To gain high efficiency and low fuel consumption, aluminum-based abradable seal coatings had been widely used in the compressor casing of aero engines or gas turbines owing to the low elastic modulus. However, the adh...To gain high efficiency and low fuel consumption, aluminum-based abradable seal coatings had been widely used in the compressor casing of aero engines or gas turbines owing to the low elastic modulus. However, the adhesive transfer phenomenon frequently occurs when the radial rubbing generates between titanium alloy blade tips and aluminum-based coating. It tends to increase scratch force and results in blades vibration and even engine jam. To eliminate this problem, a new lightweight epoxy-based abradable seal coating with high bonding strength was developed by an effective and porosity controllable mixing process that distributes spherical pores uniformly in the continuous matrix. A lightweight coating of 63% porosity with a hardness of 33.1(HR15 Y) can be reached when the content of hollow microspheres is 31 wt.%. The coating density is 0.5 g/cm3 and the bonding strength is as high as 18 MPa.The performance of the epoxy-based coating is comprehensively better than aluminum-based coatings in five essential indices. This study is expected to provide a new technical path for obtaining high-quality abradable seal coatings to guarantee the efficient and safe operation of compressors.展开更多
Aluminum-based composite abradable seal coatings are pivotal to improving the efficiency of aero engines or gas turbines.However,the adhesive transfer frequently occurs between metallic blade tips and aluminum-based c...Aluminum-based composite abradable seal coatings are pivotal to improving the efficiency of aero engines or gas turbines.However,the adhesive transfer frequently occurs between metallic blade tips and aluminum-based composite coatings,resulting in engine vibration and even jam.Many past studies had tried to solve this problem by reducing coating hardness,improving lubrication,or strengthening blade tips,but all had failed.In this paper,we proposed a novel epoxy-based composite abradable seal coating,eliminating adhesive transfer by changing metal-to-metal scraping pair to metal-to-polymer scraping pair.The coating was developed via a hierarchical structure design.Large spherical pores were uniformly distributed in the continuous epoxy matrix with fine graphite dispersion.By adding 20 vol.%graphite and 50 vol.%hollow microspheres,a self-lubricating epoxy-based coating of 0.26 friction coefficient with thermal conductivity of 0.28 W/(m·K),coating HR15 Y hardness at 54.8,and bonding strength at 18.7 MPa can be reached.When the metallic blades scrape the epoxy-based composite coating,no adhesive transfer occurs.Besides,a smooth scraped surface is formed by pseudoplastic deformation.This epoxy-based composite abradable seal coating opens a new way to improve the efficiency and reliable operations of air engine compressors.展开更多
In this work, graphene-modified epoxy-based anti-corrosion coatings were prepared and the influence of graphene on the anti-corrosion performance of the epoxy-based coatings was investigated with water contact angle t...In this work, graphene-modified epoxy-based anti-corrosion coatings were prepared and the influence of graphene on the anti-corrosion performance of the epoxy-based coatings was investigated with water contact angle test ,chemical solution immersion test, and electrochemical test. The water contact angle and chemical solution resistance of the epoxy-based coatings were improved with an increase in graphene content from 0 to 0.4%. These results prove that addition of graphene can significantly improve the hydrophobicity and impermeability of epoxy- based coatings. However, when the graphene content was increased to 0.5%, the performance of the epoxy-based coatings decreased because of graphene aggregation. Tafel polarization results show that graphene addition can significantly reduce the corrosion current density and corrosion potential of epoxy-based coatings, which enhance their anti-corrosion performance.展开更多
In this study,a series of epoxy-based azo molecular glasses with four-arm architecture was synthesized based on an intermediate(MDGA-AN),which was obtained from ring-opening reaction between 4,4'-methylene-bis(N,N...In this study,a series of epoxy-based azo molecular glasses with four-arm architecture was synthesized based on an intermediate(MDGA-AN),which was obtained from ring-opening reaction between 4,4'-methylene-bis(N,N’-diglycidylaniline)and N-methylaniline.The azo compounds were then synthesized through azo-coupling reaction between MDGA-AN and diazonium salts of 4-nitroaniline,4-aminobenzonitrile,4-aminobenzoic acid,4-fluoroaniline and 4-methoxyaniline,respectively.The azo compounds were thoroughly characterized and the photoresponsive properties of their solid films were investigated at three different wavelengths(λex=488,532 and 589 nm).The results show that the electron-withdrawing groups on the azo chromophores can significantly affect the absorption band positions in visible light range,which shift to the longer wavelength with the enhanced push-pull effect.Both photoinduced birefringence and surface-relief-grating formation are closely related to the electronwithdrawing groups and excitation wavelengths of the actinic light,which show significant influences on the growth rates and saturated values of the photoinduced variations.In this series,the azo molecular glasses containing cyano and carboxyl groups as the electron-withdrawing groups show the significantly higher efficiency for both the photoinduced birefringence growth and the SRG formation compared with others under the same light irradiation conditions.The capability of the materials as a photo-storage medium is demonstrated by holographic recording.展开更多
Three epoxy-based azo polymers （PEP-AZ-C1, PEP-AZ-CN and PEP-AZ-NT） with high chromophore density were synthesized by using post-polymerization azo-coupling reactions between epoxy-based precursor polymer （PEP-AN）...Three epoxy-based azo polymers （PEP-AZ-C1, PEP-AZ-CN and PEP-AZ-NT） with high chromophore density were synthesized by using post-polymerization azo-coupling reactions between epoxy-based precursor polymer （PEP-AN） and diazonium salts of 4-chloroaniline, 4-aminobenzonitrile and 4-nitroaniline, respectively. The structures and properties of the azo polymers were characterized by using 1H-NMR, FT-IR, UV-Vis and thermal analyses. The photoinduced birefringence of the azo polymers was studied by irradiating spin-coated films of the polymers with laser beam at three different wavelengths （488, 532, and 589 nm）. The results indicate that the photoinduced birefringence of the azo polymers is related with the electron-withdrawing group on azo chromophores and the excitation wavelength. The excitation wavelength that can cause the efficient responses is determined by the absorption band positions of the a~：o chromophores, which are mainly affected by the electron-withdrawing group on the chromophores. Therefore, the,. azo polymers containing chromophores with different electron-withdrawing groups show different respon,;ive behavior to the irradiation light at different wavelengths. When irradiated with 488 nm light, PEP-AZ-Cl shows the shortest time to reach the saturated birefringence but with the lowest saturation birefringence level compared with the other two azo polymers. When irradiated with 532 nm light, PEP-AZ-CN shows the shortest time to reach the saturated birefringence. When irradiated with 532 and 589 nm light, PEP-AZ-NT shows the highest saturation birefringence level.展开更多
The purpose of this study was to evaluate the physical properties and bioactivity potential of epoxy-based dental sealers modified with synthesized bioactive glass(BAG),hydroxyapatite(HA)and fluorine substituted hydro...The purpose of this study was to evaluate the physical properties and bioactivity potential of epoxy-based dental sealers modified with synthesized bioactive glass(BAG),hydroxyapatite(HA)and fluorine substituted hydroxyapatite(FHA)nanoparticles.The synthesized powders were incorporated at 10%and 20%into the epoxy-based dental sealer.The setting time,flow and solubility and microhardness of the modified and unmodified samples were examined.The bioactivity was evaluated using FESEM-EDX and elemental mapping,ATR-FTIR and XRD.The flow value of all of the experimental groups except the FHA modified samples,was greater than 20 mm.Concerning solubility,no specimens exhibited more than 1%weight loss.The solubility value of the FHA groups was statistically significant lower than other groups(p≤0.001).The mean hardness values of all of the modified samples were significantly higher than the unmodified group(p≤0.001).Regarding bioactivity,in vitro study revealed that after 3 days immersion in SBF a compact and continuous calcium phosphate layer formed on the surface of epoxy sealers containing BAG and HA nanoparticles.Based on these results,the addition of BAG and HA nanoparticles did not adversely alter the physical properties of epoxy sealers.Additionally,they improved the in vitro bioactivity of the epoxy sealer.展开更多
An interpenetrating polymer networks (IPN) consisting of an epoxy-based polymer network and a polymethyl methacrylate network were synthesized and characterized. The IPN showed only one T-g, and hence a homogeneous-ph...An interpenetrating polymer networks (IPN) consisting of an epoxy-based polymer network and a polymethyl methacrylate network were synthesized and characterized. The IPN showed only one T-g, and hence a homogeneous-phase morphology was suggested. The second-order nonlinear optical coefficient (d(33)) of the IPN was measured to be 1.72 X 10(-7) esu. The study of NLO temporal stability at room temperature and elevated temperature (100 degrees C) indicated that the IPN exhibits a high stability in the dipole orientation due to the permanent entanglements of two component networks in the IPN system. Long-term stability of second harmonic coefficients was observed at room temperature for more than 1000 h.展开更多
基金the National Science and Technology Major Project(No.2017-VII-0012-0107)the National Program for Support of Top-notch Young Professionals。
文摘To gain high efficiency and low fuel consumption, aluminum-based abradable seal coatings had been widely used in the compressor casing of aero engines or gas turbines owing to the low elastic modulus. However, the adhesive transfer phenomenon frequently occurs when the radial rubbing generates between titanium alloy blade tips and aluminum-based coating. It tends to increase scratch force and results in blades vibration and even engine jam. To eliminate this problem, a new lightweight epoxy-based abradable seal coating with high bonding strength was developed by an effective and porosity controllable mixing process that distributes spherical pores uniformly in the continuous matrix. A lightweight coating of 63% porosity with a hardness of 33.1(HR15 Y) can be reached when the content of hollow microspheres is 31 wt.%. The coating density is 0.5 g/cm3 and the bonding strength is as high as 18 MPa.The performance of the epoxy-based coating is comprehensively better than aluminum-based coatings in five essential indices. This study is expected to provide a new technical path for obtaining high-quality abradable seal coatings to guarantee the efficient and safe operation of compressors.
基金financially supported by the National Science and Technology Major Project(No.2017-VII-0012-0107)the National Program for Support of Top-notch Young Professionals。
文摘Aluminum-based composite abradable seal coatings are pivotal to improving the efficiency of aero engines or gas turbines.However,the adhesive transfer frequently occurs between metallic blade tips and aluminum-based composite coatings,resulting in engine vibration and even jam.Many past studies had tried to solve this problem by reducing coating hardness,improving lubrication,or strengthening blade tips,but all had failed.In this paper,we proposed a novel epoxy-based composite abradable seal coating,eliminating adhesive transfer by changing metal-to-metal scraping pair to metal-to-polymer scraping pair.The coating was developed via a hierarchical structure design.Large spherical pores were uniformly distributed in the continuous epoxy matrix with fine graphite dispersion.By adding 20 vol.%graphite and 50 vol.%hollow microspheres,a self-lubricating epoxy-based coating of 0.26 friction coefficient with thermal conductivity of 0.28 W/(m·K),coating HR15 Y hardness at 54.8,and bonding strength at 18.7 MPa can be reached.When the metallic blades scrape the epoxy-based composite coating,no adhesive transfer occurs.Besides,a smooth scraped surface is formed by pseudoplastic deformation.This epoxy-based composite abradable seal coating opens a new way to improve the efficiency and reliable operations of air engine compressors.
文摘In this work, graphene-modified epoxy-based anti-corrosion coatings were prepared and the influence of graphene on the anti-corrosion performance of the epoxy-based coatings was investigated with water contact angle test ,chemical solution immersion test, and electrochemical test. The water contact angle and chemical solution resistance of the epoxy-based coatings were improved with an increase in graphene content from 0 to 0.4%. These results prove that addition of graphene can significantly improve the hydrophobicity and impermeability of epoxy- based coatings. However, when the graphene content was increased to 0.5%, the performance of the epoxy-based coatings decreased because of graphene aggregation. Tafel polarization results show that graphene addition can significantly reduce the corrosion current density and corrosion potential of epoxy-based coatings, which enhance their anti-corrosion performance.
基金financial support from the National Natural Science Foundation of China(Nos.51773108 and 51233002)
文摘In this study,a series of epoxy-based azo molecular glasses with four-arm architecture was synthesized based on an intermediate(MDGA-AN),which was obtained from ring-opening reaction between 4,4'-methylene-bis(N,N’-diglycidylaniline)and N-methylaniline.The azo compounds were then synthesized through azo-coupling reaction between MDGA-AN and diazonium salts of 4-nitroaniline,4-aminobenzonitrile,4-aminobenzoic acid,4-fluoroaniline and 4-methoxyaniline,respectively.The azo compounds were thoroughly characterized and the photoresponsive properties of their solid films were investigated at three different wavelengths(λex=488,532 and 589 nm).The results show that the electron-withdrawing groups on the azo chromophores can significantly affect the absorption band positions in visible light range,which shift to the longer wavelength with the enhanced push-pull effect.Both photoinduced birefringence and surface-relief-grating formation are closely related to the electronwithdrawing groups and excitation wavelengths of the actinic light,which show significant influences on the growth rates and saturated values of the photoinduced variations.In this series,the azo molecular glasses containing cyano and carboxyl groups as the electron-withdrawing groups show the significantly higher efficiency for both the photoinduced birefringence growth and the SRG formation compared with others under the same light irradiation conditions.The capability of the materials as a photo-storage medium is demonstrated by holographic recording.
文摘Three epoxy-based azo polymers （PEP-AZ-C1, PEP-AZ-CN and PEP-AZ-NT） with high chromophore density were synthesized by using post-polymerization azo-coupling reactions between epoxy-based precursor polymer （PEP-AN） and diazonium salts of 4-chloroaniline, 4-aminobenzonitrile and 4-nitroaniline, respectively. The structures and properties of the azo polymers were characterized by using 1H-NMR, FT-IR, UV-Vis and thermal analyses. The photoinduced birefringence of the azo polymers was studied by irradiating spin-coated films of the polymers with laser beam at three different wavelengths （488, 532, and 589 nm）. The results indicate that the photoinduced birefringence of the azo polymers is related with the electron-withdrawing group on azo chromophores and the excitation wavelength. The excitation wavelength that can cause the efficient responses is determined by the absorption band positions of the a~：o chromophores, which are mainly affected by the electron-withdrawing group on the chromophores. Therefore, the,. azo polymers containing chromophores with different electron-withdrawing groups show different respon,;ive behavior to the irradiation light at different wavelengths. When irradiated with 488 nm light, PEP-AZ-Cl shows the shortest time to reach the saturated birefringence but with the lowest saturation birefringence level compared with the other two azo polymers. When irradiated with 532 nm light, PEP-AZ-CN shows the shortest time to reach the saturated birefringence. When irradiated with 532 and 589 nm light, PEP-AZ-NT shows the highest saturation birefringence level.
基金supported by International Campus of Tehran University of Medical Sciences(IC-TUMS)and health Services grant No.9423684001.
文摘The purpose of this study was to evaluate the physical properties and bioactivity potential of epoxy-based dental sealers modified with synthesized bioactive glass(BAG),hydroxyapatite(HA)and fluorine substituted hydroxyapatite(FHA)nanoparticles.The synthesized powders were incorporated at 10%and 20%into the epoxy-based dental sealer.The setting time,flow and solubility and microhardness of the modified and unmodified samples were examined.The bioactivity was evaluated using FESEM-EDX and elemental mapping,ATR-FTIR and XRD.The flow value of all of the experimental groups except the FHA modified samples,was greater than 20 mm.Concerning solubility,no specimens exhibited more than 1%weight loss.The solubility value of the FHA groups was statistically significant lower than other groups(p≤0.001).The mean hardness values of all of the modified samples were significantly higher than the unmodified group(p≤0.001).Regarding bioactivity,in vitro study revealed that after 3 days immersion in SBF a compact and continuous calcium phosphate layer formed on the surface of epoxy sealers containing BAG and HA nanoparticles.Based on these results,the addition of BAG and HA nanoparticles did not adversely alter the physical properties of epoxy sealers.Additionally,they improved the in vitro bioactivity of the epoxy sealer.
基金This work was supported by the Natural Science Foundation of Guangdong Province (980279, 980346)and the National Natural Science Foundation of China (19604015).
文摘An interpenetrating polymer networks (IPN) consisting of an epoxy-based polymer network and a polymethyl methacrylate network were synthesized and characterized. The IPN showed only one T-g, and hence a homogeneous-phase morphology was suggested. The second-order nonlinear optical coefficient (d(33)) of the IPN was measured to be 1.72 X 10(-7) esu. The study of NLO temporal stability at room temperature and elevated temperature (100 degrees C) indicated that the IPN exhibits a high stability in the dipole orientation due to the permanent entanglements of two component networks in the IPN system. Long-term stability of second harmonic coefficients was observed at room temperature for more than 1000 h.
