Conventional X-ray Diffraction Method Research Articles

Local crystallization investigation of amorphous alloys using a two-dimensional detector by X-ray diffraction method

Amorphous alloys without a crystalline structure exhibit excellent soft magnetic properties but are difficult to machine due to their tough mechanical properties. The authors have proposed a new machining method that improves machinability by crystallizing only the local regions involved in machining, thereby reducing local strength and toughness. To realize this method, it is necessary to evaluate the crystallinity of the local area nondestructively, but it is difficult to detect a local area of crystals precipitated in amorphous materials by the conventional X-ray diffraction method (sin2ψ method). In this paper, we attempted to investigate the crystallinity of the local area using a two-dimensional X-ray diffraction method (2D method) with a two-dimensional detector. Fe-based amorphous alloys were locally crystallized using an ultrashort pulsed laser with a beam diameter of about 66 μm. Then, it was revealed that the 2D method can evaluate even a small area of crystallization within several tens of micrometers.

Combined Approach of Mechanochemistry and Electron Crystallography for the Discovery of 1D and 2D Coordination Polymers

Mechanochemical synthesis is an attractive preparative method that combines a green approach with versatility, efficiency, and rapidity of reaction. However, it often yields microcrystalline materials, and their small crystal size is a major hindrance to structure elucidation with conventional single-crystal or powder X-ray diffraction methods. This work presents the novel approach of combining mechanochemistry with electron diffraction techniques to elucidate the crystal structure of metal–organic compounds of zinc(II) and copper(II) with 2,6-pyridinedicarboxylic acid and 4,4′-bipyridine.

Enhanced nonradiative recombination in Al x Ga1−x N-based quantum wells thinner than the critical layer thickness determined by X-ray diffraction

The optical properties of Al x Ga1−x N-based quantum wells (QWs) with various thicknesses are investigated. When the Al x Ga1−x N thickness in Al0.8Ga0.2N/AlN QWs exceeds 6 nm, the photoluminescence lifetime is drastically shortened even at cryogenic temperatures, which indicates that nonradiative recombination processes are enhanced. Interestingly, the thicknesses for the degradation of the optical properties of Al x Ga1−x N on AlN (0001) are about two orders of magnitude thinner than the critical layer thicknesses for lattice relaxation determined by a conventional X-ray diffraction method. To avoid the degradation of the QW optical properties, Al y Ga1−y N (y > x) underlying layers are effective.

Synthesis, X-ray structure, and DFT analysis of a binary complex of 3,3'-[(3-benzimidazolyl)methylene]bis(4-hydroxy-2H-1-benzopyran-2-one): 5-Methyl-1,3-thiazol-2(3H)-imine

A combined theoretical and experimental investigation on a pharmaceutically important binary complex 3,3'-[(3-benzimidazolyl)methylene]bis(4-hydroxy-2H-1-benzopyran-2-one): 5-methyl-1,3-thiazol-2(3H)-imine is presented in this manuscript. The compound crystallizes in the monoclinic crystal system with space group Cc with unit cell parameters: a = 19.8151(8) Å, b = 15.2804(6) Å, c = 8.3950(4) Å, β = 94.0990(10)°, V = 2535.36(19) Å3, Z = 4, T = 296(2) K, μ(MoKα) = 0.184 mm-1, Dcalc = 1.490 g/cm3, 35833 reflections measured (5.332° ≤ 2Θ ≤ 56.678°), 6168 unique (Rint = 0.0467, Rsigma = 0.0388) which were used in all calculations. The final R1 was 0.0435 (I > 2σ(I)) and wR2 was 0.1073 (all data). The crystal structure has been determined by the conventional X-ray diffraction method, solved by direct methods and refined by the full matrix least squares procedure. Intramolecular hydrogen bonding of the type C–H⋅⋅⋅O and O–H⋅⋅⋅O is present and the crystal structure stabilizes via N–H…O, C–H…N and O–H…N intermolecular interactions. The optimized structural parameters have been compared and the parameters like ionization potential, electron affinity, global hardness, electron chemical potential, electronegativity, and global electrophilicity based on HOMO and LUMO energy values were calculated at B3LYP/6-311G(d,p) level of theory for a better understanding of the structural properties of the binary complex.

Development of Measurement Tools for High-Throughput Experiments of Synchrotron Radiation XRD and XAFS on Powder Libraries.

We propose to minimize the sampling time for high-throughput measurements of powder X-ray diffraction (XRD) and X-ray absorption fine structure (XAFS) in synchrotron radiation. The conventional synchrotron radiation powder X-ray diffraction method requires filling of a capillary tube, but a structure-refining diffraction pattern could be obtained by transferring the crushed powder to a tape and rotating the cassette-tape tool by ±5° around the sample position. XAFS spectra could also be measured with the sample attached to the tape. The time required for sample preparation was greatly reduced, which made high-throughput experiments with powders in synchrotron radiation experiments more accessible.

Temperature evolution of Fe–27Ga structure: comparison of in situ X-ray and neutron diffraction studies

Comparative in situ X-ray and neutron diffraction studies of the phase transitions in a high magnetostriction Fe–27Ga alloy sample have been performed, with heating up to 850°C and subsequent cooling to room temperature. Different structural information (phase content, phase-transition temperatures, unit-cell behaviour) is obtained for the bulk sample and its surface, and this fact is discussed here in terms of the difference between the scattering properties of X-rays and neutrons. In particular, a gallium-deficient phase with A2-type structure was found on the surface of the sample. The results demonstrate that conventional X-ray diffraction methods are insufficient for precise structural analysis of bulk samples of galfenols and cannot be used alone to build their phase diagrams.

Insight Into the Crystallinity of Chinese Ancient Silk by Synchrotron Radiation-Based and Conventional X-ray Diffraction Methods

This study investigates the crystallinity distribution of ancient silk. Owing to the inherent multi-hierarchical structure of silk protein and the complicated structural changes that occur due to various burial environments, it is challenging but worthwhile to study ancient silk ageing behavior, which is based on the fact that ageing begins with a single fiber and then spreads to a whole fabric. Crystallinity was one of the most effective indicators found to reveal the ageing status of silk. Therefore, a synchrotron radiation-based X-ray diffraction(SR-XRD) method was employed to study the crystallinity distribution of single fibers of ancient silk unearthed from seven archaeological sites in China from historical periods including the warring states, Han dynasty, Song dynasty, and Ming dynasty. In comparison, the conventional X-ray diffraction method, which uses large amounts of samples, was also performed to determine the integral crystallinity of ancient silk. Thermal stability experiments by thermogravimetry(TG) as well as morphology observations by scanning electron microscopy(SEM) and optical microscopy(OM) all confirmed the deterioration of ancient silk. Moreover, the ageing mechanism of ancient silk was proposed with the assistance of an artificial ageing study. The results confirmed the effectiveness of SR-XRD as an ageing indicator, revealing the crystallinity distribution. This research could provide motivation to determine the deterioration status of ancient silk, and would also aid in explaining the fragility of ancient silk due to ageing.

Determination of residual stresses for helical compression spring through Debye-Scherrer ring method

In this work, the experimental study was conducted on fractured helical coil spring of a passenger car. The fracture occurred in ASTM A401 helical coil spring at the 2nd active coil, 20.24 mm from the bearing coil. A fitting Lorentz method was used to obtain the most intense peaks, which was placed at 0° and 35° X-ray incidence angles. Further, X-ray tri-axial stresses were obtained from conventional X-ray diffraction method for coil spring under consideration. The present method followed 2-D X-ray diffraction “cosα” method. FWHM of the spring was also investigated and validated with conventional X-ray diffraction method.

A short-wave X-ray diffraction method to evaluate the residual stress of welding joint for 7N01 Al alloy

The residual stress with different degree is inevitable to be introduced during the welding process for high strength 7N01 Al alloys, which will deteriorate the mechanical properties in service. Therefore, a proper characterization method is of vital importance to obtain the detailed residual stress distribution. The conventional X-ray diffraction method can only measure the residual stress of near surface but cannot determine the internal bulk stress with nondestructive way. In the present work, a new Short-Wave X-Ray Diffraction (SWXRD) test methodology was utilized, which can evaluate not only the surface but also the internal residual stress of a crystalline material by applying the monochromatic short-wave X-ray of high-energy. The results show that there is a “M” shaped distribution of residual stress of longitudinal direction (LD) in different affected zone. Furthermore, the characterization of residual stress along weld depth direction demonstrates that the middle part of weld joint is subjected to tensile stress while the rest is subjected to compressive stress.

Application of rocking-scan method to detect the low-content diamonds in a complex mixture

A method for detecting large-size diamonds with low content in a complex mixture was described. Phase identification via conventional X-ray diffraction method is unsuitable because of the large-size and low-content characteristics of the diamonds. Thus, we proposed a convenient approach (i.e., rocking scan) for assessing the presence of low-content diamonds in a complex mixture. A thorough rocking scan of the (111), (220), and (311) planes revealed the presence of low-content diamonds prepared by reducing dense carbon dioxide with alkali metals. This procedure can be successfully applied to several standard mixture samples prepared by mixing α-SiO2, α-Al2O3, graphite, and pure diamond powders, which are commercially available. We estimated that the detection limit was at or below the 0.1 wt% level by using the proposed method under the current condition. This method is straightforward, routinized, and may be specifically developed to satisfy the requirements of public and private institutions for a rapid identification of other mixture phases, of which the large-size and low-content characteristics do not allow an instant phase identification by conventional X-ray diffraction methods.

Effects of Sn microalloying on cold rolling and recrystallization textures and microstructure of a ferritic stainless steel

We investigated the effects of Sn microalloying on cold rolling and recrystallization textures and microstructure of a ferritic stainless steel. The as-received hot rolled sheets were cold rolled at 10%–90% reductions; the sheets cold rolled up to an 80% reduction were annealed at 740–880 °C for 5 min. For comparison, the cold rolling and recrystallization textures of the steel sheets with and without Sn were determined with the conventional X-ray diffraction method. The cold rolling and recrystallization metallographic microstructures were measured by scanning electron microscope and optical microscope, and the crystal orientation maps of the cold rolled and annealed samples were observed by electron backscattered diffraction. The micro-hardness was determined using a digital micro-hardness tester. Our results show that Sn microalloying in a medium chromium ferritic stainless steel plays multiple roles in the cold rolling and recrystallization processes. Sn micrcoalloying contributes to the enhancement in cold rolling texture intensity and the acceleration in cold rolling texture transformation. Sn microalloying is beneficial in promoting the recrystallization process. Recrystallization occurs preferentially in the ferritic stainless steel with Sn. Sn microalloying plays an important role in inhibiting the growth of recrystallized grains. The finer grains are obtained in ferritic stainless steel with Sn when annealing at high temperatures.

Atomic Orientation Detection using Nonlinear Optics and its Application as an Environmental Sensor

Recent advances in theoretical nonlinear optics have enhanced our understanding regarding the origin of the higher harmonic generation in particular interpreting the higher harmonic intensity data from nonlinear spectroscopy. In this work we show that the atomic bond orientation at the surface as well as the bulk of an inversion symmetric material e.g. Silicon (111) facet can be determined from nonlinear spectroscopy alone without the need to apply the conventional X-Ray diffraction method. Our simulation shows that nonlinear spectroscopy data interpreted using bond models can reliably determine atomic orientation almost in a direct way because the model is based on a very simple assumption that the radiations are created from charges along the atomic bonds. In addition we present a brief description of possible application to use nonlinear spectroscopy as an environmental sensor.

Insights into Photosystem II from Isomorphous Difference Fourier Maps of Femtosecond X-ray Diffraction Data and Quantum Mechanics/Molecular Mechanics Structural Models.

Understanding structure–function relations in photosystem II (PSII) is important for the development of biomimetic photocatalytic systems. X-ray crystallography, computational modeling, and spectroscopy have played central roles in elucidating the structure and function of PSII. Recent breakthroughs in femtosecond X-ray crystallography offer the possibility of collecting diffraction data from the X-ray free electron laser (XFEL) before radiation damage of the sample, thereby overcoming the main challenge of conventional X-ray diffraction methods. However, the interpretation of XFEL data from PSII intermediates is challenging because of the issues regarding data-processing, uncertainty on the precise positions of light oxygen atoms next to heavy metal centers, and different kinetics of the S-state transition in microcrystals compared to solution. Here, we summarize recent advances and outstanding challenges in PSII structure–function determination with emphasis on the implementation of quantum mechanics/molecular mechanics techniques combined with isomorphous difference Fourier maps, direct methods, and high-resolution spectroscopy.

Investigation of Structural Evolution in 3d-Transition Metal Ferrites MFe2O4 (M = Fe, Co, Ni and Cu) As Conversion Type Electrodes for Li-Ion Batterie

Growing demand of Li-ion batteries initiates the on-going researches on new electrode materials with improved performance. Conversion-type anode materials have been a topic of interest ever since the beginning of the 21st century due to their intrinsically high capacity, which can enhance significantly the energy density of future lithium-ion batteries [1]. For metal oxides, operating via conversion, the initial discharge involves the reduction of the transition metals to a composite material consisting of metallic nanoparticles (2-8 nm) dispersed in an amorphous Li2O matrix. Upon following charge, the metal particles are oxidized, however, the structure and composition of thus formed nanostructured metal oxide may be different comparing to the pristine oxide. Nanocrystalline transition metal Iron oxides MFe2O4 (M = Fe, Co, Ni and Cu) are especially attractive because of low cost and environmental compatibility.In this work, a comparative study of different metal ferrites as conversion type model system for Li-ion batteries, to elucidate the influence of partial substitution of Fe in the spinel structure with different 3d-cations, are reported and also a comparative study of their electrochemical eevolution mechanism is investigated using in situ diffraction and pair distribution function analysis. In order to investigate the electrochemical mechanism in detail, the structural evolution of the materials in the 1st cycle was tracked using in situ synchrotron diffraction and ex situ PDF techniques. It can be observed that the electrochemical mechanism in the first discharge cycle could occur via two different processes. Either by the direct reduction of initial material into respective binary oxide or by a Li-intercalation process in the spinel structure during the initial discharge, which is further transformed to metal nanoparticles dispersed in Li2O matrix. Due to low crystallite size and the formation of the amorphous (poorly diffracting) phases, laboratory and synchrotron conventional X-ray diffraction methods can provide only limited insight into the processes occurring upon cycling conversion-type materials. Pair Distribution Function (PDF) analysis can be used for probing local as well as the long-range structure of the material is more informative for such systems containing both crystalline and amorphous components [2]. The initial electrochemical lithiation of Fe3O4 anode operating via conversion mechanism is investigated by PDF analysis. The ex-situ PDF measurements have been performed on the samples with different lithium content, prepared by discharging in the electrochemical cell voltage range of 3.0 to 0.1 V vs. Li+/Li (See figure 1). The details of the electrochemical mechanism of transition metal ferrites as negative electrode material for Li-ion batteries will be discussed. Acknowledgement: The financial support from DFG within the Research Priority Program SPP 1473, “Materials with new Design for improved Li ion batteries-WeNDeLIB” is gratefully acknowledged. This work has benefited from the beamtime allocated by the P02.1 beamline, PETRA, Hamburg. [1] J. Cabana, L. Monconduit, D. Larcher, M. R. Palacín, Advanced Energy Materials, 22, E170-E192, 2010. [2] T. Proffen and H. Kim, Journal of Materials Chemistry, 19, 5078, 2009. Figure 1

Total scattering atomic pair distribution function: new methodology for nanostructure determination

ABSTRACTThe conventional X-ray diffraction (XRD) methods probe for the presence of long-range order towards a solution of the average crystal structure. Experimentally, structural information about long-range, periodic atomic ordering is reflected in the Bragg scattering while local atomic structural deviations from the average structure mainly affect the diffuse scattering intensities. In order to obtain structural information about both average and local atomic structures, a technique that takes in account both Bragg and diffuse scattering needs to be employed, such as the total scattering atomic pair distribution function (PDF) technique. This article introduces a PDF-based methodology that can be applied to extract precise structural information about nanoparticles such as the size of the crystalline core region, the degree of crystallinity, the atomic structure of the core region, local bonding, and the degree of the internal disorder, as a function of the nanoparticle diameter. This article sheds light on a new PDF-based methodology that can yield precise quantitative structural information about small nanocrystals from XRD data, and also describes the essential aspects of this proposed methodology as well as its great potential. This method is generally applicable to the characterisation of the nanoscale solid, many of which may exhibit complex disordered structure.

Hydration process of cement-based materials by AC impedance method

AC impedance is a new method to study the changes of pore structure and the hydration degree during the hydration and hardening process of cement paste by the change of the electrochemical parameters. Employing AC impedance method, we studied the hydration and hardening process of cement paste with fly ash and slag, and analyzed the influence of different hydration age, water-binder ratio and mineral admixture on the impedance parameters. Moreover, we compared the results with those by the conventional porosity testing method and X-ray diffraction method. The results showed that AC impedance could be taken as a new technology in cement and concrete research.

A new method for the identification and quantification of magnetite–maghemite mixture using conventional X-ray diffraction technique

The electrical explosion of Fe wire in air produced nanoparticles containing the binary mixture of magnetite (Fe3O4) and maghemite (γ-Fe2O3). The phase identification of magnetite and maghemite by the conventional X-ray diffraction method is not a simple matter because both have the same cubic structure and their lattice parameters are almost identical. Here, we propose a convenient method to assess the presence of magnetite–maghemite mixture and to further quantify its phase composition using the conventional peak deconvolution technique. A careful step scan around the high-angle peaks as (511) and (440) revealed the clear doublets indicative of the mixture phases. The quantitative analysis of the mixture phase was carried out by constructing a calibration curve using the pure magnetite and maghemite powders commercially available. The correlation coefficients, R2, for magnetite–maghemite mixture was 0.9941. According to the method, the iron oxide nanoparticles prepared by the wire explosion in this study was calculated to contain 55.8wt.% maghemite and 44.2wt.% magnetite. We believe that the proposed method would be a convenient tool for the study of the magnetite–maghemite mixture which otherwise requires highly sophisticated equipments and techniques.

Subsolidus phase relations in CaO–In 2O 3–B 2O 3 system and crystal structure of CaInBO 4

Subsolidus phase relations of CaO–In 2O 3–B 2O 3 system have been investigated mainly by the conventional solid-state reaction technique and powder X-ray diffraction method. There are nine definite three-phase regions under present experimental conditions. Six binary compounds and one ternary compound were found to exist in this system. Crystal structure of the ternary compound CaInBO 4 was determined from X-ray powder diffraction data using Rietveld method. It crystallizes in the orthorhombic space group Pnma (No. 62) with a = 10.3120(3) Å, b = 3.42519(8) Å, c = 9.5150(3) Å, V = 336.07(2) Å 3 and Z = 4. Mixed occupancies were confirmed in this structure, Ca and In atoms are distributed between two atom sites: 93.6%Ca and 6.4%In occupy one site, 93.6%In and 6.4%Ca occupy another. Two In(Ca)O 6 octahedra and two Ca(In)O 7 polyhedra are linked each other by sharing edges to form ribbons in the a– c plane and extend infinitely along the direction of the b axis. The infrared spectrum of CaInBO 4 has been measured, which is consistent with the crystallographic study. In general, compounds MRBO 4 (M and R are divalent and trivalent cations, respectively) are in a large family of monoborates with different structure types strictly depending on the relative size of the M and R ions.

Survey of the theory and experimental measurements of residual stress in Pd thin film

Different thicknesses of Pd thin film were deposited over SrTiO3 by electron beam physical vapor deposition. Residual stress for each thickness of Pd film was computed by applying conventional x-ray diffraction method and taking into account Poisson’s ratio and elastic module measured by Nanoindentation. We observed that Pd stress variation at 300 °C substrate temperature obeys the trend of type II metals with high adatom mobility. Several models alluded in the literature were compared to the stress variation of the Pd films. Two models, namely; Freund–Chason and Guisbiers–Van Overschelde–Wautelet were found to be in agreement with the experimental results in that for the thicknesses less than 30 nm, Guisbiers–Van Overschelde–Wautelet is dominant but for higher than 30 nm, variation in stress follows Freund–Chason model. Therefore, the thickness around 30 nm could be considered as coalescence thickness. Surprisingly, this transition thickness is the same thickness that Guisbiers–Van Overschelde–Wautelet and Freund–Chason models intersect. Negligible residual stress and high conductance of 30 nm Pd thin film reveal the importance of this transition thickness in microelectronic technology.

Residual Stress Relaxation Induced by Mass Transport Through Interface of the Pd/SrTiO3

Metal interconnections having a small cross-section and short length can be subjected to very large mass transport due to the passing of high current densities. As a result, nonlinear diffusion and electromigration effects which may result in device failure and electrical instabilities may be manifested. Various thicknesses of Pd were deposited over SrTiO3 substrate. Residual stress of the deposited film was evaluated by measuring the variation of d-spacing versus sin2ψ through conventional X-ray diffraction method. It has been found that the lattice misfit within film and substrate might be relaxed because of mass transport. Besides, the relation between residual intrinsic stress and oxygen diffusion through deposited film has been expressed. Consequently, appearance of oxide intermediate layer may adjust interfacial characteristics and suppress electrical conductivity by increasing electron scattering through metallic films.