Page 11 - PR 2014 2016 07 Nuclear Science and Technology

Nuclear Science and Technology | Progress Report 153

in different proportions, heated to the melting
temperatures and cooled with a constant rate
to produce annealed samples for the study.
X-ray diffraction data for Rietveld analyses
were collected at room temperature. Four
different phases were identified in the system
xLi W O - (1-x) La W O for 0≤ x ≤1, namely
2 2 7 2 2 9
LiLa(WO )2, La W O , Li W O and Li WO .
4 2 2 9 2 2 7 2 4
In the interval 0< x <1, phase LiLa(WO )
4 2
is formed for all values of x. One, two or
even three of the other phases coexist with
LiLa(WO ) in shorter intermediate intervals
4 2
of x. The cell parameters of LiLa(WO ) and Fig 7. A few X-ray diffraction patterns obtained with samples from
4 2 the system xLi W O - (1-x)La W O . Pattern for x = 0 corresponds to
2
2
9
7
2
2
the occupation factors of Li, La and O, in this the phase La W O and for x = 1 to Li W O .
2 2 9 2 2 7
phase, were also determined in the analyses.
In order to complete the study, differential
thermal analysis (DTA) and scanning electron
microscopy (SEM) were applied to samples
and single-crystal fibres grown by micro-
pulling-down (μ-PD) technique.
Hydration mechanism in
Portland cements

A study of the hydration mechanism in Port-
land cements has been initiated. The study re-
sults of a co-operation between the Polytechnic
School at Sao Paulo University and the Neutron
Diffraction Laboratory at IPEN. Neutron dif-
fraction patterns of dry and hydrated Portland
cement were measured in the high-resolution
neutron diffractometer Aurora. Hydration was
done with heavy water (D O) owing to the high
2
level of incoherent background in the pattern
if light water is used. Rietveld refinement of
the deuterated and dry cement samples gave
as result the presence of several phases in
different proportions. A list of the phases and
their weight percentages (Wt. %) refined for the
deuterated sample is as follows: 35.60 of Alite
(Ca SiO ), 0.46 Portlandite (CaO D ), 19.60 Belite
3 5 2 2
(Ca SiO ), 39.90 Calcite (CaCO ), 1.10 Anhydrite
2 4 3
(CaSO ), 1.20 Tricalcium aluminate (Ca Al O )
4 3 2 6
and 1.30 Periclase (MgO).