• Applied Chemistry for Engineering
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• v.26 no.6
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• pp.681-685
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• 2015

In this study, pure $BiVO_4$ powder and metal-doped $M-BiVO_4$ (M = Mg, Cu) powder, well known as thermochromic materials, were prepared from a mixed aqueous solution of bismuth nitrate ($Bi(NO_3)_3$) and ammonium vanadate ($NH_4VO_3$) in autoclave by hydrothermal method. The crystal structure, microstructure, and thermochromic property of samples were analyzed using FE-SEM, FT-IR, XRD, DSC, UV-Vis-NIR spectroscopy and colorimeter. When heating samples above phase transition temperature, the color of $M-BiVO_4$ (M = Mg, Cu) sample was thermally changed more clearly than that of using only pure $BiVO_4$ sample.

• Korean Chemical Engineering Research
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• v.58 no.2
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• pp.313-318
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• 2020

Bi₂WO₆ were successfully synthesized using EGME, GL, EG and water as solvents by a conventional hydrothermal method. They were characterized by XRD, DRS, BET and SEM and we also investigated the photocatalytic activity of these materials for the decomposition of Rhodamin B under visible light irradiation. The XRD results revealed the successful synthesis well-crystallized Bi₂WO₆ crystals with Aurivillius structure when EGME and EG are used as solvents. In addition, the well-crystallized Bi₂WO₆ crystals showed the flower-like structure. The Bi₂WO₆ catalysts prepared at 180 ℃ using EGME as a solvent showed the highest photocatalytic activity. The Bi₂WO₆ catalysts prepared at mole ratio of H₂O/EGME more than 50% showed high photocatalytic activity.

• Korean Chemical Engineering Research
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• v.46 no.6
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• pp.1029-1038
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• 2008

Transition-metal-oxide-incorporated hydrotalcites were prepared by hydrothermal reaction of their synthetic mixtures containing precursors of transition metal oxides and their properties of nitrogen dioxide adsorption was investigated. The dispersion of transition metal oxides on the hydrotalcites and the amount and the state of nitrogen dioxide adsorbed on them were examined by using XRD, SEM, XPS, nitrogen adsorption, a gravimetric adsorption system, FT-IR spectroscopy and temperature programmed desorption techniques. Transition metal oxides were mainly incorporated on their surface and the incorporation of iron and nickel oxides to the hydrotalcites increased their adsorption amounts of nitrogen dioxide. The dispersion of iron oxide on the hydrotalcites was effective in increasing the amount of nitrogen dioxide adsorption, while too much amount of iron oxide incorporation reduced the amount of nitrogen dioxide adsorption due to masking of surface basic sites by agglomerated iron oxide. Although the incorporation of iron oxide to the hydrotalcites lowered the adsorption strength of nitrogen dioxide, the incorporation of it with a proper amount enhanced the amount of nitrogen dioxide adsorption and the stability against the hydrothermal treatment.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.26 no.5
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• pp.175-180
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• 2016

ZnO nanoparticles were synthesized by aqueous preparation routes of a precipitation and a hydrothermal process. In the processes, the powders were formed by mixing aqueous solutions of Zn-nitrate hexahydrate ($Zn(NO_3)_2{\cdot}6H_2O$) with NaOH aqueous solution under controlled reaction conditions such as Zn precursor concentration, reaction pH and temperature. Single ZnO phase has been obtained under low Zn precursor concentration, high reaction pH and high temperature. The synthesized particles exhibited flakes (plates), multipods or rods morphologies and the crystallite sizes and shapes would be efficiently controllable by changing the processing parameters. The hydrothermal method showed advantageous features over the precipitation process, allowing the precipitates of single ZnO phase with higher crystallinity at relatively low temperatures below $100^{\circ}C$ under a wider pH range for the Zn precursor concentration of 0.1~1 M.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.2
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• pp.1555-1562
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• 2015

Metal oxide semiconductors have been applied in several areas, such as solar cells, sensor, optical elements and displays, due to the high surface area, unique electrical and optical characteristics. Zinc oxide among the metal oxide has excellent physicochemical properties. Zinc oxide is a n-type semiconductor with a wide direct transition band gap of 3.37 eV at room temperature and large exciton binding energy of 60 meV. Cation-doped zinc oxide studies were conducted to complement the electrical and optical characteristics. In this paper, Al-doped ZnO was synthesized by hydrothermal synthesis using microwaves. ZnO was synthesized by adjusting the precursor ratio and using different dopants. The optimal ZnO synthesis conditions for crystal shape and optical properties were determined. The optical properties of aluminum doped zinc oxide were then examined by SEM, XRD, PL, UV-vis absorbance spectrum, and EDS.

• Korean Journal of Crystallography
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• v.18 no.1_2
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• pp.16-20
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• 2007

Under hydrothermal conditions, a 2-dimensional copper(I) coordination polymer [$Cu_2Cl_2$(4,4'-dipyen)] (1) was prepared from [$Cu(OAc)_2]{\cdot}H_2O$, 4,4'-dipyen, and KCl. In polymer 1, copper atoms are linked by the 4,4'-dipyen ligands approximately along the b-axis and are also linked by the chloro ligands approximately along the a-axis to form a 2-D layer, a network of rectangles.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.03a
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• pp.198-198
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• 2003

본 연구는 활성알루미나, 베이어라이트, 미세결질베마이트, 슈도베마이트, 깁사이트 등의 수산화알루미늄을 각각 출발물질로 하여 알파알루미나를 제조하였고 출발물질에 따라 알파알루미나로의 전이온도와 결정성의 차이 및 비표면적, 밀도를 관찰하였다 베이어라이트는 상온에서 5시간 동안 수화반응 시켜 제조하였고, 미세결정질베마이트는 활성알루미나를 수열처리 하여서 제조하였다. 실험결과 활성알루미나, 베이어라이트, 슈도베마이트가 깁사이트와 미세결정질베마이트보다 낮은 온도에서 알파알루미나로의 전이가 일어났음을 알 수 있었고 알파알루미나의 결정성에서는 슈도베마이트가 가장 높은 것을 알 수 있었다. 그리고 130$0^{\circ}C$에서는 미세결정질 베미이트를 제외한 모든 출발물질이 알파알루미나로 전이되었음을 확인할 수 있었다.

• Journal of the Korean Ceramic Society
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• v.31 no.2
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• pp.117-128
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• 1994

Hematite particles were obtained by hydrothermal reaction of ferric hydroxide in the presence of small amount of citric acid which is acted as crystal growth controller. The effects of hydrothermal reaction condition son the morphology and crystal structure of powder were investigated using X-ray, TEM and FT-IR. Ellipsoidal or rectangular hematite particles were formed in the range of pH 10.75~11.75 as initial basicity of reactants and 3$\times$10-5 ~9$\times$10-5 mol as citric acid content. Crystallization of hematite was inhibited in the range of pH9. 0~10.5 and above citric acid content of $1.5\times$10-4 mol. Hematite particle length and aspect ratio were decreased gradually with increasing of citric acid content. Hematite particles formed at 14$0^{\circ}C$ exhibited particle properties with the length of 0.7 ${\mu}{\textrm}{m}$ and aspect ratio of 8. Hematite particles having a good acicular-type were not obtained above 22$0^{\circ}C$.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.3 no.1
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• pp.37-44
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• 1993

Calcia stabilized zirconia polycrystal (Ca-TZP) powders synthesized by hydrothermal treatment was sintered at a temperature range of $1200^{\circ}C~1400^{\circ}C$ and investigated the properties of sintered body and the behaviors of isothermal phase transformation. The sintered bodies of Ca-TZP were shown the density of about 97% and the average mean tetragonal grain size of about $0.1~0.25{\mu}m$. Also, Ca-TZP specimen was more stable during aging at $250^{\circ}C$ than that of Y-TZP ceramics.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.461-464
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• 2005

As the research on the development of the lightweight concrete block by the hydro-thermal synthetic reaction mixed with the calcareous material and bottom ash that is used less among siliceous material, we studied on the physical and chemical characteristics in the changes of hydro-thermal synthetic reaction of lightweight concrete block compounded with the PP fiber to increase flexural toughness and to prevent fragility failure. The results of the experiment are as follow. According to the increase of hydro-thermal synthetic reaction and the fiber content, compressive and flexural strength increased. Despite the changes of the hydro-thermal synthetic reaction time, tobermorite was produced on each of the specimens similarly. However, the phase of tobermorite was changed in accordance with the changes of time. Also, $CaCo_{3}$ appeared on the surface of the 9 hour hardened specimen.