Improving mechanical response of materials is of great interest in a wide range of disciplines, including biomechanics, tribology, geology, optoelectronics, and nanotechnology. It has been long recognized that spatial gradients in surface composition and structure can improve the mechanical integrity of a material. This review surveys recent results of sliding-contact, flexural, and fatigue tests on graded ceramic materials from our laboratories and elsewhere. Although our findings are examined in the context of possible applications for next-generation, graded all-ceramic dental restorations, implications of our studies have broad impact on biomedical, civil, structural, and an array of other engineering applications.

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Electrically conductive polymer nanocomposites are highly required for efficient electromagnetic interference (EMI) shielding applications. Although two-dimensional transition metal carbide/carbonitride (MXene) nanosheets with metallic electrical conductivity and layered structure show great potential for the construction of interconnected conductance networks in polymer matrices, their preferred stacking feature and intrinsic hydrophilicity inevitably cause poor dispersion in organic polymers, making it challenging to prepare MXene/polymer nanocomposites with high electrical conductivity and satisfactory EMI shielding performances at low MXene contents. Herein, we demonstrate an efficient methodology to prepare highly conductive MXene/ polypropylene (PP) nanocomposites with an ultralow percolation threshold for efficient EMI shielding application. By dip-coating MXene nanosheets onto a polyethyleneimine-grafted PP textile, followed by vacuum-assisted compression molding, an interconnected conductance network of MXene nanosheets in the PP matrix is constructed facilely and efficiently. The resultant MXene/PP nanocomposite exhibits an ultralow percolation threshold of 0.027 vol %, a high electrical conductivity of 437.5 S m −1 at a low MXene loading of 2.12 vol %, and an outstanding EMI shielding performance of more than 60 dB within the X-band, superior to most other electrically conductive polymer nanocomposites. This work provides a new approach for fabricating MXene/polymer nanocomposites with outstanding electrical conductivity for high-performance EMI shielding applications.

In this study, the morphological evolution and sintering properties of the palygorskite nanofibers were studied along with the increase of temperature, using raw palygorskite as materials. The palygorskite powder was calcined at different temperatures in the range of 100°C‐1200°C, and the microstructural evolution of the palygorskite nanofibers was investigated by thermogravimetric and differential thermal analysis (TG‐DTA), X‐ray diffraction (XRD), scanning electron microscopy (SEM), and high‐resolution transmission electron microscope (HRTEM). Furthermore, the palygorskite powder was shaped to bars by dry pressing and sintered from 700°C to 1200°C. The properties of the sintered palygorskite were characterized by bending strength, mercury intrusion porosimeter (MIP), and stepwise isothermal dilatometry (SID). The results showed that the morphology of palygorskite nanofibers maintained unchanged till 1000°C. The palygorskite nanofibers molted to bind each other and formed a solid interwoven network structure at 1100°C. Correspondingly, it was shown from the sharply decrease of the sintered palygorskite porosity from 45.46% at 1000°C to 1.82% at 1100°C that the dense sintering of palygorskite started at 1100°C. With the sintering proceeding, some closed micropores fused each other to form bigger opening pores, resulting in a slight increase of porosity at 1200°C. However, the pore size distribution got more uniform and the density of the sintered body increased. So the bending strength of the sintered body reached the maximum of 176.67 Mpa and finally the main crystalline phases of the sintered sample changed to quartz, enstatite, and kyanite. The sintering activation energy of the palygorskite was measured by means of SID with a value of 906.46 kJ·mol−1.