Mo- and W-Fiber Reinforced SiCN Ceramic Matrix Composites based on PIP process

Mo- and W-fiber reinforced CMCs can be easily manufactured via polymer infiltration and pyrolysis at 1300 °C (PIP) Mo/SiCN and W/SiCN composites are light-weight in comparison to Mo/Mo and W/W composites Mo/SiCN and W/SiCN show increased fracture strain compared to CMCs Mo/SiCN and W/SiCN can be considered as WMCs and thus need no weak interphase Microstructural and phase analyses have shown that Mo- and W-fibers are still present and thermally resistant in the SiCN matrix even at 1300 °C Thermodynamical calculations strongly recommend an additional fiber coating from C-attack! Microstructural and phase analyses have shown that Mo- and W-fibers suffer from surfacial attack, mainly by C-based materials Applying a coating as reaction barrier (e.g. Y2O3) should provide further improvement in mechanical properties New applications are feasible due to: increased fracture strain good tensile and fracture strain high stiffness high thermal conductivity low thermal expansion high thermal shock resistance anisotropic behaviour of composite according to tailor-made desig

Mo- and W-Fiber Reinforced SiCN Ceramic Matrix Composites based on PIP process

Mo- and W-fiber reinforced CMCs can be easily manufactured via polymer infiltration and pyrolysis at 1300 °C (PIP) Mo/SiCN and W/SiCN composites are light-weight in comparison to Mo/Mo and W/W composites Mo/SiCN and W/SiCN show increased fracture strain compared to CMCs Mo/SiCN and W/SiCN can be considered as WMCs and thus need no weak interphase Microstructural and phase analyses have shown that Mo- and W-fibers are still present and thermally resistant in the SiCN matrix even at 1300 °C Thermodynamical calculations strongly recommend an additional fiber coating from C-attack! Microstructural and phase analyses have shown that Mo- and W-fibers suffer from surfacial attack, mainly by C-based materials Applying a coating as reaction barrier (e.g. Y2O3) should provide further improvement in mechanical properties New applications are feasible due to: increased fracture strain good tensile and fracture strain high stiffness high thermal conductivity low thermal expansion high thermal shock resistance anisotropic behaviour of composite according to tailor-made desig

Transcriptional Regulation of Siglec-15 by ETS-1 and ETS-2 in Hepatocellular Carcinoma Cells

Sialic acid-binding immunoglobulin-like lectin 15 (Siglec-15) has been identified as a crucial immune suppressor in human cancers, comparable to programmed cell death 1 ligand (PD-L1). However, the regulatory mechanisms underlying its transcriptional upregulation in human cancers remain largely unknown. Here, we show that the transcription factors ETS-1 and ETS-2 bound to the Siglec-15 promoter to enhance transcription and expression of Siglec-15 in hepatocellular carcinoma (HCC) cells and that transforming growth factor β-1 (TGF-β1) upregulated the expression of ETS-1 and ETS-2 and facilitated the binding of ETS-1 and ETS-2 to the Siglec-15 promoter. We further demonstrate that TGF-β1 activated the Ras/C-Raf/MEK/ERK1/2 signaling pathway, leading to phosphorylation of ETS-1 and ETS-2, which consequently upregulates the transcription and expression of Siglec-15. Our study defines a detailed molecular profile of how Siglec-15 is transcriptionally regulated which may offer significant opportunity for therapeutic intervention on HCC immunotherapy

Novel ceramic matrix composites with tungsten and molybdenum fiber reinforcement

Ceramic matrix composites usually utilize carbon or ceramic fbers as reinforcements. However, such fbers often expose a low ductility during failure. In this work, we follow the idea of a reinforcement concept of a ceramic matrix reinforced by refractory metal fbers to reach pseudo ductile behavior during failure. Tungsten and molybdenum fbers were chosen as reinforcement in SiCN ceramic matrix composites manufactured by polymer infltration and pyrolysis process. The composites were investigated with respect to microstructure, flexural- and tensile strength. The single fber strengths for both tungsten and molybdenum were investigated and compared to the strength of the composites. Tensile strengths of 206 and 156 MPa as well as bending strengths of 427 and 312 MPa were achieved for W/SiCN and Mo/SiCN composites, respectively. The W fber became brittle across the entire cross section, while the Mo fber showed a superfcial, brittle reaction zone but kept ductile on the inside

Novel ceramic matrix composites with tungsten and molybdenum fiber reinforcement

Damage-tolerant ceramic matrix composites (CMC) are prone to high temperature applications under severe environmental conditions and usually utilize carbon or ceramic fibres (e.g. SiC) as reinforcements of ceramic matrices with inherent low elongation to break compared to common metals. However, CMC reveal an elongation to break and stiffness similar to the ceramic matrices, and thus need a fibre coating in order to improve the elongation to break length and thus to achieve damage tolerance of the composite. In addition, such fibers often expose a low ductility during failure. As a consequence, design criteria for components of such CMC materials are limited by the low strain of failure. In order to overcome this problem, we follow the idea of a reinforcement concept of a ceramic matrix reinforced by refractory metal fibres to reach pseudo ductile behaviour during failure. Tungsten (W) and molybdenum (Mo) fibers were chosen as reinforcement in SiCN CMC manufactured by polymer infiltration and pyrolysis process. These fibres are commercially available since they are widespread used in light bulbs, etc. , and possess an intrinsic higher elongation to break, compared to ceramic fibres, as well as high stiffness even at high temperatures. W/SiCN and Mo/SiCN composites were manufactured via filament winding and resin transfer moulding of commercially available polysilazanes, pyrolysed and re-densified by multiple reinfiltration and pyrolysis steps. These composites were investigated with respect to microstructure, flexural and tensile strength. Single fibre strengths for W and Mo were investigated and compared to the strength of the composites. Tensile strengths of 206 and 156 MPa as well as bending strengths of 427 and 312 MPa were achieved for W/SiCN and Mo/SiCN composites, respectively. W fibre became brittle across the entire cross section, while the Mo fibre showed a superficial, brittle reaction zone but kept ductile on the inside

Characterization and application of a novel low viscosity polysilazane for the manufacture of C- and SiC-fiber reinforced SiCN ceramic matrix composites by PIP process

Four unidirectional fber reinforced SiCN ceramic matrix composites were manufactured by means of polymer infltration and pyrolysis. Two carbon fbers (T800H and Granoc XN90) as well as two silicon carbide fbers (Tyranno ZMI and SA3) without fber coating were chosen. As matrix precursor, a poly(methylvinyl)silazane was investigated and utilized. The composites with the SA3 and the XN90 fber had the highest tensile strengths of 478 and 288 MPa, respectively. It is considered that these high modulus fbers with the low modulus SiCN matrix create weak matrix composites. After exposure to air (T = 1200 °C, 10 h), a signifcant decrease of the mechanical properties was found, caused by the burnout of carbon fbers and the oxidation through open pores stemming from the PIP process and SiCN/SiCN interfaces in case of the SiC fber based composites