceramic material that is used for electronic and structural materials due to its excellent mechanical properties and specific electrical characteristics according to the Yttrium addition. Hydrothermal synthesis has several advantages such as fine particle size, uniform crystalline phase, fast reaction time, low process temperature and good dispersion condition. In order to synthesize YSZ nanoparticles with high crystallinity, hydrothermal synthesis was performed at various concentrations of NaOH. The hydrothermal process was held at a low temperature (100 °C), with a short process time (2,4,8 hours); the acidity or alkalinity of solution was controlled in a range of pH 2~12 by addition of NaOH. The optimum condition was found to be pH 12, at which high solubility levels of Y(OH) and Zr(OH) were reported. The synthesized nano powder showed high crystallinity and homogenous composition, and uniform particle size of about 10 nm.

금속산화물 반도체 중 하나인 산화아연은 인체에 무해하고 친환경적이며, 우수한 화학적, 열 적 안정성의 특성을 지니며 3.37 eV의 넓은 밴드갭 에너지와 60 meV의 높은 엑시톤 바인딩 에너지로 인해 태양전지, 염료페기물의 분해, 가스센서 등 다양한 분야에 응용이 가능한 물질이다. 산화아연은 입 자 형상 및 결정성의 변화에 따라 광촉매 활성이 변하게 된다. 따라서, 다양한 실험변수와 첨가제를 사 용하여 입자를 합성하는 것이 매우 중요하다. 본 논문에서는 마이크로파 수열합성법을 사용하여 산화아연을 합성하였다. 전구체로는 질산아연을 사 용하였고, 수산화나트륨을 사용하여 용액의 pH를 11로 조정하였다. 첨가제로는 계면활성제인 에탄올아 민, 세틸트리메틸암모늄브로마이드, 소듐도데실설페이트, 솔비탄모노올레이트를 첨가하였다. 합성된 입자 는 별모양, 원추형, 씨드형태, 박막형태의 구형의 형상을 보였다. 합성된 산화아연의 물리・화학적 특성 은 XRD, SEM, TGA을 통하여 확인하였고, 광학적 특성은 UV-vis spectroscopy, PL spectroscopy, Raman spectroscopy으로 확인하였다.

본 연구에서는 고순도의 모데나이트(Mordenite) 입자를 합성하기 위하여 천연 제올라이트를 시드로 사용하여 시 드의 농도 및 수열합성 시간에 따른 천연 제올라이트 시드가 합성에 미치는 영향을 고찰하였다. 그 결과 시드가 입자의 형성 에 큰 영향을 끼치는 것을 확인할 수 있었고 시드를 3 g/100 g batch 주입하여 140°C에서 72시간 동안 수열합성을 진행하였 을 때 1-2 μm 사이즈의 고순도 모데나이트 입자를 합성할 수 있었다. 이를 통해 모데나이트 입자의 성장 기구를 규명할 수 있었으며, 모데나이트 입자 형성에 있어 시드는 첫째, 구형 모데나이트 전구체 형성 자리 공급의 역할과, 둘째 모데나이트 원 료 물질 소스 역할을 한다는 것을 알 수 있었다. 합성된 모데나이트 입자의 가스 흡착량 분석 결과 CO2 기체의 흡착량이 97.19 mg/g로 다른 가스들에 비해 비교적 높은 흡착성능을 보였으며, CO2/H2의 선택도가 가장 우수한 것으로 나타났다. 따라 서 이러한 결과들을 바탕으로 용도에 맞는 고순도 상의 모데나이트 입자를 합성할 수 있음을 확인하였고 보다 낮은 가격으로 우수한 분리성능을 갖는 분리막 소재개발에 활용할 수 있을 것이라 판단된다.

본 연구에서는 고순도의 모데나이트 입자를 합성하기 위하여 천연 제올라이트를 시드로 사용하여 시드 농도 및 수열합성 시간에 따라 시드가 미치는 영향 을 고찰하였다. 시드를 3 g/100g batch 주입하여 140°C에서 72시간 동안 수열 합성 하였을 때 1-2 μm 사이즈의 고순도 모데나이트 입자를 안정적으로 합성할 수 있었다. 이를 통해 천연 제올라이트 시드는 모데나이트 입자의 성장에서 구형 모데나이트 전구체 형성 자리를 공급하고 모데나이트 원료 물질 소스 역 할을 한다는 것을 알 수 있었다. 이러한 결과들을 바탕으로 용도에 맞는 고순도 의 모데나이트 입자를 합성할 수 있음을 확인하였고 천연제올라이트를 사용함으로써 낮은 가격으로 우수한 성능을 갖는 소재개발에 활용할 수 있을 것이라 판단된다.

In this work, uniform and nanosize(75nm) silicalite-1 crystals was hydrothermally synthesized by using 9TPAOH:0.16NaOH:25Si:495H2O solution at 80 ℃. They were applied as seed in the secondary growth process for preparing silicalite-1 membrane by template-free method. The highest ethanol/water separation factor of 119 with flux 0.58kg/m². Furthermore, these membranes (nano seed, template free silicalite-1 membrane) exhibit high permselectivity of He over SF6(123), and small gas permeation mechanism and Knudsen diffusion studies suggest that the membranes contain negligible intercrystalline or non-zeolite pores.

Hydroxyapatite (HA), which is an important calcium phosphate mineral, has been applied in orthopedics, dentistry, and many other fields depending upon its morphology. HA can be synthesized with different morphologies through controlling the synthesis method and several parameters. Here, we synthesize various morphologies of HA using two simple methods: hydrothermal combustion and solution combustion. The phase purity of the synthesized HA is confirmed using X-ray diffractometry. It demonstrates that pure phased hydroxyapatite can be synthesized using both methods. The morphology of the synthesized powder is examined using scanning electron microscopy. The effects of pH and temperature on the final powder are also investigated. At 140 oC, using the hydrothermal method, nano-micro HA rods with a hexagonal crystal structure can be synthesized, whereas using solution combustion method at 600 oC, a dense cubic morphology can be synthesized, which exhibits monoclinic crystal structures.

Porous metallic glass compact (PMGC) are developed by electro-discharge sintering (EDS) process of gas atomized Zr41.2Ti13.8Cu12.5Ni10Be22.5 metallic glass powder under of 0.2 kJ generated by a 450 μF capacitor being charged to 0.94 kV. Functional iron-oxides are formed and growth on the surface of PMGCs via hydrothermal synthesis. It is carried out at 150oC for 48hr with distilled water of 100 mL containing Fe ions of 0.18 g/L. Consequently, two types of iron oxides with different morphology which are disc-shaped Fe2O3 and needle-shaped Fe3O4 are successfully formed on the surface of the PMGCs. This finding suggests that PMGC witih hydrothermal technique can be attractive for the practical technology as a new area of structural and functional materials. And they provide a promising road map for using the metallic glasses as a potential functional application.

석탄회를 NaOH로 용융시킨 후 수열 처리에 의하여 제올라이트 A를 합성하였다. NaOH/석탄회의 비, 용융 온도, NaAlO2의 첨가량, 수열 처리 온도 및 시간이 생성된 제올라이트의 종류와 결정도에 미치는 영향에 대하여 연구하였다. 결정도가 높은 제올라이트의 생성에 필요한 최적의 NaOH/석탄회의 중량비는 1.2, 최적의 용융 온도는 550℃이었다. 용융된 석탄회로부터 Si4+ 와 Al3+의 용출은 교반 시간의 영향을 받지 않았다. 생성된 제올라이트의 형태는 첨가한 NaAlO2의 영향을 받는 것으로 나타났다. 적은 양의 NaAlO2를 첨가하면 제올라이트 X가 생성되나 NaAlO2의 양이 증가하면 단일상의 제올라이트 A가 생성되었다. 수열처리 시간과 온도가 증가하면 제올라이트 A는 hydroxysodalite로 변화하였다. 승온 속도를 낮춰 반응 온도까지의 도달시간을 증가시키면 결정도가 좋은 제올라이트 A를 얻을 수 있었다.

In this work, uniform and nanosize(75nm) silicalite-1 crystals was hydrothermally synthesized by using 9TPAOH:0.16NaOH:25Si:495H2O solution at 80 ℃. They were applied as seed in the secondary growth process for preparing silicalite-1 membrane by template-free method. And silicalite-1 membrane, which was coated by nano-size seed, showed a high EtOH/H2O separation factor of 128. The high separation factor could be explained by the role of nanosize seed. The application of nanosize seed successfully retarded the formation of interfacial voids between silicalite-1 grains. Therefore, it could be concluded that template-free hydrothermal process can produce silicalite-1 membrane with well performance.

Cubic mesocrystal CeO2 was synthesized via a hydrothermal method with glutamic acid (C5H9NO4) as a template. The XRD pattern of a calcined sample shows the face-centered cubic fluorite structure of ceria. Transmission electron microscopy (TEM) and the selected-area electron diffraction (SAED) pattern revealed that the submicron cubic mesocrystals were composed of many small crystals attached to each other with the same orientation. The UV-visible adsorption spectrum exhibited the red-shift phenomenon of mesocrystal CeO2 compared to commercial CeO2 particles; thus, the prepared materials show tremendous potential to degrade organic dyes under visible light illumination . With a concentration of a rhodamine B solution of 20 mg/L and a catalyst amount of 0.1 g/L, the reaction showed higher photocatalytic performance following irradiation with a xenon lamp (≥ 380 nm). The decoloring rate can exceed 100% after 300 min.

Nano Pd spot-coated active carbon powders were synthesized by a hydrothermal-attachment method (HAA) using PVP capped Pd colloid in a high pressure bomb at , 450 psi, respectively. The PVP capped Pd colloid was synthesized by the precipitation-redispersion method. PVP capped Pd nano particles showed the narrow size distribution and their particle sizes were less than 8nm in diameter. In the case of nano Pd-spot coated active carbon powders, nano-sized Pd particles were adhered in the active carbon powder surface by HAA method. The component of Pd was homogeneously distributed on the active carbon surface.

Fe doped TiO2 nanoparticles were prepared under high temperature and pressure conditions by mixture of metal nitrate solution and TiO2 sol. Fe doped TiO2 particles were reacted in the temperature range of 170 to 200˚C for 6 h. The microstructure and phase of the synthesized Fe doped TiO2 nanoparticles were studied by SEM (FE-SEM), TEM, and XRD. Thermal properties of the synthesized Fe doped TiO2 nanoparticles were studied by TG-DTA analysis. TEM and X-ray diffraction pattern shows that the synthesized Fe doped TiO2 nanoparticles were crystalline. The average size and distribution of the synthesized Fe doped TiO2 nanoparticles were about 10 nm and narrow, respectively. The average size of the synthesized Fe doped TiO2 nanoparticles increased as the reaction temperature increased. The overall reduction in weight of Fe doped TiO2 nanoparticles was about 16% up to ~700˚C; water of crystallization was dehydrated at 271˚C. The transition of Fe doped TiO2 nanoparticle phase from anatase to rutile occurred at almost 561˚C. The amount of rutile phase of the synthesized Fe doped TiO2 nanoparticles increased with decreasing Fe concentration. The effects of synthesis parameters, such as the concentration of the starting solution and the reaction temperature, are discussed.

Pure zirconia and x mol% calcia partially stabilized zirconia (x = 1.5, 3, and 8) nanopowders were synthesized by hydrothermal method with various reaction temperatures for 24 hrs. The precipitated precursor of pure zirconia and x mol% calcia doped zirconia was prepared by adding NH4OH to starting solutions; resulting sample was then put into an autoclave reactor. The optimal experimental conditions, such as reaction temperatures and times and amounts of stabilizer CaO, were carefully studied. The synthesized ZrO2 and x mol% CaO-ZrO2 (x = 1.5, 3, and 8) powders were characterized by XRD, SEM, TG-DTA, and Raman spectroscopy. When the hydrothermal temperature was as low as 160˚C, pure ZrO2 and x mol% CaO-ZrO2 (x = 1.5 and 3) powders were identified as a mixture of monoclinic and tetragonal phases. However, a stable tetragonal phase of zirconia was observed in the 8 mol% calcia doped zirconia nanopowder at hydrothermal temperature above 160˚C. To observe the phase transition, the 3 mol% CaO-ZrO2 and 8 mol% CaO-ZrO2 nanopowders were heat treated from 600 to 1000˚C for 2h. The 3 mol% CaO-ZrO2 heat treated at above 1000˚C was found to undergo a complete phase transition from mixture phase to monoclinic phase. However, the 8 mol% calcia doped zirconia appeared in the stable tetragonal phase after heat treatment. The result of this study therefore should be considered as the preparation of 8 mol% CaO-ZrO2 nanopowders via the hydrothermal method.

본 연구에서는 올레산을 표면개질제로 사용하여 수열법을 통해 수산화 마그네슘을 합성하였다. 수산화 마그네슘은 알카리 조건에서 올레인산과의 반응을 통해 표면 개질된 마이크로 크기의 플레이크 형상을 갖는다. 수열합성에서 수산화 마그네슘 입자 생성의 조건은 pH, 온도 그리고 반응시간이 표면개질과 입자 형상의 주요 변수임을 확인하였다. 생성된 수산화 마그네슘 입자는 FE-SEM, XRD, FT-IR 그리고 TGA를 통해 확인하였다. 유기 용매 내에서의 분산성의 확인은 개질되지 않은 수산화 마그네슘과의 침전 테스트 비교를 통해 확인하였다.

Ag spot-coated Cu nanopowders were synthesized by a hydrothermal-attachment method (HA) using oleic acid capped Ag hydrosol. Cu nano powders were synthesized by pulsed wire exploding method using 0.4 mm in diameter of Cu wire (purity 99.9%). Synthesized Cu nano powders are seen with comparatively spherical shape having range in 50 nm to 150 nm in diameter. The oleic acid capped Ag hydrosol was synthesized by the precipitation-redispersion method. Oleic acid capped Ag nano particles showed the narrow size distribution and their particle size were less than 20 nm in diameter. In the case of nano Ag-spot coated Cu powders, nanosized Ag particles were adhered in the copper surface by HAA method. The components of C, O and Ag were distributed on the surface of copper powder.