Stress Corrosion Cracking of Pressure Vessel Steel and Countermeasures by Titanium-Based & Cerium-Based Inhibitors in Subcritical Aqueous Environment

An overview of a severe kind of environmentally-assisted cracking-stress corrosion cracking (SCC) of pressure vessel steel (PVS),such as stainless steel 304, alloy 600,690 and other nickel-based alloys in subcritical (～300 ℃) aqueous environment was given. The mechanisms of SCC of metals under this inclement surrounding were briefly generalized. Herein,some pragmatic solutions to mitigate the SCC susceptibility and retard its propagation were presented. The titanium and cerium-based inhibitors addition countermeasure was highlighted.

Effect of CeO_(2) nanoparticle sizes on catalytic performances of sulfated CeO_(2)/Al_(2)O_(3) catalyst in NH_(3)-SCR reaction

The sulfated CeO_(2)/Al_(2)O_(3) catalysts with different sizes of CeO_(2)nanoparticles were prepared by using pure H_2O or acetic acid solution as impregnation solvent, and the influence of sizes of CeO_(2) nanoparticles on the catalytic performances of the sulfated CeO_(2)/Al_(2)O_(3) catalyst was studied. The catalytic performance tests show that the sulfated CeO_(2)/Al_(2)O_(3) catalyst using acetic acid solution as impregnation solvent has better catalytic activity and the resistance to K+poisoning than the sulfated CeO_(2)/Al_(2)O_(3) catalyst using pure H_(2)O as impregnation solvent. The excellent catalytic performances can be ascribed to the smaller sizes of CeO_(2) nanoparticles in CeO_(2)/Al_(2)O_(3) catalyst using acetic acid solution, which results in larger amount of adsorbed sulfate species, surface acid sites, surface active oxygen species and excellent redox property. These features are helpful for improving the catalytic performances of sulfated CeO_(2)/Al_(2)O_(3) catalyst using smaller amount of CeO_(2) to cut the costs.

Multifunctional Ce-MOF@PdNPs with colorimetric fluorescent electrochemical activity for ultrasensitive and accurate detection of diethylstilbestrol

The development of biosensors is gaining tremendous attention in various fields due to their extraordinary advantages, however, their sensitivity and accuracy are still challenging. Herein, we proposed a novel multifunctional nanocomposite Ce-MOF@PdNPs (MOF = metal-organic framework, PdNPs = Pd nanoparticles)-mediated triple-readout aptasensor for accurate and reliable detection of diethylstilbestrol (DES), in which Ce-MOF@PdNPs exhibited excellent peroxidase (POD)-like activity, fluormetric, and electro conductive properties. In addition, enzymes-assisted target recycling amplification was utilized to improve the sensitivity, that is the specific binding of aptamer and DES triggered an Exo III enzyme-assisted recycling reaction. The generated F-DNA was captured by the H3 strand linked to Ce-MOF@PdNPs immobilized on the electrode, exposing cleavage sites and activating the Nt.BbvCI enzyme-assisted recycling reaction, leading to the dissociation of Ce-MOF@PdNPs and a significant reduced electrochemical signal. The collected Ce-MOF@PdNPs solution also induced a proportional change in the color and fluorescence, achieving a colorimetric and fluormetric detection functionality. The detection limit under colorimetric mode was 0.16 and 0.76 ng/mL under fluorescence mode, and 0.87 pg/mL under electrochemical mode. This triple-readout aptasensor exhibits high sensitivity, selectivity and accuracy, providing a new idea for designing novel biosensing platforms for veterinary drug residue detection.

Corrosion behavior of rare earth cerium based conversion coating on aluminum alloy

The present paper focused on the use of the salt of rare earth cerium as corrosion inhibitor of aluminum by using cathodic electrolytic passivation method.The corrosion resistance and the microphology of the cerium passivation film were studied by the methods of electrochemical method,scanning electron microscopy(SEM),and energy dispersive spectroscopic analysis.From the results,it was shown that good corrosion resistance of cerium-based passive coating was obtained when the compositions were as follows:CeCl3·7H2O,0.05 mol/L;H2O2,30 ml/L;current density,1.1 mA/cm2;temperature,40 oC;time,9 min.SEM and EDS revealed that the cerium conversion coatings formed on the surface of aluminum alloy were related to cerium hydroxide/hydrated oxide depositions.

pH-distribution of cerium species in aqueous systems

Cerium-based oxide coatings can be obtained through either chemical or electrochemical processes on various conductor and semiconductor substrates. In both cases the films develop through a precipitation mechanism, which strongly depends on the solution chemistry. In the particular case of the electrolytic approach, the elaboration parameters play a key role on the interfacial pH modification thereby leading to an indirect precipitation mechanism. Indeed, the nucleation and growth mechanisms of crystallites and the composition of the resulting layers have been shown to be also strongly affected by the deposition conditions as well as by the substrate composition, which could in turn modify the protectiveness provided by such coatings. Therefore a better fundamental understanding of the system is required, in particular of the distribution of cerium-containing species in aqueous solution. To this end, the present work intended to develop a diagram showing the distribution as well as the relative amount of Ce（Ⅲ）/Ce（Ⅳ） species in aqueous media as a fimction of the pH range. The resulting pH-distribution diagram turned out to be a useful tool to predict the relevant precipitation mechanisms and species involved during the growth of ceriuna-containing films and to draw correlations with the characteristics of the as-deposited films.