Formation Of Cubic Boron Nitride Research Articles

Duplex Surface Treatment of AISI 1045 Steel Via Pack Boriding and Plasma Nitriding: Characterization and Tribological Studies

For the first time, formation of cubic boron nitride (c-BN), besides Fe2B and iron nitrides, was detected in boronitride coating, which was applied via a duplex diffusional surface treatment. Boronitride coating was applied on AISI 1045 steel substrates via duplex treatment of pack boriding and plasma nitriding (B-PN). Scanning electron microscope (SEM), X-ray diffractometer (XRD), and pin-on-disk wear test were utilized to evaluate microstructures, phases, and wear properties of the coatings. The surface of the as-coated sample exhibited a pebblelike and compact structure, and the cross-sectional morphology of the coatings showed a saw-tooth interface with substrate. Duplex treated sample revealed superior wear resistance in comparison with the borided one.

Neutron damage of hexagonal boron nitride: h-BN

Hexagonal boron nitride (h-BN) was neutron damaged at an integral flux of 2.40 × 1012 n cm−2 s−1 for 1, 2, 3 and 4 h. The h-BN samples undergo a transition from sp2 to sp3 hybridization as a consequence of the neutron induced damage with the formation of cubic boron nitride (c-BN) spots, as suggested both by FT–IR and Raman spectroscopy. In addition to c-BN, also a certain degree of amorphization is achieved by h-BN already at the lowest neutron fluence of 8.64 × 1015 n cm−2 as clearly evidenced by Raman spectroscopy. The Wigner or stored energy to the radiation-damaged h-BN samples was studied by DSC and also in this case there was a clear evidence that the neutron damage was partly irreversible and insensitive to the thermal annealing up to 630 °C. Electron spin resonance (ESR) was employed to further study the structural defects induced by the neutron bombardment of h-BN. Two kinds of paramagnetic defective structures centered on 11B atoms were identified.

Effects of Nitrogen Partial Pressures During RF Magnetron Sputtering on the Crystal Structure and Growth Rate of c-BN Films

The type of atmospheric gases used in sputtering deposition is an important factor in the formation of cubic boron nitride (c-BN) films. All of the c-BN films were deposited on a Si wafer using radio frequency (r.f.) magnetron sputtering with a B4C target at N2/Ar+N2 ratios of 0.2, 0.4, 0.6, 0.8 and 1.0. The characteristics of the c-BN layer were significantly enhanced at a nitrogen partial pressure of 0.6. The highest growth rate of the c-BN layer was measured at 11.6 (nm/min) at a nitrogen partial pressure of 0.6.The lowest surface roughness was obtained at a nitrogen partial pressure of 0.6 when the BCN gradient layer was clearly deposited. According to the XPS results, the c-BN phase structure improved while the BCN gradient layer was clearly observed. Overall, the growth rate, surface roughness and crystal structure of the c-BN films are significantly affected under certain atmospheric gas conditions such as at a nitrogen partial pressure of 0.6.

Single-crystal cubic boron nitride thin films grown by ion-beam-assisted molecular beam epitaxy

We investigated the formation of cubic boron nitride (c-BN) thin films on diamond (001) and (111) substrates by ion-beam-assisted molecular beam epitaxy (MBE). The metastable c-BN (sp3-bonded BN) phase can be epitaxially grown as a result of the interplay between competitive phase formation and selective etching. We show that a proper adjustment of acceleration voltage for N2+ and Ar+ ions is a key to selectively discriminate non-sp3 BN phases. At low acceleration voltage values, the sp2-bonded BN is dominantly formed, while at high acceleration voltages, etching dominates irrespective of the bonding characteristics of BN.

Thermodynamic Study on the Formation of Boron Nitride

Based on film adhesion properties with substrate, the sputtering system is favorable for the formation of cubic boron nitride (c-BN). In the present study, the standard free energy change was investigated for the formation of boron nitride with nitrogen partial pressures. It was found that the cubic phase BN is more thermodynamically stable than the hexagonal phase, with the equilibrium constant for the cubic phase BN formation reaction being lower than that for the hexagonal phase reaction.

ChemInform Abstract: Prediction of Formation of Cubic Boron Nitride by Construction of Temperature—Pressure Phase Diagram at the Nanoscale.

AbstractThe size‐dependent temperature—pressure phase diagram of BN is constructed on the basis of nanothermodynamic theory.

Prediction of formation of cubic boron nitride by construction of temperature–pressure phase diagram at the nanoscale

The size-dependent phase diagram of BN was developed on the basis of the nanothermodynamic theory. Our studied results suggest that cubic BN (c-BN) is more stable than hexagonal BN (h-BN) in the deep nanometer scale and the triple point of c-BN, h-BN and liquid shifts toward the lower temperature and pressure with decreasing the crystal size. Moreover, surface stress, which is determined by the experimental conditions, is the main reason to influence the formation of c-BN nuclei. The developed phase diagram of BN could help us to exploit new techniques for the fabrication of c-BN nanomaterials.

Effect of Al additive on the formation of cubic boron nitride in Li 3N–hBN system under HPHT

We have investigated the effect of Al on cBN formation in Li 3N–hBN system at 5.0 GPa and 1300–1650 °C. Regular cBN single crystals of 0.2–0.5 mm in size were obtained. It appears that the presence of Al in hBN powder facilitates the formation of cBN crystals with regular shape, although it does not have any catalytic action for hBN–cBN phase transformation. With increasing Al concentration, the color of cBN changed darker from amber to black and the threshold temperature for cBN formation became higher. X-ray diffraction and Raman spectroscopy indicate that AlN formed by reaction of Li 3N and Al and some B liberated in system.

Preparation and internal stress estimation of BN films by ion mixing and vapour deposition technique

Boron Nitride (BN) films were synthesized onto silicone wafer by depositing B metal vapour under simultaneous irradiation of N ions. Here, film thickness, ion beam energy and transport ratio (B/N) were selected as a preparation parameter and they were controlled in the range of 0.2-1μm, 0.2~2keV and 1~5, respectively. The BN films prepared were characterized using several analytical techniques and their internal stresses were estimated using Stoney's equation. From Fourier transform infrared spectroscopy, it was found that use of low energy N ions is effective for the formation of cubic BN (cBN) phase using ion mixing and vapour deposition (IVD) technique. At this condition, high compressive stress is measured and strong correlations were found among crystal structure, internal stress and Knoop hardness of BN films.

Influence of oxygen on the formation of cubic boron nitride by r.f. magnetron sputtering

Formation of cubic boron nitride by r.f. magnetron sputtering has been studied with O 2 addition to the common working gas Ar/N 2. The chemical and the phase composition were determined with Auger electron spectroscopy sputter depth profiling and Fourier transform infrared spectroscopy. The result shows that oxygen hinders the formation of cBN in sufficient nitrogen-supply, but facilitates the growth of cBN in insufficient nitrogen-supply. With insufficient nitrogen-supply, there exists an optimal oxygen-supply in the working gas that promoted the establishment of the stoichiometric condition in the growing film. O-concentration in the film increases with oxygen-supply in the working gas. cBN forms only when the oxygen concentration is below 5% and c N/ c B (ratio of concentration of nitrogen atoms and boron atoms) is 1 in the film.

Inducing effect of halide species in the hydrothermal synthesis of cubic boron nitride

The inducing effect of halide species on the formation of cubic boron nitride (cBN) in hydrothermal solutions was investigated. The results indicated that both Cl − and F − played an important role in promoting cBN and suppressing hBN, and the inducing effect of the latter was much stronger than that of the former. Although the inducing effect was firstly observed in the phase-selective synthesis (PSS) method, by which pure cBN micro-crystals were synthesized, it was also applicable in both high-temperature in-situ reaction (HTISR) and conventional hydrothermal synthesis (CHS) methods. When the concentration of Cl − and F − was high enough, pure cBN could also be expediently synthesized by the CHS method.

Effect of Al on the Formation of Cubic Boron Nitride Using Ni3Al Solvent under High Pressure

Cubic boron nitride (cBN) was synthesized using a Ni3Al alloy as a solvent under high pressure and high temperature. The range of cBN formation was determined to be between 4.5 and 6.5 GPa. In the temperature range between 1300 and 1900 °C at about 6 GPa, it seems that the formation mechanism of cBN changed. In the lower-temperature region (<1400 °C), cBN was formed by a reaction between AlN and BN, possibly under solid-state conditions. In the higher-temperature region (>1400 °C), molten Ni3Al infiltrated the starting hexagonal BN layer with rapid cBN precipitation.

The Enthalpy of Formation of Cubic Boron Nitride

AbstractFor Abstract see ChemInform Abstract in Full Text.

Effect of substrate temperature and ion bombardment on the formation of cubic boron nitride films: A two-step deposition approach

The influence of substrate temperature and ion bombardment on the formation of cubic boron nitride (c-BN) films has been examined with bias-assisted magnetron sputtering of h-BN for argon and nitrogen as the working gases. It is shown through a two-step deposition approach that higher substrate temperatures are required only to establish an appropriate h-BN base layer which is mandatory as a nucleation base for c-BN. For nitrogen as the working gas the energy of the bombarding ions can also be reduced after c-BN-nucleation. Hence, the conditions for the formation of c-BN films are more restrictive for the initial growth stage than for the later c-BN growth once the nucleation into c-BN has been established. Corresponding results for argon and nitrogen display characteristic differences which lead to the conclusion that the establishment of full BN surface stoichiometry is a key condition for c-BN growth.

Growth, doping and applications of cubic boron nitride thin films

Abstract This article reviews the growth techniques and growth parameters for the formation of cubic boron nitride (c-BN) thin films. It is generally accepted that the impact of energetic ions or neutral atoms is crucial to achieve c-BN film growth. Furthermore, c-BN nucleation is only observed within certain thresholds for the deposition parameters, including the substrate temperature. However, the temperature threshold exists only for the nucleation and not for the growth of c-BN. We will show that three independent characterization methods are necessary for the non-ambiguous identification of the c-BN phase within BN films. The cylindrical thermal spike model developed to describe the formation of diamond-like phases by ion deposition can be used to explain the c-BN nucleation and growth. A short introduction and the basic ideas of this model will be given. Finally, possible tribological applications of c-BN films and the doping of c-BN films will be discussed.

Properties of cubic boron nitride films with buffer layer control for stress relaxation using ion-beam-assisted deposition

Significant ion irradiation during film growth is required for the formation of cubic boron nitride (cBN) films. Meanwhile, a huge level of intrinsic stress possibly induced by the ion bombardment has been frequently reported to result in cracking and/or lack of adhesion of deposited cBN films. The present work has been performed to investigate the interfacial and/or the buffer layer structures with better matching to the cBN film by relaxation of the film stress using ion-beam-assisted deposition (IBAD). Boron nitride films have been synthesized on Si(100) wafer and tungsten carbide (WC) substrates by depositing boron vapor under simultaneous bombardment with nitrogen ions and nitrogen–argon mixture ions in the energy range of 0.5–10 keV. Cubic BN films with enhanced tribological properties have been explored by inserting a BN layer with various B/N compositions as a controlled buffer at the interface. Significant relaxation of the film stress has been observed for the buffer layer with a boron-rich (B-rich) composition (B/N∼10) with hardness maintained at a relatively high value (∼30 GPa). A structural analysis by Fourier transform infra-red spectroscopy (FTIR) and cross-sectional transmission electron microscopy (TEM) confirms that polycrystalline films with a high cBN fraction were synthesized on the B-rich layer. Formation of the cBN films with a B-rich buffer layer enabled the tribological characterizations to be performed, and the tribological properties have been observed to be significantly enhanced with the insertion of the B-rich buffer and the enhancement of atomic intermixing at the initial stage of cBN layer growth. Using the nanoindentation method, the hardness of the cBN films with a high cubic fraction was found to be as high as the values for the bulk cBN.

On Nucleation of Cubic Boron Nitride in the BN−MgB2 System

X-ray powder diffraction with synchrotron radiation was used to study the formation of cubic boron nitride (cBN) in the MgB2−BN system at pressures to 6.8 GPa and temperatures to 2000 K. For the fo...

Cisplatin, radiation, and adjuvant hysterectomy compared with radiation and adjuvant hysterectomy for bulky stage Ib cervical carcinoma

Powder diffraction of synchrotron radiation at pressures up to 6.3 GPa and DTA at ambient pressure were used to study phase equilibria in the Li3N-BN system at temperatures up to 1820 K. The construction of the Li3N-BN quasibinary section of the Li-B-N ternary system has been refined. The melting of the high-pressure phase of Li3BN2has been shown to be of an incongruent nature. The existence of the Li3BN2(O) ⇄ L + BN peritectic equilibrium at 1620 K and 5.3 GPa has been established. It was shown that this peritectic reaction defines the lowest possible temperature of formation of cubic boron nitride in the Li3N-BN system (1670 ± 50 K in the 5.3–6.3 GPa range).

Extended model for stress-induced formation of c-BN in ion-assisted deposition

Abstract A simple model is presented that describes the formation of cubic boron nitride (c-BN) during ion-assisted film deposition in terms of compressive stress. The extended static stress model is based on the rate equations of Davis, taking into account the balance of vacancies and interstitials formed in the film during ion bombardment. The model explains the lower boundary of the c-BN growth domain in the diagram of ion-to-atom arrival ratio and ion energy in terms of a critical minimum stress necessary for c-BN formation. The stress as a function of ion energy and ion-to-atom arrival ratio can be described in terms of the momentum transferred to the film by the ions as the single independent variable. In the case of the bombarding species also representing the film forming atoms (direct energy input), the boundary of the c-BN growth domain is predicted to shift to lower ion-to-atom arrival ratios for constant ion energy. Once c-BN has formed, the ion energy and ion-to-atom arrival ratio can be lowered to keep c-BN growing due to the increase of the Young's modulus of c-BN compared to h-BN.

Cylindrical spike model for the formation of diamondlike thin films by ion deposition

/nS of nT rearrangements and nS atoms in the spike volume as the crucial parameter characterizing the ability of a given ion–target combination to achieve complete rearrangement of the spike volume. nT/nS>1 is the optimum condition for diamondlike film growth. For aC films the ion energy dependence of nT/nS agrees well with the measured sp3 bond fraction. For Ar+-ion-assisted deposition of aC we find nT/nS>1 above 50 eV with no pronounced ion energy dependence. Furthermore, our model predicts optimum conditions for the formation of cubic boron nitride between 50 eV and 3 keV.