New Applications and Markets for Non-vacuum Coatings
Friday, May 4, 2001 8:30 AM in Room Town & Country
G8-1-1 Composite Sol Gel Coatings and their Application in High Temperature Environments
D Barrow (Datec Coating Corporation, Canada)
A novel ceramic coating technology capable of fabricating high performance thick ceramic films is described. This technology (known as "sol gel composite coating technology") was first presented at this conference five years ago. Since that time, it has evolved into a commercially viable process of making cost effective ceramic coatings with a wide range of functionality. Through choices of material and control of the coating microstructure, these ceramic layers can be engineered to provide the specific functionality and tailored to meet the requirements of an application. Hard coatings for corrosion and wear, dense coatings for electrical insulation or porous coatings for high temperature performance are some examples. The advantages of this technology are ease of fabrication (coatings are deposited in air with standard spray equipment), low firing temperature (400 °C), amenable to large scale manufacture (millions of components/year) and cost. To date, Datec has developed coating formulations that provide a combination of high dielectric strength, resistance to frictional wear, excellent thermal insulation and oxidation protection in certain environments. In this talk, the technology will be described in detail and an overview of how the coatings perform in selected applications will be provided. In particular, there will be special emphasis on how these materials function in the high temperature environments found in the aerospace industry.
G8-1-2 Improvement of Corrosion Behavior of Magnesium as New Biomaterials by Surface Modification With Alkaline in Vitro
Y. Al-Abdullat (Kyoto University, Japan); H. Kuwahara (Research Institute for Applied Sciences, Kyoto, Japan); S. Tsutsumi, K. Ikeuchi (Kyoto University, Japan)
Magnesium and its alloys have recently been attracted the attention from the point of view of high specific strength, recycling, abundance of natural source and so on, especially in automobile industries. A new field of application of magnesium is in medical and dental applications. The ultimate goal of using biomaterials is to restore functions of natural living tissues and organs in the body, even the titanium have been reported that is not stable in vivo, which introduced to disease or metallic allergy. Magnesium in a low dosage is an essential element and dose not harm the tissue. To evaluation of magnesium in medical and dental applications the present study was carried out to understand pure magnesium corrosion behavior in vitro environment, simulated body fluid solution, (HBSS solution) and to improve its corrosion resistance has been investigated by surface modification technique with six different types of alkaline solutions at room temperature. 3N-Mg treated with NaHCO3 maintains a good corrosion resistance in HBSS solution from 1 to 75 days. Furthermore; this treatment has a potential to enhance apatite deposition, new bone formation, and attachment on the interface of bone and magnesium implants, though the other specimens treated with five different types in alkaline chemical solutions were failed. X-ray diffraction showed new peaks of magnesium hydroxide formed after surface modification, and also SEM shows a new microstructure as well, which attribution to improvement of corrosion resistance by a stable hydroxide film formation. We succeeded to prepare crowns and dentures for dental use by casting. The present investigation can conclude that magnesium is possible to apply to biomaterial in the near future.
G8-1-3 Low Pressure Plasma Spray Coatings: A Model for Determining Dielectric Strength
E.J. Young, E. Mateeva, J.J. Moore, B. Mishra (Colorado School of Mines)
The dielectric strength of low pressure plasma spray (LPPS) alumina coatings show dielectric strength values much higher than that of other plasma spray coatings, dielectric strength values on the order of bulk pressed alumina @footnote 1@. Here we propse a model, based on an original work of Gerson and Marshall @footnote 2@ that describes the effect of the complex structure of the LPPS coatings on their dielectric strength. This model takes into account the relative amount of amorphous and crystalline phases and their distribution in the coatings. In order to test this model initially, the dielectric strength of amorphous and polycrystalline (containing only the gamma phase) Al@sub 2@O@sub 3@ coatings produced by DC magnetron sputtering methods have been measured. The purely gamma-phase polycrystalline alumina was obtained after annealing the PVD coatings in an Ar atmosphere up to 1050°C. The crystalline fractions and the distribution of phases in the coatings were determined using x-ray diffraction (XRD) and cross-sectional transmission electron microscopy (XTEM). @FootnoteText@ @footnote 1@ E. Young, E. Mateeva, J.J. Moore. Thin Solid Films, to appear 2000. @footnote 2@ R. Gerson, T.C. Marshall. Journal of Applied Physics 30, 11 (1959).
G8-1-4 Fabrication and Characterization of Photoelectrochemical (PEC) Solar Cells Based on 0.1% Indium Doped CdSe0.7Te 0.3 Thin Film Electrode
V. Damodara Das, D. Ravishankar (Indian Institute of Technology, Madras, India)
Photo electrochemical (PEC) Solar Cells have been fabricated using aqueous poly iodide solution electrolyte and thin film photo electrodes in the form of vacuum flash-evaporated thin films of 0.1% indium doped CdSe0.7Te0.3 semiconducting photo voltaic alloy as one of the electrodes. For this, the thin films of the CdSe0.7Te0.3 alloy were prepared by the vacuum flash evaporation of the bulk alloy ingot powder on thoroughly cleaned glass substrates held at room temperature in a vacuum of 5 x 10-5 torr. The counter electrode was graphite. Different thickness films were deposited in separate depositions to study the effect of thickness on the solar cell efficiency. Also, some of the films were given different surface and heat treatments, viz., etching , photo etching and annealing to study the effect of annealing and surface treatments on the efficiency of the solar cells formed using these films as photo electrodes. @paragraph@It was found that the PEC solar cells formed exhibited increase in efficiency of conversion of light energy into electrical energy when the thin film electrodes were annealed, etched or/and photo etched. The increase in efficiency was between 80% and 100%. Also, increase in the thickness of the thin film electrodes also led to an increase in efficiency of up to 80 % when the thin film photo electrode thickness was increased by about 5 times. The results of the investigations are discussed and explained.
G8-1-5 Humidity Sensing using Spherodised Nanocrystalline Alumina Ceramics
N.D. Sali, S.V.. Bhoraskar (Pune University, India)
The synthesis of nanopcrystalline alumina using arc plasma technique with aluminium-carbon and aluminium-aluminium electrodes set has been studied. We are reporting here the application of this nanophase ceramics in humidity sensing. The higher adsorption efficiency for oxygen has been realised in the nanophase alumina as compared to the microphase alumina by the quantitative investigations using the technique of neutron activation analysis ( NAA). The nanophase powder has also been characterised using XRD,XPS. Capacitance measurements with the consolidated pellets of this powder has proved it to be a better humidity sensing device as compared to coarse grained structure by about four times in magnitude as seen through repeated series of experiments .