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1 Journal of Korean Powder Metallurgy Institute DOI: /KPMI y-y w Sm-Fe w ƒ w zá *Á w»» The Effect of Excess Samarium Oxide on the PreparationG of Sm-Fe Alloy Powder by Reduction-diffusion Method Hun Kwak, Jung Goo Lee*G and Chul Jin Choi Functional Materials Division, Korea Institute of materials Science, 531 Changwondaero, Changwon , Korea (Received August 5, 2009; Revised August 21, 2009; Accepted September 7, 2009) Abstract To produce alloy powders with only single phase by reduction-diffusion (R-D) method, the effect of excess samarium oxide on the preparation of Sm-Fe alloy powder during R-D heat treatment was studied. The quantity of samarium oxide was varied from 5% to 50% whereas iron and calcium were taken 0% and 200% in excess of chemical equivalent, respectively. The pellet type mixture of samarium, iron powders and calcium granulars was subjected to heat treatment at 1100 o C for 5 hours. The R-D treated pellet was moved into deionized water and agitated to separate Sm-Fe alloy powders. After washing them in deionized water several times, the powders were washed with acetic acid to remove the undesired reaction products such as CaO. By these washing and acid cleaning treatment, only 0.03 wt% calcium remained in Sm-Fe alloy powders. It was also confirmed that the content of unreacted α-fe in matrix gradually decreased as the percentage of samarium oxide is increased. However, there was no significant change above 40% excess samarium oxide. Keywords : Reduction-diffusion method,, magnetic powder 1. w šz z š m š. m Alnicoù Ferrite w šƒ,» p((bh)max» Ferrite 13, Alnico 3) MRI, CD, f ƒ»á»», w/» yášy w l ƒ s ƒw [1, 2]. m- yw Th 2 Zn 17 ƒ Re 2 yw w 2:17 w.» pƒ j Fe w» Re 2 yw sy y j ƒ w ƒ. ù» û j y [3]. wr, Re 2 yw w ù y w Sm-Fe-N Nd 2 Fe 14 B ƒ syy (M s =1.5T) ƒš, j»(h A =260 KG) j( 480æ ) ƒš» ƒ šp y w z j y [2]. w Sm-Fe-N j w *Corresponding Author : [Tel : ; jglee36@kims.re.kr] 336

2 y-y w Sm-Fe w ƒ w 337 w Sm-Co Nd-Fe-B š [8, 9]. w ¾ y-y w Sm-Fe-N w ƒ k w., y-y w šp Sm-Fe-N w ƒ wwš. šp Sm-Fe-N 1 w œ ƒ w Sm Fe Stoichiometry. w Sm Fe» { w w. q w α-feƒ w. w yy Sm oxide ƒ yƒ Sm-Few e w w r. Fig. 1. A typical process of preparing Sm-Fe-N magnetic powder by reduction-diffusion (R-D) method. œ yœ w, w w[4], y-y[5, 6] š [7] w. y-y 1) Sm w ƒ w, 2) z qœ v š, 3) œ» w šp w. y-y w Sm-Fe-N œ 1 ùkü. 2. x y-yœ carbonyl Fe (Kojundo Co., 99.xx%, 3-5 μm), (Kojundo Co., 99.99%) y Ca granule( 99.5%) w[10]. y-y ³w w 3 yw» yww., Fe wš» 5~50 wt.%¾ ƒw. y w w Ca w» ù, œ w ƒ w 300 Fig. 2. Raw materials. (a) Fe Powder, (b) Powder and (c) Ca granule

3 338 zá Á + 3Ca = 2Sm + 3CaO (1) Fig. 3. Typical photographs of pellet type samples (a) before R-D reaction and (b) after R-D reaction. wt.% ƒw. yw 13 MPa ƒw 16 mm pellet type r w( 3(a)). ƒ w ew g» w. r SUS crucible š k w z Ar» w 1100 o C, 5 y-y w w. y-y z r nw g r. w w z Ca w» w 2 wt% acetic acid w. XRD(Regaku, D-Max 2200) SEM (JEOL, JSM-5800) w mw ƒ y Sm-Fe w x r. 3. š y-y š» Ca w y k. 840 o C Ca z 900 Cl w ù o ƒ š [11]. x 200 o C 1100 C w» o (1) wš q. Ca w y Sm Fe ü yw Sm-Fe w x. y-y w Sm- Fe w x. + 17Fe + 3Ca +3CaO (2) y-y w Sm-Fe w CaO Ca œ. 3(b) x w œ ùküš. 3(a) (b) ƒƒ ƒ z y-y z pellet x. yw z ƒw r z( ƒ w ) w, œ y-y z z» y-y z dw.» ƒ w, nw w w. Ca(s)+H 2 O(l)Ca(OH) 2 (aq)+h 2 (g) (3) CaO(s)+H 2 O(l)Ca(OH) 2 (aq) (4) 4 w œ ùküš Fig. 4. A sequence of washing process. (a) porous sintered body, (b) generation of hydrogen gas by the reaction between Ca and H 2 O, (c) collapse of porous sintered body and (d) Sm-Fe Journal of Korean Powder Metallurgy Institute

4 y-y w Sm-Fe w ƒ w 339 Fig. 5. Typical micrographs of the powders obtained by R-D process.. y-y ( 4(a)) nw (3) w ƒ w ( 4(b))w Ca(OH) 2 w j Sm-Fe w eš kw( 4(c)). w œ z w Ca(OH) 2 w z Oven w œ ~ μm j» Sm- Fe w ( 4(d)). 5 w SEM ùküš.» 3-5 μm Fe yy w w μm j» œ xw. t ùkù»œ y-y w x, w x ƒ j w. w œ x k ( 5(b)) œ Ca. w Ca w œ z w[12]. acetic acid 2 wt% 5-30 w Ca ICP-AES(Perkin Elmer, Optima 4300) e w w, 6 ù kü. 6 œ z w 3.3 wt% Ca w w 15 w 0.03 wt% w wš z j yƒ y w % ƒw y-y w z XRD ùküš. 7 Fig. 6. Effect of acid cleaning treatment on Ca removal in R-D powder. Fig. 7. XRD patterns of the powders obtained by R-D process. (a) Excess of 5%, (b) Excess of 10%, (c) Excess of 15%, (d) Excess of 20%, (e) Excess of 25%, (f) Excess of 30%, (g) Excess of 40% and (h) Excess of 50% ƒ 5% ƒ w y-y z α-

5 340 zá Á Fig. 8. XRD patterns of the powders obtained by R-D process. (a) Excess of 5%, (b) Excess of 10%, (c) Excess of 15%, (d) Excess of 20%, (e) Excess of 25%, (f) Excess of 30%, (g) Excess of 40% and (h) Excess of 50% Feƒ w. w ƒ ƒw α-feƒ w ƒ 30% ƒw α-fe ƒ w. 8 7 XRD w SEM ùküš. gp p α-feš z EDS mw yw. 8 y-y z w α-feƒ ƒ ƒ wì w 40% ƒ w yw. 7 XRD 10% XRD X en¾ û α-fe». w ww y-y mw» w ƒ 140%. w y œ œ mw šp. x w yyœ w w šp N x w œ y w. 4. w y -yœ y y ƒ y-y w Sm-Few e w w r., 5-50% ƒw ƒ ƒ α-fe yw, 40% ƒw α-feƒ x yw.» w. šx [1] M. Katter, J. Wecker and L. Schultz: J. Appl. Phys., 70 (1911) [2] J. M. D. Coey and H. Sun: J. Magn. Mater., 87 (1990) L251. [3] J. P. Gavigan, D. Givord and H. S. Li: Concerted European action on Magnets, I.V. Mitchell (Ed.), London (1989) 163. [4] N. Imaoka et al.: J. Alloys Comp., 222 (1995) 73. [5] R. E. Cech: JOM, 26 (1974) 32. Journal of Korean Powder Metallurgy Institute

6 y-y w Sm-Fe w ƒ w 341 [6] A. Kawamoto et al.: IEEE Trans. Magn., 35 (1999) [7] V. R. Caffarena, T. Ogasaware, M. S. Pinho and J. L. Capitaneo: Latin American Applied Research, 36 (2006) 137. [8] H. Z. Gu and Y. P. Ye: Chin. Sci. Bull., 12 (1983) 735. [9] C. S. Herget: Proc. 8th Int. Workshop on Rare Earth Magnets and Their Applications, K. J. Strnet (ed), Cayton, OH (1985) 407. [10] J. C. Boareto et al.: Mater. Sci. Forum, (2007) [11] C. B. Song: Korea Journal of Materials Research 8 (1998) 720. [12] A. Verma, R. K. Sidhu, S. Mahajan, and O. P. Pandey: J. Mater. Sci. Lett., 15 (1996) 2088.