纳晶Cu-Ag双峰材料热传导行为特性研究

采用热压烧结法制备了具有双峰结构的纳晶Cu-Ag复合材料和纳晶Cu金属材料,采用激光法测定了试样在不同温度(200~400 K)下的热导率。测量结果显示,2种纳晶金属材料热导率随晶粒尺寸的增加而增加,并且随温度的降低而减小。在300 K下平均晶粒尺寸为150 nm的纳晶Cu-Ag双峰材料试样的热导率为163.45 W/m·K,分别占粗晶Cu和粗晶Ag的40.7%和38.1%。本研究引入并改进了卡皮查热阻理论模型对试样热导率进行了数值计算,计算结果与实验数据基本一致,纳晶Cu-Ag双峰材料热导率明显低于单晶Cu/Ag块体,纳晶金属材料热导率随着晶粒尺寸的增加而增加,验证了纳晶Cu-Ag双峰材料热导率在一定的晶粒尺寸范围内具有尺寸效应。

The thermal conductivity behavior of bimodal nanocrystalline Cu-Ag material

Bimodal nanocrystalline (nc) Cu-Ag and nc Cu were prepared by high pressure sintering method in argon atmosphere. The microscopic structures of the samples were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The thermal conductivity of the samples with average grain sizes ranging from 50 to 270nm were measured. The test results showed that the thermal conductivity of nc Cu-Ag and nc Cu were reduced significantly from 243.84 W/m.K to 163.45 W/m.K and 259.93 W/m.K to 180.36 W/m.K at 300K, respectively. In addition, the thermal conductivity increases with the increasing of grain size. For a better understanding of the effects of grain boundary and size on the thermal conductivity of nc material, a modified model, with special emphasis on the contributions of electron conduction, is presented by incorporating the concept of the Kapitza resistance into an effective medium approach. The theoretical calculations are in good agreement with our experimental results.