Heat treatment technology

Electron microscopy analysis was conducted using carbon replicas and thin foils. The carbon replicas were not of help for quantitative evaluation. Transmission electron microscopy of thin foils offered better results. For all the tested carbon combinations from the A to I labels, thin foils were produced for the heat treatment 450°C/30 h. The A14C3 particle size and the subgrain size were measured using the thin foils. The dispersed phase A14C3 particle size was measured on 200 to 300 thin foil structures, and it was constant and as small as 30 nm. The particle size was influenced neither by the carbon type nor by the heat treatment technology applied. 

Solution Deposition of Thin Films. Chemical methods of preparation may also be used for the fabrication of ceramic thin films (qv). MetaHo-organic precursors, notably metal alkoxides (see Alkoxides, metal) and metal carboxylates, are most frequently used for film preparation by sol-gel or metallo-organic decomposition (MOD) solution deposition processes (see Sol-GEL technology). These methods involve dissolution of the precursors in a mutual solvent control of solution characteristics such as viscosity and concentration, film deposition by spin-casting or dip-coating, and heat treatment to remove volatile organic species and induce crystaHhation of the as-deposited amorphous film into the desired stmcture. 

The advantage of sol-gel technology is the ability to produce a highly pure y-alumina and zirconia membrane at medium temperatures, about 700 °C, with a uniform pore size distribution in a thin film. However, the membrane is sensitive to heat treatment, resulting in cracking on the film layer. A successful crack-free product was produced, but it needed special care and time for suitable heat curing. Only y-alumina membrane have the disadvantage of poor chemical and thermal stability. 

The betalains serve as another example. They are very sensitive to different technological factors. They can only be maintained in foods with short shelf lives, produced with minimum heat treatment, and packaged in a dry state under reduced levels of light, oxygen, and humidity. Betalains have several applications in gelatin desserts, confectionery, dry mixes, poultry, dairy, and meat products. ... 

Heat Treatment Heat treatment can be divided into two types, treatment of fluidizable solids and treatment of large, usually metallic objects in a fluid bed. The former is generally accomplished in multicompartment units to conserve heat (Fig. 17-28). The heat treatment of large metallic objects is accomplishecTin long, narrow heated beds. The objects are conveyed through the beds by an overhead conveyor system. Fluid beds are used because of the high heat-transfer rate and uniform temperature. See Reindl, Fluid Bed Technology, American Society for Metals, Cincinnati, Sept. 23, 1981 Fennell, Ind. Heat., 48, 9, 36 (September 1981). 

Z. Zhang, K. T. V. Grattan, A. W. Palmer, R. Summers, R. Summan and S. Hughes, Cr LiSAF fluorescence lifetime based fiber optic thermometer and its application in clinical rf heat treatment, in Advances in Fluorescence Sensing Technology (J. R. Lakowicz and R. B. Thompson, eds.), Proc. SPIE 1885, 300-305(1993). 

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