Polyimide Fibers Research Articles

Sustainable Release of LiNO3 from a Fluorine‐Decorated Metal–Organic Framework Separator to Enable High‐Performance Li‐Metal Batteries in Carbonate Electrolytes

AbstractHigh‐voltage Li‐metal batteries hold great prospects for boosting energy density, while the Li‐metal anodes show poor compatibility with high‐voltage tolerant carbonate electrolytes, leading to unstable solid‐electrolyte interphase (SEI) and uncontrolled Li dendrites growth. Herein, a F‐decorated UIO‐66/polyimide (PI) functional separator encapsulated with LiNO3 (LNO@UIO‐66F/PI) is rationally designed to regulate the interfacial chemistry and Li deposition behavior. Specifically, the UIO‐66F nanoparticles in situ grown on the PI fibers form continuous electronegative nanochannels, which promote rapid and uniform Li+ flux while repelling the anion migration. Furthermore, the LiNO3 encapsulated in the UIO‐66F nanopores sustainably releases to form a thin and conductive Li3N‐rich SEI. This synergy effect induces a dense and spherical Li deposition behavior, effectively inhibiting the growth of Li dendrites. Consequently, this LNO@UIO‐66F/PI separator demonstrates highly reversible Li plating/stripping over 1000 h at an extremely high current density of 10 mA cm−2 in carbonate electrolytes, and also enables the stable cycling of Li||LiNi0.8Co0.1Mn0.1O2 cell over 1000 cycles under a high cut‐off voltage of 4.5 V, paving the way for practical application of high‐energy‐density Li‐metal batteries.

Enhanced Interfacial Properties of Carbon Fiber/Polymerization of Monomers Reactants Method Polyimide Composite by Polyimide Sizing.

Carbon fiber (CF)-reinforced polyimide (PI) resin matrix composites have great application potential in areas such as rail transport, medical devices, and aerospace due to their excellent thermal stability, dielectric properties, solvent resistance, and mechanical properties. However, the epoxy sizing agent used for traditional carbon fiber cannot withstand the processing temperature of polyimide resin, of up to 350 °C, resulting in the formation of pores or defects at the interface between the fiber and the resin matrix, leading to the degradation of the overall composite properties. To overcome this problem, in this study, a low-molecular-weight thermosetting polyimide sizing agent was prepared and the processability of the sized carbon fiber was optimized by a thermoplastic polyimide. Compared with the unsized carbon fiber polyimide composites, the interfacial properties of the composites after the polyimide sizing treatment were significantly improved, with the interfacial shear strength (IFSS) increasing from 82.08 MPa to 136.27 MPa, the interlaminar shear strength (ILSS) increasing from 103.7 to 124.9 MPa, and the bending strength increasing from 2262.2 MPa to 2562.1 MPa. The sizing agent acts as a bridge between the carbon fiber and polyimide resin, with anchorage and bonding at the interface between the fiber and resin, which are beneficial for enhancing the interface performance of composites.

Hierarchical Polyimide Nonwoven Fabric with Ultralow-Reflectivity Electromagnetic Interference Shielding and High-Temperature Resistant Infrared Stealth Performance

Designing and fabricating a compatible low-reflectivity electromagnetic interference (EMI) shielding/high-temperature resistant infrared stealth material possesses a critical significance in the field of military. Hence, a hierarchical polyimide (PI) nonwoven fabric is fabricated by alkali treatment, in-situ growth of magnetic particles and "self-activated" electroless Ag plating process. Especially, the hierarchical impedance matching can be constructed by systematically assembling Fe3O4/Ag-loaded PI nonwoven fabric (PFA) and pure Ag-coated PI nonwoven fabric (PA), endowing it with an ultralow-reflectivity EMI shielding performance. In addition, thermal insulation of fluffy three-dimensional (3D) space structure in PFA and low infrared emissivity of PA originated from Ag plating bring an excellent infrared stealth performance. More importantly, the strong bonding interaction between Fe3O4, Ag, and PI fiber improves thermal stability in EMI shielding and high-temperature resistant infrared stealth performance. Such excellent comprehensive performance makes it promising for military tents to protect internal equipment from electromagnetic interference stemmed from adjacent equipment and/or enemy, and inhibit external infrared detection.

Multifunctional carboxylated polyimide fiber membrane for gravity-driven efficient simultaneous separation of oil-in-water emulsions and methylene blue dye

The development of multifunctional nanofiber membranes with high separation efficiency for the simultaneous removal of oil–water emulsions and organic dyes is essential due to the complexity of hazardous components in real wastewater. Herein, a polyimide (PI) fiber membrane prepared by electrospinning was carboxylated and used to simultaneously separate oil-in-water emulsions and methylene blue (MB) dye for the first time. A superhydrophilic/underwater oleophobic electrostatically spun carboxylated polyimide (Cx-PI) fibrous membrane was successfully prepared through electrostatic spinning, thermal imidization, and alkaline hydrolysis to construct carboxyl and imide groups on the polyimide fibrous membrane. The resulting membranes exhibited excellent performance in gravity-driven separation for the effective removal of oil, oil-in-water emulsions, and MB dye. The separation efficiency was ≥ 99.4 % for oil-in-water emulsions stabilized with various surfactants with a flux of up to 1128.5 L m−2 h−1. In addition, the oil and dye in the emulsion could be simultaneously separated with an emulsion separation efficiency of ≥ 99.2 %, a flux of about 910.6 L m−2 h−1, and an MB dye removal rate of 98.6 %, even when the MB dye concentration was as high as 100 mg/L. The Cx-PI nanofiber membrane also demonstrated excellent stain resistance, salt resistance, high-temperature resistance, and mechanical durability. The above results indicated that the Cx-PI membranes were suitable for the separation of oil-in-water emulsions containing MB dyes under complex conditions. This study provides a promising application in solving the global water pollution caused by oily organic solvents and water-soluble dyes.

A Polyphenol–Metal Network of Propyl Gallate Gallium/Hafnium Oxide on Polyimide Fibers for Facilitating Ligament–Bone Healing

A Polyphenol–Metal Network of Propyl Gallate Gallium/Hafnium Oxide on Polyimide Fibers for Facilitating Ligament–Bone Healing

High‐performance composite paper based on heterogeneous polyimide fibers with enhanced mechanical and dielectric properties

High‐performance composite paper based on heterogeneous polyimide fibers with enhanced mechanical and dielectric properties

Investigation of the Robust Integration of Distributed Fibre Optic Sensors in Structural Concrete Components.

In recent times, the value of data has grown. This tendency is also observeable in the construction industry, where research and digitalisation are increasingly oriented towards the collection, processing and analysis of different types of data. In addition to planning data, measurement data is a main focus. fibre optic measurements offer a highly precise and comprehensive approach to data collection. It is, however, important to note that this technology is still in research regarding concrete structures. This paper presents two methods of integrating filigree sensors into concrete structures. The first approach entails wrapping a fibre around a tendon duct and analysing the installation and associated measurements. The second method involves bonding polyimide and acrylate-coated fibres with 2K epoxy and cyanoacrylate in the grooves of rebars, exposing them to chemical environments. The resulting measurement data is evaluated qualitatively and quantitatively to ascertain its resilience to environmental factors. These developed criteria are consolidated in a decision matrix. Fibre-adhesive combinations necessitate protection from chemical and mechanical influences. The limitations of the solutions are pointed out, and alternative options are proposed.

Fabrication of conductive polyimide/metal composite fibers for high temperature EMI shielding

Surface metallization of high-performance polymer fibers via electroless plating represents a significant advancement in producing lightweight, flexible and durable electromagnetic interference (EMI) shielding fabrics. The conventional process for metallization of polyimide (PI) fibers faces challenges, including complex procedures and insufficient interfacial adhesion between the metal layer and fiber matrix. Herein, carboxylate-containing PI (PIC) fibers were developed to mitigate the mechanical degradation caused by traditional alkaline etching. Conductive composite fibers (PIC/Cu) were successfully produced through a continuous electroless copper plating process. The robust PIC/Cu interfacial bonding achieved based on nanoscale mechanical interlocking through Ni nanoparticles imparts excellent flexibility and durability, evidenced by only a 4 % increase in electrical resistance after 5000 bending cycles. The dense, uniform copper layer provides high conductivity (1.3 × 104 S/cm), resulting in an optimal EMI shielding efficiency of 63.4 dB for the corresponding fabric. Moreover, PIC/Cu-Ni fibers prepared by further electroless plating of nickel layer on the surface of PIC/Cu fibers demonstrate remarkable electrical stability across temperatures ranging from 50 to 350°C, with only a 1.2 % reduction in conductivity after exposure to 350°C for 1 h. These findings advance the development of high-performance conductive PI fibers for applications in aerospace vehicles and high-temperature environments.

Distributed salinity sensor based on optical frequency domain reflectometry with polyimide coated single mode fiber

A distributed optical fiber sensor for salinity sensing is proposed and analyzed. The sensor uses a single mode fiber coated with polyimide and is based on optical frequency domain reflectometry. By applying the polyimide solution to the surface of the fiber, a layer of polyimide film is formed by heating. As the polyimide coating is very sensitive to changes in the salinity of the external solution, the polyimide film will expand or shrink as the external concentration changes. This converts the value of salt concentration into the frequency shift in the spectrum through cross-correlation. To characterize the sensor, four polyimide-coated sensors with different average coating thicknesses of 126 µm, 170 µm, 192 µm and 249 µm were fabricated. The sensitivities of -21.71 GHz/(mol/L), -28.55 GHz/(mol/L), -29.97 GHz/(mol/L) and -42.78 GHz/(mol/L) were achieved when the salinity was measured from 0 mol/L to 3.09 mol/L, respectively. The sensitivity and response time of polyimide fibers with different diameters were measured. The minimum salinity measurement uncertainty of the sensor is 0.05 mol/L. The sensor has high sensitivity and has promising applications in observing ocean parameters and ion chemical sensing.

Phytic Acid-Gallium Network on a Polyimide Fiber Woven Fabric as an Artificial Ligament for Boosting Ligament-Bone Healing and Infection Treatment.

The development of an artificial ligament with a multifunction of promoting bone formation, inhibiting bone resorption, and preventing infection to obtain ligament-bone healing for anterior cruciate ligament (ACL) reconstruction still faces enormous challenges. Herein, a novel artificial ligament based on a PI fiber woven fabric (PIF) was fabricated, which was coated with a phytic acid-gallium (PA-Ga) network via a layer-by-layer assembly method (PFPG). Compared with PIF, PFPG with PA-Ga coating significantly suppressed osteoclastic differentiation, while it boosted osteoblastic differentiation in vitro. Moreover, PFPG obviously inhibited fibrous encapsulation and bone absorption while accelerating new bone regeneration for ligament-bone healing in vivo. PFPG remarkably killed bacteria and destroyed biofilm, exhibiting excellent antibacterial properties in vitro as well as anti-infection ability in vivo, which were ascribed to the release of Ga ions from the PA-Ga coating. The cooperative effect of the surface characteristics (e.g., hydrophilicity/surface energy and protein absorption) and sustained release of Ga ions for PFPG significantly enhanced osteogenesis while inhibiting osteoclastogenesis, thereby achieving ligament-bone integration as well as resistance to infection. In summary, PFPG remarkably facilitated osteoblastic differentiation, while it suppressed osteoclastic differentiation, thereby inhibiting osteoclastogenesis for bone absorption while accelerating osteogenesis for ligament-bone healing. As a novel artificial ligament, PFPG represented an appealing option for graft selection in ACL reconstruction and displayed considerable promise for application in clinics.

Experimental and numerical study of the thermomechanical properties of flexible self-reinforced polyimide composite membrane

Polyimide membranes are favored in the aerospace field for their excellent comprehensive properties, but new application requirements demand higher strength, modulus and thermal expansion properties. Here, self-reinforced polyimide composite membranes (SRPICM) with varying fiber tow arrangement densities were fabricated by unidirectional reinforcement of polyimide fiber tows to enhance the thermomechanical properties of the membranes while maintaining the characteristics of low thickness and flexibility. A micro-scale representative volume element model with interface, and a macro-scale model containing cracks were developed based on the membranes' morphology to investigate the tensile and thermal expansion behavior of SRPICM. Experimental and numerical analyses demonstrated that fiber tows significantly improved the longitudinal tensile properties of SRPICM, with maximum increases in modulus and strength to 34.02 GPa and 1.26 GPa, respectively, over 13 times those of pure PI membranes. Further, the test results, combined with the two-scale finite element model revealed the evolution of longitudinal and transverse tensile deformation and thermal expansion behavior of SRPICM. The validity of the two-scale model was confirmed by experimental results, attributed to the practical consideration of interfacial bonding, prefabricated cracks and thermal residual stress effects during initial modeling. Notably, SRPICM with 10 fiber tows/20 mm arrangement density exhibited excellent longitudinal tensile properties (modulus and strength of 14.01 GPa and 470.89 MPa, respectively) and a longitudinal thermal expansion close to zero (0.03 μm/m°C), making it an ideal material for aerospace applications.

Particulate removal characteristics of commercial-scale DeNOx catalyst cartridge coupled filter bags

The commercial-scale DeNOx catalyst cartridge coupled with filter bag have been developed for the removal of fine particulate matter and nitrogen oxides (NOx) in flue gases. The DeNOx catalyst cartridge coupled filter bag is made up of a microporous PTFE (polytetrafluoroethylene) membrane/impregnated polyimide fiber needle-punched pleated filter bag designed for the removal of ultrafine particulates, along with a pellet selective catalytic reduction catalyst-filled cartridge for the removal of NOx. V2O5-MoO3/TiO2 catalyst was used as the DeNOx catalyst. The distribution of cleaning air velocity inside the DeNOx catalyst cartridge-coupled filter bag, which is injected with compressed air from the high-volume low-pressure (HVLP) pulse injector to remove the deposited dust cake from the surface of the filter bags during pulse-jet cleaning, was confirmed using computational fluid dynamics (CFD). The particulate removal and dust cake dislodgement characteristics of the DeNOx catalyst cartridge coupled filter bag were tested in a commercial-scale filter bag test unit under conditions simulating fossil fuel combustion flue gas. The commercial-scale DeNOx catalyst cartridge coupled filter bag was 165 mm in diameter, 2000 mm in total length, and contained approximately 12 kg of DeNOx catalyst- filled cartridges. Nine commercial-scale DeNOx catalyst cartridge coupled filter bags were installed in the commercial-scale filter test unit. The experimental conditions were as follows: flue gas temperature 200 °C, flue gas flow rate 3000Nm3/h, NO, SO2, and particulate concentration in inflow flue gas 200 ppm, 7 ppm, and 5000 mg/Nm3 respectively, resulting in different values of filtration velocities. The efficiency of bag cleaning and intervals, overall collection efficiency, fractional efficiency, and filter quality were investigated. The average bag cleaning efficiency and overall collection efficiency were 95.5%, 91.5%, and 83.3% at filtration velocities of 0.8, 1.0 and 1.2 m/min, respectively. The corresponding values for overall collection efficiency were 99.9%, 99.5%, and 98.2%. So, both bag cleaning efficiency and overall collection efficiency decreased with increased filtration velocity. The present study confirmed that DeNOx catalyst cartridge coupled filter bags have relatively higher bag cleaning efficiency, collection efficiency, and filter quality for challenging fossil fuel combustion flue gas. Particularly, the fractional efficiency for micron-sized particles was considerably higher at lower filtration velocities.

Thermal spray to embed optical fibers for the monitoring and protection of metallic structures

In the framework of using fiber optics (FO) for structural health monitoring, a true challenge is to fix the fiber onto structures guaranteeing both protection for the former and an effective adhesion on the latter. This work proposes a method to obtain such result via thermal spray technique on metallic structures, allowing its use in the most severe conditions of corrosion and wear. Since the transmission medium between the structure and the sensitive part of the optical fiber is represented by the fiber coating, three differently coated fibers were used on C-40 steel substrate: polyacrylate, polyimide and ORMOCER. In addition, the use of a primer to improve the bond on the substrate was evaluated. The adhesion between FO and metallic coating is evaluated through optical microscopy (OM) and scanning electrons microscopy (SEM) analysis. The functionality is also verified with both thermal and mechanical tests to calibrate the measuring accuracy. The results indicate that the best combination is that of the polyimide fiber, a zinc primer and aluminum coating. The proven qualities are the adhesion at the interface between the metallic coating and the fiber optics, and the preservation of the structural integrity of the fiber itself and its coating, and a precise measurement of strain acquired by fiber Bragg grating sensors (FBGs). The use of the thermal spray process is thus proved to be a solution for the optical fiber and substrate interaction, since it preserves the integrity of the optical fiber, due to the low temperature of the process, adding the protection that the metallic coating offers as well.

Lignin Biobased Eco-Friendly Dipping System for Polyimide Fiber and Its Interface Adhesive Mechanism with Rubber

Lignin Biobased Eco-Friendly Dipping System for Polyimide Fiber and Its Interface Adhesive Mechanism with Rubber

Design of Ultrathin Asymmetric Composite Electrolytes for Interfacial Stable Solid-State Lithium-Metal Batteries.

Ultrathin composite electrolytes hold great promise for high energy density solid-state lithium metal batteries (SSLMBs). However, finding an electrolyte that can simultaneously balance the interfacial stability of the lithium anode and high-voltage cathode is challenging. The present study utilized the both-side tape casting technique to fabricate ultrathin asymmetric composite electrolytes reinforced with polyimide (PI) fiber membrane, with a thickness of 26.8 μm. The implementation of this asymmetric structural design enables SSLMBs to attain favorable interfacial characteristics, such as exceptional resistance to lithium dendrite puncture and compatibility with high voltages. The suppression of lithium dendrite growth and the extension of the cycle life of lithium symmetric batteries by 4000 h are both experimental and theoretically demonstrated under the dual confinement of PI fiber membrane and Li7La3Zr2O12 ceramic fibers. Furthermore, the integration of multicomponent solid electrolyte interphase and cathode electrolyte interface interfacial layers into the lithium anode and high-voltage cathode enhance theirs cycling stability. With a gravimetric/volumetric energy density of 333.1 Wh kg-1/713.2 Wh L-1, the assembled LiNi0.8Co0.1Mn0.1O2 pouch cell demonstrates exceptional safety. The extensive application of this design concept to SSLMBs enables the resolution of electrode/electrolyte interface issues.

Robust all-fabric e-skin with high-temperature and corrosion tolerance for self-powered tactile sensing

Electronic skins (e-skins) for monitoring human and robot activities under extreme circumstances are significant for human-machine interaction in multiple scenarios, which is challenging to realize on fabric/textile materials. Herein, a core filling-encapsulation strategy for multi-layer weaving is explored to achieve a triboelectric triple-layer sandwich woven e-skin (TSW e-skin) for durable self-powered sensing in extreme environments. To construct a robust structure with environment adaptability, ultra-high molecular weight polyethylene (UPE) fibers or polyimide (PI) fibers are integrated into the triple-layer sandwich woven to provide mechanical/thermal/chemical stability, and carbon fibers (CF) are protectively embedded as a core layer for electricity collection, heat management and adaptive sensing. Hydrophobic encapsulation is improved by polydimethylsiloxane (PDMS) thin coating with morphology and mechanical compliances. The TSW e-skin demonstrates excellent mechanical strength (∼20 MPa) and thermal stability (154.5 ℃), durable superhydrophobicity (>150°), and corrosion resistance (pH 1–13), which demonstrates an open-circuit voltage of 53 V and maintains electrically stable at above 150 ℃. The weaving structure enables the e-skin regulatable electrode patterns for sensitive motion perception and touch identification for human and robotic limbs, with real-time tactile feedback even under extreme scenarios. This robust all-fabric e-skin proposes a common strategy for human-robot perception in harsh environments.

Mechanically robust, corrosion and impact resistance polyimide nanofiber/epoxy composite by mechanochemical fabrication

AbstractThis study aimed to explore the application of a mechanochemical method for effectively integrating polyimide nanofibers, which are widely recognized for their outstanding thermal and mechanical properties, into an epoxy resin matrix. The researchers observed an 87.5% reduction in the diameter of polyimide nanofibers after mechanical treatment. The dispersion, compatibility, and interface between the nanofibers and epoxy matrix were analyzed using molecular dynamics simulations and scanning electron microscopy. The addition of polyimide nanofibers significantly increased the binding energy of the composite, resulting in a 52.8% improvement. Moreover, compared to pure epoxy resin, the inclusion of modified polyimide nanofibers led to a 21.9% increase in tensile strength and an 18.8% increase in impact strength. The PI/epoxy composite also exhibited a 15.6% increase in tensile strength and a 16.4% increase in impact strength. Additionally, electrochemical corrosion analysis showed that the PI/epoxy composite had excellent corrosion resistance. In conclusion, due to the exceptional mechanical properties and strong interfacial adhesion of polyimide nanofibers, the PI/epoxy resin composite demonstrated significant overall performance improvement compared to pure epoxy resin.Highlights Mechanochemical method to disperse polyimide fiber, shorter and finer fibers were obtained Improve performance by adding small amounts Microscopic analysis of composites by Materials Studio, PIENFs efficiently improved the interaction on the phase interface Experiments have verified that PIENFs could make the mechanical properties and corrosion resistance

Bioinspired composite fiber aerogel pressure sensor for machine-learning-assisted human activity and gesture recognition

Machine-learning-assisted human activity and gesture recognition are valuable for human-computer interaction, and data acquisition often necessitates high-performance sensors. Here, inspired by spider web and bat wing airflow sensing system, polyimide fiber (PIF)/carbon black (CB) composite fiber aerogel (CFA) pressure sensor with biomimetic hair-Merkel cell sensitive unit was developed, exhibiting ultralow detection limit (2 Pa), high pressure sensitivity (S=23.1 kPa-1), wide linear detection capacity up to 67.61 kPa, and fast response/recovery time (140/100 ms). Thanks to the excellent mechanical property and environmental tolerance of CFA, it also possesses excellent low fatigue over >4000 cycles and good durability even at extreme high-temperature (200 °C) and underwater conditions. The superior signal data of the sensor, combined with the Convolutional Neural Network machine learning algorithm, achieves ultra-high prediction accuracies of 96.73% and 98.26% for human activity and gesture recognition, respectively. Additionally, CFA also has amazing thermal management properties, making it to be an ideal candidate for wearable electronics with excellent wearing comfort and safety.

Self-extinguishing polyimide sandwiched separators for high-safety and fast-charging lithium metal batteries

Developing fast-charging lithium metal battery (LMB) with high specific capacity arouses enormous attentions. Unfortunately, during the operation of fast-charging LMB, substantial amount of Joule heat generated within battery often induces inhomogeneous heat accumulation that concomitantly deteriorates the lithium dendrite growth issues, resulting in rapid capacity fading and potentially fatal thermal runaway. It is critically essential to develop advanced separator that possesses high ionic conductivity, effective dendrite inhibition and self-extinguishing property for fast-charging LMB with high-safety. Here, we report a facile approach to fabricate polyimide composite separator (denoted as PIFAP), where the polyimide fiber (PIF) membrane is sandwiched by aerogel layers of polyimide/ammonium polyphosphate composite. Notably, compared with PIF, the PIFAP features significant enhancement in flame retardance, electrolyte affinity, electrolyte adsorption and ionic conductivity. Moreover, beneficiating from the aerogel layers with uniform nanopores of ∼100 nm, the optimized PIFAP separator can enable homogeneous lithium deposition, achieving a dendrite-free lithium deposition on the surface of anode for over 1600 h, superior to the PIF and Celgard separators. The resulting “LiFePO4/PIFAP/Li” cell can exhibit a remarkably high cycling stability with 99.1 % of capacity retention after long-term cycling at a current density of 10 C.

Structure-Foldable and Performance-Tailorable PI Paper-Based Triboelectric Nanogenerators Processed and Controlled by Laser-Induced Graphene.

Laser-induced graphene (LIG) technology has provided a new manufacturing strategy for the rapid and scalable assembling of triboelectric nanogenerators (TENG). However, current LIG-based TENG commonly rely on polymer films, e.g., polyimide (PI) as both friction material and carbon precursor of electrodes, which limit the structural diversity and performance escalation due to its incapability of folding and creasing. Using specialized PI paper composed of randomly distributed PI fibers to substantially enhance its foldability, this work creates a new type of TENG, which are structurally foldable and stackable, and performance tailorable. First, by systematically investigating the laser power-regulated performance of single-unit TENG, the open-circuit voltage can be effectively improved. By further exploiting the folding process, multiple TENG units can be assembled together to form multi-layered structures to continuously expand the open-circuit voltage from 5.3 to 34.4Vcm-2, as the increase of friction units from 1 to 16. Last, by fully utilizing the unique structure and performance, representative energy-harvesting and smart-sensing applications are demonstrated, including a smart shoe to recognize running motions and power LEDs, a smart leaf to power a thermometer by wind, a matrix sensor to recognize writing trajectories, as well as a smart glove to recognize different objects.