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Ice accumulation is a human safety risk and a cause of important material damages in maritime, ground and air transportation, on ground and maritime energy exploitation and in telecommunication and electric networks. Many ice protection systems have been developed to prevent ice formation, but they are expensive to use due to their energy consumption. Passive systems, such as icephobic coatings applied on exposed surfaces, appear to be an interesting solution to prevent ice accumulation by reducing its adherence; but coating icephobicity is difficult to quantify. To measure icephobicity, the Anti-icing Material International Laboratory (AMIL) developed the Centrifuge Adhesion Test (CAT) in 2006. The test involves icing the extremity of small beams under freezing drizzle in a climatic chamber. Following icing, the beams are balanced in a centrifuge and rotated at an accelerating speed until the ice detaches and the corresponding rotation speed is measured. The adhesion shear stress is calculated from the centrifugal force evaluated at the detachment rotation speed, and the ice contact surface. The results are then reported as an Adhesion Reduction Factor (ARF) which is the ratio of the adhesion shear stress of the beams with a candidate coating with respect to uncoated beams. The higher the ARF, the more icephobic the coating; values below one indicate an increase in adhesion. For coatings with high icephobicity, the CAT apparatus sensitivity proved to be insufficient to evaluate the ARF. To remedy this, in 2009, AMIL modified the CAT apparatus to increase its sensitivity. The new CAT, called CAT-NG, can measure ARF in a range of 0.6 to 1 000 inexpensively and timely. To ensure reliable ARF factor with confidence level of 95%, the beam area exposed to icing is polished after 5 tests, or every month, to reduce the ice erosion effect on aluminum surface. Also, the ice specimen mass should be 5.5 g ± 5% with a length of 34 mm ± 5%. For glaze ice tested at -10ºC on 6061-T6 aluminum with AMIL Standard Surface roughness of 0.7 µm, the detachment speed is 7 800 RPM ± 7% when the beam is rotated at speeds increasing linearly at rate of 300 RPM/s corresponding to a shear stress of 0.51 MPa ± 7%. NomenclatureA = Area iced m² ARF = Adhesion Reduction Factor E ice = Ice Young Modulus Pa F = Centrifugal force N l beam = Beam length m l ice = Ice length in contact with substrate m m ice = Ice mass kg r = Beam radius m w beam = Beam width m Ω = Angular speed rad/s ε = Strain τ = Shear stress Pa τ bare = Average shear stress measured on 3 simultaneously iced bare beams Pa τ coated = Average shear stress measured on 3 simultaneously iced icephobic coating Pa

Abstract:The geology and geochemistry of the Canton Saint-Onge wollastonite deposit indicate that it is a skarn formed by silica metasomatism of dolomite-rich rocks. Oxygen isotopic compositions of the skarn rocks and the nearby plutons show that the fluids responsible for the metasomatism were not meteoric, but were probably associated with the Du Bras granitic pluton. However, the granite is not in contact with the wollastonite rocks at the present level of exposure, hence the fluids must have been released at greater depths. Wollastonite-rich parts of the skarn rocks are isotopically lighter than diopside-rich rocks, suggesting that wollastonite formed in regions of higher fluid flux.Résumé : La géologie et la géochimie du dépôt de wollastonite du canton Saint-Onge indiquent qu'il s'agit d'un skarn formé par le métasomatisme de la silice de roches riches en dolomie. Les compositions isotopiques de l'oxygène des roches skarnifiées et des plutons avoisinants montrent que les fluides responsables du métasomatisme n'étaient pas d'origine météorique mais qu'ils étaient plutôt associés au pluton granitique de Du Bras. Toutefois, le granite n'est pas en contact avec les roches à wollastonite au présent niveau d'affleurement; les fluides auraient donc été relâchés à de plus grandes profondeurs. Les parties riches en wollastonite des roches du skarn sont isotopiquement plus légères que les roches à diopside, indiquant que la wollastonite s'est formée dans des régions à très grand écoulement.[Traduit par la Rédaction] 1140Higgins et al.

Wollastonite is a naturally occurring anhydrous, fibrous calc-silicate mineral. As an industrial mineral it is particularly valuable for use in ceramic applications and its acicularity makes it an attractive and safe replacement for asbestos.Wollastonite is formed by the reaction of calcite with silica which gives off CO 2 ; heat is needed to drive the reaction to completion. The heat can be provided by regional or contact metamorphism, the silica can be provided by quartz mixed with a limestone protolith or from a magmatic fluid of an intruding pluton.The Canton Saint-Onge wollastonite deposit is situated near the centre of the LacSaint-Jean Anorthosite Complex. A major NE-SW trending lineament, the Lacs-SaintJean-Pipmuacan lineament, cuts the anorthosite. It stretches for over 200 km and is marked by solid state deformation and plutons of various composition and age. A lens of metasediments is preserved adjacent to this lineament. The metasediments include: hornfelsic gneiss, marbles, quartzite and the calc-silicate rocks which host the wollastonite.The wollastonite occurs in a band of calc-silicate rocks trending N040° that are in contact with marble to the south-east which is in turn in contact with the Du Bras Pluton bordering a gabbroic faciès of the anorthosite. The contact to the south-west is with the Astra syenite, a late undeformed pluton. The north-eastern contact is hidden by a valley without outcrop but on its other side there are wollastonite-free calc-silicate rocks followed by anorthosite. The wollastonite is interlayered with diopside on the millimetre to centimetre scale and strongly folded. Electron microprobe analyses of the layering shows that it is chemically abrupt, with no gradation in chemical composition between layers.Whole-rock oxygen isotope ratios were measured to determine the origin of the fluids involved in the formation of the deposit. Both granitoids and the Lac-Saint-Jean Anorthosite have 6 If the marbles are the protolith to the calc-silicate rocks some fluid must have been involved in order to lower the isotopic ratios of the latter. The data indicates that pristine meteoric water was not involved in the formation of the calc-silicate rocks, which would have resulted in lower, near zero isotopic values for the calc-silicate rocks. The fluid may 11 have been derived from one or more of the intrusions, or it may have been meteoric water that re-equilibrated with one of the intrusions. The generally lower values of the wollastonite-bearing calc-silicate rocks suggests that more fluid was involved in their formation as compared to the wollastonite-free rocks, if both came from a protolith with similar 518 O values.The stable isotope work suggests that the fluid concerned is in isotopic equilibrium with the plutons and possibly emanated from one of them. The fluid must have been rich in H 2 O to lower the partial pressure of the CO 2 and in silica in order to complete the reaction from calcite to wollastonite. The whole rock geochemistry suggests the fluid also contained...

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