Simple template-free solution route for the synthesis of Cu(OH)2 and CuO nanostructures and application for electrochemical determination three ß-blockers

The synthesis of Cu(OH)₂ nanoparticles in a solution phase has been realised with high yield at low cost by simply dropping ammonia solution into an aqueous solution of CuCl₂ at ambient temperature. Furthermore, well-defined CuO nanostructures were produced by thermal dehydration of the as-prepared Cu(OH)₂ nanostructures in the solid state. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared (FT-IR) were used to characterise the products. The electrochemical behaviour of three ß-blocker drugs on copper-oxide nanoparticle modified carbon paste electrodes was investigated. The modified electrodes showed excellent catalytic activity towards the oxidation of atenolol, carvedilol and propranolol in buffer solution. The linear concentration range of the proposed sensor for the atenolol, carvedilol and propranolol detection were 12–96, 5–37 and 10–104?µM, respectively.     

Surface chemistry of tribochemical reactions explored in ultrahigh vacuum conditions

The thermal decomposition of model extreme-pressure lubricant additives on clean iron was studied in ultrahigh vacuum conditions using molecular beam strategies. Methylene chloride and chloroform react to deposit a solid film consisting of FeCl₂ and carbon, and evolve only hydrogen into the gas phase. No gas-phase products and less carbon on the surface are detected in the case of carbon tetrachloride. Dimethyl and diethyl disulfide react on clean iron to deposit a saturated sulfur plus carbon layer at low temperatures (∼600 K) and an iron sulfide film onto a Fe + C underlayer at higher temperatures (∼950 K). Methane is the only gas-phase product when dimethyl disulfide reacts with iron. Ethylene and hydrogen are detected when diethyl disulfide is used.     

Phenomena of catalytic graphitization

In recent years the phenomena of catalytic graphitization have developed considerably. Four types of catalytic graphitization are known to produce G-, T_s-, A- and T_n- components. The review summarizes the use of elements, alloys and compounds as catalysts. The importance of catalyst particle size is stressed as well as the method of addition of the catalyst to the carbon. Extents of graphitization induced by catalysts are markedly dependent upon the existing degree of graphitization already present in the parent carbon. The effects of graphitization at different temperatures are summarized as well as the effects caused by the ambient atmosphere, for example by oxygen and nitrogen. Mechanisms of catalytic graphitization resulting in G-, T_s-, A- and T_n- components are outlined and changes in synthetic graphites caused by catalytic graphitization are presented.     

石墨化对微螺旋炭纤维热氧化动力学的影响

以乙炔为碳源,镍粉为催化剂,噻吩为助催化剂,采用化学气相沉积法制备微螺旋炭纤维;在氩气气氛中,2500℃下对所制微螺旋炭纤维进行石墨化处理.通过扫描电子显微镜观察微螺旋炭纤维的螺旋形貌和微观结构,用热重法研究微螺旋炭纤维的耐氧化性能,并探讨了微螺旋炭纤维的氧化动力学行为.结果表明:石墨化处理对微螺旋炭纤维具有显著的纯化作用,其螺旋形貌基本保持不变.微螺旋炭纤维的氧化反应较好地服从一级反应.微螺旋炭纤维石墨化前后的氧化反应活化能分别为263.004kJ/mol和297.191kJ/mol.石墨化处理明显提了微螺旋炭纤维的抗氧化性能.     

Catalytic graphitization and formation of macroporous-activated carbon nanofibers from salt-induced and H2S-treated polyacrylonitrile

We present here a facile method to produce macroporous-activated carbon nanofibers (AMP-CNFs) by post-treating electrospun cobalt(II) chloride (CoCl₂) containing polyacrylonitrile (PAN/CoCl₂) nanofibers with hydrogen sulfide (H₂S) followed by carbonization. A range of techniques including scanning and transmission electron microscopy, FTIR and Raman spectroscopy is used to examine and characterize the process. Because of the phase behavior between carbon and cobalt, cobalt particles are formed in the nanofibers, some of which leave the fibers during the heat treatment process leading to macroporous fibrous structures. The number of the macroporous increase significantly with increasing CoCl₂ concentration in the precursor H₂S-treated PAN/CoCl₂ nanofibers. The cobalt phase in the fibers also leads to catalytic graphitization of the carbon nanofibers. The produced AMP-CNFs may be a promising candidates in many applications including anode layer in lithium ion batteries, air and liquid purifiers in filters, as well as in biomedical applications.     

Catalytic Graphitization of Phenolic Resin

The catalytic graphitization of thermal plastic phenolic-formaldehyde resin with the aid of ferric nitrate(FN) was studied in detail.The morphologies and structural features of the products including onion-like carbon nanoparticles and bamboo-shaped carbon nanotubes were investigated by transmission electron microscopy(TEM),high-resolution transmission electron microscopy(HRTEM),X-ray diffraction and Raman spectroscopy measurements.It was found that with the changes of loading content of FN and residence time at 1000 ℃,the products exhibited various morphologies.The TEM images showed that bamboo-shaped carbon nanotube consisted of tens of bamboo sticks and onion-like carbon nanoparticle was made up of quasi-spherically concentrically closed carbon nanocages.     

Growth and characterization of bamboo-like multiwalled carbon nanotubes over Cu/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalyst

The growth of bamboo-like multiwalled carbon nanotubes (MWCNTs) over Cu/Al₂O₃ catalyst by chemical vapor deposition under atmospheric pressure using ethanol as the carbon source has been demonstrated. The obtained MWCNTs are dominant with bamboo-like morphology. The morphologies, graphitization degree, and microstructures of the products were characterized by transmission electron microscopy, X-ray diffraction, Raman spectroscopy, field emission scanning electron microscopy, high-resolution transmission electron microscopy, and selected area electron diffraction. The results show that the combination of Cu/Al₂O₃ catalyst and ethanol was critical for the growth of bamboo-like MWCNTs. The possible factors causing the formation of bamboo-like structures were also discussed.     

Effect of heat treatment temperature on microstructure and electrochemical properties of hollow carbon spheres prepared in high-pressure argon

Heat treatment was carried out between 800 and 1200°C to investigate its effects on the microstructure and electrochemical properties of the hollow carbon spheres (HCSs) prepared in high-pressure argon. Samples were characterized by X-ray diffraction, Raman spectroscopy, field-emission scanning electron microscopy, high-resolution transmission electron microscopy and N₂ adsorption-desorption isotherms. The graphitization of the HCSs was improved with increase of heat treatment temperature. Mesopores of ca. 4 nm in diameter were created on the HCSs after the heat treatment. The results of electrochemical performance measurements for the HCSs as anode material for lithium ion batteries indicate that the discharge capacity of the HCSs is improved after heat treatment at 800°C compared with the as-prepared HCSs and have a maximum value of 357 mAh/g and still retains 303 mAh/g after 40 cycles. However, the discharge capacity of the HCSs decreases and the cycling performance is improved with the increase of heat treatment temperature.     

Spectral and Thermodynamic Analysis of Wear Products in a B4C–ShKh15-Steel Friction Couple

We investigate the phase composition of wear products on the sliding surface of boron carbide over steel by means of thermodynamic calculations as well as scanning electron microscopy and Auger electron spectroscopy. We show that graphitization on the friction surface is attributable to the decomposition of carbon monoxide.     

Physical and tribological properties of diamond films grown in argoncarbon plasmas

Nanocrystalline diamond films have been deposited using a microwave plasma consisting of argon, 2–10% hydrogen and a carbon precursor such as C₆₀ or CH₄. It was found that it is possible to grow the diamond phase with both carbon precursors, although the hydrogen concentration in the plasma was 1–2 orders of magnitude lower than normally required in the absence of the argon. Auger electron spectroscopy, X-ray diffraction measurements and transmission electron microscopy indicate the films are predominantly composed of diamond. Surface roughness, as determined by atomic force microscopy and scanning electron microscopy indicate the nanocrystalline films grown in low hydrogen content plasmas are exceptionally smooth (30–50 nm rms) to thicknesses of 10 m. The smooth nanocrystalline films result in low friction coefficients (μ = 0.04–0.06) and low average wear rates as determined by ball-on-disk measurements.     

Multi-walled carbon nanotubes grow under low pressure hydrogen,air, and argon ambient by arc discharge plasma

Multi-walled carbon nanotubes (MWCNTs) were grown on cathode deposit by arc discharge plasma under H₂, Ar, and air ambient environment. The influence of ambient gas pressure on the structure and physical properties of carbon nanotube were compared. Herein, we highlight the influence of ambient environment and pressure to grow high quality carbon nanotubes. Field emission scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and X-ray diffraction were used for structural characterization and yield determination. The result revealed that background gas and pressure were crucial factor for growing highly crystalline and highly graphitic with I_D/I_G ratio 0.237 obtained for MWCNTs' synthesized in H₂ environment with extreme low defects.     

Growth of carbon nanostructures using a Pd-based catalyst

Carbon nanostructures were synthesized by decomposition of different carbon sources over an alumina supported palladium catalyst via Chemical Vapor Deposition (CVD). Several experimental conditions were varied to verify their influence in the synthesis products: temperature ramping rate, pre-annealing conditions, hydrogen pre-treatment, synthesis temperature and time, together with the use of different carbon sources. Depending on the experimental conditions carbon nanotubes and nanofibers with different shapes and structural characteristics were obtained. Straight, coiled and branched morphologies are the most common. Among our findings, the addition of hydrogen plays a significant role in the structure of the carbonaceous products. For example, the decomposition of acetylene on palladium catalysts at 800 degrees C in the absence of hydrogen produces only carbon micro- spheres as synthesis products. The incorporation of increasing amounts of hydrogen modifies the outcome, from thick fibers to carbon nanotubes. To verify the level of graphitization of the synthesis products we have used high resolution transmission electron microscopy (HRTEM) in addition to Raman spectroscopy. Our results, based on these complementary techniques, indicate the decomposition of acetylene on a palladium based catalyst, produces the best degree of graphitization in carbon nanotubes for a temperature of 800 degrees C and 100 cc/min of hydrogen flow. Similar hydrogen flows on the same catalyst, produced highly graphitized nanofibers by the decomposition of methane at 850 degrees C.     

石墨化对微螺旋炭纤维形貌和微观结构的影响

采用化学气相沉积法制备微螺旋炭纤维, 在氩气气氛, 2500℃下对其进行石墨化处理. 通过扫描电镜, 激光拉曼光谱和X射线晶体衍射对石墨化前后微螺旋炭纤维的形貌与微观结构进行了研究, 并初步探讨了石墨化机理. 结果表明: 石墨化处理对微螺旋炭纤维具有显著的纯化作用, 其螺旋形貌基本保持不变. 微观结构更加规整, 微螺旋炭纤维的晶面层间距d₀₀₂(0.3626～0.3378nm)减小, 晶粒尺寸L_c(1.6404～3.8590nm)和L_a(2.04～7.21nm)增大, 石墨化程度增强.     

The effects of processing conditions on the density and microstructure of hot-pressed silicon powder

Silicon powder was hot pressed into polycrystalline wafers 1.5 in ( 3.8 cm) diameter using various processing conditions. The submicrometre powder used was a by-product of the fluidized bed decomposition process of silane (SiH₄) in the production of silicon pellets. The effect of temperature (1250–1300°C), pressure (2000–3000 p.s.i.; 13.18–20.67 N mm^–2) and ambient (argon, hydrogen, vacuum) on the density of the hot-pressed powder was studied. All wafers processed had densities >92% of the theoretical density of silicon as determined by Archimedes' density measurements. Hydrogen was found to increase the densification rate of powdered silicon. The mechanism by which this occurs is believed to be the reduction of the native oxide layer of the powders resulting in increased surface transport. The microstructure of the polycrystalline wafers was examined by scanning electron microscopy, and transmission electron microscopy. The general microstructure of the polycrystalline wafers consisted of micrometre-sized grains with twins, stacking faults, and dislocations within the grains. However, under hot-pressing conditions of 1300 °C, 2000 p.s.i., and a hydrogen ambient, the grains of the wafer were on the order of 1 mm. The silicon wafers contained iron, aluminium, carbon and oxygen impurities as determined by secondary ion mass spectroscopy.     

Large scale synthesis of bundles of aligned carbon nanotubes using a natural precursor: turpentine oil

Bundles of aligned carbon nanotubes (ACNTs) have been synthesised by spray pyrolysis of turpentine oil (inexpensive precursor) and ferrocene mixture at 800°C. Turpentine oil (C₁₀H₁₆), a plant-based precursor was used as a source of carbon and argon as a carrier gas. The bundles of ACNTs have been grown directly inside the quartz tube. The as-grown ACNTs have been characterised through X-ray diffraction, Raman spectroscopy, scanning and transmission electron microscopic techniques. Scanning electron microscope images reveal that the bundles of ACNTs are densely packed and are of ～70–130?µm in length. High-resolution transmission electron microscopy and Raman spectroscopy observations indicate that as-grown multi-walled carbon nanotubes (CNTs) are well graphitised. These CNTs have been found to have outer diameters between ～15 and 40?nm. This technique suggests a low-cost route for the large-scale formation of ACNTs bundles.     

Effect of milling time in characteristics of the powder Cu-5wt.%Graphite

Composites of Cu-5wt.%Graphite were prepared by high-energy milling, under argon atmosphere for milling time of up to 50 h, to investigate the influence of the milling time on the size and dispersion of the copper and carbon phases. The formation of a monophasic carbon-copper solid solution was also investigated. The powder samples were collected at different times and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM and FESEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS) and Raman spectroscopy. Composite particles were formed by fragments of graphite embedded in the soft Cu matrix. After 50 h of milling, the Cu phase had a crystallite size of 24 nm and micro-strain of 0.26 %. The lattice parameter showed a reduction of 0.001545 nm and reached a value of 0.360152 nm. Furthermore, no carbon diffraction peak was observed in the milled powders, due to the small graphite crystallites. Meanwhile, the Raman spectra showed that the carbon phase remains crystalline, even after 50 h of milling. When the composite was annealed at 600 °C, for 1 h and under argon atmosphere, no carbon precipitate was observed. These results suggest the absence of the formation of a solid solution of carbon in copper.     

Controlled syntheses of carbon spheres in a swirled floating catalytic chemical vapour deposition vertical reactor

Onion-like graphite structures, also called carbon spheres (CSs), represent another new allotropic nanophase of carbon materials, which can be potentially used as single electron devices, magnetic refrigerators, nanodiodes, nanotransistors, nanoball bearings, insulator lubricants as well catalyst supports. In this study, carbon nanospheres were synthesised in a vertical swirled floating catalytic chemical vapour deposition reactor for the first time. This process allows for continuous and large scale production of these materials. The CSs were obtained by the pyrolysis of acetylene in an inert atmosphere. The effect of pyrolysis temperatures and the flow rate of argon carrier gas on the size, quality and quantity of the synthesised CSs were investigated. Transmission electron microscope analysis of the carbon material revealed graphitic spheres with a smooth surface and a uniform diameter that could be controlled by varying reaction conditions (size: 50–250 nm). The materials were spongy with very low density. The CS production rate was found to increase with the increase in pyrolysis temperature (900–1000°C) and with flow rates of the carbon source (70–370 mL min^?1) and carrier gas (70–480 mL min^?1). Thermogravimetric analysis, powder X-ray diffraction and carbon, hydrogen and nitrogen analysis of the samples revealed that the products mainly contained CSs (98% carbon) and Raman spectroscopy revealed that the degree of graphitisation increased with the increase in pyrolysis temperature (900–1000°C).     

Nanomaterials from shungite rocks

Size fractions of shungite rock modified by heat treatment in argon at 1400°C have been characterized by X-ray diffraction; scanning electron microscopy in combination with energy dispersive X-ray microanalysis; transmission electron microscopy; optical microscopy; and IR, Raman, and M?ssbauer spectroscopies. The material consists largely of a mixture of carbonaceous material (a variety of imperfect nanostructures), silicon carbide, quartz, glass, and carbon-encapsulated Fe and FeC _x . The size fractions obtained using an electro-mass-classifier and magnetic separator are of interest as fillers for composite materials. A significant percentage of the carbonaceous material is associated with iron in porous globules, which allows it to be concentrated by magnetic separation. The M?ssbauer spectrum of the magnetic component has low intensity, due not only to the low iron content but also to the small particle size of the iron and the loose state of the matrix. Some of the iron-carbon solid solution is in a superparamagnetic state, which transforms into a ferromagnetic state as the temperature is lowered.     

Synthesis of carbon nanotube films by thermal CVD in the presence of supported catalyst particles. Part I: The silicon substrate/nanotube film interface

The interface between the silicon substrate and a carbon nanotube film grown by thermal CVD with acetylene (C₂H₂) and hydrogen at 750 or 900 °C has been characterized by high resolution and analytical transmission electron microscopy, including electron spectroscopic imaging. Silicon (0 0 2) substrates coated with a thin (2.8 nm) iron film were heat treated in the CVD furnace at the deposition temperature in a mixture of flowing argon and hydrogen whereby nanosized particles of (Fe,Si)₃O₄ formed. These particles were reduced to catalytic iron silicides with the –(Fe, Si), ₂–Fe₂Si and ₁–Fe₂Si structures during CVD at 900 °C, and multi-wall carbon nanotubes grew from supported particles via a base-growth mechanism. A limited number of intermediate iron carbides, hexagonal and orthorhombic Fe₇C₃, were also present on the substrate surface after CVD at 900 °C. The reduction of the preformed (Fe, Si)₃O₄ particles during thermal CVD at 750 °C was accompanied by disintegration leading to the formation of a number of smaller (<5 and up to 10 nm) iron and silicon containing particles. It is believed that the formation of these small particles is a prerequisite for the growth of aligned multi-wall carbon nanotube films.     

Synthesis,structure, and properties of a Au/MnO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>–CeO<Subscript>2</Subscript> nanocatalyst for low-temperature oxidation of carbon monoxide

We have synthesized Au/MnO _x –CeO₂ nanocatalysts for the low-temperature oxidation of carbon monoxide. Gold nanoparticles applied by the deposition precipitation (DP) method were used as an active phase. The composition, structure, and textural characteristics of the materials and the charge state of the components of the catalysts were studied using X-ray diffraction, X-ray photoelectron spectroscopy, highresolution transmission electron microscopy, inductively coupled plasma mass spectrometry, and low-temperature nitrogen adsorption measurements. The carbon monoxide concentration in the catalytic oxidation products was determined by gas chromatography. The influence of calcination temperature on the charge state of the components of the surface layer of Au/ MnO_x–CeO₂ and the catalytic activity of the materials was examined. The catalytic activity of the materials was shown to be determined to a significant degree by the Mn³⁺, Au³⁺, and weakly bound oxygen concentrations in the surface layer.