Properties of Active Magnesium Oxide
Active magnesium oxide, also known as light-burned magnesium oxide or caustic magnesium oxide, is magnesium oxide formed by calcining magnesium compounds below 900°C. The chemical activity of magnesium oxide can be expressed by the iodine absorption value (adsorption performance index). The greater the chemical activity and the greater the iodine absorption value, the lighter it is. When the iodine absorption value is 120-180 mg/g, it is called high-activity magnesium oxide, when the iodine absorption value is 50-80 mg/g, it is called medium-activity magnesium oxide, and when the iodine absorption value is 19-43 mg/g, it is called low-activity magnesium oxide.
Active magnesium oxide is generally relative to heavy magnesium oxide. Since the activity of solid substances is proportional to their surface area, some people use the size of their surface area to express activity, so the specific surface area (the surface area per unit mass of substance) is introduced to regard the specific volume (ml/g) as the reciprocal of the bulk density. Generally speaking, highly active magnesium oxide is in the form of ultrafine powder, which refers to particles with a particle size of 10-1000nm. Due to the extremely small particle size of ultrafine particles, they often show special properties that conventional materials do not have in terms of magnetism, electricity, sound, heat and sensitivity. Therefore, it is widely used as a new material. The activity expressed by the citric acid activity value is 12-25. The smaller the value, the higher the activity. The activity expressed by the iodine absorption value is 80-120 (mgI/100gMgO), the specific surface area is between 5-20, and the apparent specific volume is between 6-8.5ml/g. Due to its large specific surface area, it has extremely high chemical activity and physical adsorption capacity, has good sintering performance, does not require the use of sintering aids to achieve low-temperature sintering, and is a preparation of high-functional fine inorganic materials.
Active magnesium oxide preparation process
1. Dolomite carbonization method. Dolomite or magnesite is calcined, and water is added to digest to obtain Mg(OH)2 and Ca(OH)2. After carbonization with CO2, magnesium bicarbonate and by-product calcium carbonate are obtained. After removing calcium carbonate, the mother liquor is pyrolyzed to obtain basic magnesium carbonate, which is then calcined at 800℃ for 1 to 2 hours to obtain active magnesium oxide.
2. Brine-ammonia method. After ammonia is introduced, the magnesium salt in the brine is converted into magnesium hydroxide precipitation. After the magnesium hydroxide is filtered, washed, destroyed, and dried, it is transferred to a rotary calcining furnace for calcination to obtain active magnesium oxide. The calcination temperature is preferably controlled at 500℃ for 2 hours.
3. Brine-ammonium carbonate method. Ammonium carbonate solution is added to the brine, and basic magnesium carbonate precipitation is generated after heating and precipitation. The precipitation is filtered, washed, dried, destroyed, calcined and differentiated to obtain active magnesium oxide.
Applications of Active magnesium oxide
Active magnesium oxide is widely used in luminous parts, gas sensors, various rubber products, fiberglass, fluororubber, catalysts, adsorbents, etc., showing the excellent properties of active magnesium oxide. In recent years, after continuous development and application research and development, active magnesium oxide has been widely used in rubber products, fiberglass, petrochemical industry and other fields.
