The purpose of this work was to grow SiC as binder to adhere diamond particles to graphite substrate by low pressure chemical vapor deposition （LPCVD） at 1100 ℃ and 100 Pa using methyltrichlorosilane （MTS： CH3Si...The purpose of this work was to grow SiC as binder to adhere diamond particles to graphite substrate by low pressure chemical vapor deposition （LPCVD） at 1100 ℃ and 100 Pa using methyltrichlorosilane （MTS： CH3SiCl3） as precursor. The composite coatings on graphite substrates were analyzed by various techniques. Results show that a dense SiC coating with a cloud-cluster shape was formed both on the diamond particles and the substrate after deposition, The thermal stress （290.6 MPa） strengthened the interfacial bonding between the diamond particle and the SiC coating, which is advantageous for the purpose of adhering diamond particles to graphite substrate. The applied load of sliding wear test was found to affect not only the friction coefficient, but also the wear surface morphology. With increasing loads, the asperity penetration was high and the friction coefficient decreased.展开更多
To address the challenges of insufficient thermal resistance and high-temperature stability in current environmental barrier coating(EBC)bond coats above 1500℃,this study successfully synthesized HfO_(2)–Al_(2)O_(3)...To address the challenges of insufficient thermal resistance and high-temperature stability in current environmental barrier coating(EBC)bond coats above 1500℃,this study successfully synthesized HfO_(2)–Al_(2)O_(3)–SiO_(2) powders with a dispersion-strengthened structure for EBC bond coat raw material for spraying through a solid-phase synthesis method using HfO_(2),Al_(2)O_(3),and SiO_(2) sol.The dispersion-strengthened structure with a microstructure of oxides(HfO_(2) and Al_(2)O_(3))dispersed in silicates(mullite and HfSiO4)can be achieved by systematically adjusting the component molar ratios,synthesis temperature,and time.The synthesized raw powders underwent subsequent hightemperature hot-pressing sintering to form ceramic bulks,allowing for a comprehensive characterization of the intrinsic material properties,including thermal conductivity,coefficient of thermal expansion,mechanical performance,oxidation resistance at 1600℃,and water‒oxygen corrosion resistance at 1300℃.The investigation elucidates the property evolution and related mechanisms,conclusively demonstrating the viability of the HfO_(2)–Al_(2)O_(3)–SiO_(2) system as an EBC bond coating material.Additional chemical compatibility tests with SiO_(2) at 1500℃ further validated the dispersion-strengthened structure.Notably,oxidation resistance testing at 1600℃ revealed that Al_(2)O_(3) could better capture SiO_(2) generated by the decomposition of HfSiO4 to form mullite,thus enhancing the high-temperature stability of the HfO_(2)–Al_(2)O_(3)–SiO_(2) material,benefiting from its dispersion-strengthened structure.The present study establishes a robust theoretical foundation for the development of EBC bond coatings with exceptional high-temperature endurance exceeding 1500℃.展开更多
Developing highly efficient and stable non-precious metal catalysts for water splitting is urgently required.In this work,we report a facile one-step molten salt method for the preparation of self-supporting Ni-doped ...Developing highly efficient and stable non-precious metal catalysts for water splitting is urgently required.In this work,we report a facile one-step molten salt method for the preparation of self-supporting Ni-doped Mo_(2)C on carbon fiber paper(Ni–Mo_(2)CCB/CFP)for hydrogen evolution reaction(HER).The effects of nickel nitrate concentration on the phase composition,morphology,and electrocatalytic HER performance of Ni-doped Mo_(2)C@CFP electrocatalysts was investigated.With the continuous increase of Ni(NO_(3))_(2)concentration,the morphology of Mo_(2)C gradually changes from granular to flower-like,providing larger specific surface area and more active sites.Doping nickel(Ni)into the crystal lattice of Mo_(2)C largely reduces the impedance of the electrocatalysts and enhances their electrocatalytic activity.The as-developed Mo_(2)C–3 M Ni(NO_(3))_(2)/CFP electrocatalyst exhibits high catalytic activity with a small overpotential of 56 mV at a current density of 10 mA·cm^(-2).This catalyst has a fast HER kinetics,as demonstrated by a very small Tafel slope of 27.4 mV·dec^(-1),and persistent long-term stability.A further higher Ni concentration had an adverse effect on the electrocatalytic performance.Density functional theory(DFT)calculations further verified the experimental results.Ni doping could reduce the binding energy of Mo–H,facilitating the desorption of the adsorbed hydrogen(Hads)on the surface,thereby improving the intrinsic catalytic activity of Ni-doped Mo_(2)C-based catalysts.Nevertheless,excessive Ni doping would inhibit the catalytic activity of the electrocatalysts.This work not only provides a simple strategy for the facile preparation of non-precious metal electrocatalysts with high catalytic activity,but also unveils the influence mechanism of the Ni doping concentration on the HER performance of the electrocatalysts from the theoretical perspective.展开更多
基金financially supported by the Major Achievements of Jiangsu Province(BA20130987)the Innovation Fund of Nanjing University of Aeronautics and Astronautics(No.KFJJ201440)
文摘The purpose of this work was to grow SiC as binder to adhere diamond particles to graphite substrate by low pressure chemical vapor deposition （LPCVD） at 1100 ℃ and 100 Pa using methyltrichlorosilane （MTS： CH3SiCl3） as precursor. The composite coatings on graphite substrates were analyzed by various techniques. Results show that a dense SiC coating with a cloud-cluster shape was formed both on the diamond particles and the substrate after deposition, The thermal stress （290.6 MPa） strengthened the interfacial bonding between the diamond particle and the SiC coating, which is advantageous for the purpose of adhering diamond particles to graphite substrate. The applied load of sliding wear test was found to affect not only the friction coefficient, but also the wear surface morphology. With increasing loads, the asperity penetration was high and the friction coefficient decreased.
基金funded by the Jiangxi Provincial Natural Science Foundation(20232BAB204019)the National Natural Science Foundation of China(52272063)the Aeronautical Science Foundation of China(2024Z055056001).
文摘To address the challenges of insufficient thermal resistance and high-temperature stability in current environmental barrier coating(EBC)bond coats above 1500℃,this study successfully synthesized HfO_(2)–Al_(2)O_(3)–SiO_(2) powders with a dispersion-strengthened structure for EBC bond coat raw material for spraying through a solid-phase synthesis method using HfO_(2),Al_(2)O_(3),and SiO_(2) sol.The dispersion-strengthened structure with a microstructure of oxides(HfO_(2) and Al_(2)O_(3))dispersed in silicates(mullite and HfSiO4)can be achieved by systematically adjusting the component molar ratios,synthesis temperature,and time.The synthesized raw powders underwent subsequent hightemperature hot-pressing sintering to form ceramic bulks,allowing for a comprehensive characterization of the intrinsic material properties,including thermal conductivity,coefficient of thermal expansion,mechanical performance,oxidation resistance at 1600℃,and water‒oxygen corrosion resistance at 1300℃.The investigation elucidates the property evolution and related mechanisms,conclusively demonstrating the viability of the HfO_(2)–Al_(2)O_(3)–SiO_(2) system as an EBC bond coating material.Additional chemical compatibility tests with SiO_(2) at 1500℃ further validated the dispersion-strengthened structure.Notably,oxidation resistance testing at 1600℃ revealed that Al_(2)O_(3) could better capture SiO_(2) generated by the decomposition of HfSiO4 to form mullite,thus enhancing the high-temperature stability of the HfO_(2)–Al_(2)O_(3)–SiO_(2) material,benefiting from its dispersion-strengthened structure.The present study establishes a robust theoretical foundation for the development of EBC bond coatings with exceptional high-temperature endurance exceeding 1500℃.
基金This work was financially supported by the National Natural Science Foundation of China(Grant Nos.51862024,51772140,and 51962023)Key Research and Development Program of Jiangxi Province(Grant No.20203BBE53066).
文摘Developing highly efficient and stable non-precious metal catalysts for water splitting is urgently required.In this work,we report a facile one-step molten salt method for the preparation of self-supporting Ni-doped Mo_(2)C on carbon fiber paper(Ni–Mo_(2)CCB/CFP)for hydrogen evolution reaction(HER).The effects of nickel nitrate concentration on the phase composition,morphology,and electrocatalytic HER performance of Ni-doped Mo_(2)C@CFP electrocatalysts was investigated.With the continuous increase of Ni(NO_(3))_(2)concentration,the morphology of Mo_(2)C gradually changes from granular to flower-like,providing larger specific surface area and more active sites.Doping nickel(Ni)into the crystal lattice of Mo_(2)C largely reduces the impedance of the electrocatalysts and enhances their electrocatalytic activity.The as-developed Mo_(2)C–3 M Ni(NO_(3))_(2)/CFP electrocatalyst exhibits high catalytic activity with a small overpotential of 56 mV at a current density of 10 mA·cm^(-2).This catalyst has a fast HER kinetics,as demonstrated by a very small Tafel slope of 27.4 mV·dec^(-1),and persistent long-term stability.A further higher Ni concentration had an adverse effect on the electrocatalytic performance.Density functional theory(DFT)calculations further verified the experimental results.Ni doping could reduce the binding energy of Mo–H,facilitating the desorption of the adsorbed hydrogen(Hads)on the surface,thereby improving the intrinsic catalytic activity of Ni-doped Mo_(2)C-based catalysts.Nevertheless,excessive Ni doping would inhibit the catalytic activity of the electrocatalysts.This work not only provides a simple strategy for the facile preparation of non-precious metal electrocatalysts with high catalytic activity,but also unveils the influence mechanism of the Ni doping concentration on the HER performance of the electrocatalysts from the theoretical perspective.
