The values of n and
Fig. 3 shows the TAK-242 kinetic curves of coated and uncoated samples after cyclic oxidation at different temperatures. From Fig. 3(a) and (b), the weight of coated sample losses at the beginning of cycles. According to Xu's work , the weight loss is due to the decomposition or dehydration of some unstable hydrated compounds. When the weight gain exceeds the loss factors, the weight change turns into a positive value. After several cycles, the oxidation of coated samples tends to be stable and the weight gain barely changes, while the weight gain of uncoated sample shows an increasing tendency. From Fig. 3(c) and (d), the oxidation kinetic curves present a similar changing regularity. After oxidation at 700 °C for 2 h, the weight gains of the coated and uncoated samples are 0.25 mg/cm2 and 0.26 mg/cm2 respectively. However, the weight gain of coated sample increases slowly in the next four cycles, whereas the weight gain of uncoated sample increases in a linear fashion. In the following cycles, the uncoated sample increases comparatively quickly and the coated sample increases at a very low speed. After oxidation at 700 °C for 75 h, the weight change of uncoated sample is 3.29 mg/cm2, which is 2.6 times as many as that of coated sample. After oxidation at 800 °C for 75 h, the weight change of uncoated sample is 17.2 mg/cm2, which is 3.5 times as many as that of coated sample.