Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Report on WP1/M1: Status report on silicate bonding of silicon S.Reid1, I Martin1, W. Cunningham1, J. Hough1, S. Rowan1, K. Tokmakov1, M. Lorenzini2, G. Cagnoli1, 2, E. Campagna2, E. Cesarini2, G. Losurdo2, F. Martelli2 1 2 The University of Glasgow, Glasgow, UK INFN Sezione Firenze, Sesto Fiorentino, Italy Coordinator: V. Loriette (ESPCI), M. Punturo (INFN Perugia) Sample preparation Pairs of silicon disks have been successfully bonded in Glasgow using different volumes of sodium silicate bonding solution (1 part commercial sodium silicate solution to 6 parts water, using volumes in the range 0.4l/cm2 to 0.1l/cm2). A complete set of these samples has been sent to Florence for thermal conductivity measurements, having been given 2-3 months for curing. In addition to thermal conductivity tests, mechanical strength measurements are planned both at room and low temperature (see the M5 report). Initial mechanical testing at room temperature shows that a 5cm2 silicon-silicon bond is capable of supporting a 40kg load over a period of two weeks with no observed distortion or damage (a shear force of ~100 N/cm2, 1×106 Pascals). cleaned silicon samples placed in furnace at 1000°C after ~1hr, 50 to 100nm oxide growth Fig1: Preparation of silicon samples to be bonded: the required surface flatness ≤ /10, the surfaces were thoroughly cleaned from contaminants prior to bonding, and oxidised prior to silicate bonding Considerable studies have been carried out of the dependence of bond settling time on the temperature and pH of the bonding solutions used for fused silica samples [1]. Samples of silicon have been purchased for comparison. Cryogenic system in Firenze for thermal conductivity studies A liquid Helium cryogenic facility has been set up in Firenze for carrying out both thermal conductivity and thermal expansion measurements. Initial thermal conductivity measurements were carried out on a pure silicon rod sample with purity 10-6 and resistivity 42 cm and are shown in Figure 2. The temperature dependence and magnitude of the measured conductivity are also shown to agree closely with literature values of comparable silicon samples [2]. (c) (a) (d) (b) Fig2: thermal conductivity as a function for (a) measured Si rod and (b), (c) and (d) literature data for Si samples of comparable dimensions and with resistivities of 15-25 cm, 260 cm and 5000 cm respectively [2] Cold plate Heat sink Heater Temperature sensors Fig2: Bonded Si samples, 1/2" radius and 6mm thick Fig3: Cryogenic facility in Florence for thermal conductivity studies of silicon substrates and silicate bonds Repeated measurements have been taken at room temperature and show a clear, albeit relatively small, change in the thermal conductivity of the bonded sample compared to that of the pure silicon. At room temperature, the thermal conductivity of the pure silicon is 160 W/mK and across the silicate bonded silicon disks 150 W/mK. heater on heater off steady state Fig3: rise and fall of temperature difference across the bonded and unbonded samples at heat is applied and removed. The relatively small addition of thermal resistance as a result of silicate bonding again suggests that this bonding technique fulfils the requirements for the construction of 3rd generation interferometers built and cooled through their monolithic silicon suspensions. Delays and possible alteration of the planning No delays are expected. [1] Influence of Temperature and Hydroxide Concentration on the Setting Time of Hydroxy-Catalysis Bonds, S. Reid, G. Cagnoli, E. Elliffe, J. Faller, J. Hough, I.Martin, S. Rowan, Phys. Lett. A, 363, 341-345, 2006. [2] Thermophysical Properties of Materials, Y.S. Touloukian, E.H. Buyco, Plenum, New York (1970).