Effects Of Mechanical Mixing Research Articles

Kinetic Features of Cd and Zn Cathodic Formations in the Membrane Electrolysis Process

Chromate and dichromate solutions used for the activation and passivation of cadmium and zinc galvanic coatings of metal products are widely used due to their ability to form corrosion-protective films. Therefore, in this article, we examined the kinetic features of the cathodic deposition of Cd and Zn during membrane electrolysis. As a result of comprehensive experimental and theoretical studies, the features of Cd and Zn cathodic depositions were analyzed under different hydrodynamic conditions in a submembrane zone of an anolyte. Experimental physicochemical methods such as the experimental analysis of solutions, analytical modeling, and a statistical analysis were used during the research. A regression dependence for evaluating a reaction rate constant was assessed based on the least-square approximation of the proposed model. As a result, the peculiarities of the cathodic formations for Cd and Zn during the membrane electrolysis process were analyzed. The effect of mechanical mixing with different values of the Reynolds number on the deposition of Cd and Zn on a cathode was evaluated. A change in Cd2+ and Zn2+ ion concentrations was also considered during the research. Overall, the obtained results increased the Cd deposition rate by 2.2 times using an active hydrodynamic environment with the anolyte.

Governing factors of the record-breaking marine heatwave over the mid-latitude western North Pacific in the summer of 2021

During July of 2021, the sea surface temperature of the mid-latitude western North Pacific had increased by five degrees over 10 days. This high temperature was maintained for approximately a month before it disappeared rapidly in approximately five days. The underlying mechanisms of this unprecedented marine heatwave event have not yet been researched through a quantitative approach. The development and decay processes of the marine heatwave event were investigated using heat budget analysis and one-dimensional modeling. In mid-July, an anomalous high-pressure atmospheric circulation, affecting to the reduced cloud coverage and increased solar radiation, anchored where the marine heatwave occurred. The increased solar radiation accompanied by the weakened wind reduced the vertical mixing and resulted in a thinner mixed-layer, which accelerated the sea surface warming. The impact of reduced mixing is as important as the increase in solar radiation. In mid-August, typhoon-induced entrainment mainly caused sea surface cooling. The wind-driven mechanical mixing between warm surface water and cooler subsurface water lowered the SST. Additionally, evaporative cooling by strong winds, which drives buoyancy-driven vertical mixing, contributed to the decay of the MHW. The effect of mechanical mixing on cooling is comparable to that of buoyancy-driven mixing.

Mixing, fluid infiltration, leaching, and deformation (MILD) processes on the slab-mantle wedge interface at high T and P conditions: Records from the Dalrymple Amphibolite, Philippines

The whole rock compositions of the blocks and the surrounding matrix of the Dalrymple Amphibolite are investigated in this study to determine the protolith of the blocks and the effect of mechanical mixing and fluid infiltration in the matrix of this fossil slab-mantle wedge interface. The major and trace element contents of the metamafic blocks indicate their mid-oceanic ridge basalt origin similar to the mafic lavas of the crustal section of central Palawan Ophiolite. Similarities in their rare earth and trace element patterns indicate the genetic relationship between the mafic lavas of the Palawan Ophiolite and the metamafic blocks of the Dalrymple Amphibolite. This confirms that the metamafic blocks represent the basalt to gabbro section of the oceanic lithosphere of the subducting slab.The matrix surrounding the blocks exhibit highly variable phase assemblages. In order to determine its petrogenesis, we distinguished groups of components/elements which behave similarly (Group 1 TiO2, Al2O3, Zr, Th and the light rare earth elements; Group 2 Cr, Ni and MgO) based on statistical (correlation coefficient) analyses. These groups indicate mixing of metasedimentary (Group 1) and metamafic (Group 2) end-members to form the matrix. The mixing proportions of the end-members were estimated by employing regression analysis wherein the measured concentration of fluid immobile elements (Cr, Ni, Zr, TiO2 and Al2O3) in the matrix samples were fitted against a modelled concentration by changing the end-member and their relative proportions. The end-members and mixing ratio with the highest regression value (r2) was selected to obtain the modelled composition of the matrix. The modelled and the measured matrix compositions were then used as the original (unmetasomatized) rock and the altered rock respectively in the isocon analysis, assuming that TiO2, Al2O3, Cr, Nd, Zr, and Hf are immobile. This assumption is supported by the prevalence of kyanite, ilmenite and zircon in the matrix mineral assemblage.This procedural workflow helped distinguish end-member components, estimate their mixing ratios, and determine the effects of infiltrating fluids. In particular, the whole rock composition of the matrix was controlled by mixing of a subordinate amount of metamafic blocks in a metasedimentary-dominated shear zone. This is supported by the Cr-Nb content of rutile grains included in the matrix samples which indicate mixed metamafic and metapelitic signatures. The metamafic-metasedimentary dominated matrix in the Dalrymple Amphibolite contrasts with other high-pressure/temperature (P/T) type metamorphic terranes which are dominated by low T minerals (serpentine, Mg-chlorite, and talc) derived from an ultramafic end-member, and could be reflective of conditions in warmer subduction zones. Mass balance calculations further revealed that an early fluid infiltration event likely occurred following the mixing process. This preferentially leached out elements which are either fluid-mobile (e.g. CaO and SiO2) or are not incorporated into the growing minerals in the matrix. The strong control of mineral assemblage of the matrix in its chemistry is exhibited by a number of samples which showed variable degrees of losses and gains in elements traditionally interpreted to be fluid immobile (e.g. heavy rare earth elements and Y). A later hydration event linked to retrograde metamorphic stage imprinted gains of K2O, Rb, and Ba in the matrix samples with the growth of replacement minerals (e.g. muscovite on kyanite). This later fluid infiltration event possibly masked the original loss of these fluid-mobile elements in the matrix samples during the earlier fluid-rock interaction.

Measurement of aggregates breakage of asphalt mixtures with construction and demolition waste

In this paper, the effect of mechanical mixing and compaction on the physical properties of fragile CDW used in asphalt mixtures evaluated. The paper investigates the change in aggregates gradation of CDW-asphalt mixtures after mechanical mixing and compaction. Asphalt specimens containing 0% CDW, 25% CDW, 50% CDW, and 75% CDW were prepared according to Marshall procedure. The particle size distribution test was carried out to measure the broken rate of CDW due to mechanical mixing and compacting. Three samples of each mix were tested and the average value was considered. The results reveal that the broken CDW were able to pass sieve 4.75 mm. The change in aggregates gradation was mainly due to the breakage of CDW during mixing and compaction. The breakage of CDW led to a decrease in the dosage of coarse CDW presented in aggregates retained on 4.75 mm sieve and an increase in the dosage of fine CDW presented in aggregates that passed the 4.75 mm sieve. The results also indicate that the broken rate increased as the percentage of CDW increased in the mix. The breakage of CDW has promoted a change in the density of combined mineral aggregates, the density of combined coarse aggregates, and the density of combined fine aggregates of CDW-mixtures. The breakage also contributes to a change in water absorption of combined coarse aggregates, and that measured for combined fine aggregates of CDW-asphalt mixtures. The results indicate the need for measuring the amount of broken CDW passing 4.75 mm sieve and evaluate its effect on physical properties of aggregates of CDW-asphalt mixtures.

Effect of Mechanical Mixing in Dissimilar Friction Stir Welding of Aluminum to Titanium with Zinc Interlayer

Welding of aluminum (Al) and titanium (Ti) is difficult and challenging due to their differences in chemical and physical properties, and the evolution of brittle intermetallic compounds. Formation of critical intermetallics can be minimized by using an interlayer material, which leads to ternary mechanical mixing in the weld nugget. In the present investigation, a zinc (Zn) interlayer has been used during friction stir welding (FSW) of Al–Ti. It has been found that tool offset position is one of the important parameters in controlling the amount of ternary mechanical mixing of materials. The mechanical mixing of Zn with Al and Ti alters the phase evolution and restricts the formation of the brittle Al3Ti intermetallic compound. The optimum tool offset exhibits a homogeneous mechanical mixing and inhibits the formation of brittle intermetallic compounds, which leads to a substantial increment in the mechanical properties of the weld.

Structure and mechanical properties of A356-C alloys

The paper deals with influence of mechanical mixing and vibration treatment on the structure and mechanical characteristics of the aluminum alloy containing ≤ 1 wt.% of nanodiamonds (A356-C). The alloy was obtained from industrial A356 Al-Si casting alloy by means of an integrated effect of mechanical mixing and vibration. It has been shown that the introduction of nanodiamond particles contributes to improving the alloy structure and increasing its mechanical tensile properties. The structure of the A356 aluminum alloy has been refined with introduction of 0.2 wt% nanodiamonds and application of vibration melt treatment. The introduction of nanodiamonds into the melt and the vibration melt treatment enable one to increase the yield strength and tensile strength of the A356 aluminum alloy without any change in ductility.

Effects of Mechanical Mixing on Full-Scale Digester Performance Operated at Higher Organic Loading Rates and Shorter Detention Times at the Calumet Water Reclamation Plant

Effects of Mechanical Mixing on Full-Scale Digester Performance Operated at Higher Organic Loading Rates and Shorter Detention Times at the Calumet Water Reclamation Plant

Regular build-up of the spring phytoplankton maximum before ice-break in a boreal lake

The development of phytoplankton biomass and composition in a eutrophic boreal lake was studied during the evolution of under-ice convection in spring. The results from 8 yr showed that, within a few weeks before ice-break, phytoplankton biomass regularly increased by up to two or three orders of magnitude, reaching or exceeding the biomass in summer. Accordingly, this may be the most significant single annual phytoplankton episode in the lake. The development of phytoplankton was closely coupled with that of convection created by solar radiation at water temperatures < 4°C. In addition to vertical convection which keeps phytoplankton suspended, there was also horizontal convection which transported water with likely higher abundance of phytoplankton from the shallow lake margins. The effect of mechanical mixing, which was meant to prevent anoxia in the deep water layers of the study basin, was overridden by natural convection. Stochastic variations in weather played a key role controlling light penetration into the lake and hence the abundance and composition of under-ice phytoplankton. After snow melt the proportion of motile algae was at first higher, sometimes with a maximum nearest to the ice, but later diatoms flourished throughout the convection layer. Only in the years of the shortest convection period did the proportion of motile algae remain high until the end of ice cover. More detailed information about the interaction between littoral and pelagial water masses under different mixing regimes is needed for a more profound understanding of the development of phytoplankton under-ice.

Comparative study on effect of mechanical mixing and ultrasound on the performance of a single up-flow anaerobic/aerobic/anoxic bioreactor removing CNP from milk processing wastewater

In this study, an up-flow anaerobic/anoxic/aerobic sludge bed (UAAASB) bioreactor under two different mixing conditions, ultrasound-based mixing and mechanical mixing, was evaluated for simultaneous removal of nutrients from milk processing wastewater. The process performance of the two conditions was compared. The effects of three independent variables, including HRT (6, 12, 18 h), aeration time ratio (1, 1.5, 2) and MLSS content (4000, 7000, 10000 mg/l) were investigated. The central composite design (CCD) and response surface methodology (RSM) were applied to design the experiments, model and optimize the process. In order to evaluate the performance of both systems, ten responses were monitored. The process showed similar performance in terms of sCOD removal in both systems. 83.76% and 70.11%, respectively, were achieved as TN and TP removal efficiencies in the UAAASB mixed by the ultrasonic irradiation. While in the system with mechanical mixing, the maximum TN and TP removal were obtained 57.87% and 57.47%, respectively. The results proved that the high-frequency ultrasonic irradiation (1.7 MHz) had a positive effect on removing TN and TP, sludge settling velocity and effluent turbidity.

Effect of mechanical mixing on the microstructure and mechanical properties of Al-based metal matrix composites reinforced with nanocrystalline Al-Ca intermetallics

Al-based metal matrix composites reinforced with 40 vol.% of nanocrystalline Al- Ca intermetallic particles were synthesized by hot pressing followed by hot extrusion process and the effect of manual blending as well as mechnical mixing on microstructure and mechanical properties was studied. Microstuture reveals that mannual blending leads to the agglomeration of Al-Ca intermetallic particles and on the other hand, the composites prepared by milling display a more homogeneous distribution of the reinforcing particles. Mechanical mixing has a strong impact on the mechanical properties. The strength increases from 112MPa for pure Al to 250 and 415MPa for the composites produced by blending and milling respectively. This behavior is linked to the reduced matrix ligament size characterizing the milled composites.

Hysteresis temperature dependence in filled rubbers. II. Mechanical mixing, filler microdispersion, and polymer–filler interactions

The effects of mechanical mixing and filler–filler (F–F) and polymer–filler (P–F) interactions on the normalized state of a filler microdispersion [d(x)] and the viscoelastic properties of silica-filled rubbers were studied. The rubbers were prepared with or without the addition of n-octyl-triethoxysilane (OTES) to modify F–F interactions or coupling agents such as 3-mercaptopropyl-trimethoxysilane and 3-mercaptopropyl-triethoxysilane (MPTES) to increase P–F interactions. Increased mixing improved d(x) and enhanced the hysteresis temperature dependence (HTD) by giving a higher tan δ value near the compound glass-transition temperature (Tg) but lowered tan δ at elevated temperatures for stocks containing a coupling agent. The changes in P–F and F–F interactions in rubbers with mixing and subsequent thermal treatment were shown to be responsible for the property differences observed among stocks containing different silanes. Attempts were made to quantify the efficiency for improving d(x) with various silanes. The increased P–F interactions in compounds containing MPTES showed better efficiency for improving d(x) and enhancing HTD in comparison with OTES. It was also demonstrated that the change in hysteresis near Tg was mainly governed by the degree of filler networking, whereas elevated-temperature hysteresis was strongly influenced by the P–F interactions in compounds. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Effect of Mechanical Mixing and Powder to Liquid Ratio on the Strength and Reliability of a Brushite Bone Cement

The effect of mechanical mixing on compressive strength, relative porosity and reliability of strength data of a brushite forming cement at different powder to liquid ratios (PLRs) was investigated. Mean compressive strengths were measured, associated reliability (Weibull moduli) and survival probability distributions of the data sets were analysed. Relative porosities were determined using helium pycnometry. For low PLR (2.2g/ml), no significant differences in compressive strength were observed for either mechanical or hand mixed samples, although reliability of the former was significantly increased. At high PLR (3.4g/ml), mechanically mixed cements exhibited approximately twice the mean compressive strength compared with hand mixing, although Weibull moduli remained statistically similar. At medium PLR (2.8g/ml) strength and reliability of cements were similar and independent of mixing regime. For all PLRs, a significant decrease in porosity of mechanical- compared with hand-mixed cements was observed. Mechanical mixing of a brushite cement can provide lower porosity, increased reliability and higher strength.

Optimizing Contaminant Desorption and Bioavailability in Dense Slurry Systems. 2. PAH Bioavailability and Rates of Degradation

The effects of mechanical mixing on rates of polycyclic aromatic hydrocarbon (PAH) biodegradation in dense geosorbent slurry (67% solids content, w/w) systems were evaluated using laboratory-scale intermittently mixed batch bioreactors. A PAH-contaminated soil and a phenanthrene-sorbed mineral sorbent (alpha-Al2O3) were respectively employed as slurry solids in aerobic and anaerobic biodegradation studies. Both slurries exhibited a characteristic behavior of pseudoplastic non-Newtonian fluids, and the impeller revolution rate and its diameter had dramatic impacts on power and torque requirements in their laminar flow mixing. Rates of phenanthrene biodegradation were markedly enhanced by relatively low-level auger mixing under both aerobic and anaerobic (denitrifying) conditions. Parameters for empirical models correlating biodegradation rate coefficient (k(b)) values to the degree of mixing were similar to those for correlations between mass transfer (desorption) rate coefficient (k(r)) values for rapidly desorbing fractions of soil organic matter and degree of mixing reported in a companion study, supporting a conclusion that performance-efficient and cost-effective enhancements of PAH mass transfer (desorption) and its biodegradation processes can be achieved by the introduction of optimal levels of reactor-scale mechanical mixing.

Investigation of the Effect of Mechanical Mixing on Dewatering of Fine Coal Vacuum Filter Cakes

Horizontal vacuum belt filters provide a very efficient means of filtering fine coal slurries ( nominally minus 0.5mm). Depending on the nature of the coal processed, industry' s best practice with this technology typically leads to cake discharge moisture in excess of 25% Recent work [ 1] has permitted identification of filter cake microstructure as a major limiting factor.for moisture removal that is distinct from coal properties. This result suggested that modifying and possibly controlling cake microstructure could offer potential for moisture reduction in vacuum filters. The paper discusses the findings of a laboratory study involving mechanical agitation of fine coal filter cakes during the drying phase using a helical ribbon mixer. The rational that led to the experimental approach used in this work is detailed. Test results are reported which confirm that alteration of cake microstructure during the drying phase of the vacuum filtration cycle has immediate and positive impact on cake drying. Moisture reductions up to 3% were measured with fine bituminous coal filter cakes. Analysis of the experimental results reveals that the effect of filter cake mixing on cake moisture reduction depends strongly on the time at which mixing is initiated during the drying cycle and the size distribution of the filter cake particles. The practical potential of the mixing process is also discussed.

Interlayer Diffusive Transfer and Transport of Contaminants in Stratified Formation. I: Theory

This paper deals with modeling depth-averaged solute transport and lateral-diffusive transfer in a two-layer system of contrasting permeabilities. Two-dimensional transport equations are developed, by averaging the local three-dimensional transport equations vertically across the high- and low-permeability layers. The equations account for interlayer mass transfer and the capacitance of the low-permeability layer to store and release reactive constituents by diffusion. The theory indicates that a first-order rate model can describe the process of interlayer mass transfer under quasi-steady condition. An expression for the mass-transfer rate coefficient α is obtained in terms of the transverse diffusion time (or diffusion rates) across the layers. In particular, the diffusion time in the high-permeability layer is related to transverse-vertical dispersion that accounts for the effect of mechanical mixing on the interlayer mass transfer. For small capacity ratio β< 1 the rate coefficient α shows a linear de...

Nucleation Control in Precipitation Processes by Ultrasound

The effect of an ultrasonic field on the precipitation process of barium sulphate has been investigated. Experiments in a semi-batch precipitator showed that small crystal sizes with narrow distribution are obtained with ultrasound in a very reproducible way; however, this effect could not be assigned to an improvement in micromixing. Experiments on continuous precipitation of barium sulphate in two reactors in series were carried out in order to characterise the effect of ultrasound on precipitation, by separating the nucleation and growth processes. It was concluded that the main effect of ultrasound is an enhancement of secondary contact nucleation by acoustic cavitation. This change in the precipitation process allows small crystals with uniform size and shape to be obtained without effect of mechanical mixing. It is only necessary to sonicate the mixing volume of the reactants with a low level of ultrasonic power: this is very promising for industrial applications.

Transesterification reaction of poly(ethylene‐co‐vinyl acetate) with alcohols: A kinetic study in solution and in the bulk

AbstractThe chemical kinetics of the transesterification reaction of poly(ethylene‐co‐vinyl acetate) (EVA) with aliphatic alcohols were investigated, both in solution and in bulk, in the presence of dibutyl tin dilaurate (DBTDL) as the catalyst. A Fourier Transform infrared spectrometer (FTIR) was utilized for the measurement of the extent of the reaction. Experimental results showed that the reaction carried out in solution and in the bulk follows the same mechanism, namely, a reversible second order reaction of which the equilibrium only slightly increases with temperature. Additionally, the overall forward and reverse rate constants are proportional to the square root of the concentration of the catalyst. This study has also revealed that the intrinsic rate constants in solution and in the bulk are the same, regardless of the differences in the physical conditions encountered in the bulk and solution media, in particular, the reactant concentrations and viscosity of the reacting mixture. The effects of mechanical mixing are unimportant, since the reaction rate is relatively slow as compared with the rate of diffusion.

The effect of mechanical mixing of the melt on the quality of colored flat glass

The effect of mechanical mixing of the melt on the quality of colored flat glass

The effects of mechanical mixing on some physical properties of silicate cements

The effects of mechanical mixing on some physical properties of silicate cements

Studies in silicate cements: The effects of mechanical mixing on physical properties

1. Except for results at 21 °C., mechanical mixing caused a reduction in the amount of powder required to produce standard consistency of the material. 2. Mechanical mixing of silicate causes a temperature rise in the material, believed to be mainly due to an exothermic chemical reaction, but also partly caused by frictional heating of the material. 3. The relative humidity has negligible effect on setting time and consistency, if precaution is taken to store the materials without exposure to air. 4. Mechanical mixing has little effect on compressive strength and solubility of the material, except at those temperatures where the consistency of the material was considerably reduced.