David V. Fix

Capacitive Deionization of NaCl and NaNO3 Solutions with Carbon Aerogel Electrodes

A process for the capacitive deionization of water with a stack of carbon aerogel electrodes has been developed by Lawrence Livermore National Laboratory. Unlike ion exchange, one of the more conventional deionization processes, no chemicals are required for regeneration of the system. Electricity is used instead. Water with various anions and cations is pumped through the electrochemical cell. After polarization, ions are electrostatically removed from the water and held in the electric double layers formed at the surfaces of electrodes. The water leaving the cell is purified, as desired. The effects of cell voltage and cycling on the electrosorption capacities for NaCl and NaNO 3 have been investigated and are reported here.

Capacitive deionization of NH4ClO4 solutions with carbon aerogel electrodes

A process for the capacitive deionization of water with a stack of carbon aerogel electrodes has been developed by Lawrence Livermore National Laboratory (LLNL). Unlike ion exchange, one of the more conventional deionization processes, no chemicals are required for regeneration of the system. Electricity is used instead. An aqueous solution of NH4ClO4 is pumped through the electrochemical cell. After polarization, NHin4su+and ClOin4su−ions are removed from the water by the imposed electric field and trapped in the extensive cathodic and anodic double layers. This process produces one stream of purified water and a second stream of concentrate. The effects of cell voltage, salt concentration, and cycling on electrosorption capacity have been studied in detail.

The use of capacitive deionization with carbon aerogel electrodes to remove inorganic contaminants from water

The capacitive deionization of water with a stack of carbon aerogel electrodes has been successfully demonstrated for the first time. Unlike ion exchange, one of the more conventional deionization processes, no chemicals were required for regeneration of the system. Electricity was used instead. Water with various anions and cations was pumped through the electrochemical cell. After polarization, ions were electrostatically removed from the water and held in the electric double layers formed at electrode surfaces. The water leaving the cell was purified, as desired.

Capacitive Deionization with Carbon Aerogel Electrodes: Carbonate, Sulfate, and Phosphate

Capacitive deionization with carbon aerogel electrodes is an efficient and economical new process for removing salt and impurities from water. Carbon aerogel is a material that enables the successful purification of water because of its high surface area, optimum pore size, and low electrical resistivity. The electrodes are maintained at a potential difference of about one volt; ions are removed from the water by the imposed electrostatic field and retained on the electrode surface until the polarity is reversed. The capacitive deionization of water with a stack of carbon aerogel electrodes has been successfully demonstrated. The overall process offers advantages when compared to conventional water-purification methods, requiring neither pumps, membranes, distillation columns, nor thermal heaters. Consequently, the overall process is both robust and energy efficient. The current state of technology development, commercialization, and potential applications of this process are reviewed.

Desalination with carbon aerogel electrodes

An electrically regenerated electrosorption process known as carbon aerogel CDI was developed for continuously removing ionic impurities from aqueous streams. A salt solution flows in a channel formed by pairs of parallel carbon aerogel electrodes. Each electrode has a very high BET surface area and very low resistivity. After polarization, anions and cations are removed from electrolyte by the electric field and electrosorbed onto the carbon aerogel. The solution is thus separated into two streams, brine and water. Based on this, carbon aerogel CDI appears to be an energy-efficient alternative to evaporation, electrodialysis, and reverse osmosis. The energy required by this process is about QV/2, plus losses. Estimated energy requirement for sea water desalination is 18-27 Wh gal{sup -1}, depending on cell voltage and flow rate. The requirement for brackish water desalination is less, 1.2-2.5 Wh gal{sup -1} at 1600 ppM. This is assuming that stored electrical energy is reclaimed during regeneration.

Protected silver coatings for flashlamp-pumped Nd: glass amplifiers

A durable protected silver coating was designed and fabricated for possible use on flashlamp reflectors in the National Ignition Facility to avoid tarnishing under corrosive conditions and intense visible light. This coating provides a valuable alternative for mirror coatings where high reflectance and durability are important requirements. This paper describes a protected silver coating having high reflectance from 400 nm to 10,000 nm. The specular reflectance is between 95 percent and 98 percent in the visible region and 98 percent or better in the IR region.

The Long-Term Corrosion Test Facility at the Lawrence Livermore National Laboratory

The long-term corrosion test facility (LTCTF) at the Lawrence Livermore National Laboratory (LLNL) consisted of 22 vessels that housed more than 7,000 corrosion test specimens from carbon steels to highly corrosion resistant materials such Alloy 22 and Ti Grade 7. The specimens from LTCTF range from standard weight-loss coupons to U-bend specimens for testing susceptibility to environmentally assisted cracking. Each vessel contained approximately 1000 liters of concentrated brines at 60 C or 90 C. The LTCTF started its operations in late 1996. The thousands of specimens from the LTCTF were removed in August-September 2006. The specimens are being catalogued and stored for future characterization. Previously removed specimens (e.g. 1 and 5 years) are also archived for further studies.

Properties of titanium-nitride for high-level waste packaging enhancement

A feasibility study of applying titanium-nitride (TiN) coating onto waste package surfaces was performed as part of efforts to enhance the long-term performance of high-level waste packages. The hypothesis examined in the study is that a successful TiN coating would provide an effective mass-transport barrier thus preventing corrosion. In the present work, single-layer TiN and multiple-layer TiN + Ti, TiN + Ti + TiN, and ZrO2 + TiN were deposited on Type 316L stainless steel substrates. The coated samples were tested for corrosion properties in different types of water using polarization and weight loss tests. Results of corrosion testing are presented and discussed.

Characterization of the Corrosion Behavior of Alloy 22 after Five Years Immersion in Multi-ionic Solutions

Alloy 22 (N06022) is the candidate material for the corrosion resistant, outer barrier of the nuclear waste container. Two of the potential corrosion degradation modes of the container are uniform corrosion and localized corrosion. A testing program is under way at the Lawrence Livermore National Laboratory to determine the susceptibility of Alloy 22 to these two forms of corrosion using immersion tests. Metallic coupons are being exposed to several electrolyte solutions simulating concentrated underground water from pH 3 to 10 at 60°C and 90°C. This paper describes the results obtained after more than a five-year exposure of 122 specimens to the testing electrolyte solutions. Results show little general corrosion and the absence of localized corrosion. The maximum general corrosion rate was 23 nm/yr.

Prevention of corrosion of silver reflectors for the National Ignition Facility

A durable protected silver coating was designed and fabricated for possible use on flashlamp reflectors in the National Ignition Facility to avoid tarnishing under corrosive conditions and intense visible light . This coating provides a valuable alternative for mirror coatings where high reflectance and durability are important requirements. This paper describes a protected silver coating having high reflectance from 400 nm to 10,000 nm. The specular reflectance is between 95 percent and 98 percent in the visible region and 98 percent or better in the IR region.