As an essential elastomer used in edge technologies, fluorosilicone rubber(FSR) suffers serious oxidative ageing problem when serving at high temperature. Cerium oxide is generally used as an antioxidant additive but ...As an essential elastomer used in edge technologies, fluorosilicone rubber(FSR) suffers serious oxidative ageing problem when serving at high temperature. Cerium oxide is generally used as an antioxidant additive but remains unsatisfactory. In order to obtain better antioxidant effect on improving the thermal stability of FSR, a kind of cerium-containing polymethylphenyl silicone(PSI-Ce) was synthesized and the structure was verified by Fourier-transform infrared spectroscopy(FTIR) and proton nuclear magnetic resonance(1HNMR). Due to the homogeneous dispersion on molecular scale, PSI-Ce imposed much better antioxidant effect than the commercial CeO2 did, no matter from isothermal degradation at 320 ℃ or thermal-oxidative ageing test at 230 ℃. In particular, after ageing for 72 h,FSR/PSI-Ce(2 phr) maintained 82% of tensile strength and 63% of elongation at break, in comparison to the corresponding values of 48%and 42% for FSR/CeO2(2 phr). Moreover, 2 phr PSI-Ce was equivalent to 0.046 phr CeO2 according to cerium element conservation.展开更多
We calculate the D→P transition form factors within the framework of the light-cone QCD sum rules(LCSR)with the D-meson light-cone distribution amplitudes(LCDAs).The next-to-leading power(NLP)corrections to the vacuu...We calculate the D→P transition form factors within the framework of the light-cone QCD sum rules(LCSR)with the D-meson light-cone distribution amplitudes(LCDAs).The next-to-leading power(NLP)corrections to the vacuum-to-D-meson correlation function are considered,and the NLP corrections from the high-twist D-meson LCDAs and the SU(3)breaking effect from a strange quark mass are investigated.Adopting the exponential model of the D-meson LCDAs,the SU(3)flavor symmetry breaking effects are predicted as R+,0 SU(3)=1.12 and R T SU(3)=1.39,respectively,confirming the results obtained from LCSR with pion LCDA.The numerical predictions of the form factors show that the contribution from two-particle higher-twist contributions is of great importance and the uncertainties are dominated by the inverse moment ofϕ+D(ω,μ).With the obtained form factors,the predicted Cabibbo-Kobayashi-Maskawa(CKM)matrix elements are|Vcd|=0.151+0.091−0.043|th.+0.017−0.02|exp.and|Vcs|=0.89+0.467−0.234|th.+0.008−0.008|exp..展开更多
基金financially supported by the National Natural Science Foundation of China (Nos. 51573043 and 21805086)the Fundamental Research Funds for the Central Universities (Nos. 222201817001 and 222201814004)+2 种基金supported by the Shanghai Leading Academic Discipline Project (No. B502)the Shanghai Key Laboratory Project (No. ZD20170203)Support from FSIR Advanced Material Co., Ltd.
文摘As an essential elastomer used in edge technologies, fluorosilicone rubber(FSR) suffers serious oxidative ageing problem when serving at high temperature. Cerium oxide is generally used as an antioxidant additive but remains unsatisfactory. In order to obtain better antioxidant effect on improving the thermal stability of FSR, a kind of cerium-containing polymethylphenyl silicone(PSI-Ce) was synthesized and the structure was verified by Fourier-transform infrared spectroscopy(FTIR) and proton nuclear magnetic resonance(1HNMR). Due to the homogeneous dispersion on molecular scale, PSI-Ce imposed much better antioxidant effect than the commercial CeO2 did, no matter from isothermal degradation at 320 ℃ or thermal-oxidative ageing test at 230 ℃. In particular, after ageing for 72 h,FSR/PSI-Ce(2 phr) maintained 82% of tensile strength and 63% of elongation at break, in comparison to the corresponding values of 48%and 42% for FSR/CeO2(2 phr). Moreover, 2 phr PSI-Ce was equivalent to 0.046 phr CeO2 according to cerium element conservation.
基金the National Natural Science Foundation of China(11675082,11735010)the Natural Science Foundation of Tianjin(19JCJQJC61100)。
文摘We calculate the D→P transition form factors within the framework of the light-cone QCD sum rules(LCSR)with the D-meson light-cone distribution amplitudes(LCDAs).The next-to-leading power(NLP)corrections to the vacuum-to-D-meson correlation function are considered,and the NLP corrections from the high-twist D-meson LCDAs and the SU(3)breaking effect from a strange quark mass are investigated.Adopting the exponential model of the D-meson LCDAs,the SU(3)flavor symmetry breaking effects are predicted as R+,0 SU(3)=1.12 and R T SU(3)=1.39,respectively,confirming the results obtained from LCSR with pion LCDA.The numerical predictions of the form factors show that the contribution from two-particle higher-twist contributions is of great importance and the uncertainties are dominated by the inverse moment ofϕ+D(ω,μ).With the obtained form factors,the predicted Cabibbo-Kobayashi-Maskawa(CKM)matrix elements are|Vcd|=0.151+0.091−0.043|th.+0.017−0.02|exp.and|Vcs|=0.89+0.467−0.234|th.+0.008−0.008|exp..
