Heat-activated nickel-titanium (Ni-Ti) archwires are widely used in the initial stages of orthodontic treatment. These alloys exhibit a shape memory effect which can be related to displacive (martensitic) transformation, which can be induced by temperature variation or mechanical influence (stress). Here we explored the changes of archwires microstructure, chemical composition and phase transition temperatures due to prolonged regular usage. Three forms of dental archwires with dimensions 0.016" x 0.022" (3M Unitek, Monrovia, CA, USA) were investigated: as-received, as-received + autoclaved (sterilized) and used during treatment heat-activated Ni-Ti archwires. The three forms of archwires were analyzed by powder X-ray diffraction analysis (XRD), Scanning Electronic Microscopy (SEM) in combination with Energy Dispersive Spectroscopy (EDX) and Differential Scanning Calorimetry (DSC). The room temperature the XRD pattern of the archwires show typical peaks for a Ni-Ti alloy with austenite type structure. The DSC measurements were conducted in the -50 degrees C to + 50 degrees C temperature range. The DSC analyses of the Ni-Ti archwires revealed three phase transitions. Upon heating from -50 degrees C to + 50 degrees C a phase transition occurs at -12 degrees C. No additional endo/exo effects are registered. Upon cooling the DSC registers a phase transition around 10 degrees C and around -40 degrees C. The first effect is due to the formation of an intermediate rhombohedral phase (R phase) while at -40 degrees C Ni-Ti structure transforms to martensite. The results from EDX demonstrate that there is no pronounced change in the chemical composition on the surface of the investigated orthodontic archwires. Though SEM micrographs show some changes on the surface of the wires after usual use. The results obtained within this study contribute to the establishment of some peculiarities related to the thermal behavior and the shape-memory effect of the investigated archwires.

Multi-component soda lime silica glass (SLSG) specimens, with composition from the miscibility gap in the SiO2-Na2O system, were investigated after the substitution of copper for sodium and after thermal treatment of the exchanged samples in gaseous hydrogen. The behaviour of the obtained composite materials was studied by infrared reflection spectroscopy (IRRS). Some optical absorption micro-spectrophotometry (OAMS) measurements and X-ray-diffraction (XRD) analyses complemented these investigations. It has been stated that after exchange in the CuCl molten bath, the dopant was present in the glassy matrix in the form of cuprous and cupric ions. The cuprous ions participate in the formation of semiconducting Cu2O nanoparticles. Hydrogenation of the exchanged specimens leads to the formation of metallic copper atoms which due to the van der Waals interactions precipitate in the form of colloidal copper nanoparticles. Changes of the matrix morphology are mainly related with the presence of cupric ions which behave as glass forming cations and such as these participate in the formation of mixed copper-sodium silicates. The effectiveness of these processes is substantially dependent on the exchange and hydrogenation parameters.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Three isomorphic, Mg, Mn and Zn phthalocyaninato complexes monoaxially ligated by 2-amino-3-picoline (2A3P) are obtained. They crystallise with 2A3P molecule as solvent molecule in the centrosymmetric space group P21/c of monoclinic system. The central M(II) atom in these complexes, M(II)Pc(2A3P), is coordinated by four isoindole N atoms of Pc macrocycle in equatorial position, and by ring N atom of 2A3P molecule in an axial position. The M(II) due to the interaction with an axial 2A3P molecule is significantly displaced from the plane defined by four isoindole N atoms of Pc macrocycle toward the ring N atom of 2A3P molecule. The stability of these complexes in solid was analysed by thermogravimetric measurements. The Mg and Zn complexes in solution are stable under air condition, while the Mn complex is moderately stable in solution and after several days transforms into μ-oxo manganese(III) phthalocyanine complex. The magnetic susceptibility of the MnPc(2A3P)×2A3P complex shows the Curie–Weiss behaviour in the temperature range of 300–75 K. The calculated μeff indicates on high-spin complex. Below 75 K, the μeff drastically lowered to the value of ∼3.62 μB indicating the intermediate-spin complex. In addition, the co-crystals of 2:1 composition of 2A3P:1,2-dicyanobenzene were isolated during the preparation of the MgPc(2A3P)×2A3P.

The BePc(4-Mepy), MgPc(4-Mepy)(2) were recrystallised from wet 4-picoline and the aqua M((II) phthalocyaninato complexes, BePcH2O center dot (4-Mepy) (Ia), (MgPcH2O center dot (4-Mepy))(2) (IIa) and (MgPcH2O center dot (4Mepy)(2)) -(4-Mepy) (IIb), have been obtained. Recrystallisation of ZnPc(4-Mepy) in wet 4-picoline yields the P-ZnPc in microcrystalline form. The Ia, IIa and IIIb complexes were obtained in crystalline form. The composition of the Mg complexes (IIa and IIb) depends on the crystallisation temperature. The BePcH2O center dot (4-Mepy) compound crystallises in the centrosymmetric space group of the triclinic system, while both Mg complexes crystallise in the P2(1)/n space group of the monoclinic system. In all crystals the central M(II) atom (Be and Mg) is 4 + 1 coordinated, equatorially by four N-isoindole atoms of Pc macrocycle and axially by 0 atom of water molecule. interaction of the central M atom of MgPc with axially ligated water molecule leads to the saucer-shape of the Pc ring and deviates the central M(II) atom from the N-4-isondole plane by 0.308(2), 0.482(2) and 0.537(2) angstrom in Ia, IIa and IIb, respectively. The molecules in the Ia and IIa crystals are linked together by a pair of O-H center dot center dot center dot N hydrogen bonds between the H atom of water molecule and the azamethine N atom of the other Pc into a dimeric structure, and the 4-picoline molecules are linked to the (MPcH2O)(2) dimeric structure. In IIb crystal the MgPcH2O molecule is linked by O-H center dot center dot N hydrogen bonds with two 4-picoline molecules, while the third 4-picoline molecule interacts only by the van der Waals forces. The O-H center dot center dot center dot N hydrogen bonding system and the pi-pi interactions between the aromatic Pc macrocyles are the key for the molecular arrangement and stabilisation of the structure. The stability of the solid-state complexes was analysed by thermogravimetric measurements. Only the solid-state spectrum of IIa complex exhibits an intense near IR absorption band. The spectra of IIa and IIIb in solution are identical, the Q band is blue shifted in O-donor solvents comparing with the spectrum in N-donor solvents. (c) 2008 Elsevier Ltd. All rights reserved.

Three new Be(II), Mg(II) and Zn(II) phthalocyaninato(2-) complexes with 4-picoline (4-Mepy) in the crystalline form have been obtained by recrystallization of the respective M(II)Pc in 4-picoline under water-free conditions. BePc and ZnPc in 4-picoline solution form 4 + 1 coordinated complexes, while the 4-Mepy molecules biaxially ligate MgPc. The planar phthalocyaninato(2-) macroring of BePc and ZnPc upon mono-axial ligation by the 4-Mepy molecule adopts the saucer-shape form. The interaction of the central M(II) with the ligated 4-Mepy molecule leads to a deviation of the metal from the centre cavity by similar to 0.31 angstrom and similar to 0.35 angstrom in the Be and Zn phthalocyaninato complexes, respectively. In MgPc, the Pc ring upon biaxial ligation retains a planar configuration. The axial M(II)N(4-Mepy) bond is longer than the four equatorial M(II)-N-iso bonds in Mg and Zn phthalocyaninato complexes, while in the Be complex the opposite relation between the axial and equatorial Be-N bonds is observed. Thermogravimetric analysis for all these compounds exhibits only one slope down, due to the loss of 4-Mepy molecules from the complexes, which transform finally into the respective M(II)Pc complexes in the beta-form. (C) 2007 Elsevier Ltd. All rights reserved.

Transparent glasses of the composition M2O–MgO–WO3–P2O5 (M=K,Rb,Cs), corresponding to the crystalline phases of M2MgWO2(PO4)2, have been prepared and studied by Raman and IR spectroscopy as well as DTA. Moreover, the thermally stimulated depolarization and dc conductivity have been measured. The glass transition temperature is 797, 795 and 773K for the K-, Rb- and Cs-containing glass, respectively. Raman and IR studies have shown that these glasses have very similar structure. The main building blocks are pyrophosphate groups, WO6 octahedra and magnesium–oxygen polyhedra. The dc conduction in these glasses is controlled by hopping of small polarons. The potassium containing glass was shown to be very stable whereas the rubidium and cesium glasses have significantly higher tendency for crystallization and phase separation. It seems, therefore, that the potassium containing glass is a suitable material for the preparation of samples containing non-linear and ferroelectric nanocrystals of the K2MgWO2(PO4)2 phosphate.

Phase equilibria in La2O3–Gd2O3–CuO system were studied based on samples obtained from appropriate mixtures of the starting components, prepared in air by a conventional solid state reaction. The phase relations prevalent in this system have been deduced based on X-ray diffraction patterns of well-equilibrated samples. An isothermal cross-section diagram through the system at 950°C is presented. The system is characterised with solid solutions of several well-known binary compounds such as T–La2CuO4 (orthorhombic at 950°C), tetragonal T′–Gd2CuO4, and monoclinic La2Cu2O7 (α-solid solution). The system contains also the T*-type three-component phase of tetragonal symmetry, intermediate to those of T and T′. A large solubility domain has been found between La2O3 and Gd2O3 (B solid solution of monoclinic structure form typical for RE-sesquioxides), extending deeply towards the ternary system with CuO. Lattice parameters vs. chemical composition are presented for some of the phases found in this system.

Single crystals of Pb2Sr2R1−xCaxCu3O8+δ (R=Y, Tb) superconductor were grown from PbO–NaCl flux. The Ca content was determined by means of EDX method to vary in the range 0.3–0.5. The superconducting transition temperature was found to be close to the optimal value of 70–80K. The intergrowths with another superconducting perovskite (Pb,Cu)Sr2(Y,Ca)Cu2O7 of Tc ≈ 60K was observed for Y-based crystals, what resulted in a double transition observed frequently in magnetic measurements. This tendency has not been found for Tb-based crystals which usually showed more sharp transitions. Thermogravimetric experiments showed that the oxidation process of Pb2Sr2R1−xCaxCu3O8+δ single crystals proceeds in two steps. The first one corresponds to Cu1+ oxidation (500–550°C for both R=Y and Tb), the second could be attributed to lead oxidation (830–870°C for R=Y and 80–100°C lower for Tb-based compound).

The syntheses of the magnesium phthalocyanine complexes with dry 2-methoxy-ethanol and 2-ethoxyethanol have been performed by recrystallization method using both anhydrous MgPc and aquated magnesium phthalocyanine, MgPcH2O, as a starting material. It has turned out that in the temperature range below ca. 140 degreesC, the bi-axially ligated complexes are formed, i.e., MgPc(2-methoxyethanol)(2) and MgPc(2-ethoxyethanol)(2) with 4 + 2 coordination of Mg, whereas at higher temperatures, up to about 200 degreesC, the mono-axially ligated complexes are stable, i.e., MgPc(2-methoxyethanol) and MgPc(2-ethoxyethanol) with 4 + 1 coordination of Mg.The single crystal structure of MgPc(2-ethoxyethanol) complex has been determined. The central Mg atom is displaced towards the hydroxyl group of the ligand by about 0.37 Angstrom from the (N-isoindole)(4) plane of the Pc ring. Hydrogen bonds of the type O-(HN)-N-... between the hydroxyl groups of 2-ethoxyethanol and one of the azamethine N-atoms of the Pc ring link the molecules related by a centre of symmetry. Such a packing arrangement in the crystal leads to a dimerization with the ligand-to-Pc connections. The syntheses, then nogravimetric results and structure characteristics are compared with the known MgPc complexes with O- and N-donating molecules. (C) 2004 Elsevier B.V. All rights reserved.

An inorganic–organic hybrid material has been obtained by combining organic photopolymerization and the sol–gel process. The organic and inorganic phases are formed from two interpenetrating polymeric networks. The organic phase is a copolymer of acrylamide and 2-hydroxyethylmethacrylate while the inorganic phase is a silica polymer. Morphology, structure and properties of the inorganic–organic hybrid have been investigated via Raman and IR spectroscopies, N2-adsorption (77 K), thermal gravimetric analysis (TGA) and differential thermal analysis (DTA).

Two samples of nominal composition Gd1.80Ce0.15CuO4.0 and Gd1.85Ce0.15CuO4.075 were subjected for a long-term treatment in air at 1100degreesC, comprised with a precise control of their weights vs. time of the treatment applied. The gravimetric analysis and the iodometric titration, both showed a deficiency on Cu-site, steadily increasing vs. time with a slight tendency to a saturation. The X-ray analysis of the resulting products showed that even after 272 h of sintering, the samples remained single phase of the "214" structure type. Refinement of their crystal structures as well as density measurements, both allowed confirming Cu deficient structure constitution of these samples. Results of dc-magnetization measurements, performed prior to reduction of the sample's overall oxygen content, did not show any sign of superconductivity down to 4.2 K. These preliminary results indicate that copper deficiency, developing during synthesis, may occur to be a decisive factor for the reported lack of superconductivity in Ce-doped Gd2CuO4 phase. Oxygen content reduction and further tests on the samples obtained are in progress.

Phase equilibria in Gd2O3-CeO2-CuO system were studied based on samples obtained from appropriate mixtures of the starting components, prepared by a conventional solid state reaction in air. The phase relations prevalent in this system have been deduced based on X-ray diffraction of well-equilibrated samples. An isothermal cross-section diagram through the system at 980degreesC is presented and chemical constitution of the Ce-doped Gd2CuO4 phase is proposed.