Joo-Hwan Han

Determination of three-dimensional grain size distribution by linear intercept measurement

Abstract For grains of any shape, a computer simulation technique to calculate the probability of finding a certain intercept length is suggested and the results are given for cubic, tetragonal and hexagonal grains. The distribution of linear intercepts measured is then converted into that of a three-dimensional (3D) size. The developed method is applied to determine the 3D distribution of cubo–spherical grains observed in the TiC–Ni cermet.

Fabrication of dense Zno-varistors by atmosphere sintering

Abstract ZnO varistors are fabricated by the atmosphere sintering, during which Bi 2 O 3 vapor is transferred from the atmosphere powder bed to the pure ZnO powder compacts. The residual porosity of the atmosphere sintered specimens is significantly lower than that of the conventionally liquid-phase sintered specimens. The densification process during the atmosphere sintering is discussed and the electrical characteristic of the atmosphere sintered varistors is examined.

Models of melting and liquid structure based on rotationally free atomic clusters

Abstract Atomistic models, describing the melting process of crystalline materials and the resultant liquid state, have been developed. With an increase in temperature, the inter-atomic distance of a crystal is suggested to fluctuate by the wave-like behavior of lattice vibration. At the melting point, the crystal is divided into numerous atomic clusters and the rotational symmetry of the atoms is broken. The model is adequate for describing the first-order phase transition characteristic of the melting process, which shows an abrupt increase in volume. The liquid state can, therefore, be defined as an assemblage of temporary atomic clusters. The atoms have no long-range order due to the rotational freedom of the clusters.