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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

Objective: This study aimed to evaluate whether adjuvant radiotherapy (RT) can improve the treatment outcome of patients with locally advanced gastric cancer who underwent extensive lymph node dissection (ELND). Materials and Methods: This retrospective study included patients with gastric cancer pathological stages IIA–IIIC at Taipei Tzu Chi Hospital between 2008 and 2015. Patients (a) aged >80 years, (b) with distant metastasis at diagnosis, (c) with coexisting malignancies, (d) who did not complete the prescribed RT course, and (e) who died 1 month after surgery were excluded. Among 420 patients diagnosed with gastric cancer, 98 were included. Results: The median follow-up was 24.5 months. Of 39 patients who underwent adjuvant RT, 38 also received adjuvant chemotherapy (CT). Of 59 patients who did not receive adjuvant RT, only 34 received adjuvant CT. ELND was performed in 67.3% of the patients. The 5-year overall survival (OS) rate was 40%. In the univariate analyses, adjuvant CT regimen, 5-fluorouracil + leucovorin, was associated with worst outcome, while TS-1 was associated with better survival outcome (P = 0.018). The number of involved lymph nodes was strongly related to the OS and disease-free survival (DFS) (P < 0.001). We tried using different numbers of involved lymph nodes as a cutoff point and found that adjuvant RT significantly improved both OS and DFS in patients whose involved lymph nodes were ≥4 (OS, P = 0.017; DFS, P = 0.015). In multivariate analyses, better DFS was associated with negative surgical margin (P = 0.04), earlier disease stage (P = 0.001), adjuvant radiotherapy (P = 0.045), and adjuvant CT regimen TS-1 (P = 0.001). Conclusion: Adjuvant RT could improve DFS of patients with locally advanced gastric cancer with or without ELND. When the number of involved lymph nodes is ≥4, adjuvant RT is strongly suggested.

This study reports a thermodynamic route for self-forming an ultrathin V-Nb-Mo-Ta-W high-entropy alloy layer for potential use as a promising diffusion barrier. In Cu alloy films minor-doped with 1.2 at.% of one-to-five metallic elements (V, Nb, Mo, Ta and W), the alloying elements spontaneously segregated. Under the competition of enthalpy and mixing entropy that determines the delta Gibbs free energy, one and, in particular, five alloying element(s) formed an alloy solution layer at the Cu/Si interface, whereas three alloying elements differently formed intermetallic compound clusters at the grain boundaries of Cu. Dominant factors for the final states of the alloying elements include the large positive enthalpy between Cu and the alloying elements, the negative enthalpy among the alloying elements, and the low-to-high mixing entropy among the alloying elements. The self-forming quinary alloy layer of only 1.5 nm thick provided excellent resistance to the interdiffusion of Cu and Si up to 700°C, better than practical and other newly developed barrier materials.

The influence of lithium chloride (LiCl) on the hydration structure of anionic micelles of sodium dodecyl sulfate (SDS) in water was studied using the contrast-variation small-angle neutron scattering (SANS) technique. In the past, extensive computational studies have shown that the distribution of invasive water plays a critical role in the self-organization of SDS molecules and the stability of the assemblies. However, in past scattering studies the degree of the hydration level was not examined explicitly. Here, a series of contrast-variation SANS data was analyzed to extract the intramicellar radial distributions of invasive water and SDS molecules from the evolving spectral lineshapes caused by the varying isotopic ratios of water. By addressing the intramicellar inhomogeneous distributions of water and SDS molecules, a detailed description of how the counterion association influences the micellization behavior of SDS molecules is provided. The extension of our method can be used to provide an in-depth insight into the micellization phenomenon, which is commonly found in many soft matter systems.

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.

This work investigates the corrosion mechanism of annealed equiatomic AlCoCrFeNi tri-phase alloy in 0.5 M H2SO4 aerated aqueous solution. Experimental results indicate that the B2 matrix is preferentially corroded away while grain-boundary FCC and labyrinth-like BCC endure, consistent with the tendency of formation energy for monolayer hydroxide on the (001) plane of three phases calculated by the first principle based on density function theory. Furthermore, the stable passive current density is related to lower ksp values of Co(OH)3, Fe(OH)3, and Cr(OH)3, while the annealing effect on enhancing corrosion resistance is owing to the more uniformity of passive hydroxide film.

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.

Band structure by design in 2D layered semiconductors is highly desirable, with the goal to acquire the electronic properties of interest through the engineering of chemical composition, structure, defect, stacking, or doping. For atomically thin transition metal dichalcogenides, substitutional doping with more than one single type of transition metals is the task for which no feasible approach is proposed. Here, the growth of WS

The thermodynamic parameters for a series of Fe(100−x)/2Co(100−x)/2Cux (x from 10 to 90, at. pct) alloys including their characteristic temperatures, the enthalpy and entropy changes of three phase transformations were determined systematically using differential scanning calorimetry (DSC). The corresponding vertical section of ternary Fe-Co-Cu phase diagram was predicted, and the relationships of the enthalpy and entropy changes vs Cu content were described by polynomial expressions. Metastable phase separation took place in those liquid Fe-Co-Cu alloys with the Cu content 30 ≤ x ≤ 70. The liquid phase separation temperatures were determined to outline the metastable miscibility gap, and the critical undercoolings to initiate phase separation were measured as a range of 57 K to 98 K. After such a phase separation, the liquid phase (to γ(Fe, Co)) exhibited the strongest undercooling ability in the Fe-Co-Cu alloys with x ≤ 70, whereas the solid-state undercooling for the eutectoid transformation is comparatively higher in the alloys with x > 70. The nanomechanical properties of α(Fe, Co) and (Cu) phases were measured by nanoindentation technique. In the Fe20Co20Cu60 alloy, both phases had the lowest nanohardness and reduced elastic modulus, and displayed severe creep behaviors, resulting mainly from its conspicuous liquid phase separation.

Ductile vanadium layers were alternately deposited with brittle aluminum-copper-iron-based quasicrystal-alloy layers to form multilayered coatings. The in-situ transmission electron microscopic observations of nanopillar compression revealed that the as-deposited single-layered amorphous aluminum-copper-iron alloy slightly deformed via shear banding. After annealing at 800 °C, brittle quasicrystal and intermetallic compounds were formed, so the single-layered coating cracked and peeled. In comparison, the multilayered coatings were effectively toughened. The multilayered nanopillars plastically deformed via dislocation activities and were work hardened owing to confined dislocation gliding. The as-deposited multilayered structure (amorphous alloy/crystalline vanadium) had a low 10% flow stress of 1.72 GPa, while the annealed multilayered structure (quasicrystal/vanadium) presented a high flow stress of 2.58 GPa owing to quasicrystal strengthening. Dislocation clusters were in-situ observed to glide laterally in the crystalline vanadium layers and move vertically through the vanadium and quasicrystal layers, yielding an improved plasticity.

We employ a sequential electrophoresis and electrodeposition approach to fabricate a large-area ordered macroporous Ni foam in 5 × 5 cm 2 via a template route. Images from scanning electron microscope exhibit hierarchical structures with hexagonally-arranged pores and interconnected pore channels. For as-prepared and annealed ordered macroporous Ni foams, the loading-depth profiles from nano indentation show typical elastic and plastic deformation. Upon annealing, moderate growth in grain size is observed, resulting in lower hardness and Young’s modulus. In contrast, for disordered macroporous Ni foam and solid Ni film, nano indentation results reveal larger hardness and undetermined Young’s modulus. The ordered macroporous foam reveals hardness that is 22% of that of solid Ni film, a value close to its theoretic packing density of 24%.

We show quasicrystal formation by annealing multilayers of Al, Cu and Fe. The mechanical and surface properties of quasicrystals are affected by the parameters of annealing process. Here, multilayer Al-Cu-Fe thin film samples with different compositions were sputtered on Si/SiO2 substrates and subjected to a two-step annealing process for different durations (5, 10 and 15 h). X-ray diffraction analyses indicated that the 15-h annealed sample had a sharper quasicrystal peak, which was more stable than any other phases. From the XRD data, the amount of each phase was calculated; the sample with longer annealing duration revealed a high amount of ψ-phase (84.3% crystallinity of quasicrystal) with a small amount of cubic Al50 (CuFe) 50 phase. Nanoindentation tests and contact angle measurements showed that this sample also had the greatest hardness (∼11 GPa) and the highest contact angle (127°), respectively.

The lattice distortion of a solute primarily occurs because its atomic size and chemical bonding are different from those of neighboring atoms. The lattice distortion effects in conventional and high-entropy alloys are different; however, a detailed investigation on these effects has yet to be conducted. To fill this research gap, this study produced face-centered cubic-structured dilute solutions (Ni, Ni–2 at.% W, and Ni–4 at.% W) and concentrated solutions (equiatomic CrFeNi and CoCrFeMnNi) and compared their tensile properties. For the two W-containing alloys, lattice distortion occurred only around the large and strong W atoms. However, for the two concentrated solutions, which had a similar interelement atomic size and shear modulus to the aforementioned alloys, lattice distortion occurred at all lattice sites. These two types of lattice distortion had significantly different effects on tensile properties. The strength and ductility of the alloys with a high concentration of distorted lattice points were higher than those of the alloys with a low concentration of distorted lattice points, although the alloys with a low concentration of distorted lattice points had a larger nominal atomic size difference and shear modulus difference. The mechanisms underlying the evolution of different mechanical properties under different types of lattice distortion were examined for the dilute and concentrated alloys. Moreover, the universal solid solution strengthening mechanism was observed.

Microgravity solidification provides a particular opportunity to produce an extraordinary microstructure and optimized mechanical properties. To shed further light on the influence of rapid solidification mechanism on mechanical properties, both the microgravity solidification mechanism and resultant micromechanical properties of ternary Al 57 Ag 12 Ge 31 alloy were analyzed by means of drop tube, nanoindentation and frictional sliding techniques, which was compared with equilibrium solidification condition. The solidification pathways changed with the decrease of droplet size, owing to a larger cooling rate and a higher undercooling. Consequently, the microstructure transformed from dendrites plus two-phase eutectic to two-phase eutectics, eventually to anomalous ternary eutectic, while the thickness of surface (Ge) layer decreased. The micromechanical properties of rapidly solidified alloy droplets were evidently improved with the decrease of droplet size, which is mainly ascribed to the microstructure refinement and the homogenous distribution especially of hardening (Ge) phase. The measured microhardness, yield strength, strain hardening exponent, pile-up resistance and friction coefficient were analyzed as a function of droplet size.

Band structure by design in 2D layered semiconductors is highly desirable, with the goal to acquire the electronic properties of interest through the engineering of chemical composition, structure, defect, stacking, or doping. For atomically thin transition metal dichalcogenides, substitutional doping with more than one single type of transition metals is the task for which no feasible approach is proposed. Here, the growth of WS2 monolayer is shown codoped with multiple kinds of transition metal impurities via chemical vapor deposition controlled in a diffusion-limited mode. Multielement embedment of Cr, Fe, Nb, and Mo into the host lattice is exemplified. Abundant impurity states thus generate in the bandgap of the resultant WS2 and provide a robust switch of charging/discharging states upon sweep of an electric filed. A profound memory window exists in the transfer curves of doped WS2 field-effect transistors, forming the basis of binary states for robust nonvolatile memory. The doping technique presented in this work brings one step closer to the rational design of 2D semiconductors with desired electronic properties.

In this study, AlCrSiNbZr nitride thin films were deposited on Si substrate by reactive radio frequency magnetron sputtering under the substrate bias from 0 V to −100 V at room temperature. The effect of substrate bias on structure, morphology, hardness and resistivity of the films was investigated. The results show that (111) preferred orientation was dominant phases for samples under bias of 0 V, −25 V, −50 V and − 75 V whereas amorphous-like feature was observed for samples under the bias of −100 V. In addition, crystallinity of film was enhanced when the substrate bias increased from 0 V to −50 V, but decreased when substrate bias further increased from −50 V to −100 V, suggesting that the optimized crystallinity of films was achieved under the substrate bias of −50 V. The oxygen contents of the thin films decreased significantly when the substrate bias was higher than −25 V. The hardness of the films was divided into two regions and samples under bias of −75 V and −100 V possessed higher hardness than those under bias of 0 V, −25 V and −50 V, which was mainly attributed to less oxynitride phases for samples under bias of −75 V and −100 V. The resistivity of thin films decreased as the substrate bias increased, which was mainly affected by the concentration of oxygen in films. The optimized substrate bias was −75 V with the maximum hardness and lowest resistivity.

Herein, we adopted alloying and rapid-dendrite-growth methods to improve the mechanical properties of Fe-based alloys. Three molten alloys including Fe-5Ni-5Mo-5Ge, Fe-5Ni-5Mo-5Ge-5Co, and Fe-5Ni-5Mo-5Ge-5Co-5Si were undercooled, during which (αFe) dendrites grew rapidly with the decrease of temperature (i.e., increase of undercooling). The rapid growth of (αFe) dendrites in the Fe-5Ni-5Mo-5Ge-5Co alloy at a high rate of 31.8 ms–1 caused by a large undercooling more effectively enhanced the microhardness than a Co addition did. In comparison, because of the great disparity of atom size and valence electron number between Fe and Si, a further Si addition suppressed the (αFe) dendrite growth while dramatically increasing the Vickers microhardness of the Fe-5Ni-5Mo-5Ge-5Co-5Si alloy to HV 622.

To minimize the room-temperature brittleness of AZ magnesium alloys (Mg–Al–Zn) and to inhibit grain growth at elevated temperatures for superplasticity optimization, AZ91−xSn alloys (x=0, 1, 2 and 3 wt%) were developed, processed by high-ratio hot extrusion for microstructure refinement. The mechanistic correlations of their superplasticity, from the perspectives of grain growth and boundary sliding, with the Sn content and the testing parameters were examined. With a higher Sn content, the activation energy of grain growth and diffusion-mediated boundary sliding, QG and QS, increased from 29.7 to 35.2 kJ/mol and from 114.1 to 126.5 kJ/mol, respectively. With an adequate Sn addition (2 wt%) and at a relevant strain rate and temperature, a compromise between competitive grain growth and boundary sliding was reached, and the superplasticity was optimized (elongation >1000%), following a proposed superplasticity parameter ( p Q G − Q S ) / 2.3 n G p R T + ( n G p − 1 ) log e .

Various (AlCrMoTaTi)-Six-N coatings were prepared on Si substrates through a reactive magnetron sputtering system to methodically investigate the effects of Si contents and free Si on oxidation behavior. The as-deposited Si-containing coating presented a relatively dense and compact structure compared with the Si-free coating. An oxide layer was formed on the coating surface and continued to thicken when the coatings were exposed to ambient air at elevated temperatures. At 1073 K, a two-layer structure, which consists of an amorphous Al2O3 layer with traces of other target elements followed by a rutile TiO2 + oxide of the target element mixed zone, was developed in the oxide layer. Oxidation resistance was gradually enhanced with the continued increase in Si concentration in the coatings. At 1173 K, the coatings with Si content of as low as 7.51 at.% exhibited a single order of magnitude lower oxidation rate than that of the Si-free coating. Nanohardness measurement of the coatings further confirmed the oxidation behavior. The significantly enhanced oxidation resistance may be attributed to the presence of Al and Si in the coatings.

To improve the mechanical properties, including the ductility, of cast AZ91 magnesium alloy (Mg–9Al–Zn) to provide high workability, small amounts of Sn were added to AZ91, forming AZ91−xSn (x = 1–3) alloys; following homogenization/aging treatments, high-ratio extrusion was conducted on the alloys. The correlation between the microstructural refinement and the improvement in mechanical performance was studied. In the as-cast AZ91−xSn alloys, small Mg2Sn precipitates formed in an Al-enriched α-Mg matrix, and the formation of detrimental, large eutectic β-Mg17Al12 was suppressed, resulting in an increase in hardness from Hv 68 to 77. The high-ratio extrusion greatly refined the microstructure and increased the hardness further to Hv 101. A higher Sn content resulted in the formation of more small Mg2Sn precipitates, and reduced the size of the coarse grains to 5 μm. The wrought AZ91−xSn alloys with added 2–3 wt.% Sn and extrusion had a markedly better tensile strength, 380 MPa, than that of a cast AZ91 alloy, and exhibited an elongations of 8–9%.

Both microstructure sizes and phase distributions influence the mechanical performance of multi-phase alloys. Herein, we investigated the microhardness enhancements of two Al–Cu–Ge alloys with enlarged undercoolings, corresponding to their microstructural evolutions. The similar-range undercoolings for the two alloys were obtained by a glass fluxing method, and comparatively minimum undercoolings were achieved by differential scanning calorimetry. For an Al70Cu10Ge20 alloy, the microstructure refinements of primary CuAl2 dendrite and (Al) + (Ge) pseudobinary eutectic, especially the former, dominate its large microhardness increase with high-level undercoolings. By comparison, for an Al80Cu10Ge10 alloy with a slight composition difference, a hardness drop and a limited refinement hardening effect are observed due to the early formation of primary (Al) dendrite. As undercooling increases, an alternative hardening owing to the reduced amount of (Al) dendrite as well as the larger amount and more homogenous distribution of (Al) + CuAl2 pseudobinary eutectic phases is presented. The mechanical performance of the two alloys well matches the combined values of their composing structures, following the rule of mixtures and according to their microstructure evolutions.

This study demonstrates that simply by rolling at ambient temperature, FCC type high entropy alloy Al0.5CoCrCuFeNi can be refined to have nanocrystalline structure and exhibits outstanding combination of strength and ductility. The yield strength and ultimate tensile strength are 1284 and 1344 MPa, respectively, in combination with an elongation of 7.6%. After a short annealing at 900°C for 10 min, the elongation is doubled to 15.3% with a trade-off around 20% in strength. This excellent combination of strength and ductility is attributable to the activation of quasi-dynamic recrystallisation during cold work and the limited grain growth during 900°C annealing.

The formation of graphitic nanocrystallites at the surface of amorphous carbon under large mechanical stresses was examined by using micro-Raman spectrometry, transmission electron microscopy and in-situ compressions. In the Raman analyses of severely deformed (above a strain energy density criterion of 5.9 J/m2) surface regions of nanoscratched and nanoindented amorphous carbon films, two additional sharp and narrow peaks, DGr and GGr at 1330 and 1580 cm−1, appeared from the main unchanged broad spectra, revealing the transformation of some small-range amorphous carbon to nanocrystalline graphite. Transmission electron microscopic images presented the formation of surface shear layer within which dispersed graphitic nanocrystallites (a size of about 3 nm) were formed in the remaining amorphous matrix. The in-situ nanoscopic observation of amorphous carbon nanopillars under compressions confirmed the formation of graphitic nanocrystallites at pillar edge surfaces. The formed graphite (0 0 1) and (1 0 0) lattices were well oriented along maximum resolved shear stresses, being an evidence of lattice reconstruction and suggesting a possibility of stress-induced graphitization of amorphous carbon in the absence of heat.

By using sacrificial ZnO nanorods, a self non-uniform electric field was established to yield the aqueous growth of 〈111〉 oriented, single-crystalline (Zn,Sn)-doped Pd nanodendrites on TiO2 nanotubes for synthesizing three-dimensional hydrophobic heterostructures. Structural analyses revealed that primary dendrite arms grew along a 〈111〉 direction group; symmetric branches were built on the basal plane of the arms but sprouted in another [111] direction, similar to a twin structure. Sequential growth processes different from a diffusion-limited aggregation model were suggested, including the dissolution of ZnO nanorods for forming a self non-uniform electric field, the protruding of primary arms towards a Zn2+ concentrated zone, and then the development of branches through a cation depletion zone. A strong surface enhanced Raman scattering and high photocatalytic activity, owing to the strong surface plasmon resonance on the large-surface symmetric structures and the inhibited recombination of photogenerated electron–hole pairs, suggested the high potential of the heterostructures for applications in self-cleaning photocatalysts and nano-optoelectronic devices.

This paper reviews the past and possible future development of anti-bacteria and anti-wear TaN-(Ag,Cu) nanocomposite thin films. The review starts with the development of TaN-Cu and TaN-Ag nanocomposite thin films which are prepared with co-sputtering followed by rapid thermal annealing (RTA). The incorporation of Ag–Cu atoms simultaneously into TaN film has later shown some advantages over TaN-Ag or TaN-Cu, such as wider bactericidal spectrum, lower annealing temperature, and equally low friction coefficient. Besides describing these advantages, this paper addresses some of the un-solved problems with TaN-(Ag-Cu) thin films, which include a short life time due to fast diffusion of Ag and Cu atoms out on the film surface as well as the adaptive behavior. The paper also discusses about the importance of controlled-releasing the soft metal ions in antibacterial applications. The last part of this paper also discusses briefly the adaptive behavior of these composite films. While the out-diffusion of soft metals from the composite matrix to the surface is essential for the chameleon adaptive behavior to be realized, the controlled diffusion of soft metals is definitely required. In sum, this paper addresses the developing process of anti-bacterial and anti-wear TaN-(Ag,Cu) films, along with some current problems, and provides some possible solutions.

(AlCrMoTaTi)N coatings were deposited on Si substrates via reactive magnetron sputtering. The effects of N 2 -to-total (N 2 + Ar) flow ratio ( R N ) on the coating structure and properties were examined. Alloy coatings have composite equiaxed grain structures consisting of amorphous and body-centered cubic crystal phases, whereas nitride coatings have columnar structures with single face-centered cubic crystal phase. Distinct lattice expansion and grain refinement were observed in nitride coatings as R N increased. Typical V-shaped columnar structures with faceted tops and open column boundaries transformed into denser and smaller columnar structures with domed surfaces. Increasing R N to 30% caused the hardness and modulus to reach maximum values of 30.6 and 291.6 GPa, respectively. Electrical resistivity increased from 536 μΩ cm to 8212 μΩ cm when R N increased from 10% to 50%.

TaN–(Cu,Ag) nanocomposite films were deposited by reactive co-sputtering on Si(001) and M2 tool steels. The films were then annealed using RTA (Rapid Thermal Annealing) at 200 °C–400 °C to induce the nucleation and growth of metal particles in TaN matrix and on film surface. After deposition, structures, surface morphologies, and mechanical properties were analyzed, the samples were tested for their anti-wear and anti-bacterial behaviors against Gram-negative Escherichia coli. It is found that the antibacterial efficiency against E. coli can be much improved for TaN–(Cu,Ag), comparing with that of TaN–Ag or TaN–Cu films. This could be attributed to large number of surfaced Ag and Cu particles. The tribological properties could also be improved, and are similar to TaN–Ag under a normal load of 5 N. In general, the annealing temperature for TaN–(Cu,Ag) can be as low as 200 °C. Being annealed at this temperature, the film still shows good antibacterial and anti-wear behaviors.

Cu-doped TaN films were known to have good anti-bacterial and anti-wear behaviors. However, in some of the practical applications, the depletion of surfaced Cu might eventually cause the films to lose their effectiveness against wear and bacteria. This study hence was aimed at understanding the rejuvenation process for these films. The structures, morphologies, antibacterial and mechanical properties of TaN–Cu nanocomposite thin films after multi-rejuvenating processes were the focus of this study. The results revealed that the Cu particles would re-appear on the film surface after each rejuvenation cycle, which can recover the anti-wear and anti-bacterial properties. The particle size and density appeared to decrease with the increase of rejuvenation cycle. The hardness of the samples would also decrease with the number of cycles. This was due to the slow depletion of Cu atoms, which might cause the increase of porosity and the decrease of hardness. The wear rates and friction coefficients of these rejuvenated samples depend mainly on the possibility of forming lubricious Cu films, although film hardness also played a certain role. In sum, the present study confirms that the anti-bacterial and anti-wear behaviors can be rejuvenated twice or more, under the experimental conditions adopted.

Multicomponent high-entropy nitrides have been attempted as robust diffusion barrier materials to inhibit the severe interdiffusion of Cu and Si; however, the improvement in their diffusion resistance relative to the abilities of few-component nitrides has actually not been verified. Thus, in this study, nitride barriers with different numbers of components (metallic elements), from unitary TiN to senary high-entropy (TiTaCrZrAlRu)N (with the same face-centered cubic structure and a thickness of 5 nm), were prepared. The failure of these nitride barriers in resisting the interdiffusion of Cu and Si was examined, and the activation energy of Cu diffusion through the nitrides was determined. With more components incorporated, the failure temperature of the nitrides was found to markedly increase from 550°C to 900°C, and the activation energy of Cu diffusion was effectively raised from 107 kJ/mol to 161 kJ/mol. Severe lattice distortions and random cohesions are suggested as the dominant factors for the improved diffusion-resistant ability of the multicomponent high-entropy nitrides.

An Al 0.3 CrFe 1.5 MnNi 0.5 multi-component alloy with a very effective surface hardening ability attributed to intrinsic ρ phase precipitation and applicable to complex tool components was developed. Under a conventional aging treatment in a normal atmosphere at 550 °C for 2 h, the alloy with the surface precipitation hardening layer of 74 μm thick exhibited markedly enhanced surface hardness from HV 338 to HV 840 and efficiently improved wear resistance to 1.4 times the values of SUJ2 and SKD61 steels, while high fracture toughness close to that of ductile SKD61 steel was effectively retained. Precipitation thermodynamics and growth kinetics of the surface hardening layer were also investigated. The growth of the surface hardening layer was much faster than that of the precipitation in the bulk matrix; it did not follow typical long-distance diffusion kinetics but behaves more similar to a self-induced or reaction-accelerated short-range decomposition with a thickness increase proportional to the cube of aging time. On the surface, a lower heterogeneous nucleation energy and a reduced strain energy (total 55 kJ/mol) than the regular nucleation energy in the bulk matrix (78 kJ/mol) dominated the rapid formation and growth of the intrinsic surface precipitation with significant strain relaxations.

In this study, attempts were made to prepare and characterize TaN–(Cu,Ag) nanocomposite films by using a hybrid approach combining reactive co-sputtering and rapid thermal annealing at various temperatures to induce the formation of soft metal particles in the matrix or on the surface. The films’ properties and their antiwear and antibacteria behaviors were compared with those previously studied TaN–Cu and TaN–Ag films. All three types of TaN–(soft metal) films showed good tribological properties due to the lubricious Ag and/or Cu layers. It was also found that the antibacteria efficiency of TaN–(Ag,Cu) film against either Escherichia coli or Staphylococcus aureus could be much improved, comparing with that of TaN–Ag or TaN–Cu film. The synergistic effect due to the coexistence of Ag and Cu is obvious. The annealing temperature used to develop TaN–(Cu,Ag) films with good antibacterial and antiwear behaviors could be as low as 250 °C. The lowering of the annealing temperature made these films applicable onto low-melting-point materials, such as polymers.

Direct current electropulsing was used to improve the plasticity of (Zr53Cu30Ni9Al8)99.5Si0.5 bulk metallic glasses. After the electropulsing treatment, the specimen showed reductions in both the glass transition and the crystallization temperatures while retaining its amorphous structure, and both Young's modulus and the hardness decreased while the nanoindentation loading curve became more serrated. Using the bond-interface method and Vickers indentation, the treated specimen showed more branching of semi-circular shear bands and less radial shear bands compared to its as-cast counterpart. The possible plasticity enhancement mechanism of the electropulsing treatment was also discussed.