Silver powder activation

Activation of Silver Powder for Ethylene Epoxidation at Vacuum and Atmospheric Pressures... 

Transient response techniques are used to investigate the activation of silver powder for ethylene epoxidation at vacuum and atmospheric pressures. Results indicate that the activation process is qualitatively the same in both pressure regimes. Numerical simulation of the process indicates that activation involves the concurrent incorporation of oxygen into surface and subsurface sites. The reaction selectivity parallels the incorporation of oxygen into the subsurface. 

Figure 3. TPSR spectra of the activation process over pretreated silver powder at 800 torr with a 3 1 oxygen/ethylene feed ratio.

This interpretation conflicts with that of Kilty et al. Using a silver powder, they showed that pre-adsorption of chlorine suppressed the non-activated adsorption of oxygen on a one-to-one basis. When the chlorine coverage was greater than about 0.25, this adsorption was completely suppressed and further addition of chloride began to suppress the activated associative adsorption of... 

PP/silver nanocomposite fibres were prepared with the aim of achieving permanent antibacterial activity in a common synthetic textile. The fibres were melt-spun by coextmsion of PP and PP/silver masteibatches using general conjugate spinning. Masteibatches were made up of a mixture of PP chips and nano-sized silver powder. The antibacterial efficacy of spun fibres was high when the masteibatch was used as the sheath rather than the core. The antibacterial activity of nano-silver in fibres was evaluated after a certain contact time and calculated by percent reduction of two types of bacteria. Staphylococcus aureus and Klebsiela pneumoniae. DSC and wide-angle X-ray diffraction were used for analysis of stractuie, thermal properties and crystallisation behaviour of the spun fibres. SEM was carried out in order to observe particle distribution on the nanocomposite fibres. 17 refs. (2nd International Conference on Polymer Fibres, Manchester, UK, July 2002)... 

Smetana, A.B., Klabnnde, K.J., Marchin G.R., and Sorensen, C.M. 2008. Biocidal activity of nanocrystalline silver powders and particles. Langmuir 24 7457-7464. 

The percentage of metal fuel in a formula has a decisive influence on burning time, mainly insofar as burning times become faster and faster with excess of metal. This appears to be a function of the increased heat conductivity of the mixture rather than of the increased surface area of the active fuel, since the admixture of silver powder in lieu of part of the excess fuel has been observed not to alter the burning rate. It is certainly remarkable that whatever the mechanism of action is, high metal powder content supersedes the calorific output as a factor in the burning rate up to a point where as much as 95% metal powder is present. 

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