Decreasing Resistivity of Silicon Carbide Ceramics by Incorporation of Graphene

Abstract

Silicon carbide (SiC) ceramic is an ideal material for mechanical seal because of its super hardness, high strength, low friction coefficient, good thermal conductivity, and resistance to friction and wear. However, due to relatively high resistivity of SiC ceramic, the triboelectric charge caused by rubbing of mechanical seal end-faces could not be released. It is terrible that the accumulation of triboelectric charge could cause electrochemical corrosion, which would accelerate wear. To decrease the resistivity of SiC ceramic is a desire for improving the performance of mechanical seal. In this research, decreasing resistivity of pressureless sintered SiC ceramic was investigated by conductive pathways through semiconductive grains in a body by incorporation of graphene, which has an extremely low resistivity. With the increasing of graphene from 0 to 2 wt.%, the volume resistivity of SiC ceramics sintered with graphene decreased logarithmically from >106 to around 200 Ω·cm, and the bulk density decreased gradually, from 3.132 to 3.039 g/cm3. In order to meet the requirements of mechanical seal, SiC ceramic sintered with 1 wt.% of graphene, for which the volume resistivity is of 397 Ω·cm, the bulk density is of 3.076 g/cm3, and the flexural strength is of 364 MPa, was optimized when all properties were taken into consideration. It is possible to fabricate low-resistivity SiC ceramic as a useful friction pair material for mechanical seal in a special condition, without excessive loss of their excellent mechanical properties by the introduction of partially connected graphene as conductive pathway into semiconducting ceramic.

Effects of initial α‐phase content on properties of pressureless solid‐state sintered SiC ceramics

“… 36–39 For example, PSS SiC ceramics with high electrical resistivities of 10 8 −10 11 Ω cm were fabricated by sintering in an N 2 atmosphere at T ≥ 2275°C and the high electrical resistivity was attributed to the formation of an electrically insulating C‐B‐N intergranular phase at grain boundaries 39 . On the other hand, the electrical resistivity of PSS SiC ceramics with 1 wt% B 4 C could be decreased by four orders of magnitude (10 6 →10 2 Ω cm) by adding 2 wt% electrically conductive graphene 38 . The ceramics in this study exhibited intermediate electrical resistivities (10 6 −10 7 Ω cm) comparable to those of PSS SiC ceramics sintered with 1 wt% B 4 C at 2050°C in Ar gas 38 .…”

“…On the other hand, the electrical resistivity of PSS SiC ceramics with 1 wt% B 4 C could be decreased by four orders of magnitude (10 6 →10 2 Ω cm) by adding 2 wt% electrically conductive graphene 38 . The ceramics in this study exhibited intermediate electrical resistivities (10 6 −10 7 Ω cm) comparable to those of PSS SiC ceramics sintered with 1 wt% B 4 C at 2050°C in Ar gas 38 . The reports on the electrical resistivity of PSS SiC ceramics prepared from β‐SiC powders are rarely found (Table 3), presumably due to their higher cost and lower stability at high sintering temperatures compared with α‐SiC powders.…”

Effects of initial α-phase content on the electrical, thermal, and mechanical properties of pressureless solid-state sintered SiC ceramics

“…On the other hand, the electrical resistivity of PSS SiC ceramics with 1 wt% B 4 C could be decreased (10 6 →10 2 Ω cm) by four orders of magnitude by adding 2 wt% electrically conductive graphene [21]. The ceramics in this study exhibited intermediate electrical resistivities (10 6 -10 7 Ω•cm) comparable to those of PSS SiC ceramics sintered with 1 wt% B 4 C at 2050°C in Ar gas [21]. As shown in Table 3, the reports on the electrical resistivity of PSS SiC ceramic sintered with β-SiC powders are rarely found, presumably due to their higher cost and lower stability at high sintering temperatures compared to α-SiC powders.…”

“…For example, PSS SiC ceramics with high electrical resistivities of 10 8 -10 11 Ω•cm were fabricated by sintering in an N 2 atmosphere at ≥ 2275°C and the high electrical resistivity was attributed to the formation of an electrically insulating C-B-N intergranular phase at grain boundaries [54]. On the other hand, the electrical resistivity of PSS SiC ceramics with 1 wt% B 4 C could be decreased (10 6 →10 2 Ω cm) by four orders of magnitude by adding 2 wt% electrically conductive graphene [21]. The ceramics in this study exhibited intermediate electrical resistivities (10 6 -10 7 Ω•cm) comparable to those of PSS SiC ceramics sintered with 1 wt% B 4 C at 2050°C in Ar gas [21].…”

“…As shown in Table 3, the electrical resistivity of the solid-state sintered SiC ceramics could be tuned in the range of 10 1 -10 11 Ω cm by changing the composition and sintering atmosphere [14,17,21,54]. For example, PSS SiC ceramics with high electrical resistivities of 10 8 -10 11 Ω•cm were fabricated by sintering in an N 2 atmosphere at ≥ 2275°C and the high electrical resistivity was attributed to the formation of an electrically insulating C-B-N intergranular phase at grain boundaries [54].…”