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Two new minerals, levinsonite-(Y) [(Y,Nd,Ce)Al(SO 4 ) 2 (C 2 O 4 ) · 12H 2 O] and zugshunstite-(Ce) [(Ce,Nd,La)Al(SO 4 ) 2 (C 2 O 4 ) · 12H 2 O], occur in an evaporite assemblage at Alum Cave Bluff, Great Smoky Mountains National Park, Tennessee. Electron microprobe analyses with oxalate and water assumed as stoichiometric yield the formula Y 0.33 La 0.02 Ce 0.12 Pr 0.03 Nd 0.23 Sm 0.12 Eu 0.02 Gd 0.08 Dy 0.04 Er 0.01 Al(SO 4 ) 2 (C 2 O 4 ) · 12H 2 O for levinsonite-(Y) and Y 0.00 La 0.09 Ce 0.54 Pr 0.07 Nd 0.26 Sm 0.03 Eu 0.01 Gd 0.01 Dy 0.00 Er 0.00 Al(SO 4 ) 2 (C 2 O 4 ) · 12H 2 O for zugshunstite-(Ce). Smaller ions such as Y and several MREE to HREE are enriched in the former phase, whereas the LREE are concentrated in the latter phase. The two minerals occur in intimate contact, with low-temperature conditions favoring MREE in levinsonite-(Y) and LREE in zugshunstite-(Ce). The crystal structures are based on the same fundamental building blocks, chains of alternating REE polyhedra and oxalate groups, with two sulfate tetrahedra attached to each REE polyhedron. The REE polyhedron in levinsonite-(Y) is a square antiprism defined by eight ligands ( = 2.404 A), whereas that in zugshunstite-(Ce) is a nine-fold cooordinated capped square antiprism ( = 2.507 A). The polyhedra resemble those in xenotime and monazite, respectively. The addition of one ligand in zugshunstite-(Ce) into the capping position results in relative shifts of the chains, isolated water molecules, and isolated Al(H 2 O) 6 octahedra relative to their positions in the levinsonite-(Y) structure. The source of the REE elements is likely to be the weathering of pyritiferous schist, which is reported to contain monazite and xenotime. Chelation of REE and Al by oxalate under hydrous conditions at surface temperature permits formation of the minerals.

This paper reports on screening tests which were conducted on 25 ceramics to evaluate their suitability as insulators in a Downs-type lithium electroreduction cell. Each material was exposed to molten lithium at 400[degrees]C for 100 h. Of the materials tested, beryllia, magnesia, yttria, yttrium aluminum garnet, and aluminum nitride were found to have acceptable compatibility with lithium. It is reasonable to expect that they are also compatible with molten LiCl-KCl electrolyte. These candidate materials can therefore be selected for various cell components based on fabricability or other considerations.

This paper reports on screening tests which were conducted on 25 ceramics to evaluate their suitability as insulators in a Downs-type lithium electroreduction cell. Each material was exposed to molten lithium at 400[degrees]C for 100 h. Of the materials tested, beryllia, magnesia, yttria, yttrium aluminum garnet, and aluminum nitride were found to have acceptable compatibility with lithium. It is reasonable to expect that they are also compatible with molten LiCl-KCl electrolyte. These candidate materials can therefore be selected for various cell components based on fabricability or other considerations.

Many workers have recently developed and demonstrated the use of gas sensor arrays to detect and recognize a variety of compounds. In general, a pattern recognition approach is used in which the signature of an unknown sample is compared to a library of signatures of known substances. All of these efforts have shown varying degrees of success when applied to pure compounds. Unfortunately, flavors and fragrances are never pure compounds. A prototype gas sensor array has been constructed and tested with various mixtures of interest. The results are discussed in terms of their implication to the food and fragrance industry. Early experiments on gasoline-alcohol mixtures demonstrated that the signatures do not follow a rule of mixing, but were more strongly influenced by the more volatile and/or more reactive component. This led us to examine the behavior of alcohol-water mixtures for possible quality control in the distilling industry. We discovered that the signature of alcohol dominated even at concentrations as low as ten percent. Preliminary experiments were also performed to see if the prototype sensor array could be used to automatically detect rancidity in dairy products. Flavorings and essential oils are in many cases even more complex mixtures. The behavior of representative classes of these substances were characterized in an attempt to understand their signatures on the basis of their constituents.

Measurement of hydrogen concentration in containment atmospheres in nuclear plants is a key safety capability. Current technologies require extensive sampling systems and subsequent maintenance and calibration costs can be very expensive. A new hydrogen sensor has been developed that is small and potentially inexpensive to install and maintain. Its size and low power requirement make it suitable in distributed systems for pinpointing hydrogen buildup. This paper will address the first phase of a testing program conducted to evaluate this sensor for operation in reactor containments.

The goals of this CRADA were to: (1) development and demonstrate a highly frequency-agile microwave furnace; (2) explore applications of the furnace for materials processing; and (3) develop control systems and packaging that are robust, user-friendly, and suitable for sale as a turnkey system. Microwave Laboratories, Inc. (MLI) designed, built, and successfully brought to market a benchtop Variable Frequency Microwave Furnace (VFMF). The concept has demonstrated advantages in polymer curing, waste remediation, and diamond (CVD). Through experimentation and modeling, the VFMF approach has gained credibility within the technical community.

The McNabb-Foster equations, solved using a finite difference approach, have been applied to the data reported earlier by Lauf and Altstetter for the diffusion of oxygen in dilute niobium alloys. It was assumed that the substitutional alloy atoms acted as traps for the oxygen. Ratios of the release coefficient to the trapping coefficient,p/k, were calculated at various temperatures by computer-assisted curve fitting. Trapping energies obtained from plots ofp/k vs 1/T agree fairly well with those reported earlier using the Oriani model, but differ somewhat from those obtained using a recent model proposed by McLellan. The merits and limitations of the models with respect to the treatment of experimental data are discussed. Initial fractional trap occupancies were also calculated for these alloys and plotted against 1/T, and the results are also discussed.

An intelligent gas sensor has been developed using thick‐film techniques to create a semiconducting oxide surface with carefully varied catalytic properties. An integral heater causes the surface to react with combustible gases and the resulting resistance map of the surface forms a signature that can be related to the functional groups present in the gas. For example, alcohols, ketones and alkanes have distinct, recognisable signatures on one sensor model.

A method for preparing fragmented or particulate ceramic materials for transmission electron microscopy (TEM) by embedding in a solid metal matrix such as aluminum, using vacuum hot-pressing at about 550°C, followed by mechanical thinning and ion milling, has been published. This technique is useful for most high-melting ceramic materials but may introduce thermal damage to low-melting materials or to hydrated minerals. We describe here two relatively simple techniques that can be carried out at room temperature and that do not require vacuum hot-pressing equipment.The first technique disperses the sample in a dental amalgam. Premeasured capsules contain the silver alloy powder and mercury in separate compartments. The capsule is opened and a small amount of sample is added. The capsule is then closed and compressed to release the mercury and agitated for 1 to 2 min. The material is removed from the capsule and tightly packed into a 3-mm-diam cylindrical mold for hardening overnight. The resulting pellet is then sliced and thinned as in the earlier method. Figure 1 shows a coal fly ash particle prepared by this technique.

Ceramic-metal composites, or cermets, are used for a variety of applications. In general, the ceramic phase provides hardness or wear resistance while a continuous metal phase acts as a binder and provides toughness. The alumina-based cermets described here are unique in that the metallic phase (platinum) is discontinuous and constitutes only about 1 to 2 vol % of the structure. This material was developed to serve as a high-temperature electrical insulator under conditions of severe thermal shock. Because of the small grain sizes involved, electron microscopy was used to study the relation between properties and process variables as well as to better understand the mechanism of thermal shock resistance.Platinum was intimately mixed with alumina powder by precipitation from a PtCl4 solution followed by drying. The resulting powder mixture was hot-pressed in a graphite die at 1610°C for 15 min under 69 MPa (10,000 psi) pressure. Cermets produced from Alcoa A-17 alumina powder had a final grain size of 15 ± 4 μm, while Fisher Scientific reagent-grade alumina resulted in a grain size of 4 ± 1 μm. The platinum particles ranged from 0.2 to 1.0 μm in diameter. Thermal shock resistance was tested by heating the cermet to 520°C and quenching in hot water. Cermets that were gastight after 15 quench cycles were considered acceptable. Thermal shock resistance was improved by heating the as-pressed pellet to 1630°C and air cooling.

The preparation of fragmented or particulate ceramic materials for transmission electron microscopy (TEM) examination has traditionally been difficult, particularly if a durable, permanent specimen is desired. Furthermore, most established methods for dealing with micron- and submicron-sized samples (e.g., dispersion in plastic films) do not permit selection of orientations or ion thinning. A technique has been developed that is useful for a variety of materials, permits the selection of specimen orientation, is compatible with ion milling requirements, and produces a durable specimen that can be reexamined later if necessary.