THE HYDRATION OF THE ALUMINATES OF CALCIUM: III. THE HYDRATION OF THE 5:3, 1:1, AND 3:5 CALCIUM ALUMINATES

1943 ◽  
Vol 21b (2) ◽  
pp. 34-42 ◽  
Author(s):  
W. G. Schneider ◽  
T. Thorvaldson
Keyword(s):  
Refractive Index ◽  
Water Absorption ◽  
Anisotropic Material ◽  
Quantitative Estimation ◽  
Saturated Steam ◽  
Hydrated Alumina ◽  
Tricalcium Aluminate ◽  
Calcium Aluminates ◽  
End Products ◽  
Rapid Hydrolysis

The hydration of the aluminates of calcium in saturated steam at 150° and 105 °C. was studied. A method was developed for the quantitative estimation of chemically combined and free hydrated alumina in steam treated mixtures. The rates of hydration at 150 °C. of all the aluminates of calcium were compared. At 150 °C., when conditions favouring- rapid hydrolysis are avoided, the 1:1 and 3:5 lime aluminates are apparently transformed almost quantitatively to the cubic hexahydrate of tricalcium aluminate and hydrated alumina approaching the composition of the monohydrate. The steam treated 5:3 lime aluminate gives lower water absorption and higher content of combined alumina than called for by the above end-products, indicating the formation of a less highly hydrated aluminate of lower lime–alumina ratio than the hexahydrate of tricalcium aluminate. This conclusion is supported by the presence in this product of some anisotropic material with an average refractive index of 1.58. The hydrothermal products obtained on treatment of the three aluminates at 105 °C. all contained larger amounts of this birefringent material and apparently a greater proportion of combined alumina.

THE HYDRATION OF THE ALUMINATES OF CALCIUM: IV. HYDROTHERMAL REACTIONS OF TRICALCIUM ALUMINATE AND ITS HYDRATES

1943 ◽  
Vol 21b (4) ◽  
pp. 65-72 ◽  
Author(s):  
G. M. Harris ◽  
W. G. Schneider ◽  
T. Thorvaldson
Keyword(s):  
Calcium Hydroxide ◽  
Rectangular Plate ◽  
Hydrothermal Treatment ◽  
Saturated Steam ◽  
Partial Hydrolysis ◽  
Portland Cement Concrete ◽  
Steam Curing ◽  
Hydrated Alumina ◽  
Hydrothermal Reactions ◽  
Tricalcium Aluminate

A study was made of the hydrothermal reactions of tricalcium aluminate and its hydrates between 120° and 350 °C. Homogeneous samples of the hexahydrate of tricalcium aluminate may be prepared by treatment of the aluminate or its hexagonal hydrate in saturated steam at temperatures up to 150 °C. At temperatures of 250 °C. and above, under conditions favouring rapid hydrolysis, such as the addition of water to the anhydrous aluminate or hydroaluminate before autoclaving and rapid elevation of the temperature of the autoclave, crystals of calcium hvdroxide and of a hydroaluminate of lower lime–alumina ratio appear, usually mixed with the isometric hexahydrate. The new hydroaluminate occurs as rectangular, elongated, prismatic plates of low birefringence, refractive index 1.627, and has a lime–alumina ratio probably lower than 1.5. The hexagonal hydrate of tricalcium aluminate gives on hydrothermal treatment a better yield of the low-limed hydroaluminate than does the anhydrous aluminate. Only partial hydrolysis of the hexahydrate was obtained under any of the conditions used, but the hexagonal hydrate, autoclaved for 12 hr. at 350 °C., gave products composed almost entirely of the rectangular plate hydroaluminate and calcium hydroxide. No free hydrated alumina was found in the hydrothermal products.The rectangular plate hydroaluminate of calcium may also be prepared by the action of calcium hydroxide on hydrated alumina in saturated steam at 350 °C. It is therefore a stable product under those conditions.At temperatures below 250 °C. birefringent crystalline material is also formed on autoclaving tricalcium aluminate or its hydrates under conditions favouring hydrolysis. The experimental evidence indicates that one of the products is the birefringent calcium hydroaluminate formed on autoclaving the lower calcium aluminates at temperatures of 105 to 150 °C. (5).Precast Portland cement concrete products, when subjected to steam-curing, normally contain an excess of water, and the conditions for the formation of these birefringent hydroaluminates of calcium are therefore present. The same applies to the commercial steam-curing of other materials containing free lime and hydrated alumina. The formation of these hydroaluminates may explain the peculiar effect on the tensile and compressive strength of mortar and concrete test pieces produced by hydrothermal treatment at temperatures above 150 °C. (9).

THE HYDRATION OF THE ALUMINATES OF CALCIUM: V. THE HYDROTHERMAL DECOMPOSITION PRODUCTS OF TRICALCIUM ALUMINATE AT 350 °C.

1943 ◽  
Vol 21b (11) ◽  
pp. 236-246 ◽  
Author(s):  
Herbert Johnson ◽  
Thorbergur Thorvaldson
Keyword(s):  
Calcium Hydroxide ◽  
Saturated Steam ◽  
Rectangular Plates ◽  
Hydrated Alumina ◽  
Decomposition Products ◽  
Factors Affecting ◽  
X Ray ◽  
Crystalline Product ◽  
Tricalcium Aluminate ◽  
Lower Temperature

When tricalcium aluminate is treated in saturated steam at 350 °C. hydrolysis occurs with the formation of a crystalline product of the composition 4CaO.3Al2O3.3H2O and calcium hydroxide. The same products result when a 3:1 mixture of calcium hydroxide and hydrated alumina are similarly treated. The calcium hydroxide as well as any hexahydrate of tricalcium aluminate formed at lower temperature may be removed from the hydrothermal product by extraction with a solution of acetic acid buffered with calcium acetate.The 4:3:3 calcium hydroaluminate crystallizes in colourless elongated rectangular plates with parallel extinction, positive elongation, and low birefrigence. The average refractive index is close to 1.627 and the density 2.71 (at 20 °C). The crystals are probably orthorhombic.Appreciable dehydration of the product does not occur on heating below 475° to 500 °C. Dehydration between 650° and 750 °C. in a stream of dry air appears to produce decomposition with the liberation of free alumina and probable formation of the product 12Ca0.7Al2O3.The factors affecting the yield of the 4:3:3 calcium hydroaluminate and the mechanism of the hydrothermal reactions of tricalcium aluminate and its hydrates are discussed. Readings of X-ray powder patterns of the 4:3:3 hydroaluminate and its dehydration products are given.

Water absorption in a refractive index model for bacterial spores

2009 ◽  
Author(s):  
K. M. Siegrist ◽  
E. Thrush ◽  
M. Airola ◽  
A. K. Carr ◽  
D. M. Limsui ◽  
...  
Keyword(s):  
Refractive Index ◽  
Water Absorption ◽  
Bacterial Spores ◽  
Index Model

scholarly journals Synthesis of Calcium Aluminates from Non-Saline Aluminum Dross

Materials ◽  
2019 ◽  
Vol 12 (11) ◽  
pp. 1837 ◽  
Author(s):  
Félix Antonio López ◽  
María Isabel Martín ◽  
Francisco José Alguacil ◽  
Mario Sergio Ramírez ◽  
José Ramón González
Keyword(s):  
Electron Microscopy ◽  
Milling Time ◽  
Molar Ratio ◽  
Mass Ratio ◽  
X Ray Diffraction ◽  
Reactive Milling ◽  
Tricalcium Aluminate ◽  
Transmission Electron ◽  
Calcium Aluminates ◽  
Relationship Of

The present work examines the synthesis of tricalcium aluminate (for use as a synthetic slag) from the non-saline dross produced in the manufacture of metallic aluminum in holding furnaces. Three types of input drosses were used with Al2O3 contents ranging from 58 to 82 wt %. Calcium aluminates were formed via the mechanical activation (reactive milling) of different mixtures of dross and calcium carbonate, sintering at 1300 °C. The variables affecting the process, especially the milling time and the Al2O3/CaO molar ratio, were studied. The final products were examined via X-Ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. The reactive milling time used was 5 h in a ball mill, for a ball/dross mass ratio of 6.5. For a molar relationship of 1:3 (Al2O3/CaO), sintered products with calcium aluminate contents of over 90% were obtained, in which tricalcium aluminate (C3A) was the majority compound (87%), followed by C12A7 (5%).

Complex Refractive Index Determination for Uniaxial Anisotropy with the Use of Kramers—Kronig Analysis

1997 ◽  
Vol 51 (9) ◽  
pp. 1287-1293 ◽  
Author(s):  
Kiyoshi Yamamoto ◽  
Hatsuo Ishida
Keyword(s):  
Refractive Index ◽  
Anisotropic Material ◽  
Total Internal Reflection ◽  
Optical Axis ◽  
Complex Refractive Index ◽  
Uniaxial Anisotropy ◽  
Refractive Indices ◽  
Reflection Spectra ◽  
Dispersion Theory ◽  
Single Interface

Kramers—Kronig analysis of reflection spectra from a single interface with perpendicular ( s) and parallel ( p) polarization has been theoretically studied. The reflection spectra have been simulated from the complex refractive indices based on dispersion theory by using Fresnel equations for an anisotropic material whose optical axis is normal to the surface. The errors in anisotropic complex refractive indices obtained from simulated reflection spectra by Kramers—Kronig analysis have been examined for such techniques as external and total internal reflection spectroscopies.

Properties of Clay Ceramic Incorporated with Red Mud

2014 ◽  
Vol 798-799 ◽  
pp. 509-513 ◽  
Author(s):  
Michelle Pereira Babisk ◽  
Thalissa Pizetta Altoé ◽  
Henrique Junio de Oliveira Lopes ◽  
Ulisses Soares do Prado ◽  
Monica Castoldi Borlini Gadioli ◽  
...  
Keyword(s):  
Titanium Dioxide ◽  
Water Absorption ◽  
Red Mud ◽  
Raw Materials ◽  
Linear Shrinkage ◽  
Insoluble Residue ◽  
Technological Properties ◽  
Calcium Aluminates ◽  
Clay Ceramics ◽  
Related Compounds

The red mud is a well known insoluble residue generated in the Bayer process to benefit bauxite ores. This residue is composed of ceramic related compounds such as iron oxide, sodium aluminum silicates, carbonates, calcium aluminates and titanium dioxide. The incorporation of industrial residues in clay ceramics has been extensively investigated, not only as an environmentally correct solution but also as an economic way to save raw materials. Therefore, the present work evaluated the properties of clay ceramics incorporated with up to 40 wt% of red mud. Clay bodies with different percentages of red mud were press-molded and fired at 750, 950 and 1050°C. The evaluated technological properties were linear shrinkage, water absorption and mechanical strength. Sensible changes in such properties were found with red mud addition. In particular, the ceramic fired at 1050°C displayed favorable water absorption with red mud incorporation.

Synthesis and Characterization by Ellipsometry of Cationic Membranes for Fuel Cells

2018 ◽  
Vol 930 ◽  
pp. 625-630 ◽  
Author(s):  
Bárbara Luiza Silva Cadinelli ◽  
F.C. do Nascimento ◽  
T.A.A. Faria ◽  
L.M. Freire ◽  
Ladario da Silva ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Refractive Index ◽  
Citric Acid ◽  
Water Absorption ◽  
Phthalic Acid ◽  
Electrochemical Impedance ◽  
Poly Vinyl Alcohol ◽  
Assay Condition ◽  
Swelling Degree ◽  
Order Of Magnitude

In this study, cationic membranes based on poly (vinyl alcohol) (PVA) were synthesized, crosslinked with citric acid (carboxylic group) and 4-sulpho-phthalic acid (sulphonic group) for application as proton-conducting membranes of H3O+. The membranes were prepared from the mixture of PVA with the crosslinking agents (CA), previously dissolved and separated with the mixture of these. The CAs proportions used were 10%, 30% and 50%, based on the weight of PVA, and they were crosslinked at the temperatures of 120oC and 140oC. The films were characterized by thermal stability using TGA, spectroscopy ellipsometry (relative refractive index and real part of dielectric constant), swelling degree (water absorption) and conductivity, using electrochemical impedance spectroscopy (EIS). A variation in the refractive index as a function of CA concentration was observed. This fact was corroborated with the results of dielectric constant, because the higher concentration of hydrophilic group added to the film, higher the values of dielectric constant. The membranes which showed lowest swelling degree values were crosslinked with 4-sulpho-phthalic acid (sulphonic group), for example, the PVA membrane crosslinked with 50% of 4-sulpho-phtalic acid, at 140oC, showed 6.4% of water absorption, while the membrane PVA crosslinked with the same content of CA, but of citric acid, and temperature, presented 15.8%. The conductivity of some membranes, under the assay condition evaluated, was the same order of magnitude as the commercial membranes, Nafion®. The synthesized membranes have been showing potential application as cationic polymer membranes for the transport of H3O+.

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