Electrical conductivity and dielectric behaviour of manganese and vanadium mixed oxide prepared by conventional solid state method

Investigation on electrical conductivity and dielectric properties of manganese (Mn) and vanadium (V) mixed oxides were carried out to study the extrinsic semiconductor behaviour. The XRD pattern shows that Mn–V oxide is multiphase and quantitative phase analysis was performed to determine the relative phases. Overall results indicate that with increasing temperature, the DC conductivity, AC conductivity, dielectric constant, dielectric loss factor and loss tangent of Mn–V mixed oxide increases. Activation energy of AC conduction decreases with increase in frequency, confirms that the hopping conduction is the dominant mechanism. The activation energy of DC conduction ΔEdc is 0.54 eV which is greater than ΔEdc. There are three types of dielectric constant spectrum found in the measuring temperature range 30–250 °C. This is possibly due to the extrinsic behaviour of the Mn–V oxide. Dielectric relaxation characteristic was obtained from the spectrum of the imaginary part of electric modulus. The activation energy of the relaxation process and the relaxation time at infinite temperature are 0.42 eV and 5.40 ps respectively. The Nyquist plot of complex impedance fitted the equivalent circuit model of two RC circuits in series with R and C in parallel. The relaxation time was estimated from the circuit model

Study of the elastic properties of (PbO)x(P2O5)1 − x lead phosphate glass using an ultrasonic technique

Fabrication of a series of binary (PbO)x(P2O5)1−x lead phosphate glasses with various mole fractions (x = 0.1 to 0.6) was carried out using a conventional melt-quenching method. The glass density was measured by using Archimedes principle. The ultrasonic wave velocities (Vl and Vt) of the glasses were determined at room temperature by using a nondestructive test: the digital signal processing technique of the Ultrasonic Data Acquisition System (Matec 8020, Matec Instruments, USA). The experimental data for the wave velocities and densities were then used to determine the elastic properties in each series of lead phosphate glass systems: the longitudinal, shear, bulk and Young's moduli; Poisson's ratio; and the Debye temperature. Based on the results obtained, the longitudinal, shear, bulk and Young's moduli of the glasses increased with the addition of PbO content. The Poisson's ratio obtained remains almost constant, while the Debye temperature shows a continuous decrease with the addition of PbO content

Formation of silver microbelt structures by laser irradiation of silver nanoparticles in ethanol

In the present work, we prepared silver nanoparticles by laser ablation of pure silver plate in ethanol and then irradiated the silver nanoparticles using a 532 nm Q-switched Nd:YAG pulsed laser. Transmission electron microscopic images of the sample after irradiation clearly showed formation of big structures, such as microrods and microbelts in ethanol. The obtained microbelts had a width of about 0.166 μm and a length of 1.472 μm. The reason for the formation of such a big structure is the tendency of the nanoparticles to aggregate in ethanol before irradiation, which causes fusion of the nanoparticles

Development of nanoemulsion incorporated with Hibiscus sabdariffa for cosmeceutical application

Hibiscus sabdariffa (HS) has been reported to possess a crucial content of bioactive compounds, such as phenolic acids and flavonoids, therefore, HS was recognized as a source of antioxidants. Due to that, the development of nanoemulsion incorporated with HS appears promising for cosmeceutical application. This study is focused on the formulation of oil-inwater (O/W) nanoemulsions of HS to enhance the bioaccessibility of its active compounds. The influences of hydrophiliclipophilic balance (HLB) value of surfactant and grapeseed oil (GSO) to olive oil (OO) ratio on the droplet size, zeta potential, PDI and stability of the nanoemulsions were investigated. The results showed that the smallest particle size was obtained at 145.9 nm with PDI = 0.388 and zeta-potential = -41.1 mV in the systems prepared using HLB value of 12 and 2:1 ratio of GSO to OO. Then the selected nanoemulsion which based on the lowest particle size (NE-F6, GSO:OO = 2:1, and HLB = 12) showed good stability over time and temperature without no phase separation, creaming or cracking was spotted. The pH value of the NE-F6 was obtained at 5.2

Development of nanoemulsion incorporated with Hibiscus sabdariffa for cosmeceutical application

Hibiscus sabdariffa (HS) has been reported to possess a crucial content of bioactive compounds, such as phenolic acids and flavonoids, therefore, HS was recognized as a source of antioxidants. Due to that, the development of nanoemulsion incorporated with HS appears promising for cosmeceutical application. This study is focused on the formulation of oil-inwater (O/W) nanoemulsions of HS to enhance the bioaccessibility of its active compounds. The influences of hydrophiliclipophilic balance (HLB) value of surfactant and grapeseed oil (GSO) to olive oil (OO) ratio on the droplet size, zeta potential, PDI and stability of the nanoemulsions were investigated. The results showed that the smallest particle size was obtained at 145.9 nm with PDI = 0.388 and zeta-potential = -41.1 mV in the systems prepared using HLB value of 12 and 2:1 ratio of GSO to OO. Then the selected nanoemulsion which based on the lowest particle size (NE-F6, GSO:OO = 2:1, and HLB = 12) showed good stability over time and temperature without no phase separation, creaming or cracking was spotted. The pH value of the NE-F6 was obtained at 5.2

Thermal diffusivity determination of liquid trough thermal diffusion length measurement

A new Optical Fiber Thermal Wave Resonance Cavity (OF-TWRC) technique was used to determine thermal diffusivity of liquids from the thermal diffusion length obtained from the curve of pyroelectric amplitude exponential decay with respect to cavity length and compared with the linear fitting of pyroelectric phase signal. The average thermal diffusivity of water obtained by this calculated method gives the value for water as 1.4723210cms−×. The thermal parameters for water and for other liquids agree with reported values in the literature

Measuring thermal parameter by thermal diffusion length measurement using OF-TWRC technique

The newly developed Optical Fiber TWRC technique or shortly as OF-TWRC was used to determined the thermal diffusivity of liquids from the thermal diffusion length obtained from the curve of pyroelectric amplitude exponential decay with respect to cavity length and compared with the linear fitting of pyroelectric phase signal. The average thermal diffusivity of water obtained by this calculated method gives the value for water as 1.472 x 10 -3 cm2/s. The thermal parameters for water and for other liquids agree with reported values in the literature

Optical properties of ternary TeO2-B2O3-ZnO glass system.

A series of ternary tellurite based glasses [(TeO2)70 (B203)30]100-x [ZnO]x glasses with different compositions of ZnO (x= 5 to 30 wt.% in steps of 5 wt.%) have been synthesized by melt quenching method. The role of ZnO to the glasses structure was studied by IR spectroscopy. FTIR spectra revealed broad, weak and strong absorption bands in the investigated range of wavenumber from 280-4000 cm-1 which associated with their corresponding bond modes of vibration and the glass structure. The indirect optical band gap and the direct optical band gap are in the range 2.08-3.12 and 1.54-2.36 eV, respectively. A decrease in the values of energy band gap Eg may come down to the reason that the non-bridging oxygen ion content increases with increasing ZnO content and shifting the band edge to lower energies. The optical band gap and Urbach energies were calculated from the absorption spectra measured between 190 and 900 nm at room temperature. The refractive index, n of the glasses change from 1.84-2.00 while the molar refractivities decrease from 13.06 to 12.00 with the increase of ZnO in mol%

Phytochemical and antimicrobial activities of different solvent extracts of Hibiscus sabdariffa

The use of plant extracts and phytochemicals with known antimicrobial properties is becoming commonplace worldwide and gaining great significance for therapeutic uses. Thus, the purpose of the present study is to investigate the effects of numerous extraction solvents (hexane, ethyl acetate, ethanol) on the phytochemical constituents and antimicrobial activities of Hibiscus sabdariffa. Phytochemical screening for saponins, tannins, flavonoids, phenolic and alkaloid compounds revealed that the ethanol and ethyl acetate extracts of Hibiscus sabdariffa contained all the aforementioned phytochemical constituents, for theexception of tannins and alkaloids that were absent in the ethyl acetate extract. Interestingly, the hexane extract did not affordsuch constituents. The ethanol extract exhibited stronger inhibitory activity against Bacillus subtilis (B29), Staphylococcusaureus (S276), Staphylococcus epidermis (S273), Pseudomonas aeruginosa (ATCC 15442) and Escherichia coli (E266) than ethyl acetate extract, but the difference was less evident for the hexane extract of Hibiscus sabdariffa which inhibitedonly B. subtilis, as determined by the paper disc method. Base on the findings, it can be construed that the ethanol and ethylacetate extracts of HS have prospective applications as antimicrobial agent as well as one of the sources of therapeutically useful products