Arc-heated wind tunnel

The histories of mass change rate of Specimen B and C are shown in Figure 4. The air flow of the arc wind tunnel was ejq)ected to be chemically active. However, the mass reduction rate for the arc-heated wind tunnel test was unexpectedly smaller than that for the hot gas flow test. This can possibly be attributed to the ambient pressure, because the ambient pressure for the hot gas flow test was... 

To analyze the morphology of the composite after the arc-heated wind tunnel test, the specimen was observed by SEM, and the results are presented in Figure 11. An oxide film covering the matrix can be found on the surface of the composites. The oxide film is rugged, continuous and dense. At the center of the ablation area, lots of holes form because considerable amounts of gases, such as CO and produced by the oxidation of ZrBj-ZrC-SiC matrix, and escaped during the ablation... 

Figure 11. Surface morphologies of the C/C-ZrB -ZrC-SiC composites after arc-heated wind tunnel ablation (a) a low magnification image, (b-d) high magnification images corresponding to the marked region 1 (b), 2 (c), and 3 (d)...

In this chapter, the pyrolysis of synthesized polymers, microstructure of their derived UHTC composite matrices, as well the preparation and properties of C/C-ZrB2-ZrC-SiC composites are investigated. Preparation and microstructures of the composites were studied in part I of the paper. The ablation behaviors and mechanical properties of the composites in a ground arc-jet wind tunnel and plasma torch with temperatures above 2000 °C and heating rate around 30K/s were studied in Part II. The major aims of these studies were to evaluate the possibility of producing a nano-size dispersed ZrB -ZrC-SiC matrix using these complex polymeric precursors, which are expected to exhibit improved oxidation and ablation resistance, compared to those composites with layered or large particle incorporated UHTC matrices. 

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