Shielding compounds

The presence of shielding compounds interferes with subsequent processes, as the formation of metal-support interactions is able to stabilize supported particles. Moreover, the shielding effect of the colloid protectors prevents the contact of metal particles with the reacting molecules, thus avoiding the use of unsupported colloidal particles as a catalytic system [11]. 

The reason why boiling points of completely shielded compounds rise if the halogens are replaced by others with a higher atomic number will be dealt with later in Section 51. 

Following this line of reasoning, one should not expect to find volatile nitrides, because such compounds would contain three N3 ions associated with a positive ion, which would then have a valency of nine. For shielded compounds, then, we have the following rules for volatility ... 

When the central ion of a compound, such as A1C13, is already shielded, it does not become more completely shielded by replacement of chlorine by bromine and the boiling point will therefore not be lowered but will rise, as in every shielded compound when bromine replaces chlorine. 

MgF6]4-, [A1F6]3-, [SiF6]2, [PFe]-, SF6, the first one does not exist, the last one is an extremely stable, almost inert gas (shielded compound, p. 94). 

The rules that determine the volatility of the shielded compounds will be discussed in Chapter V. Likewise the volatility of the hydrogen compounds will be dealt with there. 

The electrical conductivity in the liquid state of the halides, e.g. the chlorides, also provides a well-marked difference between the non-conducting shielded compounds and the good conducting non-shielded compounds with free ions in the melt (Biltz, Klemm)17 . Aluminium chloride here also forms a special case in so far that quite exceptionally the solid substance (coordination lattice) has a higher conductivity than the liquid (molecules A12C16). 

In the inorganic compounds which are built up of molecules both in the liquid and the solid state little or nothing of electrostatic forces appears in the cohesion energy. One speaks in this case of shielded compounds (p. 94). 

Bigg, D.M. (1984) The effect of compounding on the conductive properties of EMI shielding compounds. Adv. Polym. Technd.,... 

These compounds have a resistivity in the region of 10 -10 Q/sq and are designed for use where slow and controlled dissipation of static charges is required. EMI shielding compounds, for protection of electronic components from electrostatic discharge, offer a surface resistivity of lower than 10 i2/sq, with volume resistivity of lower than 1 cm and up to 55 dB attenuation. 

EMI shielding compounds based on stainless steel fibres are supplied as masterbatch compounds that can be added at low levels, ensuring minimal effect... 

Table 4 shows the shift ranges for the Group IV nuclei other than The most shielded compounds are the tetraiodides (as... 

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