When using a calorimeter for precise heat measurement, a bulge at the bottom of the crucible is a common failure, which not only affects the measurement results, but also may damage the instrument. Below, we will analyze in detail the reasons for the bulge at the bottom of the crucible with a calorimeter.

Material problem

The quality of the crucible material itself is crucial to the shape of the bottom. If the material selected for the crucible is not pure enough and there are impurities inside, in a high temperature environment, the thermal expansion coefficient of the impurities is different from that of the main material, which will lead to uneven heating of the crucible, which will cause the bottom to bulge. In addition, the high temperature resistance of the material is insufficient. If it is in a high temperature working state for a long time, the material structure will gradually deform, causing the bottom to bulge.

improper use

Frequent quenching and heating operations are a major cause of the bulge at the bottom of the crucible. When the calorimeter is working, the crucible needs to undergo a high-temperature combustion process. If the crucible is not allowed to cool naturally after the experiment, but directly contacts low-temperature objects, the huge temperature difference will cause the crucible to shrink instantaneously. If this is repeated, the bottom will bulge due to stress concentration. In addition, long-term overload use, such as each experiment makes the crucible withstand far more heat than its design limit, will also accelerate the deformation of the bottom of the crucible.

operation error

During the experiment, if the sample is added improperly, it may also cause problems. For example, if too many samples are poured at one time, and the samples are piled up at the bottom of the crucible, the heat generated during combustion cannot be evenly diffused, and the local heat is too high, which will cause the bottom to overheat and bulge. At the same time, if the residual combustion products in the crucible are not cleaned up in time after the experiment, these residues will be heated and expanded again in subsequent experiments, squeezing the bottom of the crucible and causing bulges.

After understanding the cause of the bulge at the bottom of the calorimeter crucible, we must strictly control the material quality of the crucible, standardize the operation process, avoid sudden cooling and overload use, and clean the crucible in time, so as to effectively reduce the bulge at the bottom of the crucible and ensure the stable operation and measurement accuracy of the calorimeter.