Phase Formation and the Electrical Properties of YSZ/rGO Composite Ceramics Sintered Using Silicon Carbide Powder Bed

Abstract

Fully stabilized zirconia/graphene composites are very promising advanced structural materials having mixed ion–electron conductivity for energy storage and energy conversion applications. The existing methods of the composite manufacturing have a number of disadvantages that limit their practical use. Thus, the search for new sintering methods is an actively developing area. In this work, we report for the first time the application of the SiC powder bed sintering technique for fully stabilized zirconia (YSZ) composite fabrication. The reduced graphene oxide (rGO) was used as a graphene derivative. As a result, well-formed ceramics with high density and crystallinity, the maximal microhardness of 13 GPa and the values of the ionic conductivity up to 10−2 S/cm at 650 °C was obtained. The effects of the sintering conditions and rGO concentration on the microstructure and conductivities of ceramics are discussed in detail. The suggested powder bed sintering technique in a layered graphite/SiC/graphite powder bed allowed well-formed dense YSZ/rGO ceramics fabrication and can become a suitable alternative to existing methods for various oxide ceramic matrix composite fabrication: both conventional sintering and non-equilibrium (SPS, flash sintering) approaches.

Mixed Electronic-Ionic Conductivity and Stability of Spark Plasma Sintered Graphene-Augmented Alumina Nanofibres Doped Yttria Stabilized Zirconia GAlN/YSZ Composites

“…To date, considerable progress has been achieved in the field of graphene/YSZ composites having improved electrical and thermal conductivity [ 9 , 10 , 19 , 20 , 21 ] and enhanced mechanical properties [ 22 , 23 , 24 ]. The percolation threshold was achieved for the tetragonal zirconia matrix upon the introduction of 1 wt.% graphene additive [ 20 ], whereas for cubic zirconia upon the addition of 1 wt.% graphene additive.…”

“…As known the major problems associated with graphene-doped materials are (i) the difficulty in homogeneous Gr distribution in the composite matrix and (ii) the damaging of Gr in the matrix during milling and sintering steps [ 5 , 22 ]. In order to overcome mentioned problems, various graphene derivatives are used nowadays for high-performance composites manufacturing instead of pristine Gr, such as graphene oxide (GO) [ 25 , 26 ], reduced graphene oxide (rGO) [ 18 , 21 , 27 , 28 ], graphene nanoplatelets (GNP) [ 3 , 10 , 23 ], etc. They have a different number of stacked graphene layers, edge functional groups, alternating lateral sizes of a sheet etc., which enhance the bonding between the matrix and the additive and thus improve the properties of resulting composites [ 29 ].…”

“…The structure of rGO is similar to pristine graphene, but contains residual functional groups and structural defects at the edge, which makes it more stable towards agglomeration in the metallic and ceramic matrices. Also, in the series of works [ 9 , 18 , 21 , 26 , 32 , 33 ] the effect of the sintering and shaping conditions on the structure and the properties of rGO/YSZ composites was studied. Based on the dilatometry data authors of [ 32 ] have shown that graphene-zirconia composites demonstrate the mixed mechanism of sintering with a grain boundary diffusion predominance.…”

“…Based on the dilatometry data authors of [ 32 ] have shown that graphene-zirconia composites demonstrate the mixed mechanism of sintering with a grain boundary diffusion predominance. Such techniques as spark plasma sintering (SPS) [ 9 , 10 , 19 , 33 ], sintering using silicon carbide bed [ 21 ], sintering in the air [ 18 ], tape casting [ 26 ] and hot pressing [ 33 ] are used in the literature to produce zirconia/graphene composites. Following [ 33 ] SPS and hot-pressing techniques were shown to be effective to produce fully dense zirconia/carbon nanofiber composites with high electronic conductivity.…”