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The DV-Xa molecular orbital (MO) calculation method was applied to the B K‐V x-ray emission spectra of hexagonal (h-), cubic (c-) and wurtzite (w -) type boron nitrides (BN). The calculated B 2p density of states (DOS) was in good agreement with the B K‐V x-ray emission. The main peaks and low-energy satellite peaks in the B K‐V x-ray emission spectra are due to the B 2p and the B 2p hybridized with N 2s, respectively. The high-energy satellite peak in the B K‐V x-ray emission spectra clearly corresponds to the p sub-band of the B 2p DOS in h-BN. However, the high-energy satellite peak observed in w -BN is not in agreement with the B 2p DOS. It is considered that the high-energy satellite peaks are due to less than four-coordinated B atoms such as have dangling bonds and defects in w -BN. In the B K‐V x-ray emission spectra of h-BN, the synthesizing p and s sub-bands of B 2p DOS could explain the polarized emission spectra very well. Copyright ” 1999 John Wiley & Sons, Ltd.

The B K X-ray emission spectrum of h-BN can be approximately reproduced by the DV-Xα calculation, using the two-dimensional model cluster constructed of a mono-layer of the planar hexagonal network. In order to verify the polarized B K X-ray emission spectrum of h-BN, the contributions of the σ, π and π ∗ subbands to its spectral feature were estimated at different take-off angles for the c axis of an h-BN crystal. The high-energy satellite band increases its intensity, remarkably, due to the contribution of the π ∗ subband with increase in take-off angle, whereas the low-energy satellite band decreases its intensity due to the contribution of the σ subband. The measured B K X-ray emission spectrum of the ion-plated h-BN thin film is in good agreement with the calculated one at a take-off angle of 90°.

Hard BN films with cubic BN (c-BN) phase and soft BN films without c-BN phase were deposited on Si wafer by a reactive ion plating process with a hot cathode plasma discharged within parallel magnetic field. These BN films were left in air with relative humidity of about 30%, 65-85% and 100% for about 3000 hours. The atmospheric degeneration of these BN films was investigated by SEM observation and EPMA measurements. Small particles such as boron oxide, boric acid or ammonium borate were formed at the surface of soft BN films left in air. All BN films were cracked after leaving in air. The cracking became faster with an increase in the relative humidity of air. The cracking of soft BN films occurred more rapidly than that of hard BN films. The cracking of hard BN films was retarded by post annealing.

The effect of VC on mechanical properties of sintered high speed steel(PX16; equivalent for SKH51) made from water atomized powder has been studied. The mechanical properties such as transverse rupture strength and microvickers hardness have been measured and optical and electron microscopic observation have been carried out. The results obtained were summarized as follow;1) Microvickers hardness of the composite increases with the increase of the mass fraction of VC.2) Transverse rupture strength decreases with the increase of the mass fraction of VC.3) In consequence of added VC, M6C type carbides were extinguished.4) Carbide grain size in this alloy is growing with the increase of the mass fraction of VC.

An investigation was carried out to synthesize cBN film on a Si wafer by means of a reactive ion plating process assisted hot cathode plasma discharged within a parallel magnetic field. The BN films prepared under various depositing conditions were analyzed by IR spectroscopy and microprobe chemical state analysis. It was found that the deposited BN films were composed of cBN and hBN, and the cBN content in the film ranged from 0% to a maximum of 82%. The cBN content was dependent on the ionization electrode current, RF power applied to a substrate and EB power(evaporation rate of Boron), and increased with increasing values of their parameters. But the BN film could not be deposited under excessive RF power because of sputtering predominantly caused by ions impinging on a substrate.The cBN content was increased remarkably by introducing Ar gas with N2 gas into the evaporation chamber. Therefore, it was assumed that thermal spikes caused by Ar ions impinging on the growing BN film play a significant role for the formation o f cBN film.

Enhanced resonant x-ray emissions were observed from mechanically milled hexagonal boron nitride nanoclusters in boron K-shell excitation using quasimonochromatic undulator radiation. The resonant x-ray emission intensity increases with decrease in size of the milled clusters. Comparison of the measured x-ray emission spectra with the calculated spectra using the discrete-variational Xa methods showed enhanced resonant x-ray emissions originate from the B1 s - n p B1 s 2 1 electron transition, with n p an unoccupied nonbonding orbital of twofold-coordination boron atoms with dangling bonds. X-ray emissions excited to n p orbitals may be possible for detecting dangling bonds in nanoclusters. [S0031-9007(96)00198-6]

Boron 2p density of states are calculated and compared with X-ray fluorescence spectra of h-BN. The high energy satellite, which was assigned to resonance X-ray scattering peak, is found to be 1s electron scattered by nonbonding unoccupied orbitals. Thus it is concluded that the resonance peak intensity is a measure of the density of dangling bonds in a nanocrystal.