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Search Publications by: Ward L. Johnson (Fed)

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Displaying 26 - 50 of 105

Resonant Acoustic Frequency Shifts Associated with Cracks in Multilayer Ceramic Capacitors

June 6, 2017
Author(s)
Ward L. Johnson, Jaemi Herzberger, Sudook A. Kim, Kirsten L. Peterson, Paul R. Heyliger, Grady S. White
Resonant ultrasound spectroscopy (RUS) was used in this study to measure shifts in resonant frequency that arise from the presence of cracks in barium-titanate-based multi-layer ceramic capacitors (MLCCs). This work was motivated by an industrial need for

Vibrational Modes of Multilayered Ceramic Capacitors

April 28, 2016
Author(s)
Kirsten L. Peterson, Ward L. Johnson, Sudook A. Kim, Paul R. Heyliger
Micron-scale spacing of interleaved electrodes and high-dielectric ceramics in multilayer ceramic capacitors (MLCCs) provide exceptionally high capacitances in small volumes. This has led to MLCCs being the preferred type of capacitor in a wide range of

Nonlinear resonant acoustic detection of cracks in multilayer ceramic capacitors

September 3, 2014
Author(s)
Ward L. Johnson, Sudook A. Kim, Grady S. White, Jaemi Herzberger
Abstract—Measurements of resonant ultrasonic frequencies of multilayer ceramic capacitors (MLCC) were performed as a function of excitation amplitude to assess the potential of nonlinear acoustic methods for sensing the presence of cracks. The ultimate

High-Temperature Electromechanical Properties of CTGS

December 1, 2013
Author(s)
Ward L. Johnson, Michal Schulz, Holger Fritze
CTGS (Ca3TaGa3Si2O14) is a commercially available, Czochralski-grown piezoelectric material from the langasite family that has an ordered crystal structure. It can be excited piezoelectrically up to at least 1285 °C, which is very close to the melting

Continuum-based free vibration of circular trigonal and isotropic plates

May 28, 2013
Author(s)
Ward L. Johnson, Paul R. Heyliger
The free vibration behavior of completely unrestrained elastic circular plates with trig- onal and isotropic material symmetry is studied using approximate solutions to the three- dimensional theory of linear elasticity. Of primary interest are 1) the

Nonlinear acoustic effects in multilayer ceramic capacitors

January 25, 2013
Author(s)
Ward L. Johnson, Sudook A. Kim, Timothy P. Quinn, Grady S. White
Nonlinear resonant acoustics was explored as an approach for nondestructively evaluating the susceptibility of BaTiO3-based multilayer ceramic capacitors to electrical failure during service. The acoustic nonlinearity was characterized through measurements

Vibrational modes of GaN nanowires in the gigahertz range

November 13, 2012
Author(s)
Ward L. Johnson, Sudook A. Kim, Roy H. Geiss, Colm Flannery, Kristine A. Bertness, Paul R. Heyliger
Monocrystalline nanowires offer an attractive basis for resonant nanoelectromechanical systems (NEMS) for a variety of applications, including mass and force sensing, and, in each of these applications, there are advantages to operation at frequencies

Thermogravimetric Analysis with a Heated Quartz Crystal Microbalance

August 11, 2012
Author(s)
Ward L. Johnson, Elisabeth Mansfield
Thermogravimetric analysis with an SC-cut quartz crystal microbalance (QCM) were demonstrated at temperatures in the range from 20 C to 450 C. A measurement system was built around a crystal sensor head that was mounted in a small tube furnace. Changes in