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# Andrew Allen <andrew.allen@nist.gov>
# requesting 3 days, at minimum=3 days
# beamline 33ID, "Agglomeration of Nanoparticles"
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# top:/home/www/beamtime-requests/req00280.txt
# UNICAT Member Beam Time Request  #280
# created Thu Aug 22 11:41:20 CDT 2002
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beamline:
	33ID

collaboration:
	Yes

collaborator+Pete:
	on

contact:
	andrew.allen@nist.gov

days:
	3

description:
	We propose to continue our previously initiated work on examining the efficacy of different dispersing agents used to disperse sub-micron and nanoparticles. It was observed in a previous experiment that at relatively high concentrations, certain dispersing agents exhibited a local structure. The influence of this structure on powder size will be further examined. The efficiency of sodium hexametaphosphate in dispersing sub-micron TiO2 powders will be examined, and compared to that of other dispersing agents. Results from USAXS analysis will be compared with equivalent zeta potential measurements of these dispersing agents. Experiments will also be conducted to evaluate the difference between the crystallite size and the particle size of selected CeO2 powders to be certified as Standard Reference Materials for X-ray powder diffracton intensity characterization.
	            Subject to availability of the BIO-CAT flow cell, experiments will be conducted on sub-micron and nano-sized SiO2 and TiO2 dispersed in suspensions with varying pH values. These pH values will be representative of the state of dispersion near and away from the iso-electric point, and thus, induce varying degrees of agglomeration in the particles. Attempting to study these systems in a conventional cell is complicated due to the settling of the particles. It is anticipated that flowing the dispersions in the fluid cell during analysis, will enable  such hurdles to be overcome.
	    If the flow cell is not available we will substute an equivalent number of time-dependent measurements on TiO2  suspensions  in a conventional cell to study the dynamics of settling where the settling time appears (from light scattering measurements) to depend on the dispersant conditions.

equipment+required:
	Standard USAXS mode with liquid cells.

experiment:
	Agglomeration of Nanoparticles

foreign+nationals:
	Andrew Allen, British
	Ajit Jilla, Indian
	{BOTH ARE REPEAT VISITS}

hazards:
	No Hazards.

minimumdays:
	3

name:
	Andrew Allen

new+request:
	on

nonmembers:
	Possibly Tom Irvine et al. if BIO-CAT liquid cell used.

unacceptable+dates:
	October 9, November 4 - 8, December 1 - 5
	
	{preferred dates after Dec 5 if possible}


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