Papers by Keyword: Hydrothermal Reaction

Abstract: The worm-like morphology of silver sulfide (Ag₂S) was successfully prepared via hydrothermal reaction at 150°C by using silver nitrate (AgNO₃) and thioacetamide(CH₃CSNH₂) as both the sliver sources and sulfur sources, β-cyclodextrin as the template agent, and water as the solvent. The worm-like of Ag₂S are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), x-ray diffraction (XRD), x-ray photoelectronspectroscopy (XPS), energy dispersivex-ray (EDX), high-resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SEAD). Ultraviolet-visible spectra (UV-vis) and photoluminescencespectroscopy (PL) were used in an optical study of the products. The results showed that the existence of β-cyclodextrin is crucial to the formation of worm-like Ag₂S, and the optoelectronics test results showed that the sample have a broad absorption in ultraviolet and visible light region.

Abstract: Hydroxyapatite (HA) is a well-known biocompatible material which is widely used in orthopedic and dental applications. Because its chemical structure is similar to the human bone so it is compatible to use as a based materials in drug delivery system for treatment of bone infection diseases. In this research we focused on fabrication of HA sphere shape by three dimension printing using calcium sulphate hemihydrate (CaSO₄·0.5H₂O) as a starting material, then the as-three dimension printed CaSO₄·0.5H₂O spheres were hydrothermally treated in 1M disodium hydrogenphosphate (Na₂HPO₄) at 100°C-180°C for 2-8 hr. The reaction was taken place and the conversion of CaSO₄·0.5H₂O was gradually changed to Ca₁₀(PO₄)₆(OH)₂. Phase analysis by X-ray diffraction indicated that monetite (CaHPO₄) was coexisted with HA when hydrothermally treated at pH 9 at low reaction temperature (<180°C). When the pH of 1M Na₂HPO₄ was adjusted to pH 11, 180°C for 6 hr, the as-three dimension printed calcium sulphate hemihydrate spheres were completely converted to HA spheres without any destruction of the sphere shape. This is confirmed that hydrothermal reaction could enhance the phase conversion of HA and the conversion time was four times faster than the normal conversion.

Abstract: Hydroxyapatite powder has been synthesized from eggshell waste using a simple hydrothermal synthesis. The process involved drying and thermal decomposition of eggshell into calcium oxide followed by a hydrothermal reaction at a temperature of as low as 90°C with ammonium di-hydrogen phosphate and water. The produced hydroxyapatite powder is extraordinarily fine with nanosize primary particles. The yield of conversion is high, ca. 90%. Hydroxyapatite pure phase can be maintained until calcination of below 900°C, at which β-tricalcium phosphate phase started to appear to transform into biphasic calcium phosphate. Its high purity as proved by XRD shown that the product fulfills medical requirement. The present invention provides an environmentally beneficial and straightforward method of producing hydroxyapatite for bone implant materials using eggshell waste.

Abstract: In this paper, the conversion of biomass-derived glycolide to ethylene glycol over Cu was investigated. As a result, Cu showed significant catalytic role for the conversion of glycolide into ethylene glycol compared to other catalysts, such as Ni and Mo. A 24.3% yield of ethylene glycol was achieved in the process. The possible formation pathway of ethylene glycol from glycolide over Cu under hydrothermal conditions was proposed.

Abstract: In these days, autoclaved aerated concrete research points to the utilization of alternative raw materials such as metakaoline. An effort is made to improve the mechanical and related heat-insulation properties of the products without significant change of present technology and price. This work studies the effect of metakaoline, as an alternative raw material to Portland cement, on final properties of autoclaved aerated concrete, especially the effect on the volume weight and compressive strength. Quantitative and qualitative mineralogical composition, especially the presence and the amount of Tobermorite and Xonotlite were observed by XRD and TG-DTA-EGA methods.

Abstract: Lizardite were synthesized by hydrothermal reaction in an Fe³⁺ doped solution/environment using nanometer SiO₂ and MgO as precursors. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FTIR). The results show that: the synthetic samples are lizardite with a thickness ranging from 60 nm to 200 nm in the temperature range 200°C~230°C.

Abstract: Rod-shaped β-FeOOH was synthesized through a well controlled hydrothermal reaction of FeCl₃ and NH₂CONH₂. By varying the preparatory conditions such as NH₂CONH₂ concentration and reaction parameter we could establish precise control on the morphology of the sample. X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and selected area electron diffraction (SAED) were used to characterize the as-prepared products. The results showed the aspect ratio and mean size of theβ-FeOOH nanorods was achieved systematic control by regulating the concentration of urea. When the experimental time increased to 96h, the morphology of the resulting β-FeOOH changed from rod to nanocubes. Furthermore, the resulting rod-shaped iron hydroxides were transformed into pseudocube α-Fe₂O₃ by increasing the synthesis temperature at 160°C.

Abstract: The conversion of cellulose under the hydrothermal condition was studied in an autoclave reactor. The reaction factors, such as oxygen supply and alkaline concentration was clearly investigated. A highest formic acid yield of about 27% was obtained. And also, other organic acid production was greatly produced. Besides formic acid, glycolic acid, acetic acid and lactic acid were also produced in alkaline oxidation of cellulose, with a total organic acid of up to 50%. It shows great potential for organic acid production from hydrothermal oxidation of cellulose.

Abstract: In this paper, hydrothermal conversion of cellulose into organic acids in the presence of metal oxides was investigated. The results showed metal oxides could enhance the conversion of cellulose into organic acids. The total yields of organic acids of 41.6% with Al₂O₃ 2.0 mmol from cellulose was achieved at 300 oC for 1 min, NaOH 2.5 M and water 2 mL. The plausible mechanism for the hydrothermal conversion of cellulose into organic acids was also discussed.

Abstract: Well-crystallised nanozeolite P has been synthesized from coal fly ash by combined method of alkaline-fusion and hydrothermal reactions. The influence of preparation parameters, such as the proportion of fly ash/NaOH, the hydrothermal reaction temperature and time on the reaction products were investigated by XRD and FESEM. Results indicated that, the optimum conditions for fabrication of a single phase of zeolite P were the mass ratio of fly ash/ NaOH =1/1, fusion temperature at 550°C and hydrothermal temperature at 100°C for 48h .The average crystallite sizes of the zeolite samples are 29.4nm. The obtained products show crystal morphology heterogeneity comprised by various euhedral forms.