Poly(p-phenylene-2,6-benzobisoxazole)(PBO)fiber and polytetrafluoroethylene(PTFE)resin have been widely acknowledged as excellent wave-transparent materials for future high-frequency applications due to their exceptio...Poly(p-phenylene-2,6-benzobisoxazole)(PBO)fiber and polytetrafluoroethylene(PTFE)resin have been widely acknowledged as excellent wave-transparent materials for future high-frequency applications due to their exceptional dielectric properties.However,the weak interfacial bonding between these two materials hampers their full potential.In this study,we successfully addressed this limitation by enhancing the surface roughness of PBO fibers and introducing active sites through the insitu grafting of silica nanowires.The added silica acted as an interfacial anchor on the PBO fiber surface,significantly improving the bonding force between PBO and PTFE.PBO/PTFE wave-transparent laminated composites were fabricated using hot compression molding.The results demonstrate that the PBO(treated with insitu grown silica)/PTFE laminated composites exhibit superior interlaminar shear strength(ILSS),flexural strength,flexural modulus,and tensile modulus compared to the pristine PBO/PTFE laminated composites.Specifically,these properties are found to be 58.6%,32.9%,138.1%,and 25.35%higher,respectively.Additionally,these composites demonstrate low dielectric constant and dielectric loss.Most notably,they achieve a wave transmittance of 91.45%at 10 GHz,indicating significant potential for wide-range applications in next-generation advanced military weapons,such as“lightweight/high-strength/wavetransparent”electromagnetic window materials,as well as civilian communication base stations.展开更多
Polymer-derived ceramics(PDCs)is a promising way to prepare ceramic-based electromagnetic functional materials,which can conveniently modulate the composition and dielectric properties of the ceramics.In this paper,Si...Polymer-derived ceramics(PDCs)is a promising way to prepare ceramic-based electromagnetic functional materials,which can conveniently modulate the composition and dielectric properties of the ceramics.In this paper,SiBCN ceramic matrix composites with excellent high-temperature wave-transparent performance were prepared through PDC method.Three hyperbranched polyborosilazanes(PBSZs)were prepared by adjusting the type of chlorosilane monomers containing different numbers of methyl groups.The carbon element of pyrolytic ceramics was tuned by adjusting the molecular structure of the precursor and the pyrolysis temperature.The lower the methyl number and pyrolysis temperature,the lower the dielectric constant of the polymer-derived SiBCN ceramics,which is favorable for electromagnetic wave(EMW)transmittance.The average EMW transmittance of SiBCN-C pyrolyzed from hyperbranched PBSZ using trichlorosilane at 1000℃ was 90.56%at room temperature.More excitingly,the excellent wave-transparent performance was also maintained in the temperature range of 100-800℃.At the test temperature of 800℃,SiBCN-C-1000 still had excellent wave-transparent performance with minimum and average EMW transmittance of 76.13%and 88.96%,respectively.This paper provided a new idea for the preparation of high-temperature wave-transparent SiBCN composite ceramics.展开更多
With the rapid development of electronic information technology,antenna systems in the fields of aviation,aerospace,transportation,and 5 G communication services are becoming more and more intensive and accurate.Polym...With the rapid development of electronic information technology,antenna systems in the fields of aviation,aerospace,transportation,and 5 G communication services are becoming more and more intensive and accurate.Polymer matrix wave-transparent composites with lightweight,low dielectric constant(∈)and dielectric loss tangent(tanδ),high temperature resistance,and excellent mechanical properties are urgently needed in order to ensure high-fidelity transmission of electromagnetic wave and protect antenna systems from external interference.This review introduces the wave transmission mechanism,key compositions(polymer matrix&reinforced fibers),and several typical testing methods for dielectric properties of polymer matrix wave-transparent composites,mainly elaborates the latest research progress and achievements of polymer matrix wave-transparent composites from polymer matrix,reinforced fibers and their surface functionalization methods,and presents the key scientific and technical problems that need to be solved urgently in the application of polymer matrix wave-transparent composites in the antenna systems.Finally,the future development trends and application prospects of the polymer matrix wave-transparent composites are also proposed.展开更多
Bisphenol A dicyanate ester resins modified by fluorine-containing liquid crystal compound(LCFE)are applied as polymer matrix(LCFE-BADCy),poly(p-phenylene-2,6-benzobisoxazole)(PBO)fibers as rein-forcements,and fluorin...Bisphenol A dicyanate ester resins modified by fluorine-containing liquid crystal compound(LCFE)are applied as polymer matrix(LCFE-BADCy),poly(p-phenylene-2,6-benzobisoxazole)(PBO)fibers as rein-forcements,and fluorine/adamantane PBO precursor(pre FABPBO)as interfacial compatibilizer to prepare the corresponding PBO fibers/FABPBO/LCFE-BADCy wave-transparent laminated composites.LCFE could improve the order degree of BADCy cured network,in favor of enhancing the wave-transparent perfor-mance,mechanical properties,and intrinsic thermal conductivity.The dielectric constant and dielectric loss of PBO fibers/FABPBO/LCFE-BADCy composites are highly temperature(25–200℃)and frequency(10^(4)–10^(7) Hz and 8.2–12.4 GHz)stable with the value of 2.49 and 0.003 under 10^(6) Hz at 25℃,and the corresponding wave transmission efficiency is 95.0%,higher than that of 92.5%for PBO fibers/BADCy com-posites.The interlamellar shear strength and flexural strength are respectively 50.7 MPa and 682.5 MPa,38.1%and 16.2%higher than those of PBO fibers/BADCy composites.Besides,the volume resistivity,breakdown voltage,heat resistance index,glass transition temperature,flame retardant grade,and ul-timate oxygen index of PBO fibers/FABPBO/LCFE-BADCy composites are respectively 5.3×10^(15)Ωcm,29.75 kV/mm,217.2℃,245.7℃,V-1 grade,and 33.6%,expected to be performed as a new generation of“lightweight/loading/wave-transparent”electromagnetic window materials in advanced military weapons and civil communication base station.展开更多
A block copolymer of PDMS-b-PGMA is synthesized by polymerizing glycidyl methacrylate(GMA)via reversible addition-fragmentation chain transfer(RAFT)polymerization applying a polydimethylsiloxane(PDMS)based macro-RAFT ...A block copolymer of PDMS-b-PGMA is synthesized by polymerizing glycidyl methacrylate(GMA)via reversible addition-fragmentation chain transfer(RAFT)polymerization applying a polydimethylsiloxane(PDMS)based macro-RAFT agent,which is then performed to functionalize the quartz fibers(QFs@PDMS-b-PGMA)via a simple coating process.Finally,the QFs@PDMS-b-PGMA/bisphenol A dicyanate ester(BADCy)wave-transparent laminated composites are fabricated by high-temperature molding.Nuclear magnetic resonance(NMR)spectroscopy,Fourier transform infrared(FT-IR)spectroscopy and size ex-clusion chromatography(SEC)demonstrate the successful preparation of PDMS-b-PGMA with expected structure.When the molar mass and coating amount of PDMS-b-PGMA are respectively 8100 g/mol and 2.0 wt.%,QFs@PDMS-b-PGMA/BADCy wave-transparent laminated composites present optimal mechan-ical properties and wave-transparent performance.The interlaminar shear strength(ILSS)and flexural strength are 53.6 and 552.0 MPa,respectively.Meanwhile,the dielectric constant and dielectric loss val-ues are 2.61 and 0.0028 at 1 MHz(wave transmittance of 93.8%),showing good stability at different frequencies(102-106 Hz and 8.4-12.4 GHz)and temperatures(25-250℃).展开更多
Comprehensive Summary Branched fluorine/adamantane PBO precursor(preFABPBO),synthesized via random co-condensation between 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoro propane,1,3-adamantanedicarbonyl dichloride,and tri...Comprehensive Summary Branched fluorine/adamantane PBO precursor(preFABPBO),synthesized via random co-condensation between 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoro propane,1,3-adamantanedicarbonyl dichloride,and trimesoyl chloride,is performed as interfacial compatibilizer,bisphenol A dicyanate ester(BADCy)resin as polymer matrix,and poly(p-phenylene-2,6-benzobisoxazole)(PBO)fibers as reinforcements to prepare PBO fibers/FABPBO-BADCy wave-transparent laminated composites by high temperature molding.The mechanical properties,wave-transparent performances,and heat resistances of PBO fibers/BADCy composites are simultaneously improved by the addition of preFABPBO.The interlaminar shear strength(ILSS)and flexural strength of PBO fibers/FABPBO-BADCy composites are 48.9 and 665.3 MPa,respectively,increased by 33.2%and 13.3%compared to those of PBO fibers/BADCy composites(36.7 and 587.4 MPa).The dielectric constant and dielectric loss values at 106 Hz are 2.53 and 0.003,respectively,lower than those of PBO fibers/BADCy composites(3.06 and 0.006),and the corresponding wave transmission efficiency is 94.8%,which also presents excellent stability over the wide temperature(25-200℃)and frequency range(103-107 Hz and 8.2-12.4 GHz).Meanwhile,the heat resistance index and glass transition temperature are 229.9℃and 247.5℃,also better than those of PBO fibers/BADCy composites(229.6℃and 247.1℃).展开更多
Poly(p-phenylenebenzobisoxazole)nanofibers(PNF),as a novel kind of nanofibers,have attracted significant attention from researchers.However,their poor ultraviolet(UV)resistance limits their potential applications.In t...Poly(p-phenylenebenzobisoxazole)nanofibers(PNF),as a novel kind of nanofibers,have attracted significant attention from researchers.However,their poor ultraviolet(UV)resistance limits their potential applications.In this work,zinc oxide(ZnO)was uniformly coated on the surface of PNF-containing polysilsesquioxane(POSS)via in-situ growth to obtain(POSS-PNF)@ZnO.Subsequently,(POSS-PNF)@ZnO wave-transparent composite paper was then fabricated using a“vacuum filtration-assisted hot-pressing”method.Based on the coordination interaction between O–Cdouble bondO groups of PNFs and ZnO,as well as the UV absorption/shielding capability of ZnO,the(POSS-PNF)@ZnO wave-transparent composite paper exhibited superior mechanical properties and UV resistance.At a hydrothermal reaction temperature of 80℃,the prepared(POSS-PNF)@ZnO wave-transparent composite paper exhibited the highest tensile strength(204.5 MPa)and toughness(12.3 MJ m^(−3)),which represents increases of 23.7%and 32.3%,respectively,compared to POSS-PNF wave-transparent paper.After 288 h of UV aging,the tensile strength retention rate was 77.4%,significantly higher than the 53.7%of POSS-PNF wave-transparent composite paper.Moreover,it exhibited excellent wave-transparent performance with a dielectric constant(ε)of 2.15 and a dielectric loss tangent(tanδ)of 0.044 at 10 GHz,resulting in a wave-transparent coefficient of 95.9%.展开更多
With the miniaturization and high-frequency evolution of antennas in 5G/6G communications,aerospace,and transportation,polymer composite papers integrating superior wave-transparent performance and thermal conductivit...With the miniaturization and high-frequency evolution of antennas in 5G/6G communications,aerospace,and transportation,polymer composite papers integrating superior wave-transparent performance and thermal conductivity for radar antenna systems are urgently needed.Herein,a down-top strategy was employed to synthesize poly(p-phenylene benzobisoxazole)precursor nanofibers(prePNF).The prePNF was then uniformly mixed with fluorinated graphene(FG)to fabricate FG/PNF composite papers through consecutively suction filtration,hot-pressing,and thermal annealing.The hydroxyl and amino groups in prePNF enhanced the stability of FG/prePNF dispersion,while the increasedπ-πinteractions between PNF and FG after annealing improved their compatibility.The preparation time and cost of PNF paper was significantly reduced when applying this strategy,which enabled its large-scale production.Furthermore,the prepared FG/PNF composite papers exhibited excellent wave-transparent performance and thermal conductivity.When the mass fraction of FG was 40 wt%,the FG/PNF composite paper prepared via the down-top strategy achieved the wave-transparent coefficient(|T|2)of 96.3%under 10 GHz,in-plane thermal conductivity(λ_(∥))of 7.13 W m^(−1)K^(−1),and through-plane thermal conductivity(λ_(⊥))of 0.67 W m^(−1)K^(−1),outperforming FG/PNF composite paper prepared by the top-down strategy(|T|2=95.9%,λ_(∥)=5.52 W m^(−1)K^(−1),λ_(⊥)=0.52 W m^(−1)K^(−1))and pure PNF paper(|T|2=94.7%,λ_(∥)=3.04 W m^(−1)K^(−1),λ_(⊥)=0.24 W m^(−1)K^(−1)).Meanwhile,FG/PNF composite paper(with 40 wt%FG)through the down-top strategy also demonstrated outstanding mechanical properties with tensile strength and toughness reaching 197.4 MPa and 11.6 MJ m^(−3),respectively.展开更多
ZrP_(2)O_(7) is a promising wave-transparent material due to its low dielectric constant and low dielectric loss,but its inherent phase transition characteristic at approximately 300℃ limits its high-temperature appl...ZrP_(2)O_(7) is a promising wave-transparent material due to its low dielectric constant and low dielectric loss,but its inherent phase transition characteristic at approximately 300℃ limits its high-temperature application.Therefore,suppressing the phase transition is necessary for ZrP_(2)O_(7),to serve in extremely harsh environments.In this work,introducing Ti and Hf into ZrP_(2)O_(7) causes significant lattice distortion and an increase in entropy,both of which synergistically limit the crystal structure transformation.In addition,enhanced phonon scattering by mismatch of atomic mass and local distortion leads to a reduction in the thermal conductivity.Lattice distortions also cause changes in both bond length and tilting angle,so that(Ti_(1/3)Zr_(1/3)Hf_(1/3))P_(2)O_(7) does not undergo sudden expansion as does ZrP_(2)O_(7).(Ti_(1/3)Zr_(1/3)Hf_(1/3))ZrP_(2)O_(7) maintains excellent dielectric properties,which highlights it as a promising high-temperature wave-transparent material.展开更多
The silica fiber reinforced silica and boron nitride-based composites （SiO2f/SiO2-BN） were prepared firstly via the sol-gel method and then the urea route, and the effects of oxidation treatment on the component, st...The silica fiber reinforced silica and boron nitride-based composites （SiO2f/SiO2-BN） were prepared firstly via the sol-gel method and then the urea route, and the effects of oxidation treatment on the component, structure, mechanical and dielectric properties of the composites were investigated. The results show that the oxidation treatment at 450 ℃ will not impair the structure of boron nitride, and carbon is the main impurity with the excessive urea. The density of SiO2f/SiO2-BN composites is 1.81 g/cm3, and the flexural strength and elastic modulus are 113.9 MPa and 36.5 GPa, respectively. After oxidation treatment, the density varies to 1.80 g/cm3, and the flexural strength and elastic modulus are decreased to 58.9 MPa and 9.4 GPa, respectively. The mechanical properties of the composites are severely damaged, but they still exhibit a good toughness. The composites show excellent dielectric properties with the dielectric constant and loss tangent being 3.22 and 0.003 9, respectively, which indicates that the oxidation treatment is ineffective to improve the dielectric properties of SiOzf/SiO2-BN composites.展开更多
Hybrid polymer membrane(TA-APTES),synthesized by tannic acid(TA)and aminopropyl trethoxysilane(APTES)based on the Schif’s base and Michael addition reaction,is deposited on the surface of poly(p-phenylene-2,6-benzobi...Hybrid polymer membrane(TA-APTES),synthesized by tannic acid(TA)and aminopropyl trethoxysilane(APTES)based on the Schif’s base and Michael addition reaction,is deposited on the surface of poly(p-phenylene-2,6-benzobisoxazole)(PBO)fbers,and then grafted with epoxy-terminated polysesquisiloxane(POSS)to obtain POSS-g-PBO@TA-APTES fbers.The POSS-g-PBO@TA-APTES fbers reinforced bisphenol A dicyanate ester(BADCy)resins(POSS-g-PBO@TAAPTES fbers/BADCy)wave-transparent laminated composites are prepared.The interlaminar shear strength and fexural strength of POSS-g-PBO@TA-APTES fbers/BADCy composites are respectively enhanced from 36.7 and 587.4 MPa to 42.8 and 645.8 MPa,increased by 16.6%and 9.9%compared with those of PBO fbers/BADCy composites.At 1 MHz,the corresponding dielectric constant and dielectric loss are reduced to 2.85 and 0.0047,respectively,lower than those of PBO fbers/BADCy(3.06 and 0.006)composites.Meanwhile,the simulated wave transmittance rate of POSS-g-PBO@TA-APTES fbers/BADCy composites with the thicknesses of 1.5–3.5 mm is higher than 86.2%at 0.3–40 GHz.The volume resistivity and breakdown strength of POSS-g-PBO@TA-APTES fbers/BADCy composites are 2.8×10^(15)Ω·cm and 19.80 kV/mm,higher than PBO fbers/BADCy composites(2.2×10^(15)Ω·cm and 17.69 kV/mm),respectively.And the corresponding heat resistant index is 221.5℃,lower than PBO fbers/BADCy composites(229.6℃).展开更多
Porous Si_(3)N_(4)ceramics are promising high-temperature wave transparent materials for use as radomes or antenna windows in hypersonic aircraft.However,a trade-off between the dielectric and thermomechanical propert...Porous Si_(3)N_(4)ceramics are promising high-temperature wave transparent materials for use as radomes or antenna windows in hypersonic aircraft.However,a trade-off between the dielectric and thermomechanical properties is still challenging.Therefore,tailoring the microstructure and properties of porous Si_(3)N_(4)is highly important.In this work,porous Si_(3)N_(4)ceramics with uniform and fine structures were obtained via dual-solvent templating combined with the freeze-casting method.The as-prepared porous Si_(3)N_(4)ceramic,with 56%porosity,possesses high mechanical properties,with flexural strength and compressive strength values of 95±14.8 and 132±4.5 MPa,respectively.The uniform spherical pore structure improved the mechanical properties,and the rod-shaped Si_(3)N_(4)grains facilitated crack deflection.The decreased pore size effectively blocks phonon transport,leading to a low thermal conductivity of only 4.2 W/(K·m).Moreover,the porous Si_(3)N_(4)ceramic maintains a small dielectric constant of 3.3,and the dielectric loss is stable between 1.0×10^(-3)-4.0×10^(-3),which guarantees its potential application in high-temperature wave-transparent components.These results significantly advanced the development of high-performance wave-transparent materials used in hypersonic aircraft.展开更多
The rapid development of radar antenna systems to meet requirements for high integration and precision places stringent requirements on the dielectric properties,mechanical properties and heat resistance of wave-trans...The rapid development of radar antenna systems to meet requirements for high integration and precision places stringent requirements on the dielectric properties,mechanical properties and heat resistance of wave-transparent composite paper.In this paper,poly(p-phenylene-2,6-benzobisoxazole)(PBO)fibers are first dissolved by trifluoroacetic acid/methyl sulfonic acid to obtain PBO nanofibers(PNF),and the amino polysilsesquioxane(NH_(2)-POSS)is dispersed uniformly inside the PNF via ultrasonic-assisted and deprotonation.The POSS-PNF composite paper is fabricated by the method of“suction filtration and hot-pressing”.Because of the uniformly dispersion of NH_(2)-POSS,the POSS-PNF composite paper has a low dielectric constant(ε,2.08)and dielectric loss tangent(tanδ,0.0047),and the wave-transparent coefficient(|T|2)is 96.7%(1 MHz),which is higher than that of PNF paper(95.5%,1 MHz).Additionally,the POSS-PNF composite paper possesses excellent tensile strength of 163.3 MPa,tensile modulus of 6.9 GPa,toughness of 9.1 MJ/m^(3),outstanding flame retardancy and excellent UV aging resistance.According to a simulation of the radome honeycomb panel,POSS-PNF composite paper has low loss and reflections of electromagnetic waves in the X-band(8.4~12.4 GHz),and wide angle of incidence(0°-80°),which favor high|T|2.The results indicate that the POSS-PNF composite paper has excellent potential for applications in the fields of aerospace,wearable flexible electronic devices and 5G communication.展开更多
基金supported by the National Natural Science Foundation of China(No.U21A2094)CASHIPS Director’s Fund(Nos.YZJJZX202015,YZJJ202304-CX,YZJJ2023QN36)+1 种基金Anhui Province Postdoctoral Researcher Research Project(No.E24F0D27)Central Government Guiding Local Government Science and Technology Development Special Fund Project(No.2022ZB09002).
文摘Poly(p-phenylene-2,6-benzobisoxazole)(PBO)fiber and polytetrafluoroethylene(PTFE)resin have been widely acknowledged as excellent wave-transparent materials for future high-frequency applications due to their exceptional dielectric properties.However,the weak interfacial bonding between these two materials hampers their full potential.In this study,we successfully addressed this limitation by enhancing the surface roughness of PBO fibers and introducing active sites through the insitu grafting of silica nanowires.The added silica acted as an interfacial anchor on the PBO fiber surface,significantly improving the bonding force between PBO and PTFE.PBO/PTFE wave-transparent laminated composites were fabricated using hot compression molding.The results demonstrate that the PBO(treated with insitu grown silica)/PTFE laminated composites exhibit superior interlaminar shear strength(ILSS),flexural strength,flexural modulus,and tensile modulus compared to the pristine PBO/PTFE laminated composites.Specifically,these properties are found to be 58.6%,32.9%,138.1%,and 25.35%higher,respectively.Additionally,these composites demonstrate low dielectric constant and dielectric loss.Most notably,they achieve a wave transmittance of 91.45%at 10 GHz,indicating significant potential for wide-range applications in next-generation advanced military weapons,such as“lightweight/high-strength/wavetransparent”electromagnetic window materials,as well as civilian communication base stations.
基金financially supported by the National Science Fund for Distinguished Young Scholars(No.52025034)the Na-tional Key Research and Development Program of China(No.2022YFB3807100/2022YFB3807101)+1 种基金the National Natural Sci-ence Foundation of China(No.22005039)the Polymer Elec-tromagnetic Functional Materials Innovation Team of Shaanxi San-qin Scholars.
文摘Polymer-derived ceramics(PDCs)is a promising way to prepare ceramic-based electromagnetic functional materials,which can conveniently modulate the composition and dielectric properties of the ceramics.In this paper,SiBCN ceramic matrix composites with excellent high-temperature wave-transparent performance were prepared through PDC method.Three hyperbranched polyborosilazanes(PBSZs)were prepared by adjusting the type of chlorosilane monomers containing different numbers of methyl groups.The carbon element of pyrolytic ceramics was tuned by adjusting the molecular structure of the precursor and the pyrolysis temperature.The lower the methyl number and pyrolysis temperature,the lower the dielectric constant of the polymer-derived SiBCN ceramics,which is favorable for electromagnetic wave(EMW)transmittance.The average EMW transmittance of SiBCN-C pyrolyzed from hyperbranched PBSZ using trichlorosilane at 1000℃ was 90.56%at room temperature.More excitingly,the excellent wave-transparent performance was also maintained in the temperature range of 100-800℃.At the test temperature of 800℃,SiBCN-C-1000 still had excellent wave-transparent performance with minimum and average EMW transmittance of 76.13%and 88.96%,respectively.This paper provided a new idea for the preparation of high-temperature wave-transparent SiBCN composite ceramics.
基金the support and funding from National Scientific Research Project(Basis Strengthening Plan)Space Supporting Fund from China Aerospace Science and Industry Corporation(2020-HT-XG)+4 种基金Fundamental Research Funds for the Central Universities(310201911qd003)China Postdoctoral Science Foundation(2019M653735)State Key Laboratory for Modification of Chemical Fibers and Polymer Materials from Donghua University(KF2001)Open Fund from Henan University of Science and Technology(2020-RSC02)financially supported by Polymer Electromagnetic Functional Materials Innovation Team of Shaanxi Sanqin Scholars.
文摘With the rapid development of electronic information technology,antenna systems in the fields of aviation,aerospace,transportation,and 5 G communication services are becoming more and more intensive and accurate.Polymer matrix wave-transparent composites with lightweight,low dielectric constant(∈)and dielectric loss tangent(tanδ),high temperature resistance,and excellent mechanical properties are urgently needed in order to ensure high-fidelity transmission of electromagnetic wave and protect antenna systems from external interference.This review introduces the wave transmission mechanism,key compositions(polymer matrix&reinforced fibers),and several typical testing methods for dielectric properties of polymer matrix wave-transparent composites,mainly elaborates the latest research progress and achievements of polymer matrix wave-transparent composites from polymer matrix,reinforced fibers and their surface functionalization methods,and presents the key scientific and technical problems that need to be solved urgently in the application of polymer matrix wave-transparent composites in the antenna systems.Finally,the future development trends and application prospects of the polymer matrix wave-transparent composites are also proposed.
基金The authors are grateful for the support and funding from National Scientific Research Project(Basis Strengthening Plan)State Key Laboratory of Solidification Processing in NWPU(No.SKLSP202103).
文摘Bisphenol A dicyanate ester resins modified by fluorine-containing liquid crystal compound(LCFE)are applied as polymer matrix(LCFE-BADCy),poly(p-phenylene-2,6-benzobisoxazole)(PBO)fibers as rein-forcements,and fluorine/adamantane PBO precursor(pre FABPBO)as interfacial compatibilizer to prepare the corresponding PBO fibers/FABPBO/LCFE-BADCy wave-transparent laminated composites.LCFE could improve the order degree of BADCy cured network,in favor of enhancing the wave-transparent perfor-mance,mechanical properties,and intrinsic thermal conductivity.The dielectric constant and dielectric loss of PBO fibers/FABPBO/LCFE-BADCy composites are highly temperature(25–200℃)and frequency(10^(4)–10^(7) Hz and 8.2–12.4 GHz)stable with the value of 2.49 and 0.003 under 10^(6) Hz at 25℃,and the corresponding wave transmission efficiency is 95.0%,higher than that of 92.5%for PBO fibers/BADCy com-posites.The interlamellar shear strength and flexural strength are respectively 50.7 MPa and 682.5 MPa,38.1%and 16.2%higher than those of PBO fibers/BADCy composites.Besides,the volume resistivity,breakdown voltage,heat resistance index,glass transition temperature,flame retardant grade,and ul-timate oxygen index of PBO fibers/FABPBO/LCFE-BADCy composites are respectively 5.3×10^(15)Ωcm,29.75 kV/mm,217.2℃,245.7℃,V-1 grade,and 33.6%,expected to be performed as a new generation of“lightweight/loading/wave-transparent”electromagnetic window materials in advanced military weapons and civil communication base station.
文摘A block copolymer of PDMS-b-PGMA is synthesized by polymerizing glycidyl methacrylate(GMA)via reversible addition-fragmentation chain transfer(RAFT)polymerization applying a polydimethylsiloxane(PDMS)based macro-RAFT agent,which is then performed to functionalize the quartz fibers(QFs@PDMS-b-PGMA)via a simple coating process.Finally,the QFs@PDMS-b-PGMA/bisphenol A dicyanate ester(BADCy)wave-transparent laminated composites are fabricated by high-temperature molding.Nuclear magnetic resonance(NMR)spectroscopy,Fourier transform infrared(FT-IR)spectroscopy and size ex-clusion chromatography(SEC)demonstrate the successful preparation of PDMS-b-PGMA with expected structure.When the molar mass and coating amount of PDMS-b-PGMA are respectively 8100 g/mol and 2.0 wt.%,QFs@PDMS-b-PGMA/BADCy wave-transparent laminated composites present optimal mechan-ical properties and wave-transparent performance.The interlaminar shear strength(ILSS)and flexural strength are 53.6 and 552.0 MPa,respectively.Meanwhile,the dielectric constant and dielectric loss val-ues are 2.61 and 0.0028 at 1 MHz(wave transmittance of 93.8%),showing good stability at different frequencies(102-106 Hz and 8.4-12.4 GHz)and temperatures(25-250℃).
基金the support and funding from the National Scientific Research Project(Basis Strengthening Plan)and State Key Laboratory of Solidification Processing in NWPU(SKLSP202103).
文摘Comprehensive Summary Branched fluorine/adamantane PBO precursor(preFABPBO),synthesized via random co-condensation between 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoro propane,1,3-adamantanedicarbonyl dichloride,and trimesoyl chloride,is performed as interfacial compatibilizer,bisphenol A dicyanate ester(BADCy)resin as polymer matrix,and poly(p-phenylene-2,6-benzobisoxazole)(PBO)fibers as reinforcements to prepare PBO fibers/FABPBO-BADCy wave-transparent laminated composites by high temperature molding.The mechanical properties,wave-transparent performances,and heat resistances of PBO fibers/BADCy composites are simultaneously improved by the addition of preFABPBO.The interlaminar shear strength(ILSS)and flexural strength of PBO fibers/FABPBO-BADCy composites are 48.9 and 665.3 MPa,respectively,increased by 33.2%and 13.3%compared to those of PBO fibers/BADCy composites(36.7 and 587.4 MPa).The dielectric constant and dielectric loss values at 106 Hz are 2.53 and 0.003,respectively,lower than those of PBO fibers/BADCy composites(3.06 and 0.006),and the corresponding wave transmission efficiency is 94.8%,which also presents excellent stability over the wide temperature(25-200℃)and frequency range(103-107 Hz and 8.2-12.4 GHz).Meanwhile,the heat resistance index and glass transition temperature are 229.9℃and 247.5℃,also better than those of PBO fibers/BADCy composites(229.6℃and 247.1℃).
基金funding from the Foundation of the National Natural Science Foundation of China(Nos.52373089 and 52403085)the Startup Foundation of Chongqing Normal University(No.23XLB011)+1 种基金the Science and Technology Research Program of Chongqing Municipal Education Commission(No.KJQN202300561)Undergraduate Innovation&Business Program in Northwestern Polytechnical University(No.S202410699657)。
文摘Poly(p-phenylenebenzobisoxazole)nanofibers(PNF),as a novel kind of nanofibers,have attracted significant attention from researchers.However,their poor ultraviolet(UV)resistance limits their potential applications.In this work,zinc oxide(ZnO)was uniformly coated on the surface of PNF-containing polysilsesquioxane(POSS)via in-situ growth to obtain(POSS-PNF)@ZnO.Subsequently,(POSS-PNF)@ZnO wave-transparent composite paper was then fabricated using a“vacuum filtration-assisted hot-pressing”method.Based on the coordination interaction between O–Cdouble bondO groups of PNFs and ZnO,as well as the UV absorption/shielding capability of ZnO,the(POSS-PNF)@ZnO wave-transparent composite paper exhibited superior mechanical properties and UV resistance.At a hydrothermal reaction temperature of 80℃,the prepared(POSS-PNF)@ZnO wave-transparent composite paper exhibited the highest tensile strength(204.5 MPa)and toughness(12.3 MJ m^(−3)),which represents increases of 23.7%and 32.3%,respectively,compared to POSS-PNF wave-transparent paper.After 288 h of UV aging,the tensile strength retention rate was 77.4%,significantly higher than the 53.7%of POSS-PNF wave-transparent composite paper.Moreover,it exhibited excellent wave-transparent performance with a dielectric constant(ε)of 2.15 and a dielectric loss tangent(tanδ)of 0.044 at 10 GHz,resulting in a wave-transparent coefficient of 95.9%.
基金the support from the National Natural Science Foundation of China(52473083,52373089,52403085)Natural Science Basic Research Program of Shaanxi(2024JC-TBZC-04)+2 种基金the Innovation Capability Support Program of Shaanxi(2024RS-CXTD-57)Natural Science Basic Research Plan in Shaanxi Province of China(2024JC-YBMS-279)Natural Science Foundation of Chongqing,China(2023NSCQMSX2547)
文摘With the miniaturization and high-frequency evolution of antennas in 5G/6G communications,aerospace,and transportation,polymer composite papers integrating superior wave-transparent performance and thermal conductivity for radar antenna systems are urgently needed.Herein,a down-top strategy was employed to synthesize poly(p-phenylene benzobisoxazole)precursor nanofibers(prePNF).The prePNF was then uniformly mixed with fluorinated graphene(FG)to fabricate FG/PNF composite papers through consecutively suction filtration,hot-pressing,and thermal annealing.The hydroxyl and amino groups in prePNF enhanced the stability of FG/prePNF dispersion,while the increasedπ-πinteractions between PNF and FG after annealing improved their compatibility.The preparation time and cost of PNF paper was significantly reduced when applying this strategy,which enabled its large-scale production.Furthermore,the prepared FG/PNF composite papers exhibited excellent wave-transparent performance and thermal conductivity.When the mass fraction of FG was 40 wt%,the FG/PNF composite paper prepared via the down-top strategy achieved the wave-transparent coefficient(|T|2)of 96.3%under 10 GHz,in-plane thermal conductivity(λ_(∥))of 7.13 W m^(−1)K^(−1),and through-plane thermal conductivity(λ_(⊥))of 0.67 W m^(−1)K^(−1),outperforming FG/PNF composite paper prepared by the top-down strategy(|T|2=95.9%,λ_(∥)=5.52 W m^(−1)K^(−1),λ_(⊥)=0.52 W m^(−1)K^(−1))and pure PNF paper(|T|2=94.7%,λ_(∥)=3.04 W m^(−1)K^(−1),λ_(⊥)=0.24 W m^(−1)K^(−1)).Meanwhile,FG/PNF composite paper(with 40 wt%FG)through the down-top strategy also demonstrated outstanding mechanical properties with tensile strength and toughness reaching 197.4 MPa and 11.6 MJ m^(−3),respectively.
基金This work was financially supported by the National Natural Science Foundation of China(Nos.52202078 and 52202126)the Leading Talent Project of the National Special Support Program(No.2022WRLJ003)+1 种基金the Guangdong Basic and Applied Basic Research Foundation for Distinguished Young Scholars(No.2021B1515020083)the Guangdong Basic and Applied Basic Research Foundation(Nos.2021A1515110293 and 2022A1515012201).
文摘ZrP_(2)O_(7) is a promising wave-transparent material due to its low dielectric constant and low dielectric loss,but its inherent phase transition characteristic at approximately 300℃ limits its high-temperature application.Therefore,suppressing the phase transition is necessary for ZrP_(2)O_(7),to serve in extremely harsh environments.In this work,introducing Ti and Hf into ZrP_(2)O_(7) causes significant lattice distortion and an increase in entropy,both of which synergistically limit the crystal structure transformation.In addition,enhanced phonon scattering by mismatch of atomic mass and local distortion leads to a reduction in the thermal conductivity.Lattice distortions also cause changes in both bond length and tilting angle,so that(Ti_(1/3)Zr_(1/3)Hf_(1/3))P_(2)O_(7) does not undergo sudden expansion as does ZrP_(2)O_(7).(Ti_(1/3)Zr_(1/3)Hf_(1/3))ZrP_(2)O_(7) maintains excellent dielectric properties,which highlights it as a promising high-temperature wave-transparent material.
基金Projects(50902150,90916019) supported by the National Natural Science Foundation of ChinaProject (9140C8203040905) supported by the State Key Laboratory Foundation of ChinaProject(S100103) supported by the Graduate Innovation Foundation of National University of Defense Technology,China
文摘The silica fiber reinforced silica and boron nitride-based composites （SiO2f/SiO2-BN） were prepared firstly via the sol-gel method and then the urea route, and the effects of oxidation treatment on the component, structure, mechanical and dielectric properties of the composites were investigated. The results show that the oxidation treatment at 450 ℃ will not impair the structure of boron nitride, and carbon is the main impurity with the excessive urea. The density of SiO2f/SiO2-BN composites is 1.81 g/cm3, and the flexural strength and elastic modulus are 113.9 MPa and 36.5 GPa, respectively. After oxidation treatment, the density varies to 1.80 g/cm3, and the flexural strength and elastic modulus are decreased to 58.9 MPa and 9.4 GPa, respectively. The mechanical properties of the composites are severely damaged, but they still exhibit a good toughness. The composites show excellent dielectric properties with the dielectric constant and loss tangent being 3.22 and 0.003 9, respectively, which indicates that the oxidation treatment is ineffective to improve the dielectric properties of SiOzf/SiO2-BN composites.
基金The authors are grateful for the support and funding from National Scientifc Research Project(Basis Strengthening Plan)China Postdoctoral Science Foundation(2019M653735)+3 种基金State Key Laboratory for Modifcation of Chemical Fibers and Polymer Materials from Donghua University(KF2001)State Key Laboratory of Solidifcation Processing in NWPU(SKLSP202103)L.Tang thanks for the Innovation Foundation for Doctor Dissertation of Northwestern Polytechnical University(CX2021036)This work is also fnancially supported by Polymer Electromagnetic Functional Materials Innovation Team of Shaanxi Sanqin Scholars.
文摘Hybrid polymer membrane(TA-APTES),synthesized by tannic acid(TA)and aminopropyl trethoxysilane(APTES)based on the Schif’s base and Michael addition reaction,is deposited on the surface of poly(p-phenylene-2,6-benzobisoxazole)(PBO)fbers,and then grafted with epoxy-terminated polysesquisiloxane(POSS)to obtain POSS-g-PBO@TA-APTES fbers.The POSS-g-PBO@TA-APTES fbers reinforced bisphenol A dicyanate ester(BADCy)resins(POSS-g-PBO@TAAPTES fbers/BADCy)wave-transparent laminated composites are prepared.The interlaminar shear strength and fexural strength of POSS-g-PBO@TA-APTES fbers/BADCy composites are respectively enhanced from 36.7 and 587.4 MPa to 42.8 and 645.8 MPa,increased by 16.6%and 9.9%compared with those of PBO fbers/BADCy composites.At 1 MHz,the corresponding dielectric constant and dielectric loss are reduced to 2.85 and 0.0047,respectively,lower than those of PBO fbers/BADCy(3.06 and 0.006)composites.Meanwhile,the simulated wave transmittance rate of POSS-g-PBO@TA-APTES fbers/BADCy composites with the thicknesses of 1.5–3.5 mm is higher than 86.2%at 0.3–40 GHz.The volume resistivity and breakdown strength of POSS-g-PBO@TA-APTES fbers/BADCy composites are 2.8×10^(15)Ω·cm and 19.80 kV/mm,higher than PBO fbers/BADCy composites(2.2×10^(15)Ω·cm and 17.69 kV/mm),respectively.And the corresponding heat resistant index is 221.5℃,lower than PBO fbers/BADCy composites(229.6℃).
基金supported by the National Natural Science Foundation of China(Grant No.52202078)the Leading Talent Project of the National Special Support Program(Grant No.2022WRLJ003)+1 种基金the Guangdong Basic and Applied Basic Research Foundation for Distinguished Young Scholars(Grant No.2021B1515020083)the Guangdong Basic and Applied Basic Research Foundation(Grant Nos.2021A1515110293 and 2022A1515012201).
文摘Porous Si_(3)N_(4)ceramics are promising high-temperature wave transparent materials for use as radomes or antenna windows in hypersonic aircraft.However,a trade-off between the dielectric and thermomechanical properties is still challenging.Therefore,tailoring the microstructure and properties of porous Si_(3)N_(4)is highly important.In this work,porous Si_(3)N_(4)ceramics with uniform and fine structures were obtained via dual-solvent templating combined with the freeze-casting method.The as-prepared porous Si_(3)N_(4)ceramic,with 56%porosity,possesses high mechanical properties,with flexural strength and compressive strength values of 95±14.8 and 132±4.5 MPa,respectively.The uniform spherical pore structure improved the mechanical properties,and the rod-shaped Si_(3)N_(4)grains facilitated crack deflection.The decreased pore size effectively blocks phonon transport,leading to a low thermal conductivity of only 4.2 W/(K·m).Moreover,the porous Si_(3)N_(4)ceramic maintains a small dielectric constant of 3.3,and the dielectric loss is stable between 1.0×10^(-3)-4.0×10^(-3),which guarantees its potential application in high-temperature wave-transparent components.These results significantly advanced the development of high-performance wave-transparent materials used in hypersonic aircraft.
基金the National Natural Science Foundation of China(52373089)State Key Laboratory of Solidification Processing at the Northwestern Polytechnical University(NPU)(SKLSP202103)+1 种基金Z.Liu thanks the Innovation Foundation for Doctor’s Dissertations of NPU(CX2023026)Y.Lin thanks the Practice and Innovation Funds for Graduate Students of NPU(PF2023034).
文摘The rapid development of radar antenna systems to meet requirements for high integration and precision places stringent requirements on the dielectric properties,mechanical properties and heat resistance of wave-transparent composite paper.In this paper,poly(p-phenylene-2,6-benzobisoxazole)(PBO)fibers are first dissolved by trifluoroacetic acid/methyl sulfonic acid to obtain PBO nanofibers(PNF),and the amino polysilsesquioxane(NH_(2)-POSS)is dispersed uniformly inside the PNF via ultrasonic-assisted and deprotonation.The POSS-PNF composite paper is fabricated by the method of“suction filtration and hot-pressing”.Because of the uniformly dispersion of NH_(2)-POSS,the POSS-PNF composite paper has a low dielectric constant(ε,2.08)and dielectric loss tangent(tanδ,0.0047),and the wave-transparent coefficient(|T|2)is 96.7%(1 MHz),which is higher than that of PNF paper(95.5%,1 MHz).Additionally,the POSS-PNF composite paper possesses excellent tensile strength of 163.3 MPa,tensile modulus of 6.9 GPa,toughness of 9.1 MJ/m^(3),outstanding flame retardancy and excellent UV aging resistance.According to a simulation of the radome honeycomb panel,POSS-PNF composite paper has low loss and reflections of electromagnetic waves in the X-band(8.4~12.4 GHz),and wide angle of incidence(0°-80°),which favor high|T|2.The results indicate that the POSS-PNF composite paper has excellent potential for applications in the fields of aerospace,wearable flexible electronic devices and 5G communication.
