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The TiAlN/Zr 3 N 4 nanomultilayer films were successfully fabricated by alternatively inserting nitrogen-rich orthorhombic o-Zr 3 N 4 monolayers onto TiAlN nanolayers via magnetron sputtering, and then the Zr 3 N 4 layer thicknesses (l Zr3N4)-dependent microstructure, hardness and deformation behavior was further explored. At a thin l Zr3N4 of =1.1 nm, Zr 3 N 4 nanolayers were forced to crystallize with a metastable cubic c-Zr 3 N 4 pseudocrystal structure and form (111)-oriented c-TiAlN/c-Zr 3 N 4 coherent interfaces with c-TiAlN sublayers, thereby achieving maximum H of 34.7 GPa yet superior toughness. For a thicker l Zr3N4 , Zr 3 N 4 nanolayers gradually transformed from the pseudocrystal c-Zr 3 N 4 to bulk-energy-stabilized o-Zr 3 N 4 ; it destroyed the coherent growth and yielded fast drop in both H and fracture toughness. Furthermore, the indenter induced deformation behavior of the nanomultilayer with l Zr3N4 = 4.2 nm was observed by transmission electron microscopy (TEM), thus indicating that severe plastic deformation in the nanomultilayer is primarily accommodated via the bending of nanolayers and formation of nanoscale longitudinal and lateral cracks rather than the formation of large-scale cracks because of crack deflections that can be attributed to layer interfaces. [ABSTRACT FROM AUTHOR]

A Cu/Al/Cu clad strip was produced successfully by the powder-in-tube method. The interface morphology, element distribution, peeling strength and tensile strength of the clad strips after annealing and further cold rolling were investigated. The experimental results indicate that the diffusional width of the intermetallic layer will increase with the annealing temperature, but the average peeling strength of the Cu/Al/Cu clad strip rises first and then falls. Further cold rolling process can significantly reduce the thickness of the intermetallic layer and improve the average peeling strength of the Cu/Al/Cu clad strip except for those annealed at 550 °C. There exists an optimal diffusional thickness (approximately 15.4 μm) for the annealed Cu/Al/Cu clad strip processed by the powder-in-tube method. The clad strips annealed at 450 °C and further cold rolled to 0.5 mm can obtain the best mechanical performance, the peeling strength, ultimate tensile strength and elongation are 17.8 N/mm, 286 MPa and 9.4%, respectively. The peeling surfaces, peeling tests and tensile tests prove that compact and uniform intermetallic compounds can provide excellent performance for Cu/Al/Cu clad strips. [ABSTRACT FROM AUTHOR]

[Display omitted] • N -rich Zr 3 N 4 nanolayers were utilized to construct TaN/Zr 3 N 4 nanomultilayered architecture. • The superior mechanical properties enabled by local c-TaN/c-Zr 3 N 4 coherent growth. • The biomimetic root-like capillary diffusion channels were endowed by the ultra-fine TaO 2 @ZrO 2 core-shell structure. • The novel channels led corrosion front terminate in same Zr 3 N 4 nanolayer with several-nm scales accuracy. The combined merits of high hardness and superior chemical inertness enable transition metal nitrides (TMNs) to be extensively coated onto the metal surfaces for avoiding erosion and corrosion attacks. However, the relatively large-size through-type diffusion channels commonly appear in the corroded layers as TMNs coatings subjected to corrosive environments. These channels can serve as short-circuit-diffusion paths for corrosive ions and worsen the corrosion-resistance ability, eventually, yielding unpredictable failure due to the heterogeneous growth of corrosion products. Obviously, comparing with the large-size through-type diffusion channels, the biomimetic multi-forked root-like capillary channels can significantly extend the diffusion distance and retard the transportation of corrosive ions by continuously deflecting and refining the diffusion paths. Herein, the nano-laminated TaN/Zr 3 N 4 architecture, consisting of alternating 10 nm-thickness c-TaN nanolayers and 2 nm-thickness N -rich o-Zr 3 N 4 nanolayers, has been fabricated by magnetron sputtering technology; it exhibits the characteristic of c-TaN/c-Zr 3 N 4 local coherent growth. Such TaN/Zr 3 N 4 nanomultilayered structure contributes to the self-adaptive assembly of TaO 2 @ZrO 2 core–shell nanostructure in the corroded layer, thereby yielding appearance of uniformly root-like capillary diffusion channels instead of the typical through-type diffusion channels in the constitute monolayers; finally, it achieves superior corrosion-resistance with homogeneously general corrosion rate and avoids the uncontrollable failures. [ABSTRACT FROM AUTHOR]

Highlights: [•] Effects of oxygen on the growth of CNTs using PECVD have been studied. [•] The OH radical has strong etching effect on CNTs. [•] The OH radical can efficiently purify CNTs and improve the activity of catalyst. [•] This study will be useful in the synthesis of high-quality aligned CNTs. [ABSTRACT FROM AUTHOR]

Abstract: We present a simple, low-cost and high-effective method for synthesizing high-quality, large-area graphene using radio frequency plasma enhanced chemical vapor deposition (RF-PECVD) on SiO2/Si substrate covered with Ni thin film at relatively low temperatures (650°C). During deposition, the trace amount of carbon (CH4 gas flow rate of 2sccm) is introduced into PECVD chamber and the deposition time is only 30s, in which the carbon atoms diffuse into the Ni film and then segregate on its surface, forming single-layer or few-layer graphene. After deposition, Ni is removed by wet etching, and the obtained single continuous graphene film can easily be transferred to other substrates. This investigation provides a large-area, low temperature and low-cost synthesis method for graphene as a practical electronic material. [Copyright &y& Elsevier]

Abstract: The effects of total CH4/Ar gas pressure on the growth of carbon nanomaterials on Si (100) substrate covered with CoO nanoparticles, using plasma-enhanced chemical vapor deposition (PECVD), were investigated. The structures of obtained products were correlated with the total gas pressure and changed from pure carbon nanotubes (CNTs) through hybrid CNTs/graphene sheets (GSs), to pure GSs as the total gas pressure changed from 20 to 4Torr. The total gas pressure influenced the density of hydrogen radicals and Ar ions in chamber, which in turn determined the degree of how CoO nanoparticles were deoxidized and ion bombardment energy that governed the final carbon nanomaterials. Moreover, the obtained hybrid CNTs/GSs exhibited a lower turn-on field (1.4V/μm) emission, compared to either 2.7V/μm for pure CNTs or 2.2V/μm for pure GSs, at current density of 10μA/cm2. [Copyright &y& Elsevier]

Abstract: We report a simple and effective one-step synthesis route for synthesizing a composite consisted of carbon nanotubes (CNTs) and graphite shell-encapsulated cobalt nanoparticles using plasma-enhanced chemical vapor deposition on Si (100) substrate covered with catalyst Co particles, discharging a mixture of H2 and CH4 gas, and characterize the obtained composite by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, high resolution transmission electron microscope, and X-ray photoelectron spectroscopy. The results show that CNTs align perpendicularly to the substrate and graphite shell-encapsulated Co nanoparticles clung to the external surfaces of aligned CNTs. The diameter of the graphite shell-encapsulated Co nanoparticles increases with increasing the H2 content in H2 and CH4 carbonaceous gas. A possible growth mechanism of the CNTs and graphite shell-encapsulated cobalt nanoparticles composite has been explored. [Copyright &y& Elsevier]

Abstract: We report a simple and effective method for syntheses of carbon nanomaterials, including a hybrid CNTs/cobalt particles shelled with graphitic layers, pure CNTs, a CNTs/carbon nanosheets (CNSs) composite and pure CNSs, on O2-thermal etched Co substrate films, in discharging different mixed gases (CH4/H2, CH4/H2/O2, CH4/Ar and CH4/Ar/O2, respectively), using radio frequency plasma enhanced chemical vapor deposition (PECVD). Being etched by O2 during the pretreatment stage, Co thin film transformed into small CoO particles and consequently the deoxidization of CoO particles may occur in PECVD process when different reactive gases are used to obtain various carbon nanomaterials. We find that the reactive gases govern the degree of how the CoO particles can be deoxidized and determine the final carbon nanomaterial products. In this work, the possible growth mechanisms for obtaining various carbon nanomaterials have been explored. [Copyright &y& Elsevier]

The TaN/AlN nanomultilayer films were successfully fabricated by alternatively inserting amorphous AlN nanolayers onto TaN nanolayers using magnetron sputtering, and then the l AlN -dependent microstructure, hardness, toughness, thermal stability and oxidation resistance were investigated. It was revealed that at l AlN = 0.4 nm, AlN nanolayers tended to crystallizing with metastable c-AlN pseudocrystal structure and forming c-TaN/c-AlN coherent interfaces, which provided maximum hardness yet superior toughness. Nevertheless, at thicker l AlN , AlN nanolayers gradually transformed from pseudocrystal c-AlN to amorphous structure and crystalline-TaN/amorphous-AlN interfaces were formed; this resulted in slight deterioration in both hardness and toughness. In addition, the vacuum annealing experiments suggested that relative thicker l AlN (above 0.4 nm) would be benefit for stabilizing the layered structure and phase structure at both 500 °C and 700 °C. Furthermore, the oxidation experiments revealed that introducing amorphous AlN nanolayers could effectively prevent appearance of porous oxidation products in TaN nanolayers and remarkably enhance oxidation resistance; particularly, thicker l AlN would be more effective to impede inward diffusion of oxygen and provide more effective protection on the underlayers against the high-temperature oxidation attack. • Amorphous AlN nanolayers were utilized to construct TaN/AlN nanomultilayers. • AlN nanolayers were forced to grow with pseudocrystal c-AlN at l AlN = 0.4 nm. • The c-TaN/c-AlN coherent interfaces contributed to superior H and toughness. • Thicker l AlN could benefit for thermal stability and oxidation resistance. [ABSTRACT FROM AUTHOR]

The powder-in-tube method was used to investigate the strengthening mechanism of surface-modified SiC p /Al composites at room temperature. A typical amorphous Al 2 O 3 layer was formed for the untreated SiC p /Al composite (C USiC). Obvious interfacial cracks were generated in the pre-oxidized SiC p /Al composite (C OSiC), because of the insufficient activation energy for the reaction between SiO 2 and Al. Comparatively, the interfacial strength of the Cu-coated SiC p /Al composite (C Cu-SiC) was significantly enhanced by the formation of the CuAl 2 phase. The composite reinforced by the low content Cu-coated SiC (6 wt%) exhibiting an ultimate strength of 196 MPa (+ 50.7% compared to the Al matrix) was processed by the low-speed and short-time ball milling process followed by the pack rolling at room temperature. For C USiC , load transfer and grain refinement were the main strengthening mechanism. While for C Cu-SiC , the precipitation strengthening of tiny CuAl 2 phase (0.6 vol.%) contributed to ~77% to the total strength increase. [ABSTRACT FROM AUTHOR]

In the context of energy conservation and waste recycling, energy-saving composite rod (ECR) was prepared by the powder-in-tube method, choosing blast furnace slag (BFS) as the core material and mild steel tube as the coating material. ECRs with BFS have the better mechanical performance than those with river sand (RS) and concrete powder (CP) due to the higher sintering strength of BFS. Under the combined effect of rolling and annealing process, the amorphous phase in BFS is transformed into high-strength calcium akermanite and gehlenite, and strong bonding interface between BFS and steel tube is formed. In addition to strengthening outer steel tube, BFS can also effectively extend the service life of ECR through restraining the corrosion reaction between corrosive medium and inner steel tube. Compared to steel rod, ECR offers tremendous potential in the steel saving. The application of ECR can achieve decreasing steel consumption and recycling industrial waste. [ABSTRACT FROM AUTHOR]

Continuous W-core SiC fiber has been regarded as a promising reinforcement, exhibiting huge potential for applying to hypersonic aircraft commonly suffering from harsh environment with high-temperature short-term characteristic. In this work, the micro/nano-scale investigation on heat treatment (HT) induced dynamic evolution of microstructure in W-core SiC fiber was performed to reveal strength degradation mechanism. It is revealed that the integrity of surface C coating can be well retained even after 1400 ℃/2 h HT avoiding the appearance of surface-dominated fracture mode. In the SiC sheath, only defects annihilation and crystallization transiting the disorder structure into well-crystallized β-SiC columnar grains instead of excessive growth happens, and thus HT induced sharp strength degradation cannot be governed by the microstructural variation of SiC sheath. After high-temperature HT, the interfacial reaction layer continuously thickens with increasing HT temperature that is proportional to fracture mirror zone radius, responsible for strength degradation induced by high-temperature short-term HT. [ABSTRACT FROM AUTHOR]

In this paper, vertical graphene nanosheets (VGNs) were grown by PECVD method. Based on SEM, TEM, Raman and XPS spectrum analysis, the defect-guided growth mechanism of the VGNs was proposed. The effects of defects on the formation of VGNs were discussed in detail. In addition, different densities of defects were produced on the grown VGNs by adjusting different Ar ion sputtering durations. Contact angles (CA) were measured to illustrate the effect of the density of the defects on the wettability of the VGNs. The CA decreases from 102.9° (without sputtering) to 91.5°, 75.1° and 47.8° respectively as the density of the defects increases. It confirms that the wettability of the VGNs could be controlled from hydrophobic to hydrophilic nature by introducing defects. [ABSTRACT FROM AUTHOR]

The combustion synthesis of TiAl intermetallics and their joining to carbon/carbon composites was realized simultaneously. The successful joint configuration involved putting a carbon/carbon composite ball into the Ti–Al powder mixtures. The effect of the residual stresses at the interface on the joining of carbon/carbon composite to TiAl intermetallics was analyzed. Investigation of the reaction products of Ti–45at.% Al mixtures showed that TiAl and Ti3Al phases were formed by combustion synthesis. The evolution of the interfacial microstructure was investigated. [ABSTRACT FROM AUTHOR]

Transition metal oxides show great potential as electrocatalysts, owing to the low cost and rich chemical states. However, the limited surface areas, low intrinsic activity and poor hydrogen evolution reaction (HER) activity greatly restrict the application for overall water splitting. Herein, we have constructed S doped NiCo 2 O 4 nanosheet arrays by Ar plasma (Ar-NiCo 2 O 4 |S) to enhance active sites and boost catalytic kinetics. Consequently, the Ar-NiCo 2 O 4 |S shows the improved performances for HER and oxygen evolution reaction (OER). Further, as bifunctional electrocatalysts, Ar-NiCo 2 O 4 |S exhibit a voltage of 1.63 V at 10 mA cm−2, as well as good stability. [ABSTRACT FROM AUTHOR]

Due to the poor wettability of the AgCuTi alloy on the quartz fiber reinforced composite (QFSC), a reliable joining of the QFSC to itself or to other metals can be hardly achieved. In this study, vertically aligned carbon nanotube (VA-CNT) composed of multi-wall carbon nanotube (MWCNT) was synthesized on the QFSC surface by a plasma enhanced chemical vapor deposition method. As a result, the final contact angle decreased from 96.5° (without VA-CNT modification) down to 30.6° (with VA-CNT modification) at 870 °C with 10min holding duration. Besides, the reaction layers at the AgCuTi/QFSC interface transformed into continuous ones and the infiltration effects became more obvious after the VA-CNT modification. Finally, a possible mechanism how VA-CNT enhanced the wettability of the AgCuTi alloy on the QFSC surface was proposed. Defective sites on the MWCNT surface with a high chemical reactivity and the nanoscale capillary structure of the VA-CNT turned out to be the essential factors to promote the wetting process. This novel surface modification approach can offer new insights on addressing the wetting issues in composites preparation, brazing and soldering, etc.. Image 1098128 [ABSTRACT FROM AUTHOR]

Abstract Brazing C/SiC composites to Ti6Al4V alloy is associated with the problem of high residual stress inducing low joining strength. To overcome this problem, negative thermal expansion Zr 2 P 2 WO 12 (ZWP) nanoparticles were introduced into AgCu brazing alloy to obtain robust C/SiC-Ti6Al4V joints. Microstructures and mechanical properties of the joints brazed with different ZWP contents were investigated. Results indicated that 3 wt% ZWP nanoparticles dispersed homogeneously among brazing seam and compatible with brazing alloy. The width of reaction layer at C/SiC side was reduced sharply. Meanwhile, the finite element analysis showed that residual stress was reduced by 52.9 MPa and stress concentration among reaction layer was eliminated. The average shear strength of the joints brazed with AgCu + 3 wt% ZWP increased to 146.2 MPa, which was 70.8% higher than that of joints brazed without ZWP. [ABSTRACT FROM AUTHOR]

To explore the synergistic effect of glass fibre and Al powder on the mechanical properties of glass-ceramics, blast furnace slag was chosen as the main material, and glass fibre and Al powder as reinforcement materials. The phase compositions, microstructures, compressive properties, and apparent density of the glass-ceramics with varying quantities of glass fibre and Al powder were investigated. The experimental results indicated that Al powder could exist as a simple substance in glass-ceramics and form a dense net coating on the surface of blast furnace slag to improve the plasticity of the glass-ceramic. The glass fibre had better reinforcement effect than Al powder because of its extremely high mechanical strength. The plasticity of glass-ceramics, however, severely decreased; the glass-ceramics exhibited brittle failure during compression. A slight increase in the content of CaSi 2 and SiO 2 in the glass-ceramics was closely related to the addition of glass fibre. Considering safety and economy, glass-ceramics with 6% Al and 14% glass fibre (S4) have the best mechanical properties. The compressive strength, strain at maximum force, and apparent density were 40 MPa, 19% and 1.974 g/cm 3 , respectively. [ABSTRACT FROM AUTHOR]

Brazing SiO 2 -BN ceramic to Ti6Al4V is often associated with the problem of brittle continuous phases and high residual stress at the reaction layer of SiO 2 -BN, inducing low joining strength. To overcome these problems, SiO 2 -BN ceramic modified with in situ synthesized carbon nanotubes (CNTs) were joined to Ti6Al4V by TiZrNiCu alloy. Results show that CNTs can improve the wettability of TiZrNiCu on SiO 2 -BN rapidly, and break the continuous reaction layer of SiO 2 -BN into fine sizes. Residual stress can also be reduced by low CTE of CNTs and fine size phases among reaction layer. The shear strength of SiO 2 -BN/Ti6Al4V joints with CNTs modified is 35.3 MPa at 970 °C for 10 min, which is 3 times higher than that of the joints without CNTs modified. [ABSTRACT FROM AUTHOR]

To reduce the production costs of glass-ceramics and broaden the application field of solid waste in steel industry, low-density and high-strength glass-ceramics were produced by using blast furnace slag as the basic material, choosing glass fiber and water glass as the strengthening agents. The effects of glass fiber and water glass on the phase composition, microstructure, apparent density, water absorption and compressive strength of glass–ceramics were investigated. The results show that the rod structure of glass fiber can be retained in the sintered samples and high content of diopside and augite significantly improve the compressive strength of glass-ceramics. Tiny spherical crystalline phases can be obtained for the glass-ceramics soaked in the moderate concentration of water glass. The BGW-2 samples fabricated with 70% blast furnace slag, 30% glass fiber and 4% water glass, exhibit excellent comprehensive properties. The bulk density, water absorption and compressive strength of BGW-2 are 1.76 g/cm 3 , 2.26% and 68 MPa, respectively. Consequently, using blast furnace slag to prepare glass-ceramics can be another applicable way to utilize blast furnace slag efficiently. [ABSTRACT FROM AUTHOR]

A robust joint between SiC and Nb was realized by using the combination of Ag-Cu-Ti + Ti composite brazing alloy and a 3D quartz-fiber braided interlayer (3D-SiO 2 -fiber). The 3D-SiO 2 -fiber, with ductile, loose and porous structure, can be filled up by the composite brazing alloy, which plays an important role in forming a sound joint. Furthermore, considerable and uniformly distributed α-Ti, Ti 2 Cu, Cu 3 Si and TiSi compounded particles in the joint effectively reduced the high coefficient of thermal expansion (CTE) mismatching between different materials. Thus the residual stress in the joint was greatly mitigated and the joint was strengthened. [ABSTRACT FROM AUTHOR]

Abstract: Ag–Cu/Cu/Ag–Cu–Ti composite interlayer was successfully designed to braze Invar alloy and SiO2–BN ceramic. The effect of Cu-foil thickness on the microstructure and mechanical properties of the brazed joints was investigated. The results showed that, compared with single Ag–Cu–Ti brazing foil, the formation of brittle Fe2Ti and Ni3Ti compounds detrimental to the joint strength was greatly inhibited by using composite interlayer. The active Ti atoms in the liquid filler reacted with SiO2–BN ceramic to form a TiN–TiB2 fine-grain layer. The desired interfacial microstructure composed of layered Ag- and Cu-based solid solutions was obtained, which was beneficial for the joint strength. The shear strength of brazed joints was 207% higher than the joints brazed with single Ag–Cu–Ti foil when a 100μm thick Cu interlayer was used. The inhibition of brittle compounds formation was attributed to the control of reaction sequences during brazing and to the addition of Cu barrier layer. [Copyright &y& Elsevier]

Abstract: The Al/Ni multilayers were characterized and diffusion bonding of TiAl intermetallics to TiC cermets was carried out using the multilayers. The microstructure of Al/Ni multilayers and TiAl/TiC cermet joint was investigated. The layered structures consisting of a Ni3(AlTi) layer, a Ni2AlTi layer, a (Ni,Al,Ti) layer and a Ni diffusion layer were observed from the interlayer to the TiAl substrate. Only one AlNi3 layer formed at the multilayer/TiC cermet interface. The reaction behaviour of Al/Ni multilayers was characterized by means of differential scanning calorimeter (DSC) and X-ray diffraction. The initial exothermic peak of the DSC curve was formed due to the formation of Al3Ni and Al3Ni2 phases. The reaction sequence of the Al/Ni multilayers was Al3Ni→Al3Ni2 →AlNi→AlNi3 and the final products were AlNi and AlNi3 phases. The shear strength of the joint was tested and the experimental results suggested that the application of Al/Ni multilayers improved the joining quality. [Copyright &y& Elsevier]

Abstract: The vacuum brazing of alumina ceramic to Ti6Al4V alloy was performed using Ag–Cu eutectic filler metal. The microstructure at the ceramic-metal interfaces and the mechanical properties of the brazed joint were examined. The microstructure of the joint brazed at 825°C for 10min consisted of α–β Ti, Ti2Cu, TiCu, Ti3Cu4, Ag-based solid solution and Ti4(Cu,Al)2O phases starting from Ti6Al4V to alumina substrate. The brazing parameters had a strong influence on the microstructure and shear strength of the joint. The brittle fracture mainly propagated in the alumina substrate. The highest shear strength was obtained when the joint was brazed at 825°C for 10min. When a Cu foil was sandwiched between two Ag–Cu brazing foils, the microstructure of the joint changed greatly and the shear strength increased correspondingly. [Copyright &y& Elsevier]

Abstract: A new process of molecular-level mixing was used to fabricate successfully the Cu–carbon nanotubes (CNTs) composite powders. The phase composition and microstructures of the composite powders were studied. Cu–CNTs composites with molecular-level dispersion have been fabricated by spark plasma sintering, and then the composites were successfully hot rolled up to 50% reduction. The tensile behavior and fractographs of the composites have been studied, the results indicate that a little amount of CNTs added in the Cu matrix can remarkably improve the tensile strength and yield strength of Cu matrix. With a higher degree of CNTs dispersion, the yield strength and tensile strength of the Cu–CNTs composites can obviously improve, but the special elongation decreases greatly. [Copyright &y& Elsevier]