The Effect of Aluminum on the Two-Stage Pe rox i d e B I each i n g of Eucalyptus regnans Stone Groundwood Pulp
The addition of aluminum nitrate (up to 100 ppm A1 on pulp) to a two-stage, acidalkali, hydrogen peroxide bleach of Eucalyptus regnans stone groundwood pulp enhanced the brightness gain of the pulp, over a range of consistencies. It is proposed that the presence of aluminum ions modifies the catalytic behaviour of the transition metal ions present in the pulp, especially manganese, reducing peroxide consumption while increasing the brightness of the pulp. The two-stage process, under optimized conditions at low consistency, consumes considerably less peroxide while achieving a greater brightness increase than a singlestage alkaline peroxide bleach.
The influence of manganese and magnesium on alkaline peroxide bleaching of radiata pine thermomechanical pulp
On examine l'action du manganese en tant que source principale de decomposition dans des conditions alcalines, ainsi que le role du magnesium, qui peut contribuer a la stabilisation des pâtes.
Measuring Sheet Resistances of Dielectrics Using Co‐Planar Hydrogel Electrochemical Cells with Practical Applications to Characterize the Protective Quality of Paints on Sculptures
Electrical properties of thin dielectric films at the solid-liquid phase boundary are an important performance characteristic of many devices, coatings and sensors. In this paper, co-polymeric hydrogels of polyacrylic acid co-sulfonic acid, swollen with a salt solution to act as the solid electrolyte, were used to assess interfaces using electrochemical impedance spectroscopy (EIS) in a co-planar geometry. Silane-modified glasses were characterized by the co-planar hydrogel EIS cell and found to be distinguishable based on their surface monolayer chemistry. EIS measurements were also made on primed and painted metal substrates, using both test panels and an outdoor sculpture, Tony Smith's Stinger. The panels were then exposed to accelerated and outdoor weathering and showed degradation on the surface paint layers, which was observable electrochemically using EIS and confirmed visually by SEM. Electrochemical spectral features were compared between data from a standard paint-test cell versus this co-planar hydrogel cell; both cell types were able to measure coating capacitance, providing useful information about the condition of the bulk coating. Yet, sheet resistance (Rs) was a spectral feature seen only by the co-planar hydrogel cell. Thus, it can be concluded that the use of such co-planar hydrogel cells can provide an earlier warning sign to coating degradation and such cells provide a new type of spectral information that is not assessable by the standard geometry.