Timothy J. Roosendaal

Bio: Timothy J. Roosendaal is an academic researcher from Pacific Northwest National Laboratory. The author has contributed to research in topics: Ultimate tensile strength & Materials science. The author has an hindex of 9, co-authored 27 publications receiving 188 citations.

Low Activation Joining of SiC/SiC Composites for Fusion Applications: Tape Casting TiC+Si Powders

Abstract: The use of SiC composites in fusion environments likely requires joining of plates using reactive joining or brazing. One promising reactive joining method uses solid-state displacement reactions between Si and TiC to produce Ti3SiC2 + SiC. We continue to explore the processing envelope for this joint for the TITAN collaboration in order to produce optimal joints to undergo irradiation studies in HFIR. One noted feature of the joints produced using tape-calendared powders of TiC+Si has been the large void regions that have been apparently unavoidable. Although the produced joints are very strong, these voids are undesirable. In addition, the tapes that were made for this joining were produced about 20 years ago and were aging. Therefore, we embarked on an effort to produce some new tape cast powders of TiC and Si that could replace our aging tape calendared materials.

Polymer-Cement Composites with Self-Healing Ability for Geothermal and Fossil Energy Applications

Abstract: Sealing of wellbores in geothermal and tight oil/gas reservoirs by filling the annulus with cement is a well-established practice. Failure of the cement as a result of physical and/or chemical stress is a common problem with serious environmental and financial consequences. Numerous alternative cement blends have been proposed for the oil and gas industry. Most of these possess poor mechanical properties, or are not designed to work in high temperature environments. This work reports on a novel polymer-cement composite with remarkable self-healing ability that maintains the required properties of typical wellbore cements and may be stable at most geothermal temperatures. We combine for the first time experimental analysis of physical and chemical properties with density functional theory simulations to evaluate cement performance. The thermal stability and mechanical strength are attributed to the formation of a number of chemical interactions between the polymer and cement matrix including covalent bonds...

Recent Advances in Intrinsic Self-Healing Cementitious Materials.

Abstract: Self-healing is a natural phenomenon whereby living organisms respond to damage. Recently, considerable research efforts have been invested in self-healing cementitious materials that are capable of restoring structural integrity and mechanical properties after being damaged. Inspired by nature, a variety of creative approaches are explored here based on the intrinsic or extrinsic healing mechanism. Research on new intrinsic self-healing cementitious materials with biomimetic features is on the forefront of material science, which provides a promising way to construct resilient and sustainable concrete infrastructures. Here, the current advances in the development of the intrinsic healing cementitious materials are described, and a new definition of intrinsic self-healing discussed. The methods to assess the efficiency of different healing mechanisms are briefly summarized. The critical insights are emphasized to guide the future research on the development of new self-healing cementitious materials.

Feature Article Current status and prospects of SiCf/SiC for fusion structural applications

Abstract: This article provides an overview of the main characteristics of SiCf/SiC that suggest the use of this SiC-based composite as a structural material for the blanket in future fusion reactors, a brief description of its structure and the role of its main constituents. The relevant fabrication processes and their ability to produce a material with the required properties are also summarised. The main part of the paper is devoted to an assessment of the state-of-the-art materials, and the basic requirements for the target material are discussed in terms of the achieved properties. The key issues and areas of uncertainty are described and suggestions for overcoming them are presented. © 2013 Elsevier Ltd. All rights reserved.