T R U C N G D A I H O C DONG THAP Tap chl Khoa hoc so 24 (02-2017)
Sir ANH HCdNG CUA N 6 N G DO TAP CHAT B LEN VI CAU TRUC VA QUA TRINH TINH THE HOA CUA MO HINH HAT NANO Fe^ j,B^
• Nguyen Trong Dung''', Trinh Thi Hu-ong", Nguyin Chinh Cu-o-ng'"^
Tom f 3t
Bdi bdo ndy ngkiin cieu su dnh huong ciia ndng do ttxp chdt B len vi cdu triic vd qud trinh tinh thi hda cua md hinh hgt nemo Fe^^B^ (v&i x = 1%, 3%, 5%). Cdc kgt nemo Fe^B^ duac tgo ra tie phuang phdp md phdng ddng luc kgc pkdn tie vai tki tuang tdc cap Pak-Doyama vd diiu kiin bien tu do. Cdc dgc tnmg vi cdu true dugc phdn tick qua hdm phdn bo xuyin tdm (RDF), kich thu&c hgt, ndng lieang vd sd phdi tri. Qud trinh tinh thi kda dugc xdc dinh thdng qua su tdch Pick tgi dinh thu hai ciia hdm phdn bd xuyen tdm tkeo cdc buac dich chuyin Cdc kit qud thu dugc cho thdy, cd su dnh hudng cua ndng do tgp chdt B len vi cdu true vd qud trink tinh thi kda.
Tie kkod: Ndng do tgp chdt B, vi cdu true, tinh tki kda, md hinh kgt nano Fe^^B^ mdpkdng dgng luc kgc phdn tie.
1. Tong quan
Fe-B la hgp kim co nhieu ung dung trong khoa hoc, cong ngh? va cuoc song. Fe-B !a vat Heu tir mem dugc ung dung nhieu trong cong nghe dien tu, sieu din. Do cung, do ben ca hpc cua Fe-B phu thugc nhieu vao thanh pfaan hoa hpc. Dien tro suat cua Fe-B vo djnh hinh lon hon so voi hpp kim Fe-B a trang thai tinh the va tiiay doi rat it khi nhiet dp thay doi. Cac nghien cuu truac day cho thay, mat dp khoi lugng Fe-B phu thugc manh vao nong dp cac thanh phan a kim nhu: Fej^B,g co mat dp 7,38 g/cm^ Feg^Bj^ co m^t dp 7,31 g/cm^ vaFe^jBjj co mat dp 7,22 g/cm^...
[9]. Vol cac dieu kien va cac phuang phap che tao Idiac nhau ma Fe-B co the ton tai 6 trang thai tinh the hoac trang thai vo dinh hinh. Phuang phap thuc nghiem (nhieu xa tia X, nhifiu xa neutron) thucmg dugc sii diong de nghien cuu vi cau tnic cua vat lieu [3]. Khi six dung phuang phap nhieu xa tia X cho thay, hgp kim vo dinh hinh Fe-B co hien tugng tach Pick t ^ finh thii hai cua ham phan bo xuyen tam, no giong nhu voi cac hgp kim vo dinh hinh khac Fe-P, Co-B, Co-P va Ni-B [7]. Mot so mo hinh khac dupc dung de nghien cuu Fe-B vo dinh hinh (nhu mo hinh s5p xep cac qua cau ciing cua Boudreaux va cpng sir) [2]: Ban dau xay dung mo hinh 2500 nguyen tu, cho dich chuyen thong ke hoi phuc vcri the tuang tac Lennard - Jones da
'•^ Nghien cmi smh, Tnrong Dai hoc Sir pham Ha Noi '"' Tniang Dai hoc Su pham Ha Noi
'"•• Hoc vien cao hpc, Truong Dai hpc Su pham Ha Noi
cho cac ket qua: Tai dinh thii hai cua ham phan bo xuyen tam xuat hi?n hien tugng tach Pick, dp cao cua hai Pick b5ng nhau, co mat dp nho hon gia tri thirc nghiem khoang 0,8 g/cm^ Ben canh do, con nhieu nghien ciiu khac xac dinh su phu thupc cua nong dp a kim B Ien vi cau tnic, vi du nghien cuu mo hinfa khoi Fe-B (2000 nguyen tu) voi the tuong tac cap Pak-Doyama, dieu kien bien tuan hoan da dugc thuc hi^n boi nhom tac gia Vo Van Hoang [8], mo fainh hat nano FeB cua nhom tac gia P. H.
Kien va cpng sir [10]. Cac nghien cuu vi cau true cua hat nano s4t, hat nano FeB cho thay xuat hien hien tupng tach Pick tai finh thu 2 cua ham phan bo xuyen tam, day la co so de giai thich hien tugng tinh the hoa cua vat lieu [4], [5], [10], Da c6 mpt so the dupc phat trien qua cac nghien ciiu nhu:
The More, the tuong tac cap Lennard - Jones, the tucmg tac cap Pak-Doyama, the Stillinger - Weber va the nhiing... tuy nhien, the tucmg tac cap Pak- Doyama van la tfae pfau hgp nhat doi vai cac mo hinfa CO so lugng lan nguyen tii, dac biet phii hgp vai vat lieu Fe-B.
2. Phu-ffng phap nghien cuu
Mo fainh faat nano Fe,^B^ (5000 nguyen tu, nong dg tap chat B la x = 1%, 3%, 5%) dugc xay dung bang phuong phap mo pfaong dpng Iuc fapc phan tu (MD) vdi the tuang tac c|p Pak-Doyama (1) va dieu kien bien ty: do.
^ h + b ) -i-c(^j+d) -i-e khiry<r.
•p(0=
khi r.i>r (1)7 1
TRUONG DAI HOC D 6 N G THAP Tap chl Khoa hoc so 24 (02-2017) trongdo: (p(i;j] (eV)Iathenangtuongtacc||);rj|
(A) la khoang each giua cac ngiQ^en tii; r ^ la ban kinh ngat (A); cac he so a, b, c, d va e dugc xac dinh theo cac thong so tiiuc nghiem nhu module dan hoi vahang so mgng [1], [6].
Bang 1. Cac tbdog s6 cua m6 hinh FCj^B^
Tirong tac Fe-Fe Fe-B B-B
a (eV/A') -0,18892 -0,22407 -0,08772
b(A) -1,82709 -1,47709 -2,17709
(eV/A") 1,70192 2,01855 0,79028
d(A) -0.50849 -2,15849 -2,85849
e(eV) -0,19829 -0,23519 -0,09208
'„(A) 3,44 3,09 3,79 Ban dau, cac hat vdi khoi l u a n g rieng P = 7,6 g/cm' dupc xay dvmg bjng each gieo nglu nhien cac nguyen tii (phan tu) vao trong kh6i hinh cau CO ban lflnhR=29A°r6i cho dich chuyen 5.105 buac thong ke hoi phuc voi so hat, the tich va nhiet do khong doi. Sau do, cac hat duoc tang nhiet voi 2.106 buoc dich chuyen de tang nhiSt do Ien 900 K o ap sudt 0 MPa Tiep theo ta cho dich chuyin 4.10' buac voi so hat, the tich va nang luong khong doi de he dat trgng thdi can bang. Cuoi cung, dva vao trang thai can bang de xac dinh vi cau true cung nhu qua trinh tinh the hoa cua cac hat.
3. Ket qua va thao luan
M6 hinh Fe,^B^ (5.000 nguyen tu) voi nong dp pha tap chatB l a x = 1%, 3%, 5%,khi dat trang thai can bang huih dang cua hat CO dang nhu a Hinh 1, kich thuoc va nang luong cua cac hat duoc the hien nhu Bang 2.
fflnh 1. Hmh dang hat nano Fe, _B^ vcH x = 1%
Bang 2. Kich thinjc vi nang InoBg cua cac hat nano Fe,,,B_ vfti s - 1 % , 3o/„^ 5o/„
N^ng do B Kich thugc (nm) I Nang lugng (eV) 72
Quan sat Hinh 1 ta thiy, hgt nano Fe JB vdi x = 1% CO dgng hinh cau dupc tao boi 2 lo^
nguyen tii, trong do nguyin tii Fe mau xam, con ngtiyen tii B mau den. Tuong tu. Bang 2 cho th%, cac hat nano Fe, ,^B,^ deu co kich thuoc nano. Khi tang nong dp tap chat B tir 1 % den 5%
thi kich thuoc ciia hat khong thay doi, nang lupng ciia he giam. Nhu vay, voi n6ng do tap chit nho hon 5%chualaiii thay d6i cau tnic hinh hpc, nhung kS tang nong dp tap chat trong Fe, ^B se dan den nang lupng cua h$ giam.
De tim hieu sau hon van de nay, chiing toi khao sat ham phan b6 xuyen tam va kit qua diroc thi hien Hmh 2.
Hinh 2. Him phan b6 xuygn tim ciia hat nano Fe,._B_ vfti X - 1 % , 3%, 5%
Quan sat Hinh 2 ta thay, cac hat nano Fe, ,B_
voi X = 1%, 3%, 5% dlu CO gia tri dinh dau den Clia ham phan bo^xuyen tam chiem im the vavi tti dinh dau tien thay doi khong dang ke. Ket qua nay chiing to, khoang each noi phSn tu giua cfc nguyen tir khdng phu thuOe vao nong dp tap chat B. Nhu vay, lien ket giira cac nguySn tii trong mo hi^nh khong ton tai ttat tu xa ma luon ton tai trat tir gan. Dp cao dinh thu nhat ciia ham phin b6 xuyen tim doi voi hat co nong dp tap chat B 1% co gii tri lon nhat. Khi tang nong dp tap chat B len thi dp cap dinh thii nhat ciia ham phin bo xuyen tam giam. Ket qua nay hoan toan phu hpp vm kit lujn o ttgn la khi tang nong dp tap chat B din din nang lupng Clia he giim.
Chiing toi ttep tuc khio sat so phpi tti ciia cat hat va thu dupc ket qua nhu H n h 3.
raOQNG D*I HCJC B 6 N G THA? Tap chi Khoa lipc so 24 (02-2017)
0.6- 0.5- 0,4- 0.3- 0.2- 0,1- 0.0-
• - • i p k l l n r f l - I H b->6pbilMx-3K c-iiphil t r i i - S H
6 8 1 0 1 2
•
1 4
Hinh 3. S^ pb6i fri csia h^t Fe,.^B^ vdi X = 1%, 3%, 5%
Ket qua Hinh 3 cho thay, so phoi tri cua cac hat nano Fej_^B^ co gia tri 14 la chu yeu. Khi tang nong do B len thi mat do s6 phoi tri 14 gi&n. Dieu do CO the Ii giai la su Snh hudng cua nong d 6 1 ^ chatBlenvi cau true ciia mo hinh la do tinh khong dong nhat trong mo hinh gay ra. Nhu vay, khi tang nong do t ^ chat B len dan den nang lugtig cua he gjam, chinh fieu nay dan den sy tiiay doi vi cau true ciia hat.
Be tim hieu them, chiing toi khao sat s\r phu tiiuOc giiia nang luong vao so buac dich chuyen, ket qua dugfc the hien nhu 6 K n h 4.
nh4t, no n5m trong pham vi co 107 b u a c dich chity^n. Dieu do chi ra, hat co nong dp t^p chat B 1% de xay ra qua trinh tinh the hoa nhdt. Khi tang nong dg tap chat B ISn 3 % , 5 % thi t a t h a y nang lugng c ^ he giam it dim. Dieu do cho thay, nong do t^p chat B anh huang tai vi cau true va qua trinh tinh the hoa.
Tiep theo, chung toi k h ^ sat ham phan bo xi^en tam, so phoi tri tai cac buac dich chuyen 8.106 budc; 1,6.107 buac; 2,4.107 buoc; 3,2.107 buoc va 4.107 budc, ket qua dugc the hi$n tren Hinh 5, Bang 3.
a l -8.10*bi a2 - 1,6.10' bii«c SS-2,4.10'biHIc a4 - 3,1.10' birftc aS - 4.10' b ~
Hinh 4. Nang Iir^ng cua hat nano Fe,.,B^ vdi X = 1%, 3%,'5%
Quan sat Hinh 4 ta thay, hat nano Fe,^B^
voi X = 1% CO gia trj nang lugng Ion nhat. Khi tang nong do tap chat B len thi nang lugng cua he giam dan. Con khi tang so budc dich chuyen l e n 4 . 1 0 7 b u d c t a t h a y rang, voi h&t CO nong dg tap chat B 1 % thi nang luang cua he giam nhieu
Hinh 5.
Fe,
Ham phSn bo xuyen tSm cua h^t nano ,B^ v6i X = 1% (a), 3 % (b), 5% (c)
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TROCfNG DAI HQC DONG THAP Tap chf Khoa hpc so 24 (02-2017 Bang 3. S6 ph6i tri cua hat nano Fe,.^B^ vfti ndng
S6birftc Tap cbit B
X - 1(%) x=3(%) x-5(%)
8.10' 1 1,6.10' 1 2,4.10' 1 3,2.10'
dd pha tap chat B vl s6 birftc dich chuyin khde nhau '4.10'
So phoi tri 13
13 12
14 14 12
14 14 13
14 14 14
14 14 14
8.10« 1 1,6.10' 1 2,4.10' 1 3,2.10' | 4.1iBS Mat d$ sd phoi tn' "
0,2871 q,2664 0,2507
0,5645 0,4602 0,2549
0,6149 0,4871 0,2441
0,6161 0,4983 0,3254
0,6163 0,5017 0,3806 KetquattenHinh5,B^g3chothayhatnano hoa hat nano FCj^^B^ voi x = 1%, x= 3%, x = 5%
Fe, ,B, voi x = 1% (Hinh 5a) co dinh thii nhat cua la rat lon. l.« X - V ^
ham phan bo xuyen tam chiem tra the, khi tang so biroc chay thi vi tri ^nh thiinhatcuahamphanbo xuyen tam khong dpi, dp cao ham ph&i bo xuyen tam tang. Khi tang so buoc chay 16n 8.10' buoc thi dinh thii hai ciia ham phan bo xuyen tam chua xuat hien hisn tupng tach Pick, so phoi tri cua hat la 13, mat dp so phoi tri la 0,2871 chung to voi sp buac chay < 8.10' buoc thi hat van ton tai o ttang thai vo dinh hinh. Khi tang so buoc chay len 1,6.10' buoc tai dinh thu hai ciia ham phSn b6 xuyen tam bat dau xuit hi$n hien ttipng tach thanh 2 Pick, so phoi tri tang len 14, mat dp so ph6i tti tang len la 0,5645 chiing t6 voi so buoc chay 1,6.10' bupc thi hat bat dau chuyin sangttangthaittnhthehoaKhi tang so buoc dich chuyen len 2,4. lO'buoc, 3,2.10' buoc, 4.10' budc thi do cao ciia dinh thii nhat va 2 Pick dinh thiihaiciiahamphanb6 xuyen tam tang chung 16 qua ttinh tinh the hoa cua m6 hinh ngay cang tang khi tang so buoc dich chuyin. Cac ket qua nay hoan toan phu hpp voi ket qua cua bao cap PL [4], [8]. Tuong tu, vdi cac hat co nong dp tap
4. Ket luan
Bai bao nay nghien cuu su anh hudng cila nong dp tap chit B len vi cau true va qua trinli titlh the hda cua mo hinh hat nano Fe^ ^B da thu dupc ket qua;
- Xay dung thanh cong cac hat nano Fe B vdi nong dp tap chat B la x = 1%, x = 3%, x = 5%
bang phuong phap dpng Iuc hpc phan tu vdi till tucmg tac cap Pak - Doyama va dieu ki$n bien tu do va chp ket qua phii hpp vdi cac kit qud [21 [4], [8].
- Xac dinh hinh dang hat nanp Fe, B (wi x = 1%, x = 3%, X = 5%) CP dang hinh clu va co kich thudc nano.
- Xac dinh su anh hudng cua nong dp tap chat B ISn vi cau ttiic hat nano Fe, __B_^. Nguyen nhan chinh dan den kit qua nay la do hieu ung nang lupng, khi tang npng dp tap chat B dan den nang lupng, sp phpi tri ciia hp giam.
- Xac dinh dupc su anh hudng ciia nong do tap chat B len qua ttinh tinh the hda ciia hat nano chit B 3% (Hinh 5b), 5% (Hnh 5c). Cac kit q S l ? '*="^,'.™r^ ta"" <• "h the hoa ciia hat nano cho thiy, ha. vdi ndng dp t p chit B 1 % dl xay ra S^h X h ^ ' T * t ? ' ' 'I- ' ' I ' l 'I f qua ttinh tinh thi hoa nhit, khi tang ndng dp tap w 5^,-*^' """^ t ^ " " 5 1 ' * " ^ ' ' ' "
chit B len din din qua trinh ttnh dfl hda cua Z ^°' ' t f ^ 7 ^ ' " ' ' " f J f .*= ""^ 8 ' ^ , . gtto. Dilu dd cho thiy c6 su anh hudng cua ning ,ui, „ ,? ^ " " J ^ ^"""f <;"J "™8 * ?>
dp tap chi. B len vi ciu ttuc va qua tti^ tinh till fa^o Fe, B T " ' " ' Tai lieu tham khao
.^J''3oLXz.:^ltl'';TZ'^^^^^
o/i.rc^S,^^ri?6i'r/^^^^^^^^^^
F e - P ™ h o u s ' ' f n " ? " ' ™ ' " ff°°°^- "^'"='^ ='™<^<^« and ferromagnetic chara^er of Fe-B and re r amorphous alloys , Physical Review B, (vol 62) p 5746-5750
tions of tfe r r t T n e • ^ "^t"' "^If"'"'' ^^ ^ ^ ^ ^ ^ d???). "Tie frequency drstiibution te- ofthe crystalhne, amoiphous and hqmdiron". Solid State Communication, (vol 36). p. 377-379,
TRUCtNG DAI HCx: D 6 N G T H A P Tgp chl Khoa hoc s 6 24 (02-2017) [5]. R. Yamamoto, H. Matsuoka and Ml Doyama (1978), "Structural relaxation of tiie dense random packing model for amorphous iron", Pkysica Status SolidiA, (vol 45), p. 305-314.
[6]. S. K. Sharma, M P. Macht and V. Naundoif (1992), "ASIMS mvestigation of impurity difiusion m amorphous F e ^ i ^ ^ o " ' -dctaMetallurgica etMaterialia, (vol 40), p. 2439-2449,
[7]. T. Fujiwara and Y. Ishii (1980), "Structural analysis of models for the amoiphous metallic alloy P^Kfrx^x"' -Journal of Physics F: Metal Physics, (vol 9), p. 1901-1911.
[8]. Vo Van Hoang, (2004), "Conqiuter simulation ofthe effects of B and P concentrations on microstmcture in amorphous Fe-B and Fe-P alloys", Pkysica B, (vol 348), p. 347-3 52.
[9]. Y. Waseda (1981), T h e stmcture of liquids, amorphous solids and solids fast ion conductors".
Progress in Materials Science, (ycA 26), p. 1-22.
[10], P. H. Kien, N. T. Thao, P K Hung (2014), "The local structure and crystalhzation of FeB nanopar". Modem Pkysics Letters B, (vol 28), p. 1450246.
T H E INFLUENCE O F T H E B-DOPED CONCENTRATION ON T H E MICROSTRUCTURE AND T H E CRYSTALLIZATION PROCESS
OF Fe, j B ^ NANO-PARTICLES MODEL Summary
Tliis, paper studies the influence of the B-doped concentration on the microstructure and the
^ ^ ^ J ^ ^ ^ ^ process of FCjJBj^ nano-particles model (with x = 1%, 3 % , 5%). The Fej^B^^ nano- partid^ were created by Molecular Dynamics Simulation metfiod witii fhe Pak-Doyama pair-interaction and tiie free boundary condition. The microstructure characteristics were analyzed through the radial distribution fimctions (RDF), particle size, energy and coordination number. The process crystallization was determmed by tiie 2"^ Pick separation of radial distribution fimction by step movements. The results indicate that there is certain influence of B-doped concentrations on microstructure and crystallization process.
Keywords: B-doped concentration, microstmcture, crystallization process, Fe,^B^ nano-particles model. Molecular Dynamics Simulation.
Ngdy nhdn bdi: 22/9/2016; Ngdy nhdn lgi: 21/10/2016; Ngdy duyit ddng: 08/12/2016.
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