An electrostatic filter containing powdered activated carbon (PAC) can retain high levels of microbes while the PAC within the structure has a high dynamic response as a chemical absorber. In water, a 2.5 '' diameter, 10 '' long pleated cartridge (without PAC) retained greater than 6 LRV (log retention value) of bacteria and >3 LRV of MS2 virus at flowrate of 1 gallon per minute (GPM). This study provides background data on the precursor filter, which uses a highly electropositive 2 rim alumina monohydrate fiber in a 2 mu m pore size media. Sub-micron particles are retained primarily by electrostatic forces. Data compare the PAC version to the precursor. The PAC filter has a higher retention of virus, and at least an equivalent retention of bacteria and fine (similar to 9 mu m) test dust. Data are shown for adsorption of dissolved iodine and chlorine by the PAC media under short (similar to 0.3 second) residence times, as compared to commercialized thin layer media containing granular activated carbon (GAC). The new PAC media has a dynamic adsorption rate at least two orders of magnitude greater than GAC media. The PAC media shows high promise as a chem-bio filter for purifying water. Preliminary data on air filter media are also presented.

A nano-aluminum-oxide fiber of only 2 nanometers in diameter was used to develop a ceramic-fiber filter. The fibers are electropositive and, when formulated into a filter material (NanoCeram(TradeMark)), would attract electro-negative particles such as bacteria and viruses. The ability to detect and then remove viruses as well as bacteria is of concern in space cabins since they may be carried onboard by space crews. Moreover, an improved filter was desired that would polish the effluent from condensed moisture and wastewater, producing potable drinking water. A laboratory- size filter was developed that was capable of removing greater than 99.9999 percent of bacteria and virus. Such a removal was achieved at flow rates hundreds of times greater than those through ultraporous membranes that remove particles by sieving. Because the pore size of the new filter was rather large as compared to ultraporous membranes, it was found to be more resistant to clogging. Additionally, a full-size cartridge is being developed that is capable of serving a full space crew. During this ongoing effort, research demonstrated that the filter media was a very efficient adsorbent for DNA (deoxyribonucleic acid), RNA (ribonucleic acid), and endotoxins. Since the adsorption is based on the charge of the macromolecules, there is also a potential for separating proteins and other particulates on the basis of their charge differences. The separation of specific proteins is a major new thrust of biotechnology. The principal application of NanoCeram filters is based on their ability to remove viruses from water. The removal of more than 99.9999 percent of viruses was achieved by a NanoCeram polishing filter added to the effluent of an existing filtration device. NanoCeram is commercially available in laboratory-size filter discs and in the form of a syringe filter. The unique characteristic of the filter can be demonstrated by its ability to remove particulate dyes such as Metanyl yellow. Its particle size is only 2 nanometers, about the size of a DNA molecule, yet the NanoCeram syringe filter is capable of retaining the dyes as the fluid is passed through the syringe, without much back-pressure. Endotoxins, which are contaminants that are part of the residue of destroyed bacteria, can cause toxic shock and are therefore of major concern in pharmaceutical products. The NanoCeram syringe filter is capable of removing greater than 99.96 percent of the endotoxins.

Alumina is a material that has been used in both dental and orthopedic applications. It is with these uses in mind that osteoblast (bone-forming cell) function on alumina of varying particulate size, chemistry, and phase was tested in order to determine what formulation might be the most beneficial for bone regeneration. Specifically, in vitro osteoblast adhesion, proliferation, intracellular alkaline phosphatase activity, and calcium deposition was observed on delta-phase nanospherical, alpha-phase conventional spherical, and boehmite nanofiber alumina. Results showed for the first time increased osteoblast functions on the nanofiber alumina. Specifically, a 16% increase in osteoblast adhesion over nanophase spherical alumina and a 97% increase over conventional spherical alumina were found for nanofiber alumina after 2 h. A 29% increase in cell number after 5 days and up to a 57% greater amount of calcium was found on the surface of the nanofiber alumina compared with other alumina surfaces. Some of the possible explanations for such enhanced osteoblast behavior on nanofiber alumina may be attributed to chemistry, crystalline phase, and topography. Increased osteoblast function on nanofiber alumina suggests that it may be an ideal material for use in orthopedic and dental applications.

Nanoscale copper powder has been produced using such an energetic method as the electric explosion of metallic wire (“EEW” process) in an inert gas. The crystalline structure of nanoparticles has been characterized by HRTEM and particle size distribution has been measured. The nanopowder has been added to motor oil and friction coefficient measured to compare with that of pure oil. SEM characterization of the worn surfaces and X-ray microanalysis have been performed to reveal both changes in topology of the worn surfaces and traces of copper.

Aluminum is a highly energetic metal that can react with a wide variety of oxidizers to produce propellants with high specific impulse. When added to kerosene rocket fuel aluminum substantially increases theoretical volumetric density Isp, potentially reducing the size of tankage and overall system weight. However, aluminum tends to agglomerate in burning liquid hydrocarbon droplets delaying combustion within the engine, reducing delivered performance. Gels were formulated of 0, 25, 30 and 55 weight percent Alex((R)) nano aluminum powder in RP-1 (kerosene) using a combination of wetting and gelling agents. The viscosity of such gels was measured as a function of aluminum content, temperature and shear rate and were found to be non-Newtonian, so called yield pseudoplastic. At loadings greater than 30 weight percent Alex((R)) no foreign gellant is necessary to achieve dynamic stability as measured by centrifuging the gels at 1300 rpm for one hour. In contrast, micron size aluminum gels required 5% fumed silica as a gellant to achieve dynamic stability, as did the gels containing 5% Alex((R)). Ignition delay of Alex((R))/RP-1 gels were determined in a laboratory bomb over the temperature range 400-600degreesT and compared to RP-1 gels without any aluminum and to neat RP-1. The data show that nano aluminum could be completely consumed during the interval of spraying in a short laboratory bomb. Moreover, the combustion of Alex((R)) accelerated the ignition of the RP-1.

Combustion tests of gaseous oxygen atomized sprays of gelled RP-1 propellant with ultra-fine aluminum powder (Alex((R)) powder) were performed in a rocket engine. The addition of aluminum particles to gelled RP-1 propellant has the potential to significantly increase the heat of reaction over RP-1 alone due to the high volumetric energy release of the aluminum, Previous studies of gelled RP-1 propellant with aluminum have yielded low combustion efficiencies. This may have been the result of incomplete combustion due to the aluminum particles being too large. Alex((R)) particles with an average size of 100 rim are formed by exploding aluminum wires. The use of these nano-sized particles can, theoretically, lead to more complete combustion, and thus, lead to performance increases such as higher flame temperature, increased specific impulse, and greater c* combustion efficiency. The gel propellants were introduced through a coaxial injector and gaseous oxygen was used to atomize the gel. The engine operating conditions were as follows: chamber pressures ranging from 1-2.8 MPa (150-400 psia), gel propellant mass flow rates ranging from 8-40 g/s, gaseous oxygen mass flow rates ranging from 14-27 g/s, and O/F ratios ranging from 0.5-3.1. The percentage of Alex((R)) particles in the gelled RP-1 propellant ranged from 0-55% by weight. The c* combustion efficiency was found to range from 70-99%. Test results indicate that the addition of Alex((R)) particles to gelled RP-1 propellant increases not only the density specific impulse, but also the c* combustion efficiency over gelled non-aluminized RP-1 propellant. Results show that among the three formulations, the 5-wt% Alex gel appears to be the best in terms of range of c* efficiencies and the least data scatter.

Spray combustion tests of gaseous oxygen atomized sprays of RP-1 gel propellants with ultra-fine aluminum particles were performed in a rocket engine. The addition of aluminum particles to RP-1 gel propellants has the potential to significantly increase the heat of reaction over neat RP-1 due to the high volumetric energy release of the aluminum. Alex® powders, which have an average particle size of 100 nanometers, are formed by exploding aluminum wires. The use of these nano-sized particles can, theoretically, lead to more complete combustion, and thus, lead to performance increases such as higher flame temperature, increased specific impulse, and greater c* combustion efficiency. The engine operating conditions were as follows: chamber pressures ranging from 1-2.8 MPa (150-400 psia); gel propellant mass flow rates ranging from 8-40 g/s; gaseous oxygen mass flow rates ranging from 14-60 g/s; and oxygen-tofuel (O/F) ratios ranging from 0.5-5.0. The percentage of Alex® particles in the RP-1 gel propellants ranged from 0-55% by weight. The c* combustion efficiency was found to range from 60-99%. Results show that among the formulations, the RP-1 gel propellant with 5% of Alex® powders by weight appears to be the best in terms of range of c* efficiencies and the least amount of data scatter.

Exciting new applications are being discovered for nanosized materials that are produced by the electroexplosion of wire.

Metallic nanopowders can be produced by applying a high power electrical pulse to a wire while in argon. the electromagnetic field created by the pulse confines the plasma until the vapor pressure of the metal exceeds the ability of the field to contain it and an explosion occurs, creating metallic clusters of spherical particles. Rapid adiabatic quenching creates defects in the particles and they behave as if they are extensively worked, with a lowering of recrystallization temperature and the release of energy when the powders reach a threshold temperature substantially below melting. The powders are highly reactive and some are pyrophoric. Applications include their use in propellants, explosives and pyrotechnics, as chemical reactants for organic synthesis, as catalysts, as conductors in microelectronics and as a sintering aid. Kilogram quantities of the following metals have been fabricated by this technique: nickel, iron, tungsten, tin, aluminum, copper, zinc, titanium, silver and indium.

Aluminum powder is an important ingredient in many propellant, explosives and pyrotechnic applications. The production of nanosized aluminum powder by the electroexplosion of metal wire has been practices in the former USSR since the mid 1970`s. Differential scanning calorimetry, differential thermal analysis and x-ray phase analysis was performed on aluminum powder both before and after air passivation, as well as aluminum that was protected under kerosene, pentane, toluene and hexane. Earlier Soviet reports of unexplained thermal releases and metastable behavior have been investigated. Anomalous behavior previously reported included phase transformations at temperatures far below melting with the release of heat and chemoluminescence and self sintering of particles with a heat release large enough to melt the powders.

Metal powders produced by the electroexplosion of metal wire are generally about 0.1micron average particle size and have metastable crystals with considerable defects. Their reactivity with oxidizers is very rapid and provides opportunities for new propellants, pyrotechnics and explosive formulations. Aluminum metal produced by this mode has been studied in Russia as a fuel in both solid and gelled propellants. Several papers have now been published confirming very rapid burning rates with this aluminum (Alex) in solid propellants. Calculated burning rates and microcinematography have indicated that such aluminum particles are completely converted to oxide at the solid/gas interface and no burning aluminum is seen in the plume. The computed life of a burning particle, which is about 40-70 nanoseconds, suggests the use of this nano aluminum as an additive for increasing the energy of very fast reactions such as detonations. Alex in water gels when ignited produces hydrogen at 2800 C, suggesting its use as a storable monopropellant. Studies are also underway to form stable gels of Alex in kerosene and study their combustion. We hope to produce a gel that would avoid the problem that coarser aluminum has of agglomeration and inefficient combustion.

A cartridge depth filter that utilizes nano alumina electropositive non-woven media was characterized for flow rate, dirt holding capacity as well as filtration efficiency for virus and bacteria. The pore size of the media is 2 microns. Sub-micron particles are primarily retained by electroadhesive forces. A dual layer version of the filter was found to retain >6 LRV of MS2 and >7.5 LRV of E coli at a face velocity of 5 cm/min. Another version of the nano alumina filter containing powdered activated carbon (PAC) and with a pore size of 3 microns had similar particle retention to the nanoalumina filter. The filter media was tested versus several other electropositive charged depth media and membranes that are commercially available. When challenged with A2 fine test dust at 100 and 250 NTU, the nano alumina as well as the PAC filter was capable of reducing turbidity to less than 0.01 NTU (beta efficiency >25,000) until reaching a specified terminal pressure drop of 30 psi. One of the competitive filters was found to leak substantial amounts of test dust. Despite the fact that the nano alumina filter depends upon ion attraction, its adsorption efficiency for virus and test dust is minimally affected by pH over the range of 4.5 to 9.5 or when in the presence of high salinity (30 g/L). When tested against an electropositive membrane (0.2 micron pore rating) a single layer of the nano alumina had a virus capacity several times greater than the membrane. The more highly efficient two layer nano alumina had a flowrate that was substantially greater than the membranes or those depth media's with pore sizes less than 1 micron. The dual layer nano alumina filter is very efficient at retaining a wide spectrum of particles, from micron to nanometer size and does so at minimal pressure drop and with significant dirt holding capacity. It is suggested as a drop in replacement for lenticular filters that are widely used in manufacture of pharmaceuticals, cosmetics, medical devices, food and drink and specialty chemicals. Manufacturers of other depth (lenticular) filters offer as many as nine different pore size ratings. The nano alumina avoids the uncertainty in selecting one pore size over another because of its ability to cover a very wide spectrum of applications. Other versions of nano alumina are configured to allow the use of conventional housings providing the user with a choice rather than being committed to a customized housing with its proprietary cartridge. The dual layer nano alumina filters are also proposed for use as point of entry (POE) or point of use (POU) applications.