We systematically study medium‐range structures including more than three neighboring atoms around iron ions (Fe2+ and Fe3+) in soda‐lime glass samples with low iron oxide concentrations (MFe2O3) and a wide number ratio of Fe2+ to all iron ions (Fe2+/ΣnFe). The precise medium‐range structures around iron ions in glass have not yet been revealed because of a lack of the appropriate measurement methods. To avoid this problem, we used element‐specific nuclear resonant inelastic scattering (NRIS) with synchrotron X‐rays to observe the vibrations of iron ions (57Fe). The vibrations are related to medium‐range structures with more than three neighboring atoms and to the potential asymmetry and the coordination environment, around iron ions. The NRIS method has high sensitivity and can measure over a wide concentration range. Linear combination fitting of the X‐ray absorption fine structure spectra, which measures only the first neighbors but is a faster than using the NRIS method, was also used additionally. A systematically produced set of glasses with 0.015–5 wt% MFe2O3 and 0–0.85 Fe2+/ΣnFe was measured with these methods. It was found that the soda‐lime glass possessed two different medium‐range structures with different iron ion valences (~2+ or ~3+), which were determined by the Fe2+/ΣnFe, and that these structures were generated during production of the glass. Moreover, these medium‐range structures were the same from 0.015 to 5 wt% MFe2O3. 相似文献
A Calvet‐type differential scanning calorimeter has been implemented on a synchrotron beamline devoted to X‐ray absorption spectroscopy. As a case study, the complex crystallization process in amorphous Ge15Sb85 phase‐change material is followed by simultaneous calorimetric and quick‐EXAFS measurements. A first crystallization at 514(1) K is related to the crystallization of an Sb‐rich phase accompanied by segregation of Ge atoms. Upon further heating, the as‐formed amorphous Ge regions crystallize at 604(1) K. A quantitative analysis of the latent heat allows a Ge11Sb89 stoichiometry to be proposed for the first crystallized phase. 相似文献
Glasses/glass-ceramics with nominal composition 34 SiO2-(45 − x)CaO-16P2O5-4.5MgO-0.5CaF2 − xFe2O3 (where x = 10, 15, 20 wt%) have been prepared by melt quenching technique. These are characterized for structural and micro structural properties by using XRD and Raman spectroscopy. Interaction of glass-ceramics samples with bovine serum albumin (BSA) has been studied using SEM and TOF-SIMS. The formation of magnetite, apatite and wollastonite phases are observed. Typical sizes of crystallites as seen from SEM measurement are 30-50 nm. The progressive addition of iron oxide to glass leads to increase in number of non-bridging oxygen, which in turn affects the response of glass-ceramics when immersed in BSA. The samples with 15 and 20 wt% Fe2O3 have shown nearly full surface coverage with BSA, while the sample with 10 wt% Fe2O3 shows poor adhesion. 相似文献
We use moving‐window two‐dimensional correlation spectroscopy (MW‐2DCOS) for phase‐specific Raman analysis of the n‐alkane (C21H44) during melting from the crystalline solid phase to the intermediate rotator phase and to the amorphous molten phase. In MW‐2DCOS, individual peak‐to‐peak correlation analysis within a small subset of spectra provides both temperature‐resolved and spectrally disentangled Raman assignments conducive to understanding phase‐specific molecular interactions and chain configurations. We demonstrate that autocorrelation MW‐2DCOS can determine the phase transition temperatures with a higher resolving power than commonly used analysis methods including individual peak intensity analysis or principal component analysis. Besides the enhanced temperature resolving power, we demonstrate that asynchronous 2DCOS near the orthorhombic‐to‐rotator transition temperature can spectrally resolve the two overlapping peaks embedded in the Raman CH2 twisting band in the orthorhombic phase, which had been only predicted but not observed because of thermal broadening near the melting temperature. Published 2016. This article is a U.S. Government work and is in the public domain in the USA. 相似文献
This paper reports the results of time‐resolved synchrotron powder diffraction experiments where jarosites with different K/H3O, K/Na and Na/H3O ratios were synthesized in situ at temperatures of 353, 368 and 393 K in order to observe the effect on kinetics and species produced. The Na/H3O sample formed monoclinic jarosite at all three temperatures, whereas the K/H3O and K/Na samples formed as rhombohedral jarosites at 353 K, and as mixtures of rhombohedral and monoclinic jarosites at the higher temperatures. The relative amount of the monoclinic phase increased with increase in temperature. Unit‐cell parameter changes with reaction time could be explained by changes in iron stoichiometry (samples become more stoichiometric with time) together with changes in K/H3O and Na/H3O ratios. The reaction kinetics have been fitted using a two‐stage Avrami model, with two different Avrami exponents corresponding to initial two‐dimensional growth followed by one‐dimensional diffusion‐controlled growth. Activation energies for the initial growth stage were calculated to be in the range 90–126 kJ mol?1. 相似文献
Mixtures of 47‐Al and 53‐Ti powders (atomic %) have been consolidated using back pressure equal‐channel angular pressing starting with both raw and ball‐milled powders. In situ synchrotron high‐energy X‐ray diffraction studies are presented with continuous Rietveld analysis obtained upon a heating ramp from 300 K to 1075 K performed after the consolidation process. Initial phase distributions contain all intermetallic compounds of this system except Al, with distribution maxima in the outer regions of the concentrations (α‐Ti, TiAl3). Upon annealing, the phase evolution and lattice parameter changes owing to chemical segregation, which is in favour for the more equilibrated phases such as γ‐TiAl, α2‐Ti3Al and TiAl2, were followed unprecedentedly in detail. An initial δ‐TiH2 content with a phase transition at about 625 K upon heating created an intermediate β‐Ti phase which played an important role in the reaction chain and gradually transformed into the final products. 相似文献
The carbon‐rich silicon carbide (C‐rich SixC1?x) micro‐ring channel waveguide with asymmetric core aspect is demonstrated for all‐optical cross‐wavelength pulsed return‐to‐zero on‐off keying (PRZ‐OOK) data conversion. Enhanced nonlinear optical Kerr switching enables 12‐Gbit per second data processing with optimized modulation depth. The inverse tapered waveguide at end‐face further enlarges the edge‐coupling efficiency, and the asymmetric channel waveguide distinguishes the polarization modes. To prevent data shape distortion, the bus/ring gap spacing is adjusted to control the quality factor (Q‐factor) of the micro‐ring. Designing the waveguide cross section at 500 × 350 nm2 provides the C‐rich SixC1?x channel waveguide to induce strong transverse electric mode (TE‐mode) confinement with a large Kerr nonlinearity of 2.44 × 10?12 cm2 W?1. Owing to the trade‐off between the Q‐factor and the on/off extinction ratio, the optimized bus/ring gap spacing of 1400 nm is selected to provide a coupling ratio at 5–6% for compromising the modulation depth and the switching throughput. Such a C‐rich SixC1?x micro‐ring with asymmetric channel waveguide greatly enhances the cross‐wavelength data conversion efficiency to favor its on‐chip all‐optical data processing applications for future optoelectronic interconnect circuits. 相似文献
Metastable LiMeO2–ZnO (Me=Fe 3+, Ti3+) solid solutions with a rock salt crystal structure have been synthesized by the solid-state reaction of ZnO with LiMeO2 complex oxides at 7.7 GPa and 1350–1450 K. The structure, phase composition, thermal stability and thermal expansion of the recovered samples have been studied by X-ray diffraction with synchrotron radiation. At ambient pressure, rock salt LiMeO2–ZnO solid solutions are kinetically stable up to 670–800 K, depending on the composition. 相似文献
This paper describes the design, construction and implementation of a relatively large controlled‐atmosphere cell and furnace arrangement. The purpose of this equipment is to facilitate the in situ characterization of materials used in molten salt electrowinning cells, using high‐energy X‐ray scattering techniques such as synchrotron‐based energy‐dispersive X‐ray diffraction. The applicability of this equipment is demonstrated by quantitative measurements of the phase composition of a model inert anode material, which were taken during an in situ study of an operational Fray–Farthing–Chen Cambridge electrowinning cell, featuring molten CaCl2 as the electrolyte. The feasibility of adapting the cell design to investigate materials in other high‐temperature environments is also discussed. 相似文献
Abstract Reaction‐induced, phase separation has been studied in polymer blends. A model crystalline‐amorphous system consisted of semicrystalline polyoxyethylene (POE) dissolved in the monomer styrene, which was used as a reactive solvent to ease processing. When the styrene was polymerized to polystyrene (PS) in the mold, phase separation and phase inversion are induced, and a polymer blend was formed. Polyoxyethylene was selected with a molar mass, Mn = 8578 g mol?1 and a polydispersity of 1.19, as determined by using gel permeation chromatography. The polymerization of styrene was initiated by using 1 wt% benzoin methyl ether and 0.2 wt% 2,2′‐azobisisobutyronitrile under ultraviolet light. The polymerization kinetics were determined by monitoring the reduction in the intensity of the C?C stretching vibration band at 1631 cm?1 in the Raman spectrum of styrene. The onset times for the liquid–solid (L–S) phase separation and crystallization of POE from styrene/PS were observed by using simultaneous small‐angle x‐ray scattering (SAXS) and wide‐angle x‐ray scattering. Onset times for L–S phase separation determined from the SAXS data were combined with the styrene polymerization kinetics to plot the L–S phase separation data onto a ternary phase diagram for the reactive system POE/styrene/PS at 45°C and 50°C. 相似文献
Amorphous SixC1-x thin films have been grown by low-pressure chemical vapour deposition at 800 K from Si2H6 and C2H2 in the x concentration range 0.5≤x<0.7. Measurements of the valence-band and core-level photoemission spectra using X-ray photoemission spectroscopy and synchrotron radiation have shown a clear change in the electronic structure for 0.55xC1-x films obtained by excimer laser annealing during growth have shown the formation of a dominant 3C-SiC phase up to x=0.6, while for higher x the growth of a poly-Si phase has been observed . PACS 81.15.Gh; 79.60.Dp 相似文献
A series of Ni dithiolene complexes Ni[S2C2(CF3)]2n (n = ?2, ?1, 0) ( 1 , 2 , 3 ) and a 1‐hexene adduct Ni[S2C2(CF3)2]2(C6H12) ( 4 ) have been examined by Ni K‐edge X‐ray absorption near‐edge structure (XANES) and extended X‐ray absorption fine‐structure (EXAFS) spectroscopies. Ni XANES for 1 – 3 reveals clear pre‐edge features and approximately +0.7 eV shift in the Ni K‐edge position for `one‐electron' oxidation. EXAFS simulation shows that the Ni—S bond distances for 1 , 2 and 3 (2.11–2.16 Å) are within the typical values for square planar complexes and decrease by ~0.022 Å for each `one‐electron' oxidation. The changes in Ni K‐edge energy positions and Ni—S distances are consistent with the `non‐innocent' character of the dithiolene ligand. The Ni—C interactions at ~3.0 Å are analyzed and the multiple‐scattering parameters are also determined, leading to a better simulation for the overall EXAFS spectra. The 1‐hexene adduct 4 presents no pre‐edge feature, and its Ni K‐edge position shifts by ?0.8 eV in comparison with its starting dithiolene complex 3 . Consistently, EXAFS also showed that the Ni—S distances in 4 elongate by ~0.046 Å in comparison with 3 . The evidence confirms that the neutral complex is `reduced' upon addition of olefin, presumably by olefin donating the π‐electron density to the LUMO of 3 as suggested by UV/visible spectroscopy in the literature. 相似文献
The general matrix theory of the photoelectron/fluorescence excitation in anisotropic multilayer films at the total reflection condition of X‐rays has been developed. In a particular case the theory has been applied to explain the oscillation structure of L2,3 XANES spectra for a SiO2/Si/SiO2/c‐Si sample in the pre‐edge region which has been observed by a sample current technique at glancing angles of synchrotron radiation. Remarkably the phase of the oscillations is reversed by a ~2° angle variation. The observed spectral features are found to be a consequence of waveguide mode creation in the middle layer of strained Si, which changes the radiation field amplitude in the top SiO2 layer. The fit of the data required the correction of the optical constants for Si and SiO2 near the Si L2,3‐edges. 相似文献
Binary mixed thin films of picene (C22H14, PIC) and pentacene (C22H14, PEN) consist of crystallites with a statistical occupation of the lattice sites by either PEN or PIC and unit cell parameters continuously changing with the mixing ratio. For high PIC ratios a PIC phase forms which corresponds to a limited intermixing of the two compounds. The growth behavior of these mixtures is investigated in situ and in real‐time using grazing incidence X‐ray diffraction. We observe a delayed phase separation in PIC‐rich blends, i.e. complete intermixing in the monolayer range and the nucleation of a pure PIC‐phase in addition to the intermixed phase starting from the second monolayer.
Growth scenario of picene‐rich pentacene‐picene blends. 相似文献
Ciprofloxacin (CfH, C17H18FN3O3) crystallizes with 2‐thiobarbituric (H2tba) and barbituric acid (H2ba) in the aqueous solution to yield salt CfH2(Htba)·3H2O ( 1 ), salt cocrystal CfH2(Hba)(H2ba)·3H2O ( 2 ), and salt CfH2(Hba)·H2O ( 3 ). The compounds are structurally characterized by the X‐ray single‐crystal diffraction. The numerous intermolecular hydrogen bonds N–H?O and O–H?O formed by water molecules, Htba?/Hba? and CfH2+ ions, and H2ba molecules stabilize the crystal structures of 1 to 3 . Hydrogen bonds form a 2D plane network in the salts of 1 and 3 and a 3D network in the salt cocrystal of 2 . There are different π‐π interactions in 1 to 3 . The compounds have been characterized by powder X‐ray diffraction, thermogravimetry/differential scanning calorimetry, and Fourier transform infrared spectroscopy. The compounds dehydration ends at 130°C to 150°C, and their oxidative decomposition is observed in the range of 250°C to 275°C. 相似文献