Chuong 1 Cau Truc.pdf

7/25/2019 Chuong 1 Cau Truc.pdf

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M u* khoa hc vt liu nghin cu mi quan h gia cu trc v tnh cht

ca vt liu Vt liu l g?

l cc vt rn c th s dng ch to cc dng c, my mc,thit b, xy dng cc cng trnh.


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M u

Kimloi

Polymer Ceramic

Composite

41

2

3

4 nhm vt liu chnh: VL kim loi,Ceramic, Polymer v Composite

1- VL bn dn

2- VL siu dn3- VL silicon

4- VL polymer dn in


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M u(tip theo)

Vai tr ca vt liu:i tng ca vt liu hc cho chuyn ngnh c kh:

nghin cu mi quan h gia tnh cht v cu trc ca vt liu

Tnh cht: - c hc (c tnh)- vt l (l tnh)

- ha hc (ho tnh)

- cng ngh v s dng

Cu trc: - nghin cu t chc t vi - cu to tinh th


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Chng 1: Cu trc tinh th v s hnh thnh

1.1 Cu to v lin kt nguyn t:

Cu to nguyn t: cc e chuyn ng bao quanh hat nhn (p+n)

1s2 2s2 2p6 3s23p63d6 4s2K L M N


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Chng 1: CU TRC TINH TH V S HNH THNH


Cc dng lin kt trong cht rn:

* Lin kt ng ho tr: hnh thnh do cc nguyn t gp chung int ho tr lin kt (Cl2, CH4.). Lin kt c tnh nh hng


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Cc dng lin kt trong cht rn:* Lin kt ion: hnh thnh do lc ht gia cc nguyn t d nhng eho tr (to ion dng) vi cc nguyn t d nhn e ho tr (to ion m) lin kt (LiF.). Lin kt khng c tnh nh hng


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Cc dng lin kt trong cht rn:* Lin kt kim loi: hnh thnh do s tng tc gia cc e t do chuynng trong mng tinh th l cc ion dng

Tnh kim loi :

+ nh kim+ Dn in, dn nhit

+ Tnh do cao


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Cc dng lin kt trong cht rn:* Lin kt hn hp: hnh thnh do trong vt liu tn ti nhiu loi lin ktkhi c s gp mt ca nhiu loi nguyn t* Lin kt yu (Van de Waals): do c s tng tc gia cc phn tb phn cc


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S sp xp cc nguyn t trong vt cht

Cht kh: cc nguyn t, phn t chuyn ng hn lon



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Cht rn tinh th: cc nguyn t c v tr hon ton xc nh (c trt tgn v trt t xa)




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Cht lng: c trt t gn, khng c trt txa

Cht rn v nh hnh: cu trc ging chtlng trc khi ng c

Cht rn vi tinh th: c cu trc tinh th trng thi c ht nano




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1.2 Khi nim v mng tinh th

Ni tm cc nguyn t bng cc ng thng tng tng

-> Mng tinh th

c s:

l hnh khng gian th tch nh nht nh nht c

trng cho tnh i xng ca mng tinh th Tnh tin c s theo ba chiu khng gian s

xy dng c ton b mng tinh th


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c s v cch biu din

b

a

c3 vc t a, b v c ln lt nm trn cc

trc Ox, Oy v Oz 3 vc t n v ln a, b v c cc hng smng

Cc gc , v l gcto bi cc vc t n v

Ba nghing (tam t) abc Mt nghing (n t) abc ==900

Trc thoi abc ===900Ba phng (mt thoi) a=b=c ==900

Su phng (lc gic) a=b c ==900, =1200

Chnh phng (bn phng) a=b c ===900

Lp phng a=b=c ===900

Cc h tinh th khc nhau ph thuc vo mi quan h gia cnh v gc


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Nt mng [[x,x,x]]: dng biu th to ca cc nguyn t

O

A

B

CD

E

F

H

x

y

zA [[1,1,0]]

B [[1,1,1]]

C [[0,1,1]]

Ch s phng [uvw]:

biu din phng ca ng thng iqua hai nt mng

Hai phng // c cng ch s

OH [010]

OB [111]

OE [101]

H phng, k hiu :cc phng c gi tr tuyt i u,v,w ging nhaukhng k th t c cng quy lut sp xp nguyn t.


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Ch s mt (ch s Miller) (hkl):

H mt, k hiu {hkl}: cc mt c gi tr tuyt i u,v,w ging nhau khng k tht c cng quy lut sp xp nguyn t.

Cch xc nh ch s mt:

Mt tinh th : Mt phng cha cc ntmng, khng i qua gc ta .

Hai mt tinh th // c cng ch s

O

A

B

CD

E

F

H

x

y

z

DFH (111), EFAB (100), ABCH(010)


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Ch s mt (ch s Miller-Bravais) (hkil):

i = - (h+k)


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1.3. Mt s cu trc tinh th in hnh ca vt rn

a) Lp phng tm khi (A2)

S nguyn t trong mt c s: N = 2

Bn knh nguyn t: rnt = a.3/4

Mt xp cht nht: {110}

Phng xp cht nht:

Mv = vnt/V = 68%

c s : Khi lp phng cnh bng a.

1.3.1. Mng tinh th in hnh ca vt liu kim loi


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L hng 8 mt: tm cc mt bn + gia cc cnh, d lh = 0,154dng.t

Kim loi c kiu mng A2: Fe, Cr, Mo, W

L hng 4 mt: trn cnh ni im gia 2 cnh i din, dlh = 0,291dng.t

L hng : Khng gian trng gia cc nguyn t;

Kch thc l hng = ng knh qu cu ln nht t lt trong l hng



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Kim loi c kiu mng A2: Fe, Cr, Ti, Mo, W, V



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Bn knh nguyn t: rnt = a.2/4Mt xp cht nht: {111}

Phng xp cht nht:

Mv = vnt/V = 74%

c s : Khi lp phng cnh bng a.

b) Lp phng tm mt (A1)



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Lp phng tm mt (A1)

L hng 8 mt: tm khi + gia cc cnh, d=0,414dng.t

L hng 4 mt: trn cc ng chokhi tnh t nh, d=0,225dng.t



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Kim loi c kiu mng A1: Fe, Au, Ag, Al, Cu, Ni,

b) Lp phng tm mt (A1)



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c) Su phng xp cht (A3)

c

a



Bn knh nguyn t: rnt = a/2; c/a = 1,633

Mt xp cht nht: (0001)

Phng xp cht nht:

Mv = vnt/V = 74%

c s : Khi lc lng cnh y a, chiu cao c.


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Kim loi c kiu mng A3: Ti Zn, Mg, Mg, Be, Cd, Zr

Su phng xp cht (A3)



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1.3.2. Mt s mng tinh th ca vt liu phi kim

1.3. Mt s cu trc tinh th in hnh ca vt rn

a) Cht rnc lin kt cng ha tr

Kim cng, graphit, fullerence, v ng nano cacbon


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1.3.2. Mt s mng tinh th ca vt liu phi kima) Cht rn c lin kt cng ha tr

Thch anh

Cristobalit

1 3 2 Mt ti h th t li hi ki


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b) Cht rn c lin kt ion



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c) Cu trc ca polyme



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1.3.2. Mt s mng tinh th ca vt liu phi kimc) Cu trc ca polyme


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c

a

1.3.3. Dng th hnh

1 4 Cc sai lch trong mng tinh th


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1.4. Cc sai lch trong mng tinh th

Phn loi: Sai lch im, Sai lch ng, Sai lch mt

Sai lch im: kch thc rt nh (nguyn t) theo 3 chiu khng gian

K/n: cc nguyn t nm sai v tr quy nh a/h tnh cht

Nguyn t tp cht

thay th xen k

Nt trng v nguyn t xen k: nguyn t chuyn ng bt khi nt mng



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1.4. Cc sai lch trong mng tinh thSai lch ng lch: kch thc rt nh (nguyn t) theo 2 chiu vln theo chiu th ba.

Lch bin: chn thm bn mt vo na trn ca mng tinhth l tng.

Trc lch

Vct Burger: ng knvng trn v trn mt phng vung gc vitrc lch khi chuyn t tinh th khng lch sangc lch. b trc lch.



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b // trc lch.

trc lch

Lch xon: hai phn ca mng tinh th trt tng i so vi nhau mthng s mng. Cc nguyn t trong vng lch sp xp theo hnh xon c.



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Mt lch :

ngha ca lch:

+ Lch bin c nh hng rt ln n qu trnh bin dng do+ Lch xon gip cho mm pht trin nhanh khi kt tinh

c trng v hnh thi lch

23

cmcmcm

V

llch

+ Ph thuc sch v trng thi gia cng

- Kim loi sch trng thi = 108cm-2- Hp kim v kim loi sau bin dng ngui : = 1010- 1012cm-2

M hnh bong bng x phng


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M hnh bong bng x phng

Lch trong thc t


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Lch trong thc t

Hp kim Titan50000 ln



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1.4. Cc sai lch trong mng tinh thSai lch mt : kch thc ln theo hai chiu o v nh theo chiu th ba,tc c dng ca mt mt.

bin gii ht v siu htb mt tinh th.

1 5 n tinh th v a tinh th


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1.5. n tinh th v a tinh th

n tinh th: l mt khi ng nht c cng kiu mng v hng smng, c phng khng i trong ton b th tch

+ b mt ngoi nhn, hnh dngxc nh+ cc n tinh th kim loi khngtn ti trong t nhin, mun c

phi dng cng ngh "nui" ntinh th.



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1.5. n tinh th v a tinh thn tinh th:

+ c tnh d hng

+ ng dng:

Tuc bin ng c phn lc

Vt liu bn dn

Ht mi



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1.5. n tinh th v a tinh tha tinh th: l tp hp ca nhiu n tinh th c cng cu trc

thng s mng nhng nh hng khc nhau

c im ca a tinh th:

-cc ht l cc n tinh th ng nht

- cc n tinh th (ht) ngn cch nhau bi cc bin gii ht

-bin ht lun b x lch khng tun theo quy lut sp xp nh trong tinh th

- khng c s ng nht v phng mng trong ton khi tnh ng hng



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1.5. n tinh th v a tinh thQuan st c cu trc a tinh th qua t chc t vi

1 6 S kt tinh v hnh thnh t chc kim loi


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1.6. S kt tinh v hnh thnh t chc kim loi

1.6.1. iu kin kt tinha) Cu trc trng thi lng:

+ c trt t gn, cn bng ng

+ cu trc gn vi trng thi rn

+ cc m nguyn t l tm mm kt

1 6 S kt tinh v hnh thnh t chc kim loi


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1.6. S kt tinh v hnh thnh t chc kim loi1.6.1. iu kin kt tinh

b) Bin i nng lng khi kt tinh+ T >T0 GL< GR

+ T GR

+ T = T0 Qu trnh kt tinh cha

xy ra.

T0 - nhit kt tinh (ng c)

c) qu ngui :

T = T -T0 < 0 ( 1-2 0C 1000 oC)

iu kin kt tinh : T < 0 (G < 0)

GL

GR

T0

Nnglngtdo,G

Nhit , T

G

T

1.6.2. Hai qu trnh ca s kt tinh


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q a) To mm

Mm : phn t rn c cu trc tinh th, kch thc ln pht

trin ln thnh ht tinh th.Mm t sinh: r > rth = 2/Gv (T tng Gv tng rth gim) .

Mm k sinh: cc ht rn l lng trong cht lng, nhp nh bmt khun c.

b) Pht trin mm: nguyn t cht lng bm ln b mt mm,c bit nhng bc lch xon



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1.6. S kt tinh v hnh thnh t chc kim loi1.6.2. Hai qu trnh ca s kt tinh



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1.6. S kt tinh v hnh thnh t chc kim loi1.6.3. S hnh thnh ht tinh th

+ Mi mm pht trin thnh 1 ht, ht pht trin trc to hn

+ Cc ht nh hng ngu nhin, khng ng hng

+ Vng bin ht c mng tinh th b x lch sai lch mt

Qu trnh kt tinh (Movie)

1.6.3. S hnh thnh ht tinh th


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Hnh dng ht tinh th ph thuc phng thc lm ngui

+ Ngui u theo mi phng + Ngui nhanh theo hai phng

+ Ngui nhanh theo mt phng + Ngui nhanh khi nhit luyn



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1.6.4. Cc phng php to ht nh khi c

Kch thc ht A ph thuc tc sinh

mm (n) v pht trin mm (v)

+T < T1(103 0C/s) : T tng n, v tng kch thc ht nh;

+T1< T < T2: T tng n tng, v gim vt liu nano;

+T > T2: T tng n gim, v gim VL v nh hnh;

VD : c khun ct vs khun kim loi



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1.6.4. Cc phng php to ht nh khi cBin tnh: thm vo kim loi lng lng t cht bin tnh lm nh ht,

thay i hnh dng ht.

Tc ng vt l : rung, siu m, c ly tm,

To mm ngoi lai: Kim loi c kiu mng tng t (Ti),hoc cht to oxyt, nitrit Al2O3, AlN, khi c thp.

Hp ph: Na (0,01%) cho hp kim nhm c

Cu ha: Mg, Ce, cc nguyn t t him



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1.6.5. Cu to thi c

a) Ba vng tinh th ca thi c

+ Lp v ngoi, ht nh mn

+ Vng tip theo ht ln hnh tr vunggc vi thnh khun

+ Vng gia c cc ht ln ng trc

b) Khuyt tt ca vt c:

+ R co v lm co do khi kt tinh kim loico li, khng c b

+ R kh do kh ha tan khng kp thot ra+ Thin tch : s khng ng nht v

thnh phn v t chc do tp chttch t.

21

3


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Chuong 1 Cau Truc.pdf