Influence Of Rotation Rate Research Articles

Effect of welding parameters on microstructure and mechanical properties of friction stir welded 5083-H112 alloy

6 mm 5083-H112 aluminum alloy sheets were friction stir welded (FSW) while rotation rate was 500–1200 rpm and the welding speed was 100–300 mm/min. The influence of rotation rate and welding speed on the welds’ microstructure and mechanical properties were evaluated. The results revealed that under the experimental parameters, the welds have good appearances and no welding defects. The nugget zones presented equiaxed recrystallized grains and the grain size decreased with the increase of welding speed or the decrease of tool rotation rate. The NZ presented the highest hardness of all FSW joints because of the formation of fine equiaxed grains by dynamic recrystallization. The joint efficiencies of the ultimate tensile strength were more than 94%. The strength increases and the elongation decreases with the increase of the rotation rate and the decrease of the welding speed.

Influence of Rotation Rate on Microstructure and Comprehensive Performance of FSWed Mg Alloy

Die-casting AZ31 Mg alloys were successfully friction stir welded at a constant welding speed and different rotation rates. More uniform and fine grains were obtained at the rotation rate of 1400 rpm due to more suitable temperature for dynamic recrystallization in this welding condition. In addition, the intensity of (0001) texture in stir zone increased with the increasing rotation rate. The results of mechanical property test indicated joint with rotation rate of 1400 rpm had better tensile property, which was associated with fine grains, uniform transition in the interface between thermo-mechanically affected zone and stir zone as well as more favorable Schmidt factor for basal slip and twinning. The corrosion resistance of joints increased with the increasing rotation rate, which is significantly related to the (0001) texture with basal plane parallel to the corroded surfaces.

Template-free synthesis of Pt-MOx (M = Ni, Co & Ce) supported on cubic zeolite-A and their catalytic role in methanol oxidation and oxygen reduction reactions characterized by the hydrodynamic study

Cubic zeolite-A (LTA) is synthesized and ion-exchanged with Pt, Ni, Co and Ce ions followed by reduction of Pt (IV) on the metal oxides (NiO, CoO and CeO2) formed in the zeolite matrix. Their catalytic performance in methanol oxidation (MOR) and oxygen reduction reactions (ORR) are evaluated. The structure, morphology and composition of these catalysts are investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectral analysis (EDS) and X-ray photoelectron spectroscopy. The activity of these electrocatalysts in methanol oxidation is analysed by cyclic voltammetry, linear sweep voltammetry, chronoamperometry and chronopotentiometry in acidic medium and compared with commercial Pt electrode. From the results of electrochemical characterization, it is observed that Pt-NiO on zeolite-A (Pt-NiO-A) exhibited high current density, lower onset potential, enhanced If/Ib values and better stability. The electrocatalytic activity of these catalysts are in the order, Pt-NiO-A > Pt-CoO-A > Pt-CeO2-A > Pt-A > Pt. The influence of rotation rate on MOR and ORR are investigated using rotating ring disc electrode (RRDE). With increasing rotation speed, the change observed in the disc (ID) and ring (IR) currents reveal the mechanism of the reactions. For oxygen reduction reaction (ORR), the number of electrons transferred (n) and % H2O2 produced is calculated. This is the first systematic study, reporting the hydrodynamic evaluation of these catalysts for MOR.

Characterization of Surface Films Formed on Aluminum during Mass-Transfer Limited Anodic Dissolution in Phosphoric Acid

Electrochemical impedance spectra recorded during the mass-transfer limited dissolution of commercially pure aluminum rotating disk electrodes in concentrated phosphoric acid are presented. The influence of rotation rate and potential on the observed capacitive and inductive semi-circles is discussed and the presence of a salt film on top of the oxide film is debated. The impedance spectra are interpreted hypothesizing the presence of a compact, barrier-type Al2O3 film only. The capacitive and inductive features are explained in terms of the capacitive charging of the barrier film, the relaxation of a surface charge at the film/solution interface and the perturbation of the film thickness. The properties of the film such as electric field strength, half-jump distance and polarizability of the film/solution interface are calculated in agreement with literature values.

Influence of Rotation Rate of Collecting Roller on the Mechanical Property of PCL/SF Tubular Scaffolds

The composite tubular scaffolds with highly oriented nanofibers used for vascular repair could improve the biomechanical properties of tubular scaffolds, satisfying the biomechanical requirement for the change of blood pressure and conducing to cell adhesion, migration and proliferation. The tubular scaffolds from poly(ε-caprolactone)(PCL) and silk fibroin (SF) composite nanofibers were successfully fabricated through electrospinning using cylindrical roller with an outer diameter (OD) of 3.0 mm. The influences of the collecting rotatation speeds on electrospun PCL/SF nanofibers orientation and radial/axial mechanical properties of the scaffolds were investigated. The results revealed that the electrospun PCL/SF tubular scaffolds fabricated at 1500 and 2000 r/min (linear velocity of 2.1, 2.8 m/s, respectively) possessed good arrangement around the circumferential direction of roller and sufficient radial strength and suture strength. The electrospun PCL/SF tubular scaffolds with circumferential-direction structure as a new vascular graft may be useful in vessel tissue engineering.

Development of a platinum rotating disc electrode for dynamic electrochemical measurements in glass melts

A configuration is described and tested that enables electrochemical measurements at a rotating disc electrode in glass melt environments. In a glass melt with 10 mass% Fe 2O 3 at 1200°C, it was possible to reach a time independent steady-state current, through rotating the electrode. In aqueous solutions, time independent electrode signals show distinct advantages to study the oxidation–reduction behaviour and the properties of polyvalent elements. The influence of rotation rate was studied and the results obtained were compared with those obtained at a static disc electrode. The rotation speed dependence of the steady-state current obtained in a molten glass environment at 1200°C was shown to obey the Levich-equation. An expected advantage of time independent signals is the concentration determination of metal ions in glass melts continuously and online. This opens new perspectives concerning the online monitoring and automatic control of the glass production processes. Furthermore, the validity of the Levich-equation opens new possibilities for diffusion coefficient measurement of metal ions in glass melts.

Preparative desalting of bovine serum albumin by continuous annular chromatography

Bovine serum albumin (BSA) was continuously desalted from alkaline salts (a mixture of sodium phosphate, sodium chloride and potassium chloride) using a size-exclusion gel as the stationary phase. An annular chromatograph was used to achieve a continuous mode of operation and therefore a reasonable throughput. Distribution and mass transfer coefficients of the substances as well as bed properties were obtained by batch chromatography. These separations were simulated mathematically applying an approximate linear chromatographic theory. It was shown experimentally and theoretically that the BSA and the salt solution could be recovered continuously in a purity higher than 98%. The influence of rotation rate on the resolution of the individual peaks was investigated.

Continuous Separation of Carbohydrates by Ion-Exchange Chromatography

A synthetic mixture of fructose, mannitol and sorbitol was continuously separated by a chromatographic method using a cation-exchange resin (Dowex 50W-X8) in its Ca2+-form as the stationary phase. An annular chromatograph (AC) was used to achieve a continuous mode of operation. Distribution and mass transfer coefficients of the three substances as well as bed properties were obtained by batch chromatography. The separation was simulated mathematically in terms of an approximate linear chromatographic theory was applied to the modeling of the behavior of the continuous separations. The influence of rotation rate, column loading, eluent flow rate and feed concentration on the resolution of the individual peaks were investigated.

Continuous chromatographic separation of fructose, mannitol and sorbitol

The separation of mixtures of fructose, mannitol and sorbitol by continuous annular chromatography on Dowex 50W-X8 has been investigated. Distribution and mass transfer coefficients of the three substances were obtained by batch chromatography. The influence of feed concentration and flow rate on these parameters were discussed. The separation was simulated numerically and compared with experimental data. With this procedure, the separation of mixtures of fructose, mannitol and sorbitol by continuous annular chromatography (CAC) was calculated in advance, using only batch data. Additionally, the influence of rotation rate, column loading, eluent flow rate and feed concentration on the resolution of the individual peaks were investigated. With these results, the operation parameters for an industrial application of the CAC for this separation problem were determined.