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1.
Salmiah Jamal Mat Rosid Susilawati Toemen Wan Azelee Wan Abu Bakar A.H. Zamani Wan Nur Aini Wan Mokhtar 《Journal of Saudi Chemical Society》2019,23(3):284-293
Carbon dioxide emission to the atmosphere is worsened as all the industries emit greenhouse gases (GHGs) to the atmosphere, particularly from refinery industries. The catalytic chemical conversion through methanation reaction is the most promising technology to convert this harmful CO2 gas to wealth CH4 gas for the combustion. Thus, supported neodymium oxide based catalyst doped with manganese and ruthenium was prepared via wet impregnation route. The screening was initiated with a series of Nd/Al2O3 catalysts calcined at 400?°C followed by optimization with respect to calcination temperatures, based ratios loading and various Ru loading. The Ru/Mn/Nd (5:20:75)/Al2O3 calcined at 1000?°C was the potential catalyst, attaining a complete CO2 conversion and forming 40% of CH4 at 400?°C reaction temperature. XRD results revealed an amorphous phase with the occurrence of active species of RuO2, MnO2, and Nd2O3, and the mass ratio of Mn was the highest among other active species as confirmed by EDX. The ESR resulted in the paramagnetic of Nd3+ at the g value of 2.348. Meanwhile nitrogen adsorption (NA) analysis showed the Type IV isotherm which exhibited the mesoporous structure with H3 hysteresis of slit shape pores. 相似文献
2.
Michael Veith Prof. Dr. Amadou L. Ndiaye Volker Huch Hailing Cui Claudia Wickleder 《无机化学与普通化学杂志》2008,634(14):2551-2556
Reaction of ligand L H2 (4,5‐bis[carboxymethylthio]‐1,3‐dithiol‐2‐thione) with neodymium silyl‐amide (Nd[N(TMS)2]3; TMS= ‐SiMe3), in a ratio 2:1, yields a neodymium‐dithiolene‐carboxylato complex ( 1 ) (Nd( L H) L ). Similarly, reaction of 2 equivalents of L′ H2 (4,5‐bis[2′‐hydroxyethyl)thio]‐1,3‐dithiol‐2‐thione) and one equivalent of neodymium silyl‐amide (Nd[N(TMS)2]3) allowed the isolation of complex 2 , with a ligand:metal ratio of 3:2. ATR‐IR spectrum of 1 displays a broad band characteristic of an OH group showing that one carboxylate group remains protonated. Emission spectrum of complex 1 under excitation in the visible region (at 360 nm i.e. on the ligand) displayed typical emission bands of the Nd3+, showing that energy transfer from the ligand to the lanthanide was achieved (i.e. “antenna effect”). No significant quenching from the remaining –OH group was detected. In the case of complex 2 , the main emission bands characteristic of the Nd3+ ion have been observed, by excitation at 495 nm. 相似文献
3.
Anhydrous neodymium(III) acetate, Nd(OAc)3 was obtained as light purple single crystals by direct oxidation of neodymium metal with malonic acid in a glass ampoule at 180 °C. It crystallizes with the monoclinic space group P21/a (no. 14) with a = 2201.7(2), b = 1850.0(1), c = 2419.0(3) pm, β = 96.127(8)°, V = 9796.8(1)·106·pm3, Z = 40 [Nd(OAc)3], R1 = 0.0430 [I0 > 2σ(I0)]. Most of the Nd3+ cations are coordinated by nine (or eight) oxygen atoms of acetate ligands which bridge these polyhedra to slightly waved layers which are stacked in the [010] direction. 相似文献
4.
Latifa Aneflous Sylvie Villain Houria Benyaich 《Journal of solid state chemistry》2004,177(3):856-865
Cerium dioxides doped or substituted by neodymium have been prepared using low- (320°C) and high-temperature (1600°C) processes. The Nd substituted ceria phase obtained at high temperature is a solid solution Ce1−xNdxO2−δ 0?x?0.30. Electrical impedance spectroscopy analyses have been performed in the temperature range 40-700°C. At temperatures above 400°C, Nyquist representations allow to separate three signals corresponding to bulk, grain boundary and electrode responses. Non-linear variations of the resistance and the capacitance as functions of temperature and composition x are observed. In the case of grain boundary and electrode interface signals, constant phase elements with non-integer exponent n have been used to represent the equivalent circuits. For each contribution, the conductance strongly increases then reaches a limit value, above x=0.10. When composition x increases, the condensation of Nd-vacancy defect clusters might be at the origin of the non-linear evolution of the conductance. Bulk and grain boundary conductions present different activation energies (0.7 and 1.3 eV). 相似文献
5.
Differential scanning calorimetry and high temperature oxide melt solution calorimetry are used to study enthalpy of phase transition and enthalpies of formation of Cu2P2O7 and Cu3(P2O6OH)2. α-Cu2P2O7 is reversibly transformed to β-Cu2P2O7 at 338–363 K with an enthalpy of phase transition of 0.15 ± 0.03 kJ mol−1. Enthalpies of formation from oxides of α-Cu2P2O7 and Cu3(P2O6OH)2 are −279.0 ± 1.4 kJ mol−1 and −538.8 ± 2.7 kJ mol−1, and their standard enthalpies of formation (enthalpy of formation from elements) are −2096.1 ± 4.3 kJ mol−1 and −4302.7 ± 6.7 kJ mol−1, respectively. The presence of hydrogen in diphosphate groups changes the geometry of Cu(II) and decreases acid–base interaction between oxide components in Cu3(P2O6OH)2, thus decreasing its thermodynamic stability. 相似文献
6.
A neodymium complex, [Nd(nta)]n ( 1 ) (H3nta = nitrilotriacetic acid) was synthesized and characterized by X-ray diffraction analysis. Compound 1 exhibits a three-dimensional network, in which the NdIII ion is coordinated by one nitrogen atom and seven carboxyl oxygen atoms with dodecahedral coordination. One striking feature is that in the Nd coordination center there is no water ligand found. 相似文献
7.
《Arabian Journal of Chemistry》2020,13(1):366-376
The synthesis of neodymium(III) bromide (NdBr3) by sintering brominating of neodymium oxide (Nd2O3) with ammonium bromide (NH4Br) was investigated. The influence of various synthesis parameters (temperature, contact time and stoichiometry) on the reaction yield was studied and optimized. The main interaction effects of the synthesis parameters on the reaction yield were also determined by a full 23 factorial designs with six replicates at the center point.This study showed that the optimum conditions for the synthesis of NdBr3 are following: contact time t = 60 min, stoichiometry in moles Nd2O3:NH4Br = 1:24 and temperature T = 400 °C. The reaction yield for these parameters was equal to 97.80%. The first order model was obtained to predict the reaction yield as a function of these three parameters. It was shown that all parameters have a significant positive influence on reaction yield. In addition it was pointed out also that the interaction effects between them are significant. 相似文献
8.
V. Parvanova 《Journal of Thermal Analysis and Calorimetry》2017,130(2):695-700
Neodymium(III) peroxotitanate is used as a precursor for obtaining Nd2TiO5. The last one possesses numerous valuable electrophysical properties. TiCl4, Nd(NO3)3·6H2O and H2O2 in mol ratio 1:2:10 were used as starting materials. The reaction ambience was alkalized to pH = 9 with a solution of NH3. The obtained neodymium(III) peroxotitanate and intermediate compounds of the isothermal heating were proved by the help of quantitative analysis and infrared spectroscopy (IRS). It has Nd4[Ti2(O2)4(OH)12]·7H2O composition. The absorption band observed in IRS at 831 cm?1 relates to a triangular bonding of the peroxo group of Ti, at 1062 cm?1—terminal groups Ti–OH and at 1491 and 1384 cm?1—the bridging OH?-groups Ti–O(H)–Ti. Nd2TiO5 was obtained by thermal decomposition of neodymium(III) peroxotitanate. The isothermal conditions for decomposition were determined on the base of differential thermal analysis, thermogravimetric and differential scanning calorimetry results in the temperature range of 20–1000 °C. The mechanism of thermal decomposition of Nd4[Ti2(O2)4(OH)12]·7H2O to Nd2TiO5 was studied. In the temperature range of 20–208 °C, a simultaneous decomposition of the peroxo groups by the separation of oxygen and hydrate water is conducted and Nd4[Ti2O4(OH)12] is obtained. From 208 to 390 °C, the terminal OH?-groups are separated and Nd4[Ti2O7(OH)6] is formed. In the range of 390–824 °C, the bridging OH?-groups are completely decomposed to Nd2TiO5. The optimal conditions for obtaining nanocrystalline Nd2TiO5 are 900 °C for 6 h and 20–80 nm. 相似文献
9.
E. I. Get’man T. A. Shul’gina S. N. Loboda L. Carrison 《Russian Journal of Inorganic Chemistry》2008,53(8):1342-1345
Isomorphic substitution of neodymium and gadolinium for calcium in synthetic hydroxovanadate Ca5 ? x M x (VO4)3(OH)1 ? x O x (M = Nd, Gd) is studied in the range 700–1000°C using X-ray powder diffraction, single-crystal X-ray diffraction (Rietveld technique), and IR spectroscopy. Single-phase solid solutions at 800°C are formed with x ≤ 0.35 for M(III) = Nd and x ≤ 0.3 for M(III) = Gd. With high x, the apatite solid solution coexists with Ca3(VO4)2, Nd2O3, and X phases. With increasing x in the homogeneous region, the intensity of the bands of stretching vibrations and librations of OH groups decrease. Single-crystal X-ray diffraction shows that neodymium and gadolinium substitute for calcium in solid solutions mostly in Ca(2) positions. 相似文献
10.
J.L.G. Fierro S. Mendioroz A.M. Olivan 《Journal of colloid and interface science》1984,100(2):303-310
Catalytically active forms of the rare earth oxides Ln2O3(Ln = La, Sm, Eu, Dy, Ho, and Yb), Pr6O11, and CeO2 have been prepared. The dehydration behavior of the precursors of these oxides has been studied by XRD, TG, DTA, TPD-MS, IR, and adsorption-desorption isotherms of N2 at −196°C. Thermal analyses show that in most cases the dehydration takes place through an intermediate oxyhydroxide LnO (OH) that decomposes to the respective oxide at around 400°C. Strongly held difficult to remove carbonates were present on the surface, e.g., for Yb2O3 it was necessary raise the outgassing temperature to 700°C to achieve carbonate decomposition. At temperatures around 500°C these oxides are well crystallized and have moderate specific surface areas (10–40 m2g−1). As a representative of the series, a detailed study of the dehydration and surface decarbonation of Yb2O3 was carried out by means of TPD-MS and infrared spectroscopy. 相似文献
11.
Chenmou Zheng Xinmin Zhang Shan He Qun Fu Deming Lei 《Journal of solid state chemistry》2003,170(2):221-226
V2O3 nanopowder with spherical particles was prepared by reducing pyrolysis of the precursor, (NH4)5[(VO)6(CO3)4(OH)9]·10H2O, in H2 atmosphere. The thermolysis process of the precursor in a H2 flow was investigated by thermogravimetric analysis and differential thermal analysis. The results indicate that pure V2O3 forms at 620°C and crystallizes at 730°C. The effects of various reductive pyrolysis conditions on compositions of V2O3 products were studied. Scanning electron micrographs show that the particles of the V2O3 powder obtained at 650°C for 1 h are spherical about 30 nm in size with more homogeneous distribution. Experiments show that nanopowder has larger adsorption capacity to gases and is more easily reoxidized by air at room temperature than micropowder. Differential scanning calorimetry experiment indicates that the temperature of phase transition of nano-V2O3 powder is −119.5°C on cooling or −99.2°C on heating. The transition heats are −12.55 J g−1 on cooling and 11.42 J g−1 on heating, respectively. 相似文献
12.
采用原位显微Raman光谱和18O同位素示踪技术,以325 nm激光为激发光源,对立方Nd2O3上过氧物种的光诱导生成过程进行了详细表征,进一步证实过氧源于分子氧对晶格氧的氧化反应. 结果还表明,325 nm激光在室温下即可诱导过氧的生成,在实验条件下,生成的过氧物种可与Nd2O3的晶格氧发生快速的氧交换反应,位于Nd2O3体相的晶格氧也可迁移至样品表层进而参与过氧的生成. 325 nm激光照射有助于促进晶格氧的迁移以及晶格氧与分子氧之间的氧交换反应. 相似文献
13.
Nik Akmar Rejab Mohamadariff Othman Wan Fahmin Faiz Wan Ahmad Mohd Fadzil Ain Zainal Arifin Ahmad 《Journal of Sol-Gel Science and Technology》2011,57(2):172-177
In this paper, we report the application of Neodymium (Nd) doped barium titanate thin films (Ba1-xNdx) TiO3 with x = 0 and 0.07 as dielectric resonator antenna. The films were prepared using the sol–gel method and dip-coating technique.
Barium acetate, titanium (IV) isopropoxide and neodymium (III) acetate hydrate were used as precursors while glacial acetic
acid and acetylacetone were used as solvents. Si wafers were used as a substrate with dipping times varying from 10, 30, and
50 s. The 0.07 films were >800 nm thick and crystallized after being annealed at 800°C for 30 min. The films were tested as
dielectric resonator antenna. It was found that, on the actual antenna circuit, the resonant frequency decreased as the (Ba0.93Nd0.07) TiO3 films thickness increased (from 0.8379, to 5.4525 μm). All samples resonate in the range of 8.68–8.83 GHz with quasi omni-directional
radiation patterns. 相似文献
14.
Marius Widerøe Truls Norby Rolf Willestofte Berg 《Journal of solid state chemistry》2011,184(7):1890-1894
A new metal oxyhydride; neodymium oxyhydride, NdHO, has been synthesized from a reactant mixture of metal hydride (CaH2 or NdH3) and neodymium oxide (Nd2O3). The unit cell dimensions decrease smoothly in the series from LaHO, CeHO, PrHO to NdHO, in line with the lanthanide contraction. The crystal structure of NdHO is described on the basis of Rietveld refinement on neutron powder diffraction data:
- Space group: P4/nmm (no. 129, D4h7).
- Axis lengths: a=7.8480(5) Å, c=5.5601(8) Å.
- Volume: V=342.46(6) Å3.
15.
New boracites containing nitrato- or fluoroanions that appear to be true low-pressure phases have been synthesized at superatmospheric pressures. The M3B7O13NO3 compounds (M = Co, Ni, Cu, Zn, Cd) transform rapidly and reversibly in the temperature region 300–500°C between probable orthorhombic and face centered cubic symmetry, while the M3B7O13F compounds (M = Mg, Mn, Fe, Co, Zn) appear to maintain rhombohedral symmetry up to their decomposition temperatures of 800–900°C. True high-pressure boracite-like phases containing F and Cr, Mn, Fe, or Co that decompose upon heating to M3B7O13F have also been isolated. 相似文献
16.
Yahong Xie Shu Yin Hisanori Yamane Takatoshi Hashimoto Tsugio Sato 《Solid State Sciences》2009,11(9):1703-1708
Nanopowder of a new tin(II) titanium(IV) oxide hydroxide fluoride, Sn1.24Ti1.94O3.66(OH)1.50F1.42 with the pyrochlore-type structure (cubic a = 10.3777(7) Å, space group Fd-3m) was prepared by using a microwave-assisted solvothermal reaction. The grain size of the nanopowder was 20–30 nm in diameter. Sn1.24Ti1.94O3.66(OH)1.50F1.42 decomposed above 300 °C, but could be sintered to relative density greater than 99% by a hydrothermal hot-pressing (HHP) method at 270 °C and 80 MPa for 4 h. The synthesized powder and solidified body obtained using HHP showed significantly different color, probably due to the difference in water content. 相似文献
17.
Tori Z. Forbes 《Journal of solid state chemistry》2010,183(11):2516-2521
Lanthanum tantalates are important refractory materials with application in photocatalysis, solid oxide fuel cells, and phosphors. Soft-chemical synthesis utilizing the Lindqvist ion, [Ta6O19]8−, has yielded a new phase, La2Ta2O7(OH)2. Using the hydrated phase as a starting material, a new lanthanum orthotantalate polymorph was formed by heating to 850 °C, which converts to a previously reported LaTaO4 polymorph at 1200 °C. The stabilities of La2Ta2O7(OH)2 (LaTa−OH), the intermediate LaTaO4 polymorph (LaTa-850), and the high temperature phase (LaTa-1200) were investigated using high-temperature oxide melt solution calorimetry. The enthalpy of formation from the oxides were calculated from the enthalpies of drop solution to be −87.1±9.6, −94.9±8.8, and −93.1±8.7 kJ/mol for LaTa−OH, LaTa-850, and LaTa-1200, respectively. These results indicate that the intermediate phase, LaTa-850, is the most stable. This pattern of energetics may be related to cation-cation repulsion of the tantalate cations. We also investigated possible LnTaO4 and Ln2Ta2O7(OH)2 analogues of Ln=Pr, Nd to examine the relationship between cation size and the resulting phases. 相似文献
18.
Nd3Si5AlON10 – Synthesis, Crystal Structure, and Properties of a Sialon Isotypic with La3Si6N11 Nd3Si5AlON10 was synthesized by the reaction of silicon diimide, aluminium nitride, aluminium oxide, and neodymium in a pure nitrogen atmosphere at 1650 °C using a radiofrequency furnace. The compound was obtained as a coarsely crystalline solid. According to the single‐crystal structure determination the title compound is isotypic with Ln3Si6N11 (Ln = La, Ce, Pr, Nd, Sm). Nd3Si5AlON10 (P4bm, a = 1007.8(1), c = 486.3(1) pm, Z = 2, R1 = 0.016, wR2 = 0.031) is built up by a three‐dimensional network structure of corner sharing SiON3 and (Si/Al)N4 tetrahedra (molar ratio Si : Al = 3 : 1). According to lattice energetic calculations using the MAPLE concept a differentiation of O and N seems to be reasonable. One of the two different sites for the tetrahedral centres is probably occupied by Si (distances: Si–O: 168.4(1), Si–N: 173.6(3)–176.0(4) pm) the second site by Si and Al with the molar ratio 3 : 1 (distances: (Si/Al)–N: 172.0(3)–176.6(2) pm). The Nd3+ ions are located in the voids of the (Si5AlON10)9– framework (distances: Nd–O: 261.07(8), Nd–N: 246.1(2)–286.6(2) pm). 相似文献
19.
On the Dimorphism of Nd3Cl[SiO4]2 On reacting NdCl3, Nd2O3, and SiO2 (molar ratio: 1 : 4 : 6) at 850 °C in evacuated silica tubes, pale violet, hydrolysis resistant neodymium(III) chloride ortho‐silicate Nd3Cl[SiO4]2 can be obtained within seven days. If equimolar amounts of NaCl are added as flux, rod‐ or platelet‐shaped, transparent single crystals of two modifications accumulate simultaneously. The one with the higher density (A‐Nd3Cl[SiO4]2) crystallizes monoclinically (C2/c, no. 15; a = 1416.6(1), b = 638.79(6), c = 872.21(9) pm, β = 98.403(7)°; Vm = 117.55 cm3/mol, Z = 4), whereas the one with the lower density (B‐Nd3Cl[SiO4]2) exhibits orthorhombic symmetry (Pnma, no. 62; a = 709.36(7), b = 1815.7(2), c = 631.48(6) pm; Vm = 122.45 cm3/mol, Z = 4). Two crystallographically independent Nd3+ cations exist in each of both crystal structures, which in the A type are surrounded by nine (1 Cl– + 8 O2–) and ten (2 Cl– + 8 O2–), whilst those in the B type by only two times eight (1 Cl– + 7 O2– and 2 Cl– + 6 O2–) anions, respectively. Thereby all oxygen atoms of both forms represent members of discrete ortho‐silicate tetrahedra ([SiO4]4–). Although both crystal structures are built of alternating anionic double layers {(Nd1)2[SiO4]2}2– and cationic single layers {(Nd2)Cl}2+, there is a higher cross‐linkage of the building units in the A‐type lattice, where the cations are coordinated by three and four tetrahedra edges of ortho‐silicate anions, compared to only two times two of them in the B type. From this an about 4% higher density of Nd3Cl[SiO4]2 results for the A‐type structure (Dx = 5.55 g/cm3) in comparison with B‐type Nd3Cl[SiO4]2 (Dx = 5.33 g/cm3). 相似文献
20.
Li4Ti5O12 nanoparticles were precipitated from ethylene glycol solution of titanium tetra isopropoxide (Ti(O-iPr)4) and Li2O2 by refluxing at 197 °C for 12 h. The obtained particles were filtered and dried at 100 °C for 12 h, and the dried powder samples were heated at 320, 500 and 800 °C for 3 h. The X-ray diffraction patterns of the obtained samples exhibited a good fit with the spinel phase. The field emission-SEM images of the dried powder sample and the samples heated at 320, 500 and 800 °C for 3 h showed a uniform spherical morphology with a particle size of 5, 8, 10 and 400 nm, respectively. According to the results of electrochemical testing, the dried powder sample and the samples heated at 320, 500, and 800 °C for 3 h showed initial capacities of 200, 310, 320, and 260 mA h/g, respectively, at a current density of 0.05 mA/cm2. Nanosized (6–8 nm) particles with good crystallinity were obtained by controlling the synthesis conditions. The sample heated at 500 °C for 3 h exhibited a high capacity and an excellent rate capability over 60 cycles. 相似文献