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Electro-deoxidation of ilmenite (FeTiO3) is an economical production method of FeTi, particularly, if the end use is hydrogen storage. In this study, we show that electro-deoxidation of impure FeTiO3 with Ti content lower than Fe, as in the case of low-grade FeTiO3 ore, results in the formation of a two-phase material consisting of FeTi and Fe2Ti. The presence of Fe2Ti is detrimental to the hydrogen storage efficacy. We show for the first time that it is possible to avoid the formation of Fe2Ti or β-Ti as a second phase under similar operating conditions only by tailoring the composition of the cathode precursor, i.e., the addition of TiO2 to low-grade FeTiO3 so that the atomic ratio of Fe:Ti in the precursor is ~ 1:1. Low-grade FeTiO3 with 10 wt% TiO2 resulted in single-phase FeTi with the atomic ratio of Fe:Ti ~ 1:1 in the precursor and in the final reduced alloy. The hydrogen storage capacity of the single-phase FeTi is nearly 36% higher as compared to the two-phase alloy consisting of FeTi–Fe2Ti.

The present communication describes an investigation on the preparation of metallized composite pellets from ilmenite concentrate. It was observed that the pellet size in the range of 8–12 mm, a binder dosage of 4 wt%, and internal carbon of 5 wt% are the optimum levels that help the pellets attain the desired drop number (~ 10) and dry strength (~ 30 kg/pellet). When subjected to reduction tests at a temperature of 1200 °C for 6 h, the composite pellets show better metallization (~ 80%) than the raw ilmenite pellets with an equal amount of reductant. The reduced ilmenite composite pellets also display a reasonable decrepitation value of 4.9%, thereby making them suitable to be used directly in arc furnaces for titania slag production. A comparative characterization study by SEM–EDS indicated that larger amounts of metallic grains are uniformly distributed throughout the matrix in the composite pellets.

In this work, an electrophoretic deposition technique was used to deposit graphene oxide (GO) on 304 stainless steel. Its corrosion performance was evaluated in a simulated polymer electrolyte membrane fuel cell environment. The corrosion current density (icorr) and interfacial contact resistance (ICR) were measured at 8.9 µA/cm2 and 19.3 mΩ cm2, respectively. The icorr of GO coated 304SS is several orders lower than bare SS 304. Similarly, the ICR of GO coated 304SS is nearly half of bare 304SS at a compaction pressure of 150 N/cm2. The potentiodynamic polarization plot indicates the prevalence of multiple corrosion mechanisms. A prolonged corrosion study for 30 days immersed in the simulated PEM cell environment shows the formation of rounded pits that corroborate the activity of pitting corrosion.

Induration of ilmenite pellets by oxidation is an essential step in the pelletization process since it decides the physical and metallurgical properties of the pellets. In this regard, the induration parameters such as temperature and roasting time have been optimized to obtain good quality ilmenite pellets made of concentrates obtained from low-grade ilmenite ores of Odisha, India. The oxidation temperature of 900 °C at a short roasting time of 15 min has been found suitable to achieve recommended requirements of various pellet properties such as cold compressive strength, porosity, metallization, tumble, and abrasion indices. X-ray diffraction and microstructural analysis indicate that the recrystallization of hematite in the oxidation process improves the mechanical strength of the pellets. In contrast, the formation of ferric pseudobrookite phase at 1000 °C and 1100 °C oxidation temperatures impairs the pellet strength.

Cold gas dynamic spraying is a relatively new coating technology in which coatings are produced by spraying metal powders at high velocity. This generates particle–substfrate bonding through severe plastic deformation at temperatures, well below the melting point of the powders. In the present study corrosion resistant nickel coatings were produced on preheated mild steel substrates by cold spraying. The substrate deposition temperature was varied systematically and post fabrication annealing was introduced to reduce the deposition impact stress. Post deposition heat treatment, although improved the interfacial bonding, lead to increased corrosion due to increase in porosity of the samples. Coatings deposited at low temperatures (∼500°C) provide the best corrosion resistance as evidenced through their microstructure.

Although FeTi is a well-known hydrogen storage material, producing FeTi on a commercial scale is quite challenging, and generally, one ends up with a multi-phase system consisting of Fe2Ti and FeTi. As Fe2Ti is inert towards hydrogen, it lowers the hydrogen storage efficacy of FeTi. However, there are some reports, which propose that the presence Fe2Ti in FeTi, primarily on the surface is inevitable and it helps in activation of FeTi. Here, we report results of targeted experiments together with first-principles density functional theory (DFT) based calculations to investigate the hydrogen storage properties of FeTi vis-a-vis origin of inertness of Fe2Ti towards hydrogen storage. The formation enthalpies, calculated using density functional theory, of FeTi–H system were found to be very close to the experimental values (−28.1 and −33.72 kJ/mol H2 for FeTiH and FeTiH2 respectively), and that of Fe2Ti–H systems was positive, indicating the inability to form stable intermetallic-hydrides. This corroborates well with the experimental observations, that the pure phase of Fe2Ti cannot store hydrogen. Further, the Gibbs free energy for FeTiH and FeTiH2 were evaluated at 298 K using first-principles quantum mechanics and statistical thermodynamics theories. The vibrational and electronic entropies were calculated using Debye theory of heat capacities. Gibbs free energy at 298 K for FeTiH and FeTiH2 were found to be −5.01 and −3.52 kJ/mol of H2, respectively. Our present study concludes that proper care must be taken to avoid or minimize the formation of Fe2Ti during the production of FeTi.

Silicon anode, even with its theoretically high specific capacity, has only seen a limited commercial adoption in lithium-ion battery (LIB) due to the durability issues. The performance of a silicon anode in a LIB is enhanced when a small amount of fluoroethylene carbonate (FEC) is added to the battery electrolyte. In this article, we analyze the effect of FEC additive on the silicon anode in both the half- and full cell configuration. Electrochemical impedance spectroscopy is used to unravel crucial intrinsic properties of the cell. It detects a fourfold drop in the cell impedance upon addition of FEC. We also employed density functional theory (DFT)-based models to understand and complement the experimental findings. At the DFT level, the solvation energy of Li+ in the ethylene carbonate (EC) electrolyte is − 224.34 kJ mol−1 whereas that in the FEC electrolyte is − 202.96 kJ mol−1. This implies that the electrolyte with the FEC additive may act as a better carrier of Li+ that with the EC additive alone.

Metallic bipolar plates (BPPs) are potential candidates to replace the conventional graphite BPPs in polymer electrolyte membrane fuel cells (PEMFCs) because they are cost-effective and easy to manufacture. In this present work, we report on the development of Ni–Mo–Cr–P electroplated AISI 1020 steel bipolar plates as a BPP material. The microstructure and composition of the Ni–Mo–Cr–P coatings were optimized varying pH of the electrolyte bath and deposition current. Compared to bare AISI 1020 steel, the coating electroplated at pH 5.5 and a pulse-current density of 0.075 A/cm2 showed an improvement in corrosion resistance by three orders of magnitude. The corrosion current densities of bare and Ni–Mo–Cr–P electroplated AISI 1020 steel in the simulated anodic environment is 1.05 × 10−2 and 4.95 × 10−5 A/cm2, respectively, while that in the simulated cathodic environment it is 3.7 × 10−2 and 4.58 × 10−5 A/cm2, respectively. The enhancement of corrosion resistance is due to the formation of a Mo and Cr based passive oxide layer. The interfacial contact resistance (ICR) of bare and Ni–Mo–Cr–P electroplated AISI 1020 steel is 53.2 and 40.06 mΩ, respectively. ICR of Ni–Mo–Cr–P is lower than the bare AISI 1020 because of the semiconducting nature of the two-layered Mo-based passive oxides. Additionally, Ni–Mo–Cr–P coated AISI 1020 steel shows a higher water contact angle than bare AISI 1020 carbon steel. A single-cell PEMFC stack with Ni–Mo–Cr–P coated AISI 1020 steel BPP shows similar polarization behavior as graphite BPP. However, the performance of Ni–Mo–Cr–P coated AISI 1020 steel BPP lacks durability, and further improvement is necessary before it can be commercially implemented.

Electrophoretic deposition was used to deposit graphene oxide on 304 stainless steel to mitigate the aggressive corrosion that occurs in steel bipolar plates of polymer electrolyte membrane (PEM) fuel cells. In this context the deposition parameters i.e., the voltage and time was systematically monitored to obtain the optimum parameters that can give a consistent coating. The deposit thickness and its surface roughness and morphology were evaluated to obtain a smooth coating. Further electrochemical testing of the coating obtained under optimized parameters was done by the dynamic polarization scanning test under PEMFC environment. The corrosion current density improved by almost four times and the polarization resistance increased by 100% indicating that graphene oxide coatings have the potential to be used as anti-corrosive coating on bipolar plates of PEMFC.

Producing large parts by chemical vapour infiltration (CVI) process is quite challenging due to non-uniform nature of temperature and gas precursor distribution. Many a times repeated experiments are required to optimize the process parameters for manufacturing composites with isotropic properties. This is not only cumbersome but also cost intensive. To address this critical issue, we develop a multiscale mathematical model for thermal gradient forced chemical vapour infiltration (TG-FCVI) process considering only heterogeneous decomposition of propylene on carbon preform. The model takes account of the flow field, mass transport, reaction kinetics and the transient nature of porosity to identify the optimum process parameters. As the time taken in deposition is very large, the flow in free channel is much faster than the pores and therefore the flow equations are solved coupling both the domains in steady state (low Mach number flow). The effect of various process parameters on composites homogeneity like temperature, temperature gradient, inlet precursor concentration and inlet gas flow rate were studied. The model was validated with the available experimental data. It has been observed that high temperature gradient and inlet concentration favours homogeneous C-C composite with high final bulk density. However, increasing temperature of reactor and reducing inlet reagent concentration causes surface pore blockage and resulting in inhomogeneity in direction of axial flow

This study has been carried out to explore the feasibility to use the low-grade ferruginous manganese ores to produce manganese nanomaterials (Mn ferrites and ϒ-MnO2). Ore samples were collected fr...

Polymer electrolyte membrane fuel cell (PEMFC) stacks suffer from the high cost and low volumetric energy of non-porous graphite bipolar plates. To resolve this problem, a bilayer coating consisting of Ni and Ni–Cr–P is deposited on AISI 1020 low-carbon steel using pulse electrodeposition. Ni/Ni–Cr–P-coated AISI 1020 is evaluated as a bipolar plate material for PEMFCs. Ni/Ni–Cr–P-coated substrates exhibit better corrosion resistance in both cathodic (air-purging) and anodic (H2-purging) environment than the bare AISI 1020 substrate and lower interfacial contact resistance (ICR) than bare AISI 1020 and stainless steel. Further, it is expected to show better water management as the Ni/Ni–Cr–P coating is more hydrophobic than the bare substrate. Preliminary studies show that Ni/Ni–Cr–P-coated AISI 1020 plate can be a suitable candidate for replacing graphite as the bipolar plate of PEMFCs.

In this work we have synthesized and characterized sodium doped SrSiO3 electrolyte, for use in low and intermediate temperature solid oxide fuel cells (SOFCs). Great interest was placed onto this material after its first report in 2012, which was later dampened by conflicting reports about the properties of this class of materials. It is imperative to resolve this issue from the viewpoint of development of low and intermediate temperature SOFCs. Here, we report the most comprehensive data till date on the properties of this class of materials. Although it is desired to synthesize a single phase material, strong evidences presented here suggest that it is a multiphase material. The reason for obtaining a multiphase material is discussed considering the reaction thermodynamics. Additional data presented here establish that at the operating temperature (~750 °C) of SOFC devices, amorphous phases in the material transforms into a crystalline phase.

A novel two step synthesis from commercial nanocarbon and a preceramic polymer afforded a nanoporous carbon hybrid with specific surface area of 1798 m2 g−1, and porosity in the range of 1–4 nm. Preliminary studies on the supercapacitive behaviour of the material through cyclic voltammetry resulted in an excellent specific capacitance of 333 F g−1.

Lithium-ion batteries (LIBs) are widely used in consumer electronics because of its high energy density, superior rate capability, and long cycling life. Lately, the demand for LIBs in other sectors such as automobiles and grid level storage has been growing because of emphasis on renewable energy. However, performance such as rate of charging, energy density, and cost of storing energy ($/kWh) of LIBs does not meet the US-DOE targets for battery electric vehicles. Since, the LIB consists of several components like cathode, anode, electrolyte and separator, its performance is limited by the performance of individual components in the assembled LIB. Further, the performance represents the full LIB and it is difficult to isolate the performance of individual components in the assembled battery. Electrochemical modelling can be extensively used to identify the limitation and improve the performance of individual components since it is an efficient, and cost effective tool. In this work, an isothermal electrochemical model is developed for LIBs with LiC6 anode; LiPF6 based electrolyte, and LiMnO4 cathode. A porous electrode theory is used to describe the insertion and de-insertion of Li+ ions into electrode. A concentrated solution theory is used to describe the transport mechanism in the electrolyte. The Butler-Volmer kinetics is used to model reactions at the electrode/ electrolyte interface. The electrochemical model developed is solved using COMSOL Multiphysics® 5.1a finite element modelling software. The modeling results are verified with the experimental results available in the literature. The model is used to evaluate the influence of various design parameters that influence the performance of LIB such as the electrode dimensions, structure, conductivity, etc. Furthermore, the electrochemical model data was used to develop machine learning techniques such as random forests (RF), support vector machine (SVM) and gradient boosting (GB) for feature-analysis of the LIB parameters. Feature analysis, an extremely important metric for estimating relative importance of a particular parameter, were studied towards understanding the relative importance of other parameters for maximizing energy and power density of a battery. Random forest techniques performed well for predicting the energy density which is depend on thickness (after current) but gradient boosting failed to predict it (as shown in Fig.1). However, gradient boosting techniques performed well for forecasting power density which depend on conductivity (after current), here random forest failed to predict this. Without such feature-analysis by machine learning techniques, it would have been very difficult to have a quantitative estimation of their ranking towards understanding the relative importance of other battery parameters for maximizing energy and power density of LIBs. Figure 1

Silicon is regarded as one of the most promising anode material for lithium ion batteries (LIBs). It has a high theoretical capacity of 3579 mAh/g. In order to make silicon commercially viable, the two key challenges need to be addressed: high volume expansion during lithiation/delithiation process and formation of unstable solid electrolyte interphase (SEI) at the silicon-electrolyte interface. Specially, to address the unstable SEI formation, different types of strategies are adopted such as; use of carbon coated silicon surface, use of nano-silicon materials, modification of the binder and use of additive in the electrolyte. Previous studies have reported1,2 that the fluoroethylene carbonate (FEC) additive improves the performance of the silicon anode. Although research efforts are focused on understanding the cause of improvement in the performance of LIBs with FEC electrolyte additive, the underlying mechanism mostly remains unclear. In this work, we studied the effect of FEC additive on the performance silicon anode in half as well as the full-cell configuration of LIBs comprising NMC cathode and attempted to find the underlying mechanism. To complement the experimental results, we provide key insights from the first principle to uncover the role of FEC additive in silicon anode LIBs. References 1. Dalavi, S., Guduru, P., & Lucht, B. L. (2012). Performance enhancing electrolyte additives for lithium ion batteries with silicon anodes. Journal of The Electrochemical Society, 159(5), A642-A646. 2. Nakai, H., Kubota, T., Kita, A., & Kawashima, A. (2011). Investigation of the solid electrolyte interphase formed by fluoroethylene carbonate on Si electrodes. Journal of The Electrochemical Society, 158(7), A798-A801.

Polymer electrolyte membrane (PEM) fuel cells are expected to play a major role in transporting humans and goods. However, one of major bottlenecks is the high materials and manufacturing cost. One way to lower the cost to a great extent is by replacing conventional graphitic bipolar plates with metallic bipolar plates (BPPs), as they costs around 30% of the total cost of stack1. That said, metallic BPPs have durability issues. Over time, they corrode and show higher interfacial contact resistance (ICR). In this work we attempt to engineer the surface of metallic BPPs, so that they perform for longer duration without degrading. To keep the process economical and commercially attractive, a bilayer coating of Ni followed by Ni-Cr-P alloy is pulsed electrodeposited on AISI 1020 low carbon steel. The electrodeposition process is optimized varying the process parameters, such as electrolyte composition, temperature and deposition current. Field emission scanning electron microscopy and energy dispersive x-ray spectroscopy are used to study the surface morphology and compositional analysis of coating, respectively. Variation in microstructure and composition the Ni/Ni-Cr-P coating is observed with change in process parameter such as pH and temperature. Corrosion studies were carried out on Ni/Ni-Cr-P coated samples using potentiodynamic technique in accelerated (0.5 M H2SO4 + 2 ppm HF) solution at 80ºC. Ni/Ni-Cr-P coated samples with higher Cr content exhibited better corrosion resistance behaviour in both cathodic (air-purging) as well as anodic (H2-purging) environment compared to the bare substrate. Long term durability of Ni/Ni-Cr-P coated samples and AISI 1020 low carbon steel samples were studied using potentiostatic polarization technique. Both coated and bare samples are placed in the accelerated electrolyte solution. Ni/Ni-Cr-P coated samples showed better durability with less change in current density, while bare samples completely disintegrate and precipitate into the solution within 2–3 hours in potentiostatic mode in both the environments. Ni/Ni-Cr-P coated sample show lower interfacial contact resistance (ICR) value than that of bare AISI 1020 steel samples. For better corrosion resistance and improvement in surface electrical property, Mo was included in the coating composition2. Ni/Ni-Mo-Cr-P coated samples show improved corrosion resistance than Ni/Ni-Cr-P coated samples and AISI 1020 low carbon steel bare samples in both anodic and cathodic PEM fuel cell environment. Reference: R. Taherian, J. Power Sources, 265, 370–390 (2014) http://dx.doi.org/10.1016/j.jpowsour.2014.04.081. H. Rashtchi et al., Fuel Cells, 16, 784–800 (2016) http://dx.doi.org/10.1002/fuce.201600062

Silicon has been identified as the best candidate element for next generation lithium-ion batteries (LIB) anode material. It is widely available and capacity is more than ten times of conventional graphite. However, using silicon anode in LIB, still remains an unfinished agenda despite very sincere global research efforts1-3. The reasons for this are ~300% expansion in volume upon lithiation, causing fracture or pulverization of the anode structure and sluggish diffusion of lithium in bulk silicon. These challenges can be addressed by using porous silicon. The porosity in silicon can accommodate the majority of the volume expansion during repeated charge-discharge cycling of battery. Most of the under-development processes for porous silicon necessitate sourcing the material from electronic grade Si-wafers. Though this is overkill for many applications, the reason for using electronic grade silicon is due to lack of a cost effective processing route for porous silicon. Here we report a novel and industrially scalable route for production of heterostructured nanoporous silicon particles with a high specific area from low grade Si raw material. We demonstrate capacity retention of more than 1000mAh/gm and columbic efficiency in excess of 98% even after 300+ cycles of operation, using this porous silicon as anode material in a coin cell. This process can also be easily integrated with existing battery fabrication methods, without requiring major changes. Our proposed method is likely to ensure a promising, high throughput process for production porous silicon and its use in lithium ion batteries. References: Y. Jin, B. Zhu, Z. Lu, N. Liu, and J. Zhu, Adv. Energy Mater., 1700715, 1–17 (2017). X. Zuo, J. Zhu, P. Müller-Buschbaum, and Y. J. Cheng, Nano Energy, 31, 113–143 (2017) http://dx.doi.org/10.1016/j.nanoen.2016.11.013. Bloomberg, Nat. , 559, 467–471 (2018) https://www.nature.com/magazine-assets/d41586-018-05752-3/d41586-018-05752-3.pdf.

The Solid Oxide Membrane (SOM) process for magnesium production involves the direct electrolysis of magnesium oxide for energy efficient and low-carbon magnesium production. In the SOM process, magnesium oxide is dissolved in a molten oxy-fluoride flux. An oxygen-ion-conducting SOM tube, made from yttria stabilized zirconia (YSZ), is submerged in the flux. The operating life of the electrolytic cell can be improved by understanding degradation processes in the YSZ, and one way the YSZ degrades is by yttria diffusion out of the YSZ. By adding small amounts of YF3 to the flux, yttria diffusion can be controlled. The diffusion of yttria into the flux was quantified by determining the yttria concentration profile as a function of immersion time in the flux and distance from the flux-YSZ interface. Yttria concentrations were determined using x-ray spectroscopy. The diffusion process was modeled using a numerical approach with an analytic solution to Fick’s second law. These modeling and experimental methods allowed for the determination of the optimum YF3 concentration in the flux to minimize yttria diffusion and improve membrane stability. Furthermore, the effects of common impurities in magnesium ores, such as calcium oxide, silica, and sodium oxide/sodium peroxide, on YSZ stability are being investigated.

Hydrogen and syngas can be produced from municipal solid waste to meet part of our energy demand. In this work, the performance of a novel, energy-efficient, solid oxide membrane (SOM) electrolyzer for the production of high purity hydrogen from steam and hydrocarbon waste such as plastics is analyzed. Energy analysis of the proposed electrolyzer shows that hydrogen can be generated at an efficiency of nearly 75%. Based on this study, design and electrode materials for commercially viable SOM electrolyzer is proposed.

This paper describes a novel Solid Oxide Membrane (SOM) electrolyzer that can utilize the energy value in any carbon and hydrocarbon reductant to lower the energy requirement for hydrogen production from steam. The Solid Oxide Membrane (SOM) electrolyzer consists of a one-end closed oxygen-ion conducting yttria stabilized zirconia (YSZ) tube with Ni-YSZ cathode coated on the outside and liquid metal anode inside the tube. In the SOM electrolyzer steam is reduced at the cathode and the oxygen produced on the anodic side reacts with the reductant supplied in the liquid metal anode. In the present study the SOM electrolyzer is evaluated using solid carbon and humidified hydrogen as reductant.

A laboratory-scale solid oxide membrane (SOM) steam electrolyzer that can potentially use energy value in waste or any source of carbon or hydrocarbon to produce high-purity hydrogen has been fabricated and evaluated. The SOM electrolyzer comprises an oxygen-ion-conducting yttria-stabilized zirconia (YSZ) electrolyte with a Ni-YSZ cermet cathode coated on one side and liquid-metal anode on the other side. The SOM electrolyzer is operated at 1000 °C by providing a steam-rich gas feed to the Ni-YSZ cermet cathode and feeding a reductant source into the liquid-metal anode. The steam is reduced over the cathode, and oxygen ions are transported through the YSZ electrolyte and are oxidized at the molten metal electrode by the reductant feed. The advantage of SOM electrolyzer over the state-of-the-art solid oxide electrolyzer is its ability to use solid, liquid, and gaseous reductant feed in the liquid-metal anode to reduce the oxygen chemical potential and drive the reaction for hydrogen production. In this study, an electrochemical process model for a SOM electrolyzer was developed. The condition of the liquid-metal anode with reductant was simulated by bubbling humidified hydrogen (3 pct H2O) in the liquid metal, and the electrochemical performance of the SOM electrolyzer was modeled. The experimental data were curve-fitted into the model to identify the various polarization losses. It showed that the performance of the SOM electrolyzer was dominated by the ohmic resistance of the YSZ membrane. Based on the results of this study, future work is needed toward increasing the performance efficiency of the SOM electrolyzer.

Despite its attractive properties, titanium is limited in use by its high price, due to the cost of smelting and processing the ore. The solid oxide membrane (SOM) process aims to consolidate most of the processing steps required for conventional titanium production into a single step, making it an energy efficient and cost effective method for producing CP billet and ingot and possibly also powders used to make titanium alloys. In the SOM process experiment, a steel crucible contains MgF2–CaF2–TiO2 flux; an inert metal/carbon rod serves as the cathode; an oxygen ion conducting yttrium stabilised zirconia (YSZ) membrane in the form of a one end closed tube contains either a liquid metal that acts as the anode or a liquid MgF2–CaF2 ionic flux that connects the YSZ membrane to an anode. During electrolysis, titanium ions are reduced at the cathode while the oxygen ions pass through the YSZ membrane and are oxidised at the anode by a reducing agent, hydrogen gas or carbon, forming steam or CO(g) res...

Solid Oxide Membrane (SOM) Electrolysis is a new energy-efficient zero-emissions process for producing high-purity magnesium and high-purity oxygen directly from industrial-grade MgO. SOM Recycling combines SOM electrolysis with electrorefining, continuously and efficiently producing high-purity magnesium from low-purity partially oxidized scrap. In both processes, electrolysis and/or electrorefining take place in the crucible, where raw material is continuously fed into the molten salt electrolyte, producing magnesium vapor at the cathode and oxygen at the inert anode inside the SOM. This paper describes a three-dimensional multi-physics finite-element model of ionic current, fluid flow driven by argon bubbling and thermal buoyancy, and heat and mass transport in the crucible. The model predicts the effects of stirring on the anode boundary layer and its time scale of formation, and the effect of natural convection at the outer wall. MOxST has developed this model as a tool for scale-up design of these closely-related processes.

Metal Oxygen Separation Technologies, Inc. (MOxST) is actively developing Solid Oxide Membrane (SOM) electrolysis technology for production of magnesium directly from its oxide. The vital component of this technology is the oxygen ion-conducting solid zirconia electrolyte separating the molten flux (a mixture of salts and oxide) and the inert anode. The zirconia not only protects the anode from the flux but also prevents anode gas back-reaction, increasing the efficiency. This makes it possible to produce low-cost high-purity magnesium and high-purity oxygen as a byproduct with no direct greenhouse gas emissions. In this paper we discuss the design modifications made to address the scaling-up challenges, particularly for producing magnesium in liquid form. The key accomplishment to date is the successful development of a prototype capable of producing few kilograms of magnesium per day. We will also describe the prerequisite properties of an inert anode and suitable materials for the same.

The solid oxide membrane (SOM) process has been used to produce magnesium by direct electrolysis of its oxide. In this process MgO is dissolved in a molten CaF2-MgF2 flux and an yttria-stabilized zirconia (YSZ) SOM membrane separates the cathode and the flux from the anode. YSZ membrane stability limits the operating life of the SOM electrolyzer. The YSZ membrane is known to degrade due to diffusion of yttrium into the flux. Yttrium diffusion can however be decreased by adding YF3 to the flux. This study investigates the long-term stability of the YSZ membrane. Yttrium composition profiles in the YSZ membrane were determined using WDS as a function of immersion time and YF3 content in the flux. An analytic solution to the diffusion equation was used to model the diffusion process. This study allows the determination of the optimum YF3 content needed in the flux to minimize yttrium diffusion and increase membrane stability.

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A laboratory-scale solid oxide membrane (SOM) steam electrolyzer that can potentially utilize the energy value of coal or any hydrocarbon reductant to produce high purity hydrogen has been fabricated and evaluated. The SOM electrolyzer consists of an oxygen-ion-conducting yttria-stabilized zirconia (YSZ) electrolyte with a Ni-YSZ cermet cathode coated on one side and liquid tin anode on the other side. Hydrogen production using the SOM electrolyzer was successfully demonstrated between 900 and 1000{sup o}C by feeding a steam-rich gas to the Ni-YSZ cermet cathode and solid carbon reductant into the liquid tin anode. It was confirmed that the energy required for hydrogen production can be effectively lowered by feeding a solid carbon reductant in the liquid tin anode. A polarization model for the SOM electrolyzer was developed. The experimental data obtained under different operating conditions were curve fitted into the model to identify the various polarization losses. Based on the results of this study, work needed toward increasing the electrochemical performance of the SOM electrolyzer is discussed.

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Solid oxide membrane (SOM) process has been successfully employed for the production of magnesium directly from its oxide. The process involves dissolving MgO in a fluoride based ionic flux and electrochemically pumping out the oxygen ions from the flux via an oxygen-ion-conducting SOM to the anode where they are oxidized, while reducing magnesium ions at the cathode. Understanding the long-term stability of the SOM in the flux is critical for the commercial success of this technology. In this study long term SOM stability is investigated under potentiostatic conditions. Additionally, study utilizes electrochemical techniques such as impedance spectroscopy and linear sweep voltammetry to investigate key concepts related to MgO dissociation and current efficiency. Results show that the dissociation potential of MgO is dependent on the partial pressures at which magnesium is generated and the membrane stability is likely related to the current efficiency.

In conventional investment casting process of aluminium alloys for the application of the aerospace industry, to assure the quality of the final casting, usually the foundry uses large runner system which results in low yield, high energy consumption and high GHGs emission. In one case of this investigation, the yield is between 5 ~ 10% which means that the current casting process wastes large amount of energy and generates lots of scraps. By applying a new casting method, the bulky runner system and the melting/holding time are significantly reduced, the quality of the casting is improved, and in the meantime the related energy consumption and GHGs emission are significantly decreased. In the investigation, the energy efficiencies and GHGs emission between the current and traditional processes are calculated and compared.