Stable superhydrophobic coatings Using PVDF/MWCNT nanocomposite

Thermally stable superhydrophobic coatings have been prepared using Polyvinylidene fluoride (PVDF)Multiwalled carbon nanotubes (MWCNTs) by spray coating method. The effects of MWCNT (0 – 66 wt%) and temperature (300 to 623 K) on wettability have been studied. A transformation from hydrophobic to superhydrophoic state was achieved with increase of CNT content. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) studies reveal that with increase in CNT content, -phase of PVDF decreases suggesting that MWCNT has strong effect on the phase separation of PVDF. Field emission scanning electron microscopy (FESEM) studies show that the coatings have rough surface with porous structure. With increase in CNT content the protrusion like structures decreased reaching micro/nano scales. The coatings were thermally stable upto 573 K exhibiting superhydrophobicity and thereafter transformed to superhydrophilic state at 623 K. Energy dispersive X-ray spectroscopy (EDXS) analysis show the absence of fluorine after annealing at 623 K suggesting decomposition of PVDF. X-ray photoelectron spectroscopy (XPS) of C1s and F1s core levels in as-deposited PVDFMWCNT coating show the presence of CF2 related species. Concentration of fluorine drastically decreases after heat treatment of the coating at 350 C. The main advantage of the present method is feasibility for application over large area and the coatings are stable upto 573 K

Catalytic current polarographic determination of traces of titanium in water after preconcentration by coflotation

A new method is reported for the-determination of trace levels of Ti(IV) in water by cofiotation and polargraphy. Ti(IV) is preconcentrated and separated by cofiotation using aluminium hydroxide as coprecipitant and sodium oleate as surfactant. Polarographic determination of titanium content in the froth is based on the catalytic wave ofTi(IV) in the presenceof chlorate and oxalate. The effect ofvarious cations and anions on the fiotation and determination of titanium has been investigated. The method has been applied to estimation of titanium in natural fresh water samples

Comparison of the oxygen sensor performance of some pyrene derivatives in silicone polymer matrix

Pyrene and its derivatives find application as fluorescent probes for monitoring the oxygen concentrations in air and various fluids. Photophysical characteristics of some commercially available derivatives of pyrene in silicone polymer matrix were studied in order to find out whether they could be employed as a substitute for pyrene in the pressure sensitive paint (PSP). The derivatives under study were: 1-pyrenyl methanol (PMO), 1-pyrenyl butanol (PBO), 1-pyrene butyric acid (PBA), and 1-pyrene acetic acid (PAA). Distinct differences were observed in the fluorescence emission spectra of the silicone coatings of derivatives depending on the functional group attached to pyrene. The oxygen quenching sensitivity (OQS) of these probes were evaluated and compared to that of pyrene. It was found that the fluorescence spectra of all silicone coatings of pyrene derivatives exhibited monomer and excimer peaks. The excimer emission of PBO in silicone matrix was oxygen sensitive whereas the coatings of the other three pyrene derivatives exhibited poor oxygen quenching. xA9; 2003 Elsevier B.V. All rights reserved

Fabrication of a Bi-luminophore Temperature Sensitive Coating by Embedding Europium Thenoyltrifluoroacetonate (EuTTA) and Perylene in Polystyrene

A new bi-luminophore system for optical sensing of temperature is described. The coating was fabricated by embedding europium thenoyltrifluoroacetonate (EuTTA) and perylene in polystyrene (PS) matrix. The luminescence emission of EuTTA was sensitive to temperature whereas perylene emission was temperature-insensitive and was used as a reference. Both luminophores were excited in the UV region of about 330 to 380 nm. The fluorescence emission of perylene and EuTTA occured at 474 nm and 615 nm respectively. The temperature sensitivities of both luminophores were influenced by (i) the type of polymer, and (ii) the concentration of luminophore in the matrix. Combining EuTTA and perylene in polystyrene matrix, a new bi-luminophore temperature sensing coating was developed. The temperature sensitivity of this coating was −1.80%/°C in the temperature range of 5 °C to 50 °C. The emission characteristics of this temperature sensitive coating displayed a fully reversible response to temperature

Polarographic determination of trace amount of titanium13; using catalytic current in the presence of chlorate

Titanium (IV) oxalate complexes are reduced catalytically in the presence of chlorate and this gives rise to an13; enhancement in sensitivity . Experimental conditions such as acid strength and the concentrations of chlorate,13; oxalate etc . were standardized to extend the linearity of calibration graph to low titanium concentrations. The13; interfering effect of other metal ions like Fe(III), Mo(VI), Cu(II), Bi(III), Pb(II), Cd(II), Ni(II), Cr(III), Cr(VI) and Zn(II) on the catalytic current of Ti(IV) was investigated . The detection limit for the determination of Ti(IV) by this method was found to be 5 ng nil-t

Simultaneous Determinatin of Palladium and Nickel in Electroplating Solutions by Differential-pulse Polarography

Differential-pulse polarography can be successfully employed for the simultaneous determination of palladium and nickel in electroplating baths, Both palladium and nickel give peaks in ammoniacal ammonium chloride and ammoniacal ammonium tartrate media that are separated by about 250 mv. When the nickel-to-palladium ratio exceeds 100, ethylenediaminetetraacetic acid (EDTA) may be added to complex nickel and thus remove the interference due to an excess of nickel. In the presence of large amounts of palladium, dimethylglyoxime is used to enhance the peak current of nickel. The palladium peak in ammoniacal ammonium chloride buffer at pH 9,0 is not affected by the resence of either EDTA or dimethylglyoxime

Fabrication of Superhydrophobic Nanocomposite Coatings Using Polytetrafluoroethylene and Silica Nanoparticles

Superhydrophobic nanocomposite coatings were fabricated by incorporating hydrophobically modified silica (HMS) nanoparticles in polytetrafluoroethylene (PTFE) emulsion. Hydrophobicity of the coating was dependent on the concentration of HMS. Coatings containing optimum amounts of PTFE and HMS exhibited superhydrophobic property with high water contact angle (WCA) of 165◦ and low sliding angle <2◦. Scanning electron microscopic (SEM) studies have shown a binary surface topography composed of microbumps and nanoscale granules. The synergistic effect of the micro-nano-binary structure and low surface energy of PTFE was responsible for the superhydrophobicity of the coating. The method is simple and cost-effective and can be used for preparing self-cleaning superhydrophobic coatings on large areas of different kinds of substrates like glass, metal, and composites

Study of the mechanism of degradation of pyrene-based pressure sensitive paints

Even though pyrene-based pressure sensitive paints have some special advantages like high quantum efficiency, good pressure sensitivity and low temperature sensitivity, these paints exhibit steady degradation of the fluorescent intensity after each wind tunnel test. It has been reported that pyrene-based paints degrade because pyrene has a tendency to evaporate. It is necessary to understand the mechanism of degradation of pyrene-based paints in order to find a solution to this problem. Thermal aging tests and UV exposure tests of the paint specimens are carried out to study the effect of experimental parameters like temperature, pressure and UV exposure on the paint stability. This study has shown that the paint degradation in wind tunnel is mainly due to diffusion and evaporation of pyrene. The effect of pyrene concentration in the paint and the thickness of the active layer on the paint stability were also studied. xA9; 2003 Elsevier B.V. All rights reserved

Enhanced sensitivity for the differential pulse polarographic determination of Mo(VI) based on adsorption catalytic current

the adsorption catalytic current in a medium containing chlorate and 8-hydroxyquinoline (exine) is suggested for the determination of molybdenum(VI). Experimental conditions such as pH and the composition of supporting electrolyte have been optimized to get a linear calibration graph at trace levels of Mo(VI). The sensitivity for molybdenum can be considerably enhanced by this method. The influence of possible interferences on the catalytic current has been investigated. The sensitivity of the method is compared with those obtained for other DPP methods for molybdenum. A detection limit of 1.0 1Q-8 mol/L has been found

Green Inhibitors for Corrosion Protection ofMetals and Alloys: An Overview

Corrosion control of metals is of technical, economical, environmental, and aesthetical importance. The use of inhibitors is one of the best options of protecting metals and alloys against corrosion. The environmental toxicity of organic corrosion inhibitors has prompted the search for green corrosion inhibitors as they are biodegradable, do not contain heavy metals or other toxic compounds. As in addition to being environmentally friendly and ecologically acceptable, plant products are inexpensive, readily available and renewable. Investigations of corrosion inhibiting abilities of tannins, alkaloids, organic,amino acids, and organic dyes of plant origin are of interest. In recent years, sol-gel coatings doped with inhibitors show real promise. Although substantial research has been devoted to corrosion inhibition by plant extracts, reports on the detailed mechanisms of the adsorption process and identification of the active ingredient are still scarce. Development of computational modeling backed by wet experimental results would help to fill this void and help understand the mechanism of inhibitor action, their adsorption patterns, the inhibitormetal surface interface and aid the development of designer inhibitors with an understanding of the time required for the release of self-healing inhibitors. The present paper consciously restricts itself mainly to plant materials as green corrosion inhibitors