The working environment of aerospace engines is extremely harsh with temperature exceeding 1700℃and accompanied by thermal coupling effects.In this condition,the materials employed in hypersonic aircraft undergo abla...The working environment of aerospace engines is extremely harsh with temperature exceeding 1700℃and accompanied by thermal coupling effects.In this condition,the materials employed in hypersonic aircraft undergo ablation issues,which can cause catastrophic accidents.Due to the excellent high-temperature stability and ablation resistance,HfC exhibits outstanding thermal expansion coefficient matching that of C/SiC composites.2.5D needle-punched C/SiC composites coated with HfC are prepared using a plasma spraying process,and a high-enthalpy arc-heated wind tunnel is employed to simulate the re-entry environment of aircraft at 8 Mach and an altitude of 32 km.The plasma-sprayed HfC-coated 2.5D needle-punched C/SiC composites are subjected to long-term dynamic testing,and their properties are investigated.Specifically,after the thermal assessment ablation experiment,the composite retains its overall structure and profile;the total mass ablation rate is 0.07445 g/s,the average linear ablation rate in the thickness direction is-0.0675μm/s,and the average linear ablation rate in the length direction is 13.907μm/s.Results verify that plasma-sprayed HfC coating exhibits excellent anti-oxidation and ablation resistance properties.Besides,the microstructure and ablation mechanism of the C/SiC composites are studied.It is believed that this work will offer guideline for the development of thermal protection materials and the assessment of structural thermal performance.展开更多
With the rapid development of flexible and portable microelectronics,the extreme demand for miniaturized,mechanically flexible,and integrated microsystems are strongly stimulated.Here,biomass-derived carbons(BDCs)are ...With the rapid development of flexible and portable microelectronics,the extreme demand for miniaturized,mechanically flexible,and integrated microsystems are strongly stimulated.Here,biomass-derived carbons(BDCs)are prepared by KOH activation using Qamgur precursor,exhibiting three-dimensional(3D)hierarchical porous structure.Benefiting from unobstructed 3D hierarchical porous structure,BDCs provide an excellent specific capacitance of 433 F g^(-1)and prominent cyclability without capacitance degradation after 50000 cycles at 50 A g^(-1).Furthermore,BDC-based planar micro-supercapacitors(MSCs)without metal collector,prepared by mask-assisted coating,exhibit outstanding areal-specific capacitance of 84 mF cm^(-2)and areal energy density of 10.6μWh cm^(-2),exceeding most of the previous carbon-based MSCs.Impressively,the MSCs disclose extraordinary flexibility with capacitance retention of almost 100%under extreme bending state.More importantly,a flexible planar integrated system composed of the MSC and temperature sensor is assembled to efficiently monitor the temperature variation,providing a feasible route for flexible MSC-based functional micro-devices.展开更多
基金financially supported by the National Key R&D Program of China(No.2022YFB3-401900)the National Natural Science Foundation of China(No.U21A20134)the Shandong Provincial Natural Science Foundation(Excellent Young Fund,No.ZR2022YQ48).
文摘The working environment of aerospace engines is extremely harsh with temperature exceeding 1700℃and accompanied by thermal coupling effects.In this condition,the materials employed in hypersonic aircraft undergo ablation issues,which can cause catastrophic accidents.Due to the excellent high-temperature stability and ablation resistance,HfC exhibits outstanding thermal expansion coefficient matching that of C/SiC composites.2.5D needle-punched C/SiC composites coated with HfC are prepared using a plasma spraying process,and a high-enthalpy arc-heated wind tunnel is employed to simulate the re-entry environment of aircraft at 8 Mach and an altitude of 32 km.The plasma-sprayed HfC-coated 2.5D needle-punched C/SiC composites are subjected to long-term dynamic testing,and their properties are investigated.Specifically,after the thermal assessment ablation experiment,the composite retains its overall structure and profile;the total mass ablation rate is 0.07445 g/s,the average linear ablation rate in the thickness direction is-0.0675μm/s,and the average linear ablation rate in the length direction is 13.907μm/s.Results verify that plasma-sprayed HfC coating exhibits excellent anti-oxidation and ablation resistance properties.Besides,the microstructure and ablation mechanism of the C/SiC composites are studied.It is believed that this work will offer guideline for the development of thermal protection materials and the assessment of structural thermal performance.
基金support from Liao Ning Revitalization Talents Program(XLYC1907144)Dalian Youth Science and Technology Star Project Support Program(No.2017RQ104)+6 种基金National Key Research and Development Program of China(No.2020YFB0311600)National Natural Science Foundation of China(Grant Nos.22125903,51872283,22075279)Liaoning BaiQianWan Talents Program(Grant XLYC1807153)Dalian Innovation Support Plan for High Level Talents(2019RT09)Dalian National Laboratory For Clean Energy(DNL),CAS,DNL Cooperation Fund,CAS(DNL201912,DNL201915,DNL202016,DNL202019)DICP(DICP ZZBS201802,DICP I2020032)The Joint Fund of the Yulin University and the Dalian National Laboratory for Clean Energy(YLU-DNL Fund 2021002,2021009).
文摘With the rapid development of flexible and portable microelectronics,the extreme demand for miniaturized,mechanically flexible,and integrated microsystems are strongly stimulated.Here,biomass-derived carbons(BDCs)are prepared by KOH activation using Qamgur precursor,exhibiting three-dimensional(3D)hierarchical porous structure.Benefiting from unobstructed 3D hierarchical porous structure,BDCs provide an excellent specific capacitance of 433 F g^(-1)and prominent cyclability without capacitance degradation after 50000 cycles at 50 A g^(-1).Furthermore,BDC-based planar micro-supercapacitors(MSCs)without metal collector,prepared by mask-assisted coating,exhibit outstanding areal-specific capacitance of 84 mF cm^(-2)and areal energy density of 10.6μWh cm^(-2),exceeding most of the previous carbon-based MSCs.Impressively,the MSCs disclose extraordinary flexibility with capacitance retention of almost 100%under extreme bending state.More importantly,a flexible planar integrated system composed of the MSC and temperature sensor is assembled to efficiently monitor the temperature variation,providing a feasible route for flexible MSC-based functional micro-devices.
文摘提出了一种2.5维(2.5D)系统封装高速输入/输出(I/O)全链路的信号/电源完整性(Signal integrity/power integrity,SI/PI)协同仿真方法。首先通过电磁全波仿真分析SiP内部“芯片I/O引脚-有源转接板-印刷电路板(即封装基板)-封装体I/O引脚”这一主要高速信号链路及相应的转接板/印刷电路板电源分配网络(Power distribution network,PDN)的结构特征和电学特性,在此基础上分别搭建对应有源转接板和印刷电路板两种组装层级的“信号链路+PDN”模型,并分别进行SI/PI协同仿真,提取出反映信号链路/PDN耦合特性的模块化集总电路模型,从而在电路仿真器中以级联模型实现快速的SI/PI协同仿真。与全链路的全波仿真结果的对比表明,模块化后的协同仿真有很好的可信度,而且仿真时间与资源开销大幅缩减,效率明显提升。同时总结了去耦电容的大小与布局密度对PDN电源完整性的影响及对信号完整性的潜在影响,提出了去耦电容布局优化的建议。
