Kab lus no muaj cov lus piav qhia txog yam xws li X-ray diffraction. Lub hauv paus ntawm lub cev ntawm qhov tshwm sim thiab nws cov ntawv thov tau piav qhia ntawm no.
Technologies tsim cov ntaub ntawv tshiab
Innovation, nanotechnology yog tus qauv ntawm lub ntiaj teb niaj hnub no. Cov xov xwm yog tag nrho ntawm cov lus ceeb toom ntawm cov ntaub ntawv tshiab revolutionary. Tab sis ob peb tus neeg xav txog dab tsi cov cuab yeej tshawb fawb loj uas cov kws tshawb fawb xav tau los tsim tsawg kawg ib qho kev txhim kho me me hauv cov thev naus laus zis uas twb muaj lawm. Ib qho ntawm cov xwm txheej tseem ceeb uas pab tib neeg ua qhov no yog X-ray diffraction.
electromagnetic hluav taws xob
Ua ntej koj yuav tsum piav qhia tias hluav taws xob hluav taws xob yog dab tsi. Txhua lub cev txav mus los ua kom muaj hluav taws xob hluav taws xob nyob ib puag ncig nws tus kheej. Cov teb no pervade txhua yam nyob ib puag ncig, txawm tias lub tshuab nqus tsev ntawm qhov chaw sib sib zog nqus tsis pub dawb los ntawm lawv. Yog hais tias nyob rau hauv xws li ib daim teb muaj ib ntus perturbations uas yuav propagate nyob rau hauv qhov chaw, lawv hu ua electromagnetic hluav taws xob. Los piav txog nws, cov ntsiab lus xws li wavelength, zaus thiab nws lub zog yog siv. Dab tsi yog lub zog yog intuitive, thiab lub wavelength yog qhov kev ncua deb ntawmzoo tib yam theem (piv txwv li, nruab nrab ntawm ob qho tib si maxima). Qhov siab dua qhov wavelength (thiab, raws li, qhov zaus), nws lub zog qis dua. Nco qab tias cov ntsiab lus no tsim nyog los piav txog qhov X-ray diffraction yog qhov tseeb thiab succinctly.
YElectromagnetic spectrum
Txhua yam ntawm cov hluav taws xob hluav taws xob haum rau ntawm qhov tshwj xeeb. Nyob ntawm qhov wavelength, lawv paub qhov txawv (los ntawm qhov ntev tshaj mus rau qhov luv):
- xov tooj cua;
- terahertz nthwv dej;
- infrared nthwv dej;
- pom nthwv dej;
- ultraviolet nthwv dej;
- X-ray nthwv dej;
- gamma hluav taws xob.
Yog li, cov hluav taws xob uas peb xav tau muaj qhov luv luv wavelength thiab lub zog siab tshaj plaws (uas yog vim li cas qee zaum hu ua nyuaj). Yog li ntawd, peb tau los ze zog los piav txog qhov X-ray diffraction yog dab tsi.
keeb kwm ntawm X-rays
Qhov siab dua lub zog hluav taws xob, qhov nyuaj dua nws yog kom tau txais nws cov khoom tsim tawm. Tom qab ua hluav taws, ib tug neeg tau txais ntau cov hluav taws xob infrared, vim nws yog qhov hloov cua sov. Tab sis rau qhov sib txawv ntawm X-rays los ntawm cov qauv spatial tshwm sim, yuav tsum tau siv zog ntau. Yog li, hom hluav taws xob hluav taws xob zoo li no tau tso tawm thaum lub tshuab hluav taws xob raug tshem tawm ntawm lub plhaub ntawm lub atom, uas nyob ze rau lub nucleus. Cov electrons nyob saum toj no yuav ua rau lub qhov tshwm sim, lawv cov kev hloov pauv thiab muab X-ray photons. Tsis tas li ntawd, thaum lub sij hawm ntse deceleration ntawm nqi hais nrog loj (piv txwv li,electrons), cov kab hluav taws xob siab no yog tsim. Yog li, qhov sib txawv ntawm X-rays ntawm cov iav siv lead ua yog nrog los ntawm kev siv nyiaj ntau ntawm lub zog.
Ntawm qhov ntsuas kev lag luam, qhov hluav taws xob no tau txais raws li hauv qab no:
- Lub cathode emits lub zog hluav taws xob siab.
- Electron collides nrog cov khoom ntawm lub anode.
- Lub electron decelerates sharply (thaum emitting X-rays).
- Hauv lwm qhov xwm txheej, qhov decelerating particle knocks ib qho hluav taws xob tawm ntawm lub atom qis orbit los ntawm cov khoom siv anode, uas kuj tsim X-rays.
Nws tseem yuav tsum nkag siab tias, zoo li lwm yam hluav taws xob hluav taws xob, X-rays muaj lawv tus kheej spectrum. Qhov hluav taws xob no nws tus kheej yog siv dav heev. Txhua leej txhua tus paub tias cov pob txha tawg lossis qhov loj hauv lub ntsws yog nrhiav nrog kev pab ntawm x-rays.
qauv ntawm cov khoom siv crystalline
Tam sim no peb los ze rau qhov X-ray diffraction txoj kev yog. Txhawm rau ua qhov no, nws yog qhov yuav tsum tau piav qhia yuav ua li cas lub cev khov kho. Hauv kev tshawb fawb, lub cev muaj zog hu ua txhua yam khoom hauv lub xeev crystalline. Ntoo, av nplaum los yog iav yog cov khoom, tab sis lawv tsis muaj qhov tseem ceeb: ib lub sij hawm ua qauv. Tab sis crystals muaj cov cuab yeej zoo kawg no. Lub npe ntawm qhov tshwm sim no muaj nws cov ntsiab lus. Ua ntej koj yuav tsum to taub tias cov atoms nyob rau hauv lub siv lead ua yog tsau rigidly. Cov ntawv cog lus ntawm lawv muaj qee qhov elasticity, tab sis lawv muaj zog heev rau cov atom txav mus rau sab hauv.gratings. Xws li ntu tuaj yeem ua tau, tab sis nrog lub zog sab nraud muaj zog heev. Piv txwv li, yog hais tias ib tug hlau siv lead ua yog bent, taw tes defects ntawm ntau hom yog tsim nyob rau hauv nws: nyob rau hauv tej qhov chaw, lub atom tawm ntawm nws qhov chaw, tsim ib tug qhov chaw, nyob rau hauv lwm tus neeg, nws txav mus rau qhov tsis ncaj ncees lawm txoj hauj lwm, tsim ib tug interstitial defect. Nyob rau ntawm qhov chaw ntawm qhov khoov, cov khoom siv lead ua poob nws cov qauv siv lead ua slim, dhau los ua qhov tsis zoo, xoob. Yog li ntawd, nws yog qhov zoo dua tsis txhob siv daim ntawv clip uas tsis tau khoov ib zaug, txij li cov hlau tau poob nws cov khoom.
Yog tias cov atoms ruaj khov, lawv tsis tuaj yeem sib cais los ntawm ib leeg, ib yam li hauv cov kua. Lawv yuav tsum npaj lawv tus kheej hauv txoj hauv kev kom txo qis zog ntawm lawv cov kev sib cuam tshuam. Yog li ntawd, cov atoms line up in a lattice. Nyob rau hauv txhua lub lattice muaj qhov tsawg kawg nkaus ntawm atoms teem nyob rau hauv ib tug tshwj xeeb txoj kev nyob rau hauv qhov chaw - qhov no yog lub elementary cell ntawm siv lead ua. Yog tias peb tshaj tawm nws tag nrho, uas yog, muab cov npoo nrog ib leeg, hloov mus rau txhua qhov kev taw qhia, peb yuav tau txais tag nrho cov siv lead ua. Txawm li cas los xij, nws tsim nyog nco ntsoov tias qhov no yog ib qho qauv. Txhua yam siv lead ua tiag tiag muaj qhov tsis xws luag, thiab nws yuav luag tsis tuaj yeem ua tiav qhov kev txhais lus tseeb tiag. Niaj hnub nimno silicon nco hlwb nyob ze rau lub zoo meej crystals. Txawm li cas los xij, kom tau txais lawv yuav tsum muaj qhov tsis txaus ntseeg ntawm lub zog thiab lwm yam kev pab. Hauv chav kuaj, cov kws tshawb fawb tau txais cov qauv zoo meej ntawm ntau yam, tab sis, raws li txoj cai, tus nqi ntawm lawv cov kev tsim yog siab dhau. Tab sis peb yuav xav tias tag nrho cov muaju yog qhov zoo tagnrho: hauv ib qho twgkev taw qhia, tib lub atoms yuav nyob ntawm tib qhov deb ntawm ib leeg. Cov qauv no hu ua ib lub lattice.
Study of crystal structure
Nws yog vim qhov tseeb tias X-ray diffraction ntawm crystals yog ua tau. Cov qauv ntu ntu ntawm cov muaju tsim qee cov dav hlau hauv lawv, uas muaj cov atoms ntau dua li lwm cov lus qhia. Qee lub sij hawm cov dav hlau no tau teeb tsa los ntawm symmetry ntawm crystal lattice, qee zaum los ntawm kev sib koom ua ke ntawm atoms. Txhua lub dav hlau tau muab nws tus kheej lub npe. Qhov kev ncua deb ntawm cov dav hlau me me: ntawm qhov kev txiav txim ntawm ob peb angstroms (nco, ib qho angstrom yog 10-10 meter lossis 0.1 nanometer).
Txawm li cas los xij, muaj ntau lub dav hlau ntawm tib qho kev taw qhia hauv ib qho siv lead ua tiag tiag, txawm tias me me. X-ray diffraction raws li ib txoj kev siv qhov tseeb no: tag nrho cov nthwv dej uas tau hloov cov kev taw qhia ntawm cov dav hlau ntawm tib qho kev taw qhia tau sau tseg, muab cov teeb liab pom tseeb ntawm qhov tso zis. Yog li cov kws tshawb fawb tuaj yeem nkag siab txog cov lus qhia twg cov dav hlau no nyob hauv cov siv lead ua, thiab txiav txim siab cov qauv sab hauv ntawm cov qauv siv lead ua. Txawm li cas los xij, cov ntaub ntawv no ib leeg tsis txaus. Ntxiv nrog rau lub kaum sab xis ntawm inclination, koj kuj yuav tsum paub qhov kev ncua deb ntawm cov dav hlau. Yog tsis muaj qhov no, koj tuaj yeem tau txais ntau txhiab tus qauv sib txawv ntawm cov qauv, tab sis tsis paub cov lus teb meej. Cov kws tshawb fawb kawm li cas txog qhov kev ncua deb ntawm lub dav hlau yuav tau tham hauv qab no.
Diffraction phenomenon
Peb twb tau muab qhov tseeb ntawm lub cev ntawm qhov X-ray diffraction ntawm lub spatial lattice ntawm crystals. Txawm li cas los xij, peb tseem tsis tau piav qhia lub ntsiab lusphenomena ntawm diffraction. Yog li, diffraction yog sib npaug ntawm obstacles los ntawm nthwv dej (xws li electromagnetic sawv daws yuav). Qhov tshwm sim no zoo li ua txhaum txoj cai ntawm linear optics, tab sis nws tsis yog. Nws yog ze ze rau kev cuam tshuam thiab yoj zog ntawm, piv txwv li, photons. Yog hais tias muaj teeb meem nyob rau hauv txoj kev ntawm lub teeb, ces vim yog diffraction, photons tuaj yeem "saib" nyob ib ncig ntawm lub ces kaum. Qhov kev taw qhia ntawm lub teeb mus deb npaum li cas los ntawm txoj kab ncaj nraim nyob ntawm qhov loj ntawm qhov teeb meem. Qhov kev cuam tshuam me me, qhov luv ntawm electromagnetic yoj ntev yuav tsum yog. Yog vim li cas X-ray diffraction ntawm ib tug crystals yog nqa tawm siv xws li luv luv nthwv dej: qhov kev ncua deb ntawm lub dav hlau yog heev me me, optical photons tsuas yuav tsis "crawl" ntawm lawv, tab sis tsuas yog yuav tsum tau reflected los ntawm qhov chaw.
Lub tswv yim no muaj tseeb, tab sis hauv kev tshawb fawb niaj hnub no suav tias nqaim dhau. Txhawm rau nthuav nws cov ntsiab lus, nrog rau kev paub dav dav, peb nthuav qhia txoj hauv kev rau kev tshwm sim ntawm nthwv dej diffraction.
- Hloov tus qauv spatial ntawm nthwv dej. Piv txwv li, kev nthuav dav ntawm lub kaum sab xis ntawm cov kab hluav taws xob nthwv dej, qhov deflection ntawm nthwv dej lossis cov nthwv dej ntawm qee qhov kev xav. Nws yog rau chav kawm ntawm phenomena uas yoj khoov ib ncig ntawm obstacles belongs.
- Decomposition ntawm nthwv dej rau hauv spectrum.
- Hloov pauv hauv nthwv dej polarization.
- Kev hloov pauv ntawm theem qauv ntawm nthwv dej.
Qhov tshwm sim ntawm qhov sib txawv, ua ke nrog kev cuam tshuam, yog lub luag haujlwm rau qhov tseeb tias thaum lub teeb ntawm lub teeb coj mus rau qhov nqaim hauv qab nws, peb tsis pom ib qho, tab sis ob peblub teeb maxima. Qhov deb tshaj plaws yog los ntawm nruab nrab ntawm lub qhov, qhov siab dua nws qhov kev txiav txim. Tsis tas li ntawd, nrog rau qhov tseeb ntawm qhov kev sim, tus duab ntxoov ntxoo los ntawm ib rab koob zoo tib yam (ntawm chav kawm, nyias) muab faib ua ob peb kab txaij, thiab lub teeb siab tshaj plaws tau pom raws nraim tom qab koob, thiab tsis yog qhov tsawg kawg nkaus.
Wulf-Bragg formula
Peb twb tau hais saum toj no tias qhov kawg ntawm lub teeb liab yog qhov suav ntawm tag nrho cov X-ray photons uas tau cuam tshuam los ntawm cov dav hlau nrog tib qhov kev xav hauv cov siv lead ua. Tab sis ib qho kev sib raug zoo tseem ceeb tso cai rau koj los xam cov qauv kom raug. Yog tsis muaj nws, X-ray diffraction yuav tsis muaj txiaj ntsig. Tus qauv Wulf-Bragg zoo li no: 2dsinƟ=nλ. Ntawm no d yog qhov kev ncua deb ntawm cov dav hlau nrog tib lub inclination lub kaum ntse ntse, θ yog lub kaum sab xis glancing (Bragg lub kaum sab xis), lossis lub kaum sab xis ntawm qhov xwm txheej ntawm lub dav hlau, n yog qhov kev txiav txim ntawm qhov siab tshaj plaws diffraction, λ yog lub wavelength. Txij li thaum nws paub ua ntej uas X-ray spectrum yog siv los muab cov ntaub ntawv thiab ntawm lub kaum sab xis ntawm qhov hluav taws xob poob, cov qauv no tso cai rau peb los laij tus nqi ntawm d. Peb twb tau hais me ntsis siab dua tias yog tsis muaj cov ntaub ntawv no nws tsis tuaj yeem tau txais cov qauv ntawm cov khoom raug raug.
Tam sim no daim ntawv thov ntawm X-ray diffraction
Cov lus nug tshwm sim: nyob rau hauv dab tsi yog qhov kev tshuaj ntsuam no xav tau, tsis txhob tshawb fawb txog txhua yam hauv ntiaj teb cov qauv, thiab tsis yog tib neeg, thaum tau txais cov tshuaj tshiab, xav tias qhov txiaj ntsig zoo li cas tos lawv. ? Muaj plaub lo lus teb.
- Yog, peb tau paub peb lub ntiaj teb zoo heev. Tab sis txhua txhua xyoo cov zaub mov tshiab tau pom. Qee zaum lawv cov qauv txawmtwv tsis muaj x-ray yuav tsis ua haujlwm.
- Ntau tus kws tshawb fawb tab tom sim txhim kho cov khoom ntawm cov khoom uas twb muaj lawm. Cov tshuaj no raug rau ntau hom kev ua haujlwm (siab, kub, lasers, thiab lwm yam). Qee zaum cov ntsiab lus tau ntxiv los yog tshem tawm ntawm lawv cov qauv. X-ray diffraction ntawm crystals yuav pab kom nkag siab txog qhov kev hloov kho sab hauv tau tshwm sim hauv qhov no.
- Rau qee cov ntawv thov (xws li, cov xov xwm nquag, lasers, nco daim npav, cov khoom siv kho qhov muag ntawm cov tshuab soj ntsuam), cov khoom siv lead ua yuav tsum sib phim heev. Yog li ntawd, lawv cov qauv raug kuaj xyuas siv txoj kev no.
- X-ray diffraction yog tib txoj hauv kev kom paub seb muaj pes tsawg thiab theem twg tau txais thaum lub sijhawm sib txuas hauv cov tshuab sib txuas. Ceramic ntsiab ntawm cov cuab yeej siv niaj hnub tuaj yeem ua piv txwv ntawm cov tshuab zoo li no. Lub xub ntiag ntawm cov theem tsis xav tau tuaj yeem ua rau muaj qhov tshwm sim loj.
Space exploration
Ntau tus neeg nug: "Vim li cas peb xav tau cov chaw soj ntsuam loj hauv lub ntiaj teb, vim li cas peb thiaj xav tau lub rover yog tias tib neeg tseem tsis tau daws teeb meem ntawm kev txom nyem thiab kev ua tsov ua rog?"
Txhua tus muaj lawv tus kheej qhov laj thawj rau thiab tawm tsam, tab sis pom tseeb tias tib neeg yuav tsum muaj npau suav.
Yog li ntawd, saib cov hnub qub, hnub no peb tuaj yeem hais nrog kev ntseeg siab: peb paub ntau ntxiv txog lawv txhua hnub.
X-rays los ntawm cov txheej txheem tshwm sim hauv qhov chaw tsis ncav cuag peb lub ntiaj teb, lawv tau nqus los ntawm huab cua. Tab sis qhov noLub electromagnetic spectrum nqa ntau cov ntaub ntawv hais txog lub zog siab phenomena. Yog li ntawd, cov cuab yeej uas kawm X-rays yuav tsum tau coj tawm ntawm lub ntiaj teb mus rau hauv lub orbit. Tam sim no cov chaw nres tsheb tam sim no tab tom kawm cov khoom hauv qab no:
- remnants ntawm supernova tawg;
- centers of galaxies;
- neutron hnub qub;
- dub qhov;
- kev sib tsoo ntawm cov khoom loj (galaxies, pawg ntawm galaxies).
Tshwj xeeb, raws li ntau txoj haujlwm, kev nkag mus rau cov chaw nres tsheb no tau muab rau cov menyuam kawm ntawv thiab cov menyuam kawm ntawv. Lawv kawm X-rays los ntawm qhov chaw sib sib zog nqus: diffraction, cuam tshuam, spectrum dhau los ua qhov lawv nyiam. Thiab qee cov tub ntxhais hluas cov neeg siv ntawm cov chaw soj ntsuam no tab tom nrhiav pom. Ib tus nyeem ntawv zoo yuav, tau kawg, kwv yees tias lawv tsuas muaj sijhawm los saib cov duab daws teeb meem thiab pom cov ntsiab lus tsis meej. Thiab ntawm chav kawm, qhov tseem ceeb ntawm kev tshawb pom, raws li txoj cai, tsuas yog nkag siab los ntawm cov kws tshawb fawb loj. Tab sis cov xwm txheej zoo li no txhawb cov tub ntxhais hluas kom mob siab rau lawv lub neej rau kev tshawb nrhiav chaw. Thiab lub hom phiaj no tsim nyog nrhiav.
Yog li, qhov ua tiav ntawm Wilhelm Conrad Roentgen qhib kev nkag mus rau kev paub txog hnub qub thiab muaj peev xwm kov yeej lwm lub ntiaj teb.
