Efficient preparation of low-cost multi walled carbon nanotubes (MWCNTs) will make them more competitive in the application of lithium ion battery composite additives and conductive paste. For a long time, the catalyst with high activity is the key factor to prepare MWCNT. In this paper, rare earth elements (RE) were introduced into layered double/triple hydroxides (LDH/LTHs) catalyst for the first time to prepare a composite catalyst with high activity, and then MWCNT with high yield was prepared by chemical vapor deposition (CVD). Temperature and the introduction of RE elements will strongly affect the yield of MWCNTs. La, Ce, Dy and Pr can improve the catalytic efficiency of LTHs while Eu, Er and Nd reduce their catalytic efficiency. Specifically, the addition of Dy element can nearly double the productivity of CNTs at 650 °C, reaching to 3093%. Further analysis shows that the strong magnetic effect of Dy element can surround the iron nanoparticles, effectively inhibiting the fusion of iron particles at high temperatures, and improving the catalytic activity of the catalyst.

High-rate carbon nanotube/magnetic-sheet composites are in situ synthesized by fluidized bed for EMA. An RL value of −40.0 dB is achieved at a frequency of 5.0 GHz.

Carbon nanotubes have the significant disadvantage of insufficient magnetic loss as a microwave absorbing material, while transition metal catalysts for the preparation of carbon nanotubes still limit the cost reduction. In this study, a facile in-situ strategy was developed to synthesize CNTs/laterite composites, smartly employing the catalysts performance of laterite to realize the synthesis of CNTs and simultaneously construct three-dimensional (3D) "caterpillar" structure. As expected, the exposed CNTs with high crystallinity in caterpillar-like CNTs/ laterite composites are believed to provide a good conductive 3D network and abundant paths for trapping of incident electromagnetic waves, as well as the iron nanoparticles produced by hydrogen reduction during the in situ catalytic growth of carbon nanotubes on laterite significantly increase the magnetism of the materials and thus increase the magnetic loss. As a result, the RL curves of the CNTs/laterite-paraffin composites show a maximum reflection loss of-77 dB at 3.2 GHz with 4 mm thickness. Generally, this synthesis strategy presented in this study paves a new way for the fabrication of low-cost CNTs-based composite with high performance for microwave absorbing.

In this work, single-walled carbon nanotubes (SWNTs) were synthesized by a scalable floating catalyst chemical vapor deposition (FCCVD) method, in which Gd was used as growth promotor to improve the yield and quality of SWNTs. Based on the characterization results of electron microscope, thermogravimetric analysis and Raman spectroscopy, the application of Gd leads to a great increase in the production of large-diameter SWNTs with a narrow diameter distribution and an enhanced thermal stability. The newly developed FCCVD technique makes it possible to produce large-diameter SWNTs at a low cost, and the generated structurally homogenous SWNTs are suitable for their applications in the fields of electronic systems and electromagnetic shielding, etc.

Natural catalysts used in the synthesis of carbon nanotubes have significant cost advantages due to their huge reserves, but natural minerals often require complicated pretreatments to obtain satisfactory products. In this study, red sandstone was directly used as a catalyst for the synthesis of multi-carbon nanotubes by chemical vapor deposition without complicated pretreatment. The SEM, TEM, Raman and TG characterization of the products at different growth temperatures ([Formula: see text]C, [Formula: see text]C and [Formula: see text]C) showed that [Formula: see text]C is the optimal condition for the growth of multi-walled carbon nanotubes (MWCNTs) by red sandstone. High-quality multi-wall carbon nanotubes can be obtained with a relatively high yield, and the [Formula: see text] of the product reaches 1.78, which exceeds that of many commercial multi-wall carbon nanotubes. Compared with other natural materials as catalysts for the synthesis of MWCNTs, red sandstone has a huge cost advantage because it can catalyze the synthesis of high-quality MWCNTs at [Formula: see text]C without complicated pretreatment.

Carbon nanotube (CNT) long array with higher aspect ratio is an ideal electrode material for high performance supercapacitors due to its excellent conductivity and high specific surface area (SSA). How to quickly and concisely prepare high-quality CNT long-arrays is the key to achieving large-scale application. Herein, high-quality spring-like CNT (tube diameter 5–8[Formula: see text]nm) long arrays (100–400[Formula: see text][Formula: see text]m) with high purity (96.2% after purification) and ultrahigh graphitization ([Formula: see text]) were fabricated in a high yield (eight times) by a self-supporting catalyst chemical vapor deposition (CVD) method, and its formation process was first investigated under specific conditions of iron content in catalyst, growth temperature and carbon source species. The SSAs can reach 728[Formula: see text]m 2 /g, which is more than twice that of MWCNTs on the market. The high graphitization and ultra-large SSAs of this spring-like CNT arrays as electrodes exhibit potential electrochemical performance.

The excellent capacitance performance of DWCNTs with high BET area and electrical conductivity far exceeds that of MWCNTs and they are cost-effective compared to SWCNTs on the market.

Low-cost catalysts are of great significance for the batch synthesis of carbon nanotubes. In this study, the low-cost red soil was directly used as a natural catalyst to catalyze the growth of multi-walled carbon nanotubes (MWCNTs). The results of SEM, TEM, Raman, TG and carbon yields of the products consistently showed that 400 degrees C calcined red soil lead to high quality MWCNTs growth, the Raman IG/ID of the product is 1.66, which indicates that the product has exceeded the graphitization of many industrially synthesized MWCNTs. The high catalyzation efficiency may be attributed to the fact of composition characteristics that red soil lacks alkali metals and alkaline earth metals but is rich in iron and aluminum oxide, making the composition of red soil similar to the catalyst composition used in the synthesis of carbon nanotubes by common chemical vapor deposition method. Meanwhile the impurity content is less than other natural catalytic materials. The porous structure formed after proper calcination has also played a positive role to the catalytic growth of MWCNTs, which improved catalyst utilization by facilitating the gas phase diffusion. We explored a technique for synthesis of high-quality MWCNTs at low cost using soil as a catalyst.

Carbon onions have shown potential applications in many fields due to their low density, tunable conductivity, excellent thermal and chemical stability. In this study, we report an efficient method for synthesis of gram-scale hollow carbon onions (HCNOs). A chemical vapor deposition (CVD) process was carried out at 700 degrees C with magnesium oxide supported cobalt as catalyst. Abundant HCNOs were obtained by leaching the CVD product in hydrochloric acid when the precursor weight ratio of cobalt and magnesium oxide is 5%. Scanning electron microscopy and transmission electron microscopy images indicate the sample is composed of hollow polyhedral particles with diameter of 10-50 nm. The thermogravimetric analysis indicates the purity of HCNOs is about 99%. X-ray diffraction and Raman spectra demonstrates a moderate graphitization of HCNOs in which graphite carbon and defective carbon both present. The graphite carbon can provide good conduction that is beneficial to introduce the microwave, while the defects can provide abundant polarization center to stimulate the formation of multiple dielectric resonances. The calculated reflection loss curve of HCNOs with a thin thickness of 2 mm exhibit wide absorption bandwidth at high frequency (13.5-16.9 GHz), indicating an excellent microwave absorption performance at high frequency. (C) 2020 Elsevier Ltd. All rights reserved.

研究了Sc含量以及固溶、时效热处理对6061铝合金组织和力学性能的影响.结果 表明,添加Sc可以有效细化铸态6061铝合金晶粒尺寸,提高力学性能,Sc的最佳添加量为0.2 mass％.固溶+时效可以进一步提高6061铝合金的力学性能,不含Sc的6061铝合金最佳热处理工艺为570℃×1h固溶+175℃×8h时效,含0.2 mass％ Sc的6061铝合金为570℃×1h固溶+185℃×5 h时效,时效过程中析出的与基体存在共格关系的β"(Mg5 Si6)针状相、Al3Sc纳米颗粒起强化作用.

碳纳米管作为一种一维纳米材料具有独一无二的力学、光学、电子、热稳定及化学稳定特性,主要被应用于锂离子电池电极材料、金属、树脂、塑料、橡胶的改性增强领域.但碳纳米管也存在缺点,尤其是其合成结构的不可控性,严重阻碍了它的进一步应用.因此,探索出制备高品质大规模碳纳米管的生产技术迫在眉睫.目前,碳纳米管常用的合成方法有化学气相沉积、电弧放电和激光烧蚀,相比于其他两种方法,电弧放电法更为经济、高效.采用电弧法合成的碳纳米管纯度高达90％,石墨化程度远胜化学气相沉积法.同时,单次电弧实验时间在1～30 min之间,电源输出功率在750～3000 W之间,且单次碳纳米管产量高达15 g,复合石墨电极的转化率高于75％.根据引弧介质的不同,电弧法可分为真空电弧放电与溶液电弧放电.溶液中碳纳米管的产量很低,因此溶液电弧放电法未得到推广;目前真空介质的研究则非常成熟,真空电弧放电法具有合成设备简单、操作便捷、产物品质高等优势,但其生长机理存在较大争议.电弧法的影响参数主要包括电源类型、引弧气体类型与压力以及催化剂体系.其中,最为成熟的工艺是采用直流电源、氦气引弧、钇镍两相催化进行放电实验.本文归纳了电弧放电法制备碳纳米管的研究进展,分别介绍了电弧放电法生长碳纳米管的装置构造与反应机理、对电弧放电法产生影响的参数,分析了电弧放电法合成碳纳米管面临的难题以及可改善空间,以期为制备高品质、高石墨化程度、规模化的碳纳米管提供借鉴.

研究了不同导热填料对碳纳米管水性红外辐射散热涂料性能的影响,通过在涂料体系中添加不同比例的无机导热填料,研究填料组分和含量对涂层散热温差及红外辐射率的影响规律,并结合涂层热导率参数及填料颗粒结构,研究辐射增强散热的影响因素.研究发现,AlN和SiC对涂层热导率和红外辐射率均具有正面作用,当亚微米SiC添加量为20％ 时,涂层的散热温差比未添加SiC前提升4℃,并发现涂层热导率和辐射率的提升对提高其散热性能具有显著作用.

Carbon nanotube/nanocapsule composite, mainly consisted of single walled carbon nanotube bundles with a length of a few hundred nanometres and nickel encapsulated carbon nanocapsules with 5-20 nm in diameter, have been fabricated by a facile arc discharge experiment. The cross-linked nanotube bundles provide a three-dimensional porous, conductive network and the nanocapsules adhere to nanotube bundles through Van der Waals forces to form hierarchical structures, which is beneficial to the dissipation and absorption of microwaves. The calculated reflection loss curve of the composite reflects such hierarchical structures with a thin thickness of 2 mm exhibit wide absorption bandwidth at high frequency (13.0-17.8 GHz), indicating that the as-prepared carbon nanotube/nanocapsule composite is applicable in the field of microwave absorption. (C) 2019 Elsevier B.V. All rights reserved.

Recently, the development of high-performance bifunctional oxygen catalysts integrated with flexible conductive scaffolds for rechargeable metal-air batteries has attracted considerable interest, driving by fast-growing wearable electronics. Herein, we report a flexible bifunctional oxygen catalyst thin film consisting of Co-N-C bifunctional catalysts embedding in carbon nanotube (CNT) networks. The catalyst is readily prepared by pyrolysis of cobalt-based zeolitic imidazolate frameworks (ZIF-67) that are in-situ synthesized in CNT networks. Such catalyst film demonstrates very high catalytic activities for oxygen reduction (onset potential: 0.91V, and half-wave potential: 0.87V vs. RHE) and oxygen evolution (10mA cm(-2) at 1.58V) reactions, high methanol tolerance property, and long-term stability (97% current retention). Moreover, our integrated catalyst film shows very good structure flexibility and robustness. Based on the obtained film air electrodes, flexible Zn-air batteries demonstrate low charging and discharging overpotentials (0.82V at 1 mA cm(-1)) and excellent structure stability in the bending tests. These results indicate that presently reported catalyst films are potential air electrodes for flexible metal-air batteries. (C) 2019 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.

Air cathodes with a high catalytic activity of oxygen reduction reactions (ORR), long-term stability, and fast channels for mass and charge transportations are highly desirable for the development of fuel cells and metal-air batteries. Herein, we report a freestanding high-performance air electrode originated from an interconnected and highly conductive carbon nanotube (CNT) network film with iron impurity. The air electrode film where PtFe alloy nano-particles with average size of similar to 5 nm homogeneously are confined on CNTs is realized via a transient Joule heating induced alloying of the iron nanoparticles with platinum for 250 ms. Benefiting from the well-alloyed structure and the stabilized anchoring sites, the low-platinum-containing (1.7 wt %) hybrid film shows ORR mass activity over 6 times higher than that of commercial 20 wt % Pt/C catalyst. Besides, it demonstrates excellent long-term stability and high tolerance against methanol poisoning. High electrical conductivity, mechanical strength, and porous networks are well-retained for this freestanding air electrode film, integrating ORR catalysts, current collectors, and porous electrodes. Fiber Zn-air batteries assembled with these self-supported air cathodes show high discharging capacity (31.3 mA h cm(-3) at 10 mA cm(-3)) and excellent stability even after repeated applications, presenting a proof of concept and their potential applications for flexible and wearable energy supplies.

Electricity-driven water splitting to produce hydrogen fuels and oxygen is considered among the most promising technologies for sustainable energy. Despite considerable progress over the past decade in this field, no water-splitting electrocatalyst with selectivity between the oxygen and hydrogen evolution reactions (OER and HER) has been reported so far, to the best of our knowledge. Here, we develop a unique, customizable water-splitting electrocatalyst by systematically modulating the doping of the nonmetal element sulfur (S) into cobalt molybdate using thioacetamide (TAA) as a sulfur precursor. The resultant S-doped cobalt molybdate electrocatalysts showed unexpectedly high selectivity, i.e., the OER and HER activities could be freely adjusted through tuning the sulfur doping level. In the case of a high TAA/cobalt molybdate mass ratio of 1.6, the S-doped sample was highly selective for HER, achieving an excellent electrocatalytic activity comparable to those of previously reported state-of-the-art transition-metal (Co, Ni, and Fe)-based HER electrocatalysts. In sharp contrast, when the TAA/cobalt molybdate mass ratio was as low as 0.4, the S-doped sample was remarkably selective for OER with outstanding catalytic activity that even outperformed the commercial RuO2 catalyst.

An adaptive and stable gum bio-electrolyte was developed, which enabled Zn-ion batteries that have very competitive performances in terms of capacity, energy density, power density, rate capability and cyclability.

In this study, an electrochemical biosensor was developed for highly sensitive and specific detection of target miRNA-155. The structure was formed by the hybridization of a tetrahedral DNA nanostructure-based biomolecular probe assembled on 3D nitrogen-doped reduced graphene oxide/gold nanoparticles (3D N-doped rGO/AuNPs) electrode surface. Upon addition of target miRNA-155, the gold and silver nanorod/thionine/complementary DNA (AuAgNR/Thi/F) was hybridized with the target, and used for signal amplification, catalyzing the reduction of Thi as an electron mediator. Due to the signal amplification by the enhanced immobilization of DNA on the surface of 3D N-doped rGO/AuNPs electrode and AuAgNR/Thi, coupling the low background signal produced by blank solution, electrochemical performance of the device was optimized to be proportional to miRNA-155 concentration in the range of 1 x 10(-11) to 1 x 10(-4) M with a detection limit of 1 x 10(-12) M. In addition, direct detection in serum is demonstrated with high specificity. Thus, this biosensor is potentially applicable for microRNA detection in medical research and early clinical diagnosis.

As a promising energy-storage device, rechargeable Zn-air batteries have attracted considerable interests. Herein, a bifunctional oxygen electrode film prepared by adhering NiCo2 O4 nanosheets to a nitrogen and oxygen dual-doped carbon nanotubes film in a large scale is reported. The resulting self-supporting film electrode is multifunctional, which integrates a porous conducting structure for air diffusion and charge transfer, high-performance catalysts for oxygen reduction and evolution, and novel structural flexibility. The composite film demonstrates excellent oxygen reduction/evolution reaction catalytic activities with low Tafel slopes (50 mV dec-1 for oxygen reduction reaction; 92 mV dec-1 for oxygen evolution reaction). Without any additional current collector, gas diffusion layer, or binder, the obtained bifunctional film performs as an "all-in-one" air electrode in a Zn-air battery. A 50-cm-long cable-shaped Zn-air battery based on such a film air electrode exhibits high operating potentials (≈1.2 V at 0.25 mA cm-2 ), low charging-discharging overpotentials (≈0.7 V), and stable cycling performance. Moreover, the flexible cable Zn-air batteries show excellent stability under different deformation conditions. The proposed concept of constructing scalable, all-in-one, freestanding, and flexible air electrodes would pave the way to develop next-generation wearable and portable energy-storage devices.