Hydrothermal growth technique

The in situ membrane growth technique cannot be applied using the zeolite-based ceramic porous membrane as support, under hydrothermal conditions in a solution containing sodium hydroxide. The high pH conditions will cause membrane amorphization and lead to final dissolution. Therefore, we tried to synthesize an aluminophosphate zeolite such as AlP04-5 [105] over a zeolite porous ceramic membrane. For the synthesis of the AlP04-5-zeolite-based porous membrane composite, the in situ membrane growth technique [7,13,22] was chosen. Then, the support, that is, the zeolite-based porous ceramic membrane, was placed in contact with the synthesis mixture and, subsequently, subjected to a hydrothermal synthesis process [18]. The batch preparation was as follows [106] ... 

Hydrothermal-growth is usually defined as the use of an aqueous solvent at elevated temperature and pressure to dissolve a solute which would be insoluble under ordinary conditions. The advantages of the hydrothermal technique are a low growth temperature, a AT close to 0 at liquid/solid interface, an easily scalable technique, the reduction of most of the impurities from source. The disadvantages are the presence of intermediate products, the lithium or sodium or potassium incorporation when such solvents as LiOH, NaOH or KOH are used, the slow growth rates ( 10 mils per day), the inert liner needed, the occasional incorporation of OH and H2O. 

Some electrical and structural properties of crystals grown by various techniques, melt-growth, hydrothermal growth, SCVT and CVT are summarized in the following table. 

Beyond the abundant natural sources of quartz and other silicas, techniques for synthetic production of these materials have provided a significantly wider range of applications [27,34], Large, high-quality crystals of quartz can be grown by the well-established technique of hydrothermal growth in an autoclave filled with a solution of... 

In a second approach for thin film synthesis, a layer of pre-synthesized seed crystals is deposited on the substrate, followed by some means of binding it to the surface and subsequent hydrothermal synthesis of the desired zeolite film on the seed layer. This and the previous growth technique are advantageous if a very strong bond to the substrate is desired. Furthermore, for a select group of zeolites it has been shown that substantial crystal... 

Synthetic emeralds. Emeralds can be synthesized either by flux-growth or hydrothermal processes. The flux-growth techniques is used by Chatham Research Laboratories in San Francisco, United States and Les fitablissements Cdramiques Pierre Gilson, while the hydro-thermal synthesis once utilized by Union Carbide (1965-1970) is currently employed by Biron and Vacuum Ventures. Synthetic emeralds are easily distinguished from naturals by their lower indices of refraction and densities, and by their distinct inclusions. 

Chen et al. [30] reported fabrication of Nafion/zeolite nanocomposite man-branes by hydrothermal growth of acid-functionalized zeolite nanocrystals into commercial Nafion membranes for DMFCs. The presence of zeolite nanocrystals in the composite is confirmed by X-ray diffraction techniques. The tensile strength and water uptake were studied and the performance was compared with that of the... 

Abbreviations used ACRT - Accelerated Crucible Rotation Technique, CZG - Czochralski Growth, EV Growth, HPS-High-pressure Solution Growth, HYG - Hydrothermal Growth, LPE-Liquid Phase Epitaxy. 

A hydrothermal technique operating at 450°C has been shown to yield samples with narrow transition temperature widths (24)(25). Growth times on the order of 3 days were found to yield crystals 1mm in diameter. 

The nonlinear optical oxide crystals recently developed are grown by flux (and hydrothermal solution for KTP) techniques to prevent decomposition (KTP, KTA, LBO) or to obtain a low temperature phase (BBO). The intrinsic nonstoichiometry and the impurity contents of the as-grown crystals is determined by the solutions and temperatures used for growth. The intrinsic defect concentrations in these materials are relatively low, compared to the more traditional nonlinear optical oxides having the... 

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