Hydrothermal preparation

Recent advances in fabricating novel metal oxide electrodes have been made by exploiting hydrothermal preparation techniques [93, 94], An example is... 

A comparison of boehmite with other raw materials is included in Table 6. In this table the soda and lithia contents of compositions based on a range of raw materials and the resultant properties are detailed. The level of / "-alumina was always higher with the hydrate-type raw material the hydrothermally prepared raw materials gave the highest content of / " -alumina. 

Liu, Q., Mao, D., Chang, C. and Huang, F. (2007) Phase conversion and morphology evolution during hydrothermal preparation of orthorhombic I iMiiO, nanorods for lithium ion battery application, journui of Power Sources, 173, 538-544. 

Hennings, D. Rosenstein, G. Schreinemacher, H. 1991. Hydrothermal preparation of barium titanate from barium-titanium acetate gel precursors. J. Euro. Ceram. Soc. 8 107-115. 

Theoretical calculations [43] based on first principles molecular dynamics discussed in Sect. 3.2.6 have suggested that Mg Al LDHs are most stable for n = 3 (i.e. x = 0.25) and indeed many minerals, including hydrotalcite itself, have this stoichiometry [4]. It has been reported that the synthesis of LDHs (with benzoate or terephthalate anions in the interlayers) from solutions containing Mg/Al = 2, leads to LDHs having the same composition when the synthesis is carried out at moderate temperatures but LDHs with Mg/Al = 3 (plus AlOOH) when the reaction is carried out under hydrothermal conditions [44]. It was proposed that the latter ratio represents the thermodynamically most favorable product. A similar observation has been reported [45] for solutions with Ni VPe = 2, where hydrothermal preparation led to segregation of an LDH with Ni VPe = 3 and Ni Fe 204. An attempt to synthesize a Co sAl LDH resulted in partial oxidation of the Co and formation of a Co o.yCo o.s LDH with complete migration of Al " from the layers to generate interlayer aluminum oxy-species [46]. 

Chem. Phys. 8 125-133 Ardizzone, S. Formaro, L. (1985) Hydrothermal preparation of goethite crystals. Surface Techn. 26 269-274... 

Booy M. Swaddle, T.W. (1978) Hydrothermal preparation of magnetite from iron chelates. Can. J. Chem. 56 402-403 Boquet, S. Pollard, R.J. Cashion, J.D. (1990) Dynamic magnetic phenomena in fine particle goethite. Phys. Rev. B46 11657-11664... 

Chen H, Ma J, Zhao Z, Qi L (1995) Hydrothermal preparation of uniform nanosize rutile and anatase particle. Chem Mater 7 663-671... 

Hydrothermal synthesis of ZnSe and CdSe, using powdered Se with either Zn or Cd heated to 180°C in a water filled autoclave, yields 70-100 nm particles without the need of any stabilizer or capping agent. While most hydrothermal synthesis routes of chalcogenides involve the preparation of binary systems, more complicated ternary compounds can also be prepared. For example, Znln2S4, a ternary chalogenide photocatalyst has been hydrothermally prepared and found to photocatalytically reduce water under visible... 

The most widely used zeolite in petroleum refining so far is Y zeolite. Currently, REUSY zeolite is the main active component of RFCC catalysts. However, in the course of hydrothermal preparation of ultrastable Y zeolite, nonframework aluminum debris formed by dealumination could block the channels thus influencing the ion-exchange ratio of rare earth as well as the accessibility of active sites [2],... 

Table 2.2 shows the catalytic performances of various Cu and Ce catalysts for CO PROX reactions in excess H2 at 90 °C. Ce oxides, Ce-CTAB and Cu-CTAB were completely inactive for CO oxidation at 90 °C. In contrast, the hydrothermally-prepared Cu/Ce-CTAB catalyst (7.5 wt%Cu) exhibited good catalytic performance for the CO PROX, with 91.9-96.1% CO conversion and 99.4—99.8% 02 selectivity at 90°C in a feed of C0/02/H2= 1 1 50 (Table 2.2). Table 2.3 summarizes the performance of the Cu/Ce-CTAB catalyst under various reaction conditions, different W/F, reaction temperatures and feed compositions. Notably, high CO conversions and 02 selectivities were also achieved in reactant feeds containing substantial amounts of H20 and C02. The CO conversions and 02 selectivities at W/F = 2.24 gcath mol-1 and 90 °C were 85.7% and 98.7%, respectively when H20 (10%) existed, and 81.4% and 98.2%, respectively when H20 (10%) and C02 (20%) co-existed. 

Hydrothermal preparations have also resulted in several layered materials such as Na3M02O4H(PO4)2-2H2O and alkylammonium derivatives of M04Og(PO4)2 . These show properties comparable to the materials described in the next... 

Tani, E., Yoshimura, M., and Somiya, S., Hydrothermal preparation of ultrafine monoclinic ZrOj powder, J. Am. Ceram. Soc., 64, C181, 1981. 

The common six- and seven-coordinate uranyl-based polyhedra are also observed in the extended structures of uranyl molybdates containing M02O7 units. For example, the mineral iriginite, [(U02)Mo207(H20)2](H20), and the hydrothermally prepared [(U02)Mo207(H20)2], which is formed under more basic conditions, contain electroneutral sheets of [(U02)Mo207 (H20)2]. "... 

Typical UV-Vis spectra of Ti-P and Ox-Ti-P samples are shown in Fig. 2. Isolated Ti(IV) in tetrahedral coordination was reported to exhibit an absorption band at about 212 nm [18a]. The presence of this band has been considered as an evidence for the incorporation of Ti into the framework of various titaniiun silicate molecular sieves such as TS-1, TS-2, TS-48 and Ti-p. The Ox-Ti-P samples had a band at about 220 nm, similar to that of hydrothermally prepared Ti-P [4,10,12]. The relatively high wavelength of this band may be due to the presence of water molecules in the coordination sphere of titanium [18b]. Ti(IV) in an octahedral coordination in a separate phase such as Ti02 is expected to absorb at about 340 nm [18a]. No such band was present in our UV-Vis spectra indicating the absence of segregated Ti02 particles. In conclusion, our UV-Vis data... 

Fig. 7.3. SEM images of the tubular Ag2Se hydrothermally prepared from AgCI, Se and NaOH at 155 °C.

Pattern B was collected from an anhydrous FeP04 powder obtained by decomposition (holding at 80°C in vacuum for 12 h) of the hydrothermally prepared dihydrate FeP04 2H20. The compound has a monoclinic crystal structure with unit cell dimensions a = 5.48, b = 7.48, c s 8.05 A, P s 95.7°. 

Chitosan has been utilized along with hydrothermally prepared nano-ZnO nanoparticles for DNA hybridization detection. The detection limit is obtained as 1.09 x 10"11 mol L 1 of complementary target [66], A MWNTs/nanoZnO/CH modified nanocomposite GCE electrode has been used for DNA immobilization via physisorption. This biosensor can effectively discriminate different DNA sequences related to PAT gene in the transgenic com, with detection limit of 2.8 x K)"12 mol/L of target sequence [67], In another report they have deposited ZnO nanoparticles, MWNTs and CH layer onto glassy carbon electrode to immobilize ssDNA probe. A remarkable synergistic effect of the ZnO nanoparticles and MWNTs has been achieved after ssDNA probe immobilization for fabrication of sensitive electrochemical DNA biosensor. The modified electrode shows a wide linear response for DNA hybridization detection. (1.0 x 10"11 to 1.0 x 10"6 mol/L) with detection limit of 2.8 x 1 O 12 mol/L [68],... 

P. Norby, A.N. Christensen, and I.G.K. Andersen, Hydrothermal Preparation of Zeolite Li-A(BW), LiAlSi04 H20, and Structure Determination from Powder Diffraction Data by Direct Methods. Acta Chem. Scand. Sen, A, 1986, 40, 500-506. 

The application of non-hydrothermally prepared stevensites as support for hydrodesulfurization catalysts... 

The boehmite system (y-AlOOH), originally studied by Zocher and Torok [63] and Bugosh [64] was further developed by Lekkerkerker and coworkers [65]. They extended the hydrothermal preparation pioneered by Bugosh [64] by starting from an aqueous aluminum alkoxide mixture acidified with hydrochloric acid [65a]. They studied the phase behavior of both charge stabilized aqueous dispersions of colloidal boehmite rods [65b,c] as well as sterically stabilized colloidal boehmite rods in an organic solvent (cyclohexane) [65d-f]. 

S. 1. Hydrothermal preparation of y-MnOOH and P Mn02 nanowires/nanorods... 

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