Good Interphase Research Articles

Balancing salt concentration and fluorinated cosolvent for graphite cathode-based dual-ion batteries

High-concentration electrolytes (HCEs) are favored in graphite cathode-based dual-ion batteries (DIBs) due to their high oxidative stability and good interphase compatibility with both anode and cathode. Although a localized high-concentration electrolyte (LHCE) with the similar solvation structure as HCE is proposed for graphite cathode by adding weakly solvated fluorinated cosolvents, the balance between salt concentration and fluorinated cosolvent has not been investigated. Herein, various electrolytes were prepared by introducing tris(2,2,2-trifluoroethyl) phosphate (FTEP) into the HCE composed of potassium bis(fluorosulfonyl)imide (KFSI) and triethyl phosphate (TEP), and the moderate concentrated electrolyte at the TEP/FTEP volume ratio of 5:1 can stabilize K/graphite DIBs with the capacity of 45 mAh g−1 after 300 cycles at 0.5 A g−1. The abundant ion–solvent complexes as HCE and the entrance of FTEP contribute to building stable FSI−-derived cathode/electrolyte interphase with the KF-rich inner layer. Importantly, FTEP replaces partial TEP solvents to coordinate with FSI−, enhancing the electrolyte oxidative stability, whereas their weak interaction further suppresses the solvent co-intercalation. As a proof, this electrolyte enables high output voltage (3.75 V) and good cyclability of dual-ion full cells coupled with tellurium anode. This work will promote the development of fluorinated cosolvent-modified LHCEs for high-performance DIBs.

Kirchhoff rod-based three-dimensional dynamical model and real-time simulation for medical-magnetic guidewires

Background and Objective: Magnetic guidewire, fabricated from hard-magnetic soft composites, has recently emerged as an appropriate candidate for magnetic actuation systems to perform intravascular surgical navigation, owing to its elastic, magnetically steerable properties and good interphase with biological tissues. A suitable and efficient mathematical model for the magnetic guidewire is essential in the system to execute remote manipulation and active control. Methods: This paper presents a real-time Kirchhoff rod-based dynamical modeling approach, the magneto-elastic rod model, to simulate magnetic guidewire, which provides accurate simulations for two- and three-dimensional dynamic deflections induced by external magnetic fields and obtains deformed guidewire shapes in quasi-static status. Results: The proposed model is capable of describing the intrinsic principles of elastic body actuation by torques generated from the hard-magnetic soft matrix. The effectiveness of the developed model is validated, and the real-time simulation application is conducted via the semi-implicit numerical integration method. Conclusions: It has been shown that the presented dynamical model captures large nonlinear deformations and transient responses of the magnetic guidewire in an imitated human blood environment, which could offer robust support for the construction of a simulated magnetically driven surgical system.

Viscoelastic Characterization and Degradation Stability Investigation of Poly(butylene-adipate-co-terephthalate) – Calcium-Phosphate Glass Composites

In this work new biodegradable composite materials based on poly(butylene-adipate-co-terephthalate) (PBAT) reinforced with water-soluble calcium-phosphate glass (CPG) microparticles at different filler concentration (0, 4, 10, 20 and 40 wt%) were characterized by dynamic-mechanical analysis (DMA), aging and fragmentation tests. DMA results showed increasing storage modulus (E′) values with the filler content, without a significant modification of the glass transition temperature (Tg), translating in a reinforcing effect of the filler particles with good interphase adhesion. The creep compliance decreased with the increase of the CPG content, confirming a greater resistance of the composites to deformation under constant stress. The stability to weathering agents and the degree of fragmentation in laboratory-scale composting conditions were also tested, obtaining a higher sensitivity to degradation of the PBAT-based composites with the increase of CPG content. Overall, the addition of CPG particles in a PBAT matrix produced stiffer composites, with modulation of the properties based on the filler content, enhancing at the same time their degradation rate, making them a promising and more sustainable alternative to traditional polymers.Graphical

Research on the Strengthening Advantages on Using Cellulose Nanofibers as Polyvinyl Alcohol Reinforcement.

The present work aims to combine the unique properties of cellulose nanofibers (CNF) with polyvinyl alcohol (PVA) to obtain high-performance nanocomposites. CNF were obtained by means of TEMPO-mediated ((2,2,6,6-Tetramethylpiperidin-1-yl)oxyl) oxidation, incorporated into the PVA matrix by means of compounding in a single-screw co-rotating internal mixer and then processed by means of injection molding. It was found that CNF were able to improve the tensile strength of PVA in 85% when 4.50 wt % of CNF were added. In addition, the incorporation of a 2.25 wt % of CNF enhanced the tensile strength to the same level that when 40 wt % of microsized fibers (stone groundwood pulp, SGW) were incorporated, which indicated that CNF possessed significantly higher intrinsic mechanical properties than microsized fibers. SGW was selected as reference for microsized fibers due to their extended use in wood plastic composites. Finally, a micromechanical analysis was performed, obtaining coupling factors near to 0.2, indicating good interphase between CNF and PVA. Overall, it was found that the use of CNF is clearly advantageous to the use of common cellulosic fibers if superior mechanical properties are desired, but there are still some limitations that are related to processing that restrict the reinforcement content at low contents.

Development and Characterization of Peanut Shell Flour–Polypropylene Composite

In this socioeconomic era, natural fillers are continuously being identified and investigated for the development of cost-effective, sustainable composites. Current work explores the potential of peanut shell flour (PNSF) as filler in polypropylene (PP) matrix. Five levels of filler loading of PNSF (10, 20, 30, 40 and 50) by weight percentage (wt%) are taken at two levels of maleic anhydride polypropylene (MAPP) coupling agent at 2% and 4% by weight. There is a decrease in the tensile, flexural and impact strength of the composites at all levels of filler loadings compared to unfilled and incompatible composites, while flexural modulus is increased by 243% at 50 wt% filler loading and 4 wt% MAPP. Storage modulus of the composite is increased by 35.2% compared to neat PP while reduced by 65% for incompatible composites. Overall, there is improvement in all the mechanical properties with incorporation of MAPP, and the best results are obtained at 4 wt% of MAPP. SEM shows good interphase between filler and matrix and relatively less voids with addition of coupling agent up to 30 wt% filler loading. Moisture absorption of the composites is restricted to 0.3% with addition of coupling agent even at maximum PNSF loading which indicates the utility of composites for outdoor applications.

Characterization of flexible Poly(vinyl butyral)/wood flour composites

The purpose of this study is to deeply characterize a flexible poly(vinyl butyral) (PVB)/wood flour (WF) recycled composite produced by an efficient and simplified processing strategy. The mixing of the PVB/WF composite (25, 40 and 55 wt%) was performed in a single screw extruder equipped with a Maillefer screw with mixer block type pineapple in the metering zone, with the screw operating in starved feed condition in its feeding zone. Thermogravimetric analysis showed that the thermostability of PVB is the limiting factor for the composite processing window and that prior drying of wood flour and PVB is important to avoid hydrolytic degradation. Although SEM analysis has shown the presence of WF aggregates when a high content of reinforcement is added, the extrusion process disperses the wood flour relatively well. The composites have a good interphase adhesion even without a coupling agent. Relative and true density linearly increased with wood flour incorporation, as predicted by the simple rule of mixture. The hardness of pure PVB is 18 Shore D and the composite with 55% WF has 60 Shore D hardness, an increase of 230%. The incorporation of the WF reduced the PVB damping effect but did not change significantly the glass transition temperature, kept around 30 °C. This study is very positive when the objective is the production of a flexible and natural composite from recycled materials in a simple and economically attractive way.

All ‘green’ composites comprising flax fibres and humins' resins

The use of all “green” composite materials is a great environmental option for several applications such as construction or automotive. A new type of all green composites has been prepared by compression moulding flax fibres with humins as the matrix. Humins are macromolecular heterogeneous furanic co-products from biorefinery operations. For the first time the potential of humins as a whole thermoset-like matrix in combination with natural fibres was studied. The raw industrial humins were cross-linked with and without catalyst. The effect of the process conditions on the final properties of the composites was studied. Good tensile properties were measured by tensile test and Dynamic Mechanical Analysis. Observations of the fracture surface were done by Scanning Electron Microscope, revealing a void-free morphology. The study finally focused on the water absorption behaviour, underlining the more hydrophobic nature of the humins' composites compared to the raw flax mat. The good adhesion between the fibre and the matrix was underlined. Humins interacts with the hydrophilic fibres thus creating a good interphase, leading to improved properties. The study demonstrated the possibility of using a biorefinery co-product as a thermoset matrix for preparing composites materials.

Interleaved MWCNT buckypaper between CFRP laminates to improve through-thickness electrical conductivity and reducing lightning strike damage

With the recent development in fabrication of various electrically conductive composites using various conductive fillers, there is a new trend among researchers to realize electrically conductive carbon fiber reinforced composite (CFRP) for lightning strike protection. Traditional epoxy-based CFRP does not provide enough electrically conductive paths to the incident lightning current for the fast dissipation, leading to evaporation of resin and fiber damage around lightning attachment zone. In this work, multiwall carbon nanotube (MWCNT) buckypaper (BP) are interleaved between CFRP laminates to replace the resin rich area with epoxy impregnated BP. This interleaved BP not only effectively enhanced the in-plane and through-thickness electrical conductivity of the CFRP laminate but also improved resistance against lightning strikes. Electrical conductivity is improved by 697% and 643% in in-plane and through-thickness direction respectively. SEM confirmed the proper impregnation of BP and good interphase between carbon fiber and BP layers. Simulated lightning test of 40 kA is conducted on pristine and BP-interleaved composites. Improved electrical conductivity in BP composite proved to be highly effective against lightning strike confirmed by the residual mechanical test.

Regulating the Microstructure of Intumescent Flame-Retardant Linear Low-Density Polyethylene/Nylon Six Blends for Simultaneously Improving the Flame Retardancy, Mechanical Properties, and Water Resistance.

A compatibilizer was melt-blended with intumescent flame-retardant linear low-density polyethylene/nylon six blends (LLDPE/PA6/IFR) by different methods, and the effect of microstructure on the flame retardancy, mechanical properties, and water resistance was investigated. Melt-blending compatibilizers with LLDPE/PA6/IFR above the polyamide-6 (PA6) melt temperature formed the microstructure with IFR dispersion in the LLDPE matrix and good interphase adhesion between the PA6 phase and the matrix. Compared with the blends with the lack of compatibilizers, although good interphase adhesion improved the mechanical properties and water resistance, IFR dispersion in the LLDPE matrix reduced the flame retardancy sharply. To obtain the microstructure with IFR dispersion in the PA6 phase and strong interface adhesion of the PA6 phase with a matrix, a novel method in which a compatibilizer was melt-blended with LLDPE/PA6/IFR between the melt temperatures of LLDPE and PA6 was employed. The results showed that the flame retardancy, mechanical properties, and water resistance were improved simultaneously.

Electrochemical Interphases for High-Energy Storage Using Reactive Metal Anodes.

Stable electrochemical interphases play a critical role in regulating transport of mass and charge in all electrochemical energy storage (EES) systems. In state-of-the-art rechargeable lithium ion batteries, they are rarely formed by design but instead spontaneously emerge from electrochemical degradation of electrolyte and electrode components. High-energy secondary batteries that utilize reactive metal anodes (e.g., Li, Na, Si, Sn, Al) to store large amounts of charge by alloying and/or electrodeposition reactions introduce fundamental challenges that require rational design in order to stabilize the interphases. Chemical instability of the electrodes in contact with electrolytes, morphological instability of the metal-electrolyte interface upon plating and stripping, and hydrodynamic-instability-induced electroconvection of the electrolyte at high currents are all known to cause metal electrode-electrolyte interfaces to continuously evolve in morphology, uniformity, and composition. Additionally, metal anodes undergo large changes in volume during lithiation and delithiation, which means that even in the rare cases where spontaneously formed solid electrode-electrolyte interphases (SEIs) are in thermodynamic equilibrium with the electrode, the SEI is under dynamic strain, which inevitably leads to cracking and/or rupture during extended battery cycling. There is an urgent need for interphases that are able to overcome each of these sources of instability with minimal losses of electrolyte and electrode components. Complementary chemical synthesis strategies are likewise urgently needed to create self-limited and mechanically durable SEIs that are able to flex and shrink to accommodate volume change. These needs are acute for practically relevant cells that cannot utilize large excesses of anode and electrolyte as employed in proof-of-concept-type experiments reported in the scientific literature. This disconnect between practical needs and research practices makes it difficult to translate promising literature results, underscoring the importance of research designed to reveal principles for good interphase design. This Account considers the fundamental processes involved in interphase formation, stability, and failure and on that basis identifies design principles, synthesis procedures, and characterization methods for enabling stable metal anode-electrolyte interfaces for EES. We first review results from experimental, continuum theoretical, and computational analyses of interfacial transport to identify fundamental connections between the composition of the SEI at metal-electrolyte interfaces and stability. Design principles and tools for creating stable artificial solid-electrolyte interphases (ASEIs) based on polymers, ionic liquids, ceramics, nanoparticles, salts, and their combinations are subsequently discussed. Interphases composed of a second electrochemically active material that stores charge by different processes from the underlying metal electrode emerge as particularly attractive routes toward so-called hybrid electrodes that enable facile scale-up of ASEI designs for commercially relevant EES.

Effect of Sodium Hydroxide Treatments on the Tensile Strength and the Interphase Quality of Hemp Core Fiber-Reinforced Polypropylene Composites.

The formulation of greener composite materials by substituting glass fibers with natural fibers is a current field of research. If such natural fiber reinforcements come from industrial side streams, as hemp core fibers (HCFs) come from the extraction of hemp strands for the textile industry, an additional advantage can be identified. Nonetheless, such by-product fibers show some drawbacks, such as high lignin contents, which can make it difficult to obtain a good interphase between the fibers and the matrix and to obtain a good fiber individualization. A digestion treatment at different NaOH contents is proposed to eliminate soluble lignin and extractives from the surface of the fibers. At the same time, the use of a coupling agent solves incompatibilities between the fibers and the matrix. The composites were tensile tested and the impact of the proposed treatments is evaluated and discussed. Later, the Kelly-Tyson modified equation and a modified rule of mixtures—the micro-mechanic models—is used to study the impact of such treatments on the quality of the interphase between the polymer and the reinforcement. Both treatments showed a high impact on the tensile strength and the quality of the interphase, obtaining competitive composite materials reinforced with HCFs derived from a by-product.

Towards a good interphase between bleached kraft softwood fibers and poly(lactic) acid

Abstract An increasing environmental consciousness on society led to the development of materials with a lower environmental impact. In this sense, in the recent years, the substitution of synthetic or mineral fibers by natural fibers, as polyolefin matrices reinforcement, has been an active and interesting topic of research, as well as the development of competitive matrices based on renewable resources. PLA is a biodegradable polymer with higher mechanical properties than polypropylene (PP). Moreover, the interphase between polylactic acid (PLA) and natural fibers, in order to obtain relevant mechanical properties, is still unsolved. Nowadays, and to the best knowledge of the authors, there are few relevant works published about these biodegradable material reinforced showing satisfactory mechanical properties. The present work pretends to obtain PLA biocomposites with a good interphase that allow a relevant improvement on mechanical properties when reinforced. Thus, different amounts of diglyme were added to bleached kraft softwood fibers with the purpose of avoiding fiber agglomeration during compounding. Moreover, stone groundwood (SGW) and fluff pulps were also used as reinforcements. Then, and the results were compared to the previous ones in order to determine the influence both of the lignin on fiber surface, via XPS analysis, and the dispersion within the matrix. The fiber treated with 2/3 of diglyme followed a lineal and positive progression of the tensile strength when increasing reinforcement contents were added. Moreover, the 30 wt% reinforced PLA biocomposite exhibited a tensile strength of the same magnitude than 20 wt% of glass fibers reinforced PP composites, bringing to light the feasibility of substituting the synthetic matrix commodities and obtaining new and biodegradable generation of composites.

Aspects of Titanate Coupling Agents and their Application in Dental Polymer Composites: A Review

Silanes are extensively used in dental composites to facilitate chemical bonding among the phases of composites. Despite their popularity, the dental application of silanes as coupling agents is still restricted by a few limitations, which include their hydrolytic instability in aqueous oral environment and their inefficiency to bond with nonsilica fillers. Titanate coupling agents can provide good interphase bonding, improve mechanical properties, enhance filler homogenous dispersibility, and modify the rheological behavior of composites. Moreover, moisture resistance can be improved by adding a small amount of titanates. This review aims to evaluate the efficiency of using titanate coupling agents in dental polymer composites and denture bases, particularly when titanium-based fillers are impregnated.

Flexural properties of fully biodegradable alpha-grass fibers reinforced starch-based thermoplastics

This work has the aim of study the flexural properties of alpha-grass reinforced starch-based composites. The composite materials contain alpha-fibers in the range from 5 to 35 wt%. The reinforcing fibers were submitted to an alkali treatment to create a good interphase between the fibers and the matrix. It was observed that a mild 2.5 h cooking process was enough to create a good interphase, while longer periods rendered lesser improvements. The surface charges of the fibers and the matrix were determined by polyelectrolyte titration, and it was found that after the alkaline treatment both were similar. The composite materials were injection molded and tested under flexural conditions. All the flexural properties of the studies composites increased linearly with the reinforcement contents. The micromechanics of the flexural modulus and strength were studied and compared with that of tensile modulus and strength. It was established that the efficiency factors for the tensile and flexural properties were statistically similar. Three different methods were used to compute the intrinsic flexural strength from the available data. Finally the Weibull theory was used to study the best prediction of the standard deviation of the intrinsic flexural modulus.

Effect of Milling Conditions on the Microstructure and Interphase Exchange Coupling of Nd2Fe14B/α-Fe Nanocomposites

The effects of milling conditions on the microstructure and interphase exchange coupling of Nd2Fe14B+10 wt% α-Fe nanocomposites were investigated. The α-Fe crystallite size is critical for obtaining an efficient interphase exchange coupling. The problem of damaging the Nd2Fe14B crystal structure during milling was addressed by using different milling conditions. Nd2Fe14B+ 10 wt% α-Fe powder samples were prepared through mechanical milling for 6h with Ø = 10mm and Ø = 15mm balls respectively. The restoration of the Nd2Fe14B crystal structure after annealing was confirmed by XRD, with a limited growth of α-Fe crystallites. The magnetic behavior was investigated from hysteresis curves and dM/dH vs. H plots. The samples milled with small balls show a good interphase exchange coupling, however, milling with larger diameter balls determined higher coercivities due to the reduced damaging of the Nd2Fe14B crystal structure during milling. The best exchange coupling was obtained for the samples annealed at 750°C for 1.5minutes, with a maximum coercive field of about 0.65 T. The Nd2Fe14B /α-Fe exchange coupling was analyzed as a function of milling and annealing conditions.

An excellent ozone-resistant polymethylvinylsiloxane coating on natural rubber by thiol-ene click chemistry

Natural rubber (NR) as renewable resource is a kind of cheap and versatile elastomer. A disadvantage of NR is that the ozone resistance is not good, which needs to be improved for its wider application. In this study, polymethylvinyl- siloxane (PMVS) coating on natural rubber (NR) was realized for the first time by using thiol-ene click reaction under UV irradiation, simultaniously realizing the fast crosslinking of PMVS layer and the covalent crosslinking between PMVS layer and NR layer. As a result, a good interphase adhesion between PMVS coating and NR was obtained. The coating of the crosslinked PMVS layer on NR resulted in an obvious increase in the ozone resistance of NR. Our study provides a new and high efficient strategy to prepare elastomer materials with good ozone resistance.

High-Performance-Tensile-Strength Alpha-Grass Reinforced Starch-Based Fully Biodegradable Composites

Though there has been a great deal of work concerning the development of natural fibers in reinforced starch-based composites, there is still more to be done. In general, cellulose fibers have lower strength than glass fibers; however, their specific strength is not far from that of fiberglass. In this work, alpha-fibers were obtained from alpha-grass through a mild cooking process. The fibers were used to reinforce a starch-based biopolymer. Composites including 5 to 35% (w/w) alpha-grass fibers in their formulation were prepared, tested, and subsequently compared with those of wood- and fiberglass-reinforced polypropylene (PP). The term “high-performance” refers to the tensile strength of the studied composites and is mainly due to a good interphase, a good dispersion of the fibers inside the matrix, and a good aspect ratio. The tensile strength of the composites showed a linear evolution for fiber contents up to 35% (w/w). The strain at break of the composites decreased with the fiber content and showed the stiffening effects of the reinforcement. The prepared composites showed high mechanical properties, even approaching those of glass fiber reinforced composites.

Development of an osteoconductive PCL-PDIPF-hydroxyapatite composite scaffold for bone tissue engineering

Hydroxyapatite (HAP)-containing poly-ε-caprolactone (PCL)-polydiisopropyl fumarate (PDIPF) composite (Blend) was developed as an alternative for bone tissue engineering. The physicochemical, mechanical and biocompatibility properties of these composites were evaluated using two osteoblast-like cell lines (UMR106 and MC3T3E1) and compared with the blend without HAP and PCL/HAP films. The increment in the elastic modulus and the decrease in the elongation-at-break of Blend-HAP suggest that the mechanical properties of the HAP scaffolds have improved significantly. The addition of HAP to both PCL and Blend significantly improves the cell biocompatibility and osteogenicity of the scaffolds. Evidence for this notion is based in several observations: (a) HAP-polymer increases proliferation of osteoblastic cells; (b) HAP included in the blend increases the ALP expression in UMR106 cells; (c) HAP-Blend increases the type-I collagen production in both cell lines, and d) higher levels of the osteogenic transcription factor Runx-2 were detected when MC3T3E1 osteoblasts were induced to differentiate and mineralize on HAP-polymer scaffolds. In conclusion, a novel biocompatible HAP-Blend composite with uniform dispersion of semi-nano HAP particles and good interphase compatibility has been prepared successfully. The development of HAP-Blend composite, with improved physical, mechanical and osteoinductive properties, may potentially be used in bone tissue-engineering applications.

Effects of short-fiber shape on tensile properties of reinforced rubber

The tensile properties under various conditions were investigated to ascertain the optimum conditions to yield the best tensile properties. Fiber aspect ratio (AR: length of fiber/diameter of fiber), diameter ratio (DR: sphere diameter of dumbbell/diameter of fiber), interphase condition and fiber content were all considered as variables which impact the tensile strength, tensile moduli, pull-out force. In general, under good interphase conditions the tensile strength increased when the fiber aspect ratio was more than 20. The short-fiber reinforced SBR with a big end (DR = 3) did not show the dilution effect under interphase conditions when the fiber aspect ratio was more than 20. In case of short-fiber reinforced NR, when the specimen had DR = 3 and AR≥20, the dilution effect only showed up in the no-coated one. The tensile moduli were significantly improved due to the fiber aspect ratio, fiber content and good interphase at the same diameter ratio. The pull-out force increased with the diameter ratio, and keeping the diameter ratio the same, better interphase conditions also resulted in a higher pull-out force. Overall, it was found that the fiber aspect ratio, fiber diameter ratio, and interphase condition all have an important effect on tensile properties.