Journal of Materials Chemistry C
·
2019
·Vol. 7
·期 23
·7035-7044
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IF 6.641
Yongqiang Guo,Kunpeng Ruan,Xutong Yang,Tengbo Ma,Jie Kong,Nannan Wu,Jiaoxia Zhang,Junwei Gu,Zhanhu Guo
A novel kind of fully carbon-based filler (f-MWCNT-g-rGO) is constructed by a reaction between melted urea functionalized multi-walled carbon nanotubes (f-MWCNTs) and graphene oxide (GO) followed by chemical reduction. The corresponding highly thermally conductive polyimide (f-MWCNT-g-rGO/PI) nanocomposites are then fabricated through the combined method of in situ polymerization, electrospinning and hot pressing. An improved thermal conduction model is also proposed and established considering the filler/matrix interfaces, filler dispersion and alignment, etc. The f-MWCNT-g-rGO fillers have a hierarchical “line-plane” structure. The fabricated f-MWCNT-g-rGO/PI nanocomposites possess an outstanding thermal conductivity coefficient (λ), and excellent thermal stabilities and mechanical properties. Specifically, the f-MWCNT-g-rGO/PI nanocomposites reach the maximum λ of 1.60 W m−1 K−1 at a relatively low loading of f-MWCNT-g-rGO fillers (10 wt%, the mass ratio of rGO to f-MWCNT is 2 : 1). In addition, the theoretical λ value calculated by our established thermal conduction model is more in line with the experimental λ values compared with other traditional models. Owing to the high thermal conductivities while preserving good mechanical properties and thermal stabilities at a relatively low loading of f-MWCNT-g-rGO filler, the f-MWCNT-g-rGO/PI nanocomposites are expected to be used as thermal pads in light emitting diode (LED) substrates and liquid crystal displays.
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MACROMOLECULAR MATERIALS AND ENGINEERING
·
2019
·Vol. 304
·期 4
·1800709
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IF 3.038
Hui Tong,Jing Fu,Aftab Ahmad,Tao Fan,Yudong Hou,Ju Xu
Polymer dielectrics, with advanced dielectric properties and heat resistance, are critical for high-temperature capacitors in various applications. However, the high performance of heat resistance and dielectric properties are quite difficult to achieve all together due to their mutual implication. Here, by intensively investigating the correlation between molecular structure and properties, polyimide dielectrics with i) enhanced dielectric constant by introducing sulfonyl group, ii) low dissipation factor by introducing flexible linkage, and iii) high T g (glass transition temperature) by retaining an aromatic structure, are obtained. The sulfonyl-containing polyimides with different flexible linkages exhibit simultaneously a high dielectric constant (4.50–5.98), low dissipation factor (0.00298–0.00426), and outstanding breakdown strength (most above 500 MV m −1 ), as well as superior heat resistance ( T g : 244–304 °C). Specifically, the polyimide (SPI-1) with sulfonyl group in diamine moiety and para-para linkage shows stable dielectric properties up to 150 °C, and the discharged energy density and charge–discharge efficiency can be as high as 7.04 J cm −3 and 91.3% at 500 MV m −1 , respectively.
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Journal of Energy Storage
·
2024
·
IF 8.9
Yushan Xu,Xinrun Yu,Xiaodong Wang,Juan Yu,Pei Huang
Polymer-derived nitrogen-doped porous carbon networks display stable electrochemical properties and have been extensively studied as electrode materials. However, the precise control of pore morphology and size distribution remains challenging. Herein, the pore structure of polyimide membranes was initially established by controlling the coating thickness. Subsequent to carbonization, the pore morphology and surface area were further controlled. The resulting optimized porous carbon exhibits a uniform pore distribution, a large specific surface area, and appropriate heteroatom content. In a three-electrode system, it achieves a specific capacitance of 328.4 F g −1 at 0.5 A g −1 . Additionally, the symmetric supercapacitor delivers an impressive energy density of 20.3 Wh kg −1 at 350 W kg −1 in a 6 M KOH electrolyte, retaining 88.5 % of its specific capacity after 5000 cycles. Notably, the specific capacitance of a flexible solid-state device is 151.6 mF cm −2 at 2 mA cm −2 . This work introduces a simple, environmentally friendly approach for producing porous carbon from polyimide with adjustable morphology.
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POLYMERS FOR ADVANCED TECHNOLOGIES
·
2015
·Vol. 27
·期 3
·414-418
·
IF 1.757
Sude Ma,Yan Wang,Chun Liu,Qian Xu,Zhonghua Min
In order to decrease the resistance–capacitance delay and signal crosstalk in ultra large-scale integrated circuits (ULSIC), dielectric materials with ultra low dielectric constants are developed to be the replacement of silicon dioxide. Introduction of air on the matrix material is an important method to reduce the dielectric constant, and polyimide (PI) is the most promising polymer to prepare porous matrix material for its distinct advantages. PI membrane with nanopores was prepared by the method of template method (i.e. thermolysis of polystyrene nanospheres in the matrix) following the synthesis of template. The nanoporous membrane was characterized by Fourier transformer infrared, scanning electron microscopy, thermogravimetric analysis, and the dielectric constant of which was measured. Results showed that uniform nanopores about 100–200 nm were formed in the PI membrane, and dielectric constant of which was decreased to 2.08 from 3.34. The nanoporous membrane can be applied as potential low- k dielectric material in ULSIC. Copyright © 2015 John Wiley & Sons, Ltd.
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RSC Advances
·
2016
·Vol. 6
·期 41
·34825-34832
·
IF 3.289
Zhenxun Huang,Jianqing Zhao
In this study, various amounts of an amino-derivative of pure silica zeolite nanocrystals (A-PSZN) were blended with fluorinated poly(amic acid) (FPAA) to form a FPAA/A-PSZN precursor solution, and the fluorinated polyimide (FPI)/A-PSZN hybrid films were prepared via spin-coating and following thermal imidization of the FPAA/A-PSZN solution. A series of FPI/A-PSZN hybrid films were investigated scientifically based on the dielectric constant (k), water absorption, dynamic mechanical and thermal and mechanical properties. It is found that the k value decreases from 3.11 for pristine FPI to 2.65 for the FPI/7 wt% A-PSZN hybrid, which is attributed to the air within the micropore of A-PSZN and the inhibited molecular polarization originating from the internal cross-linking structure of hybrids. Due to the effective phase interconnection and the inherent excellent property of A-PSZN, on the other hand, the incorporation of A-PSZN results in the improvement of the storage modulus, glass transition temperature, thermal stability, Young's modulus, tensile strength and the decrease of water absorption, and thermal expansion coefficients for materials. The results indicate that the incorporation of A-PSZN is a promising approach to reduce the k value and improve the comprehensive properties of FPI, and the FPI/A-PSZN hybrid materials are potentially useful in the microelectronic industry.
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RSC Advances
·
2017
·Vol. 7
·期 35
·21953-21961
·
IF 3.108
Yao Cheng,Shiyu Zhang,Juan Li,Jun Sun,Jianjun Wang,Chuanxiang Qin,Lixing Dai
Partially unzipped carbon nanotubes (PUCNTs) were prepared via a facile longitudinal unzipping method and then covalently bonded with 4,4′,4′′-triaminotriphenylamine (TAPA) for the first time to obtain functionalized PUCNTs (f-PUCNTs). Polyamide acid (PAA)-based composites with f-PUCNTs were prepared by using in situ polymerization, and the f-PUCNTs/PAA composite solution was wet-spun to obtain composite fibers which were finally transferred into f-PUCNTs/PI composite fibers after heat treatment. f-PUCNTs not only combined the advantages of carbon nanotubes and graphene, but also possessed groups which could covalently bond with the PI matrix, leading to a relatively strong reinforcing effect on the matrix. The tensile strength and Young's modulus of the composite fiber containing 1.0 wt% f-PUCNTs increased to 165% and 208% relative to those of PI fiber, respectively, and to 137% and 153% relative to those of the composite fiber containing the same amount of PUCNTs, respectively. Meanwhile, the thermal properties also increased obviously, e.g. the 5% weight loss temperature and glass transition temperature of the composite fiber containing 1.0 wt% f-PUCNTs were 50 °C and 13 °C higher than those of PI fiber, respectively.
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RSC Advances
·
2017
·Vol. 7
·期 4
·1956-1965
·
IF 3.108
Xiao Chen,Haohao Huang,Xia Shu,Shumei Liu,Jianqing Zhao
This paper introduces an effective approach to fabricate novel graphene/polyimide nanocomposite films with a low dielectric constant. Graphene fluoroxide (GFO) nanosheets were produced through the exfoliation of graphite fluoroxide (GiFO) in N-methyl-2-pyrrolidone (NMP). GFO nanosheets reacted with 4,4′-diaminodiphenyl ether (ODA) to become ODA-functioned GFO (GFO-ODA) with amine end groups, which provided reactive sites for covalent bonding with PI chains. GFO-ODA/PI composite films were prepared via the thermal imidization of a GFO-ODA/PAA solution. In this composite, GFO-ODA nanosheets were chemically bonded to the PI matrix. The dielectric constant of the films depended on the loading of GFO-ODA and its minimum value reached 2.75 (at 106 Hz) when the content of GFO-ODA was 1.0 wt%. Strong GFO-ODA nanosheets facilitate the load transfer and enhance the mechanical properties of PI films. GFO-ODA/PI film with 1.0 wt% loading had a Young's modulus ∼40% larger than pure PI film. In addition, the incorporation of GFO-ODA increased the glass transition temperature of the films and had no significant effect on the thermal stability.
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Polymers
·
2017
·Vol. 9
·期 6
·233
·
IF 3.364
Fei Wang,Leishan Shao,Qiyao Bai,Xinyuan Che,Bin Liu,Yinghan Wang
Vertical alignment of liquid crystal (LC) was achieved in an easy and effective way: in situ photopolymerization of dodecyl acrylate (DA) monomers initiated by polyimide based on 3,3′,4,4′-benzophenonetetracarboxylic dianhydride and 3,3′-dimethyl-4,4′-diaminodiphenyl methane (BTDA-DMMDA PI). The alignment behavior and alignment stabilities were characterized by a polarizing optical microscope (POM), which showed a stable vertical alignment after 12 h of thermal treatment. The chemical structures, morphology, and water contact angles of alignment films peeled from LC cells with and without DA monomers were analyzed by means of a Fourier transform infrared spectrometer (FTIR), a scanning electron microscope (SEM), and a contact angle tester, separately. The results confirmed that the DA monomers underwent self-polymerization and grafting polymerization initiated by the BTDA-DMMDA PI under ultraviolet irradiation, which aggregated on the surfaces of PI films. The water contact angles of the alignment films were about 15° higher, indicating a relative lower surface energy. In conclusion, the vertical alignment of LC was introduced by the low surface free energy of PI films grafted with DA polymer and intermolecular interactions between LC and DA polymers.Keywords:vertical alignment;photopolymerization;alignment stability;surface free energy
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高影响因子
ELECTROCHIMICA ACTA
·
2016
·
IF 4.803
Jinchao Li,Suqin Liu,Zhen He,Zhi Zhou
A series of semi-fluorinated sulfonated polyimides (6F-SPIs) are designed and synthesized via a one-step high-temperature polycondensation reaction. The sulfonation degrees of 6F-SPIs are controlled through changing the ratio of sulfonated diamine to non-sulfonated diamine in the casting solution. The physico-chemical properties and single cell performance of 6F-SPI membranes are thoroughly evaluated and compared to a non-fluorinated SPI membrane (6H-SPI-50) and a Nafion 115 membrane. The results show that the designed 6F-SPI membrane with a 50% sulfonation degree (6F-SPI-50) possesses the highest proton selectivity (1.613 × 10 5 S min cm −3 ) among all tested membranes. Besides, the 6F-SPI-50 membrane exhibits a promising performance for vanadium redox flow batteries (VRFBs), showing higher coulombic efficiencies (96.90–99.20%) and energy efficiencies (88.25–64.80%) than the Nafion 115 membrane (with coulombic efficiencies of 90.60–96.70% and energy efficiencies of 81.04–60.10%) at the current densities ranging from 20 to 100 mA cm −2 . Moreover, the 6F-SPI-50 membrane shows excellent chemical stability in the VRFB system. This work paves the way for the development of a new class of 6F-SPI membranes for the VRFB application.
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TRIBOLOGY INTERNATIONAL
·
2016
·
IF 2.259
Yuanliang Zhao,Xiaowen Qi,Yu Dong,Jian Ma,Qinglong Zhang,Laizhou Song,Yulin Yang,Qingxiang Yang
Polyimide (PI)/nano-SiO 2 composites were successfully fabricated via a novel in-situ polymerization. Microstructure, thermal properties, mechanical performance and tribological behaviors of these composites were investigated. The results indicate that nano-SiO 2 dispersed homogeneously. Compared with pure PI, thermal stability and heat resistance are higher about 10 °C with the addition of 5 wt% nano-SiO 2 . Compressive strength and modulus of composite with 5 wt% nano-SiO 2 increase by 42.6 and 45.2%, respectively. The coefficient of friction (COF) of composite with 5 wt% nano-SiO 2 decrease by 6.8% owing to the thick and uniform transfer films. Excess nano-SiO 2 could adversely affect the COF of PI/nano-SiO 2 composite. Additionally, wear resistance deteriorates obviously since transfer film exfoliates easily and nano-SiO 2 aggregates on the surface of transfer films.
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高影响因子
MATERIALS LETTERS
·
2014
·
IF 2.269
Xiaozhu Shi,Junping Duan,Jianjun Lu,Miaoqing Liu,Lijuan Shi
A typical of network-like polyimide/silica composite microspheres with a high SiO 2 content was successfully prepared by a suspension polymerization method. The microstructure, morphology, surface composition and thermal property were characterized by infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and thermogravimetric analyzer (TGA), respectively. The results showed that the size of PI/SiO 2 composite microspheres with 20–25 μm presented rough surface and an interpenetrating network had formed inside the spheres. The temperature of 5% weight loss was at about 503 °C, having higher thermal stability than pure PI.
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ELECTROCHIMICA ACTA
·
2017
·
IF 4.798
Tingxia Wang,Xin Li,Yimin Jiang,Yaxin Zhou,Lingpu Jia,Chunming Wang
An efficient electrocatalyst based earth-abundant materials for hydrogen evolution reaction (HER) is a prerequisite for improving the efficiency of producing hydrogen. However, the synthesis of such electrocatalysts by a simple and environmentally friendly method is still a tremendous challenge. Herein, NiSe nanoparticles were in situ deposited on the reduced graphene oxide-polyimide/carbon nanotube (RGO-PI/CNT) film by a green electrodeposition method. The NiSe nanoparticles on the RGO-PI/CNT (NiSe-RGO-PI/CNT) film was employed directly as a highly active HER electrocatalyst. The RGO-PI/CNT film allowed NiSe nanoparticles to grow rapidly on its surface. NiSe nanoparticles with a small size of 35–45 nm were distributed uniformly on the surface of the RGO-PI/CNT film. The good dispersity of NiSe nanoparticles permitted the exposure of more active sites, which enhanced the activity of HER on the NiSe-RGO-PI/CNT film. The NiSe-RGO-PI/CNT film performed well HER behaviors featured by a low overpotential (270 mV), a small Tafel slope (61 mV dec −1 ) and a considerable stability. The efficient HER performance of the NiSe-RGO-PI/CNT film was originated from the synergistic effect between the RGO-PI/CNT film and NiSe nanoparticles. This exploration provided a straightforward and green method to prepare a film electrocatalyst for HER.
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高影响因子
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