Chemical Vapor Infiltration Of Tac, Of ​​sic / Tac Modified The C / C Composites Preparation And Mechanical Properties

It is an effective opproach to improve the mechanical properties, oxidation-resistant and ablation-resistant properties of C/Ccomposites by midifying interface and matrix. In this article,oxidation-resistant fiber-coating had been prepared by chemical vapor infiltration to modify the interphase of C/C composites and. The C/C composites with PyC/TaC,PyC/SiC/TaC multilayered fiber-coating had been prepared. The preparation process, microstructure and mechanical properties of the new C/C composites were investigated. The fracture mechanism of modified C/C composites with different fiber-coating had been analyzed by the means of scanning electron microscope(SEM) and so on.TaC fiber-coating was prepared on the surface of carbon fiber with TaCl₅-C₃H₆-Ar system by chemical vapor deposition(CVD) and the influence of different TaC coating thickness to the mechanical properties of carbon fiber with TaC coating were investigated. Within the area of this experiment, with the increasing of thickness of TaC coating, the tensile strength of carbon fiber increases and the tensile modulus of carbon fiber decreases.TaC coating was prepared on the surface of carbon fiber in the perform by chemical vapor infiltration(CVI). The influence of CVI-TaC process parameters, such as deposition temperature, deposition pressure and the amount of dilute gas, on the deposition rate and the deposition uniformity were investigated overall. The deposition rate of TaC in the carbon fiber felt increases firstly with the increase of temperature,reaches the maximum value at 950℃.The fiber coatings with multilayered PyC/TaC,PyC/SiC/TaC fabricating were prepared by chemical vapor infiltration on the surface of carbon fiber. The coatings enwrap around the carbon fiber evenly and compactly forming cannular microstructure in modified C/C composites; The coating combines with carbon fiber and matrix better without obvious cracks.CVI-TaC modified C/C composites with different content TaC were prepared by chemical vapor infiltration and impregnation/carbonization process. The flexural properties and fracture mechanism of the composites had been analyzed. The flexural strength of CVI-TaC modified C/C composites with 5% TaC is 270MPa, decreased somewhat as compared with which of C/C composites(322MPa),exhibites "pseudo-plastic" behaviors. The flexural strength of CVI-TaC modified C/C composites with 10% TaC is 185MPa, exhibites toughness fracture behaviors. Both of modified C/C composites has no obvious change with fracture behaviors after high temperature treat at 2000℃.The tensile properties and compressive properties of CVI-TaC modified C/C composite with 5% TaC were investigated. The tensile strength of this composite is 135MPa,decreased somewhat as compared with which of C/C composites(192MPa);The compressive strength of this composites has no obvious change with it of C/C composites.With the optimization of structure of interface, CVI-SiC/TaC modified C/C composites were prepared, the flexural properties and fracture mechanism of the composites had been analyzed. The flexural strength of CVI-SiC/TaC modified C/C composites is up to 522MPa greatly higher than that of C/C composites,exhibites brittleness fracture behaviors;The flexural strength of this modified C/C composites decreased greatly after high temperature treat at 2000℃, and The fracture behaviors of those composites change from brittleness fracture to toughness fracture.In a word, using CVI technique to modify interface of C/C composites,the modified C/C composites can be prepared with excellent mechanical properties,it was best to the design and preparation of C/C composites with high performance in the further.