Temperature‐dependent Changes of the Crystal Structure of Li2B4O7

The crystal structure of Li₂B₄O₇ was studied by single crystal X‐ray diffraction whilst the substance was cooled down from room temperature to ?150 °C. The title compound crystallizes in the tetragonal, non‐centrosymmetric space group I 4₁cd (no. 110), a = 9.475(5) Å (r.t.), c = 10.283(6) Å (r.t.), R values for seven different data sets vary from 2.6 to 2.9 %. Low‐temperature single crystal examinations were combined with low‐temperature powder X‐ray diffraction experiments (?189 – +27 °C). The results are discussed in comparison with data earlier obtained at high temperatures (20 – 500 °C). No phase transitions or abrupt changes of the crystal structure were observed. The coordination sphere of the lithium ions is that of a distorted tetrahedron and remains almost unchanged, although the coordination number of the lithium ions decreases slightly with rising temperature, similarly to what was found for LiB₃O₅. An expected rigidity of the boron‐oxygen groups was confirmed. The thermal deformations of the [B₄O₇]^2? framework occur according to the hinge mechanism. This indicates that the LiO₄ chains change their winding on cooling, which leads to deformations along c.     

Nitridation of V5Al8 films with NH3 by Rapid Thermal Processing (RTP)

V₅Al₈ films (thickness about 100 nm) were deposited on sapphire substrates by RF‐sputtering and nitridated with NH₃ at 600‐1250 °C (1 min) in a RTP system. The as deposited and nitridated films were investigated by ESCA (electron spectroscopy for chemical analysis), XRD (X‐ray diffraction), XRR (X‐ray reflectometry), AFM (atomic force microscopy) and SEM (scanning electron microscopy). Formation of an aluminum nitride layer at the surface and precipitation of V(Al) in the bulk was found. In the temperature regime from 600 °C to 900 °C a considerable amount of oxygen is incorporated in the aluminum nitride layer. The roughness of the surface increased with increasing temperature and at 1250 °C a partially detaching of the AlN layer could be observed.     

Deposition of copper‐doped iron sulfide (CuxFe1−xS) thin films using aerosol‐assisted chemical vapor deposition technique

Copper‐doped iron sulfide (Cu_xFe_1?xS, x = 0.010–0.180) thin films were deposited using a single‐source precursor, Cu(LH)₂Cl₂ (LH = monoacetylferrocene thiosemicarbazone), by aerosol‐assisted chemical vapor deposition technique. The Cu‐doped FeS thin films were deposited at different substrate temperatures, i.e. 250, 300, 350, 400 and 450 °C. The deposited thin films were characterized by X‐ray diffraction (XRD) patterns, Raman spectra, scanning electron microscopy, energy dispersive X‐ray analysis (EDX) and atomic force microscopy. XRD studies of Cu‐doped FeS thin films at all the temperatures revealed formation of single‐phase FeS structure. With increasing substrate temperature from 250 to 450 °C, there was change in morphology from wafer‐like to cylindrical plate‐like. EDX analysis showed that the doping percentage of copper increased as the substrate temperature increased from 250 to 450 °C. Raman data supports the doping of copper in FeS films. Copyright © 2010 John Wiley & Sons, Ltd.     

The Crystal Structure of ζ2‐Al3Cu4‐δ

The crystal structure of the ζ₂‐phase Al₃Cu_4‐δ was determined by means of X‐ray powder diffraction: a = 409.72(1) pm, b = 703.13(2) pm, c = 997.93(3) pm, space group Imm2, Pearson symbol oI24‐3.5, R_I = 0.0696. ζ₂‐Al₃Cu_4‐δ forms a distinctive a × √3a × 2c superstructure of a metal deficient Ni₂In‐type‐related structure. The phase is meta‐stable at ambient temperature. Between 400 °C and 450 °C it decomposes into ζ₁‐Al₃Cu₄ and η₂‐AlCu. Entropic contributions to the stability of ζ₂‐Al₃Cu_4‐δ are reflected in three statistically or partially occupied sites.     

Influence of thermal annealing on the microstructure,hardness and corrosion behavior of TiAlSiCuN nanocomposite films

Nanocomposite TiAlSiCuN films were deposited on high speed steels by filtered magnetic arc ion plating. Detailed properties of the films annealed at various temperatures are studied. After thermal annealing at different temperatures ranging from 400 to 800 °C, changes in the film micro‐structure, chemical and phase composition, surface morphology, hardness and polarization curve properties were systematically characterized by X‐ray diffraction, X‐ray photoelectron spectroscopy, scanning electron microscopy, nano‐indenter and electrochemical workstation, respectively. It was found that the TiAlSiCuN films could be fully oxidized at 800 °C, Al and Ti atoms all diffused outwards and formed dense protective Al₂O₃ and TiO₂ layer. Simultaneously, the TiAlN phase gradually disappeared. The films annealed at 400 °C obtained the highest hardness because of the certain grain growth and little generated oxides. Besides, the certain formation of dense protective Al₂O₃ layer made the TiAlSiCuN film annealed at 600 °C present the least corrosion current density and the corrosion voltage. Copyright © 2016 John Wiley & Sons, Ltd.     

Synthesis and Structure of Europium Aluminium Garnet (EAG)

Europium aluminium garnet (Eu₃Al₅O₁₂, EAG) was synthesized by an aqueous sol‐gel process and subsequent thermal annealing at 800 – 850 °C. Eu₃Al₅O₁₂ crystallizes cubic ( and its crystal structure was refined from X‐ray powder data. The refined oxygen position in the structure of EAG yields four shorter and four longer distances between europium and the eight surrounding oxygen atoms, forming a distorted dodecahedron. Pure Eu₃Al₅O₁₂ can be treated at temperatures around 1000 °C before it converts into perovskite‐like EAP near 1300 °C.     

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.     

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.     

Cs2[PdCl4] — neue Ergebnisse zu einer „altbekannten”︁ Verbindung

Hochtemperatur‐Cs₂[PdCl₄] — New Results on a “wellknown” Compound Two modifications of Cs₂[PdCl₄] have been characterized by X‐ray powder and single crystal diffraction, respectively. The crystal structures are described and the group‐subgroup‐relations between these structures are discussed. In addition to the tetragonal (P4/mmm (No. 123), a = 7.4158(8) Å, c = 4.6792(6) Å) and the orthorhombic (Cmcm (No. 63), a = 10.529(1) Å, b = 10.310(1) Å, c = 9.460(1) Å) modification DSC investigations and high‐temperature X‐ray diffraction experiments with synchrotron radiation show the existence of another modification or of yet unknown decomposition products. The phase transformation from the orthorhombic to the tetragonal polymorph is completely finished at 100 °C. The second effect is detected at 319 °C.     

Alumina‐supported nickel catalyst for liquid‐phase reactions: an expedient and efficient heterogeneous catalyst for hydrogenation reactions

The preparation of a new nickel(0)/Al₂O₃ catalyst for hydrogenation reactions is described. The nickel(0)/Al₂O₃ catalysts were prepared by impregnation of alumina with a solution of a nickel(II) salt. After drying, the nickel(II) salt was reduced under mild conditions into nickel(0) using t‐BuONa‐activated sodium hydride in tetrahydrofuran at 65 °C. The nickel(0)/Al₂O₃ catalysts obtained were characterized by transmission electron microscopy and energy‐dispersive X‐ray spectroscopy. The supported catalysts were successfully used in solution‐phase hydrogenation of double and triple bonds. Although the activity of the nickel(0)/Al₂O₃ is comparable to non‐supported nickel(0) reagents, it has the advantage of being reusable more than ten times with only a slight decrease of reactivity. Copyright © 2003 John Wiley & Sons, Ltd.     

Synthesis of W‐doped TiO2 by low‐temperature hydrolysis: Effects of annealing temperature and doping content on the surface microstructure and photocatalytic activity

A series of tungsten‐doped Titania photocatalysts were synthesized using a low‐temperature method. The effects of dopant concentration and annealing temperature on the phase transitions, crystallinity, electronic, optical, and photocatalytic properties of the resulting material were studied. The X‐ray patterns revealed that the doping delays the transition of anatase to rutile to a high temperature. A new phase W_yTi_1‐yO₂ appeared for 5.00 wt% W‐TiO₂ annealed at 900 °C. Raman and diffuse reflectance UV–Vis spectroscopy showed that band gap values decreased slightly up to 700 °C. X‐ray photoelectron spectroscopy showed that surface species viz. Ti³⁺, Ti⁴⁺, O^2?, oxygen‐vacancies, and adsorbed OH groups vary depending on the preparation conditions. The photocatalytic activity was evaluated via the degradation of methylene blue using LED white light. The degradation rate was affected by the percentage of dopants. The best photocatalytic activity was achieved with the sample labeled 5.00 wt% W‐TiO₂ annealed at 700 °C.     

(Meta)stabiles CaC2

(Meta)stable CaC₂ One out of four modifications of CaC₂ is the so‐called metastable Calcium Carbide, CaC₂‐III, which was synthesized as pure material. It forms by heating monoclinic CaC₂‐II (C2/c) above 150 °C and remains stable after cooling down to room temperature. The structure was refined from X‐ray powder patterns (C2/m, Z = 4, a = 722.6(1) pm, b = 385.26(7) pm, c = 737.6(1) pm, β = 107.345(2)°). After grinding CaC₂‐III transforms back into CaC₂‐II. Heating CaC₂‐III induces a reversible phase transition into the cubic modification (CaC₂‐IV) at 460 °C. Differences between the three different structures of CaC₂ I–III, being stable at ambient conditions are also shown by ¹³C‐MAS‐NMR measurements, especially the presence of two distinct types of carbon atoms in the structure of the title compound.     

Eine neue Modifikation der Laves‐Phase CaLi2

A New Modification of the Laves Phase CaLi₂ A new modification of CaLi₂ (β‐CaLi₂) was obtained by simultaneous deposition of calcium and lithium on a sapphire substrate. This compound crystallizes cubic in the MgCu₂‐structure type (Fd3¯m, a = 885.6(1) pm, R_p=5.1 %, R_wp=6.6 %, structure analysis with the Rietveld‐method) and transforms at 150 °C into the well‐known hexagonal α‐CaLi₂. The thermal behavior was studied by temperature‐dependent X‐ray diffraction.     

Thermal stability of the layered modification of Cu0.5ZrTe2 in the temperature range 25–900 °C

The thermal stability of the layered modification of the Cu_0.5ZrTe₂ polycrystalline intercalation compound, synthesized at room temperature, has been studied in the temperature range 25–900 °C. A change in the occupation of the octahedral and tetrahedral coordinated sites in the interlayer space of the zirconium ditelluride was observed using in‐situ time‐resolved synchrotron X‐ray powder diffraction experiments. The formation of the rhombohedral CuZr₂Te₄ phase, which is stable in the temperature range 300–700 °C, has been observed. The copper intercalation at room temperature leads to the formation of a phase in which the Cu atoms occupy only octahedral sites in the interlayer space. At temperatures above the decay temperature of the rhombohedral CuZr₂Te₄, a layered phase with Cu atoms uniformly distributed between octahedral and tetrahedral sites in the interlayer space is stable. The changes in the crystal structure independent of temperature are in agreement with the previously proposed model, according to which the stability of the layered or the rhombohedral phase is determined by the entropy factor associated with the distribution of the intercalated atoms between the octahedral and tetrahedral sites in the interlayer space.     

Synthesis and Structural Characterization of Ternary Compounds Belonging to the Series RE2+mNi4+mAl15+4m (RE = rare earth metal)

The investigation of selected alloys in the Al‐rich part of ten RE‐Ni‐Al systems (RE = rare earth metal) has proved the existence of eight new ternary compounds: five with stoichiometry “R₄Ni₆Al₂₃” (mC66‐Y₄Ni₆Al₂₃‐type, for RE = Pr, Nd, Tb, Dy, Ho) and three with stoichiometry “R₃Ni₅Al₁₉” (oC108‐Gd₃Ni₅Al₁₉‐type, for RE = Sm, Dy and Er). In addition, the existence of R₄Ni₆Al₂₃ (RE = Ce and Gd) and of Gd₃Ni₅Al₁₉ has been confirmed. Lattice parameters have been determined and compared with those previously reported in literature. The samples have been synthesized from pure elements by induction melting, annealed at 800 °C and then water quenched. Micrographic characterization was carried out using a light optical microscope (LOM) and a scanning electron microscope (SEM). The structural characterization was performed by X‐ray powder diffraction.     

High-throughput and time-resolved energy-dispersive X-ray diffraction (EDXRD) study of the formation of CAU-1-(OH)2: microwave and conventional heating

Aluminium dihydroxyterephthalate [Al₈(OH)₄(OCH₃)₈(BDC(OH)₂)₆] ? x H₂O (denoted CAU‐1‐(OH)₂) was synthesized under solvothermal conditions and characterized by X‐ray powder diffraction, IR spectroscopy, sorption measurements, as well as thermogravimetric and elemental analysis. CAU‐1‐(OH)₂ is isoreticular to CAU‐1 and its pores are lined with OH groups. It is stable under ambient conditions and in water, and it exhibits permanent porosity and two types of cavities with effective diameters of approximately 1 and 0.45 nm. The crystallization of CAU‐1‐(OH)₂ was studied by in situ energy‐dispersive X‐ray diffraction (EDXRD) experiments in the 120–145 °C temperature range. Two heating methods—conventional and microwave—were investigated. The latter leads to shorter induction periods as well as shorter reaction times. Whereas CAU‐1‐(OH)₂ is formed at all investigated temperatures using conventional heating, it is only observed below 130 °C using microwave heating. The calculation of the activation energy of the crystallization of CAU‐1‐(OH)₂ exhibits similar values for microwave and conventional synthesis.     

Ordered Mesoporous Thin Films of Rutile TiO2 Nanocrystals Mixed with Amorphous Ta2O5

Ordered mesoporous thin films of composites of rutile TiO₂ nanocrystals with amorphous Ta₂O₅ are fabricated by evaporation‐induced self‐assembly followed by subsequent heat treatment beyond 780 °C. Incorporation of selected amounts of Ta₂O₅ (20 mol %) in the mesoporous TiO₂ film, together with the unique mesoporous structure itself, increased the onset of crystallization temperature which is high enough to ensure the crystallization of amorphous titania to rutile. The ordered mesoporous structure benefits from a block‐copolymer template, which stabilizes the mesostructure of the amorphous mixed oxides before crystallization. The surface and in‐depth composition analysis by X‐ray photoelectron spectroscopy suggests a homogeneous intermixing of the two oxides in the thin film. A detailed X‐ray absorption fine structure measurement on the composite film containing 20 mol % Ta₂O₅ and heated to 800 °C confirms the amorphous nature of the Ta₂O₅ phase. Photocatalytic activity evaluation suggests that the rutile nanocrystals in the synthesized ordered mesoporous thin film possess good ability to assist the photodegradation of rhodamine B in water under illumination by UV light.     

Phase transition in polyamide‐66/montmorillonite nanocomposites on annealing

The crystalline‐phase transition in polyamide‐66/montmorillonite nanocomposites before melting was investigated by in situ X‐ray diffraction and is reported for the first time in this work. The phase‐transition temperature in the nanocomposites was 170 °C, 20 °C lower than that in polyamide‐66. The lower phase‐transition temperature of the nanocomposites could be attributed to the γ‐phase‐favorable environment caused by silicate layers. Meanwhile, the addition of silicate layers changed the crystal structure of the polyamide‐66 matrix and influenced the phase‐transition behavior. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 63–67, 2003     

A Convenient Synthesis of 2‐Amino‐3‐cyano‐4‐aryl‐1,4,5,6‐tetrahydrobenzo[h]chromenes Derivatives Using KF‐Al2O3 as Catalyst

Abstract

A series of new 2‐amino‐3‐cyano‐4‐aryl‐1,4,5,6‐tetrahydrobenzo[h]chromenes derivatives were synthesized by the reaction of malononitrile with 2‐arylmethylidene‐3, 4‐dihydro‐1(2H)‐naphthalenone in N,N‐dimethylformamide (DMF) at 80°C catalyzed by KF‐Al₂O₃. The structure of the product was confirmed by x‐ray analysis.     

Influence of thermal annealing on the structural and optical properties of maghemite (γ‐Fe2O3) nanoparticle thin films

In this study, maghemite (γ‐Fe₂O₃) nanoparticles were initially synthesized via chemical co‐precipitation and then deposited by spray pyrolysis as thin films on white glass substrates. The thin films were annealed for 8 h at 400, 450, 500, 550, and 600 °C in an oven. The structural studies of maghemite nanoparticles were carried out using X‐ray diffractometer. Structural properties that we investigated by X‐ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, SEM, and Energy dispersive X‐ray analysis (EDS). Optical properties of the samples were also investigated by ultraviolet‐visible (UV–vis) spectroscopy. The results showed that maghemite nanoparticles have crystalline structure with domain that increases in size with increasing annealing temperature. The optical band gap values were found to reduce from 2.9 to 2.4 eV with increase in annealing temperature. Copyright © 2015 John Wiley & Sons, Ltd.