Ib tsab xov xwm hais txog dielectrics. Kab lus no coj ua ke cov ntaub ntawv los ntawm ntau yam kev qhia txog hluav taws xob engineering thiab phau ntawv. Cov qauv txheej txheem, lub sijhawm hluav taws xob ntawm dielectrics tau piav qhia. Lub dielectric yog cov khoom uas nws cov khoom siv hluav taws xob tseem ceeb yog muaj peev xwm ua kom sib txawv hauv qhov hluav taws xob.
Cov yam ntxwv tshwj xeeb ntawm dielectrics yog qhov muaj kev sib koom ua ke zoo thiab tsis raug nqi hauv cov molecules uas ua rau cov tshuaj. Ntawm cov tam sim no hom kev sib txuas rau dielectrics siv hauv hluav taws xob thiab xov tooj cua engineering, qhov feem ntau yog covalent tsis-polar, covalent polar lossis homeopolar, ionic lossis heteropolar, tus txais-txais. Lub zog ntawm kev sib txuas txiav txim siab tsis tsuas yog cov qauv thiab cov khoom siv yooj yim ntawm cov khoom, tab sis kuj tseem muaj nyob hauv nws ntawm kev chaotically lossis kev ua kom ncaj qha rau lub sijhawm hluav taws xob hauv micro- lossis macroscopic tag nrho ntawm cov khoom.
Lub sijhawm hluav taws xob tshwm hauv qhov system ntawm ob qhov nqi hluav taws xob ntawm qhov sib npaug sib npaug thiab qhov sib txawv hauv kos npe ± q, nyob ntawm qhov deb ntawm ib leeg, thiab txiav txim siab los ntawm qhov sib piv? = qw.
Xws li cov txheej txheem ntawm kev tsub nqi feem ntau hu ua dipole, thiab cov txheej txheem tsim los ntawm cov txheej txheem them nqi no hu ua dipole.
Covalent daim ntawv cog lus
tshwm sim thaum atoms sib xyaw ua ke rau hauv cov molecules, vim qhov uas cov khoom siv hluav taws xob muaj txiaj ntsig tau sib raug zoo thiab lub plhaub hluav taws xob sab nrauv tau ntxiv rau lub xeev ruaj khov.
Molecules nrog covalent tsis-polar bond tshwm sim thaum atoms ntawm tib lub npe, xws li H2, O2, Cl2, C, S, Si, thiab lwm yam. thiab muaj cov qauv sib npaug. Raws li qhov xwm txheej ntawm qhov chaw nruab nrab ntawm qhov zoo thiab tsis zoo, lub sijhawm hluav taws xob ntawm cov molecule yog xoom, cov lwg me me tsis yog ncov qaumteb qabteb thiab cov khoom (dielectric) yog tsis-ncov qaumteb qabteb.
Yog tias cov lwg me me nrog covalent sib cog tau tsim los ntawm cov atoms sib txawv vim kev sib koom ua ke ntawm cov khoom siv hluav taws xob, piv txwv li, H2O, CH4, CH3Cl, thiab lwm yam. txheeb ze ib leeg Nrog kev sib koom ua ke ntawm cov atoms thiab, yog li ntawd, xwm txheej ntawm cov chaw nruab nrab ntawm cov nqi, cov lwg me me yuav tsis yog-ncov qaumteb qabteb. Nrog kev npaj asymmetric vim kev txav chaw ntawm cov chaw them nqi ntawm qee qhov deb, hluav taws xob tau tshwm sim, cov molecule hu ua ncov qaumteb thiab cov khoom (dielectric) yog ncov qaumteb qabteb. Cov qauv kev teeb tsa ntawm cov tsis-ncov qaumteb qabteb thiab cov qauv molecules tau qhia hauv daim duab hauv qab no.
Txawm hais tias nws yog lub ncov qaumteb los yog tsis muaj dielectric, qhov muaj lub sijhawm hluav taws xob hauv cov molecules ua rau pom qhov pom hluav taws xob hauv lub cev hauv txhua lub tshuab me me ntawm cov khoom. Nrog rau qhov tsis meej pem ntawm lub sijhawm hluav taws xob ntawm cov molecules vim lawv tau them nyiaj sib nrig, tag nrho cov hluav taws xob hauv dielectric yog xoom. Yog tias lub sijhawm hluav taws xob ntawm cov lwg me me tau tsom mus rau feem ntau hauv ib qho kev qhia, tom qab ntawd lub tshuab hluav taws xob tau tshwm sim hauv qhov ntim tag nrho ntawm cov khoom.
Qhov tshwm sim no tau pom nyob rau hauv cov tshuaj nrog qhov tshwm sim (spontaneous) polarization, tshwj xeeb, hauv ferroelectrics.
Ionic thiab pub-lees txais cov ntawv cog lus
tshwm sim thaum cov khoom tsim los ntawm tsis zoo li atoms. Hauv qhov no, lub atom ntawm ib qho tshuaj lom neeg muab tawm, thiab lwm qhov txuas los yog ntes ib lub tshuab hluav taws xob. Raws li qhov tshwm sim, ob ions tau tsim, nruab nrab ntawm lub sijhawm hluav taws xob tshwm sim.
Yog li, raws li tus qauv ntawm cov molecules, dielectrics tuaj yeem faib ua peb pawg:
- non-polar dielectrics, lub sijhawm hluav taws xob ntawm cov molecules uas sib npaug rau xoom;
- ncov qaumteb qabteb dielectrics, lub sijhawm hluav taws xob ntawm cov molecules uas tsis yog xoom;
- ionic dielectrics, uas lub sijhawm hluav taws xob tshwm sim ntawm cov ions ntawm cov tshuaj lom neeg uas ua rau cov tshuaj.
Lub xub ntiag ntawm lub sijhawm hluav taws xob hauv dielectrics, tsis hais txog qhov laj thawj rau lawv tshwm sim, txiav txim siab lawv cov khoom tseem ceeb - muaj peev xwm ua kom sib txawv hauv qhov hluav taws xob.
