John N. Hryn

Atomic layer deposition for the conformal coating of nanoporous materials

Atomic layer deposition (ALD) is ideal for applying precise and conformal coatings over nanoporous materials. We have recently used ALD to coat two nanoporous solids: anodic aluminum oxide (AAO) and silica aerogels. AAO possesses hexagonally ordered pores with diameters d ∼ 40nm and pore length L ∼ 70 microns. The AAO membranes were coated by ALD to fabricate catalytic membranes that demonstrate remarkable selectivity in the oxidative dehydrogenation of cyclohexane. Additional AAO membranes coated with ALD Pd films show promise as hydrogen sensors. Silica aerogels have the lowest density and highest surface area of any solid material. Consequently, these materials serve as an excellent substrate to fabricate novel catalytic materials and gas sensors by ALD.

Operating Parameters of Aluminum Electrolysis in a KF-AlF3 BASED Electrolyte

Sustained, stable operation of low-temperature, potassium-cryolite-based aluminum electrolysis in 20 and 100 ampere cells fitted with vertical metal anodes and wetted cathodes was performed. The current efficiency, the amount of consumed alumina, and the amount of aluminum produced during electrolysis were calculated based on the measured amount of oxygen evolved on the anode. The purity of the recovered aluminum was analyzed throughout electrolysis. The cell voltage anomalies caused by the presence of sodium fluoride in the electrolyte were studied using a quasi-reference electrode.

Development in Lost Foam Casting of Magnesium

Preliminary work was conducted in the casting of magnesium using the lost foam casting process. The lost foam or expendable pattern casting (EPC) process is capable of making extremely complicated part shapes at acceptable soundness levels and with low manufacturing costs. Standard test shapes were used to determine the ability of the magnesium to fill the mold and to assess the types of defects encountered. This paper will briefly explain how this project evolved including the developmental strategies formed, the products selected, the casting trials performed, and the casting results.

Initial 1000A Aluminum Electrolysis Testing in Potassium Cryolite-Based Electrolyte

Aluminum electrolysis testing in a 1000A cell at 750°C is described. The cell was fitted with 3 vertically oriented aluminum-bronze anodes and 3 wetted cathodes, maintaining an anode-to-cathode distance of 2.2 cm. The electrodes were immersed in a KF-AlF3 electrolyte with a cryolite ratio of 1.3. Alumina was automatically fed to the cell to maintain a dissolved alumina concentration of 5 wt%, confirmed by analysis. Boron nitride was used as the cell liner material. During electrolysis, the voltage was stable near 4.0 volts at a current density of 0.5 A/cm2. Oxygen gas evolved from the cell was measured with an oxygen sensor. During the 24-hour initial electrolysis test, the anodes were protected by a dense oxide layer.