V.M. Sglavo – CerSciTech - UNITN 2011 Processing ... · V.M. Sglavo – CerSciTech - UNITN 2011...
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V.M. Sglavo – CerSciTech - UNITN 2011 • sintering • reaction bonding (Si (s) + NH 3(g) Si 3 N 4(s) + Si (s) ) • dimox (directed metal oxidation) (2 Al (s) + 3/2 O 2(g) Al 2 O 3(s) ) • thermal spray ( thick coatings) • from powders • from melt • from vapour/gas (CVD, sputtering) • from solution (sol-gel) • from techno-polyimers Processing technologies for ceramic materials Problems: • high temperatures (Al 2 O 3 : 2050°C; ZrO 2 : 2700°C) • high volumetric shrinkage upon solidification (≈20-25%) • large crystalline grains ( limited mechanical resistance) Problems: limited productivity ( thin coatings, powders, microcomponents)
Transcript of V.M. Sglavo – CerSciTech - UNITN 2011 Processing ... · V.M. Sglavo – CerSciTech - UNITN 2011...
V.M. Sglavo – CerSciTech - UNITN 2011
• sintering!• reaction bonding (Si(s) + NH3(g) � Si3N4(s) + Si(s))!• dimox (directed metal oxidation) (2 Al(s) + 3/2 O2(g) � Al2O3(s))!• thermal spray (� thick coatings)!
• from powders!
• from melt!
• from vapour/gas (CVD, sputtering)!
• from solution (sol-gel)!
• from techno-polyimers!
Processing technologies for ceramic materials
Problems:!• high temperatures (Al2O3: 2050°C; ZrO2: 2700°C)!• high volumetric shrinkage upon solidification (≈20-25%)!• large crystalline grains (� limited mechanical resistance)!
Problems:!limited productivity (� thin coatings, powders, microcomponents)!
V.M. Sglavo – CerSciTech - UNITN 2011
processing from powders!
T
T
gas (reacting)
sintering!
reaction bonding, dimox!
V.M. Sglavo – CerSciTech - UNITN 2011
gas!gas + powder!
plasma (T≈4000°C)!
fused powder!
thermal spraying (plasma spraying)!
typically, Ar + N2
V.M. Sglavo – CerSciTech - UNITN 2011
Journal of Thermal Spray Technology, Volume 6(1) March 1997--37!Thin Solid Films, 127 (1985)93-105!
typical structure of thermal barrier!
V.M. Sglavo – CerSciTech - UNITN 2011
typical structure of coating for biomedical application (hydroxyapatite- HA)!
Ti alloy
TiO2-HA HA
Biomaterials, Volume 25, Issue 18, August 2004, Pages 4393-4403!
V.M. Sglavo – CerSciTech - UNITN 2011
gas B!
gas A!
CVD (chemical vapour deposition)!
gas D!
p, T
C!
Steps: 1. reaction between A & B (gas) è C (solid) & D (gas)"2. condensation of C (on the substrate) – by nucleation & growth"
V.M. Sglavo – CerSciTech - UNITN 2011
Typical applications
Ceramic processing and sintering, 2nd ed., M.N. Rahaman, M. Dekker ed., 2003!
V.M. Sglavo – CerSciTech - UNITN 2011
Other examples
aA(g) + bB(g) = cC(s) + dD(g)
K ≈ (pD)d / (pA)a (pB)b
ΔG0 = - R T ln K
• K é if pA e pB are low
• if K é: polycrystalline coating (under T control)
Ceramic materials: science and engineering., C.B. Carter & M.G. Norton, Springer, 2007!
V.M. Sglavo – CerSciTech - UNITN 2011
Typical deposition velocity
Ceramic materials: science and engineering., C.B. Carter & M.G. Norton, Springer, 2007!
V.M. Sglavo – CerSciTech - UNITN 2011
Typical reactors for CVD deposition
MPACVD reactor for diamond coatings
Ceramic processing and sintering, 2nd ed., M.N. Rahaman, M. Dekker ed., 2003!
V.M. Sglavo – CerSciTech - UNITN 2011
Sputtering!
Ceramic materials: science and engineering., C.B. Carter & M.G. Norton, Springer, 2007!
normally at room temperature
V.M. Sglavo – CerSciTech - UNITN 2011
alkoxides water solution!(Si(OR)4)! “Sol”!
“Gel”! glass!ΔT >0
Si(OR)4 + H2O
(OR)3Si-OH + ROH
(OR)3Si-OH + Si(OR)4 (OR)3Si-O-Si(OR)3 + ROH
(OR)3Si-OH + (OR)3Si-OH (OR)3Si-O-Si(OR)3 + H2O
Sol-gel!
ceramic!
ΔT >0
V.M. Sglavo – CerSciTech - UNITN 2011
Ceramic processing and sintering, 2nd ed., M.N. Rahaman, M. Dekker ed., 2003!
Process scheme
V.M. Sglavo – CerSciTech - UNITN 2011
Hydrolysis
pH > 2.5
pH < 2.5
Ceramic materials: science and engineering., C.B. Carter & M.G. Norton, Springer, 2007!
V.M. Sglavo – CerSciTech - UNITN 2011
Condensation
acid pH
basic pH
Ceramic materials: science and engineering., C.B. Carter & M.G. Norton, Springer, 2007!
V.M. Sglavo – CerSciTech - UNITN 2011
sol gel of alkoxydes
powders!
thin films!
fibres!
Ceramic materials: science and engineering., C.B. Carter & M.G. Norton, Springer, 2007!
385
V.M. Sglavo – CerSciTech - UNITN 2011
polimer! ceramic!
forming!(plastic)!
thermolysis!sintering!
silicone, polycarbosilane, polysilazane, …! SiC, SiOC, SiON, Si3N4, …!
From technopolymers!
V.M. Sglavo – CerSciTech - UNITN 2011
Ceramic processing and sintering, 2nd ed., M.N. Rahaman, M. Dekker ed., 2003!
