Total mass loss

The bulk technique is used when measurement of concentration profile is not available. In this technique, many grains of similar size and shape are heated to and held at the desired temperature for a given duration. After the experiment, the total mass loss or gain of the component by the grains is measured. From the mass loss or gain, the diffusion coefficient is calculated. To obtain diffusivity from mass loss experiments (most Ar and He diffusivities in minerals are obtained this way), it is necessary to assume that the initial concentration of the diffusion component is uniform. It is also necessary to assume the effective shape of the diffusing grains (cf. Section 3.2.11). 

If a single grain of thin wafer of thickness I is used and total mass loss or gain is measured instead of the concentration profile, the diffusion coefficient may be obtained by fitting the data to Equation 3-52d ... 

After heating, the sample turned bulklike with black color, and EDX data showed that the residues contained S in addition to a large amount of I and Ag. X-ray diffraction patterns of the residues gave the main diffraction peaks of Agl, indicating that the residues were mainly Agl crystallite. Total mass losses of samples 1-VI obtained from TGA lie between the total organics content and total mass amount of C + H + O in the samples from the elemental analysis, for which the data are tabulated in Table 4.4.4. The difference may be caused by the residual S in the particle surface. This result supports that heating mainly resulted in the decomposition of organics in the powders. 

The total mass loss of a material in a pre-flashover fire that will result in a lethal mixture can be theoretically determined as the product of the LC50 and the volume in which the products of combustion are distributed. For post-flashover fires, it is necessary to correct the LC50 measured in the bench-scale test to account for the increased CO production in these fires.67 NIST conducted a series of full-scale validation tests and determined that the smoke from the bench-scale method reproduces that from room fires to within a factor of 3.66... 

The cone calorimeter is also used to quantify the corrosivity of products of combustion as described in ASTM D 5485. The Cone Corrosimeter uses the same load cell, specimen holder, retainer frame, spark igniter, conical heater, and exhaust system as the cone calorimeter. A heated stainless steel sampling tube is connected to a funnel placed on top of the conical heater. A gas sample is continuously drawn from the tube at a rate of 4.5 L/min. The sampling tube is connected with silicone rubber tubing to the pump via an 11.2L exposure chamber, a filter, and a flow meter. A target is placed in the exposure chamber at the start of the test and exposed to the corrosive atmosphere of the gas sample for 60 min or until the specimen has lost 70% of its total mass loss, whichever occurs first. 

Thermal decomposition (dehydration) of air-dried X-ray amorphous CPH proceeds in different ways. Similar to the decomposition of X-ray amorphous hydroxides, it occurs gradually at a wide temperature range, while the total mass loss at isothermal dehydration gradually increases at elevated temperatures. 

ASTM E 595-90 Standard Test Method for Total Mass Loss and Collected Volatile Condensable Materials from Outgassing in a Vacuum Environment, 8 pp (DOD Adopted) (FSC 9330) (MR) (Comm E-21)... 

As already mentioned, different modelling approaches were applied (a) the complete system of balance equations of all the species with QSSA for the single propagating radical (b) discrete section method (c) the method of moment. These comparisons demonstrate the equivalence between these techniques, not only with respect to total mass loss, but also in terms of intermediate liquid components (alkanes, alkenes and a—oj dialkenes). 

The theoretical gravimetric density of the effective hydrogen is 9.6 mass%. The thermogravimetric analysis for prepared Ca(BH4)2 shows that the total mass loss up to 800 K is 9.2 mass%, which supports the overall reaction of Eq. 15.13. On the other hand, the in situ X-ray diffraction analysis indicated that the dehydrogenation reaction of Ca(BH4)2 is as follows ... 

Mulley and Cavendish (30) found that TG could be used to analyze mixtures of calcium hydrogen orthophosphate 2-hydrate (brushite) and anhydrous calcium hydrogen orthophosphate (monetite) based on their loss of water on heating. The water loss on the heating of brushite corresponds to 2.5 moles per mole of compound, while the monetite evolves 0.5 mole per mole of compound. The total mass-loss on heating a mixture of the two compounds is... 

In the temperature range 300-500°C, a small gradual mass-loss (1-2%) was observed for all compounds in air, 02, or N2 atmospheres. The effect of changing the atmosphere altered the decomposition temperatures only slightly. It was found that when heating to higher temperatures, 600°C, the mass-loss was dependent on the atmosphere. In all cases, the total mass-loss was found to be between 5 and 6%. The stoichiometry of this reaction was assumed to be... 

When two elements form a compound in a chemical system, the amount of heat liberated is a measure of the stability of the compound. The greater this heat of formation (enthalpy, AH) the greater the stability of the compound. When carbon is combined with oxygen to form CO2, it is found experimentally that 393 kJ of heat is evolved per mole of CO2 formed. If we use the Einstein relationship, we can calculate that this would correspond to a total mass loss of 4.4 X 10 g for each mole of CO2 formed (44 g). Although chemists do not doubt that this mass loss actually occurs, at present there are no instruments of sufficient sensitivity to measure such small changes. 

Both mass gain and loss contribute total mass loss of the sample, indicating severe carbon fiber oxidation. 

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