| Electromagnetic attenuation technology is one that electromagnetic wave was attenuated by materials. There are many inorganic electromagnetic attenuation materials, such as expansible graphite, iron powder and copper powder, which are widely used in the fields of aerospace, pharmaceutical and food. These inorganic materials have many disadvantages, including fixed interference media type, single interference object, narrow attenuation band, short duration and environment hazard. With the development of economy and society. The new electromagnetic attenuation materials is to be researched to meet need. Hence, we proposed a new concept-applying biological materials to the electromagnetic attenuation field. Biological materials can absorb and scatter electromagnetic wave because of their special structure and components. Given the characteristics of diversity of species, complex structure, flexible and convenient preparation and environmentally friendly, biological materials have better electromagnetic attenuation characteristics. The study focused on the selection and preparation of biological electromagnetic attenuation materials, and the determination and enhancement of their attenuation characteristics.Static test was employed by Fourier transform infrared spectroscopy. Absorption spectrum of seven microbial materials was measured. Components and the corresponding absorption band were analyzed. Then the study were subjected to reflection measurements in the range of4000-400cm-1(2.5-25μm). Specular reflection spectrum method was used to calculate the real (n) and imaginary (k) parts of the complex refractive index. The complex refractive index of real part n and imaginary part k in infrared band was n≥1and k≥0, respectively, which can meet the theory of interaction between matter and light. In the3-5μm band, the mass extinction coefficient of entomogenous fungi Bb3088spores and entomogenous fungi Ma2677spores were0.8968m2/g and1.0589m2/g. In8-14μm, mass extinction coefficient of the two fungal spores were0.7137m2/g and0.7203m2/g, respectively, which indicated good electromagnetic attenuation performance. Entomogenous fungi Bb3088spores and entomogenous fungi Ma2677spores were selected as biological electromagnetic attenuation materials.The yield of entomogenous fungi Bb3088spores and entomogenous fungi Ma2677spores is low in the present fermentation condition. In order to improve the yield of spores, fermentation medium and culture conditions were optimized in this research. Conidial yields of entomogenous fungi Bb3088spores and entomogenous fungi Ma2677spores reached to11.2mg/g and24.5mg/g, which increased by72.31and52.17%compared with the unoptimized conditions. However, in solid fermentation, the conidia, mycelium and solid media substrate were mixed together, which made it difficult to separate the fungal conidia from their substrate. In order to obtain highly pure spores, the collection method of spores was studied. Dual cyclone method was used as the optimal spore collection method. Three factors influencing spore production were optimized by response surface methodology. The optimal parameters were substrate height and column ratio18%, harvest time4min and drying time44h. The maximum estimated yield of entomogenous fungi Bb3088spores was20.9mg/g, which was221.5%higher than that of the original conditions. Under the optimized harvest parameters, using the dual cyclone equipment conidia separator as a harvest method, the conidia yield of entomogenous fungi Ma2677spores rose to42.2mg/g and increased by162.1%in total. In order to verify the purity of spores collected by dual cyclone method, the spore separation efficiencies were further compared for two representative biocontrol fungi. Fungal conidia could be separated completely from hypha and substrate. Displaying a visually smooth powder similar to talcum, it showed that the dual cyclone method is a good method for separating spores.Static testing only takes into account the effects of microbial composition on electromagnetic attenuation. To comprehensively explore the absorption and scattering effect of the selected microorganisms, dynamic smoke box test was carried out. The test bands were visible light, middle infrared and far infrared band, and the test contents were smoking transmissivity, mass extinction coefficient and time in infrared band. In the visible and middle infrared band, the transmissivity of entomogenous fungi Bb3088spores was less than15%. Its mass extinction coefficient was more than1m2/g and attenuation time was more than60s. Hence, the entomogenous fungi spores of Bb3088could be used as biological electromagnetic attenuation materials in visible and middle infrared band. In middle infrared band only, the transmissivity of entomogenous fungi Ma2677spores was less than15%. Mass extinction coefficient was more than1m2/g. Its attenuation time was more than60s. Thus, it can be used as biological attenuation materials in middle infrared band. Entomogenous Fungi Bb3088and entomogenous fungi Ma2677spores were proven to have better electromagnetic attenuation characteristics by the static test and smoke box test. The excellent attenuation characteristics were determined by the components and morphology. In order to further improve the attenuation capability of the the two fungal spores, the components of entomogenous fungi Bb3088and entomogenous fungi Ma2677spores were analyzed by high liquid chromatography.-mass spectrometry method. The electromagnetic attenuation characteristics of lecithin and ergosterol which are highly contained in spores were analyzed by mixed them with entomogenous fungi Bb3088spores in the ratio of1:1, respectively. The results showed that corresponding spectral absorption peaks were increased by19%and11%. When entomogenous fungi Ma2677spores were mixed with lecithin and ergosterol in the ratio of1:1respectively, the corresponding spectral absorption peaks were increased by22%and14%. Therefore, to make one certain band absorption peak increase so as to improve the electromagnetic attenuation property, the component content of the microorganisms can be increased by mutation, molecular modification and optimization of fermentation conditions. |
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