THE DIFFERENTIAL THERMAL ANALYSIS OF NATURAL AND SYNTHETIC HYDRATES OF CALCIUM SULPHATE

1960 ◽  
Vol 38 (6) ◽  
pp. 936-943 ◽  
Author(s):  
W. E. P. Fleck ◽  
M. H. Jones ◽  
R. A. Kuntze ◽  
H. G. McAdie
Keyword(s):  
Heating Rate ◽  
Calcium Sulphate ◽  
Endothermic Effect ◽  
Exothermic Effect ◽  
Uniform Heating ◽  
Heating Rates ◽  
Sample Concentration ◽  
Naturally Occurring ◽  
Lower Temperature ◽  
Dehydration Behavior

A variety of naturally occurring forms of calcium sulphate dihydrate produce substantially identical differential thermograms under conditions of uniform heating rate and particle size. These thermograms closely resemble those for synthetic dihydrate and β-hemihydrate, showing four endothermic effects and one exothermic effect below 500 °C. Two of these endothermic effects, at about 170° and 300 °C, respectively, which have not been reported previously, were found to be easily masked by changes in heating rate or sample concentration. Resolution of the several effects was improved by using different heating rates at different stages of the thermogram. Thermograms of the α-hemihydrate were similar, except that the endothermic effect at 300 °C was not evident and the exothermic effect occurred at a much lower temperature than for the dihydrate. No conspicuous differences were found in the temperatures corresponding to the various endothermic and exothermic effects which might be correlated with the general dehydration behavior of the particular material. The endothermic effect at about 170 °C appears to be associated with part of the hemihydrate to soluble anhydrite transition, possibly arising during the removal of the last traces of water.

Exothermic effects in soils during thermal analysis

Clay Minerals ◽  
2002 ◽  
Vol 37 (4) ◽  
pp. 575-582 ◽  
Author(s):  
K. Emmerich ◽  
W. Smykatz-Kloss
Keyword(s):  
Thermal Analysis ◽  
Organic Matter ◽  
Heating Rate ◽  
Analytical Methods ◽  
Endothermic Effect ◽  
Oxidation Reactions ◽  
Heating Rates ◽  
Decisive Influence

AbstractThis paper addresses the application of thermal analytical methods (DTA/DSC/TG/ MS) in soil investigations, especially the interrelation of exothermic effects and analytical or preparative parameters. For the superimposed decomposition/ oxidation reactions of siderites, FeCO3, the heating rate is shown to have a decisive influence because low heating rates tend to suppress the endothermic effect. In mixtures of small amounts of organic matter (glucose and starch) with talc, the phyllosilicate acts as a catalyst by influencing the intensity of combustion of the organic matter.

Experimental Research on Molding Biomass’s Carbonization Homogeneity

2013 ◽  
Vol 634-638 ◽  
pp. 759-763
Author(s):  
Wei Hu ◽  
Jian Hang Hu ◽  
Hua Wang ◽  
Kun Sang ◽  
Juan Qin Li ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Heating Rate ◽  
Temperature Difference ◽  
Small Dimension ◽  
Carbonization Temperature ◽  
Maximum Temperature ◽  
Exothermic Effect ◽  
Pyrolysis Process ◽  
Heating Rates ◽  
Maximum Temperature Difference

Molding biomass’s carbonization homogeneity was studied through doing research on temperature difference of surface and inside of biomass by making experiments. Molding biomass’s size is larger than that of small dimension biomass and carbonization in whole biomass is different to some extent. But endothermic and exothermic effect in pyrolysis process and mass transfer of volatile are beneficial to carbonization homogeneity. When biomass average heating rate becomes larger, the maximum temperature difference of surface and inside becomes larger, besides that the temperature of biomass is higher when molding biomass’s carbonization is homogeneous. Maximum temperature differences were 30, 76, 137 °C respectively when biomass average heating rates were 5, 10, 20 °C/min. In order to ensure homogeneity, carbonization should reach the temperature which lignin decomposes strongly at releasing heat violently. Carbonization temperature should be higher than 450 °C. Besides, biomass average heating rate shouldn’t be too high and it should be under 20 °C /min.

Thermal Desorption of Deuterium from GaN(0001)

2001 ◽  
Vol 693 ◽  
Author(s):  
Y. Yang ◽  
J. Lee ◽  
B. D. Thoms ◽  
D. D. Koleske ◽  
R. L. Henry
Keyword(s):  
Heating Rate ◽  
Hydrogen Desorption ◽  
Heating Rates ◽  
Exponential Factor ◽  
First Order ◽  
Barrier Heights ◽  
Temperature Programmed ◽  
Lower Temperature ◽  
Desorption Model ◽  
Dominant Peak

AbstractThe recombinative desorption of deuterium from GaN(0001) has been investigated using temperature programmed desorption (TPD) with variable heating rates. With a heating rate of 1°C/s, molecular deuterium desorption peaks at 410 C in agreement with related previous work. However, the shape of the curve indicates a secondary peak at around 280°C which is merged into the lower temperature shoulder of the dominant peak. By changing linear heating rate from 0.05 C/s to 8°C/s desorption peak temperatures from 380°C to 570°C were observed. Fitting to a pseudo-first-order desorption model results in a hydrogen desorption barrier, Ed, from surfaceof 1.1eV and a pre exponential factor, n, of 2 x 106s-1. Both are below expected values and are assumed to be due to a variation of desorption barrier heights. If a typical pre-exponential factor of 1 x 1013s-1is assumed, reanalysis of the desorption data produce a desorption barrier of 2.0 eV, in agreement with the existence of the surface adsorption barrier at room temperature.

Maximum heating rates for producing undistorted glassy carbon ware determined by wedge-shaped samples

1996 ◽  
Vol 11 (9) ◽  
pp. 2368-2375 ◽  
Author(s):  
Hossein Maleki ◽  
Lawrence R. Holland ◽  
Gwyn M. Jenkins ◽  
R. L. Zimmerman ◽  
Wally Porter
Keyword(s):  
Heating Rate ◽  
Treatment Process ◽  
Gaseous Product ◽  
Pyrolysis Mass Spectrometry ◽  
Heating Rates ◽  
Gaseous Products ◽  
Volatile Products ◽  
Solid Bodies ◽  
Polymeric Carbon ◽  
Maximum Heating

Polymeric carbon artifacts are particularly difficult to make in thick section. Heating rate, temperature, and sample thickness determine the outcome of carbonization of resin leading to a glassy polymeric carbon ware. Using wedge-shaped samples, we found the maximum thickness for various heating rates during gelling (300 K–360 K), curing (360 K–400 K), postcuring (400 K–500 K), and precarbonization (500 K–875 K). Excessive heating rate causes failure. In postcuring the critical heating rate varies inversely as the fifth power of thickness; in precarbonization this varies inversely as the third power of thickness. From thermogravimetric evidence we attribute such failure to low rates of diffusion of gaseous products of reactions occurring within the solid during pyrolysis. Mass spectrometry shows the main gaseous product is water vapor; some carboniferous gases are also evolved during precarbonization. We discuss a diffusion model applicable to any heat-treatment process in which volatile products are removed from solid bodies.

scholarly journals Towards a better representation of the solar cycle in general circulation models

2007 ◽  
Vol 7 (20) ◽  
pp. 5391-5400 ◽  
Author(s):  
K. M. Nissen ◽  
K. Matthes ◽  
U. Langematz ◽  
B. Mayer
Keyword(s):  
Solar Cycle ◽  
Heating Rate ◽  
General Circulation ◽  
Temperature Response ◽  
General Circulation Models ◽  
Short Wave ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Heating Rates ◽  
Radiation Scheme

Abstract. We introduce the improved Freie Universität Berlin (FUB) high-resolution radiation scheme FUBRad and compare it to the 4-band standard ECHAM5 SW radiation scheme of Fouquart and Bonnel (FB). Both schemes are validated against the detailed radiative transfer model libRadtran. FUBRad produces realistic heating rate variations during the solar cycle. The SW heating rate response with the FB scheme is about 20 times smaller than with FUBRad and cannot produce the observed temperature signal. A reduction of the spectral resolution to 6 bands for solar irradiance and ozone absorption cross sections leads to a degradation (reduction) of the solar SW heating rate signal by about 20%. The simulated temperature response agrees qualitatively well with observations in the summer upper stratosphere and mesosphere where irradiance variations dominate the signal. Comparison of the total short-wave heating rates under solar minimum conditions shows good agreement between FUBRad, FB and libRadtran up to the middle mesosphere (60–70 km) indicating that both parameterizations are well suited for climate integrations that do not take solar variability into account. The FUBRad scheme has been implemented as a sub-submodel of the Modular Earth Submodel System (MESSy).

INVESTIGATION OF THERMAL DEGRADATION OF POULTRY PROCESSING DEWATERED SLUDGE USING THERMOGRAVIMETRIC ANALYSIS METHOD

2015 ◽  
Vol 76 (5) ◽  
Author(s):  
N. Aniza ◽  
S. Hassan ◽  
M. F. M. Nor ◽  
K. E. Kee ◽  
Aklilu T.
Keyword(s):  
Particle Size ◽  
Thermogravimetric Analysis ◽  
Thermal Degradation ◽  
Heating Rate ◽  
Degradation Process ◽  
Heating Rates ◽  
Initial Stage ◽  
Poultry Processing ◽  
Effect Of Particle Size ◽  
Dewatered Sludge

Thermal degradation of Poultry Processing Dewatered Sludge (PPDS) was studied using thermogravimetric analysis (TGA) method. The effect of particle size on PPDS samples and operational condition such as heating rates were investigated. The non-isothermal TGA was run under a constant flow of oxygen at a rate of 30 mL/min with temperature ranging from 30ºC to 800ºC. Four sample particle sizes ranging between 0.425 mm to 2 mm, and heating rate between 5 K/min to 20 K/min were used in this study. The TGA results showed that particle size does not have any significant effect on the thermogravimetry (TG) curves at the initial stage, but the TG curves started to separate explicitly at the second stage. Particle size may affect the reactivity of sample and combustion performance due to the heat transfer and temperature gradient. The TG and peak of derivative thermogravimetry (DTG) curves tend to alter at high temperature when heating rate is increased most likely due to the limitation of mass transfer and the delay of degradation process. 

Effect of uniform heating rate on the nature of thermoluminescence of glass

1963 ◽  
Vol 20 (9) ◽  
pp. 476-477
Author(s):  
R. V. Lipchanskaya ◽  
V. S. Aksenov
Keyword(s):  
Heating Rate ◽  
Uniform Heating

scholarly journals Effect of heating rates on the microstructure and gas permeation properties of carbon membranes

2018 ◽  
Vol 14 (3) ◽  
pp. 378-381
Author(s):  
Norazlianie Sazali ◽  
Wan Norharyati Wan Salleh ◽  
Ahmad Fauzi Ismail ◽  
Kumaran Kadirgama ◽  
Mohamad Shahrizan Moslan ◽  
...  
Keyword(s):  
Heating Rate ◽  
High Performance ◽  
Room Temperature ◽  
Gas Permeation ◽  
Carbon Membrane ◽  
Heating Rates ◽  
Polymer Blending ◽  
Carbon Membranes ◽  
Permeation Properties ◽  
Fine Turning

High performance tubular carbon membrane (TCM’s) for CO2 separation were prepared by controlling the carbonization heating rates in range of 1-7 oC/min carbonized at 800 oC under Argon environment. A single permeation apparatus was used to determine the gas permeation properties of the membrane at room temperature. Fine turning of the carbonization condition was necessary to obtain the desired permeation properties. The preparation of PI/NCC-based TCM at low heating rate caused the gas permeance for the examined gas N2 and CO2 decreased whereas the selectivity of CO2/N2 increased. It was also identified that the gas permeation properties of the resultant TCM and its structure was highly affected by the heating rate. The best carbonization heating rate was found at 3oC/min for the fabrication of TCM derived via polymer blending of PI/NCC for CO2/N2 separation.

scholarly journals Synthesis and characterization of a new conjugated polymer containing bithiazole group and its thermal decomposition kinetics

2020 ◽  
Vol 39 (2) ◽  
pp. 227
Author(s):  
Adnan Kurt ◽  
Hacer Andan ◽  
Murat Koca
Keyword(s):  
Thermal Decomposition ◽  
Heating Rate ◽  
Conjugated Polymer ◽  
Three Dimensional ◽  
Heating Rates ◽  
Diffusion Type ◽  
Optimum Heating ◽  
Rate Loss ◽  
Kinetics Of

A new conjugated polymer containing a bithiazole group is prepared by the polycondensation of 2,2'-diamino-4,4'-bithiazole and terephthaldialdehyde in the presence of glacial acetic acid. The kinetics of thermal degradation of the new polymer are investigated by thermogravimetric analysis at different heating rates. The temperature corresponding to the maximum rate loss shifts to higher temperatures with increasing heating rate. The thermal decomposition activation energies of the conjugated polymer in a conversion range of 3–15 % are 288.4 and 281.1 kJ/mol by the Flynn–Wall–Ozawa and Kissinger methods, respectively. The Horowitz–Metzger method shows that the thermodegradation mechanism of the conjugated polymer proceeds over a three-dimensional diffusion type deceleration D3 mechanism. The optimum heating rate is 20 ºC/min.

scholarly journals Investigation of Primary Recrystallization and Decarbonization with Different Heating Rates of Intermediate Annealing Using Nb-Containing Grain-Oriented Silicon Steel

Metals ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1655
Author(s):  
Xin Tian ◽  
Shuang Kuang ◽  
Jie Li ◽  
Jing Guo ◽  
Yunli Feng
Keyword(s):  
Heating Rate ◽  
Electron Backscatter Diffraction ◽  
Optical Microscope ◽  
Primary Recrystallization ◽  
Silicon Steel ◽  
Intermediate Annealing ◽  
Heating Rates ◽  
Average Grain Size ◽  
The Matrix ◽  
20 Nm

An Nb-containing grain-oriented silicon steel was produced through double-stage cold rolling in order to investigate the effect of the heating rate during intermediate annealing on primary recrystallization and decarburization behavior. The microstructure and texture were observed and analyzed by an optical microscope and an electron backscatter diffraction system. A transmission electron microscope was used to observe the precipitation behavior of inhibitors. The decarburization effect during intermediate annealing was also calculated and discussed. The results show that primary recrystallization takes place after intermediate annealing. As the heating rate increases, the average grain size decreases gradually. The textures of {411}<148> and {111}<112> were found to be the strongest along the thickness direction in all of the annealed specimens and are mainly surrounded by HEGB and HAGB (> 45°). A large number of inhibitors with the size of 14~20 nm precipitate are distributed evenly in the matrix. The above results indicate that the higher heating rate during intermediate annealing contributes to both an excellent microstructure and magnetic properties. From the calculation, as the heating rate increases, decarbonization tends to proceed in the insulation stage, and the total amount of carbonization declines.

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