Hybrid Dispersion Research Articles

RANGE ENHANCEMENT IN ROF NETWORKS THROUGH HYBRID DISPERSION COMPENSATING SCHEME

A hybrid dispersion compensating approach utilizing fiber grating and optical phase conjugator is investigated in this paper. A comparative analysis of non-compensated link, fiber grating based compensated link and hybrid compensated link is also presented. These different schemes are evaluated in 1100 km long Radio over fiber (RoF) based network. It is reported that compensated links provide larger transmission range than non-compensated link. The hybrid compensated link outperforms fiber grating based compensated link by offering acceptable Bit Error Rate (BER) of 10-8 over a successful transmission over the distance of 850 km.

In situ polymerization of aniline on the surface of manganese oxide nanosheets for reducing fire hazards of epoxy

Layered manganese dioxide (MnO2) is a promising nanofillers for reducing the fire hazards of polymeric materials due to its excellent catalytic charring effect. However, its poor dispersion in polymer matrices hindered its full performance. In this work, polyaniline (PANI) coatings were uniformly coated on the surface of MnO2 nanosheets by in-situ polymerization method to form binary hybrids (PANI-MnO2 hybrids). The prepared PANI-MnO2 hybrids were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR), Thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and Scanning electron microscopy (SEM). SEM results of the fractured surface indicated the dispersibility and interfacial interaction between MnO2 and epoxy (EP) matrix were obviously improved, leading to superior fire safety performance of epoxy-based composites. By adding 2 wt% of PANI-MnO2 hybrids, the peak heat release rate (PHRR), total heat release (THR), total smoke production (TSP) and peak smoke production rate (PSPR) values of EP composites were decreased by 34.7%, 37.1%, 44.4%, and 27.0% respectively, compared to those of pure EP. The good dispersion and interfacial interaction of PANI-MnO2 hybrids and the catalysis and physical barrier of MnO2 nanosheets contributed to the superior fire safety performance of EP composites.

Application of graphene oxide nanosheets and HPAM aqueous dispersion for improving heavy oil recovery: Effect of localized functionalization

Using efficient methods to recover heavy oil is crucial for economic success. Polymer flooding is a very efficient way to sweep oil reservoirs at both macroscopic and microscopic scales by increasing the viscosity of injected water. Recently, it was shown that addition of nanomaterials to polymer solutions may improve the flooding performance and recovery. In this work, two different types of graphene oxide (GO) nanofillers with different different location of OH group functionalization (functionalization mainly on basal plane (S-GO) and functionalization mainly on the edges (E-GO)) were synthesized to improve the rheological behavior and oil recovery efficiency of a partially hydrolyzed polyacrylamide (HPAM) solutions. To characterize the chemical structure of both GOs, thermogravimetric analysis (TGA) and Raman spectroscopy were employed. Frequency sweep, creep, creep recovery, shear start-up, and strain sweep tests were also utilized to evaluate the viscoelastic behavior of HPAM solutions, with or without the nanofillers in both linear and nonlinear viscoelastic regions. Cryo-SEM images of the hybrid dispersion of HPAM/GOs were captured to assess the dispersion state of all systems. A core flooding set up was used to evaluate the effectiveness of all dispersions in improving the viscous oil recovery by polymer injection. Rheological properties showed that addition of 0.2 wt% of both GOs reduced dynamic moduli. However, due to the better dispersion of S-GO in a HPAM solution, incorporation of 0.2 wt% of S-GO to the HPAM solution, improved the oil recovery by 7.8% compared to the HPAM solution.

Hybrid Dispersion Dirac Semimetal and Hybrid Weyl Phases in Luttinger Semimetals: A Dynamical Approach

AbstractIt is shown that hybrid Dirac and Weyl semimetals can be realized in a 3D Luttinger semimetal with quadratic band touching (QBT). This is illustrated using a periodic kicking scheme. In particular, the focus is on a momentum‐dependent driving (nonuniform driving) and the realization of various hybrid Dirac and Weyl semimetals is demonstrated. A unique hybrid dispersion Dirac semimetal with two nodes is identified, where one of the nodes is linear while the other is dispersed quadratically. Next, it is shown that by tilting QBT via periodic driving and in the presence of an external magnetic field, one can realize various single/double hybrid Weyl semimetals depending on the strength of external field. Finally, it is noted that in principle, phases that are found in this work can also be realized by employing the appropriate electronic interactions.

Studies on synthesis and characterization of aqueous hybrid silicone-acrylic and acrylic-silicone dispersions and coatings. Part II

Aqueous silicone-acrylic (SIL/ACR) and acrylic-silicone (ACR/SIL) dispersions with hybrid particle structure were synthesized, respectively, by polymerization of acrylic/styrene monomers in silicone resin dispersion (SIL) and of silicone monomers in two acrylic/styrene copolymer dispersions (ACR A and ACR B). A comprehensive study of the effect of SIL/ACR or ACR/SIL (w/w) ratio, i.e. of the silicone component content in the dispersion solids, on the properties of such hybrid dispersions, coatings and films was conducted. It was found that increasing the SIL/ACR ratio from 0 to 1/9, 1/6 and 1/3 (or decreasing ACR/SIL ratio accordingly) influenced quite significantly the appearance of hybrid dispersion particles and thus also the properties of dispersions (particle size, MFFT, Tg of dispersion solids) as well as the properties of coatings (contact angle, surface free energy, water resistance, water vapor permeability, hardness, impact resistance) and films (% swell in toluene, % of toluene-soluble fraction, tensile strength, elongation at break) made from these dispersions were affected. Based on the results of these investigations some dispersions may be selected for further testing as binders in architectural paints.

Ultrafast Pulse Manipulation in Dispersion-Flattened Waveguides With Four Zero-Dispersion Wavelengths

On-chip formation and manipulation of ultrashort pulses would be of great interest to ultrafast optics and integrated photonics communities. One of key issues is dispersion-assisted nonlinear interactions of broadband frequency components. In this article, we show for the first time that a bilayer waveguide for quasi-TE mode without using a slot produces a quite flat and saddle-shaped dispersion profile. Different from previously reported TE-mode waveguides with flattened dispersion, the proposed waveguide exhibits a greatly simplified structure with no need for a high-aspect-ratio slot and has quite small group delay difference in a wide spectral range with four zero-dispersion wavelengths (ZDWs). We study supercontinuum generation in hybrid dispersion regime for the first time, in which the broadened spectrum covers a bandwidth with all ZDWs. It is found that one can obtain greatly improved spectral flatness in supercontinuum generation, with a power variation as small as 3 dB over a bandwidth of >500 nm. Moreover, the proposed waveguides are particularly suitable for low-distortion pulse propagation over a long distance, which is important for on-chip ultrashort pulse delivery.

Polythiophene-coated multi-walled carbon nanotube-reinforced epoxy nanocomposites for enhanced mechanical, electrical and thermal properties

In this paper, epoxy nanocomposites were developed via polythiophene–carbon nanotube with different loadings of 0–1.0 wt%. Polythiophene–carbon nanotube (PTh–CNT) hybrids produced using in situ chemical polymerization method and the microstructures, morphology and properties of the PTh–CNT hybrids and epoxy nanocomposites were studied using Fourier-transform infrared (FTIR), scanning electron microscopy (SEM), transition electron microscopy (TEM), mechanical (tensile and flexural properties), electrical, dynamic mechanical thermal analysis (DMTA) and thermogravimetric techniques (TGA). Mechanical analysis demonstrated that nanocomposites containing 0.5% PTh–CNT hybrids exhibited the highest properties among all nanocomposites and showed 78% and 51% increment of Young’s modulus and strength. The fracture analysis of samples and extent of fillers dispersion were visualized by SEM and demonstrated that dispersion of hybrids within epoxy matrix related to the hybrid nature (PTh–CNT ratio) and its concentration that are the key factors affected final properties of nanocomposites. DMA thermograms represented higher modulus for all epoxy/PTh–CNT nanocomposites systems as compared to epoxy/CNT and the pristine epoxy. Electrical conductivity measurements showed that conductivity of epoxy filled nanocomposites increased up 10−1 S cm−1 for epoxy/PTh–CNT nanocomposites. In addition, epoxy/PTh–CNT nanocomposites were also compared to pure epoxy and epoxy/CNT nanocomposites and showed higher thermal stability. The PTh–CNT particles enhanced electrical, thermal and fracture toughness of nanocomposites, confirming the synergistic effect of PTh–CNT as multifunctional filler.

Wideband Leaky-Wave Antennas Loaded With Gradient Metasurface for Fixed-Beam Radiations With Customized Tilting Angles

We propose a hybrid dispersion compensation method to design wideband fixed-beam leaky-wave antennas (LWAs), with the tilting angle customizable in both forward and backward quadrants. In a previous work, a triangular dispersive prism constituted by metallic pins was presented to compensate for the dispersion of traditional LWAs and achieve a squint-free radiation in a relative bandwidth of 20%. However, that design suffered from the drawbacks of large geometry and limited angular range. To overcome these limitations, here a broadband gradient metasurface based on geometric phase theory is loaded in front of the prism to customize the radiation angle and reduce the total prism size. In addition, a novel ridged gap waveguide is employed to improve the linearity of LWA dispersion, which is beneficial to maintain the bandwidth of LWA with reduced size. Two examples are presented to demonstrate the excellent performance of the designed antennas. One antenna radiates at an angle of 39.5° in a squint-free bandwidth of 20%, but the prism size is decreased to a quarter of the original one, while the other realizes a broadside radiation with a squint-free bandwidth of 18%. Good agreement is exhibited between simulated and experimental results. The proposed method can be further extended to compensate for the dispersion of antenna arrays and improve the angular stability of the radiation beams in a large frequency band.

Polypyrrole doped graphene oxide reinforced epoxy nanocomposite with advanced properties for coatings of mild steel

In this paper epoxy coatings containing Polypyrrole–Graphene Oxide (PPy–GOs) hybrid nanocomposites with various weight fraction (0.5, 1 and 2 wt%) were prepared to investigate the effect of PPy-GO on the enhancement of anti-corrosion properties in epoxy based nanocomposite coatings on mild steel. PPy–GOs hybrids, PPy and GO were characterized by FT-IR, XRD, SEM and TEM analysis and their effect on the anticorrosion performance of the composite coatings, the epoxy (E), epoxy mixed with PPy-GO (EPGs), PPy (EP) and physically mixture of PPy and GO (EP + G) coatings were studied by electrochemical impedance spectroscopy (EIS), potentiodynamic polarization and Open Circuit Potential (OCP). The results demonstrated that the dispersion of PPy-GO hybrids in the epoxy coatings improved corrosion performance of coating compared to the other coatings and maximum corrosion resistance is achieved via adding 0.5 wt.% PPy-GO. This behavior related to the better dispersion and interaction between PPy-GOs hybrids and epoxy matrix compared to other fillers.

The Engagement of Hybrid Dispersion Compensation Schemes Performance Signature for Ultra Wide Bandwidth and Ultra Long Haul Optical Transmission Systems

This paper presents the performance signature of the engagement of hybrid symmetrical hybrid compensation techniques for ultra wide bandwidth and ultra long haul optical transmission systems. These schemes that are namely optigrating, ideal dispersion compensation fiber Bragg Grating (IDCFBG), and dispersion compensation fiber (DCF). The combination of mixing these techniques together which is called hybrid symmetrical dispersion compensation techniques in that case. The employment of these mixing schemes is in symmetrical configuration with the presence of Erbium doped fiber amplifiers in order to upgrade optical fiber system capacity to reach transmission distance up to 432 km and transmission data rate up to 320 Gb/s. Maximum signal quality factor, minimum bit error rate (BER), output optical signal to noise ratio, electrical received power after APD photodetector, noise figure, and gain are the major interesting performance parameters for measuring the system operation efficiency. It is observed that the optimum case for maximum quality factor and minimum BER is achieved with 15 m EDFA amplifier length and 150 mW EDFA pump power.

Multifunctional Nanocomposites with High Strength and Capacitance Using 2D MXene and 1D Nanocellulose.

The family of two-dimensional (2D) metal carbides and nitrides, known as MXenes, are among the most promising electrode materials for supercapacitors thanks to their high metal-like electrical conductivity and surface-functional-group-enabled pseudocapacitance. A major drawback of these materials is, however, the low mechanical strength, which prevents their applications in lightweight, flexible electronics. A strategy of assembling freestanding and mechanically robust MXene (Ti3 C2 Tx ) nanocomposites with one-dimensional (1D) cellulose nanofibrils (CNFs) from their stable colloidal dispersions is reported. The high aspect ratio of CNF (width of ≈3.5 nm and length reaching tens of micrometers) and their special interactions with MXene enable nanocomposites with high mechanical strength without sacrificing electrochemical performance. CNF loading up to 20%, for example, shows a remarkably high mechanical strength of 341 MPa (an order of magnitude higher than pristine MXene films of 29 MPa) while still maintaining a high capacitance of 298 F g-1 and a high conductivity of 295 S cm-1 . It is also demonstrated that MXene/CNF hybrid dispersions can be used as inks to print flexible micro-supercapacitors with precise dimensions. This work paves the way for fabrication of robust multifunctional MXene nanocomposites for printed and lightweight structural devices.

Polyurethane/Acrylic Hybrid Waterborne Dispersions: Synthesis, Properties and Applications

Polyurethane (PU)/acrylic hybrid dispersions are an important class of polymeric dispersions that are produced on an industrial scale. In this review, we detail the design and synthesis of PU/acrylic dispersions, with a particular focus on how the structure of the hybrid can be tuned toward commercial applications. After a brief introduction, we describe the building blocks used in each polymer and their role in the synthesis/application of the final dispersion. Subsequently, we discuss the range of procedures that have been developed for the synthesis of such hybrids and how the structure of the hybrids influences the physical properties of films cast from the dispersion. Finally, we highlight commercial applications of PU/acrylic hybrids, with a focus on potential future developments.

Design and characterization of an oxides hybrid dispersion strengthened iron based composite with a graded and architectural microstructure

A graded Fe based composite reinforced with tetragonal yttria stabilized zirconia, monoclinic zirconia, wüstite and at a less extent, Zr0.978Fe0.022O1.978 (tetragonal) and Zr0.85Y0.15O1.93 (cubic) was developed by high energy ball milling, compaction and sintering. Solid state sintering entailed (i) the growth of Fe grains which remained submicrometric and (ii) the coarsening of oxides reinforcements forming an interconnected network in the bulk graded composite.The increase of oxide reinforcements volume fraction enabled to obtain a material with a graded electrical resistivity and a slightly graded hardness; the bending resistance of the as-developed material was however decreased because of the weakness of the reinforcements – matrix bonds.

Copper matrix composites reinforced by rGO-MoS2 hybrid: Strengthening effect to enhancement of tribological properties

The potential of reduced graphene oxide-molybdenum sulfide (rGO-MoS2) hybrid as a self-lubricating reinforcement in the Cu-based composites for enhancement of mechanical and tribological properties is presented. The rGO-MoS2 was synthesized by a hydrothermal approach using highly dispersed graphene oxide as a platform material to grow the MoS2 nanosheets. The Cu-rGO-MoS2 composites having 2 wt% of rGO-MoS2 were prepared at 600, 650, 700 and 750 °C to probe the effect of sintering temperature on mechanical and tribological properties. Microscopic images of Cu-rGO-MoS2 composites based on SEM and HRTEM measurements along with corresponding area elemental distribution suggested the nearly uniform dispersion of rGO-MoS2 hybrid in the copper matrix via multidimensional interactions. The composites exhibited significantly improved hardness compared to pure copper, and it was attributed to freezing of the movement of the dislocations by rGO-MoS2. Incorporation of rGO-MoS2 in Cu resulted in a remarkable reduction in both the coefficient of friction and the wear rate. The improved friction and wear performances of composites have been ascribed to the self-lubricating action of rGO-MoS2 hybrid and the formation of rGO-MoS2 containing tribo-film on the counter face steel ball which facilitated the sliding events and protected the tribo-pair against the wear.

Heavy oil recovery by surface modified silica nanoparticle/HPAM nanofluids

Recent studies showed that the presence of dispersed nanoparticles (NPs) can increase the efficiency of polymer flooding. The network structure of polymer/NP hybrid dispersion has a significant impact on oil recovery. In this work, the surface of SiO2 NPs was modified by chemical grafting of octyltriethoxysilane (SiO2-OTES), oleic acid (SiO2-OAA) and stearic acid (SiO2-SAA) in an attempt to stimulate higher degree of interaction with partially hydrolyzed polyacrylamide (HPAM). Thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and Fourier transform infrared (FTIR) spectroscopy were employed to characterize the modified silica NPs. In addition, ζ-potential, cryo-scanning electron microscopy (cryo-SEM), and linear and nonlinear rheology were used to evaluate the characteristics of the hybrid dispersion of HPAM/unmodified and modified SiO2 NPs. ζ-potential measurements showed that the addition of HPAM improved the colloidal stability of the modified and unmodified SiO2 NPs dispersed in deionized (DI) water. Moreover, the addition of HPAM reduced the size of the NP aggregates by effective steric repulsion. Small and large shear oscillatory deformation results showed that SiO2-OTES NPs improved the HPAM network significantly. Nevertheless, HPAM/NPs network formed with all the different SiO2 NPs severely decreased the intra-cycle shear-thickening behavior of the polymer. Lastly, the addition of 0.2 wt% SiO2-OTES NPs to the HPAM solution increased the ultimate oil recovery from 71.4% to 75.7% OOIP.

The Influence of Macromolecular Structure and Composition on Mechanical Properties of Films Cast from Solvent‐Free Polyurethane/Acrylic Hybrid Dispersions

AbstractPolyurethane (PU) /acrylic dispersions are of great commercial interest due to the synergetic combination of the PU and acrylic polymers. In this work, a series of PU/acrylic dispersions is synthesized by a solvent‐free technique and the influence of colloidal structure, grafting between the two polymers, and the nature of the two polymer phases themselves on the mechanical properties of films cast from the dispersions is explored. TEM analysis shows that the particles have a PU shell/acrylic core structure which is translated into the morphology of films cast from the dispersions. This particle/film morphology leads to the acrylic copolymer acting as a filler material and allows high Tg copolymers to be employed, leading to films with very high mechanical strength. Grafting of the PU and acrylic phases leads to increased compatibility but has little effect on the mechanical properties which are largely determined by the hardness of both the diol used in the PU synthesis and more importantly the acrylic (co)polymer composition. This work allows us to propose a series of design principles in order to synthesize PU/acrylic hybrids with controlled mechanical properties.

Hybrid Dispersion Compensating Modules: A Better Solution for Mitigating Four-Wave Mixing Effects

Four-wave mixing effects mitigation techniques in wavelength division multiplexing systems which utilize hybrid configurations of dispersion compensating devices like dispersion compensating fiber, fiber bragg grating and optical phase conjugator are presented in this paper. These configurations have been simulated and the output results have been compared to find out the best alternative for four-wave mixing mitigation purpose. The comparison is carried out on the basis of parametric analysis and optimized parameter values. Optimization of important parameters has been done keeping a constraint on values of quality factor and minimum bit error rate values.

The effect of cellulose nanocrystals and pH value on the flotation process for extraction of minerals

Nowadays, the development of the new flotation reagents is focused on the environmental-friendly technologies and reducing the costs of industrial wastes treatment and re-cultivation as well. Biopolymer particles are anattractive object for designing effective non-toxic processes of enrichment and extraction of valuable mineral raw materials. The effect of cellulose nanocrystals particles on the electrokinetic properties of hybrid and individual dispersions of silica and titania was studied. The obtained data will allow to implement an effective flotation process of titanium-containing or titanium oxide ores on the example of leucoxene ores of the Yaregskoye deposit, Komi Republic (Russia). Calculations of the interaction of the minerals surface (titania and silica) with nanosized cellulose particles based on the theory of DLVO are presented.

Correlating microstructure and performance of PU/(meth)acrylic hybrids as hardwood floor coating

In this work chemically grafted PU/(meth)acrylic hybrid dispersions for wood floor coating applications were synthesized using functional monomers containing hydroxyl groups as well as different vinyl functionalities (acrylic, allylic and methacrylic) to graft the polyurethane and acrylic polymer phases. A complete study of the effect of the type of functional monomer and polymerization mode of (meth)acrylic monomers (batch and semibatch) on the polymer characteristics, particle and film morphology and final properties of the films as wood floor coatings is presented. It is shown that using monomers with lower reactivity during the acrylic polymerization, such as glycidyl mono-allyl ether, limits the formation of a gel fraction, whilst more reactive double bonds, such as the of glycidyl methacrylate, leads to high gel content and significantly higher molar mass of the gel fraction. Using TEM analysis it is demonstrated that more homogeneous particle and film morphologies were obtained in the case of grafted hybrids. The impact of these features on the properties of the coating is discussed. It is shown that grafted polymer films had higher Young´s modulus and strain hardening than the non-grafted ones and this effect is more pronounced in the case of functional monomers that led to hybrids with higher gel content. Finally, it is shown that the wood floor coatings prepared with these PU/(meth)acrylic hybrid dispersions had final properties comparable to a commercially available reference coating.

Studies on Synthesis and Characterization of Aqueous Hybrid Silicone-Acrylic and Acrylic-Silicone Dispersions and Coatings. Part I

The objective of the study was to investigate the effect of the method of synthesis on properties of aqueous hybrid silicone-acrylic (SIL-ACR) and acrylic-silicone (ACR-SIL) dispersions. SIL-ACR dispersions were obtained by emulsion polymerization of mixtures of acrylic and styrene monomers (butyl acrylate, styrene, acrylic acid and methacrylamide) of two different compositions in aqueous dispersions of silicone resins synthesized from mixtures of silicone monomers (octamethylcyclotetrasiloxane, vinyltriethoxysilane and methyltriethoxysilane) of two different compositions. ACR-SIL dispersions were obtained by emulsion polymerization of mixtures of the same silicone monomers in aqueous dispersions of acrylic/styrene copolymers synthesized from the same mixtures of acrylic and styrene monomers, so the compositions of ACR and SIL parts in corresponding ACR-SIL and SIL-ACR hybrid dispersions were the same. Examination of the properties of hybrid dispersions (particle size, particle structure, minimum film forming temperature, Tg of dispersion solids) as well as of corresponding coatings (contact angle, water resistance, water vapour permeability, impact resistance, elasticity) and films (tensile strength, elongation at break, % swell in toluene), revealed that they depended on the method of dispersion synthesis that led to different dispersion particle structures and on composition of ACR and SIL part. Generally, coatings produced from hybrid dispersions showed much better properties than coatings made from starting acrylic/styrene copolymer dispersions.