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Determining atomic structure of intercalated metallic layer under graphene is a hot-topic due to the potential applications in electronic engineering. In this study, Pb-intercalated graphene (PbG) is fabricated on SiC substrate and the atomic structure and electronic properties of the intercalated Pb atoms underneath graphene are investigated by scanning tunneling microscopy/spectroscopy (STM/STS). As the crystal facet of intercalated Pb atoms can be arranged in (111) (unit cell, 0.35 nm × 0.35 nm) and (110) (unit cell, 0.61 nm × 0.35 nm), mottled moire pattern (period, 2.5 nm) and striated moire pattern (period, 2.1 nm) are formed. Atomic arrangement of the intercalated Pb is sensitive to tip scanning resulting in the conversion of the two moire patterns. Nevertheless, the crystal orientation of moire patterns is always aligned with zigzag direction of graphene. As revealed by STS, PbG performs the similar electronic states to those of free-standing graphene due to the shielding effects of Pb intercalation. The crystallographic relationship between graphene and Pb atoms is also confirmed by density functional theory (DFT) calculations. The study provides crucial for understanding the structure of intercalated Pb atoms underneath a graphene layer, which may enable the development of new 2D materials capped by graphene.

Polyethylene terephthalate (PET) as one of the main crude oil-based derivatives, produces a significant amount of waste that is difficult to degrade. Currently, microbial degradation of PET is an eco-friendly, efficient, and economical method. This study was conducted to propose a novel screening strategy for PET-degrading bacteria, and evaluate their degradation efficiency of PET. Two strains, Pseudomonas nitroreducens S8 and Pseudomonas monteilii S17, were isolated and could utilize PET as a carbon source by co-culture. The combined use of both bacteria gave a synergistic effect on the disruption of the PET surface through colonization behavior, which could enhance the subsequent degradation of PET. Its time of reaching a peak value of PET degradation rate (94.5% at 6 d) was 2 days earlier than these of single bacteria. A similar synergistic effect was also observed in the metabolization of PET monomers, and the metabolic rate was expressed as 82.4% of bis (2-hydroxyethyl) terephthalate (BHET), 64.0% of mono (2-hydroxyethyl) terephthalate (MHET), and 20.0% of terephthalic acid (TPA), respectively. This study is novel in showing the degradation of PET waste by combinations of bacterial pretreatment and enzymatic treatment, which can be a promising method.

It is reported that indium-coated SiC buffer layer can be directly transferred into graphene layer during low temperature annealing, forming as indium-intercalated graphene (InG). Atomic structures of InG as well as transformation mechanism are investigated by scanning tunneling microscopy (STM), Raman and X-ray photoelectron spectroscopy (XPS). InG on top of one-layered intercalated indium (called O-InG) exhibits Moire patterns with period of 3.2 nm, and the atomic arrangement of indium atoms is detected. While, no Moire patterns are observed on InG intercalated by two-layer of indium atoms (called T-InG). Both the two InG regions bind perfectly with the already existing epitaxial graphene (EG), exhibiting as an unbroken sheet of quasi-free-standing graphene layer. This finding provides a simple strategy and benefits to industrial fabrication of large-scale InG with regular SiC steps.

As a novel surface strengthen technology laser cladding was widely used in surface engineering. In this work, Ni60 + 25%WC + 10%TiC composite coatings were fabricated on the TC4 by laser cladding technology. Field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and frictional wear were used in the study of coatings. The results showed that dendrites is the main crystal type in the coatings, there were some bulk type crystal generated in 400 mm/min scanning speed. XRD results showed that some of the metalloceramics phases, such as TiC, VC, WC were formed in the coatings, some of the intermetallic compounds such as AlNi3, Al0.96B0.04Ni3, NiTi and C0.12Fe1.88 also formed, which improving the hardness, and the hardness tests results showed that the hardness of the coatings increased by 300% compared to the substrate, of above 1100 HV0.3. The max friction coefficient in 600 mm/min was 0.39, because of the unmelted TiC and WC particles fallen off from coatings, so the mechanism of the coating was abrasive wear. The friction coefficient is decreased to 0.11 and 0.19 when the scanning speed is 500 mm/min and 400 mm/min, respectively.

Developing approaches to effectively manipulate the magnetic states and phase transition is critical to the application of transition metal dichalcogenides (TMDs) in spintronic or phase-switching d...

Sub-monolayer TiO2 over-layers were deposited on SnO2 nanowires (NWs) by atomic layer deposition. X-ray photoelectron spectroscopy, Mott–Schottky plots and photoluminance spectra were used to investigate the band structure and the separation of electron–hole pairs at the SnO2/TiO2 interface. The results showed that the valence band maximum of SnO2 NWs shifted to lower binding energies after functionalization, and significant upward band edge bending at the interface was confirmed. The rearrangement of energy band accelerated the separation of photo-generated electron–hole pairs leading to the improvement of photocatalytic degradation rate of methyl orange (MO, C14H14N3NaO3S) under UV irradiation.

Titanium carbide (TiC) coatings were fabricated by laser cladding on Ti-6Al-4V alloy with TiC and carbon nanotube (CNT) mixed powders. Scanning electron microscope (SEM) with energy dispersive spec...

To clarify the effect of amorphous/amorphous (A/A) interfaces during ion irradiation, the He ion irradiation responses of ZrCu/ZrCuNiAlSi A/A nanolaminates (A/ANLs) as well as ZrCu and ZrCuNiAlSi single-layered amorphous thin films were examined. The results showed the A/ANLs exhibited superior irradiation resistance compared with the corresponding single-layered thin films, as the former possessed better microstructure stability and higher He ion solubility than the latter during He ion irradiation. Besides, A/ANLs having more interfaces exhibited even better irradiation resistance than those having less. The enhanced irradiation resistance of A/ANLs was attributed to the sink effect of A/A interfaces, which effectively reduced the amount of radiation-induced “defects” and He bubbles.

Although high-energy facets on metal oxides are usually active and preferred for gas sensing, it is difficult to expose them according to thermodynamics. In this work, nanocomposites of SnO2 and graphene are prepared by a hydrothermal method. The SnO2 nanoparticles change from a lance shape to an octahedral shape as the concentration of HCl in the solution is increased gradually from 6.5 to 10 vol %. However, the SnO2 nanoparticles have an elongated octahedral shape if the concentration of HCl is increased further. The octahedral SnO2 nanoparticles are mainly surrounded by high-surface-energy {221} facets, thus facilitating gas sensing. First-principles calculation shows that the surface energy and adsorption energy of the {221} facets are larger than those of the stable {110} facets, and so, the gas adsorption capacity on the {221} facets is better. Furthermore, because the Fermi level of the SnO2{221} facet is higher than that of graphene, the electrons are transferred from SnO2 nanoparticles to graphene sheets, enabling effective electron exchange between the composite and external NO2 gas. The excellent gas-sensing properties of the octahedral SnO2/graphene composites are ascribed to the high-surface-energy {221} facets exposed.

Free volume gradient was introduced using intermittent magnetron sputtering processes to fabricate two different series of CuZr/CuZr metallic glass multilayers, forming heterogeneous atomic structure in glass/glass interfaces. Multilayers in series 1 have identical bi-layer thickness but different modulation ratios, while those in series 2 have the modulation ratio of 1/1 but different bi-layer thicknesses. Nanoindentation was subsequently carried out to evaluate the shear banding deformation of the fabricated multilayers. Despite that all the multilayers were only consisted of a single monophase (i.e., CuZr metallic glass), their shear banding deformation behaviors were dependent upon both the modulation ratio and bi-layer thickness. Upon annealing treatment, such dependence nearly vanished in both series of the multilayers. It was proposed that free volume gradient plays a crucial role in the observed unusual shear banding deformation behaviors. Specifically, asymmetric and symmetric free volume gradients in series 1 and 2, respectively, induce different stress states in glass/glass interfacial regions, which may alter the initiation and propagation processes of shear bands in CuZr/CuZr multilayers.

Two-phase flow regime identification in a horizontal pipe was realized based on the liquid phase velocity information and the machine learning method. Ultrasound Doppler velocimetry was employed to measure the liquid velocity. Statistical features extracted from the velocity time series data, such as mean, root mean square, and power spectral density, were used to realize real-time flow regime identification. In addition, two novel parameters—maximum velocity ratio and maximum velocity difference ratio—were proposed to identify plug and decaying slug flow. Different classification algorithms were employed to achieve a high identification accuracy. Moreover, transient flow regime identification with a fast response was realized based on two classification algorithms—long–short term memory and convolutional neural network. The results show that the accuracy of real-time flow regime identification based on a flow regime map can reach up to 93.1% using support vector machine, the maximum velocity ratio and maximum velocity difference ratio are effective in identifying plug and decaying slug flow, and transient flow regime identification under slug flow condition can be realized with an accuracy of 94% based on a convolutional neural network (CNN). Decaying slugs with long lengths confuse the CNN and are responsible for the error in identification. The results presented herein are expected to expand the available knowledge on two-phase flow regime identification.

To surmount the issues of a limited specific surface area and slow electrolyte diffusion in composite electrocatalysts, three-dimensional (3D) porous hollow nanocubes are fabricated, in which bimetal Ni–Co phosphide composites are covered with nanoparticles. The abundant hollow space provides more active sites for the catalyst, and simultaneously ensures efficient mass transfer and electron transport during the hydrogen evolution reaction (HER). A plasma-assisted approach is employed for smart N-doping in the Ni–Co phosphide hollow nanocubes (N–Ni–Co–P HNCs). The N–Ni–Co–P HNC catalyst exhibits a remarkable HER performance in 1 M KOH, evidenced by the low overpotentials of 47.9 mV and 150.5 mV at the current density of 10 mA cm−2 and 50 mA cm−2, respectively, as well as the excellent long-time stability. Essentially, the N doping tailors the electronic states and optimizes the free energy of hydrogen adsorption (ΔGH*) greatly, and the 3D porous hollow structure with porous nanoparticles stacked enlarges the specific active area substantially. Their synergistic effects result in the remarkably enhanced catalytic activity for the HER.

ObjectiveTo examine the protective effects of appropriate personal protective equipment for frontline healthcare professionals who provided care for patients with coronavirus disease 2019 (covid-19).DesignCross sectional study.SettingFour hospitals in Wuhan, China.Participants420 healthcare professionals (116 doctors and 304 nurses) who were deployed to Wuhan by two affiliated hospitals of Sun Yat-sen University and Nanfang Hospital of Southern Medical University for 6-8 weeks from 24 January to 7 April 2020. These study participants were provided with appropriate personal protective equipment to deliver healthcare to patients admitted to hospital with covid-19 and were involved in aerosol generating procedures. 77 healthcare professionals with no exposure history to covid-19 and 80 patients who had recovered from covid-19 were recruited to verify the accuracy of antibody testing.Main outcome measuresCovid-19 related symptoms (fever, cough, and dyspnoea) and evidence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, defined as a positive test for virus specific nucleic acids in nasopharyngeal swabs, or a positive test for IgM or IgG antibodies in the serum samples.ResultsThe average age of study participants was 35.8 years and 68.1% (286/420) were women. These study participants worked 4-6 hour shifts for an average of 5.4 days a week; they worked an average of 16.2 hours each week in intensive care units. All 420 study participants had direct contact with patients with covid-19 and performed at least one aerosol generating procedure. During the deployment period in Wuhan, none of the study participants reported covid-19 related symptoms. When the participants returned home, they all tested negative for SARS-CoV-2 specific nucleic acids and IgM or IgG antibodies (95% confidence interval 0.0 to 0.7%).ConclusionBefore a safe and effective vaccine becomes available, healthcare professionals remain susceptible to covid-19. Despite being at high risk of exposure, study participants were appropriately protected and did not contract infection or develop protective immunity against SARS-CoV-2. Healthcare systems must give priority to the procurement and distribution of personal protective equipment, and provide adequate training to healthcare professionals in its use.

Ultrahigh hardness (yield strength) was achieved in magnetron sputtering nanoscale Cu/Al multilayers upon annealing. The microstructure and mechanical properties of the multilayers were systematically investigated by X-ray diffraction, transmission electron microscopy, energy dispersive X-ray spectroscopy and nanoindentation. Annealing promoted diffusion of Cu and Al atoms in the interfaces and the sharp interface turned to mix, resulting in the formation of Cu/Al intermetallic compounds and its deformation at nanoscale. The Cu/Al intermetallic compounds mainly including Al2Cu grew toward to Al layers and would reducing the effective length between the reduced adjacent layers. As the annealing temperature was increased from 100 °C to 500 °C, various kinds and larger size Cu/Al intermetallic compounds emerged, causing the hardness to first increase, reaching an unusually high peak (never reached before in other thin metallic multilayer systems), and then remain nearly unchanged. The physical mechanisms underlying such remarkable enhancement were explored in terms of interface alloying, reduced layer thickness and grain size effects.

The creep behavior of nanocrystalline body-centered cubic Mo thin films was evaluated using nanoindentation testing. The creep rate and the corresponding strain rate sensitivity (m) were found to be strongly dependent upon indentation size and loading strain rate (LSR). Other than the mechanism of diffusion along indenter tip-sample interface previously proposed for face-centered cubic metals and metallic glasses, alternative mechanisms involving surface effect enhanced screw dislocation activities, inverse indentation size effect of hardness and LSR dependent microstructural and stress states, were proposed to interpret the observed dependence of penetration depth and LSR of m.

The microstructure evolutions of Cu/Ru multilayered films with equal individual layer thickness h ranging from 1.5 nm to 200 nm were investigated. Based on systematic X-ray diffraction and transmission electron microscopy analyses, as h was varied, structure transition between face-centered cubic and hexagonal close-packed lattice was observed in Ru constituent layer. This structure transition was found to influence the length-scale dependent cracking behavior and fracture toughness of the Cu/Ru multilayers. In direct contrast to previous study that fracture toughness would decrease dramatically when h was reduced below 25 nm, the fracture toughness of Cu/Ru multilayer increased monotonically as h was as small as 1.5 nm. Along with the reduction of h, the coupling effects from the increased interface transparency as well as lattice structure transformation were considered as the main reasons for the enhanced toughness. In this way, the fracture toughness between fcc/hcp multilayers with structure transformation and fcc/bcc multilayers without structure transformation had been compared and discussed in detail.

Heterointerface in a nanoscale metallic layered composite could improve its crack resistance. However, the influence of metallic interface structures on crack propagation has not been well understood at atomic scale. By using the method of molecular dynamics (MD) simulation, the crack propagation behavior in Cu-Nb bilayer is compared with that in Cu-Ni bilayer. We find that the weak Cu-Nb interface plays an important role in hindering crack propagation in two ways: (i) dislocation nucleation at the interface releases stress concentration for the crack to propagate; (ii) the easily sheared weak incoherent interface blunts the crack tip. The results are helpful for understanding the interface structure dependent crack resistance of nanoscale bicrystal interfaces.

The rational design and preparation of earth-abundant, stable and efficient electrocatalysts for hydrogen production is currently the subject in extensive scientific and technological researches toward the future of a clean-energy society. Herein, a mace-like MoS2/NiCo2S4 hierarchical structure is designed and synthesized on carbon fiber paper via a facile hydrothermal method, and evaluated as electrocatalyst for hydrogen evolution reaction. In the MoS2/NiCo2S4/carbon fiber paper hierarchical structures, MoS2 nanosheets are dispersively distributed on the surface of NiCo2S4 nanowires, which provides an enlarged surface area, abundant interfaces and catalytic active sites. As for hydrogen evolution reaction, such MoS2/NiCo2S4/carbon fiber paper heterostructures give rise to a hydrogen evolution reaction catalytic current density of 10 mA cm−2 with a lower overpotential of 139 mV and a smaller Tafel slope of 37 mV·dec−1 than those of MoS2/carbon fiber paper and NiCo2S4/carbon fiber paper counterparts, exhibiting a prominent electrocatalytic performance. Moreover, the electrocatalytic properties change little after 5000 CV cycles and continual electrolysis for 12 h without obvious decay, respectively, demonstrating high durability and stability. The excellent hydrogen evolution reaction performances endow the hierarchical configuration MoS2/NiCo2S4/carbon fiber paper with promising alternative in HER and other related renewable energy fields.

Ferromagnetic (FM) two-dimensional (2D) transition metal dichalcogenides (TMDs) have potential applications in modern electronics and spintronics and doping of TMDs with transition metals can enhance the magnetic characteristics. In this work, the structural stability, electronic states, and magnetic properties of Mn-doped monolayer/bilayer MoS2 are studied systematically by first-principles calculations. Substitutional Mn dopants at the Mo sites are energetically favorable in both monolayer and bilayer MoS2 under the S-rich condition which is common in the synthesis of MoS2 nanosheets. Two Mn dopants participate in the FM interaction in monolayer MoS2 and magnetic coupling of two Mn dopants via the double-exchange mechanism can be mediated by the nearest neighboring S. Magnetic coupling can be ascribed to the competition between the double-exchange, direct-exchange, and super-exchange interactions, which take place between two Mn dopants in bilayer MoS2 with the MniMnMo, MniMnS and MnMo–MnMo configurations. Our results reveal the geometrical dependence of magnetic-exchange coupling suggesting that Mn-doped monolayer/bilayer MoS2 has large potential in spintronic devices.

Monoclinic vanadium dioxide VO2 (M) with hexagonal structure is synthesized by hydrothermal method, and the phase evolution is evidenced. Interestingly, the hexagonal morphology comes into being as a result of the low-energy coherent interfaces, (21)1//(2)2 and (2)1//(020)2. The size of hexagonal particles is well controlled by changing the concentration of precursor solutions. Hexagonal particles exhibit excellent thermochromic properties with a narrow hysteresis of 5.9 °C and high stability. In addition, the phase transition temperature can be substantially reduced down to 28 °C by simply W doping.

The dependence of microstructure, hardness (H) and strain rate sensitivity (m) of nanocrystalline (NC) body-centered cubic Nb thin films at various annealed temperature were experimentally evaluated. The annealed temperatures ranged from 100 to 400 °C, and kept for 30 min respectively. Despite nearly unchanged grain sizes upon annealing, the strengthening effect was observed in nanoindentation hardness testing as annealing temperature was increased above 200 °C. In particular, the strain rate sensitivity of NC Nb increased significantly after annealing at 100 °C and slightly decreased at higher annealing temperatures. Competitive mechanisms underlying the different variation trends of hardness and strain rate sensitivity of NC Nb annealed in the two different temperature regimes were proposed.

Ta/Zr 61 Cu 17.5 Ni 10 A l7.5 Si 4 crystalline/amorphous (C/A) nanolaminates with different Ta and ZrCuNiAlSi layer thicknesses were deposited by magnetron sputtering on both Si and polyimide substrates. Nanoindentation and uniaxial tensile tests were separately performed to study their size-dependent hardness and plasticity. Tensile plasticity was evaluated by considering both the tensile cracks and nanoindentation morphologies observed under scanning electron microscope (SEM). C/A nanolaminates with crystalline layer thickness of 40 nm and amorphous layer thickness of 5 nm exhibited the best tensile plasticity, which was much better than pure Ta and Zr 61 Cu 17.5 Ni 10 A l7.5 Si 4 monolayers. For nanolaminates having identical Ta layer thickness, the hardness always increased with decreasing amorphous layer thickness. Combined with cross-sectional high resolution transmission electron microscopy (HRTEM) observation, the size-dependent deformation mechanisms of C/A nanolaminates were discussed.

The adhesion of coating to substrate is an important factor governing the performance and durability of coated engineering components. Existing evaluation methods cannot produce quantitative measurement of bonding strength for strong adherent coating. This paper proposes a novel evaluation method based on the cyclic spherical indentation (CSI) test, which uses successive indentations of a spherical ball onto a coated specimen to induce the detachment of the coatings along the interface. Compared with earlier methods, this method creates only adhesive failures, which only occur during elastic deformation of the substrate, yet it is applicable to coating with strong bonding. The evaluation method creates a curve of shear stress range versus failure cycles for each coating/substrate system. These curves can be used directly to compare the bonding strength of hard coatings.

The effect of thin coating on the strength, plasticity and resistance to annealing-induced embrittlement was investigated for Zr 50.7 Cu 28 Ni 9 Al 12.3 bulk metallic glass (BMG). To maintain the BMG structure in the most extent, very thin amorphous CuZr and crystalline W coatings were used. The crystalline coating performed much better in improving BMG plastic deformation than the amorphous one, for its superior retarding effect on shear band (SB) dynamics. Besides the coatings, softer layers near the sputtered surfaces also contributed to the enhanced plasticity of the coated BMG. The presence of these softer layers also led to the slightly lower strength of both amorphous CuZr and crystalline W coated BMGs relative to the uncoated ones. The BMG with crystalline W coating exhibited much better resistance to annealing-induced embrittlement than the amorphous CuZr-coated and uncoated ones, due to its much enhanced decomposition processes upon annealing. These experimental results provide useful guidance on choosing suitable coating materials to elevate BMG plasticity and avoid annealing-induced embrittlement.

In order to study the intrinsic size effect of nanolaminates with unequal modulation ratios, CuTa/Cu nanolaminates with identical Cu layer volume fraction but different Cu layer thicknesses were prepared by varying the number of Cu layers. The hardness and indentation morphology of each CuTa/Cu nanolaminate was characterized by means of nanoindentation and scanning electron microscope. Furthermore, the microstructures of CuTa/Cu nanolaminates with different interfacial configurations were examined under high resolution transmission electron microscopy. The deformation of CuTa/Cu nanolaminates was found to be dominated by the thickness ratio between CuTa and Cu layers as well as the interfacial microstructure.

Nanoscale amorphous CuZr/crystalline Cu multilayers were synthesized to study their strain rate sensitivity and plastic deformation mechanisms via nanoindentation testing. Despite the dramatically reduced microstructural length scale, nearly constant strain rate sensitivity of the multilayers was obtained at a wide range of individual layer thickness (10~100 nm). The scenarios that the two constituent layers mutually confined by each other might exhibit quite different strain rate sensitivities relative to the monolithic ones were proposed. Specifically, compared with the monolithic Cu and CuZr layers, respectively, the confined Cu layers should exhibit gentler increases in strain rate sensitivity while confined CuZr layers exhibit reduced strain rate sensitivity, as Cu layer thickness decreases. Correspondingly, corresponding deformation mechanisms accommodating the co-deformation of the two constituent layers were discussed in detail.

Atomic scale study of the character and motion of dislocations in Al 2 Cu will provide insights into understanding the superior mechanical properties of Al Al 2 Cu alloys. Using atomistic simulations, we studied seven potential slip systems (110) 〈 001 〉 , (010) 〈 001 〉 , (310) 〈 001 〉 , (010) 〈 100 〉 , (110) 〈 1 1 ¯ 0 〉 , (110) 1 2 〈 1 1 ¯ 1 〉 and (112) 1 2 〈 1 ¯ 1 ¯ 1 〉 in Al 2 Cu with body centered tetragonal structure. We found that three edge dislocations with Burgers vector 〈 001 〉 on glide planes (110), (010), and (310), show an extended core and are predicted to be glissile at room and moderate temperatures. Other four edge dislocations associated with slip systems (010) 〈 100 〉 , (110) 〈 1 1 ¯ 0 〉 , (110) 1 2 〈 1 1 ¯ 1 〉 and (112) 1 2 〈 1 ¯ 1 ¯ 1 〉 and three screw dislocations with Burgers vectors 〈 001 〉 , 〈 110 〉 , and 1 2 〈 1 ¯ 1 ¯ 1 〉 show a condensed core, and exhibit significantly higher Peierls barrier for glide at room temperature. Furthermore, the interaction of dislocation dipole associated with slip system (110) 〈 001 〉 results in the climb of the extended-core dislocation at room temperature through three stages: the extended core condenses, the leading partial dislocation climbs accompanying the creation of vacancies (resulting in a non-planar core), and the two partials with non-planar core collectively glide on the neighboring slip planes associated with atomic shuffles.

Annealing-induced embrittlement in metallic glasses (MGs) due to the running off of free volume (FV) is detrimental to their practical applications. By adding crystalline W coatings, we demonstrated that the majority of free volume (FV) could be preserved and redistributed in a Zr50.7Cu28Ni9Al12.3 bulk metallic glass (BMG) upon annealing as, thermodynamically, it was unfavorable for the FV to migrate from BMG into crystalline W. Correspondingly, the strength and ductility of the BMG were both enhanced relative to as-cast ones, due likely to decomposition processes such as the formation of Zr- and Cu-rich clusters in the BMG. The results of this study may be applied to avoid annealing-induced embrittlement in BMGs and construct a simple yet effective method to elevate both the strength and ductility of BMGs. Keywords: Bulk metallic glass, Crystalline coating, Annealing, Relaxation, Free volume

The spin-polarized first-principles calculations are performed to study the structural, electronic and magnetic properties of a single and two identical transition metal (TM) atoms X (X = V, Cr, Mn, Fe, Co and Ni) doped ZnS dilute magnetic semiconductors (DMS). The single V-, Cr-, Fe- and Ni-doped ZnS systems exhibit the magnetic half-metallic (HM) characters, while Mn- and Co-doped ZnS systems display magnetic semiconducting characters. For two identical TM atoms doped ZnS systems, the two identical V, Cr and Ni atoms are in a ferromagnetic (FM) coupling under the double-exchange (DE) mechanism, leading V-, Cr- and Ni-doped ZnS systems to be HM with FM coupling. While two identical Mn- and Co-doped ZnS systems are semiconductors with antiferromagnetic (AFM) coupling consisting with the superexchange (SE) mechanism. Specifically, two identical Fe atoms display a competition between the SE and DE mechanisms. The Zn 70 Fe 2 S 72 system is metal with AFM coupling at the nearest separation of two Fe atoms while HM with FM coupling at the farther separations of two Fe atoms.

To clarify the real size of shear transformation zone (STZ) and its correlation with the plasticity of metallic glass, STZ sizes of a Zr-based bulk metallic glass (BMG) in three different structural states (as-cast, annealed and confining annealed) were examined using both rate-change and statistical methods upon nanoindentation. STZ sizes (less than 24 atoms) obtained by the statistical method approached the real STZ size of very few atoms, and showed no correlation with BMG plasticity. In sharp contrast, STZ sizes (hundreds of atoms) obtained by the rate-change method not only were much larger than the real STZ size but also exhibited a positive correlation with BMG plasticity. These discrepancies were discussed in terms of the structural evolution of BMGs upon nanoindentation.

Metal oxides with high-energy facets usually have more active surface sites to facilitate gas adsorption. In this work, the ZnO/graphene composites are synthesized hydrothermally and the morphology of ZnO nanoparticles can be changed from nanorods to nanoplates with the high-energy {0001} polar surface exposed by changing the density of sodium citrate in the reaction. The ZnO{0001}/graphene composites have better sensing properties to NO2 at room temperature (RT). Based on first-principles calculation, the adsorption energy of NO2 on the ZnO{0001} facet is more negative than that on the {01 1 ¯ 0} surface indicating stronger interactions between the former and NO2. Furthermore, the ZnO{01 1 ¯ 0} surface shows semiconducting characteristics, whereas the ZnO{0001} polar surface is metallic. The metallic characteristics promote charge transfer at the interface between ZnO and graphene and enhance the NO2 detection sensitivity.

The development of slug flow along a horizontal pipe was quantitatively investigated through particle image velocimetry. Quantitative information is essential to understand the hydraulic behavior of the slug flow and is a reference for numerical simulations. The flow in the horizontal pipe of 11.5 m length and 0.051 m diameter was maintained in a fully turbulent condition with 0.41 m/s gas superficial velocity and 0.50 m/s liquid superficial velocity. PIV measurement was carried out at three locations along the pipe, and a sophisticated ensemble averaging technique was applied to obtain the statistical flow properties. Morphological analysis revealed the unsteadiness of Taylor bubble and variation of bubble population in the slug region. From the velocity information, the similarity of velocity fields in the slug body and tail is found. In addition, the occurrence of local maximum velocity and an increase of the mixing eddy length in the slug nose were observed. Moreover, a modified 1D mixture model to predict the slug translational velocity was proposed based on the local maximum velocity in the slug tail. We believe this study clearly shows the strength of PIV method to improve the understanding of physics in the slug flow.

Controllable degradation behavior of hydroxyapatite (HA) plays a crucial role in successful long-term implantation of a bone tissue substitute. In this study, electron beam irradiation (EBI) was carried out as an efficient strategy to modify HA structure. The degradation characteristics, bioactivity and cell response of the irradiated HA were comprehensively evaluated. The results showed that EBI with absorbed dose of 3.42, 10.27 and 20.54 Gy did not introduce newly-formed phase or impurity, but created crystal defects and nanovoids, which were formed from oxygen deficiencies, into HA lattice with irradiation dose-dependence. The dissolution rate of the irradiated HA enhanced continuously with increasing irradiation dose, as a result of constantly increasing crystal defects and enlarging voids, where the main reactive sites for the degradation of HA formed. The Ca2+ and PO43- releasing of HA with the highest irradiation dose enhanced by 92.75% and 138.85% respectively compared to that of the pristine HA after 28 days’ immersion. SBF immersion results suggested the irradiated HA with raising EBI doses exhibited preferable performance in bioactivity as well. Moreover, the results from CCK-8 assay and SEM observation showed that the irradiated HA were beneficial to the proliferation and attachment of osteoblasts.

Amorphous Zr-B-N thin films were prepared on Si substrates by DC reactive magnetron sputtering as diffusion barriers for advanced Cu interconnection. To evaluate its thermal stability and barrier performance, Cu/Zr-B-N/Si stacked structures were annealed in high vacuum at temperatures varying from 500 °C to 700 °C for 30 min. The Zr-B-N films remained amorphous after annealing at 600 °C and crystalized at 650 °C, effectively block the intermixing of Cu and Si atoms. However, the thin films became invalid after annealing at 700 °C and high-resistivity Cu3Si compounds formed, revealing the significant atomic diffusion between Cu and Si. The excellent barrier performance and high thermal stability of Zr-B-N is attributed to the stable amorphous structure. Therefore, the amorphous Zr-B-N thin film can be exploited as a promising diffusion barrier for Cu interconnect technology.

Doping is an effective way to modulate the properties of two-dimensional (2D) materials to cater to new applications. In this work, the codoping effects of transition metals (TM) and nonmetals (NM) on the electronic states and magnetic polarization in monolayered MoS2 are investigated by first-principles calculation. The NM-doped MoS2 possesses semiconducting characteristics, but the B-, N-, and F-doped ones are magnetic showing a magnetic moment of 1.0 μ B per dopant. The metal dopants can induce magnetization in the monolayered MoS2, and the magnetic moment is related to the total number of outer electrons in the TM. In the case of codoping, the S and Mo atoms are substituted by the NM and TM atoms, respectively, and hence, the semiconducting characteristics are maintained despite the reduced band gap. Spin polarization resulting from codoping depends on the number of outer electrons in the TM and NM dopants. Spin polarization occurs if the total number of the outer electrons is odd, but does not if it is even. The magnetic moment of the codoped monolayered MoS2 is always 1 μ B and magnetism is enhanced considerably by (V + B) and (Mn + F) codoping.

Fatigue failure of hard coatings usually occurs at much lower loads than failure under static loading. Hence one way to evaluate coating adhesion should be cyclic loading close to service conditions. In this study, a new method of adhesion measurement for hard coatings is introduced based on interfacial fatigue under repeated indentation. Mono- and multi-layered coatings with different interfacial states are evaluated by a repeated-indentation test. Detachment of the coatings occurs initially at the rim of the indenter imprint, apparently as a result of adhesive failure. In contrast to monolayer coatings, peeling of multilayer coatings depends on the lowest strength of the interfaces. This study also demonstrates that the adhesion determined by the repeated-indentation test is sensitive to the interfacial state, allowing an optimised or weakened interface to be clearly revealed.

Ti-Si-N coatings are deposited on titanium alloy by arc-enhanced magnetron sputtering at different negative bias voltages and their corrosion resistance in blood, effects on platelet activation, endothelial cell functions are studied. The Ti-Si-N coatings are made up of crystalline TiN and amorphous Si 3 N 4 phases and show better corrosion resistance compared with titanium alloy. Reduced platelet receptor activation is observed on the Ti-Si-N coatings and that deposited at −100 V shows the longest clotting time and smallest platelet activation. Ti-Si-N coatings also enhance the endothelial cell proliferation and spreading as well as the endothelial nitric oxide synthase (eNOS) expression.

For the bulk and (001) surface of Ti2CoSn Heusler alloy, the electronic and magnetic properties in bulk and the surface effect on the structural, electronic and magnetic properties of the alloy for different terminations of (001) surface have been studied by using first-principles calculations. The spin-gapless semiconductor (SGS) ferromagnetism with the magnetic moment of 3.00 μB/f.u. is confirmed in the bulk Ti2CoSn alloy with Hg2CuTi-type structure. For two ideal terminations (TiCo, TiSn) and three modified terminations (CoCo*, TiTi*, SnSn*), the density of states (DOS) indicates that all terminations destroy the SGS character. Furthermore, we find that the atomic magnetic moments (AMM) decrease for the most atoms on the outmost three layers due to structural relaxation of these atoms inward. Both the DOS and AMM of the central layer L9 are similar to the corresponding bulk characters because surface effects fade out at the position of the inner layer, 12 A below the surface.

The microstructure and deformation/strengthening behavior of Cu/Ru (face-centered cubic (fcc)/hexagonal close-packed) and Cu/Cr (fcc/body-centered cubic) multilayered films with equal individual layer thickness h ranging from 0.8 to 200 nm were investigated. Based on systematic X-ray diffraction and transmission electron microscopy analyses, as h was varied, interface structure transitions from semi-coherent to fully coherent structures were observed in Cu/Ru rather than Cu/W. These structure transitions were found to play crucial roles in length-scale dependent strengthening mechanisms. Specifically, the multilayer strength derived for relatively large h ( ≥ 50 nm ) followed the classic Hall–Petch relation, while the load-bearing effect was proposed to be the dominant mechanism for relatively small h ( 50 nm ≥ h ≥ 4 nm ). More importantly, as h was further reduced to below 4 nm in Cu/Ru, a strengthening mechanism based on dislocation loop crossing several coherent interfaces was proposed and quantitatively evaluated, The number of layers needed to be crossed by the dislocation loop was found to determine the strength.

The structural, electronic, and magnetic properties of the stoichiometric (001) surface of double perovskite Sr2FeMoO6 have been studied by using a 10-layer FeMoO4 and SrO terminated (001)-oriented slab model and the first-principles projector augmented wave potential within the generalized gradient approximation as well as taking into account the on-site Coulomb repulsive (U = 2.0 eV for Fe and 1.0 eV for Mo). An outwards relaxation is observed for several layers near surface, and the accompanying layer rumpling has a decrease tend from surface layer to inner layer. Along Fe–O–Mo–O–Fe or Mo–O–Fe–O–Mo chains, the oxygen atom is closer to the adjacent Mo atom than to the adjacent Fe atom. In FeO6 or MoO6 octahedra, the two axial TM−O bonds are not equal, and especially, the surface dangling bond makes the remaining one axial TM−O bond slightly shorter than four equally equatorial TM−O bonds. The half-metallic nature and a complete (100%) spin polarization character ensure the FeMoO4 and SrO terminated (001)-oriented slab of double perovskite Sr2FeMoO6 a potential application in spintronics devices. The Fe+3 and Mo+5 ions are still in the (3d5, S = 5/2) and (4d1, S = 1/2) states with positive and negative magnetic moments respectively and thus antiferromagnetic coupling via oxygen between them. There is no direct interaction between two nearest Fe–Fe or Mo–Mo pairs, whereas the hybridizations between Fe 3d and 4s, O 2s and 2p, as well as Mo 4d, 5s and 5p orbitals are fairly significant. Copyright © 2016 John Wiley & Sons, Ltd.

Employing the first-principles calculations, we have investigated the structural, electronic and magnetic properties of quaternary Heusler alloy TiZrCoIn. The TiZrCoIn alloy with type (I) configuration is predicted to be half-metallic ferromagnet at its equilibrium lattice constant 6.525 A with an indirect band gap of 0.930 eV in minority spin channel. The total magnetic moment is 2 μ B /f.u., following the Slater–Pauling rule μ t =Z t −18. Moreover, the negative formation energy indicates the thermodynamical stability of this alloy. The band gap of minority spin channel is determined by the bonding (t 2g ) and antibonding (t 1u ) states created from the hybridizations of the d states of transition metal atoms Ti, Zr and Co. In addition, the HM, character is kept as hydrostatic strain ranged from −10% to 7.6% and tetragonal strain ranged from −19% to 27%.

The electronic structures, magnetic properties, half-metallicity and optical properties of Zn 1 - x Mo x S ( x =0.00, 0.25, 0.50, 0.75, 1.00) are studied by spin-polarized first-principles calculation. Excepting the Zn 0.5 Mo 0.5 S system with a tetragonal structure, the other systems Zn 1 - x Mo x S ( x =0.00, 0.25, 0.75, 1.00) are all in the cubic structure. The lattice constants (volumes) of the Mo doped systems are larger than those of the pure ZnS due to the atomic radius of 2.01 A for Mo atom larger than that of 1.53 A for Zn atom. Although pure ZnS is a nonmagnetic semiconductor with a wide band gap of 3.12 eV, due to incompletely filled Mo-4d orbital both the moderate Mo doped systems Zn 0.5 Mo 0.5 S and Zn 0.25 Mo 0.75 S are magnetic metal, especially the less Mo doped system Zn 0.75 Mo 0.25 S and the completely Mo doped system MoS are magnetic half-metal. For Zn 0.75 Mo 0.25 S system with a magnetic half-metal character as one example, the conducted spin-up channel is only contributed by the threefold degenerate t 2g ( d x y , d y z , d z x ) states due to the tetrahedral crystal field of the S atoms pushing the spin-up channel of the double degenerate e g ( d z 2 , d x 2 - y 2 ) states down below the Fermi level E F . Mo doping not only influences the shape of the original broad absorption peak ranging from 2.5 to 20 eV of pure ZnS, but also leads to two new narrow absorption peaks appeared in the ranges from 0 to 3 eV and from 33 to 43 eV. Moreover, their maximum absorption rate and the corresponding energy increase with increasing Mo content. These results are very useful for Zn 1 - x Mo x S to be applied in optical detectors and spintronics devices.

CuTa monolayers with different Ta contents (34 at% and 37 at%) and CuTa/Cu multilayers with varying nanoscale Cu layer thickness (3–24 nm) were prepared by magnetron sputtering. Their microstructure and mechanical properties were investigated by means of high resolution transmission electron microscopy (HRTEM) and nanoindentation testing. The microstructure of CuTa34 was pure amorphous phase while that of CuTa37 was amorphous phase embedded with nanoparticles. Adding Cu layers into the two different CuTa monolayers led to CuTa-Cu interfaces with different microstructures. For CuTa34/Cu, the interface was relatively straight and the Cu layers exhibited textured growth. For CuTa37/Cu, the interface was wavy and GBs (grain boundaries) were formed in the Cu layers. To investigate the influence of the two different microstructures on multilayer deformation, the residue indentation morphologies of CuTa/Cu were observed under scanning electronic microscope (SEM). For both CuTa34/Cu and CuTa37/Cu, SBs (shear bands) could be effectively inhibited if the Cu layers had a proper thickness. Dominant deformation mechanisms and size effects were proposed and discussed for CuTa/Cu thin films possessing different interfaces and Cu layer structures.

Adsorptions of SO 2 on Al-, Ca-, Co-, Cu-, Ge-, Ni-, and Si-doped (8, 0) boron nitride nanotube (BNNT) have been studied using first-principles approach based on density functional theory in order to exploit their potential applications as SO 2 gas sensors. The electronic properties of the BNNT-molecule adsorption adducts are strongly dependent on the dopants. The most stable adsorption geometries, adsorption energies, charge transfers, and density of states of these systems are thoroughly discussed. This work reveals that the sensitivity of (8, 0) BNNT based chemical gas sensors for SO 2 can be drastically improved by introducing appropriate dopant. Si is found to be the best choice among all the dopants.

In this paper, we use the first-principles calculations based on the density functional theory to investigate the structural, electronic and magnetic properties of a symmetry Ti 2 CoSn (110) surface. The relaxations of the atoms are mainly occurred on the outmost three layers and the layer rumpling has a decrease tend from surface to inner layers. Unfortunately, the half-metallic character confirmed in bulk Ti 2 CoSn is destroyed on the (110) surface. The surface effects are mainly occurred on the outmost three layers, leading to not only a shift toward higher energy region in both channels of the DOS, a small surface state produced around the Fermi level in spin-down channel, but also a reduction in atomic magnetic moments with respect to those in the inner layers which are extremely close to the corresponding bulk values.

The structural, magnetic, electronic and optical properties of the Zn0.5Cr0.5SZB, Zn0.5Cr0.5SW and Zn0.5Cr0.5SRS are studied by spin-polarized first-principles calculation. After optimization Zn0.5Cr0.5SZB system changes its original cubic structure of ZnSZB to a tetragonal structure, while Zn0.5Cr0.5SW and Zn0.5Cr0.5SRS still remain their original hexagonal structure of ZnSW and tetragonal structure of ZnSRS, respectively. The total moments of these Cr doped ZnS systems are mainly contributed by local magnetic moments of Cr2+ ion. Zn0.5Cr0.5SZB, Zn0.5Cr0.5SW and Zn0.5Cr0.5SRS are all half-metal with 100% spin polarization. The Zn0.5Cr0.5SW has the biggest static dielectric constant ɛ1(0) and refractive index n(0). The Zn0.5Cr0.5SZB, Zn0.5Cr0.5SW and Zn0.5Cr0.5SRS have tow absorption regions in the ranges of 0–27 eV and 41–55 eV, but the absorption width decreases for Zn0.5Cr0.5SW, Zn0.5Cr0.5SZB and Zn0.5Cr0.5SRS successively. The results will give a guide for design and application of the Zn0.5Cr0.5SZB, Zn0.5Cr0.5SW and Zn0.5Cr0.5SRS in spintronic devices and optical detectors.

The indentation size effect (ISE) of Zr-based metallic glass (MG) thin films at both as-deposited and annealed states was investigated. Nanoindentation tests performed at various penetration depths and applied strain rates demonstrated inverse ISE at shallow indentation depth and normal ISE at deep indentation depth, for both as-deposited and annealed MGs. Moreover, it was found that the normal ISE was strongly strain rate dependent and the structure-relaxed MG exhibited more pronounced ISE than that of the as-deposited one. Microstructural inhomogeneity caused by difference of areas between the preexisted liquid like flow units and the created free volume upon deformation was proposed to be a key parameter in dominating the pronounced ISE in structure-relaxed MG and the strong strain rate dependence of ISE.