Controllable Core–Shell BaTiO₃@Carbon Nanoparticle-Enabled P(VDF-TrFE) Composites: A Cost-Effective Approach to High-Performance Piezoelectric Nanogenerators

Piezoelectric nanogenerators (PENGs), as a promising solution to harvest mechanical energy from ambient environment, have attracted much attention over the past decade. Here, the core–shell structured BaTiO3@Carbon (BT@C) nanoparticles (NPs) were synthesized by a simple surface-modifying method and then used to fabricate the efficient PENGs with poly­[(vinylidene fluoride)-co-trifluoroethylene] (P­(VDF-TrFE)). The carbon shell with the uniform thickness of 10–15 nm can increase the content of the polar β phase in P­(VDF-TrFE) and significantly enhance the interfacial polarization between BT NPs and the polymer matrix during the poling process. Out of all compositions, the 15 wt % BT@C/P­(VDF-TrFE) PENG exhibited the optimal piezoelectric performance with an output voltage of ∼17 V and a maximum power of 14.3 μW under bending–releasing mode. More importantly, the PENG can also efficiently harvest other types of mechanical energy from human activities and exhibits stable output after 1500 bending–releasing cycles. When the PENG was bent and beat by bicycle spokes, a peak voltage of 16 V was generated, which can light up 12 white LEDs directly and charge the commercial capacitors. Our research provides a new strategy to fabricate flexible and efficient PENGs from a nanoscale viewpoint; it can be hopefully applied in energy-harvesting systems and wearable electric sensors

Controllable Core–Shell BaTiO₃@Carbon Nanoparticle-Enabled P(VDF-TrFE) Composites: A Cost-Effective Approach to High-Performance Piezoelectric Nanogenerators

Piezoelectric nanogenerators (PENGs), as a promising solution to harvest mechanical energy from ambient environment, have attracted much attention over the past decade. Here, the core–shell structured BaTiO3@Carbon (BT@C) nanoparticles (NPs) were synthesized by a simple surface-modifying method and then used to fabricate the efficient PENGs with poly­[(vinylidene fluoride)-co-trifluoroethylene] (P­(VDF-TrFE)). The carbon shell with the uniform thickness of 10–15 nm can increase the content of the polar β phase in P­(VDF-TrFE) and significantly enhance the interfacial polarization between BT NPs and the polymer matrix during the poling process. Out of all compositions, the 15 wt % BT@C/P­(VDF-TrFE) PENG exhibited the optimal piezoelectric performance with an output voltage of ∼17 V and a maximum power of 14.3 μW under bending–releasing mode. More importantly, the PENG can also efficiently harvest other types of mechanical energy from human activities and exhibits stable output after 1500 bending–releasing cycles. When the PENG was bent and beat by bicycle spokes, a peak voltage of 16 V was generated, which can light up 12 white LEDs directly and charge the commercial capacitors. Our research provides a new strategy to fabricate flexible and efficient PENGs from a nanoscale viewpoint; it can be hopefully applied in energy-harvesting systems and wearable electric sensors

Controllable Core–Shell BaTiO₃@Carbon Nanoparticle-Enabled P(VDF-TrFE) Composites: A Cost-Effective Approach to High-Performance Piezoelectric Nanogenerators

Piezoelectric nanogenerators (PENGs), as a promising solution to harvest mechanical energy from ambient environment, have attracted much attention over the past decade. Here, the core–shell structured BaTiO3@Carbon (BT@C) nanoparticles (NPs) were synthesized by a simple surface-modifying method and then used to fabricate the efficient PENGs with poly­[(vinylidene fluoride)-co-trifluoroethylene] (P­(VDF-TrFE)). The carbon shell with the uniform thickness of 10–15 nm can increase the content of the polar β phase in P­(VDF-TrFE) and significantly enhance the interfacial polarization between BT NPs and the polymer matrix during the poling process. Out of all compositions, the 15 wt % BT@C/P­(VDF-TrFE) PENG exhibited the optimal piezoelectric performance with an output voltage of ∼17 V and a maximum power of 14.3 μW under bending–releasing mode. More importantly, the PENG can also efficiently harvest other types of mechanical energy from human activities and exhibits stable output after 1500 bending–releasing cycles. When the PENG was bent and beat by bicycle spokes, a peak voltage of 16 V was generated, which can light up 12 white LEDs directly and charge the commercial capacitors. Our research provides a new strategy to fabricate flexible and efficient PENGs from a nanoscale viewpoint; it can be hopefully applied in energy-harvesting systems and wearable electric sensors

Processable Dispersions of Graphitic Carbon Nitride Based Nanohybrids and Application in Polymer Nanocomposites

Graphitic carbon nitride (g-C₃N₄) nanosheets are endowed with extraordinary chemical and thermal stability and good optical and photoelectrochemical properties and are expected to be used in a wide range of fields. The direct dispersion of hydrophobic g-C₃N₄ nanosheets in water or organic solvents without the assistance of dispersing agents is considered to be a great challenge. Here we report novel g-C₃N₄/organic-modified montmorillonite (OMMT) nanohybrids, which were synthesized through electrostatic interaction and then introduced into polystyrene (PS) matrix to fabricate nanocomposites by a simple solvent blending–precipitation method. Hybridizing g-C₃N₄ with OMMT could easily form stable aqueous colloids through electrostatic stabilization. These nanohybrids were evenly dispersed in PS and showed strong interfacial interactions with the polymer matrix. It is noted that the generation of total gaseous products was dramatically inhibited by combining g-C₃N₄ with OMMT. Moreover, flame retardancy was improved upon incorporation of the nanohybrids into PS host. These improvements were due to the strong interactions at interface of ternary systems, synergism between g-C₃N₄ and OMMT, and physical barrier effect of the two components. This work provides a new pathway to manufacture well-dispersed polymeric materials with enhanced fire safety

Graphite-like Carbon Nitride/Polyphosphoramide Nanohybrids for Enhancement on Thermal Stability and Flame Retardancy of Thermoplastic Polyurethane Elastomers

Many efforts have been made to enhance the fire safety of thermoplastic polyurethane elastomers (TPUs) by reducing the heat release rate and smoke emission. Suppressing the emission of smoke and reducing toxic gases generated in the case of TPU burning play a key role to enable TPU meet the eco-friendly and safety requirements. In this work, poly diaminodiphenyl phosphonic methane (PDMPD) with higher thermal stability and catalytic char formation capacity was synthesized; graphitic carbon nitride/PDMPD (CPDMPD) hybrids were fabricated, and their effect on the thermal behavior and flame retardancy of TPU composites was studied. The peak heat release rate (PHRR), the total heat release, the CO yield, and the smoke release of TPU show an obvious reduction on account of addition of CPDMPD hybrids according to the cone tests. TPU/CPDMPD4 is endowed with a reduction of 49.0% of the PHRR. In this work, molecular designing and physical function are integrated to prepare versatile additives of polymers with optimized thermal stability and flame retardancy

Bioinspired Lamellar Barriers for Significantly Improving the Flame-Retardant Properties of Nanocellulose Composites

The traditional addition of phosphorus-containing flame retardants could improve the flame retardance of polymeric materials, but it usually deteriorates the mechanical strength and thermal stability. Herein, we report an interlayer-confined synthesis of multilayer zirconium phosphate-reduced graphene oxide (ZrP-RGO) nanoplates, which were incorporated into cellulose nanofibers to fabricate the hierarchical nanocellulose composites through a structural inspiration of nacre. The lamellar barriers consisting of highly aligned ZrP-RGO nanoplates along a planar orientation contribute to suppressing heat and mass transfer between the flame zone and underlying matrix, which gives rise to 75.1%, 71.4%, and 54.6% reductions in the peak heat release rate, peak smoke release rate, and peak CO production rate of nanocellulose composites, respectively. Moreover, the hierarchical nanocellulose composites simultaneously achieve better thermal stability, mechanical strength, and toughness compared to pure cellulose nanofibers. The formation of bioinspired lamellar barriers provides an innovative idea to significantly improve the flame retardance of nanocellulose composites, as well as thermal stability and mechanical properties

Bioinspired Lamellar Barriers for Significantly Improving the Flame-Retardant Properties of Nanocellulose Composites

The traditional addition of phosphorus-containing flame retardants could improve the flame retardance of polymeric materials, but it usually deteriorates the mechanical strength and thermal stability. Herein, we report an interlayer-confined synthesis of multilayer zirconium phosphate-reduced graphene oxide (ZrP-RGO) nanoplates, which were incorporated into cellulose nanofibers to fabricate the hierarchical nanocellulose composites through a structural inspiration of nacre. The lamellar barriers consisting of highly aligned ZrP-RGO nanoplates along a planar orientation contribute to suppressing heat and mass transfer between the flame zone and underlying matrix, which gives rise to 75.1%, 71.4%, and 54.6% reductions in the peak heat release rate, peak smoke release rate, and peak CO production rate of nanocellulose composites, respectively. Moreover, the hierarchical nanocellulose composites simultaneously achieve better thermal stability, mechanical strength, and toughness compared to pure cellulose nanofibers. The formation of bioinspired lamellar barriers provides an innovative idea to significantly improve the flame retardance of nanocellulose composites, as well as thermal stability and mechanical properties

Toward Flame Retardancy, Antimelt Dripping, and UV Resistance Properties of Polylactic Acid Based on Eco-Friendly Core–Shell Flame Retardant

To enhance the flame retardancy of polylactic acid (PLA), the exploration of bioderived flame retardants has captured the focus of researchers globally. Herein, a core–shell bioderived flame retardant is prepared through electrostatic self-assembly using ammonium polyphosphate (APP) as the core and chitosan (CS)/tannic acid (TA) bilayer as the shell. In addition, the Fe3+ ion is introduced into the outermost TA shell through coordination with the phenolic hydroxyl group, which can reduce the droplets during combustion. The prepared flame retardant, APP@CS@TA-nBL-Fe3+, has core–shell structure (where “nBL” represents the number of coating layers of CS and TA bilayer) and excellent flame retardancy for PLA. With 5 wt % flame retardant, PLA/5% APP@CS@TA-2BL-Fe3+ attains the highest LOI value (31.6%) and achieves UL-94 V-0 rating in vertical combustion tests with light melt droplets. Furthermore, cone calorimetry results reveal that a reduction of 17.6% in the peak heat release rate and a 22.3% decrease in total heat release were achieved. Meanwhile, the Fe3+ catalyzes the matrix to form a micro-cross-linked char layer blocking the heat and oxygen exchange. Moreover, PLA/5% APP@CS@TA-2BL-Fe3+ not only has a 99.98% reduction in UV transmittance but also has better mechanical properties after UV aging than that of neat PLA. This study presents a convenient and environmentally friendly approach for preparing efficient biobased flame retardants for PLA, aiming to broaden the application of PLA

Effect of Functionalized Graphene Oxide with Organophosphorus Oligomer on the Thermal and Mechanical Properties and Fire Safety of Polystyrene

A novel organophosphorus oligomer was synthesized to functionalize graphene oxide. Subsequently, the functionalized graphene oxide (FGO) was incorporated into polystyrene (PS) to enhance the integration properties of the matrix. The effect of FGO on the thermal properties, fire safety, and mechanical properties of PS nanocomposites was investigated. The results showed that the introduction of FGO significantly increased the maximum decomposition temperature (<i>T</i>_max) (25 °C increase), reduced the total heat release (20.8% reduction), and peak heat release rate (38.2% reduction) of PS. In addition, the thermogravimetric analysis/infrared spectrometry analysis results indicated that the amount of organic volatiles and toxic carbon monoxide of PS was remarkably reduced. The physical barrier effect of FGO and the synergistic effects between the organophosphorus oligomer and FGO were the main causations for these properties improvements. Homogeneous dispersion of FGO into the polymer matrix improved the mechanical properties of FGO/PS nanocomposites, as demonstrated by tensile tests results

Multifunctional High-Efficiency Additive with Synergistic Anion and Cation Coordination for High-Performance LiNi_0.8Co_0.1Mn_0.1O₂ Lithium Metal Batteries

Safety and high energy density have long restricted the large-scale practical application of lithium metal batteries because of the unbridled growth of lithium dendrites and the rapid deteriorating cycle performance of the LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode. Herein, an additive of RbNO3 with multiple functions is proposed for dendrite-free NCM811 lithium metal batteries. Benefiting from the electrostatic shielding effect formed by Rb+ during the Li+ deposition process and the solvation effect of NO3– to regulate lithium deposition, a high Coulombic efficiency of 95.02% (compared with the low Coulombic efficiency of 89.37% in the blank electrolyte) is acquired in Li//Cu cells, and the uniform growth of the lithium metal deposition with a large strawberry-like morphology is achieved. Moreover, when a cathode of NCM811 matches with a lithium metal anode, an extraordinary capacity retention of 93.67% after 200 cycles with a high Coulombic efficiency of 99.7% in the electrolyte with the RbNO3 system (a capacity retention of 80.1% with a Coulombic efficiency of 98.0% for the blank electrolyte) is achieved at 1C. This work provides guidance for the development of high-efficiency additives with dual synergistic regulation effects of anions and cations for lithium metal batteries in the future