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State of the art: alumina ceramics for energy applications

Description: Prominent ceramic raw materials and products manufacturers were surveyed to determine the state of the art for alumina ceramic fabrication. This survey emphasized current capabilities and limitations for fabrication of large, high-density, high-purity, complex shapes. Some directions are suggested for future needs and development.
Date: January 1, 1978
Creator: Hauth, W.E. & Stoddard, S.D.
Partner: UNT Libraries Government Documents Department

Microwave sintering of large alumina bodies

Description: The application of microwaves as an energy source for materials processing of large alumina bodies at elevated temperatures has been limited to date. Most work has concerned itself with small laboratory samples. The nonuniformity of the microwave field within a cavity subjects large alumina bodies to areas of concentrated energy, resulting in uneven heating and subsequent cracking. Smaller bodies are not significantly affected by field nonuniformity due to their smaller mass. This work will demonstrate a method for microwave sintering of large alumina bodies while maintaining their structural integrity. Several alumina configurations were successfully sintered using a method which creates an artificial field or environment within the microwave cavity.
Date: January 1, 1993
Creator: Blake, R. D. & Katz, J. D.
Partner: UNT Libraries Government Documents Department

Stress relief of ceramic components in high voltage assemblies. Final report

Description: Two types of ceramic packages were evaluated to determine the effectiveness of encapsulating the ceramic components in beta eucryptite filled epoxy. The requirements (no high voltage breakdown, no ceramic cracking, and no encapsulant cracking) were met by the spark gap assembly, but the sprytron assembly had cracking in the encapsulant after thermal cycling. The encapsulation of the ceramic component in beta eucryptite filled epoxy with a stress decoupling material selectively applied in the stress concentrated areas were used to prevent cracking in the sprytron encapsulant. This method is proposed as the standard encapsulation process for high voltage ceramic components.
Date: February 1, 1979
Creator: Heinen, R.J.
Partner: UNT Libraries Government Documents Department

Photoresist dip coating on thin film networks. Final report

Description: Application of liquid photoresist by dip coating was investigated as potentially more reliable and repeatable than the current roller coating process. Resist viscosity, extraction rate, and substrate orientation were found to affect applied resist thickness and uniformity. The data accumulated in this effort will be used in future work to develop an improved photoresist application process.
Date: July 1, 1980
Creator: Hughs, R.W. & Barner, G.E.
Partner: UNT Libraries Government Documents Department

Sizing single crystal sapphire

Description: Although there are several significant advantages to using single crystal sapphire as substrate material for hybrid microcircuits, the sizing of this material can be far more troublesome than the sizing of alternate material, such as polycrystal alumina. The work done in developing a satisfactory method of sizing single crystal sapphire is described. The results of sizing using grinding wheels, wire saws, and laser scribers are given. It was concluded that laser scribing is a viable method of sizing if the sapphire is grown parallel to the r plane. This takes advantage of the easy crystal cleavage planes and reduces the risk of edge chipping and nonperpendicular breaking.
Date: March 1, 1976
Creator: Bushmire, D. W.
Partner: UNT Libraries Government Documents Department

HVEM (high voltage electron microscopy) studies of the sintering of MgO nanocrystals prepared by Mg(OH) sub 2 decomposition

Description: Hot-stage high voltage electron microscopy (HVEM) combined with high resolution electron microscopy (HREM) has been employed to study the microstructural evolution during in-situ decomposition of thin Mg(OH){sub 2} flakes and during early stage sintering of the resultant nanocomposite. The decomposition reaction is known to be pseudomorphic and topotactic, resulting in a regular composite of highly nearly cubic MgO nanocrystals interspersed with a roughly equal volume of pores. This structures was characterized by selected area and optical diffraction techniques as well as by HREM, depending on its microstructural scale. Immediately after decomposition and in the early stages of sintering the fine scale and regular, nearly periodic nature of the microstructure gave rise to diffuse small angle diffraction rings that could be used as a measure of coarsening during in-situ heating in the temperature range 350--900{degree}C. Consistent result were obtained from electron diffraction, optical diffraction and Fourier transforms of digitized images. These measurements were complementary of direct imaging by HREM or conventional imaging techniques. 27 refs., 14 figs.
Date: May 1, 1990
Creator: Thangaraj, N.; Westmacott, K.H. & Dahmen, U.
Partner: UNT Libraries Government Documents Department

Ion-beam mixing of ceramic alloys: preparation and mechanical properties

Description: Techniques used to produce unique states of pure metals mixed into ceramic materials are presented. The samples were prepared by irradiating a 1-MeV Fe/sup +/ beam on Al/sub 2/O/sub 3/ crystal surfaces over which a thin chromium or zirconium film had been evaporated. The limitations of using noble gas ion beams are noted. Micro Knoop hardness tests performed near the surfaces of the samples indicated a significant increase in the hardness of most samples prepared by ion beam mixing.
Date: January 1, 1981
Creator: Lewis, M.B. & McHargue, C.J.
Partner: UNT Libraries Government Documents Department