Stabilization of monodisperse electrosprays in the multi-jet mode via electric field enhancement

The electrospray of conducting liquids operated in the cone-jet mode is well known to have the unique ability of generating droplets uniform in size over a phenomenal range of sizes depending primarily on the liquid flow rate and physical properties. Since there is a monotonic dependence of size on flow rate, the liquid flow rates that can be dispersed are modest if the goal is to produce very small (below a few micrometers in diameter) droplets. Yet, this is precisely the application niche for which few, if any, atomization alternatives are available. Multiplexing the spray source is indispensable for the electrospray capabilities to have an impact in high-value-added applications. We report here on a novel approach to multiplexing based on a well-known, but hitherto unexploited, regime of operation, the multi-jet mode. Ordinarily, such a mode is rather unsteady and the range of flow rates at which appreciable multiplexing is achieved is small. However, if the multi-jet mode is anchored by some sharp features (e.g., grooves, ridges, etc.) machined at the outlet of the atomizer, to intensify the electric field at discrete points around its perimeter, then the cone-jets are simultaneously anchored at these features and a stable mode of operation is identified over several hundreds of volts and a broad range of flow rates. Most importantly, so long as the machining is accurately reproduced from point to point, droplets generated do not vary significantly in size from spray to spray. As a result, a compact, inexpensive and versatile multiplexing system is realized without sacrificing droplet monodispersity.     

Multiple electrosprays emitted from an array of holes

Orifices instead of needle capillaries can be used for electrospraying liquids in steady cone-jet mode. This novel device has been used for multiplexing cone-jet menisci anchored at the rim of orifices drilled on a slide. The stability and reliability of the electrospraying process from holes improve substantially when orifices are drilled in dielectric materials with hydrophobic surfaces. The manufacturing process of high compactness multi-electrospray atomizers becomes much easier and cheaper if holes instead of needles are used as emitters. Very cheap multi-hole electrospray atomizers, bearing up to 37 holes and with a compactness of up to 115 emitters per square centimeter, have been home-made and successfully operated. The current and droplet size distribution of the spray issued from these atomizers agreed quite well with those issued from a single source of electrospray, provided that the same flow rate was being electrosprayed throughout each one of the orifices of the multi-injector, and that this value was equal to that issued from the single electrospray source.     

单分散高聚物的阴离子法合成

概述了单分散聚合物的概念，单分散聚合物在化学化工、化学建材、医药卫生、标准计量等领域的应用以及阴郭子合成单分散高聚物过程中单体与溶剂的精制及处理、催化剂的种类、单体、引发剂、终止剂的加入方式及搅拌方法等条件。     

Bulk density of monodisperse materials

A cluster model is used to calculate the bulk density of monodisperse systems. The values calculated with the help of the model are consistent with the experimental data. the dependence obtained can be used to determine the properties of ceramic and composite materials. Translated from Ogneupory i Tekhnicheskaya Keramika, No. 7, pp. 21–23, July, 1997.     

单分散微米磷酸锂的制备

以提锂后的尾液为原料,与Na2CO3和Na3PO4·12H2O反应,在较为温和的水热条件下(120～150℃)、较短的反应时间内(3～10 h)制得了单分散的球形Li3PO4颗粒,粒径约5～8μm,产率达到90%以上.该方法是一种环境友好的绿色化学制备方法,全过程接近污染物零排放,不仅解决了尾液的环境污染问题,而且还提高了盐湖资源的综合利用率.     

Sinterability of monodisperse TiO2 powders

Sintering of monodisperse titania powders with a relatively large grain size (0.84±0.24 µm) is investigated. It is established that the use of nonagglomerated monodisperse powders makes it possible to fabricate ceramics with a density of 99.5% of the theoretical value and a narrow distribution of pore sizes without preliminary milling and by relatively simple technological means, namely, cold pressing and casting into gypsum molds followed by sintering at a relatively low temperature. In combination with a high density such a structure makes the developed ceramic material applicable for the production of porous membranes for microbiology and medicine.Translated from Ogneupory i Tekhnicheskaya Keramika, No. 9, pp. 11–13, September, 1996.     

单分散介孔二氧化硅微球的制备

在Stober方法基础上制备了单分散二氧化硅微球,系统研究了反应条件对成球粒径以及单分散性的影响。通过多种测试手段,发现随着正硅酸乙酯和氨水浓度的提高,成球的粒径逐渐增大;而温度的提高会促使氨水挥发而使得成球的粒径降低;反应时间在反应初期对成球粒径的影响很大,然后逐渐趋于平缓。经对煅烧前后产物的小角X射线衍射对比分析,发现煅烧后产物的峰强度增加,并且重叠峰向右漂移,指示表面活性剂分子从孔中移除并发生了孔径收缩现象,同时发现不同反应条件对产物的织构性质有一定的影响。研究了相关的反应机理,认为在碱性条件下二氧化硅微球由正硅酸乙酯的水解和缩聚两步过程完成的,该方法为制备单分散介孔二氧化硅微球提供了一种简单有效的并且可重复的路径,从而可能用于大批量生产。     

Dynamics of a pulsating monodisperse mixture

Dynamics equations for a monodisperse two-phase mixture are derived with regard to interphase forces due to a difference in velocity, the associated mass effect, and changes in the velocity field near particles. Numerical solutions are given for low-frequency (10^-1-10² Hz) pulsation of the carrier phase. It was found that the residence time of the disperse phase in a column depends primarily on its retention capacity and pulsation frequency.     

Dual thermo-responsive and ion-recognizable monodisperse microspheres

A novel type of dual stimuli-responsive microspheres that simultaneously exhibit ion-recognition property based on the supramolecular host-guest complexation of crown ether receptors (benzo-18-crown-6-acrylamide) (BCAm) with specific ions and thermo-sensitivity based on the phase transition of poly(N-isopropylacrylamide) (PNIPAM) is fabricated in this study. The prepared poly(N-isopropylacrylamide-co-benzo-18-crown-6-acrylamide) (P(NIPAM-co-BCAm)) microspheres are characterized by FT-IR spectroscopy, UV-vis absorption spectroscopy, scanning electron microscopy (SEM), and dynamic light scattering (DLS). SEM images and DLS data show that the synthesized microspheres exhibit nearly perfect spherical shape and high monodispersity. Moreover, according to the DLS results, P(NIPAM-co-BCAm) microspheres exhibit satisfactory thermo-responsive behavior and ion-recognition property. In K⁺ solutions, due to the formation of crown ether/K⁺ complexes, the LCST of P(NIPAM-co-BCAm) microspheres shifts to a higher temperature and the colloidal stability is increased. The P(NIPAM-co-BCAm) microspheres undergo a volume change from shrunken state to swollen network isothermally at a certain temperature by the addition of metal ions. Due to dual thermo-responsive and ion-recognition behaviors, this kind of microspheres would serve as promising candidates for sensors, controlled drug delivery systems and possibly new biomaterials.     

Preparation and modification of monodisperse hydrogel microspheres

Monodisperse hydrogel microspheres were prepared by precipitation polymerization of acrylamide and comonomers in ethanol and propan-2-ol and their mixtures. The size of the microspheres varied from 0.2 to 1.3 μm as a function of the solubility parameter of the dispersants. The applicability of the three-component solubility parameter approach by Paine was examined. Seeded polymerization of styrene using the seed microspheres mentioned above yielded unique composite microspheres whose surface property changed gradually with the content of styrene.     

Structural parameters of porous monodisperse ceramic materials

A method for determining the parameters of the porous structure of ceramic materials made from monodisperse particles and fibers that makes it possible to allow for the difference in the sizes of the interparticle and interfiber contacts is suggested. Analytical dependences for determining the coordination number of fiber systems as a function of the porosity and the size of the interfiber contacts are obtained. Examples of calculations are presented. Translated from Ogneupory i Tekhnicheskaya Keramika, No. 2, pp. 15–18, February, 2000.     

Synthesis of nearly monodisperse ultrafine antimony pentoxide

Nearly monodisperse antimony pentoxide with a mean diameter of 2 nm and polydispersity of 0.047 was prepared through a simple method based on reflux oxidization system. By adjusting the synthetic parameters (kinds of stabilizing agents, size and purity of original Sb₂O₃ etc.), the controllable synthesis of ultrafine Sb₂O₅ can be easily achieved. Detailed investigations about the effects of experimental parameters on the colloid stability and size distribution of the final products were carried out. The particles were characterized using various experimental techniques such as transmission electron microscopy (TEM), X-ray diffraction (XRD) and particle size distributions.     

单分散聚乙二醇的高效合成

以廉价的2~4聚的聚乙二醇为原料，开发了一种基于环硫酸酯的单端延伸法合成单分散聚乙二醇的方法。以苄基作为保护基，重复利用环硫酸酯的亲核开环、水解反应对苄基化聚乙二醇的羟基端进行延伸，以55%～86%的产率得到苄基化的6~16聚的单分散聚乙二醇衍生物，最后通过催化氢化脱去苄基，以95%～99%的产率得到6~16聚的单分散聚乙二醇。中间体及终产物的结构均经NMR和MS确证。反应进程易于监控，反应效率高，无与目标产物的聚合度接近的聚乙二醇杂质，中间体及终产物易于分离纯化。     

The structure of monodisperse high-porosity ceramic materials

A fairly instructive and rigorous geometric model based on a basic unit cell in the form of a dodecahedron for the structure of high-porosity materials is proposed and analyzed. Its porosity can be increased through an increase in the number of contacting particles per edge of the polyhedron. It is advisable to use the model in the analysis and optimization of the pore structure of efficient thermal-insulating materials manufactured by different processes, such as with the use of foams and burn-out fillers. Translated from Steklo i Keramika. No. 3, pp. 18–19, March, 1997.     

Kinetics of ion exchange in monodisperse resin

Ion-exchange kinetics within a conventional strong base resin, Dowexl-8X®, and a resin with uniform particle size, Dowex® Monosphere® Tough Gel® TG550A®, were investigated using neutron activation analysis and radio-tracer techniques. The kinetics of ion exchange were measured in a batch and in a “shallow-bed” flow system. The experimental data were compared with the results of model computations. The diffusivities of several anions within TG550A and Dowexl-8X were deduced. It was found that at 25°C Br^-, Cl^-, OH^-, and Na⁺ diffuse within TG550A with the diffusion coefficients = 6.0 × 10^-7 cm²/s, = 1.2 × 10^-6 cm²/s, = 7.0 × 10^-8 cm²/s, and = 5 × 10^-7 cm²/s. Diffusion of anions within a conventional resin, Dowexl®, was slower: = 3.5 × 10^-7 cm²/s, = 6 × 10^-7 cm²/s, = 2.7 × 10^-8 cm²/s, and = 5 × 10^-7 cm²/s. A higher rate of ion diffusion and the bead-size uniformity may make monodisperse Dowex Monosphere Tough Gel TG550A resin attractive for analytical applications. The difference in properties between conventional and monodisperse resins is not sufficient to affect the large volume applications of resins. © 1997 John Wiley & Sons, Inc. J Appl Polm Sci 65:1271–1283, 1997     

轻便型闪光灯

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单分散磁性Fe3O4纳米颗粒溶剂热合成及性能

采用溶剂热还原方法,以FeCl3·6H2O和乙二醇为原料,在160 ℃相对低温条件下成功合成四氧化三铁纳米颗粒.利用X射线衍射仪、场发射扫描电子显微镜和振动样品磁强计等手段对产物进行分析和表征.结果表明:产物Fe3O4为反尖晶石结构,其16 h、24 h合成产物平均粒径分别为145 nm和495 nm.颗粒间没有明显团聚,大小均匀,分散性好,表现出良好的单分散性.研究了反应时间对Fe3O4粒径的影响,24 h产物的饱和磁化强度为79.3 emu/g,显示出较高的磁性能.