The influence of some impurity ions on the increase/decrease in the resistance against irradiation of metal oxides with X‐rays and electrons (low‐dense excitation) or ∼2 GeV Au198 and U238 ions providing a superhigh density of electronic excitations along cylindrical tracks (LET > 30 keV nm−1) has been investigated for fcc MgO single crystals with close ion masses or Lu3Al5O12 and Gd2SiO5 with large unit cells and heavy cations. The radiation effects have been studied using the methods of low‐temperature vacuum ultraviolet spectroscopy (up to 40 eV), cathodoluminescence and thermoactivation spectroscopy. The step‐by‐step annealing of the radiation‐induced absorption, scattering, and luminescence has been performed at the heating of irradiated crystals up to ∼70% of a melting point. Possible experimental manifestations of the temperature‐stable nanosize 3D defects created, according to theoretical predictions, via rearrangement of many host ions at the collapse of discrete solitons (breathers) are detected in Lu3Al5O12 and Gd2SiO5 crystals irradiated with swift heavy ions (fluence of 1012 ions cm−2).
The structural-phase state and tribological characteristics of detonation coatings based on Ti–Si–C before and after pulsed-plasma exposure have been experimentally investigated. The authors of the research used a detonation set-up of CCDS2000 to obtain coatings. The modification of coating surfaces was carried out by a pulsed-plasma flow using the “Impulse-6” installation. The results of the research have shown that the modification of coatings surface by a pulsed-plasma effect causes an increase in the microhardness of the surface layer and in its wear resistance. It was determined that after such type of treatment, there is an increase in the content of the Ti3SiC2 phase. According to the results of XRD analysis, the improvement in the mechano-tribological properties of detonation spraying coatings of the Ti–Si–C system as a result of pulsed-plasma treatment is associated with an increase in the content of Ti3SiC2 phases in the coatings, as well as the formation of carbide and oxide phases on the surface layer.
This study is aimed at obtaining a coating of aluminum oxide containing α-Al2O3 as the main phase by detonation spraying, as well as a comparative study of the structural, tribological and mechanical properties of coatings with the main phases of α-Al2O3 and γ-Al2O3. It was experimentally revealed for the first time that the use of propane as a combustible gas and the optimization of the technological regime of detonation spraying leads to the formation of an aluminum oxide coating containing α-Al2O3 as the main phase. Tribological tests have shown that the coating with the main phase of α-Al2O3 has a low value of wear volume and coefficient of friction in comparison with the coating with the main phase of γ-Al2O3. It was also determined that the microhardness of the coating with the main phase of α-Al2O3 is 25% higher than that of the coatings with the main phase of γ-Al2O3. Erosion resistance tests have shown (evaluated by weight loss) that the coating with α-Al2O3 phase is erosion-resistant compared to the coating with γ-Al2O3 (seen by erosion craters). However, the coating with the main phase of γ-Al2O3 has a high value of adhesion strength, which is 2 times higher than that of the coating with the main phase of α-Al2O3. As the destruction of coatings by the primary phase, α-Al2O3 began at low loads than the coating with the main phase γ-Al2O3. The results obtained provide the prerequisites for the creation of wear-resistant, hard and durable layered coatings, in which the lower layer has the main phase of γ-Al2O3, and the upper layer has the main phase of α-Al2O3.
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