In this paper, we synthesized and investigated the structural, optical, and electrical properties of spin-coated zinc-tin-oxide thin films with varying molar ratios and total precursor concentrations ...for photocatalytic applications. The structural studies were carried out using XRD and Raman spectroscopy. XRD and Raman analysis confirms that all the polycrystalline films are composed of ZnO and Zn2SnO4 mixed phases. UV–Vis and fluorescence spectroscopy were used to investigate the optical properties and estimate the band gap of the thin films. Dual absorption edges are observed in the UV–Vis absorption spectra of films prepared with a Zn/Sn = 2 M ratio. Photoluminescence studies confirm the dominated near band edge (NBE) emission for films prepared with a Zn/Sn = 2 M ratio. The electrical resistivity and Hall Effect measurement were carried out on all the studied compositions. The Haacke's figure of merit (FOM) is found to be in the range of 3 × 10−6 to 9 × 10−7 for the studied samples. The as-grown films were subjected to photocatalytic degradation studies using methyl orange (MO) dye under UV light irradiation. We achieved MO degradation efficiency as high as 80% in less than 90 min.
In this article, the capping action of Sodium carboxymethyl cellulose (NaCMC) on ZnS nanoparticles synthesized by microwave-assisted method is reported. The X-ray diffraction and electron diffraction ...studies corroborated nanocrystalline nature of cubic ZnS. Discontinuous cluster growth of particles was implied by optical absorption studies. This was reflected in transmission electron microscope images. Fourier-transform infrared studies confirmed NaCMC capping on the surface of ZnS nanoparticles. Effective encapsulation of ZnS nanoparticles by NaCMC was further supported by Raman scattering, thermal studies and photoluminescence studies. Surface modification of ZnS nanoparticles with NaCMC appear to be suitable for specific biomedical applications due to the nontoxicity of ZnS and NaCMC.
The structure and properties of vacuum-evaporated silver (Ag) nanoparticulate films on softened poly(1-vinylpyrrolidone-
co
-vinyl acetate) P(VP-
co
-VAc), containing pyrrolidone and acetate moieties ...are reported. The particulate films are characterized by optical spectroscopy, field-emission scanning electron microscopy, transmission electron microscopy, atomic force microscopy (AFM), X-ray diffraction (XRD) and electrical resistance measurements. The broadening of the optical spectra, red-shift and increase in the intensity values of the plasmonic resonance peak with decrease in substrate temperatures has a strong dependence on the particle size, shape and inter-particle separation. Microscopy studies show smaller particles with larger gaps at higher temperatures. AFM studies indicate a reduction in the surface roughness with increase in substrate temperature. XRD studies indicate the formation of nanocrystallites of silver with preferred orientation. Lower thickness silver films and films deposited at higher substrate temperatures exhibit negative temperature coefficient of resistance indicating that these films are particulate. When the films are exposed to atmospheric air, the films show an irreversible increase in resistance with pressure. The extent of polymer–metal interaction caused by the strongly interacting amide group on the pyrrolidone moiety and the feebly interacting acetate moiety of the copolymer is discussed.
We report the annealing temperature dependence on the physical properties of TiO
2
(titania) thin films grown using solgel spin-coating method for various concentrations of precursors and ...stabilizers. X-ray diffraction (XRD) and atomic force microscopy (AFM) images, respectively, provided the structural properties and surface morphology of the films. The XRD results confirm the anatase phase in the films, and a comparative study on morphology has shown that the better uniformity and lower roughness in the films grown at 350 °C compared to films grown at 450 °C for different concentrations. The optical properties of titania thin films were investigated by UV–Vis transmittance and photoluminescence (PL) spectra. All the films exhibited high transmittance, and the indirect bandgap obtained for the films annealed at 350 °C and 450 °C varies between 3.45 and 3.34 eV. The PL spectra provide information regarding defect states in the film for different concentrations. The electrical resistivity of the sample with molar ratio 0.2:0.4 M film decreased for both temperatures compared to other samples.
•A Laser Doppler Vibrometer (LDV) was used to obtain online data acquisition of work piece vibration.•Fast Fourier Transform (FFT) analyzer used to transform the acousto-optic emission (AOE) signals ...into frequency domain.•Artificial neural network used to predict surface roughness, tool wear and work piece vibrations.
Machining of stainless steel is difficult due to their hardening tendency. In boring of stainless steels, tool wear and surface roughness are affected by vibration of boring bar. In this paper, tool wear, surface roughness and vibration of work piece were studied in boring of AISI 316 steel with cemented carbide tool inserts. A Laser Doppler Vibrometer was used for online data acquisition of work piece vibration and a high-speed Fast Fourier Transform analyzer was used to process the acousto optic emission signals for the work piece vibration. Experimental data was collected and imported to artificial neural network techniques. A multilayer perceptron model was used with back-propagation algorithm using the input parameters of nose radius, cutting speed, feed and volume of material removed. The artificial neural network was used to predict surface roughness, tool wear and amplitude of work piece vibration. The predicted values were compared with the collected experimental data and percentage error was computed.
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•ZnS nanoparticles prepared by co-precipitation method followed by microwave irradiation.•Increase in the ZnS nanoparticle size with increase in time of irradiation.•Williamson-Hall ...method to find the zero strain crystallite size.•Reduced defect states due to microwave irradiation evidenced by photoluminescence.
In this communication, we report the synthesis of ZnS nanoparticles by chemical precipitation of Zn2+ ions with S2- ions in aqueous solution. Freshly formed ZnS nanoparticles (NPs) in colloidal suspension were microwave irradiated for different time intervals in a domestic microwave oven. Effect of microwave irradiation (MWI) time on microstructure, surface morphology and optical properties of NPs are studied using various characterization tools. The structural analysis confirms the influence of MWI time on cubic and crystalline nature of the samples which are in good agreement with selected area electron diffraction (SAED) pattern. The size of the NPs increased with increase in time of MWI. The size increase is consistent with literature reports that microwave irradiation accelerates not only the nucleation but also crystal growth. The band gap of the material tends to decrease as a function of irradiation time. The role of MWI time on surface defect removing process is also explained in detail.
The aim of the study is to apply a plasma nitriding process to the 90CrMoV8 steel commonly employed in wood machining, and to determine its efficiency to improve both mechanical and electrochemical ...properties of the surface. Treatments were performed at a constant N2:H2 gas mixture and by varying the temperature and process duration. The structural and morphological properties of nitrided layers were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) coupled with EDS microanalyses. Surface hardening and hardness profiles were evaluated by micro hardness measurements. To simulate the wood machining conditions, electrochemical tests were carried out with an oak wood electrolyte with the purpose of understanding the effects of the nitriding treatment on the corrosion resistance of the tool in operation.
X-ray diffraction analyses revealed the presence of both γ′ (Fe4N) and ε (Fe2–3N) nitrides with a predominance of the ε phase. Moreover, α-Fe (110), γ′ and ε diffraction peaks were shifted to lower angles suggesting the development of compressive stresses in the post nitrided steel. As a result, it was shown that nitriding allowed a significant hardening of steel with hardness values higher than 1200HV. The diffusion layers were always composed of an outer compound layer and a hardened bulk layer which thickness was half of the total diffusion layer one. No white layer was observed. Similarly, no traces of chromium nitrides were detected. The temperature seemed to be a parameter more influent than the process duration on the morphological properties of the nitrided layer, while it had no real influence on their crystallinity. Finally, the optimal nitriding conditions to obtain a thick and hard diffusion layer are 500°C for 10h.
On the other hand, to verify the effect of these parameters on the corrosion resistance, potentiodynamic polarization tests were carried out in an original “wood juice” electrolyte. After corrosion, surface was then observed at the SEM scale. Electrochemical study indicated that the untreated steel behaved as a passive material. Although the very noble character of steel was somewhat mitigated and the corrosion propensity increased for nitrided steels, the passive-like nature of the modified surface was preserved. For the same optimized parameters as those deduced from the mechanical characterization (500°C, 10h), surface presented, in addition to a huge surface hardening, a high corrosion resistance.
► Modification of 90CrMoV8 steel by plasma nitriding for wood machining. ► Enhancement of hardness and wear resistance without losing intrinsic protectiveness. ► Electrochemical tests in wood juice as the electrolyte. ► After plasma treatment high and durable corrosion resistance. ► Optimal nitriding parameters are 500 °C, 10 hours for best good behaviors.
In the plasma ionic environment of nitrogen and hydrogen at 4:1 ratio, nitriding had been realized in the plasma laboratory. Nitriding of steel samples was followed at the lower temperature of 450 °C ...and also at the higher temperature of 550 °C while the sample was biased at the fixed − 250 V. Steel nitrided at 550 °C had shown a significantly enhanced resistance to corrosion in comparison to that of steel nitrided at 450 °C. X-ray diffraction studies of nitrided steels had shown the presence of nitrides of iron (FexN). Scanning electron microscopic and the electron dispersive spectroscopic analyses (SEM + EDS) of the cross section of the nitrided steels had shown the nitrided layer and the elemental distribution from top to the core. Following structural analysis, microhardness and the potentiodynamic polarization tests were performed. A significant improvement in hardness (~ 1180 Hv) and the case depth ~ 150 µm was obtained after nitriding at the higher temperature. Corrosion resistance was also found to be significantly improved. These achievements might be attributed to the presence of FexN, CrN phases and also to the nitrogen solid solution.
The current report focuses on the properties of Zinc–Tin-Oxide (ZTO) thin films coated on quartz substrates via spin coating technique. The two parameters considered during the thin film preparation ...and post deposition treatment include the cation concentration (Zn and Sn) in the precursor solutions and air annealing temperatures. Films were grown by using precursor solutions with different concentrations in the range 0.2–0.6 M and annealed at various temperatures between 600 and 900 °C. The X-ray diffraction studies revealed that the films annealed at 700 °C exhibit high crystallinity with a mixed phase of Zn2SnO4 and SnO2 for all the cation concentrations. FESEM images infer the growth of these films with closely packed porous structure uniformly covering the substrate. Raman spectra revealed the presence of characteristic vibrational modes of Zn2SnO4 at 378 and 669 cm−1 for higher cation concentration samples annealed at 700 °C. The optical studies revealed that the films exhibited high transmittance and the bandgap estimated was found in the range of 3.6–3.9 eV for all films. The visible light emissions due to defect centres located within the forbidden gap in ZTO films was evident through the photoluminescence studies. The electrical measurements of the annealed samples for different cationic concentrations yielded resistivity values in the range of 103 to 102 Ω-cm.
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•Investigated systems show interesting photophysics in DMSO–water mixture.•Inter-chromophoric interaction is present in highly substituted systems.•DFT calculation results support the ...experimental findings.•Strongly modulated photochemistry at low DMSO content (XDMSO=0.1–0.3).•Can lead in designing artificial photosynthetic antenna system by placing suitable trapping site.
The photophysical behavior of a series of flexible di-2-pyridylaminomethyl substituted ligands systematically substituted on a rigid benzene core and their corresponding mono-metallic Re(I) complexes have been investigated by steady state and time-resolved fluorescence spectroscopy in different composition of DMSO–water binary solvent mixtures. Unusual fluorescence properties in lower DMSO content (XDMSO=0.1–0.3) solvent mixtures is consistent with fascinating property of DMSO, which is known to perturb the hydrogen bonding ability of water with the solute. Spin allowed inter-ligand π–π* transition is more apparent in (1, 3) substituted systems. The calculated spectroscopic parameters of the complexes are significantly different from the ligands, mainly due to ligand to metal charge transfer. The experimental observations are in very good agreement with the theoretical results obtained at B3LYP/6-31G(d,p)/LANL2DZ level of density functional theory (DFT) calculation. Natural bond orbital (NBO) analysis and examination of frontier molecular orbitals reveal that the basic architecture of the symmetrically substituted multi-chromophoric ligand can induce excitation energy hopping, similar to an artificial antenna system.
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