440 research outputs found
Total scattering and pair distribution function analysis for studies of nanomaterials
No full textPair Distribution Function (PDF) analysis is a powerful method for characterization of atomic structure in nanostructured materials where conventional crystallographic techniques may be challenged. We here review the use of total scattering and PDF for characterization of nanomaterials and show how detailed structural information can be obtained. Through examples from the literature, we introduce the use of different types of PDF modeling, such as real-space Rietveld refinement, modeling using discrete structure models, and Reverse Monte Carlo (RMC) methods. The examples cover a range of different types of nanomaterials, including crystalline nanoparticles, nanoclusters, as well as highly disordered nanostructured compounds, illustrating the versatility of the PDF method.</p
Synthetic methodologies
No full textThe great variety of inorganic materials and the fact that they comprise elements with widely varying chemistry, drawn from every corner of the periodic table, imply that there will always be the need for myriad ways to make materials. We describe, in this chapter, some general routes for the preparation of inorganic solids, emphasizing recent advances. We particularly emphasize developing an understanding of the preparation of solids through in situ studies, which oftentimes reveal the role of fugitive intermediates phases, that may not be recognized at the outset as playing a role in reaching the target material. Many recent examples of topochemical conversions of solids are also presented. The long-held goal of atom-by-atom control of the preparation of complex materials is bearing fruit, and some examples of these are presented. These atom-by-atom routes show no sign of displacing more traditional preparative methods because of issues of generality and scale
Modification of magnetic and electronic properties, in particular superconductivity, by low temperature insertion of fluorine into oxides
No full textLow-temperature fluorination routes have been successfully employed to control the transition metal oxidation state in a range of systems, leading to an ability to manipulate the electronic and magnetic properties. Following on from the initial studies on the use of F2 gas to introduce superconductivity in cuprate systems, such as La2CuO4 and Sr2CuO3, such studies have been extended to other transition metal oxide systems. In addition to the use of F2 gas, further studies have targeted the use of alternative solid-state fluorinating reagents, with a view to more accurately controlling the F content. In this chapter we will illustrate the work performed using the different fluorinating reagents, highlighting their advantages and disadvantages
In situ scattering studies of material formation during wet-chemical syntheses
No full textTime-resolved in situ X-ray and neutron scattering can provide unique insight into material formation processes. Here, the use of such experiments for studies of wet-chemical material synthesis is described. We focus especially on techniques that can provide atomic structural information, i.e., powder diffraction and total scattering, and also describe how the combination with other techniques (small angle scattering and X-ray spectroscopy) can be used. Through examples, we illustrate the different kinds of information that can be obtained. This includes knowledge of crystallization kinetics and activations energies, insight into particle and crystallite growth mechanisms, and structural understanding of nucleation processes.</p
Solid-state NMR of energy storage materials
No full textElectrochemical energy storage in batteries and supercapacitors underlies portable technology and is enabling the shift away from fossil fuels and toward electric vehicles and increased adoption of intermittent renewable power sources. Understanding reaction and degradation mechanisms is the key to unlocking the next generation of energy storage materials. This chapter will highlight the diverse applicability and chemical sensitivity of solid-state NMR as a tool for studying bulk and interfacial structures and dynamics. NMR interactions relevant to inorganic battery and supercapacitor materials will be described before moving into sections on lithium battery cathodes, anodes, solid electrolytes, interfaces, and finally supercapacitors. While battery materials vary in maturity, each section focuses on materials that are either in commercial use or development. Multinuclear NMR studies of mechanisms, atomic structure, and ion dynamics are succinctly described and an effort is made to summarize the state of the field for each class of materials
Solar Fuels: Approaches to Catalytic Hydrogen Evolution
No full textIn response to political and environmental motivations to develop alternative energy resources, researchers have taken a variety of approaches to develop solar energy conversion technologies. Solar fuel production is an area of enormous promise where, in analogy to natural photosynthesis, sunlight drives the conversion of energy-poor molecules (H_2O and CO_2) to energy-rich ones (O_2, H_2, and (CH_2O)_n). To realize a solar-driven water splitting device based on earth-abundant materials, new chemistry is needed, including materials for light harvesting and electrocatalysts for fuel production. In this chapter, we focus on molecular hydrogen production catalysts capable of evolving H_2 at low overpotentials. Recent synthetic advances in catalyst design, detailed electrochemical and photochemical studies, and developments in mechanistic understandings are covered
Flux Growth and Crystal Structure Refinement of Calcite Type Borate GaBO3
No full textA single crystal of gallium borate, GaBO3, 4 × 4 × 0.2 mm3 in size has been grown by spontaneous crystallization with a molten flux based on a Bi2O3-3B2O3 solvent. From single crystal X-ray diffraction measurement, GaBO3 was found to crystallize in the trigonal calcite type, space group R-3c, with cell dimensions a = 4.56590(10) and c = 14.1764(4) Å, Z = 6. Layers of distorted [GaO6] octahedra are interleaved by layers of triangular planar [BO3] unites. The transmission spectrum on a single crystal indicated that the band gap of GaBO3 is 3.62 eV
Solid-state electrolytes for lithium-ion batteries
No full textThis chapter aims to provide a systematic overview of the current state of the research in the field of solid-state electrolytes for all-solid-state Li batteries. The desired functional properties and ion transport mechanism of solid-state electrolytes are explained, followed by a detailed survey on the existing understanding of the metal oxides, sulfides, and halides for fast Li ion conduction. Emphasis is also given on the oxide-based Li ion solid electrolyte, covering the structures of perovskites, Na super ionic conductors (NASICONs)-type, Li super ionic conductors (LISICONs) and Li-stuffed garnets with their chemical composition-crystal structure-ionic conductivity relationships and electrochemical stability discussed. Examples of all-solid-state Li batteries and the evaluation of their performance in terms of capacity and cycle numbers are reported.<br/
Introduction: A short history of single site catalysis
No full textThis chapter provides an outline of the contents of the book. A sketch of the historic development of molecular heterogeneous catalysis is given as a context to the selection of collected chapters
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