Decomposition Of Iron Pentacarbonyl Research Articles

Early particle formation and evolution in iron-doped flames

In flame synthesis of nanoparticles, the temperature history experienced by the nascent particle aerosol defines the morphology, composition, and crystallinity of the resulting nanomaterial. Commonly, flame-synthesis processes are modeled with an isothermal approximation assuming that the particle temperature replicates that of the surrounding gas phase, avoiding inclusion of an additional internal coordinate in the population balance model, and thus reducing the computational cost. This simplification neglects the influence of matter- and energy-exchange as well as thermochemistry between the particle and reactive gas phase, impacting the particle temperature. In this work, we investigate the temperature history of the particles in incipient formation stages and their evolution in iron-doped flames, prototypical for many other transition-metal (oxide) synthesis systems. The temperature and relative volume-fraction distributions of early particles forming in H2/O2/Ar flames doped with iron pentacarbonyl were determined for the first time, based on spectrally and spatially resolved flame emission measurements and pyrometric analysis of the continuum emission emanating from the nascent particle aerosol. The nascent particle temperature was found to be several hundred degrees above the gas-phase temperature for all physically reasonable assumptions concerning particle composition and emission efficiency. Early particles volume fraction rises sharply shortly after the decomposition of iron pentacarbonyl and decreases steeply in the flame front, in excellent agreement with previous particle-mass spectrometry/quartz-crystal microbalance measurements. By modeling the evaporation process of isothermal iron particles, we show that vanishing of particles in the flame front cannot be explained by evaporation of particles that are in thermal equilibrium with the gas phase. A single-particle Monte-Carlo simulation based on a simple model comprising Fe-monomer condensation, concurrent with oxidation, reduction, etching, and evaporation occurring at the particle surface, captures both the flame structure with respect to early particle formation and their excess temperature compared to the gas phase.

Investigation of the combustion of iron pentacarbonyl and the formation of key intermediates in iron oxide synthesis flames

The information of the gas phase kinetics are relevant for the development of detailed reaction mechanisms as well as for process design and control in flame synthesis. In this study, the decomposition of iron pentacarbonyl and the reaction pathways towards iron oxide clusters and particles in laminar H2/O2/Ar low-pressure synthesis flames are investigated. Gas-phase species are analyzed by photoionization and electron ionization mass spectrometry. The extraction of a representative sample from the particle-laden flow of a synthesis flame by an intrusive sampling technique for the analysis is challenging, because iron-intermediate species can condense easily. Cations can be extracted from the flame with a high efficient ion sampling technique that results in high sensitivity. Iron-containing cations provide evidence of the presence of key intermediates, e.g., Fe(OH)2, Fe(OH)3, Fe2O3, and larger Fe-O-clusters which are the dominant intermediates with respect to particle formation and need to be considered in future gas-phase reaction mechanisms.

The role of nickel traces in fine chemicals for hydrodechlorination reactions with zero-valent iron

Two different types of nanoscale zero-valent iron (nZVI) were synthesized according to the same standard procedure: reduction of dissolved Fe(II) with sodium borohydride – one starting from a commercial iron salt having pro analysi (p.a.) purity, and another from microscale iron with an extraordinary degree of purity, derived from the decomposition of iron pentacarbonyl. The ZVI samples exhibited similar hydrodechlorination activities towards hexachlorobenzene as an example for higher chlorinated aromatics and carbon tetrachloride as an aliphatic model substance. However, only the sample derived from the iron salt (p.a.) was able to dechlorinate monochlorobenzene (MCB) at a measurable rate whereas the nZVI derived from the very pure precursor (nZVIpure) did not show this ability. Closer inspection lead us to the finding that the observed activity could be attributed to a Ni content as small as 0.005 wt-% of the former nZVI sample which was named nZVIimpure accordingly. It was demonstrated that such a small amount of Ni develops its catalytic activity for the hydrodechlorination of MCB only under acidic conditions. Although acidic conditions might not be common for studies with ZVI, higher Ni contents (e.g. of reagent grade iron sources) could have an influence under ambient conditions.

Effect of Purity, Surface Modification and Iron Coating on Ignition and Combustion of Boron in Air

ABSTRACT Combustion characteristics of boron powders with varying purity, surface treatment and iron dopant loadings were investigated. Particles were ignited by a CO2 laser and burned in air. Commercial 95% and 99% pure boron powders were used as the starting materials; the former powder was also washed with acetonitrile to reduce the inhibiting oxide layer. All powders were coated with iron by thermal decomposition of iron pentacarbonyl. Optical emission of single burning particles was captured in order to determine combustion temperatures and burn times as a function of particle size. All materials ignited at approximately the same CO2 laser beam energy. For all materials, two-stage combustion patterns were detected for longer emission pulses produced by particles burning in air, which became difficult to resolve for shorter burn times. It was observed that higher purity boron particles burn faster. A reduction in the natural oxide layer thickness achieved by acetonitrile wash did not appreciably change the burn time of boron particles. However, it did lead to a brighter emission during second stage combustion, to oscillatory emission patterns, and to formation of nitride caps on the surface of quenched boron particles. Coating boron with iron was effective for commercial 95% pure boron. It was less effective for washed boron and even less effective for boron of higher purity. Boron coated with iron burned faster than un-coated boron; the effect appeared to scale with the amount of iron present. Additionally, boron coated with iron burned at a higher temperature than the un-coated powders. The increase in the burn rate and temperature caused by the iron coating are consistent with the proposed reaction mechanism, in which iron serves as a shuttle catalyst that is oxidized by external oxygen and then reduced by boron.

Temperature mediated morphological and magnetic phase transitions of iron/iron oxide Core/Shell nanostructures

Understanding how thermal decomposition of Iron penta carbonyl transformed from spherical shaped Iron/Iron oxide Coe/Shell nanoparticles into flower shaped hollow nanoparticles followed by spherical shaped hollow nanoparticles is crucial scientifically as well as technologically. Presently, it is mentioned that how shape and size distribution of nanoparticles can be tuned by post annealed treatment in air environment. Crystal structure and phase of as synthesized and post annealed samples were confirmed by X-ray diffraction (XRD) and Raman spectroscopy. Morphological transformations were estimated with transmission electron microscope (TEM). Particle size and distribution was attained by using free software ImageJ and it has been observed that as synthesized and heat treated samples at 1000 °C have particle size of ∼9 nm and ∼18 nm, respectively by XRD calculations which is in good agreement with TEM. The measurements taken by vibrating sample magnetometer (VSM) show interesting change in magnetic phase from superparamagnetic phase of as synthesized nanoparticles to strong ferromagnetic phase after heat treatment. Low temperature magnetic characterizations of Core/Shell nanoparticles are explained in detail in some extent by physical property measurement system (PPMS).

Surface Effects and Critical Dimensions of Iron Nanoparticles

The surface effects on the critical dimensions of ferromagnetic nanoparticles have been studied. Iron nanoparticles with different mean diameter from 5.9 nm to 21.4 nm were prepared by thermal decomposition of iron pentacarbonyl in the presence of oleic acid/octyl ether. The heating response of these ferromagnetic nanoparticles suspended in water were measured experimentally during which the same amount of iron nanoparticles and di-ionized water were irradiated by an alternating magnetic field and the increase in temperature of the system was measured. The heating performance of the nanoparticles was described in terms of Specific Absorption Rate (SAR) which depends on the heating rate. The heating rate was calculated from the initial slope of the heating curve at an inflection point whereby there is minimum heat loss to the surrounding. Results were analyzed to find the critical diameters for the transition from single-domain to superparamagnetic regime and from single-domain to multi-domain regime. Also, the frequency and current dependence of SAR were studied. The maximum value of SAR was obtained when the applied frequency and current were at 175 kHz and 15 A, respectively. An equation for the critical radius for the transition from single-domain to multi-domain regime with low anisotropy was derived and numerically solved by using a program written in C++ and results were analyzed to find the effect of surface parameters on the critical diameter of nanoparticles. The SAR as a function of nanoparticle’s diameter shows two maxima which can be connected with the two critical dimensions. One is DC1 at 18 nm for the transition from single-domain to multi-domain configuration and the second is DC2 at 10 nm for the transition from single-domain to superparamagnetic regime. Comparison of these experimental results with the bond order-length-strength correlation theory was discussed.

Electron Beam Induced Surface Activation of Ultrathin Porphyrin Layers on Ag(111)

We demonstrate how a focused electron beam can be used to chemically activate porphyrin layers on Ag(111) such that they become locally reactive toward the decomposition of iron pentacarbonyl, Fe(CO)5. This finding considerably expands the scope of electron beam induced surface activation (EBISA) and also has implications for electron beam induced deposition (EBID). The influence of the porphyrin layer thickness on both processes is studied in detail using scanning tunneling microscopy (STM) and scanning electron microscopy (SEM) as well as Auger electron spectroscopy (AES) and scanning Auger microscopy (SAM). While a closed monolayer of porphyrin molecules does exhibit some activity toward Fe(CO)5 decomposition after electron irradiation, a growth enhancement is found for bi- and multilayer films. This is attributed to a partial quenching of activated centers in the first layer due to the close proximity of the silver substrate. In addition, we demonstrate that the catalytic decomposition of gaseous Fe(CO)5 on Ag(111) can be effectively inhibited by introducing a densely packed monolayer of 2H-tetraphenylporphyrin (2HTPP) molecules.

Synthesis and characterization of elemental iron and iron oxide nano/microcomposite particles by thermal decomposition of ferrocene

AbstractThe unique chemical and physical properties of the nano and microscale materials have led to important roles in the several scientific and technological fields. The magnetic nano/microparticles are of great interest because of its potential applications in, e.g., hyperthermia, magnetic resonance imaging (MRI), catalytic applications, etc. The decomposition of iron pentacarbonyl is one of the most common methods for the preparation of magnetic iron oxide and iron nanoparticles. However, Fe(CO)5 is severely toxic and alternative precursors should be used. Here, we describe the recent advances in the synthesis and characterization of the elemental iron and iron oxide nano/microcomposite particles by the thermal decomposition of ferrocene. The described synthesis process is based on simple nontoxic approaches including, for example, a solventless process. The particle size and size distribution as well as their composition, crystallinity, shape, and magnetic properties can be controlled via the synthesis conditions.

Double Convective Assembly Coatings of FePt Nanoparticles to Prevent Particle Coalescence during Annealing

FePt nanoparticles suspension was synthesized by reduction of platinum acetylacetonate and decomposition of iron pentacarbonyl in the presence of oleic acid and oleyl amine. FePt nanoparticles were coated on a substrate by convective assembly from the suspension. To prevent the coalescence during the annealing of FePt nanoparticles double convective coatings were tried. First convective coating was for silica particle assembly on a silicon substrate and second one was for FePt nanoparticles on the previously coated silica layers. It was observed by scanning electron microscopy (SEM) that FePt nanoparticles were dispersed on the silica particle surface. After annealing at for 30 minutes under nitrogen atmosphere, FePt nanoparticles on silica particles were maintained in a dispersed state with slight increase of particle size. On the contrary, FePt nanoparticles that were directly coated on silicon substrate showed severe particle growth after annealing due to the close-packing of nanoparticles during assembly. The size variation during annealing was also verified by X-ray diffractometer (XRD). It was suggested that pre-coating, which offered solvent flux oppose to the capillary force between FePt nanoparticles, was an effective method to prevent coalescence of nano-sized particles under high temperature annealing.

Magnetization of microorganism cells by thermal decomposition method

The bio-limited forming technology, a new technology organically integrating microbiology, manufacturing science and materials science, is used in the manufacturing of magnetic or conductive microstructures of different standard shapes. This paper explores the feasibility of magnetizing microorganism with thermal decomposition method. The principle of thermal decomposition of iron pentacarbonyl has been adopted to investigate the cells of Spirulina (a type of nature micro-helical microorganism) coated with pure iron. Further analysis have been conducted on the observations results of hollow micro-helical magnetic particles form, components and the phase structure obtained by using various tools including optical microscopy, scanning electron microscopy (SEM), energy dispersive X-ray detector (EDX), transmission electron microscopy (TEM), and X-ray diffraction analysis (XRD). Results showed that Spirulina cells could be coated with iron particles after the completion of thermal decomposition process, with well-kept shape of natural helixes and consistent components of different sampling points on the surface layer and thickness of layer. After the heat treatment at 700°C, the type of the surface iron layer formed was α-Fe. The paper also investigates the kinetics of the cell magnetization technology by thermal decomposition.

Prevention of Coalescence During Annealing of FePt Nanoparticles Assembled by Convective Coating

FePt nanoparticle suspension was synthesized by reduction of platinum acetylacetonate and decomposition of iron pentacarbonyl in the presence of oleic acid and oleyl amine. The composition of the synthesized nanoparticles was Fe40Pt60. To prevent the coalescence during annealing of FePt nanoparticles we tried two steps of convective coating, where first coating was for silica particle assembly on a silicon substrate and second one was for FePt nanoparticles on the silica layers. It was observed by scanning electron microscopy that FePt nanoparticles were dispersed on the silica surface. After being annealed at 700 degrees C for 30 minutes under nitrogen atmosphere, the particle size of FePt nanoparticles increased slightly from 4 nm to 6 nm but dispersity of the nanoparticles was maintained. Magnetic hysteresis of Fe40Pt60 nanoparticles coating on silica layer after annealing showed typical characteristics of hard magnetic materials, and no incorporation of soft magnetic materials. It was suggested that convective self-assembly with the parallel use of pre-coating that offers solvent flux weakening capillary force between FePt nanoparticles was an effective method to prevent coalescence of nano-sized particles under high temperature annealing.

High-temperature XRD study of thermally induced structural and chemical changes in iron oxide nanoparticles embedded in porous carbons

Magnetic carbon-based nanomaterials have promising applications in many fields owing to their biocompatibility and thermal/mechanical stability. This study describes a high-temperature X-ray diffraction (XRD) study of the chemical and structural transformations suffered by superparamagnetic iron oxide nanoparticles embedded in porous carbons. The nanoparticles were prepared from the decomposition of iron pentacarbonyl over porous carbons, resulting in nanometer-sized iron oxides homogeneously dispersed into the carbon matrix. The thermally induced changes in these materials were followed by in situ high-temperature XRD, using synchrotron radiation. The growing of the nanoparticles and of the carbon crystallites were first observed, followed by the reduction of the iron oxides to form α-Fe (at temperatures as low as 400 °C in some cases) and γ-Fe(C). The temperatures at which these chemical reactions occurred were dependent on the total time spent on heating and on the nature of the iron oxides formed in the as prepared materials. A noticeably large thermal expansion coefficient was also observed for the iron oxide nanocrystals. The formation of austenitic iron, stabilized by the presence of carbon, was found to be only partially reversible upon cooling.

Size distribution function for iron clusters formed during the synthesis of carbon nanotubes by Fe(CO)5 decomposition

We have experimentally studied the size distribution function of iron clusters formed during the decomposition of iron pentacarbonyl (Fe(CO)5) in a mixture of acetylene with a buffer gas (AR, H2). It is established that the average size of synthesized particles is 2.2–2.5 nm and weakly depends on the gas-mixture pressure. This behavior is explained by the liquid-solid phase transition in catalytic particles. The experimental data agree with theoretical dependences of the melting temperature of Fe-C clusters on the particle size and carbon content.

Synthesis and characterization of Fe and Fe 3O 4 nanoparticles by thermal decomposition of triiron dodecacarbonyl

Magnetic nanoparticles possess numerous potential applications, e.g., hyperthermia, magnetic resonance imaging (MRI), catalytic applications, etc. Decomposition of iron pentacarbonyl is one of the most common methods for preparation of magnetic iron oxide and iron nanoparticles. However, Fe(CO) 5 is severely toxic and alternative precursors should be used. The present manuscript presents a new simple method for preparation of iron oxide and iron nanoparticles, by thermal decomposition of Fe 3(CO) 12 in diethylene glycol diethyl ether with oleic acid as a stabilizer. The obtained magnetite (Fe 3O 4) nanoparticles were annealed at 300, 700 and 900 °C under inert atmosphere. The annealing temperature allowed control of size and size distribution of the nanoparticles, as well as their composition, crystallinity and magnetic properties. The as-prepared nanoparticles and the nanoparticles annealed at 300 °C are superparamagnetic with blocking temperatures of 22 and ∼140 K, respectively, while the nanoparticles annealed at 700 and 900 °C are ferromagnetic. The nanoparticles annealed at 900 °C are composed of pure Fe as the major phase (90%) and Fe 3O 4. Characterization of the obtained nanoparticles has been accomplished by routine methods such as transmission electron microscopy, powder X-ray diffraction, superconducting quantum interference, elemental analysis and Mössbauer spectroscopy.

One-Step Synthesis and Characterization of Ultrastable and Amorphous Fe3O4 Colloids Capped with Cysteine Molecules

A one-step sonochemical synthesis of a uniformly dispersed aqueous solution of amorphous Fe3O4 nanoparticles capped with dl-cysteine (cys) has been achieved. During the sonication, several processes or chemical reactions occurred: the decomposition of iron pentacarbonyl (Fe(CO)5), the formation of amorphous Fe3O4 nanoparticles, the capping of the Fe3O4 with cysteine molecules, the formation of a surface chemical bond of Fe−S between Fe3O4 particles and sulfur from cysteine, and the formation of cystine by linking two cysteine molecules. These capping cystine and cysteine molecules acted both as antioxidants and stabilizers, and the capped Fe3O4 colloids could be stable as long as 3 months at room temperature. Usually, the size of the amorphous Fe3O4 nanoparticles capped with Cys was found to be 20−30 nm. The products were characterized by a number of analytical techniques, such as XRD, DSC, TGA, XPS, TEM, HRTEM, Raman Spectroscopy, magnetic measurements, and spot tests.

A Cheap Gas–Liquid–Solid Method for Nanodeposition of Iron on the Surface of Flaky Graphite Powder

A cheap gas-liquid-solid method to prepare a nanodeposition of iron on the surface of a micrometer-size flaky graphite powder is described. This method is suited not only for spherical, but also nonspherical small substrates. The method is only a one-step process, in which decomposition of iron pentacarbonyl is induced by nitrogen gas in a 90 degrees C reactor. This synthetic route simplifies the operation procedure and manufacturing equipment, and decreases the reaction temperature, compared with conventional liquid-solid-phase methods and gas-solid-phase methods.

Iron Oxide Shell as the Oxidation-Resistant Layer in SmCo5@Fe2O3 Core–Shell Magnetic Nanoparticles

This paper presents a synthesis of magnetic nanoparticles of samarium cobalt alloys and the use of iron oxide as a coating layer to prevent the rapid oxidation of as-made Sm-Co nanoparticles. The colloidal nanoparticles of Sm-Co alloys were made in octyl ether using samarium acetylacetonate and dicobalt octacarbonyl as precursors in a mixture of 1,2-hexadecanediol, oleic acid, and trioctylphosphine oxide (TOPO). Such Sm-Co nanoparticle could be readily oxidized by air and formed a CoO antiferromagnetic layer. Exchange biasing was observed for the surface oxidized nanoparticles. In situ thermal decomposition of iron pentacarbonyl was used to create iron oxide shells on the Sm-Co nanoparticles. The iron oxide shell could prevent Sm-Co nanoparticles from rapid oxidation upon the exposure to air at ambient conditions.

Ultrasonic-assisted preparation of monodisperse iron oxide nanoparticles

Monodisperse iron oxide nanoparticles with 5–20 nm can be synthesized by an inexpensive and simple ultrasonic-assisted method at low temperature. This is based on the decomposition of iron pentacarbonyl in cis–trans decalin. The high energy emitted by ultrasonic irradiation at a short time can promote the crystallization process simultaneously. At low temperature, these crystalline nucleuses can grow to monodisperse nanoparticles. Effects of ultrasonic treatment, the concentration of surfactant and the refluxing time on the size and size distribution of iron oxide nanoparticles were investigated. The morphology and crystal structure of iron oxide nanoparticles obtained at different conditions were characterized by high-resolution transmission electron microscope, X-ray diffraction and selected area electron diffraction.

Transformation to L10 structure in FePd nanoparticles synthesized by modified polyol process

FePd nanoparticles were prepared by the modified polyol process, i.e. simultaneous reduction of palladium acetylacetonate and thermal decomposition of iron pentacarbonyl in a solvent. The well-dispersed FePd particles, with the average particle size of ~8.4 nm, were obtained using diphenyl ether as a solvent. The structure of FePd nanoparticles transformed to L10 structure from face centered cubic (fcc) structure after annealing at 600 °C for 1 h in vacuum. The coercivity of the ordered FePd nanoparticles increased to ~2 kOe at 5 K from ~0.6 kOe in the fcc as-made FePd nanoparticle. On the other hand, FePd nanoparticles, synthesized based on the conventional modified polyol process using dioctyl ether as a solvent, showed no structural transformation after annealing up to 700 °C. This is explained in terms of the interruption of thermal diffusion of Fe and Pd atoms during the thermal treatment due to the mixture of interstitial carbon impurity in the synthesis process using dioctyl ether as a solvent.

Laser‐induced synthesis of iron–iron oxide/methylmethoxysilicone nanocomposite

AbstractThe IR laser irradiation of a gaseous mixture of iron pentacarbonyl–methoxytrimethylsilane–ethene in argon induces ethene‐photosensitized decomposition of iron pentacarbonyl into elemental iron and decomposition of methyltrimethoxysilane into species that polymerize into methylmethoxysilicone. These two concurrent gas‐phase processes allow formation of iron–iron oxide/methylmethoxysilicone nanocomposite. Spectral analyses and electron microscopy reveal the nanocomposite as consisting of iron clusters oxidized in outer layers and covered with the organosilicon polymer. The procedure shows its potential for gas‐phase synthesis of iron‐based clusters embedded in a polymer matrix. Copyright © 2004 John Wiley & Sons, Ltd.