scholarly journals Insights into the Microstructural Evolution Occurring during Pyrolysis of Metal-Modified Ceramers Studied through Selective SiO2 Removal

Materials ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3276
Author(s):  
Aitana Tamayo ◽  
Juan Rubio ◽  
Fausto Rubio ◽  
Mᵃ Angeles Rodriguez
Keyword(s):  
Structural Characteristics ◽  
Domain Size ◽  
Ceramic Composites ◽  
Silicon Oxycarbide ◽  
Crosslinking Degree ◽  
Molecular Precursors ◽  
Textural Characterization ◽  
Polymer Derived Ceramic ◽  
Ultimate Properties ◽  
Lower Carbon

Silicon oxycarbide ceramers containing 5% aluminum, zirconium, and cobalt with respect to the total Si amount are prepared from a commercial polysiloxane and molecular precursors and pyrolyzed at temperatures ranging from 500 to 1000 °C. HF etching is carried out to partially digest the silica phase, thus revealing structural characteristics of the materials, which depend upon the incorporated heteroatom. From the structural and textural characterization, it was deduced that when Al enters into the ceramer structure, the crosslinking degree is increased, leading to lower carbon domain size and carbon incorporation as well. On the contrary, the substitution by Zr induced a phase-separated SiO2-ZrO2 network with some degree of mesoporosity even at high pyrolysis temperatures. Co, however, forms small carbidic crystallites, which strongly modifies the carbonaceous phase in such a way that even when it is added in a small amount and in combination with other heteroatoms, this transient metal dominates the structural characteristics of the ceramer material. This systematic study of the ceramer compounds allows the identification of the ultimate properties of the polymer-derived ceramic composites.

Microcrystalline Ceramic Composites by Active Filler Controlled Reaction Pyrolysis of Polymers

1992 ◽  
Vol 274 ◽  
Author(s):  
Peter Greil ◽  
Michael Seibold ◽  
Tobias Erny
Keyword(s):  
Composite Materials ◽  
Dimensional Change ◽  
Ceramic Composites ◽  
Silicon Oxycarbide ◽  
Preceramic Polymers ◽  
Active Filler ◽  
Polymer Derived Ceramic ◽  
Property Changes ◽  
Low Dimensional ◽  
Carbide Inclusions

ABSTRACTPyrolytic conversion of preceramic polymers such as polysilanes, -silazanes, or -siloxanes to ceramics may be significantly influenced by the resence of active filler dispersoids. Based on thermodynamic and microstructural considerations a variety of suitable polymer-filler systems can be found which allow the fabrication of microcrystalline composite materials with low dimensional change upon polymer- ceramic conversion. As an example the active filler controlled reaction pyrolysis of polysiloxane with addition of titanium powder was investigated. A composite material with microcrystalline titanium carbide inclusions embedded in an amorphous (< 1000 °C) or nanocrystalline (>1000 °C) silicon oxycarbide matrix was formed. Property changes with increasing pyrolysis temperature can be attributed to various microstructural transformations. Thus, a variety of potential fillers may be used to tailor the microstructure of polymer-derived ceramic composite materials in order to fabricate bulk materials and components with a broad range of compositions and properties.

scholarly journals Graphene Oxide-Embedded Extracellular Matrix- Derived Hydrogel as a Multiresponsive Platform for 3D Bioprinting Applications

2021 ◽  
Vol 7 (3) ◽  
Author(s):  
Laura Rueda-Gensini ◽  
Julian A Serna ◽  
Javier Cifuentes ◽  
Juan C Cruz ◽  
Carolina Muñoz-Camargo
Keyword(s):  
Graphene Oxide ◽  
Mechanical Stability ◽  
Light Exposure ◽  
Structural Characteristics ◽  
Elastic Response ◽  
Cellular Interaction ◽  
3D Bioprinting ◽  
In Situ Reduction ◽  
Crosslinking Degree

Decellularized extracellular matrices (dECMs) have shown enormous potential for the biofabrication of tissues due to their biomimetic properties that promote enhanced cellular interaction and tissue regeneration. However, biofabrication schemes requiring electrostimulation pose an additional constraint due to the insulating properties of natural materials. Here, we propose a methacryloyl-modified decellularized small intestine submucosa (SISMA) hydrogel, embedded with graphene oxide (GO) nanosheets, for extrusion-based 3D bioprinting applications that require electrostimulation. Methacryloyl biochemicalmodification is performed to enhance the mechanical stability of dECM constructs by mediating photo-crosslinking reactions, and a multistep fabrication scheme is proposed to harness the bioactive and hydrophilic properties of GO and electroconductive properties of reduced GO. For this, GO was initially dispersed in SISMA hydrogels by exploiting its hydrophilicity and protein adsorption capabilities, and in situ reduction was subsequently performed to confer electroconductive abilities. SISMA-GO composite hydrogels were successfully prepared with enhanced structural characteristics, as shown by the higher crosslinking degree and increased elastic response upon blue-light exposure. Moreover, GO was homogeneously dispersed without affecting photocrosslinking reactions and hydrogel shear-thinning properties. Human adipose-derived mesenchymal stem cells were successfully bioprinted in SISMA-GO with high cell viability after 1 week and in situ reduction of GO during this period enhanced the electrical conductivity of these nanostructures. This work demonstrates the potential of SISMA-GO bioinks as bioactive and electroconductive scaffolds for electrostimulation applications in tissue engineering and regenerative medicine.

Composites Obtained from Alumina and Polymer Derived Ceramic

2018 ◽  
Vol 912 ◽  
pp. 141-146 ◽  
Author(s):  
Glauson Aparecido Ferreira Machado ◽  
Rosa Maria Rocha ◽  
Ana Helena Almeida Bressiani
Keyword(s):  
Heat Treatment ◽  
Silicon Carbide ◽  
Linear Shrinkage ◽  
Density Variation ◽  
Silicon Oxycarbide ◽  
Alternative Route ◽  
Preceramic Polymer ◽  
Pure Alumina ◽  
Polymer Derived Ceramic ◽  
Alumina Composites

Alumina-mullite composites with low shrinkage can be made by reaction bond using mixtures of alumina, aluminum and silicon carbide. In this work, an alternative route is used to produce alumina composites with low shrinkage. Here alumina samples containing additions of 10 and 20 wt% of a preceramic polymer were warm-pressed and treated in the range of 900 -1500°C to produce alumina based composites. The obtained composites were analyzed by linear shrinkage and compared to pure alumina samples sintered at the same temperature range. It were also evaluated the density variation and crystalline phases formed during heat treatment of alumina composites. Results showed that alumina-silicon oxycarbide and alumina-mullite composites were obtained with lower shrinkage than pure alumina samples.

Polymer Derived Ceramic Seals for Application in SOFC

2007 ◽  
Vol 534-536 ◽  
pp. 1061-1064 ◽  
Author(s):  
Sung Jin Hong ◽  
Deug Joong Kim
Keyword(s):  
Thermal Expansion ◽  
Thermal Properties ◽  
Glass Matrix ◽  
Ceramic Composite ◽  
Ceramic Composites ◽  
Filler Materials ◽  
N2 Atmosphere ◽  
Polymer Derived Ceramic ◽  
Oxycarbide Glass

Polymer derived ceramic composites have been developed for SOFC seals. The formation and properties of the ceramic composite derived from a mixture with polysiloxane and filler were investigated. In the presence of filler materials such as ZrO2 and AlCo, the thermal properties of the ceramic composite could be controlled. The mixtures with polymethylsiloxane and fillers were prepared and their conversions to ceramic composites by annealing in N2 atmosphere were studied. The microcrystalline composites with filler embedded in a silicon-boron-oxycarbide glass matrix were formed. The thermal expansion behaviors were measured and discussed.

Carbon-Nanotube-Reinforced Polymer-Derived Ceramic Composites

2004 ◽  
Vol 16 (22) ◽  
pp. 2036-2040 ◽  
Author(s):  
L. An ◽  
W. Xu ◽  
S. Rajagopalan ◽  
C. Wang ◽  
H. Wang ◽  
...  
Keyword(s):  
Carbon Nanotube ◽  
Ceramic Composites ◽  
Reinforced Polymer ◽  
Polymer Derived Ceramic

Microanalyses Of Structural Defects In Polymer-Derived Ceramic Fibers

1990 ◽  
Vol 48 (2) ◽  
pp. 262-263
Author(s):  
H. A. Freeman ◽  
J. A. Rabe
Keyword(s):  
Surface Defects ◽  
Fiber Strength ◽  
Thermal Exposure ◽  
Ceramic Composites ◽  
Silicon Oxynitride ◽  
Structural Defects ◽  
Ceramic Fibers ◽  
High Fiber ◽  
Polymer Derived Ceramic ◽  
Primary Fracture

Microanalyses were performed with a Cameca MBX scanning electron microprobe and a JEM 2000FX analytical electron microscope to determine the composition of foreign defect structures found on primary fracture surfaces of ceramic fibers derived from melt-spun Si-N-C-O polymeric precursors. The defects were the critical flaws responsible for deterioration of tensile strength in these fibers after thermal exposure in the range of 1400°C and above. High fiber strength is necessary to provide reinforcement and toughening in structural ceramic composites during high temperature use.Among the defects found were roughly spherical internal nodular flaws which contained Pb (Fig. 1) as well as others (Fig. 2) containing both Pb and Sn. Granular aggregates were also seen in which Fe and Cr were detected. Other nodular surface defects contained Ca, minor Al, and levels of 0 higher than that in the surrounding fiber (Fig. 3) . Extremely fine whisker growths at discrete sites along the length of some fibers were identified as silicon oxynitride by electron diffraction.

scholarly journals Synthesis and electrochemical performance of a polymer-derived silicon oxycarbide/boron nitride nanotube composite

RSC Advances ◽  
2017 ◽  
Vol 7 (35) ◽  
pp. 21576-21584 ◽  
Author(s):  
M. A. Abass ◽  
A. A. Syed ◽  
C. Gervais ◽  
G. Singh
Keyword(s):  
Boron Nitride ◽  
Electrochemical Performance ◽  
Boron Nitride Nanotubes ◽  
Silicon Oxycarbide ◽  
Boron Nitride Nanotube ◽  
Electrochemical Applications ◽  
Polymer Derived Ceramic ◽  
New Type

Synthesis of a new type of composite consisting of boron nitride nanotubes (BNNTs) filler in polymer-derived ceramic silicon oxycarbide (SiOC) for electrochemical applications is demonstrated.

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