The Fabrication Of Large Scale DVB Foam Microsheres Or Shells By Microfluidic

With the character of pure C, H component, high mechanical strength, micron or submicron porous distribution and achievable functional modification, divinylbenzene (DVB) foam microspheres or shells were important targets container which were used for inertial confinement fusion (ICF) as well as inertial fusion energy fuel. At present, the main factors which limited of preparation and application to low density porous DVB foams were precise molding and microstructure control technology. It is necessary to find a suitable method for the preparation of large diameter DVB with controlled diameter.The methods for preparing DVB foams include emulsion encapsulated technology, triple orifice technique and microfluidic technology. Among them, microfluidic can obtain monodisperse emulsion droplets in sequence, stability and controllable by adopting the special configuration pipeline. However, as for controlling diameter of emulsion droplets in micron, submicron range, it is a great challenge for preparation of large diameter DVB foam by microfluidic technology. In addition, challenge also exists in microfluidic chip fabrication with large diameter pipeline. Furthermore, the formation mechanism of emulsion droplets is also an important problem. As lacking for the theory analysis form experimental phenomena observation of droplet generation, many scholars used the computational fluid dynamics (CFD) method to construct microfluidic pipeline, and to simulate the process of droplets producing. These simulations are mainly concentrated in micron or submicron, but millimeter ignored.This paper adopted the numerical simulation to achieve the job which contained pipeline designing, droplets formation mechanism analysis and stability controlling conditions of emulsion droplets. The pipelines consisted co-flowing, focus flowing and double Y structure.The formation mechanism controlled by different velocities was obtained by analyzing the monodispersed emulsion droplets formation process, and the multi-droplet formation was further investigated. The results showed that emulsion droplets could be obtained controllable in dripping regime with a certain velocity ratio of two phase fluids, but multi-droplets generation mechanism presented more complex.With the simulation analysis and optimization of the design of pipeline by numerical, PDMS microfluidic chip was fabricated by removing mould method in simplification and rapid which observed smooth, good fidelity, longevity and apt to surface modification. Numerical simulation was proved reliability and instruction for large diameter DVB emulsion droplet preparation after PDMS slab used in droplet generation.Monodispersed DVB emulsion droplets were obtained controllable by using DVB solution as the dispersed phase, PVA aqueous as continuous phase. Double DVB emulsion droplets were formed controllable in wall thickness and diameter by using DVB solution as the oil phase, PVA aqueous as the water phase, D2O/H2O as internal phase as well. Then, DVB foams was collected after the horizontal rotating thermocuring, CO2supercritical drying. As a result, DVB foams microspheres with density about200mg/cm3, particle size distribution in0.6-3mm, and DVB foam shells with density about150mg/cm3, particle size distribution in3-5mm were obtained. The tests showed that sphericity was exceeded99%, concentricity below4.5%which was fulfillment for the requirement of ICF and IFE targets.