Hey Weiran, good question. Actually the pronunciation in the two examples is different. So first -tion in station. I think it can either be pronounced like a /sh/ or a /ts/. The vowel is pronounced like a short vowel o [ɔ]. Listen here for some examples: https://nl.forvo.com/word/station/#nl (number 1 and 3 are the clearest in my opinion). The -tion in internationaal can be pronounced like a /sh/ or even a /tsh/. But, unlike the previous word, this time the vowel is pronounced like a long o [o]. Listen here for an example: https://nl.forvo.com/word/internationaal/#nl . I hope this was helpful.