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[en] Studies of heavy-ion collisions at E/A ∼ 10 MeV/u to 20 MeV/u with the production of nucleons and other particles at forward angles with velocities several times that of the projectile have been observed by many groups (TAM, ORNL, MSU, HMI). This is usually attributed to projectile fragmentation with Fermi motion of the light particle which is often described by a source temperature T/sub s/, accounting for the additional velocity component. However, experiments reported by Borcea et al. and those done at the Hahn-Meitner Institute (VIKSI) have suggested that high-energy alpha particles observed near theta = O⁰ in ²⁰Ne-induced collisions, E/A ≤ 20 MeV/u, may arise from mechanisms such as cluster transfer reactions. Here we report observation of a similar phenomenon with a variety of projectiles (Z ≥ 8), E/A = 9 to 40 MeV/u

[en] Mechanical tests show that fibrous monolithic ceramics can exhibit graceful failure in bending due to marked crack deflection at silicon nitride/boron nitride interfaces. Model sandwich specimens were manufactured from polycrystalline silicon nitride with interphases consisting of mixtures of silicon nitride and boron nitride. The interfacial fracture resistances of the specimens were measured, and the results were correlated to the failure behavior of fibrous monolithic ceramics. It was found that the three modes of failure observed in fibrous monoliths can be correlated with the interfacial fracture resistance. In addition, anisotropy in the properties of the interphases were found to have a profound influence on crack deflection

[en] A resonant time-of-flight measurement system has been put into operation at the ATLAS facility for the determination of the energy of heavy ion beams. The system provides continuous, nondestructive monitoring of the beam energy. The system provides relative energy determination with a precision of ΔE/E ≅ 10^-4. Absolute energy is determined to an accuracy of 10^-3. A variety of beam tests have been performed to study the properties of the system. (orig.)

[en] Evaporation residues have been studied for reactions induced by 291 MeV ₂₀Ne ions on ₁₂C, ₂₇Al, ₄₀Ca targets. The analysis of many velocity spectra of individually resolved residue masses shows clear evidence for fusion-like residues with incomplete momentum transfer

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[en] Fibrous monolithic ceramics are an example of a laminate in which a controlled, three-dimensional structure has been introduced on a submillimeter scale. This unique structure allows this all-ceramic material to fail in a nonbrittle manner. Materials have been fabricated and tested with a variety of architectures. The influence on mechanical properties at room temperature and at high temperature of the structure of the constituent phases and the architecture in which they are arranged are discussed. The elastic properties of these materials can be effectively predicted using existing models. These models also can be extended to predict the strength of fibrous monoliths with an arbitrary orientation and architecture. However, the mechanisms that govern the energy absorption capacity of fibrous monoliths are unique, and experimental results do not follow existing models. Energy dissipation occurs through two dominant mechanisms--delamination of the weak interphases and then frictional sliding after cracking occurs. The properties of the constituent phases that maximize energy absorption are discussed. In this article, the authors examine the structure of Si₃N₄-BN fibrous monoliths from the submillimeter scale of the crack-deflecting cell-cell boundary features to the nanometer scale of the BN cell boundaries