IV. CON CLUSION
203 NGHIEN CUU SÚ ANH HUONG CUA QUA TRINH NHU Q MM AU LEN CAC LIEN KET TRONG M A N G WO3 B A N G PHUONG P H A P P H O RAMAN
Le Van Ngoc. Huynh Thanh Dat. Trdn Tuan. Duang Ai Phuong. Le Quang Tri
204 NGHIEN COU CHE TAO SENSO DO U"NG S U A T DUA TREN BANG TÚ CAu TRUC NANO Fe-Co-Si-B ^ . Fe-Co-Si-B ^ .
Pham Due ThSng, Nguven Hiru Tuan. Do Thi Huong Giang. Trdn Mau Danh va Nguyen HCni Ditc
883
HOI N G H I V A T L Y C H A T R A N T O A N Q U O C L A N T H l T 5 - V u n g T a u 12-14/11/2007
NGHIEN C i r u CHE TAO SENSO DO iTNG SUAT DUA TREN BANG TlT CAU TRUC NANO Fe-Co-Si-B
Pham Due Thang, Nguyen Huu Tuan, Do Thi Huong Giang, Tran Mau Danh va Nguyen Hun Due Bp mon Vat lieu va Linh kien tir tinh nano, Khoa Vat ly ky thuat va Cong nghe nano,
Trucmg Dai hoc Cong nghe, Dai hoc Quoc gia Ha Noi,
Nha E3, 144 Xuan Thuy, Cau Giay, Ha Noi, Viet Nam; E-mail: pdtliantirrf vnu-cdu-vn
TOM TAT
Cac sensa do ung suat da dirge che tao don gian tir cac bang tir (FesoCo2o)7sSii2B|(,. Ung suat tac dung len senso dugc xac dinh thong qua viec do tin hieu dien tren cuon day cam Ímg cuon xung quanh bang tir. Sensa su dung bang tir dirge xir ly nhiet 6 250 ''C co dp nhay len den 4.2 niV/MPa vdi tinh on dinh caọ Cac ket qua khao sat cho thay dp nhay cua senso phu thuoc manh vao cac tinh chat noi tai cua vat lieụ Moi lien he giija cau true nano cua vat lieu va cac tinh chat cua senso se dugc thao iuan. Co the diing cac sensa nay de phat hien cac irng suat trong cac cong trinh xay dung dan dung.
High-sensitive stress sensor is simply constructed based on magnetostrictive {FeHuCo2o)^8Sii2Bio ribbon which acts as a sensitive magnetic core inside an induction coil. The stress can be determined indirectly by measuring the change in the output voltage in the two-coil system. The results shown that the sensitivity highly depends on the intrinsic properties of the ribbon. The optimum with both a high sensitivity of 4.2 mV/MPa and a linear stress dependence was obtained in the 250 °C-annealed ribbon. This is attributed to the correlation between the magnetic and magnetoelastic softness governed by the fine nanograin structurẹ These high sensitivity and simple fabrication sensors are widely applicable to various stress delecting fields. Til- khoa (Keywords): Nanostructure, inverse magnetostriction, stress sensor.
G I O I T H I E U
Hieu ung tir giaọ dupe phat hien lan dau tien vao nam 1842 [1]. Do la hien tugng hinh dang va kich thuoc cua vat lieu tir thay doi khi tinh chat tir noi tai cua no bi bi^n doị Cac y^u t6 c6 the lam thay doi tinh ch^t tir noi tai cua vat lieu bao gom sir thay doi cua nhiet dp hoac su xuit hien cua tir truang ngoaị Su thay doi the tich cua vat lieu do anh huang cua nhiet dp diroc eoi la hien tugng tir giao tu phat hay tir giao
the tich ^TLI giao xuki hien khi dat vat lieu trong tir
truong ngoai dupe goi la tir giao cuong birc hay tir giao tuyen tinh Joulẹ
Ngugc vol cac hien tuo-ng tren la mot hieu irng
ciing rat ly thii, do la hieu ung tir giao ngugc hay con goi la hieu ung Villarị Trong hieu ung nay, khi tac dung ung suat ca hoc len mot vat lieu tir giao thi tinh chat tir noi tai cua vat lieu se bi thay doị Dua tren cac hieu irng tir giao/tir giao ngugc, nhieu nghien cuu gan day da tap trung vao viec che tao thu cac sensa irng dung trong viec do tir truong, irng suat, ap suat, dp djch chuyen, dp rung, ... [2-8]. Trong cac cong trinh nay, cac hpp kim v6 dinh hinh vdi thanh phan ca ban la Fe nhu Fe-Si, Fe-Si-B vdi tinh tir mem tuyet vdi va the hien ca hai hieu ung tir giao va tir giao ngugc da dugc sir dung rong raị Tuy nhien dp tir tham ciia cac vat lieu loai nay de bi bao hoa dudi tac dung cua mot ung suat nhọ Ngoai ra khi tiep tuc tang irng suat, dp nhay cua senso ung suat sir dung cac vat lieu nay bi suy giam. De khac phuc nhirng nhugc diem nay, ngudi ta da tien hanh thay mot phan Fe bang cac nguyen to kim loai chuyen tiep khac, vi du nhu Co [11].
Trong bai bao nay, viec che tao va khao sat mot so tinh chat ca ban nhu cau true tinh the, vi cau true va tinh chat tir cua vat lieu tir giao dang bang cau true nano (Fe8oCo2o)78Sii2Bio se dugc trinh bay Tiep theo, hieu ling tir giao ngugc cua cac sensa do irng suat sir dung vat lieu nay se dugc nghien cirụ
THUC NGHIEM
Cac bang mong Fe-Co-Si-B dugc che tao bang phuang phap nguoi nhanh tir hgp kim (Fe8oCo2o)78Sii2Bio su dung cac kim loai co dp sach cao (Fe 99,99%, Co 99.99%, Si 99,5% va B 99,5%). Cac vat lieu ban dau dugc can theo thanh phan danh dinh CO tinh den su bii trir cua cac nguyen to de bi oxi hoa va bay haị Hon hpp cac kim loai nay dupe nau nong chay thanh hpp kim Fe-Co-Si-B dang khoi bang 16 cao tan trong moi truong chan khong caọ
Hgp kim khoi tren dupe nau nong chay ó nhiet dp Tnc = 1130 °C trong mot ong thach anh vdi moi
truoTig khi Argon bao ve (p^, = 200 mbar) bang 16
cam irng cao tan. Hpp kim nong chay dugc phun qua mot khe hep len be mat mot trong bang Cu quay vdi tdc dp cao 20 m/s. Nho su trao doi nhiet tire thi vdi trong, hpp kim nong chay nguoi vdi toe dp cue nhanh
cd 10*' °C/s va tao thanh cac bang hop kim v6 dinh
hinh cd chieu day 30 [am va chieu rong 8 mm.
De CO dugc cau triic toi uụ bang v6 dinh hinh
HOI N G H I V A T L Y C H A T R A N T O A N Q U O C L A N THlT 5 - Vung Tau 12-14/11/2007
Fe-Co-Si-B dugc xu ly nhiet bang each u nhiet trong
moi truong khi Argon tai cac nhiet dp 7„ = 160 ^C,
250 "C va 350 V trong thai gian 30 phiit. Cau true tinh the cua cac bang tir dugc khao sat bang nhieu xa tinh the cua cac bang tir dugc khao sat bang nhieu xa ke tia X Siemens D-5000 su dung budc song CU/CQ. Cau true vi mo cua cac bang tir dupe quan sat qua kinh hien vi dien tir quet phat xa trudng (FE-SEM) Hitachi S-4800, Tinh chat tir cua cac mau dugc khao
sat thong qua phep 6o dudng cong tir tre tai nhiet dp
phong tren tir ke mau rung.
Nham khao sat hieu irng tir giao ngugc, mot he do don gian da dugc nghien ciru che tao vdi sa do nguyen ly dugc mo ta tren hinh lạ He do bao gom hai cuon day sa cap va thir cap dupe cuon dong true tren hai dau cua mot ong Teflon. Cuon day so cap gom 4 lop day bang Cu dudng kinh (|>i = 0.1 mm, moi Idp cd 540 vdng. Cuon day nay dugc noi vdi mot may phat am tan de phat tin hieu kich thich dudi dang mot tir trudng xoay chieụ Cuon thu cap gom 2 Idp day Cu
dudng kinh ^2 = 0 2 mm, moi Idp cd 246 vdng, dugc
noi vdi may khuech dai lock-in de do tin hieu dien the cua maụ Cac mau bang tir co chieu dai ia 15 mm dupe dat trong Idng cua hai cuon day {xem hinh lb). Mot dau mau dugc gan cd dinh, dau kia dupe noi vdi thiet bi tao irng suat keọ
Cuon sa cap Cuon thu cap
Bang tir U n g stiat
(a)
la tan so cong hudng (v la van tdc ciia song am trong mau va / la chieu dai ciia mau) [9, 10].
Do hieu ung tir giao, tir trudng xoay chieu se gay ra mot su bien dang bien dieu, the hien dudi dang mot song tir giao doc theo bang tir. Hien tugng nay se lam xuat hien nipt suat dien dong cam irng trong cuon thiJ cap nhu la ket qua ciia hieu irng tii giao ngupc:
V(t)= VoS\ni2nfot+(p) (2)
Trong do bien dp cua the hieu cam irng - tin hieu cua
sensa V„ dupe xac djnh bdi cong thirc
Vo = HoyikHE/pf] (3)
vdi ^ la dp tir tham, E la suat Young, k la he so tuong
tae tir-ca va p la mat dp khoi lupng ciia bang tir. Khi tac dung mot irng suat keo a doc theo chieu dai ciia bang tir, tinh chat tir noi tai ciia vat lieu, vi du dp tir tham ji, bi thay doi dan se den su thay doi cua
tin hieu sensó V„. Bang each thay doi gia tri irng suat keo chiing ta cd the thu dupe su phu thuoc cua V^ vao