Academic literature on the topic 'Rock Salt Cathode Materials'

Abstract Nowadays, general energy storage and electric vehicles urgently need to develop advanced lithium-ion batteries (LIB) with high specific energy and low cost, and one of the great challenges is to invent cheap cathode materials. Manganese-based cathode materials have been widely studied due to the low prices and high reserves of precursors, such as lithium-rich manganese-based (LMR) and Mn-based disordered rock-salt (DRX) cathodes. Inspired by the concept of layered-layered intergrown structure in LMR, we design a spinel-rock salt intergrown nano-composite. The as-developed cathode (Li1.7Ni0.12Mn1.48O4) shows a partially intergrown structure of spinel- and DRX-phases. Most importantly, the material enables the combination of the structural and electrochemical merits of the individual spinel and rock-salt phases, and it yields ultrahigh-capacity in comparison with the LMR or DRX and displays outstanding rate performance. It is hoped this novel intergrown cathode with low cost can inspire the design of advanced cathode for LIB.

Nowadays, many researchers have been studying on the layered rock salt-type structure as cathode materials for the lithium ion batteries. LiCoO2is the most commonly used cathode material but Co is costly and toxic. Thus, alternative cathode materials which are cheaper, safer and having higher capacity are required. Replacing Co with Ni offered higher energy density battery but it raised interlayer mixing or cation disorder that impedes electrochemical properties of batteries. This paper has reviewed some recent research works that have been done to produce better and safer cathode materials from the structural perspective.

The rechargeable lithium-ion batteries have been dominating the portable electronic market for the past two decades with high energy density and long cycle-life. However, applications of lithium-ion batteries in large-scale stationary energy storage are likely to be limited by the high cost and availability of lithium resources. The room temperature Na-ion secondary battery have received extensive investigations for large-scale energy storage systems (EESs) and smart grids lately due to similar chemistry of “rocking-chair” sodium storage mechanism, lower price and huge abundance. They are considered as an alternative to lithium-ion batteries for large-scale applications, bringing an increasing research interests in materials for sodium-ion batteries. Although there are many obstacles to overcome before the Na-ion battery becomes commercially available, recent research discoveries corroborate that some of the cathode materials for the Na-ion battery have indeed advantages over its Li-ion competitors. Layered oxides are promising cathode materials for sodium ion batteries because of their high theoretical capacities. In this publication, a review of layered oxides (NaxMO2, M = V, Cr, Mn, Fe, Co, Ni, and a mixture of 2 or 3 elements) as a Na-ion battery cathode is presented. O3 and P2 layered sodium transition metal oxides NaxMO2 are a promising class of cathode materials for Na secondary battery applications. These materials, however, all suffer from capacity decline when the extraction of Na exceeds certain capacity limits. Understanding the causes of this capacity decay is critical to unlocking the potential of these materials for battery applications. Single layered oxide systems are well characterized not only for their electrochemical performance, but also for their structural transitions during the cycle. Binary oxides systems are investigated in order to address issues regarding low reversible capacity, capacity retention, operating voltage, and structural stability. Some materials already have reached high energy density, which is comparable to that of LiFePO4. On the other hand, the carefully chosen elements in the electrodes also largely determine the cost of SIBs. Therefore, earth abundant-based compounds are ideal candidates for reducing the cost of electrodes. Among all low-cost metal elements, cathodes containing iron, chromium and manganese are the most representative ones. The aim of the article is to present the development of Na layered oxide materials in the past as well as the state of the art today.

Ti⁴⁺ and F⁻ co-dopants expand the lattice spacing of Ni-rich cathode materials and form ultra-thin rock salt phases on the surface of the cathode, thereby improving the electrochemical performance of lithium-ion batteries.

Cation disordered rock salts (DRX), a new class of cathode materials for Li ion batteries, have attracted lots of attention in recent years, due to their fascinatingly simple cubic structure, highly diverse composition, and great electrochemical performance. As cations in DRX are randomly distributed in a long-range, how the cations (Li and transition metal) are arranged in a shorter range is an intriguing question for the community of cathode materials research. In this work, we study the vibrational structure of a series of DRXs with well controlled compositions and revealed significant anisotropy of cation arrangements. Based on the results, we propose a scheme that describes how the structural anisotropy could exist in rock salt structures but shows an overall cubic Fm-3m diffraction pattern. Furthermore, we raise a model of Li transport based on the scheme we proposed, which complements the theory of Li percolation in DRX. The electrochemical behavior of the cathodes used in the study supports the model.

Disordered Li-excess rock salt (DRX) cathodes are a promising class of high capacity (and voltage) cathodes for next-generation Li-ion batteries. Compared to conventional Li-ion cathodes which are generally restricted to Co/Ni-based compositions with specific cation ordering, DRX materials have a wide compositional design space based on earth abundant metals such as Mn, Ti, Mo, Al, Zr, V, and Nb. Furthermore, Li-rich oxyfluoride DRX cathodes have demonstrated specific energies up to 1,000 Wh/kg which exceeds that of state-of-the-art layered LiNixMnyCo1-x-yO2 (NMC) cathodes (~700 Wh/kg). Despite such scientific advancements, widespread adoption of DRX cathodes has been hindered by several technical challenges. First, most of the high fluorine content DRX compositions are synthesized using mechano-chemical synthesis that has inherent limitation in scalability and maintaining a uniform particle-size and morphology. Further, DRX compositions have about 3-4 order lower electronic conductivity compared to layered cathodes requiring a high carbon loading in the electrode (up to 25%) compromising energy density. The focus of this talk will be on developing alternate synthesis method for Li-Mn rich DRX compositions. Specifically solid-state and sol-gel synthesis methods to produce DRX cathodes with the nominal composition Li1.2Mn0.4+xTi0.4-xO2-xFx (x = 0-0.3). Detailed advanced characterization (i.e., neutron total scattering and electron microscopy) and modelling efforts (i.e., Reverse Monte Carlo simulations) to understand how SRO impacts cathode performance will be presented. Different choice of precursors based on thermodynamic and kinetic consideration that minimizes formation of LiF impurity phases will be proposed. Acknowledgment This work was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Vehicle Technologies Office, under the Applied Battery Materials Program, of the U.S. Department of Energy under Contract No. DE-AC05-00OR22725

High-entropy materials with tailorable properties are receiving increasing interest for energy applications. Among them, (disordered) rock-salt oxyfluorides hold promise as next-generation cathodes for use in secondary batteries. Here, we study the degradation behavior of a high-entropy oxyfluoride cathode material in lithium cells in situ via acoustic emission (AE) monitoring. The AE signals allow acoustic events to be correlated with different processes occurring during battery operation. The initial cycle proved to be the most acoustically active due to significant chemo-mechanical degradation and gas evolution, depending on the voltage window. Irrespective of the cutoff voltage on charge, the formation and propagation of cracks in the electrode was found to be the primary source of acoustic activity. Taken together, the findings help advance our understanding of the conditions that affect the cycling performance and provide a foundation for future investigations on the topic.

Cation-disordered rock-salt cathode material is a promising material for next-generation lithium-ion batteries due to their extra-high capacities. However, the drawbacks of large first-cycle irreversible capacity loss, severe capacity decay, and lower discharge voltage have undoubtedly hindered their application in commercial systems. In this study, cation doping (Mo4+) and atomic layer deposition (ALD) techniques were used to synthetically modify the Li1.2Ti0.4Mn0.4O2 (LTMO) material to improve the cycling stability. First, the optimal Mo-doped sample (Mo01) with the best electrochemical performance among the different doping amounts was selected for further study. Second, the selected sample was subsequently coated with an Al2O3 layer by the ALD technique to further optimize its electrochemical performance. Results show that the LTMMO/24Al2O3 sample, under optimal conditions, could obtain a specific discharge capacity of up to 228.4 mAh g−1 after 30 cycles, which is much higher than that of the unmodified LTMO cathode material. Our work has provided a new possible solution to address some of the capacity fading issues related to the cation-disordered rock-salt cathode materials.

Growing demand for Lithium-ion batteries for electric transportation and grid-scale storage will inevitably put resource constraints in terms of availability of key critical battery materials such as cobalt, nickel, lithium, and graphite. Specifically limited global reserve of elements such as cobalt and nickel will lead to severe supply chain issues driving the cost and contributing to market uncertainty. Given such scenario, there has been a significant effort in the global research community to develop high performance battery materials derived from relatively earth abundant elements. The talk will highlight ongoing research at PI’s Laboratory and collaborators on developing cobalt-free disorder rock salt (DRX) cathodes for next generation Li-ion. Most practical Li-ion cathode materials have well-ordered structures (e.g., spinel, layered, olivine), while the DRX compounds do not require any cation ordering. Instead, Li transport is achieved by percolation through a cation-disordered within the dense crystalline rock salt structure. Since DRX compounds do not necessitate a layered structure, they do not necessarily require cobalt metal and can be synthesized from an extremely wide variety of common metals, including Ti, Mn, Ni, Al, Nb, Mo, V, Zr, etc. Therefore, such class of materials provides plenty of chemical options for cathode design for Li-ion. Another key enabling aspect for this class of cathodes is the role of fluorine in stabilizing the high voltage oxygen redox and capacity retention. The talk will focus specifically on synthesis and structural design of Li-Mn-Ti-OF based DRX compositions and pathways for improving high voltage redox and stability. This work performed at Oak Ridge National Laboratory is supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Vehicle Technologies Office, under the Applied Battery Materials Program, of the U.S. Department of Energy under Contract No. DE-AC05-00OR22725

Transition metals (TMs) are ‘elements whose atoms have partially filled d-shell, or which can give rise to cations with an incomplete d-shell’. In TMs, the d-shell overlaps with next higher s-shell. Most of the TMs exhibit more than one (multiple) oxidation states. Some TMs, such as silver and gold, occur naturally in their metallic state but, most of the TM minerals are generally oxides. Most of the minerals on the planet earth are metal oxides, because of large free energies of formation for the oxides. The thermodynamic stability of the oxides is determined from the Ellingham diagram. Ellingham diagram shows the temperature dependence of the stability (free energy) for binaries such as metal oxides. Ellingham diagram also shows the ease of reducibility of metal oxides. TM oxides of general formulas MO, M2O3, MO2, M2O5, MO3 are known to exist, many of them being the ultimate products of oxidation in air in their highest oxidation states. In addition, TM oxides also exist in lower oxidation states which are prepared under controlled conditions. The nature of bonding in these oxides varies from mainly ionic (e.g. NiO, CoO) to mainly covalent (e.g. OsO4). Simple binary oxides of the compositions, MO, generally possess the rock salt structure (e.g. NiO), while the dioxides, MO2, possess the rutile structure (e.g. TiO2); many sesquioxides, M2O3, possess the corundum structure (e.g. Cr2O3). TMs form important ternary oxides like perovskites (e.g. CaTiO3), spinels (e.g. MgFe2O4) and so on. In TM oxides, the valence (outer) d-shell could be empty, d0 (e. g. TiO2), partially filled, dn (1≤ n≤ 9) (e.g. TiO, VO, NiO etc.) or completely filled, d10 (e.g. ZnO, CdO, Cu2O etc.). The outer d electrons in TM oxides could be localized or delocalized. Localized outer d electrons give insulators/semiconductors, while delocalized/itinerant d electrons make the TM oxide ‘metallic’ (e.g. ReO3, RuO2). Partially filled dn states are normally expected to give rise to itinerant (metallic) electron behaviour. But most of TM oxides with partially filled d shell are insulators because of special electronic energy (correlation energy) involved in d electron transfer to adjacent sites. Such insulating TM oxides are known as Mott insulators (e. g. NiO, CoO etc.). Certain TM oxides are known to exhibit both localized (insulating) and itinerant (metallic) behaviour as a function of temperature or pressure. For example, VO2 shows a insulator–metal transition at ~340K. Similar transitions are also known for V2O3, metal-rich EuO and so on. The chemical composition and bonding of TM oxides, which determine the crystal and electronic structures, give rise to functional properties. Table 1 gives representative examples. Properties like ionic conductivity and diffusion are governed by both the crystal structure and the defect structure (point defects), whereas properties such as magnetism and electron transport mainly arise from the electronic structures of the materials. Accordingly, TM oxides provide a platform for exploring functional materials properties. Among the various functional materials properties exhibited by transition metal oxides, the present thesis is devoted to investigations of lithium ion battery cathodes, inorganic pigments and magnetic perovskites. Over the years, most of the lithium containing first row transition metal oxides of rock salt derived structure have been investigated for possible application as cathode materials in lithium ion batteries (LIBs). First major breakthrough in LIBs research was achieved by electrochemically deinserting and inserting lithium in LiCoO2. A new series of cathode materials for LIBs were prepared by incorporating excess lithium into the transition metal containing layered lithium oxides through solid solution formation between Li2MnO3–LiMO2 (M = Cr, Mn, Fe, Co, Ni), known as lithium-rich layered oxides (LLOs). LLOs exhibit improved electrochemical performance as compared to the corresponding end members and hence received significant attention as a potential next generation cathode materials for LIBs in recent times. LiCoO2 (R-3m) crystallizes in the layered α-NaFeO2 structure with the oxygens in a ccp arrangement. Li+ and Co3+ ions almost perfectly order in the octahedral sites (3a and 3b) to give alternating (111) planes of LiO6 and CoO6 octahedra. Table 1. Materials properties exhibited by representative TM oxides. Property Example(s) Ferroelectricity BaTiO3, PbTiO3, Bi4Ti3O12 Nonlinear Optical Response LiNbO3 Multiferroic response BiFeO3, TbMnO3 Microwave dielectric properties Ba3ZnTa2O9 Relaxor Dielectric Properties Pb3MgNb2O9, Colossal Magnetoresistance Tl2Mn2O7 Metallic ‘Ferroelectricity’ Cd2Re2O7 Superconductivity AOs2O6(A = K, Rb, Cs) Redox deinsertion/insertion of LiCoO2 lithium Photocatalysis/water splitting TiO2 Pigment Ca(1-x)LaxTaO(2-x)N1+x (yellow-red), YIn1-xMnxO3 (blue) Metallic Ferromagnetism CrO2 Antiferromagnetism NiO, LaFeO3 Zero thermal expansion ZrW2O8 The reversible capacity of LiCoO2 in common LIBs is relatively low at around 140 mA h g-1 (half of theoretical capacity), corresponding to: LiCo3+O2 → Li0.5Co3+0.5Co4+0.5O2 + 0.5Li+ + 0.5e– . Substitution of one or more transition metal ions in LiCOO2 has been explored to improve the electrochemical performance. The structure of LLOs is described as a solid solution or nano composite of Li2MnO3 (C2/m) and LiMO2 (R-3m). The electrochemical deinsertion/insertion behaviour of LLOs is complex and also not yet understood completely. The present thesis consists of four parts. After a brief introduction (Part 1), Part 2 is devoted to materials for Li-ion battery cathode, consisting of three Chapters 2.1, 2.2 and 2.3. In Chapter 2.1, we describe the synthesis, crystal structure, magnetic and electrochemical characterization of new LiCoO2 type rock salt oxides of formula, Li3M2RuO6 (M = Co, Ni). The M =Co oxide adopts the LiCoO2 (R-3m) structure, whereas the M = Ni oxide also adopts a similar layered structure related to Li2TiO3. Magnetic susceptibility measurements reveal that in Li3Co2RuO6, the oxidation states of transition metal ions are Co3+, Co2+ and Ru4+, whereas in Li3Ni2RuO6, the oxidation states are Ni2+ and Ru5+. Li3Co2RuO6 orders antiferromagnetically at ~10K. On the other hand, Li3Ni2RuO6 presents a ferrimagnetic behaviour with a Curie temperature of ~100K. Electrochemical Li-deinsertion/insertion studies show that high first charge capacities (between ca.160 and 180 mA h g−1) corresponding to ca.2/3 of theoretical capacity are reached albeit, in both cases, capacity retention and cyclability are not satisfactory. Chapter 2.2 presents a study of new ruthenium containing LLOs, Li3MRuO5 (M = Co and Ni). Both the oxides crystallize in the layered LLO type LiCoO2 (α-NaFeO2) structure consisting of Li[Li0.2M0.4Ru0.4]O2 layers. Magnetic susceptibility data suggest that the oxidation states of transition metals are Li3Co3+Ru4+O5 for the M = Co compound and Li3Ni2+Ru5+O5 for the M = Ni compound. Electrochemical investigations of lithium deintercalation–intercalation behaviour reveal that both Co and Ni phases exhibit attractive specific capacities of ca. 200 mA h g-1 at an average voltage of 4 V, that has been interpreted as due to the oxidation of Co3+ and Ru4+ in Li3CoRuO5 and Ni2+ to Ni4+ in the case of Li3NiRuO5. Thus, we find that ruthenium plays a favourable role in LLOs than in non-LLOs in stabilizing higher reversible electrochemical capacities. In Chapter 2.3, we describe the synthesis, crystal structure and lithium deinsertion–insertion electrochemistry of two new LLOs, Li3MRuO5 (M=Mn, Fe) which are analogs of the oxides described in Chapter 2.2. The Li3MnRuO5 oxide adopts a structure related to Li2MnO3 (C2/m), while the Li3FeRuO5 oxide adopts a near-perfect LiCoO2 (R-3m) structure. Lithium electrochemistry shows typical behaviour of LLOs for both oxides, where participation of oxide ions in the electrochemical processes is observed. A long first charge process with capacities of 240 mA h g-1 (2.3 Li per f.u.) and 144 mA h g-1 (1.38 Li per f.u.) is observed for Li3MnRuO5 and Li3FeRuO5, respectively. Further discharge–charge cycling points to partial reversibility. X-ray photoelectron spectroscopy (XPS) characterisation of both pristine and electrochemically oxidized Li3MRuO5 reveals that in the Li3MnRuO5 oxide, Mn3+ and Ru4+ are partially oxidized to Mn4+ and Ru5+ in the sloping region at low voltage, while in the long plateau, O2- is also oxidized. In the Li3FeRuO5 oxide, the oxidation process appears to affect only Ru (4+ to 5+ in the sloping region) and O2- (plateau), while Fe seems to retain its 3+ state. Another characteristic feature of TMs is formation of several coloured solid materials where d–d transitions, band gap transitions and charge transfer transitions are involved in the colouration mechanism. Coloured TM oxides absorbing visible light find important applications as visible light photocatalyst (for example, yellow BiVO4 for solar water splitting and red Sr1-xNbO3 for oxidation of methylene blue) and inorganic pigments [for example, Egyptian blue (CaCuSi4O10), Malachite green (Cu2CO3(OH)2), Ochre red (Fe2O3)]. Pigments are applied as colouring materials in inks, dyes, paints, plastics, ceramic glazers, enamels and textiles. In this thesis, we have focused on the coloured TM oxides for possible application as inorganic pigments. Generally, colours arise from electronic transitions that absorb visible light. Colours of the inorganic pigments arise mainly from electronic transitions involving TM ions in various ligand fields and charge transfer transitions governed by different selection rules. The ligand field d–d transitions are parity forbidden but are relaxed due to various reasons, such as distortion (absence of center of inversion) and vibronic coupling. The d-electrons can be excited by light absorption in the visible region of the spectrum imparting colour to the material. Charge transfer transitions in the visible region are not restricted by the parity selection rules and therefore give intense colours. Here we have investigated the colours of manganese in unusual oxidation state (Mn5+) as well as the colours of different 3d-TM ions in distorted octahedral and trigonal prismatic sites in appropriate colourless crystalline host oxides. These results are discussed in Part 3 of the thesis. In Chapter 3.1, we describe a blue/green inorganic material, Ba3(P1−xMnxO4)2 (I) based on tetrahedral Mn5+O4 :3d2 chromophore. The solid solutions (I) which are sky-blue and turquoise-blue for x ≤ 0•25 and dark green for x ≥ 0•50, are readily synthesized in air from commonly available starting materials, stabilizing the Mn5+O4 chromophore in an isostructural phosphate host. We suggest that the covalency/ionicity of P–O/Mn–O bonds in the solid solutions tunes the crystal field strength around Mn(V) such that a blue colour results for materials with small values of x. The material could serve as a nontoxic blue/green inorganic pigment. In Chapter 3.2, an experimental investigation of the stabilization of the turquoise-coloured Mn5+O4 chromophore in various oxide hosts, viz., A3(VO4)2 (A = Ba, Sr, Ca), YVO4, and Ba2MO4 (M = Ti, Si), has been carried out. The results reveal that substitution of Mn5+O4 occurs in Ba3(VO4)2 forming the entire solid solution series Ba3(V1−xMnxO4)2 (0 < x ≤ 1.0), while, with the corresponding strontium derivative, only up to about 10% of Mn5+O4 substitution is possible. Ca3(VO4)2 and YVO4 do not stabilize Mn5+O4 at all. With Ba2MO4 (M = Ti, Si), we could prepare only partially substituted materials, Ba2M1−xMn5+xO4+x/2 for x up to 0.15, that are turquoise-coloured. We rationalize the results that a large stabilization of the O 2p-valence band states occurs in the presence of the electropositive barium that renders the Mn5+ oxidation state accessible in oxoanion compounds containing PO43−, VO43−, etc. By way of proof-of-concept, we synthesized new turquoise-coloured Mn5+O4 materials, Ba5(BO3)(MnO4)2Cl and Ba5(BO3)(PO4)(MnO4)Cl, based on the apatite – Ba5(PO4)3Cl – structure. Chapter 3.3 discusses crystal structures, and optical absorption spectra/colours of 3d-transition metal substituted lyonsite type oxides, Li3Al1-xMIIIx(MoO4)3 (0< x ≤1.0) (MIII = Cr, Fe) and Li3-xAl1-xMII2x(MoO4)3 (0< x ≤1.0) (MII = Co, Ni, Cu). Crystal structures determined from Rietveld refinement of PXRD data reveal that in the smaller trivalent metal substituted lyonsite oxides, MIII ions occupy the octahedral (8d, 4c) sites and the lithium ions exclusively occur at the trigonal prismatic (4c) site in the orthorhombic (Pnma) structure; on the other hand, larger divalent cations (CoII/CuII) substituted derivatives show occupancy of CoII/CuII ions at both the octahedral and trigonal prismatic sites. We have investigated the colours and optical absorption spectra of Li3Al1-xMIIIx(MoO4)3 (MIII = Cr, Fe) and Li3-xAl1-xMII2x(MoO4)3 (MII = Co, Ni, Cu) and interpreted the results in terms of average crystal field strengths experienced by MIII/MII ions at multiple coordination geometries. We have also identified the role of metal-to-metal charge transfer (MMCT) from the partially filled transition metal 3d orbitals to the empty Mo – 4d orbitals in the resulting colours of these oxides. B The ABO3 perovskite structure consists of a three dimensional framework of corner shared BO6 octahedra in which large A cation occupies dodecahedral site, surrounded by twelve oxide ions. The ideal cubic structure occurs when the Goldschmidt’s tolerance factor, t = (rA + rO)/{√2(rB + rO)}, adopts a value of unity and the A–O and B–O bond distances are perfectly matched. The BO6 octahedra tilt and bend the B – O – B bridges co-operatively to adjust for the non-ideal size of A cations, resulting deviation from ideal cubic structure to lower symmetries. Ordering of cations at the A and B sites of perovskite structure is an important phenomenon. Ordering of site cations in double (A2BB'O6) and multiple (A3BB'2O9) perovskites give rise to newer and interesting materials properties. Depending upon the constituent transition metals and ordering, double perovskite oxides exhibit a variety of magnetic behaviour such as ferromagnetism, ferrimagnetism, antiferromagnetism, spin-glass magnetism and so on. We also have coupled magnetic properties such as magnetoresistance (Sr2FeMoO6), magnetodielectric (La2NiMnO6) and magnetooptic (Sr2CrWO6) behaviour. Here we have investigated new magnetically frustrated double perovskite oxides of the formula Ln3B2RuO9(B = Co, Ni and Ln = La, Nd). The Chapter 4.1 describes Ln3B2RuO9 (B = Co, Ni and Ln = La, Nd) oxides (prepared by a solid state metathesis route) which adopt a monoclinic (P21/n) A2BB'O6 double perovskite structure, wherein the two independent octahedral 2c and 2d sites are occupied by B2+ and (B2+1/3Ru5+2/3) atoms, respectively. Temperature dependence of the molar magnetic susceptibility plots obtained under zero field cooled (ZFC) condition exhibit maxima in the temperature range 25–35K, suggesting an antiferromagnetic interaction in all these oxides. Ln3B2RuO9 oxides show spin-glass behavior and no long-range magnetic order is found down to 2 K. The results reveal the importance of competing nearest neighbour (NN), next nearest neighbor (NNN) and third nearest neighbour (third NN) interactions between the magnetic Ni2+/Co2+ and Ru5+ atoms in the partially ordered double perovskite structure that conspire to thwart the expected ferromagnetic order in these materials.

The Solid oxide membrane (SOM) electrolysis is an innovative green technology that produces technologically important metals directly from their respective oxides. A yttria-stabilized zirconia (YSZ) tube, closed at one end is employed to separate the molten salt containing dissolved metal oxides from the anode inside the YSZ tube. When the applied electric potential between the cathode in the molten salt and the anode exceeds the dissociation potential of the desired metal oxides, oxygen ions in the molten salt migrate through the YSZ membrane and are oxidized at the anode while the dissolved metal cations in the flux are reduced to the desired metal at the cathode. Compared with existing metal production processes, the SOM process has many advantages such as one unit operation, less energy consumption, lower capital costs and zero carbon emission. Successful implementation of the SOM electrolysis process would provide a way to mitigate the negative environmental impact of the metal industry. Successful demonstration of producing ytterbium (Yb) and silicon (Si) directly from their respective oxides utilizing the SOM electrolysis process is presented in this dissertation. During the SOM electrolysis process, Yb2O3 was reduced to Yb metal on an inert cathode. The melting point of the supporting electrolyte (LiF-YbF3-Yb2O3) was determined by differential thermal analysis (DTA). Static stability testing confirmed that the YSZ tube was stable with the flux at operating temperature. Yb metal deposit on the cathode was confirmed by scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS). During the SOM electrolysis process for silicon production, a fluoride based flux based on BaF2, MgF2, and YF3 was engineered to serve as the liquid electrolyte for dissolving silicon dioxide. YSZ tube was used to separate the molten salt from an anode current collector in the liquid silver. Liquid tin was chosen as cathode to dissolve the reduced silicon during SOM electrolysis. After electrolysis, upon cooling, silicon crystals precipitated out from the Si-Sn liquid alloy. The presence of high-purity silicon crystals in the liquid tin cathode was confirmed by SEM/EDS. The fluoride based flux was also optimized to improve YSZ membrane stability for long-term use.

The beginning of the story of food is what is termed food production. This might sound logically like the process of making food, such as a chef or food company might, but this term is rather generally used in food science to refer to the so-called primary production of food, from growth of crops to harvesting of fish and minding and milking of cows. Primary production is, for example, what farmers do, producing the food that is brought to the farm-gate, from where the processors take over. So the food chain runs, according to your preference for a snappy soundbite, from grass to glass (for milk), farm to fork, slurry to curry, or (taking the food chain to its logical conclusion, and including the role of the human gut charmingly but appropriately in the chain) from farm to flush. But where do these raw materials that are yielded by primary production actually come from? It is often said that all things found on earth can be divided into categories of animal, vegetable, and mineral. To these could perhaps be added two more categories, microbial and synthetic (man-made). Within these five groups can essentially be placed everything we know as food, so using this classification to consider where our food comes from seems like a good starting point for this book. Perhaps the simplest group to start with is minerals, which might intuitively seem an unlikely source of foodstuffs (do we eat metal or rock?), until we consider where salt comes from and how much of it we add to our food (in other words, probably too much). Our bodies, however, absolutely need for us to consume certain metals and other chemical elements to survive, beyond the sodium and chloride we get from salt, and so many extracted minerals find their way from deposits in the earth into food products. This is particularly important where their biological effects are a desirable outcome (such as in carefully formulated nutritional products). In addition, products such as milk contain minerals like calcium, magnesium, zinc, and more, because the infant or calf needs them to thrive.

Diluted magnetic semiconductor (DMS) materials have gained a lot of attention in the last decade due to their possible use in spintronics. In this chapter, the effect of transition metal (TM) i.e., Mn and Fe doping on the structural, electronic, magnetic as well as optical properties of pure and doped LuN has been presented from the first principles density functional theory (DFT) calculation with the Perdew-Burke-Ernzerhof-generalized gradient approximation (PBE-GGA) and Tran Blaha modified Becke-Johnson potential (TB-mBJ) as correlation potentials. The predicted Curie temperature is expected to be greater than room temperature in order to better understand the ferromagnetic phase stability, which has also been confirmed through the formation and cohesive energies. The calculated lattice constants for perfect LuN (rock-salt structure) are in good agreement with the experimental values. Interestingly, doping of Mn and Fe on pure LuN displays indirect band gap to a direct band gap with half metallic and metallic character. The detailed analyses combined with density of state calculations support the assignment that the Half-magnetism and magnetism are closely related to the impurity band at the origin of the hybridization of transition states in the Mn-doped LuN. Absorption spectra are blue shifted upon increase in dopant contents and absorption peaks are more pronounced in UV region. The refractive index and dielectric constant show increase in comparison to the pure LuN. According to the Penn’s model, the predicted band gaps and static actual dielectric constants vary. These band gaps are in the near visible and ultraviolet ranges, as well as the Lu0.75TM0.25N (TM = Fe, Mn) materials could be considered possible candidates for the production of optoelectronic, photonic, and spintronic devices in the future.

ABSTRACT: This study investigates the characteristics of hydraulic fractures (HFs) formed in low permeability reservoirs that are bounded by salt layers. Three layered systems are modeled, where the thickness of the bounding salt layers differs with respect to the thickness of the shale layer (same thickness, thinner salt, and thicker salt). The width and total height of the models are the same. The interface properties match the properties of the weaker material, which is the salt. Both the shale and salt zones are modeled as homogeneous and impermeable materials, and water injection is modeled in the center of the middle shale layer. An additional model of hydraulic fracturing in the middle of a homogeneous and isotropic shale is included. All models are subjected to the maximum (major) principal stress in the vertical direction and the minimum (minor) principal stress in the horizontal direction with fixed boundary conditions. The hybrid finite-discrete element modeling technique is used for these analyses. Results show that the contrast between the mechanical properties and thickness of layers influence the state of stress in the layers. Specifically, the orientation of the major and minor principal stresses switch in the target shale layer. This leads to creation of inclined HFs in the bounded shale as opposed to vertical HFs that would form in a thick shale layer under normal anisotropic stress conditions. The thicker are the bounding salt layers, the more horizontally inclined the HFs are in the shale. These analyses inform us that the design of hydraulic stimulations is influenced by the properties and thickness contract between the reservoir and bounding layers. 1. INTRODUCTION Unconventional fossil energy reservoirs usually comprise relatively thin layers of shale or mudstone (consider a thickness of about 10 m) bounded by other lithologies such as sandstone, salt, or limestone. It is well known that deformational characteristics and type, intensity, and height of fractures in multi-lithological layered formations are controlled by the contrast in the mechanical properties and thickness of the layers, type of the interfaces, and the in-situ confining stress (Narr and Suppe, 1991; Gross et al., 1995; Rijken and Cooke, 2001; Lorenz, et al., 2002; Underwood et al., 2003; Laubach, et al., 2009; Ferrill, et al., 2014; McGinnis, et al., 2017).

Abstract Abu Dhabi subsurface fault populations triggered basin system in diverse directions, because of their significant role as fluid pathways. Studying fault infill materials, fault geometries, zone architecture and sealing properties from outcrops as analogues to the subsurface of Abu Dhabi, and combining these with well data and cores are the main objectives of this paper. The fault core around the fault plane and in areas of overlap between fault segments and around the fault tip include slip surfaces and deformed rocks such as fault gouge, breccia, and lenses of host rock, shale smear, salt flux and diagenetic features. Structural geometry of the fault zone architecture and fault plane infill is mainly based on the competency contrast of the materials, that are behaving in ductile or in a brittle manner, which are distributed in the subsurface of Abu Dhabi sedimentary sequences with variable thicknesses. Brittleness is producing lenses, breccia and gouge, while, ductile intervals (principally shales and salt), evolved in smear and flux. The fault and fractures are behaving in a sealy or leaky ways is mainly dependent on the percentage of these materials in the fault deformation zone. The reservoir sections distancing from shale and salt layers are affected by diagenetic impact of the carbonates filling fault zones by recrystallized calcite and dolomite. Musandam area, Ras Al Khaima (RAK), and Jabal Hafit (JH) on the northeast- and eastern-side of the UAE represents good surface analogues for studying fault materials infill characteristics. To approach this, several samples, picked from fault planes, were analysed. NW-trending faults system show more dominant calcite, dolomite, anhydrites and those closer to salt and shale intervals are showing smearing of the ductile infill. The other linked segments and transfer faults of other directions are represented by a lesser percentage of infill. In areas of gravitational tectonics, the decollement ductile interval is intruded in differently oriented open fractures. The studied outcrops of the offshore salt islands and onshore Jabal Al Dhanna (JD) showing salt flux in the surrounding layers that intruded by the salt. The fractures and faults of the surrounding layers and the embedment insoluble layers are highly deformed and showing nearly total seal. As the salt behaving in an isotropic manner, the deformation can be measured clearly by its impact on the surrounding and embedment's insoluble rocks. The faults/fractures behaviour is vicious in migrating hydrocarbons, production enhancement and hydraulic fracturing propagation.

Solar thermal power plants are a promising option for future solar electricity generation. Their main advantage is the possibility to utilize integrated thermal storage capacities, allowing electricity generation on demand. In state of the art solar thermal power plants, two-tank molten-salt thermal energy storages are used. Significant cost reductions are expected by using thermocline thermal energy storage by storing the liquid storage material inside a single tank when compared to a two tank storage system. By embedding a low cost solid filler material inside the storage tank further cost reductions can be achieved. In earlier studies [1, 2] several potential filler materials have been investigated. In these study quartzite turned out to be a promising candidate due to its satisfying thermal stability and availability. At a temperature of approx. 573°C the crystal structure of quartzite changes from trigonal α-quartz phase to the hexagonal β-quartz phase [3]. This quartz conversion results in a volume change [4] that may cause cracking of the quartzite crystals due to weight loads in a packed bed. Since these thermal tests of the study mentioned were limited to 500°C this dunting was not considered. Thus, despite of the published studies there is a need for further, more detailed analysis. One trend in today’s development of solar thermal power plants is to use molten salt as storage material and heat transfer fluid at operating temperatures of 560°C and above. Accordingly, the quartz inversion might limit the applicability of quartzite as a filler material at elevated operating temperatures. Due to this concern, an investigation has been started to investigate the utilizability of natural rocks as low cost filler materials. In the first phase of this investigation a comprehensive literature survey was conducted. Based on this study, magmatic and sedimentary rocks turned out to the most promising rock classes for this application. For the further investigation, basalt was chosen as a suited representative for magmatic and quartzite for sedimentary rocks. In lab-scale tests, these candidate materials were investigated with respect to their: • Calcite content • Thermal stability up to 900°C in air • Thermal stability up to 560°C in molten salt • Cyclic stability between 290°C and 560°C in molten salt • Specific heat capacity up to 600°C In this paper the results of these investigations are presented and future activities are outlined.

Parabolic trough power systems that utilize concentrated solar energy to generate electricity are a proven technology. Industry and laboratory research efforts are now focusing on integration of thermal energy storage as a viable means to enhance dispatchability of concentrated solar energy. One option to significantly reduce costs is to use thermocline storage systems, low-cost filler materials as the primary thermal storage medium, and molten nitrate salts as the direct heat transfer fluid. Prior thermocline evaluations and thermal cycling tests at the Sandia National Laboratories’ National Solar Thermal Test Facility identified quartzite rock and silica sand as potential filler materials. An expanded series of isothermal and thermal cycling experiments were planned and implemented to extend those studies in order to demonstrate the durability of these filler materials in molten nitrate salts over a range of operating temperatures for extended timeframes. Upon test completion, careful analyses of filler material samples, as well as the molten salt, were conducted to assess long-term durability and degradation mechanisms in these test conditions. Analysis results demonstrate that the quartzite rock and silica sand appear able to withstand the molten salt environment quite well. No significant deterioration that would impact the performance or operability of a thermocline thermal energy storage system was evident. Therefore, additional studies of the thermocline concept can continue armed with confidence that appropriate filler materials have been identified for the intended application.

Abstract In recent years, retrievability (and various permutations of this term) has emerged around the world as a means to achieve and enhance public acceptance of deep geological disposal of long-lived radioactive wastes/materials (LLRMs). In this debate, it is often erroneously suggested that post-closure retrievability of the emplaced LLRMs cannot be accomplished in salt. In October 1996, the U.S. Department of Energy (DOE) submitted the Waste Isolation Pilot Plant (WIPP) Compliance Certification Application (CCA) to the U.S. Environmental Protection Agency (EPA) for review and approval. The CCA included a feasibility analysis defining a five-phased approach to post-closure waste removal from the WIPP rock salt repository based on currently available equipment and technologies. The feasibility analysis addressed highly adverse workers’ safety and waste retrieval conditions, including: 1. Radioactivity. 2. Hazardous constituents. 3. Gas. 4. Brine. 5. Rock integrity (instability). The concluding statement in the CCA was that “In no case, however, are the conditions expected to render removal impossible”. In May 1998, the EPA announced that WIPP complied with all applicable radioactive waste management and disposal regulations. This announcement was preceded by intense EPA and public scrutiny and oversight, which included successfully overcoming two legal challenges. Hence, the global application of the WIPP waste-removal feasibility analysis is: LLRM emplaced in a rock salt repository can be removed during the post-closure period with currently available technologies!

With the recent discoveries of the pre-salt reservoir, new areas of the Brazilian coast rose to prominence, especially for the Santos Basin. This area is adjacent to the Campos Basin, which now accounts for around 80% of Brazilian production. In this new area, in addition to the difficulties of drilling in salt rock, the deployment of subsea production systems have also to overcome new challenges, since environmental conditions are more severe than those in the Campos Basin. Other important issues are: the water depth of about 2200 meters; the high pressure for gas injection riser; and the high CO2 content, requiring special attention to the materials that will be in contact with the production fluid. At this new production frontier, priority was given to the use of floating units with storage capacity like VLCC hulls, in order to export oil production through shuttle tankers, as no pipeline grid is available. Depending on the motions level of these VLCC vessels, the selection of a viable configuration of riser becomes crucial. Thus, some alternatives have been studied and the Steel Lazy Wave Riser (SLWR) configuration was one of the options considered to be used for production and gas injection riser functions, besides being possibly used for risers with large diameters. As this area of the Santos Basin presents more severe conditions, the free-hanging configuration (SCR) was not feasible, even with the use of VLCCs with optimized motions. In this case, the SLWR configuration was better suited to overcome the problems faced by free-hanging configuration. This paper aims to present a set of variables and its right combination involved in SLWR configuration to make it feasible, considering some key points in the design of SLWRs, for example: motions level of the floating unit, thermal insulation required for the flow assurance of production risers; difficulties faced during the installation process and the need of using clad pipes or lined pipes due to the high level of corrosion imposed by CO2 fluid content.

Contimuum Damage Healig Mechanics is an extension of CDM recently developed by the authors to model healing process in a variety of materials including rock salt, sinterized metals, ceramics, and polymer-matrix composties, bone and so. on. While the theoretical framework, of CDHM is general, parameter identification depends on the particular material being modeled and the specific material tests that are feasible to conduct for that class of materials. This presentation deals with the application of CDHM to the specific field of fiber-reinforced polymer-matrix composites. An overview of CDHM will be presented followed by a description of parameter identification. Results are shown in order in validate the numerical model of healing behavior of damaged polymeric matrix composite. Healed and not healed cases discussed in order show the model capability and to describe possible evoltution of the healed system.