Inhibitory effects of Ficus sycomorus leaves extracts on the corrosion of mild steel and aluminium in 1 M hydrochloric acid (HCl) solution was studied at temperature of 30°C using gravimetric technique. Corrosion rates of mild steel and aluminium in the aggressive medium were found to increase as temperature increased, but decreased upon the addition of leaves extract of Ficus sycomorus compared to the blank. At 30°C, the inhibition efficiency increased with increase in inhibitor concentration reaching 87.84% for mild steel and 98.92% for Aluminium in the presence of 5 g/L of Ficus sycomorus leaves extracts. The results obtained show that aluminium had correlation coefficients (R 2 ) of 0.999 and 0.876 for Langmuir and Temkin isotherms respectively while Mild steel had correlation coefficients of 0.989 and 0.751 for Langmuir and Temkin isotherms respectively. However, the inhibitor adsorption was found to fit Langmuir adsorption isotherm better than Temkin isotherm. The free energy of adsorption (∆G°a ds ) has negative values and this indicates that the adsorption of Ficus sycomorus on the metal surface follows a spontaneous process.

No abstract

Thin films of copper sulfide (CuS) with varying concentrations of mercury (Hg) and nickel (Ni) impurities (0.01M-0.03M) were grown on glass substrates at room temperature (300K) using chemical bath deposition technique. Spectral transmittance and reflectance of the thin films were measured with a spectrophotometer in the UV-Vis-IR region of the electromagnetic spectrum. The effects of the impurities on other optical spectra obtained theoretically were quantitatively evaluated from the spectrophotometer data. The energy band gap increased for all Hg impurity concentrations to a maximum of 3.25 eV for 0.02M Hg impurity as against 2.65 eV for as grown CuS thin film, while the band gap decreased for all Ni impurity concentrations to a minimum of 1.85 eV for O.01M Ni impurity. The absorbance increased with both Hg and Ni impurity concentrations while the transmittance decreased with Ni impurities and increased with Hg impurities. The results also show increase in absorption coefficient and decrease in reflectance for both Hg and Ni impurities with a maximum reflectance of 70% for as grown thin film down to 10% wlth 0.01 Ni impurity. Values for the refractive index reduced to 1.0 with 0.01M of both impurities from a maximum of 2.4 for as grown CuS thin film. Also, results of the absorbance, transmittance and reflectance as presented here converged at 300 nm and diverged to 900 nm wavelength limit.

Thin films of iron sulfide (FeS 2) prepared by CBD technique were doped with aluminum (Al: 0.02-0.04M) and strontium (Sr: 0.02-0.04M) impurities at room temperature of 26 o C. X-Ray diffraction (XRD) and four-point probe were used to analyze the structural and electrical properties of the thin films. The XRD results show that 0.02M of strontium impurities produced polycrystalline structure of the thin films with diffraction peak values located at Bragg's angles, 2ϴ of 14.71 o , 25.03 o and 34.95 o , while the un-doped polycrystalline FeS 2 thin films have diffraction peaks at 2ϴ values of 19.81 o , 24.43 o , 31.45 o and 36.73 o. Clearly, the contributing inphase reflections for the different diffraction angles occur from different orientations of lattice planes and/or different crystallite sizes caused by the Sr impurity. On the other hand, 0.02M of aluminum dopant produced mono-crystalline structure of the FeS 2 thin film with 2ϴ value of 24.97 o and a broadened full width at half maximum (FWHM). It is remarkable that the single peak of the mono-crystal due to Al impurity coincides with the highest intensity and sharper peak of the un-doped FeS 2 thin film. The electrical resistivity of the thin films decreased while the conductivity increased with increase in impurity concentrations with non-uniform changes occurring from 0.02M for both impurities. The film thickness remained between 0.09-0.1µm but showed a more dramatic increase with impurity concentration from 0.02M for both impurities.

Chemical bath deposited nickel oxide (NiO) thin film samples were grown at room temperature of 30 °C on glass substrates. Samples k1, k2, and k3 were annealed for one hour at temperatures of 100 °C, 200 °C and 300 °C respectively, while as grown sample k4 served as a reference. A second set of samples k5, k7, and k8 were annealed at a constant temperature of 300 °C for time durations of 1H, 2H and 3H respectively, with as grown sample k6 as a reference. The spectral absorbance, transmittance and reflectance of all the thermally treated thin film samples were measured with a spectrophotmeter (D model Avantes Spec 2048 version 7.0) in the UV-VIS-NIR region of 300-900 nm wavelength. The results show distinctive variations in all the spectral properties for different combinations of annealing time and temperature, each starting at a threshold wavelength of 300 nm and ending with a distinctive minimum or maximum value. Deduced graphical values of the refractive index also show distinctive variations. For annealing time of 3 hours at a temperature of 300 °C, the results produced symmetric reflectance and symmetric refractive index with maximum values of 8% and 0.293 occurring at 500 nm wavelength and photon energy of 2.5 eV respectively. Direct transition band gap energy obtained for all the samples lie between 3.68-3.84 eV. The results reported in this paper clearly indicate that optimum combinations of production parameters of nickel oxide thin films can yield specific values of the properties for specific applications.