Yamato Hayashi

Fabrication process and electrical properties of BaTiO3/Ni nanocomposites

Abstract A new capacitor, based on tetragonal BaTiO 3 /Ni micro- and nanocomposites, was made from BaTiO 3 and NiO. The NiO powders were reduced to micro- and nano-sized metal particulates during early stages of sintering, and the mixtures were pressureless-sintered in flowing argon gas atmosphere. TEM observation revealed that the nano-sized Ni particulates were homogeneously dispersed within matrix grains. The fracture toughness was improved 2.5 times by the Ni dispersion. The dielectric constant was also improved extremely by these Ni dispersion.

Fabrication of MgO based nanocomposites with multifunctionality

The nanocrysialline FeCo alloy dispersed MgO nanocomposites were fabricated by the reduction and sintering of mixtures. The powder mixtures of nano-sized FeCo alloy and MgO were obtained by the solution chemical processes and hydrogen reduction of MgO, Fe- and Co-nitrates powders. Fully densitified MgO/FeCo alloy nanocomposites were fabricated by a pulse electric current sintering (PECS) method. The fracture toughness increased with increasing volume fraction of FeCo alloy. Moreover, an inverse magnetostrictive response to applied stress was obserserved, because of the FeCo alloy dispersions, which indicates promise for incorporating multifunctions such as stress sensing into the structural ceramics with high fracture toughness.

Fabrication of metastable ZrO2-x single nano-sized particles

Metastable ZrO2−x particles were successfully prepared by inert gas condensation (IGC) process. To control oxygen vacancies in metastable ZrO2−x, the samples were annealed between 100 and 400 °C for 2 h under low oxygen partial pressures (PO2=10−15 Pa). After annealing, metastable ZrO2−x samples with various oxygen vacancies (0.26<x<0.81) were successfully fabricated; also, the particle sizes were less than 10 nm.