The resistance of Sylramic-iBN and Hi-Nicalon SiC fiber tows was measured at elevated temperature in air. Resistivity could not be directly measured, since the fibers passed through a furnace with varying temperature along the length. The resistivity of the isothermal section of the fiber tow was modeled by a series circuit of finite elements. Existing data for Hi-Nicalon resistivity vs temperature was used to verify the model and then extend it to Sylramic-iBN, for which there is no literature data readily available. The model matched experimental values with low overall error (<±14%). Fiber resistivity decreased by more than two orders of magnitude when heating from 25°C to 1400°C. Sylramic-iBN tow resistance was also measured during a 500 hour hold at 1315°C. The resistance increased by more than 140% during heat treatment. The resistance change correlated well with the decrease in SiC fiber diameter that resulted from oxidation.

Fabrication of 3D-printed ceramic parts with high complexity and high spatial resolution often demands low wall thickness as well as high stiffness at the green state, whereas printing simpler geometries may tolerate thicker, more compliant walls with the advantage of a rapid binder-burn-out and sintering process. In this work, the influence of the binder system on the thermophysical properties of 3D-printed stabilized zirconia ceramics was investigated. Samples were fabricated with the lithography-based ceramic manufacturing (LCM) technology using two different photosensitive ceramic suspensions (LithaCon 3Y230 and LithaCon 3Y210), with the same ZrO powder. A significant difference in stiffness in the green state (~3 MPa vs. ~32 MPa for LithaCon 3Y230 and LithaCon 3Y210, respectively) was measured, associated with a rather loose or a linked network formed in the binder due to photopolymerization. Both materials reached high relative densities, that is, >99%, exhibiting a homogeneous fine-grained microstructure. No significant differences on the coefficient of thermal expansion (11.18 ppm/K vs. 11.17 ppm/K) or Young's modulus (207 GPa vs. 205 GPa) were measured, thus demonstrating the potential of tailoring binder systems to achieve the required accuracy in 3D-printed parts, without detrimental effects on material's microstructure and thermophysical properties at the sintered state.

Overall, 8-mol% yttria-stabilized zirconia (8YSZ), unlike 3YSZ, is optically transparent and stable against low-temperature degradation but has insufficient mechanical properties due to its large grain size. The influence of the grain size of 8YSZ on mechanical properties was investigated to develop an 8YSZ suitable for dental restoration. Modulation of the grain size and relative density was achieved via a two-step sintering (TSS) process, and the corresponding kinetic window was established. The conditions of TSS employed herein yielded a relative density of more than 99% while maintaining a small grain size of 0.75 μm. On the other hand, the highest biaxial strength and the highest total transmittance attained were 833 MPa and 34.6% (1-mm-thick, 39.1% for a 0.5-mm thick sample) in the TSS 8YSZ with a grain size of 1.25 μm. These results suggest that strength has improved only when grain size reduction and increased relative density are achieved at the same time. The results demonstrate that the ceramic processing method has a significant effect on the mechanical and optical properties of 8YSZ needed for dental restoration and provide a new insight that contrasts previous studies focused on the starting material.