Mechanical Properties of Porous β‑Tricalcium Phosphate Composites Prepared by Ice-Templating and Poly(ε-caprolactone) Impregnation

In this study ceramic scaffolds of the bioresorbable and osteoconductive bioceramic β-tricalcium phosphate (β-TCP) were impregnated with the bioresorbable and ductile polymer poly­(ε-caprolactone) (PCL) to investigate the influence of the impregnation on the mechanical properties of the porous composites. The initial β-TCP scaffolds were fabricated by the ice-templating method and exhibit the typical morphology of aligned, open, and lamellar pores. This pore morphology seems to be appropriate for applications as bone replacement material. The macroporosity of the scaffolds is mostly preserved during the solution-mediated PCL impregnation as the polymer was added only in small amounts so that only the micropores of β-TCP lamellae were infiltrated and the surface of the lamellae were coated with a thin film. Composite scaffolds show a failure behavior with brittle and plastic contributions, which increase their damage tolerance, in contrast to the absolutely brittle behavior of pure β-TCP scaffolds. The energy consumption during bending and compression load was increased in the impregnated scaffolds by (a) elastic and plastic deformation of the introduced polymer, (b) drawing and formation of PCL fibrils which bridge micro- and macrocracks, and (c) friction of ceramic debris still glued together by PCL. PCL addition also increased the compressive and flexural strength of the scaffolds. An explanatory model for this strength enhancement was proposed that implicates the stiffening of cold-drawn PCL present in surface flaws and micropores

Investigation of Ice-Templated Porous Electrodes for Application in Organic Batteries

Application and investigation of porous composite electrodes for organic batteries fabricated by an ice-templating method are reported for the first time. The possibility to produce polymer composite electrodes with highly aligned, parallel pores is demonstrated and electrochemical investigations are presented to examine their suitability for application in organic batteries. The performance of such ice-templated porous electrodes is experimentally compared with planar electrodes of similar composition against zinc and lithium counter electrodes, respectively. Fundamental properties limiting the performance of ice-templated porous electrodes are discussed and further means to overcome those limitations are proposed

In Situ Synthesis of Photocatalytically Active Hybrids Consisting of Bacterial Nanocellulose and Anatase Nanoparticles

Bacterial nanocellulose (BNC) is an extraordinary biopolymer with a wide range of potential technical applications. The high specific surface area and the interconnected pore system of the nanofibrillar BNC network suggest applications as a carrier of catalysts. The present paper describes an in situ modification route for the preparation of a hybrid material consisting of BNC and photocatalytically active anatase (TiO₂) nanoparticles (NPs). The influence of different NP concentrations on the BNC biosynthesis and the resulting supramolecular structure of the hybrids was investigated. It was found that the number of colony forming units (CFUs) and the consumption of glucose during biosynthesis remained unaffected compared to unmodified BNC. During the formation of the BNC network, the NPs were incorporated in the whole volume of the accruing hybrid. Their distribution within the hybrid material is affected by the anisotropic structure of BNC. The photocatalytic activity (PCA) of the BNC-TiO₂ hybrids was determined by methanol conversion (MC) under UV irradiation. These tests demonstrated that the NPs retained their PCA after incorporation into the BNC carrier structure. The PCA of the hybrid material depends on the amount of incorporated NPs. No alteration of the photocatalyst’s efficiency was found during repeated PCA tests. In conclusion, the in situ integration of photocatalytically active NPs into BNC represents an attractive possibility to extend its fields of application to porous filtering media for drinking water purification and air cleaning