scholarly journals The Effects of Trace Metal Cations on the High Temperature Reactions of an Halloysite Mineral

2021 ◽  
Author(s):  
◽  
Susan Margaret Maciver
Keyword(s):  
Experimental Data ◽  
High Temperature ◽  
Rate Constants ◽  
Theoretical Models ◽  
Solid State Reactions ◽  
Free Energies ◽  
Reaction Sequence ◽  
X Ray ◽  
Sodium Calcium ◽  
High Temperature Reactions

<p>This thesis describes a kinetic study of the high temperature solid state reactions of a well characterized halloysite mineral and five of its cation-saturated forms, the cations used being sodium, calcium, manganese, copper and iron (Ill). The reaction sequence may be represented by the idealised equations: The formation of mullite from metakaolinite has been studied in the temperature range 1020° - 1200°C, by X-ray analysis. Comparison of the experimental data with several theoretical models suggests that up to 90% conversion the reaction takes place by exponential nucleation followed by crystal growth. There is, however, some evidence for diffusion occurring as a rate controlling process, especially at high degrees of conversion to mullite. The rate constants and experimental thermodynamic functions have been evaluated for all halloysite samples. The free energies of activation (111-128 k cal.mole-1) and the rate constants are independent of the starting materials, but the enthalpies of activation (51-118 k cal.mole-1) and the entropies of activation (0 to -50 cal.deg.-1 mole-1) are not.</p>

scholarly journals The Effects of Trace Metal Cations on the High Temperature Reactions of an Halloysite Mineral

2021 ◽  
Author(s):  
◽  
Susan Margaret Maciver
Keyword(s):  
Experimental Data ◽  
High Temperature ◽  
Rate Constants ◽  
Theoretical Models ◽  
Solid State Reactions ◽  
Free Energies ◽  
Reaction Sequence ◽  
X Ray ◽  
Sodium Calcium ◽  
High Temperature Reactions

<p>This thesis describes a kinetic study of the high temperature solid state reactions of a well characterized halloysite mineral and five of its cation-saturated forms, the cations used being sodium, calcium, manganese, copper and iron (Ill). The reaction sequence may be represented by the idealised equations: The formation of mullite from metakaolinite has been studied in the temperature range 1020° - 1200°C, by X-ray analysis. Comparison of the experimental data with several theoretical models suggests that up to 90% conversion the reaction takes place by exponential nucleation followed by crystal growth. There is, however, some evidence for diffusion occurring as a rate controlling process, especially at high degrees of conversion to mullite. The rate constants and experimental thermodynamic functions have been evaluated for all halloysite samples. The free energies of activation (111-128 k cal.mole-1) and the rate constants are independent of the starting materials, but the enthalpies of activation (51-118 k cal.mole-1) and the entropies of activation (0 to -50 cal.deg.-1 mole-1) are not.</p>

Extracting hydrophobic free energies from experimental data: relationship to protein folding and theoretical models

Biochemistry ◽  
1991 ◽  
Vol 30 (40) ◽  
pp. 9686-9697 ◽  
Author(s):  
Kim A. Sharp ◽  
Anthony Nicholls ◽  
Richard Friedman ◽  
Barry Honig
Keyword(s):  
Experimental Data ◽  
Protein Folding ◽  
Theoretical Models ◽  
Free Energies

Niobium-bearing arsenides and germanides from elemental mixtures not involving niobium: a new twist to an old problem in solid-state synthesis

2018 ◽  
Vol 74 (5) ◽  
pp. 623-627 ◽  
Author(s):  
Sviatoslav Baranets ◽  
Hua He ◽  
Svilen Bobev
Keyword(s):  
High Temperature ◽  
Solid State ◽  
Diffraction Data ◽  
Alkaline Earth ◽  
Alkaline Earth Metals ◽  
X Ray Diffraction ◽  
X Ray ◽  
High Temperature Reactions ◽  
First Time ◽  
Synthetic Work

Three isostructural transition-metal arsenides and germanides, namely niobium nickel arsenide, Nb0.92(1)NiAs, niobium cobalt arsenide, NbCoAs, and niobium nickel germanide, NbNiGe, were obtained as inadvertent side products of high-temperature reactions in sealed niobium containers. In addition to reporting for the very first time the structures of the title compounds, refined from single-crystal X-ray diffraction data, this article also serves as a reminder that niobium containers may not be suitable for the synthesis of ternary arsenides and germanides by traditional high-temperature reactions. Synthetic work involving alkali or alkaline-earth metals, transition or early post-transition metals, and elements from groups 14 or 15 under such conditions may yield Nb-containing products, which at times could be the major products of such reactions.

Über eine neue Präparationstechnik in der Feststoffchemie, I Hochtemperatursynthesen mit CO2-Laser / A New Preparation Technique in Solid State Chemistry, I High Temperature Reactions with CO2-Laser

1979 ◽  
Vol 34 (3) ◽  
pp. 371-374 ◽  
Author(s):  
Hk. Müller-Buschbaum ◽  
H. Pausch
Keyword(s):  
High Temperature ◽  
Laser Radiation ◽  
Solid State ◽  
Co2 Laser ◽  
Solid State Reactions ◽  
Solid State Chemistry ◽  
Preparation Technique ◽  
Temperature Method ◽  
High Temperature Reactions

Abstract A new high temperature method using a CO2-Laser radiation is reported. Its application on solid state reactions in air or in defined gas atmospheres is described.

Ein gemischtvalentes Oxometallat mit Cr3+ anstelle von Ti3+: Ba2Ti44+Cr2O13 / A Mixed Valent Oxometallate with Cr3+ Instead of Ti3+ Ba2Ti44+ Cr2O13

1994 ◽  
Vol 49 (7) ◽  
pp. 911-914 ◽  
Author(s):  
S. Möhr ◽  
Keyword(s):  
Crystal Structure ◽  
High Temperature ◽  
Single Crystals ◽  
Lattice Energy ◽  
Structure Type ◽  
Oxidation States ◽  
X Ray ◽  
High Temperature Reactions ◽  
The Stability

Abstract Single crystals of Ba2Ti3+Cr2Oi3 were prepared by C02-LASER high temperature reactions and investigated by X-ray work. The compound crystallizes with monocli­nic symmetry, a = 15.0185, b = 3.9419, c = 9.0764 Å. β = 98.137°, Z = 2. Ba2Ti4Cr2O13 is isotypic to Na2Ti6O13. The crystal structure is discussed with respect to ordered or disordered distributions of Ti4+ and Cr3+ using calculations of Coulomb terms of lattice energy. It is shown, that the stability of this structure type will be decre­ased by replacement of Na+ by ions with higher oxidation states.

In situsynchrotron powder diffraction study of active belite clinkers

2007 ◽  
Vol 40 (6) ◽  
pp. 999-1007 ◽  
Author(s):  
Ángeles G. De la Torre ◽  
Khadija Morsli ◽  
Mohammed Zahir ◽  
Miguel A.G. Aranda
Keyword(s):  
High Temperature ◽  
High Resolution ◽  
Powder Diffraction ◽  
Polymorphic Transformation ◽  
High Energy ◽  
Dicalcium Silicate ◽  
Polymorphic Transformations ◽  
X Ray ◽  
High Temperature Reactions

The clinkerization processes to form belite clinkers, with theoretical compositions close to 60 wt% of Ca2SiO4, have been studiedin situby high-resolution high-energy (λ = 0.30 Å) synchrotron X-ray powder diffraction. In order to obtain active belite cements, different amounts of K2O, Na2O and SO3have been added. The existence range of the high-temperature phases has been established and, furthermore, Rietveld quantitative phase analyses at high temperature have been performed for all patterns. The following high-temperature reactions have been investigated: (i) polymorphic transformations of dicalcium silicate, \alpha_{\rm L}'-Ca2SiO4↔ \alpha_{\rm H}'-Ca2SiO4from 1170 to 1230 K, and \alpha_{\rm H}'-Ca2SiO4↔ α-Ca2SiO4from 1500 to 1600 K; (ii) melting of the aluminates phases, Ca3Al2O6and Ca4(Al2Fe2)O10, above ∼1570 K; and (iii) reaction of Ca2SiO4with CaO to yield Ca3SiO5above ∼1550 K. Moreover, in all the studied compositions the temperature of the polymorphic transformation \alpha_{\rm H}'-Ca2SiO4↔ α-Ca2SiO4has decreased with the addition of activators. Finally, active belite clinkers were produced as the final samples contained α-belite phases.

scholarly journals Einkristall-Röntgenstrukturanalyse von Ba3CeIVRu2IVO9, Ba3LnIII,Ru2IV/VO9 (Ln = Sm, Dy, Er) und Ba3Ti2,4Ru0,6O9 / Single Crystal X-Ray Analysis of Ba3CeIVRu2IVO9, Ba3LnIII,Ru2IV/VO9 (Ln = Sm, Dy, Er) and Ba3Ti2,4Ru0,6O9

1996 ◽  
Vol 51 (1) ◽  
pp. 79-84 ◽  
Author(s):  
Hk. Müller-Buschbaum ◽  
B. Mertens
Keyword(s):  
High Temperature ◽  
Lattice Energy ◽  
Solid State Reactions ◽  
Hexagonal Symmetry ◽  
X Ray ◽  
Valence States ◽  
Group D ◽  
Symmetry Space ◽  
Perovskite Type ◽  
Symmetry Space Group

Single crystals of (I) Ba3CeRu2O9, (II) Ba3SmRu2O9, (III) Ba3DyRu2O9, (IV) Ba3ErRu2O9 and (V) Ba3Ti2 4Ru0,6O9 have been prepared by high temperature solid state reactions. The compounds were examined by X-ray techniques. They crystallize with hexagonal symmetry, space group D46h-P63/mmc with (I): a = 5.8738(7), c = 14.585(4); (II): a = 5.9137(5), c = 14.651(2); (III): a = 5.8805(5), c = 14.506(1); (IV): a = 5.8737(9), c = 14.470(3); (V): a = 5.7265(6), c = 14.006(2) Å, Z = 2. The crystal structures belong to the 6 L-perovskite type. Calculations of the Coulomb terms of the lattice energy led to the valence states (I): CeIV/RuIV and (II)-(IV): LnIII,/RuIV/V. (V) shows a partial statistic distribution of TiIV and RuIV.

X-ray powder diffraction data for rhombohedral AlPt

2006 ◽  
Vol 21 (4) ◽  
pp. 318-319
Author(s):  
Mark A. Rodriguez ◽  
David P. Adams
Keyword(s):  
Thin Film ◽  
High Temperature ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Lattice Parameter ◽  
Unit Cell ◽  
Powder Diffraction Data ◽  
Space Group ◽  
X Ray ◽  
High Temperature Reactions

X-ray powder diffraction data for a rhombohedral AlPt phase formed by self-propagating, high-temperature reactions of Al∕Pt bi-layer films are reported. Multilayer Al∕Pt thin film samples, reacted in air or vacuum, transformed into rhombohedral AlPt with space group R-3(148). Indexing and lattice parameter refinement of AlPt powders (generated from thin-film samples) yielded trigonal/hexagonal unit-cell lattice parameters of a=15.623(6) Å and c=5.305(2) Å, Z=39, and V=1121.5 Å3.

Annealing induced structural changes and microcracking in Mo-Mo3Si

2002 ◽  
Vol 753 ◽  
Author(s):  
X.-L. Wang ◽  
J. H. Schneibel ◽  
Y. D. Wang ◽  
J. W. Richardson
Keyword(s):  
Electron Microscopy ◽  
Experimental Data ◽  
High Temperature ◽  
Structural Changes ◽  
Thermal Stresses ◽  
Annealing Temperature ◽  
Composition Analysis ◽  
X Ray Diffraction ◽  
X Ray ◽  
Scanning Electron

ABSTRACTCast Mo-Mo3Si intermetallic composites develop microcracks after annealing at high temperature. Neutron diffraction, x-ray diffraction, composition analysis, and scanning electron microscopy have been used to characterize the structural changes induced by annealing of Mo-Mo3Si. It is shown that the observed cracking cannot be attributed to differential thermal stresses that developed on cooling from the annealing temperature. Instead, the experimental data suggest that the cracks were initiated at high temperature, possibly due to diffusion of Si atoms from supersaturated α-Mo to Mo3Si.

Failure Analysis of Burner Muffle in Shell Gasifier

2014 ◽  
Author(s):  
Wen Liu ◽  
Jin Shi ◽  
Qiuping Chen ◽  
Guoshan Xie ◽  
Yufeng Zhou ◽  
...  
Keyword(s):  
Experimental Data ◽  
High Temperature ◽  
Failure Analysis ◽  
Structural Study ◽  
Cooling Water ◽  
Optical Microscope ◽  
Current Work ◽  
Economic Losses ◽  
X Ray Diffraction ◽  
X Ray

The failure of burner muffles in shell gasifiers has been a common problem, which directly leads to unexpected shutdown in operation of the gasifier and huge economic losses for the factory. Therefore, the experiment of the failure analysis to the burner muffle was conducted in the current work. The microstructure of the burner muffle after failure was measured by means of optical microscope, SEM (scanning electro-microscope) and X-ray diffraction. The reason of failure was obtained based on the analysis of experimental data together with the structural study of the gasifier. It is indicated that the failure of burner muffle is accounted for slag overflow and “backfire”, which lead to local temperature increasing. Cooling water tubes of Burner muffle were partially melted due to oxidation and sulphidation at high temperature, resulting into water leaks.

Sign in / Sign up

Export Citation Format

Share Document