Silicon Micro-Strip Detectors

Silicon micro-strip detectors are fundamental tools for the high energy physics. Each detector is formed by a large set of parallel narrow strips of special surface treatments (diode junctions) on a slab of very high quality silicon crystals. Their development and use required a large amount of work and research. A very synthetic view is given of these important components and of their applications. Some details are devoted to the basic subject of the track reconstruction in silicon strip trackers. Recent demonstrations substantially modified the usual understanding of this argument.

Modelling of the pedestal growth of silicon crystals

The pedestal method is an alternative to the well-known floating zone method, both of which are performed with high-frequency electromagnetic heating. Unlike the floating zone method, in the pedestal method a single crystal is pulled upwards from the melt. It allows one to lower feed rod quality requirements and simplify the process control due to the absence of open melting front. As the pedestal method has not been widely used in industry for silicon crystals, its development requires extensive numerical modelling. The present work describes application of the previously created mathematical model for crystals with diameters higher than it is currently possible in the experimental setup, as well as for the cone growth phase. Supplementary free surface heating, that prevents melt centre freezing during the seeding phase, has been added at the beginning of cone phase. After multiple sets of simulations, an optimal scheme of heating control for cone growth was proposed.

Formation of Coarse Silicon Near the Surface of Al–7Si–Mg Semi-solid Castings

Primary type polyhedral silicon crystals were observed in the vicinity of oxides located at or near the surface of strontium modified semi-solid Al–7Si–Mg castings. The coarse silicon polyhedrons were observed mainly on the outer side of oxides surrounding the macrosegregation regions. The silicon crystals most likely nucleated on AlP-particles located near the oxides. These AlP particles may nucleate on the wetted surface of oxides, or form at different locations in the interdendritic regions.

INVESTIGATION OF THE INFLUENCE OF THE MODIFIERS P, SR, TI AND COMBINATIONS OF THEM ON THE STRUCTURE AND MECHANICAL PROPERTIES OF ALSI25 ALLOY

The most commonly used elements to modify primary silicon crystals in the structure of hypereutectic aluminum-silicon alloys are phosphorus and sulfur. Phosphorus has been shown to have the highest coefficient of modification with respect to the primary silicon and is therefore a preferred modifier. There are also data on the positive effect of the modifiers Sb, Sr, Ti, and B on the silicon crystals in the structure of this type of alloys. The influence of the modifiers phosphorus, strontium, titanium and combinations of them on the size and shape of both the primary silicon crystals and the silicon crystals in the composition of the eutectic of the AlSi25 alloy has been studied in this work. Mechanical tests have been performed to determine both the strength and the plastic parameters of the investigated alloy (in unmodified and modified state). The classic for this type of alloys modifier - phosphorus - has been introduced into the melt by the ligature CuP10. Strontium has been introduced by the ligature AlSr10, and titanium - by the ligature AlTi5B1, the two ligatures in the form of rods. The investigated alloy has also been modified by combinations of the used modifiers: phosphorus and strontium, phosphorus and titanium.The influence of the used modifiers on the structure and mechanical properties of AlSi25 alloy has been discussed.

INVESTIGATION OF THE INFLUENCE OF DIFFERENT MODIFIERS ON THE EUTECTIC SI IN THE COMPOSITION OF ALSI18 ALLOY

The structure of hypereutectic aluminum-silicon alloys consists of primary silicon crystals arranged in a eutectic matrix. In the present work the influence of different types of modifiers on the size and shape of the silicon crystals in the composition of the eutectic of the AlSi18 alloy has been studied. The classic for this type of alloys modifier (phosphorus), as well as the nanomodifiers SiC and nanodiamonds (ND) have been used. The results of the microstructural analysis show that the three modifiers used affect differently the shape and size of the eutectic silicon of the investigated alloy.