Piezoelectric properties of noncovalently functionalized 2D nanomaterials incorporated poly(vinylidene fluoride) nanocomposites

We report here for the first time the role of noncovalently functionalized 2D nanomaterials on the ferroelectric and piezoelectric behavior of poly(vinylidene fluoride) (PVDF) nanocomposites. Graphene oxide (GO), expanded graphite (EG) and hexagonal boron nitride (h-BN) were noncovalently modified via Li-salt of 6-amino hexanoic acid (Li-AHA), denoted as m-GO, m-EG and m-BN, in order to de-agglomerate and de-stack them, which were subsequently incorporated into the PVDF matrix via solution mixing, followed by compression molding. Simultaneously, PVDF nanocomposites with unmodified 0.08 wt% of 2D nanomaterials were also prepared using the same methodology. PVDF/m-BN nanocomposite showed a higher extent of polar phase (~36%) associated with PVDF phase as compared to PVDF/m-GO and PVDF/m-EG nanocomposites. Further, the highest permittivity (~58 at 10⁻¹ Hz) was achieved in PVDF/m-BN nanocomposite, which was also reflected in higher remnant polarization (~61 nC/cm²) and a significantly higher d₃₃ value (~53 pm/V). Moreover, a higher output peak to peak voltage (~13 V) was obtained for the sensor device fabricated from PVDF/m-BN nanocomposite. Thus, the role of Li-AHA-modified 2D nanomaterials in improving the morphology, dielectric, ferroelectric, and piezoelectric characteristics of the PVDF nanocomposites was clearly established.     

Improving toughness of ultra-high molecular weight polyethylene with ionic liquid modified carbon nanofiber

Ionic liquids (ILs) with long alkyl substituted groups, including 1-docosanyl-3-methylimidazolium bromide (IL-1) and 1-docosanyl-3-methylimidazolium hexafluorophosphate (IL-2), were synthesized and used to modify the surface of carbon nanofibers (CNF). The nanocomposite film prepared by solution-blending of ionic liquid modified CNF (i-CNF) and ultrahigh molecular weight polyethylene (UHMWPE) displayed better toughness when compared with pure UHMWPE even at very low concentrations (e.g. 0.4 wt%). The effect of ionic liquids on the elongation-to-break ratio of this nanocomposite system was investigated. The ionic liquid with hexafluorophosphate as the anion was more efficient to increase the toughness of UHMWPE due to the improved compatibility of IL with UHMWPE in the polymer matrix than that of the bromide. The rheological behavior of molten nanocomposites revealed that the storage modulus and the complex viscosity decreased with increasing ionic liquid content in the high frequency region. However, a reverse trend was observed when the frequency was less than 0.05 s⁻¹. In-situ monitoring in the change of crystallinity of the nanocomposite during tensile deformation suggested a mechanism of sliding between UHMWPE crystal regions and the surface of carbon nanofibers.     

Nanocomposite powders of hydroxyapatite-graphene oxide for biological applications

The repair of bone fractures is a clinical challenge for patients with impaired healing, such as osteoporosis. Currently, different strategies have been developed to design new biomaterials, enhancing their interactions with biological systems and conducting the cellular behavior in the desired direction to help fracture healing. In the present work, hydroxyapatite-graphene oxide (HA-GO) nanocomposites were produced and the morphological and physicochemical influences of the addition of 0.5 wt%, 1.0 wt% and 1.5 wt% of GO to HA were observed. FEG-SEM and TEM analyses of HA-GO nanocomposites showed HA nanoparticles adhered to the surface of the GO sheets, suggesting an effective method to form nanostructured graphene-based biomaterials. As confirmation, physicochemical analyses by Raman, FTIR and TGA demonstrated a strong affinity between HA and GO, according to the increase of concentration from 0.5 wt% to 1.5 wt% GO in the HA-GO nanocomposites. Also, in order to evaluate the HA-GO nanocomposites behavior under biological microenvironment, in vitro bioactivity and indirect cytotoxicity tests were performed. FEG-SEM analyses confirmed the positive results for the bioactivity properties of HA-GO nanocomposite and indirect cytotoxicity demonstrated that even with a decrease in the hDPSCs viability and proliferation, when increasing to 1.5 wt% of GO concentration, high level of cell viability was exhibited by HA-GO nanocomposites. These biological results suggested the 0.5 wt% HA-GO nanocomposite as a potential bioactive bone graft and a promising biomaterial for bone tissue regeneration, when compared to the pure HA.     

Ferro-/pyroelectric response of 0.57BF-0.31PMN-0.12PT ternary ceramic far away from morphotropic phase boundaries

A ternary BiFeO₃-Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ (BF-PMN-PT) solid solution with a composition far away from morphotropic phase boundaries (MPB) has been synthesized by solid-state reaction method. XRD analysis revealed a pure perovskite phase without any trace of pyrochlore phase. The system exhibited a broad phase transition with transition temperature T_c ~ 285 °C. The hysteresis loop of the ceramics displayed high remanent polarization (Pr ~ 41.23 μC/cm²) and coercive field (E_c ~ 35.41 kV/cm). The true-remanent polarization after removing the non-remanent components was evaluated by remanent hysteresis and PUND tasks, which revealed the actual usable polarization component for memory devices. Time-dependent compensated plots confirmed the resistive-leakage free characteristic of the BF-PMN-PT ceramics which makes them useful for application in devices like actuators where the electric field is switched at different rates. Fatigue test showed the ferroelectric parameters (switching and non-switching polarization values) do not vary over 10⁷ cycles which is important especially in electromechanical transducers and memory devices. A large piezoelectric charge coefficient (d₃₃ ~ 115 pC/N) was observed for the investigated ceramics.     

Low-temperature exfoliated graphene oxide incorporated with different types of natural rubber latex: Electrical and morphological properties and its capacitance performance

A simple with cost-effective method in the production and fabrication of graphene-based rubber nanocomposites as electrode materials is still remain a global challenge. In this work, we proposed one- and two-step approaches to fabricate an exfoliated graphene oxide (GO) as nanofiller in three different types of rubber latex polymer, namely, low ammonia natural rubber latex (NRL), radiation vulcanized NRL (RVNRL), and epoxy NRL 25 (ENRL 25). The electrical conductivity and capacitive behavior of nanocomposite samples were investigated under a four-point probe and cyclic voltammetry measurements, respectively. Meanwhile, the morphological properties were observed using field emission scanning electron microscopy, energy dispersive X-ray, optical polarization microscope, high-resolution transmission electron microscopy, Fourier-transform infrared spectroscopy, micro-Raman spectroscopy, and X-ray diffraction. The thermal stabilities of the nanocomposites were also investigated by thermogravimetric analysis. Among all, the GO/RVNRL polymer nanocomposite samples performed a better homogeneity with an improved electrical conductivity (~8.6 × 10⁻⁴ Scm⁻¹) as compared with the GO/ENRL 25 (~3.1 × 10⁻⁴ Scm⁻¹) and GO/NRL (~2.6 × 10⁻⁴ Scm⁻¹) polymer nanocomposite samples. In addition, the GO/RVNRL polymer nanocomposite electrodes showed acceptable specific capacitance (5 Fg^-1). The successfully fabricated conductive GO-based rubber nanocomposites are suitable for new supercapacitor electrodes.     

SiO2-covered graphene oxide nanohybrids for in situ preparation of UHMWPE/GO(SiO2) nanocomposites with superior mechanical and tribological properties

The modified Hummer technique was used in the preparation of graphene oxide (GO) nanosheets, and then SiO₂ decorated GO [GO(SiO₂)] nanosheets were synthesized via the sol–gel method. Then, ultrahigh-molecular-weight polyethylene (UHMWPE) nanocomposites loaded with 0.5, 1, 1.5, and 2 wt % of GO(SiO₂) were prepared using magnesium ethoxide/GO(SiO₂)-supported Ziegler–Natta catalysts via the in situ polymerization. Morphological study of the prepared polymer powders was assessed using field-emission scanning electron microscopy, which showed that GO(SiO₂) nanohybrids have been uniformly dispersed and distributed into the UHMWPE matrix. Also, the neat UHMWPE and its nanocomposites were evaluated with different analyses, including viscosity-average molecular weight measurement, differential scanning calorimetry, thermogravimetric analysis, tensile test, scratch hardness, and pin-on-disk test. The characterization of the UHMWPE nanocomposites indicated that many characterizations, including the mechanical, thermal, and tribological properties of UHMWPE, were significantly improved by incorporation of these new nanosheets in spite of the molecular weight reduction of the polymeric matrix and the improved flowability and processability of the produced nanocomposite. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47796.     

Cellulose nanocrystal-mediated assembly of graphene oxide in natural rubber nanocomposites with high electrical conductivity

This study reports a green and powerful strategy for preparing cellulose nanocrystal (CNC)/graphene oxide (GO)/natural rubber (NR) nanocomposites hosting a 3D hierarchical conductive network. Due to good dispersibility and amphiphilic nature of CNC, well dispersed CNC/GO nanohybrids were prepared. Hydrogen bonding interactions between CNC and GO greatly enhanced the stability of the CNC/GO nanohybrids. CNC/GO nanohybrids were introduced into NR latex under sonication and the mixture was cast. Self-assembled CNC/GO nanohybrids preferentially dispersed in the interstice between latex microspheres allowing the construction of a 3D hierarchical conductive network. By combining strong hydrogen bonds and 3D conductive network, both electrical conductivity and mechanical properties (tensile strength and modulus) have been significantly improved. The electrical conductivity of the nanocomposite with 4 wt% GO and 5 wt% CNC exhibited an increase of nine orders of magnitude compared to the nanocomposite with only 4 wt% GO; meanwhile, the electrical percolation threshold was 3-fold lower than for NR/GO composites.     

High-Performance and Biobased Polyamide/Functionalized Graphene Oxide Nanocomposites through In Situ Polymerization for Engineering Applications

In this study, biobased polyamide/functionalized graphene oxide (PA-FGO) nanocomposite is developed using sustainable resources. Renewable PA is synthesized via polycondensation of hexamethylenediamine (HMDA) and biobased tetradecanedioic acid. Furthermore, GO is functionalized with HMDA to improve its compatibility with biobased PA and in situ polymerization is employed to obtain homogeneous PA-FGO nanocomposites. Compatibility improvement provides simultaneous increases in the tensile strength, storage modulus, and conductivity of PA by adding only 2 wt% FGO (PA-FGO2). The tensile strength and storage modulus of PA-FGO2 nanocomposite are enhanced dramatically by ≈50% and 30%, respectively, and the electrical conductivity reached 3.80 × 10^–3 S m⁻¹. In addition, rheology testing confirms a shear-thinning trend for all samples as well as a significant enhancement in the storage modulus upon increasing the FGO content due to a rigid network formation and strong polymer-filler interactions. All these improvements strongly support the excellent compatibility and enhanced interfacial interactions between organic–inorganic phases resulting from GO surface functionalization. It is expected that the biobased PA-FGO nanocomposites with remarkable thermomechanical properties developed here can be used to design high-performance structures for demanded engineering applications.     

Chemically modified graphene oxide/polybenzimidazobenzophenanthroline nanocomposites with improved electrical conductivity

Graphene/polybenzimidazobenzophenanthroline nanocomposites were prepared through the liquid-phase exfoliation of graphene oxide (GO) and reduced graphene oxide (rGO) in methanesulfonic acid with subsequent solution mixing. Various chemical and combined chemical-thermal methods were examined to be effective for producing rGO with highly graphitic structure and excellent electrical conductivity. Raman and X-ray photoelectron spectroscopy showed higher degree of reduction of the GO with the combined chemical-thermal method compared to other chemical reduction processes. Structural characterization of the nanocomposites by X-ray diffraction, scanning electron microscopy and transmission electron microscopy showed good exfoliation and dispersion of both GO and rGO fillers in the polymer matrix. The thermogravimetric analysis found that the nanocomposites with rGO have higher onset and maximum weight loss temperatures than those with GO. Compared with the pure polymer, the electrical conductivity of the nanocomposites containing 10 wt% GO and GO reduced by the combined chemical-thermal treatment showed a remarkable increase by four and seven orders of magnitude, respectively. Long-term in-situ thermal reduction was performed to further improve the conductivities of the nanocomposites.     

Enhanced thermal conductivity and dimensional stability of flexible polyimide nanocomposite film by addition of functionalized graphene oxide

Polyimide (PI) nanocomposites with both enhanced thermal conductivity and dimensional stability were achieved by incorporating glycidyl methacrylate‐grafted graphene oxide (g‐GO) in the PI matrix. The PI/g‐GO nanocomposites exhibited linear enhancement in thermal conductivity when the amount of incorporated g‐GO was less than 10 wt%. With the addition of 10 wt% of g‐GO to PI (PI/g‐GO‐10), the thermal conductivity increased to 0.81 W m^?1 K^?1 compared to 0.13 W m^?1 K^?1 for pure PI. Moreover, the PI/g‐GO‐10 composite exhibited a low coefficient of thermal expansion (CTE) of 29 ppm °C^?1. The values of CTE and thermal conductivity continuously decreased and increased, respectively, as the g‐GO content increased to 20 wt%. Combined with excellent thermal stability and high mechanical strength, the highly thermally conducting PI/g‐GO‐10 nanocomposite is a potential substrate material for modern flexible printed circuits requiring efficient heat transfer capability.     

Mn‐Loaded Mesoporous Silica Nanocomposite: A Highly Efficient Humidity Sensor

We report a relative humidity sensor based on manganese‐nanoparticle‐loaded mesoporous silica SBA‐15 using a facile hydrothermal route. The as‐developed nanocomposite material (Mn/SBA‐15) possesses a high surface area and a high pore volume. The obtained samples were characterized by using low‐angle X‐ray Diffraction (XRD), Fourier‐transform infrared spectroscopy (FTIR), N₂ adsorption–desorption, high‐resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), and energy‐dispersive X‐ray (EDX) spectroscopy techniques. The Mn/SBA‐15 exhibited, improved humidity response and recovery time as compared to pure SBA‐15 in the 11%–92% RH range. Optimal results were obtained for the 5 wt% Mn‐loaded SBA‐15 sample, which displayed excellent linearity, low hysteresis, and high humidity response. A change in ~5 orders of magnitude in resistance was observed over 11%–92% RH range. The investigation of humidity sensing properties of Mn/SBA‐15 nanocomposite shows that this material has good prospects as humidity sensor.     

Hybrid Nanocomposites of Hydroxyapatite,Eu2O3, Graphene Oxide Via Ultrasonic Power: Microstructure,Morphology Design and Antibacterial for Biomedical Applications

Post-implantation infections are regarded as a major issue in the biomedical field. Further, many investigations are continuous towards developing antibacterial biocompatible materials. In this regard, hydroxyapatite (HAP), erbium oxide (Eu₂O₃), and graphene oxide (GO) were introduced in nanocomposites combinations, including single, dual, and triple constituents. The nanoparticles of HAP, Eu₂O₃, and nanosheets of GO are synthesized separately, while dispersed in the nanocomposites simultaneously. The morphological investigation showed that HAP was configured in a rod-like shape while the nano ellipsoidal shape of Eu₂O₃ was confirmed. The particle size of the ternary nanocomposite containing HAP/Eu₂O₃/GO reached the length of 40 nm for the rods of HAP and around 28 nm for the length axis of ellipsoidal Eu₂O₃ nanoparticles. The roughness average increased to be about 54.7 nm for HAP/GO and decreased to 37.9 nm for the ternary nanocomposite. Furthermore, the maximum valley depth (R_v) increased from HAP to the ternary nanocomposite from 188.9 to 189.8 nm. Moreover, the antibacterial activity was measured, whereas the inhibition zone of HAP/Eu₂O₃/GO reached 13.2?±?1.1 mm for Escherichia coli and 11.4?±?0.8 mm for Staphylococcus aureus. The cell viability of the human osteoblast cell lines was evaluated to be 98.5?±?3% for the ternary composition from 96.8?±?4% for the pure HAP. The existence of antibacterial activity without showing cytotoxicity against mammalian cells indicates the compatibility of nanocomposites with biomedical applications.

     

Ag/αFe2O3-rGO novel ternary nanocomposites: Synthesis,characterization, and photocatalytic activity

In this research, novel ternary Ag/αFe₂O₃-rGO nanocomposites with various contents of GO were synthesized via a facile one-pot hydrothermal method. Ag/αFe₂O₃-rGO nanocomposites were characterized by X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectrometer (EDX), photoluminescence (PL) spectroscopy, and Fourier transform infrared (FTIR). The results showed that hematite nanoparticles and Ag nanoparticles were well decorated on the graphene surface. Photocatalytic activity of Ag/αFe₂O₃-rGO ternary nanocomposites and pure Ag/αFe₂O₃ was investigated for photodegradation of Congo red dye solution as a model pollutant under UV light irradiation. The ternary nanocomposite with 1.8?mg/ml GO aqueous solution concentration shows higher degradation efficiency under UV light irradiation than the pure Ag/αFe₂O₃ and the nanocomposites with other GO aqueous solution concentrations. It was observed that the adsorption of the dyes on the nanocomposites surface is dependent on the graphene content due to a decrease in the recombination rate, particles size, and increase charge carrier transfer. The results show that the Ag/αFe₂O₃-rGO nanocomposite can be used as an excellent photocatalytic material for degradation of Congo red dye in wastewater. A possible photocatalytic mechanism was proposed for degradation of Congo red dye.     

Micromechanical properties of hydroxyapatite nanocomposites reinforced with CNTs and ZrO2

This study examined the mechanical properties, wettability, and tribology of hydroxyapatite (HA)–zirconia (ZrO₂)–carbon nanotube (CNTs) ceramic nanocomposites (with various CNT ratios (x): 1, 5, and 10 wt%). HA–ZrO₂–CNT-x powders were hydrothermally synthesized. Hot isostatic pressing (HIP) and cold isostatic pressing were used to manufacture solid and dense tablets; consolidation was performed by sintering the nanocomposites under Ar gas at 1150 °C during HIP. The microstructure and morphology of the nanocomposites were characterized via transmission electron microscopy, energy-dispersive X-ray spectroscopy, powder X-ray diffractometry, Fourier transform infrared (FTIR), and scanning electron microscopy. The effects of ZrO₂ and CNTs on the mechanical characteristics of the nanocomposites were examined via nanoindentation, reciprocating wear, and Vickers hardness tests. The microhardness of HA–ZrO₂–CNT-1% and HA–ZrO₂–CNT-5% increased by 36.8% and 66.67%, respectively, compared with that of pure HA. The nanohardness of the HA–ZrO₂–CNT-1%, HA–ZrO₂–CNT-5%, and HA–ZrO₂–CNT-10% samples was 8.3, 9.65, and 8.02 Gpa, and the corresponding elastic modulus was 83.72, 114.34, and 89.27 GPa, respectively. Both of these parameters were higher than those of pure HA. However, in the nanocomposite reinforced with 10% CNT, as opposed to those with lower CNT ratios, their values were lower. Additionally, HA–ZrO₂–CNT-10% was the most hydrophilic nanocomposite synthesized in this study with a contact angle of 48.8°.     

In situ development of bio‐based polyurethane‐blend‐epoxy hybrid materials and their nanocomposites with modified graphene oxide via non‐isocyanate route

We developed a series of sunflower oil‐based non‐isocyanate polyurethane (NIPU)‐blend‐epoxy hybrid materials (HNIPUs) and their nanocomposites with amine‐functionalized graphene oxide (AF‐GO). Firstly, carbonated sunflower oil (CSFO) containing five‐membered cyclocarbonate groups was synthesized by the reaction of epoxidized sunflower oil with carbon dioxide (CO₂) at a pressure of 50 bar and temperature of 110 °C. Then, a series of HNIPUs were synthesized using a mixture of CSFO and a commercially available epoxy resin in various amounts (10, 20 and 30 wt% with respect to CSFO) using isophorone diamine as the curing agent. The HNIPU with 30 wt% epoxy showed the best mechanical properties. Finally, nanocomposites of 30 wt% HNIPU‐based composition were prepared with various amounts of AF‐GO (0.3, 0.6 and 1.0 wt%) and were characterized using Fourier transform infrared and ¹H NMR spectroscopies, X‐ray diffraction and scanning electron microscopy. These results emphasize the potentiality of this environmentally friendly approach for preparing renewable HNIPU and nanocomposite materials of high performances. © 2018 Society of Chemical Industry     

Annealing temperature dependence of local piezoelectric response of (Pb,Ca)TiO3 ferroelectric thin films

In this work, we have systematically investigated the piezo/ferroelectric response of (Pb, Ca)TiO₃ thin films prepared by polymeric precursor method using simultaneously topography, piezoresponse force microscopy (PFM) and local piezoelectric hysteresis loop measurements. The thin films were grown on Pt/Ti/SiO₂/Si substrates and annealed at 400, 500 and 600 °C and subjected to structural characterization using x-ray diffraction, infrared and micro-Raman spectroscopy. The ferroelectric domains structure and the piezoelectric response evolved as a function of thermal annealing temperature as well as the density of active grains (number of switchable domains) progressively increased. Another important characteristic of these films is the onset of large area showing the coexistence of active (stronger piezoresponse signal) and inactive (weak or non piezoresponse signal) grains embedded in the polycrystalline perovskite matrix. A combination of out-of-plane (OP) and in-plane (IP) PFM images revealed local features of polarization component magnitudes in samples surface. Well-defined local piezoelectric hysteresis loop was achieved on top of individual nanometer-scale grains in both samples annealed at 500 and 600 °C, and the switching behavior is evident.     

Polyaniline nanorod adsorbed on reduced graphene oxide nanosheet for enhanced dielectric,viscoelastic and thermal properties of epoxy nanocomposites

In this work, polyaniline nanorod adsorbed on reduced graphene oxide (P@G) hybrid filler was prepared via in situ polymerization of aniline monomer in the presence of reduced graphene oxide as template. Fourier transform infrared, X-ray diffraction, field emission scanning electron microscopy, and high-resolution transmission electron microscopy images revealed the formation of P@G hybrid. The P@G hybrid was dispersed in dichlorobenzene and then introduced into epoxy resin at different loadings. The epoxy nanocomposites containing 9 wt% P@G hybrids (E/P@G9) exhibited a maximum DC conductivity of 1.34 × 10⁻⁵ S/cm that is eight orders higher compared to pure epoxy. At 10³ Hz, a dielectric constant (ε′) of 163 was attained for E/P@G9, nearly 34 times higher than pure epoxy. A percolation threshold of 4 vol% was observed for ε′. Dynamic mechanical studies showed that significant enhancement in storage modulus values were exhibited for 3 and 5 wt% of hybrids. The glass transition temperature showed a maximum shift of 10°C to higher temperatures at 3 wt% loading of P@G hybrids (E/P@G3). The tensile strength, Young's modulus, and impact strength of the E/P@G3 nanocomposites enhanced by 19.7, 72, and 12%, respectively. The thermal stability of the epoxy nanocomposites also enhanced with the addition of P@G hybrid.     

Ferroelectric switching and current characteristics dependence on ferroelectric polarization direction of microwave synthesized BiFeO3 nanocubes

Herein, we studied the ferroelectric switching and current characteristics of BiFeO₃ (BFO) nanocubes dispersed on the surface of a Nb-doped SrTiO₃ (Nb:STO) substrate based on the ferroelectric polarization orientation. The microwave synthesis method afforded BFO nanocubes with an average size of ～50 nm, which were dispersed on the Nb:STO substrate surface and the substrate was subsequently subjected to heat treatment at 500 °C for 1 h. The piezoelectric d₃₃ hysteresis loop, ferroelectric domain structure, and ferroelectric polarization switching characteristics of the 50-nm-sized BFO nanocubes were examined using piezoresponse force microscopy. Finally, atomic force microscopy confirmed the dependency of current characteristics on the ferroelectric polarization orientation of the BFO nanocubes, verifying the applicability of BFO nanocubes as storage media for ferroelectric polarization information.     

Synthesis and characterization of β-TCP/CNT nanocomposite: Morphology,microstructure and in vitro bioactivity

In this study, β-TCP/CNT nanocomposite has been synthesized by solution precipitation method. Then, the effects of the different percentage of CNT (CNT1β-TCP, CNT3β-TCP, CNT5β-TCP) and surfactant (CNT1β-TCP1SDBS, CNT1β-TCP2SDBS, CNT1β-TCP3SDBS) on β-TCP/CNT nanocomposite powder were studied. The X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and Transmission electron microscopy (TEM) analyses were used to characterize the samples. The observations revealed that the microstructure of 1 wt% CNT could provide dispersion without agglomeration in nanocomposite powder; however, a higher concentration of CNT powder in the nanocomposite resulted in the formation of Ca₂PO₇ phase. Implementing 2 wt% of SDBS as a surfactant modified the shape, size, and distribution of CNT particles on nanocomposites. Finally, the nanocomposite sample was immersed in simulated body fluid (SBF) to evaluate the in vitro bioactivity. It obviously showed an apatite layer on the surface after 7 days of immersion in SBF. Taken together, this nanocomposite might be potentially to be used as bone repair biomaterial.     

BaTiO3 nanocubes-Gelatin composites for piezoelectric harvesting: Modeling and experimental study

Flexible composites containing BaTiO₃ nanoparticles into Gelatin bio-polymer matrix were designed and investigated. Following the idea that the electric field concentration in corners/edges at the interfaces between dissimilar materials give rise to enhanced effective permittivity in composites, cuboid-like BaTiO₃ nanoparticles have been employed as nanofillers into Gelatin matrix by using an inexpensive solution-based processing method. As predicted by finite element method simulations developed for cubic-like inclusions into a homogeneous polymer matrix, the experimental permittivity of xBT-(1-x)Gelatin composites increases when increasing the high-permittivity filler addition. For the composition x = 40 wt% (corresponding to 12 vol% BaTiO₃ addition), permittivity reaches ε_r ～15.7 with respect to ε_r ～9.8 of pure Gelatine (measured at 10⁵ Hz), while the average piezoelectric coefficient d₃₃ as determined by piezoelectric force microscopy shows a remarkable increase up to 21 pm/V in composites with x = 40 wt%, in comparison to ～7 pm/V in pure Gelatin. By using the experimentally determined material constants, the simulated piezoelectric voltage output vs. time has shown a similar increase (about a doubling of its amplitude) of the harvesting signal in the composite with x = 40 wt% BT, with respect to one of the polymer matrix, thus demonstrating the beneficial role of embedding BT nanoparticles into the biopolymer for increasing the mechanical harvesting response.