Solid State Reactions in the Al‐Si‐C System

The study is aimed to prevent the formation of the aluminium carbide compound Al₄C₃ that negatively affects Al‐Si‐C based materials. The reaction products of elementary aluminium, silicon and graphite as well as aluminium with either β‐SiC or α‐SiC without and with graphite at temperatures 1200°‐2500 °C under different atmospheres and reaction times were characterized using powder X‐ray diffraction and scanning electron microscopy (SEM) with an energy dispersive X‐ray (EDX) analysis. The results of the powder diffraction study show that under the conditions (1450 °C; 8 h; vacuum) the formation of Al₄C₃ could be prevented. The reaction products at those conditions consist of the ternary compound Al₄SiC₄ besides SiC and residual carbon. The ternary aluminium silicon carbide Al₄SiC₄ crystallizes in a hexagonal crystal system with unit cell dimensions a = 327.64(4) pm, b = 2171.2(6) pm and space group P6₃mc (no. 186). The crystal structure of Al₄SiC₄ is isostructural with Al₅C₃N and consists of layers of Al₄C₃ and SiC.     

Chemical and structural transformations in manganese aluminum spinel of the composition Mn1.5Al1.5O4 during heating and cooling in air

Single phase cubic spinel of the composition Mn_1.5Al_1.5O₄ is synthesized. Its crystal structure refinement shows that 0.4Mn+0.6Al are in the octahedral sites and 0.7Mn+0.3Al are in the tetrahedral sites. High temperature X-ray diffraction is used to analyze Mn_1.5Al_1.5O₄ behavior during heating and cooling in air. In a temperature range of 600°C to 700°C, initial spinel splits into layers, and the sample represents a twophase system: cubic spinel Mn_0.4Al_2.4O₄ and a phase based on β-Mn₃O₄. Above 900°C the sample again turns into single phase cubic spinel. The role of oxidizing processes in the decomposition of Mn_1.5Al_1.5O₄ caused by oxygenation and partial oxidation of Mn²⁺ to Mn³⁺ is shown. A scheme of structural transformations of manganese aluminum spinel during heating from room temperature and cooling from 950°C is proposed.     

Crystal structure and transport properties of Pd5HgSe

The Pd₅HgSe compound was synthesised by heating of stoichiometric mixture of elements at 400 °C by means of the evacuated silica glass tube technique. Its crystal structure was refined by Rietveld method from powder X-ray diffraction data. Pd₅HgSe adopts tetragonal symmetry, space group P4/mmm, unit cell parameters a = 4.0128(2) Å, c = 7.0378(6) Å, V = 113.33(2) Å³, Z = 1. The crystal structure of Pd₅HgSe is composed of alternating slabs of the AuCu₃-type cuboctahedra [HgPd₁₂] and the PtHg₂-type rectangular prisms [SePd₈]. The title compound crystallizes in the Pd₅TlAs structure type. The electric resistivity as well as the Seebeck coefficient measurements suggests semimetallic behaviour.     

Darstellung der freien Dodekawolframatoaluminiumsäure H5[AlO4W12O36] · 6 H2O mittels Gefriertrocknung

Preparation of the Free 12-Tungstoaluminium Acid H₅[AlO₄W₁₂O₃₆] · 6 H₂O by Means of the Cryogenic Method The title compound was first prepared in solid state from its aqueous solution by means of the cryogenic method and characterized by chemical and thermal analyses, IR and UV spectroscopy. From X-ray heating patterns the formation of a new cubic phase 1/2 Al₂O₃ · 12 WO₃ (I) at 400°C was found, being stable till 830°C: a = 378 pm (600°C). High-resolution ²⁷Al NMR (MAS-technique) was used to determine the tetrahedral coordination of aluminium in the title compound and the octahedral coordination in I. The degradation of the doped WO₃-phase I into Al₂(WO₄)₃ begins at 600°C. Above 830°C tetragonal WO₃ and Al₂(WO₄)₃ coexist.     

Die Verbindung La5Br4Al4 und ihre topologische Verwandtschaft mit dem Ln3ClGa4‐Typ

The Compound La₅Br₄Al₄ and the Topological Relation with the Ln₃ClGa₄ Structure Type The compound La₅Br₄Al₄ can be prepared from La metal, LaBr₃ and Al filings at 950 °C with a yield of 20 %. It crystallizes tetragonally in I4/mcm with a = b = 8.292(1)Å, c = 20.122(4)Å. In the crystal structure 3 sheets of Br/La, La/Al, and La/Br atoms, respectively, are stacked along [001] and are connected by single layers of Br atoms. The Al atoms form undulated nets of condensed Al₈ and Al₄ rings. The La atoms are arranged in tetragonal antiprisms, centered by the second kind of crystallographically different La atoms. These units are connected to sheets. In La₃ClGa₄ the identical 3 sheets formed by La, Ga, Cl atoms are present, however, not separated by the additional layers of Br atoms as in La₅Br₄Al₄.     

Comparative analysis of the composition, structure, and catalytic activity of the NiO-CuO-TiO2 on Titanium and NiO-CuO-Al2O3 on aluminum composites

The catalytically active oxide structures based on Al and Ti prepared by plasma-electrolytic oxidation (PEO) and additionally modified by impregnation with an aqueous solution of nickel and copper nitrates followed by annealing were studied. The oxide film-metal composites were studied using X-ray diffraction and X-ray spectroscopic analysis, X-ray electron spectroscopy, and electron microscopy. The catalytic activity of the composites in the reaction of CO oxidation was studied. In spite of differences in the elemental composition and morphology, the initial oxide layers on Al and Ti were comparable in terms of activity. Microgranules of size ～ 1 µm and formations from tens to hundreds of nanometers in size were detected on the surface of PEO layers. The modified layers contained crystalline CuO, NiO, and Al₂O₃ or TiO₂ phases. The surface layers of the modified structures about 3 nm in thickness on AMg5 aluminum alloy and VT1-0 titanium had the same elemental composition but exhibited different activity in the reaction of CO oxidation to CO₂.     

Lix(Al0.8Zn0.2) alloys as anode materials for rechargeable Li-ion batteries

The influence of the lithium content in the starting composition, depth of discharge, binder and electrolyte on the cycle stability was investigated. The structural changes in Li_x(Al_0.8Zn_0.2) electrodes during electrochemical lithium extraction and reinsertion were studied by in situ synchrotron diffraction. The crystal structure of the new compound Li₄Al_3.42Zn_11.58 was determined by single-crystal X-ray diffraction and can be described as combination of the CaCu₅ and MgFe₆Ge₆ structure types. The phase equilibria at 150 °C in the Li–Al–Zn system were investigated on six alloys, prepared along the lithium extraction–insertion line.     

Die Kristallstruktur des Natriumoxohydroxoaluminathydrates Na2[Al2O3(OH)2] · 1,5 H2O

The Crystal Structure of the Sodium Oxohydroxoaluminate Hydrate Na₂[Al₂O₃(OH)₂] · 1.5 H₂O The crystal structure of the sodium oxohydroxoaluminate hydrate Na₂[Al₂O₃(OH)₂] ·s 1.5 H₂O (up to now described as Na₂O · Al₂O₃ · 2.5 H₂O and Na₂O · Al₂O₃ · 3 H₂O, respectively) was solved. The X-ray single crystal diffraction analysis (tetragonal, space group P-42₁m, a = 10.522(1) Å, c = 5.330(1) Å, Z = 4) results in a polymeric layered structure, consisting of AlO_3/2(OH) tetrahedral groups. Between these layers the Na⁺ ions are situated, which form tetrameric groups of face-linked NaO₆ octahedra. The involved O^2? ions are due to Al? O? Al bridges, Al? OH groups and water of crystallization. ²⁷Al and ²³Na MAS NMR investigations confirm the crystal structure analysis. The relations between the crystallization behaviour of the compound and the constitution of the aluminate anions in the corresponding sodium aluminate solution and in the solid, respectively, are discussed.     

Synthese und Kristallstruktur einer Neuen hexagonalen Modifikation von Al2S3 mit fünffach koordiniertem Aluminium

Synthesis and Crystal Structure of a Novel Hexagonal Modification of Al₂S₃ with Five-coordinated Aluminum A new hexagonal high temperature modification of Al₂S₃ could be prepared by chemical vapour transport with iodine (860 → 750°C) or by annealing of α -Al₂S₃ at 550°C. According to the single crystal X-ray structure determination the novel form of Al₂S₃ crystallizes in space group P 6₁ (No. 169) with a = 6.491(1), c = 17.169(4) Å, V = 626.5 ų, Z = 6; R = 0.0253. In this modification one half of the aluminum atoms are tetrahedrally coordinated [d(Al? S): 2.226–2.267 Å], whereas the other half are in trigonal bipyramidal coordination of five S atoms with bond lengths of 2.272–2.315 Å (equatorial) and 2.495–2.521 Å (axial). Aluminum in AlS₅ coordination is observed for the first time in this compound. The crystal structure is isotypic to In₂Se₃ and AlInS₃. In addition, results of a refinement of the α -Al₂S₃ crystal structure are reported which were obtained on crystals prepared also by chemical vapour transport with iodine.     

Tl3Al7S12 — ein neues Al-reiches Thioaluminat: Darstellung,Kristallstruktur und Eigenschaften

Tl₃Al₇S₁₂ — a Novel Al-rich Thioaluminate: Preparation, Crystal Structure, and Properties The new ternary phase Tl₃Al₇S₁₂ was prepared from the binary compounds Tl₂S and Al₂S₃ at 700 °C under vacuum. The structure of a yellow plateshaped single crystal was determined at room temperature. The compound crystallizes in the monoclinic polar space group P2₁ (No. 4) with a = 9.040(2), b = 12.381(2), c = 9.569(2) Å and β = 95.91(2)°. The polymeric anionic part of the structure can be described as a puckered layer-like arrangement of cornersharing [AlS₄]-tetrahedra parallel to (001). The aluminium-sulfur layers are connected via single sulfur atoms. The voluminous monovalent thallium atoms bridge the layers of the anionic framework. The mean Al? S bond lengths are 2.227 Å for μ₂-S? Al and 2.298 Å for μ₂-S? Al. In the strongly asymmetric coordination sphere of thallium the Tl? S bond lengths vary from 3.009(9) to 3.907(9) Å and contain four short and two or three longer distances. A rather short Tl…?Tl distance of 3.619(3) Å is observed between two of the three crystallographically independent Tl atoms, so that a weak bonding interaction has to be discussed. Vibrational spectroscopic data for the new phase are reported and discussed.     

Thermal behavior of LDH 2CuAl.CO<Subscript>3</Subscript> and 2CuAl.CO<Subscript>3</Subscript>/Pd

Cu/Al layered double hydroxide (LDH) can be used as a catalyst for important processes such as cross-coupling reactions. This property may be improved by adding palladium by either impregnation or intercalation. Therefore, the LDH matrix and its composites with Pd⁰ or [PdCl₄]^2? have been prepared. By powder X-ray diffraction, FT-infrared spectroscopy, thermogravimetric and elemental analysis it was determined the LDH formula Cu₄Al₂(OH)₁₂CO₃.4H₂O, with malachite as the second phase. The LDH thermal decomposition occurs between 120 and 600 °C, having as intermediates the double oxi-hydroxide and the mixed oxide phases. At 800 °C the residue is composed of CuO and CuAl₂O₄. The composites were obtained employing [PdCl₄]^2? and Pd₂(dba)₃ as precursors, and the solvent choice for this process was shown to be of significant importance: the materials obtained using DMF had Pd impregnated in the surface, while the usage of water promoted the intercalation of [PdCl₄]^2? in the LDH matrix. The thermogravimetric analysis was able to distinguish the mode of supporting palladium between the composites being a reliable characterization for such task.     

Nonanatrium-bis(hexahydroxoaluminat)-trihydroxid-hexahydrat (Na9[Al(OH)6]2(OH)3 · 6H2O) – Kristallstruktur,NMR-Spektroskopie und thermisches Verhalten

Nonasodium Bis(hexahydroxoaluminate) Trihydroxide Hexahydrate (Na₉[Al(OH)₆]₂(OH)₃ · 6H₂O) – Crystal Structure, NMR Spectroscopy and Thermal Behaviour The crystal structure of the nonasodium bis(hexahydroxoaluminate) trihydroxide hexahydrate Na₉[Al(OH)₆]₂(OH)₃ · 6H₂O (4.5 Na₂O Al₂O₃ · 13.5 H₂O) (up to now described as 3 Na₂O · Al₂O₃ · 6H₂O, 4Na₂O · Al₂O₃ · 13 H₂O and [3 Na₂O · Al₂O₃ · 6H₂O] [xNaOH · yH₂O], respectively) was solved. The X-ray single crystal diffraction analysis (triclinic, space group P1 , a = 8.694(1) Å, b = 11.344(2) Å, c = 11.636(3) Å, α = 74.29(2)°, β = 87.43(2)°, γ = 70.66(2)°, Z = 2) results in a structure, consisting of monomeric [Al(OH)₆]^3? aluminate anions, which are connected by NaO₆ octahedra groups. Furthermore the structure contains both, two hydroxide anions only surrounded by water of crystallization and OH groups of [Al(OH)₆]^3? aluminate anions and a hydroxide anion involved in three NaO₆ coordination octahedra directly and moreover connected with a water molecule by hydrogen bonding. The results of ²⁷Al and ²³Na-MAS-NMR investigations, the thermal behaviour of the compound and possible relations between the crystal structure and the conditions of coordination in the corresponding sodium aluminate solution are discussed as well.     

Thermolysis preparation of cadmium(II) oxide nanoparticles from a new three-dimensional cadmium(II) supramolecular compound

The reaction of cadmium(II) chloride and 4-pyridine carboxylic acid (4-Hpyc) produces a new threedimensional supramolecular compound [Cd(4-pyc)₂(H₂O)4] _n (1). Compound 1 is characterized by IR spectroscopy and elemental analyses. The single crystal X-ray data show an infinite three-dimensional structure formed by the hydrogen bonding and π-π stacking interactions. The CdO nanoparticles are obtained by direct calcination at 400°C, 500°C and 600°C in the air atmosphere as well as by thermolysis in oleic acid at 200°C. The obtained cadmium(II) oxide nanoparticles are characterized by X-ray diffraction and scanning electron microscopy. This study demonstrates another potential application of cadmium(II) supramolecular compounds in the preparation of nanoscale cadmium(II) oxide materials with a specific size and morphologies.     

AES and LEED investigation of Al segregation and oxidation of the (100) face of Fe85Al15 single crystals

The surface segregation and oxidation behavior of Fe₈₅Al₁₅(100) were investigated by means of AES and LEED. Sputter cleaning of the surface causes preferential Al removal and leads to an Al depleted surface layer. The segregation of Al to the Fe₈₅Al₁₅(100) surface was studied in the temperature range from 300 to 800°C. At 375 to 400°C a weak c(2 × 2) LEED pattern is found. At temperatures in excess of 600°C thermodynamic equilibrium is approached very rapidly. At such temperatures Al segregation leads to a well-ordered (1 × 1) LEED structure with bright and sharp spots at a low background intensity. Oxidation at room temperature leads to disordered oxygen adsorption, whereas at 700°C a (6 × 6) superstructure is observed in addition to the matrix spots. This superstructure is attributed to the formation of a thin Al₂O₃ overlayer on the Fe₈₅Al₁₅(100) surface.     

Versuche zur Hydrierung kubischer ternärer intermetallischer Phasen

Hydrogenation Reactions of Cubic Ternary Compounds The Zintl compound LiAlSi reacts at temperatures above 535°C and a pressure of 80–82 bar with hydrogen. A new phase with the formula LiAlSi_0.9 has been found. The reaction is reversible, at DTG measurements Proved. The new phases MgPd₂Ga and MgPd₂In, which have been characterised by X-ray investigation, decompose under hydrogen atmosphere irreversibly to Pd₁₁Ga₉, PdH and MgPd₃.     

La5Al3Ni2 – an Intermetallic Phase Observed upon Crystallization of La50Al25Ni25 Metallic Glass

The yet unknown intermetallic phase La₅Al₃Ni₂ was obtained by partially crystallizing amorphous La₅₀Al₂₅Ni₂₅ at 550 K (further heating above 600 K leads to irreversible disappearance of this phase), and its crystal structure was determined from X‐ray powder diffraction data. The crystal structure of the La₅Al₃Ni₂ phase constitutes a new structure type (Cmcm, a = 14.231Å, b = 6.914Å, c = 10.460Å, oC40) and is built from [Al₃Ni₂] chains surrounded by La atoms. In the ternary system La‐Al‐Ni La₅Al₃Ni₂ is located on the section La₅₀Al_50−nNi_n (0 ≤ n ≤ 50) with the binary compounds LaAl and LaNi as end members. Strikingly, also the crystal structures of the end members can be conceived as chain structures with Al and Ni chains surrounded by La, respectively.     

Inducing Complexity in Intermetallics through Electron–Hole Matching: The Structure of Fe14Pd17Al69

We illustrate how the crystal structure of Fe₁₄Pd₁₇Al₆₉ provides an example of an electron–hole matching approach to inducing frustration in intermetallic systems. Its structure contains a framework based on IrAl_2.75, a binary compound that closely adheres to the 18−n rule. Upon substituting the Ir with a mixture of Fe and Pd, a competition arises between maintaining the overall ideal electron concentration and accommodating the different structural preferences of the two elements. A 2×2×2 supercell results, with Pd‐ and Fe‐rich regions emerging. Just as in the original IrAl_2.75 phase, the electronic structure of Fe₁₄Pd₁₇Al₆₉ exhibits a pseudogap at the Fermi energy arising from an 18−n bonding scheme. The electron–hole matching approach's ability to combine structural complexity with electronic pseudogaps offers an avenue to new phonon glass–electron crystal materials.     

Determination of the cubic to hexagonal structure transition in the metastable system TiN-AlN

Structural transitions of metastable Ti_1–xAl_xN coatings on technically relevant substrates were determined as a function of the Ti/Al ratio. Ti_1–xAl_xN films with different Ti/Al ratios were deposited on high speed steel (HSS) substrates at substrate temperatures of 300?° and 500?°C by means of reactive magnetron sputtering ion plating (MSIP). A Ti/Al compound target was used as well as a cluster arrangement of one Ti and one Al target for comparison. The composition of the films was determined by electron probe microanalysis (EPMA), the crystallographic structure by thin film X-ray diffraction (XRD). The analyses revealed that films deposited with Ti/Al ratios of 44/56 and 36/64 had grown in cubic NaCl structure, a film with a Ti/Al ratio of 32/68 was two-phase, and a Ti/Al ratio of 25/75 led to a hexagonal film in wurtzite structure. Only small differences of the lattice parameters could be observed in dependence of temperature: At 300?°C the lattice parameters of the cubic structure corresponded exactly to Vegard‘s law, whereas they slightly decreased in the films deposited at 500?°C. The application of a cluster arrangement instead of a compound target resulted in nearly the same lattice parameters and peak shapes.     

Die Kristallstruktur von (Al0,5Ga0,5)CuOAsO4 – Kupfer zwischen planarer und geschlossener Koordination

The Crystal Structure of (Al_0,5Ga_0,5)CuOAsO₄ – Copper Intermediate between Planar and Closed Coordination Single crystals of the new oxide arsenate (Al_0.5Ga_0.5)CuOAsO₄ (monoclinic, P2₁/c, a = 734.3(2) pm, b = 1024.79(9) pm, c = 563.4(2) pm, β = 99.93(1)°, Z = 4) were obtained by reaction of Al/As/Cu/Ga-alloys with oxygen. The crystal structure was determined from four-circle diffractometer data (w2R = 0.039 for 1211 F² values and 76 parameters). The structure contains [Cu₂O₆] double squares arranged in slabs perpendicular to the a axis such that a [4 + 1]-coordination of the copper atoms by oxygen atoms results which is intermediate between square-planar and square-pyramidal. Along [100] layers of corner sharing (Al/Ga)O₄ and AsO₄ tetrahedra are alternating with buckled Cu layers.     

Präparative und röntgenographische Untersuchungen über das System Al2S3?ZnS (Temperaturbereich 800–1080°C)

Einkristalle von α-ZnAl₂S₄ mit Spinellstruktur (a = 10,009₃ Å) lassen sich durch chemische Transportreaktion bei 740°C erhalten. Beim Erhitzen der Verbindung auf 800–900°C tritt Zerfall in eine ZnS-arme defekte Spinellphase und in eine ZnS-reiche Phase mit defekter Wurtzitstruktur ein. Bei 830–860°C liegen die Grenzen des zweiphasigen Bereichs etwa bei Zn_0,98Al_2,01S₄ (kubische α-Phase, a = 10,007₂ Å (25°C)) und Zn_1,80Al_1,47S₄ (hexagonale Wurtzitphase, a = 3,76₀, c = 6,1₅ Å (25°C)). Mischungen von ZnS, Al und S entsprechend der Zusammensetzung Zn_xAl_8/3?2x/3S₄ mit 0,33 ≤ x ≤ 0,98, die auf 830–860°C (70–140 h) erhitzt worden sind, liefern nach Abkühlung auf Raumtemperatur homogene Produkte mit defekter Spinellstruktur. Die bei der Zusammensetzung Al₂S₃ · ZnS beobachtete Mischungslücke setzt sich bei höherer Temperatur unter Verschiebung der Phasengrenzen und Ausbildung von Hochtemperatur-Phasen fort. Eine Hochtemperaturmodifikation des ZnAl₂S₄ existiert bis 1080°C nicht. Mischungen von ZnS, Al und S mit 0,44 ≤ x ≤ 0,85, die auf 1060–1080°C (72–96 h) erhitzt worden sind, zeigen nach Abkühlung auf Raumtemperatur eine bisher nicht beschriebene rhomboedrische Hochtemperaturphase (γ-Phase), deren Struktur als eine Defektstruktur des ZnIn₂S₄-Typs aufgefaßt werden kann. Bei x = 1,00 erhält man nach thermischer Behandlung bei 1060–1080°C ein zweiphasiges Produkt, das neben der γ-Phase eine orthorhombische Phase (β-Phase, Überstruktur des Wurtzit-Typs) enthält. Die β-Phase tritt als einzige Phase auf, wenn für die Ausgangsmischung gilt: 1,40 ≤ x ≤ 1,70. Die Löslichkeit von Al₂S₃ in ZnS (Wurtzit) unter Bildung einer statistischen Defektstruktur des Wurtzit-Typs reicht bei 1060–1080°C bis Zn_1,70?1,80Al_1,53?1,47S₄(Al₂S₃ · (2,2-2,5) ZnS). Preparative and X-Ray Investigations on the System Al₂S₃? ZnS (Temperature Region 800–1080°C) Single crystals of α-ZnAl₂S₄ with spinel structure (a = 10.009₃ Å) have been obtained by chemical transport reaction at 740°C. Heating of the compound to 800–900°C leads to decomposition and formation of a ZnSαpoor defect spinel phase and a ZnS-rich phase with a defect wurtzite structure. The boundaries of the two-phase region at 830–860°C are approximately Zn_0,98Al_2.01S₄ (cubic α-phase, a α 10.007₂ Å (25°C)) and Zn_1.80Al_1.47S₄ (hexagonal wurtzite-phase, a = 3.76₀, c = 6.1₅ Å (25°C)). Mixtures of ZnS, Al and S with the composition Zn_xAl_8/3?2x/3S₄ and 0.33 ≤ x ≤ 0.98, which are heat treated at 830–860°C (70–140 h), yield after cooling to room temperature homogeneous products with a defect spinel structure. The miscibility gap at the composition Al₂S₃ · ZnS continues at higher temperatures with a shift of the phase boundaries and formation of high-temperature phases. A high-temperature modification of ZnAl₂S₄ does not exist up to 1080°C. When mixtures of ZnS, Al and S with 0.44 ≤ x ≤ 0.85 are heat treated at 1060–1080°C(72-96 h), a rhombohedra1 high-temperature phase (γ-phase) is obtained after cooling to room temperature, which has not previously been observed. I t s structure can be described as a defect structure of the ZnIn, S, type. With x = 1.00, after thermal treatment a t 1060-1080°C, a two-phase product is obtained, containing γ-phase in addition to an orthorhombic phase (β-phase, super-lattice of the wnrtzite type). The β-phase is the only phase occuring in products with 1.40 ≤ x ≤ 1.70. The solubility of Al, S, in ZnS (wurtzite) at 1060-1080°C with formation of a defect wurtzite structure, in which the cations are disordered, reaches as far as Zn_l.70?1.80Al_l.53?1.47S₄[Al₂S₃·(2.2-2.5)ZnS].