Study On The Humidity Controlling Material Of Magnesium Oxide And Its Application

In this paper, complex humidity-controlling materials with magnesium oxide were prepared through physical foaming method by adding modified mineral material and using light magnesium oxide as the main raw material. First used to modify the mineral materials with moisture absorption characteristics, then analyzed its microstructure,specific surface area, pore volume, pore size and moisture absorption/desorption characteristics. Magnesia based porous materials were prepared through physical and chemical foaming method by using light magnesium oxide as the main raw material,potassium dihydrogen phosphate as activator, boric acid as retarder. Using a single variable method to explore the effects in physical properties of foaming agent types and dosage and magnesium oxide to phosphate ratio(M/P) of magnesium oxide based porous material. Finally, humidity controlling composite materials with magnesium oxide were prepared by adding the modified mineral materials. The effect of additive amount of modified mineral material to the moisture absorption quantity and speed of composite material was studied. The humidity regulation of composite material in simulation space was obtained. The applicability of the composite was evaluated.The specific research contents and experimental results are as follows:(1) Diatomite and sepiolite good moisture absorption performance were selected as the research objects in this chapter. They was modified by acid leaching and calcined.Properties of samples were characterized by XRD, XPS, FT-IR, SEM, pore specific surface analyzer. The humidity controlling principle of diatomite as well as acid leaching and calcined effect on its specific surface area, pore structure and the moisture absorption and desorption performance had been studied. The results showed that acid leaching and calcined changed the pore structure and specific surface area of diatomite and sepiolite.The main factors to determine the moisture absorption ability were its structure and surface properties. After acid leaching and calcined, the moisture absorption rate of diatomite can be multiplied. After acid leaching and calcination, the calcite impurities in pores were dissolved and sepiolite fibers become thin and short, the moisture absorption rate can be reached 1.018%。(2) Magnesia based porous materials were prepared through physical and chemical foaming method. A single variable method was used to explore the effects in physical properties of foaming agent types and dosage and magnesium oxide to phosphate ratio(M/P) of magnesium oxide based porous material. The results showed that magnesia based porous materials with different pore size distribution could be prepared through physical and chemical foaming method by using light magnesium oxide(extensive source, simple preparation process and energy saving) as the main raw material,potassium dihydrogen phosphate as activator, boric acid as retarder. The material properties are closely related to its apparent density and porosity. Porous materials with density of 490 kg/m3, thermal conductivity of 0.1725W/(m·K) and compression strength of 0.304 MPa can be prepared in terms of F4 as foaming agent, adding amount is 0.75%,M/P is 4:1, boric acid content is 10%, water to cement ratio of 0.9.(3) Complex humidity-controlling materials with magnesium oxide which used physical foaming technology could be prepared by mixing with water into a paste after casting with adding modified mineral materials. The effect of additive amount of modified mineral material to the moisture absorption quantity and speed of composite material was studied. Pore structure in magnesium oxide matrix was characterized.Mechanical properties and thermal properties of the composites were studied. The results show that: diatomite and sepiolite were evenly attached in the surface of magnesium oxide based humidity controlling composite materials. When the additive amount of modified mineral material is 20%, Composite humidity-controlling materials with thermal conductivity of 0.1362W/(m·K), compression strength of0.568 MPa, saturated moisture content of 3.1529 g in 85%RH, saturated moisture liberation of 2.8581 g in 25%RH could be obtained. It has good moisture absorption performance in high humidity.