131,040 research outputs found
Assessment of wear resistance of tin and tin alloy coatings
No full textThis thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.Tin alloy coatings have traditionally been used as corrosion resistant bamens due to their inert nature and comprehensive coverage, and have seldom been considered in physically demanding applications, such as wear resistant coatings owing to misconceptions associated with the soft nature of tin metal. The alloying of tin with copper has already been shown to significantly increase its mechanical properties, as demonstrated by the adoption of tin-copper alloys for use as bearing materials. Unfortunately, its cyanide plating technology makes tin-copper environmentally unsustainable, whilst the process requires constant regulation and monitoring, and there are disposal costs associated with the cyanide waste products. The tin-nickel alloy, however, can be produced with minimal supervision and its plating process uses less harmful precursors, making it an alternative consideration. The research documented in this thesis assesses this increase by quantifying the resistance of tin, tin-nickel and tin-copper coatings to removal from sliding wear. As tin is a soft material and behaves dissimilarly to conventional coatings in a sliding wear environment, traditional wear assessment techniques are not appropriate. A novel approach is therefore devised and implemented, and this involves the continually monitoring the effect of damage introduced to the surface of the tin and tin alloy coatings, from an abrading ceramic ball. Using an elemental detection tool, it is possible to analyse wear scars that exhibit progressively depleted coating material, by identifying the underlying substrate material as it becomes exposed. In this way, it is possible to quantify the improvements made to tin from alloying with nickel and copper. The large volume of data acquired from this research is presented in a matrix format to enable simultaneous depiction of multiple parameters, and to allow quick and easy interpretation. The tin-nickel coating is found to be comparable to tin-copper in terms of resistance to removal. Despite tin-copper being slightly superior over the range of test conditions used, tin-nickel as been shown to be an environmentally friendly and cost effective alternative coating alloy to tin-copper.Funding was obtained from ITRI Ltd
Indium tin oxide overlayered waveguides for sensor applications
No full textThe use of indium tin oxide (ITO) thin films as electrodes for integrated optical electrochemical sensor devices is discussed. The effect of various thicknesses of ITO overlayers exhibiting low resistivity and high transparency on potassium ion-exchanged waveguides fabricated in glass substrates is investigated over the wavelength range 500-900 nm. ITO overlayers are formed by reactive thermal evaporation in oxygen, followed by annealing in air to a maximum temperature of 320°C. With air as superstrate, losses in the waveguides were found to increase dramatically above 30nm ITO thickness for TE polarization, and above 50nm thickness for TM. Losses were increased over the whole wavelength range for a superstrate index close to that of water. A one-dimensional multilayer waveguide model is used in the interpretation of the experimental results
Antonius-Tin T. Bui oral history interview and transcript
No full textThis recording and transcript form part of a collection of oral history interviews conducted by the Chao Center for Asian Studies at Rice University. This collection includes audio recordings and transcripts of interviews with Asian Americans native to or living in Houston.Antonius-Tin T. Bui (they/them) was born in Bronx, NY in 1992. They identify as queer, gender-nonbinary, Vietnamese-American artist, whose parents Paul and Van Bui, two Vietnamese refugees have made huge sacrifices to provide a future for their four kids and extended family. Antonius moved to Houston before pursuing a BFA at the Maryland Institute College of Art (MIC/A). Since graduating in 2016, Antonius has received fellowships from the Vermont Studio Center, Kala Art Institute, Tulsa Artists Fellowship, Halcyon Arts Lab, Houston Center for Contemporary Craft, Washington Project for the Arts, and Yaddo. These opportunities have greatly expanded Antonius' practice beyond just hand-cut paper techniques.
They are currently interested in complicating Vietnamese history and queerness through performance, textiles, and photography. Antonius has exhibited at various institutional, private, public, and underground venues, including the Vietnam Veterans Memorial, Corcoran Gallery of Art, Hillyer Art Space, Lawndale Art Center, Living Arts, 108 Contemporary, Artscape, the Philbrook Museum, Experimental Action 2019, and the Museum of Human Achievement. Most recently, Antonius exhibited two series of their works "ReModel Minority," and "End Your Silence (Self Immolation)" which is a series of Zippo lighters with engraved texts, in HAAA's inaugural exhibition, "Faces in the Pandemic" that is on view in Fondren Library, Aug - Nov 2020. In this interview, Antonius speaks of their childhood, their parents' stories and family history, their upbringing, experiences in school, and a heartfelt story about their come-out experience with their parents. They also spoke of their artistic practices and their passion and vision for art, and an optimistic future they look forward to
Carbon-Air Fuel Cells with Molten Tin Anodes
No full textCarbon-air fuel cells are a prospective technology for efficient conversion of the chemical energy of solid carbonaceous fuels directly to electrical energy. Although CO2 is a product, undiluted by the nitrogen and excess oxygen in typical flue gases, such fuel cells can be considered more environmentally-benign than conventional electrical energy production if carbonaceous wastes are used as fuel. In effect, disposal of this carbonaceous wastes would result in CO2 emissions e.g. from landfill sites, while oxidation of them into a fuel cell would result in energy and neat CO2 which is far more amenable to subsequent treatment. In addition, depending on the operating potential difference of the fuel cell, CO2 emission rates per kWh output can be significantly less than from conventional power stations.
Considering that Ni / yttrium-stabilised zirconia (YSZ) anodes in conventional (H2 / O2) solid oxide fuel cells (SOFCs) are irreversibly affected by deposition of carbon and sulphur poisoning, some molten metal anodes offer better alternatives, with high electrical conductivities and stabilities when operating on carbonaceous fuels. Tin (Sn) fulfils these requirements and is non-toxic, has a low melting point and vapour pressure, forms oxide(s) that can be reduced by CO (and H2), and could be purified of ash, based on its immiscibility with molten metals, and of dissolved metals by electrochemical processes.
The thermodynamics, kinetics and materials stability of a solid oxide fuel cell with a 90 μm thick lanthanum strontium manganite (LSM)-YSZ cathode, a 2 mm thick YSZ electrolyte and a 5 mm thick molten tin anode (Sn(l)-SOFC) were studied by electrochemical measurements and X-ray analysis. Platinum wires and mesh were used as current collectors at the cathode, while graphite rods or lanthanum strontium titanate (LST) / lanthanum cerium strontium titanate (LCST) pellets were used at the anode. Sn(l)-SOFC performance was tested in the absence of fuel (battery mode) at 900 °C using flow rates of 60 mL min-1 of air at the surface of the cathode and 30 mL min-1 of helium at the surface of the anode. For the Sn(l)-SOFC operating in fuel cell mode, helium or hydrogen were fed into a 10 mm thick anode at flow rates of 30 and 20 mL min-1, respectively, and activated carbon particles were sited on the surface of the melt.
Thermodynamic analysis of the open circuit voltages (OCVs) measured in the temperature range between 600 and 900 °C, determined that the global reaction occurring in the Sn(l)-SOFC when operating without fuel was oxidation of molten tin at the Sn anode | electrolyte interface. This result was confirmed by current density transients of a Sn(l)-SOFC operating at its maximum power density (constant potential difference) and post-mortem analysis of the fuel cell components. Accumulation of tin dioxide at the Sn anode | electrolyte and Sn anode | graphite current collector surfaces was responsible for the degradation of the Sn(l)-SOFC longer term performance.
The kinetics of the Sn(l)-SOFC operating in absence of fuel were studied using the polarization curves and impedance spectra measured at 900 °C and a mathematical model of the ohmic and polarization losses. The model inputs included kinetic parameters reported in the literature for the electrolyte and cathode, enabling prediction of the anode activation and concentration overpotentials; the model outputs were a charge transfer coefficient of ca. 0.67, an exchange current density of ca. 353 A m-2 and a limiting current density of ca. 3 273 A m-2. These values indicated that the kinetics of the whole Sn(l)-SOFC were limited by the mass transport processes occurring at the anode, since the exchange and limiting current densities associated to the cathode were one order of magnitude higher.
Modelling of the Sn(l)-SOFC with a 200 μm thick electrolyte and negligible ohmic losses at the current collectors resulted in a maximum power density of ca. 1 477 W m-2 at a cell voltage of ca. 0.45 V and a current density of ca. 3 273 A m-2, corresponding to the limiting current density. This maximum power density was approximately 1 000 W m-2 lower than the maximum power density predicted for a conventional SOFC with identical LSM-YSZ cathode and YSZ electrolyte (same dimensions and microstructure), but replacing the molten tin anode by a 100 μm thick Ni-YSZ anode operating on hydrogen. Even though the predicted power density of a Sn(l)-SOFC was lower than that of a conventional SOFC, this result seemed to be promising since the Sn(l)-SOFC kinetics could be enhanced by reducing the molten tin anode thickness and improving its contact with the electrolyte by applying pressure over the melt.
When the Sn(l)-SOFC was operated in fuel cell mode, the kinetics of tin dioxide reduction by carbonaceous fuels was found to be slow and did not have significant effects in the kinetics of the fuel cell, even when a stirred molten tin anode was used. By contrast, even though the rate of tin dioxide formation at the Sn anode | electrolyte interface was higher than the rate of reduction of tin dioxide by hydrogen, the presence of this fuel improved the anode kinetics. This condition was observed in the results reported by CellTech Power Inc. using a quiescent molten tin anode and the results obtained during this research project using a stirred molten tin anode, which suggested that hydrogen oxidation occurred in parallel with tin oxidation at the Sn anode | YSZ electrolyte interface and possibly at the SnO2 | Sn interface.Open Acces
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Laser processing of solution based antimony doped tin oxide thin films
No full textAntimony doped Tin oxide (SnO2:Sb, or ATO) is of interest as an alternative to Indium Tin Oxide (ITO) for large area optoelectronic applications. There is a particular interest in the potential for solution based coatings based on nanoparticulate suspensions of SnO2:Sb. However, solution processed films typically require a high temperature (~700⁰C) annealing step to achieve the desired electrical and optical properties. This is disadvantageous for applications that would benefit from low cost, low temperature/flexible substrates. As an alternative to conventional high temperature annealing, excimer laser processing can provide highly localized energy dissipation, and is an attractive technique to functionalise coated materials. Therefore the work presented in this thesis investigates the use of excimer laser processing to optimise the electrical and optical properties of solution deposited SnO2:Sb thin films for use in electroluminescent display devices. Thin films of SnO2:Sb were deposited using dip coating, inkjet printing and the spin coating technique. By varying the numbers of spin coatings deposited, a series of samples were prepared on Eagle XG glass substrates with different thicknesses of SnO2:Sb (ranging from 0.2 μm to 1.4 μm). The initial sheet resistance, optical transmission and crystal structure of the deposited films was studied. The films were subsequently post processed using three different annealing techniques: (i) Laser Processing: samples were laser processed in air to optimise the sheet resistance and optical transmission
A study of tin oxides in silicate based glasses
No full textThe roles of tin in two silicate based glass systems have been investigated by
NMR and Môssbauer spectroscopies and by physical property measurements of the
glasses.
The first glass system investigated was the stannous silicate (binary SnO-Si02)
glass. Glasses with SnO contents ranging from 17 to 72 mol.% have been made by
melting pelleted powder in an alumina crucible. It was found that alumina crucibles are
unsuitable for making glass with <20 mol.% SnO because of attack on the crucible at the
high melting temperature (_>_1600°C). Silica crucibles will not withstand such high
temperature and tin will attack a platinum crucible. The ability of this system to form glass
past the orthosilicate composition has been discussed in terms of the polarizing power of
Sn2+ and the structure of SnO. The 119Sn NMR results did not give much structural
information due to the high chemical shift anisotropy of Sn 2+ site but they showed that
the glass also contains trace amounts of Sn4+species. The 29Si MAS NMR results
showed that SnO does not depolymerise the silicate network to the same extent as Na20
or even Pb0. Computer simulations of the 29 Si MAS NMR spectra showed that, for SnO
<-30 mol.%, the disposition of Qn species is consistent with the binary model, which
means that SnO is acting the role of modifier. For compositions > 30 mol.% SnO, the Qn
distribution follows the statistical model and this has been interpreted as SnO now acting
as an intermediate. The 119Sn MOssbauer results confirmed this interpretation. The Sn2+
isomer shift decreases with increase of SnO which is indicative of increasing covalent
character of the Sn—O bonds while the larger quadrupole splitting suggests distortion of
the SnO polyhedral structure in the glass. The relation of the Sn 2+ isomer shift to the
quadrupole splitting and the temperature dependence of the isomer shift of Sn2+ indicate
the formation of Si—O—Sn linkages at high SnO contents. The decrease of the viscosity
of the glass with increasing SnO is small when compared to the decrease of the viscosity
in alkali metal and alkaline-earth oxides silicates when the respective modifier oxide is
increased in those glasses. The variation of the density, thermal expansion and refractive
index with SnO content showed discontinuities in the region of 30-45 mol.% SnO. This
has been interpreted as being the point where SnO changes its role from that of modifier
to intermediate.
The results of differential thermal analysis and devitrification of SnO-Si02 glasses
showed that glass with 40 mol.% SnO can be heat treated in the temperature range of
570° to 680 °C to produce metastable SnSiO3 crystals. SnSiO 3 decomposed to
SnO + Si02 at temperatures above —700°C and, at temperatures greater than 720°C,
oxidation of SnO to Sn02 and Si02(glass) to Si02 (cristobalite) took place.
The second glass system is tin-doped float glass. This is glass of the float
composition remelted with tin(II) oxalate in silica crucibles under normal atmosphere
conditions. In this way it has been demonstrated that we can mimic the tin oxide
distribution found within the tin diffusion region in float glass. Synthesis of the glass has
shown that both Sn2+ and SO+ can be assimilated simultaneously in the glass but there is
a solubility limit for SO+. The 1195n Mbssbauer results showed that Sn2+ and SO+
played different structural roles in the glass. The environment of Sn2+ in glass is similar
to that in amorphous SnO while the SO + structure in glass does not change significantly
compared to crystalline Sn02. The Debye temperatures and recoil free fractions showed
that Sn2+ is less rigidly bound to the network modifier site while SO + is rigidly bound at
network former sites in the glass. The different structural roles of 5n 2+ and SO+ in the
glass were reflected in the some of the physical properties of the glasses
Tin and silver recovery from Coal Creek, AK
No full text"The U.S. Bureau of Mines investigated the recovery of tin and silver from the Coal Creek deposit in the Talkeetna Mountains, Alaska. Approximately 5 million st of reserves grading 0.2 pct Sn with silver credits of 0.2 Tr oz/st have been delineated by drilling. A 10- to 25-pct-Sn gravity concentrate was produced by treating the minus 20-mesh ore with a spiral, then regrinding to minus 65 mesh and tabling. Sulfide contamination in the gravity concentrate was as high as 60 pct. Sulfide flotation of this concentrate produced tailings containing 40 to 50 pct Sn. Overall recovery was 76 pct for tin but only 5 to 10 pct for silver because of losses during sulfide flotation. Other methods tested to clean the concentrate included cassiterite flotation, gangue flotation, nitric acid leaching, and wet and dry magnetic separation. Tin beneficiation tests on the minus 325-mesh fraction included cassiterite flotation, vanning, sulfide flotation, and fuming. The bench-scale and locked- cycle tests were used to estimate the mass flows for a 1,000-st/d plant." - NIOSHTIC-2NIOSH no. 1000915
Solid-state N.M.R. studies of platinum and tin compounds
No full textHigh-resolution solid-state N.M.R. studies of dilute spins are now possible using cross-polarisation and MAS techniques. A systematic evaluation has been undertaken to determine their applicability to spin-½ metal nuclei, in particular (^195)Pt and (^119)Sn. In addition, an extensive (^13)C and (^31)p solid-state N.M.R. study has been carried out on a selection of Pt(II) complexes, supplying information on isotropic (scalar) coupling constants and shielding anisotropy. The majority of (^119)Sn and (^195)Pt spectra exhibit a multitude of spinning sidebands due to the large shielding anisotropy present. The tin systems under study have been of type R(_3)SnX (where R = Alkyl, phenyl and X = F, OH, CI); some are shown to be polymeric in the solid-state with penta-coordinate tin present. Where possible, correlations with X-ray crystallographic data and solution-state N.M.R. studies are giving. The interactions present in Pt(IV) compounds containing directly bonded quadrupolar nuclei have been studied and imply motional activity present in the solid- state. A more comprehensive study of these effects is given for two tin systems (Ph(_3)SnCl and (NH(_4))(_2)SnCl(_6)), whereby observed splittings can be accounted for by a combination of (^119)Sn-Cl dipolar and scalar coupling. The interplay of tensor properties between spin-½ nuclei, namely (1) dipolar coupling, (11) indirect (scalar) coupling and (111) shielding anisotropy is explored in solid-state (^195)pt-(^31)p and (^119)sn-(^19)f systems. The theory for such tensorial interplay is given for an AX(_2) system
Tin-based composite anodes for potassium-ion batteries
No full textAn anode based on the tetragonal tin (Sn) phase that can alloy electrochemically with potassium is demonstrated for potassium-ion batteries.</p
A MODEL ON MHD CONVECTIVE TIN-OXIDE (TiO2) NANOFLUID FLOW OVER A CYLINDERICAL POROUS PLATE
No full textAbstract: In this study, a model of MHD convective tin-oxide(TiO2) nanofluid flow over a cylindrical porous plate was examined. The governing equations of continuity, momentum, energy, and concentration modelled in terms of partial differential equations with boundary conditions were non-dimensionalised using the Buckingham’s π-theorem and then were transformed into ordinary differential equations using the regular perturbation technique, each of these equations was solved in isolation using Frobenius Method which gave the analytic solutions. The solutions obtained for the momentum, energy, and concentration were subjected to analysis which gave the results for the temperature profile, concentration profile, and velocity profile graphically. It was observed that, when the radiation parameter was increased, the temperature profile dropped; as the chemical reaction was increased, the concentration profile and the velocity profile were reduced; again as the magnetic field number was increased, it lowered the profile of the velocity. The velocity profile was enhanced with an increase in the porosity parameter, and this, as a result, tended to increase in the size of the pore spaces of the porous medium; the concentration profile, temperature profile, and velocity profile all improved as the nanofluid volume fraction increased.
Keywords: Nanofluid, MHD flow, Convection, Cylindrical Porous Plate, Analytical Solutions.
Title: A MODEL ON MHD CONVECTIVE TIN-OXIDE (TiO2) NANOFLUID FLOW OVER A CYLINDERICAL POROUS PLATE
Author: Tombotamunoa W. J. Lawson, Isobeye George, Alalibo T. Ngiangia
International Journal of Mathematics and Physical Sciences Research
ISSN 2348-5736 (Online)
Vol. 11, Issue 1, April 2023 - September 2023
Page No: 101-121
Research Publish Journals
Website: www.researchpublish.com
Published Date: 20-September-2023
DOI: https://doi.org/10.5281/zenodo.8362486
Paper Download Link (Source)
https://www.researchpublish.com/papers/a-model-on-mhd-convective-tin-oxide-tio2-nanofluid-flow-over-a-cylinderical-porous-plateInternational Journal of Mathematics and Physical Sciences Research, ISSN 2348-5736 (Online), Research Publish Journals, Website: www.researchpublish.co
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