Non-homogeneous Dispersion Research Articles

Comparison of elvaloy and styrene-butadiene-styrene added polymer modified bitumen

One of the methods used to produce road pavements resistant to increased traffic volume and harsh environmental conditions is to improve the properties of bituminous binders, such as high temperature resistance and aging resistance, by using various additives. Styrene-Butadiene-Styrene and Elvaloy are two different commercial additives that are frequently used in pavement construction. In this study, the performance of three different B50/70 grade pure bitumens was modified by using Elvaloy at 1.6%, 1.7%, and 1.8%, and five different B50/70 grade pure bitumens were modified using 4.0%, 4.5%, and 5.0% Styrene-Butadiene-Styrene. Penetration, softening point, elastic recovery, flash point, storage stability, dynamic shear rheometer, beam bending rheometer, rotational thin film oven, and pressure aging vessel tests were applied to the binders in accordance with the Polymer Modified Bitumen technical specifications. According to the test results, it was determined that the additive rates for both modifiers are the optimum values in accordance with the specification. The results of the storage stability tests also showed that the non-homogeneous dispersion of the Styrene-Butadiene-Styrene modified binders during mixing had a significant effect on the behaviour of the binder after storage.

Investigation of tribological properties of polypropylene (PP)—Acrylonitrile butadiene styrene (ABS) blends reinforced with graphene nano-platelets (GNPs)

The tribological response of PP-ABS/GNPs nanocomposites fabricated via extrusion and injection molding with varying wt% GNPs fractions were examined under varying normal load and sliding speed wear test parameters. The specimens with 3% GNPs and 11% GNPs respectively exhibited the lowest and highest specific wear rates and COF under all test conditions. Increased load led to significantly reduced COF values, whereas increased sliding speed led to a slight reduction in COF by contributing to the formation of a continuous transfer layer. Addition of GNPs helped to retain the worn material on the contact surface and led to improved wear resistance up to the weight fraction of 3% after which non-homogeneous dispersion of GNPs occurred.

Characterization of UV Light Curable Piezoelectric 0-0-3 Composites Filled with Lead-Free Ceramics and Conductive Nanoparticles

Lead-free piezoelectric materials are essential for our healthy future but offer lower performance than lead-based materials. Different material combinations are explored to improve the performance of lead-free materials. By filling the UV light curable photopolymer resin with 30 vol.% lead-free piezoelectric ceramics and with up to 0.4 wt.% conductive nanofillers, thin and flexible piezoelectric 0-0-3 composites are formed. Two particle sizes of Potassium Sodium Niobate (KNN) and Barium Titanate (BTO) ceramics were used with four conductive nanofillers: Graphene Nanoplatelets (GNPs), Multi-Walled Carbon Nanotubes (MWCNTs), and two types of Graphene Oxide (GO). Resulting high viscosity suspensions are tape-cast in a mold as thin layers and subsequently exposing them to UV light, piezoelectric composite sensors are formed in 80 s. Even low nanofiller concentrations increase relative permittivities, however, they strongly reduce curing depth and increase undesirable dielectric losses. Non-homogeneous dispersion of nanofillers is observed. In total, 36 different compositions were mixed and characterized. Only six selected material compositions were investigated further by measuring mechanical, dielectric, and piezoelectric properties. Results show KNN composite performance as piezoelectric sensors is almost six times higher than BTO composite performance.

Non-homogeneous dispersion of graphene in polyacrylonitrile substrates induces a migrastatic response and epithelial-like differentiation in MCF7 breast cancer cells

BackgroundRecent advances from studies of graphene and graphene-based derivatives have highlighted the great potential of these nanomaterials as migrastatic agents with the ability to modulate tumor microenvironments. Nevertheless, the administration of graphene nanomaterials in suspensions in vivo is controversial. As an alternative approach, herein, we report the immobilization of high concentrations of graphene nanoplatelets in polyacrylonitrile film substrates (named PAN/G10) and evaluate their potential use as migrastatic agents on cancer cells.ResultsBreast cancer MCF7 cells cultured on PAN/G10 substrates presented features resembling mesenchymal-to-epithelial transition, e.g., (i) inhibition of migratory activity; (ii) activation of the expression of E-cadherin, cytokeratin 18, ZO-1 and EpCAM, four key molecular markers of epithelial differentiation; (iii) formation of adherens junctions with clustering and adhesion of cancer cells in aggregates or islets, and (iv) reorganization of the actin cytoskeleton resulting in a polygonal cell shape. Remarkably, assessment with Raman spectroscopy revealed that the above-mentioned events were produced when MCF7 cells were preferentially located on top of graphene-rich regions of the PAN/G10 substrates.ConclusionsThe present data demonstrate the capacity of these composite substrates to induce an epithelial-like differentiation in MCF7 breast cancer cells, resulting in a migrastatic effect without any chemical agent-mediated signaling. Future works will aim to thoroughly evaluate the mechanisms of how PAN/G10 substrates trigger these responses in cancer cells and their potential use as antimetastatics for the treatment of solid cancers.Graphical

Biodegradable Poly(Butylene Adipate-Co-Terephthalate) and Thermoplastic Starch-Blended TiO2 Nanocomposite Blown Films as Functional Active Packaging of Fresh Fruit

Biodegradable polymers can be used for eco-friendly, functional, active packaging to preserve food quality. Incorporation of titanium dioxide (TiO2) nanoparticles into polymer packaging enhances ethylene-scavenging activity and extends the shelf-life of fresh produce. In this study, TiO2 nanoparticles were incorporated into biodegradable poly(butylene adipate-co-terephthalate) (PBAT)- and thermoplastic cassava starch (TPS)-blended films to produce nanocomposite packaging via blown-film extrusion. The effects of TiO2 on morphology, packaging properties, and applications as functional packaging for fresh produce were investigated. Increased TiO2 in the film packaging increased amorphous starch content and hydrogen bonding by interacting with the TPS phase of the polymer blend, with negligible chemical interaction with the PBAT component and identical mechanical relaxation in the PBAT phase. Surface topography indicated void space due to non-homogeneous dispersion causing increased oxygen and carbon dioxide permeability. Homogeneous dispersion of fine TiO2 nanoparticles increased mechanical strength and reduced oxygen, carbon dioxide, and water vapor permeability. Films containing TiO2 also showed efficient oxygen-scavenging activity that removed residual oxygen from the package headspace dependent on the levels and morphology of nanoparticles in the film matrices. Banana fruit packaged in films containing TiO2 recorded slower darkening color change and enhanced shelf-life with increasing TiO2 content.

The enhanced mechanical properties and strain-hardening capability of CNT/Al composites achieved by heterogeneous micro-laminated architecture

A smart approach was adopted to fabricate a heterogeneous 1.5 wt% CNT/Al matrix possessing enhanced mechanical properties. The heterostructured-composite showed an excellent ultimate compressive strength of 372.19 MPa, which was approximately 33% and 76% higher than that of its homogeneous counterpart (279.83 MPa) and the monolithic Al (211.56 MPa), while keeping almost the same ultimate strain (40.5%) to that of the Al matrix (41.1%). It was proved that the discontinuous addition of CNTs to the matrix via several stages of low-energy milling (in the presence of PCA) followed by a high-energy dry-milling stage (without PCA) brought about a nonhomogeneous dispersion of CNTs in the matrix providing the opportunity for the development of heterogeneous microlaminated architecture, and finally enhanced the combination of strength and ductility of the resultant composite. The process would be technologically applicable for developing strong and ductile metal-matrix composites with different nanofillers.

Ruthenium-Iridium Nanocrystals Anchored Homogeneously on MOF-Derived Support for Efficient and Stable Oxygen Evolution in Acidic and Neutral Media

Achieving efficient and stable oxygen evolution reaction (OER) in acidic or neutral medium is of paramount importance for hydrogen production via proton exchange membrane water electrolysis (PEM-WE). Supported iridium based nanoparticles (NPs) are the state-of-the-art OER catalysts for PEM-WE, but the non-homogeneous dispersion of these NPs on the support together with their non-uniform sizes usually lead to catalyst migration and agglomeration under strongly corrosive and oxidative OER conditions, eventually causing the loss of active surface area and/or catalytic species and thereby the degradation of OER performance. Here, we design a catalyst comprising surface atomic-step enriched ruthenium-iridium (RuIr) nanocrystals homogeneously dispersed on a metal organic framework (MOF) derived carbon support (RuIr@CoNC), which shows outstanding catalytic performance for OER with high mass activities of 2041, 970 and 205 A gRuIr -1 at an overpotential of 300 mV and can sustain continuous OER electrolysis up to 40, 45 and 90 hours at 10 mA cm-2 with minimal degradation, in 0.5 M H2SO4 (pH = 0.3), 0.05 M H2SO4 (pH = 1) and PBS (pH = 7.2) electrolytes, respectively. Comprehensive experimental studies and density functional theory (DFT) calculations reveal that the good performance of RuIr@CoNC can be attributed, on one hand, to the presence of abundant atomic steps which maximize the exposure of catalytically active sites and lower the limiting potential of the rate-determining step of OER; on the other hand, to the strong interaction between RuIr nanocrystals and the CoNC support which endows homogeneous dispersion and firm immobilization RuIr catalysts on CoNC. The RuIr@CoNC catalysts also show outstanding performance in a single cell PEM electrolyzer, and their large-quantity synthesis is demonstrated.

Architectural design of MWCNT reinforced AlSi10Mg matrix composites with comprehensive mechanical properties

In the present study, we reported a powder processing technique for fabricating a heterogeneous AlSi10Mg matrix reinforced by CNTs with enhanced comprehensive mechanical properties. The as-designed composite with 2 wt.% CNT exhibited excellent compressive yield strength of 211 MPa, which was 384% higher than that of the as-received AlSi10Mg (44 MPa), and similar ultimate strain (31.5%) to that of the matrix (32.5%). It was found that the combination of low-energy wet-milling and high-energy dry-milling as well as addition of the as-received matrix powders/CNTs in the dry-milling stage resulted in non-homogeneous dispersion of CNTs in the matrix, facilitating the development of heterogeneous architecture, and finally giving rise to high strength and acceptable ductility. The applied strategy shed light on the development of strong and ductile composites with different metallic matrices and reinforcements.

The Effect of Different Oxygen Surface Functionalization of Carbon Nanotubes on the Electrical Resistivity and Strain Sensing Function of Cement Pastes.

Different studies in the literature indicate the effectiveness of CNTs as reinforcing materials in cement–matrix composites due to their high mechanical strength. Nevertheless, their incorporation into cement presents some difficulties due to their tendency to agglomerate, yielding a non-homogeneous dispersion in the paste mix that results in a poor cement–CNTs interaction. This makes the surface modification of the CNTs by introducing functional groups on the surface necessary. In this study, three different treatments for incorporating polar oxygen functional groups onto the surface of carbon nanotubes have been carried out, with the objective of evaluating the influence of the type and oxidation degree on the mechanical and electrical properties and in strain-sensing function of cement pastes containing CNTs. One treatment is in liquid phase (surface oxidation with HNO3/H2SO4), the second is in gas phase (O3 treatment at 25 and 160 °C), and a third is a combination of gas-phase O3 treatment plus NaOH liquid phase. The electrical conductivity of cement pastes increased with O3- and O3-NaOH-treated CNTs with respect to non-treated ones. Furthermore, the oxygen functionalization treatments clearly improve the strain sensing performance of the CNT-cement pastes, particularly in terms of the accuracy of the linear correlation between the resistance and the stress, as well as the increase in the gage factor from 28 to 65. Additionally, the incorporation of either non-functionalized or functionalized CNTs did not produce any significant modification of the mechanical properties of CNTs. Therefore, the functionalization of CNTs favours the de-agglomeration of CNTs in the cement matrix and consequently, the electrical conductivity, without affecting the mechanical behaviour.

A Circular Economy Virtuous Example—Use of a Stabilized Waste Material Instead of Calcite to Produce Sustainable Composites

This work reports and analyzes the mechanical properties of some composites obtained using stabilized waste with epoxy resins E-227. For comparison, correspondent composite samples were realized using calcite as a filler. The recovered stabilized waste was obtained by means of a new method to stabilize municipal solid waste incineration (MSWI) fly ash (FA), based on the use of bottom ash (BA). The aim of this paper is to show that the stabilization process, which can be considered a zero—waste treatment, produces inert materials, that can be reused as a filler. The production of new filler was made on a pilot plant, designed to verify the transferability of the proposed stabilization technology. Mechanical analysis revealed that flexural modulus raises by increasing the filler content around 30% wt, independently of filler type, stabilized sample or calcium carbonate. Mechanical properties are lower in the samples with the high amount of filler due to the crowding effect. The morphology of composite materials showed a non-homogeneous dispersion of particles in stabilized sample filler, characterized by large particle agglomerates. Finally, according to the ESCAPE simplified method, the obtained composites result more sustainable in comparison with the corresponding ones produced by using natural resources (like calcite). These findings open new possibilities for the reuse of the stabilized material, in frame of circular economy principles, with environmental and economic advantages.

Study of mechanism involved in synthesis of graphene oxide and reduced graphene oxide from graphene nanoplatelets

Graphene, a wonder material has inspired quest among researchers due to its numerous applications and exceptional properties. This paper highlights the mechanism and chemistry behind the fabrication of graphene oxide by using phosphoric acid. Chemical functionalization is of prime importance which avoids agglomeration of nanoparticles to attain inherent properties. As non-homogeneous dispersion limits its utilization due to interfacial interactions which restrict reactive sites to produce intercalated network. Thus, chemically functionalized graphene leads to stable dispersion and enhances thermal, mechanical and electrical properties of the resultant polymer composite materials. Solubility of graphene in aqueous solution is the major issue because graphene is hydrophobic, to rectify this oxygen containing hydrophilic groups must be introduced to make it compatible and this can be attained by covalent functionalization. Among all nanofiller GO has shown average particle size i.e. 95 nm and highest surface charge density. The characteristic changes were estimated using Raman spectra.

DURABILITY PERFORMANCE AND DIMENSIONAL STABILITY OF POLYPROPYLENE FIBER REINFORCED CONCRETE

In this study, the durability performance and dimensional stability of polypropylene fiber reinforced concrete mixture were investigated. For this purpose, two series of concrete mixtures, including a 0.45 water/cement ratio was prepared both in the absence and presence of fiber. A CEMI 42.5 R type portland cement and crushed limestone aggregate with a maximum particle size of 25 mm were used. In addition to the control mixture without fiber, three different concrete mixtures were prepared by adding polypropylene fiber as 0.4%, 0.8% and 1% of total volume into the mixture. The time-dependent fresh state properties, strength, ultrasonic pulse velocity, transport properties, drying shrinkage and freeze-thaw resistance of concrete mixtures, sodium sulfate attack and abrasion were investigated comparatively. Test results demonstrated that utilization of fiber affected the fresh properties of the concrete mixtures negatively. However, the 0.8% fiber-bearing mixture showed the highest performance in terms of durability and dimensional stability. Beyond this utilization ratio, the durability performance of the concrete mixture was negatively affected. The risk of nonhomogeneous dispersion of the fiber in the mixture was relatively high in the excess fiber-bearing mixture. Consequently, with the formation of flocculation in the mixture the void ratio of concrete mixture increased.

Ternary Cu–CNT–AlN composite coatings consolidated by cold spray deposition of mechanically alloyed powders

Ternary copper (Cu)–carbon nanotube (CNT)–aluminum nitride (AlN) composite coatings were consolidated by the cold gas dynamic spray (CGDS) deposition of mechanically alloyed (MA) powders. The MA powder and CGDS coating samples were characterized by weight and size measurements, optical microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD). The porosity and roughness of the coatings were examined by porosimetry and profilometry, respectively. Also, the wettability of the coatings in saturated liquid R134a refrigerant was investigated. The EDX analysis depicted the non-homogeneous dispersion of the AlN as well as the CNT. The XRD results revealed that the composite powders and coatings had undergone microstraining and grain size reduction due to deformation. Metallographic examination showed that the coating internal microstructures had lamellar and compacted features, which evidenced the severe deformation that resulted from the impact during particle deposition. Although the coatings had externally porous surfaces, they had dense and non-porous internal microstructures. Moreover, smaller pores were located inside the larger pores or craters on the surfaces. The addition of 10 vol.% and 20 vol.% AlN into the Cu–5CNT mixture produced ternary Cu–CNT–AlN composite coatings with fine pores that were directly open to the surfaces. Lastly, the coatings with AlN were more wettable in liquid R134a than the plain Cu plate and pure Cu and Cu–5CNT coatings.

Enzymatic degradation of graphene/polycaprolactone materials for tissue engineering

Graphene/polycaprolactone composites have proven to be promising substrates for biodegradable tissue engineering scaffolds for electro-responsive tissue types. The degradation behaviour of these materials will be critical to any future application. To that end, the effect of chemically converted reduced graphene oxide (CCG) on the enzymatic degradation of graphene/polycaprolactone composites in phosphate buffered saline was examined. Two types of graphene/polycaprolactone composites were tested; a simple blend and our previously developed covalently-linked composites. A number of graphene concentrations of each type were tested. Covalently linked graphene/polycaprolactone (cPCl-CCG) showed a consistent degradation profile maintaining the graphene:PCL ratio throughout the degradation process. However, the mixed blended sample (mixPCl-CCG) showed inconsistent graphene loss indicative of non-homogeneous dispersion throughout the polymer matrix. Increasing the graphene concentration up to 1 wt% did not change the rate of degradation but at higher concentrations degradation was slowed. The degradation products were also shown to be non-toxic to the proliferating cells.

Dispersion of SiC particles in mechanical stirring of A356-SiCp liquid

In order to clarify the dispersion of SiC particles in straight-blade mechanical stirring of Al-SiCp liquid, the dispersion of SiC particles in A356-3.5% SiCp (volume fraction) liquid in a cylindrical crucible was studied. The relationship between rotating speed of stirrer and radial relative deviation of SiCp content in A356 liquid between the center and the periphery of crucible was established in the conditions of 35° for the gradient angle α of blade and 10 mm/s for the speed of moving up and down of stirrer. The results show that the radial relative deviation of SiCp content increases gradually with increasing the rotating speed of stirrer. When the rotating speed of stirrer is 200 r/min, the vertical dispersion of SiC particles in A356 liquid is even, but the radial relative deviation of SiCp content is 0.24. Consequently, the nonhomogeneous dispersion of SiC particles in A356 liquid is mainly resulted from the nonhomogeneous radial dispersion of SiC particles.

Extrusion of Nanocellulose‐Reinforced Nanocomposites Using the Dispersed Nano‐Objects Protective Encapsulation (DOPE) Process

AbstractCross‐linked alginate capsules a few millimeters in diameter have been formed by immersion in a CaCl2 solution. When adding cellulose whiskers or microfibrillated cellulose to the aqueous alginate solution, nanocomposite capsules containing 40 wt.% cellulosic nanoparticles were obtained. The morphology and compression strength of these capsules were investigated by microscopic observations and crushing tests, respectively. The capsules were extruded with a thermoplastic polymer. Visual inspection of the ensuing films shows a nonhomogeneous dispersion of the capsules that kept their integrity after extrusion. It results in preliminary disappointing mechanical properties of the composite films. However, further investigation is in progress to optimize this simple and ecofriendly process. magnified image

Application and Non-Homogeneous Index Grey Model NIGM(1,1,k)

To improve the modeling accuracy of grey model and broaden its application fields, a non-homogeneous index grey model (termed NIGM(1,1,k)) was built, which is based on the non-homogeneous dispersion index function and the formula computing the parameters of grey model NIGM(1,1,k) was proposed through the least square method. The function of the time response sequence of the proposed grey model was solved by taking differential equations as a deductive reasoning tool. The proposed grey NIGM(1,1,k) model has the characteristic of high precision as well as high adaptability. Examples validate the practicability and reliability of the proposed model.

Slip ratio in dispersed viscous oil–water pipe flow

In this article, dispersed flow of viscous oil and water is investigated. The experimental work was performed in a 26.2-mm-i.d. 12-m-long horizontal glass pipe using water and oil (viscosity of 100 mPa s and density of 860 kg/m 3) as test fluids. High-speed video recording and a new wire-mesh sensor based on capacitance (permittivity) measurements were used to characterize the flow. Furthermore, holdup data were obtained using quick-closing-valves technique (QCV). An interesting finding was the oil–water slip ratio greater than one for dispersed flow at high Reynolds number. Chordal phase fraction distribution diagrams and images of the holdup distribution over the pipe cross-section obtained via wire-mesh sensor indicated a significant amount of water near to the pipe wall for the three different dispersed flow patterns identified in this study: oil-in-water homogeneous dispersion (o/w H), oil-in-water non-homogeneous dispersion (o/w NH) and Dual continuous (Do/w & Dw/o). The phase slip might be explained by the existence of a water film surrounding the homogeneous mixture of oil-in-water in a hidrofilic–oilfobic pipe.

Formation of Phosgene During Welding Activities in an Atmosphere Containing Chlorinated Hydrocarbons

The formation of phosgene During welding activities in an atmosphere containing chlorinated hydrocarbons was investigated. Four different chlorinated hydrocarbons were studied under laboratory conditions. Results are presented as time-averaged phosgene concentration in a total volume of 250 L of air being purged through a 52-L reaction vessel during 20 min. It was found that the formation of phosgene was in the order dichloromethane < Freon-22 < carbon tetrachloride << trichoroethylene. Local concentrations may be higher depending on dispersion phenomena. The interpretation in terms of occupational health was rather difficult because of the interaction with smoke particles and because of possible nonhomogeneous dispersion of phosgene around the workers. In the case of dichloromethane and carbon tetrachloride the short-term maximum allowable concentration (MAC) of phosgene was not attained at the respective MAC values of the chlorinated hydrocarbons themselves. In the case of trichloroethylene and Freon-22, however, the short-term MAC-value of phosgene was attained even when the concentration was still much below the respective MAC-values.

The use of high-sensitivity differential scanning calorimetry to characterise dilute aqueous dispersions of surfactants

Four synthetic surfactants, consisting of alkyi chains of either 16 or 18 carbon units, with a polar head of either three or seven ethylene oxide units (termed C16(EO)3 C18(EO)3, C16(EO)7 and C18(EO)7) have been studied using thermal analysis in both their hydrated and non-hydrated states. The non-hydrated samples were investigated using differential thermal analysis (DTA), and dilute aqueous dispersions were studied using high-sensitivity differential scanning calorimetry (HSDSC). The non-hydrated (EO)3 surfactants exhibited a single melting transition, whilst the equivalent experiment for the (EO)7 systems revealed a pre-melting transition, which could be a change in crystal structure. Multiple transitions were observed with all of the hydrated samples following HSDSC investigation. These transitions are probably related to different levels of hydration of a non-homogeneous dispersion of the surfactant in the water. The following general conclusions were reached: the surfactants exhibit a phase transition at a temperature which is predominantly determined by the alkyl chain length, but the increasing chain length of the head group (polyoxyethylene) causes a decrease in transition temperature. It has proved possible to estimate the probable contribution to the enthalpy of transition that is associated with a methylene group and an ethylene oxide unit. This allows predictions to be made regarding the behaviour of similar surfactants. It was concluded that HSDSC is potentially of great value for studies of dilute solutions/dispersions of surfactants.