Nanostructured Te-doped SnS thin films (SnS1−xTex, x = 0.0, 0.020, 0.027, 0.032, 0.036) were deposited on fluorine doped tin oxide (FTO) substrate from aqueous solution containing 2 mM SnCl2 and ...16 mM Na2S2O3 and various amounts of 5 mM TeO2 solution. The pH, temperature, time, and deposition potential (E) of the solution were kept at 2.1, 60 °C, 30 min and −1 V, respectively. The deposited films were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), photoluminescence (PL) and UV–Vis. XRD patterns obviously indicated that the synthesized films were polycrystalline with orthorhombic structure and by increasing the amount of Te concentration, the crystallinity was decreased. The FESEM images showed that the morphology of the nanostructures was changed with increasing Te content. PL and UV–Vis analysis were used to investigate the optical properties of materials. The PL spectra showed a red shift with increasing of Te concentration. The UV–Vis spectra showed that the optical bandgap energy decreased from 1.44 to 1.28 eV with an increase in the Te concentration. Solar cell devices were assembled using the deposited films as working electrodes and FTO as the counter electrodes. The conversion efficiency of solar cell based on SnS with Te-doping was increased compared with the SnS without Te-doping solar cell.
•SnS1−xTex thin films were prepared by electrodeposition method on FTO glass substrates.•The XRD patterns obviously showed that the synthesized film was polycrystalline.•The UV–Vis shows a variation in the optical band-gap energy of SnS1−xTex films from 1.28 to 1.44 eV.•SnS1−xTex films would be suitable for the absorber layers in solar cells.•The solar cell based on Te-doped SnS has higher conversion efficiency compared with SnS solar cell.
ZnO nanosheets and nanoflakes were grown on alumina particles in the absence of surfactants via heterogeneous precipitation using urea, zinc acetate and bayerite as precursors. Thermo-gravimetric ...analysis （TGA）, X-ray diffraction （XRD） and Fourier transform infrared spectroscopy （FTIR） were used and the results indicated the formation of only two phases： wurtzite-type ZnO and γ-Al2O3. ZnO nanoflakes were grown on alumina particles in the samples with ZnO content of 40 and 60 wt%, By increasing the ZnO content to 80 wt%, a porous hierarchical structure of ZnO with nanosheet arrays appeared. Both of these nanoflakes and nanosheets were about 40-80 nm in thickness and about 1-2 μm in diameter. It was proposed that Zns（CO3）2（OH）6 nuclei undergo higher growth rates in thin sheets at edges of bayerite particles with a higher surface energy. The Brunauer-Emmett-Teller （BET） measurements proved a reachable high surface area for hierarchical structures of ZnO nanosheets, which could mainly be attributed to their unique growth on alumina particles. Also, UV absorption results revealed that ZnO--Al2O3 compositions still show the UV characteristic absorption of ZnO, which can evidence the presence of photocatalytic properties in ZnO-Al2O3 compositions.
Alpha-alumina–boron nitride (α-Al2O3–BN) nanocomposite was synthesized using mixtures of aluminum nitride, boron oxide and pure aluminum as raw materials via mechanochemical process under a low ...pressure of nitrogen gas (0.5MPa). The phase transformation and structural evaluation during mechanochemical process were investigated by X-ray diffractometry (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and differential thermal analysis (DTA) techniques. The results indicated that high exothermic reaction of Al–B2O3 systems under the nitrogen pressure produced alumina, aluminum nitride (AlN), and aluminum oxynitride (Al5O6N) depending on the Al value and milling time, but no trace of boron nitride (BN) phases could be identified. On the other hand, AlN addition as a solid nitrogen source was effective in fabricating in-situ BN phase after 4h milling process. In Al–B2O3–AlN system, the aluminothermic reaction provided sufficient heat for activating reaction between B2O3 and AlN to form BN compound. DTA analysis results showed that by increasing the activation time to 3h, the temperature of both thermite and synthesis reactions significantly decreased and occurred as a one-step reaction. SEM and TEM observations confirmed that the range of particle size was within 100nm.
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•Some new fluorescent azo-pyrazole-sulfonamide hybrids have been synthesized.•According to the values of universal index of electrophilicity (ω), the dye 5d has the highest ω.•The ...values of ionization potential from photoelectron emission spectrometry are in the range from 5.58 to 6.07 eV.•The highest photocurrent is obtained for individual DSSC based on dye with –NO2 group.
In this study, we have designed and investigated four new low-emitting fluorescent dyes consisting of sulfonamide derivatives with substitution groups in the LUMO moiety. In these dyes, sulfonamide linked with pyrazole group played an important role in complementing the acceptor moieties. The optical properties of dyes were evaluated by the UV–VIS absorption, photoluminescence spectroscopy and photoluminescence decay time analysis in the non-doped solid film. The strong effect of substitution by –NO2 group was impressive, when, the dyes ionization potential photon energy values reached to 5.58, 5.82, 5.83 and 6.07 eV. According to X-ray diffraction, dyes were not amorphous and value of crystallite size was ∼100 nm. The dyes have a promising application as a hole layer in dye sensitized solar cells (DSSCs), due to the separation distribution of HOMO-LUMO, thermal stability, small crystal size, high PLQY, high optical band gap and high electron affinity. Finally, the DSSCs devices were fabricated based on the synthesized dyes and the results showed that the efficiency of the DSSCs based on a dye with –NO2 group is higher (3.27%) than that of the other dyes.
Detecting the sudden temperature increase of the milling vial, detecting the sudden total pressure increase inside the vial as well as XRD analysis from the synthesized phases are techniques that can ...be used to determine the ignition time in mechanically self-sustaining reactions (MSRs) induced by ball milling. In the present study a novel technique based on the Gene Expression Programming (GEP) algorithm is presented to estimate the ignition time in MSRs induced by high energy planetary mills, without any experimental testing. In other words, only by knowing some of the milling and reaction parameters comprised of ΔH/CP, ball to powder weight ratio (BPR), vial spinning rate, arithmetic mean of melting points of reactants, average diameter of balls and amount of used process control agent (PCA), one can predict the ignition time in the mentioned systems. Accordingly, most of the systems that are based on the MSR mode were gathered from the literature, and the data obtained from them are trained and tested by the GEP modeling algorithm. The results indicated a very good agreement between the experimental data and the predicted ones. The biogeography based optimization (BBO) was also utilized to optimize the milling parameters. Experiments were performed at the optimized parameters to proof the validity of the analysis. Given the broad range of the parameters used, it was found that our analysis and model are fully functional to accurately estimate the optimal conditions for planetary mills experiments which show the potential application of these calculations and analysis in materials science and engineering.
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•In this work the ignition time in mechanically induced self-sustaining reactions has been estimated.•Henceforward, it is not necessary to measure the vial temperature for determining the ignition time.•By knowing the milling parameters and without any experimental work one can predict the ignition time.•The results indicated a good agreement between the experimental data and the predicted ones.•The optimization results based on the BBO algorithm obtained a minimum ignition time.
► Al
2O
3/B
4C has been synthesized starting with Al, B
2O
3 and C (graphite). ► Reactions occurred in MSR mode. ► By increasing milling time, an exothermic reaction occurs before aluminum melting. ► ...The quantity of 9Al
2O
3·2B
2O
3 extremely decreased with an increase in milling time. ► It was found the particle size below 100
nm after more 4
h.
In this research, Al
2O
3/B
4C nanocomposite was successfully synthesized by combining of mechanically induced self-propagating reaction of aluminum, graphite and boric acid powders mixture. For this purpose the starting materials were activated in a planetary ball mill under Argon atmosphere. The structural evaluation of powder particles was investigated by X-ray diffraction, FTIR spectrometer and scanning electron microscopy (SEM). The effect of activation time on the combustion temperature and the reaction products was discussed based on STA experiments. The results indicated that the reaction between Al and B
2O
3 (aluminothermic reaction) is highly exothermic and should be in combustion mode. According to XRD analyses, the Al
2O
3/B
4C nanocomposite was fabricated after 4
h of high energy ball milling. Simultaneous thermogravimetric analyzer (STA) results showed that increasing the activation time to 3
h can decrease the temperature of combustion reaction to590
°C. SEM observations confirmed that the range of particle size was within 100
nm.
The Mg/HA/MgO nanocomposites were fabricated with pure magnesium and the addition of different amounts of hydroxyapatite and periclase nanopowders using a blend-cold press-sinter powder metallurgy ...technique to improve the bio-corrosion and mechanical properties of the resulting material. Potentiodynamic polarization, immersion and mechanical tests were used to investigate bio-corrosion and mechanical properties of the nanocomposites produced. The compositions of the corrosion products and surface morphologies of the corroded specimens were characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, transmission electron microscopy, and field-emission scanning electron microscopy. The corrosion resistance of the nanocomposites is shown to increase from 0.25kΩcm2 to 1.23kΩcm2 with the addition of 10wt.% MgO; additionally, decreasing the amount of HA from 27.5 to 12.5wt.% is shown to yield an increase in the compressive failure strain from 4.2 to 11.5%. The corrosion products of the composite surface are shown to be primarily Mg(OH)2, HA and Ca3(PO4)2. During immersion in SBF solution, the growth of the Mg(OH)2 nanorods on the nanocomposites increased the contact angle between the SBF solution and the substrate; as a result, the corrosion rate and hydrogen evolution rate decreased. The cell culture results indicate that Mg/HA/MgO nanocomposite is biocompatible with osteoblasts.
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•The lowest corrosion rate and hydrogen evolution rate were measured for Mg/12.5HA/10MgO (wt.%) nanocomposite.•The Mg(OH)2 nanorods were synthesized on the Mg/HA/MgO nanocomposites during immersion in SBF solution.•The compressive failure strain of Mg/HA/MgO nanocomposites increased as wt.% HA decreased.•Osteoblast cells were observed to adhere on the surface of Mg/HA/MgO nanocomposites.
In this research, Al2O3/B4C nanocomposite was successfully synthesized by combining of mechanically induced self-propagating reaction of aluminum, graphite and boric acid powders mixture. For this ...purpose the starting materials were activated in a planetary ball mill under Argon atmosphere. The structural evaluation of powder particles was investigated by X-ray diffraction, FTIR spectrometer and scanning electron microscopy (SEM). The effect of activation time on the combustion temperature and the reaction products was discussed based on STA experiments. The results indicated that the reaction between Al and B2O3 (aluminothermic reaction) is highly exothermic and should be in combustion mode. According to XRD analyses, the Al2O3/B4C nanocomposite was fabricated after 4 h of high energy ball milling. Simultaneous thermogravimetric analyzer (STA) results showed that increasing the activation time to 3 h can decrease the temperature of combustion reaction to590 degree C. SEM observations confirmed that the range of particle size was within 100 nm.
The influence of milling parameters (time and atmosphere) on the mechanochemical synthesis of nanocrystalline hydroxyapatite (n-HAp) using different raw materials was studied. Two distinct chemical ...reactions were activated for various milling times under air or in a high purity argon (99.998vol%) atmosphere. Then, the mechanically activated powder was heat treated at 800°C for 1h to produce n-HAp with high degree of crystallinity. Results revealed that the phase purity of products under both milling atmospheres was strongly influenced by the chemical composition of raw materials. The synthesized powders exhibited average sizes about 32 and 27nm under air atmosphere, and about 32 and 34nm under argon atmosphere. The fraction of crystalline phase drastically decreased after 80h of milling under both atmospheres. In addition, the fraction of crystalline phase for the annealed sample at 800°C was higher than the mechanosynthesized specimens. The results of morphological evaluation confirmed the formation of n-HAp with different morphologies each of which can be used for particular purpose.
In the present research, polycrystalline magnesium oxide (MgO) bodies were fabricated using spark plasma sintering (SPS) at different temperatures and times from MgO nanopowder. Microstructural ...development, densification, and optical properties were investigated during SPS. The critical pressure of plastic deformation of the MgO compacts during sintering was also analyzed. The results showed that the plastic deformation phenomenon had a profound effect on the grain size and optical properties. In addition, the optical properties and microstructure of MgO bodies were strongly dependent on sintering temperature and time. Full-dense infrared-transparent magnesium oxide with a relative density of 99.99% was prepared at 1200 °C for 5 min under the pressure of 80 MPa. The spark plasma sintered MgO demonstrated the highest infrared transmittance of 72% in the 3–7 μm wavelength range, which was comparable with the values reported for MgO single crystal.
