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以桦木单板为基材,利用NaBH_4处理后直接进行化学镀镍制备电磁屏蔽复合材料.研究NaBH4浓度和浸渍时间、施镀时间和NaOH浓度对表面电阻率的影响.分别采用扫描电镜(SEM)和X射线衍射(XRD)分析对比NaBH_4前处理和胶体钯活化所得复合材料的表面形貌和组织结构,利用频谱仪和直拉法分别测定电磁屏蔽效能和镀层附着强度.结果表明:利用4g/L的NaOH配制3g/L的NaBH_4溶液,前处理5～10min,化学镀镍20min,此条件下制备的复合材料的表面电阻率低于150mΩ/cm~2,在9kHz～1.5GHz频段,电磁屏蔽效能高于60dB.NaBH_4前处理所得复合材料的电磁屏蔽效能高于胶体钯活化;从表面形貌上观察,两种方法均可得到均匀、连续和致密的镀层,镀层完全覆盖了木材表面,具有金属光泽; XRD分析表明,NaBH_4前处理所得镀层厚些,且结晶状态更佳,木材和镀层之间为物理结合;强度测试显示两种方法所得镀层均与木材表面结合牢固.

Electromagnetic shielding composite was prepared by direct electroless nickel plating on birch veneer as substrate treated with NaBH_4.The effects of NaBH_4 concentration and immersion time, plating time, and NaOH concentration on the surface resistivity of composites were investigated.The morphology and structure of composites obtained under NaBH_4 pretreatment and Pd colloid activation were analyzed and compared by using scanning electron microscope (SEM) and X-ray diffraction(XRD).And the electromagnetic shielding effectiveness (ESE) and adhesion strength of the layer were measured by spectrum analyzer and vertical pulling method, respectively.The results show that the surface resistivity of the composite is lower than 150mΩ/cm~2, and the ESE is higher than 60dB in the frequencies from 9kHz to 1.5GHz, which the composite was obtained under the conditions that the substrate was treated in 3g/L NaBH_4 solution containing 4g/LNaOH for 5-10min, and then plated for 20min.The ESE of composite obtained under NaBH_4 treatment is higher than that with Pd colloid.It was observed from morphologies that the layers deposited by the two methods are all uniform, continuous and compact, and the whole wood surface is covered, which has obvious metallic sheen.XRD analysis indicates that the layer obtained by using NaBH_4 pretreatment is thicker and has better crystalline structure, and high physic adhesion between the layer and wood.Adhesion strength measurement shows that the layers deposited by the two methods are bonded with wood firmly.