Bioactive Ceramics - New Processing Technologies for Immobilization of Microorganisms for Filtration and Bioreactor Applications

2007 ◽  
Vol 336-338 ◽  
pp. 1683-1687 ◽  
Author(s):  
Dietmar Koch ◽  
Christian Soltmann ◽  
Georg Grathwohl
Keyword(s):  
Porous Ceramic ◽  
Sol Gel ◽  
Ceramic Composites ◽  
High Rate ◽  
Wide Field ◽  
Separation Processes ◽  
Processing Technologies ◽  
Wide Range ◽  
Sol Gel Transition ◽  
New Processing

The metabolism of biocomponents and microorganisms is widely used for the production of medical products as well as for biotechnological processes. The productivity of the related reactions can be improved by the immobilization of the living species in granules or in a gel matrix. Since these structures can suffer during operation due to their weakness a new type of porous ceramic composites was developed where the biological phase is immobilized in a rigid inorganic matrix of high permeability for fluids. During the so-called freeze gelation process (FGP) both, a highly efficient immobilization of the biocomponents and an ideal permeability is achieved. A high versatility is then offered due to the particular advantages of the freezing step necessary for the sol-gel transition and the preservation of embedded microorganisms. While the freezing conditions are decisive for the resulting porosity of the biocer, they are also crucial for the survival rate of the embedded biocomponents. The porosity can be adjusted over a wide range by controlling the composition and the freezing conditions. By the directional ice crystal growth large pore channels can be achieved inside the biocers. Thus, the embedded biocomponents are easily accessible by external reagents and biochemical reactions can proceed with a high rate. Furthermore, cell division is conceivable inside the biocers by safe immobilization at the same time. These biocers allow a wide field of applications depending on the class of immobilized biospecies. Biocatalysis with enzymes can also be applied as bioaccumulation and absorption/desorption of metal ions for separation processes of contaminated water or highly selective filters for metallic complexes in solution.

scholarly journals Major Role of Voluminosity in the Compressibility and Sol–Gel Transition of Casein Micelle Dispersions Concentrated at 7 °C and 20 °C

Foods ◽  
2019 ◽  
Vol 8 (12) ◽  
pp. 652
Author(s):  
Floriane Doudiès ◽  
Anne-Sophie Arsène ◽  
Fabienne Garnier-Lambrouin ◽  
Marie-Hélène Famelart ◽  
Antoine Bouchoux ◽  
...  
Keyword(s):  
Equilibrium Dialysis ◽  
Sol Gel ◽  
Casein Micelle ◽  
New Information ◽  
Wide Range ◽  
Sol Gel Transition ◽  
The Cost ◽  
Micelle Hydration ◽  
Gel Transition

The objective of this work is to bring new information about the influence of temperatures (7 °C and 20 °C) on the equation of state and sol–gel transition behavior of casein micelle dispersions. Casein micelle dispersions have been concentrated and equilibrated at different osmotic pressures using equilibrium dialysis at 7 °C and 20 °C. The osmotic stress technique measured the osmotic pressures of the dispersions over a wide range of concentrations. Rheological properties of concentrated dispersions were then characterized, respectively at 7 °C and at 20 °C. The essential result is that casein micelle dispersions are less compressible at 7 °C than at 20 °C and that concentration of sol–gel transition is lower at 7 °C than at 20 °C, with compressibility defined as the inverse to the resistance to the compression, and that is proportional to the cost to remove water from structure. From our interpretations, these two features were fully consistent with a release of soluble β-casein and nanoclusters CaP and an increased casein micelle hydration and apparent voluminosity at 7 °C as compared with 20 °C.

Multi-Purpose Porous Ceramic Material

2018 ◽  
Vol 931 ◽  
pp. 594-597
Author(s):  
Yu.S. Bagaiskov
Keyword(s):  
Ceramic Material ◽  
Construction Material ◽  
Porous Ceramic ◽  
Ceramic Composites ◽  
Refractory Clay ◽  
Treatment Processes ◽  
Wide Range ◽  
Porosity And Permeability ◽  
And Performance ◽  
Criteria For Evaluation

The main criteria for evaluation of ceramic products’ properties are strength, structural and mechanical, and thermophysical properties. To produce ceramic composites with a wide range of structural, mechanical, strength, and performance properties depending on application, various additives (flux agents, sintering agents, fillers) and heat treatment processes are used. Studies to determine a rational mixture composition have been carried out. A multipurpose material, comprising particles of the basic chamotte filler (burned clay) with a bonding agent in the form of refractory clay from the Latnenskoye deposit with a field spar fluxing agent, an additional filler made of heat-resistant silicon carbide, and an adhesive component in the form of powdered dextrin, is suggested. According to the combination of its ensured parameters, the obtained ceramic material can be multipurpose. Its degree of porosity and permeability make the material filtering, sound-proofing, and heat-retaining; considering the low density, it can be used as a lightweight construction material.

scholarly journals Unravelling a Novel Sol-Gel Transition Mechanism in Polymer Self-Assemblies: An Order-Order Transition Based on Specific Molecular Interactions Between Hydrophilic and Hydrophobic Polymer Blocks

2021 ◽  
Author(s):  
Lukas Hahn ◽  
Theresa Zorn ◽  
Josef Kehrrein ◽  
Tobias Kielholz ◽  
Benedikt Sochor ◽  
...  
Keyword(s):  
Self Assembly ◽  
Sol Gel ◽  
Analytical Techniques ◽  
Order Transition ◽  
Dynamics Simulation ◽  
Aqueous Polymer ◽  
Transition Mechanism ◽  
Wide Range ◽  
Spherical Micelles ◽  
Sol Gel Transition

Using a wide range of state-of-the art analytical techniques and molecular dynamics simulation, a novel mechanism for macromolecular interactions are described. Distinct interactions between the hydrophilic and hydrophobic blocks in amphiphilic triblock copolymers lead to an order-order transition from spherical micelles to worm-like micelles upon cooling the aqueous polymer solutions below room temperature. Macroscopically, this this leads to reversible gelation. This novel mechanism represent a novel building block to better understand polymer self-assembly.<br>

scholarly journals The Rheology of PEOT/PBT Block Copolymers in the Melt State and in the Thermally-Induced Sol/Gel Transition. Implications on the 3D-Printing Bio-Scaffold Process

Materials ◽  
2019 ◽  
Vol 12 (2) ◽  
pp. 226 ◽  
Author(s):  
Veronica Vanzanella ◽  
Marco Scatto ◽  
Erwin Zant ◽  
Michele Sisani ◽  
Maria Bastianini ◽  
...  
Keyword(s):  
Phase Transition ◽  
Block Copolymers ◽  
3D Printing ◽  
Sol Gel ◽  
Rheological Characterization ◽  
Thermally Induced ◽  
Low Viscosity ◽  
Oscillatory Shear Flow ◽  
Wide Range ◽  
Sol Gel Transition

Poly(ethyleneoxideterephthalate)/poly(butyleneterephthalate) (PEOT/PBT) segmented block copolymers are widely used for the manufacturing of 3D-printed bio-scaffolds, due to a combination of several properties, such as cell viability, bio-compatibility, and bio-degradability. Furthermore, they are characterized by a relatively low viscosity at high temperatures, which is desired during the injection stages of the printing process. At the same time, the microphase separated morphology generated by the demixing of hard and soft segments at intermediate temperatures allows for a quick transition from a liquid-like to a solid-like behavior, thus favoring the shaping and the dimensional stability of the scaffold. In this work, for the first time, the rheology of a commercial PEOT/PBT material is studied over a wide range of temperatures encompassing both the melt state and the phase transition regime. Non-isothermal viscoelastic measurements under oscillatory shear flow allow for a quantitative determination of the material processability in the melt state. Additionally, isothermal experiments below the order–disorder temperature are used to determine the temperature dependence of the phase transition kinetics. The importance of the rheological characterization when designing the 3D-printing scaffold process is also discussed.

scholarly journals Unravelling a Novel Sol-Gel Transition Mechanism in Polymer Self-Assemblies: An Order-Order Transition Based on Specific Molecular Interactions Between Hydrophilic and Hydrophobic Polymer Blocks

2021 ◽  
Author(s):  
Lukas Hahn ◽  
Theresa Zorn ◽  
Josef Kehrrein ◽  
Tobias Kielholz ◽  
Benedikt Sochor ◽  
...  
Keyword(s):  
Self Assembly ◽  
Sol Gel ◽  
Analytical Techniques ◽  
Order Transition ◽  
Dynamics Simulation ◽  
Aqueous Polymer ◽  
Transition Mechanism ◽  
Wide Range ◽  
Spherical Micelles ◽  
Sol Gel Transition

Using a wide range of state-of-the art analytical techniques and molecular dynamics simulation, a novel mechanism for macromolecular interactions are described. Distinct interactions between the hydrophilic and hydrophobic blocks in amphiphilic triblock copolymers lead to an order-order transition from spherical micelles to worm-like micelles upon cooling the aqueous polymer solutions below room temperature. Macroscopically, this this leads to reversible gelation. This novel mechanism represent a novel building block to better understand polymer self-assembly.<br>

Viscoelasticity of Dental Tissue Conditioners during the Sol-gel Transition

2005 ◽  
Vol 84 (4) ◽  
pp. 376-381 ◽  
Author(s):  
H. Murata ◽  
H. Chimori ◽  
T. Hamada ◽  
J.F. McCabe
Keyword(s):  
Molecular Weight ◽  
Sol Gel ◽  
Influential Factor ◽  
Rheological Parameters ◽  
Dental Tissue ◽  
Ethanol Content ◽  
Composition And Structure ◽  
Wide Range ◽  
Sol Gel Transition ◽  
Gel Transition

Formation of tissue conditioners is a process of polymer chain entanglements. This study evaluated the influence of composition and structure on dynamic viscoelasticity of concentrated polymer solutions based on poly(ethyl methacrylate) (PEMA) used as tissue conditioners through the sol-gel transition. The hypothesis was that the ethanol content is the most influential factor in determining gelation speed. Rheological parameters were determined with the use of a controlled-stress rheometer. Analysis of variance by orthogonal array L16(45) indicated that the strong polar bonding of ethanol (contribution ratio ρ = 53.8%; confirming the hypothesis) and molecular weight of polymer powders (ρ = 26.7%) had a greater influence on the gelation times of PEMA-based systems than did the molar volume of plasticizers (ρ = 9.0%) and concentration of polymers ( i.e., powder/liquid ratio) (ρ = 4.5%). The results suggest that the gelation of tissue conditioners based on PEMA can be controlled over a wide range by varying the polymer molecular weight, and especially ethanol content.

TEM visualization of surface replicated acid and base catalyzed sol-gel glasses

1986 ◽  
Vol 44 ◽  
pp. 448-449
Author(s):  
George C. Ruben ◽  
Merrill W. Shafer
Keyword(s):  
Elevated Temperatures ◽  
Sol Gel ◽  
Basic Medium ◽  
Glass Transition Point ◽  
Structural Space ◽  
Acid And Base ◽  
Organometallic Precursors ◽  
New Processing ◽  
Gel Glasses ◽  
Physical Phenomena

Traditionally ceramics have been shaped from powders and densified at temperatures close to their liquid point. New processing methods using various types of sols, gels, and organometallic precursors at low temperature which enable densificatlon at elevated temperatures well below their liquidus, hold the promise of producing ceramics and glasses of controlled and reproducible properties that are highly reliable for electronic, structural, space or medical applications. Ultrastructure processing of silicon alkoxides in acid medium and mixtures of Ludox HS-40 (120Å spheres from DuPont) and Kasil (38% K2O &62% SiO2) in basic medium have been aimed at producing materials with a range of well defined pore sizes (∼20-400Å) to study physical phenomena and materials behavior in well characterized confined geometries. We have studied Pt/C surface replicas of some of these porous sol-gels prepared at temperatures below their glass transition point.

Sol-gel transition in silica alkaline solutions. A NMR study

1994 ◽  
Vol 91 ◽  
pp. 901-908 ◽  
Author(s):  
H Zanni ◽  
P Nieto ◽  
L Fernandez ◽  
R Couty ◽  
P Barret ◽  
...  
Keyword(s):  
Sol Gel ◽  
Alkaline Solutions ◽  
Nmr Study ◽  
Sol Gel Transition ◽  
Gel Transition

Mesoscopic gelation of chitosan and genipin at below critical concentrations

2017 ◽  
Author(s):  
Christoph Engwer ◽  
Ronja Loy ◽  
Ioannis S. Chronakis ◽  
Ana C. Mendes ◽  
Francisco M. Goycoolea
Keyword(s):  
Sol Gel ◽  
Crosslinking Agent ◽  
Small Deformation ◽  
Macroscopic Appearance ◽  
Critical Concentrations ◽  
Gelation Kinetics ◽  
Gardenia Jasminoides ◽  
Sol Gel Transition ◽  
Low Cytotoxicity ◽  
High Concentrations

Genipin is increasingly used as a crosslinking agent for chitosans due to its low cytotoxicity as a naturally occurring extract of the plant <i>Gardenia jasminoides</i>. Genipin reacts with the primary amino groups of chitosan to form blue hydrogels. We studied the gelation kinetics of different chitosans varying in their properties (molar mass 34 000-213 000 g mol<sup>-1</sup>, degree of acetylation 9-20%) and genipin in detail. We found that critical sol-gel transition times obtained from dynamic light scattering were in good agreement with the results obtained by small deformation oscillatory rheometry and microviscosimetry at high concentrations of chitosan. However, at below critical concentrations, we found a second regime of gelation that followed the same Ross-Murphy's gelation kinetics. The macroscopic appearance of these samples was a suspension of weak gel-like particles that were sensitive to mechanical forces. We believe that the material is a mesoscopic gel, as described for other polymers. To the best of our knowledge, this is the first time that this phenomenon has been described for the gelling system of chitosan and genipin.

Application of the ceramic membrane with hydrophobic skin layer to separation of activated sludge

1997 ◽  
Vol 35 (8) ◽  
pp. 137-144 ◽  
Author(s):  
Tsuyoshi Nomura ◽  
Takao Fujii ◽  
Motoyuki Suzuki
Keyword(s):  
Activated Sludge ◽  
Pore Size ◽  
Ceramic Membrane ◽  
Membrane Separation ◽  
Porous Ceramic ◽  
Porous Membrane ◽  
Skin Layer ◽  
Gas Permeation ◽  
Wide Range ◽  
Cake Layer

Porous membrane of poly(tetrafluoroethylene) (PTFE) was formed on the surface of porous ceramic tubes by means of heat treatment of the PTFE particles deposit layer prepared by filtering PTFE microparticles emulsified in aqueous phase. By means of inert gas permeation, pore size was determined and compared with scanning electron micrograph observation. Also rejection measurement of aqueous dextran solutions of wide range of molecular weights showed consistent results regarding the pore size. Since the membrane prepared by this method is stable and has unique features derived from PTFE, it is expected that the membrane has interesting applications in the field of water treatment. Membrane separation of activated sludge by this composite membrane and original ceramics membrane showed that the PTFE membrane gives better detachability of the cake layer formed on the membrane. This might be due to the hydrophobic nature of the PTFE skin layer.

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