Biography:

Wonbong Choi is a tenured, Full Professor in the Department of Materials Science and Engineering and Mechanical and Energy Engineering at University of North Texas, Denton. He has obtained his PhD in Materials Science and Engineering from the North Carolina State University (NCSU) in 1997. After his PhD, he has worked in the industry research laboratory as a Senior Researcher and Project Manager at Samsung (SAIT). He was a Leading Scientist in the carbon nanotubes for Tera-level nano electronics device project. He has been awarded the prestigious Materials Research Society (MRS) Medal for 2006. He has awarded MRS Fellow in 2009. He has successfully conducted numerous granted projects funded by AFOSR, DARPA, NSF, SRC, DOE and Samsung. He is the author/co-author of over 80 patents, one book (“GRAPHENE” CRC Press 2011), 10 book chapters, over 240 publications, which includes 140 peer-reviewed journal articles and over 70 conference proceedings. His research articles have been cited over 10,000 times with H-index of 51 (Google Scholar). He serves as a reviewer for more than 20 international journals and serves on the Editorial Board of five journals.

Abstract:

Next-generation energy storage devices, such as Li-ion batteries (LIBs) and Li^-sulfur batteries (LiS), demand high energy, power and better safety. Conventional graphite anode falls short of fulfilling all these necessities. Carbon nanostructural materials (graphene and carbon nanotubes) have gained the spotlight as promising anode materials for energy storage; they exhibit unique physico-chemical properties such as large surface area, short Li⁺ ion diff usion length, and high electrical conductivity, in addition to their long-term stability. Among all published literatures in Li-ion battery, nanostructured carbon materials occupy ~70%. Such an impressive figure signifies high interest and promising future of this class of materials in energy storage devices and compels us to consider the involved issues deeply. Carbon-nanostructured materials have issues with low areal and volumetric densities for the practical applications in electric vehicles, portable electronics, and power grid systems, which demand higher energy and power densities. One approach to overcoming these issues is to design and apply a three-dimensional (3D) electrode accommodating a larger loading amount of active anode materials while facilitating Li⁺ ion diffusion. Furthermore, 3D nanocarbon frameworks can impart a conducting pathway and structural buff er to high-capacity non-carbon nanomaterials, which results in enhanced Li⁺ ion storage capacity. In this presentation, the current status of the design and fabrication of 3D carbon nanostructures will be reviewed. Our recent progress on 3D carbon nanomaterials for LIBs and Li-S batteries will be presented. Finally, the superior performance of 3D carbon nanotube-sulfur will be presented along with its mechanistic analysis.

Biography:

Muge Acik is currently an Argonne Scholar-Named Fellow at Argonne National Laboratory. She obtained a B.S. in chemistry from Izmir Institute of Technology (Turkey), a M.S. in materials science and nanoengineering from Sabanci University (Turkey), and a Ph.D. in materials science and engineering from the University of Texas at Dallas. Prior to Argonne, she also worked for Texas Instruments Inc. as a Process Development Engineer for memory device production. Her work as the PI covers the analysis of surfaces and interfaces of the graphene-based thin films using in situ spectroscopy, and the discovery of new perovskite growth methods for energy harvesting and nanoelectronics. Indeed, she is the recipient of 2015 Distinguished Joseph Katz Postdoctoral Fellowship, 2011 MRS Graduate Student Silver Award, and 2011 MRS Best Poster Award.

Abstract:

Methyl ammonium lead trihalide (MAPbX3) perovskites have great potential as light harvesters for energy harvesting due to their unique optical and electronic properties. The conventional growth techniques apply spin-coated precursors on a substrate followed by annealing for the processing of the lead halide perovskites; however, use of toxic solvents and high temperature hinder device stability and performance. To avoid annealing processes, the solution-based methods have been developed. I will introduce a new one-step solution technique to facilitate in situ crystal formation of methyl ammonium lead bromide and methyl ammonium lead chloride perovskites at the micron (~1-10 μm) to nano scale (< 500 nm) (Fig.1). As a substrate-free approach, the crystal pre-growth allows crystallization in alcohols (methanol, ethanol, 2-propanol, 1-butanol, and 2-butanol) at room temperature followed by a direct precipitation of the perovskite material for a large-area deposition. This room-temperature process able technique, however, differs from the in situ growth of methyl ammonium lead iodide crystals in alcohols that eliminates treatment at the boiling point of the alcohols. The high-energy synchrotron XRD, wide angle x-ray scattering (WAXS), Fourier transform infrared (FTIR) in transmission/reflection geometry (ATR, % R), UV-Vis-NIR (% R), micro Raman spectroscopy, and the solid state 1H, 13C, and 207Pb –MAS NMR are performed for characterization. The perovskite crystals show improvement in air/moisture for their chemical stability (<1.5 months). The thermo gravimetric analysis and in situ techniques also determine their thermal stability (~150-300°C). The poor yield of methyl ammonium lead iodide in toluene confirms that the alcohols catalyze the growth process through a substitutional reaction mechanism. Indeed, the theoretical calculations reveal that the growth of the perovskites in alcohols is exothermic. These materials will eventually find their use in applications of photovoltaics,3,4 photo detectors, optical-thermal sensors, light emitting diodes, light-emitting field-eff ect transistors, lasers, solar fuels, batteries, super capacitors, radiation detectors, data storage, hydrogen fuel cells, and photo catalysis.

Biography:

Alexander Kobryn has his expertise in predictive and descriptive modeling of equilibrium and time-dependent non-equilibrium phenomena in soft condensed matter systems such as molecular and macromolecular liquids and solutions, electrolytes and polyelectrolytes, gels and polymer blends, with the use of methods from statistical physics, theoretical physics, and theoretical and computational chemistry to research quantum and classical systems on multiple time and length scales, in nanoconfined geometries, and in nanoporous media. Successful applications include, in particular, polymer design rules for self-assembly of functionalized ionomers, explanation of the gelation mechanism and prefiguring of the gelation ability of multifunctional oligomeric electrolyte gelators, modeling of the active layer nanomorphology and dynamics of polymer blends that are building blocks for inexpensive organic and organic-metallic-halide solar panels, controlled fluid flow in MEMS and NEMS with CFD coupled to molecular properties of fluid and channel materials, etc.

Abstract:

Both descriptive and predictive modeling of structural properties of blends of PCBM or organic-inorganic hybrid perovskites of the type CH₃NH₃PbX₃ (X=Cl, Br, I) with P3HT, P3BT or some squaraine SQ dye sensitizer, including adsorption on TiO₂ clusters having rutile (110) surface, is presented with the use of a methodology that allows computing the microscopic structure of blends on the nanometer scale and getting insight on miscibility of its components at various thermodynamic conditions. The methodology is based on the integral equation theory of molecular liquids in the reference interaction site representation/model (RISM) and uses the universal force field. Input parameters for RISM, such as optimized molecular geometries and charge distribution of interaction sites, are derived with the use of the density functional theory methods. To compare the diff usivity of the PCBM in binary blends with P3HT and P3BT, respectively, the study is complemented with MD simulation. A remarkably good agreement with available experimental data and results of alternative modeling/simulation is observed for PCBM in P3HT system. We interpret this as a step-in validation of the use of our approach for organic photovoltaic and support of its results for new systems that do not have reference data for comparison or calibration. For the less studied P3BT, our results show that expectations about its performance in binary blends with PCBM may be overestimated, as it does not demonstrate the required level of miscibility and short-range structural organization. The performance of P3BT with perovskites, however, seems as expected. The calculated nanoscale morphologies of blends of P3HT, P3BT or SQ with perovskites, including adsorption on TiO₂, are all new and serve as an instrument in rational design of organic/hybrid photovoltaics. They are used in collaboration with experts who make prototypes or devices for practical applications.

Biography:

Servet Turan is a Professor at Materials Science and Engineering at the Anadolu University in Eskisehir, Turkey. He has received his BSc in 1988 at Istanbul Technical University and MSc in 1990 at Leeds University whereas, he finished his PhD degree at Cambridge University in 1995. Since then, he has been at Anadolu University. His research interests include the lithium-ion batteries, thermoelectric materials, advanced ceramics and electron microscopy based techniques for characterisation of all sorts of materials including in-situ heating.

Abstract:

Nowadays, garnet type solid electrolytes are extensively studied electrolytes for Li-ion batteries along with other types of electrolytes such as Perovskite, LISICON and LIPON. Cubic Li₇La₃Zr₂O₁₂ (LLZO) phase is relatively recently found composition that shows satisfying ionic conductivity. However, the room temperature stable form of LLZO is tetragonal and either adding stabilizers or increasing sintering temperature have been employed to stabilize cubic phase at room temperature. Recently, it was found that the cubic phase stabilization temperature could be lowered by using solution-based synthesis. However, there is a lack of knowledge on how the anions acting for the stabilization of cubic LLZO. In this work, the effect of (NO₃)^2- and Cl^- ions on the cubic phase stabilization was discussed through the sol-gel synthesis. Zr (NO₃)² and ZrOC_l2 were selected as (NO₃)^2- and Cl^- anion sources, respectively. 20 mole % Al content as cubic stabilizer was kept constant. After calcination, as-synthesized powders were sintered by using both conventional powder bed sintering and spark plasma sintering (SPS). Crystal structures of calcined powders and sintered pellets were measured by using X-Ray Diff raction (XRD). Combined TGA-FTIR was used to analyze exhaust gases at ppm level. Grain size as well as particle morphology were evaluated by using scanning electron microscope (SEM). True densities and ionic conductivities of sintered pellets were measured by using Archimedes method and AC impedance spectroscopy, respectively. Results showed that high purity cubic LLZO phase in a powder form was obtained after calcination at 1000°C by using ZrOC_l2 precursor whereas larger size (NO₃)^2- anions inhibit the cubic phase stabilization. Since there were (NO₃)^2- anions in the solution that came from LiNO₃ and La(NO₃)³, it can be concluded that a limited (NO₃)^2- anion concentration was needed to stabilize cubic phase.

Biography:

Rahim Munir is a doctoral candidate at King Abdullah University of Science and Technology (KAUST) and affiliated with the KAUST Solar Center (KSC), where he works on understanding the structure-properties-performance relationship for perovskite solar cells. He completed his MSc degree from the Korea Advanced Institute of Science and Technology (KAIST). He leads a team of scientists from KAUST to perform x-ray based experiments at Cornell High Energy Synchrotron Source (CHESS). Munir is an active member of the Materials Research Society (MRS) and played major leading roles in the MRS KAUST Student Chapter. He publishes articles on his personal blog and is a volunteer science writer for MRS Bulletin. He has given several invited talks about leadership and communication skills and has encouraged students of Saudi universities to pursue science and engineering as their career. Recently, he organized the “Academic Writing” symposia during the 2016 MRS Fall Meeting in Boston. In his free time, he enjoys reading Oriental philosophy.

Abstract:

Organic-inorganic hybrid lead halide perovskite semiconductors have attracted a great deal of attention because of their remarkable optoelectronic properties which make them potentially suitable as active materials in photovoltaics, light emission, and photodetection. The key reason for its popularity is that it can yield good semiconductor properties despite being solution processed in ambient conditions and requires no vacuum or excessive heating. To date, the most efficient perovskite solar cells have been fabricated using spin coating, for which several ink and solvent engineering methods have been developed and perfected. However, this is a wasteful process which cannot be easily scaled up to continuous large area fabrication, where existing solvent engineering methods, such as anti-solvent dripping, are also unlikely to work. Here we compare the ink solidification and film formation mechanisms of CH₃NH₃PbI₃ in DMF by spin-coating versus blade-coating using in-situ time-resolved optical metrology and x-ray scattering. We show signifi cant differences in the process kinetics and formation of complex intermediate phases between the two processes at room and intermediate temperatures. To overcome these challenges in the context of blade coating, the sample is heated during deposition. We observe high-quality film formation for T > 100^oC, namely in conditions which inhibit the formation of the crystalline intermediate complex phases. In doing so, we achieve fast and direct formation of the perovskite phase with solar cells yielding PCE > 17%.

Biography:

Dr. Shih-Feng Chou is an Assistant Professor in the Department of Mechanical Engineering at The University of Texas at Tyler. He completed his PhD from Auburn University in 2011 followed by working as a research associate at Dartmouth College from 2012 to 2013 and a senior fellow at University of Washington from 2014 to 2016. He has expertise in fabrication of electrospun nanofi bers and evaluation of their mechanical and pharmaceutical properties. His goal is to inform the field on how to decouple mechanical performance and drug release behaviors of implantable biomaterials.

Abstract:

Electrospun Nano fibers are advantageous in drug loading efficiency with the ability to tune release rates based on polymer compositions. As a result, the mechanical behaviors of the Nano fibers may be signifi cantly aff ected by polymer compositions and drug loading. However, effects of drug loading on the mechanical properties and release behaviors of fi ber-based delivery system have not been fully investigated. Here, we studied the mechanical behaviors and pharmaceutical performance of blend polycaprolactone (PCL) and poly(D,L-lactic-co-glycolic) acid (PLGA) Nano fibers at various blend ratios with drug loading up to 40 wt.%. Results from uniaxial tensile tests suggested that Nano fibers made from various PCL/PLGA blends and drug loadings exhibited strong drug-polymer interactions. Average Young’s moduli and tensile strength of blank PCL/PLGA Nano fibers gradually increased with increasing PLGA contents in the blend Nano fibers. However, TFV loaded Nano fibers revealed a different trend in mechanical properties as comparing to blank Nano fibers, indicating the eff ects of drug-polymer interactions. In particular, PCL/PLGA 20/80 Nano fi bers received minimal changes in mechanical properties due to off setting effects in drug-polymer interactions at drug loading up to 40 wt.%. Tensile samples collected from the release media at predetermined time points showed signifi cant decreases in average Young’s modulus and tensile strength as compared to the blank Nano fibers. The additional loss of mechanical properties was associated with drug release and biodegradation of polymer matrix. Interestingly, TFV release rates increased in prestretched Nano fibers. Mechanical assessments on drug partition in PCL/PLGA Nano fibers suggested higher drug content in the PCL phase than in the PLGA phase. This study contributes signifi cantly to the understanding of drug-polymer interactions in electrospun drug-eluting Nano fibers and provides important information for implantable therapeutic biomaterials in future clinical applications.

Biography:

Bheeshma P Singh is working as SERB Indo-USA Post-doctoral fellow since January 2017 in Dept. of Chemistry at University at Buffalo, SUNY in the group of Prof. Paras N Prasad. His expertise mainly includes the nanomaterials synthesis and its bimodal applications such as efficient NIR to NIR biomarkers, ferro fluid based hybrid nanostructure for hyperthermia in cancer therapy, LEDs and all inorganic perovskite quantum dots for display applications.

Abstract:

CaWO₄:Tm³⁺, Yb³⁺, Li⁺ nano-phosphors with intense NIR to NIR (excitation by 980 nm, emission at ~800 nm) up conversion were synthesized by a facile polyol route. The nanoparticles were of the order of ~20 to 60 nm. The XRD patterns confirmed a single-phase tetragonal scheelite structure having space group I41/a, irrespective of doping of small amounts of RE³⁺ and alkali ions. The incorporation of Li+ ions altered the crystal field symmetry around the Tm³⁺ ions, which increased the f–f transition probabilities of the RE³⁺ ions, and thus increased the up conversion intensities. Compared with CaWO₄:Tm³⁺, Yb³⁺, the NIR to NIR up conversion emission intensity of 10 mol% Li⁺ substituted CaWO₄:Tm³⁺, Yb³⁺ nanocrystals increased by 20-fold and can be pumped by ~1mW power 980 CW laser. The brightest CaWO₄:Tm³⁺, Yb³⁺, Li⁺ nano-phosphor was applied for non-invasively visualizing the tumors in nude mice and successfully detected deep tumors in the thigh muscles. Results were based on oxide based UCNPs used for in vivo NIR-to-NIR bio-imaging which opens the window of achieving improved features using non-fl uoride based UCNPs for bio-imaging.

Biography:

Sam Solomon is working as an Associate Professor in the Department of Physics, Mar Ivanios College, and Thiruvananthapuram, India. He has MSc in Physics and PhD in microwave materials. He received the Junior Research Fellowship from the Council of Scientifi c and Industrial Research - India in 1992, Dr. S Vasudev award for the best major research project from the Council of Science and Technology in 2008 and the Post-doctoral Research Award from the University Grants Commission in 2009. He was selected by the University of Kerala for the Commonwealth Fellowship in 2005. He has 83 papers in reputed journals and more than 50 conference presentations. He supervised six PhD and is a reviewer of Elsevier and Springer publications.

Abstract:

Solid oxide fuel cells (SOFCs) are a class of fuel cells characterized by the use of a solid material as the electrolyte. SOFCs use a solid electrolyte to conduct negative oxygen ions from the cathode to the anode. The electrochemical oxidation of the oxygen ions with hydrogen or carbon monoxide thus occurs on the anode side. The purpose of this presentation is to discuss the synthesis and characterization methods of nanomaterials for electrolytes in solid oxide fuel cells.

Synthesis: One of the efficient methods for the synthesis of nano particles is the modified combustion technique. In this method stoichiometric amounts of chemicals are made in to a solution and heated. The solution boils and undergoes dehydration followed by decomposition leading to a smooth deflation producing foam. On persistent heating, the foam gets auto-ignited due to self-propagating combustion, giving a voluminous fluffy nanopowder. The obtained powder is annealed in oxygen atmosphere below 700^oC to eliminate the trace amount of organic impurity that may remain in the sample.

Characterization: Structure of the as-prepared powder can be identifi ed by the powder X-ray diff raction (XRD) technique and the particle size using transmission electron microscopy. The powder can be pressed into disc pellets of thickness 2 mm using a hydraulic press with a pressure of 100 MPa, and then sintered at optimized temperatures. The surface morphology of the sample is analyzed using scanning electron microscopy (SEM). The impedance spectroscopic study is carried out by making the pellet in the form of a disc capacitor.

Conclusion & Significance: The impedance spectroscopic studies establish the feasibility of the materials to use as an electrolyte in SOFCs.

Biography:

Clederson Paduani is currently working as an Associate Professor at Universidade Federal de Santa Catarina in Florianópolis, SC, Brazil. He has been working with DFT calculations in clusters, solids and nanostructures, after completing his Post-doctoral degree at CNRS, Grenoble, UCSC, CA, VCU, VA, and UPenn, PA.

Abstract:

Hydrogen, as an energy carrier, is nowadays considered as one of the best alternatives for mobile and stationary power sources for both propulsion and fuel cells. However, one of the major drawbacks of this technology is the problem of storing hydrogen safely, since in liquid and gas form, this demands high pressure or cryogenic reservoirs. An alternative is the use of solid state hydrogen storage, wherein the light metal hydrides represent a promising solution. However, since these are usually highly stable compounds, where the hydrogen atoms are held by strong covalent bonds, high temperatures are required for the hydrogen desorption. In order to surpass this difficulty the addition of catalysts has been considered, such as transition metals and nanostructured agents. In this study first, principle calculations based on density functional theory are performed to investigate the role of catalysts in dehydrogenation from clusters of light metal hydrides. It is shown that the addition of titanium and nanostructured carbonaceous catalysts contributes for a significant gain in the energy cost for hydrogen desorption from the metal hydrides. The combined addition of titanium with carbon fullerenes is even more beneficial for decreasing the energy cost of dehydrogenation. This effect is confirmed for different metal hydrides like alanates and boranates. For example, the calculated energy cost for H-removal from the magnesium boro-hydride is 4.18 eV, which decreases to 4.08 eV upon the addition of the fullerene C60, and to 3.32 eV in the presence of C67. The combined addition of Ti and these fullerenes lead to a decrease of energy cost for the H-removal to 4.04 eV and 2.78 eV, respectively. The energetics of dehydrogenation is also investigated in super-halogen clusters of light metal hydrides, and the results show that the hydrogen release is substantially less energy demanding in these highly reactive moieties. Results of van der waals-corrected DFT calculations show a rather significant gain in the energy cost for H desorption with the addition boron-doped fullerene catalysts. In the source of this effect is the disturbance introduced in the distribution of bonding charge upon the hybridization of states in the interplay between the hydride cluster and the fullerene with a consequent weakening of the hydrogen bonds, leading therein to an enhanced kinetics for the hydrogen release.

Biography:

Chika Anthony Okonkwo has his expertise in products development and production with acquired knowledge in an interrelated electromechanical technology and chemical, and bio chemical engineering. This current cost-effective and high specifi c capacitance product enhancement is supplementary contribution out of numerous conceptualized, designed, and fabricated products that solve problems in energy conversion/storage and materials processing. These achievements accounted for his years of experience in research institute (National Agency for Science and Engineering Infrastructures NASENI Abuja Nigeria) and doctoral research in chemical and biochemical engineering Xiamen University China. Still, he is very optimistic for functional energy material from biomasses for high efficiency of solar cells and high specific capacitance of supercapacitor.

Abstract:

Statement of the Problem: High ions storage target for supercapacitors still suffer from limited mesopores which hampers accommodation of most ionic sizes and also slows competitive/huge commercialization of electrochemical double layer capacitors especially where high power and rapid responses are necessary. Mesopores as indispensable factor of high ions storage, attract many diverse materials in researches over decades for this reason to improve specific capacitance and directly obtain high energy and power densities. Carbonaceous materials or its composites have shown that due to inherent/intrinsic adjustable property, mesopores are high predictable in carbon materials especially in variable shape/structural forms which usually improve by activation with potassium hydroxide (KOH). However, dual shape/structure by simple cost-effective preparation method (salt encapsulated sand template) has not been previously studied. This study centers on describing the interstice/ intramesopores dual form in a systematic steps sand induces surface roughness which metamorphous into honeycomb-shape/flakes carbon.

Methodology & Th eoretical Orientation: Typical acid anhydrous decomposition was employed to produce silicon carbide particles from the sand to induce rough surface on carbon flakes during the castor seed shell break down. The residual acid in the carbon was deprotonated by hydrothermal process to prevent acid salt formation in the presence of potassium hydroxide during activation process and also to reduce the formation of water molecules that may inhibit anhydrous KOH activation of the carbon. Imperative porosity characterization, structural/functional group investigation, and fundamental shape morphology were conducted to compare the two major samples. Conventional graphite symmetric electrodes were prepared as electrochemical double layer capacitors in 6 M KOH electrolyte.

Findings: The interstice / intra-mesopores mixture consists of high specific surface area of fl akes and honeycomb-shape carbon required to boast the mesopores porosity. N2 adsorption-desorption curve shows type IV isotherm to confirm the presence of mesopores, wherefore related dV/dD particle distribution shows predominating mesopores range (2–50 nm) inset. Energy transmittance across the sample molecules shows effect of dual molecular related shapes of carbon consistently across the FTIR spectra. Oxygen-containing functional groups content satisfi es the conditions for surface wettability and enhancement of ions transfer rate as represented in XPS chemical state. As supercapacitors electrode, the superior sample exhibited high specific capacitance (481 Fg-1) in 6 M KOH as electrolyte. Almost no decay occurred aft er charging/discharging test of 15000 cycles and the capacitance retention remains 96 %.

Conclusion & signifi cance: Indeed the degree of improvement in this study really shows that ions storage largely depends on mesopores to make high specific capacitance in the right context of better carbonaceous materials. This template decomposition of castor seed shell is quite promising, however more organic carbonaceous or composites are necessarily good approach to achieving the expectancy of ultra-high specifi c capacitance of supercapacitors.

Biography:

Dr. Mazharul M Islam has been working as senior research fellow at the Mulliken Center for Theoretical Chemistry of the University of Bonn Germany. He has got the expertise on theoretical modeling using various first principles DFT approaches. His interest of research activities has covered a wide variety of areas such as the ion conductivity in solid state materials having applications in green energy sources, the investigation of photocatalytic activities of TiO₂ due to its various industrial applications, the modeling of basic mechanisms of corrosion processes of metallic materials during their applications in construction, power generation etc, and the characterization of mesoporous oxide supported metal oxide catalysts having applications in industries. He was awarded with couple of honors and awards, various funding and huge number of collaborations in his career. He has published 3 scholarly books, 2 scholarly book chapters and 53 articles in peer reviewed journals so far.

Abstract:

Li-ion batteries (LIBs) have a great combination of high energy and power density capacities, which has made the LIB technology as the prime choice for portable electronics, power tools, and hybrid/full electric vehicles. The electrochemical performance of LIBs strongly depends on the electrode properties. The conventional Li-ion batteries use Li metal and carbonbased materials, typically graphite, as anode materials. However their applications are limited due to safety issues caused by dendrites formation. Therefore alternative anode materials are employed for the next generation LIBs which cover titanium oxide based materials as well as alloying/de-alloying materials with Si. In the present contribution, the stoichiometric and defect properties of lithium titanim oxides and various LixSiy compounds are investigated theoretically using the first-principles density functional theory (DFT) methods. We have considered two diff erent Li₂Ti₃O₇ structures: ramsdellite and layered types. In ramsdellite Li₂Ti₃O₇ Li⁺ can migrate along the ‘one dimensional channel’ or along crystallographic ac plane. Our calculated EA for Li⁺ diffusion in the one dimensional channel ranges from 0.20−0.92 eV and that in the ac plane ranges from 0.30−0.85 eV. However due to the large energy difference between the initial and final stages for Li diffusion in the case of ac plane shows that these pathways are kinetically prohibited. Therefore, the ramsdellite Li₂Ti₃O₇ is a qasi-one-dimensional ion conductor. In the layered Li₂Ti₃O₇, Li migrates along the crystallographic b direction by a vacant tetrahedral cite as well as along the ab plane in a direct pathway. The ab-plane migration is the most likely as it has a smaller activation barrier (0.4 eV) compared to the tetrahedral migration pathway (0.95 eV). Recent studies have provided evidence for the formation of various stable Li silicide crystalline phases such as LiSi, Li₄.7Si₂, Li₁₂Si₇, Li₇Si₃, Li₁₃Si₄, Li₁₅Si₄, and Li₂₂Si₅ during lithiation. In the present study, we have studied LiSi and Li₁₃Si₄ in order to search for a fast Li ion conductor. Our study shows that the interlayer interactions due to the van der Waals (vdW) forces play a key role for the structure and energetic properties of LixSiy materials. In case of LiSi, Li migrates to the 1st and 2nd nearest distance by a Li point defect. The activation energy for the both possible pathways range between 0.2 to 0.25 eV, indicating a very fast ion conduction in LiSi compounds. On the other hand, Li migration in Li13Si4 is slightly more complex. Li migrates either in a direct migration pathway or by a tetrahedral pathway. The activation energy for the direct migration pathway is 0.65 eV whereas that for the tetrahedral pathway is 0.75 eV. Therefore we conclude that Li₁₃Si₄ is slower ionic conductor than LiSi.

Biography:

Hussein Alrobei is a Ph.D. student under the supervision of Manoj K Ram. He has background in the fi eld of photo electrochemical, advanced materials, polymers and energy. He has been involved on photo electrochemical properties on various metal oxides, polymers and conducting polymers, and recently his patent on Nano-hybrid structured regioregular polyhexylthiophene blend films for production of photo electrochemical energy has been approved.

Abstract:

The purpose of this paper is to present a literature review of a sampling of the current available research documents that discuss experimental and potential industrial processes of producing gaseous hydrogen fuel utilizing various nanotechnology products and techniques. While the production of essentially pure hydrogen gas (H2) is not a new concept and has been used in laboratories and industry for a number of decades, the development of nanotechnology and its unique products has opened the door for an explosion of new research to establish processes for making hydrogen in ways that are much more environmentally conscious, safer, and potentially will allow production from totally renewable sources. The current and recent research includes work done producing hydrogen from a number of sources with water being the source used most. The promise of potentially producing sufficient hydrogen to meet the world energy needs using water as the source for the hydrogen and solar energy as the source of the power to fuel the production is reason enough to justify the investment in the research into this field of study. Because of the attractiveness of this approach and the significant amount of work being done with water and solar, we concentrate our review in that area. We touch upon other methods but remain with the water/solar concentration. The common theme in all the papers reviewed is the utilization of nanotechnology in all of the research looked at.