Comparison and Analysis of Sodium Silicate and Epoxy Bonded NdFeB Magnets

Sodium silicate bonded and epoxy bonded magnetic NdFeB materials are fabricated, respectively. The magnetic properties, temperature coefficient, heat-corrosion and compressive strength of both bonded magnets are investigated. Results reveal that sodium silicate bonded magnet has a similar comprehensive property to epoxy bonded one. Compared to the epoxy bonded magnets, the sodium silicate bonded NdFeB has better temperature coefficient between 20 and 100 °C. The α value of the sodium silicate bonded NdFeB is-0.127 %/°C while the β value is-0.275 %/°C between 20 and 200 °C. DSC thermogram shows that sodium silicate as a bonder in magnet could exist at a higher temperature (above 1000 °C), which is far bigger than the curie point of NdFeB magnet powder. The weight gains of sodium silicate bonded magnet obtained in heat-corrosion resistance test are smaller than those of epoxy bonded one. Compressive strength test shows that sodium silicate bonded magnet has a larger compressive strength (35 MPa) than that of epoxy bonded magnet (27 MPa). Compared to the epoxy, the sodium silicate as bonder in the bonded magnet shows more compact. As a result, the sodium silicate bonded NdFeB bears better magnetic properties, temperature coefficient, heat-corrosion resistant and compressive strength.