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Paper is a widely used packaging material and is nowadays regaining importance, e.g., as bio-based and biodegradable material. Moreover, new technologies such as polymer-fiber composites, printed electronics and the deep drawing of paper are developing. The process stability and also the resulting quality of paper converting processes such as coating, metallization, printing, and the printing of electronics are highly affected by the hygroexpansion of paper. In order to reduce production instability and to choose and develop paper substrates with ideal characteristics, critical parameters need to be known. This paper offers an extensive overview of those parameters, starting at a molecular and microscopic level with the effect of the constituents and morphology of single fibers, before moving on to paper contents, chemical modifications and additives and finally concluding with paper production and fiber network modification. It was found that the major influences are single fiber sorption, inter-fiber contacts, microfibril angle, fiber morphology (length, width, curliness) and fiber orientation. This review gives new ideas and insights for technologists working in research, development and production optimization of paper-based products. [ABSTRACT FROM AUTHOR]

Nowadays, the scientific community emphasizes the use of reversible and non-toxic materials in the field of cultural heritage. Biopolymers are one of the alternative materials to synthetic polymers and solvents that are dangerous for human health and for the environment, applied in consolidation and coating treatment. Natural biopolymers may be divided into polysaccharide, protein, and polyester: All of them are low cost, eco-friendly, and biocompatible, besides many physicochemical characteristics such as being transparent, soluble in water, hydrogel, and film-forming, and can be easily functionalized. The addition of nanoclay, essential oil, and active molecules improves the physicochemical properties of biopolymers and proposes smart response abilities to the new composite material. This work is intended to provide an overview of the development of biopolymers by considering the most general aspects and scanning the diverse substrates of application for the conservation and protection of cultural heritage. [ABSTRACT FROM AUTHOR]

Here we review and summarize the groundbreaking scientific researches of the late Professor Larry L. Hench, including several of his key discoveries in materials science and engineering. First, we provide a statistical overview of his exceptional scientific performance using Scopus, Web of Science, and other Web sites to extract statistical data on his scientific publications and patents. Professor Hench achieved an exceptionally high h-index of 77 (Scopus) for the field of materials science and engineering, which resulted from his 340 research papers, 210 conference papers, 41 patents, 24 books, 4 editorial notes, and 3 biographies starting in 1967. Then, we summarize and highlight his seminal articles, books, and patents in several research areas, such as bioactive glasses, optical gel glasses, biocomposites/coatings, glass-ceramics, biophotonics, advanced ceramics, semiconducting and ionic conducting glasses, glass corrosion, and nuclear waste disposal. Prof. Hench not only discovered the first man-made material to form a chemical bond with bone and initiated a whole new field-bioactive glasses and glass-ceramics-but also made several other important scientific discoveries. It is quite clear that he was one of the most influential materials scientists/engineers of all time! We hope that this review is not only useful for all persons interested in materials science and engineering but also encourages students and younger investigators to make use of this accumulated knowledge to design novel materials and discover new applications for glasses and ceramics. [ABSTRACT FROM AUTHOR]

With development of present energy-saving society, lightweight and green development in the automotive and aerospace industries have put forward urgent demands for heat-resistant cast aluminum alloys. Present cast aluminum alloys are of lightweight and have excellent mechanical properties when serving in ambient environment. However, when serving at temperatures of 200–300 ℃ or even higher, the alloys inevitably soften and the high-temperature mechanical properties decline rapidly, hardly meeting the requirements for high-performance equipments. This paper summarizes the development process of classic heat-resistant aluminum alloys, especially the microstructural characteristics of heat-resistant cast aluminum alloys in the past decade, and reviews the current microstructure tuning strategies of heat-resistant aluminum alloys from the aspects of intrinsic heat resistance of the second phases, phase interface modification, diffusion-controlled phase transition, grain boundary stabilization and composite material design. Finally, we propose the prospects for the future development of heat-resistant aluminum alloys. [ABSTRACT FROM AUTHOR]

Carbon materials have excellent thermophysical properties, and different dimensions of carbon materials are attractive candidates for enhancing high-performance aluminum matrix composites for thermal management. This paper reviews the preparation processes of carbon/aluminum composite materials in various dimensions and summarizes the main factors affecting the thermal conductivity of carbon/aluminum composites from the perspectives of metal matrix, reinforcement, and interface. Finally, we summarize the experimental progress of interfacial modification of different carbon/aluminum composites and put forward the future research direction in this field. [ABSTRACT FROM AUTHOR]

As a class of thermosetting resins with exceptional overall performance, cyanate esters have not received sufficient attention for their potential applications in 3D printing. In this paper, polytetrafluoroethylene micropowder is used for the first time as a thixotropic agent to regulate the rheological properties of liquid bisphenol E cyanate monomer for direct ink writing of cyanate ester resins in 3D printing. Due to their appropriate compatibility, the mixed inks exhibit high storage modulus and shear-thinning behavior, enabling the printed structures to maintain their shape well during printing and subsequent curing processes. The printed samples have good mechanical strength and excellent thermal stability. At the same time, the presence of polytetrafluoroethylene endows the composite materials with low dielectric constant and hydrophobicity. The latter property leads to high hygrothermal stability of the composites. The cyanate ester-polytetrafluoroethylene composite developed here offers a reliable method for 3D printing high performance cyanate ester, efficiently enhances the processibility of the cyanate ester based materials. [ABSTRACT FROM AUTHOR]

This paper investigated the specific compressive strength (specific strength) of fly ash-based geopolymer composites with four hardwood extractives and two softwood extractives, as well as specific wood extractives. Additionally, the effect of the portion of pine wood (i.e., sapwood and heartwood) and wood pretreatment with NaOH were considered. Geopolymer paste (with extractives) and geopolymer wood composites (GWCs) were cured at 60 °C for 24 h. The samples were stored in a climate chamber (20 °C, 65% RH) for 7 days before finally testing under compression. From the results, the specific strengths of geopolymers with hardwood extractives were not significantly affected. However, geopolymers containing pine extractives showed the most significant reduction in specific strength. There were no significant differences in the specific strengths of geopolymers containing polyphenols and resin acid. Generally, geopolymers containing fatty acids recorded the lowest specific strengths. There was no difference between the GWCs with untreated sapwood and heartwood. However, the wood pretreatment led to a 21% and 10% increase in the specific strengths of GWCs with sapwood and heartwood, respectively. The findings of this study form the basis for improved GWCs production and a wide range of applications for green composite materials. [ABSTRACT FROM AUTHOR]

Owing to the high demand for electronic devices and electric vehicles, a huge effort has been directed to the exploration and development of new batteries with good cycling stability, satisfactory high specific capacity and safety. In this paper, we report the designed synthesis of the vanadium oxide with mixed valence H2V3O8 and the composite H2V3O8/PEDOT:PSS using low cost and easy hydrothermal method. Electrochemical activity of the vanadium oxyhydroxide H2V3O8 and the composite H2V3O8/PEDOT:PSS as cathodes materials for high performance lithium–ion batteries was evaluated vs. Li+/Li at various current rates. Compared with pure H2V3O8, composite H2V3O8/PEDOT:PSS cathode exhibits higher specific capacity (390 mAh g−1 at 0.05 A g−1 whereas, an initial discharge capacity of 300 mAh g−1 is observed at 0.3 A g−1), more excellent rate performance and longer cycle life. The composite H2V3O8/PEDOT:PSS cathode delivers excellent specific capacity of ca. 390 mAh g−1 and a 97.5% capacity retention are achieved even after 350 cycles at current density of 0.05 A g−1. Higher electrochemical capacity and stability of the new composite cathode are mainly ascribed to a cooperative effect between the conductive polymer (PEDOT:PSS) with good electrical conductivity and the unique nano-sized H2V3O8 rods with short diffusion pathway for lithium ions diffusion. [ABSTRACT FROM AUTHOR]

This paper reviews a literature survey on the usage of volcanic particle materials as an alternative filler material in polymer composites. Also, it highlights different types of volcanic particle materials and their potential effect on the performance of polymer composites. The review begins with Fourier transform infrared (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM) analysis of different volcanic materials. Then, it reviews the thermal and mechanical properties of polymer composites that filled with different volcanic particle materials such as volcanic ash, pumice, perlite, and tuff. Reviewed articles have demonstrated that volcanic particle materials can serve as a polymer composite filler. However, there are several factors such as volcanic particle type, size, surface treatment, dispersion, filler concentration, and interfacial interaction with polymer matrix that should be considered and optimized to achieve a balanced polymer composite with its desired properties. Further, the review provides some insights on the gap in the research of volcanic particle material in polymer composites. In particular, the research of volcanic particle materials in different kind of polymers especially bio-based and recycled ones according to the cost-effective and green applications was suggested to be focused. [ABSTRACT FROM AUTHOR]

The heat transfer performance of the graphene network in the polymer is not so satisfactory due to the high interfacial thermal resistance between layered graphene. This paper constructs partially stacked graphene sheets models with random vacancies by the molecular dynamics to investigate the effect of vacancy coverage rate, stacking length and stacking forms on the heat transfer coefficient. The results indicate that the heat transfer coefficient of the whole system mainly depends on the effective thermal conductivity of the stacking region. As the vacancy coverage rate increases, the effective thermal conductivity of the stacking region increases rapidly and then decreases slowly due to the synthetic effect of the interfacial thermal resistance and in-plane thermal resistance. Further studies reveal the positive correlation between the stacking length and the effective thermal conductivity of the stacking region. However, the effective thermal conductivities of models with different stacking lengths converge to a similar value approximately at a high vacancy coverage rate. Finally, the stacking form is proved to have a slight influence on the effective thermal conductivity. This work is of practical importance for the design and application of graphene networks in composites materials. [ABSTRACT FROM AUTHOR]

The detection method with potential ability to diagnose drugs in human serum rapidly, highly sensitivity and selectivity is of vital importance for clinical diagnosis. In this paper, an electrochemical sensor on the basis of composite material modified by zeolitic imidazolate framework (ZIF) on carbon nanofiber (CNF) surface is constructed, which is used for ultra-sensitive determination of adrenaline (AD). CoMnZIF-CNF combines the good conductivity of carbon nanofibers and the high electrocatalysis of CoMnZIF, which can improve the reaction activity and the sensing effect of adrenaline. The proposed sensor shows a good linear relationship between AD concentration from 5 to 1000 μM, and the detection limit is 0.22 μM. Meanwhile, CoMnZIF-CNF demonstrated the remarkable selectivity, significant repeatability and stability, as well as excellent reproducibility. Besides, through the analysis of AD in serum electrolyte, the practicability of the sensor was evaluated and the recovery rate was between 97.51 and 102.53%. On the basis of the results, the prepared sensor has a vital application prospect in detecting AD in actual sample analysis. [ABSTRACT FROM AUTHOR]

Traditional epoxy resin materials are widely used in coatings, composite materials, electronic packaging materials, etc. They are usually made of unsustainable fossil resources and cannot be recycled under mild conditions. Degradable thermosetting resins with dynamic covalent structure provide a potential solution to this conflict. In this paper, using biomass energy vanillin, m-xylylenediamine and 1, 6-hexanediamine as raw materials, two dynamic imine bond curing agents were synthesized, and then cured with DGEBA to prepare two bio-based imine epoxy vitrimers. The thermal and mechanical properties of two imine epoxy vitrimers were studied and compared in detail. Results showed that the two types of polymers exhibit excellent thermal stability and solvent resistance. At the same time, the tensile strength, modulus and elongation at break were comparable to or even better than those of conventional bisphenol A epoxy resin. In addition, due to the hydrolysis of the dynamic imine bonds, vitrimers had degradable characteristic, and its degradation also exhibited temperature, solvent and acidity dependence. More importantly, the recyclable carbon fiber reinforced polymer composites made of these two vitrimers could be completely degraded under weak acid conditions, and the nondestructive recycling of carbon fiber composites could be realized. We envision that this vitrimers with simple process, excellent comprehensive properties and degradability will make it a potential candidate for applications in sustainable structural materials. [ABSTRACT FROM AUTHOR]

Nanoindentation technology is an advanced method to explore the microscopic mechanical properties of layer or block materials. Grid nanoindentation coupled with statistical analysis is effective to give an insight into multiphase materials just like cement paste, mortar and concrete. However, traditional statistical methods, such as deconvolution analysis and Gaussian Mixture Model (GMM), are limited by the nondeterminacy of normal distribution assumption, computational instability due to random selection of initial values, and some problems induced by large amount of calculation. In this paper, clustering analysis, an advanced analysis method for mixed data and widely used in machine learning field, is developed to deal with grid nanoindentation test data. Calculation results suggested that K-medoid clustering is suitable and highly efficient to explain grid nanoindentation tests. Furtherly, clustering method is more robust than deconvolution analysis and GMM when data size is reduced. In addition, normal distribution assumption is not always available for the mechanical properties of some mineral phases in cement pastes. This work offers a new optional mathematical tool to interpret and understand the multiphase properties of cementitious materials probed by grid nanoindentation technology. [ABSTRACT FROM AUTHOR]

The research presented in this paper aims to improve on the accuracy and computational efficiency of previously reported stochastic models for predicting the electromechanical properties of conductive polymer composite (CPC) materials with nanoparticle constituents. The proposed approach provides a means of quantifying the degree of particle dispersion in a mixture—a parameter that is most often reported as qualitative- and process-specific. CPC-based sensors have recently garnered attention in the field of structural health monitoring due to their atomic similarities with composite materials that are an increasingly popular commodity among numerous industries. In this study, CPCs composed of carbon black nanoparticles and phenolic-based resin epoxy are manufactured and characterized both experimentally and via computational methods. A high-fidelity stochastic modeling solution is proposed to estimate electromechanical properties of such CPCs. Qualitative analysis on the fidelity of the stochastic model is demonstrated. The potential uses for the model and validation techniques are discussed. [ABSTRACT FROM AUTHOR]

Nickel-based superalloys such as Hastelloy X (HX) are widely used in gas turbine engines for their exceptional oxidation resistance and high-temperature strength. The addition of ceramic reinforcement further enhances these superalloys' mechanical performance and high-temperature properties. For this reason, this paper investigates the microstructure and mechanical property of laser powder bed fusion (LPBF) additively manufactured HX–1 wt% WC (tungsten carbide) composite specimens. The results demonstrate that the LPBF-fabricated composite was observed to have several pores and microcracks, whilst only pores were detected in the as-fabricated pure HX. Compared to the fabricated pure HX, the tensile yield strength of such HX composite parts was increased by 13% without undue sacrifices to ductility, suggesting that the very limited number of microcracks were not sufficient to degrade the mechanical performance. The significantly increased dislocations were considered to be the primary contributor for the mechanical performance enhancement in the LPBF-fabricated composite material. The findings offer a promising pathway to employ LPBF process to fabricate advanced microcrack-free composites with high-strength through a careful selection of ceramic reinforcement materials. [ABSTRACT FROM AUTHOR]

Piezoresistivity is an electromechanical effect characterized by the reversible change in the electrical resistivity with strain. It is useful for electrical-resistance-based strain/stress sensing. The resistivity can be the volumetric, interfacial or surface resistivity, though the volumetric resistivity is most meaningful scientifically. Because the irreversible resistivity change (due to damage or an irreversible microstructural change) adds to the reversible change that occurs at lower strains, the inclusion of the irreversible effect makes the piezoresistivity appear stronger than the inherent effect. This paper focuses on the inherent piezoresistivity that occurs without irreversible resistivity changes. The effect is described by the gage factor (GF), which is defined as the fractional change in resistance per unit strain. The GF can be positive or negative. Strong piezoresistivity involves the magnitude of the fractional change in resistivity much exceeding the strain magnitude. The reversible effect of strain on the electrical connectivity is the primary piezoresistivity mechanism. Giant piezoresistivity is characterized by GF ≥ 500. This critical review with 209 references covers the theory, mechanisms, methodology and status of piezoresistivity, and provides the first review of the emerging field of giant piezoresistivity. Piezoresistivity is exhibited by electrically conductive materials, particularly metals, carbons and composite materials with conductive fillers and nonconductive matrices. They include functional and structural materials. Piezoresistivity enables structural materials to be self-sensing. Unfortunately, GF was incorrectly or unreliably reported in a substantial fraction of the publications, due to the pitfalls systematically presented here. The most common pitfall involves using the two-probe method for the resistance measurement. [ABSTRACT FROM AUTHOR]

Transition metal phosphides have received extensive attention as anode materials of sodium ion batteries due to their high theoretical specific capacity and low redox potentials. However, the large volume change during the insertion/extraction of sodium ions often leads to a poor electrochemical performance and thus limits their practical application. Herein, we rationally designed three-dimensional hierarchical Ni5P4 nanospheres wrapped by rGO nanostructures (Ni5P4@rGO) through a sequential hydrothermal synthesis and phosphidation of highly folded spherical α-Ni(OH)2. The graphene nanosheets can effectively prevent the collapse of spherical α-Ni(OH)2 and aggregation of Ni5P4 active materials during phosphidation. Besides, the strong coupling between the nickel phosphide and graphene layers leads to excellent electrochemical performance of Ni5P4@rGO composite as anode materials of SIBs, delivering a specific capacity of 304 mA h g–1 at 0.2 A g–1 after 200 cycles. The strategy developed in this paper may shed light on the morphology-controlled synthesis of transition metal phosphides with high performance for energy storage devices. [ABSTRACT FROM AUTHOR]

The expansion of the optical response range and the high photoelectron holes separation and the transfer efficiency are prerequisites for the excellent hydrogen evolution performance of the catalyst. In this paper, amorphous CoSx is combined with rare-earth complex LaMnO3 and under the characterization of SEM, TEM, XRD and XPS, the successful synthesis of the composite catalyst was demonstrated; characterization results by UV–Vis, BET and electrochemical workstations show that the composite material exposes more active sites, and the close contact interface formed between the two effectively improves the separation and transmission of photogenerated carriers, and the ability of the composite material to sense light is also significantly enhanced. After optimizing the hydrogen production conditions of the composite catalyst, the hydrogen production under visible light (≥ 420 nm) for 5 h reached 458.8 μmol, which was about 6.8 and 4.5 times that of pure LaMnO3 and CoSx, and the hydrogen evolution stability of the material is very good. Studies have shown that amorphous CoSx is a good material that can replace precious metals for hydrogen production. [ABSTRACT FROM AUTHOR]

In this review, recent progress in the mechanical, thermal and interfacial properties of graphene/CNT multiphase polymer composites is examined. Progress in the mechanical and thermal properties of CNT (1D) and graphene (2D) nanostructure materials is also reviewed and compared. Furthermore, this review highlights the improvements in the mechanical, thermal and interfacial properties of two- and three-phase composites, owing to the addition of graphene/CNT. In particular, analysis of several notable papers on hybrid composites (graphene/CNT) provides an intensive review of synergetic effects on the overall properties of the corresponding composites. This holistic review describes an improved interface between fibers and a nanofiller-reinforced matrix. Although the presence of nanofillers even at low loadings confers an overall improvement in composite properties, the exact ratios of individual fillers and combined forms remain to be discussed in depth. Finally, potential applications, current challenges and future perspectives for use of these multiphase composites are discussed with regard to their extraordinary capabilities and promising developments in graphene/CNT family-based composite materials. [ABSTRACT FROM AUTHOR]

There has been much effort to provide eco-friendly and biodegradable materials for the next generation of composite products owing to global environmental concerns and increased awareness of renewable green resources. An increase in the use of natural materials in composites has led to a reduction in greenhouse gas emissions and carbon footprint of composites. In addition to the benefits obtained from green materials, there are some challenges in working with them, such as poor compatibility between the reinforcing natural fiber and matrix and the relatively high moisture absorption of natural fibers. Green composites can be a suitable alternative for petroleum-based materials. However, before this can be accomplished, there are a number of issues that need to be addressed, including poor interfacial adhesion between the matrix and natural fibers, moisture absorption, poor fire resistance, low impact strength, and low durability. Several researchers have studied the properties of natural fiber composites. These investigations have resulted in the development of several procedures for modifying natural fibers and resins. To address the increasing demand to use eco-friendly materials in different applications, an up-do-date review on natural fiber and resin types and sources, modification and processing techniques, physical and mechanical behaviors, applications, life-cycle assessment, and other properties of green composites is required to provide a better understanding of the behavior of green composites. This paper presents such a review based on 322 studies published since 1978. [ABSTRACT FROM AUTHOR]

This paper reports on the post-processing disintegration of melt-infiltrated aluminum-carbon nanotube (Al-CNT) composites. The paper shows that un-optimized processing conditions can lead to the deterioration of the consolidated composite into micro-scale powder over time. Extensive characterization of the disintegration process over unprecedented post-processing times of ~2.5 years was conducted. The effect of post-processing time on the morphological and phase changes is discussed. The paper points to the importance and need to evaluate the long-term properties of Al-CNT composites. [ABSTRACT FROM AUTHOR]

This paper presents a new, simple, accessible and environmentally friendly method to prepare gold-reduced graphene oxide composites (Au/rGO) with gold concentration of 2.5 wt%, 5 wt% and 10 wt%. The Au/rGO materials with low Au concentration present AuNPs of low dimensions and proved good catalytic activity for formic acid (FA) decomposition in aqueous solution. The most of the structural characteristics are not dependent of the gold content such as: large surface area (234-278 m2 g−1), good crystallinity of graphenes, few layers of carbon in the graphene support (5-6 layers), medium density of structural defects in graphene, the presence of remanent oxygenated groups on the graphene surface, very good dispersion of AuNPs on both sides of the graphene sheets. The AuNPs size instead is strongly dependent on the Au concentration: The smallest nanoparticles were obtained for Au2.5/rGO (3-5 nm) and the largest for Au10/rGO (10-14 nm). The position of the energy levels (conduction band and valence band) relative to the Fermi level also changes with the Au content. [ABSTRACT FROM AUTHOR]

In the present review, the recent progress in describing the intricacies of mechanical and thermal properties of all types of graphene- and modified graphene-based polymer nanocomposites has been comprehensively examined. The effectiveness of microscopy bouquet for the intrinsic characterization of graphene family and their composites was clearly demonstrated in this research. Furthermore, the utility of the dynamic mechanical analysis and thermo-gravimetric analysis employed for thermal characterization that has been reported by various researchers was exhaustively analyzed in this paper. This research primarily focused on the analyses of several good articles concerned with hybrid graphene composites and the synergetic effect of graphene with other nanofiller to assess its effect on the mechanical properties of its corresponding composites. Such systematic analysis of previous literatures imparted a direction to the researchers about the solution of improved interfacial properties as well as the enhanced dispersion into the vicinity of the matrix. This current research has suggested that the presence of the graphene filler even at very low loadings has shown considerable improvement in the overall mechanical properties of graphene. Further studies to optimize the value of the filler need to be addressed in order to gain complete understanding of the properties of graphene. The potential applications, current challenges, and future perspectives pertaining to these nanocomposites were elaborately discussed in the current study with regard to the multi-scale capabilities and promising developments of the graphene-family-based nanocomposites materials. [ABSTRACT FROM AUTHOR]

Metal-zeolite composite catalysts have found numerous applications in adsorption, gas separation, petroleum refining and chemical industry. The key issue in the design of these catalysts is localization of the metal within the zeolite structure. This paper focuses on a new approach to the synthesis of nickel-zeolite composite catalysts selectively containing metal nanoparticles inside the zeolite pores. In the catalysts prepared by conventional impregnation, metal particles from the external surface of the zeolites were selectively removed by extraction with bulky polymer molecules of poly-4-styrenesulfonic acid. The method is particularly suitable for the ZSM-5 zeolite with relatively narrow micropores. The nickel zeolite catalysts were tested in hydrogenation of toluene and 1,3,5-tri-isopropyl benzene (TIPB). The removal of nickel particles from the zeolite external surface leads to a considerable decrease in the hydrogenation rate of the bulky TIPB molecules, while toluene hydrogenation rate was affected to a much lesser extent and was almost proportional to the nickel content. The proposed methodology can be extended to other types of microporous catalysts. [ABSTRACT FROM AUTHOR]

In this study, a novel and excellent structure-damping composites (PVDF&PDA-CF3D/EP) with high damping and mechanical properties were prepared by coating double layers of polyvinylidene fluoride (PVDF) and polydopamine (PDA) on the surface of the three-dimensional braided carbon fibers (CF3D). The dynamic mechanical analysis and logarithmic decrement measurements were employed to determine the damping characteristic of composites. Results show that there is an increase of approximately 160% in the damping factor of PVDF&PDA-CF3D/EP at low temperature and low strain, compared with that of CF3D/EP. The shear strength of the composites was performed to investigate the synergy effects of PVDF&PDA on the improvement in the interfacial bonding strength between fibers and epoxy matrix. Owing to the optimum of the interface, the flexural strength, flexural modulus and impact strength of PVDF&PDA-CF3D/EP increase by 22%, 11.8% and 18.1%, respectively, compared with those of PVDF-CF3D/EP. Finally, the synergic reinforcing mechanism on the damping and mechanical properties of the composites is discussed in the paper. Therefore, this work provides a general path to make good structure-damping composites which possess great potential application in the industrial field. [ABSTRACT FROM AUTHOR]

Effective thermal conductivity models for nanosheet-based composites are less common than those for composites containing spherical nanoparticle. A novel theoretical model for effective thermal conductivity is proposed aiming to the sheet-like nanoparticle polymer composites in this paper, and comparative analysis is made with other relevant models as well as experimental data. The effective thermal conductivity of the anisotropic nanoparticle is obtained by analysing the differential equations of a sheet-like nanoparticle with an interphase layer in both in-plane and through-plane directions in a cylindrical coordinate system. Then the present model is established based on the Nan’s model and the solutions of these differential equations. The present model which contains the effects of detailed geometry and anisotropy of nanosheet as well as interphase layer are analysed and validated with other models and experimental data. The results of present model are in good agreement with some available experimental results. [ABSTRACT FROM AUTHOR]

This paper is the second of a two-part series assessing the feasibility of using the J-integral with full-field deformation data from digital image correlation (DIC) to characterize toughness in continuous fiber, SiC/SiC ceramic matrix composites (CMCs). In part I, line and area integral adaptations of the J-integral were validated with analytical and experimental deformation fields. It was found that variability in experimental data and contour truncation at the crack wake introduced error and path-dependency, but this could be mitigated through data filtering. In this paper, the line and area integral methods were evaluated for cross-ply and longitudinal CMC tensile specimens. It is demonstrated that these approaches cannot be used for quantitative characterization, but can be successfully used to examine qualitative trends. For both architectures, area integral measurements of the potential energy release rate, J, were larger (and arguably more accurate) than line integral measurements. Resistance curves were characteristic of tough materials, but the stress intensity magnitudes were larger in the longitudinal laminates than the cross-ply (for equivalent crack extension). Experimentally derived bridging laws showed that fiber bridging tractions were largest in the cross-ply laminates, which was attributed to a lower volume fraction of longitudinal fibers. Quantitative, single-value measurements of fracture toughness could not be established since (1) noise in the DIC data masked strain signals indicative of first matrix cracking, and (2) widespread matrix cracking rendered the J-integral invalid (regardless of size and position, the boundaries of the line and area contours inevitably intercepted microcracks). Rather, gross estimates of toughness and stress intensity factors were made under the assumption that the limitations in the spatial resolution of the DIC data essentially transforms regions with fine microcracking along the contour into continuous regions of elastic deformation. When evaluated with the J-integral, the smoothed deformation fields manifest as resistance curves indicative of a tough material. Thus, the J-integral was valuable for qualitative assessments of toughening mechanisms in the CMCs. [ABSTRACT FROM AUTHOR]

For 3D-printing circuits, highly electrical conductive composite filaments were prepared through thin-film transition technique and hot extrusion-drawing. In the filaments, flaky silver powders with nanoscale thickness and smooth flat surface were used as electrical conductive phase, and thermoplastic polyvinyl butyral was used as binder phase. The thermal properties of the electrical conductive composites were studied by thermogravimetric analysis, X-ray diffraction, and Fourier transform infrared spectrophotometric. Results showed that the electrical conductive composites possessed highly thermal stability up to 350 °C. Moreover, the scanning electron microscopy revealed that thin-film transition technique made the flaky silver powders in the cured conductive films present a face-to-face contact pattern and the well-ordered orientation remain in the composite filaments, which could greatly decrease the volume resistivity of composite filaments. The as-prepared composite filaments showed a low volume resistivity of 7.02 × 10−4 Ω cm at only 55 wt% (11.08 vol%) of flaky silver powder filling rate. The solvent-free 3D printing used composite filaments show low volume resistivity and well mechanical properties that prove the potential application in 3D-printing circuits. [ABSTRACT FROM AUTHOR]

A strong strain hardening ability in ultra-high strength spring steel 60Si2CrVAT was achieved by the design of multiphase microstructures using a quenching-partitioning-tempering process. The microstructure consisted of ~ 70% martensite/bainite and ~ 30% retained austenite, which was obtained at an optimized partitioning temperature of 380 °C. The corresponding yield strength ratio and the product of strength and elongation were 0.81 and 34,828 MPa%, respectively. Interestingly, this sample exhibited a double-stage strain hardening characteristic with a concave-down shape, which was distinct from that of the other samples. The excellent performance of the ultra-high strength spring steel was mainly due to the interactions between the multiple phases and the stability of the retained austenite during cold deformation. This paper provides a new way of obtaining a strong strain hardening ability in ultra-high strength steels, which is expected to be applicable to the cold coiling process. [ABSTRACT FROM AUTHOR]

Polymer composite materials are being increasingly used in primary load-bearing structures in several advanced industrial fields such as aerospace vessels, railway wagons and mega-scaled wind turbines where detection of subcritical damage initiation can significantly reduce safety issues and maintenance costs. It is therefore crucial to inspect these composite structures in order to assess their structural health and to ensure their integrity. Non-destructive testing techniques (NDT) are used for this purpose, making it possible to monitor mechanical damage of composite materials under in situ or ex situ service conditions. This paper reviews the capabilities of the most common NDT techniques used to inspect the integrity of composite materials. Each technique has a detection potential and cannot allow a full diagnosis of the mechanical damage state of the material. Thus, depending on the occurring damage mechanism and the conditions of use, one technique will be preferred over another, or several techniques should be combined to improve the diagnosis of the damage state of the structures. [ABSTRACT FROM AUTHOR]

Adequate micro-modeling for composites is the basic and key precondition for their property prediction. This study takes fiber-reinforced composites (FRCs) as an example and focuses on the linkages among fiber content, porosity and aggregation in the microstructure of composites, as well as their effect on the overall mechanical properties. A novel two-parameter agglomeration model is developed to take both the tightly packed filler assemblies and the porosity into account, in which the fiber weight fraction is used as an independent variable to express the volumetric composition. Meanwhile, an improved two-scale approach based on Mori-Tanaka (M-T) homogenization theory is utilized to predict the effective properties of FRCs. Three typical FRCs: three-dimensional (3D) randomly distributed FRCs, two-dimensional (2D) randomly distributed ones and unidirectionally (UD) distributed ones, are investigated in detail. The proposed model and method are validated by available experimental data. A parametric study reveals that due to the synergistic influence of fiber content, porosity and local aggregation, a maximum stiffness of FRCs can be achieved by making fibers uniformly dispersed in the matrix and setting the fiber weight fraction to be a certain transition value, which is characterized as a best possible condition with high fiber content and low porosity. [ABSTRACT FROM AUTHOR]

This paper reports polyaniline-nitroprusside (PANI-NP) composite prepared via in situ polymerization of polyaniline in the presence of sodium nitroprusside complex using ammonium persulphate oxidant. Comparison between the MB dye elimination from aqueous solution using polyaniline and polyaniline-nitroprusside composite is investigated with UV-visible spectroscopy. The maximum adsorption capacity for PANI and PANI-NP composite at 25 °C are 412.80 and 496.85 mg g, respectively. About 80% removal of MB occurs in 1 h using pure PANI from (50 mg MB/100 mL) aqueous solution and 99.37% removal is observed in just 5 min, when PANI-NP composite is used. Adsorption kinetics is in good agreement with pseudo-first order for polyaniline and pseudo-second order for polyaniline-nitroprusside composite. The adsorption data fits well with the Langmuir model for both PANI and PANI-NP composite. Langmuir and Tempkin model suggests chemisorption type of interactions between the MB and adsorbents. Thermodynamic study revealed that the adsorption of MB on PANI and PANI-NP composite is exothermic and spontaneous in nature. Moreover, regeneration and reuse of PANI-NP composite as adsorbent is possible only at higher temperature. FTIR studies further confirm the successful adsorption of MB on PANI and PANI-NP composite. On the basis of vey short equilibrium adsorption time and very high adsorption capacity for MB dye, PANI-NP composite could be used as a most efficient adsorbent for the removal of cationic dyes from any real sample. [ABSTRACT FROM AUTHOR]

Layered composite materials formed by the transition metal oxides, including the niobates, titanates, titanoniobates, and tantalates, have been studied as a kind of new photocatalytic materials because of their unique structures and properties. Their photocatalytic performance could be modified by adjusting the laminate composition, selecting appropriate phase structure, exchanging interlayer cations or intercalated-pillaring, exfoliated-assembling, etc. The purpose of this present paper is to review the main factors affecting photocatalytic performance of the layered composite transition metal oxides and to provide reference for further construction of new photocatalytic materials. [ABSTRACT FROM AUTHOR]

In this paper, we synthesized a new cathode material (CuBiS) by a solvothermal method for high-performance lithium-sulfur batteries. CuBiS with a unique flower structure was characterized using the X-ray diffraction, energy-dispersive X-ray spectrometer, and scanning electron microscopy. It is shown that the CuBiS/S flower exhibits a high initial capacity of 1343 mAh g at 0.2 C, and although a capacity fade in subsequent cycles occurs due to polysulfide dissolution and shuttle mechanism, 487 mAh g at 0.2 C can be retained after 100 cycles with the 90-95 % coulombic efficiency. [ABSTRACT FROM AUTHOR]

One of the most important factors to determine the mechanical properties of a fibre composite material is the orientation of the fibres in the matrix. This paper presents Hessian matrix-based algorithms to retrieve the orientation of individual fibres out of steel fibre reinforced cementitious composites samples scanned with an X-ray computed tomography scanner. The software implemented with the algorithms includes a massive data filtering component to remove noise from the data-sets and prepare them correctly for the analysis. Due to its short computational times and limited need for user intervention, the software is able to process and analyse large batches of data in short periods and provide results in a variety of visual and numerical formats. The application and comparison of these algorithms lead to further insight into the material behaviour. In contrast to the usual assumption that the fibres act only along their main axis, it is shown that the contribution of hooked-end fibres in other directions may be noticeable. This means that fibres, depending on their shape, should act as orthotropic inclusions. The methods can be used by research laboratories and companies on an everyday basis to obtain fibre orientations from samples, which in turn can be used in research, to study stress-strain behaviour, as input to constitutive models or for quality assurance. [ABSTRACT FROM AUTHOR]

This paper reports on the morphologies of poly(methyl methacrylate) (PMMA)/mesoporous silica (MCM-41) composites prepared by melt compounding with various MCM-41 contents in the range of 0.1-5 wt%, the interactions between the polymer and filler in these composites, and their thermomechanical, mechanical and thermal degradation properties. The composites formed transparent films at low filler loadings (<0.5 wt%) because of well-dispersed, unagglomerated particles. The presence of polymer did not alter the pore dimensions in the MCM-41 structure and it maintained its hexagonal structure, even though the polymer chains partially penetrated the pores during composite preparation. The PMMA interacted with the MCM-41 through hydrogen bonding. The glass transition temperature, as well as storage and loss modulus of PMMA increased with addition of, and increase in the amount of, MCM-41 due to the interaction of the polymer chains with the porous filler which restricted the mobility of the polymer chains and increased the stiffness of the composites. The thermal stability of PMMA apparently increased in the presence of MCM-41, although this observation probably was the result of delayed mass loss because of the trapping of volatile degradation products in the pores of MCM-41. The presence of MCM-41, up to 1.0 wt%, increased the impact strength of PMMA. [ABSTRACT FROM AUTHOR]

In this paper, (3-mercaptopropyl)trimethoxysilane (MPTS)- and copper-coated carbon fiber (M-Cu-CF) was obtained by electroless plating method. The M-Cu-CF was evaluated by FTIR, XRD, TGA, and SEM. It was found that the MPTS and Cu were coated on the fiber surface successfully. The M-Cu-CF was utilized as a conductive filler in silicone rubber (SR) for thermal and electrical conductivity applications and exhibited good dispersion and compatibility with the matrix. The effect of M-Cu-CF content on the thermal conductivity and volume resistivity of silicone rubber composites was investigated. The results showed that the thermal conductivity of the M-Cu-CF/SR composites reached 1.99 W (m K) with only 4.0 wt% filler loading, approximately 2.10 times higher than that of raw-CF/SR composites at the same loading. And with the increase of M-Cu-CF loading, the least volume resistivity of M-Cu-CF/SR composites was 3.5 × 10 Ω cm. [ABSTRACT FROM AUTHOR]

The thermal degradation of plant-based fibres at high temperature is a main issue when manufacturing vegetal fibres/thermoplastic composites due to the high melting point of engineering polymers such as polyamide 6 (PA6). This paper aims at investigating the influence of the thermo-compression forming process parameters, such as the temperature and consolidation time, on the mechanical properties of continuous flax fibre-reinforced PA6 composites. Woven fabric flax/PA6 composites were prepared by compression moulding using a film-stacking process under different consolidation conditions according to a two-factor Doehlert design of experiments. Tensile and flexural properties were assessed. A second-order polynome was used to correlate the processing parameters and the mechanical properties (i.e. stiffness, strength and strain at break). Fracture mode changes with the consolidation conditions. The weakening of the fibres and eventually of the composite performances was ascribed to the increase in flax fibre thermal degradation. [ABSTRACT FROM AUTHOR]

This paper first presents an analytical model for a new kind of braided composite called 3D surface-core 4-directional braided composite. Taking into account the braiding process, three types of microstructural unit-cell models are established with respect to the interior, surface, and corner regions. According to the spatial paths and squeezing deformation of yarns in the material, different braiding angles and cross-section shapes are adopted. By using the volume averaging method, the total stiffness is calculated and the engineering elastic constants are obtained. The effect of braiding angle and fiber volume fraction on the stiffness is addressed. The theoretical predictions are in good agreement with the experimental data. The effects of edge cuttings on the longitudinal tensile properties of the new material and 3D 4-directional braided composites are experimentally compared. The proposed structure has obvious advantage to restrain the degradation of mechanical properties caused by cuttings. [ABSTRACT FROM AUTHOR]

This paper presents an extensive set of measurements from complementary surface analysis techniques performed for characterizing deuterium retention in carbon fiber composite SepcarbNB31 subsequently to a deuterium beam exposition: adsorption isotherm measurements and Hg porosimetry to characterize the porous network, coupled deuterium beam exposure and in situ µ-NRA analysis to follow the dynamics of the penetration of the retained deuterium in the material, TEM and Raman microscopy to investigate the change in the material structure induced by ion irradiation, and finally TPD to estimate the respective proportion of deuterium retained in the surface layer and in the bulk material. The parameters extracted from this set of characterizations are introduced in a 2D Monte Carlo model which couples the propagation of deuterium and eroded carbon atoms in a network of rectilinear pores and plasma-surface interaction parameters from the SRIM code. The simulations reproduce satisfactorily the main features of the measured deuterium concentration profile and behavior of the retained deuterium amount with incident fluence, validating the physical picture of deuterium retention in CFC as due to the simultaneous implantation of the incident ions in the few 10-nm-depth layer the closest to the surface and penetration of atoms deeper in the material (several tens of microns) through the pore network. [ABSTRACT FROM AUTHOR]

Compaction of the preforms to a desired fiber volume fraction in liquid composite molding has a significant influence on the subsequent injection process and mechanical properties of the final composites. Hence, knowledge of the compaction of the fabric preforms is important for improving the composite product quality and developing the mold filling simulation. In this paper, the compaction behavior of four types of carbon non-crimp fabrics (NCFs) was experimentally studied. The investigation of compaction behavior included the influence of number of cyclic compaction, number of layers, stitching pattern, compaction speed, and the lubrication (wet states). The results show that the compaction curves tend to be stable and repeatable with an elastic deformation from the third cycle. Other factors affecting the compaction behavior can be explained by the nesting effect, considering the special structure of the NCFs. Gaps between fiber tows created by the stitches may provide room for the adjacent fibers to embed or nest in. Meanwhile, the relaxation of the preforms after compaction was discussed in terms of the energy dissipation. The results elucidate that the lubrication and compaction speed have no significant effect on the compaction process, but exhibit influence on the relaxation. Finally, the microstructural observation of the laminates backs up the experimental analysis and highlights the deformation of fibers at the tow gaps. The change of the internal parameters, including the shape and dimensions of the tows and the gaps, with the compaction degree was statistically studied. It also provides geometrical parameters for establishing predictive models of carbon NCFs with different compaction degrees. [ABSTRACT FROM AUTHOR]

This paper investigates the influence of magnetic field-assisted filler alignment technology on the morphology and the thermal conductivity of magnetite-filled epoxy composites. A magnetic field was applied during the solidification of the composite in order to change the position of the filler and its distribution in the polymer matrix. It is shown that the applied procedure leads to the filler being oriented along the direction of the magnetic field, and as a result, the thermal conductivity is improved by up to 120 % compared to a composite with randomly oriented filler obtained without the assistance of a magnetic field. This positive effect is caused by the appearance of conductive paths at a much lower content of the filler when the composite solidification is assisted by a magnetic field, relative to an equivalent isotropic sample. These morphological changes were confirmed by microscopic and X-ray microtomography imaging. The temperature dependences of thermal conductivity were also investigated over a broad temperature range for a magnetite-filled epoxy composite sample and compared to the bulk magnetite reference, showing that thermal behaviour of the magnetite-filled composite is stable, which is a promising result when considering the future application of the technology. [ABSTRACT FROM AUTHOR]

A strong isotropic material that is both biocompatible and biodegradable is desired for many biomedical applications, including rotator cuff repair, tendon and ligament repair, vascular grafting, among others. Recently, we developed a technique, called 'bioskiving' to create novel 2D and 3D constructs from decellularized tendon, using a combination of mechanical sectioning, and layered stacking and rolling. The unidirectionally aligned collagen nanofibers (derived from sections of decellularized tendon) offer good mechanical properties to the constructs compared with those fabricated from reconstituted collagen. In this paper, we studied the effect that several variables have on the mechanical properties of structures fabricated from tendon slices, including crosslinking density and the orientation in which the fibers are stacked. We observed that following stacking and crosslinking, the strength of the constructs is significantly improved, with crosslinked sections having an ultimate tensile strength over 20 times greater than non-crosslinked samples, and a modulus nearly 50 times higher. The mechanism of the mechanical failure mode of the tendon constructs with or without crosslinking was also investigated. The strength and fiber organization, combined with the ability to introduce transversely isotropic mechanical properties makes the laminar tendon composites a biocompatible material that may find future use in a number of biomedical and tissue engineering applications. [ABSTRACT FROM AUTHOR]

Morphable structures exhibit 2D to 3D out-of-plane deformations when exposed to an external stimulus. The current state-of-the-art of morphable structures is based on smart materials or heterogeneous composite materials, where their anisotropic properties can help induce surface morphing in response to different stimuli. This work proposes an alternative approach based on bio-inspired active skins that exhibit 2D to 3D deformations when subjected to uniaxial strains. In particular, the localized compression generated from the free-hinging motion of a re-entrant auxetic geometry was used as the driving force to induce surface morphing in the form of out-of-plane deformations. The geometry was optimized to enhance this inability, which could lower the critical stress and strain for out-of-plane buckling. In addition, geometrical imperfections were introduced to facilitate controlled surface morphing (i.e., programmable buckling directions and selective deformations). Overall, this design principle validated that surface morphing could be achieved using a single material without relying on composites and materials. [ABSTRACT FROM AUTHOR]

In this study, we present an alternative fabrication technique to obtain functionally graded polymer–metal composites. The aim is to obtain a composite material with a graded damping factor, which is provided by the presence of pseudoelastic nickel–titanium (NiTi) fibres within an epoxy resin matrix. A preliminary dynamic mechanical characterisation of the NiTi wire revealed a pre-strain dependency of its damping factor. By fabricating wires with curved geometries in the free state, we were able to obtain fibres with a graded level of pre-strain when straightened. This feature in turn imparts a graded damping response. When encapsulating the straightened fibres in an epoxy resin, the graded damping response is transferred to the composite. [ABSTRACT FROM AUTHOR]

An essential challenge faced by pseudocapacitive electrode materials is insufficient charge storage capability with high intrinsic electrical resistance and structural instability. With an exponential increase in the demand for a pollutant-free environment, ternary metal compounds are being extensively explored as an attractive solution to these problems. Herein, we have addressed a solution to the above-listed issues by synthesizing novel and binder-free NiMnCo layered double hydroxide (NiMnCo-LDH) nanosheets on Fe-substituted NiCo2O4 (FexNi1−xCo2O4) nanorods supported on nickel foam via a facile hydrothermal method followed by chemical bath deposition. The highly defined and well-distributed porous Fe-substituted NiCo2O4 nanorod structure integrated with the ternary NiMnCo-LDH nanosheets provide ultra-fast kinetics of charge transfer, increased charge storage capacity, and high structural stability. The nanocomposite electrode delivers a high specific capacity of 281 mAh/g at a scan rate of 5 mV/s (265 mAh/g at 1 A/g) with a capacitance retention of 92% after 5000 cycles at 2 A/g. The effect of Fe in NiCo2O4 is further validated by performing density-functional theory (DFT) calculations to obtain atomic insights on electrical conductivity using the density of states (DOS) and band structures. Finally, a symmetric supercapacitor based on FexNi1−xCo2O4@NiMnCo LDH was assembled which delivered an impressive energy density of 105 Wh/kg and a power density of 1112 W/kg, proving FexNi1−xCo2O4@NiMnCo-LDH as an electrode material to be used for applications of energy storage. [ABSTRACT FROM AUTHOR]

The interest in studying cellulose especially bacterial cellulose (BC) and BC-based composites has increased dramatically, due to their outstanding properties. Among them, BC-based electroconductive composites seem to capture more attention because of their perfect structure and controllable synthesis as well as potential values. Meanwhile, the development of carbon fibers is becoming a hot spot in recent years. Here, we concentrate on describing their numerous approaches, and some improvements in the process, which are discussed in greater details with an emphasis on their functional properties and potential applications. The challenges in commercial scale applications are discussed and the efficiencies of various electroconductive composites are compared, in order to exploit its far-reaching application value. [ABSTRACT FROM AUTHOR]

Biodegradable coatings and films of cellulose nanofibers (CNFs) or a combination of CNFs and inorganic fillers, such as clay or calcium carbonate (CaCO), can provide a replacement for non-biodegradable plastic coatings as barrier layers in packaging boards. In this work, transparent composite films were prepared from CNFs of Pinus radiata and Eucalyptus using different amounts of clay and CaCO as fillers. The impact of raw material (softwood vs. hardwood), TEMPO oxidation levels and filler type (clay vs. CaCO) on film properties was studied. Pinus radiata CNF films had superior mechanical properties to Eucalyptus CNF films, but no significant differences were observed in the barrier and optical properties. Clay seemed to work better as filler compared to CaCO, in terms of its impact on film properties. Composite films with CaCO as filler were highly brittle with inferior properties to clay-CNF films, and an uneven distribution and agglomeration of the CaCO mineral particles was evident in SEM images. Based on the results, clay as filler in CNF coatings is preferred for targeting packaging board applications. Rheological characterisation of the CNF suspensions revealed shear-thinning behaviour, with the CNF from Eucalyptus having higher viscosities and lower power-law indices when compared to the CNF from P. radiata. [ABSTRACT FROM AUTHOR]

LiNiO2 (LNO) was synthesized by co-precipitation method and then modified by Nb2O5. Doped material N0 (doping molar ratio is 1%), doped and coated composite modified materials N1 and N2 (doping molar ratio is 1%, coating molar ratio is 0.5% and 1%, respectively) were obtained. XRD results show that Nb modified materials have good layered structure and low Li–Ni mixing. SEM image shows that the surface of the modified materials is more compact and smoother. EDS and TEM diagrams indicate that N1 and N2 samples can be successfully doped and coated with Nb compound. The electrochemical performance test results show that the Nb doping–coating composite modified materials have a significant impact on the cycle performance of LiNiO2, among which N1 has the best cycle performance. In the voltage range of 2.75–4.3 V, the initial discharge specific capacity of N1 at 0.1 C is 221.20 mAh/g, which is about 20 mAh/g higher than that of LiNiO2 material. And the capacity retention rate of N1 is 80.70% after 100 cycles at 1 C, which is also much higher than that of LiNiO2 (67.46%). [ABSTRACT FROM AUTHOR]