Ceramics

Microsilica recovered from silicon-production off-gases offers a secondary feedstock for silica-based ceramics. This study evaluates its consolidation by spark plasma sintering (SPS), with purchased commercial nanosilica serving as a reference. Both feedstocks were processed at a monitored die temperature of 1300 °C, 50 MPa, and a 10 min hold. Characterization combined powder microscopy, qualitative X-ray diffraction, hydrostatic weighing, ultrasonic contact impedance (UCI), and axial compression. Mean hydrostatic densities were 2.246 ± 0.007 and 2.254 ± 0.007 g·cm⁻³ for microsilica and nanosilica, respectively. Mean maximum nominal stresses were 208 ± 13 and 188 ± 6 MPa for Ø14 × 2 mm disks; values are mean ± sample standard deviation (n = 3 per feedstock). The microsilica specimens exhibited a 10.3% higher mean maximum nominal stress under this loading configuration and higher comparative UCI indications. Both cooled ceramics showed reflections consistent with α-cristobalite. The study extends earlier waste-processing work through a comparison with commercial nanosilica that relates powder characteristics and phase identity to replicate property measurements under a common SPS schedule. The results demonstrate the material feasibility of consolidating microsilica waste into coherent ceramic bodies and support further development of this utilization route.

The photoluminescence (PL) and photoluminescence excitation (PLE) spectra of an EFG-grown (−201) β-Ga₂O₃ single crystal were recorded at 7 and 300 K at the FinEstBeAMS beamline of the MAX IV Laboratory. Excitation–emission maps and fixed-wavelength PLE profiles covered 4.50–10.50 eV at both temperatures. Each temperature series was normalized to its own 5.00 eV intensity and, alternatively, to its own maximum; the reported ratios therefore describe excitation dependence within one series and not an absolute difference in luminescence yield between temperatures. At 7 K, integrated emission at 10.50 eV retains 95.4% of its 5.00 eV value and 89.2% of its maximum. At 300 K, the PLE half-height is 4.55 eV, and the maximum occurs at 4.75–4.80 eV, followed by a decrease to 2.26% of the 5.00 eV value and 2.03% of the maximum at 10.50 eV. Room-temperature ellipsometry on the same factory-polished face places the PLE rise in the rapidly increasing absorption region and yields a penetration depth of approximately 0.24 μm near the PLE half-height and 37 nm at 5.90 eV. A constrained depth-dependent calculation does not reproduce the full decline, so surface capture is retained as one possible pathway rather than an established mechanism. The emission is described by the same effective bands at 3.55, 3.37 and 3.07 eV used in the preceding laser study. Their balance is nearly constant at 7 K, whereas the low-energy spectral weight increases at 300 K under deep-VUV excitation. These spectra provide quantitative reference profiles for energy conversion and carrier capture in β-Ga₂O₃.

The rapid development of advanced structural systems imposes increasingly severe thermomechanical demands on engineering materials operating under extreme service environments. Consequently, the development of high-performance structural materials capable of enduring such harsh conditions has become a primary research focus. Owing to their high melting points, elevated hardness, and thermodynamic stability, (Ti,W)C solid-solution ceramics have emerged as promising candidate materials for high-temperature and extreme-environment structural components. This review presents a systematic overview of recent advancements in (Ti,W)C-based ceramics across processing, microstructural, and performance domains. Specifically, the effects of consolidation techniques—including hot pressing (HP), spark plasma sintering (SPS), and reactive sintering (RS)—on densification kinetics, grain growth behavior, and core–rim microstructural evolution are critically discussed. Furthermore, the governing strengthening and toughening mechanisms, such as solid-solution strengthening, secondary-phase dispersion, and crack-tip shielding (predominantly crack deflection and bridging), are comprehensively examined, alongside their behavioral response and degradation-mitigation mechanisms under extreme service environments. Finally, current processing bottlenecks, brittleness issues, and manufacturing challenges are critically outlined, providing prospective research directions for the future development and engineering application of (Ti,W)C ceramics.