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Effect of structural singularities on superwettability of SiO₂-based coatings
(Universidade Federal de São Carlos, 2019-11-07) Castro, Lucas Daniel Chiba de; Larocca, Nelson Marcos; https://lattes.cnpq.br/5019620288988253; Pessan, Luiz Antonio; https://lattes.cnpq.br/8276650236213537; https://lattes.cnpq.br/7987133332464161
A detailed study on the correlation between structural singularities and wettability of neat and chemically modified coatings prepared from layer-by-layer (LbL) assembled silica nanoparticles (SiO₂) was performed. Nanoporous-driven superhydrophilicity of neat SiO₂-based coatings might not be mainly governed by thickness as usually reported in literature; instead, superficial homogeneity should be carefully considered and, if a uniform nanoporous structure is obtained, superhydrophilic behavior should be observed. Here, highly homogeneous structures were achieved by employing water-based dipping suspensions containing above 0.03 wt% of SiO₂ with 7nm and 22nm of diameter. Aiming the completely opposite wetting behavior, chemically modified hierarchical structures were prepared using two different approaches: random roughened surfaces were obtained by exploring stacking defects spontaneously arisen after 15, 30 and 45 assembly cycles of small SiO₂ particles; while a particular structure, commonly known as raspberry-like, was obtained by depositing small SiO₂ (“berries”) over the first deposited large SiO₂ (“cores”). As an intrinsic feature of the studied system, the average slope of random roughened surfaces seems to be constant and virtually independent of the number of deposited layers. Additionally, the local slopes were always lower than a critical value (Φcrit) required to stabilize the solid-liquid-air interface, therefore, and a fully wetted Wenzel state with water contact angle (WCA) of approximately 130⁰ was invariably observed. On the other hand, since the local slopes of the raspberry-like structure follow a nearly spherical curvature, small SiO₂ can stabilize the solid-liquid-air interface by increasing the local contact angle and avoiding the deep penetration of water into the surface asperities. For the studied conditions, WCA as large as 167⁰ was observed. The small berries might also play an important role in the pinning effect of the solid-liquid-air contact line, bringing to life the phenomena so-called Lotus Effect.
Construções políticas das concepções ambientais/climáticas na Argentina: mudanças e continuidades
(Universidade Federal de São Carlos, 2019-11-07) Braga, Patricia Benedita Aparecida; Andrade, Thales Haddad Novaes de; https://lattes.cnpq.br/5882842888759363; https://lattes.cnpq.br/0569884644750105
Argentina sanctified the UNFCCC in 1993 and accomplished its differentiated obligations, the creation of the National Comunications (mapping of causes and possible solutions for climate changes in a national scale). Thus, the present work has the general goal of understanding the historical and contextual meaning attributed by the Argentinian State to the climate changes, by the tracing of ideational and contextual changes. In specific terms, there are four purposes: to understand Argentina's participation in the genesis of the global environmental debate; to analyse the country's possible pioneerism in the South America region in the way of handling the environment issue; to highlight how the idea of environment has changed throughout the years (from primordial element of possible economical and political transformation to a instrumentalized unit by the principle of economical gain and loss); and, description and processual analysis of institutional and ideational aspects and agents involved in the construction of the climate and environmental issues by the Argentinian State. As an analytical guide the discursive institutionalism and its dialogue with other institutionalisms (rational choice, historical and sociological) was operationalized by the selection of works by Argentinian intellectuals who worked with this theme. In methodological terms, the process tracing, the documental analysis and semistructured interviews conducted the analysis. In general terms, it is concluded that the Argentinian State was the exponent in the genesis of the debate on the global environmental issue and in the handling of this issue as a political problem, besides being the pioneer regarding the ideational conception of environment as a central changer of the international economical reality (Péron). And, that the conceptions about climate changes in current times goes beyond the relative capacity of the country of changing the causes of the problem and the ideational understanding of the "State", by his agents (of several natures) of understanding the gains and losses of acting in the face of the phenomenon, clearly shown by directions and discreet changes, whether in national terms or international ones.