木炭粉-石蜡复合材料的介电特性和微波吸收性能研究

Research of dielectric properties and microwave absorption of composites of charcoal powder and wax

微波吸波材料在民用和军用领域均有较大的需求,而木材作为一种古老且储量丰富的天然材料,其碳化粉体与高分子材料复合用于吸波材料的系统研究较少。本研究以马尾松粉体和固态石蜡为原料,经过无氧高温炭化-热熔浇铸-冷压联合工艺制备出了木炭粉-石蜡复合材料,然后使用同轴空气线法结合理论模拟测试分析了石蜡、木粉-石蜡和木炭粉-石蜡复合材料的介电参数和吸波性能,并使用单因素法系统地探索了炭化温度、炭粉含量和材料厚度对该复合材料的介电参数和吸波性能的影响规律,并讨论其吸波机理。结果显示炭-蜡复合体在炭化温度为670℃、炭粉质量分数为40%和厚度为2.5 mm时的吸波性能最佳,其有效吸收频段覆盖了11.2~18 GHz(共6.80 GHz),反射损耗峰值高达-26.41 dB,吸收率超过了99%。其吸波机理主要为分散在石蜡中的木炭粉在微波的辐射下可能成为偶极子,当木炭粉的碳化程度和质量分数越高时,其石墨化程度和偶极子体积浓度增大,同时粉体颗粒之间接触的机会也会随之增多,从而加剧了材料的极化和损耗程度,最终宏观地反映为复合介电常数的增大。但是过高的温度和浓度会导致隧道效应和趋肤效应,从而降低木炭粉-石蜡复合材料的吸波性能。

Microwave absorption materials are in demand in both civilian and military fields,while wood,as an ancient and abundant natural material,has received less systematic research on the use of carbonized powder and polymer composites as microwave absorption materials.This study used Pinus massoniana powder and solid paraffin as raw materials to prepare charcoal powder wax composites through a combined process of oxygen-free high-temperature carbonization,hot melt casting,and cold pressing.Then,the coaxial transmission line method combined with theoretical simulation was used to analyze the dielectric parameters and absorption properties of wax,wood powder-wax composites,and charcoal powder-wax composites.The single factor method was used to systematically explore the influence of carbonization temperature,charcoal powder content,and material thickness on the dielectric parameters and absorption performance of the composites,and the absorption mechanism was discussed.The results showed that the charcoal-wax composite exhibited the best absorption performance at a carbonization temperature of 670℃,a carbon powder mass fraction of 40%,and a thickness of 2.5 mm.Its effective absorption frequency range covered 11.2~18 GHz(a total of 6.80 GHz),with a peak reflection loss of-26.41 dB and an absorption rate of over 99%.The main absorption mechanism was that the charcoal powder dispersed in wax may become dipoles under microwave radiation.As the carbonization temperature and mass fraction of charcoal powder increased,its graphitization degree and dipole volume concentration increased.At the same time,the chances of contact between powders also increased.As a result,the polarization and loss of the material were exacerbated.Ultimately,it reflected an increase in the complex dielectric constant from a macro perspective.However,excessive temperature and concentration could lead to tunneling and skin effect,thereby reducing the absorption performance of the charcoal-wax composites.