Key Engineering Materials Vol. 380

Abstract: Thin film coatings of fluorine doped tin oxide on glass were first produced in the 1940’s as part of the World War II effort. Generically known as TCO (Transparent Conductive Oxide) Coatings, the primary use was for antifogging coatings for aircraft transparencies using an electrical current to heat the glass assembly. Nearly 60 years later, these coatings are still used in cockpit glazings. Although the first generation coatings were applied using spray pyrolysis on heated glass panes, by 1990 these coatings were being applied directly on the float glass ribbon during the primary glass manufacturing operation, using Atmospheric Pressure Chemical Vapor Deposition (APCVD). As part of a color suppressed multi-layer structure, these coatings met the aesthetic and performance criteria for architectural low E glazings, and spawned new applications in electrochromic devices, heated freezer doors, radiant glass heaters, EMI/RFI Shielding, and the largest growing segment in glass – thin film photovoltaic panels. In this paper we discuss the characteristics of the on-line production, the performance characteristics of the coatings, the end use requirements, and the massive infrastructure in place worldwide to support the volume requirements. We compare the properties of SnO2:F to other emerging TCO materials such as zinc oxide.

Abstract: Considering the status of wood utilization in rapidly depleting forests, the various innovations introduced to meet the challenges of short supply, and to overcome some of the main defects of various species of wood are explained, particularly with reference to tropical countries like India. The associated developments in wood adhesives and wood joints are also briefly discussed. Some recommendations are suggested for new approaches

Abstract: The lack of a low cost, high volume method to produce carbon nanotubes has greatly limited their commercialization. Carbon nanofibers have a similar structure and properties as nanotubes and are a commercially viable alternative to them. In recent years many of the difficulties of commercial nanofiber production have been overcome through innovations in their manufacturing process. It is now possible to produce carbon nanofibers of different grades, such as thinner and thicker walled ones, and low heat treated and high heat treated ones. Most significantly, commercial quantities can now be produced of carbon nanofibers that have been surface functionalized with carboxylic acid groups, making them suitable for further functionalization and new classes of applications, such as biomedical sensors and drug delivery. Despite their cost advantages and availability more widespread use of carbon nanofibers has been hampered by uncertainties in their molecular structure and a lack of physical property measurements. However, recent theoretical and experimental studies have addressed these deficiencies showing that these fibers have a cone-helix structure under the usual manufacturing conditions. Additionally, small amounts of a segmented carbon nanotube structure, commonly called a bamboo structure, are also present. When the conical nanofibers were heat treated they were found to transform to a stacked cone structure. Advances in surface functionalization have allowed a variety of groups to be incorporated on them, significantly enhancing their properties and potential applications. Finally, the recent development of a new method to measure the elastic properties and morphology of single nanofibers has clearly demonstrated the high strength of these fibers. These nanofibers now represent a well understood and well characterized graphitic carbon nanomaterial that can be manufactured at low cost in large quantities, and have the potential to bring widespread use of nanotechnology to a variety of fields.

Abstract: About 32 million tons of aluminum is melted every year. A significant amount is lost to dross during primary and secondary melting operations. Typically, to overcome the dross loss, either a nitrogen cover or a chemical cover is used over the molten metal. A new method, that uses a cover of low-ionization air, has proven to be effective in significantly reducing the dross. The method, low-ionization plasma melting, and its impact on the environment and on melting energy efficiency are discussed in relation to some of the other historical innovations for aluminum processing.

Abstract: Mill-scale is a porous, hard and brittle coating of several distinct layers of iron oxides (predominantly Fe3O4) formed during the fabrication of steel structures. It is magnetic in nature with iron content up to as high as 93%. About 1240 million metric tons of steel was produced in 2006 globally, 1.5 % of which by weight accounts for the mill-scale waste. Thus, 18.6 million metric ton of mill scale waste was produced in one year alone. Most of the steel mill-scale waste (almost 80%) end ups in a landfill; a small fraction of it is also used to make reinforced concrete in Russia and some Asian countries. A purer commercial form of this oxide in combination with nickel and zinc oxide is used in making ceramic magnets (soft ferrites) which are an integral part of all the audio-visual and telecommunication media on this planet as well those in the space. The mill-scale waste could be a valuable technological resource if properly processed and converted into nanoscale species, in particular nanoscale iron particles for hydrogen fuel cell, medical imaging and water remediation applications. In order to achieve the much-discussed and sought-after hydrogen economy via an ‘econo’ viable and ‘enviro’ friendly route, a roadmap for utilizing the mill-scale waste has been developed. The method consists of reacting heated iron with steam, also appropriately called metal-steam reforming (a route well-known to the metallurgists for centuries) generating high purity hydrogen, with a twist. The innovation lies in the conversion of the coarse oxide scale into nanoscale iron by a novel solution-based technique. This produces highly uniform zerovalent iron particles as small as 5 nm. The scope of utilizing the mill-scale waste is broadened several folds as nanoscale iron and nanomagnetite find potential applications in de-arsenification of drinking water, destruction of perchlorate and reduction of hexavalent chromium ions in water sources. In addition, nanoscale iron and magnetite are finding increasing application as the preferred contrasting agents in magnetic resonance imaging - MRI.