Chromic oxide electrical resistivity

The dependence of the electrical resistivity of chromic oxide on the oxidation-reduction state of the surface has been investigated. The resistivity of oxidized chromia at 500 varies with the total excess oxygen according to the relation p = On addition of hydrogen at 500 ... 

Chromic oxide was first reported to be an oxygen-excess (p-type) semiconductor by Bevan, Shelton, and Anderson ). This conclusion was based on the fact that the electrical resistivity increases with decreasing oxygen pressure and increases even further when hydrogen or carbon monoxide is made the ambient gas. Hauffe and Block 2), however, found that the dependence of the conductivity, k, on oxygen pressure was much lower than was expected the observed dependency was of the form ... 

The good solvent resistance of polyethylene and other olefins precludes the use of solvent-type cements. Several commercial rubber-type adhesives produce moderate adhesion with polyethylene that has been surface treated. One technique for surface treatment is to dip polyethylene in a chromic acid bath (made up of concentrated sulfuric acid 150 parts by weight, water 12 parts, and potassium dichromate 7.5 parts) for about 30 sec at 70°C. The parts are rinsed with water after this treatment. Still another effective surface treatment for producing cementable surfaces on polyethylene is electrical discharge. The open oxidizing flame method is also used extensively for this purpose. 

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