Droplet size evolution during coalescence in semiconcentrated model blends

Control of the phase structure evolution in flowing immiscible polymer blends during their mixing and processing is fundamental for tailoring of their performance. This review summarizes present state of understanding and predictability of the phase structure evolution in flowing immiscible polymer blends with dispersed structure. Results of the studies of the droplet breakup in flow, important for determination of the droplet breakup frequency and of the size distribution of the daughter droplets, are reviewed. Theories of the flow-induced coalescence providing equations for collision efficiency are discussed. Approximate analytic expressions reliably describing dependence of the collision efficiency on system parameters are presented. Available theories describing the competition between the droplet breakup and coalescence in flow are summarized and approximations used in their derivation are discussed. Problems with applicability of available theories on prediction of the droplet size evolution during mixing and processing of immiscible polymer blends, which have not been broadly discussed so far, are addressed.

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A Study on Diesel Fuel Drop Size Distribution

10.1115/imece2000-1653 ◽

2000 ◽

Author(s):

Badih A. Jawad

Keyword(s):

Droplet Size ◽

Drop Size ◽

Optical Measurement ◽

Optical Signal ◽

Diesel Fuels ◽

Intermittent Behavior ◽

Size Evolution ◽

Cylindrical Volume ◽

Droplet Size Distributions ◽

Collimated Beam

Abstract A pulsed Malvern drop-size analyzer, based on Fraunhofer diffraction, was utilized to determmine droplet size size ranges of diesel fuels under different conditions of injection. the effects of fuel properties, design and operating parameters on the formation of diesal spray are discussed. In these studies, the spray is formed by injecting a calibrated amount of fuel into air with the frequency of the intermittent behavior controlled by the speed of the fuel pump. In this study, an injection cycle was tailored so that it was divided into several increments which were injected sequentially. A two mm diammeter collimated beam illuminated a cylindrical volume perpendicular to the axis of the fuel spray, and its attenuation was recorded and stored on the oscilloscope. With the optical measurement being synchronized to the needle lift of the injector, the output of the needle lift transducer and the optical signal was recorded simultaneously. Thus, the arrival and the duration of the spray at various positions along its axis were measured. The droplet size distributions were obtained directly as penetration measurements were made. However, by applying a delay time through the synchronization feature of the sizer, information about droplet size evolution within the same spray was possible. Distribution widths are plotted as a function of time for different chamber pressures, injection pressures, different positions, and different fuels. Coagulation seems to be a dominant phenomenon in these studies.

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Investigation of irradiation-induced nucleation processes in silicon and germanium

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100137495 ◽

1995 ◽

Vol 53 ◽

pp. 224-225

Author(s):

Harry A. Atwater ◽

C.M. Yang ◽

K.V. Shcheglov

Keyword(s):

Room Temperature ◽

Crystal Size ◽

Initial Distribution ◽

Engineering Control ◽

Size Evolution ◽

Silicon And Germanium ◽

Ge Quantum Dot ◽

And Control ◽

Germanium Quantum Dots ◽

Kinetics Of

Studies of the initial stages of nucleation of silicon and germanium have yielded insights that point the way to achievement of engineering control over crystal size evolution at the nanometer scale. In addition to their importance in understanding fundamental issues in nucleation, these studies are relevant to efforts to (i) control the size distributions of silicon and germanium “quantum dots𠇍, which will in turn enable control of the optical properties of these materials, (ii) and control the kinetics of crystallization of amorphous silicon and germanium films on amorphous insulating substrates so as to, e.g., produce crystalline grains of essentially arbitrary size.Ge quantum dot nanocrystals with average sizes between 2 nm and 9 nm were formed by room temperature ion implantation into SiO2, followed by precipitation during thermal anneals at temperatures between 30°C and 1200°C[1]. Surprisingly, it was found that Ge nanocrystal nucleation occurs at room temperature as shown in Fig. 1, and that subsequent microstructural evolution occurred via coarsening of the initial distribution.

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