Showing papers in "Composites Part A-applied Science and Manufacturing in 2020"

Synchronously improved electromagnetic interference shielding and thermal conductivity for epoxy nanocomposites by constructing 3D copper nanowires/thermally annealed graphene aerogel framework

Abstract: 3D copper nanowires-thermally annealed graphene aerogel (CuNWs-TAGA) framework is firstly prepared by freeze-drying followed by thermal annealing from CuNWs, graphene oxide (GO) and L-ascorbic acid. Epoxy resin is then poured back into the above 3D CuNWs-TAGA framework to fabricate the CuNWs-TAGA/epoxy nanocomposites. CuNWs with average diameter of about 120 nm and length of approximate 10 μm are successfully prepared. When the mass fraction of CuNWs-TAGA is 7.2 wt% (6.0–1.2 wt% CuNWs-TAGA), the thermal conductivity coefficient (λ) value of the CuNWs-TAGA/epoxy nanocomposites reaches the maximum of 0.51 W/mK. Meantime, the CuNWs-TAGA/epoxy nanocomposites exhibit the maximum electromagnetic interference shielding effectiveness (EMI SE) value of 47 dB and electrical conductivity (σ) of 120.8 S/m, ascribed to perfect 3D CuNWs-TAGA conductive network structures. Meanwhile, the corresponding elasticity modulus, hardness, glass transition temperature (Tg) and heat-resistance index (THRI) of the CuNWs-TAGA/epoxy nanocomposites increase to 4.69 GPa, 0.33 GPa, 126.3 °C and 181.7 °C, respectively.

Multilayer WPU conductive composites with controllable electro-magnetic gradient for absorption-dominated electromagnetic interference shielding

Abstract: A well-designed multilayered waterborne polyurethane (WPU) shielding composites with absorption-dominated shielding feature are realized by constructing a controllable electro-magnetic gradient. Using the layer-by-layer casting method with reasonable arrangement of Fe3O4@rGO and MWCNT nanofiller, an ordered multilayer shielding network can be constructed to provide the WPU composites with positive electrical conductivity gradient and negative magnetic gradient. Hence, the penetrating microwave would undergo a particular “absorption-reflection-reabsorption” process and interface polarization loss induced absorption process between impedance matching layer and high conductive layer, leading to rather low microwave reflection with effect electromagnetic interference shielding effeteness (EMI SE). With the increase of electro-magnetic gradient, the EMI SE of the Fe3O4@rGO/MWCNT/WPU composites reaches 35.9 dB, while the power coefficient of reflectivity can be significantly decreased to 0.27. This work offers a feasible strategy for designing absorption-dominated shielding material with tunable electromagnetic performance that suitable for next-generated smart electronic devices.

Fabrication and investigation on ternary heterogeneous MWCNT@TiO2-C fillers and their silicone rubber wave-absorbing composites

Abstract: Ternary heterogeneous MWCNT@TiO2-C wave absorbent was firstly prepared, using glucose, MWCNT, and titanium isopropoxide as raw materials, through the solvothermal process followed by post-heat treatment. Afterwards, MWCNT@TiO2-C/silicone rubber wave-absorbing composites were fabricated via solution casting and subsequent curing process. XRD, Raman, XPS, and TEM analyses demonstrated the MWCNT@TiO2-C fillers were successfully synthesized with TiO2 and amorphous carbon coated on the surface of MWCNT. When the MWCNT@TiO2-C/silicone rubber wave-absorbing composites contained 25 wt% MWCNT@TiO2-C fillers and with the thickness of 2.5 mm, it displayed the minimum reflection loss of −53.2 dB and an effective absorption bandwidth of 3.1 GHz. Remarkable wave-absorbing performances for MWCNT@TiO2-C/silicone rubber composites could be attributed to the synergetic effect of interfacial polarization loss and conduction loss.

Recent advances in MXenes composites for electromagnetic interference shielding and microwave absorption

Abstract: The rapid development and widespread use of electronic devices have produced abundant electromagnetic waves, which affects the operation of other electronic equipment and even results in hazardous effects to human health. Therefore, lightweight, high-performance electromagnetic interference (EMI) shielding and microwave absorption (MA) materials are essential for controlling electromagnetic pollution and protecting the human body and other surrounding systems in civil or military applications. A new 2D MXene materials has attracted expanded attention latterly, which has special layered structure, large specific surface area, abundant natural defects and special metallic features. It has been extensively studied in electromagnetic interference shielding and microwave absorption. This paper introduces the synthesis methods and the characteristics of Ti3C2Tx MXene, and summarizes the latest research and applications of Ti3C2Tx MXene in the properties of electromagnetic shielding and microwave absorption in recent years. The prime novelty part of this review is to emphasize the effects of the synthesis process, structural design and the introduction of various materials to form different composites on the electromagnetic properties of Ti3C2Tx MXene. In the end, future prospects have been proposed to conquer the current barriers to prepare most progressive EMI shielding and MA materials for coming use objectively.

Hierarchical flower-like Fe3O4/MoS2 composites for selective broadband electromagnetic wave absorption performance

Abstract: The brilliant electromagnetic wave (EMW) absorbers are urgent with the extensive attention of electromagnetic pollution. Herein, the binary Fe3O4/MoS2 composites are successfully synthesized via a facile hydrothermal method, where the different morphologies of 3D MoS2 nanoflowers decorated with the monodispersed Fe3O4 particles by tailoring the molar ratio of Fe3O4 to MoS2. Moreover, we find that the dielectric/magnetic loss and good impedance matching have dramatically contributed to the enhanced EMW absorption ability for binary Fe3O4/MoS2 composites compared to pristine Fe3O4 nanoparticles. Meanwhile, the effective absorption bandwidth (EAB, RL 90% absorption) of 6.1 GHz at thin thickness of 2.0 mm could be obtained while it exhibits the strongest minimum reflection loss (RLmin) of −64.0 dB with ultra-thin thickness of 1.7 mm. Noticeably, even for the low frequency of C (4–8 GHz) and X (8–12 GHz) bands, the 100% frequency occupy ratio can be realized while the RL intensity is still not severely deteriorated, which is superior than most of MoS2-based absorbers that have been reported so far. Hence, it can be expected that the Fe3O4/MoS2 composites in this work featured with strong absorption intensity, selectable wide bandwidth (especially for 100% coverage both for C and X bands) as well as ultra-thin thickness (EAB of 6.1 GHz at 2.0 mm) will ensure it an attractive EMW absorber.

Bamboo-like short carbon fibers@Fe3O4@phenolic resin and honeycomb-like short carbon fibers@Fe3O4@FeO composites as high-performance electromagnetic wave absorbing materials

Abstract: In recent years, the development of an electromagnetic wave (EMW) absorbing material with low cost, wide bandwidth and strong absorption strength has been widely explored. In this study, SCFs@Fe3O4 was used as the precursor (S1), and two methods are explored to ameliorate the ultra-high complex permittivity. The method of adding phenolic resin has achieved ideal results, and its bamboo-like SCFs@Fe3O4@phenolic resin (PR) (S5) has excellent property. In addition, the electromagnetic properties can be improved by calcining the precursor at 700 °C in a tubular furnace protected by Ar gas, and the obtained honeycomb-like porous SCFs@Fe3O4@FeO (S4) composite has superior EMW absorption performance. The excellent EMW absorption performance comes from its unique porous structure. The sample also has a dual loss mechanism of dielectric and magnetic loss. Among them, conduction loss, interfacial polarization, Debye relaxation, hysteresis loss, natural ferromagnetic resonance and exchange resonance play an important role in the process of EMW absorption. It exhibits an effective absorption bandwidth (EAB) of 6.1 GHz with a thin thickness of 1.9 mm. Noting that, by adjusting the thickness (1–5 mm), reflection loss (RL) lower than −10 dB can be achieved in the range of 4–18 GHz, which covers the entire C, X and Ku bands. In this study, we not only successfully prepared honeycomb-like porous SCFs@Fe3O4@FeO and bamboo-like SCFs@Fe3O4@PR, but also proposed two simple methods to solve the excessively high complex permittivity of carbon materials. This has important reference value for the subsequent research of EMW absorbing materials.

Lightweight, flexible MXene/polymer film with simultaneously excellent mechanical property and high-performance electromagnetic interference shielding

Abstract: How to obtain high strength while remain the good shielding performance of MXene film is a big challenge, which limits its further application. Herein, we report on fabrication of mechanically strong and high-performance EMI shielding Ti3C2Tx composite film by incorporating of poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT/PSS) and then treatment with concentrated sulfuric acid to remove the insulating PSS. By introducing of 30 wt% PEDOT:PSS into Ti3C2Tx film and with acid post-treatment, the EMI SE of composite film with thickness of ~6.6 μm is up to 40.5 dB while the tensile strength is 38.5 ± 2.9 MPa and the increment in tensile strength is as high as 155% when compared to that of Ti3C2Tx film. It achieves a good balance between shielding performance and mechanical property, which has not been achieved in reported literatures. The combination of mechanical and shielding performances portfolio outperforms the counterpart of other polymer composites filled with MXene.

Hierarchical nest-like structure of Co/Fe MOF derived CoFe@C composite as wide-bandwidth microwave absorber

Abstract: Recently, metal–organic frameworks (MOFs) derived carbonaceous materials have attracted much interest as prospective microwave absorbers due to their porous structure, aperture adjustable, and topological diversity. Herein, a facile strategy was developed to regulate the morphology of CoFe-MOF-74 by adjusting the molar ratio of Co/Fe, and the hierarchical nest-like structure consisted of a large number of CoFe-MOF-74 nanorods was formed as the molar ratio of Co/Fe was 3:1. After pyrolysis at 800 °C in an argon atmosphere, porous CoFe@C nanorod-built hierarchical nest-like structures were obtained, which displayed superior microwave absorption performance with low filler loading of 10 wt%. The maximum reflection loss (RL) was −61.8 dB at 12.7 GHz with a thickness of 2.8 mm, and the corresponding effective absorbing bandwidth (RL

2D Ti3C2Tx MXene/polyvinylidene fluoride (PVDF) nanocomposites for attenuation of electromagnetic radiation with excellent heat dissipation

Abstract: The present study deals with novel, and cost-effective preparation of 2D MXene (Ti3C2Tx) filled polyvinylidene fluoride (PVDF) polymer nanocomposite for the attenuation of electromagnetic interference (EMI). The obtained nanocomposite showed remarkable shielding effectiveness (SE) of 48.47 ± 3.5 dB for 22.55 vol% filler contents at a thickness of 2 mm. Formation of conducting network along with the assembly of micro capacitor network preserved for its high EMI shielding performance. The absorption dominated EMI shielding mechanism explained by the strong resonance, and interfacial polarization favors the loss of incident EM energy confirmed from dielectric measurements. Besides, the enhanced thermal conductivity of MXene-PVDF nanocomposites about 0.767 ± 0.034 Wm−1K−1 at 22.55 vol% filler content depicts that a large amount of incident EM wave attenuated majorly by dielectric components which would be dissipated as heat quickly. The fabricated MXene-PVDF nanocomposites could be a potential candidate for EMI shielding materials and promising multifaceted electronic utilization.

Ultra-thin and highly flexible cellulose nanofiber/silver nanowire conductive paper for effective electromagnetic interference shielding

Abstract: Exploring an electromagnetic interference (EMI) shielding material with lightweight, flexible and easy fabricating process to deal with the increasingly serious electromagnetic environment pollution has become a current developing trend. Here, we reported a novel cellulose nanofiber (CNF)/silver nanowire (AgNW) conductive paper with a distinctive hierarchical structure by a facile “blending-filtration-peeling” process. Results showed that the obtained paper with a thickness of ~40 μm exhibited excellent tensile strength of ~49.1 MPa, a low percolation threshold of 1.4 vol% AgNWs, no significant changes in electrical conductivity after 2000 bending. The outstanding synergy between green CNFs and AgNWs endowed the paper with high EMI shielding effectiveness of up to 39.3 dB in X band and effective shielding effects on electromagnetic signals for realistic mobile phone communication. The special CNF/AgNW papers are expected to broaden new application fields as electronic devices e.g. flexible electronic components or effective ultra-thin EMI shielding materials for daily demands.

Lightweight, flexible and superhydrophobic composite nanofiber films inspired by nacre for highly electromagnetic interference shielding

Abstract: Inspired by the hierarchical structure of nacre, this study prepared a lightweight, flexible, and superhydrophobic polyacrylonitrile (PAN)@SiO2-Ag composite nanofibrous film with high performance electromagnetic-interference shielding via electrospinning. SiO2 incorporated into PAN electro-spun films provided the adhesion site for Ag nanoparticles (AgNPS). AgNPS were then deposited onto the surface of PAN@SiO2 electrospinning nanofibers via facile wet electroless deposition, thus endowing the resulting nanofibers with a core–shell structure. After finishing with a PTDT agent, PAN@SiO2-Ag composite nanofiber films had super hydrophobic property, and their water contact angle reached 156.99°. This scenario also presented high conductivity (approximately 17,788 S/m), average shielding effectiveness (SE), specific SE (SSE), and SSE/t, achieving 82 dB, 367 dB cm3g−1 and 73,478 dB cm2g−1, respectively. This study provides an easy method to prepare bioinspired composite films with high conductive and electromagnetic shielding and high potential applications, such as in wearable and flexible sensors.

Multifunctional 3D-MXene/PDMS nanocomposites for electrical, thermal and triboelectric applications

Abstract: Highly conductive and flexible materials have many applications in the electrical and electronic fields, while the realization of high electrical/thermal conductivity by a green, simple and efficient approach is still challenging. Herein a simple method was proposed to construct three-dimensional Ti3C2Tx (3D-MXene) skeleton without using adhesive agents. After incorporated into polydimethylsiloxane (PDMS) matrix, the resultant 3D-MXene/PDMS nanocomposites exhibited excellent electrical conductivity of 5.5 S/cm, which was nearly 14 orders of magnitude higher than that of the neat PDMS. On the other hand, the nanocomposites show a thermal conductivity enhancement of about 220% at a low MXene content of 2.5 vol% in comparison with neat PDMS. Moreover, the output current of 3D-MXene/PDMS based triboelectric nanogenerators (TENGs) was greatly enhanced because of the significantly decreased electrical resistance. This finding can be applied to TENGs with capacitor structures and can also widen the practical applications of MXene in the field of thermal management, sensors and energy harvesters.

Interlayer Controllable of Hierarchical MWCNTs@C@FexOy Cross-linked Composite with Wideband Electromagnetic Absorption Performance

Abstract: Magnetic multi-walled carbon nanotube (MWCNTs) hybrids are a promising high-performance electromagnetic (EM) absorber with the merits of wideband, thin thickness and lightweight etc. Even so, it remains a challenge to achieve a wideband absorption under a thickness (d

Multifunctional sponges with flexible motion sensing and outstanding thermal insulation for superior electromagnetic interference shielding

Abstract: Although electrically conductive polymer composites (ECPCs) are promising in the application of electromagnetic interference (EMI) shielding, how to endow the ECPCs multifunctionality is still a huge challenge. In this work, the novel polyurethane@polydopamine@silver nanoparticles (PU@PDA@Ag) sponges with excellent compressibility, flexible motion sensing, outstanding thermal insulation and superior EMI shielding properties were successfully fabricated by a facile bio-response method, which could be obtained by following two steps: (i) PDA was decorated on the surface of PU sponges by dopamine self-polymerization. (ii) Ag nanoparticles were in-situ grown on the surface of PU sponges by electroless plating. PU@PDA@Ag sponge had the maximum EMI shielding effectiveness (SE) of 84 dB, and the corresponding specific SE and absolute SE were 2625 dB cm3 g−1 and 5250 dB cm2 g−1, much higher than those of other shielding foams/sponges. Meanwhile, PU@PDA@Ag sponge possessed low thermal conductivity (52.72 mW/mK), excellent compression resilience and piezoresistive properties.

Construction of core-shell PPy@MoS2 with nanotube-like heterostructures for electromagnetic wave absorption: Assembly and enhanced mechanism

Abstract: Herein, a novel core-shell PPy@MoS2 nanotube-like heterostructures were prepared with hollow polypyrrole nanotubes and intertwined MoS2 nanosheets as core and the outer shell, respectively, by combining chemical oxidative polymerization and hydrothermal process. The unique heterostructures endowed the designed composite with highly enhanced electromagnetic wave absorbing performance. In contrast to pristine hollow PPy nanotubes and MoS2 nanoflowers, the fabricated PPy@MoS2 composite not only possessed excellent reflection loss (RL) performance, but also displayed a broad absorbing bandwidth, which might be ascribed to the good impedance matching and multifarious loss pathways including dipole polarization, interfacial polarizations and conductive loss. Impressively, the widest bandwidth (RL

Achieving excellent dielectric performance in polymer composites with ultralow filler loadings via constructing hollow-structured filler frameworks

Abstract: Dielectric polymer composites are promising candidates for pulsed power capacitors. Enhanced dielectric performance is usually achieved at the expense of high filler loadings. Herein, we report the realization of significantly enhanced dielectric performances in epoxy composites with ultralow BaTiO3 loadings via constructing hollow-structured BaTiO3 frameworks with hierarchical interfaces in epoxy. An enhanced dielectric permittivity of 22 @10 kHz, which is about 5 times that of the epoxy matrix, is achieved in the composite with merely 5 vol% BaTiO3, while the dielectric loss keeps low (tanδ ≈ 0.032 @10 kHz). Meanwhile, a greatly improved energy density which is about 250% that of the epoxy matrix and a high discharge efficiency (η = 89.7%) are achieved simultaneously. It is believed that, the hollow-structured BaTiO3 frameworks with hierarchical interfaces leads to strengthened interfacial polarization and ensures continuous transmission of polarization, which collectively improve the dielectric energy-storage performance.

High thermal conductive shape-stabilized phase change materials of polyethylene glycol/boron nitride@chitosan composites for thermal energy storage

Abstract: Phase change materials (PCMs) applied in the energy storage and temperature control system are crucial for energy conservation and environmental protection. In this work, boron nitride (BN)@chitosan (CS) scaffolds with three-dimensional (3D) porous structures were fabricated. And effective thermal conductive pathways could be created in the resultant scaffolds. By introducing polyethylene glycol (PEG) into the BN@CS scaffolds, composite PCMs with large latent heat of fusion and excellent shape-stability were obtained. In particular, a high thermal conductivity up to 2.77 W m−1 K−1 could be reached at a relatively low content of BN (27 wt%). Moreover, they also exhibited a satisfactory energy storage density of 136 J g−1. This work demonstrated a facile and environmentally friendly strategy to simultaneously achieve enhancement of thermal conductivity, high energy storage density, shape stability and outstanding thermal repeatability for composite PCMs, which held promising potential in waste heat recovery, cooling system and temperature control system.

MXene-wrapped bio-based pomelo peel foam/polyethylene glycol composite phase change material with enhanced light-to-thermal conversion efficiency, thermal energy storage capability and thermal conductivity

Abstract: Phase change materials (PCMs) have attracted great interest from researchers and have been widely developed in the field of solar thermal energy storage. Herein, a novel bio-based pomelo peel foam (PPF)/polyethylene glycol (PEG) composite PCM was designed and prepared via the simple impregnation process, which is further modified with low loading of MXene nanosheets for the purpose of improving its light-to-thermal conversion efficiency, thermal energy storage capability and thermal conductivity. With the incorporation of MXene nanosheets into PPF, the light-to-thermal conversion efficiency was improved obviously, the loading of PEG in form-stable composites phase change materials (FCPCMs) increased from 86.9 wt% (FCPCM-1) to 96.2 wt% (FCPCM-2, FCPCM-3 and FCPCM-4), and the thermal conductivity of obtained PPF@MXene/PEG FCPCMs was also improved (from 0.25 W/mK to 0.42 W/mK). It shows that the obtained PPF@MXene/PEG FCPCMs can be fully utilized in the field of solar thermal energy storage.

Highly thermally conductive polypropylene/graphene composites for thermal management

Abstract: As an indispensable part of electronic devices, efficient thermal management materials can promote heat dissipation of electronic products quickly, thereby greatly improving their reliability, stability and service life. Here, a simple “in-situ building” approach was developed to fabricate highly thermally conductive polypropylene (PP)/graphene composites with three-dimensional graphene framework. Different from conventional filler modification, a unique matrix functionalization method, inspired by mussel, was carried out to form the interaction (hydrogen bonding and π-π conjugate) between PP and graphene, which greatly reduced interfacial thermal resistance. The obtained composite exhibits a quite high through-plane thermal conductivity (10.93 W·m−1·K−1, almost 55 times higher than that of pure PP), and shows excellent heat dissipation when used as a thermal management material in LED integration. The composite has the potential application in heat dissipation of high power and highly integrated electronic devices.

Synergistic effects of hybrid conductive nanofillers on the performance of 3D printed highly elastic strain sensors

Abstract: In this work, thermoplastic polyurethane based conductive polymer composites containing carbon nanotubes (CNTs) and synthesized silver nanoparticles (AgNPs) were used to fabricate highly elastic strain sensors via fused deposition modeling. The printability of the materials was improved with the introduction of the nanofillers, and the size and content of the AgNPs significantly influenced the sensing performance of the 3D printed sensors. When the CNTs:AgNPs weight ratio was 5:1, the sensors exhibited outstanding performance with high sensitivity (GF = 43260 at 250% strain), high linearity (R2 = 0.97 within 50% strain), fast response (~57 ms), and excellent repeatability (1000 cycles) due to synergistic effects. A modeling study based on the Simmons' tunneling theory was also undertaken to analyze the sensing mechanism. The sensor was applied to monitor diverse joint movements and facial motion, showing its potential for application in intelligent robots, prosthetics, and wearable devices where customizability are usually demanded.

Flexible and alternant-layered cellulose nanofiber/graphene film with superior thermal conductivity and efficient electromagnetic interference shielding

Abstract: Inspired by sedimentary rock structure, we demonstrate a flexible heterogeneous multilayered film with high thermal conductivity (TC) and excellent electromagnetic interference (EMI) shielding performance by stacking and concentrating graphene nanosheets (GNS) into alternating conductive layers. Typically, the multilayered film with alternating cellulose nanofiber (CNF) layers and conductive CNF/GNS layers was fabricated by alternating vacuum filtration. Arising from the unique nacre-like oriented structure and highly concentrated conductive filler, high-efficiency phonon and electron transmission paths can be formed in the obtained multilayered CNF@GNS film. As a result, the optimal film with only 25 wt% GNS reveal a high in-plane TC of 33.55 W/(m·K), which increases by 144.6% comparing to the homogeneous CNF/GNS film. Simultaneously, the multilayered films exhibit the effective EMI shielding performance with the highest shielding effectiveness (SE) of 27.4 dB, which is mainly attributed to the enhancing impedance matching and multiple microwave reflections induced by the unique alternating multilayer structure.

Review of z-pinned laminates and sandwich composites

Abstract: Z-pinned laminates and sandwich materials are an important class of composites with current applications in aircraft and emerging uses in other light-weight engineered products. This paper reviews research advances in the manufacture, microstructural chacterisation, mechanical properties, environmental durability and other functional properties (e.g. electrical, thermal, damage sensing) of z-pinned composite materials and structures. The review reveals that z-pins can be used in create novel multifunctional laminates that uniquely combine a multitude of important properties including high interlaminar fracture and fatigue resistance, superior impact damage tolerance, increased thermal and electrical conductivities, damage sensing, and high-performance joining. Similarly, z-pins can impart sandwich composites with a novel combination of multifunctional properties that include high structural, damage tolerance, electrical and damage sensing properties. Research gaps in our understanding of z-pinned laminates and sandwich composites are identified. Future research opportunities to create next-generation z-pinned materials with even more versatile multifunctional properties are described.

Multifunctional light-responsive graphene-based polyurethane composites with shape memory, self-healing, and flame retardancy properties

Abstract: It is a challenge to manufacture light responsive polymer composite that possesses shape memory, self-healing, and flame retardancy capacities. Herein, multi-functionalized graphene oxide (mfGO) wrapped with nitrogen-, phosphorus-, and silicon- containing units was prepared via in-situ polymerization and subsequently was incorporated into a diselenide-containing polyurethane (dPTD) matrix to fabricate composite. The successful functionalization of mfGO was initially confirmed by a series of measurements. Taking advantage of the crystallization-induced and photo-thermal effects of mfGO as well as the dynamic exchange characteristic of diselenide bonds, the dPTD-mfGO2 composite containing 2 wt% of mfGO exhibited admirable shape memory and self-healing behaviors under visible-near infrared light within 3 min, and its shape memory characteristics and healing efficiencies were kept above 90% and 76% after three cycles, respectively. Further combustion experiments demonstrated that dPTD-mfGO2 composite showed superior LOI (24.9%) and UL-94 rating (V-2) without flaming drips, owing to the synergistic catalyzing carbonization and barrier effect of mfGO. Additionally, the dPTD-mfGO2 composite possessed an improved water contact angle of 109.5°. These findings suggest that the introduction of 2 wt% mfGO to the dPTD matrix can synergistically improve the toughness, shape memory, self-healing, flame retardancy, and water resistance as compared with the neat dPTD. This work provides a promising pathway to fabricate stimulus-responsive composite materials with versatile functions.

The composition design of MOF-derived Co-Fe bimetallic autocatalysis carbon nanotubes with controllable electromagnetic properties

Abstract: MOF-derived magnetic carbon nanotubes microwave absorbers have been prepared by some researchers, but how to control the length and quantity of MOF-derived carbon nanotubes is still a big challenge. In this work, the number and length of carbon nanotubes were regulated by introducing Fe atoms into the bimetallic Zn-Co MOFs and optimizing the composition proportion of Zn2+ and Co2+ in the precursor. When the molar ratio of Zn2+ and Co2+ was 1:1, the carbon nanotubes was most; When changed to 6:1, the obtained absorbers possess not only strong absorption capability but also wide absorption bandwidth only under 15 wt% filling loading. The excellent performance ascribed to the strong interfacial polarization and impedance matching. The dielectric loss mainly resulted from the conductive network formed by a suitable number of long carbon tubes. We believe that this research will provide a necessary reference for future MOFs-derived magnetic carbon nanotubes microwave absorbers.

Design of network Al2O3 spheres for significantly enhanced thermal conductivity of polymer composites

Abstract: It is of great significance to realize high thermal conductivity of polymer composites, which are used in electronic devices. However, traditional polymer composites exhibit limited thermal conductivity due to high interfacial thermal resistance. Herein, network Al2O3 (N-Al2O3) with multidimensional continuous structures is fabricated by a feasible strategy and first used as fillers for phenolic resin (PR), achieving significantly enhanced thermal conductivity of 4.01 Wm−1 K−1, enhanced by 1800% compared with neat matrix. The unique N-Al2O3 is responsible for the excellent thermal conductivity, which contributes to the continuous thermal transfer pathways with decreased interfacial thermal resistance. Additionally, owing to the interpenetrating structure of N-Al2O3 and PR, composites display improved mechanical properties and thermal stability. Dielectric loss tangent of composites decreases with increasing N-Al2O3, which is unusual and desired for thermal interface materials used in electronic devices. Therefore, our strategy offers new guidelines in fabricating high-quality composites for commercial applications.

Structural design and environmental applications of electrospun nanofibers.

Abstract: Nanofibers have attracted extensive attention and been applied in various fields due to their high aspect ratio, high specific surface area, flexibility, structural abundance, etc. The electrospinning method is one of the most promising and effective ways to produce nanofibers. The electrospun nanofibers-based films and membranes have already been demonstrated to possess small pore sizes, larges specific surface area, and can be grafted with different functionalities to adapt to various purposes. The environmental applications of nanofibers are one of the essential application fields, and great achievements have been made in this field. To well summarize the development of nanofibers and their environmental applications, we review the nanofiber fabrication methods, advanced fiber structures, and their applications in the field of air filtration, heavy metal removal, and self-cleaning surface. We hope this review and summary can provide readers a comprehensive understanding of the structural design and environmental applications of electrospun nanofibers.

Vertically aligned silicon carbide nanowires/reduced graphene oxide networks for enhancing the thermal conductivity of silicone rubber composites

Abstract: Ice-templated assembly strategy is an effective method to construct filler networks. The filler networks can be used to increase the thermal conductivity of polymer composites. Herein, silicon carbide nanowires, reduced graphene oxide and cellulose nanofiber were used as assembly units to construct vertically aligned filler networks by ice-templated assembly strategy. Polydimethylsiloxane grafted with poly(ethylene glycol) could enhance the interfacial interaction and improve the wettability between silicone rubber and the filler networks. Silicon carbide/reduced graphene oxide/silicone rubber composites were prepared by infiltrating the filler networks with silicone rubber. The thermal conductivity of the composites increased with increasing the contents of silicon carbide and reduced graphene oxide. The thermal conductivity of the composite with 1.84 vol% filler network was as high as 2.74 W/(m·K), exhibiting significant enhancement of thermal conductivity of 16 times compared with silicone rubber. This work provides an insight for preparing highly thermally conductive silicone rubber composites.

3D compaction printing of a continuous carbon fiber reinforced thermoplastic

Abstract: This study reports a three-dimensional compaction printing (3DCP) technique for a continuous carbon fiber reinforced thermoplastic (CFRTP). A hot-compaction roller was equipped with a fused filament fabrication (FFF)-based 3D printer to press the filament against the printer bed immediately after the printing to reduce voids and improve adhesion between the filaments. Unidirectional CFRTP coupon specimens were fabricated and the tensile and bending properties of the specimens were investigated. The test results showed that the tensile and bending properties of the printed CFRTP were improved by the hot compaction during 3D printing. Voids in the specimen were visualized using scanning electron microscopy and X-ray computed tomography, and it was confirmed that the hot compaction reduced the void content. The experimental results showed that 3DCP was superior to conventional FFF in the fabrication of CFRTP parts for structural applications.

Mechanically robust ANF/MXene composite films with tunable electromagnetic interference shielding performance

Abstract: MXene-based materials have been widely studied recently for effective electromagnetic interference (EMI) shielding due to the prominent intrinsic electrical conductivity. Nevertheless, the poor mechanical performance of pure MXene films limits the practical application in EMI shielding. Thus, we integrate MXene with aramid nanofiber (ANF) to develop a composite film with layered structure through a simple vacuum-assisted filtration method. The resulting ANF/MXene (20/80) composite exhibits a high electrical conductivity of 879.0 S/cm, EMI shielding effectiveness (SE) of 40.6 dB and specific SE (SSE/t, SE divided by the density and thickness) of 50,491 dB∙cm2∙g−1 with an ultrathin thickness of 3.2 μm. Furthermore, the ANF/MXene (60/40) realizes a balance between mechanical properties and EMI shielding performance with the strength of 201.3 MPa and SE of 28.1 dB, which enables the ANF/MXene composite films as promising EMI shielding materials with excellent mechanical robustness.

Simultaneous improvements in fire resistance and alarm response of GO paper via one-step 3-mercaptopropyltrimethoxysilane functionalization for efficient fire safety and prevention

Abstract: A flame-retardant graphene oxide (GO) based nanocomposite paper was prepared for efficient fire alarm response via a one-step and green 3-mercaptopropyltrimethoxysilane (MPTS) functionalization process. Such MPTS modification not only improves thermal stability and flame resistance of GO network, but produces ultra-fast flame detection and efficient fire early warning response. Typically, the MPTS-GO-10 wt% paper shows a flame detection response signal of about 1.0 s and improved fire early warning response time at a relatively temperature of 200 °C. The structural observation and analysis suggest that the thermal reduction behavior of GO network can be promoted by the sulfydryl groups of MPTS molecules at high temperature, thus producing the rapid and sensitive transition of electrical resistance form insulating GO into conductive reduced GO network. The MPTS functionalization developed here show promising to tailor fire early warning response of flame-retardant GO based fire alarm sensor for potential fire safety and prevention applications.