Group VB Elements Research Articles

Growth morphologies and mechanisms of non-equilibrium solidified MC carbide

Growth morphologies and mechanisms of the carbide of group IVB and VB elements (MC carbide), a typical faceted crystal, were studied with an estimated cooling rate from 102 to 105 K/s. Results showed that although the growth morphologies of the MC carbide vary remarkably with solidification cooling rate, the solid/liquid interface is always atomically smooth, and the growth mechanisms are always lateral growth. The growth mechanism transition from lateral to continuous growth mode, which was predicted by the classic crystal growth theory, was not observed for the TiC type MC carbide within the estimated cooling rate range of 102–105 K/s.

Growth morphology and mechanism of MC carbide under quasi-rapid solidification conditions

The carbide of group IVB and group VB elements, i.e. MC carbide, is an important constitution and strengthening phase for many alloy tool steels and cast nickel-base superalloys. Since the as-solidified growth morphology, size and distribution have an important influence on both the mechanical properties and hot workability, research on the solidification behavior of MC carbide is an important subject for cast superalloys and many high alloy tool steels. The growth morphology and mechanisms of MC carbide, under slow-cooling and rapid solidiication conditions, has been studied intensively as functions of the solidiication cooling rate. The solidiication behavior of MC carbide under quasi-rapid solidification conditions has not been reported in open literature. In this paper, the growth morphology and mechanism of an MC carbide (TiC type) under quasi-rapid solidification conditions is studied in a laser surface alloyed coating on a titanium aluminide alloy Ti–48Al–2Cr–2Nb (at.%). The growth morphology of the quasi-rapidly solidified MC carbide with a cooling rate of 4 × 102°C is found to be dendritic with strong faceted, double zigzag brick-stacking growth characteristics on the dendrite arms. The growth mechanism of the MC carbide is found to be a brick-stacking/double zigzag micro-branching lateral growth from steps on the intersecting {111} planes.

Fungal volatilization of arsenic and antimony and the sudden infant death syndrome

Fungal volatilization of antimony and other group Vb elements has been proposed to have a causal role in the sudden infant death syndrome (SIDS; cot death). The ability of fungi to produce volatile arsenic and antimony compounds in pure culture was examined using Scopulariopsis brevicaulis, reported as an inhabitant of PVC cot mattress covers, and Phaeolus schweinitzii, a wood decay fungus known to be a good volatilizer of arsenic. Volatile arsenic compounds were detected from all cultures grown on arsenic-supplemented media, but antimony volatilization was not reliably detected. Although antimony levels above the baseline sensitivity of the analytical technique were detected in four (out of 24) of the samples analyzed, the concentrations recorded were too low to be reliably interpreted as evidence for volatilization. Our results are discussed in relation to hypotheses regarding the causes of SIDS.

Fungal volatilization of arsenic and antimony and the sudden infant death syndrome.

Fungal volatilization of antimony and other group Vb elements has been proposed to have a causal role in the sudden infant death syndrome (SIDS; cot death). The ability of fungi to produce volatile arsenic and antimony compounds in pure culture was examined using Scopulariopsis brevicaulis, reported as an inhabitant of PVC cot mattress covers, and Phaeolus schweinitzii, a wood decay fungus known to be a good volatilizer of arsenic. Volatile arsenic compounds were detected from all cultures grown on arsenic-supplemented media, but antimony volatilization was not reliably detected. Although antimony levels above the baseline sensitivity of the analytical technique were detected in four (out of 24) of the samples analyzed, the concentrations recorded were too low to be reliably interpreted as evidence for volatilization. Our results are discussed in relation to hypotheses regarding the causes of SIDS.

Pressure-induced Phase Transition Sequence of the Group VB Elements and the Structure Change Seen from a New Point of View.

On the basis of the results of the diffraction studies by the present authors and those published in the literature, new structural systematics of the high pressure phases of the Group VB elements are proposed, in which the general transition sequence is expressed as rhombohedral A7 - (distorted) primitive simple cubic- distorted body-centered-cubic-body-centered-cubic. Investigation of the atomic arrangements of the high pressure phases shows that the network of the densest atomic planes changes gradually through the transition sequence.

The coordination environment of Ag and Cu in ternary chalcogenide glasses

An analysis is made of the information provided by the method of isotopic substitution in neutron diffraction on the metal atom coordination environment in M-A-X glasses, where M denotes Ag or Cu, A a Group IVB or VB element, and X a chalcogen. It is found that the M-X coordination number is low (~ 3–4) but there is no clear correlation between its precise value and whether the material is a semiconductor or fast-ion conductor. When the concentration of M is high it is possible to measure the M-M partial pair distribution function g M-M(r) . In those systems for which results are available it is found that, irrespective of the electrical conductivity mechanism, short M-M nearest-neighbour distances are present. However, the first peak in g M-M(r) is more clearly defined in the case of semiconducting glasses.

Crystal structure of the high pressure phases of bismuth bi iii and bi iii′ by high energy synchrotron x-ray diffraction

Abstract This paper reports the results of a synchrotron X-ray diffraction study on the crystal structures of Bi 111 and Bi 111′ which have been known to form under high pressure but have, for a long time, been unsolved. Powdered samples were compressed in a cubic-type multi-anvil press, MAXID, and diffraction data were collected using an Imaging Plate with monochromatized radiation of an energy of 49.7 keV. It was possible to identify at 3.8 GPa forty-eight reflections for Bi I11 in the sin θ / δ range from 1.6 nm−1 to 5.6 nm−1, which were indexed in terms of a tetragonal unit cell with a=0.8659 nm and c═ O·4238 nm (2=10). Analysis based on the observed intensities of the reflections led to a structure in which atoms form a distorted body-centered cubic lattice. It is of the same type as the structure of the high pressure phase of antimony Sb 11. When pressure was increased across the suggested transition pressure 4.3 GPa between Bi III and Bi III′ to 6.6 GPa, no change in the diffraction pattern was observed, indicating that there is no distinction between the two phases as long as the crystal structure is concerned. Discussion is given on the sequence of high pressure phase transitions in the Group Vb elements.

Studies of cluster anions C n X? (X=N, P, As, Sb, Bi) produced by laser ablation

A series of cluster anions C n X− are produced from laser ablation of appropriate samples, where X is selected as a group-VB element. The recorded mass spectra of these cluster anions display a drastic even/odd alternation on ion intensities: For C n N−, only anions with oddn can be observed; For C n P− and C n As−, cluster anions with evenn are produced but with lower signal intensities; For C n Sb−, the signal intensity of clusters does not show even/odd alternation; Finally, for C n Bi−, the intensities of cluster anions with evenn are higher than those with oddn. This parity effect can be attributed to the linear structure of the cluster anions, and the parity reversal of C n X− from C n N− to C n Bi− can be explained from the electronegativity decreasing of the heteroatom X as it descends in the group. The Huckel model was applied to account the structural feature of these clusters.

Phenylmercury(II) Haloacetates and their Complexes with Group VB Donors

Abstract Haloacetic acids cleave one of the two Ph-Hg bonds of diphenylmercury under mild conditions providing thereby a direct synthetic route to a number of phenylmercury(I1) haloacetates, PhHgOOCR (R = CH2I, CH2Br, CH2C1, CC13 or CF3) in nearly quantitative yield. Interaction of these arylmercuric haloacetates with ligands having atoms of Group VB elements (N, P, As or Sb) as donors, gives rise to molecular adducts of 1:l or 2 : l (in case of diphos) stoichiometry which are monomeric and non-electrolytesin nitrobenzene.

Nonequilibrium synthesis of NbAl3 and Nb-Al-V Alloys by Laser Cladding: Part I. Microstructure

NbAl3, like many ordered intermetallic compounds, appears to have great potential for application as high-temperature structural material because of the high melting point and stability in high- temperature oxidizing environments. However, the D022 (tI8) lattice structure shows limited ductility at room temperature. Addition of group IVB, VB, and VIB elements to A13X (D022 type of compounds) as partial replacement of X is a method being applied by various researchers to promote ductility in these materials by activation of numerous dislocations and ordered twin- ning. In this study, V was added in different amounts to improve the ductility of NbAl3. How- ever, this has an adverse effect on the oxidation response of the system, as is explained in Part II of this article. This article deals with the microstructure evolution, phase identification, and characterization of laser-clad (rapidly solidified) nominal NbAl3 and also studies the effect of V additions on the final microstructure in this system. Laser cladding of nominal NbAl3 produces two metastable unreported phases [body-centered tetragonal (bct) and base-centered orthorhombic phases]. Addition of V suppresses the primary phase (NbAl3) in the Nb-Al-V system.

Observations made during the growth of trihalides of group Vb elements

Single crystals of antimony triiodide (SbI 3), bismuth triiodide (BiI 3), antimony tribromide (SbBr 3) and arsenic triiodide (AsI 3) have been grown from the vapour. Experiments have been carried out both by oscillating and without oscillating the source-zone temperature. In the case of crystals grown without oscillation, it has been found that dendritic growth favours the growth of platelets. When the temperature is oscillated, the surfaće morphology is found to depend upon the supersaturation. Etching studies and Vickers microhardness studies have also been made.

Elastic moduli of binary bcc solid solutions of Group Vb elements

Elastic moduli of binary bcc solid solutions of Group Vb elements

Aluminum oxide adherence on Fe-Cr-Al alloys modified with group IIIB, IVB, VB, and VIB elements

A recent theory, explaining the effect of reactive elements on oxide adherence, states that sulfur adversely affects adherence and that reactive elements improve adherence by tying up sulfur as refractory sulfides. This theory is supported by work presented here, which correlates adherence behavior of Fe-Cr-Al alloys containing group IIIB through VIB elements with the stability of the sulfides that these elements form. Results show that poor adherence is produced by elements that form sulfides less stable than Al2S3 (VB and VIB elements), while good adherence is produced by elements which form sulfides more stable than Al2S3 (IIIB and IVB elements). In addition, the relative stability of sulfides, oxides, nitrides, and carbides must be considered. For example, group-IIIB elements are effective at much lower concentrations than group-IVB elements, because they react preferentially with S while group IVB elements react with C, N, and O before S.

Influence of stoichiometry on the electrical activity of impurities in Hg(1−x)Cd(x)Te

Elements from groups IB, IIIB, VB, and VIIB have been added to crystals of Hg(1−x)Cd(x)Te grown using the accelerated crucible rotation technique. Assessment on both as-grown and annealed (in Hg vapor) samples was carried out using Hall effect measurements to establish the electrical activity and stability of each dopant. Chemical analysis by atomic absorption spectroscopy and laser scan mass spectrometry determined the total levels of dopants in each crystal. The behavior of dopants in these crystals is compared to that found in Bridgman and epitaxial material and discussed in terms of the stoichiometry of melts and crystals at the growth temperature. It is concluded that group VB and VIIB elements are prevented from occupying Te sites when there is a high Hg vacancy concentration present during growth. Gold, which is inactive in Bridgman material, is found to be an active acceptor in a crystal grown using the accelerated crucible rotation technique. Group IB and IIIB elements are acceptors and donors, respectively, on metal sites irrespective of stoichiometry.

Effect of temperature on generation and decomposition of the group Vb element hydrides and estimation of the kinetic stability of gaseous bismuth hydride by atomic-absorption spectrometry

During work on atomic-absorption determination of arsenic, antimony and bismuth by the hydride-generation method with sodium tetrahydroborate, the thermal and kinetic stabilities of the hydrides at various generation temperatures were studied. The arsenic and antimony hydrides are very stable even at 40° but bismuth hydride is very unstable both thermally and kinetically, even at 25°. The approximate rate constants for the decomposition of gaseous bismuth hydride at 0, 10, 25 and 40° were found to be 0.05, 0.10, 0.24 and 0.29min −1 respectively.

On the reactivity of less common halopseudohalogens towards metalcarbon- and metalmetal-bonded compounds

Freshly generated solutions of iodine azide (IN 3) and iodine isocyanate (INCO) in acetonitrile or carbon tetrachloride add oxidatively to tertiaryaryl derivatives of group VB elements, Ar 3M (Ar = Ph, p-tolyl, p-ClC 6H 4 or p-FC 6H 4, and M = As, Sb or Bi) and diaryltellurium(II), Ar 2Te (Ar = Ph or p-CH 3OC 6H 4) at −10°C to −5°C to give stable covalent monomeric products, Ar 3MIX and Ar 2TeIX, respectively (where X = N 3 or NCO). The mode of bonding of the pseudohalide group to M has been established by solid-state IR spectra. Ar 3MI(N 3) failed to react with CS 2 but reaction with PhNCY (Y = O or S) gave cyclic tetrazole derivatives. Contrasting behaviour was also observed in the metathetic reaction of Ar 2MIX and Ar 2TeIX with silver pseudohalides [AgX′ (X′ = NCO or NCS)]. The tetraorgano compounds, R 4M (M = Sn or Pb, and R = Ph or p-tolyl), and Bu 3SnPh failed to react with IN 3 and Bu 3SnPhINCO but IN 3 cleaved one tin-aryl bond from Ar 4Sn in the presence of AlCl 3. Addition of IN 3 and INCO across the olefinic bond of Ph 3SnCH 2CHCH 2 is preferred to tin-allyl bond cleavage. Reactions of hexaaryldileads with IN 3 and INCO under appropriate conditions proceeded with the cleavage of a PbPb bond. Parallel reactions of cyanogen halides (CNI and CNBr) resulted in the formation of corresponding triaryllead halides and pseudohalide derivatives.

Pressure-induced superconductivity of arsenic: Evidence for a structural phase transition

The group VB elements P, As, Sb and Bi are normally nonsuperconductors since they are either semiconductors or semimetals at ambient pressure. Under high pressure all of them are turned into superconductors. We have investigated the pressure dependence of T c for As up to a pressure of 28 GPa quantitatively for the first time. Employing a 3He/ 4He dilution refrigetor we have discovered that T c increases monotonously and steeply with pressure in the A7-rhombohedral phase from below 0.05 K at 10 GPa to a pronounced maximum at approximately 24 GPa with T c, max2.7 K. Our results are in strong disagreement with a previous publication. In addition, a faint resistance anomaly is observed in the same pressure range. It is concluded that both phenomena point to the occurence of a structural phase transition in agreement with an unpublished X-ray investigation by another group of authors. The continuous rise of T c with pressure in the A7 phase is so far a rather rare phenomenon among the B-group elements. Interestingly enough, quite similar behavior has also recently been reported for the A7 phases of P and Sb. We suggest that this unusual feature is related to a pressure-induced phonon softening in connection with a gradual weakening of the covalent bonds. The effect is believed to stand in close connection with the continuous reduction of the rhombohedral distortion of the crystal lattice towards simple cubic with increasing pressure. An interesting prediction for the shape of the melting curve of As at very high pressure can be made.

The Removal of Group Vb Elements (As,Sb,Bi) From Molten Copper Using a Na<SUB>2</SUB>CO<SUB>3</SUB> Flux

The Removal of Group Vb Elements (As,Sb,Bi) From Molten Copper Using a Na<SUB>2</SUB>CO<SUB>3</SUB> Flux

The Removal of Group Vb Elements (As,Sb,Bi) From Molten Copper Using a Na2CO3Flux

The mechanism for the removal of the group Vb elements, As, Sb, Bi, from molten copper using a Na2CO3 flux has been investigated in order to develop a pyrometallurgical copper refining process. Experiments were carried out in an argon atmosphere using 300g of molten copper containing various amounts of the group Vb elements and oxygen. The temperature range of this study was 1150–1250°C. The arsenic content in copper decreased rapidly from about 2500 to 200 ppm within 10 min of adding the Na2CO3 flux (5% of the weight of the molten copper). Antimony behaved in the same manner as arsenic except that under the same experimental conditions, the time required for elimination was longer. However, the Na2CO3 flux had little effect on the removal of Bi from the copper.While the effect of temperature was found to have only a little influence, the oxygen content in copper had a large effect on the arsenic and antimony elimination reaction. The removal rate increased with increasing oxygen contents in copper.The mechanism for the removal of these elements are discussed based on the observed evolution of CO2 and on X-ray radiographic data. The removal of arsenic and antimony can be accounted for by the equation2(As or Sb) + 5O + Na2CO3 = 2Na (As or Sb) O3 + CO2 (1)where X represents the element X dissolved in molten copper.

Free radicals derived from 1,4-diaza-1,3-butadiene: II. Adducts with metal carbonyls and reactions with derivatives of group VB elements

The paramagnetic adducts formed when photochemically generated Mn(CO) 5 or Re(CO) 5 radicals are trapped by N, Nt́-di-t-butyl-1,4-diaza-1,3-butadiene (t-Bu-DAB) have been characterized by ESR spectroscopy. Adducts containing phosphorus have also been observed but attempts to produce adducts containing As, Sb or Bi have been unsuccessful. In a number of systems an identical ESR spectrum was observed. This has been shown to arise from the N, N′-di-t-butylpyrazinium cation.