Sonication Energy Research Articles

Effect of Sonication Energy on the Yield of Graphene Nanosheets by Liquid-phase Exfoliation of Graphite

We demonstrate the high concentration exfoliation of graphene nanosheets in dimethyl formamide (DMF) as a solvent from graphite powder. UV-Vis-NIR spectroscopy shows low power bath sonication yields less concentration of graphene nanosheets exfoliation, whereas the high power probe sonication yields high concentration graphene nanosheets exfoliation. The concentration of graphene nanosheets exfoliation depends on amount of energy supplied, and there exists a linear relationship between the concentration of graphene and energy supplied during sonication. TEM micrograph confirms the exfoliation of graphene nanosheets. AFM studies shows; high power sonication for longer time reveals graphene exfoliation with fewer graphene layers. The strategy of bath sonication followed by probe sonication of grapheme solution shows the stable suspension of graphene nanosheets even after one month.

Concentrated Fenofibrate Nanoparticle Suspensions from Melt Emulsification for Enhanced Drug Dissolution

AbstractConcentrated fenofibrate (FNB) nanoparticle suspensions are produced via an oil/water melt emulsification process from the micronized drug particles dispersed in water above the drug melting point. Sonication energy enables forming nanosized melt droplets, and nanosized solid particles upon subsequent cooling. Stabilization achieved via surface‐active molecules is necessary to prevent coalescence of the droplets or agglomeration of the solid nanoparticles. Judicious selection of stabilizer and concentration resulted in 150‐nm drug particles with solid loading up to 30 %. The hydrophilic‐lipophilic‐balance concept is applicable, facilitating selection of surfactants based on their chemical structure. The strong in vitro dissolution rate enhancement suggests improved FNB bioavailability.

MRI-guided high-intensity focused ultrasound ablation of bone: evaluation of acute findings with MR and CT imaging in a swine model.

To evaluate hyperacute (<1 hour) changes on magnetic resonance (MR) and computed tomography (CT) imaging following MR-guided high-intensity focused ultrasound (MRgHIFU) in a swine bone model as a function of sonication number and energy. Experimental procedures received approval from the local Institutional Animal Care and Use Committee. MRgHIFU was used to create distal and proximal ablations in the right femur of eight pigs. Each target was dosed with four or six sonications within similar volumes. The energy dosed to the distal target was higher (419 ± 19 J) than the proximal target (324 ± 17 J). The targeted femur and contralateral control were imaged before and after ablation using MR at 3T. Qualitative changes in signal on T1-weighted, T2-weighted, and T1-weighted postcontrast images were assessed. Ablation dimensions were calculated from postcontrast MRI. The 64-slice CT images were also obtained before and after ablation and qualitative changes were assessed. MRgHIFU bone ablation size measured on average 8.5 × 21.1 × 16.2 mm (transverse × craniocaudal × anteroposterior). Interestingly, within similar prescribed volumes, increasing the number of sonications from 4 to 6 increased the depth of the intramedullary hypoenhanced zone from 2.9 mm to 6.5 mm (P < 0.001). There was no difference in the appearance of low versus high energy ablations. CT imaging did not show structural abnormalities. The number of MRgHIFU focal sonications can be used to increase the depth of treatment within the targeted bone. Unlike CT, T2-weighted and contrast-enhanced MR demonstrated the hyperacute structural changes in the femur and surrounding soft tissue.

Optimization of low energy sonication treatment for granular activated carbon colonizing biomass assessment

This study is aimed at optimizing a low energy sonication (LES) treatment for granular activated carbon (GAC)-colonizing biomass detachment and determination, evaluating detachment efficiency and the effects of ultrasound exposure on bacterial cell viability. GAC samples were collected from two filters fed with groundwater. Conventional heterotrophic plate count (HPC) and fluorescence microscopy with a double staining method were used to evaluate cell viability, comparing two LES procedures, without and with periodical bulk substitution. A 20 min LES treatment, with bulk substitution after cycles of 5 min as maximum treatment time, allowed to recover 87% ÷ % of attached biomass, protecting detached bacteria from ultrasound damaging effects. Observed viable cell inactivation rate was 6.5÷ 7.9% cell/min, with membrane-compromised cell damage appearing to be even higher (11.5% ÷ 13.1% cell/min). Assessing bacterial detachment and damaging ultrasound effects, fluorescence microscopy turned out to be more sensitive compared to conventional HPC. The optimized method revealed a GAC-colonizing biomass of 9.9×107 cell/gGAC for plant 1 and 8.8×107 cell/gGAC for plant 2, 2 log lower than reported in literature. The difference between the two GAC-colonizing biomasses is higher in terms of viable cells (46.3% of total cells in plant 1 GAC-colonizing biomass compared to the 33.3% in plant 2). Studying influent water contamination through multivariate statistical analyses, a possible combined toxic and genotoxic effect of chromium VI and trichloroethylene was suggested as a reason for the lower viable cell fraction observed in plant 2 GAC-colonizing population.

Preparation of concentrated stable fenofibrate suspensions via liquid antisolvent precipitation

A major challenge in achieving size stability for relatively high concentration of fine particles from poorly water-soluble drug fenofibrate (FNB) is addressed through T-mixing based liquid antisolvent precipitation in the presence of ultrasonication and judicious use of stabilizers. Multiple stabilizers were screened in a batch mode prior to their continuous formation via T-mixing. In both cases, the stable suspensions maintained their size after 2 days of storage at room temperature, with the smallest particle size of d50: ∼1.2 µm was achieved through a combination of HPMC with SDS or PF-68. The influence of processing parameters, such as sonication energy, sonication probe insert depth and solvent/antisolvent flow rate, on the particle size distribution (PSD) in T-mixing were investigated, to identify optimum processing conditions. Optimal operating and formulation conditions also allowed increase in the drug loading from 0.32% to 4% (w/v), while keeping the median size 2.5 µm. Interestingly, the primary particles observed in the SEM were spherical and under 100 nm in diameter, indicating agglomeration. It was shown that the stabilized particles could be centrifuged and did not show size growth upon resuspension, allowing for increase in the drug loading up to 27% (w/v), which is a significant novel outcome.

Ultrasonically Enhanced Effectiveness of Various Surfactants on Diesel Removal from Contaminated Soil

The use of ultrasound to enhance the efficiency of surfactant-aided soil washing was investigated with a series of laboratory tests on diesel-contaminated soil. Test conditions included the power and duration of sonic energy, the surfactant type, and mixing time. The results of the study show that the use of ultrasound in the soil washing process significantly enhanced the remediation of the contaminated soil. The degree of enhancement varied with sonication energy, treatment time, and mixing duration.

Sonication-assisted dispersion of carbon nanotubes in aqueous solutions of the anionic surfactant SDBS: The role of sonication energy

Sonication is a powerful technique to promote the dispersion of carbon nanotubes (CNTs) and enhance their solubility; this is necessary for CNT applications, especially in the biochemical and biomedical fields. In this study, batch experiments were conducted to evaluate the role of sonication energy on the dispersion of CNTs in the presence of a widely used anionic surfactant, sodium dodecylbenzene sulfonate (SDBS). It was observed that the concentration of dispersed CNTs in the SDBS solution depended on the sonication energy, but not the sonication time or output power of the sonicator alone. The amount of dispersed CNTs was positively correlated with the concentrations of SDBS and CNTs, and the length of the CNTs. The promotion of oxygen-containing functional groups on the dispersed CNTs was observed at relatively low sonication energies. The optimal energy, i.e. the minimum energy supplied by sonication to achieve a saturated suspension of dispersed CNTs in the SDBS solution, was CNT diameter-dependent, because of the larger vdW forces between tubes of smaller diameter. An exponential decay curve was constructed for the optimal energy values as a function of the outer CNT diameter, to assist in determining the energy needed to disperse CNTs.

Disintegration of Sludge by Sonication and Improvement of Methane Production Rates in Batch Anaerobic Digesters

AbstractSludge pretreatment prior to anaerobic digestion has been found to reduce sludge production in wastewater treatment. Sludge disintegration using physical, chemical, biological, or mechanical methods can increase biogas production and reduce sludge quantities. Ultrasonication is one of the most effective means of mechanical disintegration. This study aims to investigate ultrasonication as a means for solubilizing waste activated sludge (WAS) to enhance its digestability. Sonication was applied by the use of two different probes providing different powers and energies into the sludge after which the soluble chemical oxygen demand (sCOD) increases were measured. The samples were then digested anaerobically in 250 mL serum bottles for about 50 days. Along with the biogas measurements, the rate of methane production is calculated to be able to quantify the effect of pretreatment and compare the results between different applications. The results showed that with the increase of sonication power and sonication time, sCOD increased. An introduction of higher sonication energy made the sCOD rise sharply, however, this increase was not indefinite; it became gradually lower with the further increase of energy. The results indicated that specific methane production, specific methane yield, and the first order methane generation rate increased with increasing energy input.

Fabrication and properties of CNTs/carbon fabric hybrid multiscale composites processed via resin transfer molding technique

Carbon nanotubes (CNTs) are effective fillers/reinforcements regarding improving the properties of polymer. In the present paper, carboxylic acid functionalized CNTs were used to modify epoxy with intent to develop a nanocomposite matrix for hybrid multiscale composites combining benefits of nanoscale reinforcement with well-established fibrous composites. CNTs were dispersed in epoxy by using high energy sonication. At low contents of CNTs, hybrid multiscale composites specimens were manufactured via resin transfer molding (RTM) process. The processibility of CNTs/epoxy systems was explored with respect to their viscosity. The dispersion quality and re-agglomeration behavior of CNTs in epoxy were characterized using optical microscope. A CNTs loading of 0.025wt% significantly improved the glass transition temperatures (Tg) of the hybrid multiscale composites. Scanning electron microscopy (SEM) was used to examine the fracture surface of the failed specimens. It is demonstrated that the addition of small amount of CNTs (0.025wt%) to epoxy for the fabrication of multiscale carbon fabric composites via RTM route effectively improves the matrix-dominated properties of polymer based composites. Hybridization efficiency in carbon fiber reinforced composites using CNTs is found to be highly dependent on the changes in the dispersion state of CNTs in epoxy.

Excitonic homogeneous broadening in single-wall carbon nanotubes

We present a review on the excitonic homogeneous linewidth, with an emphasis on original experiments by means of nonlinear spectral hole-burning. We address three specific aspects of the excitonic homogeneous broadening: (i) the variation of the homogeneous linewidth with the sonication energy, revealing the influence of extrinsic processes such as exciton-defect interactions, (ii) the collision-induced broadening due to exciton–exciton interactions, investigated by power-dependent measurements, and (iii) the phonon-induced dephasing due to exciton–phonon interactions, deduced from temperature-dependent experiments. We discuss the specific properties of one-dimensional excitons in carbon nanotubes in the context of the homogeneous broadening.

Feasibility of ultrasound-guided high intensity focused ultrasound ablating uterine fibroids with hyperintense on T2-weighted MR imaging

PurposeTo retrospectively investigate whether uterine fibroids with hyperintense on pretreatment T2-weighted magnetic resonance imaging (MRI) could be treated with ultrasound-guided high intensity focused ultrasound (USgHIFU). Materials and methods282 patients with 282 symptomatic uterine fibroids who underwent USgHIFU treatment were retrospectively analyzed. Based on the signal intensity of T2-weighted MRI, uterine fibroids were classified as hypointense, isointense and hyperintense. Hyperintense fibroids were subjectively further subdivided into heterogeneous hyperintense, slightly homogeneous hyperintense and markedly homogeneous hyperintense based on the signal intensity of fibroid relative to myometrium and endometrium on T2-weighted MRI. Enhanced MRI was performed within one month after HIFU treatment. Non-perfused volume (NPV, indicative of successful ablation) ratio, treatment time, treatment efficiency, energy effect ratio and adverse events were recorded. ResultsThe median volume of uterine fibroids was 70.3cm3 (interquartile range, 41.1–132.5cm3). The average NPV ratio, defined as non-perfused volume divided by the fibroid volume after HIFU treatment, was 76.8±19.0% (range, 0–100%) in the 282 patients. It was 86.3±11.9% (range, 40.9–100.0%) in the group with hypointense fibroids, 77.1±16.5% (range, 32.2–100.0%) in isointense fibroids, and 67.6±23.9% (range, 0–100.0%) in hyperintense fibroids. The lowest NPV ratio, lowest treatment efficiency, more treatment time, more sonication energy and pain scores were observed in the slightly homogeneous hyperintense fibroids, and the NPV ratio was 55.8±26.7% (range, 0–83.9%) in this subgroup. ConclusionBased on our results, the heterogeneous and markedly homogeneous hyperintense fibroids were suitable for USgHIFU, and only the slightly homogeneous hyperintense fibroids should be excluded.

Evaluation of microalgae cell disruption by ultrasonic treatment

Microalgae are a promising feedstock for biofuels because of their capability to produce lipids. Cell disruption is necessary to maximize lipid extraction. Sonication conditions were evaluated for breaking heterotrophic (Schizochytrium limacinum) and autotrophic (Chlamydomonas reinhardtii) microalgae cells. Cell disruption was estimated by Nile red–lipids fluorescence quantification in S. limacinum and by the release of intracellular chlorophyll and carotenoids in green microalga C. reinhardtii. In both species, approximately 800J/10mL was the energy input necessary to maximize cell disruption, regardless of the cell concentrations studied. Increasing sonication time produced increasing amount of free radicals, quantified by the formation of hydroxyterephthalate. Sonication energy beyond the level needed for cell disruption induced oxidation of arachidonic acid, a polyunsaturated fatty acid typically found in marine lipids. Careful control of sonication conditions is necessary to maximize oil extraction at the lowest operational cost and to prevent oil from free radical-induced degradation.

Synthesis of NaP zeolite at room temperature and short crystallization time by sonochemical method

NaP zeolite nano crystals were synthesized by sonochemical method at room temperature with crystallization time of 3h. For comparison, to insure the effect of sonochemical method, the hydrothermal method at conventional synthesis condition, with same initial sol composition was studied. NaP zeolites are directly formed by ultrasonic treatment without the application of autogenous pressure and also hydrothermal treatment. The effect of ultrasonic energy and irradiation time showed that with increasing sonication energy, the crystallinity of the powders decreased but phase purity remain unchanged. The synthesized powders were characterized by XRD, IR, DTA TGA, FESEM, and TEM analysis. FESEM images revealed that 50nm zeolite crystals were formed at room temperature by using sonochemical method. However, agglomerated particles having cactus/cabbage like structure was obtained by sonochemical method followed by hydrothermal treatment. In sonochemical process, formation of cavitation and the collapsing of bubbles produced huge energy which is sufficient for crystallization of zeolite compared to that supplied by hydrothermal process for conventional synthesis. With increasing irradiation energy and time, the crystallinity of the synthesized zeolite samples increased slightly.

Experimental assessment on potential for processiblity of carbon nanotubes/epoxy system used as nanocomposites

In this study, carboxylic acid functionalized carbon nanotubes (CNTs) were used to modify epoxy with intent to develop a nanocomposite matrix for hybrid multiscale composites combining benefits of nanoscale reinforcement with well-established fibrous composites. CNTs were dispersed in epoxy by using high energy sonication, followed by the fabrication of epoxy/CNTs composites. The processibility of CNTs/epoxy systems was explored with respect to their dispersion state and viscosity. The dependences of viscosity, mechanical and thermomechanical properties of nanocomposite system on CNTs content were investigated. The dispersion quality and reagglomeration behavior of CNTs in epoxy and the capillary infiltration of continuous fiber with the epoxy/CNTs dispersion were characterized using optical microscope and capillary experiment. As compared with neat epoxy sample, the CNTs nanocomposites exhibit flexural strength of 126.5 MPa for 1 wt% CNTs content and impact strength of 28.9 kJ m−2 for 0.1 wt% CNTs content, respectively. A CNTs loading of 0.1 wt% significantly improved the glass transition temperatures, Tg, of the nanocomposites. Scanning electron microscopy (SEM) was used to examine the fracture surface of the failed specimens. It is demonstrated that the properties of CNTs/epoxy system are dispersion-dominated and interface sensitive. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers

Investigation on some matrix‐dominated properties of hybrid multiscale composites based on carbon fiber/carbon nanotube modified epoxy

AbstractContinuous fiber reinforced polymer‐based composites have outstanding fiber‐dominated properties but unsatisfactory matrix‐dominated performances. In this investigation, carbon fiber reinforced epoxy composites modified with carbon nanotubes (CNTs) were fabricated to evaluate the effects of CNTs on some matrix‐dominated properties of the resulting hybrid multiscale composites. Carboxylic acid functionalized multiwalled CNTs were dispersed in epoxy by using high energy sonication, followed by the fabrication of the composites laminates with the epoxy/CNTs dispersion. The dispersion quality of CNTs in epoxy and the capillary infiltration of continuous fiber with the epoxy/CNTs dispersion were characterized using optical microscope and capillary experiment to optimize the processing parameters. A CNTs loading of 1 wt % significantly improved the flexural strength and interlaminar shear strength of the composites containing varying scale reinforcements by 51.8% and 34.2%, respectively, as compared to the control carbon/epoxy composites. Scanning electron microscopy was used to examine the fracture surface of the failed specimens. The moisture absorption behavior of the carbon fiber/epoxy composites with and without CNTs was investigated by comparing the weight gain and shear properties degradation in distilled water and 1.5 wt % brine. The integration of CNTs in composites is found to contribute to the medium‐dependent moisture adsorption behavior. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Molecular dynamics study of epoxy/clay nanocomposites: rheology and molecular confinement

To investigate the effect of nanoparticles on molecular confinement, epoxy/clay nanocomposites in 6 % wt were prepared by low shear mixer and ultrasonication methods. According to the XRD results, high energy sonication can significantly increase the intergallery space compared to that of the low shear mixer and, therefore, provide more interfacial area for polymer-particle interaction. Rheological measurements, including dynamic mechanical moduli, continuous relaxation spectrum and zero-shear viscosity, were carried out in the linear region to reveal the solid-like characteristics induced in the pure epoxy. The longest Rouse relaxation time, which was determined from the value of zero-shear viscosity, was employed to study the segmental friction. It is clear that the chain relaxation process was slowed by the polymer-particle interactions, which created very high monomeric friction. We introduce the ratio of monomeric friction coefficients (ζnano/ζepoxy) as the strength of immobilization to correlate the increasing elasticity, longer relaxation time and molecular confinement quantitatively. Because more monomers can be immobilized on a clay surface due to their strong affinity, the friction ratio increased to 359.48 for the sonicated sample, whereas weak polymer-particle affinity resulted in much lower growth, with a friction ratio of 2.11 for the low shear mixing method.

Effect of dispersion conditions on the thermo-mechanical and toughness properties of multi walled carbon nanotubes-reinforced epoxy

In this work, multi wall carbon nanotubes (MWCNTs) dispersed in a polymer matrix have been used to enhance the thermo-mechanical and toughness properties of the resulting nanocomposites. Dynamic mechanical analysis (DMA), tensile tests and single edge notch 3-point bending tests were performed on unfilled, 0.5 and 1wt.% carbon nanotube (CNT)-filled epoxy to identify the effect of loading on the aforementioned properties. The effect of the dispersion conditions has been thoroughly investigated with regard to the CNT content, the sonication time and the total sonication energy input. The CNT dispersion conditions were of key importance for both the thermo-mechanical and toughness properties of the modified systems. Sonication duration of 1h was the most effective for the storage modulus and glass transition temperature (Tg) enhancement for both 0.5 and 1wt.% CNT loadings. The significant increase of the storage modulus and Tg under specific sonication conditions was associated with the improved dispersion and interfacial bonding between the CNTs and the epoxy matrix. Sonication energy was the influencing parameter for the toughness properties. Best results were obtained for 2h of sonication and 50% sonication amplitude. It was suggested that this level of sonication allowed appropriate dispersion of the CNTs to the epoxy matrices without destroying the CNT’s structure.

A new analytical approach based on asymmetrical flow field-flow fractionation coupled to ultraviolet spectrometry and light scattering detection for SWCNT aqueous dispersion studies

This work demonstrates the potential of asymmetrical flow field-flow fractionation (A4F) coupled to Ultraviolet spectrometry (UV) and multi-angle light scattering (MALS) for the study of single-walled carbon nanotube (SWCNT) dispersion in aqueous solutions containing a surfactant. The results indicate that this technique is a powerful analytical tool that is able to evaluate SWCNT dispersion states in aqueous media and, more importantly, determine the presence or absence of aggregates, the numbers and sizes of different SWCNT populations and the SWCNT size distribution. Dynamic light scattering was employed to complete and demonstrate the relevance of the data that were obtained via A4F-UV-MALS. Two different anionic surfactants that are used to disperse SWCNTs were then studied. The dispersing powers of the surfactants were experimentally evaluated based on their structural organizations. This study demonstrates that surfactant concentration and sonication energy are key parameters that control the SWCNT dispersion state and SWCNT structural integrity therein.

Multi-wall carbon nanotube aqueous dispersion monitoring by using A4F-UV-MALS

In this work, the potentiality of asymmetrical flow field-flow fractionation (A4F) hyphenated to UV detector and multi-angle light scattering (MALS) was investigated for accurately determining multi-walled carbon nanotube (MWCNT) length and its corresponding dispersion state in aqueous medium. Fractionation key parameters were studied to obtain a method robust enough for heterogeneous sample characterization. The main A4F conditions were 10(-5) mL min(-1) NH(4)NO(3), elution flow of 1 mL min(-1), and cross flow of 2 mL min(-1). The recovery was found to be (94 ± 2)%. Online MALS analysis of eluted MWCNT suspension was performed to obtain length distribution. The length measurements were performed with a 4% relative standard deviation, and the length values were shown to be in accordance with expected ones. The capabilities of A4F-UV-MALS to size characterize various MWCNT samples and differentiate them according to their manufacturing process were evaluated by monitoring ball-milled MWCNT and MWCNT dispersions. The corresponding length distributions were found to be over 150-650 and 150-1,156 nm, respectively. A4F-UV-MALS was also used to evaluate MWCNT dispersion state in aqueous medium according to the surfactant concentration and sonication energy involved in the preparation of the dispersions. More especially, the presence or absence of aggregates, number and size of different populations, as well as size distributions were determined. A sodium dodecyl sulfate concentration of 15 to 30 mmol L(-1) and a sonication energy ranged over 20-30 kJ allow obtaining an optimal MWCNT dispersion. It is especially valuable for studying nanomaterials and checking their manufacturing processes, size characterization being always of high importance.

Effect of oxytocin on uterine fibroids treated by ultrasound ablation

To explore the effect of oxytocin on uterine fibroids treated by ultrasound ablation. Eighty-two single points in 29 uterine fibroids from 26 patients were sonicated with magnetic resonance imaging guided by high intensity focused ultrasound before and after using oxytocin. The required total energy, sonication time required to reach 60°C and the acoustic energy for increasing 1°C of temperature at the single point before and after using oxytocin were compared. Before intravenous infusion of oxytocin, the average total sonication energy required to reach 60°C was (5320 ± 910) J and it took (21 ± 20) seconds for sonicating a single point, the energy required for increasing 1°C was (255 ± 302) J. In contrast, after intravenous infusion of oxytocin, the average total sonication energy required to reach 60°C was (2890 ± 325) J, and it took (12 ± 7) seconds for sonicating a single point, the energy required for increasing 1°C was (126 ± 94) J. Those three index all reached statistical difference (P = 0.002, P = 0.001, P = 0.002, respectively). It seemed that Oxytocin could significantly decrease the energy required for ablating uterine fibroids, shorten treatment time and improve the treatment efficiency.