Three-dimensional silica fiber reinforced silicon nitride based composites were fabricated by preceramic polymer infiltration and pyrolysis method using perhydropolysilazane as a precursor. The effects of precoating a...Three-dimensional silica fiber reinforced silicon nitride based composites were fabricated by preceramic polymer infiltration and pyrolysis method using perhydropolysilazane as a precursor. The effects of precoating and high temperature calcination on the microstructures of the composites were investigated by scanning electron microscopy. For the composite without a precoating, the fracture surface is plain, and the fiber/matrix interfaces become very unclear after calcination at 1 600 ℃ due to intense interfacial reactions. The composite with a precoating shows tough fracture surface with distinct fiber pull-outs, and the fiber/matrix interfaces are still clear after calcination at 1 600 ℃. It is the appropriate precoating process that contributes to the good interfacial microstructures for the composite.展开更多
Polyimide(PI)composite films were synthesized incorporating amino modified silicon nitride(Si_(3)N_(4))nanoparticles into PI matrix via in situ polymerization technique.The mechanical and thermal performances as well ...Polyimide(PI)composite films were synthesized incorporating amino modified silicon nitride(Si_(3)N_(4))nanoparticles into PI matrix via in situ polymerization technique.The mechanical and thermal performances as well as the hydrophobic properties of the as prepared composite films were investigated with respect to the dosage of the filler in the PI matrix.According to Thermogravimetric(TGA)analysis,meaningful improvements were achieved in T5(5%weight loss temperature)and T10(10%weight loss temperature)up to 54.1℃ and 52.4℃,respectively when amino functionalized nano Si_(3)N_(4) particles were introduced into the PI matrix.The differential scanning calorimetry(DSC)results revealed that the glass transition temperature(Tg)of the composites was considerably enhanced up to 49.7℃ when amino functionalized Si_(3)N_(4) nanoparticles were incorporated in the PI matrix.Compared to the neat PI,the PI/Si_(3)N_(4) nanocomposites exhibited very high improvement in the tensile strength as well as Young’s modulus up to 105.4%and 138.3%,respectively.Compared to the neat PI,the composites demonstrated highly decreased water absorption behavior which showed about 68.1%enhancement as the content of the nanoparticles was increased to 10 wt%.The SEM(Scanning electron microscope)images confirmed that the enhanced thermal,mechanical and water proof properties are essentially attributed to the improved compatibility of the filler with the matrix and hence,enhanced distribution inside the matrix because of the amino groups on the surface of Si_(3)N_(4) nanoparticles obtained from surface functionalization.展开更多
Perhydropolysilazane,a low viscosity preceramic polymer with good wettability and high char yield,was used to fabricate three-dimensional silica fiber reinforced silicon nitride matrix composites through the repeated ...Perhydropolysilazane,a low viscosity preceramic polymer with good wettability and high char yield,was used to fabricate three-dimensional silica fiber reinforced silicon nitride matrix composites through the repeated infiltration-curing-pyrolysis cycles.With the increase of the pyrolysis temperature from T_(1),T_(2)to T_(3),the density of the composites increased all through,but the flexural strength showed a maximum value at T_(2)followed by a sharp decrease.The composite prepared at T_(2)exhibited a good ceramization of the preceramic polymer,a high flexural strength of 144.9 MPa and excellent dielectric property.The high performance of the composite resulted from the good state of the silica fibers,controlled fiber/matrix interfacial microstructures and high-purity dense silicon nitride matrix.展开更多
文摘Three-dimensional silica fiber reinforced silicon nitride based composites were fabricated by preceramic polymer infiltration and pyrolysis method using perhydropolysilazane as a precursor. The effects of precoating and high temperature calcination on the microstructures of the composites were investigated by scanning electron microscopy. For the composite without a precoating, the fracture surface is plain, and the fiber/matrix interfaces become very unclear after calcination at 1 600 ℃ due to intense interfacial reactions. The composite with a precoating shows tough fracture surface with distinct fiber pull-outs, and the fiber/matrix interfaces are still clear after calcination at 1 600 ℃. It is the appropriate precoating process that contributes to the good interfacial microstructures for the composite.
基金the National Natural Science Foundation of China(51373044)Natural Science Foundation of Heilongjiang Province of China(E2017018).
文摘Polyimide(PI)composite films were synthesized incorporating amino modified silicon nitride(Si_(3)N_(4))nanoparticles into PI matrix via in situ polymerization technique.The mechanical and thermal performances as well as the hydrophobic properties of the as prepared composite films were investigated with respect to the dosage of the filler in the PI matrix.According to Thermogravimetric(TGA)analysis,meaningful improvements were achieved in T5(5%weight loss temperature)and T10(10%weight loss temperature)up to 54.1℃ and 52.4℃,respectively when amino functionalized nano Si_(3)N_(4) particles were introduced into the PI matrix.The differential scanning calorimetry(DSC)results revealed that the glass transition temperature(Tg)of the composites was considerably enhanced up to 49.7℃ when amino functionalized Si_(3)N_(4) nanoparticles were incorporated in the PI matrix.Compared to the neat PI,the PI/Si_(3)N_(4) nanocomposites exhibited very high improvement in the tensile strength as well as Young’s modulus up to 105.4%and 138.3%,respectively.Compared to the neat PI,the composites demonstrated highly decreased water absorption behavior which showed about 68.1%enhancement as the content of the nanoparticles was increased to 10 wt%.The SEM(Scanning electron microscope)images confirmed that the enhanced thermal,mechanical and water proof properties are essentially attributed to the improved compatibility of the filler with the matrix and hence,enhanced distribution inside the matrix because of the amino groups on the surface of Si_(3)N_(4) nanoparticles obtained from surface functionalization.
文摘Perhydropolysilazane,a low viscosity preceramic polymer with good wettability and high char yield,was used to fabricate three-dimensional silica fiber reinforced silicon nitride matrix composites through the repeated infiltration-curing-pyrolysis cycles.With the increase of the pyrolysis temperature from T_(1),T_(2)to T_(3),the density of the composites increased all through,but the flexural strength showed a maximum value at T_(2)followed by a sharp decrease.The composite prepared at T_(2)exhibited a good ceramization of the preceramic polymer,a high flexural strength of 144.9 MPa and excellent dielectric property.The high performance of the composite resulted from the good state of the silica fibers,controlled fiber/matrix interfacial microstructures and high-purity dense silicon nitride matrix.
