Weak Interfacial Interaction Research Articles

Highly integrated sulfur cathodes with strong sulfur/high-strength binder interactions enabling durable high-loading lithium–sulfur batteries

Abstract The development of high-sulfur-loading Li–S batteries is a key prerequisite for their commercial applications. This requires to surmount the huge polarization, severe polysulfide shuttling and drastic volume change caused by electrode thickening. High-strength polar binders are ideal for constructing robust and long-life high-loading sulfur cathodes but show very weak interfacial interaction with non-polar sulfur materials. To address this issue, this work devises a highly integrated sulfur@polydopamine/high-strength binder composite cathodes, targeting long-lasting and high-sulfur-loading Li–S batteries. The super-adhesion polydopamine (PD) can form a uniform nano-coating over the graphene/sulfur (G–S) surface and provide strong affinity to the cross-linked polyacrylamide (c-PAM) binder, thus tightly integrating sulfur with the binder network and greatly boosting the overall mechanical strength/conductivity of the electrode. Moreover, the PD coating and c-PAM binder rich in polar groups can form two effective blockades against the effusion of soluble polysulfides. As such, the 4.5 mg cm−2 sulfur-loaded G–S@PD-c-PAM cathode achieves a capacity of 480 mAh g−1 after 300 cycles at 1 C, while maintaining a capacity of 396 mAh g−1 after 50 cycles at 0.2 C when the sulfur loading rises to 9.1 mg cm−2. This work provides a system-wide concept for constructing high-loading sulfur cathodes through integrated structural design.

Green synthesis of soluble graphene in organic solvent via simultaneous functionalization and reduction of graphene oxide with urushiol

The poor dispersion and weak interfacial interaction are the main problems in the graphene based polymer composites. The complicated modification of graphene is usually needed. In this paper, a green and facile method is reported for the synthesis of functionalized reduced graphene oxide under mild conditions. The proposed method is based on the simultaneous reduction and surface function of graphene oxide by urushiol extracted from the sap of lacquer trees. The presence of the unsaturated long alkyl chains of urushiol not only improves the dispersion of resultant graphene in various organic solvents, but also makes graphene easily form covalent connection with polymer matrix. These features endow this urushiol functionalized graphene with great potential in the construction of graphene based polymer composites.

A chemically bonded supercapacitor using a highly stretchable and adhesive gel polymer electrolyte based on an ionic liquid and epoxy-triblock diamine network.

Despite significant advances in the development of flexible gel polymer electrolytes (GPEs), there are still problems to be addressed to apply them to flexible electric double layer capacitors (EDLCs), including interfacial interactions between the electrolyte and electrode under deformation. Previously reported EDLCs using GPEs have laminated structures with weak interfacial interactions between the electrode and electrolyte, leading to fragility upon elongation and low power density due to lower utilization of the surface area of the carbon material in the electrode. To overcome these problems, we present a new strategy for constructing an epoxy-based GPE that can provide strong adhesion between electrode and electrolyte. The GPE is synthesized by polymerization of epoxy and an ionic liquid. This GPE shows high flexibility up to 509% and excellent adhesive properties that enable strong chemical bonding between the electrode and electrolyte. Moreover, the GPE is stable at high voltage and high temperature with high ionic conductivity of ∼10−3 S cm−1. EDLCs based on the developed GPE exhibit good compatibility between the electrode and electrolyte and work properly when deformed. The EDLCs also show a high specific capacitance of 99 F g−1, energy density of 113 W h kg−1, and power density of 4.5 kW g−1. The excellent performance of the GPE gives it tremendous potential for use in next generation electronic devices such as wearable devices.

Strongly Coupled Amorphous Porous NbOx(OH)y/g‐C3N4 Heterostructure Composite for Efficient Photocatalytic Hydrogen Evolution

AbstractHeterostructure composites are promising materials in photocatalytic hydrogen evolution due to their advantage on promoting photogenerated carrier separation efficiently. However, the weak interfacial interaction can block electron transfer and complicate synthesis methods restrict the practical application of catalysts. Here, we report an interfacial enhanced amorphous porous NbOx(OH)y/g‐C3N4 heterostructure composite through a spontaneous coupling process. It was characterized by XRD, TEM, FT‐IR, XPS, NH3‐TPD and CO2‐TPD, ect., which demonstrated that NbOx(OH)y possess amorphous porous structures with high specific surface area (205 m2/g) and plenty of acidic sites (418 μmol/g) as well as basic sites (184 μmol/g) contributed from uncoordinated Nb and ‐OH. These acidic and basic sites electrostatically attract ‐NHx and C‐OH on the surface of g‐C3N4 to form hydrogen bonds (Nb‐O‐H⋅⋅⋅NH2, Nb‐O⋅⋅⋅H‐O‐C), showing a strong electron interaction between NbOx(OH)y and g‐C3N4. When tested as a photocatalyst for water splitting under visible light, the optimal NbOx(OH)y/CN‐0.05 heterostructure composite exhibits a hydrogen evolution rate of 53 μmol/g/h, which is about 14 times higher than that of g‐C3N4 (3.8 μmol/g/h) and is even superior than P25 (16 μmol/g/h). These present findings lay a foundation for the synthesis of strongly interacting heterogeneous composites.

Enhancement of thermal conductivity and mechanical properties of silicone rubber composites by using acrylate grafted siloxane copolymers

Thermally conductive composites have attracted much attention due to their application in the thermal management of electronics. But most of the thermally conductive composites exhibit poor filler dispersion and weak filler-polymer interfacial interaction, which would deteriorate the mechanical properties and impede the enhancement of thermal conductivity. Herein, three new copolymers were synthesized through hydrosilylation reaction of poly(dimethylsiloxane-co-methylhydrosiloxane) (PDMS-PHMS) with methyl methacrylate (MMA), glycidyl methacrylate (GMA), and 3-(trimethoxysilyl)propyl methacrylate (MPS), respectively. The copolymers were used to enhance the thermal conductivity and mechanical properties of Al2O3/silicone rubber (SR) composites. MPS grafted PDMS-PHMS and GMA grafted PDMS-PHMS could increase the bound rubber content of Al2O3/SR compounds, and increase the crosslink density and filler-rubber interaction of Al2O3/SR vulcanizates. The addition of MPS grafted PDMS-PHMS into an Al2O3/SR (500/100) composite could increase the tensile strength and elongation at break from 1.72 MPa and 33.0% to 3.69 MPa and 56.9%, respectively, and increase the thermal conductivity from 1.42 to 1.73 W/(m·K). The MPS grafted PDMS-PHMS/Al2O3/SR composite was successfully used as a thermal interface material between a LED chip and a heat sink, showing outstanding thermal management capability as a thermally conductive composite.

Interlaminar fracture toughness and conductivity of carbon fiber/epoxy resin composite laminate modified by carbon black-loaded polypropylene non-woven fabric interleaves

Polypropylene nonwoven fabric (PPNWF) loaded with conductive carbon black (CB@PPNWF) was prepared by manually brushing method, and then was used as interleaf material to improve the Mode I interlaminar fracture toughness (GIC) and interlaminar conductivity of carbon fiber/epoxy resin (CF/EP) composite laminate. The effects of post-treatment temperature and pressure on the properties of the composites, and the microstructure and relevant enhancement mechanism of the composite were investigated systematically. The results show that although PPNWF is a typical non-polar polymer with weak interfacial interaction with EP, CB@PPNWF has significantly improved the GIC of CF/EP composite laminate without reducing the interlaminar conductivity by means of the synergistic effects of CB particles and PPNWF. At post-treatment temperature of 80 °C and pressure of 3 MPa, compared to that of the control sample, the initial GIC (0.66 kJ/m2) and the propagation GIC (1.18 kJ/m2) of CB@PPNWF/CF/EP composite laminate were increased by 91.3% and 136%, respectively. The toughening mechanism mainly includes the deflection of matrix crack, the interface debonding of CB particles, the interfacial interaction enhancement of PP/EP by CB particles, and the bridging, pulling out and breakage of PP fibers.

Effect of metallic fillers on the hardness of polystyrene composites: An experimental investigation

In this study, the effects of composite thickness (2.5-7.5 mm), filler content (15-45%w/w) and particle sizes (20-100 µm) on the hardness of Polystyrene metal composites were examined. The metals comparatively considered were aluminium particles and iron fillings. It was observed that smaller metal particle sizes in the composite matrix and greater filler proportions will lead to improvement in hardness. Composite thickness did not have a significant effect on the hardness of the metal composites. PS-Al composite is harder than PS-Fe composite with the optimal hardness being 43.7 and 11 respectively. The factor levels that will optimise hardness for PS-Al composite are thickness of 7.5 mm, filler of 39% and particle size of 20 µm. For PS-Fe composites they are thickness of 5.9 mm, filler of 45% and particle size of 34µm. The metallic composites (PS-Al and PS-Fe) exhibited contrasting mechanical strength when viewed under SEM with a homogenous micro-structure of high interfacial interaction between the metal particles (Aluminium) and the PS resin matrix while the PS-Fe metallic composite under micro-structural analysis displayed relatively moderate to low tensile strength and hardness with weak interfacial interaction between the Iron particles and the PS resin.

Multifunctional microporous activated carbon nanotubes anchored on graphite fibers for high-strength and high-rate flexible all-solid-state supercapacitors

Flexible all-solid-state supercapacitors (ASSSCs) based on stable gel electrolyte have attracted enormous attention due to their potential application for wearable and portable electronic devices, but usually suffer from lack of structural stability for integrated devices during the bending and folding process, mainly due to the weak interfacial interaction force between electrode materials and gel electrolyte. We report a novel high-strength ASSSC based on activated multiwalled carbon nanotubes anchored on graphite fibers (GF@aMWNTs) by electrostatic assembly and electrophoretic deposition (EPD). With high areal density of aMWNTs, the GF@aMWNTs fabricated by EPD technique exhibit the maximum tensile strength of 47.9 ± 2.0 MPa for the sandwich-type GF@aMWNT/PVA/GF@aMWNT films, mainly attributed to the microporous aMWNTs as an important “bridging” role in the combination of GF electrodes and PVA electrolyte. The assembled symmetric ASSSC based on the GF@aMWNT electrodes, can provide an outstanding specific capacitance of 177 F g−1 at 1 A g−1, a maximum power density of 25 kW kg−1 (13.1 Wh kg−1) as well as excellent capacitance stability in cycling test and bending state. This high-rate ASSSC is anticipated to open up an exciting route to enhance the structural strength of integrated devices for high-efficient energy storage.

Improving the Dynamic Mechanical Properties of XNBR Using ILs/KH550-Functionalized Multilayer Graphene.

Graphene has been considered an ideal nanoscale reinforced phase for preparing high-performance composites, but the poor compatibility and weak interfacial interaction with the matrix have limited its application. Here a highly effective and environmentally friendly method for the functionalization of graphene is proposed through an interaction between as-exfoliated graphene and (3-aminopropyl) triethoxysilane (KH550), in which 1-butylsulfonate-3-methylimidazolium bisulfate (BSO3HMIm)(HSO4) ionic-liquids-modified graphene was prepared via an electrochemical exfoliation of graphite in (BSO3HMIm)(HSO4) solution, then (BSO3HMIm)(HSO4)-modified graphene as a precursor was reacted with amine groups of KH550 for obtaining (BSO3HMIm)(HSO4)/KH550-functionalized graphene. The final products as filler into carboxylated acrylonitrile‒butadiene rubber (XNBR) improve the dynamic mechanical properties. The improvement in the dynamic mechanical properties of the nanocomposite mainly depends on high interfacial interaction and graphene’s performance characteristics, as well as a good dispersion between functionalized graphene and the XNBR matrix.

Low-temperature epitaxy of transferable high-quality Pd(111) films on hybrid graphene/Cu(111) substrate

The continuous pursuit of miniaturization in the electronics and optoelectronics industry demands all device components with smaller size and higher performance, in which thin metal film is one heart material as conductive electrodes. However, conventional metal films are typically polycrystalline with random domain orientations and various grain boundaries, which greatly degrade their mechanical, thermal and electrical properties. Hence, it is highly demanded to produce single-crystal metal films with epitaxy in an appealing route. Traditional epitaxy on non-metal single-crystal substrates has difficulty in exfoliating away due to the formation of chemical bonds. Newly developed epitaxy on single-crystal graphene enables the easy exfoliation of epilayers but the annealing temperature must be high (typical 500–1,000 °C and out of the tolerant range of integrated circuit technology) due to the relative weak interfacial interactions. Here we demonstrate the facile production of 6-inch transferable high-quality Pd(111) films on single-crystal hybrid graphene/Cu(111) substrate with CMOS-compatible annealing temperature of 150 °C only. The interfacial interaction between Pd and hybrid graphene/Cu(111) substrate is strong enough to enable the low-temperature epitaxy of Pd(111) films and weak enough to facilitate the easy film release from substrate. The obtained Pd(111) films possess superior properties to polycrystalline ones with ~ 0.25 eV higher work function and almost half sheet resistance. This technique is proved to be applicable to other metals, such as Au and Ag. As the single-crystal graphene/Cu(111) substrates are obtained from industrial Cu foils and accessible in meter scale, our work will promote the massive applications of large-area high-quality metal films in the development of next-generation electronic and optoelectronic devices.

Comparative study of tribological properties of carbon fibers and aramid particles reinforced polyimide composites under dry and sea water lubricated conditions

Moving components used under air and lubricated conditions are constantly subjected to friction and wear, which poses a challenge to their reliability and service life. This work addressed the influence of short carbon fibers (SCF) and aramid particles (AP) on tribological performance of polyimide (PI) composites adding with polytetrafluoroethylene under dry and sea water lubrication conditions. A systematic study on the tribological mechanisms of SCF- and AP-reinforced PI composites was carried out. Under the controlled sliding conditions (i.e., velocity, pressure, and working conditions), the AP was more effective than SCF for enhancing the tribological performance under dry condition, but reversed under lubrication. Hard SCF exposed to the sliding interface could cause removal of the wear debris, thereby the tribofilm was patchy to lose excellent lubricated property. When sliding occurred under sea water lubrication, the weak interfacial interaction was beneficial to the formation of a robust boundary film for SCF-reinforced PI composite rather than AP-reinforced PI composite. Moreover, tribo-chemical reactions occurring between polytetrafluoroethylene and copper sustained the lubrication property of tribofilm and prevented tribo-corrosion when subjected to lubricated condition.

Porous graphene oxide/chitosan nanocomposites based on interfacial chemical interactions

Graphene or graphene oxide reinforced chitosan composites were widely demonstrated to exhibits potential applications in bone tissue engineering for their excellent biocompatibility and osteoinductivity. Nevertheless, the poor mechanical properties that caused by the weak interfacial interactions between graphene or graphene oxide and chitosan limit their applications to a great extent. In the study, graphene oxide reinforced chitosan with chemical interfacial bonding (CN bond) through the amide reaction significantly improved the interfacial interactions and then the mechanical properties of the composites. The compression testing demonstrated effects of the interfacial modification on the mechanical properties of composites. X-ray photoelectron spectroscopy (XPS) results indicated that the new formation of CN bond between graphene oxide and the chitosan matrix. ReaxFF molecular dynamics simulations were carried out to investigate the interactions between graphene oxide and chitosan at the atomistic scale. In vitro cytocompatibility testing demonstrated that the interfacial chemical modifications exhibit no effects on the biocompatibility of the composites. Thus, a meaningful way was proposed in this study to obtain the graphene oxide/chitosan biocomposites for tissue engineering with improved mechanical properties and excellent biocompatibility.

Enhanced mechanical and electrical insulating properties of (poly(para-phenylene terephthamide)) PPTA-based specialty paper with nanoscale PPTA fibers

Poly (para-phenylene terephthamide) PPTA-based specialty paper suffers from limited mechanical and electrical insulation properties due to weak interfacial interactions between chemically inert PPTA microfibers. Herein, in order to activate the fiber surface, PPTA nanofibers were prepared through DMSO/KOH deprotonation process. Whereafter, a composite paper with reinforced concrete structure was constructed by combining PPTA microfibers and PPTA nanofibers through vacuum-assisted filtration process. The results show that the composite paper has a high mechanical strength of ~ 84.8 MPa, high Young’s modulus of ∼ 2.4 GPa, and elongation at break of ∼ 7%. Meanwhile, the Weibull distribution model predicts the dielectric breakdown strength of composite paper as high as 74.4 kV/mm. In addition, the composite paper also exhibited high-temperature resistance and UV resistance, indicating great advantages for operating under high temperature and electrical insulation conditions.

Drug loading/release and bioactivity research of a mesoporous bioactive glass/polymer scaffold

Abstract Mesoporous materials have attracted widespread attention in the field of drug delivery. Nevertheless, the weak interfacial interaction between them and drug molecules affects drug loading capacity and release kinetics. In this work, mesoporous bioactive glass (MBG) was functionalized via polydopamine to enhance the interfacial interaction with dexamethasone (DEX). Concretely, on the one hand, the amine groups of polydopamine could form hydrogen bonds with the hydroxyl groups of MBG. On the other hand, the catechol groups could form π-π bonds with the benzene rings of DEX molecules. Subsequently, DEX-loaded polydopamine-functionalized MBG (pMBG@DEX) was incorporated into polyglycolic acid/poly-1-lactic acid (PGPL) to construct a scaffold (PGPL/pMBG@DEX) via laser additive manufacturing process. The results indicated that the loadage of DEX increased by about 40% after polydopamine functionalization, from 1.28 to 1.75 μg/mg. More importantly, the burst effect was avoided. The enhanced intermolecular interaction between pMBG and DEX may be primarily responsible for this phenomenon, as it acts as a driving force to drug loading and a restraining force to drug release. PGPL/pMBG@DEX scaffold also exhibited significantly enhanced cell differentiation, mechanical properties and biomineralization activity.

Enhancing the strength, toughness, and electrical conductivity of twist-spun carbon nanotube yarns by π bridging

The weak interfacial interactions between carbon nanotube (CNT) always results in low stress load transfer efficiency in CNT yarns, herein we fabricated strong, highly conducting CNT yarns at room temperature using molecules having aromatic end groups, π bridging neighboring CNTs. The resulting CNT yarns have high tensile strength with 1697 ± 24 MPa, toughness with 18.6 ± 1.6 MJ/m3, and electrical conductivity with 656.2 S/cm, which are 3.9, 2.5, and 3.5 times, respectively, as high as that of the neat CNT yarn. The specific tensile strength of the resulting CNT yarn is higher than that for previously reported CNT yarns fabricated at room temperature, even that for some CNT yarns fabricated using corossive environments or extreme temperature. This π bridging strategy provides a promising avenue for fabricating high performance CNT yarns under ambient conditions.

Highly toughened and heat-resistant poly(l-lactide) materials through interfacial interaction control via chemical structure of biodegradable elastomer

Three biodegradable elastomers with different chemical structures, i.e., polyurethane (PU), poly(l-lactide)-b-polyurethane-b-poly(l-lactide) (LPUL) and poly(d-lactide)-b-polyurethane-b-poly(d-lactide) (DPUD) triblock copolymers were prepared to blend with commercial poly(l-lactide) (PLLA) to provide weak, medium and strong interfacial interactions through weak van der Walls, interfacial chain entanglement and interfacial stereocomplex (SC) crystallization, respectively. Morphology analysis indicated that the size of dispersed phase in the amorphous PLLA matrix decreased with increasing PLLA or PDLA content of the biodegradable elastomers and agglomeration of dispersed particles occurred obviously during matrix crystallization for PLLA/PU and PLLA/LPUL blends due to the relatively weak interfacial interactions, while agglomeration did not occur apparently for PLLA/DPUD blends due to the strong interfacial interaction arisen from the interfacial SC crystallites. With well-tuned and stabilized phase morphology, PLLA/DPUD exhibited the best toughening efficiency for both the amorphous and highly crystalline PLLA matrix. Moreover, the PLLA/DPUD showed the highest mechanical strength and crystallization rate, attributing to the presence of interfacial SC crystallites, which could reinforce the mechanical strength and work as efficient nucleating agents for crystallization of PLLA matrix. In addition, PLLA/DPUD blends showed superior heat resistance over PLLA/PU and PLLA/LPUL blends by processing on conventional machine. All the excellent performances were attributed to the special interfacial interaction originated from interfacial SC crystallites of PLLA/DPUD blends.

Investigation of suitable graphene reinforcements for copper based PIM feedstock

Abstract Graphene holds a remarkable potential as a reinforcement material for copper matrix due to its outstanding mechanical and electrical properties. However, noticeable increment in performance of graphene reinforced metal matrix composites is restricted due to inhomogeneous distribution and weak interfacial interaction between graphene reinforcement and metal matrix. Poor dispersion of graphene nanoplatelets can be attributed to absence of functional groups on graphene sheets, graphene oxide in contrast holds a large number of functional groups on its surface and edges, which make it dispersible in a wide range of matrices. In this research work, we investigate potential of graphene nanoplatelets and graphene oxide as reinforcement for copper based feedstock. During this study, two different approaches, solvent based mixing and copper grafting, have been employed as dispersion methods. A radical approach for incorporation of graphene in metal matrix is also devised, by taking benefit from functional nature of graphene oxide and anchoring copper particles on graphene oxide sheets. Successful growth of copper particles along with simultaneous reduction of graphene oxide have been observed by using scanning electron microscopy and infrared spectroscopy analysis. Copper particles as intercalation species present a viable potential to resist re-agglomeration of graphene sheets while enhancing the interfacial interaction between copper matrix and graphene at the same time. Copper graphene nanocomposite can potentially be used as a reinforcement for copper based powder injection molding feedstock.

Mechanical and Thermal Properties of Blends Between Poly(Butylene Succinate) and Polyamide 12

Abstract This research aimed to improve properties of poly(butylene succinate) (PBS) by melt blending with polyamide 12 (PA12) in the PBS/PA12 ratios of 100/0, 80/20, 70/30, 50/50, 30/70, 20/80, and 0/100 wt%. PBS and PA12 were immiscible blend which the PBS/PA12 70/30 and 50/50 wt% blends presented co-continuous morphology. Blending PA12 into PBS enhanced Young’s modulus following the rule of mixer, which PBS/PA12 50/50 wt% blend had the highest tensile strength and elongation at break. Nevertheless, impact strength was reduced indicating weak interfacial interaction. The melting temperatures were closed to those of neat polymers, however, the degradation temperature was reduced slightly.

Influence of Gmelina Wood on Mechanical Properties and Morphology of Epoxy Composites

Lignocellulosic filler such as gmelina wood flour is an alternative of synthetic reinforcements which is ecofriendly, abundant in nature and inexpensive. This research aims to investigate the effects of gmelina wood filler addition on tensile properties, impact strength and morphology of epoxy composites. Filler volume fractions evaluated were10, 20, 30 and 40 percent with 30 mesh filler size. Hand lay-up method was used to manufacture the composites. Tensile strength, tensile modulus, elongation and impact strength were determined based on ASTM standard. Results show that filler addition up to some extents improves the mechanical properties of materials. The optimum tensile properties and impact strength are achieved when 10 percent filler is added into epoxy matrix. Further addition of filler degrades the tensile and impact properties of composites. This phenomenon is due to the existence of weak interfacial interaction between the gmelina wood filler and epoxy matrix for higher filler volume concentration beyond 10 vol. %. The scanning electron micrograph of tensile fracture surface reveals that there are voids, agglomeration and pull-out mechanism which are the cause of the composites failure.

High-efficiency water-selective membranes from the solution-diffusion synergy of calcium alginate layer and covalent organic framework (COF) layer

Covalent organic framework (COF) is an emergent class of ordered porous materials with high stability. The fabrication of thin and continuous COF membrane for small molecule separation remains challenging due to the relatively large pore size of COF materials and weak COF-substrate interfacial interaction. Herein, a two-dimensional COF layer was spin-coated on a porous substrate followed by constructing a bio-inspired calcium alginate (Alg-Ca) layer to obtain a dual-layer membrane with a thickness less than 100 nm. The Alg-Ca layer afforded a superhydrophilic surface to capture water molecules, and the porous COF layer rendered selective water channels. The dual-layer membrane synergistically strenthened the solution-diffusion mechanism through the manipulation of the membrane structure and transport process. The synergy of two layers endowed the membrane with superior water-selective performance with permeation flux of 3614 g/(m2h) and water content in permeate of 99.7 wt% for n-butanol dehydration. The fabrication of dual-layer membrane in this study may offer a new strategy for highly efficient separation of liquid small molecule mixtures.