The purpose of this investigation was to study the possibility of using, as electrolyte for the deposition of aluminum, systems containing aluminum phosphate dissolved in fused borate and phosphate mixtures. Aluminum coated metals combine the mechanical properties of the base metal and chemical resistance of aluminum. Electroplating, gives an even and controlled thickness of coating and imparts corrosion resistance. Methods for the deposition of aluminum previously investigated have not been used commercially, to any extent. Electrodeposition of aluminum was attempted, most frequently from nonaqueous organic solutions and from fused mixtures. Aluminum halides, especially aluminum chloride, was the solutes most frequently used. It is known that aluminum oxide is peptized by aluminum chloride. Severe corrosion is expected on articles electroplated in the presence of aluminum chloride. In the present investigation, the use of aluminum halides was avoided. Aluminum phosphate was employed in the system 5Na₂O.10Li₂O.6B₂O₃ as well as in the eutectic mixture of sodium metaphosphate and sodium pyrophosphate. ln none of the investigations was an electrodeposit of aluminum obtained. Investigation of the borates-phosphate mixtures comprised determination of a "fluid range"-composition diagram of the sodium oxide-lithium oxide-boric oxide system. The "fluid range" is a temperature range from an upper value at which, on cooling, liquid becomes viscous, to a lower value at which the solid first appears. These data were plotted on composition diagram which appears as a limiting composition curve and two isothermal, fluid range-composition curves at 600 and at 660 °C. The limiting composition is expressed as the minimum content of the boric oxide which will eliminate all carbon dioxide from the boric acid and alkali carbonates mixture. The area encircled between the 660 °c, upper fluid range and the limiting composition curve is a composition region in which electrodeposition of solid aluminum may be possible. In this region, a mixture of the composition 5Na₂O.10Li₂O.6B₂O₃ was taken as the solvent for the aluminum phosphate, and the fluid range-composition curve of this mixture was determined. It was found that the addition of aluminum phosphate to the molten 5Na₂O.10Li₂O.6B₂O₃ has little effect on the fluid range up to 18.68 per cent by weight of aluminum phosphate. Because the fused electrolyte is very corrosive, its action on different containers was studied. These containers included those made of porcelain, nickel, ampco metal, armco iron, plumbago, graphite and platinum. Except for the graphite and the platinum, no material was suitable for use as a container. No aluminum was electrodeposited from the molten bath of 5Na₂O.10Li₂O.6B₂O₃ or from its solution with aluminum phosphate. Both aluminum anode and platinum cathode were covered with black deposits after electrolysis. The deposits were studied by chemical methods, spectrographical analysis and X-ray analysis. Final results showed that they consisted primarily of carbon. A search for the source of this carbon, formed in the electrodeposition, indicated that it came from the carbon dioxide absorbed from the air by the fused electrolyte. A mechanism for the reaction was proposed. Electrochemical properties of the electrolyte 5Na₂O.10Li₂O.6B₂O₃ as well as those of its solution with aluminum phosphate were studied. Both the molten 5Na₂O.10Li₂O.6B₂O₃ and the molten mixture of 9.4 per cent of aluminum phosphate and 90.6 per cent of 5Na₂O.10Li₂O.6B₂O₃ showed no decomposition potential on electrolyzing with aluminum anode and platinum cathode. If platinum electrodes were used for borates-phosphate system, the current was constant when stirred, when moisture was added, and when the electrodes were immersed periodically. The decomposition potential determined for the borates-phosphate system with platinum electrodes was about 1.40 volts, at 600 ± 10 °C. Qualitative electrodeposition tests showed that no aluminum could be deposited from either electrolyte. Quantitative electrodeposition test with the molten 5Na₂O.10Li₂O.6B₂O₃ showed that the weight loss of the aluminum anode consisted of both electrolytic loss and direct chemical attack. Also, a eutectic mixture of the sodium metaphosphate and sodium pyrophosphate was used as the solvent to dissolve aluminum phosphate for electrolysis. The molten mixture had a strong oxidizing power, the aluminum anode became passive, and a strong anode effect was observed, if an aluminum anode was used. Black coatings were formed on the copper cathode with either an aluminum anode, or an anode of an alloy of 75 per cent of aluminum and 25 per cent of copper, or a platinum anode. The black coating on the copper cathode was found by chemical analysis to be a copper compound. / Ph. D.

The purpose of this investigation was to study fundamentally the difference in structure of aluminum phosphates synthesized in various mediums. / Master of Science

Indiana University-Purdue University Indianapolis (IUPUI) / Several studies have found that resin-based amorphous calcium phosphate (ACP) composites can function well for applications that do not require high mechanical demand. Milled tricalcium phosphate (TCP), a new calcium-phosphate-releasing material, is crystalline in nature, suggesting it to be strong. In the present study, we investigated the use of a TCP-filled composite resin as a possible tooth restorative-material. An experimental TCP-based composite was prepared using monomer with a mixture of 34.3 percent by mass of EBPADMA, 34.2 percent by mass of HmDMA, and 30.5 percent by mass of HEMA. TCP fillers were added to the monomer mixture at different levels (30 percent, 40 percent, 50 percent, and 60 percent by weight). A universal testing machine (Sintech Renew 1121; Instron Engineering Corp., Canton, MA) was used to measure the compressive strength and modulus. FTIR was used to measure the degree of conversion. The depth of cure was determined according to the ISO standards for dental resin 4049 using the scrapping technique. Knoop hardness numbers were obtained by a microhardness tester (M-400; Leco Co., St. Joseph, MI). The viscosities of the experimental resin were determined in a viscometer (DV-II+ Viscometer; Brookfield, Middleboro, MA). The data were analyzed using a one-way analysis of variance (ANOVA). A 5-percent significance level was used for all the tests. Resin composites with 30-percent TCP filler showed the highest compressive strength and hardness values. Also, this group showed the lowest degree of conversion. Resin composites with 60-percent TCP filler showed the highest degree of conversion. However, this group showed the lowest compressive strength, depth of cure, and hardness. Resin composites with 50-percent filler showed the highest compressive modulus. Resin composites with 40-percent filler showed higher viscosity values than resin composites with 30-percent filler. In conclusion, increasing the filler level significantly reduced the compressive strength, hardness, and depth of cure, but increased the degree of conversion. Also, resin composites with the lowest filler level (30 percent) had the highest compressive strength, depth of cure, and hardness. From these results, it can be concluded that the experimental TCP-filled resin used in this study cannot be used as restorative material.

Indiana University-Purdue University Indianapolis (IUPUI) / Calcium phosphate-filled restorative materials were developed to provide calcium (Ca) and phosphate (PO4) ions, which have been proposed to enhance remineralization of demineralized tooth structure. Recently, tricalcium phosphate (TCP)-filled restorative materials were introduced as an alternative to amorphous calcium phosphate. The TCP filler has a more crystalline structure than ACP and is therefore potentially stronger. The aim of the present study was to examine TCP-filled restorative resins at different concentration levels at different time intervals to characterize the concentrations of Ca and PO4 ions released, and to measure the water sorption (WS) of these resins. An in vitro study was conducted by formulating resin composite using TCP as the filler mixed with EBPADMA, HmDMA, and HEMA as the resin matrix. One-hundred- sixty samples were prepared, 40 samples of each filler concentration (30 percent, 40 percent, 50 percent, and 60 percent) by weight. From each filler concentration, 5 samples of each of the 8 time points (time intervals of 4 h, 8 h, 12 h, 24 h, 3 d, 7 d, 14 d, and 21 d) were immersed in 100-ml deionized water. Calcium and PO4 ions were measured using atomic absorption spectroscopy and light spectroscopy, respectively. Water sorption (WS) was measured according to ISO 4049 specification and then the WS and the diffusion coefficient were calculated. The significance level was set at p = 0.001. The results indicated that Ca and PO4 ion release increased with increasing filler level at a rate faster than being linear. In addition, WS results were very high and failed to meet the ISO 4049 specification requirement. Diffusion coefficient results were also high. One-way ANOVA test for only 21-day data revealed that there is a statistically significant difference in filler level percent, and two-way ANOVA testing revealed that there is a statistically significant interaction between time and filler level percent on the Ca, PO4 released and WS. It can be concluded that the concentrations of Ca and PO4 released and WS were affected by composition of the monomers, filler level and type, dispersion, and the absence of coupling agent. Although this TCP-filled restorative material may release Ca and PO4, it cannot serve as a restorative material due to high WS values. Further study is needed to improve the material and evaluate its ability in promoting remineralization of the tooth structure in order for it to serve its purpose.