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91.
Most researches on graphene/polymer composites are focusing on improving the mechanical and electrical properties of polymers at low graphene content instead of paying attention to constructing graphene’s macroscopic structures. In current study the homo-telechelic functionalized polyethylene glycols (FPEGs) were tailored with π-orbital-rich groups (namely phenyl, pyrene and di-pyrene) via esterification reactions, which enhanced the interaction between polyethylene glycol (PEG) molecules and chemical reduced graphene oxide (RGO) sheets. The π–π stacking interactions between graphene sheets and π-orbital-rich groups endowed the composite films with enhanced tensile strength and tunable electrical conductivity. The formation of graphene network structure mediated by the FPEGs fillers via π–π stacking non-covalent interactions should account for the experimental results. The experimental investigations were also complemented with theoretical calculation using a density functional theory. Atomic force microscope (AFM), scanning electron microscope (SEM), X-ray diffraction (XRD), nuclear magnetic resonance (NMR), thermal gravimetric analysis (TGA), UV–vis and fluorescence spectroscopy were used to monitor the step-wise preparation of graphene composite films. 相似文献
92.
Longzhi Li Xiaowei Jiang Zhiguo Bian Jianwei Wang Fumao Wang Zhanlong Song 《Drying Technology》2019,37(2):173-185
Microwave lignite drying with assistance of biomass-derived char was addressed and effect of bio-char on drying rate and energy consumption was investigated in this work. Effective diffusion coefficient and activation energy for the drying process were also analyzed. The results indicated the drying process was largely dependent on the variation of sample temperature. Bio-char originated from pine wood was most favorable for lignite drying, considering its better promoting effect and advanced security. There existed an optimal bio-char addition ratio for drying process at different power. The corresponding optimal ratio was 10% at 231?W and 15% at 385?W, at which the biggest drying rate and the least energy consumption were reached. It was compared lignite drying initiated at 385?W was better for energy conservation. Effective diffusivity was improved and activation energy was simultaneously reduced, with the addition of bio-char. The minimum activation energy was 15.54?W?·?g?1, which was gained at bio-char addition ratio of 10%. The results revealed the effect of bio-char on depressing activation energy could rival that of metal-based additives. The drying process with assistance of microwave and bio-char could present technical and economical benefits on lignite upgrading. 相似文献
93.
《Carbon》2015
High performance of electrocatalysts for direct methanol fuel cells was demonstrated by three-dimensional (3D) graphene (GR) decorated with platinum (Pt)–gold (Au) alloy nanoparticles (3D-GR/PtAu). The 3D-GR/PtAu composite with a morphology like a crumpled paper ball was synthesized from a colloidal mixture of GR and Pt–Au alloy nanoparticles with aerosol spray drying. The 3D-GR/PtAu had a high specific surface area and electrochemical surface area of up to 238 and 325 m2/g(Pt), respectively, and the electrocatalytic applications of the 3D-GR/PtAu were examined through methanol oxidation reactions. The 3D-GR/PtAu had the highest electrocatalytic activity for methanol oxidation reactions compared with commercial Pt–carbon black and Pt-GR. The 3D-GR/PtAu was also highly sensitive electrocatalytic activity in the methanol oxidation reaction compared with the 2D-GR/Pt–Au. Furthermore, the electrocatalytic activity of the 3D-GR/PtAu had the highest performance among the catalysts containing Pt, Au, and GR for the methanol oxidation reactions. The increased electrocatalytic activity is attributed to the high specific surface area of the 3D formation and the effective surface structure of the Pt–Au alloy nanoparticles. 相似文献
94.
Cadmium Sulfide and Ferrous doped Cadmium Sulfide thin films have been prepared on different substrates using an electrodeposition technique. Linear sweep voltammetric analysis has been carried out to determine deposition potential of the prepared films. X-ray diffraction analysis showed that the prepared films possess polycrystalline nature with hexagonal structure. Surface morphology and film composition have been analyzed using Scanning electron microscopy and Energy dispersive analysis by X-rays. Optical absorption analysis showed that the prepared films are found to exhibit Band gap value in the range between 2.3, 2.8 eV for Cadmium Sulfide and Ferrous doped Cadmium Sulfide. 相似文献
95.
《Ceramics International》2020,46(4):4235-4239
In the work, we focused on the intrinsic dielectric behavior of Mg2TiO4 spinel ceramic by P–V–L theory and infrared spectra analysis. Ti–O bonds have larger bond ionicity values, thus playing an important role in dielectric polarization. The theoretical dielectric constant was predicted by calculating the bond susceptibility of each chemical bond. Furthermore, Ti(1)–O bonds are responsible for the structural stability of Mg2TiO4 ceramic. Based on classical dispersion theory, permittivity and loss corresponding to each infrared active mode were quantified, and then the crucial contribution of low-frequency modes to intrinsic dielectric properties were determined. 相似文献
96.
《Ceramics International》2020,46(6):7122-7130
This study examines three novel approaches for enhancing the thermoelectric (TE) properties of atomic-layer-deposited (ALD) ZnO thin films: 1) Hf-doping, which preserved the crystallinity of ZnO and provided effective phonon scattering owing to Hf's similar atomic radius to and large mass difference with Zn, leading to high power factor (PF) and low thermal conductivity (κ); 2) controlling the distribution of Hf into an alternating scattered phase/clustered phase superlattice, which balanced the high PF of the scattered phases with the low κ of the clustered phases, while providing significant energy-filtering effect to raise the Seebeck coefficient; 3) introducing 18O/16O periodicity into the Hf:ZnO films—by alternately using H216O and H218O as oxidants in the ALD processes, which further suppressed κ without compromising PF. The combination of the three approaches resulted in a maximum improvement in ZT of ~1600% over that of the undoped ZnO. 相似文献
97.
《Journal of the European Ceramic Society》2019,39(2-3):340-345
The Ca(1+2y)Sn(1-x)Si(1+y)O(5-2x+4y) low-permittivity microwave dielectric ceramics were prepared through solid-state reaction at 1350–1450 °C for 5 h. The relations between microwave dielectric properties and phase compositions for non-stoichiometric Ca(1+2y)Sn(1-x)Si(1+y)O(5-2x+4y) ceramics have been investigated. A single CaSnSiO5 phase with abnormally positive temperature coefficient of resonant frequency (τf = + 62.5 ppm/°C) was synthesised at 1450 °C. This composition was an effective τf compensator of CaSiO3 and Ca3SnSi2O9 phases with typically negative τf value. The CaSiO3 second phase was related to the Sn deficiency in the CaSn(1-x)SiO(5-2x) (0 < x < 1.0) composition, whereas the Ca3SnSi2O9 second phase was obtained by controlling the Ca:Sn:Si ratios on the basis of the Ca(1+2y)SnSi(1+y)O(5+4y) (0 < y < 1.0) composition. A promising low-permittivity millimetre-wave ceramic with most excellent microwave dielectric properties (εr = 10.2, Q×f = 81,000 GHz and τf = −4.8 ppm/°C) was produced from the Ca(1+2y)SnSi(1+y)O(5+4y) (y = 0.4) ceramic. 相似文献
98.
《International Journal of Hydrogen Energy》2020,45(53):28860-28869
Developing highly active, stable and sustainable electrocatalysts for overall water splitting is of great importance to generate renewable H2 for fuel cells. Herein, we report the synthesis of electrocatalytically active, nickel foam-supported, spherical core-shell Fe-poly(tetraphenylporphyrin)/Ni-poly(tetraphenylporphyrin) microparticles (FeTPP@NiTPP/NF). We also show that FeTPP@NiTPP/NF exhibits efficient bifunctional electrocatalytic properties toward both the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER). Electrochemical tests in KOH solution (1 M) reveal that FeTPP@NiTPP/NF electrocatalyzes the OER with 100 mA cm−2 at an overpotential of 302 mV and the HER with 10 mA cm−2 at an overpotential of 170 mV. Notably also, its catalytic performance for OER is better than that of RuO2, the benchmark OER catalyst. Although its catalytic activity for HER is slightly lower than that of Pt/C (the benchmark HER electrocatalyst), it shows greater stability than the latter during the reaction. The material also exhibits electrocatalytic activity for overall water splitting reaction at a current density of 10 mA cm−2 with a cell voltage of 1.58 V, along with a good recovery property. Additionally, the work demonstrates a new synthetic strategy to an efficient, noble metal-free-coordinated covalent organic framework (COF)-based, bifunctional electrocatalyst for water splitting. 相似文献
99.
Piezo-phototronic effect has been extensively investigated for the third generation semiconductor nanowires. Here, we present a demonstration that piezo-phototronic effect can even be applied to tune polarization-sensitive photodetectors based on cation-mixed organic–inorganic perovskite nanowires. A big anisotropic photoluminescence (PL) with linearly polarized light-excitation was found due to a strong spontaneous piezoelectric polarization besides the anisotropic crystal structure and morphology. The piezo-phototronic effect was utilized to tune the PL intensity, and an improved anisotropic PL ratio from 9.36 to 10.21 for linearly polarized light-excitation was obtained thanks to the modulation by piezo-potential. And a circularly polarization-sensitive PL characterized with circular dichroism ratio was also discovered, which was found to be modulated from 0.085 to 0.555 (with a 5.5-fold improvement) within the range of applied strain. The circular dichroism was resulted from the joint effects of the modulated Rashba spin–orbit coupling and the asymmetric carriers separation and recombination for right- and left-handed helicity due to the presence of effective piezo-potential. These findings not only reveal the promising optoelectronic applications of piezo-phototronic effect in perovskite-based polarization-sensitive photodetectors, but also illuminate fundamental understandings of their polarization properties of perovskite nanowires. 相似文献
100.
《能源学会志》2020,93(6):2381-2387
To enhance the activity of catalysts for CO removal, the perovskite-type catalysts La1-xSrxCoO3 (x = 0, 0.2, 0.4, 0.6, and 0.8) with different Sr2+ doping amount were synthesized by flame spray synthesis (FSS) method. The perovskite-type catalyst synthesized by FSS has a much larger specific surface area (SSA) than that prepared by other conventional methods. The SSA of catalyst increases with the increase of Sr2+ doping amount and the SSA of La0.2Sr0.8CoO3 reaches 31.65 m2/g. Compared with other conventional methods, FSS method significantly improves the activity of catalyst and makes it close to the performances of catalysts with surface modification. The substitution of La3+ by Sr2+ promotes the generation of secondary phase Co3O4 and SrCO3. The catalytic activity of La1-xSrxCoO3 increases with the addition of Sr2+, which results from the increasing active sites and oxygen vacancies. Interestingly, La0.4Sr0.6CoO3 performs the highest activity for CO oxidation and the CO conversion reaches 50% at 148.6 °C and 90% at 165.9 °C. The oxidation of CO over La1-xSrxCoO3 catalyst may follow a combination of MvK and L-H mechanisms according to the experimental results of H2-TPR. Moreover, the catalyst exhibits good catalytic activity in consecutive oxidation cycles. In consecutive oxidation experiments with La0.4Sr0.6CoO3, the CO conversion reaches 50% at 168.8 °C and 90% at 197.8 °C in the eighth oxidation cycle. These results prove that FSS method can further improve the activity of catalysts and is suitable for the preparation of efficient catalysts. 相似文献