scholarly journals Effect of the Noble Metals Addition on the Oxidation Behavior of Ni3Al

2018 ◽  
Vol 2018 ◽  
pp. 1-19 ◽  
Author(s):  
J. J. Ramos-Hernandez ◽  
J. Porcayo-Calderon ◽  
J. G. Gonzalez-Rodriguez ◽  
Jan Mayén ◽  
G. Lara-Rodriguez ◽  
...  
Keyword(s):  
Noble Metals ◽  
Oxidation Behavior ◽  
Surface Composition ◽  
Xrd Analysis ◽  
Intermetallic Alloy ◽  
Oxide Growth ◽  
X Ray ◽  
Crystallographic Planes ◽  
Kinetics Of ◽  
Duplex Oxide

This paper discusses the effect of the addition of noble metals on the microstructure, mechanism, and oxidation kinetics of the Ni3Al intermetallic alloy. Ni3Al was doped with 1% (atomic percent) of Au, Ag, Pd, and Pt. Oxidation behavior of the alloys was evaluated at 900, 1000, and 1100°C in O2 for 24 hours. XRD analysis showed that the addition of noble metals favored the oxide growth on preferential crystallographic planes. In addition, the preferential substitution of the noble metals in the Ni3Al structure modifies the surface composition by increasing the Al/Ni ratio. It was observed that most of the alloys showed a subparabolic behavior, and only the intermetallic base and the alloy doped with Ag show a parabolic behavior at 900°C. The developed oxides were analyzed both superficially and in cross section by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDXA). It was evident that only the intermetallic base showed the formation of a duplex oxide scale (Al2O3/NiO). The alloys doped with noble metals showed the oxide growth practically of pure Al2O3. This was due to a decrease in the diffusion of the Ni cations because of the presence of the noble metals in the crystalline structure.

Effect of Compressive Stress on the High-Temperature Oxidation Behavior of a Fe-20Ni Alloy in Air

2018 ◽  
Vol 921 ◽  
pp. 168-176
Author(s):  
Chang Hai Zhou ◽  
Rui Yun Pan ◽  
Hai Tao Ma
Keyword(s):  
Compressive Stress ◽  
High Temperature Oxidation ◽  
Oxidation Behavior ◽  
Oxide Scales ◽  
External Scale ◽  
X Ray Diffraction ◽  
Temperature Oxidation ◽  
X Ray ◽  
High Temperature Oxidation Behavior ◽  
Kinetics Of

The oxidation behavior of Fe-20Ni alloy under compressive stress in air was studied at 800, 900 °C. The results examined by using scanning electron microscope (SEM) and X-ray diffraction (XRD) indicates that the oxide scales were consisted of an external scale and a subscale which has an intragranular scale (above 5 h at 800 °C and 900 °C) and an intergranular scale. Compared with the unstressed specimen, the growth kinetics of external scale was accelerated by an applied compressive stress. Besides, the compressive stress induced an increase in the growths of intragranular scale and intergranular scale formed on the specimens oxidized at 900 °C. However, the effect of compressive stress on the growth of intergranular scale and intragranular scale was not obvious in the case of 800°C. In addition, cracks developed in the subscale for the specimens oxidized under 2.5 MPa compressive stress when the oxidation time exceeded 20 h.

Reaction Process of Al-TiO2-C-Ti-Fe Multiphase System during Combustion Synthesis

2007 ◽  
Vol 336-338 ◽  
pp. 2340-2343 ◽  
Author(s):  
Song He Meng ◽  
Xing Hong Zhang ◽  
Wei Feng Zhang
Keyword(s):  
Intermetallic Compounds ◽  
Xrd Analysis ◽  
Reaction Process ◽  
Multiphase System ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Reaction Characteristics ◽  
Lower Temperature ◽  
Kinetics Of

The reaction process and kinetics of Al-TiO2-C-Ti-Fe system were investigated by differential scanning calorimetry (DSC) analysis, X-ray diffraction (XRD) analysis and scanning electron microscope (SEM). In order to obtain the information of reaction process for complicated system, the reaction characteristics of Al-TiO2, Al-TiO2-C and Al-TiO2-C-Ti systems are explored firstly. The results show that the reaction process varies with temperature in Al-TiO2-C-Ti-Fe system. At the lower temperature, the dominating reaction in Al-TiO2-C-Ti-Fe system is that between Al and Ti, Al and Fe, and so TiAlx, FeAlx, and Ti2Fe intermetallic compounds form. With the temperature increasing, the intermetallic compounds are decomposed. Then the decomposed Ti and Al react with C and TiO2 respectively and the stable TiC, Al2O3 and Fe three phases form in the final product.

Layer-by-Layer Oxidation of Silicon

1991 ◽  
Vol 222 ◽  
Author(s):  
T. Yasaka ◽  
M. Takakura ◽  
S. Miyazaki ◽  
M. Hirose
Keyword(s):  
Photoelectron Spectroscopy ◽  
Oxidation Rate ◽  
Pure Water ◽  
Oxygen Adsorption ◽  
Native Oxide ◽  
Oxide Growth ◽  
Layer By Layer ◽  
X Ray ◽  
P Type ◽  
Kinetics Of

ABSTRACTGrowth kinetics of native oxide on HF-treated Si surfaces terminated with Si-H bonds has been studied by angle-resolved x-ray photoelectron spectroscopy. The oxide growth rate in pure water for an n+ Si(100) surface is significantly high compared to that of p+, and the n or p type Si oxidation rate is in between. This is explained by the formation of ions through electron transfer from Si to adsorbed O2 molecules and the resulting enhancement of the oxidation rate. The oxide growth on Si(100) is faster than (110) and (111) as interpreted in terms of the steric hindrance for molecular oxygen adsorption on the hydrogen terminated silicon 1×1 surface structures.

scholarly journals Kinetics of Duplex Oxide Growth on 9Cr Steels Exposed in CO2: Application of Dimensional Metrology

2017 ◽  
Vol 87 (5-6) ◽  
pp. 617-629 ◽  
Author(s):  
Joy Sumner ◽  
Nigel Simms ◽  
Aya Shin ◽  
Jonathan Pearson
Keyword(s):  
Oxide Growth ◽  
Dimensional Metrology ◽  
Kinetics Of ◽  
Duplex Oxide

Catalytic CO2 Reforming of Methane over Perovskite Noble Metals

2011 ◽  
Vol 356-360 ◽  
pp. 1070-1074
Author(s):  
Hamidreza Arandiyan ◽  
Jun Hua Li
Keyword(s):  
Continuous Flow ◽  
Noble Metals ◽  
Carbon Deposition ◽  
Sol Gel ◽  
Xrd Analysis ◽  
Good Resistance ◽  
X Ray ◽  
Cell Parameters ◽  
Catalytic Stability ◽  
Perovskite Type

A series of perovskite-type oxides catalyst LaAl1-xNixO3 (0≤x≤1) and modified by substitute noble metal La0.4Al0.2Ni0.8M0.6O3 (M=Pt, Pd, Ru, Rh, Ir) prepared by the sol-gel method shows high activity, stability, good resistance to carbon deposition and sintering of the catalyst for the reforming of methane reaction. The reaction was studied under continuous flow using a mixture of CH4:CO2=1:1. Catalysts were characterized by using BET, XRD, SEM, EDS, and HR-TEM. The specific surface area of catalysts varied greatly from 3.07 to 10.18 m2/g with the different substitution (x) following calcination at 850°C. XRD analysis of the solids shows LaNiO3 and/or LaAlO3 as the main phases present on the solids depending on the degree of substitution and more intense peaks and cell parameters showed formation of Ni-Al solid solutions. SEM coupled to an energy dispersive X-ray spectrometer (EDS) shows the possibility to obtain a solid solution of LaAl1-xNixO3 (0≤x≤1) with propionic acid as solvent. The obtained results revealed that the Rh and Ru catalysts showed the highest activity and also showed a high catalytic stability without any decrease in methane conversion up to 3000min of reaction.

Effect of Mechanical Activation on Extracting Indium from Neutral Leach Residue of Zinc Calcine

2011 ◽  
Vol 201-203 ◽  
pp. 1810-1815
Author(s):  
Yan Juan Zhang ◽  
Xuan Hai Li ◽  
Liu Ping Pan ◽  
Yan Song Wei
Keyword(s):  
Mechanical Activation ◽  
Lattice Distortion ◽  
Xrd Analysis ◽  
Leach Residue ◽  
Leaching Kinetics ◽  
X Ray Diffraction ◽  
Activation Time ◽  
X Ray ◽  
Kinetics Of ◽  
Positive Effect

This study was concerned with the effects of mechanical activation (MA) on structural characterization for neutral leach residue of zinc calcine (NLR) and kinetics of indium extraction from NLR in sulphuric acid. The X-ray diffraction (XRD) analysis showed that MA caused the decrease in crystalline phase and increase in lattice distortion. The activation time, reaction temperature and H2SO4concentration had positive effect on indium extraction from NLR. The activation energies of the unactivated, milled for 30 and 60 min NLR samples calculated for indium extraction were 39.3, 32.1, and 30.4 kJ/mol, respectively, which indicated that MA increased the leaching kinetics of indium extraction from NLR. The empirical orders of the unactivated, activated for 30 and 60 min samples for extracting indium with respect to H2SO4concentration were 0.52, 0.51, and 0.51, respectively.

scholarly journals High-Temperature Oxidation Behavior and Kinetics of Forged 12Cr-MoVW Steel

2017 ◽  
Vol 62 (2) ◽  
pp. 1099-1104
Author(s):  
Yong Hwan Kim ◽  
Jeong-Jung Oak ◽  
Ki-Chang Bae ◽  
Wook Jin Lee ◽  
Yong Ho Park
Keyword(s):  
High Temperature Oxidation ◽  
Oxidation Behavior ◽  
X Ray Diffraction ◽  
Protective Oxide ◽  
Cross Sectional ◽  
Temperature Oxidation ◽  
Protective Oxide Layer ◽  
X Ray ◽  
High Temperature Oxidation Behavior ◽  
Kinetics Of

AbstractThe oxidation kinetics of forged 12Cr-MoVW steel was investigated in an air (N2+O2) atmosphere at 873-1073 K (Δ50 K) using thermogravimetric analysis. The oxidized samples were characterized using X-ray diffraction, and the surface and cross-sectional morphologies were examined using scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy. The forged 12Cr-MoVW steel samples exhibited parabolic behavior and a low oxidation rate compared with their as-cast counterparts. A protective oxide layer was uniformly formed at relatively low temperature (≤973 K) for the forged samples, which thus exhibited better oxidation resistance than the as-cast ones. These oxides are considered solid-solution compounds such as (Fe, Cr)2O3.

Oxidation Behavior of Aluminide Coated Ti-Al-Cr-Nb-Zr-Y Alloys at High Temperatures

2015 ◽  
Vol 227 ◽  
pp. 345-348 ◽  
Author(s):  
Eddy Basuki ◽  
Djoko Prajitno ◽  
Pawawoi
Keyword(s):  
Oxidation Resistance ◽  
Oxidation Behavior ◽  
Aluminide Coating ◽  
Diffraction Method ◽  
Complex Oxides ◽  
Intermetallic Alloy ◽  
X Ray Diffraction ◽  
X Ray ◽  
Interdiffusion Process ◽  
Pack Aluminizing

In this study the oxidation behavior of diffusion aluminide coating containing layers of TiAl3 and TiAl2, develop on a substrate of Zr-Y doped α2-Ti3Al/γ-TiAlCrNb intermetallic alloy using pack aluminizing method, was investigated isothermally at 800°C, 900°C, and 1000°C under atmospheric air pressure. The pack cementation was carried out at 850°C for 25 hours in a pack containing 20%-wt Al, 2%-wt NH4Cl, and 78%-wt Al2O3.The phases in the coatings and oxide layers were examined by optical and scanning electron microscopy as well as X-ray diffraction method, while chemical composition of the oxides and phases were examined with EDS attached on the SEM. The experimental results showed that the addition of Zr and Y increases the oxidation resistance of the coating by formation of complex oxides mainly of Al2O3 at the coating surfaces and sub-surface. Combination of oxidation and interdiffusion process cause transformation of TiAl3 layer to TiAl2 that decrease the oxidation resistance through the formation of TiO2 rod crystals on the junction between TiAl2 and Al2O3 in the outer layer.

Kinetics of ultrasound-assisted silver leaching from sintering dust using thiourea

2016 ◽  
Vol 5 (1) ◽  
Author(s):  
Jun Chang ◽  
Erdong Zhang ◽  
Changjiang Yang ◽  
Junwen Zhou ◽  
Jinhui Peng ◽  
...  
Keyword(s):  
Noble Metals ◽  
Order Kinetic ◽  
X Ray Diffraction ◽  
Water Leaching ◽  
X Ray ◽  
Diffusion Controlled ◽  
Order Kinetic Model ◽  
Thiourea Concentration ◽  
Kinetics Of ◽  
Leaching Efficiency

AbstractIn the process of steel manufacture, up to tens of millions of tons of sintering dusts are produced annually in China, which contain noble metals such as Ag. Therefore, the recovery of Ag from sintering dust could be a potential economic and environmental activity. The present work attempts to use ultrasound for leaching silver from the water-leaching residue of sintering dust (WLR-SD) by acidic thiourea at atmospheric pressure. The effects of particle size, leaching temperature, and thiourea concentration were assessed on the leaching efficiency. Mineralogical changes of the WLR-SD were estimated using X-ray fluorescence, X-ray diffraction, and scanning electron microscope. The results have shown that under the conditions used, up to 94% silver could be leached. The leaching kinetics was estimated to follow the first-order kinetic model, and the activation energy was estimated to be 20.7 kJ/mol, confirming an internal diffusion-controlled leaching process. The order of the reaction with respect to the thiourea concentration was estimated to be 0.68.

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