Metalorganic Route Research Articles

Influence of the Processing Method on the Quality of the Protective Coatings for SOFC Applications

Protective layers for Solid Oxide Fuel Cells (SOFC) interconnects (IC) were developed. The contacting layers are made of La0.8Sr0.2Mn0.5Co0.5O3 (LSMC) and were prepared by wet powder spraying. In order to avoid IC oxidation and a dramatic increase of ASR, MnCo2O4 spinel protective coatings were processed either by Atmospheric Plasma Spraying (APS) or by a Metal Organic route (MO). The influence of the processing method of these layers on the resistance of their assembly with an IC was investigated on Crofer22APU and F17TNb substrates. The measured ASR is stable after about one hundred hours. Their efficiency in Single Repeated Unit (SRU) configuration was also investigated. The MO process gave the thinnest layer, thereby the lowest resistance. The APS process gives thicker and denser layers, thus preventing completely the chromium diffusion through the cathode, but a slightly higher resistance is observed.

Effect of gas flow on the growth of In-rich AlInN films by metal-organic chemical vapor deposition

Indium-rich AlInN are grown by metal-organic (MO) chemical vapor deposition using trimethylaluminum, trimethylindium, and ammonia. Under the conservation of MO influx, the effects of gas flow in the MO route on AlInN growth and Al-related parasitic reaction are investigated. With an increase in this gas flow, the suppression of Al-related parasitic reaction, i.e., enhancement in Al content incorporation and improvement of crystalline quality, is satisfactorily shown until the occurring of severe phase separation. Accordingly, Al content x in AlxIn1−xN can be tuned from x=0.02 to 0.26. The Raman spectra of those AlInN samples with phase separation are analyzed by the resonant excitation effect and two-mode behavior for A1(LO). Finally, we propose a phase diagram to interpret the phase separation and Al content evolution under the influence of gas flow.

Optimization of Reaction Conditions for the Metalorganic Modification of MCM-41

The modification of periodic mesoporous silica with organic groups following an optimized metalorganic route is described. Organolithium and Grignard reagents (n-butyllithium and allyl-magnesium bromide) were used to directly substitute silicon atoms with organic moieties in the channel walls of the silica host. A detailed study of several representative reactions with respect to reaction parameters, that is, reaction temperature, reaction time, and reagent concentration, shows that the degree of surface substitution can be controlled within a broad range and up to very high levels while still maintaining the integrity of the ordered silica host. The functionalized mesoporous materials can also retain high surface areas and pore volumes. Furthermore, the reactions can be performed at low temperatures compared to the more traditional grafting techniques on the basis of organosilanes.

Metalorganic modification of periodic mesoporous silica: aromatic nitrogen functionalities

The channel walls of periodic mesoporous silica were modified with nitrogen-containing aromatic molecules through a metalorganic route, utilizing the lithiated aromatic core under mild reaction conditions and short reaction times. The functionalities grafted to the silica walls include primary and tertiary amines, as well as pyridine, pyrimidine and nitrobenzene. The new hybrid materials were characterized with X-ray diffraction, electron microscopy, thermogravimetry, nitrogen sorption, as well as Raman and UV-vis spectroscopies. The metalorganic modification of mesoporous molecular sieves with functional aromatics proves to be a fast, simple and economic method for the design of novel mesoporous inorganic–organic hybrid systems.

A simple metalorganic route to organically passivated mercury telluride nanocrystals

Nanocrystalline HgE (E = S, Se, Te) particles are an important class of materials that may have applications in the opto-electronics industry, notably as potential replacements for rare-earth dopants in optical fibers or in opto-electronic modulators. Organometallic routes to nanoparticles can produce materials of a superior quality, but often require highly toxic precursors, such as metal alkyls. We report here, for the first time, a simple route to organically passivated HgTe nanoparticles, which avoids the use of compounds such as dimethylmercury. This method can be used to prepare a wide range of HgE nanomaterials.

On the synthesis and manipulation of InAs quantum dots

A novel metalorganic route to small (ca. 2 nm diameter) InAs nanocrystals has been developed. The nanocrystals were analysed by a number of methods including HRTEM, photoluminescence and electronic spectroscopy. Distinct quantum size effects were observed in the optical properties, attributable to the nanoparticles having dimensions smaller than the Bohr exciton diameter of InAs (ca. 740 A). The nanoparticles were spin coated into a thin film, the morphology of which was investigated by atomic force microscopy (AFM).

Novel polyol-derived sol route for fabrication of PZT thin ferroelectric films

A novel polyol based metalorganic route has been developed and employed to deposit PZT thin films on Pt/Ti/SiO 2/Si substrates by sol–gel processing. Differential thermal analysis (DTA), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR), and X-ray diffraction collectively indicated PZT with perovskite phase structure was formed at approximately 550°C which is approximate 100°C lower than that in metal-alkoxide routes. The films are crackfree and have single perovskite phase structure with columnar crystals perpendicular to the substrate plane. The pyrolysis effect on microstructure and ferroelectric properties of the film was investigated. PZT film, which was pyrolyzed at 450°C and then annealed at 550°C for 1 h, has the coercive field of 60 kV/cm, the remnant polarization of 14 μC/cm 2, the spontaneous polarization of 47.5 μC/cm 2 and the switching voltage of 6 V.

A novel metalorganic route for the direct and rapid synthesis of monodispersed quantum dots of indium phosphide

Download options Please wait... Article information DOI https://doi.org/10.1039/A806419I Article type Paper Download Citation Chem. Commun., 1998, 2459-2460 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions A novel metalorganic route for the direct and rapid synthesis of monodispersed quantum dots of indium phosphide M. Green and P. O’Brien, Chem. Commun., 1998, 2459 DOI: 10.1039/A806419I To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Social activity Tweet Share Search articles by author Mark Green Paul O’Brien

Production of doped ZnO powders for varistor applications using sol-gel techniques

The electrical behaviour of ZnO varistors is controlled by the characteristics of the ceramic microstructure which depends strongly on the properties of the initial powder. This paper describes a study of the effect of different chemical methods to synthesise doped ZnO powders. The ceramic powders were synthesised by the following routes: a) classical mixing of oxides (for comparison purposes), b) aqueous solution of inorganic salts and c) hydrolysis and polycondensation of metalorganic compounds in an organic solvent. The physicochemical characteristics of these powders were evaluated using a scanning electron microscope and thermoanalytical instrumentation. Standard spray drying technology was used to pelletise the powders to obtain an agglomerated powder suitable for uniaxial pressing. The discs were sintered in an electric furnace under air atmosphere using several temperature programmes. The ceramic microstructure was characterised using SEM and X-ray diffraction. The effects of powder processing route on sintering and microstructural development are discussed. Powders prepared by the metalorganic route exhibited somewhat lower sintering temperatures than conventional powders. However, the rate of sintering was slower for metalorganic and aqueous solution powders. These observations were related to powder morphology. The ZnO−Bi2O3−CoO system exhibited the best varistor characteristics as it was expected, whereas the binary systems supported much lower voltages at low currents than ternary systems.

Novel metalorganic route for fabrication of B a T i O3 thin ferroelectric films

A novel diol based metalorganic route has been developed and employed to deposit BaTiO3 films on Si and Pt coated Si substrates. Differential thermal analysis, thermogravimetric analysis, x-ray photoelectron spectroscopy, and x-ray diffraction collectively indicated that BaTiO3 was formed through the reaction of Ba and Ti oxides at approximately 500 °C. The films were single phase, had no crystallographic texture, and contained no detectable impurities.

Preparation of nickel nanoparticles by metalorganic route

Nickel particles of sizes in the range 5–11 nm have been prepared by the decomposition of a suitable metalorganic compound on the surfaces of micrometer-sized potassium bromide crystallites. Infrared absorption spectra of nanocomposites comprising these particles dispersed in potassium bromide matrix have been delineated. Effective medium theory is used to explain the experimental results.

Processing of Bi [sbnd](Pb) [sbnd]Sr [sbnd]Ca [sbnd]Cu oxide superconductor thin films by metal alkoxide route

High- T c superconducting thin films in the Bi Pb Sr Ca Cu O system were prepared through reaction controls in organic solution by a metal-organic route. Thin films with preferred orientation were successfully prepared on MgO (100) single crystal substrates by a dip coating method. The films of the (243) phase (high- T c phase) and the (232) phase (low- T c phase) were synthesized from solutions with composition of Bi:Pb:Sr:Ca:Cu = 2:0.35:2:2:3 and Bi:Sr:Ca:Cu = 2:2:1:2, respectively. The J c of films was much improved through the UV irradiation during calcination as well as the proper selection of composition for starting solutions. A film prepared from a solution composition of Bi:Pb:Sr:Ca:Cu = 2:0.35:2:2:3 with UV irradiation showed the sharp onset of T c at 117 K, zero resistance at 79.5 K and J c of 840 A/cm 2 (77.3 K) after heat treatment at 845°C.

Nanocomposites by sol-gel and ion-exchange routes

Nanocrystalline materials are interesting both from the point of view of basic physics as well as technological applications. Preparation of nanocomposites is necessary to facilitate investigation of the effect of small size of a material on various physical properties. The method of preparing composites of nanosized metal particles dispersed in a glass matrix by the conventional melt-quench technique is reviewed. The versatility of sol-gel method in making nanocomposites is brought out. Results obtained on the metal organic route to certain glass-metal nanocomposites are described. The effectiveness of the ion exchange reaction followed by reduction treatment in the synthesis of ultra fine metal particles in a glassy environment is stressed upon. Finally, the glass-in-glass nanocomposites prepared by an ion exchange process and possessing very high electrical conductivity are discussed.

Glass-metal nanocomposite synthesis by metal organic route

Glass-metal nanocomposites incorporating ultrafine particles of iron, nickel, cobalt and manganese, respectively, in a silica glass matrix have been prepared by heat treatment of a gel derived from a sol containing silicon tetraethoxide and a suitable metal organic compound. Metal particles in all the nanocomposites are isolated and spherical-shaped with diameters ranging from 3 to 10 nm. Films of these nanocomposites with thickness of the order of a few micrometres have been prepared on glass slides by a simple dip-and-pull technique. Optical absorption spectra of the nanocomposite films have been measured over the wavelength range 200 to 2000 nm. Effective medium theories of Maxwell-Garnett and Bruggeman, respectively, have been used to calculate theoretically the optical absorption of these materials. The Maxwell-Garnett theory gives results which are in better agreement with experimental data than those obtained from Bruggeman formalism. The filling factor f as estimated from the least-squares fit of the experimental results with the Maxwell-Garnett theory has a value in the range 1 to 4%.