AEROGEL-SILICA V NG DNG

AEROGEL-SILICA V NG DNGGVHD:PGS.TS Nguyn Ngc Hnh

KHOA K THUT HA HCTRNG I HC BCH KHOA TP. H CH MINHTIU LUN

AEROGEL-SILICA V NG DNG

MC LC

31.Gii thiu silica-aegogel

31.1.nh ngha:

31.2.Lch s:

31.3.Phn loi silica-aerogel:

41.4.Sn xut:

52.Synthesis of Aerogel by Sol-Gel Process

52.1.Sol gel process

62.2.Ha hc ca qu trnh Sol-Gel

72.3.Tin cht ca qu trnh Sol-Gel.

72.4.C ch phn ng:

82.4.2.Nc ha tan silica v khong sn: (Water Soluble Silicates and Minerals).

102.4.3.B mt a nc v k nc (Hydrophilic and Hydrophobic Surfaces):

112.4.4.Lm kh aerogel (Drying of Alcogel):

122.4.5.Sy kh siu ti hn ca aerogel:

122.4.6.mi trng p sut Sy kh v Thay i b mt ha hc.

132.4.7.ng bng kh:

153.ng dng:

204.THAM KHO

1. Gii thiu aegogel

1.1. nh ngha:

L vt liu tng hp c ngun gc t mt loi gel trong thnh phn cht lng ca gel c thay th bng mt loi kh. Kt qu lm cho gel c t trng thp v cch nhit. N cn c cc tn gi sau: khi ng bng, khng kh rn, khi rn. Do tnh cht m v phn tn nh sng trong vt liu nn trong ging nh polyetilen b p li thnh mt khi.1.2. Lch s:

Cng ging nh cc loi truyn thuyt m bn tng c khc, truyn thuyt v Aerogel kh b n v th v. Tt c nhng g m chng ta bit l vo cui nhng nm 1920, gio s ha hc ngi M c tn Samuel Kistler (1900 - 1975) c mt cuc c vi ng nghip ca mnh l Charles Learned. Kistler tin rng s tn ti mt loi gel khng lng (mt c tnh c hu ca gel) vi mt cu trc v cng c bit, l mng li cc l rng v cng nh c gi l nanopore.

Sau khi th nghim v gp nhiu tht bi, cui cng th Kistler tr thnh ngi u tin thay th c trng thi lng ca gel thnh trng thi kh to ra mt loi gel mi khng tn ti trng thi lng. Vo nm, 1931, ng cng b pht hin ca mnh trong bi vit "Coherent Expanded Aerogels and Jellies", ng trn tp ch khoa hc Nature.1.3. Phn loi Aerogel: C ba loi Aerogel ph bin nht hin nay l silica, carbon v oxit kim loi, tuy nhin trong th nghim ln thc t th silica vn thng c s dng hn c. Khi nhc n Aerogel, rt c th ngi ta ang m ch n loi silica. Cc bn cng khng nn nhm ln gia silica v silicon, silica (silic ixt) l loi vt liu ch yu sn xut ra thy tinh cch nhit cn silicon l mt cht bn dn dng trong cc vi mch.

Khng ging nh silica aerogel vi bit danh l khi xanh hay khi lnh, khi rn (do hnh th m o ca n), carbon aerogel c mu en v khi s ln c cm gic ging nh ang s ln nhng hn than. Chng c din tch b mt ln, xp cao v kh nng dn in tt. Cc tnh cht ny lm cho aerogels carbon rt hu ch i vi t in, pin v h thng kh mui.

Aerogel oxide kim loi lm t xt kim loi v s dng nh l cht xc tc trong cc phn ng ha hc. Chng cng c ng dng trong ngnh cng nghip thuc n, si nano carbon v thm ch l to ra t tnh. Aerogel oxit kim loi nh st hay crom ngoi cc tnh cht tng t ngi anh em silica ph bin th chng cn c mt im khc, l mu sc rt p. Aerogel crom c mu xanh l cy hoc xanh dng rt m; Aerogel oxit nhm, titania, zirconia c mu xanh hoc trng; Aerogel oxit st c mu hoc vng c; ngoi ra cn c mu tm hoa oi hng, mu vng sng, mu hng pht... Mi loi oxit kim loi s to ra mt loi mu khc nhau.

Aerogel silica c mu xanh da tri, mu ny c to ra khi cc nh sng trng gp cc phn t silica ca aerogel v xy ra hin tng tn x (Rayleigh). Cc phn t s tn x nh sng, nhng tia sng c bc sng ngn th b tn x d dng hn so vi sng di. Bi v mu xanh v mu tm c bc sng ngn nht nn chng d b tn x hn cc nh sng c th nhn thy khc. Mt khc, do mt ngi nhy cm vi cc bc sng mu xanh lam hn nn chng ta s khng th nhn thy c mu tm.

1.4. Sn xut:

Aerogel c sn xut bng cch ly thnh phn lng ra khi gel bng k thut kh siu ti hn. iu ny cho php cht lng c lm kh t t m khng gy ra hin tng sp vt liu. Aerogel u tin c sn xut t silicagel

Aerogel bt u xut hin nh mt loi gel v c gi l Alcogel - ci tn ny m ch gel silica (Silic ixt) v cc phn ti ru (Alcohol) nm bn trong cc l rng ca n. V c bn, ch cn cho ru bay hi khi silica l chng ta s to ra cu trc ny, ging nh chng ta thi khng kh qua mt ming bt bin thm nc vy, n s b kh i. Thay v ch da trn s bc hi, gel kh siu ti hn (Supercritically) c ch to qua cc cng on nh sau:

Nhit v p sut phi t n im siu ti hn - mc m khng c s khc bit gia cht lng v cht kh.

Gim p sut trong khi nhit vn trn im ti hn. Khi p sut gim, cc phn t c gii phng di dng kh v lng vi mt khng dy c

Kh gel bng ngun nhit. Trc khi lm lnh, s c mt lng ru nh c ngng t li thnh cht lng, sau s c chuyn thnh dng hi nh ban u.

Kim tra thnh phm cui cng. Nhng g cn li s l mt cht rn bng silica, nhng thay v dng lng th n li cha y khng kh.

im siu ti hn s lm kh cc cht lng alco khin mt phn ca alcogel bin thnh kh, trong khi cu trc l rng ca silica vn khng b sp . Acogel sau khi b kh ru s c gi l Aerogel (ru b thay th bng kh). Gim 50 n 99% khi lng ban u, Aerogel l loi vt liu nh, linh hot v rt hu dng.

2. Tng hp Aerogel bng phng php sol-gelQu trnh sol-gel l mt phng php rt ph bin v ng tin cy tng hp vt liu, c bit l cc oxit kim loi vi s ng nht kch thc ht nh, v hnh thi a dng [5-10]. N lin quan n qu trnh chuyn i ca mt h t pha lng "sol" thnh pha rn "gel".Qu trnh sol-gel thng thng c th c chia thnh cc bc sau: hnh thnh dung dch, c lai, gi gel, kh, v c c. Mt vi nhng u im quan trng ca qu trnh sol-gel l s n gin ca n, v thc t l n l mt bin php kinh t v hiu qu ca sn xut vt liu cht lng cao. qu trnh sol-gel c ng dng trong sn xut knh cht lng cao cho cc thnh phn quang hc v si, lp ph mng mng, v bt oxit tt [11-15]2.1. Qu trnh sol gel: Qu trnh Sol-gel c ngha l s tng hp mt mng li v c ca mt phn ng ha hc trong dung dch nhit thp hoc s hnh thnh ca mt mng li v nh hnh i nghch vi kt tinh t dung dch. c im r rng nht ca phn ng ny l s chuyn i t mt dung dch keo (cht lng) sang mt hai -hoc a pha gel (rn) dn n khi nim "qu trnh sol-gel".

S hnh thnh huyn ph ng nht ca cc ht keo th c hiu theo tnh ton tc lng gi nh rng cc ht c hnh cu p dng nh lut Stokes . Tc lng l

= nht ca mi trng xung quanh, r = bn knh ca ht keo, = mt vt liu ht keo, v = mt vt cht bao quanh.

R rng hn, mt sol l huyn ph dng keo ca cc ht rn trong mt cht lng trong pha phn tn nh (1-1000 nm). V vy, lc hp dn l lc khng ng k v khong cch ngn, chng hn nh lc ht van der Waals v in tch b mt, chi phi cc tng tc. qun tnh pha phn tn l nh n th hin chuyn ng brown, mt bc di chuyn ngu nhin c truyn bi va chm vi cc phn t ca mi trng huyn ph. Sol c th c tng hp bi 2 k thut, phn tn v ngng t ca cc htGel ha l qu trnh m mt sol chy t do c chuyn i thnh mt mng li rn 3D m mi trng dung mi bao quanh. Mt loi gel l mt giu na rn trong cht lng. Tht th v khi cht lng m khng cho php cc mng li rn sp , v cc mng li rn khng cho php cht lng chy ra ngoi [17] im bt u ca gel ha thng c xc nh bi mt s gia tng t ngt v nht v p ng n hi n sc cng. (The point of gelation is typically identified by an abrupt rise in viscosity and an elastic response to stress.). Tng hp aerogel, s gel ha thun tin nht gy ra thng qua mt s thay i trong pH ca dung dch phn ng. Trng thi c hc ca gel ph thuc rt nhiu vo s lng cc lin kt trong mng. R rng l ln hn cc mc lin kt ngang, cng hn cu trc c hnh thnh.

2.2. Ha hc ca qu trnh Sol-Gel

C mt s thng s nh hng n phn ng thy phn v ngng t (qu trnh Sol-Gel), bao gm hot ha ca alkoxide kim loi, t l nc/alkoxide, pH dung dch, nhit , bn cht ca cht tan, v cht thm vo. Mt quan tm khc na l cht xc tc thng c thm vo kim sot thnh phn v mc ca thy phn v ngng t . Bng cch thay i nhng thng s qu trnh ny, vt liu vi nhng vi cu trc khc nhau v b mt ha hc c th thu c. Vic x l tip na l sol, c th tng hp c nhng vt liu ceramic nhng dng khc nhau. Nhng tm phim mng c th c sn xut trn cht nn bng phng php spin coating v dip-coating. Khi m sol c cast vo khun, gel t s hnh thnh. Vi vic lm kh v gia nhit tip theo , gel s c chuyn ha thnh ceramic c hoc l cc ht thy tinh. Nu cht lng trong gel t c loi b di iu kin siu ti hn, mt vt liu cc k xp v mt cc k thp gi l aerogel thu c. Bng chng ca thy phn silicate v ngng t hnh thnh polysilicate gel v phn t c thy trong nhiu h thin nhin nh opals v agates. Alkoxide kim loi u tin c tng hp t SiCl4 v alcohol bi Ebelman, ngi tm ra hp cht gel li di p sut kh quyn v Si-(OC2H5)4 c th c xem nh l t tin cho vt liu thy tinh.

2.3. Tin cht ca qu trnh Sol-Gel.

Tin cht l nhng vt liu u tin cho qu trnh sol-gel.

1/. Cc tin cht c th ha tan c trong mi trng phn ng.

2/. Chng phi nng ng tham gia vo qu trnh hnh thnh gel.

Mt s mui, oxide, hydroxides, complexes, alkoxides, acylates, v amines c s dng nh tin cht nu ha tan c trong dung mi thch hp. Alkoxide l nhng tin cht sol-gel thng dng nht , bi v chng lc no cng c sn. Bradley v nhng cng s gii thch ha tnh c bn ca tin cht. Nht l d on loi tin cht s dng cho mc ch c th. phn ng ca tin cht khng ch ph thuc vo cu trc ha hc m cn ph thuc vo iu kin phn ng. So snh vi tin cht ca nhng cht khc, nng lng to thnh mng ca Si th cao to thnh mt dng gel. l ti sao nhng tin cht alkoxide t tin khc c th c thay th bi nhng tin cht khc r hn nh l silicon alkoxide (TEOS, TMOS) v nhng tin cht c th tan trong nc nh Na2SiO3 cho qu trnh sol-gel.

Aerogels k nc c thu t tin cht m khng c s iu chnh v phng din ha hc c gi l tin cht hydrophobic (k nc), v i vi hydrophilic (a nc) th gi l tin cht hydrophilic nh bng 1.

2.4. C ch phn ng:2.4.1. i vi Silicon Alkoxide.

silica gel c tng hp bng cch thy phn tin cht monomer tetra hoc tri silicon alkoxide bng axit v c ( HCl, C2O4H4) hoc bazo ( NH3, NH4OH) nh l mt cht xc tc. Cc phn ng sol gel xy ra trong s hnh thnh mng li silica [25,26]

S thy phn:

S ngng t:

2.4.2. Nc ha tan silica v khong sn: (Water Soluble Silicates and Minerals).Natri silicat (Na2SiO3) , ang v c th s lun lun th l ngun vt liuvi gi r nht ca axit silixic tng i tinh khit m t silica gel c th c tng hp. Silicat natri phn ng vi nc cung cp axit silixic v sau l axit silixic polymerizes v to silica gel nh trong cc phn ng sau y:

Cc axit silixic ngng t to thnh cc ht silica nh, cc chui v do to thnh mt mng li dn n lng silic ioxit gel nh hnh di y.

Hn na, c mt s bo co c sn v tng hp silica gel s dng nhm, canxi silicat, wollestonite, v vv [27-29].

N l iu hin nhin t cc phn ng (2) - (5) rng cu trc ca sol-gel thy tinh pht trin lin tc l sn phm ca k tip phn ng thy phn v ngng t (v ngc li phn ng, tc l, este ha v cn hoc thy phn -kh trng hp) [15]. V vy, kin thc v c ch v ng hc ca cc phn ng ny s cung cp ci nhn su sc v gel v gel c ngun gc t thy tinh.

Phn ng thy phn c xc tc bi vic b sung mt axit hoc mt bazo [29]. Trong thc tdng cui cng ca thy phn silica ph thuc vo pH ca dung dch. mc pH thp (c tnh axit cao), cc ht silica c xu hng to thnh mt chui thng vi mt lin kt ngang thp. iu ny dn n mt gel mm, l o ngc v c th c phn tn li trong dung dch. Nh gi tr pH tng ln, s lng qua cc lin kt gia cc polymer cc chui cng tng. pH cao (rt bazo), cc polymer tr nn phn nhnh nhiu v s lng lin kt ngang tng ln. pH thp, thy phn xy ra bi s tn cng lc in t vo cc nguyn t oxy ca nhm alkoxit, trong khi pH cao , thy phn v trng hp xy ra bi i nhn tn cng vo ion Si (Si4 +). Nguyn t, ion, hoc nhm m c i lc mnh m i vi cc in t c gi l cc ion, trong khi cc ion dng c gi l nucleophiles. Ni chung, tt c cc ion l cc tc nhn oxy ha v tt c nucleophiles l cht kh.

Qu trnh gel ha vi cc nhm nh hn ha tan v ti kt ta vo cc chui ln hn cc phn t nh hn gim trong s nhng s h tr ca cc phn t ln hn pht trin cho ti khi chng tp hp thnh dng fractan. Qu trnh ny c gi l s chn mui (nh tng) Ostwald [30].2.4.3. B mt a nc v k nc (Hydrophilic and Hydrophobic Surfaces):

Tn k nc Hydrophobic v a nc Hydrophilic pht sinh t s kt hp ca "thy - hydro", c ngha l nc trong ting Hy Lp, "phobos" c ngha l "ght" trong ting Hy Lp, v "philic" c ngha l "yu thng" trong ting Hy Lp. Nhng thut ng m t lc y r rt v lc ht gia nc v b mt. Nh th hin trong

Hnh 1, a nc hay k nc c phn bit vi cc gi tr ca gc tip xc: nh hn hoc ln hn 90 .

Bng 1: Cc tin cht tng hp silica aerogel

Khi nng lng b mt ca rn l thp, n khng thm nc t b mt ca n v ngc li, cho thy s k nc hoc a nc. Hin nay, cc b mt k nc c s dng trong ngnh cng nghip cho mt lot cc ng dng bao gm cht ph k nc cho chng r st, loi b du ra khi nc, qun l s c trn du, v cc qu trnh tch ha hc tch ring cc hp cht khng phn cc v c cc. tng hp ca aerogel k nc v a nc, hai bc chnh l lin quan n: (a) tng hp alcogel bng qu trnh sol-gel v (b) lm kh ca alcogel bng cc k thut khc nhau.

2.4.4. Lm kh aerogel (Drying of Alcogel):

Sau khi hnh thnh gel bng cch thy phn v phn ng ngng t, mt mng li Si-O-Si c hnh thnh. S lo ha l thut ng ch tng cng mng li gel, n c th lin quan n ngng t thm, ha tan, ti kt ta ca ht sol, chuyn pha trong cht rn hoc pha lng. iu ny dn n mt cht rn xp trong dung mi b mc kt. Qu trnh loi b phn ln dung mi t gel (m trong trng hp ca mt alkoxit c ngun gc t gel ch yu l cn v nc) c gi l sy kh. Trong qu trnh sy kh, nt mng gel xy ra do lc mao dn c hnh thnh trong cc l rng tt bi mt phn cch ca hi nc. Phng trnh Laplace c p dng trong trng hp ny, khi bn knh mao qun cng nh, cht lng s dng lncao hn, hoc p sut thy tnh s cao hn. v vy nng lng b mt chu trch nhim cho s gia tng ca ct cht lng trong mt mao qun, ln ca p sut mt phn cch trong mt mao mch c th c tnh bng cch cn bng cc lc tnh l,

ng knh ca cc l rng trong gel l nm, m cc cht lng gel phi tc dngp lc thy tnh cao. Cc mt khum trong cc l rng v cc sc cng b mt c gng ko cc ht vi nhau khi cht lng trong cc l rng bc hi. Cc lc lng ny c th hot ng trong mt cch m chng c gng ng tp hp l rng, sau l cu trc. Nh vy, gel vi cc l rt tt c xu hng nt gy v thu nh trong qu trnh sy. trnh ng sut sy kh ny Kistler m t qu trnh tng hp u tin ca mt aerogel bi sy kh siu ti hn trong u nhng nm 1930 [31], v cc qu trnh tng hp aerogel khc nhau c bo co t .Trong nhng nm 1970, silica aerogel c tng hp bng cac1ch sy kh siu ti hn nhit cao ca mt loi gel t c tng hp t qu trnh thy phn TMOS trong methanol [32]. trong nhng nm 1980, cc nh nghin cu t c mt hiu bit mi v tim nng ca aerogel, v silica da trn Teos, tng hp t tn km v t c hi hn so vi TMOS. Qu trnh sy siu ti hn nhit thp, s dng CO2 lng c p dng.[33]2.4.5. Sy kh siu ti hn ca aerogel:

Trong phng php sy kh siu ti hn, gel c sy kh mt im ti hn loi b cc lc mao dn, nh m t di y. Ngay sau khi cht lng bt u bc hi khi gel, sc cng b mt to ra mt khum lm trong cc l rng ca gel. Khi s bay hi ca cht lng tip tc, lc nn hnh thnh xung quanh chu vi ca l rng v n co rt li Cui cng, sc cng b mt gy ra s sp ca thn gel [34]. ngn chn sc cng b mt hnh thnh, gel c sy kh siu ti hn trong mt ni hp, nh th hin trong hnh 2.

Khi nhit v p sut trong ni hp ang tng trn mt im ti hn (cho nhit ti hn methanol v cc gi tr p sut ti hn 243 C v 7.9MPa, resp.), Cht lng c chuyn ha thnh mt cht lng "siu ti hn", trong mi phn t c th di chuyn t do v sc cng b mt chm dt. Nu khng c sc cng b mt, mt khum khng hnh thnh. Cc hi c sau t t thot ra khi ni hp, cho n khi p sut trong ni hp t n p sut kh quyn. Cui cng, ni hp c ra bng nit kh (~ 3bar) loi b cc phn t dung mi b mc kt t gel kh. Phng php sy kh ca alcogels c gi l "sy kh siu ti hn". Hnh 3 cho thy chu k nhit p sut sau khi sy siu ti hn ca alcogels.

2.4.6. Mi trng p sut Sy kh v Thay i b mt ha hc.Theo truyn thng, silica aerogel c tng hp bng cch s dng phng php sy siu ti hn, nhng iu ny c mt s hn ch v hiu qu chi ph ca n, qu trnh lin tc, v an ton bi v nhit cao v p sut cn thit tip cn cc im quan trng. Nu carbon dioxide lng c s dng nh mt dung mi nhit thp ca qu trnh sy siu ti hn, bn ha hc ca aerogel trong bu kh quyn s b gim dn, v cc ht aerogel l a nc. khc phc nhng vn ny, Brinker gii thiu mt phng php sy p sut thng hp dn v mt thng mi sn xut silica aerogel [35]. Trong qu trnh ny, b mt ca gel t c bin i ha hc bng cch thay th cc nhm chc k nc bng cch thay th ca H t nhm hydroxyl bng cch lm kh p sut bnh thng. Nhm silanol b mt (Si-OH) trn cc cm silica ln cn tri qua cc phn ng ngng t dn n co rt khng th phc hi ca mng gel trong qu trnh sy, nh th hin trong hnh 4. Qu trnh ny c th to ra cc b mt vi nng lng cc thp, lm gim ng k sc cng b mt. V vy, n l cn thit thay i b mt alcogel vi cc i l sa i thch hp, do b mt ca aerogel c tr li k nc.

C mt s cht c kh nng lm thay i cc tnh cht lm m ca b mt, c ngha l, thuc th k nc. Chng bao gm methyltrimethoxysilane (MTMS), hexamethyl disilazane (HMDZ), dimethylchlorosilane (DMCs), dimethyldichlorosilane (DMDC), trimethylchlorosilane (TMCS), trimethylethoxysilane (tmes), v hexadecyltrimethoxysilane (HDTMS). Sa i b mt ca gel qua s thay th ca H t Si-OH bi nhm khng phn cc oraryl alkyl l mt bc quan trng trong phng php sy p sut thng. Ngn chn cc phn ng ngng t ca cm silica, v ni rng ra, ngn nga co rt ca gel trong qu trnh sy. T sy kh p sut bnh thng c th lm gim chi ph sn xut ca cc aerogel, tm quan trng ca n c thay i t mt khu vc quan tm khoa hc thun ty trong mt trong s dng thc t.2.4.7. ng bng kh:

Mt kh nng khc trnh ranh gii pha gia cht lng v pha kh trong qu trnh sy sy kh l ng bng kh. Cht lng trong l rng b ng bng v sau thng hoa trong chn khng. c mt s n lc s dng phng php ny sn xut aerogel [36-38]. Tuy nhin, giai on gi ha phi c m rng n nh mng li gel, dung mi c thay th bi mt dung mi khc vi mt h s gin n thp v p sut cao thng hoa, v nhit ng bng thp l t c bng cch thm mui. Mt nhc im na l mng c th b ph hy bi s kt tinh ca dung mi trong cc l rng. Cryogels do ch thu c nh bt.

3. ng dng:Aerogel c tnh cht c o m chng hp dn gii khoa hc v cng ngh

Table :Typical properties of silica aerogels.

Property

Value

T trng

0.030.35g/cm3Din tch b mt

6001000m2/g

% solids

0.13

15%

ng knh l xp

~20nm

ng knh ht

25nm

Chit sut

1.01.08

H s gin n nhit

2.0-4.0106

Hng s in mi

~1.1

Vn tc m thanh truyn qua

100m/s

Do cc tnh cht c o, c s dng cho nhng ng dng khc nhau c trnh by trong bng sau:

Table :Applications of the aerogel perspective to properties.

PropertyThuc tnhApplication

dn nhit(i) Cch in tt (i) Lm cht cch nhit trong xy dng v thit b

(ii) Trong sut(ii) Lu tr cng ngh phim nh

(iii) Chu c nhit cao(iii) Xe t, thit b khng gian

(iv) Trng lng nh(iv) Dng lm thit b trong pin mt tri

Mt / xp(i) Rn tng hp nh nht(i) Xc tc

(ii) Din tch b mt ln(ii)Cm n

(iii) Multiple compositions(iii) Lu tr nhin liu

(iv) Trao i ion

(v) Lc cht kh nhim

(vi) Nguyn liu cho phn ng tng hp

(vii) Cht mang trong to mu

(viii) Template

Optical(i) Transparent(i) Light weight optics

(ii) Low refractive index(ii) Cherenkov detectors

(iii) Multiple composition(iii) Light guides

Acoustic(i) Low speed of sound(i) Sound proof rooms

(ii) Acoustic impedance matching in ultrasonic distance sensors

Mechanical(i) Elastic(i) Energy absorber

(ii) Light weight(ii) Hypervelocity particle trap

Electrical(i) Lowest dielectric constant(i) Dielectrics for Ics

(ii) High dielectric strength(ii) Spacers for vacuum electrodes

(iii) High surface area(iii) Capacitors

3.1. Aerogel trong tng hp:

Tc nhn aerogel c s dng l silicon alkoxide kt hp vi cc oxit kim loi. Mt s nghim cu mi tng hp ra cc silica aerogel vi nhiu ng dng khc nhau. Cu trc v thuc tnh ca silica-aerogel ion oxit c lm kch thc nano c nghin cu bi calas v cng s. Hnh 5 cho thy 1 silica-aerogel c tng hp bng cch lm kh bi p sut xung quanh. Nhng nghin cu nh th ny cho ra cc vt liu khc nhau nh synthesis of silica-titania, silica-carbon, silica and alumina microfibers, hay activated carbon powder composite aerogels.

3.2. Aerogel c s dng nh cht thm ht

Tng hp Gel k nc hp th cc dung mi hu c v cc loi du c nghin cu bi A. Venkateshwara Rao v cc cng s. H nghin cu s hp th v gii hp ca aerogel silica siu k nc hp thu 11 dung mi hu c v 3 loi du. Hnh di ny cho thy s hp th v gii hp cht hu c khc nhau:

Trc hp thNgay lp tc khi bt u hp th t=0T=20 phtT=40 phtT= sau gii hp

3.3. Aerogel as a SensorAerogel c l xp ln, kh nng tip xc ln, kh nng hot ng b mt cao. Cho nn c s dng lm cm bin. Mt nghin cu ca wang v cc cng s trn ht silica aerogel mng mng cho thy in tr chng gim khi m tng. B mt aerogel modified t b nh hng bi m hn so vi aerogel a nc v c th c s dng chng n mn, tc nhn k nc nh hnh v:

3.4. Aerogel l vt liu trong vi mch in tr do hng s in mi thp.

Silica aerogel mng mng c ng dng rng ri trong cc vi mch in t do tnh cht rt c bit ca chng do hng s in mi cc thp, xp cao, n nh nhit cao.

3.5. Aerogel l cht xc tc

Do din tch b mt ln dn n nhiu ng dng nh hp th ha cht trong qu trnh chy trn. Tnh nng ny n c tim nng l cht xc tc hoc nguyn liu cho cht xc tc. Aerogel h tr trong xc tc hn tp khi cc phn ng l lng hay kh. Chng c c trng bi din tch b mt tht cao trong mt n v khi lng, xp cao lm cho chng rt c gi tr trong xc tc. Mt s xc tc Aerogel c lit k di y:

Tng hp nitril t hidrocarbon s dng NO

Isobuten c th chuyn i thnh methacrylonitrile

Tng hp metanol t CO

3.6. Aerogel trong vic lu tr media

Do din tch b mt v xp cao nn c th lm b lc kh, ht m trong cc phim nh v lu tr nhin liu hidro. Aerogel cn c bit n l siu t in c tr khng rt thp hn so vi cc siu t in thng thng.3.7. Aerogel c s dng l t bo trong cc tm phim nng lng mt tri3.8. Aerogel l vt liu cch nhit

Do xp cao, bn trong rng cho nn nh c tnh ny m kh nng cch nhit ca Aerogel l cc tt.3.9. Trong nh, t lnh, ca s v ca s tng nh.3.10. Qun o trang phc v chn

3.11. Trong khng gian c Nasa dng lm knh chng bi v nhit

4. THAM KHO

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HV: o Cng Thanh + Nguyn Th Kim Lin