Strong, tough, and almost fully dense C fiber reinforced celsian matrix composites have been fabricated by impregnation of the fiber tows with the matrix slurry, winding on a drum, drying, stacking the prepreg tapes i...Strong, tough, and almost fully dense C fiber reinforced celsian matrix composites have been fabricated by impregnation of the fiber tows with the matrix slurry, winding on a drum, drying, stacking the prepreg tapes in the desired orientation, and hot pressing. The monoclinic celsian phase in the matrix was produced in situ, during hot pressing, from amphosous BAS. The unidirectional composites having ≈20 vol% of fibers exhibited graceful failure with extensive fiber pullout in three point bend tests at room temperature. Values of ultimate flexural strength and fracture toughness were 379MPa and 8 3MPa·m 1/2 , respectively.展开更多
The silicon nitride based ceramics obtained by the addition of β-Si3N4 seeds was fabricated using celsian as the additive and by pressureless sintering. The microstructure of the material was observed and analyzed us...The silicon nitride based ceramics obtained by the addition of β-Si3N4 seeds was fabricated using celsian as the additive and by pressureless sintering. The microstructure of the material was observed and analyzed using XRD, SEM, and TEM and the mechanical response of this array microstructure was characterized for flexural strength and fracture behavior. The result shows that the growth of the larger aspect ratio grains initiate mainly from the seeds through the heterogeneous nucleation mechanism during the process of phase transformation, and the intergranular phase BaAl2Si20s services as good refractory materials. In contrast to conventional processing, a stable bimodal microstructure and complicated component with a lower cost can be achieved using the abovementioned process theoretically and practically.展开更多
BAS (BaAl 2Si 2O 8) glass ceramic was prepared by a sol gel process and the SiC W/BAS composites were fabricated by hot pressing. The transformation from hexacelsian to celsian, the microstructure and mechanical prope...BAS (BaAl 2Si 2O 8) glass ceramic was prepared by a sol gel process and the SiC W/BAS composites were fabricated by hot pressing. The transformation from hexacelsian to celsian, the microstructure and mechanical properties of the composites was investigated. The results show that the transformation promoted by adding celsian seeds is retarded in the composite by the presence of SiC whisker. SiC whisker has a good effect of improving the mechanical properties of BAS glass ceramic matrix. The toughening mechanisms are crack deflection and whisker fracture. The strengthening mechanism is loading transition. The amorphous phase at SiC W/BAS matrix interface damages the fracture toughness and high temperature strength of the composites.展开更多
以煤矸石、碳酸钡和氧化铝为原料,采用同相反应热压烧结法制备了原位生长莫来石棒晶增强 BAS 复合材料,借助于 XRD 和 SEM 研究烧成温度和配比对复合材料的相组成、结构和性能的影响。结果表明:热压烧结制备的致密均匀的复合材料,各相...以煤矸石、碳酸钡和氧化铝为原料,采用同相反应热压烧结法制备了原位生长莫来石棒晶增强 BAS 复合材料,借助于 XRD 和 SEM 研究烧成温度和配比对复合材料的相组成、结构和性能的影响。结果表明:热压烧结制备的致密均匀的复合材料,各相结合紧密,均匀分布,莫来石呈针状或棒状,形成空间网络结构;温度的升高,有利于材料的致密化和力学性能的改善,在1450℃×1h×20 MPa 时,按 m(BaO):m(Al_2O_3):m(SiO_2)=30:15:55的配比制备的材料可以获得优异的力学性能。弯曲强度为215 MPa,断裂韧性为3.8 MPa·m^(1/2),比纯钡长石基体材料分别提高169%和111%。展开更多
文摘Strong, tough, and almost fully dense C fiber reinforced celsian matrix composites have been fabricated by impregnation of the fiber tows with the matrix slurry, winding on a drum, drying, stacking the prepreg tapes in the desired orientation, and hot pressing. The monoclinic celsian phase in the matrix was produced in situ, during hot pressing, from amphosous BAS. The unidirectional composites having ≈20 vol% of fibers exhibited graceful failure with extensive fiber pullout in three point bend tests at room temperature. Values of ultimate flexural strength and fracture toughness were 379MPa and 8 3MPa·m 1/2 , respectively.
基金This work was financially supported by the Scientific Research Foundation for the Returned Overseas Chinese Scholars of the Minis-try of Education of China (05-04) and the projects to tackle the Key Problem in Science and Technology of Shaanxi Province, China(No.2004K07-G13).
文摘The silicon nitride based ceramics obtained by the addition of β-Si3N4 seeds was fabricated using celsian as the additive and by pressureless sintering. The microstructure of the material was observed and analyzed using XRD, SEM, and TEM and the mechanical response of this array microstructure was characterized for flexural strength and fracture behavior. The result shows that the growth of the larger aspect ratio grains initiate mainly from the seeds through the heterogeneous nucleation mechanism during the process of phase transformation, and the intergranular phase BaAl2Si20s services as good refractory materials. In contrast to conventional processing, a stable bimodal microstructure and complicated component with a lower cost can be achieved using the abovementioned process theoretically and practically.
文摘BAS (BaAl 2Si 2O 8) glass ceramic was prepared by a sol gel process and the SiC W/BAS composites were fabricated by hot pressing. The transformation from hexacelsian to celsian, the microstructure and mechanical properties of the composites was investigated. The results show that the transformation promoted by adding celsian seeds is retarded in the composite by the presence of SiC whisker. SiC whisker has a good effect of improving the mechanical properties of BAS glass ceramic matrix. The toughening mechanisms are crack deflection and whisker fracture. The strengthening mechanism is loading transition. The amorphous phase at SiC W/BAS matrix interface damages the fracture toughness and high temperature strength of the composites.
