Examples of our past work
CLIENT: Cannot reveal due to a confidentiality agreement.
PROJECT: A major manufacturer of fire suppression systems was contacted by one of its customers that reported a greasy residue on an installed fire suppression system in a restaurant kitchen. The customer was concerned that the nozzles were inoperative and that the system would fail and not respond when the extinguishing media (proprietary potassium salts of organic acids) was called. The customer proffered that the fire extinguishing media was "leaking" from the nozzles. Analysis of the material was necessary in determining its source and in the preparation of a procedure to clean and maintain the system.
ANALYSIS: Joseph E. Sabol was called to apply his expertise in chemical analysis to the project. The residue was analyzed by Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). FTIR reveals the presence of various molecular bond types, e.g., carbon-carbon, carbon-hydrogen, etc., which are necessary in determining the molecular structure of the specimen. SEM reveals a magnified image of the specimen and its elemental composition.
RESULTS: The FTIR spectrum of the residue revealed a molecular structure that was essentially identical to corn oil that was mixed with partially burned oils (carbon-carbon double bonds) and burned protein (amide bonds.) The FTIR spectrum of the residue showed no similarity to the FTIR spectra the proprietary fire extinguishing materials. SEM of the residue revealed an elemental composition that was consistent with burnt corn oil and protein, but no potassium. SEM of the proprietary potassium salts confirmed their composition.
CONCLUSION: The residue did not have the chemical features of the proprietary fire extinguishing materials and it was unlikely that the residue originated from the fire extinguishing materials. The residue did have the chemical features of burned corn oil and protein and likely was from cooking ingredients that accumulated and burned on the fire suppression system nozzles.
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CLIENT: Cannot reveal due to a confidentiality agreement.
PROJECT: A major manufacturer of silicon semiconductor wafer processing equipment wanted to improve the particle removal efficiency of its equipment and processes and reduce raw material (cleaning bath chemicals) costs through a better understand the chemical activity of the cleaning bath solutions. Removal of particles from silicon semiconductor wafers by wet chemical processes generally involves etching of the surface, from undercutting the particles by the cleaning chemicals, and the electrical potentials of the surface and the particles in solution (zeta potential.) The etching of silicon surfaces and the zeta potential are themselves dependent on the concentrations of the species present in solution, the total ionic strength of the solution, and pH of the solution. The client wanted advice on the ionic activity of the etching solutions as a function of the concentrations of hydrofluoric acid (HF), hydrochloric acid (HCl), ammonia (NH3), and water and the pH.
ANALYSIS: Joseph E. Sabol was called to apply his expertise in modeling chemical equilibria of complex mixtures. The cleaning/etching bath is composed of nine distinct chemical species and involves nine independent chemical equilibria, including weak acids and the formation of HF dimers. In addition, the activity coefficients of the ionic species are a function of the total ionic strength, which is a function of the concentrations of the ionic species. Computer programs were written to model the activity (through concentration and activity coefficients of the species) as a function of HF concentration and pH and to produce a guide for experiments on particle removal and cleaning of silicon semiconductor wafers.
RESULTS: When HF solutions have either HCl (to lower the pH) or NH3 (to raise the pH) added, the ionic strength of the resulting solution increases and the particle removal efficiency decreases. The computer models enabled the client to understand how to adjust the pH for a given HF concentration, but not to compromise the particle removal efficiency. Use of lower concentrations of HF is desirable for several reasons.
CONCLUSION: The client gained a better understanding of the nine-component HF/HCL/NH3/water cleaning solution mixture as a function of the raw material concentrations and pH and was able to adjust the cleaning solution to maximize the particle removal efficiency.
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