The high cost of using the niobium(Nb)barrier for manufacturing magnesium diboride(MgB2)mono-and multi-filamentary wires for large-scale applications has become one of the barriers to replacing current commercial niob...The high cost of using the niobium(Nb)barrier for manufacturing magnesium diboride(MgB2)mono-and multi-filamentary wires for large-scale applications has become one of the barriers to replacing current commercial niobium-titanium superconductors.The potential of replacing the Nb barrier with a low-cost iron(Fe)barrier for multifilament MgB2 superconducting wires is investigated in this manuscript.Therefore,MgB2 wires with Fe barrier sintered with different temperatures are studied(from 650°C to 900°C for 1 h)to investigate the non-superconducting reaction phase of Fe-B.Their superconducting performance including engineering critical current density(Je)and n-value are tested at 4.2 K in various external magnetic fields.The best sample sintered at 650°C for 1 h has achieved a Je value of 3.64×10^(4) A cm^(−2) and an n-value of 61 in 2 T magnetic field due to the reduced formation of Fe2B,better grain connectivity and homogenous microstructure.For microstructural analysis,the focused ion beam(FIB)is utilised for the first time to acquire three-dimensional microstructures and elemental mappings of the interface between the Fe barrier and MgB2 core of different wires.The results have shown that if the sintering temperature can be controlled properly,the Je and n-value of the wire are still acceptable for magnet applications.The formation of Fe2B is identified along the edge of MgB2,as the temperature increases,the content of Fe2B also increases which causes the degradation in the performance of wires.展开更多
Sustainable ammonia synthesis at ambient conditions that relies on renewable sources of energy and feedstocks is globally sought to replace the Haber-Bosch process.Here,using nitrogen and water as raw materials,a nont...Sustainable ammonia synthesis at ambient conditions that relies on renewable sources of energy and feedstocks is globally sought to replace the Haber-Bosch process.Here,using nitrogen and water as raw materials,a nonthermal plasma catalysis approach is demonstrated as an effective powerto-chemicals conversion strategy for ammonia production.By sustaining a highly reactive environment,successful plasma-catalytic production of NH_(3) was achieved from the dissociation of N_(2) and H_(2)O under mild conditions.Plasma-induced vibrational excitation is found to decrease the N_(2) and H_(2)O dissociation barriers,with the presence of matched catalysts in the nonthermal plasma discharge reactor contributing significantly to molecular dissociation on the catalyst surface.Density functional theory calculations for the activation energy barrier for the dissociation suggest that ruthenium catalysts supported on magnesium oxide exhibit superior performance over other catalysts in NH_(3) production by lowering the activation energy for the dissociative adsorption of N_(2) down to 1.07 eV.The highest production rate,2.67 mmol gcat.^(-1) h^(-1),was obtained using ruthenium catalyst supported on magnesium oxide.This work highlights the potential of nonthermal plasma catalysis for the activation of renewable sources to serve as a new platform for sustainable ammonia production.展开更多
Magnesium diboride(MgB_(2))magnets have the potential to be the next-generation liquid-helium-free magnet for magnetic resonance imaging(MRI)application due to their relatively high superconducting transition temperat...Magnesium diboride(MgB_(2))magnets have the potential to be the next-generation liquid-helium-free magnet for magnetic resonance imaging(MRI)application due to their relatively high superconducting transition temperature,high current density and low raw material cost compared with current commercial niobium-titanium(Nb-Ti)magnets.A typical superconducting magnet includes several coils.To produce an ultra-stable magnetic field for imaging in MRI,a superconducting electromagnet operating in a persistent mode is crucial.Superconducting coils of the electromagnet in MRI are short-circuited to operate in the persistent mode by connecting coils with superconducting joints.Per-sistent joints have been demonstrated for in-situ and ex-situ wires of both mono-and multi-filamentary structures,made predominantly by PIT techniques similar to those used in wire production.To realise further engagement of MgB_(2)in MRI applications,enhancing the performance of MgB_(2)superconducting joints is essential.This literature review summarises research and development on MgB_(2)superconducting joining technology.展开更多
Nine mercapto-azobenzene dervatives with "push-pull" structure are synthesized.The synthesis procedure is simple and easily operated.The structures of the compounds are characterized and confirmed by element...Nine mercapto-azobenzene dervatives with "push-pull" structure are synthesized.The synthesis procedure is simple and easily operated.The structures of the compounds are characterized and confirmed by elementary analysis,1H-NMR,IR and UV.These compounds will be novel function material molecules in the field of molecular electronics.展开更多
基金support from the Australian Research Council(ARC)Linkage Project(LP200200689).
文摘The high cost of using the niobium(Nb)barrier for manufacturing magnesium diboride(MgB2)mono-and multi-filamentary wires for large-scale applications has become one of the barriers to replacing current commercial niobium-titanium superconductors.The potential of replacing the Nb barrier with a low-cost iron(Fe)barrier for multifilament MgB2 superconducting wires is investigated in this manuscript.Therefore,MgB2 wires with Fe barrier sintered with different temperatures are studied(from 650°C to 900°C for 1 h)to investigate the non-superconducting reaction phase of Fe-B.Their superconducting performance including engineering critical current density(Je)and n-value are tested at 4.2 K in various external magnetic fields.The best sample sintered at 650°C for 1 h has achieved a Je value of 3.64×10^(4) A cm^(−2) and an n-value of 61 in 2 T magnetic field due to the reduced formation of Fe2B,better grain connectivity and homogenous microstructure.For microstructural analysis,the focused ion beam(FIB)is utilised for the first time to acquire three-dimensional microstructures and elemental mappings of the interface between the Fe barrier and MgB2 core of different wires.The results have shown that if the sintering temperature can be controlled properly,the Je and n-value of the wire are still acceptable for magnet applications.The formation of Fe2B is identified along the edge of MgB2,as the temperature increases,the content of Fe2B also increases which causes the degradation in the performance of wires.
基金partially supported by the Australian Research Council(ARC)the National Science Fund for Distinguished Young Scholars(grant number 51925703)。
文摘Sustainable ammonia synthesis at ambient conditions that relies on renewable sources of energy and feedstocks is globally sought to replace the Haber-Bosch process.Here,using nitrogen and water as raw materials,a nonthermal plasma catalysis approach is demonstrated as an effective powerto-chemicals conversion strategy for ammonia production.By sustaining a highly reactive environment,successful plasma-catalytic production of NH_(3) was achieved from the dissociation of N_(2) and H_(2)O under mild conditions.Plasma-induced vibrational excitation is found to decrease the N_(2) and H_(2)O dissociation barriers,with the presence of matched catalysts in the nonthermal plasma discharge reactor contributing significantly to molecular dissociation on the catalyst surface.Density functional theory calculations for the activation energy barrier for the dissociation suggest that ruthenium catalysts supported on magnesium oxide exhibit superior performance over other catalysts in NH_(3) production by lowering the activation energy for the dissociative adsorption of N_(2) down to 1.07 eV.The highest production rate,2.67 mmol gcat.^(-1) h^(-1),was obtained using ruthenium catalyst supported on magnesium oxide.This work highlights the potential of nonthermal plasma catalysis for the activation of renewable sources to serve as a new platform for sustainable ammonia production.
基金thankful for the support from the Australian Research Council(ARC)Linkage Project(LP200200689).
文摘Magnesium diboride(MgB_(2))magnets have the potential to be the next-generation liquid-helium-free magnet for magnetic resonance imaging(MRI)application due to their relatively high superconducting transition temperature,high current density and low raw material cost compared with current commercial niobium-titanium(Nb-Ti)magnets.A typical superconducting magnet includes several coils.To produce an ultra-stable magnetic field for imaging in MRI,a superconducting electromagnet operating in a persistent mode is crucial.Superconducting coils of the electromagnet in MRI are short-circuited to operate in the persistent mode by connecting coils with superconducting joints.Per-sistent joints have been demonstrated for in-situ and ex-situ wires of both mono-and multi-filamentary structures,made predominantly by PIT techniques similar to those used in wire production.To realise further engagement of MgB_(2)in MRI applications,enhancing the performance of MgB_(2)superconducting joints is essential.This literature review summarises research and development on MgB_(2)superconducting joining technology.
文摘Nine mercapto-azobenzene dervatives with "push-pull" structure are synthesized.The synthesis procedure is simple and easily operated.The structures of the compounds are characterized and confirmed by elementary analysis,1H-NMR,IR and UV.These compounds will be novel function material molecules in the field of molecular electronics.