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Sythesis of mesoporous phosphates via solid state reaction at low temperatureLiu, Qi 25 August 2010 (has links)
Indiana University-Purdue University Indianapolis (IUPUI) / Three parts consist of my thesis work centered on the synthesis of inorganic
phosphates and then metal organic frame work (MOF). The first part is the synthesis of mesoporous chromium phosphates using the room temperature solid state reaction (SSR)approach. One of the major aims of this work is to fill the gap of lacking a low cost, low
or zero pollution, easy method to synthesize phosphates. The room temperature solid state reaction has been demonstrated in this work is such a method. Mesoporous chromium phosphates were prepared using the solid state reaction at low temperature using CrCl3.6H2O, and NaH2PO4.2H2O as precursors and the surfactant cetyltrimethyl ammonium bromide (CTAB) as template. The synthesized chromium phosphates were characterized by XRD, EDS, HR-TEM, N2-physisorption, TG-DSC and UV-Vis spectroscopies. The results indicate that chromium phosphate mesophases were formed only at atomic ratios of P/Cr ≥ 1.8. The mesophase for P/Cr = 2.0 phosphate possessed the highest ordering of pore array, with a specific surface area as high as 250.78 m2/g and an average pore size of 3.48nm. The catalytic performance of the chromium phosphates was examined by employing a model reaction, namely the dehydration of isopropanol to propene. The results indicated that all synthesized chromium phosphates exhibited
significantly higher isopropanol conversions and propene yields than that synthesized via the conventional precipitation route. The highest propene selectivity (96.43%) at the highest isopropanol conversion (93.10%) has been obtained over the mesoporous chromium phosphate catalyst synthesized with a P/Cr atomic ratio of 2.0. The formation
mechanism of the mesoporous chromium phosphate was investigated by FTIR technique.The results show that CTAB template plays a key role in the formation of mesoporous chromium phosphates.
Mesoporous lithium manganese phosphates were also successfully synthesized
using the same approach of solid state reaction (SSR) at low temperature by using LiC2O3.6H2O, MnCl2.6H2O and NH4H2PO4.2H2O as precursors and the surfactant cetyltrimethyl ammonium bromide (CTAB) as template. The synthesized lithium manganese phosphates were characterized by XRD, EDS, SEM, HR-TEM, N2-physisorption. The results show that the synthesized meoporous lithium manganese phosphates exhibited a high specific surface area (256.63 m2/g) and a narrow pore size distribution. The electrochemical tests of Li-ion batteries were performed and the results
show that the charge voltage could increase to be 3.60 V while the first time discharge capacity could be as high as 100 mAh/g.
The Nitro-Cu-MOF complexes, a new class of metal organic frameworks, have
been successfully synthesized using a conventional thermal reaction. The obtained Nitro-Cu-MOFs have a specific surface area of 576.27 m2/g and a pore volume of 0.32 m3/g.The gas uptake of the obtained Nitro-Cu-MOFs at 60 psi is 68 mg/g (sorbate/sorbent) at 298 K for carbon dioxide, which is much higher than that of the Cu-MOFs, 31 mg/g at
298 K for carbon dioxide.
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Surface studies of potentially corrosion resistant thin film coatings on chromium and type 316L stainless steelJohnson, Stephanie Lee January 1900 (has links)
Doctor of Philosophy / Department of Chemistry / Peter M. Sherwood / This work is a detailed study of the interaction between two phosphorous-containing acids and the metals chromium and 316L stainless steel. The objective of this work is to investigate the formation of unique thin films on the two metals and to probe the surface chemistry of these films through the use of core level and valence band X-ray photoelectron spectroscopy (XPS).
Chromium forms a wide array of oxides and can exist at several valencies. Valence band XPS is used in conjunction with band structure and multiple scattered wave X[alpha] calculations to distinguish which states are present in the resultant films. Both 99.99% chromium and 316L stainless steel foils were treated with orthophosphoric acid and 1-hydroxyethylidene-1,1-diphosphonic acid, otherwise known as etidronic acid. Two methods developed in the Sherwood research laboratory for forming oxide-free films on metal surfaces are utilized in this work.
Core level XPS results did not provide sufficient information to draw conclusions regarding the products formed in the reactions. The valence band results showed clear evidence of multiple forms of phosphates forming on the metal surfaces as evidenced by the subtle differences in separation between the phosphorous 3p and 3s peaks as well as differences in separation between the O2s and phosphorous 3s peaks. The Valence Band XPS results were interpreted by X-[alpha] cluster and band structure calculations.
Films formed on chromium foil from the orthophosphoric acid were found to be condensed phosphates that are stable in air. Etidronic acid formed very thin phosphate films on chromium with both treatment methods as well as on 316L stainless steel when the bench top method was applied. Treatment of etched 316L steel in the anaerobic cell generated an etidronate film. This sample was the only etidronate film formed, all other etidronate-based films were generated from disassembled portions of the etidronate ion to form phosphate films.
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