Functional Nano Structure Materials Lab. Research

Organic/Inorganic Hybrid Coating

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Mold casting processes

  • Sand mold casting process
  • Shell mold process
  • Investment casting process
  • Shaw process
  • Full mold process

[Shell mold casting]

  • Centrifugal casting process
  • Die casting process
  • Vacuum casting process
  • Low pressure casting process
  • Squeeze casting process

[Ceramic mold prepared through investment casting process]

Technology of Application

Cast Steel
Automatic Engine Parts & Others

[Parts of an automobile]


[Defense Industry]

Precision casting

  • Wax pattern injection

  • Tree assembly

  • Wax Tree cleaning

  • Shell mold coating

  • Stucco coating

  • Shell mold drying

  • De-waxing

  • Firing for shell mold

  • Casting

  • Remove fot
    shell mold and gate
    Heat-treatment Final product
  • Shell mold coating

  • Casting

Ceramic mold prepared through investment casting process

  • (a) Wax pattern (injection molding)
  • (b) Multiple patterns assembled to wax sprue
  • (c) Shell built immerse into ceramic slurry immerse into fine sand (few layers)
  • (d) dry ceramic melt out the wax fire ceramic (burn wax)
  • (e) Pour molten metal cool, solidify
  • (f) Break ceramic shell (Vibration or water blasting)
  • (g) Cut off parts (high-speed friction saw) finishing (polish)

Sand mold process

  • Mass production and simple process
  • Use of organic binder with low degradation temperature

    - Blow-hall production

    - Low fracture under high temperature

    - Poor dimension stability

    - Environmental pollution

  • Thick mold thickness
  • Simple shape and thick product

mold process

Mold process using inorganic binder

  • Use of inorganic binder

    - Heat treatment (1000 ℃)

    - Better dimension stability

    - Better mechanical and thermal properties

  • Enhancement of collapsibility
  • Faster processing time
  • High glassification efficiency

    - Enough fracture strength for thin-wall casting

Development of new inorganic binder and new process

  • Preparation of ceramic mold and core having high fracture strength in sand mold process
  • Application into the precision casting

Organic/Inorganic Hybrid Coating

Advantages and drawbacks
  • High fracture strength
  • Easy processability
  • Enhancement of collapse
  • High thermal stability
  • Low conversion ratio of inorganic precursor
  • Loss of inorganic binder by the burning of organic binder
  • Non-homogeneous coating of inorganic binder on the surface of stating particle
New coating process
  • Improvement the addition effect of inorganic precursor
  • High glassification efficiency
  • High dimension stability
  • Enhancement of the mechanical and thermal properties
  • Simple process
Reaction mechanisms
(1) Sol-gel reaction

NaOMe + H2O MeOH + NaOH Sodium methoxide Methanol Sodium hydroxide

nSi(OEt)4 + 4nH2O (n+ 1)SiO2 + 4nEtOH Tetraethyl orthosilicate Silica Ethanol

(2) Glassification (Heat treatment)

2NaOH + SiO2 Na2O·SiO2 + H2O Sodium hydroxide Sodium silicate

SiO2 precursors

Silicate type w/o sol-gel reaction

(Tetraethyl orthosilicate)

Na2O precursor

(Sodium methoxide)