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Variations in Crystalline Structures and Electrical Properties of Single Crystalline Boron Nitride Nanosheets.

ABSTRACT: We report the studies of (1) the basic mechanism underlying the formation of defect-free, single crystalline boron nitride nanosheets (BNNSs) synthesized using pulsed laser plasma deposition (PLPD) technique, (2) the variation in the crystalline structure at the edges of the hexagonal boron nitride (h-BN) nanosheets, and (3) the basic electrical properties related to the BNNSs tunneling effect and electrical breakdown voltage. The nanoscale morphologies of BNNSs are characterized using scanning electron microscope (SEM) and high-resolution transmission electron microscope (HRTEM). The results show that each sample consisted of a number of transparent BNNSs that partially overlapped one another. Varying the deposition duration yielded different thicknesses of sample but did not affect the morphology, structure, and thickness of individual BNNSs pieces. Analysis of the SEM and HRTEM data revealed changes in the spatial period of the B3-N3 hexagonal structures and the interlayer distance at the edge of the BNNSs, which occurred due to the limited number of atomic layers and was confirmed further by x-ray diffraction (XRD) study. The experimental results clearly indicate that the values of the electrical conductivities of the super-thin BNNSs and the effect of temperature relied strongly on the direction of observation.

SUBMITTER: Aldalbahi A

PROVIDER: S-EPMC4643278 | biostudies-other | 2015

REPOSITORIES: biostudies-other

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Project description:The practical application of polymer composites in the electronic and communications industries often requires multi-properties, such as high thermal conductivity (TC), efficient electromagnetic interference (EMI) shielding ability with low electrical conductivity, superior tribological performance, reliable thermal stability and excellent mechanical properties. However, the integration of these mutually exclusive properties is still a challenge, ascribed to their different requirement on the incorporated nanofillers, composite microstructure as well as processing process. Herein, a well-designed boron nitride nanosheet (BN)/graphene nanosheet (GNP)/polyphenylene sulfide (PPS) composite with a dual-segregated structure is fabricated via high-pressure molding. Rather than homogenous mixing of the hybrid fillers, GNP is first coated on PPS particles and followed by encapsulating the conductive GNP layers with insulating BN, forming a BN shell-GNP layer-PPS core composite particles. After hot-pressing, a dual segregated structure is constructed, in which GNP and BN are distinctly separated and arranged in the interfaces of PPS, which on the one hand gives rise to high thermal conductivity, and on the other hand, the aggregated BN layer can act as an “isolation belt” to effectively reduce the electronic transmission. Impressively, high-pressure is loaded and it has a more profound effect on the EMI shielding and thermal conductive properties of PPS composites with a segregated structure than that with homogenous mixed-structure composites. Intriguingly, the synergetic enhancement effect of BN and GNP on both thermal conductive performance and EMI shielding is stimulated by high pressure. Consequently, PPS composites with 30 wt% GNP and 10 wt% BN hot-pressed under 600 MPa present the most superior comprehensive properties with a high TC of 6.4 W/m/K, outstanding EMI SE as high as 70 dB, marvelous tribological performance, reliable thermal stability and satisfactory mechanical properties, which make it promising for application in miniaturized electronic devices in complex environments.

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Variations in Crystalline Structures and Electrical Properties of Single Crystalline Boron Nitride Nanosheets.

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