Decrease In Void Fraction Research Articles

The void fraction of rf-sputtered SrTiO 3 film characterized by spectroscopic ellipsometry

RF-sputtered SrTiO 3 thin film was investigated by Spectroscopic Ellipsometry. The spectra calculated by using Brugman-Effective Medium Approximation theory compared with the experimental curves for delta and psi of SrTiO 3 thin films. Good agreement was found between experimental and calculated curves. The effective void fraction obtained in experiments is 28–38 % with difference thickness of SrTiO 3 films. The decrease in void fraction with increasing O 2 pressure during reactive sputtering growth was explained in terms of non-stoichiometry of the oxygen.

Liquid single- and gas—liquid two-phase flows of magnetic fluid in the presence of a high non-uniform parallel magnetic field

The effect of a non-uniform parallel high magnetic field on flow control characteristics is investigated experimentally for a magnetic fluid single-phase flow and an air—magnetic fluid two-phase flow in a vertical channel. It is found that as the magnetic field strength is increased, the friction factor of the single-phase flow increases significantly. For the two-phase flow, the friction pressure loss and the head pressure loss, which is smaller than the friction loss, are negligibly small compared with the magnetic pressure loss. In the case where air is injected 27.9d upstream from the maximum magnetic field, the air flow is blocked by the magnetic force in the entrance of the magnetic field, which leads to increases in both local void fraction and pressure drop there. In the case where air is injected 1.43d downstream from the maximum magnetic field, the air flow is accelerated, resulting in a decrease in void fraction and an increase in pressure rise. In the latter case and under the present range of experimental conditions, the magnetic pumping head reaches 0.02 MPa at the highest, and the maximum circulation flow rate reaches twice as high as non-magnetically driven flow rate.

Effects of dust properties on gas cleaning using rigid ceramic filters

Coupons of rigid ceramic filtration media have been conditioned using fine gasifier char and calcium carbonate dusts and both the cake resistance and the stress needed to detach the cake from the medium have been measured. For gasifier char, cake resistance appears to be independent of face velocity and proportional to areas cake loading, while cake removal stress is approximately independent of loading. For calcium carbonate, broadening the size distribution increases the cake resistance but slightly reduces the cake removal stress. Increases in particle size and cake void fraction decrease both cake resistance and cake removal stress. However, since increase in particle size seems often to be accompanied by decrease in cake void fraction, the range of commonly-observed cake resistivities and removal stresses is narrower than might otherwise be expected.

Intrinsic Stress in a-Germanium Films Deposited by RF-Magnetron Sputtering

AbstractThin a-Ge films deposited by rf-magnetron sputtering undergo a change from compressive to tensile stress as the argon gas pressure is increased. Spectroscopic ellipsometry, neutron activation analysis, and a dual laser beam reflection technique were used to determine the film's void fraction content, Ar/Ge atomic percent, and stress, respectively. The results of these three measurements indicate that as the film's Ar/Ge content increases, the void fraction decreases and the intrinsic stress becomes compressive. These findings are consistent with currently accepted bombardment mechanisms.

Thickness-dependent void fraction of rf-sputtered amorphous Ge films by spectroscopic ellipsometry

In this letter it is shown that vapor deposited thin films prepared under conditions of low adatom mobility, such as amorphous Ge films in the present study, exhibit a nonlinear decrease in void fraction, and hence an increase in density with increasing film thickness. Fractal modeling of the internal void network structure in this class of vapor deposited films shows that the void boundaries define the surfaces of growth cones and these voids are, in general, not expected to be distributed uniformly with film thickness.

Analysis of the Permeability of Granulated Iron Sinter Feeds Using the Ergun Equation

Granulated sinter mixes of three iron ore types were prepared with a range of water contents in a laboratory investigation. The mean diameter of the granulated mixes and the void fraction of beds of the mixes were determined experimentally. Pressure drop measurements over a range of flow rates were made in a laboratory permeameter with pressure tappings at several depths in the bed. The Ergun equation was applied to the results to determine the shape factor of the granulated mixes. Pressure readings down the bed were used to estimate the local void fraction in the bed using the Ergun equation and the calculated granule shape factors. It was found that there was a decrease in void fraction with depth in the bed. The significance of this and the variation of shape factor values with the amount of water used for granulation is examined in relation to the strength of granules of the sinter mixes. The experimental and mathematical techniques presented may be useful in interpreting the behavior of the permeability of sinter beds after ignition.

Influence of pressure on the closure of voids during plastic deformation

Metals in the as-cast condition usually contain voids, which defects are formed during solidification due to material shrinkage and gas entrapment. It is important that the void fraction is reduced or preferably eliminated in the subsequent process of hot working. It is well known that void closure is more easily obtained if plastic deformation takes place under the influence of hydrostatic pressure. Consequently it is of the utmost importance that this fact is taken into consideration when a rolling or forging schedule is planned. The influence of pressure on the closure of voids is analysed. The theoretical analysis is carried out by means of plane-strain upper-bound solutions, assuming a rigid-perfectly-plastic material. It is often observed by people in industry that it is in the last few passes of a deformation schedule that hydrostatic pressure is of greatest importance. From the present work, however, it is concluded that the pressure at the beginning of a schedule is of great importance as well. If the pressure is sufficiently high it will result in a mechanism of favourable void closure, that is, a rapid decrease in void fraction at the beginning of the deformation comprising no extension of the voids perpendicular to the compression direction. After some deformation in the favourable manner, void closure will still take place according to the same mechanism even if the pressure is changed into a moderate tensile stress.

紙のＺ方向における圧縮弾性

The compressive modulus. B' and the compressive viscosity η of a handmade paper were measured for the Z-direction (the direction perpendicular to the surface). The modulus was obtaind by the dynamic and the static methods while the viscosity was obtained by the dynamic method. The value of B' increased from 107 to 1010 (dyn/cm2) by application of pressure while the value of η from 104 to 107 (poise). It was also found that these values increased with the apparent density of the paper. The water absorbed in the paper also affected on these values.The structure of the cross section parallel to the Z-direction in the paper was observed by means of the scanning electron microscope in order to clarify the correlation between the structure and the modulus. It was found that B' incrased with the decrease of void fraction which was measured with the electron micrograph.

Local properties of vertical mercury-argon two-phase flow in a circular tube under transverse magnetic field

Experimental data are presented in this paper on the profiles of local void fraction, bubble impaction rate, bubble velocity and its spectrum, and also bubble length and its spectrum, of mercury-argon two-phase slug flow flowing upwards in a vertical circular tube in the presence of a transverse magnetic field. Decrease in void fraction and increase in bubble velocity are significant when the magnetic flux density is larger than 0.3∼0.4 T(Ha ⋍ 100) . This effect is discussed by analyzing the bubble size distribution. Recovery of local void fraction profile in the downstream of an obstacle and diffusion of void injected from only one nozzle in the presence of magnetic field are also discussed.

The rate coefficient for the quenching reaction Na ∗ + H 2 → NaH + H : A Netten,Proc of 11 th Internat Conf on Phenom in Ionized Gases, Prague 1973, 46

Experimental data are presented in this paper on the profiles of local void fraction, bubble impaction rate, bubble velocity and its spectrum, and also bubble length and its spectrum, of mercury-argon two-phase slug flow flowing upwards in a vertical circular tube in the presence of a transverse magnetic field. Decrease in void fraction and increase in bubble velocity are significant when the magnetic flux density is larger than 0.3∼0.4 T(Ha ⋍ 100). This effect is discussed by analyzing the bubble size distribution. Recovery of local void fraction profile in the downstream of an obstacle and diffusion of void injected from only one nozzle in the presence of magnetic field are also discussed.