Electrorheological Fluids of GO/Graphene-Based Nanoplates

Due to their unique anisotropic morphology and properties, graphene-based materials have received extensive attention in the field of smart materials. Recent studies show that graphene-based materials have potential application as a dispersed phase to develop high-performance electrorheological (ER) fluids, a kind of smart suspension whose viscosity and viscoelastic properties can be adjusted by external electric fields. However, pure graphene is not suitable for use as the dispersed phase of ER fluids due to the electric short circuit caused by its high electrical conductivity under electric fields. However, graphene oxide (GO) and graphene-based composites are suitable for use as the dispersed phase of ER fluids and show significantly enhanced property. In this review, we look critically at the latest developments of ER fluids based on GO and graphene-based composites, including their preparation, electrically tunable ER property, and dispersed stability. The mechanism behind enhanced ER property is discussed according to dielectric spectrum analysis. Finally, we also propose the remaining challenges and possible developments for the future outlook in this field.

Qualitative assessment of air pollution in the working area of energy-intensive materials production by nanoscale aerosols with a solid dispersed phase

The presence of grinding, mixing, and fractionation of solid components of formulations leads to the formation of aerosols in the air of the working area with a wide range of dispersion of the solid phase - all this characterizes the organization of technological processes for the production of energy-intensive materials. The study aims to give a qualitative assessment of possible air pollution of the working area of energy-intensive materials production by nanoscale aerosols with a solid dispersed phase. The researchers carried out the sampling of the working area air and flushes from solid horizontal surfaces to produce energy-intensive materials. We carried out the sampling by forced circulation of the test air through the absorption devices of Polezhaev. Scientists used Triton TX-114 solution with a mass concentration of 2.0 mg/dm3 as an absorption medium. The researchers performed flushing from surfaces using cloth tampons moistened with Triton TX-114 solution with a mass concentration of 2.0 mg/dm3. We determined the particle sizes in the samples using NanotracULTRA (Microtrac). Scientists found aluminum and nitrocellulose particles with sizes from 36 to 102 nm in the air of the working area and flushes from horizontal surfaces. The study of the fractional composition of RDX and aluminum powders of the ASD-1 brand showed the presence of nanoscale particles in them. Nanoscale dust particles pollute the air of the working area and solid horizontal surfaces at certain stages of the production of energy-intensive materials. There are nanoscale particles in the composition of powders of some standard components of formulations. Flushes from solid horizontal surfaces are an adequate qualitative indicator of the presence of nanoaerosols in the air of the working area.

Effects of lower alcohols on nanocomposite particles for inhalation prepared using O/W emulsion

BACKGROUND: Inhalable nanocomposite particles using O/W emulsions were studied. The effect of the composition of the dispersed phase on the nanoparticles in the nanocomposite particles was reported, however, the effect on the inhalation characteristics of nanocomposite particles has not been investigated. OBJECTIVE: The aim of this study was to study the effects of lower alcohols in the dispersed phase of O/W emulsions on inhalable nanocomposite particles. METHODS: Nanocomposite particles were prepared using a spray dryer from O/W emulsion. A mixed solution of dichloromethane and lower alcohols in which rifampicin (RFP) and poly(L-lactide-co-glycolide) were dissolved was used as a dispersed phase, and an aqueous solution in which arginine and leucine were dissolved was used as a continuous phase. RESULTS: We succeeded in preparing non-spherical nanocomposite particles with an average diameter of 9.01–10.91 μm. The results of the fine particle fraction (FPF) measurement showed that the higher the hydrophobicity of the lower alcohol mixed in the dispersed phase, the higher the FPF value. The FPF value of the nanocomposite particles was significantly increased by using ethanol and 1-propanol. CONCLUSIONS: The results were revealed that mixing 1-propanol with the dispersed phase increased the amount of RFP delivered to the lungs.

Application of Thermal and Cavitation Effects for Heat and Mass Transfer Process Intensification in Multicomponent Liquid Media

In this paper, the authors consider the processes of dynamic interaction between the boiling particles of the dispersed phase of the emulsion leading to the large droplet breakup. Differences in the consideration of forces that determine the breaking of non-boiling and boiling droplets have been indicated in the study. They have been determined by the possibility of using the model to define the processes of displacement, deformation, or fragmentation of the inclusion of the dispersed phase under the influence of a set of neighboring particles. The dynamics of bubbles in a compressible liquid with consideration for interfacial heat and mass transfer has also been analyzed in the paper. The effect of standard and system parameters on the intensity of cavitation processes is considered. Physical transformations during the cavitation treatment of liquid are caused not only by shock waves and radiated pressure pulses but also by extreme thermal effects. At the stage of ultimate bubble compression, vapor inside the bubble and the liquid in its vicinity transform into the supercritical fluid state. The model analyzes microflow features in the inter-bubble space and quantitatively calculates local values of the velocity and pressure fields, as well as dynamic effects.

Controlled Release Modeling of Urea from Chitosan Microspheres: Effect of Stirring Speed and Volume Ratio of Continuous to Dispersed Phase

The purpose of this study was to determine the release kinetics and diffusion coefficient of chitosan microspheres containing urea based on changes in the stirring speed and the volume ratio of the continuous to dispersed phase (CP/DP). Chitosan microspheres filled with urea were prepared using the emulsion cross-linking method. The initial stage of this method has formed an emulsion then slowly dripped with glutaraldehyde saturated toluene as a crosslinker. Urea-loaded chitosan microspheres were washed and dried and then tested for release in an aqueous medium. The calculated cumulative release was used to determine the release kinetics and diffusion coefficient of chitosan microspheres. The appropriate release kinetics model was Simple Power Law with the Burst Effect because it produces an R2 value of 0.99. The mechanism of urea release from chitosan microspheres is Case II the transport mechanism represents pure relaxation behavior. Determination of the diffusion coefficient values from 1,180 x 10-14 up to 1,433 x 10-14 cm2/sec.

A Newly Developed Empirical Predictive Model for the Dispersed Phase (DP) Holdup in Rotating Disc Contactors

Newly novel developed correlations were derived to predict the dispersed phase (DP) holdup in a rotating disc contactor (RDC) extraction column. DP holdup is one of the significant parameters in the design of liquid–liquid contactors and for calculating their production capacity. Despite the availability of quite a large number of holdup prediction correlations for the RDC, most of these correlations are either general in nature or valid for a limited range of operating conditions. This study conducted an experimental and theoretical investigation of the RDC holdup under the influence of varying geometries, including variations in the dispersed phase distributor, speed of the disc, flow rate, and physical characteristics of the system. The analysis revealed that the holdup decreased with an increasing distributor hole diameter and increased with an increasing disc speed and total flow rate. The effect of the physical properties on the holdup was larger than the effect of the disc speed. Using the measurements of over 150 runs, two RDC column holdup predictive models were proposed and evaluated. The first correlation was derived in terms of the distributor hole diameter, operating parameters, system physical properties, and column geometry. The second correlation excluded the column geometry. These correlations, which consider the distributor hole inlet diameter in predicting the DP holdup for an RDC column, were presented for the first time in this study. The predictive capability of these correlations was evaluated via their standard deviation (SD) and mean average percentage error (MAPE). The respective SD and MAPE of the two correlations were 1.7 and 5.2% for the first correlation and 1.6 and 11.4% for the second.

The Effect of Length Scale on Flow Properties of Micro, Nano and Macro-Emulsions

<p>Flow properties of a complex fluid depend on not only the characterizations of the components that make up the system but also the interactions between the phases. One of the most significant factors that affect these interactions is the length scale of the dispersed phase. According to Stokes law, the root of complex fluid rheological models, the velocity of a moving particle in a fluid is a function of the viscosity of the fluid and also the size of the moving droplet. The main aim of this research is to understand the crucial elements that define and control the rheological behaviour of complex fluids and thereby provide evidence for proposed modifications of the available rheological models to include parameters that capture the deduced crucial elements. In particular, by adjusting different aspects of Stokes law. The modified models can then be applied to a wider range of complex fluid systems, including emulsions, regardless of the chemicals that form the system. The complex fluids used in this research to develop the above are emulsions with droplets ranging over four orders of magnitude, 10 nm to 100 µm. Within a single base chemical system microemulsions, nanoemulsions and macroemulsions could be formed. The length scale and flow properties of each group were examined and the effect of length scale on rheological properties was investigated. Critical elements there were identified include: • Use of the appropriate viscosity value for the fluid through which the dispersed phase diffuses. It is often assumed that the viscosity of the pure continuous phase fluid can be used as the reference viscosity in the Stokes equation. In a real system the viscosity of the continuous phase can be strongly affected, and thereby defined by, the presence of the dispersed phase itself and the interfacial layer. Hence it is paramount that the appropriate reference viscosity is used. It is noted that the standard assumption is often applicable for highly diluted suspensions that are composed of rigid spheres. However, the research undertaken here demonstrates that this assumption must be reconsidered for more concentrated systems and particularly for emulsions. We recommend that for such systems the viscosity of the pure continuous phase is replaced by the constant viscosity of the sample at a zero shear rate. • Consideration of structural factors that also affect the viscosity. In particular it is often assumed that: 1- the droplets/particles are spherical and non-deformable; and 2- the dispersed phase presents as a single length scale, i.e. the system is a monodisperse system. The inclusion of these assumptions limits dramatically the applicability of the available models to fit and describe the real flow behaviour and thereby does not allow for predictability of behaviours. Typically models have been modified by adding experimental factors rather than explicitly incorporating the above factors into the development of a model. In this work the deviation from these rheological models are explained and correlated to the deviation from spherical structure and monodispersity. • Defining the relative viscosity as the ratio between the sample viscosity and the reference viscosity is common practice in the application of most rheological models. The viscosity of water tends to be taken as the reference viscosity. This leads to no agreement between the well-known rheological models and the experimental data, especially when applied to analysis of microemulsion rheology. In this work, we show that by taking the viscosity of the relevant ternary surfactant solution as the reference viscosity, the existing models can be applicable to microemulsions. This work sheds light on the relationship between the non-Newtonian behaviour of nanoemulsions and their underlying thermodynamic instability. In these systems the Newtonian behaviour is not evident till a shear rate of 100/s is reached. On the other hand the Newtonian viscosity is observed in thermodynamically stable systems, e.g. surfactant solutions and microemulsions, beyond a shear rate of 5/s or less. The Newtonian region also was observed in normal emulsions with narrow size distributions, dilute monodisperse coarse emulsions or dilute normal emulsions prepared in a Warring blender while a short chain alcohol is added to the system. By adding the short chain alcohol to the system not only the densities of the two phases are made similar and the emulsification is eased but also the polydispersity of the final emulsion is decreased. Finally a single model to be applicable to different types of emulsions with droplet sizes over five orders of magnitude was proposed. However the relationship is applicable to the systems with a low degree of polydispersity and once polydispersity is introduced the flow behaviour becomes complicated and the proposed model is not applicable.</p>

The Effect of Length Scale on Flow Properties of Micro, Nano and Macro-Emulsions

<p>Flow properties of a complex fluid depend on not only the characterizations of the components that make up the system but also the interactions between the phases. One of the most significant factors that affect these interactions is the length scale of the dispersed phase. According to Stokes law, the root of complex fluid rheological models, the velocity of a moving particle in a fluid is a function of the viscosity of the fluid and also the size of the moving droplet. The main aim of this research is to understand the crucial elements that define and control the rheological behaviour of complex fluids and thereby provide evidence for proposed modifications of the available rheological models to include parameters that capture the deduced crucial elements. In particular, by adjusting different aspects of Stokes law. The modified models can then be applied to a wider range of complex fluid systems, including emulsions, regardless of the chemicals that form the system. The complex fluids used in this research to develop the above are emulsions with droplets ranging over four orders of magnitude, 10 nm to 100 µm. Within a single base chemical system microemulsions, nanoemulsions and macroemulsions could be formed. The length scale and flow properties of each group were examined and the effect of length scale on rheological properties was investigated. Critical elements there were identified include: • Use of the appropriate viscosity value for the fluid through which the dispersed phase diffuses. It is often assumed that the viscosity of the pure continuous phase fluid can be used as the reference viscosity in the Stokes equation. In a real system the viscosity of the continuous phase can be strongly affected, and thereby defined by, the presence of the dispersed phase itself and the interfacial layer. Hence it is paramount that the appropriate reference viscosity is used. It is noted that the standard assumption is often applicable for highly diluted suspensions that are composed of rigid spheres. However, the research undertaken here demonstrates that this assumption must be reconsidered for more concentrated systems and particularly for emulsions. We recommend that for such systems the viscosity of the pure continuous phase is replaced by the constant viscosity of the sample at a zero shear rate. • Consideration of structural factors that also affect the viscosity. In particular it is often assumed that: 1- the droplets/particles are spherical and non-deformable; and 2- the dispersed phase presents as a single length scale, i.e. the system is a monodisperse system. The inclusion of these assumptions limits dramatically the applicability of the available models to fit and describe the real flow behaviour and thereby does not allow for predictability of behaviours. Typically models have been modified by adding experimental factors rather than explicitly incorporating the above factors into the development of a model. In this work the deviation from these rheological models are explained and correlated to the deviation from spherical structure and monodispersity. • Defining the relative viscosity as the ratio between the sample viscosity and the reference viscosity is common practice in the application of most rheological models. The viscosity of water tends to be taken as the reference viscosity. This leads to no agreement between the well-known rheological models and the experimental data, especially when applied to analysis of microemulsion rheology. In this work, we show that by taking the viscosity of the relevant ternary surfactant solution as the reference viscosity, the existing models can be applicable to microemulsions. This work sheds light on the relationship between the non-Newtonian behaviour of nanoemulsions and their underlying thermodynamic instability. In these systems the Newtonian behaviour is not evident till a shear rate of 100/s is reached. On the other hand the Newtonian viscosity is observed in thermodynamically stable systems, e.g. surfactant solutions and microemulsions, beyond a shear rate of 5/s or less. The Newtonian region also was observed in normal emulsions with narrow size distributions, dilute monodisperse coarse emulsions or dilute normal emulsions prepared in a Warring blender while a short chain alcohol is added to the system. By adding the short chain alcohol to the system not only the densities of the two phases are made similar and the emulsification is eased but also the polydispersity of the final emulsion is decreased. Finally a single model to be applicable to different types of emulsions with droplet sizes over five orders of magnitude was proposed. However the relationship is applicable to the systems with a low degree of polydispersity and once polydispersity is introduced the flow behaviour becomes complicated and the proposed model is not applicable.</p>

Study of the conservation properties in two-way coupled dispersed multiphase flows using finite volume methods

In order to simulate dispersed multiphase flows, the coupling level must be determined according to the volume fraction in the system. The volume fraction is the ratio of the total volume of the dispersed phases over the total volume of the flow. In dilute flows, with volume fractions smaller than 10-6, only the influence of carrier phase over the dispersed phase is considered which is known as one-way coupling. Nonetheless, in dispersed flows with higher volume fractions, the effect of the dispersed phase over the continuous one should be taken into consideration, known as two-way coupling. This effect normally is applied as a source term in the conservation equations of the carrier phase. Depending on the numerical method and the discrete operators employed, these source terms can lead to some issues when aiming to preserve physical properties like mass, momentum and energy. Moreover, in order to validate the two-way coupling method, a particle-laden turbulent flow benchmark case with a mass loading of 22% is simulated by means of large eddy numerical simulation (LES). The aim of this work is to study the conservation properties of dispersed multiphase flows like momentum, kinetic energy and thermal energy through two-way coupling between dispersed and continuous phases.