Advanced Materials Technologies / 3D Printing of Hierarchical Porous Silica and -Quartz

The ability to macroscopically shape highly porous oxide materials while concomitantly tailoring the porous network structure as desired by simple and environmentally friendly processes is of great importance in many fields. Here, a purely aqueous printing process toward deliberately shaped, hierarchically organized amorphous silica and the corresponding polycrystalline quartz analogues based on a direct ink writing process (DIW) is presented. The key to success is the careful development of the solgel ink, which is based on an acidic aqueous sol of a glycolated silane and structuredirecting agents. The resulting 3D (DIW) printed silica consists of a macroporous network of struts comprising hexagonally arranged mesopores on a 2D hexagonal lattice. Together with a printed porous superstructure on the millimeter scale, welldefined pore sizes and shapes on at least three hierarchy levels can thus be fabricated. The introduction of devitrifying agents in the printed green part and subsequent heat treatment allows for the transformation of the silica structure into polycrystalline quartz. While small pores (micro and mesopores below 10 nm) are lost, the printed morphology and the macroporous network of struts is preserved during crystallization.1605N20(VLID)266643

Type I interferons as radiosensitisers for pancreatic cancer

Background: Radiotherapy is an established treatment for malignant localised disease. Pancreatic cancer however seems relatively insensitive to this form of therapy. Methods: Pancreatic cancer cell lines MiaPaca-2 and Panc-1 were pre-treated with 3000 IU/ml IFN alpha or 100 IU/ml IFN beta followed by 0, 2, 4, or 6 Gray (Gy) irradiation. Colony forming assay was used to assess the effects on cellgrowth. To measure the surviving fraction at the clinically relevant dose of 2 Gy (SF2), cells were pre-treated with 1000-10.000 IU/ml IFN alpha or 50-500 IU/ml IFN beta followed by 2 Gy irradiation. Results: The plating efficiency was 49% for MiaPaca-2 and 22% for Panc-1. MiaPaca-2 was more radiosensitive than Panc-1 (surviving fraction of 0.28 versus 0.50 at 4 Gray). The SF2 of MiaPaca-2 was 0.77 while the SF2 of Panc-1 was 0.70. The SF2 significantly decreased after pretreatment with IFN alpha 1000 IU/ml (p < 0.001) and IFN beta 100 IU/ml (p < 0.001) in MiaPaca-2 and with IFN alpha 5000 IU/ml (p < 0.001) and IFN beta 100 IU/ml (p < 0.01) in Panc-1. The sensitising enhancement ratio (SER) for IFN alpha 3000 IU/ml was 2.15 in MiaPaca-2 and 1.90 in Panc-1. For IFN beta 100 IU/ml the SER was 1.72 for in MiaPaca-2 and 1.51 in Panc-1. Conclusions: Type I interferons have radiosensitising effects in pancreatic cancer cell lines. This radiosensitising property might lead to an improved response to treatment in pancreatic cancer. Interferon beta is the most promising drug due to its effect in clinically obtainable doses. (C) 2011 Elsevier Ltd. All rights reserved

Microstructural Influences Caused by Different Aging Strategies on the Strain-Dependent Damping of the High-Strength Aluminum Alloy AA7075

Gefördert durch den Publikationsfonds der Universität Kasse

Microstructural Influences Caused by Different Aging Strategies on the Strain-Dependent Damping of the High-Strength Aluminum Alloy AA7075

The present study focused on the influence of different aging conditions on the strain-dependent damping of the high-strength aluminum alloy AA7075. For this purpose, different artificial aging strategies were carried out after solution heat treatment with subsequent water quenching to identify correlations between microstructural evolution, hardness development, and individual material damping. The resulting material damping was measured using an experimental setup based on the principle of electromagnetic feedback. Scanning transmission electron microscopy (STEM) investigations were carried out using a scanning electron microscope (SEM) to characterize the material&rsquo;s microstructure. Depending on the aging conditions, the damping investigations revealed specific characteristic behaviors in the strain-dependent range from 1 &times; 10&minus;7 to 0.002. Peak aging conditions showed lower damping than the overaged conditions but resulted in the highest hardness. The hardness decreased with increasing aging time or temperature

Characterization of Zr-Containing Dispersoids in Al&ndash;Zn&ndash;Mg&ndash;Cu Alloys by Small-Angle Scattering

The characterization of Zr-containing dispersoids in aluminum alloys is challenging due to their broad size distribution, low volume fraction, and heterogeneous distribution within the grains. In this work, small-angle X-ray scattering (SAXS) and small-angle neutron scattering (SANS) were compared to scanning electron microscopy (SEM) and transmission electron microscopy (TEM) regarding their capability to characterize Zr-containing dispersoids in aluminum alloys. It was demonstrated that both scattering techniques are suitable tools to characterize dispersoids in a multi-phase industrial 7xxx series aluminum alloy. While SAXS is more sensitive than SANS due to the high electron density of Zr-containing dispersoids, SANS has the advantage of being able to probe a much larger sample volume. The combination of both scattering techniques allows for the verification that the contribution from dispersoids can be separated from that of other precipitate phases such as the S-phase or GP-zones. The size distributions obtained from SAXS, SANS and TEM showed good agreement. The SEM-derived size distributions were, however, found to significantly deviate from those of the other techniques, which can be explained by considering the resolution-limited restrictions of the different techniques

In Situ Small-Angle Neutron Scattering Investigation of Adsorption-Induced Deformation in Silica with Hierarchical Porosity

Adsorption-induced deformation of a series of silica samples with hierarchical porosity has been studied by in situ small-angle neutron scattering (SANS) and in situ dilatometry. Monolithic samples consisted of a disordered macroporous network of struts formed by a 2D lattice of hexagonally ordered cylindrical mesopores and disordered micropores within the mesopore walls. Strain isotherms were obtained at the mesopore level by analyzing the shift of the Bragg reflections from the ordered mesopore lattice in SANS data. Thus, SANS essentially measured the radial strain of the cylindrical mesopores including the volume changes of the mesopore walls due to micropore deformation. A H2O/D2O adsorbate with net zero coherent neutron scattering length density was employed in order to avoid apparent strain effects due to intensity changes during pore filling. In contrast to SANS, the strain isotherms obtained from in situ dilatometry result from a combination of axial and radial mesopore deformation together with micropore deformation. Strain data were quantitatively analyzed with a theoretical model for micro-/mesopore deformation by combining information from nitrogen and water adsorption isotherms to estimate the watersilica interaction. It was shown that in situ SANS provides complementary information to dilatometry and allows for a quantitative estimate of the elastic properties of the mesopore walls from water adsorption.(VLID)440244

Setting Directions: Anisotropy in Hierarchically Organized Porous Silica

Structural hierarchy, porosity, and isotropy/anisotropy are highly relevant factors for mechanical properties and thereby the functionality of porous materials. However, even though anisotropic and hierarchically organized, porous materials are well known in nature, such as bone or wood, producing the synthetic counterparts in the laboratory is difficult. We report for the first time a straightforward combination of sol–gel processing and shear-induced alignment to create hierarchical silica monoliths exhibiting anisotropy on the levels of both, meso- and macropores. The resulting material consists of an anisotropic macroporous network of struts comprising 2D hexagonally organized cylindrical mesopores. While the anisotropy of the mesopores is an inherent feature of the pores formed by liquid crystal templating, the anisotropy of the macropores is induced by shearing of the network. Scanning electron microscopy and small-angle X-ray scattering show that the majority of network forming struts is oriented towards the shearing direction; a quantitative analysis of scattering data confirms that roughly 40% of the strut volume exhibits a preferred orientation. The anisotropy of the material’s macroporosity is also reflected in its mechanical properties; i.e., the Young’s modulus differs by nearly a factor of 2 between the directions of shear application and perpendicular to it. Unexpectedly, the adsorption-induced strain of the material exhibits little to no anisotropy