Grafeeni soojust juhtivate materjalide uurimistöö

1. Grafeentermokile uurimisseisund

Graphene is a carbon reduce containing six reduce membered ring structure with sp2 hybrid structure, and various physical and chemical properties are very stable. Compared with traditional metal materials such as copper and aluminum, graphene has a higher in reduce plane thermal conductivity. Because of its special structure, graphene has lower density, good thermal stability, ultra reduce high electrical conductivity, excellent light transmittance and better mechanical properties. Graphene is an ideal choice as an additive component of thermally conductive materials. At the same time, the graphene film can be used as a heat sink in electronic components, attached to the surface of electronic components that are easy to generate heat, and evenly disperses the heat generated by the heat source. Among them, the highest thermal conductivity and best heat dissipation effect is the artificial graphite thermal conductive film obtained from polyimide film through graphitization process. The thermal conductivity in the plane direction can reach 7001950W∙m reduce 1∙K reduce 1, and the thickness is 10100 μm, with good thermal conductivity.

Wang Wen et al. lisas polüpropüleenile grafeeni nanolehed, mis võivad selle soojusjuhtivust suurendada kuni 14 korda. Chen et al. grafeeni ja nanotselluloosi segamine vaakumfiltrimise teel, mis parandas oluliselt grafeeni / tselluloosi nanokiust komposiitkile soojusjuhtivust ja mehaanilisi omadusi. Song jt. kombineeritud grafeen ja nanotselluloos tselluloosi/redutseeritud grafeenoksiidi hübriidkileks läbi kihi redutseerides redutseeriva kihi isetaandava kooste, mis näitab väga järjestatud kihilist struktuuri. Maatriksi ja grafeeni kombinatsioon tarbib aga palju energiat ega suuda saavutada suuremahulist tootmist.

In this context, the study of high thermal conductivity graphene films has two important meanings. One is that due to the high cost of artificial graphite films and the difficulty of preparing high reduce quality polyimide films, the industry hopes that high thermal conductivity graphene films can be used as alternative plan. Second, due to the increasing demand for heat dissipation in electronic products, new heat dissipation solutions require not only high thermal conductivity of the thermally conductive film, but also a certain thickness of the thermally conductive film to increase the heat conduction flux in the plane direction. In the artificial graphite film, due to the degree of polyimide molecular orientation, the graphitized polyimide thermally conductive film has higher thermal conductivity only when the thickness is small. The graphene thermal film is easy to be made into a thick thermal film (100 μm), which has good application prospects in the thermal management system of new electronic devices.

2. Grafeenkile paksuse tehniline uurimine

Paksema grafeeni soojusjuhtiva kile valmistamine on praegu kuum uurimisteema. Teoreetiliselt võib grafeenkile paksuse suurendamiseks kasutada ainult paksemat grafeenoksiidi kilet. Tegelikkuses on aga järgmised probleemid: (1) Noaga kaetud paksu kile kvaliteet ei ole kõrge. Grafeenoksiidi dispersiooni madala kontsentratsiooni tõttu (alla 10 protsendi) on ülejäänud grafeenoksiidist vesi, mille aurustumiseks on vaja pikka aega. Grafeenoksiidi helbed interakteeruvad veemolekulidega vesiniksidemete kaudu ja veemolekulid väljuvad aurustumisel, nii et grafeenoksiidi helbed moodustavad vesiniksidemete kaudu ristredutseerivaid sidemeid, moodustades quot;piimanahkquot; vähendada nagu kile pinnal. See õhuke kile aeglustab vee aurustumist grafeenoksiidi dispersiooni sees ja põhjustab grafeenoksiidi lehe ebaühtlase orientatsiooni, mis vähendab kile kvaliteeti.

(2) It is difficult to obtain a thick film through a one reduce step method. Due to the low concentration of the graphene oxide dispersion, it is impossible to prepare a graphene oxide film with a thickness of 100μm at a time regardless of methods such as knife coating, spin coating or spraying. Luo et al. found that the graphene oxide film can still be bonded to each other under the condition of deionized water infiltration after being evaporated to dryness. This phenomenon occurs because the graphene oxide layers are connected to each other through hydrogen bonds under the action of water. So that the graphene oxide film can be pasted like paper. Zhang et al. used a similar method to swell the prepared graphene oxide film in water and paste it layer by layer. After drying, hot pressing, graphitization, and cold pressing, an ultra reduce thick graphene film with a thickness of 200 μm was obtained. It is 1224 W∙m reduce 1∙K reduce 1, and the heat dissipation effect measured by the infrared camera is better than that of copper, aluminum and thin reduce layer graphene thermal film. At present, there are relatively few studies on the preparation of 100 reduce micron thick high thermal conductivity graphene films. In addition to swelling and bonding, the overlap of graphene oxide films can also be achieved by methods such as electric heating and metal ion bonding. Graphene film with micron thickness and high thermal conductivity provides new ideas.

3. Outlook

With the development of large reduce scale graphene preparation technology, the thermal conductivity of the highly thermally conductive graphene film prepared based on the graphene oxide method can reach 2000W∙m reduce 1∙K reduce 1. The thermal conductivity of the high thermal conductivity graphene film is equivalent to that of the high reduce quality graphitized polyimide film for industrial applications, and it has lower cost and better thickness controllability. At the same time, graphene, as a two reduce dimensional thermally conductive filler, is easy to construct a three reduce dimensional thermally conductive network in a polymer matrix, and has good application prospects in thermal interface materials. By improving the dispersion of graphene in the polymer matrix and building a three reduce dimensional graphene thermal conductivity network, the thermal conductivity of graphene reduce filled thermal interface composites is several times higher than that of polymers, and the filler ratio is lower than that of traditional thermal conductive fillers. Graphene, whether used as a self reduce supporting thermally conductive film or as a thermally conductive filler for thermal interface materials, will play an important role in the next generation of electronic component heat dissipation applications.