Synergistic effects of zirconia-coated carbon nanotube on crystalline structure of polyvinylidene fluoride nanocomposites: electrical properties and flame-retardant behavior

CNT modified layered α-MnO2 hybrid flame retardants: preparation and their performance in the flame retardancy of epoxy resins

In this paper, CNT modified layered α-MnO₂ hybrid flame retardants (α-MnO₂–CNTs) were synthesized through one-pot preparation. The structure and composition of the α-MnO₂–CNTs hybrid flame retardants were investigated by X-ray diffraction, TEM and SEM. Subsequently, the α-MnO₂–CNTs hybrids were then incorporated into epoxy resin (EP) to improve the fire safety properties. Compared with pure EP and the composites with CNTs or α-MnO₂, EP/α-MnO₂–CNTs composites exhibited improved flame retardancy and smoke suppression properties. With the incorporation of only 2.0 wt% of α-MnO₂–CNTs hybrid flame retardants, the peak heat release rate and total heat release of the composites showed 34% and 10.7% reduction respectively. In addition, the volatile gases such as CO and CO₂ were reduced and the smoke generation was also effectively inhibited. The improved fire safety of the composites is generally due to the network structures and the synergistic effect of α-MnO₂ and CNTs, the catalyzing charring effect, smoke suppression and the physical barrier effect of α-MnO₂ nanosheets.

In this paper, CNT modified layered α-MnO₂ hybrid flame retardants (α-MnO₂–CNTs) were synthesized through one-pot preparation.

Enhanced thermal properties of poly(lactic acid)/MoS2/carbon nanotubes composites

In this work, few-layered molybdenum disulfide (MoS₂) was functionalized with metal oxide (M_xO_y) nanoparticles which served as a catalyst for carbon nanotubes (CNT) growth in the chemical vapour deposition (CVD) process. The resulting MoS₂/M_xO_y/CNT functionalized nanomaterials were used for flame retarding application in poly(lactic acid) (PLA). The composites were extruded with a twin-screw extruder with different wt% loading of the nanomaterial. Full morphology characterization was performed, as well as detailed analysis of fire performance of the obtained composites in relation to pristine PLA and PLA containing an addition of the composites. The samples containing the addition of MoS₂/M_xO_y/CNT displayed up to over 90% decrease in carbon oxide (CO) emission during pyrolysis in respect to pristine PLA. Microscale combustion calorimetry testing revealed reduction of key parameters in comparison to pristine PLA. Laser flash analysis revealed an increase in thermal conductivity of composite samples reaching up to 65% over pristine PLA. These results prove that few-layered 2D nanomaterials such as MoS₂ functionalized with CNT can be effectively used as flame retardance of PLA.

Portable Self-Powered Piezoelectric Nanogenerator and Self-Charging Photo-Power Pack Using In Situ Formed Multifunctional Calcium Phosphate Nanorod-Doped PVDF Films

Herein, biocompatible Ca₃(PO₄)₂ nanorod-incorporated poly(vinylidene) difluoride films have been prepared via an in situ process. A good piezoelectricity (d₃₃ ≈ 56.6 pC/N) along with a large dielectric constant of ∼3.48 × 10⁵ at frequency 20 Hz has been achieved. Then, we have designed a biocompatible, highly durable, low-cost piezoelectric nanogenerator (CPNG) which shows the superiority in open-circuit voltage ∼47 V and current ∼1.8 μA generation with power density ∼47.4 mW cm^-3 under the gentle touch of a finger. Excellent mechanical to electrical energy conversion efficiency (∼65.5%) of our developed CPNG leads to fast charging of a capacitor of 1 μF in 18 s and glowing of 26 light-emitting diodes (LEDs) under finger impartation. Further, a portable light-charging power pack (LCPP) has been developed using the high dielectric film as the storage function. Under light illumination, our LCPP generates open-circuit output voltage ∼1.29 V with short-circuit current 5.7 mA cm^-2. Areal capacitance ∼1779 F m^-2 and storage efficiency ∼88% are achieved. The device is able to lighten up 22 LEDs for 10 days after charging once.

Confined Dispersion of Zinc Hydroxystannate Nanoparticles into Layered Bimetallic Hydroxide Nanocapsules and Its Application in Flame-Retardant Epoxy Nanocomposites

In many fields, nanoparticles are frequently dispersed onto kinds of nanocarriers integrated into hybrid nanocomposites to acquire advanced performance. However, the nanoparticles usually tend to agglomerate on the surface, according to traditional synthetic methods. Besides, the exposed state of loaded nanoparticles and the weak adhesion with the supporters make them fall off during practical application, leading to "second agglomeration" of the nanoparticles and attenuated synergistic effects. In this work, we engineered layered bimetallic (Ni-Co) hydroxides (NCHs) into enclosed nanocages derived from metal organic frameworks (MOFs). Zinc hydroxystannate (ZHS) nanoparticles were selected to be confined dispersed within the hollow cavity of the three-dimensional nanocages. ZHS nanoparticles were tightly immobilized, monodispersing to form a novel multiyolk@shell nanostructure with NCH nanocages. To prove the effectiveness of this structural design, the as-synthesized hybrids ZHS@NCH were introduced into the epoxy matrix to inquiry its performance. Compared to neat ZHS, neat NCH, and physical mixture of ZHS and NCH, ZHS@NCH conferred better flame retardancy, thermal stability, and mechanical properties upon the epoxy nanocomposites. With the adding amount of 6 wt % ZHS@NCH, the UL-94 rating of the nanocomposite was V-0, and the peak of heat release rate value was reduced by 69.1%, while the mechanical properties were slightly influenced. The ingenious synthetic strategy gives insights into uniform distribution of nanoparticles within nanocapsules and enlightens the facile fabrication of multiyolk@shell nanomaterials.

Er3+/Fe3+ Stimulated Electroactive, Visible Light Emitting, and High Dielectric Flexible PVDF Film Based Piezoelectric Nanogenerators: A Simple and Superior Self-Powered Energy Harvester with Remarkable Power Density

The design of an energy-harvesting unit with superior output characteristics, i.e., high power density, is a great technological challenge in the present time. Here, simple, lightweight, flexible, and cost-effective piezoelectric nanogenerators (PENGs) have been fabricated by integrating the aluminum electrodes onto Er³⁺/Fe³⁺ stimulated electroactive, visible-light-emitting, and large dielectric PVDF films in which ErCl₃·6H₂O and Fe(NO₃)₃·9H₂O act as the catalytic agents for electroactive β polymorph nucleation and the enhancement of dielectric properties. The developed PENGs exhibit excellent energy-harvesting performance with very high power density and very fast charging ability compared with the previously reported PVDF-assisted prototype nanogenerators. The PENGs lead to very large power density (∼160 and ∼55.34 mW cm^-3) under periodic finger imparting for Er³⁺- and Fe³⁺-stimulated PVDF-film-based energy-harvester units, respectively. The fabricated self-powered PENG is also able to light up 54 commercially available light-emitting diodes.

The role of cerium(iii)/yttrium(iii) nitrate hexahydrate salts on electroactive β phase nucleation and dielectric properties of poly(vinylidene fluoride) thin films

Electroactive β phase nucleation in cerium/yttrium nitrate hexahydrate salt modified PVDF thin filmsviaformation of hydrogen bonds.