giai thich gian do pha

8/6/2019 Giai Thich Gian Do Pha

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Vt liu v c

NXB i hc quc gia H Ni 2007.

Tr 94 122.

Tkho: Gin pha, h mt cu t, h hai cu t, h ba cu t.Ti liu trong Thvin in tH Khoa hc Tnhin c thc sdng cho mc

ch hc tp v nghin cu c nhn. Nghim cm mi hnh thc sao chp, in n phc

v cc mc ch khc nu khngc schp thun ca nh xut bn v tc gi.

Mc lc

Chng 3 GII THCH GIN PHA............................................................................. 23.1 Mu ....................................................................................................................... 23.2 H mt cu t (h bc 1) ............................................................................................ 53.3 bc hai (K = 2)............................................................................................................ 7

3.3.1 Trng hp to thnh tecti n gin................................................................73.3.2 Trng hp c to thnh hp cht mi ..............................................................93.3.3 H bc hai trng hp c to thnh dung dch rn .......................................... 12

3.4 H bc ba (K = 3) ..................................................................................................... 153.4.1 H bc ba to thnh tecti n gin .................................................................163.4.2 H bc ba trng hp c to thnh hp cht ho hc ...................................... 18

3.4.3 H bc ba trng hp to thnh dung dch rn ................................................ 213.5 H tng tc bc ba.................................................................................................. 24

Chng 3. Gii thch gin pha

GS. Phm Vn Tng


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Chng 3

GII THCH GIN PHA3.1 Mu

Gin pha l cc thng tin cho bit s ph thuc gia nhit , p sut, tnh cht ca hcn bng nhit ng theo thnh phn c trnh by di dng gin . Gin pha cho bitkhu vc nhit , p sut, thnh phn m mt pha no , hoc mt hn hp nhiu pha tn titrng thi cn bng nhit ng. Da vo gin cho bit phng hng tng hp mt chtrn, gii thch mi bin ho xy ra trong qu trnh tng hp mt vt liu c th. C th nigin pha vi k thut tng hp vt rn nh ci la bn i vi ngi i bin.

Chng ny ch trnh by gii thch gin pha v ng dng thc t ca n, ch khng cp n cc l thuyt nhit ng v gin pha, cng nh cc phng php thc nghimxy dng gin pha.

Csl thuyt ca gin pha l quy tc pha.

H c K cu tc lp v F pha trng thi cn bng nhit ng, nu ta ch quan tmn hai yu t vt l l nhit v p sut, th s bc t do V ca hc xc nh theo hthc V = K + 2 F. Trc ht, chng ta lm quen vi cc khi nim: cu tc lp, pha vtrng thi cn bng nhit ng, s bc t do.

Scu tc lp: l s nh nht hp phn ca h cn thit biu din thnh phn tt c

cc pha trong h. Xt vi v d c th. H ch c MgO l h c mt cu tc lp (K = 1) v gi l h bc 1 v rng ngay

n nhit nng chy th trong h cng ch c mt cht l MgO.

H gm c MgO v Al2O3 l h c hai cu tc lp v gi l h bc 2 mc d nhit v thnh phn xc nh, trong h cn sinh ra mt pha rn mi gi lspinen MgAl2O4, nhng ta cng ch cn bit thnh phn ca hai cu t l c th

biu din thnh phn ca mi pha trong h.

H CaO v SiO2 c th to thnh nhiu pha rn khc nhau nh: 3CaO.SiO2 (khiu l C3S), 2CaO.SiO2 (C2S), 3CaO.2SiO2 (C3S2), CaO.SiO2 (CS ), nhng

vn gi l h bc 2 v l mt mt ct ca gin trng thi h bc ba Ca-Si-O(hnh 87).

Thnh phn FeO l mt phn ca h bc 2 st v oxi v rng vurtit ch l mt phakhng h p thc Fe1-xO do thiu st, ng thi xut hin Fe3+ (xem chngtrc). Thnh phn hp thc FeO thc t l hn hp cn bng gia 2 pha Fe1-xOv st kim loi.


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Si

Ca O

SiO

SiO2

CaO

C3S C2S

C3S2 CS

Hnh 87Mt ct CaO-SiO2 trong h bc ba Ca-Si-O

Sbc tdo V l thng s trng thi c lp gm nhit , p sut, thnh phn cc cu tc trng cho trng thi cn bng ca h. Xt vi v d:

Nc trng thi si (ngha l cn bng nc lng v hi nc) c thnh phnkhng i ng vi cng thc H2O. xc nh y trng thi cn bng ny chcn bit mt gi tr thng s trng thi l nhit hoc p sut. Theo quy tc, y ta c K = 1, F = 2 do V = 1. H c mt s bc t do cn gi l h nht bin.

Nu ta chn t do nhit th p sut hon ton c xc nh. V d chn nhit l 100oC th p sut phi l 760mmHg. nhng vng cao nh Mexico-city cp sut kh quyn ch 560mmHg th nc si 92oC.

H gm cc oxit kim loi ngay nhit cao, gi tr p sut hi trn pha rn cng nhpha lng u v cng nh so vi p sut kh quyn, bi vy ta c th b qua nh hng ca psut n cc h cn bng gia pha lng v pha rn (gi l h ngng kt). i vi cc hngng kt c th p dng quy tc pha V = K + 1 F.

Pha: l tp hp tt c cc phn ng th ca h, ng nht v thnh phn ho hc v mitnh cht vt l, nhng phn ng th ny ngn cch vi phn ng th khc bng b mt phnchia qua c s bin i nhy vt cc tnh cht ho l. Cn phi ni thm rng, phn ca hni y c kch thc ln c th p dng vo cc khi nim nhit , p sut. Nhvy th dung dch keo, dung dch cht tan c kch thc cao phn t vn gi l mt pha. Xtvi v d, mt cc nc c nc v trn b mt c hi nc l h c 3 pha: Pha rn l nc, pha lng l nc, pha hi l hi nc. Dung dch bo ho KCl v K2SO4 v di y c

mui KCl v K2SO4, trn mt dung dch c hi nc bo ho l h cn bng c 4 pha: pha hil hi nc, pha lng l dung dch bo ho hai mui v hai pha rn KCl, K2SO4. un nngmt mu st nguyn cht ln 910oC s xy ra qu trnh bin ho th hnh Fe (thuc h lp

phng tm khi) thnh Fe (thuc h lp phng tm mt). Khi ginhit th h chai pha cng nm cn bng vi nhau. trn hoc di 910oC th h ch c mt pha. Khi giyn nhit mt thi gian ri lm lnh nhanh xung nhit phng cho Fe khngkp trv Fe th h vn c mt 2 pha nhng khng phi trng thi cn bng. V rng Fevn ang chuyn ho thnh Fe tuy vi mt tc v cng b.

Trng thi cn bng nhitngl trng thi m h khng thc hin mt cng no vimi trng hoc ngc li mi trng ngoi cng hon ton khng tc dng mt cng no


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i vi h. Trong thc t tht kh lng bit c h trng thi cn bng hay cha. trli cho cu hi ny tu tng tnh hung ring bit c th tin hnh nh sau:

1) Gi yn mi thng s trng thi (T, P, thnh phn) bng phng php thc nghimno theo di s pha ca h c thay i theo thi gian khng? Nu s pha cnthay i th h cha t trng thi cn bng. Nu s pha vn gi nguyn khng itheo thi gian th h t trng thi cn bng. y cn lu n phng dinng hc ca qu trnh l iu quy tc pha khng nhc n. V d, trn gin bchai CaO-SiO2 cho thy tu theo t l vi v ct, chng c th tng tc vi nhaucho nhiu hp cht C3S, C2S, C3S2, nhng khi ta trn vi v ct tht lu di thchng cng khng tng tc vi nhau.

2) i vi nhng h s tng tc c th xy ra vi tc quan st th tt nht l bngthc nghim xc nh trng thi cn bng khi i t hai hng: un nng dn nnhit kho st, mt khc t nhit tng i cao lm ngui lnh dn n nhit kho st ri cng xc nh s pha trong hai mu thc nghim. V d cu hi t

ra trong h CaO-SiO2 1100oC c mt pha C3S trong trng thi cn bng haykhng? Hay cu hi t ra mt cch khc l: Ti sao khi trn CaO v SiO2 theo tl 3 : 1 ri a nhit ln 1300oC thu c sn phm C3S, nhng cng t hp a ln 1100oC th khng thu c C3S? Phi chng 1100oC phn ng c thxy ra nhng vi tc qu chm? gii quyt vn ny ta phi tin hnh thcnghim theo 2 hng: un nng ln 1300oC, gi mt thi gian cho phn ng ktthc, thu c mt pha rn C3S sau lm lnh C3S t 1300oC n 1100oC v xcnh thnh phn pha thu c CaO v C2S. Hng th hai l un nng hn hpCaO v SiO2 c t l 3 : 1, nh vy t nhit phng n 1100oC gi lu mt thigian, xc nh thnh phn pha cng thu c hai pha l CaO v C2S. Hp cht C3Skhi ngui lnh t tn 1250oC b phn hu thnh CaO v C2S cn khi un nng

CaO v SiO2 n 1100oC ch c pha mi l C2S (xem hnh 102, trang 138)3) Mt phng php khc kim tra trng thi cn bng bn ca mt pha l s dng

cc cht phn ng ban u khc nhau xt tnh ng nht thu c. V dNa2Si2O5 c phi l mt pha bn nhit ng khng.

Ta tin hnh tng hp pha bng nhiu phng php khc nhau:

un nng hn hp Na2CO3 v SiO2 ly theo t l mol 1 : 2 n khong 700 750oC v gi trong vi ngy nhit .

Trn ln dung dch nc ca mui natri vi hp cht oxit silic tan trong nc (vd este etylic ca axit octosilisic) sau sy kh dung dch cho n to thnh gel,ri cui cng nung gel khong 700oC.

Phng php th ba l lm ngui nhanh mt hn hp nng chy cc cht ban u(to thu tinh) ri nung nng vi gi700oC gy nn s kt tinh thu tinh.

V rng c ba phng php u thu c silicat natri Na2Si2O5 do ta c th kt luny l mt pha bn v nhit ng.

S dng cc phng php tng hp khc nhau c ngha rt ln trong vic kim tra tnhcn bng ca kt qu thu c. S tng tc ca cc pha tinh th hoc s kt tinh cc phathu tinh thng xy ra theo vi giai on v si gn n trng thi cn bng giai oncui cng c th rt chm. Bi vy, chng minh tnh cn bng ca sn phm cui cng cn

s dng nhiu cch tng hp.


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Trng thi khng bn

Trng thi bn

Trng thi gi bn

G

Hnh 88. Biu din bng th v tr tng i ca trng thi gi bn,trng thi khng bn v trng thi bn

trng thi cn bng ca h c nng lng t do thp nht (hnh 88). Vn cn xt h t cn bng hay cha, cn phi lu n l ngoi cc tiu ca nng lng t do cn v trcc tiu khc ca nng lng t do nhng khng thp bng so vi trng thi cn bng. caoca hng ro th nng khi chuyn t trng thi gi bn sang trng thi bn c nhng lc lnn ni khng th thc hin c s chuyn . Trng thi gi bn ca kim cng nhit

phng so vi than ch c th v nguyn nhn nh vy. Hng ro nng lng (hoc gi l nnglng hot ho) ca qu trnh bin ho kim cng thnh than ch ln n ni nhit phngkim cng c to thnh t cc iu kin khc nhau vn bn vng mc du l trng thi gi

bn v nhit ng. ngha nhit ng ca trng thi gi bn hnh 88 c th hiu nh sau: qucu nm trn nh g c th ri xung bn ny hoc bn kia khi c mt s dch chuyn nh.L dnhin vic chuyn t trng thi khng bn sang trng thi bn hoc gi bn u khngcn nng lng hot ho. V d v trng thi khng bn rt him (v n l khng bn) nhngcng c khi gp. Nh sau ny s thy khu vc ca hai cht lng khng trn ln to thnh mthnh thi vm (gi l spinoal). Trong mi vm spinoal cht lng ng th l khng bnv t phn hu thnh hai cht lng khc (qu trnh ny c gi l qu trnh phn huspinoal).

3.2 H mt cu t(h bc 1)

K = 1 do V = 3 F

H c mt pha l h nh bin, c trng trng thi cn bng ca h ta cn bit hai

thng s l nhit T v p sut P, ngha l hc biu din bng mt vng c T, P thay ic lp vi nhau. H c hai pha l h nht bin, c trng trng thi cn bng gia hai phach cn bit mt thng s (hoc T hoc P), thng s kia hon ton ph thuc vo thng schn. Nh vy trng thi cn bng gia hai pha ca h bc mt c biu din trn mtng xc nh.

Phng trnh Claperon-Clauziut biu din ng cn bng nht bin .

Q =Tdp

dt

V (32)

Q l nhit chuyn pha, V l bin thin th tch khi chuyn pha. H cn bng gia ba pha

c s bc t do bng 0, ngha l trng thi cn bng gia ba pha ca h bc mt hon ton


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bar

c xc nh bng mt im. V d trng thi cn bng gia nc lng, nc v hi ncc biu din bng im A trn hnh 89 ng vi p sut hi nc 4,6 mmHg v 0,0098oC.Tt c cc im trn ng AC u c trng cho trng thi cn bng gia hai pha nc lngv hi nc. Cn bng gia nc v nc lng c biu din bng cc im trn ng

AD. Cc im trn ng AB biu din trng thi cn bng gia nc v hi nc. Hnh90 l gin trng thi ca lu hunh. Lu hunh tn ti di hai dng th hnh l S tphng bn nhit thp, S n t bn nhit cao hn. Trn gin c gii thiu ccmin ng vi cn bng nh bin, ng ng vi cn bng nht bin, im ng vi trng thicn bng v bin. V dim A c trng cho cn bng gia 3 pha l S t phng S n t vhi lu hunh.

Hnh 89Gin trng thi ca nc

Hnh 90Gin trng thi ca lu hunh

Trn gin cn trnh by cc min c trng cho trng thi gi bn, v d lu hunhlng c th tn ti trng thi gi bn trong khu vc CHE. Lu hunh t phng c th tn

ti trng thi gi bn trong min AHE.Hnh 91 v 92 l gin trng thi ca C v ca SiO2. Trong SiO2 l thnh phn ch

yu ca nhiu loi vt liu xy dng cng nh cc vt liu k thut khc, hn na n l oxitph bin th hai trong v Qut (ch thua H2O), nn ta xt k hn gin ny. Silic oxit cnhiu dng th hnh (xem chng trn) di p sut kh quyn c s bin ha lin tc:

Thch anh o573 C Thch anh

o870 C Tridimit

Lng o1710 C Cristobalit

o1470 C

Tng p sut ln s xy ra cc bin ho nh sau (hnh 92):

+ Min triimit hp li dn v khong 900 atm th mt hn+ Min cristobalit bin mt trn 1600 atm

+ T trn 1600 atm pha bn duy nht ch cn thch anh

D C

B

A

Nc

Nclng

Hinc

T

P P

AB

C

H

E

St

phng Snt

125o

1510o

Hi

T


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1000 2000 3000 4000

100

200

300

400

500

Kimcng

Lng

Than ch

oC 1000500 1500

500

lng

Thchanh

oC

1000

1500

Bar

Thchanh

SiO2

Tridimit

CristobalitHnh 91Gin trng thi ca C

Hnh 92Gin trng thi ca SiO2

Khi tng p sut ln lm bin mt triimit v cristobalit, iu ny ph hp vi gi tr ttrng ca thch anh cao hn t trng ca cc pha triimit cng nh ca cristobalit (bng 30).

Bng 30T trng ca cc dng th hnh SiO2Dng th hnh T trng (g/cm3) Dng th hnh T trng (g/cm3)

Triimit 2,298 Coezit 2,90

Cristobalit 2,334 Stisovit 4,28

Thch anh 2,467

Tng p sut s to thnh cc dng th hnh c th tch ring b hn, theo nguyn tc , p sut rt cao, trn 20.000 40.000 atm (tu thuc vo nhit ) thch anh c th binthnh dng th hnh khc nhau nh ceozit v trn 90.000 120.000 atm cn c mt dng thhnh bn na l stisovit.

3.3 bc hai (K = 2)

Trong trng hp tng qut V = 2 + 2 F = 4 F.

Nh vy, trng hp n gin nht l F = 1 c s bc t do bng 3. biu din trngthi y ca cc h nh vy phi s dng gin khng gian: mt trc biu din p sut,mt trc biu din nhit , mt trc biu din thnh phn. i tng ca ho vt liu ch

yu ch quan tm n cn bng pha trng thi rn, do ta c th b qua nh hng ca yut p sut, kho st h cn bng di p sut kh quyn. Di y ta ch trnh by gin trng thi h bc hai trn mt phng, trong mt trc biu din nhit cn mt trc biudin thnh phn ca h.

3.3.1 Trng hp to thnh tecti n gin

trng thi lng cc cu t ho tan hon ton vo nhau, trng thi rn cc cu t honton khng ho tan vo nhau, ngha l ch kt tinh ra cc cht nguyn cht khng to thnhdung dch rn, ta c gin tecti n gin (hnh 93). Min lng l khu vc nm trong vng

pha trn ng KEH.


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Min KEM c trng cho trng thi cn bng gia hai pha l pha RA v pha lng l dungdch bo ho tinh th RA. Min HEN c trng cho trng thi cn bng gia hai pha l rn Bv dung dch lng bo ho B. V d h c im biu din l C gm hai pha nm cn bng vinhau l pha rn c im biu din R, pha lng c im biu din L, t l khi lng ca hai

pha c xc nh theo quy tc n by.

A

K

L

B

H

E

P

M N

(b) A

K

B

H

E

P

M N

(c)

R

D I

Hnh 93

H bc hai trng hp to thnh tecti n gin (a),cu t A c hai dng th hnh, nhit chuyn ho gia chng ng vi im P (b),cu t B c hai dng th hnh, nhit ca chng ng vi im R v im I (c).

h C ta c:

=Lng pha lng CR

Lng pha rn CL

Min nm di ng MN biu din h ch c hai pha rn l RA v RB. Tt c cc imnm ngay trn ng KE biu din trng thi ca h ch gm mt pha lng bo ho RA haycn gi l ng kt tinh rn RA. Cng nh vy ng kt tinh RB l HE. im E gi l imtecti biu din dung dch lng bo ho ng thi RA v RB. Chng ta xt qu trnh nguilnh dung dch lng c im biu din L0 (hnh 93a). Khi ngui lnh im biu din ca ht ti L1 th bt u bo ho rn B. T tri vic lm ngui lnh tip tc h s c hai phacng nm cn bng vi nhau l tinh th rn B v dung dch bo ho rn B. Gi s lm nguilnh h cho n im C (C l im biu din thnh phn ca h ton b c rn ln lng) thim biu din thnh phn pha lng t ti L, cn im biu din thnh phn pha rn R. Khingui lnh im biu din ton b ti F, th im biu din pha lng ti E, im biu din

pha rn ti N. Pha lng E bo ho ng thi RA v RB, nn t tri h c 3 pha l rn A,rn B v lng E. Theo quy tc pha i vi h ngng kt (khng ch ti nh hng ca psut P) lc ny h v bin (h bc 2 nn K = 2, c mt 3 pha: F = 3 do V = 0). Ngha ltrong qu trnh kt tinh ng thi hai pha rn: lng E R A+ RB nhit ca h khng thay

i na mc du ta vn tip tc lm lnh. Trn hnh 93 pha nhit thp nht (st cnh AB)c trnh by hnh thi pha rn thu c khi lm lnh cc h lng khc nhau. Nu pha lng cthnh phn ng vi thnh phn tecti th lc t nhit ng vi im E s bt u kt tinhng thi c hai pha rn, do cc tinh th RA v RB thu c u c ht rt mn. Pha rn thuc sau khi mi nhn bng v xem trn knh hin vi thy mt tp hp cc ht rt nh kchthc kh u nhau, trong khi nu lm lnh hn hp lng giu A hoc giu B hn so vithnh phn tecti s thu c hn hp rn c cha cc tinh th A hoc tinh th B kh ln nmtrong mt tp hp cc ht mn ca pha rn tecti.

Trn hnh 93b ng vi trng hp cu t A trng thi rn c hai dng th hnh, nhit chuyn ho gia chng ng vi im P, cn hnh 93c th pha rn B c hai dng th hnh, mtdng c nhit chuyn ho ng vi im R (cao hn nhit tecti), mt dng khc cnhit chuyn ho thp hn nhit tecti (ng vi im I).

K

R

CM

N

Lo

E FR'

H

L

L1

A B(a)


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Cd Bi

271o

21o

144o

lng

20 40 60 80

% khi lng Hnh 94Gin trng thi h bc 2 Cd-Bi

3.3.2 Trng hp c to thnh hp cht mi

Gin c dng nh trn hnh 95 v 96. Thnh phn hp cht mi trn hai gin nyu biu din im S. Hai gin ny khc nhau ch: trn gin 95 hp cht S c cci r rt l M, l im cc i trn ng cong kt tinh hp cht S (ng E1ME2), cngin 96 ng kt tinh hp cht S ch c mt on E1P khng c im cc i. Qu trnhtng hp cht S hai trng hp ny khc nhau. Hp cht S trn hnh 95 gi l hp cht nngchy tng hp, cn hp cht S trn hnh 96 gi l hp cht nng chy khng tng hp. Khily cc cht A v B theo ng t l trong hp cht S nu nng chy (ng vi im Lo) ri kttinh hp cht S. trng hp hnh 95 khi nhit t ti im M th bt u kt tinh hp

cht S, qu trnh kt tinh din ra cho ti khi tt c cc pha lng ht. Sn phm thu c l hpcht S nguyn cht vi tinh th hon chnh. Cn trng hp hnh 96 khi lm lnh hnim L (trn ng kt tinh B) s xy ra qu trnh kt tinh B. Qu trnh kt tinh B tip tc thim biu din h ton b chy t L n G, im biu din pha lng cn li (bo ho B) chyt L n P, im biu din pha rn chy t R1n R (cc im ny u biu din B nguyncht nhng nhit khc nhau). Khi im biu din pha lng n P (nm trn ng kttinh S l E1P) s bt u kt tinh hp cht S. Lc ny trong h xy ra phn ng: dung dchlng P + rn B = hp cht S.

Nu thnh phn ban u ly A v B theo ng t l ca chng trong hp cht S th phnng ny kt thc khi ng thi ht rn B v dung dch lng P. Nu thnh phn ban u ly

tha B th phn ng kt thc khi tiu th ht dung dch lng P v cui cng thu c hai pharn l S v B. Nu thnh phn ban u ly tha A th phn ng kt thc khi tiu th ht chtrn B v qu trnh ngui lnh s tip tc kt tinh cht rn S thnh phn pha lng chy t P nE1, thnh phn pha rn chy t G n H. T dung dch E1, s kt tinh ng thi rn S v rn A.Cui cng thu c hn hp hai pha rn A v S.


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A BS

E1

E2

MA

TB

Lo

A BS

Lo

E1

TA

TB

L

PR

H

R1

G

Hnh 95H bc hai to thnh hp cht nng chytng hp

Hnh 96H bc hai to hp cht nng chykhng tng hp

Trong thc t, qu trnh ho tan rn B vo lng P kt tinh hp cht S khng xy rang nh l thuyt chng ta va trnh by. V rng rt c th nhng tinh th rn B cha tan htth b bao ph bi cc tinh th hp cht S nn khng tip xc vi dung dch lng P c.Do , qu trnh xy ra gn ng vi l thuyt trnh by trn gin chng ta phi m bomt iu kin kthut sao cho tc ho tan rn B ph hp vi tc kt tinh hp cht S vm bo tinh th rn B thng xuyn tip xc vi dung dch P.

Di y trnh by mt s gin trng thi h bc hai c to thnh hp cht ho hclin quan n cc loi vt liu v c.

Hnh 97H SiO2-Cr2O3

Hnh 98H Na2O-SiO3

V d ta xt gin trng thi ca h CaO-SiO2hnh 102. Hai oxit ny c th phn ngvi nhau to thnh 4 hp cht. Hp cht CaO.SiO2 (vit tt l CS) nng chy tng hp gn1600oC, h p cht C3S2 nng chy khng tng hp 1464

oCphn hu thnh C2S v phalng. Hp cht C2S nng chy tng hp khong 2100

oC. Hp cht C2S tn ti di haidng th hnh: trn 1450oCgi l -C2S, di 1450

oC chuyn thnh dng -C2S. Hp chtC3S nng chy khng tng hp 2150

oC thnh CaO v pha lng. Hp cht C3S khi lmngui lnh n 1250oC th phn hu thnh CaO v C2S.


11/30

11

20 40 60 80

% mol

1500

1700

1900

2100

SiO2

2300

2500

Sc2SiO5 Sc2Si2O7

2 phalng

1:1 1:2Sc2O3

Hnh 99H Sc2O3-SiO2

1300

1500

1700

1900

2100

2300

20 40 60 80

C3A CA2

Al2O3C12A7

CA CA6CaO

Hnh 100H CaO-Al2O3

MS20 40 60 80

% mol

1200

1400

1600

1800

SiO2

M2S

1543

1557

1850

1890

2 lng

MgO

Hnh 101H SiO2-MgO

Hnh 102H CaO-SiO2

Trn cc hnh 103 c vng phn lp gia hai pha lng gi l vng cupl phn lp hocmi vm spinal. Trong vng mi vm spinal, cht lng ng th l trng thi khng bnv nhit ng s t phn hu thnh hai pha lng. Trng hp ny kh ph bin trong cc hsilicat v borat. Kho st kiu gin ny c ngha ln i vi k thut silicat v k thutgm cng nh nghin cu cc qu trnh a cht.

1464

CaO

Cot

CSC3S2C2S

C3SSiO2

'C2S+C3S

1250

'C2S+CC2S3

+CS

C2S3+CS

14601450

+C2S

C3S

2050

2150

1544

870

11751436

14701680

90807060302010

2400

2200

2000

1800

1600

1400

1200

1000

2 Lng


12/30

12

A B

E

(a)

TA

TB

MN

A B

E

(b)

TA

TB

A B

E

(c)

TA

TB

Hnh 103H bc hai trng hp c s phn lp gia hai pha lng

S phn lp thnh hai pha lng c th xy ra trong mt khong nhit xc nh. Trnhnh 103a cupl phn lp nm ngay trong vng lng, cn hnh 103b th cupl phn lp xy ranhit thp hn nm trn ng kt tinh rn B, chia ng kt tinh B thnh hai phn v

vng phn lp to thnh vm spinal. im M v N u ng vi trng thi cn bng v binv lc h c 3 pha: 2 pha lng v 1 pha rn.

Khi lm ngui lnh vi tc nhanh v cu trc tinh th ca B phc tp kh kt tinh, thvng phn lp ca pha lng c thi vo khu vc gi bn pha di ng MN ca hnh103b. Hnh 103c ng vi trng hp vng phn lp hai pha lng nm trong khu vc gi bn

pha di nhit tecti.

3.3.3 H bc hai trng hp c to thnh dung dch rn

a) H to thnh dung dch rn khng hn ch: c 3 kiu gin nhtrn hnh 104.

A B

TA

TB

x(a)

x1x2

MN

H

L

PQ

R

Lo

x1

A B

TA

TB

x

M

(b) A B

TA

TB

x

M

(c) Hnh 104H bc hai trng hp to thnh dung dch rn khng hn ch

Kiu th nht (a) ng vi trng h p khi tng nng mt cu t s lm tng (hocgim) nhit bt u kt tinh ca h mt cch u n. Kiu th hai (b) ng vi trng hpkhi tng nng ca bt k mt cu t no cng lm gim nhit bt u kt tinh ca h vkiu th ba (c) l khi tng nng ca mt trong hai cu tu lm tng nhit bt u kttinh ca h.

Chng ta xt qu trnh xy ra khi lm ngui lnh hn hp L0 (hnh 104a), L0 nm trongkhu vc lng hon ton. Khi lm ngui lnh im biu din trng thi ca h thay i t L0n L. n L h bt u kt tinh. Tinh th pha rn u tin c im biu din l R giu B hnso vi dung dch lng ban u L0. Lc ny h c hai pha: dung dch lng v dung dch rn.Trong qu trnh ngui lnh tip tc im biu din ca h tng cng chy t L n P, im

biu din pha lng chy t L n Q, im biu din pha rn chy t Rn P. V d khi im


13/30

13

biu din ton bt ti H th im biu din pha lng t ti M v im biu din pha rn tti N. Theo quy tc n by ta c:

Ti H:

tinhktnrphang

lKhi

ilcnlngphanglKhi=

HM

HN

Khi im biu din h ton bt ti P th lng cht lng ht.

Hnh 105 trnh by mt s gin trng thi ca h bc hai to thnh dung dch rnkhng hn ch.

2000

2200

2400

2600

NiO MgO(1) MgOFeO

1600

2000

2400

2800

(2)

(NaAlSi3O8)(CaAl2Si2O8)

1100

1200

1300

1400

(3)

1500

anoctit anbit (NaAlSi3O8)(CaAl2Si2O8)

1380

1420

1460

1500

(4)

1540

gelemit okemanit

1580

Hnh 105Gin trng thi ca h bc haito thnh dy dung dch rn khng hn ch

Qu trnh xy ra khi lm ngui lnh khi nng chy L0 nh trnh by trn y phithc hin tc lm lnh rt chm v u n lm sao bo m lun lun gi trng thi cn

bng gia pha lng cn li v pha rn kt tinh. iu ngha l m bo s khuch tn cacc tiu phn trong pha rn cng nh trong pha lng vi tc sao cho gic trng thicn bng. iu ny rt kh thc hin. Do qu trnh kt tinh i vi cc h c gin to

thnh dung dch rn thng to ra sn phm khng cn bng, hoc l sn phm gi bn. Vrng khng th to c tc ngui lnh tht ng u v tht chm cho php gi trng thicn bng tng nhit mt. V d tinh th tch ra u tin khi lm ngui lnh khi nngchy L0 c thnh phn l X1, nu khng thi gian thit lp cn bng mi ca cc tinhth vi cht lng th thc t c th xem nh nhng tinh th mt khi h v nh vy tinhth tch ra tip theo s giu A hn so vi l thuyt. Kt qu pha rn tch ra khng ng nht:Phn trung tm l tinh th tch ra u tin c thnh phn X1, nhng theo mc cng xa tmth cng giu cu t A. S hnh thnh cu trc nh vy pht trin xung quanh tm ca mmthng xuyn xy ra khi kt tinh khi lng nng chy (hnh 106).


14/30

14

Nhn tinh thkt tinh u tin

a1a2

a3 a4

Hnh 106S khng ng nht v thnh phn khi kt tinh dung dch rn t khi nng chy

S kt tinh sai lch nh vy thng gp trong cc khong cht. V d trong plagiocla(mt dng ca phenpat) l dung dch rn gia anoctit v anbit (hnh 105-3). ni la ccha plagiocla c hnh thnh khi ngui lnh macma nng chy mt cch chm chp, tuynhin trong khi plagiocla vn thy s khng ng nht v thnh phn, trung tm thnggiu canxi cn pha ngoi th giu natri hn.

b) H to thnh dung dch rn hn ch

y l trng hp ph bin nht. V nguyn tc c th phn thnh hai kiu gin nhtrn hnh 107.

E

A B

TA

TB

M N

H K

a b

(1)

V

Lo

M

E

A B

TA

TB

N

H K

a b

(2)

P

SQ

D

L R

c

Hnh 107H bc hai to thnh dung dch rn hn ch Kiu tecti (1), kiu peritecti (2)

Kiu tecti (1) c dng tng t nh gin h bc hai to thnh tecti n gin (hnh93a) ch c iu khc l ng kt tinh TAE khng kt tinh A nguyn cht m kt tinh dungdch rn B ho tan vo A gi l dung dch rn , cng vy ng TBE kt tinh dung dch rn:A ho tan vo mng li tinh th ca B gi l dung dch rn . Cc ng HMTA, KNTB cho

bit tnh tan thay i theo nhit . nhit tecti tan l ln nht.Phn hnh v nh pha trn hnh 107-2 cho thy kiu peritecti l s t hp ca gin to

thnh dung dch rn khng hn ch (a) v gin c s phn lp trong khu vc dung dch rn(b). V d xt qu trnh ngui lnh pha lng Lo, khi im biu din ca ht ti L th bt ukt tinh dung dch rn c im biu din l R, lm ngui lnh tip tc im biu din hton b chy t L v D, im biu din pha lng chy t L v P, im biu din pha rn chyt R v N. Khi im biu din h ton bt ti im D th im biu din pha lng t tiim P, im biu din pha rn N v:

D:Lng pha rn tch ra

=Lng pha lng P cn li DN

PD


15/30

15

Lc ny h c 3 pha: pha rn c im biu din l N v pha rn mi bt u kt tinhc im biu din l M, pha lng P. Do h v bin ngha l nhit cng nh thnh phncc pha khng thay i na trong qu trnh lm lnh. Thc ra lc ny c phn ng: pha rn tan vo dung dch lng P kt tinh pha rn .

R + Lng P R

A B

TA

TB

M N

H K

(1)

E1

E2

M

A B

TA

TB

H K

(2)

E

PQ

a b c d

S

Hnh 108Gin trng thi bc hai trng hp c to thnh hp cht nng chy tng hp (1), vhp cht nng chy khng tng hp (2) cc cu t hp phn cng nh hp cht mi cth to thnh dung dch rn hn ch

Tu theo v tr im biu din dung dch ban u nm v pha phi hay pha tri im M,qu trnh v bin s kt thc bng cch s bin mt pha lng P (nu thnh phn ban u nm

pha phi im M) hoc tan ht pha rn (nu thnh phn ban u nm pha tri im M nhtrng hp ang xt). trng hp ang xt khi tinh th cui cng tan ht, h ch cn phalng P v pha rn . Lm lnh tip tc im biu din h ton b chy t D n Q, im biudin pha lng chy t P n S, im biu din pha rn chy t M n Q. Khi im biu din

h ton bn Q th git cht lng cui cng S bin mt. H ch cn mt pha rn . Khi nhit hn im V th pha rn bt u phn hu thnh pha rn v h gm hai pha. Hnh108 l gin trng thi h bc hai, trng hp c to thnh hp cht mi v hp cht mi ckh nng to thnh dung dch rn vi cu t hp phn.

Dung dch rn ca hp cht mi vi cc cu t hp phn gi l dung dch rn . hnhdung gin to thnh dung dch rn ca hp cht nng chy khng tng hp (hnh108-2),

pha trn hnh v c trnh by mt lot cc hnh nh t trng hp (a) cht S khng ho tancc cu t hp phn v cc cu t cng kt tinh ra dng nguyn cht; n trng hp (b), hpcht S c to thnh dung dch ; trng hp (c) c to thnh dung dch v dung dch ;trng hp (d) c to thnh dung dch ; dung dch v dung dch .

Trong phn trn, khi trnh by v dung dch rn ta gp cc gin trng thi hnh 78,79, 81, 82, di y gii thiu thm mt s gin thuc kiu ny.

Trn gin 79 v 111 cho thy tinh th spinen MgAl2O4 v FeAl2O4 ch ho tan thmAl2O3 ch khng ho tan MgO v FeO hay ni cch khc, cc cation Al

3+ c thi vo hctrng ca phn mng anion O2 ca tinh th spinen, cn cc cation Ca2+, Fe2+ khng thi vocc hc trng .

3.4 H bc ba (K = 3)

Trng hp tng qut


16/30

16

V = 3 + 2 F = 5 F

Nh vy, trng hp n gin nht khi h ch c mt pha th s bc t do bng 4, nghal biu din trng thi ca h cn 4 thng s v ta phi s dng khng gian nhiu chiu.

Nh phn trn ta ni khi nghin cu trng thi ngng kt (ch c cn bng pha lng v pharn) c th b qua s c mt ca pha hi. Vy quy tc pha i vi trng hp ny s l V = 3+ 1 F = 4 F. Lc h c mt pha s bc t do bng 3, ta dng mt trc biu din nhit, hai trc biu din hai thnh phn ca hai cu t, cn thnh phn ca cu t th 3 c thsuy ra mt cch d dng t hai thnh phn ca 2 cu t kia.

2000

2200

2400

2600

CaO ZrO220 40 60 80CaZrO3

1150

1200

1350

1400

Ca2SiO4 Fe2SiO420 40 60 80

1300

1250

olivin Ca-Fe

oC

+ lng

+ lng

olivin Ca-Fe+

Hnh 109H CaO-ZrO2

Hnh 110H CaO.SiO2-2FeO.SiO2

2100

1700

1900

20 40 60 80

1300

1500

oC

FeO Al2O3

Al2O3+ sp

sp

sp + lng

FeAl2O4Spinen

1500

1450

1350

1400

20 40 60 80

1300

1250

olivin Ca-Fe

oC

nefelin anoctit

Hnh 111H FeO - Al2O3

Hnh 112H hflin anoctitNa2Al2Si2O8- Ca Al2Si2O8

3.4.1 H bc ba to thnh tecti n gin

Hnh 113 gii thiu gin trng thi h A-B-C hnh thnh tecti n gin. Khi dng ccmt phng ng nhit ct gin khng gian ri chiu trc giao ln tam gic thnh phn ta sthu c gin mt phng c ghi cc ng ng nhit nh hnh 114 l gin trng thi hZn-Cd-Sn. Chng ta xt qu trnh ngui lnh hn hp nng chy thnh phn 30% Cd, 30% Snv 40% Zn. Hnh chiu ca im biu din h ny trong khng gian ln tam gic y ng viim L. Nh trn hnh v cho thy, khi lm lnh n gn 280oC th dung dch bt u bo ho

Zn, lm lnh tip tc s tch ra cc tinh th Zn. im biu din ton b ca h lun lun nm


17/30

17

L, im biu din thnh phn pha lng cn li chy t L n K (K l giao im gia ngthng k t Zn qua L v ng E3-E l ng bo ho ng thi Zn-Cd), im biu dinthnh phn pha rn nm Zn. Khi im biu din pha lng t ti K th bt u bo ho ngthi Zn v Cd nn Zn v Cd cng kt tinh. Lm lnh tip tc s kt tinh ng thi Zn v Cd,

im biu din thnh phn pha lng chy t K v E, im biu din pha rn chy t Zn ti R(R l giao im ca cnh Zn-Cd v ng thng k t E qua L). Khi im biu din thnhphn pha lng ti E, im biu din thnh phn pha rn t ti R lc ny ta c:

=ilcnElngphangL

tinhktnrphangL

LR

LE

Trong pha rn th:

=CdnrngL

ZnnrngL

RZn

RCd_

_

Pha lng E bo ho ng thi Zn, Cd, Sn, do bt u kt tinh ng thi Zn, Cd, Sn vh c 4 pha (lng E, rn Zn, rn Cd, rn Sn) ngha l s bc t do bng khng. Lm lnh tiptc nhit ca h vn gi nguyn nhit tecti, thnh phn pha lng vn gi nguyn Ecn thnh phn pha rn chy t R v L. Khi thnh phn pha rn n L th lng cht lng ht.

E1

E2E3

E'1

E'2E'3

A B

C

E

E'

TA TB

CT

t1

t'1

TE

P T1

Hnh 113

Gin trng thi h bc ba trng hp to thnh tecti


18/30

18

380

360

340

320

300

260

280

240220200

180

Sn (232) Cd

Zn

R

L

K

E

E1

E2

E3

300

260

240

220

200

180

(321)

(419)

30% Cd

30% Sn

Hnh 114Gin trng thi h Zn-Cd-Sn c cc ng ngin

3.4.2 H bc ba trng hp c to thnh hp cht ho hc

Hnh 115 l hnh chiu trn tam gic thnh phn ca gin trng thi h bc ba, trong 2 cu t B v C c to thnh hp cht nng chy tng hp. C th xem tam gic ABC

hnh 115a gm hai tam gic nh ABS v ASC ng vi h bc ba kiu tecti n gin nhxt trn hnh 114. iu cn xt y l v tr im yn nga K. y l im tecti ca h bchaiA-S. im K chim v tr thp nht trn ng AS nhng li chim v tr cao nht trn ng

bin gii E1KE2. Cn hnh 115b phc tp hn, y hp cht S cng nng chy tng hpnhng qu trnh kt tinh ca mt s khi lng bc ba xy ra kh phc tp. Chng ta thy trnhnh 115b c ba min: kt tinh A (min Ae1PEe4), kt tinh B (min Be1Pe2), kt tinh S (mine2PEe3) gp nhau P. Ngha l dung dch bo ho ng thi A, B v S nhng nm ngoi tamgic ABS. Ni P vi B ct AS M ta c Lng P + Rn B = Rn A + Rn S. Vy P l im v

bin khng tng hp, trong khi E1, E2 (trn hnh 115a) v E (trn hnh 115b) l im vbin tng hp, ngha l dung dch lng kt tinh ng thi 3 pha rn.

Ta xt qu trnh xy ra khi lm ngui lnh hn hp lng c im biu din l L. V rng Lnm trong min kt tinh A do trc ht kt tinh rn A, im biu din thnh phn pha lngcn li chy t L v K (K l giao im ca ng AL ko di ct ng e1P), im biu din

pha rn nm A. Khi im biu din pha lng t ti K th bt u bo ho B, ngha l kttinh ng thi c A v B, im biu din pha lng chy trn ng KP, im biu din pharn chy t A n R (R l giao im ca on thng PL vi on thng AB). Khi im biudin thnh phn pha lng t ti P th im biu din thnh phn pha rn t ti R. V lng

bo ho ng thi 3 pha rn A, B, S do bt u xy ra qu trnh v bin khng tng hpho tan B kt tinh A v S. Trong khi xy ra qu trnh ny th im biu din thnh phn

pha lng nm nguyn P, cn im biu din thnh phn pha rn chy t Rn L. Khi im

biu din thnh phn pha rn n L th pha lng kh ht.


19/30

19

A

B C

e1

e2 e3

e4E1 E2K

S

(a)

A

B C

e1

e2 e3

e4

E

K

S (b)

R

PM

L

Hnh 115Hnh chiu trc giao ln tam gic thnh phn ca gin trng thi h bc ba c to thnhhp cht bc hai nng chy tng hp (a)

Lng E1 rn A + rn B + rn S

Lng E2 rn A + rn C + rn S

Hnh 116 l hnh chiu ln tam gic thnh phn ca gin khng gian h bc ba c tothnh hp cht bc hai S nng chy khng tng hp.

A

B C

e1

e2

e4

L1

L2

S

P

e3

E

A

B CS1

S2

Hnh 116H bc ba to thnh hp cht bc hainng chy khng tng hp

Hnh 117Phng php phn chia ginbc ba thnhnhng tam gic nh

Xt hnh 116: im E biu din thnh phn pha lng bo ho ng thi A, B v S. Vrng E nm trong tam gic ABS nn y xy ra qu trnh v bin tng hp.

Lng E1 rn A + rn B + rn S. Trong khi lng P bo ho ng thi rn A, rn

C v rn S nhng nm ngoi tam gic ASC nn ti y xy ra qu trnh v bin khng tnghp.

Lng P + rn C rn A + rn S. Vic xt qu trnh kt tinh khi lm ngui lnh khi

nng chy c thnh phn nm trong tam gic ABC cng tng t nh trng hp ta xt trnhnh 115b. y ch cn lu mt im quan trng l tu theo v tr im biu din thnh

phn pha lng ban u nm trong tam gic no (ABS hoc ASC) ta s bit c thnh phnpha rn thu c cui qu trnh s ch gm 3 pha rn ng vi tam gic , cng nh pha lngcui cng ca qu trnh l E hoc P. V d nu im biu din thnh phn pha lng ban u L1

nm trong tam gic ASC th pha lng cui cng ca qu trnh l P v khi kt thc qu trnh


20/30

20

kt tinh ch thu c hn hp 3 pha rn l A, C, S. Nu im biu din pha lng ban u l L2nm trong tam gic ABS th pha lng cui cng ca qu trnh kt tinh sng vi im E vkhi kt thc qu trnh kt tinh s thu c hn hp 3 pha rn l A, B v S.

i vi nhng h bc 3 to thnh nhiu hp cht th vic phn chia gin thnh cc tamgic nh (gi l php tam gic c), l mt vn rt quan trng v l thuyt cng nh thc tcng nghip. V d h chng ta c to thnh hai hp cht bc hai l S1 (hp cht gia B v C)v S2 (hp cht gia A v C) nh trn hnh 117. T cc im A, B, S1, C, S2 c th dngthnh 3 tam gic nh. Trong ta d dng thy c cch ni S1 vi S2 to thnh tam gicS1CS2. Cn phn hnh thang ABS1S2 th c th phn chia theo hai cch: ni B vi S2 hoc niA vi S1. Mun bit cch phn chia no ng ta phi bit hai pha rn no cng tn ti bn vinhau. iu ny phi gii quyt bng con ng thc nghim. V d chun b hn hp hai pharn B v S2un nng chy ri lm ngui lnh n nhit phng. Tin hnh ghi gin nhiu x tia X xc nh thnh phn pha. Nu trong thnh phn pha vn thu c cc pharn ban u (B v S2) ngha l hai pha rn tn ti bn vi nhau th ta c th kc BS2

chia phn cn li thnh hai tam gic nh l ABS2 v BS2S1. Nu khi nung chy hn hp thuc hai pha rn mi l A v S1 th c ngha B v S2 khng tn ti bn vi nhau. Trongtrng hp nh vy ta ni A v S1 phn thnh hai tam gic nh AS1B v AS2S1.

(% khi lng )

TiO2 Al2TiO5 Al2O3

ZrTiO4

ZrO2

1590

1580

1610

Al2O3

56,08

Hnh 118Gin trng thi h ZrO2-TiO2-Al2O3

Hnh 118 l gin trng thi h ZrO2-TiO2-Al2O3. Trong h ny c to thnh hai hpcht bc hai l titanat nhm nng chy tng hp v titanat zirconi nng chy khng tnghp. Trong gin ny c 3 h bc 3 l oxit zirconi, oxit nhm v titanat nhm (c imtecti 1610oC); oxit zirconi, titanat nhm v titanat zirconi (c im tecti 1590oC); oxit

titan, titanat nhm v titanat zirconi (c im tecti 1580

o

C).Cc h bc ba gm 3 oxit thng c gin trng thi kh phc t p. V d h MgO-Al2O3-SiO2 c gin trng thi trn hnh 119. Trong to thnh 4 hp cht bc hai l mulit(3Al2O3.2SiO2 vit tt l A3S2), spinen (MgO.Al2O3 vit tt l MA), octosilicat magie cn gil fosterit, (2MgO.SiO2 vit tt l M2S), metasilicat magie cn gi l clinoenstatit (MgO.SiO2vit tt l MS) v hai hp cht bc ba l corierit (2MgO.2Al2O3.5SiO2 vit tt l M2A2S5),saphirin (4MgO.5Al2O3.2SiO2 vit tt l M4A5S2). Tam gic thnh phn c chia ra thnh 9tam gic nhng vi 9 sn phm rn thu c khi lm ngui lnh cc hn hp lng c thnh

phn ban u nm trong cc tam gic, l: hn hp rn M, MA, M2S; hn hp rn MA,M2S, M2A2S5; hn hp cc pha rn M2A2S5, MA, M4A5S2; hn hp cc pha rn MA, M4A5S2,A3S2; hn hp cc pha M2A2S5, S, MS; hn hp MS, M2A2S5, M2S.


21/30

21

Ta xt mt v d sau. Xc nh lng pha rn v hng pha lng cn li khi kt tinh phalng c thnh phn MgO 38%, Al2O3 46%, SiO216% n nhit ng vi im tecti 4.

T thnh phn pha lng ta tm c im biu din trn gin l L (hnh 119). L nmtrong tam gic nguyn t MA-M2S-M2A2S5 nn khi kt thc qu trnh kt tinh ng vi phalng cui cng nm giao im ca 3 min ngha l im 4. Trong qu trnh kt tinh,im biu din thnh phn pha lng chy theo L-b-c-d-4 dc trn ng bin gii ca haimin M2S v MA. Mun xc nh lng pha rn kt tinh (%) tng giai on chng tak cc on thng bL, cL, dL, 4L v ko di ct ng M2SMA MA, c, d, 4. Khi im

biu din thnh phn pha lng chy t L (1850o) n b (1670o) ch kt tinh rn MA. Khi imbiu din thnh phn pha lng n b th lng MA kt tinh l:

P = %100bMA

bL

SiO2

MgO MgO.Al2O3 Al2O3

(A3S2)

M2A2S5

M4A5S2MA

(M2S)

(MS)

AM

S

12

3

4 5

6

7b

cd

c'd'

L

89

Al2O3. SiO23 2

MgO.SiO2

MgO.SiO22

1600o

1700o

1800o

1900o

1500o

4'

Hnh 119Gin trng thi h MgO-Al2O3-SiO2 (min 5-9-3 kttinh M4A5S2, min 1-2-9-5-4 kt tinh M2A2S5)

Khi im biu din pha lng n c (1600o) th pha rn l hn hp M2S v MA vi t lkhi lng l:

2M S

MA=

_

_2

MA c'

c ' M S

v lng pha rn kt tinh l: P =cL

.100%cc'

Khi im biu din thnh phn pha lng t ti 4 lc pha lng bt u bo hoM2A2S5 v pha rn ang l hn hp M2S, MA. Lng pha rn tch ra l:

P =4 L

.100%4 4'

3.4.3 H bc ba trng hp to thnh dung dch rn


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22

S hnh thnh dung dch rn trong h bc ba lm cho gin trng thi trnn rt phctp. Sau y ch trnh by mt vi nt quan trng nht trong cn bng gia cc pha rn ca cchn gin.

Hnh 120a l gin trng thi h ABC trong B v C to thnh dy dung dch rn lintc, do bt k thnh phn no ca h, s pha cng tn ti cng khng qu hai (rn A vdung dch rn BC). T A c th k v s tia n cnh BC, mi mt tia u ng vi cn

bng gia hai pha. Hnh 120b biu din s to thnh dung dch rn gia hp cht bc hai AB2v mt pha khng tn ti AC2, thnh phn ca dung dch rn c th biu din bng cngthc AB2-xCx. Dung dch rn ny c th cng tn ti vi A to thnh mt khu vc hai phatng ng. y c th k hnh tam gic ba pha (A + C + dung dch rn thnh phn n). Victam gic c phn gin cn li, trong cng tn ti B, C v dung dch rn trn csAB2

phi tu theo tng h c th. C hai kh nng c trnh by trn hnh 120b v 120c. Ccdung dch rn trn csAB2 trong c khong thnh phn cng tn ti vi pha B (hnh 120c)vi pha C (khng biu din trn hnh v) hoc cng tn ti vi pha B trong mt khong thnh

phn, cn vi pha C trong mt khong thnh phn khc (120b). Sng n ca php tamgic c ch c th da vo thc nghim.A

B C

a

A + dung dch BC

A

B C

AB2

b2 3

3

n

A

C

AB22

3

3

n

c

Hnh 120

H bc ba c to thnh cc dung dch rn bc hai

S to thnh dung dch rn lm cho vic xt qu trnh xy ra khi ngui lnh hn hp nngchy trnn phc tp hn. Hnh 121 l hnh chiu trc giao ca gin khng gian h A-B-Ckiu trn gin 120a. Cnh AB v AC ca h ny c dng tecti n gin, cn cnh BC ngvi h to thnh dy dung dch rn lin tc nh hnh 104a, ngha l cc ng cong lng vng cong rn u khng c cc tr. H bc ba ny khng c cc im v bin m ch cng nht bin XY phn chia thnh min kt tinh bc nht v min dung dch rn BC, nhit gim dn theo hng t X n Y. Mi mt thnh phn pha lng nm cn bng vi mtthnh phn xc nh ca dung dch rn. Cc ng ni pha rn A v dung dch lng cn bngvi A trn ng lng XY u xut pht t A, cn cc ng ni im biu din dung dch

rn BC vi pha lng cn bng vi n li tn ra, thay i lch dn dn t cc im trnng XY v cc im trn ng BC. V d dung dch lng c thnh phn y cng tn ti cnbng vi dung dch BC thnh phn x.


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23

dung dch rn BC

x

A

B C

(a)

XY

A

B

y

(b)

BC

%C

dung dchrn BC

lngoC

A

Cn

aX Y

m p

r s t

Hnh 121Cn bng khi kt tinh trong h A-B-C c tothnh dung dch rn BC (a) v gin hbc hai B-C (b)

Hnh 122Con ng kt tinh trong h bc ba cto thnh dung dch rn bc hai

Kho st qu trnh xy ra khi lm ngui lnh h lng c thnh phn a (hnh 122). H nykhi ngui lnh hon ton c hai pha rn cng tn ti l rn A v dung dch rn BC c thnh

phn p. Khi ngui lnh, cht lng bt u kt tinh rn A, thnh phn pha lng cn li chuyndch t a n r (dc theo on thng A-r).

Khi thnh phn pha lng t ti r nm trn ng nht bin th bt u thot ra tinh thdung dch rn c thnh phn m. Ngui lnh tip tc, thnh phn pha lng chy trn ng XYtheo hng r s t, thnh phn dung dch rn thay i mt cch lin tc (lng s ng vidung dch rn n) lng tinh th ca hai pha (A v dung dch rn BC) cng ngy cng tng.Qu trnh kt tinh tip tc cho n khi thnh phn pha lng v pha rn t ti im t v im

p. Lc ny git cht lng cui cng mt, ch cn hai pha rn A v dung dch BC.

Mc du tin hnh ngui lnh mt cch rt chm, nhng qu trnh va trnh by trn ythng thng cui cng vn dn ti trng thi khng cn bng v khng trnh khi hin tngkt tinh phn on. Nh tinh th dung dch rn c thnh phn m mi tch ra u tin khngt c trng thi cn bng vi pha lng nhit thp th lc c th xem nh b tch rakhi h. Nu iu ny xy ra trong qu trnh kt tinh th cui cng thu c sn phm kt tinhc cu trc lp, thnh phn thay i t m cho ti dung dch giu C hn, im p. Phn gia cctinh th khng ng nht nh vy s giu B, cn phn bn ngoi giu C.

Qu trnh kt tinh c phn phc tp hn khi tinh th tch ra ban u li l dung dch rnBC (xem hnh 123). Khi chuyn dch im biu din pha lng xung di theo b mt lng,t kt tinh ra dung dch rn cng ngy cng giu C, cn nhng tinh th tch ra trc

phi thng xuyn nm cn bng vi pha lng th cng giu C. Cui cng, khi h nhit thnh phn pha lng i theo ng cong b c d e cn thnh phn dung dch rn th theo ng

p g r s. Cc ng ni pha lng v pha rn cng cn bng, quay quanh im b. Mi mt thnhphn lng nm trn ng ni s e khi ngui lnh s xy ra theo con ng ring ca mnh,nhng tt c cc con ng u ni vi nhau ti im chung e ca ng nht bin XYcho n khi no kh ht phn lng cui cng (vi dung dch c thnh phn lng b ta ang xtqu trnh xy ra imf). Cui cng thu c hn hp gm rn A vi dung dch rn t.


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A

B C

X Y

p r s t

e fdc

b

g

Hnh 123ng kt tinh h ABC c dung dch rn BC

Vic kho st y mt h nh trn y i hi phi hon thnh mt khi lng thcnghim rt ln. Do hin nay loi gin ny c cng b khng nhiu lm.

3.5 H tng tc bc baH gm hai mui khng c ion chung AX v BY l h bn cu t, v gia hai mui c

phn ng trao i to thnh hai mui khc:

AX + BY AY + BX

nhng s cu tc lp ch c ba, v c mt phng trnh lin h gia thnh phn cabn cu t (hng s cn bng ca phn ng trao i). Do h hai mui khng c ionchung l h bc ba, phn bit vi h gm ba mui c ion chung y ta gi l h bc batng tc.

Thnh phn ca h bc ba tng tc thng c biu din theo phn trm ng lng

cation v phn trm ng lng anion.

40%

70%

AX BX

AY BY

M

b

%X-

% B+ Hnh 124Cch biu din thnh phn ca h bc ba tng tc

V d h chng ta c: ng lng B+ l 40% (ng lng A+ l 60%), ng lng X

l 70% (ng lng Yl 30%). Cch tm im biu din nh sau: T cnh AX-AY ly vpha cnh BX-BY mt on b = 40% ri k mt ng thng song song vi BX-BY. T cnhAY-BY ly v pha cnh AX-BX mt on x = 70% v k mt ng thng song song viAX-BX. Hai ng thng ct nhau M l im cn tm.

Hnh 125 l gin trng thi ca h bc ba tng tc AX + BY trng hp trong hkhng to thnh hp cht ho hc mi, khng to thnh dung dch rn gia cc cu t m chto thnh cc im tecti bc hai v tecti bc ba.


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e1

e2

e3

e4

E1

E2

e'1

e'2

e'3

e'4

BXBY

M'

TAX

TBX

TAY

TBY

M

Hnh 125Gin trng thi ca h

AX + BY AY + BX

Thng thng ngi ta chiu trc giao cc im trong gin khng gian xung hnhvung y v di y chng ta s xt cc gin mt phng hnh chiu trc giao lnhnh vung y nh vy.

i lc c th biu din thnh phn ca h bc ba tng tc ln tam gic u nh sau.Gi tng ng lng ca 3 ion bt k l 100 v thnh phn ca h biu din theo phn trmng lng ca 3 ion .

Trn hnh 126 thnh phn ca hc biu din theo phn trm ng lng ca 3 ionX, A+, B+ . V rng cnh y A+B+ c 0% X, do ti y tt c A+, B+ kt hp vi Y,ngha l nh A+ chnh l AY nguyn cht, nh B+ chnh l BY nguyn cht. Ti im giahai cnh bn c thnh phn 50% X v 50% A+ (pha cnh A+X) v 50% X vi 50% B+

(pha cnh kia). Do im biu din mui AX nguyn cht nm chnh gia cnh A+X, cnim biu din BX nguyn cht nm chnh gia cnh kia, phn tam gic nh pha trn khngc ngha.

xy dng gin khng gian chng ta tin hnh nh trn hnh 125. Trn hnh 126 cv hnh chiu trc giao cc mt kt tinh ca gin khng gian nh hnh 125.

X-

B+A+

AX BX

(AY) (BY)

e1

e2

e3

e4

E1

E2

Hnh 126Tam gic thnh phn ca h tng tc bc ba AX-BY


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By gichng ta xt cc trng hp c th ca h tng tc bc ba trn hnh chiu trcgiao xung hnh vung thnh phn. Trng hp n gin nht l h kt tinh di dng cu tnguyn cht, khng to thnh dung dch rn. Hnh 127 l hnh chiu trc giao ln hnh vungy. Hnh 127a ng vi trng hp chiu phn ng l:

BX + AY AX + BY

y ta c hai h bc ba to thnh tecti n gin l AX-AY-BY v AX-BY-BX.ng cho bn l AX-BY. Cn trng hp hnh 127b th phn ng theo chiu ngc li

AX + BY AY + BX

Cho bn BX-AY chia hnh vung thnh hai h bc ba l AX-BX-AY v AY-BX-BY.

Cng nh trng hp trn y, vic xt qu trnh xy ra khi lm ngui lnh h t trngthi lng ta cn quan tm n v tr im biu din h ban u. V dim biu din h banu l K (hnh 127a) nm trong tam gic AX-BX-BY th kt thc qu trnh ngui lnh s xyra qu trnh v bin: lng E2 = rn AX + rn BX + rn BY v cui cng ta thu c sn phmcha 3 pha rn . Ta c th trnh by tm tt qu trnh ngui lnh h lng ng vi im Knh sau. Trc ht xy ra qu trnh kt tinh rn BY im biu din thnh phn pha lng cnli chy t Kn L, tip l qu trnh kt tinh ng thi rn AX v rn BY im biu dinthnh phn pha lng cn li chy trn ng ME2 (t L n E2) im biu din pha rn chyt BY n R.

Khi im biu din thnh phn pha lng n E2 th im biu din thnh phn pha rnn R, t xy ra qu trnh v bin kt tinh ng thi 3 pha rn BY, AX, BX v im biudin thnh phn pha rn chuyn t Rn K l kt thc qu trnh.

e1

e2

e3

e4AX BX

AY BY

L

M K

RE1

E2

(a)

e3

(b)

e1

e2

e4

M

E1

E2

AX BX

AY BY Hnh 127

Hnh chiu trc giao ca gin trng thi h bc ba tng tc AX-BY

Hnh 128 ng vi trng hp h bc ba tng tc thun nghch, y khng c chobn. Ta ly hai mui v mt v phng trnh phn ng vi bt k mt t l thnh phn no,khi lm ngui lnh cng thu c mt pha rn ca mui th ba. Nh vy phn ng y l

phn ng thun nghch.


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AX BX

AY BY

e1

e2

e3

e4

E

P

Hnh 128H bc 3 tng tc thun nghch

AX + BYAY+ BX

hnh ny im E l tecti bc ba, ti xy ra qu trnh kt tinh ng thi 3 mui:

Lng E rn AX + rn AY + rn BY

Cn im P l im peritecti, ho tan rn BX vo lng P kt tinh rn AX v rn BY:

Lng P + rn BX rn AX + rn BY

Theo nhit ng ta c th don vi mt h bc ba tng tc gin s c cho bnng vi cp mui c tng sinh nhit (Ho298) ln hn. iu c ngha l phn ng trao ixy ra theo chiu to nhit. iu ny c N. Beketop v I.A. Kablucop kim tra bng thcnghim i vi nhiu h.

Nhng thc ra chiu hng ca phn ng c quyt nh bi gi trGo ch khng phibng gi trHo, do vic don hng ca cho bn phi bit c gi trGo ca phnng v s ph thuc ca Go vo nhit na.

Hnh 129 l gin h clorua v sulfat natri v tali vi cho bn l clorua tali-sulfat natri,ngha l phn ng xy ra theo chiu to thnh cp mui .

H bc ba tng tc i lc kh phc tp. Hnh 130 l gin trng thi h K+, Mg2+,Cl, SO4

2. Trong h ny ngoi mui n cn to thnh mui kp nh K2Mg(SO4)2, KMgCl3,KMgClSO4.

2NaCl

2TlCl

Na2SO4

Tl2SO4

650

552

410

358

(800) (884)

(429) Hnh 129

H Na+, Ti+, Cl, SO42


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K2Cl2 MgCl2

MgSO4

K2SO41076

1000

750

800

700

778 425

875 1185

870

500

495 769

600700

800

650

700

900

1000

1000800

700

600

K2SO4

MgCl2

K2Cl3

K2Mg(SO4)2

MgSO4

KMgClSO4

K2SO4

K2Cl2

K2Cl3

Hnh 130

Gin trng thi h K+

, Mg

2+

, Cl

, SO42

Vi h K+, Cs+, Cl, SO42 th ch to thnh 2 vng dung dch rn lin tc ca clorua kali-

xezi v sulfat kali-xezi nh trn hnh 131.

K2SO4

Cs2SO4

K2Cl2

Cs2Cl2

(778) 750700

650

600

690

550

574

(1076

1050

1000

950

900800

850

750

700

(860)(632) Hnh 131

Gin trng thi h K+, Cs+, Cl, SO42

Cu hi v bi tp

1. nh ngha v minh ho cc khi nim pha, cu t, s bc t do ca h cn bng.

2. Chng minh rng i vi cc h c t hai cu t trln th thnh phn ca cu ttrong 3 pha khng th bng nhau c.

3. Xc nh s bc t do ca qu trnh phn hu nhit hirat.

4. Dng gin trng thi ca h Al2O3-SiO2 theo cc s liu sau y: Al2O3nng chy 2060oC, ca SiO2 1720oC, chng to thnh hp cht Al6Si2O13nng chy tng hp 1850oC. Trong h c cc tecti 1595oC (5% molAl2O3) v 1840oC (67% mol Al2O3). So snh gin vi gin tronggio trnh.


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5. Lp cng thc bin i thnh phn % mol sang % khi lng ca gin trngthi h bc hai (c th dng phng php ton ).

6. Xy dng gin pha ca h A-B theo cc thng tin sau y: trong h to thnh3 hp cht A2B, AB, AB2. Trong A2B v AB2 nng chy tng hp, cnAB nng chy khng tng hp to thnh A2B v pha lng.

7. Pha lng c thnh phn 40% khi lng Sn v 60% khi lng Pb lm nguilnh n nhit no th bt u kt tinh, xc nh thnh phn pha rn bt ukt tinh. Lm ngui lnh chm chp n 150oC ri gi yn mt thi gian cho nnh trng thi cn bng. Xc nh thnh phn nh tnh v nh lng ca cc

pha trong hp kim (xem hnh di y).

20 40 60 80Pb Sn

100

200

300

61,9

327oC

183oC

C232o

% khi lng Sn Gin trng thi h Pb-Sn

8. Gii thch ngha cc ng, vng trong gin trng thi ca cc hMg2SiO4-Zn2SiO4 (hnh 78), MgO-Al2O3 (hnh 79), SiO2-LiAlO2 (hnh 80),Cr2O3-SiO2 (hnh 97), CaO-ZrO2 (hnh 109).

9. Xem gin trng thi h Al2O3-Cr2O3 (hnh 82), trnh by kh nng ho tanln nhau ca hai oxit ny. Khi lm lnh mt h lng cha 60% oxit nhm, 40%oxit crm n nhit phng thu c h rn c thnh phn pha nh th notrong trng hp lm ngui lnh nhanh, lm ngui lnh t t.

10. Xc nh nhit nng chy ca hp kim c thnh phn khi lng l 70%Zn,10%Cd, 20%Sn. Mun h nhit nng chy ca hp kim xung 30oC th

phi thm bao nhiu Sn v Cd vo 100g h p kim (xem h Zn-Cd-Sn hnh114).

11. Thm 25g ZrO2 vo 75g Al2TiO5 ri nung cho nng chy hon ton, xt qutrnh xy ra khi lm lnh hn hp lng n lc thnh phn pha lng t ng

cong bin gii. Tnh lng pha rn tch ra v lng pha lng cn li (hZrO2-TiO2-Al2O3 hnh 118).

12. Lp bng qu trnh kt tinh ca hn hp lng nm trong cc hnh tam gic

a) A3S2-MA-M4A5S2

b) A3S2-M2A2S5-M4A5S2

c) M2S-M2A2S5-MS

(H MgO-SiO2-Al2O3 hnh 119).

13. Hnh di y l mt gc ca gin trng thi h CaO-SiO2-Al2O3. Xt qutrnh kt tinh hn hp lng ng vi im K.


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14. Cng vi hnh di y xt qu trnh kt tinh hn hp lng c thnh phn 8%Al2O3, 8% SiO2, 84% CaO. Tnh thnh phn phn trm ca pha lng v pha rntch ra khi im biu din ca ht ng bin gii.

db aCaO C3A Hce10 20 30

CaO

F

C3S

C2S

C3A

C3SF'

C2S

P

K

K' K"

K"'

n

34

33

3410

20

30

giai thich gian do pha

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