Preparation And Environmental Characteristics Of Aerogel Type Wood

Aerogel has a light structure and with special sound, particularly optical and thermal properties. If the special structure with functional properties can be applied to wood material with architecturally physical and environmental characteristics, there will be no doubt to create new functions for wood materials and develop their practice range. Thus, this article proposes a novel idea of targeting wood-based material with new environmental characteristics and special functions by imitating wood cell structure with wood main components to create aerogel-based materials ("Aerogel type wood" for short).This research used residues of natural light wood (Trema orientalis) as cellulose material, and dissolved them by ionic liquid, followed by supercritical drying process to prepare aerogel-type wood. The physical properties of the novel material including micro structure, chemical components structure, crystalline form and density were first characterized and tested, and then its environmental characteristics were further analyzed from angles of vision, tactile, phonics and environmental stability. These researches mainly involved the following four points: analysis of the visual environment characteristics on the basis of visual physics, visual psychology, and visual physiology; evaluation of the tactile environment characteristics from tactile roughness, contact friction, thermal properties, hard and soft nature, sliding properties and walking sense; analysis of the effect and prospect of the new formed aerogel-based wooden acoustic panels from angles of sound absorption and noise reduction; analysis of technical ways by which to improve its environmental stability and self-cleaning surfaces from angles of studying surface inorganic nanocrystalline forms to obtain superhydrophobic effect.The main research results and conclusions are as follows:(1) First, the aerogel-type wood is prepared under crafts of dissolution of wood materials by 1-propenyl-3-methylimidazolium ionic liquid and followed supercritical drying process. And then, cellulose fibers as supporting frame with incomplete three-dimensional cross-linked network are reformed after dissolution of aerogel-based timber. The reformed cellulose fibers possess microstructure that similar with light wood, stable chemical and physical properties, dry density of 0.221 g/cm3 and porosity over 87%.(2) The lightness L* of aerogel-type wood is between 80.22-84.16, and the color saturation C* is between 15.90-20.19, and the color commodity index of metric red-green axis a* is between 3.51～5.18, and the he color commodity index of metric yellow-blue axis b* is between 15.51～19.64, and the gloss value is only 4.1%. The interior decoration from aerogel-based timber shows visual and psychological impression of "nature", "comfort", "elegance" and "brightness". And in visual physiology, the stimulation of aerogel-type wood on human eye is small without causing visual fatigue, irritability and discomfort.(3) The thermal conductivity of aerogel-type wood is 0.054W/(m·K), and its thermal diffusivity is 444×10-10m2/s, indicating aerogel-type wood capable of being used as thermo-protective and heat-resistant material. The maximum diameter of the internal chamber of aerogel-based timber is 364μm, with mean diameter of 285.5p.m. The contours arithmetic mean deviation (Ra) of the surface roughness is 12.06μm. And the physiological index such as touching heart rate variability, ambulatory blood pressure shows relatively smooth change, and is similar with that of spruce wood, which provides appropriate stimulation for people, capable of being used indoors closely contacting with body parts.(4) The analysis results of the gait dynamics for people walking on the aerogel-type wood show that there is similarity for the value between aerogel-based timber and natural timber. The network structure shows strong supporting function for human body's trample, and also a degree of flexibility, capable of easing knees and absorbing the impact of fatigue. The difference value between static friction coefficient and dynamic friction coefficient is almost zero, which rarely results in physiological load on human body.(5) The mean absorption rate tested by standing wave tube method for the aerogel-type wood is 43.50%. And the sound absorption coefficient respectively reaches 82.7%in medium frequency of 1000Hz and 71.2% in high frequency of 2000Hz, showing favorable characteristics of sound absorption and noise reduction. The mean absorption rate of aerogel-based timber after being made into wooden sound-absorbing panels as core layer is increased to 57.6%, and the noise reduction coefficient reaches 0.64, achieved gradeⅡboard requirements.(6) The surface of the aerogel-based timber was in-situ covered by TiO2 nanocrystalline layer through hydrothermal crystallization process under lower temperature. And the contact angle, inhibition of mold and formaldehyde emission for the TiO2 modified aerogel-based timber were also tested and analyzed. The results indicate that this treatment endows the aerogel-type wood with good surface self-cleaning, environmental stability, durability, and a degree of air purification for organic pollutants.In conclusion, the aerogel-type wood prepared in this research possesses similar or even better indoor micro environmental characteristics, compared to natural wood. And it can provide even better indoor environments for people when it is applied in special situations. Additionally, the novel wood-based material achieved by green chemical treatment can continue to fix and store carbon absorbed during the growth stage of trees, and will also play a certain significance in areas of low-carbon and environmental protection.