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Chromium oxide thin films were grown on Al2O3 substrates by ablating a pure Cr2O3 target using a KrF excimer laser. The energy density on the target surface was 1.4 J/cm2 with a pulse repetition of 3 Hz. The thin films were calcinated at 550°C for 1 h. The structural analysis of the grown layer was achieved using FTIR spectroscopy and X-ray diffraction techniques. The XRD analysis shows the formation of Cr2O3 with crystalline size ranging from 35–40 nm, further confirming from the infrared absorption bands. The PLD deposited thin films show a predominance of the higher oxidation states of chromium while the antiferromagnetic Cr2O3 phase is mostly present in films grown in an O2 ambient. The optical and electrical properties were studied using ellipsometry, UV-vis spectroscopy and I–V techniques. The direct band gap and indirect optical band gap were determined and refractive index, extinction coefficient, absorption coefficient and dielectric constant were measured and presented in this paper. The current voltage characteristics are also part of this work.

We investigated the geometrical and electronic properties of copper-doped MoS2 by first principles calculations. The doping is done by Cu substitution with Mo (1 to 4 atoms) accompanied by study of S vacancies. Our outcomes show that the concentration of doping and vacancy of S leads to determine and finely tune the band gap in the range of 0.16 to 1.95 eV. This fine tuning of band gap results due to variation in concentration of impurity, changing dopant site, and production of S vacancies. The resulting arrangements show significant charge redistribution on replacement of local atoms with foreign atoms dictated by electronegativity determined from the Bader analysis. In addition, bonding mechanism occurring due to substitution of foreign elements is discussed. These results give pleasing data regarding fine desired value of the band gap of the MoS2 which helps its utilization in semiconductor and other opto-electronic devices in addition to understanding the electrical conductivity.

In the present work, mechanical, tribological, and electrochemical behaviors of Al Alloy 6061–(0–10) % B4C–(0.25–1.2) % graphene nanoplatelets (GNPs) composites, prepared by a combination of solution mixing and powder metallurgy, were investigated. Properties such as hardness, compressive strength, wear rates, and coefficient of friction (COF) were used to investigate the effects of GNPs on mechanical and self-lubricating tribological behavior. The corrosion resistance of composites was investigated using potentiodynamic polarization and electrochemical impedance techniques. Scanning electron microscopy, energy-dispersive X-ray spectroscopy (EDS), and EDS mapping were employed to study the distribution, the fracture profile, and wear mechanism. The AA 6061–10% B4C–0.6% GNPs composites exhibited sharp increase in hardness and compressive strength and significant decrease in wear rates and COF. However, for GNPs contents exceeding over 0.6 wt%, mechanical properties and wear performances deteriorated. Pulling out of sheared pultruded GNPs was observed during the fracture of composites. Worn surfaces of GNPs-containing composites showed the smeared graphene layer with some macro-cracks exhibiting delamination wear. It was found that the corrosion inhibition efficiency of GNPs was more pronounced in H3BO3 environment than in NaCl solution.

We investigated the geometrical and electronic properties of copper-doped MoS

The world’s present reserves in terms of fossil fuels are exhausting speedily. Such rapid energy consumption can be caused of unsustainable worldwide progress. Therefore, the researcher’s challenge is to identify the most efficient and economical energy conversion method to provide a viable replacement for the ongoing conventional energy converters. In this context, fuel cell technology (solid oxide fuel cells (SOFCs)) can play a key role and convert hydrocarbon energy into electrical energy. The conventional electrolyte YSZ based SOFCs work at high temperature ∼1000 °C. In this present research, the new ceramics electrolytes materials boron doped ceria (BDC) have been developed by auto-combustion technique. The prepared materials have been characterized by X-ray diffraction (XRD) and TEM. The crystallite sizes of all prepared samples are in the range of 50–80 nm applying Scherer’s formula. The electrical studies and fuel cell performance have been completed at temperature ≤ 700 °C. The doping of boron into ceria has significantly improved the electrical conduction of pure ceria oxide which has been studied using four-probe setup. The maximum ionic conductivity and power density of B0.20:Ce0.80 (molar ratio) electrolyte material named as E4 have been achieved and found to be 0.09 S/cm at 700 °C and 198.125 mW/cm2 at 650 °C. It has been observed that all electrochemical results are consistent with the doping of boron into ceria.

Nitrogen implanted III-V compounds semiconductors have attracted a great deal of attention of the research community due to their interesting fundamental physical properties and potential applications in optoelectronic devices. A small amount of nitrogen incorporation in gallium arsenide (GaAs) causes significant reduction in the band gap energy of fabricated alloys. In this study the GaAsN layer was prepared by implantation of nitrogen ion on thick GaAs wafer and the samples were thermally annealed for studying annealing effects. The structural, compositional and optical properties have been investigated by X-Ray Diffraction (XRD), Rutherford Backscattering Spectroscopy (RBS), Scanning Electron Microscopy (SEM), Photoluminescence (PL) and Photo-thermal Deflection Spectroscopy (PDS). The results reveal that the samples prepared with higher implantation dose and annealed at higher temperature exhibit strong optical signal of GaN, while the samples annealed at lower temperature show weak optical signal. Furthermore in PDS spectra, the band gap reduction was observed indicating the diluted nitrogen content in GaAs. We have demonstrated that annealing conditions and implanted nitrogen doses could be helpful to achieve the desired variation in band gap and low physical damages on surface.

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 SnS2nanoparticles 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.

A multilayer system of 10 alternating TiO2 and MgF2 thin film was prepared on BK7 glass substrate by electron beam and resistive thermal evaporation techniques respectively. The substrate with 20 mm diameter and thickness of 1 mm were placed in a vacuum chamber at partial pressures of 10–5 mbar for TiO2 and 10–6 mbar for MgF2 film respectively. The as-deposited films were annealed at 400 °C for an hour in ambient environment. The structural, optical and morphological properties were studied by XRD, UV–vis spectrophotometer, ellipsometery and scanning electron microscopy (SEM) respectively. The structural analysis confirms that all the thin films samples were polycrystalline in nature with tetragonal and rhombohedra phases. SEM analysis confirms the uniformity of surface and quite stable multilayer thin film structure without any micro cracks. Ellipsometery studies were carried out and refractive index and extinction coefficient as function of wavelength are obtained. The samples are found highly transparent in the range of 400–800 nm, whereas the overall absorption and reflection of the multilayer thin film was decreased for the annealed samples. It has been demonstrated that the residual reflectance of the AR coating can be significantly reduced by combining the multilayer systems with an outermost low index layer made of MgF2. The realization of such hybrid multilayer systems are extremely useful as front surface of the photovoltaic cells, optoelectronic devices and front mirror for laser.

Environmental friendly and low cost materials for photovoltaic applications always gain a keen interest to make them economical with increased performance. Quaternary compounds with I2- x -IV-VI4 arrangement offers favorable properties for optoelectronic devices. In this work, we have substituted antimony in the matrix of Cu2(x)SnS4 to form Cu2SbSnS4 (CATS) nanoparticles, where the effect of Sb substitution was investigated by the change of ratio with four different compositions. Structural properties reveal the incorporation of antimony with different amounts to significantly alter the morphology of CATS between nanosheets and nanoparticles. All samples obtained the optical bandgap between 1.28 eV and 1.35 eV, which is highly suitable for solar cells. CATS results indicate it has the potential to use in photovoltaic and photocatalytic applications.

The spatio-temporal variations in cloud optical properties and the influence of aerosols, radiation feedback and meteorological parameters were investigated at high altitudes of Diamir, Gilgit and Skardu in the Himalaya Karakoram (HK) region of northern Pakistan from 2004 to 2016. The aerosol optical depth (AOD) depicted significant variation with high values during spring months as compared to other months. The results revealed high values of cloud fraction (CF), cloud water path (CWP) and cloud optical depth (COD) in winter months, while contrasting response was observed in summer months. Due to Twomey effect, clouds become thicker and brighter with maximum COD and liberation of latent heat, which modifies temperature gradient of vertical profile. Similarly, an uneven distribution of cloud effective radius (CER) was observed throughout the study period. An increasing trend of cloud top temperature (CTT) from February to September was observed, while an opposite response was found from September to January during the study period. Likewise, minimum and maximum cloud top pressure (CTP) was found in February and November, respectively. AOD is positively correlated with CF and COD due to high humidity and the existence of hydrophilic aerosols. The results of AOD and CER correlation were in good agreement with Twomey effect. However, AOD showed contrasting relationship with CWP over Diamir and Gilgit. The negative relationships of AOD with CTP and CTT indicated the suppression of precipitation process and variability of meteorological parameters. In addition, a positive correlation was observed between COD and CTP against top of the atmosphere shortwave cloud radiative forcing (TOASWCRF), which indicates the cooling effect due to increasing COD and CTP. With TOASWCRF, a variation in CWP and CER may also lead to cooling effect due to reflection of solar radiations. While the meteorology depicted an uneven relationship with cloud optical properties at observation sites. © 2020 Elsevier B.V.

Here, the structure-dependent electronic, thermal, and transport properties of nanostructured thallium telluride (Tl8Pb x Sb2−x Te6) through controlled variation in Pb and Sb (x = 1.96, 1.97, 1.98, 1.99) concentrations have been investigated. In the temperature and concentration-dependent electrical conductivity measurements, the highest electrical conductivity 131.96 × 103 Ω − 1 m − 1 at 300 K was measured for x = 1.99 and the maximum observed Seebeck value for the optimized Tl8Pb1.96Sb0.04Te6 nanoparticles was 110.7 μV/K at 550 K. Such an increased value of the Seebeck coefficient led to the achievement of a significantly improved high-power factor, which was found to be increasing with temperature and decreasing with the increase of Pb concentration. The density functional theory calculations performed for Pb and Sb co-doped Tl5Te3 resulted in the enhanced σ e and S with a significant reduction in electronic thermal conductivity (κ e ) and is found consistent with experimentally measured κ e . The highest ZT = 0.35 and 0.18 were recorded experimentally and theoretically for Pb and Sb co-doped in Tl5Te3 nanoparticles.

Green synthesis technique of nanoparticles has advantages over physical and chemical methods due to its simplicity in preparation, environment friendly nature and less time consuming. We report a green approach for the synthesis of zincoxide nanoparticles using leave extract from melia azedarach. Melia azedarach plant has been traditionally famous for its antibacterial properties. The plant extract acts as reducing and capping agent, while zinc nitrate hexahydrate [Zn(NO3)2.6H2O] was used as a precursor. The formation of ZnO nanoparticles was observed by the color changes during the reaction. Structural, optical and morphological properties of ZnO nanoparticles were determined using x-ray diffraction, scanning electron microscope, Fourier transform spectroscopy and UV–vis spectroscopy. XRD analysis confirms the formation of wurtzite hexagonal structure NPs with significantly small average crystallite size of 7.0 nm. The energy band gap determined by UV–vis spectroscopy was measured between 2.9 eV to 5.4 eV. The antibacterial activity of ZnO nanoparticles was tested against E. coli bacteria and significant results were obtained. The anti-bacterial study proved that green-rout prepared ZnO nanoparticles are the best choice for future research concerning antibacterial activity.

An analysis has been carried out to investigate the heat and mass transfer effects in steady axi-symmetric flow of a polymeric liquid (Maxwell fluid) between two infinite stretching disks in the presence of chemical reaction. Particular attention is to compute similarity solution of the governing nonlinear partial differential equations. The series solution of transformed nonlinear ordinary differential equations are computed via homotopy analysis method. The convergence of the developed series solution is also discussed. The quantities of interest like fluid velocity, fluid pressure, temperature, concentration, skin friction coefficient, local Nusselt and local Sherwood numbers are analyzed for the influence of embedded parameters. It is observed that the skin friction coefficient is an increasing function of Deborah number and Reynolds number. It is also observed that effects of stretching parameter on skin friction coefficient at upper and lower disks are opposite. Moreover, the heat transfer rate at lower disk is increases by increasing Deborah number. It is also observed that the surface mass transfer at both disks decreases by increasing Schmidt number.

Crystalline boron carbide (B4C) powder was synthesized by carbothermal reduction of condensed boric acid-cellulose product and effect of structural homogeneity of precursor on low-temperature synthesis of B4C was investigated on basis of cellulose-derived structural development. The formation of condensed products was confirmed by FTIR and TGA analyses. The pyrolyzed products of cellulose precursor at 400 °C for 2 h were composed of fine dispersion of carbon fibers with B2O3 particles. The formation of carbon fibers favored conversion kinetics of B4C synthesis. The formation of crystalline B4C started and completed at 1100 and 1200 °C, which was one of the lowest temperatures reported for polymeric precursor route. Morphology of synthesized B4C transformed from polyhedral to equiaxed as synthesis temperature was raised from 1150 to 1200 °C. Nitrogen physisorption measurements revealed that synthesized B4C powders had mesopores with high surface area indicating large interfacial area of B2O3/carbon fibers resulting in more nucleation sites.

Cadmium selenide (CdSe) thin films were deposited on the glass substrates by using the resistive thermal evaporation method in the vacuum chamber. The effect of antimony doping on the physical properties of CdSe thin film has been investigated. The structural and surface properties such as lattice parameters, grain size, microstrain and dislocation density of the thin films were characterized by X-ray diffraction (XRD) technique. The compositional properties were studied by the mean of Rutherford backscattering (RBS) and UV–Vis–NIR spectrophotometer used to determine the refractive index, absorption coefficient and optical energy band gap of thin films. The FTIR absorption spectra confirmed the presence of CdSe vibrational mode in the range 400 cm−1 to 700 cm−1. The electrical conductivity of the films was carried out with the help of impedance analyzer, which has been increased up to 1% on Sb doping. The transmission has been reduced up to 18% with the increase in Sb doping and shifted toward lower wavelengths

We report the experimental work for the determination of wavelength standard to validate the measurements of Fourier transform spectrometer. A dc run hollow-cathode discharge with two anodes on either sides of a cathode is designed for the p recise measurements of He II lines at 4686 A. The Doppler width and ion-drift shift were measured by using each anode alternatively wh ich changes the direction of electric field fro m 0 o to 180 o . The stability of He II line has been investigated and comparable precision with respect to previous work has been obtained. Excellent wavelength accuracy with relative uncertainty in line position of the order of 10 8 is within reach of single point calibration factor.

Thin films of cadmium sulfide with very well defined preferential orientation and relatively high absorption coefficient were fabricated by thermal evaporation technique. The research is focused to the fabrication and characterization of the compositional data of CdS thin films obtained by using X-ray diffraction, scanning electron microscope along with energy dispersive X-ray spectroscopy. The optical properties were studied by using a UV-VIS-NIR spectrophotometer. The effects of silver-doping by ion exchange process on the properties of as-deposited CdS thin films have been investigated.

Thin films of CdS were fabricated by close spaced sublimation technique under vacuum of ∼10−5 mbar at a source temperature of 550 °C for various periods of time. These as-deposited thin films were immersed into Cu (NO3)2 solution at 80 ± 5 °C for variety of time to ensure Cu doping. The structural, surface, optical and electrical analyses were completed with the help of X-Ray Diffraction, Scanning Electron Microscope with Energy Dispersive X-Ray, UV-VIS-NIR Spectrophotometer and Hall Measurement System respectively. The transmittance of as-deposited sample is reduced from 80% to 30% with increasing copper immersion time. The mobility increased from 6.67 × 101 to 1.15 × 103 cm2/Vs due to the change in the carrier concentration.

We report the magnetic characteristics of Pb-doped Sr-ferrites at room temperature. The polycrystalline samples of the series \(\mathrm{Sr}_{0.5}\mathrm{Pb}_{0.5}^{2 +} \mathrm{Fe}_{12 - x}\mathrm{Pb}_{x}^{3 +} \mathrm{O}_{19}\) (x=0, 0.2, 0.4, 0.6, 0.8, 1.0) have been prepared by the standard ceramic technique with the aim to study the magnetic properties including coercivity, remanence, and energy at room temperature. The measurements show decreasing trends in coercivity and remanence from 4682 Oe to 1783 Oe and from 1833 G to 1511 G for the sample with x-content of 0.0 to 1.0, respectively. A minute addition of Pb affects the behavior of the materials by decreasing its energy product.

Synthesis of one-dimensional nanostructures, such as nanowires, is of vigorous significance for achieving the desired properties and fabricating functional devices. In this work, we report the synthesis of tin oxide (SnO2) nanowires on gold-catalyzed silicon substrate by carbothermal reduction process. SnO2 nanowires were synthesized with SnO2 and graphite powders as the source materials at atmospheric pressure and temperature of 900°C in the ambience of nitrogen (N2) gas. First, the effect of source material ratio SnO2:C on growth of SnO2 nanowires was studied. The structural, morphological and compositional properties of the samples were investigated by X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy. The scanning electron microscopy investigation reveals that uniform dense nanowires of SnO2 (diameter ~127 nm and length ~40 µm) were synthesized with vapour–liquid–solid mechanism. Ultraviolet–visible spectra estimate that the optical band gap of the synthesized SnO2 nanowires was 3.72 eV. Second, the gas sensing performance of synthesized SnO2 nanowires was investigated by testing with carbon monoxide (CO), Methane (CH4) and methanol (CH3OH) gases at different operating temperatures and concentrations. Results indicate that the synthesized SnO2 nanowires are highly promising for gas sensing applications.

Closed space sublimation (CSS) technique was used to deposit pure (99.99%) zinc selenide(ZnSe) powder on to glass substrates for fabricating the ZnSe thin films. The temperatures of source, substrate and the deposition time were optimized to deposit thin films of different thicknesses. Silver (Ag) was used as a dopant by ion exchange process in the ZnSe thin films. The structural analysis showed that as-deposited ZnSe thin films were polycrystalline having preferred orientation (111) direction. Micro structural parameters such as crystallite size, lattice parameter were determined using X-rays diffraction (XRD). Grains boundaries, roughness on surface and the grain density of the thin film samples were measured by scanning electron and atomic force microscopy before and after Ag doping.As-deposited, Ag-doped ZnSe samples before and after annealing were optically characterized by spectrophotometer in ultra violet, visible and infrared regions. The energy band gap of as-deposited ZnSe thin films for varying thicknesses were ranging from 2.62-2.67 eV which was reduced after Ag doping.The electrical properties showed that as-deposited thin films were highly resistive of the order of 10 -cm and after Ag immersion, it was reduced to 1 -cm. Deposition parameters and Ag doping 8

Distances for taking evacuation as a protective measure during early phase of a nuclear accident have been approximated using MELCOR Accident Consequence Code System (MACCS). As a reference data, the source term of Pakistan Research Reactor 1 (PARR-1) and meteorological data of Islamabad, Pakistan, have been considered. Based on comparison with published data and international radiological assessment (InterRAS) code results, it is concluded that MACCS is a rational tool for estimation of urgent protective actions during early phase of nuclear accident by taking into account the variations in meteorological and release concentrations parameters.

Sodium benzoate (SB) is used for the first time to inhibit the corrosion of Al6061-B4C composites in H3BO3 and NaCl solutions. Al6061100−x –x wt% B4C (x = 0, 5, and 10) composites are manufactured by a powder metallurgy route. The corrosion inhibition efficiency of SB is investigated as a function of the volume fractions of B4C particles by using potentiodynamic polarization and electrochemical impedance techniques. Without the use of an inhibitor, an increase of the B4C particles in the composite decreases the corrosion resistance of Al6061-B4C composites. It is found that SB is an efficient corrosion inhibitor for Al6061-B4C composites in both investigated solutions. The corrosion inhibition efficiency of SB increases with an increase in B4C content. Since SB is an adsorption type inhibitor, it is envisaged that an extremely thin layer of molecules adsorbs onto the surface and suppresses the oxidation and reduction. It is found that the inhibitor effect of SB is more pronounced in a H3BO3 environment than in NaCl solution. Further, the mechanism of corrosion inhibition by SB is illustrated by using optical and scanning electron microscopy of corroded samples. It is found that the adsorption of benzoate ions on the Al surface and its bonding with Al3+ ions forms a hydrophobic layer on top of the exposed Al surface, which enhances the protection against dissolved boride ions.

Fuel cell is undoubtedly widespread energy conversion technology, which can convert fuel (biogas) energy into electricity. Solid oxide fuel cell (SOFC) is one of the best choices among the fuel cell’s family due to high efficiency and fuel flexibility. In this study, zinc-based nanostructured [Formula: see text] electrode materials were successfully developed by solid state reaction. The proposed materials have been characterized by XRD and SEM. The electrical conductivities have been examined by four-probe DC method in the temperature range of 300–600[Formula: see text]C, the maximum values were recorded and found to be 12.019 and 5.106 S/cm at natural gas and air atmosphere, respectively. The electrochemical performance has been measured employing NK-SDC electrolyte material and their current density versus voltage and current density versus power density (I-V and I-P characteristics) have been drawn. The maximum power density was found to be 170 mW/cm2 using natural gas as a bio-fuel over a temperature of 600[Formula: see text]C.