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Cyclic torsion induced dislocation patterns and evolution process of a single-phase Al 0.1 CoCrFeNi multi-principal element alloy at varying cumulative plastic strain, γ cu , from 0.1 to 14.6, were systematically investigated in this study. The results reveal that conventional single-slip individual dislocations dominate plastic deformation at initial straining stage. Whereas, at larger γ cu up to 1.2, a large number of dislocation locks formed by mutual dislocation interactions in turn induce the extensive proliferation of multi-slip dislocations within the grain interiors. At γ cu > 4, a large number of individual multiple dislocations are gradually organized into massive two-dimensional micrometer-scale multi-slip dislocation wall segments; at γ cu > 8, profuse three-dimensional finer equiaxed low-angle dislocation cells are formed. The distinctive structural characteristics of the sample-level hierarchical dislocation cell structure in metals with low stacking fault energies are mainly caused by the gradient distribution of small but large cumulative plastic strain, which are closely related to the enhanced multiple-slip dislocation activities. [Display omitted] [ABSTRACT FROM AUTHOR]

Ceramic/metal interpenetrating network structure has been proved to have a significant effect on decreasing the coefficient of thermal expansion (CTE) of the metal matrix. In our study, a AgCuTi/SiC interpenetrating network structural composite (ASINC) was fabricated through a melt infiltration method. During the infiltration process, the AgCuTi filler melted and infiltrated into a porous SiC ceramic. Wetting behavior of the AgCuTi on the porous SiC ceramic was studied. Microstructure of the ASINC was characterized. The synthesized ASINC was fabricated as an interlayer to prepare a ZrB 2 –SiC–C ceramic/AgCuTi/ASINC/AgCuTi/GH99 brazed joint. Typical microstructure of the joint brazed at 860 °C for 10 min was investigated. The effect of holding time on the microstructure and the room-temperature shear strength of the brazed joints was studied. The maximum shear strength increased by 161% compared with the case brazed with a single AgCuTi interlayer. Microstructure evolution and mechanical strengthening mechanisms of the brazed joints were discussed in detail. [ABSTRACT FROM AUTHOR]

A novel Ag–Nb 2 O 5 braze filler is developed and successfully tested as a sealant candidate for solid oxide cells. The resultant AgNbO 3 by the reaction between Ag and Nb 2 O 5 at high temperatures turns out to be the key to enable a desirable wetting of the YSZ by the braze filler. Typical interfacial microstructure of the YSZ/AISI 310s brazed joints are characterized by a scanning electron microscopy (SEM) and a transmission electron microscopy (TEM) with an energy dispersive spectroscopy (EDS). Effects of Nb 2 O 5 contents and joining parameters on the microstructural evolution and mechanical performance of the joints are investigated. Joints with a maximum average strength of 100–110 MPa are achieved when bonding at 1150 °C/30 min with 5 mol.% Ag–Nb 2 O 5. The long-term stability of the YSZ/Ag–Nb 2 O 5 /AISI 310s joints are evaluated in air for over 350 h at 800 °C and no cracks or cell degradation are found in the joints after the aging process, indicating that the new-developed Ag–Nb 2 O 5 is a promising candidate as the sealant for the SOFC stacks. [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 To address the thermal stress issue in the brazed SiO 2f /SiO 2 -Invar joints, a novel nano-TiO 2p (p: particle) modified braze filler was developed. Wetting of the SiO 2f /SiO 2 composite by AgCuTi-based composite braze filler with different TiO 2p contents were conducted first and a TiO 2p content lower than 5 wt% was fixed. Then the microstructure evolution and mechanical performance of the SiO 2f /SiO 2 -Invar joints brazed with different TiO 2p additions and different brazing parameters were discussed. The highest shear strength of 30 ± 8 MPa was obtained at 910 °C/10 min. After using the TiO 2p modified braze filler, the fracture probability of the SiO 2f /SiO 2 -Invar joints dropped down by 75% (Taking 22 MPa as an example). Finally, a FEM was employed to get an in-depth understanding of the stress relief effects when using a TiO 2p modified braze filler. Results show that the compressive stress on the SiO 2f /SiO 2 side dropped down by 30% after using a 2 wt% TiO 2p modified braze filler. The in-situ formed Cu x Ti 6-x O (x = 2, 3) phases played a key role in relieving the residual stress of the brazed joints. The development of the novel TiO 2p modified braze filler was particularly suitable for the joining of the oxide ceramics and oxides-based composites. [ABSTRACT FROM AUTHOR]

Abstract For active brazing, excessive formation of brittle intermetallics in the brazed seam is always a big issue, which has an adverse effect on the joint property. Herein, an innovative vertical few-layer graphene (VFG) buffer layer was directly grown on the Invar surface prior to brazing. SiO 2 -BN ceramic and the Invar alloy with and without the VFG were first brazed using a Ag-Cu-Ti braze alloy. Interfacial microstructure and fracture morphologies of the brazed joints were then put into comparison. Results show that there is a 20% increase in shear strength after the VFG modification. To further discuss the effect of the interfacial microstructure variation on the joint property, Invar alloy was self-brazed. The fracture path and the tensile-shear strength of the Invar/Invar joints were discussed. Finally, the interaction between the VFG and Ti was characterized and the controlling mechanism of the intermetallic compounds formation by the VFG was proposed. This novel surface modification approach reported in this paper was promising particularly for the active brazing associated with the brittle IMCs formation issue. [ABSTRACT FROM AUTHOR]

Abstract In this study, the SiBCN ceramic and TC4 alloy were successfully brazed using TiB 2 reinforced AgTi composite filler in a vacuum furnace. The typical interfacial microstructure of the joint and the reaction products were identified through EDS, SEM and XRD. The effect of the TiB 2 content and brazing temperature on the joint microstructure and property were investigated. During the brazing process, the filler reacted with the SiBCN to form TiC + TiB + TiN + Ti 5 Si 3 reaction layer adjacent to the SiBCN. With the increase of the TiB 2 content in the composite filler, the diffusion of Ti in the brazing seam was restrained, and the reaction layer became thinner. Meanwhile, the TiB 2 volume fraction in the brazing seam increased. The increase of the brazing temperature promoted the reaction of the braze filler and the base materials. Thick reaction layer adjacent to the SiBCN and lots of Ti (s.s) and Ti 2 Ag in the brazing seam were obtained at high brazing temperature. When the SiBCN and TC4 were brazed using 6 wt% TiB 2 reinforced AgTi composite filler at 980 °C for 10 min, the maximum shear strength of the joint reached 32 MPa. Highlights • The SiBCN and TC4 were vacuum brazed using TiB 2 reinforced AgTi composite filler. • The typical microstructure of the SiBCN/TC4 joint was investigated. • Both of the TiB 2 content and brazing temperature affects the microstructure and property of the joint significantly. • The maximum strength of the joint reached 32 MPa when the joint brazed using AgTi-6TiB 2 at 980 °C for 10 min. [ABSTRACT FROM AUTHOR]

Abstract Carbon fiber reinforced carbon matrix (C f /C) composite and Ni base superalloy were brazed in vacuum using MBF 20 filler. By varying brazing temperatures and holding times, the effects of brazing parameters on the microstructure as well as its evolution and mechanical properties of the joints were investigated. The results show that the microstructural evolution of joints experiences three stages. With the rising of brazing process parameters, the dissolution of C f /C turns strong, leading to the formation of rough composite/filler interface and the increasing of amount of Cr 7 C 3 and MC complex metal carbides. The residual stress concentration in joint changes consequently. The maximum shear strength of the joint can reach 35 MPa (which is up to 92% of the shear strength of C f /C substrate), 15 MPa and 9 MPa at room temperature, 800 °C and 1000 °C, respectively. The fracture initiates and propagates in C f /C composite. Highlights • C f /C composite and GH99 superalloy were successfully brazed using MBF 20 filler in vacuum. • The microstructural evolution experiences three stages: the substrates dissolving and elements diffusing; the carbides forming; the carbides layer forming and growing. • With the rising of brazing parameters, the interfacial reaction is promoted and carbides grow into a continuous layer adjacent to C f /C. • The maximum shear strength of the joint reaches 35 MPa at room temperature, 15 MPa at 800 °C and 9 MPa at 1000 °C. [ABSTRACT FROM AUTHOR]

For the active brazing of ceramic/metal couples, formation of brittle intermetallics in the brazed seam is often a big issue that needs to be addressed. Herein, a novel vertical few-layer graphene (VFG) modified Cu-23Ti braze filler was developed to join the SiO 2f /SiO 2 composite and the Invar alloy. Microstructures of the wetting interfaces and the SiO 2f /SiO 2 -Cu23Ti-Invar brazed joints with and without the VFG modification were put into comparison. Results show that the formation of intermetallics in the brazed seam are greatly suppressed and the joint strength improves by 2 times after using a VFG-modified Cu-23Ti braze filler. Typical microstructure of the SiO 2f /SiO 2 -Invar joint brazed using a VFG-modified Cu-23Ti braze filler was characterized and the joint formation mechanism was proposed finally. [ABSTRACT FROM AUTHOR]

In order to improve the ZrC-SiC and TC4 brazed joint property, functionally graded material (FGM) layers (two SiC particles reinforced TC4-based composite layers) were designed to relieve the residual stress in the ZrC-SiC and TC4 brazed joint. The FGM layers were fabricated on the TC4 surface using laser additive manufacturing technology before the brazing. Then the TC4 coated with the FGM layers and ZrC-SiC ceramic were brazed using Ti-15Cu-15Ni (wt%) filler. According to the SEM and TEM results, the volume fractions of SiC particles in the FGM layers could reach 20% and 39% respectively. Ti from the braze filler and TC4 reacted with the ZrC-SiC ceramic to form TiC and Ti 5 Si 3 adjacent to the ZrC-SiC ceramic. The shear test results indicate that the adoption of the FGM layers and the brazing temperature both affected the joint property significantly. The FGM layers could benefit the mitigation of coefficient of thermal expansion (CTE) mismatch between the ZrC-SiC and TC4, so that the residual stress caused by the CTE mismatch in the joint was relieved and the joint strength increased. The brazing temperature would affect the microstructure of the brazing seam and then control the joint strength. When the ZrC-SiC ceramic and TC4 coated with the FGM layers were brazed at 970 °C for 10 min, the maximum shear strength could reach 91 MPa, and cracks propagated in the ZrC-SiC ceramic substrate during the shear test. [ABSTRACT FROM AUTHOR]

In this study, transparent alumina and TiAl alloy were successfully brazed at 860°C-940 °C using Ag-21Cu-4.5Ti (wt%) filler metal. The microstructure and mechanical properties of the joints were investigated. SEM and TEM analysis showed the typical interfacial microstructure of the joints brazed at 900 °C for 5min was TiAl/β-Ti + AlCuTi/AlCu 2 Ti + AlCuTi/AlCu 2 Ti + Ag(s,s) + Cu(s,s)/(Cu,Al) 3 Ti 3 O/transparent alumina. The effects of brazing temperature and holding time on the microstructure and mechanical properties of TiAl/transparent alumina joint were studied. In addition, the effects of the dissolution and diffusion of TiAl on the microstructural evolution of the brazing seam were discussed. Shear strength analysis reveals that the shear strength of the joint increases at first and then decreases when brazing temperature rises. The maximum shear strength is 49 MPa when the joint is brazed at 900 °C for 5 min. [ABSTRACT FROM AUTHOR]

Although endowed with abundant tidal resources, China's tidal power generation industry has been largely lagging behind other renewable energy alternatives such as small hydropower, photovoltaic power, wind power and biomass-based power. To probe the reasons behind this slow pace of development, an emergy evaluation and an economic analysis were conducted on the Jiangxia Tidal Power Station (JTPS), which has an installed capacity of 4.1 MW. The JTPS is the largest tidal power station in China and the fourth largest in the world. The evaluation results exhibited a total power conversion system emergy use of 1.59E+19 sej to generate 5.90E+13 J of electricity in 2014. Tidal energy only accounts for 16.54% of the total energy budget. The rest of the resources were invested to capture and convert tidal energy to electricity, thereby generating a relatively low efficiency or high transformity of 2.69E+05 sej/J. The results revealed a JTPS emergy loading ratio (ELR) and energy sustainability index (ESI) of 3.72 and 0.41, respectively, which indicates poorer environmental performance compared to other renewable energy power plants, with the exception of photovoltaic power. In addition, the economic analysis revealed a JTPS power generation cost of 2.41 CNY/kWh, which is even higher than that of concentrating solar power (CSP). The JTPS is less competitive because tidal energy has a lower quality and is more decentralized when generating electricity compared to other renewable resources. This inefficiency was exacerbated in the JTPS case due to the original multipurpose design and consequential poor site selection with respect to tidal electricity generation. These results further highlight the importance of dam site selection and the tidal range, as they are critical for the improvement of the tidal power generation environmental performance. More importantly, R&D is essential to promote the development of this technology and to ultimately utilize abundant tidal resources in an efficient and sustainable way. [ABSTRACT FROM AUTHOR]

ZrC-SiC ceramic and TC4 alloy were successfully brazed using a self-prepared Ti-15Cu-15Ni filler. The microstructure and mechanical property of the joints obtained at different brazing temperatures were investigated. The results indicated that Ti from the Ti-15Cu-15Ni and the TC4 reacted with the ZrC-SiC to form TiC phase adjacent to the ZrC-SiC ceramic. In the brazing seam, Ti 2 (Ni, Cu) intermetallic compounds zone (IMCs Zone), Hypoeutectic Zone and Hypereutectoid Zone formed. The brazing temperature affected the dissolution of TC4 into the braze filler significantly, and then determined the microstructure of the joint. The formation of α-Ti in the brazing seam could decrease the hardness and the brittleness of the brazing seam, which was beneficial to the property of the brazed joint. The joint strength reached a maximum value of 43 MPa when the joint was brazed at 970 °C and cracks propagated in the ZrC-SiC substrate near the brazing seam. [ABSTRACT FROM AUTHOR]

The multilayer Ti and Ni foils were designed to braze SiO 2 -BN diphase ceramic with Nb at 1140 °C for 5min. The interfacial microstructure was examined using scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), transmission electron microscope (TEM) and X-ray diffraction (XRD) methods, respectively. Experimental results and thermodynamical calculations showed that the interfacial microstructures between Nb and SiO 2 -BN ceramic were (βTi,Nb)-TiNi eutectic structure/TiNi + TiNi 3 /TiN + Ti 3 O 5 + TiB 2 + Ti 5 Si 3 . The effects of the Ti content in the Ti-Ni braze alloy on the microstructures of the joints were investigated. With the increase of the Ti content, less Ni 3 Nb formed in the joint and TiNi 3 phase successfully turned into TiNi and Ti 2 Ni. The effects of the Ti content in the Ti-Ni braze alloy on the shear strength of the joints showed that the optimum thickness of the TiN + Ti 3 O 5 + TiB 2 + Ti 5 Si 3 reaction area was about 13 μm and the maximum shear strength of 52 MPa was achieved when the Ti content was 45 wt.%. [ABSTRACT FROM AUTHOR]

A novel composite interlayer with a reinforced network was designed using a SiC ceramic with a network structure and Ti-Ni-Nb composite filler foils, to which the Nb and BN-SiO 2 ceramic were successfully brazed under vacuum. For a brazing temperature of 1160 °C and holding time of 10 min, the interfacial microstructure of the Nb/BN-SiO 2 ceramic joint was Nb/(βTi,Nb)-TiNi eutectic structure+(βTi,Nb) 2 Ni+SiC+TiC/TiN+Ti 2 N+TiB+Ti 5 Si 3 +TiO/BN-SiO 2 ceramic. In addition, the shear strength and nano-hardness were analyzed to evaluate the effect of the composite interlayer with a network reinforcement architecture on the mechanical properties of the joint. During brazing, the Ti-Ni-Nb filler metal infiltrated and reacted with the SiC to form the network reinforcement architecture, resulting in the residual stress being relieved and the mechanical performance of the joint being significantly improved. A maximum shear strength of 102 MPa was achieved, which was 60 MPa (142%) higher than that of the joint brazed without the network reinforcement architecture. A reduction in the residual stress on the BN-SiO 2 ceramic side from 328 MPa to 210 MPa was observed with the network reinforcement architecture, and the fracture path of the joint changed from the surface of the BN-SiO 2 ceramic to the interfacial reaction zone. [ABSTRACT FROM AUTHOR]

Emergy analysis can facilitate unified system resources accounting. By combining emergy method with input–output modeling technology, this paper developed an eco-thermodynamic input–output model of the 2007 China economy to account for the sector-specific resource intensities. The results show that the resource intensities for Chinese industry sectors present a distribution with a certain pattern which may vary over three orders of magnitude, measured in terms of resource consumption against economic capital generation. At the scale of the entire economy, the emergy intensities for the resource extraction sectors of non-metallic minerals and metallic ores are the highest. Sectors with the smallest emergy to money ratios are service sectors which rely less on primary natural resources. The sector of coal mining is found to have the largest resource intensity of 6.19E+16 seJ/1E+4 CNY among all sectors, while the sectoral intensity of scrap and waste is only 6.44E+14 seJ/1E+4 CNY, the least one. The insight obtained by juxtaposing resource intensities as well as their structures of industry sectors is useful to identify opportunities for reducing resource intensities that could enable improvements in their ecological sustainability. [ABSTRACT FROM AUTHOR]

The SiO 2f /SiO 2 composite and the Invar alloy were brazed at 860 °C from 5 min to 25 min using an AgCuTi alloy. Scanning electron microscopy (SEM) equipped with an energy dispersive spectrometer (EDS) was employed to examine the elemental distribution in the joint. X-ray diffraction (XRD) and transmission electron microscopy (TEM) was selected to accurately identify the species, morphologies and crystal structures of the reaction products. The effect of the holding time on the interfacial microstructure evolution of the joint was studied in detail. The shear strength of the joints and the fracture morphologies were closely related to the thickness of the whole reaction layer, as well as the thickness ratio of the Ti 5 Si 3 + TiO 2 layer to the Cu x Ti 6-x O layer. The maximum shear strength was 26 MPa obtained at 860 °C for 10 min. Finally, the formation of the reaction products in the joint was analyzed by thermodynamic calculations. A brazing mechanism was proposed based on the experimental results. [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]

A kind of novel composite filler was designed using FeCoNiCrCu high entropy alloy and pure Ti foil. ZrB 2 SiC C ceramic and GH99 superalloy were brazed with the composite filler. The interfacial microstructure as well as brazing mechanism was investigated. The mechanical properties were also assessed. The results show that the high entropy mixing effect of the Ti/FeCoNiCrCu composite filler keeps the activity of Ti and Cr. The solid solution forms as the matrix of brazing seam. The phase structure of (TiB + Cr B)/solid solution promise a good bond between ZSC and GH99. The interfacial reaction is affected greatly by the brazing parameters, because the activity of Ti and Cr is changed. The maximum shear strength reaches 71 MPa when the joint is brazed at 1180 °C for 60 min. Cracks primarily propagate in the ZSC away from the reaction zone. [ABSTRACT FROM AUTHOR]