MICROSCOPIC AND SURFACE ORGANIC CHEMICAL CHARACTERIZATION OF COMBUSTION-GENERATED PARTICLES

FLYASH IS ONE OF THE MOST COMMON FORMS OF ENVIRONMENTAL POLLUTION. BECAUSE OF SMALL PARTICLE SIZE, DIRECT MEASUREMENTS OF INDIVIDUAL PARTICLES HAVE BEEN RESTRICTED TO MORPHOLOGY AND ELEMENTAL COMPOSITION. ORGANIC ANALYSIS HAS BEEN ACCOMPLISHED MOSTLY BY SOLVENT EXTRACTION, THEREBY FORCING RELIANCE ON THE EFFICACY OF THE EXTRACTION CHEMISTRYTO ENSURE APPROPRIATE ANALYTICAL SIGNALS. THUS, IN THE REALM OF ORGANIC ANALYSIS, CONCLUSIONS ARE USUALLY INFERRED,AND RESULTS CAN BE AMBIGUOUS. CURRENTLY, NO ESTABLISHED TECHNIQUE EXISTS FOR THE DIRECT ANALYSIS OF ORGANIC SPECIES ON INDIVIDUAL FLYASH PARTICLES. A NEW TIME-OF-FLIGHT SECONDARY ION MASS SPECTROMETER (TOF-SIMS) HAS RECENTLY BEENBUILT WITH THE POTENTIAL FOR FILLING THIS VOID. A SAMPLE ISBOMBARDED IN VACUUM BY A PULSED BEAM OF PRIMARY IONS AT VERYLOW FLUX DENSITY SO AS TO EJECT SECONDARY IONS NOMINALLY FROM THE OUTER MONOLAYER OF A SOLID SAMPLE. CHEMICAL INTEGRITY IS PRESERVED BY THE SMALL NUMBER OF PRIMARY ION IMPACTS PER UNIT OF SAMPLE AREA. TOF-SIMS ENABLES ALL SECONDARY ION MASSES TO BE DETECTED, PROVIDING THE MOST EFFICIENT USE OF "CONSUMED" SAMPLE MATERIAL. BECAUSE MASSESCAN BE RECORDED UP TO THOUSANDS OF ATOMIC MASS UNITS AND THESECONDARY ION SPUTTERING PROCESS CAN REMOVE WHOLE MOLECULAR CLUSTERS, TOF-SIMS HAS THE POTENTIAL FOR ELEMENTAL, ISOTOPIC, CHEMICAL COMPOUND, AND ORGANIC MICROANALYSIS. SINGLE ION COUNTING YIELDS EXCELLENT DETECTION SENSITIVITY, AND INDIVIDUAL PARTICLES CAN BE ANALYZED USING EITHER A FINELY FOCUSSED PRIMARY ION BEAM (ION MICROPROBE) OR STIGMATIC SECONDARY ION OPTICS (ION MICROSCOPE) IN THE SAME INSTRUMENT. IN COLLABORATION WITH THE UNIVERSITY OF NORTH CAROLINA, THIS PROJECT ASSESES THE UTILITY OF TOF-SIMS FOR FLYASH CHARACTERIZATION USING MODEL CHEMICAL SYSTEMS, CONTROLLED EXPERIMENTAL DESIGN, AND COMPARATIVE ANALYTICAL PROTOCOLS. PHASE I FOCUSES ON THE FEASIBILITY OF THE APPROACH AND IDENTIFICATION OF THOSE AREAS REQUIRING MORE DETAILED STUDY SUITABLE TO A PHASE II PROGRAM.