X-Ray Diffraction Study of Boron Produced by Pyrolysis of Boron Tribromide

The goal of this research was to determine the composition of boron deposits produced by pyrolysis of boron tribromide, and to use the results to (a) determine the experimental conditions (reaction temperature, etc.) necessary to produce alpha-rhombohedral boron and (b) guide the development/refinement of the pyrolysis experiments such that large, high purity crystals of alpha-rhombohedral boron can be produced with consistency. Developing a method for producing large, high purity alpha-rhombohedral boron crystals is of interest because such crystals could potentially be used to achieve an alpha-rhombohedral boron based neutron detector design (a solid-state detector) that could serve as an alternative to existing neutron detector technologies. The supply of neutron detectors in the United States has been hampered for a number of years due to the current shortage of helium-3 (a gas used in many existing neutron detector technologies); the development of alternative neutron detector technology such as an alpha-rhombohedral boron based detector would help provide a more sustainable supply of neutron detectors in this country. In addition, the prospect/concept of an alpha-rhombohedral boron based neutron detector is attractive because it offers the possibility of achieving a design that is smaller, longer life, less power consuming, and potentially more sensitive than existing neutron detectors. The main difficulty associated with creating an alpha-rhombohedral boron based neutron detector is that producing large, high purity crystals of alpha-rhombohedral boron is extremely challenging. Past researchers have successfully made alpha-rhombohedral boron via a number of methods, but no one has developed a method for consistently producing large, high purity crystals. Alpha-rhombohedral boron is difficult to make because it is only stable at temperatures below around 1100-1200 °C, its formation is very sensitive to impurities, and the conditions necessary for its formation are not fully understood or agreed upon in the literature. In this research, the method of pyrolysis of boron tribromide (hydrogen reduction of boron tribromide) was used to deposit boron on a tantalum filament. The goal was to refine this method, or potentially use it in combination with a second method (amorphous boron crystallization), to the point where it is possible to grow large, high purity alpha-rhombohedral boron crystals with consistency. A pyrolysis apparatus was designed and built, and a number of trials were run to determine the conditions (reaction temperature, etc.) necessary for alpha-rhombohedral boron production. This work was focused on the x-ray diffraction analysis of the boron deposits; x-ray diffraction was performed on a number of samples to determine the types of boron (and other compounds) formed in each trial and to guide the choices of test conditions for subsequent trials. It was found that at low reaction temperatures (in the range of around 830-950 °C), amorphous boron was the primary form of boron produced. Reaction temperatures in the range of around 950-1000 °C yielded various combinations of crystalline boron and amorphous boron. In the first trial performed at a temperature of 950 °C, a mix of amorphous boron and alpha-rhombohedral boron was formed. Using a scanning electron microscope, it was possible to see small alpha-rhombohedral boron crystals (on the order of ~1 micron in size) embedded in the surface of the deposit. In subsequent trials carried out at reaction temperatures in the range of 950 °C – 1000 °C, it was found that various combinations of alpha-rhombohedral boron, beta-rhombohedral boron, and amorphous boron were produced; the results tended to be unpredictable (alpha-rhombohedral boron was not produced in every trial), and the factors leading to success/failure were difficult to pinpoint. These results illustrate how sensitive of a process producing alpha-rhombohedral boron can be, and indicate that further improvements to the test apparatus and test conditions (for example, higher purity/cleanliness) may be necessary to optimize the boron deposition. Although alpha-rhombohedral boron crystals of large size were not achieved, this research was successful in (a) developing a pyrolysis apparatus and test procedure that can serve as a platform for future testing, (b) determining reaction temperatures at which alpha-rhombohedral boron can form, and (c) developing a consistent process for analyzing the boron deposits and determining their composition. Further experimentation is necessary to achieve a pyrolysis apparatus and test procedure that can yield large alpha-rhombohedral boron crystals with consistency.

Estudo sobre o efeito dos parâmetros de processamento dos pós e sinterização do aço inox 316l reforçado com NbC

This masther dissertation presents a contribution to the study of 316L stainless steel sintering aiming to study their behavior in the milling process and the effect of isotherm temperature on the microstructure and mechanical properties. The 316L stainless steel is a widely used alloy for their high corrosion resistance property. However its application is limited by the low wear resistance consequence of its low hardness. In previous work we analyzed the effect of sintering additives as NbC and TaC. This study aims at deepening the understanding of sintering, analyzing the effect of grinding on particle size and microstructure and the effect of heating rate and soaking time on the sintered microstructure and on their microhardness. Were milled 316L powders with NbC at 1, 5 and 24 hours respectively. Particulates were characterized by SEM and . Cylindrical samples height and diameter of 5.0 mm were compacted at 700 MPa. The sintering conditions were: heating rate 5, 10 and 15◦C/min, temperature 1000, 1100, 1200, 1290 and 1300◦C, and soaking times of 30 and 60min. The cooling rate was maintained at 25◦C/min. All samples were sintered in a vacuum furnace. The sintered microstructure were characterized by optical and electron microscopy as well as density and microhardness. It was observed that the milling process has an influence on sintering, as well as temperature. The major effect was caused by firing temperature, followed by the grinding and heating rate. In this case, the highest rates correspond to higher sintering.

The Monumental Barrows of the Period 700-1100 AD at the Russian North-West

Nicholas Petrov. The Monumental Barrows of the Period 700-11 AD in the Russian North-West The research deals with the monumental barrows erected in the Russian north-west in the period of 700-1100 AD, which Russian archaeological literature has traditionally named sopka-barrows. These sopka-barrows were analysed as original sacral and funeral structures and considered in the context of cultural processes under way in that region at the time. The position occupied by the sopka-barrows in the culture of the people who erected them was reconstructed on the basis of a synthesis of various kinds of sources - archaeological, written, folklore. The high barrows are not in fact a determining type of the sites of the so-called "culture of the sopka-barrows" in modern literature, which focuses rather on settlements near to which sopka-barrows are absent. Recent excavations have revealed the presence of "surface" burial places (cremation located on the top of the barrow repeatedly rather than only once) in the majority of the sopka-barrows. The materials only provide evidence about the sacrificial nature of the graves in the "body" of the sopka-barrows. They thus offer an embodiment of one element of the widespread views about the dead man's path to the world of the dead (mountain) which is traced in folklore texts. Special attention was paid to the question of the disappearance of the tradition of erecting sopka-barrows and to the nature of their role in the culture of the region during the period 1000-1200 AD. The functioning of the sopka-barrows as funeral monuments in the second millennium AD is also traced on the inlet inhumatios found in them.

Melting of metasomatized peridotite at 4–6 GPa and up to 1200 °C: an experimental approach

The phase assemblages and compositions in a K-bearing lherzolite + H2O system are determined between 4 and 6 GPa and 850–1200 °C, and the melting reactions occurring at subarc depth in subduction zones are constrained. Experiments were performed on a rocking multi-anvil apparatus. The experiments had around 16 wt% water content, and hydrous melt or aqueous fluid was segregated and trapped in a diamond aggregate layer. The compositions of the aqueous fluid and hydrous melt phases were measured using the cryogenic LA-ICP-MS technique. The residual lherzolite consists of olivine, orthopyroxene, clinopyroxene, and garnet, while diamond (C) is assumed to be inert. Hydrous and alkali-rich minerals were absent from the run products due to preferred dissolution of K2O (and Na2O) to the aqueous fluid/hydrous melt phases. The role of phlogopite in melting relations is, thus, controlled by the water content in the system: at the water content of around 16 wt% used here, phlogopite is unstable and thus does not participate in melting reactions. The water-saturated solidus, i.e., the first appearance of hydrous melt in the K–lherzolite composition, is located between 900 and 1000 °C at 4 GPa and between 1000 and 1100 °C at 5 and 6 GPa. Compositional jumps between hydrous melt and aqueous fluid at the solidus include a significant increase in the total dissolved solids load. All melts/fluids are peralkaline and calcium-rich. The melting reactions at the solidus are peritectic, as olivine, clinopyroxene, garnet, and H2O are consumed to generate hydrous melt plus orthopyroxene. Our fluid/melt compositional data demonstrate that the water-saturated hybrid peridotite solidus lies above 1000 °C at depths greater than 150 km and that the second critical endpoint is not reached at 6 GPa for a K2O–Na2O–CaO–FeO–MgO–Al2O3–SiO2–H2O–Cr2O3(–TiO2) peridotite composition.

Distribucion geografica de Lutzomyia verrucarum (Townsend, 1913) (Diptera, Psychodidae, Phlebotominae), vector de la batonellosis humana en el Peru

Lutzomyia verrucarum (Townsend, 1913) (Diptera: Psychodidae), vector natural de la verruga peruana o enfermedad de Carrión es una especie propia del Perú. Su distribución geográfica esta entre los paralelos 5º y 13º25' de latitud Sur, se encuentra en los valles Occidentales e Interandinos de los Andes. La distribución altitudinal de Lu. verrucarum en los diversos valles es variable; asi: Occidentales, desde 1100 hasta 2980 msnm e Interandinos, de 1200 a 3200 msnm. En ciertas áreas verrucógenas no hay correlación entre la presencia de Lu. verrucarum y la enfermedad de Carrión lo que suguiere la existencia de vectores secundarios.

Fragments de mss.

Contient : Ex canonibus; versus Tranquillini de XII ventis ; Vita Gerardi de Rosselon ; De S. Bartholomeo ; Compotus Hilperici ; Regulae Isidori et Fructuosi ; ex libro Auxilii de Formoso papa ; Sermo de S. Theoderico ; Fragments de mss. de S. Rémi de Reims, contenant des actes d'associations de prières, l'épitaphe de Lothaire, des actes d'offrandes d'enfants ; Encyclique sur la mort d'André, abbé de Chezal-Benoît ; Frotharii epistolae, etc ; De S. Maria Magdal ; Acta S. Mauritii, S. Romani, S. Felicitatis ; Vita S. Hugonis Clun ; Vita ejusdem, auctore Rainaldo, abbate Vizel ; Ejusdem vita metrica ; Ivonis Carnot. epistolae ; Vitae S. Maioli, et S. Hugonis Cluniac ; Sermo S. Hugonis de S. Marcello

Latin 14145

Contient : Carmen de S. Agnete ; Ivonis panormia ; Vita S. Sulpitii ; Novitiorum institutio ; Summa Guillelmi Autissiodorensis de officiis ecelesiasticis

Fragments de mss.

Contient : Lettres de Suger et pièces relatives à Suger et à Yves, abbé de S. Denis ; Lettre du comte Étienne à Ade, sa femme, sur la croisade ; Lettres d'Yves de Chartres ; Poëme d'Adalberon, adressé au roi Robert ; Charte de l'abbaye de Gigny en 898 et passion de S. Nazaire et S. Celse ; Registre de la confrérie de S. Maur et S. Fiacre à Paris ; Ad Paulum III Augustini bibliothecarii de Via Pauli et de fontibus inducendis in eam ; Cérémonial du sacre

Latin 14801

Contient : Commentaire sur le Cantique attribué à s. Anselme; Exposition des douze patriarches ; Lettres de s. Paul ; Hugonis Cardinalis tractatus de ordine misse

Le Reid, destroyer construit en 45 jours, 1200 tonnes, 30000 hp, 40 miles à l'heure : [photographie de presse] / [Agence Rol]

Référence bibliographique : Rol, 57144

Major Empson sur AV, pesage de Paris-Nice [cycle-car, 1100 cmc, course Paris-Nice] : [photographie de presse] / [Agence Rol]

Référence bibliographique : Rol, 57958

Baudelocque sur Morgan [cycle-car, 1100 cmc, course Paris-Nice] : [photographie de presse] / [Agence Rol]

Référence bibliographique : Rol, 57960