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- 2018
- Carbon nanotubes
- Magnetic focused
- Field emission cathodes
- Travelling wave tubes
- Heat Trap
- outgassing
- lifetime
- current stability
- cathode
- thermionic emission
- Electronic Science and Technology
- Nanomaterials and Technology
- University of British Columbia
- Beijing Vacuum Electronics Research Institute
- Sun Yat-sen University
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Significant enhancement of photoactivity in one-dimensional TiO2 nanorods modified by S-, N-, O-doped carbon nanosheets
摘要： Titanium dioxide (TiO2) represents one of the most active photocatalysts among metal oxides for the degradation of pollutants and for solar water splitting to produce hydrogen. The most critical drawbacks hindering its broad practical use are the absorption majorly in the UV part of solar spectrum and slow charge dynamics. Combination of TiO2 with a suitable partner in a hybrid nanostructure can effectively address these drawbacks. Here we report a novel nanocomposite system based on one-dimensional TiO2 nanorods wrapped with a sulfur-, nitrogen-, and oxygen-doped carbon (SNOC) nanosheets. The SNOC nanosheets are synthesized by a cost-effective and facile route using eco-friendly carrageenan as a sulfur, oxygen, and carbon source and urea as a nitrogen source. Silica was used as the templating agent that leads to large surface area materials after its removal at the end of the synthesis. Therefore, the synthesized material exhibits superior photocatalytic performance for decoloring representative Rhodamine B (RhB) under visible light irradiation. SNOC shows the apparent rate constant of 7.6 × 10–3 min–1, which is almost 3 times higher than that of a SNOC material without using silica (2.8 × 10–3 min–1). This performance of doped carbon material can be assigned to the effect of large surface area and effective visible light adsorption. The TiO2 NRs / SNOC nanocomposite was investigated for photoelectrochemical water splitting showing much higher photocurrent densities (0.85 mA cm–2) than pure TiO2 nanorod arrays (0.35 mA cm–2), which was due to significant improvement in the charge transfer dynamics and co-catalytic effect of SNOC. All the materials prepared were evaluated on the basis of physical properties such as crystalline structure, optical absorption, surface topography, and electronic properties.
关键词： Water splitting,Photoelectrochemistry,Photocatalysis,Heterojunction,TiO2 nanorods,S, N, O-doped mesoporous carbon
更新于2025-09-23 15:23:52
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Development of Graphitic Domains in Carbon Foams for High Efficient Electro/Photo-to-Thermal Energy Conversion Phase Change Composites
摘要： In this research work, hierarchical porous carbon foams (CFs) with high surface area and three dimensionally (3D) interconnected macro/meso/microporous structures were prepared through pyrolysis of stabilized poly(acrylonitrile-co-divinylbenzene) P(AN-co-DVB) polyHIPE foams at 900 °C under nitrogen atmosphere. The prepared CFs revealed high surface area (540 m2 g-1), semi-ordered nanoporosity, high electrical conductivity (470 S m-1) and high graphitization degree. Further, HR-TEM observation of CFs revealed the formation of graphitic domains in the structures. The obtained CFs were employed for encapsulation of phase change materials (PCMs) e.g. paraffin (PA) and polyethylene glycol (PEG). The prepared PCMs composites revealed the excellent reversible thermal/chemical stability after frequent 200 heating/cooling cycles. Black CF/PA and CF/PEG composites can be promising structures to driven either by applying a small voltage (3-3.6 V) with high electric-to thermal efficiency (up to 85%) or by irradiating with sunlight with high photo-to thermal efficiency (up to around 91%).
关键词： paraffin and poly ethylene glycol,carbon foam,phase change materials
更新于2025-09-23 15:23:52
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Atomic layer deposition of hybrid metal oxides on carbon nanotube membranes for photodegradation of dyes
摘要： Synthetic dye pollution is a worldwide problem and quick remedies are urgently needed. Photocatalysis is a promising method to solve this problem and carbon nanotubes (CNTs) are promising components in producing high-performance composite photocatalysts. Nevertheless, the strong hydrophobicity dramatically impedes its application in aqueous environments. In this study, hydrophilic CNT-hybrid metal oxides (ZnO and TiO2) membranes were prepared by atomic layer deposition (ALD). We demonstrate that ALD is an efficient and flexible method to enhance the photocatalytic activity of CNT-based membranes, especially the membranes used in wastewater treatments. The hybrid hexagonal wurtzite ZnO and anatase TiO2 on CNTs after calcination could effectively enhance electron transfer and reduce photo-generated electron-holes recombination. The membranes exhibit preferable photocatalytic activity and stable reusability in dye degradation. This strategy of "ALD on CNTs" is expected to create other CNT-based membranes with additional functionalities and has bright prospect for wastewater treatments.
关键词： Carbon nanotubes,Photocatalytic degradation,Hybrid metal oxides,Atomic layer deposition
更新于2025-09-23 15:23:52
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A Novel Multilayer Sandwich Fabric-based Composite Material for Infrared Stealth and Super Thermal Insulation Protection
摘要： At present, infrared stealth materials for advanced detection and stealth technology is usually prepared with low emissivity coating on the surface, but there are very few efficient infrared stealth materials based on textiles with lightweight and flexible features. In this paper, we designed a carbon nanotube-doped aerogel (CNTAs) sandwich structure on polyimide (PI) fabric by hot pressing and then coated with a low emissivity Al-doped ZnO (ZAO) on the outer surface. The surface emissivity lower than 0.5 due to the existence of ZAO and the thermal conductivity of the intermediate interlayer aerogels as low as 0.013 W/(m?K). Additionally, through experiments, theoretical derivation and simulation analysis, we found the resultant composite demonstrated a high infrared stealth performance with super insulation effect, implying it will have a fine prospect in infrared stealth and thermal insulation protection fields with its unique structure and excellent properties.
关键词： Carbon Nanotube-doped Aerogel,Sandwich Structure,Infrared Stealth,Polyimide Fabric,Thermal Insulation,Al-doped ZnO
更新于2025-09-23 15:23:52
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Acceptor levels of the carbon vacancy in 4 <i>H</i> -SiC: Combining Laplace deep level transient spectroscopy with density functional modeling
摘要： We provide direct evidence that the broad Z1/2 peak, commonly observed by conventional deep level transient spectroscopy in as-grown and at high concentrations in radiation damaged 4H-SiC, has two components, namely, Z1 and Z2, with activation energies for electron emissions of 0.59 and 0.67 eV, respectively. We assign these components to Z?1/2 + e? → Z?1/2 → Z?1/2 + 2e? transition sequences from negative-U ordered acceptor levels of carbon vacancy (V_C) defects at hexagonal/pseudo-cubic sites, respectively. By employing short filling pulses at lower temperatures, we were able to characterize the first acceptor level of V_C on both sub-lattice sites. Activation energies for electron emission of 0.48 and 0.41 eV were determined for Z1(?/0) and Z2(?/0) transitions, respectively. Based on trap filling kinetics and capture barrier calculations, we investigated the two-step transitions from neutral to doubly negatively charged Z1 and Z2. Positions of the first and second acceptor levels of V_C at both lattice sites, as well as (?/0) occupancy levels, were derived from the analysis of the emission and capture data.
关键词： density functional theory,acceptor levels,deep level transient spectroscopy,negative-U ordering,carbon vacancy,4H-SiC
更新于2025-09-23 15:23:52
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A novel SiC nanowire aerogel consisted of ultra long SiC nanowires
摘要： SiC nanowire aerogel (SNA) with highly porous 3D nanowire architecture was synthesized by polymer pyrolysis chemical vapor deposition (PPCVD) process to deposit SiC nanowires in the pores of carbon foam, followed by high temperature oxidation of carbon foam. The microstructure of the prepared SNA was characterized by SEM, TEM and a large number of interweaving SiC nanowires with a diameter of 80-100 nm and a length of hundreds of micrometers form the highly porous 3D nanowire architecture of SNA. The prepared SNA possesses the performance combination of ultra-low density (30±7 mg·cm-3), high-temperature oxidation resistance (750 °C), noncombustible and fire resistance property in the fire, excellent thermal insulating property (0.03 W·m-1·k-1 at room temperature in He) and compressive strength of 0.11 MPa, which is applicable as high-temperature heat insulator, ceramic matrix composite, high temperature flue gas filter, fire-proofing material and catalyst carrier.
关键词： Carbon foam,Aerogel,SiC nanowire,CVD
更新于2025-09-23 15:23:52
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Purification and comprehensive utilization of sapphire kerf waste
摘要： Sapphire kerf waste (a fine powder) is a great potential source of high-purity α-Al2O3 and is currently discarded without reutilization, which is a waste of this resource and causes environmental problems, such as occupying space and generating dust. Herein, we report a feasible combined method to recycle valuable high-purity α-Al2O3 from sapphire kerf waste through the ultrasound-assisted leaching of nickel, diamond removal by bulk heating and a grinding process. The impurities in the waste were collected, and their existence states were characterized as independent metal nickel and diamond. The nickel impurity was removed from the waste by ultrasound-assisted leaching using a mixture of sulfuric acid and nitric acid, and the optimal leaching efficiency reached 99.67% under the conditions of sulfuric acid: nitric acid = 2:1 (v/v), 4 mol/L H+ concentration, 4 mL/g liquid-solid ratio, 45 °C, 30 min, 200 rpm, 240 W ultrasonic power and 45 kHz ultrasonic frequency. Subsequently, nickel ions in the lixivium were recycled in the form of nickel sulfate through extraction and stripping treatments. The diamond impurity was removed by bulk heating in flowing oxygen, and the optimal removal ratio was 99.65% under the conditions of 800 °C, 30 min and oxygen flow of 400 mL/min. High-purity α-Al2O3 was successfully recovered from the sapphire kerf waste after the grinding process, which had a purity higher than 99.99 wt% and an average diameter of 0.6 mm. In addition, the kinetics of leaching nickel and diamond removal were systematically analysed based on the shrinking model, and the chemical reaction was found to be the control step. The reaction mechanisms of the two processes were also studied. The economic evaluation revealed that the profit from dealing with 1 kg sapphire kerf waste with this method was $13.68. Therefore, the proposed method is promising for providing technical and economical guidance for industrial production.
关键词： Purification,Sapphire kerf waste,Carbon removal,Nickel leaching,Recycle
更新于2025-09-23 15:23:52
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Synthesis of g-C3N4/N-doped CeO2 composite for photocatalytic degradation of an herbicide
摘要： In photocatalysis, surface engineered CeO2 could be vital due to oxygen vacancies arise from multiple valency, i.e. Ce3+ and Ce4+. This study reports photocatalytic properties of g-C3N4/CeO2 composite synthesized by a facile method in the presence of l-arginine. Physicochemical properties of g-C3N4/CeO2 material were analyzed through various characterization techniques such as XRD, UV–Vis, physisorption, etc., and correlated with its photocatalytic activity. Observed bandgap of the synthesized composite material was in the visible region, around 2.8 eV which is less than that of typical ceria, but higher than bandgap of exfoliated g-C3N4. On the further side, N doping into CeO2 was confirmed through XPS analysis. It is estimated that synthesis method aided for the N doping, which further played key role in lowering the bandgap of g-C3N4/CeO2 composite. Finally, Photocatalytic activity of g-C3N4/CeO2 composite was analyzed through degradation of an herbicide i.e. diuron, and the study revealed the good performance of the catalyst.
关键词： Graphitic carbon nitride,Photocatalysis,N doping,Herbicide,CeO2
更新于2025-09-23 15:23:52
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Photocatalytic oxidative desulfurization and denitrogenation of fuels over sodium doped graphitic carbon nitride nanosheets under visible light irradiation
摘要： A cost-efficient photocatalytic oxidative denitrogenation and desulfurization system for fuels under visible light was developed on the basis of Na doped g-C3N4 nanosheets catalyst. The process adopted molecular O2 as oxidant to substitute for the expensive H2O2, and it adapted to the removal of small molecules of pyridine and thiophene. Na doped g-C3N4 nanosheets were obtained via a simple mixed-calcination pathway using NaCl as Na source. The structural, photophysical and chemical properties of the photocatalysts were characterized and compared to those of the original g-C3N4. It was verified that Na was successfully doped in the g-C3N4 lattice in a uniform chemical state. Moderate amount of Na doped in g-C3N4 generated the highly dispersed and porous nanosheets, which further improved the surface energy and reduce the recombination rate of electron-hole pairs. Na doped g-C3N4 exhibited enhanced performance simultaneously in the photocatalytic oxidative denitrogenation and desulfurization. The optimal catalyst obtained considerable removal efficiency for pyridine and thiophene, depending on its improved structural and photochemical properties by Na doping. A proposed mechanism revealed that the holes acted as the major active species for the denitrogenation and desulfurization, while the superoxide radicals originating from the combination of electron and O2 gave a promotion effect.
关键词： Pyridine,Sodium doping,Graphitic carbon nitride,Thiophene,Photocatalytic oxidation
更新于2025-09-23 15:23:52
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TiO2/MoS2 heterojunctions-decorated carbon fibers with broad-spectrum response as weaveable photocatalyst/photoelectrode
摘要： The development of efficient and recyclable photocatalysts with wide spectrum response has drawn much attention. Herein, we prepared TiO2/MoS2 heterostructures on carbon fibers (CFs) by a two-step hydrothermal method. CFs/TiO2/MoS2 exhibits a strong and wide absorption spectrum from ultraviolet to near-infrared region (> 1200 nm). Under the irradiation of visible-light, CFs/TiO2/MoS2 could degrade 97.6% Rhodamine B (RhB) after 100 min, 94.2% Acid Orange 7 (AO7) or 93.4% tetracycline hydrochloride (TC) after 60 min, and 88.7% 4-chlorophenol (4-CP) after 180 min. Moreover, CFs/TiO2/MoS2 bundles can be further weaved into a cloth (area: 4 × 4 cm2). CFs/TiO2/MoS2 cloth as a working electrode exhibits significant photocurrent (7.53 × 10?6 A/cm2) and enhanced photoelectrocatalytic efficiency (100% TC) comparing with only photocatalysis (90.7% TC) or electrocatalysis (47% TC). In particular, CFs/TiO2/MoS2 cloth shows excellent stability. Therefore, CFs/TiO2/MoS2 cloth has great potential to be used as flexible and weaveable photocatalyst/photoelectrode for degrading various pollutants.
关键词： Photoelectrocatalysis,Photocatalyst,Carbon fibers,Visible-light,TiO2/MoS2
更新于2025-09-23 15:23:52