Strength of zirconium carbide composites with disperse carbon inclusions

Effect of residual stresses on the strength of ceramic materials (Review)

“…Significant advantages of refractory carbidegraphite compositions with a high thermal strength were achieved as early as the 1980s [54,55]. The intro duction of less rigid (by 40-50 times) carbon inclu sions into a carbide matrix should inevitably decrease the efficient elastic modulus and strength of the com position, since it is fundamentally impossible to unload the matrix by transferring the major portion of an applied load to low modulus particles.…”

Role of impurities on the spark plasma sintering of ZrCx–ZrB2 composites

“…This effect slows down the lattice carbon diffusion which plays the role of the rate limiting step during the densification process. 8,9 In the same way, the grain size distribution of the raw powders represents a major parameter which strongly controls the microstructure of the sintered samples. So, the first part of this paper deals with the characterization of the starting powders used to elaborate the ZrC x -ZrB 2 composites.…”

“…8 This blocking action would depend both on the number and size of the carbon inclusions present at the grain boundary. In addition, it is well known that free carbon could seriously influence the final stoichiometry (x) of the zirconium carbide (ZrC x ) by decreasing the concentration of carbon vacancies.…”

“…The presence of free carbon as well as the occurrence of various impurities within the starting powders is supposed to influence the sintering mechanism 8,9 : the free carbon particles could have an inhibiting effect on the growth of zirconium carbide grains. 8 This blocking action would depend both on the number and size of the carbon inclusions present at the grain boundary.…”

“…Such intergranular inclusions would slow down the grain boundary motion inducing a blocking strain by a pinning like effect as already noticed during previous studies about the pressure-less sintering of non-oxide ceramics. 8 …”