Continuous carbon fiber reinforced copper matrix composites with 70%(volume fraction) of carbon fibers prepared by squeeze casting technique have been used for investigation of the coefficient of thermal expansion(CTE...Continuous carbon fiber reinforced copper matrix composites with 70%(volume fraction) of carbon fibers prepared by squeeze casting technique have been used for investigation of the coefficient of thermal expansion(CTE) and thermal conductivity.Thermo-physical properties have been measured in both,longitudinal and transversal directions to the fiber orientation.The results showed that Cf/Cu composites may be a suitable candidate for heat sinks because of its good thermo-physical properties e.g.the low CTE(4.18×10-6/K) in longitudinal orientation and(14.98×10-6/K) in transversal orientation at the range of 20-50℃,a good thermal conductivity(87.2 W/m·K) in longitudinal orientation and(58.2 W/m·K) in transversal orientation.Measured CTE and thermal conductivity values are compared with those predicted by several well-known models.Eshelby model gave better results for prediction of the CTE and thermal conductivity of the unidirectional composites.展开更多
Oxidation behaviors of carbon fiber reinforced SiC matrix composites(C/SiC)are one of the most noteworthy properties.For C/SiC,the oxidation behavior was controlled by matrix microcracks caused by the mismatch of coef...Oxidation behaviors of carbon fiber reinforced SiC matrix composites(C/SiC)are one of the most noteworthy properties.For C/SiC,the oxidation behavior was controlled by matrix microcracks caused by the mismatch of coefficients of thermal expansion(CTEs)and elastic modulus between carbon fiber and SiC matrix.In order to improve the oxidation resistance,multilayer SiC–Si_(3)N_(4) matrices were fabricated by chemical vapor infiltration(CVI)to alleviate the above two kinds of mismatch and change the local stress distribution.For the oxidation of C/SiC with multilayer matrices,matrix microcracks would be deflected at the transition layer between different layers of multilayer SiC–Si_(3)N_(4) matrix to lengthen the oxygen diffusion channels,thereby improving the oxidation resistance of C/SiC,especially at 800 and 1000℃.The strength retention ratio was increased from 61.9%(C/SiC–SiC/SiC)to 75.7%(C/SiC–Si_(3)N_(4)/SiC/SiC)and 67.8%(C/SiC–SiC/Si_(3)N_(4)/SiC)after oxidation at 800℃for 10 h.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
The increase in both power and packing densities in power electronic devices has led to an increase in the market demand for effective heat-dissipating materials with a high thermal conductivity and thermal expansion ...The increase in both power and packing densities in power electronic devices has led to an increase in the market demand for effective heat-dissipating materials with a high thermal conductivity and thermal expansion coefficient compatible with chip materials while still ensuring the reliability of the power modules.Metal matrix composites,especially copper matrix composites,containing carbon fibers,carbon nanofibers,or diamond are considered very promising as the next generation of thermalmanagement materials in power electronic packages.These composites exhibit enhanced thermal properties,as compared to pure copper,combined with lower density.This paper presents powder metallurgy and hot uniaxial pressing fabrication techniques for copper/carbon composite materials which promise to be efficient heat-dissipation materials for power electronic modules.Thermal analyses clearly indicate that interfacial treatments are required in these composites to achieve high thermal and thermomechanical properties.Control of interfaces(through a novel reinforcement surface treatment,the addition of a carbide-forming element inside the copper powders,and processing methods),when selected carefully and processed properly,will form the right chemical/mechanical bonding between copper and carbon,enhancing all of the desired thermal and thermomechanical properties while minimizing the deleterious effects.This paper outlines a variety of methods and interfacial materials that achieve these goals.展开更多
The different copper coatings with thickness varying from 0.3μm to 1.5μm were deposited on carbon fibers using either electroless plating or electroplating method. The coated fibers were chopped and composites were ...The different copper coatings with thickness varying from 0.3μm to 1.5μm were deposited on carbon fibers using either electroless plating or electroplating method. The coated fibers were chopped and composites were fabricated with melting aluminum at 700℃. The effect of the copper layer on the microstructure in the system was discussed. The results show that the copper layer has fully reacted with aluminum matrix, and the intermetallic compound CuAl2 forms through SEM observation and XRD, EDX analysis. The results of tensile tests indicate that composites fabricated using carbon fibers with 0.7-1.1μm copper coating perform best and the composites turn to more brittle as the thickness of copper coating increases. The fracture surface observation exhibits good interface bonding and ductility of the matrix alloy when the thickness of copper coating is about 0.7-1.1μm.展开更多
文摘Continuous carbon fiber reinforced copper matrix composites with 70%(volume fraction) of carbon fibers prepared by squeeze casting technique have been used for investigation of the coefficient of thermal expansion(CTE) and thermal conductivity.Thermo-physical properties have been measured in both,longitudinal and transversal directions to the fiber orientation.The results showed that Cf/Cu composites may be a suitable candidate for heat sinks because of its good thermo-physical properties e.g.the low CTE(4.18×10-6/K) in longitudinal orientation and(14.98×10-6/K) in transversal orientation at the range of 20-50℃,a good thermal conductivity(87.2 W/m·K) in longitudinal orientation and(58.2 W/m·K) in transversal orientation.Measured CTE and thermal conductivity values are compared with those predicted by several well-known models.Eshelby model gave better results for prediction of the CTE and thermal conductivity of the unidirectional composites.
基金This work was supported by the National Natural Science Foundation of China(Nos.52072303 and 51821091)the National Science and Technology Major Project(No.J2019-VI-0014-0129)。
文摘Oxidation behaviors of carbon fiber reinforced SiC matrix composites(C/SiC)are one of the most noteworthy properties.For C/SiC,the oxidation behavior was controlled by matrix microcracks caused by the mismatch of coefficients of thermal expansion(CTEs)and elastic modulus between carbon fiber and SiC matrix.In order to improve the oxidation resistance,multilayer SiC–Si_(3)N_(4) matrices were fabricated by chemical vapor infiltration(CVI)to alleviate the above two kinds of mismatch and change the local stress distribution.For the oxidation of C/SiC with multilayer matrices,matrix microcracks would be deflected at the transition layer between different layers of multilayer SiC–Si_(3)N_(4) matrix to lengthen the oxygen diffusion channels,thereby improving the oxidation resistance of C/SiC,especially at 800 and 1000℃.The strength retention ratio was increased from 61.9%(C/SiC–SiC/SiC)to 75.7%(C/SiC–Si_(3)N_(4)/SiC/SiC)and 67.8%(C/SiC–SiC/Si_(3)N_(4)/SiC)after oxidation at 800℃for 10 h.
文摘碳纤维混杂增强复合材料由于具有重量轻、可设计性强等诸多优点,广泛用于汽车、海洋、航空航天等行业.根据固化剂与环氧树脂的配比化学原理,计算出石墨烯-碳纤维混杂增强树脂基(GO-CF/EP)复合材料的最佳配比为1∶5,并采用真空浸渗热压成型工艺(VIHPS)制备1∶2~1∶7共六个配比的试样,结合形状记忆性能测试及微观形貌的观察,得到固化剂与环氧树脂实际最佳配比.实验结果表明,GO-CF/EP复合材料性能主要取决于体系中交联度的大小,交联度越大,复合材料的形状记忆性能越好,微观组织形貌也较理想.当基体配比为1∶5时,GO-CF/EP复合材料体系中交联度最大,微观形貌呈现均匀致密的状态,形状固定率最大,为95.90%;形状回复率最大,为95.40%;形状回复时间最短,为80.30 s;形状回复力最大,为9.48 N.当基体配比为1∶2或1∶7时,固化剂过量或不足,交联度较小,微观组织形貌中有大量的基体聚集区,其形状记忆性能下降,形状固定率及回复率也相应减小,分别为82.99%,81.66%,81.91%,78.75%;形状回复力分别只有5.20 N和5.50 N.
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.
文摘The increase in both power and packing densities in power electronic devices has led to an increase in the market demand for effective heat-dissipating materials with a high thermal conductivity and thermal expansion coefficient compatible with chip materials while still ensuring the reliability of the power modules.Metal matrix composites,especially copper matrix composites,containing carbon fibers,carbon nanofibers,or diamond are considered very promising as the next generation of thermalmanagement materials in power electronic packages.These composites exhibit enhanced thermal properties,as compared to pure copper,combined with lower density.This paper presents powder metallurgy and hot uniaxial pressing fabrication techniques for copper/carbon composite materials which promise to be efficient heat-dissipation materials for power electronic modules.Thermal analyses clearly indicate that interfacial treatments are required in these composites to achieve high thermal and thermomechanical properties.Control of interfaces(through a novel reinforcement surface treatment,the addition of a carbide-forming element inside the copper powders,and processing methods),when selected carefully and processed properly,will form the right chemical/mechanical bonding between copper and carbon,enhancing all of the desired thermal and thermomechanical properties while minimizing the deleterious effects.This paper outlines a variety of methods and interfacial materials that achieve these goals.
基金Project(204AA335010) supported by the National High-Tech Research and Development Program of China
文摘The different copper coatings with thickness varying from 0.3μm to 1.5μm were deposited on carbon fibers using either electroless plating or electroplating method. The coated fibers were chopped and composites were fabricated with melting aluminum at 700℃. The effect of the copper layer on the microstructure in the system was discussed. The results show that the copper layer has fully reacted with aluminum matrix, and the intermetallic compound CuAl2 forms through SEM observation and XRD, EDX analysis. The results of tensile tests indicate that composites fabricated using carbon fibers with 0.7-1.1μm copper coating perform best and the composites turn to more brittle as the thickness of copper coating increases. The fracture surface observation exhibits good interface bonding and ductility of the matrix alloy when the thickness of copper coating is about 0.7-1.1μm.