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Materials Science at Oregon State University

Graduate Student Seminars - Troy Ansell and Kyle Rozman

Date: Thursday, Oct 23rd
Presenter: Troy Ansell and Kyle Rozman, OSU Materials Science

Abstract


Troy Ansell abstract:
Development of High Temperature Ferroelectric Solid Solutions and Applications

Although focus in the field of bulk piezoelectric and ferroelectric materials for actuator applications has shifted to development of lead-free piezoelectric ceramics, lead based materials are still the dominant piezoelectric in terms of performance at high temperatures. The goal in lead- free research is to develop a material with properties in certain temperature (or time) regimes that either match or exceed the excellent properties of the ubiquitous actuator material, lead zirconate titanate (PZT). For temperatures above 400 °C (where PZT is in a paraelectric phase), only a few piezoelectric materials exhibit piezoelectric properties suitable for actuator applications. One such solid solution, PbTiO3 – BiScO3 (PT-BS), exceeds PZT in piezoelectric performance, higher Curie temperature (Tc) and depolarization temperature (Td), lower lead content, etc. Unfortunately, scandium oxides are very expensive, restricting PT-BS possible adoption in industry. The goal of this work is to investigate ternary piezoelectric solid solutions with reduced scandium content and similar material behavior as PT-BS. The properties and mechanisms of various systems to include: PbTiO3 – BiScO3 – Bi(X1/2Ti1/2)O3 (PT-BS-BXT) where X = (Zn, Mg, Ni, or Co) and PbTiO3 – (Bi1/2Na1/2)TiO3 - Bi(Zn1/2Ti1/2)O3 (PT-BNT-BZT) will be discussed. Also, some of the property correlations used to determine candidate solid solutions are discussed.

Kyle Rozman abstract:
Characterization of High Temperature Fatigue Mechanisms in Haynes 282 Nickel Based Superalloy

Electric power needs will only grow over the next decades as more humans ascend from poverty into the middle class. Currently, the majority of electric power is generated by burning fossil fuels. To help mitigate the undesirable effects of burning fossil fuels research is being done to increase the efficiency of power produced. In order to increase the efficiency of power production, the operating temperature of steam turbines must be increased, which presents a materials challenge. Haynes 282 is a nickel based superalloy which has been proposed as a potential rotor alloy for steam turbines operating at high temperature (760 °C). Other authors have previously looked at creep, oxidation, low cycle fatigue and other properties of Haynes 282; however, lacking from the literature are studies on the fatigue crack growth mechanisms in Haynes 282. This project investigated Haynes 282 from a fatigue crack growth perspective with an aim to fill this literature gap and asses the utility of Haynes 282 as a steam turbine rotor alloy.