【作者】 管洪涛；

【导师】 刘顺华；

【作者基本信息】 大连理工大学 ， 材料加工工程， 2006， 博士

【摘要】 针对目前日益严重的电磁污染,对建筑用防电磁辐射复合材料的研究也越来越迫切和广泛。为此,本文对石英和水泥为基体的两种平板复合材料进行了电磁性能研究,开发了两种建筑平板吸波材料。 首先对石英/纳米炭黑复合材料的电磁性能进行了研究。采用TEM手段对N234型纳米炭黑的颗粒形貌进行了分析,采用同轴法测定了纳米炭黑粒子的电磁参数,并以石英为基体材料,以水玻璃和聚乙烯醇(PVA)为粘结剂,对石英/炭黑复合材料在150～1500MHz频段内的电磁屏蔽效能和2～18 GHz频段内的吸波性能进行了分析。研究结果表明,炭黑属于一种电损耗介质,具有较高的电导率和较大的介电常数。石英/炭黑复合材料的电磁屏蔽效能随测试频率和炭黑含量的增加而增大。当炭黑含量达到15 vol%时,厚度为7 mm的复合平板在150～1500 MHz内的屏蔽效能可以达到-35 dB。材料的吸波性能存在一个极限值,当炭黑含量超过6.0 vol%时,入射电磁波在材料表面的反射增强,复合材料的吸波性能会下降。 通过TEM、XRD手段分析了纳米二氧化锰粒子的颗粒形貌和化学成分,用同轴法测定了二氧化锰粒子的电磁参数,并以石英为基体对石英/二氧化锰复合材料的电磁性能进行了分析。研究表明,二氧化锰属于一种介电损耗介质,具有较高的电阻率和较大的介电常数,而且其介电损耗角正切随频率的增加变化不大。二氧化锰填充石英复合材料在低频下仍然具有较好的吸波性能,且其最佳吸收性能具有频率选择性。当二氧化锰含量小于40 vol%时,复合材料在2～18 GHz频段内的吸收峰值随二氧化锰含量的增加而逐渐增大,且峰值频率逐渐向低频移动。 应用Rayleigh混合公式的扩展式和吸波性能的计算公式对炭黑或二氧化锰填充石英基体复合材料的电磁性能进行理论计算的结果表明,当炭黑或二氧化锰的含量较大时,计算值与实验值比较接近。说明Rayleigh混合公式的扩展式可以用于该复合体系吸波剂含量较大时的电磁性能计算。 水玻璃和聚乙烯醇两种粘结剂对石英基复合材料的电磁性能具有不同的影响。以水玻璃为粘结剂的试样比聚乙烯醇试样具有更高的屏蔽效能;而两者的吸波性能相差不大,但水玻璃试样吸波曲线比较平缓,而聚乙烯醇试样则具有较大的吸收峰。而且水玻璃试样具有相对较高的抗压性能。 本文首次对发泡聚苯乙烯(EPS)填充水泥基体复合材料的吸波性能进行了实验研究。首次采用EPS颗粒表面处理工艺来增强其与水泥基体的亲和性和混合时的均匀性,分别制备了不同EPS填充率和不同厚度的EPS填充水泥平板试样,并在微波暗室内测更多还原

【Abstract】 This dissertation is aimed at the increasingly severe electromagnetic pollution and both the urgency and broadness of the research on building materials for electromagnetic interference （EMI） prevention. This dissertation discusses the electromagnetic characteristics of two kinds of composite plates and explores two building materials for electromagnetic wave absorbing based on silicon dioxide （SiO₂） and cement matrices.The electromagnetic properties of nanometer carbon black （CB） filling SiO₂ composites were first studied. The micrograph and electromagnetic parameters of CB particulates were analyzed with TEM microscope and coaxial method. The electromagnetic shielding effectiveness （SE） in 150-1500 MHz and the wave absorbing properties in 2-18 GHz were studied with sodium silicate and polyvinyl alcohol （PVA） as the adhesive binders. Findings show that CB is a kind of electric loss medium and it has high electric conductivity and dielectric constants. The SE of CB composites increase with the increasing of CB content and frequency. When the CB content is 15 vol%, a plate with a thickness of 7 mm gives a SE of -35 dB. There is a critic content in CB filling composite for wave absorbing. When the CB content is over 6.0 vol%, the wave reflection on the surface of the material increases and so the wave absorbing performance decreases.The electromagnetic properties of manganese dioxide （MnO₂） particulates were discussed in this dissertation for the first time. TEM, XRD and coaxial method were applied to analyze the properties of MnO₂ particulates and SiO₂/MnO₂ composites. Results show that MnO₂ is a kind of dielectric loss medium, and it has high electric resistivity and dielectric constants. When the MnO₂ content is lower than 40 vol%, the wave absorbing peak values of MnO₂ composite increase with the increasing of MnO₂ filling fraction and the matching frequencies drift to the lower band with MnO₂ increment.The modified Rayleigh mixing formula is applied to calculate the effective electromagnetic parameters and reflection loss of CB or MnO₂ filling composites, and it indicates that when the CB and MnO₂ content is high, the calculated values are closely agree to the experimental ones. It indicates that Rayleigh mixing formula can be applied to the calculation of electromagnetic properties in high concentrations.The different influences of binders on the electromagnetic properties of SiO₂ based composites were studied. The results show that the sample with sodium silicate as theadhesive binder has a higher SE than that with PVA, but their comprehensive wave absorbing properties have not many differences, only that the absorbing curves of samples with sodium silicate as the binders are relatively flat, but PVA samples have one or more peak values. The sample with sodium silicate as the binder has a relatively higher compressive strength than that with PVA.The electromagnetic absorbing properties of expanded polystyrene （EPS） filled lightweight cement based composites were studied in this dissertation for the first time. A surface pretreatment was first used to treat the EPS beads so as to improve the affinity with cement matrix and the uniformity during mixing. Samples with different EPS filling ratio and different thickness were made and their wave absorbing properties were studied with the arched testing method in an anechoic chamber. The analysis of the changes of dielectric property during the hydration and the inner macrostructure of the EPS cement were carried out to investigate the electromagnetic absorbing mechanism of the EPS cements. The effects of thickness, filling ratio and EPS bead diameter on absorbing properties were studied. The matching thickness of the composite was also discussed. The results show that the EPS cement composite holds a good absorbing characteristic and its absorbing property increases with the EPS filling ratio until 60 vol%, and a decrease is observed afterwards. With the addition of EPS beads, the wave transparent property of the EPS filled cement composite improved gradually and so the matching thickness increased. In the frequency range of 8-18 GHz, a 20-mm-thick sample filled with 60 vol% EPS with a diameter of 2 mm can have an absorbing property of-10—15 dB, and the bandwidth of-10 dB reaches 6.2 GHz.The studies on the compressive strength of EPS filling cement composite show that the compressive strength appears to decrease linearly with the increase of EPS volume and increase gradually with the curing time. The compressive strength has a close relationship with the bonding strength at the interface between EPS and the cement matrix. The EPS bead with smaller size has more specific surface areas and more interfaces with cement matrix, and its smallness has decreased the pores and defects at the interfaces, so cement composites filled with <D2 mm EPS beads get a higher compressive strength.更多还原