Thermal Plasma Synthesis of Superparamagnetic Iron Oxide Nanoparticles

Superparamagnetic iron oxide nanoparticles were synthesized by injecting ferrocene vapor and oxygen into an argon/helium DC thermal plasma. Size distributions of particles in the reactor exhaust were measured online using an aerosol extraction probe interfaced to a scanning mobility particle sizer, and particles were collected on transmission electron microscopy (TEM) grids and glass fiber filters for off-line characterization. The morphology, chemical and phase composition of the nanoparticles were characterized using TEM and X-ray diffraction, and the magnetic properties of the particles were analyzed with a vibrating sample magnetometer and a magnetic property measurement system. Aerosol at the reactor exhaust consisted of both single nanocrystals and small agglomerates, with a modal mobility diameter of 8?C9?nm. Powder synthesized with optimum oxygen flow rate consisted primarily of magnetite (Fe₃O₄), and had a room-temperature saturation magnetization of 40.15 emu/g, with a coercivity and remanence of 26 Oe and 1.5 emu/g, respectively.     

Optical Emission Spectroscopic Study of the Synthesis of Titanium Boride Nanoparticles in RF Thermal Plasma Reactor

Thermal plasma processes have been investigated by optical emission spectroscopy during the synthesis of TiB_x nanoparticles from TiO₂, B and C precursors using argon and helium both as plasma and sheath gases. Line-rich emission spectra were observed both in Ar–He–TiO₂–B and Ar–He–TiO₂–B–C cases. Emissions detected in the spectral region of 300–1000 nm were attributed to the electronic relaxation of excited Ti(I) and ionic fragments Ti(II), as well as the molecular species of TiO. The plasma temperature was calculated from the vibration–rotation temperature of the A–X electronic transition of TiO molecule by the least-squares fitting of experimental data to theoretical spectra. The temperatures at 100 mm downstream the torch outlet were found to be between 3800 and 2700 K for the Ar–He–TiO₂–B system, and between 5100 and 4300 K for the Ar–He–TiO₂–B–C system, respectively. The morphology of as-formed nanoparticles was characterized by transmission electron microscopy. Measurements of specific surface area, evaluated on the basis of Brunauer, Emmett and Teller equation, revealed that in all experimental setups titanium boride nanoparticles were formed with a mean particle size of 17–85 nm. On the basis of X-ray diffraction patterns, the solid reaction products were composed of TiB₂, boron doped titanium indicated as Ti(B), Ti₂O₃, H₃BO₃ and TiC. The actual composition of products depended on the synthesis conditions.     

Plasma Processing Based Synthesis of Functional Nanocarbons

Our recent research has shown that plasma processing techniques, which allow versatile control of both chemical and physical aspects, have considerable potential for the innovative synthesis and functionalization of three varieties of low-dimensional nanocarbons, which show great promise in the development of nanoscience and its applications. In the case of 0-D fullerenes, the mission is the high-yield production of atom (X) encapsulated fullerenes (X@C₆₀). The formation of macro-quantities of charge-exploited Li@C₆₀ and overwhelmingly-high purity spin-exploited N@C₆₀ are realized for the first time by the control of alkali-fullerene and nitrogen double plasmas, respectively. In the case of 1-D carbon nanotubes the challenge is precise structure control, i.e., chirality control of single-walled carbon nanotubes (SWNTs). The extremely narrow-chirality distributed growth of SWNTs is realized with time-programmed and nonmagnetic-catalyzed plasma CVD. As for functionalization of SWNTs, the enhanced p-type C₆₀@SWNTs created under the substrate-bias control in collisionless plasmas are found to be effective for harvesting solar energy in the infrared wavelength range and adapted to the use for multiple exciton generation in solar cells. Concerning 2-D graphene, our aim is to overcome two serious issues for electronics applications. One is the realization of the direct growth of graphene on an insulating (SiO₂) substrate by adjusting the growth parameters using non-equilibrium diffusion plasma CVD. The other is the direct fabrication of field-effect transistor device of a narrow-width (≥20 nm) graphene nanoribbon using a new, simple, and scalable method based on rapid heating plasma CVD, which shows a clear transport gap and a high on/off ratio. Finally the prospects for the above-mentioned results are discussed together with ripple effects of the nanocarbon research on the progress of nanoscience and its applications.     

Synthesis of Nanosized Silicon Carbide Through Non-Transferred Arc Thermal Plasma

A thermal plasma system was used for the preparation of nanosized SiC powder. First SiC was synthesized by solid-state reaction using waste silicon and activated carbon powders and then plasma processing was carried out to form nanosized SiC. Phase and structural analysis was carried out by X-ray diffraction which confirmed the formation of SiC in both cases. Plasma treatment did not show any kind of change in structure and phase of SiC; except little free silicon. Morphological investigation showed the formation of 20–30 nm spherical SiC particles after plasma treatment which was initially 1–5 μm. It was found that DC current played an important role in the reduction of particle size. It was proposed that nanosized SiC was formed due to the dissociation of grains from their grain boundary due to strong plasma gas stream.     

Effects of Precursors and Plasma Parameters on Fullerene Synthesis in RF Thermal Plasma Reactor

Synthesis of fullerenes from graphite powders of different grade was studied in a radiofrequency (RF) plasma reactor. Dependence of fullerene yield on the properties and feed rate of precursors and on the helium content of plasma gas was studied in details. The fullerene yield was influenced by the mean size and the thermal conductivity of graphite particles on the one hand, and the helium content of the gas phase on the other. Soot containing fullerene mixture of 5.9% was produced in best conditions found in this work. The main component of the fullerene mixture was C₆₀. In addition, it contained about 30% of C₇₀ (corresponding to a C₆₀/C₇₀ mass ratio of 2.64). Higher fullerenes such as C₈₄ were also detected by mass spectroscopy (MS) and high performance liquid chromatography (HPLC).     

Synthesis of Nickel Oxide Nanoparticles from Thermal Decomposition of a New Precursor

Nickel oxide nanoparticles (25 nm) have been synthesized via decomposition of a new precursor nickel octanoate Ni(octa)₂ in the presence of oleylamine (C₁₈H₃₇N) and triphenylphosphine (C₁₈H₁₅P), in mild conditions. To control the particle size and morphology, combination of C₁₈H₁₅P and C₁₈H₃₇N were applied as surfactants. In this process, oleylamine was used as both the medium and the stabilizing reagent. C₁₈H₃₇N and C₁₈H₁₅P play an important role in preventing aggregation of NiO nanoparticles. The products were characterized by XRD, SEM, TEM, FT–IR, and TGA.     

Plasma Synthesis of Advanced Metal Oxide Nanoparticles and Their Applications as Transparent Conducting Oxide Thin Films

This article reviews and summarizes work recently performed in this laboratory on the synthesis of advanced transparent conducting oxide nanopowders by the use of plasma. The nanopowders thus synthesized include indium tin oxide (ITO), zinc oxide (ZnO) and tin-doped zinc oxide (TZO), aluminum-doped zinc oxide (AZO), and indium-doped zinc oxide (IZO). These oxides have excellent transparent conducting properties, among other useful characteristics. ZnO and TZO also has photocatalytic properties. The synthesis of these materials started with the selection of the suitable precursors, which were injected into a non-transferred thermal plasma and vaporized followed by vapor-phase reactions to form nanosized oxide particles. The products were analyzed by the use of various advanced instrumental analysis techniques, and their useful properties were tested by different appropriate methods. The thermal plasma process showed a considerable potential as an efficient technique for synthesizing oxide nanopowders. This process is also suitable for large scale production of nano-sized powders owing to the availability of high temperatures for volatilizing reactants rapidly, followed by vapor phase reactions and rapid quenching to yield nano-sized powder.     

Synthesis and Characterization of Titanium Oxide Nanoparticles by Plasma in Contact with Liquid

Plasma Chemistry and Plasma Processing - Two types of plasma in contact with water were employed for the synthesis of mixed-phase TiO2 in a liquid. This is glow discharge with a metal cathode and...     

纳米氧化铁的电化学合成

采用金属铁为"牺牲"阳极,不锈钢片为阴极,在无隔膜电解槽中,用电化学法合成纳米氧化铁.通过XRD、FTIR、TG DSC及粒径分布等测试方法对所得的纳米粒子进行了表征和分析.实验表明:离心后得到的胶体放置于40℃的真空干燥箱中干燥后,得到无定型纳米氧化铁粒子;经320℃煅烧3h后,粒子转化为γ Fe2O3,平均粒径为22.0nm;进一步提高煅烧温度,在540℃煅烧3h后,可得到平均粒径为35.2nm的α Fe2O3.     

Mild Microfluidic Approaches to Oxide Nanoparticles Synthesis

Oxide nanoparticles (oxide NPs) are advanced materials with a wide variety of applications in different fields. The use of continuous flow methods is particularly appealing for their synthesis due to the high control achieved over the reaction conditions and the easy process scalability. The present review focuses on the preparation of oxide NPs using microfluidic setups at low temperature (≤80 °C), since the employment of mild reaction conditions is crucial for developing sustainable and cost-effective processes. A particular emphasis will be put on the improvement over the final product features (e. g., size, shape, and size distribution) given by flow methods with respect to conventional batch procedures. The main issues that arise by treating NPs suspensions in microfluidic systems are product deposition or channel clogging; mitigation strategies to overcome these drawbacks will also be presented and discussed.     

Surface-Modified Oxide Nanoparticles: Synthesis and Application

Russian Journal of General Chemistry - This review deals with one of the most important classes of nanomaterials — oxide nanoparticles. Preparative methods for the synthesis of nanooxides,...     

钴掺杂的磁性氧化铁纳米粒子的可控合成

通过油酸盐前驱体高温热解法制备出大小均匀的钴掺杂四氧化三铁球形纳米粒子, 其钴/铁摩尔比可以通过调节油酸钴与油酸铁的比例进行调变. 当产物中钴/铁摩尔比从0.024增加到0.156, 所制备的氧化铁纳米粒子的饱和磁矩从39 emu·g^-1逐渐减小到30 emu·g^-1, 而矫顽力从0 Oe升至190 Oe. 在305℃下, 随着反应体系的热解时间由0.5 h 增加到3 h, 所制备出的氧化铁纳米粒子尺寸逐渐由7 nm增加到14 nm. 热解时间较短时, 以高价态的四氧化三铁的晶型为主, 辅之以少量的氧化亚铁; 热解时间增加至2 h, 产物的晶型为四氧化三铁和氧化亚铁的复合物; 而继续增加热解时间至3 h, 除四氧化三铁和氧化亚铁之外, 还出现少量的零价态的CoFe合金, 说明铁(钴)元素经历了由三价到二价, 最后被还原为零价的过程. 随着反应温度的升高, 产物的尺寸逐渐增大, 同时产物中氧化亚铁的含量增多.     

Decomposition of Chlorobenzene by Thermal Plasma Processing

Decomposition of chlorobenzene as a model molecule of aromatic chlorinated compounds was studied in radiofrequency thermal plasma both in neutral and oxidative conditions. Optical emission spectroscopy was applied for the evaluation of the plasma excitation and molecular rotational-vibrational temperature. Atomic (C, H, O) and molecular (CH, OH, C₂) radicals were identified, while the morphology of the formed soot was characterized by electron microscopy. Organic compounds adsorbed on the surface of the soot after plasma processing were comprised of various polycyclic aromatic hydrocarbons (PAH) and chlorinated PAH molecules. Their amount was greatly affected by experimental conditions, especially the oxygen content and plate power. The higher input power reduced the ring number of the PAH molecules. Addition of oxygen significantly reduced the amount of both PAHs chlorinated PAH molecules but enhanced the formation of polychlorinated benzene compounds.     

Reduction of Metallurgical Wastes in an RF Thermal Plasma Reactor

Recovery of metals from iron and zinc oxides, as well as from zinc-containing metallurgical wastes, such as flue dust from the Siemens–Martin process and sludge from hot galvanizing, has been studied in an rf thermal plasma reactor under reducing conditions. The product composition was estimated by thermodynamic calculations based on the minimization of the Gibbs free enthalpy. Effects of the plate power of rf generator and the feed rate of powder on the chemical and phase composition of products have been investigated in detail. It has been proved that the rf thermal plasma treatment makes possible to produce unstable species in thermodynamic terms: metallic zinc was gained in the reaction of ZnO and hydrogen. The gradient cooling along the plasma reactor led to the segregation of the iron and zinc compounds. Valuable products were made from the particular wastes by a single step thermal plasma processing.     

Modelling of Carbon Tetrachloride Decomposition in Oxidative RF Thermal Plasma

Decomposition of carbon tetrachloride in a RF thermal plasma reactor was investigated in oxygen–argon atmosphere. The net conversion of CCl₄ and the main products of decomposition were determined by GC–MS (Gas Chromatographic Mass Spectroscopy) analysis of the exhaust gas. Temperature and flow profiles had been determined in computer simulations and were used for concentration calculations. Concentration profiles of the species along the axis of the reactor were calculated using a newly developed chemical kinetic mechanism, containing 34 species and 134 irreversible reaction steps. Simulations showed that all carbon tetrachloride decomposed within a few microseconds. However, CCl₄ was partly recombined from its decomposition products. Calculations predicted 97.9% net conversion of carbon tetrachloride, which was close to the experimentally determined value of 92.5%. This means that in RF thermal plasma reactor much less CCl₄ was reconstructed in oxidative environment than using an oxygen-free mixture, where the net conversion had been determined to be 61%. The kinetic mechanism could be reduced to 55 irreversible reaction steps of 26 species, while the simulated concentrations of the important species were within 0.1% identical compared to that of the complete mechanism.     

Sol-Gel Processing of Functional and Structural Ceramic Oxide Fibers

Structural ceramic oxide fibers like α-Al₂O₃, MgAl₂O₄ (spinel), Y₃Al₅O₁₂ (YAG) and eutectic Al₂O₃−Y₃Al₅O₁₂ as well as the functional Pb(Zr_1−xTi_x)O₃ (PZT) fibers were successfully prepared by sol-gel processing. All precursors are based on metal oxohydroxopropionates. A comparative study of sol-gel routes leading to spinnable sols demonstrates the key role of propionic acid as an excellent agent for controlling hydrolysis and condensation reactions.     

Migration of Processing Oils of Thermoplastic Rubber Treated with RF Plasma

The surface modifications produced by a RF plasma treatment on a thermoplastic styrene–butadiene–styrene rubber–SBS—with a considerable amount of processing oils in its formulation (TRO) have been studied and compared to the modifications produced on an oil-free SBS rubber (TRF). The modifications produced by the plasmas on the rubber surface depended on the nature of the gas used to generate the plasma. Thus, argon plasma favored the migration of processing oils to the TRO rubber surface, producing a weak oily layer that prevented interaction of rubber with a polyurethane adhesive. On the other hand, oxygen and carbon dioxide plasmas produced important ablation of the rubber surface which resulted in a partial (CO₂ plasma) or total (O₂ plasma) removal of processing oils from the rubber surface and the creation of polar moieties that increased adhesion of the rubber surface towards a polyurethane adhesive.     

Solvothermal Synthesis of Functional Magnetic Nanoparticles for Biocatalyst

A facile and simple one-step solvothermal method has been developed to synthesize polyethyleneimine (PEI)-modified magnetic nanoparticles. Characterization of morphology, surface charges, crystal structure, and magnetic property confirmed the efficiency of this facile synthesis route. Lipase immobilized on the PEI-modified magnetic nanoparticles was used to synthesize vitamin A palmitate from vitamin A acetate and palmitic acid. The reuse of immobilized lipase can be extended to eight times by removing water during esterification with a conversion rate above 80 % for 12 h.     

Zinc Oxide Nanoparticles: Green Synthesis and Biomedical Applications

Journal of Cluster Science - Nanoparticles refer to ultrafine particles with the particle size at nanoscale. When metals and metal oxides were synthesized at nanoscale, by their unique properties...     

原位限域合成介孔碳负载四氧化三铁纳米颗粒

利用废弃蟹壳做模板制备的具有均一孔道结构的介孔碳材料做载体,在孔道内限域原位合成四氧化三铁氧化物纳米颗粒。 通过扫描电子显微镜(SEM)、透射电子显微镜(TEM)和X射线衍射(XRD)表征了材料的结构和性能。 结果表明,孔道结构呈整体式结构,孔直径在40~50 nm,长50~200 μm。 纳米颗粒为四氧化三铁,粒径在10 nm左右,尺寸单分散性好,可均匀分散在介孔孔道内。 该方法工艺路线简单,绿色环保。