Stirring Techniques Research Articles

Magnetic-based silver composite microspheres with nanosheet-assembled shell for effective SERS substrate

Well-dispersed magnetic-based silver composite microspheres (Fe3O4@SiO2@Ag) with a nanosheet-assembled shell structure were synthesized at room temperature, where sonicating and mechanical stirring techniques were both employed and played important roles during the silver shell growth process. The results show that the nanosheet-assembled silver shell could be obtained and controlled by adjusting the concentration of citrate ions as a morphology directing-reagent. The gaps in or between cross-linked nanosheets in the shell of the composite microspheres were proposed to provide sufficient “hot spots” when they were used as a SERS substrate. The SERS measurements exhibit clear enhancement signals by using R6G as a probe molecule, and even at concentrations as low as 10−14 M, all enhancement peaks could be observed clearly. The film assembled from the composite microspheres exhibited good reproducibility across the entire area. Additionally, the magnetic Fe3O4@SiO2@Ag microspheres can be separated from solution rapidly, which shortened the detection time. Considering their excellent SERS performance, this kind of composite microsphere, which has both a SERS active shell and a magnetically separable core, would be very useful as an effective SERS substrate for detecting organic pollutants in solution.

Electrokinetic and Colloidal Properties of Homogenized and Unhomogenized Palygorskite in the Presence of Electrolytes

A series of palygorskite samples modified with electrolytes containing LiCl, NaCl, KCl, CsCl, MgCl2, CaCl2, AlCl3, and FeCl3 were prepared with the aid of high-pressure homogenization and mechanical stirring techniques. The changes of electrokinetic and colloidal properties of modified palygorskite were investigated in detail through the measurement of the zeta potential, yield stress, and sedimentation volume. The influences of charge, concentration, and type of ions on the surface potential of palygorskite were compared. The correlation between the zeta potential and the colloidal properties of obtained palygorskite was discussed. The homogenization process could favor the adsorption of ions onto palygorskite surface and enhance the colloidal properties of suspension. It was found that the 0.05 mol·kg–1 AlCl3 and FeCl3 reversed the surface charge of palygorskite from negative to positive. The yield stress measurements demonstrated that the association capacity of rods depended on the surface potential and interparticle interactions of palygorskite. A stable suspension was obtained when palygorskite was dispersed in MgCl2 solutions and homogenized at 30 MPa.

Smart coating for corrosion protection by adopting nano particles

Nano containers with a shell possessing controlled release properties can be used to fabricate a new family of active coatings that can respond quickly to change the environment/integrity of the coatings. The release of corrosion inhibitors encapsulated within nano containers can prevent further corrosion. The structural evolutions and morphological characteristics of nano particles are investigated using XRD, SEM, FT-IR and AFM. The author reports an in situ encapsulation method demonstrating over an order of magnitude size reduction for the preparation of urea-formaldehyde capsules filled with a healing agent, linseed oil and corrosion inhibitors. Capsules with diameters as small as 30–40μm are achieved using stirring techniques. Cracks in paint film were successfully healed when linseed oil and nanoparticles was released from microcapsules ruptured under stimulated mechanical action. Further linseed oil healed area was found to prevent corrosion of the substrate.

Improvement of crystal qualities by solution stirring techniques

Improvement of crystal qualities by solution stirring techniques

Continuous Casting of Magnesium Alloy Billet Using Electromagnetic Techniques

Currently, magnesium billets produced by ingot casting or direct chill casting process, result in low-quality surfaces and peer productivity. Continuous casting technology for high-quality surface billets with fine-grained and homogeneous microstructure can be a solution for the cost barrier breakthrough. The latent heat of fusion per weight (J/g) of magnesium is similar to that of other metals, however, considering the heat emitted to the mould surface during continuous casting in meniscus region and converting it to the latent heat of fusion per volume, magnesium will be rapidly solidified in the mould during continuous casting, which induces subsequent surface defect formation. In this study, electromagnetic casting and stirring (EMC and EMS) techniques are proposed to control solidification process conveniently by compensating the low latent heat of solidification by volume and to fabricate magnesium billets with a high quality surface.

Friction and wear analysis of a cement kiln dust- reinforced epoxy-based functionally graded materials

The wear behaviour of new material epoxy matrix homogeneous composites and its functionally graded materials reinforced with uniform-sized cement kiln dust (CKD) is discussed in this article. The tribological behaviour of CKD particulate-reinforced homogeneous and graded epoxy composites synthesized by simple mechanical stirring and vertical centrifugal casting techniques, respectively, is investigated. Mechanical properties of graded and homogeneous composites are evaluated and compared. Sliding wear tests are performed over a range of sliding velocities (105–314 cm/s), normal loads (20–40 N), filler contents (0–20 wt%), and sliding distances (0.5–2 km) using a pin-on-disc machine. A statistics-based design of experiments approach using Taguchi's orthogonal arrays is used. This study establishes that the presence of CKD particles enhances the sliding wear resistance of graded composites. Out of all synthesized composites 10 wt% graded composite exhibits the maximum impact strength which clearly indicates that the effect of the fabrication technique is much more pronounced for impact strength. Scanning electron microscope (SEM) and optical microstructures confirm the continuous graded dispersion of CKD particles in the matrix.

Oxidation of aniline over titania pillared montmorillonite clays

Titania pillared clays (Ti-PILC) have been synthesized employing conventional stirring (method I) and ultrasonic agitation (method II) techniques followed by hydrothermal treatment. The characterization results revealed the formation of Ti-PILC with significant reduction of time when ultrasonic method was used. Subsequent hydrothermal treatment on the samples has resulted in the increase in the crystallinity and the transformation of anatase TiO2 to rutile TiO2. The rutile phase is more prominent in the samples prepared by stirring method. UV–Vis studies on the samples exhibit blue shift in the absorption band due to the quantum size effect. This indicates that a major part of TiO2 in the pillared clay could be well below 10 nm in size, which is supported by XRD and the average pore size. The pillared clay catalysts have proved to be promising in aniline oxidation with H2O2, selectively forming azoxybenzene under the working conditions. The aniline conversion and the product distribution largely depended on the catalyst concentration, H2O2 to aniline mole ratio, the nature of the solvent and the oxidant. Higher conversion of aniline and greater selectivity for azoxybenzene was obtained with methanol as the solvent.

Models for the number of independent samples in reverberation chamber measurements with mechanical, frequency, and combined stirring

The accuracy in reverberation chamber measurements relies on the chamber setup being able to generate a large number of independent measurement samples. Simple models for the number of independent samples with mechanical stirring and frequency stirring are presented, and also with several stirring techniques combined. The models are verified through measurements.

Parallel Down Flow Rinsl : Water Saving Technology in Wafer Rinse

AbstractWe had proposed parallel downflow rinse which was capable of draining out chemical carried over to rinsing bath together with wafer about twice as fast as overflow rinse. In an attempt to further improve rinsing efficiency of PDR, we have investigated (1) the effect of wafer carrier shape, and (2) removal of boundary layer on wafer surface. Boat‐type wafer holder is preferable to conventional cassette. Three stirring techniques adequate for PDR, namely, megasonic irradiation. N2 bubbling, liquid level shifting, are found effective to remove chemical ion remaining boundary layer in measuring conductivity and resistivity.

Stability and Stirring in Crystal Growth from High‐Temperature Solutions

Crystals normally grow in solution in a destabilizing supersaturation gradient. The observation of inclusion‐free growth to large crystal sizes may be described in terms of a metastable region of the supersaturation gradient which is associated with the mechanism of growth on the habit faces. Stirring has a beneficial effect on growth stability especially by reducing or removing the supersaturation inhomogeneity across the face of a polyhedral crystal. The effect of convection and of various stirring techniques is briefly described.

Effect of ultrasonic waves on the catalytic activity of silica gel

It has been found that silica gel, prepared in the presence of ultrasonic waves (90 kHz), is more active as a catalyst in the decomposition of hydrogen peroxide (0.3 wt % aqueous solution) than silica gel prepared with only the usual stirring techniques. The reaction studies carried out at 37, 44, 54 and 63 °C in a batch reactor showed that both the activation energy and the frequency factor were higher for the insonated gel than the uninsonated gel. The increase in activation energy and the catalytic activity has been explained in terms of the compensation effect. Surface area, pore volume, and pore-size distributions were also measured. The existing kinetic data on the catalytic decomposition of hydrogen peroxide (using various catalysts) has been correlated in terms of the “isokinetic temperature” and a “characteristic frequency factor.” This correlation enables the kinetic parameters of a new catalyst (for H 2O 2 decomposition) to be determined with a minimum of experimental work.

Dispersal of Particulate Matter in a Liquid Medium by Means of Sonic and Ultrasonic Waves

Conventional methods do not generally meet the physical requirements for efficient dispersal of agglomerated particulate matter in a liquid medium. Simple stirring techniques do not induce the relative motion necessary for the dispersal and require an excessive amount of mechanical power, long mixing times, bulky containers, and batch operation. With sonic and ultrasonic waves direct effects may be produced in a simple and inexpensive way by submitting the components of the suspension to strong relative motion. The particulate matter will then be rapidly dispersed due to the erosion and disaggregation processes. Theoretical studies and laboratory results have led to the development of an efficient, inexpensive, and essentially simple process. Industrial performances are possible and with low transducer power results superior to those obtained with standard apparatus may be obtained.