Papers by Author: Zainovia Lockman

Abstract: Elongated iron oxide nanopores (FNPs) were fabricated by anodisation of iron in fluoride-ethylene glycol (EG) added to it 1 ml, 1 M KOH electrolyte at three different voltages: 30 V, 40 V and 50 V. It was observed regardless of the voltage applied; the nanopores seem to be separated from one to another at the bottom part of the anodic film forming rather discreet nanotubular structure at this region. X-ray diffraction (XRD) was used to evaluate the phases present within the anodic layer. γ-FeOOH, Fe (OH)₂, and FeF₅.H₂O were detected in all samples. However, when the anodisation voltage was increased, peaks from the FeF₅.H₂O are more intense indicating either more F^- insertion in the anodic layer or crystallization of this phase at higher voltage. After annealing, XRD detected only hematite; α-Fe₂O₃ and magnetite; Fe₃O₄ indicative of phase formation or transformation had occurred during the annealing process. The annealed samples displayed an ability to adsorb Cr (VI) with almost 30 % reduction of the Cr (VI) concentration after 5 hours of exposure to the nanoporous anodic film.

Abstract: Barium zirconate titanate, BaZr_xTi_1-xO₃, (BZT) with x compositions have been widely studied as a potential candidate for antenna application. In this study, BZT film was prepared using the electrophoretic deposition (EPD) method. The EPD method was used to produce BZT composite into film for miniaturization purposes and dielectric properties improvement. The EPD process was performed with varying pH, voltages, deposition time and amount of Zr. The results showed that optimum deposition time was obtained at pH 4, 90V and 1 minute deposition time. Increasing Zr content decreased the dielectric constant of the BZT composite, and increased the loss tangent of the samples. The result is in agreement with microstructure observation that Zr addition in BZT decreased the grain size that suppressed the dielectric properties. This makes BZT is a suitable candidate for antenna application.

Abstract: Anodisation of iron foil was done to produce anodic film with nanoporous structure. The effect of anodic voltage on the morphology of the anodic oxide formed was investigated. Anodic film formed on iron foil anodised at 10 V is rather compact no obvious pores. Pores can be detected on oxide anodised at 30 V despite not very uniform. For foil anodised at 50 V, 1.8 µm thick anodic layer which consisted of uniform circular pores is observed. This film was then annealed at 450°C for 3 h in air as to induce crystallinity. The annealed nanoporous film exhibits a light illuminated photocurrent of 0.45 mA in 1 M NaOH + H₂O₂ solution.

Abstract: Fe-doped zinc oxide nanorods (ZnO NRs) were synthesized by ex-situ doping using spray pyrolysis technique. In this work, the undoped ZnO NRs were pre-synthesized via chemical vapor deposition using Zn powder and oxygen gas at 650 °C. The average length and diameter of the ZnO NRs are 4.1 ± 1.1 μm and 553.1 ± 89.6 nm, respectively. The average aspect ratio and areal density of ZnO NRs is 8.2 ± 2.9 and 6.2 ± 1.1 NRs/um², respectively. Subsequently, these undoped ZnO NRs were kept in the horizontal tube furnace, whereas the dopant solution (FeCl₃) of 0.05 M concentration was kept in the aerosol generator, which was located outside of the furnace. The Fe aerosol was flowed into the reactor when substrate temperature reached 650 °C to achieve ex-situ doping. At this temperature, some of the Fe atoms were driven into the NRs, forming Fe-doped ZnO NRs particularly at their outer layer. The presence of Fe 2p_1/2 and Fe 2p_3/2 peaks at 722.3 eV and 705.7 eV in XPS analysis indicates that Fe atoms were in the local structure of FeO. The Fe-doped ZnO NRs have poor crystal quality attributed to the low I_UV/I_Vis ratio in room temperature PL analysis.

Abstract: An ultraviolet (UV) shielding agent based on Fe-doped zinc oxide nanorods (ZnONRs) was synthesized by ex-situdoping using spray pyrolysis technique. These Fe-doped ZnO NRs could reduce the inherent photocatalytic activity of zinc oxide while still maintaining their ultraviolet filtering capability. In this work, the effect of doping duration by spray pyrolysis technique on the optical property and photocatalytic efficiency of ZnO NRs was studied. The room temperature photoluminescence (PL) analysis on the Fe-doped ZnO NRs indicates the red-shift of violet emission peak, i.e. from 378.97 nm (undoped) to 381.86 nm (60 mins.doping). Besides, the reduction of I_UV/_Vis ratio of PL reveals that the ex-situ Fe doping deteriorated the crystal quality of ZnO NRs. The photocatalytic study shows that the rate constant of Fe-doped ZnO NRs was smaller than the undoped ZnO NRs. It means that the Fe-doped ZnO NRs were less effective in degrading the RhB solution.

Abstract: An electrochemical anodization is a simple and low cost technique, to electrochemically synthesize self-organized titanium dioxide (TiO2) nanotubes (NTs) from 1M Na2SO4 electrolyte with anodization of Ti foil. The FESEM results showed that the average diameter size and length of TiO2 NTs was found between 50 to 60 nm and 2.5 μm, respectively. The surface morphology of arrays TiO2 NTs is uniformly deposited on Ti substrate. While, the cross-sectional of TiO2 NTs revealed that, the TiO2 NTs is arrays alignment and close each other deposited. From current-anodisation time analysis (I-t) indicates that TiO2 nanotubes were start formed at anodisation time 429.03 sec with current flows is 51.69 mA in electrochemical system.

Abstract: The TiO₂ anodized in organic electrolyte using 85% glycerol is used to investigate the crystalization of TiO₂ nanotubes annealed in air. The anatase start to form at 300°C and rutile appear when the temperature about 600 °C. The phase transformation is dependent on the annealing time and temperature. The anatase can be form at low temperatures when the annealing time is prolonged. The morphology of the annealed TiO₂ nanotubes changes as the function of the annealing temperature and the mechanism for the phase transformation of anatase to rutile is discussed.

Abstract: This work describes properties of 1-D ZnO nanorods arrays growth using low temperature hydrothermal method on a seeded substrate. The properties of ZnO seed were studied by varying thermal oxidation temperature from 250-450°C. The formation of ZnO nanorods was studied by varying the growth time during hydrothermal process. The optimum oxidation temperature to produce seeded ZnO template was 400°C. The formation of ZnO nanorods was further studied by varying hydrothermal reaction growth time from 1 to 24 hours. The optimum hydrothermal growth time of 4 hours produced blunt tip-like nanorods with length of ~735 nm and top diameter of ~66 nm. I-V characteristics of ZnO nanorods photodetector in dark, ambient light and UV light were also studied. The change in the photoconductivity under UV illumination was found to be 1 order of magnitude higher compared to dark and ambient light. With an incident wavelength of 370 nm and applied bias of 3V, the responsivity of photodetector was 5.0 mA/W, which was higher compared to other reported works. The increase of photosensitivity indicated that the produced ZnO nanorods were suitable for UV photodetector applications.

Abstract: This work describes the formation of WO₃ nanostructures via seeded growth hydrothermal reaction. WO₃ seed formation was first studied using thermal oxidation of W substrate from 300-500°C for 30 minutes. The optimum seeded substrates were then subjected to hydrothermal reaction at 80°C by varying precursor concentration and pH of the solution. Optimum oxidation temperature to produce WO₃ seeds was at 400°C for 30 minutes. Below 400°C, no seed was formed while above that temperature the seeds became too compact and less uniform. The optimum hydrothermal reaction parameters were obtained after 24 hrs reaction time, concentration ratio of sodium tungstate dehydrate to cetyltrimethylammonium bromide (CTAB) of 6:1 and at pH 2. By lowering the pH and increasing the precursor concentration, the growth of WO₃ nanostructures was enhanced. X-ray diffraction analysis showed that WO₃ nanostructures formed were of hexagonal structure.

Abstract: In this study, ZnO nanorods was formed on a seeded substrates prepared by thermal oxidation of Zn foil followed by hydrothermal reaction. ZnO seed was prepared via thermal oxidation process at 300°C for 10 minutes to form uniform circular nanosize grains that were suitable as a seeded template for the growth of ZnO nanorods via hydrothermal reaction. Several hydrothermal reaction parameters were studied; hydrothermal reaction temperature, ratio of zinc nitrate to hexamethylamine and pH. In hydrothermal reaction, the formation of ZnO nanorods occurs due to thermal degradation of hexamethylamine (HMT) which released hydroxyl ions that react with Zn ions in the precursor solution. Well aligned, ZnO nanorods with length of ~700 nm, base diameter of ~200 nm and top diameter of less than 30 nm needle-like structure were formed on seeded Zn substrate with concentration ratio of zinc nitrate to hexamethylamine 0.1M:0.1M, pH 6-7 at hydrothermal reaction temperature of 80°C