Diffraction Pattern Images Research Articles

Room Temperature Gas Sensing Properties of Sn-Substituted Nickel Ferrite (NiFe2O4) Thin Film Sensors Prepared by Chemical Co-Precipitation Method

Tin (Sn) substituted nickel ferrite (NiFe2O4) thin film sensors were prepared by a simple chemical co-precipitation method, which initially characterized their structure and surface morphology with the help of x-ray diffraction and scanning electron microscopy. Surface morphology of the sensing films reveals particles stick together with nearer particles and this formation leads to a large specific area as a large specific area is very useful for easy adsorption of gas molecules. Transmission electron microscopy and selected area electron diffraction pattern images confirm particle size and nanocrystallnity as due to formation of circular rings. Fourier transform infrared analysis has supported the presence of functional groups. The 3.69 eV optical band gap of the film was found which enabled better gas sensing. Gas sensors demonstrate better response and recovery characteristics, and the maximum response was 68.43%.

Donor-π-Acceptor-Type Configured, Dimethylamino-Based Organic Push-Pull Chromophores for Effective Reduction of Mild Steel Corrosion Loss in 1 M HCl.

In this work, donor−π–acceptor-type four crystalline compounds have been tested for the first time to restrict the corrosion of mild steel in 1 M HCl. The details of the compounds are: C1, 4-N,N-dimethylamino-β-nitrostyrene; C2, 2-(4-(dimethylamino) benzylidene)malononitrile; C3, ethyl 2-cyano-3-(4-(dimethylamino) phenyl)acrylate; and C4, methyl 2-cyano-3-(4-(dimethylamino)phenyl)acrylate. The corrosion inhibition potentials of the compounds have been primarily investigated by electrochemical techniques, such as linear polarization resistance, Tafel polarization curves, and electrochemical impedance spectroscopy. The secondary investigation is performed by scanning electron microscopy, fluorescence surface imaging, spectroscopic techniques (UV–visible and Fourier transform infrared spectroscopy), and X-ray diffraction patterns. The results disclosed that 50 mg L–1 of the compounds (1–4) in 1 M HCl provided the maximum inhibition efficiency as 93% (1), 88% (2), 82% (3), and 86% (4). The function of the compounds as corrosion inhibitors is explained with equilibrium corrosion potential, adsorption isotherms, and the frontier molecular orbital energies of the compounds (EHOMO and ELUMO) estimated by cyclic voltammetry curves and UV–visible spectra.

Variable range hopping and relaxation mechanism in graphene oxide sheets containing sp3 hybridization induced localization

The temperature dependent electrical properties of graphene oxide prepared by the modified Hummers method are investigated using broadband dielectric spectroscopy. The morphology and structure are confirmed by X-ray diffraction pattern and scanning electron microscope images. In the present work, we have studied the electrical properties of graphene oxide employing a recently proposed novel approach of the combined conduction and dielectric Cole–Cole formalism. The extracted dc conductivity values varies from 1.9 × 10−8 to 3.5 × 10− 5 S cm−1 as a function of temperature (153–353 K), show power-law behaviour, which is explained through Mott’s variable range hopping conduction mechanism. The density of states was found to be 6.02 × 1018 cm−3 eV−1. The conduction relaxation timescales and dielectric relaxation timescales of GO are following the power law. The physical origin of the non-Arrhenius dc conductivity behaviour of charge carriers is explained through structural heterogeneity in graphene oxide introduced due to sp2 and sp3 hybridization of carbon atoms. The range of hop was calculated to be 4.7–3.8 nm with hopping energy changing from 0.37 to 0.69 eV as a function of temperature.

Coded aperture design for solving the phase retrieval problem in X-ray crystallography

X-ray crystallography is an experimental technique used in material analysis that allows to measure the atomic positions of the elements present in a crystal. This technique is based on the X-ray diffraction patterns that provide electronic and elastic properties of the crystal of interest. Thus, the crystal can be uniquely identified by means of the phase of its diffraction patterns that are also used to analyze the material of interest. The phase of the X-ray cannot be directly measured; however, it can be recovered from the intensity of diffraction patterns. A recent work has shown that the phase signal can be recovered more efficiently when the acquisition architecture includes an optical element, known as coded aperture, such that the underlying signal is recovered from coded diffraction patterns. A coded aperture is an element that modulates the X-ray diffraction patterns by blocking some X-ray beams. The structure and the number of coded projections are crucial inasmuch they determine the quality and the acquisition time of the X-ray signal. This paper presents the analysis of a coded X-ray Crystallography system, and the design of the spatial structure of the coded aperture, such that the images are recovered with high PSNR (Peak Signal to Noise Ratio) using the minimum number of coded projections. The simulations indicate that the designed coded apertures obtain a reduction of up to 50% in the number of coded projections and an increase in the PSNR of up to 2 dB when the results are compared with the reconstructed images by using random non-designed coded aperture structures. All simulations were carried out on a set of diffraction pattern images, obtained by using the SAXS/WAXS X-ray crystallography software to simulated the diffraction patterns of a real crystal structure, called Rhombic Dodecahedron.

Optical fabrication of large area photonic microstructures by spliced lens

We experimentally demonstrate a convenient approach to fabricate large area photorefractive photonic microstructures by a spliced lens device. Large area two-dimensional photonic microstructures are optically induced inside an iron-doped lithium niobate crystal. The experimental setups of our method are relatively compact and stable without complex alignment devices. It can be operated in almost any optical laboratories. We analyze the induced triangular lattice microstructures by plane wave guiding, far-field diffraction pattern imaging and Brillouin-zone spectroscopy. By designing the spliced lens appropriately, the method can be easily extended to fabricate other complex large area photonic microstructures, such as quasicrystal microstructures. Induced photonic microstructures can be fixed or erased and re-recorded in the photorefractive crystal.

Sol-gel derived barium orthovanadate phosphors for white light-emitting diodes

The self-luminescent Ba3(VO4)2 materials were synthesized by a sol-gel method. The structural and morphological properties of the prepared materials were analyzed by X-ray diffraction (XRD) pattern and scanning electron microscope images. The XRD pattern shows that the sample crystallized in the rhombohedral phase with a space group of R3¯ m (166). The XRD pattern is consistent with the Joint Committee on Powder Diffraction Standards card values without any other impurity peaks. The self-luminescent properties of the samples were investigated by measuring the photoluminescence (PL) excitation and emission spectra by using a spectrofluorometer. The PL spectra revealed that the materials can give visible bluish-green emission under ultraviolet irradiation. The materials were further employed in making near-ultraviolet excitable white light-emitting diodes. The Ba3(VO4)2 phosphor along with a red emitting phosphor was mixed in silicone epoxy and applied to the near-ultraviolet light-emitting diode to obtain a bright white-light emission with a color rendering index of 80 and a correlated color temperature of 4075 K.

Growth of defect-free GaAsSbN axial nanowires via self-catalyzed molecular beam epitaxy

Bandgap reduction of 10% by incorporation of a dilute amount of N is reported for the first time, in axial GaAsSb nanowires (NWs) grown on Si (111) via Ga-assisted molecular beam epitaxy. Impact of N incorporation on the surface morphology, NW growth kinetics, and their structural and optical properties were examined. Dilute nitride NWs with Sb composition of 7 at% did not exhibit any noticeable planar defects, as revealed by the absence of satellite twin peaks in the selected-area diffraction pattern and high-resolution transmission electron microscopy imaging. Point defects were also minimal in as-grown dilute nitride NWs, as ascertained from the comparison of low-temperature photoluminescence spectra as well as the shape and shift of Raman modes, with in situ annealed NWs in different ambients. Evidence of enhanced incorporation of N was found in the NWs in situ annealed in N ambient, but with deteriorated optical quality due to simultaneous creation of N-induced defects. The lack of any noticeable defects in the as-grown GaAsSbN NWs demonstrates the advantage of the vapor–liquid–solid mechanism responsible for growth of axial configuration over the vapor–solid growth mechanism for core–shell NWs as well as their thin film counterpart, which commonly exhibit N-induced point defects.

Angle-resolved electron energy loss spectroscopy in hexagonal boron nitride

Electron energy loss spectra have been measured on hexagonal boron nitride single crystals employing a novel electron energy loss spectroscopic set-up composed by an electron microscope equipped with a monochromator and an in-column filter. This set-up provides high-quality energy-loss spectra and allows also for the imaging of energy-filtered diffraction patterns. These two acquisition modes provide complementary pieces of information, offering a global view of excitations in reciprocal space. As an example of the capabilities of the method we show how easily the core loss spectra at the $K$ edges of boron and nitrogen can be measured and imaged. Low losses associated to interband and/or plasmon excitations are also measured. This energy range allows us to illustrate that our method provides results of quality comparable to those obtained from non resonant X-ray inelastic scattering, but with advantageous specificities such as an enhanced sensitivity at low q and a much higher simplicity and versatility that makes it well adapted to the study of two-dimensional materials and related heterostructures. Finally, by comparing theoretical calculations against our measures, we are able to relate the range of applicability of ab initio calculations to the anisotropy of the sample and assess the level of approximation required for a proper simulation of our acquisition method.

Antibacterial activity of the thin ZnO film formed by atomic layer deposition under UV-A light

For the application of ZnO nanoparticles to water disinfection, immobilization of the ZnO nanoparticles on reactor surfaces is required; otherwise, the nanoparticles aggregate and leave the reactor over time. To overcome these limitations, we formed thin ZnO films on a glass substrate using atomic layer deposition (ALD) (n=400 at 140°C). An X-ray diffraction pattern and scanning electron microscope (SEM) images demonstrated that the thin ZnO film consisted of closely packed nano-sized grains. The grains had hexagonal wurtzite crystalline structures, which were mostly oriented vertically from the substrate. The thin ZnO film did not show a change in the optical properties of ZnO: absorbance at <380nm and band gap of 3.25eV. Furthermore, the thin ZnO films produced reactive oxygen species (ROS) such as superoxide anion, hydroxyl radical, and singlet oxygen, by irradiation with UV-A light (350–400nm), and the production of ROS was not diminished even after repeated use. Antibacterial activity against Staphylococcus aureus was observed when the ZnO films were placed under UV-A light. However, this was not evident when the ZnO films were in the dark or when the glass substrate without the ZnO film was exposed to UV-A light, suggesting that the antibacterial activity was due to ROS production by the ZnO film under UV-A light. Moreover, the bacterial cells exposed to the ZnO film under UV-A light showed a crushed morphology, indicating that the ROS facilitated the disruption of the bacterial cell membranes. Taken together, this study demonstrates that ALD firmly anchored the ZnO nanocrystalline structures on the substrate without hampering the ROS production or antibacterial activity for the purpose of water disinfection.

Anticancer activity of graphene oxide-reduced graphene oxide-silver nanoparticle composites

In the present study, a chemical route was employed to synthesize graphene oxide (GO)-reduced graphene oxide (rGO)-Ag nanoparticle (AgNP) composites from graphite and AgNO3 using vitamin C as reducing agent. Powder X-ray diffraction pattern and field emission scanning electron microscope images revealed that the AgNP were uniformly distributed on the surface of GO and rGO nanosheets. For the first time, the cytotoxicity of GO, rGO, AgNP, GO-AgNP and rGO-AgNP composites were examined against human lung cancer A549 cells using MTT assay and reported quantitatively. The rGO-AgNP showed significant cytotoxicity activity with an IC50 value of 30μg/mL towards A549 cells which is higher than that of GO (180μg/mL), rGO (160μg/mL) and GO-AgNP (100μg/mL). Compared to AgNP (6μg/mL), rGO-AgNP shows partial agglomeration of AgNP on rGO sheets, which reduces the interaction between rGO-AgNP and A549 cells leading to lesser anticancer activity than AgNP. The interaction between rGO and AgNP leads to increase in the material biocompatibility, reducing the toxicity and corrosive characteristic.

Infiltration of La0·6Sr0·4FeO3-δ nanoparticles into YSZ scaffold for solid oxide fuel cell and solid oxide electrolysis cell

La0·6Sr0·4FeO3-δ (LSF) nanoparticles were infiltrated into porous YSZ scaffold to fabricate composite LSF-YSZ oxygen electrode for both solid oxide fuel cell (SOFC) and solid oxide electrolysis cell (SOEC). X-ray diffraction (XRD) pattern and scanning electron microscopy (SEM) images have demonstrated that the formation of LSF perovskite phase and uniform distribution of nano-structural LSF particles onto inner surface of the YSZ scaffold, respectively. Polarization curves and electrochemical impedance spectra (EIS) were employed for the characterization of electrochemical properties of the cell for both power generation and high-temperature steam electrolysis. Furthermore, the long-term durability of the LSF-infiltrated cell was galvanostatically carried out under both SOFC and SOEC operations. For SOFC operation, the cell experienced a significant degradation in the initial 50 h and subsequently was sustained at a stable operation, with overall ohmic and polarization resistance variation from 0.20 to 0.25 Ω cm2 and from 0.55 to 0.60 Ω cm2, respectively. For SOEC operation, the cell showed high long-term durability operation, with almost unchangeable ohmic resistance and slightly varied polarization resistance from 0.41 to 0.43 Ω cm2.

Using flatbed scanners in the undergraduate optics laboratory—An example of frugal science

We describe the use of a low-cost commercial flatbed scanner in the undergraduate teaching laboratory to image large (∼25 cm) interference and diffraction patterns in two dimensions. Such scanners usually have an 8-bit linear photosensor array that can scan large areas (∼28 cm × 22 cm) at very high spatial resolutions (≥100 Megapixels), which makes them versatile large-format imaging devices. We describe how the scanner can be used to image interference and diffraction from rectangular single-slit, double-slit, and circular apertures. The experiments are very simple to setup and require no specialized components besides a small laser and a flatbed scanner. Due to the presence of Automatic Gain Control in the scanner, which we were not able to override, we were unable to get an excellent fit to the data. Interestingly, we found that the less-than-ideal data were actually pedagogically superior as it forced the students to think about the process of data acquisition in much greater detail instead of simply performing the experiment mechanically.

Optical properties of indium doped ZnO planar superlattice nanoribbons

The indium-doped zinc-oxide (IZO) planar superlattice nanoribbons were synthesized by a chemical vapor transport method. The x-ray diffraction pattern and high resolution transmission electron microscopy image indicate that the synthesized nanoribbons have planar superlattice structures formulated as In2O3(ZnO)m with small m (m=3,5). The Photoluminescence (PL) spectrum of the planar superlattice nanoribbons (NRs) shows only one dominant broad asymmetric excitonic emission with a peak at 3.371eV, which is about 14meV higher than the bound exciton emission in pure ZnO. The PL blueshift observed in NRs was attributed to the quantum confinement effect due to small thickness of the In/Zn-O slab. From the temperature dependence of the PL intensity, the activation energy of donor bound exciton bound to In donors in IZO was derived to be around 18.3–25.7meV. We also obtained the shrinkage parameters of the band gap of the NRs, α=1.0−1.2meV/K and β=500−520K, by using the Varshni empirical formula.

Non-spectroscopic composition measurements of SrTiO3-La0.7Sr0.3MnO3 multilayers using scanning convergent beam electron diffraction

The local atomic structure of a crystalline sample aligned along a zone axis can be probed with a focused electron probe, which produces a convergent beam electron diffraction pattern. The introduction of high speed direct electron detectors has allowed for experiments that can record a full diffraction pattern image at thousands of probe positions on a sample. By incoherently summing these patterns over crystalline unit cells, we demonstrate that in addition to crystal structure and thickness, we can also estimate the local composition of a perovskite superlattice sample. This is achieved by matching the summed patterns to a library of simulated diffraction patterns. This technique allows for atomic-scale chemical measurements without requiring a spectrometer or hardware aberration correction.

Preparation of optical active single-handed helical barium titanate nanotubes and characterization of dielectric properties

Left and right-handed helical barium titanate nanotubes are prepared with the impregnation of Ba(OH)2 into single-handed helical titania nanotubes. Wide angle X-ray diffraction pattern and transmission electron microscopy image indicate that they are constructed by nanoparticles with a partially crystalline structure. The diffuse reflectance circular dichroism spectra indicate that they exhibit optical activity which was proposed to originate from chiral defects on the inner surfaces of the nanotubes. Both the dielectric constant and tanδ decrease with increasing the frequency. At 10 and 100Hz, one dielectric constant peak at 9.6°C and one tanδ peak at 5.0°C are observed at −120°C to 180°C.

How many photons are needed to reconstruct random objects in coherent X-ray diffractive imaging?

This paper presents an investigation of the reconstructibility of coherent X-ray diffractive imaging diffraction patterns for a class of binary random `bitmap' objects. Combining analytical results and numerical simulations, the critical fluence per bitmap pixel is determined, for arbitrary contrast values (absorption level and phase shift), both for the optical near- and far-field. This work extends previous investigations based on information theory, enabling a comparison of the amount of information carried by single photons in different diffraction regimes. The experimental results show an order-of-magnitude agreement.

Single step synthesis of ZnS quantum dots and their microstructure characterization and electrical transport below room temperature

Low dimensional cubic phase ZnS quantum dots (QDs) are formed by mechanical alloying the stoichiometric mixture of Zn and S powders at room temperature. During milling process the primary mixed phase ZnS is formed at about 3.5 h of milling and strain less single phase (cubic) ZnS QDs are formed with ∼4.5 nm in size after 20 h of milling. Detailed microstructure study has been done by both Rietveld analysis of x-ray diffraction pattern and high resolution transmission electron microscope images. Dc resistivity decreases with increasing temperature which can be explained by three-dimensional hopping conduction mechanisms. Observed negative magnetoconductivity has been analyzed by wave function shrinkage model. Alternating current conductivity can be described by the correlated barrier hopping conduction mechanism. Analysis of complex impedance indicates that the grain boundary resistance is found to be dominating over the grain resistance. Relaxation behavior has been explained by the analysis of the electric modulus.

Combining Pre- and Post-Nucleation Trajectories for the Synthesis of High FAU-Content Faujasite Nanocrystals from Organic-Free Sols

The effects of synthesis conditions on the FAU/EMT content and the size of nanocrystals, formed from inorganic aluminosilicate sols, were investigated. High-resolution transmission electron microscopy imaging and comparison of experimental X-ray diffraction patterns with simulations demonstrated that all materials made starting from synthesis mixtures in the composition range (1.8–33) SiO2:1 Al2O3:(2.7–33) Na2O:(41–1000) H2O contain FAU/EMT intergrowths. Compositions with low water content increase the FAU fraction up to 0.8 but the crystal size exceeds 100 nm. Extension of the higher FAU purity to nanocrystals was achieved only by first mixing the sol at high water content compositions that favor nanocrystal formation and then—after a certain time—lowering by freeze-drying the water to levels favoring the formation of FAU. Cryogenic transmission electron microscopy and small-angle X-ray scattering from representative optically clear and colloidally stable precursor sols (aged and crystallized at ambient ...

Structural, electrical and magnetic properties of dilutely Y doped NiFe2O4 nanoparticles

Present study is focused on the structural, electrical and magnetic properties of dilutely Y doped NiFe2O4 nanoparticles. X-ray diffraction confirms the phase formation and shows that samples prepared using sol-gel method exhibit pure spinel phase except that of x = 0.05. Analysis of diffraction pattern and scanning electron microscopy images demonstrate that crystallite as well as particle sizes are increasing with concentration of Y. Presence of impurity phase is further confirmed by Raman measurement. There is no significant change in vibrational modes up to the solubility limit (x = 0.03), however, these modes are shifted towards higher wavenumber for 5% Y doped Ni ferrite due to impure phase. Incorporation of dilute amount of Y ions in host lattice results in an enhancement in the saturation magnetization, coercivity and resistivity. The enhanced saturation magnetization and resistivity is understood on the basis of exchange interactions induced by the substitution of Y3+ ions for Fe3+ ions at B-site.

Development of radiation damage during in-situ Kr++ irradiation of Fe[sbnd]Ni[sbnd]Cr model austenitic steels

In situ irradiations of 15Cr/15NiTi and 15Cr/25NiTi model austenitic steels were performed at the Intermediate Voltage Electron Microscope (IVEM)-Tandem user Facility (Argonne National Laboratory) at 600 °C using 1 MeV Kr++. The experiment was designed in the framework of cladding development for the GEN IV Sodium Fast Reactors (SFR). It is an extension of previous high dose irradiations on those model alloys at JANNuS-Saclay facility in France, aimed at investigating swelling mechanisms and microstructure evolution of these alloys under irradiation [1]. These studies showed a strong influence of Ni in decreasing swelling. In situ irradiations were used to continuously follow the microstructure evolution during irradiation using both diffraction contrast imaging and recording of diffraction patterns. Defect analysis, including defect size, density and nature, was performed to characterize the evolving microstructure and the swelling. Comparison of 15Cr/15NiTi and 15Cr/25NiTi irradiated microstructure has lent insight into the effect of nickel content in the development of radiation damage caused by heavy ion irradiation. The results are quantified and discussed in this paper.