Caracterização microestrutural e resistência à corrosão de ligas Co-Cr-Mo utilizadas em próteses dentárias

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Effect of recasting procedure upon corrosion behavior and metallic ion release of Co-Cr-Mo dental alloy in physiological

Recasting process influence upon corrosion behavior of Co-Cr-Mo dental alloy in simulated physiological serum has been investigated using chemical and electrochemical techniques. Recast Co-Cr-Mo alloy by induction (IND) or by blowtorch (FLAME) has exhibited similar dendritic structures. Both IND and FLAME alloys have presented good corrosion resistance in physiological serum. Passivation process provides this corrosion resistance. Codissolution makes this process difficult. Passive films, formed on these alloys, have been analyzed as a dual layer consisting of an inner barrier and an outer porous layer. Passive film protective characteristics are higher in FLAME than in IND alloy. On this last alloy, the passive film is more porous due to a higher Codissolution. ©Carl Hanser Verlag, München.

Desenvolvimento e caracterização de ligas de Co-Cr-Mo

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Spinpolarisierte Rastertunnelmikroskopie magnetischer Nanostrukturen am Beispiel von bcc-Co/Fe(110), Fe/Mo(110) und Kupfer-Phthalocyanin/Fe(110)

In dieser Arbeit werden, nach einer Einführung in die spinpolarisierte Rastertunnelmikroskopie und -spektroskopie als experimentelle Methode zur Untersuchung magnetischer Nanostrukturen, Ergebnisse zur spinpolarisierten elektronischen Struktur in Abhängigkeit von der Kristallstruktur am Beispiel ultradünner Co-Schichten sowie in Abhängigkeit von der Magnetisierungsrichtung für ultradünne Fe-Schichten vorgestellt. Hochaufgelöste Messungen zeigen die ortsabhängige Spinpolarisation auf einem einzelnen Kupfer-Phthalocyanin Molekül. rnrnKobalt wurde durch pseudomorphes Wachstum auf den (110)-Oberflächen der kubisch raumzentrierten Metalle Chrom und Eisen deponiert. Im Unterschied zu früheren Berichten in der Literatur lassen sich nur zwei Lagen Co in der kubisch raumzentrierten (bcc) Ordnung stabilisieren. Die bcc-Co Schichten auf der Fe(110)-Oberfläche zeigen keine Anzeichen von epitaktischen Verzerrungen. rnDickere Schichten rekonstruieren in eine dicht gepackte Struktur (hcp/fcc). Durch die bcc Ordnung wird die Spinpolarisation von Kobalt auf P=62% erhöht (hcp-Co: P=45%). rnrnDie temperaturabhängige Spinreorientierung (SRT) ultradünner Filme Fe/Mo(110) wurde mit spinpolarisierter Spektroskopie untersucht. Eine Neuausrichtung der Magnetisierung aus der senkrechten [110]-Achse in die in der Ebene liegenden [001]-Achse wird bei T=(13,2+-0,5)K festgestellt, wobei es sich um einen diskontinuierlichen Reorientierungsübergang handelt, d.h. die freie Energie weist innerhalb eines bestimmten Temperaturbereichs gleichzeitig zwei Minima auf. Weiterhin wird in der Mono- und Doppellage Fe/Mo(110 eine Abhängigkeit der elektronischen Struktur von der Ausrichtung der magnetisch leichten Achse und von der Magnetisierung beobachtet. rnrnDie Untersuchung des spinpolarisierten Ladungstransports durch ein Kupfer-Phthalocyanin-Molekül auf der Fe/Mo(110) Oberfläche liefert einen wesentlichen Beitrag zum Verständnis des Spintransports an der Grenzfläche zwischen Metall und organischem Molekül. Die HOMO-LUMO-Energielücke des freien Moleküls wird durch die Wechselwirkung mit der Metalloberfläche mit Grenzflächenzuständen gefüllt. Diese Zustände reduzieren die Spinpolarisation des durch das Molekül fließenden Tunnelstroms durch einen zusätzlichen unpolarisierten Strombeitrag um einen Faktor zwei. Spinpolarisierte hybridisierte Grenzflächenzustände mit größerem Abstand zur Fermi-Energie führen in Abhängigkeit von der Position auf dem Molekül zu weiteren Beiträgen zur effektiven Spinpolarisation. Diese Untersuchungen belegen die Möglichkeit einer effektiven Spininjektion in organische Halbleiter und damit das Potential dieser Materialien für die weitere Entwicklung von Spintronik-Bauteilen.

Decomposition studies of group 6 hexacarbonyl complexes. Part 1: Production and decomposition of Mo(CO)6 and W(CO)6

Chemical studies of superheavy elements require fast and efficient techniques, due to short half-lives and low production rates of the investigated nuclides. Here, we advocate for using a tubular flow reactor for assessing the thermal stability of the Sg carbonyl complex – Sg(CO)6. The experimental setup was tested with Mo and W carbonyl complexes, as their properties are established and supported by theoretical predictions. The suggested approach proved to be effective in discriminating between the thermal stabilities of Mo(CO)6 and W(CO)6. Therefore, an experimental verification of the predicted Sg–CO bond dissociation energy seems to be feasible by applying this technique. By investigating the effect of 104,105Mo beta-decay on the formation of 104,105Tc carbonyl complex, we estimated the lower reaction time limit for the metal carbonyl synthesis in the gas phase to be more than 100 ms. We examined further the influence of the wall material of the recoil chamber, the carrier gas composition, the gas flow rate, and the pressure on the production yield of 104Mo(CO)6, so that the future stability tests with Sg(CO)6 can be optimized accordingly.

Report to the President by the Emergency Board appointed March 15, 1949 by Executive order 10045 pursuant to Section 10 of the Railway Labor Act, as amended : to investigate and report in respect to a dispute involving the Wabash Railroad Co. and the Ann Arbor Railroad Co., carriers, and certain of their employees, represented by the Brotherhood of Locomotive Engineers, Brotherhood of Locomotive Firemen and Enginemen, Order of Railway Conductors, and Brotherhood of Railroad Trainmen : (NMB case A-3028) : St. Louis, Mo., April 6, 1949.

Signed: Roger I. McDonough, chairman, Curtis G. Shake, member, John W. Yeager, member.

Reductorij moralis fratris Petri Berchorij libri quattuordecim : perfectam officio[rum] atq[ue] mo[rum] rationem ac pene tota[m] nature co[m]plectens historia[m] nusq[uam] hactenus excusi ge[n]tiu[m] : su[m]ma fide ac dilige[n]tia ad vetera exe[m]plaria castigati.

CCBE,

In-Vivo Corrosion and Fretting of Modular TI-6AL-4V/CO-CR-MO Hip Prostheses: The Influence of Microstructure and Design Parameters

The purpose of this study was to evaluate the incidence of corrosion and fretting in 48 retrieved titanium-6aluminum-4vanadium and/or cobalt-chromium-molybdenum modular total hip prosthesis with respect to alloy material microstructure and design parameters. The results revealed vastly different performance results for the wide array of microstructures examined. Severe corrosion/fretting was seen in 100% of as-cast, 24% of low carbon wrought, 9% of high carbon wrought and 5% of solution heat treated cobalt-chrome. Severe corrosion/fretting was observed in 60% of Ti-6Al-4V components. Design features which allow for fluid entry and stagnation, amplification of contact pressure and/or increased micromotion were also shown to play a role. 75% of prosthesis with high femoral head-trunnion offset exhibited poor performance compared to 15% with a low offset. Large femoral heads (>32mm) did not exhibit poor corrosion or fretting. Implantation time was not sufficient to cause poor performance; 54% of prosthesis with greater than 10 years in-vivo demonstrated none or mild corrosion/fretting.

Evaluation of the castability of a Co-Cr-Mo-W alloy varying the investing technique

O objetivo deste estudo foi comparar a fusibilidade de ligas de Co-Cr-Mo-W (Remanium 2000), Ni-Cr (Durabond) e Co-Cr-Mo (Vera-PDI), incluídas em revestimentos à base de fosfato, sílica ou utilizando uma técnica mista. Uma rede de nylon quadrada (10 X 10 mm) com 100 espaços abertos serviu de modelo para construção de padrões de cera, que foram incluídos com revestimento à base de sílica, revestimento fosfatado e técnica mista (camada de revestimento fosfatado com 2 mm de espessura + revestimento à base de sílica). Quarenta e cinco espécimes (5 para cada condição experimental) foram fundidos sob chama de gás-oxigênio e a seguir jateados com óxido de alumínio. O número de segmentos fundidos completos foi contado para obter uma percentagem designada como "valor de fusibilidade", representando a precisão da liga em reproduzir os detalhes do molde. A análise estatística por meio de ANOVA a dois critérios e teste Tukey mostrou que, comparando-se as ligas, a Remanium 2000 teve fusibilidade estaticamente semelhante (p>0,05) à da Vera PDI e inferior à da liga Durabond (p<0,05). Considerando os resultados da técnica mista, a liga Remanium 2000 teve menor valor de fusibilidade (p<0,05) que as ligas Durabond e Vera PDI, que apresentaram valores estatisticamente semelhantes entre si (p>0,05). Concluindo, a fusibilidade da liga de Co-Cr-Mo-W (Remanium 2000) foi comparável à da liga de Co-Cr (Vera PDI) e inferior à da liga de Ni-Cr alloy (Durabond). À exceção da liga Remanium 2000, a técnica de inclusão mista aumentou consideravelmente a capacidade das ligas testadas de reproduzir os detalhes do molde, quando comparada à técnica de inclusão em revestimento fosfatado. A técnica de inclusão mista representa uma alternativa para melhorar a fusibilidade de ligas de metais básicos sem afetar a qualidade superficial das peças metálicas.

Evaluation of the castability of a Co-Cr-Mo-W alloy varying the investing technique

O objetivo deste estudo foi comparar a fusibilidade de ligas de Co-Cr-Mo-W (Remanium 2000), Ni-Cr (Durabond) e Co-Cr-Mo (Vera-PDI), incluídas em revestimentos à base de fosfato, sílica ou utilizando uma técnica mista. Uma rede de nylon quadrada (10 X 10 mm) com 100 espaços abertos serviu de modelo para construção de padrões de cera, que foram incluídos com revestimento à base de sílica, revestimento fosfatado e técnica mista (camada de revestimento fosfatado com 2 mm de espessura + revestimento à base de sílica). Quarenta e cinco espécimes (5 para cada condição experimental) foram fundidos sob chama de gás-oxigênio e a seguir jateados com óxido de alumínio. O número de segmentos fundidos completos foi contado para obter uma percentagem designada como "valor de fusibilidade", representando a precisão da liga em reproduzir os detalhes do molde. A análise estatística por meio de ANOVA a dois critérios e teste Tukey mostrou que, comparando-se as ligas, a Remanium 2000 teve fusibilidade estaticamente semelhante (p>0,05) à da Vera PDI e inferior à da liga Durabond (p<0,05). Considerando os resultados da técnica mista, a liga Remanium 2000 teve menor valor de fusibilidade (p<0,05) que as ligas Durabond e Vera PDI, que apresentaram valores estatisticamente semelhantes entre si (p>0,05). Concluindo, a fusibilidade da liga de Co-Cr-Mo-W (Remanium 2000) foi comparável à da liga de Co-Cr (Vera PDI) e inferior à da liga de Ni-Cr alloy (Durabond). À exceção da liga Remanium 2000, a técnica de inclusão mista aumentou consideravelmente a capacidade das ligas testadas de reproduzir os detalhes do molde, quando comparada à técnica de inclusão em revestimento fosfatado. A técnica de inclusão mista representa uma alternativa para melhorar a fusibilidade de ligas de metais básicos sem afetar a qualidade superficial das peças metálicas.

Evaluation of strontium-site-deficient Sr2Fe1.4Co0.1Mo0.5O6-δ-based perovskite oxides as intermediate temperature solid oxide fuel cell cathodes

In this paper strontium-site-deficient Sr₂Fe_1.4Co_0.1Mo_0.5O_6-δ-based perovskite oxides (S_xFCM) were prepared and evaluated as the cathode materials for intermediate temperature solid oxide fuel cells (IT-SOFCs). All samples exhibited a cubic phase structure and the lattice shrinked with increasing the Sr-deficiency as shown in XRD patterns. XPS results determined that the transition elements (Co/Fe/Mo) in S_xFCM oxides were in a mixed valence state, demonstrating the small polaron hopping conductivity mechanism existed. Among the samples, S_1.950FCM presented the lowest coefficient of thermal expansion of 15.62 × 10^-6 K^-1, the highest conductivity value of 28 S cm^-1 at 500 °C, and the lowest interfacial polarization resistance of 0.093 Ω cm² at 800 °C, respectively. Furthermore, an anode-supported single cell with a S_1.950FCM cathode was prepared, demonstrating a maximum power density of 1.16 W cm^-2 at 800 °C by using wet H₂ (3% H₂O) as the fuel and ambient air as the oxidant. These results indicate that the introduction of Sr-deficiency can dramatically improve the electrochemical performance of Sr₂Fe_1.4Co_0.1Mo_0.5O_6-δ, showing great promise as a novel cathode candidate material for IT-SOFCs.

Estudo morfofuncional das glândulas mamárias de Mão Pelada, Procyon cancrivorus

Para a descrição macro e microscópica das glândulas mamárias foram utilizadas três fêmeas de Mão Pelada (Procyon cancrivorus). As amostras das glândulas foram processadas conforme técnicas rotineiras para histologia. As fêmeas estudadas apresentaram 3 pares de glândulas mamárias, sendo um par de glândula mamária abdominal cranial, um par de abdominal caudal e um par de inguinal. As papilas mamárias apresentaram formato pendular, como os canídeos domésticos. Microscopicamente, a glândula mamária apresentou da porção externa para a interna: epiderme (epitélio estratificado pavimentoso queratinizado), derme (tecido conjuntivo frouxo e tecido conjuntivo denso não modelado), fibras musculares lisas e ductos papilíferos que abrem em vários ósteos papilares em formato de "chuveiro". A porção secretora glandular era caracteristicamente túbulo alveolar, com células cuboidais dispostas em camada simples. Os resultados indicam que o conjunto glandular estudado é semelhante ao da cadela (Cannis familiaris) tanto em seu aspecto macroscópico quanto em seu aspecto microscópico, este fato sugere que podemos utilizar o Mão Pelada e o Cão como modelos similares de estudo, para identificação de patologias relacionadas a este sistema.

Determination of Cr, Fe, Co, Ni, Cu, Zn, As and Pb in liquid chemical waste by energy dispersive X-ray fluorescence

A method for simultaneous determination of Cr, Fe, Co, Ni, Cu, Zn, As e Pb in liquid chemical waste using Energy Dispersive X-Ray Fluorescence (EDXRF) technique was evaluated. A small sample amount (200 mu L) was dried on a 6.35 mu m thickness Mylar film at 60 degrees C and the analyses were carried out using an EDXRF spectrometer operated with an X-ray Mo tube (Zr filter) at 30 kV/20 mA. The acquisition time was 300 s and the Ga element was utilized as internal standard at 25 mg/L for quantitative analysis. The method trueness was assessed by spiking and the detection limit for those elements ranged from 0.39 to 1.7 mg/L. This method is notable because it assists the choice of the more appropriated waste treatment procedure, in which inter elemental interference is a matter of importance. In addition, this inexpensive method allows a non-destructive determination of the elements from (19)K to (92)U simultaneously.

Preparation and characterization of Mo/W bimetallic carbides by using different synthesis methods

Molybdenum and tungsten bimetallic oxides were synthetized according to the following methods: Pechini, coprecipitation and solid state reaction (SSR). After the characterization, those solids were carbureted at programmed temperature. The carburation process was monitored by checking the consumption of carburant hydrocarbon and CO produced. The monitoring process permits to avoid or to diminish the formation of pirolytic carbon.