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The rheological properties of novel MR fluids are characterized using a parallel plate MR shear rheometer. In these MR fluids the surface of iron particles is coated with a polymer. The rheological properties are measured and compared at various magnetic field strengths, shear rates and strain amplitudes. It has been shown that these MR fluids exhibit stable and desirable rheological properties such as, low viscosity and high yield stress.

Gelcasting process as a promising method for fabrication of reliable ceramics has been utilized to develop alumina-zirconia nanocomposites from nanosized powders. Sedimentation and viscosity measurement were performed to find the accurate dispersing condition for production of alumina-zirconia nanocomposite slurry with high solid loading and low viscosity. The gelcasting was accomplished by in situ polymerization of an acrylamide base monomer. The effects of solid loading, viscosity and deairing were also studied. Finally, crack and flaw free samples with relative densities of 99%, were achieved from the optimal slurry with 35vol. % solid loading, by performing sintering at 1600°C for 2 hours. SEM micrographs showed dense microstructure with fine and homogenous dispersion of zirconia phase in the alumina matrix.

When a concentrated suspension of colloidal particles is sheared at high enough shear rates, its viscosity increases with the shear rate. Depending on the details of the interactions between particles, this increase may be continuous and the suspension is said to shear-thicken, or may be discontinuous, leading to an arrest of flow: the suspension jams. We review recent experimental evidence that both behaviors are the consequence of the formation of dynamical aggregates under flow.

The concentrated fiber suspensions in a simple shear flow are simulated numerically by taking into account the hydrodynamic interactions and fiber–fiber mechanical contacts. The orientation probability distribution of fibers, the specific viscosity and the first normal stress difference are obtained. The comparison of the specific viscosity to experimental data is made and the agreement is good. The results show that initially randomly-oriented fibers are re-oriented in the flow direction. The hydrodynamic interactions and fiber–fiber mechanical contacts result in an increase in the spread of the orientation distribution and asymmetric orientation distribution about the flow direction. Fiber's alignment with the flow direction becomes more obvious with an increasing shear rate. In a concentrated fiber suspension, the force induced by the fiber–fiber mechanical contact plays a more important role than that induced by hydrodynamic interactions. The specific viscosity of fiber suspension grows with concentration for various aspect ratios. For a fixed concentration, the larger the aspect ratio is, the higher the specific viscosity is. The specific viscosity calculated by taking into account both hydrodynamic interactions and fiber–fiber mechanical contacts is larger than that only taking into account the fiber–fiber mechanical contacts. The effect of aspect ratio on the first normal stress difference is more obvious at high concentration. Taking into account the hydrodynamic interactions or not will make a big difference in the first normal stress difference.

This research is focused on mathematical modeling of fluids with yield stress in the squeeze mode. The focus of the research is on magneto-rheological (MR) fluids but the results can be extended to any non-Newtonian fluid exhibiting a yielding behavior. There is no universally accepted mathematical model of squeeze flow of MR fluids to date because of the complexity of the flow and lack of theoretical and experimental studies. In this research, the squeeze flow problem of MR fluids is solved using perturbation techniques and squeeze force and flow field are determined. The model is verified and validated using experimental test data and it is shown that the model can be used as a design tool for design of MR devices that operate in the squeeze mode.

Resonance Acoustic MixingⓇ(RAM) technology applies an external low-frequency vertical harmonic vibration to mix ultrafine granular materials and subsequently non-Newtonian fluids. Although this system is used for various applications, its mechanism is yet not well understood, especially in the mixing of non-Newtonian fluids. To address this gap in knowledge, a phase model of the shear-thinning and shear-thickening non-Newtonian power-law fluid in a low-frequency vertical harmonic vibration container is established in this study, and the different power-law index is also considered. During the initial mixing process, there is Faraday instability at the gas–liquid interface, and Faraday waves are related to the power-law index. With the continuous input of external energy, the flow field is further destabilized, so that the uniform mixing is finally completed. In addition, the rheology of non-Newtonian fluids is consistent with the constitutive relation of power-law fluids. The dynamic viscosity of shear-thinning non-Newtonian fluid decreases rapidly with the increase of mixing time, while the shear-thickening non-Newtonian fluid decreases rapidly with the increase of mixing time. The variation of shear rate for Newtonian and non-Newtonian fluids is identical. Finally, a proper vibration parameter for the high mixing efficiency of RAM is proposed.

Time dependent analysis of the dynamic damped behavior of continua are mathematically modelled by partial differential equations. One obtains uniqueness, existence and stability (well posed problems) by the implementation of the correct initial boundary conditions. However, by taking memory effects into consideration, any change in the past of the system changes the future dynamic behavior. Classical damping descriptions fail when describing the behavior of many materials, like teflon. This is because in classical theory the operators are local ones. The implementation of fractional time derivatives into the partial differential equations is an alternative technique to overcome these problems. Thereby the time derivative operator is a global one, memory effects in structure borne sound can be calculated. In this paper the theory of fractional time derivative operators and their application in continuum mechanics is presented. The main result when using this method for damping behavior is that a global operator is needed which takes the whole history into account. We call this theory the functional calculus method instead of the well-known fractional calculus with the use of initial conditions. In order to show the efficiency of this method the calculated impulse response of a viscoelastic rod is compared with measurements. It is shown that the damping behavior is described much better than by other models with comparably few parameters. Moreover, it is the only one that works in a wide frequency range and can describe the dispersion of the resonance frequencies. The implementation of this damping description in a Boundary Element Code is an application of dynamics of 3D continua in the frequency domain.

The general author's mesomechanical concept is applied to constitutive modeling of rheological behavior of human blood. The thermomechanical properties of blood are very complicated and their mathematical modeling — although studied for many years — deserves still attention, as phenomenological descriptions do not seem to achieve the due generality and accuracy. Our mesomechanical approach is rooted within the mesoscale description of the substructure of erythrocyte aggregates and their changes in the course of different time-dependent loading paths. Good agreement of the outcomes of our model with experimental findings received under complicated conditions corroborates the usefulness of this approach.

A numerical study of pulsatile hydromagnetic flow and mass transfer of a non-Newtonian biofluid through a porous channel containing a non-Darcian porous material is undertaken. An extensively-validated biofluid dynamics variational finite element code, BIOFLOW, is employed to obtain comprehensive computational solutions for the flow regime which is described using a spatially two-dimensional momentum equation and a spatially one-dimensional mass transport equation, under appropriate boundary conditions. The Nakamura-Sawada rheological model is employed which provides a higher yield stress than the Casson model. A non-Newtonian model is justified on the basis that blood exhibits deviation from Newtonian behavior at low shear rates. The conduit considered is rigid with a pulsatile pressure applied via an appropriate pressure gradient term. One hundred two-noded line elements have been employed in the computations. The influence of magnetic field on the flow is studied via the magnetohydrodynamic body force parameter (Nm), which defines the ratio of magnetic (Lorentz) retarding force to the viscous hydrodynamic force. Blood vessel blockage effects are simulated with a Darcy-Forchheimer nonlinear drag force model incorporating a Darcian linear impedance for low Reynolds numbers and a Forchheimer quadratic drag for higher Reynolds numbers. Transformed velocity and concentration profiles are plotted for the influence of Reynolds number (Re), Darcy parameter (λ), Forchheimer inertial drag parameter (N_F), non-Newtonian parameter (β), and Schmidt number (Sc) and at various times (T). Three-dimensional profiles of velocity varying in space and time are also provided. Applications of the model include magnetic therapy, biomagnetic pharmaco-dynamics and the simulation of diseased arteries.

In this paper, effects of stationary contraction on mixing and transport of a non-Newtonian fluid in the small intestine are analyzed theoretically. A semi-analytical method is developed to solve the governing equations of fluids flow in the intestine using lubrication theory. Results indicate that the stationary contraction helps in conferring two functions – (1) shearing of the contents, and (2) bidirectional transport over a short distance. The flow resulting from contraction is symmetric and occurs in both the directions; however, they do not lead to a net flow rate in one direction. The amount of shearing developed during such flows is reflective of their mixing ability. The effort of such peristalsis is largely determined by the flow behavior index; where energy requirements of developing similar shearing forces are higher for dilatants and lower for pseudoplastics. Flow is sensitive to frequency of contraction, luminal occlusion and wavelength of the contraction.

This paper focuses on the dual quality of blood, Newtonian and non-Newtonian, in particular by exploring the energy curves. Careful investigation of the dual property of blood has been made by considering two different geometries to represent a stenosed arterial segment. We present a cautious assessment of non-Newtonian blood rheology impacts in arterial stream simulations by coupling the Newtonian and non-Newtonian models. The flow of energy through the two flow dimensions is meticulously investigated using velocity (kinetic energy), pressure, and wall shear stress (pressure energy). Besides, the proper implementation of an interface boundary condition (IBC) was emphasized to ensure consistency with the flow conditions downstream of a backward-facing step. The integration of the Newtonian and non-Newtonian models adjoins the novelty of the current research. The energy curves are obtained by implementing five different non-Newtonian models to designate a suitable non-Newtonian model for blood flow investigations. The combination of the non-Newtonian models enforced in this research is novel and particular attention is paid to the energy curves obtained. The conclusion was to elect the Carreau model as a suitable non-Newtonian rheological model for the blood flow study. This study was able to finalize the fact that the coupling of Newtonian and non-Newtonian models is necessary to obtain accurate results. For the sinusoidal waveform considered for the velocity, Carreau and the Power law models yield better results, eliminating the other non-Newtonian models from the list. With a better inlet condition imposed in the form of the Fourier series for pressure and velocity, the Carreau model yields the best results.

We have performed numerical studies of dense granular flows on an incline with a rough bottom in two and three dimensions. This flow geometry produces a constant density profile that satisfies scaling relations of the Bagnold, rather than the viscous, kind. No surface-only flows were observed. The bulk and the surface layer differ in their rheology, as evidenced by the change in principal stress directions near the surface; a Mohr–Coulomb type failure criterion is seen only near the surface. In the bulk, normal stress anomalies are observed both in two and in three dimensions. We do not observe isostaticity in static frictional piles obtained by arresting the flow.

A simple model is presented for the description of steady uniform shear flow of granular material. The model is based on a stress fluctuation activated process. The basic idea is that shear between two particle layers induces fluctuations in the media that may trigger a shear at some other position. Based on this idea, a minimum model is derived and applied to different configurations of granular shear flow.

In petroleum exploration, cellulose derivatives such as carboxymethylcellulose (CMC) are frequently used in drilling, cementing and fracturing fluids. However, under extreme drilling conditions, these additives have limited performance. In this regard, cellulose nanocrystals particles (CNCs) which are also derived from cellulose material are a suitable candidate due to their shear thinning rheology and thixotropy properties, even at low concentrations, among so many properties thanks to their crystalline structure and their nanometric dimensions.

In this work, hydrolyzed fibers from industrial cotton are acetylated using acetic anhydride and sulfuric acid as catalysts, with the aim to modify surface properties of the obtained CNCs without changing their fiber structure and morphology. FTIR analysis pointed out the acetylation success of the obtained nanocrystals whose dimensions were found to be unaltered by the modification process. SEM images of cotton nanocrystal indicate that CNC_c surface modification preserves the nanoscale dimensions of the nanoparticles. Also, TGA analysis showed thermal stability for the acetylated CNC_c.

The evolution and the origin of "solid-like state" in molten polymer/clay nanocomposites are studied. Using polypropylene/clay hybrid (PPCH) with sufficient maleic anhydride modified PP (PP-MA) as compatibilizer, well exfoliation yet solid-like state was achieved after annealing in molten state. Comprehensive linear viscoelasticity and non-linear rheological behaviors together with WAXD and TEM are studied on PPCH at various dispersion stages focusing on time, temperature and deformation dependencies of the "solid-like" state in molten nanocomposites. Based on these, it is revealed that the solid-structure is developed gradually along with annealing through the stages of inter-layer expansion by PP-MA, the diffusion and association of exfoliated silicate platelets, the formation of band/chain structure and, finally, a percolated clay associated network, which is responsible for the melt rigidity or solid-like state. The network will be broken down by melt frozen/crystallization and weakened at large shear or strong flow and, even more surprisingly, may be disrupted by using trace amount of silane coupling agent which may block the edge interaction of platelets. The solid-like structure causes characteristic non-linear rheological behaviors, e.g. residual stress after step shear, abnormal huge stress overshoots in step flows and, most remarkably, the negative first normal stress functions in steady shear or step flows. The rheological and structural arguments challenge the existing models of strengthened entangled polymer network by tethered polymer chains connecting clay particles or by chains in confined melts or frictional interaction among tactoids. A scheme of percolated networking of associated clay platelets, which may in band form of edge connecting exfoliated platelets, is suggested to explain previous experimental results.

The mechanism of phase inversion emulsification process (PIE) was studied for waterborne dispersion of highly viscous epoxy resin using non-ionic polymeric surfactants. Drop deformation and breakup, rheological properties, conductivity, and particle size measurements reveal the micro-structural transition amid emulsification. It is revealed that strong flow causes water drop to burst with the formation of droplets and huge interface. Phase inversion corresponds to an abrupt rheological transition from a type of viscous melt with weak elasticity to a highly elastic type of aqueous gel. This implies that the phase inversion equivalent to a curvature inversion. Based on this, a geometric model is postulated to correlate process variables to the particle size. The coverage and conformation of the surfactant plays key role for the particle size of the final emulsion. The interactions of thermodynamic and hydrodynamic effects are also discussed. It is concluded that the thermodynamics control the PIE while the hydrodynamics drives the creation of interface and involves every step of PIE.

Experimental miscibility studies were performed on different compositions of iPP/sPP blends, where sPP has a low syndiotacticity ([rrrr] = 81%). Combining optical microscopy, rheology, and solid state NMR spectroscopy, the miscibility of the blends was investigated at different scales in the traditionally thought to be "immiscible" iPP/sPP blends. For the composition of iPP/sPP (90/10) blend, it shows to be miscible in the melt, and furthermore, the existence of intermolecular chain interactions between sPP and iPP components was detected in the solid state.

A surfactant system L64 and alcohol mixture was employed to exfoliate MoS₂. To reduce the impact of surfactant on the quality of the nanosheet, the concentration of L64 was decreased to an extremely low value 0.0325 mM. Utilize common ultrasonic bath, the production yield of the nanosheet was increased to about 5% per hour, and statistical results from AFM showed that 40% of the nanosheet were less than 4 nm thick. Rheology characterization showed that surfactant alcohol mixtures were shear thinning fluid, yet the viscosity of L64 system varies directly with the shear rate in the high-speed shear region (higher than 400 s⁻¹), and further affect the shear strength, therefore viscosity at high-speed shear can be considered as an indicator of the effectiveness for the exfoliation system. Exfoliated MoS₂ was evaluated by hydrogen evolution reaction, and compared to the bulk MoS₂, the 4 wt% Pt/FL-MoS₂ improved the overpotential from 366 mV to 273 mV at 10 mA$•$cm${}^{-2}$. This study presented a facile and effective route to fabricate 2D MoS₂ with much less residue, and bring more opportunities to exploit clean and nontoxic system to exfoliate 2D materials.

SiO₂ is commonly used as an abrasive in optical devices and magnetorheological (MR) fluid. In this study, MR fluid with composite and free-state SiO₂ were prepared. Composite magnetic particles of CIP@SiO₂ were synthesized using the sol-gel method with tetraethyl orthosilicate (TEOS) as the silicon source. Performance test results showed that CIP@SiO₂ MR fluid exhibited superior mechanical properties compared with CIP MR fluid under zero magnetic field conditions. However, under the influence of a magnetic field, the SiO₂ shell weakened the response of CIP@SiO₂ MR fluid to the magnetic field, whereas CIP MR fluid demonstrated better rheological properties. The addition of free-state SiO₂ to CIP MR fluid significantly improved its rheological performance. At a volume fraction of 6% SiO₂, the shear stress and viscosity reached their maximum values, and further increasing the volume fraction to 8% resulted in a noticeable decrease in rheological behavior. Stability improved with an increase in magnetizable particle content. The stability of CIP MR fluid at the same concentration was superior to that of CIP@SiO₂ MR fluid, while free-state SiO₂ had a notable enhancing effect on stability. Therefore, when SiO₂ exists as a free-state abrasive, the rheological properties and stability of the MR fluid considerable improve.

Hydrogels with different weight percent of $N$-hydroxylethyl acrylamide and $N$-(2-mannosylethyl) acrylamide were prepared, using $N$, $N^{\prime }$-methylenebis (acrylamide) (MBA) (1.0wt.%) and ammonium persulfate (APS) (1.0wt.%) as the crosslinker and initiator, respectively. The successful preparation of hydrogels was confirmed by both inverted vial test and rheological measurements. These hydrogels were grinded into nanogel powders and applied as a bromelain stabilizer against high temperature by measuring the proteolytic activities of bromelain, which increased from 47% to $>$95% under nanogel protection. This indicated that nanogels can be potentially applied as an enzyme stabilizer in food industry.