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Abstract Herein, this work aims to develop a facile method for the fabrication of metallic mechanical metamaterial with a well-ordered diamond structure from a bottom-up approach using a self-assembled block copolymer for templated electrochemical deposition. By controlling the effective volume fraction of PDMS in PS-b-PDMS via solvent annealing followed by HF etching of PDMS, it is feasible to obtain nanoporous PS with diamond-structured nanochannels and used it as a template for templated electrochemical deposition. Subsequently, well-ordered nanonetwork gold (Au) can be fabricated. As evidenced by nanoindentation and micro-compression tests, the mechanical properties of the diamond-structured Au after removal of PS give the combination of lightweight and mechanically robust characteristics with an exceptionally high reduced elastic modulus of 11.9 ± 0.6 GPa and yield strength of 193 ± 11 MPa above the Hashin-Shtrikman upper bound of 72 MPa with a bending-dominated structure at equivalent density. The corresponding deformation mechanism can be elucidated by morphological observations experimentally and finite element analysis (FEA) numerically. This work demonstrates the bottom-up approach to fabricating metallic monolith with diamond structure in the nanoscale, giving a superior performance as mechanical metamaterials.

Gels, foams, and paints fall into a class of soft matter materials with widespread usage in modern technologies. This paper combines machine learning and spectral analysis techniques to develop a toolbox to model the complex interactions in this family of materials, which allows to quantitatively extract the system parameters from data.

A machine learning solution for the potential inversion problem in elastic scattering is outlined. The inversion scheme consists of two major components, a generative network featuring a variational autoencoder which extracts the targeted static two-point correlation functions from experimentally measured scattering cross sections, and a Gaussian process framework which probabilistically infers the relevant structural parameters from the inverted correlation functions. Via a case study of charged colloidal suspensions, the feasibility of this approach for quantitative study of molecular interaction is critically benchmarked and its merit over existing deterministic approaches, in terms of numerical accuracy and computationally efficiency, is demonstrated.

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.

The nanoscopic deformation of ⟨111⟩ nanotwinned copper nanopillars under strain rates between 10−5/s and 5 × 10−4/s was studied by using in situ transmission electron microscopy. The correlation among dislocation activity, twin boundary instability due to incoherent twin boundary migration and corresponding mechanical responses was investigated. Dislocations piled up in the nanotwinned copper, giving rise to significant hardening at relatively high strain rates of 3–5 × 10−4/s. Lower strain rates resulted in detwinning and reduced hardening, while corresponding deformation mechanisms are proposed based on experimental results. At low/ultralow strain rates below 6 × 10−5/s, dislocation activity almost ceased operating, but the migration of twin boundaries via the 1/4 ⟨101¯ ⟩ kink-like motion of atoms is suggested as the detwinning mechanism. At medium strain rates of 1–2 × 10−4/s, detwinning was decelerated likely due to the interfered kink-like motion of atoms by activated partial dislocations, while dislocation climb may alternatively dominate detwinning. These results indicate that, even for the same nanoscale twin boundary spacing, different nanomechanical deformation mechanisms can operate at different strain rates.

We demonstrate the fabrication of free-standing inverse opals with gradient pores via a combination of electrophoresis and electroplating techniques. Our processing scheme starts with the preparation of multilayer colloidal crystals by conducting sequential electrophoresis with polystyrene (PS) microspheres in different sizes (300, 600, and 1000 nm). The critical factors affecting the stacking of individual colloidal crystals are discussed and relevant electrophoresis parameters are identified so the larger PS microspheres are assembled successively atop of smaller ones in an orderly manner. In total, we construct multilayer colloidal crystals with vertical stacking of microspheres in 300/600, 300/1000, and 300/600/1000 nm sequences. The inverse opals with gradient pores are produced by galvanostatic plating of Ni, followed by the selective removal of colloidal template. Images from scanning electron microscopy exhibit ideal multilayer close-packed structures with well-defined boundaries among different layers. Results from porometer analysis reveal the size of bottlenecks consistent with those of interconnected pore channels from inverse opals of smallest PS microspheres. Mechanical properties determined by nanoindentation tests indicate significant improvements for multilayer inverse opals as compared to those of conventional single-layer inverse opals.

In this study multi-component (AlCrTaTiZr)NxSiy high-entropy coatings were developed by co-sputtering of AlCrTaTiZr alloy and Si in an Ar/N2 mixed atmosphere with the application of different substrate biases and Si-target powers. Their nanomechanical properties and deformation behaviors were characterized by nanoindentation tests. Because of the effect of high mixing entropies, all the deposited multi-component (AlCrTaTiZr)NxSiy high-entropy coatings exhibited a simple face-centered cubic solid-solution structure. With an increased substrate bias and Si-target power, their microstructures changed from large columns with a [111] preferred orientation to a nanocomposite form with ultrafine grains. The hardness, H/E ratio and H3/E2 ratio of (AlCrTaTiZr)N1.07Si0.15 coating reached 30.2 GPa, 0.12 and 0.41 GPa, respectively, suggesting markedly suppressed dislocation activities and a very high resistance to wear and plastic deformation, attributable to grain refinements and film densification by the application of substrate bias, a nanocomposite structure by the introduction of silicon nitrides, and a strengthening effect induced by severe lattice distortions. In the deformed regions under indents, stacking faults or partial dislocations were formed, while in the stress-released regions, near-perfect lattices recovered.

The instrumented nanoindentation test is used to investigate the mechanical properties and deformation behaviors of copper with different grain sizes. The results have shown that the critical shear stresses for the initiation of plastic deformation in the copper specimens with large grain sizes are close to the theoretical value and comparatively much lower for electroless copper films with an ultrafine grain size.

Three-dimensional ordered macroporous Ni films, known as Ni inverse opals, are fabricated via a template approach in which polystyrene (PS) microspheres (820 nm in diameter) are assembled in closely-packed colloidal crystals via a vertical electrophoresis process, followed by electroplating of Ni into the interstitial voids within the colloidal crystals and the selective removal of PS microspheres. To improve its mechanical strength, a conformal Ni-Co layer (45 ~ 64 nm) is electrodeposited on the skeletons of the Ni inverse opals by cyclic voltammetry. After coating, from nano-indentation tests, the hardness and reduced elastic modulus are enhanced considerably (172 ~ 220% for hardness; 72 ~ 79% for reduced elastic modulus), as compared to those of pristine inverse opals. After an annealing treatment for the interdiffusion of Ni and Co, the sample reveals an even stronger hardness. X-ray diffraction patterns indicate that the finite thickness of the inverse opals skeletons induces preferential growth of the (111) plane. In short, a combined effect of solid solution alloying, thickening of inverse opals skeletons for greater load bearing, and a predominant (111) plane is responsible for the improved mechanical strength of the Ni inverse opals. [ABSTRACT FROM AUTHOR]

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 (aFe) dendrites grew rapidly with the decrease of temperature (i.e., increase of undercooling). The rapid growth of (aFe) 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 (aFe) dendrite growth while dramatically increasing the Vickers microhardness of the Fe-5Ni-5Mo-5Ge-5Co-5Si alloy to HV 622. [ABSTRACT FROM AUTHOR]

To inhibit the detrimental diffusion of copper into silicon devices, an effective barrier is strongly demanded. In this study, copper(rhenium) alloy films were successfully electroless- and electroplated on silicon substrates for self-forming an ultrathin rhenium barrier layer. In pure copper films, the interdiffusion of copper and silicon already occurred at 400°C, forming silicides and increasing the electrical resistivity of the films. In comparison, not any silicide formation was observed in the electroless- and electroplated copper(rhenium) alloy films with minor incorporations of rhenium for 0.10 and 0.39 at% until 600 and 500°C, respectively, attributed to the prior segregation of rhenium and the self-formation of rhenium barrier layer at the copper/silicon interface at 400°C. A zero solubility of rhenium in copper and a small solubility in palladium catalysts facilitate the separation of rhenium from copper. The kinetics of rhenium segregation follows uphill diffusion, and the diffusivity of rhenium in copper at 400°C is estimated to be 1.5 x 10-17 cm²/s. [ABSTRACT FROM AUTHOR]

We report multi-component high-entropy materials as extraordinarily robust diffusion barriers and clarify the highly suppressed interdiffusion kinetics in the multi-component materials from structural and thermodynamic perspectives. The failures of six alloy barriers with different numbers of elements, from unitary Ti to senary TiTaCrZrAlRu, against the interdiffusion of Cu and Si were characterized, and experimental results indicated that, with more elements incorporated, the failure temperature of the barriers increased from 550 to 900°C. The activation energy of Cu diffusion through the alloy barriers was determined to increase from 110 to 163 kJ/mole. Mechanistic analyses suggest that, structurally, severe lattice distortion strains and a high packing density caused by different atom sizes, and, thermodynamically, a strengthened cohesion provide a total increase of 55 kJ/mole in the activation energy of substitutional Cu diffusion, and are believed to be the dominant factors of suppressed interdiffusion kinetics through the multi-component barrier materials. [ABSTRACT FROM AUTHOR]

In this study multi-component (AlCrTaTiZr)NxSiy high-entropy coatings were developed by co-sputtering of AlCrTaTiZr alloy and Si in an Ar/N2 mixed atmosphere with the application of different substrate biases and Si-target powers. Their nanomechanical properties and deformation behaviors were characterized by nanoindentation tests. Because of the effect of high mixing entropies, all the deposited multi-component (AlCrTaTiZr)NxSiy high-entropy coatings exhibited a simple face-centered cubic solid-solution structure. With an increased substrate bias and Si-target power, their microstructures changed from large columns with a [111] preferred orientation to a nanocomposite form with ultrafine grains. The hardness, H/E ratio and H³/E² ratio of (AlCrTaTiZr)N1.07Si0.15 coating reached 30.2 GPa, 0.12 and 0.41 GPa, respectively, suggesting markedly suppressed dislocation activities and a very high resistance to wear and plastic deformation, attributable to grain refinements and film densification by the application of substrate bias, a nanocomposite structure by the introduction of silicon nitrides, and a strengthening effect induced by severe lattice distortions. In the deformed regions under indents, stacking faults or partial dislocations were formed, while in the stress-released regions, near-perfect lattices recovered. [ABSTRACT FROM AUTHOR]

In this study, very simple periodic cathodic vacuum arc deposition was conducted to prepare multilayered structures of diamond-like carbon films with reduced surface roughness and enhanced mechanical properties compared to conventional unfiltered single-layered films. The roughness of single-layered diamond-like carbon films significantly increased from 23 to 104 nm with increasing thickness from 100 to 800 nm due to the droplet formation in plasma atmosphere. By introducing periodic deposition, the roughness of the multilayered structures with a thickness of 400 nm was reduced from 75 to 37 nm, associated with a much smaller number of surface particles. The hardness of the multilayered structures was enhanced from 27 to 34 GPa, and the interface adhesion was increased from 2.73 to 3.63 J/m2. The single- and multilayered films showed a similar amorphous structure with slightly varied ID/IG ratios from 0.9 to 0.6. The periodic deposition process was the dominant factor for the reduced roughness and enhanced mechanical properties of the unfiltered films. [ABSTRACT FROM AUTHOR]

In this study, hydroxyapatites were deposited on surface modified carbon fibers using a simulated body fluid; different amounts of COOH functional group were formed on the fiber surfaces by different degrees of KOH pretreatment. The effect of the surface functional group on the growth features of the hydroxyapatite crystals was analyzed, and the detailed stacking and structural correlations of the grown crystals to the substrate carbon fibers were examined to realize the mineralization mechanism, It was observed that hydroxyapatite nanocrystallites longitudinally constructed a crystal chain along [211] direction; several aligned crystal chains were then bundled to form a spindle structure which ultimately composed differently featured coatings. A mild KOH pretreatment created a small amount of functional group that activated few sites for hydroxyapatite nucleation compliant to the COOH bond structure, yielding a horizontally oriented olive Structure under an orientation correlation HAP [112] or [211]//C [100]. A severer treatment induced more nucleation sites; attributed to the repulsion between the close COO- ligands, the bond structure was bent, leading to the radially aligned and ball-featured growth of hydroxyapatites with a different correlation HAP [1121 or [211] //C [002]. [ABSTRACT FROM AUTHOR]

Grafting one-dimensional semiconductor nanostructures inside arrayed nanotubes of another semiconductor to form network heteroarchitectures is believed to improve photocatalytic activity on the bases of an enhanced separation of photoexcited electron-hole pairs and an enlarged surface area for light absorption and chemical reactions. Thus in this study, single-crystalline ZnO nanorod grafted anatase TiO2nanotube three-dimensional arrayed heterostructures were synthesized viaa simple solution process and acted as supporting platforms for nanoparticle deposition. The lattice orientations of the ZnO nanorods and TiO2nanotubes were examined and suggested that the rods heterogeneously nucleated on the tubes and grew along a [002] direction following a structural correlation ZnO (100)//TiO2(103). Silver nanoparticles were further deposited on the platforms to compose TiO2/ZnO/Ag multi-junction heterostructures which exhibited much superior photocatalytic activity than a conventional TiO2nanotube array did. [ABSTRACT FROM AUTHOR]

One-dimensional oxide-based nanostructures have been intensively studied because of their excellent optoelectronic properties. Due to the drawbacks of vapor-phase or aqueous solution growth, including complex processes, high synthesis temperatures, expensive precursors, and also preceding patterned seeding or subsequent patterning processes, there is an urgent need to grow patterned nanostructures by a simple and direct process at low temperatures. In the present study, stress-induced growth of one-dimensional single-crystalline ZnO and TiO2nanostructures directly from ZnO and TiO2films, respectively, in an ambient atmosphere at room temperature were developed by indentation or scratching without the use of any reaction precursors. Under large applied stresses, oxide bonds were broken, assisted by hydrolysis in the presence of moisture, and subsequently were reconstructed (defined as a bond breaking–hydrolysis–reconstruction mechanism) leading to the spontaneous growth of one-dimensional nanocrystals. The direct growth at controlled locations provides an opportunity for the simple preparation of patterned nanostructures of oxide-based materials. [ABSTRACT FROM AUTHOR]

In this study, (AICrTaTiZr)N0.7 and (AICrTaTiZr)N1 films with quinary metallic elements were developed as diffusion barrier materials for Cu interconnects. To improve the interface adhesion to Cu, an AICrTaTiZr buffer layer was deposited on the barriers to form (AICrTaTiZr)N0.7/AICrTaTiZr and (AICrTaTiZr)N1/A1CrTaTiZr bilayer structures. The as-deposited AlCrTaTiZr and (AICrTaTiZr)N0.7 films were amorphous structures, and (AICrTaTiZr)N1 possessed a nanocomposite structure. After annealing at 800°C, although Cu penetrated into the AICrTaTiZr buffer layer, the diffusion of Cu was retarded by the (AICrTaTiZr)N0.7 and (AICrTaTiZr)N1 barriers. During annealing at 900°C, the interdiffusion of Si and Cu occurred through the (AICrTaTiZr)N0.7/AICrTaTiZr bilayer, and Cu silicides formed. However, the (AlCrTaTiZr)N1 /AICrTaTiZr bilayer remained stable. Neither the interdiffusion of Cu and Si through the (AICrTaTiZr)N1/AlCrTaTiZr bilayer nor the silicide formation was identified, indicating the high diffusion resistance of the bilayer structure. [ABSTRACT FROM AUTHOR]

In this study, TiVCr and T1VCrZrY films were deposited on Si substrates by magnetron sputtering with the application of radio-frequency substrate bias of different powers from 0 to 15 W. The crystal structures, microstructure, and mechanical, electrical, and optical properties under the effect of bias were characterized. Both the TiVCr and TiVCrZrY films constructed simple solid solutions from all alloyed elements. The TiVCr films possessed a body-centered cubic crystal structure with a pyramid-like surface, while the TiVCrZrY films had a hexagonal close-packed crystal structure with a domelike surface. The microstructure and properties of the films varied with bias power. As the bias power increased, the microstructure of the films obviously changed from a porous to a dense columnar feature, and the density of the voids existing between the columns decreased. Accordingly, the physical properties of the films were improved. The hardness of the TiVCr and TiVCrZrY films was enhanced to about 11 and 14 GPa, and the electrical resistivity was lowered to 80 and 100 μΩ cm, respectively. [ABSTRACT FROM AUTHOR]

In this study, aluminum-doped zinc oxide (AZO) transparent conducting films were deposited as seed layers by sol-gel method, followed by UV exposure and subsequent thermal curing at a low temperature of 300°C. Zinc oxide nanorod arrays were then hydrothermally grown on the seed layers at 70°C. By the activation Of UV exposure, the 300°C cured AZO seed layers possessed an obvious crystallinity and a [002] texture. The well-aligned and vertical growth of high density zinc oxide nanorods with a [002] preferred orientation and strong photoluminescence was consequently accomplished on the UV-exposed seed layers. The zinc oxide nanorods were characterized as single crystals of typical wurtzite structure with a (002) lattice spacing of 0.26 nm. Highly [002] textured grains with small-angle misfits of lattice orientations in the UV-exposed seed layers dominated the aligned growth of the nanorod arrays. [ABSTRACT FROM AUTHOR]

Electromigration reliability tests of dual-damascene Cu interconnect structures with or without a NH3/He plasma treatment have been performed in this study at 400°C under a high current density of 8 MA/cm² to clarify the effect of plasma treatment on the interface structure between Cu wires and SiCN capping layers and on the early-stage electromigration behavior and electrical reliability of the interconnects. From cumulative failure probabilities, small shape factors and large median time to failure were obtained for the interconnects with the plasma treatment, indicating an improved electromigration resistance. The oxide layer on the Cu surface was removed by plasma treatment, and an alternative CuSiN interlayer was formed at the Cu/SiCN interface, enhancing interface adhesion and reducing the diffusion paths of Cu atoms. Therefore, voids nucleated inside the Cu wires, rather than at the interface, at the early stage of the electromigration tests. The change in the Cu/SiCN interface structure varied the early-stage electromigration-induced voiding behavior and then effectively improved the electrical reliability of the Cu interconnect structures. [ABSTRACT FROM AUTHOR]

To inhibit rapid Cu diffusion in interconnect structures, an effective diffusion barrier of high thermal stability is strongly demanded. Thus in this study a nitride nanocomposite film of equimolar five-element high-entropy alloy (AICrTaTiZr)N was developed and deposited by reactive sputtering. Thermal stability of the (AICrTaTiZr)N film and its barrier performance to the interdiffusion of Si and Cu were investigated under thermal annealing at 700-900°C. The (AICrTaTiZr)N film, constructed of mixed crystalline and amorphous nanocomposite structure, was found to remain thermally stable at an extremely high temperature of 900°C with low electrical resistance. Neither interdiffusion between Si and Cu through the (AICrTaTiZr)N layer nor formation of any silicides occurred. Severe lattice distortions caused by the addition of multiprincipal elements and the nanocomposite structure of nanocrystallites surrounded by an amorphous matrix without the existence of grain boundaries were expected as the dominant factors for the high thermal stability and superior diffusion resistance of the (AICrTaTiZr)N film as an effective barrier material. [ABSTRACT FROM AUTHOR]

Amorphous CoWP films have been studied as a capping or diffusion barrier layer to reduce Cu electromigration. However, the interface characterizations between the CoWP and Cu films have not been clarified. Thus, in this study, CoWP and Cu films are deposited by electroless plating, and their thermal stability and interface diffusion behaviors are investigated. By the activation of nanoscaled Pd catalysts, a continuous amorphous CoWP layer is obtained with stable concentrations of 82.5 atom % Co, 5.5 atom % W, and 12.0 atom % P, and then a smooth crystalline Cu film is directly deposited on the CoWP layer. Under thermal annealing at 500°C, the CoWP layer remains an amorphous structure, and no obvious interdiffusion between the Cu and CoWP films is found. The electrical resistivity of the CoWP layer and CoWP/Cu bilayer decreases to the lowest values of 35 and 3.3 μΩ cm, respectively. However with increasing annealing temperature to 600°C, crystallization of the amorphous CoWP occurs, and much severe interdiffusion between the Cu and CoWP films is observed. [ABSTRACT FROM AUTHOR]

In this study, the interface chemistry and adhesion strength between a porous SIOCH extra-low-dielectric-constant film and SiCN etch stop layers were investigated with different plasma treatments. An interlayer of -6 nm thick between the porous SiOCH film and SiCN layers was found to be composed of Si, N, C, and 0. The SiOCH/SiCN interface was constructed by mixing bonds, including Si-C-N, Si-N-C, Si-O-C, Si-O2, etc. Under H2 and NH3 plasma treatments, a large amount of weak Si-CH3 and SiO-CH3 bonds were broken, and more Si-O related bonds of high binding energy formed at the interfaces. Moreover, under the accumulation of sufficient shear stresses around the indented regions during nanoindentation tests, interface delamination between the porous SiOCH film and SiCN layers occurred. The interface adhesion energy between untreated porous SiOCH film and SiCN layers was accordingly measured as 1.68 J/m2. After plasma treatments, especially NH3 plasma, the adhesion strength was effectively improved to 2.13 J/m2. [ABSTRACT FROM AUTHOR]

In this study, the interface chemistry and adhesion strengths between Cu and SiCN etch stop layers have been investigated under different plasma treatments. From the examination of interface microstructures and the analyses of chemical compositions and bonding configurations, an oxide layer was found to exist at the untreated Cu/SiCN interface. After H2 and NH3 treatments, the amount of oxides was effectively reduced. Some Cu silicides formed during SiCN deposition, and Cu nitrides even formed under NH3 plasma treatment. The adhesion strengths of the Cu/SiCN interfaces were measured by nanoindentation and nanoscratch tests under which interface delamination occurred around indented regions. The adhesion energy of the untreated Cu/SiCN interface was obtained as about 4.98 and 0.98 J/m2, respectively, by nanoindentation and nanoscratch tests. After H2 and NH3 plasma treatments, the adhesion energy was effectively improved to 5.90 and 5.99 J/m2 by nanoindentation test, and to 1.74 and 2.58 J/m2 by nanoscratch test, respectively, because of the removing of oxides and the formation of Cu silicides and nitrides at the Cu/SiCN interfaces. [ABSTRACT FROM AUTHOR]

In this study, amorphous Ni-P films were deposited by electroless plating under different pH values. Their mechanical properties and delormation behavior were then investigated by instrumented nano-indentation. With increasing pH value of the plating solution from 3.75 to 6.0, the hardness and elastic modulus of the obtained Ni-P films increased from 6.1 GPa and 146 GPa to 8.2 GPa and 168 GPa respectively. From the load--indentation depth curve, the Ni-P films were found to yield at an indentation depth of 8 nm. By microstructural examination around the indented regions, early-stage plastic deformation of the amorphous Ni-P films was verified through the formation and extension of shear bands with a spacing of several lens of nanometers. Within the shear bands, flow dilatation-induced intense shear localization was expected and resulted in crystallization in the amorphous matrix. The critical shear stress and energy release rate required for the initiation of early-stage plastic yielding of the Ni-P films were calculated to be about 1.4 GPa and 3,0 J/m² respectively, both of which increased with pH values. [ABSTRACT FROM AUTHOR]

The interfacial shear strength of continuous silicon carbide fiber reinforced 7075 aluminum matrix composite (SiCf/7075Al) has been investigated in this research by pushout microindentation. The SiCf/7075Al composite specimens were processed by diffusion bonding alternate layers of SiC fibers and 7075Al alloy plates. From the measured stress-displacement curves of indentation tests, the interfacial shear strengths of the composite specimens were obtained, and the stress-displacement curves were basically divided into two regions: (1) elastic deformation and (2) interface decohesion and fiber sliding. With increasing aging time, the interfacial shear strength of the composite increased to 167 MPa for T6-treated specimens, and the variation of the interfacial shear strength well followed that of the ultimate tensile strength of 7075Al matrix alloy. With decreasing specimen thickness, the interfacial shear strength of the composite and the amplitude of stress fluctuation slightly decreased because of the stress relaxation effect near specimen surfaces. Under higher indentation velocities, both the interfacial shear strength and the amplitude of stress fluctuation became smaller. [ABSTRACT FROM AUTHOR]

The AlxCoCrCuFeNi alloys with multiprincipal elements (x = the aluminum content in molar ratio, from 0 to 3.0) were synthesized using a well-developed arc-melting and casting method, and their mechanical properties were investigated. These alloys exhibited promising mechanical properties, including excellent elevated-temperature strength and good wear resistance. With the addition of aluminum from x = 0 to 3.0, the hardness of the alloys increased from HV 133 to 655, mainly attributed to the increased portion of strong bcc phase to ductile fcc phase, both of which were strengthened by the solid solution of aluminum atoms and the precipitation of nanophases. The alloys exhibited superior high-temperature strengths up to 800 °C, among which the AlxCoCrCuFeNi alloy, especially, had enhanced plasticity and a large strain-hardening capacity. Moreover, the wear resistance of these alloys was similar to that of ferrous alloys at the same hardness level, while the alloys with lower hardness exhibited relatively higher resistance because of their large strain-hardening capacity. [ABSTRACT FROM AUTHOR]

Crystalline solid solutions are typically formed in conventional alloys based on one or two host elements. Here, in this research, four alloys containing multiprincipal metallic elements (≥ 5 elements) were prepared by casting, splat quenching, and sputtering. Their microstructures and crystal structures were investigated. It was interestingly found that solid solutions with simple fcc or bcc crystal structure were also practically formed in these alloys with multiprincipal elements. All different atoms are regarded as solutes and expected to randomly distribute in the crystal lattices without any matrix element defined. [ABSTRACT FROM AUTHOR]

The resistance of fibrous reinforced silver matrix composites to repeated make-break arc erosion has been investigated in this study. Three different types of short fibers were used as reinforcements, including graphite short fibers, Saffil short fibers, and silicon carbide whiskers. The weight losses of eroded composites increase with fiber content applied current and test number due to the worse thermal conductivity of the composites and the higher remained temperatures on contact surfaces. The composites reinforced with Saffil short fibers exhibit the best erosion resistance of all reinforcements in the study because of the small spacings between Saffil short fibers and the strengthening of strong short-fiber skeletons. The effective contribution of short fibers to arc erosion resistance depends on their sizes to construct small-spacing and deeply-embedded skeletons. [ABSTRACT FROM AUTHOR]

Part II. Proposes an electroless plating and hot-pressing process to fabricate silver matrix composites reinforced with uniformly distributed graphite and Saffil short fibers. Analysis of the arc erosion behavior of the composites; Characteristics of silver-based electrical contact materials; Illustrations of the representative surface morphologies of eroded graphite and Saffil short fibers.

Part I. Investigates the arc erosion behavior of developed silicon carbide and alumina particle reinforced silver matrix composites, using static-gap and single-spark tests. Types of failure of contact materials; Required properties for good contact materials; Characteristics of silver-based materials; Description of the surface morphologies of spark eroded composites; Factors that determine the spark erosion damage of composite materials.

In this study, an ultrathin quinary nitride film (AlCrTaTiZr)N of only 10 nm thick has been developed as a diffusion barrier layer for Cu interconnects. The (AlCrTaTiZr)N nanocomposite film was constructed of nanocrystallites embedded in an amorphous matrix. At an extremely high temperature of 900 °C, the Si/(AlCrTaTiZr)N/Cu film stack remained thermally stable. Neither interdiffusion between Si and Cu through the (AlCrTaTiZr)N layer nor formation of any silicides occurred. The nanocomposite structure and severe lattice distortions attributed to the addition of multiple elements were expected as the dominant factors for the superior diffusion resistance of the (AlCrTaTiZr)N film. [ABSTRACT FROM AUTHOR]

In this study, the mechanical properties of human dental structures have been investigated by using instrumented nanoindentation. Immersion in solutions containing Streptococcus mutans, which is the principal cause of dental caries, was applied to tooth specimens to clarify its effect on the microstructure and mechanical properties of the dental structures. With an extended time of up to 16 h, the pH value of the S. mutans solutions dropped from 7.3 to 5.8. Therefore, after immersion in the S. mutans solutions for 16 h, slight erosions of the dental structures began; after 64 h, severe tooth decay occurred with obviously etched dental features. After 128 h, the elastic modulus of enamel and dentine dropped to 85 and 67%, respectively, of the original values of untreated specimens, and the hardness dropped to 88 and 55%, respectively. [ABSTRACT FROM AUTHOR]