Raman spectrum of the surface layer with a thickness of approximately 80 nm of a porous carbon ceramic was obtained (the porosity was used equal to 5%). Spectrum analysis showed that the ceramics contains crystals of silicon carbide - 6H-SiC and silicon. The destruction of ceramics by diamond microcrystals resulted in fractoluminescence (FL). Spectrum of FL contains two bands at 1.6 and 1.9 eV. The first band is formed by breaking down the silicon crystals, and the second band is formed by breaking down the 6H-SiC crystals. The time dependence of the intensity of FL signals with a time resolution of 2 ns is obtained. Three types of signals were observed: one type of signal is formed when the 6H-SiC crystals break down, the second type of signal is formed when the silicon crystals break down, and the third type of signal is formed when these crystals break down simultaneously. The appearance of signals is associated with the formation of cracks arising from the breaking down of the barriers formed at the intersection of slip planes of dislocations in silicon carbide and silicon crystals. The size of cracks in 6H-SiC is estimated: the smallest ones is 5.5 nm, and the largest is approximately 18 nm.

When the silicon surface is destroyed, clusters of the smallest “primary” cracks are formed. Their formation leads to the appearance of “fractoluminescence” (FL) signals. The FL signals and spectra contained maxima, the number of which is equal to the number of “primary” cracks in the cluster. An analysis of the FL signals and spectra showed that, upon failure of the (100) and (110) surfaces, clusters of four “primary” cracks appeared, and (111) surfaces, of three “primary” cracks. Their sizes were estimated by the growth rate and time. It turned out that they are multiples of the crystal lattice constant a: ≈ 3a, 4a, and 6a. At the moment of formation, “primary” cracks are in a nonequilibrium state and, over time, transform into defects that look like “troughs” and “tops.” Their sizes are from 2 to 4 times smaller than the sizes of “primary” cracks.

Рассмотрены временные характеристики развития локального разрушения при кратковременной точечной нагрузке керамик SiC, широко применяемых в качестве защитных материалов против ударного воздействия на технику и человека. Методами акустической эмиссии и электромагнитной эмиссии изучена статистика соответственно зарождения и релаксации микротрещин. Показано, что длительность интервалов между появлением трещин следует степенному закону, характерному для кооперативных явлений. Временное распределение импульсов электромагнитного излучения от электрических зарядов, возникающих на берегах микротрещин и аннигилирующих при релаксации таковых после прохода ударной волны, напротив, было линейным. Временная структура релаксации трещин позволила выделить две группы повреждений различного масштаба: мельчайшие дефекты в сплошном материале и более крупные микротрещины, соединяющие соседние поры. Ключевые слова: SiC, пористая керамика, ударное разрушение, акустическая эмиссия, электромагнитная эмиссия.