Effect of Material and Process Atmosphere in the Preparation of Al-Ti-B Grain Refiner by SHS

Al-Ti-B master alloys are widely used in the aluminum industry as grain refiners for the control of the microstructure of the aluminum alloys. The SHS (self-propagating high-temperature synthesis) is an ex situ method that uses exothermic reactions to sustain the chemical reaction in a combustion wave. The advantages of SHS are the low energy requirement, simplicity and product purity. However, the raw material used has to be very pure, with a very small size leading to the necessity of a reactor with a protective gas to produce the reaction. The purpose of this investigation is to fabricate SHS master alloys with commercial standard raw materials, with lower purity and higher grain size without a reactor or protective gas in order to (1) decrease the price and (2) improve the productivity of master alloy manufacturing. The possibility of using cheap borated salts instead of expensive pure boron has been studied. Different compositions of aluminum master alloy have been developed. Bigger TiB2 grain size has been obtained when using bigger commercial raw materials. Larger titanium powder can produce an aluminum master alloy with a maximum of 30% of aluminum without reactor. In comparison, SHS reaction is much more difficult when using finer titanium powder.Basque gov: IT-2008/00348, IG-2010/00102, Spanish gov: IAP-560300-2008-

Liver fibrosis is associated with cutaneous inflammation in the imiquimod-induced murine model of psoriasiform dermatitis

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Thermal conductivity improvment of copper-carbon fiber composite by addition of an insulator : calcium hydroxide

The effects of adding calcium hydroxide (Ca(OH)2) to a copper-CF (30 %) composite (Cu-CF(30 %)) were studied. After sintering at 700 °C, precipitates of calcium oxide (CaO) were included in the copper matrix. When less than 10 % of Ca(OH)2 was added, the thermal conductivity was similar to or higher than the reference composite Cu-CF(30 %). A thermal conductivity of 322 W m−1 K−1 was measured for the Cu-Ca(OH)2(3 %)-CF(30 %) composite. The effects of heat treatment (400, 600, and 1000 °C during 24 h) on the composite Cu-Ca(OH)2(3 %)-CF(30 %) were studied. At the lower annealing temperature, CaO inside the matrix migrated to the interface of the copper matrix and the CF. At 1000 °C, the formation of the interphase calcium carbide (CaC2) at the interface of the copper and CFs was highlighted by TEM observations. Carbide formation at the interface led to a decrease in both thermal conductivity (around 270 W m−1 K−1) and the coefficient of thermal expansion (CTE (10.1 × 10−6 K−1))

Thermal expansion coefficient and thermal fatigue of discontinuous carbon fiber-reinforced copper and aluminum matrix composites without interfacial chemical bond

International audienceFully dense carbon fiber-reinforced copper and aluminum matrix (Cu-CF and Al-CF) composites were fabricated by hot press without the need for an interfacial chemical compound. With 30 vol% carbon fiber, the thermal expansion coefficients (TECs) of pure Cu and Al were decreased to 13.5 × 10−6 and 15.5 × 10−6/K, respectively. These improved TECs of Cu-CF and Al-CF composites were maintained after 16 thermal cycles; moreover, the TEC of the 30 vol% Cu-CF composite was stable after 2500 thermal cycles between −40 and 150 °C. The thermal strain caused by the TEC mismatch between the matrix and the carbon fiber enables mechanical enhancement at the matrix/carbon fiber interface and allows conservation of the improved TECs of Cu-CF and Al-CF composites after thermal cycles