Mechanical and Thermal Characterization of Annealed Oriented PAN Nanofibers

Lightweight acoustic hyperbolic paraboloid diaphragms with graphene through self-assembly nanoarchitectonics

The paper presents a study on the fabrication of a lightweight acoustic hyperbolic paraboloid (HyPar) diaphragm using self-assembly nanoarchitectonics. The diaphragm is composed of a polyacrylonitrile (PAN) network combined with graphene oxide (GO) nanolayers. Spray coating is employed as a fabrication method, providing a simple and cost-effective approach to create large-scale curved diaphragms. The results demonstrate that the PAN/GO diaphragm exhibits acoustic performance comparable to a commercially available banana pulp diaphragm while significantly reducing weight and thickness. Notably, the graphene-based diaphragm is 15 times thinner and 8 times lighter than the commercial banana pulp diaphragm. This thinner and lighter nature of the graphene-based diaphragm offers advantages in applications where weight and size constraints are critical, such as in portable audio devices or acoustic sensors.

Pre-oxidized and composite strategy greatly boosts performance of polyacrylonitrile/LLZO nanofibers for lithium-metal batteries

The active cyano-group in polyacrylonitrile has severe passivation of lithium anode under larger current density, which restricts the wide application of polyacrylonitrile(PAN) in lithium metal batteries. Herein, in order to address the excessive passivation of lithium metal by PAN, inspired by the pre-oxidation of carbon fibers, PAN was pre-oxidized at 230 °C, which transformed part of the cyano group into a more chemically stable cyclized structure. The electrochemical and mechanical properties of the composite solid electrolyte were effectively improved by introducing the fast ionic conductor Li6.25La3Zr2Al0.25O12 into PAN by electrospinning. The oxidized PAN-based composite solid electrolyte presents high ionic conductivity (3.05 × 10-3 S·cm-1) and high lithium transference number of 0.79 at 25 °C, further contributing to a high electrochemical window (5.3 V). The solid-state batteries assembled by Li||10 wt%-LLZAO@230-oxy-PAN||NCM523 behave superb electrochemical performance, delivering a high initial discharge capacity of 157 mAh g-1 at 0.2 C. After 100 cycles, the capacity retention was 93.3 %, indicating the electrolyte displays great electrochemical stability. This work provides new insights into the structural design of polymer-based high-voltage batteries.

A Novel Method to Enhance the Mechanical Properties of Polyacrylonitrile Nanofiber Mats: An Experimental and Numerical Investigation

This study addresses the challenge of enhancing the transverse mechanical properties of oriented polyacrylonitrile (PAN) nanofibers, which are known for their excellent longitudinal tensile strength, without significantly compromising their inherent porosity, which is essential for effective filtration. This study explores the effects of doping PAN nanofiber composites with varying concentrations of polyvinyl alcohol (PVA) (0.5%, 1%, and 2%), introduced into the PAN matrix via a dip-coating method. This approach ensured a random distribution of PVA within the nanofiber mat, aiming to leverage the synergistic interactions between PAN fibers and PVA to improve the composite's overall performance. This synergy is primarily manifested in the structural and functional augmentation of the PAN nanofiber mats through localized PVA agglomerations, thin films between fibers, and coatings on the fibers themselves. Comprehensive evaluation techniques were employed, including scanning electron microscopy (SEM) for morphological insights; transverse and longitudinal mechanical testing; a thermogravimetric analysis (TGA) for thermal stability; and differential scanning calorimetry (DSC) for thermal behavior analyses. Additionally, a finite element method (FEM) analysis was conducted on a numerical simulation of the composite. Using our novel method, the results demonstrated that a minimal concentration of the PVA solution effectively preserved the porosity of the PAN matrix while significantly enhancing its mechanical strength. Moreover, the numerical simulations showed strong agreement with the experimental results, validating the effectiveness of PVA doping in enhancing the mechanical properties of PAN nanofiber mats without sacrificing their functional porosity.

A Finite Element Method for Determining the Mechanical Properties of Electrospun Nanofibrous Mats

This study focuses on the mechanical properties of electrospun nanofibrous mats, highlighting the importance of the characteristics of single nanofibers in determining the overall mechanical behavior of the mats. Recognizing the significant impacts of the diameter and structural properties of the nanofibers, this research introduces a novel methodology for deriving the effects of the mechanical properties of single nanofibers on the aggregate mechanical performance of electrospun oriented nanofiber mats. For this purpose, a finite element method (FEM) model is developed to simulate the elastoplastic response of the mats, incorporating the influence of structural parameters on mechanical properties. The validation of the FEM model against experimental data from electrospun polyacrylonitrile (PAN) nanofibers with different orientations demonstrates its effectiveness in capturing the elastic-plastic tensile behaviors of the material and confirms its accuracy in terms of reflecting the complex mechanical interactions within the nanofibrous mats. Through a detailed analysis of how nanofiber diameter, orientation of fibers, length-to-width ratio, and porosity affect the mechanical properties of the mats, this research provides valuable insights for the engineering of nanofibrous materials to meet specific mechanical requirements. These findings improve our understanding of nanofibrous mat structures, allowing for better performance in diverse applications as well as highlighting the critical importance of identifying the properties of single nanofibers and their associated impacts on material design.