Tap chi Hoa hgc, T. 48 (6), Tr. 683 - 686, 2010<br />
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TONG HOP CO3O4 KICH THLf6C NANOMET BANG<br />
PHUONG PHAP DOT C H A Y GEL<br />
Den Tda sogn 24-7-2009<br />
LUU MINH DAI', NGUYEN THI TO LOAN'<br />
'Vien Khoa hgc Vdt lieu - Vien Khoa hgc vd Cdng nghe Viet Nam<br />
'Trudng Dgi hgc Suphgm Thdi Nguyen<br />
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ABSTRACT<br />
C03O4 powder has been synthesised at low temperature (600°C) by the combustion of gel<br />
prepared from polyvinyl alcohol (PVA) and cobalt nitrates. Factors affecting on synthesis<br />
process of nanometer oxides C0}04 including temperature andpH of gel formation, molar ratio of<br />
cobalt concentration and polyvinyl alcohol concentration, temperature of calcining on structure<br />
and parcticles sizes were investigated. The crystalline process and the morphology of oxides<br />
particles were considered by X-Ray diffraction (XRD), Scanning Electron Microscopy (SEM).<br />
Surface areas of oxides were determined by the BET (Brunaure-Emmet-Teller) method. Further<br />
thermal treatment at 400 - JOO^C for 2 hours yields the single phase C03O4 with a specific<br />
surface area 39.68 m'/g.<br />
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I - MC) DAU Hdn hgp dugc gia nhiet va khudy lien tuc tren<br />
may khudy tQ cho din khi Mnh thanh gel trong<br />
Phuang phdp dot chay gel d nhiet dd thap sudt, sdy khd gel vd nung mdu d nhiet dd khac<br />
tao ra nhiing san phdm oxit kfch thudc nanomet nhau trong hai gid.<br />
dugc Qng dung cho cac linh vuc xuc tdc, huynh - Gian dd nhilu xa Roughen dugc do tren<br />
quang, bao ve mdi trudng [1 - 6], sQ dung cac<br />
may SIEMENS D5000 cua DQc vdi A^^^ =<br />
hda chdt va thiet bi thdng dyng. Phuang phap<br />
nay da dugc dung dl tdng hgp mdt so oxit kim 1,5406 A d nhiet dd phdng, gdc quet 2 ^ = 0 -<br />
loai [7, 8]. Trong bai bao nay chung tdi sQ dung 70^ budc nhay 0,03°, dien dp 30KV, cudng do<br />
phuang phdp ddt chay gel d nhiet do thdp dl d'ng phdt 0,03 A. Kfch thudc hat trung binh (nm)<br />
nghien cQu tim dilu kien tdi uu tdng hgp oxit cua cac oxit dugc tfnh theo phuong triiih<br />
C03O4 kfch thudc nanomet. — 0 89 X ~<br />
Scherrer: r = -^—'—, trong dd: r la kfch thudc<br />
II - THUC NGHIEM y9cos6'<br />
hat trung binh (nm), A, la budc sdng K^cua.<br />
- Cac hod chat sQ dyng trong nghien cQu diu anot Cu (0,154056 nm), fi la do rdng cua pic<br />
la loai tinh khiet phan tfch: Co(N03)2.6H20,<br />
Qng vdi nQa chieu cao cua pic cue dai (FWHM)<br />
poll vinyl ancol, NH3, HNO3<br />
tfnh theo radian, 0 la gdc nhilu xa Bragg Qng<br />
- C03O4 dugc dilu chi bang phugng phap ddt<br />
chay gel d nhiet do thap: dung dich mudi vdi pic eye dai (do).<br />
Co(N03)2 dugc khuay trgn vdi dung dich - Anh vi cdu tnic va hinh thai hgc cua oxit<br />
polivinyl ancol (PVA) theo ti le moi tuang Qng. dugc chyp bang Idnh hiln vi dien tQ quit (SEM)<br />
<br />
683<br />
JEOL- 5300 (Nhat Ban). Nhu vay, kfch thudc hat cd xu hudng giam theo<br />
- Dien tfch b l mat rieng cua vat lieu dugc do chilu tang lugng PVA, cd thi do su tang mQc<br />
tren may COULTER-SA 3100 cua My bang do phan bd dong deu cua cdc ion kim loai trong<br />
phuong phap hap phy N2 ldng d 77 K. dung dich PVA lam cho qua trinh chay diln ra<br />
thuan lgi. Vdi ti le moi Co'^fPNA la 1/3 thu<br />
dugc dgn pha cua C03O4 cd kfch thudc hat nhd<br />
Ill - KET QUA vA T H A O LUAN nhdt. Do vay chung tdi chgn ti le moi nay cho<br />
cac thf nghiem tie'p theo.<br />
1. Khao sat anh hudng cua ty le moi<br />
Co'VPVA de'n su tao thanh pha va kich 2. Khao sat anh hudng cua nhiet do tao gel<br />
thudc hat de'n su tao thanh pha va kich thudc hat<br />
Dilu chi cdc gel vdi ti le moi Co^'^fPNA ldn Dieu chi cac gel vdi ti le moi Co'^'/PVA =<br />
Mgt la 1/1; 1/2; 1/3; 2/1 va 3/1, d 80°C va pH = 1/3, d nhiet dd 40, 60, 80 vd lOO^C, vd pH = 4.<br />
4. Sdy khd vd nung gel d 500''C trong 2 gid. Ghi Say khd va nung gel d 500°C trong 2 gid. Ghi<br />
gian do nhilu xa Ranghen cua cac mdu hot. Kit gian dd nhilu xa Ranghen cua cdc mdu hot. Kei<br />
qua dugc chi ra d bang 1. qua dugc chi ra d bang 2.<br />
<br />
Bdng 1: Cdc pha tao thanh va kfch thudc cua oxit d ti le moi Co'"" /PVA khde nhau<br />
<br />
Ty le moi<br />
3/1 2/1 1/1 1/2 1/3<br />
Co'-'/PVA<br />
Pha tao thdnh C03O4 C03O4 C03O4 C03O4 C03O4<br />
CoO CoO<br />
Kfch thudc hat,<br />
45,18 42,68 35,63 31,54 28,31<br />
nm<br />
<br />
<br />
Bdng 2: Cac pha tao thanh va kfch thudc cua C03O4 khi tao gel d nhiet do khac nhau<br />
Nhiet do tao gel, "C 40 60 80 100<br />
Pha tao thanh C03O4 C03O4 C03O4 C03O4<br />
<br />
Kfch thudc hat, nm 27,15 27,85 29,31 31,36<br />
<br />
Kit qua bang 2 cho thdy, nhiet do tao gel Ghi gian do nhilu xa Ranghen cua cac mdu bdt.<br />
anh hudng khdng dang ke den sy tao thanh pha Ket qua dugc chi ra d bang 3.<br />
cua C03O4 va chi anh hudng din kfch thudc hat Qua kit qua d bang 3 cho thdy, khi tao gel d<br />
cua oxit tao thdnh. O nhiet do 40, 60°C cac hat pH = 4 thu dugc don pha C03O4 vdi kfch thudc<br />
oxit thu dugc cd kfch thudc nhd va khac nhau nhd nhai. Do dd chung tdi chgn pH = 4 de tiln<br />
khdng nhilu. Tuy nhien thdi gian tdng hgp mdu hanh cdc thf nghiem tilp theo.<br />
d nhiet do tao gel 40°C keo ddi, vi vay nhiet do<br />
4. Khao sat anh hudng cua nhiet do nung den<br />
tao gel la 60°C dugc lya chgn cho cac thf<br />
nghiem tiep theo. su tao thanh pha va kich thudc hat<br />
Nhiet do nung mdu la ylu to rat quan trgng<br />
3. Khao sat anh hudng cua pH tao gel de'n su<br />
ddi vdi sy hinh thdnh pha va kfch thudc cua cdc<br />
tao thanh pha va kich thudc hat<br />
hat oxit tao thanh. D l tim dugc dieu kien nung<br />
Dieu che cac gel vdi cung ti le moi thfeh hgfp cho su tao thdnh C03O4 chung tdi tiln<br />
Co'-'/PVA = 1/3, d OO^C va pH tao gel la 2, 3, 4 hanh ghi gian do phan tfch nhiet cua gel giQa<br />
va 5. Sdy khd va nung gel d 500''C trong 2 gid. PVA va Co(N03)2 (hinh 1).<br />
<br />
684<br />
Bdng 3: Cac pha tao thdnh va kfch thudc cua oxit khi tao gel d pH khde nhau<br />
pH tao gel 2 3 4 5<br />
Pha tao thanh C03O4 C03O4 C03O4 C03O4<br />
CoO CoO<br />
Kfch thudc hat, nm 38,44 34,53 27,48 28,85<br />
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