Enhanced photocatalytic activity of nonstoichiometric crystalline TaO2F and Ta2O5 with carbon coating

Pure and carbon-coated tantalum-based oxides photocatalysts were synthesized via the mesocrystalline precursor transformation method by annealing pure and polydopamine-coated (NH₄)₂Ta₂O₃F₆ mesocrystals in Ar. The oxygen-poor atmosphere thermal annealing process assisted the formation of nonstoichiometric TaO₂F mesocrystals with more F and Ta₂O₅ nanorods with oxygen vacancies and the associated lower valence state Ta ions (Ta⁴⁺). Furthermore, the carbon coating, decomposed from coated polydopamine, helped to control their particle size within 100 nm by isolating the connection of (NH₄)₂Ta₂O₃F₆ subunits. Hence, as-synthesized products, particularly carbon-coated Ta₂O₅ nanosheets, owning large surface area (67.6 m² g^?1), fine particle size (<100 nm), excellent electronic conductivity, decreased bandgap energy, enhanced and extended absorption in the visible range, exhibited preferable photocatalytic activity in the photodegradation of methylene blue, reaching a 76.54 % and 41.71 % removal under ultraviolet and visible light illumination, suggesting a promising candidate for wide-range responsive photocatalytic applications.     

High-rate capability of carbon-coated micron-sized hexagonal TT-Nb2O5 composites for lithium-ion battery

With excellent specific capacity, superior cycle stability, safety and strong practical, Nb₂O₅ has been considered as one of the prospective anode materials for lithium-ion batteries (LIBs). However, current study suggests that Nb₂O₅ electrode materials for LIBs still face the vital issues of low electrical conductivity and poor rate performance. Therefore, carbon-coated TT-Nb₂O₅ materials are designed and synthesized through solid state method in this work, which present high specific capacity (228 mA h g^?1 at 0.2C), satisfactory rate properties (107 mA h g^?1 at 20 C). The outstanding electrochemical property can not only give the credit to the pseudocapacitance effect of TT-Nb₂O₅, but also attribute to introduction of carbon. The homogeneous carbon-coated materials enhance the electrical conductivity, increase the electron transmission speed and alleviate particle crushing. This research not only offers a new method for preparing excellent electrode materials, but also provides a kind of excellent anode material with prospective application for LIBs.     

NH3-SCR of NO at low temperatures over sulphated vanadia on carbon-coated monoliths: Effect of H2O and SO2 traces in the gas feed

The objective of this research is to asses the impact of the addition of H₂O, SO₂, and both in the SCR of NO at low temperatures over sulphated vanadia on carbon-coated monoliths. The sulphated catalyst keeps a 100% conversion and total selectivity to N₂ in the low temperature range, i.e. 473–500 K, when either H₂O or SO₂ is added to the gas feed. However, a decline of steady state conversion and selectivity occurs when both H₂O and SO₂ are added simultaneously because H₂O speeds up the deposition of ammonium sulphate salts. This decrease of catalyst performance is reversed when the reaction is carried out under dry conditions at temperatures higher than 473 K but not at lower temperature (453 K). Thus, the catalyst has demonstrated to be a good candidate for the SCR of NO at low temperatures even in stack gases containing traces of undesired components.     

Fabrication of carbon-coated boron carbide particle and its role in the reaction bonding of boron carbide by silicon infiltration

To tackle the dissolution problem of boron carbide particles in silicon infiltration process, carbon-coated boron carbide particles were fabricated for the preparation of the reaction-bonded boron carbide composites. The carbon coating can effectively protect the boron carbide from reacting with liquid Si and their dissolution, thus maintaining the irregular shape of boron carbide particles and preventing the growth of boron carbide particles and reaction formed SiC regions. Furthermore, the nano-SiC particles, originated from the reaction of the carbon coating and the infiltrated Si, uniformly coated on the surfaces of boron carbide particles, thus forming a ceramic skeleton of the nano-SiC particles-coated and -bonded boron carbide particles. The Vickers hardness, flexural strength and fracture toughness of the composites can be increased by 26 %, 45 %, and 37 % respectively, by using carbon-coated boron carbide particles as raw materials.     

Carbon-Coated SnO2 Nanorod Array for Lithium-Ion Battery Anode Material

Carbon-coated SnO₂ nanorod array directly grown on the substrate has been prepared by a two-step hydrothermal method for anode material of lithium-ion batteries (LIBs). The structural, morphological and electrochemical properties were investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electrochemical measurement. When used as anodes for LIBs with high current density, as-obtained array reveals excellent cycling stability and rate capability. This straightforward approach can be extended to the synthesis of other carbon-coated metal oxides for application of LIBs.     

Electrochemical performance of carbon-coated lithium manganese silicate for asymmetric hybrid supercapacitors

Nanoscale carbon-coated Li₂MnSiO₄ powder is prepared using a conventional solid-state method and can be used as the negative electrode in a Li₂MnSiO₄/activated carbon (AC) hybrid supercapacitor. Carbon-coated Li₂MnSiO₄ material presents a well-developed orthorhombic crystal structure with a Pmn2₁ space group, although there is a small impurity of MnO. The maximum specific capacitance of the Li₂MnSiO₄/AC hybrid supercapacitor is 43.2 F g⁻¹ at 1 mA cm⁻² current density. The cell delivers a specific energy as high as 54 Wh kg⁻¹ at a specific power of 150 W kg⁻¹ and also exhibits an excellent cycle performance with more than 99% columbic efficiency and the maintenance of 85% of its initial capacitance after 1000 cycles.     

光纤涂碳工艺和特性研究

介绍了利用国产拉丝设备、原材料制造碳密封涂覆光纤的工艺和产品特性。涂碳工艺稳定可靠，光纤静态疲劳参数n＞100，平均断裂应力＞60N，能够满足苛刻环境对光纤长期可靠性的要求。     

炭包覆TiO2复合物对低浓度苯的光催化降解

通过将TiO2粉末和聚乙二醇混合,随后在氮气气氛下热处理合成了炭包覆TiO2.利用粉末X射线衍射、紫外-可见漫反射光谱、透射电子显微镜和氮吸附对炭包覆TiO2复合物样品进行了表征,并研究了其对浓度为～1.2×10-5苯的光催化活性.结果表明:炭包覆量受热处理温度和聚乙二醇用量的影响,随着温度的升高和聚乙二醇量的减少而减少;TiO2的结晶度随着温度的升高而提高,但是炭包覆对TiO2晶体的生长有抑制作用.炭包覆锐钛矿样品比纯TiO2表现出对苯更高的光催化活性,这是由于炭吸附作用导致锐钛矿颗粒周围的苯浓度增加以及包覆炭可导致电荷的有效分离;另一个原因是锐钛矿相结晶度的提高.因此,要获得对苯具有高光催化活性的炭包覆TiO2需要综合考虑碳含量和锐钛矿晶体结构.

Abstract：

Carbon-coated TiO2 was synthesized by mixing TiO2 powders and polyethylene glycol,followed by heat treatment in nitrogen atmosphere. All samples were characterized by powder X-ray diffraction,UV diffuse reflectance spectroscopy,high-resolution transmission electron microscopy,and nitrogen adsorption. The photocatalytic activity of carbon-coated TiO2 for benzene degradation was investigated with a benzene concentration of ～ 1.2 × 10-5. Results showed that the residual carbon content was influenced greatly by heat treatment temperature (HTT)and the amount of PEG,which decreased and increased with increasing the temperature and the amount of PEG,respectively. The crystallinity of TiO2 was improved when the HTT increased. However,the carbon residue had an inhibition effect on the crystal growth of TiO2. The carbon-coated anatase samples were shown to exhibit higher photocatalytic activities than the pristine TiO2 because of the adsorption enrichment of benzene by carbon around the anatase particles and of the effective charge separation due to the electronic conduction of carbon. Another important factor affecting photocatalytic activity was the crystallinity of the anatase phase. High photocatalytic activity for benzene requires a balance between the carbon content and the anatase crystalline structure.     

Hydrothermal synthesis of carbon-coated lithium vanadium phosphate

A novel hydrothermal synthesis was developed to prepare carbon-coated lithium vanadium phosphate (Li₃V₂(PO₄)₃) powders to be used as cathode material for Li-ion batteries. The structural, morphological and electrochemical properties were investigated by means of X-ray powder diffraction (XRD), thermogravimetry (TG), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and constant current charge-discharge cycling. This material exhibits high initial discharge capacity of 178, 173 and 172 mAh g⁻¹ at 0.1, 0.2 and 0.5 C between 3.0 and 4.8 V, respectively. Moreover, it displays good fast rate performance, which discharge capacities of 136, 132 and 127 mAh g⁻¹ can be delivered after 100 cycles between 3.0 and 4.8 V versus Li at a different rate of 1, 2 and 5 C, respectively. For comparison, the electrochemical properties of carbon-coated lithium vanadium phosphate prepared by traditional solid-state reaction (SSR) method are also studied.     

Preparation and characterisation aspects of carbon-coated monoliths

Carbon-coated monoliths have been prepared by dipcoating cordierite monoliths in a polymer solution and subsequent carbonisation. Parameters of preparation that were varied were viscosity of the dipcoating solution, carbon precursor and carbonisation temperature. Two different commercial polymers have been used as carbon precursors, Novolac and Furan resins. Also monoliths have been coated with slurry of such resins and a commercial mesoporous activated carbon (CP-97).

The features of the final carbon that have been optimised are carbon loading, carbon layer thickness, coverage and mesoporosity. Coverage has been tested by leaching test in acid media. Both coverage and mesoporosity are considerably enhanced when the dipcoating mixture was a slurry of Furan resin and a commercial activated carbon. These features makes carbon-coated monoliths very suitable for their use as catalyst support in three-phase reactions.