中文摘要：

以醋酸钻为前驱体，乙醇为溶剂，通过浸渍、干燥及H2还原，制备了磁性纳米金属钴颗粒均匀分散在膨胀石墨（EG）纳米层面的复合材料，其中纳米金属钴颗粒呈球形，粒径为300～1000nm，主要为金属相，含少量碳化物，属于软磁性材料．在EG纳米层板上铺展的磁性纳米金属钴颗粒有较高的磁导率，因而具有良好的低频电磁屏蔽效应．通过调控铺展在纳米石墨层板上纳米金属钴的含量可以改变复合材料的导电性与导磁性，使得复合材料在较宽的频段内具有良好的电磁屏蔽效能．结果表明，在Co含量为10％～40％时，复合材料的电磁屏蔽效能较好，例如，30％Co-EG在300kHz到1．5GHz范围的电磁屏蔽效能可达62～110dB．

英文摘要：

Electromagnetic shielding involves the reflection and/or absorption of electromagnetic radiations by electromagnetic materials. Nowadays, electromagnetic radiations emanate from a wide variety of sources that interfere with electronic devices and affect the health of people. Thus, the radiation shielding at wide frequency range with high effectiveness is increasingly required to meet the high demand of today＇s society for the reliability of electronics and the health of people. Expanded graphite （EG） has been found to be a highly effective electromagnetic shielding material in the range of 1～2 GHz because of its excellent electrical conductivity. The primary mechanism of electromagnetic shielding of EG is the reflection loss due to its high conductivity, and thus its shielding effectiveness （SE） decreases sharply with the decrease of frequency. The absorption loss is a function of the product of electrical conductivity and magnetic permeability relative to copper. Thus, the metals with high magnetic permeability may play the role of absorbing electromagnetic radiations, especially at low frequencies. The composite materials of EG and magnetic metals may exhibit both absorption and reflection losses and increase the shielding effectiveness ultimately in a wide range of frequencies. In addition, there are more advantages when EG is used as a component of electromagnetic materials since it is light, flexible, corrosion resistant, and cost effective, which may make the composites more attractive than the traditional polymermatrix composites. The composites with nanoparticles of cobalt dispersed on the nano-layers of expanded graphite （EG） were prepared by the impregnation of EG with ethanol solutions of cobalt acetate, followed by drying and reduction in He. The cobalt loadings on EG were varied up to 60% by weight. The spherical particles of Co were found to be well spread on the layers of EG with sizes of mainly 3000～1 000 nm. The ratio σr/σs of the composites was found to be 0.26～0.33, indica