*Article* **Evaluation of Physical Properties of Zirconia Suspension with Added Silane Coupling Agent for Additive Manufacturing Processes**

**Jae-Gon Jang 1,†, Jin-Ho Kang 1,† , Kwang-Bum Joe <sup>2</sup> , Kumaresan Sakthiabirami 1,3, Kyoung-Jun Jang <sup>1</sup> , Mee-Jin Jun <sup>4</sup> , Gye-Jeong Oh <sup>3</sup> , Chan Park <sup>1</sup> and Sang-Won Park 1,3,\***


**Abstract:** In this study, we have analysed the effects of a silane coupling agent on the volume fraction of zirconia for digital light processing (DLP)-based additive manufacturing processes. Zirconia suspension was prepared by the incorporation of silane-modified zirconia particles (experimental group) or untreated zirconia particles (control group). Furthermore, the control and experimental group were subdivided into three groups based on the volume fraction (52, 54, and 56 vol%) of zirconia particles. The disk-shaped zirconia samples were 3D (three-dimensional) printed using the DLP technique and their physical and mechanical properties were evaluated. The addition of a silane coupling agent to the zirconia samples was found to have influence of about 6% on the hardness and biaxial flexural strength. Moreover, the decrease in minute air gaps inside the zirconia layers significantly increased the material density (visualized from the microstructure analysis). Thus, from this study, it was established that the silane-modified zirconia particles had a positive effect on the physical properties of the zirconia parts.

**Keywords:** additive manufacturing; digital light processing (DLP) technology; zirconia suspension; silane coupling agent; physical property
