Hydrothermal carbonization in the synthesis of sustainable porous carbon materials

Carbon materials are found versatile and applicable in wide range of applications. During the recent years research of carbon materials has focussed on the search of environmentally friendly, sustainable, renewable and low-cost starting material sources as well as simple cost-efficient synthesis techniques. As an alternative synthesis technique in the production of carbon materials hydrothermal carbonization (HTC) has shown a great potential. Depending on the application HTC can be performed as such or as a pretreatment technique. This technique allows synthesis of carbon materials i.e. hydrochars in closed vessel in the presence of water and self-generated pressure at relatively low temperatures (180-250 ˚C). As in many applications well developed porosity and heteroatom distribution are in a key role. Therefore in this study different techniques e.g. varying feedstock, templating and post-treatment in order to introduce these properties to the hydrochars structure were performed. Simple monosaccharides i.e. fructose or glucose and more complex compounds such as cellulose and sludge were performed as starting materials. Addition of secondary precursor e.g. thiophenecarboxaldehyde and ovalbumin was successfully exploited in order to alter heteroatom content. It was shown that well-developed porosity (SBET 550 m2/g) can be achieved via one-pot approach (i.e. exploitation of salt mixture) without conventionally used post-carbonization step. Nitrogen-enriched hydrochars indicated significant Pb(II) and Cr(VI) removal efficiency of 240 mg/g and 68 mg/g respectively. Sulphur addition into carbon network was not found to have enhancing effect on the adsorption of methylene blue or change acidity of the carbon material. However, these hydrochars were found to remove 99.9 % methylene blue and adsorption efficiency of these hydrochars remained over 90 % even after regeneration. In addition to water treatment application N-rich high temperature treated carbon materials were proven applicable as electrocatalyst and electrocatalyst support. Hydrothermal carbonization was shown to be workable technique for the production of carbon materials with variable physico-chemical properties and therefore hydrochars could be applied in several different applications e.g. as alternative low-cost adsorbent for pollutant removal from water.

PIV measurements combined with the motion tracking technique to analyze flow around a moving porous structure

To gain a better understanding of the fluid–structure interaction and especially when dealing with a flow around an arbitrarily moving body, it is essential to develop measurement tools enabling the instantaneous detection of moving deformable interface during the flow measurements. A particularly useful application is the determination of unsteady turbulent flow velocity field around a moving porous fishing net structure which is of great interest for selectivity and also for the numerical code validation which needs a realistic database. To do this, a representative piece of fishing net structure is used to investigate both the Turbulent Boundary Layer (TBL) developing over the horizontal porous moving fishing net structure and the turbulent flow passing through the moving porous structure. For such an investigation, Time Resolved PIV measurements are carried out and combined with a motion tracking technique allowing the measurement of the instantaneous motion of the deformable fishing net during PIV measurements. Once the two-dimensional motion of the porous structure is accessed, PIV velocity measurements are analyzed in connection with the detected motion. Finally, the TBL is characterized and the effect of the structure motion on the volumetric flow rate passing though the moving porous structure is clearly demonstrated.

Microstructure and tensile properties of carbon-epoxy laminates produced by automated fibre placement: Influence of a caul plate on the effects of gap and overlap embedded defects

Automated fibre placement (AFP) enables the trajectory of unidirectional composite tape to be optimized, but laying down complex shapes with this technology can result in the introduction of defects. The aim of this experimental study is to investigate the influence of gaps and overlaps on the microstructure and tensile properties of carbon-epoxy laminates. First, a comparison between a hand-layup and AFP layup, draped and cured under the same conditions, shows equivalent microstructures and tensile properties. This provides the reference values for the study. Then, gap and overlap embedded defects (more or less severe) are introduced during manufacturing, on two cross-ply layups [(0°/(90°)5/0°] and [(90°/0°)2/90°]. Autoclave cure without a caul plate results in local thickness variation and microstructural changes which depend on the defect type. This has a strong influence on mechanical performance. Use of a caul plate avoids these variations and in this case embedded defects hardly affect tensile properties.

Scaffolds porosos à base de fosfatos de cálcio para regeneração óssea

Graças ao aumento da esperança média de vida do ser humano, a engenharia de tecidos tem sido uma área alvo de enorme investigação. A utilização de estruturas tridimensionais porosas e biodegradáveis, denominadas de scaffolds, como matriz para a adesão e proliferação celular tem sido amplamente investigada. Existem atualmente diversas técnicas para a produção destas estruturas mas o grau de exigência tem vindo a aumentar, existindo ainda lacunas que necessitam ser preenchidas. A técnica de robocasting consiste numa deposição camada a camada de uma pasta coloidal, seguindo um modelo computorizado (CAD) e permite a produção de scaffolds com porosidade tamanho de poro e fração de porosidade controlados, boa reprodutibilidade, e com formas variadas, as quais podem ser idênticas às dos defeitos ósseos a preencher. O presente estudo teve como objetivo produzir scaffolds porosos à base de fosfatos de cálcio através de robocasting. Para tal, foram estudadas duas composições de pós à base de β-TCP, uma pura e outra co-dopada com estrôncio, zinco e manganês. Inicialmente os pós foram sintetizados pelo método de precipitação química por via húmida. Após a síntese, estes foram filtrados, secos, calcinados a 1000ºC e posteriormente moídos até possuírem um tamanho médio de partícula de cerca de 1,5 μm. Os pós foram depois peneirados com uma malha de 40μm e caracterizados. Posteriormente foram preparadas várias suspensões e avaliado o seu comportamento reológico, utilizando Targon 1128 como dispersante, Hidroxipropilmetilcelulose (HPMC) como ligante e polietilenimina (PEI) como agente floculante. Por fim, e escolhida a melhor composição para a formação da pasta, foram produzidos scaffolds com diferentes porosidades, num equipamento de deposição robótica (3D Inks, LLC). Os scaffolds obtidos foram secos à temperatura ambiente durante 48 horas, sinterizados a 1100ºC e posteriormente caracterizados por microscopia eletrónica de varrimento (SEM), avaliação dos tamanhos de poro, porosidade total e testes mecânicos. Ambas as composições estudadas puderam ser transformadas em pastas extrudíveis, mas a pasta da composição pura apresentou uma consistência mais próxima do ideal, tendo originado scaffolds de melhor qualidade em termos de microestrutura e de propriedades mecânicas.

Riffe und fazielle Entwicklung der florigemma-Bank (Korallenoolith, Oxfordium) im Süntel und östlichen Wesergebirge (NW-Deutschland

During the Sedimentation of the platform carbonate deposits of the Korallenoolith Formation (middle Oxfordian to early Kimmeridgian) small buildups ofcorals formed in the Lower Saxony Basin. These bioconstructions are restricted to particular horizons (Untere Korallenbank,ßorigenuna-Bank Member etc.) and represent patch reefs and biostromes. In this study, the development of facies, fossil assemblages, spatial distribution of fossils, and reefs of the ßorigenuna-Bank Member (upper Middle Oxfordian) in the Süntel Mts and the eastern Wesergebirge Mts is described; the formation of reefs is discussed in detail. Twelve facies types are described and interpreted. They vary between high-energy deposits as well winnowed oolites and quiet-water lagoonal mudstones. Owing to the significance of biota, micro- and macrofossils are systematically described. The reefs are preserved in growth position, are characterized by numerous corresponding features and belong to a certain reef type. According to their size, shape and framework, they represent patch reefs, coral knobs (sensu James, 1983), coral thrombolite reefs (sensu Leinfelder et al., 1994) or “Klein- and Mitteldickichte” (sensu Laternser, 2001). Their growth fabric corresponds to the superstratal (dense) pillarstone (sensu Insalaco, 1998). As the top of the ßorigenuna-Bank displays an erosional unconformity (so-called Hauptdiskontinuität), the top of the reefs are erosionally capped. Their maximum height amounts to at least the maximum thickness of the ßorigenuna-Bank which does not exceed 4 metres. The diversity of coral fauna of the reefs is relatively low; a total of 13 species is recorded. The coral community is over- whelmingly dominated by the thin-branched ramose Thamnasteria dendroidea (Lamouroux) that forms aggregations of colonies (77?. dendroidea thickets). Leafy to platy Fungiastrea arachnoides (Parkinson) and Thamnasteria concinna (Goldfuss) occur subordinately, other species are only of minor importance. In a few cases, the reef-core consisting of Th. dendroidea thickets is laterally encrusted by platy F. arachnoides and Th. concinna colonies, and microbial carbonates. This zonation reflects probably a succession of different reef builders as a result of changing environmental conditions (allogenic succession). Moreover, some reefs are overlain by a biostrome made of large Solenopora jurassica nodules passing laterally in a nerinean bed. Mikrobial carbonates promoted reef growth and favoured the preservation of reef organismn in their growth position or in situ. They exhibit a platy, dendroid, or reticulate growth form or occur as downward-facing hemispheroids. According to their microstructure, they consist of a peloidal, clotted, or unstructured fabric (predominately layered and poorly structured thrombolite as well as clotted leiolite) (sensu Schmid, 1996). Abundant endo- and epibiontic organisms (bivalves, gastropods, echinoids, asteroids, ophiuroids, crabs etc) are linked to the reefs. With regard to their guild structure, the reefs represent occurrences at which only a few coral species serve as builder. Moreover, microbial carbonates contribute to both building and binding of the reefs. Additional binder as well as baffler are present, but not abundant. According to the species diversity, the dweller guild comprises by far the highest number of invertebrate taxa. The destroyer guild chiefly encompasses bivalves. The composition of the reef community was influenced by the habitat structure of the Th. dendroidea thickets. Owing to the increase in encrusting organisms and other inhabitants of the thickets, the locational factors changed, since light intensity and hydrodynamic energy level and combined parameters as oxygen supply declined in the crowded habitat. Therefore a characteristic succession of organisms is developed that depends on and responds to changing environmental conditions („community replacement sequence“). The succession allows the differentiation of different stages. It started after the cessation of the polyps with boring organisms and photoautotrophic micro-encrusters (calcareous algae, Lithocodium aggregatum). Following the death of these pioneer organisms, encrusting and adherent organisms (serpulids, „Terebella“ species, bryozoans, foraminifers, thecideidinids, sklerospongid and pharetronid sponges, terebratulids), small mobile organisms (limpets), and microbial induced carbonates developed. The final stage in the community replacement sequence gave rise to small cryptic habitats and organisms that belong to these caves (cryptobionts, coelobites). The habitat conditions especially favoured small non-rigid demosponges (“soft sponges”) that tolerate reduced water circulation. Reef rubble is negligible, so that the reefs are bordered by fossiliferous micritic limestone passing laterally in micritic limestone. Approximately 10% of the study area (outcropping florigemma-Bank) corresponds to reefal deposits whereas the remaining 90% encompass lagoonal inter-reefal deposits. The reef development is a good example for the interaction between reef growth, facies development and sea-level changes. It was initiated by a sea-level rise (transgression) and corresponding decrease in the hydrodynamic energy level. Colonization and reef growth took place on a coarse-grained Substrate composed of oncoids, larger foraminifers and bioclasts. Reef growth took place in a calm marine lagoonal setting. Increasing abundance of spherical coral morphs towards the Northeast (section Kessiehausen, northwestem Süntel Mts) reflects higher turbidity and a facies transition to coral occurrences of the ßorigenuna-Bank Member in the adjacent Deister Mts. The reef growth was neither influenced by stonns nor by input of siliciclastic deposits, and took place in short time - probably in only a thousand years under most probably mesotrophic conditions. The mass appearance of solenoporids and nerineids in the upper part of the ßorigenuna-Bank Member point to enhanced nutrient level as a result of regression. In addition, this scenario of fluctuations in nutrient availability seems to be responsible for the cessation of reef corals. The sea level fall reached its climax in the subaerial exposure and palaeokarst development of the florigemma-Bank. The reef building corals are typical pioneer species. The blade-like, flattened F. amchnoides colonies are characterized by their light porous calcium carbonate skeleton, which is a distinct advantage in soft bottom environment. Thus, they settled on soft bottom exposing the large parts of its surface to the incoming light. On the other hand, in response to their light requirements they were also able to settle shaded canopy structures or reef caves. Th. dendroidea is an opportunistic coral species in very shallow, well illuminated marine environment. Their thin and densely spaced branches led to a very high surface/volume ratio of the colonies that were capable to exploit incoming light due to their small thamasterioid calices characterized by “highly integrated polyps”. In addition, sideward coalescence of branches during colony growth led to a wave-resistant framework and favoured the authochthonous preservation of the reefs. Asexual reproduction by fragmented colonies promoted reef development as Th. dendroidea thickets laterally extend over the sea floor or new reefs have developed from broken fragments of parent colonies. Similar build ups with Th. dendroidea as a dominant or frequent reef building coral species are known from the Paris Basin and elsewhere from the Lower Saxony Basin (Kleiner Deister Mts). These buildups developed in well-illuminated shallow water and encompass coral reefs or coral thrombolite reefs. Intra- and inter-reef deposits vary between well-winnowed reef debris limestone and mudstones representing considerably calmer conditions. Solenoporid, nerineids and diceratides belong to the characteristic fossils of these occurrences. However, diceratides are missing in theflorigemma-Bank Member. Th. dendroidea differs in its colonization of low- to high-energy environment from recent ramose scleractinian corals (e.g., Acropora and Porites sp.). The latter are restricted to agitated water habitats creating coral thickets and carpets. According to the morphologic plasticity of Th. dendroidea, thick-branched colonies developed in a milieu of high water energy, whereas fragile, wide- and thin-branched colonies prevail in low-energy settings. Due to its relatively rapid growth, Th. dendroidea was able to keep pace with increased Sedimentation rates. 68 benthonic foraminiferan species/taxa have been recognized in thin sections. Agglutinated foraminifers (textulariids) predominate when compared with rotaliids and milioliids. Numerous species are restricted to a certain facies type or occur in higher population densities, in particular Everticyclammina sp., a larger agglutinated foraminifer that occurs in rock building amounts. Among the 25 reef dwelling foraminiferal species, a few were so far only known from Late Jurassic sponge reefs. Another striking feature is the frequency of adherent foraminiferal species. Fauna and flora, in particular dasycladaleans and agglutinated foraminifers, document palaeobiogeographic relationships to the Tethys and point to (sub)tropical conditions. Moreover, in Germany this foraminiferan assemblage is yet uncompared. In Southern Germany similar tethyan type assemblages are not present in strata as young as Middle Tithonian.

Octane improvement of gasoline with porous solids

In this work is performed the study of the hexane isomers separation with MOFs in order to improve the octane number of gasoline. The studies were performed with MOFs: MIL-125-Amine, MIL-53(Fe)-Cl, MIL-53(Fe)-Br and Fe-TazBz(DMF). It was observed that higher loadings were obtained for high pressure and low temperature. With MOFs like MIL-53(Fe)-Cl and MIL-53(Fe)-Br the components weren’t separated. In MIL-125-Amine hexane isomers were separated according to their boiling point, but the selectivity was small. The best result was obtained with MOF Fe-TazBz(DMF), because of the higher affinity of n-hex with this MOF, the separation from the other isomers was easier.

3D Porous Architecture of Stacks of β-TCP Granules Compared with That of Trabecular Bone: A microCT, Vector Analysis, and Compression Study

International audience

MICROFLUIDIC ASSAY PERFORMANCE ENHANCEMENT USING POROUS VOLUMETRIC DETECTION ELEMENTS FOR IMPEDEMETRIC AND OPTICAL SENSING

Microfluidic technologies have great potential to help create automated, cost-effective, portable devices for rapid point of care (POC) diagnostics in diverse patient settings. Unfortunately commercialization is currently constrained by the materials, reagents, and instrumentation required and detection element performance. While most microfluidic studies utilize planar detection elements, this dissertation demonstrates the utility of porous volumetric detection elements to improve detection sensitivity and reduce assay times. Impedemetric immunoassays were performed utilizing silver enhanced gold nanoparticle immunoconjugates (AuIgGs) and porous polymer monolith or silica bead bed detection elements within a thermoplastic microchannel. For a direct assay with 10 µm spaced electrodes the detection limit was 0.13 fM AuIgG with a 3 log dynamic range. The same assay was performed with electrode spacing of 15, 40, and 100 µm with no significant difference between configurations. For a sandwich assay the detection limit was10 ng/mL with a 4 log dynamic range. While most impedemetric assays rely on expensive high resolution electrodes to enhance planar senor performance, this study demonstrates the employment of porous volumetric detection elements to achieve similar performance using lower resolution electrodes and shorter incubation times. Optical immunoassays were performed using porous volumetric capture elements perfused with refractive index matching solutions to limit light scattering and enhance signal. First, fluorescence signal enhancement was demonstrated with a porous polymer monolith within a silica capillary. Next, transmission enhancement of a direct assay was demonstrated by infusing aqueous sucrose solutions through silica bead beds with captured silver enhanced AuIgGs yielding a detection limit of 0.1 ng/mL and a 5 log dynamic range. Finally, ex situ functionalized porous silica monolith segments were integrated into thermoplastic channels for a reflectance based sandwich assay yielding a detection limit of 1 ng/mL and a 5 log dynamic range. The simple techniques for optical signal enhancement and ex situ element integration enable development of sensitive, multiplexed microfluidic sensors. Collectively the demonstrated experiments validate the use of porous volumetric detection elements to enhance impedemetric and optical microfluidic assays. The techniques rely on commercial reagents, materials compatible with manufacturing, and measurement instrumentation adaptable to POC diagnostics.