Magnesia single crystal

GUI 98] GUINEBRETIERE R., SOULESTIN B DAUGER A., heteroepitaxial growth of zirconia on magnesia single crystal p. 197-201,1998. 

Another test of validity is to check the performance of the model against experimental rate data obtained far from equilibrium. The microkinetic model presented in Table 7.3.1 predicts within a factor of 5 the turnover frequency of ammonia synthesis on magnesia-supported iron particles at 678 K and an ammonia concentration equal to 20 percent of the equilibrium value. This level of agreement is reasonable considering that the catalyst did not contain promoters and that the site density may have been overestimated. The model in Table 7.3.1 also predicts within a factor of 5 the rate of ammonia synthesis over an Fe(lll) single crystal at 20 bar and 748 K at ammonia concentrations less than 1.5 percent of the equilibrium value. 

Figure 7.16. Stucfy of an epitaxial zirconia film on a single crystal magnesia substrate [GUI 98, GUI 99]...

Thermal Expansion The thermal expansion of periclase is the greatest of all pure refractory oxides and approaches the expansion of metals. Exact expansion measurements have been carried out on single crystals of periclase and high-purity sintered magnesia, the results of which are tabulated in Tables 8.5 and 8.6. 

Magnesia (MgO) - Magnesia is also a possible support material having a good thermal stability that can be used as washcoat material as well. Hashimoto et al. have described a preparation by vapour oxidation that can lead to a large surface area and ultra-fine single crystal MgO. It is very resistant to thermal treatment and has a surface area above 72 m g after calcination at 1500°C. ... 

You react two samples of alumina and magnesia at 1400°C for 1 hour. This time the MgO is a perfect single crystal but the alumina is 100-nm grain size polycrystalline material. Will the reaction proceed more quickly... 

Examples of dislocation structures after fatigue deformation appear in a series of microstructures (Figs. 7.55-7.59) obtained by TEM. Subramanian [27] claims that these dislocation substructures are similar to that of unidirectionaUy-stressed MgO. The micrographs presented below are of single-crystal magnesia which underwent a large number of cycles (in the millions) of low strain amplitude. The maximum strain was about 0.1 % per cycle. The characteristics of the dislocation structure in MgO, having a rock-salt structure, is as follows ... 

The primary mineral, chlorite, which occurs in rocks as large crystals, possesses an interlayer sheet composed largely of Mg(OH)2. Since the mineral brucite is composed of magnesia sheets with the same basic structure, the single interlayer sheet in chlorite is termed the brucite layer. Isomorphous substitution of part of the Mg by produces a positively chained hydroxide sheet (see formula above) that props the 2 1 layers apart at a c-spacing of 14 A. This rigid interlayer contrasts with the hydrated interlayer of vermiculite, and even though chlorite and vermiculite have similar c-... 

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