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1.
In this study, we used a novel and facile hard-template etching method to manufacture mesoporous carbon hollow microspheres (MCHMs). We prove that the dielectric ability and microwave absorption of MCHMs can be adjusted by structural characteristics. When the average particle size of MCHMs is 452 nm, the paraffin composite material mixed with 10 wt% MCHMs can achieve a maximum reflection loss value of −51 dB with a thickness of 4.0 mm at 7.59 GHz. When the average particle size of MCHMs is 425 nm, the effective absorption bandwidth of the paraffin composite material mixed with 10 wt% MCHMs can achieve a broad bandwidth of 7.14 GHz with a thickness of 2.5 mm. Compared with other microwave absorbers, MCHMs possess high microwave absorption capacity and broad microwave absorption bandwidth with as low as a 10 wt% filler ratio. This excellent microwave absorption performance is due to the internal cavity and the mesoporous shell of MCHMs. By rationally designing the structure of MCHMs, excellent microwave absorption performance can be acquired. Meanwhile, this design concept based on a rational design of spherical structure can be extended to other spherical absorbers.

In this study, we used a novel and facile hard-template etching method to manufacture mesoporous carbon hollow microspheres (MCHMs).  相似文献   

2.
The anti-corrosion properties of the carbon substrates of cathode catalysts play a vital role in the commercialization of fuel cell vehicles. Our report reveals the enhanced durability of graphitized carbon black catalyst substrates in polymer electrolyte membrane fuel cells (PEMFCs), tested under simulated start-stop cycling and high potential holding conditions. Graphitized carbon treated at various temperatures is used as the support for Pt catalysts. The catalyst utilizing graphitized carbon treated at 1800 °C demonstrates superior antioxidation properties and the inhibition of Pt particle coarsening. The decay ratio of the potential at 1000 mA cm−2 has been reduced from 34.9% (commercial Pt/C) to 0.5% during high potential holding accelerated stress testing. Correspondingly, the growth of Pt particles is reduced from 0.95 nm (commercial Pt/C) to 0.08 nm; that is, the coalescence of Pt particles is effectively alleviated upon using graphitized carbon black.

The enhanced anti-corrosion properties of graphitized carbon substrates are evaluated via accelerated stress tests (ASTs). The graphitized surface properties of carbon are responsible for alleviating the coarsening and agglomeration of Pt particles.  相似文献   

3.
Polyaniline (PANI) nanorods were randomly deposited on oxidized 2D sugarcane pith-based porous carbon nanosheets by using dilute polymerization methods. The random stacked morphology of the PANI nanorods on the oxidized pith-based porous carbon nanosheets (SPCN) can be effectively controlled by simply changing the molar mass of aniline monomer. When the molar mass of the aniline monomer is increased to 0.02 M, the PANI nanorods can be randomly and uniformly stacked on the oxidized SPCN. Most of these stacked pores derived from random stack of the PANI nanorods on the oxidized SPCN are mesopore and macropore. These stacked pores not only facilitate the diffusion of ions in the stacked layer of the PANI nanorods, but also mitigate mechanical deformation of the PANI nanorods during the doping/dedoping process. Furthermore, the relationship between the properties of the oxidized SPCN/PANI-X (X represents the molar mass of aniline monomer) electrode materials and molar mass of aniline monomer is explored in detail. The oxidized SPCN/PANI-0.02 exhibits the best electrochemical performance in 1 M H2SO4. The largest specific electrode capacitance is up to 513 F g−1 at a current density of 0.25 A g−1. The oxidized SPCN/PANI-0.02 also exhibits excellent electrochemical cycling stability.

Polyaniline nanorods are randomly stacked on the oxidized sugarcane bagasse pith-based carbon sheets by using the dilute polymerization methods, which exhibits excellent electrochemical performance.  相似文献   

4.
Microwave absorbents with specific morphology and structure have fundamental significance for tuning microwave absorption (MA). Herein, N-doped carbon sphere nanoparticles and hollow capsules were successfully fabricated via oxidative polymerization of dopamine in different mixed solutions, without any template preparation or etching process. Compared to solid particles, the microwave absorbents consisting of N-doped carbon with a hollow structure showed enormously enhanced MA performance, exhibiting a broad effective absorption bandwidth (from 12.7 GHz to 17.9 GHz) and a minimum reflection loss of −27.2 dB with a sample thickness of 2.0 mm. This work paves an attractive way for simple and eco-friendly preparation of advanced light weight microwave absorbents.

N-doped carbon particles were prepared through environmentally friendly and convenient methods. N-doped carbon capsules exhibit the best microwave absorption ability compared to their spherical counterparts.  相似文献   

5.
A facile and simple pulse electrodeposition method was employed to deposit Mn2O3 nanoparticles on cathodically reduced titania nanotubes (R-TNTs) at different deposition time in the range of 3–15 min to investigate the influence of mass loading of Mn2O3 on the electrochemical performance of Mn2O3/R-TNTs nanocomposite for supercapacitor application. Mn2O3 nanoparticles were deposited on circumference of R-TNTs as well as in the nanotubes as revealed by FESEM images for all the deposited time. XPS result confirmed the presence of MnO2 (Mn4+) and MnO (Mn2+) on the Mn2O3/R-TNTs composite which provide pseudocapacitive behaviour for the electrode. Mass loading of Mn2O3 increased linearly with deposition time as confirmed by EDX analysis. The sample deposited for 12 min exhibits the highest areal capacitance of 51 mF cm−2 (which is 22 times enhancement over R-TNTs) at a current density of 0.1 mA cm−2 and specific capacitance of 325 F g−1 at 6 A g−1. The sample also show a high-rate capability by retaining 80% of its capacitance even at higher current density of 30 A g−1. Interestingly, it retained 98% of the capacitance over 5000 charge discharge cycles at 10 A g−1 after initial drop to 95% at 200th cycles suggesting an excellent long-term chemical stability. A considerably low equivalent series resistance (ESR) and charge transfer resistance (Rct) of 9.6 Ω and 0.4 Ω respectively was deduced from electrochemical impedance spectroscopy (EIS) analysis indicating good conductivity and improved charge transfer efficiency of Mn2O3/R-TNTs nanocomposite.

The mass loading of Mn2O3 by pulse electrodeposition (PED) onto reduced titania nanotubes (R-TNTs) greatly influences the electrochemical performance of the composite.  相似文献   

6.
In view of the current trend of capacitor materials, the development of capacitors with high dielectric permittivity and low dielectric loss is of great interest. In this work, the dielectric permittivity of reduced graphene oxide-incorporated styrene-butyl acrylate (rGO@SBA) composite microspheres synthesized by mini-emulsion polymerization was significantly improved. rGO with 2 wt% content gave a dielectric permittivity of 11 356 (at 1 KHz), which was 1925 times higher than that of pure SBA (5.9). SEM and TEM were conducted to observe the morphology and structure of the composite microspheres. After filling into polystyrene (PS), a segregated structure of (rGO@SBA) that enables a concentrated aggregation of rGO in SBA was fabricated. The dielectric permittivity of PS could reach 10.91 (at 1 KHz) by incorporating only 0.39 wt% rGO by using this segregated structure of (rGO@SBA). PS simply mixed with SBA microspheres and graphite (PS/rGO-SBA) was also fabricated as a comparison group to verify the effect of this segregated structure on the dielectric properties of the composites. After comparing the dielectric properties of PS composites with different structures, the enhancement in dielectric permittivity of the composites can be demonstrated.

The dielectric properties of rGO@SBA composite microspheres with core–shell structure and the effects of different preparation methods on the dielectric properties of PS were investigated.  相似文献   

7.
In the present work, TiO2 rutile nanorods and anatase nanoflakes have been grown on carbon fiber paper (CFP) by the hydrothermal method. Their photoelectrochemical properties and photocatalytic performances have been investigated. The introduction of CFP is found to improve visible light absorption intensity and effective surface areas apparently, and also make TiO2 photocatalysts easier to recycle from aqueous waste. An ultrasonic field was employed during the process of photocatalysis. Sono-photocatalytic efficiency is found to be enhanced significantly in comparison with those of photocatalysis and sonocatalysis, which indicates a positive ultrasonic synergy effect. The scavenger experiments reveal that superoxide radicals (˙O2) and hydroxyl (˙OH) are the predominant active species during the dye degradation sono-photocatalytic process assisted by CFP-supported TiO2 catalysts. To investigate the ultrasonic synergy photocatalytic effect, the generated amount of reactive oxygen species (ROS) was detected and quantitatively evaluated under visible light, ultrasound, and the combined condition of visible light and ultrasound. As a result, the present work provides an efficient way to improve photocatalytic performance and to realize easy recovery of photocatalyst, which will be helpful for better design of advanced photocatalysts for practical applications.

SEM images of TiO2(R) nanorods and TiO2(A) nanoflakes grown on CFP. And the corresponding catalytic performances under solely visible light, solely ultrasonic field, and the combined conditions of visible light and ultrasonic field.  相似文献   

8.
9.
Capacitive deionization (CDI) technology has attracted wide attention since its advent and is considered as one of the most promising technologies in the field of desalination and ion recycling. It is constructed with an electric field by applying a low voltage of direct-current to make ions migrate directionally in solution to achieve the purpose of ion separation and removal. The performance of CDI is heavily dependent on the electrode material. Carbon is widely used as CDI electrode material because of its lower price and better stability. To enhance the adsorption capacity, extensive research efforts have been made for the modification of carbon material. In this review, we enumerate and analyze four modification methods of carbon material including element doping, metal oxide modification, chemical treatment and surface coating. The influence of each modification method on CDI performance is concluded in the perspective mechanism and some constructive advice is put forward on how to effectively enhance the performance of CDI by the decoration of carbon materials.

The modification methods of carbon material and their effect on the CDI performance were reviewed.  相似文献   

10.
Activated carbon (AC) modification has been intensively studied in order to design carbon electrodes with enhanced electrochemical performance. Hexadecyltrimethylammonium bromide (HDTMA) and Tween 80 were employed for enhancing the surface activity of AC via synergism. The synergistic effects of the mixed surfactants on AC surface activity in the light of interface behaviors were studied. Both field emission scanning electron micrographs and FTIR spectra indicated a successful adsorption of loaded surfactants. AC gained a good wettability originated from the surfactants, especially in the binary mixture (T80-HDTMA). The zeta potential results unveiled the positive charge density enhancement in the mixed surfactants system. Isoelectric point and point of zero charge implicate heterogeneous distribution of charges and the extent of surfactants treatment. Tween 80 displayed a significant size control dependence on AC particles. Electrochemical characterization revealed a higher specific capacitance and a decaying resistance of specific capacitance in AC-T80-HDTMA than AC-HDTMA at high concentration. In 5 g L−1 of NaCl, AC-T80-HDTMA (0.01 : 0.01 mM) exhibits the specific capacitance of 209.79 F g−1, at 0.8 V whereas AC-HDTMA (0.01 mM) and AC exhibited 186.5 F g−1, 178.9 F g−1, respectively. Moreover, the stability testing reveals a strong attachment of HDTMA in AC-T80-HDTMA than AC-HDTMA with the loss of 0.32% and 1.32%, respectively. The hypothetical synergistic mechanism of surfactants adsorption on the surface of AC was depicted as hydrophobic interaction and steric stabilization being the main keys for the synergy between cationic and nonionic surfactants. This study demonstrates the beneficial effects of mixed surfactants on AC electrode properties and discloses the impact on electrochemical performance.

Enhancement of AC surface activity by surfactants synergism for electrochemical applications.  相似文献   

11.
Pt nanoparticles (PtNPs) well-dispersed on thiolated polyaniline (TPANI)-multiwalled carbon nanotubes (MWCNTs) were prepared for enhanced electrocatalytic oxidation of methanol in acidic media. Briefly, the preparation of nanocomposites was carried out via microwave-assisted thiol–ene reaction of 2,5-dimercapto-1,3,4-thiadiazole (DMcT) with oxidized PANI, which was synthesized in the presence of MWCNTs, yielding TPANI-MWCNTs; then, PtNPs were deposited on TPANI-MWCNTs by a microwave-assisted method to obtain PtNPs/TPANI-MWCNT nanohybrids. Fourier transform infrared spectroscopy, cyclic voltammetry (CV), transmission electron microscopy (TEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and inductively coupled plasma-atom emission spectroscopy were used to study relevant nanohybrid properties. TEM showed that PtNPs were well dispersed on TPANI-MWCNTs. TGA showed that PtNPs/TPANI-MWCNTs exhibited better thermal stability than PtNPs/TPANI-MWCNTs and PtNPs/MWCNTs. CV studies showed that PtNPs/TPANI-MWCNT-modified glassy carbon electrode (GCE) exhibited a larger electrochemically active surface area and higher electrocatalytic performance toward methanol electro-oxidation compared with those of PtNPs/PANI-MWCNTs/GCE and PtNPs/MWCNTs/GCE. Also, the PtNPs/TPANI-MWCNTs/GCE electrode possessed high stability and maintained 86% of its initial catalytic activity after 1000-cycle CV in 1.0 M CH3OH + 0.5 M H2SO4.

Pt nanoparticles (PtNPs) well-dispersed on thiolated polyaniline (TPANI)-multiwalled carbon nanotubes (MWCNTs) were prepared for enhanced electrocatalytic oxidation of methanol in acidic media.  相似文献   

12.
Electrochemical Paper-based Analytical Devices (ePADs) are an alternative to traditional portable analytical techniques due to features such as low-cost, easy surface modification with different materials, and high sensitivity. A fast and simple method to fabricate enhanced ePADs using pencil-drawing which involves the CO2 laser treatment of the carbon surface deposited on paper is described. The electrochemical performances of the devices were evaluated using cyclic voltammetry (CV) with different redox probes and electrochemical impedance spectroscopy (EIS). The electrochemical results show that a treated surface presents a lower resistance to charge transfer and changes the approach of the probe and the overlap of its orbitals with the electrode. To investigate the effects of the laser treatment process, chemical and structural characteristics were evaluated using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. These results indicated that laser treatment promoted the restoration of carbon–carbon double bonds and removed a thin layer of nanodebris present in commercial pencils, resulting in an improvement of the electrochemical kinetics. As a proof-of-concept, the Pencil-Drawing Electrode (PDE) was used for the detection and quantification of furosemide (FUR) in a sample of synthetic urine, exhibiting a limit of detection (LOD) of 2.4 × 10−7 mol L−1. The percentages of recovery of the FUR added to the samples A and B were 95% and 110%, respectively. The analysis using CO2 laser-treated PDE resulted in a fast, simple, and reliable method for this doping agent.

This study demonstrates a fast and simple method to fabricate enhanced ePADs using pencil-drawing with a CO2 laser treatment of the carbon surface deposited on paper. The sensor was applied to the detection of furosemide in a synthetic urine sample.  相似文献   

13.
Noninvasive Brain Computer Interfaces (BCI) have been promoted to be used for neuroprosthetics. However, reports on applications with electroencephalography (EEG) show a demand for a better accuracy and stability. Here we investigate whether near-infrared spectroscopy (NIRS) can be used to enhance the EEG approach. In our study both methods were applied simultaneously in a real-time Sensory Motor Rhythm (SMR)-based BCI paradigm, involving executed movements as well as motor imagery. We tested how the classification of NIRS data can complement ongoing real-time EEG classification. Our results show that simultaneous measurements of NIRS and EEG can significantly improve the classification accuracy of motor imagery in over 90% of considered subjects and increases performance by 5% on average (p < 0:01). However, the long time delay of the hemodynamic response may hinder an overall increase of bit-rates. Furthermore we find that EEG and NIRS complement each other in terms of information content and are thus a viable multimodal imaging technique, suitable for BCI.  相似文献   

14.
AIM AND BACKGROUND: While the importance of morale is well researched in the nursing literature, strategies and interventions are not so prolific. The complexities of interpersonal relationships within the clinical domain, and the critical issues faced by nurses on a daily basis, indicate that morale, job satisfaction and motivation are essential components in improving workplace efficiency, output and communication amongst staff. Drawing on educational, organizational and psychological literature, this paper argues that the ability to inspire morale in staff is a fundamental indicator of sound leadership and managerial characteristics. EVALUATION AND KEY ISSUES: Four practical concepts that could be implemented in the clinical setting are proposed. These include: role preparation for managers, understanding internal and external motivation, fostering internal motivation in nursing staff, and the importance of attitude when investing in relationships.  相似文献   

15.
The development of high efficiency and low-cost electrocatalysts for the oxygen reduction reaction (ORR) is urgently desired for many energy storage and conversion systems. Nitrogen-doped carbon xerogels (NCXs) which have been successfully applied as effective electrocatalysts for the ORR have continued to attract attention due to their competitive price and tunable surface chemistry. A new dual N-doped NCX (NCoNC) electrocatalyst is fabricated as a carbon based catalyst though a facile impregnation of peptone in a precursor and ammonia etching pyrolysis method. XPS analysis demonstrates that the NCoNC electrocatalyst not only has a high N doping amount, but also has an optimized chemical state composition of N doping, which play an important role in improving the microstructure and catalytic performance of the catalysts. XRD and HRTEM results show that the doped metal nano-particles are coated with a double carbon layer of graphene carbon (inner layer) and amorphous carbon (outer layer) forming serrated edges that facilitate the ORR process. The as-obtained NCoNC catalyst exhibits good electrocatalytic performance and excellent stability for the ORR in both acidic and alkaline environments. In particular, in alkaline electrolyte, the decrements of both the limiting current density and the half-wave potential of the NCoNC catalyst were significantly lower than those of a commercial Pt/C catalyst during accelerated aging tests. When serving as an air electrode in Zn–air batteries, the catalyst also exhibits superior catalytic performance with a peak power density of 78.2 mW cm−2 and a stable open-circuit voltage of 1.37–1.43 V. This work presents a novel tactic to regulate the microstructure and composition of carbon-based electrocatalysts by the facile and scalable dual-effect nitrogen doping method which may be conducive to promoting and developing highly efficient and promising electrocatalysts for the ORR.

This work presents a novel tactic to regulate the microstructure and composition of carbon-based catalysts by the facile and scalable dual-effect nitrogen doping method which may be conducive to promoting highly efficient electrocatalysts for ORR.  相似文献   

16.
In this study, porous carbon (3DHPC) with a 3D honeycomb-like structure was synthesized from waste biomass corncob via hydrothermal carbonization coupled with KOH activation and investigated as a capacitive deionization (CDI) electrode material. The obtained 3DHPC possesses a hierarchal macroporous and mesoporous structure, and a large accessible specific surface area (952 m2 g−1). Electrochemical tests showed that the 3DHPC electrode exhibited a specific capacitance of 452 F g−1 and good electric conductivity. Moreover, the feasibility of electrosorptive removal of chromium(vi) from an aqueous solution using the 3DHPC electrode was demonstrated. When 1.0 V was applied to a solution containing 30 mg L−1 chromium(vi), the 3DHPC electrode exhibited a higher removal efficiency of 91.58% compared with that in the open circuit condition. This enhanced adsorption results from the improved affinity between chromium(vi) and the electrode under electrochemical assistance involving a non-faradic process. Consequently, the 3DHPC electrode with typical double-layer capacitor behavior is demonstrated to be a favorable electrode material for capacitive deionization.

A porous carbon electrode with a 3D honeycomb-like structure demonstrates a high removal efficiency for the removal of chromium(vi) from water.  相似文献   

17.
In this study, Salix psammophila activated carbon (AC) was modified by immersing it in an AgNO3 solution and coating it with an N-doped TiO2 film to improve its self-regeneration performance in visible light. Ag+ was adsorbed and reduced to Ag nanoparticles by AC. Ti element only existed as Ti4+, and N element was incorporated into TiO2 mainly in the form of interstitial nitrogen. The photodegradation of Ag-N-TiO2-AC (AC coated with Ag and N co-modified TiO2) was enhanced under visible light irradiation because of its three inherent structures: (1) Ag and N co-modified TiO2 had a smaller average crystal size; (2) with a low bandgap (1.59 eV), the photoresponse region of Ag and N co-modified TiO2 was greatly extended; (3) the lifetime of the photogenerated holes was increased. With the increase in the AgNO3 dosage, the Ag-N-TiO2-AC photodegradation increased, while its adsorption decreased. Because of these synergistic effects, 0.05Ag-0.1N-TiO2-AC (where 0.05 is the dosage of AgNO3, g) presented the best self-regeneration performance under visible light irradiation.

In this study, Salix psammophila activated carbon (AC) was modified by immersing it in an AgNO3 solution and coating it with an N-doped TiO2 film to improve its self-regeneration performance in visible light.  相似文献   

18.
In this study, we investigated the effect of phase-change characteristics on the device performance of carbon-incorporated Ge2Sb2Te5 (CGST) to understand the origin of the enhanced reliability and stabilization of the device. Macroscopic and microscopic measurements confirmed that the structural stability significantly increased with the incorporation of as much as 10% carbon. After the completion of bond formation between C and Ge, the excess C (>5 atomic%) engages in bonding with Sb in localized regions because of the difference in formation energy. These bonds of C with Ge and Sb induce non-uniform local charge density of the short-range order. Finally, because the strong bonds between Ge and C shorten the short Ge–Te bonds, the high thermal stability of CGST relative to that of GST can be attributed to intensified Peierls distortion. The formation of strong bonds successfully underpins the local structures and reduces the stochastic effect. Moreover, extension of the C bonding to Sb enhances the structural reliability, resulting in highly stable CGST in the amorphous phase. Finally, the device stability of CGST in the reset state of the amorphous structure during the device switching process was significantly improved.

Charge density differences (CDDs) on Ge–C–Sb bonds in CGST(5%) and Ge–C–Sb in CGST(10%).  相似文献   

19.
合作学习对提高护理操作技能教学效果的探讨   总被引:5,自引:0,他引:5  
吴世芬  李春坚  黄煦 《护士进修杂志》2009,24(11):1016-1018
目的探讨合作学习对提高护理操作技能教学效果的影响。方法以高职护理专业学生为研究对象,实验班89人采用合作学习教学法,对照班87人采用传统教学法。结果实验班护理操作技能考核成绩及达标率优于对照班,差异有显著意义(P〈0.05,P〈0.01)。实验班取得学校护理技能操作大赛总分第一。结论合作学习可提高护理操作技能教学效果,帮助学生提高自身综合素质。  相似文献   

20.
Cycling coulombic efficiency including the 1st cycle is a crucial factor for nano-carbon based anodes. How to improve their coulombic efficiency and further prove whether the additional reversible capacity produced from the SEI film in the 1st cycle is an obstacle for their possible commercial application in Li ion batteries (LIBs). For this aim, a novel composite of Fe-encapsulated single-walled carbon nanotubes (Fe@SWNTs) with special nano-structure was designed and used as an anode material for LIBs. The resulting Fe@SWNT anode can provide much larger coulombic efficiency of 53.1% in the 1st cycle than 35.6% for pure SWNTs, implying the value increment reached ∼50%. The Fe@SWNTs can exhibit an reversible capacity of 420 mA h g−1 after 300 cycles and excellent rate performance at room temperature, being obviously better than 275 mA h g−1 for a SWNT anode. The origination of this extra improved reversible capacity can be confirmed to be derived from the reversible reaction of SEI film activated by the Fe catalyst. Meanwhile, the Fe@SWNT anodes exhibited superior low-temperature (at 5 and −15 °C) electrochemical performance, which should be associated with an improved effect of the highly conducting Fe at low temperature, and with the activation of catalyst Fe on the reversible capacity. In addition, when Fe@SWNTs were developed as carriers for attaching ZnO, the ZnO/Fe@SWNTs can deliver much better LIB performance than anodes of pure ZnO and ZnO/SWNTs. Thus, catalyst modification supplied a promising route to obtain improved coulombic efficiency and reversible capacity for LIB nano-carbon based anodes.

Fe filler enables catalytic activation for the anode to obtain improved lithium battery performance.  相似文献   

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