Alex Aning

Formation of polymer/ceramic composite grain boundary capacitors by mechanical alloying

Abstract A new technique to process ceramic/polymer grain boundary capacitors has been developed and demonstrated using BaTiO 3 as the ceramic conducting phase and LaRC-TPI polymer as the insulating phase. The particles were characterized by transmission electron microscopy and the dielectric properties of the capacitors were measured at room temperature and 100 kHz. The overall best composite grain boundary capacitor was made with 40 vol% polymer after milling the powder for 1 h. It had a dielectric constant of 58 and a dielectric loss of 0.01. The dielectric properties of the grain boundary capacitors could be manipulated by changing processing variables such as milling time and volume fraction of polymer.

Study of mechanical alloying of Sm and Fe

Mechanical alloying of Sm and Fe with the composition of SmFe3 was studied using x-ray-diffraction (XRD), Mossbauer, and magnetization measurements. Data taken as a function of milling time for up to 20 h show significant changes occurring during ball milling. The XRD studies show that the initial crystalline Bragg reflections changed to a broad maximum, which is attributed to the formation of an amorphous phase. The initial six-line pattern in the Mossbauer spectrum, characteristic of magnetic ordering, changed to a broad singlet, characteristic of a nonmagnetic material. Magnetization measurements revealed that the coercive field was at its maximum after 5 h of milling and decreased sharply as the milling time increased. The remanent magnetization was at its maximum between 5 and 10 h of milling. The final product of the ball milling, which exhibited the characteristics of an amorphous paramagnetic material in its XRD and Mossbauer spectrum, was studied after heat treatment. The XRD and the Mossbauer sp...