THE ACTION OF SATURATED STEAM ON DICALCIUM FERRITE AND ON TETRACALCIUM ALUMINOFERRITE

1937 ◽  
Vol 15b (8) ◽  
pp. 331-339
Author(s):  
D. T. Mather ◽  
T. Thorvaldson
Keyword(s):  
Calcium Hydroxide ◽  
Ferric Oxide ◽  
Prolonged Exposure ◽  
Saturated Steam ◽  
X Ray Diffraction ◽  
Similar Treatment ◽  
Rapid Action ◽  
Tricalcium Aluminate ◽  
Water Of Hydration ◽  
Diffraction Patterns

The reactions which occur when dicalcium ferrite and tetracalcium alumino-ferrite are exposed to saturated steam at temperatures between 100° and 300 °C. were studied by determining the water absorbed and the optical properties and X-ray diffraction patterns of the products. The hydration of the probable products of decomposition under the same conditions was also studied. The main results were as follows:Precipitated alumina, treated between 170° and 350 °C. and then dried over calcium oxide or "dehydrite" at 21 °C., gives a monohydrate of alumina. The product is the same whether the initial alumina contains excess combined water or has been dehydrated at any temperature below about 920 °C. On similar treatment between 100° and 170 °C. precipitated ferric oxide loses its water of hydration, giving a material with the crystalline structure of hematite. Tricalcium aluminate at temperatures between 150° and 300 °C. forms the isometric hexahydrate.On prolonged exposure between 100° and 300 °C, dicalcium ferrite is completely decomposed to calcium hydroxide and ferric oxide (hematite). The first step appears to be a rapid direct hydration of the dicalcium ferrite to a dihydrate, followed by a rapid liberation of one mole of calcium hydroxide. Then follows a slow decomposition of the hydrated monocalcium ferrite with the formation of hematite.Similar treatment of tetracalcium aluminoferrite at temperatures from 100° to 300 °C. gives as final products the hexahydrate of tricalcium aluminate, calcium hydroxide, and ferric oxide (hematite). Here again a very rapid action appears to take place, producing the hexahydrate of tricalcium aluminate and hydrated monocalcium ferrite, the latter product then decomposing slowly to calcium hydroxide and ferric oxide as in the case of the dicalcium ferrite.

scholarly journals Hydrothermal Synthesis of Leaf-Shaped Ferric Oxide Particles

2009 ◽  
Vol 6 (s1) ◽  
pp. S280-S286
Author(s):  
Keqiang Ding
Keyword(s):  
Ferric Oxide ◽  
Hydrothermal Process ◽  
Potassium Ferricyanide ◽  
X Ray Diffraction ◽  
X Ray ◽  
Oxide Particles ◽  
Ferric Oxides ◽  
Diffraction Patterns ◽  
First Time ◽  
Scanning Electron

For the first time, leaf-shaped ferric oxide particles were prepared from an aqueous solution of potassium ferricyanide [K3Fe(CN)6] by hydrothermal process. Images obtained from SEM (scanning electron microscope) revealed that leaf-shaped ferric oxides (around 1.5 μm in length) were clearly exhibited when the hydrothermal tempreature was 150°C, while as the temperature was increased to 200°C leaf-shaped ferric oxide particles with larger size were observed. XRD (X-ray diffraction) patterns testified that the obtained ferric oxides were α-Fe2O3with well-structured crystal faces. Interestingly, histograms describing the distribution of samples indicated that the distribution of obtained ferric oxide particles did not accord with gaussian distribution

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.: II. THE HYDRATION PRODUCTS OF TRICALCIUM ALUMINATE

1929 ◽  
Vol 1 (3) ◽  
pp. 201-213 ◽  
Author(s):  
T. Thorvaldson ◽  
N. S. Grace ◽  
V. A. Vigfusson
Keyword(s):  
Crystal Structure ◽  
Refractive Indices ◽  
Vapor Pressures ◽  
Hydration Products ◽  
X Ray Diffraction ◽  
X Ray ◽  
Hexagonal Form ◽  
Tricalcium Aluminate ◽  
Diffraction Patterns ◽  
Crystalline Forms

Further studies on the isometric form of hydrated tricalcium aluminate are reported. These include methods of preparation, crystalline forms, X-ray diffraction pattern, and determinations of solubility and density. The products formed when the hexagonal form of hydrated tricalcium aluminate is dehydrated at definite vapor pressures of Water at 21 °C., were studied. The density, refractive indices, heats of solution in HCl.200 H2O, and the X-ray diffraction patterns of several probable hydrates were determined. The experimental evidence given indicates that hydrates of 3CaO.Al2O3 having 6, 8, 91/2, 101/2, and 12 moles of water are formed, but that the water in excess of 8 moles is very loosely held and that its removal does not materially affect the crystal structure. The exact composition of some of the higher hydrates requires confirmation.

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.

THE HYDRATION OF DICALCIUM SILICATE AND TRICALCIUM SILICATE

1936 ◽  
Vol 14b (1) ◽  
pp. 20-30 ◽  
Author(s):  
N. B. Keevil ◽  
T. Thorvaldson
Keyword(s):  
Calcium Hydroxide ◽  
Tricalcium Silicate ◽  
Dicalcium Silicate ◽  
Crystalline Hydrate ◽  
Saturated Steam ◽  
Partial Hydrolysis ◽  
Hydration Products ◽  
X Ray Diffraction ◽  
Constant Weight ◽  
X Ray

Samples of β-dicalcium silicate, γ-dicalcium silicate, tricalcium silicate, hillebrandite and dehydrated hillebrandite were exposed to saturated steam at temperatures between 50° and 375 °C. After drying to constant weight (usually over calcium oxide) the increase in weight and the amount of free calcium hydroxide were determined. Microscopic examinations and X-ray diffraction patterns of the products were made. The hydration products were then dehydrated and similar studies of the products made. The hydrolysis of the hydration products also was studied.It was found that between 110° and 350 °C. β- and γ-dicalcium silicates may absorb water without hydrolysis to form three crystalline products. Two of these are identical with products already described (20); the third product appears to possess another characteristic crystalline structure as shown by the X-ray pattern, but to have a variable water content with a limiting composition of 2CaO∙SiO2∙H2O. The hydration product may be dehydrated without the liberation of lime.When conditions favoring hydrolyses are avoided, tricalcium silicate hydrates directly to a crystalline hydrate which probably has the limiting composition, 3CaO∙SiO2∙2H2O, although products holding from 1.3 to 2 moles of water give the same X-ray diffraction pattern. When the conditions favor partial hydrolysis, tricalcium silicate decomposes into calcium hydroxide and crystalline hydrated dicalcium silicate. Dehydration of hydrated tricalcium silicate gives one mole of lime along with dicalcium silicate.Hillebrandite exposed to saturated steam at 160 °C. remained unchanged while a sample of dehydrated hillebrandite on hydration gave a product similar to that obtained from β-dicalcium silicate.When treated with a large excess of water, the hydrated silicates hydrolyze to the same extent as the anhydrous silicates, but the final equilibrium is attained more rapidly, especially in the case of hydrated dicalcium silicate.

Evaluation of Freezing Methods by Low Temperature X-Ray Diffraction

1977 ◽  
Vol 35 ◽  
pp. 330-333
Author(s):  
T. Gulik-Krzywicki ◽  
M.J. Costello
Keyword(s):  
Biological Materials ◽  
Molecular Organization ◽  
X Ray Diffraction ◽  
Glass Capillary ◽  
X Ray ◽  
Rate Dependent ◽  
Before And After ◽  
Freeze Etching ◽  
Diffraction Patterns ◽  
Set Up

Freeze-etching electron microscopy is currently one of the best methods for studying molecular organization of biological materials. Its application, however, is still limited by our imprecise knowledge about the perturbations of the original organization which may occur during quenching and fracturing of the samples and during the replication of fractured surfaces. Although it is well known that the preservation of the molecular organization of biological materials is critically dependent on the rate of freezing of the samples, little information is presently available concerning the nature and the extent of freezing-rate dependent perturbations of the original organizations. In order to obtain this information, we have developed a method based on the comparison of x-ray diffraction patterns of samples before and after freezing, prior to fracturing and replication.Our experimental set-up is shown in Fig. 1. The sample to be quenched is placed on its holder which is then mounted on a small metal holder (O) fixed on a glass capillary (p), whose position is controlled by a micromanipulator.

Examination of Rabbit Fc Crystals

1968 ◽  
Vol 26 ◽  
pp. 140-141
Author(s):  
J. P. Robinson ◽  
P. G. Lenhert
Keyword(s):  
Molecular Weight ◽  
Flat Plate ◽  
Phosphate Buffer ◽  
Asymmetric Unit ◽  
X Ray Diffraction ◽  
X Ray ◽  
Neutral Ph ◽  
Small Crystals ◽  
Carbon Coated ◽  
Diffraction Patterns

Crystallographic studies of rabbit Fc using X-ray diffraction patterns were recently reported. The unit cell constants were reported to be a = 69. 2 A°, b = 73. 1 A°, c = 60. 6 A°, B = 104° 30', space group P21, monoclinic, volume of asymmetric unit V = 148, 000 A°3. The molecular weight of the fragment was determined to be 55, 000 ± 2000 which is in agreement with earlier determinations by other methods.Fc crystals were formed in water or dilute phosphate buffer at neutral pH. The resulting crystal was a flat plate as previously described. Preparations of small crystals were negatively stained by mixing the suspension with equal volumes of 2% silicotungstate at neutral pH. A drop of the mixture was placed on a carbon coated grid and allowed to stand for a few minutes. The excess liquid was removed and the grid was immediately put in the microscope.

Quantitative Electron Microscope with imaging plate

1994 ◽  
Vol 52 ◽  
pp. 408-409
Author(s):  
D. Shindo
Keyword(s):  
Electron Microscope ◽  
Dynamic Range ◽  
Processing System ◽  
Digital Data ◽  
Imaging Plate ◽  
Crystal Thickness ◽  
X Ray Diffraction ◽  
Resolution Electron ◽  
Electron Intensity ◽  
Diffraction Patterns

Imaging plate has good properties, i.e., a wide dynamic range and good linearity for the electron intensity. Thus the digital data (2048x1536 pixels, 4096 gray levels in log scale) obtained with the imaging plate can be used for quantification in electron microscopy. By using the image processing system (PIXsysTEM) combined with a main frame (ACOS3900), quantitative analysis of electron diffraction patterns and high-resolution electron microscope (HREM) images has been successfully carried out.In the analysis of HREM images observed with the imaging plate, quantitative comparison between observed intensity and calculated intensity can be carried out by taking into account the experimental parameters such as crystal thickness and defocus value. An example of HREM images of quenched Tl2Ba2Cu1Oy (Tc = 70K) observed with the imaging plate is shown in Figs. 1(b) - (d) comparing with a structure model proposed by x-ray diffraction study of Fig. 1 (a). The image was observed with a JEM-4000EX electron microscope (Cs =1.0 mm).

Control of the phase composition of advanced calcium phosphates using an x-ray diffractometer with a curved position-sensitive detector

2020 ◽  
Vol 86 (6) ◽  
pp. 29-35
Author(s):  
V. P. Sirotinkin ◽  
O. V. Baranov ◽  
A. Yu. Fedotov ◽  
S. M. Barinov
Keyword(s):  
Phase Composition ◽  
Calcium Phosphates ◽  
Position Sensitive Detector ◽  
Sensitive Detector ◽  
X Ray Diffraction ◽  
X Ray ◽  
Impurity Phases ◽  
Position Sensitive ◽  
Diffraction Peaks ◽  
Diffraction Patterns

The results of studying the phase composition of advanced calcium phosphates Ca10(PO4)6(OH)2, β-Ca3(PO4)2, α-Ca3(PO4)2, CaHPO4 · 2H2O, Ca8(HPO4)2(PO4)4 · 5H2O using an x-ray diffractometer with a curved position-sensitive detector are presented. Optimal experimental conditions (angular positions of the x-ray tube and detector, size of the slits, exposure time) were determined with allowance for possible formation of the impurity phases during synthesis. The construction features of diffractometers with a position-sensitive detector affecting the profile characteristics of x-ray diffraction peaks are considered. The composition for calibration of the diffractometer (a mixture of sodium acetate and yttrium oxide) was determined. Theoretical x-ray diffraction patterns for corresponding calcium phosphates are constructed on the basis of the literature data. These x-ray diffraction patterns were used to determine the phase composition of the advanced calcium phosphates. The features of advanced calcium phosphates, which should be taken into account during the phase analysis, are indicated. The powder of high-temperature form of tricalcium phosphate strongly adsorbs water from the environment. A strong texture is observed on the x-ray diffraction spectra of dicalcium phosphate dihydrate. A rather specific x-ray diffraction pattern of octacalcium phosphate pentahydrate revealed the only one strong peak at small angles. In all cases, significant deviations are observed for the recorded angular positions and relative intensity of the diffraction peaks. The results of the study of experimentally obtained mixtures of calcium phosphate are presented. It is shown that the graphic comparison of experimental x-ray diffraction spectra and pre-recorded spectra of the reference calcium phosphates and possible impurity phases is the most effective method. In this case, there is no need for calibration. When using this method, the total time for analysis of one sample is no more than 10 min.

Infrared spectroscopic study of the YPO4-YCrO4 system

1985 ◽  
Vol 50 (10) ◽  
pp. 2139-2145
Author(s):  
Alexander Muck ◽  
Eva Šantavá ◽  
Bohumil Hájek
Keyword(s):  
Spectroscopic Study ◽  
Infrared Spectra ◽  
Point Of View ◽  
Mixed Crystals ◽  
Crystal Symmetry ◽  
Infrared Spectroscopic Study ◽  
X Ray Diffraction ◽  
X Ray ◽  
Infrared Spectroscopic ◽  
Diffraction Patterns

The infrared spectra and powder X-ray diffraction patterns of polycrystalline YPO4-YCrO4 samples are studied from the point of view of their crystal symmetry. Mixed crystals of the D4h19 symmetry are formed over the region of 0-30 mol.% YPO4 in YCrO4. The Td → D2d → D2 or C2v(GS eff) correlation is appropriate for both PO43- and CrO43- anions.

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