The feasibility and sensitivity of electrochemical noise (EN), electrochemical impedance spectros... more The feasibility and sensitivity of electrochemical noise (EN), electrochemical impedance spectroscopy (EIS), and linear polarization resistance (LPR) for detection of corrosion in post-tensioning (PT) components was investigated. The use of the electrical resistance (ER) technique, as well EIS and LPR, to detect air space corrosion at the grout voids was also explored. The results showed that high sensitivity noise measurements (in the μV range) are feasible for the strand-anchorage systems. The potential and galvanic current trends for the assemblies suggest the presence of activation-passivation cycles linked to each water ingress event. The EN method was adequate to identify only one modality of corrosion, and failed to detect other potentially important forms of corrosion despite the presence of significant macrocell current. In contrast, the EIS and LPR methods more reliably detected ongoing corrosion. The ER method could sensitively detect the deterioration of grouted and bare steel strands exposed to a high humidity environment as in the air space of a grout void. The air space corrosion experiments showed that an aggressive environment may evolve in the grout void, resulting in appreciable corrosion rates.
Interest in novel uses of biogas has increased recently due to concerns about climate change and ... more Interest in novel uses of biogas has increased recently due to concerns about climate change and greater emphasis on renewable energy sources. Although biogas is frequently used in low-value applications such as heating and fuel in engines or even just flared, reforming is an emerging strategy for converting biogas to syngas, which could then be used to obtain high-value-added liquid fuels and chemicals. Interest also exists due to the role of dry, bi-, and tri-reforming in the capture and utilization of CO 2 . New research efforts have explored efficient and effective reforming catalysts, as specifically applied to biogas. In this paper, we review recent developments in dry, bi-, and tri-reforming, where the CO 2 in biogas is used as an oxidant/ partial oxidant. The synthesis, characterization, lifetime, deactivation, and regeneration of candidate reforming catalysts are discussed in detail. The thermodynamic limitation and techno-economics of biogas conversion are also discussed. In addition, there are other reactions taking place during the tri-reforming process (Walker et al., 2012). CO + H 2 O4CO 2 + H 2 DH = À 41kJ=mol (Equation ) C + H 2 O4CO + H 2 DH = 131kJ=mol (Equation )
Industrial & Engineering Chemistry Research, 2018
Cylindrical NiMg/Ce 0.6 Zr 0.4 O 2 pellet catalysts with two different sizes (large: radius = 1.5... more Cylindrical NiMg/Ce 0.6 Zr 0.4 O 2 pellet catalysts with two different sizes (large: radius = 1.59 mm; and small: radius = 0.75 mm) were produced by extrusion of powder catalysts. The small catalyst pellets had a higher specific surface area, pore volume, average pore size, radial crush strength, and resistance to breakage than the large ones. Tri-reforming tests with surrogate biogas were conducted at 3 bar and 882 °C, with the feed molar ratios of CH 4 : CO 2 : air fixed at 1.0: 0.7: 0.95 and the H 2 O/CH 4 molar feed ratio (0.35 -1.16) varied. The small catalyst pellets exhibited lower internal mass transfer resistance and higher coking resistance, compared to the large ones. CO 2 conversion decreased and H 2 /CO molar ratio increased with the increase of H 2 O/CH 4 molar feed ratio, which are consistent with the trends predicted by thermodynamic equilibrium calculations. The results indicate that the NiMg/Ce 0.6 Zr 0.4 O 2 catalyst pellets are promising for commercial scale applications.
Fluid motion induced from high intensity sound waves is called acoustic streaming 1 . SAW devices... more Fluid motion induced from high intensity sound waves is called acoustic streaming 1 . SAW devices used in biological species detection suffer from fouling that results from binding of non-specific protein molecules to the device surface. The acoustic streaming phenomenon can be ...
TiO 2 is one of the most promising candidate materials for clean-energy generation and environmen... more TiO 2 is one of the most promising candidate materials for clean-energy generation and environmental remediation. However, the larger-than 3.1 eV bandgap of perfectly crystalline TiO 2 confines its application to the ultraviolet (UV) range. In this study, the electronic and the optical properties of undoped mixed-phase TiO 2 nanoparticles were investigated using UV and inverse photoemission, low intensity Xray photoelectron (XP), and diffused reflectance spectroscopy methods. The facile solution-phase synthesized nanoparticles exhibited a midgap-states-induced energy gap of only ∼2.2 eV. The diffused reflectance spectrum showed sub-bandgap absorption due to the existence of a large Urbach tail at 2.2 eV. The UV photoemission spectrum evidenced the presence of midgap states. The 2.2 eV energy gap enables the nanoparticles to be photoactive in the visible energy range. The gas-phase CO 2 photoreduction test with water vapor under visible light illumination was studied in the presence of the synthesized TiO 2 nanoparticles which resulted in the production of ∼1357 ppm gr -1 (catalyst) CO and ∼360 ppm gr -1 (catalyst) CH 4 , as compared to negligible amounts using a standard TiO 2 (P25) sample. The synthesized nanoparticles possessed a Brunauer-Emmett-Teller (BET) surface area of ∼131 m 2 gr -1 , corresponding to a Langmuir surface area of ∼166 m 2 gr -1 . The determined interplanar distances of atomic planes by highresolution transmission electron microscopy (HR-TEM) and X-ray diffraction (XRD) methods were consistent. A detailed elemental analysis using XPS and inductively coupled plasma mass spectrometry (ICP-MS) demonstrated that the synthesized catalyst is indeed undoped. The catalytic activity of the undoped synthesized nanoparticles in the visible spectrum can be ascribed to the unique electronic structure due to the presence of oxygen vacancy related defects and the high surface area.
Correction for ‘Conversion of landfill gas to liquid fuels through a TriFTS (tri-reforming and Fi... more Correction for ‘Conversion of landfill gas to liquid fuels through a TriFTS (tri-reforming and Fischer–Tropsch synthesis) process: a feasibility study’ by Xianhui Zhao et al., Sustainable Energy Fuels, 2019, 3, 539–549.
The combined on.-line identification and optimi.zation approach developed by Bamberger and Iserma... more The combined on.-line identification and optimi.zation approach developed by Bamberger and Isermann is applied to two chemical pro-cesses systems. The first example is the un-constrained optimization of the stirred re-actors in series proposed by Garcia and Morani. The ...
Physical chemistry chemical physics : PCCP, Jan 13, 2018
Using density functional theory, we study the effect of injected electrons (simulating photoexcit... more Using density functional theory, we study the effect of injected electrons (simulating photoexcited electrons) on the energetics, structures, and binding sites available to CO2 molecules on subnanometer Pt clusters decorated onto anatase TiO2(101) surfaces, shedding light on the first and key step of CO2 photoreduction. Upon the addition of one, two, or three electrons, the O-C-O angles of adsorbed CO2 become progressively smaller in binding sites that directly contact Pt clusters, while no significant change is found in the intra bond length of the adsorbed CO2 and in the bonding distances between the adsorbed CO2 and supported clusters. The extra electrons lead to the stabilization of adsorption sites identified on neutral slabs, including previously metastable configurations, suggesting the enhancement of accessible CO2 binding sites. Furthermore, supported clusters are able to populate the electronic states of adsorbed CO2 species, facilitating the formation of the CO2- anion. T...
Municipal solid waste (MSW) management is a major concern in Indian cities. This work rigorously ... more Municipal solid waste (MSW) management is a major concern in Indian cities. This work rigorously assesses the relative costs and the environmental and health benefits of alternative MSW management methods. Management of MSW over the next 20 years for the city of Greater Mumbai was considered. A generic model was developed to determine the costs for (i) dumping on open ground, (ii) sanitary landfill without leachate treatment, (iii) landfilling with leachate treatment and (iv) regional composting and landfilling. LandGEM was used to quantify the gaseous emissions from landfill, while emissions from leachate and composting were taken from literature. The life cycle impact model of one tonne of MSW was developed using OpenLCA software and the International Reference Life Cycle Data System (ILCD) 2011 method was used for impact assessment. The cost of disposal of one tonne of waste was found to be INR344 (US$5.17), INR741 (US$11.13) and INR1367 (US$20.53), respectively, for the first th...
Waste-to-energy projects are an increasingly prominent component of future energy portfolios. Lan... more Waste-to-energy projects are an increasingly prominent component of future energy portfolios. Landfill gas (LFG)-to-energy (LFGTE) projects are particularly important as they address greenhouse gas emissions. Contaminants in LFG may hamper these projects both from environmental and economic standpoints. The purpose of this review is to highlight key aspects (LFG composition ranges, LFG flowrates, and allowable tolerances for LFGTE technologies, performance and costs for contaminant removal by adsorption). Removal of key contaminants, H2S and siloxanes, by adsorption are surveyed in terms of adsorption capacities and regeneration abilities. Based on the open literature, costing analyses are tabulated and discussed. The findings indicate economics of contaminant removal depend heavily on the feed concentrations of contaminants, allowable tolerances for the LFGTE technology, and the current market for the product. Key trends, identification of challenges, and general purification guide...
Industrial Engineering Chemistry Process Design and Development, 1986
Two approaches to the on-line identification of parameters and states in systems described by non... more Two approaches to the on-line identification of parameters and states in systems described by nonlinear ordinary differentlal equations are compared by using an example chemical process. The first approach is based on the Kalman filter approach extended to cover ...
In this paper, we present a model predictive inferential control (MPIC) strategy to address the p... more In this paper, we present a model predictive inferential control (MPIC) strategy to address the problem of controlling unmeasured output variables (such as quality) using readily available secondary measurements. First we establish the relationship between inferential control and other classical control strategies such as cascade and internal model control. Next we present a framework for incorporating the inferential control strategy within the framework of the often used model predictive control (MPC). This framework, termed model predictive inferential control (MPIC), is general enough to accommodate multiple secondary measurements as well as nonlinear estimators and controllers. The advantages of inferential control are established using two case studies. One is the Shell challenge problem which employs linear transfer function models. The second is a nonlinear, multivariable problem on the control of product composition using secondary measurements on a simulated injection pultrusion process. Problems of collinearity are addressed using principal component analysis (PCA) during the construction of the dynamic estimator. These simulations demonstrate the advantages of the proposed model predictive inferential control strategy.
ABSTRACT Since Fujishima and Honda first demonstrated photocatalytic water splitting in 1972[1], ... more ABSTRACT Since Fujishima and Honda first demonstrated photocatalytic water splitting in 1972[1], numerous investigators have extended the idea into many other semiconductors and photoreactions. Utilizing solar energy to facilitate photocatalytic conversion of carbon dioxide (CO2) with water (H2O) to fuels and chemicals such as CO, CH4, CH3OH holds great potential as a sustainable alternative energy source and as a promising method to reduce pollution and global warming. In spite of the large number of studies and materials investigated for photocatalytic CO2 conversion, efficiencies achieved to date have been very small and much work remains to be done to overcome the limitations. Metal-organic frame works (MOFs) are perhaps uniquely suited to address CO2 capture and photocatalytic conversion because of their exceptional porosities, tunable pore sizes and chemical structure. The principle of reducing CO2 in a MOF using UV radiation has recently been demonstrated by doping a photocatalyst moiety into a MOF[2]. Researchers at USF have been developing Ti-based semi-conductive MOFs that are photo-active in the visible light range. In this study, we evaluated the photocatalytic activity of a Ti-based metal-organic framework in a gas-phase CO2 reduction reaction using a robust photoreactor system. The reactor system has a small volume (<15ml) with the ability to control temperature, pressure and reaction type (batch or flow reactor). Photoreaction efficiency, product conversion and selectivity of MOF photocatalysts are analyzed in comparison to conventional TiO2 (P-25). Reactor conditions, including temperature and pressure, were optimized to improve reaction kinetics and the conversion of CO2 and water to the desired products. References: [1] Fujishima, A., & Honda, K. (1972). Electrochemical Photolysis of Water at a Semiconductor Electrode. [10.1038/238037a0]. Nature, 238(5358), 37-38. [2] Wang, C., Xie, Z., deKrafft, K. E., & Lin, W. (2011). Doping Metal–Organic Frameworks for Water Oxidation, Carbon Dioxide Reduction, and Organic Photocatalysis. Journal of the American Chemical Society, 133(34), 13445-13454. doi: 10.1021/ja203564w
ABSTRACT Metal enhanced luminescence (MEL) of certain luminophores in the presence of metallic na... more ABSTRACT Metal enhanced luminescence (MEL) of certain luminophores in the presence of metallic nanoparticles can help enhance the fluoroscence detection of a wide variety of biomolecules. Using bimetallic nanoparticles is an attractive option because important optical properties, like the wavelength corresponding to the surface plasmon resonance (SPR) peak and the scattering efficiency that dictate the enhancement/quenching of luminophore molecules, can easily be tuned by adjusting the composition, morphology, size and shape of the nanoparticles. In this study, we explore the luminescence enhancement of Cy3 dye in the vicinity of Ag-Cu bimetallic nanoparticles. We used Finite Difference Time Domain (FDTD) calculations to study the influence of composition on the AgxCu1-x bimetallic nanoparticles. Nanoparticles of various structures like alloys, core-shell and mixed metal substrates with spherical and cubical shapes, and in the size range of 25-200 nm are studied with a varying fluorophore-particle separation distance. Optimizing these parameters provides a guiding principle for the synthesizing the bimetallic nanoparticles that can yield high fluoroscence enhancements. The calculations were validated using bimetallic particles synthesized using the polyol synthesis process. The fluoroscence enhancements were measured using a confocal microscope.
Composites Part a Applied Science and Manufacturing, Nov 1, 2003
Vacuum assisted resin infusion molding (VARIM) is a recently developed promising low-cost batch p... more Vacuum assisted resin infusion molding (VARIM) is a recently developed promising low-cost batch process that has been applied to the manufacture of large-sized composite parts. The process has been successfully extended to the construction of foam-core sandwich composites by introducing a co-injection resin transfer molding (CIRTM) technique. In the CIRTM process, the sandwich is manufactured in one integral step and the bonding between the skin and the core is developed during the cure process. The structural performance and reliability of these sandwiches are dependent on the strength of the core-skin bonding. Processing conditions and material parameters such as permeability of fibers and foam; viscosity and cure kinetics of the resin; and resin infusion pressure and temperature all affect the cure. A rigorous 3D non-isothermal processing model was developed for the first time to assist in the design and optimization of the CIRTM process for sandwich construction. A simplified 1D isothermal model was also developed for real-time control and compared with the full-blown model. The effects of various processing parameters on the core-skin bonding strength were investigated with parametric studies. Based on these studies using the processing models, we develop heuristics for optimizing application-relevant parameters of the sandwich composites.
The feasibility and sensitivity of electrochemical noise (EN), electrochemical impedance spectros... more The feasibility and sensitivity of electrochemical noise (EN), electrochemical impedance spectroscopy (EIS), and linear polarization resistance (LPR) for detection of corrosion in post-tensioning (PT) components was investigated. The use of the electrical resistance (ER) technique, as well EIS and LPR, to detect air space corrosion at the grout voids was also explored. The results showed that high sensitivity noise measurements (in the μV range) are feasible for the strand-anchorage systems. The potential and galvanic current trends for the assemblies suggest the presence of activation-passivation cycles linked to each water ingress event. The EN method was adequate to identify only one modality of corrosion, and failed to detect other potentially important forms of corrosion despite the presence of significant macrocell current. In contrast, the EIS and LPR methods more reliably detected ongoing corrosion. The ER method could sensitively detect the deterioration of grouted and bare steel strands exposed to a high humidity environment as in the air space of a grout void. The air space corrosion experiments showed that an aggressive environment may evolve in the grout void, resulting in appreciable corrosion rates.
Interest in novel uses of biogas has increased recently due to concerns about climate change and ... more Interest in novel uses of biogas has increased recently due to concerns about climate change and greater emphasis on renewable energy sources. Although biogas is frequently used in low-value applications such as heating and fuel in engines or even just flared, reforming is an emerging strategy for converting biogas to syngas, which could then be used to obtain high-value-added liquid fuels and chemicals. Interest also exists due to the role of dry, bi-, and tri-reforming in the capture and utilization of CO 2 . New research efforts have explored efficient and effective reforming catalysts, as specifically applied to biogas. In this paper, we review recent developments in dry, bi-, and tri-reforming, where the CO 2 in biogas is used as an oxidant/ partial oxidant. The synthesis, characterization, lifetime, deactivation, and regeneration of candidate reforming catalysts are discussed in detail. The thermodynamic limitation and techno-economics of biogas conversion are also discussed. In addition, there are other reactions taking place during the tri-reforming process (Walker et al., 2012). CO + H 2 O4CO 2 + H 2 DH = À 41kJ=mol (Equation ) C + H 2 O4CO + H 2 DH = 131kJ=mol (Equation )
Industrial & Engineering Chemistry Research, 2018
Cylindrical NiMg/Ce 0.6 Zr 0.4 O 2 pellet catalysts with two different sizes (large: radius = 1.5... more Cylindrical NiMg/Ce 0.6 Zr 0.4 O 2 pellet catalysts with two different sizes (large: radius = 1.59 mm; and small: radius = 0.75 mm) were produced by extrusion of powder catalysts. The small catalyst pellets had a higher specific surface area, pore volume, average pore size, radial crush strength, and resistance to breakage than the large ones. Tri-reforming tests with surrogate biogas were conducted at 3 bar and 882 °C, with the feed molar ratios of CH 4 : CO 2 : air fixed at 1.0: 0.7: 0.95 and the H 2 O/CH 4 molar feed ratio (0.35 -1.16) varied. The small catalyst pellets exhibited lower internal mass transfer resistance and higher coking resistance, compared to the large ones. CO 2 conversion decreased and H 2 /CO molar ratio increased with the increase of H 2 O/CH 4 molar feed ratio, which are consistent with the trends predicted by thermodynamic equilibrium calculations. The results indicate that the NiMg/Ce 0.6 Zr 0.4 O 2 catalyst pellets are promising for commercial scale applications.
Fluid motion induced from high intensity sound waves is called acoustic streaming 1 . SAW devices... more Fluid motion induced from high intensity sound waves is called acoustic streaming 1 . SAW devices used in biological species detection suffer from fouling that results from binding of non-specific protein molecules to the device surface. The acoustic streaming phenomenon can be ...
TiO 2 is one of the most promising candidate materials for clean-energy generation and environmen... more TiO 2 is one of the most promising candidate materials for clean-energy generation and environmental remediation. However, the larger-than 3.1 eV bandgap of perfectly crystalline TiO 2 confines its application to the ultraviolet (UV) range. In this study, the electronic and the optical properties of undoped mixed-phase TiO 2 nanoparticles were investigated using UV and inverse photoemission, low intensity Xray photoelectron (XP), and diffused reflectance spectroscopy methods. The facile solution-phase synthesized nanoparticles exhibited a midgap-states-induced energy gap of only ∼2.2 eV. The diffused reflectance spectrum showed sub-bandgap absorption due to the existence of a large Urbach tail at 2.2 eV. The UV photoemission spectrum evidenced the presence of midgap states. The 2.2 eV energy gap enables the nanoparticles to be photoactive in the visible energy range. The gas-phase CO 2 photoreduction test with water vapor under visible light illumination was studied in the presence of the synthesized TiO 2 nanoparticles which resulted in the production of ∼1357 ppm gr -1 (catalyst) CO and ∼360 ppm gr -1 (catalyst) CH 4 , as compared to negligible amounts using a standard TiO 2 (P25) sample. The synthesized nanoparticles possessed a Brunauer-Emmett-Teller (BET) surface area of ∼131 m 2 gr -1 , corresponding to a Langmuir surface area of ∼166 m 2 gr -1 . The determined interplanar distances of atomic planes by highresolution transmission electron microscopy (HR-TEM) and X-ray diffraction (XRD) methods were consistent. A detailed elemental analysis using XPS and inductively coupled plasma mass spectrometry (ICP-MS) demonstrated that the synthesized catalyst is indeed undoped. The catalytic activity of the undoped synthesized nanoparticles in the visible spectrum can be ascribed to the unique electronic structure due to the presence of oxygen vacancy related defects and the high surface area.
Correction for ‘Conversion of landfill gas to liquid fuels through a TriFTS (tri-reforming and Fi... more Correction for ‘Conversion of landfill gas to liquid fuels through a TriFTS (tri-reforming and Fischer–Tropsch synthesis) process: a feasibility study’ by Xianhui Zhao et al., Sustainable Energy Fuels, 2019, 3, 539–549.
The combined on.-line identification and optimi.zation approach developed by Bamberger and Iserma... more The combined on.-line identification and optimi.zation approach developed by Bamberger and Isermann is applied to two chemical pro-cesses systems. The first example is the un-constrained optimization of the stirred re-actors in series proposed by Garcia and Morani. The ...
Physical chemistry chemical physics : PCCP, Jan 13, 2018
Using density functional theory, we study the effect of injected electrons (simulating photoexcit... more Using density functional theory, we study the effect of injected electrons (simulating photoexcited electrons) on the energetics, structures, and binding sites available to CO2 molecules on subnanometer Pt clusters decorated onto anatase TiO2(101) surfaces, shedding light on the first and key step of CO2 photoreduction. Upon the addition of one, two, or three electrons, the O-C-O angles of adsorbed CO2 become progressively smaller in binding sites that directly contact Pt clusters, while no significant change is found in the intra bond length of the adsorbed CO2 and in the bonding distances between the adsorbed CO2 and supported clusters. The extra electrons lead to the stabilization of adsorption sites identified on neutral slabs, including previously metastable configurations, suggesting the enhancement of accessible CO2 binding sites. Furthermore, supported clusters are able to populate the electronic states of adsorbed CO2 species, facilitating the formation of the CO2- anion. T...
Municipal solid waste (MSW) management is a major concern in Indian cities. This work rigorously ... more Municipal solid waste (MSW) management is a major concern in Indian cities. This work rigorously assesses the relative costs and the environmental and health benefits of alternative MSW management methods. Management of MSW over the next 20 years for the city of Greater Mumbai was considered. A generic model was developed to determine the costs for (i) dumping on open ground, (ii) sanitary landfill without leachate treatment, (iii) landfilling with leachate treatment and (iv) regional composting and landfilling. LandGEM was used to quantify the gaseous emissions from landfill, while emissions from leachate and composting were taken from literature. The life cycle impact model of one tonne of MSW was developed using OpenLCA software and the International Reference Life Cycle Data System (ILCD) 2011 method was used for impact assessment. The cost of disposal of one tonne of waste was found to be INR344 (US$5.17), INR741 (US$11.13) and INR1367 (US$20.53), respectively, for the first th...
Waste-to-energy projects are an increasingly prominent component of future energy portfolios. Lan... more Waste-to-energy projects are an increasingly prominent component of future energy portfolios. Landfill gas (LFG)-to-energy (LFGTE) projects are particularly important as they address greenhouse gas emissions. Contaminants in LFG may hamper these projects both from environmental and economic standpoints. The purpose of this review is to highlight key aspects (LFG composition ranges, LFG flowrates, and allowable tolerances for LFGTE technologies, performance and costs for contaminant removal by adsorption). Removal of key contaminants, H2S and siloxanes, by adsorption are surveyed in terms of adsorption capacities and regeneration abilities. Based on the open literature, costing analyses are tabulated and discussed. The findings indicate economics of contaminant removal depend heavily on the feed concentrations of contaminants, allowable tolerances for the LFGTE technology, and the current market for the product. Key trends, identification of challenges, and general purification guide...
Industrial Engineering Chemistry Process Design and Development, 1986
Two approaches to the on-line identification of parameters and states in systems described by non... more Two approaches to the on-line identification of parameters and states in systems described by nonlinear ordinary differentlal equations are compared by using an example chemical process. The first approach is based on the Kalman filter approach extended to cover ...
In this paper, we present a model predictive inferential control (MPIC) strategy to address the p... more In this paper, we present a model predictive inferential control (MPIC) strategy to address the problem of controlling unmeasured output variables (such as quality) using readily available secondary measurements. First we establish the relationship between inferential control and other classical control strategies such as cascade and internal model control. Next we present a framework for incorporating the inferential control strategy within the framework of the often used model predictive control (MPC). This framework, termed model predictive inferential control (MPIC), is general enough to accommodate multiple secondary measurements as well as nonlinear estimators and controllers. The advantages of inferential control are established using two case studies. One is the Shell challenge problem which employs linear transfer function models. The second is a nonlinear, multivariable problem on the control of product composition using secondary measurements on a simulated injection pultrusion process. Problems of collinearity are addressed using principal component analysis (PCA) during the construction of the dynamic estimator. These simulations demonstrate the advantages of the proposed model predictive inferential control strategy.
ABSTRACT Since Fujishima and Honda first demonstrated photocatalytic water splitting in 1972[1], ... more ABSTRACT Since Fujishima and Honda first demonstrated photocatalytic water splitting in 1972[1], numerous investigators have extended the idea into many other semiconductors and photoreactions. Utilizing solar energy to facilitate photocatalytic conversion of carbon dioxide (CO2) with water (H2O) to fuels and chemicals such as CO, CH4, CH3OH holds great potential as a sustainable alternative energy source and as a promising method to reduce pollution and global warming. In spite of the large number of studies and materials investigated for photocatalytic CO2 conversion, efficiencies achieved to date have been very small and much work remains to be done to overcome the limitations. Metal-organic frame works (MOFs) are perhaps uniquely suited to address CO2 capture and photocatalytic conversion because of their exceptional porosities, tunable pore sizes and chemical structure. The principle of reducing CO2 in a MOF using UV radiation has recently been demonstrated by doping a photocatalyst moiety into a MOF[2]. Researchers at USF have been developing Ti-based semi-conductive MOFs that are photo-active in the visible light range. In this study, we evaluated the photocatalytic activity of a Ti-based metal-organic framework in a gas-phase CO2 reduction reaction using a robust photoreactor system. The reactor system has a small volume (<15ml) with the ability to control temperature, pressure and reaction type (batch or flow reactor). Photoreaction efficiency, product conversion and selectivity of MOF photocatalysts are analyzed in comparison to conventional TiO2 (P-25). Reactor conditions, including temperature and pressure, were optimized to improve reaction kinetics and the conversion of CO2 and water to the desired products. References: [1] Fujishima, A., & Honda, K. (1972). Electrochemical Photolysis of Water at a Semiconductor Electrode. [10.1038/238037a0]. Nature, 238(5358), 37-38. [2] Wang, C., Xie, Z., deKrafft, K. E., & Lin, W. (2011). Doping Metal–Organic Frameworks for Water Oxidation, Carbon Dioxide Reduction, and Organic Photocatalysis. Journal of the American Chemical Society, 133(34), 13445-13454. doi: 10.1021/ja203564w
ABSTRACT Metal enhanced luminescence (MEL) of certain luminophores in the presence of metallic na... more ABSTRACT Metal enhanced luminescence (MEL) of certain luminophores in the presence of metallic nanoparticles can help enhance the fluoroscence detection of a wide variety of biomolecules. Using bimetallic nanoparticles is an attractive option because important optical properties, like the wavelength corresponding to the surface plasmon resonance (SPR) peak and the scattering efficiency that dictate the enhancement/quenching of luminophore molecules, can easily be tuned by adjusting the composition, morphology, size and shape of the nanoparticles. In this study, we explore the luminescence enhancement of Cy3 dye in the vicinity of Ag-Cu bimetallic nanoparticles. We used Finite Difference Time Domain (FDTD) calculations to study the influence of composition on the AgxCu1-x bimetallic nanoparticles. Nanoparticles of various structures like alloys, core-shell and mixed metal substrates with spherical and cubical shapes, and in the size range of 25-200 nm are studied with a varying fluorophore-particle separation distance. Optimizing these parameters provides a guiding principle for the synthesizing the bimetallic nanoparticles that can yield high fluoroscence enhancements. The calculations were validated using bimetallic particles synthesized using the polyol synthesis process. The fluoroscence enhancements were measured using a confocal microscope.
Composites Part a Applied Science and Manufacturing, Nov 1, 2003
Vacuum assisted resin infusion molding (VARIM) is a recently developed promising low-cost batch p... more Vacuum assisted resin infusion molding (VARIM) is a recently developed promising low-cost batch process that has been applied to the manufacture of large-sized composite parts. The process has been successfully extended to the construction of foam-core sandwich composites by introducing a co-injection resin transfer molding (CIRTM) technique. In the CIRTM process, the sandwich is manufactured in one integral step and the bonding between the skin and the core is developed during the cure process. The structural performance and reliability of these sandwiches are dependent on the strength of the core-skin bonding. Processing conditions and material parameters such as permeability of fibers and foam; viscosity and cure kinetics of the resin; and resin infusion pressure and temperature all affect the cure. A rigorous 3D non-isothermal processing model was developed for the first time to assist in the design and optimization of the CIRTM process for sandwich construction. A simplified 1D isothermal model was also developed for real-time control and compared with the full-blown model. The effects of various processing parameters on the core-skin bonding strength were investigated with parametric studies. Based on these studies using the processing models, we develop heuristics for optimizing application-relevant parameters of the sandwich composites.
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Papers by Babu Joseph