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Y Castro - One of the best experts on this subject based on the ideXlab platform.
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Electrochemical behaviour of Silica basic hybrid coatings deposited on stainless steel by dipping and EPD
Electrochimica Acta, 2008Co-Authors: Y Castro, Adrian Duran, J.j. Damborenea, A. CondeAbstract:Abstract The aim of this work is the characterisation of the corrosion behaviour of stainless steel (AISI 304) substrates coated by dipping and electrophoretic deposition (EPD) from a sol–gel basic sol. Particulate Silica sols (labelled NaSi) were prepared by basic catalysis from ethyltriethoxysilane (TEOS), methyltriethoxysilane (MTES) and sodium hydroxide. Coatings between 2 and 10 μm were prepared by using concentrated and diluted sols by dipping and EPD process and the corrosion behaviour of the coated substrates were studied through potentiodynamic and impedance spectroscopy measurements (EIS). Potentiodynamic studies of coatings produced by dipping reveal a strong dependence of the protective properties with the concentration of the sol. This behaviour was confirmed by EIS showing that only the coatings obtained from concentrated sol present enough protective properties. On the contrary, EPD coatings prepared from diluted NaSi sol showed an excellent corrosion resistance, maintaining a pure capacitive behaviour for long periods of immersion. EPD deposition is thus proposed as a good alternative method for obtaining thicker and denser coatings with good protective properties from dilute and stable sols.
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coatings produced by electrophoretic deposition from nano Particulate Silica sol gel suspensions
Surface & Coatings Technology, 2004Co-Authors: Y Castro, B Ferrari, Rodrigo Moreno, A DuranAbstract:Sol–gel technology allows the production of hybrid coatings on metals using low temperatures for densification, but has an important limitation related with the maximum coating thickness attainable, typically lower than 2 μm. The incorporation of nano-particles to the sol can make it possible to increase the coating thickness, without increasing the sintering temperature. This work deals with the preparation of thick sol–gel coating by electrophoretic deposition (EPD). Commercial SiO2 nanoparticles are suspended in an acid-catalysed SiO2 sol, whose stability is largely increased by adding tetramethylammonium hydroxide (TMAH) up to pH 6. Coatings are formed by dipping and by EPD on AISI 304 stainless steel substrates. The protective behaviour against corrosion in aggressive media (i.e. marine water) of the produced films is studied. EPD leads to coatings as thick as 5 μm with good corrosion resistance, while the suspension stability is increased by 15 times compared with that of the starting acid suspension.
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Coatings produced by electrophoretic deposition from nano-Particulate Silica sol–gel suspensions
Surface & Coatings Technology, 2004Co-Authors: Y Castro, B Ferrari, Rodrigo Moreno, A DuranAbstract:Sol–gel technology allows the production of hybrid coatings on metals using low temperatures for densification, but has an important limitation related with the maximum coating thickness attainable, typically lower than 2 μm. The incorporation of nano-particles to the sol can make it possible to increase the coating thickness, without increasing the sintering temperature. This work deals with the preparation of thick sol–gel coating by electrophoretic deposition (EPD). Commercial SiO2 nanoparticles are suspended in an acid-catalysed SiO2 sol, whose stability is largely increased by adding tetramethylammonium hydroxide (TMAH) up to pH 6. Coatings are formed by dipping and by EPD on AISI 304 stainless steel substrates. The protective behaviour against corrosion in aggressive media (i.e. marine water) of the produced films is studied. EPD leads to coatings as thick as 5 μm with good corrosion resistance, while the suspension stability is increased by 15 times compared with that of the starting acid suspension.
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Coatings produced by electrophoretic deposition from nano-Particulate Silica sol–gel suspensions
Surface and Coatings Technology, 2004Co-Authors: Y Castro, B Ferrari, Rodrigo Moreno, A DuranAbstract:Sol–gel technology allows the production of hybrid coatings on metals using low temperatures for densification, but has an\ud important limitation related with the maximum coating thickness attainable, typically lower than 2 mm. The incorporation of\ud nano-particles to the sol can make it possible to increase the coating thickness, without increasing the sintering temperature. This\ud work deals with the preparation of thick sol–gel coating by electrophoretic deposition (EPD). Commercial SiO2 nanoparticles are\ud suspended in an acid-catalysed SiO2 sol, whose stability is largely increased by adding tetramethylammonium hydroxide (TMAH)\ud up to pH 6. Coatings are formed by dipping and by EPD on AISI 304 stainless steel substrates. The protective behaviour against\ud corrosion in aggressive media (i.e. marine water) of the produced films is studied. EPD leads to coatings as thick as 5 mm with\ud good corrosion resistance, while the suspension stability is increased by 15 times compared with that of the starting acid\ud suspension.Peer reviewe
A Duran - One of the best experts on this subject based on the ideXlab platform.
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coatings produced by electrophoretic deposition from nano Particulate Silica sol gel suspensions
Surface & Coatings Technology, 2004Co-Authors: Y Castro, B Ferrari, Rodrigo Moreno, A DuranAbstract:Sol–gel technology allows the production of hybrid coatings on metals using low temperatures for densification, but has an important limitation related with the maximum coating thickness attainable, typically lower than 2 μm. The incorporation of nano-particles to the sol can make it possible to increase the coating thickness, without increasing the sintering temperature. This work deals with the preparation of thick sol–gel coating by electrophoretic deposition (EPD). Commercial SiO2 nanoparticles are suspended in an acid-catalysed SiO2 sol, whose stability is largely increased by adding tetramethylammonium hydroxide (TMAH) up to pH 6. Coatings are formed by dipping and by EPD on AISI 304 stainless steel substrates. The protective behaviour against corrosion in aggressive media (i.e. marine water) of the produced films is studied. EPD leads to coatings as thick as 5 μm with good corrosion resistance, while the suspension stability is increased by 15 times compared with that of the starting acid suspension.
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Coatings produced by electrophoretic deposition from nano-Particulate Silica sol–gel suspensions
Surface & Coatings Technology, 2004Co-Authors: Y Castro, B Ferrari, Rodrigo Moreno, A DuranAbstract:Sol–gel technology allows the production of hybrid coatings on metals using low temperatures for densification, but has an important limitation related with the maximum coating thickness attainable, typically lower than 2 μm. The incorporation of nano-particles to the sol can make it possible to increase the coating thickness, without increasing the sintering temperature. This work deals with the preparation of thick sol–gel coating by electrophoretic deposition (EPD). Commercial SiO2 nanoparticles are suspended in an acid-catalysed SiO2 sol, whose stability is largely increased by adding tetramethylammonium hydroxide (TMAH) up to pH 6. Coatings are formed by dipping and by EPD on AISI 304 stainless steel substrates. The protective behaviour against corrosion in aggressive media (i.e. marine water) of the produced films is studied. EPD leads to coatings as thick as 5 μm with good corrosion resistance, while the suspension stability is increased by 15 times compared with that of the starting acid suspension.
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Coatings produced by electrophoretic deposition from nano-Particulate Silica sol–gel suspensions
Surface and Coatings Technology, 2004Co-Authors: Y Castro, B Ferrari, Rodrigo Moreno, A DuranAbstract:Sol–gel technology allows the production of hybrid coatings on metals using low temperatures for densification, but has an\ud important limitation related with the maximum coating thickness attainable, typically lower than 2 mm. The incorporation of\ud nano-particles to the sol can make it possible to increase the coating thickness, without increasing the sintering temperature. This\ud work deals with the preparation of thick sol–gel coating by electrophoretic deposition (EPD). Commercial SiO2 nanoparticles are\ud suspended in an acid-catalysed SiO2 sol, whose stability is largely increased by adding tetramethylammonium hydroxide (TMAH)\ud up to pH 6. Coatings are formed by dipping and by EPD on AISI 304 stainless steel substrates. The protective behaviour against\ud corrosion in aggressive media (i.e. marine water) of the produced films is studied. EPD leads to coatings as thick as 5 mm with\ud good corrosion resistance, while the suspension stability is increased by 15 times compared with that of the starting acid\ud suspension.Peer reviewe
Mark A. Brzezinski - One of the best experts on this subject based on the ideXlab platform.
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Particulate Silica and Si recycling in the surface waters of the Eastern Equatorial Pacific
Deep Sea Research Part II: Topical Studies in Oceanography, 2011Co-Authors: Mohamed Adjou, Mark A. Brzezinski, Cynthia Dumousseaud, Rudolph Corvaisier, Paul Tréguer, Dave NelsonAbstract:The distributions of biogenic and lithogenic Silica concentrations and net Silica production rates in the upper 120 m of the Eastern Equatorial Pacific (EEP) were examined in December 2004, on two transects situated at 110°W (4°N to 3°S) and along the equator (110°W to 140°W). Lithogenic Silica (lSiO2) was generally
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Particulate Silica and si recycling in the surface waters of the eastern equatorial pacific
Deep-sea Research Part Ii-topical Studies in Oceanography, 2011Co-Authors: Mohamed Adjou, Mark A. Brzezinski, Cynthia Dumousseaud, Rudolph Corvaisier, Paul Tréguer, David M. NelsonAbstract:The distributions of biogenic and lithogenic Silica concentrations and net Silica production rates in the upper 120 m of the Eastern Equatorial Pacific (EEP) were examined in December 2004, on two transects situated at 110°W (4°N to 3°S) and along the equator (110°W to 140°W). Lithogenic Silica (lSiO2) was generally <10 nmol Si l?1 with maximum concentrations reaching 25 nmol l?1 in surface waters. These low concentrations confirm low atmospheric inputs of Particulate Si, consistent with reported low inputs of wind-borne material in the EEP. In spite of active upwelling of silicic acid-rich waters the biogenic Silica (bSiO2) concentrations were generally low, falling between 100 and 180 nmol Si l?1 in the upper 50 m and decreasing to less than 50 nmol Si l?1 below not, vert, similar90 m. Estimates of net bSiO2 production rates revealed that the rate of production exceeded that of dissolution in the upper euphotic layer (0-40 m) along 110°W with net production extending somewhat deeper (60-100 m) to the west along the equator. Net production rates in the surface layer were low, ranging between 5 and 40 nmol Si l?1 d?1, consistent with previous observations that diatoms are small contributors to autotrophic biomass in the EEP. Net Silica dissolution predominated in the lower euphotic layer (40-120 m), indicating active Si recycling which diminished the strength of the Silica pump in this region.
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Particulate Silica and Si recycling in the surface waters of the Eastern
2011Co-Authors: Mohamed Adjou, Mark A. Brzezinski, Cynthia Dumousseaud, Rudolph Corvaisier, David M. NelsonAbstract:The distributions of biogenic and lithogenic Silica concentrations and net Silica production rates in the upper 120 m of the Eastern Equatorial Pacific (EEP) were examined in December 2004, on two transects situated at 1101 W( 41 Nt o 31S) and along the equator (1101W to 1401W). Lithogenic Silica (lSiO2) was generally o10 nmol Si l � 1 with maximum concentrations reaching 25 nmol l � 1 in surface waters. These low concentrations confirm low atmospheric inputs of Particulate Si, consistent with reported low inputs of wind-borne material in the EEP. In spite of active upwelling of silicic acid-rich waters the biogenic Silica (bSiO2) concentrations were generally low, falling between 100 and 180 nmol Si l � 1 in the upper 50 m and decreasing to less than 50 nmol Si l � 1 below � 90 m. Estimates of net bSiO2 production rates revealed that the rate of production exceeded that of dissolution in the upper euphotic layer (0-40 m) along 1101W with net production extending somewhat deeper (60-100 m) to the west along the equator. Net production rates in the surface layer were low, ranging between 5 and 40 nmol Si l � 1 d � 1 , consistent with previous observations that diatoms are small contributors to autotrophic biomass in the EEP. Net Silica dissolution predominated in the lower euphotic layer (40-120 m), indicating active Si recycling which diminished the strength of the Silica pump in this region.
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Particulate Silica and Si recycling in the surface waters of the Eastern Equatorial Pacific
Deep Sea Research Part II: Topical Studies in Oceanography, 2011Co-Authors: Mohamed Adjou, Mark A. Brzezinski, Cynthia Dumousseaud, Rudolph Corvaisier, Paul Tréguer, David M. NelsonAbstract:International audienceThe distributions of biogenic and lithogenic Silica concentrations and net Silica production rates in the upper 120 m of the Eastern Equatorial Pacific (EEP) were examined in December 2004, on two transects situated at 110°W (4°N to 3°S) and along the equator (110°W to 140°W). Lithogenic Silica (lSiO2) was generally
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Purification, recovery, and laser-driven fluorination of silicon from dissolved and Particulate Silica for the measurement of natural stable isotope abundances.
Analytical chemistry, 1996Co-Authors: Christina L. De La Rocha And, Mark A. Brzezinski, Michael J. DeniroAbstract:A procedure for the purification, recovery, and determination of isotopic abundances of silicon from biogenic and lithogenic Particulate matter and dissolved silicic acid is reported. Purification involves the reaction of acid molybdate with dissolved silicon in natural waters or that produced by the dissolution of Particulate Silica by hydrofluoric acid. The resulting silicomolybdic acid is then quantitatively precipitated by reaction with triethylamine hydrochloride. The silicon is recovered as silicon dioxide through stepwise combustion of the dried precipitate. Fluorination of the product for isotopic analysis is accomplished by laser heating under pure fluorine generated by the decomposition of a fluorine-based salt. The resulting silicon tetrafluoride is separated from hydrogen fluoride and other fluorination byproducts cryogenically using a variable-temperature cold trap. Yields for silicon recovery are 99.9% for precipitation and greater than 95% for the purification/fluorination procedure. Reprod...
Muhsin Ciftcioglu - One of the best experts on this subject based on the ideXlab platform.
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preparation of Particulate polymeric sol gel derived microporous Silica membranes and determination of their gas permeation properties
Journal of Membrane Science, 2010Co-Authors: Berna Topuz, Muhsin CiftciogluAbstract:Abstract Monodisperse Silica sols with well-defined spherical particles ranging in size from 5 to 310 nm were prepared through Stober process. Both Particulate and polymeric sol–gel routes were employed for the preparation of stable Silica sols. The use of polymeric species in combination with Particulate Silica spheres may allow the design of predefined membrane pore structures with high thermal stability by cubic/random/close packing of monodisperse spherical particles incorporated into the polymeric network. The size and volume content of spheres were varied in order to modify the consolidation behaviour of 2-structural Silica membranes which would enhance the thermal stability. The low shrinkage level for sphere loaded 2-structural systems compared to the pure polymeric counterparts might be explained by the decrease in the structural free energy of the polymeric/Particulate 2-structural system. The thermal stability of the microporous membranes may thus be improved by incorporating Particulates into the polymeric network through the formation of a lower extent of thermally induced microcrack formation. The N2 permeation through 90 nm Silica sphere added Silica membranes remained constant when they were heat treated in the 250–400 °C range indicating the stability of the pore network.
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Preparation of Particulate/polymeric sol–gel derived microporous Silica membranes and determination of their gas permeation properties
Journal of Membrane Science, 2009Co-Authors: Berna Topuz, Muhsin CiftciogluAbstract:Abstract Monodisperse Silica sols with well-defined spherical particles ranging in size from 5 to 310 nm were prepared through Stober process. Both Particulate and polymeric sol–gel routes were employed for the preparation of stable Silica sols. The use of polymeric species in combination with Particulate Silica spheres may allow the design of predefined membrane pore structures with high thermal stability by cubic/random/close packing of monodisperse spherical particles incorporated into the polymeric network. The size and volume content of spheres were varied in order to modify the consolidation behaviour of 2-structural Silica membranes which would enhance the thermal stability. The low shrinkage level for sphere loaded 2-structural systems compared to the pure polymeric counterparts might be explained by the decrease in the structural free energy of the polymeric/Particulate 2-structural system. The thermal stability of the microporous membranes may thus be improved by incorporating Particulates into the polymeric network through the formation of a lower extent of thermally induced microcrack formation. The N2 permeation through 90 nm Silica sphere added Silica membranes remained constant when they were heat treated in the 250–400 °C range indicating the stability of the pore network.
David M. Nelson - One of the best experts on this subject based on the ideXlab platform.
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Particulate Silica and si recycling in the surface waters of the eastern equatorial pacific
Deep-sea Research Part Ii-topical Studies in Oceanography, 2011Co-Authors: Mohamed Adjou, Mark A. Brzezinski, Cynthia Dumousseaud, Rudolph Corvaisier, Paul Tréguer, David M. NelsonAbstract:The distributions of biogenic and lithogenic Silica concentrations and net Silica production rates in the upper 120 m of the Eastern Equatorial Pacific (EEP) were examined in December 2004, on two transects situated at 110°W (4°N to 3°S) and along the equator (110°W to 140°W). Lithogenic Silica (lSiO2) was generally <10 nmol Si l?1 with maximum concentrations reaching 25 nmol l?1 in surface waters. These low concentrations confirm low atmospheric inputs of Particulate Si, consistent with reported low inputs of wind-borne material in the EEP. In spite of active upwelling of silicic acid-rich waters the biogenic Silica (bSiO2) concentrations were generally low, falling between 100 and 180 nmol Si l?1 in the upper 50 m and decreasing to less than 50 nmol Si l?1 below not, vert, similar90 m. Estimates of net bSiO2 production rates revealed that the rate of production exceeded that of dissolution in the upper euphotic layer (0-40 m) along 110°W with net production extending somewhat deeper (60-100 m) to the west along the equator. Net production rates in the surface layer were low, ranging between 5 and 40 nmol Si l?1 d?1, consistent with previous observations that diatoms are small contributors to autotrophic biomass in the EEP. Net Silica dissolution predominated in the lower euphotic layer (40-120 m), indicating active Si recycling which diminished the strength of the Silica pump in this region.
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Particulate Silica and Si recycling in the surface waters of the Eastern
2011Co-Authors: Mohamed Adjou, Mark A. Brzezinski, Cynthia Dumousseaud, Rudolph Corvaisier, David M. NelsonAbstract:The distributions of biogenic and lithogenic Silica concentrations and net Silica production rates in the upper 120 m of the Eastern Equatorial Pacific (EEP) were examined in December 2004, on two transects situated at 1101 W( 41 Nt o 31S) and along the equator (1101W to 1401W). Lithogenic Silica (lSiO2) was generally o10 nmol Si l � 1 with maximum concentrations reaching 25 nmol l � 1 in surface waters. These low concentrations confirm low atmospheric inputs of Particulate Si, consistent with reported low inputs of wind-borne material in the EEP. In spite of active upwelling of silicic acid-rich waters the biogenic Silica (bSiO2) concentrations were generally low, falling between 100 and 180 nmol Si l � 1 in the upper 50 m and decreasing to less than 50 nmol Si l � 1 below � 90 m. Estimates of net bSiO2 production rates revealed that the rate of production exceeded that of dissolution in the upper euphotic layer (0-40 m) along 1101W with net production extending somewhat deeper (60-100 m) to the west along the equator. Net production rates in the surface layer were low, ranging between 5 and 40 nmol Si l � 1 d � 1 , consistent with previous observations that diatoms are small contributors to autotrophic biomass in the EEP. Net Silica dissolution predominated in the lower euphotic layer (40-120 m), indicating active Si recycling which diminished the strength of the Silica pump in this region.
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Particulate Silica and Si recycling in the surface waters of the Eastern Equatorial Pacific
Deep Sea Research Part II: Topical Studies in Oceanography, 2011Co-Authors: Mohamed Adjou, Mark A. Brzezinski, Cynthia Dumousseaud, Rudolph Corvaisier, Paul Tréguer, David M. NelsonAbstract:International audienceThe distributions of biogenic and lithogenic Silica concentrations and net Silica production rates in the upper 120 m of the Eastern Equatorial Pacific (EEP) were examined in December 2004, on two transects situated at 110°W (4°N to 3°S) and along the equator (110°W to 140°W). Lithogenic Silica (lSiO2) was generally
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The annual Silica cycle in the Sargasso Sea near Bermuda
Deep Sea Research Part I: Oceanographic Research Papers, 1995Co-Authors: Mark A. Brzezinski, David M. NelsonAbstract:The annual cycles of silicic acid and biogenic Particulate Silica (BSiO2) concentrations were examined from October 1988 through December 1992 at the JGOFS time-series site near Bermuda. Lithogenic Particulate Silica (LSiO2) concentrations were measured from August 1991 through December 1992 at the same site. Distinctly different seasonal patterns were observed in the concentration of biogenic and lithogenic phases. Integrated BSiO2 concentrations in the upper 160 m were greatest (7.6–56.3 mmol BSiO2 m−2 during an annual diatom bloom that occurred each year between January and April. In contrast, integrated LSiO2 concentrations in the upper 160 m showed an annual maximum during July and August (2.05–2.12 mmol LSiO2 m−) probably due to greater aeolian dust inputs during summer. The export of both BSiO2 and LSiO2 was examined with sediment traps deployed for 4 days each month from August 1991 through August 1992. The annual export of biogenic Silica at 150 m (47.6 ± 8.6 mmol BSiO2 m−2 y−1, s. d.) was dominated by a winter diatom bloom, which was responsible for 62% of the annual flux. In contrast, the export of LSiO2 through 150 m was highest during July and August (0.039–0.064 mmol LSiO2 m−2 day−1), coincident with the summer maxima in suspended LSiO2 concentrations. The close temporal coupling between maxima in suspended concentrations and vertical flux indicates that any delay between the appearance of BSiO2 and LSiO2 in the surface water and their subsequent export was less than our 30 day sampling interval. The standing stock of BSiO2 in the upper 160 m during non-bloom periods was very small with little temporal variability (mean = 2.7 ± 0.9 mmol m−2, s. d.). High dissolution rates of BSiO2 within sediment traps at that time (mean = 0.072 ± 0.036 day−1, s. d.) suggested that significant Silica production was occurring to maintain the observed standing stocks of BSiO2 against losses due to dissolution. Comparison of estimated BSiO2 production and export during this period indicates that at least 64–82% of the BSiO2 produced during the non-bloom period was recycled within the euphotic zone. Estimates of the annual new production by diatoms, with a mole ratio of 1:1 for Si:N within sinking siliceous particles assumed, suggest that diatoms account for up to 26–48% of the new production occurring at this site.