Rachid St. Touzani

Otto-von-Guericke-Universität Magdeburg | OvGU · Materials and Joining Technology

The present study reports on the existence of a new ternary phase, V8SiB4, in the V–Si–B system. The new phase was found in alloys heat-treated at 1400 °C for 100 h and 200 h within the Vss–V3Si–V5SiB2 phase field at 1600 °C. The crystal structure of V8SiB4 was determined by combining energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (X...

In the present work the solidification of various Mo-Ti-B alloys was studied. The alloy compositions were chosen in the direct vicinity of a U-type invariant reaction in relation to the published Mo-rich corner of the Mo-Ti-B liquidus projection. The aim of this study was to understand the solidification path of as-cast Mo-Ti-B alloys and to derive...

During attempts to synthesize new platinides in the ternary system Sr–Al–Pt, single crystals of SrAl5Pt3 and Sr2Al16Pt9 were obtained from a reaction of the elements with the nominal composition Sr4Al13Pt9. Both orthorhombic structures were refined based on single crystal x-ray diffraction data (SrAl5Pt3: Pnma, Wyckoff sequence c9, a = 2065.04(7),...

Single crystals of CaNi 2 Al 8 were obtained during attempts to synthesize CaNi 2 Al 9 from the elements in Nb or Al 2 O 3 crucibles in an induction furnace. The orthorhombic structure of CaNi 2 Al 8 was refined based on single-crystal X-ray diffraction data ( Pbam , a = 1252.30(6), b = 1443.73(7), c = 395.78(2) pm, wR 2 = 0.0423, 2225 F ² values,...

The Molybdenum rich ternary alloys Mo-M-B (M = Zr, Hf) contain, next to the Mo solid solution (bcc Mo with small amounts of Zr or Hf as substitutional atoms), the binary borides Mo2B, MB and MB2. Recently, it was found that there is also ternary Mo2MB2, but the crystal structure and further properties are currently unknown. Density functional theor...

The alloy system Mo-Si-B gained a lot of attention, as it showed superior elastic properties than currently used Ni based superalloys at elevated temperatures. In the Mo-Si-B alloy system, Mo based solid solutions play an important role as a compound and one can observe a solid solution with small amounts of Si and tiny, almost negligible, amounts...

The present study addresses the microstructural evolution and mechanical properties of three different cast V-5X (X = Nb, Ti and Mo) alloys. All alloy compositions are located in the vanadium solid solution (VSS) phase field in their respective phase diagrams. While the alloys V-5Ti and V-5Nb solidified as single-phase VSS after arc-melting, the al...

Mo-Si-B alloys provide a significantly higher creep resistance at temperatures above 1100 °C compared with Nickel-based superalloys. However, the high density of this alloy is a drawback when used as a turbine blade material. One approach to reduce the density of Mo-Si-B alloys, without decreasing the high temperature creep resistance too much, is...

The new intermetallic compound Ba6Pt22Al53 was obtained from reaction of the elements. The title compound crystallizes in the hexagonal crystal system with lattice parameters of a = 1427.5(3) and c = 1614.3(4) pm and space group P63/mcm (Z = 2) and forms a new structure type (Pearson code hP162 Wyckoff sequence l2k3j2i2hg2ecb). In the structure, th...

The presence of one-dimensional trigonal arrangements of chromium atoms (Cr3) in the structure of TiCrIr2B2 leads to a magnetic transition near ambient temperature. Herein we report an investigation of the nature of electronic and magnetic properties of TiCrIr2B2 via ab initio calculations together with ¹¹B NMR Knight shift (K) and spin-lattice rel...

Non-oxide perovskites exhibit unusual properties such as negative thermal expansion, negative thermal coefficient of resistance, positive and negative giant magnetoresistance as well as superconductivity. These uncommon properties appear to originate from the basic structure only, in strong contrast to the oxides. Ordering in nonstoichiometric comp...

Ta2OsB2 (I) and TaRuB (II) are prepared by arc-melting of stoichiometric amounts of the elements.

The title compound is synthesized from the elements (Ta ampule, 1300 K for 10 min and 825 K for 2—8 h) and characterized by single crystal XRD, Moessbauer spectroscopy, magnetic measurements, and DFT calculations.

The intermetallic compound EuAu3Al2 has been prepared by reaction of the elements in tantalum ampules. The structure was refined from single-crystal data, indicating that the title compound crystallizes in the orthorhombic crystal system (a = 1310.36(4), b = 547.87(1), c = 681.26(2) pm) with space group Pnma (wR2 = 0.0266, 1038 F(2) values, 35 para...

Nb2RuB2 and Ta2RuB2 phases were recently predicted by GGA-VASP structure optimization to crystallize in the Nb2OsB2-type structure. Although the Fe-based (Mo2FeB2 type) and Os-based (Nb2OsB2 type, superstructure variant of Mo2FeB2 type) analogues have been synthesized and characterized successfully, the Ru-based phases remained unknown. Crystal str...

Crystal Orbital Hamilton Population (COHP) bonding analysis has predicted that ScPd3B0.5 is the least stable compound of the entire series Sc2Ir6-xPdxB.Here, we report a systematic study of Sc2Ir6-xPdxB (x = 3, 5 and 6) by means of 11B nuclear magnetic resonance (NMR), Knight shift (K) and nuclear spin-lattice relaxation rate (1/T1).NMR results com...

Sr2Pd4Al5 is prepared by heating the elements in stoichiometric amounts (Nb ampoules in evacuated silica tubes, 1.

The new intermetallic compound Sr2Pd4Al5 was prepared from the elements by reaction in niobium ampoules. The structure was refined from single-crystal data, which indicate the formation of a new structure type in the orthorhombic crystal system [a = 1814.49(10), b = 431.64(4), c = 1102.47(4) pm] with space group Pnma (wR2 = 0.0251, 1666 F2 values,...

The new ternary transition metal-rich borides Ta2OsB2 and TaRuB have been successfully synthesized by arc-melting the elements in a water-cooled crucible under an argon atmosphere. The crystal structures of both compounds were solved by single-crystal X-ray diffraction and their metal compositions were confirmed by EDX analysis. It was found that T...

The title compound is prepared from the elements (Nb tube, 1073 K, 7 d) and characterized by powder XRD, XPS, 27Al MAS NMR spectroscopy, magnetic measurements, and DFT band structure calculations.

Ba3Pt4Al4 was prepared from the elements in niobium ampules and crystallizes in an orthorhombic structure, space group Cmcm (oP44, a = 1073.07(3), b = 812.30(3), c = 1182.69(3) pm) isopointal to the Zintl phase A2Zn5As4 (A = K, Rb). The structure features strands of distorted [Pt4Al4] heterocubane-like units connected by condensation over Pt/Al edg...

The elastic properties of A2FeB2 (A = Nb, Ta, Mo2FeB2-type structure) and their higher homologues A2OsB2 and the predicted “A2RuB2” (both with Nb2OsB2-type structure) have been investigated within the density functional theory (DFT) framework. Furthermore, the influence of magnetism, bonding and electronic structure on the elastic properties in the...

DFT calculations for the ternary phases Sc2M6B (M: Ir, Pd, Ni) reveal the presence of pseudogaps near their Fermi levels between 61 and 68 valence electrons leading to the prediction of new phases Sc2Ir6-xPdxB and Sc2Ir6-xNixB (x = 0—6) in the double-perovskite-like Ti2Rh6B-type structure.

Analysis of the electronic density of states of the hypothetical ternary double-perovskite-like phases "Sc2T6B (T = Ir, Pd, Ni)" reveals the presence of deep and large pseudogaps between 61 and 68 valence electrons (VE) as well as a strong peak at 69 VEs. Subsequently, crystal orbital Hamilton population (COHP) bonding analysis shows that the heter...

Highly crystalline Nb6Fe1-xIr6+xB8 (68% yield) is prepared from the elements in the molar ratio of Nb:Fe:Ir:B = 6:1:6:9 by rapid arc melting and quenching.

Detailed analytical studies of the solid solutions CeRu1–xNixSn revealed a sequence of three different structure types, CeRuSn, ZrNiAl, and TiNiSi, with increasing x value. All compounds have been synthesized and characterized by X-ray powder diffraction. The structures of CeRu0.68Ni0.32Sn, CeRu0.38Ni0.62Sn and CeRu0.14Ni0.86Sn have been refined fr...

Planar boron rings were predicted some years ago by scientists studying gas-phase boron clusters as building blocks for designing new molecular and solid-state materials. In their Communication on page 13174 ff., B. P. T. Fokwa et al. report experiments and density functional calculations used in a synergistic manner for the discovery of the new fe...

The synergistic combination of experiment and density functional theory has led to the discovery of the first ferromagnetic material, Nb6Fe1−xIr6+xB8, containing in its crystal structure iron chains embedded in stacked B6 rings. The strong ferromagnetic Fe–Fe interactions found in the iron chains induce an unexpected strengthening of the B–B intera...

The synergistic combination of experiment and density functional theory has led to the discovery of the first ferromagnetic material, Nb6Fe1−xIr6+xB8, containing in its crystal structure iron chains embedded in stacked B6 rings. The strong ferromagnetic Fe–Fe interactions found in the iron chains induce an unexpected strengthening of the B–B intera...

Powder samples and single crystals of the new ternary compound NbRuB were synthesized by arc-melting of the elements in a water-cooled crucible under an argon atmosphere. The samples have been characterized by X-ray diffraction and energy-dispersive X-ray spectroscopy (EDX) measurements. Furthermore, the crystallographic, electronic, and bonding ch...

Nb2FeB2 (U3Si2 structure type, space group P4/mbm, no. 127) is predicted to order antiferromagnetically, due to the presence of iron chains which show ferromagnetic interactions in the chains and antiferromagnetic interactions between them. “Nb2RuB2” is predicted to crystallize with the recently discovered Nb2OsB2 twofold superstructure (space grou...

Members of the solid solution series of CeRu1-xNixAl can be obtained directly by arc melting of the elements. The presented compounds with 0.1 ≤ x ≤ 0.85 crystallize in the orthorhombic space group Pnma (No. 62) in the LaNiAl structure type, while for 0.9 ≤ x ≤ 1, the hexagonal ZrNiAl-type structure is found. The orthorhombic members exhibit an ano...

The new title compound is synthesized by arc melting of the elements in a water-cooled Cu crucible under argon (ratio 7:6:8 for Nb:Os:B, 80% yield).

The new ternary metal-rich boride, Nb2OsB2, was synthesized by arc-melting the elements in a water-cooled copper crucible under an argon atmosphere. The compound was characterized from single-crystal X-ray data and EDX measurements. It crystallizes as a new superstructure (space group P4/mnc, no. 128) of the tetragonal U3Si2-structure type with lat...