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The rapid development of advanced electronic devices and applications has brought with it a growing interest in elec-tromagnetic wave-absorbing materials. Many commercial and military applications, such as data transmission, tele-communications, wireless network systems, and satellite broadcasting, as well as radars, and diagnostic and detection systems, utilize and emit electromagnetic waves. The inter-action of electromagnetic waves originating from different sources can lead to a decrease in quality and a misinterpre-tation of transferred data, and it has thus become vital to avoid such interference and electromagnetic wave pollution through the use of appropriate absorbing and shielding materials. Electromagnetic wave-absorbing materials absorb and dissipate electromagnetic energy to which they are exposed, reducing reflected and/or scattered electromag-netic components to a minimum [1]. There are various magnetic lossy materials, such as ferrites, carbonyl iron,cobalt, and so on, which when dispersed in polymers can be used as magnetic absorbers [2–5]. The main drawbacks of these materials are that they are heavy, and are only effective only in the MHz range [6, 7]. On the other hand,lossy dielectric materials stand out due to their low density and effectiveness in the GHz frequency range. Composites with conductive powders, such as carbon black and graphite [6, 8, 9], as well as continuous or discontinuous conducting fillers [10–12], are used as dielectric absorbers, generating dielectric loss by improving the electrical con-ductivity of the mixture. In this study, the electromagnetic wave-absorbing potentialsofdielectriclossymaterials,inthiscaseSiC-based ceramic woven fabrics, were investigated. These fabrics are typically used as reinforcement for high-temperaturestructural ceramic composites due to their strength and sta-bility at high temperatures [13–15]. Despite the intrinsicproperties of these woven fabrics, such as their high specific modulus and strength, low density and environmental durabilityrelated totheirstructuraluse,littleisknown about their interaction with electromagnetic radiation in the GHz range [16, 17], although they have a wide range of electrical resistance, from 10-3to 104Xm [18]. The desired property set of low weight, high environmental durability, low thickness, and wide electrical resistance range makes these materials attractive for electromagnetic wave-absorbing applications; and consequently this study focuses on the characteristics of the interaction between SiC-basedceramic woven fabrics and electromagnetic waves. The electrical conductivities of ceramic woven fabrics were modified by heat treatment in air, and the electromagnetic wave absorption potential of single and various double-layer combinations of ceramic woven fabrics were determined in the 17–40 GHz frequency range using the ‘‘free-space’’method. The effects of alternating woven fabrics in multi-layer form and oxidation on the resulting interaction withelectromagnetic waves were discussed. |
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reko34
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随着先进电子设备和应用的快速发展，电磁波吸收材料得到越来越多的关注。许多商业和军事应用方面使用和放出电磁波，例如数据传输、无线电通讯、无限网络系统、卫星广播以及雷达、诊断和探测系统。不同源电磁波的相互干涉导致质量降低和传输数据的误译，因此通过使用合适的吸收和屏蔽材料防止这类干涉和电磁波污染变得尤其重要。 电磁波吸收材料吸收和驱散它们接触的电磁能量，将反射和/或发散电磁分量降到极限[1]。存在不同种类的磁耗材料，例如铁素体、羰基铁、钴等分布在高分子材料中作为磁吸收物质[2-5]。这些材料的主要缺陷在于它们重，并且只在MHz范围有效[6,7]。另一方面，有耗介电材料因其低密度和在GHz频率范围的有效性而突出。由导电粉末如黑烟末和石墨[6,7,8]或连续或非连续导电填料[10-12]复合而成，用作介电吸收材料，通过改善混合物的电导率制造介电损耗。 本文研究了介电损耗材料——本例中为陶瓷织物——的电磁波吸收潜力。这些织物因其高温下的高强度和稳定性常用于高温陶瓷复合材料的增强物[13-15]。尽管已知这些织物的固有属性，例如其结构用途相关的高比模量和强度、低密度和环境稳定性，对其在GHz范围的电磁辐射特性了解很少[16,17]，尽管他们有很宽的电阻范围，从10-3到104Xm[18]。低重量、高环境稳定性、低厚度和广泛的电阻范围的期望属性使这些材料对电磁波吸收应用具有吸引力；于是研究集中到了基于SiC的陶瓷织物和电磁波之间的相互作用特性。通过在空气中的热处理改动陶瓷织物的导电性，在17-40GHz频率范围用“自由空间”法确定单层和双层组合的陶瓷织物的电磁波吸收潜力。讨论了多层形式交织物和氧化对与电磁波相互作用的影响。 |
2楼2014-06-10 16:19:19
