Ultrasonic Dispersion Process Research Articles

Scaling‐up of the dispersion process of nanoparticle‐agglomerates in epoxy resin with an innovative continuous ultrasonic flow‐through‐cell dispersion system

AbstractThermosets reinforced with inorganic nanoparticles show numerous benefits over the unreinforced polymer. However, to achieve reinforcement the nanoparticles have to be well separated and distributed homogeneously within the matrix. In the present study the laboratory scale discontinuous ultrasonic dispersion process was scaled up to a continuous ultrasonic dispersion process of agglomerated nanoparticles in epoxy resin (EP). Exemplarily, the dispersion experiments were carried out for a 4‐l suspension volume consisting of epoxy resin and 14 vol% TiO2‐nanoparticles was carried out as a function of the dispersion time and the amplitude of the ultrasonic cell. Following, nanocomposites were manufactured with particle contents of 2, 5, and 10 vol%. For the verification of the manufactured nanocomposites quality, particle sizes analysis and mechanical characterization were undertaken. The obtained results were compared with those of the discontinuous dispersion at laboratory scale. It has been found that comparable particle sizes and mechanical properties could be achieved, although, the volume of the suspension was 10 times higher as that one of the batchwise dispersion. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers

Enhancement of dispersion and adhesion of B 4C particles in epoxy resin using direct ultrasonic excitation

Enhancement of the mechanical properties of the B 4C/epoxy composites, which is used as a neutron shield for spent nuclear fuel cask, was achieved by direct ultrasonic dispersion of the B 4C particles in the hardener using an immersed horn, while those prepared without direct ultrasonic dispersion showed insufficient adhesion as well as some agglomerates in the epoxy resin. Degrees of agglomeration and adhesion were analyzed by means of the SEM images and the FTIR peaks belong to C–C stretching mode of the hardener ring, which was lowered and flattened by van der Waals interaction between the B 4C particles and the hardener ring substituent. The tensile strength of the B 4C/epoxy composites prepared by direct ultrasonic dispersion was maintained (or increased) compared to that for the neat epoxy matrix, while those prepared without ultrasonic dispersion were degraded significantly. Consequently, direct ultrasonic dispersion process developed in this investigation could achieve uniform dispersion as well as strong adhesion of the B 4C particles in/with the epoxy matrix enhancing the material properties without any chemical treatment resulting unwanted impurities.

G040031 カーボンナノファイバー添加PTFE膜の電気的特性に及ぼす分散状態の影響([G04003]機械材料・材料加工部門一般セッション(3))

Fluoropolymers have very low friction and various unique properties. Therefore, they are expected to be applied for sliding materials. However, because of the insulation, it is easy to accumulate static electricity. Hence, to apply to sliding materials there is need to provide electrical conductivity. Nano Carbon is expected as one of the conductive fillers that can effectively improve the electrical property by a small amount of addition, so many researchers studied about composite materials filled with nano carbon. However, because nano carbon is easily agglomerated, the problem that steady electric conductive cannot be obtained is pointed out. In this study, we prepared Carbon nanofiber (CNF) filled Polytetrafluoroethylene (PTFE) films by spin coating method, and evaluated the surface resistivity of the composite film and dispersion status of CNF, and investigated relationship between electrical conductivity and dispersion status of CNF. As a result, when the condition of ultrasonic dispersion is optimized in the case of 2wt% CNF/PTFE composite film, by optimizing the conditions of ultrasonic dispersion process, the surface resistivity of composite film has decreased to 1/100 compared with no dispersion process.

Hybrid Effect of Carbon Fiber on Piezoresistivity of Carbon Nanotube Cement-Based Composite

Cement-based nanocomposite filled with only 0.1 wt.% multi-wall carbon nanotube (MWNT) (MNFRC), or hybrid with 0.1 wt.% MWNT and 0.5 wt.% microsized short carbon fiber (SCF) (SF/MNFRC), were prepared employing surfactant ultrasonic dispersion and high-speed mixing process. The electrical resistivities (ρ), compressive stresses (σ), and longitudinal strains (εl) of these cured nanocomposites under cyclic uploading/unloading were simultaneously collected, to characterize their stress/strain-sensitive properties. There exists good piezoresisitivity and high strain sensitivity for MNFRC. The fractional change in ρ (Δρ) regularly descends or ascends following the σ, or the εl of MNFRC (the Δρ/εl sensitivity near 68). Hybrid of SCF is found to be more effective to improve the self-sensing repeatability and variation stability of the SF/MNFRC rather than the self-sensing sensitivity (the Δρ/εl sensitivity only about 64).

Rapid Extraction of Imidacloprid in Tomatoes by Ultrasonic Dispersion Liquid–Liquid Microextraction Coupled with LC Determination

A simple method for the extraction and determination of trace imidacloprid in tomatoes was developed using ultrasonic dispersion liquid–liquid microextraction coupled with liquid chromatographic separation. An ultrasonic dispersion process was applied to accelerate the formation of the fine cloudy solution without using disperser solvents, which was markedly increased the extraction efficiency and reduced the equilibrium time. The results revealed that tetrachloroethane as extraction solvent could be directly applied to the filtered tomato juice with the assistance of ultrasonic dispersion. Under the optimum condition, the enrichment factor of imidacloprid could reach 375 folds and the average recovery of samples ranged from 87.6 to 110% with RSD less than 4.5% (n = 3). Compared to the conventional sample pretreatment method, the proposed method had the advantage of short time, simple operation, high sensitivity and low consumption of organic solvent.

Synthesis and characterization of ZrO 2 hollow spheres

ZrO 2 hollow microspheres with the average diameter of about 500 nm and the shell thickness of about 50 nm were synthesized by a facile technique using carbon spheres as templates. The corresponding ZrO 2 hollow microspheres were obtained by calcining the precursors of C–Zr(OH) 4 core-shell heterostructures, which were synthesized with the precipitation of ZrCl 4 solution with aqueous ammonia on the surface of colloid carbons. SEM, XRD, TGA and BET were used to characterize the composition, morphology, size and crystal structure of synthesized products. The effects of ultrasonic dispersion and separation process on the hollow spheres were studied, and the surfactant PEG-1000 was added to tune the shell structure of synthesized ZrO 2 hollow spheres.

The I-V Characteristics and Percolation Threshold of the Cement-Based Materials Filled with Multi-Walled Carbon Nanotubes

Some multi-walled carbon nanotubes (NMWTs) were firstly dispersed in aqueous solution with surfactant ultrasonic dispersion process, then mixed into cement matrix, casting six groups cement-based materials filled with varying NMWTs additions (nwt) (NFCMs), and as comparison, the plain referential cement paste was fabricated. The ampere-volt (I-V) characteristics and percolation threshold of this type of nanocomposites were focused by four-electrode method. Results show that, the I-V features of the reference has obvious nonlinearity due to polarized reaction within cement hydrated electrolytes after being induced by passing 0~±30 V voltages, those of the NFCMs with six different nwt still have somewhat nonlinear traits, which mainly attribute to the double-layer coatings between NMWTs and out-encapsulated cement hydration isolation. The resistivity (ρ) of the NFCM nanocomposite steadily decreases with the increment of nwt, which contributes to superior capabilities of charge transporter and near-field emission of NMWTs, and the overlapped chance of physical contacts between conducting aggregates of NMWTs and bulk matrix increases by nwt enhancing; although there is still some fluctuation on ρ, but it becomes weaker and weaker by nwt increasing. The percolation threshold of the NFCMs is nwt being 2.0%, and the integrated network pathways at micro-scale form between NMWTs each other through the correspondent NFCM, also revealed in microstructure.

The Dispersivity of Multi-Walled Carbon Nanotubes (NMWTs) and Pressure-Sensitive Property of NMWTs Reinforced Cement Composite

The individual and/or combinatory impacts of two surfactants (polyoxyethylene nonyl phenyl ether 10 (Tx-100), Arabic gum powder (AG)) on the dispersivity of multi-wall carbon nanotubes (NMWTs) were firstly investigated and evaluated through naked and microstructures observation; hereafter, NMWTs with 1.0% loading were firstly dispersed in aqueous solution with surfactant ultrasonic dispersion process, and cast-mixed into cement matrix to fabricate 2 groups NMWTs reinforced cement composites (NMTRCs), associated with the plain reference. Wheatstone bridge configurations were simultaneously employed to obtain the resistances and the monoaxial stresses, to investigate the pressure-sensitive properties of these nanocomposites. Results with naked observation reveal that either Tx-100 or AG at some concentration has good dispersion effect on NMWTs, the blackness homogeneity and stability of NMWTs suspended solution could retain more than 15 d; yet microstructures results show that NMTRC with AG has more homogeneous dispersion impact and more compatible with cement hydration than that with Tx-100. Results related on the pressure-sensitive properties of NMTRCs demonstrate that, the fractional change in resistivity of NMTRC with AG linearly falls down by increment of applied pressure within elastic range, this good pressure-sensitive traits mainly contribute to the increasing chance of physical contacts, the denser of current chargers between NMWTs, and the shortened trend of the potential barrier widths between NMWTs and matrix by increment of pressure, after efficient dispersion with AG. Yet that of NMTRC with Tx-100 has not good linearity descending trend, but some exaggerate fluctuations, and that of the reference has also no any regular descending trend.