scholarly journals Study of initial stage of mechanochemical transformation in pyrite

2007 ◽  
Vol 43 (1) ◽  
pp. 57-70 ◽  
Author(s):  
D. Paneva ◽  
D. Mitova ◽  
E. Manova ◽  
H. Kolev ◽  
B. Kunev ◽  
...  
Keyword(s):  
Powder Diffraction ◽  
Photoelectron Spectroscopy ◽  
Kinetic Data ◽  
Time Interval ◽  
X Ray ◽  
First Order ◽  
Initial Stage ◽  
Mechanochemical Transformation ◽  
Shrinking Core ◽  
Core Reaction

The initial stage of transformation of pyrite to Fe(II)-sulfate as a result of mechanical milling is studied by X-ray powder diffraction (XRD), Moessbauer spectroscopy (MS), Infrared (IR) and X-ray photoelectron spectroscopy (XPS) techniques. A degree of conversion of 0.071 is achieved in the time interval of 0 36 min. The kinetic data satisfy the equation of a shrinking core reaction 1-(1-?)1/3=kt. The reaction is of the first order. The calculated rate constant is k=6.434.10-4 min-1. .

Incorporation and Role of Nitrogen During Oxynitridation of Silicon Studied by Photoelectron Spectroscopy

1999 ◽  
Vol 567 ◽  
Author(s):  
Masayuki Suzuki ◽  
Yoji Saito
Keyword(s):  
Photoelectron Spectroscopy ◽  
High Vacuum ◽  
Oxide Films ◽  
Silicon Surfaces ◽  
Gaseous Mixtures ◽  
X Ray ◽  
Initial Stage ◽  
Thermal Stability Of

ABSTRACTWe tried direct oxynitridation of silicon surfaces by remote-plasma-exited nitrogen and oxygen gaseous mixtures at 700°C in a high vacuum. The oxynitrided surfaces were investigated with in-situ X-ray photoelectron spectroscopy. With increase of the oxynitridation time, the surface density of nitrogen gradually increases, but that of oxygen shows nearly saturation behavior after the rapid increase in the initial stage. We also annealed the grown oxynitride and oxide films to investigate the role of the contained nitrogen. The desorption rate of oxygen from the oxynitride films is much less than that from oxide films. We confirmed that nitrogen stabilizes the thermal stability of these oxynitride films.

Sub-nm-Scale Depth Profiling of Nitrogen in NO- and N2-Annealed SiO2/4H-SiC(0001) Structures

2019 ◽  
Vol 963 ◽  
pp. 226-229
Author(s):  
Kidist Moges ◽  
Mitsuru Sometani ◽  
Takuji Hosoi ◽  
Takayoshi Shimura ◽  
Shinsuke Harada ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
High Temperature ◽  
Photoelectron Spectroscopy ◽  
Depth Profiling ◽  
Annealing Duration ◽  
Nanometer Scale ◽  
Pure Nitrogen ◽  
X Ray ◽  
Initial Stage

We demonstrated an x-ray photoelectron spectroscopy (XPS)-based technique to reveal the detailed nitrogen profile in nitrided SiO2/4H-SiC structures with sub-nanometer-scale-resolution. In this work, nitric oxide (NO)- and pure nitrogen (N2)-annealed SiO2/4H-SiC(0001) structures were characterized. The measured results of NO-annealed samples with various annealing duration indicate that preferential nitridation just at the SiO2/SiC interfaces (~0.3 nm) proceeds in the initial stage of NO annealing and a longer duration leads to the distribution of nitrogen in the bulk SiO2 within few nanometers of the interface. The high-temperature N2 annealing was found to induce not only SiO2/SiC interface nitridation similarly to NO annealing but also SiO2 surface nitridation.

High-temperature X-ray powder diffraction study of the tetragonal-cubic phase transition in nanocrystalline, compositionally homogeneous ZrO2–CeO2 solid solutions

2008 ◽  
Vol 23 (S1) ◽  
pp. S70-S74 ◽  
Author(s):  
L. M. Acuña ◽  
R. O. Fuentes ◽  
D. G. Lamas ◽  
I. O. Fábregas ◽  
N. E. Walsöe de Reca ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
High Temperature ◽  
Powder Diffraction ◽  
Solid Solutions ◽  
Tetragonal Phase ◽  
Room Temperature ◽  
Cubic Phase ◽  
X Ray ◽  
First Order

Crystal structure of compositionally homogeneous, nanocrystalline ZrO2–CeO2 solutions was investigated by X-ray powder diffraction as a function of temperature for compositions between 50 and 65 mol % CeO2. ZrO2-50 and 60 mol % CeO2 solid solutions, which exhibit the t′-form of the tetragonal phase at room temperature, transform into the cubic phase in two steps: t′-to-t″ followed by t″-to-cubic. But the ZrO2-65 mol % CeO2, which exhibits the t″-form, transforms directly to the cubic phase. The results suggest that t′-to-t″ transition is of first order, but t″-to-cubic seems to be of second order.

OBSERVATION OF PHASE TRANSITIONS AT THE (100) SURFACE OF Al-3 at.% Ag

1995 ◽  
Vol 02 (02) ◽  
pp. 141-145 ◽  
Author(s):  
E. WETLI ◽  
M. HOCHSTRASSER ◽  
D. PESCIA ◽  
M. ERBUDAK
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Photoelectron Spectroscopy ◽  
Short Range ◽  
Short Range Order ◽  
Elevated Temperatures ◽  
X Ray ◽  
First Order ◽  
First Order Phase Transition ◽  
First Order Phase

In the bulk binary alloy Al-3 at.% Ag , Ag 2 Al precipitates are formed below 410°C which are reversibly dissolved at elevated temperatures. We have followed this phase transition at a (100) surface as a function of temperature by monitoring the bandwidth of the Ag 4d states in X-ray photoelectron spectroscopy. Since the bandwidth measures the coordination number of the emitting atoms, it directly reveals the short-range order of the Ag atoms at the surface. The measurements show that the dissolution of the Ag -rich clusters starts at temperatures at least 100 K below the bulk transition, and the observed hysteresis behavior is indicative of a first-order phase transition at the surface.

scholarly journals Investigation of the Kinetic Regularities of the Process of Biodegradation of Betaine Surfactant by Bacteria of the Genus Pseudomonas

2021 ◽  
Vol 11 (19) ◽  
pp. 8939
Author(s):  
Anastasia S. Burlachenko ◽  
Olesya V. Salishcheva ◽  
Lyubov S. Dyshlyuk ◽  
Alexander Y. Prosekov
Keyword(s):  
Kinetic Data ◽  
Industrial Wastewater ◽  
Surfactant Concentration ◽  
Time Interval ◽  
Organic Substances ◽  
High Concentration ◽  
First Order ◽  
High Concentrations ◽  
Biological Decomposition ◽  
Toxic Organic Substances

Surfactants are extremely common organic compounds that enter the environment in large quantities in the form of household and industrial wastewater. The toxicity of surfactants for biological systems, the high concentration of substances and the duration of the bioremediation process of polluted ecosystems requires improving the biotechnology of microbial wastewater treatment for surfactants. The purpose of this work is to study the kinetic laws of the reaction of the biological decomposition of betaine surfactants. Pseudomonas bacteria were used as bio-destructors of the surfactants. Kinetic data were obtained to create the possibility of further optimization of research on the biodegradation of toxic organic substances. The strains that were promising destructors of cocamidopropylbetaine were selected. The toxicity of high concentrations of surfactants in relation to microorganisms of the genus Pseudomonas was proven. Safe values of the surfactant concentration for conducting biodegradation tests were found. A kinetic model of the biodestructive process was constructed. It proves that the processes of biodegradation are described by a kinetic equation of the first order. With the derived equation, it is possible to determine the time interval of biodegradation of cocamidopropylbetaine to the specified values by means of mathematical calculations.

Decaphenylferrocene

1995 ◽  
Vol 48 (4) ◽  
pp. 851 ◽  
Author(s):  
LD Field ◽  
TW Hambley ◽  
PA Humphrey ◽  
CM Lindall ◽  
GJ Gainsford ◽  
...  
Keyword(s):  
Solid State ◽  
High Resolution ◽  
Vibrational Spectroscopy ◽  
Powder Diffraction ◽  
Photoelectron Spectroscopy ◽  
Mossbauer Spectroscopy ◽  
57Fe Mössbauer Spectroscopy ◽  
X Ray ◽  
57Fe Mössbauer ◽  
57Fe Mossbauer Spectroscopy

Decaphenylferrocene was obtained as an extremely insoluble, maroon microcrystalline solid by heating [(η5-C5Ph5)((η6-C6H5)C5Ph4)Fe], and was characterized by 57Fe Mossbauer spectroscopy, X-ray photoelectron spectroscopy, mass, electronic and vibrational spectroscopy, solid-state 13C n.m.r. spectroscopy and high-resolution X-ray powder diffraction, which showed it to be isostructural with decaphenylnickelocene.

SELECTIVE CLEAVAGE OF FUNCTIONAL GROUPS IN THE FUNCTIONALIZED ORGANIC MONOLAYERS BY SYNCHROTRON SOFT X-RAYS

2002 ◽  
Vol 09 (01) ◽  
pp. 305-311
Author(s):  
TAI-HEE KANG ◽  
KI-JEONG KIM ◽  
CHAN-CUK HWANG ◽  
KYU-WOOK IHM ◽  
HYUN-JOON SHIN ◽  
...  
Keyword(s):  
Functional Groups ◽  
Photoelectron Spectroscopy ◽  
Aromatic Aldehydes ◽  
Photon Flux ◽  
X Rays ◽  
Organic Monolayers ◽  
Cleavage Rate ◽  
X Ray ◽  
First Order ◽  
Molecular Layers

Aminosilylated surface was treated with halide-substituted aromatic aldehydes, and the resulting molecular layers were examined with synchrotron X-ray photoelectron spectroscopy at the 2B1 SGM and 4B1 microscopy beamline in the Pohang Accelerator Laboratory. It was observed that the halide group of the film diminished upon the irradiation, but the other bands were constant in terms of the intensity and the shape. This observation indicates that the functional groups of the organic monolayers are cleaved selectively by soft X-rays. The cleavage rate was measured as a function of photon energy and normalized with photon flux. The cleavage is first-order to the concentration of the functional group. Its rate constant is sensitive to the molecular structure of the organic monolayers and the kind of substituents on the aromatic ring.

scholarly journals Crystal chemistry of mimetite, Pb10(AsO4)6Cl1.48O0.26, and finnemanite, Pb10(AsO3)6Cl2

2008 ◽  
Vol 64 (1) ◽  
pp. 34-41 ◽  
Author(s):  
Tom Baikie ◽  
Cristiano Ferraris ◽  
Wim T. Klooster ◽  
S. Madhavi ◽  
Stevin S. Pramana ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Neutron Diffraction ◽  
Powder Diffraction ◽  
Photoelectron Spectroscopy ◽  
Arsenic Speciation ◽  
X Ray ◽  
Transmission Electron ◽  
Landfill Disposal

The crystal chemistries of synthetic mimetite, Pb10(As5+O4)6(Cl2 − x O x/2), a neutral apatite, and finnemanite, Pb10(As3+O3)6Cl2, a reduced apatite, were characterized using a combination of X-ray powder diffraction, neutron diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy. Both phases conform to hexagonal P63/m symmetry; however, the temperature-driven transformation of clinomimetite to mimetite described earlier was not confirmed. The average mimetite structure is best described through the introduction of partially occupied oxygen sites. A better understanding of the mixed arsenic speciation in apatites can guide the formulation of waste form ceramics and improve models of long-term durability after landfill disposal.

High-Temperature Structural Studies of SrPbO3 and BaPbO3

2002 ◽  
Vol 55 (8) ◽  
pp. 543 ◽  
Author(s):  
J. R. Hester ◽  
C. J. Howard ◽  
B. J. Kennedy ◽  
R. Macquart
Keyword(s):  
Phase Transitions ◽  
High Temperature ◽  
High Resolution ◽  
Powder Diffraction ◽  
Room Temperature ◽  
Structural Studies ◽  
X Ray ◽  
First Order

High-resolution X-ray powder diffraction studies have shown BaPbO3 to transform from an orthorhombic Imma structure at room temperature, through an intermediate I4/mcm phase, to a cubic Pm3–mstructure above 500�C. The Imma to I4/mcm transition is first order and the I4/mcm–Pm3–m transition for BaPbO3 is tricritical in nature. We find no evidence for any phase transitions in SrPbO3 up to 760�C, the structure remaining in Pnma from room temperature to 760�C.

scholarly journals Effect of Si Content on the Corrosion Behavior of 420 MPa Weathering Steel

Metals ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 486 ◽  
Author(s):  
Sun ◽  
Yu ◽  
Zhang ◽  
Yan ◽  
Lu ◽  
...  
Keyword(s):  
Corrosion Rate ◽  
Corrosion Behavior ◽  
Photoelectron Spectroscopy ◽  
Silicon Oxide ◽  
Corrosion Products ◽  
Weathering Steel ◽  
X Ray ◽  
Initial Stage ◽  
Amorphous Compounds ◽  
Si Content

: The effect of Si content (0.12%, 0.34%, and 0.48%) on the corrosion behavior of weathering steel in a simulated marine environment was investigated in a dry/wet alternating cycle corrosion experiment. Corrosion weight gain, X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and electrochemical methods were used to measure the regularity and nature of the rust. The results show that the corrosion process could be divided into an initial stage where the corrosion rate increased and a later stage where the corrosion rate decreased before remaining stable. The corrosion rate was the lowest for a Si content in the weathering steel of 0.48%. The corrosion products of all three steel groups contains α-FeOOH, β-FeOOH, γ-FeOOH, Fe3O4, and large amounts of amorphous compounds. Furthermore, Si benefits the transformation of β-FeOOH and γ-FeOOH to stable phases. The addition of the Si alloying element is beneficial to the formation of dense and compact rust layers that enhance the electrochemical resistance of weathering steel and silicon oxide influences the self-corrosion potential of the corrosion products.

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