The calcining time mainly affects the percent conversion and sintering degree. For the different precursors, the impact effect presents linearity correlation. Therefore, compared with calcination temperature and heating rate, it is very simple. Through referring to thermogravimetric analysis, we can know that the fully resolved minimum temperature is 600 degree centigrade. At this temperature, through changing the different burning time, it can measure the citric acid activity value of magnesium oxide. Under circumstance of decompose completely, the citric acid activity value will be diminish gradually before the burning time in two hours. That is the activity heats slowly. After two hours, the activity rapidly decreases. In the vicinity of two hours, the changes of activity is very large. Therefore, it is the most optimal in two hours.
With the increase of temperature, the specific surface area gradually becomes larger. After the temperature achieves 650 degree centigrade, the specific surface area begins to decline. With the rising temperature, the citric acid activity value rises as well. In the 650 degree centigrade, it achieves a minimum value, and then, begins to increase gradually with the rising temperature. Thus it can be seen it exists a best congruent relationship between the activity of magnesium oxide and the calcination temperature. Around the 650 degree centigrade, magnesium oxide activity achieves the maximum value. What’s more, personally, I think the magnesium oxide activity is directly proportional with magnesium oxide price.