Effect of compaction pressure on shrinkage, density, and hardness of strontium hexaferrite

Abstract

Iron sand as a magnetic material has yet to be widely used; in several developed countries, magnetic materials are already commonly used in industry. A simple method for purifying iron sand is carried out by filtering iron sand with a mesh size of 80. The quality of this magnetic base material is influenced by, among other things, its density and hardness. The research aims to determine the effect of compaction pressure on the shrinkage, density, and hardness of iron sand-based strontium ferrite. The iron sand from Ketawang Indah Beach, Purworejo, was extracted mechanically 35 times with a permanent magnet and then oxidized at a temperature of 900 °C for 5 hours. Next, the iron oxide was mixed with strontium carbonate (SrCO3) using a shaker mill for 3 hours. The resulting strontium ferrite powder was compacted at 20, 40, and 60 MPa pressures, then sintered at 1100 °C for 1 hour in a furnace. Shrinkage measurements include the diameter and height of the specimen, while density measurements use the Archimedes method. The hardness obtained through the Vickers hardness, the highest shrinkage value was obtained at a pressure of 20 MPa, namely diameter shrinkage (Δd) of 2.6% and height shrinkage (Δh) of 0.5%. The highest density and hardness values were at a pressure of 60 MPa, 4.366 g/cm3, and 693 HV. An increase in pressure at a sintering temperature of 1100 °C causes a decrease in shrinkage and an increase in density and hardness values.