Crystallographic Point Of View Research Articles

Therapy modifies cystine kidney stones at the macroscopic scale. Do such alterations exist at the mesoscopic and nanometre scale?

With an incidence of 1:7000 births, cystinuria, the most frequent cause of stone formation among genetic diseases, represents a major medical problem. Twenty-five cystine stones randomly selected from cystinuric patients were investigated. From a crystallographic point of view, cystine stones are composed of micrometre size crystallites, which are made up of an aggregation of nanocrystals. Through scanning electron microscopy, the morphology and size of the crystallites have been described, while the size of the nanocrystals was investigated by means of powder neutron diffraction. Powder neutron diffraction analysis and/or scanning electron microscopy examination of cystine stones provide evidence that usual alkalinization by sodium bicarbonate associated with high diuresis significantly reduces the size of both nanocrystals and crystallites, while for other treatments, including alkalinizing drugs and thiol derivatives, the data suggest mainly changes in the topology of crystallites. Alkalinization with sodium bicarbonate affects cystine kidney stones at the mesoscopic and nanoscopic scales, while other medical treatments only alter their surface. Such an approach may help to assess the interaction between drugs and cystine stones in cystinuric patients.

Crystallography of phase transitions in metastable titanium aluminium nitride nanocomposites

The isostructural decomposition of the titanium aluminium nitride supersaturated solid solution crystallising in the face centred cubic (fcc) crystal structure into the titanium-rich fcc-(Ti,Al)N and almost titanium-free fcc-(Al,Ti)N and the transformation of metastable fcc-(Ti,Al)N into the wurtzitic aluminium nitride are discussed from the crystallographic point of view by taking the observed orientation relationships between the adjacent phases into account. It is shown that the isostructural decomposition of fcc-(Ti,Al)N into Ti-rich fcc-(Ti,Al)N and fcc-(Al,Ti)N and the transformation of the metastable fcc-(Ti,Al)N into the thermodynamically stable wurtzitic phase are concurrent processes, which are controlled not only by the thermodynamic stability of the respective compound and by the diffusivity of Al and Ti, but also by the local lattice strains. A part of the local lattice strains is regarded to result from the lattice misfit at the interfaces between the titanium aluminium nitrides having different [Al]/[Ti] concentration ratios and, in the case of the fcc/wurtzite-type interface, also having different crystal structures. The phase transition of the fcc-(Ti,Al)N to the wurtzitic one was predicted to be facilitated by stacking faults. The results of crystallographic considerations were verified experimentally by using in situ high-temperature synchrotron diffraction experiments that were performed on cathodic arc evaporated (Ti,Al)N thin films containing titanium and aluminium in different amounts.

Preliminary studies on the valorization of animal flour ash for the obtainment of active glasses

Animal flour ash, rich in phosphorous, calcium and alkaline oxides, has been used to formulate (i) controlled-release fertilizers, since they manage to release the nutrient elements (P, K) at a low rate, and (ii) bioactive glasses.(i) Four formulations were tailored using different amounts of animal flour ash (35–48wt%), potassium carbonate (10–25wt%) and a fixed amount of glassy sand (40wt%) in order to get glasses and glass-ceramics. The materials were characterised from a chemical (XRF), crystallographic (XRD) and microstructural (SEM/EDS) point of view. Moreover, in order to check the ability to release the macro- and micro-nutrients, tests were conducted to determine the kinetics of glass dissolution in different media (2% citric acid solution, 1% hydrochloric acid solution and ammonium citrate solution). The results obtained allowed to confirm all samples show a very low solubility in water (less than 1%) and high values (>40%) of P, Ca, K and Na in the other media.(ii) The rich content of phosphorous and calcium oxides makes the animal waste-derived ash a potential low-cost raw material to produce bioactive glasses. The analysis was focused on a bioactive glass, named BG_Ca, whose composition comes from the standard Bioglass® 45S5, got by increasing as much as possible the CaO content to combine a controlled behaviour during processing and a good apatite-forming ability in a simulated body fluid (SBF).This preliminary investigation shows that animal flour ash is a versatile material, which may be successfully used for several applications as various as the production of fertilisers and the preparation of bioactive glasses.

Trospium Chloride: Unusual Example of Polymorphism Based on Structure Disorder

The characterization of the solid state properties of an active pharmaceutical ingredient is a necessary step in drug development. One such API is trospium chloride, an anticholinergic drug used to treat incontinence and overactive bladder syndrome. One crystal form is known but, from the crystallographic point of view, has only been described by the X-ray powder diffraction pattern. Because, to the best of our knowledge, no crystal structures of trospium chloride have been published, we decided to prepare and describe different crystal forms. Using single-crystal X-ray diffraction, the structures of two new polymorphs and of one unstable solvate were solved. All forms were obtained from ethanol mother liquor. Both polymorphs exhibited a significant pseudosymmetrical disorder. The polymorphs were highly similar but were distinguished by their symmetry and the resulting single-crystal diffraction behavior. A detailed inspection of the molecular packing revealed that variations in the short-range disorder most likely gave rise to these two sibling polymorphs, which are hard to distinguish by X-ray powder diffraction.

Interaction mechanisms of screw dislocations with and twin boundaries in Mg

Molecular dynamics simulations were carried out to investigate the interactions between screw partials and the and twin boundaries in Mg. In the twin, the interaction was attractive and the partials were absorbed readily in the boundary. In the twin, however, they passed through the twin boundary because of a repulsive interaction when a large applied strain was applied. The total energy including the dislocation core energy and the twin boundary energy was found to be similar before and after the absorption of the partials in the twin boundary, while it increased upon the absorption of the partial in the twin boundary. The origins of the total energy variations are discussed from a crystallographic viewpoint.

Rosette patterns – a common description for both crystalline and quasicrystalline structures

Crystalline structures are generally considered to be the normal case and quasicrystals a rare peculiarity. An attempt has been made to find a generalized view for both of these long range ordered atomic arrangements. It has been shown that they can be understood in terms of an angle‐periodic rosette pattern. The three‐dimensional wall paper design patterns, normally used to describe crystalline structures, are a large subgroup of this rosette pattern supergroup, which have the additional characteristics of translational periodicity. The topic is dealt with from a combined crystallographic and solid state physics point of view. The covalent bonding in the quasicrystals is an important prerequisite for their appearance.

Analysis of Martensite Pole Figure from Crystallographic View Point

Martensite pole figures from three different steels have been studied using electron backscatter diffraction (EBSD) and mathematical models to show that the two stage transformation theory is not necessary for correct prediction of pole figure and popular orientation relationships, like Kurdjumov–Sachs. These theories can give misleading prediction. It has been proved that the use of correct crystallographic data can lead to a better texture prediction. The typical features of a pole figure in a {2 5 2}γ habit system have been studied in detail.

Structural relationships between single atom type crystal structures and intermetallic compound structures, as illustrated by Laves‐ and Hume‐Rothery phases

In comparison to the single atom type crystal structures, which are relatively simple and are concentrated in four types of structure (Cu, W, Mg, diamond), the crystal structures of intermetallic phases are manifold and often very complicated. At first sight there is no obvious connection between these types of crystal structures, however, a transition mechanism must exist for the solid‐state transition from the simple single atom type crystal structures to the intermetallic phase structures. Such a mechanism would show the inner connection between the structures. In this work the topic is dealt with from a crystallographic point of view. The transition between the structures can be described by the three steps (1) substitution of atoms, (2) systematically ejection of particular atoms from the emerging intermediate structure and (3) spatial relaxation especially of the atoms around the newly formed interstices. This general structural phase transition path will be discussed for two of the intermetallic classes, the Laves phases and the Hume‐Rothery phases. A suitable way of showing this is by making a comparison between the coordination polyhedra (atomic environments) of the single atom type crystal structures and those of the derived intermetallic crystal structures.

Heteroepitaxial growth of ZnO nanosheet bands on ZnCo2O4 submicron rods toward high-performance Li ion battery electrodes

We report the direct synthesis of ZnCo2O4 and ZnO/ZnCo2O4 submicron rod arrays grown on Ni foil current collectors via an ammonia-evaporation-induced method by controlling the ratio of Zn to Co. These three-dimensional (3D) hierarchical self-supported nanostructures are composed of one-dimensional (1D) ZnCo2O4 rods and two-dimensional (2D) ZnO nanosheet bands perpendicular to the axis of the each ZnCo2O4 rod. We carefully deal with the heteroepitaxial growth mechanisms of hexagonal ZnO nanosheets from a crystallographic point of view. Furthermore, we demonstrate the ability of these high-surface-area ZnO/ZnCo2O4 heterostructured rods to enable improved electrolyte permeability and Li ion transfer, thereby enhancing their Li storage capability (∼900 mA·h·g−1 at a rate of 45 mA·h·g−1) for Li ion battery electrodes. Open image in new window

Calculation of structural characteristics of Cd1–xCaxO (x = 0–1)

The structural characteristics of isovalent and isostructural CdO–CaO alloy system are studied from the viewpoint of crystallography. The relative atomic positions in the Cd1–xCaxO alloy lattice can be determined by the Cd(Ca)–O bond lengths, which slightly decrease with increasing Ca concentration. Equivalent cation sites and Cd(Ca)–O bond lengths demonstrate that Cd1–xCaxO (x = 0−1) alloys crystallise in cubic Fm–3m space group (rocksalt structure). Each cation site in the Cd1–xCaxO alloy lattice has the identical probability of occupying such site by Cd and Ca, leading to the equivalent cation sites in alloy structure. Our calculated lattice parameters, volume of unit cell and 2θ angles of (200) and (111) peaks in the X-ray diffraction pattern of Cd1–xCaxO (x = 0−1) alloys agree with experimental measurements, validating our current crystallographic viewpoint.

Pitfalls of local and quantitative phase analysis in partially stabilized zirconia

The addition of selected elements into the host structure of ZrO2stabilizes the tetragonal and cubic phases of zirconia, which are, in their undoped binary form, only stable at high temperatures. From the crystallographic point of view, the increasing amount of the stabilizer causes a continuous transition of the tetragonal zirconia to its cubic modification. In partially stabilized zirconia, local concentration gradients of the stabilizer are frequently present as a consequence of the production process, which results in a coexistence of zirconia domains having different degrees of tetragonality. The presence of the local concentration gradients in such samples and the continuous nature of the phase transformation are features important for many technological applications, but their analysis is not straightforward. Furthermore, these features complicate the quantitative phase analysis in partially stabilized zirconia. For the example of zirconia partially stabilized by magnesium, this contribution illustrates the capabilities and limitations of X-ray and electron backscatter diffraction. In particular, the ability of these experimental methods to reveal the gradual lattice distortion that is associated with the cubic to tetragonal phase transformation in zirconia and the reliability of the quantitative phase analysis are discussed. In this context, it is shown to what extent the choice of the microstructure model influences the result of the phase analysis.

High-Index Faceted Noble Metal Nanocrystals

The formation of novel and complex structures with specific morphologies from nanocrystals via a direct assembly of atoms or ions remains challenging. In recent years, researchers have focused their attention on nanocrystals of noble metals and their controlled synthesis, characterization, and potential applications. Although the synthesis of various noble metal nanocrystals with different morphologies has been reported, most studies are limited to low-index facet-terminated nanocrystals. High-index facets, denoted by a set of Miller indices {hkl} with at least one index greater than unity, possess a high density of low-coordinated atoms, steps, edges, and kinks within these structures and serve as more active catalytic sites. With the potential for enhanced catalytic performance, researchers have used the insights from shape-controlled nanocrystal synthesis to construct noble metal nanocrystals bounded with high-index facets. Since the report of Pt tetrahexahedral nanocrystals, researchers have achieved significant progress and have prepared nanocrystals with various high-index facets. Because of the general order of surface energy for noble metals, high-index facets typically vanish faster in a crystal growth stage and are difficult to preserve on the surface of the final nanocrystals. Therefore researchers have had limited opportunities to examine high-indexed noble metal nanocrystals with a controlled morphology and investigate their resultant behaviors in depth. In this Account, we thoroughly discuss the basic concepts and state-of-the-art morphology control of some noble metal nanocrystals enclosed with high-index facets. We briefly introduce high-index facets from both crystallographic and geometrical points of view, both of which serve as methods to classify these high-index facets. Then, we summarize various typical noble metal nanocrystals terminated by different types of high-index facets, including {hk0} (h > k > 0), {hhl} (h > l > 0), {hkk} (h > k > 0), and {hkl} (h > k > l > 0). In each type, we describe several distinct morphologies including convex, concave, and other irregular shapes in detail. Based on these remarks, we discuss key factors that may induce the variations of Miller indices in each class, such as organic capping ligands and metallic cationic species. In a look at applications, we review several typical high-indexed noble metal nanocrystals showing enhanced electrocatalytic or chemical catalytic activities.

The Mg2B25 formation and its role in the preparation of bulk MgB2 superconductors

The high boron boride phase Mg2B25 was firstly discovered during the preparation of the superconducting MgB2 material by reacting liquid Mg at 850 °C with crystalline β-rhombohedral boron powders (Reactive Liquid Mg Infiltration process, Mg-RLI). This nonsuperconducting impurity phase was later on fully characterized from the crystallographic point of view by applying the Rietveld method on X-Ray Powder Diffraction (XRPD) diagrams of a pure powder sample.In this work we monitor the growing characteristics of the crystalline Mg2B25 and MgB2 phases during the Mg-RLI process, by implementing the XRPD analysis and other microscopic characterization techniques.In order to have a clear overview of what happens during the Mg-RLI process, we have varied the MgB2 preparative conditions: samples were prepared at 700, 850 and 900 °C adopting different heating times – 1, 3, 15 and 60 h – and various packing density of the starting boron powders (1.2, 1.4 and 1.6 g/cm3). We have used, as boron reactant, β-rhombohedral crystalline high purity powders, sieved at less than 100 microns.As far as the superconducting applications are concerned, the presence of residues of the Mg2B25 phase between the MgB2 crystalline grains, even if they are not superconducting, may lead to an improvement of the superconducting characteristics of the MgB2 in high magnetic fields by inducing – inside the MgB2 matrix – nano-defects which would be able to pin the current vortices developed in the superconducting state.

Three-dimensional hierarchical self-supported multi-walled carbon nanotubes/tin(iv) disulfide nanosheets heterostructure electrodes for high power Li ion batteries

It is of great significance to improve the power density of Li ion batteries (LIBs) in pursuit of high-end products and technologies. Herein, we investigated the three-dimensional (3D) hierarchical self-supported multi-walled carbon nanotubes (MWCNTs)/tin(IV) disulfide nanosheets (SnS2 NS) heterostructured electrodes, demonstrating superior rate capabilities of 480 and 420 mAh g−1 even at the very high c-rates of 5C and 10C (charging in 6 min), respectively. The origins of the enhancement of the rate capabilities were discussed in detail by focusing on the roles of MWCNTs, which were directly grown on the metallic current collector. Furthermore, we have delicately dealt with the in-plane and plane-normal growth mechanisms of hexagonal SnS2 NS from the crystallographic point of view.

A structure created by intersecting ϵ martensite variant plates in a high-manganese steel

Microstructural evidence for a new intersection structure, which has been observed in grains oriented to near ⟨101⟩ in a polycrystalline Fe–30Mn–4Si–2Al TRIP/TWIP steel, was obtained by combined use of electron backscatter diffraction and transmission electron microscopy, and the responsible intersection mechanisms are discussed from crystallographic and thermodynamic viewpoints. A γ phase with the orientation 90° rotated from the matrix with respect to the intersection axis is produced at the intersection of two dense ϵ plates, whereas the twinning of the obstacle ϵ plate occurs when the incident plate is a fine γ/ϵ lamella or a stacking fault bundle. The results are compared with various structures reported previously, and the wide variation of the intersection reactions is interpreted by their dependence on thermodynamic stability of the phases, grain orientation and shear amount.

Modification of preferred martensitic variant distribution by high magnetic field annealing in an Ni–Mn–Ga alloy

The preferred martensitic variant distribution in Ni53Mn25Ga22ferromagnetic shape memory alloy (FSMA) samples annealed without and with a high magnetic field of 12 T applied during the annealing process was investigated by electron backscatter diffraction. It is revealed that the high magnetic field applied during annealing enhances the regular arrangement of martensitic variants from the morphological point of view and effectively modifies the preferred orientation distribution of martensitic variants without changing the misorientation between them from the crystallographic point of view. Only one texture component, \{ 1{\overline 1}0\} \langle 33{\overline 2}\rangle, exists in the sample annealed without a magnetic field, whereas two additional texture components, \{ 4{\overline 6} 3\} \langle 31{\overline 2}\rangle and \{ 1\overline 1 0\} \langle 110 \rangle, are developed in the sample annealed in a high magnetic field. The new finding that the preferred martensitic variant distribution can be efficiently modified by introducing a high magnetic field during the annealing process will shed light on the development of high-performance polycrystalline FSMAsvianovel processing techniques.

Experimental and theoretical aspects of the growth and equilibrium morphology of NaNO3

AbstractSodium nitrate (mineral nitratine, NaNO3, space group R $ \bar 3 $c at room temperature) is a material used in a great variety of fields, such as the molten salt technology. It is also of very interest from a crystallographic point of view, being iso‐structural with calcite (CaCO3). We performed several growth experiments in aqueous solution, near‐equilibrium, with the aim of finding the ideal conditions for investigating both face‐by‐face growth kinetics and surface characterization, as well as the influence of K+ and Li+ ions on the growth morphology. Single {10.4} rhombohedral crystals have been systematically grown from pure aqueous solution, while {00.1} truncated rhombohedra were obtained in the presence of K+ and Li+ ions in the mother solution. When determining the theoretical equilibrium morphology of NaNO3 crystals, the {00.1} and {10.4} surfaces were studied by using the 2D‐slab model and relaxed and athermal surface energies (surfaces energies at T = 0 K) were evaluated at DFT level (B3LYP Hamiltonian) by using the CRYSTAL06 package. The {00.1} dipolar surfaces were reconstructed by the octopolar Hartman‐Lacmann's model, already proposed for NaCl‐like lattices. This type of reconstruction is the only one which respects the bulk symmetry of the crystal. The octopolar Na+ terminated {00.1} form resulted to be more stable than the NO3– terminated one. However, the {00.1} form does not enter the theoretical athermal equilibrium shape of nitratine crystals, being γ(10.4)Na=160, γ(00.1)Na= 695 and γ(00.1)NO3=1535 erg/cm2. Finally, a simple 2D‐epitaxy model is proposed to explain the appearance of NaNO3{00.1} truncated rhombohedra in the presence of K+ and Li+ ions. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Friction and wear behaviours of Ti(C,O,N) dark decorative coatings

Reactive magnetron sputtering was used to obtain dark Ti(C,O,N) decorative coatings onto high speed steel. From a crystallographic point of view, depending by the amount of (N+O) mixture, the obtained films could be divided in two major regions: the first one with a predominant fcc crystallographic structure (for low amounts of (N+O)), and the second one containing films with amorphous structures. The best results for friction coefficient and wear rates (the minimum values) were registered for samples prepared in the beginning of the amorphous region. These two tribological parameters are mainly influenced by the carbon content in the films. Taking into account the practical goal of these kinds of films, the pure black films were obtained for higher amount of (N+O) mixture. Also for these amorphous darkest films reached in oxygen and nitrogen, the tribological properties are acceptable and the adherence reaches the maximum value.

Rhombohedral-Tetragonal Phase Coexistence and Piezoelectric Properties of (NaK)(NbSb)O3-LiTaO3-BaZrO3 Lead-Free Ceramics

The phase transitional behavior and composition-dependent piezoelectric properties of (NaK)(NbSb)O3–LiTaO3–BaZrO3 (NKNS–LT–BZ) pseudo-ternary system were investigated. A composition–temperature phase diagram was generalized within a certain range of BZ content in which a rhombohedral–tetragonal (R–T ) ferroelectric phase boundary connecting orthorhombic and cubic phase zones is formed near room temperature between two trifurcate points. Piezoelectric and electromechanical properties of NKNS–LT–BZ ceramics exhibit optimum values of d33=365 pC/N and kp=45% in the vicinity of the R–T phase coexistence zone. The dielectric and ferroelectric properties and the phase transition of NKNS–LT–BZ ceramics were discussed from a crystallographic point of view.

In-situ observation of phase transformation during rapid cooling processes

Inclusions contributing to acicular ferrite nucleation were investigated from a crystallographic point of view to understand the formation mechanism for acicular ferrite microstructure in low alloy steel laser weld metals. The sample was low carbon Ti-B weld metals with an oxygen content of 480 ppm. In this sample, intragranular acicular ferrite formation was observed from some inclusions and acicular ferrite had Kurdjumov-Sachs orientation relationship with austenite matrix. The multi-phase inclusions contributed to nucleation of acicular ferrite. They were surrounded by a Ti-enriched layer. It was confirmed by selected area diffraction and EDS analysis that the Ti-enriched layer was TiO. The acicular ferrite had Baker-Nutting orientation relationship with TiO layer on the inclusion surface. The lattice misfit was 3.0 % at the interface between the acicular ferrite and TiO.Therefore, it is considered that the TiO on the inclusion surface contributes to the heterogeneous nucleation of acicular ferrite by small lattice misfit.