Journal of Physical Chemistry C
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2014
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IF 4.835
Yunxia Huang,Yan Wang,Zhimin Li,Zi Yang,Chunhao Shen,Chuangchuang He
The porous carbons (PCs) with tunable morphologies and pore sizes were prepared by the sol–gel process via a freeze-drying technique for microwave absorption applications. The results of Raman spectroscopy and nitrogen sorption analysis showed that the graphitization degree was barely influenced as the ratio of tert-butanol (T) to resorcinol (R) decreased, while the pore morphologies changed from the disordered slit-shaped pores to the uniform cage-like pores. Dielectric properties of the as-prepared carbon samples were determined by a vector network analyzer in the frequency range of 8.2–12.4 GHz. Results showed that the effect of pore morphology on the dielectric loss of PCs was dominant in the case of similar graphitization. When the T/R ratio was 7.5, the sample with cage-like pores revealed the maximum values in the real part ε′ and the imaginary part ε″ of complex permittivity, which were 13.2–6.5 and 15.6–10.1, respectively, suggesting a better capacity of dielectric loss in the 8.2–12.4 GHz range. The proposed mechanism for the effect of the pore morphologies on microwave absorption performance was discussed.
研究领域:
材料科学
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电磁学
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DOI
高影响因子
Nanoscale
·
2014
·Vol. 6
·期 16
·9831-9838
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IF 6.739
Bang Lin Li,Ling Xiao Chen,Hao Lin Zou,Jing Lei Lei,Hong Qun Luo,Nian Bing Li
Electrochemically induced Fenton (electro-Fenton) reaction was used for efficient and controllable preparation of hydroxyl radicals, leading to the generation of luminescent quantum dots through etching of as-exfoliated MoS2 nanosheets. Morphologic changes of MoS2 nanosheets during the electro-Fenton reaction were monitored using transmission electron microscopy, showing that etching of MoS2 nanosheets induced by hydroxyl radicals resulted in rapid homogeneous fracturing of the sheets into small dots via a transition of nanoporous morphology. The as-generated dots with vertical dimensional thickness of ca. 0.7 nm and plane size of ca. 5 nm were demonstrated to be MoS2 quantum dots (MoS2-QDs), and their photoluminescence properties were explored based on quantum confinement, edge effect, and intrinsic characteristics. Moreover, the degree of etching and the concomitant porosity of MoS2 nanosheets could be conveniently tuned via the electro-Fenton reaction time, resulting in a new morphology of nanoporous MoS2 nanosheets, with potential new applications in various significant areas.
研究领域:
材料科学
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电化学
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纳米技术
✓ 已验证
产品关联
DOI
PubMed
高影响因子
RSC Advances
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2019
·Vol. 9
·期 20
·11331-11340
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IF 3.049
Jian Chen,Umair Azhar,Yongkang Wang,Jihong Liang,Bing Geng
The choice of a suitable surfactant is key to the formation of a stable water-in-CO2 (W/C) or CO2-in-water (C/W) emulsion. It is even more critical in stabilization of the emulsion containing carbon dioxide (CO2). In this study, the successful preparation of W/C emulsion was achieved by using the amphiphilic block polymer poly(ethylene glycol) methyl ether-b-poly(trifluoroethyl methacrylate) (mPEG45-b-(TFEMA)n) as a surfactant, in which CO2 was used as a solvent for the fluoromonomer, trifluoroethyl methacrylate (TFEMA). In the case of the W/C emulsion, CO2 and TFEMA were used as the continuous phase and water as the internal phase of the emulsion system. It has been found that in the length of the block polymer mPEG45-b-(TFEMA)n, the fluorine-containing chain end has a significant effect on the morphology of the polymer and the type of emulsion formed. The morphology of the polymer was observed by scanning electron microscopy which confirmed the type of emulsion formed. With the fluorine-containing end segment, the morphology of the polymer changes from a small hollow sphere in a large hollow sphere to a hollow spherical to a porous structure. Correspondingly, it could be concluded that the type of emulsion could go through the process from water-in-CO2-in-water-in-CO2 (W/C/W/C) emulsion to water-in-CO2-in-water (W/C/W) emulsion to water-in-CO2 (W/C) emulsion. Also, suitable co-surfactants were identified in this study. Investigations were also attempted to check the effect of the amount of surfactant, cross-linker and water/CO2 ratio on the type of emulsion formed as well as the morphology of the resultant polymer.
研究领域:
材料科学
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化学工程
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DOI
高影响因子
Polymers
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2021
·Vol. 13
·期 19
·3384
·
IF 4.329
Tianping Zhang,Shun Yao,Lu Wang,Weijun Zhen,Ling Zhao
Both vulcanization reaction and CO2plasticization play key roles in the temperature rise foaming process of silicone rubber. The chosen methyl-vinyl silicone rubber system with a pre-vulcanization degree of 36% had proper crosslinked networks, which not only could ensure enough polymer matrix strength to avoid bubble rupture but also had enough dissolved CO2content in silicone rubber for induced bubble nucleation. The CO2diffusion and further vulcanization reaction occur simultaneously in the CO2plasticized polymer during bubble nucleation and growth. The dissolved CO2in the pre-vulcanized silicone rubber caused a temperature delay to start while accelerating further vulcanization reactions, but the lower viscoelasticity caused by either CO2plasticization or fewer crosslinking networks was still the dominating factor for larger cell formation. There was a sudden increase in elastic modulus and complex viscosity for pre-vulcanized silicone rubbers at higher temperature because of the occurrence of further vulcanization, but CO2plasticization reduced the scope of change of rheological properties, and the loss factor was close to 1 around 170 °C, which is corresponding to the optimum foaming temperature. The foamed silicone rubber had a higher cell density and smaller cell size at a higher temperature rising rate, which is due to higher CO2supersaturation and faster vulcanization reaction. These results provide some insight into the coupling mode and effect of CO2plasticization and vulcanization for regulating cell structure in foaming silicone rubber process.Keywords:methyl-vinyl silicone rubber;temperature rise foaming process;vulcanization reaction;CO2plasticization;rheological property;cell morphology
研究领域:
材料科学
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高分子化学
✓ 已验证
DOI
PubMed
高影响因子
JOURNAL OF FIRE SCIENCES
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2018
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IF 1.296
Daikun Jia,Jiyu He,Rongjie Yang
DOPO and its derivatives are excellent phosphorus-based flame retardants, which are applied to a series of polymer materials. In this article, a DOPO derivative bearing an active terminal epoxy group was synthesized using a non-solvent method. Fourier transform infrared spectroscopy, nuclear magnetic resonance, mass spectrometry, ultra-performance liquid chromatography, differential scanning calorimetry, thermogravimetric analysis, and viscosity measurements were performed to determine its molecular structure, purity, thermal performance, and fluidity. A possible fragmentation mechanism of the as-prepared DOPO derivative was analyzed using electron ionization mass spectrometer. All the results indicate that the synthesis was successful and the product had satisfactory purity and its initial decomposition temperature (T5%) under nitrogen and air atmosphere was 246°C and 240°C, respectively. Then, as a comparison with dimethyl methyl phosphonate, triethyl phosphate, and DOPO, e-DOPO was applied to a rigid polyurethane foam to investigate its effect on the flame retardancy, thermal stability, and cell morphology of polyurethane foam by limiting oxygen index, cone calorimetry, thermogravimetric analysis, and scanning electron microscopy. The results indicate that e-DOPO has a greater effect than DOPO and can effectively reduce the heat release and smoke release and improve the limiting oxygen index and thermal performance of the polyurethane foam. The cell size of the sample containing e-DOPO was more uniform.
研究领域:
材料科学
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聚合物化学
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阻燃性
✓ 已验证
DOI
高影响因子
iScience
·
2024
·
IF 4.6
Jianjun Wang,Tingting Wu,Xianlong Wang,Jiaqi Chen,Minyi Fan,Zhichun Shi,Jiao Liu,Liang Xu,Yu Zang
The rapid development of nuclear energy posed a great threat to the environment and human health. Herein, two hydroxyl-functionalized hyper-crosslinked polymers (PIHCP-1 and PIHCP-2) containing different electron active sites have been synthesized via Friedel-Crafts alkylation reaction of the polyimides. The resulting polymers showed a micro/mesoporous morphology and good thermal and chemical stability. Rely on the high porosity and multi-active sites, the PIHCPs show an ultrahigh iodine uptake capacity reached 6.73 g g −1 and the iodine removal efficiency from aqueous solution also reaches 99.7%. Kinetic analysis demonstrates that the iodine adsorption on PIHCPs was happened on the heterogeneous surfaces in the form of multilayer chemisorption. Electrostatic potential (ESP) calculation proves the great contribution of hydroxyl groups on the iodine capture performance. In addition, the iodine capture efficiency of both adsorbents can be maintained over 91% after four cyclic experiments which ensures their good recyclability for further practical applications.
研究领域:
材料科学
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环境科学
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核工程
✓ 已验证
产品关联
DOI
PubMed
高影响因子
Scientific Reports
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2019
·Vol. 9
·期 1
·1-11
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IF 4.011
Khan Karim,Tareen Ayesha Khan,Aslam Muhammad,Ali Khan Sayed,khan Qasim,Khan Qudrat Ullah,Saeed Muhammad,Siddique Saleemi Awais,Kiani Maryam,Ouyang Zhengbiao,Zhang Han,Guo Zhongyi
Since the last decades, non-precious metal catalysts (NPMC), especially iron based electrocatalysts show sufficient activity, potentially applicant in oxygen reduction reaction (ORR), however they only withstand considerable current densities at low operating potentials. On the other hand iron based electrocatalysts are not stable at elevated cathode potentials, which is essential for high energy competence, and its remains difficult to deal. Therefore, via this research a simple approach is demonstrated that allows synthesis of nanosize Fe-doped mayenite electride, [Ca 24 Al 28 O 64 ] 4+ ·(e − ) 4 (can also write as, C 12 A 7−x Fe x :e − , where doping level, x = 1) (thereafter, Fe-doped C12A7:e − ), consist of abundantly available elements with gram level powder material production, based on simple citrate sol-gel method. The maximum achieved conductivity of this first time synthesized Fe-doped C12A7:e − composite materials was 249 S/cm. Consequently, Fe-doped C12A7:e − composite is cost-effective, more active and highly durable precious-metal free electrocatalyst, with 1.03 V onset potential, 0.89 V (RHE) half-wave potential, and ~5.9 mA/cm 2 current density, which is higher than benchmark 20% Pt/C (5.65 mA/cm 2 , and 0.84 V). The Fe-doped C12A7:e − has also higher selectivity for desired 4e − pathway, and more stable than 20 wt% Pt/C electrode with higher immunity towards methanol poisoning. Fe-doped C12A7:e − loses was almost zero of its original activity after passing 11 h compared to the absence of methanol case, indicates that to introduce methanol has almost negligible consequence for ORR performance, which makes it highly desirable, precious-metal free electrocatalyst in ORR. This is primarily described due to coexistence of Fe-doped C12A7:e − related active sites with reduced graphene oxide (rGO) with pyridinic-nitrogen, and their strong coupling consequence along their porous morphology textures. These textures assist rapid diffusion of molecules to catalyst active sites quickly. In real system maximum power densities reached to 243 and 275 mW/cm 2 for Pt/C and Fe-doped C12A7:e − composite, respectively.
研究领域:
电化学
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材料科学
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催化
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能源材料
✓ 已验证
产品关联
DOI
PubMed
高影响因子
JOURNAL OF MEMBRANE SCIENCE
·
2021
·
IF 8.742
Xixia Liu,Xingchen Lu,Zonghuan Wang,Xiaohui Yang,Guangli Dai,Jun Yin,Yong Huang
Poly(lactic- co -glycolic acid) (PLGA) is a widely used polymeric biomaterial due to its excellent biocompatibility and biodegradation. Asymmetric PLGA hollow fiber membranes (HFMs) have been extensively used as porous tubular scaffolds for tissue engineering , e.g. for nerve conduits and artificial blood vessels . PLGA HFMs are generally fabricated through a dry-jet wet spinning process, and the porous morphology of PLGA HFMs induced by polymer/solvent/nonsolvent ternary phase inversion plays a key role in their biomedical performance. In this study, PLGA was dissolved in dimethyl sulfoxide (DMSO) as the dope fluid, and deionized water with different DMSO contents was used as the bore fluid. The influence of bore fluid composition on the HFM morphology and performance was investigated by measuring phase separation time, porosity, mechanical properties , and in vitro hydrolytic degradation. The results indicated that with increased bore fluid DMSO content, the inner and outer diameters, as well as the wall thickness of the HFMs, decreased significantly; also, the inner surface became more porous and the inner surface pore size and porosity increased. Cross-sectional SEM images showed that the middle layer of the five-layered microstructure gradually changed from large voids to finger-like microvoids when the DMSO content in bore fluid increased from 0% to 60%. Furthermore, the HFMs resulting from higher DMSO content in bore fluid had a lower porosity, a faster degradation rate, a higher Young's modulus , and a lower suture retention strength . More importantly, the in vitro cell culture on the inner surface of PLGA HFMs showed that PC12 cells cultured on HFMs prepared with 60% DMSO bore fluid exhibited better cell adhesion, longer neurite length, and alignment along the HFM longitudinal axis. A ternary phase diagram and the Flory-Huggins theory were applied to analyze HFM morphological formation. The study contributes to understanding of the mechanism of HFM porous morphology formation and should guide potential application of PLGA HFMs as tissue engineering scaffolds.
研究领域:
材料科学
·
生物医学工程
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组织工程
·
生物材料
✓ 已验证
产品关联
DOI
高影响因子
危险品化学品经营许可证（带存储）