In situ Mössbauer Study of the Passive Layer Formed on the Iron Anode in Alkaline Electrolyte

1999 ◽  
Vol 64 (12) ◽  
pp. 2044-2060 ◽  
Author(s):  
Karel Bouzek ◽  
Martin Nejezchleba
Keyword(s):  
Mössbauer Spectra ◽  
Sodium Hydroxide Solution ◽  
Passive Layer ◽  
Iron Electrode ◽  
Ex Situ ◽  
Anode Surface ◽  
Alkaline Electrolyte ◽  
Mossbauer Spectra ◽  
Wide Range

In situ Mössbauer spectra of the iron electrode at anodic potential were measured in sodium hydroxide solution over a wide range of concentrations (0.1 - 14 mol l-1). It was found that the in situ Mössbauer spectra exhibit generally one sextet and one doublet corresponding to the oxide layer on the anode surface. Parameters of these spectra show only minor variations within the electrolyte concentration range of 0.1 - 7 M NaOH. A pronounced change in the spectra was observed in 14 M NaOH. The major processes taking place in the anode surface layer are based on the break-down of protective properties of the passive layer, incipient intense metal dissolution and subsequent oxidation. Important differences were also found between in situ and ex situ spectra measurements.

In Situ Studies of the Processing of Sol-Gel Produced Amorphous Materials Using Xanes, Saxs and Curved Image Plate XRD

1999 ◽  
Vol 590 ◽  
Author(s):  
DM Pickup ◽  
G Mountjoy ◽  
RJ Newport ◽  
ME Smith ◽  
GW Wallidge ◽  
...  
Keyword(s):  
Amorphous Materials ◽  
Sol Gel ◽  
Heat Treatments ◽  
Silica Gels ◽  
Ex Situ ◽  
High Count ◽  
X Ray ◽  
Image Plate ◽  
Wide Range

ABSTRACTSol-gel produced mixed oxide materials have been extensively studied using conventional, ex situ structural techniques. Because the structure of these materials is complex and dependent on preparation conditions, there is much to be gained from in situ techniques: the high brightness of synchrotron x-ray sources makes it possible to probe atomic structure on a short timescale, and hence in situ. Here we report recent results for mixed titania- (and some zirconia-) silica gels and xerogels. Titania contents were in the range 8–18 mol%, and heat treatments up to 500°C were applied. The results have been obtained from intrinsically rapid synchrotron x-ray experiments: i) time-resolved small angle scattering, using a quadrant detector, to follow the initial stages of aggregation between the sol and the gel; ii) the use of a curved image plate detector in diffraction, which allowed the simultaneous collection of data across a wide range of scattering at high count rate, to study heat treatments; and iii) x-ray absorption spectroscopy to explore the effects of ambient moisture on transition metal sites.

In Situ Synchrotron X-ray Absorption Experiments and Modelling of the Growth Rates of Electrochemically Deposited ZnO Nanostructures

2007 ◽  
Vol 1017 ◽  
Author(s):  
Bridget Ingham ◽  
Benoit N. Illy ◽  
Jade R. Mackay ◽  
Stephen P. White ◽  
Shaun C. Hendy ◽  
...  
Keyword(s):  
Growth Rates ◽  
High Resolution Electron Microscopy ◽  
Ex Situ ◽  
X Ray ◽  
Deposition Parameters ◽  
Wide Range ◽  
Electrochemically Deposited ◽  
Electrochemical Current ◽  
X Ray Absorption

AbstractZnO is known to produce a wide variety of nanostructures that have enormous scope for optoelectronic applications. Using an aqueous electrochemical deposition technique, we are able to tightly control a wide range of deposition parameters (Zn2+ concentration, temperature, potential, time) and hence the resulting deposit morphology. By simultaneously conducting synchrotron x-ray absorption spectroscopy (XAS) experiments during the deposition, we are able to directly monitor the growth rates of the nanostructures, as well as providing direct chemical speciation of the films. In situ experiments such as these are critical to understanding the nucleation and growth of such nanostructures.Recent results from in situ XAS synchrotron experiments demonstrate the growth rates as a function of potential and Zn2+ concentration. These are compared with the electrochemical current density recorded during the deposition, and the final morphology revealed through ex situ high resolution electron microscopy. The results are indicative of two distinct growth regimes, and simultaneous changes in the morphology are observed.These experiments are complemented by modelling the growth of the rods in the transport-limited case, using the Nernst-Planck equations in 2 dimensions, to yield the growth rate of the volume, length, and radius as a function of time.

In-situ AFM study of the crystallization and pH-dependent stability of ZnO(0001)-Zn surfaces

2007 ◽  
Vol 1035 ◽  
Author(s):  
Markus Valtiner ◽  
Guido Grundmeier
Keyword(s):  
Electrolyte Solutions ◽  
Ex Situ ◽  
Chemical Cleaning ◽  
Single Crystalline ◽  
Afm Imaging ◽  
Wide Range ◽  
Wet Chemical ◽  
Ph Dependent ◽  
Crystalline Surfaces

AbstractPolar ZnO(0001)-Zn surfaces can be prepared as very well defined and single crystalline surfaces by hydroxide stabilization simply by introducing hydroxides via a wet chemical cleaning step. Within this proceeding we present an in-situ AFM imaging of the crystallization process. The pH dependent stability of the resulting hydroxide-stabilized surfaces was further investigated by means of an ex-situ LEED approach. These investigations show, that it is possible to obtain high quality single crystalline ZnO(0001)-Zn surfaces in a simple way. Moreover, these surfaces turned out to be very stable within a wide range of pH values between 11 and 3 of NaClO4 based 1mM electrolyte solutions.

Ex situ and In situ TEM study of the relaxation of thin films by the modified frank-read mechanism

1992 ◽  
Vol 50 (2) ◽  
pp. 1342-1343
Author(s):  
F.K. LeGoues
Keyword(s):  
Thin Films ◽  
Strain Relaxation ◽  
Lattice Parameter ◽  
Buffer Layers ◽  
Ex Situ ◽  
In Situ Tem ◽  
Wide Range ◽  
Strong Resemblance ◽  
Image Position

In recent papers, we have described a novel mechanism for strain relaxation of thin films. Because of its strong resemblance to the well known Frank-Read sources of dislocations, it was called the “Modified-Frank-Read” (MFR) mechanism. This process was first observed during the growth of compositionally graded SiGe/Si(001) thin films, where it results in dislocations pile-ups being injected deep into an initially perfect substrate, leaving the topmost part of the film relaxed and nominally defect free. This last observation opens the door to a wide range of electronic applications since it makes it possible to grow electronic grade buffer layers of arbitrary composition and lattice parameter.The exact mechanism of the reproduction of dislocations was identified through tilting experiment and analysis of several compositionally graded SiGe/Si(001) structures. These also provided the important parameters controlling this mode of strain relaxation. We thus demonstrated that the MFR mechanism corresponds to the multiplication of “corner dislocations” (dislocations whose line forms a 90° angle) by simultaneous glide on two (111) planes.

Multiple Mössbauer Spectra Data Acquisition with an In-situ Cyclic Voltammetry System

2002 ◽  
pp. 21-24 ◽  
Author(s):  
T L Greaves ◽  
J D Cashion ◽  
A L Benci ◽  
N K Jaggi ◽  
C Hogan ◽  
...  
Keyword(s):  
Cyclic Voltammetry ◽  
Data Acquisition ◽  
Mössbauer Spectra ◽  
Mossbauer Spectra

scholarly journals In- and ex situ PXRD studies of ZnO nanoparticle growth in sub-critical water

2014 ◽  
Vol 70 (a1) ◽  
pp. C1413-C1413
Author(s):  
Espen Bøjesen ◽  
Kirsten Jensen ◽  
Christoffer Tyrsted ◽  
Nina Lock ◽  
Mogens Christensen ◽  
...  
Keyword(s):  
Hydrothermal Synthesis ◽  
Zno Nanoparticles ◽  
Aqueous Media ◽  
Ex Situ ◽  
Synthesis Methods ◽  
Zno Nanoparticle ◽  
Characterization Methods ◽  
Wide Range ◽  
In Situ Experiments

Zinc oxide (ZnO) is a material of great scientific and industrial relevance and is used widely in a variety of applications. Synthesis of ZnO nanoparticles can be performed by a wide range of methods resulting in a tremendous variety of sizes and shapes. Different in situ characterization methods have been used to investigate the ZnO formation under various synthesis conditions; these include numerous spectroscopic methods and small angle scattering. Common for these studies is that the primary focus has been to extract information on particle size and shape of ZnO, while a more rigorous microstructural and structural analysis has been lacking. Furthermore, the aforementioned studies have primarily been focused on soft chemical synthesis methods, at low temperatures and in non-aqueous media, thus omitting the widely used environmentally benign and versatile hydrothermal method. In the present work the formation of ZnO during hydrothermal synthesis has been followed using in situ powder X-ray diffraction (PXRD) combined with Rietveld refinement, thus enabling the extraction of crystallographic as well as microstructural information during the formation and growth of ZnO. Supporting ex situ syntheses and characterization by electron microcopy, high resolution PXRD and other techniques have been used to corroborate the findings from the in situ experiments. Mapping out a vast parameter space has led to a deeper understanding of the intricate mechanisms governing the nucleation and growth of ZnO nanoparticles during hydrothermal synthesis. Among the parameters studied were the influence of temperature, type of base used and the influence of different ionic salts as synthesis directing agents. The various synthesis parameters were found to influence the following structural and microstructural features: crystallite shape, morphology and size as well as the twin-fault concentration, degree of doping and crystallinity.

In situ and ex situ characterization of a Fe-Cr-Ni alloy in mouthwashes and Hank’s solution

2008 ◽  
Vol 62 (3) ◽  
Author(s):  
Dane Cestarolli ◽  
Valéria Alves ◽  
Luís Silva
Keyword(s):  
Corrosion Resistance ◽  
Electrochemical Techniques ◽  
Passive Layer ◽  
Chloride Ions ◽  
Localized Corrosion ◽  
Ex Situ ◽  
Ni Alloy ◽  
Hank’S Solution

AbstractThe aim of the present study was to classify the surface oxide layers formed on a Fe-Cr-Ni alloy according to their corrosion resistance in Hank’s solution and mouthwashes by SEM and electrochemical techniques. The SEM micrographs showed the presence of localized corrosion and the polarization curves showed that the passive layer is less stable in the presence of Hank’s solution than of mouthwashes, as a result of the presence of chloride ions.

scholarly journals Laser-heating system for high-pressure X-ray diffraction at the Extreme Conditions beamline I15 at Diamond Light Source

2018 ◽  
Vol 25 (6) ◽  
pp. 1860-1868 ◽  
Author(s):  
Simone Anzellini ◽  
Annette K. Kleppe ◽  
Dominik Daisenberger ◽  
Michael T. Wharmby ◽  
Ruggero Giampaoli ◽  
...  
Keyword(s):  
Light Source ◽  
Laser Heating ◽  
Theoretical Data ◽  
Heating System ◽  
Ex Situ ◽  
X Ray Diffraction ◽  
X Ray ◽  
Wide Range ◽  
Diamond Anvil

In this article, the specification and application of the new double-sided YAG laser-heating system built on beamline I15 at Diamond Light Source are presented. This system, combined with diamond anvil cell and X-ray diffraction techniques, allows in situ and ex situ characterization of material properties at extremes of pressure and temperature. In order to demonstrate the reliability and stability of this experimental setup over a wide range of pressure and temperature, a case study was performed and the phase diagram of lead was investigated up to 80 GPa and 3300 K. The obtained results agree with previously published experimental and theoretical data, underlining the quality and reliability of the installed setup.

Pressure acid leaching of nickel laterite ores: anin situdiffraction study of the mechanism and rate of reaction

2005 ◽  
Vol 38 (6) ◽  
pp. 927-933 ◽  
Author(s):  
Ian C. Madsen ◽  
Nicola V. Y. Scarlett ◽  
Barry I. Whittington
Keyword(s):  
Acid Leaching ◽  
Negative Temperature ◽  
Ex Situ ◽  
Nickel Laterite ◽  
X Ray ◽  
Laterite Ores ◽  
Wide Range ◽  
Processing Plants ◽  
Pressure Acid Leaching

This paper outlines the use of an innovative system for thein situinvestigation of hydrothermal reactions by X-ray diffraction. The key features are the use of: (i) a purpose-built capillary reaction vessel which allows close emulation of the conditions present in mineral processing plants; (ii) MoKα radiation, to ensure that the X-ray beam penetrates through the capillary, and (iii) an Inel CPS120 position-sensitive detector, to enable simultaneous collection of a wide range (120° 2θ) of diffraction data. The pressure acid leaching (PAL) of nickel laterite ores is used to illustrate the capabilities of this system, with a particular focus on the PAL of saprolite in strong H2SO4at 493 K. Saprolitic ore, which largely consists of serpentine mineral phases [(Mg,Fe,Ni,Al)3(Si,Al)2O5(OH)4], undergoes a number of mineralogical changes during both the acid leaching reaction and subsequent cooling, thus making it difficult to examine accurately using traditional post-reactionex situtechniques. In particular, kieserite (MgSO4.H2O), which forms during leaching, has a negative temperature coefficient of solubility, causing it to dissolve on cooling. Thein situtechnique described in this paper allows the direct observation of kieserite formation during the saprolite PAL at 493 K and its dissolution upon cooling to ambient temperature.

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