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Ceramics International
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Item-typ:Veröffentlichung, Characterization of functionalized zirconia membranes manufactured by aqueous tape casting(Elsevier {BV}, 2020-05-13); ; ; ; In this study, porous zirconia membranes were developed by aqueous tape casting. The influence of poly (methyl methacrylate) (PMMA) as a pore former, and sintering temperatures (1300, 1400, and 1500 °C) on open porosity and pore size was investigated. The rheological behaviour of the suspensions was measured. The slurries showed pseudoplastic behavior, which is desirable for tape casting. Functionalization with an amino silane precursor (3- aminopropyl triethoxysilane, APTES) was carried out to increase the hydrophilic properties of the membranes. The functionalized samples were characterized by SEM-EDX to identify the moieties attached to the surface. Membranes with open porosity ranging from 27% to 51% and average pore sizes from 0.2 to 1.4 μm were obtained. Samples sintered at 1400 °C with added pore former yielded the highest water flux, 257 Lm−2h−1, which increased to 642 Lm−2h−1 after functionalization. Membranes with tailored porosity and pore size obtained in this study are indicated for applications involving separation processes, especially for microfiltration systems.Wissenschaftlicher ArtikelBand:46Heft:10128 112 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Porous polymer derived ceramic (PDC)-montmorillonite-H3PMo12O40/SiO2 composite membranes for microbial fuel cell (MFC) applicationCeramic membranes can serve as viable alternatives to the less mechanically stable polymeric membranes utilized in microbial fuel cells (MFCs). In this work, a series of polymer-derived ceramic (PDC) proton exchange composite membranes with large ion exchange capacity (IEC) values, high cation transport numbers, and low oxygen diffusion coefficients have been synthesized at various pyrolysis temperatures using a pressing technique. These materials were composed of a polysiloxane matrix mixed with proton-conducting fillers such as montmorillonite and H3PMo12O40/SiO2 at different ratios. By tuning the average pore sizes of the membranes between 0.1 and 1 µm and their hydrophilic/hydrophobic characteristics, the maximum IEC of 0.6072 mequiv/g and cation transport number of 0.6988 were obtained, which is 67% and 72% of polymeric nafion performance, respectively. In addition, the minimal oxygen mass transfer coefficient achieved by this approach was equal to 5.62 × 10−4 cm/s, which is very close to the commercial nafion membrane value. The fabricated PDC composite membranes meet all the essential criteria required for their use in MFC applications and represent a high potential to overcome limitations of polymeric membrane.Wissenschaftlicher ArtikelBand:44Heft:16113 93 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Porous ceramics with tailored pore size and morphology as substrates for coral larval settlement(Elsevier, 2018-08-07); ; ; ; The growing demand for stony corals as ornamental aquarium animals requires defined aquacultural breeding strategies. For the sexual propagation of corals, material substrates are needed, that attract larvae and support their settlement and development. In this study, five types of highly porous ceramic materials were developed following the example of coral skeleton. The applicability of these settlement substrates was tested using larvae of the stony coral Pocillopora damicornis. Partial sintering of pressed clay pellets, freeze casting of clay and alumina-mullite based slurries and direct foaming of high alkane phase emulsified suspensions (HAPES) using alumina were employed. By the addition of mm-sized spherical polystyrene beads as sacrificial templates during freeze casting (alumina-mullite), superficial pores in the size of the larvae were created. The inorganic substrates featured open porosities between 35% (pressed clay) and 83% (foamed alumina), pore sizes ranging from nm to mm-scale and pore morphologies dominated by interparticle porosity (pressed), lamellar pores (freeze casting) and cellular pore types (direct foaming). The ceramic substrates were incubated in artificial sea water for 3 months to induce necessary biofilm formation and algae growth. Afterwards, individual substrates were exposed to 5 coral larvae, and their settlement behavior was monitored over 14 days. At the end of this period, all ceramic materials were successfully accepted as settlement substrates, with a mean settlement rate of 46.2%, and no significant differences between the substrate types. On samples with large surface superficial pores, a significantly reduced survival of settled larvae (79%) compared to the other porous materials (93–98%) was determined, suggesting a non-ideal surface topography. While alumina foam samples (HAPES) exhibit the most promising results in terms of settlement and survival of larvae, clay-based substrates provide a more economic solution for the sexual propagation of corals in aquaculture.Wissenschaftlicher ArtikelBand:44Heft:14122 172 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, On the dimensional analysis for the creep rate prediction of ceramic fibers(Elsevier {BV}, 2018-07-20); ; ; A novel semi-empirical equation for the steady-state creep rate description of ceramic fibers is here proposed. Dimensional analysis was applied to identify the relationship between the variables related to the creep rate. Besides the variables known from the Arrhenius creep equation, a temperature factor that accounts for changes with the temperature was also taken into consideration. The resultant equation shows that the creep rate is proportional to the temperature, applied stress and two material constants, as well as inversely proportional to the fiber grain size. The two material constants k and C described in the equation can be easily determined by creep tests at different temperatures under the same applied stress. Therefore, this equation can be more efficiently applied to predict the creep rate of ceramic fibers under different applied stresses and initial grain sizes. To confirm this, the proposed equation was used to fit the creep rate data set of two ceramic fibers, Nextel 720 and CeraFib 75. In summary, the equation provides a good fit (adjusted R-squared up to 0.97) and prediction for the experimental data of tests with different temperatures, applied stresses and initial grain sizes.Wissenschaftlicher ArtikelBand:44Heft:13103 89 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Microstructure and properties of Cu-Ti alloy infiltrated chopped Cf reinforced ceramics compositesNovel friction composites (C/C-Cu5Si-TiC) were prepared via reactive melt infiltration (RMI) of Cu-Ti alloy into porous C/C-SiC composites. The microstructure, physical properties and tribological behaviors of the novel material were studied. Results were compared to conventional C/C-SiC composites produced by liquid silicon infiltration(LSI). The resultant composite showed the microstructure composed of Cu5Si matrix reinforced with TiC particles and intact C/C structures. Most importantly, the composite did not present traces of free Si. As a result, the C/C-Cu5Si-TiC composite showed higher flexural strength, impact toughness and thermal diffusivity in comparison to C/C-SiC composites. Tribological properties were measured using 30CrSiMoVA as a counterpart. In general, the C/C-Cu5Si-TiC composites showed lower coefficient of friction(COF), but higher wear resistance and frictional stability. The improved wear resistance of the C/C-Cu5Si-TiC composites is credited to the formation of friction films from Cu5Si matrix. Other deformation and wear mechanisms are also described considering the microstructural observations.Wissenschaftlicher ArtikelBand:43Heft:1880 96 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Gel casting of large area micro- and sub-micropatterned thin ceramic tapes(Elsevier {BV}, 2016-01-20); ; ; ; In this study an easy-to-use ceramic processing technique based on temperature-controlled ionotropic gelation of alginate is presented. This method is the breakthrough for simultaneously large scale tape casting and high quality patterning of thin ceramic tapes. Alumina powder (d50¼ 205 nm) is used to cast flexible and on demand shapeable tapes. Compared to conventional ceramic micropatterning, ionotropic gelation combines complexity of the patterned structure over large-scale areas, a high pattern resolution down to sub-mm regime (400 nm) and tape thickness below 300 mm. Obtained green and sintered (1350 1C) micro- and sub-micropatterns are characterized by SEM and quantitative 3D-profilometry focusing on both, pattern quality and pattern aspect ratio. The results show that reproducible thin ceramic tapes featuring positive and negative patterns maintain their aspect ratios after demolding, drying and sintering. This processing route represents a versatile tool for designing tailored ceramics for e.g. microelectromechanical engineered systems, biomaterial or microfluidic applications.Wissenschaftlicher ArtikelBand:42Heft:498 91