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Protection and Restoration
Glass-like coatings and enamels are widely used for protection of metals and
alloys during hot pressing, hot rolling, and other hot working processes due to their
capability of gradually turning to liquids of varying viscosity dependent on temperature. Frit composition determines most engineering properties of a coating. A glassforming component, silica (SiO 2 ) or borate (B 2 O 3 ), is the major constituent of the
frit, forming two distinct glass, silica-based and borate-based series. Other oxides
are usually added, e.g., Na 2 O, K 2 O, and Li 2 Om, to control melting temperature of the
frit (Rossi et al., 2021). Enamels are effective as high-temperature lubricants during
hot forging. They reduce deformation resistance of a workpiece and heat transfer
between a workpiece and die, thus reducing the cooling rate. As a result, forming
accuracy is increased and durability of dies can be improved by 50% to even 150%
(Alexenko et al., 2016).
Glass‑ceramics are partially crystallized glasses composed of a combination of a
crystalline phase and an amorphous glass phase (Rahaman et al., 2018). The amount
of crystalline phase can vary over a wide range, from 1 to 99%, though normally in
the range 30–70%. Zhao (2011) emphasizes that glass-ceramics are manufactured
from base glasses, using the mechanisms of controlled nucleation and crystallization, but they exhibit special properties characteristic of both glass and ceramic
materials. Consequently, special combinations of properties can be achieved and
even materials with novel properties, known neither in glass nor in ceramic materials, can be designed in this group.
Metallic glasses are solid alloys that are not crystalline, having an amorphous
atomic arrangement inherited directly from the liquid state (Greer, 2014). They may
consist of pure metal alloys or combinations of metals and metalloids, prepared by
extremely high-speed cooling techniques, such as splat cooling. These glasses may
be binary (e.g., Ni 60 Nb 40 , Cu 50 Zr 50 , Pd 80 Si 20 , Au 73 Ge 27 , Co 75 P 25 , etc.), ternary (e.g.,
Pd 77 Au 5 Si 18 , Ni 80 Si 8 B 12 , Fe 81 Cr 2 B 17 , Ti 72 Fe 12 Si 6 , etc.), quaternary (e.g., Fe 40 Ni 40 P 14 B 6 ,
Ni 68 Cr 10 Si 10 B 12 , Fe 75 P 15 C 6 Al 4 , etc.), etc. systems (Karmakar, 2016). When a metallic glass is annealed close to its glass-transition temperature T g , the glassy structure
evolves toward a metastable equilibrium state of a supercooled liquid and many physical and mechanical properties change accordingly. At higher annealing temperatures,
property changes are initially faster, but their total extent is more limited. The yield
strain σ y /E is much higher for MGs than for any conventional metallic materials.
Based on inherent advantages of silica-based coating, organosilica coatings
have been designed recently to meet growing requirements (Song et al., 2018).
Organosilica or organically modified silica is a molecularly inorganic–organic composite with the empirical formula of R′ n Si(OR) 4–n , that combines basic advantages
of inorganic silica-based coatings and of organic groups. Generally, organosilica
monomer contains a hydrolysable siloxane group Si(OR) 4–n and reactive substituents R′, where a siloxane group can form an inorganic sol-gel coating by hydrolysis
and condensation. By changing the organic R′ moiety, the coating can be endowed
with antifouling function. Typically, poly(ethylene glycol) (PEG) as a representative
hydrophilic polymer is reported as incorporated with a silica-based coating for the
purpose of enhancing surface antifouling properties, especially protein resistance
ability and enhanced coating stability (Song et al., 2018).
Protection and Restoration
Glass-like coatings and enamels are widely used for protection of metals and
alloys during hot pressing, hot rolling, and other hot working processes due to their
capability of gradually turning to liquids of varying viscosity dependent on temperature. Frit composition determines most engineering properties of a coating. A glassforming component, silica (SiO 2 ) or borate (B 2 O 3 ), is the major constituent of the
frit, forming two distinct glass, silica-based and borate-based series. Other oxides
are usually added, e.g., Na 2 O, K 2 O, and Li 2 Om, to control melting temperature of the
frit (Rossi et al., 2021). Enamels are effective as high-temperature lubricants during
hot forging. They reduce deformation resistance of a workpiece and heat transfer
between a workpiece and die, thus reducing the cooling rate. As a result, forming
accuracy is increased and durability of dies can be improved by 50% to even 150%
(Alexenko et al., 2016).
Glass‑ceramics are partially crystallized glasses composed of a combination of a
crystalline phase and an amorphous glass phase (Rahaman et al., 2018). The amount
of crystalline phase can vary over a wide range, from 1 to 99%, though normally in
the range 30–70%. Zhao (2011) emphasizes that glass-ceramics are manufactured
from base glasses, using the mechanisms of controlled nucleation and crystallization, but they exhibit special properties characteristic of both glass and ceramic
materials. Consequently, special combinations of properties can be achieved and
even materials with novel properties, known neither in glass nor in ceramic materials, can be designed in this group.
Metallic glasses are solid alloys that are not crystalline, having an amorphous
atomic arrangement inherited directly from the liquid state (Greer, 2014). They may
consist of pure metal alloys or combinations of metals and metalloids, prepared by
extremely high-speed cooling techniques, such as splat cooling. These glasses may
be binary (e.g., Ni 60 Nb 40 , Cu 50 Zr 50 , Pd 80 Si 20 , Au 73 Ge 27 , Co 75 P 25 , etc.), ternary (e.g.,
Pd 77 Au 5 Si 18 , Ni 80 Si 8 B 12 , Fe 81 Cr 2 B 17 , Ti 72 Fe 12 Si 6 , etc.), quaternary (e.g., Fe 40 Ni 40 P 14 B 6 ,
Ni 68 Cr 10 Si 10 B 12 , Fe 75 P 15 C 6 Al 4 , etc.), etc. systems (Karmakar, 2016). When a metallic glass is annealed close to its glass-transition temperature T g , the glassy structure
evolves toward a metastable equilibrium state of a supercooled liquid and many physical and mechanical properties change accordingly. At higher annealing temperatures,
property changes are initially faster, but their total extent is more limited. The yield
strain σ y /E is much higher for MGs than for any conventional metallic materials.
Based on inherent advantages of silica-based coating, organosilica coatings
have been designed recently to meet growing requirements (Song et al., 2018).
Organosilica or organically modified silica is a molecularly inorganic–organic composite with the empirical formula of R′ n Si(OR) 4–n , that combines basic advantages
of inorganic silica-based coatings and of organic groups. Generally, organosilica
monomer contains a hydrolysable siloxane group Si(OR) 4–n and reactive substituents R′, where a siloxane group can form an inorganic sol-gel coating by hydrolysis
and condensation. By changing the organic R′ moiety, the coating can be endowed
with antifouling function. Typically, poly(ethylene glycol) (PEG) as a representative
hydrophilic polymer is reported as incorporated with a silica-based coating for the
purpose of enhancing surface antifouling properties, especially protein resistance
ability and enhanced coating stability (Song et al., 2018).