Gamma induced changes in Makrofol/CdSe nanocomposite films

2022 ◽  
Author(s):  
Ali A. Alhazime ◽  
M. ME. Barakat ◽  
Radiyah A. Bahareth ◽  
E. M. Mahrous ◽  
Saad Aldawood ◽  
...  
Keyword(s):  
Gas Flow ◽  
Lattice Parameter ◽  
Cdse Nanoparticles ◽  
Nanocomposite Films ◽  
Ex Situ ◽  
Γ Irradiation ◽  
Dielectric Parameters ◽  
Zinc Blend ◽  
X Ray ◽  
Induced Changes

Abstract In our present work, we applied ex-situ casting procedure to prepare a nanocomposite (NCP) from Makrofol polycarbonate (PC) and CdSe nanoparticles. The CdSe nanoparticles were prepared by thermolysis procedure in the presence of N2 gas flow. Rietveld refinement of x-ray data illustrated that the CdSe accustoms cubic zinc blend structure of a 6.057 Å lattice parameter and 2 nm typical grain size. Samples from the prepared NCP were exposed to γ dosages (20-250 kGy). The modifications induced in the NCP films owing to γ dosages have been studied. The γ irradiation (50-250 kGy) causes the crosslinks that reduces the optical bandgap from 4.15 to 3.81 eV; associated with an increase in dielectric parameters and refractive index. This is attributed to the increase of the mass fraction of the disordered regions as specified by XRD. The PC-CdSe NCP was found to have reaction to color modification which makes it suitable in saleable reproduction on printing press.

Inflexible stoichiometry in bulk pyrite FeS2 as viewed by in situ and high-resolution X-ray diffraction

2018 ◽  
Vol 74 (5) ◽  
pp. 436-444 ◽  
Author(s):  
Rebecca D. McAuliffe ◽  
Daniel P. Shoemaker
Keyword(s):  
Gas Flow ◽  
Lattice Parameter ◽  
Iron Pyrite ◽  
X Ray Diffraction ◽  
Intrinsic Defects ◽  
X Ray ◽  
Solubility Range ◽  
Absorber Material ◽  
Line Compound

Non-stoichiometry is considered to be one of the main problems limiting iron pyrite, FeS2, as a photovoltaic absorber material. Although some historical diffraction experiments have implied a large solubility range of FeS2−δ with δ up to 0.25, the current consensus based on calculated formation energies of intrinsic defects has lent support to line-compound behavior. Here it is shown that pyrite stoichiometry is relatively inflexible in both reductive conditions and in autogenous sulfur partial pressure, which produces samples with precise stoichiometry of FeS2 even at different Fe/S ratios. By properly standardizing in situ gas-flow X-ray diffraction measurements, no significant changes in the lattice parameter of FeS2 can be resolved, which portrays iron pyrite as prone to forming sulfur-deficient compounds, but not intrinsic defects in the manner of NiS2−δ.

scholarly journals In situ oxidation kinetics of magnetite nanoparticles by total scattering

2014 ◽  
Vol 70 (a1) ◽  
pp. C736-C736
Author(s):  
Antonio Cervellino ◽  
Ruggero Frison ◽  
Antonella Guagliardi ◽  
Giuseppe Cernuto ◽  
Norberto Masciocchi ◽  
...  
Keyword(s):  
Materials Science ◽  
Particle Diameter ◽  
Indirect Evidence ◽  
Lattice Parameter ◽  
Oxidation States ◽  
Ex Situ ◽  
Total Scattering ◽  
X Ray ◽  
Specific Subset

Iron oxide nanoparticles (NPs) show different structures as a function of oxidation state. In particular, magnetite (Fe3O4) NPs are easily oxidized in air at moderate temperatures, eventually yielding maghemite (Fe2O3). Oxidation proceeds via the creation of iron vacancies. While the vacancies may be created with a random distribution throughout the octahedral Fe sites, they eventually order over a specific subset of these sites, lowering the symmetry from F-centered (magnetite) to P-centered (cubic maghemite). By ex situ X-ray Total Scattering studies of magnetite-maghemite NPs in different oxidation states[1] we have recently studied, by the DFA method[2], the correlation between particle diameter, stoichiometry and lattice parameter in polydisperse NP samples unraveling also the size dependence of lattice parameter and composition. Moreover, we have shown indirect evidence of the formation of a polycrystalline surface layer of maghemite on a magnetite core in the intermediate oxidation states. Motivated by the excellent ex-situ results, we have also performed in-situ studies where magnetite NPs were oxidised in air at moderate temperatures (50-200 C). We present here an in-situ study performed at the X04SA-Materials Science beamline of the Swiss Light Source synchrotron[3]. Total Scattering X-ray diffraction patterns were collected every few minutes, while the oxidation was completed within several hours. The mechanism of NPs oxidation - whereas a surface oxidised layer is formed by outwards diffusion of Fe, then the vacancies so created order themselves giving rise to the maghemite-magnetite phase transition, will be examined in great detail. We will discuss, on robust statistical basis, the calculation of kinetic and diffusion constants, the temperature effect on the lattice constant and on the thickness of the surface oxidised layer; the different possible structural models for the cubic-maghemite NPs. We thank for support Fondazione Cariplo (2009-0289).

Morphological and structural evolutions of nonequilibrium titanium-nitride alloy powders produced by reactive ball milling

1992 ◽  
Vol 7 (4) ◽  
pp. 888-893 ◽  
Author(s):  
M. Sherif El-Eskandarany ◽  
K. Sumiyama ◽  
K. Aoki ◽  
K. Suzuki
Keyword(s):  
Electron Microscopy ◽  
Titanium Nitride ◽  
Gas Flow ◽  
Lattice Parameter ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Nitrogen Gas ◽  
X Ray ◽  
Grain Sizes ◽  
Transmission Electron

Nonequilibrium titanium-nitride alloy powders have been fabricated by a high energetic ball mill under nitrogen gas flow at room temperature and characterized by means of x-ray diffraction, scanning electron microscopy, transmission electron microscopy, and differential scanning calorimetry. Initial hcp titanium is completely transformed to nonequilibrium-fcc Ti–N after 720 ks of the milling time. The fcc Ti–N phase is stable at relatively low temperature and transforms at 855 K to Ti2N and δ phases. At the final stage of milling, the particle- and grain-sizes of alloy powders are 1 mm and 5 nm, respectively, and the lattice parameter is 0.419 nm.

scholarly journals In Situ Ptychography of Heterogeneous Catalysts using Hard X-Rays: High Resolution Imaging at Ambient Pressure and Elevated Temperature

2016 ◽  
Vol 22 (1) ◽  
pp. 178-188 ◽  
Author(s):  
Sina Baier ◽  
Christian D. Damsgaard ◽  
Maria Scholz ◽  
Federico Benzi ◽  
Amélie Rochet ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Elevated Temperature ◽  
Gas Flow ◽  
Heterogeneous Catalysts ◽  
Ambient Pressure ◽  
Ex Situ ◽  
X Rays ◽  
X Ray ◽  
Before And After

AbstractA new closed cell is presented for in situ X-ray ptychography which allows studies under gas flow and at elevated temperature. In order to gain complementary information by transmission and scanning electron microscopy, the cell makes use of a Protochips E-chipTM which contains a small, thin electron transparent window and allows heating. Two gold-based systems, 50 nm gold particles and nanoporous gold as a relevant catalyst sample, were used for studying the feasibility of the cell. Measurements showing a resolution around 40 nm have been achieved under a flow of synthetic air and during heating up to temperatures of 933 K. An elevated temperature exhibited little influence on image quality and resolution. With this study, the potential of in situ hard X-ray ptychography for investigating annealing processes of real catalyst samples is demonstrated. Furthermore, the possibility to use the same sample holder for ex situ electron microscopy before and after the in situ study underlines the unique possibilities available with this combination of electron microscopy and X-ray microscopy on the same sample.

Effect of silicon addition on surface morphology and structural properties of titanium nitride films grown by reactive unbalanced direct current-magnetron sputtering

2004 ◽  
Vol 19 (2) ◽  
pp. 523-534 ◽  
Author(s):  
Y.G. Shen ◽  
Z-J. Liu ◽  
N. Jiang ◽  
H.S. Zhang ◽  
K.H. Chan ◽  
...  
Keyword(s):  
Grain Size ◽  
Surface Morphology ◽  
Magnetron Sputtering ◽  
Structural Properties ◽  
Photoelectron Spectroscopy ◽  
Volume Fraction ◽  
Nanocomposite Films ◽  
Ex Situ ◽  
Scaling Analysis ◽  
X Ray

Thin films of Ti1–x–y Six Ny were produced on unheated Si(100) substrates by reactive unbalanced dc-magnetron sputtering of titanium and silicon in an Ar–N2 gas mixture. The effects of silicon incorporation on surface morphology and structural properties of these films as well as the influence of postdeposition annealing have been studied. These films were characterized ex situ in terms of their core-level electron bonding configuration by x-ray photoelectron spectroscopy, their microstructure by cross-sectional transmission electron microscopy and x-ray diffraction, their hardness by nanoindentation measurements, and their roughening kinetics by atomic force microscopy (AFM) with the scaling analysis. It was found that a linear increase in the Si concentration of the films was observed with increasing Si target current up to 2 A whereas the reverse trend was seen for the Ti concentration. The films consisted of 15–20-nm-sized TiN crystallites embedded in an amorphous SiNx matrix. They had a hardness of about 32.8 GPa with silicon concentration x = 0.1. The improved mechanical properties of Ti1–x–y Six Ny films with the addition of Si into TiN were attributed to their densified microstructure with development of fine grain size and reduced surface roughness. The reduction in grain size has been supported by means of a Monte Carlo simulation that reveals that the average size of TiN grains decreases with the volume fraction of amorphous SiNx approximately according to a power law, showing a reasonable agreement with the experimental results. By applying the height–height correlation functions to the measured AFM images, a steady growth roughness exponent α = 0.89 ± 0.05 was determined for all the films with different Si additions. It was also found that the nanocomposite films were thermodynamically stable up to 800 °C. The effect of thin SiNx layer in stabilizing nanocrystalline TiN structure is also elucidated and explained on the basis of structural and thermodynamic stability.

Reactively sputtered WOxNy films

2000 ◽  
Vol 15 (11) ◽  
pp. 2437-2445 ◽  
Author(s):  
Y. G. Shen ◽  
Y. W. Mai
Keyword(s):  
Photoelectron Spectroscopy ◽  
Film Surface ◽  
Lattice Parameter ◽  
Grain Structure ◽  
Ex Situ ◽  
Cross Sectional ◽  
Plan View ◽  
X Ray ◽  
Transmission Electron ◽  
Sputter Deposited

A combined investigation of stress relaxation in WOxNy thin films sputter deposited on silicon wafers in an Ar–N2–O2 gas mixture by in situ substrate curvature measurements and of structural properties by ex situ x-ray diffraction, x-ray photoelectron spectroscopy, transmission electron microscopy (TEM), electron energy loss spectroscopy, and transmission electron diffraction is reported. It was found that the W2N films deposited under oxygen-free conditions had a high compressive stress of 1.45 GPa. As the oxygen concentration was increased, the stress became smaller and reached almost zero for films near 10–15 at.% oxygen. These results can be understood in terms of the decrease in the lattice parameter caused by substituting nitrogen atoms with oxygen in the lattice sites and the development of an amorphous network in the WOxNy films as the incorporation of oxygen was increased. Plan view and cross-sectional TEM analyses showed that 150-nm-thick oxygen-free crystalline W2N films had a columnar microstructure with an average column width of 15–20 nm near the film surface, whereas oxygen imbedded in the films provided a finer grain structure. The effect of oxygen in stabilizing the W2N structure was also elucidated and explained on the basis of structural and thermodynamic stability.

Modification of structural, thermal and optical properties of PC-PET/CdSe NCP using gamma radiation

2021 ◽  
Author(s):  
Radiyah A. Bahareth ◽  
Kaoutar Benthami ◽  
Ali A. Alhazime ◽  
Samir A. Nouh
Keyword(s):  
Optical Properties ◽  
Gas Flow ◽  
Color Difference ◽  
Lattice Parameter ◽  
Ex Situ ◽  
Polybutylene Terephthalate ◽  
Amorphous Content ◽  
Degradation Temperature ◽  
Average Grain Size ◽  
Gamma Irradiated

In the current study we synthesized a nanocomposite (NCP) from polycarbonate/polybutylene terephthalate (PC-PET) blend and CdSe nanoparticles (NPs) through ex-situ casting methodology. CdSe NPs were synthesized using thermolysis technique with N2 gas flow. X-ray diffraction data for CdSe NPs are reported. The Rietveld refinement indicated that the synthesized CdSe acclimatizes cubic zinc blends constitution of a lattice parameter 6.057 Å and an average grain size of 2 nm. The PC-PET/CdSe NCP samples were irradiated by gamma doses between 20 and 230 kGy. The induced variations in the structure, thermal and optical properties of the gamma irradiated PC-PET/CdSe NCP have been illustrated by means of TEM, XRD, TGA, FTIR and UV-vis spectroscopes. The irradiation with doses in the range 50-230 kGy leads to the domination of crosslinking that improves the amorphous content. This increases the degradation temperature from 417 to 432oC indicative of an enhancement in the thermostability of the NCP samples. Also, the optical band gap is reduced from 4.28 to 3.76 eV which is ascribed to the enhancement in the amorphous content of the irradiated PC-PET/CdSe NCP. This specifies that the gamma irradiation causes a more compactness of the NCP and leads to appropriate spreading of CdSe NPs within the PC-PET matrix. Additionally, the CIE approach was used to describe the colored samples. It is found that the PC-PET/CdSe NCP acquires color due to gamma doses, as the color intensity reached a remarkable color difference larger than 5 (14.9) which is a reasonable challenge in saleable reproduction on printing press.

scholarly journals RF Magnetron Sputtering Deposition of TiO2 Thin Films in a Small Continuous Oxygen Flow Rate

Coatings ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 442 ◽  
Author(s):  
Octavian-Gabriel Simionescu ◽  
Cosmin Romanițan ◽  
Oana Tutunaru ◽  
Valentin Ion ◽  
Octavian Buiu ◽  
...  
Keyword(s):  
Thin Films ◽  
Magnetron Sputtering ◽  
Gas Flow ◽  
Anatase Phase ◽  
Rf Magnetron Sputtering ◽  
Ex Situ ◽  
Substrate Bias ◽  
Tio2 Thin Films ◽  
Rutile Tio2 ◽  
X Ray

Rutile titanium oxide (TiO2) thin films require more energy to crystallize than the anatase phase of TiO2. It is a prime candidate for micro-optoelectronics and is usually obtained either by high substrate temperature, applying a substrate bias, pulsed gas flow to modify the pressure, or ex situ annealing. In the present work, we managed to obtain high enough energy at the substrate in order for the particles to form rutile TiO2 at room temperature without any intentional substrate bias in a continuous gas flow. The rutile TiO2 thin films were deposited by a reactive radiofrequency magnetron sputtering system from a titanium target, in an argon/oxygen gas mixture. Investigations regarding the film’s structure and morphology were performed by X-ray diffraction (XRD), X-ray reflectivity (XRR), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDAX), while the optical properties were investigated by means of ellipsometry.

Digital x-ray mapping of nanometer-size supported bimetallic catalysts

1988 ◽  
Vol 46 ◽  
pp. 530-531
Author(s):  
L. T. Germinario
Keyword(s):  
Background Radiation ◽  
Metal Cluster ◽  
Single Element ◽  
Beam Diameter ◽  
X Rays ◽  
X Ray ◽  
Major Interest ◽  
Induced Changes

Understanding the role of metal cluster composition in determining catalytic selectivity and activity is of major interest in heterogeneous catalysis. The electron microscope is well established as a powerful tool for ultrastructural and compositional characterization of support and catalyst. Because the spatial resolution of x-ray microanalysis is defined by the smallest beam diameter into which the required number of electrons can be focused, the dedicated STEM with FEG is the instrument of choice. The main sources of errors in energy dispersive x-ray analysis (EDS) are: (1) beam-induced changes in specimen composition, (2) specimen drift, (3) instrumental factors which produce background radiation, and (4) basic statistical limitations which result in the detection of a finite number of x-ray photons. Digital beam techniques have been described for supported single-element metal clusters with spatial resolutions of about 10 nm. However, the detection of spurious characteristic x-rays away from catalyst particles produced images requiring several image processing steps.

Interfacial properties of GaSb/InAs superlattices

1993 ◽  
Vol 51 ◽  
pp. 826-827
Author(s):  
M. E. Twigg ◽  
B. R. Bennett ◽  
J. R. Waterman ◽  
J. L. Davis ◽  
B. V. Shanabrook ◽  
...  
Keyword(s):  
Gaas Substrate ◽  
Molecular Beam ◽  
Infrared Detector ◽  
Interfacial Properties ◽  
Ex Situ ◽  
X Ray Diffraction ◽  
Absorption Coefficients ◽  
X Ray ◽  
Short Period ◽  
High Optical Absorption

Recently, the GaSb/InAs superlattice system has received renewed attention. The interest stems from a model demonstrating that short period Ga1-xInxSb/InAs superlattices will have both a band gap less than 100 meV and high optical absorption coefficients, principal requirements for infrared detector applications. Because this superlattice system contains two species of cations and anions, it is possible to prepare either InSb-like or GaAs-like interfaces. As such, the system presents a unique opportunity to examine interfacial properties.We used molecular beam epitaxy (MBE) to prepare an extensive set of GaSb/InAs superlattices grown on an GaSb buffer, which, in turn had been grown on a (100) GaAs substrate. Through appropriate shutter sequences, the interfaces were directed to assume either an InSb-like or GaAs-like character. These superlattices were then studied with a variety of ex-situ probes such as x-ray diffraction and Raman spectroscopy. These probes confirmed that, indeed, predominantly InSb-like and GaAs-like interfaces had been achieved.

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