Papers by Keyword: Modified Sol-Gel Method

Abstract: BaCe_0.54Zr_0.36Y_0.1O_2.95 (denoted as BCZY10) ceramic powder was synthesized by a modified sol-gel method using metal nitrate salts as precursors. The samples were prepared using two different types of surfactants which are cationic surfactant of hexadecyldimethylammonium bromide (HTAB), nonionic surfactant of polyoxyethylene (10) oleyl ether (Brij 97), and sample without surfactant as a control. All samples were labeled as S1, S2, and S3 respectively. They were dried and calcined at T=325 °C and T=1100 °C accordingly. Chemicals bonding of the compound were analyzed using Fourier transform infrared (FTIR) spectrometry and their phase formation was identified by X-Ray Diffractometer (XRD). All the dried samples showed the adsorption peak at 3200-3700 cm^-1 that related to the overlapping of OH stretching originated from –OH terminal group and N-H stretching vibrations. The peaks appeared at 1620-1640 cm^-1 can be assigned to C=O stretching and at 1380-1450 cm^-1 can be attributed for N-H bending vibration. The adsorption peak ≈500 cm^-1 of metal-oxygen bond for all the calcined samples became pronounces indicating that the metal complexes were transformed to metal oxides. XRD results confirmed that S2 and S3 formed a single-phase of Ba (Ce,Zr)O₃ perovskite type-oxide and S1 consists of multi-phases compound which are dominated by BaCeO₃, and BaZrO₃. Therefore, the used of different type of surfactant was found to give a significant effect on the synthesizing single-phase of BCZY10 ceramics compound.

Abstract: BaCe_0.54Zr_0.36Y_0.1O_2.95 (BCZY10) ceramic powder was synthesized by a modified sol-gel method using metal nitrate salt as pre-cursors. The sample was prepared using three different types of surfactants namely polyethylene glycol (PEG) 6000, sodium dodecyl sulphate (SDS) and cetyltrimetylammonium bromide (CTAB). Thermogravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectrometry was used to analyze the thermal decomposition of the dried (T=325 °C) and calcined (T=1100 °C) powder. Standard sample prepared without surfactant is denoted as A1 while the sample that prepared using PEG, SDS and CTAB as surfactant was denoted as A2, A3, and A4 respectively. TGA results indicate that all the samples were almost completely decomposed at ~800 °C except for A2. It showed the lowest thermal decomposition temperature T_td=739 °C. The highest total weight loss ~94.7% is shown by sample A4 than others. The sample with the presence of surfactant exhibits faster reaction rate for the first decomposition stage which is t = 8 min, 11 min, and 13 min for sample A2, A3, and A4 respectively compared to A1 (t = 18 min). The A2 sample shows faster reaction rate indicates that BCZY10 compound might be formed earlier faster due to the long carbon chain posses by PEG surfactant. The higher number of carbon chain present in the surfactant may accelerate the combustion process and the formation of metal oxide compounds. FTIR spectra illustrated that the carbonate residue still remained in all the samples even after calcined at 1100 oC. This result indicates that the used of surfactant does not give a significant effect on preventing the formation of BaCO₃. However, the intensity of metal-oxygen band at ~450 cm^-1 become stronger indicates that the formation of BCZY10 compound was being enhanced.

Abstract: The modified sol-gel technique for the preparation of Со, Ni, Mo and W oxides nanoand submicron powders as well as binary composites based on them was developed. The optimal parameters of synthesis of metal oxide nanopowders with a particle size less than 100 nm were determined. The developed approach allows to obtain the nanoscale metal oxide particles with the given sizes, varying their within range 10-1000 nm. Mesoporous composites containing Mo-, Co-, Ni-oxides, Al₂O₃ and Ti-silicate were synthesized, characterized and tested in the catalytic alcohol synthesis from CO and H₂. It was found that selectivity to C₁-C₄-alcohols formed over model catalytic systems reaches 50-85% in temperature range 280-360°С.

Abstract: By adding methyl alcohol/water solution with certain concentration into sol to hydrolysis directly and sintering the fresh sol directly, lead titanate(PbTiO3) ceramics doped with magnesium are prepared by using magnesium acetate as doper to prohibit the disadvantages contained in conventional sol-gel method, such as low hydrolytic rate, high sintering temperature, long preparation period. The changes of structure, microstructure, synthesis process and electric properties of modified ceramics are studied in detail. The sizes and morphology of high purely and high density magnesium doped lead titanate nanocrystals thus obtained are observed by TEM photographs and the structures and affection of sintering temperature of to lattice constant and sizes of nanocrystals are detected by XRD. Electric properties detection results show that doped lead titanate ceramics exhibite excellent dielectric, ferroelectric and pyroelectric properties compare with pure lead titanate.