Fabrication process and mechanical properties of boron nitride nanosheet (BNNS)/copper nanocomposites질화붕소 나노시트/구리 나노복합재료의 제조 공정 및 기계적 특성 연구

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Boron nitride nanosheet (BNNS), which is consist of $sp^2$ conjugated boron and nitrogen atoms in 2-dimensional hexagonal structure, is attractive reinforcement in composite materials, due to its remarkable mechanical and thermal properties. BNNS has elastic modulus of 0.7 TPa and yield strength of 120GPa. Furthermore, it can endure high temperature system until $900^\circ C$. Thus, BNNS/metal nanocomposite is expected to be high strength and high thermal nanocomposite. In this research, we demonstrated BNNS reinforced metal nanocomposite. Molecular-level mixing process was applied to synthesize homogeneously dispersed BNNS in metal matrix. The successful fabrication of BNNS/Cu nanocomposites was confirmed by XRD and FT-IR. Hydroxide sodium assisted mechanical exfoliation produces hydroxyl functionalized BNNS. During molecular-level mixing process, hydroxyl group of BNNS and Cu ion chemically bonded together. Strong interfacial strength induces high mechanical properties. The BNNS/Cu (1.5vol. %) has yield strength of 281 MPa, ultimate tensile strength of 314 MPa and elastic modulus of 130 GPa, which are respectively 1.75, 1.23 and 1.27 times higher than those of pure Cu, which fabricated by same process. The strengthening mechanisms of the BNNS/Cu nanocomposites was composed of grain size refinement, load transfer and dislocation strengthening by CTE mismatch. Due to high thermal stability of BNNS, the BNNS/Cu nanocomposite shows high mechanical properties at high temperature. At $300^\circ C$, BNNS/Cu (1.5 vol.%) has yield strength of 178 MPa, ultimate tensile strength of 196 MPa and elastic modulus of 7.5 GPa, which are respectively 1.89, 2.04 and 2.67 times higher than those of pure Cu. From these result, we can confirm that BNNS/Cu nanocomposite is applicable to high thermal and high strength field. From high enhancement of mechanical of BNNS/Cu, BNNS/Cu system provides possibility of BNNS as a reinforcement for various metal matrix composites. Furthermore, BNNS/Metal nanocomposite could be used for high strength, multi-functional and high temperature application.
Advisors
Hong, Soon Hyungresearcher홍순형researcher
Description
한국과학기술원 :신소재공학과,
Publisher
한국과학기술원
Issue Date
2018
Identifier
325007
Language
eng
Description

학위논문(석사) - 한국과학기술원 : 신소재공학과, 2018.8,[viii, 67 p. :]

Keywords

Boron nitride nanosheet▼ametal▼ananocomposites▼amechanical property▼astrengthening mechanism; 질화붕소 나노시트▼a금속▼a나노복합재료▼a기계적 특성▼a강화 기작

URI
http://hdl.handle.net/10203/266529
Link
http://library.kaist.ac.kr/search/detail/view.do?bibCtrlNo=828537&flag=dissertation
Appears in Collection
MS-Theses_Master(석사논문)
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