Maximum Void Size Research Articles

Effects of High Temperature Process Steps on Void Size Distributions in Passivated, Narrow Aluminum Lines

ABSTRACTNarrow Al lines were passivated at 300°C and subsequently annealed at 400°C for an hour. The passivation layer was then removed and the lines analyzed for thermal stress induced voids. Effects of the multiple high temperature process steps necessary in chip manufacturing were simulated by repeated anneals. Renewed void nucleation occurred during cool-down from each anneal, leading to a systematic increase in void density. In contrast, the maximum void size did not increase with number of anneals while it did increase with aging time for a single anneal.

Design of soil layer-geosynthetic systems overlying voids

This paper presents equations, tables, and charts to design soil layer-geosynthetic systems to span voids such as tension cracks, sinkholes, dissolution cavities, and depressions in foundation soils due to differential settlements or localized subsidence. These equations, tables, and charts were developed by combining tensioned membrane theory (for the geosynthetic) with arching theory (for the soil layer), thereby providing a more complete design approach than one that considers tensioned membrane theory only. Design examples are presented to illustrate the solution of typical problems such as: selection of the required geosynthetic properties, determination of the maximum void size that can be bridged by a given system, and evaluation of the load-bearing capacity of a given system.

Effects of maximum void size and aggregate characteristics on the strength of mortar

The effects of the maximum void size and aggregate shape and roughness on the flexural strength of high strength mortar were investigated. Substantial reductions in the maximum void size and air content of quartz aggregate mortars resulted in flexural strength increases. These increases in flexural strength were somewhat lower than predicted by Griffith's theory, thus suggesting that the maximum void size did not act as the critical flaw controlling the flexural strength. Factors relating to the cement-aggregate bond, including aggregate shape and roughness, appeared to affect the flexural strength more than the maximum void size.

Void swelling in the molybdenum alloy TZM irradiated to high fluence

Microstructural development and density change measurements are reported for TZM, a commercial molybdenum base alloy, following fast neutron irradiation in EBR-II to high fluence over the temperature range 400 to 650°C. Uniformly distributed voids arrayed in a lattice and constituting 3% swelling were observed following irradiation at 650°C to 1.47 × 10 23 n/cm 2 ( E > 0.1 MeV) (53 dpa). Nonuniformly distributed rafts of voids in lattice arrays were observed following irradiation at 540°C to 1.36 × 10 23 n/cm 2. Void swelling was not resolved following irradiation at 425°C to 1.22 × 10 23 n/cm 2. Void swelling measurements corroborated density change results which showed peak void swelling behavior saturating at 590°C. Two mechanisms for the behavior observed are considered; the first is based on an apparent maximum void size of 10 nm which leads to void rafting and eventually to void swelling saturation. Saturation is predicted only after 10 24 n/cm 2 (360 dpa) with 20% swelling possible. The second mechanism considers the effect of a developing void lattice on dislocation dynamics.

Neutron irradiation-induced voids in β-silicon carbide

Pyrolytic β-silicon carbide was irradiated at temperatures between 625°C and 1500°C to neutron fluences up to 12 × 10 21 n/cm 2 ( E > 0.18 MeV). Density changes were measured and the samples were examined by transmission electron microscopy. Irradiation below 1000°C created small Frank dislocation loops on {111} planes. Irradiation at 1250°C and 1500°C produced tetrahedral voids which caused continuing expansion of the samples. Void sizes increased with increasing fluence and with increasing irradiation temperature, while void concentrations decreased with increasing temperature. One-hour post-irradiation anneals at 1700°C to 2100°C reduced the void concentration and total void volume while increasing the maximum void size.