THE DEHYDRATION OF TRICALCIUM ALUMINATE HEXAHYDRATE

1941 ◽  
Vol 19b (5) ◽  
pp. 123-128 ◽  
Author(s):  
W. G. Schneider ◽  
T. Thorvaldson
Keyword(s):  
Calcium Oxide ◽  
Low Temperatures ◽  
Slow Rate ◽  
Decomposition Products ◽  
Prolonged Heating ◽  
Dry Air ◽  
Tricalcium Aluminate ◽  
Composition Formula ◽  
Solid Decomposition ◽  
A Current

Samples of the isotropic hexahydrate of tricalcium aluminate were dehydrated in a current of dry air at various temperatures up to 1050°. The water retained and the lime liberated were determined. The results of earlier preliminary studies in this laboratory were confirmed. At low temperatures an isotropic hydrate of the composition [Formula: see text], having a refractive index of 1.543 ± 0.003, is formed. This hydrate is stable in dry air up to a temperature of approximately 275° and when once formed at lower temperatures has a very slow rate of decomposition below 350°. On continued dehydration above 275° decomposition occurs with the liberation of calcium oxide. Between 550° and 950° quantitative decomposition occurs into calcium oxide and an aluminate of the composition 12CaO∙7Al2O3. In the upper part of this temperature range prolonged heating causes slow recombination of the solid decomposition products, and above 950° this effect becomes marked. Dehydration of the hexahydrate in a current of dry nitrogen gives similar results. The experiments indicate that the system [Formula: see text] would serve as an efficient drying agent at temperatures below 100°.

scholarly journals Tungsten Oxide Based Sensor for Oxygen Detection

Proceedings ◽  
2018 ◽  
Vol 2 (13) ◽  
pp. 952 ◽  
Author(s):  
Wangi Sari ◽  
Simon Leigh ◽  
James Covington
Keyword(s):  
Metal Oxide ◽  
Linear Relationship ◽  
Tungsten Oxide ◽  
Spin Coating ◽  
Low Temperatures ◽  
Oxygen Sensor ◽  
High Response ◽  
Humid Air ◽  
Dry Air ◽  
Oxygen Detection

In this paper we report on the development tungsten oxide based chemiresistive sensors for the monitoring of oxygen at low temperatures (T ≤ 400 °C) in dry and humid air. The sensors were deposited onto alumina substrate by a combination of spin coating and a photolithographic process to define the sensing area. Our results show that the sensors comply with a linear relationship over a 0 to 20% concentration range, with a high response towards oxygen. The highest response was observed at 350 °C (ΔR/Ra = 7.8) in humid and in dry air (ΔR/Ra = 18). This result is a significant improvement over our previous experiments and we believe to take the concept of a metal-oxide based oxygen sensor a step closer.

scholarly journals Boundary lubrication.—The temperature coefficient

1922 ◽  
Vol 101 (713) ◽  
pp. 487-492 ◽  
Keyword(s):  
Experimental Method ◽  
Temperature Coefficient ◽  
Boundary Lubrication ◽  
Static Friction ◽  
Effect Of Temperature ◽  
Dry Air ◽  
Electric Grids ◽  
Continuous Sheet ◽  
A Current

The experimental method employed was that described in earlier papers. A slider having a spherical face is made to slide over a plate in an atmosphere of rigorously clean and dry air. The friction measured is static friction and the object of the experiments the determination of the effect of temperature. This has now been studied over a range of 15°C. to 110°C., and it may be said at once that the relations discovered are of a totally unexpected character. More than one attempt to study the effect of temperature was defeated by the fact that lubricating vapours were given off from the walls of the chamber in which the plate and slider were enclosed. This difficulty was completely removed by using a chamber with double walls, the inner wall being a continuous sheet of nickel. Between the walls were placed the electric grids for heating the chamber. The stream of dry air with which the chamber was flooded was also heated by being passed through a tube of silica, which was maintained at the required temperature by a coil of wire through which a current was passing. The temperature of the stream of air and the temperature of the chamber were recorded electrically.

Oxidation behavior of bulk Ti3SiC2 at intermediate temperatures in dry air

2006 ◽  
Vol 21 (2) ◽  
pp. 402-408 ◽  
Author(s):  
H.B. Zhang ◽  
Y.C. Zhou ◽  
Y.W. Bao ◽  
J.Y. Wang
Keyword(s):  
Phase Transformation ◽  
Low Temperatures ◽  
Driving Force ◽  
Oxidation Behavior ◽  
Isothermal Oxidation ◽  
Oxide Scales ◽  
Temperature Oxidation ◽  
Dry Air ◽  
High Oxidation ◽  
Anomalous Oxidation

The isothermal oxidation behavior of bulk Ti3SiC2 at intermediate temperatures from 500 to 900 °C in flowing dry air was investigated. An anomalous oxidation with higher kinetics at lower temperatures was observed. This phenomenon resulted from the formation of microcracks in the oxide scales at low temperatures. The generation of these microcracks was caused by a phase change in the oxide products, i.e., the transformation of anatase TiO2 to rutile TiO2. This phase transformation resulted in tensile stress, which provided the driving force for the formation of the microcracks during oxidation. Despite the existence of microcracks, the intermediate-temperature oxidation of Ti3SiC2 generally obeyed the parabolic rate law and did not exhibit catastrophic destruction due to the fact that cracks occurring in the oxide layers were partially filled with amorphous SiO2. Therefore, further high oxidation kinetics was prevented.

EFFECTS OF TEMPERATURE ON NO3− AND NO2− REDUCTION, NITROGENOUS GAS PRODUCTION, AND REDOX POTENTIAL IN A SATURATED SOIL

1973 ◽  
Vol 53 (2) ◽  
pp. 213-218 ◽  
Author(s):  
L. D. BAILEY ◽  
E. G. BEAUCHAMP
Keyword(s):  
Redox Potential ◽  
Nitrogen Source ◽  
Low Temperatures ◽  
Slow Rate ◽  
Gas Production ◽  
Saturated Soil ◽  
Anaerobic Conditions ◽  
Ap Horizon ◽  
Effects Of Temperature ◽  
No2 Reduction

Samples of the Ap horizon of a Huron soil were used to investigate the effects of temperature on NO3− and NO2− reduction, nitrogenous gas production, and redox potential under anaerobic conditions in the laboratory. NO3− and NO2− reduction occurred at redox potential (Eh) values of 200 and 180 mV, respectively. The rate of NO3− and NO2− reduction decreased with decreasing temperatures (30–5 C). At 5 C, NO3− reduction was completely inhibited but NO2− reduction continued at a slow rate. Gas chromatographic analyses showed that the denitrification gas was composed of N2, N2O, and NO. Decreasing the temperature decreased the production of N2, increased the production of NO, and did not significantly affect the production of N2O. The increased production of NO at low temperatures when NO2− was the nitrogen source is attributed to chemodenitrification processes.

Effect of the partial pressure of water vapour on the thermal decomposition of γ-FeOOH and on the dispersity of the solid decomposition products

1984 ◽  
Vol 19 (1) ◽  
pp. 183-188 ◽  
Author(s):  
D. G. Klissurski ◽  
J. Šubrt ◽  
V. N. Blaskov ◽  
J. Lipka ◽  
P. Hanousek ◽  
...  
Keyword(s):  
Thermal Decomposition ◽  
Partial Pressure ◽  
Water Vapour ◽  
Decomposition Products ◽  
Solid Decomposition

scholarly journals Synthesis, Polymorphism and Thermal Decomposition Process of (n-C4H9)4NRE(BH4)4 for RE = Ho, Tm and Yb

Materials ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1329
Author(s):  
Wojciech Wegner ◽  
Tomasz Jaroń
Keyword(s):  
Thermal Decomposition ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Decomposition Products ◽  
Gaseous Products ◽  
Dsc Measurements ◽  
Unit Cells ◽  
Polymorphic Forms ◽  
Solid Decomposition ◽  
Derivatives Of

In total, three novel organic derivatives of lanthanide borohydrides, n-But4NRE(BH4)4 (TBAREB), RE = Ho, Tm, Yb, have been prepared utilizing mechanochemical synthesis and purified via solvent extraction. Studies by single crystal and powder X-ray diffraction (SC-XRD and PXRD) revealed that they crystalize in two polymorphic forms, α- and β-TBAREB, adopting monoclinic (P21/c) and orthorhombic (Pnna) unit cells, previously found in TBAYB and TBAScB, respectively. Thermal decomposition of these compounds has been investigated using thermogravimetric analysis and differential scanning calorimetry (TGA/DSC) measurements, along with the analysis of the gaseous products with mass spectrometry (MS) and with analysis of the solid decomposition products with PXRD. TBAHoB and TBAYbB melt around 75 °C, which renders them new ionic liquids with relatively low melting points among borohydrides.

scholarly journals Influence of Dicalcium Silicate and Tricalcium Aluminate Compounds in Different Local Cement Brands on the Compressive Strength of Normal Concrete

2021 ◽  
Vol 318 ◽  
pp. 59-69
Author(s):  
Anthony N. Ede ◽  
Oluwarotimi Michael Olofinnade ◽  
Akpabot Ifiok Akpabot ◽  
Solomon O. Oyebisi ◽  
David O. Nduka
Keyword(s):  
Compressive Strength ◽  
Setting Time ◽  
Dicalcium Silicate ◽  
Target Strength ◽  
Strength Gain ◽  
Direct Reading ◽  
Normal Concrete ◽  
Building Collapse ◽  
Tricalcium Aluminate ◽  
Composition Formula

The mould-ability of concrete into intricate forms and the versatility of its constituent materials has made concrete to be the most preferred construction material. However, in developing nations such as Nigeria, poor quality of concrete is listed among the common causes of building collapse. Thus, this study investigated the effects of chemical compounds of four commonly used local ordinary Portland cement brands on the compressive strength of normal concrete. The cement was labelled brands A, B, C, and D, respectively, while all the other constituent materials remained constant in this study. The HACH DR 200 direct reading spectrophotometer method was used to analyze the composition of the oxide in each of the cement samples, while the Bogue composition formula was used to estimate the compound compositions of the cement samples. A designed mix proportion of 1:2:4 (cement: sand: granite) at water-cement ratio (w/c) of 0.6 was used to produce the concrete with an expected target strength of 25 N/mm2. Also, the initial and final setting time of the cement samples and the workability of the concrete mixes were determined. Forty-Eight (48) numbers cube samples were cast and tested for compressive strength at 3, 7, 14, and 28 curing days, respectively, using a 150 mm concrete cubes. The result shows the setting time of the cement samples to be within an acceptable period. Also, results indicated that the cement brands have a significant percentage of Tricalcium Silicate (C3S) content and low percentage Dicalcium Silicate (C2S) content responsible for faster hydration rate and higher early strength gain of the concrete. However, it was observed that a higher percentage of Tricalcium aluminate (C3A) leads to higher strength gain from 7 to 28 days of curing age.

scholarly journals Ohmic contacts to n-type and p-type gallium antimonide whiskers

2021 ◽  
Vol 11 (1) ◽  
pp. 1-6
Author(s):  
Anatoliy Druzhynin ◽  
Keyword(s):  
Low Temperatures ◽  
Ohmic Contacts ◽  
Gallium Antimonide ◽  
Electrical Contacts ◽  
Contact Material ◽  
Pulse Shaper ◽  
Current Transmission ◽  
Flux Layer ◽  
P Type ◽  
A Current

The ohmic contacts to the n-type conductivity gallium antimonide whiskers were created due to a current pulse shaper. It was established that I–V characteristics of GaSb whiskers at low temperatures are linear, regardless of the direction of current transmission. That allows using the investigated techniques to create electrical contacts and study their electrophysical characteristics. GaSb samples with a diameter of 12 μm and 20 μm were studied at temperatures 4.2 K and 77 K. A slide table with bath and microfurnace was made for welding ohmic contacts to GaSb whiskers. Gold microwire with a diameter of 30 μm was used as a contact material. The melting was carried out under the flux layer. It was revealed that the fusion is one of the most suitable methods for creating contacts to the whiskers grown by gas transport reactions.

scholarly journals A Synergistic Flame Retardant System Based on Expandable Graphite, Aluminum (Diethyl-)Polyphospinate and Melamine Polyphosphate for Polyamide 6

Polymers ◽  
2021 ◽  
Vol 13 (16) ◽  
pp. 2712
Author(s):  
Florian Tomiak ◽  
Angelina Schoeffel ◽  
Klaus Rathberger ◽  
Dietmar Drummer
Keyword(s):  
Flame Retardant ◽  
Expanded Graphite ◽  
Polyamide 6 ◽  
Partial Substitution ◽  
Expandable Graphite ◽  
Heating Rates ◽  
Sem Images ◽  
Decomposition Products ◽  
Solid Decomposition ◽  
Synergistic Flame Retardant

Expandable graphite (EG), aluminum (diethyl)polyphosphinate (AlPi) and melamine polyphophate (MPP) was used as flame retardant multi-material additive in a polyamide 6 (PA6) matrix. Flame inhabitation performances were conducted by cone calorimeter, LOI and UL-94 tests, synergisms identified analyzed by TGA-FTIR and TGA-GC/MS and effects found were comprehensively discussed. SEM images were used for char residue characterization. For PA6 containing 20 wt.% EG and 5 wt.% AlPi/MPP (3:2), a well working synergism in limiting oxygen indices could be identified exhibiting the highest oxygen index (OI) measured: 46%. The study shows that the synergism due to the partial substitution of EG by AlPi/MPP can be attributed to two effects: (1) When PA6/AlPi/MPP mixtures decompose predominantly CO2 evaporates in early decomposition stages. CO2 evaporations was found to be sensitive to the heating rate applied, whereas specifically high heating rates increased the CO2 yield measured. (2) Solid decomposition products of AlPi/MPP act as “glue” between expanded graphite and thus increase the mechanical residue stability.

The Vapor Pressure of Dry Air at Low Temperatures

1966 ◽  
pp. 372-378 ◽  
Author(s):  
G. Walker ◽  
W. J. Christian ◽  
R. A. Budenholzer
Keyword(s):  
Vapor Pressure ◽  
Low Temperatures ◽  
Dry Air
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