Simultaneous Dispersion Research Articles

Non-Fourier heat and mass transport enhancement by hybrid nanofluid-flow over a non-linearly stretchable surface having variable thickness

This article uses non-classical Fick's law, non-Fourier's law, and conservation laws for mass and thermal transport. The hybrid nanoparticles Cu and Al2O3 are considered. The new correlations among the thermo-physical properties of base fluid, Cu and Al2O3 are coupled with simplified nonlinear mathematical models. The resulting models are solved numerically by the finite element method (FEM). The linear shape functions are chosen for the approximation of residual equations. This approximation leads to a nonlinear algebraic system that is linearized by the Picard scheme. The numerical results are ensured to be grid-independent, and convergence is analyzed. The results are validated, and an excellent agreement is obtained between available benchmarks and current outcomes. Thermal solutal relaxation phenomena are responsible for a significant reduction in the transport of heat and mass in Newtonian fluids. These non-Fourier's and non-classical Fick's laws are capable of capturing thermal and solutal elastic phenomena, respectively. Cu and Al2O3 simultaneously act as good conductors of heat, and their simultaneous dispersion in base fluid results in a significant rise in thermal conductivity. Numerical experiments have shown that the transport of heat can be optimized by simultaneous suspension of Cu and Al2O3.

Nanoparticles of NiO and CoO simultaneously dispersed on a mesoporous carbonaceous support as bifunctional electrocatalysts for ORR and OER reactions and Zn-air battery performance

This work aims to study the effect of different atmospheres and temperatures in the synthesis of a bifunctional electrocatalyst for ORR and OER reactions in the cathode of a Zn-air battery, using a carbonaceous support for dispersing Ni and Co species. At 300 °C, NiCo2O4 with a size of 4.93 nm under O2 and 150.14 nm using air, were obtained. These materials exhibited low specific surface area and pore volume and failed to show bifunctional activity. Instead, the simultaneous dispersion of NiO and CoO nanoparticles, with a size of 2.55 nm was achieved at 300 °C under N2 (NiCo/MC-N300), leading to a surface enrichment in Co2+ and Ni2+ species, while Ni and Co nanoparticles, 12.81 nm, were obtained at 700 °C under N2 (NiCo/MC-N700). These catalysts exhibited high specific surface area and pore volume, and bifunctional electrochemical activity; as well as high specific-capacity in a home-made Zn-air battery.

Porous carbonaceous materials simultaneously dispersing N, Fe and Co as bifunctional catalysts for the ORR and OER: electrochemical performance in a prototype of a Zn-air battery.

Infiltration of the mesoporous structure of SBA-15 silica as a hard template with phenanthroline complexes of Fe3+ and Co2+ allowed the simultaneous dispersion of nitrogen, iron and cobalt species on the surface of the obtained carbonaceous CMK-3 silica replica, with potential as bifunctional heterogeneous catalysts for the cathodic oxygen reduction and evolution reactions (ORR and OER). The textural properties and mesopore structure depended on the composition of the material. The carbonaceous FeCoNCMK-3 (1/1), obtained with an Fe/Co molar ratio of 1/1, exhibited an ordered cylindrical mesoporous structure with a high mesopore volume, a rather homogeneous composition in terms of total and surface concentrations of iron and cobalt, and a balanced presence of pyridinic-, pyrrolic- and graphitic-N species. FeCoNCMK-3 (1/1) could improve the ORR kinetics by adsorption and reduction of O2 through the 4-electron mechanism with a current density of -17.37 mA cm-2, Eonset of 1.13 V vs. RHE and E1/2 of 0.75 V when compared to metal-free, monometallic or bimetallic electrocatalysts with a higher amount of cobalt than that of iron. In addition, FeCoNCMK-3 (1/1) exhibited activity for the OER, presenting lower values of Eonset (1.52 V), Ej10 (1.78 V) and the Tafel slope (76.3 mV dec-1) with respect to other catalysts. When evaluated as a cathode in a prototype of a Zn-air battery, FeCoNCMK-3 (1/1) exhibited a high open circuit voltage of 1.41 V, a peak power density of 66.84 mW cm-2, a large specific capacity of 818.88 mA h gZn-1, and cycling for 20 h but with deactivation upon cycling.

Computational investigation of homogeneous-heterogeneous reactions in fluid with transport mechanisms: A finite element simulations approach

There are numerous applications in engineering and industry for homogeneous and heterogeneous chemical reactions in fluid regimes under the influence of nanoparticles and hybrid nanoparticles. This article models homogeneous and heterogeneous chemical reactions in the flow of polymer liquid (glycerin) containing Cu-Al2O3 in the presence of heat and mass transfer. The finite element method is used to quantitatively solve these models. A 76% increase in wall shear stress for the case of simultaneous dispersion of Cu and Al2O3 in comparison of only dispersion of Cu is noticed. Similarly, 44% increase in wall heat flux in noticed due to dispersion Cu and Al2O3 in comparison of dispersion of Cu only. The vortex parameter is responsible for a significant increase in the macro-motion of the fluid particles. Macro-motion gets more influence of micro motion than the influence of micro-motion on the macro-motion of Cu-Al2O3- polymer. To control momentum boundary layer thickness, reduce the diameter of the circular pipe. Magnetic force has the opposite direction of flow. Therefore, fluid motion is a decreasing function of magnetic field intensity. Further, the Lorentz force (magnetic force) for the case of Cu-Al2O3 - polymer is stronger than that for the case of Cu- polymer. Additionally, it can be seen that Cu-Al2O3- polymer experiences more Joule heating than Cu- polymer does. The micromotion is compromised when the curvature parameter is increased. As a result, convective transport slows down and the temperature of Cu- polymer and Cu-Al2O3 - polymers decreases. The result, the rate of conversion of electrical energy into heat speeds up intensity of magnetic field increase as and therefore, fluid temperature increases.

Finite element analysis for thermal enhancement in power law hybrid nanofluid

Ethylene glycol with nanoparticles behaves as a non-Newtonian fluid and its rheology can be best predicted by the power-law rheological approach. Further nanoparticles (molybdenum disulfide and silicon dioxide) are responsible for anti-oxidation, anti-evaporation, and anti-aging. Therefore, their dispersion in ethylene glycol is considered as these properties make the nanofluid stable. This article examines the impact of molybdenum disulfide and silicon dioxide on the thermal enhancement of ethylene glycol as it is a worldwide used coolant. Moreover, simultaneous effects of temperature and concentration gradients, Joule heating, viscous dissipation, thermal radiations, and buoyancy forces are modeled and developed, and investigations are computed by the finite element method. An increase in temperature due to the composition gradient and an increase in concentration due to the temperature gradient are observed. A significant increase in the Ohmic phenomenon with an increase in the intensity of the magnetic field is observed. Numerical experiments are performed by considering single-type nanoparticles (MoS2) and hybrid-type nanoparticles (simultaneous dispersion of SiO2 andMoS2is considered). During the visualization of simulations, the effective thermal conductivity of MoS2-SiO2-ethylene glycol is observed.

Non-Fourier heat and mass transfer enhancement in magnetohydrodynamic ionized fluid

Ethylene glycol has the characteristics of plasma and off course composed of ionized particles and it is also revealed by the literature that its rheological behavior is the best characterized by the power-law rheological model. Further, nanoparticles and are antioxidant, antifriction, and antiaging, therefore, their simultaneous suspension in ethylene glycol makes the mixture an efficient coolant for engines. Here, in this study, the objective is to investigate the thermal performance of liquid mixture (the mixture of ethylene glycol and nanoparticles, and ) theoretically. For this conservation laws and correlations among the thermophysical properties are simultaneously used for the modeling of heat transfer in ethylene glycol containing nanoparticles ( and ). Models are transformed into their dimensionless form using the approach of symmetry analysis. The dimensionless models are solved numerically by the finite element method (FEM). Simulations are visualized and data is recorded in the form of graphs and numerical values. Comparative analysis has revealed that the thermal efficiency of ethylene glycol is much improved due to the simultaneous dispersion of and . It is also found that ethylene glycol with a single type of nanoparticles () is a less efficient coolant than the efficiency of ethylene glycol with hybrid nanoparticles.

Numerical study of enhancement of heat and mass transport in the flow of power-law hybrid nano liquid under chemical reaction

Ethylene glycol with nanoparticles behaves as a non-Newtonian fluid and its rheology can be best described by the power-law rheological model. Further, hybrid nanoparticles are responsible for anti-oxidation, anti-evaporation, and anti-aging. Therefore, their dispersion in ethylene glycol is considered as these properties make the nanofluid stable. This article examines the impact of hybrid nanoparticles on the thermal enhancement of ethylene glycol as it is a worldwide used coolant. Moreover, simultaneous effects of temperature and concentration gradients, Joule heating, viscous dissipation, thermal radiations, and Bouncy forces are modeled and models are solved numerically using the finite element method (FEM). An increase in temperature due to composition gradient and an increase in concentration due to temperature gradient are observed. A significant increase in the Ohmic phenomenon with an increase in the intensity of the magnetic field is observed. The thermal performance of ethylene glycol is much improved due to simultaneous dispersion of hybrid nanoparticles relative to the thermal performance of ethylene glycol with mono nanoparticles only. Highlights The simultaneous dispersion of and in ethylene glycol is recommended to improve and optimize its thermal conductivity. Hence, and -ethylene glycol is a better coolant. The use of the Newtonian rheological model for ethylene glycol (when nanoparticles are dispersed in it) is an appropriate model. Therefore, to capture accurate information from numerical/theoretical analysis, the power-law constitutive model is suggested as it is an appropriate model and that is why is used in this study. -ethylene glycol is more heat generative than -ethylene glycol. This is the draw back with –-ethylene glycol when it is used as an engine coolant. The property of ––ethylene glycol to generate heat may cause over heating in the engine en used as a coolant. Thus, it is recommended to use non-heat generating fluids as base fluids.

The influence of in-situ alloying of electro-spark deposited coatings on the multiscale morphological and mechanical properties of laser welded Al–Si coated 22MnB5

During laser welding of Al–Si coated 22MnB5 steel, the melted Al–Si coating alloys with the molten weld pool promoting α-ferrite phase formation during the heat-treatment stage of hot-stamping, which results in a fusion-zone (FZ) microstructure consisting of α-ferrite islands disbursed through a martensitic matrix. The presence of the softer ferrite phase is the main cause for premature failure of laser-welded 22MnB5 joints in the hot-stamped condition. This work showed that surface modification of the Al–Si coating using an additive manufacturing technique called electro-spark deposition (ESD) prior to laser welding prevented α-ferrite formation in the FZ post-welding and hot-stamping. This was achieved by the in-situ alloying of ferrite-suppressing carbides and austenite-stabilizing elements. These alloying agents were added to the FZ by applying different ESD-modified coatings to the material surface, which melted into the molten weld pool during laser welding, leading to the simultaneous dispersion and solid-solution strengthening of the FZ after hot-stamping, respectively. The modification of the Al–Si coating prior to welding using tungsten-carbide (WC) and Inconel 625 (In625) resulted in drastically improved mechanical properties of the welded joint in the hot-stamped condition. In fact, this study showed that by carefully modifying the as-received Al–Si coating using ESD prior to laser welding could be used as an effective method to shift failure from the FZ, where it normally occurs, to the base material (BM). This work is highly relevant to the on-going discussion in the advanced manufacturing and materials science communities regarding the production of functionally-graded components as it proposes the implementation of an advanced processing technique to achieve the production of novel materials with highly optimized properties.

Numerical study of simultaneous transport of heat and mass transfer in Maxwell hybrid nanofluid in the presence of Soret and Dufour effects

The article aims to investigate the influence of copper (Cu) and a combination of copper (Cu) and aluminum oxide (Al2O3) on the simultaneous transfer of heat and mass in sodium alginate liquid moving over a circular pipe. This transport activity is modeled by the use of conservation laws with correlations for physical quantities of Cu, Al2 O3, and sodium alginate. Through cylindrical coordinates formulation, the set of partial differential equations is obtained. These models are solved numerically by the finite element method (FEM). The relaxation time associated with momentum diffusion in Maxwell fluid plays role in controlling the viscous region. Moreover, momentum relaxation time in Cu/sodium alginate is strong than that in Cu–Al2O3/sodium alginate. It is noticed from simulations that particles of Cu/ sodium alginate have a greater velocity than the velocity of Cu–Al2O3/sodium alginate. Therefore, distortion of magnetic lines by the flow of Cu/sodium alginate is more than the distortion of magnetic lines by the flow of Cu–Al2O3/sodium alginate. The rise in the thermal conductivity of sodium alginate due to simultaneous dispersion of Cu and Al2O3 is more than the rise in thermal conductivity of sodium alginate. Thus for maximum HT, the simultaneous dispersion of Cu and Al2O3 in sodium alginate is recommended.

Physical Processes in the Thermal Vacuum System

Physical processes occurring during dehydration of heterogeneous materials in a thermal vacuum system have been analyzed. It has been demonstrated that the thermal-vacuum method provides dehydration and simultaneous wet-stock dispersion due to thermal diffusion, shock-wave and ionization effects, thereby leading to formation of novel-type nanodispersed material at minimum energy input. In recent years the intensification of production processes, as well as the solution of energy- and resource-saving problems have taken on great significance. For the sake of dehydration working-cycle improvement, combination of several process procedures in a single installation is used, resulting in both the intensification of the production process and the reduction in capital expenditures. There are the facilities, where the simultaneous use of mechanical grinding operation and the drying process is practiced. In this case, a preheated air is used as a drying agent, and this considerably increases the energy demands of the technological process. This phenomenon is attributed to the impact action and friction of material particles against grinding surfaces of the mill, to the appearance of new surfaces at crushing, and also, to the dust-gas mixture turbulence in the mill working area. That requires substantial power consumption and prevents from obtaining the product with desirable indicators, in particular, the with dispersion and moisture content, which substantially affect the quality of materials produced from fine-grained products. The analysis of fine grinding methods has shown that the most rational method of material grinding is the combination of impact loads. The impact loads facilitate the structure destruction of wet stock, while the abrasion loads acting in the field of high turbulent flows lead to the material destruction. The aim of the present work has been to define the physical processes in the thermal vacuum system, which can efficiently provide dehydration along with simultaneous dispersion of wet material, yielding a dried and ground feedstock in a short span of time.

Mixed convective transport in Maxwell hybrid nano-fluid under generalized Fourier and Fick laws

Generalized laws of Fourier and Fick based on thermal and solutal relaxation times are used in the development of the system of PDEs related to simultaneous transport of heat and species in Maxwell fluid with mono and hybrid nano particles. The developed systems of PDEs are solved numerically by using the finite element method (FEM). Implementation of the FEM algorithm is discussed. The parametric study is carried out by performing various theoretical and numerical experiments. Related outcomes are presented in the form of graphs and numerical data. Convergence is ensured and grid-independent solutions are derived. Thermal relaxation parameter tends to lower down the temperature of the fluid and thermal boundary layer becomes shorter for higher values of thermal relaxation parameter. Concentration relaxation parameter has shown a decreasing impact on the diffusion of species in Maxwell fluid. Deborah number has reduced the diffusion of momentum in Maxwell fluid. Convective transport of both heat and species is compromised when Deborah's number is increased. It is also noticed from simulations that Deborah number for mono nano-Maxwell fluid has greater value relative to that for hybrid nano-Maxwell fluid. The simulations have also confirmed that the effective thermal conductivity of the Maxwell fluid due to the simultaneous dispersion of copper and aluminium oxide is greater than the thermal conductivity of pure Maxwell fluid and mono nano-Maxwell fluid. Therefore, simultaneous dispersion of copper and aluminium oxide for optimized heat transfer. Thermal and concentration relaxation memory effects are responsible for reducing thermal and concentration boundary layer thickness respectively. It is also noted that heat transport rate in hybrid nano-Maxwell fluid is greater than that in mono nano-Maxwell fluid and pure Maxwell fluid. Thermal memory effects play significant role in increasing the wall heat flux.

Thermal enhancement in coolant using novel hybrid nanoparticles with mass transport

To enhance heat and mass transfer, the use of hybrid nano-particles in shear rate dependent viscous fluid is of great significance in view of applications. Here in the considered problem, MXene base material titanium carbide and aluminum oxide (TiC−Al2O3) hybrid nano-particles are dispersed in the C2H6O2 (Ethylene glycol) as a base fluid. The obtained hybrid nanofluid is used to analyze the thermal performance of incompressible Carreau-Yasuda boundary layer flow. The finite element method (FEM) is implemented to find the numerical solution of the boundary value problems. The effects of magnetic field, chemical reaction parameters on velocity, thermal enhancement and mass transport are explored. It is worth noticing that the thermal efficiency of the designed system is greater in the Carreau-Yasuda hybrid nanofluid than the Carreau-Yasuda nanofluid. The velocity profile in x and y−direction enhanced as the value of the Weissenberg number increased. Interestingly, the intensity of the magnetic field increased the wall shear stresses and heat transfer rate of the Carreau-Yasuda hybrid nanofluid and the Carreau-Yasuda nanofluid. For the destructive chemical reaction, mass transfer rate increases and for the case of generative chemical processes, however, the opposite tendency is observed. In contrast to the dispersion of a single type of nano-particles (i.e.Al2O3), simultaneous dispersion of hybrid nano-particles (TiC−Al2O3) in Carreau-Yasuda fluid resulted an increase in thermal efficiency of working fluid. This work gives a new pathway/paradigm to develop a new kind of efficient hybrid nanofluid to minimize energy loss.

Evaluation and Improvement of PCM Melting in Double Tube Heat Exchangers Using Different Combinations of Nanoparticles and PCM (The Case of Renewable Energy Systems)

In this work, the melting process of phase change material (PCM) in double tube heat exchangers was investigated and evaluated through the use of different combinations (1, 2, 3% Nano-Enhanced PCM and 1, 3, 5% Nano-HTF) of GQD, as well as SWCNT nanoparticles and PCM (RT82). In this study, the effect of three different methods, namely the dispersion of nanoparticles in PCM (nano-enhanced PCM), the dispersion of nanoparticles in HTF (nano-HTF), and the simultaneous dispersion of nanoparticles in PCM and HTF (nano-enhanced PCM, nano-HTF) concerning the nanoparticles participation in the thermal energy storage system in a double tube heat exchanger was evaluated. Other effective factors, such as the inlet fluid temperature, different Reynolds numbers, fin as well as new parameter of pipe, and fin thickness were also evaluated. The results showed that the highest effect of different parameters on the PCM melting process was related to the 1% nano-HTF and 3% nano-enhanced PCM nanoparticles of SWCNT, which decreased the PCM melting rate by about 39%. The evaluation of the effect of pipe and fan thickness also showed that the melting rate improved by 31% through reducing the thickness of the HTF fin and pipe. In general, the current study followed two purposes first, to examine three methods of the dispersion of nanoparticles in the thermal energy storage system; second, to reduce the thickness of the tube and fin. Findings of the study yielded positive results.

Molecular‐Level Contact of Graphene/Silver Nanowires through Simultaneous Dispersion for a Highly Stable Wearable Electrothermal Heater

AbstractSilver nanowires (AgNWs) with low sheet resistances are excellent potential candidates for high‐performance wearable electrothermal heaters operated through Joule heating. However, the thermal oxidation and electrical instability of AgNWs caused by high contact resistance and poor adhesion to different substrates considerably limit their use in devices. Graphene is used in a AgNW/graphene hybrid owing to its low oxygen permeability, lower contact resistance with AgNWs, and good van der Waals interactions. Molecular‐level contacts between AgNWs and graphene must be achieved to maximize the synergy of these properties. In this study, a multifunctional polymer possessing styrene sulfonate‐based copolymer and disulfide groups is designed; these groups allow the simultaneous dispersion of AgNWs and graphene in an aqueous solution through self‐assembly. Since this polymer promotes molecular‐level contact between AgNWs and graphene, the oxidation and Joule‐heating stabilities of the hybrid dramatically increase. In addition, a freestanding AgNW/graphene film is readily prepared, exhibiting good attachable properties on various substrates and superior stability under harsh conditions (85 °C and 85% relative humidity for 7 days). The AgNW/graphene hybrid film displays a low sheet resistance (0.36 ± 0.02 Ω sq−1) with good performance as a high‐performance electrothermal heater (200 °C at 1.5 V).

Numerical thermal study on performance of hybrid nano-Williamson fluid with memory effects using novel heat flux model

Conservation laws, non-classical heat and mass flux models, and correlations for thermos-physical properties of hybrid nanostructures and fluid are used for the formulation of problems. The numerical solutions for modeled flow problems (PDEs with suitable boundary conditions) are computed using the finite element method (FEM). These numerical solutions are used in simulations under variation of various types of parameters obtained as a result of dimensional analysis. The role of simultaneous dispersion of MoS2 and SiO2 as hybrid nanoparticles on the thermal performance of Williamson fluid and transport of species in Williamson fluid are investigated. A significant rise in the effectiveness of thermal conductivity of Williamson is observed due to the dispersion of hybrid nanostructures. It is also noted that the effectiveness of thermal conductivity due to hybrid nano-structures is higher than the effectiveness of thermal conductivity due to nano-structures. A remarkable drag on the flow of fluid due to the presence of porous medium is observed. Further, Forchheirmer porous medium offers more resistance to flow than the resistance by Darcy's porous medium. A significant decrease in temperature and concentration fields against relaxation parameters is observed. Consequently, a decline in thermal and concentration thickness is noted.

Synthesis and characterization of poly(p-phenylenediamine): TiO2 nanocomposites and investigation of conducting properties for optoelectronic application

Abstract Poly(p-phenylenediamine) is a potential precursor for designing of new materials for optoelectronic application. Synthesis and characterization of poly(p-phenylenediamine) – TiO2 nanocomposites has been demonstrated. Structural change observed due to the formation of nanocomposites was correlated with concomitant change in conducting behavior of the parent polymer. Polymer nanocomposite was synthesized through an in-situ oxidative polymerization technique with simultaneous dispersion of TiO2 nanoparticles. TiO2 nanoparticles were synthesized via sol-gel process. Structural characterization was accomplished by using conventional spectroscopic and imaging techniques. I-V measurement of the nanocomposites revealed that the nearly nonconducting poly(p-phenylenediamine) after structural modification exhibits conductivity of 10−6 S/cm leading to formation of wide band gap semiconducting materials.

Numerical study on enhancement of heat transfer in hybrid nano-micropolar fluid

Hybrid nanoparticles correlations together with governing models for the flow of micropolar fluid are used to develop novel complex coupled nonlinear set of differential equations. The solutions are computed by using the finite element method (FEM) and results are validated after convergence and grid-free analysis. The macroscopic velocity and micro-rotation field are investigated versus parametric variation. The temperature field is examined for various emerging dimensionless parameters. A significant improvement in the thermal performance of micropolar fluid due to simultaneous dispersion of Cu and Al2O3 (hybrid nanoparticles) is noted. Therefore, simultaneous dispersion of Cu and Al2O3 for significant improvement in thermal performance of micropolar fluid is recommended rather the dispersion of copper nanoparticles. Surprisingly micro rotation field for nano micropolar mixture near the vicinity of the wall is less than the micro-rotation field for hybrid nano-micropolar fluid. However, away from the wall opposite dynamics for the micro-rotation field are observed.

Preparation of mixed-matrix membranes from metal organic framework (MIL-53) and poly (vinylidene fluoride) for use in determination of sulfonylurea herbicides in aqueous environments by high performance liquid chromatography

Novel mixed-matrix membranes (MMM) were prepared from metal-organic frameworks (MOF) (MIL-53) and poly (vinylidene fluoride) (PVDF), viz MIL-53–PVDF MMM, for the simultaneous dispersion membrane extraction (DME) of seven sulfonylurea herbicides (SUs) in aqueous environments followed by high performance liquid chromatography (HPLC) determination. The MIL-53–PVDF MMM was well characterized and major factors influencing DME performances were systematically investigated including membrane type, MOF dosage, eluent type, solution pH, extraction/elution time and salinity, etc. Under optimal conditions, the MIL-53–PVDF MMM based DME coupled with HPLC exhibited excellent linearity within 0.03–10 μg L−1 for chlorimuronethyl and 0.01–10 μg L−1 for other six SUs individual. High enrichment factor of 250 was obtained, as well as low detection limits and quantification limits ranged from 3.75 to 10.30 ng L−1 and 12.49–34.30 ng L−1, respectively. Furthermore, the method attained high recoveries of 77.20–111.00% at three spiking levels of SUs, with relative standard deviations of 1.28–14.67% in tap water, seawater and surface water samples. Additionally, the MMM was readily separated from water and well regenerated, and could keep about 80% recovery after 25 cycles. Compared to that reported extraction materials, the MIL-53–PVDF MMM possessed the advantages of high enrichment ability, excellent reusability, good practicality and easy separation, indicating it was a promising alternative for the enrichment of SUs from aqueous environments.

Improved electrical conductivity of polymer/carbon black composites by simultaneous dispersion and interaction-induced network assembly

A versatile networking method is reported for conductive polymer/carbon black (CB) composites on the basis of simultaneous dispersion and interaction-induced network assembly during melt compounding via addition of a very small amount (about 1 wt%) of secondary polymer that has stronger interaction with CB than the matrix polymer. Four different systems including polyamide 6 (PA6)-modified polycarbonate (PC)/CB, thermoplastic polyurethane (TPU)-modified polyoxymethylene (POM)/CB, PA6-modified POM/CB and TPU-modified polypropylene (PP)/CB composites were investigated to demonstrate the feasibility of the method. 1 wt% secondary polymer can effectively induce assembly of CB particles, forming higher-structure loosely-packed agglomerates. Even with 0.3 wt% secondary polymer, the percolation threshold could decrease by 30%. The mechanism for the hierarchical morphology of filler arrangement is proposed on the basis of preferential wetting and infiltration of CB by secondary polymer and the assembly of dispersed CB aggregates around/in the small droplets of secondary polymer. The reduced inter-agglomerate tunnelling distance and enhanced secondary electric field are proposed as the mechanisms for improved electrical conductivity.

Porous Beads of in-situ Calcium Hexaluminate Prepared by Extrusion-Dripping

Abstract: Structures comprised of mixtures of corindon (α-Al2O3) and calcium hexaluminate (CaAl12O19 or CA6) show high refractoriness and chemical resistance. This article addresses the in situ formation of porous alumina-CA6 beads (approximately 2-3 mm) prepared by an extrusion-dripping process with sodium alginate (SA) as a coagulation agent. The best conditions for a simultaneous dispersion of aqueous mixtures of the precursor raw materials, fine alumina, and calcium carbonate (β-CaCO3 or calcite), in an SA solution were investigated by Zeta potential and apparent viscosity measurements and turbidity tests. Extrusion-dripped beads of different compositions were consolidated by the ionotropic gelation of SA in a Ca2+ solution. A net of thin coagulated-SA filaments restraining solid particles was registered by scanning electron microscopy. Different pore generation mechanisms were observed during heating up to 1500 °C. Variations in the initial Al2O3-CaCO3 ratio yielded a wide range of compositions, microstructures, and physical properties (total porosity, crystalline phase content, and pore size distribution).