Doctoral Dissertations


Hongfang Zhao

Keywords and Phrases

Investment casting; Polymer patterns


"Research described in this dissertation covers two topics. Part-I is focused on in-situ determination of neutral lipid content of microalgae using a lipophilic fluorescent dye. The traditional Nile red stain-based method for detecting microalgal intracellular lipids is limited due to varying composition and thickness of rigid cell walls. In this study, the addition of dilute acid and heating of solution, were found to greatly enhance staining efficiency of Nile red for microalgal species evaluated. Oil-in-water (O/W) microemulsion stabilized by a non-ionic surfactant was employed as a pseudo-standard that mimics lipid-bearing microalgal cells suspended in water. The average neutral lipid contents determined were very close to the results obtained by traditional gravimetric method and solid phase extraction.

Part II of the dissertation explores thermo-physico-chemical properties of polymeric pattern materials, including expanded polystyrene (EPS) foam, polyurethane foam, and epoxy stereolithography (SLA) patterns, that are used in investment casting. Density, elastic modulus, expansion coefficient, thermal degradation behavior, etc. were experimentally investigated for their effects on metal casting quality. The reduction in toxic hydrogen cyanide (HCN) generated during thermal decomposition of polyurethane pattern was achieved by increasing either oxidant level or residence time in heated zone. Thermal degradation kinetics of the pattern materials were examined with a thermogravimetric analysis and activation energies were determined by Kissinger and Flynn-Wall-Ozawa methods"--Abstract, page iv.


Nam, Paul Ki-souk
Richards, Von

Committee Member(s)

Ma, Yinfa
Reddy, Prakash
Winiarz, Jeffrey G.
Chandrashekhara, K.



Degree Name

Ph. D. in Chemistry


Missouri University of Science and Technology

Publication Date

Fall 2014

Journal article titles appearing in thesis/dissertation

  • Enhancement of lipophilic dye fluorescence in microalgae with heating or diluted acid treatment
  • Oil-in-water microemulsions as calibration standards for lipophilic dye-based determination of microalgal neutral lipids content
  • Thermal decomposition studies of EPS, polyurethane foam, and epoxy resin (SLA) as patterns for investment casting
  • Thermal degradation kinetics of epoxy stereolithography pattern for investment casting process
  • Foam pattern aging and its effect on crack formation in investment casting ceramic shells


xii, 140 pages

Note about bibliography

Includes bibliographical references.


© 2014 Hongfang Zhao, All rights reserved.

Document Type

Dissertation - Open Access

File Type




Subject Headings

Precision casting -- Thermal properties
Shell molding (Founding)
Strength of materials

Thesis Number

T 10628

Electronic OCLC #


Included in

Chemistry Commons