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DAI HOC QUOC GIA HA NOI TRl/CfNG DAI HOC KHOA HOC Tl/NHIEN NGHIEN CtJtJ CHE TAO NAM CHAM DAT HIEM NdFeB Sir DUNG B O T V A T L I E U CHE TAO BANG P H U O N G PHAP HAP THU HYDRO MA SO: QT-06-15 CHU TRIDE TAX: PCS TS LUtJ TUAN TAI CAC CAN Bp TRAM GIA : TS LlTU HOAI NAM ThS NCS TA VAN KHOA ThS PHAM THI THUONG Ha Noi - 2006 BAO CAO TOM TAT 1- Ten de tai: Nghien cihi che tao nam cham dat hiem NdFeB su dung hot vat lieu che tao b^ng phiiang phap hap thu hydro 2- Ma so: QT-06-15 3- Thol gian thiic hien : 12 thang (tir 03/2006 tdi 03/2007 ) 4- Chu tri de tai: PGS TS Lim Tua'n Tai Phong thi nghiem vat ly nhiet thap, trudng DHKH Tu nhien , Dai hoc qudc gia Ha Noi 5- Can bo tham gia de tai: PGS TS Luu Tua'n Tai ThS.NCS Ta Van Khoa ThS.Pham thi Thuong TS Luu hoai Nam Va cac cong tac vien khac 6- Muc tieu va noi dung nghien curu: - Che tao he ha'p thu hydro don gian de ap dung cdng nghe HDDR - Nghien ciiu ,tim cdng nghe HDDR thfch hop - Che tao cac nam cham ket dmh NdFeB tren co sd bdt vat lieu che tao bang phuong phap hap thu hydro (ap dung cdng nghe HDDR) dat tich nang lugng cue dai Idn hon MGOe 7- Cac ket qua dat dugc: Sau mot thdi gian thuc hien de tai, chiing tdi da thu dugc mot sd ket qua nhu sau: - Da xay dung va van hanh tot he thiet hi hap thu hydro nhiet cao (he thiei bi HDDR) - Su dung he thiei bi HDDR xay dung dugc de khao sat cac hgp kim va cac dieu kien cdng nghe quy trinh HDDR va da che tao cdng ca hai loai hot HDDR khdng di hudng va di hudng - Mot quy trinh nhiet vdi nhiet cao han va thdi gian dai hon da dugc lira chon thich hgp cho cac vat lieu cd pha tap mot lugng nhd Zr (0.1% Zr) Ket qua la da che' tao dugc nam cham ket dmh tren ca sd bdt hgp kim NdigFeys.gZroiBs di hudng che tao bang phuong phap HDDR dat tich nang lugng cue dai (BH)^,, = 9.95 MGOe 8- Tinh hinh kinh phi cua de tai: *T6ng kinh phi dugc cap: 15 trieu dong Viet nam Da quyei toan vdi tai vu xong CHU TRI DE TAI KHOA QUAN L t (K^ va ghi TO ho ten) (Ky va ghi ro ho ten) us' PGS TS Luu Tuan Tai CO QUAN CHU TRI DE TAI PHOHlioTRUOMO PGS T S t & - ^ ^ ^ * * » SUMMARY REPORT I Project Title: To investigate and fabricate the NdFeB bonded magnets use HDDR powder II Project Director: Ass.Prof.Dr Luu Tuan Tai Cryogenic laboratory,Faculty of Physics College of Natural Science, Hanoi National University IILGrant number : QT - 06-15 IV Key Project Staff: Dr Luu hoai Nam MA Phs Ta Van Khoa MA Phs Pham thi Thuong And some others V Aims and contents of the project: - To investigate the influence of temperature and time of HDDR technology condiSon o^ the hard magnetic properties of the NdFeB bonded magnets m order to find the good condition to produce NdFeB bonded magnets To investigate and fabricate the NdFeB bonded magnets use HDDR powder VI Summary of Achievements of project: - To set up the HDDR equipment - To investigate the influence of temperature and time of HDDR technology condition and addition effect of small amount of Zr on the hard magnetic properties of the NdFeB bonded magnets in order to find the good condition to produce NdFeB bonded magnets ^ e tu^ - Isotropy and anisotropy NdFeB HDDR powders were produced for the oroduction bonded magnets HDDR process with higher temperature and longer heat treatment t.me wa selected to suit for the materials with a small amount of addition of Zr, to result in produced the bonded magnets with (BH)n,ax= 9.95 MGOe Muc luc I- GI6ITHIEU II- MVC TIEU NGHIEN CIRJ CHINH CUA DE TAI W Trang? 16 Ji Ill- CAC KET QUA KHOA HOC CUA DE TAI 17 3.1 He mau hop kim NdigFcyg.xBg .18 3.2 He mau hgp kim Nd,6Fe76.xZrxB8vaix = 0.1,0.2,0.3 va 0.5 22 IV.KETLUAN 28 V TAI LIEU THAM K H A O 29 NOI DUNG BAO CAO TONG KET I Md DAU Viec che tao cac NCVC dua tren co sd cac hgp kim chua dat hiem vao nhung nam 70 da md dku cho mdt cudc each mang mdi ITnh vuc dien va dien tu Dae biet la loai nam cham SmCos va (SmPr)Co5 cd ten tren thi trudng la Recoma vdi day du cac dac tinh can thiet ciia NCVC va nang lugng tu dat dugc la (BH)max = 22 MGOe (175 KJ/m^) Tuy nhien, dieu dang , f \ f '> '^ tiec la Coban cd tru lugng it va la mot kim loai dat tien, Vi the de cd Igi ve mat kinh te, ngudi ta da tien hanh thay the mot phan nhd Co bang cac kim loai nhu: Fe, Co, Mn, Al, Zr loai nam cham nay, Sm(Co, Cu, Fe, Zr)8.5, vln dat dugc nang lugng tu rk cao la (BH)max ^ 33MGOe Song song vdi each giai quySt nhu tren, thi viec tim kiem cac vat lieu mdi lam NCVC chua it hoac khdng chua Coban da trd muc tieu cua nhieu cdng trinh nghien cuu tren the gidi Cudi nam 1983, Sagawa va cac cdng sir da cdng viec chd tao mot loai NCVC mdi tren co sd cua hgp kim Nd-Fe-B bang phuong phap bdt thieu ket vdi nang lugng tu cue dai dat (BH)max ^ MGOe, luc khang tu theo cam ung tu BHC = 11 KOe, luc khang tu theo tu MHC = 12 KOe, B, = 12.3 KG (1.23 Tesla) Pha hgp kim chinh cua loai NOI DUNG BAO CAO T O N G KET I MCf DAU Viec che tao cac NCVC dua tren ca so cac hgp kim chua dat hiem vao nhiing nam 70 da ma dku cho mot cuoc each mang mai ITnh vuc dien va dien tu Dac biet la loai nam cham SmCos va (SmPr)Co5 c6 ten tren y > f thi trudng la Recoma vdi day du cac dac tinh can thiet cua NCVC va nang lugng tu dat dugc la (BH)n,ax ^ 22 MGOe (175 KJ/m^) Tuy nhien, diSu dang tiec la Coban cd triJ lugng it va la mot kim loai dat tien Vi the de cd Igi ve mat kinh te, ngudi ta da ti^n hanh thay the mot phan nhd Co bang cac kim loai nhu: Fe, Co, Mn, Al, Zr loai nam cham nay, Sm(Co, Cu, Fe, Zr)8.5, win dat dugc nang lugng tu r4t cao la (BH)max ^ 33MGOe Song song vdi each giai quyk nhu tren, thi viec tim kiem cac vat lieu mdi lam NCVC chua it hoac khdng chua Coban da trd muc tieu cua nhieu cdng trinh nghien cuu tren the gidi Cudi nam 1983, Sagawa va cac cdng su da cdng viec chl tao mot loai NCVC mdi tren co sd cua hgp kim Nd-Fe-B bang phuong phap bdt thieu ket vdi nang lugng tu cue dai dat (BH)max = 36 MGOe, lire khang tu theo cam ung tu BHC ^ 11 KOe, lire khang tu theo tu MHC = 12 KOe, B, = 12.3 KG (1.23 Tesla) Pha hgp kim chinh cua loai vat lieu la hgp kim Nd2Fei4B Vat lieu d nhiet phdng cd mdmen tu bao hda cao Ms = 120 Am^/kg ' y I f Do nam cham ket dinh cd nhieu uu diem nhu: cd the che tao dugc cac hinh dang rat phue tap vdi chinh xac ve kich thudc tdi 0.01mm va cd the dieu chinh gia tri (BH)max theo gia tri mong mudn mot khoang tuong f , , ddi rdng(l-lOMGOe) nen nhung nam gan day nam cham ket dinh da phat trien rat manh va rdng rai Cac hgp kim dung de che tao nam cham ket dinh dugc che tao chu yeu bang phuong phap ngudi nhanh bang trdng ddng quay va sau dd xu ly nhiet, cd kich thudc hat vao khoang 30 - 40 nm (kich thudc nhd hon kich thudc cua don ddmen), ban than cac bdt loai da cd luc khang tu rat cao khac ban vdi cac bdt NdFeB dugc tao bang phuong phap nghien hgp kim khdi NdFeB Mac du kich thudc cua hat nSm mdt khoang rdng nhung tich nang lugng tinh cho cac loai bdt vao khoang 12 MGOe va dang nam cham ket dinh tich nang lugng cue dai dat dugc chi vao khoang 10 MGOe Cac dang nam cham kk dinh tao tu bdt nam cham ngudi nhanh cd rat nhieu va tinh chat tu cflng nhu nang lugng tu cua chung cung trai mot khoang nao dd, nhien cd th§ tdng k^t chung d ba loai khac sau: cac nam cham k§t dinh tao bSng phuong phap ep khudn, cac nam cham ket dinh tao bang phuong phap ep dun va cac nam cham deo Cac bdt nam cham NdFeB che tao bang phuong phap ngudi nhanh f y dung trdng ddng quay ma ta thuong goi la MQI d tren, sau ep ndng ta se thu dugc mot loai san pham quen goi la MQII, sau dd ap dung cdng nghe ep ndng khdng cd khudn ta thu dugc loai san pham MQIIL Cac nam cham cd tich nang lugng dat tdi 45 MGOe va la cac nam cham di hudng, cd th§ nghien bdt ma van cdn giir dugc tinh di hudng ciia chung va sau dd cd the dung de che tao cac nam cham ket dinh loai dj hudng Kha nang tich nang lugng cue dai ciia nam cham ket dinh che tao tir bdt MQIII cd the dat tdi 19 MGOe Tuy nhien quy tri^h cdng nghe la rat phuc tap va khd khdng f y f f t f che ddng nhat chat lugng san pham; mac du loai vat lieu da xuat hien va chiem mot ty le nhd cac san pham nam cham ket dinh ndi chung Mot nhung nguyen nhan lam cho ITnh vuc nam cham ket dinh phat trien manh me la sir phat trien ciia cac loai bdt nam cham nhu: bdt nam cham Sm2Fei7Nx, cac bdt^nam cham NdFeB che tao bang quy trinh cdng nghe HDDR, cac bdt nam cham dang hudng loai HIREM, cac bdt nam f y f cham che tao bang phuong phap bien dang ndng Phu-cng phap tach va tai hgp hydro HDDR (Hydrogenation Dispropotionation Desorption and Recombination) Hieu ung tach pha hydro da dugc khao sat ti mi vdi nhiJng dieu kien cu the khac nhu dieu kien ap suat hydro la 30 bar tai nhiet 300°C [R Harris va cac cdng sir, 1985] hay ap suSt la bar tai nhiet 720°C [Cadogan va Coey, 1986] Hieu ung tach pha (Disproportionation) cua NdFeB mdi trudng hydro la sir phan (Decomposition) hgp pha phan: a-Fe, Fe2B, va NdH2 f f \ r \ , Nam 1989, tai hoi nghj qudc te Ian thu 10 ve nam cham dat hiem va cac ung dung cua chung, Kyoto, Nhat ban, hai tac gia Takeshita va Nagayama md ta qua trinh su dung xu ly nhiet hydro de che tao bdt nam cham NdFeB vdi tich nang lugng cue dai cua vat lieu bdt la 95 KJ/m^ f f I f (12 MGOe) Ho da dung bdt trdn vdi chat ket dinh de che tao nam cham ket dinh NdFeB cd tich nang lugng la MGOe va luc khang tu la iHc = 10 KOe Sir phat trien mdi cd the canh tranh true tiep vdi ban quyen ve nam cham lanh nhanh de san xuat cac nam cham ket dinh Cflng can phai luu y rang, cac bdt NdFeB tao true tiep tu hgp kim khdi NdFeB bang phuong phap nghien thdng thuong hoac bang phuong phap tach vo t •% f f hydro (HD) cd the dung de che tao cac nam cham thieu ket nhung khdng du y f f f Idn ve lire khang tir de tao dugc cac nam cham ket dinh Su mat mat luc khang tir qua trinh nghien hoac tach vd la su sai hdng, gd ghe cua be mat cac hat (do nghien da tao cac tam mam dao tir va cac ddmen nguge khu tir) Qua trinh xu ly nhiet mdi trudng hydro dugc md ta theo cac budc nhu sau: vat lieu khdi NdFeB dugc dua vao dng Id rdi hut chan khdng tdi ap suat 10' Torr d nhiet phdng, sau dd thdi hydro vao dng Id tdi ap suat bar, rdi thuc hien quy trinh xir ly nhiet tir nhiet phdng tdi khoang 750 - 900°C Sau dd dng Id dugc hut chan khdng va tat Id de vat lieu nguoi theo Id Ket thiic qua trinh nay, vat lieu dugc kiem tra bang kinh hien VI truyen qua TEM, cho thay vat lieu bao gdm cac hat tinh the rat nhd chi cd 0.3fim cua hgp kim NdFeB, kich thudc cd the so sanh dugc vdi kich thudc ciia don ddmen ciia pha sat tir NdFeB va giai thich dugc tai luc khang tir iHc cdn giu* nguyen dugc Idn cac hat Trong thdi gian dau nhiing nam 1990, McGuiness ciing cac cdng sir da giai thich qua trinh hinh cac hat rat cd c§u true tinh thi NdFeB hai cdng trinh va da dat ten cho qua trinh xu ly nhiet hydro la qua trinh HDD (Hydrogenation Disproportionation Desorption) va sau dd dat ten lai cho qua trinh la HDDR (Hydrogenation Disproportionation Desorption and Recombination) Qua trinh FDDDR la qua trinh md rdng ciia qua trinh HD bang each nung ndng vat lieu tach vd hydro gay sir tach pha 10 *• Econet •• Station 10 •» am I • !»rtm CrOSS - sectlona Area S.I units « 1.21 cm2 Diameter 3Remanence - 579.29 +/ 0.93 mT Intrinsic Coercivity » 764.78 +/- 1.11 kA/m Inductive Coercivity - 386.4 +/- 1,16 kA/m « 56.44 +/- 0.19 kJ/m3 Maximum value S q u a r«? r>«? ?> s c-g.-i units of B.H Factor = 0.32 "• r i t i -? ' (Remanence = 5.79 +/- 0.01 kG Intrinsic Coercivity « 9.61 +/- 0.01 kOe Inductive Coer civity => +/- O.Ol kOe +/ - 0.02 MQOi Maximum value Squareness B.H « 7.09 Factor of "^ 0,32 45 (ratio^ » 1^.40 mm •• Econet • t^ i t ãã fiftm Station 10 10 ã ãô ã iM i Cross-sectional Area - l 21 i.^i cm-? cm^ n * - - Diameter Intrinsic t~ Remanence Coercivity « » 579.29 764.78 +/+/- 0.93 i,ii mT kA/m Inductive Coercivity « 386.41 +/- i,i6 kA/m « 56.44 +/- 0.19 kl/m^ S.I units Maximum value Squareness c.g.s units of B.H Factor ^ 0.32 trditi o' i Remanence -~ 5.79 +/- 0.01 kG Coercivity * 9.61 +/- 0.0 kOe Inductive Coercivity M a x i m u m v a l u e of B H = « 4.86 7.09 +/•»-/- 0.01 0.02 kOe MGOi ^ 0.32 Intrinsic Squareness Factor 46 (ratio) - 12.40 mm ** M I im-i [ * * I » ' I ^ h m < • T^.t\;^' IV, , r r -1 47 t ãã Econôt ãã M*»rU HtiMi Station 10 *• nJHK- I li S I units 21 cm2 Diameter IR»«anence « 536.69 +/ 1.98 Intrinsic Coercivity * 766.49 +/ 0.82 kA/m Inductive Coercivity = 367.29 +/ 1.83 kA/m « 49.65 +/ 0.31 k J/m Maximum value LI t) u a r t» n es':> e.g.3 units of B.H h,actor O ( ratio' iRemanence ằ Intrinsic Coercivity ãằ Inductive Coercivity ô= Maximum mT value of B.H = 5.37 +/- O.02 k6 9.63 +/- 0.01 kOe 4.62 +/- 0.02 kOe +/ - 04 MGOi 0.37 Squareness Factor = 48 (ratio) mi • • Econet 'li*' ; f •» S t a t i o n • n : r t^i !NHTO Cross-sectional S.I- units I n t r n '-: i c Inductive Maximum Area = 1.21 3Remanence = 660.as •/ 1.16 mT E • > t^ r < i v i t y = 773.21 +/ 2.06 kA/m « 431.74 +/ 0.94 kA/m = 72.38 +/- 0.20 kJ/m3 = 0- Coercivity value Squareness c.g.s 10 »» units of B.H Factor D a m e te r (ratio) :R e m a n e n ce ^^ Intrinsic Coercivity - Inductive Coercivity = Maximum cm2 value B.H '^ Factor » of 6.61 +/- 0.01 kG 9.72 +/- 0.03 kOe 5.43+/- O-01 kOe 9.10+/- 0 MBOi 0.34 Squareness 49 (ratio) 12.40 mm • Econet •» Station 10 ! M ir,if'~ t'lWi t "n-(! Cross-sectional Ar 1.21 cm2 D i a m e t er => y I - uni V ã; : Remanence ô* 643.75 */- 2.69 mT Intrinsic Coercivity *• 771,20 +/- I 24 kA/m Inductive Coercivity Intrinsic Coercivity • Inductive Coercivity * Maximum (ratlo) value Squareness of B.H Factor = = 4 +/ - 0.03 kB 9,69 +/- 0.02 kOe 5.29 +/- 0.02 kOe 8 +/ - O O S MGOI O.34 50 (ratio) 12.40 mm •• Econet •• fiT^r' , ?,nnt Station »» < f Cross-sectlona1 S.I 10 units Area - 1.21 cm2 Diameter : Rem a r t e r i t e t>43.75 +/ :^'.69 ml Intrinsic Coercivity = 7 - +/- 1.24 kA/m Inductive Coercivity = 420.31 +/- 1.73 kA/m value of B.H « 69.09 +/- 0.41 kJ/m3 Maximum Squareness Factor = 0.34 :Re«anence Intrinsic C o e r c i v i t y Inductive Coercivity M a x i m u m v a l u e of B.H S q u a r e n e s s Factor = = = = == 6.44 9.69 5.28 8.68 0.34 c.g.s (ratio) units 51 +/0.03 +/0.02 +/0.02 +/0.05 (ratio) kG kOe kOe MGOe - 12.40 mm »• Econet •• Station lO » • i-^i {• fir.' Cross-sectional 5.1- un i t s Area = 42 B9 Intrinsic Coercivity » Inductive Coercivity « value Squareness c.g.s cm2 Dlamete r ! Remanence Maximum 1.21 units of B.H » Factor = • / 9ti ml 769.94 +/- 26 430.62 +/- 1.87 kA/m 72.00 +/- 0.63 kJ/m3 O,40 kA/m (ratio) aRemanence « 6.43 +/- 0.05 kG Intrinsic Coercivity « 9.68 +/• 0.02 kOe Inductive Coercivity = 5.41 +/~ 0.02 kOe B.H « 9.05 +/- 0.08 MGOi Factor « 0.40 Maximum value Squareness of 52 (ratio) 12.40 nm »» Econet »• • t^\.r Knm Station 10 •• I'nir, ; MM> C r o s s -sec t i o n a l S.I units Area 1.21 :R e m a n e n ce 691.70 I n t; r n s c J IJ e r c i v i t y Inductive Maximum Coercivity value Squareness c.g.s units of B.H Factor - cm2 +/ 0.95 7B 96 « 451.40 « 73.16 = 0.35 D i a m e ter *- / • mT '.83 +/- 1.21 k A / m +/- 0.24 kj/m3 (ratio) :Remanence = 6.92 +/- 0.01 kG Intrinsic Coer civity «= 9.79 +/- 0.01 kOe Inductive Coercivity * 5.67 +/- 0.02 kOe of B.H = 9.95 0.03 Factor « 0.35 Maximum value B .„dedta:;st:e^fnrs:::rr in NdFeB are presented ^^^^^^^^^ ^^ ^^^^^^^ ^^^ study and Produce Anisotropy Powder NdFeB by 143 Hydrogenation II E x p e r i m e n t The samples NdigFeve-xZr^Bs (x=0.1, 0.2, 0.3, 0.5 corresponding to MAI, MA2, MA3, MAS) were prepared by arc melting method under Argon gas atmosphere, from materials being minimum cleaness of 99.9% For "Hydrogen treatrcjent" carried out by HDDR technology, the blocks of initial alloy were broken up, about Icm^ in dimensions, then were taken to reaction box The hydrogen gas got from water electrolyer, NITROX, with 99.99999% in cleanness and exited pressure up to atm The furnace of reaction box can be able to set different programe of heat temperature and time with maximum temperature of 1200°C and homogenous zone of temperature of cm After HDDR process, the alloy was grounded by ball mill and classified dimensions of powder grains by seiver with S'C/min 20'C/min Depend on luln e'C/min net of lOO^m to 125nm HDDR Fig I The HDDR Temperature Process temperature process was shown in the figure HDDR powder was mixed epoxy with rate of 2%, then pressed in cyUnder cast with diameter of 13mm and pressure of tons/cm^ polymerized at 125°C in hour The magnets was magnetized at magnetic field H = Tesla The magnetic hysteresis loop was measured by hysteresigraph Econnet The density of samples was measured by hydrostatic balance method III Results a n d D i s c u s s i o n The prepared samples are clearly texture structure along its heigh, bright color and non-oxide, it shows that the crystal directed orient of grains is unity relatively The results of non-substitution sample, NdFeB is studied in [4] and that of addition of Zr samples (MAI, MA2, MAS, MAS) is listed in table Table 1: The parameters of MAI, MA2, MAS, ^ samples p[g/cm='] B, [KG] MHC BHC [KOe] [KOe] (BH)„a, [MGOe] H/B at (BH)„ax MAI Happ = 5.92 5.1 9.4 4.01 5.2 0.3 (x=0.1) Happ = 5.91 5.79 9.61 4.86 7.09 0.32 MA2 Happ = 5.83 4.7 8.49 (x=0.2) Happ = 5.84 5.55 9.72 3.1 4.72 4.25 6.88 0.29 0.35 MA3 Happ = 5.85 4.49 8.6 3.3 4.41 0.29 (x=0.3) Happ = 5.86 5.69 9.49 4.79 6.87 0.35 MA5 Happ = 5.83 4.41 8.5 3.2 4.2 (x=0.5) Happ = 5.86 5.37 9.63 4.62 6.24 0.37 • Luu Tuan Tai, Luu Hoai Nam, Pham Thi Thuong 144 The results in table show that the alloy with x = 0.1 is the best, however it is still low Hence, the MAI sample was choiced to examine at the highest annealing temperatures of 800°C (MAla), 820°C (MAlb), 830°C (MAlc), 850°C (MAld), and still remain the above time process Its parameters is presented in table Table 2: The parameters of MAla, MAlb, MAlc, MAld samples Annealing temperature p[g/cm'] B, [KG] MHC BHC (BH)„ai H/B [KOe] [KOe] [MGOe] at (BH)„ax 4.8 5.01 7.2 7.80 0.32 0.33 [°C] MAla 800 5.92 5.81 MAlb 820 5.91 5.89 9.60 9.72 MAlc 830 5.92 6.43 9.68 5.41 9.05 0.4 MAld 850 5.95 6.67 9.76 5.48 9.23 0.35 For addition of Zr (x = 0.1), the density and orient degree are increasing with increasing of the highest temperature (exhibit in increasing of rate square coefficient) Perhap, the high melt temperature of Zr is suitable to high annealing temperature So that the MAlc and MAld samples were examined with the annealing times of hours (MAlcl, MAldl), 3.5 hours (MAlc2, MAld2), hours (MAlc3, MAld3) at the highest temperatures and the results of ones are shows in table Table 3: The parameters of MAlcl, MAlc2, MAlc3 MAldl, MAld2, MAld3 H/B [KOe] (BH)„ax [MGOe] at (BH)„a MHC BHC [KOe] samples p[g/cm'] B, [KG] MAlcl 5.92 6.43 9.68 5.41 9.05 0.4 MAlc2 5.93 6.68 9.63 5.52 9.31 0.35 MAlc3 5.95 6.44 9.69 MAldl 5.95 6.67 9.75 5.28 5.48 8.68 9.23 0.34 0.35 MAld2 6.00 6.92 9.79 5.67 9.95 0.35 MAld3 6.00 6.66 9.79 5.57 9.46 0.38 Tire parameters in the table show that the hard magnetic property s improved a little with increasing of the keeping time, however as ^ e anneahng -me ,s J l o n g (4 hours) so that the hard magtic property - ^ - - a s t n g The effect of h.gh annealing temperature is exhibited the clearest on the MAld2 ^ ^ ^ ^ The sample with a small amount Zr (x = 0.1) the long time and the h.gher temperature I d e the split and combine phase of Nd Fe B •= ; - ^ - ;;^ - ^ n ""e domain (being still smaller ' ^ " " ^ ^^kes part in proving value of decreasing effect of rough degree on the surtace gra B, study and Produce Anisotropy Powder NdFeB by Hydrogenation 145 Thus, the effect of addition of Zr made the anisotropy of material is restored, is very clear (compared with [4]) It is due to the initial material is anisotropy After splitting and recombining the initial orient of the grains is "memory" and is remam, and HDDR powder is anisotropy For addition of Zr samples, the effect of the high temperature, the long annealing time is very clearly: increasing p with increasing B, causes increasing of the maximum product energy The increasing of He may be due to Zr being nonmagnetism, that made increasing curb centre exchanged domain wall or maybe increasing of He is due to increasing of B^ IV Conclusion The addition of Zr considerably improved the hard magnetic property of NdFeB powder produced by HDDR process due to restoring anisotropy of powder grains The heat process, with higher temperature and longer time, was selected to suit for the materials with a small amount of addition of Zr, to result in produced the bonded magnets by HDDR process with (BH)„a = 9.95 MGOe The value is completely comparable to that of the bonded magnets, MQI Acknowlegdements This work is supported by the Vietnam National University research program under the grant QT.06.15 References: T Takeshita and R Nakayama, 10"^ Int Workshop on RE Magnets and their Applications, Kyoto, Japan (1989) 551-557 I R Harris and P J McGuiness, J Less-Common Metals, 172-174(1991) 12731284 [3].T Takeshita and R Nakayama, Proceedings of the U"^ International Workshop on Rare-earth Magnets and their Applications, Pittsburgh, USA, 1990, p.51 [4] Luu Tuan Tai, Proceedings of National Physics Conference, Hanoi, 23-25/11/2005
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