**Deposition of Photocatalytic TiO2 Coating by Modifying the Solidification Pathway in Plasma Spraying**

#### **Kui Wen 1,2, Min Liu 1,2, Xuezhang Liu 1,2,3,\*, Chunming Deng 2 and Kesong Zhou 1,2,\***


Received: 21 September 2017; Accepted: 11 October 2017; Published: 13 October 2017

**Abstract:** The deposition of photocatalytic TiO2 coatings with plasma spraying is attractive for large-scale applications due to its low cost and simplicity, but it is still a challenge to obtain a TiO2 coating with high anatase content. The solidification pathway of inflight melted particles was investigated in the present paper, and TiO2 coatings with enhanced photocatalytic activity were obtained without a significant loss of the microhardness. The coating microstructure, phase composition, and crystallite size were investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Photocatalytic performance was evaluated by decomposing an aqueous solution of methylene blue. Results showed that the anatase content in TiO2 coating was augmented to 19.9% from 4%, and the time constant of the activity was increased to 0.0046 h−<sup>1</sup> from 0.0017 h−1.

**Keywords:** photocatalytic coatings; solidification; plasma spraying; TiO2; microstructure
