In situ oxidation kinetics of magnetite nanoparticles by total scattering

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).

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Development of an in situ synchrotron X-ray total scattering setup under pressurized hydrogen gas

Journal of Applied Crystallography ◽

10.1107/s1600576718005101 ◽

2018 ◽

Vol 51 (3) ◽

pp. 796-801 ◽

Cited By ~ 3

Author(s):

Kouji Sakaki ◽

Hyunjeong Kim ◽

Akihiko Machida ◽

Tetsu Watanuki ◽

Yoshinori Katayama ◽

...

Keyword(s):

Pair Distribution Function ◽

Hydrogen Gas ◽

Ex Situ ◽

Sample Holder ◽

Hydrogen Storage Materials ◽

X Ray Diffraction ◽

Total Scattering ◽

X Ray ◽

Diffraction Patterns

This article describes the development of an in situ gas-loading sample holder for synchrotron X-ray total scattering experiments, particularly for hydrogen storage materials, designed to collect diffraction and pair distribution function (PDF) data under pressurized hydrogen gas. A polyimide capillary with a diameter and thickness of 1.4 and 0.06 mm, respectively, connected with commercially available Swagelok fittings was used as an in situ sample holder. Leakage tests confirmed that this sample holder allows 3 MPa of hydrogen gas pressure and 393 K to be achieved without leakage. Using the developed in situ sample holder, significant background and Bragg peaks from the sample holder were not observed in the X-ray diffraction patterns and their signal-to-noise ratios were sufficiently good. The PDF patterns showed sharp peaks in the r range up to 100 Å. The results of Rietveld and PDF refinements of Ni are consistent with those obtained using a polyimide capillary (1.0 mm diameter and 0.04 mm thickness) that has been used for ex situ experiments. In addition, in situ synchrotron X-ray total scattering experiments under pressurized hydrogen gas up to 1 MPa were successfully demonstrated for LaNi4.6Cu.

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X-Ray Absorption Spectroscopy as an in-situ Tool in Materials Science

MRS Proceedings ◽

10.1557/proc-502-127 ◽

1997 ◽

Vol 502 ◽

Author(s):

T. Ressler ◽

Joe Wong ◽

W. Metz

Keyword(s):

Absorption Spectroscopy ◽

Materials Science ◽

Ex Situ ◽

Structural Studies ◽

Time Resolved ◽

X Ray ◽

Complementary Techniques ◽

X Ray Absorption ◽

Established Technique

ABSTRACTIn addition to being an established technique for ex-situ structural studies, x-ray absorption spectroscopy (XAS) has recently been realized to be a powerful tool for in-situ time-resolved investigations in materials science. This paper describes two complementary techniques: quick-scanning EXAFS (QEXAFS) and energy-dispersive XAS (DXAS) which offer time resolution in the seconds and milliseconds range, respectively. Formation of a heterogeneous catalyst from a solid-state reaction of a precursor is presented as an example of a time-resolved XAS application.

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Structural Studies of Hydrogen Storage Alloys using X-ray/Neutron Diffraction and Total Scattering

MRS Proceedings ◽

10.1557/opl.2011.1310 ◽

2011 ◽

Vol 1334 ◽

Author(s):

Yumiko Nakamura ◽

Hyunjeong Kim ◽

Saishun Yamazaki ◽

Kouji Sakaki ◽

Thomas Proffen ◽

...

Keyword(s):

Neutron Diffraction ◽

Pair Distribution Function ◽

Ex Situ ◽

Structural Studies ◽

Hydrogen Storage Alloys ◽

Total Scattering ◽

X Ray ◽

Local Structures ◽

Rich Domain

ABSTRACTCrystal and local structures and hydrogen occupation of Mg containing materials, (Mg,Ca)Nix (x = 2, 3) intermetallic compounds and a MgCo metastable alloy, have been investigated using in-situ and ex-situ X-ray/neutron diffraction and total scattering.A C15 Laves phase (Mg0.67Ca0.33)Ni2 showed isotropic lattice expansion upon hydrogenation. Mg and Ca occupied the same site randomly. It has two hydrogen sites, Mg(Ca)2Ni2 site and M(Ca)Ni3 site.Mg2CaNi9, MgCa2Ni9, and CaNi3 compounds consisted of MgZn2-type (Mg,Ca)2Ni4 cell and CaCu5-type CaNi5 cell stacking along the c-axis. The MgZn2-type cell was occupied by only Mg in Mg2CaNi9, and randomly occupied by both Mg and Ca in MgCa2Ni9. Expansion of this cell strongly depended on the composition: larger expansion was observed in a Ca-rich composition.Local structure of a Mg-Co alloy synthesized by mechanical alloying has been studied using the PDF (Pair Distribution Function) method. The analysis suggested that material contained two 1-2 nm domains with different compositions and local structures, i.e. Mg-rich and Co-rich domains, and hydrogen was located only in the Mg-rich domain.

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Atomic Layer Deposition of LiF and Lithium Ion Conducting (AlF3)(LiF)x Alloys Using Trimethylaluminum, Lithium Hexamethyldisilazide and Hydrogen Fluoride

10.26434/chemrxiv.5459653 ◽

2017 ◽

Author(s):

Younghee Lee ◽

Daniela M. Piper ◽

Andrew S. Cavanagh ◽

Matthias J. Young ◽

Se-Hee Lee ◽

...

Keyword(s):

Lithium Ion ◽

Atomic Layer ◽

Mass Gain ◽

Alloy Film ◽

Ex Situ ◽

X Ray ◽

Layer Deposition ◽

Ion Conducting ◽

Good Agreement

<div>Atomic layer deposition (ALD) of LiF and lithium ion conducting (AlF3)(LiF)x alloys was developed using trimethylaluminum, lithium hexamethyldisilazide (LiHMDS) and hydrogen fluoride derived from HF-pyridine solution. ALD of LiF was studied using in situ quartz crystal microbalance (QCM) and in situ quadrupole mass spectrometer (QMS) at reaction temperatures between 125°C and 250°C. A mass gain per cycle of 12 ng/(cm2 cycle) was obtained from QCM measurements at 150°C and decreased at higher temperatures. QMS detected FSi(CH3)3 as a reaction byproduct instead of HMDS at 150°C. LiF ALD showed self-limiting behavior. Ex situ measurements using X-ray reflectivity (XRR) and spectroscopic ellipsometry (SE) showed a growth rate of 0.5-0.6 Å/cycle, in good agreement with the in situ QCM measurements.</div><div>ALD of lithium ion conducting (AlF3)(LiF)x alloys was also demonstrated using in situ QCM and in situ QMS at reaction temperatures at 150°C A mass gain per sequence of 22 ng/(cm2 cycle) was obtained from QCM measurements at 150°C. Ex situ measurements using XRR and SE showed a linear growth rate of 0.9 Å/sequence, in good agreement with the in situ QCM measurements. Stoichiometry between AlF3 and LiF by QCM experiment was calculated to 1:2.8. XPS showed LiF film consist of lithium and fluorine. XPS also showed (AlF3)(LiF)x alloy consists of aluminum, lithium and fluorine. Carbon, oxygen, and nitrogen impurities were both below the detection limit of XPS. Grazing incidence X-ray diffraction (GIXRD) observed that LiF and (AlF3)(LiF)x alloy film have crystalline structures. Inductively coupled plasma mass spectrometry (ICP-MS) and ionic chromatography revealed atomic ratio of Li:F=1:1.1 and Al:Li:F=1:2.7: 5.4 for (AlF3)(LiF)x alloy film. These atomic ratios were consistent with the calculation from QCM experiments. Finally, lithium ion conductivity (AlF3)(LiF)x alloy film was measured as σ = 7.5 × 10-6 S/cm.</div>

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In Situ X-Ray Diffraction Investigations during Diffusion Anneals of Ni-Cu Thin Film Diffusion Couples

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.89-91.503 ◽

2010 ◽

Vol 89-91 ◽

pp. 503-508 ◽

Cited By ~ 1

Author(s):

J. Sheng ◽

U. Welzel ◽

Eric J. Mittemeijer

Keyword(s):

Thermal Stresses ◽

Stress Generation ◽

Ex Situ ◽

Diffusion Annealing ◽

X Ray Diffraction ◽

Individual Layer ◽

X Ray ◽

Bilayer System ◽

Stress Changes

The stress evolution during diffusion annealing of Ni-Cu bilayers (individual layer thicknesses of 50 nm) was investigated employing ex-situ and in-situ X-ray diffraction measurements. Annealing at relatively low homologous temperatures (about 0.3 - 0.4 Tm) for durations up to about 100 hours results in considerable diffusional intermixing, as demonstrated by Auger-electron spectroscopy investigations (in combination with sputter-depth profiling). In addition to thermal stresses due to differences of the coefficients of thermal expansion of layers and substrate, tensile stress con-tributions in the sublayers arise during the diffusion anneals. The obtained stress data have been discussed in terms of possible mechanisms of stress generation. The influence of diffusion on stress development in the sublayers of the diffusion couple during heating and isothermal annealing was investigated by comparing stress changes in the bilayer system with corresponding results obtained under identical conditions for single layers of the components in the bilayer system. The specific residual stresses that emerge due to diffusion between the (sub)layers in the bilayer could thereby be identified.

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In situ X-ray Scattering Study of the Formation of Au Nano Crystals During Thermal Annealing

MRS Proceedings ◽

10.1557/proc-1027-d07-04 ◽

2007 ◽

Vol 1027 ◽

Author(s):

Do Young Noh ◽

Ki-Hyun Ryu ◽

Hyon Chol Kang

Keyword(s):

Thermal Annealing ◽

Bragg Reflection ◽

Ex Situ ◽

X Ray ◽

Force Microscopy ◽

X Ray Scattering ◽

Atomic Force ◽

Au Thin Films ◽

Ray Scattering

AbstractThe transformation of Au thin films grown on sapphire (0001) substrates into nano crystals during thermal annealing was investigated by in situ synchrotron x-ray scattering and ex situ atomic force microscopy (AFM). By monitoring the Au(111) Bragg reflection and the low Q reflectivity and comparing them with ex situ AFM images, we found that polygonal-shape holes were nucleated and grow initially. As the holes grow larger and contact each other, their boundary turns into Au nano crystals. The Au nano crystals have a well-defined (111) flat top surface and facets in the in-plane direction.

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Size dependent behavior of Fe3O4crystals during electrochemical (de)lithiation: an in situ X-ray diffraction, ex situ X-ray absorption spectroscopy, transmission electron microscopy and theoretical investigation

Physical Chemistry Chemical Physics ◽

10.1039/c7cp03312e ◽

2017 ◽

Vol 19 (31) ◽

pp. 20867-20880 ◽

Cited By ~ 27

Author(s):

David C. Bock ◽

Christopher J. Pelliccione ◽

Wei Zhang ◽

Janis Timoshenko ◽

K. W. Knehr ◽

...

Keyword(s):

Electron Microscopy ◽

Structural Changes ◽

Ex Situ ◽

X Ray Diffraction ◽

X Ray ◽

Size Dependent ◽

Transmission Electron ◽

Dependent Behavior ◽

X Ray Absorption

Crystal and atomic structural changes of Fe3O4upon electrochemical (de)lithiation were determined.

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A study on preparation and characterization of carbon doped TiO2 nanotubes

Malaysian Journal of Fundamental and Applied Sciences ◽

10.11113/mjfas.v6n1.167 ◽

2014 ◽

Vol 6 (1) ◽

Cited By ~ 1

Author(s):

Srimala Sreekantan ◽

Roshasnorlyza Hazan ◽

Zainovia Lockman ◽

Ishak Mat

Keyword(s):

Methyl Orange ◽

Tio2 Nanotubes ◽

Pure Tio2 ◽

Ex Situ ◽

X Ray Diffraction ◽

Methyl Orange Degradation ◽

Doped Tio2 ◽

X Ray ◽

Carbon Doped

The present study is directed to clarify the influence of carbon doping on the degradation of methyl orange. TiO2 nanotubes were prepared by anodizing titanium foils in a two electrode configuration bath with titanium foil as the anode and platinum as the counter electrode. The electrochemical bathconsists of 1 M Na2SO4 with 0.7 g ammonium fluoride, NH4F. The nanotubes obtained were further doped with carbon via in-situ and ex-situ method. Incorporation of carbon on TiO2 via in-situ method is accomplished during the anodization process by introducing oxalic acid into electrolyte while theex-situ doping involves carbon incorporation into pre-fabricated TiO2 nanotube via flame annealing using carbon blackN330. Characterization such as Scanning Electron Microscope (SEM), Energy Dispersive X-ray Analysis (EDX), and X-Ray Diffraction (XRD) are used to determine the surfacemorphology, composition of dopants, and phases exists. Well ordered nanotube with good adherence and smooth surface was obtained for both methods. When the oxide was annealed, X-ray diffraction analysis revealed the presence of anatase and rutile phase. The photocatalytic properties of thepure TiO2 and carbon doped TiO2 were tested for methyl orange degradation and the result indicated that the in-situ doped TiO2 has much better degradation than the ex-situ and pure TiO2. The percentage of methyl orange degradation for in-situ was 20% and 41% higher than ex-situ doped TiO2 and pure TiO2, respectively.

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Multipurpose diffractometer for in situ X-ray crystallography of functional materials

Journal of Applied Crystallography ◽

10.1107/s1600576721004088 ◽

2021 ◽

Vol 54 (3) ◽

Author(s):

Semën Gorfman ◽

David Spirito ◽

Netanela Cohen ◽

Peter Siffalovic ◽

Peter Nadazdy ◽

...

Keyword(s):

Electric Field ◽

Materials Science ◽

Functional Materials ◽

X Ray Diffraction ◽

Reciprocal Space Mapping ◽

X Ray ◽

X Ray Crystallography ◽

Area Detector ◽

Characterization Of Materials

Laboratory X-ray diffractometers play a crucial role in X-ray crystallography and materials science. Such instruments still vastly outnumber synchrotron facilities and are responsible for most of the X-ray characterization of materials around the world. The efforts to enhance the design and performance of in-house X-ray diffraction instruments benefit a broad research community. Here, the realization of a custom-built multipurpose four-circle diffractometer in the laboratory for X-ray crystallography of functional materials at Tel Aviv University, Israel, is reported. The instrument is equipped with a microfocus Cu-based X-ray source, collimating X-ray optics, four-bounce monochromator, four-circle goniometer, large (PILATUS3 R 1M) pixel area detector, analyser crystal and scintillating counter. It is suitable for a broad range of tasks in X-ray crystallography/structure analysis and materials science. All the relevant X-ray beam parameters (total flux, flux density, beam divergence, monochromaticity) are reported and several applications such as determination of the crystal orientation matrix and high-resolution reciprocal-space mapping are demonstrated. The diffractometer is suitable for measuring X-ray diffraction in situ under an external electric field, as demonstrated by the measurement of electric-field-dependent rocking curves of a quartz single crystal. The diffractometer can be used as an independent research instrument, but also as a training platform and for preparation for synchrotron experiments.

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