Search

Porous TiAl intermetallic samples are successfully fabricated via an elemental powder metallurgy route. Cylindrical green samples are prepared by cold pressing of Ti-48Al elemental powders under different pressures. They are subsequently sintered in a dilatometer or a tube furnace. In the sintering, chemical reactions happens through discrepant diffusions between Ti and Al caused by the Kirkendall effect, which forms pores in the material and makes it expand in the sintering. The expansion happens in an anisotropic way, in which the axial expansion is larger than the radial expansion, especially for samples pressed under low pressure. As the compacting pressure increasing, the difference between axial and radial expansions gradually diminishes. Moreover, increasing pressure also leads to higher green density and better bonding between Ti and Al particles, therefore facilitating the diffusion and reactions between Ti and Al. As a result, the samples compacted under higher pressures experience larger expansion compared to those compacted under lower pressures. However, in spite of the larger expansion, the samples compacted under higher pressures still exhibit higher sintering density and compressive strength than those compacted under lower pressures. [ABSTRACT FROM AUTHOR]

• Modified vermiculite achieved a better expansibility under microwave irradiation. • A novel quantitative analysis method of microwave energy absorption was proposed. • Influence mechanism of Mg2+ modification on microwave absorption was analyzed. This work investigated the effect of microwave power on vermiculite expansibility for different exposure time and compared the changes after Mg2+ modification. The expansion ratio of the modified vermiculite sample reached up to 5.29 at 800 W with a significant increase of 23.89 % in contrast to the raw vermiculite sample. Aimed to quantify the microwave energy absorption of vermiculite, a novel method was proposed by employing water as a medium material due to its sensitivity to microwave energy. Using this method, the effect of microwave power on microwave energy absorption of vermiculite was studied. Meanwhile, the influence mechanism of Mg2+ modification on microwave energy absorption of vermiculite was analyzed by means of energy dispersive X-ray spectroscopy and thermogravimetric-differential scanning calorimeter. Mg2+ modification could significantly improve the microwave energy absorption ability of vermiculite, which was mainly ascribed to the increase of interlayer water content through Mg2+ hydration reaction. [ABSTRACT FROM AUTHOR]