PENGARUH WAKTU DRY MECHANICAL MILLING DAN HEAT TREATMENT TERHADAP MIKROSTRUKTUR, DENSITAS DAN SIFAT
MAGNET DARI NdFeB
ABSTRAK
Telah dilakukan proses penghalusan serpihan NdFeB dengan menggunakan conventional ball mill dengan menggunakan metode dry milling dalam atmosfir gas inert dengan menggunakan gas Nitrogen (N2) saat proses milling berlangsung.
Bahan yang digunakan adalah serpihan NdFeB. Waktu milling yang menjadi parameter penelitian divariasikan selama 8 jam, 16 jam, 24 jam dan 48 jam. Kemudian serbuk NdFeB diukur diameter partikel serbuk dengan PSA, analisis struktur kristal dengan XRD, pengamatan mikrostruktur dengan SEM-EDX dan kurva histeresis dengan VSM. Untuk pengujian densitas, sifat magnetik (fluks density) dan kurva B-H dengan Permagraph dilakukan pada sampel berbentuk pelet. Sampel dalam bentuk serpihan yang telah dimilling dengan berbagai variasi waktu milling, dicetak dengan gaya 7 tonf selama 2 menit, dan dengan ditambahkan bahan perekat celuna sebanyak 3 wt%, hingga membentuk pelet dengan diameter ±1,6 cm. Selanjutnya sampel pelet di heat treatment selama 1 jam pada suhu 110ᵒC , 150ᵒC dan 170ᵒC. Sampel pelet kemudian dicoating dengan sirlak. Kemudian, sampel pelet diukur densitasnya dengan menggunakan jangka sorong. Sampel pelet yang telah dilakukan heat treatment, dimagnetisasi dengan impulse magnetizer pada tegangan 1500V DC. Sampel pelet yang telah dimagnetisasi diukur fluks density menggunakan Gaussmeter. Dari nilai densitas fluks magnet sampel, diperoleh sampel terbaik yaitu sampel hasil milling selama 48 jam pada suhu heat treatment 170ᵒC dan diperoleh fluks magnet sebesar 485,8 Gauss. Densitas tertinggi sebesar 5,740 gr/cm3 dan koersivitas pelet NdFeB yaitu 1,171 kOe dan BHmaks sebesar 0,62 MGOe.
Kata kunci : NdFeB, heat treatment , dry milling , ball mill , gas inert
EFFECT OF DRY MECHANICAL MILLING TIME AND HEAT TREATMENT ON MICROSTRUCTURE, DENSITY AND MAGNET
PROPERTIES OF NdFeB
ABSTRACT
Has been done smoothing process of NdFeB flakes using conventional ball mill by dry milling method within an inert gas atmosphere using Nitrogen gas (N2) while milling process was held. The materials used were NdFeB flakes. Milling time which became the research parameter was varied for 8 hours, 16 hours, 24 hours and 48 hours. Then NdFeB powder particle diameter was measured by PSA, the crystal structure analysis by XRD, microstructure observation by SEM-EDX and the hysteresis curve by VSM. For density test, magnetic properties (flux density) and the BH-curve by Permagraph was done on pellet form samples. Sample in flakes form which has been milled with milling time variety, was pressed with 7 tonf force for 2 minutes and with added adhesive celuna as much as 3 wt% up to become pellets form with a diameter ±1.6 cm. Further the pellet samples were given heat treatment for 1 hour at temperature 110ᵒC, 150ᵒC and 170ᵒC. Pellet samples were then coated with sirlak. Then the pellet samples density was measured using a caliper. Pellet samples that have been done heat treatment, were magnetized with the impulse magnetizer in 1500V DC voltage. Pellet samples that have been magnetized , flux density was measured using a Gaussmeter. From the magnetic flux density sample value, the best sample that obtained was the sample in milling time for 48 hours at heat treatment temperature was 170ᵒC and obtained magnetic flux density at 485.8 Gauss. The highest density at 5.74 g / cm3 and NdFeB pellet coercivity are 1.171 kOe and BHmax 0.62 MGOe.
Keywords : NdFeB, heat treatment , dry milling , ball mill , inert gas
