Hauv kev nrhiav cov thermal conductivity ntau dua rau cov khoom siv thermal interface, nce qhov sib piv ntawm thermally conductive fillers yog ib qho txiaj ntsig zoo los txhim kho cov thermal kev ua tau zoo ntawm cov khoom sib xyaw. Txawm li cas los xij, hauv kev siv tswv yim, thaum qhov sib piv ntawm thermally conductive fillers tshaj qhov pib, cov khoom hardness nce sharply, kev ua yuav nyuaj, thiab conformability yuav txo qis, thaum kev txhim kho thermal conductivity yog tsawg los yog txawm stagnates. Tom qab qhov tshwm sim no yog ib lub tswv yim tseem ceeb hauv kev tshawb fawb ntawm cov khoom siv hluav taws xob thermally - qhov tseem ceeb filling feem.
1. Hom Filler
Rau thermally conductive muab tub lim, nyob rau hauv ib tug thermally conductive composite, lub sab hauv tshav kub hloov feem ntau yog nyob rau ntawm ob nqa: electrons thiab phonons. Cov txheej txheem sib txawv ntawm cov cua sov sib txawv ua rau muaj feem cuam tshuam rau qhov tseem ceeb ntawm qhov yuav tsum tau ua rau cov muab tub lim los ua kom muaj txiaj ntsig zoo thermally conductive network:
Electronically Conductive Fillers (xws li Silver, Copper, thiab Graphene)
Cov fillers no cia siab rau kev txav mus los thiab kev sib tsoo ntawm cov hluav taws xob dawb rau kev hloov hluav taws xob. Lawv cov txiaj ntsig tseem ceeb yog nyob rau hauv qhov tseem ceeb ntawm quantum tunneling nyhuv: Thaum ob lub ntsiab lus muab tub lim tau coj mus rau hauv ob peb nanometers ntawm ib leeg, txawm tias tsis muaj kev sib cuag ncaj qha, cov hluav taws xob muaj qhov tshwm sim ntawm hla lub insulating polymer barrier nyob nruab nrab, ua tiav dhia. Qhov no txhais tau hais tias lub network uas raug txiav tawm ntawm lub cev tuaj yeem raug thermally txuas ua ntej. Yog li ntawd, qhov tseem ceeb filling feem rau cov fillers los tsim ib tug zoo thermally conductive network feem ntau yog tsawg.
Phononically Conductive Fillers (xws li, Ceramic fillers zoo li Alumina, Silicon Nitride, thiab Carbon cov ntaub ntawv zoo li Carbon Nanotubes, Graphene)
Cov fillers no cia siab rau phonons (lattice vibrations) rau kev hloov cua sov. Qhov nruab nrab txoj kev dawb ntawm phonons nyob rau hauv ib qho kev tsis sib haum xeeb polymer matrix yog luv heev. Thaum phonons taug kev ntawm ib qho kev txiav txim siab crystalline muab tub lim thiab cov matrix tsis zoo, lossis hla qhov sib txawv me me ntawm cov fillers, phonon tsis sib haum xeeb thiab tawg tau tshwm sim. Txhawm rau tsim kom muaj txoj hauv kev zoo phonon, cov fillers yuav tsum tsim kom nruj, ze li ntawm lub cev kev sib cuag kom txo tau qhov kev sib tshuam ntawm thermal kuj. Qhov kev xav tau nruj me ntsis no feem ntau ua rau muaj qhov tseem ceeb dua qhov sau feem ntau. Tsis tas li ntawd, txawm tias ntawm cov muab tub lim nrog tib lub tshuab hloov hluav taws xob, cov muab tub lim nws tus kheej cov thermal conductivity tuaj yeem cuam tshuam rau nws qhov tseem ceeb ntawm cov khoom seem. Fillers nrog cov thermal conductivity yog qhov muaj txiaj ntsig zoo ntawm kev hloov hluav taws xob, tso cai rau cov cua sov kom yooj yim dua los ntawm kev tsis zoo, thiab txuas nrog "quasi- networks," yog li pom qhov dhia tseem ceeb hauv kev ua haujlwm thermal ntawm qis qis. Hloov pauv, cov khoom siv nrog cov thermal conductivity qis dua thermally tsawg dua thiab xav tau cov khoom siv hluav taws xob zoo tshaj plaws los pab txhawb cov cua sov ntawm nws, yog li lawv cov ntsiab lus tseem ceeb tseem qis dua.
2. Filler Morphology
Morphology txiav txim siab qhov kev sib cuag ntawm cov fillers thiab qhov siab tshaj plaws ntim ntim, yog li cuam tshuam rau qhov tseem ceeb filling feem. Raws li cov yam ntxwv geometric, thermally conductive fillers tuaj yeem raug cais raws li:
Spherical Fillers
Qhov zoo ntawm spherical fillers nyob rau hauv lawv yooj yim dispersion thiab zoo flowability. Txawm li cas los xij, vim geometric symmetry, lawv tsuas tuaj yeem tsim cov tes hauj lwm los ntawm kev sib cuag, uas ua rau txo qis kev hloov hluav taws xob ntawm cov khoom. Ib qho tseem ceeb sau feem ntau yuav tsum tau ua kom tiav kev sib txuas zoo. Piv txwv li, lub filling feem rau spherical alumina feem ntau yuav tsum tau mus txog ib ncig ntawm 40% mus rau 50% los txhim kho thermal conductivity.
Anisotropic Fillers (Plate-zoo li/Fibrous)
Phaj-zoo li fillers xws li hexagonal boron nitride (h-BN) thiab graphene, los yog fibrous fillers xws li carbon nanotubes (CNTs), carbon fibers, thiab aluminium nitride whiskers, muaj qhov sib piv siab lossis ntev - rau - txoj kab uas hla. Lawv muaj qhov ua tau zoo ntawm kev sib cuam tshuam, tshwj xeeb tshaj yog thaum taw qhia hauv ib qho kev taw qhia tshwj xeeb, tsim ib lub network percolating los ntawm "bridging" cov nyhuv ntawm cov khoom qis heev. Txawm li cas los xij, cov hom fillers no nyuaj rau disperse thiab nquag mus rau entanglement los yog agglomeration.
Irregular Fillers
Cov fillers no muaj zog mechanical interlocking, ua rau muaj kev tiv thaiv ntau dua thiab muaj kev nce ntxiv hauv viscosity ntawm qis filling feem. Txawm li cas los xij, lawv cov duab tsis sib xws tuaj yeem ua rau cov ntsiab lus sib txuas ntawm cov fillers rau qee qhov. Lawv qhov tseem ceeb filling feem feem ntau yog nyob nruab nrab ntawm cov kheej kheej muab tub lim thiab phaj-zoo li/fibrous fillers. Nws yog pov thawj tias nyob rau hauv cov tswv yim engineering, ib zaug xwb -morphology muab tub lim feem ntau tawm tsam kom sib npaug siab thermal conductivity, yooj yim ntawm kev ua, thiab tag nrho cov kev ua tau zoo. Yog li ntawd, multi-morphology muab tub lim hybridization ua ib lub tswv yim tseem ceeb. Piv txwv li, kev sib txuas phaj-zoo li, fibrous, thiab spherical fillers tuaj yeem siv lawv cov txiaj ntsig zoo los tsim ntau-theem thermally conductive networks, ua tiav "point-line" thiab "point-plane" synergies, uas ua rau tag nrho cov kev ua tau zoo tshaj rau ib leeg -filler systems.
3. Filler Particle loj thiab kev faib tawm
Txoj kev tshav kub ntawm txhua qhov chaw sib cuag ntawm cov khoom ntim loj yog ncaj qha, txo cov phonon tawg thiab ua kom yooj yim hloov cov cua sov. Lawv tuaj yeem sib cuam tshuam los tsim cov kab hluav taws xob txuas ntxiv ntawm cov nqi qis dua. Txawm li cas los xij, vim hais tias cov ntsiab lus sib txuas ntawm cov khoom loj yog tsawg thiab cov interstices loj, tsim thermally conductive network yog cov lus sib txawv, ncav cuag qhov thermal conductivity txwv ntawm ib qho qis qis. Hloov pauv, cov khoom me me muaj qhov loj me me thiab thaj chaw loj dua ntawm cov khoom, tab sis phonon tawg kuj hnyav dua. Lawv xav tau cov nyiaj ntau dua los ua kom muaj txiaj ntsig zoo thermally conductive network, uas ua rau muaj qhov tseem ceeb dua qhov sau feem ntau. Hauv kev siv tswv yim, kev tshawb fawb sib xyaw ua ke ntawm ntau qhov sib txawv (piv txwv li, siv cov khoom loj los tsim cov pob txha, thiab cov khoom nruab nrab / me me los sau cov voids) yog qhov ntau. Lub tswv yim no ua kom zoo dua qhov tseem ceeb ntawm qhov tseem ceeb uas yuav tsum tau ua kom muaj cov txheej txheem thermally conductive thiab txhim kho qhov kawg thermal conductivity. Feem ntau, kev faib tawm dav dav tso cai rau kev tsim cov pob txha thermally conductive nrog ntau txoj hauv kev siv qhov tsawg kawg nkaus ntawm tag nrho cov fillers. Txawm li cas los xij, nws yog ib qho tseem ceeb uas yuav tsum nco ntsoov tias qhov kev faib tawm ntau dhau tuaj yeem qhia cov khoom loj heev, cuam tshuam rau kev ua haujlwm lossis ua rau muaj kev ntxhov siab hauv cheeb tsam. Lub optimization ntawm thermally conductive network los ntawm gradation ntawm loj thiab me me particle loj.
4. Filler Surface Properties
Txawm hais tias lub cev thermally conductive network tau tsim, kev sib raug zoo tsis zoo ntawm cov muab tub lim thiab cov resin matrix tuaj yeem yooj yim ua rau muab tub lim agglomeration. Ntxiv mus, tshav kub ntsib qhov tseem ceeb kuj (high phonon mismatch) ntawm lub interface. Qhov no yuav tsum muaj ntau dua ntawm cov muab tub lim los tsim kom muaj txoj hauv kev zoo thermal, ua rau muaj qhov tseem ceeb dua qhov sau feem ntau. Hloov kho qhov chaw muab tub lim siv cov khoom sib txuas xws li silanes tuaj yeem txhim kho kev sib raug zoo ntawm kev sib raug zoo, txo qhov cuam tshuam ntawm cov thermal tiv thaiv, thiab tso cai rau cov tsim thermally conductive network ua haujlwm tau zoo. Qhov no ua tau zoo txhim kho thermal conductivity ntawm tib qhov ntim feem thaum tseem txo cov kab mob viscosity thiab txhim kho kev ua haujlwm. Txawm li cas los xij, kev hloov kho ntau dhau tuaj yeem cuam tshuam kev muab tub lim - kev sib cuag ntawm cov neeg muab tub lim, ua rau muaj kev cuam tshuam loj zuj zus ntxiv.
