Designing heterostructure materials at the nanoscale is a well-known method to enhance gas sensing performance. In this study, a mixed solution of zinc chloride and tin (II) chloride dihydrate, ...dissolved in ethanol solvent, was used as the initial precursor for depositing the sensing layer on alumina substrates using the ultrasonic spray pyrolysis (USP) method. Several ZnO/SnO2 heterostructures were grown by applying different ratios in the initial precursors. These heterostructures were used as active materials for the sensing of H2S gas molecules. The results revealed that an increase in the zinc chloride in the USP precursor alters the H2S sensitivity of the sensor. The optimal working temperature was found to be 450 °C. The sensor, containing 5:1 (ZnCl2: SnCl2·2H2O) ratio in the USP precursor, demonstrates a higher response than the pure SnO2 (∼95 times) sample and other heterostructures. Later, the selectivity of the ZnO/SnO2 heterostructures toward 5 ppm NO2, 200 ppm methanol, and 100 ppm of CH4, acetone, and ethanol was also examined. The gas sensing mechanism of the ZnO/SnO2 was analyzed and the remarkably enhanced gas-sensing performance was mainly attributed to the heterostructure formation between ZnO and SnO2. The synthesized materials were also analyzed by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray, transmission electron microscopy, and X-ray photoelectron spectra to investigate the material distribution, grain size, and material quality of ZnO/SnO2 heterostructures.
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IJS, KILJ, NUK, PNG, UL, UM
In this paper, we report results of morphological, structural, optical analysis of ultrasonically sprayed Cu-doped SnO2 thin films and their applications in conductometric gas sensors to detect small ...traces of CO molecules. Effects of Cu-doping on morphological, structural and optical properties of SnO2 nanostructures were investigated by Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), and UV–Vis. Spectroscopy measurements. Scanning electron microscopy revealed that porosity of the film surfaces is increased with increasing Cu-doping. From the XRD patterns, the size of the crystallites and crystal quality of the films are found to be decreased with Cu-doping. UV–Vis. spectroscopy results presented that the transmittance and bandgap can be manipulated with Cu-doping where both are decreased with Cu-doping. The relation between morphology and structure of the films with CO response properties are discussed properly. The gas response of the films with different Cu-doping has been investigated at different CO concentrations at different operating temperatures. From the sensing measurements, it is found that Cu-doping improves the SnO2 based sensor response to CO gas. Furthermore, the possible sensing mechanism to enlighten the improved gas sensing behavior of the films is proposed.
•CO sensing properties of Cu-doped SnO2 films deposited by ultrasonic spray pyrolysis method is reported for the first time.•Size of the crystallites and crystal quality of the films are found to be decreased with Cu-doping.•Cu-doping and temperature improve the SnO2 based sensor response to CO gas.•A possible sensing mechanism to enlighten the improved gas sensing behavior of the films is proposed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This study unveils the outcomes of fabricating and characterizing SnO2 thin films through ultrasonic spray pyrolysis. Also, it focuses on the effect of manipulating flow rates on their structural, ...optical, and electrical characteristics. Structural analysis revealed that the films exhibited a tetragonal rutile structure and (200) crystallographic planes become preferential as the flow rate increases. Crystallite size and lattice strain were calculated using the Debye-Scherrer and Williamson-Hall methods, demonstrating that higher the flow rate resulted in larger crystallite sizes and reduced lattice strain. SEM images showed that all films have uniform and consistent film thickness and grain size enlarged with the solution flow rate as well. The films exhibited high optical transparency (>80%) in the visible spectrum, making them suitable for transparent conductive applications. The band gap of the films decreased gradually with flow rates, and the Urbach energy slightly increased. Hall effect measurements revealed higher flow rates resulted in lower sheet resistance (lowest is 1.32 × 102 Ω/sq) and higher carrier mobility (highest is 22.12 cm2/V.s), indicating improved electrical properties. These findings offer valuable perspectives for forthcoming researches.
•(200) crystallographic plane becomes preferential as the flow rate increases.•A very consistent and uniform film thickness was achieved.•Film thickness increases with higher solution flow rates, leading to larger grains.•Optical transmittance exceeding 80% in the visible spectrum, is required for TCOs.•Higher flow rates result in lower sheet resistance and higher carrier mobility.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•Ru-doped MoO2 was prepared by ultrasonic spray pyrolysis in one step.•High-dispersed ruthenium had strong interactions with MoO2.•A high concentration of ruthenium on the MoO2 ...surface enhanced hydrogen evolution activity.•Ru-MoO2 showed excellent mass activity in all pH range.
Platinum (Pt)-based catalyst is a state-of-the-art catalyst for hydrogen evolution reaction (HER) of electrochemical water splitting. Nevertheless, to minimize the overall water electrolysis cost, a new catalyst must be developed. Ruthenium (Ru)-based catalyst has recently been found to be an efficient HER catalyst in all pH ranges of electrolytes. However, they demonstrated lower HER activity than Pt-based catalysts. Hence, to maximize the electrocatalytic activity, a highly dispersed Ru-based catalyst should be studied while maintaining a high-loading amount. This study prepares a high-dispersed Ru catalyst using the ultrasonic spray pyrolysis (USP) process on a molybdenum dioxide (MoO2) support. The USP process enabled the dispersion of Ru on MoO2 with high-loading (9 wt%) and dispersion. The high dispersion of Ru and the strong interaction between Ru and MoO2 improved the HER activity.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
MISIM (metal-insulator-semiconductor-insulator-metal) structures of alternating current thin film electroluminescent (ACTFEL) devices were deposited on ATO/glass substrates by the ultrasonic spray ...pyrolysis technique. Zirconium oxide and terbium doped zinc sulfide were used as dielectric and semiconductor phosphor layers, respectively. A focused ion beam equipment was used to prepare a lamella of the MISIM structure, for cross-sectional scanning electron microscopy analysis in the STEM mode. Chemical analysis by energy-dispersive X-ray spectroscopy (EDS) elemental maps was also made for the identification of the distribution of the elements through the layers composing the MISIM structure. Characteristic Tb3+ emission bands due the 5D4 ->7FJ transitions were obtained by AC voltage application at 10 kHz with the main peak centered at 542 nm. An increase in the electroluminescent intensity and a shift of the CIE coordinates toward a purer green color with increasing the applied voltage was observed. The threshold voltage of these green electroluminescent devices was 46 Vrms, and a luminance up to 41 cd/m2 was obtained for the maximum applied voltage of 76.9 Vrms.
•MISIM devices with green electroluminescence fabricated by ultrasonic spray pyrolysis.•The color purity of the green EL devices changes with the applied voltage.•Luminance up to 41 Cd/m2 is achieved for an operation voltage of 76 V.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In this study, the optimization of the deposition temperature, which directly affects the crystallinity, morphology, and electrical conductivity of SnO2 films deposited onto Corning Eagle XG glass ...substrates using the ultrasonic spray pyrolysis technique, was investigated to tailor their physical properties for various applications. Structural analyses revealed that the films had a tetragonal rutile structure, and while films deposited at lower temperatures exhibited a higher prevalence of (200) oriented planes, yet this decreased with an increase in deposition temperature. Morphological analyses showed that the films consisted of grains with octahedral shapes, and films deposited at lower temperatures were found to be more compact. The films had bandgap energy ranges between 3.96 eV and 4.02 eV. Hall effect measurements revealed that not only the carrier concentration decreased from 4.52 × 1019 cm−3 to 0.80 × 1019 cm−3, but the mobility also decreased from 23.32 cm2/Vs to 12.85 cm2/Vs. Among all the films, it was noted that the films deposited at 350 °C had the highest figure of merit which is 12.3 × 10−4 Ω−1. It can be concluded that the changes underlying these variations are associated with structural and morphological changes depending on the substrate temperature. Also, significant results have been attained in applications where precise control over crystal structure and surface morphology is crucial.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In this study, highly transparent conducting fluorine-doped tin oxide (FTO) electrodes were fabricated using the horizontal ultrasonic spray pyrolysis deposition. In order to improve their ...transparent conducting performances, we carried out oxygen activation by adjusting the ratio of O2/(O2+N2) in the carrier gas (0%, 20%, and 50%) used during the deposition process. The oxygen activation on the FTO electrodes accelerated the substitution concentration of F (FO •) into the oxygen sites in the FTO electrode while the oxygen vacancy (VO • •) concentration was reduced. In addition, due to growth of pyramid-shaped crystallites with (200) preferred orientations, this oxygen activation caused the formation of a uniform surface structure. As a result, compared to others, the FTO electrode prepared at 50% O2 showed excellent electrical and optical properties (sheet resistance of ∼4.0 ± 0.14 Ω/□, optical transmittance of ∼85.3%, and figure of merit of ∼5.09 ± 0.19 × 10–2 Ω–1). This led to a superb photoconversion efficiency (∼7.03 ± 0.20%) as a result of the improved short-circuit current density. The photovoltaic performance improvement can be defined by the decreased sheet resistance of FTO used as a transparent conducting electrode in dye-sensitized solar cells (DSSCs), which is due to the combined effect of the high carrier concentration by the improved FO • concentration on the FTO electrodes and the fasted Hall mobility by the formation of a uniform FTO surface structure and distortion relaxation on the FTO lattices resulting from the reduced VO • • • concentration.
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IJS, KILJ, NUK, PNG, UL, UM
Dispersion of oxide nanoparticles in W, leading to the dispersion strengthening of W alloys, has emerged as a viable strategy to overcome the brittleness of W. In particular, the introduction of ...stable Y2O3 as a secondary phase refines the grain and enhances the densification of W, leading to an increase in the density of sintered alloy. Thus, analyzing the composite effects of Y2O3 on the alloy, which has homogeneous dispersion of Y2O3 nanoparticles, can allow enhanced mechanical properties of the W-Y2O3 alloy. However, to date, most studies have focused on synthesis methodology for nanocomposites, which is advantageous to grain refinement and dispersion. It is worth paying attention to the interaction in the W-Y2O3 system, such as the ternary oxide system (W-Y-O) with a low eutectic temperature and the possibility of liquid-phase sintering, which has been reported a few. In this study, the effect of Y2O3 nanoparticles on the microstructure and micro-Vickers hardness of W was experimentally evaluated. W-Y2O3 alloys with precisely controlled compositions from 1 wt% to 10 wt%Y2O3 were successfully fabricated using an ultrasonic spray pyrolysis process and a subsequent spark plasma sintering. The proposed process yielded Y2O3 nanoparticles with uniform dimensions and distributions even after sintering. Furthermore, the formation of Y2WO6 and a liquid-phase sintered structure, as products of the interaction between W and Y2O3 depending on the Y2O3 fraction, were observed, and thermodynamical formation routes were suggested. Evidently, the W-2wt%Y2O3 sintered alloy, with uniformly dispersed Y2O3 nanoparticles (<50 nm), exhibited an improved hardness of 7.21 ± 0.15 GPa, as the W grains were refined to approximately 760 nm, and their density increased to 96.48%.
•Ultrasonic spray pyrolysis process was employed to disperse 1–10 wt% Y2O3 nanoparticles in the W matrix.•Homogeneous dispersion of Y2O3 in W-Y2O3 composites was achieved even at a high fraction of Y2O3.•The Y2WO6 phase and liquid-sintered structure were observed in W alloy with a composition above 5 wt% Y2O3.•The W-2wt%Y2O3 sintered alloy exhibited improved hardness due to densification and grain refinement by Y2O3 nanoparticles.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•LaNi1-xMnxO3 synthesized by spray pyrolysis as catalyst of methane dry reforming.•Spray pyrolysis created uniform micron size particles with mesoporous structure.•Mn significantly ...increased specific surface area and stability of LaNi1-xMnxO3.•Mn substituted catalyst had a lower coke deposition and changed reforming mechanism.
Dry reforming of methane is an attractive process because it uses two important greenhouse gases, CO2 for CH4, to produce valuable syngas. However, Ni-based catalysts are prone to a high carbon deposition in the dry reforming process. Mesoporous LaNi1-xMnxO3 perovskite (with x between 0 and 1) were synthesized by ultrasonic spray pyrolysis method. The substitution of Mn in the perovskite structure increased the specific surface area (from 7.2 for LaNiO3 to 22.4 for LaNi0.4Mn0.6O3), the pore size and pore volume. Temperature programmed reduction showed a lower reduction tendency of Mn-substituted samples, suggesting high structural stability. O2- temperature-programmed desorption showed significantly higher oxygen mobility as the result of partial Mn substitution. The Mn substitution improved the catalytic activity and stability, where LaNi0.6Mn0.4O3 achieved the highest conversion and remained relatively unchanged in the time on stream tests. The Mn substituted catalysts substantially decreased the carbon deposition and changed its form from whiskers to amorphous type. The XPS analysis suggests this change is due to the reversible transformation of Mn4+ and Mn3+, resulting in higher oxygen mobility. Microstructural characterization of the used catalyst revealed a lower sintering tendency for the Mn substituted catalysts than LaNiO3. Results suggest that Mn substitution significantly changed the catalytic mechanisms, where LaNiO3 removes carbon by forming La2O2CO3 intermediate, but the stable Mn substituted perovskite with high oxygen mobility and capacity removes the carbon through a cyclic redox mechanism.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
