Heat of formation of yttrium-bismuth alloys

In the Y—Bi system the formation heats were measured using a direct isoperibol calorimeter. The following values were found for the two known compounds:

     

A direct isoperibol aneroid calorimeter

An aneroid isoperibol calorimetric apparatus is described which is particularly suitable for measurement of the reaction heat among solids. Such an apparatus contains four calorimeters and allows to carry out differential measurements. Each calorimeter includes two small electric furnaces employed for heating the solid mixture until the reaction begins and for the successive electric calibrations, respectively. The temperature trend of each calorimeter is followed by 80 thermocouples in series. The instrument characteristics are briefly discussed. Examples of its employment in the alloy thermochemistry are given.     

Determination of heats of formation of praseodymium antimonides

A systematic investigation of the heats of formation in the Pr-Sb system has been performed using a small-furnace, isoperibolic calorimeter. The compositions and the equilibrium states of the samples have been checked by metallographic and X-ray analyses. The following values have been found for the various compounds (kJ/g atom±2): Pr₂Sb:-99; Pr₅Sb₃:-112; Pr₄Sb₃:-120; PrSb:-126; PrSb₂:-97.The data available (both the results obtained in this work and those already known) are discussed briefly and related to the possible shape of the phase diagram.

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Zusammenfassung Es wurde eine systematische Untersuchung der Bildungswärmen im Pr/Sb-System unter Verwendung eines Kleinofen-Isoperibolkalorimeters ausgeführt. Die Zusammensetzung und der Gleichgewichtszustand der Proben wurden durch metallographische und röntgenographische Analyse ermittelt. Für die einzelnen Verbindungen wurden folgende Werte (kJ·mol^–1 ±2.0) gefunden: Pr₂Sb:-99; Pr₅Sb₃:-112; Pr₄Sb₃:-120;PrSb:-126; PrSb₂:-97. Die als Ergebnis dieser Arbeit erhaltenen und aus der Literatur bereits bekannte Daten werden kurz diskutiert und mit einem möglichen Phasendiagramm in Verbindung gebracht.

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-Sb, . . ( (-)^–1 ±2.0): Pr₂Sb-99; Pr₅Sb₃-112; PrSb₃-120; PrSb-126; PrSb₂-97. .

     

Heat of formation of PraseodymiumBismuth alloys

In the PrBi system the heats of formation were measured using a direct isoperibol calorimeter. The composition and equilibrium state of the samples have been checked by chemical, metallographic and X-ray analyses. The following values were found for the two known compounds (reaction in the solid state, 300 K):

The results obtained, compared with those already achieved in other REBi systems, are briefly discussed.     

A Contribution to the Study of the Alloying Behaviour of the Rare Earths with Tin

The general alloying behaviour of tin with the rare earths was summarized on the base of the available literature data. A re-examination of the La? Sn alloys has been performed using x-ray and metallographic analyses. The existence of the following phases has been observed or confirmed: . The formation heats of the La? Sn alloys have been measured using a direct isoperibol calorimeter. The values of ΔH_form (solid alloys, room temperature, K cal/g atom) are the following: . A re-examination of the Y? Sn alloys has been also carried out confirming the existence and the crystal structures of the following phases: Y₅Sn₃, Y₅Sn₄, Y₁₁Sn₁₀, YSn₂ and YSn₃. A few calorimetric measurements performed on selected Sn-rich alloys have given the following values of the ΔH_form: YSn₂ (?15.5 ± 1.0 Kcal/g atom), YSn₃ (?12.5 ± 0.5 Kcal/g atom). The results obtained are discussed briefly and are compared with the data available for other rare earth-tin alloys.     

Heat of formation of La4Bi3 and LaBi compounds

In the LaBi system the formation heats were measured using a direct isoperibol calorimeter. The following values were found:

     

Heats of formation of gadolinium—bismuth alloys

The heats of formation of Gd—Bi alloys were measured using a direct isoperibol calorimeter. The composition and equilibrium state of the samples were checked by metallographic and X-ray analyses.The following values were found for the different compounds [ΔH form, reaction in the solid state, 300 K, kcal (g-atom)^?1 ± 0.5]: Gd_5+xBi₃, ?20.0 ± 0.7; Gd₅Bi₃, ?20.9; Gd₄Bi₃, ?22.0; GdBi, ?23.1.The results obtained were compared with those already achieved for other rare earth bismuthides.     

Communication: the essential factor when implementing management systems

Internal communication within a company is essential for the implementation and proper functioning of any ISO-based quality system. Moreover, staff empowerment and distribution of responsibilities are key points in the ISO 9000:2000 quality guides. Although not specifically mentioned in the quality guides, external communication plays a fundamental role in assuring customer satisfaction and obtaining good ideas to improve company performance. This paper has two main parts. First, the importance of internal and external communication is reviewed and it is shown that managers should allocate more resources to both areas. It is also demonstrated that environmental management systems are directly derived from the quality guides. Second, the results of an enquiry to assess the efforts being made by a group of Italian senior managers to improve internal and external communication are evaluated. Received: 8 March 2002 Accepted: 12 September 2002     

Heat of formation of lanthanum-lead alloys

In the La? Pb system the heats of formation were measured, using a differential direct isoperibol calorimeter, and checking composition and state of the samples by chemical, metallographic and X-ray analyses. For the various compounds the _H (for the reaction among solid phases at 300 K) correspond to the following values (Kcal/g · at.): La₅Pb₃ = ?17.2₅ ± 0.5, La₄Pb₃ = ?16.7 ± 0.5, La₅Pb₄ = ?16.5 ± 0.5, La₃Pb₄ = ?15.3 ± 0.5, LaPb₂ = ?14.4 ± 0.5, LaPb₃ = ?13.7 ± 0.5. The results obtained are briefly discussed and compared with those calculated using the method suggested by MIEDEMA .