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X-ray reflectometry is a powerful tool for investigating rough surface and interface structures. Presently, X-ray reflectivity is based on Parratt formalism, accounting for the effect of roughness by the theory of Nevot–Croce. However, the calculated results showed a strange phenomenon in that the amplitude of the oscillation because of interference effects increases in the case of a specific roughness of the surface. We propose that the strange results originated from the currently used equation because of a serious error in which the Fresnel transmission coefficient in the reflectivity equation is increased at a rough interface, and the increase in the transmission coefficient completely overpowers any decrease in the value of the reflection coefficient because of lack of consideration in diffuse scattering. In the present study, we present a new improved formalism that corrects this error, and thereby derives an accurate analysis of X-ray reflectivity from a multilayer surface, taking into account the effect of roughness-induced diffuse scattering.
A new Matlab-based software suite called Tilt-A-Whirl has been applied to XRD data from textured gold films electro-deposited onto nickel substrates. The software routines facilitate phase identification, texture analysis via pole figure visualization, and macrostrain determination. The use of principal component analysis with multivariate curve resolution (PCA/MCR) revealed the extraction of texture components. The unusual hardness properties of one Au film (deposited from a 30% gold depleted BDT-200 bath) were found to be dependent on the (210) out-of-plane preferred orientation of the polycrystalline gold film. The progressive nucleation of Au crystallites during electro-plating has been tied to improved hardness properties of this film.
InN films have been grown on sapphire substrates nitrided by N plasma with different durations by radio-frequency plasma assisted molecular beam epitaxy (RF-MBE). In-depth investigation reveals that AlN is generated on a sapphire surface during the nitridation, and 60 min nitridation helps in the formation of an ordered and flat AlN interlayer between the substrate and the InN film, which improves the surface migration of In atoms on the substrate, and consequently helps in obtaining a single-crystalline c-plane InN film of high quality with 1.0 × 1019 cm−3 carrier density and 1350 cm2/(V·s) carrier mobility. Too short nitridation duration will result in a polycrystalline InN film, and too long nitridation duration will damage the surface quality of the newly generated AlN interlayer which consequently deteriorates the InN film quality. Control of the AlN interlayer quality plays a critical role in the growth of a high-quality InN epitaxial film on the sapphire substrate.
We present the study of the synthesis of (001) nickel oxide (NiO) epitaxial nanocrystals grown on (001) strontium titanate (SrTiO3) single crystal substrates. Pulsed laser deposition of the bismuth nickel oxide (BiNiO3, BNO) perovskite precursor followed by post-deposition processing is carried out to form the NiO nanocrystals. A detailed analysis of the dimensions of nanocrystals reveals that the morphology attained differs from the thermodynamically expected equilibrium shape. The deviations from the equilibrium shape are found to follow a systematic trend where the in-plane basal dimensions, that is, the length and width of the nanocrystals grown differ in discretized dimensions. This discretization suggests that for a given interfacial area of nanocrystals there are multiple stable basal rectangular geometries attainable.
Clenbuterol hydrochloride is an active pharmaceutical ingredient usually prescribed for treatment of respiratory diseases due to its activity as a decongestant and bronchodilator. It has also been used as a performance-enhancing drug. In the PDF-4/Organics 2012 database there are six entries related to this compound: three for its hydrochloride phase calculated using single-crystal data, two for a MeOH and a DMSO solvate of two Cu-clenbuterol complexes, and one experimental unindexed pattern. In this contribution the powder diffraction pattern and the crystal structure, determined using single crystal X-ray diffraction techniques of clenbuterol hemihydrate, C12H18Cl2N2O·0.5H2O, an unreported phase, are presented.
A new methodology based on maximum likelihood estimation for structure refinement using powder diffraction data is proposed. The method can not only optimize the parameters adjusted in Rietveld refinement but also parameters to specify errors in a model for statistical properties of the observed intensity. The results of structure refinements with relation to fluorapatite Ca5(PO4)3F, anglesite PbSO4, and barite BaSO4 are demonstrated. The structure parameters of fluorapatite and barite optimized by the new method are closer to single-crystal data than those optimized by the Rietveld method, while the structure parameters of anglesite, whose values optimized by the Rietveld method are already in good agreement with the single-crystal data, are almost unchanged by the application of the new method.
Recently, a new experimental setup for quick X-ray reflectivity (q-XRR) measurements was proposed, which is based on simultaneous recording of an X-ray reflectivity curve over all angles of interest. This new setup for q-XRR allows measurements to be done within seconds, thus permitting studies of the time evolution of chemical, thermal, and mechanical changes at the surfaces and interfaces of different materials. Since the q-XRR measurement setup utilizes an extended X-ray source and detector, it is important to develop models and to account for the following two effects: (i) diffuse scattering associated with different points of the source and (ii) sample curvature. Models accounting for both effects are presented, and their influences on interpretation of the q-XRR measurement results are discussed.
X-ray powder diffraction data, unit-cell parameters, and space group for deoxyschisandrin, C24H32O6, are reported [a = 13.083(3) Å, b = 19.563(9) Å, c = 8.805(6) Å, β = 90.472(0)°, unit-cell volume V = 2253.82 Å3, Z = 4, and space group P21]. All measured lines were indexed and are consistent with the P21 space group. No detectable impurity was observed.
A novel concept of immobilization of light water nuclear reactor fuel reprocessing waste effluent through interaction with sodium zirconium phosphate (NZP) has been established. It was found that a large number of hazardous cations could be loaded in the NZP-based matrix without significant change of three-dimensional framework structure. Starting from the raw powder diffraction data of polycrystalline solid phases, crystal structure of substituted NZP phases has been investigated using the General Structure Analysis System (GSAS) package. Cation(s) substituted NZP phases crystallize in rhombohedral symmetry (space group R-3c and Z = 6). Powder diffraction data have been subjected to Rietveld refinement to reach satisfactory structural convergence of R-factors. Unit cell parameters, inter atomic distances, bond angles, reflecting planes (h, k, l), structure factors, polyhedral (ZrO6 and PO4) distortion, and particle size have been reported. PO4 stretching and bending vibrations in the Infra red (IR) region have been assigned. SEM and EDAX analysis provide analytical evidence of fixation of cations in the matrix.
Optimization of the pore topology in organosilicate glass (OSG) is crucial in the development of dielectrics with an extremely low k-value and a relatively high Young’s modulus. In this paper, a finite-element modeling strategy is applied to develop a general understanding of the relationship between porosity, pore topology, and elastic modulus for the porous OSG thin films. This relationship in combination with the experimental elastic modulus data from nanoindentation (NI) studies is used to predict the pore structure of various OSG films. In addition, positron annihilation spectroscopy measurements are performed to determine the threshold porosity for the transition from nonoverlapping to overlapping porous structure. A similar threshold value is determined based on the finite-element modeling and experimental NI data.
A number of spatially resolved elemental imaging techniques are commonly employed to examine plutonium and other nuclear materials (e.g., scanning electron microscopy). Up until the past 10–15 years, micro-X-ray fluorescence (MXRF) instrumentation had been relatively uncommon, and even currently, it is underutilized for spatially resolved nuclear materials analysis and imaging. In the current study, a number of plutonium materials problem solving applications are presented to demonstrate the power and utility of MXRF for providing unique, spatially resolved elemental composition information. Applications discussed include identification of multiple insoluble fractions in plutonium and neptunium mixed oxide, spatially resolved imaging of plutonium residue and other elements on surface swipes, and spatial mapping of impurities in plutonium metal. The mixed oxide particle analysis demonstrated the ability to non-destructively identify particles of interest for potential extraction and analysis by other methods. The surface swipes study demonstrated the unique ability of MXRF to non-destructively image large multiple cm2 sized, non-conducting, radiologically contaminated samples. The plutonium metal investigation showed the capability of MXRF to non-destructively map elemental heterogeneity directly in an actinide matrix. Such information is extremely valuable prior to using destructive analysis (DA) trace elemental analytical chemistry techniques. If a metal is found to contain significant elemental impurity heterogeneity by MXRF, time consuming destructive sample preparation and analysis do not need to be repeated to confirm that the sample is indeed heterogeneous.
In an effort to study an alternative approach to make graphene from graphene oxide (GO), exposure of GO to high-energy X-ray radiation has been performed. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM) have been used to characterize GO before and after irradiation. Results indicate that GO exposed to high-energy radiation is converted to an amorphous carbon phase that is conductive.
X-ray powder diffraction data, unit-cell parameters, and space group for inclusion complex of β-cyclodextrin with fraxinellone, C42H70O35·C14H16O3·3H2O, are reported [a = 19.294(2) Å, b = 26.639(1) Å, c = 16.467(3) Å, β = 110.451(9)°, cell volume V = 7930.34 Å3, Z = 4 and space group C2]. All measured lines were indexed and are consistent with the C2 space group. No detectable impurities were observed.
We present a quantitative in-situ transmission electron microscope (TEM) study of stress-assisted grain growth in 75 nm thick platinum thin films. We utilized notch-induced stress concentration to observe the microstructural evolution in real time. From quantitative measurements, we find that rapid grain growth occurred above 290 MPa of far field stress and ~0.14% elongation. This value is found to be higher than that required for stable interface motion but lower than the stress required for unstable grain boundary motion. We attribute such grain growth to geometrical incompatibility arising out of crystallographic misorientation in adjoining grains, or in other words, geometrically necessary grain growth.
The strain-rate sensitivity of ultrafine-grained aluminum (Al) and nanocrystalline nickel (Ni) is studied with an improved nanoindentation creep method. Using the dynamic contact stiffness thermal drift influences can be minimized and reliable creep data can be obtained from nanoindentation creep experiments even at enhanced temperatures and up to 10 h. For face-centered cubic (fcc) metals it was found that the creep behavior is strongly influenced by the microstructure, as nanocrystalline (nc) as well as ultrafine-grained (ufg) samples show lower stress exponents when compared with their coarse-grained (cg) counterparts. The indentation creep behavior resembles a power-law behavior with stress exponents n being ∼ 20 at room temperature. For higher temperatures the stress exponents of ufg-Al and nc-Ni decrease down to n ∼ 5. These locally determined stress exponents are similar to the macroscopic exponents, indicating that similar deformation mechanisms are acting during indentation and macroscopic deformation. Grain boundary sliding found around the residual indentations is related to the motion of unconstrained surface grains.
The hardness changes caused by formation of the metastable and stable phases were examined and correlated with the microstructural changes in grain interior and grain boundary during aging at 350 °C to clarify the age-hardening and softening mechanism of a low-gold Au-Cu-Ag-Pd dental alloy. Aging in this context refers to the time-delay that occurs wherein such alloys are kept at elevated temperatures for periods upto many hours to allow precipitation or ordering to take place. During the period of increasing hardness, the matrix was separated into the Ag-rich α1 and AuCu I phases through the metastable phases, forming block-like structure. The apparent hardening was attributed primarily to lattice strain due to the tetragonality of AuCu I′ [the primer (′) here indicates a metastable phase; likewise (I) and (I′) indicate stable AuCu I and metastable AuCu I′ phases, respectively] and AuCu I phases along the c-axis, secondarily to the coherency or semicoherency strain between the metastable α1′ and AuCu I′ phases and between the α0 and AuCu I phases along the a-axis. The apparent softening was caused primarily by growth and coarsening of the lamellar structure in the grain boundaries, secondarily by coarsening of the block-like structure in the grain interior.
Ni–base alloy coatings were fabricated on 45 steel by laser cladding using a CW-CO2 laser system. The microstructure of the coatings was analyzed using optical microscope (OM), scanning electronic microscope (SEM), and x-ray diffractometer (XRD). The phase fractions, phase compositions, and solidification process in the coatings were calculated using Thermo-Calc software and compared with experimental results. The results show that a dense crack- and porous-free coating with good metallurgical bond is obtained under optimal process parameters. The coatings can be divided into three regions: clad zone (CZ), bonding zone, and heat-affected zone of the substrate. The CZ consists of γ-Ni, M7C3, CrB, and Ni3B phases. Based on the calculated results, the solidification process and reaction scheme in the coatings were discussed. The calculated results obtained from Thermo-Calc software agree with the experimental data well. It is beneficial to the coating design for a desirable microstructure and mechanical properties.