High-performance Nanocomposites Research Articles

Innovative design of environmentally friendly silicon-based polyphosphazene-functionalized hydroxyapatite nanowires: An efficient enhancement strategy for the fire safety and mechanical properties of unsaturated polyester

Non-toxic, low-smoke, high-efficiency and environmentally friendly flame retardants have become a hot issue at present. Here, polyphosphazene crosslinked by hexachlorocyclotriphosphazene (HCCP), 3-aminopropyltriethoxysilane (APTES), and dopamine (DA) was used to modify hydroxyapatite nanowires (HAPNW), obtaining a new environmentally friendly nanohybrids (f-HAPNW). Immediately afterwards, f-HAPNW was incorporated in unsaturated polyester (UPR) matrix in the presence of a nanowire structure with a high aspect ratio, accompanied by excellent interfacial compatibility. The incorporation of a small amount of f-HAPNW achieved an overall improvement in the fire safety and mechanical properties of UPR nanocomposites, including 23% decrease in total heat release rate (THR), 25.7% and 29.5% reduction in total smoke production (TSP) and the peak of CO production rate (PCOP) when the content was 2.0 wt%; 80.1% and 11.9% simultaneous increase in tensile strength and fracture elongation, and 61.2% increase in impact strength when the content was 0.5 wt%. Compared with similar previous research, the introduction of bio-based materials and environmentally friendly flame retardants in the design achieved significant flame-retardant filler efficiency, while considering the issues of reducing smoke release and environmental pollution. In general, this work innovatively prepared an environmentally-friendly hierarchical f-HAPNW structure, and achieved a comprehensive improvement in the performance of UPR nanocomposites, providing a reference idea for the design of high-performance UPR nanocomposites.

Enhanced Mechanical Properties of 3D Printed Nanocomposites Composed of Functionalized Plant-Derived Biopolymers and Calcium-Deficient Hydroxyapatite Nanoparticles

The combination of plant-derived polymer resins and mineral-based nanoparticles into three dimensional (3D) printable, high-performance nanocomposites suggests a means to improve the sustainability profile of rapid prototyping and additive manufacturing. In this work, our previously published nanocomposite biomaterial system of acrylated epoxidized soybean oil (AESO) and polyethylene glycol (PEGDA) diluent composited with calcium-deficient hydroxyapatite (nHA) nanorods was improved by the substitution of AESO with methacrylated AESO (mAESO) and the partial substitution of PEGDA with isosorbide methacrylate (IM). mAESO was used to increase the degree of crosslinking and reduce the ink viscosity. IM was synthesized by reacting the hydroxyl groups on isosorbide with methacrylic anhydride. The effects of partially replacing PEGDA with IM on the rheology and printability of the nanocomposite inks and the mechanical properties of the resulting nanocomposite materials were quantified. These masked stereolithography (mSLA) printed nanocomposites have greatly improved mechanical properties (tensile strength, Young’s modulus, and Mode-I fracture toughness) due to the shift to mAESO and IM. IM greatly improved the tensile fracture strength and Young’s modulus of the nanocomposites by acting as a reactive diluent and as a stiff segment in the polymer system. Dynamic mechanical analysis revealed that the glass transition temperature of the nanocomposite increased due to the addition of IM. However, IM decreased the strain-at–fracture, making the nanocomposites more brittle. This study demonstrates the development of high-performance mAESO-IM-nHA-based novel nanocomposites that can be easily 3D printed using desktop mSLA, suggesting a facile path forward to improved sustainability in rapid prototyping and additive manufacturing using nanocomposites for a broad range of applications.

Liquid phase exfoliated nanosheets as multifunctional fillers to semicrystalline polymers

Two-dimensional (2 D) materials have emerged as important part of high-performance polymer nanocomposites, thanks to their immaculate and tunable properties. Layered double hydroxides (LDHs), in particular, have received much attention in the polymer industry as multifunctional fillers for polyolefins and vinyl polymers. Highly exfoliated boron nitride nanosheets (BNNSs) have been a reliable partner for polyesters and polyamides, especially as thermal conductivity fillers. In this article, we have critically reviewed the latest developments in the field of polymer nanocomposites based on 2 D materials, with special emphasis on liquid phase exfoliated LDHs and BNNSs. Liquid phase exfoliation delivers few-layered or even monolayered nanosheets, and further structural modifications or surface functionalizations of these nanosheets result in better compatibility with the polymer matrix. Trace amounts of the exfoliated 2 D nanofillers can significantly alter the crystallization kinetics, mechanical properties, thermal stability, thermal conductivity and flame-retardant properties of polymers. Through this review, we aim to track down some of the important contributions in this area along with our own works, and this article is expected to fertilize considerable progress in this field.

Layered Biomimetic Composites from MXenes with Sequential Bridging.

Layer-by-layer (LbL) assembly is a widely used technique for the self-assembly of layered nanocomposites from clay sheets, carbon nanotubes, graphene oxide, nanoparticles, and other materials. Other approaches for fabricating layered nanocomposites include vacuum-assisted filtration and blade coating. They are simpler than LbL assembly, but they all introduce voids into the layered structure, thereby reducing the performance of the resulting nanocomposites. A team from Beihang University evaluated the void structure in Ti3 C2 Tx MXene composites and found that the fundamental problem with voids can be solved by the sequential nanoscale bonding of MXEne platelets with sodium carboxymethyl cellulose combined with covalent bridging with borate ions, thereby opening a new path to self-assemble two-dimensional platelets into continuous high-performance layered nanocomposites.

High-performance transparent nanocomposites based on robust organic nanoparticles for optoelectronic applications

Transparent nanocomposites, which are optically transparent and mechanically robust, have been drawn numerous interests for various applications, including adhesives, encapsulants, and other functional coatings. We demonstrated high-performance transparent nanocomposites with robust organic polystyrene nanoparticles (NPs) for optoelectronic devices. By optimizing the crosslinker concentration, the NPs improved their thermal stability and solvent resistance, allowing the NPs to be utilized in broad fields. Based on the nanoindentation results, we confirmed that the mechanical properties and elastic modulus were improved. We verified that the light-emitting diode encapsulation with this nanocomposite can enhance light-extraction efficiency by up to 10%, thereby suggesting the high optical clarity of nanocomposites with organic NPs.

Effect of CNT/CNC hybrid nanofiller on PVA/CNT/CNC nanocomposite

The idea of using a hybrid nanofiller comprised of two or more filler materials with different dimensionality can lead to a strong synergistic effect, surpass the performance of the individual filler and achieve its highest potential for improving the performance of nanocomposites. In this research, CNT/CNC hybrid filler was prepared by mixing the 6 w.t% of CNC with 0.2 g, 1.2 g, 2.2 g, 3.2 g, and 4.2 g of carbon nanotubes, respectively. The hybrid nanofiller produced was labeled as 0.2 CNT/CNC, 1.2 CNT/CNC, 2.2 CNT/CNC, 3.2 CNT/CNC, and 4.2 CNT/CNC. Subsequently, the CNT/CNC hybrid nanofiller was added as the reinforcement in 5 w.t% of polyvinyl alcohol (PVA) matrix to produce the CNT/CNC/PVA nanocomposite films using the solvent casting method. The CNC/CNC hybrid filler was characterized using viscometer and stability test while the CNT/CNC/PVA nanocomposite films were characterized using optical microscope (OM) and field emission scanning electron microscope (FESEM). The result showed that the stability of the hybrid filler could be sustained in one phase for up to 5 months. The highest viscosity of hybrid filler was at 4.2 g CNT/CNC hybrid nanofiller with 193.0 centipoises, cP. The morphology of CNT/CNC/PVA nanocomposite films from optical microscope and field emission scanning electron microscope (FESEM) revealed homogenous dispersion of hybrid nanofiller within the PVA matrix, and demonstrated the viscosity became higher due to high amounts of CNT. In conclusion, CNT/CNC can be an effective hybrid nanofiller for PVA matrix reinforcement for flexible, robust, high-performance nanocomposite.

Effect of Length of Cellulose Nanofibers on Mechanical Reinforcement of Polyvinyl Alcohol.

Cellulose nanofibers (CNF), representing the nano-structured cellulose, have attained an extensive research attention due to their sustainability, biodegradability, nanoscale dimensions, large surface area, unique optical and mechanical performance, etc. Different lengths of CNF can lead to different extents of entanglements or network-like structures through van der Waals forces. In this study, a series of polyvinyl alcohol (PVA) composite films, reinforced with CNF of different lengths, were fabricated via conventional solvent casting technique. CNF were extracted from jute fibers by tuning the dosage of sodium hypochlorite during the TEMPO-mediated oxidation. The mechanical properties and thermal behavior were observed to be significantly improved, while the optical transparency decreased slightly (Tr. > 75%). Interestingly, the PVA/CNF20 nanocomposite films exhibited higher tensile strength of 34.22 MPa at 2 wt% filler loading than the PVA/CNF10 (32.55 MPa) while displayed higher elastic modulus of 482.75 MPa than the PVA/CNF20 films (405.80 MPa). Overall, the findings reported in this study provide a novel, simple and inexpensive approach for preparing the high-performance polymer nanocomposites with tunable mechanical properties, reinforced with an abundant and renewable material.

Monodisperse branched nickel carbide nanoparticles in situ grown on reduced graphene oxide with excellent electromagnetic absorption properties

Carbide/carbon composites are new types of electromagnetic (EM) wave absorbing materials because of their good stability, light weight, easy synthesis and excellent performance. In this work, monodisperse branched nickel carbide (Ni3C) nanoparticles with controlled morphology were fabricated through high-temperature pyrolysis of nickel acetylacetonate under anhydrous and oxygen-free conditions. Then Ni3C nanoparticles were uniformly in situ grown on the surface of reduced graphene oxide (rGO) to form nickel carbide/reduced graphene oxide (Ni3C/rGO) nanocomposite. Series of characterization and performance tests were conducted, and the results showed that the EM wave absorption performance of Ni3C/rGO composite was greatly enhanced compared with that of pure phase Ni3C nanoparticles. Due to the combined effects of interfacial polarization loss, conductivity loss and surface defects, Ni3C/rGO nanocomposite exhibited strong reflection loss in 2–18 GHz band, which could attenuate the EM waves incident to the internal loss to a greater extent. When the Ni3C/rGO composite is at 3.5 mm thickness, the maximum effective absorption bandwidth can reach 3.6 GHz, and at 3.0 mm thickness, the lowest reflection loss value can reach − 42.8 dB. This high-performance nanocomposite can be a new candidate material for EM wave absorption.

Thin Film Polyamide Nanocomposite Membrane Decorated by Polyphenol-Assisted Ti3C2Tx MXene Nanosheets for Reverse Osmosis

Transition-metal carbides (MXenes), multifunctional 2D materials, have caught the interest of researchers in the fabrication of high-performance nanocomposite membranes. However, several issues regarding MXenes still remain unresolved, including low ambient stability; facile restacking and agglomeration; and poor compatibility and processability. To address the aforementioned challenges, we proposed a facile, green, and cost-efficient approach for coating a stable layer of plant-derived polyphenol tannic acid (TA) on the surface of MXene (Ti3C2Tx) nanosheets. Then, high-performance reverse osmosis polyamide thin film nanocomposite (RO-PA-TFN) membranes were fabricated by the incorporation of modified MXene (Ti3C2Tx-TA) nanosheets in the polyamide selective layer through interfacial polymerization. The strong negative charge and hydrophilic multifunctional properties of TA not only boosted the chemical compatibility between Ti3C2Tx MXene nanosheets and the polyamide matrix to overcome the formation of nonselective voids but also generated a tight network with selective interfacial pathways for efficient monovalent salt rejection and water permeation. In comparison to the neat thin film composite membrane, the optimum TFN (Ti3C2Tx-TA) membrane with a loading of 0.008 wt % nanofiller revealed a 1.4-fold enhancement in water permeability, a well-maintained high NaCl rejection rate of 96% in a dead-end process, and enhanced anti-fouling tendency. This research offers a facile way for the development of modified MXene nanosheets to be successfully integrated into the polyamide-selective layer to improve the performance and fouling resistance of TFN membranes.

Ultrahigh-power supercapacitors from commercial activated carbon enabled by compositing with carbon nanomaterials

Ultrahigh power is needed beyond the state-of-the-art supercapacitors for emerging technologies. Towards this goal, nanostructured carbon materials have been extensively studied but unfortunately encountered with the difficulty in practical applications, which is largely due to their limited packing densities. In this work, we utilize a highly dense commercial activated carbon to develop high-rate nanocomposite electrodes and ultrahigh-power supercapacitors by compositing activated carbon with carbon nanomaterials, including zero-dimensional carbon black, one-dimensional carbon nanotube, and two-dimensional graphene. Enabled by the mixed packing (forming a unique point-to-line-to-plane contact morphology), diverse electrical conduction (forming a well-interconnected three-dimensional electrical conduction network), and varied porosity (forming a well-defined hierarchical porous structure) from these multiple constituents, the optimized quaternary nanocomposite electrode possesses a good combination of facilitated electron transport and enhanced ion diffusion and thus a twofold higher rate capability (capacitance retention: 83.3% vs. 28.9% at 80 A g−1 vs. 0.5 A g−1), twofold higher power density (84.1 kW kg−1 vs. 41.9 kW kg−1), and superior high-rate cycling stability (capacitance retention: 80.2% vs. 65.9% after charge/discharge at 10 A g−1 for 30,000 cycles) than its conventional activated carbon counterpart, while its high volumetric power density (50.5 kW L−1) strengthens its practical usefulness. Our research represents a novel approach to fabricate commercially available materials into practically useful ultrahigh-power supercapacitors at low cost, which may also be employed as a universal strategy to develop high-performance nanocomposites to benefit a wider range of application technologies.

Distribution states of graphene in polymer nanocomposites: A review

Graphene has emerged as one of the promising nanoscale components of polymer nanocomposites owing to its exceptional properties. The 2D graphene material, when distributed appropriately in the host polymer can significantly alter the load, electron, and phonon transfer behavior of the nanocomposites. The in-plane strong covalent bonds in graphene are accountable for these unique properties, whereas the weak van der Waals forces existing between the adjacent monolayer graphene planes are responsible for the re-stacking or agglomeration of layers. Hence, the most critical challenge in translating these properties in high-performance graphene polymer nanocomposite is to alleviate the agglomeration of graphene. This can be achieved by improving the distribution states of graphene in the matrix by; (1) enhancing the dispersion and (2) controlling the relative lattice orientation of graphene in substrates to create an alignment or orientation. Mitigating the agglomerates during the composite fabrication will significantly extend the benefits of graphene's inherent properties to the nanocomposite. In this review article, various methods for improving dispersion and orientation of graphene in polymer nanocomposites is elucidated. A decision flowchart on the choice of dispersion or orientation based on the properties is considered and the techniques to quantify and verify the same is deliberated. Furthermore, composites' performance in terms of mechanical, electronic, and thermal enhancements due to the molecular level dispersion or anisotropic orientation of graphene is discussed. This review provides a constructive guidance in the composite processing methods and to correlate the enhancement of properties with the distribution state of graphene in composites. Predominantly epoxy and PDMS polymers are reinforced by 3D graphene as fillers due to their structural stability and wider applications. It is also witnessed that 3D graphene reinforced composites are mainly investigated for electrical and thermal properties followed by mechanical and acoustic properties.

High-performance UV-curable epoxy acrylate nanocomposite coatings reinforced with aramid nanofibers

UV-curing epoxy acrylate (EA) nanocomposite films with different amounts of aramid nanofibers (ANFs) synthesized by a bottom-up method were prepared. The effects of the ANFs on the coating microstructures, curing kinetics, optical light transmittance, mechanical properties, and thermal stability were investigated. Although the ANFs strongly absorb UV light, ANF incorporation did not decrease the final CC bond conversion of the nanocomposites. The UV transmittance of the nanocomposite films decreased dramatically with increasing ANF content, but all films maintained a high visible transmittance. Relative to neat EA, the tensile strength of the 0.05 wt% ANF-reinforced nanocomposites increased by 36%, and the elongation at break of the 0.1 wt% ANF-reinforced nanocomposites increased by 194%. This was mainly attributed to the favorable ANF mechanical properties and their strong interactions (hydrogen bonds and π–π stacking) with EA. This work demonstrates that a small amount of ANFs can enhance the UV-shielding and mechanical properties of UV-curable EA coatings without affecting the transparency or final conversion.

Facile preparation of high-performance and multifunctional PVC-based nanocomposites with segregated structure achieved by volume repulsion and toughening effects of ABS

A facile and industrially feasible approach for preparation of polyvinyl chloride (PVC)/conductive carbon black (CCB) nanocomposites with good electrical conductivity, thermal conductivity, flame retardant property and toughness has been developed in this work. Specifically, acrylonitrile–butadienestyrene elastomer containing 67 wt% butadiene content (ABS) is chosen as volume exclusion phase and toughening phase for constructing PVC/CCB nanocomposites with segregated filler network structure and sea-island phase structure. Benefiting from more intact and denser filler network provided by segregated structure, the resultant PVC/ABS/CCB nanocomposites have exhibited higher electrical and thermal conductivity than those of PVC/CCB nanocomposites. Benefiting from high elasticity of polybutadiene rubber and molecular interface compatibility between PVC and acrylonitrile-containing shell of ABS, the resultant PVC/ABS/CCB nanocomposites have also exhibited excellent toughness. In a word, the as-fabricated PVC/ABS/CCB nanocomposites have advantages of low cost, simple preparation, high mechanical property and versatile functions, endowing them great practical value.

An ultrastrong, reversible thermochromic film based on TEMPO-oxidized nanofibrillated cellulose

Despite the growing interest in polydiacetylene (PCDA)-based materials in recent years due to their thermal-stimuli responsive discoloration characteristics, it is still a huge challenge to fabricate high-performance and environment-friendly thermochromic materials. In this work, we demonstrated ultrastrong thermochromic materials based on 1,6-Diaminohexane (DH) crosslinked 2,2,6,6-tetramethylpiperidine-1-oxylradi-cal (TEMPO)-oxidized nanofibrillated cellulose (TNFC) matrix and poly-PCDA chains through a vacuum-assisted filtration assembly technique. The synergistic interactions of covalent cross-linking networks efficiently prevented crack propagation under loading, endowed the resulting TNFC-polyPCDA-DH nanocomposites with super high tensile strength of 281.63 ± 5.63 MPa and Young's modulus of 13.68 ± 1.09 GPa. Moreover, the resultant nanocomposites exhibited a rapidly reversible thermal discoloration (up to 140 °C), and excellent thermal reversible cycling performance. This strategy offers a promising approach to design and prepare flexible high-performance intelligent nanocomposite, which may be widely applied in wearable sensors, displays, and anti-counterfeiting labels.

Piezoelectric fiber composites with polydopamine interfacial layer for self-powered wearable biomonitoring

Doping polymers with ceramic nanofillers is a widely-adopted routine for developing high-performance nanocomposites. However, improving the interaction between the nanofillers and the polymer matrix for an enhanced composite performance remains highly desired in the community. Herein, we systematically investigated the barium titanate doped polyvinylidene fluoride (BTO/PVDF) piezoelectric nanocomposites in a fiber form through comprehensive phase-field simulation and detailed experimental characterization. Both experimental and theoretical results indicated that the introduction of 2.15 vol% polydopamine (PDA) coating on the BTO nanoparticles could remarkably promote the local all-trans conformation and modulus match at the nanofillers-polymer interface, giving rise to the maximum piezoelectric charge coefficient and piezoelectric voltage coefficient as well as mechanical stiffness. To demonstrate the effectiveness of the PDA modification, a polydopamine modified nonwoven piezoelectric (PMNP) textile was constructed based on the composite fiber, which showed outstanding sensitivity and long-term stability for wearable biomonitoring, including limb motion detection, facial expression identification, respiratory monitoring, and human-machine interfacing. This work endows insight into the fundamental mechanism of the interfacial coupling effect in polymer composites for the development of high-performance wearable textile bioelectronics. • Polydopamine modified nonwoven piezoelectric (PMNP) textile was developed. • The mechanism was studied via phase-field simulation and detailed characterization. • 2.15 vol% PDA coating maximizes the piezoelectric coefficient and β phase content. • Facial emotion identification and human-machine interaction was enabled by PMNPs.

A Review on the Synthesis, Properties, and Utilities of Functionalized Carbon Nanoparticles for Polymer Nanocomposites.

Carbon can form different allotropes due to its tetravalency. Different forms of carbon such as carbon nanotubes (CNTs), carbon nanofibers, graphene, fullerenes, and carbon black can be used as nanofillers in order to enhance the properties of polymer nanocomposites. These carbon nanomaterials are of interest in nanocomposites research and other applications due to their excellent properties, such as high Young’s Modulus, tensile strength, electrical conductivity, and specific surface area. However, there are some flaws that can be found in the carbon nanoparticles such as tendency to agglomerate, insoluble in aqueous or organic solvents or being unreactive with the polymer surface. In this study, the aim is to study functionalization in order to rectify some of these shortcomings by attaching different functional groups or particles to the surface of these carbon nanoparticles; this also enables the synthesis of high-performance polymer nanocomposites. The main findings include the effects of functionalization on carbon nanoparticles and the applications of polymer nanocomposites with carbon nanoparticles as nanofillers in the industry. Additionally, the different methods used to produce polymer composites such as in situ polymerization, solution mixing and melt blending are studied, as these methods involve the dispersion of carbon nanofillers within the polymer matrix.

PVA/cellulose nanocrystal nanocomposites films incorporated with copper nanoparticles; characterization and antibacterial performance

Due to their unique structure and properties, biocompatibility, adaptable surface chemistry, optical transparency, non-toxic, biodegradability, and improved mechanical properties, cellulose nanocrystals (CNCs) are considered very promising for use as reinforcement material in construction of high-performance nanocomposites. Many biodegradable polymers are used as a matrix in the manufacture of these nanocomposites, among them polyvinyl alcohol (PVA). In the current study, the nanocomposites films, PVA loaded by CNCs prepared from rice husk and PVA loaded by CNCs and copper nanoparticles (Cu-NPs) were fabricated. The prepared nanocomposite films were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA&DTA), and mechanical properties. The prepared nanocomposites films were evaluated for their antibacterial activity by disk diffusion technique against pathogenic bacteria. The results reveal that PVA films loaded by CNCs and Cu-NPs have improved tensile strength as well as efficient antibacterial activity against Gram-negative and Gram-positive strains and are promising to be used as packaging material.

Multifunctional nacre-mimetic Ti3C2Tx films with tunable conductivity and mechanical properties by controlling interlay supramolecular interactions

Nacre-mimetic strategy provides an enlightening approach to design high-performance bioinspired nanocomposites. Yet, it is still a big challenge to integrate excellent mechanical properties and tunable multifunctionality into artificial nacre materials. Herein, we develop a pioneering strategy to simultaneously modulate the electrical conductivity and mechanical properties of nacre-mimetic nanocomposite films by controlling interlay supramolecular interactions. A series of novel waterborne polyurethanes with 2-ureido-4[1H]-pyrimidinone (UPy) quadruple hydrogen bonding motifs in the side-chains were elaborately designed and synthesized, and further assembled with Ti3C2Tx MXene nanosheets to construct lamellar nacre-mimetic nanocomposite films with highly ordered nanostructure. This research revealed for the first time that merely varying the content of UPy groups on polyurethane realize significant modulation of mechanical properties, electrical conductivity, and even the electromagnetic shielding effectiveness of nacre-mimetic nanocomposites. Strikingly, the tensile strength of the nanocomposites can be improved from 87.91 to 136.96 MPa and the electrical conductivity from 3214.0 to 4136.1 S cm−1 when the UPy content is increased from 0 to 15%. Additionally, the nacre-mimetic nanocomposite film is capable of fast responsive Joule heating performance at low trigger voltage. This work would open up a new avenue for fabricating multifunctional and mechanically robust biomimetic nanocomposites.

High-Performance, Lightweight, and Flexible Thermoplastic Polyurethane Nanocomposites with Zn2+-Substituted CoFe2O4 Nanoparticles and Reduced Graphene Oxide as Shielding Materials against Electromagnetic Pollution.

The development of flexible, lightweight, and thin high-performance electromagnetic interference shielding materials is urgently needed for the protection of humans, the environment, and electronic devices against electromagnetic radiation. To achieve this, the spinel ferrite nanoparticles CoFe2O4 (CZ1), Co0.67Zn0.33Fe2O4 (CZ2), and Co0.33Zn0.67Fe2O4 (CZ3) were prepared by the sonochemical synthesis method. Further, these prepared spinel ferrite nanoparticles and reduced graphene oxide (rGO) were embedded in a thermoplastic polyurethane (TPU) matrix. The maximum electromagnetic interference (EMI) total shielding effectiveness (SET) values in the frequency range 8.2–12.4 GHz of these nanocomposites with a thickness of only 0.8 mm were 48.3, 61.8, and 67.8 dB for CZ1-rGO-TPU, CZ2-rGO-TPU, and CZ3-rGO-TPU, respectively. The high-performance electromagnetic interference shielding characteristics of the CZ3-rGO-TPU nanocomposite stem from dipole and interfacial polarization, conduction loss, multiple scattering, eddy current effect, natural resonance, high attenuation constant, and impedance matching. The optimized CZ3-rGO-TPU nanocomposite can be a potential candidate as a lightweight, flexible, thin, and high-performance electromagnetic interference shielding material.

Low-Cost, High-Performance Piezoelectric Nanocomposite for Mechanical Energy Harvesting

Lack of low-cost, large area deposition methods and photo-patternability of high-performance piezoelectric materials restrict the rapid development of efficient functional devices like sensors and energy harvesters. In this paper, we report an optimized process flow for Zinc Oxide (ZnO)/SU-8 and Barium Titanate (BTO)/SU-8 based nanocomposite thin films for mechanical energy harvesting (MEH) applications. Parametric variation of process variables for these nanocomposites reveals that 15% ZnO/SU-8 and 20% BTO/SU-8 nanocomposites show optimum results with good piezoelectric response and UV transmittance, allowing reliable lithography of the nanocomposites. Furthermore, three different types of energy harvesting devices are fabricated using these nanocomposites as piezoelectric layer. Output powers of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$223~\mu \text{W}$ </tex-math></inline-formula> (ZnO/SU-8) and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$642~\mu \text{W}$ </tex-math></inline-formula> (BTO/SU-8) are produced at resonance for the conventional cantilever type MEH devices at an input acceleration of 0.5g. Using the nanocomposites as flexible nanogenerator, open circuit voltages of 570 mV (ZnO/SU-8) and 780mV (BTO/SU-8) are obtained using regular finger pressing. The hybrid energy harvesters, based on combined piezoelectric-triboelectric transduction mechanisms, generate output voltages of 0.4V, 0.95V, 1.4V (ZnO/SU-8) and 0.7V, 1.1V and 1.9V (BTO/SU-8) in piezoelectric, triboelectric and hybrid operations, respectively.