scholarly journals Structural changes of Cr-beidellite treated up to 1350 °C in oxygen or nitrogen atmospheres

Cerâmica ◽  
2018 ◽  
Vol 64 (369) ◽  
pp. 64-68
Author(s):  
H. S. Santos ◽  
A. M. Cesio ◽  
M. Gauna ◽  
V. F. Justo ◽  
C. Volzone
Keyword(s):  
Thermal Analysis ◽  
High Temperature ◽  
Thermal Treatment ◽  
Structural Changes ◽  
Pillared Clay ◽  
Nitrogen Atmosphere ◽  
Thermal Treatments ◽  
X Ray Diffraction ◽  
X Ray ◽  
Mineralogical Phases

Abstract Beidellite clay mineral after intercalation of OH-Cr(III) species were thermally analyzed up to 1350 °C in oxygen and nitrogen atmospheres. OH-Cr-beidellite can be used as a pillared clay precursor for catalysis or as adsorbent applications. However, in this paper beidellite enriched in chromium were analyzed at different thermal treatments up to high temperature for evaluating structural changes for possible future ceramic applications. The structural changes were followed by thermal analysis and X-ray diffraction. The thermal treatment of OH-Cr-beidellite in oxygen and nitrogen atmospheres developed different mineralogical phases up to 1050 °C, but at higher temperatures, the same phases were developed in both atmosphere treatments. Eskolaite phase (Cr2O3) appeared in the sample after heating at 400 °C in oxygen atmosphere, whereas grimaldite (CrO-OH) in nitrogen atmosphere, maintaining the starting phases. At 1000 °C the raw clay minerals disappeared, as it is knew. At 1050 °C in nitrogen atmosphere, grimaldite was absent and eskolaite appeared. At 1350 °C in the samples calcined in both atmospheres, quartz, cristobalite and mullite as the main phases and in lower contents aluminum oxide and aluminum-chromium oxide [(Al,Cr)2O3] were present.

Effect of thermal treatment on lanthanide montmorillonites: dehydration

Clay Minerals ◽  
1980 ◽  
Vol 15 (4) ◽  
pp. 421-428 ◽  
Author(s):  
T. Mozas ◽  
S. Bruque ◽  
A. Rodriguez
Keyword(s):  
Thermal Analysis ◽  
Thermal Treatment ◽  
Interlayer Space ◽  
Lanthanide Ions ◽  
Water Molecules ◽  
Thermal Treatments ◽  
X Ray Diffraction ◽  
Interlayer Water ◽  
X Ray ◽  
Water Layers

AbstractHydration/dehydration behaviour and the effect of various thermal treatments on montmorillonites saturated with lanthanide ions have been investigated by X-ray diffraction, thermal analysis (DTA, TG, DTG), IR spectroscopy and sorption-desorption of water vapour techniques. Heating at 150°C under 10−5 torr did not eliminate all the interlayer water of the montmorillonite, neither did it affect the CEC. Heating above 160°C caused a reduction in CEC. At 25°C La-montmorillonite takes up a maximum of three water layers in the interlayer space, the water molecules adopting a nonacoordinated distribution around the La3+ cation.

Investigations of Crystalline Phases in Glasses under Various Annealing Conditions

2020 ◽  
Vol 28 ◽  
pp. 14-19
Author(s):  
Zamir V. Shomakhov ◽  
Akhmed M. Karmokov ◽  
Oleg A. Molokanov ◽  
Olga O. Molokanova ◽  
Rita Y. Karmokova ◽  
...  
Keyword(s):  
High Temperature ◽  
Structural Changes ◽  
Irreversible Processes ◽  
High Temperature Annealing ◽  
X Ray Diffraction ◽  
Structural And Phase Transformations ◽  
X Ray ◽  
Air Atmosphere ◽  
Annealing Conditions ◽  
Microchannel Plates

Studies of the temperature dependence of the electrical properties of glasses show that the high-temperature annealing in glasses observed irreversible processes. These processes lead to changes in electrical conductivity, dielectric permittivity, and hence the electrical capacitance, dielectric loss tangent, and other parameters. Obviously, this is due to structural changes in the glass as a result of high-temperature annealing. In this regard, this paper presents studies of structural and phase transformations in glasses used for the production of microchannel plates in the process of high-temperature annealing in vacuum and in the air atmosphere at different times. The studies were conducted by x-ray phase and X-ray diffraction analysis, as well as X-ray fluorescence elemental analysis.

A Study of Phase Reactions in a Complex 4.5 Al–3.5 Ti–Ni Base Alloy

1960 ◽  
Vol 4 ◽  
pp. 233-243
Author(s):  
John F. Radavich ◽  
W. J. Boesch
Keyword(s):  
Electron Microscopy ◽  
High Temperature ◽  
Structural Changes ◽  
Base Alloy ◽  
Phase Changes ◽  
X Ray Diffraction ◽  
High Temperature Alloy ◽  
X Ray ◽  
Nickel Base ◽  
Precipitated Phases

AbstractAn investigation of the phase changes in a complex aluminum-titanium-hardened nickel-base high-temperature alloy was carried out after solutioning at high temperatures and aging at lower temperatures. The physical distribution and size of the precipitated phases were studied by electron microscopy. X-ray diffraction and fluorescence analyses were carried out on chemically extracted residues. The results of the xtructure changes as well as correlation of some physical properties with the structural changes are presented.

XRD investigation of thermal degradation of some gamma-irradiated polyethylene terephthalate samples

2019 ◽  
Vol 33 (12) ◽  
pp. 1950111 ◽  
Author(s):  
Mihai Todica ◽  
Zoltan Kovacs-Krauss ◽  
Carmen Niculaescu ◽  
Marieta Mureşan-Pop
Keyword(s):  
Thermal Treatment ◽  
Polyethylene Terephthalate ◽  
Structural Changes ◽  
Diffraction Method ◽  
Resonance Spectroscopy ◽  
X Ray Diffraction ◽  
X Ray ◽  
Before And After ◽  
Gamma Irradiated ◽  
Different Doses

The modification of local structure of some commercial polyethylene terephthalate (PET) samples, gamma irradiated at different doses, was investigated by X-ray diffraction method before and after thermal treatment. Before the thermal treatment, the samples exposed to different doses of gamma radiations, does not show noticeable structural changes. However, the gamma exposure affects the thermal behavior of samples submitted to melting–cooling process. These modifications have been highlighted by X-ray diffraction, and confirmed also by thermal analysis and electron spin resonance spectroscopy.

Thermal analysis of rare earth gallates and aluminates

1990 ◽  
Vol 5 (1) ◽  
pp. 183-189 ◽  
Author(s):  
H. M. O'Bryan ◽  
P. K. Gallagher ◽  
G. W. Berkstresser ◽  
C. D. Brandle
Keyword(s):  
Thermal Analysis ◽  
Thermal Expansion ◽  
High Temperature ◽  
Superconducting Films ◽  
Czochralski Technique ◽  
X Ray Diffraction ◽  
X Ray ◽  
First Order ◽  
Expansion Matching ◽  
First Order Phase

Dilatometry, high-temperature x-ray diffraction, differential thermal analysis, and differential scanning calorirmetry have been performed on LaGaO3, NdGaO3, PrGaO3, SmAlO3, and LaAlO3 single crystals grown by the Czochralski technique. First order phase transitions have been located at 145°C for LaGaO3 and 785°C for SmAlO3, and ΔH has been measured for the LaGaO3 transition. Second order transitions have been identified for LaGaO3, PrGaO3, NdGaO3, and LaAlO3. The usefulness of these compounds as substrates for high temperature superconducting films is discussed in terms of thermal expansion matching.

A conformational polymorphic transition in the high-temperature ∊-form of chlorpropamide on cooling: a new ∊′-form

2009 ◽  
Vol 65 (6) ◽  
pp. 770-781 ◽  
Author(s):  
Tatiana N. Drebushchak ◽  
Yury A. Chesalov ◽  
Elena V. Boldyreva
Keyword(s):  
Phase Transition ◽  
High Temperature ◽  
Structural Changes ◽  
Molecular Conformation ◽  
Polymorphic Transition ◽  
X Ray Diffraction ◽  
X Ray ◽  
Cell Parameters ◽  
Temperature Range ◽  
Two Phases

Structural changes in the high-temperature ∊-polymorph of chlorpropamide, 4-chloro-N-(propylaminocarbonyl)benzenesulfonamide, C10H13ClN2O3S, on cooling down to 100 K and on reverse heating were followed by single-crystal X-ray diffraction. At temperatures below 200 K the phase transition into a new polymorph (termed the ∊′-form) has been observed for the first time. The polymorphic transition preserves the space group Pna21, is reversible and is accompanied by discontinuous changes in the cell volume and parameters, resulting from changes in molecular conformation. As shown by IR spectroscopy and X-ray powder diffraction, the phase transition in a powder sample is inhomogeneous throughout the bulk, and the two phases co-exist in a wide temperature range. The cell parameters and the molecular conformation in the new polymorph are close to those in the previously known α-polymorph, but the packing of the z-shaped molecular ribbons linked by hydrogen bonds inherits that of the ∊-form and is different from the packing in the α-polymorph. A structural study of the α-polymorph in the same temperature range has revealed no phase transitions.

Thermal conversion of gels to YBa2Cu3Ox, Bi2Sr2CaCu2Ox, and (Bi, Pb)2Sr2Ca2Cu3Ox and their decarbonization by low-temperature treatment with nitric acid

1996 ◽  
Vol 11 (1) ◽  
pp. 1-4 ◽  
Author(s):  
A. Deptula ◽  
T. Olczak ◽  
W. Lada ◽  
K. C. Goretta ◽  
A. Di Bartolomeo ◽  
...  
Keyword(s):  
Thermal Analysis ◽  
Nitric Acid ◽  
Thermal Treatment ◽  
Thermal Conversion ◽  
Temperature Treatment ◽  
X Ray Diffraction ◽  
X Ray ◽  
Low Temperature Treatment ◽  
Intermediate Phases ◽  
Superconducting Compounds

Thermal conversion of acetate-derived gels to YBa2Cu3Ox (Y–123), Bi2Sr2CaCu2Ox (Bi–2212), and (Bi, Pb)2Sr2Ca2Cu3Ox (Bi-2223) has been studied by thermal analysis, x-ray diffraction, and infrared spectroscopy. Carbonates formed above 200 °C during thermal treatment of all gels. Decomposition of the carbonates proved to be more difficult for Y-123 than for Bi-2212 or Bi-2223. However, all of the gels that were heated contained significant amounts of carbon after calcination. Complete decarbonization of materials was attained by treating the intermediate phases (e.g., those formed after calcination at 600 °C) with nitric acid and then subjecting them to a final thermal treatment. Removal of carbonates from the intermediate phases strongly accelerated formation of the superconducting compounds.

Study on Character of Ilmenite Modified by Thermal Treatment

2011 ◽  
Vol 284-286 ◽  
pp. 2090-2093 ◽  
Author(s):  
Xue Liang Xiong ◽  
Zhi Yang ◽  
Hong Yong Ouyang
Keyword(s):  
Thermal Analysis ◽  
Solid Solution ◽  
Differential Thermal Analysis ◽  
Thermal Treatment ◽  
Oxidation Temperature ◽  
X Ray Diffraction ◽  
Thermo Gravimetric ◽  
X Ray

The character of ilmenite was modified by pretreatment, the effect of pre-oxidation temperature and time on structure of ilmenite were investigated by X-ray diffraction(XRD) and Thermo-gravimetric/differential thermal analysis. The results indicated that new microcrystal rutile and FeTiO3·Fe2O3 solid solution were appeared on the surface of mineral below 800°C, but evident rutile crystals and pseudobrookite Fe2O3·TiO2 were appeared above 850°C with the structure of ilmenite disrupting simultaneously. The preoxidation time increased from 15min to 60min, evident microcrystal rutile and FeTiO3·Fe2O3 solid solution were appeared by degrees without structure of ilmenite breaking.

The Study of High Temperature Annealing of a-SiC:H Films

2006 ◽  
Vol 514-516 ◽  
pp. 18-22
Author(s):  
Shibin Zhang ◽  
Z. Hu ◽  
Leandro Raniero ◽  
X. Liao ◽  
Isabel Ferreira ◽  
...  
Keyword(s):  
High Temperature ◽  
Chemical Vapor ◽  
Nitrogen Atmosphere ◽  
High Temperature Annealing ◽  
X Ray Diffraction ◽  
X Ray ◽  
Metal Induced Crystallization ◽  
Vapor Deposition Technique ◽  
Crystallization Effect ◽  
Induced Crystallization

A series of amorphous silicon carbide films were prepared by plasma enhanced chemical vapor deposition technique on (100) silicon wafers by using methane, silane, and hydrogen as reactive resources. A very thin (around 15 Å) gold film was evaporated on the half area of the a- SiC:H films to investigate the metal induced crystallization effect. Then the a-SiC:H films were annealed at 1100 0C for 1 hour in the nitrogen atmosphere. Fourier transform infrared spectroscopy (FTIR), X-Ray diffraction (XRD), and scanning electron microscopy (SEM) were employed to analyze the microstructure, composition and surface morphology of the films. The influences of the high temperature annealing on the microstructure of a-SiC:H film and the metal induced metallization were investigated.

Boron Carbide-Based Ceramics Via Polymer Route Synthesis

1991 ◽  
Vol 249 ◽  
Author(s):  
Haixing Zheng ◽  
Kevin Thorne ◽  
J.D. Mackenzie ◽  
Xiaoguang Yang ◽  
M.F. Hawthome
Keyword(s):  
Thermal Analysis ◽  
Infrared Spectroscopy ◽  
High Temperature ◽  
Nmr Spectroscopy ◽  
Physical Properties ◽  
Boron Carbide ◽  
X Ray Diffraction ◽  
Polymeric Precursors ◽  
X Ray ◽  
Crystalline Boron

ABSTRACTBoron carbide is a ceramic material with excellent high temperature physical properties. As compared to conventional techniques, the preparation of boron carbide from polymeric precursors is attractive as this technique offers a number of unique advantages. In this paper, the screening of polymeric precursors to boron carbide will be discussed. Two promising boron carbide, carborane containing polymeric precursors have resulted in 60-70 wt.% ceramic yields. The chemistry of polymer synthesis and the transformations from the polymer to amorphous and crystalline boron carbide were investigated with infrared spectroscopy, NMR spectroscopy, thermal analysis, and x ray diffraction.

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