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Effects of precursors and caustic bases on structural and vibrational properties of ZnO nanostructures elaborated by hydrothermal method
摘要： The effects of zinc ions source (zinc acetate and zinc sulfate) and caustic bases (sodium and potassium hydroxides) on structural, morphological and vibrational properties of ZnO nanostructures elaborated by simple low temperature wet chemical process are studied. The samples are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), infrared (FTIR) and Raman spectroscopies. XRD results show that ZnO structures are polycristalline hexagonal wurtzite with high crystal quality. SEM images reveal that the morphologies of the nanostructures are nanopencils except in those synthesized with zinc sulfate precursor and sodium hydroxide caustic base, where pencils agglomerate to form sand rose-like morphologies. EDAX measurements confirm the purity of the elaborated specimens by the presence of only Zn and O atoms in the samples. Raman spectroscopy studies show that the peaks, related to E2 high mode, are more intense in ZnO structures elaborated with zinc acetate when NaOH is used, and in ZnO structures elaborated with zinc sulfate when KOH is employed.
关键词： alkali hydroxides,hydrothermal synthesis,ZnO,structure,morphology,source precursor
更新于2025-09-23 15:23:52
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Morphology of TiO2 Layers with a Well-Developed Acicular–Fibrous Structure in VT-20 Titanium
摘要： We have studied the effect of size factors of substrates on the formation of TiO2 layers with a well-developed acicular–fibrous structure on VT-20 titanium. The proposed technique allows a TiO2 layer with a large surface area to be produced by etching in a KOH solution (without using hydrothermal synthesis conditions), followed by heat treatment. The layers thus produced consist of fibers 20–100 nm in diameter and up to 1 μ m in length, which are strongly bonded to the substrate surface. Their phase composition is dominated by rutile. The fiber growth process is shown to be influenced by substrate etching and heat treatment conditions, weakly influenced by the curvature of the substrate, and independent of its dimensions.
关键词： large surface area,acicular structure,morphology,titania
更新于2025-09-23 15:21:21
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Distribution of Al Element of Ti–6Al–4V Joints by Fiber Laser Welding
摘要： In the process of laser welding, the uneven distribution of solute elements caused by element burning loss and ?ow of molten pool a?ects the quality of joints. In this paper, butt welding experiments were conducted on the 3 mm thick Ti–6Al–4V specimens with di?erent preset ratios of Al and Si powders by using 4 kW ?ber laser. The distribution of Al solute element and its in?uence on the microstructure and mechanical properties of the ?nal weld joint were investigated. The results showed that the self-di?usion of Al element and the ?ow of molten pool a?ects the alloy elements distribution in laser welding. And the microhardness of the welded joint with Ti–6Al–4V and 90% Al + 10% Si powders was signi?cantly higher than that with only Ti–6Al–4V, with the di?erence of about 130HV. At the same time, in the joint with 90% Al and 10% Si powders, the acicular α’ size was ?ner, and basketweave microstructure was present as well. This research is helpful to better understand the distribution of Al solute element and its in?uence on the joint quality during laser welding of Ti–6Al–4V alloy, which provides a certain reference for improving the weld or surface properties of Ti–6Al–4V alloy during laser processing.
关键词： Ti–6Al–4V alloy,structure morphology,laser welding,elements distribution,microhardness
更新于2025-09-16 10:30:52
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Effect of Different Anions Upon the WO <sub/>3</sub> Morphology and Structure
摘要： In this study the effects of various anions (SO2? 4 , ClO? 4 and PO3? 4 ) were investigated on the hydrothermal treatment of WO3 from Na2WO4 and HCl at 180 and 200 °C. The products were analyzed by XRD and SEM. With the usage of SO2? 4 the obtained product was hexagonal (h-) WO3 in the form of nanorods at both temperatures. Applying ClO? 4 resulted in a mixture of WO3 · 0.33H2O and small amount of m-WO3 at 180 °C and pure WO3 · 0.33H2O at 200 °C. The morphology was consisted of cuboid shapes arranged into spherical structures at 180 °C and longitudinal ones at 200 °C. By the application of PO3? 4 no product formed at either temperature. Using the combination of SO2? 4 and ClO? 4 the product was h-WO3 at both 180 and 200 °C with rod-like crystals; thus, the effect of ClO? 4 was overdominated by the SO2? 4 ions. Utilization of PO3? 4 together with SO2? 4 , and/or ClO? 4 to the reaction mixture completely blocks the hydrothermal formation of solid products by forming water soluble phosphotungstic acids.
关键词： PO3? 4,Hydrothermal Treatment,SO2? 4,ClO? 4,Structure,Morphology,Tungsten Oxides
更新于2025-09-09 09:28:46