Quantitative 31P NMR analysis of residual lignin structures isolated from pulps pretreated by
green liquor (GL) as a function of various operating parameters are discussed. Uncondensed phenolics
and condensed hydroxyl groups decreased as the GL charge increased, but increased with
increasing pretreatment temperature. During the cooking of pulps employing variable sulfidities
and the addition of anthraquinone (AQ) or polysulfide (PS), various hydroxyl groups exhibited no
obvious differences in the case of AQ addition, but dramatic changes were observed at variable
sulfidities when the PS was used. The results implied that PS can exert a stronger catalytic effect
under a higher sulfidity and result in more cleavage of the lignin macrostructure. The results also
demonstrated a correlation between the nature of residual lignin and the efficiency of oxygen
delignification based on the finding that the residual lignin in GL modified pulp exhibited a higher
reactivity toward oxygen delignification.
This paper describes behaviour of the ferritic-martensitic steel T91 after long-term exposure in liquid eutectic PbBi. Small specimens of the steel were pre-loaded according to the ISO Standard No. 7539-2 and subsequently exposed to PbBi. The experiment was carried out in a flowing and static liquid metal medium at 350°C. The experimental time was selected for the flowing environment at 1000 hours and for static environment at 2000 hours. After exposure, the specimens were analysed by use SEM and EDX. Surface changes of the specimens from different experimental conditions were compared and discussed. The initiation of the cracks wasn´t observed in the monitored expositions.
The electrochemical and photoelectrochemical characteristics of conducting polymer bilayers composed by polypyrrole, PPy, and poly(3-methylthiophene), PMeT, are described. The bilayers were produced by galvanostatic deposition of the polymers using different charge densities. Scanning electron micrographs indicate that the sequence of polymerization affects the surface morphology of the bilayers and, while PMeT polymerizes into the pores of the PPy film, a PPy film is formed over the PMeT film. Cyclic voltammetry of the bilayers shows the peaks corresponding to PPy and PMeT, regardless of the sequence of deposition; however, the potentials of redox processes are slightly shifted. The sequence of polymer deposition also affects the photoelectrochemical properties of the bilayers. The results show that, for a bilayer with PMeT as inner polymer and PPy as outer polymer, an enhanced photocurrent can be obtained by controlling polymer film thickness.
The study reports the results of a new treatment based on water and ethylene glycol nano-TiO2 dispersions showing photocatalytic properties that was tested on both Noto stone (calcarenite) and Carrara marble. To verify that the proposed treatments did not affect the intrinsic properties of the stone materials, colour measurement, static contact angle and water absorption by capillarity tests were carried out before and after the treatments. The efficacy of the photocatalytic activity of TiO2 nanoparticles applied to the stone substrates was evaluated by decomposition tests of organic colorants (Rhodamine B), both after indoor natural light exposition and after ageing in a Xenon lamp solar box. The specimens were also exposed to outdoors environment in order to verify their properties as self-cleaning agents to prevent soiling. The results showed that nano-TiO2 dispersions were effective and suitable for the use in the field of architectural heritage.