Elastic properties of amorphous and crystalline B1−C and boron at low temperatures

Physical properties and microstructures of Fe3Al matrix laser amorphous–nanocrystals reinforced coating

“…Broad diffraction peaks appeared at 2y ¼35 $ 471 indicating that amorphous phases were produced in such coatings. The atomic (B, C and N) packing model distortion in short program range led the solid/liquid interfacial energy to increase, which promoted the productions of amorphous phases [6]. Moreover, due to the rapid solidification rate of the laser molten pool, Fe and Si based amorphous phases were produced in such coating.…”

Disorder in tetrahedrally bonded amorphous solids

“…To emphasize the variability of Q 1 0 in the tetrahedrall y bonded amorphous system in comparison with the universality of all other amorphous solids, we plot the internal-friction plateau value Q 1 0 versus the shear modulus Gˆ»v 2 in ®gure 5. The examples of various other amorphou s solids were taken from the paper by Medwick et al (1998) , where all references are given. The most striking result is that, for HWCVD-grown a-Si : H with 1 at.% H (®gure 1), its Q 1 0 is almost three orders of magnitude below the`glassy range'.…”

“…Introduction Since the discovery of anomalous lattice vibration in amorphous solids 30 years ago (Zeller and Pohl 1971), the model of a two-level tunnelling system (TLS) has been highly successful in providing a phenomenological description of the observed thermal and elastic properties of amorphous solids (Anderson et al 1972, JaÈ ckle 1972, Phillips 1972. In this model, atoms or groups of atoms are envisaged to tunnel between diOE erent equilibrium positions with little cost of energy, giving rise to a broad distribution of low-energy excitations in addition to propagating phonons.…”

“…In his original work, Phillips (1972) argued that tunnelling states could occur naturally in some amorphous solids with an open structure and are caused by atoms with a low coordination that can tunnel between potential minima. He further speculated that, if every atom is linked to more than two neighbours, the structure is overconstrained and therefore rigid, and double wells are unlikely.…”

“…This should be the case in amorphous silicon (a-Si) and amorphous germanium (a-Ge). According to the constraint-countin g model (Phillips 1979) and its subsequent modi®cation (Thorpe 1983), glasses consist of¯oppy and rigid regions. Rigidity percolates when the number of constraints per atom exceeds the number of degrees of freedom per atom.…”