1,720,964 research outputs found
Corrosion inhibition of steel in chloride-containing alkaline solutions
No full textSome organic inhibitors of steel corrosion in saturated calcium hydroxide solutions containing 0.1 M chlorides were investigated to elucidate their interactions with the steel surface. The compounds studied were dicyclohexylammonium nitrite (DCHAMN), dicyclohexylamine (DCHA), sodium β-glycerophosphate (GPH) and 5-hexyl-benzotriazole (C6BTA). Sodium nitrite (SN) was also studied as a reference. The techniques applied were electrochemical impedance spectroscopy (EIS), polarization curves, cyclic voltammetry (CV) and Fourier transform infrared (FTIR) spectroscopy. FTIR spectra showed that DCHAMN, DCHA, GPH and C6BTA interact with the steel surface by chemisorption and some information about the mechanism also emerged. From DCHAMN solution, DCHA chemisorption is induced by slow salt hydrolysis. CV tests show that, among chemisorbed substances, only GPH avoids chloride penetration on cycling, most likely due to a quick chemisorption, while DCHAMN can only enlarge the passive potential range. Addition of SN also prevents chloride attack on cycling. Twenty days of immersion in inhibited solutions revealed that, besides SN, GPH and DCHAMN also form an impervious surface film on steel, which blocks any localized corrosion attack, whereas in the case of DCHA and C6BTA solutions, pitting corrosion is slowed down, but not avoided. DCHAMN exhibits the highest inhibiting efficiency at long immersion times, as a result of a synergetic inhibitive action which develops between nitrite and chemisorbed DCHA
Inhibition of acid corrosion of nickel by acetylenic alcohols
No full textThe inhibition of nickel corrosion by means of 3-methyl-1-butyne-3-ol (H), its halo-derivatives and 1-octyn-3-ol (OCT) has been studied by solution analysis, polarization curve recording and electrochemical impedance spectroscopy, in deaerated 1N HCl or H2SO4 solutions, at 70 °C. It has been found that the inhibiting effects of the tested additives are similar to those determined in the case of iron acid corrosion. It is assumed that on both metals they form polymeric films with the same mechanism. These compounds are more efficient in the hydrochloric acid solution than in the sulphuric one. OCT is more efficient than H; however the efficacy of the latter molecule can be improved by the substitution of the acetylenic hydrogen atom with halogen atoms, chiefly iodine, that affords an high inhibiting action on the anodic reaction
Corrosion sous tension d'aciers inoxydables en milieu acide et leur inhibition
No full textLes resultats obtenus ont confirmé que la corrosion sous tension des acyers inoxydables austénitique en melieu acide chloruré se vérifie sur les alliages à l'état actif.
Cette corion est complétement inhibée par les substances qui présentent une action remarquable sur la réaction anodique
Studio di trattamenti superficiali e di inibitori della corrosione dell'ottone all'alluminio in soluzioni acquose
No full textBenzotriazole (BTA) or 2-mercaptobenzimidazole (MBI) prefilming treatment is the most promising method to protect aluminum brass against corrosion. Both uniform and localized corrosion attack, if it occurs, can be blocked with their use
Influence of a prefilming treatment on the corrosion behaviour of Aluminium brass in aqueous solutions
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
APPLICATION OF ELECTROCHEMICAL NOISE-ANALYSIS TO STUDY THE CORROSION BEHAVIOR OF ALUMINUM COMPOSITES
No full textThis paper investigates the possibility of using electrochemical voltage noise analysis to study the corrosion behavior of a few composite materials obtained by reinforcing an aluminum matrix with either SiC particles (SiCp) or Al2O3 particles (Al(2)O(3)p) or Al2O3 fibers (Saffil, Al(2)O(3)f). The ranking of the corrosion resistances exhibited by the various materials, according to the noise analysis technique, appears to agree with the results obtained by Linear polarization resistance and weight loss measurements and with the observation of the specimen surfaces by scanning electron microscopy. The recording of both polarization curves and galvanic current densities flowing between reinforced and nonreinforced aluminum electrodes shows that the driving force for the corrosion process is the cathodic process of oxygen reduction, which can be affected by the nature and the shape of the reinforcement
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