Sustainability can be defined as the ability of meet presents needs without compromise the ability of future generations to find their own needs. In this matter, scientists have been warning about natural resource scarcity, and now several researchers are aiming their efforts to develop sustainable technologies. Here, we focus on finding novel uses to biochar, a carbon rich material made from biomass that is usually applied on soil amendment. To expand its applications, biochars were activated using two different methods: a physical activation using CO2; and a chemical one using KOH. We investigate here the dielectric properties of composites made with both activated biochars from white birch, where composites were made using silicone rubber matrix. It was also investigated the influence of composites made with biochar in powder and in flakes. All samples were characterized over the X-band frequency range. Composites made with powder presented a linear permittivity over the frequency range, while composites made with flakes presented oscillations on different frequencies. These oscillations are related to the composite surface, which induces reflection effects because of flakes arrangement in the top surface. Such effects widen opportunities to engineer new materials to be explored as radar-absorbing materials.

中文翻译：

---

白桦活化生物炭复合材料的介电特性：雷达吸收材料的可持续替代品

可持续性可以定义为满足当前需求的能力，同时又不损害后代找到自己需求的能力。在这件事上，科学家们一直在警告自然资源稀缺，现在一些研究人员正致力于开发可持续技术。在这里，我们专注于寻找生物炭的新用途，生物炭是一种由生物质制成的富碳材料，通常用于土壤改良剂。为了扩大其应用，生物炭使用两种不同的方法进行活化：使用 CO2 的物理活化；和使用 KOH 的化学物质。我们在这里研究了用来自白桦的两种活化生物炭制成的复合材料的介电性能，其中复合材料是使用硅橡胶基质制成的。还研究了用粉末和薄片生物炭制成的复合材料的影响。所有样品都在 X 波段频率范围内进行了表征。由粉末制成的复合材料在频率范围内呈现线性介电常数，而由薄片制成的复合材料在不同频率上呈现振荡。这些振荡与复合表面有关，由于顶部表面的薄片排列会引起反射效应。这种效应拓宽了设计新材料作为雷达吸收材料的机会。