Densification of TiO<SUB>2</SUB> Nanopowders by Magnetic Pulsed Compaction

Abstract

In this study, sintered bodies of TiO 2 nanopowders were fabricated by the combined application of magnetic pulsed compaction (MPC) and subsequent sintering and then, their density and shrinkage were investigated. The optimum mixing conditions of polyvinyl alcohol, water, and TiO 2 nanopowder for compaction were found to be 2-3 mass% PVA, 15-20 mass% water, and 70-85 mass% of TiO 2 powder in the sintered bulks. High pressure and rapid compaction using magnetic pulsed compaction (MPC) enhanced the density with the increasing MPC pressure up to 0.7 GPa and significantly reduced the shrinkage rate (about 15% in this case) of the sintered bulks compared to the general process (about 18%).

Thermoelectric properties of n-type 95%Bi2Te3–5%Bi2Se3 materials fabricated by magnetic pulsed compaction (MPC)

“…In this present investigation, the action of the magnetic field was enhanced using a special concentrator, where a pulsed pressure from 1 to 5 GPa could be developed during 3e300 ms in the compaction zone. Recently, this dynamic compaction method of MPC was adopted to consolidate the difficult-to-compact ceramic powders [9,10], and a higher green density nearly to the full density was achieved in the MPCed bulks relative to other conventional powder compaction processes. It has been predicted that the rapid consolidation of 95%Bi 2 Te 3 e5%Bi 2 Se 3 gas-atomized powders by MPC would deliver bulks with enhanced microstructural properties, which in turn will affect the mechanical and thermoelectric properties of the bulks.…”

“…Since consolidation technique of the powders plays a vital role in determining thermoelectric and mechanical properties of the final bulks, a lot of techniques such as extrusion [2], hot pressing [5,6], spark plasma sintering (SPS) [7] and plasma activated sintering (PAS) [8] have been previously employed to compact Bi 2 Te 3 powders. However, altogether a new powder compaction approach employing high pressure and rapid compaction, called magnetic pulsed compaction (MPC) [9,10] was introduced in this research to consolidate the gas-atomized 95% Bi 2 Te 3 e5%Bi 2 Se 3 powders. In MPC, the pulsed electric power is transformed into a mechanical pulse by means of Lorentz force, and that mechanical pulse is concentrated in thcompaction zone to attain a maximum force of 1000 kN.…”