Selected Area Diffraction Patterns Research Articles

Nano-mineralogical investigation of coal and fly ashes from coal-based captive power plant (India): An introduction of occupational health hazards

Coal derived nano-particles has been received much concern recently around the world for their adverse effects on human health and the environment during their utilization. In this investigation the mineral matter present in some industrially important Indian coals and their ash samples are addressed. Coal and fly ash samples from the coal-based captive power plant in Meghalaya (India) were collected for different characterization and nano-mineralogy studies. An integrated application of advanced characterization techniques such as X-ray diffraction (XRD), High Resolution-Transmission Electron microscopy (HR-TEM)/(Energy Dispersive Spectroscopy) EDS/(selected-area diffraction pattern) SAED, Field Emission-Scanning Electron Microscopy (FE-SEM)/EDS analysis, and Mössbauer spectroscopy were used to know their extent of risks to the human health when present in coal and fly ash. The study has revealed that the coals contain mainly clay minerals, whilst glass fragments, spinel, quartz, and other minerals in lesser quantities were found to be present in the coal fly ash. Fly ash carbons were present as chars. Indian coal fly ash also found to contain nanominerals and ultrafine particles. The coal-fired power plants are observed to be the largest anthropogenic source of Hg emitted to the atmosphere and expected to increase its production in near future years. The Multi Walled Carbon Nano-Tubes (MWCNTs) are detected in our fly ashes, which contains residual carbonaceous matter responsible for the Hg capture/encapsulation. This detailed investigation on the inter-relationship between the minerals present in the samples and their ash components will also be useful for fulfilling the clean coal technology principles.

Microstructure evolution of beryllium during proton irradiation

The effects of proton irradiation on a beryllium reflector in terms of microstructure evolution have been studied to emulate the effects of neutron irradiation. Protons were irradiated on a beryllium sample with the acceleration voltage of 120 keV and the fluence of 2.0 × 1018 ions/cm2 at room temperature. The size of the irradiation damaged layer was estimated through a Monte Carlo simulation (SRIM2012 software) and transmission electron microscopy (TEM) observation. While the irradiated sample was observed by using TEM, the size of the damaged layer was roughly 1 µm, and the value was coincident with the simulation result. The most severely damaged area was occurred at 600 nm in depth; tens-of-nanometer-sized voids were distributed. Multiple voids were observed in the entire damaged area, and were preferentially distributed along the grain boundaries, and the interfaces between the matrix and the BeO particles. Equi-axed voids, 10 nm in diameter, were observed in the grain boundary, and planar voids were observed at the interfaces. The voids were also distributed in the grains; the evolutions of the voids were observed to have been affected by the grain orientation rather than the irradiation direction. The selective area diffraction pattern (SADP) from TEM showed that the arrays of multiple voids were considerably longer along the basal plane. The beryllium atoms could be easily dislocated by proton irradiation while the basal plane was aligned along a direction perpendicular to the irradiation.

Microstructures and Hardness Properties for β-Phase Ti–24Nb–4Zr–7.9Sn Alloy Fabricated by Electron Beam Melting

Atomized, pre-alloyed Ti–24Nb–4Zr–7.9Sn (wt%) powder was used to fabricate solid, prototype components by electron beam melting (EBM). Vickers microindentation hardness values were observed to average 2 GPa for the precursor powder and 2.5 GPa for the solid, EBM-fabricated products. The powder and solid product microstructures were examined by optical and electron microscopy. X-ray diffraction analyses showed that they had bcc β-phase microstructure. However, it was found by transmission electron microscopy that the EBM-fabricated product had plate morphology with space ∼100–200 nm. Although the corresponding selected area diffraction patterns can be indexed by β-phase plus α″-martensite with orthorhombic crystal structure, the dark-field analyses failed to observe the α″-martensite. Such phenomenon was also found in deformed gum metals and explained by stress-induced diffusion scattering due to phonon softening.

Strontium oxide quantum dot decorated graphene composites for liquid petroleum gas sensing

Liquid petroleum gas-sensing behaviour of graphene/SrO quantum dots (QDs) composites was investigated. Structure and morphology of prepared materials were analysed through X-ray diffraction (XRD) and transmission electron microscopy along with selected-area diffraction pattern. The optical properties were analysed through fluorescence spectroscopy. The thermal behaviour of optimized sensing material was examined using thermogravimetric differential thermal analysis (TG-DTA). The gas-sensing properties of composites were measured by resistance change as a function of gas concentration. A notable better sensing performance was observed for liquefied petroleum gas (LPG). The enhanced gas-sensing properties with increasing amount of graphene are discussed by using defect chemistry. A good correlation is observed between the fluorescence intensity ratio (I UV/I DL) and the sensing response as a function of the amount of graphene.

Phase transformation during mechano-synthesis of nanocrystalline/amorphous Fe–32Mn–6Si alloys

Mechano-synthesis of Fe–32Mn–6Si alloy by mechanical alloying of the elemental powder mixtures was evaluated by running the ball milling process under an inert argon gas atmosphere. In order to characterize the as-milled powders, powder sampling was performed at predetermined intervals from 0.5 to 192h. X-ray florescence analyzer, X-ray diffraction, scanning electron microscope, and high resolution transmission electron microscope were utilized to investigate the chemical composition, structural evolution, morphological changes, and microstructure of the as-milled powders, respectively. According to the results, the nanocrystalline Fe–Mn–Si alloys were completely synthesized after 48h of milling. Moreover, the formation of a considerable amount of amorphous phase during the milling process was indicated by quantitative X-ray diffraction analysis as well as high resolution transmission electron microscopy image and its selected area diffraction pattern. It was found that the α-to-γ and subsequently the amorphous-to-crystalline (especially martensite) phase transformation occurred by milling development.

Show me how you walk and I tell you how you feel — A functional near-infrared spectroscopy study on emotion perception based on human gait

The ability to recognize and adequately interpret emotional states in others plays a fundamental role in regulating social interaction. Body language presents an essential element of nonverbal communication which is often perceived prior to mimic expression. However, the neural networks that underlie the processing of emotionally expressive body movement and body posture are poorly understood.33 healthy subjects have been investigated using the optically based imaging method functional near-infrared spectroscopy (fNIRS) during the performance of a newly developed emotion discrimination paradigm consisting of faceless avatars expressing fearful, angry, sad, happy or neutral gait patterns. Participants were instructed to judge (a) the presented emotional state (emotion task) and (b) the observed walking speed of the respective avatar (speed task).We measured increases in cortical oxygenated haemoglobin (O2HB) in response to visual stimulation during emotion discrimination. These O2HB concentration changes were enhanced for negative emotions in contrast to neutral gait sequences in right occipito-temporal and left temporal and temporo-parietal brain regions. Moreover, fearful and angry bodies elicited higher activation increases during the emotion task compared to the speed task. Haemodynamic responses were correlated with a number of behavioural measures, whereby a positive relationship between emotion regulation strategy preference and O2HB concentration increases after sad walks was mediated by the ability to accurately categorize sad walks.Our results support the idea of a distributed brain network involved in the recognition of bodily emotion expression that comprises visual association areas as well as body/movement perception specific cortical regions that are also sensitive to emotion. This network is activated less when the emotion is not intentionally processed (i.e. during the speed task). Furthermore, activity of this perceptive network is, mediated by the ability to correctly recognize emotions, indirectly connected to active emotion regulation processes. We conclude that a full understanding of emotion perception and its neural substrate requires the investigation of dynamic representations and means of expression other than the face.

Solid-state amorphization in a Ti2Pd intermetallic compound under fast-electron irradiation

MeV electron irradiation-induced structural changes in a C11b–Ti2Pd intermetallic compound were investigated by high-voltage electron microscopy to provide evidence for amorphous-phase formation in Ti-based (Ti>50at.%) intermetallic compounds. The Ti2Pd compound could not maintain its original structure against the MeV electrons, and a bct solid–solution phase was formed at 22, 103, and 298K. At temperatures ⩽103K, halo rings appeared in the selected area diffraction patterns after the bct-phase formation under the irradiation. This fact suggests the occurrence of solid-state amorphization; however, an amorphous single phase could not be obtained in the Ti66.7Pd33.3 alloy.

Sonochemical synthesis of nitrogen doped ZnO nanorods: effect of anions on growth and optical properties

Sonochemical synthesis of nitrogen doped zinc oxide (ZnO:N) nanorods using acetate and nitrate of the starting materials is reported. X-ray diffraction studies reveal the formation of hexagonal wurtzite phase of ZnO in both the cases whereas the crystallite size is found to be greater in acetate route. Precursor dependent growth process is observed as the time period for precipitation is found to be different with different starting materials. Electron microscopic studies show the formation of rod like structures of ZnO and ZnO:N in both acetate and nitrate routes. But, high aspect ratio and uniformity in the morphology of ZnO:N nanorods is observed in acetate route. High resolution images and selected area diffraction patterns of ZnO:N illustrate the nanorods to be c-axis oriented in both the cases. But in nitrate medium, the growth along [0001] direction is affected due to the adsorption of NO3 − ions onto polar Zn2+ surface leading to smaller length of the nanorods. FTIR studies also support these results showing the existence of sharp N–O symmetric stretching in ZnO:N in nitrate route. Photoluminescence (PL) measurements show red shift of excitonic emission band for ZnO in acetate route.

Microstructural Characterization of the Reaction Product Region Formed Due to the High Temperature Interaction of ZnO[0001] Single Crystal with Liquid Aluminum

The study was focused on the microstructure characterization at the micro- and nano scale of the reaction product region (RPR) formed due to the interaction between the liquid aluminum and ZnOSC[0001] single crystalline substrate at 1000ºC. The research was carried out on the Al/ZnO couple produced by the sessile drop method under vacuum within two different procedures: 1) classical contact heating and cooling; 2) pushing drop procedure allowing opening the Al/ZnO interface at the test temperature and, therefore, prevent influence of cooling with Al drop on interface structure. The microstructure observations of the sample after using classical contact heating procedure revealed the formation of the RPR of ∽50 μm in thickness extending into the ZnOSC single crystal substrate. It was composed of the ceramic α-Al2O3 and metallic Al(Zn) mutually interpenetrating lattices, typical for the C4 type structure. Additionally, at the ZnO/RPR interface, the presence of a thin (∽250 nm) layer of the metastable δ-Al2O3was detected. The obtained results were compared with experimental data found for the sample after pushing drop procedure resulting in the formation of two layers of ZnAl2O4 spinel and alumina, exhibiting strong epitaxial growth. The selected area diffraction patterns clearly evidenced that the crystal structure of formed Al2O3 corresponds to the tetragonal δ-phase.

Morphology of oxide particles in ODS austenitic stainless steel

In this study, identification of the crystal structure and analysis of the orientation relationship of oxide particles in an oxide dispersion strengthened austenitic stainless steel was carried out. High resolution transmission electron microscopy (HRTEM) and energy dispersive spectroscopy showed that most of the oxide particles had a faceted shape and consisted of a complex oxide, the anion-deficient fluorite structure Y2Hf2O7. Selected area diffraction patterns and HRTEM indicated that the faceted oxide particle has a cube-on-cube orientation relationship with the surrounding matrix. In addition, strain fields were observed around the oxide particle with given reflection conditions, indicating that it surrounds the oxide particle. The observed strain fields would affect glide dislocation pinning and the migration of irradiation-induced point defects.

Effect of precursor sol pH on microstructural, optical and photocatalytic properties of vacuum annealed zinc tin oxide thin films on glass

Dip coated vacuum annealed zinc tin oxide thin films on soda lime silica glass have been deposited from the precursor sols containing zinc acetate dihydrate and tin (IV) chloride pentahydrate (Zn:Sn = 67:33, atomic ratio in percentage) in 2-methoxy ethanol by varying sol pH (0.85–5.5). Crystallinity, morphology, optical and photocatalytic properties of the films strongly depend on sol pH. Measurement of grazing incidence X-ray diffraction confirms the presence of hexagonal nano ZnO in the films derived from the sols of pH < 5.5. Film crystallinity deteriorates on increasing sol pH and the film deposited from the sol of pH 5.5 shows XRD amorphous but the selected area diffraction pattern and HRTEM image evidence the presence of nano Zn2SnO4 (size, 5–6 nm). Direct band gap energy of films increases on increasing sol pH. To visualize the film surface microstructure, FESEM study has been done and a rod-like surface feature is revealed in the film deposited from the sol of pH 2.85. A dependence of precursor sol pH on the photocatalytic activity of films towards degradation of Rhodamine 6G dye under UV (254 nm) irradiation is found and the highest decomposition rate constant, ‘k’ value is obtained from the film prepared from the sol of pH 5.5. The presence of zinc deficient nano Zn2SnO4 in the film may consider for generating the highest ‘k’ value. We also measure gelling time, viscosity of sols as well as UV and FTIR studies on the films and propose chemical reactions.

Different atomic structures observed from ternary Ni-Nb-Ta metallic glasses obtained by ion beam mixing

Four sets of ternary Ni-Nb-Ta multilayered samples with overall compositions of Ni69Nb8Ta23, Ni55Nb13Ta32, Ni42Nb16Ta42 and Ni29Nb18Ta53, respectively were prepared and subjected to 185 keV xenon ion beam mixing. The experimental results showed that in the four Ni-Nb-Ta multilayered samples, metallic glasses could all be obtained at appropriate doses, supporting the prediction directly from a proven realistic Ni-Nb-Ta interatomic potential through molecular dynamics simulations, and that two different atomic structures were observed, as in the corresponding selected area diffraction patterns, the locations of the diffused bands reflected from the metallic glass phases were observed at different angles for the Ni69Nb8Ta23 and Ni29Nb18Ta53 metallic glasses. Interestingly, Voronoi tellessation analysis indicated that the observed difference in atomic structures could be attributed to the distinct coordinate number spectra, i.e., the spectrum of the Ni69Nb8Ta23 metallic glass has its coordinate number (CN) equal to 13 as dominating atomic configuration (with a weight of about 27%), whereas for the Ni29Nb18Ta53 metallic glass, CN=14 is the dominating atomic configuration (also about 27%). Moreover, the distinct atomic configurations of the obtained Ni-Nb-Ta metallic glasses could be correlated to the structures of the constituent metals of the ternary Ni-Nb-Ta system, as the first neighbor of fcc is 12 and the sum of the first and second neighbors of bcc is 14, implying the structural heredity did play a role in metallic glass formation.

Magnetic and structural properties of BiFeO3 thin films grown epitaxially on SrTiO3/Si substrates

The integration of oxides with semiconductors is important for the technological advancement of the next generation electronics. Concomitant ferroelectric and antiferromagnetic (AF) behavior is demonstrated in single crystal BiFeO3 (BFO) films grown on 20 nm SrTiO3 (STO) virtual substrates on Si(100) using molecular beam epitaxy (MBE). STO thin films are grown in an oxide MBE chamber by co-deposition of Sr, Ti, and molecular O2. Careful control of the O2 during nucleation produced commensurate growth of STO on Si. The sequence of the steps allows for the suppression of an amorphous SiO2 layer. This STO(20 nm)/Si structure was used as a virtual substrate for MBE deposition of BFO on Si without breaking vacuum. BFO was deposited using Fe and O2 plasma with an overpressure of Bi flux, the growth rate was controlled by the incoming Fe flux. The reflection high energy electron diffraction image shows a 2-D growth front with a 6-fold surface reconstruction under optimized O2 pressure of 5 × 10−8 mbar. Cross-sectional transmission electron microscopy (TEM) confirms the high crystallinity of the films and shows sharp, atomically flat interfaces. The selected area diffraction pattern (SADP) reveals that BFO grows in a distorted rhombohedral crystal structure. X-ray diffraction does not show formation of second phases and is consistent with the TEM and SADP results. The BFO films show AF behavior with a Neel temperature that exceeds 350 K, as expected (TN = 673 K) and with a residual ferromagnetic behavior that decreases with film thickness and is consistent with the G-type AF due to the canted spins. The saturation magnetization per unit volume for a 40 nm thick film was 180 emu/cm3 at an in-plane magnetic field of 8 kOe. The ferroelectric behavior of the films was verified using piezoresponse force microscopy.

Charge ordering in reactive sputtered (1 0 0) and (1 1 1) oriented epitaxial Fe3O4 films

Epitaxial Fe 3 O 4 films with (1 0 0) and (1 1 1) orientations fabricated by reactive sputtering present simultaneous magnetic and electrical transitions at 120 and 124 K, respectively. The symmetry decreases from face-centered cubic to monoclinic structure across the Verwey transition. Extra spots with different brightness at different positions appear in selected-area diffraction patterns at 95 K. The extra spots come from the charge ordering of outer-layer electrons of Fe atoms, and should be related to the charge ordering of octahedral B-site Fe atoms.

Green Synthesis of Gold and Silver Nanoparticles Using &lt;I&gt;Achyranthes aspera&lt;/I&gt; L. Leaf Extract

The importance of leaf extract of Achyranthes aspera L. as reducing agent in the synthesis of gold, silver nanoparticles (NPs) in quantitative yield, by the reaction of aqueous chloroaurate ions and aqueous silver ions with a small quantity of leaf extract is demonstrated. Changes in concentration of leaf extract can modify the phase morphology and the size of the nanoparticles can be tuned. UV-Visible spectra of the solution evidenced the variation in the dimension of anisotropic nanostructures. The formation of spherical nanostructures and nanotriangles of noble metal gold and silver nanoparticles is confirmed by transmission electron microscopy (TEM) investigations. The gold nanoparticles are poly dispersed and the average size of spherical nanoparticles is found to be 18 3±1 0 nm. The average edge length of the triangle is 27 2±2 0 nm. Selected area diffraction pattern (SAED) confirmed the polycrystalline molecular structure. SAED diffraction patterns of biogenic silver nanotriangles revealed the orientation of nanotriangles top surface normal to the electron beam.

Nanoporous Copper Dealloyed from a Nanocrystallized Ticu Alloy

Nanoporous copper (NPC) was fabricated through dealloying nanocrystallized TiSubscript text50Cu50 ribbon alloy under a free immersion condition in HF solutioSubscript textns at 25 °C. Multimodal nanoporous structure was formed due to the presence of Ti3Cu4 phase, which was co-precipitated with Ti2Cu during the heat treatment at T = 400 °C (Italic textTSubscript textg Italic textT Subscript textx). The presence of multiphases in tItalic texthe starting material caused the different behavior in the evolution of nanoporosity. In 0.03 mol/L HF solution, the bimodal nanoporous copper with a pore size of 54 nm and 184 nm was obtained in different regions where the composition differed. The ligament scale lengths in two regions were confirmed to be 54 nm and 203 nm, respectively. In 0.13 mol/L HF solution, the difference in the pore size and phase separation became weak, accompanying with the evolution of larger pores and smaller ligaments. The residue after dealloying was confirmed to be fcc Cu, indicated by the presence of Cu (111), (200), (220) and (311) in XRD patterns and TEM selective area diffraction pattern. The microstructure of the starting materials for dealloying, such as intermetallic phases, played a key role in the formation of the final multimodal nanoporous structure.

Using the TEM Condenser Lens to Switch between Image and Diffraction Modes

Central to the operation of the transmission electron microscope (TEM) (when used with crystalline samples) is the ability to go back and forth between an image and a diffraction pattern. Although it is quite simple to go from the image to a convergent-beam diffraction pattern or from an image to a selected-area diffraction pattern (and back), I have found it useful to be able to go between image and diffraction pattern even more quickly. In the method described, once the microscope is set up, it is possible to go from image to diffraction pattern and back by turning just one knob. This makes many operations on the microscope much more convenient. It should be made clear that, in this method, neither the image nor the diffraction pattern is “ideal” (details below), but both are good enough for many necessary procedures.

Nucleation and growth of Ni0 nanoparticles and thin films by TEM electron irradiation

This paper reports the generation in situ of Ni0 nanoparticles and thin films by focusing a TEM electron beam over NiO/ZrO2-CeO2 and NiO. Electron irradiation was carried out using a TEM at 80 and 100kV, concentrated over individual NiO/ZrO2-CeO2 and NiO agglomerates. The results showed that just after electron irradiation started, the reduction of NiO phase occurred and fine Ni0 nanoparticles were formed. These Ni nanoparticles were limited to a small area around the irradiated NiO/ZrO2-CeO2 and NiO agglomerates. It was found that the nanoparticles growth increased with irradiation time, and a Ni0 thin film was formed after 50min. The evolution was studied using BF images and SAD patterns. Characterization of single nanoparticles was conducted using HRTEM, STEM and EDS.

Single crystalline β-Ga2O3 nanowires synthesized by thermal oxidation of GaSe layer

β-Ga2O3 nanowires were grown by thermal oxidation of GaSe single crystal surface under a mixture of argon–air flow, without the presence of a catalyst or foreign substrate. The nanowires were obtained after annealing GaSe surface at different temperatures (720°C, 850°C and 930°C) for 5h and they were characterized by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy and selected area diffraction pattern. The lengths of the nanowires varied in the range 50–180nm, while the typical diameters of the nanowires were in the range 60–90nm. A possible mechanism has been proposed in order to explain the growth of oxide nanowires.

Microstructure of epitaxial AlN layers on sapphire substrates deposited by physical vapor deposition

ABSTRACTAsymmetric (10L) XRD peaks have been employed as a measure of epitaxial quality for aluminum nitride (AlN) nucleation layers (NL) deposited on sapphire substrate. Epitaxial AlN films have been deposited on 2-6” sapphire substrate by reactive sputtering. FWHM of AlN (103) and (105) were found to be an excellent indicator of quality of AlN films for GaN growth. AlN films produced nucleation layers with highly reproducible microstructure and GaN film growth. NLs had in-plane and out-of-plane texture as evident by the pole-figure results and selected area diffraction pattern. Based on electron microscopy results, AlN film thickness for complete atomic ordering was estimated to be 6-7 nm and most of the edge dislocations were seen in the first 20 nm of the film. Excellent thickness and texture uniformity were seen on planar and patterned sapphire substrates. A compressive stress of 2.9±0.2 GPa was seen in our BKM films. The maximum screw and edge dislocation densities of films were found to be ∼3 x 108 cm−2 and ∼9 x 109 cm−2 respectively. The root mean square roughnesses of A-polar films were found to be &lt; 0.3 nm.