Search results for: PLA based nanocomposites

Authors: S. Said, Samira M. Abdel-Azim, Aya M. Matloob

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Nowadays, one of the most important industries is how to prepare a starting material like (styrene) which is used for the preparation of many petrochemical products in simple and inexpensive ways. Oxidative dehydrogenation of ethylbenzene (using CO2 as a soft oxidant) can solve this issue when using highly effective catalysts like SnO₂ and its nanocomposites (V₂Ox/SnO₂.) This study shows the effect of different synthesis methods of SnO₂ either by ethylene glycol or MOF then, uses the impregnation method for the preparation of its nanocomposite catalysts (V₂Ox/SnO₂.). The prepared catalysts were characterized by using different analytical techniques like XRD, BET, FTIR, TGA, XPS, and H₂-TPR. Oxidative dehydrogenation experimental results demonstrated that the composite V loading of 1 and 5 wt.% V₂Ox/SnO₂ (MOF &EG) catalyst exhibited extraordinarily high catalytic performance with selectivity toward styrene formation > 90% at 500oC, which can be attributed to the superior surface, textural, and structural properties of nanocomposites catalysts.

Keywords: SnO₂, vanadium oxide, ethylbenzene dehydrogenation, styrene, CO₂

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Authors: Maryam Kiani, Abdul Basit Kiani

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Simple hydrothermal method to synthesize new nanocomposites consisting of nitrogen-doped graphene and NiFe₂O₄. By analyzing the X-Ray Powder Diffraction (XRD) images, we confirmed that the NiFe₂O₄ phase is pure and has a Face Centered Cubic (FCC) structure. The average size of the NiFe₂O₄ nanoparticles is approximately 40±2 nm. Additionally, we used X-ray photoelectron spectroscopy (XPS) to study the surface chemical composition and cation oxidation states of both the NiFe₂O₄ nanoparticles and the nitrogen-doped graphene/NiFe₂O₄ nanocomposites. A magnetic interaction between nitrogen doped graphene/NiFe₂O₄ was studied. Increases in hydrothermal synthesis temperature lead to the improved crystalline structure of NiFe₂O₄ nanoparticles, which improves the magnetic properties.

Keywords: nickel ferrite spinal, nitrogen doped graphene, magnetic nanocomposite, hydrothermal synthesis

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Authors: Vasu Velagapudi, G. Suresh

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PTFE/HNTs nanocomposites are fabricated with 4%, 6%, and 8% by weight fraction, and the optimization study of wear parameters are performed using response surface methodology (RSM). The experiments are carried out on a pin on disc (POD) wear tester under different operating parameters planned according to Taguchi L27 orthogonal array. The input factors considered are wt% HNTs addition, sliding velocity, load, and distance with three levels for each factor. From ANOVA: The factors load, speed and distance and their interactions have a significant effect on COF. Also for SWR, composition factor and interaction of load and speed are observed to be significant ( < 0.05) Optimum input parameters corresponding to desirability 1 are found to be: COF (0.11) and SWR (17.5)×10⁻⁶ (mm3/N-m) at 6.34 wt% of composition, 5N of load, 2 km of distance and 1 m/sec of velocity.

Keywords: PTFE/HNT, nanocomposites, response surface methodology (RSM), specific wear rate

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Authors: Ahmad Umar, Ahmed A. Ibrahim, Mohsen A. Alhamami

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This study introduces a facile synthesis method for synthesizing reduced graphene oxide (rGO) nanosheets with surface decoration of polyaniline (PANI). The resultant rGO@PANI nanocomposite (NC) exhibit substantial potential as advanced electrode materials for high-performance supercapacitors. The strategic integration of PANI onto the rGO surface serves dual purposes, effectively mitigating the agglomeration of rGO films and augmenting their utility in supercapacitor applications. The PANI coating manifests a highly porous and nanosized morphology, fostering increased surface area and optimized mass transport by reducing diffusion kinetics. The nanosized structure of PANI contributes to the maximization of active sites, thereby bolstering the efficacy of the nanocomposites for diverse applications. The inherent conductive nature of the rGO surface significantly expedites electron transport, thereby amplifying the overall electrochemical performance of the nanocomposites. To systematically evaluate the influence of PANI concentration on the electrode performance, varying concentrations of PANI were incorporated. Notably, an elevated PANI concentration was found to enhance the response owing to the unique morphology of PANI. Remarkably, the 5% rGO@PANI NC emerged as the most promising candidate, demonstrating exceptional response characteristics with a specific capacitance of 314.2 F/g at a current density of 1 A/g. Furthermore, this catalyst exhibits outstanding long-term stability, retaining approximately 92% of its capacitance even after enduring 4000 cycles. This research underscores the significance of the synergistic integration of rGO and PANI in the design of high-performance supercapacitors. The elucidation of the underlying mechanisms governing the improved electrochemical properties contributes to the fundamental understanding of nanocomposite behavior, thereby paving the way for the rational design of next-generation energy storage materials.

Keywords: reduced graphene oxide, polyaniline, nanocomposites, supercapacitors, energy storage

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Authors: Mohammed Omar

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Using Chenopodium murale leaf, gold nanoparticles (Au NP's) were biosynthesized effectively in an amicable strategy. The casting process was used to create composite layers of sodium alginate and polyvinyl pyrrolidone. Gold nanoparticles were incorporated into the polyvinyl pyrrolidone (PVP)/ sodium alginate (NaAlg) polymer blend by casting technique. Before and after exposure to different doses of gamma irradiation (2, 4, 6 Mrad), thin films of synthesized nanocomposites were analyzed. XRD revealed the amorphous nature of polymer blends (PVP/ NaAlg), which decreased by both Au NP's embedding and consecutive doses of irradiation. FT-IR spectra revealed interactions and differences within the functional groups of their respective pristine components and dopant nano-fillers. The optical properties of PVP/NaAlg – Au NP thin films (refractive index n, energy gap Eg, Urbach energy Eu) were examined before and after the irradiation procedure. Transmission electron micrographs (TEM) demonstrated a decrease in the size of Au NP’s and narrow size distribution as the gamma irradiation dose was increased. Gamma irradiation was found to influence the electrical conductivity of synthesized composite films, as well as dielectric permittivity (ɛ′) and dielectric losses (ε″).

Keywords: PVP, SPR, γ-radiations, XRD

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Authors: Jai Prakash, Promod Kumar, Chantel Swart, J. H. Neethling, A. Janse van Vuuren, H. C. Swart

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Ag nanoparticles (NPs) have been used as functional nanomaterials due to their optical and antibacterial properties. Similarly, TiO2 photocatalysts have also been used as suitable nanomaterials for killing cancer cells, viruses and bacteria. Here, we report on multifunctional plasmonic Ag-TiO2 nano-biocomposite synthesized by the sol-gel technique and their optical, surface enhanced Raman scattering (SERS) and antibacterial activities. The as-prepared composites of Ag–TiO2 with different silver content and TiO2 nanopowder were characterized by X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, energy-dispersed X-ray analysis (EDX), UV-vis and Raman spectroscopy. The Ag NPs were found to be uniformly distributed and strongly attached to the TiO2 matrix. The novel optical response of the Ag-TiO2 nanocomposites is due to the strong electric field from the surface plasmon excitation of the Ag NPs. The Raman spectrum of Ag-TiO2 nanocomposite was found to be enhanced as compared to TiO2. The enhancement of the low frequency band is evident. This indicates the SERS effect of the TiO2 NPs in close vicinity of Ag NPs. In addition, nanocomposites showed enhancement in the SERS signals of methyl orange (MO) dye molecules with increasing Ag content. The localized electromagnetic field from the surface plasmon excitation of the Ag NPs was responsible for the SERS signals of the TiO2 NPs and MO molecules. The antimicrobial effect of the Ag–TiO2 nanocomposites with different silver content and TiO2 nanopowder were carried out against the bacterium Staphylococcus aureus. The Ag–TiO2 composites showed antibacterial activity towards S. aureus with increasing Ag content as compared to the TiO2 nanopowder. These results foresee promising applications of the functional plasmonic metal−semiconductor based nanobiocomposites for both chemical and biological samples.

Keywords: metal-Semiconductor, nano-Biocomposites, anti-microbial activity, surface enhanced Raman scattering

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Authors: Mingmei Zhang, Xinyong Li

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Novel AgInS2/SnS2/RGO (AISR) heterojunctions photocatalysts were synthesized by simple hydrothermal method. The morphology and composition of the fabricated AISR nanocomposites were investigated by field-emission scanning electron microscopy (SEM), X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS). Moreover, the as-prepared AISR photocatalysts exhibited excellent photocatalytic activities for the degradation of Norfloxacin (NOR), mainly due to its high optical absorption and separation efficiency of photogenerated electron-hole pairs, as evidenced by UV–vis diffusion reflection spectra (DRS) and Surface photovoltage (SPV) spectra. Furthermore, laser flash photolysis technique was conducted to test the lifetime of charge carriers of the fabricated nanocomposites. The interfacial charges transfer mechanism was also discussed.

Keywords: AISR heterojunctions, electron-hole pairs, SPV spectra, charges transfer mechanism

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Authors: Nilay Tanrıver, Birgül Benli, Nilgün Kızılcan

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Polysulfone (PSU) is a specialty engineering polymer having various industrial applications. PSU is especially used in waste water treatment membranes due to its good mechanical properties, structural and chemical stability. But it is a hydrophobic material and therefore its surface aim to pollute easily. In order to resolve this problem and extend the properties of membrane, PSU surface is rendered hydrophilic by addition of the sepiolite nanofibers. Sepiolite is one of the natural clays, which is a hydrate magnesium silicate fiber, also one of the well known layered clays of the montmorillonites where has several unique channels and pores within. It has also moisture durability, strength and low price. Sepiolite channels give great capacity of absorption and good surface properties. In this study, nanocomposites of commercial PSU and Sepiolite were prepared by solvent mixing method. Different organic solvents and their mixtures were used. Rheological characteristics of PSU-Sepiolite solvent mixtures were analyzed, the solubility of nanocomposite content in those mixtures were studied.

Keywords: nanocomposite, polysulfone, rheology, sepiolite, solution mixing

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Authors: A. G. Pershina, P. S. Postnikov, M. E. Trusova, D. O. Burlakova, A. E. Sazonov

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Invention of magnetic-fluorescent nanocomposites is a rapidly developing area of research. The magnetic-fluorescent nanocomposite attractiveness is connected with the ability of simultaneous management and control of such nanocomposites by two independent methods based on different physical principles. These nanocomposites are applied for the solution of various essential scientific and experimental biomedical problems. The aim of this research is development of principle approach to nanobiohybrid structures with magnetic and fluorescent properties design. The surface of carbon-coated iron nanoparticles (Fe@C) were covalently modified by 4-carboxy benzenediazonium tosylate. Recombinant fluorescent protein TagGFP2 (Eurogen) was obtained in E. coli (Rosetta DE3) by standard laboratory techniques. Immobilization of TagGFP2 on the nanoparticles surface was provided by the carbodiimide activation. The amount of COOH-groups on the nanoparticle surface was estimated by elemental analysis (Elementar Vario Macro) and TGA-analysis (SDT Q600, TA Instruments. Obtained nanocomposites were analyzed by FTIR spectroscopy (Nicolet Thermo 5700) and fluorescence microscopy (AxioImager M1, Carl Zeiss). Amount of the protein immobilized on the modified nanoparticle surface was determined by fluorimetry (Cary Eclipse) and spectrophotometry (Unico 2800) with the help of preliminary obtained calibration plots. In the FTIR spectra of modified nanoparticles the adsorption band of –COOH group around 1700 cm-1 and bands in the region of 450-850 cm-1 caused by bending vibrations of benzene ring were observed. The calculated quantity of active groups on the surface was equal to 0,1 mmol/g of material. The carbodiimide activation of COOH-groups on nanoparticles surface results to covalent immobilization of TagGFP2 fluorescent protein (0.2 nmol/mg). The success of immobilization was proved by FTIR spectroscopy. Protein characteristic adsorption bands in the region of 1500-1600 cm-1 (amide I) were presented in the FTIR spectrum of nanocomposite. The fluorescence microscopy analysis shows that Fe@C-TagGFP2 nanocomposite possesses fluorescence properties. This fact confirms that TagGFP2 protein retains its conformation due to immobilization on nanoparticles surface. Magnetic-fluorescent nanocomposite was obtained as a result of unique design solution implementation – the fluorescent protein molecules were fixed to the surface of superparamagnetic carbon-coated iron nanoparticles using original diazonium salts.

Keywords: carbon-coated iron nanoparticles, diazonium salts, fluorescent protein, immobilization

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Authors: Glykeria A. Visvini, George N. Mathioudakis, Amaia Soto Beobide, Aris E. Giannakas, George A. Voyiatzis

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Polymeric nanocomposites have generated considerable interest in both academic research and industry because their properties can be tailored by adjusting the type & concentration of nano-inclusions, resulting in complementary and adaptable characteristics. The exceptional and/or unique properties of the nanocomposites, including the high mechanical strength and stiffness, the ease of processing, and their lightweight nature, are attributed to the high surface area, the electrical and/or thermal conductivity of the nano-fillers, which make them appealing materials for a wide range of engineering applications. Polymeric «breathable» membranes enabling water vapor permeability (WVP) can be designed either by using micro/nano-fillers with the ability to interrupt the continuity of the polymer phase generating micro/nano-porous structures or/and by creating micro/nano-pores into the composite material by uniaxial/biaxial stretching. Among the nanofillers, carbon nanotubes (CNTs) exhibit particular high WVP and for this reason, they have already been proposed for gas separation membranes. In a similar context, they could prove to be promising alternative/complementary filler nano-materials, for the development of "breathable" products. Polypropylene (PP) is a commonly utilized thermoplastic polymer matrix in the development of composite films, due to its easy processability and low price, combined with its good chemical & physical properties. PP is known to present several crystalline phases (α, β and γ), depending on the applied treatment process, which have a significant impact on its final properties, particularly in terms of WVP. Specifically, the development of the β-phase in PP in combination with stretching is anticipated to modify the crystalline behavior and extend the microporosity of the polymer matrix exhibiting enhanced WVP. The primary objective of this study is to develop breathable nano-carbon based (functionalized MWCNTs) PP composite membranes, potentially also avoiding the stretching process. This proposed alternative is expected to have a better performance/cost ratio over current stretched PP/CaCO3 composite benchmark membranes. The focus is to investigate the impact of both β-nucleator(s) and nano-carbon fillers on water vapor transmission rate properties of relevant PP nanocomposites.

Keywords: carbon nanotubes, nanocomposites, nucleating agents, polypropylene, water vapor permeability

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Authors: D. Ponnamma, E. Alper, P. Sharma, M. A. AlMaadeed

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Integrating efficient energy harvesting materials into soft, flexible and eco-friendly substrates could yield significant breakthroughs in wearable and flexible electronics. Here we present a tri phasic filler combination of one-dimensional titanium dioxide nanotubes, two-dimensional reduced graphene oxide, and three-dimensional strontium titanate, introduced into a semi crystalline polymer, Poly(vinylidene fluoride-co-hexafluoropropylene). Simple mixing method is adopted for the composite fabrication after ensuring a high interaction among the various fillers. The films prepared were mainly tested for the piezoelectric responses and the mechanical stretchability. The results show that the piezoelectric constant has increased while changing the total filler concentration. We propose an integration of these materials in fabricating energy conversion devices useful in flexible and wearable electronics.

Keywords: dielectric property, hydrothermal growth, piezoelectricity, polymer nanocomposites

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Authors: Raghvendra Singh Yadav, Ivo Kuritka, Jarmila Vilcakova, Pavel Urbanek, Michal Machovsky, David Skoda, Milan Masar

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The elastomer nanocomposites were synthesized by solution mixing method with an elastomer as a matrix and in situ thermally reduced graphene oxide (RGO) and spinel ferrite NiFe₂O₄ nanoparticles as filler. Spinel ferrite NiFe₂O₄ nanoparticles were prepared by the starch-assisted sol-gel auto-combustion method. The influence of filler on the microstructure, morphology, dielectric, electrical and magnetic properties of Reduced Graphene Oxide-Nickel Ferrite-Elastomer nanocomposite was characterized by X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, X-ray photoelectron spectroscopy, the Dielectric Impedance analyzer, and vibrating sample magnetometer. Scanning electron microscopy study revealed that the fillers were incorporated in elastomer matrix homogeneously. The dielectric constant and dielectric tangent loss of nanocomposites was decreased with the increase of frequency, whereas, the dielectric constant increases with the addition of filler. Further, AC conductivity was increased with the increase of frequency and addition of fillers. Furthermore, the prepared nanocomposites exhibited ferromagnetic behavior. This work was supported by the Ministry of Education, Youth and Sports of the Czech Republic – Program NPU I (LO1504).

Keywords: polymer-matrix composites, nanoparticles as filler, dielectric property, magnetic property

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Authors: M. Derradji, W. B. Liu

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The current work discusses the effects of adding various types of ceramic fillers on the curing behavior, thermal, mechanical, anticorrosion, and UV shielding properties of the bisphenol-A based phthalonitrile resins. The effects of different ceramic filler contents and sizes as well as their surface treatments are also discussed in terms of their impact on the morphology and mechanisms of enhancement. The synergistic effect obtained by these combinations extends the use of the phthalonitrile resins to more exigent applications such as aerospace and military. The presented results reveal the significant advantages that can be obtained from the preparation of hybrid materials based on phthalonitrile resins and open the way for further research in the field.

Keywords: mechanical properties, particle reinforced composites, polymer matrix composites (PMCs), thermal properties

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Authors: P. Pramod Kumar, Madhu Salumari, V. V. Subba Rao

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Due to their high strength-to-weight ratio, carbon nanotube (CNTs) reinforced polymer composites are being considered as one of the most promising nanocomposites which can improve the performance when used in structural applications. The buckling behavior is one of the most important parameter needs to be considered in the design of structural members like beams and plates. In the present paper, the elastic constants of CNT reinforced polymer composites are evaluated by using Mori-Tanaka micromechanics approach. Knowing the elastic constants, an analytical study is being conducted to investigate the buckling behavior of nanocomposites for different CNT volume fractions at different boundary conditions using first-order shear deformation theory (FSDT). The effect of stacking sequence and CNT radius on the buckling of beam has also been presented. This study is being conducted primarily with an intension to find the stiffening effect of CNTs when used in polymer composites as reinforcement.

Keywords: CNT, buckling, micromechanics, FSDT

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Authors: Ramanjit Kaur, N. C. Kothiyal

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The present study compares the improved mechanical strength of cement mortar nanocomposites (CNCs) using polycarboxylate superplasticizer (PCE-SP) stabilized graphene oxide or functionalized carbon nanotubes (SP-GO and SP-FCNT) as reinforcing agents. So, in the present study, GO, and FCNT have been sterically stabilized via superplasticizer. The obtained results have shown that a dosage of 0.02 wt% of SP-GO and 0.08 wt% of SP-FCNTs showed an improvement in compressive strength by 23.2% and 16.5%, respectively. On the other hand, incorporation of 0.04% SP-GO and SP-FCNT resulted in an enhanced split tensile strength of 38.5% and 35.8%, respectively, as compared to the control sample at 90 days of curing. Mercury Intrusion Porosimetry (MIP) observations presented a decline in the porosity of 0.02% SP-GO-CNCs and 0.08% SP-FCNT-CNCs by 25% and 31% in comparison to the control sample. The improved hydration of CNCs contributing to the enhancement of physicomechanical strength has also been shown by SEM and XRD studies.

Keywords: graphene oxide, functionalized CNTs, steric stabilization, microstructure, crystalline behavior, pore structure refinement

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Authors: R. Kamarudzaman, A. Kalam, N. A. Mohd Fadzil

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Oil Palm Fruit Bunch Fiber (OPEFB) was used as secondary filler in HDPE/clay nanocomposites. The composites were prepared by melt compounding which contains High Density Polyethylene (HDPE), OPEFB fibers, Maleic Anhydride Graft Polyethylene (MAPE) and four different clay loading (3, 5, 7 and 10 PE nanoclay pellets per hundred of HDPE pellets). Four OPEFB sizes (180 µm, 250 µm, 300 µm and 355 µm) were added in the composites to investigate their effects on fracture toughness. Fracture toughness of the composites were determined according to ASTM D5045 and Single Edge Notch Bending (SENB) been employed during the test. The effects of alkali treatment were also investigated in this study. The results indicate that the fracture toughness slightly increased as clay loading increased. The highest value of fracture toughness was 0.47 and 1.06 MPa.m1/2 at 5 phr for both types of clay loading. The presence of filler as reinforcement with the matrix indicates the enhancement of composites compared to those without the filler.

Keywords: oil palm empty fruit bunch, fiber, polyethylene, polymer nanocomposite, impact strength

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Authors: L. N. Shubha, M. Kalpana, P. Madhusudana Rao

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Polyaniline/gold (PANI/Au) nanocomposite was prepared by in-situ chemical oxidation polymerization method. The synthesis involved the formation of polyaniline-gold nanocomposite, by in-situ redox reaction and the dispersion of gold nano particles throughout the polyaniline matrix. The nanocomposites were characterized by XRD, FTIR, TEM and UV-visible spectroscopy. The characteristic peaks in FTIR and UV-visible spectra confirmed the expected structure of polymer as reported in the literature. Further, transmission electron microscopy (TEM) confirmed the formation of gold nano particles. The crystallite size of 30 nm for nanoAu was supported by the XRD pattern. Further, the A.C. conductivity, dielectric constant (€’(w)) and dielectric loss (€’’(w)) of PANI/Au nano composite was measured using impedance analyzer. The effect of doping on the conductivity was investigated. The antibacterial activity was examined for this nano composite and it was observed that PANI/Au nanocomposite could be used as an antibacterial agent.

Keywords: AC-conductivity, anti-microbial activity, dielectric constant, dielectric loss, polyaniline/gold (PANI/AU) nanocomposite

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Authors: Sayed M. Ahmed, Sawsan S. Darwish, Nagib A. Elmarzugi, Mohammad A. Al-Dosari, Mahmoud A. Adam, Nadia A. Al-Mouallimi

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Historical stone surfaces and architectural heritage may undergo unwanted changes due to the exposure to many physical and chemical deterioration factors, the innovative properties of the nano - materials can have advantageous application in the restoration and conservation of the cultural heritage with relation to the tailoring of new products for protection and consolidation of stone. The current work evaluates the effectiveness of inorganic compatible treatments; based on nanosized particles of silica (SiO2) dispersed in silicon based product, commonly used as a water-repellent/ consolidation for the construction materials affected by different kinds of decay. The nanocomposites obtained by dispersing the silica nanoparticles in polymeric matrices SILRES® BS OH 100 (solventless mixtures of ethyl silicates), in order to obtain a new nanocomposite, with hydrophobic and consolidation properties, to improve the physical and mechanical properties of the stone material. The nanocomposites obtained and pure SILRES® BS OH 100 were applied by brush Experimental stone blocks. The efficacy of the treatments has been evaluated after consolidation and artificial Thermal aging, through capillary water absorption measurements, Ultraviolet-light exposure to evaluate photo-induced and the hydrophobic effects of the treated surface, Scanning electron microscopy (SEM) examination is performed to evaluate penetration depth, re-aggregating effects of the deposited phase and the surface morphology before and after artificialaging. Sterio microscopy investigation is performed to evaluate the resistant to the effects of the erosion, acids and salts. Improving of stone mechanical properties were evaluated by compressive strength tests, colorimetric measurements were used to evaluate the optical appearance. All the results get together with the apparent effect that, silica/polymer nanocomposite is efficient material for the consolidation of artistic and architectural sandstone monuments, completely compatible, enhanced the durability of sandstone toward thermal and UV aging. In addition, the obtained nanocomposite improved the stone mechanical properties and the resistant to the effects of the erosion, acids and salts compared to the samples treated with pure SILRES® BS OH 100 without silica nanoparticles.

Keywords: colorimetric measurements, compressive strength, nanocomposites, porous stone consolidation, silica nanoparticles, sandstone

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Authors: O. I. H. Dimitry, N. A. Mansour, A. L. G. Saad

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Natural sodium montmorillonite (NaMMT), Cloisite Na⁺ and two organophilic montmorillonites (OMMTs), Cloisites 20A and 15A were used. Polycaprolactone (PCL)/MMT composites containing 1, 3, 5, and 10 wt% of Cloisite Na⁺ and PCL/OMMT nanocomposites containing 5 and 10 wt% of Cloisites 20A and 15A were prepared via solution intercalation technique to study the influence of organic modifier loading on particle dispersion of PCL/ NaMMT composites. Thermal stabilities of the obtained composites were characterized by thermal analysis using the thermogravimetric analyzer (TGA) which showed that in the presence of nitrogen flow the incorporation of 5 and 10 wt% of filler brings some decrease in PCL thermal stability in the sequence: Cloisite Na+>Cloisite 15A > Cloisite 20A, while in the presence of air flow these fillers scarcely influenced the thermoxidative stability of PCL by slightly accelerating the process. The interaction between PCL and silicate layers was studied by Fourier transform infrared (FTIR) spectroscopy which confirmed moderate interactions between nanometric silicate layers and PCL segments. The electrical conductivity (σ) which describes the ionic mobility of the systems was studied as a function of temperature and showed that σ of PCL was enhanced on increasing the modifier loading at filler content of 5 wt%, especially at higher temperatures in the sequence: Cloisite Na⁺<Cloisite 20A<Cloisite 15A, and was then decreased to some extent with a further increase to 10 wt%. The activation energy E_σ obtained from the dependency of σ on temperature using Arrhenius equation was found to be lowest for the nanocomposite containing 5 wt% of Cloisite 15A. The dispersed behavior of clay in PCL matrix was evaluated by X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses which revealed partial intercalated structures in PCL/NaMMT composites and semi-intercalated/semi-exfoliated structures in PCL/OMMT nanocomposites containing 5 wt% of Cloisite 20A or Cloisite 15A.

Keywords: electrical conductivity, montmorillonite, nanocomposite, organoclay, polycaprolactone

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Authors: M. Dehghan, R. Al-Mahaidi, I. Sbarski

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An industrial epoxy adhesive used in Carbon Fiber Reinforced Polymer (CFRP)-strengthening systems was modified by dispersing multi-walled carbon nanotubes (MWCNTs). Nanocomposites were fabricated using solvent-assisted dispersion method and ultrasonic mixing. Thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA) and tensile tests were conducted to study the effect of nanotubes dispersion on the thermal and mechanical properties of the epoxy composite. Experimental results showed a substantial enhancement in the decomposition temperature and tensile properties of epoxy composite, while, the glass transition temperature (Tg) was slightly reduced due to the solvent effect. The morphology of the epoxy nanocomposites was investigated by SEM. It was proved that using solvent improves the nanotubes dispersion. However, at contents higher than 2 wt. %, nanotubes started to re-bundle in the epoxy matrix which negatively affected the final properties of epoxy composite.

Keywords: carbon fiber reinforced polymer, epoxy, multi-walled carbon nanotube, DMA, glass transition temperature

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Authors: Sanjeeb Sutradhar, Archita Patnaik

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Histidine is one of the twenty-two naturally occurring essential amino acids exhibiting two conformations, L-histidine and D-histidine. D-Histidine is biologically inert, while L-histidine is bioactive because of its conversion to neurotransmitter or neuromodulator histamine in both brain as well as central nervous system. The deficiency of L-histidine causes serious diseases like Parkinson’s disease, epilepsy and the failure of normal erythropoiesis development. Gold nanocomposites are attractive materials due to their excellent biocompatibility and are easy to adsorb on the electrode surface. In the present investigation, hydrophobic fullerene-C60 was functionalized with homocysteine via nucleophilic addition reaction to make it hydrophilic and to successively make the nanocomposite with in-situ prepared gold nanoparticles with ascorbic acid as reducing agent. The electronic structure calculations of the AuNPs@Hcys-C60 nanocomposite showed a drastic reduction of HOMO-LUMO gap compared to the corresponding molecules of interest, indicating enhanced electron transportability to the electrode surface. In addition, the electrostatic potential map of the nanocomposite showed the charge was distributed over either end of the nanocomposite, evidencing faster direct electron transfer from nanocomposite to the electrode surface. This nanocomposite showed catalytic activity; the nanocomposite modified glassy carbon electrode showed a tenfold higher kₑt, the electron transfer rate constant than the bare glassy carbon electrode. Significant improvement in its sensing behavior by square wave voltammetry was noted.

Keywords: fullerene-C60, gold nanocomposites, L-Histidine, square wave voltammetry

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Authors: Sayed Mansour, Mohammad Aldoasri, Nagib Elmarzugi, Nadia A. Al-Mouallimi

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The archaeological large stone used in construction of ancient Pharaonic tombs, temples, obelisks and other sculptures, always subject to physicomechanical deterioration and destructive forces, leading to their partial or total broken. The task of reassembling this type of artifact represent a big challenge for the conservators. Recently, the researchers are turning to new technologies to improve the properties of traditional adhesive materials and techniques used in re-assembly of broken large stone. The epoxy resins are used extensively in stone conservation and re-assembly of broken stone because of their outstanding mechanical properties. The introduction of nanoparticles to polymeric adhesives at low percentages may lead to substantial improvements of their mechanical performances in structural joints and large objects. The aim of this study is to evaluate the effectiveness of clay nanoparticles in enhancing the performances of epoxy adhesives used in re-assembly of archaeological massive stone by adding proper amounts of those nanoparticles. The nanoparticles reinforced epoxy nanocomposite was prepared by direct melt mixing with a nanoparticles content of 3% (w/v), and then mould forming in the form of rectangular samples, and used as adhesive for experimental stone samples. Scanning electron microscopy (SEM) was employed to investigate the morphology of the prepared nanocomposites, and the distribution of nanoparticles inside the composites. The stability and efficiency of the prepared epoxy-nanocomposites and stone block assemblies with new formulated adhesives were tested by aging artificially the samples under different environmental conditions. The effect of incorporating clay nanoparticles on the mechanical properties of epoxy adhesives was evaluated comparatively before and after aging by measuring the tensile, compressive, and Elongation strength tests. The morphological studies revealed that the mixture process between epoxy and nanoparticles has succeeded with a relatively homogeneous morphology and good dispersion in low nano-particles loadings in epoxy matrix was obtained. The results show that the epoxy-clay nanocomposites exhibited superior tensile, compressive, and Elongation strength. Moreover, a marked improvement of the mechanical properties of stone joints increased in all states by adding nano-clay to epoxy in comparison with pure epoxy resin.

Keywords: epoxy resins, nanocomposites, clay nanoparticles, re-assembly, archaeological massive stones, mechanical properties

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Authors: Babak Safaei, A. M. Fattahi

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Polymer/carbon nanotube nanocomposites have a wide range of promising applications Due to their enhanced properties. In this work, free vibration analysis of single-walled carbon nanotube-reinforced composite plates is conducted in which carbon nanotubes are embedded in an amorphous polyethylene. The rule of mixture based on various types of plate model namely classical plate theory (CLPT), first-order shear deformation theory (FSDT), and higher-order shear deformation theory (HSDT) was employed to obtain fundamental frequencies of the nanocomposite plates. Generalized differential quadrature (GDQ) method was used to discretize the governing differential equations along with the simply supported and clamped boundary conditions. The material properties of the nanocomposite plates were evaluated using molecular dynamic (MD) simulation corresponding to both short-(10,10) SWCNT and long-(10,10) SWCNT composites. Then the results obtained directly from MD simulations were fitted with those calculated by the rule of mixture to extract appropriate values of carbon nanotube efficiency parameters accounting for the scale-dependent material properties. The selected numerical results are presented to address the influences of nanotube volume fraction and edge supports on the value of fundamental frequency of carbon nanotube-reinforced composite plates corresponding to both long- and short-nanotube composites.

Keywords: nanocomposites, molecular dynamics simulation, free vibration, generalized, differential quadrature (GDQ) method

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Authors: Mohamed Eldessouki, Ebraheem Shady, Yasser Gowayed

Abstract:

Carbon nanotubes (CNTs) are known for having high elastic properties with high surface area that promote them as good candidates for reinforcing polymeric matrices. In composite materials, CNTs lack chemical bonding with the surrounding matrix which decreases the possibility of better stress transfer between the components. In this work, a chemical treatment for activating the surface of the multi-wall carbon nanotubes (MWCNT) was applied and the effect of this functionalization on the elastic properties of the epoxy nanocomposites was studied. Functional amino-groups were added to the surface of the CNTs and it was evaluated to be about 34% of the total weight of the CNTs. Elastic modulus was found to increase by about 40% of the neat epoxy resin at CNTs’ weight fraction of 0.5%. The elastic modulus was found to decrease after reaching a certain concentration of CNTs which was found to be 1% wt. The scanning electron microscopic pictures showed the effect of the CNTs on the crack propagation through the sample by forming stress concentrated spots at the nanocomposite samples.

Keywords: carbon nanotubes functionalization, crack propagation, elastic modulus, epoxy nanocomposites

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Authors: G. Korotcenkov, V. Brinzari, B. K. Cho

Abstract:

The thermoelectric properties of nano-scaled In₂O₃:Sn films deposited by spray pyrolysis are considered in the present report. It is shown that multicomponent In₂O₃:Sn-based films are promising material for the application in thermoelectric devices. It is established that the increase in the efficiency of thermoelectric conversion at C_Sn~5% occurred due to nano-scaled structure of the films studied and the effect of the grain boundary filtering of the low energy electrons. There are also analyzed the limitations that may appear during such material using in devices developed for the market of thermoelectric generators and refrigerators. Studies showed that the stability of nano-scaled film’s parameters is the main problem which can limit the application of these materials in high temperature thermoelectric converters.

Keywords: energy conversion technologies, thermoelectricity, In2O3-based films, power factor, nanocomposites, stability

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Authors: Junkal Gutierrez, Hernane S. Barud, Sidney J. L. Ribeiro, Agnieszka Tercjak

Abstract:

Nowadays the interest on green nanocomposites and on the development of more environmental friendly products has been increased. Bacterial cellulose has been recently investigated as an attractive environmentally friendly material for the preparation of low-cost nanocomposites. The formation of cellulose by laboratory bacterial cultures is an interesting and attractive biomimetic access to obtain pure cellulose with excellent properties. Additionally, properties as molar mass, molar mass distribution, and the supramolecular structure could be control using different bacterial strain, culture mediums and conditions, including the incorporation of different additives. This kind of cellulose is a natural nanomaterial, and therefore, it has a high surface-to-volume ratio which is highly advantageous in composites production. Such property combined with good biocompatibility, high tensile strength, and high crystallinity makes bacterial cellulose a potential material for applications in different fields. The aim of this investigation work was the fabrication of novel hybrid inorganic-organic composites based on bacterial cellulose, cultivated in our laboratory, as a template. This kind of biohybrid nanocomposites gathers together excellent properties of bacterial cellulose with the ones displayed by typical inorganic nanoparticles like optical, magnetic and electrical properties, luminescence, ionic conductivity and selectivity, as well as chemical or biochemical activity. In addition, the functionalization of cellulose with inorganic materials opens new pathways for the fabrication of novel multifunctional hybrid materials with promising properties for a wide range of applications namely electronic paper, flexible displays, solar cells, sensors, among others. In this work, different pathways for fabrication of multifunctional biohybrid nanopapers with tunable properties based on BC modified with amphiphilic poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) (EPE) block copolymer, sol-gel synthesized nanoparticles (titanium, vanadium and a mixture of both oxides) and functionalized iron oxide nanoparticles will be presented. In situ (biosynthesized) and ex situ (at post-production level) approaches were successfully used to modify BC membranes. Bacterial cellulose based biocomposites modified with different EPE block copolymer contents were developed by in situ technique. Thus, BC growth conditions were manipulated to fabricate EPE/BC nanocomposite during the biosynthesis. Additionally, hybrid inorganic/organic nanocomposites based on BC membranes and inorganic nanoparticles were designed via ex-situ method, by immersion of never-dried BC membranes into different nanoparticle solutions. On the one hand, sol-gel synthesized nanoparticles (titanium, vanadium and a mixture of both oxides) and on the other hand superparamagnetic iron oxide nanoparticles (SPION), Fe2O3-PEO solution. The morphology of designed novel bionanocomposites hybrid materials was investigated by atomic force microscopy (AFM) and scanning electron microscopy (SEM). In order to characterized obtained materials from the point of view of future applications different techniques were employed. On the one hand, optical properties were analyzed by UV-vis spectroscopy and spectrofluorimetry and on the other hand electrical properties were studied at nano and macroscale using electric force microscopy (EFM), tunneling atomic force microscopy (TUNA) and Keithley semiconductor analyzer, respectively. Magnetic properties were measured by means of magnetic force microscopy (MFM). Additionally, mechanical properties were also analyzed.

Keywords: bacterial cellulose, block copolymer, advanced characterization techniques, nanoparticles

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Authors: E.A. Kuchma

Abstract:

Photodynamic therapy (PDT) is considered an alternative and minimally invasive cancer treatment modality compared to chemotherapy and radiation therapy. PDT includes three main components: a photosensitizer (PS), oxygen, and a light source. PS is injected into the patient's body and then selectively accumulates in the tumor. However, the light used in PDT (spectral range 400–700 nm) is limited to superficial lesions, and the light penetration depth does not exceed a few cm. The problem of PDT (poor visible light transmission) can be solved by using X-rays. The penetration depth of X-rays is ten times greater than that of visible light. Therefore, X-ray radiation easily penetrates through the tissues of the body. The aim of this work is to develop universal nanocomposites for X-ray photodynamic therapy of deep and superficial tumors using scintillation nanoparticles of gadolinium fluoride (GdF3), doped with Tb3+, coated with a biocompatible coating (PEG) and photosensitizer RB (Rose Bengal). PEG@GdF3:Tb3+(15%) – RB could be used as an effective X-ray, UV, and photoluminescent mediator to excite a photosensitizer for generating reactive oxygen species (ROS) to kill tumor cells via photodynamic therapy. GdF3 nanoparticles can also be used as contrast agents for computed tomography (CT) and magnetic resonance imaging (MRI).

Keywords: X-ray induced photodynamic therapy, scintillating nanoparticle, radiosensitizer, photosensitizer

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Authors: M. Emami, R. Tarighi, R. Goodarzi

Abstract:

Maximal radar wave absorbing cannot be achieved by shaping alone. We have to focus on the parameters of absorbing materials such as permittivity, permeability, and thickness so that best absorbing according to our necessity can happen. The real and imaginary parts of the relative complex permittivity (ε_r' and ε_r") and permeability (µ_r' and µ_r") were obtained by simulation. The microwave absorbing property of carbon and Ni(C) is simulated in this study by MATLAB software; the simulation was in the frequency range between 2 to 12 GHz for carbon black (C), and carbon coated nickel (Ni(C)) with different thicknesses. In fact, we draw reflection loss (RL) for C and Ni-C via frequency. We have compared their absorption for 3-mm thickness and predicted for other thicknesses by using of electromagnetic wave transmission theory. The results showed that reflection loss position changes in low frequency with increasing of thickness. We found out that, in all cases, using nanocomposites as absorbance cannot get better results relative to pure nanoparticles. The frequency where absorption is maximum can determine the best choice between nanocomposites and pure nanoparticles. Also, we could find an optimal thickness for long wavelength absorbing in order to utilize them in protecting shields and covering.

Keywords: absorbing, carbon, carbon nickel, frequency, thicknesses

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Authors: Z. Terzopoulou, I. Koliakou, D. Bikiaris

Abstract:

Tissue engineering offers a new approach to regenerate diseased or damaged tissues such as bone. Great effort is devoted to eliminating the need of removing non-degradable implants at the end of their life span, with biodegradable polymers playing a major part. Poly(ε-caprolactone) (PCL) is one of the best candidates for this purpose due to its high permeability, good biodegradability and exceptional biocompatibility, which has stimulated extensive research into its potential application in the biomedical fields. However, PCL degrades much slower than other known biodegradable polymers and has a total degradation of 2-4 years depending on the initial molecular weight of the device. This is due to its relatively hydrophobic character and high crystallinity. Consequently, much attention has been given to the tunable degradation of PCL to meet the diverse requirements of biomedicine. Poly(ε-caprolactone) (PCL) is a biodegradable polyester that lacks bioactivity, so when used in bone tissue engineering, new bone tissue cannot bond tightly on the polymeric surface. Therefore, it is important to incorporate reinforcing fillers into PCL matrix in order to result in a promising combination of bioactivity, biodegradability, and strength. Natural clay halloysite nanotubes (HNTs) were incorporated into PCL polymeric matrix, via in situ ring-opening polymerization of caprolactone, in concentrations 0.5, 1 and 2.5 wt%. Both unmodified and modified with aminopropyltrimethoxysilane (APTES) HNTs were used in this study. The effect of nanofiller concentration and functionalization with end-amino groups on the physicochemical properties of the prepared nanocomposites was studied. Mechanical properties were found enhanced after the incorporation of nanofillers, while the modification increased further the values of tensile and impact strength. Thermal stability of PCL was not affected by the presence of nanofillers, while the crystallization rate that was studied by Differential Scanning Calorimetry (DSC) and Polarized Light Optical Microscopy (POM) increased. All materials were subjected to enzymatic hydrolysis in phosphate buffer in the presence of lipases. Due to the hydrophilic nature of HNTs, the biodegradation rate of nanocomposites was higher compared to neat PCL. In order to confirm the effect of hydrophilicity, contact angle measurements were also performed. In vitro biomineralization test confirmed that all samples were bioactive as mineral deposits were detected by X-ray diffractometry after incubation in SBF. All scaffolds were tested in relevant cell culture using osteoblast-like cells (MG-63) to demonstrate their biocompatibility

Keywords: biomaterials, nanocomposites, scaffolds, tissue engineering

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Authors: D. Berdous, H. Ferfera-Harrar

Abstract:

Superabsorbent polymers (SAPs) or hydrogels with three-dimensional hydrophilic network structure are high-performance water absorbent and retention materials. The in situ synthesis of metal nanoparticles within polymeric network as antibacterial agents for bio-applications is an approach that takes advantage of the existing free-space into networks, which not only acts as a template for nucleation of nanoparticles, but also provides long term stability and reduces their toxicity by delaying their oxidation and release. In this work, SAP/nanosilver nanocomposites were successfully developed by a unique green process at room temperature, which involves in situ formation of silver nanoparticles (AgNPs) within hydrogels as a template. The aim of this study is to investigate whether these AgNPs-loaded hydrogels are potential candidates for antimicrobial applications. Firstly, the superabsorbents were prepared through radical copolymerization via grafting and crosslinking of acrylamide (AAm) onto chitosan backbone (Cs) using potassium persulfate as initiator and N,N’-methylenebisacrylamide as the crosslinker. Then, they were hydrolyzed to achieve superabsorbents with ampholytic properties and uppermost swelling capacity. Lastly, the AgNPs were biosynthesized and entrapped into hydrogels through a simple, eco-friendly and cost-effective method using aqueous silver nitrate as a silver precursor and curcuma longa tuber-powder extracts as both reducing and stabilizing agent. The formed superabsorbents nanocomposites (Cs-g-PAAm)/AgNPs were characterized by X-ray Diffraction (XRD), UV-visible Spectroscopy, Attenuated Total reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR), Inductively Coupled Plasma (ICP), and Thermogravimetric Analysis (TGA). Microscopic surface structure analyzed by Transmission Electron Microscopy (TEM) has showed spherical shapes of AgNPs with size in the range of 3-15 nm. The extent of nanosilver loading was decreased by increasing Cs content into network. The silver-loaded hydrogel was thermally more stable than the unloaded dry hydrogel counterpart. The swelling equilibrium degree (Q) and centrifuge retention capacity (CRC) in deionized water were affected by both contents of Cs and the entrapped AgNPs. The nanosilver-embedded hydrogels exhibited antibacterial activity against Escherichia coli and Staphylococcus aureus bacteria. These comprehensive results suggest that the elaborated AgNPs-loaded nanomaterials could be used to produce valuable wound dressing.

Keywords: antibacterial activity, nanocomposites, silver nanoparticles, superabsorbent Hydrogel

Procedia PDF Downloads 246