Tsinghua Lin Tuo new Task Force para-aramid fiber prepared airgel material
Para-aramid fiber as a high-performance materials, have high strength, high modulus, good heat resistance and corrosion resistance, etc., in civil defense and other fields have a wide range of applications. Para-aramid prepared airgel material, is expected to broaden the scope of application of para-aramid. But the strong interaction between the molecular chains aramid, poor processing performance, thus limiting their use in areas such as airgel. Study aramid airgel materials there are prepared based on the phase separation method or the like, but its presence lengthy preparation process, a large number of disadvantages of using an organic solvent or poor sample occurs deformation, mechanical properties, not suitable for large scale production and application. Recently, the Tsinghua University Department of Chemical Research Associate TUO new forest TF on the basis of previous work, first of all with the aid of a non-reactive surfactant (polyethylene glycol dimethyl ether) is a para-aramid nanofibers ( aramid nanofiber, ANF), then by the bottom-up method of assembling a \”suction assisted self-assembly\” and \”ice frozen oriented template\” combining, successfully assembled into a three-dimensional ANF ANF airgel (FIG. 1). The ANF applied airgel comprising adsorption, high temperature filtration, the potential field of flame retardant, insulation and damping, which reference preparation prepared material having a three-dimensional ordered for airgel. 
FIG 1.ANF step aerogels prepared suction assisted self-assembly techniques are generally used for the preparation of ice-dimensional template material is freeze-oriented films is a common method for preparing three-dimensional ordered material airgel. The combination of both can play a role in the multilayer structure is formed is suction filtered ice crystal growth in the better ordered multilayer structure along the growth of ice crystals during growth. ANF schematic diagram of a two-dimensional to three-dimensions by the assembly shown in FIG. 
Figure 2. The suction assisted self-assembly & schematic frozen ice after the template is oriented both processes, by freeze drying, to obtain ANF airgel. ANF comprising airgel and anisotropic multilayer structure (FIG. 3). Since ice crystals may be formed along the more suction multilayer structure grown regularly and orderly, the degree of ordering of the inner layer sheet airgel can reach more than 1cm. 
FIG 3.ANF airgel microstructure: a sectional view (a) ANF airgel (cross-sectional view, xz-plane); (b) a detail of FIG.; (C) ANF airgelPlan view (top-down view, xy-plane); (d) in FIG c details; interlayer spacing (e) in figure a statistics; (f) a bridge phenomenon between the sheet ( \”bridge\” phenomenon); (g ) long-range order of the layered structure meets the characteristics of conventional aerogels .ANF airgel lightweight, high porosity and the like: a density of 25 ± 2 mg / cm3, a porosity of 98.2 ± 0.1%, a specific surface area 62.88 ± 0.50m2 / g. Combined with para-aramid good heat resistance, excellent mechanical properties and other characteristics, ANF airgel showed good overall performance. Excellent in heat resistance, up to the decomposition temperature of 500 ° C. ANF airgel structure airgel anisotropy imparting anisotropic mechanical properties and thermal conductivity. Airgel radial direction (alignment direction of sheet) having a high compression strength higher, more than aerogels have been reported in the literature; axial (vertical slice alignment direction) with good resilience, in 1000 compression times – after release cycle (30% strain) can maintain stress retention of 95%. ANF at room temperature airgel axial thermal conductivity of 0.0372 ± 0.0004 W / (m · K), thermal conductivity at 200 ° C was 0.1056 ± 0.0011 W / (m · K). This outcome to the recent \”From Monomers to a Lasagna-like Aerogel Monolith: An Assembling Strategy for Aramid Nanofibers\” was published in ACS Nano: on (DOI 10.1021 / acsnano.9b01955), corresponding author of the paper and associate research fellow Lin Tuo new Beijing School of materials Science and Engineering, University of Chemical Technology Associate Professor Qiu vine. The research was supported by the National 973 Program (2011CB606102) and Tsinghua University (Department of Chemical Engineering) – support of high-performance polymer materials Joint Research Center Fund – the Yellow River Delta, Beijing Institute of Chemical Industry Co., Ltd. Bo. In addition, the team made a series of studies in recent years, progress in the field of preparation and application of nano-aramid fiber, some of the research results published in the RSC Adv.2016,6,26599-26605; J.Appl.Polym.Sci.2016, 133On J.Appl.Polym.Sci.2018,135,46697 and other magazines;, 43623; Mater.Lett.2017,202,158-161. The research results can be widely applied to an insulating sheet, a lithium ion battery separator and other areas.
