Staff

Abstract:
In this study, we present an innovative strategy for tailoring the crystalline structure and enhancing the functional properties of poly(vinylidene fluoride) (PVDF) composites reinforced with ultra-low concentrations (0.05–0.50 wt%) of multi-walled carbon nanotubes (MWCNTs). To promote the formation of the electroactive β-phase-critical for piezoelectric and electrostrictive responses-ultrasonic energy was applied during solution preparation. This approach enables significant phase transformation without high-temperature annealing or mechanical stretching, achieving over 84 % β-phase content. Beyond material synthesis, we introduce a custom-designed, in-situ experimental platform that combines an atomic force microscope (AFM) with a Sawyer-Tower electric circuit. This hybrid system allows for simultaneous, real-time measurement of electric field, electric displacement, and normal mechanical strain, enabling direct and quantitative insight into the nanoscale electromechanical coupling phenomena in the composites. Our results show that films containing up to 0.30 wt% MWCNTs exhibit enhanced and nearly hysteresis-free electrostrictive and piezoelectric behavior, making them suitable for precision nanoscale actuator applications with displacement ranges up to ∼28 nm. At higher MWCNT concentrations, increased electrical conductivity and strain hysteresis were observed, broadening the functional potential of these materials toward energy harvesting, charge storage or switching devices. The study integrates structural, electrical and electromechanical analyses with phenomenological modeling of AC/DC conductivity and band structure evolution, providing a comprehensive understanding of structure–property–function relationships. The proposed methodology offers a scalable route toward the design and calibration of multifunctional PVDF-based composites for next-generation positioning, sensing and transduction systems

Keywords:
PVDF, MWCNT, Crystalline phase, Conductivity, Piezoelectric effect, Electrostriction, AFM

Abstract:
This study examines nitrogen ion implantation's effects on the microstructure, mechanical behavior, and tribological performance of an octonary high-entropy thin film metallic glass HfMoNbTaTiVWZr. Ion implantation led to binary nitride formation, elemental redistribution, and surface modifications while maintaining significant degree of amorphization, what indicates local atomic rearrangement rather than crystallization. Structural and chemical analyses using TEM, XRD, and EDS mapping revealed phase stability changes and preferential segregation of heavy elements like hafnium and tantalum at high doses. Hardness enhancement was attributed to solid solution strengthening, fine nitride formation, increased lattice distortion, residual stress, and densification. At an optimal implantation dose (1e17 ions/cm2), hardness increased to 20 GPa, reducing the coefficient of friction and improving wear resistance. A comparison with a magnetron-sputtered (HfMoNbTaTiVWZr)N thin film showed distinct hardness-depth profiles, confirming localized strengthening effects. These findings highlight nitrogen implantation as an effective surface engineering technique for optimizing material performance in demanding applications

Keywords:
High entropy film metallic glasses, Ion implantation, Microstructure, Indentation, Surface characteristics