Abstract: In this work we carried out electrical characterization of n-GaAs implanted at 300 K with high energy (100 MeV) 28Si and 120Sn ions to a fluence of 1x1018 ions/m2 using current–voltage (I-V) measurements. The as implanted samples and samples annealed in the temperature range 373-1123 K have been investigated. Resistance of the samples obtained from I-V curves recorded over the temperature range 110K-270K indicate that the samples implanted with 28Si and annealed up to 623 K and the samples implanted with 120Sn and annealed up to 723K shows tunnel assisted hoping conduction mechanism. In the other hand, 28Si implanted samples annealed to 723K and 823K and 120Sn implanted samples annealed to 823K and 923K the electrical conduction mechanism is dominated by thermal hoping between closed defect states.
Abstract: The MWCNTs was functionalized by refluxing commercial MWCNTs (a-MWCNTs) in concentrated HNO3/H2SO4 (3:1 v/v) at 100°C for 6 hours. The dispersion of a-MWCNTs and functionalized MWCNTs (f-MWCNTs) were observed after 1 hour sonication in ethanol. Both samples were characterized by UV-vis spectroscopy for dispersion behavior. The dried f-MWCNTs and a-MWCNTs were characterized by Raman spectroscopy to estimate the defect level. The morphology of the samples were analyzed by Transmission Electron Microscopy (TEM). The f-MWCNTs was well dispersed in ethanol within 2 weeks of observations period. The colloidal stability of a-MWCNTs was low as it was easily sediment after 24 hours. The UV-vis spectra of f-MWCNTs show maximum absorbance at 250 nm meanwhile no absorbance was observed for a-MWCNTs. Analysis from Raman spectrum shows that the f-MWCNTs have relative intensity of 1.101 which is higher than a-MWCNTs that have relative intensity of 0.935. The image from TEM revealed that the f-MWCNTs have structural defects and the absence of amorphous carbon on sidewall meanwhile the a-MWCNTs indicate otherwise.
Abstract: Corrosion control of metals is about technical, economic, environmental, and aesthetic importance. Synthetic corrosion inhibitors are toxic to environment and human life. Thus, the searches for natural corrosion inhibitors are essential as they are biodegradable and non toxic. The purpose of this study is to investigate the ability of Nephelium lappaceum peel extract as a corrosion inhibitor of aluminum in 0.1M HCl solutions. Obtained data from gravimetric and thermometric analysis has shown the value of inhibition efficiency (% IE) is proportional to added inhibitor concentration and inversely proportional to the temperature. Occurred inhibition mechanism was in the form of inhibitor adsorption process on aluminum surface that allegedly preceded by physical adsorption. The SEM study also confirmed there were adsorptions of extracted inhibitor molecules onto aluminum surface. Therefore, from the observational results obtained, it can be concluded that Nephelium lappaceum peel extract was an attractive candidate for the natural corrosion inhibitor.
Abstract: Cu-based powder metallurgy friction materials were prepared by varying of Fe and C (% weight) in the friction components. The samples were compacted under the load of 24 metric tonnes and sintered at a temperature of 950 °C for 45 minutes. The friction and wear characteristics the materials developed were studied using Chase machine. The results show that Fe and C have different friction and wear characteristics. The friction coefficient of Cu-30%Fe-15%C sample maintained to be high and slightly increased after the drum temperature of 350°C and subsequently stable throughout tests. The friction of Cu-20%Fe-10%C stable until the drum temperature of 450°C and then its start to decay slightly until the end of the test. On the hand, the friction of Cu-10%Fe-5%C start to decay after sliding a few minutes at the drum temperature of 230°C. Thus, it could be postulated that the friction coefficient increased with increasing weight percentage of Fe and C in the friction components. However, the volume loss shows that there is no direct correlation with the Fe and C content. The volume loss of Cu-10%Fe-5%C was higher than the two samples which had the lowest hardness. On the hand, the volume loss of the Cu-30%Fe-15%C was slightly higher than Cu20%Fe-10%C as result of higher porosity and lower hardness. Wear mechanisms of abrasion, adhesion and thermal were observed to be operated during sliding process.
Abstract: Decolorization of azo dye, reactive black 5 (RB5) in an aqueous solution was investigated by using Fe-areca nut (Fe-AN) as heterogeneous catalyst. The effect of different parameters such as iron ions loading on supported catalyst, catalyst dosage, solution pH and initial concentration of H2O2 on the decolorization efficiency of the process were studied. The Fe-AN was prepared by impregnation process where iron ions were immobilized into areca nut and followed by calcinations process. The best reacting conditions were 4 wt% of iron ions loading on areca nut, catalyst dosage=1.0 g/L, initial pH= 2.5, [H2O2] o = 16 mM at temperature 30°C. Under these conditions, 99% decolorization efficiency of RB5 was achieved within 180 min reaction time. The results indicated that Fe-areca nut has proven to be an excellent heterogeneous catalyst for the decolorization of RB5 solution.
Abstract: The effect of dopant concentration on N, Fe co-doped TiO2 for photodegradation of methylene blue under ordinary visible light was investigated. The photocatalyst samples were prepared using solgel method with titanium tetraisopropoxide as precursor of titania. The dopant concentrations were varied from 0.50% and 1.0% and the calcinations temperature was fixed at 600oC. The prepared photocatalysts were characterized using XRD and FTIR to determine their physical properties. The results from XRD proved that photocatalyst with dopant concentration of 1.0% N, 1.0% Fe-TiO2 showing highly desirable properties in phase and crystal size. The results from FTIR revealed the presence of both the dopants in the samples. The effectivity of photocatalysts was tested by performing a standard batch photocatalytic degradation experiment with methylene blue as a model pollutant under ordinary visible light. The result showed that photocatalyst with high dopant concentration for both nitrogen and ferrum dopant (1.0 % N, 1.0% Fe-TiO2) yielded a maximum of 80.50% methylene blue degraded within five hours of irradiation time.
Abstract: In this study, biosorption of copper and zinc ions on Baker’s yeast, Saccharomyces Cerevisiae was investigated. The data of batch experiments was used to perform equilibrium and kinetic studies. The experimental results were fitted well to the Langmuir and Freundlich model isotherms. According to the parameters of Langmuir isotherm, the maximum biosorption capacities of copper and zinc ions onto immobilized yeast were 5.408mg/g and 1.479mg/g at 293 Kfor the treated beads. Competitive biosorption of two metal ions was investigated in terms of maximum sorption quantity. The binding capacity for copper ions is more than the zinc ions for both untreated and treated immobilized yeast.While, for the kinetic studies, the pseudo second order model was found the most suitable model for the present systems.
Abstract: In this study, adsorption of binary metal (Ni(II) and Pb(II)) ions from aqueous solution by using natural (NC), acid-modified (AC) and base-modified (BC) clinoptilolite were investigated to determine the effects of adsorbent dosage, metal solution’s pH and initial metal solution concentration. From the adsorption studies, the optimum dosage of adsorbent was found to be 2.0g for all adsorbents (NC, AC and BC) specifically for removal of Pb(II). In contrast, optimum dosage of for removal of Ni(II) was found to be 2.0g for NC and 4.0g for both AC and BC, respectively. The average pH for Ni(II) and Pb(II) ion solutions were 6. It was further observed that, the percentage removal of Ni(II) was largely influenced by the presence of lead due to the preference of Pb2+ ions by the natural and modified clinoptilolites.
Abstract: Biosorption process is considered as economical treatment to remove metal from the aqueous solution compared to other established methods. In this study, Saccharomyces cerevisiae was used as biosorbent and subject to immobilization process which consists of ethanol treatment for the removal of binary metals, lead (II) and nickel (II) from aqueous solution. Response surface methodology (RSM) was used to optimize effective parameters condition and the interaction of two or more parameters in order to obtain high removal of the binary metals. The parameters that have been studied were initial concentration of binary metals solution (10 - 60 mg/L), biosorbent dosage (0.2 - 1.0 g), pH (pH 2 - pH 6) and contact time (30 - 360 minutes) towards lead (II) and nickel (II) ions removal. Based on analysis of variance (ANOVA), biosorbent dosage, solution pH and contact time factor were found significant for both responses. Through optimization procedure, the optimum condition for lead (II) and nickel (II) ions removal were obtained at initial concentration of 10.0 mg/L, biosorbent dosage of 1.0 g, solution pH of pH 6, and contact time of 360.00 minutes, which resulted in 95.08 % and 21.09 % removal of lead (II) and nickel (II) ions respectively.