Synthesis of Al-substituted 11 Å tobermorite from newsprint recycling residue: a feasibility study

Newsprint recycling is responsible for significant volumes of secondary waste material for which further reprocessing and market development would be beneficial. In response to this problem, a layer lattice, ion exchange material, Al-substituted 11 Å tobermorite, has been synthesised from newsprint recycling residue comprising gehlenite (Ca₂Al₂SiO₇), akermanite (Ca₂MgSi₂O₇), β-dicalcium silicate (Ca₂SiO₄) and anorthite (CaAl₂Si₂O₈) under hydrothermal conditions at 100 °C in the presence of NaOH. The hydrogarnet phase, katoite (Ca₃Al₂SiO₁₂H₈), was also formed. Similar treatment regimes in the presence of LiOH and KOH did not yield significant quantities of Al-substituted 11 Å tobermorite. A batch sorption study confirmed that the Al-substituted 11 Å tobermorite-bearing product was effective in the exclusion of Cd²⁺, Pb²⁺ and Zn²⁺ from acidified aqueous media. The potential to enhance the yield of Al-substituted 11 Å tobermorite relative to that of katoite and thus optimise the ion exchange efficiency of the product is discussed with respect to its application to heavy metal-contaminated wastewater treatment.     

Synthesis, crystal structure, and properties of novel perovskite oxychalcogenides, Ca2CuFeO3Ch (Ch = S, Se)

Two new perovskite oxychalcogenides, Ca₂CuFeO₃S and Ca₂CuFeO₃Se, have been synthesized in evacuated quartz tubes. They crystallize in P4/nmm space group with lattice parameters a = 3.8271(1), c = 14.9485(2) Å and a = 3.8605(1), c = 15.3030(2) Å for Ca₂CuFeO₃S and Ca₂CuFeO₃Se, respectively. They appear to be the first layered chalcogenide perovskites involving calcium and are structural analogs of the corresponding Sr and Ba compounds. The new compounds exhibit semiconducting properties with energy gap decreasing from the oxysulfide to the oxyselenide. Possibility of introducing Ca²⁺ into structures of known layered oxychalcogenides and oxypnictides is discussed.     

Synthesis, structural and magnetic properties of La1−xCdxFeO3 (0.0 ≤ x ≤ 0.3) orthoferrites

Nanocrystalline La_1−xCd_xFeO₃ (0.0 ≤ x ≤ 0.3) solid solutions have been synthesized by a single-step solution combustion method at a relatively low temperature of 400 °C. The combustion-synthesized solid solutions were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and magnetic measurements. The crystal structure examined by XRD indicates that the samples were single-phase, and crystallize in an orthorhombic (space group, Pbnm no. 62) structure. The parent and doped compounds showed canted antiferromagnetic behavior associated with an increase in magnetic moment with Cd doping. The changes in magnetic properties of the materials are correlated to the changes in structural features resulting from the Rietveld structural refinement of the materials.     

Synthesis, structure refinement at 296 K and physico-chemical characterizations of KMnHP3O10

Potassium manganese(III) monohydrogentriphosphate KMnHP₃O₁₀ was synthesized by flux method and characterized by single-crystal X-ray diffraction, crystallizes in the monoclinic system with centric space group C2/c. The parameters of the unit cell are a = 12.104(1), b = 8.287(1). c = 9.150(1) Å, β = 110.97(1)° and Z = 4. The structure was solved at 296 K using 893 independent reflections and refined until R(F) = 0.022; wR(F²) = 0.045. The atomic arrangement of the title compound consists of MnO₆ octahedra linked by hydrogentriphosphate anions to form a three-dimensional framework containing tunnels parallel to the c-axis where the K⁺ cations are inserted. The structure of KMnHP₃O₁₀ contains a single Mn site which is surrounded by typical Jahn-Teller [2 + 2 + 2] distorted octahedron. The title material has been also characterized by different physico-chemical techniques: powder X-ray diffraction, IR, NMR and CI spectroscopies and DTA-TGA-DSC thermal analysis.     

Synthesis, structure and magnetic properties of Sr2Fe1−xGaxMoO6 (0 ≤ x ≤ 0.6) double perovskites

Polycrystalline Sr₂Fe_1−xGa_xMoO₆ (0 ≤ x ≤ 0.6) materials have been synthesized by solid state reaction method and studied by neutron powder diffraction (NPD) and magnetization measurements. Rietveld analysis of the temperature dependent NPD data shows that the compounds crystallize in the tetragonal symmetry in the space group I4/m. The anti-site (AS) defects concentration increases with Ga doping, giving rise to highly B-site disordered materials. Ga doping at the Fe-site decreases the cell volume. The evolution of bond lengths and the cation oxidation states was determined from the Rietveld refinement data. The saturation magnetization and Curie temperature decreased with the increasing Ga content in the samples. Low temperature neutron diffraction data analysis and magnetization measurements confirm the magnetic interaction as ferrimagnetic in the sample.     

Phase transitions and ionic mobility in hydrogen zirconium phosphates with the NASICON structure, H1±XZr2−XMX(PO4)3·H2O, M = Nb, Y

Phase transitions and the mobility of proton-containing groups in hydrogen zirconium phosphate HZr₂(PO₄)₃·nH₂O with the NASICON structure were studied by X-ray powder diffraction, ¹H, ³¹P NMR, IR spectroscopy and TG analysis. Heating HZr₂(PO₄)₃·H₂O above 420 K results in dehydration and in a rhombohedral-triclinic phase transition. Continued heating to about 490 K results in the thermal activation of cation disordering and phase transition of HZr₂(PO₄)₃ from triclinic to rhombohedral phase. Parameter “a” of HZr₂(PO₄)₃ lattice decreases during the heating. It is shown that oxonium ions in HZr₂(PO₄)₃·H₂O are characterized by high rotation and translation mobility. Rotation mobility of oxonium ions can be increased by the substitution of zirconium by yttrium or niobium.     

Double electrodeposition and heat treatment process for the fabrication of superconducting oxides on the intensified {1 1 3} <1 2 1> Ag substrate

The Tl-1223 coated conductor (Tl_0.8Pb_0.2Bi_0.2Sr_1.8Ba_0.2Ca_2.2Cu₃O_δ) was synthesized by using electrodeposition on the intensified {1 1 3} <1 2 1> Ag substrate applying the new method of the repeating electrodeposition/heat treatment. The films were fabricated conducting the first electrodeposition and then heat treatment, after that the second electrodeposition on the first electrodeposition/heat treatment coated conductors. The second electrodeposition on the first electrodeposition/heat treatment/the first electrodeposition/heat treatment coated conductor showed the better quality of the Tl-1223 phases than that of the first electrodeposition/heat treatment coated conductor, showing more compact and dense grains on the films. The thin Tl-1223 films caused by the thinning process were discussed by considering the properties of Tl and the epitaxial growth aspects. The purer Tl-1223 grains obtained at the double electrodeposition/heat treatment are due to the growth from Tl-1223 grains already synthesized during the first electrodeposition/heat treatment, facilitating the epitaxial growth easier than that of the Ag substrate. The second electrodeposition process was successfully performed, obtaining 1.9 × 10⁵ A/cm² of J_c at 0 T at 10 K.     

Synthesis, low-temperature sintering and the dielectric properties of the ZnO-(1 − x)TiO2-xSnO2 (x = 0.04-0.2)

ZnO-(1 − x)TiO₂-xSnO₂ (x = 0.04-0.2) ceramics were prepared by conventional mixed-oxide method combined with a chemical processing. Fine particle powders were prepared by chemical processing to activate the formation of compound and to improve the sinterability. One wt.% of V₂O₅ and B₂O₃ with the mole ratios of 3:1 were used to lower the sintering temperature of ceramics. The effect of Sn content on phase structure and dielectric properties were investigated. The results show that the substituting Sn for Ti accelerates the hexagonal phase transition to cubic phase, and an inverse spinel structure Zn₂(Ti_1−xSn_x)O₄ solid solution forms. The best dielectric properties obtained at x = 0.12. The ZnO-0.88TiO₂-0.12SnO₂ ceramics sintered at 900 °C exhibit a good dielectric property: ?_r = 29 and tan δ = 9.86 × 10⁻⁵. Due to their good dielectric properties, low firing characteristics, ZnO-(1 − x)TiO₂-xSnO₂ (x = 0.04-0.2) can serve as the promising microwave dielectric capacitor.     

Synthesis of layered sodium lanthanum selenide through ion exchange reactions

Layered hexagonal KLaSe2 (α-NaFeO₂-type) was synthesized using the reactive flux method and analyzed by powder XRD to determine its lattice constants (space group R-3m, a = 4.40508(5) Å, c = 22.7838(5) Å). NaLaSe₂, which normally crystallizes as a disordered rock salt structure with mixed Na+/La + 3 sites, was synthesized through a solid state ion exchange reaction at 585 °C from a 1:3 molar ratio mixture of KLaSe₂:NaI. The product of this reaction was hexagonally layered NaLaSe₂ (space group R-3m, a = 4.3497(3) Å, c = 20.808(2) Å) isostructural to KLaSe₂. This product was analyzed by comparison with members of the set of solid solutions Na_(1−x)K_(x)LaSe₂ to confirm that the extent ion exchange in this reaction was complete. Cubic (disordered) NaLaSe₂ was also reacted with KI to yield the poorly crystalline hexagonally layered product with the approximate formula Na_0.79K_0.21LaSe₂.     

Synthesis,crystal growth,structural, spectral,thermal, mechanical,linear and nonlinear optical studies of organic single crystal 4-Iodo 4-nitrostilbene (IONS): A potential NLO material

An organic nonlinear optical material 4-Iodo 4-nitrostilbene (IONS) has been synthesized and good optical quality single crystal was grown from ethyl methyl ketone solvent by the solution growth technique. Single and powder X-ray diffraction analyses reveals that the grown crystal belongs to monoclinic crystal system with noncentrosymmetric space group ‘P2₁’ and it has good crystalline nature. Functional groups and molecular structure of the title compound were confirmed by FTIR and ¹H NMR respectively. The UV–Vis–NIR absorption study reveals no absorption in the visible region and the cut-off wavelength was found to be at 412.84 nm, TG/DTA, mass spectral analysis, photoluminescence and microhardness studies have been carried out for the grown crystals and results are discussed in detail. The second harmonic efficiency of the IONS was determined by Kurtz–Perry powder technique which reveals that the IONS crystal (3.1 V) has greater efficiency i.e., 143 times to that of KDP (21.7 mV).     

Influence of the B-site ordering on the magnetic properties of the new La3Co2MO9 double perovskites with M = Nb or Ta

Double perovskites La₃Co₂NbO₉ and La₃Co₂TaO₉ have been prepared by both solid state and sol-gel synthesis. The crystal structures have been studied from X-ray and neutron powder diffraction data. Rietveld refinements show that the crystal structure is monoclinic (P2₁/n), with different degrees of ordering of B′ and B″ cations, with octahedra tilted according to the Glazer notation a⁻b⁻c⁺. Occupancy refinements show that the solid state materials are more B-site ordered than the sol-gel ones. Magnetization measurements show that these perovskites show two magnetic contributions, one with spontaneous magnetization and other with linear behaviour with the magnetic field associated to antiferromagnetic correlations. In the samples synthesized by solid state the spontaneous magnetization is more important than those synthesized by the sol-gel and present T_C of 62 K for Nb and 72 K for Ta. On the other hand, materials prepared by sol-gel have T_C 20 K for Nb and 40 K for Ta, respectively and major presence of the antiferromagnetic contribution. The competition between these magnetic behaviours is interpreted, by a microscopic point of view, as to be due to the different degrees of Co²⁺ ions disorder on the B site of the double perovskite structure. This disorder affects the ratio between the antiferromagnetic Co²⁺-O-Co²⁺ and the ferromagnetic Co²⁺-O-M⁵⁺-O-Co²⁺ couplings proposed for the system.     

Crystal structures and properties of BiMn1−xAlxO3 with x = 0.03 and 0.1

Crystal structures of BiMn_0.97Al_0.03O₃ (I) at 300 and 470 K and BiMn_0.9Al_0.1O₃ (II) at 90 and 300 K were studied with synchrotron X-ray powder diffraction. The strong Jahn-Teller distortion, observed at 300 K in I and associated with orbital order, disappeared at 470 K completely for one site and partially for the second site. The Mn/Al-O distances were very close to each other in I at 470 K and in II at 90 and 300 K indicating that orbital order did not appear in II even at 90 K. Magnetic properties of I and II were investigated with specific heat, high-temperature dc magnetic susceptibility, and ac magnetic susceptibility using different driving ac and applied dc magnetic fields and different ac magnetic field frequencies. The anomaly on the specific heat associated with a magnetic transition was strongly suppressed in II compared with that of I and BiMnO₃.     

Synthesis and magnetic properties of layered MnPSxSe3−x (0 < x < 3) and corresponding intercalation compounds of 2,2′-bipyridine

In this work, we synthesize a series of new MnPS_xSe_3−x (0 < x < 3) compounds by high temperature solid-state reaction and also obtain the corresponding intercalation compounds (Mn_1−yPS_xSe_3−x(bipy)_4y, x = 1.2, 1.8 and 2.4) via the intercalation of 2,2′-bipyridine with MnPS_xSe_3−x. XRD results confirm that MnPS_xSe_3−x compounds show the layered structure and can be regarded as the solid solution of MnPS₃ and MnPSe₃. Magnetic measurements indicate that MnPS_xSe_3−x compounds exhibit paramagnetism with negative Weiss constant in the paramagnetic temperature region, and an antiferromagnetic phase transition occurs at the Neel temperature. It is found that the magnetic properties of MnPS_xSe_3−x slab are dramatically changed after the intercalation of 2,2′-bipyridine, which is close related to the relative ratio of S and Se atom as well as the intralayered Mn²⁺ vacancies of MnPS_xSe_3−x slab.     

Crystal structure and physicochemical properties of a new organic dihydrogenmonoarsenate

A new organic dihydrogenmonoarsenate (C₃H₉N₂O₂)H₂AsO₄ (abbreviate as ECAs) is prepared by reacting H₃AsO₄ with ethyl carbazate. This compound crystallizes in the monoclinic crystal system, space group P2₁/n. Unit cell parameters are a = 4.8370(2) Å, b = 24.6270(2) Å, c = 7.6311(5) Å, β = 92.948(4)°, with, Z = 4 and ρ_m = 1.800 g cm⁻³. The structure is solved, using the direct methods and refined against F² to a reliability R factor of 0.0475. The compound is characterized by infinite [H₂AsO₄]_nⁿ⁻ ribbons, parallel to the a-direction, connected by organic cations and forming layers localized at y = 0 and 1/2. The cohesion of the framework is ensured by hydrogen bonds N(O)-H?O. The thermal properties of the compounds are investigated as well as the IR properties supported by group theoretical analyses.     

Synthesis, structure, and electrochemical characteristics of LiNi1/3Co1/3Mn1/3O2 prepared by thermal polymerization

A thermal polymerization route was adopted to synthesize layered LiNi_1/3Co_1/3Mn_1/3O₂ materials. After annealing the polymer gel containing metal salts at different temperatures from 850 to 1000 °C for different time between 6 and 25 h, powders of pure α-NaFeO₂ phase were obtained. The crystal structure, morphology and electrochemical properties of the products were investigated by XRD, SEM, electrochemical cell cycling and AC impedance spectroscopy. It is found that the powder annealed at 950 °C for 15 h shows the best electrochemical property with the first specific discharge capacity of 188 mAh/g at C/10 and 87% retention after 100 cycles. It exhibits good rate capability with the specific capacity of 169 mAh/g at 1 C and 110 mAh/g at 6 C. Adopting a slowly cooling procedure during the powder annealing can improve the electrochemical performance of the LiNi_1/3Co_1/3Mn_1/3O₂ powder.     

Crystal structure and electrical properties of new tungsten bronzes: BxWO3 (0.01 ≤ x ≤ 0.08)

Boron tungsten bronzes B_xWO₃ (0.01 ≤ x ≤ 0.08) were synthesized by hybrid microwave method from mixtures of WO₃ and amorphous boron powder. With the increase of boron content, the crystal structure of B_xWO₃ transforms from orthorhombic (x = 0.01) to tetragonal α (x = 0.048) and then to tetragonal β (0.07 ≤ x ≤ 0.08). The average size of crystallites is in the range of 1-10 μm. All samples show semiconducting behaviour in their temperature dependence of resistivity. The conduction behaviour above 80 K for samples with x = 0.01 and 0.08 can be explained using the variable-range hopping and thermally activated mechanism, respectively. Comparative experiments showed that boron bronze phases cannot be obtained by the microwave heating of pure WO₃ powder or a mixture of B₂O₃ and WO₃ under the same conditions.     

Characterization of fluorite-type oxynitride phases in the R2TaON system (R = rare-earth element)

The synthesis of reactive nitridation precursors prepared using citrate complexation/calcination route has shown interest in the study of the system R₂TaON. Novel fluorite-type phases have been evidenced in the oxide series R₂TaO_5.5 (R = NdYb, Y) and oxynitride series R_2.67Ta_1.33(O,N,□)₈. Chemical and optical analyses were performed to characterize these phases, as well as structural analogies with R₂WO₆ and R₂MoO₅ oxide families.     

Microwave-hydrothermal synthesis of Al-substituted tobermorite from zeolites

Here, we report the rapid synthesis of Al-substituted tobermorites from zeolites under microwave-hydrothermal (M-H) conditions. The synthesized phases were characterized by powdered XRD analysis, SEM and selective Cs exchange determination. Zeolites served as aluminosilicate sources and M-H conditions yielded highly crystalline Al-substituted tobermorites in 2 h at 180°C and they showed high selectivity for Cs. For example, an Al-substituted tobermorite synthesized from phillipsite showed Cs exchange K_d of 2161±465 and 118,589±44,928 from 0.02N NaCl and 0.02N CaCl₂ solutions (both contained 0.0002N CsCl), respectively. Al-substituted tobermorites are expected to be useful for the selective separation of radioactive Cs and tobermorites can be incorporated in cement and/or concrete matrix for Cs immobilization.     

Synthesis of high-silica offretite by the interzeolite conversion method

High-silica offretite (Si/Al = 7.6-8.0) with no or very little amount of erionite was successfully obtained by the interzeolite conversion of faujasite used as a starting material in the presence of both benzyltrimethylammonium hydroxide and the structure-forming alkali metal cations such as Li⁺ and Na⁺. Hydrothermal conversion of faujasite into offretite depended on the Si/Al ratio of the starting faujasite. Only faujasite with Si/Al ratio of 16-31 was converted into offretite. In this conversion, offretite was obtained in 1 day, indicating that the crystallization rate was enhanced by using faujasite as the starting material. Based on ¹³C CP/MAS NMR measurements, most of benzyltrimethylammonium cations were presented intact within zeolitic pores of the obtained offretite. As offretite was not obtained from amorphous materials (amorphous SiO₂ and γ-Al₂O₃ or Al(OH)₃), the advantage of the interzeolite conversion was demonstrated.     

(Na4BH4) guests inside aluminosilicate, gallosilicate and aluminogermanate sodalite host frameworks studied by H, B, and Na MAS NMR spectroscopy

We report tetrahydroborate aluminosilicate, gallosilicate and aluminogermanate sodalites studied by ¹¹B, ¹H and ²³Na MAS NMR spectroscopy. The spectral parameters are consistent with the local environments of each investigated nucleus obtained from the crystal structures. The ¹¹B MAS NMR spectra exhibit a sharp narrow line at about −49.0 ppm, which is assigned to BH₄⁻ enclathrated into the sodalite framework matrix. The lineshape of the signal shows no quadrupolar interactions due to discreteness and high symmetry of the BH₄⁻ unit as well as possible fast dynamic site exchange of hydrogen atoms. The ²³Na MAS NMR signals also show a narrow Gaussian lineshape, which clearly indicates a single type of sodium coordination, and a centrosymmetrical charge distribution around the sodium atom. The ¹H MAS NMR spectra can clearly distinguish between hydrogen in BH₄⁻ anions (−0.6 ppm), H₃O₂⁻ anions (1.2 ppm) and H₂O molecules (5.0 ppm). The structural properties of BH₄⁻ intercalation into sodalite framework matrix help connect the microporous materials to hydride-containing A, X and Y type zeolites.