Crystallographic Point Of View Research Articles

Synthesis and electrochemical properties of PbLi2Ti6O14 for lithium ion battery applications

Lead lithium titanium oxide with the composition PbLi2Ti6O14 has been successfully synthesized by the rheological phase reaction method and exhibited excellent electrochemical properties as an anode material for lithium ion batteries. The results show that PbLi2Ti6O14 with a three-dimensional network could reversibly accommodate about four lithium ions (146.4 mAh g−1) per unit formula along with the partial reduction of Ti4+ to Ti3+, and the multiple steps of lithium insertion during the cycling process were explained from crystallographic view point. Moreover, when the load current density was increased from 100 to 200, to 400, and then to 800 mA g−1, the corresponding charge capacity was 134.8, 119.6, 103.7, and 86.3 mAh g−1, respectively, and the capacity recovered to 128.7 mAh g−1 if the current density was returned to 100 mA g−1. Thus, the PbLi2Ti6O14, with certain specific capacity, excellent cycling performance and rate capability, can be used as a promising anode material for lithium ion battery applications.

Anisotropic Lattice Strain and Mechanical Degradation of High- and Low-Nickel NCM Cathode Materials for Li-Ion Batteries

In the near future, the targets for lithium-ion batteries concerning specific energy and cost can advantageously be met by introducing layered LiNixCoyMnzO2 (NCM) cathode materials with a high Ni content (x ≥ 0.6). Increasing the Ni content allows for the utilization of more lithium at a given cell voltage, thereby improving the specific capacity but at the expense of cycle life. Here, the capacity-fading mechanisms of both typical low-Ni NCM (x = 0.33, NCM111) and high-Ni NCM (x = 0.8, NCM811) cathodes are investigated and compared from crystallographic and microstructural viewpoints. In situ X-ray diffraction reveals that the unit cells undergo different volumetric changes of around 1.2 and 5.1% for NCM111 and NCM811, respectively, when cycled between 3.0 and 4.3 V vs Li/Li+. Volume changes for NCM811 are largest for x(Li) < 0.5 because of the severe decrease in interlayer lattice parameter c from 14.467(1) to 14.030(1) A. In agreement, in situ light microscopy reveals that delithiation leads to differe...

An origin of functional fatigue of shape memory alloys

Functional fatigue (FF) during thermal and mechanical cycling, which leads to the generation of macroscopic irrecoverable strain and the loss of dimensional stability, is a critical issue that limits the service life of shape memory alloys (SMAs). Although it has been demonstrated experimentally that such a phenomenon is related to microstructural changes, a fundamental understanding of the physical origin of FF is still lacking, especially from a crystallographic point of view. In this study, we show that in addition to the normal martensitic phase transformation pathway (PTP), there is a symmetry-dictated non-phase-transformation pathway (SDNPTP) during phase transformation cycling, whose activation could play a key role in leading to FF. By investigating crystal symmetry changes along both the PTPs and SDNPTPs, the characteristic types of defects (e.g., dislocations and grain boundaries) generated during transformation cycling can be predicted systematically, and agree well with those observed experimentally in NiTi. By analyzing key materials parameters that could suppress the SDNPTPs, strategies to develop high performance SMAs with much improved FF resistance through crystallographic design and transformation pathway engineering are suggested.

Ionic Cocrystals of Sodium Chloride with Carbohydrates

Ionic cocrystals of sodium chloride with carbohydrates were investigated from a synthetic as well as from a crystallographic point of view. The syntheses of sodium chloride cocrystals with three different carbohydrates were established and furthermore optimized on a multigram, semitechnical scale. The missing crystal structures of two ionic NaCl cocrystals with a monosaccharide or a disaccharide, e.g., d-(−)-ribose·NaCl and d-(+)-sucrose·NaCl·2H2O, respectively, were elucidated via X-ray diffraction methods using either single crystal diffraction or synchrotron powder X-ray diffraction data applying the Rietveld refinement method. In both structures, sodium chloride contact ion pair formation in the solid state is observed, which represents the only described cases for alkali chloride carbohydrate combinations crystallized from aqueous solutions.

ChemInform Abstract: Structural Transformations and Solid‐State Reactivity Involving Nano Lead(II) Coordination Polymers via Thermal, Mechanochemical and Photochemical Approaches

AbstractReview: 235 refs.

Effect of carbon on the nitridation behavior of aluminum powder

The effect of carbon on Al powder nitridation was investigated from an atomic-scale chemical and crystallographic viewpoint. Carbon delays the initiation of nitridation and melting of Al powder, possibly because of its insulation effect. Therefore, carbon provides a pathway through which a constant supply of nitrogen gas is provided before molten Al powder is fully consolidated. Carbon also alters the nitridation mechanism by acting as a reaction agent of aluminum oxides and providing the path for nitrogen gas for constant nitridation, thereby stimulating the formation of the AlN with a typical triplet band structure. As a result, when carbon covers the entire surface of the powder, about 85% nitridation can be achieved.

On the Crystal-Chemistry of Bjarebyite, BaMn2+2Al2(PO4)3(OH)3, From the Palermo #1 Pegmatite, Grafton County, New Hampshire, Usa

Abstract Bjarebyite, BaMn 2+ 2 Al 2 (PO 4 ) 3 (OH) 3 , is a rare secondary phosphate mineral in granitic pegmatites. From the crystallographic point of view it is exhaustively described in the monoclinic unit cell with a 9.0671(2) A, b 12.1500(4) A, c 4.9403(1) A, β 100.399(2)°, V 535.31(2) A 3 , and space group P 2 1 / m . Single crystal X-ray diffraction data were collected with Mo K α radiation. The hydrogen positions were located by difference Fourier map and refined in the final steps of the crystal structure anisotropic refinement, leading to an R index of 1.99%. A very good agreement was found with microprobe chemical analyses and bond valence calculations which show expected values for all the atomic sites. These features were confirmed by comparing the Raman spectra of bjarebyite and kulanite.

Relevance of weak intermolecular forces on the supramolecular structure of free or DMSO solvated 5-(4-X-benzylidene)rhodanines (X = F, Cl, Br, I)

The rhodanines of the title (Xp-Rhod, X = F, Cl, Br, I) were synthesized and characterized in solid state and in solution. The crystal structures of the four compounds show different supramolecular organizations. In the F-, Cl- and Br-derivatives, a R22(8) (CSNH)2 ring forms via NH⋯S hydrogen bonds between two neighbouring molecules to give dimers. The I-derivative is also dimeric, but exhibits R22(8) (CONH)2 rings. The two type of dimers are associated in a variety of structures through hydrogen bonding, π-stacking, CH⋯π interactions and halogen bonding. These interactions were analysed from a crystallographic point of view and their relative relevance was explored using DFT calculations. The effect produced on all these interactions by the incorporation of DMSO molecules to the lattice was analysed by comparing the crystal structures of Xp-Rhod compounds and those of corresponding Xp-Rhod⋅DMSO solvates.

SCCき裂発生挙動の力学的および結晶学的評価

To make clear micro-crack nucleation behavior by stress corrosion cracking (SCC) in austenitic stainless steel type 304, constant load tests were carried out in tetrathionate solution. After the tests, nucleation behavior of micro-cracks was discussed from crystallographic and mechanical viewpoints. Every micro-crack initiated in a single grain boundary (GB), and most of the cracks initiated at the coincidence GBs except for ∑3 or random GBs. Then, stress state at the cracked GBs was discussed on the basis of effective normal stress acting on a GB proposed by West et al.(2011). The probability of crack nucleation increased with increasing effective normal stress on GBs. Hence, stress corrosion cracks would preferentially initiate at the coincidence GBs except for ∑3 or random GBs subjected to high normal stress.

The effect of crystallographic mismatch on the obstacle strength of second phase precipitate particles in dispersion strengthening: bcc Nb particles and nanometric Nb clusters embedded in hcp Zr

A potential factor dominating the obstacle strength of second phase precipitate particles in dispersion strengthening is the crystallographic mismatch between the matrix phase and the second phase; however, yet this concept has not been fully assessed by experiments and simulations. In the present study, we experimentally investigated the obstacle strength of body centered cubic (bcc) Nb particles and nanometric Nb clusters embedded in hexagonal close packed (hcp) Zr matrix. The bcc Nb is softer than the hcp Zr in terms of shear modulus, whereas from a crystallographic viewpoint, the bcc Nb particles can be nonshearable, strong obstacles because the slip plane inside the particles is not parallel with that in the matrix. Although the bcc Nb is thermodynamically the stable configuration for Nb atoms precipitating from the Zr matrix, in the very early stage of solute agglomeration, the crystal structure of Nb nanoclusters is possibly hcp rather than bcc. The obstacle strength (α) was no greater than 0.5 for the Nb nanoclusters, whereas 0.85 ≤ α ≤ 1 for the coarse bcc Nb particles; α = 1 was obtained with the Taylor factor (M) of 5.5 and α = 0.85 with M = 6.5, respectively. These results indicate that the bcc Nb particles are strong obstacles, and that the Nb nanoclusters are weak obstacles.

On the Way to New Possible Na-Ion Conductors: The Voronoi-Dirichlet Approach, Data Mining and Symmetry Considerations in Ternary Na Oxides.

With the constant growth of the lithium battery market and the introduction of electric vehicles and stationary energy storage solutions, the low abundance and high price of lithium will greatly impact its availability in the future. Thus, a diversification of electrochemical energy storage technologies based on other source materials is of great relevance. Sodium is energetically similar to lithium but cheaper and more abundant, which results in some already established stationary concepts, such as Na-S and ZEBRA cells. The most significant bottleneck for these technologies is to find effective solid ionic conductors. Thus, the goal of this work is to identify new ionic conductors for Na ions in ternary Na oxides. For this purpose, the Voronoi-Dirichlet approach has been applied to the Inorganic Crystal Structure Database and some new procedures are introduced to the algorithm implemented in the programme package ToposPro. The main new features are the use of data mined values, which are then used for the evaluation of void spaces, and a new method of channel size calculation. 52 compounds have been identified to be high-potential candidates for solid ionic conductors. The results were analysed from a crystallographic point of view in combination with phenomenological requirements for ionic conductors and intercalation hosts. Of the most promising candidates, previously reported compounds have also been successfully identified by using the employed algorithm, which shows the reliability of the method.

Studies of Aluminum-Doped LiNi0.5Co0.2Mn0.3O2: Electrochemical Behavior, Aging, Structural Transformations, and Thermal Characteristics

This paper is dedicated to studies of the electrochemical behavior, the structural and thermal features of the Ni-rich LiNi0.5Co0.2Mn0.3O2 undoped and Al-doped (∼0.01 at.%) materials for positive electrodes of lithium batteries. We have found that structural characteristics of these materials are quite similar from the crystallographic point of view. It was demonstrated that Al substitution in the doped LiNi0.5Co0.2Mn0.3O2 is preferred at Ni sites over Co sites, and the thermodynamic preference for Al3+ substitutions follows the order: Ni>Co>Mn. The lower capacity fading of the Al-doped electrodes upon cycling and aging of the cells in a charged state (4.3 V) at 60°C, as well as more stable mean voltage behavior, are likely due to the chemical and structural modifications of the electrode/solution interface. The Al-doped LiNi0.5Co0.2Mn0.3O2 electrodes demonstrate also lower resistances of the surface film and charge-transfer as well as lower activation energies for the discharge process. From XPS studies we conclude that the modified stable and less resistive interface on the Al-doped particles comprises the Li+-ion conducting nano-sized centers like LiAlO2, AlF3, etc., which promote, to some extent, the Li+ ionic transport to the bulk. A partial layered-to-spinel transformation was established upon cycling of LiNi0.5Co0.2Mn0.3O2 cathodes.

Half-Heusler topological insulators

Abstract

Crystalline organization of the fibrous prismatic calcitic layer of the Mediterranean mussel Mytilus galloprovincialis

The outer layer of the shell of members of the genus Mytilus is made of long, slender fibres of calcite (some 1–2 μm wide and hundreds of μm long), which reach the internal surface of the shell at an angle. This microstructure has been called anvil-type fibrous calcitic and its organization, crystallography and relationships to the organic phase are poorly known. We have studied the outer calcitic layer of the Mediterranean mussel M. galloprovincialis by means of optical and scanning and transmission electron microscopy (SEM and TEM), X-ray diffraction (XRD) and atomic-force microscopy (AFM). SEM data from other species have also been gathered. All data together imply that the material is extremely well ordered both from the morphological and crystallographic viewpoints. The XRD pole figures show that there are discrete 001 and 104 maxima; therefore, the material has a well-defined sheet texture. In living animals there is an organic membrane (surface membrane) that coats the inner surface of the shell. TEM sections of the decalcified material show that this mainly proteinaceous surface layer is internally laminated and fills all the spaces left between the growing fibres. Every fibre is a monocrystal with three well developed {104} rhombohedral faces at its growth end. One of these faces is directly in contact with, and strictly parallel, to the sublayers of the surface membrane and thus to the inner shell surface. AFM experiments consisting on growing calcite onto shell pieces in which the surface membranes are preserved, show that the calcitic fibres of the shell easily regrow across the membrane, demonstrating that it is permeable to ions. In this way, prisms are able to grow despite the existence of the intermediate membrane in the living animal. Additional experiments of calcite growth onto the inner side of the surface membrane show that crystals grow onto their {104} surfaces. The surface membrane is responsible for the high degree of ordering of the fibrous calcitic layer, because it stabilizes the orientation of a rhombohedral surface, once this is parallel to the protein sublayers. This is one of the very few cases in which the influence of the organic matter on the organization of microstructures can be demonstrated.

Crystallographic analysis for acicular ferrite formation in low carbon steel weld metals

Inclusions contributing to acicular ferrite nucleation were investigated from a crystallographic point of view in low carbon low alloy steelweld metals. The samples from electro slag welding (ESW) and submerged arc welding (SAW) deposits with various cooling rates were prepared in this study. In those samples, intragranular acicular ferrite formation was observed from inclusions. The inclusions contributing to acicular ferrite formation were of multi-phase type consisting of amorphous phase, spinel type and MnS. They were surrounded by a Ti-enriched layer. It was confirmed by selected area diffraction patterns and energy-dispersive X-ray spectrometer analyses that the Ti-enriched layer was TiO. The acicular ferrite had a Baker–Nutting orientation relationship with the TiO layer on the inclusion surface. The misfit was 3.0% at the interface between the acicular ferrite and TiO. Therefore, it is considered that TiO on the inclusion surface contributes to the heterogeneous nucleation of acicular ferrite by small lattice misfit. However, themorphologies of ferrite growth which nucleated from inclusions were different in both samples. Whereas the growth of ferrites nucleated from TiO was enough in ESW, the size of nucleated ferrite in SAW was a few hundred millimetres in size. In the early stage of nucleation from TiO, ferrite had small deviation from Kurdjumov–Sachs orientation relationship (K–S relationship) in both ESW and SAW. However, there was a difference in the growth stage of ferrite. The ferrite orientations were gradually changed to fit to the K–S relationship in ESW. On the other hand, the nucleated ferrite in SAW stopped growing and the newly nucleated ferrite which had K–S relationship prior to austenite was formed adjacently because of large super cooling due to small heat input.

Serotonin in different compounds: crystallographic and computational insight

Biologically active substances are in the focus of pharmaceutical and chemical research. Serotonin, one of the most common neurotransmitters, is widely studied in relation to its effect on humans from cellular to neurological levels. Although serotonin plays a key role in some biological processes, its chemistry and crystallography are not sufficiently understood. The aim of the present study was to crystallize serotonin adipate and creatinine sulfate monohydrate, determine their crystal structures, and analyze them in a comparison with other previously known serotonin crystal structures. Special attention was paid to the interrelation between the molecular conformation and crystalline environment. This issue was addressed using crystallographic and computational chemistry (DFT-D, MD) approaches. In our research was shown that the crystal structure of the creatinine sulfate complex significantly differs from what was previously determined. The conformation of serotonin in the new structure differs from serotonin conformations in all other known complexes, as well as from the most stable conformation, predicted by the adiabatic conformational analysis using quantum chemical calculations (DFT, MP) in different phases. This work has explicitly shown the influence of different interactions on serotonin molecular conformation in the crystalline state, described from a crystallographic and theoretical point of view. It has been previously demonstrated that salt formation in the presence of different anions produces variation in pharmacological, therapeutic and physic-chemical properties. This study has shown that alterations of the anion affects the molecular geometry of the bioactive substance and invite further investigation to rationalize the geometry changes. The work was supported by the RFBR Grants No.14-03-31866, 13-03-92704, Russian Ministry of Science and Education and RAS, Siberian Supercomputer Center SB RAS Integration Grant No.130, Edinburgh Compute and Data Facility

Energy Storage in crystalline Materials based on multivalent Ions

Energy conversion and storage has become the main challenge to satisfy the growing demand for renewable energy solutions as well as mobile applications. Nowadays, several technologies exist for the conversion of electric energy into e. g. heat, light and motion or vice versa. Among a large variety of storage concepts, the conversion of electrical in chemical energy is of great relevance in particular for location-independent use. Main factors that still limit the use of electrochemical cells are the volumetric and gravimetric energy density, cyclability as well as safety. The concept for a new thin-film rechargeable battery that possibly improves these properties is presented. In contrast to the widespread lithium-ion technology, the discussed battery is based on the redox reaction of multivalent Al-ions and their migration through solid electrolytes. The ion conduction and insertion processes in the crystalline materials of the suggested cell are discussed under a crystallographic point of view to identify suitable electrode and separator materials. A multilayer-stack of all-solid-state batteries is synthesized by pulsed laser deposition and investigated in situ, i. e. during charge and discharge, by X-ray reflection and diffraction methods. The correlation between crystal structure, morphology and electrical performance is investigated in order to characterize the ion diffusion and insertion process.

Crystallographic study of Al3Zr and Al3Nb as grain refiners for Al alloys

The potency of Al3Zr and Al3Nb as grain refiners for Al alloys was investigated from a crystallographic point of view using the edge-to-edge matching (E2EM) model. The results show that both Al3Zr and Al3Nb have small values of interatomic spacing misfit and interplanar spacing mismatch with respect to Al. Furthermore, energetically favourable orientation relationships predicted by the model exist between Al and each of these two intermetallic phases. In the light of the edge-to-edge matching model predictions, it is suggested that both Al3Zr and Al3Nb are potent heterogeneous nucleation refiners for Al grains from the crystallographic point of view. The present crystallographic analysis provides a more reasonable explanation for the significant grain refinement obtained in the peritectic Al-Zr and Al-Nb alloys and also provides fresh insight into the understanding of the grain refinement mechanism of Al alloys.

An analysis method for atomistic abrasion simulations featuring rough surfaces and multiple abrasive particles

We present a molecular dynamics (MD) model system to quantitatively study nanoscopic wear of rough surfaces under two-body and three-body contact conditions with multiple abrasive particles. We describe how to generate a surface with a pseudo-random Gaussian topography which is periodically replicable, and we discuss the constraints on the abrasive particles that lead to certain wear conditions. We propose a post-processing scheme which, based on advection velocity, dynamically identifies the atoms in the simulation as either part of a wear particle, the substrate, or the sheared zone in-between. This scheme is then justified from a crystallographic order point of view. We apply a distance-based contact zone identification scheme and outline a clustering algorithm which can associate each contact atom with the abrasive particle causing the respective contact zone. Finally, we show how the knowledge of each atom’s zone affiliation and a time-resolved evaluation of the substrate topography leads to a break-down of the asperity volume reduction into its components: the pit fill-up volume, the individual wear particles, the shear zone, and the sub-surface substrate compression. As an example, we analyze the time and pressure dependence of the wear volume contributions for two-body and three-body wear processes of a rough iron surface with rigid spherical and cubic abrasive particles.

Crystallographic study of grain refinement of Al by Nb addition

The grain refinement of Al by the addition of a small amount of peritectic-forming solute, Nb, has been studied from the crystallographic point of view. Combining the observations of optical microscopy and scanning electron microscopy with the results of energy-dispersive X-ray spectroscopy and X-ray diffraction, it is confirmed that the particles observed at or near the grain centres of refined Al alloys are pro-peritectic Al3Nb particles. The crystallographic matching between the Al3Nb particles and Al grains has also been evaluated using an edge-to-edge matching model and further verified using electron backscatter diffraction and transmission electron microscopy. It is found that there are reproducible crystallographic orientation relationships between the Al3Nb particles and Al grains, and the experimental results are consistent with the predictions of the edge-to-edge matching model. This implies that the pro-peritectic Al3Nb particles are favourable nucleation sites for Al grains from the crystallographic point of view. Furthermore, the analysis of the size distribution of Al3Nb particles reveals that the Al3Nb particles at the grain centres have relatively large particle size, which also corroborates the high potency of Al3Nb according to the free growth model. It is therefore concluded that the significant grain refinement resulting from the addition of Nb is predominantly attributed to thein situformed Al3Nb particles which promote grain refinementviaenhanced heterogeneous nucleation.