O presente estudo 3 tem como tema a produção e reprodução da vida de trabalhadores migrantes temporários nordestinos da construção civil que trabalham no Campus central da Universidade Federal de Santa Catarina — UFSC, em Florianópolis/SC. Seu objetivo principal é analisar as condições de vida, trabalho, moradia e escolarização dos trabalhadores diante do crescimento das migrações na atualidade. Na pesquisa empírica foi realizado um trabalho de campo nos canteiros de obras no campus, com o propósito de identificar as empresas que prestam serviço na universidade e também quais as empresas que empregavam maior número de trabalhadores migrantes temporários nordestinos. Na coleta de dados foram realizadas entrevistas semiestruturadas com os trabalhadores migrantes e com as empresas nos canteiros de obras da universidade. A pesquisa de campo envolveu ainda conversas informais com os trabalhadores migrantes, com as empresas e registros fotográficos.

Dissertação de mestrado

Although Zn metal has been regarded as the most promising anode for aqueous batteries, it persistently suffers from serious side reactions and dendrite growth in mild electrolyte. Spontaneous Zn corrosion and hydrogen evolution damage the shelf life and calendar life of Zn-based batteries, severely affecting their industrial applications. Herein, a robust and homogeneous ZnS interphase is built in situ on the Zn surface by a vapor-solid strategy to enhance Zn reversibility. The thickness of the ZnS film is controlled via the treatment temperature, and the performance of the protected Zn electrode is optimized. The dense ZnS artificial layer obtained at 350 °C not only suppresses Zn corrosion by forming a physical barrier on the Zn surface, but also inhibits dendrite growth via guiding the Zn plating/stripping underneath the artificial layer. Accordingly, a side reaction-free and dendrite-free Zn electrode is developed, the effectiveness of which is also convincing in a MnO2 /ZnS@Zn full-cell with 87.6% capacity retention after 2500 cycles.

An In-Depth Study of Zn Metal Surface Chemistry for Advanced Aqueous Zn-Ion Batteries.

Tribology of electroless nickel coatings – A review

Self-healing polymeric materials based on microencapsulated healing agents: From design to preparation

Metallic zinc is an ideal anode due to its high theoretical capacity (820 mAh g−1), low redox potential (−0.762 V versus the standard hydrogen electrode), high abundance and low toxicity. When used in aqueous electrolyte, it also brings intrinsic safety, but suffers from severe irreversibility. This is best exemplified by low coulombic efficiency, dendrite growth and water consumption. This is thought to be due to severe hydrogen evolution during zinc plating and stripping, hitherto making the in-situ formation of a solid–electrolyte interphase (SEI) impossible. Here, we report an aqueous zinc battery in which a dilute and acidic aqueous electrolyte with an alkylammonium salt additive assists the formation of a robust, Zn2+-conducting and waterproof SEI. The presence of this SEI enables excellent performance: dendrite-free zinc plating/stripping at 99.9% coulombic efficiency in a Ti||Zn asymmetric cell for 1,000 cycles; steady charge–discharge in a Zn||Zn symmetric cell for 6,000 cycles (6,000 h); and high energy densities (136 Wh kg−1 in a Zn||VOPO4 full battery with 88.7% retention for >6,000 cycles, 325 Wh kg−1 in a Zn||O2 full battery for >300 cycles and 218 Wh kg−1 in a Zn||MnO2 full battery with 88.5% retention for 1,000 cycles) using limited zinc. The SEI-forming electrolyte also allows the reversible operation of an anode-free pouch cell of Ti||ZnxVOPO4 at 100% depth of discharge for 100 cycles, thus establishing aqueous zinc batteries as viable cell systems for practical applications. A solid–electrolyte interphase that is permeable to Zn(ii) ions but waterproof is formed using an aqueous electrolyte composition. Cycling performances in an anode-free aqueous pouch cell show promise for intrinsically safe energy storage applications.

Fluorinated interphase enables reversible aqueous zinc battery chemistries.

Nonmetallic (based on polymers or oxides) and metallic protective coatings are used to protect metal products against the harmful action of the corrosion environment. In recent years, self-healing coatings have been the subject of increasing interest. The ability of such coatings to self-repair local damage caused by external factors is a major factor contributing to their attractiveness. Polymer layers, silica-organic layers, conversion layers, metallic layers and ceramic layers, to mention but a few, are used as self-healing coatings. This paper presents the main kinds of self-healing coatings and explains their self-healing mechanisms.

https://link.springer.com/content/pdf/10.1007%2Fs10853-013-7616-y.pdf

Self-healing coatings in anti-corrosion applications

ZnO, Zn(OH)2, Zn5(OH)8Cl2·H2O, ZnCO3, and Zn5(CO3)2(OH)6 synthetic powders were prepared by chemical or solid-state method. Their crystalline phase structure, thermal behavior, and morphology were examined. Characteristic infrared absorbance bands were estimated by means of FT-IR ATR spectroscopy. X-ray photoelectron spectroscopy (XPS) allowed to calculate the modified Auger parameters (α ′) thereof to 2010.2, 2009.3, 2009.4, 2009.7, and 2009.8 eV, respectively for ZnO, Zn(OH)2, Zn5(OH)8Cl2·H2O, ZnCO3, and Zn5(CO3)2(OH)6. Finally, comparison of surface composition may be crucial to evaluation of the unknown experimental spectra of corrosion products formed on the surface of zinc alloy coatings exposed in NaCl solution.

/pdf/xps-and-ft-ir-characterization-of-selected-synthetic-3foy5lms7c.pdf

XPS and FT-IR Characterization of Selected Synthetic Corrosion Products of Zinc Expected in Neutral Environment Containing Chloride Ions

Electroless binary Ni–P and ternary Ni–W–P alloy coatings and electroless composite (Ni–P–ZrO 2 and Ni–P–W–ZrO 2 ) nickel coatings were deposited. Baths with aminoacetic acid as the complexing agent were used. ICP measurements showed that the P content depending on the type of coating is in a range of 4.7–6.3 wt.% (at pH = 6, t  = 75 °C). The tungsten content is around 1–2 wt.%. SEM examinations show that the electroless Ni–P coating has the most fine-grained structure. Grains in the form of microspheroids 20 μm in size are characteristic of the Ni–P–ZrO 2 coating. X-ray diffraction patterns show that for all the obtained coatings peak Ni(111) located around 2 θ  = 44° is the most intensive. After the coatings are heat treated at 400 °C for 1 h the peak becomes even sharper. The heat treatment results in a nearly double increase in crystallite size. The quaternary coatings' abrasion resistance is determined by the second-phase (ZrO 2 ) particles present in them.

Surface morphology and structure of Ni–P, Ni–P–ZrO2, Ni–W–P, Ni–W–P–ZrO2 coatings deposited by electroless method

Ternary Zn–Ni–Mo (1.2 wt.% Ni, 4.5 wt.% Mo) and Zn–Co–Mo (6 wt.% Co, 4 wt.% Mo) as well as reference binary Zn–Ni and Zn–Co alloy coatings were electrodeposited from citrate–sulphate baths. The influence of molybdenum on the surface morphology, structure, phase composition, corrosion and mechanical properties of the deposits was investigated. The XPS results revealed that the coatings with molybdenum contained appreciable amounts of Zn 2+ inclusions, which is probably due to the low hydrogen evolution overpotential on the ternary alloys. The increase in the interfacial pH, promoted by intensive hydrogen evolution, causes the formation of oxidized zinc species which incorporate into the coating. The presence of MoO 4 2− ions in the bath modified the morphology of the deposits — alloys with smoother surface were deposited. Polarization resistance measurements proved the beneficial influence of molybdenum on corrosion properties of examined alloy coatings. The presence of molybdenum improves the microhardness of the zinc-based alloys, but it has negative influence on the adhesion of the ternary coatings.

Bogdan Szczygieł

Papers

Self-healing coatings in anti-corrosion applications

XPS and FT-IR Characterization of Selected Synthetic Corrosion Products of Zinc Expected in Neutral Environment Containing Chloride Ions

Surface morphology and structure of Ni–P, Ni–P–ZrO2, Ni–W–P, Ni–W–P–ZrO2 coatings deposited by electroless method

Influence of molybdenum on properties of Zn–Ni and Zn–Co alloy coatings

EIS and XPS investigations on the corrosion mechanism of ternary Zn–Co–Mo alloy coatings in NaCl solution