Thermodynamics of the intermediate phases in the Mg–B system

Balducci, G.; Brutti, Sergio; Ciccioli, A.; Gigli, G.; Manfrinetti, P.; Palenzona, A.; Бутман, М. Ф.; Кудин, Л. С.

doi:10.1016/j.jpcs.2004.06.063

Cited by 46 publications

(47 citation statements)

References 9 publications

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“…Nevertheless, simulations in this sense suggested that other atoms inclusions must be kept low due to their different scattering factor. This is in agreement with a recent report on the MgeB phase diagram [38] where from semi-empirical thermodynamics calculations it was surmised that a B-rich phase may be privileged with approximate composition MgB 20 . Of course, the presence of hydrogen atoms in the lattice cannot be rejected.…”

supporting

confidence: 93%

Structural study of a new B-rich phase obtained by partial hydrogenation of 2NaH + MgB2

Pistidda¹,

Napolitano²,

Pottmaier³

et al. 2013

International Journal of Hydrogen Energy

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The structure of an unknown crystalline phase observed during the hydrogen absorption reaction of the powder mixtures 2NaH þ MgB 2 at high pressure has been studied by ab-initio structure determination from powder diffraction. The sequence of un-overlapped peaks extracted from the X-ray powder diffraction pattern could be indexed with a prim-itive cubic cell with lattice parameter a ¼ 7.319 A˚. The diffraction patterns of the peaks are matched with the Pa-3 space group. The stoichiometry of the hydrogen absorption reaction suggests the presence of a high-boron content phase in the compound under investigation. Assuming this phase to be composed only by boron atoms and therefore having a density similar to that found for boron polymorphs, the solution with a space group of Pa-3 leads to reasonable BeB interatomic distances.1.

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supporting

confidence: 93%

Structural study of a new B-rich phase obtained by partial hydrogenation of 2NaH + MgB2

Pistidda¹,

Napolitano²,

Pottmaier³

et al. 2013

International Journal of Hydrogen Energy

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“…[24][25][26][27] In principle, the following reactions to produce MgCl 2 The subtraction of Equation (2) from Equation (1) yields the relevant components for the equilibrium presented in Equation (3). Finally, supported by several experiments on the thermal stability of MgB 2 [24][25][26]30] as well as by quantum-chemical calculations on MgCl and Mg 2 Cl 2 , the temperature-dependent partial pressure curves of MgCl 2 , MgCl, and Mg 2 Cl 2 are obtained ( Figure 1). Figure 1 also contains the decomposition pressure curve for MgB 2 ; that is, for all hypothetical model reactions discussed herein, the applied HCl pressure must be higher than the partial pressure of magnesium.…”

Section: Ch]mentioning

confidence: 99%

MgCl and Mg₂Cl₂: From Theoretical and Thermodynamic Considerations to Spectroscopy and Chemistry of Species with MgMg Bonds

2008

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Recently, compounds containing metal-metal bonds between main-group elements have attracted interest to a surprising extent. [1][2][3][4][5] In spite of the latest structural results for two crystalline Mg 2 R 2 compounds (R1 = [ArNC(NiPr 2 )NAr] À ; R2 = [{ArNCMe} 2 CH] À ; Ar= 2,6-diisopropylphenyl, iPr = isopropyl) [2] and in spite of a number of theoretical contributions on molecules with MgÀMg bonds, [10][11][12] several important questions still remain to be answered, for example, concerning the unexpected disproportionation stability of the abovementioned Mg I compounds. Herein, we present the following results: 1) On the basis of quantum-chemical-assisted thermodynamic calculations, a feasible synthesis of radical monomeric Mg I halides at temperatures near 900 8C is presented.2) The nature of the MgÀMg bond is investigated by spectroscopic examination of MgCl and its linear dimer Mg 2 Cl 2 in solid inert-gas matrixes; the MgÀMg dissociation energy is obtained. 3) By comparing the thermodynamics of Mg 2 Cl 2 (1), Mg 2 Cp 2 (2, Cp = cyclopentadienyl), and a model compound Mg 2 R* 2 (3, R* = C(NH 2 )(NCH 3 ) 2 ) analogous to crystalline Mg 2 (R1) 2 , the enormous disproportionation stability of the latter compound is explained. For further investigations, for example in the field of metal-rich Mg n R m clusters (n > m), the synthesis of reactive starting materials like MgCl is absolutely necessary. Initial results on the synthesis of MgCl are reported.After the first evidence for stable alkaline earth

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“…The second phenomenon can cause the formation of various compounds characterized by higher content of B and different lattice structure. [7,8] Naturally, all electrical properties depend strongly on the compound structure; therefore, it is very important to determine the stoichiometry and the structure of produced boride.…”

Section: Introductionmentioning

confidence: 99%

Chemical composition of magnesium boride films obtained by CVD

Crociani

Carta

Kačiulis

et al. 2008

Surface & Interface Analysis

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The films of magnesium boride were grown on Si(100) substrate by chemical vapor deposition, starting from the synthesis of the single-source precursor Mg(BH 4 ) 2 . The deposition time was varied to study its influence on the film composition. The chemical composition of produced samples was investigated by the XPS technique. The depth profiling of MgB x films was carried out by using Ar ion sputtering combined with cyclic XPS measurements. The contributions of different chemical species (boride and oxides) in the depth profiles were separated by peak-fitting analysis of photoelectron B 1s and Auger Mg KLL spectra. In order to determine the correct parameters of peak fitting, the reference samples of MgB 2 and MgO were studied as well. The produced samples were composed of MgB x film covered by an overlayer of magnesium and boron oxides, whose thickness was increasing with deposition time. The surface of the films was enriched with magnesium, while the volume was characterized by the B : Mg ratio exceeding 2. XPS results confirmed that the bulk decomposition of Mg(BH 4 ) 2 precursor was successful; therefore, some other phenomenon, such as Mg segregation, was responsible for the formation of MgB x films with x > 2. In addition, a prolonged deposition time resulted in a thicker surface overlayer of Mg and B oxides, but it did not change the stoichiometry of the boride film.

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Thermodynamics of the intermediate phases in the Mg–B system

Cited by 46 publications

References 9 publications

Structural study of a new B-rich phase obtained by partial hydrogenation of 2NaH + MgB2

Structural study of a new B-rich phase obtained by partial hydrogenation of 2NaH + MgB2

MgCl and Mg₂Cl₂: From Theoretical and Thermodynamic Considerations to Spectroscopy and Chemistry of Species with MgMg Bonds

Chemical composition of magnesium boride films obtained by CVD

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Thermodynamics of the intermediate phases in the Mg–B system

Cited by 46 publications

References 9 publications

Structural study of a new B-rich phase obtained by partial hydrogenation of 2NaH + MgB2

Structural study of a new B-rich phase obtained by partial hydrogenation of 2NaH + MgB2

MgCl and Mg2Cl2: From Theoretical and Thermodynamic Considerations to Spectroscopy and Chemistry of Species with MgMg Bonds

Chemical composition of magnesium boride films obtained by CVD

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MgCl and Mg₂Cl₂: From Theoretical and Thermodynamic Considerations to Spectroscopy and Chemistry of Species with MgMg Bonds