Droplets encapsulating solid microparticles with a thin coating layer have extensive applications in the fields of biochemical, advanced materials, and inertial confinement fusion. In this work, the droplet break-up technique is employed to prepare solid-water-oil (S/W/O) conformal droplets with an ultra-thin coating layer. A microfluidic chip, consisting of a T-junction and a Y-junction, was designed and constructed for the controlled preparation of ultra-thin S/W/O conformal droplets by generating-splitting integration. The flow pattern, regime, and dynamic mechanisms of the S/W/O droplet break-up were also experimentally investigated. The results show that there are three break-up regimes: breakup, non-breakup, and transition. Two different modes are observed in the break-up regime: without solid core stagnation and with solid core stagnation. In the case of the solid core without stagnation, the neck goes through three stages: squeezing, transition, and pinch-off. When the solid core stagnates, the neck goes through one more solid core stagnation stage after squeezing. The stagnation percentage decreases as the dispersed phase capillary number increases and increases as the continuous phase capillary number increases. The coating thickness of the S/W/O droplet increases and then decreases as the continuous phase flow rate increases. The coating thickness of the daughter S/W/O droplet was significantly reduced and was less affected by the continuous phase flow rate.

A sort of ultra-light and elastic melamine sponge/graphene composite foam decorated with stretched graphene nanosheets was successfully prepared as electromagnetic interference (EMI) shielding device. For obtaining stretched graphene nanosheets, graphene oxide nanosheets are covered on the pore of melamine sponge formed the obstacle walls" with the aid of a fluid-assisted method, followed by freeze-drying and reduction treatment. This unique structure is crucial to dissipate electromagnetic waves, due to the formation of more "obstacle walls" and more closed cells for the multireflection. Only a low graphene loading of 0.105 vol%, the composite foam displayed extremely high EMI shielding performance with 37.2 dB, and a specific EMI shielding effectiveness was up to 3410dB. cm(3)/g owing to the low density of 0.011 g/cm(3). This work provides a novel methodology to produce graphene/polymer composite porous foam for highly efficient EMI shielding applications.

The ozonization modification of polystyrene (PS) was conducted in acidic condition to enhance the interfacial interaction between PS and polyvinyl alcohol (PVA). Infrared spectra results revealed that the carbonyl and hydroxyl groups were successfully introduced to the PS film by ozonization. The hydrophobic PS was turned to be hydrophilic to some extent by contact angle experiment, which led to the enhancement of interfacial adhesion between PS and PVA. In addition, the adsorption of PS to PVA was also improved. Nano indenter measurement indicated the interfacial interaction between PS film and PVA film was obviously enhanced by 40% after ozonization at room temperature for 2 h in acidic condition, which will benefit for fabricating laser inertial confinement fusion container.

Deuterated polymer shells are one kind of capsule needed in the fast ignition research.Kinds of deuterated polymer shells used in the fast ignition physical experiments were summarized in this paper.The stringent specifications on deuterated polymer shells used in the fast ignition physical experiments and different fabrication methods for these deuterated polymer shells were introduced.The factors affecting the quality of deuterated polymer shells were analyzed and the future development of deuterated polymer shells was also pointed out.

As hydrogen storage containers, titanium-doped hollow glass microspheres (HGMs) have been fabricated using the dried-gel method. A mathematical model was constructed to quantify the shell-forming process and make predictions on the wall thickness and aspect ratio of HGMs. Geometrical parameters of the HGMs were measured. The results showed that titanium doping would significantly change the compositions of gel precursor and glass melt. The multiple-step decomposition mode and loss of blowing agent in gels with more than 6.5 mol% titania reduced the blowing efficiency, thus producing greater wall thickness and smaller aspect ratio of HGMs. The measured aspect ratio decreased with increasing gel particle size, which was contrary to the predicted result. This was attributed to the poor blowing ability of large gel particles due to the limited residual time in the furnace. Moreover, the surface tension and viscosity of the glass melt were changed by titanium doping as well, which resulted in inadequate refining for heavily doped glass and consequently reduced the sphericity and surface finish of HGMs. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

SiO2-based phase change composites were prepared by sol–gel method using different phase change materials (PCMs), including stearic acid (SA), paraffin, and polyethylene glycol (PEG), and the effects of various mass fractions of PCMs were comprehensively investigated. The structures and thermal properties of these composites were characterized and analyzed by differential scanning calorimetry (DSC), X-ray diffraction (XRD), field emission scanning electron microscopy, and nitrogen adsorption–desorption measurements. The XRD and DSC results showed that the crystallinity and thermal enthalpy of paraffin in composite were the best among the three types of PCMs confined in SiO2. However, PEG in composites showed poor crystallinity and thermal enthalpy. After the extraction of the PCMs, the pore size distribution of SiO2 matrix and SEM images showed that SA/SiO2 composites possessed mesopores (20 nm) and macropores (50–150 nm), paraffin/SiO2 composites possessed mesopores and very large pores (2 μm), and PEG/SiO2 composites contained only mesopores. Among the three types of composites, paraffin/SiO2 composites exhibited the least mesopore volume. Presence of more mesopores in the composite led to worse crystallinity and thermal enthalpy of PCMs in composites. The crystallinity and thermal enthalpy of PCMs in composites were affected by the pore size and volume.

Polymer shells with high sphericity and uniform wall thickness are always needed in the inertial confined fusion (ICF) experiments. Driven by the need to control the shape of water-in-oil (W1/O) compound droplets, the effects of the density matching level, the interfacial tension and the rotation speed of the continuing fluid field on the sphericity and wall thickness uniformity of the resulting polymer shells were investigated and the spherical and concentric mechanisms were also discussed. The centering of W1/O compound droplets, the location and movement of W1/O compound droplets in the external phase (W2) were significantly affected by the density matching level of the key stage and the rotation speed of the continuing fluid field. Therefore, by optimizing the density matching level and rotation speed, the batch yield of polystyrene (PS) shells with high sphericity and uniform wall thickness increased. Moreover, the sphericity also increased by raising the oil/water (O/W2) interfacial tension, which drove a droplet to be spherical. The experimental results show that the spherical driving force is from the interfacial tension affected by the two relative phases, while the concentric driving force, as a resultant force, is not only affected by the three phases, but also by the continuing fluid field. The understanding of spherical and concentric mechanism can provide some guidance for preparing polymer shells with high sphericity and uniform wall thickness.

为了改善激光惯性约束聚变用厚壁聚合物空心微球球形度和壁厚均匀性,文中在外水相(W2)引入聚丙烯酸(PAA),对比了不同相对分子质量PAA(L-PAA,H-PAA)与传统界面改性剂聚乙烯醇(PVA)对复合乳粒形变的影响及作用机理.结果表明,PVA通过亲疏水基团可有效稳定直径900 μm复合乳粒,但大幅度降低了油水界面张力,当乳粒直径增加,油相和内水相Laplace压力降低,变形增加,PVA对直径1900 μm复合乳粒稳定性下降;与PVA体系相比,LPAA体系油水界面张力大,但黏度与PVA体系基本相同,导致乳粒形成时维持力大于剥离力,不利于乳粒形成,且LPAA分子链相对较短,空间位阻较小,复合乳粒易融合、合并;H-PAA分子链长,空间位阻较大,不仅对大小直径复合乳粒稳定效果明显,而且其油水界面张力大,有利于乳粒球形化,提高了高球形度PS微球的产率.

为提高惯性约束聚变(ICF)点火靶尺度(约2 mm)聚苯乙烯(PS)空心微球的球形度,研究了油相与外水相界面张力、初始油相质量分数和固化旋转流场转速对PS微球球形度的影响.结果表明,将双重乳液体系外水相中的表面活性剂聚乙烯醇(PVA)替换为聚丙烯酸(PAA)后,油相与外水相之间的界面张力增大了约10倍,PS空心微球的球形度显著提高,球形偏离度小于1μm的微球比例由5％增加至约50％;但是,在较宽范围内改变油相初始质量分数及旋转固化流场转速,对PS微球球形度的影响并不显著,球形偏离度值小于1μm的PS微球比例介于40％～60％之间.

在考察聚苯乙烯(PS)与聚乙烯基苄氯(PVBCl)相容性及干涉效应对测量结果影响的基础上,使用红外显微化学图像技术研究表征了PS与PVBCl混合物薄膜和微球的相分离情况,对比分析了不同处理条件下制备的微球半球壳中两种聚合物的相分离红外显微化学图像.研究结果表明建立的研究方法可以用来定性或半定量的分析球壳内PS和PVBCl两聚合物的分相情况,在测试中样品的干涉效应会对测量造成较大的不确定度,在不同温度下获得的聚合物微球样品中,40℃条件下两聚合物的分相情况更为理想.该研究为探索非均相双半球型聚合物微球制备条件以及红外显微化学图像法表征聚合物相分离提供了一种直观可行的表征方法,但受空间分辨率的影响,该方法不适合于6.25 μm×6.25 μm以下尺寸样品的分析.

为了改善臭氧处理聚苯乙烯(PS)单层球与聚乙烯醇(PVA)溶液生成的双层乳粒在油相中的分散性,提高大尺寸双层球的成活率,在双层球制备过程中采用了非离子型表面活性剂Tween 20(T-20)来改性该种PS单层球.结果表明经表面活性剂T-20改性后显著降低了PS薄膜的亲水接触角,提高了PS与PVA间的相互作用,同时也大幅度提高了PS薄膜对PVA的吸附速率.红外光谱和紫外-可见分光光度计的测试结果证明:在PVA固化过程中,由于PVA与T-20的相比太大,PS表面吸附的表面活性剂T-20部分会被PVA置换、迁移至PVA溶液中.T-20的迁移提高了制备双层球过程中水相与外油相的粘度比且显著降低PVA溶液表面张力,从而有利于实现双重乳粒在油相中的单分散.因此,T-20是制备大尺寸PS-PVA双层空心微球有效的表面活性剂.

Thick-walled polymer shells with high sphericity are always needed in the inertial confined fusion (ICF) experiments. The introduction of hexadecane (H) into the oil phase (0) was used to explore possible effects in improving the sphericity of polystyrene (PS) shells. The experimental results showed that not only the interfacial tension increased, but also the density matching levels between the inner water phase (W1) and the oil phase, and that between the W1/O compound droplets and the outer water phase (W2) were improved, probably due to the hydrophobic characteristic and low density of H. Therefore, the batch yield of PS shells with the out-of-round (delta(OOR)) values less than 1 mu m increased from 16% to 60% with increasing H mass fraction in the 0 phase from 0 to 0.6%. For wall uniformity, the yield of the PS shells with Delta t(w) less than 3 mu m also increased from 45% to 67%, but there was no further increase when H mass fraction in the 0 phase was more than 0.2%. However, when the H mass fraction was 1.0%, the PS shells became opaque, since there were many voids in the shells resulting from very low solubility of H in water. Therefore, the H concentrations in the O phase should be controlled according to the requirements of the structure. Obviously, the introduction of H into the O phase provides a novel and effective method for preparing PS shells with high sphericity. (C) 2015 Elsevier B.V. All rights reserved.

Number of emulsion particles vs. time with various sucrose (Suc) concentration in rotating flow field. (Large sized W1/O/W2 double emulsion droplets with uniform wall thickness and diameters were prepared by adopting the emulsion microencapsulation method.)

为建立高效简洁的厚壁空心微球球形度和壁厚均匀性的表征和测量方法,以内径850 μm、壁厚25μm的厚壁聚苯乙烯(PS)微球为测量对象,分析球形度和壁厚均匀性的表征方法,探讨测量过程中采样方式对表征微球球形度和壁厚均匀性的影响.研究表明:对于批量微球球形度和壁厚均匀性的表征,当抽样数目不小于30时,测量结果之间的差异很小;而对于单一微球的球形度和壁厚均匀性的表征,至少3个不同投影面的测量结果的平均值才趋于稳定.不同投影面导致球形度或壁厚均匀性较差的批次样品的测量结果有一定差异,多次投影测量可提高测量结果的可靠性.

The elastic silicone/n-hexadecyl bromide microcapsules were prepared as novel microencapsulated phase change materials by microfluidic approach with the co-flowing channels, where the double oil1-in-oil2-in-water (O1/O2/W) droplets with a core-shell geometry were fabricated. The thermal characterizations of the microcapsules were investigated using differential scanning calorimetry (DSC) and thermogravimetry analysis (TGA). The DSC results showed that the microcapsules had good energy storage capacity with melting and freezing enthalpies 76.35 Jg(-1) and 78.67 Jg(-1), respectively. The TGA investigation showed that the microcapsules had good thermal stability. The surfaces of microcapsules were smooth and the cross sections were compact from the results of optical microscope and scanning electron microscopy (SEM). Optical microscope showed that the silicone shell can provide expansion place due to its elastic property. Therefore, the silicone/n-hexadecyl bromide microcapsules showed good potential as thermal regulating textile and thermal insulation materials. (C) 2014 Elsevier B.V. All rights reserved.

To control the inner diameter change of double emulsions and to improve the surface finish of the resulting poly(-methyl styrene) (PAMS) capsules, the effects of electrolyte in the inner and outer water phases on the water migration and phase separation behaviors in the oil phase layer during curing process were investigated. The results show that addition of electrolyte only in the inner water phase leads to a migration of the water from the inner to the outer water phase and thus results in a shrinking of the double emulsions, potentially wrinkling the resulting PAMS capsules. When adding electrolyte into the inner and outer water phases at the same time, the chemical potential of the inner water phase balances with that of the outer water phase, so that the generation of water microdroplets and the migration of water in the oil phase layer during the curing process are suppressed and then the vacuoles in the shell wall of the resulting PAMS capsules are reduced. Moreover, through adjusting the concentrations of electrolyte in the inner and outer water phases, the densities of the three phases of the double emulsions can also be matched for improving the sphericity and wall thickness uniformity of the resulting PAMS capsules.

Adopting ozone modified polystyrene (PS) microsphere technique and optimi-zing technique of the structure of lobed wheels ,the interaction between PS and poly-vinyl alcohol (PVA) was improved ,and the flow field movement was also ameliorated . PS-PVA double hollow microspheres with diameter of 500-700 μm were prepared ,and the influence of density matching between initial emulsion particle and solvent on the uniformity of PVA layer was systematically studied . The results show that density contrast of solvent-particle about 0.015-0.020 g/cm3 at 20 ℃ and 0.010 g/cm3 at 37 ℃can form well homogeneous PVA layers .

为了改善臭氧处理PS单层球与PVA溶液生成的双重乳粒在油相中的分散性,采用了低分子量阴离子型表面活性剂十二烷基硫酸钠（SDS）和十二烷基苯磺酸钠（SDBS）及高分子量混合型表面活性剂十八烷基胺聚氧乙烯醚双季铵盐（PAVDA）来改性该种PS单层球,测试并分析了不同表面活性剂对相应薄膜亲水接触角及其对PVA吸附速率的影响,同时也考察并对比了静电排斥作用和空间位阻作用对双重乳粒分散性的影响。实验结果表明这三种表面活性剂均能不同程度的改善双重乳粒在油相中的分散性。其中,经SDS和SDBS处理后,双重乳粒在油相中固化时会发生絮凝作用而无法以较高成活率制得大尺寸双层球;经PAVDA处理PS单层球后,实现了以较高的成活率制得700~900μm的PS-PVA双层空心微球。同时,也表明在改善PS单层球的分散性方面,空间位阻稳定作用较静电排斥作用更为有效。

基于VMR显微镜系统,提出了一种小批量测量聚a-甲基苯乙烯(PAMS)芯轴直径和球形度的方法,初选满足技术指标的微球.小批量测量1 mm标准球,测量结果95％出现在(998.2±1.2)μm之间.测量值与标准值之间的偏差为标准值的0.06％,扩展不确定度偏差为测量值的0.24％,说明该批量测量结果准确度和稳定性较好.将此方法应用于PAMS芯轴初选,与手动测量结果相比,批量测量结果的偏差具有单向性,且最大偏差约10μtm,满足初选测量要求.

To study the influence of solidification rates of double emulsions on the sphericity of the resulting poly(α-methyl styrene)(PAMS)capsules in the microencapsulation process of PAMS capsules,the diffusion rates of fluorobenzene from oil phase to outer water phase under different conditions were experimentally measured,and the curing process of double emulsions under corresponding curing conditions were investigated.The results showed that the concentration of fluorobenzene in the outer water phase had a significant effect on the diffusion rate of fluorobenzene,which directly determined the solidification rate of double emulsions and then the sphericity of the resulting PAMS capsules.During the key phase of the solidification process of double emulsions,keeping proper concentrations of fluorobenzene in the outer water phase could remarkably reduce the solidification rate of double emulsions and consequently improve the sphericity of PAMS capsules.By optimizing the concentration of fluorobenzene in the outer water phase,the batch percentages of PAMS capsules with out-of-round less than 1 μm increased from 1.9% to 30.4%.