Chuong 1 Cau Truc.pdf
Transcript of 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
1.1 Cu to v lin kt nguyn t:
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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Chng 1: Cu trc tinh th v s hnh thnh
1.1 Cu to v lin kt nguyn t:
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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Chng 1: Cu trc tinh th v s hnh thnh
1.1 Cu to v lin kt nguyn t:
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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Chng 1: Cu trc tinh th v s hnh thnh
1.1 Cu to v lin kt nguyn t:
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
1.1 Cu to v lin kt nguyn t:
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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)
S sp xp cc nguyn t trong vt cht
1.1 Cu to v lin kt nguyn t:
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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
S sp xp cc nguyn t trong vt cht
1.1 Cu to v lin kt nguyn t:
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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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a) Lp phng tm khi (A2)
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
1.3.1. Mng tinh th in hnh ca vt liu kim loi
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a) Lp phng tm khi (A2)
Kim loi c kiu mng A2: Fe, Cr, Ti, Mo, W, V
1.3.1. Mng tinh th in hnh ca vt liu kim loi
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S nguyn t trong mt c s: N = 4
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)
1.3.1. Mng tinh th in hnh ca vt liu kim loi
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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
1.3.1. Mng tinh th in hnh ca vt liu kim loi
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Kim loi c kiu mng A1: Fe, Au, Ag, Al, Cu, Ni,
b) Lp phng tm mt (A1)
1.3.1. Mng tinh th in hnh ca vt liu kim loi
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c) Su phng xp cht (A3)
c
a
1.3.1. Mng tinh th in hnh ca vt liu kim loi
S nguyn t trong mt c s: N = 6
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)
1.3.1. Mng tinh th in hnh ca vt liu kim loi
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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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1.3.2. Mt s mng tinh th ca vt liu phi kim
b) Cht rn c lin kt ion
1 3 2 Mt ti h th t li hi ki
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1.3.2. Mt s mng tinh th ca vt liu phi kim
c) Cu trc ca polyme
1 3 2 Mt ti h th t li hi ki
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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
1 4 Cc sai lch trong mng tinh th
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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.
1 4 Cc sai lch trong mng tinh th
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1.4. Cc sai lch trong mng tinh th
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.
1 4 Cc sai lch trong mng tinh th
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1.4. Cc sai lch trong mng tinh th
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
1 4 Cc sai lch trong mng tinh th
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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.
1.5. n tinh th v a tinh 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
1.5. n tinh th v a tinh th
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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
1.5. n tinh th v a tinh th
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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
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 loi1.6.2. Hai qu trnh ca s kt tinh
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 loi1.6.3. 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
1.6. S kt tinh v hnh thnh t chc kim loi
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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
1.6. S kt tinh v hnh thnh t chc 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
1.6. S kt tinh v hnh thnh t chc kim loi
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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.
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3
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