Papers by Keyword: Hydrothermal Method

Abstract: Zinc oxide-titanium dioxide (ZnO-TiO₂) have been successfully synthesized by hydrothermal method. ZnO-TiO₂ nanocomposite were prepared at different molar ratio 100:0, 100:0, 30:70, 50:50 and 70:30. The objective of this research is to determine the effect of molar ratios on the structural and optical properties of ZnO-TiO₂ nanocomposite. The samples were analyzed using X-ray diffraction (XRD) analysis, Field-emission scanning electron microscopy (FESEM) and UV-Vis spectroscopy. Based on the XRD results, it is revealed that ZnO-TiO₂ nanocomposite consists of hexagonal wurtzite structure of ZnO and mixed of anatase/ rutile phase of TiO₂. FESEM images showed ZnO in rod-like structure while TiO₂ is formed in nanoparticle. ZnO-TiO₂ composite is formed combination of rod-like and nanoparticles. UV-Vis spectra showed that all samples exhibited good absorption towards UV region. The calculated energy band gaps of ZnO-TiO₂ composite are 2.92 eV which is slightly smaller compared to bulk ZnO and TiO₂. The tuning energy band gaps of ZnO-TiO₂ composite samples is a good indicator for use in catalytic activities.

Abstract: Zinc oxide (ZnO) had been interested today because of their unique and good properties in electronic devices. ZnO nanostructured was synthesized via hydrothermal method by varied the pH value from 7, 8, 9, 10 and 11. The effect of different pH values from 7, 8, 9, 10 and 11 was changed the morphological, structure and optical properties. The samples characterized with Scanning Electron Microscope (SEM), X-Ray Diffraction (XRD) and Ultraviolet- Visible (UV-Vis) spectroscopy. SEM is to observe the morphology images of ZnO nanostructure grains. XRD revealed the detail information on the crystallographic structure and phase formation of the materials. Lastly, UV-vis spectroscopy is to measure the band gap of optical semiconductor. From SEM result, it had shown that the hexagonal nanorods was obtained at pH 7 and pH 11 whereas nanorods is obtain at pH 8, 9 and 10. XRD revealed that the ZnO nanostructure exhibits the hexagonal wurtzite structure and the average crystallite size of ZnO nanoparticle was calculated. UV-Vis spectroscopy shows the absorption of ZnO and band determination from Tauc Plot relation plotter using UV-vis. The resulted show the pH values affect the nanostructure growth of zinc oxide semiconductor properties.

Abstract: In this work, single phase Bismuth Ferrite, BiFeO₃ was successfully synthesized by using hydrothermal method assisted with different weight (0.24 g, 0.36 g and 0.48 g) of Chitosan. Potassium hydroxide (KOH) were used as a mineralizer during the synthesis process for the precipitation. The samples were characterized for different properties such as structural and optical properties, and were then compared with previous works. The X-ray diffraction data for all the samples showed that the samples had a single phase belonging to R3c space group with perovskite rhombohedral structure at diffraction angle 32.0° to 32.5° even though the slight presence of secondary phase at diffraction angle 28° was detected. Scanning electron microscope revealed a decrement in particle size as the weight of Chitosan increased indicating effective used of Chitosan in controlling the agglomeration of the particles. All samples BiFeO3 assisted with and without Chitosan showed significant enhancement in energy gap where the obtained results showed a small energy gap values ranging from ~1.22 eV to ~1.88 eV determined from UV-vis absorbance characterization. Therefore, by the addition of Chitosan, the properties of BiFeO₃ such as structural and optical have changed as well as preventing from the particle to agglomerate.

Abstract: This work explores the potential of adsorption of Pb2+ by hydrothermally synthesized alumina. In comparison to other heavy ion removal techniques, adsorption is preferred in the current study as it has the edge of ease of operation and environment friendly characteristics. Synthesis of high surface area alumina whiskers was achieved by hydrothermal route which were subsequently employed for the active adsorption of lead ions. AACH (Ammonium Aluminum Carbonate Hydroxide), used as precursor for alumina, was calcined at three different temperatures i.e. 700, 900 and 1100 °C to form alumina whiskers. These whiskers were characterized by XRD, SEM, BET and FTIR. Various adsorption parameters such as contact time, pH, initial metal concentration were studied for lead ions. Maximal removal efficiency was obtained for the specimen having pH 4 and calcined at 700 °C for 60 minutes. Kinetic data was best described by pseudo second order model, whereas the adsorption equilibrium data obeyed the Langmuir adsorption isotherm model.

Abstract: Dye-sensitized solar cells have better development prospects than silicon cells, and their main structural composition of nanoporous semiconductor films is particularly important. It is the tin dioxide film, and the effect of preparing tin oxide film on dye-sensitized solar cells under different conditions is studied. In this paper, the SnO₂ powder was prepared by hydrothermal method, and the experiment was studied by controlled variable method. The properties of the obtained tin dioxide powder were characterized by SEM and three-dimensional ultra-depth microscope and XRD. The XRD diffraction peak is shown as tetragonal phase rutile type SnO₂, With the increase of the concentration of tin tetrachloride solution, the coarser the particle size of the tin oxide crystal in the film, the more complicated the surface morphology, so that the specific surface area of the film is larger. At 0.1 mol/L, the surface of the film is a porous structure in the form of a loose sheet is presented. After analyzing the surface microstructure and flatness of the tin dioxide film, it can be concluded that the effect of salt concentration on the specific surface area of the film is extremely large. When the salt concentration is higher or lower, the obtained two the surface of the tin oxide film is relatively flat and has poor performance. When the salt concentration is 0.1mol/L, the surface of the obtained film has a large undulation and a large specific surface area, and the ability to adsorb the dye molecules can be predicted to be the greatest, and the photoelectric conversion efficiency is optimal in the photocatalytic process.

Abstract: CuO microparticle was syntheszied by hydrothermal method. The starting precursors were used as copper (II) nitrate trihydrate (Cu (NO₃)₂·3H₂O), nitric acid (HNO₃) and sodium hydroxide (NaOH). The final pH value of the mixed solution was used 2M NaOH to adjust the pH was 8 and treated at 100-200 oC for 4-6 h in a hydrothermal vessel. The black fine powder was obtained after dried at 100 oC for 5 h. The phase and structure of CuO microparticle were characterized by X-ray diffraction (XRD). A single phase monoclinic structure synthezied by hydrothermal method at 200 oC for 4 and 6 h was obtained without calcination steps. The morphology CuO microparticle was investigated by scanning electron microscopy (SEM). It was likely grain in shape and the particle size in range of 2.94-4.06 μm. The element composition of CuO microparticle was indicated by energy dispersive X-ray spectrometry (EDX). The chemical compositions showed the characteristic X-ray energy of copper (Kα = 0.98 keV) and oxygen (Kα = 0.53 keV), respectively. The functional group of CuO microparticle was indentified by Fourier transform spectrophotometry (FTIR). The wavenumber at 690, 514 and 437 cm^-1 was corresponded to vibration of Cu-O stretching.

Abstract: In this research, CuO powder was prepared by low temperature hydrothermal method. Copper (II) nitrate trihydrate (Cu (NO₃)₂.3H₂O) and sodium hydroxide (NaOH) were used as the starting precursors. The final pH value of the mixed solution was adjusted to 9 by 4M NaOH and treated at 100 oC and 200 oC for 4 and 6 h. The black fine powder was obtained after dried at 80 oC for 4 h. The phase was characterized by X-ray diffraction (XRD). A single phase of monoclinic structure of CuO powder prepared by low temperature hydrothermal method at 200 oC for 4 and 6 h was obtained without calcination step. The morphology and particle size were investigated by scanning electron microscopy (SEM). The morphology was flower-like in shape and the average particle size in range of 0.3×0.7 μm. The element composition was indicated by energy dispersive X-ray spectrometry (EDX). The chemical compositions showed the characteristic X-ray energy of copper (Kα = 0.95 keV) and oxygen (Kα = 0.53 keV). The functional group was indentified by fourier transform spectrophotometry (FTIR). The wavenumber at 433-531 cm^-1 was corresponded to vibration of Cu-O stretching.

Abstract: Photocatalytic technology is widely used in water purification because of its environmental protection, high efficiency and energy saving. Therefore, it is extremely important for the selection and preparation of specific semiconductor materials used in the field of photocatalysis. In this work, 1T@2H MoS₂ nanosheets were fabricated by simple hydrothermal method, and the photocatalytic property of as-prepared 1T@2H MoS₂ were investigated by the photo-degradation of methylene blue (MB) water solutions under visible light irradiation via 2H MoS₂.The results indicated that compared to 2H MoS₂, the 1T@2H MoS₂ exhibited more excellent photocatalytic degradation property. After 150 minutes of irradiation under visible light, 1T@2H MoS₂ had a removal rate of 98% for MB, and 2H MoS₂ eventually reached 19%. The enhancement photocatalytic property of 1T@2H MoS₂ could be attributed to the reduced band gap energy of the hybrid-nanosheets and the increased in electron migration speed.

Abstract: It describes the development of a marketable citrogypsum which is also a by-product of citric acid production from laboratory scale to pilot scale. The modification of b-phase citrogypsum was carried out in different sodium chloride solution at 95oC for 7 hours under atmospheric pressure to α-calcium sulfate hemihydrate (α-CaSO₄∙0.5H₂O, α-HH). This can be achieved in the laboratory scale experiment. The phase analysis of a citrogypsum was confirmed by XRD technique demonstrated that mostly made up of calcium sulfate dihydrate (CaSO₄∙2H₂O, DH). The dehydration and phase transformation of citrogypsum to α-HH were conducted by DSC thermograms which were presented two endothermic peaks in the range 150-180oC of citrogypsum and an exothermic peak at 290 to 300oC, resulting that the product being α-HH when the 4M and 5M sodium chloride solutions were used. The outcome products were presented in a plate-like shape of citrogypsum but a hexagonal shape of α-HH. The experiment scaled up for modification of DH up to 100% in a batch reactor at the same condition with the 4M sodium chloride solution. The results showed that α-HH was obtained within 15 to 60 min after that calcium sulfate anhydrous (CaSO₄, AH) had been formed. The non-isothermal of DSC was an adapted method to investigate kinetics study of DH to α-HH transformation under the optimum condition with a model fitting dα/dt = -3k (α²) for predicting the process compared to the experiment values. In addition, the coefficient of determination (R²) from estimation and experiment value was 0.9940. Hence, the model equation was completely represent data.

Abstract: Here we synthesized a high-density single crystal anatase phase TiO₂/ITO nanorods array composite by one-step hydrothermal method. TiCl₄, H₂O, and HCl were used as the titanium precu-rsor, oxygen source, and inhibitors, respectively. The TiO₂ nanorods array were analyzed using X-ray diffraction (XRD), energy dispersive X-ray spectrometer (EDX), scanning electron microscopy (SEM), optical contact angle tester and ultraviolet-fluorescence spectrophotometer, separately. The nanorods in the composite grew along the [101] crystal plane, with a diameter of about 500 nm and a length of about 3 μm. The effect of PVP addition on the crystal phase and morphology of TiO₂ na-norod arrays was investigated. When the amount of PVP added was 0.5g, the diameter of nanorods was about 77-120nm, and a neat array structure appeared. In the photocatalytic experiment, methyl orange and acid red were used as degraded materials, the photocatalytic degradation rate was up to about 100%. When the hydrophilicity was the best, the optical contact angle of the sample after ultr-aviolet light irradiation was 7.2°. These results indicated that TiO₂ after doping experiments got better photocatalytic properties.