8/2/2019 ~WRL1193

1/23

BO CO TUN 1

1. Carbon nanotube- Carbon nanotube l cc ng trgraphite c ng knh vi nm v c chiu di c thln n

20cm.

-Carbon nanotube c thxem nh c to thnh do tm graphene cun li C(m,n). Ty vophng cun m carbon nanotube c cc cu trc khc nhau: armchair (m=n), zigzag (m=0),chiral (mn).

Hnh 1.2:Cc hng cun tm graphene

Cacbon nanotube thng c chia thnh cc loi sau:Cacbon nanotube n thnh (hay mt lp) (Single-wall Nanotubes SWNTs) ch c

duy nht mt tube v khng c phin graphite bao quanh.

Hnh 1.3: Cc loi cacbon nanotube: (A) Cacbon nanotube n tng (SWNTs) ;(B) Cacbon nanotube a tng (MWNTs)

zigzag(n,0)

Armchair(m,m) chiral(n,m)

A B

8/2/2019 ~WRL1193

2/23

Cacbon nanotube a thnh (hay a lp) (Multi-wall NanotubesMWNTs) gm t 230 SWCNTs c ng knh khc nhau lng vo nhau, khong cch gia cc vch caSWCNTs l 0,340,36 nm.

- Cc dng sai hng thng gp carbon nanotube l sai hng l trng, sai hngStoneWales v sai hng sp

3

.- Tnh cht

Carbon nanotube c cng ngang hoc cao hn ckim cng vi module young vng sut ko cao nht.

ng nano dn in c th mang dng in cng 4 x 09 A/cm2 tc ln hn ng000 ln.

ng nano cacbon c th truyn ti 6000 Wm*o nhit phng; so vi ng kimloi bit n nhiu qua tnh dn nhit tt ca n ch truyn 385 Wm*o.

- Carbon nanotube c tnh cht ha hc ca b mt tng i tr nn khi a vo ng dngcn nhiu hn ch. C hai nhmphng php chnh c s dng bin tnh b mt: Phng php vt l (bin tnh khng ng ha tr): Tng tc gia b mt CNTs v cht

bin tnh l lin kt vt l (lc van der Wall) hoc tng tc xp chng lin kt .Phng php ny lm tng khnng phn tn ca CNTs nhng khng khng gy

nh hng xu n thnh ng v tnh cht in ca CNTs. Tng tc gia b mt

CNTs v cht bin tnh l lin kt vt l (lc van der Wall) hoc tng tc xp

chng lin kt

Hnh 1.17 : Cc kiu tng tc vt l ca cht bin tnh v CNTs

Phng php ha hc (bin tnh ng ha tr): S dng cc tc nhn c hot tnh cao tncng vo thnh CNTs qu trnh ny thng xy ra ti nhng v tr khuyt tt v u ng,l ni d b oxy ha nht.

8/2/2019 ~WRL1193

3/23

Phng php ny to ra lin kt ha hc (lin kt cng ha tr) gia nguyn t

carbon ca CNTs v cht bin tnh. Nguyn l chung l s dng cc tc nhn c hot tnh

cao tn cng vo thnh CNTs qu trnh ny thng xy ra ti nhng v tr khuyt tt v

u ng l ni d b oxy ha nht, qu trnh gn cc nhm chc ln b mt CNTs lmtng khnng phn tn v gia cng cho CNTs tuy nhin n c th lm thay i hoc mt

cc tnh cht qu ca CNTs.

Hnh 1.21: V tr phn ng: A) Vng 5 hoc

7 cnh, B) Cacbon lai ha sp3 dc thnh ng,

C) v tr b ph hy do tc nhn oxi ha trn

khung cacbon, D) v tr cui ng (opened-end

cap)

C th tm tt cc phng php thc hin nh sau:

Bin tnh b mt bng cc cht oxi ha mnh to nhm chc cacboxyl Chc ha CNT-COOH Halogen ha CNTs

Thm vo CNTs nhng gc hirocacbon Gn y ngi ta chc nng ha CNT bng CO2Ar plasma. Phng php x l

b mt ny ang c a chung v n c th x l cng mt lc slng nhiu.

- Phng php ch to

8/2/2019 ~WRL1193

4/23

C chmc ng cacbon nano Ht xc tc c to trn . Kh cha cacbon (hirocacbon) s b phn ly thnh nguyn t cacbon v cc sn phm

phkhc do nng lng nhit nng lng plasma c vai tr ca xc tc. Cc sn phm sau khi phn ly s lng ng trn cc ht xc tc. y s xy ra qu trnh

to cc lin kt CC v hnh thnh CNTs. Ty thuc vo lin kt gia cc ht xc tc vm c cc c ch mc ng CNTs khc nhau: mc tnh ca ht ln hay mc tln to thnh CNTs.

Phngphp

Bc bay bngphng in

Bc baybng laser

CVDS dng khun

AAO

Nghin bi

Qu

trnh

CNTs to thnhtrn b mt incc cathode khiqu trnh phng

in xy ra lm

bc bay carbon in cc anode

Qu trnh

bc baycarbon do

laser cng cao

Phn hy cchydrocarbon

(nh CH4, C2H2,C2H4,C6H6)

trong s c mt

ca cc ht xctc kim loi

CNTs ln lntrong khun khi

carbon lng nghoc khi graphiteha polymer

thch hp

Nghin btgraphite to thnhnhiu mm hnh thnh cc

ng nano carbon.

uim

n gin, CNTsc t khuyt tt

schCNTs cao, t

khuyt tt,tng hp nhit thp

Sn xut cngnghip, r tin

n gin, rtin, cc ngnano ng nht

Phng php rtkinh t, cngngh khng quphc tp

Nhcim

CNTs to thnhngn v khphn tch

Gi thnh

cao nhtCu trc CNTsc nhiu khuyttt

Qu trnh nhiugiai on, khsn xut cng

nghip

Sn phm thuc ngnht khng cao

2. Vt liu st tSt t l cc cht c t tnh mnh hay kh nng hng ng mnh di tc dng ca t

trng ngoi. Tnh st tdng ch thuc tnh (t tnh mnh) ca cc cht st t.Cc c trngc bn cho vt liu st t bao gm hin tng t tr t bo ha t d lc khng t t thmnhit Curie.

Theo cch phn chia theo kh nng t ha v kh t ca vt liu ny s c 2 nhm vt liust t chnh:

Vt liu t cng: L cc vt liu st t kh t ha v kh kh t. Vt liu t mm: L cc vt liu st t d t ha v d b kh t.Cc phng php tng hp nano st t:1.1.Phng php nghin

Phng Nghin ng kt

8/2/2019 ~WRL1193

5/23

php ta

Qu

trnh

Oxit st t cnghin cng vicht hot ngb mt

uim

n gin v chto c vt liuvi khi lngln.

Nhcim

Tnh ng nhtkhng cao.

Phng php ng kt ta l mt trong nhng phng php thng c dng

to cc ht oxit st. C hai cch to oxit st bng phng php ny:

Phng php th nht l hydroxide st b oxi ha mt phn bng mt cht oxi ha

no v gi ha hn hp dung dch c t phn hp thc Fe+2 v Fe+3 trong dung mi

nc. Phng php ny c ththu c ht nan c kch thc t 30 nm100 nm.

Phng php th hai c th to ht nan c kch thc t 2 nm 15 nm. Bng

cch thay i pH v nng ion trong dung dch m ngi ta c thc c kch

thc ht nh mong mun ng thi lm thay i in tch b mt ca cc ht

c hnh thnh.

Hnh: c chhnh thnh v pht trin ht nano trong dung dch

C ch tng hp ht nan Fe3O4 nh sau: vi t phn mol hp l Fe3+/Fe

2+= 2

trong mi trng kim c pH = 914.

Fe3+

+ H2O -> Fe(OH)x3-x

(thng qua qu trnh mt proton)

8/2/2019 ~WRL1193

6/23

Fe2+

+ H2O -> Fe(OH)y2-y

(thng qua qu trnh mt proton)

Fe(OH)x3-x

+ Fe(OH)y2-y

-> Fe3O4 (thng qua qu trnh oxi ha v dehydride ha, pH

> 9, nhit 60). Tng hp cc phn ng trn chng ta c phng trnh sau:

Fe2+ + 2Fe3+ + 8OH- = Fe3O4 + 4H2O

1.2.Vi nh tng (microemulsion)L mt phng php c dng kh ph bin to ht nano. Do s gii hn v

khng gian ca cc phn t cht hot ng b mt, s hnh thnh v pht trin cc ht

nano b hn ch lm cho cc ht c kch thc rt ng nht.

Hnh: Hnh tng nc trong du v du trong nc

C ch ca phn ng xy ra trong h vi nh tng l phn ng ha hc to cc

cht mong mun s xy ra khi ta ha trn cc hvi nh tng ny li vi nhau. C 2cch cc phn t cht phn ng gp nhau:

Cch th nht: Cc phn t cht phn ng thm qua lp mng cht hot ha b

mt ra ngoi v gp nhau. Nhng thc t th t l sn phm to thnh theo cch ny l

rt nh khng ng k.

Cch th hai: Khi cc ht vi nh tng ca cc cht phn ng gp nhau, nu c

lc tc ng th 2 ht nh c th to thnh mt ht ln hn. Cc cht phn ng trong 2

ht nh s ha trn, phn ng xy ra trong lng ht ln v sn phm mong mun c

to.

8/2/2019 ~WRL1193

7/23

Hnh: C chhot ng ca phng php vi nh tng

1.3.Phng php PolyolCc ht nano c hnh thnh trc tip t dung dch mui kim loi c cha polyol.

Polyol c tc dng nh mt dung mi hoc trong mt strng hp nh mt cht kh

ion kim loi. Tin cht c th ha tan trong polyol ri c khuy v nng n nhit

si ca polyol kh cc ion kim loi thnh kim loi. Bng cch iu khin ng

hc kt ta m chng ta c ththu c cc ht kim loi vi kch thc v hnh dng

nh mong mun. Ngi ta cn thay i phng php ny bng cch a nh ng mm

kt tinh bn ngoi vo dung dch. Nh vy qu trnh to mm v pht trin ht l hai

qu trnh ring bit lm cho ht ng nht hn.

Ht nano oxit st vi ng knh 100 nm c thc hnh thnh bng cch trn t

lkhng cn i hydroxide st vi dung dch hu c. Mui FeCl2 v NaOH phn ng

vi ethylene glycol (EG) hoc polyethylene glycol (PEG) v kt ta Fe xy ra nhit

t 80 - 100C.

1.4.Phng php phn li cc tin cht hu c nhit caoPhn li tin cht cha st trong mi trng cht hot ng b mt nhit cao

c th to ra cc ht nano oxit st ng nht kch thc nh mong mun v kt tinh

tt. Phng php ny c th to ht nan kch thc 4 nm khi khng c mm kt tinh

nhng t kch thc 20 nm th cn phi c mm kt tinh.

Phng php nhit phn

8/2/2019 ~WRL1193

8/23

L phng php rt hiu qu c th ch to ht nan vi quy m ln. Phng

php ny c chia lm hai phng php nh l nhit phn bi hi v nhit phn

laser.

Hnh: Nguyn l ca phng php nhit phn bi hi

H gm b phn to bi hi dng siu m. Bi hn sc phun vo mt ci l

gia nhit phn ng xy ra v ht mn c lm kh trc khi c chuyn n mt

h thu cc ht. Vi tin cht l Fe(NO3)3th ng knh ht mn l 6 nm nhng khi

tin cht l FeCl3 th gi tr l 60 nm. Vi st acetylacetonate ht c to ra c

kch thc 5 nm v c ng nht rt cao. Nu tin cht l Fe2+ ammonium citrate

th kt qu l hnh cu rng c ng knh rt ln n 300 nm. V ca cc hnh cu l

tp hp cc ht nan nhhn c kch thc t 2040 nm ph thuc vo nhit cal.

Phng php nhit phn laser to cc ht mn t kt t vi nhau.

Hnh: Nguyn tc nhit phn laser

8/2/2019 ~WRL1193

9/23

Vng phn ng ha hc xy ra ni giao nhau ca chm hi v chm laser (06

mm) v c tch hon ton khi cc vng khc lm cho qu trnh kt m ca cc

ht c loi b gn nh hon ton. Tin cht trong trng hp ny l Fe(CO)5 khng

hp thlaser nn ethylene c dng l cht hp thnng lng laser v l cht manghi n bung phn ng phn hy Fe(CO)5. to Fe2O3ngi ta phi a khng

kh vo bng cch trn khng kh vi Ar.

1.4.1. Phng php ng kt tay l phng php tin dng nht tng hp Fe3O4v -Fe2O3. Phng php

ny thc hin nh sau trn 2 ion st II v st III theo t l 1:2 trong dung mi kim mng

nhit phng hoc trong iu kin nhit tng. ch thc v hnh dng ca Ht

nano st oxide ph thuc v loi mui s dng ( c th l chloride, sulfate, nitrate,

perchlorate) t l ion st II v st III, nhit phn ng, gi tr PH, i lc ion ca cc

cht, v cc thng s phn ng khc ( tt khuy, tc nh git dung dch kim). Gn

y c nghin cu v tng hp ng kt ta ca Ht nano Fe3O4 v cc hnh thi, cu

trc v tnh cht tcc nhit khc nhau.[11]

Phng php ny c nh hng ln n tnh cht l ha ca ht Ht nano st

oxide. Ni chung, t bo ha (saturation magnetization) MS trong cu trc ca vt liu

nano ny thng nhhn gi trtng ng dng bulk, gi snh khng c sthay i

cu hnh ion. Theo , cc gi tr thc nghim ca MS trong ht Ht nano oxide st t

nm trong khong 30-80 emu g-1, thp hn gi tr ca dng bulk 100 emu g-1. Thm vo

Ht nanos Fe3O4 rt bt n nh di iu kin chung quanh v d b oxi ha thnh

Fe2O3 hoc ha tan vo trong mt cht c tnh acid. trnh s oxi ha c th xy ra

trong khng kh, vic tng hp Ht nano Fe3O4 phi c thc hin trong iu kin kkh. Da trn im ny, Ht nano Fe3O4 c thdng tng hp Fe2O3 bng oxy ha

hoc trong mi trng giu oxy. V s oxy ha khng nh hng mnh ti Fe2O3do

bn ha hc ca pha ny trong cc iu kin kim hay acid.[11]

8/2/2019 ~WRL1193

10/23

Tuy nhin phng php ny to ra ht c khong phn bkch thc kh rng,

i khi phi qua bc sng lc kch thc. ch thc phn b rng c th to ra mt

khong rng ca nhit blocking (TB) v nhit ny ph thuc kch thc ht do

t tnh c khi khng tha mn mt vi ng dng nht nh. Kang v ng s bo co mtphng thc tng hp Ht nano Fe3O4n phn tn ng thv kch thc phn b hp

( ng knh khong 8.5 1.3 nm) bng phng php ng kt ta khng s dng cht

hot ng b mt, phn ng trong mt pha nc, t l st II/ st III = 0.5 v pH = 11-12,

v magnetie s b oxy ha trc tip bi qu trnh thi kh to thnh -Fe2O3. Ngc li,

rt nhiu cc cng b gn y m t vic to ra sn phm n phn tn hiu qu cn phi

dng cc cht hot ng b mt nh dextran hay PVA cho vo bnh phn ng hoc vo

cc ht Ht nano ph b mt trong cc bc tip theo. Cht hot ng b mt hotng nh cht bo v, kim sot kch thc v ha bn cc ht phn tn trong pha huyn

ph.[11]

Hn na, bt li ca cc phng php tng hp dung dch l gi tr pH cao ca

hn hp phn ng phi c iu chnh trong qu trnh phn ng ln tch sn phm, v

c th to ra sn phm khng ng u v kch thc phn tn rng. Ngoi ra nc thi

vi kim cao sinh ra trong qu trnh th nghim cn phi qua x l bo v mi

trng.[11]

1.4.2. Phn hy nhitPhn hy nhit dung dch hu cc s dng rng ri trong tng hp oxit st

Ht nano, v phn hy ca Fe (cup) (cup= N-nitrosophenylhydroxylamine) 3, Fe (acac) 3

(acac = acetylacetonate), hoc Fe (CO)5 theo sau bi qu trnh oxy ha c th dn n st

oxit Ht nano cht lng cao n phn tn, m thng yu cu nhit tng i cao

hn v mt qu trnh x l phc tp.[11]

Sun v Zeng [24] bo co mt qui trnh phn hy nhit tng hp Ht nano

magnetite, c iu khin kch thc v n phn tn da trn nhit cao (265 C) phn

ng ca Fe (acac) 3 trong te phenyl c s hin din ca ru, oleic acid, v oleylamine.

8/2/2019 ~WRL1193

11/23

Vi ht nano magnetit nhhn lm mm (seed), ht nano magnetite n phn tnng

knh ln n 20 nm c thc tng hp v phn tn vo dung mi khng phn cc bng

phng php pht trin trn mm (seed-mediated growth method). Qu trnh ny khng

khng yu cu la chn kch thc v d nhn rng khi lng sn xut. Qu trnh tnghp ht nano Fe3O4 c thc chuyn sang Ht nano -Fe2O3 mt cch d dng bi

nhit cao (250o C) v xy ha trong 2 h.

Thng thng, s phn hy ca n tin cht Fe (Cup)3 c th dn n -Fe2O3

n phn tn [25]. S phn hy nhit ca Fe(CO)5 sn xut Ht nano st vi cc qu

trnh oxy ha theo sau ca cc ha cht cng c th to ra ht nano -Fe2O3n phn tn

[26].V d, Hyeon bo co v vic tng hp ht nano st n phn tn, kt tinh cao,

khng cn la chn kch thc bngphng php phn hy nhit ca pentacarbonyl st

c s hin din ca axit oleic 1000C. Ht nano st to thnh c chuyn ha to

thnh monodispersed nanocrystallites -Fe2O3 bi qu trnh oxy ha c kim sot bng

cch s dng nh l oxit trimethylamine mt cht xi ha yu. ch thc ht c th

thay i 4-16 nm bng cch kim sot cc thng s thc nghim.[11]

Mc d ccphng php phn hy nhit c nhiu thun li cho sn xut ht c

n phn tn cao vi mt phn b kch thc hp, nhng bt li ln ca phng php lHt nano to thnh ni chung ch ha tan trong dung mi khng phn cc.

1.4.3. Vi nh tngVi nh tng l s phn tn ca 2 pha bn vng nhit ng v khng tan vo nhau

(du v nc) di s c mt ca cht hot ng b mt, cc cht hot ng b mt c

th to thnh 1 lp ngn cch gia 2 pha, vi u knc hng v pha du v a nc

hng vpha nc.Nh trong h hai cht (nc / surfactant hoc du / surfactant), s t

sp xp ca cc cu trc khc nhau c thc hnh thnh, rt khc bit, v d, t micelle

hnh cu v hnh tr n dng tm mng v bicontinuous microemulsions (h vi nh

tng 2 pha lin tc), c th cng tn ti vi pha du hoc pha nc [28]. Do ,

8/2/2019 ~WRL1193

12/23

microemulsion v inverse micelles route c thc s dng khng ch hnh dng v

kch thc oxit st Ht nano.[10]

Hnh 1.24 :Hvi nh tng trong du v trong nc[19]

Hnh 1.25: C chhnh thnh Ht nano bng Microemulsion[10]

c bit, nc trong du (w / o) microemulsions c hnh thnh bi nanodroplets

c thit lp trong pha nc, phn tn bi vic sp xp ca cc phn t cht hot ng

b mt trong pha du. Vidal-Vidal [28] bo co tng hp ht nano maghemite n

8/2/2019 ~WRL1193

13/23

phn tn biphng php onepot microemulsion. Cc ht hnh cu, ph mt lp n ca

oleylamine (hoc oleic acid), c phn bkch thc hp l 3,5 0,6 nm, kt tinh tt v c

gi tr t ha bo ha cao gi tr (76,3 Am2/kg cho Ht nano khng trng, 35,2 Am2/kg

cho Ht nano trng oleic acid, v Am2

/kg 33,2 cho Ht nano trng oleylamine). Hn na,kt qu cho thy oleylamine ng vai tr tc nhn ng kt ta v che ph. Tuy nhin,

cyclohexylamine chng vai tr tc nhn kt ta v khng ngn c s tp hp ca ht

thnh cm ln. Chin v Yaacob bo co tng hp oxit st t Ht nano (nhhn 10 nm)

thng qua w / o microemulsion, hn na, khi so vi cc ht c sn xut bi phng

php ca Massart, ht sn xut bng k thut microemulsion c kch thc nhhn v

c gi tr t ha bo ha cao hn.[11]

Tuy nhin, bt chp s hin din ca cht hot ng b mt, cc tp hp ca Ht

nano to thnh cn phi qua cc qu trnh ra v xl n nh hn.

1.4.4. HydrothermalHt nano st oxit c kch thc v hnh dng kim sot c c tnh quan trng

trong cng ngh do stng quan mnh m gia cc thng skch thc v tnh cht t.

Microemulsion vphng php phn hy nhit thng dn n qu trnh cng ngh phc

tp hoc yu cu nhit tng i cao. thay th, hydrothermal bao gm nhiu k

thut wetchemical nhm lm kt tinh sn phm trong mt b kn t dung dch vi nc

nhit cao (thng thng trong khong 130-250 C) vi p sut hi cao (thng trong

khong 0,3-4 Pa). K thut ny cng c s dng pht trin tinh th ht khng c sai

lch (dislocation-free single crystal particles ) v ht c hnh thnh trong qu trnh ny

c th c tnh tinh th tt hn so vi sn phm t cc qu trnh khc, do tng hp

hyrdothermal dc c nhng tinh th st oxit Ht nano c tnh tinh th cao.[11]

Mt s tc gi bo co tng hp cc Ht nano oxit st bngphng php thy

nhit [29,39,31,32]. C hai phng php chnh ty theo vic c s dng hay khng s

dng cc cht hot ng b mt c trng. V d Wang bo co phng php

hydrothernal mt giai on tng hp nano Fe3O4 (40nm) 40 C trong 6h, sn

8/2/2019 ~WRL1193

14/23

phm c t ha bo ha 85.5 emu g-1 hi thp hn so vi gi tr ca pha bulk (92 emu

g-1

). Ng ta cho rng s kt tinh tt ca ht Fe3O4 hnh thnh trong iu kin x l

hydrothermal c th l nguyn do ca vic gia tng t ha bo ha trong ht Ht nano.

Ngc li, Zheng cng b mt qu trnh hydrothermal tng hp Ht nano Fe3O4 vibn knh 27nm vi s hin din ca cht hot ng b mt sodium bis(2-

ethylhexyl)sulfosuccinate (AOT). Tnh cht t ca ht Ht nano th hin tnh siu thun

tnhit phng.[11]

Hn na, x l hydrothermal l mt trong nhng cch thnh cng pht trin

tinh th Ht nano st oxide. Gn y Daou [33] bo co v vic ht magnetie c kch

thc trung bnh 39nm v tnh n phn tn tt c tng hp bng phng php

ng kt ta 70 C t ion st II v st III trong dung dch N(CH3)4OH, tip bi qu

trnh x l hydrothermal 250 C. Ht nano magnetite trc khi x l hydrothermal c

kch thc trung bnh 12nm rt d b oxy ha khi tip xc vi khng kh. Thm vo

tng hp hydrothermal rt d to ra cc oxide st c cu trc nano bt thng nh

nanocube oxide st, hollow sphere oxide st[11]

1.4.5. SonochemicalL mt phng php c tim nng thay thcc phng php c sonochemical

c s dng rng hn trong vic tng hp vt liu l tng c nhng tnh cht c bit.

nh hng ha hc ca sng siu m bt ngun t vic to bt do m ngha l vic to

thnh, pht trin, v vra trong dung dch. S vca bong bng to ra mt im cc b

thng qua qu trnh nn ng nhit v hnh thnh sng xung kch trong pha kh ca bt

kh b v. V iu kin ta thnh nhng im nng (hotspot) ny c xc nh bng

thc nghim , 5000K trong thi gian ngn, p sut 1800atm, v tc lm ngui 1010

K/s. Nhng iu kin kht khe ny l cn thit to ra pha mi, c dng to Ht

nano c tnh n phn tn cao nhng c hiu ng ph l gy kt t cc ht.[11]

Phng php ny c p dng tng hp nhiu loi nanocomposite khc nhau

[34], bi tnh linh hot c chng minh trong vic tng hp ht nano st oxide. Do

8/2/2019 ~WRL1193

15/23

magnetite Ht nano c thc tng hp n gin bng vic chiu siu m vo st

(II) acetate trong nc di kh quyn Argon. Vijayakumar bo co mt phng php

tng hp sonochemical tng hp ht Ht nano Fe3O4 tinh khit vi kch thc ht

10nm. Ht nano Fe3O4c tng hp bng phng php ny c tnh siu thun tv t ha nhit phng l rt thp (

8/2/2019 ~WRL1193

16/23

Hnh 1.26: Tng hp cc cu trc khc nhau bng sonochemical[10]

1.4.6. Sol-gelSol-gel l mt k thut tin dng tng hp vt liu nano dng ht c tnh cht

quang v tc bit. K thut sol-gel da trn qu trnh phn ng polymer ha v c

bao gm thy phn a t, sy kh v phn hy nhit. Cc tin t (precursors) ca

alkoxide kim loi hoc phi kim c thy phn trong nc hoc cn ty theo phn

ng.[10]

M(OR)x + mH2OM(OR)xm(OH)m + mROH (A)

Khi mx, phn ng thy phn hon ton, sn phm ph c thl nc

2M(OR)xm(OH)m (OH)m1(OR)xm-M-O-M(OR)xm(OH)m1 + H2O (B)

8/2/2019 ~WRL1193

17/23

Hoc ru

2M(OR)xm(OH)m (OH)m1(OR)xm-M-O-M(OR)xm1+ROH(C)

Phng trnh c th vit li thnh

M(OR)x + x/2H2O MOx/2 + xROH (D)

Ngoi nc v ru, c th c thm acid hoc base lm tng s thy phn ca

tin t. Trong trng hp acid, s xy ra phn ng gia alkoxide v acid.

-M-OR + AOH -M-O-A + ROH (E)

Vn tc thy phn v ngng t l nhng thng s quan trng nh hng n tnhcht ca sn phm sau cng. Qu trnh thy phn chm v c kim st tt thng dn ti

ht nh v tnh cht tt hn.[10,12]

Sau khi dung dch ngng t to thnh gel, dung mi phi c tch ra. Thng,

nhit nung cao l cn thit phn hy cc tin cht hu c.[35]Kch thc ca ht sol ph thuc vo thnh phn dung dch, pH v nhit . Bng

vic kim sot cc tc nhn ny, ng ta c th iu chnh kch thc ca sn phm.

Phng php ny c thc hin thnh cng vi rt nhiu Ht nano oxide kim loi

nh TiO2, UO2, TnO2, ZrO2, CeO2, SnO2, SiO2, CuO, SnO2, ZnO, Al2O3, Sc2O3, ZnTiO3,

SrTiO3, BaZrO3, CaSnO3, v cc vt liu nano khc.[10]

S sp xp t tnh trong h sol-gel ph thuc khng ch vo cc pha to thnh m

cn vo phn th tch ca cc ht nhng s sp xp ny cng c bit nhy vi s phn

b cht v s phn tnca ht. trong trng hp nanocomposite t gel, nhng thng s

cu trc v rng ca vt liu, nhng thng sng ny c lin h vi nhau, c quyt

nh bi tc thy phn v ngng t ca tin cht gel (thng l 1 alkoxide) v ca

phn ng oxy ha gim cp trong qu trnh gel ha v cc giai on x l nhit sau

ny.[36]

8/2/2019 ~WRL1193

18/23

Ngoi cc phng php tng hp trn, ng ta cn pht trin thm nhiu phng

php khc nh Chemical Vapor Condensation (CVC), Arc Discharge Method, Laser

Pyrolysis Microbial Synthesis Ball Milling Method Cc phng php ny c pht

trin to ra cc ht Ht nano oxide kim loi nhng cc ng dng thin v Ht nanooxide st th vn cn hn ch.[10,11]

3. Phng php to hybridC rt nhiu phng php to hybrid nhng chia lm hai nhm chnh l insitu v exsitu.

3.. Phng php Ex Situ Covalent Interactions Noncovalent Interactions - Stacking

Electrostatic Interactions

3.2. Phng php In SituTrong phng php ny cc hp cht v c hnh thnh trc tip ngay trn b mt CNTs

th hoc bin tnh. Phng php in ha Phng php ng kt ta t dung dch: tp trung tm hiu:

MWCNT/oxit st tc ch to theo c ch sau:

- Trc khi ch to MWCNT/oxit st tMWCNT c bin tnh b mt vi hnhp axit nhm to cc im mang in tch m trn b mt thng qua cc nhmchc COO-.

- Sau khi phn tn MWCNT bin tnh vo hn hp tc cht, mt phn cc ionst hp ph trn b mt MWCNT thng qua cc nhm chc COO-.

- NH4OH c thm vo v phn ng ng kt ta to ra cc ht nano oxit st ttrn cc mm hnh thnh trn bn mt MWCNT.

Ta chn phng php ch to da trn nguyn tc ng kt ta hai mui st v:- y l phng php n gin nht to ht oxit st t

8/2/2019 ~WRL1193

19/23

- C th khnng to ra ht nano oxit st tc kch thc nh- Phng php c khnng to ra khi lng sn phm ln C chng kt ta:

Fe3+ + H2O -> Fe(OH)x3-x (thng qua qu trnh mt proton)

Fe2+

+ H2O -> Fe(OH)y2-y

(thng qua qu trnh mt proton)

Fe(OH)x3-x

+ Fe(OH)y2-y

-> Fe3O4 (thng qua qu trnh xi ha v dehydride ha,pH > 9, nhit 60)

- Tng hp cc phn ng trn chng ta c phng trnh sau:Fe

2++ 2Fe

3++ 8OH

-= Fe3O4 + 4H2O

Nu c xi th magnetite b xi ha thnh hdroxide theo phn ng:Fe3O4 + 0,25 O2 + 4,5 H2O-> 3Fe(OH)3

Phng php sol-gel4. Phng php nh gi

- nh gi cu trc hybrid: IR (xc nh nhm chc) XRD (xc nh cu trc tinh th),SEM (cu trc b mt), TEM, ph RAMAN (t lcng nh cht lng CNTs)

- nh gi tnh cht: BET(b mt ring) v VSM (tnh cht t)5. Quy trnh thc nghim to hybrid bng phng php dung dch

Bao gm hai giai on chnh l chc ha MTWCNTs v ch to vt liu hybrid.5.1Chc ha MTWCNTs :

Vi mc ch lm gim lin kt van der Waals gia cc ng CNTs v trnh trnghp kt b cng nh lm tng khnng phn tn trong nc v trong cc dung mihu c phc v cho nhiu mc ch bin tip theo

Bin tnh b mt CNTs bng hn hp axit l phng php n gin to nn ccnhm chcCOOH thng qua cc sai hng trn b mt CNTs c bit l hai ucui ca ng CNTs.

- Nguyn liu: MWCNT, HNO3 (65%), H2SO4 (96-98%)

MWCNTs

HNO3/H

2SO

4

Lc ra, sy

Dung dch phn ng

MWCNTs-COOH

8/2/2019 ~WRL1193

20/23

- Phn ng tin hnh trong bnh cu 3 c c h thng cnh khuy nhm m bo trongqu trnh phn ng dung dch lun c trn u

- u tin cn lng tc cht theo t l chn (t l gia MWCNT v hn hp acid l1g/400ml)

- Trn v phn tn MWCNT trong hn hp axit c bng sng siu m trong 1h.- Sau tin hnh gia nhit hn hp phn ng ln 70oC trong 3h.- Sau khi phn ng xong tin hnh qu trnh lc ra bng h thng lc chn khng vi

giy lc PTFE ng knh l 0.45 m. Lc ra nhm loi b phn cacbon v nhhnh v hn hp axit m c.

- Phn gia li trn giy lc c em sy chn khng 80oC trong 3h loi b honton H2O. Sn phm thu c cui cng l MWCNT c bin tnh.

Phng php nh gi Mc tiu

IR Phn tch xc nh s hin din ca nhm chc COOHtrong mu MWCNT sau khi c bin tnh.

Raman nh gi tnh khit ca mu MWCNT th v MWCNT bin tnh. ng thi nh gi s tn ti ca dao ngc to ra t cacbon c lai ha sp3.

XRD Cu trc tinh thTGA nh lng s b qu trnh chc haBET nh gi sthay i b mt ring khi chc ha

5.2Quy trnh ch to hybrid MWCNT/oxit st t Mc tiu Sn phm: Vt liu hybrid MWCNTs/ Fe3O4vi:

Din tch b mt ring:150-200m2/g Tnh cht t:

+ T bo ha: Ms=20-30 emu/g+ Lc t khng: Hc= 35 Oe

Quy trnh:

8/2/2019 ~WRL1193

21/23

- Cn FeCl2, FeCl3, MWCNT/COOH theo t lmol nh trc: Kho st t l gia FeCl2,

FeCl3 cho ph hp sao cho lng oxit st t to ra l ti a ng thi t l vi CNT choph hp vi s nhm chc trn b mt CNTs. (T l l thuyt l :2 nhng theo mt sthc nghim cho l t l nhhn :.5:.75 :2 :2.25 sao cho Ms l ti a.

- T l ca ion Fe so vi MWCNT ph thuc vo t l nhm chc trn cht ny.- Ha tan hn hp mui cn vo nc ct ng thi cho HCl vo sau cho dung dch sau

cng c nng HCl nh trc. HCl c cho vo dung dch ban u nhm hn chphn ng oxi ha st II thnh st III

Kho st nng HCl sao cho phn ng oxy ha Fe2+ khng xy ra ng thi khng qud nh hng n tnh cht ca CNTs. Kho st XRD xem c s c mt ca Fe2O3

hay khng? (XRD v VSM)- Dung dch c nh siu m trong khong 1 ginhm phn tn u MWCNT/COOH

trong dung dch phn ng. ( Kho st thi gian nh siu m ti u). o kch thc camu nano st t.

- Tip tc nh tng git NH4OH vo dung dch trn tin hnh phn ng, tc nh 3giy/git. Dung dch phn ng c khuy trn u trong qu trnh thc hin phn ngtrong mi trng khng kh v nhit phng. Kho st tc nh NH4OH.

MWCNT/COOH

FeCl2, FeCl

3,

HCl

NH4OH

Siu m

Ra, sy

Dung dch 1

Dung dch 2

MWCNT-oxit stt

Khuy trn

8/2/2019 ~WRL1193

22/23

- Lin tc chun pH trong qu trnh phn ng v dng phn ng khi pH t gi tr nhtrc trong khong (910) ( Kho st chnh xc gi tr pH sao cho tnh cht sn phm ttnht). Thng s tc trng.

- Tin hnh ra vi nc v cn kt hp lc chn khng loi b cht cn d li sau qutrnh phn ng.

- Sy chn khng 80oC trong 2h nhm loi ht dung mi. (Sy n khi lng khngi)Cc phng php phn tch nh gi sn phm

Phng php nh gi Mc tiu

SEM Quan st hnh dng v kch thc ht nano oxit st tBET nh gi kch thc ht mu nano oxit st t to thnh

thng qua kt quphp o din tch b mt ringVSM Xc nh cc thng s tc trng ca mu nano oxit st

t (MS, HC).TGA

TEMChng minh s hnh thnh MWCNT/ nano oxit st t

Em ngh cn c bc kho st ring qu trnh ng kt ta to oxit st t tm ra cciu kin v nng v nhit phn ng ti u. Sau mi p dng quy trnh trnMTWCNTs.

Ngoi ra, trong qu trnh to hybrid st t em cha tm c phng php kim sotc tng giai on m ch c th kim tra tnh cht sn phm cui cng ca qu trnh.

2- Trong phan thuc nghiem: Can liet ke cac dieu kien Khao sat ro rang hon va cac PP

danh gia (dua vao tinh chat can khao sat)

3- Cac phan Ly thuyet co ban deu co tren mang

4- Keywords: CNT electrical, CNT properties; Radio Absorbed Materials;

electromagnetic Absorbing .... magnetic nanoparticles

5- Neu co che cua phan phan ung dong ket tua

Em co the viet PPT va sau do chung ta se bao cao

The size and

shape of the nanoparticles can be tailored with relative success by adjusting pH, ionic

strength, temperature, nature of the salts

8/2/2019 ~WRL1193

23/23

(perchlorates, chlorides, sulfates, and nitrates), or the Fe(II/Fe(III) concentration ratio.