Papers by Keyword: Ultrasound

Abstract: Metal oxide semiconductors such as cobaltous oxide (Co₃O₄) and cuprous oxide (Cu₂O) have caught the attention of many researchers due to their wide variety of applications. The attachment of Cu₂O to Co₃O₄ was assisted by polyethylene glycol and the nanostructuring by ultrasonic sound. X-ray Diffraction (XRD) analysis of the fabricated composite reported characteristic peaks for crystalline Co₃O₄ and Cu₂O. Results from Energy Dispersive X-ray (EDX) Spectroscopy showed the presence of cobalt, copper, and oxygen atoms which supports the result obtained in XRD. Cauliflower to nearly spherical shaped Cu₂O - Co₃O₄ nanostructures were formed as observed in the Scanning Electron Micrographs (SEM) with a mean diameter of 0.5-1.0 μm. the shape of the composite and its surface morphology was altered with the use of different precursor materials for the synthesis of the Co₃O₄ seed. A blue shift in the UV-vis was observed upon the use of nitrate based precursor indicating the presence of smaller and finer particles in the composite. Overall results prove that Cu₂O and Co₃O₄ can be synthesized using a facile solution approach with the aid of PEG and ultrasonic sound its application in the field of photocatalysis is probable.

Abstract: Several studies have been made on cell growth by the ultrasound irradiation. It is important to change the output, irradiation time and duty cycle for cell growth. The duty cycle determined the proportion of the time that the ultrasound was “on”. We can control cell growth by changing these three terms. The purpose of this study is to find the optimum conditions for cell growth and examine a new factor to influence cell growth. Cell concentration was determined by measuring the absorbance with a spectrophotometer. In this study, the absorbance became highest on 10min ultrasound irradiation and the duty cycle of 67% in experimental conditions. However, when 30 min ultrasound irradiation and the duty cycles of 86%, the absorbance became close to the highest value too. The results suggested that, in addition to the duty cycle, the off time of ultrasound might also affect the cell growth.

Abstract: The article deals with the field tests of UHPFRC frames loaded by distant detonation of 50 kg of TNT and also by direct explosion of 120mm mortar shell. The paper analyses the results obtained from ultrasound diagnostics that was made before and after the explosion.

Abstract: A new method for non-destructive evaluation of the mechanical properties of structural materials has been developed. This is based on measurements of the ultrasound propagation velocity in deforming materials. Preliminarily investigations were carried out in order to relate the ultrasound propagation velocity to the mechanical characteristics of the deforming material. A detailed description of suitable devices intended for ultrasound propagation velocity measurement with high accuracy is presented. Using Zr-based alloys as an example, it is shown that the method can be used for the monitoring of zirconium billets from which nuclear reactor fuel cladding is fabricated by cold rolling.

Abstract: Currently, the use of technogenic raw materials, including wood waste is one of the trends in manufacturing of building materials. This is due to the limited resources, the need for long-distance transportation, the high material and energy cost of some technological processes of raw materials extraction and processing. All of them greatly hamper the development of the industry of building materials based on natural resources. Different cellulosic fillers of vegetable origin are used for the production of wood-cement compositions at the moment. Organic fillers along with the inherent valuable properties have a number of specific properties which have a significant effect on the processes of structure formation, structural-mechanical and construction properties of composites. The results of the research of the processes of water-soluble components removal from raw wood material are presented in the article. Processing of raw wood material was carried out in water and weak alkali solution in the research process. It is established that additional ultrasonic treatment considerably intensifies and increases the extraction of water-soluble sugars. The conducted research shows the possibility of improving the composite wood materials manufacturing technology with the aim of improving their performance without significant capital investments.

Abstract: Tool wear is an inevitable impediment in machining processes. It is the gradual failure of cutting tools due to regular use. Tool wear affects productivity, dimensional accuracy thereby indirectly representing a significant portion of the machining costs. In this paper, a novel technique has been proposed and adopted with an aim to reduce tool wear. External ultrasonic sound waves were applied in the turning process of mild steel in an attempt to reduce the cutting tool vibration thereby leading to improvements in tool life. In this unique technique ultrasonic sound has been applied from the both sides of the tool holder in the cutting process as waves to reduce tool vibrations and improvement of chip behavior at a certain optimized frequency. Experiments were carried out at 60 KHz ultrasonic frequency to determine the tool wear to the best degree possible. To investigate the cause of ultrasonic effects on tool wear, cutting tool vibration and chip morphology were also studied. The experimental results showed significant improvements in tool wear, vibration and chip behavior.

Abstract: Waste of electrical and electronic equipment (WEEE) is the fastest growing advanced type of solid waste streams in the urban environment worldwide and contains interesting amounts of precious metals. Hydrometallurgical technique is fast emerging as preferred process for the recovery of a variety of metals due to its lower energy consume and lower smelter emissions than conventional pyrometallurgical processes. In this work, a hydrometallurgical process for the recovery of gold and silver from electronic scraps was studied. In place of cyanide, thiosulfate was chosen as complexing agent for gold. Thiosulfate leaching can be considered a non-toxic process and the gold dissolution rates can be faster than conventional cyanidation. The electronic scraps, obtained from “end of life” mobile phones, were crushed and pre-treated with nitric acid before the leaching. Different parameters were studied: concentration of thiosulfate, temperature and reaction time. Moreover, the use of ultrasound to assist the hydrometallurgical gold extraction was investigated, as its application in ores leaching shows a greater metals release in shorter time and the advantage of working at lower concentration of reagents and at lower temperature. In this work, the use of ultrasound allowed a higher recovery of the precious metals than conventional leaching in all the conditions studied (different concentrations of reagents, temperature and reaction time). Moreover, the studied process allowed also the recovery of the other metals present in the waste (Cu, Sn and Ag).

Abstract: Based on the analysis of trends in the development of aviation and rocketry and ground transportation, the prospect of use of high-alloy steels, and titanium-based alloys with high strength, heat-and corrosion-resistant properties is established. It is shown, that high strength and elasticity of mentioned alloy groups adversely affect the dynamics of cutting process and the resistance of the cutting tool. Processing of small diameter holes is especially difficult due to the small longitudinal stability of the instrument, chip evacuation problems, grooves sticking to the surface almost zero cutting speed near the core. The results from the analysis of works of domestic and foreign scientists have shown that the message sent to the drill by ultrasonic vibrations of the small amplitude reduces axial force and cutting moment due to reduced friction caused by local thermal effects and relief of dislocation motion. At the same time, it is stated that the stable results of the effectiveness of ultrasound were not received in relation to the small diameter end tools until recently because of additional dynamic loads reducing the longitudinal stability and therefore it is impossible to report the instrument optimal oscillation amplitude to facilitate cutting. The working hypothesis of increase of efficiency of the ultrasonic drilling of small diameter holes proposes to consider correlation frequency supplied to the ultrasonic instrument, structural parameters and physical and mechanical properties of the material and to drive oscillations in the plane of the main cutting edges which would significantly reduce the magnitude of the oscillation amplitude. Experimental studies on ultrasound indentation, micro cutting and drilling titanium alloys have confirmed this hypothesis. It was established that at the moment the drill receives a message with the oscillation frequency of 30 kHz when machining titanium alloys, the axial cutting forces decrease by 70 – 80 % and the tool life increases by 2.2 times.

Abstract: Graphene nanoplates (GNPs) was immobilized with nanomagnetite using co-precipitation technique with the aid of ultrasound for the production of magnetic graphene nanoplate composite Fe₃O₄/G (MGNC) production. The physico-chemical properties of graphene were compared with the fabricated magnetic graphene composite using different characterization techniques. The crystalline and chemical structures of nanographene before and after magnetic immobilization were identified using X-Ray diffraction. The morphological structure of magnetic composite was identified by using Transmission Electron Microscope (TEM).it was carried out to investigate the precipitation of nanomagnetite onto the nanographene sheets. Atomic Force Microscope (AFM) analysis of magnetic graphene composites confirms the presence of magnetic nanoparticles attached to nanographene. The Vibrating sample magnetometer (VSM) confirmed the superparamagnetic properties of the prepared composite that represented with its hysteresis curve, and the saturation moment per unit mass, Ms for the MGNCs is 22.7548 emu·g−1

Abstract: This article deals with the study of direct current (DC), ultrasonic, and of electrolyte of the influence on the change of titanium dioxide sorption properties. The TiO₂ prepared by the TiCl₄ hydrolysis method. Attention is drawn to charging exchange processes the surface of titanium dioxide particles after they pass through a layer of counter ions in an aqueous medium under the influence of a DC. The stages of the end product’s formation using methods of the X-ray diffraction, the differential thermal and the infrared spectrometric and the gas adsorption analysis were proposed. Dependence of redistribution sorption active centers at the surface of TiO₂ was proved.