Electrode modification with a poly(NiII‐tetramethyldibenzotetraaza[14]annulene) film. Electrochemical behavior and redox catalysis in alkaline solutions. I

Electrochemical behavior of nanocrystalline Ti2RuFe alloy prepared by high energy ball-milling

Effect of pH and chloride on the micro-mechanism of pitting corrosion for high strength pipeline steel in aerated NaCl solutions

Hydrogen electrosorption in nanocrystalline Ti-based alloys

A study of copper electrode behavior in alkaline solutions containing benzotriazole-type inhibitors by the photocurrent response method and intensity modulated photocurrent spectroscopy

The electrochemical behavior of Fe and thin, sputter‐deposited films of in phosphate‐containing solutions was studied and compared with the behavior in borate buffer and 0.1 M NaOH. In situ X‐ray absorption near edge structure was used to simultaneously monitor changes in the samples' average valency and thickness. The reactions taking place during reduction of the passive film on iron are significantly different for all three electrolytes. In borate buffer (pH 8.4), reduction leads to a complete dissolution of the passive film. In alkaline solution, no dissolution takes place, but, instead, the passive film is converted into a lower‐valent oxide/hydroxide film during reduction. Similarly, in phosphate buffer (pH 8.4), there is no dissolution in a direct step to low cathodic potentials, but the resulting reduction product is metallic iron. In contrast to the behavior in alkaline solution, where no dissolution takes place independent of the potential, in the phosphate buffer (pH 8.4), dissolution occurs in the potential range of the active/passive‐transition. In an alkaline phosphate‐containing solution, conversion into metallic iron is possible in a direct reduction step to potential in the stability region of Fe(0); at intermediate potentials, a ferrous layer is formed in the reduction reaction. The presence of phosphate species in the electrolyte enables the further reduction of this ferrous layer into Fe(0) at lower potentials. In pure NaOH solution, the presence of on the surface hinders further reduction even at very low cathodic potentials. The factors controlling the reactions taking place during the reduction of the passive film on iron are discussed. © 1999 The Electrochemical Society. All rights reserved.

Dissolution properties of calcined gangue

Polyesters constitute nearly 10% of the global plastic market, but most are essentially non-degradable under ambient conditions or in engineered environments. A range of degradable polyesters have been developed as more sustainable alternatives; however, limitations of practical degradability and scalability have hindered their viability. Here, we utilized transesterification approaches, including in situ polymerization-transesterification, between a salicylate and a polyester to incorporate salicylate units into commercial polyester backbones. The strategy is scalable and practically relevant given that high molar mass polymers can be obtained from melt-processing of commercial polyesters using common compounders or extruders. Polylactide containing sparse salicylate moieties shows enhanced hydrolytic degradability in aqueous buffer, seawater, and alkaline solutions without sacrificing the thermal, mechanical, and O2 barrier properties of the parent material. Additionally, salicylate sequences were incorporated into polycaprolactone and a derivative of poly(ethylene terephthalate), and those modified polymers also exhibited facile degradation behavior in alkaline solution, further expanding the scope of this approach. This work provides insights and direction for the development of high-performance yet more sustainable and degradable alternatives to conventional polyesters.

Changes in morphological and structural characteristics of high amylose maize starch in alkaline solution at different temperatures

Sugars and alditols undergo an electrocatalytic oxidation in alkaline solution at cobalt‐oxide‐based glassy carbon (Co/GC) electrodes. The catalytic deposit was investigated by cyclic voltammetry and scanning electron microscopy (SEM). It is pointed out that, at relatively low coverage of cobalt, two main redox processes, CoII → CoIII and CoIII → CoIV, are observed in 0.2 M NaOH. The redox behavior of the Co/GC electrode is strongly dependent on hydroxide ion concentration, and no electrocatalytic activity is observed at pH lower than 11.5. Under voltammetric conditions the modified electrode exhibits a non‐Nernstian potential/pH shift (−88 ± 3 mV per pH unit). A reasonable explanation of the E/pH behavior in alkaline solution is given and an oxidation mechanism of CoII to CoIII is proposed in terms of hydrous cobalt oxides. No detrimental effects on the electrocatalytic oxidation of polyhydric compounds are observed in the presence of high acetonitrile concentrations (up to 40%). Inspection by SEM of the cobalt‐based deposit evidenced the presence of grain‐like microcrystallites on the glassy carbon surface.

The voltammetric behavior in alkaline solution of a nickel‐based chemically modified electrode (poly‐Ni(II)curcumin) prepared by oxidative electropolymerization of nickel‐curcumin complex for electrooxidation of aliphatic alcohols was investigated by cyclic voltammetry and rotating disk technique (curcumin=1,7‐bis[4‐hydroxy‐3‐methoxyphenyl]‐1,6‐heptadiene‐3,5‐dione). The dependence of the oxidation current on the alcohol concentration and on the number of redox centers Ni(II)/Ni(III) is discussed. From the fact that the oxidation current increases with the increase of film thickness it is evident that the electrocatalytic reaction occurs inside the polymer film. The system examined is a typical example of a redox polymer with 3D properties. It is also concluded that the reaction mechanism of alcohol oxidation is the case, according to the concept of Andrieux and Saveant, where the cross‐exchange reaction is the limiting step. The mechanism of modifying the film formation has also been discussed.

Impact of matrix composition and microstructure on nodular cast iron sewage pump corrosion behavior in alkaline solutions

Galactoglucomannan (GGM) from spruce was studied with respect to the degradation behavior in alkaline solution. Three reference systems including galactomannan from locust bean gum, glucomannan from konjac and the linear water-soluble carboxymethyl cellulose were studied with focus on molecular weight, sugar composition, degradation products, as well as formed oligomers, to identify relative structural changes in GGM. Initially all mannan polysaccharides showed a fast decrease in the molecular weight, which became stable in the later stage. The degradation of the mannan polysaccharides could be described by a function corresponding to the sum of two first order reactions; one slow that was ascribed to peeling, and one fast that was connected with hydrolysis. The galactose side group was stable under conditions used in this study (150 min, 90 °C, 0.5 M NaOH). This could suggest that, apart from the covalent connection to C6 in mannose, the galactose substitutions also interact non-covalently with the backbone to stabilize the structure against degradation. Additionally, the combination of different backbone sugars seems to affect the stability of the polysaccharides. For carboxymethyl cellulose the degradation was linear over time which further suggests that the structure and sugar composition play an important role for the alkaline degradation. Molecular dynamics simulations gave details about the conformational behavior of GGM oligomers in water solution, as well as interaction between the oligomers and hydroxide ions.

Well-aligned hierarchical hollow nanoarrays containing ZnO core and Fe(OH)3 nanotube shell have been synthesized via simple one-step hydrothermal method and etching at room temperature. The obtained catalyst has a high specific surface area, a large number of catalytic active sites and good chemical stability. The resulting Fe(OH)3-ZnO/NF nanotubes exhibits promising behavior in alkaline solution. When the current density is 10 mA cm-2, the HER and OER overpotentials (η10) of Fe(OH)3-ZnO/NF are 190 and 388 mV, respectively.

A binder-free process for the electrode preparation for supercapacitor application was suggested by drop casting graphene nanoplatelets on a carbon fiber (GnP@CF) followed by electrodeposition of Ni nanoparticles (NPs). The microstructure of the electrode showed that Ni was homogeneously distributed over the surface of the GnP@CF. XRD analysis confirmed the cubic structure of metallic Ni NPs. The Ni-GnP@CF electrode showed excellent pseudocapacitive behavior in alkaline solution by exhibiting a specific capacitance of 480 F/g at 1.0 A/g, while it was 375 F/g for Ni@CF. The low value of series resistance of Ni-GnP@CF (1 Ω) was attributed to the high capacitance. The enhanced capacitance of the electrode could be correlated to the highly nanoporous structure of the composite material, synergetic effect of the electrical double layer charge-storage properties of graphene, and the pseudocapacitive nature of Ni NPs.

Spark plasma sintering (SPS) and conventional sintering techniques were used to fabricate sintered Nd-Fe-B permanent magnets. The corrosion behaviors of both magnets in sodium chloride (NaCl), sodium hydroxide (NaOH), and sulfuric acid (H2SO4) solutions were studied. The weight-loss curves indicate that both magnets exhibit passive behavior in alkaline solution and dissolve actively in acid solution. SEM observations show that the conventional sintered Nd-Fe-B magnets exhibit typical intergranular corrosion. In the SPS magnet, however, intergranular corrosion through the Nd-rich phase is suppressed effectively due to the unique microstructure of the magnets, i.e., the grain size of the Nd2Fe14B main phase is fine and uniform, and the fine Nd-rich phase does not form along the grain boundaries of main phase as with conventional magnets, but agglomerates into the triple junctions. As a result, the SPS Nd-Fe-B magnets possess excellent corrosion resistance.