A university student has been refused bail after he allegedly threw acid in the face of a classmate before attacking him with a hammer.

With dressing on his face and in a disposable plastic jumpsuit, Rui Zhang today appeared before Waverley Local Court charged over the incident at the University of NSW yesterday afternoon.

Mr Zhang, 26, is accused of attacking fellow international student Xiaoyu Cheng, 25, inside one of the university's chemistry labs in the Chemical Sciences Building. Both are Chinese nationals and PhD students.

Mr Cheng remains in an induced coma in a critical condition. He was taken to St Vincent's Hospital but is now being treated in the burns unit of Royal North Shore Hospital.

Mr Zhang was taken for treatment for his physical injuries and mental health at Prince of Wales Hospital before fronting court this afternoon.