—
Image of PiezoMEMS actuated wing design, illustrating PZT stroke and pitch actuators and thin film wing structure (left). Image of suspended platform with individually controllable wings next to a US dime (right). From PZT-Based Piezoelectric MEMS Technology. Credit: JACerS; Wiley.
New papers that have been accepted for publication in the Journal of the American Ceramic Society are posted to “Early View” on the Wiley website and can be read even before the issue is printed. Below are summaries of selected papers currently available via Early View.
All members of The American Ceramic Society receive free online access to JACerS. To access any of the ACerS journals, or to become a member, visit www.ceramics.org.
PZT-Based Piezoelectric MEMS Technology
Gabriel L. Smith, Jeffrey S. Pulskamp, Luz M. Sanchez, Daniel M. Potrepka, Robert M. Proie, Tony G. Ivanov, Ryan Q. Rudy, William D. Nothwang, Sarah S. Bedair, Christopher D. Meyer and Ronald G. Polcawich
These US Army Research Laboratory staff members have authored this feature article as a review of recent advances in the design and fabrication of thin-film lead zirconate titanate microelectromechanical system devices. They report techniques for optimizing highly (001)/(100) oriented chemical-solution-deposited PZT films to achieve improved piezoelectric coefficients. Actuators and transducers used in communication systems and phased-array radar are fabricated from these PZT films. They also report that the large relative displacements generated by these films demonstrate mechanical mobility in MEMS devices, including insect-inspired flight actuators and ultrasonic traveling wave motors.
Following are three previews that will be incorporated in a special topical issue of the Journal to be published during August 2012. The issue is a collection of papers presented during the International Conference on Sintering held on Jeju Island, Republic of Korea, on August 26 through September 1, 2011. The guest editors for this issue are Suk-Joong L. Kang, Rajendra Bordia, Didier Bouvard and Eugene Olevsky, who also chaired the meeting.
Fundamental Aspects of Spark Plasma Sintering: I. Experimental Analysis of Scalability
Eugene A. Olevsky, William L. Bradbury, Christopher D. Haines, Darold G. Martin and Deepak Kapoor
This team from San Diego State University and US Army ARDEC conducted scalability experiments on the spark plasma sintering of similarly shaped alumina specimens of four different sizes using two different SPS devices of different scales. The team reports that, overall, SPS shows good scalability potential (in terms of relative density and grain-pore structure) within a single SPS device, but indicates substantial structure changes when switching between different SPS devices. It also reports that, because of the demonstrated possibility of a significant size impact in case of high heating rates and large specimen sizes as well as the demonstrated differences of the processing outcomes based on different SPS devices, the predictive capability of reliable modeling approaches is of great importance for the industrial implementation of SPS techniques.
Fundamental Aspects of Spark Plasma Sintering: II. Finite Element Analysis of Scalability
Eugene A. Olevsky, Cristina Garcia-Cardona, William L. Bradbury, Christopher D. Haines, Darold G. Martin and Deepak Kapoor
In the second of its two articles, the team from San Diego State University and US Army ARDEC describes a comprehensive, three-dimensional, fully coupled thermoelectromechanical finite-element model it developed for modeling spark plasma sintering. It applied the model to the simulation of SPS with four different tooling sizes and various temperature regimes. The team reports that comparison of modeling and experimental results shows that the model is reliable for qualitative predictions of the densification behavior and of the grain growth in powder specimens subjected to SPS within a given temperature regime.
Microstructural Evolution and Anisotropic Shrinkage in Constrained Sintering and Sinter Forging
Fumihiro Wakai and Rajendra K. Bordia
Wakai (Tokyo Institute of Technology) and Bordia (University of Washington) studied constrained sintering of thin films on rigid substrates as well as in stress-assisted densifications, such as sinter forging and hot pressing. They used general constitutive equations and sintering stress and viscosity tensors to describe deformation and stress states in the bodies. Wakai and Bordia report that the model predicts the evolution of the anisotropic microstructure during sintering and the effect of the local microstructure on anisotropic shrinkage.
Decomposition-Coarsening Model of SiOC/HfO2 Ceramic Nanocomposites Upon Isothermal Anneal at 1300°C
Hans-Joachim Kleebe, Katharina Nonnenmacher, Emanuel Ionescu and Ralf Riedel
These researchers from Technische Universität Darmstadt studied the variation of the crystallite size of hafnia precipitates in silicon oxycarbide-hafnia ceramic nanocomposites after annealing bulk samples. They report that their studies show that polymer-derived ceramics are prone to phase separation and local chemical changes on high-temperature treatment and are not as stable as commonly considered.
Low Temperature Crystallization of Metastable Nickel Manganite Spinel Thin Films
Song Won Ko, Heidi M. Schulze, David B. Saint John, Nikolas J. Podraza, Elizabeth C. Dickey and Susan S. Trolier-McKinstry
This team of researchers from several universities in the US used chemical solution deposition to produce single-phase metastable cubic spinel nickel manganite films having various Mn/(Mn+Ni) compositions. The team reports that metastable spinel phase appeared in pyrolyzed and postdeposition annealed films and that the complex dielectric function spectra varied as a function of the annealing conditions. It also reports the results of aging experiments used to identify variations in resistivity and temperature coefficient of resistance as functions of time.
Citric Acid-Assisted Combustion-Carbothermal Synthesis of Well-Distributed Highly Sinterable AlN Nanopowders
Aimin Chu, Mingli Qin, Rafi -ud-din, Baorui Jia, Huifeng Lu and Xuanhui Qu
These researchers from China and Pakistan synthesized aluminum nitride nanopowders by carbothermal reduction of a citric acid-assisted combustion synthesis precursor derived from AlN, glucose, citric acid and urea mixed solution. They studied the effects of citric acid on the size and morphology of the precursors and on the as-synthesized powders. They report that the decarburized AlN powders were free of hard agglomerates and exhibited well-distributed and highly sinterable spherical particles and that they were able to produce pellets with 99.05 percent of theoretical density.
DWPF Startup Frit Viscosity Measurement Round Robin Results
Jarrod V. Crum, Tommy B. Edwards, Renee L. Russell, Phyllis J. Workman, Michael J. Schweiger, Ray F. Schumacher, Don E. Smith, David K. Peeler and John D. Vienna
These authors from Pacific Northwest National Laboratory and Savannah River National Laboratory document the results of a viscosity round robin study conducted on Defense Waste Processing Facility startup frit (selected because its viscosity-temperature relationship is similar to most DWPF and Hanford high-level waste glass compositions). The ground, blended and homogenized glass was supplied to eight laboratories for viscosity measurements, which were conducted following a specified temperature schedule within a temperature range of 1150°C-950°C, with an option to measure viscosity at temperatures below 950°C if equipment was capable. Standard errors for confidence and prediction were determined for the fitted Vogel-Fulcher-Tamman-Hesse and Arrhenius equation models.