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  1. Article ; Online: Influence of Process Parameters on the Kinetics of the Micelle-to-Vesicle Transition and Ripening of Polystyrene-Block-Polyacrylic Acid

    Jil Mann / Julian K. Mayer / Georg Garnweitner / Carsten Schilde

    Polymers, Vol 15, Iss 1695, p

    2023  Volume 1695

    Abstract: Due to their ability to self-assemble into complex structures, block copolymers are of great interest for use in a wide range of future applications, such as self-healing materials. Therefore, it is important to understand the mechanisms of their ... ...

    Abstract Due to their ability to self-assemble into complex structures, block copolymers are of great interest for use in a wide range of future applications, such as self-healing materials. Therefore, it is important to understand the mechanisms of their structure formation. In particular, the process engineering of the formation and transition of the polymer structures is required for ensuring reproducibility and scalability, but this has received little attention in the literature. In this article, the influence of the addition rate of the selective solvent on the homogeneity of self-assembled vesicles of polystyrene-block-polyacrylic acid is demonstrated, as well as the influence of the reaction time and the mixing intensity on the morphology of the polymer structures. For example, it was demonstrated that the higher the mixing intensity, the faster the transition from micelle to vesicle. The experimental results are further supported by CFD simulations, which visually and graphically show an increase in shear rate and narrower shear rate distributions at higher stirring rates. Furthermore, it was demonstrated that the vesicle size is not only kinetically determined, since flow forces above a critical size lead to the deformation and fission of the vesicles.
    Keywords block copolymer ; self-assembly ; kinetics ; morphology ; micelle ; cylinder ; Organic chemistry ; QD241-441
    Subject code 660
    Language English
    Publishing date 2023-03-01T00:00:00Z
    Publisher MDPI AG
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  2. Article ; Online: Micromechanical properties of spray-dried core-shell silica aggregates along with drug release tests

    Matthäus Barasinski / Carsten Schilde / Sebastian Melzig / Merle Hübner / Georg Garnweitner / Sabrina Zellmer

    JCIS Open, Vol 6, Iss , Pp 100052- (2022)

    2022  

    Abstract: In order to enhance the quality of spray-dried products or to adjust material properties for new applications, precise control of the aggregate structure is desirable. For the purpose of preparing hierarchically structured aggregates in the micrometer ... ...

    Abstract In order to enhance the quality of spray-dried products or to adjust material properties for new applications, precise control of the aggregate structure is desirable. For the purpose of preparing hierarchically structured aggregates in the micrometer range, the formulation of the suspension can be specifically designed, utilizing defined nanoparticulate building blocks to achieve a highly uniform structure and porosity. Further adjustments can be made by combining two types of primary particles that differ in size. Thereby, a segregation effect is observed, where nanoparticles with larger particle sizes accumulate rather within the core of an aggregate and those with smaller particle sizes gather mainly near the outer surface, resulting in the formation of a shell. Furthermore, it is possible to produce tailor-made porosities using template particles (e.g. polystyrene) of different sizes as part of the coarse and fine fractions. The removal of these particles by a subsequent tempering process can lead to aggregates with defined porous structures and thus, to different mechanical aggregate properties that can be specifically set by adjusting the process and formulation parameters. As a result, a promising building kit for the hierarchically structure formation via spray drying processes were achieved.For the detailed characterization structural and mechanical material properties were investigated, using e.g. mercury intrusion and SEM. The influence of the formulation parameters of the suspension (primary particle size and template content) on the micromechanical properties of the aggregate structures was systematically investigated by nanoindentation to elucidate structure-property relationships regarding, for example elastic and plastic deformation. As a result, a correlation could be established between the experimentally determined mechanical parameters and the aggregate porosities.Such microstructures with defined properties can be used in a variety of applications, including catalysis or as drug carriers. ...
    Keywords Spray-drying ; Hierarchical porous core-shell aggregates ; Nanoindentation ; Micromechanical properties ; Drug release ; Physical and theoretical chemistry ; QD450-801 ; Chemical technology ; TP1-1185
    Subject code 660
    Language English
    Publishing date 2022-07-01T00:00:00Z
    Publisher Elsevier
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  3. Article: Numerical simulation of the behavior of lithium-ion battery electrodes during the calendaring process via the discrete element method

    Sangrós Giménez, Clara / Benedikt Finke / Carsten Schilde / Linus Froböse / Arno Kwade

    Powder technology. 2019 May 01, v. 349

    2019  

    Abstract: Calendering is a key process step in the production chain of lithium ion battery electrodes since it strongly affects the microstructure and micromechanics of the electrodes and hence, the performance and life of the battery. A comprehensive ... ...

    Abstract Calendering is a key process step in the production chain of lithium ion battery electrodes since it strongly affects the microstructure and micromechanics of the electrodes and hence, the performance and life of the battery. A comprehensive understanding is therefore necessary to find optimal levels of calendering which can help to enhance conductive and mechanical properties. Within this context, this study proposes a novel discrete element method (DEM) approach which can capture the mechanical properties of single Li [Ni1/3 Mn1/3 Co1/3]O2 (NMC) particles with an appropriate elasto-plastic contact model, as well as the mechanical behavior of the additive-binder matrix via an additional bond model [1]. With the support of real produced cathodes, the simulations were able to reproduce the calendering process while providing detailed information about the changes in electrode structural and mechanical parameters. In particular, the investigated features comprise the electrode porosity and thickness along with the specific free surface area, the contact area between NMC particles and current collector, the coordination number of NMC particles, the number of broken bonds and the directionality of the contacts together with the generated stress within the electrode. Moreover, the simulations are able to capture the viscoelastic response of the electrode, showing that the relative elastic recovery can be almost up to 17%, an important piece of information that cannot be obtained experimentally to date. Having established the fundamentals and simulation feedback, an upcoming publication is meant to complete this research by providing a numerical overview of the relations between the electrode structure and its properties affected by the calendering process and during the first electrochemical cycles.
    Keywords cathodes ; electrochemistry ; lithium batteries ; mathematical models ; mechanical properties ; microstructure ; porosity ; powders ; surface area ; viscoelasticity
    Language English
    Dates of publication 2019-0501
    Size p. 1-11.
    Publishing place Elsevier B.V.
    Document type Article
    ISSN 0032-5910
    DOI 10.1016/j.powtec.2019.03.020
    Database NAL-Catalogue (AGRICOLA)

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  4. Article: A blessing in disguise? Natural organic matter reduces the UV light-induced toxicity of nanoparticulate titanium dioxide

    Lüderwald, Simon / Vera Dackermann / Frank Seitz / Elena Adams / Alexander Feckler / Carsten Schilde / Ralf Schulz / Mirco Bundschuh

    Science of the total environment. 2019 May 01, v. 663

    2019  

    Abstract: Besides their economic value, engineered inorganic nanoparticles (EINPs) may pose a risk for the integrity of ecosystems. Among EINPs, titanium dioxide (nTiO2) is frequently used and released into surface waters in the μg range. There, nTiO2 interacts ... ...

    Abstract Besides their economic value, engineered inorganic nanoparticles (EINPs) may pose a risk for the integrity of ecosystems. Among EINPs, titanium dioxide (nTiO2) is frequently used and released into surface waters in the μg range. There, nTiO2 interacts with environmental factors, influencing its potential to cause adverse effects on aquatic life. Although factors like ultra violet (UV) light and natural organic matter (NOM) are considered as ubiquitous, their joint impact on nTiO2-induced toxicity is poorly understood. This study addressed the acute toxicity of nTiO2 (P25; 0.00–64.00 mg/L; ~60 nm) at ambient UV light (0.00–5.20 W UVA/m2) and NOM levels (seaweed extract; 0.00–4.00 mg TOC/L), using the immobility of Daphnia magna as response variable. Confirming previous studies, effects caused by nTiO2 were elevated with increasing UV radiation (up to ~280 fold) and mitigated by higher NOM levels (up to ~12 fold), possibly due to reduced reactive oxygen species (ROS; measured as •OH radicals) formation at lower UV intensities. However, contradicting to former studies, nTiO2-mediated ROS formation was not proportional to increasing NOM levels: lower concentrations (0.04–0.40 mg TOC/L) slightly diminished, whereas a higher concentration (4.00 mg TOC/L) promoted the ROS quantity, irrespective of UV intensity. Measured ROS levels do not fully explain the observed nTiO2-induced toxicity, whereas increasing acetylcholinesterase and glutathione-S-transferase activities in daphnids (in presence of 8.00 mg/L nTiO2 and elevated UV intensity) point towards neurotoxic and oxidative stress as a driver for the observed effects. Hence, despite higher •OH levels in the treatments where 4.00 mg TOC/L were present, NOM was still capable of reducing nTiO2-induced stress and ultimately adverse effects in aquatic life.
    Keywords Daphnia magna ; acetylcholinesterase ; acute toxicity ; adverse effects ; aquatic organisms ; economic valuation ; ecosystems ; environmental factors ; enzyme activity ; free radicals ; glutathione transferase ; hydroxyl radicals ; nanoparticles ; neurotoxicity ; organic matter ; oxidative stress ; plant extracts ; risk ; surface water ; titanium dioxide ; ultraviolet radiation
    Language English
    Dates of publication 2019-0501
    Size p. 518-526.
    Publishing place Elsevier B.V.
    Document type Article
    ZDB-ID 121506-1
    ISSN 1879-1026 ; 0048-9697
    ISSN (online) 1879-1026
    ISSN 0048-9697
    DOI 10.1016/j.scitotenv.2019.01.282
    Database NAL-Catalogue (AGRICOLA)

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    In stock of ZB MED Cologne/Königswinter

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  5. Article: Influence of electrostatic particle interactions on the properties of particulate coatings of titanium dioxide

    Barth, Nina / Arno Kwade / Carsten Schilde

    Journal of colloid and interface science. 2014 Apr. 15, v. 420

    2014  

    Abstract: Particulate coatings are used in a wide range of technical applications. The application affecting properties of these coatings depend strongly on the structure formation along the production process. Thus, primary and secondary particle size, size ... ...

    Abstract Particulate coatings are used in a wide range of technical applications. The application affecting properties of these coatings depend strongly on the structure formation along the production process. Thus, primary and secondary particle size, size distribution, particle morphology as well as the particle–particle and particle–fluid interactions of the used formulation affect the resulting coating properties.In this investigation titanium dioxide particles were dispersed in ethanol with a stirred media mill and stabilised electrostatically. Subsequently, the suspension was destabilised to reach specific pH* values and processed into coatings by dip coating. The influence of the pH∗ value of the suspension on the suspension’s properties such as viscosity, agglomerate size and zeta potential and on its application properties such as coating thickness, micro-mechanical properties, abrasion resistance, gloss, roughness and adhesion was examined.The electrostatic particle interactions show a significant influence on the structure formation as well as on the properties of nanoparticulate coatings. The coating properties are affected by the coating structures on micro-, meso- or macroscopic scale. Selective coating properties were related to the coating structure using the theoretical model of Rumpf. Besides other important process and formulation parameters, for the production of homogeneous, functional coatings with the desired properties a precise adjustment of the particle interactions is necessary.
    Keywords abrasion resistance ; adhesion ; coatings ; ethanol ; particle size ; roughness ; theoretical models ; titanium dioxide ; viscosity ; zeta potential
    Language English
    Dates of publication 2014-0415
    Size p. 80-87.
    Publishing place Elsevier Inc.
    Document type Article
    ZDB-ID 241597-5
    ISSN 1095-7103 ; 0021-9797
    ISSN (online) 1095-7103
    ISSN 0021-9797
    DOI 10.1016/j.jcis.2014.01.005
    Database NAL-Catalogue (AGRICOLA)

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    In stock of ZB MED Bonn / Germany

    Z 71/707: Show issues

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  6. Article: Influence of surface modification on structure formation and micromechanical properties of spray-dried silica aggregates

    Zellmer, Sabrina / Carsten Schilde / Georg Garnweitner / Maylin Lindenau / Stephanie Michel

    Journal of colloid and interface science. 2016 Feb. 15, v. 464

    2016  

    Abstract: Spray drying processes were utilized for the production of hierarchical materials with defined structures. The structure formation during the spray drying process and the micromechanical properties of the obtained aggregates depend on the particle– ... ...

    Abstract Spray drying processes were utilized for the production of hierarchical materials with defined structures. The structure formation during the spray drying process and the micromechanical properties of the obtained aggregates depend on the particle–particle interactions, the primary particle size and morphology as well as the process parameters of the spray drying process. Hence, the effect of different primary particle systems prepared as stable dispersions with various surface modifications were investigated on the colloidal structure formation and the micromechanical properties of silica particles as model aggregates and compared to theoretical considerations. The obtained results show that the structure formation of aggregates during the spray drying process for stable suspensions is almost independent on the functional groups present at the particle surface. Further, the mechanical properties of these aggregates differ considerably with the content of the bound ligand. This allows the defined adjustment of the aggregate properties, such as the strength and surface properties, as well as the formation of defined hierarchical aggregate structures.
    Keywords dispersions ; ligands ; mechanical properties ; models ; moieties ; particle size ; silica ; spray drying
    Language English
    Dates of publication 2016-0215
    Size p. 183-190.
    Publishing place Elsevier Inc.
    Document type Article
    ZDB-ID 241597-5
    ISSN 1095-7103 ; 0021-9797
    ISSN (online) 1095-7103
    ISSN 0021-9797
    DOI 10.1016/j.jcis.2015.11.028
    Database NAL-Catalogue (AGRICOLA)

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    In stock of ZB MED Bonn / Germany

    Z 71/707: Show issues

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  7. Article ; Online: Biological surface coating and molting inhibition as mechanisms of TiO2 nanoparticle toxicity in Daphnia magna.

    André Dabrunz / Lars Duester / Carsten Prasse / Frank Seitz / Ricki Rosenfeldt / Carsten Schilde / Gabriele E Schaumann / Ralf Schulz

    PLoS ONE, Vol 6, Iss 5, p e

    2011  Volume 20112

    Abstract: The production and use of nanoparticles (NP) has steadily increased within the last decade; however, knowledge about risks of NP to human health and ecosystems is still scarce. Common knowledge concerning NP effects on freshwater organisms is largely ... ...

    Abstract The production and use of nanoparticles (NP) has steadily increased within the last decade; however, knowledge about risks of NP to human health and ecosystems is still scarce. Common knowledge concerning NP effects on freshwater organisms is largely limited to standard short-term (≤48 h) toxicity tests, which lack both NP fate characterization and an understanding of the mechanisms underlying toxicity. Employing slightly longer exposure times (72 to 96 h), we found that suspensions of nanosized (∼100 nm initial mean diameter) titanium dioxide (nTiO(2)) led to toxicity in Daphnia magna at nominal concentrations of 3.8 (72-h EC(50)) and 0.73 mg/L (96-h EC(50)). However, nTiO(2) disappeared quickly from the ISO-medium water phase, resulting in toxicity levels as low as 0.24 mg/L (96-h EC(50)) based on measured concentrations. Moreover, we showed that nTiO(2) (∼100 nm) is significantly more toxic than non-nanosized TiO(2) (∼200 nm) prepared from the same stock suspension. Most importantly, we hypothesized a mechanistic chain of events for nTiO(2) toxicity in D. magna that involves the coating of the organism surface with nTiO(2) combined with a molting disruption. Neonate D. magna (≤6 h) exposed to 2 mg/L nTiO(2) exhibited a "biological surface coating" that disappeared within 36 h, during which the first molting was successfully managed by 100% of the exposed organisms. Continued exposure up to 96 h led to a renewed formation of the surface coating and significantly reduced the molting rate to 10%, resulting in 90% mortality. Because coating of aquatic organisms by manmade NP might be ubiquitous in nature, this form of physical NP toxicity might result in widespread negative impacts on environmental health.
    Keywords Medicine ; R ; Science ; Q
    Subject code 333
    Language English
    Publishing date 2011-01-01T00:00:00Z
    Publisher Public Library of Science (PLoS)
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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