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Abstract: With more than 15,000 silicon strip modules and an active silicon area of 200m2, the Compact Muon Solenoid silicon strip tracker will be the largest silicon tracker ever built. While module mass production has started in 2004, the detector construction has recently entered its crucial phase with modules being assembled onto larger substructures, which in turn are being integrated into the tracker barrel and end-cap structures. In this presentation the detector design will be introduced. The challenges and experiences of the silicon module mass production, with focus on the key components such as sensors and hybrids, will be presented. The status of the integration of modules onto the detector substructures, as well as the construction and integration of the large barrel and end-cap structures will be described. Finally, an overview will be given on the excellent performance of subsystems of the tracker as demonstrated by system tests and test beam experiments. [Copyright &y& Elsevier]

Biomorphic SiC ceramics were fabricated from four different wood precursors and their Knoop hardness and sliding wear resistance when sliding against a Si 3 N 4 ball in air were studied. Tribological experiments were performed using a pin on disk apparatus, under normal loads of 2 and 5 N, at a sliding speed of 100 mm/s. The effects of specimen porosity and microstructure on measured wear were evaluated. A commercial sintered silicon carbide ceramic was also tested for comparison. Small differences in friction coefficient comparable to monolithic SiC ceramics were obtained. Several concurrent wear mechanisms are taking place: microfracture, plastic deformation in the Si phase and oxidation of the Si and/or SiC phase. The presence of an oxide tribolayer was assessed using fluorescence microscopy. Wear rates were found to scale with SiC content and depend on residual porosity in the composite. [ABSTRACT FROM AUTHOR]

The heat capacity of biomorphic silicon carbide, a high-porosity material with specific cellular pores, is measured in the temperature range 3.5–60 K. Biomorphic silicon carbide is prepared by the chemical removal of excess silicon from the SiC/Si biomorphic composite, a product of eucalyptus wood. It is shown that the major contribution to the heat capacity of biomorphic SiC comes from surface vibrational modes. [ABSTRACT FROM AUTHOR]

The thermal conductivity of bio-SiC, a heavily defected material with specific cellular pores (channels), was studied in the temperature range 5–300 K. The bio-SiC sample was prepared from the SiC/Si biomorphic composite through the chemical removal of silicon. The thermal conductivity of silicon embedded in cellular pores of the SiC/Si biomorphic composite was determined. [ABSTRACT FROM AUTHOR]

The electrical resistivity ρ of bio-SiC, a highly porous cellular material prepared from a biomorphic composite SiC/Si based on white eucalyptus wood through the chemical removal of silicon, was measured in the temperature range 5–100 K. The electrical resistivity of bio-SiC was found to be anisotropic along and across the cellular pores. The activation energy of charge transfer in bio-SiC was estimated. The measured values of ρ for the SiC/Si biomorphic composite and bio-SiC were used to determine the electrical resistivity ρ and the carrier concentration in silicon, which is one of the constituents of the composite. [ABSTRACT FROM AUTHOR]

The thermal conductivity κ and electrical resistivity ρ of a cellular ecoceramic, namely, the SiC/Si biomorphic composite, are measured in the temperature range 5–300 K. The SiC/Si biomorphic composite is fabricated using a cellular biocarbon template prepared from white eucalyptus wood by pyrolysis in an argon atmosphere with subsequent infiltration of molten silicon into empty through cellular channels of the template. The temperature dependences κ( T) and ρ( T) of the 3C-SiC/Si biomorphic composite at a silicon content of ∼30 vol % are measured for samples cut out parallel and perpendicular to the direction of tree growth. Data on the anisotropy of the thermal conductivity κ are presented. The behavior of the dependences κ( T) and ρ( T) of the SiC/Si biomorphic composite at different silicon contents is discussed in terms of the results obtained and data available in the literature. [ABSTRACT FROM AUTHOR]

The heat capacity C p of a biocarbon template based on white eucalyptus wood is measured at a constant pressure in the temperature range T = 3.5–300 K. The phonon mean free path l for a white-eucalyptus biocarbon template is calculated from the measured dependence C p ( T) and data available in the literature on the phonon thermal conductivity and velocity of sound. It is established that, in the range 100–300 K, the phonon mean free path l is nearly constant and equal to ∼13 Å. This value is close to the smallest size of graphite-like crystallites (∼12 Å), which was derived earlier from x-ray diffraction data for a quasi-amorphous biocarbon template. [ABSTRACT FROM AUTHOR]

This paper reports on the results of a comparative investigation into the elastic and microplastic properties of biomorphic SiC/Si composites and biomorphic SiC prepared by pyrolysis of oak and eucalyptus with subsequent infiltration of molten silicon into a carbon matrix and additional chemical treatment to remove excess silicon. The acoustic studies were performed by the composite oscillator technique using resonant longitudinal vibrations at frequencies of about 100 kHz. It is shown that, in biomorphic SiC (as in biomorphic SiC/Si) at small-amplitude strains ε, adsorption and desorption of the environmental (air) molecules determine to a considerable extent the Young’s modulus E and the internal friction (decrement of acoustic vibrations δ) and that the changes in E and δ at these amplitudes are irreversible. The stress-microplastic strain curves are constructed from the acoustic data for the materials under study at temperatures of 100 and 290 K. [ABSTRACT FROM AUTHOR]

The electrical resistivity ρ and the thermopower coefficient α of a SiC/Si biomorphic composite fabricated from a porous carbon matrix [prepared through pyrolysis of wood (white eucalyptus)] by infiltrating molten Si into the empty channels of the matrix were measured in the temperature ranges 100–950 and 100–750 K, respectively. Silicon reacts chemically with the carbon of the matrix to produce 3 C-SiC, which, in combination with the excess Si unreacted with carbon, forms the SiC/Si biomorphic composite. The SiC/Si samples studied had a concentration of “excess” Si of ∼30 vol % and a porosity of ∼13–15 vol %. Measurements of ρ were carried out on samples cut either along (ρ∥) or across (ρ⊥) the tree growth direction, and α was measured on a sample cut along the tree growth direction. [ABSTRACT FROM AUTHOR]

The effect of the vibration strain amplitude on the Young modulus and ultrasonic absorption (internal friction) in biomorphic SiC ceramics is investigated in the temperature range 116–296 K. The biomorphic SiC ceramics is prepared through pyrolysis of eucalyptus with subsequent infiltration of silicon. It is demonstrated that the vibration loading of samples in air and under vacuum is accompanied by a number of unexpected effects. The behavior of the studied ceramics is governed by at least two mechanisms, which, to a large extent, are responsible for the elastic and inelastic properties of the material. One mechanism is associated with the adsorption–desorption of environmental molecules (hypothetically, owing to the presence of pores and residual carbon), and the other mechanism involves microplastic deformation due to the motion of dislocations or other (similar) structural units. © 2004 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]