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Grain boundaries and heterophase interfaces both play important roles in enhancing the strain rate sensitivity (SRS) of engineering materials as they often serve as obstacles for dislocation motion. In this work, however, we carried out nanoindentation tests on Cu/Ta multilayers prepared with a wide range of modulation periods ( Λ ) and modulation ratios ( η ) and found negative contribution of incoherent interfaces to SRS. Activation event extension aided by incoherent interface shear was suggested as the dominating mechanism for rate related deformation process in Cu/Ta multilayers. The results provided valuable insights into the fundamental roles of grain boundaries and heterophase interfaces in plastic deformation.

VO2 thin films are prepared on Si substrates by direct-current (DC) magnetron sputtering at room temperature and annealed in vacuum at different argon pressures. The VO2 thin films annealed in vacuum and in Ar are all polycrystalline with a monoclinic structure; after annealing in Ar, the particle size is reduced compared to the films annealed in vacuum. There are more boundaries for smaller particles; therefore, oxygen can easily diffuse through the boundaries, resulting in more oxygen vacancies. Annealing under Ar further prevents the samples from oxidation. As the Ar pressure increases, the V 2p3/2 peak broadens and shifts to a lower binding energy, implying that there are more oxygen vacancies after annealing. The features in the Raman spectra acquired at room temperature shift to lower frequencies after annealing in Ar, further corroborating the existence of oxygen vacancies in the thin films. Raman scattering and resistance measurements show that the critical temperature of the phase transition from monoclinic to tetragonal is reduced from 341 K to 319 K. This can be ascribed to the weaker hybridization between V 3d and O 2p orbitals as a result of oxygen vacancies. Oxygen vacancies affect the phase transition in VO2 thin films, and the optical and electrical properties as well.

The temperature coefficient of resistance (TCR) of TaNx/Ag nanocomposite thin films could be substantially tuned by changing the components, even down to zero. In the work of this paper, it is unexpectedly found that the concentration of silver incorporation in the TaNx/Ag thin films could be controlled over a broad range from 5.4 at% to 31.14 at% through changing the N2 partial pressure during magnetron sputtering. In particular, the near-zero TCR of −15 ppm K−1 and the highest resistivity of 6038 μΩ cm were obtained in the TaNx/Ag thin films with 12.39 at% Ag. The high resistivity can be attributed to the low carrier density as a result of recombination of holes in the TaNx matrix and electrons in Ag. The composites changes from p-type to n-type at a higher Ag component. The results highlight a new approach to obtain high-performance thin films with zero TCR.

Since the SOC (state of charge) of the battery of each electric vehicle directly determines whether the battery should be charged/swapped, the SOC may affect the electric vehicle’s driving behavior. In this paper, we introduce the SOC of battery into the electric vehicle’s driving behavior model and propose a car-following model for electric vehicles, and then use the proposed model to study the effects of the SOC of battery and battery swap on each vehicle’s driving behavior in the heterogeneous traffic system consisting of traditional vehicles and electric vehicles. The numerical results show that the proposed model can reproduce some complex traffic phenomena resulted by the SOC of battery and battery swap and that the influences on each vehicle’s driving behavior are directly related to the initial traffic state, the electric vehicle’s proportion, and the SOC of battery.

From the point of view of the half-metallic character and magnetization reduction, the structural, electronic and magnetic properties of the imperfect Sr 2 FeMoO 6 compound containing seven different defects of the Fe Mo or Mo Fe antisites, Fe–Mo interchange, V Fe , V Mo , V O or V Sr vacancies have been studied by using first-principles projector augmented wave (PAW) within generalized gradient approximation (GGA) as well as taking into account on-site Coulomb repulsive interaction (GGA + U). No obvious structural changes are observed for the imperfect Sr 2 FeMoO 6 compound containing Fe Mo or Mo Fe antisites, Fe–Mo interchange or V Sr vacancy defects. However, the six (eight) nearest oxygen neighbors of the vacancy move away from (close to) V Fe or V Mo (V O ) vacancies. The half-metallic character is maintained for the imperfect Sr 2 FeMoO 6 compound containing Fe Mo antisite, V Fe , V O or V Sr vacancies, while it vanishes when Mo Fe antisite, Fe–Mo interchange or V Mo vacancy are presented. So the Mo Fe antisite, Fe–Mo interchange or V Mo vacancy defects have to be avoided in order to preserve the half-metallic character of the Sr 2 FeMoO 6 compound and thus usable in spintronics devices. In Fe Mo or Mo Fe antisites, Fe–Mo interchange cases, the spin moments of Fe (Mo) cations situated on Mo (Fe) antisites are in an antiferromagnetic coupling with those of Fe (Mo) cations on the regular sites. In V Fe , V Mo , V O or V Sr vacancies cases, a ferromagnetic coupling is obtained within each cation sublattice, while two cation sublattices are coupled antiferromagnetically. The total magnetic moments μ tot ( μ B /f.u.) of the imperfect Sr 2 FeMoO 6 compound containing seven different defects decrease in the sequence of V Sr vacancy (4.38), V Mo vacancy (3.92), V O vacancy (3.51), V Fe vacancy (3.40), Fe Mo antisite (3.40), Mo Fe antisite (3.33), Fe–Mo interchange (2.47) and the mechanisms of the saturation magnetization reduction have been discussed.

The electronic structures, magnetic properties, and half-metallicity of full-Heusler alloys Zr 2 CoZ (Z=Al, Ga, In, Sn) with the Hg 2 CuTi -type structure have been studied by using the first-principles projector augmented wave (PAW) potential within the generalized gradient approximation (GGA). The Zr 2 CoZ (Z=Al, Ga, In, Sn) are found to be half-metallic ferrimagnets within a certain range of the lattice constant. The total magnetic moments ( μ t ) of the Zr 2 CoZ alloys are calculated to be 2 for Z=Al, Ga, In and 3 for Z=Sn, linearly scaled with the total number of valence electrons ( Z t ) by μ t = Z t − 18 . The origin of the band gap for these half-metallic alloys is well understood. These new Zr-based Heusler alloys are the ideal candidates for spintronic devices.

Ternary nickel cobalt phosphide (NiCoP) is believed to be a promising water-splitting electrocatalyst owing to the synergistic effect between different transition metals. Herein, nitrogen doping NiCoP (N-NiCoP) nanowire arrays on carbon fiber paper skeleton (CFP) are synthesized by a facile hydrothermal reaction and subsequent phosphorization-nigtrogenization method. Structural characterizations and density functional theory (DFT) calculations demonstrate that N dopant prefer to replace O defects rather than P atoms in NiCoP lattice. It is illustrated that the Gibbs free energy of H (ΔGH*) in Ni-Co bridge sites is lowered from −0.35 eV of NiCoP to −0.26 eV of N-NiCoP by 25.7%, moreover, the increased d-orbital electronic density of Co and Ni promotes the charge transfer of hydrogen evolution reaction (HER). Consequently, the HER performance of N-NiCoP is substantially enhanced as compared to NiCoP. For N-NiCoP, the overpotentials to reach a current density of 100 mA·cm−2 are 149 and 162.5 mV in 0.5 M H2SO4 and 1 M KOH, respectively, and their Tafel slopes are 40.1 and 59.8 mV·dec−1, respectively. N doping offers an effective and promising route for improved HER performance of NiCoP catalyst in acid and alkaline electrolytes.

Well-arranged heterogeneous interface is favored to enhance the electrocatalytic activities to utilize the synergistic effects of different crystalline phases. In this work, vertical aligned single crystal Ni3Se2 nanowires (NWs) wrapped by ultra-thin NiSe nanoflakes (NFs) with well-arranged heterogeneous interfaces along axial direction were successfully in situ grown on nickel foam (Ni foam) by a simple one-step hydrothermal method without posttreatment. The growth of Ni3Se2 NWs follows a surface reaction mechanism by which NiSe reacts with reactive Ni· atoms on surface lattice steps of Ni3Se2 nucleuses to grow both along radial and axial directions. The configurations of the products can be tuned from NiSe NFs to the core-shell NWs dominated structures by solely modulating Se molarity in chemical precursors motivated by the accelerated reaction kinetics. The hydrogen evolution reaction (HER) performance was improved with the increase of Se molarity attributing to the increased coverage of high aspect Ni3Se2/NiSe core-shell NWs arrays, metallic conductive feature of Ni3Se2 skeleton and well-arranged heterogeneous interfaces along the axial direction. The Ni3Se2/NiSe core-shell NWs with well-arranged heterogeneous interfaces may also be beneficial to other energy or environmental applications.

An identification method of slug flow using velocity information was developed in this study. Quantitative analysis of two-phase (gas–liquid) flow in horizontal pipes is essential to ensure the stability of, or to accurately estimate the thermal performance of, various engineering applications. The spatial and temporal distribution of liquid velocity was measured using the ultrasound Doppler velocimetry method under various superficial velocity conditions. From the results, we proposed a novel identification method of the slug flow based on two parameters, the maximum velocity and maximum velocity difference ratio. In addition, the ratio of liquid velocities between the slug body and the bubble area is a reliable parameter for separating the slug flow from the plug flow. Finally, we investigated the changes in moving velocity, slug frequency, and slug length along the pipeline under a wide range of superficial velocities. The results show that the liquid and gas superficial velocity have the opposite effect on the slug frequency, except in the downstream region. It was found that the slug body length increased continually along the pipe and the average slug body length in the downstream region is invariant regardless of the gas superficial velocity.

Monoclinic vanadium dioxide VO

By using first-principles calculations, we have systematically investigated the structural and electronic properties of an infinite linear monatomic Cu chain with an adsorbed CO molecule. We find that the bridge geometry is energeticabsally favored not only when the Cu–Cu bond below the molecule is unstretched, but also for a wide range of d Cu–Cu up to about 4.20 A, while the substitutional geometry is favored only in the hyperstretched situation d Cu–Cu >4.80 A. Charge density differences point out the electron transfer is from the Cu atoms to the adsorbed CO molecule. The binding mechanism of CO to Cu chain can be described by the Blyholder’s model, in terms of σ-donation of electron density from the nonbonding CO-5σ orbital into empty metal orbitals and π-backdonation from the occupied metal d orbitals to empty CO-2π ⁎ orbital. The donation/backdonation process leads to the formation of bonding/antibonding pairs, 5σ b /5σ a and 2π b ⁎ /2π a ⁎ , with the 5σ a lying above E f and the 2π b ⁎ below E f .

To exploit the potential application of nitride nanotube (BNNT), the adsorption of sulfur dioxide (SO 2 ) on pristine and Mn-doped BNNT was theoretically studied using first-principles approach based on density functional theory (DFT). The most stable adsorption geometry, adsorption energy, magnetic moment, charge transfer and density of states of these systems are discussed. SO 2 molecule is weakly adsorbed on the pristine BNNT. The Mn-doped BNNT show high reactivity toward SO 2 regardless of the Mn B site or Mn N site adsorption. The larger formation energies and analysis of density of states show the SO 2 molecules are chemically bonded to Mn-doped BNNT and the covalent interaction between the SO 2 molecule and Mn atom can be formed. Therefore, the Mn-doped BNNT can be used as SO 2 gas sensor manufacturing raw materials, and it may be a potential material for nanodevice applications.

While hillock has so far been only observed in crystalline metals, here we show that hillock appeared on the surface of CuZr metallic glass film after annealing treatment. Other than compressive stresses generated upon annealing, surface selective oxidation processes, i.e., preferential oxidation of zirconium arouses the formation of surface ZrO2 layer and Cu-enriched area in the subsurface, were proposed to play a crucial role in hillock formation in metallic glasses. Cu atoms diffused faster than Zr from the Cu-enriched area towards the film surface, promoting the formation of Cu or Cu-enriched hillocks. Different from the diffusion mechanism in crystal films, the mechanism of atom diffusion to surface with vacancy to relieve compressive thermal stresses dominated the formation of hillocks in CuZr metallic glass films.

In point of view of the half-metallic character and magnetization reduction, the structural, electronic and magnetic properties of the disordered Pb 2 FeMoO 6 compound containing seven different defects of Fe Mo and Mo Fe antisites, Fe–Mo interchange, and V Fe , V Mo , V O and V Pb vacancies have been studied by using the first-principles projector augmented wave (PAW) potential within the generalized gradient approximation taking into account on-site Coulomb repulsive energy (GGA+U). No obvious structural changes are observed for the cases of the Fe Mo and Mo Fe antisites, Fe–Mo interchange, and V Pb vacancy, however, the six (eight) nearest oxygen neighbors of the vacancy move away from (close to) V Fe or V Mo ( V O ) vacancy. The half-metallic character is maintained for the Fe Mo antisite, V Fe , V O or V Pb vacancy cases, while it vanishes in the Mo Fe antisite, Fe–Mo interchange or V Mo vacancy cases even the defect concentration reduces down to C = 6.25%. So the Mo Fe antisite, Fe–Mo interchange or V Mo vacancy defects have to be avoided in order to preserve the half-metallic character of the Pb 2 FeMoO 6 compound and thus usable in magnetoresistive and spintronics devices. In Fe Mo or Mo Fe antisite cases, the spin moments of Fe (Mo) cations situated on Mo (Fe) antisites are in an antiferromagnetic coupling with those of Fe (Mo) cations on the regular sites. On the contrary, in Fe–Mo interchange case, the spin moments of Fe (Mo) cations situated on Mo (Fe) antisites are in a ferromagnetic coupling with those of Fe (Mo) cations on the regular sites. In V Fe , V O or V Pb vacancy cases, a ferromagnetic coupling is observed within each cation sublattice, while the two cation sublattices are coupled antiferromagneticly. But in V Mo vacancy case, a ferromagnetic coupling is obtained not only within each cation sublattice but also between Fe and Mo sublattices. The saturation magnetization of the disordered Pb 2 FeMoO 6 compound decreases in the sequence of V Pb , V Mo , Fe–Mo, V O , V Fe , Fe Mo and Mo Fe cases.

Sensitivity of pristine graphene (PG) and Pd-doped graphene (Pd-G) toward a series of small gas molecules (CO, NH 3 , O 2 and NO 2 ) has been investigated by first-principles based on density functional theory (DFT). The most stable adsorption configuration, adsorption energy, charge transfer, density of states and magnetic moment of these molecules on PG and Pd-G are thoroughly discussed. It is found that four gas molecules are weakly adsorbed on PG with low adsorption energy of 0.08–0.24 eV, and the electronic properties of PG are only sensitive to the presence of O 2 and NO 2 molecules. In contrast, doping graphene with Pd dopants significantly enhances the strength of interaction between adsorbed molecules and the modified substrate. The dramatically increased adsorption energy and charge transfer of these systems are expected to induce significant changes in the electrical conductivity of the Pd-G sheet. The results reveals that the sensitivity of graphene-based chemical gas sensors could be drastically improved by introducing the Pd dopants, so Pd-G is more suitable for gas molecules detection compared with PG.

Praseodymium (Pr) is implanted into TiN coatings to improve the corrosion resistance and cytocompatibility in blood plasma. The corrosion resistance of the Pr-doped TiN coatings in blood plasma is improved based on electrochemical measurements. Pr ion implantation dramatically decreases the hemolysis rate of the TiN coatings suggesting their suitability in cardiovascular applications. The viability of vascular endothelial cells seeded on the untreated TiN coatings and two Pr implanted TiN coatings implanted for different time is assessed. The vascular endothelial cell attach and grow to confluence on the Pr implanted TiN coatings and a network composed of vascular tissues is observed from the 0.5 h Pr implanted coatings. The results suggest that Pr ion implantation can effectively improve the corrosion resistance as well as cytocompatibility of TiN coatings in blood plasma.

Nanoindentation and electron microscope techniques have been performed on sputtering deposited monolayered nanocrystalline CuNb and multilayered CuNb/Cu thin films. Microstructural features, hardness and surface morphologies of residual indentation have been evaluated to identify the effects of alloying and laminated structure on strength and plastic deformation behavior of nanocrystalline metals. By altering the content of Nb in CuNb alloy and adding crystalline Cu layers into CuNb alloy, the volume fraction of amorphous phase in CuNb alloy and interface structures changed dramatically, resulting in various trends that are related to hardness, indentation induced pileup and shear banding deformation. Based on the experimental results, the dominant deformation mechanisms of the CuNb and CuNb/Cu thin films with various Nb contents were proposed and extended to be discussed.

Built upon recent findings that nanocrystalline–amorphous multilayers could possess both high strength and ductility due to nano-layer-limited structures, depth-sensing nanoindentation was employed to evaluate the hardness and shear band deformation behavior of nanoscale crystalline–Cu / amorphous–CuZr (C/A) multilayers among a wide range of amorphous layer thickness with constant crystalline Cu layer thickness. By varying individual layer thickness of amorphous layers, both weakening and strengthening effects on the hardness of C/A multilayers were observed, comparing with that derived from the rule of mixture, for which discontinuity of dislocation motion played a crucial role. A critical amorphous layer thickness of 20 nm was identified, above which interface–dislocation–absorption dominated plastic deformation, causing the weakening effect, below which, continuous-dislocation-impediment took over and was responsible for the strengthening effect. Mechanisms underlying the observed shear band morphologies under indentation were also extendedly discussed.

The mechanical behavior of nanoscale metallic multilayers (NMMs) has attracted much attention from both scientific and practical views. Compared with their monolithic counterparts, the large number of interfaces existing in the NMMs dictates the unique behavior of this special class of structural composite materials. While there have been a number of reviews on the mechanical mechanism of microlaminates, the rapid development of nanotechnology brought a pressing need for an overview focusing exclusively on a property-based definition of the NMMs, especially their size-dependent microstructure and mechanical performance. This article attempts to provide a comprehensive and up-to-date review on the microstructure, mechanical property and plastic deformation physics of NMMs. We hope this review could accomplish two purposes: (1) introducing the basic concepts of scaling and dimensional analysis to scientists and engineers working on NMM systems, and (2) providing a better understanding of interface behavior and the exceptional qualities the interfaces in NMMs display at atomic scale.

Based on extensive first-principles calculations, we report the equilibrium atomic configuration, mechanical and electronical properties of nonplanar oxygen-passivated armchair graphene nanoribbons (O-AGNRs) under uniaxial strain. We can get more stable and stiffer structures using uniaxial strain. The mechanical properties of the O-AGNRs such as Young’s modulus exhibits nonlinear behavior with strain, and Poisson’s ratio shows a decreasing trend with increasing tensile strain. In addition, under uniaxial strain the band gaps of the nonplanar O-AGNRs not only experience a transition between direct and indirect but also change their widths and can be classified into three families according to the ribbon width of 3 n , 3 n + 1, and 3 n + 2.

Ti–Si–N coatings are synthesized on titanium alloy (Ti6Al4V) by arc-enhanced magnetron sputtering and the microstructure and tribological properties are determined. The friction coefficient of the Ti–Si–N coatings, which is smaller in human serum than ambient air, decreases gradually with Si contents. Protein gel electrophoresis shows that the small friction coefficient is due to adsorbed proteins from the human serum under sliding conditions. The cytocompatibility of the coatings is assessed in vitro by a relative nitrite assay. The Ti–Si–N coatings have a positive effect on nitric oxide synthesis on the endothelial cells. The cell morphology and spreading on the coatings are examined by fluorescence staining. The Ti–Si–N coating with 12 at% Si exhibits the best effects in promoting actin cytoskeleton formation and cell spreading compared to coatings with different Si contents and titanium alloy.

The F doping effects on the electronic structure and magnetic properties of CrO2 have been studied using the first principles projector-augmented wave potential within the GGA+U. The F-doped CrO2 with low F concentration keeps a high spin polarization. Due to F doping, five different Jahn–Teller structural distortions are observed for the octahedrons around five groups Cr atoms in F-doped CrO2, this results from the 3d electron orbitals are asymmetrically occupied. Compared with pure CrO2, the decrease of spin polarization of F-doped CrO2 is contributed by the shift of CrIB 3d state towards low energy region. The impurity moment by substituting F impurities for O atoms are aligned with the host moment and the total magnetic moment increase about 1 μ B by more substituting one F impurity for one O atom, indicating that magnetic moment can be controlled by F doping. For Cr 54 O 102 F 6 , CrIIA and CrIIB alternately arrange in a unbroken F–Cr–F zigzag chain along the 〈 111 〉 direction in the ( 1 1 ¯ 0 ) plane, but the additional magnetic moment by substituting F impurity for O does not appear to reside on the Cr ion in the vicinity of the F impurity, but is quite diffuse due to the magnetic double-exchange interaction.

The first-principles projector-augmented wave (PAW) potentials within the density function theory (DFT) framework have been used to determine the geometry structures and electronic properties of the zigzag edge AlN nanoribbons (ZAlNNRs) doped with a single Si chain under generalized gradient approximation (GGA). The average Al–Si, Si–Si, Al–N, Si–N, Al–H and N–H bond lengths are 2.39, 2.16, 1.83, 1.74, 1.59 and 1.03 A, respectively. Pure 7-ZAlNNR is an indirect semiconductor with a large band gap of 2.235 eV, while a semiconductor to metal transformation is taken place after a single Si chain substituting for a single Al–N chain at various positions. In pure 7-ZAlNNR, the HVB and LCB are mainly attributed to the edge N and Al atoms, respectively, while in a single Si chain substituting doped 7-ZAlNNR, the HVB and LCB are mainly attributed to the Si atoms. The Al–N, Al–H and Al–Si bonds are ionic bond, the Si–Si and Si–H bonds are covalent bond, the N–H and N–Si bonds are covalent bond modified ionic bond.

We report the elastic, electronic and magnetic properties of naked ZGNRs with topological line defects (LD-ZGNRs) lying symmetrically on the ribbon's middle under vertical strains at four types of line defect atoms by using a first-principles approach. By changing the position and size of the local deformation of the ribbon, the optimal position is obtained. Moreover, an apparent spin-splitting of the energy band is obtained when a local deformation is created by the vertically applied strain.

The geometric stability and hydrogen capacity of Pd-decorated graphene with experimentally realizable boron dopants and various vacancy defects including single carbon vacancy (SV), “585”-type double carbon vacancy (585 DCV) and “555-777”-type double carbon vacancy (555-777 DCV) are investigated using the first-principles calculations based on density functional theory (DFT). It is found that among the four types of defective structures, Pd′s binding energies on SV and 585 DCV defect graphene sheets exceed the cohesive energy of the Pd metal bulk, thus Pd atoms are well dispersed above defective graphene sheets and effectively prevent Pd clustering. Up to three H2 molecules can bind to Pd atom on graphene with B dopants, SV and 555-777 DCV defects. For the cases of Pd-decorated graphene with B dopants and 555-777 DCV defect, a single H2 or two H2 are molecularly chemisorbed to Pd atom in the form of Pd–H2 Kubas complex, where the stretched H–H bond is relaxed but not dissociated. Out of two adsorbed H2, the third H2 binds to Pd atom by small van der Waals (vdW) forces and the nature of bonding is very weak physisorption. Different from above two cases, three H2 are all molecularly chemisorbed to Pd atom with stretched H–H bond for Pd-decorated SV defect graphene, the hybridization of the Pd-4d orbitals with the H2-σ orbitals and the electrostatic interaction between the Pd cation and the induced H2 dipole both contribute to the H2 molecules binding, and the binding energies of 0.25–0.41 eV/H2 is in the range that can permit H2 molecules recycling at ambient conditions.

In this paper, we use car-following model to study the effects of battery exchange at the on-line charging station on the vehicle’s driving behavior and running time. The numerical results illustrate that battery exchange will produce one prominent starting process at the upstream of the charging station and one prominent braking process at the downstream of the charging station and enhance each vehicle’s running time and the system’s total running time and that the influences of battery exchange on each vehicle’s driving behavior (including the starting and braking processes, the personal running time and the system’s total running time) are directly related to each vehicle’s arrival rate at the origin, the electric vehicle’s proportion and each electric vehicle’s series number in the vehicle fleet. The results can help traffic engineer to reasonably design the on-line charging station and optimize each vehicle’s arrival rate at the origin.

Using first-principles calculations based on density-functional theory, we systematically investigate the influence of adsorbates (CO molecule and O atom) and defects (adsorb one extra Cu atom and monovacancy) on the structural and electronic properties of Cu 5-1 NW and Cu 6-1 NW. For both nanowires, CO molecule prefers to adsorb on the top site, while O atom prefers to adsorb on the center site. The hybridization between the CO and Cu states is dominated by the donation–backdonation process, which leads to the formation of bonding/antibonding pairs, 5σ b /5σ a and 2π b ⁎ /2π a ⁎ . The larger adsorption energies, larger charge transfers to O adatom and larger decrease in quantum conductance 3 G 0 for an O atom adsorbed on the Cu 5-1 NW and Cu 6-1 NW show both Cu 5-1 NW and Cu 6-1 NW can be used as an O sensor. Furthermore, the decrease in quantum conductance 1 G 0 for a CO molecule adsorbed on the Cu 6-1 NW also shows the Cu 6-1 NW can be used to detect CO molecule. So we expect these results may have implications for CuNW based chemical sensing. High adsorption energy of one extra Cu atom and relatively low formation energy of a monovacancy suggest that these two types of defects are likely to occur in the fabrication of CuNWs. One extra Cu atom does not decrease the quantum conductance, while a Cu monovacancy leads to a drop of the quantum conductance.

Nanoscale metallic multilayers are a promising structural material for fabricating the next generation of nanoscale devices. Even though the mechanical properties of the multilayers have been extensively studied, the interpretation for the strain rate sensitivity of the multilayers is still lacking. In present study, the hardness and strain rate sensitivity of Ag/W multilayers with a wide range of modulation period Λ and modulation ratio η deposited by d.c. sputtering deposition were evaluated by nanoindentation testing. X-ray diffraction and transmission electron microscopy were carried out to investigate the texture and microstructure of the multilayers. Experimental results indicated that a mechanism transition occurred as the plastic deformation of the Ag/W multilayers was accommodated by the two constituent layers together at Λ ≤ 50 nm, while the plastic deformation localized mainly in Ag layers when Λ > 50 nm. A modified rule of mixture and plastic deformation localization model was proposed to describe the variation of strain rate sensitivity for the multilayers with smaller and larger Λ, respectively.

Size effects on hardness ( H ) and strain rate sensitivity ( m ) of nanocrystalline (NC) body-centered cubic Mo thin film were examined under nanoindentation testing. Contrast to existing reports that there was no indentation size effect on hardness in NC metals, inverse indentation size effect (ISE) in NC Mo was observed for the first time at penetration depths ranging from 15 to 200 nm, at all the loading strain rates applied. In addition, the strain rate sensitivity of NC Mo exhibited strong dependence on penetration depth, increasing dramatically with decreasing penetration depth. Surface effects related to two deformation mechanisms were proposed to be responsible for the observed inverse ISE on H and depth dependent m . Specifically, the mobility of screw dislocation/component and the diffusion length of interfacial diffusion were altered as the deformed region underneath the indenter was approaching the free surface, resulting in the unusual size effects in NC Mo.

First-principle calculation was conducted to study the electronic and magnetic states in the hybrid structure of boron nitride (BN) and graphene, in particular, on the effect of hydrogen adsorption. The results illustrated that the adsorption of a hydrogen atom could inject an electron, and thus affect the electronic and magnetic states. The mid-gap states cross Fermi levels might be produced or suppressed upon hydrogen adsorption, dependent on whether the numbers of B and N atoms replaced by C atoms were the same or not. Hence, the adsorbed hydrogen atom induced a transition in the hybrid material from the semiconducting state to the metallic state. Referencing to the partial density of states (PDOS) of top and down spins, the hybrid structures with equal numbers of N and B atoms did not exhibit magnetism, while those with unequal numbers of N and B atoms did. The magnetic properties of such a hybrid structure could be changed through hydrogen adsorption and, were closely related to the adsorption sites of H atoms and the shape of graphene domains.

Intermetallic precipitates are widely used to tailor mechanical properties of structural alloys but are often destabilized during plastic deformation. Using atomistic simulations, we elucidate structural instability mechanisms of intermetallic precipitates associated with dislocation motion in a model system of Al2Cu. Interaction of non-coplanar dislocation dipoles during plastic deformation results in anomalous reactions—the creation of vacancies accompanied with climb and collective glide of dislocation associated with the dislocation core change and atomic shuffle—accounting for structural instability in intermetallic Al2Cu. This process is profound with decreasing separation of non-coplanar dislocations and increasing temperature and is likely to be operative in other non-cubic intermetallic compounds as well. Instead of gliding, dislocations in intermetallic precipitates interact to climb, leaving defects behind. Qing Zhou and colleagues at Xi’an Jiaotong University in China and their collaborators in the United States of America used molecular dynamics simulations to investigate the interactions of dislocations in intermetallic precipitates in aluminium-copper during deformation. They showed that instead of traditional glide, dislocations that do not lie on the same plane can interact by climbing then gliding along a new atomic plane without cancelling each other out, leaving vacancies behind. This defect creation happened faster at higher temperatures, creating extended dislocation cores and vacancy clusters that could facilitate precipitate dissolution. Research into intermetallic stability during deformation may thus help us avoid failure of alloys strengthened with precipitates.

Micro-arc oxidation films are fabricated on the surface of AZ31B magnesium alloy in the Na 2 SiO 3 electrolyte. The mechanical performance of magnesium alloy bonding with the adhesive is examined by single lap-shear test, and the morphology and composition of the oxidation film are characterized by scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). The data indicate that the increase of Na 2 SiO 3 solution concentration results in the decrease of bonding strength of magnesium alloy joints, while the porosity has no directly relation with the variation of the lap-shear strength. The results also show that Na 2 SiO 3 participates into the film formation and the fabricated film is mainly composed of MgO and Mg 2 SiO 4 . In particular, with the increase of Na 2 SiO 3 solution concentration, the content of MgO decreased while that of Mg 2 SiO 4 increased. Moreover, MgO could initiate the formation of the hydroxyl group, which potentially enhances surface wettability and hydrogen bonding with the adhesive. This rationale is strongly supported by the results of Fourier Transform infrared spectra (FTIR), X-ray photoelectron spectroscopy (XPS) and contact angle measuring.

Adsorption of sulfur dioxide (SO2) on intrinsic and modified graphene, including Stone–Wales (SW) defect, Al doping and a combination of these two, was theoretically studied using first-principles approach based on density functional theory (DFT). The most stable adsorption geometry, adsorption energy, magnetic moment, charge transfer and density of states of these systems are thoroughly discussed. It was found that SO2 molecule is weakly adsorbed on the intrinsic and SW defected graphenes and their electronic properties were slightly changed. The Al-doped graphene and the defect–dopant combination show high reactivity toward SO2. Compared with Al-doped adsorption system, the adsorption energy for Al-doped SW defect adsorption system can be enhanced by the introduction of a SW defect. This work reveals that the sensitivity of graphene-based chemical gas sensors for SO2 can be drastically improved by introducing dopant and defect, and the Al-doped SW graphene is more suitable for SO2 gas detection.

The magnetic properties and electronic structure of Mn2NiSi and Ni2MnSi Heusler alloys have been studied by using the first-principles. The possible non-modulated martensitic transformations in Mn2NiSi and Ni2MnSi alloys have been investigated. In both austenitic and martensitic phases, Mn2NiSi is a ferrimagnet. The antiparallel alignment of Mn (A) and Mn (B) moments is found. In martensitic Mn2NiSi, the global energy minimum occurs at c/a=1.37 with 1% decrease of the martensitic cell volume. The energy difference ΔE between the austenitic and martensitic phases is 400 meV/cell, so it is more likely to realize martensitic transformation for Mn2NiSi alloy. Unlike Mn2NiSi alloy, the global energy minimum occurs at c/a=1.02 without cell volume change in martensitic Ni2MnSi. But the energy difference ΔE between the austenitic and martensitic phases is only 0.3 meV/cell. Meanwhile, around c/a=1 an anomaly is observed in the Etot–c/a curve which is related to a very slightly martensitic distortion trend in Ni2MnSi.

Superhard ternary Ti–Si–N coatings with different Si atomic concentrations are deposited on titanium alloy substrates by arc-enhanced magnetron sputtering (AEMS) and the vascular endothelial cell compatibility is studied. In vitro studies show that the surface hydrophilicity and hemolysis are about the same as those of the titanium alloy control and platelet adhesion and protein adsorption tests suggest a close relationship between the surface energy and blood compatibility. Endothelial cells cultures reveal better proliferation and anti-platelet adhesion on the coatings compared to the titanium alloy control and the Ti–Si–N coating with 20 at% Si exhibits excellent endothelialization.

We present a systematic study of the structural and electronic properties of Cu N @( n ,0) ( N =1, 2, 4 for n =6, 7, 8 and N =12, 16 for n =10) combined systems using the first-principle calculations. We find that CuNWs encapsulated inside the (6,0) CNTs prefer to form a single linear chain on the tube axis, while those in (7,0) and (8,0) CNTs tend to form a zigzag chain. The smaller formation energies of −2.265 eV for Cu 12 @(10,0) combined system and −2.271 eV for Cu 16 @(10,0) combined system indicate that these two systems are more stable than the other systems studied here, and more complex configurations of CuNWs are expected encapsulating into broader CNTs. Besides having high stability, the Cu 16 @(10,0) combined system with quantum conductance of 3 G 0 is under the protection of the outer (10,0) CNT from oxidation, thus can be expected to have potential applications in building nanodevices. The asymmetry distribution of the down-spin and up-spin channels results in a net magnetic moment of 0.59μB for the Cu 2 @(7,0) combined system.

Ce-incorporated apatite (Ce-HA) nano-scale particles with different Ce percentage contents (atomic ratio of Ce to Ce + Ca is 5%, 10% and 20%, respectively) were synthesized via a simple wet chemical method in this study. The crystal structure, chemical groups, thermal stability, crystal morphologies and crystal sizes of the Ce-HA nano-particles were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and transmission electron microscopy (TEM). The influences of reaction temperature, reaction time, pH value, and the atomic ratio of Ce to Ce + Ca on the structure and performance of Ce-HA particles were studied. The results show that the lattice constants, particle sizes, crystallinity and thermal stability of Ce-HA vary with the doped Ce contents. With the increase of Ce content, the lattice constants of the Ce-HA nano-particles remarkably increase but the particle size, crystallinity and thermal stability gradually decrease. The reaction temperature as well as the reaction time has no significant effect on the properties of the final products, while the pH value has a direct relationship with their final chemical composition. The obtained Ce-HA nano-size particles possess potential application in preparing artificial bone implants, bone tissue engineering scaffold and other bioactive coatings.

The strain rate sensitivity (m) and activation volume (v⁎) of three nanocrystalline (NC) body-centered cubic (bcc) metals, i.e., W, Mo and Ta, with various grain sizes were evaluated by nanoindentation testing. Opposite to the conventional trend that NC bcc metals exhibit reduced m as the grain size was decreased, elevated m was observed as the grain size was reduced from ~90 nm to ~30 nm for all the samples concerned. It was proposed that the unusual variation trends of m for NC bcc metals were dominated by GB-related mechanisms when the grain size drops below a critical value.

The symmetry and electronic properties of armchair graphene nanoribbons (AGNRs) have been investigated using density functional theory calculations. For the shear strained AGNRs, the D6h (6/mmm) symmetry of the hexagonal lattice further turns into 2/m. The stability improves with increasing ribbon width under the same shear strain. Besides, the modification of the energy gap under shear strain is weak.

Misfit strain relaxation-induced morphology instability is usually observed in epitaxial heterostructures at high temperatures. In this paper, we report that this morphology instability can occur even at room temperature in epitaxial ZnO/AZO (Al-doped ZnO) core–shell nanowires (NWs). As a result, densely distributed ZnO nanodots (NDs) were self-assembled on the NWs. The growth of NDs was slowed down during aging owing to the gradually reduced misfit strain. The final size and shape of the NDs were highly depended on the shell thickness and the doping ratio. It was proved that the morphology stability could be improved by surface passivation, thinning the shell thickness, or lowering the doping ratio. The results may provide instructive suggestions for the reliable design in strain and surface engineering of nanomaterials.

Using the first-principles projector augmented wave potential within the generalized gradient approximation, we investigate the magnetic and electronic properties in the bulk and (001) surface of the Heusler alloy Ti2MnAl with Hg2CuTi-type. For the bulk, our calculations indicate that the Heusler alloy Ti2MnAl exhibits antiferromagnetic half-metallicity at the equilibrium lattice constant. Owing to the surface effects, the half-metallicity which can be observed in bulk is destroyed in five terminations. The high spin polarization only maintains in TiMn-termination. Through further studies on the atomic magnetic moments, we find that the moment of surface Ti1 is enhanced obviously, as well as the absolute value of surface Mn atomic moment.

Nano-layered films of Cu/Cu(Zr)/Zr(Ge) and Cu/Cu(Zr) were deposited on the p-SiOC:H/Si substrates by RF magnetron sputtering in Ar. Samples were subsequently annealed at temperatures ranging from 350-500^oC in vacuum, and characterized by four-point probe technique (FPPT), glancing incident angle X-ray diffraction (GIXRD), Auger electron spectroscopy (AES) and transmission electron microscopy (TEM), respectively. Results indicated that these samples have a high thermal stability and favorable electrical property when the Ge content in the Zr(Ge) nano-interlayer ranged from 26% to 79%. The fundamental relationship between the alloy content of the Zr(Ge) nano-interlayer and the property of the Cu/Cu(Zr)/Zr(Ge)/SiOC:H/Si film stacks was established, and the critical temperature of the self-formed ZrO"x/ZrSi"yO"x barrier formation was also revealed.

First-principles nonmagnetic calculations reveal a metallic character in zigzag SiGe nanoribbons (ZSiGeNRs) regardless of their width. The partial DOS projected onto the Si and Ge atoms of ZSiGeNR shows that a sharp peak at the Fermi level is derived from the edge Si and Ge atoms. The charge density contours show the Si–Ge bond is covalent bond, while for the Si–H bond and Ge–H bond, the valence charges are strongly accumulated around H atoms due to their stronger 1 s potential and the higher electronegativity of 2.20 than that of 1.90 for Si atom and 2.01 for Ge atom, so that a significant charge transformation from Si or Ge atoms to H atoms and thus an ionic binding feature. Spin–polarization calculations show that the band structures of ZSiGeNR are modified by the dangling bonds. Compared with perfect ZSiGeNR which is a ferrimagnetic semiconductor, the bands of the ZSiGeNRs with bare Si edge, bare Ge edge, and bare Si and Ge edges shift up and nearly flat extra bands appear at the Fermi level. The ZSiGeNR with bare Si edge or bare Ge edge is a ferrimagnetic metal, while ZSiGeNR with bare Si and Ge edges is a nonmagnetic metal.

The micrographs and optical properties of Al-doped ZnO (AZO) films deposited by radio frequency (RF) magnetron sputtering are presented in this paper. The AZO films termed as films I, II and III were sputtered on glass substrates heating at 300C, 400C and 500C, respectively. The micrographs, crystal structures and optical properties of AZO thin films were analyzed by using scanning electronic microscopy (SEM) images, X-ray diffraction (XRD) pattern, optical transmission and reflection spectra ranging from 350 to 1000 nm. As the substrate temperature increases to 500C, the film III exhibits a better flatness surface and a larger grain size of ~25nm with a stronger c-axis orientation. The film II has a high transmittance of greater than 92% in the visible light region. We also show that the films II and III have significant red-shift band gap ~3.00 and ~3.13eV, respectively, in comparison with that of the film I (3.31eV). This might be due to the increasing doped Al atoms which do not activate due to segregation at the grain boundaries.

Adsorption of molecular chlorine (Cl2) on intrinsic and B-, Si-, Cr-, Cu-, Fe-, Mn-, Ni-, Ti- and Au-doped graphene was theoretically studied using first-principle approach based on density functional theory in order to develop their potential applications as Cl2 gas sensors. The structural, electronic and magnetic properties of the graphene-molecule adsorption adducts are strongly dependent on the dopants. Cl2 molecule is adsorbed weakly on intrinsic and B-doped graphene; in general, strong chemisorption is observed on Si-, Cr-, Cu-, Fe-, Mn-, Ni-, Ti- and Au-doped graphene. The most stable adsorption geometries, energies, magnetic moments, charge transfers and density of states of these systems are thoroughly discussed. This work reveals that the sensitivity of graphene-based chemical gas sensors for Cl2 can be drastically improved by introducing appropriate dopant, and Ti as well as Au is the best choice among all the dopants.

The structural, energetic and electronic properties of chiral (n, m) (3⩽n⩽6, n/2⩽m⩽n) single-wall copper nanotubes (CuNTs) have been investigated by using projector-augmented wave method based on density-functional theory. The (4, 3) CuNT is energetically stable and should be observed experimentally in both free-standing and tip-suspended conditions, whereas the (5, 5) and (6, 4) CuNTs should be observed in free-standing and tip-suspended conditions, respectively. The number of conductance channels in the CuNTs does not always correspond to the number of atomic strands comprising the nanotube. Charge density contours show that there is an enhanced interatomic interaction in CuNTs compared with Cu bulk. Current transporting states display different periods and chirality, the combined effects of which lead to weaker chiral currents on CuNTs.

Using the first-principles calculation, we investigate the structural and electromagnetic properties of the zigzag edge Si nanoribbons (ZSiNRs) decorated with double C chains. The results show that double C chains decorated ZSiNRs are always metallic independent of the ribbon width. The defect states contributed from double C chains are composed of two degenerated bands across the Fermi level. The perfect ZSiNR has a FM ground state, while double C chains decorated one have an AFM ground state. The C chains are always close to straight ones thereby resulting in a transverse contraction near the C chains and thus the ribbon width. The C–Si bond displays an ionic binding feature and the C–H bond is a typical covalent one because of the electronegativity and the bound force difference between H, C and Si atoms.

We theoretically investigate the structures, relative stabilities and electronic properties of the armchair graphene nanoribbons (AGNRs) under uniaxial strain via first-principles calculations. The results show that, although each bond length decreases (increases) with increasing compression (tension) strain especially for the axial bonds a1, a4 and a7, the ribbon geometrical width d increases (decreases) with increasing compression (tension) strain due to the rotation of the zigzag bonds a2, a3, a5 and a6. For each nanoribbon, as expected, the lowest average energy corresponds to the unstrained state and the larger contract (elongate) deformation corresponds to the higher average energy. At a certain strain, the average energy increases with decreasing the ribbon width n . The average energy increases quadratically with the absolute value of the uniaxial strain, showing an elastic behavior. The dependence of the band gap on the strain is sensitive to the ribbon width n which can be classified into three distinct families n =3 I , 3 I +1 and 3 I +2, where I is an integer. The ribbon width leads to oscillatory band gaps due to quantum confinement effect.

The effect of antisite, swap and vacancy defects on the magnetic properties and spin-polarization of the full-Heusler Ti 2 FeAl alloy with the Hg 2 CuTi-type structure is studied by using the first-principles calculations within density functional theory. The perfect Ti 2 FeAl Heusler alloy exhibits a ferromagnetic half-metallic behavior with the total magnetic moment of 1 µ Β and indirect band gap of 0.543 eV. Among swap defect, only the total magnetic moment of the Ti 2 –Al swap defected is close to the perfect alloy. All defected structures destroy the half-metallicity and only Al Ti1 and Al Ti2 antisite and Fe vacancy defects maintain relatively high spin polarization.