Types and selection of crucibles for thermal analyzer experiments

Crucible type:

(1) Standard crucible. As needed, it can be completely sealed or drilled on the cover to obtain a self generated atmosphere, or a completely freely exchanged atmosphere

(2) Light aluminum crucible. This crucible has the minimum signal time constant, especially when combined with helium gas. It is very suitable for pressing thin films, sheets, or powder samples onto the bottom of the crucible. The gap between the crucible and the lid forms a naturally generated atmosphere, however, if a hole is drilled on the lid, a free exchange atmosphere can also be obtained.

(3) Aluminum oxide crucible. This crucible factory is suitable for thermogravimetric testing. It can be tested to 1600 ℃ and can be reused after cleaning. This crucible has a lid with holes to prevent the sample from boiling and splashing out.

(4) Copper crucible. This type of crucible has no lid. It is used to test the oxidation stability of copper as a catalyst sample. Usually, copper crucibles are used for testing the oxidation induction period (OIT) of polyolefins.

(5) A golden crucible. Gold is chemically stable, but it is expensive. After long-term storage, there may be some precipitation on the surface of the gold crucible. To solve this problem, the gold crucible can be heated to 500 ℃ before use. It should be noted that the metal sample may form a eutectic alloy with the gold crucible, which may melt through the crucible and damage the instrument.

(6) Platinum crucible. This type of crucible is mainly used when the testing temperature exceeds 600 ℃. Usually used for TGA testing or synchronous DSC testing. Platinum crucibles can be tested up to 1600 ℃. It should be noted that the metal sample may form a eutectic alloy with the platinum crucible, which may melt through the crucible. After cleaning, the platinum crucible can be reused

Selection of crucibles

1. Aluminum oxide crucible (ceramic crucible). In TGA experiments, it is the most commonly used crucible. It is relatively stable for the vast majority of samples and does not react with them. In the range of room temperature to 1650 ℃, aluminum oxide crucibles do not have thermal reactions. The melting point of aluminum oxide crucibles exceeds 1700 ℃ and can be reused, but the cleaning process is slightly cumbersome.

2. Platinum crucible. Platinum crucibles are also reusable crucibles. Platinum crucibles have excellent thermal conductivity. Compared with ceramic crucibles, using platinum crucibles in synchronous thermal analyzers can achieve better synchronous DSC test results. However, it should be noted that platinum may become a catalyst for certain samples, so careful analysis is necessary before use. The melting point of a platinum crucible is 1770 ℃. During high-temperature testing, a platinum crucible may form a co melting point with certain metals and compounds, resulting in a decrease in the melting point of the crucible and causing it to stick to the sensor. To solve the problem of alloy formation between metal samples and platinum crucibles, a thin layer of alumina powder can be added to the bottom of the platinum crucible, and then the metal sample can be placed on top of the alumina powder.

3. Aluminum crucible. Aluminum crucibles can only be used for low-temperature experiments in TGA experiments, and the maximum temperature cannot exceed 600 ℃ because the melting point of aluminum crucibles is 600 ℃. The aluminum crucible has good heat conduction, with thin arms and bottom, so

The tested synchronous DSC signal is good. And the aluminum crucible can be well sealed