目的观察C/C-SiC复合材料对周围骨组织细胞凋亡情况的影响。方法选用8只日本大耳白兔,雄性,随机分为2组(每组4只)。将实验材料(C/C-SiC复合材料)和对照材料(Ti)各8枚植入兔子股骨内。3个月后,将带有实验材料和对照材料股骨标本脱钙、进...目的观察C/C-SiC复合材料对周围骨组织细胞凋亡情况的影响。方法选用8只日本大耳白兔,雄性,随机分为2组(每组4只)。将实验材料(C/C-SiC复合材料)和对照材料(Ti)各8枚植入兔子股骨内。3个月后,将带有实验材料和对照材料股骨标本脱钙、进行免疫组化(Caspase-3、Bax、Bcl-2)染色。观察植入材料周围骨组织细胞生长和凋亡的表达情况,并利用Imagepro Plus 6.0图像分析软件分析棕染细胞的灰度值。然后利用SPSS 17.0统计软件进行独立样本t检验分析结果。结果实验动物麻醉及手术效果较理想。植入材料与骨结合紧密、无松动,大部分植入材料表面有新生骨组织。光镜下观察,Caspase-3、Bcl-2、Bax免疫组化呈阳性反应骨细胞胞质及部分细胞膜棕褐色染色。C/C-SiC实验组棕褐色染色平均灰度值与纯钛对照组棕褐色染色平均灰度值相比无显著差别。结论 C/C-SiC复合材料植入兔股骨内术后3个月,材料周围骨细胞凋亡程度与纯钛材料无显著差别。展开更多
Ablation under oxyacetylene torch with heat flux of 4186.8（10%kW/m2 for 20 s was performed to evaluate the ablation resistance of C/C-SiC composites fabricated by chemical vapor infiltration（CVI） combined with liqu...Ablation under oxyacetylene torch with heat flux of 4186.8（10%kW/m2 for 20 s was performed to evaluate the ablation resistance of C/C-SiC composites fabricated by chemical vapor infiltration（CVI） combined with liquid silicon infiltration（LSI） process.The results indicated that C/C-SiC composites present a better ablation resistance than C/C composites without doped SiC.The doped SiC and the ablation products SiO2 derived from it play key roles in ablation process.Bulk quantities of SiO2 nanowires with diameter of 80 nm-150 nm and length of tens microns were observed on the surface of specimens after ablation.The growth mechanism of the SiO_2 nanowires was interpreted with a developed vapor-liquid-solid（VLS） driven by the temperature gradient.展开更多
C_(f)/Ta_(x)Hf_(1−x)C–SiC composites are ideal thermal structural materials for service under extreme conditions of hypersonic vehicles.However,how to synthesize TaxHf1-xC powders and efficiently fabricate C_(f)/Ta_(...C_(f)/Ta_(x)Hf_(1−x)C–SiC composites are ideal thermal structural materials for service under extreme conditions of hypersonic vehicles.However,how to synthesize TaxHf1-xC powders and efficiently fabricate C_(f)/Ta_(x)Hf_(1−x)C–SiC composites still faces some challenges.Furthermore,mechanical properties and thermophysical properties of Ta_(x)Hf_(1−x)C vary with the composition,but not monotonically.In-depth analysis of mechanical behaviors of the C_(f)/Ta_(x)Hf_(1−x)C–SiC composites is extremely important for their development and applications.In this study,the Ta_(x)Hf_(1−x)C powders(x=0.2,0.5,0.8)were successfully synthesized via solid solution of TaC and HfC at a relatively low temperature of 1800℃,with a small amount of Si as an additive.Subsequently,the efficient fabrication of 2D-C_(f)/Ta_(x)Hf_(1−x)C–SiC composites was achieved by slurry impregnation and lamination(SIL)combined with precursor infiltration and pyrolysis(PIP).In addition,the mechanical behavior of the composites was investigated systematically.It is demonstrated that the composites present remarkable non-brittle fractures,including a large number of fiber pull out and interphase debonding.Also,the fracture failure involves a complex process of microcrack generation and propagation,matrix cracking,and layer fracture.Moreover,the interfacial bonding between the fibers and the matrix is enhanced as the Ta∶Hf ratio decreases from 4∶1 to 1∶4.As a result,C_(f)/Ta_(0.2)Hf_(0.8)C–SiC composites exhibit exceptional flexural strength of 437±19 MPa,improved by 46%compared with C_(f)/Ta_(0.8)Hf_(0.2)C–SiC(299±19 MPa).This study provides a new perception of design and fabrication of ultra-high-temperature ceramic(UHTC)matrix composites with high performance.展开更多
文摘目的观察C/C-SiC复合材料对周围骨组织细胞凋亡情况的影响。方法选用8只日本大耳白兔,雄性,随机分为2组(每组4只)。将实验材料(C/C-SiC复合材料)和对照材料(Ti)各8枚植入兔子股骨内。3个月后,将带有实验材料和对照材料股骨标本脱钙、进行免疫组化(Caspase-3、Bax、Bcl-2)染色。观察植入材料周围骨组织细胞生长和凋亡的表达情况,并利用Imagepro Plus 6.0图像分析软件分析棕染细胞的灰度值。然后利用SPSS 17.0统计软件进行独立样本t检验分析结果。结果实验动物麻醉及手术效果较理想。植入材料与骨结合紧密、无松动,大部分植入材料表面有新生骨组织。光镜下观察,Caspase-3、Bcl-2、Bax免疫组化呈阳性反应骨细胞胞质及部分细胞膜棕褐色染色。C/C-SiC实验组棕褐色染色平均灰度值与纯钛对照组棕褐色染色平均灰度值相比无显著差别。结论 C/C-SiC复合材料植入兔股骨内术后3个月,材料周围骨细胞凋亡程度与纯钛材料无显著差别。
基金supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20110006110025)the National Natural Science Foundation of China(Grant No.U1134102)
文摘Ablation under oxyacetylene torch with heat flux of 4186.8（10%kW/m2 for 20 s was performed to evaluate the ablation resistance of C/C-SiC composites fabricated by chemical vapor infiltration（CVI） combined with liquid silicon infiltration（LSI） process.The results indicated that C/C-SiC composites present a better ablation resistance than C/C composites without doped SiC.The doped SiC and the ablation products SiO2 derived from it play key roles in ablation process.Bulk quantities of SiO2 nanowires with diameter of 80 nm-150 nm and length of tens microns were observed on the surface of specimens after ablation.The growth mechanism of the SiO_2 nanowires was interpreted with a developed vapor-liquid-solid（VLS） driven by the temperature gradient.
基金support from the National Key R&D Program of China(No.2022YFB3707700)Program of Shanghai Academic/Technology Research Leader(No.23XD1424300)the National Natural Science Foundation of China(No.52332003)are greatly acknowledged.
文摘C_(f)/Ta_(x)Hf_(1−x)C–SiC composites are ideal thermal structural materials for service under extreme conditions of hypersonic vehicles.However,how to synthesize TaxHf1-xC powders and efficiently fabricate C_(f)/Ta_(x)Hf_(1−x)C–SiC composites still faces some challenges.Furthermore,mechanical properties and thermophysical properties of Ta_(x)Hf_(1−x)C vary with the composition,but not monotonically.In-depth analysis of mechanical behaviors of the C_(f)/Ta_(x)Hf_(1−x)C–SiC composites is extremely important for their development and applications.In this study,the Ta_(x)Hf_(1−x)C powders(x=0.2,0.5,0.8)were successfully synthesized via solid solution of TaC and HfC at a relatively low temperature of 1800℃,with a small amount of Si as an additive.Subsequently,the efficient fabrication of 2D-C_(f)/Ta_(x)Hf_(1−x)C–SiC composites was achieved by slurry impregnation and lamination(SIL)combined with precursor infiltration and pyrolysis(PIP).In addition,the mechanical behavior of the composites was investigated systematically.It is demonstrated that the composites present remarkable non-brittle fractures,including a large number of fiber pull out and interphase debonding.Also,the fracture failure involves a complex process of microcrack generation and propagation,matrix cracking,and layer fracture.Moreover,the interfacial bonding between the fibers and the matrix is enhanced as the Ta∶Hf ratio decreases from 4∶1 to 1∶4.As a result,C_(f)/Ta_(0.2)Hf_(0.8)C–SiC composites exhibit exceptional flexural strength of 437±19 MPa,improved by 46%compared with C_(f)/Ta_(0.8)Hf_(0.2)C–SiC(299±19 MPa).This study provides a new perception of design and fabrication of ultra-high-temperature ceramic(UHTC)matrix composites with high performance.
