College of Science and Engineering
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Browsing College of Science and Engineering by Author "Demirocak, Dervis Emre"
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Item Degradation Mechanisms in Li-ion Batteries: A State-of-the-Art Review(John Wiley & Sons, Ltd., 2017) Kabir, M. M.; Demirocak, Dervis EmreOne of the most prominent energy storage technologies which are under continuous development, especially for mobile applications, is the Li‐ion batteries due to their superior gravimetric and volumetric energy density. However, limited cycle life of Li‐ion batteries inhibits their extended use in stationary energy storage applications. To enable wider market penetration of Li‐ion batteries, detailed understanding of the degradation mechanisms is required. A typical Li‐ion battery comprised of an active material, binder, separator, current collector, and electrolyte, and the interaction between these components plays a critical role in successful operation of such batteries. Degradation of Li‐ion batteries can have both chemical and mechanical origins and manifests itself by capacity loss, power fading or both. Mechanical degradation mechanisms are associated with the volume changes and stress generated during repetitive intercalation of Li ions into the active material, whereas chemical degradation mechanisms are associated with the parasitic side reactions such as solid electrolyte interphase formation, electrolyte decomposition/reduction and active material dissolution. In this study, the main degradation mechanisms in Li‐ion batteries are reviewed.Item Development of high storage capacity complex hydrides for reversible hydrogen storage(2013) Christelle, B. B.; Srinivasan, S. S.; Egiebor, N. O.; Demirocak, Dervis Emre; Wang, X. S.; Ma, S.In this study, novel light weight complex hydrides for reversible hydrogen storage are developed and synthesized. Metal hydrides are generally known to have a good hydrogen storage capacity but possess slow kinetics, irreversibility and high activation energy barriers. Therefore, metal hydrides often require very high temperature (>350°C) to release hydrogen. This behavior makes their wide usage in hydrogen storage applications difficult. We have extensively employed a unique synthesis approach of solid state mechano-chemical process, via high energy ball milling. From this synthesis process, eight new complex hydrides have been prepared and each of them are characterized using high pressure Sievert’s type volumetric apparatus, residual gas or mass spectrometric analysis (RGA/MS), and the Fourier transform infrared spectroscopy (FT-IR) to determine their chemical and hydrogen sorption properties. The as-synthesized new complex hydrides with light weight elements such as lithium, magnesium, boron, aluminum etc. have demonstrated excellent physical and chemical behavior in terms of lower activation energies, higher reversible hydrogen storage capacity (i.e., ≥6wt%) at operating temperatures below 350°C, and faster reaction kinetics than their conventional metal hydride counterparts. Unfortunately, the residual gas analysis of these materials have revealed the evolution of some undesirable and toxic gases such as ammonia (NH3) and di-borane (B2H6) in addition to the release of hydrogen. The release of these toxic gases was eventually suppressed by catalysts added and destabilization procedures are mentioned explicitly. Among the various complex hydrides developed, two novel systems namely, Li-nMg-B-N-H and BNH6-nMgH2 have shown distinguishing properties as efficient reversible hydrogen storage materials.Item A Fuzzy Based Model for Standardized Sustainability Assessment of Photovoltaic Cells(2018) Salim, M. B.; Demirocak, Dervis Emre; Barakat, N.In this paper, a new environmental sustainability indicator (ESI) is proposed to evaluate photovoltaic (PV) cells utilizing Life Cycle Analysis (LCA) principles. The proposed indicator is based on a model that employs a fuzzy logic algorithm to combine multiple factors, usually used in multiple LCAs, and produce results allowing a comprehensive interpretation of LCA phase sub-results leading to standardized comparisons of various PV cells. Such comparisons would be essential for policymakers and PV cell manufacturers and users, as they allow for fair assessment of the environmental sustainability of a particular type of PV with multiple factors. The output of the proposed model was tested and verified against published information on LCAs related to PV cells. A distinct feature of this fuzzy logic model is its expandability, allowing more factors to be included in the future, as desired by the users, or dictated by a new discovery. It also provides a platform that can be used to evaluate other families of products. Moreover, standardizing the comparison process helps in improving the sustainability of PV cells through targeting individual relevant factors for changes while tracking the combined final impact of these changes on the overall environmental sustainability of the PV cell.Item Hydrogen Storage in the Li-Mg-N-H System–Ammonia Suppression By Addition of Ru Doped Single Walled Carbon Nanotubes(2015-07-11) Demirocak, Dervis Emre; Srinivasan, S. S.; Kuhn, J. N.; Muralidharan, R.; Li, X.; Goswami, D. Y.; Stefanakos, E. K.Abstract not available.Item Hydrogen Storage Technologies in Nanostructured Materials for NextGeneration Energy Storage and Conversion(2017-01) Demirocak, Dervis EmreHydrogen is considered as one of the promising alternative fuels to replace oil, but its storage remains to be a significant challenge. The main hydrogen storage technologies can be broadly classified as physical, chemical, and hybrid methods. The physical methods rely on compression and liquefaction of hydrogen, and currently compressed hydrogen storage is the most mature technology that is commercially available. The chemical methods utilize materials to store hydrogen, and hydrogen can be extracted by reversible (on-board regenerable) or irreversible (off-board regenerable) chemical reactions depending on the type of material. The hybrid methods take advantage of both physical and chemical storage methods. The most prominent hybrid method is the cryo-adsorption hydrogen storage which utilizes physisorption-based porous materials. In this chapter, all of the main hydrogen storage technologies are discussed in detail along with their limitations and advantages.Item In-situ atomic force microscopy analysis of morphology and particle size changes in LiFePO4 cathode(2014) Demirocak, Dervis Emre; Bhushan, B.Li-ion batteries offer great promise for future plug-in hybrid electric vehicles (PHEVs) and pure electric vehicles (EVs). One of the challenges is to improve the cycle life of Li-ion batteries which requires detailed understanding of the aging phenomenon. In situ techniques are especially valuable to understand aging since it allows monitoring the physical and chemical changes in real time. In this study, in situ atomic force microscopy (AFM) is utilized to study the changes in morphology and particle size of LiFePO4 cathode during discharge. The guidelines for in situ AFM cell design for accurate and reliable measurements based on different designs are presented. The effect of working electrode to counter electrode surface area ratio on cycling data of an in situ cell is also discussed. Analysis of the surface area change in LiFePO4 particles when the cell was cycled between 100% and 70% state of charge is presented. Among four particles analyzed, surface area increase of particles during Li intercalation of LiFePO4 spanned from 1.8% to 14.3% indicating the inhomogeneous nature of the cathode surface.Item Investigation of Catalytic Effects and Compositional Variations in Desorption Characteristics of LiNH2-nanoMgH2(2017) Srinivasan, S. S.; Demirocak, Dervis Emre; Goswami, D. Y.; Stefanakos, E. K.LiNH2 and a pre-processed nanoMgH2 with 1:1 and 2:1 molar ratios were mechanochemically milled in a high-energy planetary ball mill under inert atmosphere, and at room temperature and atmospheric pressure. Based on the thermogravimetric analysis (TGA) experiments, 2LiNH2-nanoMgH2 demonstrated superior desorption characteristics when compared to the LiNH2-nanoMgH2. The TGA studies also revealed that doping 2LiNH2-nanoMgH2 base material with 2 wt. % nanoNi catalyst enhances the sorption kinetics at lower temperatures. Additional investigation of different catalysts showed improved reaction kinetics (weight percentage of H2 released per minute) of the order TiF3 > nanoNi > nanoTi > nanoCo > nanoFe > multiwall carbon nanotube (MWCNT), and reduction in the on-set decomposition temperatures of the order nanoCo > TiF3 > nanoTi > nanoFe > nanoNi > MWCNT for the base material 2LiNH2- nanoMgH2. Pristine and catalyst-doped 2LiNH2-nanoMgH2 samples were further probed by X-ray diffraction, Fourier transform infrared spectroscopy, transmission and scanning electron microscopies, thermal programmed desorption and pressure-composition-temperature measurements to better understand the improved performance of the catalyst-doped samples, and the results are discussed.Item Investigation of polyaniline nanocomposites and cross-linked polyaniline for hydrogen storage(Advanced Materials Research, 2012) Demirocak, Dervis Emre; Kuravi, S.; Ram, M. K.; Jotshi, C. K.; Srinivasan, S. S.; Kumar, A.; Goswami, D. Y.; Stefanakos, E. K.One of the biggest challenges for the commercial application of existing hydrogen storage materials is to meet the desired high volumetric and gravimetric hydrogen storage capacity and the ability to refuel quickly and repetitively as a safe transportation system at moderate temperature and pressure. In this work, we have synthesized polyaniline nanocomposites (PANI-NC) and hypercrosslinked polyaniline (PANI-HYP) materials to provide structure and composition which could meet the specific demands of a practical hydrogen storage system. Hydrogen sorption measurements showed that high surface area porous structure enhanced the storage capacity significantly at 77.3K and latm (i.e., 0.8wt% for PANI-HYP). However at 298K, storage capacity of all samples is less than 0.5wt% at 70 bar. Hydrogen sorption results along with the surface area measurements confirmed that hydrogen storage mechanism predominantly based on physisorption for polyaniline.Item Investigation of polyaniline nanocomposites and cross-linked polyaniline for hydrogen storage(14th International Conference on Advances in Materials & Processing Technologies, 2011-07-13) Demirocak, Dervis Emre; Kuravi, S.; Ram, M. K.; Jotshi, C. K.; Srinivasan, S. S.; Kumar, A.; Goswami, D. Y.; Stefanakos, E. K.Abstract not available.Item Metal Hydrides used for Hydrogen Storage, in Nanostructured Materials for Next-Generation Energy Storage and Conversion(2017) Demirocak, Dervis Emre; Srinivasan, S. S.This chapter discusses about metal hydride technologies for on-board reversible hydrogen storage applications. The metal hydrides such as intermetallic alloys and solid solutions have interstitial vacancies where atomic hydrogen is absorbed via an exothermic reaction; however, by endothermic path, the metal hydride desorbs the hydrogen reversibly at ambient to moderate temperatures. In any case, the hydrogen storage capacity of interstitial metal hydrides is rather low (<2 wt%) due to limitation in the crystal structure and unit cell volume. In order to increase the hydrogen storage densities, transition metal assisted Mg-based hydrides and other nontransition metal complex hydrides have been reviewed as part of exploratory studies which have been aligned with the US Department of Energy 2020 technical targets. A number of useful characterization techniques (X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, thermo gravimetric analysis, differential scanning calorimetry, Fourier transform infrared spectroscopy) and hydrogen storage property measurements (kinetics, pressure-composition isotherms, thermal programmed desorption, gas chromatography-mass spectrometry) have been employed for the investigation of some candidate materials.Item A novel nitrogen rich porous aromatic framework for hydrogen and carbon dioxide storage(2013) Demirocak, Dervis Emre; Ram, M. K.; Srinivasan, S. S.; Goswami, D. Y.; Stefanakos, E. K.A nitrogen rich, p-phenylenediamine based, porous aromatic framework (NPAF) with 1790 m2 g−1 BET surface area has been synthesized by using a Yamamoto coupling technique. The NPAF has shown a hydrogen uptake of 1.87 and 0.33 wt% at 77 K per 1 atm and 298 K per 80 bar, respectively. The CO2 uptake and selectivity of the NPAF at 273 K per 1 atm is 3.64 mmol g−1 and 48, respectively.Item Passive Design Strategies to Minimize Building Energy Use in Hot and Humid Climates(2017-06-26) Demirocak, Dervis EmreAbstract not available.Item Performance of a Solar Thermal Adsorption Cooling System Based on Metal Organic Frameworks in Texas(2016-06-26) Demirocak, Dervis Emre; Kabir, M. M.In this study, the performance of the basic adsorption cooling system based on a metal organic framework, HKUST-1, is investigated and compared with that of a zeolite based system. The optimal regeneration temperature to maximize the COP of the HKUST-1-water based basic adsorption cycle is presented. The solar-thermal powered adsorption chiller model running on the HKUST-1-water based basic adsorption cycle is developed and integrated into a building model (two-story house located in Kingsville, Texas) in TRNSYS. The yearly performance of the integrated system is simulated by employing the latest typical meteorological year data (TMY3) for Kingsville, Texas. The solar fraction of the solar-assisted adsorption cooling system is also presented.Item Probing the aging effects on nanomechanical properties of a LiFePO4 cathode in a large format prismatic cell(Elsevier B.V, 2015) Demirocak, Dervis Emre; Bhushan, B.Li-ion batteries offer great promise for the future of energy storage due to their superior gravimetric and volumetric energy density. One of the challenges in promoting their expanded use is to improve the cycle life of Li-ion batteries. This requires detailed understanding of the aging phenomenon. The aging mechanism of Li-ion batteries can have both chemical and mechanical origins. While the chemical degradation mechanisms have been studied extensively, mechanical degradation mechanisms have received little attention so far. In this study, we probe the changes in mechanical properties of a LiFePO4 cathode in a large format prismatic cell. Results indicate that mechanical degradation increases by aging; in addition, local degradation is observed in the composite cathode. Implications of the degradation in mechanical properties on binder degradation are discussed in detail.Item Probing the Aging Effects on Nanomechanical Properties of a Thin Film LiFePO4(2016-06-19) Demirocak, Dervis Emre; Bhushan, B.Li-ion batteries offer great promise for the future of energy storage due to their superior gravimetric and volumetric energy density. One of the challenges in promoting their expanded use is to improve the cycle life of Li-ion batteries. This requires detailed understanding of the aging phenomenon. The aging mechanism of Li-ion batteries can have both chemical and mechanical origins. While the chemical degradation mechanisms have been studied extensively, mechanical degradation mechanisms have received little attention so far. In this study, we probe the changes in mechanical properties of a LiFePO4 cathode in a large format prismatic cell. Results indicate that mechanical degradation increases by aging; in addition, local degradation is observed in the composite cathode. Implications of the degradation in mechanical properties on binder degradation are discussed in detail.Item Reversible Hydrogen Storage Characteristics of Catalytically Enhanced Ca(Li)-nMg-B-N-H System(American Physical Society, 2013-04-13) Demirocak, Dervis Emre; Srinivasan, S. S.; Sharma, P.; Goswami, D. Y.; Stefanakos, E. K.Abstract not available.Item Reversible Hydrogen Storage in the Li-Mg-N-H System – The effects of Ru doped single walled carbon nanotubes on NH3 emission and kinetics(Elsevier Ltd, 2013) Demirocak, Dervis Emre; Srinivasan, S. S.; Ram, M. K.; Kuhn, J. N.; Muralidharan, R.; Li, X.; Goswami, D. Y.; Stefanakos, E. K.In this study, the LiNH2–MgH2 (2:1.1) complex hydride system (Li–Mg–N–H is investigated in terms of hydrogen ab/desorption kinetics and the concomitant NH3 emission levels. By selecting more intense ball milling parameters, the hydrogen ab/desorption kinetics were improved and the NH3 emission reduced. However, it is shown that NH3 emission cannot be completely eliminated during ball milling. Single walled carbon nanotubes (SWCNTs) and 20 wt.% Ru doped SWCNTs are utilized as catalysts to study their effects on NH3 emission and kinetics characteristics of the Li–Mg–N–H system. The SWCNT doped sample did not show any kinetics improvement, whereas the SWCNT-20Ru doped sample showed similar kinetics performance as that of the base sample. More importantly, the presence of SWCNT increased the NH3 emission as compared to the base sample. On the other hand, SWCNT-20Ru doping reduced the NH3 emission compared to the SWCNT doping, but did not eliminate it completely. As revealed from the mass spectrometry signals, the SWCNT-20Ru catalyst starts to decompose NH3 at a temperature as low as 200 °C.Item A Review on Nanocomposite Materials for Rechargeable Li-ion Batteries(2017) Demirocak, Dervis Emre; Srinivasan, S. S.; Stefanakos, E. K.Li-ion batteries are the key enabling technology in portable electronics applications, and such batteries are also getting a foothold in mobile platforms and stationary energy storage technologies recently. To accelerate the penetration of Li-ion batteries in these markets, safety, cost, cycle life, energy density and rate capability of the Li-ion batteries should be improved. The Li-ion batteries in use today take advantage of the composite materials already. For instance, cathode, anode and separator are all composite materials. However, there is still plenty of room for advancing the Li-ion batteries by utilizing nanocomposite materials. By manipulating the Li-ion battery materials at the nanoscale, it is possible to achieve unprecedented improvement in the material properties. After presenting the current status and the operating principles of the Li-ion batteries briefly, this review discusses the recent developments in nanocomposite materials for cathode, anode, binder and separator components of the Li-ion batteries.Item Simulation of the Advanced Adsorption Cooling Cycles for Metal Organic Frameworks(2017-11-03) Demirocak, Dervis Emre; Kolatkar, Y.Abstract not available.Item Spillover enhancement for hydrogen storage by Pt doped hypercrosslinked polystyrene(Elsevier Ltd, 2012) Demirocak, Dervis Emre; Srinivasan, S. S.; Kumar, A.; Goswami, D. Y.; Stefanakos, E. K.High surface area physisorption materials are of interest for room temperature (RT) hydrogen storage enhancement by spillover. In this study, six different commercially available hypercrosslinked polystyrenes were screened considering the specific surface area, average pore size, pore volume, and adsorption enthalpy. MN270 was selected mainly due to its high surface area and narrow pores for investigation of the spillover enhancement at RT. Two different platinum (Pt) doped MN270 samples were prepared by wet impregnation (MN270-6wt%Pt) and bridge building technique (MN270-Bridged) with an average Pt particle size of 3.9 and 9.9 nm, respectively, as obtained from X-ray diffraction analysis. Pt doping altered the surface property of MN270, and reduced the nitrogen and hydrogen uptake at 77 K and 1 atm due to pore blocking. The RT hydrogen uptake at 100 atm demonstrated a 10% enhancement (0.36 wt. %) for MN270-Bridged compared to pristine MN270, but did not show any enhancement for MN270-6wt%Pt under the same conditions. The hydrogen uptake of MN270-Bridged has little value for practical applications yet showed the effectiveness of the bridge building technique.