Differential thermal analysis is simple to operate, but in practice it is often found that the same sample is measured on different instruments, or different people are measuring on the same instrument, and the resulting differential thermal curve results are different. The peak temperature, shape, area, and peak size will vary. The main reason is that heat is caused by many factors and the heat transfer is complicated. Generally speaking, one is the instrument and the other is the sample. Although there are many influencing factors, as long as certain conditions are strictly controlled, good reproducibility can still be obtained.
To achieve a smooth baseline, the choice of reference is important. The reference material is required to undergo no change during heating or cooling. The specific heat, thermal conductivity and particle size of the reference material are as close as possible or similar to the sample throughout the heating process.
Alpha-alumina Al2O3) or calcined magnesia (MgO) or quartz sand is commonly used as a reference. If the analysis sample is metal, metal nickel powder can also be used as a reference. If the thermal properties of the sample and the reference material are far apart, the method of diluting the sample can be used to solve the problem, mainly to reduce the severity of the reaction; if there is gas generated during the heating of the sample, the gas can be reduced in a large amount to avoid the test. The sample rushed out. The selected diluent cannot have any chemical reaction or catalytic reaction with the sample. The commonly used diluents are SiC, iron powder, Fe2O3, glass beads Al2O and the like.
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