Porous Polyimide-Silica Composite: A New Thermal Resistant Flexible Material

2014 ◽  
Vol 1645 ◽  
Author(s):  
Yumeto Fukubayashi ◽  
Satoshi Yoda
Keyword(s):  
Sol Gel ◽  
Relative Dielectric Constant ◽  
Decomposition Temperature ◽  
Silicon Alkoxide ◽  
Silicate Formation ◽  
Silica Composite ◽  
Flexible Material ◽  
New Process ◽  
High Flexibility ◽  
Bimodal Porous Structure

ABSTRACTWe developed a new highly porous polyimide (PI) -silica composite with high flexibility, mechanical strength, and heat resistance. The composite was prepared by a new process consisting of (1) phase separation of a mixture of PI precursor (polyamic acid), solvent, and silicon alkoxide, induced by high-pressure CO2 (40 °C, 20 MPa), (2) silicate formation by sol-gel reaction, and (3) supercritical CO2 extraction of the solvent. The composite had a bimodal porous structure with micropores of 10-30 μm and nanopores of ∼50 nm. In the PI matrix, silica nanoparticles (< 100 nm in diameter) were highly dispersed. Porosity of the composite was 78%, which is higher than that of conventional porous PI prepared by physical foaming technique. Relative dielectric constant of the material was lower than 1.4 at 1 MHz. The porous PI-silica composite sheet was flexible enough to be folded without cracking. Notably, the Young’s modulus (0.80 GPa) and the onset decomposition temperature (600 °C) of the PI-silica composite were higher than those of conventional porous PI with similar porosity, respectively. The porous PI-silica composite is promising as a flexible thermal insulator for high-temperature use and as a thermal resistant low-k material.

scholarly journals Synthesis and characterization of Mg–Zn ferrite based flexible microwave composites and its application as SNG metamaterial

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Md Atiqur Rahman ◽  
Mohammad Tariqul Islam ◽  
Mandeep Singh Jit Singh ◽  
Md Samsuzzaman ◽  
Muhammad E. H. Chowdhury
Keyword(s):  
Low Cost ◽  
Sol Gel ◽  
Microwave Frequency ◽  
Dielectric Substrate ◽  
Dielectric Constants ◽  
Potential Candidate ◽  
Flexible Composites ◽  
Average Grain Size ◽  
Zn Ferrite ◽  
High Flexibility

AbstractIn this article, we propose SNG (single negative) metamaterial fabricated on Mg–Zn ferrite-based flexible microwave composites. Firstly, the flexible composites are synthesized by the sol-gel method having four different molecular compositions of MgxZn(1−x)Fe2O4, which are denoted as Mg20, Mg40, Mg60, and Mg80. The structural, morphological, and microwave properties of the synthesized flexible composites are analyzed using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and conventional dielectric assessment kit (DAK) to justify their possible application as dielectric substrate at microwave frequency regime. Thus the average grain size is found from 20 to 24 nm, and the dielectric constants are 6.01, 5.10, 4.19, and 3.28, as well as loss tangents, are 0.002, 0.004, 0.006, and 0.008 for the prepared Mg–Zn ferrites, i.e., Mg20, Mg40, Mg60, and Mg80 respectively. Besides, the prepared low-cost Mg–Zn ferrite composites exhibit high flexibility and lightweight, which makes them a potential candidate as a metamaterial substrate. Furthermore, a single negative (SNG) metamaterial unit cell is fabricated on the prepared, flexible microwave composites, and their essential electromagnetic behaviors are observed. Very good effective medium ratios (EMR) vales are obtained from 14.65 to 18.47, which ensure the compactness of the fabricated prototypes with a physical dimension of 8 × 6.5 mm2. Also, the proposed materials have shown better performances comparing with conventional FR4 and RO4533 materials, and they have covered S-, C-, X-, Ku-, and K-band of microwave frequency region. Thus, the prepared, flexible SNG metamaterials on MgxZn(1−x)Fe2O4 composites are suitable for microwave and flexible technologies.

scholarly journals Microstructure and Properties of SCE-Al2O3/PES-MBAE Composite

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Yufei Chen ◽  
Qiwang Dai ◽  
Xiwang Zhang ◽  
Tao Feng
Keyword(s):  
Dielectric Properties ◽  
Bisphenol A ◽  
Heat Resistance ◽  
Bending Strength ◽  
Sol Gel ◽  
Harmful Effect ◽  
Decomposition Temperature ◽  
Two Phase ◽  
Allyl Compound

SCE-Al2O3was the nano-Al2O3modified by supercritical ethanol and the surface of SCE-Al2O3was coated with active group. 4,4′-diaminodiphenylmethane bismaleimide (MBMI) was used as matrix; 3,3′-diallyl bisphenol A (BBA) and bisphenol-A diallyl ether (BBE) were used as reactive diluent, polyethersulfone (PES) as toughening agent, and SCE-Al2O3as modifier; SCE-Al2O3/PES-MBAE nanocomposite was prepared through in situ sol-gel method. The mechanism of composite toughened by PES was observed and analyzed. FTIR indicated that the reaction between MBMI and allyl compound occurred and SCE-Al2O3had doped into the polymer matrix. SEM showed that PES particle was inlaid in matrix and presented as a two-phase structure in matrix. The heat resistance, dielectric properties, and mechanical properties of SCE-Al2O3/PES-MBAE nanocomposites were evaluated. The results showed that with the incorporation of PES, although the toughness of the material improved, the heat resistance and dielectric properties of material declined, meanwhile. The adulteration of SCE-Al2O3could remedy the harmful effect caused by PES, while the content of SCE-Al2O3was reasonable. The decomposition temperature, dielectric constant, and dielectric loss of composite were 441.23°C, 3.63 (100 Hz), and 1.52 × 10−3(100 Hz); the bending strength and impact strength were 129.22 MPa and 13.19 kJ/mm2, respectively, when the content of SCE-Al2O3was 3 wt% and PES was 5 wt%.

Structural and Dielectric Properties of Screen Printed PZT(70/30) Multilayered Thick Films

2007 ◽  
Vol 124-126 ◽  
pp. 663-666 ◽  
Author(s):  
Sung Gap Lee ◽  
Sang Man Park ◽  
Young Jae Shim ◽  
Young Chul Rhee
Keyword(s):  
Screen Printing ◽  
Remanent Polarization ◽  
Thick Films ◽  
Sol Gel ◽  
Relative Dielectric Constant ◽  
Polycrystalline Structure ◽  
Coating Solution ◽  
Screen Printing Method ◽  
Xrd Patterns ◽  
Printing Method

PZT(70/30) powder was prepared by a sol-gel method and PZT thick films were fabricated by the screen-printing method on the alumina substrates. The coating and drying procedure was repeated 4 times. And then the PZT(30/70) precusor solution was spin-coated on the PZT thick films. A concentration of a coating solution was 0.5 mol/L and the number of coating was varied from 0 to 6. The porosity decreased and the grain size increased with increasing the number of coatings. The thickness of the PZT-6(6: number of coatings) films was about 60~65μm. All PZT thick films showed the typical XRD patterns of a typical perovskite polycrystalline structure. The relative dielectric constant of the PZT-6 thick film was 540. The remanent polarization and coercive field of the PZT-6 film were 23.6 μC /cm2, 12.0 kV/cm, respectively.

Formation of aramid-silica-grafted-multi-walled carbon nanotube-based nanofiber via the sol-gel route: thermal and mechanical profile of hybrids with poly(methyl methacrylate)

e-Polymers ◽  
2014 ◽  
Vol 14 (3) ◽  
pp. 177-185
Author(s):  
Ayesha Kausar
Keyword(s):  
Carbon Nanotube ◽  
Methyl Methacrylate ◽  
Sol Gel ◽  
Tensile Modulus ◽  
Electrospun Nanofibers ◽  
Decomposition Temperature ◽  
Filler Loading ◽  
Silica Network ◽  
Poly Methyl Methacrylate ◽  
Multi Walled Carbon Nanotube

AbstractIn this study, thermally and mechanically stable poly(methyl methacrylate) (PMMA)-based nanocomposites were produced through the reinforcement of electrospun aramid-silica-grafted multi-walled carbon nanotube-based nanofibers (MWCNT-Ar-Si). The multi-walled carbon nanotube was initially modified to prepare an isocyanatopropyltriethoxysilane-grafted MWCNT via the sol-gel route using 3-isocyanatopropyl-triethoxysilane and tetraethoxysilane (TEOS). The silica network was developed and linked to MWCNT by hydrolysis and condensation of TEOS. The said isocyanatopropyltriethoxysilane-grafted MWCNT was electrospun with the aramid solution. The electrospun MWCNT-Ar-Si nanofibers (0.1–1 wt.%) were then reinforced in a PMMA matrix. For comparative analysis, PMMA was also reinforced with 0.1–1 wt.% of aramid nanofibers. The tensile modulus of PMMA/MWCNT-Ar-Si 0.1 was 5.11 GPa, which was increased to 13.1 GPa in PMMA/MWCNT-Ar-Si 1. The 10% decomposition temperature of PMMA/MWCNT-Ar-Si 0.1–1 hybrids was in the range of 479–531°C. The glass transition temperature, determined from the maxima of tan δ data using dynamic mechanical thermal analysis, showed an increase with the filler loading and was maximum (301°C) for PMMA/MWCNT-Ar-Si 1 with 1 wt.% of MWCNT-Ar-Si nanofibers. In contrast, PMMA/Ar 0.1–1 hybrids showed lower values in the thermal and the mechanical profile depicting the combined effect of nanotube and aramid in electrospun nanofibers.

Synthesis and luminescence properties of colloidal lanthanide doped YVO4

2001 ◽  
Vol 667 ◽  
Author(s):  
Arnaud Huignard ◽  
Thierry Gacoin ◽  
Frédéric Chaput ◽  
Jean-Pierre Boilot ◽  
Patrick Aschehoug ◽  
...  
Keyword(s):  
Quantum Yield ◽  
Room Temperature ◽  
Sol Gel ◽  
Precursor Solution ◽  
Silica Matrix ◽  
Luminescence Quantum Yield ◽  
Colloidal Solutions ◽  
Silicon Alkoxide ◽  
Crystalline Defects ◽  
Hydroxylated Surface

ABSTRACTAqueous colloidal solutions of well dispersed YVO4:Ln (Ln = Eu, Nd) nanoparticles are synthesized through precipitation reactions at room temperature. In the case of YVO4:Eu, a luminescence quantum yield of 15% is found, which is not as high as in the bulk due to the existence of residual crystalline defects and nonradiative relaxations from the hydroxylated surface. Appropriate hydrothermal annealing and deuteration of the surface allow to rise the yield up to 38%. Incorporation of the nanocrystals into a transparent silica matrix is achieved through preliminary coating of the particles with a functionnalized silicon alkoxide and further dispersion into a sol-gel precursor solution. Such sol-gel materials doped with YVO4:Nd nanocrystals are transparent and exhibit the typical emission at 1.06 μm of the Nd3+ ion.

scholarly journals Preparation and Characteristics of an Environmentally Friendly Hyperbranched Flame-Retardant Polyurethane Hybrid Containing Nitrogen, Phosphorus, and Silicon

Polymers ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 720 ◽  
Author(s):  
Chen ◽  
Chiang
Keyword(s):  
Thermal Stability ◽  
Flame Retardant ◽  
Hybrid Material ◽  
Functional Group ◽  
Condensation Reaction ◽  
Sol Gel ◽  
Decomposition Temperature ◽  
Limiting Oxygen Index ◽  
Raman Analysis ◽  
Ring Opening Reaction

The NCO functional group of 3-isocyanatoproplytriethoxysilane (IPTS) and the OH functional group of 10-(2,5-dihydroxyphenyl)-10H-9-oxa-10-phospha-phenantbrene-10-oxide (DOPO-BQ) were used to conduct an addition reaction. Following completion of the reaction, triglycidyl isocyanurate (TGIC) was introduced to conduct a ring-opening reaction. Subsequently, a sol–gel method was used to initiate a hydrolysis–condensation reaction on TGIC–IPTS–DOPO-BQ to form a hyperbranched nitrogen–phosphorous–silicon (HBNPSi) flame retardant. This flame retardant was incorporated into a polyurethane (PU) matrix to prepare a hybrid material. Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), limiting oxygen index (LOI), UV-VIS spectrophotometry, and Raman analysis were conducted to characterize the structure and analyze the transparency, thermal stability, flame retardancy, and residual char to understand the flame retardant mechanism of the prepared hybrid material. After the flame retardant was added, the maximum degradation rate decreased from −36 to −17 wt.%/min, the integral procedural decomposition temperature (IPDT) increased from 348 to 488 °C, and the char yield increased from 0.7 to 8.1 wt.%. The aforementioned results verified that the thermal stability of PU can be improved after adding HBNPSi. The LOI analysis indicated that the pristine PU was flammable because the LOI of pristine PU was only 19. When the content of added HBNPSi was 40%, the LOI value was 26; thus the PU hybrid became nonflammable.

scholarly journals Preparation of a Novel Epoxy/SiO2 Hybrid Coating

2005 ◽  
Vol 14 (1) ◽  
pp. 096369350501400 ◽  
Author(s):  
C. H. Zhang ◽  
Y. P. Bai ◽  
L. X. Liu ◽  
Z. Q. Zhang ◽  
Q. Y. Li
Keyword(s):  
Thermal Properties ◽  
Epoxy Resin ◽  
Sol Gel ◽  
Covalent Bond ◽  
Decomposition Temperature ◽  
Hybrid Coating ◽  
Epoxy Coating ◽  
Covalent Bonds ◽  
Surface Image ◽  
Gel Technique

In this paper, epoxy/SiO2 hybrid coating was successfully prepared through sol-gel technique, the structure and thermal properties of epoxy/SiO2hybrid coating were investigated. First, γ-isocyanatopropyltriethoxysilane “(KBE-9007)” was used to modify the epoxy resin so that the ethoxysilane could be grafted on the epoxy resin. Nano-SiO2 precursor was synthesized by tetraethoxysilane(TEOS) through sol-gel technique. Then the modified epoxy resin and the nano-SiO2 precursor were mixed for 4 hours to let the macromolecules of epoxy resin graft on the surface of nano-SiO2, and modified nano-SiO2 precursor was obtained. At last, epoxy/SiO2 hybrid coating was produced by using the modified nano-SiO2 precursor. The graft reaction was confirmed by the analyses of FT-IR. The analyses of XPS indicated that there are lots of SiO2 particles and Si-C covalent bonds on the surface of epoxy/SiO2 hybrid coating, they also suggested that most TEOS had changed into SiO2 particles and Si-C covalent bond had been formed between epoxy resin and SiO2. The analyses of SEM fracture surface image of epoxy/SiO2 hybrid coating showed that SiO2 particles dispersed in epoxy matrix homogeneously and the size of the particles was between 50nm and 100 nm. Thermoanalysis Instrument was employed to detect the thermal properties of epoxy coating and epoxy/SiO2 hybrid coating, the results indicated that the thermal decomposition temperature of epoxy/SiO2 hybrid coating is 21.7 °C higher than that of epoxy coating, the thermal properties of the epoxy/SiO2 hybrid coating were improved because of the introduction of nano-SiO2.

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