Papers by Keyword: Sol Gel

Abstract: Electrical transport in materials have been studied extensively due to its great potential in spintronic technology. The introduction of the secondary phase into the manganite matrix can modify the electrical properties, subsequently improving the low-field magnetic resistance (LFMR). In this work, we study the change in electrical properties at different temperatures of polycrystalline (1-x)La_0.7Sr_0.2Ca_0.1MnO₃/xTiO₂ (LT) composites where x = 0, 0.05 and 0.1. Polycrystalline La_0.7Sr_0.2Ca_0.1MnO₃ (LSCMO) was synthesized by sol-gel method, calcined at 700 °C, and pre-sintered at 800 °C for 6 h before adding TiO₂. TiO₂ as filler was mixed with LSCMO by wet mixing and stirring for about 30 min until a homogeneous compound was formed. Composite LT was then inserted to oven up to 100 °C for 2h to remove the moisture, compacted at 10 MPa, and sintered at 1200°C for 12 h. All samples in the LSCMO phase have a rhombohedral crystal structure with space group R3c. The crystal structure parameters were studied using Rietveld refinement through GSAS II software. The sample was characterized by SEM to represent the morphology of the sample. As the TiO₂ content increased, the magnetization decreased, as observed by VSM analysis at room temperature. The electrical transport properties of pure LSCMO and LT were characterized by cryogenic from 195K to 260 K. The resistivity of LT10 is too high compared to that of LT5 and as the temperature increases, the resistivity in this range will decrease. For 200 K, the resistivity of LSCMO, LT5 and LT10 are 3.09 x 10^-2 ohm.cm, 4.40 x 10³ ohm.cm and 4.77 x 10⁴ ohm.cm respectively.

Abstract: The thin films of Zr co-doped BT (BZT) with the Zr concentrations of 0, 3%, and 5% have been deposited on the quartz substrates via the sol-gel technique with a spin coater. The microstructure and optical properties of the samples were identified by XRD and UV-Vis Spectrophotometer to investigate the properties influenced by the Zr number modification. The XRD patterns exhibited that the samples were a single-phase tetragonal structure and a shift of (101) peak was observed toward a lower angle with increasing Zr content confirming an enlargement in the lattice parameter and cell volume of the samples. On the other hand, the lattice strain and crystallite sizes reduce together with more Zr content. The optical properties examination demonstrated that the BT and BZT samples were highly transparent (~70-80%) in the visible wavelength and the absorption edges exchanged toward a lower wavelength due to the Zr doping particularly on the BZT5. The refractive index values were high categorized at ~ 4, 3.5, and 3.3 for BT, BZT3, and BZT5, respectively. Moreover, BZT possesses the lowest bandgap (3.57 eV) followed by BT (3.61) and BZT5 (3.72 eV)

Abstract: Bioactive glasses (BG) were applied in bone and dental applications as well as in tissue engineering. In this studies, a new bioglass 50S8P (50% SiO₂, 22% CaO, 20% Na₂O and 8% P₂O₅) with different aging time (3, 7, 10 and 15 days) was prepared by sol-gel method. These synthesized glasses were analyzed using X- ray powder diffraction (XRD), Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The bioactivity of all BG is evaluated by incubating the BG powder in Hank's Balanced Salt Solution (HBSS) for 7, 14 and 21 days. Thermal analyses indicated the compositions can be stabilized at 700°C. XRD confirmed the primary crystalline phase was Na₄Ca₄Si₆O₁₈. Formation of silica network is established with the existence of functional group Si-O-Si (tetrahedral), confirmed with FTIR analyses. In vitro test confirm the apatite formation on the BG surface with characteristic of carbonate group (C-O) and P-O band noticed from FTIR and morphology of apatite formation on BG surface was observe using SEM

Abstract: A perovskite manganate material La_0,667Ba_0,333Mn_1-xCu_xO₃ (x = 0.35 and 0.40) were prepared. The samples were synthesized by sol gel method. The samples were sintered at 1000^OC for 6 hours. Rietveld refinement shows that both samples are crystallized in orthorhombic structure with Pnma space group. This results is in accordance with Goldschmidt’s tolerance factor value which are 0.8698 and 0.8701 for x = 0.35 and 0.4, respectively. Subtitutions with large amount of copper ions in B-sites caused the unit cell to decrease from 236.234 ų to 236.088 ų . Futher calculation from crystallography Refinement also shows that copper subtitutions increase the crystallite size of the samples from 74.8 nm to 94.49 nm. It has been found from the SEM results that copper subtitutions also alter the morphology of the samples.

Abstract: Nanosized particles SrMnO₃ perovskite was prepared by using sol gel method. The sintering temperature was modified to 700, 1000 and 1200 °C within 6 hours. The effect of sintering in nanosized particles and structural were carefully investigated by using X-Ray Diffractometer (XRD) and Scanning Electron Microscopy (SEM). All the synthesized particles show orthorhombic structure with progression from amorphous phase on lower temperature to single phase on higher temperature of sintering. The crystallite size tends to be constant while the particle size is adjusted. The SrMnO₃ grain size also modified to larger as the sintering temperature increase indicating that structure and behavior of the particles could be improved by modified sintering temperature.

Abstract: Multilayers zinc oxide thin films were synthesized by the sol–gel spin coating process to fabricate sensing membranes in an electrolyte-insulator-semiconductor (EIS) sensor for pH detection. The effect of various layers (single, three and five layers) on the crystallinity, morphological and optical properties of ZnO films were investigated by XRD, FE-SEM, and Photoluminescence respectively. The ZnO thin films grown were polycrystalline with hexagonal wurtzite structure. The films were not smooth, with grains and porosity in between them, and become denser as film thickness increased. The PL spectra exhibit two main emission peaks at near band edge 360-380 nm region (strong and sharp UV radiation) and 450–600 nm region (broad blue, green, and yellow radiation). Sensitivity, linearity was measured to determine the sensing and reliability performance of fabricated devices. The result confirmed that, the sensitivity for the three samples increased with increased layer from 48.3 mV/pH to 82.58 mV/pH. Compared to single and three layers of the ZnO electrolyte-insulator-semiconductor (EIS), ZnO grown with five layers exhibits a higher sensitivity of 82.58 mV/pH in solutions from pH 2–12 and linearity of 99.015 %. This is due to the increased of ZnO thickness, which produces dense surface and a well-crystallized grain structure.

Abstract: In the current paper, fundamental aspects of heavy oil and wax deposition problems are defined. Wax or in another term is cloud point occur when the oil starts to precipitate. When it’s started to precipitate, it can cause major problem to industry of oil and gas. In this study, ZnO nanoparticles were chosen to study the effect of varying molar ratio from 1:1, 1:2, 1:3 to the morphology and size of the nanoparticle. The structures and properties were recognized with energy dispersive X-ray (EDX), field emission scanning electron microscopy (FE-SEM), and X-ray diffraction (XRD) methods. EDX and FE-SEM is to study the morphology of ZnO structure while XRD is to determine the purity and size of the nanoparticle. From the study, 1:1 ratio has the smallest size of nanoparticle with 10.37 nm while 1:2 and 1:3 give the size of 12.3 nm and 16.37 nm respectively. As the molar ratio is increases, the size of nanoparticle become bigger. The influenced of ZnO nanoparticles on rheological behaviour of model oils and the wax content is reported. From the study, the addition of ZnO nanoparticle reduced the rheology behaviour of crude oil by varying nanoparticle sizes, temperature and shear rate. ZnO nanoparticle can reduce the deposition of wax up to 50% with influenced of smaller nanoparticle size. Effect of size of nanoparticle highly impact the viscosity and wax content. This prove that, by introducing nanoparticle into crude oil, wax content can be reduced thus decrease the chance for crude to precipitate.

Abstract: In this study, titanium dioxide nanoparticles were synthesized for possible application in enhanced oil recovery. Sol-gel method was employed with titanium (IV) isopropoxide as the precursor. The prepared materials were characterized using Powder X-Ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), High-Resolution Transmission electron microscopy (HRTEM) and Brunauer–Emmet–Teller (BET) techniques. Reaction parameter such as calcination temperature was varied during the preparation to obtain the uniform TiO₂ nanoparticles with the smallest particle size and high surface area. The results of study revealed that 400 °C is the optimum calcination temperature in preparing TiO₂ nanoparticles producing the smallest crystallite and particle sizes. XRD results indicated that the nanoparticles have formed anatase phase at 400 °C and achieved low crystallite size of 7.27 nm with the smallest average particle size of 19.53 nm through FESEM and HRTEM observations. BET analysis had achieved the highest surface area 103.64 m²/g.

Abstract: The nano-sized TiO₂ is an important material based on its application for solar cells. The low-cost synthesis of nano-sized TiO₂ is of high demand for commercial purposes. Synthesis of TiO₂ nanoparticles was achieved via the low-temperature Sol-gel method. Surface morphology was confirmed from SEM analysis, which showed that particle size is in the range of nanometer with no aggregation, The XRD results confirm the formation of anatase phase with high crystallinity. Furthermore, as prepared nano-sized TiO₂ particles were developed as sol-gel ink which was later deposited by spin coating on glass substrate with controlled spinning speed thereafter structural and optical properties were characterized by UV-vis spectroscopy, electrochemical impedance spectroscopy and DSC-TGA. The low-cost synthesis of TiO₂ nanoparticles with highly conductive thin films can be used as a potential material for future dye-sensitized solar cells

Abstract: Aluminums doped barium ferrite (BaAlFe₁₁O₁₉) was synthesized by sol gel process at annealing temperatures, T_a, of 700 - 1000 °C and annealing time, t_a, of 2 hr. The trend of saturation magnetization, σ_s, and the product of the magnetization and external magnetic fields, σH_max, increases from T_a = 700 - 900 °C, then decreases. The maximum value of σH_max and coercivity, H_c, are 13194.74 Oeemu/g and 20.33 emu/g, respectively, at T_a = 900 °C. The H_c increases from T_a = 700 - 1000 °C and its maximum value is 4448.80 Oe at 1000 °C. The trend of the crystallize size, <D>, increases from T_a = 700 - 900 °C then they are constant until T_a = 1000 °C. The maximum of <D> is 679.18 Å at 950 °C.