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With the development of laser technology, laser-related materials have been widely studied. Both laser stealth coatings and laser protective coatings are currently the focus of attention. However, less research has been done on laser stealth and protective integrated coatings. In this paper, plasma-sprayed Y 2 O 3 –Ti 3 AlC 2 coatings were prepared with low-power (LP) and high-power (HP) parameters, and their laser stealth and laser protection properties were characterized. The LP coating and HP coating appeared to have lower reflectivity at 1064 nm because a low-reflectivity second phase and many loose flocs on the surface are introduced, which indicates excellent laser stealth performance. When irradiated by a laser, the LP coating exhibited excellent laser protection ability, and its reflectivity increased after irradiation because Ti 3 AlC 2 oxidized and decomposed and densely arranged small particles formed on the surface. The LP coating perfectly protected the 500-W laser irradiation for 20 s. In addition, the laser damage threshold of the LP coating was 5.599 s at 1000-W laser irradiation, which indicates that the LP Y 2 O 3 –Ti 3 AlC 2 coating is a potential material with laser stealth and laser protection integration. [ABSTRACT FROM AUTHOR]

C/SiC composite has been widely used as a high‐temperature material for engineering components due to its excellent thermal properties. Facing the rapid development and threat of high‐energy laser, study on the ablation resistance under laser irradiation is strongly required. In this work, a continuous high‐energy laser was applied to explore the laser ablation behavior and mechanism of C/SiC composite. From the results, C/SiC composite shows different morphologies when irradiated at various laser power densities for 500 and 700 W/cm2. We divided the ablation area into three regions; the central, transition, and edge regions, where the formation of SiO2, SiO, and the breakage of carbon fiber were observed. The generated highly reflective SiO2 layer reduces the absorption of laser energy, which is beneficial to lower the back‐surface temperature and reduce the damage of composite. In addition, we put forward the ablation physical models and ablation mechanisms irradiated at different power densities. The work provides a basis for the laser ablation resistance of C/SiC composites under different conditions. [ABSTRACT FROM AUTHOR]

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]

[Display omitted] • Ablation mechanism of metamaterials under high-energy continuous-wave laser irradiation was for the first time revealed. • The microwave absorption performance of metamaterials under extreme laser damage conditions was firstly deeply investigated. Metamaterials, typically consisting of sub-wavelength metal-atom arrays and a dielectric layer matrix such as glass fiber reinforced epoxy resin (FR-4), have been widely used in the field of stealth equipment due to their good electromagnetic parameter designability and strong absorption for electromagnetic waves at specific frequencies. In offensive and defensive confrontations, laser weapons pose a serious threat to the survival of stealth equipment. However, the interaction mechanism between the metamaterials and laser and the effect of laser ablation on microwave absorption performance are still unclear. In this work, we firstly irradiated the double arc-shaped Cu-atom array/FR-4 matrix metamaterials by using a high-energy continuous-wave laser and studied the interaction and response mechanism between them. The high temperature caused by laser irradiation leads to the melting of the metal atoms and the pyrolysis of the resin matrix. By simulating and testing the reflection loss of the metamaterials before and after irradiation, we found that the resin pyrolysis products strongly affect the impedance matching characteristics and reduce the microwave absorption properties significantly in extreme cases. Our findings help deeply understand the interaction between the metamaterials and the laser and will show guidance in the applications involving laser-metamaterial interactions. [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]

With the repaid development of laser manufacturing industry, laser protection for optical components, especially high power continuous laser, has been a major concern. Optical coatings should have a good anti-laser ablation property. However, the high-power laser ablation behavior of plasma-sprayed Ta 2 O 5 coatings is rarely investigated. In this paper, tantalum oxide coatings were prepared by plasma spraying technique and irradiated using continuous laser with 1070 nm wavelength. The phase structure, ablation surface morphology and reflectivity of the coating were characterized by XRD, SEM, and UV–Visible-near Infrared Spectroscopy. During laser irradiation, the tantalum oxide coatings experience three stages: coating oxidation, micro-cracks occurrence and mechanical failure. A finite-element simulation was also conducted to explore the change of temperature field during irradiation. The simulation results show that the change of reflectivity of tantalum oxide coating during laser irradiation is of great benefit in improving its laser protection ability. [ABSTRACT FROM AUTHOR]