Interfacial Agent Research Articles

A Dynamic Mechanical Analysis on the Compatibilization Effect of Two Different Polymer Waste-Based Compatibilizers in the Fifty/Fifty Polypropylene/Polyamide 6 Blend.

This study aims to examine the 50/50 polypropylene/polyamide 6 (iPP/PA6) system molded under confined flow conditions, both in its original state and after being modified by two different interfacial agents. This study provides two main insights. Firstly, it focuses on a polymer blend close to phase inversion. Secondly, it investigates the impact of using two different types of interfacial agents (derived from polymer waste) to enhance the compatibility between iPP and PA6. Dynamic Mechanical Analysis (DMA) has been employed to achieve these objectives. It is important to note that the investigation of the 50/50 iPP/PA6 system is a crucial focus predicted in previous studies, where a series of mechanical properties were evaluated using Box-Wilson design of experiments (DOEs) over the whole compositional range on the iPP/PA6 binary system. Thus, two interfacial modifiers, namely succinic anhydride (SA)-grafted atactic polypropylene with terminal, side, and bridge SA grafts (aPP-SASA) and succinyl-fluoresceine (SF) with bridge succinic anhydride grafting atactic polypropylene (aPP-SFSA), were employed. The authors obtained and characterized these agents. The quantity of these agents used in the blend was identified as a critical coordinate in prior studies conducted by the authors. The processing method used, compression molding under confined conditions, was chosen to minimize any orientation effect on the emerging morphology. All characterization procedures were performed on samples processed by contour machining to retain the blend morphologies as they emerged from the processing stage. Results from WAXS and SAXS synchrotron tests concluded there were no changes in the crystal morphology of the iPP or the PA6 in the blends nor any co-crystallization process throughout the compositional range. These findings, and the long period fits on the PP crystalline phase for the fifty/fifty blends we are discussing, will support the present DMA study. Finally, the efficiency of these interfacial modifiers has been concluded, even in this unfavorable scenario.

Interfacial engineering and defect passivation of SnO2 through agmatine sulfate in carbon-based perovskite solar cells

Electron transport layer has always played a crucial role in the performance of the perovskite solar cells (PSCs). Particularly, SnO2-based PSC has sparked considerable interest due to its superior properties. Even with such remarkable properties, certain challenges persist such as agglomeration of SnO2 particles which can lead to interfacial defects and poor morphology. To solve this problem, Agmatine Sulfate (AGTS) has been introduced as an interfacial modification agent which with the help of its active functional group including amide (-NH2) and hydroxyl (OH) has allowed to facilitate the interaction at the interface between SnO2 and perovskite. The interaction facilitates the growth of perovskite crystals while tuning the energy levels which has boosted the charge transfer capability of the layer. All these improvements in the properties have led to enhanced power conversion efficiency (PCE) from 11.17 % to 15.20 % for the encapsulated device. Furthermore, the modification also improved the long-term stability of the device as the AGTS-modified devices retained 87 % of their performance at 15–25 °C with humidity levels between 10 and 20 % for over a period of 31 days. Finally, the devices prepared with the AGTS also showed repeatability in their performance while boosting the overall performance of carbon-based PSCs (C–PSCs) and indicating a novel approach to not only increase but also accelerate the commercialization of C-PSC.

A Novel, Dual-Initiator, Continuous-Suspension Grafting Strategy for the Preparation of PP-g-AA-MAH Fibers to Remove of Indigo from Wastewater.

The indigo dye found in wastewater from printing and dyeing processes is potentially carcinogenic, teratogenic, and mutagenic, making it a serious threat to the health of animals, plants, and humans. Motivated by the growing need to remove indigo from wastewater, this study prepared novel fiber absorbents using melt-blow polypropylene (PP) melt as a matrix, as well as acrylic acid (AA) and maleic anhydride (MAH) as functional monomers. The modification conditions were studied to optimize the double-initiation, continuous-suspension grafting process, and then functional fibers were prepared by melt-blown spinning the modified PP. The results showed that the optimum modification conditions were as follows: a 3.5 wt% interfacial agent, 8 mg/L of dispersant, 80% monomer content, a 0.8 mass ratio of AA to MAH, a 1000 r/min stir speed, 3.5 wt% initiator DBPH grafting at 130 °C for 3 h, and 1 wt% initiator BPO grafting at 90 °C for 2 h. The highest grafting rate of the PP-g-AA-MAH was 31.2%, and the infrared spectrum and nuclear magnetic resonance spectroscopic analysis showed that AA and MAH were successfully grafted onto PP fiber. This modification strategy also made the fibers more hydrophilic. The adsorption capacity of the PP-g-AA-MAH fibers was highly dependent on pH, and the highest indigo adsorption capacity was 110.43 mg/g at pH 7. The fiber adsorption capacity for indigo increased rapidly before plateauing with increasing time or indigo concentration, and the experimental data were well described in a pseudo-second-order kinetic model and a Langmuir isothermal adsorption model. Most impressively, the modified fiber adsorption capacity for indigo remained as high as 91.22 mg/g after eight regeneration and reuse cycles. In summary, the PP-g-AA-MAH fibers, with excellent adsorption-desorption characteristics, could be readily regenerated and reused, and they are a promising material for the removal of indigo from wastewater.

Peptide‐Based Ammonium Halide with Inhibited Deprotonation Enabling Effective Interfacial Engineering for Highly Efficient and Stable FAPbI3 Perovskite Solar Cells

AbstractAmmonium iodides are intensively investigated as effective interfacial passivation agents in perovskite solar cells (PSCs) while facing a major challenge of their high reactivity with perovskites that undermines the operational stability of the PSCs. Exemplified by involving rationally designed/selected peptide into the widely adopted phenethylammonium iodide (PEAI), the present work demonstrates that the bespoke peptide‐PEAI can effectively inhibit the deprotonation of ammonium iodides and thus hinder the formation of 2D perovskite, facilitating the stability enhancement in perovskite films by multi hydrogen bonding. The additional lone pair electrons provided by peptide molecules can also enhance the passivation ability of the modified layer. Attributed to the stable co‐modifier peptide‐PEAI, the small‐area FAPbI3‐based PSCs yield a high efficiency of 25.02% with robust light and thermal stabilities. Moreover, the peptide‐PEAI‐based minimodules with an efficiency of 19.06% for a total area of 36 cm2 manifested the great application potential of this co‐modification strategy in the perovskite photovoltaics.

Study on the Effect of Interfacial Modification on the Properties of Super Standard Mica Sand Cement-Based Materials

Mica is a harmful substance in sand and occurs frequently. The application of super standard mica sand is a difficult problem in large-scale engineering. In this work, the effects of an interface modifier, mineral admixture, and a curing system on the properties of cement-based materials with super standard mica sand were studied. The strength of cement-based materials linearly decreases with the mica content in sand. When the mica content in sand exceeds 6%, the compressive strength of mortar and concrete at 28 d decreases by more than 22.3% and 33.5%, respectively. By adding the silane coupling agent (SCA) of 50% mica mass and curing in natural conditions, the compressive strength of mortar increases by 10.9%. The cement-based materials with the SCA are more suitable for curing in natural conditions, and the performance of the SCA will not be affected by adding appropriate amounts of mineral admixture. The drying shrinkage strain of the concrete, with the sand containing high mica content modified by SCA, is reduced by 10.5%, and the diffusion of chloride ions in concrete is reduced. The XRD results show that the addition of the interfacial agent does not change the hydration products. The MIP and SEM results show that the SCA can form a bridge structure between the hydration products and the mica, improve the bonding strength of the interface zone, and reduce the number of harmful pores.

Strong and flexible MXene-based nanocomposite films for atomic oxygen resistance and electromagnetic interference shielding

MXene has garnered considerable attention as a promising candidate for multifunctional artificial materials, owing to its exceptional mechanical performance and superior electric conductivity. However, macroscopically layered films assembled by MXene nanosheets are usually accompanied by serious degradation of mechanical properties. Moreover, there is a notable paucity of investigations on MXene in low Earth orbit (LEO) environment. Inspired by the layered structure of nacre, we applied polyurethane (PU) as an interfacial crosslinking agent to improve the mechanical properties of MXene films. The optimized MXene/PU (MP) nanocomposite film exhibited a tensile strength of 298.02 MPa and a toughness of 13.81 MJ m−3, surpassing those of the pure MXene film by 260 % and 1300 %, respectively. The atomic oxygen (AO) erosion yield of MP was approximately one order of magnitude lower than that of commercial Kapton films, which was attributed to the shielding effect of MXene against AO attacks. Remarkably, the MP nanocomposite film demonstrated exceptional retention of tensile strength under various extreme conditions including AO irradiation, cryogenic-high temperature, cyclic thermal shock and hot water. Contributed by multi-layer structural design and high conductivity, the MP exhibited a high electromagnetic interference shielding effectiveness (EMI SE) of 48 dB and a specific SE divided by thickness (SSE/t) of 13,479 dB cm2 g−1 at the thickness of 20 μm. Consequently, the nacre-like MP nanocomposite film with exceptional mechanical properties and high-level functional performance holds substantial promise as a multifunctional space material for LEO environments.

Influence of surface roughness and interfacial agent on the interface bonding characteristics of polyurethane concrete and cement concrete

As a new type of concrete material, polyurethane concrete has excellent physical and mechanical properties which is widely used in the maintenance and reinforcement of damaged areas of concrete pavement. Because of the difference in the performance between polymer concrete and ordinary concrete, it is of great significance to accurately evaluate the bond performance between polymer concrete and ordinary concrete in order to avoid interface damage in the subsequent use of the repaired pavement. In this study, the bonding specimens were made by changing the roughness and interfacial agent of the bonding interface between polymer concrete and cement concrete, and splitting tensile test and direct shear test were carried out to explore the bond properties between them. Polymer concrete-cement concrete composite beam specimens were made to simulate the maintenance and reinforcement of cement concrete pavements with polymer concrete in the actual projects, and the flexural performance test was carried out to explore the common mechanical characteristics of bonding specimens. The test results showed that the bond performance of polymer concrete and cement concrete was closely related to the interface roughness and the interfacial agents, and the addition of polymer concrete improves the common stress characteristic of composite beam specimens. The test results provide a basis for polymer concrete as a rapid repair material for concrete pavement repair.

Importance of an interfacial agent for stabilizing rubber domains of thermoplastic vulcanizates during strong shearing

Rubber nanoparticles in thermoplastic vulcanizate (TPV) may agglomerate during processing, leading to the deterioration of mechanical properties of TPV. This work shows how important an interfacial agent (Polyolefin Elastomer, POE) can be for stabilizing rubber particles in Ethylene-Propylene-Diene Monomer (EPDM)/polypropylene (PP) TPV during processing. The optimal type and dosage of POE was theoretically calculated. The time at which the POE interfacial agent is added is optimized based on the fragmentation kinetics of the EPDM rubber particles. The experimental results show that POE is indeed encapsulated on EPDM rubber particles in TPV, resulting in the large decrease in average size of EPDM rubber particles from 1.2 μm for TPV without encapsulation to 0.7 μm for TPV encapsulated with optimal dosage of POE. As a result, at an optimal dosage of POE, the elastic modulus, tensile strength, and elongation at break of TPV simultaneously increases by 70 %, 44 %, and 37 %, respectively.

Interface bonding properties of new and old concrete: A review

The bonding performance between new and old concrete affects the reliability and service life of the repair structure. However, the bonding interface is complex and has many influencing factors, so selecting appropriate repair materials and evaluation methods for repair structures under different service environments is important. This paper presents a comprehensive overview of the factors that influence bonding properties. These include the choice of repair materials, the condition of the existing concrete, the type of interfacial agents used, the service environment, and the testing methods employed. The paper concludes by examining the challenges and opportunities in developing interface bonding properties to provide insights and research directions for future theoretical analysis and experimental research.

Effects of styrene–acrylic emulsion on bond performance and interface microstructure of repair mortar of ternary cementitious system

AbstractThis study investigates the effects of styrene–acrylic emulsion (SAE) as a modifier and interfacial agent on the interfacial bond performance of ordinary Portland cement–aluminate cement–gypsum (PAG) repair mortar. The hydration products and interfacial microstructure are analyzed via x‐ray diffraction (XRD), x‐ray photoelectron spectroscopy (XPS), Fourier‐transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM). The results demonstrate that the addition of SAE can effectively enhance the tensile bond strength and flexural bond strength of the PAG repair mortar, and the optimal addition amount of SAE is 10 wt%. The tensile and flexural bond strengths of the PAG repair mortar with SAE interfacial agent at 40% concentration are 1.38 and 1.34 times than those of the mortar without the interfacial agent, respectively. XPS and FTIR analyses reveal that the carboxyl groups in SAE and Ca2+ generated from cement hydration form Ca2+–carboxyl complexes. The SEM and XRD analyses indicate that SAE can alter the distribution and size of crystals at the bond interface and considerably reduce the thickness of the bond interface; however, SAE cannot change the type of hydration products at the bond interface.

3D printed composites based on the magnetoelectric coupling of Fe/FeCo@C with multiple heterogeneous interfaces for enhanced microwave absorption

In this paper, the ZIF-derived carbon nanoskeleton was cleverly introduced into the carbonyl iron surface by in situ self-polymerization of dopamine on the carbonyl iron surface to build a “bridge” and multiple heterogeneous interfacial wave-absorbing agents of Fe/FeCo@C were obtained by heat treatment process. The large amount of polarization loss introduced by the designed multi-heterogeneous interfaces increases the ability of the material to attenuate electromagnetic waves. At the same time, the conductive network formed by loading nanoparticles with the lamellar structure of micrometal is employed to couple the dielectric loss depletion and the magnetic loss together, and the electromagnetic parameters are regulated by graphitization. The FDM technique was utilized to prepare filaments that can be used for 3D printing by compositing the wave absorber with PP resin and to explore the effect of FCC/PP composites on the attenuation of electromagnetic waves by utilizing dielectric-electromagnetic coupling realizations. The results show that the preparation yields an adequate absorption bandwidth of 4.75 GHz at 1.5 mm for FCC-3/PP at 40 % fill ratio, and the minimum reflection loss can reach close to −60 dB at 1.7 mm. The wave-absorbing composite materials can also be utilized to print various shaped materials, and this work provides a new option for preparing electromagnetic-absorbing composites by FDM 3D printing in the future.

Multifunctional epoxy/carbon composites with a fully reparable interface

AbstractIn this work, for the first time, carbon fibers (CFs) were coated with nanosized‐polycaprolactone (PCL) particles to obtain a functionalized self‐healable interphase, capable to fully recover the pristine interfacial shear strength with a debonded epoxy matrix. PCL nanoparticles were initially water‐dispersed at different concentrations and deposited on CFs by electrophoretic deposition. The application of various voltage levels resulted in different morphologies of the coating. Epoxy microdroplets were deposited and cured on neat and PCL‐coated fibers. After complete interfacial debonding by microdebonding tests, an electric current was applied on CFs to activate a thermal interfacial healing by Joule effect. The healing efficiency was estimated as the ratio of interfacial shear strength measured before and after healing. An outstanding repairing efficiency was obtained upon thermal mending with a complete recovery of the original interfacial shear strength, thus indicating a strong potential of the PCL nanocoating as interfacial healing agent for composite structures.Highlights CFs were coated with nanosized‐PCL particles to obtain a functionalized self‐healable interphase. Electrophoretic deposition was employed for the fiber coating. Microdebonding tests were performed to assess the fiber/matrix interfacial properties in terms of interfacial shear strength. A full recovery of the interfacial properties was obtained via thermal interfacial healing by Joule effect.

Study on Frost Resistance and Interface Bonding Performance through the Integration of Recycled Brick Powder in Ultra-High-Performance Concrete for Structural Reinforcement

This study aims to address the issues posed by frost damage to concrete structures in cold regions, focusing on reinforcement and repair methods to increase the service life of existing structures instead of costly reconstruction solutions. Due to the limitations of conventional concrete in terms of durability and strength, this research focused on ultra-high-performance concrete (UHPC) by replacing part of the cement with recycled brick powder (RBP) to strengthen ordinary C50 concrete, obtaining UHPC-NC specimens. Mechanical tests investigated the bonding performance of UHPC-NC specimens under various conditions, including interface agents, surface roughness treatments, and freeze–thaw after 0, 50, 100, and 150 cycles with a 30% replacement rate of RBP. Additionally, a multi-factor calculation formula for interface bonding strength was established according to the test data, and the bonding mechanism and model were analyzed through an SEM test. The results indicate that the interface bonding of UHPC-NC specimens decreased during salt freezing compared to hydro-freezing, causing more severe damage. However, the relative index of splitting tensile strength for cement paste specimens showed increases of 14.01% and 14.97%, respectively, compared to specimens without an interface agent. Using an interface agent improved bonding strength and cohesiveness. The UHPC-NC bonding model without an interfacial agent can be characterized using a three-zone model. After applying an interfacial agent, the model can be characterized by a three-zone, three-layer bonding model. Overall, the RBP-UHPC-reinforced C50 for damaged concrete showed excellent interfacial bonding and frost resistance performance.

Highly Hydrophobic Gelatin Nanocomposite Film Assisted by Nano-ZnO/(3-Aminopropyl) Triethoxysilane/Stearic Acid Coating for Liquid Food Packaging.

Biodegradable gelatin (G) food packaging films are in increasing demand as the substitution of petroleum-based preservative materials. However, G packaging films universally suffer from weak hydrophobicity in practical applications. Constructing a hydrophobic micro/nanocoating with low surface energy is an effective countermeasure. However, the poor compatibility with the hydrophilic G substrate often leads to the weak interfacial adhesion and poor durability of the hydrophobic coating. To overcome this obstacle, we used (3-aminopropyl) triethoxysilane (APS) as an interfacial bridging agent to prepare a highly hydrophobic, versatile G nanocomposite film. Specifically, tannic acid (TA)-modified nanohydroxyapatite (n-HA) particles (THA) were introduced in G matrix (G-THA) to improve the mechanical properties. Micro/nanostructure with low surface energy composed of nanozinc oxide (Nano-ZnO)/APS/stearic acid (SA) (NAS) was constructed on the surface of G-THA film (G-THA/NAS) through one-step spray treatment. Consequently, as-prepared G-THA/NAS film presented excellent mechanics (tensile strength: 7.6 MPa, elongation at break: 292.7%), water resistance ability (water contact angle: 150.4°), high UV-shielding (0% transmittance at 200 nm), degradability (100% degradation rate after buried in the natural soil for 15 days), antioxidant (78.8% of 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity), and antimicrobial (inhibition zone against Escherichia coli: 15.0 mm and Staphylococcus aureus: 16.5 mm) properties. It should be emphasized that the bridging function of APS significantly improves the interfacial adhesion ability of the NAS coating with more than 95% remaining area after the cross-cut adhesion test. Meanwhile, the G-THA/NAS film could maintain stable and long-lasting hydrophobic surfaces against UV radiation, high temperature, and abrasion. Based on these multifunctional properties, the G-THA/NAS film was successfully applied as a liquid packaging material. To sum up, we provide a feasible and effective method to prepare high-performance green packaging films.

Study on Flexural Strength of Interface between Full Lightweight Ceramsite Concrete and Ordinary Concrete

The efficacy of full lightweight ceramsite concrete as a restorative material has been widely acknowledged, given its light weight, strength, and durability. However, the extent of its performance in repairing existing or old concrete remains uncertain. This study examined the reparation of flexural performance with full lightweight ceramsite concrete, using 14 different combinations of old and new concrete test blocks. The primary focus of the study was on investigating the flexural bond strength of the interface between the old and the new concrete. This included understanding the effects of the interfacial roughness, interfacial agent type, and concrete curing age of the concrete on the flexural strength. The test results showed that increasing the interface roughness from 0 mm to 5 mm resulted a restoration of the flexural strength of the sample by approximately 59%. Additionally, the flexural strength of the specimens was restored by 62%–78% of their original strength with the application of different types of interfacial agent. To rank the impact of these factors on the flexural strength, a univariate analysis of variance was conducted. This allowed us to establish a mathematical formula for calculating the flexural capacity of old and new concrete interfaces, taking the three aforementioned factors into account.

The Role of Undecenoic Acid on the Preparation of Decorated MCM-41/Polyethylene Hybrids by In Situ Polymerization: Catalytic Aspects and Properties of the Resultant Materials

Functionalized polyethylene-based nanocomposites were prepared by in situ polymerization of ethylene with modified or neat MCM-41 nanoparticles (NMCM-41). Two different synthetic approaches were investigated to improve the compatibility between the hydrophobic HDPE matrix and the hydrophilic NMCM-41: (i) incorporation of UA into the polymeric matrix by copolymerization with ethylene, promoted by the zirconocene catalyst under homogeneous conditions, in the presence of pristine NMCM-41; (ii) use of undecenoic acid (UA) as an interfacial agent to obtain decorated NMCM-41 to be used as nanofiller for the in situ ethylene polymerization, catalyzed by Cp2ZrCl2/MAO under supported conditions. The strong polar character of the carboxylic group is expected to either increase the hydrophilicity of the HDPE chains (strategy i) or interact with the NMCM-41 surface and provide an additional link to the polymeric chains via copolymerization of the vinyl group under supported conditions (strategy ii). Although metallocene catalysts have been shown to copolymerize olefins with functional monomers, the presence of oxygen-containing compounds in the reaction media strongly affects the polymerization activity as a result of the interaction of functional groups with the electrophilic active center of the catalyst. Thus, UA was pre-contacted with tri(isobutyl)aluminum (TIBA) prior to its use in the polymerization to reduce the deactivating character of the carboxylic acid groups towards the zirconocene catalyst. The influence of the UA presence on the polymerization behavior of the protection step is discussed, and the polymerization activities observed for the different approaches are compared. In addition, the thermal behavior and structural details of the resulting materials have been characterized. The impact of using neat or functionalized NMCM-41 on the final dispersion within the polymeric matrix is also analyzed, which is correlated with the mechanical performance exhibited by these HDPE_UA_NMCM-41 nanocomposites.

A migrating and reactive polycarboxylate superplasticizer with coupled functions of new/old concrete interfacial agent and water reducer

New/old concrete interface is usually the weakest zone in repair of concrete substrate, wet-joint of precast elements and overlay of concrete bridge. In this study, superplasticizers with coupled functions of new/old concrete interfacial agent and water reducer were developed by using silane to modify polycarboxylate superplasticizer (PCE). With these highly reactive silane groups, this novel superplasticizer not only had a better water reduction efficiency and fluidity retention ability than commercial PCE, but also can establish a stronger interfacial bond between new and old concrete, i.e. by >35 % at 28 d age. The porosity of the new/old mortar interfacial transition zone at 28 d age was obviously reduced. Raman spectroscopy mapping showed that this novel superplasticizer with a smaller molecular weight can migrate into the old mortar well and the XPS results indicated that the superplasticizer migrated from the new mortar can react with the old mortar substrate. A moderate siloxane group content makes the new superplasticizer have a larger migrating amount, while the more siloxane groups in the new superplasticizer the higher reaction degree with the old mortar was found.

The Development of Environmentally Sustainable Poly(vinyl chloride) Composite from Waste Non-Metallic Printed Circuit Board with Interfacial Agents.

The recycling of non-metallic printed circuit boards (NMPCB) as a filler in poly(vinyl chloride) (PVC) composite would help to encourage the use of waste NMPCB, thus, reducing some environmental concerns with regard to e-waste. The objective of this study was to comprehensively evaluate the effect of different interfacial agents, namely polypropylene grafted maleic anhydride (PP-g-MAH) and ϒ-aminopropyltriethoxy silane (ATPS) on the morphology and properties of PVC/NMPCB composites. A PVC/NMPCB composite was prepared by melt compounding with varying amounts of NMPCB ranging between 10, 20 and 30 wt.%. Fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR) analysis revealed the interactions between PVC and NMPCB when using both PP-g-MAH and ATPS interfacial agent. The properties and morphology of PVC/NMPCB composites were significantly dependent on the interfacial agent treated on the NMPCB surface. The phase morphology and mechanical properties of PVC/NMPCB composites (30 wt.% of NMPCB) were improved and the result also indicated that the higher compatibility of composites with ATPS as an interfacial agent led to our obtaining the maximum Young's modulus of 484 MPa. The dynamic mechanical analysis revealed the interaction at the interface, with the Tg shifting to a lower temperature in the presence of PP-g-MAH and strong interfacial adhesion noted with the improved Tg in the presence of the ATPS interfacial agent. Further evidence of the improved interaction was observed with the increment in density in the presence of ATPS when compared with PP-g-MAH in PVC/NMPCB composite. Hence, of the two interfacial agents, ATPS showed itself to be more effective when employed as an interfacial agent for NMPCB in PVC composite for industry.

Interface-engineered composite nanofibers for boosting piezoelectric outputs of polymeric nanogenerators

Polymeric piezoelectric nanogenerators (PENGs) hold great promise for flexible energy harvesters and self-powered sensors. However, achieving high piezoelectricity in inherently piezoelectric polymers while maintaining their flexibility remains a challenge. Herein, we propose a simple yet effective approach to fabricate flexible and cost-effective PENGs based on interface-engineered composite nanofibers of poly(vinylidene fluoride) (PVDF)/carbon nanotubes (CNTs) using electrospinning. Our strategy involves the incorporation of a tailor-made interfacial coupling agent, maleic anhydride grafted PVDF (PVDF-g-MA), onto PVDF/CNTs interfaces. This mild interface-engineering strategy not only promotes interfacial interactions within composites but also stabilizes electrospinning flow jets, yielding defect-free nanofibers. More importantly, the interfacial anchoring of PVDF-g-MA molecules promotes the preferential crystallization of electroactive β-phase within PVDF matrix. By incorporating a small quantity of PVDF-g-MA (up to 1.0 wt%), our approach significantly enhances piezoelectric outputs while preserving flexibility. This eliminates the need for excessive nanofiller usage that can sacrifice the flexibility associated with conventional methods. Remarkably, the resulting composite nanofiber-based PENGs exhibit excellent piezoelectric performance, generating high output voltages (10.6 V) and remarkable power density (3.15 µW/cm2) under tiny force stimuli. Our findings open new avenues for efficient and scalable fabrication of polymeric piezoelectric nanogenerators for flexible and wearable energy harvesting and self-powered sensing applications.

Study of fly ash-slag geopolymer mortar as a rapid strengthening agent for concrete structures

A fly ash-slag geopolymer mortar (GPM) was developed as an efficient bond material for rapidly strengthening concrete structures. To determine the most significant factors affecting fluidity, setting time, and early compressive strength, we studied the following six factors using an orthogonal test: the amount of slag in the binder (SL/B), the mass ratio of sodium silicate to sodium hydroxide (SS/SH), the molarity of NaOH (MN), the mass ratio of alkali solution to binder (A/B), the superplasticizer addition to binder (SP/B), and the mass ratio of fine aggregates to binder (F/B). Different admixtures have been studied to improve the fluidity of the GPM. Bonding tests were conducted to investigate the differences in the bond behavior of the GPM. The results indicate that SL/B and A/B significantly affected the properties of the GPM. Increasing SL/B was beneficial for enhancing the early compressive strength of the GPM and decreasing its fluidity and setting time, whereas A/B exhibited the opposite trend. It is challenging to meet the requirements of high early strength and fluidity of the GPM by only changing the chemical composition, and admixtures should be added. The 1-day GPM without the interfacial agent exhibited a bond strength similar to that of the PCM at 7 days and the existing interfacial agent was not suitable for the early-strength GPM.