Hydrothermal hydrolysis

Hydrothermal hydrolysis of metal ions is useful in producing crystalline phases which contain metals in a state of partial hydrolysis, i.e., a state intermediate between that of the hydrated metal ion and that of the hydrous hydroxide. Such reactions have been used to produce numerous crystalline phases of actinides (1-4), Group IV metal ions (5-14) and lanthanides (15-21). 

Previous studies of the hydrothermal hydrolysis of tetravalent Th, U and Np (1-4) have shown a remarkable similarity in the behavior of these elements. In each case compounds of stoichiometry M(0H)2S0i, represent the major product. In order to extend our knowledge of the hydrolytic behavior of the actinides and to elucidate similarities and differences among this group of elements, we have investigated the behavior of tetravalent plutonium under similar conditions. The relationships between the major product of the hydrothermal hydrolysis of Pu(IV), Pu2(OH)2(SO.,)3 (H20) t, (I)> and other tetravalent actinide, lanthanide and Group IVB hydroxysulfates are the subject of this re-... 

The conditions under which the basic sulfates of tetraval-ent, Zr, Hf and Ce form provide analogies on which to base speculation about the hydrothermal hydrolysis of tetravalent plutonium. In the zirconium system at 100°C, the only basic sulfate observed is Zr2 (0H)2 (SOO3 ( 0), i.e., the zirconium analog of... 

I. However, as the temperature of the hydrothermal hydrolysis is raised, two forms of Zr(OH)2SOi are formed. In addition,... 

Group IVB, actinide, and lanthanide, hydrothermal hydrolysis spectroscopic studies. 58-62... 

Group IVB, actinide and lanthanide hydrothermal hydrolysis (continued)... 

Zirconium compound, hydrothermal hydrolysis and crystal structure. .. 52-57... 

Hydrothermal hydrolysis— hydrodiermal precipitation Hydrothermal electrochemical reaction Hydrothermal mechanochemical reaction Hydrothermal + ultrasonic Hydrothermal + microwave... 

The hydrothermal hydrolysis of Al3+ in aqueous KC1 solutions may be rationalized in terms of the equations ... 

In another attempt to obtain diamond from SiC, no evidence for diamond growth was found by means of XRD and SEM after hydrothermal hydrolysis of P SiC powder at 140 MPa and 800°C [57]. Formation of quartz, a second acicular phase, graphite and maybe nanosized diamond crystals was reported. TEM analysis of whiskers of the second acicular phase revealed lattice spacing of 0.9 nm, a <7-value of 0.56nm and a composition of SiOi 6Co.2- A very sharp band at 1330cm was found in a Raman spectrum and assigned to the silicon oxycarbide, SiOi 6C0.2, rather than to diamond. 

TiCl4 in oxygen [11], hydrolysis of titanium alkoxides in different conditions [12], photo-assisted sol-gel method from titanium tetrabutoxide [13], hydrothermal oxidation of metallic titanium powder [14], hydrothermal hydrolysis of titanium tetraethoxide [15], oxysulfate [16,17] and tetrabutylammonium [18], solvothermal synthesis from titanium butoxide in 2-butanol [19], crystallization of amorphous Ti02 in hydrothermal condition [20], vapor hydrolysis of titanium tetraisopropox-ide [21], destabilization of titanium lactate [22], decomposition of titania-hydrate [23], epoxide sol-gel process to aerogel of Ti02 [24], hydrolysis of aqueous solution of TiCl4 in the presence of polyethyleneglycol [25], and so forth. 

Hydrothermal hydrolysis of a Ce(IV) sulfate solution yields single crystals of Ce0S04 H2O (Lundgren, 1953). The crystal structure has been refined by Lindgren (1976) and shown to contain (CeO ) strings. Ce(IV) is eight-... 

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