Design and fabrication of advanced materials from Illinois coal wastes. Quarterly report, 1 March 1995--31 May 1995 Page: 2 of 24
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This project seeks to make use of an advanced, integrated approach for the design and
fabrication of brake and structural composite materials from coal combustion residues and
coal gasification by-products. The composite materials, which will use significant amounts
of combustion residues (20 to 50 wt %) and coal chars (10 to 30 wt %), not only will
alleviate the disposal costs and the potential environmental damage costs associated with
residues but will also convert residues into high value structural composite materials.
In the first three quarters of this project, we have probed the structural and thermal
behaviors of coal combustion residues and scrubber sludge which form the raw materials
for our brake shoe pads and structural composites. In addition, we have explored and
established protocols for the fabrication of brake composites. This was achieved by
fabricating 2.5 inch (diameter) X 1 inch (thick) disks from PCC fly ash, scrubber sludge,
and FBC spent bed ash. To characterize PCC fly ash, FBC fly ash (ADM, unitl-6), FBC
spent bed ash (ADM, unitl-6), FBC fly ash (S.I. Coal), bottom ash, and scrubber sludge
(CWLP), we undertook differential scanning calorimetry (DSC) measurements at 30*C <
T < 600*C and differential thermal analysis (DTA) at 500C < T < 1100 C. Moreover, we
subjected the residues to SEM and transmission-FTIR analyses. Based on these
characterization data the following was concluded: (a) The PCC fly ash particles are
spherical in shape and range from 0.2 pm to 15 pm. Because of their shape and since the
particles are thermally inert up to 1100*C, the PCC fly ash is an excellent raw material for
our brake and structural composite materials. The PCC fly ash is largely composed of
oxides including hematite and magnetite. The presence of these two microwave lossy
components makes sintering of materials containing PCC fly ash via microwave heating
possible. (b) The scrubber sludge particles, in general, have a shape which is whisker-like,
thus imparting it with fiber-like characteristics. Our FTIR analysis of the scrubber sludge
sample revealed that CWLP sludge does not contain calcite, hannebachite
(CaSO3.0.5H20), or bassanite. Our analysis also showed that sludge is mainly composed
of gypsum (CaSO4.2H20). However, it must be cautioned that the sludge's gypsum lattice
structure is different from the conventional gypsum lattice structure. Therefore, the
scrubber sludge particles may not display the physical and chemical properties of
conventional gypsum. Also, our DSC and DTA data suggested that before scrubber
sludge particles can be used they must be heated to 200*C to evolve out the water
associated with sludge. At 200*C < T < 10000C, our DSC and DTA data indicated the
dehydrated gypsum is thermally stable, thus. very suitable for our composites. Therefore,
the presence of scrubber sludge particles in our composites will provide mechanical
strength to our materials. (c) The FBC fly ash and FBC spent bed bottom ash particles
showed a considerable amount of fusion resulting in larger sized particles, i.e., 100 pm to
750 pm. The transmission-FTIR data on the two FBC fly ashes examined lead us to
believe that the main constituents of FBC fly ash are anhydrite, lime, portlandite, calcite,
hematite, magnetite, and various glass phases. The FBC spent bed ash is largely
composed of anhydrite, lime, portlandite, calcite, periclase, hematite, and magnetite. The
thermal stability characteristics of FBC fly ash and FBC spent bed ash, as, determined by'
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Malhotra, V.M. & Wright, M.A. Design and fabrication of advanced materials from Illinois coal wastes. Quarterly report, 1 March 1995--31 May 1995, report, December 31, 1995; United States. (digital.library.unt.edu/ark:/67531/metadc667748/m1/2/: accessed September 25, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.