Crystal Refinement Research Articles

Influence of morphology evolution on the mechanical properties of beta nucleated isotactic polypropylene in presence of polypropylene random copolymer

A promising method was developed by adding polypropylene random copolymer (co-PP) and β-nucleating agent (β-NA) simultaneously into isotactic polypropylene (iPP) matrix to improve its toughness. Results showed that the co-PP chains promoted crystal refinement, and the rubbery phases corresponding to the propylene–ethylene random segments offered superior toughness. This proves that crystal morphology, which correlates with β-NA content, is another important factor that determines toughness and tensile strength in addition to β crystal content. Furthermore, a mechanism for the morphology evolution is proposed. This study shows the feasibility of improving the mechanical properties of iPP and expanding its applications.

SPODI: High resolution powder diffractometer

The high resolution powder diffractometer SPODI (jointly operated by the Karlsruhe Institute of Technology and the Technische Universität München) is designed for structure solution and Rietveld refinement of crystal and magnetic structural parameters on polycrystalline powders. Instrumental specification (design, flexibility, peak shape, resolution etc.) as well as a variety of specialized sample environment equipment implemented for in-situ materials characterisation make the instrument attractive for studies of complex ordering phenomena.

Automated method for varying the order in which parameters are refined in powder diffraction

This paper proposes an automated method for crystal structure refinement in powder diffraction to solve some outstanding issues including a great number of manual interventions, time-consuming and low efficiency caused by manual refinement of refinement software. The automated method is based on crystal parameters sorting space, black-box model and Fullprof software. The automated method can get the best refinement result in all kinds of order of crystal parameters refinement by “optimal Rwp (the weighted profile R factor) search algorithm”. Meanwhile, an automated auxiliary system has been developed by the Python language to implement the application of the automated method to experimental data. The experimental results show that the automated method is feasible, which can save time and reduce the error rate caused by a lot of repeated manual refinement experiments, and improve the refinement efficiency.

Microstructure and mechanical properties of dissimilar Al–Cu joints by friction stir welding

Dissimilar friction stir welding between 1060 aluminum alloy and annealed pure copper sheet with a thickness of 3 mm was investigated. Sound weld was obtained at a rotational speed of 1050 r/min and a welding speed of 30 mm/min. Intercalation structure formed at the crown and Cu/weld nugget (WN) area promotes interfacial diffusion and metallurgical bonding of aluminum and copper. However, corrosion morphology reveals the weak bonding mechanism of internal interface, which causes the joint failing across the interface with a brittle–ductile mixed fracture mode. The tensile strength of the joint is 148 MPa, which is higher than that of the aluminum matrix. Crystal defects and grain refinement by severely plastic deformation during friction stir welding facilitate short circuit diffusion and thus accelerate the formation of Al4Cu9 and Al2Cu intermetallic compounds (IMCs). XRD results show that Al4Cu9 is mainly in Cu/WN transition zone. The high dislocation density and formation of dislocation loops are the major reasons of hardness increase in the WN.

Two-dimensional Cs-vacancy superstructure in iron-based superconductorCs0.8Fe1.6Se2

Single crystal neutron diffraction is combined with synchrotron x-ray scattering to identify the different superlattice phases present in ${\text{Cs}}_{0.8}{\text{Fe}}_{1.6}{\text{Se}}_{2}$. A combination of single crystal refinements and first principles modeling are used to provide structural solutions for the $\sqrt{5}\ifmmode\times\else\texttimes\fi{}\sqrt{5}$ and $\sqrt{2}\ifmmode\times\else\texttimes\fi{}\sqrt{2}$ superlattice phases. The $\sqrt{5}\ifmmode\times\else\texttimes\fi{}\sqrt{5}$ superlattice structure is predominantly composed of ordered Fe vacancies and Fe distortions, whereas the $\sqrt{2}\ifmmode\times\else\texttimes\fi{}\sqrt{2}$ superlattice is composed of ordered Cs vacancies. The Cs vacancies only order within the plane, causing Bragg rods in reciprocal space. By mapping x-ray diffraction measurements with narrow spatial resolution over the surface of the sample, the structural domain pattern was determined, consistent with the notion of a majority antiferromagnetic $\sqrt{5}\ifmmode\times\else\texttimes\fi{}\sqrt{5}$ phase and a superconducting $\sqrt{2}\ifmmode\times\else\texttimes\fi{}\sqrt{2}$ phase.

Alumina Induced Crystal Refinement and Enhanced Corrosion Resistance of Phosphate Chemical Conversion Coating on 35CrMnSi Steel

Alumina Induced Crystal Refinement and Enhanced Corrosion Resistance of Phosphate Chemical Conversion Coating on 35CrMnSi Steel

Structural perfection of (Na0.5Gd0.5)MoO4:Yb laser crystals

Czochralski-grown (Na0.5Gd0.5)MoO4 single crystals doped with different concentrations of Yb3+ ions have been investigated by X-ray diffraction. The type and concentration of point defects (different Na:Gd ratios, vacancies in Mo and O sites), and, consequently, the real compositions of the investigated crystals have been determined. The presence of additional reflections (50%) for the (Na0.5Gd0.5)MoO4:10%Yb crystal was revealed, indicating the symmetry reduction from space group I41/a to P4_ without any change in the unit cell parameters. Crystal refinement within the framework of space group I41/a revealed an increase in the unit cell parameters for both (Na0.5Gd0.5)MoO4:3%Yb and (Na0.5Gd0.5)MoO4:10%Yb crystals; it can be explained by the kinetic phase transition of order–disorder type caused by the cation ordering at the dodecahedral sites in the local regions of the crystals. The reasons for the possible symmetry reduction in scheelite family crystals are discussed.

圧粉磁芯の微視組織および磁気特性に及ぼす原料鉄粉粒子形状の影響

The coercive force of an iron powder core decreases with an increase in the circularity of raw iron powder. Microstructural observation reveals that the crystal grain size of the iron powder core is reduced through recrystallization during the stress relief annealing after the powder compaction. An analysis of the work hardening behavior through the compaction process shows that a rounder particle shape leads to a smaller particle deformation, resulting in a reduction of the crystal grain refinement through recrystallization. A grain boundary pinning model well describes the reduction of coercive force with the increase in the eventual grain size.

XRD Characterization of Crystallinity of Human Tooth Enamel under Influence of Mechanical Grinding

Crystallinity refers to the degree of structural order in a solid and has a big influence on hardness, density, transparency and diffusion. Even within materials that are crystalline completely, the de- gree of structural perfection can vary, reflecting size and elastic strain of many independent crys- talline regions (grains or crystallites) of which these materials are composed. In this work it was attempted to reduce the crystallinity of human enamel using a technique of mechanical grinding (MG) with an ultra-compact FRITSCH Mini-Mill PULVERISETTE 23 machine. Variation in the crys- tallinity through the MG was monitored by X-ray diffraction (XRD) by broadening of the diffraction peak and examined using the Williamson-Hall plot method. Crystallites in human enamel are reg- ularly arranged and oriented (in the (001) direction) perpendicularly to the interface of enamel- dentin junction. The results showed an anisotropic feature in crystallinity. Reduction of the crys- tallinity along the a-axis is due to the crystal strain rather than to the refinement of crystal, and vice versa along the c-axis. After 230 h of the MG, the length of crystallites decreased from 100 nm to 30 nm and width from 40 nm to 37 nm approximately.

Docking and Design of Oligosaccharides, Glycoproteins, and Glycolipids

Carbohydrates are infamously challenging to model, yet they affect protein structure, stability, and activity. We are developing accurate and fast methods of modeling and designing carbohydrates for applications in glycobiology. We have built a framework within the Rosetta structure and design suite for modeling saccharide ligands and complex glycoconjugates. Our intuitive and efficient data structures allow access to all torsion angles (φ, ψ, ω, and χ) and Cremer–Pople parameters for sampling ring forms and capture the high degree of flexibility, stereochemistry, and branching in carbohydrates. Rosetta's flexibility and speed enable modeling of any glycan-containing molecule in docking and refinement protocols through exploration of this vast torsional and ring-conformational diversity.Rosetta's residue-centric approach, coupled with combinatorial “patching” of standard residues with specific functional groups, allows for design algorithms that sample alternative saccharide units, enabling high-throughput screening of thousands of protein variants and glycoforms in a search for stable or functional molecules.Here, we will report three studies benchmarking monosaccharide ring conformations, oligosaccharide structure prediction, and bound–bound protein–oligosaccharide docking. We explore the relative energy surfaces of the ring forms of all D-aldohexopyranoses; we examine predicted structures of two LewisX oligosaccharides; and we compare the docking predictions of eleven antibody–glycoantigen pairs with known structures. These studies will allow us to rigorously test the Rosetta scoring (energy) function, to adapt it to the unique chemical effects of sugars.We will also present preliminary real-world applications in antibody accessibility for glycosylation enzymes, x-ray crystal refinement of an extensively glycosylated HIV-1 envelope protein trimer, and the activity of glycosylated carboxylesterases.These new approaches will provide glycobiologists and glycoengineers a new computational toolbox, further the understanding of the biomolecular mechanisms of disease, and create opportunities for a wide range of previously intractable studies.

Rapid early formation and crystal refinement of chemical conversion hopeite coatings induced by substrate sandblasting

A relatively uniform banded structure is exhibited on the crystal surface of a coating on sandblasted substrates.

Structure and Magnetic Properties of Ce3(Ni/Al/Ga)11—A New Phase with the La3Al11 Structure Type

Single crystals of Ce3(Ni/Al/Ga)11 were obtained from an Al flux reaction. Single crystals of the title compound crystallizing in the orthorhombic space group Immm (No. 71, Z = 2) with a = 436.38(14), b = 1004.5(3) and c = 1293.4(4) pm. This is a standardized unit cell of the previously published La3Al11 structure type. Wavelength dispersive microprobe provides the composition of Ce3.11(1)Ni0.03(1)Al8.95(1)Ga1.90(1). Single crystal refinement provides the composition Ce3Ni0.08Al9.13Ga1.78 with substitution of the Ni and Ga on the Al1 and Al4 sites with the Al2 and Al3 solely occupied by Al. Magnetic susceptibility measurements reveal antiferromagnetic ordering with TN = 4.8 K and there is no evidence for a ferromagnetic ordering that has been reported for Ce3Al11. The effective magnetic moment was found to be μeff = 1.9μB/Ce, which is lower than the expected value for trivalent Ce (2.54μB/Ce).

Influence of particle size on sinterability, crystallisation kinetics and flexural strength of wollastonite glass-ceramics from waste glass and fly ash

Wollastonite glass-ceramics were prepared from waste glass and fly ash by using the primary powder sintering. The sinterability, crystallisation kinetics and mechanical property of glass-ceramics have been investigated systematically with respect to the influence of particle size of raw materials. As compared to coarse powders (44 μm), fine powders (6 μm) exhibited fast sintering rate, high densification and high degree of crystallinity. The sintering kinetic analysis showed that the sintering activation energies were 229 and 157 kJ mol−1 for coarse and fine powders respectively, in well agreement with those from the linear shrinkage analysis. The activation energies of crystallisation were 245 and 317 kJ mol−1 for coarse and fine powders, respectively, suggesting high energy barrier of crystallisation for fine powders. The flexural strengths of wollastonite glass-ceramics from fine powders were increased by more than 50% as compared to that from coarse powders, resulting from the improved densification, high degree of crystallinity and crystal shape anisotropy as well as crystal refinement.

Mode parameterization of structures with very low symmetry: PZT and magnetite

The parameterization of distorted structures in terms of symmetry modes is an effective and efficient method for both their description and refinement [1]. A basis of symmetry-adapted modes transforming according to irreducible representations not only provides a hierarchical division of the degrees of freedom consistent with the mechanism at the origin of the distorted phase, but it allows the avoidance of false refinement minima, typical of highly pseudo-symmetric phases. A reduction of the number of free parameters by setting to zero negligible marginal modes is also possible. The mode description is nowadays easily applicable through freely available programs [2,3], while direct single crystal and powder diffraction refinements under this parameterization are possible combining these programs with some of the most popular refinement codes. The mode description is especially effective when dealing with distorted structures of very low symmetry compared with that of the parent phase. In these cases, the hierarchy between strong primary modes and weak marginal ones is specially pronounced, minimizing the role of many secondary modes. The physical origin of each primary distortion is usually a set of unstable degenerate normal modes. This introduces correlations among the different phases in the phase diagram that become patent in a mode description and can be used both to characterize the evolution of the relevant order parameters and as a stringent test of proposed structural models. Furthermore, the fact that each of the primary mode distortions is basically associated with the activity (instability) of a single normal mode can yield a "single mode" signature in the mode decomposition, which represents a set of subtle additional structural constrains beyond conventional crystallography. We will illustrate these considerations using the examples of the monoclinic phases of ferroelectric PbZr1-xTixO3 (PZT) and the Verwey phase of magnetite.

Sulfur Dioxide Removal using Natural Zeolitic Tuff

Adsorption of SO2 onto Jordanian zeolitic tuff (ZT) was examined in this work. ZT samples were characterized by XRD, XRF, BET and TGA analyses. The sorption process was carried out in a fixed bed column at different operating conditions. The unique measuring technique, namely UIC sulfur coulometer, for SO2 measurement was adopted in this work. Uptake of SO2 by ZT was found to increase with increasing temperature up to a temperature of 200°C and then decrease at higher temperatures. It was also found that drying of ZT, by conventional and microwave heating has a considerable effect on SO2 uptake and breakthrough time. Experimental data for adsorption isotherms were obtained and found to follow the BET isotherm model. It was found that the adsorption process is exothermic in nature. Thermal pre-treatment was found to affect the adsorption capacity and breakthrough time of ZT. The maximum adsorption capacity was obtained after thermal pretreatment of ZT at a temperature of 200°C, which could be linked to the effect of heating on the destruction of crystal structure of phillipsite, the crystal refinement of chabazite, and the formation of new aluminosilicate crystalline phases. ZT can be regenerated and the initial adsorption capacity was preserved after three regeneration cycles.

Crystal Growth of Tl4CdI6: A Wide Band Gap Semiconductor for Hard Radiation Detection

We report the synthesis, physical characterization, and crystal growth of Tl4CdI6. We show that this material has good photoconductivity and is a promising semiconductor for room temperature X-ray and γ-ray detection. Large single crystals were grown by the vertical Bridgman method and cut to dimensions appropriate for detector testing. Single crystal X-ray diffraction refinements confirm that Tl4CdI6 crystallizes in the tetragonal crystal system with a centrosymmetric space group of P4/mnc, with a calculated density of 6.87 g/cm3. Thermal analysis and high-temperature synchrotron powder diffraction studies were used to determine phase relationships and crystallization behavior during crystal growth. We have elucidated the reason for different colors encountered when synthesizing or growing single crystals of Tl4CdI6 (yellow, red, and black), and it is the presence of a small amount of TlI impurity. We report proper crystal growth conditions to obtain essentially pure yellow Tl4CdI6 crystals. The material...

A vibrational spectroscopic study of the arsenate minerals cobaltkoritnigite and koritnigite

Raman spectra of two well-defined types of cobaltkoritnigite and koritnigite crystals were recorded and interpreted. Significant differences in the Raman spectra of cobaltkoritnigite and koritnigite were observed. Observed Raman bands were attributed to the (AsO3OH)2− stretching and bending vibrations, stretching and bending vibrations of water molecules and hydroxyl ions. Both Raman and infrared spectra of cobaltkoritnigite identify bands which are attributable to phosphate and hydrogen phosphate anions proving some substitution of phosphate for arsenate in the structure of cobaltkoritnigite. The OH⋯O hydrogen bond lengths in the crystal structure of koritnigite were inferred from the Raman spectra and compared with those derived from the X-ray single crystal refinement. The presence of (AsO3OH)2− units in the crystal structure of cobaltkoritnigite and koritnigite was proved from the Raman spectra which supports the conclusions of the X-ray structure analysis.

Ultrasonic Induced Rapid Formation and Crystal Refinement of Chemical Conversed Hopeite Coating on Titanium

Hopeite coating on metals by the phosphate chemical conversion (PCC) method has received more attention for its potential biomedical use. It is difficult to get a PCC phosphate coating due to the presence of a passive oxide layer on the surface of titanium. In this research, we report on effects of ultrasonic irradiation (UI) on formation, crystal size, microstructure, and corrosion resistance of the PCC coatings on Ti. It is shown that both coatings formed with and without UI are composed of hopeite (Zn3(PO4)2·4H2O) with similar crystal shape. FE-SEM observation demonstrates that UI can significantly decrease crystal size from 50–100 to 5–20 μm within a duration time of 30–60 min. Short period PCC treatment of 5 min shows that UI can enhance the formation of coating with the increase of nucleation rate. And the nucleation rate with UI of 250 W is significantly higher than that of 50 W. The electrochemical analysis reveals that the corrosion resistance of the coatings can also be improved by ultrasonic ir...

Adachiite, a Si–poor member of the tourmaline supergroup from the Kiura mine, Oita Prefecture, Japan

Adachiite, CaFe3Al6(Si5AlO18)(BO3)3(OH)3(OH), a Si–poor member of the tourmaline supergroup, is found in the hydrothermal vein cutting emery from Nabagasako of the Kiura mine, Saiki City, Oita Prefecture, Japan. Adachiite occurs as a constituent (several to 300 µm thickness) of hexagonal prismatic crystals, and forms a zoned structure closely associated with schorl. It is transparent with brownish–purple to bluish–purple color, while the massive aggregate shows black in color. Adachiite is trigonal, R3m, a = 15.9290(2), c = 7.1830(1) Å, V = 1578.39(4) Å3, and Z = 3, determined via single crystal XRD refinement (R1 = 0.038). Adachiite is the first member of the tourmaline group formed via Tschermak–like substitution.

Synthesis, structure characterization, and thermochemistry of the coordination compounds of pyridine-2,6-dicarboxylic acid with several metals (Ca and Co)

Two solid state complexes of pyridine-2,6-dicarboxylate with Ca2+ and Co2+ ions, Ca2(DPC)2(H2O)6(H2DPC)2(s) and Co(DPC)2·Co(H2O)5·2H2O(s), were synthesized. X-ray crystallography was applied to characterize the crystal structures of the two complexes. The molecular and cell stacking structures of the two complexes were shown; the crystal data and refinement details were summarized, and the selected bond lengths and angles of the title complexes were listed. Low-temperature heat capacities of the two complexes were measured with an automated adiabatic calorimeter in the temperature ranging from 78 to 380 K. Two polynomial equations of experimental molar heat capacities as a function of the temperature were obtained by the least-squares method. The smoothed molar heat capacities and thermodynamic functions of the complexes were calculated based on the fitted polynomial equations. In addition, thermodynamic properties of the two complexes were compared.