Shear flow-induced super nanocomposite mass production!

I. Background

nature shellfish, bones and teeth, both excellent strength and toughness. Numerous studies indicate that these biological material to obtain excellent mechanical properties mainly due to organic and inorganic nanoparticles anisotropy organic – forming highly ordered layered microstructure inorganic hybrid. Inspired by the above-described biological structure, including the preparation process layer assembly, vacuum filtration, etc. microstructure regulation layered nanocomposites. However, these methods are still some drawbacks, on the one hand, large-scale preparation of a composite long-range orientational structure can not be achieved. On the other hand, multi-component nanomaterials for enhanced system, can not avoid the problem of nano materials in the preparation process reunion, reunion and nanomaterials will directly affect its overall performance. Thus far, large-scale continuous layered structure of Making Nanocomposites remains a major problem.

Second, the research results

Recently, Beijing University of Aeronautics and Astronautics Professor Liu Mingjie Task Force the use of flow-induced shear large aspect ratio the two-dimensional sheet is oriented in its direction of flow are arranged, the method having a highly ordered layered nanocomposites continuous batch prepared. For example, the tensile strength of the nanocomposites based on clays and nano-graphene oxide sheets up display 1215 ± 80 MPa, a Young\’s modulus of 198.8 ± 6.5 GPa. Further, by adding carbon nanotubes using spread prepared by ultra high toughness nanoclay group (SS- clay / CNT) reaches the toughness of nanocomposite films 36.7 ± 3.0 MJ / m 3 [ 123], a 20.4 times the natural nacre, while the tensile strength of up to 1195 ± 60 MPa. GO large aspect ratio of the nano-sheet to have better stress transfer and higher cohesive strength, well-dispersed carbon nanotubes can be enhanced by adjacent nano sheet and the mechanical properties of the bridging polymer matrix further improve the mechanical properties . The work \”Layered nanocomposites by shear-flow-induced alignment of nanosheets\” was published in top international academic journals Nature 123] on [. 剪切流诱导超强纳米复合材料实现量产! III. Highlights herein:

to provide a shearing of the hydrogel / oil interface – Rheology induced two-dimensional arrangement of sheets, preparation of highly ordered quantities layered nanocomposites.

  1. Method spreading over the paper can be easily extended to other two-dimensional packing, and provide a reference nanocomposite super layered structure prepared in bulk.

Fourth, the research results discussed ideas and specific

Preparation and Mechanism layered nanocomposite films

Figure 1 . a- dropwise a solution (10 l) and spontaneously achieve complete diffusion of the hydrogel / oil interface, forming a thin layer of solution-diffusion. The reaction solution of 0.09 wt% GO and 0.18 wt% NaAlg composition. b- Preparation of large area continuous films schematic nanocomposite, comprising the steps of the ultra-oil dispersion, crosslinking of NaAlg calcium ions, the gel film surface of the hydrogel was separated, dried and collected. A reaction solution containing GO nanosheets and NaAlg. B solution containing CaCl2. Theory c- nanosheet alignment mechanism during spreading induced shear flow. They are H and R droplet radius and height. D- two adjacent syringes solution-diffusion combined into a continuous and uniform layer of liquid. e- nanosheet fixed after orientation by methods NaAlg and Ca2 + ions in situ crosslinking. 剪切流诱导超强纳米复合材料实现量产!
comprising use of graphene oxide (GO) and sodium alginate droplets nanosheet (of NaAlg) of the reaction solution was spread over the surface of the ultra hydrogel polyacrylamide (PAAm), whereby water gel / oil interface layer to form a uniform solution. Use of the reaction solution while the extruded multiphase, ultra extended spreading process to a continuous system for preparing a thin film in order to achieve large scale fabrication of highly oriented films having a nanocomposite nanosheet. In this study, by selecting the appropriate flow rate, the distance and the moving speed between the hydrogel adjacent syringe, thereby controlling the oil / water interface to form a homogeneous gel solution super diffusion layer. At the same time, calcium chloride hydrogel calcium (Ca
2+

) diffuse from the hydrogel over the surface of the diffusion layer and the NaAlg crosslinking occurs, the GO nanosheet fixed to calcium alginate (CA), thereby forming a hydrogel CA composite film. The hydrogel film is then immersed in a water bath prepared, and dried, to obtain a continuous and uniform excellent in GO / CA nanocomposite films.

Figure 2. Regulation layered nano composite film uniformity and continuity. a- was spread relationship between the diameter d and the flow rate Q is d α Q1 / 2 (red). Wherein the solution viscosity of 6 mPa s, the moving speed of the hydrogel matrix is ​​5 mm / s. The flow rate Q and the distance L between the syringe layered nanocomposite impact film uniformity and continuity of two adjacent b-. Optimum spacing L = d (Q) -6 mm (green line). C- four kinds nanocomposite film formed in accordance with the difference in the distance L, including a discontinuous film (the DF), but a continuous uniform film (CNF), a continuous and uniform film (the CUF) and the continuous and folded film (CFF). Scanning electron microscopy (SEM) were taken from two test area of ​​the syringe and injection merge region below the region adjacent the nozzle needle (border color (middle column) and a black border (the most right column)). 剪切流诱导超强纳米复合材料实现量产!
For preparation of a uniform continuous nano composite film, the distance L between the syringe shot liquid diffusion reaction adjacent the syringe and the diameter d is critical process parameters. OF expanded diameter is regulated by adjusting the speed of a solution or solution viscosity of the aqueous gel matrix. Further, in order to achieve continuity and uniformity of the nano-composite films, two adjacent L is the distance between the important process parameters syringe. When the L value is slightly smaller than the value d, since the edge of the diffusion layer was not sufficient diffusion capacity, it can not coalesce, but so as to obtain a continuous uniform film. The results show that the optimum separation distance between two adjacent syringes satisfies L = d (Q) -6 mm, which is consistent with the theoretical analysis. Further, when the distance L is kept constant, may be regulated by increasing the uniformity of the film flow rate Q. Layered Structure Characterization Nanocomposite Films
3. FIG. a-GO TEM hyperdispersant orientation, and composite materials formed of randomly dispersed b-, 2D-SAXS and a schematic view of the azimuth angle φ. C- Preparation of the azimuth angle φ and the degree of orientation parameters graph d- Four different percentages by weight of the nano lamellar GO nanocomposite films with super spreading method. 剪切流诱导超强纳米复合材料实现量产!
cross-It discloses a cross-sectional TEM image of the arrangement state of spreading super prepared SYSTEM GO / CA nanometers GO nanosheet composite film. In contrast, prepared by Method randomly oriented nanocomposite membrane GO GO nanosheet significant interleaving structure. Characterization of the degree of orientation GO nanosheet by SAXS. Orientation GO / CA Nanocomposite Films FIG. 2D-SAXS scattering occur two strong points, and the corresponding azimuth angle ([Phi]) in FIG φ = 90 ° and 270 ° at the two peaks. Calculate the degree of orientation as high as 0.89, indicating that the highly oriented GO nanosheet In CA. The authors also of different concentrations of GO nanosheet (2,8,15 and 33 wt%) in the case where the alignment layer nanocomposite film. The corresponding TEM images and SAXS indicate GO nanosheet is highly oriented in all nanocomposite films.
Characterization of Figure 4. Layered nanocomposite films. a- strength and modulus of composites; B- diffraction vector; c-tanδ curve with temperature; the interface between the analog schematic d- nanosheets; e-GO / clay / CNT Nanocomposite Films sectional view fg- , prepared by LBL, casting and filtered method SS-GO / clay / compare composite film strength and modulus CNT nm, and the corresponding properties of natural nacre comparing ultra dispersion method; h-SS- clay / CNT nano sectional view of the composite membrane; I- using a lamination process for preparing artificial pearls bulk layer; j- photo nacre and artificial nacre at the same impact force (160N) of. 剪切流诱导超强纳米复合材料实现量产!
Effect of nano-sheet forming the interface is highly oriented essential to improve the mechanical properties of the composite. Nanosheet good dispersibility and high orientation property and a strong interaction with the polymer matrix leads to the formation of many interfaces around nanosheet, effective to inhibit the movement of polymer molecule chains. With the increase of the weight percent of the nanofiller, resulting in reduced threshold distance to the interlayer, thereby forming a critical interface. In such a critical interfaces, confinement effect of reinforcing the polymer chain movement, and due to interaction with nanosheets reduced their mobility. In addition, large aspect ratio GO nanosheet to have better stress transfer and higher cohesive strength, well-dispersed carbon nanotubes can be enhanced by adjacent nano sheet and the mechanical properties of the bridging polymer matrix further improved mechanical properties. Nanocomposite Films with a conventional preparation method (including layer assembly (LBL), pouringCompared casting and vacuum filtration), the composite material formed by ultra-spreading method has higher mechanical properties. Using ultra-spreading method, the authors also nanoclay group (SS- clay / CNT) films having high toughness nanocomposite preparation, because the material is important for practical applications.
Method using spread Surpercritical clay / CNT nanocomposite film toughness reached 36.7 ± 3.0 MJ / m

3 , is 20.4 times that of natural nacre, while the tensile strength of up to 1195 ± 60 MPa . under high stress, the critical interface can effectively prevent the formation and propagation of cracks. Furthermore, prepared to give OF SS-GO / clay / CNT Nanocomposite Films by simply laminate method used to prepare bulk artificial pearls (4 cm × 4 cm × 0.2 cm). In the same impact force, naturally Yi Beizhen layer of beads broke into pieces, and artificial pearls SS-GO / clay / CNT nanocomposite film formation occurs only certain indentation depth and not broken. V. Study Summary

The method of spreading a solution of ultra-induced shear flow based on the combination of highly ordered layered structure composite membrane, the composite layered structure solves not large continuous preparation problem area, and thus more polymer derived directly filler and a method of manufacturing a layered nanocomposite films 2D nm. This work has great potential for mass production and application of high strength films. The full text link:

https://www.nature.com/articles/s41586-020-2161-8

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