User:Somaia fayal alkasbi/Thermogravimetric analysis

Heat measurement for a constant temperature

Measurement of the change in heat released

Measuring dynamic mechanical change

Thermomechanical analysis

Thermal electrophoresis analysis

Differential thermal analysis.

Thermogravimetric analysis is a thermal analysis method in which you monitor changes in the physical and chemical properties of materials and the process takes place during an increase in temperature (with the rate of increase of temperature remaining constant). Or, the reaction may take place and the reaction time is monitored (with the temperature remaining constant and / or weight loss constant).

Thermal gravimetric analysis gives us information on the physical properties of a substance, such as evaporation and sublimation, and in the chemistry of absorption, absorption, and state change. Thermogravimetric analysis also gives information on chemical processes, such as chemical absorption, solubility, water loss, and decomposition, and information on reactions of a solid with a gas such as oxidation or an oxidation-reduction reaction.

The sample is placed in a high-temperature crucible of an inert material that does not react, such as platinum or corundum; And placed in an oven heated up to 2400 degrees Celsius. The crucible is attached to an accurate scale, and the scale reading is taken continuously during the heating process. A thermocouple is placed next to the crucible to measure the temperature. Modern thermogravimetric devices are connected to a computer that determines the highest temperature for analysis, and also regulates the heating rate and gas passage rate. During the analysis process, types of gases enter into the sample space as required, and the sample is isolated from the outside. Often nitrogen gas is used since it does not cause oxidation (and in this case, consideration must be given to isolating the crucible so that it is in a closed space and surrounded by nitrogen gas).

In other cases, gas, such as air, oxygen, or other gas, is wanted to surround the sample. Heating the sample may result in a decomposition reaction, the volatilization of gaseous compounds from it, or gases resulting from the reaction of the sample with oxygen. The change in the weight of the sample, whether by increase or decrease, is recorded. The temperature at which the change in weight occurs is also recorded, and this depends on the properties of the sample. From this data, the chemical composition of the sample can be known.

Analyzer
Thermal gravimetric analysis is based on accurately measuring three variables: weight change, temperature, and temperature change. On this basis, the device consists of an accurate balance with a cuff on which the sample is placed, and an oven that works with computer programming. The furnace can be programmed to either heat the sample at a constant rate or the heating to be for the purpose of a constant rate of change in the sample weight.

Although a constant heating rate is often used, working with a constant sample weight variation may protect the sample from unwanted reactions. For example, the data read during the polyvinyl butyral carbonization process was determined by fixing the rate of change of the sample weight at a rate of 0 and 2 (wt)% / min.

Regardless of the oven's programming, the sample is placed in an electrically heated oven equipped with a thermocouple that accurately measures the temperature. A reference sample may also be placed on another balance scale in a room isolated from the sample room. The atmosphere of the sample may be flooded with an inert gas in order to not oxidize the sample or to prevent another unwanted reaction. Another device has been devised that uses a sensitive balance that works with a quartz crystal, which can measure small samples weighing several micrograms compared to the usual devices that measure samples weighing several milligrams.

Measurement methods
The thermogravimetric analyzer continuously weighs the sample while it is heated to a temperature of 2000 ° C and is coupled with the measurement with an infrared FTIR and mass spectrometer for gaseous analysis. As the temperature increases, the sample components decompose and at the same time the percentage change in the sample weight is measured. Then plot the temperature on the horizontal axis and the change in the sample weight on the vertical axis in a graph.

Measurements can be recorded in short periods so that the resulting curve shows all the details of the change in weight more accurately. This provides an opportunity to derive more information about the characteristics of the sample (see tracer analysis). The temperature can be calibrated in the device by using several samples that have a known accurate melting point or a curie point for magnetic materials such as iron or nickel and are known to be accurate. The magnetic material is placed in a sample crucible and a magnetic field is applied to it. And the reference material (a piece of iron, for example) is heated until it reaches the Curie point, at which the iron becomes magnetic parallel, working on the equation of the weight change resulting from the external magnetic field.