Effect of magnesium content on thermal and structural parameters of Al–Mg alloys directionally solidified

In this study, the influence of magnesium content on thermal and structural parameters during the unsteady-state unidirectional solidification of Al–Mg alloys is analyzed. Using a special device, Al–Mg alloys containing 5, 10, and 15 wt% Mg were submitted to unidirectional solidification. Using a data acquisition system, the temperature variations along the casting during solidification were measured. From these results, the variations of solidification parameters as growth rate of dendrite tips, thermal gradient, cooling rate, and local solidification time were determined. The variation of global heat transfer coefficient at metal/mould interface was estimated through the adjustment of experimental temperature variation close to the interface and numerical predictions. Primary and secondary dendrite arms spacing variations during solidification were measured by optical microscopy. From these results, comparative analysis were developed to determine the influence of magnesium content.     

Investigation on certain optical,thermal, and Z-scan studies of nonlinear optical tris–sarcosine calcium chloride single crystal

Slow solvent evaporation was used to produce single crystals of Tris–Sarcosine Calcium Chloride (TSCC) from aqueous solution. The cell parameters of the grown crystals were determined using the single-crystal X-ray diffraction analysis. The existence of functional groups in TSCC was confirmed using the Fourier Transform Infrared spectrum analysis. Energy-Dispersive X-ray Analysis verified the chemical composition of the TSCC crystal. The optical transmittance of TSCC was greater than 90%, according to the UV–Vis–NIR transmittance spectrum measurements. This indicates TSCC is an appropriate material for NLO applications. The optical characteristics of the grown crystal, including band gap energy, were determined. The photoluminescence characteristics of TSCC crystal were also studied in order to better understand its optical device manufacturing. The thermal behavior of TSCC was investigated using the TGA/DTA and DSC studies. For various temperatures, the fluctuation of the dielectric constant and dielectric loss with regard to frequency variation was examined and the results were described in depth. The TSCC susceptibility χ⁽³⁾ and nonlinear refractive index n₂ values were evaluated. The saturation absorption of TSCC was revealed by open aperture Z-scan technique, and the self-defocusing performance was revealed by closed aperture Z-scan measurements.

     

Effect of γ-radiation on the optical properties of soda-lime-silicate glasses

We have studied the effect of γ-radiation on the optical constants of soda-lime-silicate glasses. As the irradiation dose grows in the interval from 3.7 to 3.7 × 10¹ Gy, the refractive index n increases, while the optical bandgap width decreases (from 3.13 to 3.05–3.09 eV); upon irradiation to a dose of 3.7 × 10² Gy, the refractive index n drops, while the optical bandgap width E _g increases up to 3.23 eV.     

Growth,structural, thermal,optical, and electrical properties of potassium succinate–succinic acid crystal

Potassium succinate–succinic acid (KSSA), semi-organic single crystals were grown by slow evaporation growth technique using water solvent. Single crystal X-ray diffraction study revealed that the KSSA crystal belongs to monoclinic system. FT-IR and FT-Raman spectral studies were performed to identify the vibrations of functional groups. TGA/DTA analyses were carried out to characterize the melting behavior and stability of the title compound. The UV–Vis–NIR spectrum showed that the grown crystal is transparent in the entire visible region. Fluorescence studies were carried out in the range of 200–700 nm. The optical nonlinearity of KSSA was investigated at 532 nm using 7 ns laser pulses, employing the open aperture Z-scan technique. The photoconductivity study was carried out to know the conducting nature of the crystal. The laser damage threshold was measured using Q-switched Nd:YAG laser (1064 nm). Electrical properties of the crystal are studied using Hall Effect measurement.     

Effect of alloy composition on structural, optical and morphological properties and electrical characteristics of GaxIn1−xP/GaAs structure

The structural, optical and morphological properties of Ga-rich Ga_xIn_1?xP layers with various gallium compositions grown on epi-ready semi-insulating (100)-oriented GaAs substrates by using Molecular Beam Epitaxy technique are presented in this study. The Ga_xIn_1?xP/GaAs structures (S1, S2 and S3) have been evaluated by means of high resolution X-ray diffraction, photoluminescence (PL) and atomic force microscopy measurements at room temperature. Experimental forward and reverse bias current–voltage (I–V) characteristics of structure S3 was investigated at room temperature due to its better characteristics when compared to the other two samples. The main electrical parameters such as ideality factor (n), barrier height (Φ _b ) and series resistance (R _s ) were extracted from forward bias I–V characteristics and Cheung’s function. In addition, Hall measurements were carried out as a function of temperature (30–300 K) and at a magnetic field of 0.4 T were presented for structure S3.     

Effect of Mg2+ ions substitution on phase formation,structural, morphological,and optical properties of Zn0.1−xMgxO structure

Journal of Materials Science: Materials in Electronics - In the present research work, Mg-doped zinc oxide Zn0.1?xMgxO (For x?=?0.000, 0.002, 0.006, 0.010) nanoparticles were...     

Effect of solution concentration on the structural, optical and conductive properties of ZnO thin films prepared by sol–gel method

ZnO thin films with different solution concentrations (0.1–0.9 mol/L) were prepared by a simple sol–gel dip-coating technique. X-ray diffraction, ultraviolet–visible spectroscopy, Hall effect measurements and photoluminescence (PL) spectroscopy were employed to investigate the effect of solution concentration on the structural,optical and electrical conductive properties of the ZnO thin films. The results showed that the ZnO thin films preferentially oriented along the (002) direction at higher solution concentration. The careful study of the optical and electrical conductive properties showed that the resistivity decreased monotonously, while the transmittance increased first and then decreased when solution concentrations changed from 0.1 to 0.9 mol/L. Photoluminescence spectra indicated that the defect-related blue emission was increased with the enhancement of solution concentration. The mechanism of the blue emission, and the reasons why high solution concentration was favorable for forming high c-axis oriented ZnO thin films and obtaining low resistivity were also discussed in detail.     

Crystal growth, structure and characterizations of a new semiorganic nonlinear optical material—β-Alanine zinc chloride

The title compound, β-alanine zinc chloride—a new semiorganic nonlinear optical crystal was grown by slow evaporation technique. Single crystals of β-alanine zinc chloride have been subjected to X-ray diffraction analysis to determine the crystal structure. The powder X-ray diffractogram of the crystal has also been recorded. The amount of carbon, nitrogen and hydrogen in the crystals was also estimated. Fourier Transform Infrared and Raman spectral measurements have been carried out on the grown crystals in order to identify the functional groups. The presence of hydrogen and carbon in the β-alanine zinc chloride was confirmed by using proton and carbon nuclear magnetic resonance spectral analyses. The percentage of zinc in the crystal was determined by atomic absorption spectroscopy. Optical behavior such as ultraviolet-vis-near infrared transmittance spectrum and second harmonic generation has been investigated. The mechanical strength and thermal behavior of the grown crystal have been analyzed.     

Influence of Yttrium on optical,structural and photoluminescence properties of ZnO nanopowders by sol–gel method

Undoped and Yttrium doped ZnO nanopowders (Zn_1−xY_xO, 0 ⩽ x ⩽ 0.05) were prepared by sol–gel method and annealed at 500 °C for 4 h under air atmosphere. The prepared nanopowders were characterized by powder X-ray diffraction, energy dispersive X-ray spectra, UV–Visible spectrophotometer and Fourier transform infrared spectroscopy. The EDS analysis confirmed the presence of Y in the ZnO system. Both atomic and weight percentages were nearly equal to their nominal stoichiometry within the experimental error. XRD measurement revealed the prepared nanoparticles have different microstructures without changing a hexagonal wurtzite structure. The calculated average crystallite size decreased from 26.1 to 23.2 nm for x = 0–0.02 then reached 24.1 nm for x = 0.05. The change in lattice parameters was demonstrated by the crystal size, bond length, micro-strain and the quantum confinement effect. The observed blue shift of energy gap from 3.36 eV (Y = 0) to 3. 76 eV (Y = 0.05) (ΔE_g = 0.4 eV) revealed the substitution of Y³⁺ ions into ZnO lattice. The presence of functional groups and the chemical bonding are confirmed by FTIR spectra. The appreciable enhancement of PL intensity with slight blue shift in near band edge (NBE) emission from 396 to 387 nm and a red shift of green band (GB) emission from 513 to 527 nm with large reduction in intensity confirm the substitution of Y into the ZnO lattice. Y-doped ZnO is useful to tune the emission wavelength and hence is appreciable for the development of supersensitive UV detector.     

Effect of ordered helium bubbles on deformation and fracture behavior of α-Zr

Radiation-induced helium bubbles are detrimental to the mechanical properties of metals, usually causing severe hardening and embrittlement. Hexagonal close-packed (HCP) α-Zr alloys are one of the primary structural materials for nuclear applications, however, the effect of helium bubbles on their deformation and fracture behaviors still remains unexplored. Here, we found that ordered helium bubbles prefer to align along the basal plane in HCP α-Zr. Micro-scale in situ tensile tests revealed that helium bubbles less than 8 nm in size can increase the critical resolved shear stress of the prismatic slip. However, once the helium bubbles are larger than 8 nm, a bubble-softening effect happens due to a decrease in number density of helium bubbles and an increase in porosity. Once the Schmid factor of basal slip is considerably higher than prismatic slip, bubble coalescence along the basal plane becomes the major failure mode in helium-irradiated α-Zr.     

Effect of sulfur and copper amounts in sol–gel precursor solution on the growth, crystal properties, and optical properties of Cu2ZnSnS4 films

Cu₂ZnSnS₄ (CZTS) thin films were deposited by sol–gel spin coating using precursor solutions prepared with copper acetate, zinc acetate, tin chloride, and thiourea in methanol and ethylenediamine followed by sulfurization. Sol–gel precursor solutions were prepared with different amounts of sulfur and copper, and their effects on film growth, crystal properties, and optical properties of CZTS films were investigated. CZTS film thickness increased with the amount of metal salt in the precursor solution. This is attributed to an increase in solution viscosity and a decrease in the solution density/viscosity ratio. All CZTS thin films exhibited kesterite structures with absorption coefficients larger than 10⁴ cm^?1 in the visible region. Band gap energy increased with increasing amounts of sulfur and decreasing amounts of copper. The blue shift of the band gap is attributed to changes in the degree of p–d hybridization related to Cu d- and S p-levels. The role of sulfur and copper on Hall mobility and carrier concentration was investigated. By optimizing the metal salt ratio in the precursor, CZTS film with a resistivity of 5.3 × 10^?2 Ωcm were prepared.     

Effect of γ-irradiation on the physical and mechanical properties of chitosan powder

In this study, locally produced chitosan powder was irradiated with pre-determined doses of γ-ray (Co-60) of 10 kGy, 25 kGy, 50 kGy and 100 kGy respectively. The properties of both chitosan powder and the chitosan film were examined and compared with unradiated chitosan. Physical characteristic of the irradiated powder and film was studied using stereo microscope. It was observed that the γ-ray induces a noticeable colour tone intensity change to the chitosan. Further investigation using Fourier Transformed Infrared Spectroscopy (FT-IR) analysis has confirmed that the chain scission reaction was occurred as a result of γ-ray exposure through the depolymerization mechanisms. Interestingly, the degree of deacetylation (DD) of chitosan measured using FT-IR showed a negligible effect due to the exposure of γ-ray radiation. Further investigation on the viscosity average molecular weight (M_v) showed a reduction of M_v from 577 kD of pure chitosan to 458 kD, 242 kD, 159 kD and 106 kD for 10 kGy, 25 kGy, 50 kGy and 100 kGy of γ-radiated chitosan respectively. In addition, the tensile strength and elongation at break showed a similar decreasing trend with increasing dosage of γ-ray.     

Electrical transport,optical and thermal properties of polyaniline–pumice composites

In this study, electrical conductivity, photoconductivity, absorbance and thermal properties of polyaniline (PANI) and polyaniline–pumice composites were investigated. Temperature dependent conductivity and photoconductivity measurements were carried out in the temperature range of 80–400 K. The measurements revealed that the dominant conduction mechanisms in polyaniline and 15% pumice doped composite were hopping conduction. The low activation energies calculated for 36% pumice doped composite indicated that this sample has highly defective and degenerate structure due to the high pumice content. Polyaniline and pumice doped composites showed semiconductor behavior with the exponential variation of inverse temperature dependence of electrical conductivity. Photoconductivities of the PANI and PANI–pumice composites under various illumination intensities were studied and it was found for all samples that the conductivity increased with increasing temperature and light intensity, but decreased with increasing pumice content in the structure. Absorbance spectrum has been determined in the wavelength range of 300–700 nm and it was found that the band gap values decreased as the pumice content was increased. Thermogravimetric analysis have shown for all samples that the mass loss has started above around 300 K due to the loss of moisture from the structures. As a result of this work, it was found that polyaniline and polyaniline–pumice composites had low resistivity and high band gaps and could be used as a window layer semiconductor in heterojunction solar cell applications.     

Impact of annealing temperature on structural,optical, and Mössbauer properties of nanocrystalline NiFe2O4

In this paper, we have investigated the effect of annealing temperature on the structural, optical, and Mössbauer properties of nanocrystalline (NC) nickel ferrites (NFOs) synthesized by the sol–gel auto-combustion method. The NFOs were characterized by X-Ray diffraction (XRD), Raman spectroscopy, Diffusion reflectance spectroscopy (DRS), and Mössbauer spectroscopy techniques. The XRD results show that the average crystallite size increases from 27.5 to 54.3 nm when increasing the annealing temperature from 200 to 1000 °C. The Ultraviolet–Visible Diffuse Reflectance Spectroscopy (UV-DRS) measurement is used to find the optical band gap observed between 1.92 and 1.75 eV for NFOs annealed at 200 and 1000 °C, respectively. The Mössbauer study confirmed that the structure transforms from mixed spinel to inverse spinel structure when moving to higher annealing temperature.

     

Effect of Zn source concentration on structural,optical and electrical properties of zinc sulphide–polyaniline (ZnS–PANI) nanocomposite thin films

Zinc sulphide–polyaniline (ZnS–PANI) nanocomposites are prepared by preparing ZnS nanoparticles in the same reaction bath for synthesis of PANI. Three different composites have been prepared by varying the concentration of zinc source. The films obtained from the colloidal dispersion are characterized by Scanning electron microscopy, energy dispersive analysis of X-rays, transmission electron microscopy, X-ray diffraction studies, Fourier transform infrared spectroscopy, UV–visible optical absorption, photoluminescence and current–voltage studies. Broadening of X-ray diffraction peaks suggest change in crystallite size and this is in agreement with the results from transmission electron microscopy. Fourier transform infrared spectra indicate crosslinking in the composite film. UV–visible absorption spectra of the film exhibit enhancement of doping level which is assigned to the existence of greater number of charges on the polymer backbone. Optical properties of the films are studied by measuring photoluminescence spectra. This shows decrease in intensity and blue shift with the increase in zinc source concentration. The blue shift indicates strong quantum confinement. Current–voltage characteristics exhibit excellent light response indicating tunneling type of conduction.     

Effect of processing routes on mechanical and thermal properties of copper–graphene composites

In this paper, copper–graphene composites were fabricated by using two different processing routes (ball milling (BM) and ultrasonication) followed by spark plasma sintering. Vickers hardness and anisotropic thermal conductivity of the composites were measured and observed that ultrasonicated fabricated composites gave better result compared with BM composite and even from pure copper. The hardness values obtained for ultrasonicated copper–graphene composite were 69?HV (57% higher) and thermal conductivity 387?W/m?K (13% higher) by using only 0.5?wt-% of graphene, while for pure copper the values were 44?HV and 341?W/m?K. The value of anisotropic thermal conductivity ultrasonicated composites was also 1.97 which is much higher than pure copper 0.94.     

Effect of Fe on the sintering and thermal properties of Mo–Cu composites

Effects of Fe on the sintering and thermal properties of Mo–Cu composites have been investigated. Mo–Cu–xFe composites are fabricated by powder metallurgy techniques with addition of various Fe contents ranging from 0.4 wt% to 2.2 wt%. The thermal properties and action mechanism of Fe to Mo–Cu composites are discussed. Results have indicated that the coefficient of thermal expansion (CTE) and thermal conductivity (TC) of Mo–Cu composites are greatly affected by the addition of Fe contents. It has also been observed that the fabricated composite powders with Fe additions exhibit high sinterability. Also, the inclusion of Fe can active the sintering course in shorter times and decline the sintering temperature thus also improving the physical properties of composites. Furthermore, it is also concluded that the utilization of steel kettle and steel balls for milling the Mo–Cu powders is also beneficial to improve the physical and thermal properties of Mo–Cu alloy.     

Effect of composition on the dielectric properties and thermal conductivity of α-SiAlON ceramics

Journal of Materials Science: Materials in Electronics - In this study, a series of dense Ym/3Si12-(m+n)Alm+nOnN16-n (m?=?1.1–1.5, n?=?1.0) ceramics were prepared by...