1 Nghiờn cu cu trỳc ca ng Nano cacbon di tỏc ng ca cỏc bc x nng lng cao nh hng ng dng mụi trng v tr : Lun ThS Vt liu v linh kin Nanụ / Nguyn ỡnh Hong ; Nghd : TS Nguyn Thanh Bỡnh M U Do cú nhiu tớnh cht rt ỏng chỳ ý nh kh nng dn in, cng cao, dn nhit tt Vt liu nano carbon (CNTs) khụng ch c ng dng cỏc vt liu nano composite, vt liu chu nhit, vt liu hp th súng in t, u dũ v u phỏt in t m cũn c s dng nhiu lnh vc khỏc nh tu v tr, lũ phn ng ht nhõn, v cỏc ng dng mụi trng[10][12][16] Trong mụi trng v tr, CNTs cú th c dựng lm v tu, cỏc linh kin in t, thit b lu tr hidro, pin lithium v pin nhiờn liu iu kin ny, cỏc thit b ny chu s tng tỏc ca nhiu loi ht, cỏc loi bc x in t cú nng lng cao nh proton, electron, alpha, photon, ntron, cỏc ion nng, vỡ vy cú th dn n s bin i v cu trỳc mng, a vo mng cỏc nguyờn t l, lm thay i cỏc tớnh cht c, húa, lý, nh hng n kh nng hot ng ca cỏc thit b ny[8] Nhm mc ớch mụ phng quỏ trỡnh tng tỏc ca cỏc bc x trờn v tr lờn cỏc vt liu nano ngi ta thng tin hnh cỏc nghiờn cu th nghim trờn mt t vi cỏc ngun bc x nhõn to, ú ch yu c to t cỏc mỏy gia tc ht v cỏc ngun ng v phúng x Lun ny ó a mt s kt qu nghiờn cu thc nghim vic nhn din cỏc ng v phúng x v xỏc nh sut lng ca chỳng c to thnh t cỏc vt liu CNTs chiu bi chựm photon hóm nng lng cc i 60 MeV trờn mỏy gia tc electron tuyn tớnh, ng thi ó kho sỏt nh hng ca cỏc ngun bc x khỏc nh: bc x hóm, tia gama, tia X, tia laser cú mt nng lng cao bng phng phỏp phõn tớch ph raman 3 Chng - ng nano carbon 1.1 Lch s hỡnh thnh ng nano carbon c to bi cỏc nguyờn t carbon, cỏc nguyờn t carbon ny liờn kt húa tr vi bng lai húa sp2 Mt s dng cu hỡnh ph bin ca vt liu carbon 1.2.1.Than chỡ Hỡnh 1.1 Cu trỳc ca than chỡ Than chỡ l dng tn ti ph bin nht ca carbon, cú mu en, t trng nh v thng gp t nhiờn 1.2.2 Kim cng Hỡnh 1.2 Cu trỳc ca kim cng c bit n l mt loi ỏ quớ vi giỏ tr s dng cao 1.2.3 Fullerene Hỡnh 1.3 Cu trỳc ca carbon C60 (mt dng ca fullerene) Fullerene l nhng phõn t cu thnh t cỏc nguyờn t cacbon, chỳng cú dng rng nh mt cu, ellipsoid 1.2.4 ng nano carbon (Carbon nanotube) - CNTs Khỏc vi fullerene, CNTs cú dng hỡnh tr rng v cú th tn ti dng n tng hoc a tng (gm cỏc ng n tng lng vo nhau) SWCNTs MWCNTs Hỡnh 1.4 Cu trỳc ca ng SWCNTs v MWCNTs Hỡnh 1.5 nh SEM ca CNTs Hỡnh 1.6 nh TEM cỏc ng carbon nano a tng 1.3 C ch mc ng nano carbon Khớ cha carbon (CnHm) s b phõn ly thnh nguyờn t carbon v cỏc sn phm ph khỏc nng lng nhit, plasma.Cỏc sn phm sau phõn ly s lng ng trờn cỏc ht xỳc tỏc v hỡnh thnh CNTs 5 C ch mc t nh ca ht xỳc tỏc C ch mc t Hỡnh 1.7 C ch mc ng nano carbon 1.4 Cỏc phng phỏp ch to ng nano carbon [3] 1.4.1 Ch to vt liu CNTs bng phng phỏp CVD Trong phng phỏp lng ng pha hi hoỏ hc (CVD) thng s dng ngun carbon l cỏc hyrụ carbon (CH4, C2H2) hoc CO v s dng nng lng nhit hoc plasma hay laser phõn ly cỏc phõn t khớ thnh cỏc nguyờn t carbon hot húa Hỡnh 1.8 H thit b ch to CNTs bng phng phỏp CVD 1.4.2 Ch to CNTs bng phng phỏp phúng in h quang Trong phng phỏp ny hi carbon c to bng cỏch phúng mt lung h quang in gia hai in cc lm bng carbon Hỡnh 1.9 H thit b ch to CNTs bng h quang in 1.4.3 Ch to ng nano carbon dựng ngun laser Mt chựm laser nng lng cao (xung hoc liờn tc) lm bay hi o mt bia graphite lũ nhit cao khong 1200 C Hỡnh 1.10 H to CNTs bng phng phỏp chựm laser 1.5 Tớnh cht ca ng nano carbon 1.5.1.Tớnh cht c Theo mt s so sỏnh thỡ ng nano carbon nh hn thộp ln v bn gp trm ln thộp (trờn cựng n v th tớch v chiu di) [15] 1.5.2.Tớnh cht nhit dn nhit ca vt liu ca SWCNTs cú t giỏ tr khong t 20-3000 W/mK trờn nhit phũng [18], Cú tỏc gi cũn cụng b dn nhit cú th t ti 6600 W/mK [13][16] 1.5.3.Tớnh cht in Ph thuc vo vộc t cun ng ca chỳng, cỏc ng nano carbon cú th hoc l cht bỏn dn hoc l kim loi Ngoi dn in ca ng nano carbon n tng cng ph thuc rt nhiu vo lc tỏc dng lờn ng [12] Hỡnh 1.11 ng nano carbon kiu armchair cú tớnh cht kim loi v nano carbon kiu zig-zag cú tớnh cht bỏn dn 1.5.4 Tớnh cht húa hc CNTs tng i tr v mt húa hc, ú tng hot tớnh húa hc ca CNTs ta phi to cỏc khuyt tt trờn b mt ca ng, gn kt vi cỏc phõn t hot ng khỏc to cỏc vi u dũ nhy vi hoỏ cht [17] 1.5.5 Tớnh cht phỏt x in t trng S phỏt x trng l quỏ trỡnh phỏt x in t t b mt ca mt pha rn vo chõn khụng, di tỏc dng ca mt in trng tnh (khong 10 V/cm) Khi ỏp mt in trng ln, cỏc in t ti b mt xuyờn hm qua hng ro th v thoỏt ngoi [12] 1.6 Cỏc sai hng cú th tn ti mng ca ng nano carbon Trong CNTs cú hai loi khuyt tt ch yu.[1] + Mt loi l sai hng im + Mt dng khuyt tt ng nano carbon l sai hng Stone Wales, sai hng ny to cp ng giỏc v cp tht giỏc Hỡnh 1.12 Sai hng Stone Wales to cp ng giỏc v tht giỏc CNTs 1.7 Mt s ng dng ca ng nano carbon 1.7.1 Cỏc ng dng v nng lng - S dng CNTs pin litium cú th tng dung lng pin lờn 10 ln, c ng dng xe hi, cỏc thit b in t cm tay[11] 8 - Vỡ vy CNTs cú th c s dng cho vic tớch tr Hidro, lm thnh pin nhiờn liu dựng cho ụ tụ.[10] Hỡnh 1.13 Mụ hỡnh s xen gia ca Li v hp th H2 1.7.2 Thit b phỏt x in t trng Yờu cu chung l ngng th phỏt x ca vt liu phi thp, mt dũng phi cú n nh cao, ng kớnh nh c nanomet, dn in cao, rng khe nng lng nh v n nh v mt húa hc CNTs ỏp ng c cỏc yờu cu ny Hỡnh 1.14 Mn hỡnh hin th s dng CNTs 1.7.3 u dũ nano v sens Do tớnh dai c s dng nh cỏc u dũ quột cỏc thit b kớnh hin vi in t AFM v STM [17] Hỡnh 1.15 Tớp STM, AFM cú gn CNTs Hỡnh 1.16 Tớp CNTs bin tớnh Hỡnh 1.17 Vt liu CNTs-COOH dựng cho xỏc nh nng cn 1.7.4 ng nano carbon to cỏc vt liu siờu bn, siờu nh Theo cỏc chuyờn gia, ng dng quan trng ca si carbon mi ny l sn xut ỏo chng n , v tu vỡ CNTs l vt liu siờu bn v siờu nh Hỡnh 1.18 o chng n siờu bn, v tu v tr lm bng CNTs 1.7.5 ng nano carbon to cỏc linh kin in t nano Hin vi s xut hin ca ng nano carbon, cựng vi kh nng ch to cỏc ng carbon cú tớnh cht nh l bỏn dn loi p hay loi n Hỡnh 1.19 Transistor trng s dng ng nanno carbon 10 Chng Lý thuyt tỏn x Raman 2.1 Hiu ng Raman Trong thớ nghim Raman, mt laser c s dng kớch thớch nhng nguyờn t, phõn t, lm thay i trng thỏi dao ng ca chỳng cỏc dao ng rung, xoay ca phõn t lm thay i mc nng lng ca chỳng, ú ỏnh sỏng ti s tỏn x cỏc tn s khỏc vi tn s ca ỏnh sỏng kớch thớch Hỡnh 2.1 C V Raman Hỡnh 2.2 Tỏn x Raman thu c kớch bng laser Hỡnh 2.3 mụ t cỏc quỏ trỡnh tỏn x khỏc nhau, ú cú c nhng phonon rng ca cỏc mi tờn ch kh nng ca tỏn x Tỏn x thng xy nht l tỏn x Rayleigh, tỏn x ny l tỏn x n hi, õy l kt qu ca quỏ trỡnh phỏt mt photon vi cựng bc súng vi ỏnh sỏng kớch thớch Hỡnh 2.3 Nguyờn lý ca quỏ trỡnh tỏn x raman 11 2.2 Tỏn x Raman cng hng Thụng thng, phõn t c kớch thớch lờn trng thỏi nng lng o sau ú nú hi phc, kt qu l mt photon c phỏt Quỏ trỡnh tỏn x ny c gi l tỏn x cng hng nu mt hoc nhiu chuyn di gia cỏc trng thỏi nng lng thc ca phõn t 2.3 Cỏc mode dao ng ca ng nano carbon Hỡnh 2.4 Ph tỏn x Raman ca CNTs a tng.[4] + Mode RBM: l dao ng cỏc nguyờn t carbon dao ng theo hng hng tõm ca ng vi tn s 100 500 cm-1 +Mode D: cú tn s c khong 1330 cm-1 c gi l mode sai hng mng, hay mt trt t ca mng, ca graphene + Mode G cú tn s c khong 1590 cm-1 Mode ny s dao ng mt nguyờn t carbon lõn cn mng lc giỏc Hỡnh 2.5 Mt s mode dao ng ca CNTs Ta cú th xỏc nh c mc trt t cu trỳc ca vt liu CNTs qua t s cng gia mode D v mode G, ID/IG Nu 12 ID/IG cng ln thỡ chng t mu cng cú nhiu khuyt tt V ngc li [9],[6] 2.4 Ph k raman 2.4.1 Cu to ca ph k Raman Hỡnh 2.6 S ca ph k Raman Hỡnh 2.7 Ph k Raman ca hóng Renishaw Ph k Raman gm cỏc chớnh nh sau: Khi phỏt Laser Khi dn quang v u dũ Mỏy n sc Khi thu nhn tớn hiu Cỏc in t, hin th khỏc 2.4.2 u im ca phng phỏp Phng phỏp ny khụng yờu cu phi phỏ mu hay trớch mt phn nh ca mu nghiờn cu ú bo ton c mu, khụng cn phi tip xỳc trc tip vi mu, l phng phỏp phõn tớch nhanh, di ph rng 100 cm-1 n 4000 cm-1 cú kh nng nghiờn cu hu ht cỏc 13 hp cht hu c v vụ c, cú kh nng phõn tớch cỏc mu cú kớch thc khong àm Chng Ngun bc x nng lng cao 3.1 Tia v tr Khong 89% thnh phn ca tia v tr l proton (ht nhõn hidro), 10% l ht anpha (ht nhõn Helium), 1% l cỏc ht nng khỏc Cỏc ht ny cú th cú nng lng lờn n 1020 eV, cao hn nhiu ln so vi cỏc mỏy gia tc ht cú th to Hỡnh 3.1 Ph nng lng ca tia v tr Cỏc tia v tr cú th c to t cỏc v n siờu (supernova), t cỏc l en (black holes), hot ng ca mt tri hay tng tỏc ca cỏc tia v tr vi vt cht gia cỏc Hỡnh 3.2 S nh hng ca cỏc tia v tr theo cao Nhng iu kin v tr, cỏc v tinh thng phi bay cỏch mt t c 500 km Ni chu nh hng mnh ca tt c cỏc tia, cỏc ht cú nng lng cao nh proton, electron, alpha, photon, ntron, 14 cỏc ion nng, cỏc ht c bn, súng in t cú nng lng cao cú th dn n s bin i v cu trỳc, cỏc tớnh cht c, húa, lý, vy s nh hng n kh nng hot ng ca cỏc thit b ny 3.2 Ngun bc x nhõn to Nhm mc ớch mụ phng quỏ trỡnh tng tỏc ca cỏc bc x trờn v tr lờn cỏc vt liu nano ngi ta thng tin hnh cỏc nghiờn cu th nghim trờn mt t vi cỏc ngun bc x nhõn to, ú ch yu c to t cỏc mỏy gia tc ht v cỏc ngun phúng x 3.2.1 Mỏy gia tc tuyn tớnh Hỡnh 3.3.Mỏy gia tc electron tuyn tớnh, Pohang, Hn Quc Hỡnh 3.4 Ni t mu c chiu x Nguyờn lý hỡnh thnh bc x hóm[14] Hỡnh 3.5 Nguyờn lý to bc x hóm 15 A* +e e+A * e+A A +e A+ +e A++e, Thông l- ợ ng photon h m 10 60MeV 10 10 10 10 20 30 40 50 60 70 Nă ng l- ợ ng photon h m (MeV) Hỡnh 3.6 Ph bc x hóm thu c t bn mỏy gia tc 3.2.2 Ngun Americium-241, phỏt tia X Phỏt 1,24x109 tia X mi giõy Nng lng tia X: 0,0595 MeV ( 0,0208 nm) 3.2.3 Ngun Radium-226, phỏt gamma Phỏt 1,85x105 tia gamma mi giõy Nng lng gamma: 4,78 MeV (2,59x10-4nm) Chng Thc nghim Trong thớ nghim ny, chỳng tụi s dng mu nghiờn cu l ng nano carbon c ch to ti Vin Khoa hc Vt liu - Vin KH&CN Vit Nam ng nano carbon cú ng kớnh t 15- 90 nm, tinh kit l 97%, v phn cũn li l cht v carbon vụ nh hỡnh [4] Hỡnh 4.1: S thớ nghim chiu x CNTs bng bc x hóm Do vy mụ phng quỏ trỡnh chiu x cho sỏt vi iu kin v tr hn, chỳng tụi ó tin hnh chiu x mu nano carbon bng tia X 16 vi nng lng l 0,0595 MeV nm v Gamma vi nng lng l 4,78 MeV thi gian 12 ngy liờn tc 4.1 Nghiờn cu s nh hng ca bc x laser lờn CNTs Hỡnh 4.2 Ph Raman ca CNTs cha chiu Hỡnh 4.3 Tn s mode D v mode G ca CNTs cha chiu Hỡnh 4.4 T s v cng ID/IG ca ng nano carbon cha chiu x Khi tng cng laser, CNTs b chiu sỏng mnh hn, nhit ca CNTs tng, dn ti s gión n vỡ nhit, liờn kt carbon-carbon di vy nú lm gim lc liờn kt gia carbon-carbon [5], [17], vy lm gim nng lng ca phonon Vỡ vy, tng cng laser, thỡ mode D v G chuyn v tn s thp hn 17 Bng Tn s mode D, G , t s ID/IG theo cng laser ca CNTs cha chiu x Cng laser Tn s (KW/cm2) mode D 1331,5 15 1331,2 30 1329,4 60 1326,7 30 1329,5 15 1331,3 1331,5 Tn s mode T G ID/IG 1583 1,09 1583,4 1,2 1580,8 1,2 1577,8 1,14 1580,8 1,17 1583 1,12 1582,8 1,22 s Quỏ trỡnh dch chuyn thun nghch chiu bi cng laser khỏc v T s ID/IG ca CNTs cha chiu, khỏ l n nh xung quanh giỏ tr t 1,1-1,2 ó chng t rng, CNTs khụng b h hng chiu bi chựm laser cú cng cao Kt qu ny trựng vi kt qu ca cỏc bi bỏo khỏc [5],[8] 4.2 Nghiờn cu s nh hng ca bc x hóm lờn CNTs 4.2.1 Cỏc ng v phúng x cú th to thnh chiu bc x hóm Do c chiu x bng photon cú nng lng rt ln, lờn ti 60 MeV, cỏc ng v phúng x mi ó c to thnh Cỏc ng v c nhn din cn c vo nng lng ca cỏc tia gamma (E) v thi gian bỏn ró (T1/2) bng h ph k gamma vi ờtect bỏn dn Gecmani siờu tinh khit (HPGe) Hỡnh 4.5 H ph k gamma HPGe 18 Bng Cỏc ng v phúng x c nhn din t CNTs TT 10 11 12 13 14 15 16 17 ng v 24 Na 43 Sc 44 Sc 46 Sc 47 Sc 48 Sc 48 V 52 Mn 54 Mn 52 Fe 55 Co 56 Co 57 Co 58 Co 56 Ni 57 Ni 99 Mo Thi gian bỏn ró 14,959 gi 3,891 gi 3,927 gi 83,79 ngy 3,3492 ngy 43,67 gi 15,9735 ngy 5,591 ngy 312,3 ngy 8,275 gi 17,53 gi 77,27 ngy 271,79 ngy 70,86 ngy 6,077 ngy 35,60 gi 65,94 gi Kiu phõn ró EC; + EC; + EC; + EC; + EC; + EC; + EC; + EC; + EC EC; + EC; + EC; + - Nng lng [keV] 1368,63; 2754,03 372,76; 1931,3 1157,03; 1499,43 889,277; 1120,54 159,377 983,52; 1037,6; 1312,1 983,52; 1312,10 744,23; 935,54; 1434,07 834,45 168,69; 377,75 477,2; 931,3; 1408,4 846,77;1037,84; 1238,28 122,06; 136,47 810,77; 863,96 158,38; 749,95; 811,85 127,16; 1377,63 140,51; 739,5; 777,92 Hỡnh 4.6 Ph gamma c trng ca ng nano carbon 10 Suất lợng (/giây/gam) Mẫu CNTs 10 10 10 10 10 10 Na24 Sc43 Sc44 Sc46 Sc47 Sc48 V48 Mn52Mn54 Fe52 Co55 Co56 Co57 Co58 Ni56 Ni57 Mo99 Đồng vị phóng xạ Hỡnh 4.7 Sut lng to thnh cỏc ng v phúng x mu ng nano carbon chiu bi chựm photon hóm 60 MeV 19 4.2.2 S nh hng lờn cu trỳc ca CNTs c chiu bc x hóm (a) (b) Hỡnh 4.8 nh SEM ca CNTs (a) ban u v (b) sau c chiu bng bc x hóm Hỡnh 4.9 Ph Raman ca CNTs sau chiu bng bc x hóm, Hỡnh 4.10 (a)Tn s mode D, (b)Tn s mode G, v (c)t l cng ca chỳng ca CNTs sau chiu bng bc x hóm 20 Bng Tn s mode D, G , t s ID/IG theo cng laser ca CNTs sau c chiu bng bc x hóm Cng laser (KW/cm2) 15 30 60 30 15 Tn s mode D 1331,9 1331,2 1325,6 1323 1328,8 1332,1 1332,4 Tn s mode G 1581,3 1581,4 1575,7 1570,7 1578,6 1581,3 1581,9 T s ID/IG 1,22 1,26 1,23 1,3 1,44 1,4 1,28 iu ny l sau c chiu vi chựm photon 60 MeV, CNTs ó b h hi mt phn v cu trỳc 4.3 S nh hng ca tia X v tia Gamma lờn cu trỳc CNTs Mu CNTs c chiu x vi cỏc ngun ng v phúng x khỏc nhau, ú l ng v phúng x Americium-241 v ngun ng v phúng x Radium -226 Hỡnh 4.11 Ph Raman ca CNTs sau chiu bng tia X Hỡnh 4.12 Ph Raman ca CNTs sau chiu bng tia Gamma 21 1584 1330 1328 1326 Ch- a chiếu Chiếu tia X Chiếu tia Gamma 1324 Tần số -Mode G Tần số -Mode D 1332 1580 1576 Ch- a chiếu Chiếu tia X Chiếu tia Gamma 1572 15 30 45 60 45 30 15 15 30 45 60 45 30 15 Mật độ laser (KW/cm ) C- ờng độ laser (KW/cm ) 1.8 1.6 ID/IG 1.4 1.2 1.0 0.8 Ch- a chiếu Chiếu tia X Chiếu tia Gamma 0.6 0.4 15 30 45 60 45 30 15 C- ờng độ laser (KW/cm ) Hỡnh 4.13 dch tn s ca (a) nh D v (b) nh G v (c) t l v cng nh ca CNTs cha chiu, v sau chiu bng tia X, tia Gamma Bng Tn s mode D, G , t s ID/IG theo cng laser ca CNTs sau c chiu bng tia X Cng laser (KW/cm2) 15 30 60 30 15 Tn s mode D 1330,7 1330,8 1327,3 1324,9 1328,6 1331,5 1331,5 Tn s mode G 1582,7 1581,2 1577,8 1572,8 1578,2 1582,1 1582,9 T s ID/IG 0,98 0,98 0,91 0,88 0,96 0,97 1,01 22 Bng5 Tn s mode D, G , t s ID/IG theo cng laser ca CNTs sau c chiu bng tia Gamma Cng laser (KW/cm2) 15 30 60 30 15 Tn s mode D 1331 1330,3 1326,8 1323,3 1328,4 1330,4 1330,5 Tn s mode G 1582 1581,6 1577,6 1572,8 1578,4 1582,8 1582,3 T s ID/IG 1,3 1,27 1,25 1,16 1,32 1,39 1,45 Quan hỡnh 4.13c, t s ID/IG ca CNTs chiu bi tia X nh hn lỳc cha chiu v t s ID/IG ca CNTs chiu bi tia Gamma thỡ li ln hn lỳc cha chiu T õy ta cú th kt lun c rng, chiu mu CNTs vi tia X thỡ mu CNTs li tr nờn tt hn, cú th tia X cú nng lng thớch hp mt mt va to cỏc sai hng mi, mt khỏc li tỏi cu trỳc li cỏc sai hng ó tn ti trc ú Chớnh vỡ th m t s ID/IG gim xung rừ rt Mu CNTs ban u cú nhiu sai hng, v cú cha nhiu carbon vụ nh hỡnh Khi c chiu bng tia X vi nng lng va phi, cỏc nguyờn t carbon b dao ng v sau mt khong thi gian di, nguyờn t carbon t sp xp vo v trớ ỳng mng Khi chiu mu CNTs vi tia Gamma, thỡ mu CNTs ó b h hng nhiu hn nhiu hn vỡ nng lng ln ca tia Gamma Do nng lng mnh hn nhiu ln so vi tia X, nờn nú cú kh nng lm CNTs h hng cao hn nhiu, vy m t s ID/IG tng lờn T s ID/IG lỳc ny cng thay i mnh hn theo cng laser u ú cng khng nh rng CNTs ó tr lờn xp hn, d b suy yu hn so vi lỳc cha chiu 23 KT LUN Tớnh cht bỏn dn chim u th hn so vi tớnh kim loi ó c rỳt t ph Raman ca mu Tớnh cht ca CNTs di nh hng ca bc x laser, bc x hóm, tia X v Gamma ó c nghiờn cu S nh hng ng thi ca c hai loi bc x ny lờn cu trỳc ca CNTs cng c nghiờn cu bng phng phỏp ph Raman Bc x laser khụng lm thay i tớnh cht ca CNTs, bc x ny thụng qua nhit cao ch lm cho CNTs gión n vỡ nhit Bc x hóm cú nng lng rt cao, ó lm thay i tớnh cht ca CNTs, gõy cỏc phn ng ht nhõn, to cỏc ng v phúng x, qua cỏc phn ng ht nhõn cú th to cỏc ht nhõn mi, ng thi cng gõy nhiu sai hng mng Nh vy cú th nh hng n tin cy, n nh ca cỏc linh kin in t Bc x tia X cú nng thớch hp cú th lm gim bt cỏc sai hng mng ca CNTs, lm nõng cao cht lng ca CNTs Bc x Gamma, nng lng cao ó lm thay i cu trỳc ca CNTs, phỏ v liờn kt, gõy cỏc sai hng mng Kt qu ca thớ nghim ny, cú th cung cp nhng thụng tin quan trng v CNTs, c bit l CNTs c dựng cỏc mụi trng c bit Bng cỏc loi chiu x khỏc ta cú th: i) a cỏc nguyờn t mi vo ng nano carbon bng quỏ trỡnh phõn ró ht nhõn; ii) to cỏc khuyt tt ng nano carbon thun tin cho vic gn thờm cỏc nhúm chc nhy húa, sinh; iii) ng thi cng cú th ci thin c phm cht ca CNTs thụng qua quỏ trỡnh chiu x Kt qu ny cú th m mt cụng ngh x lý CNTs núi riờng v cỏc vt liu nano núi chung bng phng phỏp chiu x nng lng cao 24 TI LIU THAM KHO David J Appelhans et al (2010), Embedded ribbons of graphene allotropes: an extended defect perspective, New Journal of Physics, 12, 125006 G Compagnini et al (2005), New assignment of crystalline and ion-irradiated graphite phonon spectra, Journal of Raman spectroscopy, 26, pp 917 M Daenen et al (2003), The Wondrous World of Carbon Nanotubes, Eindhoven University of Technology, pp 8-21 M S Dresselhaus et al (2007), The big picture of raman scattering in carbon nanotubes , Vibrational spectroscopy, vol 45, pp 7181 Nguyen Duc Dung et al (2008), Carbon-Nanotube Growth over Iron Nanoparticles Formed on CaCO3 Support by Using Hydrogen Reduction, Journal of the Korean Physical Society, 52, pp.1372-1377 Nguyen Dinh Hoang, Nguyen Ngoc Trung, Pham Duc Khue, Nguyen Thi Thanh Bao, Phung Viet Tiep, Dao Duy Thang, Nguyen Thanh Binh, Vu Thi Bich (2011), The synergistic effect of bremsstrahlung photons and intense laser radiation on the structural properties of carbon nanotubes , Adv Nat Sci: Nanosci Nanotechnol 2, 035010 A Jorio et al (2002), G-band resonant Raman study of 62 isolated single-wall carbon nanotubes,Phys Rev B, 65, 155412 A.V.Krasheninnikov, K.Nordlund (2010), Ion and electron irradiation effects in nanostructured materials, Journal of Applied Physics, 107, 071301 Amit et al (2009), Effect of intense laser and energetic ion irradiation on Raman modes of multiwalled Carbon Nanotubes, Thin Solid Films, 517, pp 43224324 10 Seung Mi Lee et al (2000), Hydrogen adsorption and storage in carbon nanotubes, Synthetic Metals, 113, pp 209216 11 Seung Woo Lee et al ( 2010), High-power lithium batteries from functionalized carbon-nanotube electrodes, Nature Nanotechnology , 5, pp.531-537 25 12 W I Milne, K B K Teo, Vu Thien Binh (2003), Electrical and field emission investigation of individual carbon nanotubes from plasma enhanced chemical vapour deposition, Diamond and Related Materials,12, pp 422428 13 Eric Pop et al (2005), Thermal conductance of an individual single-wall carbon nanotube above room temperature, Nano Letters, 6, pp 96100 14 Md Shakilur Rahman et al (2009), "Measurement of 90 isomeric yield ratios for Zr(, n)89m,gZr, natZr(, xn1p)86m,gY, 89 87m,g,86m,g Y reactions with 50-, 60-, and 70-MeV and Y(,xn) bremsstrahlung", Nuclear Instruments and Methods in Physics Research vol B267, pp 3511- 3518 15 J.-P Salvetat et al (1999), Mechanical properties of carbon nanotubes, Applied Physics A, 69, pp 255260 16 Bui Hung Thang, Nguyen Van Chuc, Pham Van Trinh, Ngo Thi Thanh Tam and Phan Ngoc Minh (2011), Thermal dissipation media for high power electronic devices using a carbon nanotubebased composite, Advances in Natural Sciences: Nanoscience and Nanotechnology, 2, 025002 17 Ren-Jang Wu et al (2008), Application of mCNTs/NaClO4/Ppy to a fast response, room working temperature ethanol sensor, Sensors and Actuators B: Chemical, 134, pp 213218 18 Da Jiang Yang et al (2002), Thermal conductivity of multiwalled carbon nanotubes, Physical Review B, 165440 19 Qing Zhang et al (2006), Inuences of temperature on the Raman spectra of single-walled carbon nanotubes, Smart Mater.Struct., 15, pp.1-4 [...]... lng ca CNTs Bc x Gamma, nng lng cao ó lm thay i cu trỳc ca CNTs, phỏ v liờn kt, gõy ra cỏc sai hng mng Kt qu ca thớ nghim ny, cú th cung cp nhng thụng tin quan trng v CNTs, c bit l khi CNTs c dựng trong cỏc mụi trng c bit Bng cỏc loi chiu x khỏc nhau ta cú th: i) a cỏc nguyờn t mi vo trong ng nano carbon bng quỏ trỡnh phõn ró ht nhõn; ii) to ra cỏc khuyt tt trong ng nano carbon thun tin cho vic gn... Americium-241, phỏt tia X Phỏt ra 1,24x109 tia X trong mi giõy Nng lng tia X: 0,0595 MeV ( 0,0208 nm) 3.2.3 Ngun Radium-226, phỏt gamma Phỏt ra 1,85x105 tia gamma trong mi giõy Nng lng gamma: 4,78 MeV (2,59x10-4nm) Chng 4 Thc nghim Trong thớ nghim ny, chỳng tụi s dng mu nghiờn cu l ng nano carbon c ch to ti Vin Khoa hc Vt liu - Vin KH&CN Vit Nam ng nano carbon cú ng kớnh t 15- 90 nm, tinh kit l 97%,... photons and intense laser radiation on the structural properties of carbon nanotubes , Adv Nat Sci: Nanosci Nanotechnol 2, 035010 7 A Jorio et al (2002), G-band resonant Raman study of 62 isolated single-wall carbon nanotubes,Phys Rev B, 65, 155412 8 A.V.Krasheninnikov, K.Nordlund (2010), Ion and electron irradiation effects in nanostructured materials, Journal of Applied Physics, 107, 071301 9 Amit... thụng qua nhit cao ch lm cho CNTs gión n vỡ nhit Bc x hóm do cú nng lng rt cao, ó lm thay i tớnh cht ca CNTs, gõy ra cỏc phn ng ht nhõn, to ra cỏc ng v phúng x, qua cỏc phn ng ht nhõn cú th to cỏc ht nhõn mi, ng thi cng gõy ra nhiu sai hng mng Nh vy cú th nh hng n tin cy, n nh ca cỏc linh kin in t Bc x tia X cú nng thớch hp cú th lm gim bt cỏc sai hng mng trong ca CNTs, lm nõng cao cht lng ca CNTs... hay do tng tỏc ca cỏc tia v tr vi vt cht gia cỏc sao Hỡnh 3.2 S nh hng ca cỏc tia v tr theo cao Nhng trong iu kin v tr, cỏc v tinh thng phi bay cỏch mt t c 500 km Ni chu nh hng mnh ca tt c cỏc tia, cỏc ht cú nng lng cao nh proton, electron, alpha, photon, ntron, 14 cỏc ion nng, cỏc ht c bn, súng in t cú nng lng cao cú th dn n s bin i v cu trỳc, cỏc tớnh cht c, húa, lý, do vy s nh hng n kh nng hot ng... spectroscopy, 26, pp 917 3 M Daenen et al (2003), The Wondrous World of Carbon Nanotubes, Eindhoven University of Technology, pp 8-21 4 M S Dresselhaus et al (2007), The big picture of raman scattering in carbon nanotubes , Vibrational spectroscopy, vol 45, pp 7181 5 Nguyen Duc Dung et al (2008), Carbon-Nanotube Growth over Iron Nanoparticles Formed on CaCO3 Support by Using Hydrogen Reduction, Journal... 749,95; 811,85 127,16; 1377,63 140,51; 739,5; 777,92 Hỡnh 4.6 Ph gamma c trng ca ng nano carbon 7 10 Suất lợng (/giây/gam) Mẫu CNTs 6 10 5 10 4 10 3 10 2 10 1 10 Na24 Sc43 Sc44 Sc46 Sc47 Sc48 V48 Mn52Mn54 Fe52 Co55 Co56 Co57 Co58 Ni56 Ni57 Mo99 Đồng vị phóng xạ Hỡnh 4.7 Sut lng to thnh cỏc ng v phúng x trong mu ng nano carbon khi chiu bi chựm photon hóm 60 MeV 19 4.2.2 S nh hng lờn cu trỳc ca CNTs... energetic ion irradiation on Raman modes of multiwalled Carbon Nanotubes, Thin Solid Films, 517, pp 43224324 10 Seung Mi Lee et al (2000), Hydrogen adsorption and storage in carbon nanotubes, Synthetic Metals, 113, pp 209216 11 Seung Woo Lee et al ( 2010), High-power lithium batteries from functionalized carbon-nanotube electrodes, Nature Nanotechnology , 5, pp.531-537 25 12 W I Milne, K B K Teo, Vu... J.-P Salvetat et al (1999), Mechanical properties of carbon nanotubes, Applied Physics A, 69, pp 255260 16 Bui Hung Thang, Nguyen Van Chuc, Pham Van Trinh, Ngo Thi Thanh Tam and Phan Ngoc Minh (2011), Thermal dissipation media for high power electronic devices using a carbon nanotubebased composite, Advances in Natural Sciences: Nanoscience and Nanotechnology, 2, 025002 17 Ren-Jang Wu et al (2008), Application... chiu x cho sỏt vi iu kin v tr hn, chỳng tụi ó tin hnh chiu x mu nano carbon bng tia X 16 vi nng lng l 0,0595 MeV nm v Gamma vi nng lng l 4,78 MeV trong thi gian 12 ngy liờn tc 4.1 Nghiờn cu s nh hng ca bc x laser lờn CNTs Hỡnh 4.2 Ph Raman ca CNTs khi cha chiu Hỡnh 4.3 Tn s mode D v mode G ca CNTs khi cha chiu Hỡnh 4.4 T s v cng ID/IG ca ng nano carbon khi cha chiu x Khi tng cng laser, CNTs b chiu sỏng