Topotactic transition in C<sub>4</sub>AlB<sub>24</sub>

Giese, R. F.; Economy, James; Matkovich, V. I.

doi:10.1107/s0365110x66001634

Cited by 17 publications

(6 citation statements)

References 2 publications

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“…All B-B and B-C bonds in CsA12.1Bsx are only 0.02 to 0"05 A longer than those in boron carbide, supporting the suggestion (Hoard & Hughes, 1967) that this ternary phase is in fact an aluminum stabilized twinned derivative of the more simple boron carbide. The suggestion is strengthened further by the observation that 'C4A1B24' undergoes a topotactic transition with loss of A1 at about 2000 °C to the boron carbide structure (Giese, Economy & Matkovich, 1966). This type of transition now seems reasonable since similar intericosahedral bonding exists for both structures; however, the details of the mechanism are still not entirely clear.…”

Section: Discussionmentioning

confidence: 92%

Crystal structure of C₈Al_2.1B₅₁

Perrotta¹,

Townes²,

Potenza³

1969

Acta Crystallogr Sect B

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X-ray analysis of CsA12.1Bsx (C2/m 2/c 21/m; a=5.690, b=8.881, e=9.100 A) based on full-matrix refinement of complete three-dimensional data gives a distorted hexagonal close-packed B12 icosahedral structure in which each icosahedral B atom is six coordinated. Half of the icosahedral B atoms form single B-B bonds between icosahedra; the remaining half are linked to C by single B-C bonds. Statistically distributed intericosahedral B atoms on a center of symmetry complete a tetrahedral environment about C and develop linear C-B-C chains similar to those found in rhombohedral boron carbide. Indeed, all B-B and B-C bond distances closely approximate values obtained for rhombohedral boron carbide. Aluminum atoms are located on partially occupied sites between icosahedra and in all cases A1-B and A1-C nearest neighbor contacts are at least 0.2 A. smaller than the sum of the appropriate covalent radii. Interestingly, an A1 atom competes statistically with the B atom in the C-B-C chain such that when AI is present, B is not. The stoichiometry presented here leads to questions concerning the bonding schemes described in previous analyses based on different stoichiometries. Isotropic refinement gave Re = 0.050 for 762 observed diffraction maxima.

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Section: Discussionmentioning

confidence: 92%

Crystal structure of C₈Al_2.1B₅₁

Perrotta¹,

Townes²,

Potenza³

1969

Acta Crystallogr Sect B

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“…Two product ions appear when SiH2A ions are injected into methane, namely, SiCH4~and S1CH5+, products which were also reported by Stewart, Henis, and Gaspar. 4 The reactions producing these products can hardly be anything except what is shown in (31) and (32), viz.…”

Section: Resultsmentioning

confidence: 99%

“…(a) C4 + StH4. As shown in Table I, injection of 1-eV (lab) C~ions, produced by the impact of 100-eV electrons on methane, into monosilane produces ions at mje [28][29][30][31]41, and 42, which in this system can be only Si+, SiH+, SiH2 + , SiHs+, SiCH+, and SiC,H2 + , respectively. The dependence of the cross sections on relative kinetic energy indicates that all processes are exothermic, with the possible exception of SiH+ formation.…”

Section: Resultsmentioning

confidence: 99%

“…SiH% + CH, -> SiCH4+ + H2 (31) SiHa+ + CH4 -SiCH5+ + H (32) Available thermochemical data3-32 •35 show (31) to be thermoneutral while (32) is endothermic by 8 kcal; the dependence of the cross sections on relative kinetic energy indicates both reactions to be exothermic. Since the combined uncertainties in the reported enthalpies of forma-tion3-35 of SiCHg^a nd SiH2+ exceed 8 kcal/mol, we feel it most probable that (32) is actually exothermic even for ground-state ions.…”

Section: Resultsmentioning

confidence: 99%

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Ion-molecular reactions in monosilane-methane mixtures

Cheng¹,

Yu²,

Lampe³

1973

J. Phys. Chem.

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High-pressure mass spectrometry and tandem mass spectrometry have been used to study the collision reactions of primary ions of methane with monosilane and of primary ions of monosilane with methane. All primary ions of each constituent undergo at least one ion-molecule reaction with the opposite molecule, but by far the most predominant such "cross" reaction is hydride transfer from monosilane to the primary ions of methane, producing the SiHs+ ion. Reaction cross sections and rate constants for the various processes are presented.

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“…Their earlier works on the structures of higher borides have shown that the aspect ratio of AlB 2 flakes can range anywhere from 30 to 300 with a thickness of a few microns. [14][15][16][17][18][19][20] With a modulus of 448 GPa, 14,15 AlB 2 flakes provided a significant reinforcement to the epoxy, raising its modulus to 276-303 GPa at 60 vol% content. The composites were also very resistant to damage i.e., drilling holes or bullet holes.…”

Section: Introductionmentioning

confidence: 99%

Microstructural characterization and wear properties of in situ AlB₂–reinforced Al–4Cu metal matrix composite

Fıçıcı

Köksal

2015

Journal of Composite Materials

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Aluminium matrix composites have been extensively studied for several decades due to the potential advantages over classical low-density materials. Low-density composites can offer high wear and corrosion resistance, high strength, and favorable thermal electrical properties that attract the attention of various industries such as aerospace and automotive. This study investigates the dry sliding wear behavior of AlB2–Al–4Cu composites with 5, 10, 20, and 30% weight reinforcement. In situ developed AlB2 flakes were incorporated as the reinforcing compound in the Al–4Cu matrix. The composite samples were tested against a steel disk using a pin-on-disk wear rig. The effect of reinforcement ratio, applied load, sliding velocity on the wear rate and friction coefficient of the composite samples was investigated. In addition, the worn surfaces have been characterized in terms of wear patterns. Compared to the matrix alloy, composite samples exhibited better wear resistance and lower friction coefficient to varying degrees of magnitudes.

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Topotactic transition in C₄AlB₂₄

Cited by 17 publications

References 2 publications

Crystal structure of C₈Al_2.1B₅₁

Crystal structure of C₈Al_2.1B₅₁

Ion-molecular reactions in monosilane-methane mixtures

Microstructural characterization and wear properties of in situ AlB₂–reinforced Al–4Cu metal matrix composite

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Topotactic transition in C4AlB24

Cited by 17 publications

References 2 publications

Crystal structure of C8Al2.1B51

Crystal structure of C8Al2.1B51

Ion-molecular reactions in monosilane-methane mixtures

Microstructural characterization and wear properties of in situ AlB2–reinforced Al–4Cu metal matrix composite

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Product

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Topotactic transition in C₄AlB₂₄

Crystal structure of C₈Al_2.1B₅₁

Crystal structure of C₈Al_2.1B₅₁

Microstructural characterization and wear properties of in situ AlB₂–reinforced Al–4Cu metal matrix composite