Preparation of Nd-Fe-B/α-Fe nanocomposite by chemical reduction method

• Main Author: Lim, Darryl Yu Zhi.
• Other Authors: Raju Vijayaraghavan Ramanujan
• Format: Final Year Project
• Language: English
• Published: 2009
• Subjects: DRNTU::Engineering::Materials::Magnetic materials
• Online Access: http://hdl.handle.net/10356/15369
• Institution: Nanyang Technological University

Nanocomposite Nd-Fe-B alloys consisting of exchange coupled soft α-Fe phase and hard Nd2Fe14B phase have attracted considerable attention due to its high (BH)max. In this project, the magnetic properties of Nd-Fe-B based nanocomposite magnet prepared by solution techniques are studied. Nd-Fe-B based alloys are prepared by using the chemical reduction method. Reduction of Fe2+ and Nd3+ ions were achieved by using BH4- ions followed by heat treatment to obtain the desire phase. Different alloy samples were prepared using different synthesis conditions. Sodium borohydride is dissolved in a basic solution of pH 13 and pH 11 respectively to investigate the effect of pH. NdBO3 is found to be present in samples which were prepared in the basic and slightly acidic Fe3+ and Nd3+ salts solution. This is due to the formation of Nd(BO2)3 during synthesis which was converted to NdBO3 after thermal treatment. Glycine and calcium hydride are also added to minimize the NdBO3 byproduct in the final composition. Powders investigated using X-ray diffraction before thermal treatment indicates that they are amorphous. It is observed that the addition of glycine to inhibit the formation of Nd(BO)2 during reduction process is not fruitful. Hence, to reduce NdBO3, all the samples were heat treated in the presence of CaH2. The magnetic properties of the powders are found to be poorer as compared to the samples obtained by traditional ball milling or melt spinning methods.