Papers by Steffen Witzleben
Research Square (Research Square), Feb 7, 2024
This paper presents the effects of different amounts of bers and foaming agent, as well as differ... more This paper presents the effects of different amounts of bers and foaming agent, as well as different ber sizes, on the mechanical and thermal properties of y ash-based geopolymer foams reinforced with Miscanthus x giganteus bers. The mechanical properties of the geopolymer foams were measured through compressive strength, and their thermal properties were characterized by thermal conductivity and X-ray micro-computed tomography. Furthermore, design of experiment (DoE) were used to optimize the thermal conductivity and compressive strength of Miscanthus x giganteus reinforced geopolymer foams. In addition, the microstructure was studied using X-ray diffraction (XRD), Field emission scanning electron microscopy (SEM) and Fourier-Transform Infrared Spectroscopy (FTIR). Mixtures with a low thermal conductivity of 0.056 W (m K) -1 and a porosity of 79 vol% achieved a compressive strength of only 0.02 MPa. In comparison, mixtures with a thermal conductivity of 0.087 W (m K) -1 and a porosity of 58 vol% achieved a compressive strength of 0.45 MPa.
Biomolecules, Dec 6, 2019
Bone tissue engineering is an ever-changing, rapidly evolving, and highly interdisciplinary field... more Bone tissue engineering is an ever-changing, rapidly evolving, and highly interdisciplinary field of study, where scientists try to mimic natural bone structure as closely as possible in order to facilitate bone healing. New insights from cell biology, specifically from mesenchymal stem cell differentiation and signaling, lead to new approaches in bone regeneration. Novel scaffold and drug release materials based on polysaccharides gain increasing attention due to their wide availability and good biocompatibility to be used as hydrogels and/or hybrid components for drug release and tissue engineering. This article reviews the current state of the art, recent developments, and future perspectives in polysaccharide-based systems used for bone regeneration.
Advanced Materials Technologies
Separation and Purification Technology
International Journal of Molecular Sciences, 2021
Dental stem cells have been isolated from the medical waste of various dental tissues. They have ... more Dental stem cells have been isolated from the medical waste of various dental tissues. They have been characterized by numerous markers, which are evaluated herein and differentiated into multiple cell types. They can also be used to generate cell lines and iPSCs for long-term in vitro research. Methods for utilizing these stem cells including cellular systems such as organoids or cell sheets, cell-free systems such as exosomes, and scaffold-based approaches with and without drug release concepts are reported in this review and presented with new pictures for clarification. These in vitro applications can be deployed in disease modeling and subsequent pharmaceutical research and also pave the way for tissue regeneration. The main focus herein is on the potential of dental stem cells for hard tissue regeneration, especially bone, by evaluating their potential for osteogenesis and angiogenesis, and the regulation of these two processes by growth factors and environmental stimulators. ...
The hydration of Portland cement lead to Calcium silicate hydrates which are prominent for their ... more The hydration of Portland cement lead to Calcium silicate hydrates which are prominent for their high mechanical strength. Cement clinker production causes up to 7 % to the global CO2emissions. One of several strategies in order to reduce this large carbon footprint are the use of supplementary cementing material (SCMs), e.g. natural and artificial puzzolanes[1]. The application of SCM ́s possess several disadvantages when it comes to practical application. The, decreased in the evolvement of strength is an unfavourable disadvantage. A promising starting point for an extensive use of SCM ́s is the use of approaches of biomineralisation to effect crystal shape and size. Nature provides many examples for materials of high mechanical strength and chemical resistance like shells (Calcium carbonate) diatoms (SiO2) or bones (Calcium phosphates). Calcium silicate hydrates are not known in biomineralization processes. Focusing on the functional groups involved in biomineralisation processes...
Calcium silicate hydrate, the reaction product of cement with water, is the main binding phase in... more Calcium silicate hydrate, the reaction product of cement with water, is the main binding phase in hardened cement pastes and the principal reason for the strength of concrete. Therefore it is of major importance in various fields of research [1]. Cement clinker as the corresponding “startingmaterial” and essential component for concrete-formation, is produced by high-temperature treatment of carbonate minerals. This leads to release of carbon dioxide, mainly resulting from processand fuel-combustion-emissions. Due to rising global production volumes (4.3 billion t in 2014) caused by economic growth, cement manufacturing contributes up to 7 % to the worldwide man-made CO2-emissions. One conceivable approach to produce sustainable cements is clinker substitution by natural puzzolanes. [2] However, they are not suitable for all kinds of cements, for instance because of low early strength. In order to solve this issue, application of organic additives or so-called templates which direct...
Large bone defects require fabricated bone constructs that consist of three main components: an a... more Large bone defects require fabricated bone constructs that consist of three main components: an artificial extracellular matrix scaffold, stem cells with the potential to differentiate into osteoblasts, and bioactive substances, such as osteoinductive growth factors to direct the growth and differentiation of cells toward osteogenic lineage within the scaffold.
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Papers by Steffen Witzleben