Special issue on infrared extinction technology
2020, 49(7): 20201018.
doi: 10.3788/IRLA20201018
As an important means to weaken the performance of infrared imaging equipments or systems, artificially prepared infrared extinction materials have become the research object of many countries, and have achieved staged research results. The research status of artificially prepared infrared extinction materials is introduced from metal materials, expanded graphite, nano-materials, water-based foam, biomaterials and composite materials. The particle aggregation models of extinction materials such as particle and cluster, cluster and cluster are described. Several typical extinction calculation methods such as Mie scattering method, discrete dipole approximation method, T matrix method, and finite-difference time-domain method are introduced. According to the analysis, the infrared extinction materials prepared manually in the future will develop in the direction of long duration, low cost, various forms of release, environmental protection and non-toxic.
2020, 49(7): 20201019.
doi: 10.3788/IRLA20201019
In order to promote the research and application transformation of anti-infrared smoke screen materials, the research status, main problems and development trend of the materials were systematically analyzed from the material development and research on extinction performance. The results show that the research of carbon black and red phosphorus based hot smoke materials mainly focus on the improvement of the formula. The cold smoke materials, such as layered super-molecular, ultrafine ceramic powder, nano powder and biomaterials, have made remarkable achievements in structural design and synthesis technology. At present, there are some problems in the research, such as the lack of environment-friendly anti-infrared smoke screen materials, the difficulty of extinction theory innovation and so on. In the future, low cost-effectiveness ratio and environment-friendly anti-infrared smoke materials will become the development focus in this field.
2020, 49(7): 20201020.
doi: 10.3788/IRLA20201020
Carbon coated ferrite precursor was prepared by one-pot hydrothermal method, which was calcined at 950 ℃ with N2 protection to obtain carbon coated ferromagnet composite materials. The morphology and composition of the materials were analyzed by XRD, FT-IR and SEM, and the effects of reaction time, the ratio of starch and glucose on the morphology and IR extinction of the composite were studied. The IR extinction coefficients of materials in the range of 2.5-25 μm were measured and calculated by KBr method of FT-IR. The results show that the samples have good morphology and extinction performance, that were prepared under the conditions of reaction time of 20 h and 18 h and the ratio of starch and glucose of 9:3 and 6:10. In the range of 4-10 μm, the extinction coefficient of sample 5 and 7 is greater than 0.3 m2/g and the maximum is 0.37 m2/g.
2020, 49(7): 20201021.
doi: 10.3788/IRLA20201021
Graphite and aluminum powders are typical aerosol particles whose infrared (IR) extinction properties are important to the IR obscuring performances of the smoke ammunitions containing these powders. Mass extinction coefficients (MECs) of the two materials with different sizes are measured in a smoke chamber. The relationship between the powder size and the IR extinction property is analyzed, with the difference between their extinction properties being discussed. Moreover, test accuracy is studied at different temperatures of the target and the background. The results show that the IR extinction property gets better as the size of the graphite powder decreases. Due to its better dispersivity, larger radius-thickness ratio and larger IR refractive index, aluminum powder shows better extinction properties than graphite powder of the same size. The IR MECs of aluminum powder (1 000 meshes) are respectively 1.78 m2/g (3.7- 4.8 μm) and 2.01 m2/g(7.5-14 μm), with those of graphite powder of the same size being 1.02 m2/g and 1.01 m2/g respectively. In addition, test results are found to be closely related to the initial temperatures of the target and the background, showing the necessity of appropriate settings of the temperature.
2020, 49(7): 20201022.
doi: 10.3788/IRLA20201022
The extinction and attenuation characteristics of seven modes of sandstorm in China for 0.86 -20 μm band infrared radiation were analyzed based on Mie scattering theory and Monte Carlo method. The results show that for the small size dust particles, the extinction effect is mainly the result of scattering in the near and middle infrared, and for the large size dust particles, the infrared extinction is the result of absorption and scattering. The attenuation rate difference of single scattering and multiple scattering of sandstorm are compared. The attenuation rate of multiple scattering is less than that of single scattering under the same condition, and the difference decreases with the increase of visibility. The multiple scattering attenuation rate calculated based on Monte Carlo method is more comprehensive than the extinction coefficient to reflect the influence of sandstorm on infrared radiation intensity attenuation. The infrared attenuation intensity of six kinds of large particle mode sandstorm is greater than that of small particle mode sandstorm, and the attenuation rate increases with the increase of wavelength. The attenuation rate of the small particle mode duststorm fluctuates obviously with the change of wavelength, with a peak value in the range of 7.9–12.5 μm, and is not sensitive to the wavelength in the range of 13–20 μm.
2020, 49(7): 20201023.
doi: 10.3788/IRLA20201023
Aqueous foam is widely used as a kind of stealth way in the scene of optoelectronic countermeasure. The existing optoelectronic jamming stealth technology has such problems as short acting time, single band and environmental pollution, which makes it difficult to effectively counter dual-mode and multi-mode precision guidance weapons. Aiming at the above problems, the aqueous foam formulation was studied. The extinction performance experiments of aqueous foam against visible light, infrared (3−5 μm, 8−14 μm), laser (1.06 μm, 10.6 μm), millimeter wave (3 mm, 8 mm) and centimeter wave (2 cm, 3 cm)were implemented. The shielding and interference effects of aqueous foam aiming at thermal imagery of 8−14 μm band were measured. The extinction mechanism of aqueous foam was discussed. The study shows that the curtain barrier formed by aqueous foam cloud or compositing with artificial fog is expected to acquire a new type of smokescreen weapon with the advantages such as full-wave band and environment friendly.
