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Polymer dielectric capacitors are widely utilized in pulse power devices owing to their high power density. Because of the low dielectric constants of pure polymers, inorganic fillers are needed to improve their properties. The size and dielectric properties of fillers will affect the dielectric breakdown of polymer‐based composites. However, the effect of fillers on breakdown strength cannot be completely obtained through experiments alone. In this paper, three of the most important variables affecting the breakdown strength of polymer‐based composites are considered: the filler dielectric constants, filler sizes, and filler contents. High‐throughput stochastic breakdown simulation is performed on 504 groups of data, and the simulation results are used as the machine learning database to obtain the breakdown strength prediction of polymer‐based composites. Combined with the classical dielectric prediction formula, the energy storage density prediction of polymer‐based composites is obtained. The accuracy of the prediction is verified by the directional experiments, including dielectric constant and breakdown strength. This work provides insight into the design and fabrication of polymer‐based composites with high energy density for capacitive energy storage applications. The effects of single variable and multivariable coupling on the breakdown strength of polymer‐based composites are studied by high‐throughput stochastic breakdown simulation, and a machine learning database is established to obtain breakdown prediction. A universal energy storage density prediction is obtained by combining the breakdown prediction with the classical dielectric formula, and the predictions' accuracy is verified.

Due to the increasing number of patients with bone defects, bone nonunion and osteo-myelitis, tumor and congenital diseases, bone repair has become an urgent problem to be solved. In this study, the 3D-printed scaffolds of ternary composites containing mesoporous bioglass fibers of magnesium calcium silicate (mMCS), gliadin (GA) and polycaprolactone (PCL) were fabricated using a 3D Bioprinter. The compressive strength and in vitro degradability of the mMCS/GA/PCL composites (MGPC) scaffolds were improved with the increase of mMCS content. In addition, the attachment and proliferation of MC3T3-E1 cells on the scaffolds were significantly promoted with the increase of mMCS content. Moreover, the cells with normal phenotype attached and spread well on the scaffolds surfaces, indicating good cytocompatibility. The scaffolds were implanted into the femur defects of rabbits, and the results demonstrated that the scaffold containing mMCS stimulated new bone formation and ingrowth into the scaffolds through scaffolds degradation in vivo. Moreover, the expression of type I collagen into scaffolds was enhanced with the increase of mMCS content. The 3D-printed MGPC scaffold with controllable architecture, good biocompatibility, high compressive strength, proper degradability and excellent in vivo osteogenesis has great potential for bone regeneration.

Graphene-based polymer composites with improved physical properties are of great interest due to their lightweight, conductivity, and durability. They have the potential to partially replace metals and ceramics in several applications which can reduce energy and cost. The obtained properties of graphene-based polymer composites are often linked to the way graphene is dispersed in the polymer matrix. Preparation techniques like solution mixing, melt blending, and in-situ polymerization have been used to obtain graphene-based polymer composites. Dispersing and aligning graphene fillers within the composite is a key factor in enhancing the thermal and electrical conductivity values of the composites due to graphene’s anisotropic properties. The effect of the preparation methods of these composites on their physical-chemical properties is discussed in this review where we presented the advances that were achieved so far in the preparation techniques used showing the highest values ever achieved for electrical and thermal conductivity for these graphene-based polymer composites. Also, we presented the possible applications where graphene-based composites can be utilized.

“Biochar” (BC) is the solid residue recovered from the thermal cracking of biomasses in an oxygen-poor atmosphere. Recently, BC has been increasingly explored as a sustainable, inexpensive, and viable alternative to traditional carbonaceous fillers for the development of polymer-based composites. In fact, BC exhibits high thermal stability, high surface area, and electrical conductivity; moreover, its main properties can be properly tuned by controlling the conditions of the production process. Due to its intriguing characteristics, BC is currently in competition with high-performing fillers in the formulation of multi-functional polymer-based composites, inducing both high mechanical and electrical properties. Moreover, BC can be derived from a huge variety of biomass sources, including post-consumer agricultural wastes, hence providing an interesting opportunity toward a “zero waste” circular bioeconomy. This work aims at providing a comprehensive overview of the main achievements obtained by combining BC with several thermoplastic and thermosetting matrices. In particular, the effect of the introduction of BC on the overall performance of different polymer matrices will be critically reviewed, highlighting the influence of differently synthesized BC on the final performance and behavior of the resulting composites. Lastly, a comparative perspective on BC with other carbonaceous fillers will be also provided.

A facile in situ polymerization was developed for grafting renewable cardanol onto the carbon fiber (CF) surfaces to strengthen the fiber–matrix interface. CFs were chemically modified with hydroxyl groups by using an aryl diazonium reaction, and then copolymerized in situ with hexachlorocyclotriphosphazene (HCCP) and cardanol to build cardanol-modified fibers (CF-cardanol). The cardanol molecules were successfully introduced, as confirmed using Raman spectra and X-ray photoelectron spectroscopy (XPS); the cardanol molecules were found to increase the surface roughness, energy, interfacial wettability, and activity with the matrix resin. As a result, the interlaminar shear strength (ILSS) of CF-cardanol composites increased from 48.2 to 68.13 MPa. In addition, the anti-hydrothermal ageing properties of the modified composites were significantly increased. The reinforcing mechanisms of the fiber–matrix interface were also studied.

In recent decades, with the advancement of micro-electro-mechanical systems technology, traditional materials have become insufficient to meet the demands of cutting-edge technology for various material properties. Composites have attracted widespread attention as an effective and viable solution. Silicon carbide whiskers (SiCw) have emerged as excellent reinforcements due to their high thermal conductivity, low thermal expansion coefficient, high melting point, superior mechanical properties, and high chemical stability. This article provides a comprehensive review of the reinforcement mechanisms and current research state of SiCw-reinforced composites. The reinforcement mechanisms include mainly grain refinement, load transfer, and crack bridging. The composites are categorized based on the type of the matrix: ceramic-based, metal-based, and polymer-based composites. The influence and parameter performance of the reinforcement mechanism on SiCw-reinforced composite materials with different matrices vary. However, the key to improving SiCw-reinforced composites lies in understanding the interplay of properties between the matrix and the reinforcement, as well as the ordered and regular distribution and binding at the interface. Finally, the current state and limitations of SiCw-reinforced composites are summarized, and future development trends are discussed. This article represents a great contribution to the future applications of SiCw-reinforced composite materials.

Polymer-based dielectric composites show great potential prospects for applications in energy storage because of the specialty of simultaneously possessing the advantages of fillers and polymer matrices. However, polymer-based composites still have some urgent issues that need to be solved, such as lower breakdown field strength (Eb) than polymers, dielectric mismatch, and the poor interface between the matrix and the filler. Hence, this review provides a systematic summary of recent research advances in improving the energy storage properties of polymer-based composites from several aspects, mainly including polymer matrix types, optimization of filler shapes, surface modification of fillers, and design of multi-layer composite structures. Finally, some existing challenges and future perspectives are outlined and discussed to facilitate the further development of polymer-based composites in the energy storage field. We believe this review will help researchers better understand the current development status of polymer-based composites in the energy storage field, and push it forward to a new research stage.

Calcium carbonate, which is widely employed as a filler added into the polymer matrix, has large numbers of applications owing to the excellent properties such as low cost, non-toxicity, high natural reserves and biocompatibility. Nevertheless, in order to obtain the good filling effect, calcium carbonate needs to be surface modified by organic molecules so as to enhance the dispersion and compatibility within the composites. This review paper systematically introduces the theory, methods, and applications progress of calcium carbonate with surface modification. Additionally, the key factors that affect the properties of the composites as well as the current difficulties and challenges are highlighted. The current research progress and potential application prospects of calcium carbonate in the fields of plastics, rubber, paper, medicine and environmental protection are discussed as well. Generally, this review can provide valuable reference for the modification and comprehensive utilization of calcium carbonate.

Electromagnetic shielding materials are special materials that can effectively absorb and shield electromagnetic waves and protect electronic devices and electronic circuits from interference and damage by electromagnetic radiation. This paper presents the research progress of intrinsically conductive polymer materials and conductive polymer-based composites for electromagnetic shielding as well as an introduction to lightweight polymer composites with multicomponent systems. These materials have excellent electromagnetic interference shielding properties and have the advantages of electromagnetic wave absorption and higher electromagnetic shielding effectiveness compared with conventional electromagnetic shielding materials, but these materials still have their own shortcomings. Finally, the paper also discusses the future opportunities and challenges of intrinsically conductive polymers and composites containing a conductive polymer matrix for electromagnetic shielding applications.

With the rapid development of electronic technology and the integration of electronic chips, electromagnetic wave pollution and thermal management have become two critical issues hindering the growth of electronic equipment. Traditional polymer-based electronic packaging materials have very low thermal conductivity and almost no electromagnetic wave absorption ability. Therefore, the development of polymer-based composites with efficient electromagnetic wave absorption and thermally conductive performances is currently a hot research topic in the field of microelectronic packaging. At present, the addition of thermally conductive and dielectric (magnetic) fillers to the polymer matrix is an effective way to solve this problem. In this review, firstly, we briefly introduce the mechanism of action of electromagnetic wave absorbing materials and thermally conductive materials, respectively. Then, we list the relevant representative fillers which can be used in electromagnetic wave absorption and thermal management and summarize the current research progress of these materials. Finally, we present the current challenges facing the field and prospects for future development. Graphical Abstract In this review, we give a detailed overview of the research progress on the microwave absorption and thermally conductive properties of the composites with different fillers and microstructures.