scholarly journals Thermomechanical Characterisation of Mullite Zirconia Composites Sintered from Andalusite for High Temperature Applications

Ceramics ◽  
2019 ◽  
Vol 2 (4) ◽  
pp. 587-601 ◽  
Author(s):  
Thierry Chotard ◽  
Lizeth Arbelaez Morales ◽  
Marie-Laure Bouchetou ◽  
Jacques Poirier
Keyword(s):  
Acoustic Emission ◽  
High Temperature ◽  
Thermal Shock ◽  
Amorphous Phase ◽  
Important Influence ◽  
X Ray Diffraction ◽  
Bending Tests ◽  
Thermomechanical Behaviour ◽  
Zirconia Composites ◽  
Ultrasonic Techniques

Mullite-Zirconia refractories are well known for their good resistance to corrosion and thermal shock. In this study, several mullite-zirconia composites were developed from andalusite, alumina and zircon sintered at 1600 °C for 10 hours. The samples were subjected to thermal shock carried out after heating at 1200 °C, in order to study the mechanical and thermomechanical behaviour as a function of the amount of zirconia dispersed in the mullite matrix. It appears that that the amorphous phase (SiO2), determined by X-ray diffraction, produced by the decomposition of andalusite, increases considerably with the amount of final zirconia in the composite and has a very important influence on the porosity. This amorphous phase seems also to have an important influence on the mechanical properties of the material. The characterisation of the thermomechanical behaviour (elastic properties and damage monitoring) was carried out thanks to ultrasonic techniques (US echography and Acoustic Emission). The “surprising” evolution (increase) of the Young’s modulus E of the material after being submitted to repeated thermal shocks is highlighted and explained. The acoustic emission technique carried out at high temperature and also coupled to 4-points bending tests (at room temperature) demonstrates its effectiveness for providing a better understanding of the chronology of the involved mechanisms involved at microstructural scale.

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.

scholarly journals Effect of Arc Power on the Wear and High-temperature Oxidation Resistances of Plasma-Sprayed Fe-based Amorphous Coatings

2019 ◽  
Vol 38 (2019) ◽  
pp. 639-646
Author(s):  
Jinheng Luo ◽  
Na Shi ◽  
Ya-Zhe Xing ◽  
Chaoping Jiang ◽  
Yongnan Chen
Keyword(s):  
High Temperature ◽  
Amorphous Phase ◽  
High Temperature Oxidation ◽  
Steel Substrate ◽  
Atmospheric Plasma ◽  
X Ray Diffraction ◽  
Temperature Oxidation ◽  
Arc Power ◽  
Plasma Sprayed ◽  
Amorphous Coatings

AbstractAtmospheric plasma spraying (APS) technique is employed to prepare Fe-based amorphous coatings on T91 steel substrate under various arc powers of 30 kW, 35 kW and 40kW. The morphology and microstructure of both Fe-based powders and amorphous coatings are characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). In addition, the wear resistance and high-temperature oxidation resistance of the plasma-sprayed coatings at various arc powers are studied. It is found that with increasing the arc power, the content of the porosity and the amorphous phase in the coatings declines. Specifically, under 30 kW, 35 kW and 40 kW arc power, the porosity of the coatings is 7.96%, 6.13% and 5.75%. Correspondingly, the relative content of amorphous phase from the coatings is measured to be 96.07% (mass fraction), 73.89% and 65.54%. Moreover, under 40 kW arc power, it gives the coating the highest micro-hardness having more compact microstructure and more dispersive α-Fe grains. Besides, the coatings fabricated at high arc power exhibit less wear induced weight loss and less weight gain from high-temperature oxidation comparing with those fabricated at lower arc power.

scholarly journals Complex phase evolution of Brushite-based calcium phosphate CaHPO4·2H2O using in situ high temperature X-ray diffraction and thermal analysis

2020 ◽  
Author(s):  
Mouatamid El Hazzat ◽  
Adnane El Hamidi ◽  
Mohammed Halim ◽  
said ARSALANE
Keyword(s):  
Thermal Analysis ◽  
Infrared Spectroscopy ◽  
High Temperature ◽  
Calcium Phosphate ◽  
Amorphous Phase ◽  
Phase Evolution ◽  
High Temperature Treatment ◽  
X Ray Diffraction ◽  
X Ray

Abstract This study focused on a detailed examination of the thermal behavior of Brushite-based calcium phosphate (CaHPO 4 .2H 2 O, DCPD) to identify and characterize the intermediate phases which have been the subject of previous several controversies. For that, in situ high-temperature X-ray diffraction supported by infrared spectroscopy, thermal analysis, and scanning electron microscopy analysis were used and the results showed that the progressive thermal stress of DCPD in air resulted in a heterogeneous formulation consisting of dibasic calcium phosphate anhydrous (CaHPO 4 , DCPA) and an amorphous phase, which appears at low temperatures (~160 °C) and persists up to 375 °C. The deep examination of the amorphous phase by infrared spectroscopy revealed that its chemical composition is similar to that of disordered calcium pyrophosphate (Ca 2 P 2 O 7 , CPP) with the appearance of a characteristic band δ(P-O-P), located at 740 cm -1 . This IR band is shifted to low frequencies (725 cm -1 ) as the temperature is increased, indicating the crystallization of the amorphous phase into γ-CPP. The high temperature treatment (≥ 375 °C) leads to b-CPP polymorph. According to the present characterization results, obtaining pure DCPA from the thermal dehydration of DCPD is not effective and leads to biphasic materials including an amorphous phase.

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

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.

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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