Reticulated Porous Foam Ceramics with Different Surface Chemistries

The aim of this study was to discuss the influence of different filter surface chemistries on the properties of foam filters. For reliable results, it is essential to ensure comparable structural properties (cell size and strut thickness) for all different surface chemistries (Al₂O₃, MgAl₂O₄, 3Al₂O₃·2SiO₂, SiO₂, and TiO₂) possess the same structural properties (cell size and strut thickness). Filters made of 100% of the investigated materials and alumina skeletons coated with the investigated materials were prepared. The coated alumina samples were sintered in one and two steps. The processing route with two sintering steps resulted in improved mechanical properties and comparable shrinkage and strut thickness. The 100% bulk foams possessed different pore sizes due to the differences of the material shrinkage. In this study, a comparison of the experimental investigated properties of the ceramic foam filters and the theoretically calculated values for foam materials derived from the bulk material properties is established.     

Nanotwin formation and its physical properties and effect on reliability of copper interconnects

Ultra-fine grained copper with a large amount of nano-scale twin boundaries has high mechanical strength and maintains normal electrical conductivity. The combination of these properties may lead to promising applications in future Si microelectronic technology, especially as interconnect material for air-gap and free-standing copper technologies. Based on first principles calculations of total energy and in-situ stress measurements, high stress followed by stress relaxation during the Cu film deposition seems to have contributed to nanotwin formation. Nanoindentation studies have shown a larger hardness for copper with a higher nanotwin density. The effect of Cu nanotwin boundaries on grain growth was investigated by scanning electron microscopy (SEM), electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). The presence of a high density of nanotwin boundaries may improve the reliability of Cu interconnects.     

Filtration Efficiency of Functionalized Ceramic Foam Filters for Aluminum Melt Filtration

Metallurgical and Materials Transactions B - The influence of filter surface chemistry on the filtration efficiency of cast aluminum alloys was evaluated for four different filter coating...     

Microstructure in copper interconnects - Influence of plating additive concentration

Downscaling of copper interconnects is demanding more knowledge about the microstructure and grain growth mechanisms in sub 100 nm dimensions. Large grains are needed to reduce the resistivity and to increase the reliability of narrow lines. Plating additives are used for a void free filling of the interconnecting vias and lines. Fractions of these additives are incorporated into the copper as impurities during electrochemical deposition. In the present paper the role of additive concentration on grain growth is investigated. Interconnect lines from 72 nm to 1.9 μm line width were completely filled with copper using different additive concentrations in the electrolyte. The impurity level was measured by time of flight secondary ion mass spectrometry. The samples were stored at room-temperature to achieve self-annealing or tempered at low and high temperatures. Self-annealing slows down with increasing additive concentration whereas bamboo-like grains are present after annealing all samples at high temperatures. Grain growth was studied as well as the average grain size, resistivity, and {1 1 1} texture.     

Coarse-grained refractory composites based on Nb-Al2O3 and Ta-Al2O3 castables

Coarse-grained refractory composites, with grain sizes between 20 and 5000?µm, based on Nb-Al₂O₃ and Ta-Al₂O₃ castables were produced for the first time and characterised in terms of shrinkage after sintering, splitting tensile strength, compressive strength, porosity and the measurement of the elastic properties (E, G and $\nu$). After sintering at a temperature of 1600?°C, the shrinkage of the composites was 1.5% and 0.3%. Measured values of splitting tensile strength were between 5.5 and 15?MPa and the ones of compressive strength were between 23 and 89?MPa. Values of E and G were between 117 and 45?GPa and 48–17?GPa, respectively, for samples with 11–45?vol% refractory metal. Poisson's ratio was found to be very sensitive to the bonding between the fine matrix and coarse-grained particles of the composites. Its value increased from 0.25 for good bonding to $\nu =0.43$ in case of poor bonding between the coarse metal particles and the fine ceramic matrix. DTA/TG measurement under air atmosphere showed that the metal-ceramic composites start to oxidise at temperatures above 450?°C.