Academic literature on the topic 'Sonochemical analysis'

The application limits of optical and sonochemical methods to determine the sizes of cavitation bubbles and their derivatives have been analyzed. The effect of cavitation fields generated using an ultrasonic magnetostrictive oscillator and jet hydrodynamic emitter on the parameters of their acoustic signals has been examined. The bubbles size depending on emitter type and parameters has been determined using sonochemical analysis. The character of the dependence was estimated according to Minnaert formula. The bubbles dispersity in the flotation zone may be controlled by varying conditions of cavitation excitation.

Nanospheres of a new coordination polymer {[Cd2(µ-HL)(µ-L)(NO3)3(H2O)]·H2O}n (1) were easily prepared by a sonochemical method from cadmium(II) nitrate and HL (HL, pyridine-2-carboxaldehyde isonicotinoyl hydrazone) in ethanol. Single crystals of 1 were also obtained using a branched tube method. The crystal structure of 1 indicates that the µ-HL/µ-L− blocks act as linkers between the Cd(II) centers, assembling them into 1D tooth-shaped interdigitated chains, which are further interlinked into a complex 3D H-bonded network with a rare hms (3,5-conn) topology. Nanoparticles of 1 were characterized by elemental analysis, FT-IR spectroscopy, and powder X-ray diffraction (XPRD), while their spherical morphology was confirmed by transmission electron microscopy (TEM). Furthermore, in the presence of a surfactant, the thermolysis of sonochemically generated nanoparticles of 1 led to the formation of cadmium oxide nanospheres (cubic CdO) with an average diameter of 10 nm. This study extends the application of sonochemical synthetic methods for the generation of phase pure nanoparticles of coordination polymers and their thermolysis products.

While the sonochemical grafting of molecules on silicon hydride surface to form stable Si–C bond via hydrosilylation has been previously described, the susceptibility towards nucleophilic functional groups during the sonochemical reaction process remains unclear. In this work, a competitive study between a well-established thermal reaction and sonochemical reaction of nucleophilic molecules (cyclopropylamine and 3-Butyn-1-ol) was performed on p-type silicon hydride (111) surfaces. The nature of surface grafting from these reactions was examined through contact angle measurements, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Cyclopropylamine, being a sensitive radical clock, did not experience any ring-opening events. This suggested that either the Si–H may not have undergone homolysis as reported previously under sonochemical reaction or that the interaction to the surface hydride via a lone-pair electron coordination bond was reversible during the process. On the other hand, silicon back-bond breakage and subsequent surface roughening were observed for 3-Butyn-1-ol at high-temperature grafting (≈150 °C). Interestingly, the sonochemical reaction did not produce appreciable topographical changes to surfaces at the nano scale and the further XPS analysis may suggest Si–C formation. This indicated that while a sonochemical reaction may be indifferent towards nucleophilic groups, the surface was more reactive towards unsaturated carbons. To the best of the author’s knowledge, this is the first attempt at elucidating the underlying reactivity mechanisms of nucleophilic groups and unsaturated carbon bonds during sonochemical reaction of silicon hydride surfaces.

While the sonochemical grafting of molecules on silicon hydride surface to form stable Si–C bond via hydrosilylation has been previously described, the susceptibility towards nucleophilic functional groups during the sonochemical reaction process remains unclear. In this work, a competitive study between a well-established thermal reaction and sonochemical reaction of nucleophilic molecules (cyclopropylamine and 3-Butyn-1-ol) was performed on p-type silicon hydride (111) surfaces. The nature of surface grafting from these reactions was examined through contact angle measurements, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Cyclopropylamine, being a sensitive radical clock, did not experience any ring-opening events. This suggested that either the Si–H may not have undergone homolysis as reported previously under sonochemical reaction or that the interaction to the surface hydride via a lone-pair electron coordination bond was reversible during the process. On the other hand, silicon back-bond breakage and subsequent surface roughening were observed for 3-Butyn-1-ol at high-temperature grafting (≈150 °C). Interestingly, the sonochemical reaction did not produce appreciable topographical changes to surfaces at the nano scale and the further XPS analysis may suggest Si–C formation. This indicated that while a sonochemical reaction may be indifferent towards nucleophilic groups, the surface was more reactive towards unsaturated carbons. To the best of the author’s knowledge, this is the first attempt at elucidating the underlying reactivity mechanisms of nucleophilic groups and unsaturated carbon bonds during sonochemical reaction of silicon hydride surfaces.

The purpose of this paper is to carry out an economic and industrial evaluation on an industrial scale of NiFe2O4 production using sonochemical synthesis methods. The method used is to calculate gross profit margin (GPM), payback period (PBP), cumulative net present value (CNPV), total investment cost (TIC) and profitability index (PI). NiFe2O4 nanoparticles were synthesized with the main raw materials being Fe(NO3)3.9H2O, Ni(NO3)2.6H2O, and NaOH (1:2:8). The calculation results of GPM and CNPV/TIC from the NiFe2O4 industry using the sonochemical synthesis method show the payback period (PBP) in the third year. So that in the third year onwards it can be predicted that the industry will experience profits. This research is expected to be a reference for technical and economic analysis to produce NiFe2O4 in humidity sensor applications on an industrial scale.

The present work deals with the use of sonochemical and conventional mixing process for the preparation of calcium zinc molybdate (CZM) nanoparticles using calcium chloride and sodium zinc molybdate as a precursor material without addition of any emulsifying agent. This new process is useful to control the size and shape of the CZM nanoparticles. The formed product was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and differential thermal analysis (DTA). The formation of CZM was confirmed through XRD, FTIR and elemental analysis. The pH and conductivity results show that sonochemical process takes less time compared to conventional process for the preparation of CZM nanoparticles. The use of sonochemical process during the preparation of CZM nanoparticles results in reduction of the size and nearly the cubic shape is obtained due to the improved solute transfer rate, rapid nucleation, and formation of a large number of nuclei in the presence of cavitation.

Silicon nanocrystals in a range from 2 nm to 5 nm were prepared from Zintl salt, soldium silicide (NaSi) by sonochemical method. This synthesis permits that the reaction be completed in only a few hours and the easy alkyl-modification of nanocrystals surface at room temperature and ambient pressure. The average size of nanocrystals measured by the dynamic light scattering analysis was 2.7 nm. The high-resolution transmission electron micrograph confirmed the material identity of nanocrystals as crystalline silicon. FT-IR spectra are consistent with the surface states of nanocrystals that are chlorine-or butyl-capped. The emission peak center moved to a longer wavelength (up to 430 nm) with the reaction time, under a 325 nm excitation.

Ultrasonic descalers are used in dentistry to remove calculus and other contaminants from teeth. One mechanism which may assist in the cleaning is cavitation generated in cooling water around the descaler. The spatial distribution of cavitation around three designs of descaler tips and under three load conditions has been observed using sonochemiluminescence from a luminol solution and compared with the vibratory motion of the tips in a water bath, characterised by scanning laser vibrometry. The type of cavitation was confirmed by acoustic emission analysed by a ‘Cavimeter’ supplied by NPL. Surface profilometry and SEM of eroded hydroxyapatite pellets was performed to quantitatively study the erosion caused by a descaler tip in both contact and non-contact modes. Densitometry was used to study the erosion of black ink from a glass microscope slide, and determined that under the majority of conditions, no erosion was demonstrated via cavitation, by descalers operating in non-contact mode, although significant erosion was demonstrated with the tip in contact with the slide.

Ultrasonic instruments are used with the aid of an irrigant such as NaOCl in endodontic treatments to remove dentin debris and calculus from infected root canals. This cleaning process may be assisted by various factors, such as acoustic streaming, and the production of radicals and microjets from the collapse of transient cavitation bubbles. The aim of this project is to understand the principal factors affecting the performance of a number of different endosonic files in order to correlate to their cleaning efficiencies. Characterisation includes detecting transient cavitation activity, mapping the areas of cavitation, assessing the file vibration movements and the streaming effects produced by the files. Experiments to assess the cleaning efficiencies of the files include: emulsification, dye removal with a dental irrigant, ink and hydroxyapatite paste removal from model systems designed to mimic the structure of a tooth. The results show that there is a correlation between the sonochemical output and the cleaning efficiencies, and this brings in further study on the possible factors that may affect the production of transient cavitation and the vibration profiles of the endosonic files. Lastly, a series of computational simulation of the acoustic pressure fields from different endosonic files were performed. Correlations of the simulated and experimental results showed the difference in ultrasonic output of the endosonic files is strongly related to their design. This work provides the basis and techniques necessary to perform a comprehensive study on the design of the endosonic files in order to enhance and optimise their cleaning efficiencies during clinical use and to inform future endodontic practice.

Робота виконана на кафедрі хімії і технології неорганічних речовин Національного університету “Львівська політехніка” Міністерства освіти і науки України
У дисертації наведено результати досліджень з очищення водних середовищ від ароматичних сполук, зокрема бензену і толуену. Встановлено вплив температури, тривалості кавітаційного оброблення та кисню на їх деструкцію. Виявлено ефект кавітаційного ініціювання розкладу ароматичних сполук, зокрема внаслідок змішування кавітаційно обробленої та вихідної стічної вод. Ефективність розкладу бензену підтверджено дослідженнями з використанням гідродинамічного кавітатора. Досліджено кавітаційне окиснення бензену гіпохлоритними водами. Вивчено корозійну агресивність досліджуваних водних середовищ. Розроблену технологію очищення апробовано на реальних стічних водах. Визначено технологічні параметри кавітаційного очищення стічних вод від ароматичних сполук. Виконано узагальнені енергетичні та техніко-економічні розрахунки технологічного процесу.
The thesis presents results of research aimed at establishing an effective method of treatment of aqueous media from aromatic compounds, especially benzene and toluene. The influence of cavitation processing on the treatment of aqueous media has been investigated. In order to identify general patterns of the process and determine the direction of further research, the decomposition of benzene was studied under adiabatic conditions at room temperature. Studies have been carried out on cavitation destruction of benzene under various hydrodynamic conditions: with intensive mechanical stirring, without mechanical stirring, in which oxygen absorption was limited, to confirm the participation of atmospheric oxygen in the decomposition of benzene. It was established by spectrophotometric studies and determination of the amount of chemical oxygen consumption, that under the action of cavitation treatment, benzene is gradually transformed, namely its concentration decreases, not its destruction with accumulation in the reaction medium of the corresponding organic fragments of linear structure. The highest benzene conversion rate was observed at 10.2 W ultrasonic radiation. This is probably due to the fact that in the reaction system under the action of cavitation formed a system of parallel-sequential reactions, in which the rate of destruction of benzene with the participation of water sonolysis products is the highest, compared with processes occurring at other capacities of the ultrasonic emitter. Isothermal studies at different temperatures have been performed to establish the kinetic indices of cavitation degradation of benzene. It was first discovered that at a temperature of 313 K the rate of cavitation oxidation of benzene is much lower than that of 303 and 323 K. The effect detected is due to the formation at the temperature of highly dispersed bubbles - Babston, which are characterized by high resistance to collapse. The effect of the cavitation initiation of the destructive oxidation of aromatic compounds in the presence of an oxygen system was first discovered. It is that the decomposition of aromatic compounds occurs even after cavitation excitation ceases, but only if some energy is introduced into the reaction medium by the ultrasonic radiation. It was found that due to the cavitation initiation of the process, the oxidation rate of benzene is higher, and the energy consumption, respectively, is lower than with the constant excitation of cavitation by ultrasonic radiation.The values of the rate constants of the benzene decomposition process for the reaction initiation mode are approximately 2.2 ... 2.4 times higher than those for the stationary mode. However, the overall speed of the process of destruction of benzene to a concentration equal to the maximum permissible, in the case of cavitation initiation of the process and in the stationary mode of excitation of cavitation, are almost the same. The effectiveness of wastewater treatment from aromatic compounds in the case of mixing cavitation-treated wastewater and output (untreated) wastewater was first revealed. The content of cavitation treated wastewater in the mixture is not more than 10%. The high efficiency of cavitation degradation of benzene has been confirmed by studies performed using a jet-type hydrodynamic cavitator with a drive power of 1.1 kW. It is found that the energy consumption for the transformation of benzene in the hydrodynamic cavitator is less than when using an ultrasonic emitter. The main regularities obtained during the study of the destruction of benzene were confirmed using model solutions containing toluene. Based on a comparative sonochemical analysis of the intensity of development of cavitation fields in water and wastewater simulations, the possibility of oxidation of benzene and toluene, the reaction mechanism in an aqueous-organic medium in the mode of cavitation process initiation, is established. Based on UV spectroscopic studies, the effect of hypochlorite wastewater on the effectiveness of cavitation treatment has been identified. It is established that almost complete destruction of benzene occurs at a molar ratio of benzene: sodium hypochlorite is less than stoichiometric. This indicates a significant role in the oxidation of benzene cavitation phenomena. Using the dependence of the carbon steel corrosion potential on the exposure time in the medium, the corrosiveness of the tested aqueous media relative to the material of the equipment and communications existing in the production was established. The developed energy-saving cavitation technology for wastewater treatment from aromatic compounds was tested. The technological foundations of the process of cavitation wastewater treatment from aromatic compounds are formulated; the technological parameters for the implementation of this process are determined. The generalized energy and technical and economic calculations of energy-saving cavitation technology for wastewater treatment from aromatic compounds have been performed. Based on the results obtained in experimental studies of the decomposition of benzene in cavitation fields generated using both an ultrasonic emitter and a hydrodynamic jet cavitator, as well as analysis of information sources, several variants of technological schemes for conditioning olefin wastewater have been developed.
В диссертации приведены результаты исследований по очистке водных сред от ароматических соединений, в частности бензола и толуола. Установлено влияние температуры, продолжительности кавитационной обработки и кислорода на их деструкцию. Обнаружен эффект кавитационного инициирования разложения ароматических соединений. Эффективность разложения бензола подтверждена исследованиями с использованием гидродинамического кавитатора. Исследовано кавитационное окисления бензола гипохлоритнимы водами. Изучена коррозионная агрессивность испытуемых водных сред. Апробировано технологию очистки на реальных сточных водах. Определены технологические параметры кавитационной очистки сточных вод от ароматических соединений. Выполнены энергетические и технико-экономические расчеты технологического процесса.

碩士
國立成功大學
機械工程學系碩博士班
96
Now, there are many methods which can produce nano-powder. Using high intensity ultrasound is one way of those methods. The ultrasound is generated using a piezoelectric transducer and is amplified thru a horn emersed in liquid. Enormous cavitation bubbles are then produced around the horn tip and cause the effects of materials refined and sonochemistry. But this method will make the horn tip be quickly eroded by cavitation bubbles. The erosion not only shortens the life time of the horn, but also pollutes the sample in sonochemical cell. In this study, we design a sonochemical cell so that the problem of the horn tip erosion can be avoided. First, we use the software COMSOL to simulate the acoustic field in the cell. The idea is to find a resonant acoustic mode in which the largest acoustic pressure is moved from the horn tip to the inside of the cell. The size of the cell must be designed so that the resonant frequency corresponding the mode matches that of the piezoelectric transducer. Once the resonant mode is achieved, very large normalized acoustic pressure can be obtained away from the horn tip. So we design a cell which the resonance properties and the acoustic pressure field modal accord with the demands. Experimentally, we use hydrophones to measure the acoustic field in the cell and confirm the results of the simulation. A novel horn with enlarged cross-sectional area is proposed and used to excite the resonant acoustic mode. It is shown that this method can generate cavitation bubble field at a location inside the cell accord with the demands. That is, we can avoid tip erosion by cavitation bubbles also prove that the cell has a big effect to acoustic pressure field.

碩士
國立成功大學
機械工程學系碩博士班
97
Sonochemical effects of high intensity ultrasound come mainly from acoustic cavitation. Cavitation bubble collapse in liquid is so violent that very high local pressure and temperature, combined with extraordinarily cooling, provide a unique environment for driving chemical reactions under extreme conditions. In general, high power ultrasonic sonochemical systems utilize a metal horn to amplify the intensity of the ultrasound generated from a piezoelectric transducer. As a result, cavitation bubbles form near the horn tip, causing severe erosion of the horn, contamination of the sample, and degeneration of the system resonance. In the study, the COMSOL finite element software is used first to construct a tool for designing and analyzing the ultrasonic sonochemical system. Different physical modules, namely piezoelectric module, structural module, and acoustic module, are coupled together. In order to eliminate the cavitation erosion, an enlarged horn is designed for reducing the energy density of the ultrasound transmitted to the sonochemical cell. Numerical results show that an ideal resonant mode can be found by adjusting the immersed depth of the horn and the radius of the sonochemical cell so that the greatest amplitude of the acoustic pressure is located away from the horn tip. Experimentally, it is confirmed that the various resonant modes observed in the numerical analysis indeed exist. The most important finding of the present study is that focused cavitation field can be generated away from the horn by careful design of the components of the resonant sonochemical system.

A novel sonochemical method is developed to infuse silicon carbide nanoparticles (SiC) into expandable thermoplastic micro-spheres (Expancel) containing acrylonitrile and methylacrylonitrile polymer. Expancel micro-spheres consists a drop of liquid hydrocarbon encapsulated by a gas proof thermoplastic polymeric shell. These micro spheres expand ∼4 to 5 times of their original size (10μm) and drastically decrease it’s density from ∼1000kg/m3 to ∼30kg/m3, when exposed to the heat. To fabricate nanocomposite foam the Expancel microspheres were first dispersed in hexane along with known percentage of SiC nanoparticles and irradiated with high intensity ultrasonic horn for about 30min at room temperature. The excess n-hexane is removed using a high vacuum for 12h and heating at 60°C for 1h successively. The dry powder is transferred into a rectangular stainless steel mold and the mold is heated to ∼190°C at a heating rate of 10°C for 30 min using a MTP-14 programmable compression molding under a pressure of ∼ 3000lbs. The test coupons were cut precisely from the panels to carry out thermal, morphological and mechanical characterizations. The as-prepared nanophased foam samples were characterized by scanning electron microscopy (SEM), thermo gravimetric analysis (TGA) and differential scanning calorimetry (DSC). The SEM studies have shown that the SiC are well dispersed over the entire volume of the matrix with minimal, agglomeration. The foam cells structures are well ordered and uniform in size and spherical in shapes. The TGA and DSC analyses indicate that the nanophased foam materials are thermally more stable than the corresponding neat systems. Compression tests have been carried out for both nanophased and neat foams systems. Test results show a significant increase in compressive strength and modulus of the nanophased foams over the neat system. This enhancement in compressive properties has been observed repeatedly for multiple batches. Details of the synthesis procedure, thermal and mechanical characterization are presented in this paper.