ESTIMATING THE DEGREE OF PERFECTION
OF THE CRYSTALLINE STRUCTURE OF KAOLIN
E. I. Evtushenko,
O. K. Sysa,
I. Yu. Moreva,
and O. V. Starodubtseva
Translated from Novye Ogneupory, No. 4, pp. 79 – 81, April, 2010.
Original article submitted October 1, 2009.
A technique of estimating the structural instability of substances is developed on the basis of studies on hydro
thermal modification of clay ores. It is suggested that estimation of the degree of perfection of the crystalline
structure of mono- and poly-mineral clays be performed on the basis of a determination of the strength of indi
vidual junctions in suspensions.
Keywords: structural instability, clay ore, kaolin, estimation technique
The technological features of clay and kaolin from dif-
ferent deposits depends on their disperseness, texture, and
mineral composition. Thus, clay-forming minerals may dif-
fer substantially in terms of the perfection (order) of their
crystalline lattice. For laminar silicates the perfection of the
structure is determined by the structure of the aluminosilicate
layers proper and the order in which these layers are
superposed within the crystallites . In a number of cases
the influence of imperfection in the crystalline lattice may
prove to be one of the more significant factors that determine
the rheological production properties of dispersed systems,
distinctive features in the forming of finished articles, and as
a consequence, the quality of ceramic [1 – 3].
A number of methods of studying and estimating the
structural disorder of clay ore have now been developed.
These includes methods based on the increase in the cation
exchange capacity of such material and the decrease in the
dimensions of the crystals composing the mineral as well as
from data of infrared spectroscopy and differential-thermal
as well as x-ray phase analysis of the material , for exam
ple, from the variation in the 002 reflection half-width  or
the method proposed by Hinkley . However, these meth
ods cannot always be applied for correlating the indices of
the properties of a mineral with its physical structure. For ex
ample, the values of the Hinkley index of crystallinity Ch de
crease with the presence of any type of defects in the super
position of layers. The properties of clay are, moreover, “in
sensitive” to a very common type of defect (displacement of
vacant positions in the octahedral lattices) that reduces the
value of Ch. Thus, it is extremely important to develop a new
method of estimating the structural instability of clay ore that
would take into account the integral action of nonequlibrium
defects and the overall structural instability of the material.
In  it is shown that the structural instability of clay ore
can be controlled through the use of preliminary hydrother-
mal processing at different saturated vapor temperatures. A
method of estimating the degree of perfection of the structure
of the material from the strength of the individual junctions
that form between the particles in clay dross was developed
on the basis of data of various studies. The calculation is per
formed in accordance with a model proposed by N. B. Ur’ev
[7, 8] for weakly aggregated suspensions:
is the rate of displacement corresponding to com
plete disintegration of the structure, sec
, effective vis
cosity corresponding to complete disintegration of the struc
ture, Pa × sec; and d, mean dimension of the particles. M.
It was established that for all the different types of kaolin
which we studied (kaolin from the Prosyanovsk, Glukhovets,
Kyshtym, and Zhuravlinolog deposits), the strength of indi
vidual junctions falls more than 90% with an increase in the
pressure and temperature of hydrothermal processing (Fig. 1).
Calculations of the strength of individual junctions have
Refractories and Industrial Ceramics Vol. 51, No. 2, 2010
1083-4877/10/5102-0070 © 2010 Springer Science+Business Media, Inc.
V. G. Shukhov State Technological University, Belgorod, Russia.