Ntawm ntau qhov tshwm sim hauv physics, cov txheej txheem diffusion yog ib qho yooj yim thiab nkag siab tshaj plaws. Tom qab tag nrho, txhua txhua tag kis sawv ntxov, npaj nws tus kheej tsw qab tshuaj yej los yog kas fes, ib tug neeg muaj lub sijhawm los soj ntsuam cov tshuaj tiv thaiv no hauv kev xyaum. Cia peb kawm ntxiv txog cov txheej txheem no thiab cov xwm txheej rau nws qhov tshwm sim hauv cov xeev sib txawv.
Dab tsi yog qhov txawv txav
Lo lus no yog hais txog kev nkag mus ntawm cov molecules lossis atoms ntawm ib yam khoom ntawm cov qauv zoo sib xws ntawm lwm qhov. Nyob rau hauv cov ntaub ntawv no, lub concentration ntawm nkag mus rau lub tebchaw yog leveled.
txheej txheem no tau piav qhia thawj zaug los ntawm tus kws tshawb fawb German Adolf Fick hauv xyoo 1855
Lub npe ntawm lo lus no tau tsim los ntawm Latin verbal noun diffusio (kev sib tham, sib faib, faib).
Diffusion hauv kua
Cov txheej txheem raws li kev txiav txim siab tuaj yeem tshwm sim nrog cov tshuaj hauv peb lub xeev ntawm kev sib sau ua ke: gaseous, kua thiab khoom. Rau cov piv txwv ntawm qhov no, tsuas yog saibkitchen.
Cub-boiled borscht yog ib qho ntawm lawv. Nyob rau hauv qhov kev cuam tshuam ntawm qhov kub thiab txias, cov molecules ntawm glucosin betanin (ib yam khoom uas cov beets muaj xws li cov xim liab liab nplua nuj) sib npaug nrog cov dej molecules, muab nws lub cim burgundy xim. Cov ntaub ntawv no yog ib qho piv txwv ntawm diffusion hauv cov kua.
Ntxiv rau borscht, cov txheej txheem no tuaj yeem pom hauv khob tshuaj yej lossis kas fes. Ob leeg ntawm cov dej haus no muaj xws li ib tug nplua nuj ntxoov ntxoo vim hais tias cov tshuaj yej nplooj los yog kas fes hais, yaj nyob rau hauv dej, tusyees kis ntawm nws cov molecules, coloring nws. Qhov kev txiav txim ntawm tag nrho cov nrov instant dej qab zib ntawm lub nineties yog tsim los ntawm tib lub ntsiab cai: Yupi, Caw, Zuko.
Interpenetration of gases
Txuas ntxiv mus saib ntxiv rau qhov tshwm sim ntawm cov txheej txheem hauv nqe lus nug hauv chav ua noj, nws tsim nyog sniffing thiab txaus siab rau lub qab ntxiag aroma emanating los ntawm ib pob paj ntawm cov paj tshiab ntawm lub rooj noj mov. Vim li cas qhov no tshwm sim?
Smell-carrying atoms and molecules are in active motion and, ass, are mixed with particles twb nyob rau hauv cov huab cua, thiab yog haum sib npaug dispersed nyob rau hauv lub ntim ntawm chav tsev.
Qhov no yog qhov tshwm sim ntawm kev nthuav dav hauv cov pa roj. Nws yog ib qho tsim nyog sau cia tias qhov nqus pa ntawm huab cua kuj tseem nyob rau hauv cov txheej txheem hauv kev xav, nrog rau cov ntxhiab tsw qab ntawm cov borscht tshiab tshiab hauv chav ua noj.
Diffusion hauv solids
Lub rooj noj mov nrog paj yog npog nrog cov ntaub pua rooj daj daj. Nws tau txais qhov ntxoov ntxoo zoo sib xws ua tsaug raumuaj peev xwm ntawm diffusion kom dhau los ntawm cov khib nyiab.
txheej txheem ntawm muab cov ntaub pua plag ib co ntxoov ntxoo tshwm sim nyob rau hauv ob peb theem raws li hauv qab no.
- Particles ntawm daj xim diffused nyob rau hauv tus number case tank rau cov ntaub ntawv fibrous.
- Lawv thiaj li tau nqus los ntawm sab nrauv ntawm cov ntaub dyed.
- kauj ruam tom ntej yog rov diffuse cov xim, tab sis lub sij hawm no mus rau hauv lub fibers ntawm lub web.
- Thaum kawg, cov ntaub kho cov xim pigment, yog li ua xim.
Diffusion ntawm gases hauv hlau
Feem ntau, hais txog cov txheej txheem no, xav txog kev sib cuam tshuam ntawm cov khoom hauv tib lub xeev ntawm kev sib sau. Piv txwv li, diffusion hauv solids, solids. Txhawm rau ua pov thawj qhov tshwm sim no, ib qho kev sim yog nqa tawm nrog ob lub phaj hlau nias rau ib leeg (kub thiab txhuas). Kev sib cuam tshuam ntawm lawv cov molecules siv sijhawm ntev heev (ib millimeter hauv tsib xyoos). Cov txheej txheem no yog siv los ua cov hniav nyiaj hniav kub txawv txawv.
Txawm li cas los xij, cov tebchaw hauv cov xeev sib txawv kuj muaj peev xwm nthuav tawm. Piv txwv li, muaj cov pa paug hauv cov khoom tawg.
Thaum qhov kev sim nws tau ua pov thawj tias cov txheej txheem zoo li no tshwm sim hauv lub xeev atomic. Txhawm rau qhib nws, raws li txoj cai, koj xav tau qhov kub thiab txias ntau ntxiv.
Ib qho piv txwv ntawm xws li gaseous diffusion hauv cov khib nyiab yog hydrogen corrosion. Nws manifests nws tus kheej nyob rau hauv cov xwm txheej qhov twgHydrogen atoms (Н 2) uas tau tshwm sim nyob rau hauv cov chav kawm ntawm qee cov tshuaj tiv thaiv nyob rau hauv lub zog ntawm qhov kub thiab txias (los ntawm 200 mus rau 650 degrees Celsius) nkag mus rau ntawm lub structural hais ntawm cov hlau.
Ntxiv rau hydrogen, kev nthuav tawm ntawm cov pa oxygen thiab lwm yam gases tuaj yeem tshwm sim hauv cov khoom khib nyiab. Cov txheej txheem no, imperceptible rau lub qhov muag, ua rau muaj kev phom sij ntau, vim tias cov qauv hlau tuaj yeem tawg vim nws.
Diffusion ntawm cov kua hauv cov hlau
Txawm li cas los xij, tsis yog cov roj molecules tuaj yeem nkag mus rau hauv cov khib nyiab, tab sis kuj yog kua. Raws li nyob rau hauv cov ntaub ntawv ntawm hydrogen, feem ntau cov txheej txheem no ua rau corrosion (thaum nws los txog rau hlau).
Ib qho piv txwv ntawm cov kua diffusion hauv cov khib nyiab yog corrosion ntawm cov hlau hauv qab dej (H 2 O) lossis cov tshuaj electrolyte. Rau feem ntau, cov txheej txheem no paub ntau dua nyob rau hauv lub npe ntawm rusting. Tsis zoo li hydrogen corrosion, hauv kev xyaum nws yuav tsum tau ntsib ntau zaus.
Cov xwm txheej kom nrawm nrawm. Diffusion coefficient
Tau nrog cov tshuaj uas cov txheej txheem hauv kev txiav txim siab tuaj yeem tshwm sim, nws tsim nyog kawm txog cov xwm txheej rau nws qhov tshwm sim.
Ua ntej ntawm tag nrho, qhov nrawm ntawm kev sib kis nyob ntawm lub xeev tag nrho ntawm cov khoom sib cuam tshuam. Qhov ntau dua qhov ntom ntawm cov khoom uas cov tshuaj tiv thaiv tshwm sim, nws tus nqi qeeb qeeb.
Nyob rau hauv qhov no, kev nthuav tawm hauv cov kua thiab cov pa roj yuav ib txwm ua haujlwm ntau dua li cov khoom khib nyiab.
Piv txwv li, yog cov muajupoov tshuaj permanganate KMnO4 (potassium permanganate) pov rau hauv dej, lawv yuav muab cov xim zoo nkauj raspberry. hauv ob peb feeb Xim. Txawm li cas los xij, yog tias koj nchuav cov pob zeb ntawm KMnO 4 rau ntawm cov dej khov thiab muab tso rau hauv lub tub yees, tom qab ob peb teev, poov tshuaj permanganate yuav. tsis muaj peev xwm tag nrho cov xim khov H
2O.
Los ntawm qhov piv txwv yav dhau los, ib qho kev txiav txim siab ntxiv txog cov kab mob sib kis tuaj yeem kos tau. Ntxiv rau lub xeev ntawm kev sib sau ua ke, qhov kub thiab txias kuj cuam tshuam rau tus nqi ntawm kev sib cuam tshuam ntawm cov khoom.
Txhawm rau txiav txim siab qhov kev vam khom ntawm cov txheej txheem raws li kev txiav txim siab ntawm nws, nws tsim nyog kawm txog lub tswv yim xws li diffusion coefficient. Qhov no yog lub npe ntawm qhov muaj nuj nqis ntawm nws qhov nrawm.
Hauv cov qauv feem ntau, nws txhais tau nrog lub peev Latin tsab ntawv D thiab hauv SI system nws ntsuas hauv square metres ib thib ob (m² / s), qee zaum hauv centimeters ib thib ob (cm 2 /m).
Lub diffusion coefficient yog sib npaug ntawm cov teeb meem tawg los ntawm ib chav tsev saum npoo ntawm ib chav tsev ntawm lub sijhawm, muab qhov sib txawv ntom ntom ntawm ob qhov chaw (nyob ntawm qhov deb sib npaug ntawm chav tsev ntev) yog sib npaug rau ib qho. Cov txheej txheem uas txiav txim siab D yog cov khoom ntawm cov khoom uas cov txheej txheem tawg ua rau nws tus kheej tshwm sim, thiab lawv hom.
Qhov kev vam khom ntawm cov coefficient ntawm qhov kub thiab txias tuaj yeem piav qhia siv qhov sib npaug Arrhenius: D=D0exp(-E / TR).
Nyob rau hauv qhov kev txiav txim siab mis E yog qhov tsawg kawg nkaus lub zog yuav tsum tau ua kom cov txheej txheem; T - kub (ntsuas hauv Kelvin, tsis yog Celsius); R-gas tas li yam ntxwv ntawm ib tug zoo tagnrho gas.
Ntxiv rau tag nrho cov saum toj no, tus nqi diffusion hauv cov khib nyiab, kua hauv gases cuam tshuam los ntawm lub siab thiab hluav taws xob (inductive lossis high-frequency). Tsis tas li ntawd, ntau nyob ntawm qhov muaj cov tshuaj catalytic, feem ntau nws ua raws li qhov tshwm sim rau qhov pib ntawm active dispersion ntawm hais.
Diffusion equation
qhov tshwm sim no yog ib daim ntawv tshwj xeeb ntawm cov kab zauv sib txawv ib nrab.
Nws lub hom phiaj yog txhawm rau nrhiav kev vam khom ntawm cov ntsiab lus ntawm cov khoom ntawm qhov loj thiab kev sib koom ua ke ntawm qhov chaw (hauv qhov nws diffuses), nrog rau lub sijhawm. Nyob rau hauv cov ntaub ntawv no, tus muab coefficient characterizes lub permeability ntawm nruab nrab rau cov tshuaj tiv thaiv.
Feem ntau, cov kab zauv diffusion yog sau raws li nram no: ∂φ (r, t)/∂t=∇ x [D(φ, r) ∇ φ (r, t)].
Nyob hauv nws φ (t thiab r) yog qhov ntom ntawm cov khoom tawg ntawm qhov taw tes r ntawm lub sijhawm t. D (φ, r) - generalized diffusion coefficient ntawm ceev φ ntawm point r.
∇ - vector sib txawv tus neeg teb xov tooj uas nws cov khoom yog ib feem derivatives hauv kev tswj hwm.
Thaum lub diffusion coefficient yog qhov ntom ntom, qhov sib npaug yog non-linear. Thaum tsis yog - linear.
Tau txiav txim siab lub ntsiab lus ntawm kev nthuav dav thiab cov yam ntxwv ntawm cov txheej txheem no hauv ib puag ncig sib txawv, nws tuaj yeem raug sau tseg tias nws muaj ob qho zoo thiab tsis zoo.
