Заглавная страница Избранные статьи Случайная статья Познавательные статьи Новые добавления Обратная связь КАТЕГОРИИ: АрхеологияБиология Генетика География Информатика История Логика Маркетинг Математика Менеджмент Механика Педагогика Религия Социология Технологии Физика Философия Финансы Химия Экология ТОП 10 на сайте Приготовление дезинфицирующих растворов различной концентрацииТехника нижней прямой подачи мяча. Франко-прусская война (причины и последствия) Организация работы процедурного кабинета Смысловое и механическое запоминание, их место и роль в усвоении знаний Коммуникативные барьеры и пути их преодоления Обработка изделий медицинского назначения многократного применения Образцы текста публицистического стиля Четыре типа изменения баланса Задачи с ответами для Всероссийской олимпиады по праву Мы поможем в написании ваших работ! ЗНАЕТЕ ЛИ ВЫ?
Влияние общества на человека
Приготовление дезинфицирующих растворов различной концентрации Практические работы по географии для 6 класса Организация работы процедурного кабинета Изменения в неживой природе осенью Уборка процедурного кабинета Сольфеджио. Все правила по сольфеджио Балочные системы. Определение реакций опор и моментов защемления |
CneKaHMe OAHOKOMnOHeHTHblX CMCTeMСтр 1 из 10Следующая ⇒
Harpes nopowKosoro TeJJa BbI3bIBaeT B HeM onpe.u.eJJeHHbi e 113Me HeHl1.H, CJJy)l(aUJ,11e XapaKTep11CTl1 KOH cmOOllU npou,ecca cneKaHl1.H. ,lJ,ocTaTO'IHO O'leBl1.llHO, 'ITO.llOJ])KHbl 6bITb 06beKT11BHbi e npl1'111Hbl (11x npl1H.HTO Ha3bIBaTb 06UJ1Cyu.1,11e CllJlbl) TaKl1X 113MeHeHl1H, a 11X pea JJ113au,m1 11 KOHKpeTHbl H pe3yJJbTaT 3aBl1C.HT OT Toro, KaK npOl1CXO.lll1T nepeMeUJ,eH11e semecTBa B HarpesaeMOM nopowKOBOM TeJJe, T. e. KaKo BbI MexaHU3Mbl MacconepeHoca. B npou,ecce Harpesa npo11cXO.ll.HT noA3Y itecmb 11 peKpucmOJ1J1ll30ll, UR 11acT11u., a TaK)l(e (B 6oJibWl1HCTBe cJJy11a es) ynAomHeHue nopowKosoro TeJJa.
CTaAMM cneKaHMR
Bcio CJJO)l(HYIO nocne.u.osareJJbHOCTb npou,eccos, npo11cxo.u.Hm11x np11 Harpese nopOWKOBOfO Tena, 06bI'IHO crnpaIOTCH pa3.U.eJJl1Tb Ha CTa .ll.1111,.llJJH Ka)l(.llOH 113 KOTOpblX MO)l(HO.llOCTaTO'IHO TO'IHO yKa3aTb.llBl1- )l(yUJ,11e c11JJbI 11 Ha1160JJee cymecTBeHHble MexaHl13MbI MacconepeHoca. Xorn TaKoe.u.eneH11e y.u.o6Ho, HO OHO B JHa1111TenbHOH Mepe ycJJOBHO, TaK KaK B 3aBl1C11MOCTl1 OT Ha'laJJbHblX CBOHCTB nopOWKOBOfO Tena 11 ycnos11i1 cneKaHl1H KaK11e-To HBJJemrn 6y.u.yT npo11cxo.u.11Tb nocJJe.u.o BaTeJJbHO 11)]11 0.llHOBpeMeHHO, nepeKpbIBaH 0.llHY 11n11.u.a)l(e HeCKOnb KO CTa.lll1H. )J.nH cneKaeMOfO nopOWKOBOfO TeJJa xapaKTepHbl HeKOTOpble reo MeTp1111ecK11e 3neMeHTbl (p11c. 21 8), onpe.u.eJJHeMble noHHTl1HMl1 «WeH- Ka», «Me)l('laCTH'-IHb H KOHTaKT», «1130Me'fPl1llecKa.H nopa» 11 np. 51.E. fery311H Bb1llen11JJ TPl1 npl1HU.11Ill1aJJbHO OTJ111llHbIX COCTO.HH11H nopowKosoro Tena B npou.ecce ero ttarpesa, K)l(.lloe 113 KOopbIX co orneTcrnyeT onpeneneHHOH crnn1111. Ha nep6ou (Ha11anbH011) crnn1111 np011CXO.lll1T np11neKaH11e nopOWl1HOK (11aCTl1U.) K npyr npyry, co npoBO)l(.llaIOllleec.H yBeJJ11'1eH11eM nJJOUJ,a.lll1 KOHTaKTa Me)l(.lly HHM11; Ka)l(lla.H 11acT11u.a coxpaH.HeT CTPYKTYPHYJO 11H.ll11BHllYMbHOCTb, T. e. rpa Hl1U.a Me)l(lly HHM11 coxpaHHeTC.H 11 c HdlcoxpaH.HeTC.H noH.HT11e «KOH TaKT Me)l(lly qacT11u,aM11». Ha 6mopoil cTan1111 nop11cToe TeJJo MO)l(eT 6bITb npencrnBJJeHO B 811.lle COBOKYilHOCTH.llByx 6ecnop.H.ll0'1HO nepe Me)l(aJOUJ,11XCH cpa3 - cpa3bI semecrna (11acT11U.bI) 11 cpa3bI «nycTOTb» (nopbI); Ha 3TOH CTa.ll.1111 cpopM11poBaH11e JaMKHYTbIX nop eme He 3a KaH'll1BaeTC.H, a KOHTaKTbl Me)l(lly qacT11u.aMH e 11cqe3aJOT 11 rpaHl1- U.bl Me)l(lly H11Ml1 OKa3bIBaIOTC.H pacnoJJO)l(eHHbIMl1 npo113BOJlbHO, BHe CBH311 c Ha'laJJbHbIM pacnono)l(eHl1eM rpaH11U. Me)l(lly 11CXO.llHblMl1 no pOWl1HKaMl1. Ha mpembell CTa.lll111 B nopoWKOBOM Tene B OCHOBHO 11MeIOTCH Jll1Wb JaMKHYTbie 1130nl1pOBaHHble nopbl, 1111cno 11 06m1111 06beM KOTOpbIX MOryT yMeHbWaTbCH. 0rMeTl1M, 'ITO.lla)l(e 3Tl1 BeCbMa yKpynHeHHbie TPl1 CTa.lll111 He MOryT 11MeTb qeTKOfO pa3rpaHl1'1eHH.H: 3aMKHYTbi e (113on11poBaHHbi e) nopbl BC'fPe'laIOTC.H B peaJJbHOM no pOWKOBOM Tene Ha paHHeH CTa.lll111 Harpesa (Hanp11Mep, eme np11 cpopMoBaHl111 3afOTOBK11), a HeKOTOpbie Ha'laJJbHbie KOHTaKTbl Me)l(lly 11acT11u,aM11 coxpaH.HIOTC.H snJJOTb no TPeTbei1 crnn1111 cneKaHl1.H. Ll,nH 6onee nernnbttoro aHaJJ113a npou.eccos, conposo)l(llaIOUJ,11X HarpeB nopoWKOBbIX Ten, qaCTO Bb.lleJJ.HIOT weCTb CTa.ll11H cneKaHl1.H I) pa3s11T11e 11 so3Hl1KH0BeH11e c nocneny10m11M pa3Bl1Tl1eM CBH3e11 Me)l(lly 11acT11U.aM11; 2) o6pa30BaHl1e 11 pOCT «WeeK» Me)l(qaCTl1'1HblX KOHTaKTOB; 3) 3aKpbITl1e CKB03HOH nop11CTOCTl1 B nopoWKOBOM TeJJe; 4) ccpep011.lll13aU,11H nop; 5) ynJJOTHeH11e no pOWKOBOfO Tena 3a C'leT yca.llKl1 11Jon11poBaH HblX nop; 6) yKpynHeH11e (Koanecu,eHU.11.H) nop. Pa36umue C6Jl3etl Me)l(lly 11acT11U.aMH Ha1111- HaeTCH cpa3y c HarpeBOM nopoWKOBOfO TeJJa, a T. e. Ha caMOM paHHeM 3Tane cneKaHl1H. 3TO - n11cpcpy3110HHbl H npou.ecc, np11BO.llHUJ,l1H K
Pttc. 218. ct>parMeHT nopowKoBOro TC!la ao (a) H nocJie (6) ttarpesa H J:lBYX'IUCTll'IH<UI MO,llC)lb cncKaHHH (6): a - pa.llHYC 'laCTHllbl; p - pam1yc «WCHKll»; X - paattyc CC'ICHHH o6paJylOUlCroCSI KOHTaKrn; )' - noJJOBtlHa
BCJll1'111Hbl c6JllllKCHHH UCHTpOll •1aCT11U 8 o6pa30BaHHIO H pa3BHTHIO Me)l(l.laCTH'-IHblX rpaHHU H, CJie,llOBaTeJibHO, yeeJIH'IeHHIO npO"IHOCTH H 3JieKTponpOBO,llHOCTH nopOlllKOBOfO TeJia. PeJyJihTaT 3TOH CTll,llHH - BOJHHKHoBeHHe «llleeK», T. e. nepeMbI"leK Me)l()ly "laCTHUaMH (nopOlllHHKaMH). Poem «llleeK» KOHTaKTOB - ecTecTBeHttoe npo.aomKeHHe npouecca Me)l("laCTH"IHOfO CB.ff3b1BaHm1; ero He06XO,llHMOe ycJIOBHe - nepeHOC BeIUeCTBa B o6JiaCTb Me)l("laCTH"IHOfO KOHTaKTa, KOTOpblH MO)l(eT 6b Tb ocymecTBJieH c noMOIUblO pa3Hb X TpaHcnopTHbIX MexaHH3MOB, Bbl- 3bIBaIOIUHX HJIH He Bbl3blBaIOIUHX ynJIOTHeHHe npH cneKaHHH. nopOlll KOBOe TeJIO CTaHOBHTC.ff 6oJiee npO"IHblM H 3JleKTponpoBO,llHb M. B Ka KOH-TO MOMeHT npHKOHTaKTHbl H yroJI Me)l()ly "laCTHUaMH (nepBOHa l{aJibHO eeCbMa OCTpbIH) npHTYnJIHeTC.ff HaCTOJlbKO, "ITO Me)l(JepeH Hbie (Me)l(4aCTH4Hble) rpaHHUbl Ha"IHHaIOT nepeMeIUaTbC.ff H HX nep BOHa"laJibHOe pacnoJio)l(eHHe HapylllaeTC.H. CneKaeMoe nopolllKOBoe TeJIO no CTpyKType npH6JIH)l(aeTC.ff K COCTO.HHHIO, KOTOpoe 51.E. fery- 3HH HaJBaJI coeoKYnHoCTbIO.aeyx 6ecnop.H.ll04HO nepeMe)l(aIOIUHXCH cpa3 semecTBa H nyCTOTbl. 06bI4HO C"IHTaIOT, "ITO pOCT «llleeK» npOHC XO,llHT,llOBOJlbHO 6bICTpO H xapaKrepH3yeT Ha"laJibHbIH 3Tan cneKa HH.ff, KOTOpblH MO)l(eT OKaJaTbC.ff JaKJIIO"IHTeJibHbl M (HanpHMep, npH cneKaHHH nopOlllKOBb X aHTH<l>PHKUHOHHblX HJ)leJIHH). 0.aHaKO 3Ta CTll,llH.ff MO)l(eT npO,llOJI)l(aTbC.ff H BO epeM.H 6oJiee n03,llHHX CTll,llHH cne KaHH.ff, nepeKpbIBa.H HX. 301cpblmue CKB03Hoii nopucmocmu (nopOBbIX KaHanoB) HBJI.HeTCH pe3yJihTaTOM pOCTa «rneeK» H npHBO,llHT K no.HBJieHHIO H30JIHpOBaH Hb X rpynn nop HJIH,lla)l(e OT,lleJibHb X nop. npH 3TOM 06IUHH (cyMMap Hb H) o6'beM nop B nopOlllKOBOM Telle yMeHblllaeTC.H H npoHCXO,llHT ero ynJioTHeHHe (yca,uKa). facTo cneKaHHe JaKaH•meaIOT Ha 3TOH cTa .llHH. CcjJepouiJu3au,Ufl nop, KaK H npe,llh.llYIUaH CTa.llHH, CBHJaHa c poc TOM «llleeK»: semecrno c HeKOTOpblX Y"laCTKOB nosepXHOCTH nop ne peMemaeTC.ff B o6JiaCTb Me)l(l{aCTH"IHOfO KOHTaKTa, a CaMH nopbl (KaK HJOJIHpoeaHHbie, TaK " coo6ma10mHec.H) oKpyrnHIOTCH, npHo6peTa.H ccpepH"IHOCTb. lpH,llOCTaTO"IHO)J)IHTeJlbHOH H30TepMH4eCKOH Bbl,llep)l( Ke H Bb COKOH TeMnepaTYpe cneKaHH.ff BnOJIHe B03MO)l(H0 nOJIY4HTb H)leaJibHble ccpepH"leCKHe nopbl. 3Ta CTll,llH.ff oco6eHHO Ba)l(Ha B CB.ff3H c BJIH.ffHHeM nopMCTOCTH Ha MexaHM"leCKHe CBOHCTBa nopOlllKOBb X MaTepMaJIOB H H3,lleJIMH, H3-3a 4ero Ha npaKTHKe cneKaHMe,llOBO,ll.ffT HMeHHO,llO 3TOH CTll,llHH. YcaiJKa u3011upoeaHHblX nop - o.aHa HJ HaH6oJiee Ba)l(HbIX CTa.llHH cneKaHH.ff, Tpe6y10ma.H BblCOKHX TeMnepaTYP H,llOCTaTO"IHO 60JiblllOH )J)IHTeJibHOCTH Bb,llep)l(KH (HanpHMep, HeCKOJlbKO COTeH "laCOB) npH M30TepMH4eCKOM Harpeee. ToJibKO ee JaeepllleHMe MO)l(eT npHBeCTH K nOJIY4eHHIO 6ecnopMCTOf0 (KOMnaKTHoro) nopOlllKOBOfO reJia, HO qaCTO 3TO OKa3bIBaeTC.ff 3KOHOMH4eCKH HeUeJiecoo6pa3HblM HJIH npaK TH"leCKH He,llOCTH)l(HMbIM. YKpynHeHue (Koa.11ecu,eHU,Ufl) nop JaKJIIO"laeTCH B pocTe KpynHh X nop 3a C"leT yMeHbllleHHSI pa3MepoB H HC4e3HOBeHH.ff MeJIKHX, H30JIHpO BaHHblX nop. 06ma.H nopHCTOCTb npM 3TOM coxpaH.HeTCSI HeHJMeHHOH, a q11cJ10 nop yMeHbrnaeTCH npM yeeJIM"leHHH MX cpe.aHero pa3Mepa. YnJIOTHeHMe nopornKoeoro TeJia Ha TIOH CTa.aMM cneKaHMH He npo11c- xo.a11T.
14.1.2.,QBMlKY°-'Me CMnbl cneKaHMH
B HCXO,llHOM COCTOSIHHH (.ao Harpeea) nopOlllKOBOe TeJIO npe,llCTaB JISleT co6oif CHCTeMy, y.aaneHHYIO OT COCTOSIHHSI TepMO,llHHaMMl{eCKOfO paBHOBeCHSI O,llHOBpeMeHHO no MHOfHM napaMeTpaM. 3To CB.H3aHO npe)l(,lle ecero c HaJIH"IHeM CHJlbHO pa3BHTOH CB060,llHOH noeepXHOC TH OT,lleJibHb X nopolllHHOK (Me)l(cpa3Ha.H noeepXHOCTb pa3,lleJia eeme CTBo-nycTOTa) H nosepXHOCTH Me)l()ly,llHCnepCHb MH 3JieMeHTaMH HX CTpYKTYPbl (pa3BeTBJieHHa.H ceTKa Me)l(KpHCTaJIJIHTHb X rpaHHU, MHKPOnOJIOCTH BHyTpH nopolllHHOK H.ap.), a TaK)l(e c.aecpeKTHOCTblO caMOH KpHCTaJIJIHl{eCKOH CTpYKTYPbl semecTBa.
IlpH: Harpese ceo6o.aHaH 3HeprHH nopornKosoro TeJia.llOJI)l(Ha no HH)l(aTbCH Ja C"leT H3MeHeHHH B CHCTeMe, CTpeMSIIUHXCSI KaK MHHH MH3MpOBaTb nosepXHOCTH mo6oro BH,lla, TaK H yMeHblllHTb KOHUeHT paUHIO MHKpOHCKa)l(eHHH B 3JieMeHTaX CTpyKTypblnopOlllHHOK. Ilpouecc npeepameHMH nopolllKOBoro KOHfJIOMeparn B nJIOTHOe TeJIO MO)l(HO paccMaTpMBaTb KaK aHaJIOf XHMH' eCKOH peaKUHH H xa paKTepH30BaTb TepMO,llHHaMM"leCKHM ypaBHeHHeM nOHH)l(eHH.ff CB0- 6o;LlHOH 3HeprnH /J.F: !J.F = !J.H - T · !J.S, (14.1) r.ne !J.H H /J.S - HJMeHeHMe TenJiocq.nep)l(aHHSI H 3HTpOnHH CHCTeMbl COOTBeTCTBeHHO. TaK KaK npM cneKaHMH o.nHocpaJHOH CHCTeMhIHe npo11cxo.nMT Ja- MeTHoro HJMeHeHHSI ee XHMH"leCKOfO COCTaBa, Heo6XO.llHMOe)J)I.ff npe BpameHHSI MCXO.l(HOH nopMCTOH MaCCbl B nJIOTHOe TeJIO noHH)l(eHH: CB060.l(HOH 3HeprnH noJIHOCTblO CB.H3aHO c yMeHbllleHHeM CB060.l(HOH noeepXHOCTH, ceoifcTBeHHOH cneKaeMOMY nopolllKOBOMY reJiy. YMeHh rneHMe nJIOIUa.l(H noeepxHOCTH COOTBeTCTByeT yMeHbllleHHIO.l(OJIH noeepXHOCTHOH 3HeprnH B o6meii (cyMMapHOH) CB060.llHOH 3HeprHH
CHCTeMbl..l(pyrHMH CJIOBaMH, HarpeBaeMaH Macca Bemecrna TIO,lJ,Bepra eTCH H3MeHeHHHM, CTpeMHlll.HMCH MHHHMH3HpOBaTb B HeH CB06o.n. HYJO TIOBepxHOCTb. c 3TOH TQqKH 3peHHH MO)l(HO paCCMOTpeTb mo6y10 s - TIJIOlll.a,lJ,b 3TOH noBepXHOCTH pa3,lJ,eJia. L(aBJieHHe !l.p MO)J{HO HaHTH H3 YCJIOBHH MHHHMyMa TepMO,lJ,HHaMH qeCKOfO TIOTeHUHaJia d<I> = 0 npH + v2 = const: H3 rneCTH OTIHCaHHb X Bbillie CTa,lJ,HH H y6e,lJ,HTbCH, qTo Ha KIDK)J,OH H3 HHX npoHCXO,lJ,HT yMeHbllieHHe TIOBepXHOCTH; qeM 60Jibllie cyMMapHaH !l.p = p1 - p2 = aJ dS/ dV). (14.5) TIJIOlll.a,lJ,b TIOBepXHOCTH H KOHUeHTpaUHH.n.ecpeKTOB B HCXO,lJ,HOM no pOllIKOBOM TeJie, TeM 60Jibllie H.D.BH)l(}'lll.He CHJibl.D.JIH BCex CTa,lJ,HH npouecca ero cneKaHHH. L(pyroii no.n.xo.n., TO)J{e OCHOBaHHb H Ha repMO,lJ,HHaMffqeCKHX npHH UHnax, Be,lJ,eT K 6011ee «MeXaHHqecKOH» KOHUeTIUHH.D.Blll.HX CHJI cneKaHH5(. TipH,lJ,OCTaToqHo Bh COKHX TeMnepaTYpax.D.JIH rnep.n.oro TeJia B CBH3H c Bb COKOH TIO,lJ,BH)l(HOCTblO aTOMOB MO)l(HO cqHTaTb, qTo no BepXHOCTHaH 3HeprHH 3KBHBaJieHTHa TIOBepXHOCTHOMY HaTH)J{eHHIO, T. e. CHJie, CTpeMHlll.eHCH yMeHhllIHTb TIJIOlll.a,lJ,b TIOBepXHOCTH H TIOHH- 3HTb H36bITOK 3HeprHH, CBH3aHHblH c BeJIHqHHOH TIOBepXHOCTH. B CBH- 3H c,lJ,HcnepCHOCTblO HarpeBaeMOH nopOllIKOBOH MaCCbl K cneKaHHIO npHMeHHMbl KJiacc11qecKHe TepMO,lJ,HHaMHqeCKHe ypaBHeHHH KanHJI JIHpHOCTH, CBH3b1BaJ0111.He TIOBepXHOCTHOe HaTH)J{eHHe, KpHBH3HY no BepXHOCTH H BHYTpeHHee.n.aBJieHHe. MexaH11qecKoe paBHoBecHe Ha rpaHHUe.D.Byx cpa3, pa3.n.e11eHHh X HeTIJIOCKOH TIOBepXHOCThlO, MO)l(HO oueHHTb ypaBHeHHeM JlaTIJiaca. HcKpHBJieHHe noBepxHoCTH 03HaqaeT H3MeHeHHe noBepxHoCTHOH 3HeprHH, TaK KaK npOHCXO,lJ,HT H3MeHeHHe TIJIOlll.a,lJ,H TIOBepXHOCTH. c HaJIHqHeM HCKpHBJieHHOH TIOBepXHOCTH pa3,lJ,eJia CBH3aHa CHJia HJIH noBepXHOCTHOe (Me)J{cpa3HOe).n.aBJieHHe !l.p, 51.BJIHIOlll.eecH pa3HOCTblO .n.aBJieHHH p1H p2Ha rpaHHUY pa3.n.e11a co CTOpOHhIcoorneTCTBYJOlll.HX cpa3:
(14.2) PaBHOBec11e cpa3 He npe.n.noJiaraeT paBeHCTBa.n.aBJieHHH co cTopo HhI KIDK)J,OH H3 cpa3 H ocymecTBJIHeTCH, Kor.n.a B HHX 6Y.D.YT paBHbl TeMnepaTypbl (Tl = = T) H XHMHqecKHe TIOTeHUHaJihI: µI(P p T) = µ2(P2• T) = µ npH +"'2 = const, (14.3) r.n.e H "'2 - 06beMblcocymecTByIOlll.HX cpa3; µI H µ2 - XHMHqecKHe TIOTeHUHaJiblcpa3. TepMO.D.HHaMHqecKHH noTeHUHaJI CHCTeMhI c yqeTOM rpaHHqHoii 3HeprHH HMeeT BH.D. (14.4) r.n.e a.1,2 -y.n.eJihHaH TIOBepxHOCTHaH 3HeprHH Ha rpaHHUe pa3,lJ,eJia cpa3; YqHThrnaH, qrn.D.JIH KIDKJJ.OH ToqKH noBepxHocTH Me)J{cpa3HOH rpaHHUhl cnpaBe,lJ,JIHBO BhJpa)J{eHHe r.n.e RI H - rnaBHbJe pa.n.HYChl KPHBH3Hhl, ypaBHeHHe (14.5) MO)J{ HO nepen11caTh: !l.p = Pi - P2 = a.1,2[(1/ RI) + (1/)] y[(l / RI) + (1/)], (14.7) r.n.e y - TIOBepXHOCTHOe HaTH)J{eHHe (cHJia, CTpeMHlll.aHCH yMeHbllIHTb TIJIOlll.a,lJ,b TIOBepXHOCTH), KOTOpoe.D.JIH TeMnepaTyp cneKaHHH npHMepHO COOTBeTCTByeT a.1,2' T. e. y a.1,2" qaCTHblH CJiyqaii ypaBHeHHH (14.7).D.JIH ccpep11qeCKOH TIOBepXHOC- TH, Kor.n.a R1= = R: !l.p = 2a.1 / R 2y/ R. (14.8) MexaHHqecKoe paBHOBecHe Ha Btterntteii noBepxttoCTH «llieHKH» (pHC. 218): PT = Pn - y/[(l/p) - (l/x)], (14.9) r.n.e pT -.n.aBJieHHe (ttanpH)f(ettHe) B rnep.n.oM TeJie (qacTHUe); p " - .n.aBJieHHe co cTopOHhInophI. TipaKTffqeCKH Bcer.n.a x«a, a p«x H ypaB HettHe (14.9) npHHHMaeT BH,lJ,: (14. IO) Be11Hq11tta y/p npe.n.crnBJIHeT co6oii pacrnrnBa10111.ee ttanpH)J{ett11e, CTpeMHlll.eecH C,lJ,BHHYTh (paCTHHYTh) KpaH «llieHKH» B CTopotty nophl, a p " ecTh.n.aBJieHHe ra3a B nopax, npenHTCTBYJOlll.ee pacrn11peHHJO «rneii KH». Ec1111 pacrnrHBa10111.ee ttanpH)J{ettHe npeo611a.n.aeT tta.n. p ", TO KOH TaKT MO)J{eT paCTH, T. e. Me)J{cpa3HOe.n.aBJieHHe co CTOPOHbl rnep.n.oii cpa3bl H eCTb.D.Blll.aH cHJia npouecca pOCTa Me)J{qacTHqHblX KOHTaK TOB. B 6oJihllIHHCTBe c11yqaeB nopHCTOCTh cneKaeMoro nopornKoooro TeJia B nepHO.D. poem '«UleeK» HBJIHeTCH OTKpblTOH H oen11q11Ha Pn 3K BHBaJieHTHa.n.aBJieHHJO aTMoccpephIcneKaHHH (npaKTHqecKH 0, 1 MTia), a pa.n.11yc p 06h1qtto oqetth MaJI. Tio3TOMY B ttaqane cneKaHHH c11e.n.yeT O)J{H,lJ,aTb 3HaqHTeJihHOH.D.Blll.eH CHJibl -pT; Otta TeM 60Jibllie, qeM Bb llie noBepXHOCTHOe HaTH)J{eHHe H MeHbllie pa3Mep «UleHKH». c poc-
TOM «llleHKH» H yBeJmqeHHeM pa,aHyca p 3Ta.llBHxyIUCUI CHJia yMeHb rnaeTCH. B rn6JI. 50 npHeeaeHbIHeKoTOpb1e JHaqeHHH y/p. MexaHHqecKoe paeHoeecHe Me)l(tj:>aJHb X aaeJieHHH MH HJOJIHpo eaHHOH ctj:>epHqeCKOH nopbl pa,aHyca r Bb pa)l(aIOT KaK pT = pn - 2 y/ r, (14.11) rae eeJIHqHHa 2y/ r npeacrnBJIHeT co6oi1 HanpH)l(eHHe, CTpeMHIUeecH a.n,pyraH CBH3aHa c HepaBHOBeCHOH KOHUeHTpaUHeH BaKaHCHH B6JIH- 3H H30fHyTOH noeepXHOCTH. .Il.aBJieHHe napoB eemecTBa Hat(BOfHYTOH noeepXHOCThlO «llleHKH» H BhinYKJIOH noeepXHOCThlO qaCTHUhl MO)l(HO Bhlpa3HTh ypaBHeHHHMH (14.12) H (14.13) COOTBeTCTBeH HO: (14.12) YMeHblllHTb noeepxHOCTb nopbI nyreM yMeHbllleHHH ee pa3Mepa; B p- - Po = 2yVo, (14.13) CJiyqae 2y/ r>pn yca,aKa nopbl B03MO)l(Ha H ee.l(BHxyIUeH CHJIOH HBJIH eTCH eeJIHqHHa -pT, KOTOpyIO MO)l(HO paccMaTpHBaTb KaK C)l(HMaIOIUee HanpH)l(eHHe,.n,eiiCTBYJOIUee Ha Me)l(QJa3HYJO rpaHHUY co CTOpOHblTBep .n,oro TeJia B o6JiaCTH, OKpaIOIUeH nopy. lpe.n,noJIO)l(HTb eeJIHqHHY Pn B Ka)l(.l(OM OTL{eJibHOM CJiyqae oqeHb TpY.llHO. c O.l(HOH CTOPOHbl, B peJyJibTaTe yeeJIHqeHHH TeMnepaTypbl npH Harpeee, yMeHbllleHHH o6beMa nopbl, o6pa3oBaHHH napoB BO.llblB CBH3H c BOCCTaHoBJieHHeM OKCH.nOB Ha noeepxHoCTH nopbI, HcnapeHHH eemecTBa H npoqHx tj:>aK p 0 RTa rae p -.n,aeJieHHe napa eemecTBa Ha.a HJOfHyTOH noeepxHoCThIO; Po - .n,aBJieHHe napa eemecTBa Ha.ll nJioCKOH noeepxHoCThIO; - o6beM aToMa HJIH MOJieKYJihleemecTBa qaCTHUbl B TBep.n,oM COCTOHHHH; R - raJOBCUI nocTOHHHaH. IlpeHe6peraH eeJIHqHHOH 1/x, KOTopaH MHOfO MeHbllle 1/p, ypaB- HeHHe (14.12) npHHHMaeT BH.l( ropoe 3Ta eeJIHqHHa MO)l(eT 6bITb > 0, 1 Mila. C.n,pyrow cTopoHhI, BCJieL{CTBHe B03MO)l(HOfO OKHCJieHHH qaCTHU cneKaeMOfO eemecTBa, .n,HtjJQ:>yJHH raJOB H3 nopbl H apyrnx npHqHH tJ,aBJieHHe ra3a B 3aMKHY - p - Po =- yVo -· Po RT p (14.14) TOH nope MO)l(eT 6b Tb < 0, 1 MOa. OrMeTHM, qro 6oJiblllaH eeJIHqHHa -pT BilOJIHe B03MO)l(Ha H paccMaTpHBaeMaH.ll,BHxyIUaH CHJia 6y.n,eT yee JIHqHeaTbCH c B03pacTaHHeM 3HaqeHHH noeepXHOCTHOfO HaTH)l(e HHH H yMeHbllleHHeM HaqaJihHOfO pa3Mepa nophl. KpHBHJHa noeepxHOCTH qacTHUhI H «rneHKH» onpe.n,eJIHeT cyme CTBOBaHHe eme L{Byx.llBHxyIUHX CHJI cneKaHHH, OL{Ha H3 KOTOph X - OTJIHqHoe OT paBHOBeCHOfO tJ,aBJieHHe napa Ha,a TBep.n,h M eemecTBOM,
.Il.aBJieHHe napa.Ha,a BOfHyTOH noeepXHOCThlO «llleHKH» MeHbllle (p<po), a Ha,ll BhinYKJIOH noeepXHOCThlO qacTHUbl 60J1hllle (p>po), 4eM Ha.Ll n11ocKoH noeepxHoCThIO. AHaJIOfH4Hhie paccy)l(.l(eHHH cnpaBeMH BhIH LlJIH JII06hIX.upymx noeepxHocTeH pa3Hoff KpHBH3Hhl. On11caHHaH pa3HHUa B.uaBJieHHH napOB eemecTBa Ha.Ll noeepXHOCTHMH pa3JIH4- HOH KpHBH3Hhl COJ.n,aeT.l(BHxyIUyIO CHJIY MexaHH3Ma ero nepeHOCa qepe3 ra30BYIO tj:>aJy. 3Ta.llBH)l(YIUaH CHJia yeeJIH4HBaeTCH c B03pacTa HHeM JHaqeHHH noeepXHOCTHOfO HaTH)l(eHHH H KpHBH3Hbl noeepXHO CTH H yMeHblllaeTCH Ha npOTH)l(eHHH cneKaHHH. <t>opMyJibl (14.12)-(14.14) He co.n,ep:>KaT MaCCbl 4aCTHU H, CJie.l(O BaTeJihHO, MOfyT 6hITh npHMeHHMhl K 4aCTHUaM, Macca KOTOpblX paB Ha HYJIIO, T. e. K y3JIOBhIM eaKaHCHHM B KpHCTaJIJIH4eCKOH perneTKe eemecTBa. Ha 3TO enepBhie o6paTHJ1 BHHMaHHe EJI. n11HeC, KOTOphlM LlJIH oueHKH OTKJIOHeHHH KOHUeHTpaUHH BaKaHCHM OT paBHOBeCHOH H3-3a KpHBH3Hhl Me:>Ktj:>a3HOH rpaHHUbl npeL{J]O:>KHJI ypaBHeHHH LlJIH o6JiaCTH «llleHKH» (14.1 5) H BbmyKJIOH noeepXHOCTH 4aCTHUbl (14.16): (14.15) (14.16) r.ne c - KOHUeHTpaUHH BaKaHCHH B npHKOHTaKTHOM o6JiaCTH eew,e CTBa B6JIH3H «llleHKH» HJIH BbinyKJIOM noeepXHOCTH 4aCTHUbl; co - paBHOBCCHaH KOHUCHTpaUHH BaKaHCHH, co =e-E,lkT (E - 3HepmH o6paJoeaHHH yJJioeoH- eaKaHCHH; k - nocToHHHaH EoJIUMaHa); npH TeMnepazype nJiaBJICHHH eemecrna co o6billHO COCTaBJIHeT BeJIHllHHY He Bblllle 10-3-10-4, a npH KOMHaTHOH TeMnepazype nopH.LJ;Ka 10-1s.
TaKHM o6pa30M, cymecrnyeT paJHOCTb (rpa.LJ;HCHT) KOHUCHTpaUHH BaKaHCHH Me)l(,l(y paJJIHllHbIMH no pacnOJIO)J(CHHIO B o6beMe noporn KOBOfO TeJia noBepXHOCT5IMH H Me)l(,l(y noeepxHOCTHMH pa3HOH KpH BHJHbl. 3ToT rpa.ri:HeHT KOHUCHT)JaUHH BaKaHCHH npe.LJ;CTaBJIHeT co6oH .LJ.BHIUYIO CHJIY.ri:ml>ct>YJHOHHoro TpaHcnoprn eemecrna. Ha nporn )J{CHHH cneKaHHH 3Ta.LJ;BHIUaH CHJia YMCHbrnaeTCH, TaK KaK y6b1Ba CT rpa.ri:HeHT KOHUCHTpaUHH BaKaHCHH Me)l(,l(y paJJIHllHblMH yqaCTKa MH nopOlllKOBOfO TeJia. .lJ.Hct>cl>YJHOHHbIH TpaHcnopTHbl H MexaHHJM MO)J{CT 6b Tb CBHJaH eme c O.LJ;HOH.LJ;BHIUCH CHJIOH, onpe.ri:eJIHCMOH HepaBHOBCCHOCTbIO KOH UCHTpaUHH BaKaHCHH c B6JIH3H HJOJIHpoeaHHOH cct>epHllCCKOH nopbl pa.ri:Hyca r: (C - C0)/C0 = 2yV/ k Tr. (14.17) B TBep.ri:oM eemecrne B6JIHJH paccMaTpHBaeMoH nopb1 KOHUCHTpa UHH BaKaHCHH c Bblllle paBHOBCCHOH (pHC. 219) H TeM 60Jibllle, lleM MeHbllle paJMep nopbI. CJie.LJ;oBaTeJibHo, Me)l(,l(y o6JiacrnMH cneKaeMo ro nopornKoeoro reJia, Y.LJ.aJieHHbIMH OT noeepxHOCTeH MeJIKHX cct>e
KOHUCHTpaUHH BaKaHCHH Me)l(,l(y rpaHHUaMH JepeH, HaXO.LJ.HIUHMHCH no.LI. pa3HblMH no BeJIHllHHe HJIH JHaKY HanpH)J{CHHHMH, npe.LJ.CTaBJIH eT co6oH-.LJ.BIUYIO CHJIY MexaHHJMa nepeHoca eemecrna, CBHJaH HOro c npoueccoM.LJ.Hcl>cl>YJHOHHOH noJIJyqeCTH.
MexaHM3MbI MacconepeHoca
B HarpeeaeMoM nopornKOBOM TeJie BOJMO)J{Hbl cJie.LJ.yIOmHe Mexa HHJMbITpaHcnoprn eemecrna: nepeHoc llepeJ raJoey10 ct>aJy; noeepx HOCTHaH.LJ.Hcl>cl>YJHH; o6beMHaH.LJ.Hcl>cl>YJHH; BHJKOe TelleHHe; TelleHHe, BbIJbIBaeMoe BHelllHHMH HarpyJKaMH (rop51qee npeccoBaHHe, cneKa HHe no.ri: ii,aBJICHHeM H noii,o6Hble CJiyqaH). BnepBbie (I949 r.) Jaii,aqy o epe MeHH6H JaBHCHMOCTH xop.LJ.bI x (pa.ri:H- yca KOHTaKTa) pelllHJI)I(. KyqHHCKHH x2-t;M..o x5 -t;M=O x5-t;t.L..a .LJ.JIH TJJCX MexaHHJMOB MacconepeHOCa - o6beMHOH H noeepXHOCTHOH.LJ.Hcl> cl>YJHH, a TaK)J{e nepeHoca qepeJ raJo BYIO cl>aJy.,ll.JIH 3TOfO HM 6bIJIH HCnOJib JOBaHbl 4 MO.LJ.eJIH HJ KpHCTaJIJIHlleCKHX TeJI: cct>epa- nJiocKOCTh; ii,ee cct>epbI, a 8 PHlleCKHX nop, H 3THMH noeepXHOCTHMH, a TaK)J{e Me)l(,l(y COCC.LJ;HHMH nopaMH paJHOfO paJMepa TaK)J{e cymecTByIOT rpa.LJ;HCHTbl KOHUCHTpa UHH BaKaHCHH, onpe.ri:eJIHIOIUHe HanpaBJieHHe.LJ.Hcl>cl>YJHOHHoro nepe Hoca eemecTea. . fpa.ri:HeHT KOHUCHTpaUHH BaKaHCHH MO)J{CT 6bITb TaK)J{e CBHJaH c TeM, llTO BHYTJJH llaCTHU MC)J{JepeH KOHTaKTHPYIOIU HC B TOlJKe; CTep)J{eHb HaBHTaH Ha Hero npOBOJIOKa; nyqoK npoBOJIOK. KyqHHCKHH yKaJaJI, llTO B o6JiaCTb KOHTaKTHOfO neperneHKa Be meCTBO MO)J{CT nepeHOCHTbCH He TOJib KO BCJie.LJ.CTBHe TpaHcnopTa B o6beMe x 1-t;M=O x 5 -t;t.L=O x 4 -t;M<FO Hbie (MC)J{KpHCTaJIJIHTHbl e) rpaHH 06pa3ua, HO H HHblMH TpaHcnopTHbl z a e
• • ••••• • •• • •• Ubl HaXO.ll;HTCH no.LJ. HanpH)J{CHHCM H KOHUCHTpaum1 BaKaHCHH c B6JIH3H HHX OTJIHllaeTCH OT paBHOBeCHOH C: C = C0 exp(cr V/k 7), (14.18) MH nyrnMH - no ero ceo6oii,Hoi1 no eepxHoCTH H qepe3 OKpy)J{aJOIUYIO ra JOBYIO cpeii,y. KHHeTHKa npHneKaHHH oii,Hocl>aJ HbIX qacTHU, KOHTaKTHPYIOIU HX B TOll
P11c. 220. CxeMa pa31111'1HhtX Me xaHl13MOB B3lll1MHOro np11neKaHl1SI TBCptl,bl X c<t>ep1111eCKl1X '!aCT11U, KOH TaKT11pyt01Ul1X np11 t = 0 B TO'!Ke (t.l -113MCHCHl1C paCCTOSIHl1H MC)l( • • f.LJ.e cr - HanpH)J{CHHe,.LJ.CHCTBYI01Uee Ha MC)J{JepeHHOH (Me)J{KpHCTaJI JIHTHOH) rpaHHUe (noJIO)J{HTeJibHOe e cJiyLJae pacrnrnea10mero H OTJJH uaTeJibHoe B cJiyqae C)J{HMa10mero Ke (pHc. 220), B npouecce HJOTepMH LJeCKOH BbI.LJ.ep)J{KH MO:>KeT 6bITb onHCa Ha ypaBHeHHeM BH.LJ.a x"('r) = A(T)t HJIH x" - t, llY UCHTpaMl1 'lllCT11U): a - BSl3Koe TC'ICH11e; 6 -o6beMHaSI n11<1>lf>Y311SI, He np11eonst1Uast K ycanKe; s - o6beMHtlSI n11<t>lf>Y311SI np11 HMl1'11111 CTOKa B o6JJaCTl1 KOHTaKTa; i! - no eepXHOCTHtlSI n11<1><Py311si; iJ - ne P11c. 219. CxeMa (a) 11 rpa<!>11K (6) pacnpct1,CJICHl1SI HaKaHC11H B6JJl1311 nopbt YCHJIHH). BoJHHKaIOIUHH rpa.LJ.HCHT me n - noKaJaTeJib CTeneHH, JaBH CHIUHH OT KOHKpeTHOfO TpaHcnopTHOfO peHoc BCIUCCTBtl '!epe3 raJOBYIO lf>aJy; e - np11neKaH11e non BJJHst HHeM npH)l(HMtllOIUHX yc1111111i MexaHHJMa nepeMemettHH eemecrna; x" (t) - HJMeHettHe pa,n,Hyca Me)l(qCTWIHOro KOHTaKTa BO epeMeHH npH H30TepMH'IeCKOM BbI,Uep)((Ke t; A(1) -QlYHKUHH, KOHKpeTHblH BH,ll, KOTOPOM JaBHCHT OT TeMnepa TYPbl cneKaHHH, reoMeTpHH npHKOHTaKTHoro yqaCTKa H Tex KOHCTaHT eemecrna, KOTOpb e onpe,LI,eJIHIOT OCHOBHOM MexaHH3M npHneKaHHH (TeMnepazypbInJiaBJieHH!f, TeMnepazypbIKHneHHH,,LI,ecpeKTHOCTH qa CTHU, COCTOHHHH noeepXHOCTH qaCTHU, XHMWi eCKOfO COCTaBa MaTe PHaJia H,LI,p.). <l>opMyJia 04.19) c yqeTOM H3MeHeHHH pa,n,Hyca a caMOM KOHTaKTH pyiomeH: 'IaCTHUblMO)l(eT 6b1Tb JanHCaHa no-,LI,pyroMy:
x" 51.E. feryJHH noJiyqHJI ypaetteHHH, COOTBeTCTBYIOIUHe,LI,BYM npe ,LI,eJibHblM CJiyqaHM: a),ll,JIHHa ceo6o,LI,ttoro npo6era MOJieKyJI (aTOMOB) eemecrna 'A npe eocxo,LI,HT JIHHeHHbl H pa3Mep o6JiaCTH KOH,LI,ettcau;HH ('A» p, T.e. Ma
Jlble,LI,aBJieHHH aTMoccpepb1 cneKaHHH): x3/ a = (18/n)0•5 (µ/ R1) 1 •5 (8pof d2) t HJIH x3/ a - t, (14.22) r,LI,e µ - Macca ttarpeeaeMoH: 11acTHUbI; d - nJIOTHoCTb eemecTea 11ac THUbI B KOH,LI,eHCHpoeaHHOM cpa3e; 6),ll,JIHHa ceo6o,LI,Horo npo6era MoJieKYJI (aToMoB) eemecrna MeHb we JIHHeHHOfO pa3Mepa o6JiaCTH KOH,LI,ettcau;HH ('A «p, T.e. 60JibWHe -;;{t) = A'(T)t, a (14.20) ,LI,aBJieHHH raJOBOM aTMOCcpepbl cneKaHHH): r,LI,e m -noKaJaTeJib CTeneHH, 3aBHCHIUeM OT KOHKpeTHOfO TpaHcnopT x5/ a = {40yp08 /(n(6µR1) • p']} HJIH x5/ a - t, (14.23) 2 4 0 5 2 HOfO MexattHJMa nepeMeIUeHHH eemecTea. IlpH yca,n,Ke ccpepH'IeCKOM nopbl JaBHCHMOCTb H3MeHeHHH ee pa ,ll,Hyca OT epeMeHH 6y,LI,eT aHaJIOrH'IHOM. llepeHoc «ew,ecmBa ttepe3 za30By10 <jJa3y. H,LI,eaJibHaH MO,LI,eJib,,LI,eMOH CTpHPYIOIUaH 3TOT BH,ll, TpattcnopTHOro MexaHH3Ma, npHBe,LI,eHa Ha pHC. 220, a. B CBH3H c JaBHCHMOCTblO ynpyroCTH napa Ha,D, noeepxHOC TblO OT ee KpHBH3Hbl, eemecTBo HcnapHeTCH c BbinYKJibIX yqacTKOB qacTHU H KOH,LI,eHCHpyeTCH Ha BOrHYTOM noeepxHOCTH KOHTaKTHbIX ne perneMKOB. 3TOT MeXaHH3M lJaCTO eme Ha3bIBalOT «HCnapeHHe- KOH ,LI,eHcau;HH». Ott,LI,OJI)l(eH npHBO,LI,HTb K poczy «rneeK» H ccpepoH,LI,HJaUHH nop H 6y,LI,eT,LI,eMCTBOBaTb,ll,O Tex nop, noKa B nopolIIKOBOM TeJie co xpaHHeTCH 3aMeTHaH pa3HHUa B KpHBH3He Me)((,l(y OT,ll,eJibHbIMH yqaCT KaMH noeepxttocTH paJ,LI,eJia eemecrno- nopa. HanpaBJieHHbIM nepe Hoc eemecrna B 30HY Me)l('laCTH'IHOro KOHTaKTa npHBO,ll,HT K ynpo'l HeHHIO H yJiyqrneHHIO 3JieKTponpOBO,ll,HOCTH nopOlIIKOBoro TeJia, HO He MO)l(eT Bbl3BaTb H3MeHeHHe ero 06beMa, T.e. yca,LI,KY. B JIHTeparype npHBO,LI,HTCH paJJIH'IHbie KOJIWiecrneHHbie JaBHCHMOCTII KHHeTHKH poem «lIIeeK» no MexaHH3MY HCnapettHe- KOH,LI,eHcau;HH. TaK, ypaetteHHe KyqHHcKoro HMeeT BHLI.
r,LI,e M - MOJieKYiiHpHaH (aTOMHaH) Macca eemecrna; t - npo,LI,oJI )l(HTeJibHOCTb H30TepMHlJeCKOM Bb,LI,ep)((KH npH cneKaHHH. Y EJI. IlHtteca attaJiom11ttoe Bbipa)l(ettHe,ll,JIH npHneKaHHH HMeeT BH,ll,.
x7/a3 - t. r,LI,e 8 - napaMeTp KpHCTaJIJIH11ecKoi1 perneTKH eemecrna; p' -,LI,aeJie HHe raJa aTMoccpepbI cneKaHHH. IlepeHOC eemecTBa qepe3 raJOBYIO cpa3y aKTHBHpyeTCH c yeeJIH lJeHHeM TeMnepazypbl (po 3KCnoHeHUHaJibHO pacTeT c TeMnepazypoii), napu;HaJibttoro,LI,aeJieHHH napa eemecrna H noeepxttocTttoro ttaTH)l(e HHH. PaccMaTpHeaeMbIH MexaHHJM MO)l(eT HrpaTb cKOJibKO-HH6y,LI,b cy mecTeeHHYIO pOJib JIHlIIb,ll,JIH MaTepHaJIOB c OTHOCHTeJibHO BbICOKHM ,LI,aBJieHHeM napoe npH TeMnepazype cneKaHHH (He HH)l(e I-I0 Ila), T.e. KOr,LI,a KOJIH'leCTBO nepeHeCeHHOfO qepe3 raJOBYJO cpa3y MaTepHaJia MO)l(eT 6bITb 3HalJHTeJibHbIM, JIH60,ll,JIH cneKaHHH MeTaJIJIOB c BOCCTa HaBJIHBalOIUHMHCH HJIH,LI,Hccou;HHPYIOIU HMH oKcH,LI,aMH. B nocJie,LI,HeM CJiyqae,LI,aBJieHHe napoe MeTaJIJia Ha,D, noeepxHoCTblO 11aCTHU nopornKa npH Harpeee 6y,LI,eT 60JibWe, lJeM MOHO O)l(H,ll,aTb, HCXO,ll,H H3 ynpyro CTH napoe Ha,LI, noeepXHOCTblO KOMnaKTHOfO MeTaJIJia: B npouecce BOC CTaHOBJieHHH HJIH,ll,HCCOUHaUHH OKCH,LI,a BXO,ll,HIUHe B Hero aTOMbl Me TaJIJia BbICB060)((,l(alOTCH H o6Jia,D,alOT noBbIWeHHOH no,LI,BH)l(HOCTblO, 06Jier11aiomei1 HX nepexo,LI, e napoeyio cpaJy. lloBepxHocmHaR ou</J<Py3ua. Ha cxeMe B03MO)l(H0f0 BJaHMO,LI,eMCTBHH ,LI,Byx conpHKaCalOIUHXCH ccpepH'leCKHX qaCTHU, HJIJIIOCTpHpyiomeH: H,LI,eaJIH3HpOBaHHbIM 3JieMeHT npouecca cneKaHHH (pHC. 218, 6), noKaJa HO, 11To nocJie ttarpeea H Bb,LI,ep)l(KH npH onpe,LI,eJieHHOM TeMnepazype OHM qepe3 HeKOTOpoe epeMH CpaCTalOTCH. IlepeHOC BeIUeCTBa B 3TOM CJiyqae npoHCXO,ll,HT K noeepXHOCTH o6pa3YIOIUHXCH nepeMbI'leK, KaK 3TO noKaJaHo CTpeJIKaMH, H qacTHLJ,bl c6JIH)l(alOTCH, Bbl3bIBaH o6myio yca,LI,KY eceii CHCTeMbI; yeeJIH'leHHe KOHTaKTHOH noeepXHOCTH H C6JIH )l(eHHe qacTHU (yca,LI,Ka) npH cneKaHHH no 3TOH cxeMe CBH3aHO c
noeepxHOCTHOH,UHcpcpyJHeH JierKono,UBIDKHblX a,n,cop6HpoeaHHb X aTO MOB (a,n,aTOMOB) H nepeMemeHHeM aTOMOB B TOHKOM.uecpeKTHOM no C(TpYKTYPe noeepXHOCTHOM CJIOe TOJIIUHHOH 8s. CTpH 3TOM HCXO,USIT HJ TOfO, l.fTO nO,UBH)l(HOCTb noeepXHOCTHbl X aTOMOB JaBHCHT OT JaHHMa eMOfO HMH Mecm: HaHMeHee no,UBH)l(Hbl aTOMbl, Jie)l(aIUHe BHyTpH KOHTaKTHblX yqaCTKOB; JaTeM, B nopSI)lKe BOJpaCTaHHSI no,UBH)l(HOC TH, HJlYT aTOMbl Ha rpaHHuax KOHTaKTHblX yqacTKOB, aTOMbl B yrny6- JieHHSIX H ena,D,HHaX noeepXHOCTH, aTOMbl Ha pOBHblX yqaCTKaX H, Ha KOHeu, aTOMbl Ha BblCTynax noeepXHOCTH. TaK KaK aTOMbl Ha KOHTaKT HblX yqacTKax MeHee no,aBH)l(HbI, o6Jia,aaSI MeHbIIIHM JanacoM ceo6o.u HOH 3HepruH, qeM Ha ecex JlPYfHX yqaCTKaX noeepXHOCTH, TO OT CB0- 60,UHblX, HeKOHTaKTHblX yqaCTKOB K KOHTaKTHblM nepeXO.UHT JHalfH TeJibHO 6oJibIIIe aTOMOB, lfeM B o6paTHOM HanpaeJieHHH. B peJyJihTaTe npOHCXO)lHT paCIIIHpeHHe KOHTaKTHOfO yqaCTKa c O)lHOBpeMeHHblM c6JIIDKeHHeM reoMeTpHl.feCKHX ueHTpOB conpHKacaIOIUHXCSI l.faCTHU, T.e. npOHCXO.UHT yca,n,Ka. 0.uHaKo O.UHHM HJ rnaBHblX He,UOCTaTKOB paCCMOTpeHHOH cxeMbl SIBJISieTCSI TO, 'ITO B HeH He npe)lCTaBJieHa nopa - OCHOBHOH 3JieMeHT CTpYKTYPblpeaJibHOfO nopOIIIKOBOfO 6pHKeTa. CT03TOMY B JII060H CHC TeMe ynpomeHHOfO HJo6pa)l(eHHSI Heo6XO)lHMO noKaJaTb no MeHb IIIeH Mepe TpH conpHKaca10mHecS1 qacTHUbI(pHc. 218, a). Tor.ua He TpY.UHO JaMeTHTb, 'ITO l.fHCJIO aTOMOB, yxo)lSIIUHX c BbinYKJib X qacTeH ceo60,UHb X noeepXHOCTeH nopbl, paeHO lfHCJIY aTOMOB, BXOMIUHX B meJIH, KOTOpble npHJieraIOT K KOHTaKTHbIM yqaCTKaM. CJie)lOBaTeJib HO, no)l BJIHSIHHeM noeepxHOCTHOH MHrpauHH aTOMOB nopa 6y)leT ccpepOH)lHJHpoeaTbCSI (pHC. 218, 6), He HJMeHSISICb B o6beMe, H yca,n,Ka 6pHKeTa KaK peJyJibTaT noeepXHOCTHOH)lHcpcpyJHH npH H30TepMH HOCTHaSI.UH<t><t>YJHSI npHBO,UHT K yeeJIHlfeHHIO H COOTBeTCTBeHHO K ynpoqHeHHIO Me)l(l.faCTH'IHblX KOHTaKTOB. 3TOT TpaHcnopTHb H Mexa: HHJM cneKaHHSI oco6eHHO 60JibIIIOe JHal.feHHe HMeeT B Hal.faJibHbIH nepHO.U cneKaHHSI. OpH JarpSIJHeHHH noeepxHoCTH paJJIHlfHoro po.ua XHMHlfeCKHMH npHMeCSIMH (oKCH,UaMH, MexaHHl.feCKHMH BKJIIOl.feHHSIMH UH T.n.), a TaK)l(e Bb XO,UaMH Ha noeepXHOCTb.UHCJIOKaUHOHHblX JIHHHH, nepeHOC MaCCbl,Ua)l(e npH JHal.fHTeJibHOH,UHcpcpyJHOHHOH no,UBH)l(HOCTH a,n,a TOMOB He 6y.ueT HMeTb MeCTa. <l>HJHl.feCKH 3TO OJHaqaeT, l.fTO Ha no eepXHOCTH OTCyTCTByeT rpa,n,HeHT XHMHlfeCKOfO noTeHUHaJia (cpopMaJib HO Vµ = 0). 0pM 3TOM CJie,UyeT Yt.fHTbIBaTb, 'ITO HJ-Ja HaJIHl.fHSI Ha noeepXHOCTH TaKHX «CTOnopOB», 3HeprHSI aKTHBaUHH npouecca MO )l(eT oKaJaTbCSI HaCTOJibKO BbICOKOH, l.fTO 6y.ueT COHJMepHMa c 3Hep rueH aKTHBaUHH o6beMHOH)lHcpcpyJHH. 0.uHaKO B TO)Ke epeMSI BeJIH l.fHHa K03cpcpHuHeHTa noeepXHOCTHOli)lHcpcpyJHH MO)l(eT cymecTBeH HO npeBOCXO)lHTb BeJIHl.fHHY K03cpcpHuHeHTa o6beMHOH)lHcpcpyJHH B CBSIJH c cymecTBeHHO 60JiblllHM JHal.feHHeM npe,U3KCnOHeHUHaJibHO ro MHO)l(HTeJISI, He JaBHCSIIUefO OT TeMneparypbl. B o6JiaCTH 6oJiee BbICOKHX TeMnepaTYP B nepeHoce MaCCbI MOfYT HrpaTb pOllb npHnoeepXHOCTHb e CJIOH, xapaKTepHJyIOIUHeCSI pa3l1Hl.f HOH cTeneHblO)lecpeKTHOCTH (npHl.fHHblKOTOpOH MOfYT 6bITb paJHbl MH, HanpHMep KpHBHJHa noeepXHOCTH, y.uaneHHe OT Me)l(cpaJHOli rpaHHUbl, nJIOTHOCTb.,UHCJIOKauHH, HaJIHl.fHe qepo,UHblX aTOMOB " .up.) H COOTBeTCTBeHHO pa3lIHl.fHOH,UHcpcpyJHOHHOH no,UBH)l(HOCTblO B HHX aTOMOB. PocT KOHTaKTa e CBSIJH c nepeHocoM Macchino MexaHHJMY noeepx- HOCTHOH.UH<t><l>YJHH no 51.E. feryJHHY HMeeT BH)l l.feCKOM cneKaHHH 6eJyCJIOBHO He MO)l(eT HMeTb MeCTO. x7/ a3 = (28Dsy 8/ k 1)• HJIH x7/ a3 •. (14.24) BMecTe c TeM e yeeJIHl.feHHH npolfHOCTH Me)l(l.facTHlfHOro cuenJie HHSI (OCHOBHOH npHJHaK cneKaHHSI) noeepXHOCTHaSI H npHnoeepx HOCTHaSI MHrpauHSI aTOMOB HrpaIOT oqeHb Ba)l(HYIO pOJib (3HepruSI aK THBaUHH HHJKa, a JHal.feHHSI Ko3cpcpHuHeHTOB caMo,aHcpcpyJHH Ds BbICOKH), TaK KaK npOHCXO)lHT yeeJIHl.feHHe Me)l(l.faCTHl.fHb X KOHTaK TOB H 6eJ yMeHbllleHHSI CyMMapHOfO o6beMa nop. CToeepXHOCTHaSI)lHcp cpyJHSI aTOMOB BblJbIBaeT CfJia)l(HBaHHe noeepXHOCTH conpHKacaIOIUHXCSI lfaCTHU, 'ITO yeeJIHlfHBaeT HCTHHHYIO noeepXHOCTb KOHTaKTa H npH- 80,UHT K ccpepoH)lHJaUHH nop, a TaK)l(e o6ecnel.fHBaeT nepeMeIUeHHe aTOMOB c noeepXHOCTeH KpynHblX nop Ha noeepXHOCTb MeJIKHX (npH coo6ma10mHxcS1 nopax), T.e. e noJio)l(eHHe 6oJihIIIeH TepMO.UHHaMH qecKoH ycTOHlfHBocTH. TaKHM o6paJOM, Ha ecex 3Tanax (cTa,D,HSIX) cneKaHHSI noeepx-
B Bbipa)l(eHHH (14.24) JlJISI noeepxHoCTHoro CJIOSI napaMeTp peIIIeT KH 8 no)lJle)l(HT JaMeHe Ha TOJIIUHHY CJIO 8s, B KOTOPOM,UHcpcpyJHSI aTOMOB HMeeT MeCTO B Mepy BeJIHl.fHHbl K03cpcpHuHeHTa caMO,UHcpcpy JHH Ds; no KyqHHCKOMY l.fHCJieHHb H coMHO)l(HTeJih 28.UOJI)l(eH 6bITb JaMeHeH Ha 56. OTMeTHM, 'ITO noeepxHOCTHaSI,aHcpcpyJHSI ol.feHh qyecTBHTeJihHa K aTMoccpepe cneKaHHSI " ee COCTaBy, TaK KaK a,n,cop6UHSI Ha noeepXHO CTH HJ raJOBOH cpaJbl MO)l(eT cymecTBeHHO noBJIHSITb Ha BeJIHl.fHHbl y H Ds 06oe.MHOR ou<f}(jJy3u11. B caMoM o6meM BH)le nepeMeIUeHHe aTOMOB e 06beMe qaCTHUbl (nopOIIIHHKH) npe,UCTaBJISieT co6oH: TpaHcnopTHbl H MexaHHJM, KOTOpbIH SIBJISieTCSI OCHOBOH MHOfHX npoueccoe, npoHC- XOJJ;.SIIUHX B TBep,D,OM KpHCTaJIJIH' eCKOM TeJie, B TOM qHcJie H noporn KOBOM. <l>opMyJIHpOBaHHe H pa3BHTHe OCHOBHb X npe,D,CTaBJieHHH 0 MexaHH3Me,D,HQ>Q>yJHOHHOfO 6Jiy)K,[l,aHH.SI aTOMOB B KpHCTaJIJIHqecKOH perneTKe CB.Sl3aHo c pa60TaMH 51.11. <l>peHKem:1: nepeMeIUeHHe aTOMOB B KpHCTaJIJIHqecKOH perneTKe eCTb nocJie,D,OBaTeJibHOe 3aMeIUeHHe HMH BaKaHCHH, npHqeM K03Q><l>HUHeHT,D,HQ>Q>y3HH aTOMOB D CB.Sl3aH c pae HOBeCHOH KOHUeHTpauHeH BaKaHCHH co H K03Q><l>HUHeHTOM HX,D,HQ> <l>Y3HH D'eb pmKeHHeM
(14.25) yKa3aHHbIX B Ta6JI. 51: 1. BowymOJ1 no6epxHocmb «1UeiiKu»-6blnyKJ10J1 no6epxHocmb itacmuu,. BaKaHCHH,D,BC.SI H3 o6JiaCTH HX BblCOKOH KOHUeHTpaUHH e6m-t3H BOfHYTOH noeepXHOCTH «IIIeHKH» B o6JiaCTb 6oJiee HH3KOH HX KOH ueHTpaUHH B6JIH3H BbinYKJIOH noeepXHOCTH qaCTHU. IlpH 3TOM aTOMbl ,n,eHTC.SI e npoTHBonoJIO)l(HOM ttanpaBJiemrn. PeJyJibTaTOM 3Toro TpattcnopTHOro nYTH.SIBJI.SleTC.SI pOCT npHKOHTaKTHbIX yqaCTKOB, c<t>e pOHAH3aUHH nop. EcJIH aTOMb, «CTeKaIOIUHe» K eorHYTOH noeepxHo CTH «IIIeeK», H,D,YT JIHIIIb c noeepXHOCTH qacTHU, TO, KaK 3TO CJie,n,yeT H3 paCCMOTpeHH.SI MO,D,eJIH H3 Tpex qaCTHU (pHC. 218, 6), He CJie,n,yeT C yqeTOM BeJIHqHH C0= e-E, t kr H D' = D e -£, 1 kr (D - TeMneparyp O)l(H,D,aTb yca,n,KH cneKaeMoro nopornKoeoro TeJia. 0 0 HO HeJaBHCHMa.SI eeJIHqHHa, E. - 3HeprH.SI aKTHBaUHH,D,BIDKeHH.SI aTo MOB HJIH BaKaHcHM:)
r,n,e £0- 3tteprn.SI aKTHBaUHH,n,H<t><i>YJHH. HHIO K03Q><l>HUHeHTa,D,H<l><l>Y3HH H, KaK npaBHJIO, K noHH)l(eHHIO ee 3HeprHH aKTHBaUHH £0. ,Un.SI onHCaHH.SI,D,HQ>Q>yJHOHHb X nOTOKOB aTOMOB HMeIOTC.SI,D,Ba ypae HeHH.SI <l>HKa: m = -DS(oC/ox) (14.27) 2. Bowymaa no6epxHocmb «weuKU»-zpaHUU,bl 3epeH. BaKaHCHH,D,BH .SI qepe3 KpHCTaJIJIHqeCJ<YIO perneTJ<Y H3 o6JiaCTH KOHTaKTa K rpa HHUaM 3epeH, cymecTByIOIUHM BHyTpH qacTHU, r,n,e KOHUeHTpaUH.SI eaKaHCHH HIDKe. BaKaHCHH no ceTKe rpaHHU JepeH MOfYT Bb XO,D,HTb Ha ra6apHTHYIO noeepXHOCTb cneKaeMoro nopornKoeoro TeJia. ATOMhI, ,D,BHfa.SICb B npomeonoJIO)l(HOM HanpaBJieHHH,,D,OCTHraIOT npHKOHTaKT Hb X yqacTKOB, cnoco6crny.S1 pocry «IIIeeK» H cQ>epoH,D,HJaUHH nop. TaK KaK aTOMblMOfYT nocrynaTb OT BHeIIIHHX ra6apHTHb X noeepXHOCTeM:
T a 6 JI " u a 51. IlyrH AHciKllY3HH aroMOB H ee 3C1Hi>eKTW ope cneKaHHH nopOIDKOBblX Te.JI
ac;at = D(a 2 c ax2), (14.28) r,n,e m - KOJIHqecrno eemecrna,,n,HQ>Q>yH,D,Hpy10m ee e e,n,HHHUY epe MeHH qepe3 nJIOIUa,D,J<Y s npH rpa,n,HeHTe KOHUeHTpaUHH BaKaHCHH oC/ox; 3HaK «MHHYC» 03HaqaeT, qTQ,D,HQ>Q>yJH.SI aTOMOB npoHCXO,D,HT B crnpotty y6bIBaHH.SI HX KOHUettTpaUHH. OTMeTHM, qrn HaBcTpeqy no TOJ<Y aTOMOB,D,BH)l(eTC.SI paBHbIH HM no BeJIHqHHe (HO He Macce!) no TOK BaKaHCHH. B rn6JI. 51 npHee,n,ettbIcee,n,eHH.SI 06 HCToqHHKax H36b T04HbIX ea KaHcHM: H MeCTaX (CTOKax), J<Y,D,a BaKaHCHH,D,BH)l(YTC.SI H r,n,e OHH «OCe ,D,aIOT», a TaIOKe yKa3aHbl 3Q>Q>eKTbl, K KOTOpblM MO)l(eT npHBO,D,HTb 06beMHa.SI,D,HQ>Q>yJH.SI aTOMOB. HH)l(e npHee,n,eHbI 6oJiee,n,eTaJibHbie xapaKTepHCTHKH cJiyqaee,
' CJIY'mll c'IHTaCTCll MaJioeepoHTHbIM.
cneKaeMoro nopOWKOBOro TeJia, CJie.uyeT npH3HaTb B03MO)l(HOCTb yca.u KH B pe3yJihTaTe TpaHcnoprn MaTepttaJia no 3TOMY nyrH. 0TMeTHM, 'ITO.UBH)l(eHHe aTOMOB B,UOJib rpaHHU 3epeH HBJIHeTCH.UHCP<f>Y3HOHHbIM npoueccoM, O,UHaKo He MO)l(eT 6bITb o6bHCHeHO c no3HUHH BaKaHCH OHHoro MexaHH3Ma o6Metta, TaK KaK rpaHHUhI JepeH, CTporo roeopH, He HBJIHJOTCH KpHCTaJIJIH'leCKHMH TeJiaMH. TeM He Mettee C'IHTaeTCH, 'ITO Bblpa)l(eHHe (14.26),UJIH K03<f><f>ttutteHTa,Utt<f><f>y3HH cnpaBe,UJIHBO ",UJIH rpaHH'IHOH.Utt<f><f>Y3HH. B Ka)l(,UOM KOHKpeTHOM KpHCTaJIJIHlJeC KOM eemecTBe nptt onpe.ue11ettttoi1: TeMneparype Ko3<f><f>ttutteHT.utt<t> <f>yJHH no rpaHHUaM 3epeH 06bilJHO BbIWe K03<f><f>ttUHeHTa 06beMHOH CaMO,Utt<f><f>y3HH, XOTH no KpHCTaJIJIHlJeCKOH peweTKe BellleCTBa npH cneKaHHH MHrpttpyeT TaK)l(e 60JibWOe KOJIHlJeCTBO aTOMOB " KHHeTH Ka npouecca npttneKaHHH 'laCTHU 6y.ueT onpe.ueJIHThCH Hatt6011ee Me.u JieHHOH CTa,UHeH, T.e. o6beMHOH CaMO,Utt<f><f>Y3HeH. 3. BomymaR noaepxHocmb «U1eu1Cu»-OuCJ101cal(uu.. Il,tt<f><f>YJHOHHbi e noTOKH no 3TOMy nyrH no CBOeH CYlllHOCTH " pe3yJihTaTaM MOfYT 6bITb onHCaHbl aHaJIOrHlJHO npe,UbI.UYllleMy CJiyqaJO, O,UHaKo ClJHTalOT CH MaJIOBepOHTHbIMH. 4. MeJ11Cue c</Jepu'lecKue nopbL-KpynHble nopbl. C yqeTOM JaBHCHMOCTH KOHUeHTpaUHH BaKaHCHH OT pa.uttyca nopbl (l4.17), c11e.uyeT npH- 3HaTb HaJIHlJHe rpa.utteHTOB KOHUeHTpaUHH BaKaHCHH Me)l(,Uy noeepx HOCTHMH nop pa3Horo pa3Mepa. B pe3yJihTaTe.utt<f><f>YJHH qepe3 Kpttc TaJIJIH'leCKYJO peweTKY eemecTBO nepeHOCHTCH c noeepXHOCTH Kpyn HblX nop Ha noeepXHOCTb MeJIKHX, MeJIKHe nopbl HClJe3alOT (paCTBO PHIOTCH), a 6011ee KpynHbie yeeJIH'IHBaJOTCH B pa3Mepax; npH 3TOM o6mtti1: cyMMapHbI H 06beM nop He MeHHeTCH, T.e. yca.uKa He HMeeT MeCTa. 5. C</Jepu'lecKue nopb1-2pam11{ bl 1epeH.. Il,Btt)l(etttte eaKaHCHH qepe3 KpHCTaJIJIH'lecKyJO peweTKY eemecTBa H.ua11ee no rpattttUaM K noeepx HOCTH MO)l(eT npHBO.UHTb K yca.uKe nop. EcJIH)l(e rpaHHUa BblXO.UHT K KpynHOH nope, TO CKopee c11e.uyeT O)l(H,UUTb yKpynHeHHH (KOaJiecueH UHH) 3TOH nopbl. 6. C</Jepu'lecKue nopbl-OUCJIOKat{uu.. Il,tt<f><f>yJHH no 3TOMY nyTH MO )l(eT npHBO,UHTb K TeM)l(e pe3yJihTaTaM, 'ITO " B npe,UbI.UYllleM c11yqae, O,UHUKO CUM 3TOT CJiylJaH ClJHTaeTCH MaJIOBepOHTHbl M. ' 7 H 8. C11y'latt C'IHTaJOTCH MaJioeepoHTHbI MH. 9. fpaHUl(bl 1epeH. fpaHHUbl 3epeH MOfYT 6b!Tb " HCTO'IHHKUMH " CTOKUMH,UJIH BUKUHCHH B 3UBHCHMOCTH OT.UdiCTBYIOlllHX Ha HHX HU" npH)l(eHHHX. TeopttH Kpttna (BH3Koro TelJeHHH) no Ha6appo-XeppttHry OCHOBaHa Ha 3THX npe,UCTaBJieHHHX " MO.>KeT 6bITb npttMeHeHa K cne KUHHIO. Ha rpaHttuax, r.ue.ueticTByIOT pacrnrnea10mtte ttanpH.>KeHHH, KOHUeHTpaUHH BaKaHCHH 6011ee BbICOKH B cpaBHeHHH co C)l(aTbIMH rpaHHUaMH..IJ,m1 cneKaeMoro nopOWKOBOro TeJia c CHJibHO pa3BHTOH ceTKOH rpaHHU 3epeH.utt<t><f>Y3HH aTOMOB no 3TOMY MexaHH3MY MO)l(eT npHBO.UHTb K pocry «WeeK» " yca.uKe nopoWKOBOro TeJia. AHaJIH3HpyH npttee.ueHHYJO rn611ttuy B03MO)l(Hb X nyrei1.utt<t><f>yJHH, c11e.uyeT o6paTHTb BHHMaHHe Ha CJie,UylOlllHe MOMeHTbl: a) eCJIH HCKJIIO'IHTb H3 paCCMOTpemrn lJeTblpe.UH<t><f>Y3HOH HbIX nyrH c yqaCTHeM.UHCJIOKaUHH, TO H3 OCTaBWHXCH nHTH CJiyqaeB, TpH CBH- 3aHbl c rpaHHUaMH 3epeH, 'ITO yKa3bIBaeT Ha HX cymecTBeHHYIO pOJib nptt cneKaHtttt; 6) npHHHTO ClJHTaTb, 'ITO c TO'IKH 3peHHH Macconepettoca no Me xaHH3MY o6beMHOH.Utt<f><f>Y3HH Hatt6011ee Ba)l(HblMH HBJI51IOTC51 CJiyqaH l, 2, 4 " 5. flO,UTBep)l(,UeHHe, 'ITO 06beMHaH.Utt<f><f>Y3HH HBJIHeTCH MeXaHH3MOM, o6bilJHO KOHTpOJIHPYIOlll HM CKOpOCTb cneKaHH51 nopOWKOBblX TeJI, 6b JIO no11yqeHO MHOrHMH HCCJie.uoeaTeJIHMH, H3YlJaBWHMH KHHeTHKY npMneKaHH51 lJaCTHU Ha MOUeJIHX, npM'leM BO MHOfHX CJIYlfaHX pe3yJib TaTbl 3KcnepMMeHTOB y.uoe11eTBop11TeJibHO coena.uaIOT c npe.ucKaJaH HhIMH no TeOpHH. 51.E. fery3HH npoaHaJIH3HpOBaJI,UBa B03MO)l(Hb!X BapttaHTa 06beM HOH.Utt<f><f>Y3HH npH np11neKaHHH.ueyx c<f>eptt'leCKHX lJaCTHU B 3aBH CHMOCTH OT CTpYKTYPhl o6JiaCTH KOHTaKTHOro nepewei1:Ka. B nepBOM H3 HHX CTOKOM H36bITO'IHbIX BaKaHCHH, B03HHKWHX B6JIH3H BOfHYTOH noeepXHOCTH «WeHKH», HBJIHeTCH BhmyKJiaH noeepXHOCTb nopOWH HOK (T.e. npeunoJiaraeTCH, 'ITO Me)l(,Uy 'laCTHUaMH OTCYTCTByeT Me)l(Je peHHaH rpaHHUa, HanpMMep npH cneKaHHH CB060.UHO HaCbinaHHOro nopowKa) " pOCT nJIOllla.UH KOHTaKTOB He conpOBO)l(,UaeTCH C6JIH)l(e HHeM ueHTpOB 'laCTHU, T.e. ycauKa nopoWKOBOro TeJia OTCYTCTByeT (pHC. 220, 6); 11,JIH 3TOfO CJiy'laH pOCT KOHTaKTa MO)l(eT 6b!Tb onHCaH Bbipa)l(eHHeM
(14.29) Bo BTOpOM eapttaHTe CTOKOM H36b TO'lHblX BaKaHCHH HBJIHeTCH rpa HHUa Me)l(,Uy npttneKUIOlllHMHCH nopOWHHKUMH " pOCT n11oma.uH KOH TaKTa conpoBO)l(,UaeTCH c6JIH)l(eHHeM ueHTpOB lJUCTHU (pHC. 220, 6). Bb1pa.>Ketttte 11,JIH poem KOHTaKTa HMeeT BH.U
(14.30) Ha pttc. 22 l no.uaHHhIM Ky'IHHCKoro npttee.ueHhICTpYKTYPhIKOH TaKTHbI X 0611acTeH, B03HHKUIOlllHX npH B3UMMHOM npttneKaHHH Meu HblX npOBOJlOK (l 050 °C, 50 '1), Kor.ua B o6JlaCTH KOHTaKTa eCTb CTOKH
PHc. 221. CrpyK-rypbl KOHTaKTHbIX 96nacTeil:, BOJHHKaJOIUHX npH BJaHMHOM npHneKaHHH Me,llHbIX npoBOJIOK
BaKaHeHH.B BH,l(e Me:)l<:JepeHHb X rpaHHU (pHe. 221, a) H Kor,n;a eTOKOB BaKaHeHH HeT (pHe. 221, 6). OrMe'leHo, 'ITO poeT IIJIOI.IJ;a,ll;H KOHmKT HOfO neperneH:Ka eonpOBO)l{,ll.aeTeSI e6JIIDKeHHeM ueHTPOB KOHmKTH PYJOI..UHX npoBOJIOK JIHIIIh B eJiyqae HaJIH'IHSI B ueM Me:)l<:JepeuuoH: rpa HHUhI. OrMeTHM, 'ITO npH eneKaHHH qaeTHU, <i>opMa KOTOpbIX OTJIH'IHa OT e<l>epH'leeKOH HJIH UHJIHH.n;pH'leeKOH, 3aKOH poem pa,n;1fYea nepe IIIeHKa x MOXeT OTJIH'laTbCSI OT npHBe,n;eHHOro Bb IIIe x 5 - t H, KaK IlOKa3aHO 3KenepHMeHTaJibHO, eOOTBeTCTBOBaTb JaBHeHMOeTH x3 - t. TaKoe BJIHSIHHe <l>oPMhIqaeTHU Ha JaKoH poem x MoxeT HMeTb MeeTo H B CJiyqae.n;pyrHX paeeMaTPHBaeMb X MexaHH3MOB Maeeonepeuoea. B.R. lHHee npe.n;JIO)KHJI Bblpa)KeHHe, oueHHBaIOI.IJ;ee BpeMSI tn IlOJI HOfO He'le3HOBeHIDI («.n;H<t><l>Y3HOHHOfO» 3apaemHHSI) H30JIHpOBaH
0 Me BemeeTBa, r.n;e HeT,n;pyrHX HeTO'IHHKOB BaKaHeHH, a HX eTOKOM SIBJISieTCSI ero BHeIIIHSIH ra6apHTHa.H IlOBepxuoeTb:
tn = (kT/(yyD)r. (14.31) B mo6oH: MOMeHT BpeMeHH H30TepMH'leeKOH BbI,n;ep)KKH t npH ene KaHHH mKaSI H30JIHpOBaHHaSI e<t>epH'leeKaH nopa 6y,n;eT HMeTb pa,n;Hye r, paBHb H
Ha pHe. 222 noKaJaHhInoCJie,n;oeareJibHb e 3TailhIJanoJIHeHHH nopbI BemeeTBOM BeJie.n;eTBHe ee BaKaHeHOHHOro paeTBopeHHSI. no R.E. fery3HHY H 11.M. J1H$IIIHUY.n;H<t><l>Y3HOHHblH MexaHH3M
a.=(iJ «1, .190 PHc. 222. nocne.noaareJJbHbl e 3Tailbl JaJ1e'H1BaHID1 nopbl npH ee noaaKaHCHOHHOM pacTBOpeHHH B OKp}')l(aJOIUeH KpHCTaJIJIH'leCKOH cpe.ne
T.e. pOJib.n;H<l><l>Y3HOHHOro MexaHH3Ma B03paemeT Ha 003,ll;HHX eTa.n;HHX eneKaHHSI. Ba3KOe mettenue. 0KoJio rneeTH.l(eeSITH JieT TOMY HaJa,n; H.11. <l>peu KeJib e<t>opMyJIHpoBaJI H KOJIH'leeTBeHHO peIIIHJI,n;Be Ja,n;a'IH, eBSI3aH Hbie e peaJIH3au;HeH npH eneKaHHH nopoIIIKOBOfO TeJia MexaHH3Ma Maeeonepeuoea nyreM BSI3Koro Te'leHHH: o JanJihIBaHHH HJOJIHpo BaHHOH nopblH 0 eJIHSIHHH,n;Byx eonpHKaeaIOI.IJ;HXeSI nopOIIIHHOK. <l>yu,n;aMeHTaJibHoe IlOJIO)KeHHe ero TeopeTH'leeKHX npe,n;emBJieHHH - aHaJIOrHSI Me)K,11,y BH3KHM re•1eHHeM aMop$Hh X Tell (npoHeXOM J..UHM no MeXaHH3MY uenoporoBOH IlOJI3yqeeTH nyreM KoonepaTHBHO ro nepeMeI.IJ;eHHSI aTOMOB B Mepy K03$$HUHeHm BH3KOeTH, HBJIHIO meroeSI KOHemHTOH BemeeTBa) H KpHeTaJIJIH' eeKHX BemeeTB,,n;JIH KOTOpbIX OHO mKXe SIBJISieTCH npoueeeoM uenoporoBOH IlOJIJyqeeTH, HO nepeMeI.IJ;eHHe aTOMOB He SIBJISieTCSI npoueeeoM KOOnepaTHBHbIM, a eeTb pe3yJibTaT He3aBHeHMbIX 3JieMeHmpHb X aKTOB (eKa'IK006pa3HbIX nepeMemeHHH aTOMOB) no,n; BJIHSIHHeM KanHJIJISlpHoro.n;aBJieHHSI, Bb 3BaHHOro KpHBH3HOH noBepxuoeTH qaeTHU HJIH paJJIH'IHeM HanpSI )KeHHH B o6beMe nopOIIIKOBOfO reJia no BeJIH'IHHe HJIH 3HaKY. npHpaBHHB pa60TY eHJI noBepxuoeTHOro HaTSIXeHHSI As { As = = -y[d(S)/dt]} pa6ore.n;e<i>opMaUHH Av [ Av = 2ri(di:./dt)2 V, r,n;e di:./ dt eKopoeTb.n;e<t>opMaUHH KOHmKTHPYIOJ..UHX qaeTHU; f. H 2 v -eooTBeT eTBeHHO OTHOeHTeJibHaSI.n;e<t>opMaUHSI H eyMMapHblH o6beM,n;Byx.n;e <t>opMHpyeMblX e<t>ep], noeJie eooTBeTeTBYIOJ..UHX npeo6pa30BaHHH no JiyqHM Bblpa)KeHHe,n;JISI oueHKH poem KOHTaKTa Ha nepBbIX eTa,ll;HSIX eneKaHHH (pHe. 220, a) x2/a0= (3/2)(y/ri)t HJIH x2/a0 - t, (14.33) r,n;e ao - Ha'laJibHb H pa3Mep e<t>epb; ri - K03$$HUHeHT BH3KOeTH BemeeTBa npH,n;aHHOM eoeTOSIHHH eTPYKTYPhI, B eBSI3H e qeM ri -!JI. ,llJISI IlOJIHOro eJIHSIHHSI.n;Byx KOHTaKTHPYIOJ..UHX e<t>ep (x ao) Heo6- XO,ll;HMO BpeMSI tn, paBHOe (14.34) Ha PHC. 223 npHBe,lleH KHHOMOHTIDK, H306pIDKaIOIUHH BeCb npo uecc CJIHSIHHSI c<t>ep B pe)l(HMe BSl3Koro TelleHHSI. L(Jrn IlOJIHOro 3anJibIBaHHSI H30JIHpOBaHHOH c<t>epHlleCKOH nopbl HallaJibHOro pa.uHyca ro, KOTOpblH 60Jibllle pa3Mepa 3epHa HJIH 6JIOKa, r.ue oHa pacnoJio.>KeHa, Heo6xo,llHMO epeMsi: tn, paeHoe tn = (4/3)(ri/y)r0• (14.35) Pa.uHyc r TaKOH nopbI e npouecce H3orepMHlleCKOH Bb,llep.>KKH t paeeH r = r0 - (3/4)(y/ri)t. (14.36) Ha pHc. 224 noKa3aHbInoCJie.uoeareJibHb e 3Tanb13anoJIHeHHS1 nopbI eemecTBOM BCJie,llCTBHe.UH<i><l>Y3HOHHO-BSl3KOro TelleHHSI. llpuneKaHue noiJ BJIUJlHUeM npuJ1CUMa10U{UX ycwmii. TelleHHe eeme CTBa, Bbl3bIBaeMoe BHeIIIHHMH Harpy3KaMH (pHC. 220, e), CBSl3aHO c .ue<t>opMauHeit qacmu.
14.1.4. non3y'l8CTb KpMCT&nnM'l8CKMX Ten
51.E. fery3HH, nonyJisi:pHO H3Jrnrasi: <l>H3HlleCKYJO npHpo.uy SIBJieHHH, conpOBO)l(,llaIOIUHX Harpee nopOIIIKOBOro TeJia, c<t>opMyJIHpOBaJI CJie .UYI01Uee onpe.ueJieHHe: «CneKaHHe -.UH<l><l>Y3HOHHasi: noJIJyqecTb no.a eoJ.ueitcTBHeM CHJI noeepxHoCTHoro HaTsi:.>KeHHSI». TaKoe noHHMaHHe po.ucrneHHOCTH npoueccoe cneKaHHSI H noJIJyqecTH B03HHKJIO eme Y 51.H. <l>peHKeJisi:, a 3areM 6bIJIO paJBHTO e pa6ornx Ha6appo, XeppHH ra,.6JI. IlHHeca H KyqHHCKoro.
·pa, O,llHH KOHeu KOTOporo 3aKpenJieH, a K.upyroMy no.u Belll
MaTepHaJia MOHOKpHCTaJIJia), HanpSl)l(eHHSI B JII06bIX.ueyx TOlJKax e o6'beMe KpHCTaJIJia coeepllleHHO O,llHHaKOBbl. Pa3- JIHllHSI B03HHKaIOT Ha noeepXHOCTH: K TopueBb M noeepx HOCTSIM KpHCTaJIJia npHJIO.>KeHblpacrnrHBaIOmHe, a K 60- KOBb M - C)l(HMaIOmHe Hanpsi:.>KeHHSI, C03,llaHHbie H no.u .uep)l(HBaeMb e rpy3oM, no.ueeII1eHHb M K KpHCTaJIJiy. Ta
TpaUHSI BaKaHCHH no cpaeHeHHIO c paBHOBeCHOH noBb IIIeHa, a Ha 6oKOBb X noeepxHocrnx - noHH.>KeHa. CJie.uoeareJibHO,.UOJI.>KeH BOJ HHKHYTb (H B03HHKaeT!) HanpaBJieHHb H noTOK BaKaHCHH OT Topue Bb X noeepXHOCTeH KpHCTaJIJia K ero 6oKOBb M noeepXHOCTSIM (HJIH noToK aroMoB e npoTHBonoJIO.>KHOM HanpaBJieHHH). B pe3yJibTaTe KpH CTaJIJI YTOHlJaeTCSI (aTOMbIyIIIJIH OT 6oKOBOH noeepxHOCTH!) H Y.llJIH HSleTCsi: (aTOMblnpHIIIJIH K ropueBb M noeepXHOCTSIM!). 3'ro H ecTb noJI- 3YlJ:eCTb KpHCTaJIJia B CBSl3H C.UH<i><i>Y3HOHHb M MeXaHH3MOM vnepeMe meHHSI aTOMOB, KOTOpyIO Il03TOMY Ha3bIBaIOT.UH<l><l>Y3HOHHOH noJIJy lJeCTblO. · CneKaHHe nopoII1Koeoro rena, co.uep.>Kamero H30JIHpoeaHHb e nopbI HJIH SIBJISIIOIUerocsi: npocTpaHCTBeHHOH KOHCTpYKUHeH, B KOTOpoit nepeMe.>KaIOTCsi: conpHKaca10mHecsi: nopoIIIHH KH H nycrorn (nopb1), conpoeo)l(,llaeTcsi: non JyqecTbIO eemecTea 3Toro TeJia. MexaHH3MbI .ue<t>opMaUHH (non3yqeCTH) KpHCTaJIJIH qecKoro TeJia B o6JiaCTH,llOCTaTOlJHO Bb COKHX TeMneparyp cneKaHHSI MOfYT 6bITb pa3JIHll Hb MH. Bbl,lleJISIIOT HenoporoBbie MexaHH3MbI, onpe,lleJISIIOIUHe.ue<t>opMHpOBaHHe npH CKOJib yro.uHo MaJib X HanpSl)l(eHHSIX cr, H MexaHH3- Mbl noporOBbie, npOSIBJISIIOIUHe ce6si: npH Hanpsi:.>KeHHSIX cr, npeBOCXO,llSllUHX HeKOTOpoe npe.ueJibHoe 3HalleHHe cr'. IlpH HenoporoeoM MexaHH3Me.ue<t>opMHpoeaHHSI (cr < cr') KpHC TaJIJIHlJeCKOe TeJIO Be,lleT ce6si: no.uo6HO HblO Pl!lc. 225. HanpaBJJeHHb1e TOHOBCKOH)l(H,ll,KOCTH, OTJIHlJaSICb OT Hee TeM, noTOKH B3K3HCHH (- -)
KHM o6pa30M, B6JIH3H TopueBb X noeepXHOCTeH KOHUeH-
Pttc. 223. 0ocJJe,noBaTeJJbHOCTb KHHOKa,npoB, HJJJJIOCTpl!lpYJOlllHX CJIHHHHe BH3KHX ccj>ep 'ITO K03<l><l>HUHeHT TeKyqeCTH ero eemecTBa JaBHCHT OT CTpYKTYPHOro COCTOSIHHSI TeJia H MO.>KeT H3MeHSITbCSI BO epeMeHH.IlpH cr > cr' B036y)l(,llaIOTCSI noporoBbie MexaHH3Mbl, npH KOTOpblX IlOJI3yqeCTb MO.>KeT SIBJISITbCSI CJie,ll- If 3TOMOB(-), B03HH K3IOUlHe Ha 6oKOBblX If TopueBblX nosepXHOCTHX MOHOKpHCT3JJJJ3 no.n BJJl!IH HHeM COJ.nasaeMbIX HanpH- )l(eHHH
CTBHeM nepeMemeHHH.llHCJIOKaUHH, conpoBmK,D,aiomerocH npeo,D,o JieHHeM paJJIHtIHOfO po,D,a npenHTCTBHH, npH'IeM O,ll,HOBpeMeHHO MO ryr,D,eHCTBOBaTb H HenoporOBb e MeXaHHJMb. 061.UHM npHJHaKOM Bcex MexaHHJMOB HenoporoBOH nomyqeCTH HBJrneTCH HanpaBJieHHbIH.llH<l><l>YJHOHHbIH flOTOK BaKaHCHH (HJIH, qTO TO)Ke CaMoe, flOTOK aTOMOB B npOTHBOflOJIO)l(HOM HanpaBJieHHH), KOTOpbIH BOJHHKaeT B npe,D,eJiax Ka)l(,ll,OfO HJ 3JieMeHTOB CTpYKTYPbl HJ-Ja rpa,D,HeHTa KOHU,eHTpaU,HH BaKaHCHH (pHC. 226). 3TOT noTOK MO )l(eT npHBeCTH K HJMeHeHHIO <t>opMbl COOTBeTCTBYIOJ.Uero 3JieMeHTa CTpYKTYPhI6eJ HJMeHeHHH ero o6beMa. CymecrneHHbIM B 3TOM npo uecce HBJIHeTCH TO, qTQ HeO,D,HOpO,ll,Hbi e.llH<l><l>YJHOHHbl e flOTOKH B npe,D,eJiax OT,D,eJibHOfO 3JieMeHTa CTpYKTYPbl He COJ,D,alOT MaKpOCKO nHqecKOfO noToKa e Macwrn6ax Bcero nopowKoBoro TeJia.)l.e<t>opMH poBaHHe Bcex 3JieMeHTOB CTpYKTYPbI,T. e. KpHCTaJIJIHqecKoro noporn KOBOfO TeJia KaK ueJioro, HBJIHeTCH npoueccoM caMocornacoBaHHbIM B TOM CMblCJie, qTo Ha HX rpaHHU,aX paJ,D,eJia He BOJHHKalOT HapyweHHH CflJIOWHOCTH H HJMeHeHHe <t>opMbl,D,aHHOfO 3JieMeHTa CTpYKTYPbl Ja BHCHT OT HJMeHeHHH <t>opMbl 3JieMeHTOB, HaXO,lJ,HJ.UHXCH c HHM B He nocpe,D,CTBeHHOM coce,D,CTBe (pHc. 227). 3ToT npouecc no,D,o6eH,D,e<t>op MHpoBaHHIO COBOKYilHOCTH conpHKaCalOIUHXCH peJHHOBb X o6oJioqeK, JanoJIHeHHbIX necKOM, BCJie,D,CTBHe,ll,BH)l(eHHH (nepecblnaHHH) nec qHHOK B Ka)l(,ll,OH HJ HHX. CaMocornacoBaHHoe HJMeHeHHe <t>opMbI3Jie MeHTOB CTpYKTYPbl nopOWKOBOfO TeJia npHBO,ll,HT K HanpaBJieHHOMY
---- 2
Plic. 226. CxeMa A1t<txl>yJ1toHHblX noTOKOR BUKUHCltH (/) It UTOMOB (2) R nOJllt KpltCTUJlJllt'lecKOM o6paJue noA ttarpyJKoi! P11c. 227. CxeMa Aecl>oPM1tpoBUH1tll nOJ11tKp1t CTUJlJlw1ecKoro o6paJua BCJleAcrn11e n11<t><f>y J1tOHHO-BS1JKoro npeo6pa30BUHltll <f>opMbl 3CpeH, HUXOllllll\ltXCSI non BOJAeilcTBlteM HanplllKeHltll a (McxaH1tJM Ha6appo-Xepp11Hra- Jl11<t>urnua) nepeMemeHHIO HX ueHTpOB Tjf)l(eCTH, KOTopoe no,D,o6Ho nepeMeme HHIO MOJieKYJI npH reqeHHH BHJKOH)l(H,D,KOCTH. 11.M. JlH<t>llIHU noKa JaJI, qTo 3TOT npouecc,ll,OJI)l(eH conpOBO)l(,ll,aTbCH CKOJib)l(eHHeM KpH CTaJIJIOB (qacTHU),D,pyr OTHOCHTeJibHO,D,pyra. TaKHM o6paJOM, BHJKOe TeqeHHe KpHCTaJIJIHqecKHX TeJI npH MaJibIX HarpyJKax H.llH<l><l>YJHOH HOe nepepacnpe,D,eJiemi:e Bemecrna Ja cqeT rpa,D,HeHTa KOHUeHTpaUHH BaKaHCHH B 06beMe 3JieMeHTOB ero CTpYKzypbl - H,D,eHTH'IHb e npo uecCb, B OCHOBe KOTOpblX Jie)l(HT BaKaHCHOHHb H MeXaHHJM. lo3TOMY npHHHTO fOBOpHTb 0.llH<l><l>YJHOHHO-BHJKOM TeqeHHH (.llH<l><l>YJHOH HOH nomyqeCTH) nopOWKOBb X TeJI npH cneKaHHH, KOTOpoe HMeeT MeCTO npH BbinOJIHeHHH ycJIOBHH '1'2»8/ L, r,D,e 'I' - yroJI paJopHeHTHPOBKH coce,D,HHX KpHCTaJIJioB; npH 8/ L 10-4 yroJI 'I'.llOJI)l(eH 6b Tb > 1°; 8 - aTOMHh H,D,HaMeTp; L - JIHHeHHb H paJMep KpHCTaJIJia. PaccMoTpeHHh H MexaHHJM Ha6appo-XeppHHra-JIH<t>wHua OT HOCHTCH K H,D,eaJIHJHPOBaHHOMY KpHCTaJIJIH'IeCKOMY TeJiy, r,D,e ceTKa «aMop<t>HJOBaHHbIX» rpaHHU HBJIHeTCH e,D,HHCTBeHHb M npHJHaKOM HepaBHOBeCHOCTH, TOf,D,a KaK B peaJibHb X nopOllIKOBblX TeJiaX HMeeT CH JHaqHTeJibHOe KOJIHqecrno O,ll,HHOqHb X KpaeBb X,ll,HCJIOKaUHH, He KOHCepBaTHBHOe,ll,BH)l(eHHe («nepenoJIJaHHe») KOTOPb X B noJie Ha npH)l(eHHH MO)l(eT cymecTBeHHO onpe,D,eJIHTb KHHeTHKY nomyqeCTH. c 3THM, BH,ll,HMO, CBHJaHa 3KCnepHMeHTaJibHO Ha6JIIO,D,aeMaH HeyCTaHO BHBWaHCH flOJIJyqeCTb B pe)l(HMe HenoporoBOfO,D,e<t>opMHpOBaHHH H ee JaBHCHMOCTb OT npe,D,b CTOpHH o6paJua. 0KoJio TpH,D,UaTH JieT TOMY HaJa,D, M.<I>. 3rn6H H P.A. <l>eppaJIJia
|
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Последнее изменение этой страницы: 2016-04-23; просмотров: 337; Нарушение авторского права страницы; Мы поможем в написании вашей работы! infopedia.su Все материалы представленные на сайте исключительно с целью ознакомления читателями и не преследуют коммерческих целей или нарушение авторских прав. Обратная связь - 18.116.80.236 (0.518 с.) |