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Cov hlau tsis zoo siv dav siv thiab nws cov qauv wrought yog resistant rau corrosion nyob rau hauv ambient tej yam kev mob vim lub passivation txheej muaj xws li chromium oxide. Corrosion thiab yaig ntawm cov hlau feem ntau cuam tshuam nrog kev puas tsuaj ntawm cov khaubncaws sab nraud povtseg, tab sis tsis tshua muaj qhov tshwm sim ntawm qhov tsis sib xws, nyob ntawm qib microscopic. Hauv kev ua haujlwm no, nanoscale chemical deg heterogeneity, kuaj pom los ntawm spectroscopic microscopy thiab chemometric tsom xam, npaj txhij txog dominates pob txha thiab corrosion ntawm txias dov cerium hloov super duplex stainless hlau 2507 (SDSS) thaum nws kub deformation. Txawm hais tias X-ray photoelectron microscopy tau pom tias muaj kev tiv thaiv zoo ntawm cov txheej txheem Cr2O3, qhov kev ua haujlwm ntawm cov khaub thuas dov SDSS tsis zoo vim qhov kev faib hauv zos ntawm Fe3+ nplua nuj nanoislands ntawm Fe / Cr oxide txheej. Qhov kev paub txog atomic scale no muab kev nkag siab tob ntawm stainless hlau corrosion thiab xav tias yuav pab tiv thaiv corrosion ntawm cov hlau zoo sib xws.
Txij li thaum lub invention ntawm stainless hlau, lub anti-corrosion zog ntawm ferrochrome tau raug ntaus nqi mus rau chromium, uas tsim muaj zog oxides / oxyhydroxides thiab qhia ib tug passivating cwj pwm nyob rau hauv feem ntau ib puag ncig. Piv rau cov pa (austenitic thiab ferritic) stainless hlau 1, 2, 3, super duplex stainless hlau (SDSS) muaj kev tiv thaiv corrosion zoo dua thiab cov khoom siv zoo heev. Ua kom muaj zog txhua yam tso cai rau kev sib dua thiab ntau dua kev tsim qauv. Hauv qhov sib piv, SDSS kev lag luam muaj kev tiv thaiv siab rau pitting thiab crevice corrosion, ua rau lub neej ntev kev pab cuam, yog li nthuav nws daim ntawv thov rau kev tswj cov pa phem, ntim tshuaj, thiab kev lag luam offshore roj thiab roj 4. Txawm li cas los xij, qhov nqaim ntawm kev kho cua sov kub thiab tsis zoo formability cuam tshuam lawv cov kev siv dav dav. Yog li ntawd, SDSS tau hloov kho los txhim kho cov haujlwm saum toj no. Piv txwv li, kev hloov kho Ce tau qhia hauv SDSS 2507 (Ce-2507) nrog cov ntsiab lus nitrogen siab 6,7,8. Lub ntiaj teb tsis tshua muaj (Ce) ntawm qhov tsim nyog concentration ntawm 0.08 wt.% muaj txiaj ntsig zoo rau cov khoom siv kho tshuab ntawm DSS, vim nws txhim kho cov nplej refinement thiab grain ciam zog. Hnav thiab corrosion kuj, tensile lub zog thiab tawm los lub zog, thiab kub ua hauj lwm kuj zoo dua 9. Cov nitrogen ntau tuaj yeem hloov cov ntsiab lus nickel kim, ua rau SDSS tau txais txiaj ntsig ntau dua 10.
Tsis ntev los no, SDSS tau ua plastically deformed ntawm ntau qhov kub thiab txias (cryogenic, txias thiab kub) kom ua tiav cov khoom siv zoo heev6,7,8. Txawm li cas los xij, qhov zoo tshaj plaws corrosion kuj ntawm SDSS vim tias muaj cov yeeb yaj kiab oxide nyias nyob rau saum npoo yog cuam tshuam los ntawm ntau yam xws li qhov sib txawv ntawm qhov sib txawv vim muaj qhov sib txawv ntawm cov theem sib txawv nrog cov ciam teb sib txawv, tsis xav tau precipitates thiab cov lus teb sib txawv. deformations ntawm austenitic thiab ferritic theem 7. Yog li ntawd, txoj kev tshawb fawb ntawm microscopic domain zog ntawm cov yeeb yaj kiab mus rau theem ntawm cov qauv hluav taws xob tau dhau los ua qhov tseem ceeb rau kev nkag siab SDSS corrosion thiab yuav tsum muaj cov txheej txheem sim ua haujlwm nyuaj. Txog tam sim no, cov txheej txheem ntog-rhiab heev xws li Auger electron spectroscopy11 thiab X-ray photoelectron spectroscopy12,13,14,15 thiab nyuaj X-ray photoemission microscopy (HAX-PEEM)16 feem ntau ua tsis tiav los kuaj cov tshuaj sib txawv hauv cov txheej txheem saum npoo. chemical xeev ntawm tib lub caij nyob rau hauv ntau qhov chaw ntawm nanoscale qhov chaw. Ob peb cov kev tshawb fawb tsis ntev los no tau txheeb xyuas thaj tsam ntawm oxidation ntawm chromium nrog kev pom kev zoo ntawm austenitic stainless steels17, martensitic steels18 thiab SDSS19,20. Txawm li cas los xij, cov kev tshawb fawb no tau tsom mus rau cov txiaj ntsig ntawm Cr heterogeneity (piv txwv li, Cr3 + oxidation xeev) ntawm kev tiv thaiv corrosion. Lateral heterogeneity nyob rau hauv lub xeev oxidation ntawm cov ntsiab lus tuaj yeem tshwm sim los ntawm cov tebchaw sib txawv nrog tib lub ntsiab lus, xws li hlau oxides. Cov tebchaw no, uas tau txais ib qho me me raws li kev kho mob thermomechanical, yog nyob ze rau ib leeg, tab sis sib txawv ntawm cov muaj pes tsawg leeg thiab oxidation state16,21. Yog li ntawd, txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau oxide zaj duab xis thiab tom qab pitting, nws yog ib qho tsim nyog yuav tsum nkag siab txog qhov sib txawv ntawm qhov chaw ntawm qhov microscopic. Txawm hais tias cov kev xav tau no, kev kwv yees ntau yam xws li lateral heterogeneity nyob rau hauv oxidation, tshwj xeeb tshaj yog rau Fe ntawm nano- thiab atomic scale, tseem tsis muaj, thiab nws correlation nrog corrosion kuj tseem unexplored. Txog thaum tsis ntev los no, cov tshuaj hauv lub xeev ntawm ntau lub ntsiab lus, xws li Fe thiab Ca22, ntawm cov qauv hlau tau ua kom muaj nuj nqis siv cov khoom siv hluav taws xob xoo hluav taws xob (X-PEEM) hauv nanoscale synchrotron hluav taws xob chaw. Ua ke nrog chemically rhiab heev X-ray absorption spectroscopy (XAS), X-PEEM enables XAS ntsuas nrog siab spatial thiab spectral daws teeb meem, muab tshuaj cov ntaub ntawv hais txog cov muaj pes tsawg leeg ntawm cov ntsiab lus thiab lawv cov tshuaj lub xeev nrog spatial daws mus rau nees nkaum-peb nanometer scale. . Qhov kev soj ntsuam spectromicroscopic ntawm qhov pib no ua kom yooj yim rau kev soj ntsuam tshuaj hauv zos thiab tuaj yeem pom cov tshuaj hloov pauv hauv qhov chaw ntawm txheej hlau uas tsis tau tshawb xyuas yav dhau los.
Txoj kev tshawb no txuas ntxiv qhov zoo ntawm PEEM hauv kev tshawb xyuas cov tshuaj sib txawv ntawm nanoscale thiab nthuav qhia qhov kev pom zoo ntawm atomic-theem saum npoo ntawm kev tsom xam rau kev nkag siab txog tus cwj pwm corrosion ntawm Ce-2507. Nws siv ib pawg K-means24 chemometric mus kom ze los qhia txog cov tshuaj lom neeg thoob ntiaj teb (hetero) homogeneity ntawm cov ntsiab lus koom nrog, uas nws cov tshuaj tau nthuav tawm hauv cov ntaub ntawv txheeb cais. Nyob rau hauv sib piv rau corrosion pib los ntawm kev puas tsuaj ntawm cov chromium oxide zaj duab xis nyob rau hauv ib txwm cov ntaub ntawv, tsawg passivation thiab qis corrosion kuj yog tam sim no ntaus nqi mus rau lub zos Fe3 + nplua nuj nanoislands nyob ze Fe / Cr oxide txheej, uas tej zaum yuav muaj kev tiv thaiv. Cov oxide rhuav tshem cov yeeb yaj kiab dotted thiab ua rau corrosion.
Tus cwj pwm corrosive ntawm deformed SDSS 2507 yog thawj zaug soj ntsuam siv electrochemical ntsuas. Ntawm daim duab. Daim duab 1 qhia txog Nyquist thiab Bode nkhaus rau cov qauv xaiv hauv cov kua qaub (pH = 1) aqueous tov ntawm FeCl3 ntawm chav tsev kub. Cov electrolyte raug xaiv ua raws li tus neeg sawv cev oxidizing muaj zog, ua tus cwj pwm nyiam ntawm zaj duab xis passivation kom tawg. Txawm hais tias cov khoom siv tsis tau txais kev ruaj khov pitting ntawm chav tsev kub, qhov kev tshuaj ntsuam tau muab kev pom rau cov xwm txheej tsis ua haujlwm thiab tom qab corrosion. Qhov sib npaug Circuit Court (Daim duab 1d) tau siv los ua kom haum rau electrochemical impedance spectroscopy (EIS) spectrum, thiab cov txiaj ntsig sib haum tau pom nyob rau hauv Table 1. Cov semicircles tsis tiav tshwm sim hauv cov tshuaj kho thiab kub ua haujlwm, thaum compressed semicircles tshwm nyob rau hauv txias-dov counterparts. (Fig.1). Hauv EIS spectroscopy, lub vojvoog ntawm lub voj voog ntawm lub voj voog tuaj yeem suav tias yog qhov polarization tsis kam (Rp) 25,26. Rp ntawm kev daws-kho kev khiav dej num hauv Table 1 yog hais txog 135 kΩ cm-2, txawm li cas los xij, qhov tseem ceeb ntawm kev ua haujlwm kub thiab txias-kub khiav khiav yog qis dua, 34.7 thiab 2.1 kΩ cm-2, feem. Qhov kev txo qis hauv Rp no qhia txog kev cuam tshuam ntawm cov yas deformation ntawm passivation thiab corrosion kuj, raws li qhia nyob rau hauv cov ntaub ntawv dhau los 27,28,29,30.
ib tug Nyquist, b, c Bode impedance thiab theem daim duab, thiab d sib piv cov qauv Circuit Court sib npaug, qhov twg RS yog cov electrolyte tsis kam, Rp yog cov polarization tsis kam, thiab QCPE yog cov oxide ntawm cov theem tsis tu ncua siv los ua qauv tsis zoo tagnrho capacitance (n). Kev ntsuas EIS yog ua los ntawm qhov qhib qhov hluav taws xob.
Qhov sib npaug sib npaug tau pom nyob rau hauv Bode zajlus, nrog lub toj siab nyob rau hauv ntau zaus sawv cev rau cov electrolyte tsis kam RS26. Raws li qhov zaus txo qis, qhov impedance nce thiab pom lub kaum sab xis tsis zoo, qhia tias muaj peev xwm dominance. Lub kaum sab xis nce, khaws qhov siab tshaj plaws ntawm qhov ntau zaus, thiab tom qab ntawd txo qis (Daim duab 1c). Txawm li cas los xij, nyob rau hauv tag nrho peb qhov xwm txheej, qhov siab tshaj plaws no tseem tsawg dua 90 °, qhia tias tsis yog tus cwj pwm zoo tshaj plaws vim muaj kev cuam tshuam ntawm kev ua haujlwm. Yog li, QCPE tsis tu ncua theem lub caij (CPE) yog siv los sawv cev ntawm cov khoom siv hluav taws xob sib txuas uas tshwm sim los ntawm qhov chaw roughness lossis inhomogeneity, tshwj xeeb tshaj yog nyob rau hauv atomic scale, fractal geometry, electrode porosity, non-uniform potential, and geometry with the shape of electrodes31,32. CPE impedance:
qhov twg j yog tus lej xav txog thiab ω yog angular zaus. QCPE yog ib qho kev ywj pheej tsis tu ncua uas yog proportional rau qhov zoo qhib qhov chaw ntawm electrolyte. n yog ib tug dimensionless lub hwj chim tooj piav qhia txog qhov sib txawv ntawm lub capacitor los ntawm qhov zoo tshaj plaws capacitance, piv txwv li qhov ze n yog mus rau 1, qhov ze ntawm CPE yog kom ntshiab capacitive, thaum yog n yog ze rau xoom, nws zoo li resistive. Qhov sib txawv me me ntawm n, ze rau 1, qhia txog tus cwj pwm tsis zoo ntawm lub ntsej muag tom qab kev ntsuam xyuas polarization. QCPE ntawm txias dov SDSS yog siab dua li nws cov counterparts, txhais tau hais tias qhov saum npoo zoo tsis zoo li qub.
Raws li kev tiv thaiv corrosion feem ntau ntawm cov hlau tsis muaj steel, cov ntsiab lus siab Cr ntawm SDSS feem ntau ua rau muaj kev xeb zoo heev ntawm SDSS vim tias muaj cov yeeb yaj kiab tiv thaiv oxide nyob rau saum npoo 17. Cov yeeb yaj kiab zoo li no feem ntau yog nplua nuj hauv Cr3 + oxides thiab / lossis hydroxides, feem ntau yog ua ke nrog Fe2+, Fe3+ oxides thiab / lossis (oxy) hydroxides33. Txawm hais tias muaj qhov sib txawv ntawm qhov sib txawv, cov txheej txheej oxide passivating, thiab tsis pom qhov tawg tawg raws li kev ntsuas microscopic 6,7, tus cwj pwm corrosion ntawm kub ua hauj lwm thiab txias-dov SDSS yog txawv, yog li kev kawm tob ntawm cov yam ntxwv microstructural yog tsim nyog rau steel deformation.
Lub microstructure ntawm deformed stainless hlau yog quantitatively kawm siv intrinsic thiab synchrotron high-zog X-rays (Cov duab ntxiv 1, 2). Ib qho kev soj ntsuam ntxaws ntxaws muaj nyob rau hauv Cov Lus Qhia Ntxiv. Txawm hais tias muaj kev pom zoo dav dav ntawm hom theem loj, qhov sib txawv ntawm cov theem feem ntau tau pom, uas tau teev nyob rau hauv Cov Lus Qhia Ntxiv 1. Cov kev sib txawv no yuav yog vim cov theem tsis sib xws ntawm qhov chaw thiab hauv ntim, uas cuam tshuam los ntawm qhov sib txawv ntawm X-ray diffraction (XRD) nrhiav qhov tob. ) nrog lub zog sib txawv ntawm qhov xwm txheej photons34. Cov feem ntau austenite siab nyob rau hauv txias dov cov qauv txiav txim los ntawm XRD los ntawm ib lub chaw soj nstuam qhia tau hais tias zoo dua passivation thiab ces zoo corrosion kuj 35, thaum ntau qhov tseeb thiab statistical tshwm sim qhia tawm qhov sib txawv tiam sis nyob rau hauv theem feem. Tsis tas li ntawd, qhov corrosion kuj ntawm steel kuj nyob ntawm qib ntawm grain refinement, grain loj txo, nce nyob rau hauv microdeformations thiab dislocation ceev uas tshwm sim thaum lub sij hawm thermomechanical kev kho mob36,37,38. Cov qauv ua haujlwm kub tau pom tias muaj ntau yam zoo, qhia txog micron-loj nplej, thaum lub nplhaib du tau pom nyob rau hauv cov qauv txias-kuav los tiag (Ntxiv daim duab 3) tau qhia txog cov txiaj ntsig tseem ceeb rau nanosize hauv kev ua haujlwm dhau los. Qhov no yuav tsum nyiam cov yeeb yaj kiab passive. tsim thiab nce corrosion kuj. Qhov siab dua dislocation ntom feem ntau yog txuam nrog qis tsis kam rau pitting, uas pom zoo nrog kev ntsuas electrochemical.
Kev hloov pauv hauv cov tshuaj hauv lub xeev ntawm microdomains ntawm cov ntsiab lus tseem ceeb tau kawm txog kev siv X-PEEM. Txawm hais tias muaj ntau cov ntsiab lus alloying, Cr, Fe, Ni thiab Ce39 raug xaiv ntawm no, vim Cr yog lub hauv paus tseem ceeb rau kev tsim cov yeeb yaj kiab tsis zoo, Fe yog lub ntsiab tseem ceeb rau cov hlau, thiab Ni txhim kho passivation thiab sib npaug ntawm ferrite-austenitic theem. Cov qauv thiab kev hloov kho yog lub hom phiaj ntawm Ce. Los ntawm kev kho cov kab hluav taws xob synchrotron, XAS ntes cov yam ntxwv tseem ceeb ntawm Cr (L2.3 ntug), Fe (L2.3 ntug), Ni (L2.3 ntug), thiab Ce (M4.5 ntug) los ntawm qhov chaw. -2507 SWB. Kev txheeb xyuas cov ntaub ntawv tsim nyog tau ua los ntawm suav nrog kev ntsuas lub zog nrog cov ntaub ntawv luam tawm (xws li XAS ntawm Fe L2, 3 ribs40,41).
Ntawm daim duab. Daim duab 2 qhia X-PEEM dluab ntawm kub-ua hauj lwm (Fig. 2a) thiab txias-dov (Daim duab. 2d) Ce-2507 SDSS thiab coj XAS Cr thiab Fe L2,3 ntug ntawm ib tug zuj zus cim txoj hauj lwm. Lub L2,3 XAS ntug tshawb txog qhov tsis muaj 3d lub xeev ntawm electrons tom qab photoexcitation ntawm 2p3/2 (L3 edge) thiab 2p1/2 (L2 edge) spin-orbit splitting theem. Cov ntaub ntawv hais txog lub xeev valence ntawm Cr tau txais los ntawm X-ray diffraction tsom xam ntawm L2,3 ntug hauv daim duab 2b, d. Txuas kev sib piv. 42, 43 tau pom tias plaub lub ncov A (578.3 eV), B (579.5 eV), C (580.4 eV), thiab D (582.2 eV) tau pom nyob ze ntawm ntug L3, xav txog octahedral Cr3+ ions, sib xws Cr2O3. Cov kev sim spectra yog pom zoo nrog cov theoretical xam, raws li qhia nyob rau hauv panels b thiab e, tau los ntawm ntau yam siv lead ua teb xam ntawm Cr L2.3 interface siv ib tug siv lead ua teb ntawm 2.0 eV44. Ob qhov chaw ntawm kub ua hauj lwm thiab txias dov SDSS yog coated nrog ib tug kuj zoo li txheej ntawm Cr2O3.
a Thermal image of X-PEEM hot-formed SDSS corresponding to edge b Cr L2.3 and edge c Fe L2.3, d Thermal image X-PEEM of cold-rolled SDSS corresponding to edge e Cr L2.3 and f Fe L2.3 of side (e). XAS spectra plotted ntawm ntau yam spatial txoj hauj lwm cim rau ntawm thermal dluab (a, d) los ntawm cov txiv kab ntxwv dotted kab nyob rau hauv (b) thiab (e) sawv cev rau simulated XAS spectra ntawm Cr3+ nrog ib tug siv lead ua teb nqi ntawm 2.0 eV. Rau cov duab X-PEEM, lub thermal palette yog siv los txhim kho cov duab nyeem, qhov twg xim ntawm xiav mus rau liab yog proportional rau qhov siv ntawm X-ray nqus (los ntawm qis mus rau siab).
Txawm hais tias qhov chaw ib puag ncig ntawm cov khoom siv hlau no, cov tshuaj hauv lub xeev ntawm kev ntxiv ntawm Ni thiab Ce alloying ntsiab rau ob qho tib si cov qauv tseem zoo ib yam. Daim duab ntxiv. Ntawm daim duab. 5-9 qhia X-PEEM dluab thiab coj mus rau XAS spectra rau Ni thiab Ce ntawm ntau txoj haujlwm nyob rau saum npoo ntawm cov khoom ua haujlwm kub thiab txias. Ni XAS qhia lub xeev oxidation ntawm Ni2+ hla tag nrho qhov ntsuas ntawm qhov kub-ua haujlwm thiab txias-dov cov qauv (Kev Sib Tham Ntxiv). Nws yog ib qho tseem ceeb hais tias nyob rau hauv cov ntaub ntawv ntawm kub-ua hauj lwm specimens, lub XAS teeb liab ntawm Ce tsis pom, thaum lub spectrum ntawm Ce3 + ntawm txias-dov cov qauv yog pom nyob rau hauv ib tug taw tes. Kev soj ntsuam ntawm Ce me ntsis hauv cov qauv txias-dov tau pom tias Ce feem ntau muaj nyob rau hauv daim ntawv ntawm precipitates.
Nyob rau hauv thermally deformed SDSS, tsis muaj kev hloov pauv hauv zos hauv XAS tau pom ntawm Fe L2.3 ntug (Daim duab 2c). Txawm li cas los xij, raws li qhia hauv daim duab. 2f, Fe matrix microscopically hloov nws cov tshuaj hauv lub xeev ntawm xya qhov kev xaiv xaiv nyob rau hauv txias dov SDSS. Tsis tas li ntawd, txhawm rau kom tau txais lub tswv yim tseeb ntawm cov kev hloov pauv hauv lub xeev Fe ntawm cov chaw xaiv hauv daim duab 2f, cov kev tshawb fawb hauv cheeb tsam tau ua tiav (Fig. 3 thiab Supplementary Fig. 10) uas cov cheeb tsam me me raug xaiv. XAS spectra ntawm Fe L2,3 ntug ntawm α-Fe2O3 systems thiab Fe2+ octahedral oxides tau ua qauv siv multiplet siv lead ua teb suav nrog siv lead ua teb ntawm 1.0 (Fe2+) thiab 1.0 (Fe3+)44. Peb nco ntsoov tias α-Fe2O3 thiab γ-Fe2O3 muaj qhov sib txawv hauv zos symmetries45,46, Fe3O4 muaj kev sib xyaw ntawm Fe2+ & Fe3+,47, thiab FeO45 raws li kev sib txawv ntawm Fe2+ oxide (3d6). Peb nco ntsoov tias α-Fe2O3 thiab γ-Fe2O3 muaj qhov sib txawv hauv zos symmetries45,46, Fe3O4 muaj kev sib xyaw ntawm Fe2+ & Fe3+,47, thiab FeO45 raws li kev sib txawv ntawm Fe2+ oxide (3d6).Nco ntsoov tias α-Fe2O3 thiab γ-Fe2O3 muaj qhov sib txawv hauv zos symmetries45,46, Fe3O4 ua ke ob qho tib si Fe2+ thiab Fe3+,47 thiab FeO45 nyob rau hauv daim ntawv ntawm formal divalent oxide Fe2+ (3d6).Nco ntsoov tias α-Fe2O3 thiab γ-Fe2O3 muaj qhov sib txawv hauv zos symmetries45,46, Fe3O4 muaj kev sib txuas ntawm Fe2+ thiab Fe3+,47 thiab FeO45 ua raws li kev sib txawv ntawm Fe2+ oxide (3d6). Tag nrho Fe3 + ions hauv α-Fe2O3 tsuas muaj Oh txoj haujlwm, thaum γ-Fe2O3 feem ntau yog qhia raws li Fe3+ t2g [Fe3 + 5/3V1/3]eg O4 spinel nrog cov chaw ua haujlwm hauv xws li txoj haujlwm. Yog li, Fe3 + ions hauv γ-Fe2O3 muaj ob txoj haujlwm Td thiab Oh. Raws li tau hais hauv kev ua haujlwm dhau los, txawm hais tias qhov kev siv zog ntawm ob qhov sib txawv, lawv qhov kev siv qhov sib piv piv txwv li / t2g yog ≈1, thaum nyob rau hauv cov ntaub ntawv no qhov pom kev siv piv piv txwv li / t2g yog hais txog 1. Qhov no txwv tsis pub muaj tsuas yog Fe3+ nyob rau hauv cov ntaub ntawv no. Xav txog cov ntaub ntawv ntawm Fe3O4 nrog kev sib txuas ntawm Fe2+ thiab Fe3+, nws paub tias qhov tsis muaj zog (muaj zog) thawj zaug hauv L3 ntug ntawm Fe qhia tias qhov me me (ntau dua) tsis nyob hauv lub xeev t2g. Qhov no siv rau Fe2+ (Fe3+), uas qhia txog kev nce hauv thawj lub cim qhia txog kev nce hauv cov ntsiab lus ntawm Fe2 + 47. Cov txiaj ntsig no qhia tau tias Fe2 + thiab γ-Fe2O3, α-Fe2O3 thiab / lossis Fe3O4 predominate nyob rau hauv qhov chaw txias-dov ntawm cov khoom sib xyaw.
Enlarged photoemission electron thermal dluab ntawm (a, c) thiab (b, d) XAS spectra hla Fe L2,3 ntug ntawm ntau qhov chaw nyob hauv cheeb tsam xaiv 2 thiab E hauv daim duab. 2d ib.
Cov ntaub ntawv tau txais kev sim (Fig. 4a thiab Supplementary Fig. 11) tau npaj thiab muab piv nrog cov ntshiab compounds 40, 41, 48. Yeej, peb hom sib txawv ntawm kev sim pom Fe L-edge XAS spectra (XAS-1, XAS-2 thiab XAS-3: Fig. 4a) tau pom qhov chaw sib txawv. Tshwj xeeb, ib qho spectrum zoo ib yam li 2-a (xws li XAS-1) hauv daim duab 3b tau pom nyob rau tag nrho cheeb tsam ntawm kev txaus siab, ua raws li 2-b spectrum (labeled XAS-2), thaum lub spectrum zoo ib yam li E-3 tau pom hauv daim duab. 3d (xws li XAS-3) tau pom nyob hauv qee qhov chaw nyob. Feem ntau, plaub qhov ntsuas yog siv los txheeb xyuas cov xeev valence tam sim no hauv cov qauv sojntsuam: (1) L3 thiab L2 spectral nta, (2) lub zog ntawm L3 thiab L2 nta, (3) L3-L2 lub zog sib txawv, (4) L2 siv piv / L3. Raws li kev soj ntsuam pom (Daim duab 4a), tag nrho peb Fe Cheebtsam, uas yog Fe0, Fe2+, thiab Fe3+, muaj nyob rau saum npoo ntawm SDSS kawm. Qhov ntsuas qhov sib piv L2 / L3 kuj tau qhia tias muaj tag nrho peb yam.
Ib qho kev sib txawv ntawm peb qhov kev sim cov ntaub ntawv (cov kab khoom XAS-1, XAS-2 thiab XAS-3 sib raug rau 2-a, 2-b thiab E-3 hauv daim duab 2 thiab daim duab 3) piv rau simulated XAS Comparison spectra, octahedrons Fe2+, Fe3+, crystal field values ​​. 0 eof V. b-d Cov ntaub ntawv ntsuas kev ntsuas (XAS-1, XAS-2, XAS-3) thiab cov ntaub ntawv zoo LCF cov ntaub ntawv (khoom dub kab), thiab kev sib piv XAS-3 spectra nrog Fe3O4 (mixed xeev ntawm Fe) thiab Fe2O3 (ntshiab Fe3+) qauv.
Ib qho kev sib xyaw ua ke (LCF) haum ntawm peb tus qauv 40,41,48 tau siv los ntsuas qhov muaj pes tsawg leeg ntawm cov hlau oxide. LCF tau siv rau peb xaiv Fe L-edge XAS spectra uas qhia qhov sib txawv siab tshaj plaws, xws li XAS-1, XAS-2 thiab XAS-3, raws li qhia hauv daim duab 4b-d. Rau LCF fittings, 10% Fe0 tau txiav txim siab nyob rau hauv tag nrho cov rooj plaub vim lub me ledge peb pom nyob rau hauv tag nrho cov ntaub ntawv thiab qhov tseeb hais tias ferrous hlau yog lub ntsiab ntawm cov hlau. Qhov tseeb, qhov tob ntawm kev soj ntsuam ntawm X-PEEM rau Fe (~ 6 nm) 49 yog qhov loj dua li qhov kwv yees oxidation txheej tuab (me ntsis> 4 nm), tso cai rau kev tshawb pom cov teeb liab los ntawm cov hlau matrix (Fe0) hauv qab txheej passivation. Qhov tseeb, qhov tob ntawm kev soj ntsuam ntawm X-PEEM rau Fe (~ 6 nm) 49 yog qhov loj dua li qhov kwv yees oxidation txheej tuab (me ntsis> 4 nm), tso cai rau kev tshawb pom cov teeb liab los ntawm cov hlau matrix (Fe0) hauv qab txheej passivation. Действительно, пробная глубина X-PEEM для Fe (~ 6 нм)49 больше, чем предполагаемая толщмна слоя 4 яки ( что позволяет обнаружить сигнал от железной матрицы (Fe0) под пассивирующим слоем. Qhov tseeb, qhov kev sojntsuam X-PEEM qhov tob rau Fe (~ 6 nm) 49 yog ntau dua li qhov xav tau ntawm cov txheej txheem oxidation (me ntsis> 4 nm), uas ua rau nws muaj peev xwm txheeb xyuas cov teeb liab los ntawm cov hlau matrix (Fe0) hauv qab txheej passivation.Qhov tseeb, X-PEEM pom Fe (~ 6 nm) 49 ntxaum tshaj li qhov xav tau tuab ntawm oxide txheej (tsuas yog tshaj 4 nm), tso cai rau kev tshawb pom cov teeb liab los ntawm cov hlau matrix (Fe0) hauv qab txheej passivation. Ntau qhov sib xyaw ua ke ntawm Fe2+ thiab Fe3+ tau ua tiav los nrhiav kev daws teeb meem zoo tshaj plaws rau cov ntaub ntawv soj ntsuam pom. Ntawm daim duab. Daim duab 4b qhia txog kev sib xyaw ntawm Fe2+ thiab Fe3+ hauv XAS-1 spectrum, qhov twg cov proportions ntawm Fe2+ thiab Fe3+ nyob ze, kwv yees li 45%, uas qhia txog kev sib xyaw oxidation xeev ntawm Fe. Whereas rau XAS-2 spectrum, qhov feem pua ​​​​ntawm Fe2+ thiab Fe3+ dhau los ua ~ 30% thiab 60%, feem. Cov ntsiab lus ntawm Fe2 + yog qis dua li ntawm Fe3+. Fe2 + rau Fe3 piv ntawm 1: 2 txhais tau hais tias Fe3O4 tuaj yeem tsim ntawm tib qhov piv ntawm Fe ions. Tsis tas li ntawd, rau XAS-3 spectrum, feem pua ​​​​ntawm Fe2+ thiab Fe3+ hloov mus rau ~ 10% thiab 80%, qhia txog kev hloov dua siab tshiab ntawm Fe2+ rau Fe3+. Raws li tau hais los saum no, Fe3 + tuaj yeem los ntawm α-Fe2O3, γ-Fe2O3 lossis Fe3O4. Txhawm rau nkag siab txog qhov yuav tshwm sim ntawm Fe3+, XAS-3 spectra yog npaj nrog rau ntau yam Fe3+ cov qauv hauv daim duab 4e qhia qhov zoo sib xws nrog txhua tus qauv thaum Peak B raug txiav txim siab. Txawm li cas los xij, qhov kev siv ntawm lub xub pwg nyom (A: los ntawm Fe2 +) thiab qhov sib piv ntawm B / A qhia tias qhov spectrum ntawm XAS-3 nyob ze tab sis tsis zoo ib yam li ntawm γ-Fe2O3. Piv rau tej γ-Fe2O3, Fe 2p XAS kev siv ntawm A SDSS ncov yog me ntsis siab dua (Fig. 4e), uas qhia tau hais tias ntau dua Fe2+ siv. Txawm hais tias lub spectrum ntawm XAS-3 zoo ib yam li ntawm γ-Fe2O3, qhov twg Fe3 + yog tam sim no nyob rau hauv ob lub Oh thiab Td txoj hauj lwm, kev txheeb xyuas ntawm txawv valence xeev thiab kev sib koom tes tsuas yog los ntawm lub L2,3 ntug los yog lub L2 / L3 siv piv yog tseem muaj teeb meem. ib lub ntsiab lus rov tshwm sim ntawm kev sib tham vim qhov nyuaj ntawm ntau yam cuam tshuam nrog qhov kawg spectrum41.
Ntxiv rau qhov spectral kev ntxub ntxaug ntawm cov tshuaj xeev ntawm cov cheeb tsam xaiv ntawm kev txaus siab tau piav qhia saum toj no, lub ntiaj teb tshuaj lom neeg heterogeneity ntawm cov ntsiab lus tseem ceeb Cr thiab Fe raug soj ntsuam los ntawm kev faib tag nrho XAS spectra tau txais ntawm cov qauv saum npoo siv K- txhais tau tias kev sib koom ua ke. Cov ntug profiles Cr L tau teeb tsa nyob rau hauv ib txoj kev xws li tsim ob qhov kev pom zoo ntawm pawg spatially faib nyob rau hauv cov khoom kub-ua hauj lwm thiab txias-dov cov qauv qhia hauv Fig. 5. Nws yog qhov tseeb tias tsis muaj kev hloov pauv hauv zos tau pom, txij li ob lub centroids ntawm XAS Cr spectra zoo sib xws. Cov duab spectral ntawm ob pawg no yuav luag zoo ib yam rau cov sib xws rau Cr2O342, uas txhais tau hais tias Cr2O3 cov khaubncaws sab nraud povtseg kuj sib npaug ntawm SDSS.
ib pawg ntawm K- txhais tau tias L-edge Cr cheeb tsam, b sib xws XAS centroids. Cov txiaj ntsig ntawm K- txhais tau tias X-PEEM kev sib piv ntawm txias-dov SDSS: c pawg ntawm K-txhais tau tias ntug cheeb tsam ntawm Cr L2,3 thiab d sib thooj XAS centroids.
Txhawm rau ua piv txwv FeL ntug daim ntawv qhia nyuaj, plaub thiab tsib pawg ua kom zoo dua qub thiab lawv cov centroids cuam tshuam (spectral distributions) yog siv rau cov khoom kub ua hauj lwm thiab txias-dov, raws li. Yog li ntawd, qhov feem pua ​​​​(%) ntawm Fe2+ thiab Fe3+ tuaj yeem tau txais los ntawm kev kho cov LCF qhia hauv daim duab.4. Lub peev xwm pseudoelectrode Epseudo ua haujlwm ntawm Fe0 tau siv los nthuav tawm cov microchemical inhomogeneity ntawm cov oxide zaj duab xis saum npoo. Epseudo yog kwv yees kwv yees los ntawm txoj cai sib xyaw,
where \(\rm{E}_{\rm{Fe}/\rm{Fe}^{2 + (3 + )}}\) equals \(\rm{Fe} + 2e^ – \to\rm { Fe}^{2 + (3 + )}\), which is 0.440 and 0.036 V, respectively. Cov cheeb tsam uas muaj peev xwm qis dua muaj cov ntsiab lus siab dua ntawm Fe3+ cov tebchaw. Lub peev xwm faib nyob rau hauv cov qauv thermally deformed muaj cov cim txheej nrog qhov kev hloov siab tshaj plaws ntawm 0.119 V (Fig. 6a,b). Qhov kev faib tawm muaj peev xwm no muaj feem cuam tshuam nrog qhov chaw saum npoo av (Fig. 6a). Tsis muaj lwm yam kev hloov pauv ntawm txoj haujlwm tau pom nyob rau hauv lub hauv paus lamellar sab hauv (Fig. 6b). Ntawm qhov tsis sib xws, rau kev sib xyaw ntawm cov oxides sib txawv nrog cov ntsiab lus sib txawv ntawm Fe2+ thiab Fe3+ hauv cov khaub thuas dov SDSS, qhov tsis sib xws ntawm cov pseudopotential tuaj yeem pom (Daim duab 6c, d). Fe3 + oxides thiab / lossis (oxy) hydroxides yog cov khoom tseem ceeb ntawm corrosion nyob rau hauv steel thiab permeable rau oxygen thiab dej 50. Hauv qhov no, nws tuaj yeem pom tias cov Islands tuaj nplua nuj hauv Fe3 + tau muab faib rau hauv zos thiab tuaj yeem suav tias yog thaj chaw corrosion. Nyob rau hauv cov ntaub ntawv no, lub gradient nyob rau hauv lub peev xwm teb, es tsis yog tus nqi ntawm lub peev xwm, yuav suav hais tias yog ib qho kev qhia rau lub localization ntawm active corrosion regions51. Qhov no inhomogeneous faib ntawm Fe2 + thiab Fe3 + nyob rau saum npoo ntawm txias dov SDSS tuaj yeem hloov cov tshuaj lom neeg hauv zos thiab muab thaj chaw zoo dua hauv oxide zaj duab xis tawg thiab xeb, yog li tso cai rau lub hauv paus hlau matrix mus txuas ntxiv corrode, ua rau inhomogeneity. thiab txo cov yam ntxwv tiv thaiv ntawm txheej passivating.
K-mean pawg ntawm Fe L2,3 ntug cheeb tsam thiab sib thooj XAS centroids rau a-c kub-ua haujlwm X-PEEM thiab d-f txias-dov SDSS. a, d K-txhais tau tias pawg phiaj xwm sib tshooj ntawm X-PEEM duab. Kev kwv yees pseudoelectrode muaj peev xwm (epseudo) tau hais nrog rau K-txhais tau cov duab kos. Lub ci ci ntawm X-PEEM duab xws li cov xim hauv daim duab 2 yog ncaj qha proportional rau X-ray absorption siv.
Qhov sib txawv ntawm Cr tab sis cov tshuaj sib txawv ntawm Fe ua rau cov keeb kwm sib txawv ntawm oxide zaj duab xis tawg thiab corrosion qauv hauv kub dov thiab txias dov Ce-2507. Cov cuab yeej no ntawm txias dov Ce-2507 yog paub zoo. Hais txog kev tsim cov oxides thiab hydroxides ntawm Fe nyob rau hauv atmospheric huab cua, cov nram qab no cov tshuaj tiv thaiv raug kaw nyob rau hauv no ua hauj lwm raws li qhov nruab nrab cov tshuaj tiv thaiv:
Raws li kev ntsuas ntawm X-PEEM, cov tshuaj tiv thaiv saum toj no tshwm sim hauv cov xwm txheej hauv qab no. Lub xub pwg me me sib xws rau Fe0 yog txuam nrog cov hlau hauv qab hlau. Cov tshuaj tiv thaiv ntawm cov hlau Fe nrog ib puag ncig ua rau tsim cov Fe (OH) 2 txheej (kev sib npaug (5)), uas ua kom nrov Fe2+ teeb liab hauv XAS ntawm L ntug ntawm Fe. Lub sijhawm ntev ntawm huab cua yuav ua rau tsim Fe3O4 thiab / lossis Fe2O3 oxides tom qab Fe (OH) 252,53. Ob hom ruaj khov Fe, Fe3O4 thiab Fe2O3, kuj tuaj yeem tsim nyob rau hauv Cr3 + nplua nuj txheej tiv thaiv, qhov twg Fe3O4 nyiam cov qauv zoo sib xws thiab cohesive. Lub xub ntiag ntawm ob qho tib si tshwm sim hauv cov xeev sib xyaw oxidation (XAS-1 spectrum). XAS-2 spectrum feem ntau sib raug rau Fe3O4. Thaum XAS-3 spectra pom ntawm ob peb txoj haujlwm qhia ua tiav kev hloov pauv mus rau γ-Fe2O3. Txij li cov X-rays tsis muaj qhov tob tob ntawm kwv yees li 50 nm, cov teeb liab los ntawm cov txheej hauv qab ua rau muaj kev siv ntau dua ntawm A ncov.
XRD spectrum qhia tau hais tias Fe tivthaiv hauv oxide zaj duab xis muaj txheej txheej txheej, uas yog ua ke nrog Cr oxide txheej. Nyob rau hauv sib piv rau passivation yam ntxwv ntawm corrosion vim lub zos inhomogeneity ntawm Cr2O317, txawm lub uniform txheej ntawm Cr2O3 nyob rau hauv txoj kev tshawb no, tsis tshua muaj corrosion kuj tau pom nyob rau hauv cov ntaub ntawv no, tshwj xeeb tshaj yog rau cov qauv txias-dov. Cov cwj pwm pom tau tuaj yeem nkag siab tias qhov heterogeneity ntawm cov tshuaj oxidation lub xeev ntawm txheej sab saum toj (Fe) cuam tshuam rau kev ua haujlwm corrosion. Kev hloov qeeb ntawm cov hlau lossis cov pa oxygen ions hauv cov lattice vim yog tib lub stoichiometry ntawm sab sauv (Fe oxide) thiab cov khaubncaws sab nraud povtseg (Cr oxide) 52,53 ua rau muaj kev sib raug zoo (adhesion) ntawm lawv. Qhov no, nyob rau hauv lem, txhim kho corrosion kuj. Yog li ntawd, txuas ntxiv stoichiometry, piv txwv li ib lub xeev oxidation ntawm Fe, yog qhov zoo dua rau kev hloov pauv sai ntawm stoichiometric. Thermally deformed SDSS muaj qhov sib txawv ntau dua thiab cov txheej txheem tiv thaiv denser, uas muab kev tiv thaiv corrosion zoo dua. Txawm li cas los xij, rau SDSS txias, qhov muaj Fe3 +-nplua nuj Islands tuaj nyob rau hauv cov txheej txheem tiv thaiv ua rau kev ncaj ncees ntawm qhov chaw thiab ua rau galvanic corrosion ntawm cov substrate nyob ze, uas ua rau txo qis Rp (Table 1) hauv EIS spectra thiab nws corrosion. tsis kam. Yog li ntawd, hauv zos faib cov Islands tuaj nplua nuj nyob rau hauv Fe3+ vim yog cov yas deformation feem ntau cuam tshuam rau kev ua haujlwm corrosion, uas yog qhov ua tiav hauv txoj haujlwm no. Yog li, txoj kev tshawb no nthuav tawm spectromicrographs ntawm qhov txo qis hauv corrosion kuj vim cov yas deformation ntawm SDSS cov qauv kawm.
Tsis tas li ntawd, thaum lub ntiaj teb tsis tshua muaj alloying nyob rau hauv dual-theem steels ua tau zoo dua, kev sib cuam tshuam ntawm cov khoom ntxiv no nrog tus neeg hlau matrix nyob rau hauv cov nqe lus ntawm corrosion cwj pwm tseem tsis yooj yim raws li spectroscopic microscopy soj ntsuam. Lub teeb liab Ce (raws li XAS M-ntug) tsuas yog tshwm sim ntawm ob peb txoj haujlwm thaum lub caij txias dov, tab sis ploj thaum lub sij hawm kub deformation ntawm SDSS, qhia tias lub zos deposition ntawm Ce nyob rau hauv lub steel matrix es tsis txhob ntawm homogeneous alloying. Txawm hais tias cov khoom siv kho tshuab ntawm SDSS tsis tau txhim kho 6,7, lub xub ntiag ntawm REE txo qhov loj ntawm kev suav nrog thiab xav tias yuav txwv pitting ntawm lub hauv paus chiv keeb54.
Hauv kev xaus, qhov haujlwm no nthuav tawm cov txiaj ntsig ntawm qhov chaw heterogeneity ntawm qhov corrosion ntawm 2507 SDSS hloov nrog cerium los ntawm kev txheeb xyuas cov ntsiab lus tshuaj ntawm cov khoom siv nanoscale. Peb teb cov lus nug ntawm yog vim li cas stainless hlau corrodes txawm thaum coated nrog ib tug tiv thaiv oxide txheej los ntawm quantitatively kawm lub microstructure, tshuaj lub xeev ntawm nto nta thiab teeb liab ua siv K- txhais tau tias pawg. Nws tau raug tsim los hais tias Fe3+-nplua nuj Islands tuaj, suav nrog lawv cov octahedral thiab tetrahedral kev sib koom ua ke thoob plaws hauv cov qauv sib xyaw Fe2 + / Fe3+, yog qhov chaw ntawm oxide zaj duab xis puas tsuaj thiab ib qho chaw ntawm corrosion ntawm txias dov SDSS. Nanoislands dominated los ntawm Fe3 + ua rau tsis zoo corrosion kuj txawm nyob rau hauv lub xub ntiag ntawm ib tug txaus stoichiometric Cr2O3 passivating txheej. Ntxiv rau cov txheej txheem kev nce qib hauv kev txiav txim siab cov txiaj ntsig ntawm nanoscale chemical heterogeneity ntawm corrosion, txoj haujlwm tam sim no yuav tsum txhawb nqa cov txheej txheem engineering los txhim kho corrosion kuj ntawm stainless hlau thaum lub sij hawm steelmaking.
Txhawm rau npaj cov Ce-2507 SDSS ingots siv hauv txoj kev tshawb no, cov khoom sib xyaw, suav nrog Fe-Ce master alloy kaw nrog cov hlau ntshiab, tau yaj hauv 150 kg nruab nrab zaus induction rauv los tsim cov hlau molten thiab nchuav rau hauv cov pwm pwm. Qhov ntsuas tshuaj muaj pes tsawg leeg (wt %) yog teev nyob rau hauv Cov Lus Qhia Ntxiv 2. Lub ingot yog thawj zaug kub tsim rau hauv cov blocks. Tom qab ntawd cov hlau yog annealed ntawm 1050 ° C rau 60 feeb mus rau ib qho kev daws teeb meem, thiab tom qab ntawd quenched hauv dej rau chav tsev kub. Cov qauv kawm tau kawm hauv kev nthuav dav siv TEM thiab DOE los kawm cov theem, qhov loj me thiab morphology. Cov ncauj lus kom ntxaws ntxiv txog cov qauv thiab cov txheej txheem tsim khoom tuaj yeem pom hauv lwm qhov chaw 6,7.
Cov txheej txheem cylindrical qauv (φ10 mm × 15 mm) rau kub nias nrog lub axis ntawm lub tog raj kheej mus rau lub deformation kev taw qhia ntawm lub block. High-temperature compression tau ua nyob rau ntawm qhov tsis tu ncua ntawm tus nqi ntawm 0.01-10 s-1 ntawm ntau qhov kub thiab txias hauv thaj tsam ntawm 1000-1150 ° C siv Gleeble-3800 thermal simulator. Ua ntej deformation, cov qauv tau muab tso rau hauv qhov ntsuas kub ntawm qhov ntsuas ntawm 10 ° C s-1 rau 2 min kom tshem tawm qhov kub ntawm gradient. Tom qab ua tiav qhov ntsuas kub tsis sib xws, cov qauv raug deformed mus rau qhov tseeb tus nqi ntawm 0.7. Tom qab deformation, nws yog tam sim ntawd quenched nrog dej kom tswj lub deformed qauv. Tom qab ntawd lub hardened specimens raug txiav thaum uas tig mus rau cov kev taw qhia ntawm compression. Rau qhov kev tshawb fawb tshwj xeeb no, peb tau xaiv cov qauv thermally deformed ntawm 1050 ° C, 10 s-1 vim muaj kev soj ntsuam ntau dua microhardness dua li lwm cov qauv 7.
Bulk (80 × 10 × 17 mm3) cov qauv ntawm cov khoom siv Ce-2507 tau sim ntawm peb-theem asynchronous ob-yob deformation tshuab LG-300, uas muab cov cuab yeej zoo tshaj plaws ntawm tag nrho lwm cov chav kawm deformation6. Tus nqi strain thiab thickness txo yog 0.2 m·s-1 thiab 5% rau txhua txoj kev, feem.
Ib qho Autolab PGSTAT128N electrochemical workstation tau siv los ntsuas electrochemically ntsuas SDSS tom qab txias dov mus rau 90% thickness txo (1.0 sib npaug qhov tseeb hom) thiab kub nias rau 0.7 muaj tseeb hom ntawm 1050 oC thiab 10 s-1. Lub chaw ua haujlwm muaj peb-electrode cell nrog cov calomel saturated electrode raws li cov khoom siv electrode, graphite counter electrode, thiab cov qauv SDSS ua cov electrode ua haujlwm. Cov qauv raug txiav rau hauv lub tog raj kheej nrog txoj kab uas hla ntawm 11.3 hli, mus rau sab ntawm cov xov tooj tooj liab tau soldered. Tom qab ntawd cov qauv tau nchuav nrog epoxy resin, tawm hauv qhov chaw ua haujlwm qhib ntawm 1 cm2 raws li cov khoom siv hluav taws xob ua haujlwm (qhov qis dua ntawm cov qauv cylindrical). Siv kev saib xyuas thaum kho cov epoxy thiab tom qab xuab zeb thiab polishing kom tsis txhob tawg. Qhov chaw ua hauj lwm yog lapped thiab polished nrog lub pob zeb diamond polishing ncua kev kawm ntawv nrog ib tug particle loj ntawm 1 micron, ntxuav nrog distilled dej thiab ethanol thiab qhuav nyob rau hauv cov huab cua txias. Ua ntej kev ntsuas electrochemical, cov qauv polished tau raug rau huab cua rau ob peb hnub los tsim cov oxide zaj duab xis. Cov tshuaj aqueous ntawm FeCl3 (6.0 wt.%), stabilized nrog HCl rau pH = 1.0 ± 0.01, tau siv los ua kom cov corrosion ntawm stainless hlau 55, vim nws pom nyob rau hauv ib puag ncig hnyav uas muaj chloride ions tam sim no nrog lub zog oxidizing thiab qis pH raws li teev los ntawm ASTM. Cov qauv tsim yog G48 thiab A923. Cov qauv tau muab tso rau hauv qhov kev sim tshuaj rau 1 teev ua ntej kev ntsuas tau coj mus rau hauv lub xeev ze rau qhov chaw ruaj khov. Rau cov kev daws teeb meem, cov qauv ua haujlwm kub thiab txias txias, qhov ntsuas impedance zaus yog 1 × 105 ~ 0.1 Hz, thiab qhov qhib-circuit muaj peev xwm (OPS) yog 5 mV, uas yog 0.39, 0.33, thiab 0.25 VSCE, feem. Txhua qhov kev ntsuam xyuas electrochemical ntawm ib qho qauv tau rov ua dua tsawg kawg peb zaug nyob rau hauv tib lub sijhawm los xyuas kom meej cov ntaub ntawv rov tsim dua tshiab.
Rau HE-SXRD kev ntsuas, 1 × 1 × 1.5 mm3 duab plaub duplex steel blocks tau ntsuas ntawm lub zog siab Brockhouse wiggler kab ntawm CLS, Canada kom muaj nuj nqis ntawm theem kev sib xyaw56. Kev sau cov ntaub ntawv tau ua nyob rau hauv chav tsev kub hauv Debye-Scherrer geometry lossis thauj geometry. Lub wavelength ntawm X-rays calibrated rau LaB6 calibrant yog 0.212561 Å, uas sib haum mus rau 58 keV, uas yog ntau dua li Cu Kα (8 keV) feem ntau siv los kuaj X-ray qhov chaw. Cov qauv yog muab tso rau ntawm qhov deb ntawm 740 mm los ntawm lub detector. Qhov ntsuas qhov ntim ntawm txhua tus qauv yog 0.2 × 0.3 × 1.5 mm3, uas yog txiav txim siab los ntawm cov nqaj loj thiab cov qauv tuab. Txhua qhov ntawm cov ntaub ntawv no tau sau los ntawm Perkin Elmer cheeb tsam ntes, tiaj tus X-ray ntes, 200 µm pixels, 40 × 40 cm2, siv lub sijhawm raug 0.3 vib nas this thiab 120 ntas.
X-PEEM kev ntsuas ntawm ob lub qauv xaiv tau ua tiav ntawm PEEM kawg chaw nres tsheb ntawm Beamline MAXPEEM kab hauv MAX IV lub chaw kuaj mob (Lund, Sweden). Cov qauv tau npaj ib yam li rau kev ntsuas electrochemical. Cov qauv npaj tau khaws cia hauv huab cua rau ob peb hnub thiab degassed hauv lub tshuab nqus tsev ultrahigh ua ntej raug irradiated nrog synchrotron photons. Lub zog daws teeb meem ntawm cov nqaj yog tau los ntawm kev ntsuas cov ion tso zis spectrum ntawm N 1 s mus rau 1 \ (\ pi _g^ \ast\) ntawm thaj av excitation nrog hv = 401 eV hauv N2 thiab kev vam khom ntawm photon zog ntawm E3/2.57. Spectral haum muab ΔE (spectral linewidth) ~ 0.3 eV tshaj qhov ntsuas lub zog. Yog li ntawd, lub beamline zog daws teeb meem yog kwv yees li E / ∆E = 700 eV / 0.3 eV > 2000 thiab flux ≈1012 ph/s los ntawm kev siv ib tug modified SX-700 monochromator nrog ib tug Si 1200-kab mm−1 grating rau Fe ntug 2p, L2 Crp, 3 ntug 2p, L2, L2,3 ntug, thiab Ce M4,5 ntug. Yog li ntawd, lub beamline zog daws teeb meem yog kwv yees li E / ∆E = 700 eV / 0.3 eV > 2000 thiab flux ≈1012 ph/s los ntawm kev siv ib tug hloov SX-700 monochromator nrog ib tug Si 1200-kab mm−1 grating rau Fe ntug, 2p L2 Cr 3. L2.3 ntug, thiab Ce M4.5 ntug. Таким образом, энергетическое разрешение канала пучка было оценено как E/∆E = 700 эВ/0,3 э∉ 2000 от 2000 и 2000 при использовании модифицированного монохроматора SX-700 с решеткой Si 1200 штрихов/мм для Fe кромка, 2p, 2 кромка, 2p, L2, 2 кромка Ni 2p L2,3 и кромка Ce M4,5. Yog li, lub zog daws teeb meem ntawm cov kab teeb tsa tau kwv yees li E / ∆E = 700 eV / 0.3 eV> 2000 thiab flux ≈1012 f / s siv qhov hloov kho SX-700 monochromator nrog Si grating ntawm 1200 kab / hli rau Fe edge 2p L2 edge . L2.3, Ce edge M4.5.因此，光束线能量分辨率估计为E/ΔE = 700 eV/0.3 eV > 2000 和通量≈1012 ph/s 通过乽用单色器和Si 1200 线mm−1 光栅用于Fe 2p L2,3 边缘、Cr 2p L2,3 边缘、Ni 2p L2,3 边缘和Ce M4,5因此 ， 光束线 能量 分辨率 为 为 δe = 700 EV/0.3 EV> 2000 和 ≈1012 PH/S 通0X过单色器 和 SI 1200 线 mm-1 光栅 于 Fe 2P 2P 2P L2.3 边缘、Cr 2p L2.3 边缘、Ni 2p L2.3 边缘 缘 。Yog li, thaum siv hloov kho SX-700 monochromator thiab 1200 kab Si grating. 3, Cr edge 2p L2.3, Ni edge 2p L2.3 thiab Ce edge M4.5.Tshaj tawm lub zog photon hauv 0.2 eV cov kauj ruam. Ntawm txhua lub zog, PEEM cov duab raug kaw siv lub TVIPS F-216 CMOS ntes nrog 2 x 2 binning fiber optic kev sib txuas muab 1024 × 1024 pixels hauv 20 µm thaj chaw saib. Lub sij hawm raug ntawm cov duab yog 0.2 vib nas this, nruab nrab 16 ntas. Lub photoelectron duab zog yog xaiv nyob rau hauv xws li ib txoj kev raws li muab lub siab tshaj plaws thib ob electron teeb liab. Tag nrho cov kev ntsuas yog ua nyob rau hauv ib txwm tshwm sim ntawm ib tug linearly polarized photon beam. Yog xav paub ntxiv txog kev ntsuas, saib kev kawm yav dhau los58. Tom qab kawm tag nrho cov txiaj ntsig hluav taws xob (TEY) 59 hom kev kuaj pom thiab nws daim ntawv thov hauv X-PEEM, qhov ntsuas qhov tob ntawm txoj kev no kwv yees li ntawm ~ 4-5 nm rau Cr teeb liab thiab ~ 6 nm rau Fe teeb liab. Lub Cr qhov tob yog ze heev rau oxide zaj duab xis thickness (~ 4 nm) 60,61 thaum lub Fe qhov tob yog loj dua oxide zaj duab xis thickness. XAS sau ze ntawm Fe L ntug yog sib xyaw ntawm hlau oxide XAS thiab FeO los ntawm matrix. Nyob rau hauv thawj rooj plaub, qhov kev siv ntawm cov emitted electrons yog vim tag nrho cov muaj peev xwm ntawm electrons pab rau TEY. Txawm li cas los xij, lub teeb liab hlau ntshiab yuav tsum muaj lub zog kinetic ntau dua rau cov hluav taws xob kom dhau los ntawm cov txheej txheem oxide, ncav cuag qhov chaw, thiab tau sau los ntawm cov ntsuas. Hauv qhov no, Fe0 teeb liab feem ntau yog vim LVV Auger electrons thiab lwm cov electrons tawm los ntawm lawv. Tsis tas li ntawd, TEY kev siv zog tau pab los ntawm cov electrons decays thaum lub sij hawm electron khiav txoj kev 49 ntxiv txo cov spectral kos npe ntawm Fe0 nyob rau hauv daim ntawv qhia hlau XAS.
Kev sib xyaw cov ntaub ntawv mining rau hauv cov ntaub ntawv cubes (X-PEEM cov ntaub ntawv) yog lub kauj ruam tseem ceeb hauv kev rho tawm cov ntaub ntawv ntsig txog (tshuaj lom neeg lossis lub cev muaj zog) hauv ntau txoj kev. K-txhais tau hais tias kev sib koom ua ke tau siv dav hauv ntau qhov chaw, suav nrog lub zeem muag ntawm lub tshuab, kev ua cov duab, tsis muaj kev saib xyuas tus qauv lees paub, kev txawj ntse txawj ntse, thiab kev txheeb xyuas cais24. Piv txwv li, K-txhais tau hais tias kev sib koom ua ke tau zoo siv rau kev sib koom ua ke hyperspectral duab data62. Hauv cov ntsiab lus, rau cov ntaub ntawv ntau yam, K-txhais tau tias algorithm tuaj yeem yooj yim pab pawg raws li cov ntaub ntawv hais txog lawv cov cwj pwm (photon zog yam ntxwv). K-txhais tau hais tias pawg yog ib qho algorithm rau kev faib cov ntaub ntawv rau hauv K tsis sib tshooj (pawg), qhov twg txhua pixel belongs rau ib pawg tshwj xeeb nyob ntawm qhov chaw faib khoom ntawm cov tshuaj inhomogeneity hauv cov hlau microstructural muaj pes tsawg leeg. K-txhais tau hais tias algorithm muaj ob kauj ruam: thawj kauj ruam xam cov K centroids, thiab cov kauj ruam thib ob muab txhua tus taw tes rau ib pawg nrog cov neeg nyob sib ze. Qhov nruab nrab ntawm lub ntiajteb txawj nqus ntawm ib pawg yog txhais raws li tus lej lej ntawm cov ntaub ntawv cov ntsiab lus (XAS spectra) ntawm pawg ntawd. Muaj ntau qhov sib txawv los txhais cov centroids nyob sib ze li Euclidean nrug. Rau cov duab input ntawm px, y (x thiab y yog kev daws teeb meem hauv pixels), CK yog qhov nruab nrab ntawm lub ntiajteb txawj nqus ntawm pawg; Cov duab no tuaj yeem muab faib ua pawg (pawg) rau hauv K pawg siv K-means63. Cov kauj ruam kawg ntawm K- txhais tau tias pawg algorithm yog:
Kauj ruam 2. Xam cov degree ntawm kev koom tes ntawm tag nrho cov pixels raws li centroid tam sim no. Piv txwv li, nws yog xam los ntawm Euclidean nrug d ntawm qhov chaw thiab txhua pixel:
Kauj Ruam 3 Muab txhua pixel rau qhov ze tshaj plaws centroid. Tom qab ntawd rov xam cov K centroid txoj haujlwm hauv qab no:
Kauj Ruam 4. Rov ua cov txheej txheem (kev sib npaug (7) thiab (8)) kom txog rau thaum lub centroids converge. Cov txiaj ntsig zoo kawg ntawm pawg muaj feem cuam tshuam nrog qhov kev xaiv zoo tshaj plaws ntawm thawj centroids63. Rau PEEM cov ntaub ntawv qauv ntawm cov duab hlau, feem ntau X (x × y × λ) yog lub voos xwmfab ntawm 3D array cov ntaub ntawv, thaum lub x thiab y axes sawv cev rau cov ntaub ntawv spatial (pixel daws teeb meem) thiab λ axis sib haum rau lub zog spectral hom ntawm photons. K-txhais tau hais tias algorithm tau siv los tshawb txog cov cheeb tsam uas txaus siab rau X-PEEM cov ntaub ntawv los ntawm kev sib cais pixels (pawg lossis sub-blocks) raws li lawv cov yam ntxwv spectral thiab rho tawm qhov zoo tshaj plaws centroid (XAS spectral nkhaus) rau txhua qhov ntsuas (cluster). Nws yog siv los kawm txog spatial faib, kev hloov hauv zos spectral, tus cwj pwm oxidation thiab tshuaj lom neeg lub xeev. Piv txwv li, K-txhais tau hais tias pawg algorithm tau siv rau Fe L-edge thiab Cr L-edge cheeb tsam nyob rau hauv kub-ua hauj lwm thiab txias-dov X-PEEM. Ntau tus lej ntawm K-clusters (cov cheeb tsam microstructural) tau sim kom pom cov pawg zoo tshaj plaws thiab cov centroids. Thaum lub teeb pom kev zoo, cov pixels tau muab rov qab rau qhov tseeb pawg centroids. Txhua qhov kev faib xim sib raug rau qhov nruab nrab ntawm pawg, uas qhia txog qhov chaw ntawm cov khoom siv tshuaj lom neeg lossis lub cev. Cov centroids muab rho tawm yog cov kab sib txuas ntawm cov ntshiab spectra.
Cov ntaub ntawv txhawb nqa cov txiaj ntsig ntawm txoj kev tshawb fawb no muaj los ntawm tus kws sau WC raws li kev thov tsim nyog.
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