Production Of Nitride Research Articles

Particle size dependence in low temperature nitridation reaction for Fe 16N 2

Low temperature nitridation of α-Fe powder was studied by reduction of α-Fe 2O 3 with three particle sizes using flow hydrogen. Most suitable α-Fe 2O 3 powder had an average particle size of 60 nm. After hydrogen reduction, the α-Fe showed average particle size of about 120 nm. The yield of ferromagnetic Fe 16N 2 obtained at 140 °C for 100 h was the highest of its nitrided product among the products nitrided in a temperature range of 130–170 °C. Thermal decomposition of iron pentacarbonyl was also applied to obtain a narrow particle size distribution of monodispersed α-Fe spherical particles of 30 nm. It was performed in the presence of oleic acid stabilizer in octyl ether solvent.

Production and characterization of indium oxide and indium nitride

Thin films of indium oxide 200 nm thick and indium nitride 150 nm thick were produced by reactive sputtering deposition onto soda lime substrates. The Indium cathode was kept under vacuum attached to a high voltage dc. The In xOy films were obtained in argon-oxygen mixture with total pressure between 2 and 7 Pa, current density between 0.04 and 0.56 mA/cm² and substrate temperature of 300 K. The In xNy films were obtained in argon-nitrogen mixture with total pressure between 1 and 5 Pa, current density between 0.18 and 14 mA/cm² and substrate temperature of 320 K. Results revealed that thin films give rise to high conductivity, are transparent and have a carrier density of 10(19) cm- 3 for In xOy and 10(17) cm- 3 for In xNy. These results were obtained mainly from temperature dependent alpha and sigma measurements. The reduced chemical potential was calculated considering three different scattering mechanisms i.e. interaction with optically polarized phonons, interaction with ionized impurities and interaction with grains, in order to identify the main scattering mechanism, which resulted to be due to impurities.

Role of boron carbide in carbothermic formation of hexagonal boron nitride

Formation of hexagonal boron nitride by carbothermic reduction of boric oxide under nitrogen atmosphere at 1500 °C was investigated. Experiments were performed for durations in the range of 15 min to 3 h. Reaction products were subjected to powder X-ray diffraction analysis, chemical analysis and were examined by scanning electron microscope. Formation of hexagonal boron nitride was found to be complete in 3 h with most forming in the initial 2 h. Boron carbide was found to exist in the reaction products of the experiments in which hexagonal boron nitride formation was not complete. The aim of this study was to investigate the role of boron carbide in the carbothermic production of hexagonal boron nitride. For this purpose, conversion reaction of boron carbide into hexagonal boron nitride was studied. Boron carbide used in these experiments was produced in the same conditions that hexagonal boron nitride was formed, but under argon atmosphere. It was found that formation of hexagonal boron nitride from boron carbide—boric oxide mixtures was slower than activated carbon—boric oxide mixtures. It was concluded that boron carbide is not a necessary intermediate product in the carbothermic production of hexagonal boron nitride.

Laser/sol–gel synthesis: a novel method for depositing nanostructured TiN coatings in non-vacuum conditions

In this work results of experiments on the in situ production of titanium nitride by the reaction of titania sol-gel with a nitrogenous admixture under laser irradiation are reported. A diode laser beam at different powers and traverse speeds was applied to the mixture placed on EN43 mild steel and 316L stainless steel substrates. Composite coatings of titanium nitride and titanium oxide with a hardness of 17-21 GPa have been achieved by this new method. Surface morphology and microstructure of the deposited coatings and substrate surface layers were examined using optical microscopy, scanning electron microscopy, and field-emission gun scanning electron microscopy. Chemical composition was determined by energy-dispersive X-ray analysis. The phases were identified by X-ray diffraction. Results of microhardness and nanohardness at the top surface were evaluated.

A novel method for the production of aluminium nitride

A method has been developed to produce thick (> 400 mu m) AlN surface layers oil aluminium plates at 540 degrees C, under nitrogen at atmospheric pressure. A critical element of the process is the use of Mg powder placed in close proximity to the Al plate surface. The Mg reduces/disrupts the natural, protective oxide film on the Al surface. The nitride layers form through two distinct modes, one growing outward from the Al plate surface and the other growing into the Al. (c) 2006 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Enhancement of direct nitridation of silicon by common metals in silicon nitride processing

Catalytic effects of metals, which are often involved in the fabrication of silicon nitride product, on the direct nitridation of silicon were investigated. Silicon granules impregnated with 0.125–2.0% by mass of ytterbium, yttrium, calcium, lutetium, magnesium or cerium were nitrided in a tubular flow reactor operated at temperature in the range of 1300–1390 °C. Enhanced selectivity of α-silicon nitride formation was observed when calcium, yttrium or ytterbium was used. It was also found that a stepwise increase in the nitridation temperature from 1300 to 1390 °C enhanced the conversion of silicon while keeping high content of α-silicon nitride. Yield of α-silicon nitride over 95% was achievable within 3 h of the reaction from an addition of calcium or ytterbium to silicon raw material. It is suggested that characteristic of the impregnated metal, rather than the presence of liquid phase formed during the reaction, has the dominant effects on the α-silicon nitride formation.

WITHDRAWN: A new approach to the mass production of titanium carbide, nitride and carbonitride whiskers by spouted bed chemical vapor deposition

This article has been withdrawn at the request of the author(s) and/or editor. The Publisher apologizes for any inconvenience this may cause. The full Elsevier Policy on Article Withdrawal can be found at http://www.elsevier.com/locate/withdrawalpolicy.

Low-temperature solvothermal synthesis of nanocrystalline indium nitride and Ga–In–N composites from the decomposition of metal azides

Nanocrystalline InN powders have been synthesized through metal azide decomposition in superheated toluene and refluxing hexadecane solvents near 280 °C. The metal azide intermediates were formed in situ through the metathesis reaction of InBr3 and NaN3. The InN products from toluene consist of ∼10 nm hexagonal (wurtzite) structured crystallites in aggregated arrangements. InN from hexadecane and lower temperature toluene reactions produced more poorly crystalline InN that appears to contain a cubic (zinc blende) component. Coordinating amine solvents led to decomposition of the nitride to indium metal. Several reactions were undertaken to produce mixed metal nitrides of the form Ga1−zInzN where z is 0.5 and 0.75. The mixed metal nitride products are analytically consistent with composite versus solid-solution formation, however some metal mixing is observed. Data from X-ray diffraction, electron microscopy, thermal analysis, elemental analysis, and several spectroscopic methods are combined to form a consistent picture of the bulk and surface structures for these nanocrystalline InN materials.

A new approach to the mass production of titanium carbide, nitride and carbonitride whiskers by Spouted Bed Chemical Vapor Deposition

A new approach, the Spouted Bed Chemical Vapor Deposition (SBCVD) was used for the first time for the mass production of titanium carbide, nitride and carbonitride whiskers. The product is an ingot consisting of a large number of interweaving whiskers and filling up the whole space in the reaction tube. For reaction tubes of same size, the amount of whiskers obtained by SBCVD is by an order of magnitude more than that obtained by traditional chemical vapor deposition (TCVD). The large amount of SBCVD is ascribed to the replacement of the bulk substrate by numerous metallic powders, which are floated in the vapor phase by the upward stream of the flowing gaseous reactant and encircled in the reaction zone up and down during the whole period of whisker growth, forming a spouted bed. The new method also provided direct evidence of the VLS whisker growth mechanism, and thus clarified some confusion about this mechanism.

Nitrides as a nuclear fuel option

Nitrides have been proposed to be a suitable material for fast neutronic systems from beginning of the development of nuclear fuel. Starting with the production of uranium nitride and sesquinitrides up to mixed plutonium uranium nitrides, today's developments are inert nitride matrix materials to burn plutonium or to transmute long-lived actinides in accelerator-driven sub-critical systems (ADS) or fast reactors (FR). Several authors proposed zirconium nitride as possible inert matrix material for this reason. Mixed zirconium nitrides can be fabricated by carbothermal nitridation of the oxides in a narrow temperature window. Obtaining high quality material with low carbon and oxygen content is still the major challenge. Producing mixed nitride fuels by special shaping methods, as for example direct coagulation casting or freeze drying, in comparison to conventional powder compaction enables to use this material in special shapes to optimize burn up.The history of nitride fuels at PSI will be shown up to today's CONFIRM project, dealing with plutonium zirconium nitride fuels.

3,6‐Di(azido)‐1,2,4,5‐Tetrazine: A Precursor for the Preparation of Carbon Nanospheres and Nitrogen‐Rich Carbon Nitrides

3,6‐Di(azido)‐1,2,4,5‐Tetrazine: A Precursor for the Preparation of Carbon Nanospheres and Nitrogen‐Rich Carbon Nitrides

Effects of dilution and preheating on SHS of vanadium nitride

An experimental investigation of self-propagating high-temperature synthesis (SHS) of vanadium nitride (VN) was conducted with vanadium powder compacts in gaseous nitrogen. Effects of sample density, nitrogen pressure, diluent content, and sample preheating on the degree of conversion, flame-front velocity, and combustion temperature were studied. Experimental observations showed that the SHS process of the vanadium/nitrogen reaction was characterized by the steady propagation of a planar combustion front, followed by a prolonged afterburning reaction. The flame-front velocity increased with nitrogen pressure, but decreased with sample density. For the undiluted samples, a low degree of nitride conversion between 45 and 55% was obtained, primarily due to the formation of a liquid phase at nitrogen pressures higher than 0.79 MPa. The dilution of vanadium compacts with the nitride product VN powders suppressed the liquid formation, leading to a substantial increase in the degree of conversion. In addition, the conversion percentage of VN-diluted samples was further increased by properly preheating the sample prior to ignition. Under the condition with 30 wt.% dilution and preheating at 100–200 °C, it was found that a conversion over 90% was achieved. Based upon the XRD analysis, the δ-VN was identified as the dominant nitride phase synthesized in this study.

Zirconium nitride/silver nanocomposite structures for biomedical applications

Silver zirconium nitride films deposited by unbalanced magnetron sputtering were studied by means of x-ray diffraction, transmission electron microscopy, x-ray photoelectron spectroscopy, spectroscopic ellipsometry, and nanoindentation. Coatings were deposited on silicon substrates at room temperatures with bias voltages in the −45 to −160 V range. The concentration of zirconium and silver was regulated by controlling the power to the sputtering guns. The nitrogen concentration was selected so that the nitrogen flow rate corresponded to the production of stoichiometric zirconium nitride. The films consisted of nanocrystals of zirconium nitride embedded in a silver matrix. The grain size was deduced from the width of the XRD peaks using the Scherrer formula and was found to decrease with the addition of silver. The chemical and phase composition was determined from XPS measurements. The optical constants were measured using spectroscopic ellipsometry. A correlation between film structure/composition and optical constants was established. The mechanical properties of the coatings were evaluated using nanohardness testing and were found to depend on composition and deposition parameters. Optimum mechanical properties were achieved for a silver content of 6% and a substrate bias of −160 V.

Effect of CaF<sub>2</sub> Addition and Type of Alumina on Production of Aluminum Nitride

Effect of CaF<sub>2</sub> Addition and Type of Alumina on Production of Aluminum Nitride

Synthesis and structure of 2,5,8-triazido-s-heptazine: an energetic and luminescent precursor to nitrogen-rich carbon nitrides.

Derivatized s-triazine (C3N3) precursors have seen significant recent use in the production of carbon nitride materials. Larger polycyclic molecular precursors, such as those containing an s-heptazine core (C6N7 or tri-s-triazine), may improve stability and order in carbon nitride products. In this Communication, we describe the synthesis and crystal structure of 2,5,8-triazido-s-heptazine (2). Synthesis of 2 was achieved from melon, an oligomeric s-heptazine synthesized by the pyrolysis of NH4SCN. Melon was converted to molecular 2,5,8-trichloro-s-heptazine, which was then transformed to the triazide upon reaction with (CH3)3SiN3. The crystal structure of 2 verifies that the s-heptazine is planar and the azides adopt a pinwheel-like C3h arrangement around the periphery. The s-heptazine core shows pi delocalization in the C-N bonds around the periphery (av. 1.33 A), while the internal planar C-N bonds are longer (1.40 A). The heptazine units pack into parallel, but offset, layered sheets in the crystal. The triazide 2 exhibits photoluminescence at 430 nm and rapidly and exothermically decomposes upon heating at 185 degrees C to produce a tan thermally stable carbon nitride powder with a formula near C3N4.

Emcore's MOCVD production seminar

This year’s International Conference on Nitride Semiconductors (ICNS-5) saw a gathering of GaN experts discussing their work. Representatives from companies and Japanese universities specialising in nitride production attended a series of lectures providing insight into research and commercial developments in GaN processing. This is a short news story only. Visit www.three-fives.com for the latest advanced semiconductor industry news.

On the dynamics of unipolar and bipolar pulsed d.c. discharges used for plasma CVD

Investigations of the development of discharges relevant for the production of titanium nitride (TiN) coatings using titanium tetrachloride (TiCl 4) as a feedstock gas have shown that under certain loading conditions the spreading of the discharge during the pulse is too slow. Recently, we have demonstrated that the ignition and spreading behaviour can be very much improved by the superposition of short high voltage pulses at the beginning of each conventional pulse. However, an extra high voltage power supply is needed. In the present work we investigate another possibility to get a better performance of the ignition and spreading behaviour of the discharge, the bipolar operation of the voltage power supply. Discharge current measurements and video observations reveal for this operation mode a very much improved ignition and spreading behaviour during the negative voltage pulses for durations of the positive voltage pulses of at least 50 μs. The reason might be that at the end of the pulse-off time which follows after the more powerful positive pulse more charge carriers remain and hence, the density of charge carriers should be high enough to allow a better ignition of the discharge at the beginning of the negative pulse.

Metalorganic chemical vapor deposition of group III nitrides—a discussion of critical issues

Metalorganic chemical vapor deposition (MOCVD) is recognized as the method of choice for the large-scale production of nitride based optoelectonic and electronic devices. (Al, Ga, In)N alloys with In and Al compositions below 40% have been intensively investigated for applications in light emitting and electronic devices. However, due to the difficulties in epitaxial growth, less attention was directed to the fabrication of materials with higher Al and In mole fractions. In this article, critical issues in the growth of (Al, Ga, In)N by MOCVD are discussed in relation to the diverse chemical properties of the group-III nitrides and their impact on the growth process.

Facile Azidothermal Metathesis Route to Gallium Nitride Nanoparticles

This report describes a straightforward, metathesis (exchange) reaction between gallium chloride and sodium azide that produces gallium nitride nanoparticles below 210 °C. Slowly heating these two reagents together circumvents rapid, exothermic reactions, which can decompose the nitride product. The resulting GaN powders are nanocrystalline and crystallize to the hexagonal phase upon annealing. Well-formed nanoparticles (ca. 50 nm) are clearly resolved in annealed samples, while as-synthesized particles sizes are near 10 nm.

Production of ultrafine iron nitride by double nitriding

Production of ultrafine iron nitride by double nitriding