Electron spin resonance techniques were employed to investigate the effects of the absorbed dose and post-irradiation conditions on the evolution and decay of free-radicals in cross-linked polytetrafluoroethylene(XPTF...Electron spin resonance techniques were employed to investigate the effects of the absorbed dose and post-irradiation conditions on the evolution and decay of free-radicals in cross-linked polytetrafluoroethylene(XPTFE),induced byγ-ray radiation.Chain-end free-radicals,chain alkyl free-radicals,and tertiary alkyl free-radicals were detected when XPTFE was irradiated under Ar atmosphere.The corresponding peroxy free-radicals were formed upon exposure of irradiated XPTFE to air;the freeradicals concentration first increased linearly with increasing absorbed dose and then gradually saturated.The free-radicals yield under air atmosphere was greater than that under Ar,and the peroxy free-radicals were preserved for a relatively long time when irradiated XPTFE was stored under air atmosphere.The chain alkyl free-radicals may be converted to chain end free-radicals byβ-scission,while chain end free-radicals are more sensitive to oxygen than chain alkyl free-radicals.When the annealing temperature was raised above the a-transition temperature of XPTFE,the decay of the free-radicals was greatly affected and accelerated by the motion of the molecules over the long range.展开更多
A coarse-grained molecular dynamics simulation model was developed in this study to investigate the friction process occurring between Fe and polytetrafluoroethylene(PTFE).We investigated the effect of an external loa...A coarse-grained molecular dynamics simulation model was developed in this study to investigate the friction process occurring between Fe and polytetrafluoroethylene(PTFE).We investigated the effect of an external load on the friction coefficient of Fe–PTFE using the molecular dynamics simulations and experimental methods.The simulation results show that the friction coefficient decreases with the external load increasing,which is in a good agreement with the experimental results.The high external load could result in a larger contact area between the Fe and PTFE layers,severer springback as a consequence of the deformed PTFE molecules,and faster motion of the PTFE molecules,thereby affecting the friction force and normal force during friction and consequently varying the friction coefficient.展开更多
Although some progress in plasma modification of the polytetrafluoroethylene(PTFE) surface has been made recently,its adhesion strength still needs to be further improved.In this work,the surface of a PTFE sample was ...Although some progress in plasma modification of the polytetrafluoroethylene(PTFE) surface has been made recently,its adhesion strength still needs to be further improved.In this work,the surface of a PTFE sample was treated with a two-step in-situ method.Firstly,the PTFE surface was treated with capacitively coupled Ar plasma to improve its mechanical interlocking performance;then,Ar+NH_(3)+CH_(4) plasma was used to deposit an a-CNx:H cross-linking layer on the PTFE surface to improve the molecular bonding ability.After treatment,a high specific surface area of 2.20 and a low F/C ratio of 0.32 were achieved on the PTFE surface.Its surface free energy was increased significantly and its maximum adhesion strength reached77.1 N·10 mm^(-1),which is 56% higher than that of the single-step Ar plasma-treated sample and32% higher than that of the single-step Ar+CH_(4)+NH_(3) plasma-treated sample.展开更多
Herein,a novel Janus-structured multifunctional membrane with integrated electromagnetic interference(EMI)shielding and personalized thermal management is fabricated using shear-induced in situ fibrillation and vacuum...Herein,a novel Janus-structured multifunctional membrane with integrated electromagnetic interference(EMI)shielding and personalized thermal management is fabricated using shear-induced in situ fibrillation and vacuum-assisted filtration.Interestingly,within the polytetrafluoroethylene(PTFE)-carbon nanotube(CNT)-Fe_(3)O_(4)layer(FCFe),CNT nanofibers interweave with PTFE fibers to form a stable“silk-like”structure that effectively captures Fe_(3)O_(4)particles.By incorporating a highly conductive MXene layer,the FCFe/MXene(FCFe/M)membrane exhibits excellent electrical/thermal conductivity,mechanical properties,and flame retardancy.Impressively,benefiting from the rational regulation of component proportions and the design of a Janus structure,the FCFe/M membrane with a thickness of only 84.9μm delivers outstanding EMI shielding effectiveness of 44.56 dB in the X-band,with a normalized specific SE reaching 10,421.3 dB cm^(2)g^(-1),which is attributed to the“absorption-reflection-reabsorption”mechanism.Furthermore,the membrane demonstrates low-voltage-driven Joule heating and fast-response photothermal performance.Under the stimulation of a 3 V voltage and an optical power density of 320 mW cm^(-2),the surface temperatures of the FCFe/M membranes can reach up to 140.4 and 145.7℃,respectively.In brief,the FCFe/M membrane with anti-electromagnetic radiation and temperature regulation is an attractive candidate for the next generation of wearable electronics,EMI compatibility,visual heating,thermotherapy,and military and aerospace applications.展开更多
Nitrogen-doped carbon materials encapsulating 3 d transition metals are promising alternatives to replace noble metal Pt catalysts for efficiently catalyzing the oxygen reduction reaction(ORR). Herein, we use cobalt s...Nitrogen-doped carbon materials encapsulating 3 d transition metals are promising alternatives to replace noble metal Pt catalysts for efficiently catalyzing the oxygen reduction reaction(ORR). Herein, we use cobalt substituted perfluorosulfonic acid/polytetrafluoroethylene copolymer and dicyandiamide as the pyrolysis precursor to synthesize nitrogen-doped carbon nanotube(N–CNT) encapsulating cobalt nanoparticles hybrid material. The carbon layers and specific surface area of N–CNT have a critical role to the ORR performance due to the exposed active sites, determined by the mass ratio of the two precursors. The optimum hybrid material exhibits high ORR activity and stability, as well as excellent performance and durability in zinc–air battery.展开更多
Polytetrafluoroethylene(PTFE)is a low-background polymer that is applied to several applications in rare-event detection and underground low-background experiments.PTFE-based electronic substrates are important for re...Polytetrafluoroethylene(PTFE)is a low-background polymer that is applied to several applications in rare-event detection and underground low-background experiments.PTFE-based electronic substrates are important for reducing the detection limit of high-purity germanium detectors and scintillator calorimeters,which are widely applied in dark matter and 0υββdetection experiments.The traditional adhesive bonding method between PTFE and copper is not conducive to working in liquid nitrogen and extremely low-temperature environments.To avoid adhesive bonding,PTFE must be processed for surface metallization owing to the mismatch between the PTFE and copper conductive layer.Low-background PTFE matrix composites(m-PTFE)were selected to improve the electrical and mechanical properties of PTFE by introducing SiO_(2)/TiO_(2) particles.The microstructures,surface elements,and electrical properties of PTFE and m-PTFE were characterized and analyzed following ion implantation.PTFE and m-PTFE surfaces were found to be broken,degraded,and cross-linked by ion implantation,resulting in C=C conjugated double bonds,increased surface energy,and increased surface roughness.Comparably,the surface roughness,bond strength,and conjugated double bonds of m-PTFE were significantly more intense than those of PTFE.Moreover,the interface bonding theory between PTFE and the metal copper foil was analyzed using the direct metallization principle.Therefore,the peel strength of the optimized electronic substrates was higher than that of the industrial standard at extremely low temperatures,while maintaining excellent electrical properties.展开更多
The preparation of graphene(GN)and graphene-intercalated halloysite nanotubes(HNTs)to form nanomaterials was achieved by using HNTs template.As a promising application,a series of the polytetrafluoroethylene(PTFE)nano...The preparation of graphene(GN)and graphene-intercalated halloysite nanotubes(HNTs)to form nanomaterials was achieved by using HNTs template.As a promising application,a series of the polytetrafluoroethylene(PTFE)nanocomposite filled with GN and GN/HNTs at different mass fractions were prepared.The mechanical and friction properties of PTFE nanocomposites depending on the mass fraction of graphene-intercalated HNTs(GN/HNTs)were intensively investigated.The comparison between the effects of GN and GN/HNTs serving as fillers on properties of PTFE was presented.The results showed that in terms of enhancing the tensile strength of PTFE,the enhancement effect of GN is superior to GN/HNTs,and in terms of the elongation at break,the GN/HNTs filler could reserve more toughness than GN.The Young’s modulus of the GN/HNTs incorporated into PTFE is about 1.9 times larger than pure PTFE,and is superior to GN/HNTs.The friction coefficient of PTFE nanocomposites filled with GN and GN/HNTs was slightly higher than pure PTFE and the latter was lower than the former.The volume wear rate of PTFE nanocomposites filled with GN/HNTs was obviously lower than the case with GN,which exhibited the better wear resistance of GN/HNTs used as filler.展开更多
In this paper,sulfonic groups functionalized annealed bio-based carbon microspheres loaded polytetrafluoroethylene(A-BCMSs-SO_(3)H@PTFE)fibers with high activity,high stability,and easy regeneration were successfully ...In this paper,sulfonic groups functionalized annealed bio-based carbon microspheres loaded polytetrafluoroethylene(A-BCMSs-SO_(3)H@PTFE)fibers with high activity,high stability,and easy regeneration were successfully fabricated by a simple method using low-cost raw materials.The characterization results showed that the annealed biomass carbon microspheres derived from waste Camellia oleifera shells were evenly distributed on the polytetrafluoroethylene fibers and the sulfonic groups can be successfully loaded on the surface of annealed biomass carbon microspheres by room temperature sulfonation.Subsequently,the as-prepared A-BCMSs-SO_(3)H@PTFE fibers were applied to the acidcatalyzed synthesis of liquid biofuel 5-ethoxymethylfurfural.The catalytic experiment results indicated that the annealing temperature and time during catalyst preparation have a significant effect on the activity and selectivity of A-BCMSs-SO_(3)H@PTFE fibers.The results of catalytic reaction kinetics showed that the yield of 5-ethoxymethylfurfural can reach more than 60%after 72 h of acid-catalyzed reaction.The stability test showed that the as-prepared A-BCMSs-SO_(3)H@PTFE fibers still maintained a stable acid catalytic activity after four recycles.展开更多
基金supported by the Fund for Strengthening Technical Fields of Basic Plan(No.2021-JCJQ-JJ-0128)National Key R&D Program of China(No.2019YFF0302201)the National Key Laboratory of Materials Behavior and Evaluation Technology in the Space Environment Harbin Institute of Technology(No.6142910190203)。
文摘Electron spin resonance techniques were employed to investigate the effects of the absorbed dose and post-irradiation conditions on the evolution and decay of free-radicals in cross-linked polytetrafluoroethylene(XPTFE),induced byγ-ray radiation.Chain-end free-radicals,chain alkyl free-radicals,and tertiary alkyl free-radicals were detected when XPTFE was irradiated under Ar atmosphere.The corresponding peroxy free-radicals were formed upon exposure of irradiated XPTFE to air;the freeradicals concentration first increased linearly with increasing absorbed dose and then gradually saturated.The free-radicals yield under air atmosphere was greater than that under Ar,and the peroxy free-radicals were preserved for a relatively long time when irradiated XPTFE was stored under air atmosphere.The chain alkyl free-radicals may be converted to chain end free-radicals byβ-scission,while chain end free-radicals are more sensitive to oxygen than chain alkyl free-radicals.When the annealing temperature was raised above the a-transition temperature of XPTFE,the decay of the free-radicals was greatly affected and accelerated by the motion of the molecules over the long range.
基金Project supported by the National Natural Science Foundation of China(Grant No.51605418)the Natural Science Foundation of Hebei Province,China(Grant Nos.E2016203206 and E2019203033)。
文摘A coarse-grained molecular dynamics simulation model was developed in this study to investigate the friction process occurring between Fe and polytetrafluoroethylene(PTFE).We investigated the effect of an external load on the friction coefficient of Fe–PTFE using the molecular dynamics simulations and experimental methods.The simulation results show that the friction coefficient decreases with the external load increasing,which is in a good agreement with the experimental results.The high external load could result in a larger contact area between the Fe and PTFE layers,severer springback as a consequence of the deformed PTFE molecules,and faster motion of the PTFE molecules,thereby affecting the friction force and normal force during friction and consequently varying the friction coefficient.
文摘Although some progress in plasma modification of the polytetrafluoroethylene(PTFE) surface has been made recently,its adhesion strength still needs to be further improved.In this work,the surface of a PTFE sample was treated with a two-step in-situ method.Firstly,the PTFE surface was treated with capacitively coupled Ar plasma to improve its mechanical interlocking performance;then,Ar+NH_(3)+CH_(4) plasma was used to deposit an a-CNx:H cross-linking layer on the PTFE surface to improve the molecular bonding ability.After treatment,a high specific surface area of 2.20 and a low F/C ratio of 0.32 were achieved on the PTFE surface.Its surface free energy was increased significantly and its maximum adhesion strength reached77.1 N·10 mm^(-1),which is 56% higher than that of the single-step Ar plasma-treated sample and32% higher than that of the single-step Ar+CH_(4)+NH_(3) plasma-treated sample.
基金support from the National Natural Science Foundation of China(NSFC,Grant No.52175341)Shandong Provincial Natural Science Foundation(Grant No.ZR2022JQ24)Funding Project of Jinan City’s New Twenty Items for Colleges and Universities(Grant No.202333038).
文摘Herein,a novel Janus-structured multifunctional membrane with integrated electromagnetic interference(EMI)shielding and personalized thermal management is fabricated using shear-induced in situ fibrillation and vacuum-assisted filtration.Interestingly,within the polytetrafluoroethylene(PTFE)-carbon nanotube(CNT)-Fe_(3)O_(4)layer(FCFe),CNT nanofibers interweave with PTFE fibers to form a stable“silk-like”structure that effectively captures Fe_(3)O_(4)particles.By incorporating a highly conductive MXene layer,the FCFe/MXene(FCFe/M)membrane exhibits excellent electrical/thermal conductivity,mechanical properties,and flame retardancy.Impressively,benefiting from the rational regulation of component proportions and the design of a Janus structure,the FCFe/M membrane with a thickness of only 84.9μm delivers outstanding EMI shielding effectiveness of 44.56 dB in the X-band,with a normalized specific SE reaching 10,421.3 dB cm^(2)g^(-1),which is attributed to the“absorption-reflection-reabsorption”mechanism.Furthermore,the membrane demonstrates low-voltage-driven Joule heating and fast-response photothermal performance.Under the stimulation of a 3 V voltage and an optical power density of 320 mW cm^(-2),the surface temperatures of the FCFe/M membranes can reach up to 140.4 and 145.7℃,respectively.In brief,the FCFe/M membrane with anti-electromagnetic radiation and temperature regulation is an attractive candidate for the next generation of wearable electronics,EMI compatibility,visual heating,thermotherapy,and military and aerospace applications.
基金financial support from the Ministry of Science and Technology of China(Grants 2016YFB0600901 and 2013CB933100)the National Natural Science Foundation of China(Grants 21573222 and 91545202)+1 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB17020200)financial support from CAS Youth Innovation Promotion(Grant No.2015145)
文摘Nitrogen-doped carbon materials encapsulating 3 d transition metals are promising alternatives to replace noble metal Pt catalysts for efficiently catalyzing the oxygen reduction reaction(ORR). Herein, we use cobalt substituted perfluorosulfonic acid/polytetrafluoroethylene copolymer and dicyandiamide as the pyrolysis precursor to synthesize nitrogen-doped carbon nanotube(N–CNT) encapsulating cobalt nanoparticles hybrid material. The carbon layers and specific surface area of N–CNT have a critical role to the ORR performance due to the exposed active sites, determined by the mass ratio of the two precursors. The optimum hybrid material exhibits high ORR activity and stability, as well as excellent performance and durability in zinc–air battery.
基金supported by the National Natural Science Foundation of China(Nos.12141502 and 12005017).
文摘Polytetrafluoroethylene(PTFE)is a low-background polymer that is applied to several applications in rare-event detection and underground low-background experiments.PTFE-based electronic substrates are important for reducing the detection limit of high-purity germanium detectors and scintillator calorimeters,which are widely applied in dark matter and 0υββdetection experiments.The traditional adhesive bonding method between PTFE and copper is not conducive to working in liquid nitrogen and extremely low-temperature environments.To avoid adhesive bonding,PTFE must be processed for surface metallization owing to the mismatch between the PTFE and copper conductive layer.Low-background PTFE matrix composites(m-PTFE)were selected to improve the electrical and mechanical properties of PTFE by introducing SiO_(2)/TiO_(2) particles.The microstructures,surface elements,and electrical properties of PTFE and m-PTFE were characterized and analyzed following ion implantation.PTFE and m-PTFE surfaces were found to be broken,degraded,and cross-linked by ion implantation,resulting in C=C conjugated double bonds,increased surface energy,and increased surface roughness.Comparably,the surface roughness,bond strength,and conjugated double bonds of m-PTFE were significantly more intense than those of PTFE.Moreover,the interface bonding theory between PTFE and the metal copper foil was analyzed using the direct metallization principle.Therefore,the peel strength of the optimized electronic substrates was higher than that of the industrial standard at extremely low temperatures,while maintaining excellent electrical properties.
基金This work was funded by the Talent Introduction Fund of Yangzhou University(2012),the Zhenjiang High Technology Research Institute of Yangzhou University(2017),the Key Research Project-Industry Foresight and General Key Technology of Yangzhou(YZ2015020)the Innovative Talent Program of Green Yang Golden Phoenix(yzlyjfjh2015CX073)+3 种基金the Yangzhou Social Development Project(YZ2016072)the nJiangsu Province Six Talent Peaks Project(2014-XCL-013)the Jiangsu Industrial-Academic-Research Prospective Joint Project(BY2016069-02)The authors also acknowledge the Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions and the Top-notch Academic Programs Project of Jiangsu Higher Education Institutions(PPZY2015B112).The data of this paper originated from the Test Center of Yangzhou University.
文摘The preparation of graphene(GN)and graphene-intercalated halloysite nanotubes(HNTs)to form nanomaterials was achieved by using HNTs template.As a promising application,a series of the polytetrafluoroethylene(PTFE)nanocomposite filled with GN and GN/HNTs at different mass fractions were prepared.The mechanical and friction properties of PTFE nanocomposites depending on the mass fraction of graphene-intercalated HNTs(GN/HNTs)were intensively investigated.The comparison between the effects of GN and GN/HNTs serving as fillers on properties of PTFE was presented.The results showed that in terms of enhancing the tensile strength of PTFE,the enhancement effect of GN is superior to GN/HNTs,and in terms of the elongation at break,the GN/HNTs filler could reserve more toughness than GN.The Young’s modulus of the GN/HNTs incorporated into PTFE is about 1.9 times larger than pure PTFE,and is superior to GN/HNTs.The friction coefficient of PTFE nanocomposites filled with GN and GN/HNTs was slightly higher than pure PTFE and the latter was lower than the former.The volume wear rate of PTFE nanocomposites filled with GN/HNTs was obviously lower than the case with GN,which exhibited the better wear resistance of GN/HNTs used as filler.
基金financially supported by the National Natural Science Foundation of China(21966023,21665018)the Natural Science Foundation of Jiangxi Province,China(20171ACB21035)
文摘In this paper,sulfonic groups functionalized annealed bio-based carbon microspheres loaded polytetrafluoroethylene(A-BCMSs-SO_(3)H@PTFE)fibers with high activity,high stability,and easy regeneration were successfully fabricated by a simple method using low-cost raw materials.The characterization results showed that the annealed biomass carbon microspheres derived from waste Camellia oleifera shells were evenly distributed on the polytetrafluoroethylene fibers and the sulfonic groups can be successfully loaded on the surface of annealed biomass carbon microspheres by room temperature sulfonation.Subsequently,the as-prepared A-BCMSs-SO_(3)H@PTFE fibers were applied to the acidcatalyzed synthesis of liquid biofuel 5-ethoxymethylfurfural.The catalytic experiment results indicated that the annealing temperature and time during catalyst preparation have a significant effect on the activity and selectivity of A-BCMSs-SO_(3)H@PTFE fibers.The results of catalytic reaction kinetics showed that the yield of 5-ethoxymethylfurfural can reach more than 60%after 72 h of acid-catalyzed reaction.The stability test showed that the as-prepared A-BCMSs-SO_(3)H@PTFE fibers still maintained a stable acid catalytic activity after four recycles.
