Standard X-ray Diffraction Research Articles

Study on Ca-doping effects and structural stability in Bi2Sr2-xCaxCuO6+δ (0 ≤ x ≤ 1.2) compounds by Rietveld refinement and high-pressure Raman spectroscopy

The lattice distortion induced by element doping is regarded as an effective approach to improve the superconductivity of Bi-based superconductors. In this study, a series of Bi2Sr2-xCaxCuO6+δ (x = 0, 0.2, 0.4, 0.6, 0.8, 1.0 and 1.2) ceramic samples are prepared by Pechini sol-gel method. The Ca-doping effects, structural stability and superconductivity of Bi-2201 phase are studied by electron microscopy, high-pressure Raman spectroscopy, the standard four-probe technique, X-ray diffraction and Rietveld refinements. Results indicate that all samples are constituted by Bi-2201 main phase and Ca8.56Sr5.44Bi16O38 impurity. It can be determined that Ca atoms have entered Bi-2201 orthorhombic lattice and preferentially occupied the Sr-sites. When Ca atoms are introduced and high-pressure is exerted, the Bi-2201 lattice can present a relatively high structural stability. Meanwhile, the correlations between doping amount x, Cu–O–Cu bond angle (θ), carrier concentration of CuO2 planes and superconducting onset transition temperature (Tc,onset) are discussed particularly. It should be noted that the Bi-2201 lattice has the largest θ, the highest carrier concentration and the highest Tc,onset value of 84.98 K when x = 0.8.

On the potential of eddy current characterization of the ferritic content of recovered 316L powders after LaserPowder bed fusion fabrication

An original container was designed to measure the ferritic content of powder batches by the Eddy Current (EC) technique. As opposed to the standard X-Ray Diffraction (XRD) or Electronic BackScatter Diffraction (EBSD) methods, the EC measurements can be implemented on powder batches of significant sizes, say a hundred grams or so. Using a methodology based on the multiple recycling of an initially ferrite-free virgin powder, it was shown that the EC signals are sensitive to the ferritic content of the recovered powder. On the other hand, in the frequency range scanned by the sensor, the EC signals are virtually independent on the oxygen concentration within the tested powder.

Biasing the Formation of Solution-Unstable Intermediates in Coordination Self-Assembly by Mechanochemistry.

Due to the reversible nature of coordination bonds and solvation effect, coordination self-assembly pathways are often difficult to elucidate experimentally in solution, as intermediates and products are in constant equilibration. The present study shows that some of these transient and high-energy self-assembly intermediates can be accessed by means of ball-milling approaches. Among them, highly aqueous-unstable Pd3 L11 and Pd6 L14 open-cage intermediates of the framed Fujita Pd6 L14 cage and Pd2 L22 , Pd3 L21 and Pd4 L22 intermediates of Mukherjee Pd6 L24 capsule are successfully trapped in solid-state, where Pd=tmedaPd2+ , L1=2,4,6-tris(4-pyridyl)-1,3,5-triazine and L2=1,3,5-tris(1-imidazolyl)benzene). Their structures are assigned by a combination of solution-based characterization tools such as standard NMR spectroscopy, DOSY NMR, ESI-MS and X-ray diffraction. Collectively, these results highlight the opportunity of using mechanochemistry to access unique chemical space with vastly different reactivity compared to conventional solution-based supramolecular self-assembly reactions.

Influences of Both N,N,N- and N,N,C-Coordination Modes of Tolyl-terpyridine on the Photophysical Properties of Cyclometalated Ru(II) Complexes: Combined Experimental and Theoretical Investigations on Acid/Base-Dependent Reversible Cyclometalation.

With the goal of developing a new strategy for the synthesis of luminescent Ru(II) complexes, we have prepared herein a new set of bis-tridentate complexes of the type [(py-bpy-Ph-X)Ru(tpy-PhCH3)]ClO4 (X = -CH3, -CH2Br, and -CHO) incorporating both non-cyclometalated and cyclometalated coordination motifs of two isomeric forms of methylphenyl-terpyridine (tpy-PhCH3). Thorough characterization of the synthesized complexes is carried out using standard analytical tools and single crystal X-ray diffraction. Detailed investigations on their photophysical and electrochemical behaviors are carried out in MeCN. The presence of a carbanionic center in the cyclometalating unit increases the absorption spectral window of the complexes into a longer-wavelength region. The complexes also exhibit room-temperature luminescence in the NIR domain with enhanced excited-state lifetimes (up to 20.1 ns) compared to their non-cyclometalated counterpart, [Ru(tpy-PhCH3)2]2+. In the presence of acid, the non-coordinated nitrogen atom in the secondary coordination sphere of the complexes allows fine-tuning of the absorption and emission spectral properties. Excess acid induces de-coordination of the Ru-C bond, which is signaled by a remarkable alteration of their spectral profiles. Cleavage of the Ru-C bond is also possible upon treating the acidified solution of the complexes with visible light. Restoration of the Ru-C bond is again feasible upon treating the solution with base at an elevated temperature (∼70 °C). In essence, "on-off" and "off-on" switching of emission is facilitated upon alternating treatment of the Ru(II) complexes with acid, base, and temperature. DFT and TD-DFT calculations are also performed for assignments of the spectral bands as well as to understand structural changes associated with the switching behaviors of the complexes.

11 Raman Spectroscopy to Monitor Short-Term and Transient RCS Aerosol Exposure

Abstract Exposure to respirable crystalline silica (RCS) at concentrations at or below the OSHA permissible exposure limit (PEL) of 50 µg/m3 are challenging to monitor with the current industry standard methods X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR). In particular, the assessment of short-term or transient exposure to RCS concentration calls for more sensitive analytical methods that are able to quantify RCS from low dust amounts within the desired uncertainty limits. Here, we present results from a verification study of a Raman spectroscopy-based Identifier system including dedicated respirable air samplers (badges) for the collection of airborne RCS. The air sampling badges concentrate the analyte onto dedicated 1 mm2 collection membranes suitable for direct-on-filter (DOF) Raman analysis. The sampling efficiency of the badges was assessed experimentally and shown to closely adapt the respirable sampling convention according to ISO 7708, with a low sampler bias of < 10%. Using a fully automated Raman-based bench-top reader, the limit of detection (LOD) and limit of quantification (LOQ) were determined empirically with 0.1 and 0.3 µg, respectively. The limits are approx. an order of magnitude lower than for the current industry standards and enable the relevant monitoring of short-term or transient exposure of workers to RCS, as they typically occur in construction or mining environments. The optimized workflow of the Identifier system makes it an attractive alternative to the industry standards XRD and FTIR, with the opportunity to monitor exposure down to the action level.

Influence of Ni interlayer on hydrogen absorption and cyclicity in Gd thin films

The Pd/Gd bilayers and Pd/Ni/Gd trilayers were prepared onto glass substrates by magnetron sputtering. Detailed XPS in-situ studies of the Pd/Gd bilayers allowed to estimate the thickness of the mixed layer at about 4 nm. Further studies showed that the additional Ni interlayer can significantly reduce the interface mixing during the deposition process, leading to the formation of a rather narrow Ni–Gd interface. The structure of the obtained layers before and after the hydrogenation was examined by the standard X-ray diffraction method. The hydrogenation kinetics was studied in-situ at room temperature and pressure up to 1 bar using simultaneous measurements of resistivity and optical transmittance. Furthermore, hydrogen absorption by electrochemical method was monitored using optical transmittance. It was found that the use of an additional 4 nm Ni layer significantly improved the cyclicity of the hydrogen absorption/desorption from the electrolyte, while maintaining low switching time (10 s).

Biologically mediated synthesis of CuO nanoparticles using corn COB (Zea mays) ash for photocatalytic hydrogen production

This research article reports the green synthesis of copper oxide (CuO) nanoparticles (NPs) using the aqueous extract of corn cob ash from agricultural residue. This agricultural residue was subjected to a calcination for use as a stabilizing agent. As-synthesized NPs were characterized by various methods such as SEM/EDS, FT-IR, XRD and UV–Visible spectroscopy. The results revealed that the corn cob ash extract acts as an excellent stabilizing agent for the formation of CuO NPs. The XRD peaks match the standard X-ray diffraction patterns of CuO, confirming a monoclinic crystal structure. The SEM images revealed that the NPs are agglomerated, porous and with rough edges. Meanwhile, the EDS analysis confirmed the existence of Cu and O elements in NPs synthesized by the green route. The absorbance band is at 350 nm and the band gap is around 1.65 eV. Hydrogen evolution was observed on green synthesized CuO in the photocatalysis measurement.

Digital image correlation after focused ion beam micro-slit drilling: A new technique for measuring residual stresses in hardmetal components at local scale

A new method has been developed for measuring residual stresses at the surface of hardmetal components with higher spatial resolution than standard X-ray diffraction methods. It is based on measuring the surface displacements produced when stresses are partially released by machining a thin slit perpendicularly to the tested surface. Slit machining is carried out by focused ion beam (FIB). Measurement of the displacement fields around the FIB slit are performed by applying an advanced digital image correlation algorithm based on Fourier analysis with sub-pixel resolution. This method compares SEM images of the same area of the hardmetal surface before and after slitting. The method has been successfully applied to as-ground and femto-laser textured surfaces showing good correlation with the standard sin2ψ XRD technique. It is concluded that texturing induced by laser pulses in the femtoseconds regime is not perfectly adiabatic, since residual stresses are reduced by 15%.

Ediacaran cap dolostones from south China: Petrography, dolomite stoichiometry, and crystal architecture

Using the global Ediacaran cap dolostones to understand the post-Marinoan Earth is based on the premise that the original environmental features have not been diagenetically altered. On the southwest side of the Yangtze Block in southeast China, the Doushantuo cap dolostones that are part of the shelf-to-slope transition are characterized by distinctive petrographic, stoichiometric, and crystal architectural features that recorded their genesis and evolution. Standard petrographic and X-ray diffraction analyses show that these cap dolostones are formed of populations of near-stoichiometric (average molar %Ca = 50.8 %; n = 73), highly ordered (average cation ordering of 0.83; n = 73) dolomite. Six microfacies recognized in the cap dolostones indicate that the rocks have experienced early cementation, dolomitization, fracture filling, recrystallization, and late-stage dolomite precipitation. All of the matrix dolomite crystals from the Liujing, Duodingguan, and Chuanyandong sections, and >95 % of those from the Wuhe section, are formed of unzoned dolomite crystals that are each formed of numerous subcrystals (200–700 nm wide, <2 μm long). In contrast, the zoned dolomite crystals from the Wuhe section are characterized of different degrees of etching between their cores and cortices, and/or between different growth zones. The zoned dolomite crystals demonstrate that the Doushantuo cap dolostones were initially formed via replacive dolomitization followed by multiple phases of dolomite precipitation in a manner similar to many Phanerozoic marine dolostone counterparts. The homogeneity in the dolomite populations and crystal architecture and the increases in dolomite stoichiometry and cation ordering in the Doushantuo cap dolostones suggests that they have been pervasively recrystallized.

Effect of interfacial mixed layer on hydrogen absorption in yttrium thin films

Pd/Y bilayers and Pd/Ti/Y trilayers were prepared in a UHV chamber by DC/RF magnetron sputtering. The characterization of the Pd-Y and Ti-Y interfaces was performed immediately after the deposition using in-situ X-ray photoelectron spectroscopy (XPS). The results indicated significant interface mixing for the Pd/Y bilayers. Further studies showed that the additional Ti layer deposited between the palladium and yttrium layers can significantly reduce the mixing of the Pd-Y layers during the deposition process at room temperature, leading to the formation of a sharp Ti-Y interface. The structure of the obtained layers before and after the hydrogenation was examined by the standard X-ray diffraction method. The hydrogenation kinetics was studied in-situ at room temperature and pressure up to 1 bar using simultaneous measurements of resistivity and optical transmittance. It was found that for a thickness of Ti equal to 5 nm, the shortest transition time to the YH3 phase was obtained while maintaining a short switching time.

STRUCTURAL-PHASE STATE AND MECHANICAL PROPERTIES OF A TITANIUM MATRIX COMPOSITE BASED ON TI64 ALLOY AND TIB2 CERAMICS OBTAINED BY LASER CLADDING

The paper presents experimental studies on the synthesis of a titanium matrix composite based on Ti64 titanium alloy and TiB2 ceramic particles by laser surface cladding. The weight percentage of TiB2 ceramics in the composite was 5, 10, and 15%. The phase composition of the resulting materials was analyzed by standard X-ray diffraction and synchrotron X-ray diffraction. It was found that the structure of the titanium matrix composite with 5 wt % ceramics consists of TiB nanowhiskers, and that of samples with higher ceramics content exhibits TiB whiskers with a width of several micrometers. The addition of TiB2 ceramics leads to an increase in Young’s modulus and nano-/microhardness of composite samples compared to Ti64 alloy. The indentation method was used to study the formation of a phase that does not correspond to TiB2 ceramics and microscale TiB whiskers and has elastic properties exceeding the elastic properties of the original Ti64 matrix phase. Analytical predictions showed an increase in the effective elastic properties of the formed heterogeneous material with the predicted new phase. It was also found that a lower friction coefficient can be achieved by forming a structure with nanowhiskers, while higher Young’s modulus and microhardness can be obtained by forming a structure with microwhiskers.

Hirshfeld atom refinement of metal-organic frameworks for accurate positioning of hydrogen atoms and disorder analysis.

The application of Hirshfeld atom refinement (HAR) fragmentation is demonstrated for the refinement of metal-organic framework (MOF) crystal structures. The presented method enables anisotropic refinement of imidazolate hydrogen atoms, as well as complex analysis of solvent disorder within MOF pores. The data used were derived from standard resolution in-house single crystal X-ray diffraction measurements, demonstrating that high quality structural analysis of MOFs no longer requires access to neutron or synchrotron facilities.

Investigations of the Mn–Ni–Sm ternary system by means of anomalous X-ray diffraction, X-ray absorption and DFT calculations

Various applications benefit from the use of compounds combining lanthanides and 3d metals because of their fundamental physicochemical properties. To tune compositions for dedicated applications and to overcome the criticality of raw materials or geopolitical tension, a better understanding of the binary, ternary and even quaternary systems is needed. The present work focuses on the ternary Mn-Ni-Sm system, which is particularly interesting for energy storage applications as it forms hydrogen absorbing intermetallic compounds. The fruitful combination of standard X-ray diffraction, anomalous X-ray diffraction close to the Mn 3d edge, X-ray absorption near edge structure, electron probe micro-analysis and first-principles calculations provides a better understanding of the physicochemical properties and phase equilibrium of this ternary system. In particular, the atomic substitution of Mn atoms in the Ni sites has been investigated for the stacking AB2/AB5 Sm2MnyNi7-y system. The Mn atoms substitute preferentially in the AB5 sub-units, whereas Sm vacancies are observed in the AB2 sub-units inducing an antagonist variation in cell volume units. In the SmMnyNi12-y system, the preferential localization of Mn atoms has been highlighted in site 8i for the SmMn4Ni8 compound.

Template-free hydrothermal synthesis of lithium iron tavorite with complex morphologies driven by phase transformation

Materials science is increasingly relying on sustainable methods for the synthesis of advanced materials. This work demonstrates the first template-free approach for the crystallization of tavorite, LiFePO4(OH), in the form of hollow microspheres and unique core (single crystal)–shell (aggregated particles) cross-like dendrites. The different morphologies have been obtained by hydrothermal synthesis. The kinetic pathways of crystallization reveal how the transformation of two different thermodynamically unstable phases, such as giniite (Fe5(PO4)4(OH)2⋅2H2O) and lithium sulfate (Li2SO4), leads to the same tavorite structure, but with different morphologies based on the different mechanisms for crystal growth. Additionally, we provide standardized powder X-ray diffraction data and insights into the influence of the iron precursor on the crystal morphology of tavorite.

Elastic Molecular Crystals: Their Deformation-Induced Reversible Unit Cell Changes with Specific Poisson Effect

Abstract Detailed investigation of macroscopic deformation and nanoscopic structural changes in flexible organic crystals poses challenges for investigators. Herein, applied stress and subsequent relaxation of elastic organic crystals resulted in reversible macroscopic crystal deformation. X-ray diffraction with a curved stage-jig revealed reversible nanoscopic structural unit cell changes in the crystal structure under the bending stress and relaxation. The crystal lattice changed quantitatively under the applied macroscopic stress-strain (%). This method enables quantitative monitoring of the dynamic nanoscopic structural changes in detail associated with crystal deformation through the use of standard laboratory X-ray diffraction analysis. Importantly, the developed method offers a way of quantitatively measuring reversible structural changes, without synchrotron X-ray analysis. Moreover, the analysis derives Poisson’s ratio, i.e., the ratio of the change in the width per unit width of materials. It is important in materials science, and normally has a positive value in the range of 0.2–0.5. However, the crystals show not only the “Poisson effect” but also the unusual “negative Poisson effect”. This novel approach for investigation generates unprecedented opportunities for understanding dynamic nano-structural unit cell changes in flexible organic crystals.

Microstructural modifications induced in Si+-implanted yttria-stabilised zirconia: a combined RBS-C, XRD and Raman investigation.

The structural differences in (100)-, (110)- and (111)-oriented cubic yttria-stabilised zirconia (YSZ) single crystals after implantation with 2 MeV Si+ ions at the fluences of 5 × 1015, 1 × 1016 and 5 × 1016 cm-2 were studied using Rutherford backscattering spectrometry in the channelling mode (RBS-C), X-ray diffraction (XRD) and Raman spectroscopy. The RBS-C results show that the damage accumulation in the 〈110〉 direction exhibits a lower level of disorder (<0.3) than the other orientations (<0.6) and it seems that the (110) crystallographic orientation is the most resistant to radiation damage. The experimental results from the RBS measurement were compared with the results from the XRD measurements. The XRD data were analysed using the standard two-beam dynamical X-ray diffraction theory and the pure isotropic strain was deduced from the fit for the fluence of 5 × 1015 cm-2. It was shown that the maximum value of the isotropic strain does not depend on the surface orientation. The increase in signal intensity at ∼689 cm-1 is probably related to an increase in implantation defects such as oxygen vacancies.

Trifunctional Silyl Groups as Anchoring Units in the Preparation of Luminescent Phosphole-Silica Hybrids.

A synthetic strategy to β-silylphospholes with three methoxy, ethoxy, chloro, hydrido, or phenyl substituents at silicon has been developed, starting from trimethoxy, triethoxy, or triphenyl silyl substituted phenyl phosphanides and 1,4-diphenyl-1,3-butadiyne. These trifunctional silylphospholes were attached to the surface of uniform spheric silica particles (15 μm) and, for comparison, to a polyhedral silsesquioxane (POSS)-trisilanol as a molecular model to explore their luminescent properties in comparison with the free phospholes. Density functional theory calculations were performed to investigate any electronic perturbation of the phosphole system by the trifunctional silyl anchoring unit. For the immobilized phospholes, cross-polarization magic-angle-spinning NMR measurements (13C, 29Si, and 31P) were carried out to explore the bonding situation to the silica surface. Thermogravimetric analysis and X-ray photoelectron spectroscopy measurements were performed to approximate the amount of phospholes covering the silica surface. Identity and purity of all novel phospholes have been established with standard techniques (multinuclear NMR, mass spectrometry, and elemental analysis) and X-ray diffraction for the POSS derivative.

A simple gas introduction system for cryogenic powder X-ray diffraction

A simple system is described for the introduction of gases into standard X-ray diffraction capillaries mounted in situ in the X-ray beam of laboratory X-ray diffraction instruments. This system retains many of the advantages of the standard Norby cell, but does not require custom machining and has less stringent space restrictions. The system has been used to study the crystallization and interaction of volatile organics at cryogenic temperatures, but gas–solid interactions could also be studied at elevated temperatures using this approach.

Combustion synthesis CuO nanoparticles: Application to photocatalytic activity

Copper oxide nanoparticle (NPs) was prepared by a green Chemistry approach. The synthesized NPs were characterized by XRD, SEM, FT-IR, and UV–Vis spectrophotometer. The XRD peaks matches with the standard X-ray diffraction patterns confirming monoclinic crystal phase. FT-IR absorption exhibits the existence of metal oxygen stretching bond at 422 cm−1. SEM study shows that the particles were highly porous in nature having irregular shape and are agglomerated. EDX spectrum confirms the presence of Cu and O in the synthesized NPs. The band gap was found to be 1.65 eV from UV– Vis studies. An enhanced photo degradation of Rose Bengal dye was indicated by synthesized NPs.

Assessing extreme maturities – Challenging examples from immature Jordanian to overmature Far Eastern unconventional formations

Thermal maturity is often readily available from optical vitrinite reflectance measurements, but in marine sediments with absence of terrigenous organic material (vitrinite macerals) or formations older than the Devonian, this technique has limitations. Raman spectroscopy has been applied as an alternative measurement to infer thermal maturity in challenging formations. Organic-rich outcrop samples from the Jordanian Lajjoun and Sultani deposits and from a Far East shale were characterized for their key geochemical properties (bulk chemical and mineral composition, total organic carbon content) and thermal maturity. Bulk mineral and chemical abundances were quantified using standard X-ray diffraction and X-ray fluorescence techniques. Total organic carbon (TOC) content was calculated from programmed temperature pyrolysis. Thermal maturity was determined and compared using conventional vitrinite reflectance and a novel, rapid laser Raman spectroscopy method. The Jordanian samples are organic-rich (16.3–17.4 wt% TOC), while the Far Eastern sample is relatively organic-lean (2 wt% TOC). Programmed pyrolysis shows that the Jordanian samples seem immature with high remaining hydrocarbon generative potential (S2), whereas the sample from the Far East appears to be overmature with extremely low S2 value. These findings were confirmed by the results from organic petrography as well as through Raman spectroscopic measurements. The Far Eastern samples are suggested to be highly mature (4.6–5.7% VRE), whereas the Jordanian samples were found to be immature (0.4–0.5% VRE). Robust Raman maturity determination allows to define and refine petrophysical properties of kerogen and thus enhance the accuracy in predicting hydrocarbon in place and the potential for its recovery.