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Anti-laser damage has become a major concern because of the rapid evolution of high power continuous-wave laser technology. While phenolic matrix composite coatings exhibit good anti-laser property, they show low reflectivity during laser irradiation, resulting in high energy absorption. A novel composite coating that consists of Al(OH)3 and nano-copper fillers with phenolic resin matrix has been designed to solve the low reflectivity problem. X-ray diffraction reveals that Al2O3 particles generate on the surface of the coating during laser irradiation because of the dehydration reaction of Al(OH)3. The endothermic effect of this dehydration reaction and the transpiration of nano-copper particles have a significant cooling effect on the coating. The reflectivity of coating is monitored in real time during laser irradiation. It is confirmed that the reflectivity gradually increases with the accumulation of Al2O3 particles. According to the temperature of back-surface substrates, the improved reflectivity does lead to a better anti-laser property of the coating. The laser ablation behavior of the composite coating was studied in detail through different laser parameters. The results show that both laser power density and irradiation time have effect on the micro-morphologies and reflectivity of the coating. [ABSTRACT FROM AUTHOR]

High-energy lasers can cause severe damage to conventional materials in an extremely short time. Highly reflective coatings are effective against damage, but they cannot withstand high laser power densities. In this study, a composite coating with two characteristics, namely, reflection and energy consumption, was designed and prepared. TiO 2 and BN powders, as light reflective media, were introduced into a boron-modified phenolic resin (BPF) to prepare an anti-laser composite coating. The results show that the initial reflectivity of the composite coating can reach 78.8% at a wavelength of 1064 nm. After damage-free protection for 0.4 s, ablation occurred in the irradiation region. Owing to the formation of residual char, which is the pyrolysis product of BPF, the coating maintained its protective performance. When the composite coating was irradiated at 1000 W/cm2 for 10 s, the back-surface temperature was 186 °C, which indicates decent anti-laser performance. We also studied the role of BN by setting a control experiment. The high conductivity and energy consumption caused by the evaporation of B 2 O 3 , which is the oxidation product of BN, helped in improving the anti-laser performance. The residual char with high porosity and degree of graphitization proved to be effective to isolate laser energy. This study provides a new design for protection of conventional materials against laser damage. [ABSTRACT FROM AUTHOR]

Despite many years of use of boron-modified phenolic resin (BPF) in the aerospace and auto industry, it is still unknown if such resin can be used in extreme environments, especially under exposure to high energy continuous-wave (CW) laser that can totally destroy many traditional materials in several seconds. Compression molded BPF plates are tested with high energy CW laser to study the laser ablation behavior. Results reveal that the laser parameters including irradiation time and laser power density have a great effect on the ablation morphology and mass ablation rate. BPF keeps decomposing into residual char due to the high temperature caused by laser. The graphite structure of residual char is gradually improved during laser irradiation, resulting in improved thermal stability of residual char. In addition, the micro-morphologies reveal that the residual char possess porous structure which leads to the thermal insulation property and minimizes the ablation damage propagating into the BPF bulk. Both the improved thermal stability and the thermal insulation property of the residual char can mitigate the ablation damage caused by the high energy CW laser. Unlabelled Image • Laser ablation behavior of boron-modified phenolic resin was first proposed. • The degree of graphitization of the formed residual char was demonstrated to keep increasing during laser ablation. • The porous structure of residual char is proved to be the key factor leading to the thermal insulation property. • The reason why boron-modified phenolic resin owns excellent laser ablation resistance is clearly proposed. [ABSTRACT FROM AUTHOR]