First-principles quantum molecular dynamics study of Ti_xZr_1−xN(111)/SiN_y heterostructures and comparison with experimental results

Abstract

The heterostructures of five monolayers B1–TixZr1−xN(111), x = 1.0, 0.6, 0.4 and 0.0 (where B1 is a NaCl-type structure) with one monolayer of a Si3N4-like Si2N3 interfacial layer were investigated by means of first-principles quantum molecular dynamics and a structure optimization procedure using the Quantum ESPRESSO code. Slabs consisting of stoichiometric TiN and ZrN and random, as well as segregated, B1–TixZr1−xN(111) solutions were considered. The calculations of the B1–TixZr1−xN solid solutions, as well as of the heterostructures, showed that the pseudo-binary TiN–ZrN system exhibits a miscibility gap. The segregated heterostructures in which Zr atoms surround the SiyNz interface were found to be the most stable. For the Zr-rich heterostructures, the total energy of the random solid solution was lower compared to that of the segregated one, whereas for the Ti-rich heterostructures the opposite tendency was observed. Hard and super hard Zr–Ti–Si–N coatings with thicknesses from 2.8 to 3.5 μm were obtained using a vacuum arc source with high frequency stimulation. The samples were annealed in a vacuum and in air at 1200 °C. Experimental investigations of Zr–Ti–N, Zr–Ti–Si–N and Ti–Si–N coatings with different Zr, Ti and Si concentrations were carried out for comparison with results obtained from TixZr1−xN(111)/SiNy systems. During annealing, the hardness of the best series samples was increased from (39.6 ± 1.4) to 53.6 GPa, which seemed to indicate that a spinodal segregation along grain interfaces was finished. A maximum hardness of 40.8 GPa before and 55 GPa after annealing in air at 500 °C was observed for coatings with a concentration of elements of Si≽ (7–8) at.%, Ti ≽ 22 at.% and Zr ⩽ 70 at.%.

Arc-Evaporated Nanoscale Multilayer Nitride-Based Coatings for Protection Against Wear, Corrosion, and Oxidation

“…Such material characteristics as hardness, elasticity, adhesive and cohesive strength, durability, thermal and chemical stability and others are particularly important in this regard [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15].…”

Multilayered vacuum-arc nanocomposite TiN/ZrN coatings before and after annealing: Structure, properties, first-principles calculations

“…The relaxation of the atomic coordinates and of the supercell was considered to be complete when atomic forces were < 1.0 mRy/Bohr (25.7 meV/Å), stresses were smaller than 0.05 GPa, and the total energy during the structural optimization iterative process was changing by < 0.1 mRy (1.36 meV). In the large supercell calculations, the chosen reduced energy cut-off and the mesh of k-points were used in order to spare computing time without compromising accuracy [36]. Such computational conditions were proved to be quite justified [37].…”

Влияние толщины бислоя наноструктурного многослойного покрытия MoN/CrN на его микроструктуру, твердость и элементный состав

“…При переходе нитридных покрытий в наноструктурное состояние [5] отмечается существенное улучшение их физико-механических и три-бологических свойств, повышение стойкости к темпе-ратурным воздействиям [6][7][8][9], улучшение коррозионной стойкости [10][11][12][13][14] и т. д. Одним из способов реализации перехода покрытий в наноструктурное состояние явля-ется осаждение многослойных композиционных матери-алов [15][16][17], в которых чередование слоев из разных составляющих [14,18] служит хорошим диффузионным барьером [19] и обеспечивает повышение стабильности свойств при внешних воздействиях [20]. В этом случае сверхтвердое состояние многослойных нанокомпозитов предполагает подавление процессов роста зародышевых трещин, генерирования и распространения дислокаций, обеспечивающих пластический сброс деформации при уменьшении размеров нанокристаллитов до 10 nm [21], и отсутствие характерной для наноструктурных матери-алов аномальной зависимости Холла−Петча [22].…”