Steel foam for structures: A review of applications, manufacturing and material properties

The objective of this paper is to provide a state-of-the-art review for the structural application, manufacturing, material properties, and modeling of a new material: steel foam. Foamed steel includes air voids in the material microstructure and as a result introduces density as a new design variable in steel material selection. By controlling density the engineering properties of steel components may be altered significantly: improvement in the weight-to-stiffness ratio is particularly pronounced, as is the available energy dissipation and thermal resistivity. Full-scale applications of steel foams in civil structures have not yet been demonstrated. Therefore, existing applications demonstrating either proof-of-concept for steel foam, or full-scale use of aluminum foams in situations with clear civil/structural analogs are highlighted. Adoption of steel foam relies on the manufacturing method, particularly its cost, and the resulting properties of the steel foam. Therefore, published methods for producing steel foam are summarized, along with measurements of steel foam structural (modulus, yield stress, etc.) and non-structural (thermal conductivity, acoustic absorption, etc.) properties. Finally, existing models for predicting foamed steel material properties are summarized to highlight the central role of material density. Taken in total the existing research demonstrates the viability of steel foams for use in civil/structural applications, while also pointing to areas where further research work is required. © 2011 Elsevier Ltd. All rights reserved

Ceramic dielectric materials for high energy storage capacitors

WO 93/11548. Multilayer capacitors comprise layers of a dielectric material interleaved with metallic electrodes. To improve the energy storage of such capacitors when operating in field strengths greater than 20 kV/mm, the dielectric material is a modified ceramic material comprising a base material and an additive. The base material is a ferroelectric ceramic material having (i) its ferroelectric Curie temperature either greater than or lower than the working temperature of the capacitor, (ii) a large value of spontaneous polarisation near 0 °K and (iii) a large Curie constant. The additive forms mixed crystals with the base material without significantly changing its crystal structure, spontaneous polarisation or Curie constant, but reduces its ferroelectric Curie temperature to a value at least 50 °C below the capacitor working temperature. If the base material is barium titanate, the preferred additive is at least 40 atomic per cent strontium titanate