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Various boron contents of AlCrNbTiBN coatings were prepared by radiofrequency reactive magnetron cosputtering on both 304 stainless steel and 100 silicon substrates. Boron-doped AlCrNbTiN coatings resulted in a dense structure and a decrease in the grain size. As compared to boron-free coatings, the hardness of AlCrNbTiBN coatings increased from 25.8 to 31.1 GPa at a boron content of 3.3 at. %. The AlCrNbTiBN coatings exhibited favorable hardness due to the increased dense structure, defect density, grain refinement, and solid solution strengthening. The wear test at 700 °C showed that coatings without boron reveal three times the wear rate than those coatings doped with boron. In this study, the multicomponent (AlCrNbTiBN) coating demonstrated favorable mechanical and tribological properties. This implies that AlCrNbTiBN coatings might provide promising applicability in the wear-resistant field at high temperatures. Furthermore, boron-doped multicomponent nitride coating appears to enhance coating’s mechanical properties and wear resistance, indicating potential development in the near future.

Inspired by Mantis shrimp, this work aims to suggest a bottom-up approach for the fabrication of nanonetwork hydroxyapatite (HAp) thin film using self-assembled polystyrene

We outline a machine learning strategy for quantitively determining the conformation of AB-type diblock copolymers with excluded volume effects using small angle scattering. Complemented by computer simulations, a correlation matrix connecting conformations of different copolymers according to their scattering features is established on the mathematical framework of a Gaussian process, a multivariate extension of the familiar univariate Gaussian distribution. We show that the relevant conformational characteristics of copolymers can be probabilistically inferred from their coherent scattering cross sections without any restriction imposed by model assumptions. This work not only facilitates the quantitative structural analysis of copolymer solutions but also provides the reliable benchmarking for the related theoretical development of scattering functions.

To lower the charge leakage of a floating gate device and improve the operation performance of memory devices toward a smaller structure size and a higher component capability, two new types of floating gates composed of pn-type polysilicon or np-type polysilicon were developed in this study. Their microstructure and elemental compositions were investigated, and the sheet resistance, threshold voltages and erasing voltages were measured. The experimental results and charge simulation indicated that, by forming an n-p junction in the floating gate, the sheet resistance was increased, and the charge leakage was reduced because of the formation of a carrier depletion zone at the junction interface serving as an intrinsic potential barrier. Additionally, the threshold voltage and erasing voltage of the np-type floating gate were elevated, suggesting that the performance of the floating gate in the operation of memory devices can be effectively improved without the application of new materials or changes to the physical structure.

Herein, this work aims to fabricate well-ordered nanonetwork epoxy resin modified with poly(butyl acrylate)-b-poly(methyl methacrylate) (PBA-b-PMMA) block copolymer (BCP) for enhanced energy dissipation using a self-assembled diblock copolymer of polystyrene-b-poly(dimethylsiloxane) (PS-b-PDMS) with gyroid and diamond structures as templates. A systematic study of mechanical properties using nanoindentation of epoxy resin with gyroid- and diamond-structures after modification revealed significant enhancement in energy dissipation, with the values of 0.36 ± 0.02 nJ (gyroid) and 0.43 ± 0.03 nJ (diamond), respectively, when compared to intrinsic epoxy resin (approximately 0.02 ± 0.002 nJ) with brittle characteristics. This enhanced property is attributed to the synergic effect of the deliberate structure with well-ordered nanonetwork texture and the toughening of BCP-based modifiers at the molecular level. In addition to the deliberate structural effect from the nanonetwork texture, the BCP modifier composed of epoxy-philic hard segment and epoxy-phobic soft segment led to dispersed soft-segment domains in the nanonetwork-structured epoxy matrix with superior interfacial strength for the enhancement of applied energy dissipation.

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To develop strong refractory high-entropy alloys for use at elevated temperatures as well as to overcome grain-boundary brittleness, an equimolar HfMoNbTaTiZr alloy was prepared, and a minor amount of boron (0.1 at.%) was added into the alloy. The microstructures of the alloys were characterized, and their macro-to-microscale mechanical properties were measured. The microstructural observations indicated that the matrices of both the alloys were composed of a body-centered cubic solid-solution structure, and the added boron induced the precipitation of hexagonal close-packed borides (most likely the (Hf, Zr)B2) at the grain boundaries. The modulus and hardness of differently oriented grains were about equivalent, suggesting a diminished anisotropy, and many small slips occurred on multiple {110} planes. While the hardness of the matrix was not increased, the intergranular precipitation of the borides markedly raised the hardness of the grain boundaries. Owing to the enhanced grain boundary cohesion, the work hardenability and ductility were effectively improved with the addition of boron.

Most medium entropy alloys (MEAs) exhibit excellent mechanical properties, but their applications are limited because of their high density. This study explores a series of lightweight nonequiatomic Ti65(AlCrNbV)35-xZrx (x = 3, 5, 7, and 10) MEAs with a low density, high strength, and high ductility. To achieve solid solution strengthening, Zr with a large atomic radius was used. In addition, various thermomechanical treatment parameters were adopted to further improve the MEAs’ mechanical properties. The density of the MEAs was revealed to be approximately 5 g/cm3, indicating that they were lightweight. Through an X-ray diffraction analysis, the MEAs were revealed to have a single body-centered cubic structure not only in the as-cast state but also after thermomechanical treatment. In terms of mechanical properties, all the as-cast MEAs with Zr additions achieved excellent performance (>1000 MPa tensile yield strength and 20% tensile ductility). In addition, hot rolling effectively eliminated the defects of the MEAs; under a given yield strength, hot-rolled MEAs exhibited superior ductility relative to non-hot-rolled MEAs. Overall, the Ti65(AlCrNbV)28Zr7 MEAs exhibited an optimum combination of mechanical properties (yield strength > 1200 MPa, plastic strain > 15%) after undergoing hot rolling 50%, cold rolling 70%, and rapid annealing for 30 to 50 s (at a temperature of approximately 850 °C) with a heating rate of 15 K/s. With their extremely high specific yield strength (264 MPa·g/cm3) and high ductility (22%), the Ti65(AlCrNbV)28Zr7 MEAs demonstrate considerable potential for energy and transportation applications.

To understand the dominance of lattice distortion and cocktail effect for an appropriate element selection and optimistic design of multicomponent protective hard coatings, in this study, four groups of Ta-based high-entropy nitride coatings, including (AlCrTa2TiZr)Nx, (HfNbTaTiZr)Nx, (MoNbTaTiZr)Nx and (Al2Cr2HfMoNbTa)Nx, were deposited by sputtering in an N2 + Ar mixed atmosphere. The structures, mechanical properties, wear resistance and oxidation resistance of the coatings were investigated, and the roles of different constituent metallic elements in their performance were examined. Experimental results indicated that, similar to conventional nitride coatings, the sputtering yield and resputtering loss of metallic elements determined the chemical composition. While the high mixing entropy of multiple metallic elements yielded a solid-solution structure, the N2-to-total flow ratio dominated the film structure and growth orientation. A certain level of lattice distortion generated similarly high mechanical properties no matter which metallic elements were added, but the cocktail effect of the constituents decided the tribological and oxidation resistance of the coatings.

Cu with nanotwin (NT) possesses great electrical, mechanical, and thermal properties and has potential for electronic applications. Various studies have reported the effect of NT orientation on Cu mechanical properties. However, its effect on Cu stress-relaxation behavior has not been clarified, particularly in nano-scale. In this study, Cu nanopillars with various orientations were examined by a picoindenter under constant strain and observed by in situ TEM. The angles between the twin plane and the loading direction in the examined nanopillars were 0°, 60°, to 90°, and a benchmark pillar of single-crystal Cu without NT was examined. The stress drops were respectively 10%, 80%, 4%, and 50%. Owing to the interaction by NT, the dislocation behavior in nanopillars was different from that in bulk or in thin film samples. Especially, the rapid slip path of dislocations to go to the free surface of the nanopillar induced a dislocation-free zone in the 0° nanopillar, which led to work-softening. On the contrary, a high dislocation density was observed in the 90° nanopillar, which was generated by dislocation interaction and obstruction of dislocation slip by twin planes, and it led to work-hardening. The findings reveal the NT orientation in Cu nanopillars affected stress relaxation significantly.