Precipitation in Solution-Treated Al-4wt%Cu under Cyclic Strain

Solution-treated Al-4wt%Cu was strain-cycled at ambient temperature and above and the precipitation behavior investigated by TEM. In the temperature range 100°C to 200°C precipitation of Θ´´ appears to have been suppressed and precipitation of Θ´ promoted via cyclic strain. Anomalously rapid growth of precipitates appears to have been facilitated by a vacancy super-saturation generated by dislocation motion, with a diminishing effect observed at higher temperatures due to the faster recovery of non-equilibrium vacancy concentrations. Θ´ precipitates generated under cyclic strain are considerably smaller and more finely dispersed than those typically produced via quench-aging due to their heterogeneous nucleation on dislocations, and possess a low aspect ratio and rounded edges of the broad faces due to the introduction of ledges into the growing precipitates by dislocation cutting. Frequency effects indicate that dislocation motion, rather than the extremely small precipitate size, is responsible for the observed reduction in aspect ratio. Accelerated formation of grain boundary precipitates appears partially responsible for rapid inter-granular fatigue failure following cycling at elevated temperatures, producing fatigue striations and ductile dimples coexistent on the fracture surface.

Physical Compatibility of Ibuprofen Lysine Injection with Selected Drugs During Simulated Y-site Injection

PURPOSE To study the physical compatibility of ibuprofen lysine injection (NeoProfen, Ovation Pharmaceuticals Inc., Deerfield, IL) with medications commonly used in the premature neonatal population during simulated Y-site administration. MATERIALS AND METHODS Commonly used intravenous medications in preterm infants were evaluated for physical compatibility with ibuprofen lysine injection. A 20-mL sample of ibuprofen lysine drug product solution was mixed with a 20-mL sample of each of the 34 medications at concentrations used clinically. The mixtures were stored at room temperature and each sample was evaluated for turbidity and physical appearance at time 0 (immediately after preparation) and at 4 hours after preparation. RESULTS The following drugs were deemed compatible with ibuprofen lysine: ceftazidime, epinephrine, furosemide, heparin lock flush, diluted insulin, morphine sulfate, phenobarbital, potassium chloride, and sodium bicarbonate. Diluted dopamine was initially compatible at time 0 but showed a small precipitate at the 4-hour time point. CONCLUSION Of the 37 drug solutions tested, 14 preparations (10 medications; several with more than one diluent) showed physical compatibility with ibuprofen lysine, 1 was compatible at time 0 and incompatible at 4 hours, and 1 could not be evaluated. The remaining preparations were considered to be incompatible.

A HREM study of the interfaces between TiO2 precipitates and the Al2O3 matrix in star sapphire

The asterism, or star effect, present in star sapphire (Ti-doped A12O3) single crystals is known to arise from the needle-like rutile(r) (TiO2) precipitates in the sapphire(s) matrix. The specific orientation relationship between the precipitates and the matrix is {100}r//{0003}s and <011>r//<1010>s . In this work we report a HREM study of the rutile/sapphire interface.The cross-section perpendicular to the needle axis of a very small precipitate, which is coherent, or has just one misfit dislocation at its interface, is a rhombus; the precipitate/matrix interface (habit plane) is {111}r{1123}s. As the coherency break down and misfit dislocations are introduced into the interface, the shape of the cross-section becomes nearly square; the two orthogonal interfaces are {100}r//0003}s and {011}r//{1120}s. Larger precipitates show rectangular interfaces elongated along the {100}r//{0003}s interface (Fig.l). A regular array of misfit dislocations with Burger vector b = 1/3<0001>S are present at the {011}r//{1120}s interface, the mean distance between every two adjacent 1/3<0001>S misfit dislocations being 8.7 nm which compensates exactly the 5.9% lattice mismatch estimated from the lattice constants of these two structures. Similarly, a regular array of misfit dislocations with Burgers vector b = 1/3<1010>S at the {100}r//{0003}s interface compensates the 4.5% lattice mismatch at that interface.

Electron microscopy characterization of monoclinic SiAs precipitates in heavily As+-implanted silicon

Silicon wafers have been implanted with As+ ions at an energy of 100 keV and a dose of 1 × 1017 cm−2 and subsequently annealed at 1050°for 15 min. This results in a peak As concentration of 7 × 1021 cm−3, which is far beyond the solid solubility value of arsenic in silicon at this annealing temperature. Rod-like precipitates, dislocations, and small precipitate-like defects have been observed by transmission electron microscopy. From the analysis of several diffraction patterns taken on a number of rod-like particles at different tilt angles, it has been unambiguously found that they have the structure of the monoclinic SiAs compound previously reported in literature. The stoichiometry of the precipitates has been confirmed by x-ray microanalysis. To our knowledge, this is the first time that this SiAs phase is detected in As+-implanted silicon.

An Auger Electron Spectroscopy (AES) Investigation into the Effect Annealing on the Phase Distribution of Ion Implanted Oxygen in Silicon

ABSTRACTBuried oxide layers, formed by high dose ion implantation, have been examined using Auger depth profiling. The phase distribution of oxygen in the wings of the implant profile and effects of high temperature annealing, have been investigated. Ion beam induced cascade mixing, which occurs during sputter etching, limits the minimum detectable size of SiO2 precipitates. However, it is possible to minimise this effect by reducing the ion beam energy. At very small precipitate sizes (<100Å) silicon atoms at the edge of the precipitate particles will make a major contribution to the Si KLL Auger spectrum. A previously reported theoretical model has been expanded to take account of this phenomenon.