Glass solutions formation

An example of solid solution formation by separate deposition of binary layers followed by annealing to interdiffuse the two layers is given for Cu3BiS3 deposition [32]. Bi2S3 (film thickness ca. 90 nm) was deposited at room temperature from a Bi(N03)3/triethanolamine/thioacetamide bath onto glass slides. CuS (300-600 nm thick) was then deposited on this film from a CuCli/tri-ethanolamine/ammonia/NaOH/thiourea bath at room temperature. The films were annealed at 250°C for 1 hr. Formation of the CusBiSs phase could be seen from the XRD pattern. Measurement of precipitated powders (prepared by putting the Bi2S3 precipitated in the first deposition in the CuS deposition solution) annealed at 300°C showed more clearly the formation of the solid solution. 

From solutions of Bi and Pb nitrates, complexed with triethanolamine and ammonia, mixed sulphides were deposited with thiourea on glass at pH values between 9.5 and 11 and at 100°C (initially) followed by slow cooling in the solution [35]. Elemental analyses showed the presence of both metals in the films. It is not clear whether solid solution formation occurred in the as-deposited films, although the lattice parameters did vary non-monotonicaUy, depending on composition. 

Other structures may exist owing to interactions between the drug and carriers. Ford addresses the following systems glass solutions and glass suspensions, amorphous precipitations in a crystalline carrier, compound or complex formation, and combinations of these systems. 

Fig. 7 Buchi/Brinkmann Lab Scale Spray-Dryer. A stock solution or suspension is pumped from the beaker through a nozzle which sits above the large glass particle formation vessel on the left-hand side. The nozzle atomizes the feedstock at temperatures ranging from ambient to 250° C into the particle formation vessel, using air or an inert gas such as nitrogen to dry and move particles into the cyclone and collection chamber on the right-hand side. Product temperature is monitored by a temperature probe mounted between the particle formation vessel and the cyclone. Solvent or water are exhausted through a fine particle filter bag in series with the cyclone, which also collects fines.

Figure 8. Schematic illustration of spin-glass cluster formation in ilmenite-rich members of the ilmenite-hematite solid solution (after Ishikawa et al. 1985). Dashed lines show ferrimagnetic clusters surrounding Fe cations within the (001) Ti layers. Atoms labelled F have fmstrated spins.

The analysis of the crystallinity of the MB-template loaded zeolite crystals by nitrogen physisorption at 77 K gives no reductions of the Nz uptake capacity valid for NaY (ca. 170 ml Nz (NTP)/g dry faujasite) if the MB was added to the aluminate or water glass solutions (samples 1 and 2) prior to the gel formation. A drastic (ca. 40%) reduction of the Nz uptake capacity is found if the MB is added with the NaX seeds (sample 3) after the gel formation. The water uptake capacity of samples 1-3 is comparabie to the vaiue for dye-free NaY, i.e. ca. 25 wt%. 

Step 2 Loss of soluble silica in the form of Si(OH)4, resulting from breaking of Si-O-Si bonds and the formation of Si-OH (silanols) at the glass solution interface ... 

Mixtures or solutions with SiO NajO ratios greater than 4 1 are not necessary for the formation of insoluble crystalline species, as indicated by Wegst and Wills (178), who first made the tetrasilicate. Apparently this species in one or more crystalline forms can eventually crystallize out of commerciar water glass solution of 3.3 1 ratio at 25 C, as mentioned by McCulloch (180). What nucleates such crystals is unknown, but on very rare occasions the whole contents of a container partly filled with concentrated sodium silicate solution of this type has been known to crystallize to a solid mass. This usually occurs after the solution has been aged for several years and indicates the advisability of cleaning out storage tanks occasionally. 

Sulaiman [38] has synthesized fly ash zeolites (FAZ) from coal fly ash. It has been reported that the hydrothermal reaction of magnetically pre-treated fly ash can produce stable zeolites P by initiating its activation in aqueous NaOH solution at 70 °C for 48 h. The crystallinity of the zeolites has been found to increase with the increase in temperature and reaction time. It has been concluded that the mineral transformation takes place due to dissolution of aluminosilicate glass and formation of zeolites P. 

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