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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]