Properties of CNTs/MoSi₂ composites prepared by spark plasma sintering

Abstract

Molybdenum disilicide (MoSi₂) based composites with various contents of carbon nanotubes (CNTs) were fabricated by spark plasma sintering (SPS) in vacuum under a pressure of 25 MPa. The composites obtained under a sintering temperature of 1500 °C and time of 10 min exhibited optimum mechanical properties at room temperature in terms of fracture toughness and transverse rupture strength. MoSi₂ based composite with 6.0% CNTs (volume fraction) had the highest fracture toughness, transverse rupture strength and hardness, which were improved by about 25.7%, 51.5% and 24.4% respectively, as compared with pure MoSi₂. A Mo_4.8Si₃C_0.6 phase was detected in CNTs/MoSi₂ composites by both X-ray diffraction (XRD) method and microstructure analysis with scanning electron microscopy (SEM). It is believed that the fine grains and well dispersed small Mo_4.8Si₃C_0.6 particles had led to a higher hardness and strength of CNTs/MoSi₂ composites because of their particle pullout, crack deflection and micro-bridging effects.

Keywords

CNTs/MoSi₂ composite / spark plasma sintering / mechanical property / microstructure / strengthening and toughening mechanism

References

[1] VasudevanA K, PetrovicJ J. A comparative overview of molybdenum disilicide composites [J]. Mater Sci Eng A, 1992, 155: 1-17

[2] PetrovicJ J. Mechanical behavior of MoSi₂ and MoSi₂ composites [J]. Mater Sci Eng A, 1995, 192/193: 31-37

[3] JengY L, LaverniaE J. Review processing of molybdenum disilicide [J]. J Mater Sci, 1994, 29: 2557-2571

[4] WangJ, FengP, NiuJ, GuoR, LiuZ, AkhtarF. Synthesis, microstructure and properties of MoSi₂–5 vol%Al₂O₃ composites [J]. Ceram Int, 2014, 40: 16381-16387

[5] EsmaeilyS, KermaniM, RazaviM, RahimipourM R, ZakeriM. An investigation on the in situ synthesis–sintering and mechanical properties of MoSi₂–xSiC composites prepared by spark plasma sintering [J]. Int J Refract Metal Hard Mater, 2015, 48: 263-271

[6] WangZ, LiS, WangM, WuG, SunX, LiuM. Effect of SiC whiskers on microstructure and mechanical properties of the MoSi₂–SiC_w composites [J]. Int J Refract Metal Hard Mater, 2013, 41: 489-494

[7] LiuH, WuW, ZouJ, NiD, KanY, ZhangG. In situ synthesis of ZrB₂–MoSi₂ platelet composites: Reactive hot pressing process, microstructure and mechanical properties [J]. Ceram Int, 2012, 38: 4751-4760

[8] SharifA A. Effects of Re- and Al-alloying on mechanical properties and high-temperature oxidation of MoSi₂ [J]. J Alloys Compd, 2012, 518: 22-26

[9] HagiharaK, NakanoT. Fracture behavior and toughness of NbSi₂-based single crystals and MoSi₂ (C11_b)/ NbSi₂(C40) duplex crystals with a single set of lamellae [J]. Acta Mater, 2011, 59: 4168-4176

[10] KoI, KangH, DohJ, YoonJ, ShonI. Properties and densification of nanocrystalline MoSi₂–Si₃N₄ composite from mechanically alloyed powders by pulsed current-activated sintering [J]. J Alloys Compd, 2010, 502: L10-L13

[11] IijimaS. Helical microtubules of graphitic carbon [J]. Nature, 1991, 354: 56-58

[12] CollinsP G, ZettlA, BandoH, ThessA, SmalleyR E. Nanotube nanodevice [J]. Science, 1997, 278: 100-102

[13] TreacyM M J, EbbesenT W, GibsonJ M. Exceptionally high Young’s modulus observed for individual carbon nanotubes [J]. Nature, 1996, 381: 678-680

[14] KimH N, ChangS N, KimD K. Enhanced microhardness of nanocrystalline carbon nanotube-reinforced Cu composite using planar shock-wave compaction [J]. Scr Mater, 2009, 61: 871-874

[15] ShimizuY, MikiS, SogaT, ItohI, TodorokiH, HosonoT, SakakiK, HayashiT, KimYA, EndoM, MorimotoS, KoideA. Multi-walled carbon nanotube-reinforced magnesium alloy composites [J]. Scr Mater, 2008, 58: 267-270

[16] KimS W, ChungW S, SohnK S, SonC Y, LeeS. Improvement of flexure strength and fracture toughness in alumina matrix composites reinforced with carbon nanotubes [J]. Mater Sci Eng A, 2009, 517: 293-299

[17] PangL X, SunK N, RenS, SunC, FanR H, LuZ H. Fabrication and microstructure of Fe3Al matrix composite reinforced by carbon nanotube [J]. Mater Sci Eng A, 2007, 447: 146-149

[18] ZhangH, WuH, GuS. Preparation and properties of MoSi₂ based composites reinforced by carbon nanotubes [J]. Ceram Int, 2013, 39: 7401-7405

[19] GuillonO, Gonzalez-JulianJ, DargatzB, KesselT, SchierningG, RäthelJ, HerrmannM. Field-assisted sintering technology/spark plasma sintering: Mechanisms, materials, and technology developments [J]. Adv Eng Mater, 2014, 16: 830-849

[20] GaoL, HongJ S, MiyamotoH, TorreS D D L. Bending strength and microstructure of Al₂O₃ ceramics densified by spark plasma sintering [J]. J Eur Ceram Soc, 2000, 20: 2149-2152

[21] ScitiD, MonteverdeF, GuicciardiS, PezzottiG, BellosiA. Microstructure and mechanical properties of ZrB₂–MoSi₂ ceramic composites produced by different sintering techniques [J]. Mater Sci Eng A, 2006, 434: 303-309

[22] Álvarez-ClemaresI, BorrellA, AgouramS, TorrecillasR, FernándezA. Microstructure and mechanical effects of spark plasma sintering in alumina monolithic ceramics [J]. Script Mater, 2013, 68: 603-606

[23] AnstisG R, ChantikulP, LawnB R, MarshallD B. A critical evaluation of indentation techniques for measuring fracture toughness: І, direct crack measurements [J]. J Am Ceram Soc, 1981, 64: 532-538

[24] HenagerC H, BrimhallJ J L, HirthJ P. Synthesis of a MoSi₂/SiC composite in situ using a solid state displacement reaction between Mo₂C and Si [J]. Script Metall Mater, 1992, 26: 585-589

[25] MaloyS A, HeuerA H, LewandowskiJ J, PetrovicJ J. Carbon addition to molybdenum disilicide: Improved hightemperature mechanical properties [J]. J Am Ceram Soc, 1991, 74: 2704-2706

[26] ZhangH, WangD, ChenS, LiuX. Toughening of MoSi₂ doped by La₂O₃ particles [J]. Mater Sci Eng A, 2003, A345: 118-121

[27] CarterD H, HurleyG F. Crack deflection as a toughening mechanism in SiC-whisker-reinforced MoSi₂ [J]. J Am Ceram Soc, 1987, 70: C79-C81

[28] BhattacharyaA K, PetrovicJ J. Hardness and fracture toughness of SiC-particle-reinforced MoSi₂ composite [J]. J Am Ceram Soc, 1991, 74: 2700-2703

[29] FaberK T, IwagoshiT, GhoshA. Toughening by stress-induced microcracking in two-phase ceramics [J]. J Am Ceram Soc, 1988, 71: C399-C401