Synthesis and microstructure of Fe3C encapsulated inside chain-like carbon nanocapsules

Aligned array of chain-like carbon nanocapsules was successively prepared by a simple CVD process. XRD and HRTEM analyses revealed the carbon nanochains were filled with Fe₃C particles other than Fe. EELS and elemental mapping displayed that there exist a few N atoms doping in the nanochains wall. Electron beam irradiation indicated that the nanochain was formed by the converging of conjoint multi-nanocapsules. Periodic supply of ferrocene and the coalescent of adjacent nanocapsules were the two dominant factors for the growth of nanochains structures.     

One-pot synthesis of Pt/carbon nanotubes by self-regulated reduction for electrocatalysis

This paper describes a method for size-controlled synthesis of Pt nanoparticles and their attachment to the sidewalls of multiwall carbon nanotubes (CNTs) by self-regulated reduction of sodium n-dodecyl sulfate (SDS), without surface pretreatment. The size of the Pt nanoparticles is controlled by adjusting the concentration of SDS. When Pt/CNTs are heated to 500 degrees C in N2 atmosphere, Pt nanochains are formed on the CNTs; some of these nanochains contain small islands. Electrochemical measurements confirm that the electroactivities of the Pt/CNT nanocatalysts increase with a decrease in the size of the Pt nanoparticles. Additionally, comparing with the heated Pt/CNT nanocatalysts containing smooth Pt nanochains, the heated Pt/CNT nanocatalysts containing Pt nanochains with small Pt islands show higher electrocatalysis activities and stability.     

Morphology and diameter controllable synthesis of boron nanowires

Different morphology and diameter boron nanowires were synthesized by means of chemical vapor deposition on silicon substrates through controlling the growth temperature and the thickness of catalyst Au films. Smooth boron nanowires were fabricated at the temperature ranged from 800 to 900°C. The diameter of boron nanowires increased slightly with the growth temperature increasing. Boron nanochains with the periodic modulated diameter could be fabricated at the temperature of 950°C. As the thickness of Au films increases, the diameter and length of boron nanowires increase dramatically. The growth process of boron nanowires and nanochains was also discussed.     

Transformation of carbon nanotubes to diamond in microwave hydrogen plasma

Multiwall carbon nanotubes (MWCNTs), synthesized by microwave plasma enhanced chemical vapor deposition, were used as the precursor to synthesize diamond in a pure hydrogen microwave discharge. Diamond-scratched silicon wafers, with and without precoated MWCNTs, were placed side by side on a substrate holder. Diamond was formed on both wafers with the consumption of MWCNTs. The present results suggest that the solid–gas–solid transformation mechanism is involved in this process.     

Electrical breakdown of individual Si nanochains and silicide nanochains

Electron transport across individual Si nanochains and silicide nanochains is investigated using a micro-manipulator in a transmission electron microscope. The current increases nonlinearly with increasing the bias voltage. Electrical breakdowns occur with a current typically as large as 10(1)-10(2) nA. Furthermore, some FN plots exhibit a bend presumably due to the formation of a heavily distorted nanotube of carbon.     

纳米碳管结构差异对树脂炭包覆硅/纳米碳管复合材料电化学性能的影响

采用聚乙烯醇（PVA）树脂炭化的方法，制备了PVA树脂炭包覆硅／不同纳米碳管复合材料，通过X-射线、高分辩电镜观察和电化学性能测试等手段比较研究了单壁、双壁和多壁纳米碳管作为弹性导电网络缓解硅在充放电过程中体积变化方面的效果。结果表明，单壁纳米碳管和双壁纳米碳管比多壁纳米碳管能够更好地缓解硅在循环过程中产生的结构和体积变化，这主要是因为其长径比大，缠裹效果更好。单壁纳米碳管和双壁纳米碳管具有相近的直径、长径比及宏观分布形式，但在循环过程中，双壁纳米碳管的结构稳定性好于单壁纳米碳管，进而其缓解硅结构变化的效果更好。     

纳米Ag链的制备及其在聚氨酯基柔性导电复合材料中的应用

针对柔性聚合物基导电复合材料的导电性差和柔性差这2个关键问题,分别从导电填料的柔性化及降低填料含量2方面着手,以脱氧核糖核酸（DNA）大分子链作为模板,制备了大小均一、链状排列的柔性纳米Ag链及纳米Ag链填充的聚氨酯基柔性导电复合材料。利用SEM对纳米Ag链/Ag包Cu粉/聚氨酯导电复合材料的界面结构进行了表征,探讨了纳米Ag链/Ag包Cu粉/聚氨酯导电复合材料导电性及柔性的机制。研究发现:保持导电填料总质量分数为76%、纳米Ag链的质量分数为4%时,纳米Ag链/Ag包Cu粉/聚氨酯导电复合材料的电阻率及形变前后的电阻变化比值达到最佳值,分别为2.13×10-4 Ω·cm和3.6;当以纳米Ag链为单一填料时,制得的纳米Ag链/聚氨酯导电复合材料具有优异的柔性;泡沫法制备的纳米Ag链/聚氨酯导电复合材料可以在低填料质量分数时达到更高的导电性,当纳米Ag链质量分数为60%时,方阻为56 Ω/sq,低于共混法制备的填料质量分数为65%时的纳米Ag链/聚氨酯导电复合材料（98 Ω/sq）。      

短切炭纤维的CVI处理及其在CFRC中的分散性

采用CVI法对短炭纤维进行表面处理, 借助超声波对其进行预分散, 用新型分散剂羟乙基纤维素(HEC)和超细粉硅灰对其进行分散, 并研究了其在水泥基体中的分散性; 在SEM电镜下观察了短炭纤维增强水泥基复合材料(CFRC)的断口形貌, 用炭纤维质量变动系数定量评价了短炭纤维在CFRC中的分散性。结果表明, 采用CVI预处理和超声波预分散, 在分散剂HEC和硅灰不同掺量下, 炭纤维的分散性均得到显著改善。炭纤维的分散性随HEC掺量的增加而提高, 当HEC掺量为水泥质量的0.6%、 硅灰掺量为水泥质量的10%时, 两种分散剂的协同作用使炭纤维质量变动系数最小, 此时炭纤维在水泥基体中的分散性最理想。      

多壁碳纳米管／硅橡胶复合材料的湿度敏感特性

采用多壁碳纳米管和硅橡胶制备多壁碳纳米管／硅橡胶复合材料。研究了该复合材料的导电网络和湿敏特性。通过透射电镜观察经过化学修饰和未修饰的多壁碳纳米管的表面形貌,扫描电镜观察多壁碳纳米管／硅橡胶复合材料形成的导电网络结构;分析该复合材料的导电机理,研究多壁碳纳米管／硅橡胶感湿特性。结果表明,相对湿度在11％-98％的范围,...     

Relative concentrations of carbon related defects in silicon

Irradiation induced defects in silicon are technologically important as they impact the electronic properties. Calculations based on density functional theory employing hybrid functionals have been previously used to investigate the structures and relative energies of defect clusters formed between vacancies, self-interstitials, carbon and oxygen atoms in silicon. In this study we employ a model to calculate the relative concentrations of carbon related defects in silicon. It is calculated that the carbon content has a significant impact upon the concentration of carbon-related defects. The C_iC_s defect is the most populous for all the conditions considered followed by the C_iO_iSi_I and the C_iO_i defects. C_iO_iSi_I and the C_iO_i become increasingly important for silicon with high carbon concentrations.     

Preparation and microstructural evolution of carbon/carbon composites

Carbon/carbon (C/C) composites with characteristic matrix-crack pattern are key intermediate materials for preparation of carbon/silicon carbide (C/C–SiC) composites. The C/C composites were prepared by pyrolyzing carbon fiber/phenolic resin preform. The change of density, open porosity, mass loss and specially the microstructural evolution of the composites during pyrolysis at 200–900 °C was analyzed, which provided important information for preparation of C/SiC composites by infiltration of silicon. An increasing number of regular spacing cracks were formed above 400 °C. After pyrolysis at 900 °C, the pore volume was 0.17 cm³/g, and the pores in the radius range of 2.44–122.19 μm occupied 81% of the pore volume.     

Integration of a carbon nanotube based electrode in silicon microtechnology to fabricate electrochemical transducers

An original approach was developed and validated for the fabrication of a carbon nanotube (CNT) electrode synthesized directly onto a carbon buffer thin film deposited on a highly doped monocrystalline silicon surface. The buffer layer of amorphous carbon thin film was deposited by physical vapour deposition on the silicon substrate before CNT synthesis. For this purpose, nickel was deposited on the carbon buffer layer by an electrochemical procedure and used as a catalyst for the CNT growth. The CNT synthesis was achieved by plasma enhanced chemical vapour deposition (PECVD) in an electron cyclotron resonance (ECR) plasma chamber using a C(2)H(2)/NH(3) gas mixture. In order to evaluate the electrochemical behaviour of the CNT-based electrode, the carbon layer and the silicon/carbon interface were studied. The resulting buffer layer enhanced the electronic transport from the doped silicon to the CNTs. The electrode surface was studied by XPS and characterized by both SEM and TEM. The electrochemical response exhibited by the resulting electrodes modified with CNTs was also examined by cyclic voltammetry. The whole process was found to be compatible with silicon microtechnology and could be envisaged for the direct integration of microsensors on silicon chips.     

Y-junction multibranched carbon nanofibers

Multibranched carbon nanofiber (CNF) is produced by a thermal chemical vapor deposition method using camphor as precursor. Nickel and cobalt catalyst was deposited on silicon substrate by e-beam evaporation and used as substrate for the growth of carbon nanomaterials. Branched carbon nanofibers were grown on the nickel thin film at 900 degrees C, whereas spherical carbon beads formed on the cobalt thin film. These fibers followed base growth mechanism devoid of any catalyst particle at the tip of fibers.     

Study on silicon carbide nanowires produced from carbon blacks and structure of carbon blacks

Silicon carbide nanowires were produced from carbon blacks at 1473 K and their microstructure was characterized by TEM, X-ray diffraction, FTIR and Raman spectroscopy. Nanowires of uniform diameters, the smallest averaging 10 nm, and narrow size distribution were obtained from graphitized carbon blacks, and their morphology depends on the properties of carbon black pecursors. High concentration of stacking faults and twins was detected. In addition to silicon carbide nanowires, a silicon carbide layer, about 20 nm thick, was formed on the surface of carbon black aggregates. The interior of the aggregates did not react and analysis of the data showed that it is composed of a mixture of amorphous carbon and small graphitic crystallites. The small lateral sizes of these crystallites remain unchanged during the graphitization process which is limited to the outer layer of the aggregates.     

Photoabsorption in carbon and silicon layer of phosphorous doped camphoric carbon/p-silicon (n-CC/p-Si) solar cell

Photoresponse characteristics of heterostructure solar cells, fabricated by depositing a phosphorous (P) doped carbon (n-C) layer on a p-type silicon (Si) substrate (n-C/p-Si cell), have been studied. The camphoric carbon (CC) targets containing varying amounts of P ranging from 1% to 7% by mass were used in a pulsed laser deposition chamber for the deposition of the carbon layers of the cells under analysis. The quantum efficiency of these cells was measured in the ultraviolet-visible-infrared region (300-1200 nm), which is found to vary with the P content in the carbon layer. The individual contributions of the carbon and silicon regions to the overall photoresponse are extracted by deconvoluting the overall photoresponse spectra. The relative contribution of the carbon region is found to increase with the P content up to 5 wt.% P in the carbon layer of the cell and decreases thereafter. This trend is similar to that of the optoelectronic properties of the P-doped CC films.     

Investigation of silicon implanted with carbon ions

The properties of silicon single crystals implanted with carbon ions were studied by two independent methods. It is demonstrated that the concentration of implanted carbon can be monitored by measuring the density of divacancies.     

Ultrasonically carbon coated Si nanoparticles for lithium ion batteries

A new and simple method for making nano-sized silicon/carbon composite materials was developed. The composite powders were prepared by dispersing HF-etched SiNPs in CHCl3, followed by bath sonication. Transmission Electron Microscopy (TEM) was used to identify the carbon layer outside the silicon particle. Impedance spectroscopy and cyclic voltammetry confirmed the improved electrode conductivity due to the carbon layer and the subsequent increased involvement of the silicon in the lithiation/delithiation process. The optimal composition of the composite, 20 wt.% SiNP/C, and 20 wt.% graphite, exhibited excellent cyclability after ten cycles with a reversible discharging capacity near 465 mAhg(-1) which is 1.5 times larger than that of the graphite and SiNPs electrode without ultrasonic process.     

Superhydrophobic carbon nanotube/silicon carbide nanowire nanocomposites

The composite film of carbon nanotubes and silicon carbide nanowires was synthesized directly on the silicon substrate by the catalyst-assisted method. The carbon nanotubes crimped together decorated with silicon carbide nanowires covering the whole substrate. The appropriate amount of aluminum powders is a crucial factor to achieve the composite film. The composite film exhibited excellent intrinsic superhydrophobicity without any further functionalization. By using the nano/micropillar composite structure model, the presence of silicon carbide nanowires is found to be the key factor that results in the superhydrophobicity of the films. The feasible synthesis of the superhydrophobic coating could have potential application in water-repelling devices, like biochemical sensors and microfluidic systems.     

In-vitro cellular behavior on amorphous carbon containing silicon

Amorphous carbon has been studied for its biological properties. Doping can alter the film structure to achieve certain desirable properties, like lowering of stress. The incorporation of a secondary element however also alters the film surface properties, which in turn, the biological response. We have investigated the response of fibroblast and osteoblast-like cells on amorphous carbon and amorphous carbon containing silicon. The amorphous carbon with the highest silicon concentration exhibits higher surface energy, with higher polar component. Both cell types adhered, spread and proliferated well on all films, especially on the one with the highest silicon content.     

First-principles computational design and synthesis of hybrid carbon–silicon clathrates

Type I and Type II silicon clathrates (Si₄₆ and Si₁₃₆), which can be considered as analogs of carbon fullerene materials, are composed with face-sharing Si₂₀, Si₂₄, and Si₂₈ cages linked through sp ³-covalent bonds. Besides silicon clathrates, theoretical computations have shown that both Type I carbon clathrate (C₄₆) and Type II carbon clathrate (C₁₃₆) may exist as metastable phases under high pressures. However, the energies of formation for the Type I and Type II carbon clathrates are extremely high and neither Type I nor Type II carbon clathrates have been synthesized. The objective of this investigation was to develop Type I hybrid carbon–silicon clathrates by substituting atoms on the silicon clathrate framework with C atoms. A first-principles computational approach was first utilized to design the framework structure and to identify appropriate guest atoms that are amenable to the formation of hybrid carbon–silicon clathrate compounds. A new class of Type I clathrates based on the carbon–silicon system was discovered as potential candidates. Some of the promising candidate clathrates were synthesized using an industrial arc-melting technique. The yield and stability of these newly discovered clathrates were evaluated. In addition, the electronic properties of selected clathrate materials were predicted using first-principles computations, which showed profound influences of the electronic properties by C atom substitution on the Si framework and insertion of guest atoms into the cage structure.