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Nidhi S. Bhattacharyya - One of the best experts on this subject based on the ideXlab platform.
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Dielectric characterization and microwave absorption of expanded graphite integrated polyaniline multiphase nanocomposites in X-band
IEEE Transactions on Dielectrics and Electrical Insulation, 2019Co-Authors: Utpal Jyoti Mahanta, Jyoti Prasad Gogoi, Dipangkar Borah, Nidhi S. BhattacharyyaAbstract:Design optimization for broadband microwave absorption and fabrication of a metal backed single layer microwave absorber based on polyaniline (PA)/expanded graphite (EG) reinforced Novolac Phenolic Resin (NPR) composites was investigated in the frequency ranges of 8.2–12.4 GHz. To study the effect of multiphase reinforcers on microwave absorption, PA/EG reinforcers were synthesized by in situ polymerization of aniline in acid medium followed by incorporation of EG in (x=0.15 and 0.25 wt%) proportions and characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy (TEM) analysis. TEM analysis showed that polyaniline of dimension 1.5 and 0.25 for 30 and 20 wt % composites respectively, showing as viable dielectric microwave absorbing materials. Reflection loss (RL) values for different composites were optimized by varying the thickness based on transmission line theory and a RL∼ −32 dB at 9.7 GHz with −10 dB bandwidth of 2.4 GHz is obtained for single layer absorber fabricated from 30 wt% composites of thickness 3.0 mm.
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Design optimization and fabrication of a wideband microwave absorber based on dual-phase dielectric semi-metallic nanocomposite
Journal of Physics and Chemistry of Solids, 2019Co-Authors: Utpal Jyoti Mahanta, Nidhi S. Bhattacharyya, Imdadul Hussain, Paragjyoti Gogoi, Jyoti Prasad GogoiAbstract:Abstract Dual-phase nanocomposites consisting of dielectric polyaniline (PA) of diameter ∼50 nm and semi-metallic expanded graphite (EG) were synthesized by in situ emulsion polymerization technique. This involved integrating EG in varied proportions of EG (0.00, 0.15, and 0.25 wt %) into PA and mixing with Novolac Phenolic Resin (NPR) (10, 20, and 30 wt %) to tailor the microwave absorption properties ofrelative complex permittivity er(ω) = er′ – jer″, where er′ and er″ are real and imaginary parts of complex permittivity in the X-band frequency. The measured frequency-dependent er(ω) values showed significantly enhanced values for PA/EG–NPR nanocomposites with er′ ∼ 14.5 er″ ∼ 25.6, and (er″/er′) > 1.5 compared with PA–NPR nanocomposites with (er″/er′) > 0.25 and were analyzed using the principle of capacitance variation with filler concentration. Based on the Transmission Line Model, design optimization of single-layer microwave absorbers was performed for the developed nanocomposites. The fabricated absorber exhibited measured reflection loss RLm ∼32 dB at 9.7 GHz and RLm −17 dB at 10.9 GHz for 30 wt % PA/EGNPR (EG = 0.15) composite of thickness 3 mm and 20 wt % PA/EG–NPR (EG = 0.25) of thickness 2.5 mm, respectively, with −10 dB absorption bandwidth of 2.4 and 1.7 GHz in the X-band. A triangular-lattice perforated design for PA/EG composite was proposed to enhance the broad impedance matching and absorption bandwidth in the X-band.
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Development of BaAlxFe12−xO19-NPR nanocomposite as an efficient absorbing material in the X-band
Journal of Magnetism and Magnetic Materials, 2015Co-Authors: S. Ozah, Nidhi S. BhattacharyyaAbstract:Abstract An efficient BaAlxFe12−xO19- Novolac Phenolic Resin (NPR) nanocomposite material is developed to use as absorbing material in the X band. The material developed has a hexagonal structure of nanosize aluminium substituted barium ferrite, as is confirmed by X-ray diffraction pattern studies. The average grain size of barium nanoparticles is found to be ~26 nm. Measurement of complex permittivity and complex permeability in the X-band indicates increase of the properties with increase in Al3+ ions in the ferrite. A measured absorption study has been carried out on absorber fabricated on a metal backing based on the transmission line theory. Substitution of Fe3+ with Al3+ is found to increase the absorption properties of barium ferrite. Reflection loss measurement of the samples shows an enhancement of absorption from −27.56 dB to −40.06 dB with the variation of Al3+ substitution, x=1.0–1.6 in the BaAlxFe12−xO19 in NPR matrix.
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Expanded graphite—Phenolic Resin composites based double layer microwave absorber for X-band applications
Journal of Applied Physics, 2014Co-Authors: Jyoti Prasad Gogoi, Nidhi S. BhattacharyyaAbstract:In this investigation, double layer microwave absorbers are designed and developed with paired combination of 5 wt. %, 7 wt. %, 8 wt. %, and 10 wt. % expanded graphite-Novolac Phenolic Resin (EG-NPR) composites, in the frequency range of 8.2–12.4 GHz. The thickness and compositional combination of the two layers constituting the absorber are optimized to achieve minimum value of reflection loss (dB) and a broad microwave absorption bandwidth. Double layer combinations showing −25 dB absorption bandwidth >2 GHz and −30 dB absorption bandwidth >1 GHz are chosen for fabrication. The total thickness of the fabricated double layer microwave absorber is varied from 3 mm to 3.4 mm. Absorption bandwidths at −10 dB, −20 dB, −25 dB and −30 dB are determined for the fabricated structure. The maximum −25 dB and −30 dB absorption bandwidth of 2.47 GHz and 1.77 GHz, respectively, are observed for the double layer structure with (5 wt. %–8 wt. %) EG-NPR composites with total thickness of 3.2 mm, while −10 dB bandwidth c...
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single layer microwave absorber based on expanded graphite Novolac Phenolic Resin composite for x band applications
Composites Part B-engineering, 2014Co-Authors: Jyoti Prasad Gogoi, Nidhi S. Bhattacharyya, Satyajib BhattacharyyaAbstract:Abstract Expanded graphite–Novolac Phenolic Resin (EG/NPR) composites in (5, 7, 8 and 10) wt.% of EG are developed as dielectric radar absorbing material in the X-band. Complex permittivity (er = e r ′ – jer″) of the composites measured in X-band are used to compute the reflection loss (RLc) of conductor backed single layer EG/NPR composites by optimizing the composites thickness (d). Practical reflection loss measurements are carried out using free space technique. Impedance matching condition and quarter wavelength criteria are used for analysis of the reflection loss performance of the composites. The 5 wt.% EG/NPR composite shows measured reflection loss peak of value ∼−43 dB at 12.4 GHz which is in close agreement with that of calculated reflection loss value ∼ −53 dB at the same frequency. The reflection loss peak shifts towards low frequency with increase in wt.% of EG and a −10 dB absorption bandwidth ∼1 GHz is found for conductor backed single layer absorber with 7, 8 and 10 wt.% EG/NPR compositions.
Jyoti Prasad Gogoi - One of the best experts on this subject based on the ideXlab platform.
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High-Performance Broadband Microwave Absorbers Using Multilayer Dual-Phase Dielectric Composites
Journal of Electronic Materials, 2019Co-Authors: Utpal Jyoti Mahanta, Munu Borah, Nidhi Saxena Bhattacharyya, Jyoti Prasad GogoiAbstract:In search of high-performance broadband microwave absorption, the design of double-layer dielectric microwave absorbers based on dual-phase polyaniline (PA)/expanded graphite (EG) composites synthesized by in situ polymerization of aniline in different concentrations (0.00 wt.%, 0.15 wt.% and 0.25 wt.%) of EG was optimized. The developed composite reinforcers, viz. PA/EG_ x =0.15,0.25 and PA/EG_ x =0.00 (PA), were mixed at different loadings (10 wt.%, 20 wt.% and 30 wt.%) with Novolac Phenolic Resin to form PG and PA composites, then their complex permittivity and permeability in the X-band were characterized. Using the transmission-line model, the reflection loss of single-layer absorbers of different PG and PA composites was estimated (RL_c) and measured (RL_m). Based on the best results, the design of the double-layer absorber was optimized by tuning the impedance matching between layers by adjusting the arrangement and thickness of the layers in the composites. Promising microwave absorption with RL_m ∼ − 48 dB at 9.4 GHz along with − 20-dB and − 30-dB absorption bandwidths of 3 GHz and 2 GHz were obtained for the double-layer design comprising PG5–PA3 composite material layers. Moreover, a partially perforated double-layer design is proposed, showing enhanced absorption bandwidth due to frequency-independent impedance matching at the interface between air and the perforated layer, facilitated by the effective permittivity of the latter.
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Dielectric characterization and microwave absorption of expanded graphite integrated polyaniline multiphase nanocomposites in X-band
IEEE Transactions on Dielectrics and Electrical Insulation, 2019Co-Authors: Utpal Jyoti Mahanta, Jyoti Prasad Gogoi, Dipangkar Borah, Nidhi S. BhattacharyyaAbstract:Design optimization for broadband microwave absorption and fabrication of a metal backed single layer microwave absorber based on polyaniline (PA)/expanded graphite (EG) reinforced Novolac Phenolic Resin (NPR) composites was investigated in the frequency ranges of 8.2–12.4 GHz. To study the effect of multiphase reinforcers on microwave absorption, PA/EG reinforcers were synthesized by in situ polymerization of aniline in acid medium followed by incorporation of EG in (x=0.15 and 0.25 wt%) proportions and characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy (TEM) analysis. TEM analysis showed that polyaniline of dimension 1.5 and 0.25 for 30 and 20 wt % composites respectively, showing as viable dielectric microwave absorbing materials. Reflection loss (RL) values for different composites were optimized by varying the thickness based on transmission line theory and a RL∼ −32 dB at 9.7 GHz with −10 dB bandwidth of 2.4 GHz is obtained for single layer absorber fabricated from 30 wt% composites of thickness 3.0 mm.
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Design optimization and fabrication of a wideband microwave absorber based on dual-phase dielectric semi-metallic nanocomposite
Journal of Physics and Chemistry of Solids, 2019Co-Authors: Utpal Jyoti Mahanta, Nidhi S. Bhattacharyya, Imdadul Hussain, Paragjyoti Gogoi, Jyoti Prasad GogoiAbstract:Abstract Dual-phase nanocomposites consisting of dielectric polyaniline (PA) of diameter ∼50 nm and semi-metallic expanded graphite (EG) were synthesized by in situ emulsion polymerization technique. This involved integrating EG in varied proportions of EG (0.00, 0.15, and 0.25 wt %) into PA and mixing with Novolac Phenolic Resin (NPR) (10, 20, and 30 wt %) to tailor the microwave absorption properties ofrelative complex permittivity er(ω) = er′ – jer″, where er′ and er″ are real and imaginary parts of complex permittivity in the X-band frequency. The measured frequency-dependent er(ω) values showed significantly enhanced values for PA/EG–NPR nanocomposites with er′ ∼ 14.5 er″ ∼ 25.6, and (er″/er′) > 1.5 compared with PA–NPR nanocomposites with (er″/er′) > 0.25 and were analyzed using the principle of capacitance variation with filler concentration. Based on the Transmission Line Model, design optimization of single-layer microwave absorbers was performed for the developed nanocomposites. The fabricated absorber exhibited measured reflection loss RLm ∼32 dB at 9.7 GHz and RLm −17 dB at 10.9 GHz for 30 wt % PA/EGNPR (EG = 0.15) composite of thickness 3 mm and 20 wt % PA/EG–NPR (EG = 0.25) of thickness 2.5 mm, respectively, with −10 dB absorption bandwidth of 2.4 and 1.7 GHz in the X-band. A triangular-lattice perforated design for PA/EG composite was proposed to enhance the broad impedance matching and absorption bandwidth in the X-band.
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Expanded graphite—Phenolic Resin composites based double layer microwave absorber for X-band applications
Journal of Applied Physics, 2014Co-Authors: Jyoti Prasad Gogoi, Nidhi S. BhattacharyyaAbstract:In this investigation, double layer microwave absorbers are designed and developed with paired combination of 5 wt. %, 7 wt. %, 8 wt. %, and 10 wt. % expanded graphite-Novolac Phenolic Resin (EG-NPR) composites, in the frequency range of 8.2–12.4 GHz. The thickness and compositional combination of the two layers constituting the absorber are optimized to achieve minimum value of reflection loss (dB) and a broad microwave absorption bandwidth. Double layer combinations showing −25 dB absorption bandwidth >2 GHz and −30 dB absorption bandwidth >1 GHz are chosen for fabrication. The total thickness of the fabricated double layer microwave absorber is varied from 3 mm to 3.4 mm. Absorption bandwidths at −10 dB, −20 dB, −25 dB and −30 dB are determined for the fabricated structure. The maximum −25 dB and −30 dB absorption bandwidth of 2.47 GHz and 1.77 GHz, respectively, are observed for the double layer structure with (5 wt. %–8 wt. %) EG-NPR composites with total thickness of 3.2 mm, while −10 dB bandwidth c...
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single layer microwave absorber based on expanded graphite Novolac Phenolic Resin composite for x band applications
Composites Part B-engineering, 2014Co-Authors: Jyoti Prasad Gogoi, Nidhi S. Bhattacharyya, Satyajib BhattacharyyaAbstract:Abstract Expanded graphite–Novolac Phenolic Resin (EG/NPR) composites in (5, 7, 8 and 10) wt.% of EG are developed as dielectric radar absorbing material in the X-band. Complex permittivity (er = e r ′ – jer″) of the composites measured in X-band are used to compute the reflection loss (RLc) of conductor backed single layer EG/NPR composites by optimizing the composites thickness (d). Practical reflection loss measurements are carried out using free space technique. Impedance matching condition and quarter wavelength criteria are used for analysis of the reflection loss performance of the composites. The 5 wt.% EG/NPR composite shows measured reflection loss peak of value ∼−43 dB at 12.4 GHz which is in close agreement with that of calculated reflection loss value ∼ −53 dB at the same frequency. The reflection loss peak shifts towards low frequency with increase in wt.% of EG and a −10 dB absorption bandwidth ∼1 GHz is found for conductor backed single layer absorber with 7, 8 and 10 wt.% EG/NPR compositions.
Satyajib Bhattacharyya - One of the best experts on this subject based on the ideXlab platform.
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single layer microwave absorber based on expanded graphite Novolac Phenolic Resin composite for x band applications
Composites Part B-engineering, 2014Co-Authors: Jyoti Prasad Gogoi, Nidhi S. Bhattacharyya, Satyajib BhattacharyyaAbstract:Abstract Expanded graphite–Novolac Phenolic Resin (EG/NPR) composites in (5, 7, 8 and 10) wt.% of EG are developed as dielectric radar absorbing material in the X-band. Complex permittivity (er = e r ′ – jer″) of the composites measured in X-band are used to compute the reflection loss (RLc) of conductor backed single layer EG/NPR composites by optimizing the composites thickness (d). Practical reflection loss measurements are carried out using free space technique. Impedance matching condition and quarter wavelength criteria are used for analysis of the reflection loss performance of the composites. The 5 wt.% EG/NPR composite shows measured reflection loss peak of value ∼−43 dB at 12.4 GHz which is in close agreement with that of calculated reflection loss value ∼ −53 dB at the same frequency. The reflection loss peak shifts towards low frequency with increase in wt.% of EG and a −10 dB absorption bandwidth ∼1 GHz is found for conductor backed single layer absorber with 7, 8 and 10 wt.% EG/NPR compositions.
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Single layer microwave absorber based on expanded graphite–Novolac Phenolic Resin composite for X-band applications
Composites Part B: Engineering, 2014Co-Authors: Jyoti Prasad Gogoi, Nidhi S. Bhattacharyya, Satyajib BhattacharyyaAbstract:Abstract Expanded graphite–Novolac Phenolic Resin (EG/NPR) composites in (5, 7, 8 and 10) wt.% of EG are developed as dielectric radar absorbing material in the X-band. Complex permittivity (er = e r ′ – jer″) of the composites measured in X-band are used to compute the reflection loss (RLc) of conductor backed single layer EG/NPR composites by optimizing the composites thickness (d). Practical reflection loss measurements are carried out using free space technique. Impedance matching condition and quarter wavelength criteria are used for analysis of the reflection loss performance of the composites. The 5 wt.% EG/NPR composite shows measured reflection loss peak of value ∼−43 dB at 12.4 GHz which is in close agreement with that of calculated reflection loss value ∼ −53 dB at the same frequency. The reflection loss peak shifts towards low frequency with increase in wt.% of EG and a −10 dB absorption bandwidth ∼1 GHz is found for conductor backed single layer absorber with 7, 8 and 10 wt.% EG/NPR compositions.
Mehdi Salami-kalajahi - One of the best experts on this subject based on the ideXlab platform.
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Chemical incorporation of epoxy-modified graphene oxide into epoxy/Novolac matrix for the improvement of thermal characteristics
Carbon Letters, 2020Co-Authors: Hamidreza Ebrahimi, Hossein Roghani-mamaqani, Mehdi Salami-kalajahi, Sina Shahi, Amin AbdollahiAbstract:Chemical incorporation of epoxy-modified graphitic layers in epoxy/Novolac Phenolic Resin matrices was carried out through co-curing of epoxy and Novolac Resins using triphenylphosphine as catalyst. First, (3-glycidyloxypropyl) trimethoxysilane (GPTMS) was grafted on graphene oxide (GO) surface to obtain epoxidized GO layers. Then epoxy Resin and GPTMS-modified GO were incorporated into thermosetting reaction using Novolac Resin in the presence of triphenylphosphine. Covalent attachment of GPTMS-modified GO to the Resin matrices resulted in a hybrid composite with high thermal characteristics. Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis (TGA), X-ray diffraction, and Raman spectroscopy were used for approving modification of GO with GPTMS. The images resulted from scanning and transmission electron microscopies exhibited GO layers with lots of creases turning to smooth layers with a few thin ripples after modification with GPTMS. TGA results showed that thermal characteristics of Resins were improved by the addition of GPTMS-modified GO. Char residue of the hybrid composites containing 0.5 and 1 wt% of GPTMS-modified GO reached 28.1 and 34.3%, respectively. Also, their maximum thermal degradation temperature was also increased by the incorporation of GPTMS-modified GO.
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Nanohybrids of Novolac Phenolic Resin and carbon nanotube-containing silica network
Journal of Thermal Analysis and Calorimetry, 2017Co-Authors: Akbar Noparvar-qarebagh, Hossein Roghani-mamaqani, Mehdi Salami-kalajahi, Bahareh KariminejadAbstract:Two different methods were used for preparation of Novolac Phenolic Resin nanohybrids containing carbon nanotube and silica/siloxane moieties. Oxidized carbon nanotube was modified with furfuryl alcohol and 3-(trimethoxysilyl)propyl methacrylate (MPS) to obtain CNTFASi. Carbon nanotube xerogel (CNTFAX) was then obtained by incorporation of CNTFASi into silica/siloxane network by using tetraethyl orthosilicate (TEOS). The first nanohybrid was prepared by addition of CNTFAX into the Novolac Phenolic Resin matrix. Incorporation of (3-glycidyloxypropyl) trimethoxysilane-modified Novolac Phenolic Resin, CNTFASi, and TEOS into silica/siloxane network results in the second nanohybrid. These two types of nanohybrids were compared from the viewpoint of thermal properties. Successful modification of carbon nanotube and Novolac Phenolic Resin was proved by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and thermogravimetric analysis results. Molar ratios of furfuryl alcohol in CNTFA and MPS in CNTFASi are 597 and 108 μmol g^−1, respectively. Formation of silica/siloxane xerogel network in CNTFAX was evaluated by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The results showed that nanotubes with smooth surface are incorporated into the spongy silica/siloxane matrix. Char residue of CR is decreased from 58.2 to 50.6% by the addition of only 4 mass% of CNTFAX. Finally, char residue of 71.1% for the nanohybrid of modified Novolac Resin with 4 mass% of CNTFASi shows 12.8% increase in char residue with respect to the neat cured Resin.
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Nanohybrids of Novolac Phenolic Resin and carbon nanotube-containing silica network: Two different approaches for improving thermal properties of Resin
Journal of Thermal Analysis and Calorimetry, 2016Co-Authors: Akbar Noparvar-qarebagh, Hossein Roghani-mamaqani, Mehdi Salami-kalajahi, Bahareh KariminejadAbstract:Two different methods were used for preparation of Novolac Phenolic Resin nanohybrids containing carbon nanotube and silica/siloxane moieties. Oxidized carbon nanotube was modified with furfuryl alcohol and 3-(trimethoxysilyl)propyl methacrylate (MPS) to obtain CNTFASi. Carbon nanotube xerogel (CNTFAX) was then obtained by incorporation of CNTFASi into silica/siloxane network by using tetraethyl orthosilicate (TEOS). The first nanohybrid was prepared by addition of CNTFAX into the Novolac Phenolic Resin matrix. Incorporation of (3-glycidyloxypropyl) trimethoxysilane-modified Novolac Phenolic Resin, CNTFASi, and TEOS into silica/siloxane network results in the second nanohybrid. These two types of nanohybrids were compared from the viewpoint of thermal properties. Successful modification of carbon nanotube and Novolac Phenolic Resin was proved by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and thermogravimetric analysis results. Molar ratios of furfuryl alcohol in CNTFA and MPS in CNTFASi are 597 and 108 μmol g−1, respectively. Formation of silica/siloxane xerogel network in CNTFAX was evaluated by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The results showed that nanotubes with smooth surface are incorporated into the spongy silica/siloxane matrix. Char residue of CR is decreased from 58.2 to 50.6% by the addition of only 4 mass% of CNTFAX. Finally, char residue of 71.1% for the nanohybrid of modified Novolac Resin with 4 mass% of CNTFASi shows 12.8% increase in char residue with respect to the neat cured Resin.
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Organic–inorganic nanohybrids of Novolac Phenolic Resin and carbon nanotube: High carbon yields by using carbon nanotube aerogel and Resin incorporation into aerogel network
Microporous and Mesoporous Materials, 2016Co-Authors: Akbar Noparvar-qarebagh, Hossein Roghani-mamaqani, Mehdi Salami-kalajahiAbstract:Abstract CNTCOOH was prepared from oxidation of carbon nanotube. Subsequently, CNTSi was prepared by grafting (3-glycidyloxypropyl) trimethoxysilane (GPTES) to the surface of CNTCOOH by a ring opening reaction of epoxy groups. Then, CNTA was obtained by formation of silicon oxide network between CNTSi and tetraethyl orthosilicate (TEOS). Finally, CNTA was used as an additive in Novolac Resin matrix to yield RCNTA composites with high carbon yield values. Additionally, modification of Novolac Resin by GPTES gives MR with silicon ethoxide moieties on its structure. Then, MRCNTA composites were obtained by formation of silica/siloxane network from MR, CNTSi, and TEOS. RCNTA composites were thermally compared with MRCNTA composites. Results from Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and thermogravimetric analysis showed that CNT and Novolac Resin were successfully modified. Aerogel formation was proved by Raman, X-ray diffraction, and scanning and transmission electron microscopies. BET shows that incorporation of CNT into the aerogel network results in lower cumulative pore volume value. The pore size of SA and CNTA ranges from 2 to about 100 nm which shows that both of them can be included in the mesoporous materials category. Finally, MRCNTA composites reached to the maximum increase of char yields; 11.94% increase of char yield was achieved by MRCNTA4 composite.
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Functionalization of carbon nanotubes by furfuryl alcohol moieties for preparation of Novolac Phenolic Resin composites with high carbon yield values
Colloid and Polymer Science, 2015Co-Authors: Akbar Noparvar-qarebagh, Hossein Roghani-mamaqani, Mehdi Salami-kalajahiAbstract:Carbon nanotube (CNT) was oxidized to obtain CNTCOOH. Then, furfuryl alcohol (FA) moieties were grafted to convex surface and end caps of CNTCOOH by an esterification reaction to yield CNTFA. CNTFA in three different contents was added into Novolac Resin matrix to improve its carbon yield value and thermal properties. Results from Fourier transform infrared, X-ray photoelectron, and Raman spectroscopies in addition to thermogravimetric analysis showed that CNT was successfully oxidized and modified with FA moieites. Morphological study and dispersion of nanotubes in the Novolac Resin matrix were studied by scanning and transmission electron microscopies and X-ray diffraction. FA graft content in CNTFA is calculated to be 8.2 %. Also, char value of the Novolac Resin was increased by 7.1 % by the addition of only 6 wt% of CNTFA.
Adélio Mendes - One of the best experts on this subject based on the ideXlab platform.
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Composite-alumina-carbon molecular sieve membranes prepared from Novolac Resin and boehmite. Part II: Effect of the carbonization temperature on the gas permeation properties
International Journal of Hydrogen Energy, 2015Co-Authors: Margot A. Llosa Tanco, David A. Pacheco Tanaka, Adélio MendesAbstract:Abstract The influence of carbonization temperature on the permeation properties and aging of thin (4 μm) supported carbon molecular sieve membranes (c-CMSM), prepared from in house synthesized Novolac Phenolic Resin loaded with boehmite nanoparticles, were studied. Just after membrane carbonization (fresh membrane), high permeance to N2 and O2 and low O2/N2 permselectivities were observed; the highest permeations were observed for carbonization end temperatures between 500 °C and 700 °C. After leaving the c-CMSM 1 day in the air, a large decrease in the permeation and considerable increase in the permselectivity were observed due to the reduction of the pore size by oxygen chemisorption and water physical adsorption; the permeability to H2 and H2/N2 ideal permselectivity for a membrane carbonized at 550 °C are close to palladium membranes for low temperature (
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Composite-alumina-carbon molecular sieve membranes prepared from Novolac Resin and boehmite. Part I: Preparation, characterization and gas permeation studies
International Journal of Hydrogen Energy, 2015Co-Authors: Margot A. Llosa Tanco, David A. Pacheco Tanaka, Sandra C. Rodrigues, Miguel Texeira, Adélio MendesAbstract:Abstract Supported composite alumina-carbon molecular sieve membranes (c-CMSM) were prepared from in house prepared Novolac Phenolic Resin loaded with boehmite nanoparticles in a single dipping-drying-carbonization step. A porous α-alumina tube support was dipped into a N -methyl-2-pyrrolidone solution containing polymerized Novolac Resin loaded with boehmite, subsequently dried at 100 °C and carbonized at 500 °C under nitrogen environment. The structure, morphology and performance of the membranes were examined by scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), carbon dioxide adsorption and permeation of N 2 , O 2 , He, H 2 and CO 2 . SEM showed carbon membranes with a thin and very uniform layer with a thickness of ca. 3 μm CO 2 adsorption isotherms indicated that the produced carbon membranes presented a microporous structure. The c-CMSM exhibited good gas separation properties. The permselectivity surpass the Robeson upper bound for polymeric membranes, especially regarding ideal permselectivities of pairs H 2 /N 2 = 117, and He/O 2 = 49. Aging effects were observed after membrane exposure to ambient air. However with a thermal treatment under nitrogen atmosphere the permeance of nitrogen increases.
