Transport and solvent sensing characteristics of styrene butadiene rubber nanocomposites containing imidazolium ionic liquid modified carbon nanotubes

Obtaining strong interfacial interaction between filler and polymer matrix is very crucial for the fabrication of polymer nanocomposites with superior performance. Present study is aimed to fabricate high performance styrene butadiene rubber (SBR) nanocomposites with imidazolium type ionic liquid modified multiwalled carbon nanotube (MWCNT). Ionic liquid facilitates the dispersion of MWCNT in rubber matrix and it is obvious from transmission electron microscopy images. Diffusion of toluene through SBR nanocomposite membranes has been investigated as a function of surface modified MWCNT (f-MWCNT) content to analyze the chain dynamics and filler-polymer interactions. O₂ gas barrier effect of nanocomposites with special reference to the filler loading is explored. The substantial improvement in the barrier effect in presence of filler interpreted on the grounds of a theoretical model describing permeability of heterogeneous systems. Finally solvent sensing characteristics of prepared nanocomposites are also analyzed and it is observed that prepared nanocomposites can be used as a flexible solvent sensor.     

Quantification of Porosity in Ceramic Matrix Composites Using Thermography

Thermography is one of the Non-Destructive Evaluation methods used to qualitatively estimate the amount of porosity in as-manufactured ceramic matrix composite (CMC) parts. Through-transmission (TT) thermography allows for comparison of thermal diffusivity caused by differences in material density and porosity at different locations in the part. In this study, volume fraction of pores and its distribution in CMC samples containing different amounts of porosity was quantified using optical microscopy and X-ray computed tomography scans. TT thermography was done on the same specimens and images were analyzed to determine the distribution of thermal diffusivity. Comparison of porosity measurements and thermal diffusivity images shows an inverse correlation. A simple two-phase analytical model describing this relationship is derived for composites and its solution is shown to compare favorably with experimental data. In the absence of porosity data, the model can be used to estimate porosity directly from thermal diffusivity data.     

Room temperature multiferroic properties of BiFeO3–MnFe2O4 nanocomposites

The novel functionalities of multiferroic magneto-electric nanocomposites have spawned substantial scope for fast-paced memory devices and sensor applications. Following this, herein we report the development of nanocomposites with soft ferromagnetic MnFe₂O₄ and ferroelectric BiFeO₃ to fabricate a system with engineered multiferroic properties. A modified sol-gel route called Pechini method is demonstrated for the preparation of the (1-x) BiFeO₃-x MnFe₂O₄ (x = 10%, 30%, 50%, 70%) nanocomposites. The crystallographic phase, structure, and morphology are characterized by XRD, FESEM, and HRTEM. The accurate crystallite size and lattice strain are determined by Williamson-Hall plot method and a comparative study with Scherer's equation is carried out. TEM image evidences the interface between BiFeO₃ and MnFe₂O₄ nanoparticles in the composite. The room temperature magnetic response reveals the strong dependence of magnetic saturation, remanent magnetization, and coercivity of the nanocomposites on MnFe₂O₄ addition. The dielectric response and impedance analysis of the prepared nanocomposites are observed. The electrical performance of the composite is affected by grain, grain boundaries, and oxygen vacancies. The unsaturated P-E loops exhibit the leaky ferroelectric behavior for the nanocomposite. The intrinsic magnetoelectric coupling between ferroelectric BiFeO₃ and ferromagnetic MnFe₂O₄ has been determined by varying H_dc/H_ac and its maximum coupling coefficient (α) is found to be 25.39 mV/cmOe for 70% BiFeO₃ -30% MnFe₂O₄ nanocomposite. These distinctive and achievable characteristics of the nanocomposite would enable the designing of magnetic field sensors, spintronic devices, and multiferroic memory devices.     

Effect of reinforcement on the barrier and dielectric properties of epoxidized natural rubber–graphene nanocomposites

The influence of epoxidation level of natural rubber (i.e., ENR25, ENR50) on the dielectric and oxygen gas barrier properties of thermally reduced graphene oxide (GR) and graphite (GT) (with 2%·w/w) filled nanocomposites are investigated here. GR, GT filled epoxidized natural rubber (ENR) nanocomposites were fabricated by mechanical mixing using environment friendly two‐roll mill mixing method. Raman spectroscopy and Fourier transform infrared spectroscopy studies were carried out to investigate the extent of chemical interactions between GR and ENR. Morphological studies were done using transmission electron microscopy to evaluate the distribution of GR and GT in the ENR. The improved gas barrier and dielectric properties of GT‐ENR and GR–ENR composites synthesized by a novel green ecofriendly method is correlated with the chemical interactions among GT, GR, and ENR. POLYM. ENG. SCI., 55:2439–2447, 2015. © 2015 Society of Plastics Engineers     

Electrospun polyvinyl alcohol membranes incorporated with green synthesized silver nanoparticles for wound dressing applications

Electrospun membranes have the potential to act as an effective barrier for wounds from the external environment to prevent pathogens. In addition, materials with good antibacterial properties can effectively fight off the invading pathogens. In this paper, we report the development of a novel electrospun polyvinyl alcohol (PVA) membrane containing biosynthesized silver nanoparticle (bAg) for wound dressing applications. Plant extract from a medicinal plant Mimosa pudica was utilized for the synthesis of bAg. Synthesized bAg were characterized by Ultraviolet-Visible (UV) Spectroscopy and Fourier Transform Infrared Spectroscopy (FTIR). The morphology of bAg was obtained from Transmission Electron Microscopy (TEM) and found that they were spherical in morphology with average particle size 7.63?±?1.2?nm. bAg nanoparticles incorporated PVA membranes were characterized using several physicochemical techniques such as Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDS) and X-Ray Diffraction (XRD) analysis. Experimental results confirmed the successful incorporation of bAg in PVA fibers. PVA nanofiber membranes incorporated with bAg showed good mechanical strength, excellent exudate uptake capacity, antibacterial activity, blood compatibility and cytocompatibility.

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Polylactic acid/nano chitosan composite fibers and their morphological,physical characterization for the removal of cadmium(II) from water

This work discusses the fabrication of polylactic acid (PLA)/nano chitosan (nCHS) composite fibers by electrospinning method for Cd²⁺ metal ion adsorption from water. Here nCHS was synthesized by ionic gelation method and which is used as a reinforcement for PLA. The scanning electron microscopic analysis revealed that the addition 0.1 wt% nCHS has decreased the fiber diameter as well as the secondary pore size and hence imparted unique properties to electrospun composite fibers. The positive zeta potential values for the composites indicated their higher stability, though; the inclusion of nCHS reduced the crystallinity of the neat membranes. The contact angle measurements showed that the hydrophilicity of the composite was increased up to 0.1 wt% nCHS, and hence the surface energy was increased. Inverse gas chromatography results suggested that the basic character of the composites has intensified with the increase in nCHS addition. The adsorption capacity of the neat electrospun PLA and PLA–nCHS composites for Cd²⁺ ions were investigated and studies revealed that adsorption capacity of the composite was two times faster (approximately 70%) in comparison with neat PLA fibers. The increase in surface area as well as presence nCHS improved the adsorption capacity of the electrospun membrane.     

Nonlinear optical absorption studies of sol–gel derived Yttrium Iron Garnet (Y3Fe5O12) nanoparticles by Z-scan technique

Sol–gel synthesized Yttrium Iron Garnet (Y₃Fe₅O₁₂) nanoparticles were subjected to open aperture Z-scan studies in order to investigate the nonlinear optical (NLO) properties of these materials. The investigations were carried out using a Q-switched resonant Nd:YAG laser at a wavelength of 532 nm with different laser powers. Strong reverse saturable absorption (RSA) has been found when the sample is irradiated by the laser pulse of 10 Hz. The studies show that the material is highly nonlinear, which makes it useful for optical limiting applications.     

Development of oral-fluid-impervious and fracture-resistant silver–poly(methyl methacrylate) nanoformulations for intra-oral/extra-oral rehabilitation

Poly(methyl methacrylate) (PMMA) based dental prosthetic materials have an inferior transverse resistance value and a high water-retention capacity. These drawbacks cause frequent prosthesis fractures both inside and outside the mouth, which require the remaking or repair of the prosthesis. The mechanical and physical durability of the polymer matrix can be improved by the incorporation of a multifunctional filler. In this study, we focused on the reinforcing effect of silver nanoparticles (AgNPs) on the flexural properties of PMMA. Apart from that, the transport behavior of water and saliva through this composite matrix was also studied extensively. Morphological analyses with scanning electron microscopy (SEM) and atomic force microscopy imaging techniques confirmed the uniform distribution of nanoparticles in the matrix with an increased surface roughness proportionate to the amount of AgNPs. The flexural strength and modulus were enhanced by the addition of up to 5 wt % AgNPs (p < 0.05); we also observed a significant increase in the fracture resistance. The SEM micrographs of the fractured ends of AgNP-reinforced groups had smaller cracks compared to the large multidirectional cracks in the unreinforced group. The diffusion of oral fluid through the composite was investigated in detail as a function of the AgNP content, the nature of the solvent (water or saliva), and the temperature (5, 28, 37, or 60°C). The water and saliva uptake, diffusion, sorption, and permeation constants were investigated and were found to decrease with increasing AgNP loading. The transport properties could have been related to the morphology of the nanocomposites and followed the Korsmeyer–Peppas model. At high concentrations, the AgNPs formed a local filler–filler network in the polymer matrix. This network hindered the transport of water and saliva through the polymer. The outcome deduced from this study confirmed that the reinforced nanocomposites improved the durability of the denture base and could be an effective replacement for the conventional denture base. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47669.     

Hydrated metal salt and Y3Fe5O12–Na0.5K0.5NbO3-incorporated P(VDF-HFP) films: a promising combination of materials with multiferroic and energy harvesting properties

Journal of Materials Science - The composite approach is very effective in developing multiferroic systems with remarkable magnetoelectric coupling coefficients. In this work, P(VDF-HFP)-based...