The effect of pyrolytic carbon(PyC) thickness on the tensile property of mini T800 carbon fiber reinforced SiC matrix composites(C/SiC) was studied. PyC interphase was prepared by chemical vapor infiltration(CVI) proc...The effect of pyrolytic carbon(PyC) thickness on the tensile property of mini T800 carbon fiber reinforced SiC matrix composites(C/SiC) was studied. PyC interphase was prepared by chemical vapor infiltration(CVI) process using C3H6–Ar as gas source, the PyC thickness was adjusted from 0 to 400 nm, and then the SiC matrix was prepared by CVI process using methyltrichlorosilane(MTS)–H2–Ar as precursor and gas source. The results showed that the tensile strength of mini T800-C/SiC increased first and then decreased with the increase of the PyC thickness. When the thickness of PyC was 100 nm, the average strength reached the maximum value of 393 ± 70 MPa. The Weibull modulus increased from 2.0 to 8.06 with the increase of PyC thickness, and the larger the Weibull modulus, the smaller the dispersion, which indicated that the regulation of PyC thickness was conducive to improve tensile properties.展开更多
Oxidation behaviors of carbon fiber reinforced SiC matrix composites(C/SiC)are one of the most noteworthy properties.For C/SiC,the oxidation behavior was controlled by matrix microcracks caused by the mismatch of coef...Oxidation behaviors of carbon fiber reinforced SiC matrix composites(C/SiC)are one of the most noteworthy properties.For C/SiC,the oxidation behavior was controlled by matrix microcracks caused by the mismatch of coefficients of thermal expansion(CTEs)and elastic modulus between carbon fiber and SiC matrix.In order to improve the oxidation resistance,multilayer SiC–Si_(3)N_(4) matrices were fabricated by chemical vapor infiltration(CVI)to alleviate the above two kinds of mismatch and change the local stress distribution.For the oxidation of C/SiC with multilayer matrices,matrix microcracks would be deflected at the transition layer between different layers of multilayer SiC–Si_(3)N_(4) matrix to lengthen the oxygen diffusion channels,thereby improving the oxidation resistance of C/SiC,especially at 800 and 1000℃.The strength retention ratio was increased from 61.9%(C/SiC–SiC/SiC)to 75.7%(C/SiC–Si_(3)N_(4)/SiC/SiC)and 67.8%(C/SiC–SiC/Si_(3)N_(4)/SiC)after oxidation at 800℃for 10 h.展开更多
Seawater electrolysis is an extremely attractive approach for harvesting clean hydrogen energy,but detrimental chlorine species(i.e.,chloride and hypochlorite)cause severe corrosion at the anode.Here,we report our rec...Seawater electrolysis is an extremely attractive approach for harvesting clean hydrogen energy,but detrimental chlorine species(i.e.,chloride and hypochlorite)cause severe corrosion at the anode.Here,we report our recent finding that benzoate anions-intercalated NiFe-layered double hydroxide nanosheet on carbon cloth(BZ-NiFe-LDH/CC)behaves as a highly efficient and durable monolithic catalyst for alkaline seawater oxidation,affords enlarged interlayer spacing of LDH,inhibits chlorine(electro)chemistry,and alleviates local pH drop of the electrode.It only needs an overpotential of 320 mV to reach a current density of 500 mA·cm^(−2)in 1 M KOH.In contrast to the fast activity decay of NiFe-LDH/CC counterpart during long-term electrolysis,BZ-NiFe-LDH/CC achieves stable 100-h electrolysis at an industrial-level current density of 500 mA·cm^(−2)in alkaline seawater.Operando Raman spectroscopy studies further identify structural changes of disorderedδ(NiIII-O)during the seawater oxidation process.展开更多
基金supported by the National Natural Science Foundation of China (Nos. 51702261, 51821091, and 51802263)the Natural Science Foundation of Shaanxi Province (Project No. 2019JQ-634)the Fundamental Research Funds for the Central Universities。
文摘The effect of pyrolytic carbon(PyC) thickness on the tensile property of mini T800 carbon fiber reinforced SiC matrix composites(C/SiC) was studied. PyC interphase was prepared by chemical vapor infiltration(CVI) process using C3H6–Ar as gas source, the PyC thickness was adjusted from 0 to 400 nm, and then the SiC matrix was prepared by CVI process using methyltrichlorosilane(MTS)–H2–Ar as precursor and gas source. The results showed that the tensile strength of mini T800-C/SiC increased first and then decreased with the increase of the PyC thickness. When the thickness of PyC was 100 nm, the average strength reached the maximum value of 393 ± 70 MPa. The Weibull modulus increased from 2.0 to 8.06 with the increase of PyC thickness, and the larger the Weibull modulus, the smaller the dispersion, which indicated that the regulation of PyC thickness was conducive to improve tensile properties.
基金This work was supported by the National Natural Science Foundation of China(Nos.52072303 and 51821091)the National Science and Technology Major Project(No.J2019-VI-0014-0129)。
文摘Oxidation behaviors of carbon fiber reinforced SiC matrix composites(C/SiC)are one of the most noteworthy properties.For C/SiC,the oxidation behavior was controlled by matrix microcracks caused by the mismatch of coefficients of thermal expansion(CTEs)and elastic modulus between carbon fiber and SiC matrix.In order to improve the oxidation resistance,multilayer SiC–Si_(3)N_(4) matrices were fabricated by chemical vapor infiltration(CVI)to alleviate the above two kinds of mismatch and change the local stress distribution.For the oxidation of C/SiC with multilayer matrices,matrix microcracks would be deflected at the transition layer between different layers of multilayer SiC–Si_(3)N_(4) matrix to lengthen the oxygen diffusion channels,thereby improving the oxidation resistance of C/SiC,especially at 800 and 1000℃.The strength retention ratio was increased from 61.9%(C/SiC–SiC/SiC)to 75.7%(C/SiC–Si_(3)N_(4)/SiC/SiC)and 67.8%(C/SiC–SiC/Si_(3)N_(4)/SiC)after oxidation at 800℃for 10 h.
基金supported by the National Natural Science Foundation of China(No.21575137).
文摘Seawater electrolysis is an extremely attractive approach for harvesting clean hydrogen energy,but detrimental chlorine species(i.e.,chloride and hypochlorite)cause severe corrosion at the anode.Here,we report our recent finding that benzoate anions-intercalated NiFe-layered double hydroxide nanosheet on carbon cloth(BZ-NiFe-LDH/CC)behaves as a highly efficient and durable monolithic catalyst for alkaline seawater oxidation,affords enlarged interlayer spacing of LDH,inhibits chlorine(electro)chemistry,and alleviates local pH drop of the electrode.It only needs an overpotential of 320 mV to reach a current density of 500 mA·cm^(−2)in 1 M KOH.In contrast to the fast activity decay of NiFe-LDH/CC counterpart during long-term electrolysis,BZ-NiFe-LDH/CC achieves stable 100-h electrolysis at an industrial-level current density of 500 mA·cm^(−2)in alkaline seawater.Operando Raman spectroscopy studies further identify structural changes of disorderedδ(NiIII-O)during the seawater oxidation process.
