USE OF PLASMA DEPOSITION TO MAKE BULK CORUNDUM PRODUCTS
WITH CHANNEL POROSITY
A. A. Bochegov,
A. V. Ermakov,
S. V. Nikiforov,
and I. V. Vandysheva
Translated from Novye Ogneupory,No.10,pp.3–6,October, 2015.
Original article submitted July 15, 2015.
The use of a technology for the plasma deposition of bulk ceramic products to make permeable diaphragms
with channel porosity is described along with the results that have been obtained.
Key words: refining of metals, electrochemical processes, plasma-sprayed corundum ceramic, plasma depo
sition technology, porous ceramic diaphragms, channel porosity.
One of the main trends in improving the processes used
to obtain and refine metals by the electrolysis of ionic melts
is optimizing these processes and the design of the electroly-
sis baths in order to minimize total costs, reduce energy use,
and obtain metal of the prescribed degree of purity. The in-
ventor of the technology — the Institute of High-Tempera-
ture Electrochemistry in the Ural Division of the Russian
Academy of Sciences — believes that the use of an electroly-
sis bath having a porous ceramic diaphragm impregnated
with a salt electrolyte will make it possible to reduce the unit
consumption of electric power by an order of magnitude
while saving large amounts of expensive electrolytes.
In the course of designing the diaphragm, a corundum
ceramic was chosen as the material to make it because it is
the most stable in alkali and alkaline-earth chlorides [1, 2]
and has good dielectric properties, high refractoriness, and
high heat resistance [3, 4]. The diaphragm should be in the
form of a tall crucible in which the middle part is porous and
the bottom and the top part of the wall are made of a dense
ceramic. The middle part has an open porosity of about 30%.
The porosity is mainly channel porosity, with the channels
being of variable cross section. The average diameter of the
pores in the membrane layer is 6 – 10 mm and specific water
permeability (in the absence of excess pressure) is
0.1 – 0.2 g/(cm
The main electrochemical processes take place inside the
thin (100 – 150 mm) electrolyte-filled membrane layer of the
ceramic diaphragm, which is distinguished by the minimal
dimensions that characterize its channel porosity. The re-
maining thickness of the wall of the diaphragm, containing
diverging channels, provides a reserve supply of electrolyte
and imparts the necessary structural strength.
The molten electrolyte comes into contact with air only
above the level of the melt, so that evaporation of the salts is
reduced to a minimum. The short distance between the elec-
trodes, which makes it possible to increase current density,
sharply reduces the energy content of the process and the
amount of heat that is released (Fig. 1).
Several variants of technologies that have traditionally
been used to make porous ceramics – film formation, com
bustion of additives, outgassing, pressing of narrow-fraction
powders with a binder, etc. — were considered as possibili
ties for solving the given problem. Plasma deposition was
chosen for this purpose, it being the technology that is most
familiar and convenient to use at factories which make bulk
ceramic products .
The classic  plasma-deposition technology for making
bulk ceramics includes several operations:
1. A dividing layer of the necessary thickness is applied
to a steel 3 – 20 mandrel (model) that exactly reproduces the
internal shape of the product in order to keep the deposited
ceramic from adhering to the mandrel.
2. A layer of the ceramic material (corundum powder) is
deposited on the coated mandrel. Layer-by-layer deposition
proceeds until the wall of the product that is being made
reaches the necessary thickness.
Refractories and Industrial Ceramics Vol. 56, No. 5, January, 2016
1083-4877/16/05605-0443 © 2016 Springer Science+Business Media New York
Ural Innovative Technologies, Ekaterinburg, Russia.
Ural Precious Metals, Ekaterinburg, Russia.
Ural Federal University, Ekaterinburg, Russia.