Energy Dispersive X-ray Diffraction Measurements Research Articles

Salt Bath Nitriding of Fe3Al Based Intermetallic Compound

Iron aluminide Fe3Al was produced in a vacuum arc melting furnace. The alloy was heat treated by salt bath nitriding at 580 °C for durations of 3, 6, and 9 h. The nitride layers formed on the surface were characterized with light optical microscopy (LOM), scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDXS), X-ray diffraction (XRD), and micro hardness measurements. The results showed that the nitride layer thickness increased with an increase in nitriding duration, while the layer hardness did not vary. The nitride layers were composed chiefly of iron nitride and aluminum nitride phases. The dry sliding friction and wear behaviors of nitrided iron aluminides were determined. The results revealed that the wear resistance decreased with increase in the length of nitriding.

Fabrication of a highly flexible low-cost H2 gas sensor using ZnO nanorods grown on an ultra-thin nylon substrate

A “highly flexible low-cost” H2 gas sensor was fabricated via inclined and vertically well-aligned ZnO nanorods on a “cheap, thin (15 µm), and highly flexible” nylon substrate using the hydrothermal method. Morphological, crystallinity, and optical properties of the prepared ZnO nanorods were studied by field emission scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray analysis, X-ray diffraction, and photoluminescence measurements. Results revealed the formation of aligned hexagonal-like nanorods with high aspect ratio and density. The results confirmed the formation of wurtzite ZnO phase with a preferred orientation along the (002) direction with high crystallinity, excellent quality, and few defects. The sensitivity and response time behaviors of the ZnO-based gas sensor to hydrogen gas at different operation temperatures and in various hydrogen concentrations were investigated. Under 500 ppm of H2 exposure at different temperatures from room temperature to 180 °C, the sensitivity increased from 109 to 264 %. When the exposed H2 gas increased from 750 to 2000 ppm at a fixed temperature of 75 °C, the sensitivity also sharply increased from 246 to 578 %. Moreover, both the response and recovery time of the device during both tests were enhanced. The hydrogen gas sensing mechanisms of ZnO nanorods in low and high operation temperatures were discussed.

Influence of Graphene (0.01 wt. %) on Structural, Morphological and Photovoltaic Properties of TiO<sub>2</sub>-Based DSSC Using Electrolyte Gel

Titanium dioxide (TiO2) based dye-sensitized solar cells (DSSCs) doped with reduced graphene oxide, rGO also known as graphene were fabricated at concentrations of 0.01 wt.% . The performance of TiO2/graphene based DSSC and TiO2 based DSSC were studied using electrolytes; PAN-based gel electrolyte. The thin films were characterized using several characterizations such as scanning electron microscope (SEM), Energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and current-voltage (I-V) measurement. The micrograph images obtained by SEM demonstrated that the thin films are highly porous. The XRD characterization showed that the crystalline particle of thin films is an anatase state and high percentage of carbon composition can be determined using EDX analysis. Through I-V characteristic, the current density Jsc, open circuit-voltage Voc, fill-factor FF, and efficiency η of the TiO2-based DSSC were 0.196 mA/cm2, 0.44 V, 0.496 and 0.043% respectively. I-V characteristic showed an increase in values for rGO/TiO2 based DSSC such as Jsc = 1.177 mA/cm2, Voc = 0.66 V, FF = 0.656 and η = 0.509%. The addition of rGO concentration has improved the efficiency of DSSC while the use of electrolyte gel can sustain the stability of the cell.

Peculiarities of selective laser melting process for permalloy powder

The new soft magnetic material based on the permalloy powder was successfully used for a three dimensional sample fabrication via selective laser melting process. The microstructures of the Fe-80%Ni-alloy samples as a function of the laser influence parameters were studied by optical and scanning electron microscopes equipped with energy-dispersive microanalysis, X-ray diffraction and micro hardness measurements. The effects of external magnetic fields (EMF) on the growing structures during the laser melting were estimated. The reduction in coherent-scattering regions of magnetic phases under SLM with EMF is accompanied by the coercivity growth.

Thermal stability of plasma-sprayed La2Ce2O7/YSZ composite coating

A composite coating composed of La2Ce2O2 (LCO) and yttria-stabilized zirconia (YSZ) in a weight ratio of 1:1 was deposited by the plasma spraying using a blended YSZ and LCO powders, and the stability of the LCO/YSZ interface exposed to a high temperature was investigated. The LCO/YSZ deposits were exposed at 1300°C for different durations. The microstructure evolution at the LCO/YSZ interface was investigated by quasi-in-situ scanning electron microscopy assisted by X-ray energy-dispersive spectrum analyses and X-ray diffraction measurements. At an exposure temperature of 1300°C, the grain morphology of LCO splats in contact with YSZ splats changed from columnar grains to quasi-axial grains with interface healing, and some grains tended to disappear during the thermal exposure. The results indicate that the phases in LCO–YSZ composite coating are not stable at 1300°C. The element La in the LCO splat diffused towards the adjacent YSZ splat during the exposure, generating the reaction product layers composed of La2Zr2O7 between the LCO and YSZ splats. After exposed for 200h, the composite coating consisted of a mixture of mainly La2Zr2O7 and CeO2 and a minor amount of YSZ, accounting for the unusual decrease in the thermal conductivity at the late stage of exposure.

ZnO nanoflakes on silver wires with antibacterial effects

ZnO structures were electro-hydrothermally grown on copper and silver wires. To characterize the structures, multiple analyses including field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction and photoluminescence measurements were performed on the ZnO structures on the wires. Results indicate that ZnO nanoflakes were densely deposited on the silver wire but poor ZnO structures were grown on the copper wire.Furthermore, OD 600 antibacterial tests revealed that ZnO flakes on the silver wire exhibited better antibacterial capability than the silver wire without ZnO nanoflakes. Because of possible integration with silver-related materials and flexibility of wire structures, ZnO nanoflake-coated silver wires have potentials for future antiseptic and biomedical applications.

Ruthenium nanoparticles supported on mesoporous MCM-41 as an efficient and reusable catalyst for selective oxidation of arenes under ultrasound irradiation

Mesoporous MCM-41 was used as a support for the uniform dispersion of ruthenium nanoparticles having an average particle size of ∼5 nm. The obtained nanocomposite, MCM-41-Ru, was characterized using inductively coupled plasma, transmission electron microscopy, energy dispersive X-ray analysis, X-ray diffraction, and BET surface area measurements. The material was employed as an efficient and recyclable catalyst in the ultrasound-assisted oxidation of arenes. It was observed that ultrasound irradiation in combination with KBrO3 as the oxidant, in the presence of MCM-41-Ru nanoparticles, accelerates the oxidation reaction to afford the desired products in good yields. The recovered catalyst retained activity for successive runs, with a continuous change in the nature of its active sites.

Metal–insulator transitions in (V1-xCrx)2O3 thin films deposited by reactive direct current magnetron co-sputtering

Vanadium oxides are promising candidates for application in memory devices based on the control of their various metal–insulator transitions. We report here on the thin films deposition of the strongly correlated system (V1-xCrx)2O3 over a wide range of composition 0≤x≤0.60 by reactive DC magnetron co-sputtering of pure V and Cr targets. Thin films were characterized by Scanning Electron Microscopy, Energy Dispersive X-ray spectroscopy, X-ray diffraction and transport measurements. These studies demonstrates the existence of compressive stress reaching 0.8GPa in 200nm thick films, whereas thicker 1μm films exhibit lower internal stress. This compressive stress modifies significantly the phase diagram of the 200nm films, shifting the critical chromium content triggering the bandwidth-controlled metal–insulator transition from x=0.011 in unstressed films to more than 0.04. This work highlights the need for an accurate control of the Cr content and of the compressive stress to stabilize the Mott insulator phase in (V1-xCrx)2O3 thin films.

Enhancement of phosphors-solubility in ZnO by thermal annealing

We have demonstrated the effect of annealing temperature on the diffusion density of phosphors in zinc oxide. The P-dopant P430 was sprayed on ZnO pellets and annealed at different temperatures from 500 to 1000 °C with a step of 100 °C for one hour using a programmable furnace. The concentration of P was controlled by varying the annealing temperature and the maximum solubility of P (3% At) was achieved at annealing 800 °C determined by energy dispersive X-ray diffraction (EDX) measurements. X-ray diffraction (XRD) confirmed the hexagonal structure of ZnO and showed that the growth direction was along the c-axis. We observed a maximum up shift in the (002) plane at an annealing temperature of 800 °C, suggesting that P atoms replaced Zn atoms in the structure which results in the reduction of the lattice constant. Room temperature photoluminescence (PL) spectrum consists of a peak at 3.28 eV and related to band edge emission, but samples annealed at 800 and 900 °C have an additional donor acceptor pair peak at 3.2 eV. Hall effect measurements confirmed the p-type conductivity of the sample annealed at 800 °C.

Joining of ceramic matrix composites to high temperature ceramics for thermal protection systems

The current work reports a novel approach for the integration of external protective SiC multilayers with ceramic matrix composite (Cf/SiC) with the view of application in aerospace heat protection systems. The integration method is based on diffusion brazing bonding. As a joining agent the MAX-Phase Ti3SiC2, produced by self-propagating high temperature synthesis, has been employed. The pressure applied during the joining process and its effect on the microstructure of the integrated structure is discussed. Microstructural analysis of the resulting joints is conducted using scanning electron microscopy coupled with energy dispersive spectroscopy and X-ray diffraction measurements. Analysis of the joints showed that the bonds are uniform, dense, with few crack vertical to the interface which are not detrimental for the performance of the joints. Ground re-entry tests showed that the joints survive 5 re-entry cycles at 1391 and 1794°C without any detectable damage.

In-situ Studies of Lithium/Silver Vanadium Phosphorous Oxide Batteries Using Synchrotron based Energy Dispersive X-ray Diffraction

The powerful synchrotron analysis technique energy dispersive x-ray diffraction (EDXRD) has been utilized to achieve greater insight into the distribution of silver nanoparticles formed on initial reduction of lithium / silver vanadium phosphorous oxide, Ag2VO2PO4, and silver vanadium diphosphate, Ag2VP2O8, (SVOP family of materials) batteries. By combining the results of EDXRD measurements with ex-situ methods, we are able to effectively probe the discharge mechanism of the bimetallic materials to understand the reduction displacement discharge process.

Tribocorrosion Behavior of Calcium- and Phosphorous-Enriched Titanium Oxide Films and Study of Osteoblast Interactions for Dental Implants

Titanium (Ti) dental implants are frequently exposed simultaneously to a corrosive environment and cyclic micromovements at implant/abutment and implant/bone interfaces, becoming part of a tribocorrosion system. Thus, wear debris and corrosion products/ions can be released to peri-implant tissues and induce inflammatory reactions leading to implant failure. Moreover, the poor osseointegration is also one of the main problems affecting dental implants lifetime. Surface modification strategies have been proposed to design novel Ti oxide-based multifunctional surfaces that are able to simultaneously improve cellular functions and provide enhanced tribocorrosion resistance. Hence, the main objective of this work was the synthesis of Calcium (Ca)- and Phosphorous (P)-enriched Ti oxide films aimed to display superior wear/corrosion performance and simultaneously, to enhance osteoblast–material interactions. Ca- and P-enriched films were synthesized by plasma electrolytic oxidation (PEO) and their characteristics were assessed by Field emission scanning electron microscopy, profilometry, energy-dispersive X-ray spectroscopy, X-ray diffraction, and water contact angle measurements. PEO-treated samples were subjected to pin-on-disk reciprocating sliding tests in artificial saliva at 37 °C. The viability of MG63 cells cultured on PEO-treated samples was investigated by MTT assay, and their adhesion ability by SEM and confocal laser scanning microscopy. The wear/corrosion behavior of Ti was improved after PEO treatments and the electrolyte composition appeared to play a crucial role both on its corrosion tendency and mechanical wear resistance. It is believed that this improvement is related to the higher rutile/anatase ratio exhibited by Ca- and P-enriched surfaces. Osteoblasts were well spread on these surfaces displaying improved viability/proliferation compared to Ti.

Removal of Protein Capping Enhances the Antibacterial Efficiency of Biosynthesized Silver Nanoparticles.

The present study demonstrates an economical and environmental affable approach for the synthesis of “protein-capped” silver nanoparticles in aqueous solvent system. A variety of standard techniques viz. UV-visible spectroscopy, transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) measurements were employed to characterize the shape, size and composition of nanoparticles. The synthesized nanoparticles were found to be homogenous, spherical, mono-dispersed and covered with multi-layered protein shell. In order to prepare bare silver nanoparticles, the protein shell was removed from biogenic nanoparticles as confirmed by UV-visible spectroscopy, FTIR and photoluminescence analysis. Subsequently, the antibacterial efficacy of protein-capped and bare silver nanoparticles was compared by bacterial growth rate and minimum inhibitory concentration assay. The results revealed that bare nanoparticles were more effective as compared to the protein-capped silver nanoparticles with varying antibacterial potential against the tested Gram positive and negative bacterial species. Mechanistic studies based on ROS generation and membrane damage suggested that protein-capped and bare silver nanoparticles demonstrate distinct mode of action. These findings were strengthened by the TEM imaging along with silver ion release measurements using inductively coupled plasma atomic emission spectroscopy (ICP-AES). In conclusion, our results illustrate that presence of protein shell on silver nanoparticles can decrease their bactericidal effects. These findings open new avenues for surface modifications of nanoparticles to modulate and enhance their functional properties.

Investigating the Discharge Mechanism of Electrodes Using in-Situ Energy Dispersive X-Ray Diffraction

Polyanionic electrode materials such as lithium iron phosphate (LiFePO4) have demonstrated significant success, but are hampered by low conductivity. Conductive additives such as carbon are often used and are most frequently employed by coating or simply being mixed with the active material. These additives have shown success, however they decrease the volumetric capacity of the electrode. Bimetallic materials like silver vanadium oxide (Ag2V4O11) offer the ability to discharge multiple electrons per formula unit cell, generate a conductive network in-situ and thus provide high volumetric energy density. The design of bimetallic materials that form conductive networks in-situ can be used to eliminate the need for conductive additives. In these materials, a polyanionic metal center can be combined with a metal that reduces to form a conductive metal. By utilizing active cathode materials that form conductive networks in-situ we can reduce or potentially eliminate the need for conductive additives that do not add to the capacity of the cell and require additional processing, thereby reducing processing complexity while providing a greater overall energy density. In one such polyanionic material, silver vanadium diphosphate (Ag2VP2O8), both the vanadium and silver ions are reduced during discharge [1]. The silver metal formation provides a conductive matrix which allows for higher power output. By determining the spatial location of silver as well as the discharge conditions under which the silver network is formed we can optimize the formation of this network, thereby improving performance of these electrodes [2]. In this study we use the combination of in-situ energy dispersive x-ray diffraction (EDXRD) and ex-situ x-ray absorption spectroscopy (XAS) measurements to spatially resolve the formation of the conductive silver network in Ag2VP2O8electrodes and to determine the effect of increased current on the discharge processes. Li/ Ag2VP2O8 coin cells were discharged to various depths of discharge and left intact for in-situ EDXRD measurements performed at the National Synchrotron Light Source at Brookhaven National Laboratory. The height of the incident beam was set to 20 μm, and the width of the slits on the detector was set so that the gauge volume (volume of cathode measured) was 0.02 x 2 x 2 mm3 (see Fig. 1A). The coin cells were placed on a 3-axis stage so that diffraction patterns as a function of position could be obtained. Fig. 1B shows an example of EDXRD spectra obtained within the cathode as a function of beam position. By measuring the intensity of the Ag and Ag2VP2O8peaks we can determine the spatial distribution of silver metal within the cathode. In addition to determining the location of silver, we can separate the Ag+ to Ag0 and V4+ to V3+reduction processes using XAS, the results of which are shown in Fig. 1C. By measuring the fractions of reduced silver and vanadium in cells discharged at different rates, we find that silver is reduced preferentially at lower discharge rates, and conversely at higher rates more vanadium is reduced. By combining the results from spatially-resolved EDXRD and XAS measurements, it is possible to determine the conditions under which a more isotropic silver network is formed. In addition to materials where conductive networks are formed in-situ, these techniques have applications for a broader range of electrode materials. Using these techniques it may be possible to determine the effect of discharge rate on the reduction processes in any material with multiple metal centers or structural changes as a function of discharge, and we will present our results in this broader context. 1. E. S. Takeuchi, C. Y. Lee, P. J. Cheng, M. C. Menard, A. C. Marschilok, K. J. Takeuchi, Silver vanadium diphosphate Ag2VP2O8: Electrochemistry and characterization of reduced material providing mechanistic insights. J Solid State Chem 200, 232-240 (2013); published online EpubApr (DOI 10.1016/j.jssc.2013.01.020). 2. K. C. Kirshenbaum, D. C. Bock, Z. Zhong, A. C. Marschilok, K. J. Takeuchi, E. S. Takeuchi, In situ profiling of lithium/Ag2VP2O8 primary batteries using energy dispersive X-ray diffraction. Physical chemistry chemical physics : PCCP 16, 9138-9147 (2014); published online EpubApr 16 (10.1039/c4cp01220h). Figure 1

Assembly of polypyrrole nanotube@MnO2 composites with an improved electrochemical capacitance

Abstract A facile strategy is presented to fabricate polypyrrole nanotube@manganese dioxide (PPy@MnO 2 ) composites. The effect of KMnO 4 concentration on the morphology and property of PPy@MnO 2 composites is investigated. The microstrucutres and properties of the resulting PPy@MnO 2 composites are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray diffraction (EDX), X-ray diffraction (XRD), thermo-gravimetric analysis (TGA) and electrochemical measurements. The results indicate that the PPy@MnO 2 composites possess high specific capacitance and good cyclic stability due to the coating of MnO 2 onto PPy nanotubes. The specific capacitance of 403 F/g for the PPy@MnO 2 composite is obtained from galvanostatic charge–discharge experiment at a current density of 1 A/g, exhibiting the potential application for supercapacitors.

High mobility In2O3:H as contact layer for a-Si:H/c-Si heterojunction and μc-Si:H thin film solar cells

The crystallization process of hydrogen doped In2O3:H (IOH) films is investigated with energy-dispersive X-ray diffraction measurements. At annealing temperatures between 125 and 150°C crystallization of 220nm thin films occurs within only 2min, and the percentage of the crystalline phase does not change anymore when the temperature is raised above the crystallization temperature of 150°C. Maximum electron mobilities above 100cm2/Vs have been reached after crystallization. The IOH films were integrated as front contact into amorphous/crystalline silicon heterojunction cells and compared to In2O3:Sn (ITO) front contacts. Cells with ITO/IOH bilayer front contacts show a slightly lower open circuit voltage because of the a-Si:H passivation layer degradation caused by the longer annealing process needed for the crystallization of the bilayers, while all cells reach total area efficiencies around 20%. IOH films were also implemented as silver free back contact for μc-Si:H cells, and show higher short-circuit current densities than ZnO:Al back contacts because of the higher near-infra-red transmission of IOH.

Flexible and Conductive Graphene-Poly (diallyldimethylammoniumchloride) Buckypaper.

This paper describes the fabrication and characterization of flexible, conductive reduced graphene oxide (rGO)-poly(diallyldimethylammoniumchloride) (PDDA) buckypaper (BP). PDDA acts as a reducing agent to prepare an rGO-PDDA nanosheet dispersion from graphite oxide. The incorporation of PDDA as a "glue" molecule successfully binds rGO nanosheets into BPs with strong interlayer binding. The resulting BPs were characterized by scanning electronic microscopy (SEM), Raman, energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and resistivity measurements. The sp2 structure was greatly restored by the PDDA-induced reduction. Moreover, rGO was chemically doped from the adsorbed PDDA, which causes the Raman G band to shift from ~1585 to ~1610 cm(-1). This chemical doping substantially increased the density of the free charge carriers in rGO and thereby further enhanced the electrical conductivity of the rGO-BP. Good inter-layer connection in the rGO percolating network was obtained after thermal annealing at higher than ~250 °C. The resulting rGO-PDDA-BPs exhibited an isotropic sheet resistance as low as ~100 Ω/sq, which indicates a reduction by six orders of magnitude compared to the GO-BPs resistance before annealing. This PDDA-induced reduction with a low-temperature annealing process preserved the BPs' structural integrity and mechanical flexibility, thus overcoming the fragility problems with high-temperature annealing.

Enhancement of P Diffusion Density in Bulk ZnO for p-type Conductivity

In this paper, we have demonstrated the effect of annealing temperature on the diffusion density of phosphors in Zinc Oxide. The spin on p-dopant was sprayed on ZnO pellets and annealed at different temperatures from 500 to 1000 ̊C with a step of 100 ̊C for one hour using a programmable furnace. The concentration of P was controlled by varying the annealing temperature and the maximum solubility of P (14% At) was achieved at annealing 800 ̊C determined by Energy Dispersive X-Ray Diffraction (EDX) measurements. X-Ray Diffraction (XRD) confirmed the hexagonal structure of ZnO and showed that growth direction was along C-axis. We observed a maximum up shift in (002) plane at annealing temperature 800 ̊C, suggested that P atoms replaced Zn atoms in structure which results in the reduction of lattice constant. Room temperature photoluminescence (PL) spectrum consists of peak at 3.28eV and related to band edge emission, but samples annealed at 800 and 900 ̊C have an additional donor acceptor pair peak at 3.2 eV. Hot probe method confirmed the p-type conductivity of sample annealed at 800 ̊C.

Dry Sliding Wear Behaviours of Valve Seat Inserts Produced from High Chromium White Iron

Abstract In this present study, wear behaviours of high chromium white iron valve seat inserts and tappets used in the automotive sector were investigated. Wear behaviours of three different rates of high chromium white cast irons (containing 10, 12 and 14% chromium) were examined under heavy service conditions. For that purpose, the produced valve seat inserts were characterized through Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), X-ray diffraction (XRD) and hardness measurements. They were tested at a sliding speed of 1 ms−1, under 120 N load and for six different sliding distances (500, 1000, 1500, 2000, 2500, 3000 m) by using a standard wear apparatus (pin-on-disk type). The result showed that as the amount of Cr increased in the alloys, their hardness decreased. The decrease in the hardness were considered to be as the result of transformation of M7C3 carbides into M23C6 carbides in the structure. This decrease in hardness with increasing chromium content also increased the weight loss. Thus, it was determined that the white iron with 14% Cr (which had a greater amount of M23C6 carbides) was subjected to the highest wear.

Microstructure and mechanical properties of fly ash blended cement pastes

Regarding the wide use of fly ash in normal and high-strength concrete, this study aims to investigate the microstructure and mechanical properties of fly ash blended cement pastes. To fulfill the aim of this study, multiple techniques, including scanning electron microscopy with backscattered electron and energy-dispersive X-ray spectroscopy detectors, thermo-gravimetric analysis, X-ray diffraction, instrumented nanoindentation and ultrasonic measurements, were applied on fly ash blended cement pastes at different water to binder ratios. Through this study, the mechanical properties of fly ash blended cement pastes were reported, and the results showed that the incorporation of fly ash significantly influenced the microstructure and mechanical properties of calcium-silicate-hydrates gel.