The effect of microwave modification of colloidal TiO2 suspensions under extended periods of treatment is presented. The nanoparticulate TiO2 is compared and contrasted to similar convection hydrothermally treated TiO2 and a commercial titania product, namely Degussa P25. Microwave-treated samples were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy to determine their physicochemical characteristics. Comparative surface area analyses were performed by N2 adsorption and calculated from a Brunauer-Emmett-Teller (BET) isotherm. The complementary techniques of XRD and TEM showed good correlation between observed and calculated particle sizes (by application of the Scherrer equation), with the material being highly crystalline anatase TiO2, as identified by XRD and Raman. This investigation identified that extended periods of microwave hydrothermal treatment do not greatly enhance the crystallinity and primary grain size. Treatment of >180 min has a negative effect on crystallite growth; however, treatment up to this time had a significant effect on the material's surface area. The limiting regime of Ostwald ripening for hydrothermal treatment is discussed in relation to the mechanism of microwave treatment, that is, rapid heating to temperature and extremely rapid rates of crystallization. The effect of these property modifications are further discussed in relation to photocatalytic and photoelectrochemical applications of TiO2 nanoparticles.

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1 This article will form part of a virtual special issue on advanced neutron scattering instrumentation, marking the 50th anniversary of the journal.QUOKKA is a 40 m pinhole small-angle neutron scattering instrument in routine user operation at the OPAL research reactor at the Australian Nuclear Science and Technology Organisation. Operating with a neutron velocity selector enabling variable wavelength, QUOKKA has an adjustable collimation system providing source-sample distances of up to 20 m. Following the largearea sample position, a two-dimensional 1 m 2 position-sensitive detector measures neutrons scattered from the sample over a secondary flight path of up to 20 m. Also offering incident beam polarization and analysis capability as well as lens focusing optics, QUOKKA has been designed as a general purpose SANS instrument to conduct research across a broad range of scientific disciplines, from structural biology to magnetism. As it has recently generated its first 100 publications through serving the needs of the domestic and international user communities, it is timely to detail a description of its asbuilt design, performance and operation as well as its scientific highlights. Scientific examples presented here reflect the Australian context, as do the industrial applications, many combined with innovative and unique sample environments. research papers J. Appl. Cryst. (2018). 51, 294-314 Kathleen Wood et al. QUOKKA 295 Figure 1 QUOKKA instrument layout. research papers J. Appl. Cryst. (2018). 51, 294-314 Kathleen Wood et al. QUOKKA 297 Figure 3(a) Attenuator wheel. (b) Automatic aperture changer. (c) Sample environment area, showing the extendable bellows on the left and the 20position sample changer on the right. Downstream of the sample changer, the entrance to the detector tank is visible. (d) Beamstop mechanism, with the six beamstops all in the 'in beam' position.research papers J. Appl. Cryst. (2018). 51, 294-314 Kathleen Wood et al. QUOKKA 299 research papers J. Appl. Cryst. (2018). 51, 294-314 Kathleen Wood et al. QUOKKA 301 research papers J. Appl. Cryst. (2018). 51, 294-314 Kathleen Wood et al. QUOKKA 313

Recent atomic force microscopy (AFM) surface images of surfactant adsorbed at solid and solution interfaces have shown apparent micellar aggregates familiar from bulk self-assembly. This contradicts the classical picture of laterally unstructured bilayers within which neutron reflectometry (NR) measurements have previously been analyzed. Applying both techniques to surfactant adsorption on quartz, we show that film thickness and coverage parameters derived from NR results are generally consistent with those from AFM and bulk self-assembly. NR by itself allows us to distinguish between actual bilayer and probable aggregate adsorption, which will be of particular importance when a solution's rheology makes AFM imaging impractical.