Thermo gravimetric analyzer(TGA) is a device that measures the relationship between the mass of a sample and temperature or time under a program-controlled temperature and a certain atmosphere. In the early literature related to thermo gravimetric method, a few researchers used to call it “thermo gravimetric analysis method”. In fact, this title is inappropriate, because some samples will have almost the same mass during the experiment. or increase in quality. For example, when many metals are heated to a certain temperature in an air atmosphere, they tend to begin to gain weight due to oxidation reactions.
THERMO GRAVIMETRIC ANALYZER(TGA)
Thermo gravimetric analyzer(TGA) analyzers are unavoidable to fail. Generally, failures can only be dealt with after finding the right cause:
Abnormal fluctuation of TG curve
In the daily testing process of TG, the TG curve will occasionally appear sawtooth peak, which is mainly caused by the following factors:
1). Whether there is a vibration source during the sample test
The measurement accuracy of the analytical balance of the thermo gravimetric analyzer(TGA) is generally very high, and the weight readability accuracy of the type thermo gravimetric analyzer(TGA) is 0.1ug (ie, one millionth). If there is a vibration source around the instrument during the sample testing process, such as the beating of building construction outdoors, the rapid passing of a large transport vehicle on the road outside the window, or the loud noise and vibration of the instrument in the building, it will cause the analyzer to malfunction. Therefore, the instrument is generally required to be placed in a relatively quiet and stable environment.
2). Whether the gas filter is blocked
The clogging of the gas filter is another main reason for the abnormal fluctuation of the TG curve. Generally, the sample will decompose some smoke or solid small particles during the measurement process. Driven by the airflow, it is carried out by the gas when passing through the filter, while the solid particles are blocked and adsorbed by the filter membrane. When the thermo gravimetric analyzer(TGA) is used for a long time, the solid particles in the exhaust gas will gradually enrich, and after reaching a certain level, the filter membrane in the filter will be partially or completely blocked, so that the exhaust gas cannot be discharged smoothly. The blocked airflow will flow back around the balance bracket, causing the balance to shake, resulting in inaccurate balance testing and abnormal fluctuations in the TG curve.
In order to prevent this phenomenon, it is usually necessary to check whether the exhaust emission of the instrument is smooth before each sample measurement. The method is to first open the circulating water, keep the water temperature constant, put the sample well, and cover the furnace cover to ensure that the furnace body is sealed. Open the gas pressure reducing valve to adjust the air pressure to 0.05Mpa, turn on the protective gas and purge gas switches, and control the gas flow to 20mL/min. Determine whether the air path is open. In addition, the gas filter needs to be replaced regularly, usually every 2-3 months, which can be determined according to the specific situation, such as the number of samples to be measured or the nature of the thermal changes of the samples.
The degree of TG test is reduced
There are several reasons for the decrease in the degree of thermo gravimetric analyzer(TGA) after being used for a period of time:
1). Whether the exhaust pipe of the furnace cover and the balance bracket are clean
Usually, after the instrument has been used for a period of time, some black smoke and dust will adhere to the inside of the furnace cover and exhaust pipe, which may fall into the balance bracket or furnace body in the furnace body driven by the airflow, which will affect the accuracy of the balance test. Therefore, it is necessary to regularly clean the furnace cover and exhaust pipe to prevent pollutants from accumulating or falling into the furnace to ensure the accuracy of the analytical balance measurement.
2). There will be some residues after the decomposition of the sample slowly attached to the long-term sample support rod, which will affect the test degree of TG. Therefore, it is necessary to periodically burn the support rod to 800°C at high temperature in an atmosphere of air or oxygen. The cooling section can be increased, but high temperature and constant temperature are not allowed. Specifically, it is generally once a week, which can be determined according to the frequency of sampling and the pollution of the instrument. residues, improve the test degree of TG.
Any more question please contact us www.upwelltest.com or email :info@upwelltest.com
