Tungsten colloidal

Tungsten trisulfide [12125-19-8] chocolate-brown powder, slightly soluble in cold water, but readily forming a colloidal solution in hot... 

The properties of a tungsten oxide monolayer on 0.18 pm silica particles were studied by Leland and Bard The material was prepared by a controlled WCI hydrolysis technique. These particles differ from the colloidal Q-particles that they are small in only one dimension thus these layers are related to the semiconductor... 

Greater durability of the colloidal Pd/C catalysts was also observed in this case. The catalytic activity was found to have declined much less than a conventionally manufactured Pd/C catalyst after recycling both catalysts 25 times under similar conditions. Obviously, the lipophilic (Oct)4NCl surfactant layer prevents the colloid particles from coagulating and being poisoned in the alkaline aqueous reaction medium. Shape-selective hydrocarbon oxidation catalysts have been described, where active Pt colloid particles are present exclusively in the pores of ultramicroscopic tungsten heteropoly compounds [162], Phosphine-free Suzuki and Heck reactions involving iodo-, bromo-or activated chloroatoms were performed catalytically with ammonium salt- or poly(vinylpyrroli-done)-stabilized palladium or palladium nickel colloids (Equation 3.9) [162, 163],... 

Tungsten trisulfide [12125-19-8], WS3, is a chocolate-brown powder, slighdy soluble in cold water, but readily forming a colloidal solution in hot water. It is prepared by treating an alkah-metal thiotungstate with HC1 (52). Tungsten trisulfide is soluble in alkali carbonates and hydroxides. 

Electrophoretic deposition (EPD) is a colloidal process in which the charged colloidal particles are driven by a dc electric field to deposit on a substrate, forming a condensed film. This process is a combination of electrophoresis and deposition (Sarkar and Nicholson 1996). It has a long history and the first application was in 1927 for Th02 and tungsten deposition on a platinum cathode. Recently, photocatalyst semiconductor nanoparticles/microparticles have also been assembled by this... 

Stein DJ, Hetherington DL, Cecchi JL. Investigation of the kinetics of tungsten chemical mechanical polishing in potassium iodate based slurries (role of colloid species and surface chemistry). J Electrochem Soc 1999 146(5) 1934-1938. 

The colloidal solution may also be prepared by dissoh-ing tungsten tetrachloride in alcohol and ether (equal volumes) and then diluting with alcohol and water. The solution obtained acts as a positive colloid and coagulates immediately when small quantities of neutral salts, hydroxides, or strong acids are added. On passing an electric current through the solution, a deep blue precipitate separates at the cathode. ... 

Colloidal Tungsten Trisulphide.—It W as obser% ed by Berzelius that when the freshly precipitated trisulphide is washed with water, it dissolves to a slight extent, forming a yellow solution. If the precipitate is boiled with pure water it dissolves in considerable quantity, yielding a brownish-yellow solution. Winssinger obtained a dark brown solution of tungsten trisulphide by adding to a solution of sodium thiosulphate a little more dilute hydrochloric acid than was... 

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