Co-reporter:Pingping Yu, Yingzhi Li, Xinyi Yu, Xin Zhao, Lihao Wu, and Qinghua Zhang
Langmuir September 24, 2013 Volume 29(Issue 38) pp:12051-12058
Publication Date(Web):September 24, 2013
DOI:10.1021/la402404a
A combination of vertical polyaniline (PANI) nanowire arrays and nitrogen plasma etched carbon fiber cloths (eCFC) was fabricated to create 3D nanostructured PANI/eCFC composites. The small size of the highly ordered PANI nanowires can greatly reduce the scale of the diffusion length, allowing for the improved utilization of electrode materials. A two-electrode flexible supercapacitor based on PANI/eCFC demonstrates a high specific capacitance (1035 F g–1 at a current density of 1 A g–1), good rate capability (88% capacity retention at 8 A g–1), and long-term cycle life (10% capacity loss after 5000 cycles). The lightweight, low-cost, flexible composites are promising candidates for use in energy storage device applications.
Co-reporter:Pingping Yu, Xin Zhao, Yingzhi Li, Qinghua Zhang
Applied Surface Science 2017 Volume 393() pp:37-45
Publication Date(Web):30 January 2017
DOI:10.1016/j.apsusc.2016.09.119
Highlights
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Hierarchical porous graphene foam prepared by templating and embossing method..
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Vertically PANI nanowires aligned on interconnected porous graphene sheets.
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The fRGO-F/PANI device exhibited 939 F g−1 at 1 A g−1.
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ED and PD of fRGO-F/PANI device was 20.9 Wh kg−1 and 103.2 kW kg−1.
Co-reporter:Feng Gan;Jie Dong;Wenjun Tan;Dianbo Zhang;Xin Zhao
Journal of Materials Science 2017 Volume 52( Issue 16) pp:9895-9906
Publication Date(Web):25 April 2017
DOI:10.1007/s10853-017-1099-1
A series of co-polyimides (co-PIs) containing pyrimidine rings were synthesized by reacting the self-synthesized diamine 2,5-bis(4-aminophenyl)-pyrimidine (PRM) with commercial 4,4’-diaminodiphenyl ether (ODA) and aromatic 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA). A series of co-PI fibers were produced using a two-step wet-spinning method, including extrusion, coagulation, washing, drying, thermal imidization and hot-drawing processes. Orientation structures of the precursor co-PAA fibers formed in the wet-spinning process, and their effects on the thermomechanical properties of the as-spun co-PI fibers were discussed. An interesting phenomenon has been found that glass transition temperatures (Tgs) of as-spun co-PI fibers decreased with increasing orientation factors, which was explained based on some previous works. Two-dimensional wide-angle X-ray diffraction spectra of the final co-PI fibers showed that samples with higher PRM contents show highly oriented and well-ordered crystalline structures, which account for the enhanced mechanical properties when incorporating PRM moieties. The co-PI fiber with the PRM/ODA molar ratio of 6/4 showed an optimum tensile strength and modulus of 3.1 and 90 GPa, respectively, showing a great potential in light advanced composites.
Co-reporter:Chaoyi Chen, Xin Zhao, Hai-Bei Li, Feng Gan, Junxian Zhang, Jie Dong, Qinghua Zhang
Electrochimica Acta 2017 Volume 229(Volume 229) pp:
Publication Date(Web):1 March 2017
DOI:10.1016/j.electacta.2017.01.172
Two naphthalene-based polyimide derivatives are fabricated through a facile condensation polymerization by 1,4,5,8-naphthalenetetracarboxylic dianhydride (NT) with different two diamines, e.g., urea and ethylenediamine, respectively. Their structures with morphologies are studied and the electrochemical properties are investigated as cathode materials for rechargeable lithium-ion batteries (LIBs). By comparison to NT, the polymers with carbonyl functionalities as electroactive groups show improved stability in electrolyte. The obtained derivative (NOP) from NT and urea with more redox active sites exhibits a higher discharge capacity and better rate performance, which might be attributed to its relatively lower molecule weight of the framework and the introduction of additional carbonyl group inherited from urea unit. It displays an average reversible capacity of 174.5 mAh g−1 at 20 mA g−1 and a good rate performance with a high value of 133.5 mAh g−1 at 500 mA g−1. With an optimized polymerization conditions, its capacity could remain 153 mAh g−1 after 60 cycles of charge-discharge processes at 50 mA g−1, making it a potential material for greener and sustainable electrode for electrochemical storage devices.
Co-reporter:Jie Dong;Cairan Yang;Yang Cheng;Tingting Wu;Xin Zhao;Qinghua Zhang
Journal of Materials Chemistry C 2017 vol. 5(Issue 11) pp:2818-2825
Publication Date(Web):2017/03/16
DOI:10.1039/C7TC00196G
High-performance fibers with a low dielectric constant and good mechanical properties as well as excellent thermal stability are in demand for the next generation of advanced radar-wave-transparent composites. In this study, an effective method is proposed to prepare amine-functionalized hyperbranched polysiloxane (NH2-HBPSi) reinforced polyimide (PI) composite fibers with exceptional dielectric behavior, mechanical and thermal properties. The amino-functionalized NH2-HBPSi were grafted to PI chains during in situ polymerization, promoting the uniform dispersion of the NH2-HBPSi nanoparticles and forming strong interfacial interactions between NH2-HBPSi and the PI matrix. The composite fiber containing 10 wt% NH2-HBPSi exhibited a 10% and 26% increase in tensile strength and modulus compared to the pure PI fiber. Owing to the dielectric confinement effect from NH2-HBPSi, the dielectric constants of the NH2-HBPSi/PI composites were reduced drastically and the value could reach as low as 2.2 at 108 Hz. The composite fiber demonstrated better specific strength, specific modulus and lower dielectric constant than the commonly used E-glass, S-glass and quartz fibers. These results provide useful information for designing molecular architecture and fabricating high-performance reinforcing fibers in the future radomes.
Co-reporter:Yang Cheng, Jie Dong, Cairan Yang, Tingting Wu, Xin Zhao, Qinghua Zhang
Polymer 2017 Volume 133(Volume 133) pp:
Publication Date(Web):20 December 2017
DOI:10.1016/j.polymer.2017.11.015
•Series of poly(benzobisoxazole-co-imide) fibers containing plank-shaped benzobisoxazole moiety have been successfully prepared.•The benzobisoxazole moiety is beneficial for highly oriented and periodic lamellar crystals in the resulted PBOI fibers.•Maximum improvement of 153% in tensile strength and 282% in modulus were achieved by incorporating the benzobisoxazole units.•Tg of the resulted PBOI fibers increased as high as 30 °C.A novel heterocyclic and plank-shape diamine monomer, 2,6-(4,4′-diaminodiphenyl) benzo[1,2-d:5,4-d'] bisoxazole (PBOA), was successfully synthesized from readily available compounds of 4,6-diaminoresorcinol dihydrochloride (DAR) and p-aminobenzoic acid (PABA). A series of poly(benzobisoxazole-co-imide) (PBOI) fibers based on 3,3′,4,4′-biphenyltetracarboxylic anhydride (BPDA), 4,4′-diaminodiphenyl ether (ODA) and PBOA were fabricated via a two-step wet-spinning method. PBOA was characterized in detail, and the effect of the monomer in the polymer backbones on the fibers' microstructure and properties were described. 2D wide-angle X-ray diffraction indicated that the incorporated PBOA in the BPDA-ODA polyimide backbone is beneficial for forming well-defined crystalline regions in the resulted fibers during the thermal stretching process and significantly improving the crystallinity and crystal orientation of the drawn PBOI fibers. Small-angle X-ray scattering patterns of the drawn PBOI fibers suggested the presence of typical periodic lamellar crystal in the fibers. It is shown that increasing PBOA contents will result in higher values of the long period (L) and the lamellar thickness (lC). Maximum improvements of 153% in tensile strength and 282% in modulus were achieved when increasing the molar content of PBOA in the mixed diamine from 10 mol% to 50 mol%. Correspondingly, the temperature at the maximum degradation rate (Td-max) and glass transition temperature (Tg) of resulted PBOI fibers in nitrogen increased by 28 and 30 °C, respectively, making these novel polymeric fibers as good reinforcements in fabricating advanced composites.Download high-res image (262KB)Download full-size image
Co-reporter:Junxian Zhang, Xin Zhao, Zilong Huang, Ting Xu, Qinghua Zhang
Carbon 2016 Volume 107() pp:844-851
Publication Date(Web):October 2016
DOI:10.1016/j.carbon.2016.06.064
Flexible solid-state fiber supercapacitors are fabricated by directly electrodepositing ultrathin manganese dioxide (MnO2) nanosheets on commercial carbon fiber yarns. The deposition process is well controlled and the composition of MnO2 in fiber electrodes is optimized to enable fiber SCs to possess high specific capacitance. Conductive carbon fibers concurrently serve as current collectors in fiber SCs and as flexible substrates for the deposition of MnO2. A single MnO2/CFs fiber electrode exhibits a specific volumetric capacitance of 58.7 F cm−3 with a specific gravimetric capacitance of 428 F g−1 based on the MnO2 mass. Two hybrid carbon fiber electrodes are assembled together in parallel with polyvinyl pyrrolidone/Na2SO4 gel, which is used as both an electrolyte and a separator. The assembled flexible device exhibits a high volumetric energy density of 3.8 mW h cm−3 at a power density of 89 mW cm−3 with a good flexibility (CV curves almost unchanged after 2000 bending times) and a superior long cycle stability (an 85.8% capacitance retention after 10000 cycles). Moreover, the integrated SCs could power a commercial light-emitting-diode (LED), demonstrating its strong potential for the practical applications of flexible energy storage devices.
Co-reporter:Jie Dong, Yuting Fang, Feng Gan, Jinyin An, Xin Zhao, Qinghua Zhang
Composites Science and Technology 2016 Volume 135() pp:137-145
Publication Date(Web):27 October 2016
DOI:10.1016/j.compscitech.2016.09.021
Carbon nanotubes (CNTs) have been gained attention and interest to be as ideal reinforcement fillers due to their exceptional theoretical mechanical properties for a long time. To date, the reinforcing effect of the CNTs in most composite systems is still not satisfied. In the present study, by incorporating a novel NH2-MWCNTs/NMP suspension into the polyimide matrix in situ polymerization, a series of PI/NH2-MWCNTs composite fibers have been fabricated using wet-spinning technique. Detailed studies based on different spectroscopic characterizations suggested that there exist multiple interfacial interactions between NH2-MWCNTs and polyimides (PIs) including the hydrogen bonding and π-π interaction. Wide-angle X-ray scattering measurements revealed the evolution of the aggregation structure of these composite fibers during heat-drawing process, and the results illustrated that the incorporated amino functionalized CNTs showed beneficial effects on the packing and orientation of PI molecular chains. Attributed to the above advantages, the resulting composite fiber containing 0.4 wt% NH2-MWCNTs presented a tensile strength of 2.41 GPa (approximately a 47% increase over neat PI fiber), and the modulus of 99 GPa (27% raises compared with neat PI fiber). Meanwhile, dimensional stability of the PI fibers also has been improved by this effective approach.
Co-reporter:Ting Xu, Xin Zhao, Junxian Zhang, Jie Dong, Qinghua Zhang
Applied Surface Science 2016 Volume 369() pp:207-214
Publication Date(Web):30 April 2016
DOI:10.1016/j.apsusc.2016.02.005
Highlights
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PS/PDA with well-defined core/shell structures was prepared in aqueous solution.
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Au NPs were coated on PS/PDA by in-situ reduction and self-assembly approach.
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PS/PDA/Au had homogeneous and dense Au coatings with different shape.
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Hierarchical spheres exhibited a well-defined core/shell structure maintaining the spherical morphology.
Co-reporter:Shihua Wang;Jie Dong;Zhentao Li;Yuan Xu;Wenjun Tan;Xin Zhao ;Qinghua Zhang
Journal of Applied Polymer Science 2016 Volume 133( Issue 31) pp:
Publication Date(Web):
DOI:10.1002/app.43727
ABSTRACT
Polyimide (PI) fibers with enhanced mechanical properties and high thermal and dimensional stability were prepared via a two-step dry-spinning process through the introduction of 3,3′,4,4′-biphenyl tetracarboxylic dianhydride (BPDA) containing biphenyl units into rigid homopolyimide of pyromellitic dianhydride (PMDA) and 4,4′-oxydianiline. The attenuated total reflectance–Fourier transform infrared spectra results imply that the incorporated BPDA moieties accelerate the imidization process and increase the imidization degree (ID) of the precursor fibers; this was attributed to the increased molecular mobility of the polymer chains. Two-dimensional wide-angle X-ray diffraction spectra indicated that the prepared PI fibers possessed a well-defined crystal structure and polymer chains in the crystalline region were highly oriented along the fiber axis. The PI fiber, with the molar ratio of PMDA/BPDA being 7/3, showed optimum tensile strength and modulus values of 8.55 and 73.21 cN/dtex, respectively; these were attributed to the high IDs and molecular weights. Meanwhile, the PI fibers showed better dimensional stability than the commercial P84 fiber, and this is beneficial for its security applications. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43727.
Co-reporter:Ting Xu, Yalong Qi, Xin Zhao, Qinghua Zhang
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2016 Volume 498() pp:139-145
Publication Date(Web):5 June 2016
DOI:10.1016/j.colsurfa.2016.03.034
•PS/PDA with well-defined core/shell structures was prepared in aqueous solution.•Au NPs were coated on PS/PDA by the interaction between PDA and Au NPs.•PS/PDA/Au had homogeneous and dense Au coatings.•Green approach can be extened to fabricate different metal/polymer.Hierarchical organic/inorganic composites have been extensively studied, and considerable efforts have been focused on the assemble behaviors of metal nanoparticles (NPs) on soft templates. In this report, a ternary hierarchical nanostructure was successfully fabricated by assembling Au NPs on polystyrene (PS)/Polydopamine (PDA) hybrid microspheres. The ultrathin PDA coatings were firstly synthesized on PS microspheres by pH-induced polymerization of dopamine. Enough amino and hydroxyl groups from PDA were beneficial for Au NPs assembling on the polymer spheres by means of electrostatic interactions. Finally, the as-prepared PS/PDA microspheres serve as templates to immobilize Au nanoparticles on the surface of the composite spheres to form PS/PDA/Au microspheres with uniform size. The isolated products demonstrated a well-defined core/shell/shell nanostructure without sacrificing the spherical PS morphology. Field emission scanning electron microscopy and transmission electronic microscopy verified these hierarchical structures with the PDA ultrathin film connecting between the inner PS core and the outer Au NPs coating. X-ray diffraction and X-ray photoelectron spectroscopy confirmed the existence of PDA and Au coatings on the surface of the composite particles. This green process for preparation of metal-coated polymer spheres supplies potential applications in biosensors, electronics and medical diagnosis.
Co-reporter:Chaoqing Yin, Jie Dong, Dianbo Zhang, Jinyou Lin, Qinghua Zhang
European Polymer Journal 2015 Volume 67() pp:88-98
Publication Date(Web):June 2015
DOI:10.1016/j.eurpolymj.2015.03.028
•Novel polyimide fibers containing benzimidazole and benzoxazole units were prepared.•Marked changes occur on crystal behavior with tiny chemical structure difference.•Mechanical and hydrophobic properties of the PI fibers have been greatly enhanced.A series of rigid-rod co-polyimides (co-PI) containing benzimidazole and benzoxazole moieties were synthesized by the reaction of 2-(4-aminophenyl)-5-aminobenzimidazole (BIA) and 5-amino-2-(4-aminobenzene)benzoxazole (BOA) with 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA). The corresponding co-PI fibers with various diamine ratios were prepared by the two-step wet-spinning process. The small chemical structure difference between benzimidazole and benzoxazole moieties leads to unexpected great changes on the aggregation structures and properties of the obtained fibers. The two-dimensional wide-angle X-ray diffraction (WAXD) spectra imply that the co-PI fibers containing more than 70% molar ratio of BIA show better-defined ordered crystal structures, while for those samples with more BOA contents, a new ordered lateral packing occurs. Meanwhile, the equatorial scattering streaks in the small-angle X-ray scattering (SAXS) patterns for the co-PI fibers suggest the presence of microvoids, whose sizes were evaluated by means of Guinier and Ruland’s method. The optimum tensile strength and modulus of co-PI fibers are as high as 1.74 and 74.4 GPa, respectively, at the BIA/BOA molar ratio of 7/3. Besides, the co-PI fibers exhibit excellent thermal and thermo-oxidative stabilities due to the rigid molecular chains. The introduction of BOA units in the polymer backbones have apparently improved the hydrophobic properties of PI fibers.
Co-reporter:Xin Zhao, Chaoyi Chen, Zilong Huang, Lei Jin, Junxian Zhang, Yingzhi Li, Lili Zhang and Qinghua Zhang
RSC Advances 2015 vol. 5(Issue 81) pp:66311-66317
Publication Date(Web):29 Jul 2015
DOI:10.1039/C5RA10916G
Two types of ternary composites were fabricated by reversing the deposition sequence of polyaniline (PANI) and MnO2 layers on plasma treated carbon cloth (m-CC), i.e., PANI@MnO2@m-CC and MnO2@PANI@m-CC. By comparison, PANI@MnO2@m-CC displayed a unique porous structure and possessed a better electrochemical performance than that of MnO2@PANI@m-CC. The morphological transformation of MnO2 petals into nanoparticles while anchoring PANI nanorods increases the interactions between the two pseudoactive materials. An asymmetric supercapacitor was fabricated by using PANI@MnO2@m-CC as the positive electrode and activated microwave exfoliated graphite oxide (‘a-MEGO’)@m-CC as the negative electrode. The asymmetric supercapacitor showed a maximum energy density of 33.9 W h kg−1 (at a power density of 319.0 W kg−1) and power density of 17.2 kW kg−1 (at an energy density of 14.3 W h kg−1) at an operating voltage of 2.0 V, suggesting PANI@MnO2@m-CC is a promising electrode candidate for supercapacitors.
Co-reporter:Chaoqing Yin;Zixin Zhang;Jie Dong ;Qinghua Zhang
Journal of Applied Polymer Science 2015 Volume 132( Issue 7) pp:
Publication Date(Web):
DOI:10.1002/app.41474
ABSTRACT
A series of co-polyimide fibers were prepared by thermal imidization of copolyamic acids derived from 3,3′,4,4′-biphenyltertracarboxylic dianhydride (BPDA) and pyromellitic dianhydride (PMDA) in various molar ratios with 2-(4-aminophenyl)−5-aminobenzimidazole (BIA). The dynamic mechanical behaviors of these polyimide (PI) fibers revealed that the glass transition temperature (Tg) was significantly improved upon increasing PMDA content. Heat-drawing process led to dramatic change on the glass transition behavior of BPDA/BIA system, but had a small impact on BPDA/PMDA/BIA co-polyimide fibers. This difference for PI fibers is attributed to the different degree of ordered structure of the fibers affected by heat-drawing. The incorporation of PMDA obviously improved the dimensional stability against high temperature, due to the restricted movement of polymer chains. In addition, the obtained fibers show excellent mechanical and thermal properties because of the strong hydrogen bonding due to the incorporation of benzimidazole moieties. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41474.
Co-reporter:Chaoqing Yin;Jie Dong;Zixin Zhang;Qinghua Zhang;Jinyou Lin
Journal of Polymer Science Part B: Polymer Physics 2015 Volume 53( Issue 3) pp:183-191
Publication Date(Web):
DOI:10.1002/polb.23606
ABSTRACT
Co-polyimide (co-PI) fibers with outstanding mechanical properties were fabricated via thermal imidization of polyamic acids, derived from a new design of combining the amide and benzimidazole diamine monomers, 4-amino-N-(4-aminophenyl)benzamide (DABA) and 2-(4-aminophenyl)-5-aminobenzimidazole (BIA), with 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA). The crystalline structure and micromorphology of the prepared co-PI fibers were investigated by synchrotron wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS). The two-dimensional WAXD spectra imply that the co-PI fibers possess a structure between smectic-like and three-dimensionally ordered crystalline phase, and all the obtained fibers are highly oriented along the fiber axis. SAXS patterns exhibit a pair of meridional scattering streaks for the homo-PI (BPDA/BIA) fiber, suggesting the presence of periodic lamellar structure. The incorporation of DABA into the polymer chains destroyed the lamellar structure but led to smaller size of microvoids upon increasing DABA moiety, based on SAXS analysis. The co-PI fibers, with the molar ratio of BIA/DABA being 7/3, exhibited the optimum tensile strength and modulus of 1.96 and 108.3 GPa, respectively, attributed to the well-defined ordered and dense structure. The chemical structure and molecular packing significantly affected the thermal stability of fibers, resulting in the different glass transition temperatures (Tg) from 350 to 380 °C. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 183–191
Co-reporter:Gang Deng;Shihua Wang;Xin Zhao ;Qinghua Zhang
Polymer Engineering & Science 2015 Volume 55( Issue 9) pp:2148-2155
Publication Date(Web):
DOI:10.1002/pen.24057
As one type of high performance fibers, polyimide fibers can be prepared from polyamic acid (PAA) solution by dry-spinning technology. The transformation from the precursor of polyamic acid to polyimides via thermal cyclization reaction in the dry-spinning process is a main distinguishing feature, which is very different from other fibers produced by dry-spinning such as cellulose acetate fiber and polyurethane fiber. In this report, the dry-spinning formation of polyimide fibers with trilobal cross section from PAA solution in N,N-dimethylacetamide is simulated via a one-dimensional model based on a viscoelastic constitutive equation, combined with profile degree equation of cross section and imidization kinetics equation. The glass transition temperature, imidization degree and profile degree of the filament along the spinline are predicted by the model, as well as relative parameters such as solvent mass fraction and temperature. As a simulated result, solidification of polyimide fibers take place about 150 cm from the spinneret which is farther than for cellulose acetate fiber (70 cm). Moreover, the final profile degree of fiber is affected by many spinning parameters, such as spinning temperature, surface tension, spinning solution concentration, major, and minor axis length of the spinneret hole. POLYM. ENG. SCI., 55:2148–2155, 2015. © 2015 Society of Plastics Engineers
Co-reporter:Yingtao Chen;Qinghua Zhang
Journal of Polymer Research 2015 Volume 22( Issue 5) pp:
Publication Date(Web):2015 May
DOI:10.1007/s10965-015-0726-2
A new aromatic heterocyclic diamine monomer, 2,2-bis (4’-aminophenyl)- 5,5-bi-1H-benzimidazole (BAPBBI), was synthesized via a one-step reaction of 3,3’,4,4’-biphenyltetramine and p-aminobenzoic acid in polyphosphoric acids with the high yield and purity. FTIR, 1H NMR, 13C NMR, mass spectra and elemental analysis were employed to confirm the chemical structures. A series of copolyimide films containing the bi-benzimidazole moieties were prepared by the reaction of pyromellitic dianhydride (PMDA), 4,4’-oxydianiline (ODA) and BAPBBI with various molar ratios. The combination of polybenzimidazole and polyimide by introducing BAPBBI into the main chains brings the highly rigid structure and the enhanced macromolecular interactions, resulting in the enhancement in the thermal stability and the mechanical properties. For instance, these polyimides are endowed with a higher glass transition temperature of 408–438 °C and an initial thermal decomposition of 550–580 °C. They exhibit a strong tensile strength of 123–233 MPa, and a tensile moduli of 2.66–12.84 GPa without post stretching. Meanwhile the stretched films at 450 °C exhibited the enhanced mechanical properties with the tensile strength of 195–554 MPa and the tensile modulus of 4.69–38.57 GPa.
Co-reporter:Chaoqing Yin;Jie Dong;Zhentao Li;Zixin Zhang;Qinghua Zhang
Polymer Bulletin 2015 Volume 72( Issue 5) pp:1039-1054
Publication Date(Web):2015 May
DOI:10.1007/s00289-015-1324-5
Theoretical ternary phase diagrams in good agreement with experiment cloud point data of water/N,N-dimethylacetamide (DMAc)/polyamic acid (PAA), ethylene glycol (EG)/DMAc/PAA and ethanol/DMAc/PAA systems were constructed based on the extended Flory–Huggins theory of the polymer solutions. Binary interaction parameters were calculated and optimized accurately to construct the theoretical phase diagrams. The surface and cross-section microstructures of the as-spun fibers were analyzed by the dual diffusion theory and phase separation mechanism based on the ternary diagrams. With the concentration of DMAc in coagulation increasing, sponge-like and less skin–core
structures with rougher surface were observed for fibers prepared from water/DMAc/PAA system, as the homogeneous region and metastable two-phase region enlarged in this case and it favors the nucleation and growth demixing mechanism. Further increasing concentration of DMAc in coagulation resulted in the formation of porous structures. On the other aspect, fibers prepared from EG/DMAc/PAA system exhibited a noncircular cross-section and an obvious skin–core structure, while circular cross-section and dense structures were obtained in fibers from ethanol/DMAc/PAA system. The results are in accordance with predicted ones based on theoretical ternary phase diagram.
Co-reporter:Chaoqing Yin, Jie Dong, Wenjun Tan, Jinyou Lin, Dajun Chen, Qinghua Zhang
Polymer 2015 Volume 75() pp:178-186
Publication Date(Web):28 September 2015
DOI:10.1016/j.polymer.2015.08.025
•Polyimide fibers containing benzimidazole under various draw ratios were prepared.•Microstructure of fibers treated in both static and drawing conditions was studied.•Crystallization and orientation of fibers were improved with heat stretching.•The drawn fibers displayed enhanced mechanical and thermal properties.Structural evolution induced by cyclization reaction and heat-drawing of polyimide (PI) fibers containing the 2-(4-aminophenyl)-5-aminobenzimidazole moiety was studied by means of synchrotron radiation wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS). WAXD results indicate that the drawing process induces an increase in the crystallinity and crystal orientation of PI fibers, leading to improvement of the mechanical properties. SAXS results reveal that lamellar structures formed upon heat-drawing. A mechanism for strain-induced phase transitions has been proposed to correlate the structural information with WAXD/SAXS patterns. Dynamic mechanical analysis (DMA) of the obtained fibers shows an obvious α relaxation process above room temperature, which is found to be crystallinity dependent, the intensity of tan δ decreases significantly after heat-drawing. The stretched fiber exhibits a negative value of the linear coefficient of thermal expansion (CTE), while the unstretched PI fiber exhibits a positive value. Moreover, heat-drawing increases the thermal stability of the prepared fibers. These improvements may be related to the aggregation structure of the high performance fibers.
Co-reporter:Pingping Yu, Xin Zhao, Zilong Huang, Yingzhi Li and Qinghua Zhang
Journal of Materials Chemistry A 2014 vol. 2(Issue 35) pp:14413-14420
Publication Date(Web):04 Jul 2014
DOI:10.1039/C4TA02721C
Free-standing three-dimensional hierarchical porous reduced graphene oxide foam (RGO-F) was first fabricated by a “dipping and dry” method using nickel foam as a template. Three-dimensional (3D) RGO-F with high conductivity provides large porosity compared to conventional graphene films. Polyaniline (PANI) nanowire arrays aligned on the foam (RGO-F/PANI) were synthesized by in situ polymerization. A symmetric supercapacitor with high energy and power densities was fabricated using a RGO-F/PANI electrode. The highly flexible RGO-F/PANI foam can directly serve as an electrode with no binders or conductive additives. Owing to the well-ordered porous structure and high electrochemical performance of the RGO-F/PANI composite, the symmetric device exhibits high specific capacitance (790 F g−1) and volumetric capacitance (205.4 F cm−3), and it shows a maximum energy density and power density of 17.6 W h kg−1 and 98 kW kg−1. Moreover, the device possesses an excellent cycle life with 80% capacitance retention after 5000 cycles.
Co-reporter:Jie Dong;Chaoqing Yin;Zixin Zhang;Xinyu Wang;Haibei Li;Qinghua Zhang
Macromolecular Materials and Engineering 2014 Volume 299( Issue 10) pp:1170-1179
Publication Date(Web):
DOI:10.1002/mame.201400081
Rigid-rod polyimides (PI) containing benzimidazole moieties were synthesized and spun into fibers by a wet-spinning method. The resultant fibers exhibited an optimum tensile strength of 2.15 GPa and an initial modulus of 105 GPa with a low elongation of 2.2%. The PI fibers consisting of various ratios of 2,2′-bis(trifluoromethyl)-4,4′-diaminobiphenyl (TFMB) and 2-(4-aminophenyl)-5-aminobenzimidazole (BIA) were investigated by Fourier transform infrared spectroscopy and two-dimensional wide angle X-ray diffraction (2D WAXD). Direct evidence of hydrogen-bonding involving the NH groups of BIA and the imide carbonyls is presented. Qualitative and quantitative information of this molecular interaction was obtained and discussed. This has been considered as a main factor responsible for the significantly improved mechanical properties of the PI fibers. 2D WAXD and molecular mechanics modeling were used to simulate the structure of the aromatic PI fibers. As a result, the addition of BIA in the main chains is to increase the regularity of the molecule packing, which plays an important role in the enhanced strength of the PI fibers with more BIA loadings.
Co-reporter:Jie Dong, Chaoqing Yin, Jinyou Lin, Dianbo Zhang and Qinghua Zhang
RSC Advances 2014 vol. 4(Issue 84) pp:44666-44673
Publication Date(Web):28 Aug 2014
DOI:10.1039/C4RA07129H
The development of crystalline structure and morphology for polyimide (PI) fibers in the heat-drawing process was investigated by simultaneous synchrotron wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS). WAXD results indicated that the drawing process resulted in a high crystal orientation and ordered crystal structure. Especially, as the drawing ratio increases to 2.0, a well-defined crystalline structure forms in the fibers. We propose that the highly oriented molecular chains induce the formation of crystalline regions. Namely, an orientation-induced crystallization occur with stretching in the case of the heat-drawing polyimide fibers. The meridional scattering streaks in the SAXS patterns for the as-spun fibers suggest the presence of periodic lamellar structure in the fibers. These crystalline lamellae may evolve to more complete crystalline regions. The size of microvoids in the cross-section of the PI fibers is analyzed by SAXS. As a result, the drawing process leads to the orientation of microvoids along the fiber, and to reduced diameter of the microvoids in the fiber. Dynamic thermomechanical analysis indicates that the activation energy Ea of α relaxation increases with the increase in the crystallinity and orientation in the fibers.
Co-reporter:Yuxuan Du, Xin Zhao, Zilong Huang, Yingzhi Li and Qinghua Zhang
RSC Advances 2014 vol. 4(Issue 74) pp:39087-39094
Publication Date(Web):14 Aug 2014
DOI:10.1039/C4RA06301E
Manganese oxide/carbon nanofiber (MnOx/CNF) composites were successfully fabricated as freestanding electrodes through incorporating different manganese sources of nanostructured MnO2 or Mn(CH3COO)2·4H2O into polyacrylonitrile (PAN) solution by electrospinning and a subsequent carbonization method. The MnO2 with a rod-like hierarchical core–corona nanostructure was self-prepared by a hydrothermal method using polyvinylpyrrolidone (PVP) to control the size and morphology of nanoparticles. The morphologies and structures of the MnOx/CNF composites were characterized by means of field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. MnOx/CNFs produced from Mn(CH3COO)2·4H2O exhibited good flexibility with uniform dispersion of small MnOx particles in the loose structures of the CNFs. In contrast, MnOx/CNFs derived from MnO2 displayed relative brittle mechanical properties. The electrochemical performances of the two composites were investigated by cyclic voltammetry, galvanostatic charging/discharging and impedance measurement techniques. The resulting MnOx/CNFs demonstrated excellent electrochemical performance with great rate capability, low internal resistance and long-term cycling stability. Composites produced from Mn(CH3COO)2·4H2O delivered a specific capacitance of 211 F g−1 at 0.25A g−1 in 0.5 M Na2SO4 electrolyte These results suggest that such freestanding MnOx/CNF composites would be promising electrodes for high-performance supercapacitors.
Co-reporter:Pingping Yu, Yingzhi Li, Xin Zhao, Lihao Wu, and Qinghua Zhang
Langmuir 2014 Volume 30(Issue 18) pp:5306-5313
Publication Date(Web):2017-2-22
DOI:10.1021/la404765z
We report the synthesis of reduced graphene oxide (RGO) sheet wrapped polyaniline (PANI) nanowire arrays grown on nitrogen-doped carbon fiber cloth (eCFC). The RGO coating layer is important to accommodate volume change and mechanical deformation of the coated PANI nanowires arrays during the long-term charge/discharge processes. The resulting hierarchical symmetric supercapacitor based on RGO/PANI/eCFC composites shows an enhanced capacitive behavior with a maximum energy density of 25.4 Wh kg–1, a maximum power density of 92.2 kW kg–1 and a specific capacitance of 1145 F g–1, which is higher than that of PANI/eCFC (1050 F g–1) and GO/PANI/eCFC (940 F g–1). Moreover, the assembled supercapacitor exhibits excellent charge/discharge rates and a good cycling stability, retaining over 94% of its initial capacitance after 5000 cycles.
Co-reporter:Jie Dong;Chaoqing Yin;Yumei Zhang ;Qinghua Zhang
Journal of Polymer Science Part B: Polymer Physics 2014 Volume 52( Issue 6) pp:450-459
Publication Date(Web):
DOI:10.1002/polb.23438
ABSTRACT
Copolyimides were synthesized in N-methyl-2-pyrrolidone (NMP) to prepare polyimide (PI) solutions with various concentrations, and gels can form in PI/NMP solution with a suitable concentration or at a low temperature. Gel–sol transition in the PI/NMP solution has been investigated through a combination of polarized optical microscope, differential scanning calorimeter measurement, and rheological measurements. According to Winter–Chambon theory, the critical gel point is 12 wt %, and the loss tangent (tan δ) shows frequency independence. Gel–sol transition temperature (Tgel) for the 13 wt % solution is around 65 °C. Below the Tgel, the gel exhibits strong optical planar texture, indicating the formation of a fully anisotropic phase, which has a great importance for the fabrication of PI fibers by gel-spinning. Dynamic temperature sweep measurements show that the formation of the gel from solution is thermoreversible and is significantly delayed in the cooling process. Under the favorable conditions, the tensile strength and modulus of the fibers derived from the solution are about 0.7 and 12.5 GPa using gel-spinning method, which is believed to afford broad application potential in preparing high-performance PI fibers. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014, 52, 450–459
Co-reporter:Longxiu Zhu, Xin Zhao, Yingzhi Li, Xinyi Yu, Chen Li, Qinghua Zhang
Materials Chemistry and Physics 2013 Volume 137(Issue 3) pp:984-990
Publication Date(Web):15 January 2013
DOI:10.1016/j.matchemphys.2012.11.012
As one of the most promising candidates, graphene exhibits a potential application in post-silicon nanoelectronics. However, it is a key issue to produce high-quality graphene in large scale. Here, a facile method is demonstrated to produce graphene dispersions by exfoliation of expanded graphite in the co-solvent with N,N-dimethylformamide (DMF) and water. We confirm that the optimal ratio of DMF to water for graphene exfoliation is 9:1 (v:v) by means of UV–Vis absorption spectra. This exfoliation results in large flakes ∼2 μm in diameter, which can potentially be improved by adjusting the sonication power. The relatively perfect hexagonal structure of graphene is confirmed by Raman spectroscopy and the as-prepared graphene nanosheet film the as-prepared graphene nanosheet film possesses good electrical conductivity (∼8.3 × 103 S m−1). DC electrical transport phenomena for the deposited film of graphene nanosheets are well described in terms of conduction models for non-crystal semiconductor. This convenient approach provides an extensive route to prepare high-quality graphene nanosheets.
Co-reporter:Pingping Yu, Yingzhi Li, Xin Zhao, Lihao Wu, Qinghua Zhang
Synthetic Metals 2013 Volumes 185–186() pp:89-95
Publication Date(Web):1 December 2013
DOI:10.1016/j.synthmet.2013.10.010
•Hybrid PANI/surfactant exfoliated graphene was produced.•PANI nanowire arrays were aligned vertically on substrate.•Nanocomposites showed higher specific capacitance than that of pure PANI.•Composite electrode remained a high specific capacitance of 90% after 2000 cycles.Combining conducting polyaniline (PANI) nanowires with surfactant (tetrabutylammonium hydroxide) stabilized microwave-exfoliated graphene (TMEG) sheets leads to hierarchical nanostructure PANI/TMEG composites. PANI nanowires array are aligned vertically on TMEG substrate via in situ polymerization. TMEG, a support material, provide more active sites for nucleation of PANI and improve mechanical strength the electrode, and thus reducing the swelling/shrinking during the doping/dedoping. The PANI/TMEG composite electrode containing 10% TMEG exhibits an excellent specific capacitance as high as 1255 F g−1 at 1 A g−1, which is much higher than pure PANI (626 F g−1) and TMEG (115 F g−1). Moreover, the composite electrode exhibits 90% capacitance retention after 2000 cycles. The remarkable electrochemical performance is attributed to the hierarchical nanostructure electrode, which leads to reducing the diffusion length, facilitating the ionic motion and enhancing the rate performance of the electrode. The attractive characteristics showed in these TMEG supercapacitors make them potential candidates for future energy storage systems.
Co-reporter:Qingming Xia;Junpeng Liu;Jie Dong;Chaoqing Yin;Yuxuan Du;Qian Xu ;Qinghua Zhang
Journal of Applied Polymer Science 2013 Volume 129( Issue 1) pp:145-151
Publication Date(Web):
DOI:10.1002/app.38709
Abstract
A new synthesis route was developed to produce the diamine monomer containing benzimidazole units, 6,4′-diamino-2-phenylbenzimidazole (BIA), which was easily prepared by the reduction of 6,4′-dinitro-2-phenylbenzimidazole synthesized via a reaction between 4-nitro-1,2-phenylenediamine and 4-nitrobenzoyl chloride. The composition and structure of the products were confirmed by Fourier transform infrared, NMR, and elemental analysis. A series of polyimides were prepared by the polycondensation of BIA and various dehydrates, pyromellitic dianhydride, 3,3′,4,4′-biphenyl tetracarboxylic dianhydride, 4,4′-oxydiphthalic anhydride, and benzophenone tetracarboxylic dianhydride via a traditional two-step procedure. The polyimides exhibit excellent thermal stability up to 540°C and high glass transition temperature (Tg) in the range of 382–409°C. The polyimide films are tough and flexible and possess good mechanical properties of tensile strength of 222–232 MPa and modulus of 3.1–5.6 GPa without stretching. The polyimides are amorphous state in wide-angle X-ray diffraction patterns, whereas small-angle X-ray diffraction patterns show the existence of molecular aggregation. The rigid-rod structure and intermacromolecular hydrogen bond are likely responsible for the excellent properties of the polyimides. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Co-reporter:Yuan Xu;Shihua Wang;Zhentao Li;Qian Xu;Qinghua Zhang
Journal of Materials Science 2013 Volume 48( Issue 22) pp:7863-7868
Publication Date(Web):2013 November
DOI:10.1007/s10853-013-7310-0
Polyimide fibers were prepared by dry spinning a polyamic acid solution to get the precursor fibers and then the precursor fibers were transferred into the polyimide fiber by heat treatment. The imidization degree (ID) of the precursor fibers obtained at various spinning conditions was investigated using FTIR and TGA analysis. As a result, the IDs of the precursor fibers increased with elevating spinning temperature. Meanwhile, the IDs measured by FTIR and TGA were much higher than the values from our model prediction. The tensile strength of precursor fibers exhibited a slight dependency on IDs. On the other hand, the complete imidization and hot stretching led to a great improvement in the mechanical properties. Subglass transition and glass transition of the stretched polyimide fibers were observed in DMA, and the activation energy of these transitions was 346 and 981 kJ mol−1, respectively.
Co-reporter:Jie Dong, Chaoqing Yin, Xin Zhao, Yingzhi Li, Qinghua Zhang
Polymer 2013 Volume 54(Issue 23) pp:6415-6424
Publication Date(Web):1 November 2013
DOI:10.1016/j.polymer.2013.09.035
Graphene possesses unprecedented physical and chemical properties and has been thought to be ideal filler for reinforcing fibers' mechanical properties. However, graphene is difficultly dispersed in polymer which severely restrict to prepare high-strength and high-modulus composites. In this work, we report an effective method to fabricate a kind of organ-soluble polyimide (PI)/graphene composite fiber using in situ polymerization. Graphene oxide (GO) is modified by 4,4′-diaminodiphenyl ether (ODA) to obtain the GO-ODA nanosheets which exhibit excellent dispersibility and compatibility with the organ-soluble PI matrix. WAXD results show that these 2D nanosheets have a significant influence on the crystallization, aggregation or assembly behaviors of the polymer chains. The PI/graphene composite fiber containing 0.8 wt% of GO-ODA presents a tensile strength of 2.5 GPa (1.6 times higher than the pure PI fiber), and tensile modulus of 126 GPa (223% raises compared with pure PI fiber). Furthermore, the incorporation of graphene significantly improves the glass transition temperature and thermal stability of the composite fibers. Thanks to the excellent hydrophobic properties of graphene, the hydrophobic behavior of the composite fibers is greatly improved. This effective approach shows a potential application in fabricating multifunctional polymer-based composite fibers.
Co-reporter:Yingzhi Li, Xin Zhao, Pingping Yu, and Qinghua Zhang
Langmuir 2013 Volume 29(Issue 1) pp:493-500
Publication Date(Web):December 3, 2012
DOI:10.1021/la303632d
Oriented arrays of polyaniline (PANI) nanorods grown on expanded graphite (EG) nanosheets are fabricated by in situ polymerization to achieve excellent electrochemical properties for applications as supercapacitor electrodes. EG serves as an excellent 3D conductive skeleton that supports a highly electrolytic accessible surface area of redox-active PANI and provides a direct path for electrons. The porous and ordered nanostructure provides a larger contact surface area for the intercalation/deintercalation of protons into/out of active materials and shortens the path length for electrolyte ion transport. The maximum specific capacitance of 1665 F g–1 at 1 A g–1 is observed in the PANI/EG electrode with 10% EG content. The composite electrode material also exhibits significant rate capability and good long-term cycling stability. The results demonstrate that PANI is effectively utilized with the assistance of EG conductive skeletons in the electrode. Such 3D composite nanoarchitecture is very promising for the next generation of high-performance electrochemical supercapacitors.
Co-reporter:Pingping Yu, Yingzhi Li, Xinyi Yu, Xin Zhao, Lihao Wu, and Qinghua Zhang
Langmuir 2013 Volume 29(Issue 38) pp:12051-12058
Publication Date(Web):2017-2-22
DOI:10.1021/la402404a
A combination of vertical polyaniline (PANI) nanowire arrays and nitrogen plasma etched carbon fiber cloths (eCFC) was fabricated to create 3D nanostructured PANI/eCFC composites. The small size of the highly ordered PANI nanowires can greatly reduce the scale of the diffusion length, allowing for the improved utilization of electrode materials. A two-electrode flexible supercapacitor based on PANI/eCFC demonstrates a high specific capacitance (1035 F g–1 at a current density of 1 A g–1), good rate capability (88% capacity retention at 8 A g–1), and long-term cycle life (10% capacity loss after 5000 cycles). The lightweight, low-cost, flexible composites are promising candidates for use in energy storage device applications.
Co-reporter:Yingzhi Li, Qinghua Zhang, Xin Zhao, Pingping Yu, Lihao Wu and Dajun Chen
Journal of Materials Chemistry A 2012 vol. 22(Issue 5) pp:1884-1892
Publication Date(Web):06 Dec 2011
DOI:10.1039/C1JM13359D
In this work, polyhedral oligosilsesquioxane (POSS) was functionalized by direct sulfonation, and the porous and ordered hierarchical nanostructure of polyaniline/sulfonated polyhedral oligosilsesquioxane (PANI/SOPS) was subsequently fabricated by in situ polymerization. The morphologies of the PANI/SOPS nanocomposites can be controlled by adjusting the concentration of SOPS. The measurement of X-ray diffraction pattern and ultraviolet-visible spectra demonstrates the molecular level dispersion of SPOS in the PANI matrix. Synergetic interaction between PANI and SOPS significantly improves the porosity and the stability of the electrode, yielding excellent electrochemical properties. Compared to pure PANI, the PANI/SOPS electrode exhibits a higher specific capacitance of 1810 F g−1, faster oxidation/reduction at high current changes and better cyclic stability, which is attributed to the nano-architecture of the electrode materials and the support of the SOPS nanoparticles. This result suggests that the construction of the porous and ordered hierarchical nanostructure is a novel and effective way for improving the electrochemical properties of conducting polymers.
Co-reporter:Junpeng Liu, Qinghua Zhang, Qingming Xia, Jie Dong, Qian Xu
Polymer Degradation and Stability 2012 Volume 97(Issue 6) pp:987-994
Publication Date(Web):June 2012
DOI:10.1016/j.polymdegradstab.2012.03.010
A new aromatic heterocyclic diamine monomer containing bis-benzimidazole rings, 2,2′-p-phenylene-bis(5-aminobenzimidazole) (PBABI), was synthesized from 2,2′-p-phenylene-bis (5-nitrobenzimidazole) with high yield via the reaction between 4-nitro-1,2-phenylenediamine and terephthalyl chloride. The composition and structure of the resulting diamine monomer were studied by means of FTIR, 1H and 13C NMR and elemental analysis. A series of polyimides holding bis-benzimidazole rings in main chain were produced by reacting PBABI with the aromatic dianhydrides 3,3′,4,4′-biphenyl tetracarboxylic dianhydride, 4,4′-oxydiphthalic anhydride, benzophenone tetracarboxylic dianhydride and pyromellitic dianhydride via a conventional, two-step procedure. X-ray diffraction and differential scanning calorimetry were employed to investigate the polyimides, revealing them essentially amorphous. The polyimides possess thermal stabilities of up to 560 °C for a 5% weight loss and glass transition temperatures above 450 °C. In addition, these high performance polymers have excellent mechanical properties, exhibiting tensile strengths of 120–180 MPa and tensile moduli of 4.83–5.79 GPa without any stretching. The rigid-rod structure of polyimides and the hydrogen bonding of their inter-macromolecular chains are most likely responsible for the outstanding properties of the polyimides.
Co-reporter:Yuehui Ma, Qinghua Zhang
Applied Surface Science 2012 Volume 258(Issue 19) pp:7774-7780
Publication Date(Web):15 July 2012
DOI:10.1016/j.apsusc.2012.04.147
Abstract
A modified electroless silver-plating process has been devised for the preparation of monodispersed, polystyrene/silver (PS/Ag) composite microspheres with tunable shell thickness. Tailoring was achieved by altering the concentration of the silver precursor in the plating bath. PS/Ag composite microspheres were characterized by field-emission scanning electron microscopy, ultraviolet–visible absorption, X-ray diffraction and thermogravimetric analysis. The results showed that a dense, stable and uniform silver nanoshell was formed on the surface of PS microspheres in the presence of poly(vinylpyrrolidone) and glucose. The bulk conductivity of the PS/Ag composites increased from 1.16 S/m to 3.57 × 104 S/m, corresponding to a shell thickness of 35–198 nm. The PS/Ag composite microspheres with diameters of ca. 3 μm might have great potential to be used as fillers in anisotropic conductive films because of the uniform diameter, low density and good conductivity of the microspheres.
Co-reporter:Chengqiang Pan, Yingzhi Li, Yuehui Ma, Xin Zhao, Qinghua Zhang
Journal of Power Sources 2011 Volume 196(Issue 15) pp:6228-6231
Publication Date(Web):1 August 2011
DOI:10.1016/j.jpowsour.2011.03.027
Antimony doped tin oxide supported on carbon black (ATO/C) has been synthesized using an in situ co-precipitation method, and platinum–ATO/C nanoparticles have been prepared using a consecutive polyol process to enhance the catalyst activity for the methanol oxidation reaction. The Pt–ATO/C electrocatalyst is characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microcopy (SEM), energy dispersive X-ray spectroscopy (EDS) and cyclic voltammetry. The Pt–ATO/C catalyst exhibits a relatively high activity for the methanol oxidation reaction compared to Pt–SnO2/C or commercial Pt/C catalyst. This activity can be attributed to the high electrical conductivities of the Sb-doped SnO2, which induces the electronic effects with Pt catalysts. Pt–ATO/C is a promising methanol oxidation catalyst with high activity for the reaction in direct methanol fuel cells.Graphical abstractHighlights► Antimony doped tin oxide supported on carbon black is synthesized using an in situ co-precipitation. ► Pt–ATO/C nanoparticles are prepared using a consecutive polyol process. ► The nanoparticles enhance the catalyst activity for the methanol oxidation reaction. ► Pt–ATO/C is a promising methanol oxidation catalyst in direct methanol fuel cells.
Co-reporter:Yingzhi Li, Xin Zhao, Qian Xu, Qinghua Zhang, and Dajun Chen
Langmuir 2011 Volume 27(Issue 10) pp:6458-6463
Publication Date(Web):April 13, 2011
DOI:10.1021/la2003063
A porous and mat-like polyaniline/sodium alginate (PANI/SA) composite with excellent electrochemical properties was polymerized in an aqueous solution with sodium sulfate as a template. Ultraviolet–visible spectra, X-ray diffraction pattern, and Fourier transform infrared spectra were employed to characterize the PANI/SA composite, indicating that the PANI/SA composite was successfully prepared. The PANI/SA nanofibers with uniform diameters from 50 to 100 nm can be observed on scanning electron microscopy. Cyclic voltammetry and galvanostatic charge/discharge tests were carried out to investigate the electrochemical properties. The PANI/SA nanostructure electrode exhibits an excellent specific capacitance as high as 2093 F g–1, long cycle life, and fast reflect of oxidation/reduction on high current changes. The remarkable electrochemical characteristic is attributed to the nanostructured electrode materials, which generates a high electrode/electrolyte contact area and short path lengths for electronic transport and electrolyte ion. The approach is simple and can be easily extended to fabricate nanostructural composites for supercapacitor electrode materials.
Co-reporter:Xin Zhao, Qinghua Zhang and Dajun Chen, Ping Lu
Macromolecules 2010 Volume 43(Issue 5) pp:2357-2363
Publication Date(Web):February 9, 2010
DOI:10.1021/ma902862u
Graphene, flat carbon nanosheets, has generated huge activity in many areas of science and engineering due to its unprecedented physical and chemical properties. With the development of wide-scale applicability including facile synthesis and high yield, this exciting material is ready for its practical application in the preparation of polymer nanocomposites. Here we report that nanocomposites based on fully exfoliated graphene nanosheets and poly(vinyl alcohol) (PVA) are prepared via a facial aqueous solution. A significant enhancement of mechanical properties of the graphene/PVA composites is obtained at low graphene loading; that is, a 150% improvement of tensile strength and a nearly 10 times increase of Young’s modulus are achieved at a graphene loading of 1.8 vol %. The comparison between the experimental results and theoretical simulation for Young’s modulus indicates that the graphene nanosheets in polymer matrix are mostly dispersed randomly in the nanocomposite films.
Co-reporter:Xin Zhao, Qinghua Zhang, Yanping Hao, Yingzhi Li, Ying Fang, and Dajun Chen
Macromolecules 2010 Volume 43(Issue 22) pp:9411-9416
Publication Date(Web):October 28, 2010
DOI:10.1021/ma101456y
Despite great recent progress with graphene-based materials, the development of strong and cost-efficient multifunctional graphene-filled polymer composites has not yet to be achieved. A key challenge in the fabrication of nanoplatelet-filled polymer composites is the ability to realize the nanometer-level dispersion and the planar orientation of nanosheets in polymer matrices. In this report, ultrathin multilayer (PVA/GO)n films were successfully fabricated by bottom-up layer-by-layer (LBL) assembly of poly(vinyl alcohol) (PVA) and exfoliated graphene oxide (GO), in which exfoliated GO nanosheets were used as the building blocks. Typical tapping-mode atomic force microscope (AFM) and field emission scanning electron microscope (FESEM) images demonstrate an ordered arrangement of organic and inorganic layers. A significant enhancement of mechanical properties has been achieved, that is, a 98.7% improvement of elastic modulus (Er) and a 240.4% increase of hardness. This may be attributed to the well-defined layered architecture with high degree of planar orientation and nanolevel assemblies of GO nanosheets in the polymer matrices.
Co-reporter:Liang Jin, Qinghua Zhang, Yuan Xu, Qingming Xia, Dajun Chen
European Polymer Journal 2009 Volume 45(Issue 10) pp:2805-2811
Publication Date(Web):October 2009
DOI:10.1016/j.eurpolymj.2009.07.011
A one-pot synthetic method to produce aromatic polyimides with high molecular weights from corresponding diamines and dianhydrides was developed, in which polyphosphoric acid (PPA) played a role of an excellent media for one-step synthesis of completely cyclized polyimides. The polymerization was carried out in the solid content of 10 wt/v% at 220 °C. The resulting products exhibited a homogeneous solution in the non-volatilizable PPA instead of precipitation form of the polyimides. The content of P2O5 in PPA had an influence on the molecular weight of the products, and the high percentage of P2O5 resulted in the relative high inherent viscosity. FTIR and Carbon-13 NMR were employed to analyze the structures and TGA was used to evaluate the thermal stability. The polyimides prepared by this one-step route exhibited good thermal properties and high values of activation energies for the degradation, on comparison with the polyimides prepared in DAMc by two-step polymerization method.
Co-reporter:Gang Deng;Qingming Xia;Yuan Xu ;Qinghua Zhang
Journal of Applied Polymer Science 2009 Volume 113( Issue 5) pp:3059-3067
Publication Date(Web):
DOI:10.1002/app.30236
Abstract
As one type of high-performance fibers, the polyimide fibers can be prepared from the precursor polyamic acid via dry-spinning technology. Unlike the dry-spinning process of cellulose acetate fiber or polyurethane fiber, thermal cyclization reaction of the precursor in spinline with high temperature results in the relative complex in the dry-spinning process. However, the spinning process is considered as a steady state due to a slight degree of the imidization reaction from polyamic acid to polyimide, and therefore a one-dimensional model based on White-Metzer viscoelastic constitutive equation is adopted to simulate the formation of the fibers. The changes of solvent mass fraction, temperature, axial velocity, tensile stress, imidization degree, and glass transition temperature of the filament along the spinline were predicted. The effects of spinning parameters on glass transition temperature and imidization degree were thus discussed. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Co-reporter:Qinghua Zhang;Jing Li;Xin Zhao ;Dajun Chen
Polymer International 2009 Volume 58( Issue 5) pp:557-563
Publication Date(Web):
DOI:10.1002/pi.2568
Abstract
BACKGROUND: The development of carbon nanotube-reinforced composites has been impeded by the difficult dispersion of the nanotubes in polymers and the weak interaction between the nanofiller and matrices. Efficient dispersion of carbon nanotubes is essential for the formation of a functional nanotube network in a composite matrix.
RESULTS: Multiwalled carbon nanotubes (MWNTs) were incorporated into a polyimide matrix to produce MWNT/polyimide nanocomposites. To disperse well the MWNTs in the matrix and thus improve the interfacial adhesion between the nanotubes and the polymer, ‘branches’ were grafted onto the surface of the nanotubes by reacting octadecyl isocyanate with carboxylated MWNTs. The functionalized MWNTs were suspended in a precursor solution, and the dispersion was cast, followed by drying and imidization to obtain MWNT/polyimide nanocomposites.
CONCLUSION: The functionalized MWNTs appear as a homogeneous dispersion in the polymer matrix. The thermal stability and the mechanical properties are greatly improved, which is attributed to the strong interactions between the functionalized MWNTs and the polyimide matrix. Copyright © 2009 Society of Chemical Industry
Co-reporter:Qinghua Zhang, Fang Fang, Xin Zhao, Yingzhi Li, Meifang Zhu and Dajun Chen
The Journal of Physical Chemistry B 2008 Volume 112(Issue 40) pp:12606-12611
Publication Date(Web):September 12, 2008
DOI:10.1021/jp802708j
Well-dispersed multiwalled carbon nanotube (MWNT)/polystyrene composites have been prepared. Transmission and scanning electron microscopy were employed to observe the distribution of the MWNTs in the composites in a microscopic scale, indicating a nanotube network formed in the matrix. The dispersion of the nanotubes in the polymer was monitored by oscillatory rheology. It was found that the addition of MWNTs in the polymer had a drastic influence on the rheological behavior of the composites. As the MWNT loading increased, Newtonian behavior disappeared at low frequency, suggesting a transition from liquid-like to solid-like viscoelastic behavior. A more homogeneous dispersion or a greater loading of the nanotubes in the matrix produced stronger solid-like and nonterminal behavior, and the composites exhibited less temperature dependence at elevated temperature, compared to the matrix melt.
Co-reporter:Qinghua Zhang;Hui Xiong;Weixia Yan;Dajun Chen ;Meifang Zhu
Polymer Engineering & Science 2008 Volume 48( Issue 11) pp:2090-2097
Publication Date(Web):
DOI:10.1002/pen.21079
Abstract
Multiphase polymer composites of carbon black (CB), polypropylene (PP) and low density polyethylene (LDPE) were prepared by melt-mixing method to reduce the amount of CB in the conductive composites. SEM images showed that CB preferably located in LDPE phase and formed electrically conductive path. The measurement of conductive properties showed that the ternary materials possessed lower percolation than binary composites of CB/PP or CB/LDPE, the former was ∼6 wt% and the latter was 9–10 wt%. Positive temperature coefficient (PTC) effects of the binary and ternary composites were investigated, indicating that the latter exhibited a relatively high PTC intensity. A rheological percolation estimated by a power law function is 2.66 wt% of CB loading, suggesting an onset of solid-like behavior at low frequencies. This difference between the electrical and rheological percolation thresholds may be understood in terms of the smaller CB–CB distance required for electrical conductivity as compared with that required to impede polymer mobility. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers
Co-reporter:Qinghua Zhang, Sanjay Rastogi, Dajun Chen, Dirk Lippits, Piet J. Lemstra
Carbon 2006 Volume 44(Issue 4) pp:778-785
Publication Date(Web):April 2006
DOI:10.1016/j.carbon.2005.09.039
A new method was developed to disperse carbon nanotubes (CNTs) in a matrix polymer and then to prepare composites by melt processing technique. Due to high surface energy and strong adsorptive states of nano-materials, single-walled carbon nanotubes (SWNTs) were adsorbed onto the surface of polymer powders by spraying SWNT aqueous suspected solution onto fine high density polyethylene (HDPE) powders. The dried SWNTs/powders were blended in a twin-screw mixture, and the resulting composites exhibited a uniformly dispersion of SWNTs in the matrix polymer. The electrical conductivity and the rheological behavior of these composites were investigated. At low frequencies, complex viscosities become almost independent of the frequency as nanotubes loading being more than 1.5 wt%, suggesting an onset of solid-like behavior and hence a rheological percolation threshold at the loading level. However, the electrical percolation threshold is ∼4 wt% of nanotube loading. This difference in the percolation thresholds is understood in terms of the smaller nanotube–nanotube distance required for electrical conductivity as compared to that required to impede polymer mobility. The measurements of mechanical properties indicate that this processing method can obviously improve the tensile strength and the modulus of the composites.
Co-reporter:Qing-Hua Zhang, Mian Dai, Meng-Xian Ding, Da-Jun Chen, Lian-Xun Gao
European Polymer Journal 2004 Volume 40(Issue 11) pp:2487-2493
Publication Date(Web):November 2004
DOI:10.1016/j.eurpolymj.2004.06.020
An aromatic polyimide was synthesized via a one-step polycondensation reaction between biphenyltetracarboxylic dianhydride (BPDA) and 4,4′-oxydianiline (ODA) in p-chlorophenol. The polyimide (BPDA–ODA) solution dopes were spun into fibers by means of dry-jet wet spinning. The as-spun fibers were drawn and treated in heating tubes for improving the mechanical properties. The thermal treatment on the fibers resulted in a relatively high tensile strength and modulus. Thermal mechanical analysis (TMA) was employed to study the linear coefficient of thermal expansion (CTE). Thermal gravimetry analysis (TGA) spectra showed that the BPDA–ODA fibers possessed an excellent property of thermo-oxidative degradation resistance. The sonic modulus Es of the polyimide fibers was measured.
Co-reporter:Qing-Hua Zhang;Meng-Xian Ding;Wei-Qiang Luo;Da-Jun Chen;Lian-Xun Gao
Journal of Applied Polymer Science 2004 Volume 92(Issue 3) pp:1653-1657
Publication Date(Web):1 MAR 2004
DOI:10.1002/app.20110
High-performance polyimide fibers possess many excellent properties, e.g., outstanding thermal stability and mechanical properties and excellent radiation resistant and electrical properties. However, the preparation of fibers with good mechanical properties is very difficult. In this report, a biphenyl polyimide from 3,3′,4,4′-biphenyltetracarboxylic dianhydride and 4,4′-oxydianiline is synthesized in p-chlorophenol by one-step polymerization. The solution is spun into a coagulation bath of water and alcohol via dry-jet wet-spinning technology. Then, the fibers are drawn in two heating tubes. Thermal gravimetric analysis, thermal mechanical analysis, and dynamic mechanical analysis (DMA) are performed to study the properties of the fibers. The results show that the fibers have a good thermal stability at a temperature of more than 400°C. The linear coefficient of thermal expansion is negative in the solid state and the glass transition temperature is about 265°C. DMA spectra indicate that the tanδ of the fibers has three transition peaks, namely, α, β, and γ transition. The α and γ transition temperature, corresponding to the end-group motion and glass transition, respectively, extensively depends on the applied frequency, while the β transition does not. The activation energy of α and γ transition is calculated using the Arrhenius equation and is 38.7 and 853 kJ/mol, respectively. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1653–1657, 2004
Co-reporter:Qing-Hua Zhang;Mian Dai;Meng-Xian Ding;Da-Jun Chen;Lian-Xun Gao
Journal of Applied Polymer Science 2004 Volume 93(Issue 2) pp:669-675
Publication Date(Web):22 APR 2004
DOI:10.1002/app.20514
As one member of high performance fibers, aromatic polyimide fibers possess many advantages, such as high strength, high modulus, high and low temperature resistance, and radiation resistance. However, the preparation of the high performance fibers is so difficult that the commercial fibers have not been produced except P84 with good flame retardancy. In this report, a polyimide was synthesized from 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA) and 4,4′-oxydianiline (ODA) and the fibers were prepared from its solution by a dry-jet wet-spinning process. The formation of the as-spun fibers in different coagulation bath composition was discussed. Scanning electron microscope (SEM) was employed to study the morphology of the as-spun fibers. As a result, the remnant solvent existed in the as-spun fibers generated from coagulation bath of alcohol and water. There were many fibrils and microvoids with the dimension of tens of nanometers in the fibers. One could observe the obvious fibrillation and the drawn fibers. The measurement for the mechanical properties of the fibers with a drawing ratio of 5.5 indicated that tensile strength and initial modulus were 2.4 and 114 GPa, respectively. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 669–675, 2004
Co-reporter:Qinghua Zhang;Xianhong Wang;Yanhou Geng;Dajun Chen;Xiabin Jing
Journal of Polymer Science Part B: Polymer Physics 2002 Volume 40(Issue 22) pp:2531-2538
Publication Date(Web):27 SEP 2002
DOI:10.1002/polb.10316
Polyaniline (PANI) in an emeraldine-base form, synthesized by chemical oxidation polymerization, was doped with camphor sulfonic acid (CSA). The conducting complex (PANI–CSA) and a matrix, polyamide-66, polyamide-11, or polyamide-1010, were dissolved in a mixed solvent, and the blend solution was dropped onto glass and dried for the preparation of PANI/polyamide composite films. The conductivity of the films ranged from 10−7 to 100 S/cm when the weight fraction of PANI–CSA in the matrices changed from 0.01 to 0.09, and the percolation threshold was about 2 wt %. The morphology of the composite films before and after etching was studied with scanning electron microscopy, and the thermal properties of the composite films were monitored with differential scanning calorimetry. The results indicated that the morphology of the blend systems was in a globular form. The addition of PANI–CSA to the films resulted in a decrease in the melting temperature of the composite films and also affected the crystallinity of the blend systems. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2531–2538, 2002
Co-reporter:Yingzhi Li, Qinghua Zhang, Xin Zhao, Pingping Yu, Lihao Wu and Dajun Chen
Journal of Materials Chemistry A 2012 - vol. 22(Issue 5) pp:NaN1892-1892
Publication Date(Web):2011/12/06
DOI:10.1039/C1JM13359D
In this work, polyhedral oligosilsesquioxane (POSS) was functionalized by direct sulfonation, and the porous and ordered hierarchical nanostructure of polyaniline/sulfonated polyhedral oligosilsesquioxane (PANI/SOPS) was subsequently fabricated by in situ polymerization. The morphologies of the PANI/SOPS nanocomposites can be controlled by adjusting the concentration of SOPS. The measurement of X-ray diffraction pattern and ultraviolet-visible spectra demonstrates the molecular level dispersion of SPOS in the PANI matrix. Synergetic interaction between PANI and SOPS significantly improves the porosity and the stability of the electrode, yielding excellent electrochemical properties. Compared to pure PANI, the PANI/SOPS electrode exhibits a higher specific capacitance of 1810 F g−1, faster oxidation/reduction at high current changes and better cyclic stability, which is attributed to the nano-architecture of the electrode materials and the support of the SOPS nanoparticles. This result suggests that the construction of the porous and ordered hierarchical nanostructure is a novel and effective way for improving the electrochemical properties of conducting polymers.
Co-reporter:Pingping Yu, Xin Zhao, Zilong Huang, Yingzhi Li and Qinghua Zhang
Journal of Materials Chemistry A 2014 - vol. 2(Issue 35) pp:NaN14420-14420
Publication Date(Web):2014/07/04
DOI:10.1039/C4TA02721C
Free-standing three-dimensional hierarchical porous reduced graphene oxide foam (RGO-F) was first fabricated by a “dipping and dry” method using nickel foam as a template. Three-dimensional (3D) RGO-F with high conductivity provides large porosity compared to conventional graphene films. Polyaniline (PANI) nanowire arrays aligned on the foam (RGO-F/PANI) were synthesized by in situ polymerization. A symmetric supercapacitor with high energy and power densities was fabricated using a RGO-F/PANI electrode. The highly flexible RGO-F/PANI foam can directly serve as an electrode with no binders or conductive additives. Owing to the well-ordered porous structure and high electrochemical performance of the RGO-F/PANI composite, the symmetric device exhibits high specific capacitance (790 F g−1) and volumetric capacitance (205.4 F cm−3), and it shows a maximum energy density and power density of 17.6 W h kg−1 and 98 kW kg−1. Moreover, the device possesses an excellent cycle life with 80% capacitance retention after 5000 cycles.
Co-reporter:Jie Dong, Cairan Yang, Yang Cheng, Tingting Wu, Xin Zhao and Qinghua Zhang
Journal of Materials Chemistry A 2017 - vol. 5(Issue 11) pp:NaN2825-2825
Publication Date(Web):2017/02/09
DOI:10.1039/C7TC00196G
High-performance fibers with a low dielectric constant and good mechanical properties as well as excellent thermal stability are in demand for the next generation of advanced radar-wave-transparent composites. In this study, an effective method is proposed to prepare amine-functionalized hyperbranched polysiloxane (NH2-HBPSi) reinforced polyimide (PI) composite fibers with exceptional dielectric behavior, mechanical and thermal properties. The amino-functionalized NH2-HBPSi were grafted to PI chains during in situ polymerization, promoting the uniform dispersion of the NH2-HBPSi nanoparticles and forming strong interfacial interactions between NH2-HBPSi and the PI matrix. The composite fiber containing 10 wt% NH2-HBPSi exhibited a 10% and 26% increase in tensile strength and modulus compared to the pure PI fiber. Owing to the dielectric confinement effect from NH2-HBPSi, the dielectric constants of the NH2-HBPSi/PI composites were reduced drastically and the value could reach as low as 2.2 at 108 Hz. The composite fiber demonstrated better specific strength, specific modulus and lower dielectric constant than the commonly used E-glass, S-glass and quartz fibers. These results provide useful information for designing molecular architecture and fabricating high-performance reinforcing fibers in the future radomes.
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