Synthesis Of Boron Nitride Research Articles

Microstructural Observation of Boron Nitride Films Synthesized by Ion Implantation

We report on the synthesis of boron nitride (BN) films by ion implantation and demonstrate the results of microstructural observation of the films. Boron films were initially prepared on single-crystal Si(100) substrates by rf sputtering. Then, 30 keV N2+ was implanted at doses ranging from 1×1017 ions/cm2 to 6× 1017 ions/cm2 to synthesize BN. No substrate heating was used in the sputtering and implantation processes. Chemical composition analysis of the films was carried out by Auger electron spectroscopy. Transmission electron microscopy was employed for microstructural observation. Mixed-phase BN, including t-BN, c-BN, w-BN and B25N, was identified in the implanted films. The BN formation mechanism was discussed and compared with theoretical models. The results of this work are consistent with the stress-induced BN formation model in several aspects.

Synthesizing boron nitride nanotubes filled with SiC nanowires by using carbon nanotubes as templates

A method is described to synthesize silicon carbide (SiC)-filled boron nitride (BN) nanotubes (NT) simultaneously in high yield by using carbon nanotubes (CNTs) as templates. This method combines both carbon nanotube-substitution reaction and confined reaction. Through the CNT-substitution reaction, CNTs react with boron oxide vapor in the presence of nitrogen gas to form BN NTs, whose diameters and lengths are similar to those of the starting CNTs. The formation of the SiC filling is proceeded by the penetration of SiO vapor into the cavity of the nanotubes and subsequent reaction of SiO vapor with the inner carbon layers or volatile carbon mono-oxide in the interior to form SiC nanowires. The filled length can be up to the entire length of the nanotubes. SiC-filled (BN)xCy nanotubes also form in the product.

Synthesis of poly(borazinylamine)

1,3,5-Trichloroborazine (TCB) was prepared from the reaction of ammonia chloride with boron trichloride. TCB along with hexamethyldisilazane and boron trichloride were used to synthesize boron nitride (BN) preceramic polymer poly(borazinylamine). This study showed that, the lower the reaction temperature, the higher the synthetic yield. Poly(borazinylamine)'s solubility mainly depended on the ratio of TCB, (Me3Si)2NH, and BCl3. The solvent used in the reaction had a large effect on the ceramic yield of poly(borazinylamine). A soluble poly(borazinylamine) with good synthesis and ceramic yields was obtained when the reaction temperature was −15°C, cyclohexane was the solvent, and the ratio of TCB : (Me3Si)2NH : BCl3 was 1 : 6 : 1. By means of infrared and mass spectroscopy analyses, the structure of the poly(borazinylamine) was identified. Thermal decomposition of the poly(borazinylamine) precursor to hydrolyzed BN was also examined. Hydrolyzed BN was obtained at 1000°C, where the ceramic yield was 35–45%. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 863–868, 1999

Synthesis of poly(borazinylamine)

1,3,5-Trichloroborazine (TCB) was prepared from the reaction of ammonia chloride with boron trichloride. TCB along with hexamethyldisilazane and boron trichloride were used to synthesize boron nitride (BN) preceramic polymer poly(borazinylamine). This study showed that, the lower the reaction temperature, the higher the synthetic yield. Poly(borazinylamine)'s solubility mainly depended on the ratio of TCB, (Me3Si)2NH, and BCl3. The solvent used in the reaction had a large effect on the ceramic yield of poly(borazinylamine). A soluble poly(borazinylamine) with good synthesis and ceramic yields was obtained when the reaction temperature was −15°C, cyclohexane was the solvent, and the ratio of TCB : (Me3Si)2NH : BCl3 was 1 : 6 : 1. By means of infrared and mass spectroscopy analyses, the structure of the poly(borazinylamine) was identified. Thermal decomposition of the poly(borazinylamine) precursor to hydrolyzed BN was also examined. Hydrolyzed BN was obtained at 1000°C, where the ceramic yield was 35–45%. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 863–868, 1999

Combustion synthesis of boron nitride powder

A combustion synthesis (SHS) process developed in our previous study for the synthesis of Si3N4 has been tested for the synthesis of boron nitride (BN) powder. Boron and NaN3 powders were used as the reactants. In addition to ammonium halides, KHF2, FeCl3, NaNH2, or a mixture of 50 mol% FeCl3 and 50 mol% NaNH2 was added to the reactants to examine their catalytic effect. These powders were mixed and pressed into a cylindrical compact. The compact was wrapped up with an igniting agent (i.e., Mg + Fe3O4) and the synthesis reaction was triggered by the combustion of the igniting agent. It was found that only those reagents containing both halogen and hydrogen can exert effectively the catalytic effect. The BN powder as-synthesized is mostly in the form of agglomerated fine particles (0.1–1 μm in diameter) and is hexagonal in crystalline structure. Effects of various experimental parameters on the product yield were investigated. A possible reaction mechanism was proposed, which explains the effects of the experimental parameters on the synthesis reaction.

Cubic boron nitride synthesis by pyrolysis of certain polyammoniates of boron hydrides of metals at high pressure

Pyrolysis of certain polyammoniates of boron hydrides of metals (PABH Mes) at high pressures not exceeding 7.0 GPa and at a temperature not exceeding 1770 K was examined. These compounds have a general formula Me(BH 4 ) n · m NH 3 , where n is determined by the metal valency, m =1–8, Me: Li, Mg, Zn, Al, Sc, La, Zr, Cr, Co. P,T regions of cubic boron nitride (cBN) synthesis in the process of PABH Me pyrolysis were determined. It was ascertained that the P,T regions differed widely for different compounds. The kinetics of cBN formation in the process of pyrolysis of PABH Mg and PABH Al were studied. Cubic boron nitride crystals were examined using the method of scanning electron microscopy (SEM). A mechanism of cubic boron nitride formation in the process of PABH Me pyrolysis is suggested.

ChemInform Abstract: Synthesis of Boron Nitride by Self‐Propagating Reactions at High Pressure.

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Synthesis of Boron Nitride by Self‐Propagating Reactions at High Pressure

Peculiarities of the formation of BN in a self‐propagating reaction between LiBF4 and Li3N have been studied under a wide range of p,T conditions within the region of thermodynamic stability of cBN. Boron nitride crystallized mainly in the form of highly ordered hBN (1700–2100 K), of mesographitic BN (2200–3000 K), or of turbostratic BN (>3000 K). Cubic boron nitride was obtained with a low yield (up to 14 vol%) as a result of precipitation from the metastable eutectic liquid in the BN‐Li3N system. These results give further evidence for an alternative metastable behavior in the BN phase formation under high pressures.

Cubic boron nitride synthesis in low-density supersonic plasma flows

We report on the growth of cubic boron nitride films on {100} silicon using a low density, supersonic plasma jet generated by a direct-current arc discharge expanded to low pressures. The arc discharge was operated on source gas mixtures of nitrogen and argon, with boron trichloride injected downstream of the expansion nozzle. The films were analyzed by infrared absorption and x-ray photoelectron spectroscopy. Phase selectivity was obtained by the application of a negative bias to the substrate so as to bombard the surface with energetic ions during deposition. The deposition process was found to be highly sensitive to substrate temperature and substrate bias voltage.

High pressure diamond and cubic boron nitride synthesis

Abstract Diamond and cubic boron nitride (c-BN) are most exciting materials for the twenty-first century owing to their exceptional physicochemical properties and the resulting potential applications. Two different routes have been developed for the preparation of such materials: high-pressure high-temperature synthesis (HP-HT), and low-pressure high-temperature synthesis (LP-HT). Film deposition by PVD or CVD is satisfactory for many applications, but HP-HT synthesis may be more appropriate for the growth of single crystals for selective developments. Whereas diamond is only stable thermodynamically under HP-HT conditions, for c-BN the options seem wider. The historical HP-HT synthesis of both materials is presented. In addition, new potential preparation routes for c-BN could be an important advantage of this material in the near future.

Synthesis of Boron Nitride from Boron Oxide Using Super-Critical Ammonia

Hexagonal boron nitride was synthesized from boron oxide using super critical ammonia and solid CaO below the melting point of B 2 O 3 by the following reaction: B 2 O 3 (s)+2NH 3 (super-critical fluid) + 3CaO (s)=2BN (s)+3Ca(OH) 2 (s). The experiment was carried out at 623-753 K and the initial ammonia pressure was 3.0-40.0 MPa. The mean diameter of obtained BN particles was 0.2-0.3 μm. The yield of BN increased with increasing temperature, initial ammonia pressure and the addition of CaO. The thermochemical calculation showed that the CaO addition suppressed the decomposition loss of ammonia during the reaction.

Reaction of diborane and ammonia gas mixtures in a chemical vapor deposition hot-wall reactor

Boron nitride has been deposited by chemical vapor deposition from diborane and ammonia gas mixtures, in the form of either films or powders depending on the pressure in the reactor. IR analysis of the boron nitride deposits has been used to obtain the composition of the films. In the temperature range studied, 600-850 o C, the effect of the deposition temperature on the reaction kinetics has been interpreted by assuming a change in the relative concentration of activated species arising from diborane and ammonia molecules. This change modifies the reaction path followed in the boron nitride synthesis through the formation of different intermediate compounds: aminodiborane in the low-temperature range (<700 o C) and borazine at the higher temperatures (≥775 o C)

Hexagonal boron nitride synthesis by nitrogen ion implantation of boron films

Boron was evaporated from an electron-gun-heated tantalum crucible and deposited as 1000 Å films onto KBr disks and polished Ti-6A1-4V cylindrical substrates. The films were then bombarded by 50 keV N 2 + ions for doses ranging from 0.5 × 10 17 to 3 × 10 17 N 2 + cm -2. The highest dose was retained for implantation at different substrate temperatures ( i.e. room temperature, 150°C, 300°C, 450°C and 600°C). The implanted films were characterized by X-ray photoelectron spectroscopy and IR and UV-visible spectroscopies. Hexagonal boron nitride formation as a function of dose and substrate temperature was studied.

Transmission electron microscopy studies of boron nitride thin films produced by pulsed laser deposition

We are synthesizing boron nitride films by pulsed laser ablation in order to study the deposition conditions necessary to produce the cubic phase (cBN) which has a number of useful applications as a hard coating, semiconductor, and optical material. The yield of cubic material is controlled in part by the simultaneous irradiation of the growing film with a low energy beam of N2 and Arions. In order to understand how this transformation process occurs, we are using TEM to investigate how the microstructure and phase distribution varies with film deposition conditions.In many ways analogous to carbon, boron nitride forms both sp3- and sp2-bonded phases. The cubic phase (cBN), which is sp3 bonded, has the zinc blende structure, and in addition, BN can also form an sp3 bonded hexagonal phase with the wurtzite structure (wBN). An sp2-bonded hexagonal structure (hBN) is the stable room temperature phase, but like its analog, graphite, the sp2-bonded material can also exist in a highly disordered state, often referred to as turbostratic (tBN).

Low temperature synthesis of boron nitride from condensed diborane and ammonia using synchrotron radiation

Synchrotron radiation was used to form boron nitride from a mixture of diborane (B2H6) and ammonia condensed on a silver substrate at 78 K. Photoemission and near-edge x-ray absorption fine structure results show valence band and near-edge features characteristic of the hexagonal phase of boron nitride.

Chemical Preparation and Shock Wave Compression of Carbon Nitride Precursors

Two synthetic routes have been developed to produce high‐molecular‐weight organic precursors containing a high weight fraction of nitrogen. One of the precursors is a pyrolysis residue of melamine‐formaldehyde resin. The second precursor is the byproduct of an unusual low‐temperature combustion reaction of tetrazole and its sodium salt. These precursors have been shock compressed under typical conditions for diamond and wurtzite boron nitride synthesis in an attempt to recover a new ultrahard carbon nitride. The recovered material has been analyzed by X‐ray diffraction, FTIR, and Raman microprobe analysis. Diamond is present in the recovered material. This diamond is extraordinarily well ordered relative to diamond shock synthesized from carbonaceous starting materials.

Synthesis of boron nitride

The authors examine the boric oxide—ammonia route with special stress on the yield and composition of the intermediate addition compound (BN) x (B2O3) y (NH3) z . It has been concluded that B2O3 and NH3 present in the addition compound formed between 350°C and 900°C cannot be further reacted to convert the B2O3 into BN and the BN yield remains at around 66%. A formula (BN)12·7(B2O3)7·5NH3 has been suggested for the addition compound.

Synthesis of boron nitride from triammoniadecaborane and hydrazine under pressure

Boron nitride (BN) of low crystallinity was synthesized from triammoniadecaborane (TAD) and hydrazine at 125 MPa below 650° C. TAD itself was pyrolysed at 600° C and 125 MPa to form a mixture of amorphous boron and boron nitride containing BH and NH bonds. The infrared spectrum of the pyrolysed product of TAD itself at 600° C and 125 MPa showed the BNB absorption at 800cm−1 due to the formation of B3N3 structures. The X-ray diffraction (XRD) of the reaction product from TAD and hydrazine at 600° C had broad diffractions centred at 2η=25.5° and 43.0° (CuKα). The BH absorption at 2500cm−1 decreased in intensity on increasing the N/B ratio from 0.3 to 0.85, and disappeared finally at a ratio of N/B=1.3. The reaction product at 125 MPa had a porous structure. The electron diffraction of the specimen changed from faint rings to spots on circular rings after heat treatment at 800° C for 10 h. The heat-treated specimen, however, did not give sharp reflections corresponding to hexagonal BN in the XRD profile. BN of low crystallinity was transferred to cubic BN at 1200° C and 6.5 GPa in a 90% yield, which was higher than that of well-crystallized BN in the presence of AIN.

Synthesis of boron nitride via a polymeric vinylpentaborane precursor

It has been noted that when poly(alkenylpentaboranes) are pyrolyzed in the presence of a suitable reactant they can serve as precursors to other important nonoxide ceramics. Reported herein is the high-yield synthesis of boron nitride from the soluble oligomer poly(2-vinylpentaborane). The reaction conditions for conversion of the polymer to boron nitride are specified, and the two-step process is defined. 21 references, 1 figure.

Shock-induced synthesis. I. Cubic boron nitride from ammonia borane

Direct cubic boron nitride synthesis from ammonia borane (NH 3BH 3) was achieved in a high-pressure shock-compression experiment. The lattice spacing of the cubic boron nitride was 3.655 Å and there was evidence that the material contained some α-Fe and γ-Fe.