Tuning of shear thickening behavior and elastic strength of polyvinylidene fluoride via doping of ZnO-graphene

ZnO rice like nonarchitects are grafted on the graphene carbon core via a rapid microwave synthesis route. The prepared grafted systems are characterized via XRD, SEM, RAMAN, and XPS to examined the structural and morphological parameters. Zinc oxide grafted graphene sheets (ZnO-G) are further doped in β-phase of polyvinylidene fluoride (PVDF) to prepare the polymer nanocomposites (PNCs) via mixed solvent approach (THF/DMF). β-phase confirmation of PVDF PNCs is done by FTIR studies. It is observed that ZnO-G filler enhances the β-phase content in the PNCs. Non-doped PVDF and PNCs are further studied for rheological behavior under the shear rate of 1–100 s⁻¹. Doping of ZnO-G dopant to the PVDF matrix changes its discontinuous shear thickening (DST) behavior to continues shear thickening behavior (CST). Hydrocluster formation and their interaction with the dopant could be the reason for this striking DST to CST behavioral change. Strain amplitude sweep (10⁻³% -10%) oscillatory test reveals that the PNCs shows extended linear viscoelastic region with high elastic modulus and lower viscous modulus. Effective shear thickening behavior and strong elastic strength of these PNCs present their candidature for various fields including mechanical and soft body armor applications.     

Polymeric Nanocomposites for Environmental and Industrial Applications

Polymeric nanocomposites (PNC) have an outstanding potential for various applications as the integrated structure of the PNCs exhibits properties that none of its component materials individually possess. Moreover, it is possible to fabricate PNCs into desired shapes and sizes, which would enable controlling their properties, such as their surface area, magnetic behavior, optical properties, and catalytic activity. The low cost and light weight of PNCs have further contributed to their potential in various environmental and industrial applications. Stimuli-responsive nanocomposites are a subgroup of PNCs having a minimum of one promising chemical and physical property that may be controlled by or follow a stimulus response. Such outstanding properties and behaviors have extended the scope of application of these nanocomposites. The present review discusses the various methods of preparation available for PNCs, including in situ synthesis, solution mixing, melt blending, and electrospinning. In addition, various environmental and industrial applications of PNCs, including those in the fields of water treatment, electromagnetic shielding in aerospace applications, sensor devices, and food packaging, are outlined.     

Are nanoclay-containing polymer composites safe for food packaging applications?—An overview

The growth in polymer-based innovative packaging technology has brought about a revolution in extending the shelf life of many food and aquatic products. One of the emerging areas in this field is polymer nanocomposite (PNC) technology, which involves the incorporation of various chemicals and nanoadditives into polymers to improve their inherent properties or to add required functionality. Because the nanoparticles may interact with food components during processing, storage, or distribution and may migrate into food, PNC-based packaging materials require awareness and understanding of their potential impact on human health and the environment. Interest in migration and cytotoxic analysis of PNC has gained considerable momentum in recent years. The focus of this article is on clay-containing PNCs because the global trend in PNCs shows that 50% of all nanofillers constitute nanoclays of either natural or synthetic origin. This article presents a summary of perspectives on international regulations on test parameters and migration of chemicals from materials that come into contact with food, followed by a critical review of (1) complaints concerning the polymers, compatibilizers, and adhesive tie layers used in polymeric packages, (2) migration of constituents from PNC-based films/articles, and (3) toxicity evaluation of nanoclays and migration of nanoclays from PNCs. Finally, we believe a review article of this nature will help academic and industrial researchers who want to bring advanced PNC-based products into the market for food packaging applications. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47214.     

Crosslinked polymer nanocapsules

Polymer nanocapsules (PNCs) are an important class of nanocarriers, but applications of conventional non‐crosslinked PNCs have been significantly limited because they are susceptible to environmental conditions. Synthesis and applications of crosslinked PNCs (CPNCs) with robust covalently stabilized nanostructures have attracted great interest over the past decade. Three major categories of template synthesis approaches for the preparation of CPNCs have been established: (1) cavitation of shell‐crosslinked nanostructures, (2) vesicle‐based crosslinking and (3) emulsion interfacial crosslinking. This article provides a critical and comprehensive review of these approaches. Several special cases of the synthesis of CPNCs are also reviewed. © 2016 Society of Chemical Industry     

SiC基高性能材料的研究进展

作为先进高温结构陶瓷材料的典型代表SiC烧结体材料具有优良的性能,应用十分广泛,但是,单一的SiC烧结体材料的断裂韧性低和难以烧结致密的缺点使得其应用受到一定的限制。近年来,研究SiC材料在结构材料方面的应用大多倾向于SiC基复合材料方向发展。本文介绍了纤维补强型和颗粒弥散增强型SiC基复合材料近五六年来的研究情况。     

Precipitation of cesium lead halide perovskite nanocrystals in glasses based on liquid phase separation

Incorporation of cesium lead halide perovskite nanocrystals (CsPbX₃ PNCs, X = Cl, Br, I) into glasses can significantly improve their stabilities and extend their application areas. Precipitation of CsPbX₃ PNCs in glasses is mainly based on thermal treatment; however, the formation of mechanism is not clarified. Here, several in situ methods are employed to illustrate the precipitation mechanism of CsPbX₃ PNCs. It is found that precipitation of CsPbX₃ PNCs in glasses is based on the liquid phase separation in solid amorphous matrix, followed by crystallization in the supercooled state. Liquid phase separation process determines the composition of CsPbX₃ PNCs, and cooling process has strong effect on the crystallinity and quality of CsPbX₃ PNCs. These results clarify the precipitation mechanism of CsPbX₃ PNCs in glasses and provide important guideline for the development of CsPbX₃ PNCs embedded glasses for opto-electronic applications.     

聚合物/石墨烯复合材料制备与性能研究进展

首先综述了聚合物/石墨烯复合材料的制备方法,重点介绍了两种近些年新开发的制备方法;之后综述了聚合物/石墨烯复合材料的结构设计与性能;最后对聚合物/石墨烯复合材料的研究前景进行了展望。     

液体树脂灌注成型技术（LRI）的数值建模计算研究

近几年在树脂膜渗透成型工艺（RFI）的基础上开发出了一种新型的航空复合材料制造工艺：液体树脂灌注成型工艺（LRI,Liquid Resin Infusion）。由于LRI是在一个真空膜下进行的,它不需要特殊的模具,所以大大降低了制造成本,并且用这种工艺可以制出大而厚的复杂部件,但是这也使得我们很难了解到整个工艺过程中内部参数的变化情况。为了指导实际的制造工艺,优化制造方案和参数,并减少制造缺陷,开发和运用有效的数值计算模型就变的非常的必要。最近Celle等人利用有限元方法（FEM）开发出了一种有关LRI的基础数值模型,本文将要介绍在这种基础模型上开发出的对LRI的数值建模计算方法和它的应用。并与实验结果进行对比和讨论。结果表明：本文所做的数值建模计算结果与实验结果有着较好的一致性,能较为有效地对LRI成型工艺进行模拟计算。关键词树脂传递模塑（RTM）;树脂膜渗透（RFI）;液体树脂灌注成型（LRI）;有限元方法（FEM）;数值建模     

Ion-exchange controlled precipitation of CsPbX3 nanocrystals in glasses

Embedding CsPbX₃ (XCl, Br, I) perovskite nanocrystals (PNCs) into glasses can significantly improve the chemical and thermal properties, and show promising applications in photonic fields. Spatially controlled precipitation of PNCs in glasses is necessary for the fabrication of structured devices. Here, we report that spatially controlled precipitation of CsPbX₃ PNCs in the surface layer of glasses through ion-exchange in molten cesium nitrate salt. Spatial distribution and average diameter of CsPbX₃ PNCs are mainly determined by the distribution of Cs⁺ and halide ions, and composition of CsPbX₃ PNCs is mainly determined by the composition of host glass. Through ion-exchange, CsPbCl_3?xBr_x and CsPbBr_3?xI_x PNCs with tunable compositions are precipitated in the surface layer of glasses, and efficient photoluminescence spanning from blue to cyan, green, yellow, orange, and red is realized. Our results demonstrate that ion-exchange is promising to fabricate planar and linear waveguides and various microstructures based on CsPbX₃ PNCs embedded glasses.     

Contrast on tensile and flexural properties of glass powder reinforced epoxy composites: Pilot study

Epoxy resin was filled with glass powder to optimize the tensile and flexural strength of the composite for structural applications by a research center in the University of Southern Queensland (USQ). To reduce costs, the center wishes to fill as much glass microspheres as possible subject to maintaining sufficient strength of the composites in structural applications. This project varies the percentage by weight of the glass powder in the composites. After casting the composites to the molds, they were cured at ambient conditions for 24 h. They were then postcured in a conventional oven and subjected to tensile and flexural tests. The contribution of the study was that if tensile and flexural properties were the most important factors to be considered in the applications of the composites, the maximum amount of glass powder can be added to the resin will be five (5) percent. It was also found that the fractured surfaces examined under scanning electron microscope were correlated with the tensile and flexural strength It is also hoped that the discussion and results in this work would not only contribute toward the development of glass powder reinforced epoxy composites with better material properties, but also useful for the investigations of tensile and flexural properties in other composites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Lead-free NaNbO3-based ferroelectric perovskites and their polar polymer-ceramic composites: Fundamentals and potentials for electronic and biomedical applications

Ferroelectric lead-free NaNbO₃-based ceramics are the most promising candidates to a wide range of advanced technological applications as sensors, transducers and actuators. In special, (K,Na)NbO₃ (KNN) and (Ba,Na)(Ti,Nb)O₃ (BTNN) show interesting structural properties, including morphotropic phase boundaries regions that lead to exceptional dielectric, piezoelectric and ferroelectric responses. Also, the biocompatibility of these compounds allows their application as biomedical sensors, medical devices, and bone tissue replacement. In this way, high impact applications can be achieved with ferroelectric lead free NaNbO₃ – based (NN-based) ceramics. In this review, we will explore the strategies for the improvement of ferroelectric, dielectric and structural properties reviewing the effects of the synthesis process, microstructure and chemical composition of lead-free complex perovskite ceramics, specially KNN and BTNN, as well as, PVDF-KNN and PVDF-BTNN polymer-ceramic and the (PVDF-TrFE)-KNN copolymer-ceramic composites to provide new insights and research opportunities for the development and improvement of fundamental properties of such systems considering their potential for technological applications, especially for the biological ones.     

Energy storage density and efficiency of polyetherimide nanocomposites diminished by the temperature dependent charge hopping

The utilization of renewable energies requires extensive use of energy storage equipment such as dielectric capacitor. Polyetherimide nanocomposites (PEI PNCs) have high energy storage performance, and become the next generation advanced dielectric s However, the quantitative relation between the charge transport and energy storage of PEI PNCs is not very clear, restricting further improvement of their performance. Considering the charge injection from electrodes and the charge hopping transport inside the dielectric, the energy storage and release model of capacitors was established. Firstly, the conductivities of PEI PNCs were simulated, and the charge transport parameters were determined by comparing with the experiments. Then, the electric displacement-electric field (D-E) loops of PEI PNCs were simulated, and the discharged energy density and energy efficiency were calculated from them. The simulation results are consistent with the experiments, and the quantitative relationship between charge injection and transport parameters and energy storage performance is established. In addition, it is found that the energy storage density and efficiency are diminished by the increase of hopping distance at high temperatures. Increasing the hopping barrier, reducing the hopping distance and its temperature dependence through nano-doping can significantly improve the energy storage performance under high temperatures and high electric fields.     

Thermal Aging Properties of Graphite Fiber Reinforced Peek and Graphite Fiber Reinforced Bmi Composites

Graphite fiber reinforced poly(ether ether ketone) (PEEK) and graphite fiber reinforced bismaleimide (BMI) composite materials are two kinds of advanced fiber-reinforced polymer matrix composites with good thermal stability and excellent mechanical properties at high temperature. They are currently receiving considerable attention. the main limitation on their application is the lack of knowledge regarding their behaviors during extended use at high temperature. Thermal aging properties are the main parameters for new polymer matrix composites that will be used in advanced spacecraft structural components. From the results of thermal aging effects on the properties—including interlaminar shear strength, drop-weight impact strength, and impact energy—of graphite/PEEK and graphite/BMI composites, it is found that unidirectional graphite fiber reinforced composites retain higher strength compared to multidirectional, and that multidirectional graphite/PEEK composites keep higher property retentions than multidirectional graphite/BMI composites after thermal aging at 190°C. From scanning electron photomicrographs, it is also found that graphite/PEEK composites have better fiber/resin adhesion, intraply adhesion, and microcrack resistance compared to graphite/BMI composites after thermal aging.     

P(VDF-TrFE)-based polymer nanocomposites comprising of reduced graphene oxide decorated with CoFe2O4@MCM 41 for efficient microwave absorption in X-band

Lightweight polymer nanocomposites (PNCs) dispersed with nanofiller RGO/CoFe₂O₄@MCM41, namely RCM (using hydrothermal process), have been prepared and characterized. Using the solution cast technique, PNCs {(P(VDF-TrFE)/LiTFSI/EMIMTFSI) + x wt% RCM, where x = 5, 7.5, and 10 in wt%} have been successfully synthesized. The synthesized PNCs possess good structural, thermal, mechanical, and magnetic properties because of the dispersed nanofiller within the polymeric matrix, which forms a 3-dimensional interconnected conducting network. The optimized PFE15Li50IL7.5RCM polymer nanocomposite also exhibits total shielding effectiveness (SE_T) of ~19.88 dB at 9.2 GHz for a thickness of 1.18 mm corresponding to 89.07% effective absorption (A_eff) in the X-band (8.2–12.4 GHz).     

Structural,viscoelastic, and vulcanization study of sponge ethylene–propylene–diene monomer composites with various carbon black loadings

In this article, we report the effect of various carbon nanoparticle concentrations on the structural, curing, tan δ, viscosity variation during vulcanization, thermal, and mechanical characteristics of ethylene–propylene–diene monomer polymer sponge composites. The purpose of this study was to develop high‐strength, foamy‐structure polymer composites with an optimum filler to matrix ratio for advanced engineering applications. We observed that the structural, vulcanization, viscoelastic, and mechanical properties of the fabricated composites were efficiently influenced with the progressive addition of carbon content in the rubber matrix. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39423.     

Magnetoresistive polyaniline-magnetite nanocomposites with negative dielectrical properties

Magnetic polyaniline (PANI) polymer nanocomposites (PNCs) reinforced with magnetite (Fe₃O₄) nanoparticles (NPs) have been successfully synthesized using a facile surface initiated polymerization (SIP) method. The chemical structures of the PANI/Fe₃O₄ PNCs are characterized by Fourier transform infrared (FT-IR) spectroscopy. The thermal stability of the PANI/Fe₃O₄ PNCs is performed by thermogravimetric analysis (TGA). Both transmission electron microscopy (TEM) and scanning electron microscopy (SEM) are used to characterize the morphologies of the PANI, Fe₃O₄ nanoparticles (NPs) and the PNCs. X-ray diffraction (XRD) shows a significant effect of the Fe₃O₄ NPs on the crystallization structure of the formed PANI. The dielectrical properties of these PNCs are strongly related to the Fe₃O₄ nanoparticle loadings and unique negative permittivity is observed in all the samples. Temperature dependent resistivity analysis from 50 to 290 K reveals a quasi 3-dimension variable range hopping (VRH) electron conduction mechanism for the nanocomposite samples. The PNCs do not show hysteresis loop with zero coercivity, indicating the superparamagnetic behavior at room temperature. The PNCs with 30 wt% Fe₃O₄ NP loading exhibit a larger positive magnetoresistance (MR = 95%) than 53% of the pure PANI.     

Nanocrystalline Fe‐Ni alloy/polyamide 6 composites of high mechanical performance made by ultrasound‐assisted master batch technique

The focus of this study is to improve the dispersion state of nanocrystalline (nc) Fe‐Ni particles in polyamide 6 (PA6) matrix and the filler‐matrix interfacial interactions to provide Fe‐Ni alloy/PA6 nanocomposites of remarkable mechanical performance for engineering applications. nc Fe₄₀Ni₆₀ particles were chemically synthesized. Then Fe₄₀Ni₆₀/PA6 nanocomposites of various nanofiller loading were prepared by compounding via a newly modified master batch technique called ultrasound assisted master batch (UMB), followed by injection molding (IM). Their mechanical properties, morphology and structural parameters were characterized and compared with the corresponding properties of Fe₄₀Ni₆₀/PA6 nanocomposites made by solution mixing (SM) and IM. The study reveals that the UMB process is more cost effective and time efficient, simpler and easier to scale up compared with the SM process. In addition, UMB nanocomposites exhibit superior mechanical properties and distinctive morphology compared with the corresponding SM ones. Moreover, structural analyses indicate that physical structural changes occurred in PA6 due to presence of alloy particles are affected differently by the different compounding methods, profound understanding of such phenomenon is focused throughout the article. These distinctive advantages recommend that UMB technique can be of great potential in commercial production of polymer nanocomposites (PNCs). It is concluded that the sonication of nc Fe₄₀Ni₆₀ particles in dilute polymer solution during UMB compounding, a new step that is incorporated for the first time in the master batch process, is mainly responsible for the good wetting between nanoparticles and polymer chains, strong filler‐matrix interactions and consequently the remarkable mechanical performance of UMB PNCs. POLYM. COMPOS., 35:2343–2352, 2014. © 2014 Society of Plastics Engineers     

Magnetic high density polyethylene nanocomposites reinforced with in-situ synthesized Fe@FeO core-shell nanoparticles

Magnetic high density polyethylene (HDPE) polymer nanocomposites (PNCs) with different loadings of iron@iron oxide core-shell nanoparticles (NPs) were fabricated by in-situ thermal decomposition of organometallic iron precursors in the HDPE-xylene solution. Attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) measurement indicated that the HDPE chains were physically adsorbed onto the surface of NPs instead of forming chemical bonding during the formation of these PNCs. Transmission electron microscopy (TEM) micrographs revealed that the iron core NPs surrounded with iron oxide shell were formed in the HDPE hosting matrix with good dispersion, an inter-network structure was formed when the particle loading reached 10.0 wt%. Mössbauer spectrum analysis showed that the oxidization content of the iron NPs decreased with increasing the particle loading. The X-ray diffraction (XRD) analysis and differential scanning calorimetry (DSC) characterization demonstrated that the crystalline structure of HDPE matrix was not influenced by the incorporation of the NPs; however, fusion heat and crystalline fraction of the HDPE matrix decreased with the introduction of these NPs. The melt rheological behaviors were significantly changed as indicated by different complex viscosities, storage moduli and loss moduli between pristine HDPE and its PNCs. Magnetic property investigation revealed a soft ferromagnetic behavior for these HDPE PNCs at room temperature and the coercivity was decreased with increasing the particle loading. Thermal gravimetric analysis (TGA) demonstrated that the thermal stability of these HDPE PNCs was enhanced in the presence of the NPs. Dielectric properties of the HDPE PNCs were also investigated and discussed in detail.     

Polymeric Nanocomposites (PNCs) for Wastewater Remediation: An Overview

A decline in the world’s freshwater resources poses a major domestic and industrial challenge. Amelioration efforts that proffer possible water management and reclamation technology is therefore, of utmost priority. One of the most promising solutions to water conservation is to recycle wastewater. The use of polymeric nanocomposites (PNCs) in water treatment/remediation processes provides possible solution to recycling. This overview focused on PNCs; to highlight trends in their fabrication, characterization and application procedures for wastewater remediation and monitoring. Key issues bothering on the regeneration and reuse of PNCs were discussed, along with projections for their rational design for safe application.     

Processing of advanced ceramic composites: issues of producibility,affordability, reliability,and tailorability

Abstract

The significant advantages of advanced ceramic materials when compared to metals are severely compromised by high manufacturing costs and brittleness related problems. The development of ceramic matrix composites usually involves processing–property tradeoffs that, in most cases, make advanced performance components unaffordable for general commodity applications. Some new, mainly reaction formed composites, however, seem to offer a way out of this dilemma. The present paper reviews processes and properties of such low cost, high value added components with emphasis on reactively synthesised ceramic–metal composites of near net shape. After property and cost evaluations, the production methods and the resulting composites are assessed with respect to future applications.