The oxidation resistance of isotropic pitch-based carbon fibers are sudied by thermogravimetric analysis,scanning electron microscope and mechanical propefties measure. The change of weight loss,microtextule and mecha...The oxidation resistance of isotropic pitch-based carbon fibers are sudied by thermogravimetric analysis,scanning electron microscope and mechanical propefties measure. The change of weight loss,microtextule and mechanical properties on condition of thermostatical oxidation and nonisothermal oxidation are separately mainly discussed.The results during isothermic oxidation at 316℃ showed that the weight loss of isotropic pitch-based carbon fiber increased and the strength, module rapidly decreased with prolongation of time, but the surface of carbon fiber is smoother and has not surface such as etching pits etc. The weight of isotropic pitch-based carbon fiber decreased more rapidly during the experiment of thermo-variable weight loss after 500℃ than before 500℃.展开更多
Theoretical consideration was conducted on a relation between pore diameter and interfacialarea between pores and fibers when pores uniforinly distribute in C/C composites. It was shownthat bonding at the fiber/matrix...Theoretical consideration was conducted on a relation between pore diameter and interfacialarea between pores and fibers when pores uniforinly distribute in C/C composites. It was shownthat bonding at the fiber/matrix interface apparently decreased with decreasing a pore diameter,and consequently a new idea of microspace modification concept was proposed for controllingfracture behavior of C/C composites. Four types of C/C composites with various pore structureswere fabricated by hot-pressing, and their fracture behavior was investigated by three pointbending tests. The fracture behavior of the C/C composites was changed from brittle one topseudo ductile one with decreasing the pore diameter. This result supported the validity of themicrospace modification concept proposed in this paper.展开更多
In this work,pitch-based carbon fibers were utilized to reinforce silicon carbide(SiC)composites via reaction melting infiltration(RMI)method by controlling the reaction temperature and resin carbon content.Thermal co...In this work,pitch-based carbon fibers were utilized to reinforce silicon carbide(SiC)composites via reaction melting infiltration(RMI)method by controlling the reaction temperature and resin carbon content.Thermal conductivities and bending strengths of composites obtained under different preparation conditions were characterized by various analytical methods.Results showed the formation of SiC whiskers(SiC_(w))during RMI process according to vapor–solid(VS)mechanism.SiC_(w) played an important role in toughening the C_(pf)/SiC composites due to crack bridging,crack deflection,and SiC_(w) pull-out.Increase in reaction temperature during RMI process led to an initial increase in thermal conductivity along in-plane and thickness directions of composites,followed by a decline.At reaction temperature of 1600℃,thermal conductivities along the in-plane and thickness directions were estimated to be 203.00 and 39.59 W/(m×K),respectively.Under these conditions,bending strength was recorded as 186.15±3.95 MPa.Increase in resin carbon content before RMI process led to the generation of more SiC matrix.Thermal conductivities along in-plane and thickness directions remained stable with desirable values of 175.79 and 38.86 W/(m×K),respectively.By comparison,optimal bending strength improved to 244.62±3.07 MPa.In sum,these findings look promising for future application of pitch-based carbon fibers for reinforcement of SiC ceramic composites.展开更多
文摘The oxidation resistance of isotropic pitch-based carbon fibers are sudied by thermogravimetric analysis,scanning electron microscope and mechanical propefties measure. The change of weight loss,microtextule and mechanical properties on condition of thermostatical oxidation and nonisothermal oxidation are separately mainly discussed.The results during isothermic oxidation at 316℃ showed that the weight loss of isotropic pitch-based carbon fiber increased and the strength, module rapidly decreased with prolongation of time, but the surface of carbon fiber is smoother and has not surface such as etching pits etc. The weight of isotropic pitch-based carbon fiber decreased more rapidly during the experiment of thermo-variable weight loss after 500℃ than before 500℃.
文摘Theoretical consideration was conducted on a relation between pore diameter and interfacialarea between pores and fibers when pores uniforinly distribute in C/C composites. It was shownthat bonding at the fiber/matrix interface apparently decreased with decreasing a pore diameter,and consequently a new idea of microspace modification concept was proposed for controllingfracture behavior of C/C composites. Four types of C/C composites with various pore structureswere fabricated by hot-pressing, and their fracture behavior was investigated by three pointbending tests. The fracture behavior of the C/C composites was changed from brittle one topseudo ductile one with decreasing the pore diameter. This result supported the validity of themicrospace modification concept proposed in this paper.
基金This work is supported by the National Key R&D Program of China(No.2018YFB1106600)the National Natural Science Foundation of China(Nos.51602257,92060202,51872229,and 51972269)+2 种基金the State Key Laboratory of Advanced Technology for Materials Synthesis and Processing(Wuhan University of Technology,No.2021-KF-10)the Creative Research Foundation of the Science and Technology on Thermostructural Composite Materials Laboratory(No.JCKYS2020607001)the Shaanxi Province Foundation for Natural Science(No.2020JQ-169).
文摘In this work,pitch-based carbon fibers were utilized to reinforce silicon carbide(SiC)composites via reaction melting infiltration(RMI)method by controlling the reaction temperature and resin carbon content.Thermal conductivities and bending strengths of composites obtained under different preparation conditions were characterized by various analytical methods.Results showed the formation of SiC whiskers(SiC_(w))during RMI process according to vapor–solid(VS)mechanism.SiC_(w) played an important role in toughening the C_(pf)/SiC composites due to crack bridging,crack deflection,and SiC_(w) pull-out.Increase in reaction temperature during RMI process led to an initial increase in thermal conductivity along in-plane and thickness directions of composites,followed by a decline.At reaction temperature of 1600℃,thermal conductivities along the in-plane and thickness directions were estimated to be 203.00 and 39.59 W/(m×K),respectively.Under these conditions,bending strength was recorded as 186.15±3.95 MPa.Increase in resin carbon content before RMI process led to the generation of more SiC matrix.Thermal conductivities along in-plane and thickness directions remained stable with desirable values of 175.79 and 38.86 W/(m×K),respectively.By comparison,optimal bending strength improved to 244.62±3.07 MPa.In sum,these findings look promising for future application of pitch-based carbon fibers for reinforcement of SiC ceramic composites.
