Banca de QUALIFICAÇÃO: JORGE COSTA SILVA FILHO

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
STUDENT : JORGE COSTA SILVA FILHO
DATE: 16/06/2023
TIME: 14:00
LOCAL: Por participação remota
TITLE:

Technologies of graphene derivatives related to clean energies in the manufacture of sintered rare earth magnets

PAGES: 112
BIG AREA: Engenharias
AREA: Engenharia de Materiais e Metalúrgica
SUBÁREA: Metalurgia de Transformação
SPECIALTY: Metalurgia de Pó
SUMMARY:

The present work describes a new methodology to manufacture of sintered Neodymium-Iron-Boron (NdFeB) magnets, we used the traditional route of powder metallurgy and added the reduced graphene oxide (rGO) during mechanical milling. Thus, we obtained the NdFeB-rGO magnetic powder composite, which was used to manufacture the magnets. In this process, we evaluated: the effect of different amounts of rGO (1 to 5 mg) on the milling of Nd_14.19 (Nd_14.19Fe_75.59B_5.77Co_3.30Dy_0.43Cu_0.16Al_0.37Ga_0.20) alloy; The effect of milling time (7 a 45 min) on the grounding of 2.5 mg of rGO with Nd_14.19; And the milling time of 2.5mg de rGO with other metal alloys.  The alloy mixtures studied were the Pr_14.20 (Pr_14.20Fe_65.21B_5.90Co_14.40Cu_0.2Nb_0.09) and the Pr_14.55 (Pr_14.55Fe_65.62B_5.85Co_13.6Cu_0.3Nb_0.09) with raw alloy (LBF-1) Pr_20.05Fe_balB₅Cu₂, here they are called Pr_14.55 and Pr_15.95, respectively.The other alloy mixture studied used the Nd_14.19 with the Nd_12.36Fe_75.05B_5.55Dy_6.08Cu_0.99 (LBF-2) named Nd_14,01. For these studies, the rGO was produced through the thermal reduction of GO, which was previously synthesized by the adapted- and modified-Hummer method. X-ray diffraction and Raman spectroscopy analysis revealed the formation of GO and the reduction to rGO. Then, the rGO was added to the magnetic powder Nd_14.19, we observed that the rGO worked as a lubricant agent among the material, the milling vase walls, and spheres. Therefore, the rGO prevents the welding of the Nd_14.19 magnetic powders with the milling vase. The spheres and the magnetic powder did not adhere to the internal walls of the vase and could be easily removed. Moreover, the Nd_14.19-rGO magnetic powder composite did not ignite when exposed to air. Similar results were observed to the alloy mixtures evaluated in this work. Through this study, we verified that the best squareness ratio of 0.8 was observed to the sintered magnets of Nd_14.19, which were ground for 30 min and with 2.5mg of rGO. This sample presents the best magnetic properties. In fact, these magnets present remanence (Br) varying from 0.47T (0.1% wt rGO) to 1.13 T (0.02% wt rGO), the intrinsic coercivity (iHc) from 263.50 kAm^-1 (0.1% wt rGO) to 765.07 kAm^-1 (0.02% wt rGO), and the maximum energy product (BH_max) from 19.82 kJm^-3 to 181.25 kJm^-3.  For the alloy mixture of the Pr_14.55 and Pr_15.95 we evaluated the mixture proportion of each alloy and the raw alloy (LBF-1) and during different milling times with 2.5 mg of rGO.  Better magnetic properties were observed for the alloy mixture of 2.5g of LBF-1/Pr_14.55, for the mixture of 4.5g of LBF-1/Pr_14.95, and for the mixture of 1.5 g of LBF-2/Nd_14.01. 

COMMITTEE MEMBERS:
Presidente - Interno ao Programa - 1545089 - DANIEL ZANETTI DE FLORIO
Membro Titular - Examinador(a) Interno ao Programa - 1734912 - ROOSEVELT DROPPA JUNIOR
Membro Titular - Examinador(a) Externo à Instituição - MOHAMMED ELMASSALAMI MOHAMED - UFRJ
Membro Titular - Examinador(a) Externo à Instituição - SÔNIA GUIMARAES
Membro Suplente - Examinador(a) Interno ao Programa - 1734908 - FABIO FURLAN FERREIRA
Membro Suplente - Examinador(a) Externo ao Programa - 1925199 - ANIBAL DE ANDRADE MENDES FILHO
Membro Suplente - Examinador(a) Externo à Instituição - ANITA CANAVARRO BENITE - UFG
Membro Suplente - Examinador(a) Externo à Instituição - SERGIO ANTÔNIO ROMERO - USP