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Graphite and SiO 2 composite was prepared by hot-pressing at 1300 °C for 3 h under a uniaxial load of 20 MPa. The ablation behavior of graphite and SiO 2 composite by high-intensity continuous laser was investigated. The X-ray diffraction, scanning electron microscopy, 3D-super-depth-digital microscopy, Raman spectroscopy and reflectivity were used to characterize the sample. The results show that under low laser power (500 W/cm 2 ), and no obvious damage appears, while just the irradiation area changes from grey to white and the reflectivity increases. With the laser power increasing, some heat-absorbing chemical reactions between graphite and SiO 2 occurred on the surface, and SiC was produced, which can increase the energy consumption of the surface and thus reduce the absorbed laser energy of the interior. Moreover, at the center of irradiation area, the formation of columnar structure graphite is beneficial to obstruct laser energy conduction from surface to interior material. [ABSTRACT FROM AUTHOR]

Abstract Composite coatings consisting of flake graphite and SiO 2 fillers in a hyperbranched polycarbosilane (HBPCS) matrix were designed and prepared to meet the requirements of laser protection. The laser ablation behavior of the composite coatings were investigated. Control experiments were designed to study the performance of SiO 2 during laser irradiation. The results show that the introduction of SiO 2 changes the anti-laser protective mechanism and can improve the anti-laser property of the coating. High power laser irradiation results in pyrolysis of HBPCS and the formation of SiC particles. Chemical reactions between SiO 2 , graphite, and SiC play an important role in consuming energy, and provide an excellent cooling effect to the substrate, leading to decreased temperature. SiC particles formed on the surface of the laser ablation area act as a shield to prevent the laser from irradiating deeper layers of the coating. Due to the cooling effect and thermal stability of SiC, the proposed coating shows a good anti-laser property. [ABSTRACT FROM AUTHOR]

Further utilization of polymer matrix composites (PMCs) in the aerospace industry is threatened by the development of laser weapons, resulting from weak oxidation resistance, low operation temperature and poor anti-laser ablation performance of the PMCs. Preparing an adhesive inorganic coating on the surface of components is an effective method to improve the laser irradiation resistance. Anti-laser ablation coatings composed of ZrO as pigment and sodium silicate as binder with different curing agents (including SiO and NaSiF) are fabricated on the PMCs substrate with brush painting. Influence of the different curing agents on anti-laser ablation of the coatings at the laser wavelength of 1064 nm is investigated. The rear surface temperature of substrate with coatings, containing SiO and NaSiF, decreases from 240 to 60 and 70 °C, respectively, when testing at 1000 W for 5 s. After irradiation test at 1000 W for 10 s, the coating with SiO as curing agent shows slight molten state on the surface, while the coating with NaSiF is broke down, because coating containing SiO possesses more compact microstructure and fewer cracks than that with NaSiF. [ABSTRACT FROM AUTHOR]

Abstract: Ultra high temperature ceramics (UHTCs) based composite ZrB2/20vol.% Cu was prepared by spark plasma sintering (SPS) at 1650C° for 3min. The ablation behavior of composite irradiated for 2–20s by 20MW/m2 high-intensity continuous laser was investigated. The phase and microstructure evolution of ZrB2/20vol.% Cu during ablation was demonstrated by XRD and SEM, respectively. The results reveal that no macroscopic damage but only one ablated layer with 40μm in thickness is observed even after being ablated for 20s. It implies that ZrB2/20vol.% Cu composite exhibits good ablation resistance against high-intensity continuous laser. The continuous Cu in composite evaporates preferentially, which impacts on the following ablation behavior. The generated ZrO2 at the spot center shows different forms such as closely packed nano-ZrO2, micron ZrO2 or melting ZrO2 for different ablation time. The melting ZrO2 is helpful to promote the ablation resistance of ZrB2/20vol.% Cu. [Copyright &y& Elsevier]