Novrita Idayanti

Magnetic properties of cobalt ferrite synthesized by mechanical alloying

Cobalt ferrite (CoFe2O4) is a well-known hard magnetic material with high coercivity and moderate magnetization. These properties, along with their great physical and chemical stability, make CoFe2O4 suitable for many applications such as generator, audio, video-tape etc. In this study, the magnetic properties of cobalt ferrite synthesized via the mechanical alloying using α-Fe2O3 of Hot Strip Mill (HSM) waste and cobalt carbonate as the precursors have been investigated. Structural and magnetic properties were systematically investigated. The X-ray diffraction (XRD) pattern exhibited the single phase of cobalt ferrite when the sintering temperature was 1000 °C. Permagraph measurements of the sintered sample revealed a saturation magnetization (Ms) of 77-83 emu/g and coercivity (Hc) of 575 Oe which closely to the magnetic properties of references; Ms = 47.2-56.7 emu/g and Hc =233-2002 Oe.Cobalt ferrite (CoFe2O4) is a well-known hard magnetic material with high coercivity and moderate magnetization. These properties, along with their great physical and chemical stability, make CoFe2O4 suitable for many applications such as generator, audio, video-tape etc. In this study, the magnetic properties of cobalt ferrite synthesized via the mechanical alloying using α-Fe2O3 of Hot Strip Mill (HSM) waste and cobalt carbonate as the precursors have been investigated. Structural and magnetic properties were systematically investigated. The X-ray diffraction (XRD) pattern exhibited the single phase of cobalt ferrite when the sintering temperature was 1000 °C. Permagraph measurements of the sintered sample revealed a saturation magnetization (Ms) of 77-83 emu/g and coercivity (Hc) of 575 Oe which closely to the magnetic properties of references; Ms = 47.2-56.7 emu/g and Hc =233-2002 Oe.

The implementation of hybrid bonded permanent magnet on permanent magnet generator for renewable energy power plants

This paper describes application of permanent magnet on permanent magnet generator (PMG) for renewable energy power plants. Permanent magnet used are bonded hybrid magnet that was a mixture of barium ferrite magnetic powders 50 wt % and NdFeB magnetic powders 50 wt % with 15 wt % of adhesive polymer as a binder. Preparation of bonded hybrid magnets by hot press method at a pressure of 2 tons and temperature of 200°C for 15 minutes. The magnetic properties obtained were remanence induction (Br) =1.54 kG, coercivity (Hc) = 1.290 kOe, product energy maximum (BHmax) = 0.28 MGOe, surface remanence induction (Br) = 1200 gauss, density = 3.83 g/cm3, and curie temperature of 400°C. Magnet samples were implemented on PMG at speed of 100–600 rpm. The maximum power at nominal speed was 93 Watt.

Magnetic and microwave absorbing properties of Al and Zn substituted barium hexaferrites in X-band region

In this study, the Al and Zn substituted barium hexaferites with x = 0, 0.5, and 1 were prepared using wet mechanical alloying along with calcination at 1200°C and sintering at 1250°C. X-ray diffraction (XRD) characterization shows that single phase of M-type barium hexaferrites are formed in substitution amount x 0 and 0.5, and there are W-type barium hexaferrites peaks detected at x = 1. The addition of AlZn decrease the coercivity from 1.721 to 0.986 kOe at x = 0 and 1 respectively. Increasing the composition from x = 0.5 to x = 1 also reduce the magnetization saturation significantly. The microwave absorption of the prepared AlZn substituted barium hexaferrites with thickness 2 mm in X-band region is still relatively low, the maximum return loss is achieved when substitution amount x is 1 with value of 12.2 dB at 10.5 GHz. Increasing the substitution amount x of AlZn from 0 to 1 only slightly increases the value of return loss and shifts to lower frequencies.

Preparation of barium hexaferrite powders using oxidized steel scales waste

Research on preparation of barium hexaferrite powders has been done using Hot Strip Mill scales as raw materials. Hot Strip Mill scales are oxidized steel scales waste from steel industrial process. The method used for preparing the barium hexaferrite powders was solid state reaction method. Oxidized steel scales were milled using ball mill for 10 hours, then screened through a 250 mesh sieve to obtain powders with maximum size of 63 µm. Powders were roasted at 600°C temperature for 4 hours to obtain hematite (Fe2O3) phase. Roasted powders were then mixed with barium carbonate, and were subsequently milled for 16 hours. After mixing, powders were calcined with an increasing rate of 10°C/min and maintained at 1100°C for 3 hours. Calcination process was performed to acquire barium hexaferrite phase. X-ray Diffraction (XRD) characterization in conjunction with RIR analysis showed that 85 wt. % of barium hexaferrite is formed. The magnetic properties of powders were characterized using Permagraph. It is found...