The regulation of the burning rate pressure exponent for the ammonium perchlorate/hydroxylterminated polybutadiene/aluminum(AP/HTPB/Al)composite propellants under high pressures is a crucial step for its application i...The regulation of the burning rate pressure exponent for the ammonium perchlorate/hydroxylterminated polybutadiene/aluminum(AP/HTPB/Al)composite propellants under high pressures is a crucial step for its application in high-pressure solid rocket motors.In this work,the combustion characteristics of AP/HTPB/Al composite propellants containing ferrocene-based catalysts were investigated,including the burning rate,thermal behavior,the local heat transfer,and temperature profile in the range of 7-28 MPa.The results showed that the exponent breaks were still observed in the propellants after the addition of positive catalysts(Ce-Fc-MOF),the burning rate inhibitor((Ferrocenylmethyl)trimethylammonium bromide,Fc Br)and the mixture of Fc Br/catocene(GFP).However,the characteristic pressure has increased,and the exponent decreased from 1.14 to 0.66,0.55,and 0.48 when the addition of Ce-FcMOF,Fc Br and Fc Br/GFP in the propellants.In addition,the temperature in the first decomposition stage was increased by 7.50℃ and 11.40℃ for the AP/Fc Br mixture and the AP/Fc Br/GFP mixture,respectively,compared to the pure AP.On the other hand,the temperature in the second decomposition stage decreased by 48.30℃ and 81.70℃ for AP/Fc Br and AP/Fc Br/GFP mixtures,respectively.It was also found that Fc Br might generate ammonia to cover the AP surface.In this case,a reaction between the methyl in Fc Br and perchloric acid caused more ammonia to appear at the AP surface,resulting in the suppression of ammonia desorption.In addition,the coarse AP particles on the quenched surface were of a concave shape relative to the binder matrix under low and high pressures when the catalysts were added.In the process,the decline at the AP/HTPB interface was only exhibited in the propellant with the addition of Ce-Fc-MOF.The ratio of the gas-phase temperature gradient of the propellants containing catalysts was reduced significantly below and above the characteristic pressure,rather than 3.6 times of the difference in the blank propellant.Overall,the obtained results demonstrated that the pressure exponent could be effectively regulated and controlled by adjusting the propellant local heat and mass transfer under high and low pressures.展开更多
The development of highly active and enantioselective ligands and catalysts for the asymmetric hydrogenation of ketone has been the goal of synthetic chemists for more than fifty years.Herein,a series of ferrocene-bas...The development of highly active and enantioselective ligands and catalysts for the asymmetric hydrogenation of ketone has been the goal of synthetic chemists for more than fifty years.Herein,a series of ferrocene-based tetradentate ligands were developed and applied in Ir-catalysed asymmetric hydrogenation of ketone.The hydrolytic ring-opening of the oxazoline moiety of ligand f-amphox leads to the accidental discovery of a highly efficient and enantioselective tetradentate ligand f-phamidol which showed extraordinarily high reactivity and enantioselectivity(up to 99%yield,up to>99%ee and up to 1,000,000 TON).In addition,two types of other tetradentate ligands f-phamida and f-phamide were also synthesized and evaluated.展开更多
基金the support of the National Natural Science Foundation of China grant number 51776175。
文摘The regulation of the burning rate pressure exponent for the ammonium perchlorate/hydroxylterminated polybutadiene/aluminum(AP/HTPB/Al)composite propellants under high pressures is a crucial step for its application in high-pressure solid rocket motors.In this work,the combustion characteristics of AP/HTPB/Al composite propellants containing ferrocene-based catalysts were investigated,including the burning rate,thermal behavior,the local heat transfer,and temperature profile in the range of 7-28 MPa.The results showed that the exponent breaks were still observed in the propellants after the addition of positive catalysts(Ce-Fc-MOF),the burning rate inhibitor((Ferrocenylmethyl)trimethylammonium bromide,Fc Br)and the mixture of Fc Br/catocene(GFP).However,the characteristic pressure has increased,and the exponent decreased from 1.14 to 0.66,0.55,and 0.48 when the addition of Ce-FcMOF,Fc Br and Fc Br/GFP in the propellants.In addition,the temperature in the first decomposition stage was increased by 7.50℃ and 11.40℃ for the AP/Fc Br mixture and the AP/Fc Br/GFP mixture,respectively,compared to the pure AP.On the other hand,the temperature in the second decomposition stage decreased by 48.30℃ and 81.70℃ for AP/Fc Br and AP/Fc Br/GFP mixtures,respectively.It was also found that Fc Br might generate ammonia to cover the AP surface.In this case,a reaction between the methyl in Fc Br and perchloric acid caused more ammonia to appear at the AP surface,resulting in the suppression of ammonia desorption.In addition,the coarse AP particles on the quenched surface were of a concave shape relative to the binder matrix under low and high pressures when the catalysts were added.In the process,the decline at the AP/HTPB interface was only exhibited in the propellant with the addition of Ce-Fc-MOF.The ratio of the gas-phase temperature gradient of the propellants containing catalysts was reduced significantly below and above the characteristic pressure,rather than 3.6 times of the difference in the blank propellant.Overall,the obtained results demonstrated that the pressure exponent could be effectively regulated and controlled by adjusting the propellant local heat and mass transfer under high and low pressures.
基金X.Zhang is indebted to the National Key R&D Program of China(No.2021YFA1500201)the Shenzhen Science and Technology Innovation Committee(SSTIC)(No.KQTD2015071710315717)+5 种基金Stable Support Plan Program of Shenzhen Natural Science Fund(No.20200925161222002)Key-Area Research and Development Program of Guangdong Province(No.2020B010188001)Innovative Team of Universities in Guangdong Province(No.2020KCXTD016)National Natural Science Foundation of China(No.21991113)G.Q.Chen gratefully acknowledges the National Natural Science Foundation of China(Nos.21901107 and 22171129)SSTIC(No.JCYJ20210324104202007)for financial support.
文摘The development of highly active and enantioselective ligands and catalysts for the asymmetric hydrogenation of ketone has been the goal of synthetic chemists for more than fifty years.Herein,a series of ferrocene-based tetradentate ligands were developed and applied in Ir-catalysed asymmetric hydrogenation of ketone.The hydrolytic ring-opening of the oxazoline moiety of ligand f-amphox leads to the accidental discovery of a highly efficient and enantioselective tetradentate ligand f-phamidol which showed extraordinarily high reactivity and enantioselectivity(up to 99%yield,up to>99%ee and up to 1,000,000 TON).In addition,two types of other tetradentate ligands f-phamida and f-phamide were also synthesized and evaluated.
