Desenvolvimento e avaliação tribológica de emulsão O/A a partir de óleo vegetal epoxidado para aplicação em fluídos de corte

The cutting fluids are lubricants used in machining processes, because they present many benefits for different processes. They have many functions, such as lubrication, cooling, improvement in surface finishing, besides they decreases the tool wear and protect it against corrosion. Therefore due to new environment laws and demand to green products, new cutting fluids must be development. These shall be biodegradable, non-toxic, safety for environment and operator healthy. Thus, vegetable oils are a good option to solve this problem, replacing the mineral oils. In this context, this work aimed to develop an emulsion cutting fluid from epoxidized vegetable oil, promoting better lubrication and cooling in machining processes, besides being environment friendly. The methodology was divided in five steps: first one was the biolubricant synthesis by epoxidation reaction. Following this, the biolubricant was characterized in terms of density, acidity, iodo index, oxirane index, viscosity, thermal stability and chemical composition. The third step was to develop an emulsion O/A with different oil concentration (10, 20 and 25%) and surfactant concentration (1, 2.5 and 5%). Also, emulsion stability was studied. The emulsion tribological performance were carried out in HFRR (High Frequency Reciprocating Rig), it consists in ball-disc contact. Results showed that the vegetable based lubricant may be synthesized by epoxidationreaction, the spectra showed that there was 100% conversion of the epoxy rings unsaturations. In regard the tribological assessment is observed that the percentage of oil present in the emulsion directly influenced the film formation and coefficient of friction for higher concentrations the film formation process is slow and unstable, and the coefficient of friction. The high concentrations of surfactants have not improved the emulsions tribological performance. The best performance in friction reduction was observed to emulsion with 10% of oil and 5% of surfactant, its average wear scar was 202 μm.

Estudo da sinterização e oxidação anódica na produção de um capacitor eletrolítico de nióbio

It seeks to find an alternative to the current tantalum electrolytic capacitors in the market due to its high cost. Niobium is a potential replacement for be lighter and cheaper than tantalum. They belong to the same table group periodically and thus exhibit several physical and chemical properties similar. Niobium is used in many technologically important applications, and Brazil has the largest reserves, around 96%. These electrolytic capacitors have high specific capacitance, so they can store high energy in small volumes compared to other types of capacitors. This is the main attraction of this type of capacitor because is growing demand in the production of capacitors with capacitance specifies increasingly high, this because of the miniaturization of various devices such as GPS devices, televisions, computers, phones and many others. The production route of the capacitor was made by powder metallurgy. The initial niobium poder was first characterized by XRD, SEM and laser particle size to then be sieved into particle size 400mesh. The powder was then compacted at pressure of 150MPa and sintered at 1400, 1450 and 1500°C using two sintering time 30 and 60min. Sintering is an important part of the process as it affects properties as porosity and surface cleaning of the samples, which greatly affected the quality of the capacitor. After sintering the samples were underwent a process of anodic oxidation (anodizing), which created a thin film of niobium pentoxide over the whole surface of the sample, this film is the dielectric capacitor. The anodizing process variables influenced a lot in film formation and consequently the capacitor. The samples were characterized by electrical measurements of capacitance, loss factor and ESR (equivalent series resistance). The sintering has affected the porosity and in turn the specific area of the samples. The capacitor area is directly related to the capacitance, that is, the higher the specific area is the capacitance. Higher sintering temperatures decrease the surface area but eliminate as many impurities. The best results were obtained at a temperature of 1400°C with 60 minutes. The most interesting results were compared with the specific capacitance and ESR for all samples.

Estudo da sinterização e oxidação anódica na produção de um capacitor eletrolítico de nióbio

It seeks to find an alternative to the current tantalum electrolytic capacitors in the market due to its high cost. Niobium is a potential replacement for be lighter and cheaper than tantalum. They belong to the same table group periodically and thus exhibit several physical and chemical properties similar. Niobium is used in many technologically important applications, and Brazil has the largest reserves, around 96%. These electrolytic capacitors have high specific capacitance, so they can store high energy in small volumes compared to other types of capacitors. This is the main attraction of this type of capacitor because is growing demand in the production of capacitors with capacitance specifies increasingly high, this because of the miniaturization of various devices such as GPS devices, televisions, computers, phones and many others. The production route of the capacitor was made by powder metallurgy. The initial niobium poder was first characterized by XRD, SEM and laser particle size to then be sieved into particle size 400mesh. The powder was then compacted at pressure of 150MPa and sintered at 1400, 1450 and 1500°C using two sintering time 30 and 60min. Sintering is an important part of the process as it affects properties as porosity and surface cleaning of the samples, which greatly affected the quality of the capacitor. After sintering the samples were underwent a process of anodic oxidation (anodizing), which created a thin film of niobium pentoxide over the whole surface of the sample, this film is the dielectric capacitor. The anodizing process variables influenced a lot in film formation and consequently the capacitor. The samples were characterized by electrical measurements of capacitance, loss factor and ESR (equivalent series resistance). The sintering has affected the porosity and in turn the specific area of the samples. The capacitor area is directly related to the capacitance, that is, the higher the specific area is the capacitance. Higher sintering temperatures decrease the surface area but eliminate as many impurities. The best results were obtained at a temperature of 1400°C with 60 minutes. The most interesting results were compared with the specific capacitance and ESR for all samples.

Growth and characterization of anodic Films on InP in KOH and (NH4)2S

The current-voltage characteristics of InP were investigated in (NH4)2S and KOH electrolytes. In both solutions, the observation of current peaks in the cyclic voltammetric curves was attributed to the growth of passivating films. The relationship between the peak currents and the scan rates suggests that the film formation process is diffusion controlled in both cases. The film thickness required to inhibit current flow was found to be much lower on samples anodized in the sulphide solution. Focused ion beam (FIB) secondary electron images of the surface films show that film cracking of the type reported previously for films grown in (NH4)2S is also observed for films grown in KOH. X-ray and electron diffraction measurements indicate the presence of In2O3 and InPO4 in films grown in KOH and In2S3 in films grown in (NH4)2S.

Emulsion-Based RIR-MAPLE Deposition of Conjugated Polymers: Primary Solvent Effect and Its Implications on Organic Solar Cell Performance.

Emulsion-based, resonant infrared matrix-assisted pulsed laser evaporation (RIR-MAPLE) has been demonstrated as an alternative technique to deposit conjugated polymer films for photovoltaic applications; yet, a fundamental understanding of how the emulsion target characteristics translate into film properties and solar cell performance is unclear. Such understanding is crucial to enable the rational improvement of organic solar cell (OSC) efficiency and to realize the expected advantages of emulsion-based RIR-MAPLE for OSC fabrication. In this paper, the effect of the primary solvent used in the emulsion target is studied, both experimentally and theoretically, and it is found to determine the conjugated polymer cluster size in the emulsion as well as surface roughness and internal morphology of resulting polymer films. By using a primary solvent with low solubility-in-water and low vapor pressure, the surface roughness of deposited P3HT and PCPDTBT polymer films was reduced to 10 nm, and the efficiency of P3HT:PC61BM OSCs was increased to 3.2% (∼100 times higher compared to the first MAPLE OSC demonstration [ Caricato , A. P. ; Appl. Phys. Lett. 2012 , 100 , 073306 ]). This work unveils the mechanism of polymer film formation using emulsion-based RIR-MAPLE and provides insight and direction to determine the best ways to take advantage of the emulsion target approach to control film properties for different applications.

Multiscale morphology design of hybrid halide perovskites through a polymeric template

Hybrid halide perovskites have emerged as promising active constituents of next generation solution processable optoelectronic devices. During their assembling process, perovskite components undergo very complex dynamic equilibria starting in solution and progressing throughout film formation. Finding a methodology to control and affect these equilibria, responsible for the unique morphological diversity observed in perovskite films, constitutes a fundamental step towards a reproducible material processability. Here we propose the exploitation of polymer matrices as cooperative assembling components of novel perovskite CH3NH3PbI3 : polymer composites, in which the control of the chemical interactions in solution allows a predictable tuning of the final film morphology. We reveal that the nature of the interactions between perovskite precursors and polymer functional groups, probed by Nuclear Magnetic Resonance (NMR) spectroscopy and Dynamic Light Scattering (DLS) techniques, allows the control of aggregates in solution whose characteristics are strictly maintained in the solid film, and permits the formation of nanostructures that are inaccessible to conventional perovskite depositions. These results demonstrate how the fundamental chemistry of perovskite precursors in solution has a paramount influence on controlling and monitoring the final morphology of CH3NH3PbI3 (MAPbI3) thin films, foreseeing the possibility of designing perovskite : polymer composites targeting diverse optoelectronic applications.

Resistance of an epoxy coating with an organic inhibitor to cathodic disbondment in sea water

In this study, the effect of anti-corrosion inhibitor addition to epoxy coating, on the disbanding rate was evaluated. First to determination of mechanism, the bare steel substrates were immersed in the 3.5% NaCl solution and the solution containing 1 mM anti corrosion. The Electrochemical Impedance Spectroscopy was performed after 5 and 24 hour. The results indicated a lower corrosion rate in the presence of inhibitor. During the time, charge transfer resistance, was decreased for the substrates immersed in NaCl solution, and increased for the substrates immersed in NaCl solution containing 1 mM anti corrosion. This result can be related to more stability of corrosion products in presence of anti-corrosion and film formation. The coated substrates, with four different concentration of anticorrosion in coating, were protected under -1.2 voltage in the 3.5% NaCl solution. After 12 and 24 hour, the EIS test and disbanding area measurement, were evaluate. The lower disbanding rate, more charge transfer resistance and less double layer capacitance for the coating containing 0.75w% inhibitor, were observed. The result of Pull-off test after 1 day immersion in 3.5% NaCl solution, showed more wet adhesion for the coating containing 0.75w% inhibitor. The images of FE-SEM electron microscope and surface analyses EDX on the coated substrate after disbanding and the bare substrate immersed in 3.5w% NaCl containing 1 mM inhibitor, were proved the formation of stabilized film.

Synthesis of waterborne polyurethane-urea dispersions with chain extension step in homogeneous and heterogeneous media

Hypothesis: The possibility of tailoring the final properties of environmentally friendly waterborne polyurethane and polyurethane-urea dispersions and the films they produce makes them attractive for a wide range of applications. Both the reagents content and the synthesis route contribute to the observed final properties. Experiments: A series of polyurethane-urea and polyurethane aqueous dispersions were synthesized using 1,2-ethanediamine and/or 1,4-butanediol as chain extenders. The diamine content was varied from 0 to 4.5 wt%. Its addition was carried out either by the classical heterogeneous reaction medium (after phase inversion step), or else by the alternative homogeneous medium (prior to dispersion formation). Dispersions as well as films prepared from dispersions have been later extensively characterized. Findings: 1,2-Ethanediamine addition in heterogeneous medium leads to dispersions with high particle sizes and broad distributions whereas in homogeneous medium, lower particle sizes and narrow distributions were observed, thus leading to higher uniformity and cohesiveness among particles during film formation. Thereby, stress transfer is favored adding the diamine in a homogeneous medium; and thus the obtained films presented quite higher stress and modulus values. Furthermore, the higher uniformity of films tends to hinder water molecules transport through the film, resulting, in general, in a lower water absorption capacity.

Étude sur les propriétés physicochimiques et électrochimiques des liquides ioniques redox et leur application en tant qu’électrolyte dans les supercapaciteurs

Ce mémoire porte sur les recherches et les développements dans le domaine des électrolytes à base de liquide ionique redox. Une nouvelle famille de liquide ionique redox basée sur le ferrocenylsulfonyl(trifluoromethylsulfonyl) (FcNTf) a été développée et étudiée pour la première fois afin de démontrer le potentiel de ces liquides ioniques dans les dispositifs de stockage d’énergie. En premier lieu, les liquides ioniques redox (RILs) composés de l’anion électroactif et du cation d’alkylimidazolium sont synthétisés et caractérisés. L’impact de la variation des chaînes alkyles du cation sur les propriétés physicochimiques et électrochimiques du RIL a été étudié. À une faible concentration en solution, l’impact du cation a peu d’influence sur l’ensemble des propriétés. Cependant, à haute concentration (>50 % massique) et sans électrolyte de support, la formation de films en oxydation a été observée à l'électrode positive. Ce point est intéressant pour les futures recherches et développements dans le domaine, puisque la variation des chaînes alkyles du cation des liquides ioniques redox et la formation de films lors de l’oxydation du FcNTf est peu connue et comprise en littérature. De plus, l’optimisation des conditions de solution d'électrolyte RIL dans les supercapaciteurs est aussi présentée. En deuxième lieu, la mise en application des RILs dans les supercapaciteurs a été testée. La performance énergétique et le mécanisme d’autodécharge ont été ciblés dans cette étude. En présence de l’électrolyte redox, la contribution des réactions faradaiques permet d'accomplir un gain énergique de 287 % versus les systèmes purement capacitifs. À cause de la formation de film à l’électrode, l’électrolyte redox FcNTf joue un rôle primordial dans la prévention de l’autodécharge versus les liquides ioniques qui étaient connus jusqu’à présent. Finalement, ce mémoire a permis de mieux comprendre les effets structure-propriétés relative aux modifications du cation chez les liquides ioniques redox.

Étude sur les propriétés physicochimiques et électrochimiques des liquides ioniques redox et leur application en tant qu’électrolyte dans les supercapaciteurs

Ce mémoire porte sur les recherches et les développements dans le domaine des électrolytes à base de liquide ionique redox. Une nouvelle famille de liquide ionique redox basée sur le ferrocenylsulfonyl(trifluoromethylsulfonyl) (FcNTf) a été développée et étudiée pour la première fois afin de démontrer le potentiel de ces liquides ioniques dans les dispositifs de stockage d’énergie. En premier lieu, les liquides ioniques redox (RILs) composés de l’anion électroactif et du cation d’alkylimidazolium sont synthétisés et caractérisés. L’impact de la variation des chaînes alkyles du cation sur les propriétés physicochimiques et électrochimiques du RIL a été étudié. À une faible concentration en solution, l’impact du cation a peu d’influence sur l’ensemble des propriétés. Cependant, à haute concentration (>50 % massique) et sans électrolyte de support, la formation de films en oxydation a été observée à l'électrode positive. Ce point est intéressant pour les futures recherches et développements dans le domaine, puisque la variation des chaînes alkyles du cation des liquides ioniques redox et la formation de films lors de l’oxydation du FcNTf est peu connue et comprise en littérature. De plus, l’optimisation des conditions de solution d'électrolyte RIL dans les supercapaciteurs est aussi présentée. En deuxième lieu, la mise en application des RILs dans les supercapaciteurs a été testée. La performance énergétique et le mécanisme d’autodécharge ont été ciblés dans cette étude. En présence de l’électrolyte redox, la contribution des réactions faradaiques permet d'accomplir un gain énergique de 287 % versus les systèmes purement capacitifs. À cause de la formation de film à l’électrode, l’électrolyte redox FcNTf joue un rôle primordial dans la prévention de l’autodécharge versus les liquides ioniques qui étaient connus jusqu’à présent. Finalement, ce mémoire a permis de mieux comprendre les effets structure-propriétés relative aux modifications du cation chez les liquides ioniques redox.

Role of silver doping in oxygen incorporation of oxide thin film

A distinctive characteristic of silver in oxygen incorporation of oxide thin films during pulsed laser ablation has been discovered. Optical emission spectroscopy studies of laser-induced plume of Ag-target indicates the presence of AgO species whose concentration increases with an increase in oxygen partial pressure. The formation of AgO in laser-plume has been found to be very useful for the realization of high temperature superconducting YBa2Cu3O7-delta (YBCO) and giant magnetoresistive La0.7MnO3-delta (LMO) thin films with dramatically superior quality if the target materials contained a small amount of silver. The improvement in the quality of these films is brought about by the supply of atomic oxygen to oxide lattices during their formation. This becomes possible due to the fact that Ag, after it is ablated with other constituent materials in the target, gets moderately oxidized in an oxygen atmosphere and the oxidized species dissociate back into Ag and nascent O at the substrate surface. The nascent oxygen is very highly reactive and is easily assimilated into the lattice of these compounds. (C) 1997 Elsevier Science S.A.

Analysis of amorphous indium-gallium-zinc-oxide thin-film transistor contact metal using Pilling-Bedworth theory and a variable capacitance diode model

It is widely reported that threshold voltage and on-state current of amorphous indium-gallium-zinc-oxide bottom-gate thin-film transistors are strongly influenced by the choice of source/drain contact metal. Electrical characterisation of thin-film transistors indicates that the electrical properties depend on the type and thickness of the metal(s) used. Electron transport mechanisms and possibilities for control of the defect state density are discussed. Pilling-Bedworth theory for metal oxidation explains the interaction between contact metal and amorphous indium-gallium-zinc-oxide, which leads to significant trap formation. Charge trapping within these states leads to variable capacitance diode-like behavior and is shown to explain the thin-film transistor operation. © 2013 AIP Publishing LLC.

Optical and electrical properties of amorphous zinc tin oxide thin films examined for thin film transistor application

Structural, electronic, and optical properties of amorphous and transparent zinc tin oxide films deposited on glass substrates by pulsed laser deposition (PLD) were examined for two chemical compositions of Zn:Sn=1:1 and 2:1 as a function of oxygen partial pressure PO2 used for the film deposition and annealing temperature. Different from a previous report on sputter-deposited films Chiang et al., Appl. Phys. Lett. 86, 013503 2005 , the PLD-deposited films crystallized at a lower temperature 450 °C to give crystalline ZnO and SnO2 phases. The optical band gaps Tauc gaps were 2.80−2.85 eV and almost independent of oxygen PO2 , which are smaller than those of the corresponding crystals 3.35−3.89 eV . Films deposited at low PO2 showed significant subgap absorptions, which were reduced by postthermal annealing. Hall mobility showed steep increases when carrier concentration exceeded threshold values and the threshold value depended on the film chemical composition. The films deposited at low PO2 2 Pa had low carrier concentrations. It is thought that the low PO2 produced high-density oxygen deficiencies and generated electrons, but these electrons were trapped in localized states, which would be observed as the subgap absorptions. Similar effects were observed for 600 °C crystallized films and their resistivities were increased by formation of subgap states due to the reducing high-temperature condition. High carrier concentrations and large mobilities were obtained in an intermediate PO2 region for the as-deposited films.

Investigation of RuO2/Ta2O5 thin film evolution by thermogravimetry combined with mass spectrometry

The thermal evolution process of RuO2–Ta2O5/Ti coatings with varying noble metal content has been investigated under in situ conditions by thermogravimetry combined with mass spectrometry. The gel-like films prepared from alcoholic solutions of the precursor salts (RuCl3·3H2O, TaCl5) onto titanium metal support were heated in an atmosphere containing 20% O2 and 80% Ar up to 600 °C. The evolution of the mixed oxide coatings was followed by the mass spectrometric ion intensity curves. The cracking of retained solvent and the combustion of organic surface species formed were also followed by the mass spectrometric curves. The formation of carbonyl- and carboxylate-type surface species connected to the noble metal was identified by Fourier transform infrared emission spectroscopy. These secondary processes–catalyzed by the noble metal–may play an important role in the development of surface morphology and electrochemical properties. The evolution of the two oxide phases does not take place independently, and the effect of the noble metal as a combustion catalyst was proved.

Thin film deposition and characterization of pure and iron-doped electron-beam evaporated tungsten oxide for gas sensors

Pure Tungsten Oxide (WO3) and Iron-doped (10 at%) Tungsten Oxide (WO3:Fe) nanostructured thin films were prepared using a dual crucible Electron Beam Evaporation techniques. The films were deposited at room temperature in high vacuum condition on glass substrate and post-heat treated at 300 oC for 1 hour. From the study of X-ray diffraction and Raman the characteristics of the as-deposited WO3 and WO3:Fe films indicated non-crystalline nature. The surface roughness of all the films showed in the order of 2.5 nm as observed using Atomic Force Microscopy (AFM). X-Ray Photoelectron Spectroscopy (XPS) analysis revealed tungsten oxide films with stoichiometry close to WO3. The addition of Fe to WO3 produced a smaller particle size and lower porosity as observed using Transmission Electron Microscopy (TEM). A slight difference in optical band gap energies of 3.22 eV and 3.12 eV were found between the as-deposited WO3 and WO3:Fe films, respectively. However, the difference in the band gap energies of the annealed films were significantly higher having values of 3.12 eV and 2.61 eV for the WO3 and WO3:Fe films, respectively. The heat treated samples were investigated for gas sensing applications using noise spectroscopy and doping of Fe to WO3 reduced the sensitivity to certain gasses. Detailed study of the WO3 and WO3:Fe films gas sensing properties is the subject of another paper.