**4. Conclusions**

This paper describes the influence of surface modification and fabrication methods of alumina ceramic on the adhesion between ceramic and elastomer in interpenetrating phase composites. The application of the HIP process for the fabrication of ceramic foams is rare, due to the difficulty of gaining IPCs afterward. Owing to the use of HIP, a low degree of porosity of the ceramic preforms was achieved, which provides higher mechanical properties of the composites. However, for such porosity, it is difficult to obtain a composite structure with interpenetrating of phases. Hence, silane coat applications were analyzed. The tests were carried out for dense and porous alumina ceramic as well as alumina– elastomer composites. The porous ceramic preforms were obtained by sintering methods whereas composites used infiltration of reactive elastomer mixture into ceramic pores. The fabricated composites were characterized by the microstructure with two three-dimensional and topologically interpenetrating phases. To improve the adhesion between alumina ceramics and urea-urethane elastomer in IPCs, hot isostatic pressing of alumina ceramic was utilized. Moreover, the porous ceramic preform was coated by coupling agen<sup>t</sup> solution. The impact of HIP sintering and silane solution coat was investigated on roughness, wettability, microstructure, as well as mechanical properties of materials based on alumina ceramic.

The results are summarized as follows:


**Author Contributions:** Conceptualization, P.K.; methodology, P.K.; software, P.K.; validation, P.K., A.B., K.P., M.M., J.K.; formal analysis, P.K. and A.B.; investigation, P.K.; resources, P.K. and K.P.; data curation, P.K., A.B., K.P.; writing—original draft preparation, P.K.; writing—review and edit, P.K., A.B., K.P., M.M., J.K.; visualization, P.K.; supervision, P.K. and A.B.; project administration, P.K., M.M. and J.K.; funding acquisition, M.M. and J.K. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by a Scholarship from the Dean of Faculty of Civil Engineering and Geodesy, Military University of Technology, number 1/DPH/2020.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** All data are included in the manuscript.

**Acknowledgments:** The authors would like to acknowledge Artur Ozi ˛ebło and Adam Witek for support in ceramic specimens fabrication, Zbigniew Jaegermann for shear tests carrying out, Oskar Czemierowski for contact angle measurements, and Maciej Spychalski for topography investigation.

**Conflicts of Interest:** The authors declare no conflict of interest.
