High-intensity Ultrasonic Irradiation Research Articles

Effect of high-intensity ultrasonic irradiation on the modification of solidification microstructure in a Si-rich hypoeutectic Al–Si alloy

Effect of high-intensity ultrasound irradiation in modifying complex solidification microstructure is explored in a high Si containing Al–Si alloy and the origin of microstructural changes explained on the basis of nucleation and growth behaviour. Complete suppression of dendritic growth and dramatic refinement to globular morphology were observed for primary α-Al grains. Strong supportive evidence is presented towards enhanced and prolonged heterogeneous nucleation triggered by cavitation induced increase in the equilibrium melting point and effective dissipation of latent heat at the solidification front. Morphological evolution of eutectic Si and intermetallic particles is found to be dominated by coarsening and spherodisation from strong fluid flow in areas of intense cavitation near the ultrasonic radiator. Outside the region of direct energy transfer, Si particle morphology appears to be controlled predominantly by the imposed cooling conditions. Extremely fine and short Si-platelets observed in the intergranular spaces near the radiator are explained on the basis of probable rapid cooling of final liquid pockets of small volume and large surface area, rather than refinement through ultrasound.

A facile synthesis of SrWO 4 nanobelts by the sonochemical method

SrWO 4 nanobelts have been synthesized via a facile and fast sonochemical route. The samples were characterized by XRD, SEM and TEM techniques. Experimental results showed that the concentration of Na 2EDTA and high-intensity ultrasonic irradiation played important roles in controlling the morphologies of SrWO 4. Room-temperature photoluminescence of SrWO 4 with various morphologies have also been investigated. Results showed that SrWO 4 nanobelts possessed good photoluminescent properties, suggesting that SrWO 4 nanobelts could be used in novel optoelectronic devices.

Study on bulk polymerization of methyl methacrylate initiated by low intensity ultrasonic irradiation

AbstractMethyl methacrylate (MMA) was polymerized in bulk solutions using low intensity ultrasonic radiation of 0.25 W/cm2. The polymerization occurred after 1 h of irradiation time was applied. The polymerization rate was greatly accelerated either by increasing the amount of poly (methyl methacrylate) (PMMA) granular added into the system or by elongating the irradiation time. However, it was found that the reaction rate increased with the decreasing of the ultrasonic frequencies when the exposure time of the polymerization under the irradiation was less than 3 h. Experimental results verified that the polymerization was initiated by free radicals, which were mainly generated from the degradation of PMMA macromolecular chains, the friction between the polymer macromolecular chains and the solvent monomer. These findings were obviously different from those obtained when high intensity ultrasonic irradiation was used. The polymers fabricated in this study by using ultrasound irradiation have a narrower molecular weight distribution compared to those obtained from the polymerizations induced by the conventional initiators. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Sonochemical synthesis and rheological properties of shear thickening silica dispersions

A sonochemical method has been developed to synthesize shear thickening fluid. This shear thickening fluid (STF) is composed of hard silicon dioxide nanoparticles and polyethylene glycol (PEG) liquid polymer. The combination of flow-able and hard components at a particular composition, results a material with remarkable rheological properties that is suitable for liquid body armor applications. In the present study nine types of STF’s have been synthesized with two different types of silica nanoparticles (15 nm and 200 nm) and polyethylene glycol at various weight fractions using a high intensity ultrasonic irradiation. The resultant STF samples were tested for their rheological and thermal properties. The advantages and disadvantages of this process have been discussed.

Microwave processing and characterization of EPON 862/CNT nanocomposites

Abstract In this research we have studied the cure behavior of epoxy resin system using microwave and regular oven heating in the presence and absence of multi-walled carbon nanotubes (CNTs). For this we have used a high temperature EPON 862 resin as matrix and CNTs as reinforcements. The EPON 862 Part A resin was reinforced with 0.1 wt%, 0.2 wt% and 0.3 wt% of CNTs using high intensity ultrasonic irradiation. The curing agent EPI Cure W (Part B) was mixed with EPON 862 resin using a non-contact mixing method (Thinky, Japan). In this technique the material container is set at 45° angle and revolves and rotates (2000 rpm) at the same time. Dual centrifugal forces were given to the material that keep pressing material to outward and down along with the slope of inner wall of the container. The trapped air and initial reaction volatiles were removed from the reaction mixture using a vacuum desiccator. Finally the mixture was cured using a 2.45 GHz (Sharp BP210) microwave oven for only 10 min instead of 8 h of conventional oven heating (curing schedule is 4 h at 120 °C and post-curing at 170 °C for 4 h). Thermal and flexural tests were performed for all samples including thermally cured and microwave cured epoxy samples of neat EPON 862, EPON 862/0.1 wt% CNTs, EPON 862/0.2 wt% CNTs and EPON 862/0.3 wt% of CNTs. The highest improvement (17%) in strength was found with only 0.2 wt% CNTs loading in EPON 862 as compared with the neat EPON 862 regular oven heating.

Effect of high-intensity ultrasound on superconducting properties of polycrystalline YBa2Cu3O7-x

High intensity ultrasonic irradiation (sonication) of alkane slurries of polycrystalline YBa2Cu3O7_x leads to a significant modification of the grain morphology and, if performed with enforced oxygen flow, results in the increase of the superconducting transition temperature. Sonication with added Fe(CO)5 produces magnetic Fe2O3 nanoparticles deposited on the surface of YBa2Cu3O7-x (YBCO) granules. Upon sintering these nanoparticles should act as efficient pinning centers utilizing both condensation and magnetic contributions to the free energy. The developed method could become a major technique to produce practically useful high-pinning nanocomposite materials based on YBa2Cu3O7-x superconductor.

Evidence for a Plasma Core during Multibubble Sonoluminescence in Sulfuric Acid

Multibubble sonoluminescence arises from the cavitation of bubbles owing to high-intensity ultrasonic irradiation of liquids. The spectrum of multibubble sonoluminescence in concentrated sulfuric acid sparged with Ar, at relatively low acoustic power, consists of a broad continuum extending into the UV with SO and Ar emission lines on top of this continuum. The observation of the Ar lines indicates that an optically opaque plasma is probably generated inside the bubble during cavitation. There are three distinct light-emitting morphologies for multibubble sonoluminescence from an ultrasonic horn; as the acoustic intensity is increased, the emission changes from filamentous, to bulbous, to cone shaped, and it is only from the filamentous emission that strong atomic and molecular emissions are observed.

Catalyst-free SiO2 sonogels

The sol-gel process has been used extensively to produce a great variety of glasses and ceramics using tetraetoxisilane (TEOS) as precursor of the SiO2 matrix. The majority of synthetic approaches have been focused on the alkoxide-alcohol-water system. In all cases the alkoxide reactions occur through an acid and/or basic catalyzed hydrolysis condensation process. The sonication of acidified water/TEOS has been used as an alternative method to stimulate the hydrolysis of the alkoxide and avoid the use of ethanol as common solvent. These so-called sonogels have been extensively studied, and interesting new properties have been well established. In this work the occurrence of a reaction between neutral water and TEOS activated by high intensity ultrasonic irradiation is evidenced. As a result of this reaction high purity SiO2 gels are obtained. An ad-hoc experimental setup was used which allows control of the reaction atmosphere during the sonication step, as well as recording of the pH and temperature of the system. The sonication scheme consisted of successive irradiation and short silent periods. A reaction scheme is proposed based on the formation and recombination of radicals during the ultrasonic irradiation step, which results mainly in the formation of a poly-hydroxylated Si species, while the poly-condensation reactions occur after the irradiation step. The high purity SiO2 sonogels obtained are of interest due to their potential applications as supports for non-linear optical materials, catalytic active phases or in drug delivery.

A novel method for the preparation of water-soluble and small-size CdSe quantum dots

A novel method for the preparation of water-soluble and small-size CdSe quantum dots has been reported under high-intensity ultrasonic irradiation. The as-prepared products have been characterized by absorption spectra, X-ray powder diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM).

Hydrotreating of Heavy Gas Oil Derived from Athabasca Bitumen Over Co–Mo/γ-Al2O3 Catalyst Prepared by Sonochemical Method

Co–Mo/γ-Al2O3 oxide containing 9.8 wt% Mo and 2.9 wt% Co was prepared by high-intensity ultrasonic irradiation of Mo(CO)6, Co2(CO)8, and γ-Al2O3 in decahydronapthalene under air flow. The oxidic Co–Mo catalyst thus formed was characterized by elemental analysis, BET N2 adsorption and XRD. The surface sites on the sulfided Co–Mo/γ-Al2O3 catalyst were characterized by infrared spectroscopy of CO adsorption. Hydrodenitrogenation (HDN) and hydrodesulfurization (HDS) activities were evaluated for heavy gas oil derived from Athabasca bitumen in a trickle bed reaction system using the following conditions: temperatures ranging from 370 to 400 °C, a pressure of 8.8 MPa, a liquid hourly space velocity of 1 h−1, and a H2/feed ratio of 600 ml/ml. The dispersion, nature of active sites and hydrotreating activity of this catalyst were compared with the conventionally prepared Co–Mo/γ-Al2O3 catalyst containing similar wt% of Mo and Co. The Co–Mo catalyst prepared by sonochemical method has higher HDN and HDS rate constants than the conventional catalyst due to an improved dispersion of MoS2.

Preparation and characterization of calcium phosphate–albumin colloidal particles by high ultrasonic irradiation

Using high intensity ultrasonic irradiation, we prepared calcium phosphate–albumin colloidal particles from aqueous solutions of Ca(H2PO4)2 and Ca(OH)2 in the presence of bovine serum albumin (BSA). The effect of concentration of BSA (2–5 g/L) properties of the colloidal particles was studied at constant temperature. The effect of a resting period on the size distribution of the colloidal particles was also investigated. Morphology, phase composition, average diameter, size distribution and zeta potential were obtained by transmission electron microscopy, X-ray diffraction, particle size determination by PCS and electrokinetic measurements.

Sonochemical one-directional growth of montmorillonite–polystyrene nanocomposite

Montmorillonite–exfoliated polystyrene (MMT-PS) nanocomposite was one-pot synthesized by high-intensity ultrasonic irradiation. Moreover, the MMT-PS exhibited one-directional growth during the sonication.

Sonochemical synthesis of nanocrystalline TiO 2 by hydrolysis of titanium alkoxides

A novel sonochemical method to directly prepare anatase nanocrystalline TiO 2 has been established. TiO 2 particles were synthesized by the hydrolysis of titanium tetraisopropyl in the presence of water and ethanol under high-intensity ultrasonic irradiation (20 KHz, 100 W/cm 2) at 90 °C for 3 h. The product structure and the particle sizes were dependent upon the reaction temperature, the acidity of the medium and the reaction time. Characterization was accomplished using various different techniques, such as powder X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetry-differential thermal analysis (TG-DTA), and Fourier transform infrared (FT-IR) spectroscopy. The TEM images showed that the particles of TiO 2 were columnar in shape and the average sizes were ∼3×7 nm. The formation mechanism of nanocrystalline TiO 2 under high-intensity ultrasonic irradiation was also discussed.

Bulk polymerization of methyl methacrylate initiated by high intensity ultrasonic irradiation and ESR study

High-intensity ultrasound was used to initiate the bulk polymerization of methyl methacrylate. The polymerization rate varied with the sonication time, the intensity of the ultrasound, and the initiator concentration of poly (methyl methacrylate) in the monomer. Electron spin resonance (ESR) spectra, obtained by the spin trapping technique, testified that free radicals were produced during the sonication process, and the concentration of radicals also changed with the sonication condition. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1731–1735, 2002

High Intensity Focused Ultrasound as Noninvasive Therapy for Multilocal Renal Cell Carcinoma: Case Study and Review of The Literature

Noninvasive tumor ablation can be achieved by extracorporeally induced high intensity focused ultrasound. Clinical high intensity focused ultrasound performed to date for renal tumors have only been experimental in nature. We present specific details on a patient with renal cell carcinoma who underwent high intensity focused ultrasound with curative intent and long-term followup examinations. Ultrasound waves were generated by a cylindrical piezoelectric element focused by a paraboloid reflector. High intensity focused ultrasound was applied to 3 tumors in 3 sessions with the patient under general anesthesia or sedation analgesia, followed by magnetic resonance imaging for 6 months. After treatment magnetic resonance imaging showed necrosis in the 2 tumors in the lower kidney pole within 17 and 48 days, respectively. The necrotic tumor area shrank thereafter within 6 months. The tumor in the upper pole was not affected by treatment due to absorption of the ultrasound energy by the interposed ribs. General anesthesia was required to apply high energy levels of focused ultrasound. Absorption of high intensity focused ultrasound in the tissue induced sharply demarcated thermonecrosis. For 50 years patients have been treated with high intensity focused ultrasound for different indications, focusing on the brain, eyes, prostate, liver and bladder. For the kidney experimental but only few clinical studies indicate sufficient tissue ablation. In our case contactless noninvasive application of high intensity focused ultrasound to 2 renal carcinomas achieved thermal ablation. When high intensity focused ultrasound energy was coupled correctly, no lesions occurred outside of the target area. Successful high intensity focused ultrasound application depended on optimum energy coupling, a sufficiently high ultrasound energy level and general anesthesia.

A safe sonochemical route to iron, cobalt and nickel monoarsenides

In this paper, we report a safe method for the preparation of transition metal arsenides. At room temperature, well-crystallized and monodispersed arsenides particles were successfully obtained under high-intensity ultrasonic irradiation for 4 h from the reaction of transition metal chlorides, arsenic (which is the least toxic arsenic feedstock) and zinc in ethanol. Characterization by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), electron diffraction (ED), and X-ray photoelectron spectroscopy (XPS) shows that the product powders consist of nanosize particles. The ultrasonic irradiation and the solvent are both important in the formation of the product.

Sonochemical Preparation of Supported Hydrodesulfurization Catalysts

Sonochemical preparation of Co and Ni promoted MoS(2) supported on alumina was achieved by high-intensity ultrasonic irradiation of isodurene solutions containing molybdenum carbonyl, dicobalt octacarbonyl, elemental sulfur, and Al(2)O(3) or Ni-Al(2)O(3) under Ar flow. The sonochemically prepared catalysts were characterized by elemental analysis, XPS, SEM, TEM, and XEDS, and hydrodesulfurization (HDS) activity evaluated for thiophene and dibenzothiophene substrates. The TEM studies on the sonochemically prepared catalysts indicate the formation of layered hexagonal MoS(2) (lattice fringes approximately 6.2 A) on the alumina support. The sonochemically prepared Co-Mo-S/Al(2)O(3), Ni-Mo-S/Al(2)O(3), and Co-Ni-Mo-S/Al(2)O(3) are extremely active catalysts for the HDS of thiophene and dibenzothiophene, with activities severalfold those of comparable commercial catalysts under identical conditions. The layered structure of MoS(2) remained intact after 120 h of HDS, and the catalyst is reusable.

A novel method for the preparation of III–V semiconductors: sonochemical synthesis of InP nanocrystals

A novel method for the preparation of III–V semiconductor has been provided in this paper. At room temperature, InP nanocrystals with diameter of ≈9 nm were successfully obtained under high-intensity ultrasonic irradiation for 4 h from the reaction of InCl 3·4H 2O, yellow phosphorus and KBH 4 in the mixed solvents of ethanol and benzene. Changing some parameters can effectively control the size of the products and possible explanations were offered. The products were characterized by X-ray powder diffraction, transmission electron microscope and electron diffraction pattern. The ultrasonic irradiation and the solvents are both important in the formation of the product.

Sono-oxidation treatment of humic substances in drinking water

Currently humic substances are removed from the raw water prior to chlorination by the conventional coagulation and filtration method using aluminium sulphate. Application of high-intensity (>10 W/cm 2) ultrasonic irradiation in conjunction with oxidative process using commercial oxidants H 2O 2 was investigated as an alternative. Sono-oxidation and sonodegradation of natural and synthetic humic substances have been followed over time by measuring total organic carbon (TOC) and absorbance by ultraviolet spectrometer (UV–VIS). It took approximately 60 min to reduce TOC by half and to have a complete degradation of humic acid.

Sonochemical Synthesis of Nanocrystalline Silver Tellurides Ag2Te and Ag7Te4

In this paper, we report a simple and clean method of producing nanocrystalline silver tellurides in organic solvent systems by high-intensity ultrasonic irradiation at room temperature. Ag2Te and Ag7Te4 are prepared in an ethylenediamine system and an ethanol system, respectively. The products were mainly characterized by X-ray powder diffraction and transmission electron microscopy. The ultrasonic irradiation and the solvents are both important in the formation of products. The possible mechanism of the nanocrystalline Ag2Te formation in ethylene-diamine under high-intensity ultrasonic irradiation is also discussed.