L sot Debvi cosh V 2, (3.77)
c Toanphan
L* , CH , £ xiic npi S. f((p) la ' l^[>:b\T • ham <Pf>.
sd ciia cac thong sd: va tdng be mat tiep
Luru do 3.3 : Quy trinh khop (Fitting) dac trimg C-V cho he dien cue ban din Nano-Xop
Dir lieu
Ly thuyet: C,^,,,,,„ (cp) = f( (p^ , L ^ CH , l^Zỵ, S ) Thuc nghiem : C]*^llf!^r = g((p) -
Sem,
Khdp cpft, va Loebye theo ham
^ T o a n p h a n ( ^ )
I
Khdp CH theo ham C-^p3^p^,^^((p) tai vung phan cue am
Khdp kich thude hat nho L* theo ham Cj^ar^^^^ni^)
tai viing phan cue duong
Khdp long be mat tiep xiic theo ham Cj^g^p^^Jcp) tai vung gan cp^
i
Khdp phan bd L* ciia hat nho va hat Idn theo ham CjQg^p^^^((p)
k
Kiem tra phan bd kich thude L* theo ham ^2 / ^ —
Ket luan
Trong chuong 3 luan an da xay dung duoc mo hinh ly thuyet mo phdng qua trinh thiel lap can bang cua chuyen tiep Ban dan - Dien giai đi vdi he hat kich thude nho va md hinh de tinh (phuong phap sd) dac tnmg dien dung dien hoa ciia dien cue ban din nano-xop.
Mo hinh chuyen tiep SEI dua tren viec giai bang phuong phap sd he phuong trinh lien tuc theo thdi gian va phuong trinh Poisson cho ca 2 loai hat tai cua ban din. Cac dieu kien bien khong bi anh hudng khi ta thay đi kich thude hat den vimg kich thude co viing dien tich khong gian. Dieu kien ban d£u ( I =0 ) láy tai trang thai vimg phing dam bao tinh chinh xac ciia gia thuyeị Mo hinh nay cd mdi sd uu diem sau :
* Cd the tinh dinh lugfng phan bd nong do hat tai va dien trudng trong
he hat nho, la cin thiéi de nghien curu tinh chait phu thuoc vao kich thude hat.
* Theo doi dugc thay doi tinh chat theo thdi gian.
Mo hinh tinh dien dung dien hoa ciia chuyen tiep SEI dua tren md hinh cac ldp dien tich kep ciia be mat tiep xiic ban dan - dung dich dien giaị Cong thiic loan hoc ciia dien dung dien hoa tung ldp dien tich cd dang chung la tich ciia ham dac trung tinh chat vat lieu va ham dac trung cho CSLU hinh phan bo dien tich. Quy trinh tinh dac trung C-V dugfc thuc hien theo mach tuong duong ciia mo hinh chuyen tiep vdi gia thiet sut thé roi tren ca 3 viing dien tich . Md hinh nay cd the ap dung de tinh dac trung dien dung dien hoa- the phan cue cho dien cue ban dan nano-xop. Dac trung (C-V) tinh theo mo hinh nay la ham sd ciia cac thong sd vai heu chát ban dan , kich thude hat, tinh chát ciia be mat tiep xiic va dung dich dien giaị Quy trinh khdp ket qua linh loan ly thuyet va thuc nghiem cho ta nhung thong tin quan trong ve he nano-xop .
Kel qua ap dung cac mo hinh ly thuyet irinh bay d tren cho he dien cue
ban dan Ti02 loai n tiep xiic vdi dung dich chiia cap Redox T/P' se trinh bay
CHUONG 4. DIEN ClTC TIO, CAU TRUC NANO - XOP
He thdng hoa sir phu thuoc boat tinh cua vat lieu vao cau triic, hinh thai hoc va moi trudng liep xiic ...w la co sd cho dinh hudng iing dung ciia vat lieụ Trong chuong nay cua luan an se trinh bay mot sd ket qua thuc nghiem hen quan den boat tinh quang dien hoa cua Ti02 trong mdi quan he vdi cau triic pha vat heu cung nhu hinh thai hoc ciia cac loai dien cue trong moi irudng dien giai khac nhaụ
4.1 Cau true va hinh thai hoc ciia dien cue TiOj
Cac dien cue TiOo dugc che tao de nghien ciiu gdm 3 loai nhu sau :
- Dien cue Ti02 cd cau tnic nano-xop, che tao theo quy trinh sol-gel. - Dien cue Ti02 nano-xop, che tao tir hot Ti02 thuong pham P25
(DEGUSSA) cua hang MERK (do hat - 25nm) va MCB (do hat -200 nm).
- Dien cue Ti02 ed cau triic mang the khdi, dac, dugc che tao theo phuong phap dot (Pyrolysis) kim loai Ti nhu trinh bay d chuong 2 .
4.1.1 Dien cue Ti02 cdu true nano-xop, che tao bdng sol-gel
Dien cue loai nay dugc che tao lir sol cua Ti02 (phan 2.1 chuong 2) tren
de dan trong sudt ITO cd dien trd be mat = lOfi/u . Miu dien cue dugc nung thieu ket d nhiet do 450-500^C khoang 0,5 gid. De cd mang TiOs day, qua trinh phu tao mang va nung dugc lap lai vai Ian.
Tiép xiic dien cua dien cue dugc tao d vimg ITO khong phu Ti02 bang keo dan bac (Ag). Cira s6 lam viec cua dien cue TiỌ la 1cm' (Icmxlcm) . Phan cdn lai dugc phu bang Epoxy tranh tiep xuc dien vdi dung dich dien giaị Dien cue dugc nhiing vao dung dich dien giai can nghien cuu va thuc hien cac phep do dac trung I-V va C-V nhu mo la d phan 2.2 chuong 2 ciia luan an.
S I E M E N S D 5 0 0 0 . X-Ra
1
Hinh 4.1 : Nhieu xg tia Xmdng dien cue Ti02 che tao bdng sol-gel
Cau iriic cua cac mau dien cue neu tren dugc khao sat bang phuong phap nhieu xa tia X tren may D5000 cua hang Siemens. Mau mang thieu ket 6 nhiet do ^ 500^C cho pha TiỌ Anatase nhu tren hinh 4.1 (dudng tren) . Neu mane TiỌ duoc thieu ket d
nhiet dp 750^C thi cau triic TiỌ se chuyen sang pha Rutile (hinh 4.1 dudng dudi) . Ket qua na\" hoan loan phij hgp vdi cong bd cua cac nhom nghien ciru iren the eidi [13.27].
Hinh anh hien y\ dien tú
quel (SEM - Scanning Electron Microscop}) cua mau dien cue
TiO sdl-iicl ircn hinh 4.2 cho
tha\ cac ha! TiO co kfch ihuov
Hmh 4.2 : anh SEM cua man nian;^ TiO
che tao bang phuong phap sol-gel cho miu cd đ trong sudt (Transparence) rat lot. Day la uu diem ciia loai miu nay vi no cho anh sang kich thich xuyen sau vao ldp TiOo, tao dieu kien cho nghien ciiu cac qua trinh vat ly xay ra tren be mat tiep xiic npi (internal surfaces) giira chai ban din va dien giaị
Mat khac dien cue loai nay che tao tir cac hoa chát lien dinh luong đi dat tien va quy trinh tao dugc ldp Ti02 cd do day co lÔm trd len thudng gap khd khan. Tren thuc te, dien cue loai nay dugc che tao cho cac nghien ciiu va cac ling dung cao caip nhu pin quang dien hoa hay cira so dien sac ...w ma d đ yeu ciu ve dp trong sudt ciia dien cue la vaii de lien quyet. Cac miu loai
nay ta se ggi la dien cue TiÔ sol-eel
4J2 Dien cue Ti02 cdu true nano-xop che tao tit vat lieu thucmg pham P25 (DEGUSSA)
SIEnEMS K H e . x - R * , Lab 1 9 - S « p - 1 9 ^ 7 1 B S 9
Ngudi ta thudng dung dien cue TiOj cau tnic nano-xop che tao tir b6i Ti02 cd kich thude hat nho (c9 nanomet) trong nhimg ling dung dai tra . M6l trong nhirng thuong pham dugc sir dung rgng rai tren