Rotational and vibrational relaxation of the NO3 - ion in molten binary systems (M,Ag)NO3 (M = Li,Na and K) by Raman spectroscopy

Polarized and depolarized Raman scattering spectra for the totally symmetric stretching υ₁ mode of nitrate ions (D_3h symmetry) in the molten binary systems (M1,Ag)NO₃(M1= Li, Na, and K) have been measured. Vibrational and rotational autocorrelation³ functions, C_v(t) and C_r(t), respectively, have been evaluated from Fourier transformation of the spectra. The shifts in the peak frequencies are deeply correlated with the polarizability of silver in these mixtures. The vibrational relaxation rate increases with increasing mole fraction of silver nitrate in (K,Ag)NO₃, but does not vary so much in (Li,Ag)NO₃ and (Na,Ag)NO₃. The vibrational relaxation time negatively deviates from additivity on the order of (Na,Ag)NO₃< (Li,Ag)NO₃< (K,Ag)NO₃. In the systems (Na,Ag)NO₃ and (K,Ag)NO₃ rotational relaxation time becomes slower with increasing concentration of AgNO₃. The Ag⁺ coordinating to several nitrate ions in these mixtures appreciably restricts the rotational motion of the nitrate ions. On the other hand, rotational motion becomes easier in the mixture system (Li,Ag)NO₃ mainly because the different preferential sites of the two cations coordinating to an NO₃ ^-ion, and partly because the exchange rates of these cations around the NO_-3 ^-ion are high.     

Influence of the temperature and phase state of K,Ca/NO<Subscript>3</Subscript> and K,Mg/NO<Subscript>3</Subscript> binary systems on the vibrational anharmonicity and orientational mobility of the nitrate ion

The absorption spectra of homogeneous and heterophase melts and glasses of the K,Ca/NO₃ and K,Mg/NO₃ systems are studied by IR Fourier spectroscopy. The temperature-phase dependences for the first and second order spectra are analyzed, and the anharmonicity constants for internal vibrations of the nitrate ion are estimated. The influence of finely dispersed Al₂O₃ powder on the structural-dynamic properties of the K,Ca/NO₃ and K,Mg/NO₃ systems is studied. A mechanism for charge transfer in heterophase nitrate glasses is proposed. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 76, No. 2, pp. 176–181, March–April 2009.     

Temperature dependence of thermal property for lead nitrate crystal

Thermal property was measured in a lead nitrate crystal, Pb(NO₃)₂, at temperatures from 90 to 340 K by use of ac calorimetry technique. The heat capacity derived from the measurements showed temperature dependence with thermal hysteresis, in the temperature region from 240 to 300 K. The anomaly of the heat capacity was found in the vicinity of 275.22 K. The broad temperature variation in the heat capacity was observed in the region from 235 to 260 K.     

The adsorption of and reaction of NO2 on Ag(1 1 1)-p(4 × 4)-O and formation of surface nitrate

The adsorption and reaction of nitrogen dioxide on the Ag(1 1 1)-p(4 × 4)-O surface has been investigated with RAIRS, TPRS and STM. At 300 K NO₂ initially reacts with the oxygen overlayer to form nitrate in p(3 × 3) and p(4 × 4) structures, which convert to a new p(3 × 3) at saturation coverage. Surface pitting during nitrate adsorption is suggestive of the incorporation of silver atoms into the NO₃ structure. With heating NO₃ decomposes into NO₂ and O at 396 K and 497 K, and oxygen desorbs at 578 K.     

(TPP)NO3的合成、表征与分子识别NO

在氯仿与无水乙醇的混合溶剂(体积比为1:1)中,四苯基卟啉(TPP)与Ce(NO₃)·6H₂O混合反应后,得产物Ce(TPP)NO₃. 通过紫外-可见光谱、红外光谱、荧光光谱、质谱、核磁共振氢谱的分析与表征,四苯基卟啉与铈原子以四齿方式进行配位,在同一个铈原子上还有一个硝酸根配位. 向Ce(TPP)NO₃的二氯甲烷溶液中通入NO气体,NO可以配位在同一个铈原子上,得到新的配合物Ce(TPP)(NO)NO₃,向此溶液中通入N₂,金属卟啉配合物可以恢复为配合物Ce(TPP)NO₃.     

Long-range magnetic order in copper nitrate monohydrate Cu(NO<Subscript>3</Subscript>)<Subscript>2</Subscript> · H<Subscript>2</Subscript>O

The magnetic phase diagram of copper nitrate monohydrate Cu(NO₃)₂ · H₂O and the basic parameters of its magnetic subsystem have been determined by measuring the thermodynamic properties of this compound. This compound becomes antiferromagnetically ordered at T _N = 3.6 K, undergoes the spin-flop and spin-flip transitions at H _C1 ～ 0.06 T and H _C2 ～ 1.1 T, respectively, at low temperatures. The magnetization of Cu(NO₃)₂ · H₂O at T _SR = 2.7 K exhibits an additional anomaly, which is likely attributed to the spin-reorientation transition.     

Radiolysis of ferrous ammonium sulphate in alkali nitrate and alkali halide matrices

Radiolysis of ferrous ammonium sulphate (FAS) dispersed in (a) alkali nitrates [KNO₃, NaNO₃, Ba(NO₃)₂, CO(NH₃)₆(NO₃)₃] (b) alkali halides [KCl, KBr] and (c) binary mixtures of above [KNO₃ + KCl, Ba(NO³)₂ + BaCl₂) has been extensively investigated. FAS becomes oxidized and Fe³⁺ formation seems to depend upon the nitrate concentration and gamma dose but is independent of halide concentration. Mossbauer studies confirm these findings and it appears that basic ferric sulphate may be formed during the oxidation process.     

Transformations of radicals and ions in irradiated sodium sulfate doped with nitrate ions

The structure and properties of the paramagnetic centers formed by γ-irradiation at 77 K in sodium sulfate doped with nitrate ions have been investigated by the EPR method. The NO^2? ₃, NO₂ and SO^? ₄ radicals have been identified. The orientation of NO^2? ₃ relation to crystallographic axes is determined. In the 77-400 K temperature range the transformations of observable radicals have been studied. The mechanisms of their formation and thermal annealing have been discussed. The symmetry of nitrate ions in sodium sulfate was investigated by diffuse reflectance infrared Fourier transform spectroscopy. At the concentration of NO^? ₃ up to 5.5 × 10¹⁸ g^?1 the nitrate ion was supposed to have a planar or pyramidal configuration of the D_3h or C_3V symmetries. At the concentration of the dopant higher than 5.5 × 10¹⁸ g^?1 the nitrate ions with the C_2V symmetry were observed.     

Comparitive study of structure changes with temperature in univalent and divalent ionic nitrate crystals

The temperature dependence of the d.c. resistivity and dielectric constant of polycrystalline samples of Pb(NO₃)₂, Ba(NO₃)₂ and Sr(NO₃)₂ were found to show anomalies in the high temperature region. In addition, sharp peaks were obtained in both differential thermal analysis (DTA) and thermomechanical analysis (TMA) curves in the same temperature range. The observed anomalies were attributed to orientational disorder of the nitrate group leading to an order-disorder phase transition which is reported here for the first time. A comparison is made between the role of NO₃^?ions in both the divalent and univalent nitrates, taking NaNO₃ as representative. The TMA curve for Sr(NO₃)₂ showed a pronounced peak at 325°C. This peak was related to a sudden increase in the expansion coefficient associated with the rotation of the NO₃^? group leading to a solid state phase transformation. Energy diagrams describing the conduction mechanism and showing a fractionization of energy barriers in the case of divalent nitrates are introduced.     

Electronic Spectra and the Mechanism of Complexing of Uranyl Nitrate in Water–Acetone Solutions

Based on the analysis of electronic absorption and luminescence spectra, the processes of complexing in an aqueous solution of uranyl nitrate hexahydrate (UO₂(NO₃)₂·6H₂O) on gradual addition of small amounts of acetone have been investigated. In a pure aqueous solution, uranyl exists as the UO₂·5H₂O complex. It is shown that addition of acetone to the solution leads to displacement of some water molecules from the first coordination sphere of uranyl and formation of uranyl nitrate dihydrate complexes, UO₂(NO₃)₂·2H₂O. It has been established that the stability of these complexes is determined by the decrease in both the water activity and the degree of hydration of uranyl and nitrate. This is the result of the local increase in the concentration of the molecules of acetone (due to its hydrophobicity) in those regions of the solution in which there are uranyl and nitrate ions. The experimental facts supporting the proposed mechanism are given.     

Investigation of uranyl nitrate extraction from ketone solutions by dimethyl sulfoxide

Based on an analysis of low-temperature luminescence spectra (T=77 K) of UO₂(NO₃)₂·6H₂O solutions in acetone, the mechanisms of formation of a wide group of uranyl complexes in uranyl extraction from solutions by dimethyl sulfoxide are studied. It is shown that to increase the coefficient of uranyl distribution between the solution and solid phase (in the form of UO₂(NO₃)₂·2DMSO) it is necessary to add sulfoxide in small amounts, of about 0.35–0.5 mole per mole of uranyl. One-time introduction of DMSO in amounts of 1–3 mole per mole of uranyl leads to the formation of a number of uranyl complexes that are well soluble in acetone, and to a corresponding decrease in the distribution coefficient. The role of entropy and enthalpy in improvement of the stability of chelate complexes of uranyl nitrate is evaluated. Belarusian State University, 4, F. Skorina Ave., Minsk, 220050, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 3, pp. 358–362, May–Jene, 1997.     

The effect of alloy composition on the interaction of NO2 with tin-lead alloys

The interaction of NO₂ with SnPb alloys is presented. Five different compositions of the alloy were used with an NO₂ concentration of 140 ppm. A plot of the rate of weight gain versus sample composition is presented which indicates that NO₂ interacts with all compositions tested with the rate of weight gain decreasing slightly as the percent of lead goes from zero to 100 percent. Reaction products obtained were Pb(NO₃)₂ and an amorphous tin containing product which is probably tin nitrate. The alloys undoubtedly contain mixtures of the two materials.     

Vitreous solid state electrolytes in the system of RNO3–Zn(NO3)2–KHSO4–P2O5

The structure and electric conductivity of glasses in the system RNO₃–Zn(NO₃)₂–KHSO₄–P₂O₅ (R = Na, K) obtained at different temperatures were investigated by IR and impedance spectroscopy. Glasses fused at 250–350 °C demonstrated an increase of their ionic conductivity in 10³ times in comparison with the same compositions fused at 550 °C. The influence of the chemical composition on the structure and properties of the obtained glasses was analyzed. It is proposed that the high ionic conductivity of glasses obtained at low temperatures is related to the incorporation of the nitrate ions between long (PO₃)_n chains, similar to the iodide ions; this resulted in a maximal coordination of the local conduction space for the cation associated with a disordered glass network.     

Metal/electrolyte surface chemistry: The adsorption of nitric acid and water on Ag(110)

The adsorption of HNO₃/H₂O mixtures on Ag(110) was investigated to learn more about the chemistry of the metal/electrolyte interface. The experiments were performed in ultrahigh vacuum (UHV) using thermal desorption spectroscopy (TDS), low energy electron diffraction (LEED), and electron stimulated desorption ion angular distribution (ESDIAD) over temperatures of 80–650 K and coverages of 0–10 monolayers (ML). As this is the first known study of HNO₃ in UHV, the mass spectrometer cracking pattern for HNO₃ is here reported. HNO₃ adsorbs irreversibly on the clean surface at 80 K and loses its acidic proton to form an adsorbed surface nitrate (NO₃) below 150 K. The saturation amount of adsorbed NO₃ is 0.4 ± 0.1 ML for which adsorption occurs in either a normal or split c(2 × 2) structure. N03 is stable on the surface up to 450 K beyond which it decomposes directly to gaseous NO₂ and NO and adsorbed atomic oxygen. NO₃ decomposition is first order with an activation energy E_a = 151±4 kJ mol⁻¹ and a pre-exponential factor of A = 10^15.4±0.4s⁻¹. NO₃ stabilizes adsorbed H₂O by about 8 kJ mol⁻¹ and is hydrated by as many as three H₂O molecules. Multilayers of HNO₃/H₂O desorb at 150–220 K and show evidence of extensive hydrogen bonding and hydration interactions. No evidence for HNO₃-induced corrosion or other surface damage was detected in any of these experiments.     

Conductivity studies of starch-based polymer electrolytes

A proton-conducting polymer electrolyte based on starch and ammonium nitrate (NH₄NO₃) has been prepared through solution casting method. Ionic conductivity for the system was conducted over a wide range of frequency between 50 Hz and 1 MHz and at temperatures between 303 K and 373 K. Impedance analysis shows that sample with 25 wt.% NH₄NO₃ has a smaller bulk resistance (R _b) compared to that of the pure sample. The amount of NH₄NO₃ was found to influence the proton conduction; the highest obtainable room temperature conductivity was 2.83 × 10⁻⁵ S cm⁻¹, while at 100 °C, the conductivity in found to be 2.09 × 10⁻⁴ S cm⁻¹. The dielectric analysis demonstrates a non-Debye behavior. Transport parameters of the samples were calculated using the Rice and Roth model and thus shows that the increase in conductivity is due to the increase in the number of mobile ions.     

Characterizations of octahedral zinc oxide synthesized by sonochemical method

The ultrasonic reaction of zinc nitrate hexahydrate (Zn(NO₃)₂·6H₂O) and hexamethylenetetramine (C₆H₁₂N₄) was investigated by varying the concentration of the reactants, the irradiation time, and the type of sonicator. The morphology, composition, and phase structure of the products were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) and ultraviolet-visible (UV-vis) spectroscopy. Octahedral zinc oxide (ZnO) micropowders were formed at low concentrations, 0.05 M, of Zn(NO₃)₂·6H₂O and C₆H₁₂N₄ in both lab-made sonicator and commercial ultrasonic bath. However, at concentrations between 0.1 and 1.0 M Zn(NO₃)₂-C₆H₁₂N₄ mainly plate-like zinc hydroxide nitrate hydrate (Zn₅(OH)₈(NO₃)₂(H₂O)₂) resulted with only a small fraction of ZnO, irrespective of the irradiation time employed, highlighting the sensitivity of the system to the concentration of the starting materials. Heat treatment of Zn₅(OH)₈(NO₃)₂(H₂O)₂ at 350 °C in air affords a ZnO phase of irregular morphology. Octahedral ZnO is found to exhibit slightly lower IR absorption and similar UV absorption to that of commercial prismatic hexagonal ZnO, although an extra peak due to small quantities of Zn₅(OH)₈(NO₃)₂(H₂O)₂ is observed.     

Enhanced magnetization of nanoparticles of Mg x Fe(3? x )O4 (0.5≤ x ≤1.5) synthesized by combustion reaction

For the first time nanocrystalline magnetic particles of Mg _x Fe_(3−x)O₄ with x ranging from 0.5 to 1.5 have been synthesized by a combustion reaction method using iron nitrate Fe(NO₃)₃.9H₂O, magnesium nitrate Mg(NO₃)₂.6H₂O, and urea CO(NH₂)₂ as fuel without intermediate decomposition and/or calcining steps. X-ray diffraction patterns of all systems showed broad peaks consistent with cubic inverse spinel structure of MgFe₂O₄. The absence of extra reflections in the diffraction patterns of as-prepared materials ensures the phase purity. The mean crystallite sizes determined from the prominent (311) peak of the diffraction using Scherrer’s equation and transmission electron microscopy micrographs were c.a. 40 nm with spherical morphology. Fourier transform infrared spectra of the as-prepared material showed traces of organic and metallic salt by-products; however, these could be removed by washing with deionized water. Typical hysteresis curves were obtained for all specimens in magnetic field up to 14 T between 4 and 340 K. The saturation magnetization was 48.3 emu/g and 31.3 emu/g, 44.8 emu/g, and 28.4 emu/g for x=1.0 and 0.8 at 4 K and 340 K, respectively. The saturation magnetization, M _s , of nanoparticles of the MgFe₂O₄ specimen is about 50% higher when compared to the bulk. The enhanced magnetization measured in our nanoparticles MgFe₂O₄ specimens may be attributed to the uncompensated magnetic moment of iron ions between the A- and B-sites, i.e., changes in the inversion factor. Our magnetization results of MgFe₂O₄ specimens are comparable to the existing data for the same compound but with different particle size and prepared by different synthesis methods.     

Spatial distribution and formation of nitrate radical NO<Stack><Subscript>3</Subscript><Superscript>2−</Superscript></Stack> in Antarctic calcitic evaporates

Nitrate radical NO₃²⁻ in calcitic evaporate was discovered in Antarctica. The distribution and formation of nitrate radical NO₃²⁻ in the calcite have been studied by pulse and continuous-wave electron spin resonance. In samples that had been annealed to destroy the NO₃²⁻, regeneration of the radical by γ-rays or UV light indicated that the radical was formed by UV light (with wavelengths less than 340 nm) from solar rays, not by environmental radiation. The nonuniform spatial distribution of the nitrate radical, which was deduced from high ratios of local spin density to total spin density, suggests that the nitrate impurity was introduced into the calcium carbonate after carbonate grain formation. Formation of the carbonate-containing nitrate requires the presence of high amounts of nitrate and a dry climate. Formation of the nitrate radical requires sample exposure to UV light. These conditions are satisfied in the environment of Antarctica.     

IR Spectral Analysis of the Mixed Crystal System of AgNO3 and Sr(NO3)2

IR spectroscopy is utilized to analyse the mixed crystal system of AgNO₃ and Sr(NO₃)₂ in the ordered phase II and disordered phases of silver nitrate. The study aims mainly to clearify the change and the affect of partial replacement of Ag⁺ ion by Sr⁺⁺ ion in the mixed crystal system of the two metal nitrates. The change in the rotational energy barrier of the nitrate group was also checked.     

Flower-like Ni3(NO3)2(OH)4@Zr-metal organic framework (UiO-66) composites as electrode materials for high performance pseudocapacitors

Zr-metal organic frameworks (Zr-MOFs, UIO-66) as a kind of crystalline porous material possess controllable porous structure and strong thermal stability up to 753 K. In this paper, we synthesized Ni₃(NO₃)₂(OH)₄, Zr-MOF with high specific surface area (1073 m² g⁻¹) and Ni₃(NO₃)₂(OH)₄@Zr-MOF composite for pseudocapacitor material. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were taken to characterize the structure and morphology of Ni₃(NO₃)₂(OH)₄, Zr-MOF, and Ni₃(NO₃)₂(OH)₄@Zr-MOF. The porous structure of Zr-MOF favors the utilization of the active material Ni₃(NO₃)₂(OH)₄ and interfacial charge transport and provides short diffusion paths for ions, which results in a high specific capacitance. Electrochemical properties are evaluated by cyclic voltammetry (CV) and galvanostatic charge/discharge measurement. A maximum specific capacitance (SC) of 992 F/g was obtained from CV at a scan rate of 5 mVs⁻¹, which is higher than Zr-MOF (∼134 F g⁻¹) and Ni₃(NO₃)₂(OH)₄ (∼753 F g⁻¹). Meanwhile, the Ni₃(NO₃)₂(OH)₄@Zr-MOF composite electrode exhibits a good cycling stability over 3000 cycles.