Effect of Cubic and Hexagonal Boron Nitride Additions on the Synthesis of Ag-SnO2 Electrical Contact Material


JOURNAL OF NANOELECTRONICS AND OPTOELECTRONICS, vol.14, no.7, pp.1010-1015, 2019 (Journal Indexed in SCI) identifier

  • Publication Type: Article / Article
  • Volume: 14 Issue: 7
  • Publication Date: 2019
  • Doi Number: 10.1166/jno.2019.2592
  • Page Numbers: pp.1010-1015
  • Keywords: Ball Milling, Composite Powders, Cubic Boron Nitride, Hexagonal Boron Nitride, Silver-Based Electrical Contact Materials, Tin Dioxide, PARTICLE-SIZE, TRANSFER BEHAVIOR, EROSION BEHAVIOR, DENSIFICATION, MORPHOLOGY, AGTIB2


This study investigated the effect of different types of boron nitride (BN) additions on the synthesis and characterization of Ag-SnO2 based electrical contact material. For this aim, two different reinforcement materials, namely cubic boron nitride (cBN) and hexagonal boron nitride (hBN) powders were added separately to powder mixture containing commercial elemental silver (Ag) and tin dioxide (SnO2) powders. In order to avoid agglomeration and to decrease the tendency of cold welding among powder particles, stearic acid was also added to both compositions as a process control agent (PCA). Ball milling experiments of these two different powder mixtures were conducted in a high-energy planetary type ball mill with a ball-to-powder weight ratio of 10: 1 and a milling speed of 300 rpm. Characterization of the starting and milled powders was carried out using scanning electron microscopy (SEM) and laser diffraction analysis (Mastersizer). It was found that the size and shape of milled powders significantly affected by the type of BN content. The lubricating effect of hBN leads to a rapid decrease of particle size, especially in the very early stages of milling process. On contrary, cBN influences ball milling efficiency at later stages of milling operation. As a result of this effort, cBN was found to be more effective as compared to hBN in terms of achieving particle size reduction. The minimum particle size (6.234 mu m) is obtained using cBN reinforcement after the milling duration of 25 h. Eventually, a refined and homogenized microstructure (equiaxed morphology) is obtained for the Ag8SnO2-cBN powder mixture after milled for 25 h. Excessive or prolonged milling durations promote powder contamination which is a major problem in sustaining electrical conductivity and therefore optimum milling duration was determined as 25 h.