The plugging of the surface pores in the preforms which often occurs in isothermal CVI technology seldom happens in the thermal gradient CVI process,namely,the overcrusting is avoided.

• 热梯度化学气相沉积工艺中避免了等温沉积工艺中预制体表面孔隙过早堵塞的现象,适合制备轴对称的环形、管型件。