TAP CHi KHOA HQC OHSP TPHCM NguySn Anh Tiln va tgk
\JNGHIEN ClTU TONG HOfP VAT LIEU NANG Tlf TINH LaFeOj BANG PHlTONG PHAP DONG KET TUA
N G U Y E N ANN TlfeN', PHAN PHU'O'C HOAl NHAN"
TOM TAT
Nghien cicu nay, da tong liqp vgt lieu nano LaFeOs bdng pfiuang phap dong icet tua thong qua giai dogn thiiy phan cdc cation La(UI) vd Fe(lU) trong nuac soi Kit qua phdn tich bdng cdc phuang phap DTA-TGA, MS. XRD, SEM, TEM. VSM cho thdy cdc tinh thi nano LafeOj hinh thdnh sau idti nung Icit tiia a 85ffC voi kich thuac 50-70 nm; Hc=42.53 Oe, M,=0.01 emu/g: M,=0.24 emu/g.
Tif Itltda: v^t lieu nano, LaFe03, tinh chat tir, phuong phap dong ket tua.
ABSTRACT
Synthesis of nanosized magnetic LaFeOj material by coprecipitation method Nanosized LaFeOi material has been synthesized by the coprecipitation method via hydrolysis of La (111) and Fe (Ul) cations in boiling water. The DTA-TGA, MS, XRD, SEM, TEM, VSM results showed that LaFeOi crystals formed after calcinating the powder of the coprecipitation at 85Cf^C have particle sizes in range of 50-70 nm, Hc=42.53 Oe. Mr=O.Ol emu/g, Ms=0.24 emu/g.
Keywords: nanomaterial, LaFeOs, magnetic properties, coprecipitation method.
I. Mor d^u
Hien nay, vat li?u nano LaFeOa do chung co tinh chat tm viet hon so voi vat lieu dang kh6i nen da dugc nghien cuu ung dung trong nhieu ITnh virc nhu: Dien tu [1], hSp phy ion kim loai nang trong chat long [6], cam biSn nhay hoi c6n [4]... va dang thu hut dugc nhiiu nha nghien ciiu quan tam. Vat lieu nano LaFeOs cung dugc nghien ciiu nhieu cho muc dich lam chit xuc tac cho cac phan ung oxi hoa timg phin hidrocacbon, CO,NO„m-xylen...[2-3].
D6 t6ng hgp vat lieu LaFeOs voi cac dac tnmg nhu kich thuoc nanomet, don pha, do d6ng nhdt cao, khong co sir kit tu giira cac hat, can phan tich so sanh cac phucmg phap t6ng hgp cua cac tac gia di truoc dS tim kijm cac dieu kien t6i uu il tong hgp chung.
Tren co so cdc cong trinh da cong b6, phuang phap sol-gel (trong trudng hgp rieng, d6ng kSt tua cdc cation La^* va Fe'* tir dung dich) dugc lua chon, do san pham
* TS, Tru'&ng Ogi hpc Sir pham TPHCM; Email: [email protected]
" SV. Trud-ng Bgi hpc Su phgm TPHCIM
TAP CHi KHOA HOC DHSP TPHCM So 3(81) nam 2016
dieu che bang phucmg phap d6ng kk tua co tinh d6ng nhit cao, do tinh khiit hoa hpc va be mat rieng Ion. Tuy nhien, nhu chiing ta da bik bot oxit dieu chi bing phuang pliap dong ket tiia cac cation kim loai thuang co do kSt tu Ion, gay anh huong khong t6t den vat li|u dugc san xuat tir chung. Cac yeu to anh huong den sir ket tu giiia cac hat CO the ke den nhu nong do cac tien chit, gia tri pH ciia moi truong, nhiet do, ban chit dung mdi, su co mat chit trg gel, thii tu kk tiia, t6c d6 them tac nhan kit tiia, t6c d6 khuay... [5, 9], cho nen rit kho dl thiit lap dugc mot nguyen nhan duy nhit gay n6n sir ket tu. Ngoai ra, cac cation kim loai khac nhau bit diu kit tiia va kit tiia bit diu bj hoa tan a nhung gia tri pH khac nhau [10]. Cho nen dl kit tiia ddng thcri tir hai cation kim loai tro len phan Ion cac tac gia nho tir tir dung dich chira hSn hgp cac cation vao dung dich tac nhan kit tiia vai mgt gia tri pH dinh truac [5, 9]. Song nlu thuy phan tir tir cac cation kim loai trong nuoc soi tnroc, sau do dl nguoi rii moi them vao tac nhan kit tiia thich hgp de tong hgp vat lieu nano oxit thi gia tri pH khong anh huang den kit qua thu dugc. DiSu chi vat lieu LaFeOj kich thudc nanomet bing phirang phdp dm gian nay chira diroc cdng bS.
Trong bai bao nay cong bl cac kit qua nghien cim tdng hgp vat lieu nano tir tinh LaFeOj bang phuang phap ding kit tua thong qua giai doan thuy plian cac cation La'*
va Fe * frong nuoc soi vol tac nhan kit tiia la dung dich NH3 5%.
2. Thirc nghidm va phircmg phap nghien ciiu 2.1. Hoa chdt, dfing CII
^ La(N03)3.6H20, Fe{N03)3.9H20, dung djch NH3 25% (d=0,91g/ml), PVA nuac
cat hai lan, giay lgc bang xanh. ' _ C6c thiiy tinh chiu nhi^t 100 ml, 200 ml, 500 ml, pipet, buret, may khuiy tir gia
nhiet, con ca tu, bep dien, 16 nung, chen nung, tu siy.
2.2. Thuc nghiem
Nho vao mpt cic nuac nong (>90«C) tren may khuiy tir dung dich chila h6n hop dong moi La(N03)3 va Fe(N03)3. Sau khi cha hit muli, he keo duoc dun them 5 - 7 phut sau do de ngugi den nhiet dp phong rii cho tir tir dung dich amoniac 5% vao cic to dugc o tren, lugng amoniac cho vao lay du dl kit tiia hit cac cation La'* va Fe'*
l t o r 2 ' o c h ^ ' Z^^' P''-''>Phtalein). Kit tua dugc khuiy diu tren may khuiy ti, nhiet dg phong (khoang 3 ngay).
tir n h i f t ' d - ' v ' " ' ^ ' • * ' ^ T " ' " ' " " ' " '*' ™ « ' ™ " S moi truong ap suit khong khi tu nhtet dg phong den cae nhiet dg khac rfiau dl kiim tra su hoan thien viec kit ti,^ va tao pha dong nhat LaFeOs, toe dp nang nhiet lOX/phut ' " ™?" ^'*'^ " « ' " * ™
TAP CHI KHOA HOC BHSP TPHCM Nguyin Anh Tiin va tgk
2.3. Phirangphdp nghien ciru
Gian dl phan tich nhiet cila miu dugc ghi tren may DTG-60H (Hang Shimadzu Nhat Ban) trong moi truimg khong khi kho vol tic do nang nhiet lOVphiit, nhiet dp tfii da 1100°C. Pha khii lugng (MS) xac dinh su mit khdi lugng CO2 va H2O theo nhiet dp nung dugc xac dinh tren may QMS 403C.
Gian dl nhilu xa tia X dugc ghi tren may D8-ADVANCE (Dire) voi birc xa CuK„ (^=1,5406A), 28=10-80°, buoc do 0,03°, thoi gian dimg mSi buoc Is.
Anh vi eiu iriic va hinh thai hge dugc chup bang kinh hiln vi dien tir quet (SEM) tren may FESEM S4800 HITACHI (Nhat Ban) va kinh hiln vi dien tu truyin qua (TEM) h-en may JEOL-1400 (Nhat Ban).
Cac dac trung tir tinh (duang cong tir tri, lire khang tir H^, d6 tir du M, va dp tir hoa Ms) cila mau vat lieu dugc nghien cuu g nhiet dp phong bing tir kl miu rung (VSM) tren may MICROSENE EVl 1 (Nhat Ban).
3. Ket qua va thao luan 3.1. Ket qua phdn tich nhiet
Tir gian do phan tich nhiet khii lugng (ducmg TGA, Hinh 1) cho thiy dp hut khii lugng trong toan bp qua trinh nung mlu la 42,22%, 1cm hom rit nhilu so voi tinh toan theo phuong trinh ti lugng (1) la 18,20%.
La(OH)3 + Fe(OH)3 —LaFe03 + 3H,0 (1) Dieu nay co the giai thich la do thanh phan ket tiia sau khi phai khd d nhift do
phong khdng chi eo La(0H)3 va Fe(0H)3, ma con chira mot lugng dang ke mudi baza- cacbonat vdi thanh phan thay ddi la La2(C03)3.^(OH)2x. Hien tugng tao muli baza dac trung ddi vdi tit ca cac ion nguyen td dat hiem, trong dd de tao thanh nhat ddi ion La'*
- ion kim loai cd ban kinh ldn nhat trong day dat hiem [7]. Su cd mat CO2 trong mlu nghien ciiu (mac dau Ichdng sii dung tac nhan ket tiia la CO^'s) la do su hda tan CO2 cd mat trong khdng khi bdi dung dich NH3 va su hap thu CO2 cua kit tiia. Hien tugng tuong tu dugc chimg minh trong cdng trinh [7], dac tnmg cho he Ln203 - H2O - CO2 (Ln - cac nguyen td dit hilm) xay ra tham chi khi ap suit rieng phin ciia CO2 trong khdng khi la rit thip. Do dd khi nung kit tiia 6 nhiet do cao xay ra su mat khdi lugng la H2O va CO2 (Hinh 2). Dudng TGA tren Hinh 1 cho thiy tit ca cac qua trinh mit khdi lugng diu xay ra vdi hieu irng thu nhiet dac trung cho qua trinh giai hap phu bl mat, bay hgi nudc, phan ung nhiet phan mudi bazo-cacbonat.
Tir gian do phd MS Hinh 2 cho thay, neu nhu su mat nudc hoan toan xay ra din nhiet dp khoang 550°C, thi qua trinh mit CO2 kit thuc d nhiet dp cao hon (~750°C), phu hgp vdi ket qua ve nhiet do tren dudng TGA d Hinh 2.
Tir kit qua phan tich nhiet, chgn nhiet dp nung mau d 750°C, 850°C va 950°C dl nghien ciru sir hinh thanh dan pha LaFeOs, kit qua pho XRD dugc chi ra d Hinh 3. Tii
TAP CHi KHOA HOC DHSP TPHCM Sd 3(81) nam 2016
gian dd cho thiy cac pic dac trung dan pha tinh thl LaFeOs hiu nhu hoan thien d 750°C, chi cd 3 pic vdi cudng dp ylu ddi vdi mlu ket tua nung d 750°C irng vai thanh phin pha hda hpc La203. 6 850°C va 950°C ta khdng quan sat thiy cac pic tap chit.
Quan sat mlu vat lieu sau klii nung d 850°C bang kinh hiln vi dien tu quet SEM va hiln vi dien tir noiyln qua TEM (Hinh 4) cho thiy cac hat cd dang hinh ciu hoac hinh ciu bien canh ylu vdi kich thudc cac hat rieng re ~ 50 - 70 nm.
'OiriQA. „ „ m ^ n j n TOA, %
400 600 800 Tenip[°C]
Hinh 1. Gidn S DTA-TGA cUa mdu Ml
Hinh 2. Gidn di MS lach CO, vdHjO cua mdu kit tita
M=S^1 e m u / ? !it b f ^ \ r / " " ""^^ '^^ " > » g '^ H-42.53 Oe va dd tir du emu^g HTnhl ^ ^ g ij. oiem dac biet doi vdi mau vat lieu nano LaFeOj la tai tir T t ^ ^ l ^ ' ' ' l ' " ^ ^ '^ ^ ° ^ « ^^' ' ^ («.^^
TAP CHi KHOA HOC DHSP TPHCM Nguyen Anh TiSn vA tgk
tmdmg 15 kOe dudng cong tir hda tilp tue di len, cd nghia la thl hien tinh chit cua vat lieu siSu thuan tir, thich hgp khi lam viec d til hTjdng cao. [1]
r I ti n .
• LaFeCh o L a z O s
k^A-u—f,^
„,~L
JI- * * - 850°C
• ^ II ^ r ' V — - — ^ -
3 0 40 50 2 - T h e t a — S c a l e
•an.. 750°C
Hinh 3. Gidn dd XRD cdc mdu LaFeOj sau khi nung a cdc nhiSt dd khdc nhau
Hinh 4. Aril SEM (a) vd TEM (b) ctia mdu LaFeOs sau nung 850°C Bdng 1. Cac d|c tnmg tir tinh cua mau vat h$u nano LaFeOs nung 850°C
TT 1
Ki hieu mau LaFeOs
Luc khang tir (He), Oe
42,53
Dp tir hda (Mj), emu/g 0,24
Dp hi du (M,), emu/g
0,01
TAP CHi KHOA HOC DHSP TPHCM So 3(81) nam 2016
emu/g
n nn U.UU
n -jn U..ZU _^f00^^
'•
L a F e 0 3 - -850«»C
^-.^^
-5 0 5 Applied F i d d (kOe)
-ffiw/i 5. Bo thi duang cong tic tre cita mdu vdt lieu LaFeOs nung a 85Q°C 4. Ket lu^n
Da tdng hgp vjt lieu nano LaFeOs bing phuang phap ddng kit tua thdng qua giai doan thiiy phan tir tit cac cation La'* va Fe'* trong nudc sdi vdi tac nhan kit tiia la dung dich NHs 5%. Vat lieu nano LaFeOs tao thanh sau khi nung kit tiia d 850°C cd kich thudc hat - 5 0 - 7 0 nm, cac djc trung tir tinh do d nhiet dp phdng la Hc=42.53 Oe, M,=0.01 emu/g, M5=0.24 emu/g va thl hien tinh chit cua vat lieu sieu thuan tir.
TAI LI£U THAM KHAO
1. Nguyin Van Du (2009), Nghien cicu mpt sS linh chdt dien, tic cua perovskite La,.
A^FeO,, Luan van Thac si, Tnrdng Dai hpc Cdng nghe, DHQG Ha Ngi.
2. Luu Minh Dai, Dao Ngpc NhiSm, Dd Trang Kien (2012), "Tdng hgp perovskite LaFeOs cau tnic nano bang phuong phap dlt chay gel va img dung xilc tac cho phan ung 0X1 hda CO", Tap chi Hoa hoc, 50(2), tr.l44 - 147.
3. Le Hai Dang (2011), Tdng hgp vat lieu kiiu perovskite kich thicdc nanomet va nghien cuu hoat linh xiic tdc oxi hoa cua chiing. Luan an Tiln sT Hda hoc, Trudng Dai hoc Supham HaNdi. e . . '*' nmo!"' t"^ ^^"' "^ '^'"^^ °'™8' ^8"yen Hiing Manh, Nguyin Ngoc Toan (2U10 , Nghien cuu cdng nghe che tao vat lieu nhay khi LaFeOj bing phuong phap sol-gel tao phuc iing dung trong cam biln nhay hai cin". Tap chi Khoa hoc Bai hoc Quocgia Hd Npi, Khoa hpc Ttr nhien va Cdng nghe, Sd 26 tr 36 - 43
5. Nguyen Anh TiSn, Hoang Thi Tuyit (2015), "Tdng hgp, ciu tnic va tii tinh ciia vSt h|u nano NiFejO, bang phuang phap ddng kit tiia". Tap chi Hoa hoc, 53(4), tr.441 -
TAP CHl KHOA HOC DHSP TPHCM Nguyh Anh Tiin va tgk
6. Do Ki6n Trung (2011), Nghien ciru tong hap perovskit LaFeOs bang phirang phdp dot chdy gel va ddnh gid khd nang xiic tdc oxi lioa CO, fidp phu asen, sdt, mangan, Luan van Thac sT Hoa hpc, Trirong D^i hoc Sir pham, D^i hpc Thai Nguyen.
7. Kozo N., Wakita H., Mochizuki A., "The synthesis of crystalline rare earth carbonates", Bull. Chem. Soc. Japan, Vol. 46, pp.152 - 156.
8. Tatsio Fujii, Ikkoh Matsusue, Makoto Nakanishi, Jun Takada (2011), "Formation and superparamagnetic behaviors of LaFeOs nanoparticles", Springer Science- Business Media, Vol. 205, pp. 97 - 100.
9. S. S. Yattinahalli, S. B. Kapatkar, N. H. Ayachit, S. N. Mathad (2013), "Synthesis and Structural Characterizationof Nanosized Nickel Ferrite", Internanonal Journal of Self-Propagating High-Temperature Synthesis, Vol. 3, pp.147-150.
10. HaaapcHKo B.A., AHTOHOBHH B.H., HeBCKan E.M. (1979), fudpojius uoHoe Memannoe e pajSaeneuHbtx pacmeopax, 192tr.
(Ngay Tda so^n nh$n 6t^c bar. 19-02-2016: ngay phan bi$n danh glA: 28-02-2016;
ng^y chap nh$n dang: 17-3-2016)
