- 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 5 MGOe 7- Cac ket qua dat d
Trang 1DAI HOC QUOC GIA HA N O I 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
Trang 2BAO 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 do 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 ra 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 5 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 khi hydro trong nhiet do 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 trong quy trinh HDDR va da che tao thanh cdng ca hai loai hot HDDR khdng di hudng va di hudng
- Mot quy trinh nhiet vdi nhiet do 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)
Trang 3Ket 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
KHOA QUAN L t
(K^ va ghi TO ho ten)
u s'
CHU TRI DE TAI
(Ky va ghi ro ho ten)
PGS TS Luu Tuan Tai
CO QUAN CHU TRI DE TAI
PHOHlioTRUOMO
PGS T S t & - ^ ^ ^ * * »
Trang 4SUMMARY 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
Trang 5Muc luc
I- GI6ITHIEU Trang?
II- MVC TIEU NGHIEN CIRJ CHINH CUA DE T A I - - 1 6
W 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
Trang 6NOI DUNG BAO CAO T O N G KET
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 thanh muc tieu cua nhieu cdng trinh nghien cuu tren the gidi Cudi nam 1983, Sagawa va cac cdng su da thanh cdng trong 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
do MHC = 12 KOe, B, = 12.3 KG (1.23 Tesla) Pha hgp kim chinh cua loai
Trang 7vat lieu nay la hgp kim Nd2Fei4B Vat lieu nay d nhiet do phdng cd mdmen
tu bao hda cao Ms = 120 Am^/kg
' y 1 I f
Do nam cham ket dinh cd nhieu uu diem nhu: cd the che tao dugc cac
hinh dang rat phue tap vdi do chinh xac ve kich thudc tdi 0.01mm va cd the
dieu chinh gia tri (BH)max theo gia tri mong mudn trong mot khoang tuong
ddi rdng(l-lOMGOe) nen trong 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 nay nhd hon kich thudc cua don ddmen), ban than cac bdt loai nay da
cd luc khang tu rat cao khac ban vdi cac bdt NdFeB dugc tao ra bang
phuong phap nghien hgp kim khdi NdFeB Mac du kich thudc cua hat nSm
trong mdt khoang rdng nhung tich nang lugng tinh cho cac loai bdt nay vao
khoang 12 MGOe va trong dang nam cham ket dinh tich nang lugng cue dai
dat dugc chi vao khoang 10 MGOe Cac dang nam cham kk dinh tao ra tu
bdt nam cham ngudi nhanh cd rat nhieu va tinh chat tu cflng nhu nang lugng
tu cua chung cung trai ra trong mot khoang nao dd, tuy nhien cd th§ tdng k^t
chung d ba loai khac nhau sau: cac nam cham k§t dinh tao ra bSng phuong
phap ep khudn, cac nam cham ket dinh tao ra 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 khi 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 thanh 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
Trang 8nang 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 do ddng nhat chat lugng san pham; mac du loai vat lieu nay da xuat hien
va chiem mot ty le nhd trong cac san pham nam cham ket dinh ndi chung
Mot trong nhung nguyen nhan lam cho ITnh vuc nam cham ket dinh
phat trien manh me la do 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 trong hydro HDDR (Hydrogenation
Dispropotionation Desorption and Recombination)
Hieu ung tach pha trong khi hydro da dugc khao sat ti mi vdi nhiJng
dieu kien cu the khac nhau nhu trong dieu kien ap suat khi hydro la 30 bar
tai nhiet do 300°C [R Harris va cac cdng sir, 1985] hay ap suSt la 1 bar tai
nhiet do 720°C [Cadogan va Coey, 1986] Hieu ung tach pha
(Disproportionation) cua NdFeB trong mdi trudng khi hydro la sir phan ra
(Decomposition) hgp thanh 3 pha thanh 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 trong 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 nay trdn vdi chat ket dinh de che tao nam cham
ket dinh NdFeB cd tich nang lugng la 8 MGOe va luc khang tu la iHc = 10
KOe Sir phat trien mdi nay 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
Trang 9luu y rang, cac bdt NdFeB tao ra true tiep tu hgp kim khdi NdFeB bang
phuong phap nghien thdng thuong hoac bang phuong phap tach vo trong
t •% f f
hydro (HD) cd the dung de che tao cac nam cham thieu ket nhung khdng du
y f f f
do Idn ve lire khang tir de tao dugc cac nam cham ket dinh Su mat mat luc
khang tir do qua trinh nghien hoac tach vd la do su sai hdng, gd ghe cua be
mat cac hat (do nghien da tao thanh cac tam mam dao tir va cac ddmen
nguge khu tir)
Qua trinh xu ly nhiet trong mdi trudng khi 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 do phdng, sau dd thdi khi hydro vao dng Id tdi
ap suat 1 bar, rdi thuc hien quy trinh xir ly nhiet tir nhiet do 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 nay cd the so sanh dugc vdi kich
thudc ciia don ddmen ciia pha sat tir NdFeB va giai thich dugc tai sao luc
khang tir iHc cdn giu* nguyen dugc do Idn trong cac hat
Trong thdi gian dau nhiing nam 1990, McGuiness ciing cac cdng sir
da giai thich qua trinh hinh thanh cac hat rat min cd c§u true tinh thi NdFeB
trong hai cdng trinh va da dat ten cho qua trinh xu ly nhiet trong hydro la
qua trinh HDD (Hydrogenation Disproportionation Desorption) va sau dd
dat ten lai cho qua trinh nay 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 ra sir tach pha
Trang 10Nd2Fei4B thanh cac pha thanh phan NdH2, Fe tu do, Fe2B (da dugc chi rd bang ket qua phan tich nhieu xa tia X) va pha Nd2Fei4B van cdn nguyen khdng phan ra Khi hut chan khdng, hydro dugc tach ra va cac pha thanh phan tai hgp lai nhung d muc do nguyen tu do vay cac hat tinh the NdFeB tao thanh cd kich thudc rat nhd, chi cd 0.3fim
Hinh \ Sado dai cuang ciia quy trinh HDDR
Quy trinh HDDR tdng quat dugc dua ra trong hinh 1, nd chi h\hu dd
f "*,
dai cuong ciia cau true vi md sau mdi cdng doan cua quy trinh HDDR
Trang 116 qua trinh dhu (hydrogenation) hydro tham nhap vao viing bien hat
(noi cd thanh ph4n pha giau Nd) cua Nd2Fei4B tao ra NdH2.7 Do cd su khac nhau ve thdng sd mang giiia kim loai, hgp kim va hydrid cua chung, nen khi cac nguyen tir hydro tham nhap vao cau true da lam gian mang khien^mau bi
thdi gian (phut)
Hinh 2, Duang cong ddng nhiet cua dien traphu thudc vao thai gian
cua quy trinh HDDR
tach vd thanh cac thanh phan be nhd
Trong giai doan thu hai (Disproportionation), nguyen tu hydro tiep tuc hap thu vao pha NdaFe^B trong cac hat lam cho cac hat nay phan ra thanh: neodym hydrid, Fe va Fe2B Do dd giai doan phan ra nay cd the dugc md ta dudi dang phan ung nhu sau:
6 750°C: NdzFeuB + (2±x)H2 02NdH2±x +12Fe + FczB Trong dd gia tri x phu thudc vao ap suat cua khi hydro, d hinh 1 thi x = 0.2
Tiep theo hai qua trinh tren la qua trinh Desorption, nguyen tir hydro sau khi tham nhap va lam phan ra mau thi dugc hut ra khdi mau, NdH2±x mat
hydro tao thanh Nd 0 nhiet do cao, cac chat cdn lai sau khi tach hydro lai
Trang 12kk hgrp vai nhau tao thanh hgp chat NdFeB (co thanh ph4n hoa hoc nhu ban
dau) dudi dang tinh the nhd min hon so vdi ban dau, day chinh la qua trinh tai hgp (Recombination) 6 day hai qua trinh Desorption va Recombination xay ra mot each ddng thdi, Neodymhydrid tach hydro, Nd phan ung vdi
Fe2B va Fe tao thanh hgp chk NdFeB
Qua trinh HDDR dugc mieu ta dai cuong d tren, thuc ra la qua trinh cdng nghe phuc tap phu thudc vao nhieu yeu td Mot trong.nhimg ylu td anh
hudng tdi qua trinh HDDDR dd la ap suk khi hydro trong budng phan img,
Oliver Gutfleisch ciing cdng su da nghien cuu anh hudng nay thdng qua su thay ddi dien trd mau trong qua trinh HDDR tai cac gia tri khac nhau ciia ap suat khi hydro
Sir giam dien trd chii ylu la do su hinh thanh Fe, Neodymhydrid Gia tri dien trd dat trang thai can bSng sau qua trinh phan ra phu thudc vao ap
% ^
^ A A
0 4 8 12
Thoi gian (phut)
Hinh 3 Do thi bieu thi phan ung phan ra phu thuoc vao thai gian
Trang 13ch4m sao (tuong ung vdi P = 0.2 bar) Gia tri dien trd tang khi Nd phan ung
ket hgp vdi Fe va Fe2B tao thanh Nd2Fei4B Tir hinh 2 ta thSy, toe do phan
ung nay khdng phu thudc vao ap suat hydro ban dau
m
Hinh 3 cho biet ty le ciia phan ung phan ra phu thudc vao thoi gian o
750°C ddi vdi ap suat khi hydro khac nhau Dd thi nay cho hik sir phu thudc
rat Idn ve mat ddng lire hoc ciia co ch§ HDDR vao ap suat khi hydro Vi du
ta thay rang, d nhiing phiit dau tien, tdc do phan ra trong ap suat la P == lat
Idn hon mot bac so vdi tdc do phan ra trong ap suat 0.2 at Ket qua nay
chung td mot dieu la cd the dung ap suat hydro vdi tu each la mot anh hudng
r t I f
"nhay cam" ciia thiet bi kiem tra de tdi uu hda quy trinh HDDR
Qua trinh HDDR da dugc ung dung trong viec che tao cac bdt NdFeB
bang phuong phap nguyen tu hda trong khi tro tai hang Rhone Poulenc d
New Jersey, USA Nguyen tu hda trong khi tro la mdt phuong phap don
gian, cung dugc su dung de che tao cac bdt kim loai, hgp kim khac (vi du
•J ^
nhu cac thep, nhdm ) da dugc su dung de tao ra cac hat NdFeB dang cau
cd dudng kinh nhd hon 200|am Hgp kim NdFeB dugc nau chay rdi dap nhd
dua vao mot cai dTa cd mot vdi phun vdi dudng kinh vai milimet dat tai day
dTa quay Vat lieu dugc nau chay va phun ra do ap suat nen cao bang khi Ar
dl nhan dugc cac giot hgp kim sau khi hda ran roi xudng day cua thiet bj la
noi tap hgp de thu lai cac hat vat lieu Cac hat vat lieu tao ra bang phuong
phap nay cd luc khang tir [He - 287.7 KA/m {- 3 KOe) va sau khi ddng nhat
tai 500°C - 900°C trong mot gid thi iHc se tang len 636 KA/m (8 KOe) Tilp
theo cac hat NdFeB dugc dua vao quy trinh xu ly nhiet trong khi hydro (qua
trinh HDDR) vdi nhiet do xu ly la 850°C thi luc khang tir tang len dat tdi gia
tri 795.7 KA/m (- 10 KOe) do luc nay cac hat da cd kich thudc khoang
0.1 |im, cd the so sanh vdi kich thudc cua don ddmen ciia pha sat tir NdFeB
Trang 14Mot kho khan la bgt NdFeB thu dugc sau qua trinh HDDR chi la bot
dang huong Neu su dung bgt nay dk che tao nam cham kk dinh chi -dat
dugc (BH)n,ax = 40 KJ/m^ (5 MGOe) Neu chi tao nam cham thieu kk tu bot
nay thi hau nhu khdng trd thanh nam cham do sir Idn len rat nhanh ciia cac
hat sieu nhd D I nang cao chat lugng bdt vat lieu, chn phai lam th^ nao dk
bdt tao ra bang phuong phap nay trd thanh bdt di hudng
Tai hoi nghi quoc te \kn thii 11 (nam 1990), Takeshita va Nagayama
f ^
cdng bd hg da tao dugc bdt di hudng ciia hgp kim Ndi2.6Fe7oCon 4B6 bang
hieu ung pha tap Ho da thu nghiem tren mot loat cac nguyen td pha tap la:
Al, Ga, In, Si, Ge, Sn, Ti, Zr, Hf, V, Nb, Ta, Cu, Zn, Sb, Bi va tim thay hieu
f f r
ung mong mudn ddi vdi cac nguyen td: 0.1% nguyen tir Zr, 0.1% nguyen tir
Hf va cd 2% nguyen tu Ga Vdi bdt tao ra tir hgp kim NdFeB pha tap 0.1%
Zr, ho da che tao dugc nam cham ket dinh di hudng vdi Br = 8.4 KG, iHc =
9K0e va tich nang lugng cue dai (BH)niax = 18 MGOe, tuy nhien tai thdi
diem nay hg khdng giai thich gi ve hieu ung pha tap
O hoi nghi qudc te tai St Louis nam 1992, tac gia McGuiness va cac
cdng su da bao cao viec che tao bdt vat lieu di hudng bang phuong phap
HDDR tir hgp kim NdieFej^-xBgZrx (x == 0.1, 0.2, 0.3) Ho thay rang cac tinh
chat tir noi tai cua vat lieu rat nhay vdi nguyen td pha tap vao va cac dieu
f f 1 f f
kien ciia qua trinh HDDR Vat lieu tdt nhat de che tao nam cham ket dinh di
hudng chua 0.1% Zr vdi lire khang tir noi tai iHc ^ 700 KA/m ( - 9 KOe) va
(BH)max = 150 KJ/m^ ( 13 MGOe) Ho gia thiSt r^ng di hudng cua bdt vat
lieu la do ddng gdp uu tien dinh hudng cua cac hat NdFeB sau qua trinh tai
hgp cd kich thudc cd nhd hon micromet va mire do di hudng cua nam cham
ket dinh phu thudc vao cau triic cua hgp kim due ban dau, phu thudc vao
kich thudc cua cac hat bdt, tir dd cac hat bdt tai hgp hinh nhu se djnh hudng
trong viing dinh hudng ban dau ciia cac hat tinh the trong khdi hgp kim
Trang 15Peixin va cac cong sir (1992) da chi tao dugc cac nam cham kk dinh
tu>ot HDDR cua hgp kim (PrNd),2.5Fe69Co,,.5Ga,B6 vai cac thong so B, = 1.1 Tesla, iHc = 690 KA/m (~ 8.6 KOe) Ying va cac cong sir da che tao nam cham tu bgt HDDR cua hgp phan: Ndi3Fe74.4Co5.5B7Zro.i co cac thong s6 nhu sau: B^ = 0.74 Tesla, [He = 744 KA/m (9.3 KOe) va tich nang lugng cue dai (BH)^ax = 98 Kj/m^ (~ 12MG0e)
Phuong phap HDDR con dugc dung de chi tao cac nam cham due NdFeB vai gia tri luc khang tu cao
Zhang cung cac cong sir (1991) da ap dung quy trinh HDDR trong dieu kien khdng xay ra qua trinh tach vd (HD) cho cac mang mdng cua hgp kim Nd2.iFei4B cd do day cd 4-^5mm Hieu ung tach vd khdng xay ra khi
\ f f
hat cd be mat rat Idn, lam giam tinh tir cung rat nhanh
Trong de tai nay chiing tdi da chon nguyen td pha tap la Zr, va da dat dugc nhimg ket qua rat kha quan
I L MUC TIEU CUA DE TAI
-Nghien cim anh hudng cua nhiet do, thdi gian va nguyen td pha tap Zr trong cdng nghe HDDR
f
-Tim dugc qui trinh nhiet va thdi gian thich hgp che tao dugc bdt HDDR dang hudng va dj hudng
f f
-Che tao dugc nam cham ket dinh NdFeB tir bdt HDDR cd tich nang
lugng cue dai Idn hon 5MG0e
Trang 16III.CAC KET QUA C HINH CUA DE TAI
Nhu da ndi trong pfian trudc, viec nghien ciru chi tiet cac qua trinh vat
ly va tinh the xay ra tronu cong nghe HDDR da dugc thuc hien d nhieu noi tren the gidi va cho cac kci qua kha tudng minh Chinh vi vay d day chiing tdi chi tap truiig vao kliao sal cac dieu kien va cac thdng sd cdng nghe nham tim dugc quy trinh cdny riyhe thich hgp tuong irng vdi he thdng thiet bi hien
cd, cho phep che tao duxic cac nam cham ket dinh cd nang lugng cao, phan
ly giai chi dii'ng lai d thao luan dinh tinh cd the chap nhan dugc
linh 1 Anh chnn '< rrofJuid theo mat celt doc (a) vd ngang (b)
ciui li'.h' kim Nd/r^Fe-o.^Zr^Bs v61 x 0 J
Trang 17Cac hgp kim ban dau Ndi6Fe76.xZrxB8 vdi x = 0, 0.1, 0.2, 0.3, 0.5 dugc
che tao bang phuong phap ndng chay hd quang, trong mdi trudng khi Ar tir
cac nguyen lieu ban d4u cd do sach tdi thilu la 99,9% Hgp kim sau khi n4u
cd mau xam sang, be ngang mau thay rd c4u true textua theo hudng vudng
gdc vdi day ndi Kiem tra cau tnic ddmen ciia cac mat cat dgc theo phuong
textua (a) va vudng gdc vdi phuong textua (b) bSng chk Idng tir (ferrofluid)
cho ta thay (hinh 1) d hinh (a) cau tnic ddmen tir cd dang dieu xi ga cdn d
hinh (b) cd dang cac bgt tir, cho thay ddmen tir ciing xap xep theo phuong
textua Nhu vay cac hat tinh the dugc djnh hudng tuong ddi ddng nhk theo
mot phuong tinh the
\ f f it^
Sau khi dap nhd bang cdi sat, cac mau hgp kim cd kich thudc khoang
1-^3 cm dugc dua vao budng phan ung Sau khi hut chan khdng dat gia tri
f y \ f
chan khdng so cap, ddng thdi vdi viec hut chan khdng bang bom khuech tan,
Id boat ddng de nang nhiet do budng phan ung len den lOO^C vdi tdc do
nhiet la 6°C/ phiit Khi dat chan khdng cao 5x10"^ mbar, hydro dugc dua vao
budng phan ling tir budng luu giir hydro bang bdt LaNi5 cho tdi ap suat
f \ f \ \
hydro xap xi bang 1 atm Bat dau tir day, nhiet do cua budng phan img dugc
thay ddi theo mot chuong trinh nhiet xac djnh tiiy theo timg me mau
3.1 He mau hgp kim Ndi6Fe76B8
He mau NdieFcyeBg da dugc xu ly nhiet theo cac quy trinh nhiet khac
nhau va dugc ky hieu tuong ung la^Mla, M l b va Mlc
Vdi he mau cd ky hieu Mia, quy trinh sir ly nhiet dugc thuc hien nhu
> -> > >
tren so dd hinh 15 O qua trinh dau Id boat ddng nang nhiet do budng phan
ung tir nhiet do phdng Troom len tdi lOO'^C vdi tdc do la 6°C/phut (tdc do nay
phii hgp vdi qua trinh vira bom chan khdng vira tang nhiet do cho budng
phan irng) Khi budng phan ung dat do chan khdng cao 5x10"^ mbar, hydro
Trang 18dugc lay tir budng luu trii hydro dua vao buong phan ung cho tdi ap suk
t T(^C) 800X
6^'C/phut 20=C/phut Theo 16 8^C/phut 26^C/phut t
Hinh 2 Quy trinh nhiet cua mdu Mia
hydro xap xi bang latm, bat dau cho nhiet do cua budng phan ung tang len
tdi 200°C vdi tdc do tang nhiet la 20°C/phut; rdi dk nhiet do tang theo id
nung len tdi 700°C; nhiet do tiep tuc dugc tang len tdi 800°C vdi tdc do tang nhiet la 8°C/phut va giiJ budng phan img tai nhiet do nay trong vdng 2.5 gid Sau qua trinh giir nhiet, budng phan img dugc giam nhiet do xudng 200°C
f f \
tuong ling vdi tdc do 200°C/phiit va cudi ciing budng phan ung dugc giam
r f f
xudng den nhiet do phdng Troom vdi tdc do giam nhiet la 26°C/phut
Quy trinh nhiet ciia mau M l b , budng phan img dugc tang nhiet do tir nhiet do phdng Troom l^n tdi 800°C va dugc giir tai nhiet do nay trong 2.5 gid
la hoan toan tuong tu nhu ddi vdi quy trinh nhiet cua mau Mia, nhung sau
f •>
qua trinh nay thi tat id va hut chan khdng de ngudi theo Id
Ddi vdi he mau M l c thi quy trinh nhiet ciing tuong tu nhu quy trinh nhiet cua he mau M l b nhung chi tang nhiet den nhiet do cao nhat la 700''C, sau dd giir trong 2.5 gid rdi de ngudi theo Id.Sau khi thuc hien xong quy trinh HDDR, cac mau deu dugc nghien nhd bang may nghien bi, rdi phan
Trang 19loai hat theo hai loai: d < 100)im va d > lOOjim bang may ray Bdt vat lieu
HDDR dugc trdn vdi epoxy r^n vdi ty le 2% trgng lugng, roi dugc ep trong
6^C/phut 20X/phiJt Theo 16 8^C/phut t
Hinh 3 Quy trinh nhiet cua mdu Mlb
khudn thep ((t)12 hoac (t)15 mm) vdi ap suat 6 tan/cm Tiep theo dd la
polymer hda trong nhiet do 125°C/gid, cac mau dugc nap tir trong tir trudng
xung 5 Tesla, sau dd dugc xac dinh cac thdng sd cua nam cham Cac thdng
sd cua he mau Ml (a, b, c) dugc liet ke trong bang 1
Bang 1 Cdc thong so cua he mdu Ml
Br [KG]
4.2 4.04 4.05 4.1 3.98 4.04
MHC
[KOe]
7.78 7.55 7.95 • 8.03 7.54 7.60
BHC
[KOe]
3.15 3.12 3.10 3.25 3.10 3.25
(BH)max
[MGOe]
3.36 3.33 3.45 3.61 3.32 3.36 Tir bang cac thdng so cua he mau M l , ta nhan thay rang, trong ca 3
oai mlu, vdi cac hat cd kich thudc d > lOOfim ludn cho ket qua tdt hon so
Trang 20vdi mau cung loai co kich thuac hat d < lOO^m Di^u nay co thi la do
nghien be mat cac hat Ion it bi go ghe hon cac hat nho do do it xuat hien cac
domen ngugc ichur tir tinh ciia hat, bieu hien ra la gia tri lire khang tir va gia
tri tir du ndi chung vdi d > lOO^im dku Idn hon
Ta cQng nhan thay rang, cac ket qua v^ nam cham da dugc cai thien
dang ke, tuy cac gia tri nay van cdn thap so vdi cacjcet qua da dugc cdng bo
la 5 MGOe ddi vdi loai HDDR ding hudng (cd mot ket qua da cdng bo cua
6X/phut 20X/phut Theo 16 8X/phut t
Hinh 4 Quy trinh nhiet ciia mdu M2
nhdm Takeshita, (BH)max ciia loai nay len tdi 8 MGOe nhung khdng ndi rd
ve cac dieu kien vat lieu)
t f "w
De cai thien cac ket qua da dat dugc, mot he mau mdi da dugc sir
dung de khao sat ty mi hon quy trinh nhiet, he M2 Quy trinh nhiet cho he
mau nay dugc chon gidng nhu quy trinh nhiet cua mau M l b , nhung thay ddi
gia tri nhiet do cao nh4t la: 750°C, 810°C va 850^C tuong img vdi ky hieu a,
b, c vdi thdi gian giij nhiet la 3 gid va do hat dugc lira chon bang may ray
cd: 100 |Lim < d < 125 ^m Cac ket qua cua he mau nay dugc tdng hgp trong
bang 2
Trang 21Bang 2 Cdc thong so cua he mdu M2
B [KG]
4.69 5.08 4.41
MHC
[KOe]
8.50 8 38 8.54
BHC
[KOe]
3.08 3.15 3.20
(BH)niax
[MGOe]
4.13 4.58 4.15
f f •\ T
Tir bang ket qua tren ta nhan thay rang, vdi nhimg thay ddi chinh la do
hat cd 125 |j.m va tuong ddi ddng deu trong khoang 100-^125 |im, thdi gian
giir d nhiet do cao nhat thay ddi dai hon (3 gid), ket qua mau M2b thu dugc
da dat dugc gia tri thdng thudng van cdng bd ve loai bdt HDDR dang hudng
nay Ta thay rang gia trj BHC gan nhu khdng thay ddi nhung gia tri Br co
tang, cd th§ la do do hat ddng deu hon, thdi gian tach pha va tai hgp dai hon
cho phep phan ung xay ra hdan tdan tren toan bd the tich mau Nhu vay quy
trinh nhiet cho mau M2b la quy trinh nhiet thich hgp nhat vdi lugng mau
khoang 30 gam, dat dugc (BH)niax ^ 4.58 MGOe
D§ nang cao ch4t lugng bdt vat lieu, can phai lam the nao dd de bdt
tao ra bang phuong phap nay trd thanh bdt di hudng, chimg tdi da chon
phuong phap pha tap vao hgp kim NdFeB mot lugng Zr de cd dugc hgp kim
Ndi6Fe76-xZrxB8 vai x = 0.1, 0.2, 0.3, 0.5 Cac ket qua cua cac he mau nay se
dugc trinh bay trong phan sau
3.2 He mau ho-p kim NdieFeTe-xZr.Bg vdi x = 0.1, 0.2, 0.3, 0.5
He mau NdieFcye-xZrxBg dugc xu ly nhiet tuong tu nhu quy trinh xu ly
nhiet cua he mau M2b va dugc ky hieu la M3a, M3b, M3c, M3d tuomg ung
v a i x = 0.1,0.2, 0.3, 0.5
Trang 22Tuong tu nhu doi voi cac he mau Ml va M2, sau khi thuc hien xong
quy trinh HDDR, cac mau d§u dugc nghien nho bang may nghiln bi, rdi
Hinh 5 Quy trinh nhiet cua mdu M3
phan loai hat bang may ray cd dudng kfnh lOOjim < d < 125|im Bdt vat lieu
HDDR dugc trdn vdi epoxy rSn vdi ty le 2% trong lugng, rdi dugc ep trong
khudn thep {^\3 mm) vdi ap suat 6 t§n/cm^ trong tir trudng 1 Tesla, song
song vdi phuong ep TiSp theo dd la polymer hda trong nhiet do 125''C/gid,
cac mau dugc nap tir trong tir trudng xung 5 Tesla, sau dd dugc xac dinh cac
thdng sd ciia nam cham
Cac thdng sd ciia he mau dugc tdng ket trong bang 3 Tir cac ket qua
thu dugc ta thay ring vdi thanh phan hgp kim pha tap 0.1 % Zr (x = 0.1) cho
cac ket qua tdt nhk, dat tich nang lugng (BH)rnax cao nhk 7.09 MGOe Tuy
nhien, gia tri nay cdn thap so vdi ket qua ma mot sd cdng trinh cua cac tac
gia khac da dat dugc tren ciing loai bdt HDDR di hudng
Trang 23'"lapp ~ ^
Bang;
p[g/cm^]
5.9249 5.9197 5.8398 5.8429 5.8511 5.8609 5.8327 5.8617
3 Cdc thong so ciia mdu M3
Br [KG]
5.1 5.79 4.7 5.55 4.49 5.69 4.41 5.37
MHC
[KOe]
9.4 9.61 8.49 9.72 8.6 9.49 8.5 9.63
BHC
[KOe]
4.01 4.86 3.1 4.72 3.3 4.79 3.2 4.62
(BH)max
[MGOe]
5.2 7.09 4.25 6.88 4.41 6.87 4.2 6.24
H/B
at (BH)„ax 0.3 0.32 0.29 0.35 0.29 0.35
0.37
Do vay, he mau M3a da dugc chon de khao sat quy trinh nhiet ti mi
hon Quy trinh nhiet cho he mau nay dugc chon nhu ban dau nhung thay ddi
nhiet do cao nhat la: 800°C (M3al), 820°C (M3a2), 830^C (M3a3) va 850°C
(M3a4), thdi gian giii tai nhiet do cao nhat nay van la 3 gid Cac ket qua cua
he mau nay dugc dua ra trong bang 4
Tir cac kk qua d bang 4, ta nhan thay rang, ddi vdi viec pha tap Zr,
X = 800, 820, 830 or 850X
O
6^C/phut 20-~C/phut Theo 16 8^C/phut t
Trang 24max
nhiet do cao nhSt cua quy trinh nhiet tang len lam tich nang lugng (BH)
tang (dat 9.23 MGOe), mat do tang, ddng thdi do djnh huong cung tang thi
hien qua he s6 vuong ty le tang khi nhiet do cao nhat tang DiSu nay cung co
the la do Zr co nhiet do nong chay cao (2125K) nen thich hgp voi viec nhiet
Br
[KG]
5.81 5.89 6.43 6.67
MHC
[KOe]
9.60 9.72 9.68 9.76
BHC
[KOe]
4.8 5.01 5.41 5.48
(BH)niax
[MGOe]
7.2 7.80 9.05 9.23
H/B
at (BH)max 0.32 0.33 0.4 0.35
' ' f 1
Vay neu ta chon che do thdi gian dai hon tai nhiet do cao nhat, cd the
dat dugc nhimg ket qua nhu mong dgi Chinh vi ly do nay cac he mau M3a3
va M3a4 da dugc chon de khao sat sir thay ddi thdi gian giir nhiet tai nhiet
do cao nhat, vdi thdi gian giir nhiet la 3.5 va 4 gid Ta se cd cac he mau
tuong ling: M3a31, M3a41 (giij trong 3 gid); M3a32, M3a42 (giir trong 3.5
gid); M3a33, M3a43 (giij trong 4 gid) Cac ket qua cua he mau nay dugc
dua ra trong bang 5
X = 830 or 850'^C
6^C/phut 20^C/phut Theo 16 8"C/phut
Hinh 7 Quy trinh xu ly nhiet ciia he M3a3 vd M3a4