Accutom 100

A pre-sintered zirconia block (Ceramill Zolid HT + Preshades: A2 shade, Amann Girrbach, Koblach, Austria) containing Y₂O₃ (6.0–7.0 wt%), HfO₂ (≤5 wt%), Al₂O₃ (≤0.5 wt%), and other oxides (≤1 wt%) was cut using a high-speed ultra-precision cutter equipped with a diamond wheel (Accutom-100, Struers, Cleveland, OH, USA). The cut specimens were sintered for 2 h at 1450 °C in a sintering furnace (Ceramill Therm, Amann Girrbach, Koblach, Austria) according to the manufacturer’s instructions. The final sizes of specimens were 10.0 mm × 10.0 mm × 1.0 mm for the hardness test (n = 5/group), X-ray diffraction (XRD) analysis (n = 1/group), and field-emission scanning electron microscopy (FE-SEM) measurement (n = 2/group). The specimen for the flexural strength measurement had a final size of 16.0 mm × 4.06 mm (±0.03) × 1.63 mm (±0.03) (n = 30/group, ISO 6872). The specimens for measuring the optical properties had a final size of 10.0 mm × 10.0 mm with a thicknesses = 0.52 (±0.005), 1.01 (±0.012), 1.52 (±0.005), and 2.03 mm (±0.010) (n = 20/group).

Dilatometry tests were conducted on PPS polymer materials to measure the length change as a function of time and calculate the linear coefficient of thermal expansion in the operation temperature range of a compressor. The specimens were cut with a Struers Accutom 100 to a size of 3 × 3 × 15 $\mathrm{m}{\mathrm{m}}^3$ and water cooled to avoid overheating. A TA Instruments TMA Q400 was used for thermal expansion measurements in a temperature range of −50 to 300 °C and a heating rate of 2 K/min. On the large sample dimension of 15 mm, the length was recorded as a function of time.

The samples were cut (Accutom-100, Struers GmbH, 8903 Birmensdorf, CH) and ground with a diamond cup wheel to ensure parallel surfaces. For three-point bending tests, both ground surfaces were further polished with abrasive cloth (SiC Foil ranging from P1000 to P4000) and diamond suspensions down to 1 µm (DiaPro, Struers ApS., Ballersrup, DK) before beveling the edges to prevent stress concentration. The samples for SENB tests were pre-notched using a 300- $\mathrm{\mu }$ m diameter wire saw (3242, well Diamantdrahtsägen GmbH, Mannheim, DE). The notches were manually sharpened using a razor blade (35010, MARTOR KG, Solingen, DE) and 250 nm diamond paste (DP-Paste P, Struers ApS., Ballersrup, DK) to yield notch radii lower than 25 μm. The dimensions of the notches were estimated with a digital microscope (VHX-6000, Keyence Deutschland GmbH, Neu-Isenburg, DE). The final sample sizes varied depending on the quantity of coated platelets used in the initial suspension. The smallest sample sizes (length l x width b x thickness w) were 15 × 1.2 × 1.2 mm³ and 15 × 0.6 × 1.2 mm³ for the three point bending and SENB tests, respectively. The largest three-point bending and SENB samples were, respectively, 15 × 2.4 × 2.4 mm³ and 15 × 1 × 2 mm³ in size. Size effects are not expected to play a significant role for samples with these dimensions^{6 (link)}.

The zirconia (Table 1) used in this study, Cercon xt ML (Dentsply Sirona, Charlotte, NC, USA) and Lava Esthetic (3M, St. Paul, MN, USA), were both precolored (A2 shade) 5Y-zirconia. Both zirconia samples had a multilayered structure, and a cutting machine was used (Accutom-100, Struers, Copenhagen, Denmark) to cut the specimens according to the layer fraction specified by the manufacturers (Figure 1). The upper and lower surfaces of the cut specimens were then sequentially dry polished with SiC-abrasive papers of 800, 1200, 2000, 3000, and 5000 grit sizes to reach a thickness of 1.25 mm for each layer (n = 5/layer), which was confirmed using micrometers (MDC-25PX, Mitutoyo, Kanagawa, Japan). Thereafter, sintering was carried out using a furnace (inLab Profire, Dentsply Sirona, Charlotte, NC, USA) following the manufacturer’s instructions for conventional and high-speed sintering (Table 2). Because the Lava Esthetic did not provide a high-speed sintering schedule, the schedule used for Cercon xt ML was applied for high-speed sintering of Lava Esthetic. The final dimensions of the sintered specimens were 10.0 × 10.0 × 1.016 mm³ (±0.008).