Sealing glass composition

Table 11.4 Selected SOFC sealing glass compositions and properties. 

In carefully dried (vacuum-baked) and sealed glass containers gaseous S2O can be kept at 20 °C and partial pressures of below 1 mbar (100 Pa) for several days but at 180 °C the decomposition to SO2 and sulfur is complete within 1 min. At higher partial pressures gaseous S2O decomposes at 20 °C to SO2 and a yellow, relatively stable solid polymeric sulfuroxide of composition S>30 (see below). This decomposition is accelerated by traces of water and by irradiation with UV radiation [18]. 

Many barium aluminosilicate-based compositions will eventually react with the chromium oxide or aluminum oxide scales on the metal interconnect or metal edge rails to form barium chromate or a celsian phase at the interface [6], This can cause a mechanical weakness that is easily delaminated. Also, compositions that contain boron can react over time with water (steam) to produce B2(OH)2 or B(OH)3 gas. This can decompose the glass and greatly limit the lifetime of the seal. Thus many of the new investigations have emphasized low or no boron glass compositions. 

The arrangement is then placed in a furnace, heated to 800°C, and the pressure decay test is repeated. The setup can be subjected to thermal cycles with pressure decay tests at room temperature and at 800°C. A good hermetic seal, however, will not show any pressure decay at a low pressure differential. The results of one series of tests using a glass composite material that has a glass transition temperature (Tg) of about 700°C, at 5 psi are shown in Figure 5.10. The combination of pressure and thermal cycle tests showed that the seal is capable of withstanding the pressure... 

Saponification (see Section 7.4) is carried out to extract more recalcitrant lipids, and the yields are higher than for conventional solvent extraction (Stern et al. 2000). 3 ml of 0.5 M methanolic NaOH is added to 0.1 g of the shard powder and heated at 70°C for 3 hours in a sealed glass vial. After cooling, the supernatant is acidified with HC1 and extracted with three aliquots of 3 ml //-hexane. The hexane will not mix with the methanolic solution (unlike the DCM MeOH used above), but will absorb the lipids and can be transferred into a new clean vial. The removal of excess hexane is carried out as above. Saponification will hydrolyze and methylate any ester functionalities, which removes the requirement to derivatize the samples (Section 7.4) unless other molecules are suspected of being present. However, any wax esters or triacylglycerols will also be hydrolyzed to their fatty acid methyl esters and alcohols therefore, if information on their composition is required, then conventional solvent extraction is recommended as a first step. For subsequent characterization of the lipid extract, see Chapter 7. 

All solvents for these solution thermolysis reactions were freshly distilled and all reactions were done in sealed glass tubes heated in a thermostatted oven. Over a wide range of solvents (DMF, naphthalene, diphenylmethane, benzene, toluene, and decalin) there was no significant variation in either isomerization rate or product composition. Reactions were done at 125°C, 155°C and 195°C and the only limitation was that DMF could not be used as the solvent in reactions at 195°C it led to substantial substrate destruction (polymer forming reactions of substrate with DMF ). Isomer compositions were ascertained both by HPLC and by NMR. 

C. All copolymerizations were carried out without solvent. Below 80 °C azobisisobutyronitrile was used as initiator. At 100 °C the reactions were initiated thermally. At temperatures of 50°, 60°, and 80 °C the reactions were carried out in dilatometers. At 20°C small flasks were used, and the reactions were conducted in a temperature-controlled room over a period of days. At 100 °C sealed glass tubes were preferred. The reactions were stopped at yields below 5%. The composition of the copolymers was determined by oxygen analysis in the analytical laboratories of BASF. The method for determining oxygen was developed in the Untersuchungslaboratorium of BASF (18). 

Figure 8. Radiolysis experiments on cement pastes leading to know the total pressure and the composition of gases according to the duration of gamma irradiation 3) sealed glass phial around a test-bar 4x4x16 cm b mini-containers out of stainless of500 cm (allowing a quasi-integral filling of cement paste) with outlets for P(H2) measurement in line.

Table 2-3. Composition of the newly developed sealing glass...

What are the compositions of some of the common sealing glasses ... 

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