scholarly journals Behavior of Two Foundry Cobalt-Based Alloys Exposed to a Hot Complex Gaseous Mixture Simulating the Atmosphere in a Waste-to-Energy Boiler. Part 1: Case of the Alloy Exposed to the Complex Gas Stream

2018 ◽  
Vol 5 ◽  
pp. 1-5
Author(s):  
Lionel Aranda ◽  
Thierry Schweitzer ◽  
Patrice Berthod ◽  
Christophe Rapin ◽  
Didier Souchon ◽  
...  
Keyword(s):  
Water Vapor ◽  
High Temperature ◽  
Working Conditions ◽  
Gaseous Mixture ◽  
The Other ◽  
Waste To Energy ◽  
Gas Mixture ◽  
Refractory Materials ◽  
X Ray Diffraction ◽  
X Ray

The refractory materials required for waste-to-energy boilers endure severe working conditions, such as exposure to heat and hot oxidation / corrosion. Thanks to their high temperature properties cobalt-based alloys may respond to these properties requirements. In this work two model alloys based on cobalt and rich in chromium were elaborated by casting and samples were prepared by cutting and polishing. These samples were exposed, one to a hot complex gaseous mixture particularly aggressive reproducing the atmosphere in WtE boilers in service (presence of water vapor, di-oxygen, carbon di-oxide, hydrogen chloride), and the other to synthetic ashes, both for more than two hundreds hours. After test the samples were characterized by X-ray diffraction and SEM observations. On sample exposed to the complex gas stream a {10 to 15μm}-thick oxide scale formed on the surface of the sample exposed to the gas mixture. It involved all the elements of the alloy and it obviously developed both inwards and outwards as suggested by the position of the oxidized carbides.

scholarly journals Behavior of Two Foundry Cobalt-Based Alloys Exposed to a Hot Complex Gaseous Mixture Simulating the Atmosphere in a Waste-to-Energy Boiler. Part 2: Case of the Alloy Immersed in Synthetic Ashes

2018 ◽  
Vol 5 ◽  
Author(s):  
Lionel Aranda ◽  
Thierry Schweitzer ◽  
Patrice Berthod ◽  
Christophe Rapin ◽  
Didier Souchon ◽  
...  
Keyword(s):  
Working Conditions ◽  
Gaseous Mixture ◽  
Oxidation Mechanism ◽  
Waste To Energy ◽  
Post Mortem ◽  
X Ray Diffraction ◽  
Active Oxidation ◽  
X Ray ◽  
The One

Currently cobalt-based alloys are seemingly not really envisaged for constituting waste-to-energy boilers, although that the WtE working conditions are similar to those encountered in some applications in which Co-based superalloys are successfully used. To test the behavior of the cast chromium-rich cobalt-based alloys’ family, two model alloys belonging to the later one were cast and samples were exposed during more than ten days to a hot complex gaseous mixture and to synthetic ashes. After test the samples were characterized by X-ray diffraction and SEM observations. The results of the characterization of the first sample, the one exposed to the hot complex gaseous atmosphere, were presented in the first part of this work. This second part concerns the post-mortem analysis of the second sample, the one immersed in ashes. It appears first that this one was not protected by any external oxide scale. Instead, a mixture of oxides and chlorides formed and reaction between these corrosion products with ashes obviously led to an intermediate liquid phase. Internal oxidation/chloridation of the chromium carbides network obviously occurred over a 500μm-depth from the surface happened. The responsibility of an active oxidation mechanism analogous to what was earlier observed on steels is envisaged.

scholarly journals In-Situ Isothermal Crystallization of Poly(l-lactide)

Polymers ◽  
2021 ◽  
Vol 13 (19) ◽  
pp. 3377
Author(s):  
Zirui Huang ◽  
Meiling Zhong ◽  
Haibo Yang ◽  
Enqin Xu ◽  
Dehui Ji ◽  
...  
Keyword(s):  
High Temperature ◽  
Nucleation Rate ◽  
Low Temperatures ◽  
Isothermal Crystallization ◽  
The Other ◽  
Wide Angle ◽  
X Ray Diffraction ◽  
X Ray ◽  
Different Temperatures

The isothermal crystallization of poly(l-lactide) (PLLA) has been investigated by in-situ wide angle X-ray diffraction (WAXD) and polarized optical microscopes (POM) equipped with a hot-stage accessory. Results showed that the spherulites of PLLA were formed at high temperature, whereas irregular morphology was observed under a low temperature. This can be attributed to the varying rates of crystallization of PLLA at different temperatures. At low temperatures, the nucleation rate is fast and hence the chains diffuse very slow, resulting in the formation of imperfect crystals. On the other hand, at high temperatures, the nucleation rate is slow and the chains diffuse fast, leading to the formation of perfect crystals. The change in the value of the Avrami exponent with temperature further verifies the varying trend in the morphological feature of the crystals.

XRD Studies on Transformation of Dolomite under CO2 and N2 Atmosphere

2020 ◽  
Vol 1010 ◽  
pp. 355-360
Author(s):  
Siti Sarahah Sulhadi ◽  
Maratun Najiha Abu Tahari ◽  
Salma Samidin ◽  
Wan Nor Roslam Wan Isahak ◽  
Muhammad Rahimi Yusop ◽  
...  
Keyword(s):  
High Temperature ◽  
Crystallite Size ◽  
Fluidized Bed ◽  
Chemical Reactions ◽  
Fluidized Bed Reactor ◽  
The Other ◽  
X Ray Diffraction ◽  
X Ray ◽  
Xrd Studies ◽  
Significant Chemical

In this study, dolomite was heated under CO2 and N2 gases using fluidized bed reactor from 85 °C to 835 °C. Dolomite under N2 atmosphere did not show any significant changes on its crystallite size, suggesting there is no significant chemical reaction. On the other hand, dolomite under CO2 atmosphere shows no significant changes on its crystallite size until it reaches high temperature (> 800 °C) where MgO started to be observed in X- ray diffraction. This shows that few chemical reactions started to happen in this reaction condition.

Phase Transition and Thermal Expansion of Ba3RB3O9 (R = Sm–Yb, and Y)

2017 ◽  
Vol 36 (8) ◽  
pp. 763-769 ◽  
Author(s):  
Rayko Simura ◽  
Shohei Kawai ◽  
Kazumasa Sugiyama
Keyword(s):  
Phase Transition ◽  
Thermal Expansion ◽  
High Temperature ◽  
Thermal Expansion Coefficient ◽  
Room Temperature ◽  
The Other ◽  
X Ray Diffraction ◽  
X Ray ◽  
Melting Temperatures ◽  
Type Phase

AbstractHigh temperature powder X-ray diffraction measurements of Ba3RB3O9 (R=Sm–Yb, and Y) were carried out at temperatures ranging from room temperature to just below the corresponding melting temperatures (1,200–1,300 °C). No phase transition was found for the H-type phase (R$\overline 3 $) with R=Sm–Tb and the L-type phase (P63 cm) with R=Tm–Yb. On the other hand, phase transition from the L phase to the H phase was observed for R=Dy–Er, and Y at around 1,100–1,200 °C. The obtained axial thermal expansion coefficient (ATEC) of the a-axis was larger than that of the c-axis for the H phase, and the ATEC of the c-axis was larger than that of the a-axis for the L phase. The observed anisotropic nature of ATEC is attributed to the distribution of the BO3 anionic group with rigid boron–oxygen bonding in the structures of the H and L phases.

Nb and Ta Substituted Bi(Pb)-Sr-Ca-Cu-O Superconductors

1998 ◽  
Vol 12 (29n31) ◽  
pp. 3335-3337 ◽  
Author(s):  
O. Smrčková ◽  
D. Sýkorová ◽  
P. Vaśek
Keyword(s):  
Magnetic Susceptibility ◽  
High Temperature ◽  
Critical Current Density ◽  
High Temperature Phase ◽  
The Other ◽  
Weak Links ◽  
Temperature Phase ◽  
Superconducting Properties ◽  
X Ray Diffraction ◽  
X Ray

The influence of stoichiometric replacement of Bi by Nb and Ta in the Bi(Pb)-based superconducting system has been investigated. The properties were detected by the measurement of resistivity, magnetic susceptibility and critical current density. X-ray diffraction technique has been used for crystallographic and phase analysis. The study reveals that for both substituents an addition of small amount of them enhances the content of the high temperature phase and improves superconducting properties. On the other hand greater amount of substituents deteriorates weak links in the sample.

High temperature X-ray diffraction investigation of an aluminium-silicon-corundum system

2007 ◽  
Vol 2007 (suppl_26) ◽  
pp. 369-374 ◽  
Author(s):  
D. Garipoli ◽  
P. Bergese ◽  
E. Bontempi ◽  
M. Minicucci ◽  
A. Di Cicco ◽  
...  
Keyword(s):  
High Temperature ◽  
X Ray Diffraction ◽  
X Ray

The Electron Effect of Aromatic Group: Control Conformation of 2-Aromatic Cyclododecanone Derivatives

2020 ◽  
Vol 24 (10) ◽  
pp. 1139-1147
Author(s):  
Yang Mingyan ◽  
Wang Daoquan ◽  
Wang Mingan
Keyword(s):  
1H Nmr ◽  
13C Nmr ◽  
Nmr Spectra ◽  
Coupling Constants ◽  
The Other ◽  
Repulsive Interaction ◽  
X Ray Diffraction ◽  
X Ray ◽  
Electron Effect ◽  
Group Control

2-Phenylcyclododecanone and 2-cyclohexylcyclododecanone derivatives were synthesized and characterized by 1H NMR, 13C NMR, HR-ESI-MS and X-ray diffraction. Their preferred conformations were analyzed by the coupling constants in the 1H NMR spectra and X-ray diffraction, which showed the skeleton ring of these derivatives containing [3333]-2-one conformation, and the phenyl groups were located at the side-exo position of [3333]-2-one conformation due to the strong π-π repulsive interaction between the π- electron of benzene ring and π-electron of carbonyl group. The cyclohexyl groups were located at the corner-syn or the side-exo position of [3333]-2-one conformation depending on the hindrance of the other substituted groups. The π-π electron effect played a crucial role in efficiently controlling the preferred conformation of 2-aromatic cyclododecanone and the other 2-aromatic macrocyclic derivatives with the similar preferred square and rectangular conformations.

scholarly journals High-pressure synthesis and crystal structure of the mixed-cation borate Ga4In4B15O33(OH)3

2019 ◽  
Vol 74 (4) ◽  
pp. 357-363
Author(s):  
Daniela Vitzthum ◽  
Hubert Huppertz
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
High Temperature ◽  
Diffraction Data ◽  
X Ray Diffraction ◽  
Synthesis And Crystal Structure ◽  
X Ray ◽  
Mixed Cation ◽  
High Pressure High Temperature ◽  
Pressure Synthesis

AbstractThe mixed cation triel borate Ga4In4B15O33(OH)3 was synthesized in a Walker-type multianvil apparatus at high-pressure/high-temperature conditions of 12.5 GPa and 1300°C. Although the product could not be reproduced in further experiments, its crystal structure could be reliably determined via single-crystal X-ray diffraction data. Ga4In4B15O33(OH)3 crystallizes in the tetragonal space group I41/a (origin choice 2) with the lattice parameters a = 11.382(2), c = 15.244(2) Å, and V = 1974.9(4) Å3. The structure of the quaternary triel borate consists of a complex network of BO4 tetrahedra, edge-sharing InO6 octahedra in dinuclear units, and very dense edge-sharing GaO6 octahedra in tetranuclear units.

The Application of X-Ray Diffraction at Elevated Temperatures to Study the Mechanism of Formation of Sodium Tripolyphosphate

1961 ◽  
Vol 5 ◽  
pp. 276-284
Author(s):  
E. L. Moore ◽  
J. S. Metcalf
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Amorphous Phase ◽  
Elevated Temperatures ◽  
Sodium Tripolyphosphate ◽  
X Ray Diffraction ◽  
Mechanism Of Formation ◽  
X Ray ◽  
Temperature Form ◽  
High Temperature Form

AbstractHigh-temperature X-ray diffraction techniques were employed to study the condensation reactions which occur when sodium orthophosphates are heated to 380°C. Crystalline Na4P2O7 and an amorphous phase were formed first from an equimolar mixture of Na2HPO4·NaH2PO4 and Na2HPO4 at temperatures above 150°C. Further heating resulted in the formation of Na5P3O10-I (high-temperature form) at the expense of the crystalline Na4P4O7 and amorphous phase. Crystalline Na5P3O10-II (low-temperature form) appears after Na5P3O10-I.Conditions which affect the yield of crystalline Na4P2O7 and amorphous phase as intermediates and their effect on the yield of Na5P3O10 are also presented.

Mechanical Alloying Behavior in the Nb-Si, Ta-Si, and Nb-Ta-Si Systems

1988 ◽  
Vol 133 ◽  
Author(s):  
K. S. Kumar ◽  
S. K. Mannan
Keyword(s):  
High Temperature ◽  
Mechanical Alloying ◽  
Mechanical Milling ◽  
Room Temperature ◽  
Crystalline Compound ◽  
X Ray Diffraction ◽  
X Ray ◽  
Β Phase ◽  
Α Phase

ABSTRACTThe mechanical alloying behavior of elemental powders in the Nb-Si, Ta-Si, and Nb-Ta-Si systems was examined via X-ray diffraction. The line compounds NbSi2 and TaSi2 form as crystalline compounds rather than amorphous products, but Nb5Si3 and Ta5Si3, although chemically analogous, respond very differently to mechanical milling. The Ta5Si3 composition goes directly from elemental powders to an amorphous product, whereas Nb5Si3 forms as a crystalline compound. The Nb5Si3 compound consists of both the tetragonal room-temperature α phase (c/a = 1.8) and the tetragonal high-temperature β phase (c/a = 0.5). Substituting increasing amounts of Ta for Nb in Nb5Si3 initially stabilizes the α-Nb5Si3 structure preferentially, and subsequently inhibits the formation of a crystalline compound.

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