Abstract
The process of consolidation of TiN nanopowders under a hydrostatic pressure of 3 GPa was evaluated from the evolution of substructure parameters of compacts obtained after different exposure of powder bodies under constant pressure at room temperature. It has been established that in compaction, changes in the substructure reflect deformation processes of the porous body, which are accompanied by relaxation processes and the corresponding decrease in microstresses. The sintering of consolidated 80 wt% TiN - 20 wt% TiB2 powders at 3 GPa in the temperature range 1300℃ - 1600℃ leads to the substitution of N atoms by B atoms in TiN and possibly to the substitution of B atoms by N atoms in TiB2. The presence of oxygen in powders promotes the formation of titanium oxynitride, which increases the microhardness of specimens.
Highlights
The physicomechanical properties of ceramics can be improved by sintering of nanosized powders with retention of nanosized grains [1]-[4]
Processes of deformation of a porous powder body are accompanied by the fragmentation of particles and their rearrangement. These effects show themselves as a change in the size of crystallites that form particles and microdistortions of the lattice. This is why we analyzed the process of consolidation of TiN powder in the field of high quasihydrostatic pressure considering the evolution of the substructure parameters of compacts obtained after holding the powder under constant pressure
Under the action of constant compressive quasihydrostatic stresses, a porous compact from TiN nanopowder deforms at a small rate, which manifests itself in the character of change in D and Δa/a with time
Summary
The physicomechanical properties of ceramics can be improved by sintering of nanosized powders with retention of nanosized grains [1]-[4]. Among efficient methods of densification of nanopowders, it is compaction under high quasihydrostatic pressures. Such baric pretreatment (BP) consists in compression of powder briquettes by high quasihydrostatic pressure (as a rule, to 5 GPa) and enables one to obtain a compact with a density to 90% [5]. The advantage of the method of baric compaction is a homogeneous distribution of the density over the volume, which increases the efficiency of subsequent sintering. (2016) Obtaining at High Pressure the TiN-TiB2 Ceramic Nano-Composite. In the absence of vacuum treatment, air remains in porous briquettes, which increases their porosity and the amount of oxynitride formed in sintering
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