M. S. Lehmann

Isotope effects in the bonds of β-CrOOH and β-CrOOD

Samples of orthorhombic chromium oxide hydroxide, β-CrOOH, and the deuterated compound, β-CrOOD, were prepared hydrothermally. The crystal structures were determined by powder profile refinement technique using neutron diffraction data. Unit cells are: β-CrOOH: a = 4.862(2)A, b = 4.298(2) A, c = 2.995(1) A; β-CrOOD: a = 4.873(5) A, b = 4.332(7) A, c = 2.963(2) A, with Z = 2. The space group is P21nm or Pnnm. Distances found for the hydrogen atoms using space group P21nm are: OD···O: 2.58(2) A, OD: 1.07(2) A, OH···O: 2.46(2) A, and OH: 1.10(2) A, showing large isotope effects.

Rate of reactions between D2O and CaxAlyOz

The rate of the reaction between D/sub 2/O and the calcium aluminum oxides Ca/sub 3/Al/sub 2/O/sub 6/, Ca/sub 5/Al/sub 6/O/sub 14/, CaAl/sub 2/O/sub 4/, and CaAl/sub 4/O/sub 7/ was investigated by on-line neutron diffraction powder methods at temperatures from room temperature to 100/sup 0/C. The rate of the reaction increases with increasing calcium content of the compounds and with increasing temperature for each of the compounds. The crystallographic stable hydrate Ca/sub 3/Al/sub 2/(OD)/sub 12/ is obtained from CaAl/sub 4/O/sub 7/ and CaAl/sub 2/O/sub 4/ at temperatures above 63/sup 0/C, from Ca/sub 5/Al/sub 6/O/sub 14/ at temperatures above 49/sup 0/C, and from Ca/sub 3/Al/sub 2/O/sub 6/ at temperatures as low as 7/sup 0/C.

Time resolved powder neutron diffraction investigations of reactions of solids with water

The reactions of brownmillerite (C4AF) with D2O as well as those of a mixture of C12A7 and CaSO4. 2D2O with D2O were investigated by on-line powder neutron diffraction. The crystalline reaction products in the hydrolysis of C4AF are Ca3Al2(OD)12 with Ca(OD)2. For the sulphate containing system a precursor phase was observed before the formation of deuterated ettringite, Ca6Al2(OD)12(SO4)3. 26D2O.