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Coincidence of reciprocal lattice point (CRLP) model was used to predict the stable orientation relationships of metal/α-Al 2 O 3 hetero interfaces from geometrical considerations. The predicted stable orientation relationships (ORs) between various metals and α-Al 2 O 3 agreed well with the experimentally observed ORs at the hetero interfaces fabricated by film growth processes. In the bcc metal/α-Al 2 O 3 systems with different fabrication processes such as internal oxidation, Burgers and Pitsch–Schrader ORs were experimentally observed, which have not been predicted as the most stable orientation relationships by CRLP. However, these ORs are predicted in CRLP as secondary stable orientations.

Surface reactions between a (0 0 0 1) C -plane sapphire and NH 3 , with He as an inert carrier gas, were investigated at high temperatures over 1200 °C using the in situ gravimetric monitoring method. Although the sapphire substrate was stable up to 1400 °C under a He atmosphere, decomposition started to occur at 1300 °C under a 0.1 atm NH 3 +He and the decomposition rates were found to be lower than those in 0.1 atm H 2 +He at each temperature. These results imply that sapphire can be decomposed by NH 3 and/or hydrogen generated by the decomposition of NH 3 over 1300 °C. The decomposition rate in NH 3 +He was decreased with increase in NH 3 flow time, and the decomposition rate became constant after 60 min of NH 3 flow. Moreover, the activation energy for sapphire decomposition before 60 min of NH 3 flow was different from that after 60 min of NH 3 flow time, which indicates that the surface reaction between sapphire and NH 3 and/or hydrogen generated from NH 3 changes depending on the time of NH 3 flow. The dependence of the surface reactions and rate-limiting reactions between sapphire and NH 3 on the time of NH 3 flow is discussed.

In this paper, we characterized aluminum/sapphire interface structure by using high-resolution transmission electron microscopy. It was found that step structures of sapphire formed at the aluminum/sapphire interfaces during the liquid-phase bonding. It was discovered that the addition of silicon in aluminum significantly reduces the step growth at the interface. Silicon was found to segregate and precipitate at the interface. These results suggest that the strong preference of silicon at the interface may inhibit the step growth reactions during liquid-phase bonding. [doi:10.2320/matertrans.MC200810]

The thermal stabilities of Al- and N-polarity AlN layers grown on (0 0 0 1) sapphire substrates were investigated at temperatures ranging from 1100 to 1400 °C in various gas flows (He, H 2 and H 2 +NH 3 ). Decomposition of AlN occurred in flowing H 2 , while it did not occur in He or H 2 +NH 3 flow. The decomposition rate in H 2 increased with an increase in the temperature over 1200 °C, and the decomposition rate of the Al-polarity AlN layer was found to be lower than that of the N-polarity AlN layer at each temperature. The decomposition reaction of AlN and the relationship between the polarities of the AlN layers and their different decomposition rates are discussed.

The thermal stability of (0001) sapphire was investigated at atmospheric pressure using the in situ gravimetric monitoring (GM) method. The weight change of a sapphire substrate was monitored at various hydrogen partial pressures in carrier gas (P) at temperatures over 1200 °C. Although the sapphire substrate was stable up to 1450 °C in an inert carrier gas (P = 0.0 atm), sapphire decomposition started to occur at 1200 °C in H2 carrier gas (P = 1.0 atm). Moreover the activation energy and order of reaction for sapphire surface decomposition changed at approximately 1300 °C. These results indicate that the rate-limiting reaction for sapphire decomposition shifts near 1300 °C. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We have succeeded in growing single crystals of SmPt2Si2 and have performed electrical resistivity, magnetization and specific heat measurements. The magnetic susceptibility shows that SmPt2Si2 is an Ising magnet with the crystalline-electric-field ground state of Jz=+-3/2. We have found the existence of two magnetically ordered states, i.e., an antiferromagnetically (AFM) ordered phase (I) setting in at TN=5.1 K and a field-induced magnetization plateau phase (II). In the phase I, unlike the usual AFM states, a pronounced Curie-Weiss contribution remains in magnetic susceptibility, indicating the existence of "partially disordered" Sm ions. Largely enhanced Sommerfeld-coefficient (350 mJ/K2mol) in the phase I can be attributed to formation of Kondo sublattice with heavy quasiparticles in the partially disordered Sm ions. These findings may reflect substantial magnetic frustrations inherent in SmPt2Si2., Comment: 13 pages, 7 figures, 1 table, to appear in J. Phys. Soc. Jpn. Vol.83, (2014)

The interface between chemical vapor deposition (CVD) coated layers and cemented carbide substrate of coated cemented carbide inserts was analyzed by analytical electron microscopy (AEM). This analysis was carried out from the viewpoint of the adhesion of the coated layer. From the results of elemental analysis, it became clear that the amounts of W and Co diffused from the substrate into the coated layer were different among three coating conditions. A columnar TiCN grain produced in relatively low temperature scarcely contained these elements, and they were detected only at the grain boundary. On the other hand, these elements diffused inside the grains when the shape of the grain was granular as TiN. Strong adhesion of coated layer was obtained when a proper amount of these elements was diffused. Coated inserts containing an interfacial layer with suitable diffused materials and main columnar TiCN layer showed good cutting performance.