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 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).


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 trong 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 thanh muc tieu cua nhieu cdng trinh nghien
cuu tren the gidi. Cudi nam 1983, Sagawa va cac cdng sir da thanh cdng
trong 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 ^ 3 6
MGOe, luc khang tu theo cam ung tu BHC = 11 KOe, luc khang tu theo tu
do 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 trong 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 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

7


vat 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
f

,

,

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


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 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


luu 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

10


Nd2Fei4B 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.

11


6 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
1.05

t = 0 phiit)

1.00

~a
CL

Ap suat hydro

• P==0.7bar

•

0.95

• P==0.2bar
T = 750°C

•«

0.90

•

•

0.85

'•••.•.

»
••

• • • • • • • • •«•

•

0.80
0.75

0.70
-50

0

50

100
150
thdi gian (phut)

200

250

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

12


kk 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
f

^

suat khi hydro ciia he. Tai ap suat cao hon, qua trinh phan ra xay ra nhanh
0.40
han

Id

Q,
00

jz

CL

0.35

Ap suat hydro

0.30

• p = 1.0bar

0.25

• p = 0.7bar

0.20

A p = 0.35bar
#• •

0.15

le c

o

0.10

P

0.05


^.

%

A

A

D p = 0.2bar
T=750°C

^

0.00

0

4

8

12

16

20

Thoi gian (phut)


Hinh 3. Do thi bieu thi phan ung phan ra phu thuoc vao thai gian.
f

>

hon, khien cho trang thai can bang dien tra dat dugc nhanh hon, nhu duong
f

cong cham tron tren hinh 2 (tuong ung vai P = 0.7 bar) so vai duong cong

13


ch4m 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
\

f

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.

14



Mot 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
f


f

r

•\

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
f

f

^

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.
15


Peixin 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
t

>

f

hgp phan xung quanh hgp thuc 2:14:1 tai nhiet do phdng, tuy nhien de chac
f

f

\

chan, do Idn cua mat cat vat lieu can phai nhd nhu vay va qua trinh tang

nhiet phai nhanh cd 40''C/1 phiit tir nhiet do phdng len nhiet do tach pha tir
770°C -^830°C. Day la khoang nhiet do tdi uu vi ngay dudi khoang nhiet do
nay, cac tinh the sat tu do dang cay van cdn tdn tai d gan hgp thuc do phan
ung Peritectic khdng hoan toan, cdn tren khoang nhiet do dd se xuat hien cac
\

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.
IL
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

16



III.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
17
OAI HOC QMOC O'^ HA NO)


Cac 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)
f

f

,

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,
\

•>

f

t

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, Mlb 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


18


dugc 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 Mlb, 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

19


loai 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
' T(^C)


800"'C

*

200=0^^

Ngupi theo to

^

Giur trong 2.5 gid

700X

100=C

6^C/phut 20X/phiJt

Theo 16

8^C/phut

t

Hinh 3. Quy trinh nhiet cua mdu Mlb.
r

f

'y


f

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
MIU

Mia

Mlb

Mlc

MHC

BHC

(BH)max

[KOe]

[KOe]

[MGOe]

4.2


7.78

3.15

3.36

5.8056

4.04

7.55

3.12

3.33

<100

5.5907

4.05

7.95 •

3.10

3.45

>100


5.7930

4.1

8.03

3.25

3.61

<100

5.5367

3.98

7.54

3.10

3.32

>100

5.7355

4.04

7.60


3.25

3.36

d(}im)

P [g/cm^]

Br [KG]

<100

5.5396

>100

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
20


vdi 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
X = 750, 810 or 850'^C


T(^C)

700=0

y^
•x>

en

'^

1

i

^

2

m

IOO'CJ/^

\

O

\

\


\

100=C

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 Mlb, 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.


21


Bang 2. Cdc thong so cua he mdu M2.
MHC

BHC

(BH)niax

[KOe]

[KOe]

[MGOe]

4.69

8.50

3.08

4.13

5.9107

5.08

8..38


3.15

4.58

5.8502

4.41

8.54

3.20

4.15

P [g/cm^]

B. [KG]

M2a

5.8432

M2b
M2c

MIU

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.
22


Tuong 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

810=C


-o
o

i ^

c
9

3

o

^

at

^-f

i the

x>
a»
m

toom

6=*C/phut 20=C/phut

Theo 16

8^'C/phut

|.

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.

23


Bang;3. Cdc thong so ciia mdu M3
Mau

p[g/cm^]

Br
[KG]

MHC

BHC

(BH)max

H/B

[KOe]

[KOe]

[MGOe]

M3a

Happ — 0

5.9249

5.1

9.4

4.01

5.2

at (BH)„ax
0.3

(x=0.1)

l^app ~ 1

5.9197

5.79

9.61

4.86

7.09

0.32

M3b

Happ — 0

5.8398

4.7

8.49

3.1

4.25

0.29

(x=0.2)

Happ = 1

5.8429

5.55

9.72

4.72

6.88

0.35

M3c

Happ — 0

5.8511

4.49

8.6

3.3

4.41

0.29

(x=0.3)

Happ = 1

5.8609

5.69

9.49

4.79

6.87

0.35

M3d

Happ = 0

5.8327

4.41

8.5

3.2

4.2

(x=0.5)

'"lapp ~ ^

5.8617

5.37

9.63

4.62

6.24

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

Hinh 6. Quy trinh nhiet ciia he mdu M3al, M3a2, M3a3 vd M3a4
24

t


nhiet do cao nhSt cua quy trinh nhiet tang len lam tich nang lugng (BH) max
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
do xu ly cao.
Bang 4. Cdc thong so cua mdu M3al, M3a2, M3a3 vd M3a4
Mau

Nhiet do li

M3al

[°C]
800

M3a2
M3a3

M3a4

820
830
850
'

p[g/cm^]
5.9202
5.9197
5.9257
5.9580

Br

MHC

BHC

H/B

(BH)niax

[KG] [KOe] [KOe] [MGOe] at (BH)max
5.81 9.60
4.8
7.2
0.32
5.89 9.72
5.01

7.80
0.33
6.43 9.68
5.41
9.05
0.4
6.67 9.76
5.48
9.23
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
25