H. W. King

Relationships between Textures and Surface Roughness, Frictional Behavior, Erosion and Corrosion Properties of TiN Films

TiN coated films were prepared by a reactive ion physical vapor deposition method. In this research, we studied the relationships between textures and friction coefficient, erosion-corrosion resistance and corrosion resistance in textured TiN films. The surface roughness of (115) textured TiN films is lower than that of (111) textured TiN films. The friction coefficient of (115) textured surface is similar with that of (111) textured surface of TiN coated films. The erosion-corrosion and corrosion resistance of (115) textured surface is better than that of (111) textured surface of TiN coated films.

Crack growth in lead magnesium niobate: lead titanate ceramics by cyclic electric fields

Pre-existing cracks introduced by a Vickers diamond hardness indenter in PMN-0.3PT, which displays piezoelectric properties, increase in length under the action of low frequency cyclic electric fields applied normal to the crack. A minimum applied field of 1.1 x Ec is required to cause crack growth. In applied fields of 1.85-5.70 x Ec cracks grow to a common limiting length which is approximately 0.8 times the separation between the electrodes. New cracks are not generated at the corners of a Vickers diamond indent by applied fields up to 5.70 x Ec.

X-Ray Measurement of Thermal Expansion in Electrostrictive 0.9PMN-0.1PT

Using high temperature X-ray diffraction, the thermal expansion coefficient (α) of a 0.9Pb(Mg1/3Nb2/3)O3-0.1PbTiO3 ceramic is found to decrease from 4 × 10−5 C−1 to 3 × 10−6 C−1 on going from the cubic to the pseudocubic phase. The lattice stiffening indicated by this order of magnitude decrease in α occurs at a distinct temperature (Tα) which is some 80°C above the Tm temperature. Since the structural phase transformation is a necessary, but not sufficient, condition for the transition to the relaxor state, the relaxor region of the phase diagram must be reexamined by direct structural investigation.

EFFECT OF CYCLIC ELECTRIC FIELDS ON CRACK GROWTH IN A MODERATELY SOFT PIEZOELECTRIC CERAMIC

Pre-existing cracks, introduced by a Vickers diamond hardness indenter in BM500 (Navy Type II) PZT, exhibit visible growth and thickening when subjected to low frequency electric fields with amplitudes above a threshold on the order of 1.66 Ec. Thickening, but no growth, of cracks is also observed after cycles of a field of 1.64 Ec. The threshold field is related to the ferroelectric, piezoelectric and elastic properties of the ceramic. At fields above the threshold, cracks grow to a limiting size after a relatively low number of cycles, and then increase in width, as opposed to length, when further electric cycles are applied. The maximum size to which field-induced cracks grow is of the order of the separation of the electrodes. Changes observed in the resonance peaks of impedance spectra may be used as a basis for non-destructive identification of defects in piezoelectrics.