Properties Of Nanocomposites Research Articles

Mechanical and thermal properties of rigid PVC and graphene nanocomposites obtained by melt–mixing

The effect of graphene (0.01, 0.1, 0.5 and 1 wt%) on the mechanical properties and thermal stability of rigid PVC was investigated. The morphology and thermal properties were analyzed by scanning electron microscopy (SEM) and thermogravimetric thermal analysis (TGA). Additionally, tensile properties, impact strength and hardness were determined. It was found that the addition of graphene can increase the impact strength and hardness and extend the thermal stability time of PVC.

Induced porous structure with a slight change in mechanical properties of hydroxyapatite-based nanocomposites synthesized from waste bovine bone and their bioactivity

Porous hydroxyapatite (HAp) ceramics have been widely used in several biomedical applications. However, efforts to enhance the porous structure in HAp ceramics often lead to a decline in their mechanical properties. In the present study, by adding a small amount of aluminum nitride (AlN) nanoparticles to HAp ceramics, we achieved the formation of porous HAp with a slight change in grain size and mechanical properties. The starting powder of the HAp was obtained from a natural source of bovine bone. The HAp/xAlN nanocomposites were fabricated by a simple conventional technique. The 0.06 mol% AlN-added sample (HAp/0.06AlN) presented the maximum mechanical properties (Vickers hardness = 3.68 GPa, elastic modulus = 94.04 GPa, and fracture toughness = 0.97 MPa∙m1/2) with favorable porosity. Simulated body fluid and cell viability assays showed that all the studied nanocomposites possessed desirable bioactivity with high cell viability. The HAp/0.06AlN samples were coated with antimicrobial agents. The samples coated with silver nitrate (AgNO3) had high antibacterial efficiency against S. aureus (66.2%) and P.aeruginosa (67.3%). Based on the obtained results, the nanocomposites exhibited promising potential for development and utilization in biomedical applications.

The effects of interfacial layers on dielectric properties of an acrylic co-polymer containing polymer-grafted reduced graphene oxide

In this study, the influence of interfacial layers, in addition to other effective parameters, on the dielectric efficiency of polymer nanocomposites in the rubbery state is presented. For this purpose, reduced graphene oxide (rGO) was grafted by poly (butyl acrylate) chains (rGO-PBA) via surface-initiated atom transfer radical polymerization (SI-ATRP) and incorporated into an acrylic co-polymer matrix with the glass-transition temperature (Tg) well below room temperature. The rGO exhibited poor dispersion and uneven distribution in acrylic co-polymer, whereas polymer grafted-rGO showed excellent dispersion. The grafted chains can penetrate and form entropic interactions with the matrix chains, which results in a strong interfacial region. The immobilized interfacial layer was characterized by DSC and dielectric measurements. The dielectric measurements in different temperatures provided the means to evaluate the contribution of the interfacial layers on dielectric properties. The findings confirmed that there exists an optimum chain mobility in which the chain polarization shows a major contribution to the dielectric properties of polymer nanocomposites. Reduction of temperature to a certain degree exhibited more rise in the dielectric properties of polymer/rGO-PBA nanocomposites than pure matrix which can be correlated to the interfacial region.

Multiscale analysis for characterization of tensile properties in extrusion-based 3D printed carbon nanocomposites

In this study, we proposed a multiscale modeling methodology to predict tensile properties of carbon-based nanocomposites produced through extrusion-based 3D printing. This stepwise method integrates results across scales, from the nanoscale to the macroscale. The stochastic continuum model, informed by molecular dynamics, captures the direction-dependent stiffness of nanocomposites at the atomic level, integrating the transverse isotropic properties and morphological variations, along with process-induced uncertainties in a microscale domain. Considering the variable periodic layered filament shape determined by the printing conditions, we defined the geometry of the representative volume element and derived its homogenized equivalent effective properties. We validated the results of our model by comparing them with experimental stress-strain curves. Using this approach, we simulated the nonlinear response and analyzed the off-axis tensile characteristics of the specimens under various printing conditions. The alignment and orientation of the graphene flakes played pivotal roles in determining the mechanical properties of the nanocomposites. The proposed approach effectively assessed the overall behavior of nanocomposites produced using an extrusion-based 3D printing process, helping to accurately predict the mechanical properties and investigate the effects of the parameters on the macroscopic nonlinear response in applications using 3D printed nanocomposites.

Effects of chitosan and TiO2 nanoparticles on the antibacterial property and ability to self-healing of cracks and retrieve mechanical characteristics of dental composites

The aim of this study was to improve the self-healing properties of dental nanocomposite using nanoparticles of TiO2 and chitosan. We evaluated flexural and compressive strength, crack-healing, and self-healing lifespan after 3 months of water aging. The effect of the developed composite on cell viability and toxicity was assessed by an MTT assay on human alveolar basal epithelial cells (A549 cell line). The nanocomposite included 7.5 wt% polyurea-formaldehyde (PUF) and 0, 0.5, and 1 wt% n-TiO2 and chitosan. After the fracture, the samples were put in a mold for 1–90 days to enable healing. Then, the fracture toughness of the healed nanocomposites and the healing yield were measured. The flexural strength of the nanocomposite improved by adding 0.5 wt% n-TiO2, while the compressive strength increased after adding 0.5 wt% chitosan (p > 0.1). When these two materials were used simultaneously, the flexural strength was improved by around 2%; however, the compressive strength was unaffected. Compared to the other sample, the nanocomposite with 0.5 wt% n-TiO2 and chitosan had higher KIC-healing and self-healing efficiency. Self-healing efficacy had no significant effect of water aging over 90 days compared to one day (p > 0.1), demonstrating that the PUF nanocapsules were not damaged.

Core-shell structure polydopamine and polyethylenimine co-assisted MoS2-BaTiO3/polyarylene ether nitrile nanocomposites for high-temperature resistant organic dielectrics

In this work, a novel nanoparticle ((MoS2-BT)@(PDA+PEI)) was constructed through two-dimensional molybdenum disulfide (MoS2) and zero-dimensional barium titanate (BT) via in-situ polymerization and co-modification of polydopamine (PDA) and polyethylenimine (PEI). Then the nanofillers were dispersed in the Polyarylene ether nitrile (PEN) matrix by film casting to obtain PEN/(MoS2-BT)@(PDA+PEI) nanocomposite dielectric films. Subsequently, the latter were subjected to chemical crosslinking at high temperature to obtain CPEN/(MoS2-BT)@(PDA+PEI) nanocomposites. The effects of filler content on the properties of PEN matrix composite films were investigated. The results indicate excellent compatibility between (MoS2-BT)@(PDA+PEI) and the PEN matrix due to the introduction of an organic modification layer, resulting in overall good performance of nanocomposite films, including good thermal stability with a glass transition temperature (Tg) exceeding 240 °C after chemical crosslinking. The dielectric constant of CPEN nanocomposites containing 40wt% of the hybrid nanoparticles is 20.2 and the dielectric loss is 0.032 at 1kHz, the dielectric constant-temperature coefficient of all CPEN nanocomposites is less than 6×10-4 °C-1 at the temperature range of 25-220 °C. In short, the incorporation of (MoS2-BT)@(PDA+PEI) effectively enhances the thermal, mechanical, and dielectric properties of PEN-based nanocomposites.

Evaluation of the Antimicrobial, Cytotoxic, and Physical Properties of Selected Nano-Complexes in Bovine Udder Inflammatory Pathogen Control.

Mastitis in dairy cows is a worldwide problem faced by dairy producers. Treatment mainly involves antibiotic therapy, however, due to widespread antibiotic resistance among bacteria, such treatments are no longer effective. For this reason, scientists are searching for new solutions to combat mastitis, which is caused by bacteria, fungi, and algae. One of the most promising solutions, nanotechnology, is attracting research due to its biocidal properties. The purpose of this research was to determine the biocidal properties of nanocomposites as a potential alternative to antibiotics in the control of mastitis, as well as to determine whether the use of nanoparticles and what concentration is safe for the breeder and the animal. In this study, the effects of Ag, Au, Cu, Fe, and Pt nanoparticles and their complexes were evaluated in relation to the survival of bacteria and fungi isolated from cattle diagnosed with mastitis, their physicochemical properties, and their toxicity to bovine and human mammary epithelial cells BME-UV1 and HMEC (human microvascular endothelial cells). Moreover, E. coli, S. aureus, C. albicans, and Prototheca sp. invasion was assessed using the alginate bead (bioprinted) model. The NPs were tested at concentrations of 25, 12.5, 6.25, 3.125, 1.56 mg/l for Au, Ag, Cu and Fe NPs, and 10, 5, 2.5, 1.25, 0.625 mg/l for Pt. With the exception of Fe and Pt, all exhibited biocidal properties against isolates, while the AgCu complex had the best effect. In addition, nanoparticles showed synergistic effects, while the low concentrations had no toxic effect on BME-UV1 and HMEC cells. Synergistic effects of nanoparticles and no toxicity to bovine and human cells might, in the future, be an effective alternative in the fight against microorganisms responsible for mastitis, and the implementation of research results in practice would reduce the percentage of dairy cows suffering from mastitis. The problem of increasing antibiotic resistance is posing a global threat to human's and animal's health, and requires comprehensive research to evaluate the potential use of nanoparticles - especially their complexes - as well as to determine whether nanoparticles are safe for the breeders and the animals. The conducted series of studies allows further consideration of the use of the obtained results in practice, creating a potentially new alternative to antibiotics in the treatment and prevention of mastitis in dairy cattle.

Pro-angiogenic and antibacterial copper containing nanoparticles in PLGA/amorphous calcium phosphate bone nanocomposites

Large bone defects after trauma demand for adequate bone substitutes. Bone void fillers should be antibacterial and pro-angiogenic. One viable option is the use of composite materials like the combination of PLGA and amorphous calcium phosphate (aCaP).Copper stimulates angiogenesis and has antibacterial qualities. Either copper oxide (CuO) nanoparticles (NPs) were therefore added to PLGA/aCaP/CuO in different concentrations (1, 5 and 10 w/w %) or copper-doped tricalcium phosphate NPs (TCP with 2% of copper) were electrospun into PLGA/CuTCP nanocomposites.Bi-layered nanocomposites of PLGA/aCaP with different copper NPs (CuO or TCP) and a second layer of pristine PLGA were fabricated. Two clinical bacterial isolates (Staphylococcus aureus and Staphylococcus epidermidis) were used to assess antibacterial properties of the copper-containing materials. For angiogenesis, the chorioallantoic membrane (CAM) assay of the chicken embryo was performed.The higher the CuO content, the higher were the antibacterial properties, with 10 % CuO reducing bacterial adhesion most effectively. Vessel and cell densities were highest in the 5 % CuO containing scaffolds, while tissue integration was more pronounced at lower CuO content. The PLGA/aCaP/CuO (1 % CuO) behaved similar like PLGA/CuTCP in all angiogenic and antibacterial readouts, based on the same copper fraction.We conclude that CuO NPs or CuTCP NPs are useful components to increase angiogenic properties of nanocomposites and at the same time exhibiting antibacterial characteristics.

Nonlinear thermal buckling analysis of temperature-dependent porous annular and circular microplates reinforced by graphene platelets by using isogeometric analysis method

In this research, by using isogeometric analysis (IGA) method, nonlinear thermal buckling analysis of porous circular and annular microplates reinforced by graphene platelets (GPLs) under uniform temperature rise is performed by taking both the temperature dependence of the material properties and the size effects into account. The closed-cell metal foam scheme combined with the Halpin-Tsai micromechanics model and the rule of mixture is utilized to identify the effective material properties of the porous nanocomposites for three GPL dispersion patterns and three porosity distributions. With the aid of the virtual work principle, the classical and the non-classical motion equilibrium formulation based on the higher-order shear deformation theory in conjunction with the modified strain gradient (MSG) theory for the nonlinear temperature-dependent buckling behaviour are established. The higher-order NURBS basis functions capable of accomplishing easily the smoothness of arbitrary continuity order are successfully utilized to solve the nonlinear governing equations by satisfying the C2-continuity of the displacement field required by the MSG theory. The thermal buckling behaviour is assessed in detail by using various parameters such as the thickness-to-radius ratio, the porosity coefficient, the GPL weight fraction and the material length scale as well as the porosity distribution scheme and the GPL dispersion pattern. The results show the significance of incorporating the temperature dependency of the material properties when analyzing the thermal buckling behaviour and present the combination scheme of porosity and GPL distributions for enhancing the thermal buckling resistance.

Water and Oxygen Barrier Properties of All-Cellulose Nanocomposites.

Hydroxypropyl cellulose (HPC) is potentially interesting as a biobased, rigid food packaging material, but its stiffness and strength are somewhat low, and its water and oxygen transport rates are too high. To improve these characteristics, we investigated nanocomposites of HPC and cellulose nanocrystals (CNCs). These high-aspect-ratio nanoparticles display high stiffness and strength, and their high crystallinity renders them virtually impermeable. Exchanging the counterions of sulfate-ester decorated CNCs with cetyltrimethylammonium ions affords particles that are dispersible in ethanol (CTA.CNC) and allows solvent casting of HPC/CTA.CNC nanocomposite films, which, even at a CTA.CNC content of 90 wt %, are highly transparent. The introduction of CTA.CNC considerably increases the Young's modulus (Ey) and upper tensile strength (σUTS). For example, in the nanocomposite with 90% CTA.CNC, Ey = 7.6 GPa is increased 20-fold and σUTS = 42.7 MPa is more than doubled in comparison to HPC, whereas the extensibility (1.1%) remains appreciable. Composites with a CTA.CNC content of 70 wt % or less show a lower water vapor permeability (6.4-9.2 × 10-5 g μm m-2 s-1 Pa-1) than the neat HPC (1.5 × 10-4 g μm m-2 s-1 Pa-1), whereas the oxygen permeability (5.6 × 10-7-1.3 × 10-6 cm3 μm m-2 s-1 Pa-1) is reduced by 1 order of magnitude compared to HPC (3.2 × 10-6 cm3 μm m-2 s-1 Pa-1). The biobased nanocomposites retain their mechanical integrity at a relative humidity of 75% but readily disintegrate in water.

Preparation and properties of polyvinylidene fluoride dielectric nanocomposites for energy storage applications through synergistic addition of ionic liquid‐modified graphene oxide nanosheets and functionalized barium titanate hybrid fillers

AbstractTo tackle the challenge of filler agglomeration and low interfacial bonding strength during manufacturing filled polymer dielectric nanocomposites containing graphene oxide (GO) nanosheets, the author proposed an interface design strategy based on the synergistic hybridization of ionic liquid (IL) modification and different dimensional fillers. GO nanosheets were functionalized by IL, and then polyvinylidene fluoride (PVDF) dielectric nanocomposites (GO‐g‐IL/PVDF) were prepared and evaluated. Based on this, hydroxylated barium titanate BT‐OH@GO‐g‐IL/PVDF ternary nanocomposites were further prepared. A comprehensive analysis of the morphology, mechanical, thermal, electrical, and dielectric properties of the PVDF dielectric nanocomposites was systematically conducted. The results showed that IL was successfully grafted on GO, benefiting an increase in the filler dispersion and interfacial bonding strength. GO‐g‐IL also promoted β‐crystal formation of PVDF and increment of crystallinity. DSC test further revealed that the inclusion of BT‐OH@GO‐g‐IL as dielectric nanofillers promoted the formation of multiple crystal types in PVDF and accelerated the crystallization process. The incorporation of GO‐g‐IL facilitated the formation of localized conductive networks within the PVDF matrix, leading to enhanced electronic displacement polarization and an improved dielectric constant. The dielectric constants of the GO‐g‐IL/PVDF composites containing 2% and 8% of GO‐g‐IL were measured to be 24.28 and 78.46, which were found to be 2.6 and 8.4 times higher than that of pure PVDF. However, the dielectric loss also increased sharply at high nanofiller loading. The dielectric constant and loss of the BT‐OH@GO‐g‐IL/PVDF nanocomposites were found to be 40.32 and 0.38, with a content of 2% for GO‐g‐IL and 20% for BT‐OH.Highlights A facile interface design strategy based on ionic liquid (IL) integrating GO nanosheets and hydroxylated barium titanate (BT‐OH) to form BT‐OH@GO‐g‐IL compounding nanofiller has been proposed. PVDF dielectric nanocomposites containing BT‐OH@GO‐g‐IL compounding nanofiller were systematically investigated and compared. The effects of interfacial interactions between BT‐OH@GO‐g‐IL and PVDF contribute to the uniform dispersion and comprehensive property improvements of PVDF dielectric nanocomposites. This work provides a novel strategy for the fabrication of PVDF dielectric nanocomposites, inspiring the research and development of PVDF in the energy storage applications areas in the future.

Nanoengineering of Lanthanide‐Doped BaGdF5‐Graphene Oxide as a Tunable‐Nanocomposite Platform for Biological Applications

AbstractInorganic nanohosts doped with lanthanide ions are an indispensable tool for multimodal bioimaging and MRI applications due to their distinctive optical, magnetic, and biocompatible properties. Nanocomposites of such nanoprobes with functionalization capabilities could also enable their use in targeted therapy‐based applications. However, the influence of nanocomponents especially their proportion in a nanocomposite in modulating the physio‐chemical and biocompatibility properties of the nanocomposite is still elusive. To address this knowledge gap, we have engineered nanocomposites variants using an environmentally benign one‐step synthesis with ionic liquids. We have synthesized two nanocomposites, differing in the proportion of lanthanide‐doped ternary fluoride nanoparticles (as nanophase material with luminescent and magnetic traits) and graphene oxide (as host matrix phase with tunable functionalization potential for theranostics applications). We found that with increased GO nanomaterial, nanocomposites showed reduced crystallite size and photoluminescence properties without significantly affecting the magnetic traits. Thus, implying nanocomponents ratio has differential effect on the nanocomposite properties. To assess biocompatibility, we have employed sensitive biomarkers such as craniofacial development, cardiac rhythm, and overall survivability of zebrafish larvae. Remarkably, biocompatibility improved when the proportion of the GO was increased within the nanocomposite as compared to when the nanocomponents were assessed individually. Our results also revealed that biocompatibility of nanocomposites also depends on the synergistic interplay between the nanocomponents due to the spatial arrangement of each nanocomponent in the nanocomposites. Overall, our study offers an intriguing avenue for tuning the biocompatibility of such nanocomposites, rendering them as an application‐independent biocompatible‐platform for theranostics applications.

High-Performance PEEK/MWCNT Nanocomposites: Combining Enhanced Electrical Conductivity and Nanotube Dispersion.

High-performance engineering thermoplastics offer lightweight and excellent mechanical performance in a wide temperature range. Their composites with carbon nanotubes are expected to enhance mechanical performance, while providing thermal and electrical conductivity. These are interesting attributes that may endow additional functionalities to the nanocomposites. The present work investigates the optimal conditions to prepare polyether ether ketone (PEEK)/multi-walled carbon nanotube (MWCNT) nanocomposites, minimizing the MWCNT agglomerate size while maximizing the nanocomposite electrical conductivity. The aim is to achieve PEEK/MWCNT nanocomposites that are suitable for melt-spinning of electrically conductive multifilament's. Nanocomposites were prepared with compositions ranging from 0.5 to 7 wt.% MWCNT, showing an electrical percolation threshold between 1 and 2 wt.% MWCNT (107-102 S/cm) and a rheological percolation in the same range (1 to 2 wt.% MWCNT), confirming the formation of an MWCNT network in the nanocomposite. Considering the large drop in electrical conductivity typically observed during melt-spinning and the drawing of filaments, the composition PEEK/5 wt.% MWCNT was selected for further investigation. The effect of the melt extrusion parameters, namely screw speed, temperature, and throughput, was studied by evaluating the morphology of MWCNT agglomerates, the nanocomposite rheology, and electrical properties. It was observed that the combination of the higher values of screw speed and temperature profile leads to the smaller number of MWCNT agglomerates with smaller size, albeit at a slightly lower electrical conductivity. Generally, all processing conditions tested yielded nanocomposites with electrical conductivity in the range of 0.50-0.85 S/cm. The nanocomposite processed at higher temperature and screw speed presented the lowest value of elastic modulus, perhaps owing to higher matrix degradation and lower connectivity between the agglomerates. From all the process parameters studied, the screw speed was identified to have the higher impact on nanocomposite properties.

One-step preparation of silver nanoparticle containing polymer nanocomposites via stereolithography technique

As a technique that uses ultraviolet light to cure photo-polymers layer by layer with high spatial resolution and surface quality, stereolithography (SLA) allows for precise process control and optimization for various UV-curable polymers and their nanocomposites with various nanoparticles. In this study, UV-curable polymer nanocomposites were prepared with the addition of different contents of silver nitrate via SLA technique for use in antibacterial applications. In-situ synthesis of AgNPs was achieved during the SLA process without any additional treatments. The effect of AgNO3 addition on the curing of the resin and the mechanical properties of the nanocomposite specimens were investigated. To understand the fracture mechanism of the nanocomposite samples, the fractured surfaces of the samples were evaluated by SEM, and the AgNO3 content of the nanocomposite was evaluated by EDX. The nanocomposites containing 0.3 wt. % AgNO3 exhibited improved mechanical properties. Further increasing the AgNO3 content to 3 wt. % led to deterioration in the physical and mechanical properties of the polymer nanocomposites.

Analyzing Temperature – Dependent Structural Changes and Frequency Response of a Ferroelectric Nanocomposite Based on Triglycine Sulfate with Oxidized Multiwalled Carbon Nanotubes

The present work is a continuing study on anomalous properties of the ferroelectric nanocomposite from triglycine sulfate (TGS) and oxidized multiwalled carbon nanotubes (OMWCNT). In this study, the nature of frequency response in a region of 102–107 Hz at low temperatures (63–273 K) will be clarified by analyzing structural changes when reducing temperature. It was found that the interaction between TGS and OMWCNT inhibited the switching of SO4 - groups, leading to a significant increase in relaxation time, activation energies and coercive fields. Consequently, the domain – wall freezing occurred at higher temperatures than those in pure TGS.

Electrochemical characterization and structural analysis of (In2O3)/(Fe2O3) nanocomposites for high-performance supercapacitors

This study presents a comprehensive investigation of the electrochemical characteristics and structural properties of novel nanocomposites with varying compositions of (In2O3)x/(Fe2O3)1-x, where x ranges from 1 to 0. These nanocomposites were synthesized using a versatile and cost-effective co-precipitation method. The crystallographic structure and morphology of the synthesized samples were thoroughly analyzed using Powder X-ray diffraction (PXRD) and Tunneling Electron Microscopy (TEM). Advanced analytical techniques were employed including Positron Annihilation Lifetime Spectroscopy (PALS) and Coincidence Doppler Broadening Spectroscopy (CDBS) to uncover critical insights into the structural and molecular properties of these nanocomposites. PALS analysis revealed valuable insights into the pore characteristics of the nanocomposites, while CDBS identified crucial molecular interactions within the materials. Electrochemical characterization of the nanocomposites is carried out using cyclic voltammetry (CV), galvanostatic charge/discharge (GCD) and electrochemical-impedance-spectroscopy (EIS) measurements. The (In2O3)0.3/(Fe2O3)0.7 nanocomposite exhibits a remarkable specific capacitance of 945 F g-1 at 1 A g-1 and exceptional rate performance, retaining 93.6% of its specific capacitance at a six-fold higher current density. Moreover, this nanocomposite electrode demonstrates outstanding cyclic stability, maintaining 92.1% of its specific capacitance even after 3000 GCD cycles at 8 A g-1. These findings suggest that the novel composition and integrated electrochemical properties of the (In2O3)0.3/(Fe2O3)0.7 nanocomposite hold great promise for enhancing the performance of next-generation electrochemical capacitors. This research contributes valuable insights into the design and development of advanced energy storage materials with applications in various high-performance energy storage devices.

Development of a continuous magnetic dispersive solid phase extraction method for the extraction of seven widely used pesticides from fruit juices

Generally, food safety monitoring is vital issue to preserve human health and guarantee a longer lifespan. In present study, a continuous mode of magnetic dispersive solid phase extraction method based on using magnetic covalent organic framework@metal organic framework nanocomposite as sorbent has been proposed. The developed method has been tested for the extraction of some pesticides (pirimicarb, terbutryn, fenthion, triticonazole, hexaconazole, diniconazole, and haloxyfop-R-methyl) from commercial fruit juices prior to their analysis by high performance liquid chromatography–tandem mass spectrometry. In the current research, the properties of nanocomposite were characterized by scanning electron microscopy, Fourier–transform infrared spectrophotometry and X–ray diffraction techniques. In the next step, the synthesized nanocomposite was employed as an efficient sorbent in the developed extraction procedure that was done in a narrow bore tube. Under optimum extraction conditions, extraction recoveries were in the ranges of 67–83 %. Moreover, the limits of detection and quantification of the selected analytes were in the ranges of 17–43 and 56–143 ng L−1, respectively. Finally, the proposed method was successfully applied in the analysis of the opted pesticides in sixty fruit juice samples.

Nonlinear dynamical characteristics of carbon nanotube-reinforced composite beams with piezoelectric actuators and elastically restrained ends under thermo-electro-mechanical loads

Nonlinear free vibration and dynamical responses of carbon nanotube (CNT) reinforced composite beams with surface-bonded piezoelectric layers and tangentially restrained ends under thermo-electro-mechanical loads are investigated in this paper. The properties of constitutive materials are assumed to be temperature-dependent and effective properties of nanocomposite are estimated using an extended rule of mixture. Unlike previous studies, the present work considers the effects of tangentially elastic constraints of two ends on the nonlinear dynamic characteristics of hybrid beams. Motion equation is established within the framework of Euler-Bernoulli beam theory taking into account von Kármán nonlinearity. Analytical solution is assumed to satisfy simply supported boundary conditions and Galerkin procedure is employed to obtain a time ordinary differential equation including both quadratic and cubic nonlinear terms. This differential equation is numerically solved employing fourth-order Runge-Kutta scheme to determine the frequencies of nonlinear free vibration and nonlinear transient response. Parametric studies are executed to examine numerous influences on the nonlinear dynamical characteristics of hybrid nanocomposite beams. The study reveals that tangential constraints of ends substantially effect the frequencies and dynamic response of the beam, especially at elevated temperatures. The results also indicate that nonlinear dynamic responses can be controlled effectively by means of piezoelectric actuators and elasticity of tangential constraints of ends should be considered in design of piezo-CNTRC beams.

Enhanced mechanical and thermal properties of phenolic-type phthalonitrile nanocomposites with fumed silica nanoparticles

Enhancing the mechanical properties and thermal stability of phthalonitrile polymers by hybrid modification holds significant importance in broadening their thermal-structural applications within high-temperature environments. Herein, fumed silica nanoparticles were considered as modifiers for a class of phenolic-type phthalonitrile resin, i.e., PN75, and their effects on mechanical properties and thermal stability were explored. First, contact angle tests (CA) were employed to show that the PN75 melt had good wettability on hydrophilic fumed silica (FS) and poor wettability on hydrophobic fumed silica (RFS). FS had a relatively satisfactory dispersion within PN75, which was indicated by scanning electron microscope (SEM), followed by FS/PN75 nanocomposites were prepared by melt blending under vacuum, with maximum FS addition 3 wt% of PN75. Second, the flexural strength and modulus of nanocomposites were increased by 23.5% and 11.9%. Finally, thermal stability of the FS/PN75 was promoted from 21.6% to 25.6% in char residue at 800 °C in the air atmosphere by the thermogravimetric analysis (TGA), which was contributed by the high heat-resistance and the shielding effect of FS. This work would inspire in-depth studies on modification and design of phthalonitrile-based hybrid composites for extreme thermal environment.

Enhanced rheological properties of carbon nanotubes reinforced natural rubber/butadiene rubber nanocomposites

AbstractEffects of carbon nanotubes (CNTs) content and the in situ surface modification via bis(triethoxysilylpropyl) disulfide (Si75) and (3‐aminopropyl) triethoxysilane (KH550) on the rheological properties of rubber nanocomposites are explored. Results from the strain sweep demonstrate that the filler network of the nanocomposite is enhanced when the hydroxylated CNT (HCNT) is incorporated. The promotion of filler–rubber interaction in nanocomposite reinforced with modified CNT is validated by both stress relaxation and strain sweep measurements. The die swell ratio (B) declines with increasing HCNT content and rises with a heightened shear rate. Compared to those without HCNT, B of the nanocomposites, which contained 5 phr HCNT, decreased by 5.4%, 7.0%, and 17.3% at 50, 200, and 500 s−1, respectively. The Si75‐modified HCNT and the carboxylated CNT (CCNT) reduce the B‐value of the extrudates at 500 s−1 by 3.7% and 3.0%, respectively. However, the extrudates filled with KH550‐modified HCNT or CCNT showed a larger B due to pre‐crosslinking, as demonstrated by stress relaxation and swelling tests. Furthermore, it is also found that the application of KH550 has an acceleration effect on the curing reaction, increasing the curing efficiency by 8.5%.Highlights The promotion of filler–rubber interaction is validated by RPA. The dimensional stability of the composites is improved after incorporating CNT. The extrudates with Si75 exhibit a reduced B and improved surface morphology. CNT content increase raises MH, ML, and shortens the t10 of the composite.