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Item type:Publication, Access status: without files , Strategy for spray coating of highly porous and light weighting particles using spouted bed technologyPublicationtype: Doctoral Thesis31 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Spray coating of cellulose aerogel particles in a miniaturized spouted bed(Springer, 2021-07-04); ; ; ; Aim of this work is to apply protective and homogeneous shellac coating layers on the surface of hydrophilic open-pore cellulose aerogel particles with low densities ≤ 0.1 g/cm3 and high specific surface areas in the range of ~ 400–450 m2/g while keeping the aerogels’ microstructure intact during processing. For this purpose, an innovative miniaturized spouted bed setup was used. Successful process settings for application of enclosed films on aerogel surfaces without intrusion of coating material into the pores were determined. Precise control of coating layer thickness in the range of 10–50 µm was achieved due to variation of coating solution amount without agglomeration and clogging events occurring during processing. Comparison of bulk densities and specific surface areas before and after coating proved the intactness of the porous structure. Coating of particles loaded with vanillin led to controlled release, enhancing release half-life times from 20 to 1600 min. Overall, a successful strategy for coating of organic low-density aerogels was developed.Publicationtype: Journal ArticleScopus© Citations 13 218 261 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Particle formulation of hydroalcoholic rosemary (Rosmarinus officinalis L.) extracts using a spouted bedIn this study, spouted bed technology was applied to the protection and functionalization of polyphenolic rosemary extracts. First, solid–liquid extraction was performed at 25 °C with ethanol–water. The ethanol–water ratio was chosen to obtain high phenolic acid and diterpene concentrations in the extract. The selected solvent composition gave liquid extracts that could be directly added to a coating mixture for feeding into a spouted bed apparatus. Thus, no preliminary solvent exchange or evaporation of the extraction solvent to dryness was required. Food grade Paselli MD 6 maltodextrin and HiCap 100 modified starch were used as inert core and shell materials in the spouted bed encapsulation process under mild operating conditions. The antioxidant activity of the fresh extract was retained during processing, which indicated that the active constituents were preserved and quantitatively transferred into the encapsulated formulations, which were readily soluble in water. The obtained powders were composed of nearly spherical particles. Their compositions, water solubilities, and particle morphologies make them a strong candidate for food and beverage applications as natural antioxidants, preservatives, or functional ingredients.Publicationtype: Journal Article136 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Characterization of waxes as possible coating material for organic aerogels(2019-12-01); Aerogels require nontoxic coatings which are good barriers to the environment and do not affect the fragile porous network. There is a wide range of coating materials available for a variety of applications and functionalities. Waxes, for example, are good moisture barrier candidates and do not require additional solvents during processing. Hence, in this work four different natural waxes were tested concerning their application as coating material for porous aerogels. Therefore, beeswax, candelilla wax, rice bran wax and sunflower wax were investigated regarding their thermic properties, moisture barrier properties and wettability. Beeswax and rice wax proved favourable for coating aerogels. Beeswax shows low water vapour permeability, low minimum film forming temperature and forms continuous films. The water vapour permeability of rice wax is higher compared to beeswax, but there is no minimum film forming temperature in the temperature range of 20 °C–80 °C and the appearance of the rice wax films is homogeneous. Candelilla wax and sunflower wax are not suitable for coating of aerogels. Candelilla wax forms discontinuous films which diminish its water barrier properties. Sunflower wax has the highest water vapour permeability, forms porous films and forms cracks on the surface of the film during solidification below 62 °C.Publicationtype: Journal Article223 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , 5 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Novel technique for measurement of coating layer thickness of fine and porous particles using focused ion beam(2019-02-01); ; ; ; A novel technique for the measurement of the coating layer thickness of fine particles was developed in this work based on cross-sectioning of micrometre-sized single coated particles using focused ion beam (FIB) milling. This technique was tested on two batches of aerogel particles coated with thin coatings in a spouted bed. The FIB milling procedure consisted of two steps. First, the desired part of the coated particle was removed using a high ion beam current. The resulting cross-sectioned area was then polished using a lower ion beam current to make the cross-section clearly visible. The FIB milling process was controlled with simultaneous scanning electron microscopy (SEM). Afterwards, the coating layer thickness was evaluated using the SEM images. The coating layer was successfully applied on the porous aerogel microparticles in the spouted bed. The coating uniformity of the highly porous particles increased with increasing sprayed coating solution amount, with up to 91% of the particle pores being covered. The FIB-cross-sectioning technique using an ion beam of 2.50 nA for the first milling and 0.43 nA for polishing of the surface resulted in successful generation of cross-sections of representative particles with a visible particle core and coating layer. A coating layer thickness of approximately 700 nm was achieved on particles with sizes of below 45 μm.Publicationtype: Journal Article262 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Functionalization of aerogel particles by coating in a spouted bed(2018-04-22); ; ; Aerogels are porous and light-weighting materials with high specific surface area. Due to their properties they have been investigated as carriers of active ingredients. However, open pore structure limits their application because of changing their structure when they are exposed to liquids. Therefore, there is a protective layer on the surface of the aerogels needed, which preserves loaded drug or enables storage in liquid containing media. Furthermore, the knowledge of thickness of the applied coating layer is essential in order to predict the storage or release behavior. In this work a novel technique for measurement of coating layer thickness of fine particles is presented. This method is based on cross-sectioning of single coated particles in micrometer size range with focused ion beam (FIB). This technique has been tested on two batches of produced aerogel particles coated with thin coating layers in a spouted bed.Publicationtype: Conference Paper172 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Coating of fine Aerogel particles using spouted bed technologyAerogels are porous and light-weighting materials with high inner surface area. Their properties enable to use them in many fields, e.g. as acoustic and thermal insulation materials, catalyst, adsorber or drug carriers. However, open pore structure does not allow their application in different areas because of change of the structure caused by liquid-contact. Therefore there is a protective layer on their surface needed, which provides new fields of application, e.g. in food products. In this work coating of the protein-based aerogel microspheres (dP < 100 μm) with shellac using spouted bed technology was performed. This method enables applying of dense, uniform and thin coating layer on fine particles. To improve the uniformity of the coating layer the specific surface area before and after the coating procedure was measured and showed clear decrease after longest coating time. To investigate the behavior ofaerogels in water containing medias the particles were exposed to water drops using sessile drop protocol. The coating protects the aerogel particles from water influence.Publicationtype: Conference Paper168 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Coating of protein-based aerogels using spouted-bed technology(Wiley-VCH, 2016-08-29); ; ; ; Publicationtype: Journal Article102 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Bonded-particle extraction and stochastic modeling of internal agglomerate structures(Elsevier, 2016-06-16); ; ; ; The discrete element method (DEM) is an effective computational technique that is used to investigate the mechanical behavior of various particle systems like, for example, agglomerates. However, for systems of perfectly spherical and non-overlapping particles, the structural input is almost always based only qualitatively on experimentally observed structures. In this paper, we consider the case of agglomerates where particles are nearly spherical and connected by bonds. A novel bonded-particle extraction (BPE) method is proposed for the automated approximation of such agglomerate structures from tomographic data sets. This method can be effectively used in conjunction with various commercial or open-source DEM simulation systems. By BPE, sphere-like primary particles are represented each by exactly one (perfect) sphere, and the set of spheres is non-overlapping. Furthermore, the solid bridge bonds between primary particles are retained. Having derived such a simple description of complex tomographic data sets, one can perform DEM simulations with well-established models like the bonded-particle model. Moreover, it is shown that a larger data base of statistically equivalent microstructures can be generated by a stochastic modeling approach. This approach reduces the need for (time-consuming) experimental agglomerate production and characterization.Publicationtype: Journal Article71