Groups IVA Research Articles

The reactions of transition metal nitrides of groups IVA, VA and VIA with chlorine, bromine and hydrogen chloride

We have reacted various transition metal nitrides with chlorine, bromine and hydrogen chloride to form the same binary metal halides as are formed by reaction with the metal.

Mechanical properties of niobium alloyed with elements of groups IVa?VIa

1. A fairly substantial increase in the strength of niobium at room temperature, with satisfactory ductility, is obtained by alloying with small quantities (0.5–2 at. %) of elements from groups IVa–VIa. 2. The increase in strength due to different elements differs and depends under the conditions investigated on the difference in the atomic size of niobium and the alloying element and also its activity with respect to interstitial impurities (the latter in the case of insufficiently pure "binary" alloys).

Deviations from additivity of lattice spacings in transition metal alloy systems

Abstract Using published lattice spacing/composition curves, deviations Δa from additivity of lattice spacings have been calculated for solid solutions in the metals of groups IVA, VA and VIA of the periodic table of transition metals of group numbers 4 to 11 from the three long periods. The results are presented as typical diagrams. Where the components have the same group number, Δa is zero unless one component is from the first long period, when Δa is positive. In such cases the Δa/composition curves are similar in form. Pairs of systems involving a common component also frequently correspond with similar Δa/composition curves. For solvents of group VIA of the periodic table solutes of lower and higher group number give negative and positive Δa values, respectively. This regularity is less marked for group VA solvents, and lost for group IVA solvents, for solid solutions in which Δa is predominantly negative. The results are discussed, and it is suggested that they are consistent with the operation of ...

Photoemission studies of the band structures of transition metal dichalcogenides. I. Groups IVA and IVB

Photoemission spectra have been recorded for the dichalcogenides of several metals in groups IVA and IVB, using incident photon energies of 21.2, 40.8 and 48.4 eV. Considerable structure is resolved in the valence bands which are based mainly on chalcogen p orbitals. An interpretation given in terms of a simple LCAO model is in qualitative agreement with recent band structure calculations.

Force Constants and Mean Amplitudes of Vibration of Hexahalo Species of Groups IVA and VIA

The GVFF constants and mean am plitudes of vibration have been calculated for 21 hexahalo species of group IVA and VIA elements. The influence of the cation on these constants is discussed. It has been found that the chemical bonds in the environment of a light cation are relatively stronger than in that of a heavy cation in case of inorganic cations while the situation is opposite in case of organic cations.

Chemical fractionation in iron meteorites and its interpretation

Published analyses of trace and minor elements in iron meteorites have been compiled and the distributions interpreted with the chemical groups defined by Wasson. When each element is plotted against Ni on log scales, groups are often clearly resolved with all the members of a group falling within the limits of sampling and analytical error on a straight line. The lines for groups IIIa,b and IVa are generally parallel with IIa,b plotting on a steeper gradient. In contrast to Ga and Qe, many elements show variations within a group which may approach that shown by all the iron meteorites. Group I members have a fairly uniform concentration of elements which are severely fractionated in the other major groups. There are also fewer correlations of elements in group I. Thus the genetic significance of the chemical classification is strengthened by the addition of more parameters which may be used in the definition of the groups. Relationships between groups lia and lib and between Ilia and Illb are confirmed. More important is the record of events during the formation of iron meteorites that the fractionations of elements provide. Two fractionations have occurred, a primary event which established the bulk composition of each group and a secondary event which fractionated the elements within each group. Group I appears to have escaped the secondary fractionation. An examination of possible fractionation mechanisms suggests that the secondary process took place during solidification of iron cores in the parent bodies. The elements It, Os, Pt, Bu and Rh would be enriched in the early Ni-poor solid whilst As, Au, Co, Mo, P, Pd and Sb would concentrate in later solid and produce the observed positive correlations with Ni. These trends are largely those predicted from the binary phase diagrams of Fe, although Cr and Ge behave otherwise. The magnitude of the fractionations could be predicted from the distribution coefficients of elements between solid and liquid Fe-Ni. Unfortunately these can only be guessed and confirmation awaits experiments to indicate their magnitude. The primary fractionation which established the chemical differences between the groups might have occurred during condensation.

Observations on solid solubilities in the transition elements of groups IV to VII

Available data are graphically presented and briefly discussed for the solid solubilities of the elements of Groups IIIA to VIIA, and of Groups VIII and IB of the Periodic Table in the body-centred cubic transition metals of Groups IVA to VIIA. There is a general tendency for the solid solubility in a solvent metal for which the component of bonding due to d electrons is strong to decrease rapidly and systematically as the d-component of bonding in the solute element decreases. This supports the suggestion that extensive solid solution formation in the transition elements depends intimately on the degree to which the bonding characteristics of the solvent metal can be reproduced in the solid solution. The data presented also suggest that the theoretical treatment of the cohesion of the noble metals, and those immediately following them in their respective series, may be inappropriate for the transition metals without due allowance for the directional properties resulting from the variable participation of d electrons in the bonding processes.

Cooling rates and thermal histories of iron and stony-iron meteorites

Cooling rates of meteorite parent bodies are calculated on the basis of theoretical thermal models. These calculated cooling rates are compared with meteorite cooling rates derived by diffusion-growth analysis of the metal phase of iron and stony-iron meteorites. Previous thermal calculations are extended to include effects of melting, redistribution of radioactive heat sources, and surface heating. For a range of assumed conditions, the cooling rates depend strongly on the extent of internal redistribution of radioactive elements. Cooling rates calculated for uniform and fractionated parent bodies exceeding 100 km in radius can differ by a factor of more than 3. Since the distribution of radioactive materials is uncertain, size estimates for bodies with a radius exceeding 100 km can only be narrowed to a range of values bounded by the uniform and the fractionated case. This range of body sizes is still compatible with an origin of iron and stony-iron meteorites in asteroidal bodies. The present calculations are not consistent with the development of iron meteorites by surface heating of parent bodies. The core model appears to be appropriate for some iron meteorites. However, the variable cooling rates for iron meteorite groups IIIa and IVa are explained by a model where small iron bodies are distributed throughout a large region of the parent body from the deep interior out to a fractional radius of 0.90 to 0.96. It is proposed that such a distribution of iron meteorites could be produced by a zone melting process

Der Einfluß chemischer Reaktionen in einer siliziumhaltigen Kohlenstoffmatrix auf die Spektrallinienintensität

Thermochemical reactions taking place in graphite electrodes if burnt in a d.c. arc and their influence on the intensity of spectral lines have been investigated. For this purpose oxides and other compounds of Ti, Zr, V, Ta, Mo and W mixed with varying amounts of SiC or SiC-C were used. The reaction products after burning these samples were identified by X-ray diffraction analysis. It can be shown, that under these conditions both silicides and carbides are formed of the elements of groups IVa–VIa of the periodic table. For studying the influence of thermochemical reactions on spectral line intensities, mixtures of several elements and their compounds in a SiC- and SiC-C-matrix were burnt and the intensities of suitable spectral lines measured. It was found, that not only the favoured thermo-chemical reaction influenced the line intensities but also the physical properties of the reaction products and the matrix have an effect on the parameters of the d.c. arc and in this way on the spectral line intensities.

The distribution of trace quantities of germanium between metal, silicate and sulflde phases

The distribution of trace quantities of Ge between metal, silicate and sulfide phases has been studied hydrothermally at controlled P O 2 by means of oxygen buffer techniques. Radioactive Ge 68-labeled olivine of varying Mg and Fe composition and Ge 68-labeled iron were synthesized for this study. At 900°C and 500 bars, Ge is strongly siderophile in the iron-olivine system even at the equilibrium P O 2 of iron-wüstite. Similar strongly siderophilic behavior of Ge was also observed in the Fe-FeS system at this temperature and pressure. Thermodynamic data indicate that the free energy of formation of germanium dioxide lies between that of the iron oxide and nickel oxide at all temperatures. In the presence of metallic iron, the reduction of GeO 2 to Ge and the formation of Fe-Ge alloy are spontaneous reactions. If nickel is added to the system, the metal phase (Fe-Ni alloy) can exist at a higher P O 2 than pure iron. At the low Ni content of about 10 per cent, as found in most iron meteorites, the change in P O 2 Of metal-wüstite from iron-wüstite is small and is unlikely to affect the siderophilic behavior of Ge. A discussion is given to indicate that the diffusion of Ge out of the metal phase is possible if the Ni content of the metal is very high. From these results, it seems unlikely that a simple one-stage separation of metal from silicate would cause the extremely low Ge content observed in some iron meteorites e.g. iron meteorites of chemical groups IVA and IVB. Other possible fractionation processes involving Ge are also discussed.

Phase diagrams of plutonium with metals of groups IIA, IVA, VIII, and IB

Phase diagrams of plutonium with metals of groups IIA, IVA, VIII, and IB

The iron meteorites, their thermal history and parent bodies

Cooling rates are determined for the formation of the Widmanstätten pattern in 193 iron meteorites in order to obtain information on the number and possible types of parent meteorite bodies. About two thirds of the meteorites cooled between 1 and 10°C 10 6 yr although the total variation in cooling rates is 0.4–500°C/10 6yr. These variations indicate that the iron meteorites formed in more than one parent body, the Widmanstätten pattern formed at low pressures, and the maximum sized parent body was about 300 km in radius if the irons formed in its core. Evidence is presented to show that meteorites, within each Ga-Ge group are genetically related. Characteristic plessite structures were observed for each of these groups. The cooling rate variations in both Ga-Ge groups I and IIIb are small (2–3°C/10 6yr and 1–2°C 10 6 yr., respectively) and independent of chemical composition. These meteorites probably formed in the cores of parent bodies about 200 km in radius. The cooling rate variations in both groups IIIa and IVa are large ( 1.5–10°C/10 6 yr and 7–90°C/ 10 6 yr, respectively) and vary with the Ni content, decreasing as the Ni content increases. These meteorites probably formed in isolated regions spread throughout parent bodies 150–200 km in radius. These regions consisted of molten metal at the time of formation.

Raman studies on species in aqueous solutions. Part II. Oxy-species of metals of Groups VIA, VA, and IVA

Raman and infrared spectra have been measured of solutions of oxides of metals of Groups VIA, VA, and IVA in aqueous hydrofluoric, hydrochloric, and perchloric acids. Evidence was obtained for the existence in such solutions of fluoro- and chloro-complexes of molybdenum and tungsten with cis-dioxo-ligands, of mono-oxo-pentahalogeno-species of niobium and vanadium, and of unsubstituted halogeno-complexes of tantalum, titanium, zirconium, and hafnium. Polynuclear complexes were formed in perchloric acid solutions.

Über die Bestimmung von Sauerstoff, Stickstoff und Wasserstoff in Oxiden und Hartstoffen durch Hochtemperatur-Vakuumentgasung

A new method for high-temperature vacuum-degassing has been described and applied to the determination of very small quantities of hydrogen, oxygen and nitrogen in refractory materials as well as large amounts of these elements in hydrides, oxides and nitrides. A closed graphite capsule is used to prevent the loss of oxygen (as CO2) and the evaporation of low-melting oxides. In the analysis of highly refractory oxides addition of Si or Si alloys is required. The analysis of nitrides and hydrides does not cause any difficulties if the degassing temperature is high enough. Yet, difficulties arise with the very stable nitrides of the metals of the IVa and Va groups of the periodic system. Several samples are analyzed according to the method described and to standard techniques and the results are compared.

Spectroscopic studies of inorganic fluoro-complexes. Part I. The 19F nuclear magnetic resonance and vibrational spectra of hexafluorometallates of Groups IVA and IVB

The infrared, Raman, and 19F n.m.r. spectra of the hexafluoro-anions of the Group IVA and IVB elements have been measured. We conclude that the predominant species present in aqueous solutions of the ammonium salts are the octahedral AF62– ions (except where A = Pb, when no definite conclusions could be drawn). In solution, the HfF72– ion dissociates into HfF62– and F–. Fluorine exchange is much more rapid when A is Zr, Hf, or Pb than when A is Si, Ge, Sn, or Ti. The tin–fluorine coupling constants in the SnF62– ion are appreciably solvent-dependent.

The chemical classification of iron meteorites: I. A study of iron meteorites with low concentrations of gallium and germanium

The concentrations of Ga and Ge have been determined in 34 iron meteorites. The meteorites were chosen either because they were found to have Ga or Ge concentrations below the detection limits of previous investigators, or because they were similar in structure and Ni content to meteorites of the former sort. All but 3 of the meteorites belong to one of the following two classes: ataxites with greater than 13% Ni, or fine octahedrites with less than 9·5% Ni. On the basis of the new results it is possible to resolve Ga Ge group IV of Lovering et al. (1957) into two distinct groups, designated Ga Ge groups IVa and IVb, and having 12 and 6 members respectively. Three meteorites have Ga and Ge concentrations similar to meteorites in Group III, whereas the remaining 13 meteorites cannot be assigned to any of the known Ga Ge groups. Certain regularities are to be seen in plots of Ge vs. Ga concentration and Ge vs. Ni concentration. These are discussed in terms of the multiple parent-body hypothesis and also in terms of planetary fractionation processes. Evidence is discussed which indicates that Ga Ge groups I, IVa and possibly IVb represent fully resolved groups, whereas the remaining groups are complex. An attempt at resolving the latter groups on the basis of detailed chemical studies is proposed.

Electrodeposition of Refractory Metals

A refractory metal, it is commonly agreed, is a metal with a high melting point. There is no agreement, however, on the lower limit of melting temperature which defines the group. This is usually set by the individual author so as to include the metals he wishes to discuss and exclude the others. Since the greatly increased interest at present in refractory metals stems largely from the need for structural materials for high-temperature application which cannot be met by ferrous or common non-ferrous (i.e., cobalt-based) alloys, one may set the melting point of iron, 1535°C, as a lower limit to the melting temperature of a metal to be considered refractory. The metals that melt above 1535°C are those in Groups IVA, VA, VIA of the Periodic System, the six platinum metals, and rhenium. Since we have been speaking of structural applications, we will eliminate from consideration the platinum metals and rhenium (and a few actinides and lanthanides) because of their scarcity and are left with the nine metals of Groups IVA-VIA: titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, and tungsten. It is on precisely this group of metals that the interest of electrochemists has been centred for many years and in the electrodeposition of which some significant new developments have emerged.

The far infrared spectra (650 to 200 cm −1) of some monosubstituted benzene derivatives

The far infrared spectra (650 to 200 cm −1) are reported for a series of phenyl derivatives of groups IVA, VA, VIA and VIIA. Assignments are made for the stronger bands.

New Elements as Potential Refractories

EXAMINATION of a Lothar–Meyer plot with reference to the synthesis of elements up to 102, and the possibility of producing even higher elements, lead to some rather interesting speculations. On observation of the Lothar–Meyer plot of melting points (Fig. 1) several different types of characteristic periodic variations become apparent. Within Groups IA (lithium to caesium), IB (zinc to mercury), IIA (beryllium to barium), IIIA (boron to thallium), IVA (carbon to lead) and IVB (titanium to hafnium) the melting points tend to decrease with increasing atomic number. Within groups VB (vanadium to tantalum), VIA (oxygen to polonium), VIB (chromium to tungsten), VIIA (fluorine to astatine), VIIB (manganese to rhenium), VIIIA (helium to radon) and VIIIB (iron to osmium) the melting points tend to increase with increasing atomic number. Groups IIIB (scandium to lanthanum), VA (nitrogen to bismuth) and VIIIB (cobalt to iridium and nickel to platinum) exhibit an intermediate behaviour in which the melting points first increase and then decrease with increasing atomic number; and group IB (copper to gold) exhibits a slight minimum.

The solubility of oxygen in transition metal alloys

The solubility of oxygen in niobium and solid-solution alloys of niobium with other transition metals of Groups IVA, VIA, VIIA and VIIIA has been measured. The solubility of oxygen in niobium over the temperature range 700°C–1550°C obeys the relation: − log e N = 8,6 oo/ RT + 0.516 where N is the atomic fraction of oxygen in solution. Additions of molybdenum, rhenium and ruthenium to niobium all reduce oxygen solubility, zero solubility being reached when the electron/atom ratio of the alloy is about 5.75. Additions of titanium increase the oxygen solubility, but zirconium, which forms a very stable oxide ZrO 2, reduces oxygen solubility markedly. It is concluded that the solubility of oxygen in transition metal alloys is largely electronic in nature, solubility being small if the electron/atom ratio of the alloy exceeds 5.75, and being very much larger in alloys of a lower electron/atom ratio, the oxygen dissolving with a positive charge.