Propriedade Microestrutural do Refinamento da Liga Amorfa Al54Nb45B7

The presence of niobium in the alloy creates regions of intermetallic phases contained in Al54Nb45B7 amorphous alloy which becomes a potent heterogeneous nucleation on the substrate for nucleation with dendritic presence of aluminum oxides due to diffusive processes on the surface of the amorphous alloy Al54Nb45B7. This alloy is extremely low cost, but with applications in many sectors of the chemical and petrochemical industry in emphasis because its mechanical deformation is high due to the presence of (Nb or B) in the aluminum acting mainly as grain refiners to improve their mechanical and thermal properties by using the mechanical alloying. The combined use of Niobium and Boron (intermetallic phases are formed by adding powder of Al and Nb), instead of Niobium or Boron, individually, is a highly effective way to refine the grain size of alloy Al Nb-B in their microstructure without causing inconvenience in your network for unwanted deformations. To that end the present study compared the effect of grain refining promoted by the addition of niobium and the addition of Boron in Al54Nb45B5 obtained by high energy mill under argon atmosphere and analyzed by diffraction of X rays (XRD), scanning electron microscopy and Energy Dispersive (SEM / EDS). DOI: http://dx.doi.org/10.17807/orbital.v8i3.80

On the closure problem of the effective stress in the Eulerian-Eulerian and mixture modeling approaches for the simulation of liquid-particle suspensions

© 2019 Author(s). We address the closure problem of the phasic effective stress tensors in the Eulerian-Eulerian and mixture models, considering suspensions of identical particles dispersed in Newtonian liquids. First, after briefly describing the modeling approaches, we review the key mechanisms generating phasic stress and discuss the shortcomings of some constitutive expressions in reproducing important experimental observations. For dilute suspensions, these include the mixture viscosity rise with solid concentration whilst for dense suspensions, the occurrence of particle migration and the change of mixture rheology from Newtonian to non-Newtonian. We then use computational fluid dynamics simulations to compare results based on various stress tensor closures. In a first case study, the simulation results of a laminar flow in a horizontal pipe of a dilute suspension of particles dispersed in a Newtonian liquid are compared to experimental data obtained from the literature. We show that both the Eulerian-Eulerian and mixture models can predict pressure drops accurately but only if they are coupled with suitable experimental closures for the mixture rheology. In a second case study, we simulate the laminar flow of a dense suspension of identical particles dispersed in a Newtonian liquid through an abrupt expansion. We show that the particle concentration profile in the upstream tube, which develops owing to shear-induced particle migration, strongly affects the flow patterns downstream of the expansion. This migration must be modeled via an appropriate closure for the solid effective stress tensor; this allows capturing the sophisticated flow patterns in the expansion section

Investigation of the Effect of Ultrasound Parameters on Continuous Sonocrystallization in a Millifluidic Device

© 2016 American Chemical Society. Continuous-flow crystallization of adipic acid in a millichannel chip equipped with a piezoelectric element is presented and investigated experimentally and numerically. A single, straight channel chip (cross section: 2 mm × 5 mm, length: 76 mm) made of glass, which is ultrasonically transparent, was designed and fabricated. The piezoelectric element allows studying the effect of different ultrasound frequencies in the kHz to MHz range. Ultrasound was applied in burst mode to reduce heating; this allowed operating at higher levels of input power. To accurately control the temperature of the fluid, Peltier elements were used to cool the bottom and top surfaces of the chip. Crystallization was performed in isothermal conditions, ensuring that the temperature and in turn the supersaturation were kept uniform along the channel. The effect of ultrasound frequency and sonication time was studied. Crystal size distributions at different operating conditions were obtained by laser diffraction. The distributions were narrow, with coefficients of variation â0.5, while the mean sizes were small (â30 μm) and decreased when the sonication time increased. The crystal production rate increased by increasing the sonication time; this suggests that ultrasound enhances nucleation. On the other hand, in crystal breakage experiments, no difference in the size distribution of the seed crystals entering and leaving the device was observed, and hence, in this setup, ultrasound does not cause breakage. Numerical simulations of wave propagation in aqueous solution were utilized to predict the probability of cavitation, adopting a suitable cavitation threshold. The simulations showed that high pressure amplitudes are achievable inside the channel at low frequencies. The size range of bubbles which undergo violent collapse at different pressure amplitudes and frequencies was quantified. By increasing the frequency in the simulations, it was observed that the probability of transient cavitation decreases. The theoretical prediction of negligible transient cavitation at higher frequencies, in conjunction with the absence of crystals at such frequencies, indicates a strong link between transient cavitation and sonocrystallization

Propriedade Microestrutural do Refinamento da Liga Amorfa Al54Nb45B7

The presence of niobium in the alloy creates regions of intermetallic phases contained in Al54Nb45B7 amorphous alloy which becomes a potent heterogeneous nucleation on the substrate for nucleation with dendritic presence of aluminum oxides due to diffusive processes on the surface of the amorphous alloy Al54Nb45B7. This alloy is extremely low cost, but with applications in many sectors of the chemical and petrochemical industry in emphasis because its mechanical deformation is high due to the presence of (Nb or B) in the aluminum acting mainly as grain refiners to improve their mechanical and thermal properties by using the mechanical alloying. The combined use of Niobium and Boron (intermetallic phases are formed by adding powder of Al and Nb), instead of Niobium or Boron, individually, is a highly effective way to refine the grain size of alloy Al Nb-B in their microstructure without causing inconvenience in your network for unwanted deformations. To that end the present study compared the effect of grain refining promoted by the addition of niobium and the addition of Boron in Al54Nb45B5 obtained by high energy mill under argon atmosphere and analyzed by diffraction of X rays (XRD), scanning electron microscopy and Energy Dispersive (SEM / EDS). DOI: http://dx.doi.org/10.17807/orbital.v8i3.80

Single-sided lateral-field and phototransistor-based optoelectronic tweezers

Described herein are single-sided lateral-field optoelectronic tweezers (LOET) devices which use photosensitive electrode arrays to create optically-induced dielectrophoretic forces in an electric field that is parallel to the plane of the device. In addition, phototransistor-based optoelectronic tweezers (PhOET) devices are described that allow for optoelectronic tweezers (OET) operation in high-conductivity physiological buffer and cell culture media