Das Dreistoffsystem Nickel—Chrom—Bor

The ternary system Ni?Cr?B was established at 1000°C by X-ray diffraction and metallographic examinations. Binary chromium resp. nickel borides and two ternary borides Cr₃NiB₆ and Cr₂Ni₃B₆ were confirmed. Differential thermoanalysis of binary Ni?B-alloys showed the possibility of a metastable solidification according the partial system Ni?Ni₂B up to 19 at % B. The melting temperatures of ternary alloys were established.     

On the structural and magnetic properties of the ternary silicides Ce6M1.67Si3 (M=Co, Ni) and Ce5Ni1.85Si3

Contrary to that reported previously, the ternary silicide “Ce₆Ni₂Si₃” does not exist. The melting of this alloy, followed or not by annealing, leads to the existence of the two new ternary compounds, Ce₆Ni_1.67Si₃ and Ce₅Ni_1.85Si₃. The investigation of these ternary silicides based on nickel and Ce₆Co_1.67Si₃ by X-ray diffraction on single crystal reveals an ordered distribution between Ni (or Co) and Si atoms. The nickel or cobalt positions in the chains of face-shared octahedra of cerium are not fully occupied with a strong delocalisation of their electron density. The structural investigations of these compounds confirm that the “Ce₆Ni₂Si₃” and “Ce₅Ni₂Si₃” structural type have to be rewritten as Ce₆Ni_2−xSi₃ and Ce₅Ni_2−xSi₃. Magnetisation and specific heat measurements evidence a magnetic ordering at 3.8(2) K for Ce₆Ni_1.67Si₃ and a heavy fermion behaviour for Ce₆Co_1.67Si₃.     

Das Dreistoffsystem Nickel-Kupfer-Bor

The ternary system nickel-copper-boron was established at 700°C by means of X-ray diffraction and metallographic examinations. Confirming the well known binary nickel borides no ternary boride was found.The solubility of boron in the nickel-copper solid solution is very small and has its maximum of about 0.3 at% in the binary system copper-boron.Differential-thermoanalysis shows a quasibinary eutectic between Ni₃B and copper solid solution.

---

---

Mit 5 Abbildungen     

Mn5Si3-type host-interstitial boron rare-earth metal silicide compounds RE5Si3: Crystal structures, physical properties and theoretical considerations

A series of binary rare-earth metal silicides RE₅Si₃ and ternary boron-interstitial phases RE₅Si₃B_x (RE=Gd, Dy, Ho, Lu, and Y) adopting the Mn₅Si₃-type structure, have been prepared from the elemental components by arc melting. Boron “stuffed” phases were subsequently heated at 1750 K within a high-frequency furnace. Crystal structures were determined for both binary and ternary series of compounds from single-crystal X-ray data: hexagonal symmetry, space group P6₃/mcm, Z=2. Boron insertion in the host binary silicides results in a very small decrease of the unit cell parameters with respect to those of the binaries. According to X-ray data, partial or nearly full boron occupancy of the interstitial octahedral sites in the range 0.6-1 is found. The magnetic properties of these compounds were characterized by the onset of magnetic ordering below 100 K. Boron insertion induces a modification of the transition temperature and θ_p values in most of the antiferromagnetic binary silicides, with the exception of the ternary phase Er₅Si₃B_x which was found to undergo a ferromagnetic transition at 14 K. The electrical resistivities for all binary silicides and ternary boron-interstitial phases resemble the temperature dependence of metals, with characteristic changes of slope in the resistivity curves due to the reduced electron scattering in the magnetically ordered states. Zintl-Klemm concept would predict a limiting composition RE₅Si₃B_0.6 for a valence compound and should then preclude the stoichiometric formula RE₅Si₃B. Density functional theory calculations carried out on some RE₅Si₃Z_x systems for different interstitial heteroatoms Z and different x contents from 0 to 1 give some support to this statement.     

Electrochemical Synthesis of Ti–Si–B Compounds in Chloride–Fluoride Molten Salts

Metals, semiconductors, and their binary and ternary compounds can be produced by electrolyzing molten salts of the components. For a Ti–Si–B system, reduction potentials of all three elements are close, which significantly alleviates the problem. Using thermodynamic calculations, voltammetric measurements, and electrolysis we demonstrate the possibility of producing metal-like refractory compounds. Binary compounds TiB₂, Ti₅Si₃, and SiB₄ and a new ternary compound Ti₅Si₃B₃ are produced electrochemically.     

The thermodynamic characteristics of formation of alloys in the Ge-Ga-Mn and Si-Ni-Al systems

The enthalpies of mixing of ternary system melts were determined by high-temperature calorimetry under isoperibolic conditions. For the Ge-Ga-Mn system, measurements were taken at 1780 ± 5 K along five ray sections with constant ratios between the atomic fractions of germanium and gallium up to a ～0.6 mole fraction of manganese; the x _Ge/x _Ga ratios were 0.8/0.2, 0.7/0.3, 0.5/0.5, 0.3/0.7, and 0.15/0.85. For the Si-Ni-Al system, measurements were taken at 1770 ± 5 K along five ray sections with constant ratios between the atomic fractions of silicon and nickel up to a ～0.6 mole fraction of aluminum; the x _Si/x _Ni fratios were 0.85/0.15, 0.7/0.3, 0.5/0.5, 0.3/0.7, and 0.15/0.85. The formation of melts in these systems was found to be exothermic over the composition range studied. The integral enthalpies of melt formation were maximum along the x _Ge/x _Ga = 0.8/0.2 section in the Ge-Ga-Mn system (?18.8 ± 3.3 kJ/mol) and along the x _Si/x _Ni = 0.5/0.5 section in the Si-Ni-Al system (?67.8 ± 3.4 kJ/mol). An analysis of the isolines of the integral enthalpies of mixing led us to conclude that the Ge-Mn and Ga-Mn binary systems had the strongest influence on the thermodynamic characteristics of melt formation in the Ge-Ga-Mn system, the predominant influence being that of the Ge-Mn binary system. An analysis of the energy characteristics of melt formation in the Si-Ni-Al ternary system showed that the major contribution was made by the interaction of components in the Si-Ni and Ni-Al boundary binary systems, the influence of the Si-Ni system being stronger.     

Stability and crystal chemistry of the ternary borides M2(Ni21−xMx)B6 (M Ti,Zr, Hf)

A crystallochemical study was undertaken to investigate the structural stability and the compositional extent of the ternary borides M₂(Ni_21−xM_x)B₆ (M  Ti, Zr, Hf). This phase often occurs during the production of MB₂ joints by means of Ni–B brazing alloys. Samples with the nominal compositions M₂Ni₂₁B₆ and M₃Ni₂₀B₆ were synthesized by arc melting and characterized by optical and electron microscopy, and X-ray diffraction. Crystal structure refinements were performed by the Rietveld method. The compositional boundaries of the ternary phases were experimentally determined and found strictly related to the M/Ni size ratio. The stability of this structure is mainly determined by the capability of the structure to expand under the effect of the Ni substitution by the M atom. The CALPHAD modeling of the three M–Ni–B ternary systems in the Ni-rich corner of the phase diagram, performed on the basis of the obtained structural data, shows a good agreement with experimental results.     

Ternary systems Sr-{Ni,Cu}-Si: Phase equilibria and crystal structure of ternary phases

Phase relations were established in the Sr-poor part of the ternary systems Sr-Ni-Si (900 °C) and Sr-Cu-Si (800 °C) by light optical microscopy, electron probe microanalysis and X-ray diffraction on as cast and annealed alloys. Two new ternary compounds SrNiSi₃ (BaNiSn₃-type) and SrNi_9−xSi_4+x (own-type) were found in the Sr-Ni-Si system along with previously reported Sr(Ni_xSi_1−x)₂ (AlB₂-type). The crystal structure of SrNi_9−xSi_4+x (own-type, x=2.7, a=0.78998(3), c=1.1337(2) nm; space group P4/nbm) was determined from X-ray single crystal counter to be a low symmetry derivative of the cubic, parent NaZn₁₃-type. At higher Si-content X-ray Rietveld refinements reveal the formation of a vacant site (□) corresponding to a formula SrNi_5.5Si_6.5□_1.0. Phase equilibria in the Sr-Cu-Si system are characterized by the compounds SrCu_2−xSi_2+x (ThCr₂Si₂-type), Sr(Cu_xSi_1−x)₂ (AlB₂-type), SrCu_9−xSi_4+x (0≤x≤1.0; CeNi_8.5Si_4.5-type) and SrCu_13−xSi_x (4≤x≤1.8; NaZn₁₃-type). The latter two structure types appear within a continuous solid solution. Neither a type-I nor a type-IX clathrate compound was encountered in the Sr-{Cu,Ni}-Si systems.Structural details are furthermore given for about 14 new ternary compounds from related alloy systems with Ba.     

Some aspects of the electroless co-deposition of silicon and titanium on a nickel-base superalloy

A nickel-base superalloy, IN 738 LC, has been silicotitanized by immersion in a KC1—NaCl—Na₂SiF₆—K₂TiF₆—Si—Ti melt at various temperatures, times and melt compositions. The relationship between the deposition time and the weight gain is parabolic. The deposition rate is determined by diffusion processes. Its energy of activation is 31 kcal/mole.The phases occurring in the silicon- and titanium-containing zones of coatings produced under various conditions are described. In most cases four zones are present: two exterior layers are characterized by columnar, crystalline, binary or ternary Ti—Ni—Si compounds; two near-substrate layers consist of intermetallic phases distributed at random.As primary phases Ni₃Si₂, TiNiSi₂ and a new, cubic compound, Ti₃Ni₈Si₈ could be identified; after diffusion-annealing these phases are transformed into the stable modifications Ni₃Si and Ti₆Ni₁₆Si₇ (G-phase), respectively.     

Magnetische Messungen in den Systemen Co—Se,Ni—Se und Co—Ni—Se

The magnetic behavior of the binary systems Co?Se and Ni?Se was investigated within the temperature region from 100 to 300 K. Both phases Co_1?x Se and CoSe₂ behave like antiferromagnetics following theCurie-Weiss law with magnetic moments between 2.22 and 3.16 μ_B. For the corresponding phases Ni_1?x Se and NiSe₂ the results indicate a feeblePauli paramagnetism. For some alloys a slight positive temperature coefficient could be observed. Three quasibinary sections of the ternary phase (Co_1?y Ni _y )_1?x Se and one section of (Co_1?y Ni _y )Se₂ were investigated in the ternary system Co?Ni?Se. For all sections the increase of the Ni-content resulted in a continuous shift fromCurie-Weiss behavior toPauli paramagnetism. Due to the change from negative to positive temperature coefficients some ternary alloys have a temperature-invariant paramagnetism.     

A Novel Boron-Rich Scandium Borocarbide; Sc4.5−xB57−y+zC3.5−z(x=0.27, y=1.1, z=0.2)

A novel ternary boron-rich scandium borocarbide Sc_4.5−xB_57−y+zC_3.5−z (x=0.27, y=1.1, z=0.2) was found. Single crystals were obtained by the floating zone method by adding a small amount of Si. Single-crystal structure analysis revealed that the compound has an orthorhombic structure with lattice constants of a=1.73040(6), b=1.60738(6) and c=1.44829(6) nm and space group Pbam (No. 55). The crystal composition ScB_13.3C_0.78Si_0.008 calculated from the structure analysis agreed with the measured composition of ScB_12.9C_0.72Si_0.004. The orthorhombic crystal structure is a new structure type of boron-rich borides and there are six structurally independent B₁₂ icosahedra I1—I6, one B₈/B₉ polyhedron and nine bridging sites all which interconnect each other to form a three-dimensional boron framework. The main structural feature of the boron framework structure can be understood as a layer structure where two kinds of boron icosahedron network layer L1 and L2 stack each other along the c-axis. There are seven structurally independent Sc sites in the open spaces between the boron icosahedron network layers.     

New Phosphides with Transition and Rare-Earth Metals and Their Crystal Structures

Abstract

The interaction between components in systems M-M′- P (M -Zr, Hf, Nb, Mo, W, Mn, Re; M′-V, Cr, Fe, Co, Ni, Cu), Ln-{Fe, Co, Ni, Cu}-P (Ln-rare-earth metals) and M-{Si, B}-P (M-Cr, Mo, W, Mn, Re, Co, Ni, Cu) have been investigated and isotermal sections for 47 ternary systems have been built. 98 new phosphides have been synthesized and the crystal structure for 76 has been determined. The structures of new compounds belong to the known structure types, such as MgCu₂, Mg₆ Cu₁₆ Si₇, TiNiSi, Zr₂ Fe₁₂P₇, Hf₂ CO₄ P₃, CeAl₂ Ga₂, ZrFe₄Si₂, Nb₄ CoSi, Mo₅ SiB₂, MgZn₂, HfCuSi₂. The structures of several phosphides represent the new types: Nb₂P, α-Ni₈P₃, Zr₂Ni_l-xP, Tb,_1?xNiP, SmNi₄P₂, Nd₃Ni₇P₅, Ni₃,₃₆Si₁,₇₆P₆, Mo₂Ni₆P₃, Re_0,6, Ni_0,4P · The obtained experimental data allowed us to make the following conclusions:     

Phase equilibria in Cu-Al-Zr system at 1073 K and aluminum concentration of less than 55 at %

X-ray diffraction and electron probe microanalysis were used to investigate phase equilibria in the ternary Cu-Al-Zr system at 1073 K in the Zr-rich region. The fragment of the isothermal section of the system was plotted. The regions of homogeneity of the ternary ZrCu₂Al and ZrCu _x Al_{2 ? x} phases were investigated. The type of phase equilibria between binary and ternary compounds of the Al-Cu-Zr system was established. It was found out that, at a Zr concentration above 55 at %, ternary compounds are not formed, and the Zr₃Al and Zr₂Cu phases were in equilibria with ??-Zr at 1073 K.     

Study on the effect of increasing the chain length of the alkanol in excess molar enthalpies of mixtures containing 2-methoxy-2-methylpropane, 1-alkanol,decane

Excess molar enthalpies for the ternary system {x₁ 2-methoxy-2-methylpropane + x₂ ethanol + (1 − x₁ − x₂) decane} and the involved binary mixture {x ethanol + (1 − x) decane} have been measured at the temperature of 298.15 K and atmospheric pressure, over the whole composition range. No experimental excess enthalpy values were found in the currently available literature for the ternary mixture under study. The results were fitted by means of different variable-degree polynomials. Smooth representations of the results are presented and used to construct constant excess molar enthalpy contours on Roozeboom diagrams. The excess molar enthalpies for the binary and ternary system are positive over the whole range of composition. The binary mixture {x ethanol + (1 − x) decane} is asymmetric, with its maximum displace toward a high mole fraction of decane. The ternary contribution is also positive, and the representation is asymmetric.     

The Ternary System Nickel/Silicon/Titanium Revisited

The constitution of the ternary system Ni/Si/Ti is investigated over the entire composition range using X‐ray diffraction (XRD), energy dispersive X‐ray spectroscopy (EDS), differential thermal analysis (DTA), and metallography. The solid state phase equilibria are determined for 900 °C. Eight ternary phases are found to be stable. The crystal structures for the phases τ₁NiSiTi, τ₂Ni₄Si₇Ti₄, τ₃Ni₄₀Si₃₁Ti₁₃, τ₄Ni₁₇Si₇Ti₆, and τ₅Ni₃SiTi₂ are corroborated. For the remaining phases the compositions are determined as Ni₆Si₄₁Ti₅₃ (τ₆), Ni₁₆Si₄₂Ti₄₂(τ₇), and Ni₁₂Si₄₅Ti₄₃ (τ₈). The reaction scheme linking the solid state equilibria with the liquidus surface is amended to account for these newly observed phases. The discrepancies between previous experimental conclusions and modeling results are addressed. The liquidus surface is dominated by the primary crystallisation field of τ₁NiSiTi, the only congruently melting phase.     

Crystal structure and magnetism of the FexNi8-xSi3 materials, 0 ≤ x ≤ 8

The crystal structure and magnetic properties of the materials Fe_xNi_8-xSi₃ with 0 ≤ x ≤ 8 have been investigated to estimate any possible magnetocaloric effect and compare it to that in known magnetocalorics. Two structural ranges could be identified in this system by X-ray and neutron diffraction. The structure of the samples with 0 ≤ x ≤ 4 is related to the trigonal structure of Ni₃₁Si₁₂. Doubled c lattice parameters compared to the one in Ni₃₁Si₁₂ are observed in the samples with x = 2 and x = 3. The average structure of Fe₂Ni₆Si₃ has been determined by X-ray single-crystal diffraction. The compounds with the compositions 5 ≤ x ≤ 8 crystallize in cubic Fe₃Si-type structure. Magnetic measurements have shown that the compound Fe₃Ni₅Si₃ displays a phase transition close to room temperature. However, its magnetocaloric effect is much smaller than the one in the promising magnetocaloric materials.     

Crystal chemistry of the G-phases in the {Ti, Zr, Hf}-Ni-Si systems

Ternary compounds M₆Ni₁₆Si₇ (M=Ti, Zr, Hf) have been investigated by X-ray powder/single crystal and neutron powder diffraction. Compounds with Zr and Hf crystallize in the ordered Th₆Mn₂₃ type (Mg₆Cu₁₆Si₇-type, space group ), whereas Ti₆Ni_16.7Si₇ contains an additional Ni atom partially occupying the 24e site (M2 site, x=0.4637,0,0; occ.=0.119) inside a Ti octahedron; Ti atoms occupy a split position. Ti₆Ni_16.7Si₇ represents a new variant of the filled Th₆Mn₂₃ type structure. Ab initio calculations confirm the structural difference: additional Ni atoms favour the 24e site for Ti₆Ni_16.7Si₇, however, for the Zr and Hf-based compounds the unoccupied site renders an energetically lower ground state. Enthalpies of formation of Ti₆Ni₁₇Si₇, Zr₆Ni₁₆Si₇, and Hf₆Ni₁₆Si₇ were calculated to be −68.65, −74.78, and −78.59 kJ/(mol of atoms), respectively.     

The ternary system cerium-rhodium-silicon

Phase relations have been established in the ternary system Ce-Rh-Si for the isothermal section at 800 °C based on X-ray powder diffraction and EPMA on about 80 alloys, which were prepared by arc melting under argon or by powder reaction sintering. From the 25 ternary compounds observed at 800 °C 13 phases have been reported earlier. Based on XPD Rietveld refinements the crystal structures for 9 new ternary phases were assigned to known structure types. Structural chemistry of these compounds follows the characteristics already outlined for their prototype structures: τ₇—Ce₃RhSi₃, (Ba₃Al₂Ge₂-type), τ₈—Ce₂Rh_3−xSi_3+x (Ce₂Rh_1.35Ge_4.65-type), τ₁₀—Ce₃Rh_4−xSi_4+x (U₃Ni₄Si₄-type), τ₁₁—CeRh₆Si₄ (LiCo₆P₄-type), τ₁₃—Ce₆Rh₃₀Si_19.3 (U₆Co₃₀Si₁₉-type), τ₁₈—Ce₄Rh₄Si₃ (Sm₄Pd₄Si₃-type), τ₂₁—CeRh₂Si (CeIr₂Si-type), τ₂₂—Ce₂Rh_3+xSi_1−x (Y₂Rh₃Ge-type) and τ₂₄—Ce₈(Rh_1−xSi_x)₂₄Si (Ce₈Pd₂₄Sb-type). For τ₂₅—Ce₄(Rh_1−xSi_x)₁₂Si a novel bcc structure was proposed from Rietveld analysis. Detailed crystal structure data were derived for τ₃—CeRhSi₂ (CeNiSi₂-type) and τ₆—Ce₂Rh₃Si₅ (U₂Co₃Si₅-type) by X-ray single crystal experiments, confirming the structure types. The crystal structures of τ₄—Ce₂₂Rh₂₂Si₅₆, τ₅—Ce₂₀Rh₂₇Si₅₃ and τ₂₃—Ce_33.3Rh_58.2−55.2Si_8.5−11.5 are unknown. High temperature compounds with compositions Ce₁₀Rh₅₁Si₃₃ (U₁₀Co₅₁Si₃₃-type) and CeRhSi (LaIrSi-type) have been observed in as-cast alloys but these phases do not participate in the phase equilibria at 800 °C.     

Solid state phase equilibria in the Gd-Si-B system at 1270 K

Solid state phase equilibria in the ternary Gd-Si-B phase diagram have been proposed at 1270 K using X-ray diffraction, scanning electron microscopy and electron probe microanalysis. Prior to this work, the binary systems Gd-B, Gd-Si and Si-B have also been reinvestigated. The main characteristic of the ternary diagram is the occurrence of two new ternary compounds Gd₅Si₂B₈ and Gd₅Si₃B_0.64. The former crystallizes in tetragonal symmetry, space group P4/mbm with unit cell parameters a=7.2665(3), c=8.2229(7) Å, the second one presents hexagonal symmetry, space group P6₃/mcm with unit cell parameters a=8.5080(4),c=6.4141(2) Å. The X-ray structures of the two structurally related phases Gd₅Si₃B_0.64 and host binary Gd₅Si₃ have been refined from three-dimensional single-crystal intensity data to the final R values of 0.036 (R_w=0.046) and 0.046 (R_w=0.055) for 457 and 401 reflections, respectively with [F>4σ(F)]. Both structures exhibit the Mn₅Si₃-type structure, with in addition for Gd₅Si₃B_0.64 a partial occupancy by boron of the normally vacant interstitial site at the center of the Gd₆ octahedron, which corresponds to the origin of the unit cell. Bonding between the interstitial boron atoms and the gadolinium ones forming the Gd₆B polyhedra is indicated by the decrease in the corresponding Gd-Gd distances and consequently in the unit cell volume. Finally, the Gd-Si-B phase diagram is compared with the previously reported Er-Si-B, at 1070 K.     

Synthesis and crystal structures of the new metal-rich ternary borides Ni12AlB8, Ni12GaB8 and Ni10.6Ga0.4B6—examples for the first B5 zig-zag chain fragment

Single crystals of the new borides Ni₁₂AlB₈, and Ni_10.6Ga_0.4B₆ were synthesized from the elements and characterized by XRD and EDXS measurements. The crystal structures were refined on the basis of single crystal data. Ni₁₂AlB₈ (oC252, Cmce, a=10.527(2), b=14.527(2), c=14.554(2) Å, Z=12, 1350 reflections, 127 parameters, R₁(F)=0.0284, wR₂(F²)=0.0590) represents a new structure type with isolated B atoms and B₅ fragments of a B-B zig-zag chain. Because the pseudotetragonal metric crystals are usually twinned. Ni_10.6Ga_0.4B₆ (oP68, Pnma, a=12.305(2), b=2.9488(6), c=16.914(3) Å, Z=4, 1386 reflections, 86 parameters, R₁(F)=0.0394, wR₂(F²)=0.104) is closely related to binary Ni borides. The structure contains B-B zig-zag chains and isolated B atoms. Ni₁₂GaB₈ is isotypical to the Al-compound (a=10.569(4), b=14.527(4) and c=14.557(5) Å).