纳米级PbCO3的制备与应用

PbCO3作为燃烧催化剂被广泛应用于推进剂中,但目前推进剂中使用的PbCO3颗粒尺寸大、粒度分布不均匀,严重地影响了固体推进剂的燃烧性能[1~3]。纳米粒子因其尺寸小,比表面积大,且随着粒径减小,比表面积急剧变大,活性中心数迅速增加,大大增强了纳米粒子的催化活性,使得各种纳米级     

H2O + Fe(NO3)3 + Ni(NO3)2 ternary system isotherms at 0 °C and 30 °C

H₂O + Ni(NO₃)₂ binary system were investigated in the temperature range from −25 °C to 55 °C. The solid-liquid equilibria of the ternary system H₂O + Fe(NO₃)₃ + Ni(NO₃)₂ were studied using a synthetic method based on conductivity measurements. Tow isotherms were established at 0 °C and 30 °C, and the appearing stable solid phases are iron nitrate nonahydrate (Fe(NO₃)₃·9H₂O), iron nitrate hexahydrate (Fe(NO₃)₃·6H₂O), nickel nitrate hexahydrate (Ni(NO₃)₂·6H₂O) and nickel nitrate tetrahydrate (Ni(NO₃)₂·4H₂O).     

Diagramme polythermique du systeme ternaire H2O—Al(NO3)3—Mg(NO3)2

The solid—liquid equilibria of the ternary system H₂O—Al(NO₃)₃—Mg(NO₃)₂ were studied at –30, –20, –10 and 0°C by using a synthetic method which allows to detemine all the characteristic points of isothermal sections. The stable solid phases which appear are respectively: ice, Al(NO₃)₃·9H₂O, Mg(NO₃)₂·9H₂O and Mg(NO₃)₂·6H₂O. Neither double salts nor mixed crystals are observed in the temperature and composition field studied. Polytherm diagram layout show two invariant transformations correspond with an eutectic point and a peritectic point.This revised version was published online in November 2005 with corrections to the Cover Date.     

Dinuclear tetrapyridyl pendant-armed azamacrocyclic complexes of Co(II), Ni(II), Cu(II) and Cd(II)

The coordination capability of the new tetrapyridyl pendant-armed azamacrocyclic ligand L, towards Co(II), Ni(II), Cu(II) and Cd(II) ions was studied. The ligand and the complexes were characterized by microanalysis, LSI mass spectrometry, IR, UV-Vis and NMR spectroscopy, magnetic studies and conductivity measurements. Crystal structures of [Co₂L(CH₃CN)₂](ClO₄)₄·2CH₃CN and [Cd₂L(NO₃)₂](NO₃)₂·2H₂O complexes have been determined. The X-ray studies show the presence of dinuclear endomacrocyclic complexes with the metal ion in a similar distorted octahedral environment, coordinated by one pyridyl bridgehead group, two amine nitrogen atoms and two pyridyl pendant-arms. The sixth coordination position around the metal ion is completed by one acetonitrile molecule in [Co₂L(CH₃CN)₂](ClO₄)₄·2CH₃CN and by one monodentate nitrate anion in [Cd₂L(NO₃)₂](NO₃)₂·2H₂O. Different sort of intramolecular non-classical hydrogen bonds were found in the crystal lattice of both structures.     

Synthesis of MnOOH nanorods by cluster growth route from [Mn12O12(RCOO)16(H2O)n] (R=CH3, C2H5). Rational conversion of MnOOH into Mn3O4 or MnO2 Nanorods

Single-crystalline nanorods of γ-MnOOH (manganite) phase with diameters of 120 nm and lengths of 1100 nm have been prepared using a new cluster growth route under low-temperature hydrothermal conditions starting from [Mn₁₂O₁₂(CH₃COO)₁₆(H₂O)₄]·2CH₃COOH·4H₂O or [Mn₁₂O₁₂(C₂H₅COO)₁₆(H₂O)₃]·4H₂O without any catalyst or template agents. The so-obtained nanorods were studied by X-ray diffraction (XRD), infrared (IR) spectroscopy, Raman spectroscopy and high resolution transmission electron microscopy (HRTEM). Their thermal conversion opens an access to Mn₃O₄ (hausmannite) and β-MnO₂ (pyrolusite) nanorods, respectively, under argon or air atmosphere. A coercive field of 12.4 kOe was obtained for the Mn₃O₄ nanorods.     

The thermal decomposition of some Cr(III) complexes

The thermal decomposition reactions of the following chromium(III) complexes were investigated: Cr(CH₃COO)₃·2 H₂O, [C_r3O(CH₃COO)₆(H₂O)₃]Cl·2 H₂O and [Cr₃O(CH₂ClCOO)₆(H₂O)₃]Cl·6H₂O. Simultaneous TG/DTG/DTA were applied nonisothermal conditions. From the recorded curves, the activation energiesE _a were calculated for all the thermal decomposition steps. Appropriate chemical reactions were attributed to the thermal effects, with consideration to the X-ray diffraction and IR spectra results.

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Zusammenfassung Für die Untersuchung der thermischen Zersetzungsreaktion der Chrom(III)-Komplexe Cr(CH₃COO)₃·2H₂O [C_r3O(CH₃COO)₆·(H₂O)₃]Cl2H₂O und [C_r3O(CH₂ClCOO)₆·(H₂O)₃]C₁₆H₂O wurde simultane TG/DTG/DTA unter nichtisothermen Bedingungen eingesetzt. Ausgehend von den aufgezeichneten Kurven wurden für alle Schritte der Zersetzungsreaktion die E_a-Werte berechnet. In Übereinstimmung mit röntgenographischen und IR-spektroskopischen Ergebnissen wurden den thermischen Effekten passende chemische Reaktionen zugeordnet.

     

Gamma-ray induced decomposition of some divalent and trivalent nitrates

Gamma-ray induced decomposition of some divalent nitrates, viz. Mg(NO₃)₂·6H₂O, Ca(NO₃)₂·4H₂O, Sr(NO₃)₂, Ba(NO₃)₂, Zn(NO₃)₂·6H₂O, Cd(NO₃)₂·4H₂O, Hg(NO₃)₂·2H₂O, Mn(NO₃)₂·4H₂O, Cu(NO₃)₂·3H₂O and trivalent nitrates, viz. Al(NO₃)₃·9H₂O, Fe(NO₃)₃·9H₂O, Cr(NO₃)₃·9H₂O, Y(NO₃)₃·6H₂O, In(NO₃)₃·3H₂O, La(NO₃)₃·6H₂O, Ce(NO₃)₃·6H₂O, Pr(NO₃)₃·6H₂O, Bi(NO₃)₃·5H₂O has been studied in solid state at room temperature. G(NO ₂ ^– ) values (after applying appropriate dose correction) have been found to vary in the range 0.12–3.16 and 0.069–2.15 for divalent and trivalent nitrates respectively. G'-values were calculated by dividing G by the ratio of number of electrons in nitrate ion to the total number of electrons in the nitrate salt. Cation size, its polarizing power, available free space in the crystal lattice and the number and location of water molecules seem to play a dominant role in radiolytic decomposition. For Zn, Sr, In, La and Ce nitrates dose variation studies have been carried out.     

Etude de l’isotherme 25°C du système quasi quaternaire H2O-Zn(NO3)2·6H2O-Cu(NO3)2·3H2O-NH4NO3;I- Isoplèthes 4 masse% NH4NO3, 8 ma

The solid-liquid equilibria of the quasi-quaternary system H₂O-Zn(NO₃)₂·6H₂O-Cu(NO₃)₂·3H₂O-NH₄NO₃ were studied at 25°C by using a synthetic method based on conductivity measurements. Three isoplethic sections has been established at 25°C and the stable solid phases which appear are: NH₄NO₃(IV), Zn(NO₃)₂·6H₂O, anhydrous Cu(NO₃)₂, Cu(NO₃)₂·3H₂O and metastable Cu(NO₃)·2.5H₂O. Neither double salts, nor mixed crystals are observed at these temperatures and composition range.     

Cu(II) and Pd(II) complexes of N-(2-hydroxybenzyl)aminopyridines

N-(2-Hydroxybenzyl)aminopyridines (Lⁱ) react with Cu(II) and Pd(II) ions to form complexes in the compositions Cu(Lⁱ)₂(CH₃COO)₂ · nH₂O (n = 0, 2, 4), Pd(Lⁱ)₂Cl₂ · nC₂H₅OH (n = 0, 2) and Pd(L²)₂Cl₂ · 2H₂O. In the complexes, the ligands are neutral and monodentate which coordinate through pyridinic nitrogen. Crystal data of the complexes obtained from 2-amino pyridine derivative have pointed such a coordinating route and comparison of the spectral data suggests the validity of similar complexation modes of other analog ligands. Cu(II) complex of N-(2-hydroxybenzyl)-2-aminopyridine (L¹), [Cu(L¹)₂(CH₃COO)₂] has slightly distorted square planar cis-mononuclear structure which is built by two oxygen atoms of two monodentate carboxylic groups disposed in cis-position and two nitrogen atoms of two pyridine rings. The remaining two oxygen atoms of two carboxylic groups form two Cu and H bridges containing cycles which joint at same four coordinated copper(II) ion. IR and electronic spectral data and the magnetic moments as well as the thermogravimetric analyses also specify on mononuclear octahedric structure of complexes [Cu(L²)₂(CH₃COO)₂ · 2H₂O] and [Cu(L³)₂(CH₃COO)₂ · 4H₂O] where L² and L³ are N-(2-hydroxybenzyl)-2- or 3-aminopyridines, respectively.     

Calorimetric study and thermal analysis of [Gd4/3Y2/3(Gly)6(H2O)4](ClO4)6·5H2O and [ErY(Gly)6(H2O)4](ClO4)6·5H2O (Gly: glycin)

Two solid-state coordination compounds of rare earth metals with glycin, [Gd_4/3Y_2/3(Gly)₆(H₂O)₄](ClO₄)₆·5H₂O and [ErY(Gly)₆(H₂O)₄](ClO₄)₆·5H₂O were synthesized. The low-temperature heat capacities of the two coordination compounds were measured with an adiabatic calorimeter over the temperature range from 78 to 376 K. [Gd_4/3Y_2/3(Gly)₆(H₂O)₄](ClO₄)₆·5H₂O melted at 342.90 K, while [ErY(Gly)₆(H₂O)₄](ClO₄)₆·5H₂O melted at 328.79 K. The molar enthalpy and entropy of fusion for the two coordination compounds were determined to be 18.48 kJ mol⁻¹ and 53.9 J K⁻¹ mol⁻¹ for [Gd_4/3Y_2/3(Gly)₆(H₂O)₄](ClO₄)₆·5H₂O, 1.82 kJ mol⁻¹ and 5.5 J K⁻¹ mol⁻¹ for [ErY(Gly)₆(H₂O)₄](ClO₄)₆·5H₂O, respectively. Thermal decompositions of the two coordination compounds were studied through the thermogravimetry (TG). Possible mechanisms of the decompositions are discussed.     

Preparation and Optical Properties of Gold-Dispersed BaTiO3, PGO (Pb5Ge3O11) and PLT (Pb1-1.5xLaxTiO3) Thin Films by Sol-Gel Process

Gold-dispersed BaTiO₃, PGO and PLT thin films, which will be used for third-order nonlinear optical devices, were prepared by sol-gel process with spin-coating using HAuCl₄4H₂O, Ba(CH₃COO)₂, Ti[O(CH₂)₃CH₃]₄, Pb(CH₃COO)₂3H₂O, Ge[O-n-C₄H₉]₄, La(CH₃COO)₃1.5 H₂O as starting materials. The thin films were heat-treated in air at temperatures ranging from 400 to 800 for 1 h. The nonlinear optical property of these thin films was measured by the degenerate four-wave mixing (DFWM) method using a frequency-doubled Nd: YAG laser with 20 ps pulse duration. Third-order nonlinear susceptibility χ⁽³⁾ of gold-dispersed BaTiO₃, PGO and PLT thin films with 5 vol% of gold were 1.410⁻⁶ esu, 3.510⁻⁷ esu respectively. The large χ⁽³⁾ may be ascribed to the high dielectric constant of the films.     

New Cooling Mixtures Containing Sodium Acetate Trihydrate

Binary cooling mixtures consisting of CH₃COONa·3H₂O and NH₄NO₃, Al(NO₃)₃·9H₂O, or Ni(NO₃)₂·6H₂O were developed. They allow the initial temperature to be decreased by 18-19°C. Application of the mixtures does not require additional consumption of water.     

Studies on synthesis, characterization and thermochemistry of Mg2[B2O4(OH)2]·H2O

A new magnesium borate Mg₂[B₂O₄(OH)₂]·H₂O has been synthesized by the method of phase transformation of double salt at hydrothermal condition and characterized by XRD, IR, TG and DSC. The enthalpy of solution of Mg₂[B₂O₄(OH)₂]·H₂O in 0.9764 mol L^–1 HCl was determined. With the incorporation of the enthalpies of solution of H₃BO₃ in HCl (aq), of MgO in (HCl+H₃BO₃) (aq), and the standard molar enthalpies of formation of MgO(s), H₃BO₃(s), and H₂O(l), the standard molar enthalpy of formation of –(3185.78±1.91) kJ mol^–1 of Mg₂[B₂O₄(OH)₂]·H₂O was obtained.This revised version was published online in November 2005 with corrections to the Cover Date.     

Role of inorganic and organic anions in the formation of metallosupramolecular assemblies of silver(I) coordination polymers with the twisted ligand bis(4-pyridylthio)methane

Reaction of the twisted pyridyl dithioether ligand bis(4-pyridylthio)methane (4bpytm) with silver(I) salts afforded four complexes with 1:1 stoichiometries, namely [Ag(4bpytm)](NO₃) (1), [Ag(4bpytm)](ClO₄) (2) and [Ag(4bpytm)](ClO₄) ½CH₂Cl₂ ½dmf (2·Solv), [Ag(CH₃COO)(4bpytm)]·H₂O (3) and [Ag(CF₃COO)(4bpytm)] (4). X-ray structural analysis of these complexes showed that one-dimensional structures are obtained for 1, 2·Solv and 4 whereas a two-dimensional network is formed in 3. The ligand 4bpytm acts as an N,N′-bis(monodentate) bridging system in all cases except in 3, where an unprecedented coordination mode is obtained with the ligand acting in a tridentate manner using its two pyridine nitrogen atoms and a sulfur atom. The coordination polymers are assembled through secondary contacts: Ag···Ag in 4, Ag···S in 1, 2·Solv and 4, Ag···O in 2·Solv, and hydrogen bonding interactions between crystallization water that join the polymeric layers in 3. All of these weak interactions link the low-dimensional complexes to give high-dimensional supramolecular structures and further stabilize the crystal structures in the solid state.     

Efficient one-pot synthesis of 2,3-dihydroquinazolin-4(1H)-ones from aromatic aldehydes and their one-pot oxidation to quinazolin-4(3H)-ones catalyzed by Bi(NO3)3·5H2O: Investigating the role of the catalyst

An efficient and novel synthesis of 2,3-disubstituted 2,3-dihydroquinazolin-4(1H)-ones via one-pot, three-component reaction of isatoic anhydride, primary amines and aromatic aldehydes catalyzed by Bi(NO₃)₃·5H₂O under solvent-free conditions is described. Oxidation of these 2,3-dihydroquinazolin-4(1H)-ones to their quinazolin-4(3H)-ones was also successfully performed in the presence of Bi(NO₃)₃·5H₂O. This new method has the advantages of convenient manipulation, short reaction times, excellent yields, very easy work-up, and the use of commercially available, low cost and relatively non-toxic catalyst. The role of Bi(NO₃)₃·5H₂O was also investigated in these transformations.     

Anion effect on the construction of copper(II) coordination polymers with the twisted ligand bis(4-pyridylthio)methane

The reaction of CuSO₄ · H₂O with 4-bpytm [4-bpytm = bis(4-pyridylthio)methane] in EtOH afforded the complex [Cu(SO₄)(4-bpytm)(H₂O)₃] · H₂O (1 · H₂O) while the reaction of 4-bpytm with Cu(NO₃)₂ · 3H₂O in EtOH afforded the complex [Cu(NO₃)₂(4-bpytm)₂] · H₂O (2 · H₂O). The reaction of 4-bpytm with Cu(NO₃)₂ · 3H₂O in EtOH/dmf under microwave irradiation afforded the pseudo-polymorph [Cu(NO₃)₂(4-bpytm)₂] · Solv (2 · Solv). Compound 1 · H₂O forms helical chains while compounds 2 · H₂O and 2 · Solv are 2D coordination polymers with a (4,4) topology based on rhombic grids in 2 · H₂O and on a parquet motif in 2 · Solv. The 3D supramolecular organization through hydrogen bonding is analyzed for the three compounds and their thermal behaviour was also investigated.     

Self assembly of asymmetric tetranuclear Cu(II) [2 × 2] grid-like complexes and of a dinuclear Ni(II) complex from pyridyl-phenol Schiff base ligands

Self assembly of N-salicylidene 2-aminopyridine (L1H) with Cu(NO₃)₂·3H₂O affords [Cu₄(L1)₄(NO₃)₃(CH₃OH)][Cu(L1)(NO₃)₂](2-aminopyridinium)(NO₃)·5CH₃OH (1) which is composed of an asymmetric [2 × 2] grid-like cationic complex that co-crystallizes with a Cu(II) mononuclear anion. This remarkable tetranuclear unit presents three penta-coordinated and one hexa-coordinated Cu(II) sites. This quadruple helicate structure reveals strong anti-ferromagnetic coupling (J = −340(2) cm⁻¹) between Cu(II) ions through a double alkoxo bridge. Reacting L1H with Cu(NO₃)₂·3H₂O in slightly different conditions affords however a more symmetric tetranuclear grid-like complex: [Cu₄(L1)₄(NO₃)₂(OH)₂](2-aminopyridinium)(OH)·CH₃OH) (2). A dinuclear Ni(II) complex, [Ni₂(L2)₂(L2H)₂(NCS)₂(CH₃OH)₂]·2CH₃OH (3), obtained with another related donor ligand (L2H = N-salicylidene 3-aminomethylpyridine) was also prepared.     

Low-Density Forsterite (Mg2SiO4) Powders Prepared from Modified Alkoxides

2MgO-SiO₂ low-density powders have been prepared from alkoxide precursors modified with acetic anhydride. The resultant solutions did not gel, but formed precipitates. These consisted of an organic magnesium compound and amorphous silica. Tapping densities comparable with those of forsterite aerogels were obtained, with the density increasing as the precursor solution concentration increased. Crystalline forsterite formed around 790°C. Higher initial solution concentrations led to greater amounts of MgO in the powders after heating to 1000°C. Transmission electron microscopy showed primary particles between 20 and 30 nm which formed loose fractal agglomerates. By altering the preparation conditions, powders with morphologies more like aerogels than xerogels could be produced.     

Thermal decomposition of cobalt nitrato compounds: Preparation of anhydrous cobalt(II)nitrate and its characterisation by Infrared and Raman spectra

The thermal decomposition of Co(NO₃)₂·6H₂O (1) as well as that one of NO[Co(NO₃)₃] (Co(NO₃)₂·N₂O₄) (2) was followed by thermogravimetric (TG) measurements, X-ray recording and Raman and IR spectra. The stepwise decomposition reactions of 1 and 2 leading to anhydrous cobalt(II)nitrate (3) were established. In N₂ atmosphere, cobalt oxides are finally formed whereas in H₂/N₂ (10% H₂) cobalt metal is produced. Rapid heating of cobalt(II)nitrate hexahydrate causes melting (formation of a hydrate melt) and therefore side reactions in the hydrate melt by incoupled reactions and evolution/evaporation of different species as, e.g., HNO₃, NO₂, etc. In case of larger amounts in dense packing in the sample container, the formation of oxo(hydoxo)nitrates is possible at higher temperature. For 2, its thermal decomposition to 3 was followed and its decomposition mechanism is proposed.     

Synthesis and characterization of Cu(II) complexes of pyrazine-2,3-dicarboxylicacid

Four copper(II) coordination polymers, {[Cu(pz(COO)₂)(H₂O)]₄·HBr}_n (1), {[Cu(pz(COO)₂)(NH₃)₂]·H₂O}_n (2), {[Cu₃H₂(pz(COO)₂)₄(H₂O)₃]·2H₂O}_n (3) and {[Cu₂(pz(COO)₂)₂(NH₃)₂(H₂O)₃][Cu(pz(COO)₂)(NH₃)(H₂O)₂][Cu(pz(COO)₂)(NH₃)(H₂O)]·2H₂O}_n (4) were synthesized using pyrazine-2,3-dicarboxylic acid, CuBr₂, 2-(2-aminoethylamino)ethanol/triethanol amine/ammonia in a methanol:water (1:1) solution, and the mixed ligand complexes were characterized by spectroscopic methods, thermal and elemental analysis, and magnetic susceptibility. Complexes 2 and 4 were also characterized by means of single crystal X-ray crystallography. The characterizations show that the complexes have polynuclear molecular structures, except for complex 2, and all of the complex structures form polymeric chains. Complex 4 has a pseudo-merohedral twin structure.