Ultrasonic Mixing Research Articles

Studies on Sono-Chemical Biodiesel Production Using Smoke Deposited Nano MgO Catalyst

The comprehensive study of smoke deposited nano sized MgO as a catalyst for biodiesel production was investigated. The transesterification reaction was studied under constant ultrasonic mixing for different parameters like catalyst quantity, methanol oil molar ratio, reaction temperature and reaction time. An excellent result of conversion was obtained at 1.5 wt% catalyst; 5:1 methanol oil molar ratio at 55°C, a conversion of 98.7% was achieved after 45 min. The conversion was three to five times higher than those are reported for laboratory MgO in literature. This was mainly due to the enhancement of surface area of the catalyst and the activity of ultrasonic waves. Catalyst is easily recovered and reused up to eight times with easy regeneration steps. © 2013 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0)

Hierarchical sulfonated graphene oxide–TiO2 composites for highly efficient hydrogen production with a wide pH range

Synthesizing highly efficient photocatalyst for hydrogen production still remains a great challenge, especially generating hydrogen from water with a wide pH range. In this work, for the first time, the hierarchical sulfonated graphene oxide (SG)–TiO2 composites were successfully synthesized by ultrasonic mixing SG sheets and TiO2 spheres. SG–TiO2 composites exhibit high hydrogen production efficiency with a wide pH range (from pH=3 to pH=11). Under neutral pH (pH=7), SG–TiO2-2 composite with the optimal amount of 2% SG sheets achieves the highest hydrogen evolution rate (ca. 260μmol/h), which is more than 11 times higher than that of pure TiO2 and P25. The high hydrogen evolution rate can be owed to the promising properties of SG–TiO2 composites, including large surface area, efficient light absorption ability and high charge separation efficiency. More interestingly, SG–TiO2 composites can perform excellent hydrogen production activity under different pH conditions, even under alkaline condition, where the hydrogen production efficiency of GO–TiO2 composites usually decreased dramatically under such condition. This particular phenomenon can be attributed to the tight coordination between the SG sheets and TiO2 spheres, which prevents the damage of SG–TiO2 composites in the alkaline solution. Consequently, these novel SG–TiO2 composites can be widely applied in the practical clean energy production field.

An experimental investigation of mixing of carbon nanotube/polymer composite in a batch-type screw mixer

We develop a miniaturized batch-type screw mixer (BSM) for uniform mixing of polymer resin and nanoparticles, based on the stretching of material elements. This stretching is induced by the combination of recirculating cross-sectional flows in deep channels of the screw and high shear stress developed at flight regions. The BSM is used to produce a polymer nano-composite composed of multi-walled carbon nanotubes and polydimethylsiloxane resin. The mixing performance of the BSM is characterized quantitatively by estimating two different types of mixing efficiencies (i.e., dispersive mixing and distributive mixing) via transmitted light microscope images. The developed BSM highly improves the mixing performance rather than that of a conventional ultrasonic mixing device.

Mechanical characterization of copper coated carbon nanotubes reinforced aluminum matrix composites

In this investigation, carbon nanotube (CNT) reinforced aluminum composites were prepared by the molecular-level mixing process using copper coated CNTs. The mixing of CNTs was accomplished by ultrasonic mixing and ball milling. Electroless Cu-coated CNTs were used to enhance the interfacial bonding between CNTs and aluminum. Scanning electron microscope analysis revealed the homogenous dispersion of Cu-coated CNTs in the composite samples compared with the uncoated CNTs. The samples were pressureless sintered under vacuum followed by hot rolling to promote the uniform microstructure and dispersion of CNTs. In 1.0wt.% uncoated and Cu-coated CNT/Al composites, compared to pure Al, the microhardness increased by 44% and 103%, respectively. As compared to the pure Al, for 1.0wt.% uncoated CNT/Al composite, increase in yield strength and ultimate tensile strength was estimated about 58% and 62%, respectively. However, in case of 1.0wt.% Cu-coated CNT/Al composite, yield strength and ultimate tensile strength were increased significantly about 121% and 107%, respectively.

A study of reaction kinetics in Al – 2% MWCNT composites

A composite obtained from pure aluminum and multiwall carbon nanotubes by mechanical milling in a high-power mill and ultrasonic mixing is studied. The apparent activation energy and the order of the reaction between carbon nanotubes and aluminum are determined using the Kissinger and Crane equations and differential scanning calorimetry under non-isothermal conditions.

Scratch Resistance and Adhesion Properties of PEEK Coating Filled with h-BN Nanoparticles

Effects of h-BN particles on mechanical properties and adhesion of semi-crystalline poly (ether-ether-ketone) (PEEK) coatings were studied. PEEK powder was mixed with various contents of h-BN nanoparticle in ethanol under ultrasonic mixing. As-mixed powders were sprayed onto low carbon steel substrate with thermal spray technique. The hardness, scratch hardness, specific scratch wear rate, prevailing deformation mechanisms and adhesion were obtained from scratch tests by varying the applied load. The damage geometry on scratched polymer surfaces and scratch wear volume loss were examined using scanning electron microscope (SEM) and surface profilometer, respectively. The results indicated that the addition of h-BN content improved the hardness of the composite. In addition, the specific scratch wear rate and the adhesion between PEEK coatings and substrate decreased with increasing h-BN content. The poor adhesion resulted from the reductions of flow-ability and viscosity between PEEK and substrate caused by heat dissipation from the h-BN particles.

Ultrasonic Preparation of Hierarchical Graphene‐Oxide/TiO2 Composite Microspheres for Efficient Photocatalytic Hydrogen Production

Hierarchical graphene oxide (GO)-TiO2 composite microspheres with different GO/TiO2 mass ratios were successfully prepared by mixing GO and TiO2 microspheres under ultrasonic conditions. Ultrasonication helped the GO and TiO2 microsphere to uniformly mix on the microscale. The results showed that the GO-TiO2 composites that were prepared by ultrasonic mixing exhibited significantly higher hydrogen-evolution rates than those that were synthesized by simple mechanical grinding, owing to synergetic effects, including enhanced light absorption and scattering, as well as improved interfacial charge transfer because of the excellent contact between the GO sheets and TiO2 microspheres. In addition, GO-TiO2-3 (3 wt.% GO) showed the highest hydrogen-generation rate (305.6 μmol h(-)), which was about 13 and 3.3-times higher than those of TiO2 microsphere and GO-P25 (with 3 wt.% GO), respectively. Finally, a tentative mechanism for hydrogen production is proposed and supported by photoluminescence and transient photocurrent measurements. This work highlights the potential applications of GO-TiO2 composite microspheres in the field of clean-energy production.

Effect of Solids Loading on Resonant Mixed Al‐Bi2O3 Nanothermite Powders

AbstractSensitive nanoenergetic powders, such as nanothermites, have traditionally been processed by ultrasonic mixing of very low solids loaded suspensions in organic solvents, which has restricted their use and application due to high solvent content and associated handling issues. In this work, we report on the performance and mixing quality of nanothermite mixtures prepared in a LabRAM resonant mixer at high solids loadings as compared to ultrasonic mixing. Specifically, the aluminum‐bismuth(III) oxide (Al/Bi2O3) system processed in the polar solvent N,N‐dimethylformamide (DMF) was investigated. It was found that the performance and overall quality of mixing was strongly correlated to the volumetric solids loading during processing; increasing volumetric solids loading decreases separation of particles, leading to more particle interaction and more intimate mixing. The measured performance of this system processed at 30 vol‐% was similar to traditionally ultrasonicated mixtures. Increasing the solids loading above 30 vol‐% yielded diminishing returns in performance and may introduce additional safety concerns since dry powders are very sensitive to electrostatic discharge. This mixing approach uses significantly less solvent than traditional ultrasonic mixing, results in a higher density final material, and is amenable to scaling. In addition, solvent wetted nanothermite mixed at 30 vol‐% solids loading can be mixed and deposited from a single applicator and was observed to be over five orders of magnitude less sensitive to electrostatic discharge than dry powders. This relative insensitivity enables the safe deposition of high density nanothermite ink onto devices.

Demonstration of Noncontact Ultrasonic Mixing of Droplets

The noncontact ultrasonic mixing of two droplets is demonstrated, for the first time, by controlling the acoustic field using the following two methods: (1) by changing the distance between the vibrator and the reflector and (2) by modulating the driving voltage amplitude applied to the vibrator. The operating principle is confirmed by measuring the acoustic pressure distribution and the temporal change in the acoustic pressure near the mixing position. We also show that the stable mixing of droplets with high repeatability is feasible by method (2), which does not involve the use of mechanically moving parts.

Development of a lead-free composite solder from Sn–Ag–Cu and Ag-coated carbon nanotubes

The microelectronic applications of lead-free solders pose ever-increasing demands. We seek to improve the solder by forming composites with Ag-coated single-walled carbon nanotubes (Ag-coated SWCNTs). These were incorporated into 96.5Sn–3.0Ag–0.5Cu solder alloy with an ultrasonic mixing technique. Composite solder pastes with 0.01–0.10 wt% nanotube reinforcement were prepared. The wettability, melting temperature, microstructure and mechanical properties of the composite solders were determined, and their dependency on nanotube loading assessed. Loading with 0.01 wt% Ag-coated SWCNTs improved the composite solder’s wetting properties, and the contact angle was reduced by 45.5 %, while over loading of the coated nanotubes up to 0.10 wt% degraded the wettability. DSC results showed only slight effects on the melting behavior of the composite solders. Cross-section microstructure analysis of the spreading specimens revealed uniform distribution of the intermetallic compounds throughout the solder matrix, and EDS analysis identified the phases as β-Sn, Ag3Sn and Cu6Sn5. The mechanical properties of composite specimens, compared with those of unloaded 96.5Sn–3.0Ag–0.5Cu solder, had a maximal improvement in the shear strength of 11 % when the nanotube loading was 0.01 wt% of Ag-coated SWCNTs.

Facile synthesis of poly(methylsilsesquioxane) and MgO nanoparticle composite dielectrics

Abstract

Low Frequency Dielectric Study of PAPA-PVA-GR Nanocomposites

A new polymer poly(2, 2-bis ((4-acetylbenzoyloxy) methyl) propane-1,3-diyl bis(4-acetylbenzoate)) (PAPA) was synthesized by solution polymerization of pentaerythretole with terephthaloyl chloride. This polymer was characterized by FT-IR spectroscopy. Graphene (GR) was prepared using hydrothermal method. Evaluation of graphene structure was performed using FT-IR and XRD. Polymer composites were prepared by ultrasonic mixing of PAPA and PVA with different GR percentages. Composites films were prepared by a conventional solvent casting technique. The morphological image of the composite materials was studied by scanning electron microscopy (SEM) and the surface topography of these composite materials was studied by Atomic Force Microscopy (AFM). Effects of GR nanoparticles percentage on dielectric properties of PAPA/PVA/GR nanocomposites film at low frequency (100Hz-100 kHz) were studied.

Optimization of the Production of Biodiesel Assisted by Ultrasonic and Microwave

The transesterification reaction of present study was assisted by ultrasonic mixing and microwave irradiation. Central composite design (CCD) was employed to optimize the transesterification reaction conditions of biodiesel production from soybean oil. A mathematical model predicted that the theoretical conversion rate of soybean oil of 102.19% could be obtained under the following reaction conditions: amount of catalyst used, 1.4wt%; reaction temperature, 57.89oC; and methanol/oil molar ratio, 8.11:1, assisted by 1-min ultrasonic mixing and 2-min microwave irradiation. This result indicated that there are a wide range of reaction conditions to obtain conversion rate approach 100% assisted by ultrasonic mixing and microwave irradiation. Combined the ultrasonic mixing and microwave irradiation are very efficiency process to produce biodiesel. The total reaction time was shorter than those obtained in previous studies

Ultrasonic dual mode mixing and its effect on tensile properties of SiO2-epoxy nanocomposite

Dispersion of nanoparticles and its effect on the tensile properties were investigated by preparing nanocomposites via mechanical mixing (MM) and optimized ultrasonic dual mode mixing (UDMM) routes. The MM of SiO2 nanoparticles in epoxy resin was employed using glass rod stirring and the UDMM was employed by ultrasonic vibration along with magnetic stirring to produce SiO2-epoxy nanocomposite. Taguchi method was used for optimization of the process parameters of UDMM route considering the tensile strength of the base epoxy. Field emission scanning electron microscopy (FE-SEM) micrographs revealed an improved dispersion quality of SiO2 nanoparticles especially for the UDMM route. Consequently, quality of dispersion affects tensile strength (max 49.2%) along with ductility and absorbed failure energy at low nanoparticle content. Moreover, elastic modulus increases with increasing content of nanoparticle, e.g. in one case 62.55% for 20 wt.% of SiO2 nanoparticles.

Fabrication and Performance Evaluation of Piezoelectric Strain Sensors Made from PVDF/MWNT Nanocomposites

In this study, we fabricated piezoelectric strain sensors from multi-walled carbon nanotubes (MWNTs) and PVDF nanocomposites, i.e., PVDF/MWNT for measuring dynamic strains. The influence of MWNT loading on the sensor performance was evaluated by changing the MWNT loading as 0.0wt%, 0.05wt%, 0.2wt%, and 0.3wt%. To increase MWNT dispersion in PDVF matrix, a mixing process by using a planetary stirring machine and sonication processing by using an ultrasonic mixer were firstly employed together to produce nanocomposite films. Then, these films were stretched under uniaxial loading and poled under 60MV/m to fabricate the strain sensors. Moreover, crystallinity of the PVDF/MWNT nanocomposites was analyzed by using X-ray diffraction (XRD) analysis, and the fractured surfaces of pre-stretched PVDF/MWNT nanocomposites were observed by using a polarized optical microscope (POM). The piezoelectricity and signal tracking capability of the PVDF/MWNT nanocomposites sensors in vibration were investigated. From experimental results, the piezoelectricity, i.e., the sensor output voltage of the PVDF/MWNT nanocomposites reaches to a maximum peak value at 0.05wt% MWNT loading, and then decreases with further more addition of MWNTs. The result of XRD intensity was consistent with the piezoelectric sensor output results of PVDF/MWNT nanocomposites. From POM observations, compared to that of pure PVDF, the spherulite's size in the PVDF/MWNT nanocomposites becomes smaller and its number increases. Moreover, there should exist an optimum content of MWNTs, which can result in high piezoelectric properties of the nanocomposite strain sensors.

Preparation and properties of poly HTBN-based urethane-urea/organo reactive montmorillonite nanocomposites

With ultrasonic assistant mixing way, an intercalated mixture of polyol/organo reactive montmorillonite (ORMMT) was pretreated. The prepolymer composed MMT clay was prepared by reaction of polyol/ORMMT mixture with toluene diisocyanate (TDI). The resultant prepolymer reacted with extender (DMTDA) and then the polyurethane-urea/organo reactive montmorillonite (PUU/ORMMT) nanocomposites were obtained. The structure, morphology and properties of PUU/ORMMT nanocomposites were characterized by FT-IR, TEM, AFM, strain-stress machine, TGA, and dynamic mechanical analysis (DMA). The results showed that when the OMMT content is 3%, the PUU/ORMMT nanocomposities performed super mechanical properties. Because of the presence of ORMMT, both T g of the soft segment and tanδ of the PUU increased, and the decomposition temperature for the first step and the second step increased respectively. TEM images showed that the organophilic MMT particles in the PUU composite exhibit a high degree of intercalation and exfoliation.

The Influence of Nanofillers on the Mechanical Properties of Carbon Fibre Reinforced Methyl Methacrylate Composite

The influence of different types of nanofillers – carbon nanotubes (CNT) and organically modified nanoclay – on the flexural properties and nail penetration resistance of carbon fiber reinforced methyl methacrylate (MMA) composite have been investigated. An ultrasonic mixing was used to distribute various content of nanofillers (0.7 wt.% – 3.0 wt.%) in MMA resin. Scanning electron microscopy and X-ray diffraction analyses confirmed formation of intercalated MMA clay nanocomposites. Two different stacking sequences, [0/90]3 or [0/90/45]2, and two types of carbon fibre, with or without epoxy binder, were used for composites preparation. The composites with stacking sequence of [0/90]3 show higher resistance to the mechanical loading. Epoxy binder increases fibre adhesion interaction with MMA resin, however, almost does not influences on the fibre reinforced composite strength properties. The results demonstrated that only low content (up to 1 wt.%) of organically modified nanoclay Cloisite 10A increases the carbon fibre reinforced composites resistance to flexure and nail penetration. The low content of CNT also increases flexural stress and modulus, but decreases resistance to the nail penetration.DOI: http://dx.doi.org/10.5755/j01.ms.18.3.2434

Surface reconstruction enhancing activity of Pt/C for formic acid electrooxidation by ultrasonic mixing with Pb/C and electrochemical activation process

The control for surface of catalysts is intrinsically required to improve catalytic efficiency. In current work, we demonstrate that the surface of Pt/C catalyst can be effectively reconstructed by ultrasonic mixing with Pb/C in an acidic environment and electorchemical activation process. As a result, the surface-reconstructed Pt/C catalyst exhibits a significant enhancement of activity of a ca. 10-fold improvement in mass activity and a ca. 38-fold improvement in specific activity as compared with a pure Pt/C catalyst for formic acid electroxidation (FAEO). The evidences show that some of Pb species are transferred from Pb/C to surface of Pt/C catalyst probably through the dissolution–adsorption pathway during ultrasonic mixing and electorchemical activation processes. The presence of Pb on surface of Pt not only isolates the continuous Pt sites through the third-body effect but also modifies electronic band structure of platinum via electronic effect, which leads to that the direct pathway is preferably occurred and the CO formation is effectively inhibited. These results provide useful information for further understanding the promotion mechanism of Pb ad-atom during FAEO and rationally controlling the catalytic surface to improve catalytic efficiency.

Influence of different synthesis approach on doping behavior of silver nanoparticles onto the iron oxide–silica coreshell surfaces

Silver (Ag) nanoparticles with the crystallite size ranging from 13–24 nm were successfully doped onto the surface of iron oxide–silica coreshell particles. In the process, iron oxide particles having a size distribution within 8–19 nm were prepared by using a reverse co-precipitation method followed by the formation of iron oxide-core with silica shell (with 50–150 nm diameter of silica spheres) by using a modified Stober method. The reduction of Ag ions was done at room temperature in a solution containing polyvinylpyrrolidone and ethanol by using mechanical and ultrasonic mixing. Four different synthesis approaches were used in doping of Ag nanoparticles. The phase, morphology, optical and magnetic properties of the synthesized powders were characterized by using X-ray diffraction, scanning electron microscope (SEM), transmission electron microscope, UV–visible spectrometer (UV–Vis) and vibrating sample magnetometer. Spherical morphology of the Ag nanoparticles was found to deposit on the iron oxide-silica surfaces. The particle size distribution is depending on the synthesis approach used. The UV–Vis absorption peak at 404–410 nm of wavelength confirmed the existence of the Ag nanoparticles.

Improving the performance of polymer solar cells by adjusting the crystallinity and nanoscale phase separation

In this paper, we report a high-performance P3HT/PCBM bulk-heterojunction solar cell with a power conversion efficiency of 4.85% fabricated by adjusting the polymer crystallinity and nanoscale phase separation using an ultrasonic irradiation mixing approach for the polymer. The grazing incidence X-ray diffraction, UV/Vis spectroscopic, and atomic force microscopic measurement results for the P3HT/PCBM blend films reveal that the P3HT/PCBM film fabricated by ultrasonic irradiation mixing of the P3HT and PCBM solutions for 10 min has a higher degree of crystallinity, a higher absorption efficiency, and better phase separation, which together account for the higher charge transport properties and photovoltaic cell performance.