CHROMIAN SPINEL AS A PETROGENETIC INDICATOR: PART 1. THEORY

1965 ◽  
Vol 2 (6) ◽  
pp. 648-672 ◽  
Author(s):  
T. N. Irvine
Keyword(s):  
General Formula ◽  
Cross Section ◽  
Solid Solutions ◽  
Chromian Spinel ◽  
Triangular Prism ◽  
Chemical Analyses ◽  
Calorimetric Data ◽  
Activity Ratios ◽  
Petrogenetic Indicator ◽  
Spinel Solid Solutions

Previous investigators have shown that natural chromium-bearing spinel solid solutions adhere closely to the general formula (Mg, Fe++) (Cr, Al, Fe+++)2O4 and may therefore be graphically portrayed in a triangular prism, the length of which represents the ratios MgO/FeO, and the cross section the relative proportions of Cr2O3, Al2O3, and Fe2O3. In this paper, theoretical expressions are derived whereby the prism may be "contoured" for conditions of isothermal–isobaric equilibrium according to (a) the spinel compositions that may coexist with olivine or pyroxene having specific MgO/FeO ratios; (b) the activity ratios of Cr/Al, Cr/Fe+++, or Al/Fe+++ that obtain in the environments in which the spinel solid solutions form, and (c) the oxygen fugacities that accompany formation of spinel in systems containing olivine (forsterite–fayalite) and orthopyroxene (enstatite–ferrosilite). Rough "working" values for the thermochemical coefficients involved are estimated from limited calorimetric data and chemical analyses of spinel–olivine and spinel–orthopyroxene pairs.

The Coordination Chemistry of Phosphoryl Compounds Containing the — N(CH3)2 Group, Part VIII

1972 ◽  
Vol 27 (7) ◽  
pp. 759-763 ◽  
Author(s):  
M. W. G. De Bolster ◽  
W. L. Groeneveld
Keyword(s):  
Coordination Chemistry ◽  
General Formula ◽  
Ligand Field ◽  
Chemical Analyses ◽  
X Ray ◽  
Physical Measurements ◽  
Ligand Field Spectra ◽  
Chloride Adduct ◽  
Ligand Field Parameters ◽  
Group Part

A number of new solvates and adducts containing bisphenyldimethylaminophosphine oxide is reported. The solvates have the general formula M[(C6H5)2P(O)N(CH3)2]42+(anion-)2, in which M = Mg, Ca, Mn, Fe, Co, Ni, Cu, Zn and Cd, and the anions are ClO4- and BF4-. The adducts have the general formula M[(C6H5)2P(O)N(CH3)2]2Cl2, where M stands for the same series of metals.The compounds are characterized and identified by chemical analyses and physical measurements.Ligand-field and vibrational spectra have been investigated; values for the ligand-field parameters are reported. It is concluded that coordination takes place via the oxygen atom of the ligand.X-ray powder patterns were used in combination with ligand-field spectra to deduce the coordination around the metal ions.The interesting behaviour of the nickel (II) chloride adduct upon heating is discussed and it is shown that both a square pyramidal and a tetrahedral modification exists.

scholarly journals Some Aspects of Spinodal Decomposition in Spinel Solid Solutions

1995 ◽  
Vol 50 (6) ◽  
pp. 525-532
Author(s):  
N. Burkert ◽  
R. Grüne ◽  
H. Schmalzried ◽  
S. Rahman
Keyword(s):  
Spinodal Decomposition ◽  
Solid Solutions ◽  
Common Property ◽  
Transport Theory ◽  
Decomposition Reaction ◽  
Sufficient Evidence ◽  
Spinel Crystal ◽  
Linear Transport Theory ◽  
Spinel Solid Solutions ◽  
Quasi Binary System

Abstract Decomposition morphologies of supersaturated spinel solid solutions in the quasi-binary system Co2TiO4-CoAl2O4 at 973 K show all pertinent features of spinodal decomposition. Since the decomposition morphology may not be considered as sufficient evidence for a spinodal process, the thermodynamics of the spinel solid solutions and the linear transport theory of spinodal decomposition were combined to corroborate the experimental results of the early decomposition reaction.Simultaneous ordering, a common property of ternary and higher nonequilibrium solid solutions, was also observed. These ordering processes occur locally in distinct regions of the spinel crystal. Moreover, the spinodal wavelength λ increases in time according to λ ∞ t, which is unusual and will be discussed in the light of cation diffusion in semiconducting oxides with two cation sublattices.

scholarly journals Clinopyroxene Solid Solutions in the CaMgSi2O6 – Ca0,5AlSi2O6 Cross-Section at High P-T Parameters

2020 ◽  
Vol 34 ◽  
pp. 37-54
Author(s):  
S. V. Banushkina ◽  
◽  
A. I. Turkin ◽  
A. I. Chepurov ◽  
◽  
...  
Keyword(s):  
Cross Section ◽  
Solid Solutions ◽  
Atmospheric Pressure ◽  
High Pressures ◽  
Experimental Investigations ◽  
Electric Resistance ◽  
Resistance Furnace ◽  
Mineral Association ◽  
Electric Resistance Furnace ◽  
Piston Cylinder

Clinopyroxenes (Cpx) are one of the main rock-forming minerals, but stoichiometry of their compositions was called into question. In particular, an idea of hypothetical calcium molecule Eskola (CaEs, Ca0,5AlSi2O6) existence was expressed. This minal has structure vacancy and silica excess. Numerous experimental investigations in CMAS-system (CaO-MgO-Al2O3-SiO2) have showed that the question of non-stoichiometric Cpx existence remains open. This paper presents the results of an experimental study of the diopside Di (CaMgSi2O6) – calcium molecule Eskola CaEs (Ca0,5AlSi2O6) cross-section in the CMAS-system. The experiments were carried out in the following pressure and temperature range: P=10-4 – 3,0 GPa; T=966 – 15250C. Experiments at atmospheric pressure (10-4 GPa) were performed on a vertical shaft electric resistance furnace; high-pressure ones were performed on a "piston-cylinder" type apparatus. Samples obtained were analyzed using electron microprobe (EMP), scanning electron microscope (SEM) and Raman spectrometer. Depending on the P-T conditions, the samples contain the following phases: anorthite An, garnet Grt, diopside Di, clinopyroxene Cpx, quartz Qtz (tridymite Tr – for experiments at atmospheric pressure), and glass L. The data array on the composition of clinopyroxenes crystallized in this cross-section with diopside in various associations is generalized and supplemented. Clinopyroxenes were found to form quaternary solid solutions of diopside Di (CaMgSi2O6) – enstatite En (Mg2Si2O6) – calcium molecule Tschermak CaTs (CaAl2SiO6) – calcium molecule Eskola CaEs (Ca0,5AlSi2O6). The CaTs and CaEs minals contents are positively correlated with the amount of aluminum in clinopyroxene, and this relationship is particularly pronounced for CaTs. It is confirmed that clinopyroxenes in this cross-section can contain an excess of silica at both atmospheric and high pressures. Apparently, the cation vacancy that exists in pyroxene structure can participate in ordering processes. As a result the pyroxenes of another structure (not diopside – C2/c-symmetry) can be crystallized from total compositions in the Di-CaEs cross-section. Additional research is needed to support this hypothesis. Besides, at present investigation it was not possible to establish an unambiguous relationship between the Cpx composition and P-T-parameters, since it is also associated with both the mixture initial composition and the mineral association. Further experiments are required to justify any geothermobarometric dependence.

scholarly journals ABO4 type scheelite phases in (Ca/Sr)MoO4 - BiVO4 - Bi2Mo3O12 systems: synthesis, structure and optical properties

2021 ◽  
Vol 8 (2) ◽  
pp. 20218204
Author(s):  
Z. A. Mikhaylovskaya ◽  
E. S. Buyanova ◽  
S. A. Petrova ◽  
A. V. Klimova
Keyword(s):  
Optical Properties ◽  
Solid State ◽  
General Formula ◽  
Solid Solutions ◽  
Triple System ◽  
Complex Oxides ◽  
Vanadium Content ◽  
Energy Gaps ◽  
Munk Function ◽  
State Technique

The cation deficient complex oxides of (Ca/Sr)MoO4 - BiVO4 - Bi2Mo3O12 triple system are promising photocatalysts and pigments. Compounds with general formula of Ca1−1.5x-yBix+yФxMo1-yVyO4  and Sr1−1.5x-yBix+yФxMo1-yVyO4 were synthesized byconvention solid state technique in the range of 550–720 °C. Two wide regions of the solid solutions (ordinary and superstructured scheelite-type phases respectively) were found for each system. The diffuse scatering of homogeneous samples was investigated in the range of 190–1100 nm. Energy gaps calculated with linear approximation of Kubelka-Munk function decreases with bismuth and vanadium content.

XXXIII.—Applications of Elliptic Functions to Wind Tunnel Interference

1948 ◽  
Vol 62 (3) ◽  
pp. 316-318
Author(s):  
L. M. Milne-Thomson
Keyword(s):  
Wind Tunnel ◽  
General Formula ◽  
Cross Section ◽  
Elliptic Functions ◽  
Focal Distance ◽  
Jacobian Elliptic Functions

SummaryA general formula is obtained for the interference velocity when an aerofoil with elliptically distributed circulation is in a closed or open wind tunnel of any cross-section. The mapping of the section on the interior of a circle is given in terms of the Jacobian elliptic functions appropriate to the ellipse and rectangle. The result is worked out for an aerofoil which spans the focal distance in a tunnel whose section is an ellipse.

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