Low substrate temperature synthesis of carbon nanowalls by ultrasonic spray pyrolysis

In this paper, we report the synthesis of two-dimensional wall like carbon nanostructures (i.e. carbon nanowalls) by ultrasonic spray pyrolysis of ethanol and fullerene mixture. At higher temperature carbon nanofibers were formed on the substrate placed at the center of the reactor tube, whereas carbon nanowalls were observed on the substrate placed downstream of the tube below 100 °C. Spaces between the nanowalls changed with distance of the substrates from the furnace. Qualitative analysis of materials was performed using scanning electron microscopy, transmission electron microscopy and Raman spectroscopy.     

Synthesis and characterization of carbon nanotubes via ultrasonic spray pyrolysis method on zeolite

Ultrasonic spray pyrolysis method for the synthesis of carbon nanotubes (CNTs) has been investigated with zeolite supporting material. Single wall carbon nanotubes (SWCNTs) were obtained at 850 °C in nitrogen environment. Such deposition system makes it possible to grow CNTs without reducing agent at atmospheric pressure in a simple setup. Iron and cobalt acetate were used as catalyst and ethanol as carbon source for the synthesis of CNTs. Results show that nature of zeolite and cobalt concentration play important roles for SWCNTs production. Interestingly, we notice that in catalyst particles of sharp shape, nucleation of a nanotubes cap occurs dominantly in the forward direction.     

己烷低耗喷雾热解法大规模制备多壁碳纳米管

以己烷为碳源,二茂铁为催化剂前躯体,应用喷雾热解法,制备了多壁碳纳米管(MWCNTs).采用酸沥滤和空气氧化对MWCNTs进行纯化.利用SEM、TEM、XRD、EDS、TGA及Raman光谱分析等方法分别对原生和纯化MWCNTs进行表征.为制得优质、高产MWCNTs,对制备工艺参数作了优选,分别研讨了最佳制备参数,包括:二茂铁升华温度、己烷中二茂铁浓度、热解温度和时间,己烷与H2的流量比.MWCNTs具有典型的腊肠状(Sawsage-like)构型,长度大于数十微米,内、外管径分别为15nm～45nm及25nm～70nm,MWCNTs的纯度和产率的质量分数分别高于95%和70%.     

One step synthesis process for fabricating NiFe2O4 nanoparticle loaded porous carbon spheres by ultrasonic spray pyrolysis

In the present work, the porous hollow carbon spheres loaded with NiFe₂O₄ nanoparticles have been successfully prepared via ultrasonic spray pyrolysis technique at 700?°C and the associated formation mechanism has been studied. The as-prepared NiFe₂O₄/carbon microspheres with the diameter of about 3–5?µm and the specific surface area of 236.6889?m²?g^?1 exhibit good monodispersity and an abundance of mesopores of about 40?nm size. Notably, the 20?nm NiFe₂O₄ nanoparticles are encapsulated by carbon microspheres and disperse homogeneously inside the carbon matrix. We could tune the relative content of ferrite and carbon sphere via adjusting the composition of the solution used for synthesis and the carbonization temperature. Consequently, some interesting properties can be obtained by combining the magnetic NiFe₂O₄ nano powder and the electrically conductive porous carbon, which renders the resulting composite suitable for promising applications in electromagnetic wave absorption, treatment of polluted water, catalyst design, energy storage, batteries and so on.     

喷雾热解法在硅衬底上生长定向碳纳米管阵列(英文)

以向日葵油的甲基酯为碳源,二茂铁为催化剂前驱体,Ar为载气,通过喷雾热解法在硅衬底上合成定向碳纳米管阵列。结果表明,在硅衬底上原位形成Fe催化剂纳米颗粒。由拉曼光谱、透射电镜图和X-射线衍射谱图显示所制定向碳纳米管阵列具有较好的石墨化程度,其直径为1 0～3 0 nm,管壁约为1 0 nm。所制定向碳纳米管阵列中残留的催化剂含量可以忽略。     

流动催化热解法制备高质量多壁碳纳米管的研究

以甲烷为碳源,N2和H2作载气,二茂铁作催化剂前驱体,采用流动催化热解法制备出大量高质量取向性好的多壁碳纳米管(MWCNTs)。利用扫描电子显微镜(SEM),透射电子显微镜(TEM)和Raman光谱对碳纳米管的形貌和结构进行了表征。该制备过程工艺简单并且成本低廉,对实现碳纳米管的规模生产具有重要意义。     

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.     

Microstructure and superconducting properties of Y-Ba-Cu-O films prepared by chemical spray pyrolysis

Y-Ba-Cu oxide superconducting films were prepared by spray pyrolysis on (100) MgO substrates and alumina coated with a silver buffer layer. Acetate, nitrate, and oxide precursors were used as starting materials. The optimum starting compounds have been assessed and the effectiveness of rapid thermal processing as a fabrication tool for annealing of highT _c superconducting films has been established. The superconducting behavior was found to be strongly dependent on the type of the precursor used, on the method of heat treatment, and on the substrate material. The films show preferred orientation and good adherence to the substrate. Transport measurements indicated that the films exhibited a superconducting transition with an onset temperature between 83–93 K and ending between 52–74 K. The critical current density was found to be strongly dependent on film processing.     

Carbon dioxide as a carbon source for synthesis of carbon nanotubes by chemical vapor deposition

Carbon dioxide was successfully used as carbon source in the synthesis of carbon nanotubes (CNTs) by chemical vapor deposition (CVD) over Fe/CaO catalyst. The product was evaluated using both transmission electron microscopy (TEM) and Raman spectroscopy. Crooked and branching structures of multi-walled carbon nanotubes (MCNTs) with diameters of around 50 nm were observed on the TEM micrographs. Raman spectrum results show that the nanotubes have small defects, which is in agreement with the results of TEM. The influence of reaction variable such as furnace temperature and types of support media was also studied and the reaction mechanism was then discussed in this paper.     

Crystalline alumina films prepared by nebulized spray pyrolysis

Crystalline alumina films have been successfully deposited on Si(100) and amorphous silica substrates by the nebulized spray pyrolysis technique. The surface morphology of the films has been studied by various microscopic techniques. The films exhibit satisfactory microhardness and frequency independent capacitance.     

Aerosol spray pyrolysis synthesis of water-splitting ferrites for solar hydrogen production

Aerosol spray pyrolysis (ASP) was employed for the synthesis of oxygen-deficient doped ferrite systems to be used as redox materials for the production of solar Hydrogen from water via a two-step thermochemical water-splitting cycle. In the first step (water splitting) the reduced state of a metal oxide is oxidized by taking oxygen from water and producing hydrogen; in the second step (regeneration) it is reduced again by delivering some of its lattice oxygen. Redox materials of the iron spinel family doped with other bivalent metals (Zn, Ni, Mn) were synthesized via ASP, characterized and evaluated with respect to their water-splitting activity. Organic additives, like citric acid, in the precursor solutions were found to result in products with finer particle size and to enhance the water-splitting activity of the synthesized materials. Material performance (water splitting activity, hydrogen yield, regeneration capability) was found to depend on the dopants’ kind and stoichiometry; in particular high percentages of Zn dopant seem to enhance the overall materials’ performance. ASP synthesized materials have demonstrated higher water conversion and hydrogen yields than materials of the same composition synthesized through solid-state routes. The ASP synthesis process was scaled-up successfully maintaining the favorable characteristics of the synthesized materials.     

Rapid synthesis of a BN/CNT composite particle via spray routes using ferrocene/ethanol as a catalyst/carbon source

Boron nitride (BN)/carbon nanotube (CNT) composite particles in submicrometer-sizes were successfully prepared using a spray pyrolysis method. Using an ultrasonic nebulizer, BN nanoparticles, ferrocene (as catalyst), and ethanol (as solvent and carbon source) were sprayed into a tubular furnace (fixed temperature of 800 °C) under an Argon flow of 1 L/min. Ethanol was used as a solvent as well as a carbon source because of its non-polluting nature, low cost, harmless byproducts (e.g. CO), and ease of handling. An aggregated BN particle with the growth of a multiwall-CNT (10 nm in thickness) on the surface could be produced. No BN phase changed because the process was completed in a matter of seconds. The present novel synthesis method could be broadly applied in the fabrication of various composite materials with the growth of CNT on the particle surface using a simple, fast and continuous process.     

Stoichiometry and superconductive properties of YBaCuO films deposited by spray pyrolysis

The dependence of the stoichiometry and the superconducting characteristics of YBaCuO films deposited by spray pyrolysis on the spraying solution composition and the deposition conditions is reported. It has been found that a proper optimization of the starting materials concentration in the spraying solution results in superconducting films with zero resistance temperature of 91 K and a transition to superconducting state within a 3 K range. X-ray diffraction and resistance vs temperature measurements have been used to monitor the crystal composition and the conductive characteristics of the films as a function of the spraying solution composition and the deposition parameters.     

Optical constants of CdS thin films prepared by spray pyrolysis

CdS thin films were prepared by spray pyrolysis techniques. Variable angle spectroscopic ellipsometry was used for optical constant calculations. Multiple angle measurements were taken in the most sensitive angle of incidence region. The sensitive regions of angle of incidence were obtained theoretically using 3-dimensional graph ofδψ andδΔ. Real partn and imaginary partk of the complex refractive index of the samples were calculated in the wavelength range 470–650 nm, taking into account surface roughness. Bruggeman’s effective medium approximation is used for analysis of the surface rough layer of the thin films.     

超声喷雾热解法制备ZnO薄膜及性能研究

以醋酸锌水溶液为前驱体溶液,使用自制的超声喷雾热解系统在玻璃基板上制备得到了ZnO薄膜.经X射线衍射(XRD),扫描电镜(SEM)分析得到ZnO薄膜的晶体结构和微观形貌.测试结果表明,ZnO薄膜为六角纤锌矿结构,在450～500℃下制备的薄膜显示出良好的结晶性能,并且沿(002)晶面择优取向生长,薄膜具有优良的均匀性和致密性.同时,制备得到的薄膜在可见光区也表现出80%以上的高透过率.     

Low cost synthesis of high-Tc superconducting films on metallic substrates via ultrasonic spray pyrolysis

Ultrasonic spray pyrolysis technique has been used to deposit both in situ and ex situ high temperature superconducting films (HTSC) of Y₁Ba₂Cu₃O_x(YBCO) and Bi₂Sr₂CaCu₂O_x (BSCCO) compounds over various substrates. Nitrate precursor solutions are used to deposit films of ∼10 μm thickness. Both low temperature spray with substrate temperature T_s < 500 °C and high temperature deposition with T_s = 550-900 °C are carried out. Superconducting properties of these films are observed to vary with various parameters such as concentration of spray solution, deposition temperature and nature of substrate and annealing process. Best quality films show T_c (R = 0) of 89 K and J_c of ∼4 × 10⁴ A/cm² at 77 K and ∼ 10⁵ A/cm² at 20 K. X-ray diffraction pattern reveals that the films are textured along c-axis. Successful attempt has been made to deposit in situ superconducting films over polycrystalline Ag for coated conductor applications. Various deposition and annealing conditions are optimized to control the diffusion of Ag from substrate to film, which otherwise can segregate into the grain boundaries and make the films non-superconducting.     

Optical and electrical properties of zinc oxide films prepared by spray pyrolysis

Zinc oxide thin films were prepared on glass substrates from an aqueous solution of zinc acetate by spray pyrolysis. These films were characterized using X-ray diffraction, scanning electron microscopy and optical transmission. The films were highly transparent to the visible radiation and electrically conductive. Films deposited at optimum conditions exhibited a resistivity of 3·15×10⁻³ Ωm along with a transmittance of 98% at 550 nm.     

Evaluation of photocatalysis of Au supported ZnO prepared by the spray pyrolysis method

Environmental pollution by organic dyes used in industry is a serious problem in developing countries. Environmentally friendly treatment methods are being studied because conventional methods require chemical or additional decomposition treatment. In particular, oxidation via a photocatalyst is a promising alternative due to its chemical and physical stabilities and low cost. However, electron-hole recombination limits the photocatalytic activity in semiconductor photocatalysts such as ZnO and TiO₂. This study investigates control of electron-hole recombination of the photocatalyst by loading Au on ZnO (Au/ZnO). Using the Ultrasonic Spray Pyrolysis (USP) method, Au/ZnO particle generation is easily achieved under various conditions. XRD analysis confirms the crystal peaks of ZnO and Au. The EDX mapping and STEM images of the particles show that the Au crystals are well dispersed in the inner and outer portions of ZnO. The photocatalytic decomposition rate of organic dye (Rhodamine-B) is faster than that of ZnO in all Au/ZnO particles, and the best photocatalytic activity occurs in particles with 0.1 mass% Au supported on ZnO particles. In addition, optimal photolysis activity occurs in 100 mL of 5 mg/L RhB aqueous solution and 10 mg dose of Au/ZnO particles.     

Synthesis of mixed-phase titania films by low-temperature ultrasonic spray pyrolysis

Fully dense TiO₂ films with (1) mixed-phase rutile and anatase and (2) anatase (sole phase) were deposited on fused quartz substrates by ultrasonic spray pyrolysis at nominally 400 °C. The presence and absence of insulation around the entrainment pathway traversing 20 cm above the substrate/hot plate were investigated (174 °C vs 122 °C). The thick films were assessed in terms of mineralogies (qualitative and quantitative), microstructures (topography, thickness and grain size), and visible light transmission (optical and microstructural considerations). With insulation, opaque mixed anatase (∼ 30 vol.%; < 50 nm) and rutile (∼ 70 vol.%; ∼ 1 μm) were observed; without insulation, only transparent anatase (< 50 nm) was observed.     

One-pot synthesis of hematite-alumina hollow sphere composite by ultrasonic spray pyrolysis technique with high adsorption capacity toward PAHs

A hybrid nanocomposite of alumina and hematite was synthesized by ultrasonic spray pyrolysis technique. The study of microscopic images, mapping analysis, and XRD patterns revealed that the Al₂O₃ – Fe₂O₃ nanocomposite was composed of separated spherical particles with a thin layer ball-shaped structure that metal oxides are uniformly distributed in the wall of hollow sphere particles, led to a coherent and monotonous construction. A series of coefficients of equilibrium sorption of polycyclic aromatic hydrocarbons (PAHs) as hazardous materials were measured on the prepared composite material in a batch technique. The free or pure Al₂O₃ or Fe₂O₃ showed negligible removal efficiency for the mentioned analytes. The various significant variables, such as initial analyte concentration, solution pH, adsorbent dose, and contact time to remove analyte, were studied in the aqueous solutions. Adsorption data were modeled to Langmuir, Freundlich, and Temkin isotherms, and a good correlation found in the case of Langmuir isotherm and adsorption capacity for anthracene, phenanthrene, and naphthalene were 370, 333, and 322 mg g^?1, respectively. Investigation of the kinetic models proved a pseudo-second-order, and the prepared adsorbent can be reused more than 7 times without a significant decrease of adsorption performance.