1) A process for densification of ceramic via sequential cold sintering and low
temperature conventional sintering, the process comprising –
a) uniformly mixing a precursor component with a solvent that can
partially solubilise the precursor component to form a paste;
b) transferring the paste to a cold sintering equipment and subjecting it to
10 a compressive pressure ≤500MPa and temperature of ≤ 500°C to obtain
a cold sintered pellet (CSP);
c) transferring the cold sintered pellet (CSP) to a muffle furnace and
subjecting it to conventional sintering involving pressureless thermal
treatment of said pellet to temperature ranging between 500°C – 1500°C
15 to obtain a completely densified cold sintered pellet – conventional
sintering (CSP-CS);
in which the precursor component is a preferably an oxide ceramic, either
as a single compound or a composite in which the single compound is mixed
with a phase stabilising dopant.
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2) The process for densification of ceramic via sequential cold sintering and
low temperature conventional sintering as claimed in claim 1, wherein the
oxide ceramic is at least one of aluminium oxide, zirconium oxide, silica,
magnesium oxide and titanium oxide.
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3) The process for densification of ceramic via sequential cold sintering and
low temperature conventional sintering as claimed in any of the preceding
claims, wherein step a) further comprises addition of hygroscopic ceramic
powders selected from oxides, carbonates and fluorides such as yttrium
30 oxide, magnesium oxide, boehmite, boron trioxide and silica in amounts ≤
20wt.% which may also act as the phase stabilizing agent.
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4) The process for densification of ceramic via sequential cold sintering and
low temperature conventional sintering as claimed in any of the preceding
claims, wherein the precursor component is selected from at least one of
partially stabilized zirconia powder, magnesia-zirconia in-situ stabilizing5 powder mix and alumina-boehmite powder mix.
5) The process for densification of ceramic via sequential cold sintering and
low temperature conventional sintering as claimed in any of the preceding
claims, wherein the particle size of the precursor component is preferably
10 d50<100μ.
6) The process for densification of ceramic via sequential cold sintering and
low temperature conventional sintering as claimed in any of the preceding
claims wherein the particle size of the precursor component is more
15 preferably d50<50μ.
7) The process for densification of ceramic via sequential cold sintering and
low temperature conventional sintering as claimed in any of the preceding
claims wherein the particle size of the precursor component is still more
20 preferably d50<10μ.
8) The process for densification of ceramic via sequential cold sintering and
low temperature conventional sintering as claimed in any of the preceding
claims wherein the partially stabilised zirconia powder (3YSZ) is prepared
25 by electrofusion method by stabilising zirconia with yttria through melting
of monoclinic zirconia with yttria powder to produce 3YSZ.
9) The process for densification of ceramic via sequential cold sintering and
low temperature conventional sintering as claimed in any of the preceding
30 claims wherein the resultant densified 3YSZ material is pure tetragonal
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phase obtained by phase change during the cold sintering step and sintered
at relatively low conventional sintering cycle.
10) The process for densification of ceramic via sequential cold sintering and
5 low temperature conventional sintering as claimed in any of the preceding
claims, wherein the solvent is selected from at least one of water, acetic acid,
sulphuric acid, formic acid, zirconia oxynitrate hydrate, sodium hydroxide,
xylene and dimethylformamide.
10 11) The process for densification of ceramic via sequential cold sintering and
low temperature conventional sintering as claimed in any of the preceding
claims wherein the ratio of alumina: boehmite in alumina-boehmite powder
mix is 10:90 to 90:10.