Röntgenanalyse der Systeme Wolfram‐Kohlenstoff und Molybdän‐Kohlenstoff

Westgren, Arne; Phragmén, Gösta

doi:10.1002/zaac.19261560105

Cited by 67 publications

(20 citation statements)

References 2 publications

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“…[9] This means that carbon atoms occupy all the octahedral holes formed naturally by the tungsten atoms. So, the loss of a carbon atom will create a vacancy in the lattice of WC.…”

Section: Introductionmentioning

confidence: 99%

Crystal Structure and Carbon Vacancy Hardening of (W_0.5Al_0.5)C_1−x Prepared by a Solid‐State Reaction

Yan

Zhao

et al. 2005

ChemPhysChem

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Novel solid solutions of aluminum in tungsten carbide (WC) with or without carbon vacancies, which can be expressed by the chemical formula (W(0.5)Al(0.5))C(1-x) (x=0.0-0.5), have been synthesized by the solid-state reaction of W(0.5)Al(0.5) alloy and the proper amount of carbon at around 1673 K in vacuum. The reaction time decreases from 73 to 50 h on increasing the carbon vacancy concentration from 0 to 50 %. The formation of the intended products is certified, by X-ray diffraction, environmental scanning electron microscopy-energy-dispersive X-ray analysis, and inductively coupled plasma-atomic emission spectroscopy, even though the carbon vacancy concentration reaches the astonishing value of 50 %. The as-prepared (W(0.5)Al(0.5))C(1-x) samples have been identified as the hexagonal WC-type structure belonging to the space group P6m2 (Z=1). Moreover, the crystallographic results reveal that the substituting aluminum atoms in the WC are located in the 1a site (the W atom position of the WC structure) and the cell parameters decrease slightly with increasing vacancy concentration. The hardness of the (W(0.5)Al(0.5))C(1-x) system increases up to a maximum 2659 kg mm(-2) at a carbon vacancy concentration of about 35 %, and the density of (W(0.5)Al(0.5))C(1-x) is far lower than that of WC.

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“…[9] This means that carbon atoms occupy all the octahedral holes formed naturally by the tungsten atoms. So, the loss of a carbon atom will create a vacancy in the lattice of WC.…”

Section: Introductionmentioning

confidence: 99%

Crystal Structure and Carbon Vacancy Hardening of (W_0.5Al_0.5)C_1−x Prepared by a Solid‐State Reaction

Yan

Zhao

et al. 2005

ChemPhysChem

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“…The point that volume changes accompanying order-disorder transformations may be of significant importance for the thermodynamic description of the system was presented by C. Wagner ( 9 ) . He also considered the problem of whether the transition between a substantially ordered structure and a substantially disordered structure involves a discontinuous (heterogeneous) traiisformation, or whether the degree of order decreases continuously with increasing temperature.…”

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confidence: 99%

Ternary Phase Equilibria in Transition Metal-Boron-Carbon-Silicon Systems. Part 1. Related Binary Systems. Volume 1. Mo-C System

Rudy¹,

Chang²,

Windisch³

1965

109

112

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“…The lattice parameter of (W 0.8 Al 0.2 )C 0.7 is calculated to be a = 2.9082(1), c = 2.8372(1) , which is quite close to that of WC [9,10] Because W, Al occupies the same lattice site in the cell of (W 0.8 Al 0.2 )C 0.7, [2] and the atomic ratio of metal to carbon is 1:0.7, it is deduced that there are many carbon vacancies, approximately 30 % compared with WC, in the lattice of (W 0.8 Al 0.2 )C 0.7 The indexing result of the (W 0.8 Al 0.2 )C 0.7 is presented in Table 1. In tungsten carbides system, WC almost cannot become carbon deficient as evidenced by the binary W-C equilibrium diagram.…”

mentioning

confidence: 67%

Synthesis and Characterization of the Off‐Stoichiometric Compound (W_0.8Al_0.2)C_0.7

Yan¹,

Ma²,

Zhao³

et al. 2005

Adv Eng Mater

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Gibbs free energy change of the aggregating process of five tetrahedrons to one decahedron is favorite [14] resulting in the formation of Si nucleus with five fold twin structure.Recently Liu et al reported that the Si crystals growth would be restricted by solute since these fine Si grains were surrounded by Al solute at large undercooling, [16] resulting in near equiaxed fine Si crystals. In present rapid solidification process, the undercooling was larger, and diffusion distance of both Si and Al atoms would be limited. When the Si nucleus was formed, it would trigger the crystallization of the Si atom clusters existed in the Si-rich zone. So under the influence of solute atom suppression and small diffusion ability, spherical primary Si particles with nanograins were formed. It is obvious that rapid solidification and higher Si content in the Al-Si alloy would benefit to the formation of Si atom clusters, Si-rich zone and the spherical primary Si particles.In summary, the microstructures of the as-quenched Al 60 Si 40 alloy obtained by melt-spinning technique consist of spherical primary Si, nanosize fcc-Al particles and amorphous matrix. It has been found that spherical primary Si particles are constituted by many nanosize Si grains and some of them are of twin relationship. In the center region of the spherical primary Si fivefold twin structures have been found, which are believed to be the nucleus. High Si content in the Al-Si alloy and rapid cooling are beneficial to the formation of the spherical primary Si particles. ExperimentalThe alloy ingot with the composition of 60 at% Al and 40 at% Si was prepared by arc melting of the mixture of Al (99.997 % purity) and Si (99.9995 % purity) elements in argon atmosphere. Ribbon samples with 20-30 lm in thickness and 2.0 mm in width were prepared by the melt spinning technique (speed of the wheel is 30 m/s). Near the wheel side was selected for the studies. The phase structures of the as-quenched alloys were characterized by the high-resolution electron microscopy (HREM) and selected area electron diffraction (SAED) in the JEM2010F TEM with a field emission gun. The operating voltage is 200 kV. The thin foil specimen for TEM analysis was prepared by ion thinning.

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Röntgenanalyse der Systeme Wolfram‐Kohlenstoff und Molybdän‐Kohlenstoff

Cited by 67 publications

References 2 publications

Crystal Structure and Carbon Vacancy Hardening of (W_0.5Al_0.5)C_1−x Prepared by a Solid‐State Reaction

Crystal Structure and Carbon Vacancy Hardening of (W_0.5Al_0.5)C_1−x Prepared by a Solid‐State Reaction

Ternary Phase Equilibria in Transition Metal-Boron-Carbon-Silicon Systems. Part 1. Related Binary Systems. Volume 1. Mo-C System

Synthesis and Characterization of the Off‐Stoichiometric Compound (W_0.8Al_0.2)C_0.7

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Röntgenanalyse der Systeme Wolfram‐Kohlenstoff und Molybdän‐Kohlenstoff

Cited by 67 publications

References 2 publications

Crystal Structure and Carbon Vacancy Hardening of (W0.5Al0.5)C1−x Prepared by a Solid‐State Reaction

Crystal Structure and Carbon Vacancy Hardening of (W0.5Al0.5)C1−x Prepared by a Solid‐State Reaction

Ternary Phase Equilibria in Transition Metal-Boron-Carbon-Silicon Systems. Part 1. Related Binary Systems. Volume 1. Mo-C System

Synthesis and Characterization of the Off‐Stoichiometric Compound (W0.8Al0.2)C0.7

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Crystal Structure and Carbon Vacancy Hardening of (W_0.5Al_0.5)C_1−x Prepared by a Solid‐State Reaction

Crystal Structure and Carbon Vacancy Hardening of (W_0.5Al_0.5)C_1−x Prepared by a Solid‐State Reaction

Synthesis and Characterization of the Off‐Stoichiometric Compound (W_0.8Al_0.2)C_0.7