Carbon fibre-reinforced ultra-high temperature ceramics(UHTCs)are considered a class of promising materials for several applications,the most appealing ones being in the aerospace sector.Reinforcement is necessary to ...Carbon fibre-reinforced ultra-high temperature ceramics(UHTCs)are considered a class of promising materials for several applications,the most appealing ones being in the aerospace sector.Reinforcement is necessary to overcome the brittleness and low thermal shock resistance of ceramics and is often provided through the addition of carbon fibres or other carbon-based phases,such as nanotubes,graphene,and graphite.The present work is focused on the toughening of UHTCs through incorporation of 30-50 vol% thin,ordered graphite layers from conventional filter paper followed by hot pressing sintering.Cellulose filter paper was selected because it undergoes thermolysis with no melting stage forming a strong carbonaceous residue that can be used as toughener.Microstructure and mechanical properties of toughened composites were compared to those of other materials reinforced with short carbon fibres and the effect of different distribution of graphite was studied.Addition of graphite allowed toughness to be increased from 3−4 MPa·m^(1/2)(for unreinforced materials)to 5.1−5.5 MPa·m^(1/2),similar to results obtained with short fibre reinforcement.The high-temperature properties,such as strength and toughness as well as oxidation resistance at 1500℃,were also examined.展开更多
A new additive technique for manufacturing of short fibre-reinforced ultra-refractory ceramics is presented.This technique allows the fabrication of solvent-free,thin(~100µm),flexible,and easy-to-handle sheets su...A new additive technique for manufacturing of short fibre-reinforced ultra-refractory ceramics is presented.This technique allows the fabrication of solvent-free,thin(~100µm),flexible,and easy-to-handle sheets suitable for fabricating homogeneous or layered structures.A large range of compositions,in terms of matrix and fibre volumetric contents,from 0%to 100%is possible.The amount of short carbon fibres incorporated in the sheets ranged from 20 to 50 vol%,whereas the fibre length ranged from 3 to 5 mm.The matrix composition investigated with this technique consisted of ZrB_(2)/SiC/Y_(2)O_(3).By increasing the fibre amount from 35 to 50 vol%,an improvement of mechanical properties was observed.Four-point flexural strength(σ)ranged from 107 to 140 MPa,depending on the amount of carbon fibres(Cf).The same holds true for the work of fracture,ranging from 108 to 253 J/m^(2).Functionally graded composites were fabricated by overlapping sheets with a fibre gradient(0%-50%).展开更多
Ultra-high-temperature ceramic matrix composites(UHTCMCs)based on a ZrB_(2)/SiC matrix have been investigated for the fabrication of reusable nozzles for propulsion.Three de Laval nozzle prototypes,obtained by sinteri...Ultra-high-temperature ceramic matrix composites(UHTCMCs)based on a ZrB_(2)/SiC matrix have been investigated for the fabrication of reusable nozzles for propulsion.Three de Laval nozzle prototypes,obtained by sintering with either hot pressing(HP)or spark plasma sintering(SPS),were tested 2-3 times in a hybrid rocket motor for proving reusability.Sections were extracted after oxidation tests to study the microstructural changes and oxidative and thermomechanical stresses induced by the repeated tests.Compared to a reference graphite nozzle,no measurable erosion was observed for the UHTCMC-based nozzles.The oxidation mechanism consisted in the formation of a ZrO_(2)intermediate layer,with a liquid silicon oxide(SiO_(2))layer on the surface that was displaced by the action of the gas flux towards the divergent part of the nozzle,protecting it from further oxidation.Both specimens obtained by HP and SPS displayed similar performance,with very slight differences,which were attributed to small changes in porosity.These tests demonstrated the capability of complex-shaped prototypes made of the developed UHTCMCs to survive repeated exposure to environments representative of a realistic space propulsion application,for overall operating time up to 30 s,without any failure nor measurable erosion,making a promising step towards the development of reusable rocket components.展开更多
基金supported by project CARBOSPACE“Ultra-refractory ceramic composites for Aerospace Defense Transport Energy”project ECOSISTER(National Recovery and Resilience Plan(NRRP),Mission 04 Component 2 Investment 1.5-NextGenerationEU,Call for tender n.3277 dated 30/12/2021,Award Number:0001052 dated 23/06/2022)project INFINITE“Liquid phase sintering of C fiber reinforced ultra-high temperature ceramics composites”.
文摘Carbon fibre-reinforced ultra-high temperature ceramics(UHTCs)are considered a class of promising materials for several applications,the most appealing ones being in the aerospace sector.Reinforcement is necessary to overcome the brittleness and low thermal shock resistance of ceramics and is often provided through the addition of carbon fibres or other carbon-based phases,such as nanotubes,graphene,and graphite.The present work is focused on the toughening of UHTCs through incorporation of 30-50 vol% thin,ordered graphite layers from conventional filter paper followed by hot pressing sintering.Cellulose filter paper was selected because it undergoes thermolysis with no melting stage forming a strong carbonaceous residue that can be used as toughener.Microstructure and mechanical properties of toughened composites were compared to those of other materials reinforced with short carbon fibres and the effect of different distribution of graphite was studied.Addition of graphite allowed toughness to be increased from 3−4 MPa·m^(1/2)(for unreinforced materials)to 5.1−5.5 MPa·m^(1/2),similar to results obtained with short fibre reinforcement.The high-temperature properties,such as strength and toughness as well as oxidation resistance at 1500℃,were also examined.
基金support by the European Union’s Horizon 2020 committee under research and innovation programme for the project C3 HARME:Next Generation Ceramic Composites for Harsh Combustion Environment and Space (Grant No.685594).
文摘A new additive technique for manufacturing of short fibre-reinforced ultra-refractory ceramics is presented.This technique allows the fabrication of solvent-free,thin(~100µm),flexible,and easy-to-handle sheets suitable for fabricating homogeneous or layered structures.A large range of compositions,in terms of matrix and fibre volumetric contents,from 0%to 100%is possible.The amount of short carbon fibres incorporated in the sheets ranged from 20 to 50 vol%,whereas the fibre length ranged from 3 to 5 mm.The matrix composition investigated with this technique consisted of ZrB_(2)/SiC/Y_(2)O_(3).By increasing the fibre amount from 35 to 50 vol%,an improvement of mechanical properties was observed.Four-point flexural strength(σ)ranged from 107 to 140 MPa,depending on the amount of carbon fibres(Cf).The same holds true for the work of fracture,ranging from 108 to 253 J/m^(2).Functionally graded composites were fabricated by overlapping sheets with a fibre gradient(0%-50%).
基金This work received support by the EU's Horizon 2020 research and innovation programme under Grant No.685594(C^(3)HARME:Next Generation Ceramic Composites for Harsh Combustion Environment and Space)project CARBOSPACE(Ultrarefractory Ceramic Composites for Aerospace Defense Transport Energy).
文摘Ultra-high-temperature ceramic matrix composites(UHTCMCs)based on a ZrB_(2)/SiC matrix have been investigated for the fabrication of reusable nozzles for propulsion.Three de Laval nozzle prototypes,obtained by sintering with either hot pressing(HP)or spark plasma sintering(SPS),were tested 2-3 times in a hybrid rocket motor for proving reusability.Sections were extracted after oxidation tests to study the microstructural changes and oxidative and thermomechanical stresses induced by the repeated tests.Compared to a reference graphite nozzle,no measurable erosion was observed for the UHTCMC-based nozzles.The oxidation mechanism consisted in the formation of a ZrO_(2)intermediate layer,with a liquid silicon oxide(SiO_(2))layer on the surface that was displaced by the action of the gas flux towards the divergent part of the nozzle,protecting it from further oxidation.Both specimens obtained by HP and SPS displayed similar performance,with very slight differences,which were attributed to small changes in porosity.These tests demonstrated the capability of complex-shaped prototypes made of the developed UHTCMCs to survive repeated exposure to environments representative of a realistic space propulsion application,for overall operating time up to 30 s,without any failure nor measurable erosion,making a promising step towards the development of reusable rocket components.
