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Open access

Esra Yildiz

Abstract

In the present study, ZrO2co-doped with Gd3+/Sm3+and Gd3+/Er3+ions have been synthesized using Pechini method. Phase composition, morphology and photoluminescence properties of the synthesized phosphors were investigated by using X-ray powder diffraction (XRD), differential thermal analysis/thermal gravimetry (DTA/TG), scanning electron microscopy (SEM) and photoluminescence spectrofluorometer (PL). After heating at 1200 °C, XRD revealed that the phosphors were crystallized as monoclinic and tetragonal multiphases. SEM images indicated that the phosphors consist of fine and spherical grains with a size around 200 nm to 250 nm. Luminescence studies of these phosphors have been carried out on the emission and excitation, along with lifetime measurements

Open access

Talat Zeeshan, Safia Anjum, Hina Iqbal and Rehana Zia

Abstract

A series of copper substituted cobalt chromium ferrites, CuxCo1 - xCr0.5Fe1.5O4 (x = 0, 0.2, 0.4, 0.6, 0.8, 1.0) has been synthesized, by employing powder metallurgy method. Calcination of the samples has been carried out for 24 hours at 1100 °C. The resultant materials have been investigated by using a variety of techniques, including X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FT-IR), vibrating sample magnetometer (VSM)), scanning electron microscopy (SEM), and ultraviolet visible spectroscopy (UV-Vis). The XRD patterns confirmed that all compositions had a cubic spinel structure with a single phase and the lattice parameter was found to increase with increasing copper concentration. FT-IR spectroscopy has been used for studying the chemical bonds in the spinel ferrite. Shifting of the bands ν1 and ν2 has been observed. It has been revealed from VSM analysis that saturation magnetization and coercivity decrease with rising the Cu+2 doping. Magnetic properties have been explained on the basis of cation distribution. Scanning electron microscopy (SEM) has been used to study the surface morphology of prepared samples. UV-Vis analysis revealed the optical absorption of the samples. An increase in band gaps has been observed with increasing copper concentration in the sample.

Open access

A. Adamkiewicz and A. Waliszyn

Abstract

This article indicated at erosion as one of the causes of degradation of surfaces washed by fluids and conditions of its occurrence. Corrosive – erosive theory of metal surface degradation has been discussed linking it with an instance of destructive processes taking place in cylinder liner blocks of combustion engines. Physics and conditions influencing processes on liquid – washed operational surface phase boundary have been justified. Out of the contemporary hypotheses explaining the physics of cavitation erosion, the bubble theory has been considered. A mathematical model of erosion has been presented in the context of cavitation implosion energy determining crash interactions of liquid cumulative fluxes on the washed surface. Occurring plastic deformations have been graphically explained linking them with the occurrence of fatigue micro-cracks and later with erosive pits. Influence of initial steel hardness on intensity of cavitation erosion has been checked. Discussion of ways to increase metal surface resistance to cavitation erosion has been carried out.

Open access

Nouman Rafiq, Waqar A.A. Syed, Aulia Rifada, M. Asad Ghufran, Ijaz-Ur-Rehman Shah, Ahsan Ali and Wiqar Hussain Shah

Abstract

We report a simple approach for synthesizing monodispersed, crystalline and size-tunable tin sulfide nanoparticles for environment friendly next generation solar cell applications. Both SnS and SnS2 nanoparticles could be a potential nanomaterial for solar cells. The structural, morphological, thermal and optical properties were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), diffuse reflectance spectroscopy (DRS) and Fourier transform infrared spectroscopy (FT-IR). The XRD spectra revealed hexagonal and orthorhombic phases of SnS and SnS2 nanoparticles, respectively, where the grains size ranged from 11 nm to 30 nm. The weight percentage as a function of temperature was determined using TGA analysis. Functional groups were observed by FT-IR. The energy bandgap was determined as 1.41 eV showing usefulness of the nanoparticles in next generation environmental friendly solar energy applications.

Open access

A.M. Abd-Elnaiem, M. Mohamed, R.M. Hassan, M.A. Abdel-Rahim, A.A. Abu-Sehly and M.M. Hafiz

Abstract

Effect of annealing temperature on the structural and optical properties of As30Te60Ga10 thin film was studied using various techniques such as differential scanning calorimetry (DSC), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The DSC analysis revealed that the As30Te60Ga10 glass has a single glass transition and crystallization peak while XRD results confirmed that the as-prepared and annealed films have crystalline nature. The coexistence of the crystalline phases in the investigated films could be attributed to the formation of orthorhombic As, hexagonal Ga7Te10, and monoclinic As2Te3 phases. It was found that the average crystallite size and optical parameters of the studied films depend on the annealing temperature. For example, the optical band gap decreased from 1.54 eV to 1.11 eV as the annealing temperature increased from 300 K to 433 K.

Open access

Ziaul Raza Khan, Munirah, Anver Aziz and Mohd. Shahid Khan

Abstract

High-quality CdS nanocrystalline thin films were grown by sol-gel spin coating method at different solution temperatures on glass substrates. As-deposited films exhibited nanocrystalline phase with hexagonal wurtzite structure and showed good adhesion and smooth surface morphology. It was clearly observed that the crystallinity of the thin films improved with the increase in solution temperature. Crystallites sizes of the films also increased and were found to be in the range of 10 mm to 17 nm. The influence of the growth mechanism on the band and sub-band gap absorption of the films was investigated using UV-Vis and photothermal deflection spectroscopy (PDS). The band gap values were calculated in the range of 2.52 eV to 2.75 eV. The band gap decreased up to 9 % with the increase in solution temperature from 45 °C to 75 °C. Absorption coefficients estimated by PDS signal showed the significant absorption in low photon energy region of 1.5 eV to 2.0 eV. The dark and illuminated I-V characteristics revealed that the films were highly photosensitive. The results demonstrated the potential applications of sol-gel grown CdS nanocrystalline thin films as photoconductors and optical switches.

Open access

Jiyong Deng, Qiang Tao, Dong Yan, Xianwei Huang and Yunfeng Liao

Abstract

Small molecules of ThQuTh, CzQuTh, CzQuCz and TPAQuCz were designed and synthesized, based on quinoxaline acceptor, and electron donating groups, i.e. alkyl-thioephene, carbazole and triphenylamine on both side chains and molecular backbones. Their thermal, optical and electrochemical properties were systematically compared and studied. The absorption spectra of the small molecules were strongly affected by the donor units attached to quinoxaline. Strong electron donating groups, such as carbazole on the molecular backbone would lower optical band gap, resulting in a wide absorption and the strong donor on the side chain would enhance the absorption intensity in short wavelength region. The highest occupied molecular orbital (HOMO) energy levels of the four molecules were up-shifted with increasing the electron donating properties of donor units. The bulk-heterojunction organic solar cells with a device structure of ITO/PEDOT:PSS/SMs:PC61BM/LiF/Al were fabricated, in which the small molecules functioned as donors while PC61BM as acceptor. Because the electron-donating ability of carbazole (Cz), triphenylamine (TPA) is higher than that of thiophene (Th), CzQuTh, CzQuCz and TPAQuCz show higher power conversion efficiency (PCE) than that of ThQuTh. Furthermore, being the strongest in absorption intensity and widest in absorption spectrum, TPAQuCz has the highest power conversion efficiency. Further improvement of the device efficiency by optimizing the device structure is currently under investigation

Open access

A.J. Nagajothi, R. Kannan and S. Rajashabala

Abstract

Chitosan has been successfully incorporated as a filler in a polyethylene oxide (PEO) and lithium trifluoromethanesulfonate (LiCF3SO3) matrix with a combination of plasticizers, namely 1,3-dioxolane (DIOX) and tetraethylene glycol dimethylether (TEGDME). The composite gel-polymer electrolyte (CGPE) membranes were prepared by solution casting technique in an argon atmosphere. The prepared membranes were subjected to SEM, TG/DTA and FT-IR analyses. A Li/CGPE/Li symmetric cell was assembled and the variation of interfacial resistance was measured as a function of time. The lithium transference number (Li+ t) was measured and the value was calculated as 0.6 which is sufficient for battery applications. The electrochemical stability window of the sample was studied by linear sweep voltammetry and the polymer electrolyte was found to be stable up to 5.2 V.

Open access

A. Komorek, D. Grygiel, R. Bieńczak and J. Godzimirski

Abstract

The results of conducted by the authors of the article numerical analyzes, indicate the importance of normal stresses, perpendicular to the adhesive joint, during the impact destruction of block adhesive samples. This kind of stresses are responsible for the occurrence of tearing or chipping in a joint. The very significant influence of adhesion in the impact-bonded adhesive joint was the reason for testing this parameter in joints made with adhesives with different Young’s modulus. It was assumed that adhesives differing in stiffness will have different adhesive properties, which should affect the impact strength of the adhesive joints. It was also assumed that the adhesion in the joint can be assessed by analyzing the surfaces of joint damage. Cylindrical butt joints connected with various adhesives were used to carry out the tests, in which they were loaded on tear-off. The nature of tested joints damage was usually cohesive or cohesive-adhesive. The assessment of the nature of joint damage allowed to determine whether they were the result of the loss of cohesion by the adhesive (cohesive damage) or the effect of poor adhesion between the hardened joint and adherends (adhesive damage). The assessment of the nature of the destruction was carried out by three methods: visual, using an optical microscope and using an electron microscope. As a result of the carried out observations, it was found that the visual method is the least useful and not very reliable, especially in the case of transparent or low-contrast in relation to the glued material joints. The use of electron microscope allows to obtain the most reliable results, however, the possible magnification is too large and the assessment of the entire weld fracture is difficult because it does not fit in the field of observation. Observations conducted using optical microscopy at a slight magnification (5-10 times), in most cases allow to determine the nature of the destruction to a satisfactory degree, with limitations such as in the visual method.

Open access

Steponas Ašmontas, Jonas Gradauskas, Algirdas Sužiedélis, Aldis Šilénas, Edmundas Širmulis, Vitas Švedas, Viktoras Vaičikauskas, Vytautas Vaičiūnas, Ovidijus Ž Žalys and Vitaliy Kostylyov

Abstract

Photovoltage formation across Si p-n junction exposed to laser radiation is experimentally investigated. Illumination of the junction with 1.06 μm wavelength laser radiation leads to formation of classical photovoltage Uphdue to intense electronhole pair generation. When the photon energy is lower than the semiconductor forbidden energy gap, the photovoltage U is found to consist of two components, U = Uf+ Uph. The first Uf is a fast one having polarity of thermoelectromotive force of hot carriers. The second Uphis classical photovoltage with polarity opposite to Uf. It is found that Ufis linearly dependent on laser intensity. The classical photovoltage is established to decrease with the rise of radiation wavelength due to decrease in two-photon absorption coefficient with wavelength. Predominance of each separate component in the formation of the net photovoltage depends on both laser wavelength and intensity