Study On Smart Humidity-control Materials

For mankind,it has always been a pursuit for indoor comfort that has control in the temperature,humidity,air quality,etc.However,buildings and other man-made structures consume a quantity of primary energy in the world.This is not conducive to the sustainable development of society.Therefore,building energy conservation has become an important means to deal with the global energy crisis and to achieve low-carbon and sustainable development.It is an effective way to solve the contradiction between individual demand and social situation to develop new materials with low energy consumption or even no energy consumption to improve the comfort of building interior environment.Air relative humidity and volatile organic compounds(VOCs)are the two key factors that influence building comfort and health,while water vapor has an important effect on the activity of VOCs catalyst at room temperature.In this paper,a series of porous materials were prepared,meanwhile,the water vapor adsorption and capillary condensation for them were regulated by controlling the pore size.Eventually,it has realized humidity control and indoor air pollutant(eg.formaldehyde)removal without energy consumption.Inspired by the functional microstructure of the ant nest,a humidity control material was prepared by sintering of modified low-grade sepiolite.A hierarchical porous structure accelerates the diffusion of water vapor.Meanwhile,Ca Cl₂ was added subtly to enhance absorption/desorption of water vapor in response to the change of air relative humidity.The water vapor adsorption-desorption content reaches 350 g·m^-2 with a steady performance after 10 cycles.The flexural strength of the specimen is excessive,10 MPa.Furthermore,two model houses were used to evaluate the performance of the material in a real indoor environment for 30 days.The results indicated that it could narrow indoor humidity fluctuation by more than 10%RH spontaneously and the humidity mainly maintained in a scope of healthy range(RH 40-70%,WHO recommendation)without extra energy consumption.This invention makes it possible for large-scale fabrication of this material in the form of wall bricks for smart indoor humidity control.To enhance the control of indoor humidity,we further using Ca Cl₂ as additive.Low-temperature sintering generated a super hygroscopic interior structure,and further silane modification produced bricks with superhydrophobic surfaces.These superhydrophobic surfaces can promote the moisture storage and prevent the Ca Cl₂solution from leaking even after the surface is wiped 100 times.Meanwhile,the superhydrophobic surfaces make the wall-bricks easy to clean;also,these materials possess antifouling and antifungal properties.The 24 h and saturated moisture adsorption-desorption contents reached 400 and 1700 g·m^-2,respectively.Furthermore,a test was performed using model houses in a real environment,which indicates that the wall-bricks can narrow the daily indoor humidity fluctuations by more than 20%in both wet and dry seasons.The white wall-brick can also be dyed with different colors and thus shows promise for applications in interior decorations of houses.According to the fluctuation of indoor air relative humidity,Mn O₂ with different pore sizes were prepared for exploring the water vapor absorption-desorption contents in high-low humidity environment.Capillary condensation can be effectively weakened for large mesoporous?-Mn O₂ under high humidity,and thus it avoids liquid water film from preventing the contact between O₂,HCHO and the catalyst surface,meanwhile,the water vapor adsorption under low humidity still remained.It can make full use of the water vapor to promote the catalytic reaction.The as-synthesized?-Mn O₂ catalyst exhibits a good performance for low-level HCHO at room temperature in a wide range of relative humidity(RH 33–85%).The doped K⁺in the layers brings more oxygen vacancy and thus improves the activation of O₂.The?-Mn O₂ catalyst achieved 93%removal efficiency for 1.0 mg·m^-3 HCHO under GHSV of 600 L·g^-1h^-1 at 25°C,and the removal efficiency kept 90%during 200 h test.Large mesoporous?-Mn O₂ can be loaded onto the surface of smart humidity control brick or other interior decoration materials to capture formaldehyde in the air and purify the indoor air.The above new materials can provide functional materials for passive energy-saving buildings,which can improve the health and comfort of buildings.At the same time it does not bring the energy consumption,and can promote sustainable development of the society with green and mild way.