Sonic Dispersion Research Articles

Tuning interfacial charge transfer for efficient visible-light-driven photodegradation and simultaneous H2 evolution

The edge-graphitized carbon nitride (C3N4Cg) was prepared by secondary pyrolysis to construct ZnO/C3N4Cg (ZCN) type-Ⅱ heterojunction photocatalyst via a facile sonication dispersion method, which achieved ∼7.04-fold and ∼18.3-fold enhanced visible-light-driven photocatalytic performance for refractory micropollutant removal and simultaneous hydrogen (H2) evolution respectively compared to conventional ZnO/g-C3N4 Step-scheme heterojunction. The apparent quantum efficiency of the ZCN0.4 heterojunction reaches 0.92% (λ = 420 nm). Such excellent performance stems from that the edge-graphene moieties stitched onto the interface of heterojunction extend light absorption to the full visible spectrum, meanwhile, the built-in electric field generated during Fermi level alignment accompanying favorable band-bending structure provides an effective pathway for the rapid migration of photoinduced electrons via the edge graphene channel to improve interfacial charge separation efficiency. Interestingly, the midgap states introduced in ZCN heterojunction could temporarily retain photoexcited electrons to effectively inhibit the in situ carrier recombination for improved photocatalytic H2 evolution. Moreover, ZCN/peroxymonosulfate system exhibited excellent anti-interference performance against complex water bodies under visible illumination due to the synergistic effect between the co-existing anions and organic matter. Meanwhile, the eco-friendly nature of the ZCN/peroxymonosulfate system showed no biotoxicity of reaction filtrate on cell proliferation after treatment, which avoided secondary contamination. Considering the outstanding performance in photocatalysis, the ZCN system exhibits broad potential for practical applications in water pollution control and green energy production.

Effect of Dispersion Method on Ink Rheology and Microstructure of Microporous Layer for PEMFCs

In the modern design of proton exchange membrane fuel cells (PEMFCs), a microporous layer (MPL) is often introduced between the gas diffusion layer and catalyst layer to facilitate water management and reduce contact resistance. In this study, an experimental investigation of MPL fabrication, particularly on ink preparation, is carried out to assess the relationship between ink properties and MPL’s microstructure. Two dispersion methods for ink preparation, i.e., sonication and ball-milling, are employed. Rheological and agglomerate size measurements of the inks are performed. Structural properties of the MPL are characterized by the Brunauer–Emmett–Teller method. The MPL inks prepared by ball-milling and sonication dispersion are found to have different rheological properties. The viscosity of ball-milled inks is around 20 mPa·s, whereas for sonicated inks it is about one order of magnitude lower. The surface cracks of the MPL by ball-milling appear to be more extensive and fewer in number than those by sonication. A distinct layer structure forms when the inks are dispersed by ball-milling, whereas sonicated inks penetrate the gas diffusion substrate. The MPL fabricated by a ball-milled ink for 2 h has the most uniform microstructural characteristics among the cases tested.

The Influence of Nanoparticle Dispersions on Mechanical and Thermal Properties of Polymer Nanocomposites Using SLA 3D Printing

The synergistic integration of nanocomposites and 3D printing has opened a gateway to the future and is soon expected to surpass its rivalry with traditional manufacturing techniques. However, there is always a challenge associated with preparing a nanocomposite resin for polymerization-based 3D printing, which is the agglomeration of nanoparticles. Due to the high surface-area-to-volume ratio, the nanoparticles form clusters in the composite matrix, which affects the final properties. This paper aims to analyze the effects of graphene oxide (GO) dispersion on the mechanical and thermal properties of 3D-printed nanocomposites. In particular, a well-dispersed sonication dispersion route is employed for analyzing high and poor GO dispersions and their effects on different properties. After different microscopic analyses and testing, the optimum sonication condition was 30 min at an amplitude of 70%. In terms of mechanical properties, both tensile and compression strength first increased and then decreased gradually with different dispersions as well as varying GO concentrations. Furthermore, there was less or no effect on thermal stability. GO of 0.05 wt.% had the highest compression and tensile strength, while beyond 0.05 to 0.5 wt.%, both strengths reduced slowly. These 3D-printed nanocomposites have found their application in automotive, sports, and biomedical fields.

Optimization of Carbon Nanotube Dispersions in Water Using Response Surface Methodology.

The aim of this work was to demonstrate an optimization methodology to reliably obtain stable macrodispersions (i.e., for ≥24 h) of carbon nanotubes in water using sonication. Response surface methodology (RSM) was utilized to assess and optimize the sonication parameters for the process. The studied input parameters were (i) sonication time (duration), (ii) amplitude (of vibration), and (iii) pulse-on/off (duration) of the sonicator. The analyzed responses were mean diameter and size distribution of multiwalled carbon nanotube (MWNT) aggregates in water, which were measured by the dynamic light scattering technique. A semiempirical model was developed and statistically tested to estimate the magnitude of sonicator parameters required to obtain specified MWNT macrodispersions (i.e., aggregates’ mean diameter and distribution) in water. The results showed that MWNT aggregates of 2 ± 0.5 μm can be obtained by optimizing sonicator parameters to a sonication time of 89 s, amplitude of 144 μm, and pulse-on/off cycle of 44/30 s. These process settings for 100 mg/L MWNTs in a 30 mL aliquot of deionized water would consume 863 J/mL of sonication energy. Contrary to the popular belief, “sonication time” and/or “sonication energy input” were not found to be proportional to the degree of dispersion of MWNTs in water. This might be the reason for the frequent disparity and nonreproducibility of sonication results reported in scientific literature, especially for dispersing nanomaterials in a number of different systems. The amplitude of vibration was noted to be the most sensitive parameter affecting MWNT aggregates’ diameter and distribution in water. The characterization of MWNTs was performed using electron microscopy, surface area analyzer, thermogravimetric analyzer, and zeta potential analyzer. This study can be helpful in evaluating sonication dispersion of particulate matter in other incompressible fluids such as graphene dispersion in organic solvents.

Effect of Dispersion Conditions on the Thermal and Mechanical Properties of Carbon Nanofiber–Polyester Nanocomposites

In this study, sonication dispersion technique was employed to infuse 0.1–0.4 wt.% carbon nanofibers (CNFs) into polyester matrix to enhance thermomechanical properties of resulting nanocomposites. The effect of dispersion conditions has been investigated with regard to the CNF content and the sonication time. X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM) micrographs revealed excellent dispersion of 0.2 wt.% CNF infused in polyester, resulting in enhanced mechanical responses. Polyester with 0.2 wt.% CNF samples resulted in 88% and 16% increase in flexural strength and modulus, respectively, over the neat one. Quasi-static compression tests showed similar increasing trend with addition of CNF. Fracture morphology study of tested samples revealed relatively rougher surface in CNF-loaded polyester compared to the neat due to better interaction between the fiber and the matrix. Dynamic mechanical analysis (DMA) study exhibited about 35% increase in the storage modulus and about 5 °C increase in the glass transition temperature (Tg). A better thermal stability in the CNF-loaded polyester was observed from the thermogravimetric analysis (TGA) studies. Best results were obtained for the 0.2 wt.% CNF loading with 90 mins of sonication and 50% sonication amplitude. It is recommended that this level of sonication facilitates suitable dispersion of the CNF into polyester matrices without destroying the CNF's structure.

Asymmetric Polysulfone-Cloisite 15A® Nanocomposite Membrane for Gas Separation

Defect-free asymmetric Polysulfone (PSF)-Cloisite 15A® nanocomposite membrane was fabricated with the intention to investigate the gas permeation behavior of the resulting material combination. Various weights of Cloisite 15A® organoclay were added into PSF matrices by solution intercalation method assisted by sonication dispersion. The gas permeation properties of the PSF-Cloisite 15A® nanocomposite membranes were evaluated by pure gases: nitrogen, methane, and carbon dioxide. The distribution of Cloisite 15A® particles in PSF matrices was analyzed by SEM. The gas flux of the PSF-Cloisite 15A® nanocomposite membranes declined as the Cloisite 15A® weight loading increased. The CO2/CH4 and CO2/N2 pure gas selectivity of PSF nanocomposite with 0.5 wt. % of Cloisite 15A® loading exceeded that of neat PSF membrane. The decrease in flux followed by the increase in pure gas selectivity was related to the way in which the clay layers were dispersed in the PSF matrices. Considerable improvement in CO2 selectivity was attainable even by incorporating low amount of such layered structure nanoparticle which can be attractive in producing robust materials for CO2-removal membranes from CO2-containing gas streams such as post-combustion and natural gas streams.

Numerical Simulation of CO2 Dispersion From Punctures and Ruptures of Buried High-pressure Dense Phase CO2 Pipelines with Experimental Validation

Carbon capture and storage (CCS) presents an option for significantly reducing the amount of carbon dioxide (CO 2 ) released into the atmosphere and mitigating the effects of climate change. Pipelines are considered to be the most likely method for transporting captured CO 2 and their safe operation is of paramount importance as their contents are likely to be in the region of several thousand tonnes and CO 2 poses a number of concerns upon release due to its unusual physical properties. To this end, National Grid initiated the COOLTRANS (CO 2 Liquid Pipeline Transportation) research programme to consider the pipeline transportation of high-pressure dense phase CO 2 . Part of this work involved the development of a mathematical model for predicting the dispersion of pure CO 2 following the venting, puncture, or rupture, of such a transportation pipeline during normal operational conditions. In this paper, we describe the use of a computational fluid dynamic (CFD) tool that can be used to numerically simulate the near-field sonic dispersion from such releases, above and below ground. The model is shown to qualitatively and quantitatively reproduce observed experimental results. Validated flows at the top of the crater formed by below ground releases presented here for a range of scenarios provide the basis for developing robust source conditions for use in CFD studies of far-field dispersion, and for use with pragmatic quantified risk assessment (QRA) models.

Fabrication of bio-based epoxy–clay nanocomposites

Epoxy–clay nanocomposites derived from renewable soybean oils and organo modified montmorillonite clay were prepared. Improved efficiency and performance were achieved through application of new, low viscosity, glycidyl esters of epoxidized fatty acids (EGS) as the epoxy monomer and 4-methyl-1,2-cyclohexanedicarboxylic anhydride as the comonomer. Tensile testing showed that 1 wt% of clay improved nanocomposite strength and modulus by 22% and 13%, respectively, compared to neat polymer. Tensile modulus could be increased up to 34% by nanocomposite clay without any sacrifice of strength. Three types of dispersion techniques, mechanical stirring, high speed shearing, and ultrasonication, were carried out to disperse the clay directly into the epoxy or anhydride portion of the thermoset system without the need of additional solvent. Dispersion of the clay particles into monomer was assessed by means of solubility parameters and optical and scanning electron microscopies, and quality of dispersion further confirmed by small angle X-ray scattering and transmission electron microscopy. Sonication dispersion of clay into the epoxy portion was needed to optimize the dispersion and exfoliation of clay and the higher mechanical and thermal strength of the nanocomposites. The nanocomposites’ morphologies were a mix of intercalated and exfoliated structures, dependent on the dispersion technique. The optimum tensile strength and glass transition temperatures of the nanocomposites were a function of clay concentration and dispersion morphology.

Ignition and Combustion of Super-Reactive Thermites of AlMg/KMnO4

Abstract Al1-xMgx (x=0.1, 0.2, 0.3, 0.4, 0.5) alloys (designated here after as AlMg alloys) were prepared by mechanical ball milling. The thermites were prepared by sonication dispersion method. AlMg/KMnO4 thermites with different Al/Mg ratios were investigated by differential scanning calorimetry (DSC), ignition and combustion measurements. The results show that the reaction temperatures of AlMg/KMnO4 thermites decrease obviously with the increase of Mg contents, indicating that the thermal reactivity of AlMg/KMnO4 thermites is superior to that of Al/KMnO4. Furthermore, it is found that both the reaction temperatures and the burning velocities of AlMg/KMnO4 thermites decrease from 723 to 493 K, and from 254 to 204 mg/s, respectively, as the content of Mg increases from 0.1 to 0.5, among which the Al0.5Mg0.5/KMnO4 thermite displays the largest flame splash range. It is expected that AlMg/KMnO4 will be the most promising energetic material in ordnance applications.

Nanocomposites as Advanced Materials for Aerospace Industry

Polymer nanocomposites, consisting of nanoparticles dispersed in polymer matrix, have gained interest due to the attractive properties of nanostructured fillers, as carbon nanotubes and layered silicates. Low volume additions (1- 5%) of nanoparticles provide properties enhancements comparable to those achieved by conventional loadings (15- 40%) of traditional fillers. Structural nanocomposites represent reinforcement structures based on carbon or glass fibers embedded into polymeric matrix modified with nanofillers. Structural composites are the most important application of nanaocomposites, in aerospace field, as, laminates and sandwich structures. Also, they can by used as anti-lightning, anti-radar protectors and paints. The paper presents the effects of sonic dispersion of carbon nanotubes and montmorrilonite on the mechanical, electrical, rheological and trybological properties of epoxy polymers and laminated composites, with carbon or glass fiber reinforcement, with nanoadditivated epoxy matrix. One significant observation is that nanoclay contents higher than 2% wt generate an increase of the resin viscosity, from 1500 to 50000- 100000 cP, making the matrix impossible to use in high performance composites. Also, carbon nanotubes provide the resin important electrical properties, passing from dielectric to semi- conductive class. These effects have also been observed for fiber reinforced composites. Contrarily to some opinions in literature, the results of carbon nanotubes or nanoclays addition on the mechanical characteristics of glass or carbon fiber composites seem to be rather low.

A theoretical study on formation shear radial profiling in well-bonded cased boreholes using sonic dispersion data based on a parameterized perturbation model

Interpretation of sonic data can be challenging in the presence of a steel casing that has a strong influence on elastic waves propagating along a borehole. The cement annulus behind the casing together with drilling-induced near-wellbore alteration causes radial heterogeneity in the propagating medium. It is necessary to study the influence of such heterogeneities on borehole waves and estimate the radial extent of near-wellbore alteration in terms of radial variation of velocities away from the casing. To this end, we based our study on the model of a fluid-filled well-bonded cased borehole surrounded by a cylindrically layered formation. The formation is isotropic and purely elastic, and can be either fast or slow. Borehole monopole and dipole dispersions for this kind of model can be obtained from a root finding mode-search routine. A modified perturbation model based on Hamilton’s principle is used to predict changes in borehole dispersions caused by formation heterogeneities. A two-layer formation model as the reference state is introduced, which always provides normal dispersive reference dispersion for calculations of perturbation integrals for fast and slow formations. Radial variations of the formation shear velocity can be expressed in terms of a parametric exponential profile. Consequently, estimation of these parameters in the assumed profile yields the radial variation of the formation shear slowness away from the casing. Numerical results using synthetic examples are presented to demonstrate the validity of this radial profiling methodology.

Effect of OPS Dispersion Method on the Free Volume of Polyurethane by Positron Annihilation Lifetime Spectroscopy (PALS)

The free volume of octaphenyl polyhedral oligomeric silsesquioxane (OPS) modified polyurethane prepared from different dispersion method was investigated using Positron annihilation lifetime spectroscopy (PALS). The relationships of free volume and mechanical property were analyzed. Our results showed that OPS decreased the original free volume hole size and fraction, but varied with the dispersion method. For the sonication dispersion samples, the tensile was conform to the free volume fraction, while the elongation at break was against the free volume hole size. In the high shear dispersion process, the tensile increased and no apparent change was seen on the elongation at break.

Epoxy-Layered Silicate and Epoxy MWCNTs Nanocomposites

The paper deals with the rheological properties of epoxy resin additivated with organically modified montmorillonites, carbon nanotubes and nanocarbon. The paper also presents the influence of nanoadditives over composites mechanical properties. The epoxy polymer is diglycidyl ether of bisphenol A (DGEBA) and the curing agent is an aliphatic tetraamine. Organically modified montmorillonites Cloisite 30B and Cloisite 93A, MWCNTs and laser synthesized nanocarbon were used to synthesize nanocomposites by dispersing each in an epoxy resin. The dispersion was achieved through mechanical and sonic methods. The epoxy resin additivated with nanosized fillers was rheologically tested to study the dispersion influence. The sonic dispersion of nanoadditives is observed to drastically influence the rheological behavior of the suspensions. Newtonian fluid behavior disappears as the additive loading increases. The work mentions the influence of nanoadditives on the manufacturing process of epoxy /glass fibre and epoxy/ carbon fibre laminated composites.

Estimation of formation shear and borehole-fluid slownesses using sonic dispersion data in well-bonded cased boreholes

New inversion algorithms have been developed for estimating the formation shear and borehole-fluid slownesses, using either the borehole Stoneley or dipole flexural dispersion in well-bonded cased boreholes surrounded by a fast or slow isotropic and purely elastic formation. Two inversion algorithms have been developed for each type of formation. The first algorithm inverts either the measured borehole Stoneley or flexural dispersion at select frequencies for the formation shear slowness when all other model parameters are known. The second algorithm inverts either the borehole Stoneley or flexural dispersion for both the formation shear and borehole-fluid compressional slownesses. Optimal bandwidths for the inversion of the Stoneley and dipole flexural dispersions for the formation shear slowness range from about 5 to 8 kHz. The well-bonded cased borehole dispersion sensitivity to formation shear slowness becomes larger at these higher frequencies than in an open-hole. Moreover, the Stoneley dispersion sensitivity to the borehole-fluid compressional slowness is so large that it becomes necessary to input an extremely accurate estimate of fluid compressional slowness in the inversion algorithm. Inverted formation shear slowness from the Stoneley data in a fast formation exhibits an uncertainty of about 3%, whereas the input borehole-fluid slowness has an uncertainty of 0.5%. Given a certain amount of uncertainty in the borehole-fluid slowness, one can then estimate possible variances in the inverted formation shear slowness. In contrast, inversion of the flexural dispersion for formation shear slowness is less sensitive to the input borehole-fluid compressional slowness in the preferred frequency band of 5 to 8 kHz. Inverted formation shear slownesses in slow formations that use either the Stoneley or flexural dispersion are also far less sensitive to uncertainties in the borehole-fluid compressional slowness.

A comparative study of borehole size and tool effect on dispersion curves

Sonic wave dispersion characteristics are one of the most important targets of study, particularly in estimating shear wave velocity from borehole sonic logging. We have tested dispersion characteristics using monopole and dipole sources. Theoretical dispersion curves were computed for tool-absent and tool-included models having the same physical properties but different diameters (including Φ520 mm, Φ150 mm, and Φ76 mm). Comparisons were made between boreholes of different sizes and between tool-absent and tool-included models. Between the tool-included and the tool-absent boreholes, a close similarity in dispersion curve shape was revealed for the monopole source, and a significant difference was shown for the dipole source. However, for the cut-off frequency, particularly in the engineering boreholes (Φ76 mm and Φ50 mm), a significant difference was observed for signals from the monopole source, but approximately the same cut-off frequencies were found with the dipole source. This indicates the need of careful choice of source frequency in monopole-source sonic logging, particularly in an engineering borehole.The results of numerical experiments show that cut-off frequency is exponentially proportional to the inverse of borehole radius, irrespective of the mode type and the presence of a tool, and that the cut-off frequencies for each borehole environment could be expressed as an exponential function, rather than the inversely proportional relationship between the cut-off frequency and the borehole radius that was previously generally recognised. From the direct comparison of dispersion curves, the effects on the dispersion characteristics of borehole size and the presence of the tool can be revealed more clearly than in previous studies, which presented the dispersion curve and/or characteristics for each borehole environment separately.

Changes in microbial community structure and function within particle size fractions of a paddy soil under different long-term fertilization treatments from the Tai Lake region, China

Greenhouse gas (GHG) production and emission from paddy soils impacts global climate change. Soil particle size fractions (PSFs) of different sizes act as soil microhabitats for different kinds of microbial biota with varying conditions of redox reactions and soil organic matter (SOC) substrates. It is crucial to understand the distribution of soil microbial community structure within PSFs and linkage to the GHG production from paddy soils of China. The change of bacterial and methangenic archaeal community and activity relating to CH 4 and CO 2 production with PSFs under different fertilizer applications was studied in this paper. The fertilization trial was initiated in a paddy soil from the Tai Lake region, Jiangsu, China with four treatments of non-fertilized (NF), fertilized with inorganic fertilizers only (CF), inorganic with pig manure (CFM) and inorganic with straw return (CFS), respectively since 1987, and the PSFs (<2 μm, 2–20 μm, 20–200 μm, and 200–2000 μm) were separated by a low energy sonication dispersion procedure from undisturbed samples. Analysis of bacterial community within different size particles was conducted by PCR-DGGE. The results indicated significant variation of bacterial community structure within different PSFs. The methane was predominantly produced in the coarser fractions, while more species and higher diversity of bacteria survived in the size of <2 μm fractions, in which the bacterial community structure was more significantly affected by fertilizer application practices than in the other coarser fractions. Higher bacterial species richness and more diversities in the smallest size fractions was due to the vicinity between microbes, access to carbon resource outside the microaggregates, and smaller pore size as protective agent suitable habitats for microbes rather than high SOC. Whereas, higher CO 2, CH 4 production and methanogenic archaeal community in coarser fractions may be contributed to storage of labile organic carbon in these fractions. It indicated that availability of SOC in PSFs is mainly factor affected survival of methanogenic archaeal community structure, whereas, bacterium community habitation more affected by physical protection of their location in PSFs. Their activity greatly depended on liability of SOC access to PSFs. Fertilizer application caused more change of bacteria community in clay fraction and greatly increased bacterium and methanogen activity in coarser fractions but only a slight effect on methanogenic archaeal community in the particle size fractions.

Redox and structural properties of quinone-functionalized phosphatidylcholine liposomes

Quinone-functionalized liposomes can be prepared by the sonic dispersion of a phosphatidylcholine anthraquinone (DPPC-AQ) with simple phospholipids such as DPPC (at 52°C) and DOPC (at room temperature). These small (ca. 25-30-nm diameter), unilamellar liposomes typically contain 4-12 mol % phospholipid quinone, which can be reduced and reoxidized by solution reagents

The adsorption of endotoxin molecule in a microporous polyethylene hollow fibre membrane

The microporous polyethylene hollow fibre membrane is capable of adsorbing small-sized lipopolysaccharides (LPS) prepared by sonication dispersion, column chromatography on Sephadex G-75 and filtration through a filter membrane with a nominal pore size of 0.025 micron. Small-sized LPS had a one-thousandth of endotoxin activity as compared to intact LPS, when determined by the Synthetic Chromogenic Substrate method of LAL with a specific endotoxin activity of 73.7 ng/micrograms LPS. Fluorescent microscopy of fluorescein conjugated LPS on a microporous polyethylene hollow fibre showed that fluorescein-LPS was adsorbed through the entire depth of the membrane texture. Accordingly the adsorption capacity of the filter for small-sized LPS was determined as 1.65 mg LPS/3.68 m2 surface/116 mg fibre/module.

Elevation of alkaline phosphatase by retinol in bovine endothelial cells and its possible relationship to lipid biosynthesis

Alkaline phosphatase (EC 3.1.3.1) activity in bovine aortic endothelial cells in culture was stimulated in a synergistic manner by 10 −6 M retinol and by 10 −7 M dexamethasone. An early exposure to retinol was required for maximum stimulation and could be reproduced by the addition, during growth, of 2 μg/ml compactin. The induced enzyme activity in cell lysates prepared from cells treated with retinol and dexamethasone had a V max that was 50-fold that of the controls. The stimulatory effect of retinol could be partially reversed by the addition of sonic dispersions made from cholesterol and phosphatidylcholine. The incorporation of [ 14C]acetate into saponifiable and non-saponifiable cellular lipids was inhibited by 10 −6 M retinol but the activities of 3-hydroxy-3-methylglutaryl coenzyme A reductase (EC 1.1.1.34) and 3-hydroxy-3-methylglutaryl coenzyme A synthase (EC 4.1.3.5) remained unaffected. The results suggest that retinol might inhibit lipid biosynthesis through an alternate mechanism.

Computer controlled sonic fuel system

The computer controlled sonic fuel system employs a fuel computer to convert engine manifold pressure, temperature and RPM into variable fuel pulses which are directed onto the active surface of a sonic fuel dispersion unit. This sonic dispersion unit converts pulses of fuel into a substantially nonpulsating fuel-air mixture having a fuel-air ratio which remains substantially constant regardless of variations in engine manifold pressure, temperature and RPM.