Conventional X-ray Diffractometry Research Articles

Strong-field photoelectron holography in the subcycle limit

Strong-field photoelectron holography is promising for the study of electron dynamics and structure in atoms and molecules, with superior spatiotemporal resolution compared to conventional electron and X-ray diffractometry. However, the application of strong-field photoelectron holography has been hindered by inter-cycle interference from multicycle fields. Here, we address this challenge by employing a near-single-cycle field to suppress the inter-cycle interference. We observed and separated two distinct holographic patterns for the first time. Our measurements allow us not only to identify the Gouy phase effect on electron wavepackets and holographic patterns but also to correctly extract the internuclear separation of the target molecule from the holographic pattern. Our work leads to a leap jump from theory to application in the field of strong-field photoelectron holography-based ultrafast imaging of molecular structures.

Effect of post heat treatment on the phase composition and strength of laser welded joints of an Al–Mg–Li alloy

In the present work, the effects of laser beam welding and post-weld heat treatment on the phase composition and mechanical properties of the 1424 alloy (Al–Mg–Li) joints were investigated. Holding the joints at a certain temperature was followed by quenching and artificial aging. The structural studies were carried out using electron microscopy, conventional X-ray diffractometry, and synchrotron radiation diffractometry. The heat treatment conditions were optimized to favor the formation of strengthening phases in the welds, the presence of which imparted mechanical strength to the joints. For the first time, 1424 Al alloy joints with a weld strength of σuts = 500 MPa have been obtained; this value of strength was achieved by applying post-weld annealing followed by quenching and artificial aging.

Phase separation process preventing thermal embrittlement of a Zr-Cu-Fe-Al bulk metallic glass

The structural changes and mechanical properties of a Zr63Cu22Fe5Al10 bulk metallic glass (BMG), and a Zr63Cu27Al10 one made for comparison, were studied on annealing below the crystallization temperature. The phase composition of the samples was studied by conventional X-ray diffractometry and high-resolution transmission electron microscopy including the atomic-scale elemental mapping. The samples were mechanically tested in compression. The Zr63Cu22Fe5Al10 bulk metallic glass shows a high strength and good deformability at room temperature both in the as-cast state and after prolonged structural relaxation below the crystallization temperature. The reasons for such behavior are discussed in the present work.

Some crystallographic considerations on the novel orthorhombic ZrO2 stabilized with Ta doping

Some crystallographic considerations on the novel orthorhombic ZrO2 (o-ZrO2) stabilized at ambient conditions by Ta substitutional doping are presented. Specifically, how the Ta-doped o-ZrO2 was observed for the first time by conventional X-ray diffractometry (XRD) is reported, after which the ab initio and non-ab initio procedures used to resolve its crystal structure are detailed. The crystal structure is then explicitly reported (i.e., space group and cell parameters, as well as atomic positions of the asymmetric unit). It is also shown that this novel Ta-doped o-ZrO2 has a crystal structure similar, but not identical, to the high-pressure o-ZrO2. Additionally, given that the crystal structure of the Ta-doped o-ZrO2 is identified as being a symmetry-breaking distortion of the typical tetragonal ZrO2 (t-ZrO2) stabilized with the commonest dopants, a complete analysis is also made of the structural distortions relating both the Ta-doped o-ZrO2 and the high-pressure o-ZrO2 to the t-ZrO2. Finally, a justification for the apparent greater immunity of the Ta-doped o-ZrO2 to aging is provided.

Structural and compositional inhomogeneities in Bismuth-Substituted rare earth iron garnet epitaxial films

Structural and compositional inhomogeneities in the free-standing epitaxial films of rare earth iron garnet films are characterized using high-resolution X-ray diffraction and energy dispersive X-ray fluorescence. These analyses show a variation in the lattice parameters as well as in chemical compositions, displaying inconsistency from the top and the bottom of the film, suggesting an inhomogeneous distribution of rare earth content. With these variations, intricate changes often occur in the magneto-optics properties. While with conventional X-ray diffraction techniques, the films appeared to be free of gross defects, our high-resolution rocking curves reveal variations in defect density and multiple lattice parameters. These results suggest that epitaxial films presumed to be homogeneous based on conventional X-ray diffractometry, may not be so. Therefore, films found to exhibit exotic physical properties should be carefully examined for the presence of structural and compositional anomalies to optimize the magneto-optic response. If such defects are present, the experimental results may be compromised due to sample imperfections, rather than intrinsic phenomena.

Crystallization behavior of Fe- and Co-based bulk metallic glasses and their glass-forming ability

In the present work we study and compare the crystallization behavior of Fe- and Co-based good bulk glass formers with an exceptionally high glass-forming ability leading to the critical thickness of cast samples reaching 1 cm. For Fe-based alloys we also investigate the effect of opposite C/B content ratio on the glass-forming ability and the crystallization behavior. The structure and phase composition of the glassy samples were examined by conventional X-ray diffractometry and transmission electron microscopy while thermal stability and phase transformations were studied by differential scanning calorimetry. The reasons for high glass-forming ability are discussed. The glass-forming ability of the studied alloys depends on both factors: the type of crystallization reaction and characteristic temperatures.

Crystal growth limitation as a critical factor for formation of Fe-based bulk metallic glasses

In the present work we study the formation mechanism and crystallization behavior of Fe-based bulk metallic glasses influenced by the addition of rare-earth elements. Samples are characterized by conventional X-ray diffractometry, optical microscopy, and high-resolution field-emission-gun scanning and transmission electron microscopy. In the rare-earth-containing alloys, bulk metallic glasses are formed with populations of quenched-in nuclei. Consequently, crystallization on isothermal annealing occurs without any incubation period. This behavior, not typical of bulk metallic glasses in general, implies that in the rare-earth-containing alloys glass formation is possible only because of restricted crystal growth: both on cooling from the molten and on heating from the glassy state, growth of the primary χ-Fe36Cr12Mo10 crystals is too slow to be significant on a reasonable timescale. The low growth rate is connected with large inhomogeneous strain in the growing nanoparticles, while nucleation of eutectic colonies is hampered by slow diffusion of a rare-earth alloying element.

Atomic structure changes and phase transformation behavior in Pd–Si bulk glass-forming alloy

Synchrotron-radiation studies allowed continuous acquisition of X-ray diffraction spectra for binary Pd 81Si 19 bulk metallic glass forming alloy in the glassy, crystalline and liquid state. Such an investigation allowed determination of structural changes in the liquid and glassy states using real-space radial RDF(R) and atomic pair PDF(R) distribution functions. Crystallization behavior of this alloy was also studied by conventional X-ray diffractometry, transmission electron microscopy and differential scanning calorimetry in isochronal and isothermal mode.

Role of the uncompensated interface spins in polycrystalline exchange-biased systems

This work reports on the evolution of the exchange-bias (EB) field and the shape of the magnetization curves with the thickness of the non-magnetic spacer layer (SL, either Cu or Al2O3) of polycrystalline Co/IrMn/SL/Co films as well as their modifications caused by different post-deposition annealing treatments. Conventional x-ray diffractometry, small-angle x-ray reflectivity and cross-section transmission electron microscopy were used for the structural characterization. The hysteresis loops traced on the as-made films without SL present a pattern of two oppositely displaced subloops; it was observed that the positively shifted subloop gradually vanishes with the increase in the SL thickness. Our study points out that the significant decrease in the EB field of the top-pinned Co layers after magnetic annealing could be attributed to relaxation of the bottom interfacial IrMn spin structure caused by the heating. This relaxation mechanism might be considered as an alternative to the commonly accepted IrMn and Co interdiffusion and defect creation at the interface. Models for the uncompensated spins' configurations at each of the ferromagnet (FM)/antiferromagnet (AF) and AF/FM interfaces are proposed in order to explain the modifications of the magnetic behaviour with the SL thickness and with the annealing.

A new physical–chemical process for the efficient production of cellulose fibers from Spanish broom ( Spartium junceum L.)

A novel and efficient method for the extraction of cellulose fibers from Spanish broom ( Spartium junceum L.) is presented. The method is based on the sequential combination between an initial chemical stage (alkaline digestion) and a subsequent physical–chemical stage, consisting of compression with hot air in an autoclave followed by rapid decompression (DiCoDe process, digestion–compression–decompression). The alkaline mother liquor deriving from the initial digestion step can be conveniently recycled after centrifugation followed by ultrafiltration. The process is characterized by the production of fibers with excellent physical–chemical properties, such as high mechanical resistance and high elasticity, and rapid production times. The fibers obtained after the DiCoDe process can be further softened and whitened by means of enzymatic digestion. Fibers were morphologically characterized by scanning electron microscopy (SEM), while their composition and physical–chemical properties were determined by conventional methods, including colorimetry, TAPPI protocols, IR spectroscopy, and X-ray diffractometry.

SU-GG-I-152: Structure and Composition Kidney-Stone Analyses Using Coherent-Scatter Computed Tomography: Early Results with a Novel Laboratory Method

Purpose: Many kidney stones have a heterogeneous composition in layers about a central core. At present, infrared spectroscopy (IRS) or conventional x-ray diffractometry are used to determine stone composition which is required to determine appropriate follow-up care for recurrence prevention. Both methods are limited requiring that stones be crushed prior to examination and a bulk measure of composition is obtained. We are currently conducting a clinical trial using coherent-scatter computed tomography (CSCT) as an ex-situ technique of stone analysis. We believe this technique will provide detailed structural information, including the initial nucleating mineral at the core of the stone. Method and Materials: Our ongoing prospective trial examines urinary calculi from 100 consecutive eligible patients undergoing either percutaneous nephrolithotripsy or ureteroscopy. All calculi removed intra-operatively are analyzed with CSCT and then the same samples are sent for IRS (the standard of care at our center). Stone analyses from the two modalities are compared for overall bulk composition and the CSCT data analyzed to determine composition of the core. Results: Of the first 25 stones examined, 12 had core minerals that were not the primary component reported by IRS. In four, IRS reported 100% cystine where CSCT showed a distinct UA core inside cystine. In another, IRS reported 85% struvite while CSCT showed a calcium oxalate monohydrate core inside a struvite outer layer. Conclusion: We are finding a significant fraction of stones in which IRS does not report the mineral component at the core of the stone as a large component of bulk composition. This raises the question whether recurrence rates could be improved by targeting the core component.

Assessment of Strain Energy by Measuring Dislocation Density in Copper and Aluminium Prepared by ECAP and ARB

In order to estimate the strain energies of pure Cu and pure Al prepared by ECAP and ARB processes, dislocation densities remaining in these metals after each process were analyzed by the Warren-Abervach method based on the Williamson-Hall plot from a series of data taken by conventional X-ray diffractometry. The measured dislocation density was higher by several times in pure Cu than in pure Al regardless of ECAP and ARB, resulting in the higher strain energy stored in pure Cu than in pure Al. Also, the dislocation density was found to be lower in the f.c.c. phase in pure Cu than that in the lath martensite phase in high Cr ferritic steels. Furthermore, it was observed that the amount of stored strain energy in pure Al depended considerably on its purity.

Stoichiometric Study of Iron Sulfide Prepared by Mechanochemical Reaction

In the present study, pure elemental powders of Fe and S were mixed to give the desired compositions of Fe50S50. A SPEX 8000D high-energy ball mill was used to synthesize iron sulfide powders under an Ar-filled atmosphere. The prepared powders were examined by conventional X-ray diffractometry and synchrotron X-ray absorption spectroscopy. The experimental results revealed that mechanochemical reactions occurred during the ball milling process for all the compositions. The Fe50S50 phase was obtained after ball milling for 20 h. Extended X-ray absorption fine structure (EXAFS) results revealed that the nearest neighbor bond lengths of the radial distribution function (RDF) for iron decreased when iron sulfides formed. X-ray absorption near edge structure (XANES) of S K-edges distinguished better the structural evolution of these iron sulfides.

Devitrification of Hf–Pd–Ni glassy alloy on heating

The thermal expansion and volume change in a Hf 70Pd 20Ni 10 glassy alloy were studied by X-ray diffractometry using in situ heating in a high energy monochromatic Synchrotron beam radiation. Devitrification behavior of the Hf 70Pd 20Ni 10 glassy alloy was investigated by using conventional X-ray diffractometry, transmission electron microscopy, differential scanning and isothermal calorimetries. The formation of nanoscale cF96 Ti 2Ni-type particles embedded in the residual glassy matrix was observed upon annealing. The kinetics of devitrification and the obtained Avrami exponent value of 2.6 indicate that the primary cF96 precipitates are formed by the steady state nucleation and diffusion-controlled growth of nuclei.

Application of thermally stimulated current measurement to the polymorphic characterization of drug substances

The thermal stimulated current measurement was used as an innovative analytical equipment to evaluate the polymorphic properties of terfenadine and Compound A, being developed by Takeda Pharmaceutical Company, Limited. At first, terfenadine, which is known to have polymorphs, was used as a model sample for thermally stimulated current (TSC) analyses. The TSC curves of amorphous and two polymorphs were distinctly different from each other. Therefore, it was considered that TSC measurement could be a useful technique to evaluate the crystalline properties of drug substances. The polymorphs of compound A were difficult to distinguish the characteristics of polymorphs from conventional powder X-ray diffractometry and also differential scanning calorimetry. Forms A and B of compound A were clearly differentiated by the thermal stimulated current properties that were adequate to characterize each form. Thus, it was shown that TSC was extremely useful and powerful tool for identification of complicated polymorphs, which were not distinguished by conventional methods.

Thermal Behavior of Ursodeoxycholic Acid in Urea: Identification of Anomalous Peak in the Thermal Analysis

The objective of this study was to clarify the thermal behavior of ursodeoxycholic acid (UDCA) in mixtures with urea. Physical mixtures of UDCA and urea in various ratios were prepared, and the thermal analysis of these sample mixtures was investigated using conventional differential scanning calorimetry (DSC) and variable-temperature powder X-ray diffractometry (VTXRD). The hot-stage microscopy (HSM) and powder X-ray diffractometry (PXRD) were used as complementary techniques. From the DSC results of all sample mixtures, it was found that there was no endothermic peak at the melting temperature of intact UDCA crystals. The DSC thermograms of each ratio showed only the endothermic peak at about 136°C due to the melt of urea and the anomalous endothermic peak at about 155°C–157°C. The VTXRD study revealed that the crystals of urea completely disappeared at a temperature of 140°C. At this temperature, it was identified that the VTXRD pattern obtained was of UDCA crystals. The crystalline peaks gradually decreased in intensity at a temperature of 150°C. When the temperature was up to 160°C, the identical crystalline peaks of UDCA crystals completely disappeared. It was concluded that the anomalous endothermic peak at 155°C–157°C was the peak due to the dissolution of UDCA crystals in the surrounding melted urea.

Formation of celsian from mechanically activated BaCO3–Al2O3–SiO2 mixtures

A ternary mixture BaCO3–Al2O3–SiO2 was mechanically activated for different lengths of time. Chemical composition of the mixture corresponded to BaAl2Si2O8–BAS. As a function of activation time, reaction course was followed in the temperature range 750–1200°C. Reaction of celsian formation was followed using thermogravimetry as well as conventional and high-temperature X-ray diffractometry. The obtained data show that reaction rate increases with prolonged activation time, under the same conditions of thermal treatment. Formation of hexacelsian via a series of solid state reactions involving Ba-silicates, was favoured with increasing activation time. Direct formation of monoclinic celsian was retarded, however, with prolonged activation.

Influence of aging heat treatment on mechanical properties of biomedical Ti-Zr based ternary alloys containing niobium.

Titanium-zirconium based alloys containing a small amount of niobium were investigated in order to evaluate their possible use as biomedical materials. Zirconium, which belongs to the IVa group, is known to have good corrosion resistance and biocompatibility similar to titanium. As the titanium-zirconium system shows a complete solid solution, a wide variation of alloy design is available and large quantities of solid-solution hardening must be possible. Niobium, having a beta-phase stabilizing effect, was chosen as a ternary element in order to control desirably the microstructure. There have been no reports which suggest its harm to a living body. The alloys containing 2% or 3% niobium showed the highest hardness value after aging heat treatment at 773 K. In contrast to this, no alteration of hardness was seen in specimens aged at 1073 K. Through conventional X-ray diffractometry and in situ X-ray analysis using a hot stage, beta-phase precipitation in the A matrix was identified. From the above results, it is concluded that alloys containing 2%-3% niobium are hopeful candidates for new kinds of biomedical alloys, when they are heat treated under suitable conditions.

Fe<SUB>2</SUB>Si<SUB>5</SUB>-B系合金のβ化と熱起電力に及ぼすCu添加の影響

The formation behavior of a β-phase in the newly proposed Fe2Si5-B alloy with a small amount of Cu and their thermo-electric power were examined. The results are summarized as follows: The as-solidified structure of the Fe2Si5 based alloys with B and Cu was found to be mostly the α single phase by conventional X-ray diffractometry while a few B-rich and ε phase were observed by SEM. The β-phase formation rate in a conventional (FeSi2)99B1 alloy was increased by the addition of Cu, but still quite a long annealing period was necessary to attain the complete formation of β-phase. In the case of the Cu-added (Fe2Si5)99B1 alloy, the β formation was completed by annealing at 1073 K for 1.8×102 s. It is 100 times shorter than that in the binary Fe2Si5. The thermoelectric power of the newly proposed (Fe2Si5)99B1 alloy elucidated to be comparable with the conventional (Fe2Si5)99B1 alloy. The Si phase retained in the final state also found to cause no deterioration on the thermoelectric power.

Study of nanocrystalline Ta(N,O) diffusion barriers for use in Cu metallization

In this study, the film properties and the barrier behaviour of 50 nm thin reactively sputtered Ta(N,O) diffusion barriers between Cu and Si were investigated. Auger electron microscopy, glancing-angle x-ray diffractometry and atomic force microscopy revealed that the Ta(N,O) films exhibit quasi-amorphous/nanocrystalline properties. Using sheet resistance measurements, scanning electron microscopy, Auger electron spectroscopy depth profiling and conventional x-ray diffractometry the 50 nm thin Ta(N,O) films were found to be effective diffusion barriers between Cu overlayers and Si substrates even after 1 h annealing at 600°C.