Sintering powder glass

An alternative elution technique is to transfer the powder (e.g. for bromophenol blue) to a glass column fitted with a glass-wool plug or glass sinter, and elute the dye with ethanol containing a little ammonia. The eluted solution, made up to a fixed volume in a small graduated flask, may be used for colorimetric/ spectrophotometric analysis of the recovered dye (see Chapter 17). A calibration curve must, of course, be constructed for each of the individual compounds. 

Fig. 3.5.8 Schematic and NMR image of C4F8 gas at 80 kPa in a hybrid phantom containing Vycor glass, a nanoparticulate AI2O3 powder, a nanoparticulate ZnO powder and sintered ceramics made from each of these powders. Dashed boxes indicate the regions of interest (ROIs) from which the isotherms in Figure 3.5.9 were extracted. Adapted from Ref. [21].

A furnace is constructed within a high-pressure vessel and the objects to be sintered are placed in it. Powders or pieces containing interconnected pores are encapsulated in impervious envelopes of a ductile metal such as platinum or, in the case of metals and some ceramics, of glass. Sintered bodies in which residual pores are isolated need not be enclosed. A neutral gas such as nitrogen or argon is introduced at a suitable pressure while the temperature is raised to the required level. 

Glass-ceramics can also be made starting from a powdered glass followed by a single step combined sintering and controlled crystal nucleation and growth steps. This route is the one most relevant to the electroceramics context. 

The crude product mixture invariably contains quantities of metal powders which can readily be removed by filtration through a pad of Celite on a glass sinter. Careful removal is especially important if product decomposition is catalyzed by metal particles, for example, [Ti(77-C6H6)2] (which undergoes autocatalytic decomposition in solution in the presence of finely divided Ti). ... 

Solids can be prepared as single crystals, glasses, thin films, powders, or sintered powder compacts (ceramics). Powders may be noncrystalline or polycrystalline, exhibit-... 

Sintered Glass. Glass-ware of controlled porosity used for filtration, aeration, etc. it is made by carefully heating powdered glass so that the surfaces of the particles begin to melt and adhere to one another. Sintering. The general term for the densification by heat of a powder compact to produce a polycrystalline... 

Additives such as pigments are added to the glass powder. A sintering process is initiated during heat treatment at temperatures of approximately 500°-800°C to produce a raw glass-ceramic in the form of a cylindrical ingot. 

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