Thermodynamic studies on the systems M–Te–O (M = Nd,Sm)

The standard Gibbs energies of formation of Nd₂TeO₆ and M₆TeO₁₂ (where M = Nd, Sm) were determined from vapour pressure measurements. The vapour pressure of TeO₂(g) was measured by employing thermogravimetry-based transpiration technique. The temperature dependence of the vapour pressure of TeO₂(g) over the mixtures Nd₂TeO₆+Nd₆TeO₁₂, generated by the incongruent vapourisation reaction, 3Nd₂TeO₆(s) → Nd₆TeO₁₂(s)+2TeO₂(g)+O₂(g), was measured in the temperature range 1,408–1,495 K. Similarly, the vapour pressure of TeO₂(g) over the mixtures M₆TeO₁₂+M₂O₃ (where M = Nd, Sm), generated by the incongruent vapourisation reaction, M₆TeO₁₂(s) → 3M₂O₃(s)+TeO₂(g)+½O₂(g), was measured in the temperature range 1,703–1,773 and 1,633–1,753 K for Nd₆TeO₁₂(s) and Sm₆TeO₁₂(s), respectively. Enthalpy increments of M₂TeO₆(s) (where M = Nd, Sm) were determined by inverse drop calorimetric method in the temperature range 573–1,273 K. The thermodynamic functions, viz., heat capacity, entropy and free energy functions, were derived from the measured values of enthalpy increments. A mean value of ?2,426.2 ± 0.6 and ?2,417.9 ± 1.1 kJ mol^?1 was obtained for $ \Updelta_{\text{f} } H_{298}^{\text{o}} $ (Nd₂TeO₆, s) and $ \Updelta_{\text{f}} H_{298}^{\text{o}} $ (Sm₂TeO₆, s), respectively, by combining the value of $ \Updelta_{\text{f}} G^{\text{o}} $ (Nd₂TeO₆, s) and $ \Updelta_{\text{f}} G^{\text{o}} $ (Sm₂TeO₆, s) derived from vapour pressure data and the free energy functions derived from the drop calorimetric data.     

Recent progress in nanocrystalline Sm–Co based magnets

Sm–Co alloys are the most promising candidates for high temperature applications in advanced power systems owing to their high Curie temperature and high thermal stability of the magnetic performance. The recently developed nanocrystalline Sm–Co based magnets exhibit great potentials for magnetic performance enhancement and are expected to enlarge applications to services under extreme conditions. However, there have been few comprehensive reviews on the development of the nanocrystalline Sm–Co magnets so far. The efforts in this article are paid to review the recent progress in both experimental and modeling studies on the nanocrystalline Sm–Co magnets. Particularly, the latest advances in nanostructuring technologies, doping modulation, data-driven composition design and strategies for enhancement of magnetic properties have been introduced and evaluated. Finally, new challenges and opportunities regarding the future development of high-performance nanocrystalline Sm–Co based magnets are proposed.     

Enthalpies of formation of SmCo alloys in the composition range 10–22 at. % Sm

Several intermetallic compounds exist in the composition range 10–22 at.% Sm(Sm₂Co₁₇, SmCo₅, Sm₂Co₇) but their preparation as single-phase specimens is very difficult. In order to determine the enthalpies of formation of these compounds, measurements were carried out on four alloys containing respectively 12.9 at.% Sm, 16.4 at.% Sm, 17 at.% Sm and 19.8 at.% Sm, annealed in the temperature range 950–1100 °C. The compositions of the phases present in each specimen were deduced from the characterization of the measured alloys by scanning electron microscopy, electron microanalysis and X-ray diffraction.The heats of formation were deduced from solution calorimetry in molten tin. The variation of the experimental results as a function of the samarium content enabled the enthalpy of formation of SmCo₅ ( − 40.8 kJ mol⁻¹) to be determined. The same ΔH_f value as determined for the phase quenched from 950 °C was measured for SmCo₅ kept at room temperature after very slow cooling. This result did not confirm the eutectoid decomposition previously reported for SmCo₅.The extrapolation of the measured values for the higher and lower samarium contents leads to the evaluation of the enthalpies of formation of Sm₂Co₁₇ (−152 kJ mol⁻¹) and Sm₂Co₇ (−99kJ mol⁻¹).     

Ternary Germanides RE 2Ge2Mg (REY, La–Nd, Sm, Gd, Tb)

Summary. The ternary rare earth metal-magnesium-germanides RE₂Ge₂Mg (RE=Y, La–Nd, Sm, Gd, Tb) were synthesized by reaction of the elements in sealed tantalum tubes in a water-cooled sample chamber of an induction furnace. The germanides were characterized through their X-ray powder patterns. The structures of Ce₂Ge₂Mg and Pr₂Ge₂Mg were refined from X-ray single crystal diffractometer data: Mo₂FeB₂ type, P4/mbm, a=750.6(1), c=442.4(1)pm, wR2=0.0378, 386 F² values, 12 variable parameters for Ce₂Ge₂Mg, and a=745.7(1), c=439.2(1)pm, wR2=0.0462, 448 F² values, 12 variable parameters for Pr₂Ge₂Mg. The lanthanum compound shows a homogeneity range La_2+xGe₂Mg_1–x. The structure of a single crystal with x=0.249(5) was refined from X-ray data: a=770.52(7), c=447.4(1)pm, wR2=0.0481, 322 F² values, 13 variable parameters. The RE₂Ge₂Mg structures can be considered as a 1:1 intergrowth of CsCl and AlB₂ related slabs of compositions REMg and REGe₂.     

Effect of cooling rate and Al content on solidification behavior and microstructure evolution of as-cast Mg–Al–Ca–Sm alloys

Journal of Thermal Analysis and Calorimetry - In the present study, the Mg–xAl–2Ca–2Sm (x = 3, 5, 9 and 15) alloys were fabricated in sand mold with stepped type, and...     

Preparation and thermal analysis kinetics of the core–nanoshell composite materials doped with Sm

The core–nanoshell composite materials with magnetic fly-ash hollow cenosphere as core and nano SmFeO₃ as shell were synthesized by high-energy ball milling method. The magnetic fly-ash hollow cenosphere, samarium nitrate, and iron nitrate were used as raw materials. The synthesis and growth kinetics of the composite materials were investigated using the thermogravimetry and differential thermal analysis (TG–DTA) at different heating rates. The results show that the precursor of the composite materials decomposes in three steps. The apparent activation energy of each stage was calculated using the Doyle–Ozawa and Kissinger methods. The reaction order, frequency factor, and rate equations were also determined. The activation energy of the nano crystallite growth is calculated to be 16.12 kJ mol^?1 according to kinetics theory of nano crystallite growth. It can be inferred that the crystallite grows primarily by means of an interfacial reaction during the thermal treatment. The magnetic properties and microwave absorbing properties of samples were analyzed by the vibrating sample magnetometer analysis and vector network analyzer. The results indicated that the exchange coupling interaction happens between ferrite of magnetic fly-ash hollow cenosphere and nanosized ferrite coating, which cause outstanding magnetic properties. In the frequency between 1 MHz and 1 GHz, the absorbing effectiveness of the composite absorbers can achieve ?32 dB. The magnetic properties of the composite material are better than those of single phase. So it is consistent with requirements of the microwave absorbing material at the low-frequency absorption.     

Hydrothermal Synthesis,Crystal Structures,and Fluorescence Properties of Ni(II)–Ln(III) Complexes (Ln = Sm,Pr, Eu)

Three novel 3d–4f heterometal complexes [Ln(NiL)₃(Btca)(NO₃)] · xH₂O (Ln = Sm(III) (I), Pr(III) (II), Eu(III) (III) (H₂L = 2,3-dioxo-5,6,14,15-dibenzo-1,4,8,12-tetraazacyclo-pentadeca-7,13-dien, H₂Btca = benzotriazole-5-carboxylic acid) were solvothermally synthesized and characterized by singlecrystal X-ray diffraction (CIF files CCDC nos. 1555557 (I), 1555555 (II), 1555556 (III)). They crystallized in the monoclinic space group P2₁/n for I (x = 1.5) and C2/c for (II) and (III) (x = 1), respectively. In these complexes, the central Ln(III) and external nickel ions are bridged by macrocyclic oxamide groups. The metal center of Ln(III) resides in a distorted bicapped square antiprism surrounding with six oxygen atoms of three oxamide groups, two oxygen atoms of Btca^2– ion and two oxygen atoms of NO₃^-. Furthermore, there are C–H···O and/or C–H···N hydrogen bond interactions among nitrate, benzotriazole-5-carboxylate, macrocyclic oxamide and water to form three-dimensional superamolecular architecture. The fluorescence properties of the compounds I and II are also discussed.     

Enantiospecific Synthesis of (–)-Cuspareine and (–)-Galipinine

An enantiospecific route to the synthesis of tetrahydroquinoline alkaloids (–)-cuspareine and (–)-galipinine is reported. Coupling of an iodide derivative of D-serine with aromatic dithianes and Pd-catalyzed intramolecular C–N coupling are the key steps in the synthesis.     

三元体系Sm(NO~3)~3-ACAP-H~2O相平衡研究及Sm(ACAP)~2(NO~3)~3的合成和表征

在30℃时采用等温溶度法研究了三元体系Sm(NO~3)~ 3- ACAP- H~ 2OACAP, 4-acetylantipyrine,4-乙铣基安替比林)的相平衡,绘制了体系的溶度图及饱和溶液的折光率一组成图,发现并制备了未见文献报道的同成分溶解的化合物Sm(ACAP)~2(NO~3)~3,通过化学分析,元素分析,摩尔电导(DMF),IR和TG-DTG 对其进行了物理化学性质表征,初步探讨了阴离子对ACAP与稀土相互作用的影响.     

SmⅠ_2和SmⅠ_3的合成和性质

SmI_2和SmI_3虽早已合成,但因它们的化学性质不够稳定,所以它们的物化性质如熔点、Sml_2的结构等研究的很少,现有的数据互不吻合。SmI_2的水合物也未见有研究报道。本工作利用DTA、TG、X射线粉末法及化学分析(重量法)研究了Sm与HgI_2的反应过程,确定了该体     

三元体系Sm(NO~3)~3-ACAP-H~2O相平衡研究及Sm(ACAP)~2(NO~3)~3的合成和表征

在30℃时采用等温溶度法研究了三元体系Sm(NO_3)_3-ACAP-H_2O(ACAP,4-acetylan-tipyrine,4-乙酰基安替比林)的相平衡,绘制了体系的溶度图及饱和溶液的折光率一组成图.发现并制备了未见文献报道的同成分溶解的化合物Sm(ACAP)_2(NO_3)_3.通过化学分析、元素分析、摩尔电导(DMF),IR和TG-DTG对其进行了物理化学性质表征.初步探讨了阴离子对ACAP与稀土相互作用的影响.     

Thermal analysis of W-free Co–(Ni)–Al–Mo–Nb superalloys

CuAl layered double hydroxide (CuAl-LDH) was synthesized by co-precipitation. Sodium phenyl phosphate (SPP) and sodium dodecyl sulfate (SDS) are used to modify CuAl-LDH for preparing CuAl-(SPP)LDH and CuAl-(SDS)LDH, which were incorporated into epoxy resin (EP) to obtain EP/CuAl-(SPP)LDH and EP/CuAl-(SPP)LDH nanocomposites. The results indicate that SPP and SDS are intercalated into the interlayers of CuAl-LDH, and CuAl-(SPP)LDH has larger layer spacing than CuAl-(SDS)LDH. The thermal stability and flame-retardant performances of EP/CuAl-(SPP)LDH nanocomposites were better than those of EP/CuAl-(SDS)LDH composites. Compared with those of EP/4CuAl-(SDS)LDH nanocomposites, the peak heat release rate (PHRR) of EP/4CuAl-(SPP)LDH nanocomposites is reduced 25.8% and 55.6%, and peak smoke production rate (PSPR) value of EP/4CuAl-(SPP)LDH nanocomposites is reduced 27.6% and 46.2%, value of EP/4CuAl-(SPP)LDH nanocomposites is reduced 27.6% and 46.2%, respectively. The improved flame retardancy and smoke suppression performances of EP/CuAl-(SPP)LDH nanocomposites were attributed to the combination of copper compounds and SPP, promoting the formation of swollen, continuous and compact char layers on the surface of EP nanocomposites during combustion, eventually restraining the decomposition of EP nanocomposites.

     

Pyrolysis kinetics of ethylene–propylene (EPM) and ethylene–propylene–diene (EPDM)

The thermal degradation kinetics of several ethylene–propylene copolymers (EPM) and ethylene–propylene–diene terpolymers (EPDM), with different chemical compositions, have been studied by means of the combined kinetic analysis. Until now, attempts to establish the kinetic model for the process have been unsuccessful and previous reports suggest that a model other than a conventional nth order might be responsible. Here, a random scission kinetic model, based on the breakage and evaporation of cleavaged fragments, is found to describe the degradation of all compositions studied. The suitability of the kinetic parameters resulting from the analysis has been asserted by successfully reconstructing the experimental curves. Additionally, it has been shown that the activation energy for the pyrolysis of the EPM copolymers decreases by increasing the propylene content. An explanation for this behavior is given. A low dependence of the EPDM chemical composition on the activation energy for the pyrolysis has been reported, although the thermal stability is influenced by the composition of the diene used.     

Determination of the stability constants of Pb–(DIPSO)x–(OH)y and Pb–(AMPSO)x–(OH)y systems

In this work, complexation between lead ion and the ligands 3-[N,N-bis(2-hydroxyethyl)amino]-2-hydroxypropanesulfonic acid (DIPSO) and N-(1,1-dimethyl-2-hydroxyethyl)-3-amino-2-hydroxypropanesulfonic acid (AMPSO), which are commercial pH buffers, is presented. Both ligands form complexes with lead in their pH buffer range (between pH 6.5 and 8.5 for DIPSO and between pH 8.0 and 9.0 for AMPSO). The final models and the overall stability constants, which are reported here, were determined by direct current polarography and glass electrode potentiometry [only for the Pb–(DIPSO)_x–(OH)_y system] at 25.0 °C and 0.1 M KNO₃ ionic strength. For the Pb–(DIPSO)_x–(OH)_y system, the proposed final model contains PbL, PbL₂, PbL₂(OH), and PbL₂(OH)₂ with stability constants, as log β, of 3.4 ± 0.1, 6.35 ± 0.15, 12.8 ± 0.2, and 18.0 ± 0.3, respectively. For the Pb–(AMPSO)_x–(OH)_y system, the species observed are PbL, PbL(OH), and PbL(OH)₂ with stability constants, as log β, of 2.9 ± 0.5, 9.4 ± 0.1, and 14.5 ± 0.2, respectively. For AMPSO, the possible adsorption of the ligand at the mercury electrode surface was evaluated by alternating current polarography through calculation of the capacitance of the double layer.     

Syntheses and Crystal Structures of Sm(OAr)2(THF)3·THF and Sm(OAr)2(DME)2 (Ar = C6H2-tert-Bu3-2,4,6)

Reaction of SmI2(THF)x with 2 equivalents of NaOAr (Ar = C6H2-tert-Bu3-2,4,6)1,2-dimethoxyethane (DME) leads to the ligand-exchange reaction, and a DME-solvated complex of Sm(Oar)2(DME)2 2 was obtained. Complex 1 crystallizes in monoclinic, space group P21/c with a =10.366(5), b = 33.024(15), c = 16.123(7) (A), β= 93.197(8)°, V= 5511(4) A3, Z= 4, C52H9oO6Sm, Mr = 961.59, Dc = 1.159 g/cm3, F(000) = 2048,μ(MoKα) = 1.107 mm-1, R = 0.0844 and wR = 0.1401for 4694 observed reflections. Complex 2 crystallizes in monoclinic, space group C2/c with a =27.222(5), b = 10.6140(19), c = 17.398(4) (A), β = 110.245(3)°, V = 4716.4(16) (A)3, Z = 4,C44H78O6Sm, Mr = 853.41, Dc = 1.202 g/cm3, F(000) = 1808,μ(MoKα) = 1.285 mm-1, R = 0.0361and wR = 0.0830 for 5210 observed reflections.     

高氯酸稀土Sm(Ⅲ)开环冠醚(EO4)配合物的晶体结构

The crystal of title compounds belongs to orthorhombic system with space group P2₁2₁2₁ (No.19). The cell parmeters are a=1.432 16(3) nm, b=1.457 20(3) nm， c=3.005 85(6) nm, and V=6 273.0(2) nm³, Z=8, μ(Mo Kα)=22.21 cm^-1， D_c=1.802 g·cm^-3, F(000)=3 416.00, Finally R₁=0.033 and wR₂=0.073 (I>2.00σ(I)), S=1.023. Every center atom Sm(Ⅲ) is surrounded by the two aether chains, the title compound has ten-coordinate structure and the coordination polyhedron shows a Bicapped Square Antiprism. In the crystal, the title compound has the flack of double moleculars and non-symmetry. The anion ClO₄^- does not take part in the coordination. CCDC: 238709.     

Asymmetric synthesis of (–)-leiocarpin A via (–)-(S)-goniothalamin employing Julia–Kocienski olefination

A concise and enantioselective syntheses of antileukemic natural products such as (–)-(S)-goniothalamin and (–)-leiocarpin A has been accomplished in excellent yields. By employing reported conditions on suitable substrates via Julia–Kocienski olefination, intramolecular lactonization, and subsequently dehydroxylative olefination, (–)-(S)-goniothalamin was synthesized. Then Sharpless asymmetric dihydroxylation–intramolecular Michael addition on (–)-(S)-goniothalamin provided (–)-leiocarpin A.     

Synthesis and Crystal Structure of a Novel 1D Chain-like Organic Inorganic Hybrid Rare Earth Derivative of Polyoxometalate: H_(0.5)[Sm(H_2O)_6]_(0.25)[Sm(H_2O)_5]_(0.25){[Sm(H_2O)_7][Sm(H_2O)_2-(DMSO)][SiW_(11)O_(39)]}·4.5H_2O

Polyoxometalates may be versatile inorganic building blocks for the construction of molecular-based materials. By means of their multiple coordination requirements and oxophilicity, lanthanide cations are suitable to link polyoxometalate building blocks to form new classes of materials with potentially useful magnetic and luminescent properties1-4. Peacock and Weakley studied the interactions between the [α-SiW11 O39]8? isomer and lanthanide cations5, and they reported that the [α-SiW11O39…