Decomposition Of Organometallic Compounds Research Articles

Підвищення довговічності турбокомпресора в внаслідок ремонтного впливу

A turbocharger is a unit of modern internal combustion engines designed to boost it. Since a drive of the turbocharger is most often carried out from the energy of the exhaust gases, the conditions of its operation can not be called favorable: the temperature of the exhaust gases sometimes reaches 7000C, high chemical activity of the exhaust gases, high speed of rotation of the turbine. The consequence of difficult operating conditions is the wear of its elements. One of the main causes of wear of the active elements of the turbocharger is abrasive wear. Various methods of restoration and strengthening can be used to restore machine parts. However, not all methods can provide the necessary resource for the restoration and strengthening of parts working in abrasive and corrosive environments. One of the modern directions of increasing the wear resistance and other properties of reducing coatings is the use of composite materials. This article presents the results of research on the development of a new method for restoring and strengthening parts with composite materials based on the use of chemical vapor deposition of metals CVD - method (Chemicikal Vapor Deposition) by decomposition of organometallic compounds. It is shown that the developed composite material obtained by the CVD-method of decomposition of organometallic compounds provides an increase in wear resistance of at least 2.0...2.2 times in comparison with new parts composite material. Vapor-phase deposition of metals, Chemicikal Vapor Deposition-method, decomposition of organometallic compounds.

State of the Art of the Bi- and Trimetallic Nanoparticles on the Basis of Gold and Iron

Recently reported patents and experimental articles on the synthesis, properties, and main applications of core-shell nanoparticles, containing iron or its oxides and gold, as well as trimetallic systems on their basis, are reviewed. These nanostructures were obtained by a series of methods, including reduction in reverse micelles, decomposition of organometallic compounds, electron-beam, laser and gamma-irradiation, sonolysis and electrochemical methods. (Fe or Fe(X)O(y))/Au nanoparticles are subject to be functionalized with organic moieties, may expand their main applications, which consist of catalysis, biological and biomedical uses.

Organometallic based gold decoration, formation and durability

The present study proposes a complete characterisation of the liquid gold silver layer on glass, from the application of the initial product, to the final metallic film obtained. The decomposition of organometallic compounds, during the heating, has been followed using different spectroscopic methods (infrared, nuclear magnetic resonance, mass spectrometry, etc.) which were coupled with thermal analyses and microscope observations (SEM, TEM, etc.). In the present paper the steps of the formation of the film will be briefly described, and a special attention is given to the study of the adhesion mechanisms which operates at the interface between the gold film and the glass substrate. Specific adhesion tests have been performed by aging the system in controlled solutions and observing the loss of adhesion after a given immersion duration. In depth concentration profiles obtained by secondary ion mass spectrometry and Rutherford back-scattering spectrometry reveal, during the process, a migration of the precious metals into the substrate. That migration ensures a good adhesion for the film. That ‘diffusion’ of gold into the glass substrate does not follow the classical diffusion laws and does not seem to be the only explanation for the occurrence of a good adhesion between to two partners. The results also suggest an essential role played by flux agents as vanadium, whose interaction with the alkaline modifiers of the bulk glass constitutes a critical factor for the durability of decorations.

Pressure and solvent induced low-temperature synthesis of monodisperse superparamagnetic nanocrystals: The case of Fe 3O 4 in alkanols

The synthesis of nanoparticles via the decomposition of organometallic compounds has been studied extensively, but the effect of pressure has received little attention. Here we firstly focus on the pressure effect, and utilize it as well as the solvent and temperature effects to develop a “green” cheap low-temperature (140–200 °C) strategy via the decomposition of iron oleate in alcohol (or other alkanols) using oleic acid as the protecting reagent. The obtained monodisperse Fe 3O 4 nanocrystals (NCs) exhibit satisfying superparamagnetism. The mechanism of the process has been investigated and it was shown both high pressure and alkanol as the solvent can facilitate the formation of magnetite NCs. Furthermore, the solvent used in the preparation can control the shape, size and dispersion of NCs. In addition, the effects of reactant concentration, reaction time, temperature, and the mol ratio of oleic acid on the Fe 3O 4 NCs have also been discussed.

Carbon-Centered Strong Bases in Phosphonium Ionic Liquids

Phosphonium ionic liquids (PhosILs), most notably tetradecyl(trihexyl)phosphonium decanoate (PhosIL-C(9)H(1)9COO), are solvents for bases such as Grignard reagents, isocyanides, Wittig reagents (phosphoranes), and N-heterocyclic carbenes (NHCs). The stability of the organometallic species in PhosIL solution is anion dependent. Small bases, such as hydroxide, react with the phosphonium ions and promote C-H exchange as suggested by deuterium-labeling studies. A method to dry and purify the ionic liquids is described and this step is important for the successful use of basic reagents in PhosIL. NHCs have been generated in PhosIL, and these persistent solutions catalyze organic transformations such as the benzoin condensation and the Kumada-Corriu cross-coupling reaction. Phosphoranes were generated in PhosIL, and their reactivity with various organic reagents was also tested. Inter-ion contacts involving tetraalkylphosphonium ions have been assessed, and the crystal structure of [(n-C(4)H(90)(4)P][CH(3)CO(2).CH(3)CO(2)H] has been determined to aid the discussion. Decomposition of organometallic compounds may also proceed through electron-transfer processes that, inter alia, may lead to decomposition of the IL, and hence the electrochemistry of some representative phosphonium and imidazolium ions has been studied. A radical derived from the electrochemical reduction of an imidazolium ion has been characterized by electron paramagnetic resonance spectroscopy.

Synthesis of nanoparticles in Langmuir monolayer

A novel approach to create ultrathin planar nanoparticulate structures based on the controllable synthesis of nanoparticles directly in Langmuir monolayer at the gas/liquid interface and subsequent deposition of monolayer is introduced. In this approach, all initial reagents are present only in monolayer and reactions of nanoparticles synthesis are initiated by decomposition of organometallic compounds under electromagnetic radiation. The changes in the shape of compression isotherm of stearic acid (SA)/iron pentacarbonyl mixed monolayer under the varying of the time of exposure to the ultraviolet light have been studied. STM images of mixed monolayers deposited onto the graphite substrate revealed synthesized iron isotropic and anisotropic magnetic nanoparticles with the characteristic size varied from 20 to 150 Å in dependence on the ultraviolet exposure time and monolayer compression.

Nanostructured Molybdenum Carbide: Sonochemical Synthesis and Catalytic Properties

The preparation of nanophase materials has been the focus of intense study in materials science.1,2 A variety of chemical and physical preparative methods have been applied to produce materials with nanometer structure, including metal evaporation,3 decomposition of organometallic compounds,4 and reduction of metal salts.5,6 Sonochemical decomposition of transition metal carbonyl compounds has also been proven to be a useful technique to generate nanophase transition metals.7,8 Recently, molybdenum and tungsten carbides have been examined as heterogeneous catalysts because their activity is often similar to that of the platinum group metals.9-11 For catalytic applications, high surface area materials are generally needed; the preparation of interstitial carbides of molybdenum and tungsten with high surface areas, however, is very difficult. We present here a simple sonochemical synthesis of nanostructured molybdenum carbide from the ultrasonic irradiation of molybdenum hexacarbonyl. In addition, we have examined the catalytic activity and selectivity of these materials for the dehydrogenation of alkanes. The chemical effects of ultrasound arise from acoustic cavitation: the formation, growth, and implosive collapse of bubbles in a liquid.12,13 The collapse of bubbles generates localized hot spots through adiabatic compression or shock wave formation within the gas of the collapsing bubble. This local heating produces a wide range of high-energy chemistry. The conditions formed in these hot spots have been experimentally determined, with transient temperatures of ∼5000 K, pressures of∼1800 atm, and cooling rates in excess of 1010 K/s.14,15 Using these extreme conditions, we have explored a variety of applications of ultrasound to materials chemistry.16 A slurry of molybdenum hexacarbonyl (1 g in 50 mL of hexadecane) was sonicated with a high-intensity ultrasonic horn (Sonic and Materials, model VC-600, 0.5 in Ti horn, 20 kHz, 100 W cm-2) at 90 °C for 3 h under argon to yield a black powder. The powder was filtered inside an inert atmosphere box (Vacuum Atmospheres, <1 ppm O2), washed several times with purified, degassed pentane, and heated at 100 °C under vacuum. X-ray powder diffraction17 (XRD) showed extremely broad peaks centered at a d spacing of 2.4, 1.5, and 1.3 A (Figure 1), which did not match body-centered cubic (bcc) lines of molybdenum metal. After the heat treatment at 450 °C under helium flow for 12 h, sharper peaks in the XRD were observed at d spacing values of 2.39, 1.49, and 1.27 A which accurately correspond to face-centered cubic (fcc) molybdenum carbide, Mo2C (Figure 1). The synthesis of Mo2C is particularly prone to substantial oxygen contamination.9 Even after heat treatment at 450 °C under helium, oxygen was still present at about 4 wt %. Since the presence of oxygen could poison the catalytic activity, it was removed prior to catalytic studies by heating in a flowing 1:1 CH4/H2 mixture at 300 °C for 1 h, then at 400 °C for 1 h, and finally at 500 °C for 48 h. The flow rate of the CH4/H2 mixture was 27.5 cm3 (STP)/min. After this carburization, excess carbon, hydrogen, and oxygen had been largely removed. The elemental analysis results showed the sample was very pure (theoretical for Mo2C, 94.11 % Mo, 5.89 % C; exptl., 93.86 % Mo, 5.68 % C, 0.08 % H, 0.06 % N), which corresponds to a stoichiometry of Mo2C0.97. The XRD was essentially unchanged by carburization.

TfI14: Ferroelectric thin films for memory applications: Sol-gel processing and decomposition of organo-metallic compounds

Abstract Pb(ZrxTi1–x)O3 (PZT), Bi4Ti3O12 and BaTiO3 films as well as SrTiO3 films are considered for nonvolatile memory applications and high density dynamic random access memories. These perovskite systems are frequently deposited by a sol-gel or MOD technique. Processing and the properties of the thin films are summarized.

Nanoscale platinum(0) clusters in glassy carbon: synthesis, characterization, and uncommon catalytic activity

The preparation of nanoscale metal clusters is important because of their potential for high catalytic activity. Successful methods for the preparation of metal clusters include metal ion reduction to give small crystallites on various surfaces or colloidal dispersions, metal ion reduction into polymer films coated on electrode surfaces, decomposition of organometallic compounds, evaporation of metals, and sol-gel processes. We expected that the incorporation of metals on the molecular level in a carbon precursor, followed by thermolysis, would result in a conductive, dimensionally stable carbon matrix containing metal particles of controlled composition, size, and catalytic activity. We report here the synthesis of nanoscale platinum(0) clusters in their catalytic activity with respect to H{sup +} and dioxygen reduction. Platinum was incorporated into a glassy carbon precursor by the reaction of poly(phenylenediacetylene) with (ethylene)bis(triphenylphosphine)platinum(O). The coordination of the platinum complex to the triple bond of the oligomer was carried out in approximately 1:4 and 1:2 ratios. The resulting oligomers were heated to 600 degrees Celsius to give platinum-doped glassy carbon as pellets or thin films on conventional glassy carbon. Electrocatalytic activity of the thin films were evaluated and found to have similar current densities to those of electroformed platinum microparticles. However, the filmsmore » can be prepared with up to two orders of magnitude lower platinum loadings without sacrificing catalytic activity.« less

Deposition of thin metal and metal silicide films from the decomposition of organometallic compounds

Abstract The deposition of metal silicide thin films can be undertaken using volatile organometallic complexes. Organometallic vapor phase epitaxy or metal-organic chemical vapor phase epitaxy has a number of potential advantages over conventional chemical vapor deposition and molecular beam epitaxy technologies, and a number of novel thin film materials may be made from organometallic compounds. Plasma-, pyrolytic- and photolytic- assisted decomposition of organometallic complexes have been undertaken in an effort to make a variety of metallic and metal silicide thin films. These efforts are comprehensively reviewed.

Tunable Uv Laser Photolysis of Organometallic Compounds with Product Detection by Laser Mass Spectroscopy

ABSTRACTWe use tunable UV laser light in the region 200-320 nm, produced by frequency doubling the output of a dye laser for the decomposition of organometallic compounds. This method has been applied to TMA, trimethylaluminum AI(CH3)3. Only theTMA monomer absorbs UV light for λ&gt;220nm. TMA decomposes by one-photon absorption mainly into two channels: aluminum plus organic fragments and aluminummonomethyl plus organic fragments. The ratio [A1]/[AICH3] is wavelength dependent. Finally, we present a mechanism to explain the photolysis of trimethyl compounds of group III elements (Al,Ga,In).

Fine Metal Particle Formation from Organometallic Compounds by Laser Ignited Mild Explosive Reaction

ABSTRACTFine metal particles are deposited on a surface by explosive decomposition of organometallic compounds with single pulse laser irradiation. This new technique has the following characteristics:(1) High quantum efficiency of ca. 105, that depends on the size of the reaction chamber used and the concentration of organometallic compounds.(2) Formation of uniform spherical particles of ca. 0.3 µm size under some reaction conditions.(3) Rapid formation of metal particles. Most of the starting materials are decomposed within a few miliseconds.The key points of this decomposition reaction are:(1) Formation of high density active species in the gas phase by the irradiation with high power lasers.(2) Propagation of a thermal chain reaction.

Free Radical Generation by Ultrasound in Aqueous and Nonaqueous Solutions

The physical principles underlying the oscillatory behavior of minute gas bubbles in liquids exposed to ultrasound are reviewed. Results from mathematical analyses suggest that these oscillations sometimes become unstable leading to transient cavitation in which a bubble violently collapses during a single acoustic half-cycle producing high temperatures and pressures. The role that micronuclei, resonant bubble size, and rectified diffusion play in the initiation of transient cavitation is explained. Evidence to support these theoretical predictions is presented with particular emphasis on sonoluminescence which provides some non-chemical evidence for the formation of free radicals. Acoustic methods for conducting sonochemical investigations are discussed. In aqueous solutions transient cavitation initially generates hydrogen atoms and hydroxyl radicals which may recombine to form hydrogen and hydrogen peroxide or may react with solutes in the gas phase, at the gas-liquid boundary or in the bulk of the solution. The analogies and differences between sonochemistry and ionizing radiation chemistry are explored. The use of spin trapping and electron spin resonance to identify hydrogen atoms and hydroxyl radicals conclusively and to detect transient cavitation produced by continuous wave and by pulsed ultrasound is described in detail. The study of the chemical effects of cavitation in organic liquids is a relatively unexplored area which has recently become the subject of renewed interest. Examples of the decomposition of solvent and solute, of ultrasonically initiated free-radical polymerization and polymer degradation are presented. Spin trapping has been used to identify radicals in organic liquids, in polymer degradation and in the decomposition of organometallic compounds.

Free radical generation by ultrasound in aqueous and nonaqueous solutions.

The physical principles underlying the oscillatory behavior of minute gas bubbles in liquids exposed to ultrasound are reviewed. Results from mathematical analyses suggest that these oscillations sometimes become unstable leading to transient cavitation in which a bubble violently collapses during a single acoustic half-cycle producing high temperatures and pressures. The role that micronuclei, resonant bubble size, and rectified diffusion play in the initiation of transient cavitation is explained. Evidence to support these theoretical predictions is presented with particular emphasis on sonoluminescence which provides some non-chemical evidence for the formation of free radicals. Acoustic methods for conducting sonochemical investigations are discussed. In aqueous solutions transient cavitation initially generates hydrogen atoms and hydroxyl radicals which may recombine to form hydrogen and hydrogen peroxide or may react with solutes in the gas phase, at the gas-liquid boundary or in the bulk of the solution. The analogies and differences between sonochemistry and ionizing radiation chemistry are explored. The use of spin trapping and electron spin resonance to identify hydrogen atoms and hydroxyl radicals conclusively and to detect transient cavitation produced by continuous wave and by pulsed ultrasound is described in detail. The study of the chemical effects of cavitation in organic liquids is a relatively unexplored area which has recently become the subject of renewed interest. Examples of the decomposition of solvent and solute, of ultrasonically initiated free-radical polymerization and polymer degradation are presented. Spin trapping has been used to identify radicals in organic liquids, in polymer degradation and in the decomposition of organometallic compounds.

Semiconductors: Photochemical processing

The formation of thin layers of inorganic materials on semiconductor surfaces by the photo initiated decomposition of organometallic compounds is a technique that is receiving increasing attention. Deposition of these layers by heating (pyrolysing) such compounds has become a standard technology, and has acquired the acronym mocvd (metallo-organic chemical vapour deposition).

Preparation of ferroelectric PZT films by thermal decomposition of organometallic compounds

Preparation of ferroelectric PZT films by thermal decomposition of organometallic compounds

金属の還元:有機金属化合物の分解

金属の還元:有機金属化合物の分解