Passive thermal control coatings (TCC's) have been widely used to tune the thermal equilibrium of spacecraft surfaces since 1970s. Development of new TCC's with improved thermo-physical properties and radiation hardness are essential to the space assets that fly in harsh environments. Herein, we fabricated calcium orthophosphate based inorganic white paint, which possess relative low solar absorptance (α s ) of 0.095 and thermal emittance (ε H ) of 0.88. Noticeably, the Ca 3 (PO 4 ) 2 coating shows excellent space radiation tolerance and thermal control capacity. After performing 90 keV proton irradiation at a fluence of 4×10 15 cm -2 , the α s of ZnO coating increases from 0.160 to 0.213 while the Ca 3 (PO 4 ) 2 coating rises from 0.095 to 0112, which only degrades one third (0.017) of the ZnO coating (0.053). Furthermore, after performing simulated solar irradiation test, the surface temperature of Ca 3 (PO 4 ) 2 paint is 14.4 °C lower than that of ZnO coating, evidencing its prominent thermal-optical performance. Besides, we also found that Ga 2 O 3 based liquid-glass white paint is a good candidate for thermal equilibrium of spacecraft.
Space exploration is inseparable from advanced antiradiation materials with exceptional properties. Among these, nonlinear optical materials and devices, such as irradiation-resistant saturable absorbers (SAs), have garnered significant attention, particularly due to their critical role in integrated photonics for space use. This study presents a comprehensive evaluation of the space adaptability of two-dimensional (2D) W2N3 under simulated space radiation conditions. When subjected to 60Co γ-ray irradiation at doses exceeding 45 years of accumulation in a typical low-Earth orbit, W2N3 retained its robust third-order nonlinear saturable absorption across the visible- to near-infrared spectral range. Femtosecond transient absorption spectra offer a comprehensive view of the carrier dynamics of W2N3 before and after irradiation, delving into radiation effects and damage mechanisms that are otherwise elusive to conventional techniques. The synthesized W2N3 nanosheets were successfully employed as efficient SAs for Q-switched mode-locking in a Yb-doped fiber laser. The laser system operated at ∼1 μm NIR with high pulse energy and low saturation power, highlighting the remarkable potential of W2N3 for integration into lasers, modulators, and other photonic devices. Notably, the irradiated W2N3 demonstrated an identical mode-locking performance compared to its pristine counterpart. These findings provide valuable guidance for the rational design and screening of nonlinear optical materials capable of withstanding space radiation, offering significant implications for future space-based photonic applications.
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