Liquid phase preparation, amorphous solid

Metastable amorphous solids can in general be prepared from stable phases by bringing in excess free energy [5]. In the case of water, amorphous solids have been prepared from stable phases in all three aggregate states from the gas, the liquid, and the crystalline solid [131]. 

Inorganic non-oxide materials, such as III-V and II-VI group semiconductors, carbides, nitrides, borides, phosphides and silicides, are traditionally prepared by solid state reactions or gas-phase reaction at high temperatures. Some non-oxides have been prepared via liquid-phase precipitation or pyrolysis of organometallic precursors. However, amorphous phases are sometimes formed by these methods. Post-treatment at a high temperature is needed for crystallization. The products obtained by these processes are commonly beyond the manometer scale. Exploration of low temperature technique for preparing non-oxide nanomaterials with controlled shapes and sizes is very important in materials science. 

Chemical precipitation is a widely used method for synthesizing solid materials from solution. This method utilizes a liquid-phase reaction to prepare insoluble compounds that are crystalline or amorphous precipitates. The precipitate usually is composed of fine particles, and of course, ceria-based fine particles can be synthesized by this method. Usually ceria preparation is carried out by calcination of the hydroxide or oxalate gel precipitated using the reaction of aqueous solution of inorganic cerium salt (Ce(N03)3 CeCl, CeS04, and (NH4)2Ce(N03) ) with alkali solution (NaOH, NH4OH and (NH2)2-H20) or oxalic acid. - ... 

Quasicrystalline phases have received much attention since first reported by Shechtman et al. [3.92] in 1984 for Al-Mn. Within the last few years, various preparation techniques have been applied for the preparation of alloys in the quasicrystalline state. Liquid-phase quenching [3.92, 93] and relatively slow cooling from the melt [3.94], sputter or vapor deposition [3.95,96], ion-beam techniques [3.97-100], heat treatment of the amorphous phase [3.93,101, 102], and solid-state reaction during interdiffusion [3.103-106]. Recently it was demonstrated that the quasicrystalline phase can be produced by mechanical alloying [3.107-112],... 

The fact that zeolite seed crystals can improve the mechanical strength of the synthesized discs, was reported in synthesis of zeolite ZSM-5 with vapor phase method. Zeolite ZSM-5 disc was prepared with ethylenediamine (EDA) and ammonia solution (or distilled water) as liquid phase while the mixture of amorphous aluminosilicate gel, zeolite ZSM-5 seed crystals was the solid phase. The obtained ZSM-5 discs not only have high mechanical strength (up to 3.5 X lO Pa/m ) but also high relative crystallinity. It was also found that the mechanical strength would further increase by replacing the water with ammonia solution in liquid phase. The increase of mechanical strength of zeolite seed crystal may result from the fact that seeds serve as binders to cause close assembly of small zeolite ZSM-5 particles. 

Chemical precipitation is a popular method for synthesizing solid materials from solution in which a liquid-phase reaction is utilized to prepare insoluble compounds. The precipitates are composed of crystalline or amorphous fine particles. Usually, rare earth oxides are prepared by calcinations of the hydroxide or oxalate gel precipitated from a reaction of an aqueous or alcohol solution of inorganic salt (nitrate, chloride, sulfate, and ammonium nitrate, etc.) with an alkali solution (NaOH, NH4OH, and (NH2)2 H20) or an oxalic acid solution [15-21]. However, it is very difficult to obtain ultrafine particles because of growth and sintering of the particles during the calcinations. 

The earliest commercial methods used slurry polymerizations with liquid hydrocarbon diluents, like hexane or heptane. These diluents carried the propylene and the catalyst. Small amounts of hydrogen were fed into the reaction mixtures to control molecular weights. The catalyst system consisted of a deep purple or violet-colored TiCls reacted with diethyl aluminum chloride. The TiCb was often prepared by reduction of TiCU with an aluminum powder. These reactions were carried out in stirred autoclaves at temperatures below 90 °C and at pressures sufficient to maintain a liquid phase. The concentration of propylene in the reaction mixtures ranged between 10-20%. The products formed in discrete particles and were removed at 20-40% concentrations of solids. Unreacted monomer was withdrawn from the product mixtures and reused. The catalysts were deactivated and dissolved out of the products with alcohol containing some HCl, or removed by steam extraction. This was followed by extraction of the amorphous fractions with hot liquid hydrocarbons. 

Mo are single phase, supersaturated solid solutions having an fee structure very similar to that of pure Al. Broad reflection indicative of an amorphous phase appears in deposits containing more than 6.5 atom% Mo. As the Mo content of the deposits is increased, the amount of fee phase in the alloy decreases whereas that of the amorphous phase increases. When the Mo content is more than 10 atom%, the deposits are completely amorphous. As the Mo atom has a smaller lattice volume than Al, the lattice parameter for the deposits decreases with increasing Mo content. Potentiodynamic anodic polarization experiments in deaerated aqueous NaCl revealed that increasing the Mo content for the Al-Mo alloy increases the pitting potential. It appears that the Al-Mo deposits show better corrosion resistance than most other aluminum-transition metal alloys prepared from chloroaluminate ionic liquids. 

Olah et al. reported the triflic acid-catalyzed isobutene-iso-butylene alkylation, modified with trifluoroacetic acid (TFA) or water. They found that the best alkylation conditions were at an acid strength of about//q = —10.7, giving a calculated research octane number (RON) of 89.1 (TfOH/TFA) and91.3 (TfOH/HaO). Triflic acid-modified zeohtes can be used for the gas phase synthesis of methyl tert-butyl ether (MTBE), and the mechanism of activity enhancement by triflic acid modification appears to be related to the formation of extra-lattice Al rather than the direct presence of triflic acid. A thermally stable solid catalyst prepared from amorphous silica gel and triflic acid has also been reported. The obtained material was found to be an active catalyst in the alkylation of isobutylene with n-butenes to yield high-octane gasoline components. A similar study has been carried out with triflic acid-functionalized mesoporous Zr-TMS catalysts. Triflic acid-catalyzed carbonylation, direct coupling reactions, and formylation of toluene have also been reported. Tritlic acid also promotes transalkylation and adaman-tylation of arenes in ionic liquids. Triflic acid-mediated reactions of methylenecyclopropanes with nitriles have also been investigated to provide [3 + 2] cycloaddition products as well as Ritter products. Tritlic acid also catalyzes cyclization of unsaturated alcohols to cyclic ethers. ... 

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