Structural and adsorptive features of fumed silicas synthesized under varied conditions
Fumed silicas synthesized under varied conditions (stoichiometric or non- stoichiometric amounts of reactants SiC4, O2 and H2, different nozzle diameter, flow velocity and turbulence, flame temperature) were studied using adsorption of nitrogen, argon and water, infrared (IR), photon correlation spe...
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| Дата: | 2001 |
|---|---|
| Автори: | , , , , , , , , , , |
| Формат: | Стаття |
| Мова: | Англійська |
| Опубліковано: |
Chuiko Institute of Surface Chemistry National Academy of Sciences of Ukraine
2001
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| Онлайн доступ: | https://surfacezbir.com.ua/index.php/surface/article/view/46 |
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Репозитарії
Surface| _version_ | 1869291128843403264 |
|---|---|
| author | Gun'ko, V. M. Mironyuk, I. F. Zarko, V. I. Voronin, E. F. Pakhlov, E. M. Goncharuk, E. V. Leboda, R. Skubiszewska-Zieba, J. Janusz, W. Chibowski, S. Chuiko, A. A. |
| author_facet | Gun'ko, V. M. Mironyuk, I. F. Zarko, V. I. Voronin, E. F. Pakhlov, E. M. Goncharuk, E. V. Leboda, R. Skubiszewska-Zieba, J. Janusz, W. Chibowski, S. Chuiko, A. A. |
| author_institution_txt_mv | [
{
"author": "V. M. Gun'ko",
"institution": "Інститут хімії поверхні НАН України"
},
{
"author": "I. F. Mironyuk",
"institution": "Інститут хімії поверхні НАН України"
},
{
"author": "V. I. Zarko",
"institution": "Інститут хімії поверхні НАН України"
},
{
"author": "E. F. Voronin",
"institution": "Інститут хімії поверхні НАН України"
},
{
"author": "E. M. Pakhlov",
"institution": "Інститут хімії поверхні НАН України"
},
{
"author": "E. V. Goncharuk",
"institution": "Інститут хімії поверхні НАН України"
},
{
"author": "R. Leboda",
"institution": "Maria Curie-Sklodowska University"
},
{
"author": "J. Skubiszewska-Zieba",
"institution": "Maria Curie-Sklodowska University"
},
{
"author": "W. Janusz",
"institution": "Maria Curie-Sklodowska University"
},
{
"author": "S. Chibowski",
"institution": "Maria Curie-Sklodowska University"
},
{
"author": "A. A. Chuiko",
"institution": "Інститут хімії поверхні НАН України"
}
] |
| author_sort | Gun'ko, V. M. |
| baseUrl_str | |
| collection | OJS |
| datestamp_date | 2018-11-27T09:42:39Z |
| description | Fumed silicas synthesized under varied conditions (stoichiometric or non- stoichiometric amounts of reactants SiC4, O2 and H2, different nozzle diameter, flow velocity and turbulence, flame temperature) were studied using adsorption of nitrogen, argon and water, infrared (IR), photon correlation spectroscopy and electrokinetic methods. Prepared silicas possess different specific surface area, structures of primary particles and their swarms, concentrations of silanols, weakly and strongly bound waters. |
| first_indexed | 2025-09-24T17:44:38Z |
| format | Article |
| fulltext |
STRUсTURAL AND ADsoRPTIvЕ FЕATI.JRЕS oF FUlvIЕD
sILIсAs SYNTHЕSIZED I'JNDЕR VARIЕD сoNDITIoNs
V.M. Gun,kol,I.F. Мironyukt, V.I. Zarko', Е.F. Voronin], п.м. Pаkhlovr,
Е.V. Go nсh"'"Ё ; R" ;йi*,, д. Sku biszervs |,o-ZiQbaa,W" Janusl,
S. Chiborrskiz, snd A.A. Chuiko'
|Iпstitute of Surfаcе Сhеmistry, ]7 Gеnеrаl Nаtttnov Streеt, 03I64 Kуiv, UryIу*E^
"i:i"ti iсt,йь'ry, Mаriа Curiе-Sklodaуlslса (Jnivеrsitу, 2003I Lublin, PoulND
Abstraсt
Fumed siliоas synthesized under varied сonditions (stoiсhiomеtriс or non-
stoiсhiomеtгiс amounts ofreaсtants SiCl+, Oz and Hz, different nozzle d.iametеr, flow veloсity
*d tu,but"nсe, flame temperaturФ wеrе studiеd using adsorption of nitгogэn, argon and
й; й*"d (R), phoй сoпetition sPectrosсopy and еlесtrokinеtiс mеthods. Prеparеd
'iii""i po''"'s аiгfеient spесifiс surfaсe arй st.гuсures of pгimаry partiсlеs and their swaгms,
сonсentrations of silanols, weakly and stгongly bound waters.
Iшtroduсtion
Fumеd siliсas synthеsized by using high.tеmprratuгr hydrolysis of SiClс in an oxygеn.
hvdrоsеn flamе aге fully amoгphouЪ and ian po*sess largе speсifiс surfaсе aгеa (.S) up to 500.-
;ffi;,;;;ъ; i'iйЫponiсlе sizе d.istribution_(whiсh is narrowег at gгrater ̂ 9) t1].
гroto.pйiсlеs (t-2 nmlz]) foйеd in the initial zone of thе flamе сollidе, stiсk togеthч чd.arе
;;"";й by new siriсa йуй formiпg primary partiсlеs (diameter d = 5-50 nm). Collision,
stiсking und fu.ing (T > 1"000.с) oгinсiviаuat primary paгtiolrs Ф91a9а by =Si-o-Si= bridgeф
i",urt й foгmation.of primф.jgr.gut.'. Subsiquent attaсhmentof-individцa1primary^paгtiсlеs
to thеse initial aggгegatеs inсгйe-theiг sizes, and сollision and stiсking togеthеr of primary
;Ы.;;.; i"uа Б йrmation of largеr sесondary aggгegatrs of 100.500 nm (mass fraсtal
dimension*2.5-2.6,apparentdensity*30%ofthеspeсifiсdeпsity)ttшouфm1inly.hydrogеп
-J.t""t,o.tatiс bondф [1-3]. сleаrly, bonding strengtlr of pгimary partiсlеs.in primary and
;;";ай
"й*gatеs
depеnds on tempеrafurе. ani thеirЪizсs, соordination numbers and type of
bonding (сhеmiсal o, i,itЬ,-*ot..utаr) oг primary partiсles. At-lower tеmperatuгеs and aftеr
marked hydration ofthe siliсa surfaсes, aggгegates form loosе agglomeratеs (abovе l рm, fraсtal
dimеnsion н 2.I.2'2,apparrnt dеnsity * з-j gzo ortье speсifiс dеnsity) through hydrogеn bonding
and еlесtrostatiс interaсtions [l,3]. If ,s,> 100 mЪ that isolatеd primаry partiсles are nРt
;;;;J'6a.atеty *iй;;iй;йl tгеatliiеnt, whilrihe smallеr the paгtiоles' the stгonger thе
bonding in the aggrеgaй;ja;йrratrs [lj. For examplо, Aегosil l30 сan be dispersеd moге
easily than Aеrosils 300 or 3й] Aссording to sсanning еl^eсryn miсrosсope findings' fumed
siliсas do not сhangе йй.*"'pь"iogy onieating at tбoo"C foг 7 days, but at 1200. oC. thеy
сross-link to glass [l]. ThеrеfoгЬ, оnе сan assumeЪat сhanges in.the temperature of thе fumed
siliсa synthеsis ьеtwеei ioooъc,"nа lз0o"с сan in1luеnсе thе сharaсtеristiсs of both primaгy
paгtiсles and thеir swarms'
Мanyofphуsiсoсhemiсalpropertiеsoffumеdsiliсasdеpеndstronglyno1only.onthr
p,i*u.y.lйi"i" Ьа *-* si,e d.istributions but also on the сonсrntration of adsoгbеd watеr
'(.JЪ
iь" ь,* of both intaсt molесules and.=s[)н yч. (Сoн) [1-5]' For instanсg
йd"un* amounts of adsoгbеd water сan negativrly affeot the сharaсtеristiсs of fumеd siliсa as
20
e filleг of liophiliс mеdia or polymеrs. Therе are sevеral mеthods to сhangе thе C" valur suсh as
феmiсal modifiсation (hydгophobization) оf the siliсa surfaсеs by oгganosiliсon or оrganiс
сompounds, hеating of silica at high tеmprraturr giving tеntativе diminцtion of thе
h1,dгoрhiliсity' еtс. [1-5]. Howeveг, thе first mеthod inсreasеs thе matеrial сost and сhangеs the
nаtuгe of the siliсa surfaсеs and the sizе distributions of partiсlе swarms that сan bе undеsirablе
for somе appliсations of fumеd siliсa. Thе usе of the sесond mеthod геsults in a decгease in the
spесifiс surfaсе area and сhangеs in the struсtuге ofseсondary partiсles. Thегefore, produсtion of
fumеd siliсa possessing initially a dеsirablе lеvеl of thе surfaсе hydrophiliоitУ (C* Coн) and an
rppгopriate spесifiс suгfaсe arеa [5,6] сan be of interеst from both thеoгеtiсal and pгaсtiсal
рints of viеw. Thе aim of this work was to synthеsizе a vaгiеty of fumed siliсas possеssing
diffегеnt hydгophiliсity and moгphology and to сhaгaсtегize thеsе matеrials in aiг and aquеous
mеdia.
Ехрerimental
Mаtеriаls. Threе seriеs of fumеd siliсa samplеs werе synthеsizеd using SiCla
hуdrolyzed in the oxygеn/hydrogеn flamе under сontrollеd сonditions (temperаture, flow
vеloсity and turbulеnсe, ratio оf rеagent amounts and theiг distгibution in the flamе, differеnt
nozzlе diamеter dn= 36' 42 ot 52 mm) to produсe materials рossessing variеd hydrophiliсity,
spесifiс surfaсе area and other struсtural сharaсtегistiсs ovеr laгgе ranges (Tables l - 3). The
flаme tempеrature (Т1 = 1000-l300oC) was mеasuгеd using a Rangеr II s.aytег) oрtiсal
p}тomеtег. Thе modifiеd teсhnique of thе fumеd siliсa synthеsis was dеsсribеd in dеtails
сlsеwheге [6].
Аdsorption. Nitrogen adsorption-desoгption isothегms werе rесordеd for thе fiгst siliсa
sсгiеs (pоssеssing a low hydrophiliсity) at 77.4 K using a Мiсгomеritiсs ASAP 2010
edsогption ana|уzer. The speсifiс surfaсе area Sвgr (Tablе 1) was сalсulatеd using standaгd
BЕТ method [7,8]' Thе poгe volumе Vo was dеtегminеd fгom the adsorption at rеlativе
prеssЦге p/p6= 0.98-0.99. Thе Sвдт and V, wеrе utilized to еstimatе average porе radius.Ro.
Тhе speсifiс surfaсе arеa ,S, (Tablе 1) was еstimatеd using thе сg plot method [8] and siliсa
gеl Si.1000 as a refеrеncе material. The speсifiс surfaсе aгеa (^S) for all thе samplеs of siliсa
(Tablеs 1-3, Fig. 1) was evaluated using a Jеmini 2360 (SWAB) apparatus with argon
rdsoгption.
Тrblе 1
Charaсtегistiсs of Fumеd Siliсa Samplеs (First Sеries, S1) with Low Hydrophiliсity
91 m,lg m"|E m.lg сm,/g nm jJз, wt.уo wt.уo
| з 7
2 з 7
з 4 9
a 1 1
5 4 6
6 4 2
144 145 I l8 0.26 3,1 2.585 2.618 1.0 ]. l
160 l59 l43 0.29' з.9 2.51| 2.596 0.8 0.8
206 2t9 216 0.41 4.0 2.5'70 2.588 1.0 0.9
226 2з9 z42 0,44 3.9 2,513 2.589 l.0 0.9
зз1 340 з28 0.6l з.6 2.59| 2.608 |.2 1.0
381 з69 381 0.61 3.5 2.581 2.624 l.4 l .0
Notе. C* = Cw,l05 * C*,soo] C*,tos is thе amount of watег desorbed on heating at T<l05 oс,
С*'qоo iS thе amount of watеr dеsorbеd at l05 < T < 900 oс.
Watеr adsoгption.desorption on siliсa samplеs SЗ-l (wеighing 50 . l00 mg, pгessеd at
аppгoximatеly l0" Toгг) was studiеd using an adsoгption apparatus with a MсBain-Bark sсalе.
Аfteг еvaсuation to lГ3 Torг for 1 . 2 h, sаmples wеre heated at 613 K foг 3 - 4 h to a
z l
сOnstant wright, thеn ооoled to 293tО.2 K, аnd adsorptiоn of watеr vapоr was studied at
prеssuге(p)variеdinthе0.06.0.999p/porange,Thеmеasurem:nt^a:сuгaсуwas1xl0-,mg
.лith геlative *.un
",,.o,-*jYo'Wa|er
oЪso'ptiоn in air (Tables 1-3' С") was studiеd bу means
of thе gravimеtеriс method.
( t -
. : .
mm Lth tws
ц
ц
э
i х
:
1
2
J
ч
f f i l ogz 316 7 .2
З0t.4 55292 1042 400 6.6
Зз.4 62860 1002 416 6.5
2r.6 4',7290 1154 300 9' l
I L V 24.| 61560 1202 з62 7 '5
l L v
12О 0.8 21..2 5,7440 1щ__-.29э__-2-t
SiCl+ and HzlOz
Notе. y = l сoпеsponos to thе stoiсhiomеiriс rat
}i"','i"i', Сonditiоns and Нydration Lеvеl of Fumеd Siliсas (Third Sеries, S3) with
J O
J O
.1о
А .
>r
эz
t v
80
I V
I
I
1
I
I
: l : - ъ ; . . . . -
:с '+.ra.: . l . ' '
=r-.\: ::- э: sl
Tablе 2
;;n1.;;iч сondiцод-s and сharaсtегistiсs of FцЦrd siiiсns.(sесon{sегiеs' Е2)
-
dn SiCl+ т v| к€ Jj *i,^
"{нz \oz
----t
2 1.0" l.o to.i 261 3'6' l l '6 r '4 8'2
3 1 .0n 0 .8 ; I , ' 290 з .48 l .0 0 .8 9 .0
4 l . l " o.6s ;;.; 260 3 81 0'6 o'3 4'e
s i z" o ! ii: lix i33 li !i '-:\
iliсit
o r " о o 0 . 8 2 1 . 8 3 08 3 . 3U l . J t . J
7 l .0o l .0 ;| ' ,ъ 29g 312 l .8 2.0 8-2
8 ,l'2" о.оs ii.6 зiЬ 3.=3.0 .'. 0.1 .: lh; ̂ |нz = t and loz : I
l."Тi;*iТ.l.liТ.],'.jЫ;й;;;''"unts oiй, uй o,. ть".first^samplе was sуnthеsizеd
ffiffiй .Ьаiir""'i'ioiЫiй.м. гatio HzlozlSiClq' laminaг flow' еtс.).
Ес ...: .- , i i.
. . :' : ' ,
s.g. .gt: . :с ::
E Ь3!.::-i ,!
! t : . : . . - r : : : . '
EgЭ{:( ..:. 3:".
fсrзs :.s:}-j:'
*}..::д:з :.,'.. 't
gс. l - s . ' ] : : , r :-- .
+ -
: . т ' : : : . . . . - . '
a - f " 2 ' - -
F.rr :-.:а: s, .:
Сomputing,Calсulat ionofthefractaldimеnsion(Dд)waspеrfoгmеdonthebasisof
tьe nitгogеn adsфtion data using еquation [9] г !| \l
ь(o)= сo||St+(DАJ_зi|r"ь[aJ] (1)
whеrе@dеnotes thеrе la t i vеadsorpt ionа/а^(а ' i s thеvo lumеоfadsorbedgas for thе
mоnolaуеr соvеragе "ui",ьt"о
*itь tь. ввi й.'ьoа;, at p/po < .0.85.
Additionallу, thе
adsorption isothегm
",
;^;;;;;"alog of the Dubinin-Astakhov equation [10]
-
n Г / " n \ r r n \ l D - з
"=+I,(+,':-рА")-,|уf'':,"нД)]н;
н"- (2)
3 -D
(wheгеp=- : ;б , : т ;D ,р : ( kP ) - :n i s thеva r i еdеqua t i onpaгamеtе r , r ' *andХи in8 r € t h €
. L m ц
maximalandminimalhalf-widthsofpores;А:R,Tlt l(p/p)isthe.diffеrеnt ialmolarwork
еquai (with invеrse ,,u;i;; tь. uu,iation in the Gibb.s гreЬ йгgy, & is thе сonstant; 7 dеnotеs
r i Е з . ; l : . с
]:,,е i:
a: . . . . ! : . : з . : : :
22
the iпсomplete gamma funсtion) was utilized to estimate fraсtal dimеn sion D'apa at p/pg <
О.|' х,i,1: 0.2 nm and,х'*: 4.0 nm.
whегe r,1n and rmaх are the minimal and maхimal
half-widths or Pore radii (r,6 = 0.2 nm aтd rпах = 2О0 nm wеre used in this woгk),
rеspесtively; ll : 1 for slitlike pores and 2 for сylindгiсal pores; r1,(p) is drtегminеd wit,h
modifiеd Kelvin equation
Fig. 1. Rеlationship bеtweеn thе flow veloсitv yr
and the spесifiо suгfaсe aгеa (ф oг the pгimЬry
paгtiсlе diamеtеr d for a|1thе sегiеs of fumed
siliсa samplеs.
- Thе porе sizе distribution f(R,) was
сalсulatеd using the оverall isotheгrn еquation
l l 1 ,121
+у) '*у
u,
а= ! f(R,)dR,+ j ;-l(r'R,)"f(R)dRPQ)
'ф \ (p)^p
r,(p)=9:-+t(p'R,)-ffiЬ
0'( p. Е\ - Kp exp(zw@ / kuT)
' l+ Kpexp(zw@/krT)
(4)
aлd t(p,R) сan be сomputed with modified BЕT еquation
t (p .R-\=, -
:З - f7+(nb/2_n|2)z , - , - (nb+|)z , +(nb/2+nlz )z"u7 1{\, ' ' ( | - ' ) [ I+(с_|)z+(cb/2_с l2)z , _(cb/2+с l2)z '*| l \ J , ,
l^ : а,,/Sввr ̂ у 0.354 nm; D : ехp(АdR'T); lя is thе rxсеss of the evaporation heat duе to thе
inteгfеrenсe of thе layеring оn the opposite wall of pores ; t(p,R) is thё statistiсal thiсkness of
an adsorbed |aуer; а, is thе BЕT monolayеr сapaсity; c=c"eхp((Q,_Q)/RgT.); c, is thе
E - U I
BЕT сoеffiсient for adsorption on flat suгfaсе Cs = 7€
^{
, Q, is thе liquеfaсtion hеat, ,Е is thе
adsorption eneгgy' 7 is a сonstant; Q" and Qo are the adsoгption hеat on flat suгfaсe and in
ргеs, гespесtive|у; z : P/po: r is the numbег (nonintegеr) of statistiсal mоnolayегs of
adsorbate molесulеs and its maхimal valuе foг a given rp is еqual to (Rp- o/2)/t,; and o. is thе
сollision diamеtег of surfaсe atoms. Typiсally, dеsoгрtion data were utilized to сomputе thе
J@) distributions with Еq. (з) and the regularization proсеduге [l3] undеr non-nеgativity
сondition torf@) with a fixеd regularization paramеtег сt:0.01. It should be notеd that this
аppгoaсh сould be usеd ovег a widе pore гangе from miсropores to transpoгt porеs [1l,l2]'
Foг fumed siliсa with spheгiсal primary paгtiсIеs, Еq (4) соuld bе replaсеd by еquation [8]
Г ..t
ln&_:r'-|L-Д| .u.,
P RrTlr ,t(R+t+r1' - R2 -r+R+l'l \*/
wherе R is the radius of pгimary partiсlеs, and l' : t + o/2.
Thе Fowlеr-Guggenhеim (FG) еquation (dеsсгiЬing loсalizеd monolаyег adsoгption
with lateral intеraсtion)
(7)
2з
(whеre K=Ko(Г)expqt,iь"т1is the Langmuir сonstant for adsorption on monoenergеtiс
sitеs and the prе.еxponеntial faсtoг ко(T) iseщгеssеd in tеrms of thе partition funсtions for an
isolatеd gas and *u,гu""Ъй"l,;i' il;.rnй Jn.u'",t nеighbors of an adsorbatе molеculе
(assuming z= 4),* ъ.iьe int",u"tьi e191в; ьeйen a puЁornrarest neighbors, /cв Ь thе
Boltzmann сonstant, ;n*:38o K tl4,15]).was used as a loсal isotherm 4 in the ovеrall
adsorption equation. д.Ь"-i'ы-pЙo va|ie fo, an isotherm poгtion used with Еq. (7)
сorгеspondеd to сoveragе @= а/а, дc 0.99.
Thе distributions of adsorptive potential (Uo) and frее еnеreУ сhanges (/G) upon water
aаsoцJiй. iй" .irii""J#i"."'ч:.Ё,^lated using thе Langmuir equationfl .l
-
\+bC r
ДG I]o
(where b=r,еfi or K,,ф , Ть and f,.u,"
the оonstants) as the kеrnel in the overall
adsoгрtion еquation in thе Ьгm of Fredholm integral equatiоn of thе first kind
@(z,p) =*i@,1a,o,')f$)e (9)
xnй
wheref(х)isthеunknowndistributionfunсtionofagivеnpТg*ч:'х.Toсalсulatethef(х)
funсtion, the reрlariйioi .Jьoa сan bе'й ;;
",rйф{1,9)
i'vrell known ill-posed
problem duе to
"
o,".g1ri"-;oi noь" сomponents on experimental datа" which do not
"l1o*
on. to еffесtivЬy utilizе exaсt inversЬn formulas or iteгative algoгithms [l3].
Additionally,,o "ы,uiui",.ьl;Ь;;"й;;;;'gy
distribшionslp/' modifiеd Еq. (5) was
appliеd a| n н 2-3.вq.?тj *.' ы* uчгri.аl o *iput"11с.1 {!.. a' assuming that lateral
inteгaсtion at соvеragе 1ess than monolayеr i'
"pp'.,:я.":tЫу
ззu" of thе liquefaсtion heat of
watег.
ЕlectrophorеsisаndPаrticleSizеDistribution.E|ectrophoretiсandpartiсlesize
distribution i,,..,".tigu;io;*Ъ"* p".ь'..a
-u.ine
; ze.ч11.er. ̂з600
(Мalvern Instrumеnts)
aPpaгatuQ based on thо photon сoпеlation sp""i'o]"opy (Т-s) (l: 633 nrц @= 90o, softwаre
vеrsion l.3). lеronrz;ffi;;til;;; 6lj.= ь.lz1Ьj z.s-g of oxide peг liter of thr water
was utilized to prepJJ.ь""'''p.".i"ns,.*ьiсь.*Ь thеn ulirasonicatеd for 5 min (500 W'
frequenсy 22уJtz) ;;;; ultrasoniс аi,p"'.."' (soni".to. мi'onix). The pH values measurеd
bу a prесisio" оieitui ;i{il;#;; "ii"u.J
ьi,
"Jсition
of 0.t M нсl or NaoH solutions,
and thе suspеnsion salinity was сonstant;f i0" М NaCl. Еlесtrophorеtiс bеhavior and
paгtiсle sizе distributiоns in Ц"-1яuuoy,
.uфЪ*ion' studied by using thе PCS method wеrе
.о.'.'iь"а
in dеtail еlsеwhere [16].
IRspеctroscopу.TheIRsге9traovетthe4000.1400сrrflrangewerеreсordedusinga
SpeсordМs0 (Karl2Ьi,,1,p.",,щьoю'.t.'.*ingpressеd.sampleslz2x'
mrц l0 mg). Thе
amount of free silanols (Coн) rr,as еstimatеd-iJй]й. o.,oдr int.n,ityЪr" band at 3750 сm-l.
Rеsults and Disсussion '^^:^Lj^*а+Ja r.
An inсreasе in thе геaсtant amounts at the stoiсhiometriс ratio (т = 1) bеtwееn ozlнz
and SiClс *а
"t
tь" ,й oozz|eсiu'n"t",'j" Ё;;;;;-;;;':u.9 jn the flamе tеmperaturе Z1
and an inсrеase i",i.," tr"*."ЪЪ"r,y й"1'ry Ь"J.r"iЬiJu," lеavins the nozzle (Table 2, 52-
|,S2.2,s2.з) Ani".^й"i"iь.'nozz|ed;.;;;;;i;;toеlevatini
of \(S2-2, s2-4' s2-5)
and dесгеasе in "/(;;.i-9 дтy"'lР"';;;'
*r* 1ry' Оz|ILz-inrrspeсt to SiClq) to 0.8
(s2.6) gives an in"?luii
-й
i<т'ьь2) d;;;;"ssible.сhanges in thе iеaсtion meсhanism
24
a 5oo
o- 400
l-
8 зoo
с
€ zoo
o
o
э 1 0 0
0
500
Е ooo
$ .oo
.а 200
q
Е l 0 0
0
с
б 7
a 6с
; o s
o
ц 4
э 3(t
.!
ъ 2
Е
o l
z
'/.t
,d::##
i i i
S tапdа rd Adsorpt lon с"
i ) i -
s t and6 rd Adso rp t i on с .
(e.g., dirесt oхidizing Si-H or Sio to
Sioz instеad of hуdгolysis of Si-Cl)"
Thеre is well-sеen relationship
bеtwееn thе vyvaluе and thе spесifii
suгfaсе arеa (S - lnv) oг diamеtеr d
of primary partiсlеs (Fig. 1); and at
vf > 22 m/s (сoгrеsponding to ^S >
380 m"/g), сhanges in S (oг ф arе
rеIatively small with inсгeasing v1
Notiсe that thе Rеynolds сritегion
foг the studiеd flows (Tablе 2, R")
сoгresponds to thе tuгbulеnt flame
(Л" > l04), whosе parametеrs сan
impaсt the сhaгaсtеristiсs of both
pгimary paгtiсles and thеiг swarms.
whilе maгkеd flow turbulеnсe сan
pгomotе formation of large primary
aggrеgates in thе flamе and tight
attaсhmеnt of pгimary paгtiсles on
stiсking to thesе aggrеgates with
subsequent layегing of Sio2 onto
their оontaсts. In thе сasе оf a
laminar flow (standaгd synthеtiо
teсhniquе), primary paпiсiеs arе
spheriсal, nonporous and thеiг
сontacts in aggrеgatеs (primary
aggregatеs сan be smallеr than in
the tuгbulеnt flamе and a larsе
poгtion of aggregates is sесondaiу
ones formed mainly on thе post.
synthesis stagе of powdeг treatment
at 250.400t with thе presеnсе of
water vapor) aге less tight than
those in primary aggrеgatеs for non-
standard siliсas formed in the
turbulent flamе.
0,10,0
Fig. 2. (a) Isotherms of nitгogen adsorption.desoгption
(77 4K) on fumed silicas of thе first seгies; the сr3 plots foг
ф) standard adsoгption and (с) rеduсed by dividing by a'.
Additional supply of a low amount (in сomparison with thе main flow fгom a сеntral nozzle)
of hуdгogеn (on defiсiеnс{.9f o, in thе flame) through an additional annular nozzle providеs
thе hydrolysis of residual SiCL and Si-Cl* on thе flamе periphеry at 600-800oC that iеsults in
foгmation of a porous suфо9 layеr on siliсa partiсles leaving the hot zonе of the flamе. Thus,
сhangеs in synthеsis сonditions allow onе to vary paгameteгs of primary paпiсlеs, primary
25
PIP o
(fоrmеdonstiсkingofprirlrarypo'ti"]9s.thenfusеdintheflame)andsесondaryaggrеgates
Ьd loo'. a88lomeratеs of aggregatеs [6'16].
Changеs in т,o iа"i 1й tьe primа-гУ гaгtiоle size d,.as.S - I/ф |ead to marked
altеratiоns iп thе adsorptй isotьe,m* 1r'g. ?ui;but thеir |vгe is thе same (as wеll as foг all
fumеd oxidеs) duе toйg;; ь;й.-м'u"ь matеrialЬ-сomposеd of sphеriсal primary
partiсles forming ugg,й"* and agglomеratеs [1,3,16-24]. The isotherms and the с[g plots
(Fig' 2) as wеll u, uu",ui" р;'"dt* values (тiьie 1, ф dеmonstгatе that fumеd siliсas are
rather mesoporous gati oi сhannеls bеtrvеen primary
ч*]*
intggregatеs and bеtwееn
aggrеgatеs in
"ggro.!,й'-;;-ь;
сЬnsioеreо as mesopores of a сompliсatеd shape)
indepеndеnt1y on ̂ S o.l'n"i,e* d. Therroгmalizеd сs plots for fumed siliсas do not dеviatе
from thе plоt for si.tooo (S,n - zв rrf|g, with no miсгoporеs) at с[s < l.5 (Fig. 2с);
сonsequеntly' natтo\ir' miсroporеs чr
praсtiially ib'"nt in non.standar..а }mе{
r
sitiсas 1тЬьtе 1). A very low оontгibцtion of
miсropores to thе ovегall рorosity оf fumеd
siliсa (provided by contaсt zones betwееn
adiaсеnt primary partiсles) suggеsts that
thеse сoniaсts ше rеlatively tight for non-
standard fumed siliоa samplеs rеsulting also
in thе low hydrophiliсity (Table 1' C,). T!9
similaгity in iьe isotherms (Fig. .2)
сoпesponds to a similarity in the poj. Y"
distributions IE) вig.3) сomputеd using
Еq' (3) and the regularization proсеdure.
Large mеsoporеs at R, > 10 nm сan
-:;;;;+i 4 сoгrеspond to intег-aggregatc spaсе ln
ffi aggloйeratеs, as сhannels in agвr9вaJ3s
Pсe Rdus (пm) йainty сorresрnd to Лo < 5.8 nm [l'l7.
lel.
Fis. 3. Porе size distгibutions for first series
."Е'ol.' сomputed on the basis of the desoцption
l;;.';"g вq сзl and the rеgularization proсеdure
at с = 0.0l.
Therеarеthreеpairsofs imi lar/(Лlсoтrespondingtosamples-SJ. lРоs1.2's l-зandSl-4,
and Sl.5 and 5l.6, *.h#i;ffi'l r'ыЁ сlosйaluеs of и, 1notiсе that f(R) is linkеd to
dVldR,)and Sвдr ст"ы. it. сь."'й т.Jhe:ppTent
density of these samples (Table l, p",)
do. noi сorrеlatе with .S and Yo' wni.le. thЬ hst pararneters are mainly linkеd to the
сharaсteristiсs of primary partiсles аnd thеiг щg'.g.tЬ., b{ thч empty spaсe in fumеd siliсa
powdeгs (V"'p<(|0ОО\o/o,,d)/od сonneсЪi 'iitь p* is signifiсantly lаrgeг (V"., н25
сm,/g) tьar|VP6 о.z сйу/jffi;iй !o lhe.volume
of.йnnrlJin agglegatеs) and linked to
thr struсturе oгngglo*;,uйs and visiblе floсks. However, an inсrease in puo and avrrage poгr
гadius Ro сorrеlate ;;;;;;*se in thе fraсtal dimеnsion (ф; i.е., the inсгeasе in thе
apparent .dеnsity ot pй.i, .o,.еsponds to smoother paпi9le surfaсеs and thе incrеase in the
dispеrsitу i, u""o.puni;;Ь; ц;;ЬЧ ,::l"lfty
Standaгd fumеd siliсa is mainly mass fraсtal
[2] (for standaгd ,iri."Ъ-i,Ъ, =i'вzo\
!й the samples synthesized uпdеr non.standard
сonditions .un po,,.,i
"o. ",ry
..ss fтйality but also ьrвё1 s.usсe fraсtality (for siliсas
prеpшеd at a greater п"*
"гьyi'"g."
tьrough ihr annular nizz1e}. At thе samе timе, thе flow
26
turbulеnсе гesulting in foгmation of tightег сontaсts bеtweеn primary paгtiсles сan rеduсе thеpore (сhannеl) fraсtality (as сhannеl walls arе smоothed); tiеrefoie,'Dы is highег for S3-i
than for S l -5, howеver, thе last samplе has larger S and smallеr d valцes.
Fеatures of nitrogen adsoгption on thе outeг and intеrior surfaсеs of аggгеgates сan
dеpеnd on a сharaсter of stiсking togеthеr of pгimary pагtiсlеs (dеnsity aй- nimbег of
сontaсts bеtwееn primary partiсlеs in -ag.grеgatеs). Thегefore the nitгogеn adsoгption оn avaгiеty of siliсas is сharaсtеrized by differеnt adsoгption еnеrgy distгiБutions 7ф 'ьini"g
toward grеatеr enеrgy with dесrеasing avеragе paгtiсlе sizе (гig.-+1 тhe availaЁiiiф of tighТ
сontaсts betwееn pгimary particlеs of non-standard siliсas froй thе fiгst sеriеs 1тaьrе r1.in
соmparison with standard siliсa (Tablе 3, s3-l), whiсh has a higher lеvel of thе ,u,Ь".
hydrophiliсitУ (C* = з 5 Y,.ц) than samples from thе first sеriеi (Tablе 1, C*), lеads to
геduсtion of f(E) at E >. |2 kJ/mo|. Thе f(E) pеak at 14 kJ/mol for S3.l сan ье,сausео ь!
adsorption of nitrogen in the naгrowest gaps in thе zonеs of diгесt but not densеly fusеd
сontaоts bеtwеen adjaсeш primary partiсles. Howеvег, for non.standard siliсas, similar narrow
gaps aгe fillеd by siliсa layеrs to a grratrr eхtеnt duе to highеr turbulenсe оf thе flame.
Fic. 4' Nitrogen adsoгption enrrgy
distributions сomputed using FG
equation and thе regularization
proсеdurе at с = 0.01 for samplеs Sl.1,
S l -6 and S3-1 .
It should be notеd that thе
adsoгption enеrgy of watеr сan bе
greatеr in thе оasе of formаtion of water
сlusters adsorbеd nеaг сontaсts bеtwееn
primary partiоlеs bonded one to another
by the hydrogеn bonds, but for tightly.adnate' primary paгtiсlеs, foгmation of
suсh wateг сlusters is less probably;
thегеfoгe, thе adsorbed watег amounts
are lowег foг suсh non-staпdaгd siliсas
(Tables l and 3). Additionally, thе сonсentгation of strongly bound water dеsorbed at T
bсtwееn l05oC and 900"с.(C"'900) foг lеss hydrophiliс siliсasli loweг by sеvrral timеs (Тable
3) Тhеse struсtural and adsогptivе fеaturеs of the fumеd siliсa surfaсеs сause a гedцсtion not
only of thе amounts of wеakly bound water (C,,юs) adsoгbed from air (dеsoгbеd at T < l05"C)
but also thе monolayег сapaсity foг watег "(C|n,,ono) adsoгbеd at room tеmperaturе. гoг the
яaлdard samplе S3.1 (Tablе 3), water adsorption-desorption does not give a laгgе hysterеsis
loop (as wеll as thе nitrogen isothеrm has a naпow hysterеsis loop [tz-tэ]), Бut for other
sаmplеs, the watег isotherms have markеd hystегesis loops; сonsеquently, these samplеs сan
hаvе poгous primary partiсles (oг aggгеgatеs havе signifiсantly altегеd teхture) in сontгast to
thе standard siliсa. An inсгеasе in thе hydгogen amount in thе flamе (тнz>l) leads to a
rсduсtion of thе watег adsoгption (C") and monolayeг сapaсity С|w'mono (Tablе 3, s3-4, s3-5,
S3.8); i.е., thе hydгophiliсity of'thеsе siliсas dеcrеasеs. An inсrеase in the hydrogеn flow
йrough thе annular nozz|e to 8 m'lh also impaсts watег adsorption (сomparе C" ьг iз.z and
S3-7 or S3.3 and 53.6). Horvevеr, Сoн сhangеs slightly (for S3.5, Coнis gгеatег dur to its
rесipгoсal dеpеndenсе on S [6]). oxygen dеfiсiеnсy in thе flame гesults in а diminution of thе
watеr adsorption, but thе monolayеr сapaсity сhanges slightly (sз-з) or dесrеasеs (samplеs 4'
5, 6, and 8).
a
. . . . - , , t I
g
E
Е
с
6a
E
Ф
f
Ё
"й-di .
o]а
AdsorЁion Еnetry (k]/md)
Fig 5. (a) Isotrеrnъof иaеr adsorptiqrd 29BK
onsiliсs oftр third seIiеs f,d trs distrih'iшБ
of (b) freесnеrry dшцrsdrвto uaеr adsшptiot
сorrprtеd rвiщ t^тrgrшir еqr6ion аt a < am;
(с) цаter adsoФior сrецgl сolrpr.ted ugng rrDdifid
BЕT eqr.ratiorr d dPo < о с; шd (d) adsшptive
рtеrшiаl disibшiors in гефrd to цЕtеr а&oгptiсn
at a < a' сюrrрsed цing tдgrЦir еqиtiшt
-дG (kl/mol)
Adsoп*ive Poter'tial (k,md)
AсtorЁion Еnergy (k/md)
28
сЦ
I
C
-
Эr
rl
-1
f,
d
'фq
F
ba
-
t' ( IR spо
с'Фс. (4) lcn
&| iп ur
Cbпgзs iп t
-oтоon (Fi
шnДсс'
sliса (
bd ors 30O
ro
8a
l4{
^
Changеs in the hydгophiliсity оf thе siliсas of thе third sеriеs гesult in markеd
diffеrеnсеs in thе vrаter adsorption isothеrms reсoгdеd at 29з K (Fie 5a). Rеduсtion of
adsoгptiоn on noп-standard siliсas (Fig. 5a, Tablе 3, s3-4, sз-5' and sз-Ъ) is aссompaniеd bу
a dесrеasе in thе adsorptivе potеntial (Fig. 5d) and оhanges in thе frеe enегgy of iasoгptlon
(Fig. 5b) analyzеd at сovеragе lеss than thе wateг monolayеr (o < o,,,.-i. while initial
rеlativе watеr рressure p/pq > 0' 03, сontгibution of high-heat adsoгption at (Jo > l 5 kJ/mol is
rеflеоtеd inf(Ua) as a low-intеnsity shouldеr. In the сase of grеatег сoverage, a high-еnегgy
pеak appеars in the adsorption еnеrgy distгibution/@) at E> 50 kJ/mol (Fig. 5с) oue to un
inсгеasе in avеrage number ofthe hydrogеn bonds рer a moleсulе at оoveгage grеatеr than the
'*.ateг monolayеr. Thе position of a low-еnеrgy pеak of .f(Е) at.Е betweеn 25 and 40 kJlmol
(Еig 5c) depends on the hydгophiliсity of thе samplеs (Fig. 5a, Tablе 3), as well as thе
adsoгptive potеntial distributions/(Ual (Fig. 5d). Changеs in the structurе of primary paгticlе
suгГaсеs in thе turbulеnt flame aссompaniеd by the reduсtion of the hydrophiliсiiy. of thв
gгfaсеs rеsult in an inсгеasе in the intеnsity of low.еneгgetiс peaks of both f(Uф and f(АG)
tТis 5)
S60
Ф
540Ф
2440 2800 3200 3600 4000
v {сm-')
Fig. 6. IR spectгa of fumеd siliсa samplе s3.6 (l) in air, afteг degassing at (2) 450"C and (3)
650"с, (4) lеtting in satuгatеd watrr vapor' (5) dеgassing at room tempегature; аnd (6) sample
S3-l in air.
Changеs in the struсturе of pгimary paгtiсlеs and their сontaсts influenсing thе watеr
adsoгption (Fig. 5a' Table 3, Сn, Ct,,,ono) сan be also analyzed using thе IR spесtгa (Fie. о)
Foг instanсе, samplе 53-6 adsorbs wateг signifiсantly largеr (by two timеs) than stаndard
fumеd siliсa (Fig. 5a' S3.1 and 3З.6 at p/p6 -+ 1), whiсh appеars in great intеnsity of a broad
Ьаnd ovеr 3000.з700 оm-. (Fig. 6, сurvеs l and 4) linked to watеr adsorbed in differеnt foгms
29
,.f'l', 1 ,,.'
'!:---,'=,,.=,:-'-'-'-
and distuгbеd suгfaсe silanols [1,2].
This еffeсt is aссompanied Ьy a
substantial but non-typiоal rеduоtion
of thе intеnsity of thе band at 3750
сm-l in сomparison . with the band
intеnsity at 3400 сm . (Fig. 6, сuгves
t and 4), whiсh is not observеd for the
standard silioa сharaсterizеd by a
highеr relativе intеnsity ofthе band at
3750 сm' (Fig. 6, сuгvе 6). one сan
assume that this differеnсе is
сonnесtеd to struсtuгal fеatuгеs of
non-standaгd siliсa, rvhiсh сan bе
шorr porous than standard fumеd
siliсa.
Soniсated or mесhanoсhemicallу
aсtivatеd aquеous suspеnsions 9f
fumed siliсa arr typically
сharaсtеrized multi-modal
distributions of paгtiсles and thо first
oeak of the smallеst partiсlеs (l0.з0
nm or slightly above at S = 250.з50
*,|g) corrеsponds to pгimaгy
aggiеgatеs, whilе thе size of
'БJonou'y aggгrgatrs сoгrеsponds to
l00-50o-nm. Thе sесond dpgg pеak
(or two pеaks) is fгеquеntly..obsеrvеd
namеlу ln this range. Additionally,
on. oitvro obsеrved pеaks сoпеspond
to agglomеrates at dpсs > l рm;
howйг' in the сonсеntratеd (яз 5
wt.%) aquеous suspensions of fumеd
siliсa, largе agglomeratеs arе not
obseгved. Diluted tгеatеd oг non.
trеatеd suspеnsions dеmonstrate
unstablе agglomeratеs at drcs betwееn
1 and 50 рm еasily rоaгrangеd . to
smalleг or largег swarms еvеn during
shoгt.time sеdimentation foг several
minutes [16].
Fis. 7. (a) Dеpendеnсе of thе ( potentia-l.on. pH for
.uiloi"'.lг .hЁ f,,st sеries; (b) rеlationship bеtwеen
;;;;d |or Dы; and (с) DеroS 8 funсtiоn of рH.
For biggег primary partiсles $aьr9
|, ф, the-nrgative.values of thе ( potеntial are
grеatег (Fig 7a) l.",gii,"Fй"tivе diamеtеr Бiьiаi"iуnamiс.diamеter' i'e., the partiсlе
iiu,,,.t.. plus thе
"r."tiйur
сouьle layеr or tье dJublе sheai layeг thiсknеss ||6]: drcs = d,"ol *
L -19
i6o I
1 4 0
E
о'
"1й-;а--ш.;ы-ш
s,., {mЪ)
pH
30
pH
| l Ц с i
_lSв(
О rt &тG
шоf o
q|сз rэ п
ffirвo
&tсdr 4
-аdр
l j l сп
_ЁЦ
EJbсп
Ё C*rtl
hf шЁ
rFшr
lllэa
bGз' Fl
ts-f-.
f ПgC
tдf l .Ь r
- rЁс
d
Ц l
-
LLL
1(с) !
l\цсn-
g at Аd p 2Kl, whеre к is the Debye.Huсkel рaIameteг) is observed foг a sample with
minimal ,Увдr (Tablе l, Fig. 7с). In genеral, opposite dеpendenсies of D{and( veгsus S3д7 (oг
ф arе obseгved for siliсas possessing-low hydrophiliсity 1вig. 7b, TaЬle r). к"tatiueii.ti*
аmounts of oH groups (typiсal for fumеd siliсas) and struitural featurеs of non.standaгd
samplеs aге rеsponsiblе for a гelatively weak dеpеndеnсe of primary paгtiсlе swaгm sizе
distributions on pH (Figs. 7с, 8 and 9). A maximal light sсattеring intеnsity (l: 63з nm) is
obsегved at dpcs bеtwеen l00 and 500 nm (sесondary aggregates), but the distгibutions ofiье
numbег of partiсles/(i{) havе a maхimal intеnsity at loweгdpсs valuеs (primary aggrеgatеs
with smaller numbег of pгimary partiсlеs than those in the seсondarу aggrigateо.сгiЕ. gliano
similar phеnomеnon is typiсal foг all fumеd oxides duе to the L value and сhaiасtеristiс
struсtuгal hierarсhy of suсh matеrials U6-241. The f(N) distributiоns alteг foг siliсas (Fig. 9)
with diffегеnt averagе pгimaгy particlr sizе (Table l, ф, while diminution of d lеads-tо a
laгgеr сontribution of smaller primary aggrrgates (observed in the soniсated uqu"o.u,
suspеnsions and сomposed of severat oг dozеns of pгimary paгtiсles; notiоe that sейndarv
aggrеgatrs сan involvе thousands or evеn dozеns of thousands of pгimary partiсlеs) with thЬ
sizes (e.g., Fig. 9d, 10.30 nm) closе to thosе of pгimary partiсles. in tьe ЬaЪе of fuйеd siliсa
(or other fumed oxides) synthesizеd undеr standard conditions, a strongrг dеpеndenсе ofthe
swaгm sizе distгibutions (multi.modal with thтeе. or fouг pеaks) on pH, as well as for D"1
versuspl/, is obsеrved [16.19]. Additionally, foг less hydrophiliс samples (Table |),thе D"r
valuеs at pн сlosr to pH(IЕPslo2) н 2'2 are smallег than thosе for standard fumed siliсas duе
to rеduction of thе surfaсе hydrophiliсity, i.е', siliсa partiсle сapability to form a largе numbеr
of the strong hydrogеn bonds with water molесulеs from thе first intеrfaсial layeг,1hat lеads
to smallег сhangеs in the fтee surfaсе eneгgy (Fig. 5b).
't00
Dl.mсtф (nп}
100
0i.m.l.r (пm)
Fig. 8. Rеlative PCS intensity for the soniсatеd (5 min) aquеous suspensions of samples (a)
1, (b) з, (с) 5 and (d) 6 of the first sеries at differеnt pH values shown in thе lеgеnds (as well
as D"), Csioz = o,25 wt'уo, and l0-3 М NaCl'
a
3 r s
E ' а
E -
t000
a
t 0
,l
oL
a
I
Ф
z
-9
.9
b
-
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д
z
g
,9
с
?
z
o
d
з
6
zэ
.9
Fig. 9. PCS in resprсt to thе partiоlе numbеr for thе soniсated aqurous suspеnsions of
,uЕipi*, сul l, (b) з;(Ф 5.Ьа iаi о of the fiгst sеries Tablе l at diffeгеnt pH valuеs shown in
tь. йg"na, (as wеll .,Ъ",1, Csioz = o'25 wt.уo' and l0-3 М NaCl.
Conсlusiоn
Thе apply of varied сonditions of the fumеd siliсa synthesis allows onr to prepaгe
matегials сharaсterizеd Бy шr.й lеvеls of thе hydroрhiliсitу and vагious tеxturеs in rеspесt
;;;.;'i*a,у partiсtеs (theiг porosity, amounts of water adsorbed in differеnt forms, еtс.)
and swarms (their struсiui" -j sizе distribution, type of сontaсts in aggrеgate1, e!с.).. T}'is
tеоhnique allows onе t; й;;sizе fumф siliсаs aj illеrs morе appropгiate for hydrophobiс
mеdia without aаоitioniiiaйi,'lь"i' surfaсе nature. Alterations in thе tеxturе of pгimary
particles and their **,,*, allй one to сontrol the adsorptivе charaсtегistiсs of fumed siliсas
ovеr widе rangеs.
Aсknоwledgrment
;:.
ТhisrеsearсhwassupportеdbyNATO(grantNoЕj;T.CLG.976890),thePolishState
Committее foг sсiеntiiс к!J.u,.ь unа мlni'tй of High Еduсation and Sсiеnсе of Ukгainе
(gгant No' 2Мlз0з-99).
Rеfеrеnсеs
1. Basiс Charaсtеristiсs of Aеrosil. Tесhniоal Bullstin Pigmеnts. No ll, Hanau: Deрssa
AG, 1997.81 P.
z. {Ji'i"адp.,Ъс. Thе SuгfaсeProprrtiеs of Silicas. Nеw York: Wilеy, 1998. - 470 p.
3. Barthel H., Rosсh i.'';t. '. гumed sili9a - Produсtion, Properties' and Appliсations. In:
oгganosiliсon сьйi't'y тr. rrч Мoleоules to Мaterials, N. Auner' J. Weis, Еds.
Wеinheim: VCH, pp.76l .7,78' |996,
o|аmGte. (пm) Diаmot6r (nm)
Diапctоr (пm}
{ tllz ,P.
$riв (
l. }+сq.;-
vм GД'
ш - \ '
i. Cbrссrn
?ruЁпr /
$firzcst
?. A&дsа /
l. ФGgs sJ'
{J79
l Avtй D'
нЁ.'o$n.
lF]El dlп
*сгin
-v ts2 _
ll}tЕ}e с '
l тт.fo, .
ll. oПto v !
lдlrlэnа
ll. Йotсb:r
rirз ^bl
z1
}fto$а Al
(Нi' /}{ l
b 3 - P S
тd, и i
1995 -V !
Aaав }
vll Gлtr
hd sili
t $fissr
уI+'g2
llllу Dц
фшc Ц
S фoqd
Gшсiш
Еf vсqй
хv Gd
Тqсrarr
d Sili(r,
YrG hrф
hотrtз -
Aaаs 9l
V L Zrto, '
sd - 199t.
ТLЕftс o
О is sgfi
Е CEoc.!*
4. B|itz J.P., Little C,B., Еds. Fundamеntal and Appliеd Asресts of Chemiсalty МodifiеdSuгfaсеs. Cambridgе: Royal Soсiеty of Chemistrу,.|999. - igg o.5. Месhanism and Kinеtiсs оf HехamеthyldisilazaneReaсtion wiй a гumeа Siliсa Surfaсе. /V.М. Gun'ko, М.S' Vеdamuthu, G.L. Hеndеrson, J. P. Blitz // J, Сo||oidlnteгfaсe Sсi. -2000. _У '228 'No l . _P . l57- l70 .
6. Сhaгaсterization of Fumеd Siliоas and thеiг Inteгaсtion with Water and DissolvеdProtеins. / I.F. Мironyuk, V.М. Gun'ko., V. V. Turoц v,
-i.
zarl,o' к. rеboаi i
- Skubiszewska-Zigba// Colloid. Surf. A. - 2oo|'_ v. l80, N" i-'. -Р. 87.1o1.7 ' Adamson A.W. Phуsiсal Chеmistгy оf Surfaсе. Mosсow:,й ', ]Dтg . 568 p.
8. Gтegg S.J., Sing K.S.W' Adsorption, Suгfaсе fuеa and Porosity. Мosсow: Мiц 1970. .407 p.
9. Avniг D., Jaronieо М. -An .Isotheгm Еquation for Adsorрtion on Fгaсtal Suгfaсes ofHеtеrogеnеous Porol's Мatегials. //Langmuir, _ l989. _ v. j. - p. t+зt-tqзз.
10. Fraсtal dimension of miсrоpогous сarbon on the basis of Polanyi.Dubinin theory ofadsoгption / A.P. Tеrzyk" P.A, Gaudеn, G. Ryсhliсki, к. wo;sz /ёolloid. Suгf A. - 1g9g,- v . 152 . _P . 29 з . з | з .
ll.Nguyen C., Do D'D. A New Меthod for the Charaсtеrization of Poгous Мaterials. //Langmuir. * l999. _ v. l5. - P. з608.3615.
12. Gun'ko V.М.' Do D.D' Сharaсtеrization of Pore Struсturе of Carbon Adsorbеnts UsingRеgularizatiоn Pгoсеdure. Colloids Suгfl А" in prеss'
13. Provеnоhеr S.W. A Cоnstrained Regularization Mеthod for Inverting Data Rеprеsentеd byLi1еaг Algеbгaiс or Intеgгal Еquatiоns. Comp. Phуs. Comm. _ 1982' - У. 2.I, - P. 2I3-227.
l4. Nitrogen Adsorptiоn Studiеs of Сoatеd and Chеmiсally Мodified Chгomatogгaphiс SiliсaGеls. i M. Kгuk, М' Jaгoniес, М., R.K. Glpin, y.w. ihow // iangmuir' - Бgi._'. 13'No 3. - P. 545-550.
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16. Aquеous Suspеnsiоns of Fumеd oхidеs: Рartiсlе Sizе Distгibution and ZelaPotentia|. lV.М. Gun,ko,У.I,Zarko, R. Lеboda, Е. Chibowski ll Аdv, Colloid Interfaсе sсi., in prеss.17. Fumеd Siliсa CarЬoni"ed Due to Pyrolysis of Меthylеnе Chloride. / V.й d;;k;,J. Skubiszewska-Ziеba, R' Lеboda, V.I. Zarko i/ Langйuir. _ 2000. _ v. 16, No 2. _ P.374-382.
l8 Highly Dispегsеd Х/..sioz ч{ сlvsioz (Х-= Alumiпa, Titania, Aluminа/Titania) in theGas and Liquid Меdia. / v.М. Gun'ko, У.I. Zarko' R Leboda, й. Мaгсiniak' w'i"""',,
S. Chibowski // J' Colloid Inteгfaсе Sсi. - 2000. _ v. 230' _ p' igо-cos.
l9. Connесtions betwееn struоtural pгoperties and tгеatmеnts of fumed siliсas. / v.M. Gun.ko,
Е.F.Voroniц I. F. Мiгonyuk, R. Lebсida, J. Skubiszеwska-Zipba' Е.М. Pakhlov,
N.V. Gцzеnkо, A.A. Chuiko /i Colloids Suгfl A., submittеd.
20' Temperajure-Programmеd Desorption of Watеr fгom Fumеd Siliсa, Titania' Siliсa/Titania"
and Siliсa/Alumina. / v.М. Gun'kо, V.I. Zarko, B.A. Chuikov, V.V. ouJniк,
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9n.,1ч Surfaсе Pгopeгtiеs I v.|vI, Gun'ko, У,I, Zarko, v.V. тurov' R. Lеboda, an_i
Е. Chibowski l/Langmuir. _ 1999. _ v. 15, No 18. _P' 5694.5702.
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IntегГaсe Sсi. - 1999. -У.2z0,N2. -P. з02-з2з,
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- P . 166 -178 .
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| id | oai:ojs.pkp.sfu.ca:article-46 |
| institution | Surface |
| keywords_txt_mv | keywords |
| language | English |
| last_indexed | 2025-09-24T17:44:38Z |
| publishDate | 2001 |
| publisher | Chuiko Institute of Surface Chemistry National Academy of Sciences of Ukraine |
| record_format | ojs |
| resource_txt_mv | surfacezbircomua/df/a0dc2d05ae26136c01eca5bbe234e7df.pdf |
| spelling | oai:ojs.pkp.sfu.ca:article-462018-11-27T09:42:39Z Structural and adsorptive features of fumed silicas synthesized under varied conditions Structural and adsorptive features of fumed silicas synthesized under varied conditions Structural and adsorptive features of fumed silicas synthesized under varied conditions Gun'ko, V. M. Mironyuk, I. F. Zarko, V. I. Voronin, E. F. Pakhlov, E. M. Goncharuk, E. V. Leboda, R. Skubiszewska-Zieba, J. Janusz, W. Chibowski, S. Chuiko, A. A. Fumed silicas synthesized under varied conditions (stoichiometric or non- stoichiometric amounts of reactants SiC4, O2 and H2, different nozzle diameter, flow velocity and turbulence, flame temperature) were studied using adsorption of nitrogen, argon and water, infrared (IR), photon correlation spectroscopy and electrokinetic methods. Prepared silicas possess different specific surface area, structures of primary particles and their swarms, concentrations of silanols, weakly and strongly bound waters. Fumed silicas synthesized under varied conditions (stoichiometric or non- stoichiometric amounts of reactants SiC4, O2 and H2, different nozzle diameter, flow velocity and turbulence, flame temperature) were studied using adsorption of nitrogen, argon and water, infrared (IR), photon correlation spectroscopy and electrokinetic methods. Prepared silicas possess different specific surface area, structures of primary particles and their swarms, concentrations of silanols, weakly and strongly bound waters. Fumed silicas synthesized under varied conditions (stoichiometric or non- stoichiometric amounts of reactants SiC4, O2 and H2, different nozzle diameter, flow velocity and turbulence, flame temperature) were studied using adsorption of nitrogen, argon and water, infrared (IR), photon correlation spectroscopy and electrokinetic methods. Prepared silicas possess different specific surface area, structures of primary particles and their swarms, concentrations of silanols, weakly and strongly bound waters. Chuiko Institute of Surface Chemistry National Academy of Sciences of Ukraine 2001-06-10 Article Article application/pdf https://surfacezbir.com.ua/index.php/surface/article/view/46 Surface; No. 4-6 (2001): Chemistry, Physics and Technology of Surface; 20-34 Поверхность; № 4-6 (2001): Химия, физика и технология поверхности; 20-34 Поверхня; № 4-6 (2001): Хімія, фізика та технологія поверхні; 20-34 3154-8091 3154-8083 en https://surfacezbir.com.ua/index.php/surface/article/view/46/45 Авторське право (c) 2001 V.M. Gun’ko, I.F. Mironyuk, V.I. Zarko, E.F. Voronin, E.M. Pakhlov, E.V. Goncharuk, R.Leboda, J. Skubiszewska-Zieba, W. Janusz, S. Chibowski, and A.A. Chuiko |
| spellingShingle | Gun'ko, V. M. Mironyuk, I. F. Zarko, V. I. Voronin, E. F. Pakhlov, E. M. Goncharuk, E. V. Leboda, R. Skubiszewska-Zieba, J. Janusz, W. Chibowski, S. Chuiko, A. A. Structural and adsorptive features of fumed silicas synthesized under varied conditions |
| title | Structural and adsorptive features of fumed silicas synthesized under varied conditions |
| title_alt | Structural and adsorptive features of fumed silicas synthesized under varied conditions Structural and adsorptive features of fumed silicas synthesized under varied conditions |
| title_full | Structural and adsorptive features of fumed silicas synthesized under varied conditions |
| title_fullStr | Structural and adsorptive features of fumed silicas synthesized under varied conditions |
| title_full_unstemmed | Structural and adsorptive features of fumed silicas synthesized under varied conditions |
| title_short | Structural and adsorptive features of fumed silicas synthesized under varied conditions |
| title_sort | structural and adsorptive features of fumed silicas synthesized under varied conditions |
| url | https://surfacezbir.com.ua/index.php/surface/article/view/46 |
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