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A microfocus camera with a focus of 7 pm fwhm and a flux of 10u photons/s at the ESRF in Grenoble was used to investigate the microstructure of liquid crystalline polymer samples of 4-oxybenzoate-co-6-oxy-2-naphthoate (73:27) (Vectra A950 from Hoechst-Celanese). These samples show isotropic scattering when examined by means of a conventional X-ray camera with a large focus (2 mm). In melt-pressed thin films, we observed local variations of the direction of molecular orientation, which is due to the presence of disclinations. Except at the center of the disclinations, the order parameter is nearly constant within the scanned area. In samples cut out of the center part of an injection-molded bar, we detected a four-point scattering pattern due to a zigzag chain conformation.

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This paper shows the application of T-shaped micromixers for the generation of aerosols with nanoscale droplets by the mixing of a hot vapor-gas mixture with a cold gas. The fast mixing within a T-shaped micromixer leads to a high supersaturation of the vapor and therefore to an instantaneous, homogeneous nucleation and particle growth. Different mixer geometries, mixing ratios, and gas temperatures have been investigated by numerical simulation to yield optimum mixing results over a wide range of operational parameters. Optimized microreactor geometries were designed and fabricated in silicon with Pyrex glass lids. Special attention was paid to thermal insulation and particle deposition at the channel walls. This concerns not only the mixing chip, but also the design of the fluidic mount with only few bends and corners. Initial experimental results for particle deposition and aerosol generation are presented. High temporal temperature gradients up to 10 6 K/s lead to a rapid condensation and forming of nanosized particles with a mean diameter of 20-50 nm and a narrow size distribution.Keywords Aerosol Á Nanoparticle Á Micromixer Á Microreactor Á Process engineering Nomenclature A M cross section area of mixing channel (m 2 ) C friction correction factor (-) d h hydraulic diameter (m) d p particle diameter (m) h specific enthalpy (J/kg) L channel length (m) L m characteristic mixing length (m) L m90 mixing length 90% mixed (m) P momentum density (kg/m 2 s) Re Reynolds number (-) St Stokes number (-) T temperature (K or°C) DT L spatial temperature gradient (K/m) DT s temporal temperature gradient (K/s) u (fluid) velocity (m/s) " u mean (fluid) velocity (m/s) _ V volume flow (m 3 /s) x spatial coordinate along channel (m) Y mass fraction of vapor in gas (kg/kg) a _ V mixing quality (-) g dynamic viscosity (kg/s m) kheat conductivity (W/m 2 K) q density (kg/m 3 ) q P particle density (kg/m 3 ) r _ V max ðTÞ maximal standard deviation of temperature over volume flow (K) s m characteristic mixing time (s)